WorldWideScience

Sample records for roll clouds observed

  1. Kontur: Observations of cloud streets and open cellular structures

    Science.gov (United States)

    Brümmer, B.; Bakan, S.; Hinzpeter, H.

    1985-08-01

    In September and October 1981 the experiment KonTur (Convection and turbulence) was conducted over the North Sea. Its objectives were to investigate organized convective patterns, like cloud streets (boundary layer rolls) and cellular cloud structures. Two aircraft (British Hercules C-130 and German Falcon 20) performed detailed measurements within these patterns. Several cases of cloud streets and open cells were observed. Boundary layer rolls appear to be connected with an inflection point in the cross-roll wind component. The aspect ratio of the rolls (wavelength versus depth) is between three and four in accordance with other observations and linear stability analysis. Four scales of motion are involved: the mean flow, the roll circulation, individual clouds and turbulence. The vertical transport are dominated at lower levels by turbulence and at higher levels by roll-scale motions. Open cellular cloud structures are connected with large air-sea temperature differences due to cold air outbreaks from the northwest. The aspect ratio of the cells is of the order of 10. The bulk contribution to the total transport of heat and momentum originates from the cloudy walls of the cells. A vertical cross section through a composite open cell is presented.

  2. Design of Rolling State Observers for Application to Control of Thickness and Tension in Rolling Mills

    Directory of Open Access Journals (Sweden)

    Hamid R. Koofigar

    2011-09-01

    Full Text Available This study focuses on the necessity of designing state observers to be used in controller synthesis for rolling processes. This is motivated by the fact that using several kinds of sensors for measuring all of process variables is technically and economically avoided. On the other hand, using exact measurement in feedback control systems could considerably improve the quality of products. In other word, there is a trade-off between high quality and the implementation limitations, managed here by developing rolling state observers. The proposed observers estimate the states not measured directly by the installed sensors. This technique is applicable to both hot rolling and cold rolling processes. Simulation results demonstrate the performance of the proposed estimation algorithm.

  3. Potential New Lidar Observations for Cloud Studies

    Science.gov (United States)

    Winker, Dave; Hu, Yong; Narir, Amin; Cai, Xia

    2015-01-01

    The response of clouds to global warming represents a major uncertainty in estimating climate sensitivity. These uncertainties have been tracked to shallow marine clouds in the tropics and subtropics. CALIOP observations have already been used extensively to evaluate model predictions of shallow cloud fraction and top height (Leahy et al. 2013; Nam et al 2012). Tools are needed to probe the lowest levels of the troposphere. The large footprint of satellite lidars gives large multiple scattering from clouds which presents new possibilities for cloud retrievals to constrain model predictions.

  4. MERIS full-resolution total column water vapor: Observing horizontal convective rolls

    Science.gov (United States)

    Carbajal Henken, C. K.; Diedrich, H.; Preusker, R.; Fischer, J.

    2015-11-01

    This study presents the first analysis of small-scale convective structures observed in a total column water vapor (TCWV) field obtained from full-resolution Medium Resolution Imaging Spectrometer (MERIS) near-infrared measurements. The high-resolution MERIS TCWV field for a high-pressure event occurring in May over central Europe allows the detection of horizontal convective rolls, due to the observation of parallel bands of alternating low- and high-TCWV values. The bands are aligned parallel to the boundary layer winds obtained from a numerical weather prediction model and radiosonde data. Closer examination further reveals that cloud streets observed in the east extend along bands of maximum TCWV. From a quantitative analysis of the TCWV data, combined with auxiliary data, it is shown that the roll wavelength and aspect ratio can be determined, which are found to be 6.5 km and 4.2, respectively, for this case study.

  5. CALIPSO Observations of Aerosol Properties Near Clouds

    Science.gov (United States)

    Marshak, Alexander; Varnai, Tamas; Yang, Weidong

    2010-01-01

    Clouds are surrounded by a transition zone of rapidly changing aerosol properties. Characterizing this zone is important for better understanding aerosol-cloud interactions and aerosol radiative effects as well as for improving satellite measurements of aerosol properties. We present a statistical analysis of a global dataset of CALIPSO (Cloud-Aerosol Lidar and infrared Pathfinder Satellite Observation) Lidar observations over oceans. The results show that the transition zone extends as far as 15 km away from clouds and it is ubiquitous over all oceans. The use of only high confidence level cloud-aerosol discrimination (CAD) data confirms the findings. However, the results underline the need for caution to avoid biases in studies of satellite aerosol products, aerosol-cloud interactions, and aerosol direct radiative effects.

  6. Molecular Clouds: Observation to Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Kane, J O; Ryutov, D D; Mizuta, A; Remington, B A; Pound, M W

    2004-05-06

    Our ongoing investigation of how 'Pillars' and other structure form in molecular clouds irradiated by ultraviolet (UV) stars has revealed that the Rayleigh-Taylor instability is strongly suppressed by recombination in the photoevaporated outflow, that clumps and filaments may be key, that the evolution of structure is well-modeled by compressible hydrodynamics, and that directionality of the UV radiation may have significant effects. We discuss a generic, flexible set of laboratory experiments that can address these issues.

  7. Global cloud climatology from surface observations

    Energy Technology Data Exchange (ETDEWEB)

    Warren, S. [Univ. of Washington, Seattle, WA (United States)

    1995-09-01

    Surface weather observations from stations on land and ships in the ocean are used to obtain the global distribution, at 5{sup o}x5{sup o} latitude-longitude resolution, of total cloud cover and the average amounts of the different cloud types: cumulus, cumulonimbus, stratus, stratocumulus, nimbostratus, altostratus, altocumulus, cirrus, cirrostratus, cirrocumulus, and fog. Diurnal and seasonal variations are derived, as well as interannual variations and multi-year trends. 3 refs., 3 figs.

  8. Feature Extraction Method of Rolling Bearing Fault Signal Based on EEMD and Cloud Model Characteristic Entropy

    Directory of Open Access Journals (Sweden)

    Long Han

    2015-09-01

    Full Text Available The randomness and fuzziness that exist in rolling bearings when faults occur result in uncertainty in acquisition signals and reduce the accuracy of signal feature extraction. To solve this problem, this study proposes a new method in which cloud model characteristic entropy (CMCE is set as the signal characteristic eigenvalue. This approach can overcome the disadvantages of traditional entropy complexity in parameter selection when solving uncertainty problems. First, the acoustic emission signals under normal and damage rolling bearing states collected from the experiments are decomposed via ensemble empirical mode decomposition. The mutual information method is then used to select the sensitive intrinsic mode functions that can reflect signal characteristics to reconstruct the signal and eliminate noise interference. Subsequently, CMCE is set as the eigenvalue of the reconstructed signal. Finally, through the comparison of experiments between sample entropy, root mean square and CMCE, the results show that CMCE can better represent the characteristic information of the fault signal.

  9. Sky cover from MFRSR observations: cumulus clouds

    Directory of Open Access Journals (Sweden)

    E. Kassianov

    2011-01-01

    Full Text Available The diffuse all-sky surface irradiances measured at two nearby wavelengths in the visible spectral range and their model clear-sky counterparts are two main components of a new method for estimating the fractional sky cover of different cloud types, including cumulus clouds. The performance of this method is illustrated using 1-min resolution data from ground-based Multi-Filter Rotating Shadowband Radiometer (MFRSR. The MFRSR data are collected at the US Department of Energy Atmospheric Radiation Measurement (ARM Climate Research Facility (ACRF Southern Great Plains (SGP site during the summer of 2007 and represent 13 days with cumulus clouds. Good agreement is obtained between estimated values of the fractional sky cover and those provided by a well-established independent method based on broadband observations.

  10. Mars - Are observed white clouds composed of H2O.

    Science.gov (United States)

    Wells, R. A.

    1972-01-01

    A total of 252 occurrences of white clouds are studied. Water abundances are compared with those of white clouds as a function of latitude on Mars. It appears not necessarily to be the case that observed cloud frequencies will always follow water abundances. Martian white cloud frequencies tend to follow the distribution of water both seasonally and latitudinally on the planet, which strongly suggests that most white clouds are formed from water vapor.

  11. CloudSat observations of multi layered clouds across the globe

    Science.gov (United States)

    Subrahmanyam, K. Venkata; Kumar, Karanam Kishore

    2017-07-01

    Vertically resolved multi-layer cloud distributions over the globe using 4 years of CloudSat/CALIPSO observations during 2007-2010 are discussed. The quantitative information on the frequency of occurrence of one- to five-layered clouds across the globe is established, which are of immense importance from the global climate standpoint. After segregating the CloudSat observations into different seasons, the 4 years of mean global maps of frequency of occurrence of one to five-layered clouds are discussed in details. These global maps provide much needed quantification of vertically resolved multi-layer clouds by revealing when and where the frequency of occurrence of multi-layer clouds are maximum including the number of layers. On an average, it is observed that over the globe one-, two-, three-, four- and five-layer clouds occur 53, 20, 3.5, 0.4 and 0.04 % of the time respectively. High fraction of single layer clouds is observed over the descending limbs of Hadley cell where relatively large lower tropospheric stability is found. The regions where multi-layer clouds are more frequent are identified and discussed along with large scale circulation. Apart from quantifying the frequency of occurrence of multi-layer clouds, the latitudinal distribution of zonal mean occurrence of cloud base and top altitudes of each cloud layer is constructed for boreal winter and summer. These analyses provide the cloud base and top altitudes of one to five-layered clouds, which are important to understand the vertical structure of the multi-layered clouds. The significance of the present study lies in establishing the global distribution of vertically resolved multi-layer clouds and the role of large-scale dynamics in controlling their distribution for the first time.

  12. Relationship between Cloud Characteristics and Radar Reflectivity Based on Aircraft and Cloud Radar Co-observations

    Institute of Scientific and Technical Information of China (English)

    ZONG Rong; LIU Liping; YIN Yan

    2013-01-01

    Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong,Jilin,Northeast China.The aircraft provided in situ measurements of cloud droplet size distribution,while the millimeter-wavelength cloud radar vertically scanned the same cloud that the aircraft penetrated.The reflectivity factor calculated from aircraft measurements was compared in detail with simultaneous radar observations.The results showed that the two reflectivities were comparable in warm clouds,but in ice cloud there were more differences,which were probably associated with the occurrence of liquid water.The acceptable agreement between reflectivities obtained in water cloud confirmed that it is feasible to derive cloud properties by using aircraft data,and hence for cloud radar to remotely sense cloud properties.Based on the dataset collected in warm clouds,the threshold of reflectivity to diagnose drizzle and cloud particles was studied by analyses of the probability distribution function of reflectivity from cloud particles and drizzle drops.The relationship between reflectivity factor (Z) and cloud liquid water content (LWC) was also derived from data on both cloud particles and drizzle.In comparison with cloud droplets,the relationship for drizzle was blurred by many scatter points and thus was less evident.However,these scatters could be partly removed by filtering out the drop size distribution with a large ratio of reflectivity and large extinction coefficient but small effective radius.Empirical relationships of Z-LWC for both cloud particles and drizzle could then be derived.

  13. INTEGRAL observations of the Small Magellanic Cloud

    CERN Document Server

    McBride, V A; Bird, A J; Dean, A J; Hill, A B; McGowan, K E; Schurch, M P E; Udalski, A; Soszynski, I; Finger, M; Wilson, C A; Corbet, R H D; Negueruela, I

    2007-01-01

    The first INTEGRAL observations of the Small Magellanic Cloud (carried out in 2003) are reported in which two sources are clearly detected. The first source, SMC X-1, shows a hard X-ray eclipse and measurements of its pulse period indicate a continuation of the long-term spin-up now covering ~30 years. The second source is likely to be a high mass X-ray binary, and shows a potential periodicity of 6.8s in the IBIS lightcurve. An exact X-ray or optical counterpart cannot be designated, but a number of proposed counterparts are discussed. One of these possible counterparts shows a strong coherent optical modulation at ~2.7d, which, together with the measured hard X-ray pulse period, would lead to this INTEGRAL source being classified as the fourth known high mass Roche lobe overflow system.

  14. Supernova Driving. III. Synthetic Molecular Cloud Observations

    Science.gov (United States)

    Padoan, Paolo; Juvela, Mika; Pan, Liubin; Haugbølle, Troels; Nordlund, Åke

    2016-08-01

    We present a comparison of molecular clouds (MCs) from a simulation of supernova (SN) driven interstellar medium (ISM) turbulence with real MCs from the Outer Galaxy Survey. The radiative transfer calculations to compute synthetic CO spectra are carried out assuming that the CO relative abundance depends only on gas density, according to four different models. Synthetic MCs are selected above a threshold brightness temperature value, T B,min = 1.4 K, of the J = 1 - 0 12CO line, generating 16 synthetic catalogs (four different spatial resolutions and four CO abundance models), each containing up to several thousands MCs. The comparison with the observations focuses on the mass and size distributions and on the velocity-size and mass-size Larson relations. The mass and size distributions are found to be consistent with the observations, with no significant variations with spatial resolution or chemical model, except in the case of the unrealistic model with constant CO abundance. The velocity-size relation is slightly too steep for some of the models, while the mass-size relation is a bit too shallow for all models only at a spatial resolution dx ≈ 1 pc. The normalizations of the Larson relations show a clear dependence on spatial resolution, for both the synthetic and the real MCs. The comparison of the velocity-size normalization suggests that the SN rate in the Perseus arm is approximately 70% or less of the rate adopted in the simulation. Overall, the realistic properties of the synthetic clouds confirm that SN-driven turbulence can explain the origin and dynamics of MCs.

  15. Multi-spacecraft observation of a magnetic cloud

    Science.gov (United States)

    de Lucas, A.; Dal Lago, A.; Schwenn, R.; Clua de Gonzalez, A. L.; Marsch, E.; Gonzalez, W. D.

    2009-12-01

    During the time operation of the Helios mission, from 1974 to 1986, a large number of magnetic clouds was identified by the magnetic field and solar wind sensors onboard the probes. Among these magnetic clouds, some of them were identified by at least two probes, provided that IMP-8 and ISEE-3 were monitoring the dayside magnetosphere. The magnetic cloud observed on from DOY 029 to DOY 030/1977 by Helios 1, Helios 2, and IMP-8 represents a potential multi-spacecraft observed magnetic cloud. Despite the interaction with the high-speed stream that compressed the magnetic cloud, the minimum variance analysis technique showed the same direction of rotation of the magnetic field inside the magnetic cloud. This helped to associate the observation of the magnetic cloud at multi-spacecraft.

  16. CloudSat observations of cloud-type distribution over the Indian summer monsoon region

    Directory of Open Access Journals (Sweden)

    K. V. Subrahmanyam

    2013-07-01

    Full Text Available The three-dimensional distribution of various cloud types over the Indian summer monsoon (ISM region using five years (2006–2010 of CloudSat observations during June-July-August-September months is discussed for the first time. As the radiative properties, latent heat released and microphysical properties of clouds differ largely depending on the cloud type, it becomes important to know what types of clouds occur over which region. In this regard, the present analysis establishes the three-dimensional distribution of frequency of occurrence of stratus (St, stratocumulus (Sc, nimbostratus (Ns, cumulus (Cu, altocumulus (Ac, altostratus (As, cirrus (Ci and deep convective (DC clouds over the ISM region. The results show that the various cloud types preferentially occur over some regions of the ISM, which are consistent during all the years of observations. It is found that the DC clouds frequently occur over northeast of Bay of Bengal (BoB, Ci clouds over a wide region of south BoB–Indian peninsula–equatorial Indian Ocean, and Sc clouds over the north Arabian Sea. Ac clouds preferentially occur over land, and a large amount of As clouds are found over BoB. The occurrence of both St and Ns clouds over the study region is much lower than all other cloud types.The interannual variability of all these clouds including their vertical distribution is discussed. It is envisaged that the present study opens up possibilities to quantify the feedback of individual cloud type in the maintenance of the ISM through radiative forcing and latent heat release.

  17. Supernova Driving. III. Synthetic Molecular Cloud Observations

    CERN Document Server

    Padoan, Paolo; Pan, Liubin; Haugbølle, Troels; Nordlund, Åke

    2016-01-01

    We present a comparison of molecular clouds (MCs) from a simulation of supernova-driven interstellar medium (ISM) turbulence with real MCs from the Outer Galaxy Survey. The radiative transfer calculations to compute synthetic CO spectra are carried out assuming the CO relative abundance depends only on gas density, according to four different models. Synthetic MCs are selected above a threshold brightness temperature value, $T_{\\rm B,min}=1.4$ K, of the $J=1-0$ $^{12}$CO line, generating 16 synthetic catalogs (four different spatial resolutions and four CO abundance models), each containing up to several thousands MCs. The comparison with the observations focuses on the mass and size distributions and on the velocity-size and mass-size Larson relations. The mass and size distributions are found to be consistent with the observations, with no significant variations with spatial resolution or chemical model, except in the case of the unrealistic model with constant CO abundance. The velocity-size relation is sl...

  18. Evaluation of Cloud Microphysical Parameterizations in Cloud Resolving Model Simulations using the ARM observations

    Science.gov (United States)

    Liu, Z.; Muhlbauer, A.; Ackerman, T. P.

    2011-12-01

    Clouds modulate the distribution of energy and water within the atmosphere and regulate the hydrological cycle. Cloud microphysical parameterizations are critical for the representation of cloud microphysical properties in both cloud-resolving and climate models. In this study, we analyze the capabilities of a cloud-resolving model (CRM) with advanced bulk microphysics schemes to simulate the microphysical properties and evolution of convective clouds and anvil cirrus over the Southern Great Plains (SGP) site in the mid-latitudes and Kwajalein Atoll in the tropics. For evaluating simulated cloud properties, we use observations from the Atmospheric Radiation Measurement (ARM) Program 1997 summer Intensive Observations Period at the SGP site and the Kwajalein Experiment (KWAJEX) field campaign. The CRM simulations are evaluated with the ARM and KWAJEX observations, in particular using precipitation records, radiative fluxes, and radar reflectivity values observed by the ARM millimeter wavelength cloud radar (MMCR) and the Kwajalein precipitation radar. Preliminary analysis of the ARM SGP case shows that although the precipitation events during this period are well captured by the model, the outgoing longwave radiation (OLR) is considerably underestimated and the model generates too much high cloud, which is inconsistent with the MMCR observations. In our study we especially focus on the causes of the overproduction of ice and high clouds in the CRM simulations. Improvements of the ice microphysics scheme and resulting impacts on the simulation are presented.

  19. New insights about cloud vertical structure from CloudSat and CALIPSO observations

    Science.gov (United States)

    Oreopoulos, Lazaros; Cho, Nayeong; Lee, Dongmin

    2017-09-01

    Active cloud observations from A-Train's CloudSat and CALIPSO satellites offer new opportunities to examine the vertical structure of hydrometeor layers. We use the 2B-CLDCLASS-LIDAR merged CloudSat-CALIPSO product to examine global aspects of hydrometeor vertical stratification. We group the data into major cloud vertical structure (CVS) classes based on our interpretation of how clouds in three standard atmospheric layers overlap and provide their global frequency of occurrence. The two most frequent CVS classes are single-layer (per our definition) low and high clouds that represent 53% of cloudy skies, followed by high clouds overlying low clouds, and vertically extensive clouds that occupy near-contiguously a large portion of the troposphere. The prevalence of these configurations changes seasonally and geographically, between daytime and nighttime, and between continents and oceans. The radiative effects of the CVS classes reveal the major radiative warmers and coolers from the perspective of the planet as a whole, the surface, and the atmosphere. Single-layer low clouds dominate planetary and atmospheric cooling and thermal infrared surface warming. We also investigate the consistency between passive and active views of clouds by providing the CVS breakdowns of Moderate Resolution Imaging Spectroradiometer cloud regimes for spatiotemporally coincident MODIS-Aqua (also on the A-Train) and CloudSat-CALIPSO daytime observations. When the analysis is expanded for a more in-depth look at the most heterogeneous of the MODIS cloud regimes, it ultimately confirms previous interpretations of their makeup that did not have the benefit of collocated active observations.

  20. Giant Molecular Cloud Formation in Disk Galaxies: Characterizing Simulated versus Observed Cloud Catalogs

    Science.gov (United States)

    Benincasa, Samantha M.; Tasker, Elizabeth J.; Pudritz, Ralph E.; Wadsley, James

    2013-10-01

    We present the results of a study of simulated giant molecular clouds (GMCs) formed in a Milky Way-type galactic disk with a flat rotation curve. This simulation, which does not include star formation or feedback, produces clouds with masses ranging between 104 M ⊙ and 107 M ⊙. We compare our simulated cloud population to two observational surveys: the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey and the BIMA All-Disk Survey of M33. An analysis of the global cloud properties as well as a comparison of Larson's scaling relations is carried out. We find that simulated cloud properties agree well with the observed cloud properties, with the closest agreement occurring between the clouds at comparable resolution in M33. Our clouds are highly filamentary—a property that derives both from their formation due to gravitational instability in the sheared galactic environment, as well as to cloud-cloud gravitational encounters. We also find that the rate at which potentially star-forming gas accumulates within dense regions—wherein n thresh >= 104 cm-3—is 3% per 10 Myr, in clouds of roughly 106 M ⊙. This suggests that star formation rates in observed clouds are related to the rates at which gas can be accumulated into dense subregions within GMCs via filamentary flows. The most internally well-resolved clouds are chosen for listing in a catalog of simulated GMCs—the first of its kind. The cataloged clouds are available as an extracted data set from the global simulation.

  1. GIANT MOLECULAR CLOUD FORMATION IN DISK GALAXIES: CHARACTERIZING SIMULATED VERSUS OBSERVED CLOUD CATALOGS

    Energy Technology Data Exchange (ETDEWEB)

    Benincasa, Samantha M.; Pudritz, Ralph E.; Wadsley, James [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada); Tasker, Elizabeth J. [Department of Physics, Faculty of Science, Hokkaido University, Kita-ku, Sapporo 060-0810 (Japan)

    2013-10-10

    We present the results of a study of simulated giant molecular clouds (GMCs) formed in a Milky Way-type galactic disk with a flat rotation curve. This simulation, which does not include star formation or feedback, produces clouds with masses ranging between 10{sup 4} M{sub ☉} and 10{sup 7} M{sub ☉}. We compare our simulated cloud population to two observational surveys: the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey and the BIMA All-Disk Survey of M33. An analysis of the global cloud properties as well as a comparison of Larson's scaling relations is carried out. We find that simulated cloud properties agree well with the observed cloud properties, with the closest agreement occurring between the clouds at comparable resolution in M33. Our clouds are highly filamentary—a property that derives both from their formation due to gravitational instability in the sheared galactic environment, as well as to cloud-cloud gravitational encounters. We also find that the rate at which potentially star-forming gas accumulates within dense regions—wherein n{sub thresh} ≥ 10{sup 4} cm{sup –3}—is 3% per 10 Myr, in clouds of roughly 10{sup 6} M{sub ☉}. This suggests that star formation rates in observed clouds are related to the rates at which gas can be accumulated into dense subregions within GMCs via filamentary flows. The most internally well-resolved clouds are chosen for listing in a catalog of simulated GMCs—the first of its kind. The cataloged clouds are available as an extracted data set from the global simulation.

  2. A cosmic ray-climate link and cloud observations

    CERN Document Server

    Laken, Benjamin A; Calogovic, Jasa; Dunne, Eimear M; 10.1051/swsc/2012018

    2012-01-01

    Despite over 35 years of constant satellite-based measurements of cloud, reliable evidence of a long-hypothesized link between changes in solar activity and Earth's cloud cover remains elusive. This work examines evidence of a cosmic ray cloud link from a range of sources, including satellite-based cloud measurements and long-term ground-based climatological measurements. The satellite-based studies can be divided into two categories: 1) monthly to decadal timescale correlations, and 2) daily timescale epoch-superpositional (composite) analysis. The latter analyses frequently focus on high-magnitude reductions in the cosmic ray flux known as Forbush Decrease (FD) events. At present, two long-term independent global satellite cloud datasets are available (ISCCP and MODIS). Although the differences between them are considerable, neither shows evidence of a solar-cloud link at either long or short timescales. Furthermore, reports of observed correlations between solar activity and cloud over the 1983 to 1995 per...

  3. Observations of chemical differentiation in clumpy molecular clouds

    CERN Document Server

    Buckle, J V; Wirström, E S; Charnley, S B; Markwick-Kemper, A J; Butner, H M; Takakuwa, S

    2006-01-01

    We have extensively mapped a sample of dense molecular clouds (L1512, TMC-1C, L1262, Per 7, L1389, L1251E) in lines of HC3N, CH3OH, SO and C^{18}O. We demonstrate that a high degree of chemical differentiation is present in all of the observed clouds. We analyse the molecular maps for each cloud, demonstrating a systematic chemical differentiation across the sample, which we relate to the evolutionary state of the cloud. We relate our observations to the cloud physical, kinematical and evolutionary properties, and also compare them to the predictions of simple chemical models. The implications of this work for understanding the origin of the clumpy structures and chemical differentiation observed in dense clouds are discussed.

  4. Global Observations of Cloud-Sensitive Aerosol Loadings in Low Level Marine Clouds

    Science.gov (United States)

    Cermak, J.; Andersen, H.; Fuchs, J.; Schwarz, K.

    2016-12-01

    This contribution presents a method to characterize the nonlinear relationship between aerosols and cloud droplets in marine boundary layer clouds based on global MODIS observations.Clouds play a crucial role in the climate system as their radiative properties and precipitation patterns significantly impact the Earth's energy balance. Cloud properties are determined by environmental conditions, as cloud formation requires the availability of water vapour ("precipitable water") and condensation nuclei in sufficiently saturated conditions. The ways in which aerosols as condensation nuclei in particular influence the optical, micro- and macrophysical properties of clouds are one of the largest remaining uncertainties in climate-change research. In particular, cloud droplet size is believed to be impacted, and thereby cloud reflectivity, lifetime, and precipitation susceptibility. However, the connection between aerosols and cloud droplets is nonlinear, due to various factors and processes. The impact of aerosols on cloud properties is thought to be strongest with low aerosol loadings, whereas it saturates with high aerosol loadings. To gain understanding of the processes that govern low cloud water properties in order to increase accuracy of climate models and predictions of future changes in the climate system is thus of great importance. In this study, global Terra MODIS L3 data sets are used to identify at what aerosol loadings cloud droplet size shows the greatest sensitivity to changes in aerosol loading in marine boundary layer clouds. MODIS observations are binned in classes of aerosol loading to identify at what loading aerosol impact on cloud droplets is the strongest and at which loading it saturates. Results are connected to ERA-Interim and MACC data sets to identify connections of detected patterns to meteorology and aerosol species.

  5. Giant Molecular Cloud Formation in Disk Galaxies: Characterizing Simulated versus Observed Cloud Catalogues

    CERN Document Server

    Benincasa, Samantha M; Pudritz, Ralph E; Wadsley, James

    2013-01-01

    We present the results of a study of simulated Giant Molecular Clouds (GMCs) formed in a Milky Way-type galactic disk with a flat rotation curve. This simulation, which does not include star formation or feedback, produces clouds with masses ranging between 10^4 Msun and 10^7 Msun. We compare our simulated cloud population to two observational surveys; The Boston University- Five College Radio Astronomy Observatory Galactic Ring Survey and the BIMA All-Disk Survey of M33. An analysis of the global cloud properties as well as a comparison of Larson's scaling relations is carried out. We find that simulated cloud properties agree well with the observed cloud properties, with the closest agreement occurring between the clouds at comparable resolution in M33. Our clouds are highly filamentary - a property that derives both from their formation due to gravitational instability in the sheared galactic environment, as well as to cloud- cloud gravitational encounters. We also find that the rate at which potentially s...

  6. Observational evidence for cloud cover enhancement over western European forests

    Science.gov (United States)

    Teuling, Adriaan J.; Taylor, Christopher M.; Meirink, Jan Fokke; Melsen, Lieke A.; Miralles, Diego G.; van Heerwaarden, Chiel C.; Vautard, Robert; Stegehuis, Annemiek I.; Nabuurs, Gert-Jan; de Arellano, Jordi Vilà-Guerau

    2017-01-01

    Forests impact regional hydrology and climate directly by regulating water and heat fluxes. Indirect effects through cloud formation and precipitation can be important in facilitating continental-scale moisture recycling but are poorly understood at regional scales. In particular, the impact of temperate forest on clouds is largely unknown. Here we provide observational evidence for a strong increase in cloud cover over large forest regions in western Europe based on analysis of 10 years of 15 min resolution data from geostationary satellites. In addition, we show that widespread windthrow by cyclone Klaus in the Landes forest led to a significant decrease in local cloud cover in subsequent years. Strong cloud development along the downwind edges of larger forest areas are consistent with a forest-breeze mesoscale circulation. Our results highlight the need to include impacts on cloud formation when evaluating the water and climate services of temperate forests, in particular around densely populated areas.

  7. Global CALIPSO Observations of Aerosol Changes Near Clouds

    Science.gov (United States)

    Varnai, Tamas; Marshak, Alexander

    2011-01-01

    Several recent studies have found that clouds are surrounded by a transition zone of rapidly changing aerosol optical properties and particle size. Characterizing this transition zone is important for better understanding aerosol-cloud interactions and aerosol radiative effects, and also for improving satellite retrievals of aerosol properties. This letter presents a statistical analysis of a monthlong global data set of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar observations over oceans. The results show that the transition zone is ubiquitous over all oceans and extends up to 15 km away from clouds. They also show that near-cloud enhancements in backscatter and particle size are strongest at low altitudes, slightly below the top of the nearest clouds. Also, the enhancements are similar near illuminated and shadowy cloud sides, which confirms that the asymmetry of Moderate Resolution Imaging Spectroradiometer reflectances found in an earlier study comes from 3-D radiative processes and not from differences in aerosol properties. Finally, the effects of CALIPSO aerosol detection and cloud identification uncertainties are discussed. The findings underline the importance of accounting for the transition zone to avoid potential biases in studies of satellite aerosol products, aerosol-cloud interactions, and aerosol direct radiative effects.

  8. Modeling and Extended State Observer Based Dynamic Surface Control for Cold Rolling Mill System

    Directory of Open Access Journals (Sweden)

    Xu Li

    2016-01-01

    Full Text Available The modeling and control problems are investigated for cold rolling mill system. Firstly, we establish a monitor automatic gauge control (MAGC model for a practical cold rolling mill system. The new model is with mismatched uncertainties. Then, an extended state observer (ESO is developed to estimate uncertainties. In the general high-order systems, the ESO is also used to estimate states. By dynamic surface control method, we design the controller to guarantee stabilization of the cold rolling mill system. Furthermore, we extend proposed method to general high-order systems, in which we analyze the difference from cold rolling mill system. Finally, simulation results for MAGC system are presented to demonstrate the effectiveness of the proposed control strategy.

  9. Design of Fault Diagnosis Observer for HAGC System on Strip Rolling Mill

    Institute of Scientific and Technical Information of China (English)

    DONG Min; LIU Cai

    2006-01-01

    By building mathematical model for HAGC (hydraulic automation gauge control) system of strip rolling mill, treating faults as unknown inputs induced by model uncertainty, and analyzing fault direction, an unknown input fault diagnosis observer group was designed. Fault detection and isolation were realized through making observer residuals robust to specific faults but sensitive to other faults. Sufficient existence conditions and design of the observers were given in detail. Diagnosis observer parameters for servo valve, cylinder, roller and body rolling mill were obtained respectively. The effectiveness of this diagnosis method was proved by actual data simulations.

  10. A cosmic ray-climate link and cloud observations

    Directory of Open Access Journals (Sweden)

    Dunne Eimear M.

    2012-11-01

    Full Text Available Despite over 35 years of constant satellite-based measurements of cloud, reliable evidence of a long-hypothesized link between changes in solar activity and Earth’s cloud cover remains elusive. This work examines evidence of a cosmic ray cloud link from a range of sources, including satellite-based cloud measurements and long-term ground-based climatological measurements. The satellite-based studies can be divided into two categories: (1 monthly to decadal timescale analysis and (2 daily timescale epoch-superpositional (composite analysis. The latter analyses frequently focus on sudden high-magnitude reductions in the cosmic ray flux known as Forbush decrease events. At present, two long-term independent global satellite cloud datasets are available (ISCCP and MODIS. Although the differences between them are considerable, neither shows evidence of a solar-cloud link at either long or short timescales. Furthermore, reports of observed correlations between solar activity and cloud over the 1983–1995 period are attributed to the chance agreement between solar changes and artificially induced cloud trends. It is possible that the satellite cloud datasets and analysis methods may simply be too insensitive to detect a small solar signal. Evidence from ground-based studies suggests that some weak but statistically significant cosmic ray-cloud relationships may exist at regional scales, involving mechanisms related to the global electric circuit. However, a poor understanding of these mechanisms and their effects on cloud makes the net impacts of such links uncertain. Regardless of this, it is clear that there is no robust evidence of a widespread link between the cosmic ray flux and clouds.

  11. Vertical Structures of Anvil Clouds of Tropical Mesoscale Convective Systems Observed by CloudSat

    Science.gov (United States)

    Yuan, J.; Houze, R. A., Jr.; Heymsfield, A.

    2011-01-01

    A global study of the vertical structures of the clouds of tropical mesoscale convective systems (MCSs) has been carried out with data from the CloudSat Cloud Profiling Radar. Tropical MCSs are found to be dominated by cloud-top heights greater than 10 km. Secondary cloud layers sometimes occur in MCSs, but outside their primary raining cores. The secondary layers have tops at 6--8 and 1--3 km. High-topped clouds extend outward from raining cores of MCSs to form anvil clouds. Closest to the raining cores, the anvils tend to have broader distributions of reflectivity at all levels, with the modal values at higher reflectivity in their lower levels. Portions of anvil clouds far away from the raining core are thin and have narrow frequency distributions of reflectivity at all levels with overall weaker values. This difference likely reflects ice particle fallout and therefore cloud age. Reflectivity histograms of MCS anvil clouds vary little across the tropics, except that (i) in continental MCS anvils, broader distributions of reflectivity occur at the uppermost levels in the portions closest to active raining areas; (ii) the frequency of occurrence of stronger reflectivity in the upper part of anvils decreases faster with increasing distance in continental MCSs; and (iii) narrower-peaked ridges are prominent in reflectivity histograms of thick anvil clouds close to the raining areas of connected MCSs (superclusters). These global results are consistent with observations at ground sites and aircraft data. They present a comprehensive test dataset for models aiming to simulate process-based upper-level cloud structure around the tropics.

  12. Benchmark Comparison of Cloud Analytics Methods Applied to Earth Observations

    Science.gov (United States)

    Lynnes, Chris; Little, Mike; Huang, Thomas; Jacob, Joseph; Yang, Phil; Kuo, Kwo-Sen

    2016-01-01

    Cloud computing has the potential to bring high performance computing capabilities to the average science researcher. However, in order to take full advantage of cloud capabilities, the science data used in the analysis must often be reorganized. This typically involves sharding the data across multiple nodes to enable relatively fine-grained parallelism. This can be either via cloud-based file systems or cloud-enabled databases such as Cassandra, Rasdaman or SciDB. Since storing an extra copy of data leads to increased cost and data management complexity, NASA is interested in determining the benefits and costs of various cloud analytics methods for real Earth Observation cases. Accordingly, NASA's Earth Science Technology Office and Earth Science Data and Information Systems project have teamed with cloud analytics practitioners to run a benchmark comparison on cloud analytics methods using the same input data and analysis algorithms. We have particularly looked at analysis algorithms that work over long time series, because these are particularly intractable for many Earth Observation datasets which typically store data with one or just a few time steps per file. This post will present side-by-side cost and performance results for several common Earth observation analysis operations.

  13. MODIS Observations of Enhanced Clear Sky Reflectance Near Clouds

    Science.gov (United States)

    Varnai, Tamas; Marshak, Alexander

    2009-01-01

    Several recent studies have found that the brightness of clear sky systematically increases near clouds. Understanding this increase is important both for a correct interpretation of observations and for improving our knowledge of aerosol-cloud interactions. However, while the studies suggested several processes to explain the increase, the significance of each process is yet to be determined. This study examines one of the suggested processes three-dimensional (3-D) radiative interactions between clouds and their surroundings by analyzing a large dataset of MODIS (Moderate Resolution Imaging Spectroradiometer) observations over the Northeast Atlantic Ocean. The results indicate that 3-D effects are responsible for a large portion of the observed increase, which extends to about 15 km away from clouds and is stronger (i) at shorter wavelengths (ii) near optically thicker clouds and (iii) near illuminated cloud sides. This implies that it is important to account for 3-D radiative effects in the interpretation of solar reflectance measurements over clear regions in the vicinity of clouds.

  14. Benchmark Comparison of Cloud Analytics Methods Applied to Earth Observations

    Science.gov (United States)

    Lynnes, C.; Little, M. M.; Huang, T.; Jacob, J. C.; Yang, C. P.; Kuo, K. S.

    2016-12-01

    Cloud computing has the potential to bring high performance computing capabilities to the average science researcher. However, in order to take full advantage of cloud capabilities, the science data used in the analysis must often be reorganized. This typically involves sharding the data across multiple nodes to enable relatively fine-grained parallelism. This can be either via cloud-based filesystems or cloud-enabled databases such as Cassandra, Rasdaman or SciDB. Since storing an extra copy of data leads to increased cost and data management complexity, NASA is interested in determining the benefits and costs of various cloud analytics methods for real Earth Observation cases. Accordingly, NASA's Earth Science Technology Office and Earth Science Data and Information Systems project have teamed with cloud analytics practitioners to run a benchmark comparison on cloud analytics methods using the same input data and analysis algorithms. We have particularly looked at analysis algorithms that work over long time series, because these are particularly intractable for many Earth Observation datasets which typically store data with one or just a few time steps per file. This post will present side-by-side cost and performance results for several common Earth observation analysis operations.

  15. Observations of ejecta clouds produced by impacts onto Saturn's rings.

    Science.gov (United States)

    Tiscareno, Matthew S; Mitchell, Colin J; Murray, Carl D; Di Nino, Daiana; Hedman, Matthew M; Schmidt, Jürgen; Burns, Joseph A; Cuzzi, Jeffrey N; Porco, Carolyn C; Beurle, Kevin; Evans, Michael W

    2013-04-26

    We report observations of dusty clouds in Saturn's rings, which we interpret as resulting from impacts onto the rings that occurred between 1 and 50 hours before the clouds were observed. The largest of these clouds was observed twice; its brightness and cant angle evolved in a manner consistent with this hypothesis. Several arguments suggest that these clouds cannot be due to the primary impact of one solid meteoroid onto the rings, but rather are due to the impact of a compact stream of Saturn-orbiting material derived from previous breakup of a meteoroid. The responsible interplanetary meteoroids were initially between 1 centimeter and several meters in size, and their influx rate is consistent with the sparse prior knowledge of smaller meteoroids in the outer solar system.

  16. Global surface-based cloud observation for ISCCP

    Science.gov (United States)

    1994-01-01

    Visual observations of cloud cover are hindered at night due to inadequate illumination of the clouds. This usually leads to an underestimation of the average cloud cover at night, especially for the amounts of middle and high clouds, in climatologies on surface observations. The diurnal cycles of cloud amounts, if based on all the surface observations, are therefore in error, but they can be obtained more accurately if the nighttime observations are screened to select those made under sufficient moonlight. Ten years of nighttime weather observations from the northern hemisphere in December were classified according to the illuminance of moonlight or twilight on the cloud tops, and a threshold level of illuminance was determined, above which the clouds are apparently detected adequately. This threshold corresponds to light from a full moon at an elevation angle of 6 degrees or from a partial moon at higher elevation, or twilight from the sun less than 9 degrees below the horizon. It permits the use of about 38% of the observations made with the sun below the horizon. The computed diurnal cycles of total cloud cover are altered considerably when this moonlight criterion is imposed. Maximum cloud cover over much of the ocean is now found to be at night or in the morning, whereas computations obtained without benefit of the moonlight criterion, as in our published atlases, showed the time of maximum to be noon or early afternoon in many regions. Cloud cover is greater at night than during the day over the open oceans far from the continents, particularly in summer. However, near noon maxima are still evident in the coastal regions, so that the global annual average oceanic cloud cover is still slightly greater during the day than at night, by 0.3%. Over land, where daytime maxima are still obtained but with reduced amplitude, average cloud cover is 3.3% greater during the daytime. The diurnal cycles of total cloud cover we obtain are compared with those of ISCCP for a

  17. Multiple Satellite Observations of Cloud Cover in Extratropical Cyclones

    Science.gov (United States)

    Naud, Catherine M.; Booth, James F.; Posselt, Derek J.; van den Heever, Susan C.

    2013-01-01

    Using cloud observations from NASA Moderate Resolution Imaging Spectroradiometer, Multiangle Imaging Spectroradiometer, and CloudSat-CALIPSO, composites of cloud fraction in southern and northern hemisphere extratropical cyclones are obtained for cold and warm seasons between 2006 and 2010, to assess differences between these three data sets, and between summer and winter cyclones. In both hemispheres and seasons, over the open ocean, the cyclone-centered cloud fraction composites agree within 5% across the three data sets, but behind the cold fronts, or over sea ice and land, the differences are much larger. To supplement the data set comparison and learn more about the cyclones, we also examine the differences in cloud fraction between cold and warm season for each data set. The difference in cloud fraction between cold and warm season southern hemisphere cyclones is small for all three data sets, but of the same order of magnitude as the differences between the data sets. The cold-warm season contrast in northern hemisphere cyclone cloud fractions is similar for all three data sets: in the warm sector, the cold season cloud fractions are lower close to the low, but larger on the equator edge than their warm season counterparts. This seasonal contrast in cloud fraction within the cyclones warm sector seems to be related to the seasonal differences in moisture flux within the cyclones. Our analysis suggests that the three different data sets can all be used confidently when studying the warm sector and warm frontal zone of extratropical cyclones but caution should be exerted when studying clouds in the cold sector.

  18. Meteorological observations in support of a hill cap cloud experiment

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, Morten

    1998-06-01

    Humid air flows form a hill cap cloud over the Agana mountain ridge in the north-east of Tenerife. The HILLCLOUD project utilised this cloud formation to investigate the chemical and physical properties of cloud aerosols by land based observations. The project was part of the second Aerosol characterisation Experiment (ACE-2) of the International Global Atmospheric chemistry project (IGAC). The present report describes meteorological observations in support of the hill cap cloud experiment. Time-series of wind speed, wind direction, temperature and humidity were collected at ground-based meteorological stations during a period starting one year in advance of the main campaign. A series of radiosonde detecting the upstream stability and wind profile were launched during the main campaign. (au) 5 tabs., 32 ills., 6 refs.

  19. LACROS: the Leipzig Aerosol and Cloud Remote Observations System

    Science.gov (United States)

    Bühl, Johannes; Seifert, Patric; Wandinger, Ulla; Baars, Holger; Kanitz, Thomas; Schmidt, Jörg; Myagkov, Alexander; Engelmann, Ronny; Skupin, Annett; Heese, Birgit; Klepel, André; Althausen, Dietrich; Ansmann, Albert

    2013-10-01

    The study of interactions between aerosol particles, atmospheric dynamics and clouds and their resulting corresponding indirect effects on precipitation and radiative transfer demand new measurement strategies combining the strength of lidar, radar, and in-situ instrumentation. To match this challenge the Leipzig Aerosol and Cloud Remote Observations System (LACROS) has been set up at TROPOS, combining the strengths of a unique set of active and passive remote sensing and in-situ measurement systems.

  20. Linking numerical simulations of molecular cloud structure with observations.

    Science.gov (United States)

    Kainulainen, Jouni

    2015-08-01

    Understanding the physical processes that control the life-cycle of the cold interstellar medium (ISM) is one of the key themes in the astrophysics of galaxies today. This importance derives from the role of the cold ISM as the birthplace of new stars, and consequently, as an indivisible constituent of galaxy evolution. In the current paradigm of turbulence-regulated ISM, star formation is controlled by the internal structure of individual molecular clouds, which in turn is set by a complex interplay of turbulence, gravity, and magnetic fields in the clouds. It is in the very focus of the field to determine how these processes give rise to the observed structure of molecular clouds. In this talk, I will review our current efforts to confront this paradigm with the goal of observationally constraining how different processes regulate molecular cloud structure and star formation. At the heart of these efforts lies the use of numerical simulations of gravo-turbulent media to A) define physically meaningful characteristics that are sensitive to the different cloud-shaping processes, and B) determine if and how such characteristics can be recovered by observations. I will show in my talk how this approach has recently led to new constraints for some fundamental measures of the molecular cloud structure. Such constraints allow us to assess the roles of turbulence and gravity in controlling the ISM structure and star formation. I will also highlight specific recent results, focusing on the nature of filamentary structures within molecular clouds. These results may provide a novel set of observational constraints with which to challenge the turbulence-regulated ISM paradigm. Finally, I will discuss the current challenges and open questions in understanding the link between molecular cloud structure and star formation, and speculate on key directions to aim the near-future studies.

  1. HST/WFC3 Observations of Uranus' 2014 Storm Clouds

    Science.gov (United States)

    Irwin, Patrick Gerard Joseph; Simon, Amy A.; Wong, Michael H.; Orton, Glenn S.; Toledo, Daniel

    2016-10-01

    In November 2014 Uranus was observed with the Wide Field Camera 3 (WFC3) instrument of the Hubble Space Telescope as part of the Hubble 2020: Outer Planet Atmospheres Legacy program, OPAL. OPAL annually maps Jupiter, Uranus and Neptune (and also Saturn from 2018) in several visible/near-IR wavelength filters. The Uranus 2014 OPAL observations were made on the 8 – 9th November at a time when a huge convective storm system, first observed by amateur astronomers, was present at 30 – 40°N. The entire visible atmosphere, including the storm system, was imaged in seven filters spanning 467 – 924 nm, capturing variations in the coloration of Uranus' clouds and also vertical distribution due to wavelength dependent changes in Rayleigh scattering and methane absorption. Here we analyse these new HST observations with the NEMESIS radiative-transfer and retrieval code, in multiple-scattering mode, to determine the vertical cloud structure in and around the convective storm cloud system.The same storm system was also observed in the H-band (1.4 – 1.9 µm) with the SINFONI Integral Field Unit Spectrometer on the Very Large Telescope (VLT) on 31st October and 11th November (Irwin et al., 2016, 10.1016/j.icarus.2015.09.010). To constrain better the cloud particle sizes and scattering properties over a wide wavelength range we also conducted a limb-darkening analysis of the background cloud structure in the 30 – 40°N latitude band by simultaneously fitting: a) these HST/OPAL observations at a range of zenith angles; b) the VLT/SINFONI observations at a range of zenith angles; and c) IRTF/SpeX observations of this latitude band made in 2009 at a single zenith angle of 23°, spanning the wavelength range 0.8 – 1.8 µm (Irwin et al., 2015, 10.1016/j.icarus.2014.12.020).We find that the HST observations and the combined HST/VLT/IRTF observations are well modeled with a three-component cloud comprised of: 1) a thin 'deep' cloud at a pressure of ~2 bars; 2) a methane

  2. WESTERBORK OBSERVATIONS OF HIGH-VELOCITY CLOUDS - THE DATA

    NARCIS (Netherlands)

    WAKKER, BP

    1991-01-01

    The results of Westerbork * observations of small-scale structure in high-velocity clouds (HVCs) at 1' angular and 1 km s-1 velocity resolution are presented in the form of a table of observational parameters, maps of hydrogen column density, velocity-right ascension cuts, and histograms of the line

  3. WESTERBORK OBSERVATIONS OF HIGH-VELOCITY CLOUDS - DISCUSSION

    NARCIS (Netherlands)

    WAKKER, BP; SCHWARZ, UJ

    1991-01-01

    Six high-velocity cloud fields were observed with 1' and 1 km s-1 resolution, using the Westerbork Synthesis Radio Telescope. The structures seen in earlier observations at 10' resolution break up into a disorderly collection of concentrations. The presence of much substructure has important implica

  4. Validation of Satellite-Based Objective Overshooting Cloud-Top Detection Methods Using CloudSat Cloud Profiling Radar Observations

    Science.gov (United States)

    Bedka, Kristopher M.; Dworak, Richard; Brunner, Jason; Feltz, Wayne

    2012-01-01

    Two satellite infrared-based overshooting convective cloud-top (OT) detection methods have recently been described in the literature: 1) the 11-mm infrared window channel texture (IRW texture) method, which uses IRW channel brightness temperature (BT) spatial gradients and thresholds, and 2) the water vapor minus IRW BT difference (WV-IRW BTD). While both methods show good performance in published case study examples, it is important to quantitatively validate these methods relative to overshooting top events across the globe. Unfortunately, no overshooting top database currently exists that could be used in such study. This study examines National Aeronautics and Space Administration CloudSat Cloud Profiling Radar data to develop an OT detection validation database that is used to evaluate the IRW-texture and WV-IRW BTD OT detection methods. CloudSat data were manually examined over a 1.5-yr period to identify cases in which the cloud top penetrates above the tropopause height defined by a numerical weather prediction model and the surrounding cirrus anvil cloud top, producing 111 confirmed overshooting top events. When applied to Moderate Resolution Imaging Spectroradiometer (MODIS)-based Geostationary Operational Environmental Satellite-R Series (GOES-R) Advanced Baseline Imager proxy data, the IRW-texture (WV-IRW BTD) method offered a 76% (96%) probability of OT detection (POD) and 16% (81%) false-alarm ratio. Case study examples show that WV-IRW BTD.0 K identifies much of the deep convective cloud top, while the IRW-texture method focuses only on regions with a spatial scale near that of commonly observed OTs. The POD decreases by 20% when IRW-texture is applied to current geostationary imager data, highlighting the importance of imager spatial resolution for observing and detecting OT regions.

  5. Correlation between atmospheric electric fields and cloud cover using a field mill and cloud observation data

    Science.gov (United States)

    Nakamori, Kota; Suzuki, Yasuki; Ohya, Hiroyo; Takano, Toshiaki; Kawamura, Yohei; Nakata, Hiroyuki; Yamashita, Kozo

    2017-04-01

    It is known that lightning and precipitations of rain droplets generated from thunderclouds are a generator of global atmospheric electric circuit. In the fair weather, the atmospheric electric fields (AEF) are downward (positive), while they are upward (negative) during lightning and precipitations. However, the correlations between the AEF, and the cloud parameters such as cloud cover, weather phenomenon, have been not revealed quantitatively yet. In this study, we investigate the correlations between the AEF and the cloud parameters, weather phenomenon using a field mill, the 95 GHz-FALCON (FMCW Radar for Cloud Observations)-I and all-sky camera observations. In this study, we installed a Boltek field mill on the roof of our building in Chiba University, Japan, (Geographic coordinate: 35.63 degree N, 140.10 degree E, the sea level: 55 m) on the first June, 2016. The sampling time of the AEF is 0.5 s. On the other hand, the FALCON-I has observed the cloud parameters far from about 76 m of the field mill throughout 24 hours every day. The vertical cloud profiles and the Doppler velocity of cloud particles can be derived by the FALCON-I with high distance resolutions (48.8 m) (Takano et al., 2010). In addition, the images of the clouds and precipitations are recorded with 30-s sampling by an all-sky camera using a CCD camera on the same roof during 05:00-22:00 LT every day. The distance between the field mill and the all-sky camera is 3.75 m. During 08:30 UT - 10:30 UT, on 4 July, 2016, we found the variation of the AEF due to the approach of thundercloud. The variation consisted of two patterns. One was slow variation due to the movement of thunderclouds, and the other was rapid variation associated with lightning discharges. As for the movement of thunderclouds, the AEF increased when the anvil was located over the field mill, which was opposite direction of the previous studies. This change might be due to the positive charges in the upper anvil more than 14 km

  6. Carbon chemistry in dense molecular clouds: Theory and observational constraints

    Science.gov (United States)

    Blake, Geoffrey A.

    1990-01-01

    For the most part, gas phase models of the chemistry of dense molecular clouds predict the abundances of simple species rather well. However, for larger molecules and even for small systems rich in carbon these models often fail spectacularly. Researchers present a brief review of the basic assumptions and results of large scale modeling of the carbon chemistry in dense molecular clouds. Particular attention is to the influence of the gas phase C/O ratio in molecular clouds, and the likely role grains play in maintaining this ratio as clouds evolve from initially diffuse objects to denser cores with associated stellar and planetary formation. Recent spectral line surveys at centimeter and millimeter wavelengths along with selected observations in the submillimeter have now produced an accurate inventory of the gas phase carbon budget in several different types of molecular clouds, though gaps in our knowledge clearly remain. The constraints these observations place on theoretical models of interstellar chemistry can be used to gain insights into why the models fail, and show also which neglected processes must be included in more complete analyses. Looking toward the future, larger molecules are especially difficult to study both experimentally and theoretically in such dense, cold regions, and some new methods are therefore outlined which may ultimately push the detectability of small carbon chains and rings to much heavier species.

  7. Evolution in Cloud Population Statistics of the MJO: From AMIE Field Observations to Global-Cloud Permitting Models Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Kollias, Pavlos [McGill Univ., Montreal, QC (Canada). Atmospheric and Oceanic Sciences Dept.

    2017-02-09

    This is a multi-institutional, collaborative project using a three-tier modeling approach to bridge field observations and global cloud-permitting models, with emphases on cloud population structural evolution through various large-scale environments. Our contribution was in data analysis for the generation of high value cloud and precipitation products and derive cloud statistics for model validation. There are two areas in data analysis that we contributed: the development of a synergistic cloud and precipitation cloud classification that identify different cloud (e.g. shallow cumulus, cirrus) and precipitation types (shallow, deep, convective, stratiform) using profiling ARM observations and the development of a quantitative precipitation rate retrieval algorithm using profiling ARM observations. Similar efforts have been developed in the past for precipitation (weather radars), but not for the millimeter-wavelength (cloud) radar deployed at the ARM sites.

  8. Airborne lidar and radiometric observations of PBL- and low clouds

    Science.gov (United States)

    Flamant, P. H.; Valentin, R.; Pelon, J.

    1992-01-01

    Boundary layer- and low altitude clouds over open ocean and continent areas have been studied during several field campaigns since mid-1990 using the French airborne backscatter lidar LEANDRE in conjunction with on-board IR and visible radiometers. LEANDRE is an automatic system, and a modification of the instrumental parameters, when airborne, is computer controlled through an operator keyboard. The vertical range squared lidar signals and instrument status are displayed in real time on two dedicated monitors. The lidar is used either down- or up-looking while the aircraft is flying above or below clouds. A switching of the viewing configuration takes about a minute. The lidar measurements provide a high resolution description of cloud morphology and holes in cloud layers. The flights were conducted during various meteorological conditions on single or multilayer stratocumulus and cumulus decks. Analysis on a single shot basis of cloud top (or bottom) altitude and a plot of the corresponding histogram allows one to determine a probability density function (PDF). The preliminary results show the PDFs for cloud top are not Gaussian and symmetric about the mean value. The skewness varies with atmospheric conditions. An example of results recorded over the Atlantic ocean near Biarritz is displayed, showing: (1) the range squared lidar signals as a function of time (here 100 s corresponds to about 8 km, 60 shots are averaged on horizontal); the Planetary Boundary Layer (PBL) - up to 600 m - is observed at the beginning of the leg as well as on surface returns, giving an indication of the porosity; (2) the cloud top altitude variation between 2.4 to 2.8 km during the 150 to 320 s section; and (3) the corresponding PDF. Similar results are obtained on stratocumulus over land. Single shot measurements can be used also to determine an optical porosity at a small scale as well as a fractional cloudiness at a larger scale. A comparison of cloud top altitude retrieved from

  9. In situ observation of rolling contact fatigue cracks by laminography using ultrabright synchrotron radiation

    Directory of Open Access Journals (Sweden)

    Y. Nakai

    2015-10-01

    Full Text Available In rolling contact fatigue (RCF, cracks usually initiate from inclusions beneath the surface and propagate to the contact surface. In the present study, synchrotron radiation computed laminography (SRCL imaging was performed to observe flaking defects during the RCF of a high-strength steel. Specially fabricated inclusion-rich steel plate specimens were employed in the experiments. For the in situ observation of crack propagation, a compact RCF testing machine was developed, and a 4D analysis scheme was applied to the data obtained by SRCL. RCF tests were carried out near the measurement hatch of the beam line used SRCL to enable the successive observation of crack initiation and growth behaviors. Specimens before and after the occurrence of flaking were observed by SRCL, and flaking defects and cracks under the surface were successfully detected. As a result, details of the crack initiation and flaking process in RCF could be discussed. Shear-type horizontal cracks were found to initiate after the initiation and propagation of tensile-type vertical cracks along inclusions, where the face of the vertical cracks was perpendicular to the rolling direction and rolling surface. Therefore, the formation of vertical cracks is considered to affect shear-type crack formation and flaking, where the shape and length of inclusions also affect the initiation and propagation of vertical cracks.

  10. Westerbork HI observations of two High-Velocity Clouds

    NARCIS (Netherlands)

    Stoppelenburg, PS; Schwarz, UJ; van Woerden, H

    1998-01-01

    Westerbork HI synthesis observations are presented for the directions of the stars 4 Lac and HD 135485. Interstellar absorption lines at high velocities had been reported in the UV spectrum of 4 Lac, setting an upper limit of 1.2 kpc on the distance of the associated, small HI cloud (Bates et al. 19

  11. LABOCA observations of giant molecular clouds in the south west region of the Small Magellanic Cloud

    CERN Document Server

    Bot, Caroline; Boulanger, Francois; Albrecht, Marcus; Leroy, Adam; Bolatto, Alberto D; Bertoldi, Frank; Gordon, Karl; Engelbracht, Chad; Block, Miwa; Misselt, Karl

    2010-01-01

    The amount of molecular gas is a key for understanding the future star formation in a galaxy. Because H2 is difficult to observe directly in dense and cold clouds, tracers like CO are used. However, at low metallicities especially, CO only traces the shielded interiors of the clouds. mm dust emission can be used as a tracer to unveil the total dense gas masses. The comparison of masses deduced from the continuum SIMBA 1.2 mm emission and virial masses in a sample of giant molecular clouds (GMCs), in the SW region of the Small Magellanic Cloud (SMC), showed a discrepancy that is in need of an explanation. This study aims at better assessing possible uncertainties on the dust emission observed in the sample of GMCs from the SMC and focuses on the densest parts of the GMCs where CO is detected. New observations were obtained with the LABOCA camera on the APEX telescope. All GMCs previously observed in CO are detected and their emission at 870microns is compared to ancillary data. The different contributions to t...

  12. Parameters of Warm Molecular Clouds from Methyl Acetylene Observations

    CERN Document Server

    Alakoz, A V; Promislov, V G; Johansson, L E B; Winnberg, A

    2002-01-01

    The results of a survey of 63 galactic star-forming regions in the 6_K-5_K and 5_K-4_K methyl acetylene lines at 102 and 85 GHz, respectively, are presented. Fourty-three sources were detected at 102 GHz, and twenty-five at 85 GHz. Emission was detected towards molecular clouds with kinetic temperatures 20-60 K (so-called ``warm clouds''). The CH3CCH abundances in these clouds appeared to be about several units X 10^(-9). Five mapped sources were analyzed using the maximum entropy method. The sizes of the mapped clouds fall within the range between 0.1 and 1.7 pc, virial masses - between 90-6200 Msun, and densities - between 6 X 10^4 and 6 X 10^5 cm^(-3). The CH3CCH sources spatially coincide with the CO and CS sources. Chemical evolution simulations showed that the typical methyl acetylene abundance in the observed clouds corresponds to an age of ~ 6 X 10^4 years.

  13. High-Resolution CH Observations of Two Translucent Molecular Clouds

    Science.gov (United States)

    Chastain, Raymond J.; Cotten, David; Magnani, Loris

    2010-01-01

    We present high-resolution (1farcm3 × 1farcm6) observations of the CH 2Π1/2 (F = 1-1) emission line at 3335 MHz in two high-latitude translucent clouds, MBM 3 and 40. At the assumed cloud distances, the angular resolution corresponds to ~0.05 pc, nearly an order of magnitude better than previous studies. Comparisons of the CH emission with previously obtained CO(1-0) data are difficult to interpret: the CO and CH line emission correlates in MBM 40 but not in MBM 3. In both clouds, there is a spatial offset in the peak emission, and perhaps in velocity for MBM 40. The difference in emission characteristics for the two tracers are noticeable in these two nearby clouds because of the high spatial resolution. Since both CH and CO are deemed to be reliable tracers of H2, our results indicate that more care should be taken when using one of these tracers to determine the mass of a nearby molecular cloud.

  14. The First Observed Cloud Echoes and Microphysical Parameter Retrievals by China’s 94-GHz Cloud Radar

    Institute of Scientific and Technical Information of China (English)

    WU Juxiu; WEI Ming; HANG Xin; ZHOU Jie; ZHANG Peichang; LI Nan

    2014-01-01

    By using the cloud echoes fi rst successfully observed by China’s indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows. (1) The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds, and it can reveal the microscopic structure and small-scale changes of clouds. (2) The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar refl ectivity factor is larger (over-10 dBZ). (3) The radar’s sensitivity is comparatively higher because the minimum radar refl ectivity factor is about-35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio (LDR) of stratocumulus (commonly -11 to -14 dBZ; decreases with increasing turbulence). (4) After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle eff ective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar refl ectivity factor.

  15. Quantitative comparisons of satellite observations and cloud models

    Science.gov (United States)

    Wang, Fang

    Microwave radiation interacts directly with precipitating particles and can therefore be used to compare microphysical properties found in models with those found in nature. Lower frequencies (minimization procedures but produce different CWP and RWP. The similarity in Tb can be attributed to comparable Total Water Path (TWP) between the two retrievals while the disagreement in the microphysics is caused by their different degrees of constraint of the cloud/rain ratio by the observations. This situation occurs frequently and takes up 46.9% in the one month 1D-Var retrievals examined. To attain better constrained cloud/rain ratios and improved retrieval quality, this study suggests the implementation of higher microwave frequency channels in the 1D-Var algorithm. Cloud Resolving Models (CRMs) offer an important pathway to interpret satellite observations of microphysical properties of storms. High frequency microwave brightness temperatures (Tbs) respond to precipitating-sized ice particles and can, therefore, be compared with simulated Tbs at the same frequencies. By clustering the Tb vectors at these frequencies, the scene can be classified into distinct microphysical regimes, in other words, cloud types. The properties for each cloud type in the simulated scene are compared to those in the observation scene to identify the discrepancies in microphysics within that cloud type. A convective storm over the Amazon observed by the Tropical Rainfall Measuring Mission (TRMM) is simulated using the Regional Atmospheric Modeling System (RAMS) in a semi-ideal setting, and four regimes are defined within the scene using cluster analysis: the 'clear sky/thin cirrus' cluster, the 'cloudy' cluster, the 'stratiform anvil' cluster and the 'convective' cluster. The relationship between Tb difference of 37 and 85 GHz and Tb at 85 GHz is found to contain important information of microphysical properties such as hydrometeor species and size distributions. Cluster

  16. Dust properties inside molecular clouds from coreshine modeling and observations

    CERN Document Server

    Lefèvre, Charlène; Juvela, Mika; Paladini, Roberta; Lallement, Rosine; Marshall, D J; Andersen, Morten; Bacmann, Aurore; Mcgee, Peregrine M; Montier, Ludovic; Noriega-Crespo, Alberto; Pelkonen, V -M; Ristorcelli, Isabelle; Steinacker, Jürgen

    2014-01-01

    Context. Using observations to deduce dust properties, grain size distribution, and physical conditions in molecular clouds is a highly degenerate problem. Aims. The coreshine phenomenon, a scattering process at 3.6 and 4.5 $\\mu$m that dominates absorption, has revealed its ability to explore the densest parts of clouds. We want to use this effect to constrain the dust parameters. The goal is to investigate to what extent grain growth (at constant dust mass) inside molecular clouds is able to explain the coreshine observations. We aim to find dust models that can explain a sample of Spitzer coreshine data. We also look at the consistency with near-infrared data we obtained for a few clouds. Methods. We selected four regions with a very high occurrence of coreshine cases: Taurus-Perseus, Cepheus, Chameleon and L183/L134. We built a grid of dust models and investigated the key parameters to reproduce the general trend of surface bright- nesses and intensity ratios of both coreshine and near-infrared observation...

  17. Observation and investigation of a dynamic inflection point in current-voltage curves for roll-to-roll processed polymer photovoltaics

    DEFF Research Database (Denmark)

    Medford, Andrew James; Lilliedal, Mathilde Raad

    2010-01-01

    Inflection point behaviour is often observed in the current-voltage (IV) curve of polymer and organic solar cells. This phenomenon is examined in the context of flexible roll-to-roll (R2R) processed polymer solar cells in a large series of devices with a layer structure of: PET-ITO-ZnO-P3HT......:PCBM-PEDOT:PSS-Ag. The devices were manufactured using a combination of slot-die coating and screen printing; they were then encapsulated by lamination using a polymer based barrier material. All manufacturing steps were carried out in ambient air. The freshly prepared devices showed a consistent inflection point in the IV...

  18. Cloud radar deployment for Indian Monsoon observations: Preliminary Results

    Science.gov (United States)

    Chakravarty, K.; Kalapureddy, M.; Pa, M.; Deshpandy, S.; Das, S.; Pandithurai, G.; Prabhakaran, T.; Chandrasekar, C. V.; Goswami, B.

    2013-12-01

    .04290 N, 73.86890 E, 1.35 km AMSL) from a scanning mobile platform since May, 2013. The initial results of the above cloud radar observations on Indian monsoon will be discussed.

  19. Lidar observations of high-altitude aerosol layers (cirrus clouds)

    Science.gov (United States)

    Deleva, Atanaska D.; Grigorov, Ivan V.

    2013-03-01

    Aerosols, clouds and aerosol-cloud interactions are recognized as the key factors influencing the climate. Clouds are the primary modulators of the Earth's radiative budget. This paper focuses on the detection of high-altitude aerosol layers in the troposphere over mid-latitude lidar station in Sofia, Bulgaria. They are situated in the height-region 6 km÷16 km, with thickness in the range 0.2 km÷5 km and have varying optical characteristics. On the basis of the general utilized classification of the Cirrus clouds, high values of the calculated atmospheric backscatter coefficient and Angströmexponent estimation results we conclude that the registered strongly scattered aerosol layers are Cirrus clouds. Lidar measurements are performed with an aerosol lidar, equipped with Nd:YAG laser at wavelengths 532 nm and 1064 nm. Mainly, lidar data are presented in terms of vertical atmospheric backscatter coefficient profiles. We also include 2Dcolormap in height-time coordinates build on the basis of so called range corrected signals. It shows in general changes of the aerosol stratification over the lidar station during the measurement period. We employed HYSPLIT backward trajectories and DREAM forecasts to analyze the lidar profile outlines and characterize the events during which Cirrus cloud samples were observed. So was remarked that most of the results were obtained during Saharan dust long-way transport over the city of Sofia. Reported experimental examples are extracted from regular lidar investigations of the atmosphere within the frame of European project EARLINET.

  20. Spatial characteristics of the tropical cloud systems: comparison between model simulation and satellite observations

    OpenAIRE

    Guang J. Zhang; Zurovac-Jevtic, Dance; Erwin R Boer

    2011-01-01

    A Lagrangian cloud classification algorithm is applied to the cloud fields in the tropical Pacificsimulated by a high-resolution regional atmospheric model. The purpose of this work is toassess the model’s ability to reproduce the observed spatial characteristics of the tropical cloudsystems. The cloud systems are broadly grouped into three categories: deep clouds, mid-levelclouds and low clouds. The deep clouds are further divided into mesoscale convective systemsand non-mesoscale convective...

  1. Satellite observations of cloud regime development: the role of aerosol processes

    OpenAIRE

    E. Gryspeerdt; Stier, P.; D. G. Partridge

    2013-01-01

    Many different interactions between aerosols and clouds have been postulated based on correlations between satellite retrieved aerosol and cloud properties. Previous studies highlighted the importance of meteorological covariability to the observed correlations. In this work, we make use of multiple temporally-spaced satellite retrievals to observe the development of cloud regimes. The observation of cloud regime development allows us to account for the influences of cloud fraction (C...

  2. CSIR NLC mobile lidar observation of cirrus cloud

    CSIR Research Space (South Africa)

    Sivakumar, V

    2011-09-01

    Full Text Available and with less frequent content of super-cooled water. Apart from the cirrus cloud observations, the figure clearly illustrates the temporal evolution of the planetary boundary layer (PBL). At the beginning of the observation, the PBL is observed... at the height range just above 2 km and later it gradually decreased to 1.2 ? 1.5 km during the middle of the observation. Thereafter, a slow increase in the PBL is noted indicating the decrease in atmosphere stability. It is important to note here...

  3. Reduced-order observer-based robust synchronisation control of cold rolling mills with measurement delay

    Science.gov (United States)

    Jiao, Xiaohong; Mei, Zhisong

    2010-10-01

    To improve the quality of strip thickness, synchronisation control is investigated for cold rolling mills driven by dual-cylinder electro-hydraulic servo systems. Realising synchronised control in hydraulic automatic gauge control (HAGC) systems of cold rolling mills has challenges with not only the inherent nonlinearities of hydraulic servo systems and uncertainties of load variation but also measurement delay of strip thickness. Since all states are not measurable in practice, output feedback robust synchronisation control problem should be addressed for uncertain nonlinear systems with output delay. Thus, a reduced-order observer-based robust synchronous controller is presented by employing Lyapunov functional stability theory. The controller designed by incorporating the integral of the position synchronisation error of two pistons into state variables successfully guarantees asymptotic convergence to zero of both tracking errors and synchronisation error simultaneously regardless of the nonlinearities and uncertainties as well as the measurement delay. Simulation results in a model obtained from a real cold strip rolling mill demonstrate the effectiveness of the approach.

  4. Comprehensive Radar Observations of Clouds and Precipitation over the Tibetan Plateau and Preliminary Analysis of Cloud Properties

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    Intensive fi eld experiment is an important approach to obtain microphysical information about clouds and precipitation. From 1 July to 31 August 2014, the third Tibetan Plateau Atmospheric Science Experiment was carried out and comprehensive measurements of water vapor, clouds, and precipitation were conducted at Naqu. The most advanced radars in China, such as Ka-band millimeter-wave cloud radar, Ku-band micro-rain radar, C-band continuous-wave radar and lidar, and microwave radiometer and disdrometer were deployed to observe high spatial-temporal vertical structures of clouds and precipitation. The C-band dual-linear polarization radar was coordinated with the China new generation weather radar to constitute a dual-Doppler radar system for the measurements of three-dimensional wind fi elds within convective precipitations and the structure and evolution of hydrometeors related to precipitation process. Based on the radar measurements in this experiment, the diurnal variations of several important cloud properties were analyzed, including cloud top and base, cloud depth, cloud cover, number of cloud layers, and their vertical structures during summertime over Naqu. The features of refl ectivity, velocity, and depolarization ratio for diff erent types of clouds observed by cloud radar are discussed. The results indicate that the cloud properties were successfully measured by using various radars in this fi eld experiment. During the summertime over Naqu, most of the clouds were located above 6 km and below 4 km above ground level. Statistical analysis shows that total amounts of clouds, the top of high-level clouds, and cloud depth, all demonstrated a distinct diurnal variation. Few clouds formed at 1000 LST (local standard time), whereas large amounts of clouds formed at 2000 LST. Newly formed cumulus and stratus clouds were often found at 3-km height, where there existed signifi cant updrafts. Deep convection reached up to 16.5 km (21 km above the mean sea level

  5. Cloud Computing Test Bed for NASA Earth Observation

    Science.gov (United States)

    Klene, S. A.; Murphy, K. J.; Fertetta, M.; Law, E.; Wilson, B. D.; Hua, H.; Huang, T.

    2014-12-01

    In order to develop a deeper understanding of utilizing cloud computing technologies for using earth observation data processing a test bed was created to ease access to the technology. Users had expressed concerns about accruing large compute bills by accident while they are learning to use the technology. The test bed is to support NASA efforts such as: Developing a Science Data Service platform to handle big earth data for supporting scalable time and space searches, on-the-fly climatologies, data extraction and data transformation such as data re-gridding. Multi-sensor climate data fusion where users can select, merge and cache variables from multiple sensors to compare data over multiple years. Facilitate rapid prototype efforts to provide an infrastructure so that new development efforts do not need to spend time and effort obtaining a platform. Once successful development is done the application could then scale to very large platform on larger or commercial clouds. Goals of the test bed are: To provide a greater understanding of cloud computing so informed choices can be made on future efforts to handle the over 15 Petabytes of NASA earth science data. Provide an environment where a set of science tools can be developed and reused by multiple earth science disciplines. Develop a Platform as a Service (PaaS) capability for general earth science use. This talk will present the lessons learned from building a community cloud for earth science data.

  6. Electron cloud observations at the ISIS Proton Synchrotron

    CERN Document Server

    Pertica, A

    2013-01-01

    The build up of electron clouds inside a particle accelerator vacuum chamber can produce strong transverse and longitudinal beam instabilities which in turn can lead to high levels of beam loss often requiring the accelerator to be run below its design specification. To study the behaviour of electron clouds at the ISIS Proton Synchrotron, a Micro-Channel Plate (MCP) based electron cloud detector has been developed. The detector is based on the Retarding Field Analyser (RFA) design and consists of a retarding grid, which allows energy analysis of the electron signal, and a MCP assembly placed in front of the collector plate. The MCP assembly provides a current gain over the range 300 to 25K, thereby increasing the signal to noise ratio and dynamic range of the measurements. This paper presents the first electron cloud observations at the ISIS Proton Synchrotron. These results are compared against signals from a beam position monitor and a fast beam loss monitor installed at the same location.

  7. An Evaluation of the Observational Capabilities of A Scanning 95-GHz Radar in Studying the 3D Structures of Marine Stratocumulus Clouds

    Science.gov (United States)

    Bowley, Kevin

    Marine stratocumulus clouds play a critical role in Earth's radiative balance primarily due to the role of their high albedo reflecting incoming solar radiation, causing a cooling effect, while weakly reflecting outgoing infrared radiation. Characterization of the 3-Dimensional (3D) structure of these cloud systems over scales of 20-40 km is required to accurately account for the role of cloud inhomogeneity and structure on their shortwave forcing and lifetime, which has important applications for Global Climate Models. For first time, such 3D measurements in clouds were made available from a scanning cloud radar during the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program's Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) field campaign in the Azores Islands. The scanning radar observations were complemented by a suite of zenith-pointing active and passive remote sensors that were deployed to provide a detailed description of marine stratus over a long-term observation period in the ideal marine environment commonly found at the Azores. The scanning cloud radar observations present a shift from a multi-instrument, vertically pointing 'soda-straw' observation technique to a radar-only, 'radar-centric' observation technique. The scanning radar observations were gridded using a nearest-neighbor type scheme devised to take the natural variability of the observed field into account. The ability of the scheme to capture primary cloud properties (cloud fraction, cloud boundaries, drizzle detection) was assessed using measurements from the vertically pointing sensors. Despite the great sensitivity of the scanning cloud radar (-42.5 dBZ at 1 km range), the drop in sensitivity with range resulted in an artificial thinning of clouds with range from the radar. Drizzle-free cloud structures were undetectable beyond 5 km from the radar. Cloud fields containing drizzle were generally detectable to ranges exceeding 10 km from

  8. CALIPSO Observations of Near-Cloud Aerosol Properties as a Function of Cloud Fraction

    Science.gov (United States)

    Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Wood, Robert

    2015-01-01

    This paper uses spaceborne lidar data to study how near-cloud aerosol statistics of attenuated backscatter depend on cloud fraction. The results for a large region around the Azores show that: (1) far-from-cloud aerosol statistics are dominated by samples from scenes with lower cloud fractions, while near-cloud aerosol statistics are dominated by samples from scenes with higher cloud fractions; (2) near-cloud enhancements of attenuated backscatter occur for any cloud fraction but are most pronounced for higher cloud fractions; (3) the difference in the enhancements for different cloud fractions is most significant within 5km from clouds; (4) near-cloud enhancements can be well approximated by logarithmic functions of cloud fraction and distance to clouds. These findings demonstrate that if variability in cloud fraction across the scenes used to composite aerosol statistics are not considered, a sampling artifact will affect these statistics calculated as a function of distance to clouds. For the Azores-region dataset examined here, this artifact occurs mostly within 5 km from clouds, and exaggerates the near-cloud enhancements of lidar backscatter and color ratio by about 30. This shows that for accurate characterization of the changes in aerosol properties with distance to clouds, it is important to account for the impact of changes in cloud fraction.

  9. Discrepancies between Observational Data and Theoretical Forecast in Single Field Slow Roll Inflation

    Science.gov (United States)

    Amorós, Jaume; de Haro, Jaume

    2016-12-01

    The PLANCK collaboration has determined, or greatly constrained, values for the spectral parameters of the CMB radiation, namely the spectral index n s , its running α s , the running of the running β s , using a growing body of measurements of CMB anisotropies by the Planck satellite and other missions. These values do not follow the hierarchy of sizes predicted by single field, slow roll inflationary theory, and are thus difficult to fit for such inflation models. In this work we present first a study of 49 single field, slow roll inflationary potentials in which we assess the likelyhood of these models fitting the spectral parameters to their currently most accurate determination given by the PLANCK collaboration. We check numerically with a MATLAB program the spectral parameters that each model can yield for a very broad, comprehensive list of possible parameter and field values. The comparison of spectral parameter values supported by the models with their determinations by the PLANCK collaboration leads to the conclusion that the data provided by PLANCK2015 TT+lowP and PLANCK2015 TT,TE,EE+lowP taking into account the running of the running disfavours 40 of the 49 models with confidence level at least 92.8 %. Next, we discuss the reliability of the current computations of these spectral parameters. We identify a bias in the method of determination of the spectral parameters by least residue parameter fitting (using MCMC or any other scheme) currently used to reconstruct the power spectrum of scalar perturbations. This bias can explain the observed contradiction between theory and observations. Its removal is computationally costly, but necessary in order to compare the forecasts of single field, slow roll theories with observations.

  10. Discrepancies between Observational Data and Theoretical Forecast in Single Field Slow Roll Inflation

    Science.gov (United States)

    Amorós, Jaume; de Haro, Jaume

    2016-09-01

    The PLANCK collaboration has determined, or greatly constrained, values for the spectral parameters of the CMB radiation, namely the spectral index n s , its running α s , the running of the running β s , using a growing body of measurements of CMB anisotropies by the Planck satellite and other missions. These values do not follow the hierarchy of sizes predicted by single field, slow roll inflationary theory, and are thus difficult to fit for such inflation models. In this work we present first a study of 49 single field, slow roll inflationary potentials in which we assess the likelyhood of these models fitting the spectral parameters to their currently most accurate determination given by the PLANCK collaboration. We check numerically with a MATLAB program the spectral parameters that each model can yield for a very broad, comprehensive list of possible parameter and field values. The comparison of spectral parameter values supported by the models with their determinations by the PLANCK collaboration leads to the conclusion that the data provided by PLANCK2015 TT+lowP and PLANCK2015 TT,TE,EE+lowP taking into account the running of the running disfavours 40 of the 49 models with confidence level at least 92.8 %. Next, we discuss the reliability of the current computations of these spectral parameters. We identify a bias in the method of determination of the spectral parameters by least residue parameter fitting (using MCMC or any other scheme) currently used to reconstruct the power spectrum of scalar perturbations. This bias can explain the observed contradiction between theory and observations. Its removal is computationally costly, but necessary in order to compare the forecasts of single field, slow roll theories with observations.

  11. Giant aerosol observations with cloud radar: methodology and effects

    Science.gov (United States)

    Guma Claramunt, Pilar; Madonna, Fabio; Amodeo, Aldo; Bauer-Pfundstein, Matthias; Papagiannopoulos, Nikolaos; Pappalardo, Gelsomina

    2017-04-01

    Giant aerosol particles can act as Giant Cloud Condensation Nuclei (GCCN), and determine the droplet concentration at the cloud formation, the clouds albedo and lifetime, and the precipitation formation. In addition, depending on their composition, they can also act as IN. It is not yet clear if they can also expedite rain processes. The main techniques used nowadays in measuring aerosols, which are lidar and sun photometer, cannot retrieve aerosol microphysical properties for particles bigger than a few microns, which means that they do not account for giant aerosols. Therefore, the distribution and impact in the atmosphere and climate of these particles is not well known and the aerosol transport models largely underestimate them. Recent studies have demonstrated that cloud radars are able to detect ultragiant volcanic aerosols also at a large distance from the source. In this study, an innovative methodology for the observation of giant aerosols using the millimeter wavelength radar has been developed and applied to 6 years of measurements carried out at CNR-IMAA Atmospheric Observatory (CIAO), in Potenza, South Italy, finding more than 40 giant aerosol events per year and a good agreement with the aerosol climatologic data. Besides, the effects of giant aerosols in the local and regional meteorology have been studied by correlating several atmospheric variables in the time period following the observation of giant particles. The meteorological situation has been assessed through the data classification into cases characterized by different pressure vertical velocities at the upper atmosphere (400 hPa), Giant aerosols are correlated to lower values of the Cloud Optical Depth (COD) in presence of stable or unstable atmospheric conditions while higher values are found for an intermediate stability. The giant aerosols effects on the Liquid Water Path (LWP) are closely linked to those in the Aerosol Optical Thickness (AOD). The highest increases in the LWP occurs

  12. Electron Cloud Observations during LHC Operation with 25 ns Beams

    CERN Document Server

    Li, Kevin; Iadarola, Giovanni; Mether, Lotta; Romano, Annalisa; Rumolo, Giovanni; Schenk, Michael

    2016-01-01

    While during the Run 1 (2010-2012) of the Large Hadron Collider (LHC) most of the integrated luminosity was produced with 50 ns bunch spacing, for the Run 2 start-up (2015) it was decided to move to the nominal bunch spacing of 25 ns. As expected, with this beam configuration strong electron cloud effects were observed in the machine, which had to be mitigated with dedicated 'scrubbing' periods at injection energy. This enabled to start the operation with 25 ns beams at 6.5 TeV, but e-cloud effects continued to pose challenges while gradually increasing the number of circulating bunch trains. This contribution will review the encountered limitations and the mitigation measures that where put in place and will discuss possible strategies for further performance gain.

  13. Ammonia observations of the nearby molecular cloud MBM 12

    CERN Document Server

    Gomes, J F; Pascual, S; Patel, N; Morales, C; Torrelles, J M; Gomez, Jose F.; Trapero, Joaquin; Pascual, Sergio; Patel, Nimesh; Morales, Carmen; Torrelles, Jose M.

    2000-01-01

    We present NH3(1,1) and NH3(2,2) observations of MBM 12, the closest known molecular cloud (65 pc distance), aimed to find evidence for on-going star formation processes. No local temperature (with a T_rot upper limit of 12 K) nor linewidth enhancement is found, which suggests that the area of the cloud we mapped (~ 15' size) is not currently forming stars. Therefore, this close ``starless'' molecular gas region is an ideal laboratory to study the physical conditions preceding new star formation. A radio continuum source was found in Very Large Array archive data, close but outside the NH3 emission. This source is likely to be a background object.

  14. Galactic Edge Clouds I: Molecular Line Observations and Chemical Modelling of Edge Cloud 2

    CERN Document Server

    Ruffle, P M E; Roberts, H; Lubowich, D A; Henkel, C; Pasachoff, J M; Brammer, G

    2007-01-01

    Edge Cloud 2 (EC2) is a molecular cloud, about 35 pc in size, with one of the largest galactocentric distances known to exist in the Milky Way. We present observations of a peak CO emission region in the cloud and use these to determine its physical characteristics. We calculate a gas temperature of 20 K and a density of n(H2) ~ 10^4 cm^-3. Based on our CO maps, we estimate the mass of EC2 at around 10^4 M_sun and continuum observations suggest a dust-to-gas mass ratio as low as 0.001. Chemical models have been developed to reproduce the abundances in EC2 and they indicate that: heavy element abundances may be reduced by a factor of five relative to the solar neighbourhood (similar to dwarf irregular galaxies and damped Lyman alpha systems); very low extinction (Av < 4 mag) due to a very low dust-to-gas ratio; an enhanced cosmic ray ionisation rate; and a higher UV field compared to local interstellar values. The reduced abundances may be attributed to the low level of star formation in this region and are...

  15. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. II: Multi layered cloud

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, H.; McCoy, Renata; Klein, Stephen A.; Xie, Shaocheng; Luo, Yali; Avramov, Alexander; Chen, Mingxuan; Cole, Jason N.; Falk, Michael; Foster, Mike; Del Genio, Anthony D.; Harrington, Jerry Y.; Hoose, Corinna; Khrairoutdinov, Marat; Larson, Vince; Liu, Xiaohong; McFarquhar, Greg; Poellot, M. R.; Von Salzen, Knut; Shipway, Ben; Shupe, Matthew D.; Sud, Yogesh C.; Turner, David D.; Veron, Dana; Walker, Gregory K.; Wang, Zhien; Wolf, Audrey; Xu, Kuan-Man; Yang, Fanglin; Zhang, G.

    2009-05-21

    Results are presented from an intercomparison of single-column and cloud resolving model simulations of a deep, multi-layered, mixed-phase cloud system observed during the ARM Mixed-Phase Arctic Cloud Experiment. This cloud system was associated with strong surface turbulent sensible and latent heat fluxes as cold air flowed over the open Arctic Ocean, combined with a low pressure system that supplied moisture at mid-level. The simulations, performed by 13 single-column and 4 cloud-resolving models, generally overestimate the liquid water path and strongly underestimate the ice water path, although there is a large spread among the models. This finding is in contrast with results for the single-layer, low-level mixed-phase stratocumulus case in Part I of this study, as well as previous studies of shallow mixed-phase Arctic clouds, that showed an underprediction of liquid water path. The overestimate of liquid water path and underestimate of ice water path occur primarily when deeper mixed-phase clouds extending into the mid-troposphere were observed. These results suggest important differences in the ability of models to simulate Arctic mixed-phase clouds that are deep and multi-layered versus shallow and single-layered. In general, the cloud-resolving models and models with a more sophisticated, two-moment treatment of the cloud microphysics produce a somewhat smaller liquid water path that is closer to observations. The cloud-resolving models also tend to produce a larger cloud fraction than the single column models. The liquid water path and especially the cloud fraction have a large impact on the cloud radiative forcing at the surface, which is dominated by the longwave flux for this case.

  16. Coherent dust cloud observed by three Cassini instruments

    CERN Document Server

    Khalisi, Emil

    2015-01-01

    We revisit the evidence for a "dust cloud" observed by the Cassini spacecraft at Saturn in 2006. The simultaneous data of 3 instruments are compared to interpret the signatures of a coherent swarm of dust that could have remained floating near the equatorial plane. The conspicuous pattern, as seen in the dust counters of the Cosmic Dust Analyser (CDA) and in the magnetic field (MAG), clearly repeats on three consecutive revolutions of the spacecraft. The data of the Radio Plasma and Wave Science (RPWS) appear less decisive but do back our conclusions. The results support the idea of a "magnetic bubble" as reported from both Voyager flybys in the early 1980ies. That particular cloud, which we firstly discovered in the CDA data, is estimated to about 1.36 Saturnian radii in size, and probably broadening. Both the bulk of dust particles and the peak of the magnetic depression seem to drift apart, but this can also be an effect of hitting the cloud at different parts during the traverse.

  17. Microphysical Effects of Cloud Seeding in Supercooled Stratiform Clouds Observed from NOAA Satellite

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on the satellite retrieval methodology, the spectral characteristics and cloud microphysical properties were analyzed that included brightness temperatures of Channels 4 and 5, and their brightness temperature difference (BTD), the particle effective radius of seeded cloud track caused by an operational cloud seeding and the microphysical effects of cloud seeding were revealed by the comparisons of their differences inside and outside the seeded track. The cloud track was actually a cloud channel reaching 1.5-km deep and 14-km wide lasting for more than 80 min. The effective radius of ambient clouds was 10-15μm, while that within the cloud track ranged from 15 to 26 μm. The ambient clouds were composed of supercooled droplets, and the composition of the cloud within the seeding track was ice. With respect to the rather stable reflectance of two ambient sides around the track, the visible spectral reflectance in the cloud track varied at least 10%, and reached a maximum of 35%, the reflectance of 3.7 μm in the seeded track relatively decreased at least 10%. As cloud seeding advanced, the width and depth were gradually increased. Simultaneously the cloud top temperature within the track became progressively warmer with respect to the ambient clouds,and the maximum temperature differences reached 4.2 and 3.9℃ at the first seeding position for Channels 4 and 5. In addition, the BTD in the track also increased steadily to a maximum of 1.4℃, compared with 0.2-0.4℃ of the ambient clouds. The evidence that the seeded cloud became thinner comes from the visible image showing a channel, the warming of the cloud tops, and the increase of BTD in the seeded track.The seeded cloud became thinner mainly because the cloud top descended and it lost water to precipitation throughout its depth. For this cloud seeding case, the glaciation became apparent at cloud tops about 22min after seeding. The formation of a cloud track in the supercooled stratiform clouds was

  18. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. I: Single layer cloud

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Stephen A.; McCoy, Renata; Morrison, H.; Ackerman, Andrew; Avramov, Alexander; DeBoer, GIJS; Chen, Mingxuan; Cole, Jason N.; DelGenio, Anthony D.; Falk, Michael; Foster, Mike; Fridlind, Ann; Golaz, Jean-Christophe; Hashino, Tempei; Harrington, Jerry Y.; Hoose, Corinna; Khairoutdinov, Marat; Larson, Vince; Liu, Xiaohong; Luo, Yali; McFarquhar, Greg; Menon, Surabi; Neggers, Roel; Park, Sungsu; Poellot, M. R.; Schmidt, Jerome M.; Sednev, Igor; Shipway, Ben; Shupe, Matthew D.; Spangenberg, D.; Sud, Yogesh; Turner, David D.; Veron, Dana; Von Salzen, Knut; Walker, Gregory K.; Wang, Zhien; Wolf, Audrey; Xie, Shaocheng; Xu, Kuan-Man; Yang, Fanglin; Zhang, G.

    2009-05-21

    Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a cold-air outbreak mixed-phase stratocumulus cloud observed during the ARM Mixed-Phase Arctic Cloud Experiment. The observed cloud occurred in a well-mixed boundary layer with a cloud top temperature of –15°C. While the cloud was water dominated, ice precipitation appears to have lowered the liquid water path to about 2/3 of the adiabatic value. The simulations, which were performed by seventeen single column and nine cloud-resolving models, generally underestimate the liquid water path with the median single-column and cloud-resolving model liquid water path a factor of 3 smaller than observed. While the simulated ice water path is in general agreement with the observed values, results from a sensitivity study in which models removed ice microphysics indicate that in many models the interaction between liquid and ice phase microphysics is responsible for the strong model underestimate of liquid water path. Although no single factor is found to lead to a good simulation, these results emphasize the need for care in the model treatment of mixed-phase microphysics. This case study, which has been well observed from both aircraft and ground-based remote sensors, could be benchmark for model simulations of mixed-phase clouds.

  19. Observations of Cloud Condensation Nuclei in North China

    Institute of Scientific and Technical Information of China (English)

    SHI Lixin; DUAN Ying

    2008-01-01

    Using a DMT (Droplet Measurement Technologies) continuous flow streamwise thermal gradient cloud condensation nuclei (CCN) counter mounted on a Cheyenne ⅢA aircraft, about 20 flights for aircraft mea-surements of CCN over North China were conducted in the autumn of 2005 and spring of 2006. According to the design for aircraft observation, the method of spiral ascent or descent in the troposphere was used for the vertical measurement of CCN, and some certain levels were chosen for horizontal measurement. The vertical distributions of CCN concentrations show that most CCN particles are concentrated in the low level of troposphere and CCN concentration decreased with height increasing. It suggests that the main source of CCN is from the surface. This result is consistent with former studies during 1983-1985 in China with a static thermal gradient CCN counter. The comparison of vertical observations between polluted rural area near Shijiazhuang and non-polluted rural area near Zhangjiakou shows that there is about five times difference in CCN concentration. But over two polluted cities, Shijiazhuang and Handan, there is no notable difference in CCN concentration. The horizontal flight measurements for penetrating the cumulus clouds experiment show the apparent decrease of CCN in clouds. It confirms that cloud has a definite consumptive effect on CCN particles because some CCN particles can form cloud droplets.The surface measurements of CCN in Shijiazhuang City were made during June-August 2005. The eta-tistical CCN data show the great difference in concentration at the same supersaturation (S) in Shijiazhuang summertime. The minimum CCN concentrations were 584, 808, and 2431 cm-3, and the maximum concen-trations were 9495, 16332, and 21812 cm-3 at S=0.1%, 0.3%, and 0.5%, respectively. CCN has a diurnal variation cycle. From 0600 BT, the concentration began to increase and reached the maximum at about noon. Then it generally decreased throughout the afternoon. The

  20. Observational and model evidence for positive low-level cloud feedback.

    Science.gov (United States)

    Clement, Amy C; Burgman, Robert; Norris, Joel R

    2009-07-24

    Feedbacks involving low-level clouds remain a primary cause of uncertainty in global climate model projections. This issue was addressed by examining changes in low-level clouds over the Northeast Pacific in observations and climate models. Decadal fluctuations were identified in multiple, independent cloud data sets, and changes in cloud cover appeared to be linked to changes in both local temperature structure and large-scale circulation. This observational analysis further indicated that clouds act as a positive feedback in this region on decadal time scales. The observed relationships between cloud cover and regional meteorological conditions provide a more complete way of testing the realism of the cloud simulation in current-generation climate models. The only model that passed this test simulated a reduction in cloud cover over much of the Pacific when greenhouse gases were increased, providing modeling evidence for a positive low-level cloud feedback.

  1. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. Part II: Multi-layered cloud

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, H; McCoy, R B; Klein, S A; Xie, S; Luo, Y; Avramov, A; Chen, M; Cole, J; Falk, M; Foster, M; Genio, A D; Harrington, J; Hoose, C; Khairoutdinov, M; Larson, V; Liu, X; McFarquhar, G; Poellot, M; Shipway, B; Shupe, M; Sud, Y; Turner, D; Veron, D; Walker, G; Wang, Z; Wolf, A; Xu, K; Yang, F; Zhang, G

    2008-02-27

    Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a deep, multi-layered, mixed-phase cloud system observed during the ARM Mixed-Phase Arctic Cloud Experiment. This cloud system was associated with strong surface turbulent sensible and latent heat fluxes as cold air flowed over the open Arctic Ocean, combined with a low pressure system that supplied moisture at mid-level. The simulations, performed by 13 single-column and 4 cloud-resolving models, generally overestimate the liquid water path and strongly underestimate the ice water path, although there is a large spread among the models. This finding is in contrast with results for the single-layer, low-level mixed-phase stratocumulus case in Part I of this study, as well as previous studies of shallow mixed-phase Arctic clouds, that showed an underprediction of liquid water path. The overestimate of liquid water path and underestimate of ice water path occur primarily when deeper mixed-phase clouds extending into the mid-troposphere were observed. These results suggest important differences in the ability of models to simulate Arctic mixed-phase clouds that are deep and multi-layered versus shallow and single-layered. In general, models with a more sophisticated, two-moment treatment of the cloud microphysics produce a somewhat smaller liquid water path that is closer to observations. The cloud-resolving models tend to produce a larger cloud fraction than the single-column models. The liquid water path and especially the cloud fraction have a large impact on the cloud radiative forcing at the surface, which is dominated by the longwave flux for this case.

  2. Observation and investigation of a dynamic inflection point in current-voltage curves for roll-to-roll processed polymer photovoltaics

    DEFF Research Database (Denmark)

    Medford, Andrew James; Lilliedal, Mathilde Raad

    2010-01-01

    Inflection point behaviour is often observed in the current-voltage (IV) curve of polymer and organic solar cells. This phenomenon is examined in the context of flexible roll-to-roll (R2R) processed polymer solar cells in a large series of devices with a layer structure of: PET-ITO-ZnO-P3HT...... that the findings are applicable to various other device structures based on semiconducting oxides. The findings may have influences on the possibilities and scale-up of polymer solar technologies.......:PCBM-PEDOT:PSS-Ag. The devices were manufactured using a combination of slot-die coating and screen printing; they were then encapsulated by lamination using a polymer based barrier material. All manufacturing steps were carried out in ambient air. The freshly prepared devices showed a consistent inflection point in the IV...

  3. Dust aerosol impact on the retrieval of cloud top height from satellite observations of CALIPSO, CloudSat and MODIS

    Science.gov (United States)

    Wang, Wencai; Sheng, Lifang; Dong, Xu; Qu, Wenjun; Sun, Jilin; Jin, Hongchun; Logan, Timothy

    2017-02-01

    Dust aerosol effect on the retrievals of dusty cloud top height (DCTH) are analyzed over Northwest China using cloud products from MODerate Resolution Imaging Spectroradiometer (MODIS) on Aqua, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and CloudSat for the Spring season of March-May over the years 2007-2011. An excellent agreement is found between CloudSat and CALIPSO derived DCTHs for all cloud types, suggesting that the effect of dust aerosols plays a small role in DCTHs determination for lidar and radar measurements. However, the presence of dust aerosols greatly affects the retrievals of DCTHs for MODIS compared with pure clouds and the active sensors derived results. The differences of DCTHs retrieving from CloudSat and MODIS range from -2.30 to 6.8 km. Likewise, the differences of DCTHs retrieving from CALIPSO and MODIS range from -2.66 to 6.78 km. In addition, the results show that the differences in DCTHs for active and passive sensors are dependent on cloud type. On the whole, dust aerosols have the largest effect on cloud top heights (CTH) retrieved of nimbostratus (Ns), followed by altocumulus (Ac) and altostratus (As), the last is cirrus (Ci) over Northwest China. Our results also indicate that the accuracy of MODIS-derived retrievals reduces accompanied with a decrease of height.

  4. Satellite observations of cloud regime development: the role of aerosol processes

    OpenAIRE

    E. Gryspeerdt; Stier, P.; D. G. Partridge

    2014-01-01

    Many different interactions between aerosols and clouds have been postulated, based on correlations between satellite retrieved aerosol and cloud properties. Previous studies highlighted the importance of meteorological covariations to the observed correlations. In this work, we make use of multiple temporally-spaced satellite retrievals to observe the development of cloud regimes. The observation of cloud regime development allows us to account for the influences of clo...

  5. Observing simulations: molecular clouds and their journey in the galaxy

    Science.gov (United States)

    Duarte-Cabral, A.; Dobbs, C. L.

    2016-05-01

    In order to have a global picture of the cycle of matter in galaxies, we need to understand the interplay of large-scale galactic phenomena with the formation of giant molecular clouds (GMCs) and, ultimately, their subsequent star formation (SF). In this work, we study the population of GMCs within a smoothed particle hydrodynamics (SPH) simulation of a spiral galaxy, and investigate the link between the GMC properties and position with respect to spiral arms, both directly from the simulation (with the 3D densities of H2 and CO) and from an observer's perspective (with CO emission in PPV space).

  6. QUANTIFYING OBSERVATIONAL PROJECTION EFFECTS USING MOLECULAR CLOUD SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Beaumont, Christopher N. [Institute for Astronomy, University of Hawai' i, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Offner, Stella S.R. [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Shetty, Rahul; Glover, Simon C. O. [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Goodman, Alyssa A., E-mail: beaumont@ifa.hawaii.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States)

    2013-11-10

    The physical properties of molecular clouds are often measured using spectral-line observations, which provide the only probes of the clouds' velocity structure. It is hard, though, to assess whether and to what extent intensity features in position-position-velocity (PPV) space correspond to 'real' density structures in position-position-position (PPP) space. In this paper, we create synthetic molecular cloud spectral-line maps of simulated molecular clouds, and present a new technique for measuring the reality of individual PPV structures. Using a dendrogram algorithm, we identify hierarchical structures in both PPP and PPV space. Our procedure projects density structures identified in PPP space into corresponding intensity structures in PPV space and then measures the geometric overlap of the projected structures with structures identified from the synthetic observation. The fractional overlap between a PPP and PPV structure quantifies how well the synthetic observation recovers information about the three-dimensional structure. Applying this machinery to a set of synthetic observations of CO isotopes, we measure how well spectral-line measurements recover mass, size, velocity dispersion, and virial parameter for a simulated star-forming region. By disabling various steps of our analysis, we investigate how much opacity, chemistry, and gravity affect measurements of physical properties extracted from PPV cubes. For the simulations used here, which offer a decent, but not perfect, match to the properties of a star-forming region like Perseus, our results suggest that superposition induces a ∼40% uncertainty in masses, sizes, and velocity dispersions derived from {sup 13}CO (J = 1-0). As would be expected, superposition and confusion is worst in regions where the filling factor of emitting material is large. The virial parameter is most affected by superposition, such that estimates of the virial parameter derived from PPV and PPP information

  7. VLT Observations of the Gas Cloud G2

    Science.gov (United States)

    Gillessen, Stefan

    2014-01-01

    In 2011, we discovered a small, compact gas cloud G2 that is falling on a near-radial orbit toward the massive black hole in the Galactic Center. The orbit is well-constrained and the pericenter passage will occur in early 2014. Our data beautifully show that G2 gets tidally sheared apart due to the massive black hole's force. We expect that in addition to the tidal effects, hydrodynamics will become important when G2 collides with the hot ambient gas around Sgr A*. This might be a unique opportunity in the next years to observe how gas feeds a massive black hole.

  8. An Observational Study of the Relationship between Cloud, Aerosol and Meteorology in Broken Low-Level Cloud Conditions

    Science.gov (United States)

    Loeb, Norman G.; Schuster, Gregory L.

    2008-01-01

    Global satellite analyses showing strong correlations between aerosol optical depth and 3 cloud cover have stirred much debate recently. While it is tempting to interpret the results as evidence of aerosol enhancement of cloud cover, other factors such as the influence of meteorology on both the aerosol and cloud distributions can also play a role, as both aerosols and clouds depend upon local meteorology. This study uses satellite observations to examine aerosol-cloud relationships for broken low-level cloud regions off the coast of Africa. The analysis approach minimizes the influence of large-scale meteorology by restricting the spatial and temporal domains in which the aerosol and cloud properties are compared. While distributions of several meteorological variables within 5deg 5deg latitude-longitude regions are nearly identical under low and high aerosol optical depth, the corresponding distributions of single-layer low cloud properties and top-of-atmosphere radiative fluxes differ markedly, consistent with earlier studies showing increased cloud cover with aerosol optical depth. Furthermore, fine-mode fraction and Angstrom Exponent are also larger in conditions of higher aerosol optical depth, even though no evidence of systematic latitudinal or longitudinal gradients between the low and high aerosol optical depth populations are observed. When the analysis is repeated for all 5deg 5deg latitude-longitude regions over the global oceans (after removing cases in which significant meteorological differences are found between the low and high aerosol populations), results are qualitatively similar to those off the coast of Africa.

  9. FAME-C: cloud property retrieval using synergistic AATSR and MERIS observations

    Directory of Open Access Journals (Sweden)

    C. K. Carbajal Henken

    2014-05-01

    Full Text Available A newly developed daytime cloud property retrieval algorithm FAME-C (Freie Universität Berlin AATSR MERIS Cloud is presented. Synergistic observations from AATSR and MERIS, both mounted on the polar orbiting satellite ENVISAT, are used for cloud screening. For cloudy pixels two main steps are carried out in a sequential form. First, a micro-physical cloud property retrieval is performed using an AATSR near-infrared and visible channel. Cloud phase, cloud optical thickness, and effective radius are retrieved, and subsequently cloud water path is computed. Second, two independent cloud top height products are retrieved. For cloud top temperature AATSR brightness temperatures are used, while for cloud top pressure the MERIS oxygen-A absorption channel is used. Results from the micro-physical retrieval serve as input for the two cloud top height retrievals. Introduced are the AATSR and MERIS forward models and auxiliary data needed in FAME-C. Also, the optimal estimation method with uncertainty estimates, which also provides for uncertainty estimated of the retrieved property on a pixel-basis, is presented. Within the frame of the ESA Climate Change Initiative project first global cloud property retrievals have been conducted for the years 2007–2009. For this time period verification efforts are presented comparing FAME-C cloud micro-physical properties to MODIS-TERRA derived cloud micro-physical properties for four selected regions on the globe. The results show reasonable accuracies between the cloud micro-physical retrievals. Biases are generally smallest for marine stratocumulus clouds; −0.28, 0.41μm and −0.18 g m−2 for cloud optical thickness, effective radius and cloud water path, respectively. This is also true for the root mean square error. Also, both cloud top height products are compared to cloud top heights derived from ground-based cloud radars located at several ARM sites. FAME-C mostly shows an underestimation of cloud top

  10. Global synthesis of long-term cloud condensation nuclei observations

    Science.gov (United States)

    Schmale, Julia; Henning, Silvia; Stratmann, Frank; Henzing, Bas; Schlag, Patrick; Aalto, Pasi; Keskinen, Helmi; Sellegri, Karine; Ovadnevaite, Jurgita; Krüger, Mira; Jefferson, Anne; Whitehead, James; Carslaw, Ken; Yum, Seong Soo; Kristensson, Adam; Baltensperger, Urs; Gysel, Martin

    2016-04-01

    Cloud condensation nuclei (CCN) are aerosol particles with the ability to activate into droplets at a given super saturation and therefore influence the microphysical and optical properties of clouds. To predict cloud radiative properties understanding the spatial and temporal variability of CCN concentrations in different environments is important. However, currently, the effects of atmospheric particles on changes in cloud radiative forcing are still the largest contribution of uncertainty in climate forcing prediction (IPCC, 2013). Numerous intensive field campaigns have already explored detailed characteristics of CCN in many locations around the world. However, these rather short-term observations can generally not address seasonal or inter-annual variations and a comparison between campaign sites is difficult due to the higher influence of specific environmental circumstances on short-term measurements results. Here, we present results of more long-term CCN and aerosol number concentrations as well as size distribution data covering at least one full year between 2006 and 2014. The 12 locations include ACTRIS stations (http://www.actris.net/) in Europe, and further sites in North America, Brazil and Korea. The sites are located in different environments allowing for temporal and spatial characterization of CCN variability in different atmospheric regimes. Those include marine, remote-continental, boreal forest, rain forest, Arctic and monsoon-influenced environments, as well as boundary layer and free tropospheric conditions. The aerosol populations and their activation behavior show significant differences across the stations. While peak concentrations of CCN are observed in summer at the high altitude sites, in the Arctic the highest concentrations occur during the Haze period in spring. The rural-marine and rural-continental sites exhibit similar CCN concentration characteristics with a relatively flat annual cycle. At some stations, e.g. in the boreal

  11. Towards improved understanding of cloud influence on polar surface energy budgets using CloudSat and CALIPSO observations

    Science.gov (United States)

    Kay, J. E.; L'Ecuyer, T. S.; McIlhattan, E.; Chepfer, H.; Morrison, A.

    2015-12-01

    The spaceborne radar CloudSat and the spaceborne lidar platform Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) have provided nearly a decade of groundbreaking observations of polar cloud and precipitation processes. Specifically relevant to this AGU session, the CloudSat 2B-FLXHR-LIDAR product (hereafter, 2BFLX) is an observationally constrained radiative flux and heating rate calculation that leverages constraints from A-train observations, including CloudSat+CALIPSO. The surface radiative fluxes calculated within 2BFLX represent an important advance because unlike top-of-atmosphere (TOA) fluxes, surface radiative fluxes cannot be directly measured by satellite, yet directly impact surface heating, sea ice melt, and ice sheet mass balance. In this presentation, we will highlight the influence of supercooled liquid on polar surface radiation budgets constrained within 2BFLX data. We will also use 2BFLX data in concert with the fully attenuated signal and cloud phase information from CALIPSO as an observational constraint on polar cloud-climate feedbacks in the Community Earth System Model (CESM).

  12. Evaluating and improving cloud phase in the Community Atmosphere Model version 5 using spaceborne lidar observations

    Science.gov (United States)

    Kay, Jennifer E.; Bourdages, Line; Miller, Nathaniel B.; Morrison, Ariel; Yettella, Vineel; Chepfer, Helene; Eaton, Brian

    2016-04-01

    Spaceborne lidar observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite are used to evaluate cloud amount and cloud phase in the Community Atmosphere Model version 5 (CAM5), the atmospheric component of a widely used state-of-the-art global coupled climate model (Community Earth System Model). By embedding a lidar simulator within CAM5, the idiosyncrasies of spaceborne lidar cloud detection and phase assignment are replicated. As a result, this study makes scale-aware and definition-aware comparisons between model-simulated and observed cloud amount and cloud phase. In the global mean, CAM5 has insufficient liquid cloud and excessive ice cloud when compared to CALIPSO observations. Over the ice-covered Arctic Ocean, CAM5 has insufficient liquid cloud in all seasons. Having important implications for projections of future sea level rise, a liquid cloud deficit contributes to a cold bias of 2-3°C for summer daily maximum near-surface air temperatures at Summit, Greenland. Over the midlatitude storm tracks, CAM5 has excessive ice cloud and insufficient liquid cloud. Storm track cloud phase biases in CAM5 maximize over the Southern Ocean, which also has larger-than-observed seasonal variations in cloud phase. Physical parameter modifications reduce the Southern Ocean cloud phase and shortwave radiation biases in CAM5 and illustrate the power of the CALIPSO observations as an observational constraint. The results also highlight the importance of using a regime-based, as opposed to a geographic-based, model evaluation approach. More generally, the results demonstrate the importance and value of simulator-enabled comparisons of cloud phase in models used for future climate projection.

  13. Spatial and Temporal Distribution of Clouds Observed by MODIS Onboard the Terra and Aqua Satellites

    Science.gov (United States)

    King, Michael D.; Platnick, Steven; Menzel, W. Paul; Ackerman, Steven A.; Hubanks, Paul A.

    2012-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) was developed by NASA and launched aboard the Terra spacecraft on December 18, 1999 and Aqua spacecraft on May 4, 2002. A comprehensive set of remote sensing algorithms for the retrieval of cloud physical and optical properties have enabled over twelve years of continuous observations of cloud properties from Terra and over nine years from Aqua. The archived products from these algorithms include 1 km pixel-level (Level-2) and global gridded Level-3 products. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. Results include the latitudinal distribution of cloud optical and radiative properties for both liquid water and ice clouds, as well as latitudinal distributions of cloud top pressure and cloud top temperature. MODIS finds the cloud fraction, as derived by the cloud mask, is nearly identical during the day and night, with only modest diurnal variation. Globally, the cloud fraction derived by the MODIS cloud mask is approx.67%, with somewhat more clouds over land during the afternoon and less clouds over ocean in the afternoon, with very little difference in global cloud cover between Terra and Aqua. Overall, cloud fraction over land is approx.55%, with a distinctive seasonal cycle, whereas the ocean cloudiness is much higher, around 72%, with much reduced seasonal variation. Cloud top pressure and temperature have distinct spatial and temporal patterns, and clearly reflect our understanding of the global cloud distribution. High clouds are especially prevalent over the northern hemisphere continents between 30 and 50 . Aqua and Terra have comparable zonal cloud top pressures, with Aqua having somewhat higher clouds (cloud top pressures lower by 100 hPa) over land due to

  14. Multiwavelength observations of the M15 intermediate velocity cloud

    CERN Document Server

    Smoker, J V; Keenan, F P; Davies, R D; Pollacco, D L

    2002-01-01

    We present Westerbork Synthesis Radio Telescope HI images, Lovell Telescope multibeam HI wide-field mapping, Wisconsin H-alpha Mapper facility images, William Herschel Telescope longslit echelle CaII observations, and IRAS ISSA 60 and 100 micron coadded images towards the intermediate velocity cloud located in the general direction of the M15 globular cluster. When combined with previously-published Arecibo data, the HI gas in the IVC is found to be clumpy, with peak HI column density of 1.5x10^(20) cm^(-2), inferred volume density (assuming spherical symmetry) of 24 cm^(-3)/(D kpc), and maximum brightness temperature at a resolution of 81x14 arcsec of 14 K. The HI gas in the cloud is warm, with a minimum FWHM value of 5 km/s, corresponding to a kinetic temperature, in the absence of turbulence, of 540 K. There are indications in the HI data of 2-component velocity structure in the IVC, indicative of cloudlets. This velocity structure is also tentatively seen in the CaK spectra, although the SNR is low. The m...

  15. Jets and Outflows From Star to Cloud: Observations Confront Theory

    CERN Document Server

    Frank, A; Cabrit, S; Hartigan, P; Arce, H G; Bacciotti, F; Bally, J; Benisty, M; Eislöffel, J; Güdel, M; Lebedev, S; Nisini, B; Raga, A

    2014-01-01

    In this review we focus on the role jets and outflows play in the star and planet formation process. Our essential question can be posed as follows: are jets/outflows merely an epiphenomenon associated with star formation or do they play an important role in mediating the physics of assembling stars both individually and globally? We address this question by reviewing the current state of observations and their key points of contact with theory. Our review of jet/outflow phenomena is organized into three length-scale domains: Source and Disk Scales ($0.1-10^2$ au) where the connection with protostellar and disk evolution theories is paramount; Envelope Scales ($10^2-10^5$ au) where the chemistry and propagation shed further light on the jet launching process, its variability and its impact on the infalling envelope; Parent Cloud Scales ($10^5-10^6$ au) where global momentum injection into cluster/cloud environments become relevant. Issues of feedback are of particular importance on the smallest scales where p...

  16. Determination of cloud-top height from stereoscopic observation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new and accurate method is presented based on the cloud movement (height and position), the spherical and plane triangular relationships of the spacecraft, the center of the earth, the projected-cloud and the true-cloud for determination of cloud-top height and position. Synthetic stereo images that have spatial resolution of 1.25 km from a single satellite are used to test this method. It is demonstrated that the cloud-top structure can be determined from the stereoscopic measurements of geo-synchronous satellite with vertical accuracy of approximately 500 m. The vertical accuracy can be better with lower orbiters.

  17. Observation of Clouds Using the CSIR Transportable LIDAR: A Case Study over Durban, South Africa

    Directory of Open Access Journals (Sweden)

    Lerato Shikwambana

    2016-01-01

    Full Text Available The Council for Scientific and Industrial Research (CSIR transportable Light Detection And Ranging (LIDAR was used to collect data over Durban (29.9°S, 30.9°E during 20–23 November 2012. Aerosol measurements have been carried out in the past over Durban; however, no cloud measurements using LIDAR have ever been performed. Therefore, this study further motivates the continuation of LIDAR for atmospheric research over Durban. Low level clouds were observed on 20–22 November 2012 and high level clouds were observed on 23 November 2012. The low level cloud could be classified as stratocumulus clouds, whereas the high level clouds could be classified as cirrus clouds. Low level cloud layers showed high extinction coefficients values ranging between 0.0009 and 0.0044 m−1, whereas low extinction coefficients for high level clouds were observed at values ranging between 0.000001 and 0.000002 m−1. Optical depth showed a high variability for 20 and 21 November 2012. This indicates a change in the composition and/or thickness of the cloud. For 22 and 23 November 2012, almost similar values of optical depth were observed. Cloud-Aerosol LIDAR and Infrared Pathfinder Satellite Observations (CALIPSO revealed high level clouds while the CSIR LIDAR could not. However, the two instruments complement each other well to describe the cloudy condition.

  18. Modeling of Protostellar Clouds and their Observational Properties

    CERN Document Server

    Zhilkin, A G; Zamozdra, S N

    2009-01-01

    A physical model and two-dimensional numerical method for computing the evolution and spectra of protostellar clouds are described. The physical model is based on a system of magneto-gasdynamical equations, including ohmic and ambipolar diffusion, and a scheme for calculating the thermal and ionization structure of a cloud. The dust and gas temperatures are determined during the calculations of the thermal structure of the cloud. The results of computing the dynamical and thermal structure of the cloud are used to model the radiative transfer in continuum and in molecular lines. We presented the results for clouds in hydrostatic and thermal equilibrium. The evolution of a rotating magnetic protostellar cloud starting from a quasi-static state is also considered. Spectral maps for optically thick lines of linear molecules are analyzed. We have shown that the influence of the magnetic field and rotation can lead to a redistribution of angular momentum in the cloud and the formation of a characteristic rotationa...

  19. Effect of CALIPSO Cloud Aerosol Discrimination (CAD) Confidence Levels on Observations of Aerosol Properties near Clouds

    Science.gov (United States)

    Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Liu, Zhaoyan

    2012-01-01

    CALIPSO aerosol backscatter enhancement in the transition zone between clouds and clear sky areas is revisited with particular attention to effects of data selection based on the confidence level of cloud-aerosol discrimination (CAD). The results show that backscatter behavior in the transition zone strongly depends on the CAD confidence level. Higher confidence level data has a flatter backscatter far away from clouds and a much sharper increase near clouds (within 4 km), thus a smaller transition zone. For high confidence level data it is shown that the overall backscatter enhancement is more pronounced for small clear-air segments and horizontally larger clouds. The results suggest that data selection based on CAD reduces the possible effects of cloud contamination when studying aerosol properties in the vicinity of clouds.

  20. Estimating seasonal variations in cloud droplet number concentration over the boreal forest from satellite observations

    Directory of Open Access Journals (Sweden)

    R. H. H. Janssen

    2011-08-01

    Full Text Available Seasonal variations in cloud droplet number concentration (NCD in low-level stratiform clouds over the boreal forest are estimated from MODIS observations of cloud optical and microphysical properties, using a sub-adiabatic cloud model to interpret vertical profiles of cloud properties. An uncertainty analysis of the cloud model is included to reveal the main sensitivities of the cloud model. We compared the seasonal cycle in NCD, obtained using 9 yr of satellite data, to surface concentrations of potential cloud activating aerosols, measured at the SMEAR II station at Hyytiälä in Finland. The results show that NCD and cloud condensation nuclei (CCN concentrations have no clear correlation at seasonal time scale. The fraction of aerosols that actually activate as cloud droplet decreases sharply with increasing aerosol concentrations. Furthermore, information on the stability of the atmosphere shows that low NCD is linked to stable atmospheric conditions. Combining these findings leads to the conclusion that cloud droplet activation for the studied clouds over the boreal forest is limited by convection. Our results suggest that it is important to take the strength of convection into account when studying the influence of aerosols from the boreal forest on cloud formation, although they do not rule out the possibility that aerosols from the boreal forest affect other types of clouds with a closer coupling to the surface.

  1. Airborne observations of the microphysical structure of two contrasting cirrus clouds

    Science.gov (United States)

    O'Shea, S. J.; Choularton, T. W.; Lloyd, G.; Crosier, J.; Bower, K. N.; Gallagher, M.; Abel, S. J.; Cotton, R. J.; Brown, P. R. A.; Fugal, J. P.; Schlenczek, O.; Borrmann, S.; Pickering, J. C.

    2016-11-01

    We present detailed airborne in situ measurements of cloud microphysics in two midlatitude cirrus clouds, collected as part of the Cirrus Coupled Cloud-Radiation Experiment. A new habit recognition algorithm for sorting cloud particle images using a neural network is introduced. Both flights observed clouds that were related to frontal systems, but one was actively developing while the other dissipated as it was sampled. The two clouds showed distinct differences in particle number, habit, and size. However, a number of common features were observed in the 2-D stereo data set, including a distinct bimodal size distribution within the higher-temperature regions of the clouds. This may result from a combination of local heterogeneous nucleation and large particles sedimenting from aloft. Both clouds had small ice crystals (developing case the ice concentrations at the lowest temperatures are best explained by homogenous nucleation.

  2. Retrieval of liquid water cloud properties from ground-based remote sensing observations

    NARCIS (Netherlands)

    Knist, C.L.

    2014-01-01

    Accurate ground-based remotely sensed microphysical and optical properties of liquid water clouds are essential references to validate satellite-observed cloud properties and to improve cloud parameterizations in weather and climate models. This requires the evaluation of algorithms for retrieval of

  3. RF radiation observations of positive cloud-to-ground flashes

    Science.gov (United States)

    Shao, X. M.; Rhodes, C. T.; Holden, D. N.

    1999-04-01

    During the summers of 1995 and 1996 we conducted broadband HF-UHF and narrowband VHF radio frequency (RF) observations of positive cloud-to-ground (+CG) flashes at Langmuir and Los Alamos laboratories, New Mexico. These observations indicate that positive leaders to ground produce no or very weak radiation from HF to UHF. The broadband system was able to record 2 ms data each time it was triggered. For a +CG the system was usually triggered by the return stroke, and a 1 ms pretrigger period was coincident with the positive leader process. It was commonly observed that no or little radiation was associated with the leader process in the 1 ms pretrigger period. The narrowband VHF system employed a logarithmic power amplifier and recorded one 1 s data each time it was triggered. The narrowband observations show that strong and often continuous radiation occurs at the beginning of the +CGs, but the radiation usually becomes intermittent and impulsive during the last few tens of milliseconds preceding the return strokes. The observations for most of the +CGs also show complete lack of radiation a few ms before the beginning of the return strokes, suggesting that the ongoing downward positive leaders were quiet at VHF, at least during the final few ms. The results of this study for natural positive leaders are in agreement with the results obtained from laboratory gap discharges and rocket-triggered lightning.

  4. Networked Observation of Precipitating Cloud Systems in Oklahoma

    Science.gov (United States)

    Collis, S. M.; Giangrande, S. E.; Bharadwaj, N.

    2012-12-01

    Radars are inherently limited in their ability to resolve fine structure of cloud systems and completely image a volume of space. Both the radial nature of sampling and the issues of beam width mean that upper level features are often missed or poorly resolved. While constant azimuth scans (RHIs) give amazing insight into the vertical structure they are not capable of sampling full storm structure in within a time commensurate with the evolution of the storm system. This presentation will show results from the ARM multi-scale remote sensing facility in Lamont, Oklahoma where there is a network of three X-Band and a C-Band radar deployed. Taking care in quality control and using a flexible mapping methodology enables the combining of information from multiple sources. We will showcase some sample storm reconstructions highlighting the advantages of using the full capabilities of the observing system.

  5. Analysis of co-located MODIS and CALIPSO observations near clouds

    Directory of Open Access Journals (Sweden)

    T. Várnai

    2012-02-01

    Full Text Available This paper aims at helping synergistic studies in combining data from different satellites for gaining new insights into two critical yet poorly understood aspects of anthropogenic climate change, aerosol-cloud interactions and aerosol radiative effects. In particular, the paper examines the way cloud information from the MODIS (MODerate resolution Imaging Spectroradiometer imager can refine our perceptions based on CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization lidar measurements about the systematic aerosol changes that occur near clouds.

    The statistical analysis of a yearlong dataset of co-located global maritime observations from the Aqua and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation satellites reveals that MODIS's multispectral imaging ability can greatly help the interpretation of CALIOP observations. The results show that imagers on Aqua and CALIPSO yield very similar pictures, and that the discrepancies – due mainly to wind drift and differences in view angle – do not significantly hinder aerosol measurements near clouds. By detecting clouds outside the CALIOP track, MODIS reveals that clouds are usually closer to clear areas than CALIOP data alone would suggest. The paper finds statistical relationships between the distances to clouds in MODIS and CALIOP data, and proposes a rescaling approach to statistically account for the impact of clouds outside the CALIOP track even when MODIS cannot reliably detect low clouds, for example at night or over sea ice. Finally, the results show that the typical distance to clouds depends on both cloud coverage and cloud type, and accordingly varies with location and season. In maritime areas perceived cloud free, the global median distance to clouds below 3 km altitude is in the 4–5 km range.

  6. Total cloud cover from satellite observations and climate models

    Directory of Open Access Journals (Sweden)

    P. Probst

    2010-09-01

    Full Text Available Global and zonal monthly means of cloud cover fraction for total cloudiness (CF from the ISCCP D2 dataset are compared to same quantity produced by the 20th century simulations of 21 climate models from the World Climate Research Programme's (WCRP's Coupled Model Intercomparison Project phase 3 (CMIP3 multi-model dataset archived by the Program for Climate Model Diagnosis and Intercomparison (PCMDI. The comparison spans the time frame from January 1984 to December 1999 and the global and zonal average of CF are studied. The restriction to total cloudiness depends on the output of some models that does not include the 3D cloud structure. It is shown that the global mean of CF for the PCMDI/CMIP3 models, averaged over the whole period, exhibits a considerable variance and generally underestimates the ISCCP value. Very large discrepancies among models, and between models and observations, are found in the polar areas, where both models and satellite observations are less reliable, and especially near Antarctica. For this reason the zonal analysis is focused over the 60° S–60° N latitudinal belt, which includes the tropical area and mid latitudes. The two hemispheres are analyzed separately to show the variation of the amplitude of the seasonal cycle. Most models overestimate the yearly averaged values of CF over all of the analysed areas, while differences emerge in their ability to capture the amplitude of the seasonal cycle. The models represent, in a qualitatively correct way, the magnitude and the weak sign of the seasonal cycle over the whole geographical domain, but overestimate the strength of the signal in the tropical areas and at mid-latitudes, when taken separately. The interannual variability of the two yearly averages and of the amplitude of the seasonal cycle is greatly underestimated by all models in each area analysed. This work shows that the climate models have an heterogeneous behaviour in simulating the CF over

  7. Aerosols, clouds, and precipitation in the North Atlantic trades observed during the Barbados aerosol cloud experiment - Part 1: Distributions and variability

    Science.gov (United States)

    Jung, Eunsil; Albrecht, Bruce A.; Feingold, Graham; Jonsson, Haflidi H.; Chuang, Patrick; Donaher, Shaunna L.

    2016-07-01

    Shallow marine cumulus clouds are by far the most frequently observed cloud type over the Earth's oceans; but they are poorly understood and have not been investigated as extensively as stratocumulus clouds. This study describes and discusses the properties and variations of aerosol, cloud, and precipitation associated with shallow marine cumulus clouds observed in the North Atlantic trades during a field campaign (Barbados Aerosol Cloud Experiment- BACEX, March-April 2010), which took place off Barbados where African dust periodically affects the region. The principal observing platform was the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter (TO) research aircraft, which was equipped with standard meteorological instruments, a zenith pointing cloud radar and probes that measured aerosol, cloud, and precipitation characteristics.The temporal variation and vertical distribution of aerosols observed from the 15 flights, which included the most intense African dust event during all of 2010 in Barbados, showed a wide range of aerosol conditions. During dusty periods, aerosol concentrations increased substantially in the size range between 0.5 and 10 µm (diameter), particles that are large enough to be effective giant cloud condensation nuclei (CCN). The 10-day back trajectories showed three distinct air masses with distinct vertical structures associated with air masses originating in the Atlantic (typical maritime air mass with relatively low aerosol concentrations in the marine boundary layer), Africa (Saharan air layer), and mid-latitudes (continental pollution plumes). Despite the large differences in the total mass loading and the origin of the aerosols, the overall shapes of the aerosol particle size distributions were consistent, with the exception of the transition period.The TO was able to sample many clouds at various phases of growth. Maximum cloud depth observed was less than ˜ 3 km, while most clouds were less than 1 km

  8. Observational evidence against strongly stabilizing tropical cloud feedbacks

    Science.gov (United States)

    Williams, Ian N.; Pierrehumbert, Raymond T.

    2017-02-01

    We present a method to attribute cloud radiative feedbacks to convective processes, using subcloud layer buoyancy as a diagnostic of stable and deep convective regimes. Applying this approach to tropical remote sensing measurements over years 2000-2016 shows that an inferred negative short-term cloud feedback from deep convection was nearly offset by a positive cloud feedback from stable regimes. The net cloud feedback was within statistical uncertainty of the National Center for Atmospheric Research Community Atmosphere Model (CAM5) with historical forcings, with discrepancies in the partitioning of the cloud feedback into convective regimes. Compensation between high-cloud responses to tropics-wide warming in stable and unstable regimes resulted in smaller net changes in high-cloud fraction with warming. In addition, deep convection and associated high clouds set in at warmer temperatures in response to warming, as a consequence of nearly invariant subcloud buoyancy. This invariance further constrained the magnitude of cloud radiative feedbacks and is consistent with climate model projections.

  9. Observation and Schmid factor analysis of multiple twins in a warm-rolled Mg–3Al–1Zn alloy

    Energy Technology Data Exchange (ETDEWEB)

    Xin, Renlong, E-mail: rlxin@cqu.edu.cn [College of Materials Science and Engineering, Chongqing University, Chongqing 400045 (China); Wang, Maoyin [College of Materials Science and Engineering, Chongqing University, Chongqing 400045 (China); Huang, Xiaoxu [College of Materials Science and Engineering, Chongqing University, Chongqing 400045 (China); Danish–Chinese Center for Nanometals, Materials Research Department, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, DK-4000 Roskilde (Denmark); Guo, Changfa; Liu, Qing [College of Materials Science and Engineering, Chongqing University, Chongqing 400045 (China)

    2014-02-24

    This study aims to understand the features of twinning that occurred during warm-rolling of Mg–3Al–1Zn alloys. The rolling was performed at 150 °C with the c-axis of most grains nearly parallel to the transverse direction. Electron backscatter diffraction analysis was conducted to examine microstructural evolution of the rolled sample. Multiple twins including {10−12} extension twin, {10−11} contraction twin, {10−11}–{10−12} and {10−12}–{10−11} double twins and {10−12}–{10−11}–{10−12} tertiary twins were observed in the rolled sample. These twins were present even in the same grain orientation. Based on the applied rolling deformation, an effective Schmid factor was calculated to understand the activation of twinning. Calculated Schmid factor maps were obtained as a function of (0001) pole. The activation of {10−12}–{10−11} double twin was explained by the statistical analysis of Schmid factors for primary {10−12} twin and secondary {10−11} twin.

  10. Processing Doppler Lidar and Cloud Radar Observations for Analysis of Convective Mass Flux Parameterizations Using DYNAMO Direct Observations

    Science.gov (United States)

    2014-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Processing Doppler Lidar and Cloud Radar Observations...campaign the data gathered from the High Resolution Doppler Lidar (HRDL) and the 94-GHz cloud Doppler radar Report Documentation Page Form ApprovedOMB No...00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Processing Doppler Lidar and Cloud Radar Observations for Analysis of Convective Mass Flux

  11. VEx/VIRTIS and TNG/NICS cloud tracked winds at Venus' lower cloud level using nightside observations

    Science.gov (United States)

    Machado, Pedro; Peralta, Javier; Luz, David; Gonçalves, Rúben

    2016-04-01

    We present results based on observations carried out with the Near Infrared Camera and Spectrograph (NICS) of the Telescopio Nazionale Galileo (TNG), in La Palma, on July 2012. We observed for periods of 2.5 hours starting just before dawn, for three consecutive nights. We acquired a set of images of the night side of Venus with the continuum K filter at 2.28 microns, which allows to monitor motions at the lower cloud level of the atmosphere of Venus, close to 48 km altitude. Our objective has been to measure the horizontal wind field in order to characterize the latitudinal zonal wind profile, to study variability, to help constrain the effect of large scale planetary waves in the maintenance of superrotation, and to map the cloud distribution. We will present first results of cloud tracked winds from ground-based TNG observations and winds retrieved from coordinated space-based VEx/VIRTIS observations. The cloud deck extends in altitude from 45 to 70 km, and can be divided into three main regions, centered at 48, 54 and 60 km. The lowest of these is the lower cloud, where fundamental dynamical exchanges that help maintain superrotation are thought to occur. The lower venusian atmosphere is a strong source of thermal radiation, with the gaseaous CO2 component allowing radiation to escape in windows at 1.74 and 2.28 μm. At these wavelengths radiation originates below 35 km, and unit opacity is reached at the lower cloud level, close to 48 km. Therefore, in these windows it is possible to observe the horizontal cloud structure, with thicker clouds seen silhouetted against the bright thermal background from the low atmosphere. Our objective is to provide direct absolute wind measurements and a map of cloud distribution at the lower cloud level in the Venus troposphere, in order to complement Venus Express (VEX) and other ground-based observations of the cloud layer wind regime. By continuous monitoring of the horizontal cloud structure at 2.28 μm (NICS Kcont filter

  12. Evaluation of GISS SCM Simulated Cloud and Radiative Properties Using Both Surface and Satellite Observations

    Science.gov (United States)

    Kennedy, A. D.; Dong, X.; Xi, B.; Del Genio, A.; Wolf, A.; Minnis, P.; Khaiyer, M.; Doelling, D.; Nordeen, M.; Keyes, D.

    2009-05-01

    To evaluate the GISS SCM simulated cloud fractions, three years of surface and GOES satellite data have been collected at DOE ARM Southern Great Plains (SGP) site during 1999-2001. The GOES derived total and high cloud fractions from both 0.5° and 2.5° grid boxes are in excellent agreement with surface observations, suggesting that the ARM point observations can represent large areal observations. Compared to the ARM radar-lidar observed cloud fractions, the SCM simulated most mid-level clouds, overestimated low clouds, and underestimated total and high clouds with additional missed during the summer season. Further studies have revealed that the model simulated cloud fractions are strongly dependent on the large-scale synoptic pattern and its associated variables such as vertical motion and relative humidity. Because a significant amount of clouds over ARM SGP occur during synoptically quiescent conditions, the model has issues producing enough high cloud cover. This work suggests that alterations need to be made to the stratiform cloud scheme to better represent the sub-grid scale cloud variability in this case. The model simulated radiation budget is also evaluated with two years of collocated ARM surface radiation and CERES and GOES TOA radiation over the SGP site during March 2000-Dec. 2001. For this comparison, the model simulated surface and TOA radiation budgets agree well with surface and satellite observations (˜10 W m-2). Model simulated cloud optical depth, however, is about an order of magnitude higher than CERES/GOES retrievals, which may explain why the radiation budget is reasonable and yet total cloud fraction has a negative bias compared to observations. Further study is warranted to better understand how this impacts cloud radiative forcing.

  13. FAME-C: cloud property retrieval using synergistic AATSR and MERIS observations

    Science.gov (United States)

    Carbajal Henken, C. K.; Lindstrot, R.; Preusker, R.; Fischer, J.

    2014-11-01

    A newly developed daytime cloud property retrieval algorithm, FAME-C (Freie Universität Berlin AATSR MERIS Cloud), is presented. Synergistic observations from the Advanced Along-Track Scanning Radiometer (AATSR) and the Medium Resolution Imaging Spectrometer (MERIS), both mounted on the polar-orbiting Environmental Satellite (Envisat), are used for cloud screening. For cloudy pixels two main steps are carried out in a sequential form. First, a cloud optical and microphysical property retrieval is performed using an AATSR near-infrared and visible channel. Cloud phase, cloud optical thickness, and effective radius are retrieved, and subsequently cloud water path is computed. Second, two cloud top height products are retrieved based on independent techniques. For cloud top temperature, measurements in the AATSR infrared channels are used, while for cloud top pressure, measurements in the MERIS oxygen-A absorption channel are used. Results from the cloud optical and microphysical property retrieval serve as input for the two cloud top height retrievals. Introduced here are the AATSR and MERIS forward models and auxiliary data needed in FAME-C. Also, the optimal estimation method, which provides uncertainty estimates of the retrieved property on a pixel basis, is presented. Within the frame of the European Space Agency (ESA) Climate Change Initiative (CCI) project, the first global cloud property retrievals have been conducted for the years 2007-2009. For this time period, verification efforts are presented, comparing, for four selected regions around the globe, FAME-C cloud optical and microphysical properties to cloud optical and microphysical properties derived from measurements of the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite. The results show a reasonable agreement between the cloud optical and microphysical property retrievals. Biases are generally smallest for marine stratocumulus clouds: -0.28, 0.41 μm and -0.18 g m-2 for

  14. Global observations of cloud-sensitive aerosol loadings in low-level marine clouds

    Science.gov (United States)

    Andersen, H.; Cermak, J.; Fuchs, J.; Schwarz, K.

    2016-11-01

    Aerosol-cloud interaction is a key component of the Earth's radiative budget and hydrological cycle, but many facets of its mechanisms are not yet fully understood. In this study, global satellite-derived aerosol and cloud products are used to identify at what aerosol loading cloud droplet size shows the greatest sensitivity to changes in aerosol loading (ACSmax). While, on average, cloud droplet size is most sensitive at relatively low aerosol loadings, distinct spatial and temporal patterns exist. Possible determinants for these are identified with reanalysis data. The magnitude of ACSmax is found to be constrained by the total columnar water vapor. Seasonal patterns of water vapor are reflected in the seasonal patterns of ACSmax. Also, situations with enhanced turbulent mixing are connected to higher ACSmax, possibly due to intensified aerosol activation. Of the analyzed aerosol species, dust seems to impact ACSmax the most, as dust particles increase the retrieved aerosol loading without substantially increasing the concentration of cloud condensation nuclei.

  15. ISOCAM observations of the Chamaeleon I dark cloud

    Science.gov (United States)

    Persi, P.; Marenzi, A. R.; Olofsson, G.; Kaas, A. A.; Nordh, L.; Huldtgren, M.; Abergel, A.; André, P.; Bontemps, S.; Boulanger, F.; Burggdorf, M.; Casali, M. M.; Cesarsky, C. J.; Copet, E.; Davies, J.; Falgarone, E.; Montmerle, T.; Perault, M.; Prusti, T.; Puget, J. L.; Sibille, F.

    2000-05-01

    We present the results of an ISOCAM survey of the Chamaeleon I dark cloud conducted in two broad-band filters at 6.7 and 14.3 mu m. In an area of 0.59 sq.deg. we have detected a total of 282 mid-IR sources with 103 sources observed in both filters. Combining the ISOCAM observations with the I, J, and K_s data obtained with DENIS, we have found 108 pre-main-sequence (PMS) stars in the region, of which 34 were previously unidentified. Several of these newly discovered young stellar objects are relatively faint suggesting a population in Cha I of very low mass objects that probably includes brown dwarfs in their early contraction phases. Finally, most of the PMS stars show the spectral index computed between 2.2 and 14.3 mu m typical of Class II sources. The luminosity function (LF) derived for our detected PMS stars is discussed. ISO is an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA. Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Tables 3 and 4 are only available with the on-line publication at http://link.springer.de/link/service/journals/00230/

  16. Intercomparison of cloud model simulations of Arctic mixed-phase boundary layer clouds observed during SHEBA/FIRE-ACE

    Directory of Open Access Journals (Sweden)

    Mikhail Ovchinnikov

    2011-06-01

    Full Text Available An intercomparison of six cloud-resolving and large-eddy simulation models is presented. This case study is based on observations of a persistent mixed-phase boundary layer cloud gathered on 7 May, 1998 from the Surface Heat Budget of Arctic Ocean (SHEBA and First ISCCP Regional Experiment - Arctic Cloud Experiment (FIRE-ACE. Ice nucleation is constrained in the simulations in a way that holds the ice crystal concentration approximately fixed, with two sets of sensitivity runs in addition to the baseline simulations utilizing different specified ice nucleus (IN concentrations. All of the baseline and sensitivity simulations group into two distinct quasi-steady states associated with either persistent mixed-phase clouds or all-ice clouds after the first few hours of integration, implying the existence of multiple equilibria. These two states are associated with distinctly different microphysical, thermodynamic, and radiative characteristics. Most but not all of the models produce a persistent mixed-phase cloud qualitatively similar to observations using the baseline IN/crystal concentration, while small increases in the IN/crystal concentration generally lead to rapid glaciation and conversion to the all-ice state. Budget analysis indicates that larger ice deposition rates associated with increased IN/crystal concentrations have a limited direct impact on dissipation of liquid in these simulations. However, the impact of increased ice deposition is greatly enhanced by several interaction pathways that lead to an increased surface precipitation flux, weaker cloud top radiative cooling and cloud dynamics, and reduced vertical mixing, promoting rapid glaciation of the mixed-phase cloud for deposition rates in the cloud layer greater than about 1-2x10-5 g kg-1 s-1. These results indicate the critical importance of precipitation-radiative-dynamical interactions in simulating cloud phase, which have been neglected in previous fixed-dynamical parcel

  17. Intercomparison of cloud model simulations of Arctic mixed-phase boundary layer clouds observed during SHEBA/FIRE-ACE

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, H.; Zuidema, Paquita; Ackerman, Andrew; Avramov, Alexander; de Boer, Gijs; Fan, Jiwen; Fridlind, Ann; Hashino, Tempei; Harrington, Jerry Y.; Luo, Yali; Ovchinnikov, Mikhail; Shipway, Ben

    2011-06-16

    An intercomparison of six cloud-resolving and large-eddy simulation models is presented. This case study is based on observations of a persistent mixed-phase boundary layer cloud gathered on 7 May, 1998 from the Surface Heat Budget of Arctic Ocean (SHEBA) and First ISCCP Regional Experiment - Arctic Cloud Experiment (FIRE-ACE). Ice nucleation is constrained in the simulations in a way that holds the ice crystal concentration approximately fixed, with two sets of sensitivity runs in addition to the baseline simulations utilizing different specified ice nucleus (IN) concentrations. All of the baseline and sensitivity simulations group into two distinct quasi-steady states associated with either persistent mixed-phase clouds or all-ice clouds after the first few hours of integration, implying the existence of multiple equilibria. These two states are associated with distinctly different microphysical, thermodynamic, and radiative characteristics. Most but not all of the models produce a persistent mixed-phase cloud qualitatively similar to observations using the baseline IN/crystal concentration, while small increases in the IN/crystal concentration generally lead to rapid glaciation and conversion to the all-ice state. Budget analysis indicates that larger ice deposition rates associated with increased IN/crystal concentrations have a limited direct impact on dissipation of liquid in these simulations. However, the impact of increased ice deposition is greatly enhanced by several interaction pathways that lead to an increased surface precipitation flux, weaker cloud top radiative cooling and cloud dynamics, and reduced vertical mixing, promoting rapid glaciation of the mixed-phase cloud for deposition rates in the cloud layer greater than about 1-2x10-5 g kg-1 s-1. These results indicate the critical importance of precipitation-radiative-dynamical interactions in simulating cloud phase, which have been neglected in previous fixed-dynamical parcel studies of the cloud

  18. New near-IR observations of mesospheric CO2 and H2O clouds on Mars

    Science.gov (United States)

    Vincendon, Mathieu; Pilorget, Cedric; Gondet, Brigitte; Murchie, Scott; Bibring, Jean-Pierre

    2011-11-01

    Carbon dioxide clouds, which are speculated by models on solar and extra-solar planets, have been recently observed near the equator of Mars. The most comprehensive identification of Martian CO2 ice clouds has been obtained by the near-IR imaging spectrometer OMEGA. CRISM, a similar instrument with a higher spatial resolution, cannot detect these clouds with the same method due to its shorter wavelength range. Here we present a new method to detect CO2 clouds using near-IR data based on the comparison of H2O and CO2 ice spectral properties. The spatial and seasonal distributions of 54 CRISM observations containing CO2 clouds are reported, in addition to 17 new OMEGA observations. CRISM CO2 clouds are characterized by grain size in the 0.5-2 μm range and optical depths lower than 0.3. The distributions of CO2 clouds inferred from OMEGA and CRISM are consistent with each other and match at first order the distribution of high altitude (>60 km) clouds derived from previous studies. At second order, discrepancies are observed. We report the identification of H2O clouds extending up to 80 km altitude, which could explain part of these discrepancies: both CO2 and H2O clouds can exist at high, mesospheric altitudes. CRISM observations of afternoon CO2 clouds display morphologies resembling terrestrial cirrus, which generalizes a previous result to the whole equatorial clouds season. Finally, we show that morning OMEGA observations have been previously misinterpreted as evidence for cumuliform, and hence potentially convective, CO2 clouds.

  19. Quantifying retrieval uncertainties in the CM-SAF cloud physical property algorithm with simulated SEVIRI observations

    Directory of Open Access Journals (Sweden)

    B. J. Jonkheid

    2012-02-01

    Full Text Available The uncertainties in the cloud physical properties derived from satellite observations make it difficult to interpret model evaluation studies. In this paper, the uncertainties in the cloud water path (CWP retrievals derived with the cloud physical properties retrieval algorithm (CPP of the climate monitoring satellite application facility (CM-SAF are investigated. To this end, a numerical simulator of MSG-SEVIRI observations was developed that calculates the reflectances at 0.64 and 1.63 μm for a wide range of cloud parameters, satellite viewing geometries and surface albedos. These reflectances are used as input to CPP, and the retrieved values of CWP are compared to the original input of the simulator.

    It is shown that the CWP retrievals are very sensitive to the assumptions made in the CPP code. The CWP retrieval errors are generally small for unbroken single-phase clouds with COT >10, with retrieval errors of ~3% for liquid water clouds to ~10% for ice clouds. When both liquid water and ice clouds are present in a pixel, the CWP retrieval errors increase dramatically; depending on the cloud, this can lead to uncertainties of 40–80%. CWP retrievals also become more uncertain when the cloud does not cover the entire pixel, leading to errors of ~50% for cloud fractions of 0.75 and even larger errors for smaller cloud fractions. Thus, the satellite retrieval of cloud physical properties of broken clouds and multi-phase clouds is complicated by inherent difficulties, and the proper interpretation of such retrievals requires extra care.

  20. Observation of Oil Flow Characteristics in Rolling Piston Rotary Compressor for Reducing Oil Circulation Rate

    Science.gov (United States)

    Song, S. j.; Noh, K. Y.; Min, B. C.; Yang, J. S.; Choi, G. M.; Kim, D. J.

    2015-08-01

    The oil circulation rate (OCR) of the rolling piston rotary compressor is a significant factor which affects the performance of refrigeration system. The increase of oil discharge causes decreasing of the heat transfer efficiency in the heat exchanger, pressure drop and lack of oil in lubricate part in compressor. In this study, the internal flow of compressor was visualized to figure out the oil droplet flow characteristics. The experiments and Computational Fluid Dynamics (CFD) simulations were conducted in various frequency of compressor to observe the effect of operation frequency on oil droplet flow characteristics for reducing OCR. In situ, measurement of oil droplet diameter and velocity were conducted by using high speed image visualization and Particle Image Velocimetry (PIV). The flow paths were dominated by copper wire parts driving the motor which was inserted in compressor. In order to verify the reliability of CFD simulation, the tendency of oil flow characteristics in each flow path and the compressor operating conditions were applied in CFD simulation. For reducing OCR, the structure such as vane, disk and ring is installed in the compressor to restrict the main flow path of oil particle. The effect of additional structure for reducing OCR was evaluated using CFD simulation and the results were discussed in detail.

  1. Radiative budget and cloud radiative effect over the Atlantic from ship-based observations

    Directory of Open Access Journals (Sweden)

    J. Kalisch

    2012-10-01

    Full Text Available The aim of this study is to determine cloud-type resolved cloud radiative budgets and cloud radiative effects from surface measurements of broadband radiative fluxes over the Atlantic Ocean. Furthermore, based on simultaneous observations of the state of the cloudy atmosphere, a radiative closure study has been performed by means of the ECHAM5 single column model in order to identify the model's ability to realistically reproduce the effects of clouds on the climate system.

    An extensive database of radiative and atmospheric measurements has been established along five meridional cruises of the German research icebreaker Polarstern. Besides pyranometer and pyrgeometer for downward broadband solar and thermal radiative fluxes, a sky imager and a microwave radiometer have been utilized to determine cloud fraction and cloud type on the one hand and temperature and humidity profiles as well as liquid water path for warm non-precipitating clouds on the other hand.

    Averaged over all cruise tracks, we obtain a total net (solar + thermal radiative flux of 144 W m−2 that is dominated by the solar component. In general, the solar contribution is large for cirrus clouds and small for stratus clouds. No significant meridional dependencies were found for the surface radiation budgets and cloud effects. The strongest surface longwave cloud effects were shown in the presence of low level clouds. Clouds with a high optical density induce strong negative solar radiative effects under high solar altitudes. The mean surface net cloud radiative effect is −33 W m−2.

    For the purpose of quickly estimating the mean surface longwave, shortwave and net cloud effects in moderate, subtropical and tropical climate regimes, a new parameterisation was created, considering the total cloud amount and the solar zenith angle.

    The ECHAM5 single column model provides a surface net cloud effect that is more

  2. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. Part I: Single layer cloud

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Stephen A.; McCoy, Renata B.; Morrison, Hugh; Ackerman, Andrew S.; Avramov, Alexander; de Boer, Gijs; Chen, Mingxuan; Cole, Jason N.S.; Del Genio, Anthony D.; Falk, Michael; Foster, Michael J.; Fridlind, Ann; Golaz, Jean-Christophe; Hashino, Tempei; Harrington, Jerry Y.; Hoose, Corinna; Khairoutdinov, Marat F.; Larson, Vincent E.; Liu, Xiaohong; Luo, Yali; McFarquhar, Greg M.; Menon, Surabi; Neggers, Roel A. J.; Park, Sungsu; Poellot, Michael R.; Schmidt, Jerome M.; Sednev, Igor; Shipway, Ben J.; Shupe, Matthew D.; Spangenberg, Douglas A.; Sud, Yogesh C.; Turner, David D.; Veron, Dana E.; von Salzen, Knut; Walker, Gregory K.; Wang, Zhien; Wolf, Audrey B.; Xie, Shaocheng; Xu, Kuan-Man; Yang, Fanglin; Zhang, Gong

    2009-02-02

    Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a cold-air outbreak mixed-phase stratocumulus cloud observed during the Atmospheric Radiation Measurement (ARM) program's Mixed-Phase Arctic Cloud Experiment. The observed cloud occurred in a well-mixed boundary layer with a cloud top temperature of -15 C. The observed average liquid water path of around 160 g m{sup -2} was about two-thirds of the adiabatic value and much greater than the average mass of ice crystal precipitation which when integrated from the surface to cloud top was around 15 g m{sup -2}. The simulations were performed by seventeen single-column models (SCMs) and nine cloud-resolving models (CRMs). While the simulated ice water path is generally consistent with the observed values, the median SCM and CRM liquid water path is a factor of three smaller than observed. Results from a sensitivity study in which models removed ice microphysics suggest that in many models the interaction between liquid and ice-phase microphysics is responsible for the large model underestimate of liquid water path. Despite this general underestimate, the simulated liquid and ice water paths of several models are consistent with the observed values. Furthermore, there is evidence that models with more sophisticated microphysics simulate liquid and ice water paths that are in better agreement with the observed values, although considerable scatter is also present. Although no single factor guarantees a good simulation, these results emphasize the need for improvement in the model representation of mixed-phase microphysics.

  3. Martian clouds observed by Mars Global Surveyor Mars Orbiter Camera

    OpenAIRE

    Wang, Huiqun; Ingersoll, Andrew P.

    2002-01-01

    We have made daily global maps that cover both polar and equatorial regions of Mars for Ls 135°–360° and 0°–111° using the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) red and blue wide-angle swaths taken from May 1999 to January 2001. We study the seasonal distribution of condensate clouds and dust clouds during roughly 1 Martian year using these daily global maps. We present the development and decay of the tropical cloud belt and the polar hoods, the spatial and temporal distributi...

  4. Direct atmosphere opacity observations from CALIPSO provide new constraints on cloud-radiation interactions

    Science.gov (United States)

    Guzman, R.; Chepfer, H.; Noel, V.; Vaillant de Guélis, T.; Kay, J. E.; Raberanto, P.; Cesana, G.; Vaughan, M. A.; Winker, D. M.

    2017-01-01

    The spaceborne lidar CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) directly measures atmospheric opacity. In 8 years of CALIPSO observations, we find that 69% of vertical profiles penetrate through the complete atmosphere. The remaining 31% do not reach the surface, due to opaque clouds. The global mean altitude of full attenuation of the lidar beam (z_opaque) is 3.2 km, but there are large regional variations in this altitude. Of relevance to cloud-climate studies, the annual zonal mean longwave cloud radiative effect and annual zonal mean z_opaque weighted by opaque cloud cover are highly correlated (0.94). The annual zonal mean shortwave cloud radiative effect and annual zonal mean opaque cloud cover are also correlated (-0.95). The new diagnostics introduced here are implemented within a simulator framework to enable scale-aware and definition-aware evaluation of the LMDZ5B global climate model. The evaluation shows that the model overestimates opaque cloud cover (31% obs. versus 38% model) and z_opaque (3.2 km obs. versus 5.1 km model). In contrast, the model underestimates thin cloud cover (35% obs. versus 14% model). Further assessment shows that reasonable agreement between modeled and observed longwave cloud radiative effects results from compensating errors between insufficient warming by thin clouds and excessive warming due to overestimating both z_opaque and opaque cloud cover. This work shows the power of spaceborne lidar observations to directly constrain cloud-radiation interactions in both observations and models.

  5. Millimeter continuum observations of Galactic center giant molecular cloud cores

    Science.gov (United States)

    Lis, D. C.; Carlstrom, J. E.; Keene, Jocelyn

    1991-01-01

    Results are presented of observations of 1.3- and 0.8-mm continuum emission toward the cores of three Galactic center molecular clouds with ongoing massive star formation, Sagittarius B2, C, and D, which were made in order to study possible variations in the high-mass star formation rate per unit mass between the Galactic center and the disk. The luminosity-to-mass ratio, based on the mass estimates derived from the millimeter continuum emission, is used as a tracer of the high-mass star formation rate in GMC cores. The magnitude of errors involved in using millimeter continuum emission for determining the core mass is estimated through radiative transfer modeling. It is inferred from the present millimeter data, along with previously published far-infrared data, that the Sgr C and D cores are very similar in terms of mean dust optical depth and temperature. The luminosity-to-mass ratios derived for the Sgr C and D cores are found to be consistent with those of typical disk GMC cores with comparable far-infrared luminosities.

  6. Microphysical characteristics of convective clouds over ocean and land from aircraft observations

    Science.gov (United States)

    Padmakumari, B.; Maheskumar, R. S.; Anand, Vrinda; Axisa, Duncan

    2017-10-01

    The Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) is a field campaign conducted in India with an instrumented research aircraft. On 29 October 2010, a cyclonic circulation over the Bay of Bengal persisted throughout the day. A special mission was conducted over the Bay of Bengal on this day with the objective of characterizing marine and continental clouds on the same day and finding contrasting/similar signatures of their microphysical properties. The research aircraft sampled growing convective clouds over the ocean and over land. High concentrations of aerosol and cloud condensation nuclei (CCN) were observed over land compared to ocean. Over ocean, higher liquid water content (LWC) and lower cloud droplet number concentrations (Nc) were observed, and droplets reached the threshold of precipitation initiation at lower cloud depths. Over land, clouds contained lower LWC and higher Nc, hence droplets did not reach the threshold of precipitation initiation at a warm temperature as in ocean clouds. Over the ocean larger droplets or drizzle were observed at lower cloud depth than over land. The maximum LWC was found to be very similar at higher altitudes. The convective clouds over land were modified by pollution aerosol with contrasting microphysical properties to those over the ocean.

  7. What is a GMC? Are observers and simulators discussing the same star-forming clouds?

    Science.gov (United States)

    Pan, Hsi-An; Fujimoto, Yusuke; Tasker, Elizabeth J.; Rosolowsky, Erik; Colombo, Dario; Benincasa, Samantha M.; Wadsley, James

    2015-11-01

    As both simulations and observations reach the resolution of the star-forming molecular clouds, it becomes important to clarify if these two techniques are discussing the same objects in galaxies. We compare clouds formed in a high-resolution galaxy simulation identified as continuous structures within a contour, in the simulator's position-position-position (PPP) coordinate space and the observer's position-position-velocity space (PPV). Results indicate that the properties of the cloud populations are similar in both methods and up to 70 per cent of clouds have a single counterpart in the opposite data structure. Comparing individual clouds in a one-to-one match reveals a scatter in properties mostly within a factor of 2. However, the small variations in mass, radius and velocity dispersion produce significant differences in derived quantities such as the virial parameter. This makes it difficult to determine if a structure is truly gravitationally bound. The three cloud types originally found in the simulation in Fujimoto et al. are identified in both data sets, with around 80 per cent of the clouds retaining their type between identification methods. We also compared our results when using a peak decomposition method to identify clouds in both PPP and PPV space. The number of clouds increased with this technique, but the overall cloud properties remained similar. However, the more crowded environment lowered the ability to match clouds between techniques to 40 per cent. The three cloud types also became harder to separate, especially in the PPV data set. The method used for cloud identification therefore plays a critical role in determining cloud properties, but both PPP and PPV can potentially identify the same structures.

  8. A comparison of global reanalyses to satellite observations: quantifying errors in Cloud Fraction and TOA cloud radiative forcings

    Science.gov (United States)

    Dolinar, E. K.; Dong, X.; Xi, B.

    2014-12-01

    As the improvements of observing systems, model parameterizations, and advanced assimilation techniques, a few reanalyses data sets become available; however, it is necessary to understand their strengths and biases before exploiting them. In this study, we investigate five contemporary reanalyses (20CR, CFSR, Era-Interim, JRA-25, and MERRA). In detail, we first compared the cloud fraction, TOA radiation fluxes and cloud radiative forcings using CERES MODIS SYN1deg and EBAF products on the global scale. We then analyze the differences and similarities between these parameters in tropical and mid-latitudes under convective and subsidence regimes. It is important to note that CERES MODIS and EBAF results are used as reference to evaluate these simulated parameters, and these data cover the period from 03/2000 to 02/2012. The preliminary results show that most of the reanalyses under estimate cloud fraction on global average, and the SW, LW, and Net CRFs are biased by as much as 3.9 (CFSR), -8.7 (JRA-25), and -5.7 (JRA-25) Wm-2, respectively. Convective and subsidence regimes are identified as the strong ascending and descending branches of the large general circulation in the tropics and mid-latitudes. This metric helps to identify the physical characteristics in specific areas and the types of clouds that reside there. Clouds are typically over estimated in convective areas while in the subsidence region clouds are under estimated. Sensitivity studies show that these regimes exhibit different regressive behaviors when comparing cloud fraction to CRFs, especially in the LW CRF. The error analysis reveals information that can be useful for modelers so that they may develop better parameterizations for clouds and how they interact with incoming solar and outgoing infrared radiation.

  9. A Linearized Prognostic Cloud Scheme in NASAs Goddard Earth Observing System Data Assimilation Tools

    Science.gov (United States)

    Holdaway, Daniel; Errico, Ronald M.; Gelaro, Ronald; Kim, Jong G.; Mahajan, Rahul

    2015-01-01

    A linearized prognostic cloud scheme has been developed to accompany the linearized convection scheme recently implemented in NASA's Goddard Earth Observing System data assimilation tools. The linearization, developed from the nonlinear cloud scheme, treats cloud variables prognostically so they are subject to linearized advection, diffusion, generation, and evaporation. Four linearized cloud variables are modeled, the ice and water phases of clouds generated by large-scale condensation and, separately, by detraining convection. For each species the scheme models their sources, sublimation, evaporation, and autoconversion. Large-scale, anvil and convective species of precipitation are modeled and evaporated. The cloud scheme exhibits linearity and realistic perturbation growth, except around the generation of clouds through large-scale condensation. Discontinuities and steep gradients are widely used here and severe problems occur in the calculation of cloud fraction. For data assimilation applications this poor behavior is controlled by replacing this part of the scheme with a perturbation model. For observation impacts, where efficiency is less of a concern, a filtering is developed that examines the Jacobian. The replacement scheme is only invoked if Jacobian elements or eigenvalues violate a series of tuned constants. The linearized prognostic cloud scheme is tested by comparing the linear and nonlinear perturbation trajectories for 6-, 12-, and 24-h forecast times. The tangent linear model performs well and perturbations of clouds are well captured for the lead times of interest.

  10. Long-term Numerical Simulations of Clouds in Contrast to ARM Observational Data

    Science.gov (United States)

    Zeng, X.; Tao, W.; Peters-Lidard, C.; Lang, S.; Simpson, J.; Kumar, S.; Eastman, J.; Shie, C.; Geiger, J.

    2006-05-01

    Two 20-day continental cases in the middle latitude are simulated with a three-dimensional (3D) cloud- resolving model (CRM) in contrast to Atmospheric Radiation Measurement (ARM) data. All numerical experiments, as compared with observations, give reasonable simulations of surface rainfall but over prediction of cloud residues in the upper troposphere. Such modeling phenomenon on the over prediction of cloud residues was also noticed by Wu et al. (1998) in the simulation of oceanic clouds. Surface fluxes from a land surface model are compared with those from observations. Using the two kinds of surface flux data, the sensitivity of clouds to surface fluxes is studied, showing that the surface fluxes from the land surface model brings about the reasonable simulation of cloud fraction in the lower troposphere.

  11. What is a GMC? Are Observers and Simulators Discussing the Same Star-forming Clouds?

    CERN Document Server

    Pan, Hsi-An; Tasker, Elizabeth J; Rosolowsky, Erik; Colombo, Dario; Benincasa, Samantha M; Wadsley, James

    2015-01-01

    As both simulations and observations reach the resolution of the star-forming molecular clouds, it becomes important to clarify if these two techniques are discussing the same objects in galaxies. We compare clouds formed in a high resolution galaxy simulation identified as continuous structures within a contour, in the simulator's position-position-position (PPP) co-ordinate space and the observer's position-position-velocity space (PPV). Results indicate that the properties of the cloud populations are similar in both methods and up to 70% of clouds have a single counterpart in the opposite data structure. Comparing individual clouds in a one-to-one match reveals a scatter in properties mostly within a factor of two. However, the small variations in mass, radius and velocity dispersion produce significant differences in derived quantities such as the virial parameter. This makes it difficult to determine if a structure is truely gravitationally bound. The three cloud types originally found in the simulation...

  12. An Attempt to Improve Kessler-Type Parameterization of Warm Cloud Microphysical Conversion Processes Using CloudSat Observations

    Institute of Scientific and Technical Information of China (English)

    尹金方; 王东海; 翟国庆

    2015-01-01

    Improvements to the Kessler-type parameterization of warm cloud microphysical conversion processes (also called autoconversion) are proposed based on a large number of CloudSat observations between June 2006 and April 2011 over Asian land areas. The emphasis is given to the vertical distribution of liquid water content (LWC), particularly, the threshold values of LWC for autoconversion. The results warrant a new approach to the numerical parameterization of autoconversion in warm clouds. One feature of this new approach is that the autoconversion threshold, which has been treated as a constant in previous parameter-ization schemes, is diagnosed as a function of altitude by using a relationship between LWC and height (H) derived from CloudSat observations: LWCdig = −500.0 ln ?H 9492.2 ? . Under this framework, the threshold LWC decreases with increasing H, allowing autoconversion to occur in clouds with low LWC (approximately 0.3 g m−3) at levels above 5.5 km. Autoconversion rates calculated based on the new parameterization are compared to those calculated based on several commonly used parameterization schemes over a range of LWCs from 0.01 to 1.0 g m−3. The new scheme provides reasonable simulations of autoconversion at various vertical levels.

  13. Analysis of co-located MODIS and CALIPSO observations near clouds

    Directory of Open Access Journals (Sweden)

    T. Várnai

    2011-11-01

    Full Text Available This paper aims at helping synergistic studies in combining data from different satellites for gaining new insights into two critical yet poorly understood aspects of anthropogenic climate change, aerosol-cloud interactions and aerosol radiative effects. In particular, the paper examines the way cloud information from the MODIS imager can refine our perceptions based on CALIOP lidar measurements about the systematic aerosol changes that occur near clouds.

    The statistical analysis of a yearlong dataset of co-located global maritime observations from the Aqua and CALIPSO satellites reveals that MODIS's multispectral imaging ability can greatly help the interpretation of CALIOP observations. The results show that imagers on Aqua and CALIPSO yield very similar pictures, and that the discrepancies – due mainly to wind drift and differences in view angle – do not significantly hinder aerosol measurements near clouds. By detecting clouds outside the CALIOP track, MODIS reveals that clouds are usually closer to clear areas than CALIOP data alone would suggest. The paper finds statistical relationships between the distances to clouds in MODIS and CALIOP data, and proposes a rescaling approach to statistically account for the impact of clouds outside the CALIOP track even when MODIS cannot reliably detect low clouds, for example at night or over sea ice. Finally, the results show that the typical distance to clouds depends on both cloud coverage and cloud type, and accordingly varies with location and season. The global median distance to clouds in maritime clear-sky areas is in the 4–5 km range.

  14. A multiwavelength observation and investigation of six infrared dark clouds

    Science.gov (United States)

    Zhang, Chuan-Peng; Yuan, Jing-Hua; Li, Guang-Xing; Zhou, Jian-Jun; Wang, Jun-Jie

    2017-02-01

    Context. Infrared dark clouds (IRDCs) are ubiquitous in the Milky Way, yet they play a crucial role in breeding newly-formed stars. Aims: With the aim of further understanding the dynamics, chemistry, and evolution of IRDCs, we carried out multiwavelength observations on a small sample. Methods: We performed new observations with the IRAM 30 m and CSO 10.4 m telescopes, with tracers HCO+, HCN, N2H+, C18O, DCO+, SiO, and DCN toward six IRDCs G031.97+00.07, G033.69-00.01, G034.43+00.24, G035.39-00.33, G038.95-00.47, and G053.11+00.05. Results: We investigated 44 cores including 37 cores reported in previous work and seven newly-identified cores. Toward the dense cores, we detected 6 DCO+, and 5 DCN lines. Using pixel-by-pixel spectral energy distribution (SED) fits of the Herschel 70 to 500 μm, we obtained dust temperature and column density distributions of the IRDCs. We found that N2H+ emission has a strong correlation with the dust temperature and column density distributions, while C18O showed the weakest correlation. It is suggested that N2H+ is indeed a good tracer in very dense conditions, but C18O is an unreliable one, as it has a relatively low critical density and is vulnerable to freezing-out onto the surface of cold dust grains. The dynamics within IRDCs are active, with infall, outflow, and collapse; the spectra are abundant especially in deuterium species. Conclusions: We observe many blueshifted and redshifted profiles, respectively, with HCO+ and C18O toward the same core. This case can be well explained by model "envelope expansion with core collapse (EECC)". The final datacubes (HCO+, HCN, N2H+, C18O) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/598/A76

  15. Expanding Curtain Observations of Cloud Vertical Structure and Layering to Model-Relevant Spatial Scales

    Science.gov (United States)

    Miller, S.; Bankert, R.; Forsythe, J.; Mitrescu, C.; Reinke, D.; Austin, R.

    2007-12-01

    Clouds, representing perhaps the most obvious physical manifestations of atmospheric dynamics at work, remain in many ways an enigmatic and unifying intellectual challenge to researchers of all disciplines within the atmospheric sciences. Given the universally acknowledged importance of cloud systems in determining the state of current and future climate through radiative, chemical, dynamic, and thermodynamic processes tied intimately to the hydrological cycle, it is no wonder that so much recent attention has been given to better understanding the non-linear feedbacks involving clouds and ways to improve their handling in numerical weather prediction (NWP) models. In terms of operational community interests, knowledge of cloud vertical structure, ceiling (cloud base) height, and phase is key to aviation safety assurance in the private, commercial, and defense-agency sectors alike. The launch of the NASA Earth System Science Pathfinder CloudSat (cloud radar; 3 mm wavelength) mission in 2006 changed forever the way we view cloud systems from the space platform--providing vertically-resolved 'cuts' through the cloudy troposphere. The Cloud Profiling Radar (CPR) system resolves nearly all radiatively significant cloud structures present in the column at vertical resolutions sufficient to afford scientists the opportunity to examine new hypotheses on cloud formation (leading potentially to new/improved cloud process parameterizations) and make observationally-based discoveries bordering on the frontiers of our current understanding. At the same time, the non-scanning nature of the CPR (providing so-called 'curtain' observations) represents in some respects a frustrating tease to the potential of a three-dimensional scanning system, relegating its utility to the realms of research as opposed to full spatial environmental characterization and data assimilation. This research examines ways to extend via statistical methods the curtain slices provided by CloudSat into the

  16. Observational evidence of high ice concentration in a shallow convective cloud embedded in stratiform cloud over North China

    Science.gov (United States)

    Yang, Jiefan; Lei, Hengchi; Hou, Tuanjie

    2017-04-01

    In this study we observed the microphysical properties, including the vertical and horizontal distributions of ice particles, liquid water content and ice habit, in different regions of a slightly supercooled stratiform cloud. Using aircraft instrument and radar data, the cloud top temperature was recorded as higher than -15°C, behind a cold front, on 9 September 2015 in North China. During the flight sampling, the high ice number concentration area was located in the supercooled part of a shallow convective cloud embedded in a stratiform cloud, where the ambient temperature was around -3°C. In this area, the maximum number concentrations of particles with diameter greater than 100 μm and 500 μm ( N 100 and N 500) exceeded 300 L-1 and 30 L-1, respectively, and were related to large supercooled water droplets with diameter greater than 24 μm derived from cloud-aerosol spectrometer probe measurements. The ice particles types in this region were predominantly columnar, needle, graupel, and some freezing drops, suggesting that the occurrence of high ice number concentrations was likely related to the Hallett-Mossop mechanism, although many other ice multiplication processes cannot be totally ruled out. The maximum ice number concentration obtained during the first penetration was around two to three orders of magnitude larger than that predicted by the Demott and Fletcher schemes when assuming the cloud top temperature was around -15°C. During the second penetration conducted within the stratiform cloud, N 100 and N 500 decreased by a factor of five to ten, and the presence of columnar and needle-like crystals became very rare.

  17. Mesoscale Variability in Coastal Stratocumulus Clouds Observed During Uppef2012

    Science.gov (United States)

    2014-03-01

    Johnson , and A. Spice, 1994: The measurement and parameterization of effective radius of droplets in warm stratocumulus clouds. J. Atmos. Sci., 51, 1823...mesoscale cellular convection during AMTEX75. J. Atmos. Sci., 37, 1027–1040. Schubert, W. H., J. S. Wakefield, E. J. Steiner , and S. K. Cox, 1979a

  18. Observational evidence for cloud cover enhancement over western European forests

    NARCIS (Netherlands)

    Teuling, A.J.; Taylor, C.; Meirink, J.F.; Melsen, L.A.; Miralles, D.G.; Heerwaarden, van C.C.; Vautard, R.; Stegehuis, A.I.; Nabuurs, G.J.; Vilà-Guerau De Arellano, J.

    2017-01-01

    Forests impact regional hydrology and climate directly by regulating water and heat fluxes. Indirect effects through cloud formation and precipitation can be important in facilitating continental-scale moisture recycling but are poorly understood at regional scales. In particular, the impact of

  19. High-Resolution Images of Diffuse Neutral Clouds in the Milky Way. I. Observations, Imaging, and Basic Cloud Properties

    CERN Document Server

    Pidopryhora, Yurii; Dickey, John M; Rupen, Michael P

    2015-01-01

    A set of diffuse interstellar clouds in the inner Galaxy within a few hundred pc of the Galactic plane has been observed at an angular resolution of ~1 arcmin combining data from the NRAO Green Bank Telescope and the Very Large Array. At the distance of the clouds the linear resolution ranges from ~1.9 pc to ~2.8 pc. These clouds have been selected to be somewhat out of the Galactic plane and are thus not confused with unrelated emission, but in other respects they are a Galactic population. They are located near the tangent points in the inner Galaxy, and thus at a quantifiable distance: $2.3 \\leq R \\leq 6.0$ kpc from the Galactic Center, and $-1000 \\leq z \\leq +610$ pc from the Galactic plane. These are the first images of the diffuse neutral HI clouds that may constitute a considerable fraction of the ISM. Peak HI column densities range from $N_{HI} = 0.8-2.9 \\times 10^{20}$ cm$^{-2}$. Cloud diameters vary between about 10 and 100 pc, and their HI mass spans the range from less than a hundred to a few thou...

  20. Improved identification of clouds and ice/snow covered surfaces in SCIAMACHY observations

    Directory of Open Access Journals (Sweden)

    J. M. Krijger

    2011-10-01

    Full Text Available In the ultra-violet, visible and near infra-red wavelength range the presence of clouds can strongly affect the satellite-based passive remote sensing observation of constituents in the troposphere, because clouds effectively shield the lower part of the atmosphere. Therefore, cloud detection algorithms are of crucial importance in satellite remote sensing. However, the detection of clouds over snow/ice surfaces is particularly difficult in the visible wavelengths as both clouds an snow/ice are both white and highly reflective. The SCIAMACHY Polarisation Measurement Devices (PMD Identification of Clouds and Ice/snow method (SPICI uses the SCIAMACHY measurements in the wavelength range between 450 nm and 1.6 μm to make a distinction between clouds and ice/snow covered surfaces, specifically developed to identify cloud-free SCIAMACHY observations. For this purpose the on-board SCIAMACHY PMDs are used because they provide higher spatial resolution compared to the main spectrometer measurements. In this paper we expand on the original SPICI algorithm (Krijger et al., 2005a to also adequately detect clouds over snow-covered forests which is inherently difficult because of the similar spectral characteristics. Furthermore the SCIAMACHY measurements suffer from degradation with time. This must be corrected for adequate performance of SPICI over the full SCIAMACHY time range. Such a correction is described here. Finally the performance of the new SPICI algorithm is compared with various other datasets, such as from FRESCO, MICROS and AATSR, focusing on the algorithm improvements.

  1. Dense Cloud Cores revealed by ALMA CO observations in the low metallicity dwarf galaxy WLM

    Science.gov (United States)

    Rubio, M.; Elmegreen, B.; Hunter, D.; Cortes, J.; Brinks, E.; Cigan, P.

    2017-03-01

    Understanding stellar birth requires observations of the clouds in which they form. These clouds are dense and self-gravitating, and in all existing observations, they are molecular with H2 the dominant species and CO the best available. When the abundances of carbon and oxygen are low compared to hydrogen, and the opacity from dust is also low, as in primeval galaxies and local dwarf irregular galaxies CO forms slowly and is easily destroyed, so it cannot accumulate inside dense clouds. Then we lose our ability to trace the gas in regions of star formation and we lose critical information on the temperatures, densities, and velocities of the material that collapses. I will report on high resolution observations with ALMA of CO clouds in the local group dwarf irregular galaxy WLM, which has a metallicity that is 13% of the solar value and 50% lower than the previous CO detection threshold and the properties derived of very small dense CO clouds mapped..

  2. Extrasolar Storms: Mapping Cloud Cover Evolution with Joint HST-Spitzer Observations

    Science.gov (United States)

    Apai, Daniel; Extrasolar Storms Team

    2017-01-01

    Observations of directly imaged and transiting exoplanets and brown dwarfs reveal the wide-spread presence of condensate clouds. These clouds profoundly influence the energy transport through ultracool atmospheres and impact their pressure-temperature profiles. Yet, the structure and properties of these cloud layers remain mostly unexplored and pose one of the great challenges to our understanding ultracool atmospheres. I will show how using HST and Spitzer jointly -- by exploiting their photometric stability and sensitivity and combining their wavelength ranges -- allows us to address this challenge. With time-resolved spectroscopy and photometry of rotating brown dwarfs - rotational phase mapping — we are exploring the longitudinal structure of condensate clouds and with multiple epoch observations we are following the evolution of the cloud cover. These new observations are opening a new window on the dynamics of ultracool atmospheres.

  3. Evaluating the Cloud Cover Forecast of NCEP Global Forecast System with Satellite Observation

    CERN Document Server

    Ye, Quanzhi

    2011-01-01

    To assess the quality of daily cloud cover forecast generated by the operational global numeric model, the NCEP Global Forecast System (GFS), we compose a large sample with outputs from GFS model and satellite observations from the International Satellite Cloud Climatology Project (ISCCP) in the period of July 2004 to June 2008, to conduct a quantitative and systematic assessment of the performance of a cloud model that covers a relatively long range of time, basic cloud types, and in a global view. The evaluation has revealed the goodness of the model forecast, which further illustrates our completeness on understanding cloud generation mechanism. To quantity the result, we found a remarkably high correlation between the model forecasts and the satellite observations over the entire globe, with mean forecast error less than 15% in most areas. Considering a forecast within 30% difference to the observation to be a "good" one, we find that the probability for the GFS model to make good forecasts varies between...

  4. Multispectral imaging observations of Neptune's cloud structure with Gemini-North

    Science.gov (United States)

    Irwin, P. G. J.; Teanby, N. A.; Davis, G. R.; Fletcher, L. N.; Orton, G. S.; Tice, D.; Hurley, J.; Calcutt, S. B.

    2011-11-01

    Observations of Neptune were made in September 2009 with the Gemini-North Telescope in Hawaii, using the NIFS instrument in the H-band covering the wavelength range 1.477-1.803 μm. Observations were acquired in adaptive optics mode and have a spatial resolution of approximately 0.15-0.25″. The observations were analysed with a multiple-scattering retrieval algorithm to determine the opacity of clouds at different levels in Neptune's atmosphere. We find that the observed spectra at all locations are very well fit with a model that has two thin cloud layers, one at a pressure level of ˜2 bar all over the planet and an upper cloud whose pressure level varies from 0.02 to 0.08 bar in the bright mid-latitude region at 20-40°S to as deep as 0.2 bar near the equator. The opacity of the upper cloud is found to vary greatly with position, but the opacity of the lower cloud deck appears remarkably uniform, except for localised bright spots near 60°S and a possible slight clearing near the equator. A limb-darkening analysis of the observations suggests that the single-scattering albedo of the upper cloud particles varies from ˜0.4 in regions of low overall albedo to close to 1.0 in bright regions, while the lower cloud is consistent with particles that have a single-scattering albedo of ˜0.75 at this wavelength, similar to the value determined for the main cloud deck in Uranus' atmosphere. The Henyey-Greenstein scattering particle asymmetry of particles in the upper cloud deck are found to be in the range g ˜ 0.6-0.7 (i.e. reasonably strongly forward scattering). Numerous bright clouds are seen near Neptune's south pole at a range of pressure levels and at latitudes between 60 and 70°S. Discrete clouds were seen at the pressure level of the main cloud deck (˜2 bar) at 60°S on three of the six nights observed. Assuming they are the same feature we estimate the rotation rate at this latitude and pressure to be 13.2 ± 0.1 h. However, the observations are not

  5. HST WFC3 Observations of Uranus' 2014 Storm Clouds and Comparison with VLT/SINFONI and IRTF/Spex Observations

    Science.gov (United States)

    Irwin, Patrick G. J.; Wong, Michael H.; Simon, Amy A.; Orton, G. S.; Toledo, Daniel

    2017-01-01

    In November 2014 Uranus was observed with the Wide Field Camera 3 (WFC3) instrument of the Hubble Space Telescope as part of the Hubble 2020: Outer Planet Atmospheres Legacy program, OPAL. OPAL annually maps Jupiter, Uranus and Neptune (and will also map Saturn from 2018) in several visible near- infrared wavelength filters. The Uranus 2014 OPAL observations were made on the 89th November at a time when a huge cloud complex, first observed by de Pater et al. (2015) and subsequently tracked by professional and amateur astronomers (Sayanagi et al., 2016), was present at 30-40deg N. We imaged the entire visible atmosphere, including the storm system, in seven filters spanning 467924 nm, capturing variations in the coloration of Uranus clouds and also vertical distribution due to wavelength dependent changes in Rayleigh scattering and methane absorption optical depth. Here we analyse these new HST observations with the NEMESIS radiative-transfer and retrieval code in multiple-scattering mode to determine the vertical cloud structure in and around the storm cloud system. The same storm system was also observed in the H-band (1.4-1.8 micrometers) with the SINFONI Integral Field Unit Spectrometer on the Very Large Telescope (VLT) on 31st October and 11th November, reported by Irwin et al. (2016, 10.1016j.icarus.2015.09.010). To constrain better the cloud particle sizes and scattering properties over a wide wavelength range we also conducted a limb-darkening analysis of the background cloud structure in the 30-40deg N latitude band by simultaneously fitting: a) these HSTOPAL observations at a range of zenith angles; b) the VLTSINFONI observations at a range of zenith angles; and c) IRTFSpeX observations of this latitude band made in 2009 at a single zenith angle of 23deg, spanning the wavelength range 0.8-1.8 micrometers (Irwin et al., 2015, 10.1016j.icarus.2014.12.020). We find that the HST observations, and the combined HSTVLTIRTF observations at all locations are well

  6. Case study of the 9 April 2009 ‘brown’ cloud: Observations of usually high cloud droplet concentrations in Saudi Arabia

    Science.gov (United States)

    Delene, D. J.

    2009-12-01

    Cloud droplets nucleate on aerosol particles termed cloud condensation nuclei (CCN). It is well known that a larger number concentration of CCN results in a larger number concentration of droplets in developing cumulus clouds. However, the conditions where dust particles can serve as cloud condensation nuclei (CCN) and hence change cloud droplet concentration and precipitation formation processes is uncertain. Aircraft measurements of cloud droplet concentration between 13:20 and 13:30 UTC during the 9 April 2009 flight near Riyadh, Saudi Arabia, show total cloud droplet concentration (3-50 µm in diameter) of 800 to 1200 #/cm-3 at a altitude of 18000 ft. Typical cloud droplet concentration for this type of cloud in the Riyadh region is approximately 400 #/cm-3 and is typical of observation made between 13:00 and 13:20 UTC during the 9 April 2009 flight at 18,000 ft. Photographs of ice accumulation on the unprotected leading edge of the aircraft’s wing due to the freezing of super cooled droplets show a color changed from white during the time of low droplet number condensation to brown during the high droplet number concentration. It is hypothesized that high droplet number concentration observations were the result of ingestion of a large about of dust particles by the cloud. : Case Study of the 9 April 2009 ‘Brown’ Cloud: Observations of Usually High Cloud Droplet Concentrations in Saudi Arabia.

  7. Observations of regional and local variability in the optical properties of maritime clouds

    Energy Technology Data Exchange (ETDEWEB)

    White, A.B. [Univ. of Colorado at Boulder/National Oceanic and Atmospheric Administration, Boulder, CO (United States); Fairall, C.W. [Environmental Technology Lab., Boulder, CO (United States)

    1996-04-01

    White and Fairall (1995) calculated the optical properties of the marine boundary layer (MBL) clouds observed during the Atlantic Stratocumulus Transition Experiment (ASTEX) and compared their results with the results obtained by Fairall et al. for the MBL clouds observed during the First International Satellite Climatology Program (ISSCP) Regional Experiment (FIRE). They found a factor of two difference in the optical depth versus liquid water relationship that applies to the clouds observed in each case. In the present study, we present evidence to support this difference. We also investigate the local variability exhibited in the ASTEX optical properties using measurements of the boundary layer aerosol concentration.

  8. Observations of H2O maser sources in Orion-Monoceros Molecular Clouds with VERA

    CERN Document Server

    Hirota, T

    2004-01-01

    We present results of phase-referencing VLBI observations of water maser sources in Orion-Monoceros Molecular Clouds with VERA (VLBI Exploration of Radio Astrometry), which is newly constructed Japanese VLBI network. Main topics of this poster are (1) the aim of one of the first scientific projects for VERA "3-Dimensional Structure and Kinematics of Orion-Monoceros Molecular Cloud Complex"; (2) current status (sensitivity and astrometric accuracy) of phase-referencing VLBI observations with VERA; and (3) results of VLBI observations of water sources in Orion-Monoceros Molecular Clouds with VERA.

  9. A 35-GHz Polarimetric Doppler Radar and Its Application for Observing Clouds Associated with Typhoon Nuri

    Institute of Scientific and Technical Information of China (English)

    ZHONG Lingzhi; LIU Liping; FENG Sheng; GE Runsheng; ZHANG Zhe

    2011-01-01

    Millimeter-wavelength radar has proved to be an effective instrument for cloud observation and research.In this study, 8-mm-wavelength cloud radar (MMCR) with Doppler and polarization capabilities was used to investigate cloud dynamics in China for the first time. Its design, system specifications, calibration,and application in measuring clouds associated with typhoon are discussed in this article. The cloud radar measurements of radar refiectivity (Z), Doppler velocity (Vr), velocity spectrum width (Sw) and the depolarization ratio (LDR) at vertical incidence were used to analyze the microphysical and dynamic processes of the cloud system and precipitation associated with Typhoon Nuri, which occurred in southern China in August 2008. The results show the refiectivity observed using MMCR to be consistent with the echo height and the melting-layer location data obtained by the nearby China S-band new-generation weather radar (SA),but the Ka-band MMCR provided more detailed structural information about clouds and weak precipitation data than did the SA radar. The variation of radar refiectivity and LDR in vertical structure reveals the transformation of particle phase from ice to water. The vertical velocity and velocity spectrum width of MMCR observations indicate an updraft and strong turbulence in the stratiform cloud layer. MMCR provides a valuable new technology for meteorological research in China.

  10. Observations of sulfur dioxide uptake and new particle formation in a midlatitude cumulus cloud

    Science.gov (United States)

    Peter, J. R.; Siems, S. T.; Jensen, J. B.; Gras, J. L.; Ishizaka, Y.; Hacker, J. M.

    2006-08-01

    Airborne measurements, obtained during the Asian Aerosol Characterisation Experiment (ACE-Asia), of SO2 and condensation nuclei (CN) concentrations were made in the local environment of a cumulus cloud band. Conserved quantities, wet equivalent potential temperature θq, and total water content Q, were used to identify the sources of air detrained on the downwind side of the cumulus band. It was found that ~65% of the detrained air originated from below cloud base and the remainder was air that had been entrained from the free troposphere upwind of the cloud and subsequently been detrained. Calculation of the sources of the detrained air parcels enabled a prediction of the concentration of SO2 and CN, assuming that SO2 and CN experienced no processing within cloud. A comparison of the predicted concentration of SO2 and CN was made with those observed. The concentration of SO2 observed was less than predicted and the amount of SO2 scavenged within cloud was calculated. The CN concentration observed was also less than predicted and, moreover, inclusion of the loss of CN to cloud droplets due to Brownian scavenging resulted in an enhanced decrease of the number concentration of CN predicted. Clear air regions around the cloud exhibited no indication of being a major source of new particles. It was concluded that new particles were formed within cloud.

  11. Observations of mesospheric CO2 and H2O clouds on Mars

    CERN Document Server

    Vincendon, Mathieu; Gondet, Brigitte; Murchie, Scott; Bibring, Jean-Pierre

    2011-01-01

    Carbon dioxide clouds, which are predicted by models on solar and extra-solar planets, have been discovered near the equator of Mars. The most comprehensive identification of Martian CO2 ice clouds has been obtained by the near-IR imaging spectrometer OMEGA. CRISM, a similar instrument with a higher spatial resolution, cannot detect these clouds with the same method due to its shorter wavelength range. Here we present a new method to detect CO2 clouds using near-IR data based on the comparison of H2O and CO2 ice spectral properties. The spatial and seasonal distributions of about 50 CRISM observations containing CO2 clouds are reported, in addition to new OMEGA observations. These clouds are characterized by grain size in the 0.5-2 micrometer range and optical depths between 0.1 and 0.3. The distributions of CO2 clouds inferred from OMEGA and CRISM are consistent with each other and match at first order the distribution of high altitude clouds. At second order, discrepancies are observed. We report the identi...

  12. Understanding and Improving CRM and GCM Simulations of Cloud Systems with ARM Observations

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiaoqing

    2014-02-25

    The works supported by this ASR project lay the solid foundation for improving the parameterization of convection and clouds in the NCAR CCSM and the climate simulations. We have made a significant use of CRM simulations and ARM observations to produce thermodynamically and dynamically consistent multi-year cloud and radiative properties; improve the GCM simulations of convection, clouds and radiative heating rate and fluxes using the ARM observations and CRM simulations; and understand the seasonal and annual variation of cloud systems and their impacts on climate mean state and variability. We conducted multi-year simulations over the ARM SGP site using the CRM with multi-year ARM forcing data. The statistics of cloud and radiative properties from the long-term CRM simulations were compared and validated with the ARM measurements and value added products (VAP). We evaluated the multi-year climate simulations produced by the GCM with the modified convection scheme. We used multi-year ARM observations and CRM simulations to validate and further improve the trigger condition and revised closure assumption in NCAR GCM simulations that demonstrate the improvement of climate mean state and variability. We combined the improved convection scheme with the mosaic treatment of subgrid cloud distributions in the radiation scheme of the GCM. The mosaic treatment of cloud distributions has been implemented in the GCM with the original convection scheme and enables the use of more realistic cloud amounts as well as cloud water contents in producing net radiative fluxes closer to observations. A physics-based latent heat (LH) retrieval algorithm was developed by parameterizing the physical linkages of observed hydrometeor profiles of cloud and precipitation to the major processes related to the phase change of atmospheric water.

  13. Simultaneous radar and aircraft observations of mixed-phase cloud at the 100-m-scale

    Science.gov (United States)

    Field, P.; Hogan, R.; Brown, P.; Illingworth, A.; Choularton, T.; Kaye, P.; Hirst, E.; Greenaway, R.

    2003-04-01

    Determination of cloud phase is important for predicting the radiative impact of clouds. Previous work by some of the authors has shown that even the presence of thin (~100 m) supercooled liquid layers above and below ice cloud significantly increase the reflection of solar radiation to space. We present 100-m-scale in situ and simultaneous radar observations of mixed-phase clouds over the UK. Particle sphericity, as determined by the aircraft mounted Small Ice Detector, appears to be a good indication of phase in these types of cloud where any newly produced ice will quickly grow in highly ice supersaturated conditions into non-spherical particles. During 1-d aircraft transects the dominant phase of the cloud was determined in contiguous 100 m horizontal segments. The resulting structure reveals that mixed-phase clouds can exhibit alternating regions of ice and liquid of varying horizontal scale that may be the result of the 1-d transect of the aircraft intercepting undulating liquid layers or turbulent activity. High differential reflectivity signals measured by the radar can be indicative of the nearby presence of liquid water giving rise to highly ice saturated conditions conducive to the growth of pristine crystals with high axial ratios. Although this is the case for discrete cloud layers it is not always true within a deep frontal cloud.

  14. 3D modeling of GJ1214b's atmosphere: formation of inhomogeneous high clouds and observational implications

    CERN Document Server

    Charnay, Benjamin; Misra, Amit; Leconte, Jérémy; Arney, Giada

    2015-01-01

    The warm sub-Neptune GJ1214b has a featureless transit spectrum which may be due to the presence of high and thick clouds or haze. Here, we simulate the atmosphere of GJ1214b with a 3D General Circulation Model for cloudy hydrogen-dominated atmospheres, including cloud radiative effects. We show that the atmospheric circulation is strong enough to transport micrometric cloud particles to the upper atmosphere and generally leads to a minimum of cloud at the equator. By scattering stellar light, clouds increase the planetary albedo to 0.4-0.6 and cool the atmosphere below 1 mbar. However, the heating by ZnS clouds leads to the formation of a stratospheric thermal inversion above 10 mbar, with temperatures potentially high enough on the dayside to evaporate KCl clouds. We show that flat transit spectra consistent with HST observations are possible if cloud particle radii are around 0.5 micron, and that such clouds should be optically thin at wavelengths > 3 microns. Using simulated cloudy atmospheres that fit th...

  15. Microphysical Properties of Single and Mixed-Phase Arctic Clouds Derived from AERI Observations

    Energy Technology Data Exchange (ETDEWEB)

    Turner, David D. [Univ. of Wisconsin, Madison, WI (United States)

    2003-06-01

    A novel new approach to retrieve cloud microphysical properties from mixed-phase clouds is presented. This algorithm retrieves cloud optical depth, ice fraction, and the effective size of the water and ice particles from ground-based, high-resolution infrared radiance observations. The theoretical basis is that the absorption coefficient of ice is stronger than that of liquid water from 10-13 mm, whereas liquid water is more absorbing than ice from 16-25 um. However, due to strong absorption in the rotational water vapor absorption band, the 16-25 um spectral region becomes opaque for significant water vapor burdens (i.e., for precipitable water vapor amounts over approximately 1 cm). The Arctic is characterized by its dry and cold atmosphere, as well as a preponderance of mixed-phase clouds, and thus this approach is applicable to Arctic clouds. Since this approach uses infrared observations, cloud properties are retrieved at night and during the long polar wintertime period. The analysis of the cloud properties retrieved during a 7 month period during the Surface Heat Budget of the Arctic (SHEBA) experiment demonstrates many interesting features. These results show a dependence of the optical depth on cloud phase, differences in the mode radius of the water droplets in liquid-only and mid-phase clouds, a lack of temperature dependence in the ice fraction for temperatures above 240 K, seasonal trends in the optical depth with the clouds being thinner in winter and becoming more optically thick in the late spring, and a seasonal trend in the effective size of the water droplets in liquid-only and mixed-phase clouds that is most likely related to aerosol concentration.

  16. Statistical Assessment of Shapes and Magnetic Field Orientations in Molecular Clouds through Polarization Observations

    CERN Document Server

    Tassis, K; Hildebrand, R H; Kirby, L; Vaillancourt, J E

    2009-01-01

    We present a novel statistical analysis aimed at deriving the intrinsic shapes and magnetic field orientations of molecular clouds using dust emission and polarization observations by the Hertz polarimeter. Our observables are the aspect ratio of the projected plane-of-the-sky cloud image, and the angle between the mean direction of the plane-of-the-sky component of the magnetic field and the short axis of the cloud image. To overcome projection effects due to the unknown orientation of the line-of-sight, we combine observations from 24 clouds, assuming that line-of-sight orientations are random and all are equally probable. Through a weighted least-squares analysis, we find that the best-fit intrinsic cloud shape describing our sample is an oblate disk with only small degrees of triaxiality. The best-fit intrinsic magnetic field orientation is close to the direction of the shortest cloud axis, with small (~24 deg) deviations toward the long/middle cloud axes. However, due to the small number of observed clou...

  17. Improving Convection and Cloud Parameterization Using ARM Observations and NCAR Community Atmosphere Model CAM5

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guang J. [Univ. of California, San Diego, CA (United States)

    2016-11-07

    The fundamental scientific objectives of our research are to use ARM observations and the NCAR CAM5 to understand the large-scale control on convection, and to develop improved convection and cloud parameterizations for use in GCMs.

  18. Cirrus cloud-temperature interactions over a tropical station, Gadanki from lidar and satellite observations

    Energy Technology Data Exchange (ETDEWEB)

    S, Motty G, E-mail: mottygs@gmail.com; Satyanarayana, M., E-mail: mottygs@gmail.com; Krishnakumar, V., E-mail: mottygs@gmail.com; Dhaman, Reji k., E-mail: mottygs@gmail.com [Department of Optoelectronics, University of Kerala, Kariavattom, Trivandrum-695 581, Kerala (India)

    2014-10-15

    The cirrus clouds play an important role in the radiation budget of the earth's atmospheric system and are important to characterize their vertical structure and optical properties. LIDAR measurements are obtained from the tropical station Gadanki (13.5{sup 0} N, 79.2{sup 0} E), India, and meteorological indicators derived from Radiosonde data. Most of the cirrus clouds are observed near to the tropopause, which substantiates the strength of the tropical convective processes. The height and temperature dependencies of cloud height, optical depth, and depolarization ratio were investigated. Cirrus observations made using CALIPSO satellite are compared with lidar data for systematic statistical study of cirrus climatology.

  19. Airplane investigation of a case of convective cloud bands over the North Sea

    Science.gov (United States)

    Martin, T.; Bakan, S.

    1991-09-01

    During the experiment KONTROL 1985, an interesting case of prefrontal, nonprecipitating cloud bands parallel to the front at distances of about 25 km was observed over the North Sea. Spectral analysis of high frequency airplane measurements is discussed, putting special emphasis on the significance of the resulting spectral signals. A smaller scale roll circulation of a few kilometers wavelength mainly below cloud base could be inferred from these data. The rolls transport momentum downwards, but heat and moisture upwards into the cloud layer where transport is taken over by individual cloud elements. In addition, reasons for the existence, spacing and orientation of the larger scale cloud bands are discussed.

  20. Observational Insights into the Factors that Modulate Aerosol Impacts on Warm Clouds

    Science.gov (United States)

    L'Ecuyer, T. S.

    2016-12-01

    A large number of modern satellite datasets provide complementary evidence of aerosol influences on the microphysical, macrophysical, and radiative properties of warm clouds. This presentation will demonstrate that these observations are now sufficiently mature and abundant to qualitatively distinguish a wide range of independent, robust aerosol signatures from transient effects that may be artifacts of the methodology or datasets adopted. In some cases, modeled and observed aerosol influences on cloud properties diverge to such a degree that we can identify model biases with some confidence. More generally, however, quantitative relationships derived from satellite datasets are subject to numerous sources of uncertainty owing to inaccurate retrieval methodologies, a lack of knowledge of aerosol nucleation rate, and the strong covariation of cloud properties, aerosol abundance, and environmental conditions. To establish the significance of new observationally-derived estimates of aerosol effects we will examine their sensitivity to uncertainties in observed aerosol and cloud properties, the source of aerosol proxy adopted, local environmental conditions, and the relative vertical placement of cloud and aerosol layers. The analysis reveals that while some aerosol signatures are robust, others depend on the specific choice of datasets employed or fail to exceed realistic noise levels imposed by uncertainties in current satellite products. For example, many relationships that are robust in specific regions at certain times of year are not universal globally. Common to all observed relationships is the fact that aerosol signatures exhibit profound sensitivity to local meteorology and cloud morphology reinforcing the notion that aerosol-cloud interactions vary significantly between scenes, even over relatively large time and space domains. The results caution against the use of universal relationships to represent aerosol-cloud interactions globally but provide a

  1. RACORO Extended-Term Aircraft Observations of Boundary-Layer Clouds

    Energy Technology Data Exchange (ETDEWEB)

    Vogelmann, A. M.; McFarquhar, Greg; Ogren, John A.; Turner, David D.; Comstock, Jennifer M.; Feingold, G.; Long, Charles N.; Jonsson, Haf; Bucholtz, Anthony; Collins, Donald R.; Diskin, G. S.; Gerber, H.; Lawson, Paul; Woods, Roy; Andrews, Elizabeth; Yang, Hee-Jung; Chiu, Christine J.; Hartsock, Daniel; Hubbe, John M.; Lo, Chaomei; Marshak, A.; Monroe, Justin; McFarlane, Sally A.; Schmid, Beat; Tomlinson, Jason M.; Toto, Tami

    2012-06-30

    A first-of-a-kind, extended-term cloud aircraft campaign was conducted to obtain an in-situ statistical characterization of boundary-layer clouds needed to investigate cloud processes and refine retrieval algorithms. Coordinated by the Atmospheric Radiation Measurement (ARM) Aerial Facility (AAF), the Routine AAF Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) field campaign operated over the ARM Southern Great Plains (SGP) site from 22 January to 30 June 2009, collecting 260 h of data during 59 research flights. A comprehensive payload aboard the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft measured cloud microphysics, solar and thermal radiation, aerosol properties, and atmospheric state parameters. Proximity to the SGP's extensive complement of surface measurements provides ancillary data that supports modeling studies and enables evaluating a variety of surface retrieval algorithms. The five-month duration enabled sampling a range of conditions associated with the seasonal transition from winter to summer. Although about two-thirds of the cloud flights occurred in May and June, boundary-layer cloud fields were sampled under a variety of environmental and aerosol conditions, with about 75% of the flights occurring in cumulus and stratocumulus. Preliminary analyses show how these data are being used to analyze cloud-aerosol relationships, determine the aerosol sizes that are responsible for nucleating cloud drops, characterize the horizontal variability of the cloud radiative impacts, and evaluate air-borne and surface-based cloud property retrievals. We discuss how conducting an extended-term campaign requires a simplified operating paradigm that is different from that used for typical, short-term, intensive aircraft field programs.

  2. Observing molecular hydrogen clouds and dark massive objects in galactic halos

    OpenAIRE

    F. De Paolis(University of Lecce and INFN, Lecce, Italy); Ingrosso, G.; Jetzer, Ph.; Quadir, A.; Roncadelli, M.

    1995-01-01

    Molecular hydrogen clouds can contribute substantially to the galactic halo< dark matter and may lead to the birth of massive halo objects (MHOs) observed indirectly by microlensing. We present a method to detect these molecular clouds in the halo of M31 using the Doppler shift effect. We also consider the possibility to directly observe MHOs in the halo of M31 via their infrared emission.

  3. Analysis of high altitude clouds in the martian atmosphere based on Mars Climate Sounder observations

    Science.gov (United States)

    Puspitarini, L.; Määttänen, A.; Fouchet, T.; Kleinboehl, A.; Kass, D. M.; Schofield, J. T.

    2016-11-01

    High altitude clouds have been observed in the Martian atmosphere. However, their properties still remain to be characterized. Mars Climate Sounder (MCS) aboard Mars Reconnaissance Orbiter (MRO) is an instrument that measures radiances in the thermal infrared, both in limb and nadir views. It allows us to retrieve vertical profiles of radiance, temperature and aerosols. Using the MCS data and radiative transfer model coupled with an automated inversion routine, we can investigate the chemical composition of the high altitude clouds. We will present the first results on the properties of the clouds. CO2 ice is the best candidate to be the main component of some high altitude clouds due to the most similar spectral variation compared to water ice or dust, in agreement with previous studies. Using cloud composition of contaminated CO2 ice (dust core surrounded by CO2 ice) might improve the fitting result, but further study is needed.

  4. Understanding Seasonal Variability in thin Cirrus Clouds from Continuous MPLNET Observations at GSFC in 2012

    Directory of Open Access Journals (Sweden)

    Lolli Simone

    2016-01-01

    Full Text Available Optically thin cirrus cloud (optical depth < 0.3 net radiative forcing represents one of the primary uncertainties in climate feedback, as sub-visible clouds play a fundamental role in atmospheric radiation balance and climate change. A lidar is a very sensitive optical device to detect clouds with an optical depth as low as 10−4. In this paper we assess the daytime net radiative forcing of subvisible cirrus clouds detected at Goddard Space Flight Center, a permanent observational site of the NASA Micro Pulse Lidar Network in 2012. Depending on their height, season and hour of the day, the solar albedo effect can outweigh the infrared greenhouse effect, cooling the earthatmosphere system rather than warming it exclusively. As result, based on latitude, the net forcing of sub-visible cirrus clouds can be more accurately parameterized in climate models.

  5. Constraining cloud lifetime effects of aerosols using A-Train satellite observations

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Minghuai; Ghan, Steven J.; Liu, Xiaohong; Ecuyer, Tristan L.; Zhang, Kai; Morrison, H.; Ovchinnikov, Mikhail; Easter, Richard C.; Marchand, Roger; Chand, Duli; Qian, Yun; Penner, Joyce E.

    2012-08-15

    Aerosol indirect effects have remained the largest uncertainty in estimates of the radiative forcing of past and future climate change. Observational constraints on cloud lifetime effects are particularly challenging since it is difficult to separate aerosol effects from meteorological influences. Here we use three global climate models, including a multi-scale aerosol-climate model PNNL-MMF, to show that the dependence of the probability of precipitation on aerosol loading, termed the precipitation frequency susceptibility (S{sub pop}), is a good measure of the liquid water path response to aerosol perturbation ({lambda}), as both Spop and {lambda} strongly depend on the magnitude of autoconversion, a model representation of precipitation formation via collisions among cloud droplets. This provides a method to use satellite observations to constrain cloud lifetime effects in global climate models. S{sub pop} in marine clouds estimated from CloudSat, MODIS and AMSR-E observations is substantially lower than that from global climate models and suggests a liquid water path increase of less than 5% from doubled cloud condensation nuclei concentrations. This implies a substantially smaller impact on shortwave cloud radiative forcing (SWCF) over ocean due to aerosol indirect effects than simulated by current global climate models (a reduction by one-third for one of the conventional aerosol-climate models). Further work is needed to quantify the uncertainties in satellite-derived estimates of S{sub pop} and to examine S{sub pop} in high-resolution models.

  6. Long-term Behaviour Of Venus Winds At Cloud Level From Virtis/vex Observations

    Science.gov (United States)

    Hueso, Ricardo; Peralta, J.; Sánchez-Lavega, A.; Pérez-Hoyos, S.; Piccioni, G.; Drossart, P.

    2009-09-01

    The Venus Express (VEX) mission has been in orbit to Venus for more than three years now. The VIRTIS instrument onboard VEX observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. Images in the ultraviolet range are used to study the upper cloud at 66 km while images in the infrared (1.74 μm) map the opacity of the lower cloud deck at 48 km. Here we present an analysis of the overall dynamics of Venus’ atmosphere at both levels using observations that cover a large fraction of the VIRTIS dataset. We will present our latest results concerning the zonal winds, the overall stability in the lower cloud deck motions and the variability in the upper cloud. Meridional winds are also observed in the upper and lower cloud in the UV and IR images obtained with VIRTIS. While the upper clouds present a net meridional motion consistent with the upper branch of a Hadley cell the lower cloud present more irregular, variable and less intense motions in the meridional direction. Acknowledgements This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07. RH acknowledges a "Ramón y Cajal” contract from MEC.

  7. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    Science.gov (United States)

    Pistone, Kristina; Praveen, Puppala S.; Thomas, Rick M.; Ramanathan, Veerabhadran; Wilcox, Eric M.; Bender, Frida A.-M.

    2017-04-01

    There are multiple factors which affect the micro- and macrophysical properties of clouds, including the atmospheric vertical structure and dominant meteorological conditions in addition to aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood. As bio- and fossil fuel combustion has increased in southeast Asia, corresponding increases in atmospheric aerosol pollution have been seen over the surrounding regions. These emissions notably include black carbon (BC) aerosols, which absorb rather than reflect solar radiation, affecting the atmosphere over the Indian Ocean through direct warming in addition to modifying cloud microphysical properties. The CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment) field campaign was conducted during the winter monsoon season (February and March) of 2012 in the northern Indian Ocean, a region dominated by trade cumulus clouds. During CARDEX, small unmanned aircraft were deployed, measuring aerosol, radiation, cloud, water vapor fluxes, and meteorological properties while a surface observatory collected continuous measurements of atmospheric precipitable water vapor (PWV), water vapor fluxes, surface and total-column aerosol, and cloud liquid water path (LWP). We present observations which indicate a positive correlation between aerosol and cloud LWP only when considering cases with low atmospheric water vapor (PWV)

  8. October Cloud Increases Over the Arctic Ocean as Observed by MISR and CALIPSO

    Science.gov (United States)

    Wu, Dong L.; Lee, Jae N.

    2011-01-01

    The Beaufort and East Siberian Sea (BESS) shows a large increase in surface air temperature (SAT) in the recent decade for months of Sep-Nov, and NASA's Terra satellite have provided valuable measurements for this important decade of the intensified Arctic warming. In particular, MISR data since 2000 and CALIPSO cloud measurements since 2006 reveal a significant increase of low cloud cover in October, which is largest in the daylight Arctic months (March-October). Causes of the warming remain unclear; but increased absorption of summer solar radiation and autumn low cloud formation have been suggested as a positive ice-temperature-cloud feedback in the Arctic. The observed increase of low cloud cover supports the theorized positive ice-temperature-cloud feedback, whereby more open water in the Arctic Ocean increases summer absorption of solar radiation, and subsequent evaporation, which leads to more low clouds in autumn. Trapping longwave radiation, these clouds effectively lengthen the melt season and reduce perennial ice pack formation, making sea ice more vulnerable to the next melt season

  9. Subtropical and Polar Cirrus Clouds Characterized by Ground-Based Lidars and CALIPSO/CALIOP Observations

    Directory of Open Access Journals (Sweden)

    Córdoba-Jabonero Carmen

    2016-01-01

    Full Text Available Cirrus clouds are product of weather processes, and then their occurrence and macrophysical/optical properties can vary significantly over different regions of the world. Lidars can provide height-resolved measurements with a relatively good both vertical and temporal resolutions, making them the most suitable instrumentation for high-cloud observations. The aim of this work is to show the potential of lidar observations on Cirrus clouds detection in combination with a recently proposed methodology to retrieve the Cirrus clouds macrophysical and optical features. In this sense, a few case studies of cirrus clouds observed at both subtropical and polar latitudes are examined and compared to CALIPSO/CALIOP observations. Lidar measurements are carried out in two stations: the Metropolitan city of Sao Paulo (MSP, Brazil, 23.3°S 46.4°W, located at subtropical latitudes, and the Belgrano II base (BEL, Argentina, 78ºS 35ºW in the Antarctic continent. Optical (COD-cloud optical depth and LR-Lidar Ratio and macrophysical (top/base heights and thickness properties of both the subtropical and polar cirrus clouds are reported. In general, subtropical Cirrus clouds present lower LR values and are found at higher altitudes than those detected at polar latitudes. In general, Cirrus clouds are detected at similar altitudes by CALIOP. However, a poor agreement is achieved in the LR retrieved between ground-based lidars and space-borne CALIOP measurements, likely due to the use of a fixed (or low-variable LR value in CALIOP inversion procedures.

  10. Subtropical and Polar Cirrus Clouds Characterized by Ground-Based Lidars and CALIPSO/CALIOP Observations

    Science.gov (United States)

    Córdoba-Jabonero, Carmen; Lopes, Fabio J. S.; Landulfo, Eduardo; Ochoa, Héctor; Gil-Ojeda, Manuel

    2016-06-01

    Cirrus clouds are product of weather processes, and then their occurrence and macrophysical/optical properties can vary significantly over different regions of the world. Lidars can provide height-resolved measurements with a relatively good both vertical and temporal resolutions, making them the most suitable instrumentation for high-cloud observations. The aim of this work is to show the potential of lidar observations on Cirrus clouds detection in combination with a recently proposed methodology to retrieve the Cirrus clouds macrophysical and optical features. In this sense, a few case studies of cirrus clouds observed at both subtropical and polar latitudes are examined and compared to CALIPSO/CALIOP observations. Lidar measurements are carried out in two stations: the Metropolitan city of Sao Paulo (MSP, Brazil, 23.3°S 46.4°W), located at subtropical latitudes, and the Belgrano II base (BEL, Argentina, 78ºS 35ºW) in the Antarctic continent. Optical (COD-cloud optical depth and LR-Lidar Ratio) and macrophysical (top/base heights and thickness) properties of both the subtropical and polar cirrus clouds are reported. In general, subtropical Cirrus clouds present lower LR values and are found at higher altitudes than those detected at polar latitudes. In general, Cirrus clouds are detected at similar altitudes by CALIOP. However, a poor agreement is achieved in the LR retrieved between ground-based lidars and space-borne CALIOP measurements, likely due to the use of a fixed (or low-variable) LR value in CALIOP inversion procedures.

  11. Observations of Cloud Top Entrainment Instability Induced by Aircraft Wake Downwash

    Science.gov (United States)

    Walcek, C. J.

    2012-12-01

    Aircraft produce considerable turbulence and generate 20-80 m/s downward velocity impulses immediately below the airframe and wings. This downward-propagating air produces turbulent vortices that descend 100-300 meters before dissipating. If an aircraft flies very close to the tops of stratiform clouds, it can induce mixing between cloudy air and clear air pushed into the cloud from above cloud top. Here we present photographs and evidence that aircraft flying close to the tops of stable stratiform clouds can trigger the release of cloud-top entrainment instability (CTEI). Negatively-buoyant air can be produced as warm air forced into a cloud from above cloud top mixes with colder cloudy air, inducing evaporation and further cooling below the cloud temperature, thus initiating turbulent downdrafts that can propagate the CTEI mechanism that ultimately dissipates and evaporates the top several hundred meters near cloud top. Photographs taken from observation chase planes flying 1-2 km above another aircraft flying very close to cloud top show 50-100 m wide swaths cleared within 3-4 seconds after fly-over, and growth rates of 2-3 m/s lateral to the flight track are observed. Ultimately "canal cloud" or "hole punch" features 2-3 km wide are generated in 20-30 minutes following the flyover from this mechanism. Here the mechanism of aircraft downwash is reviewed, CTEI is described, and evidence of the importance of evaporation and entrainment is provided from unpublished results from the late 1940s-era "project CIRRUS" and more recent images of hole-punch and canal-clouds. Since the propagation of this turbulent process occurs in turbulent filaments of mixtures of clear and cloudy air, modeling this process will require resolutions of less than several meters, yet require simulation domains several 1000s of meters wide. Similarly, measurements of dissipated cloud regions induced by aircraft would require resolutions of several meters or 10s of Hz to unambiguously

  12. Using Roving Cloud Observations from the S'COOL Project to Engage Citizen Scientists

    Science.gov (United States)

    Lewis, P. M.; Oostra, D.; Moore, S. W.; Rogerson, T. M.; Crecelius, S. A.; Chambers, L. H.

    2011-12-01

    Students' Clouds Observations On-Line (S'COOL) is a hands-on project, which supports NASA research on the Earth's climate. Through their observations, participants are engaged in identifying cloud-types and levels and sending that information to NASA. The two main groups of S'COOL observers are permanent locations such as regularly participating classrooms, and non-permanent locations or Rovers. These non-permanent locations can be a field trip, vacation, or just an occasional observation from a backyard. S'COOL welcomes participation from any interested observers, especially from places where official weather observations are few and far between. This program is offered to citizen scientists all over the world. They are participating in climate research by reporting cloud types and levels within +/- 15 minutes of a satellite overpass and sending that information back to NASA. When a participant's cloud observation coincides with a satellite overpass, the project sends them an email with a MODIS image of the overpass location, and a comparison of the satellite's cloud data results next to their ground-based report. This allows for the students and citizen scientists to participate in ground-truthing the CERES satellite data, to determine the level of agreement/disagreement. A new tool slated for future use in cloud identification, developed by the S'COOL team, is a mobile application. The application is entitled "Cloud Identification for Students" or "CITRUS". The mobile application utilizes a cloud dichotomous key with images to help with cloud identification. Also included in the application is a link to the project's cloud-reporting page to help with data submission in the field. One of the project's recent and most unique roving observers is a solo ocean rower who has traversed many of the world's ocean basins alone in a rowboat. While rowing across the oceans, she has recently been making cloud observations, which she sends back to us for analysis. In doing so

  13. Fewer clouds in the Mediterranean: consistency of observations and climate simulations

    Science.gov (United States)

    Sanchez-Lorenzo, Arturo; Enriquez-Alonso, Aaron; Calbó, Josep; González, Josep-Abel; Wild, Martin; Folini, Doris; Norris, Joel R.; Vicente-Serrano, Sergio M.

    2017-02-01

    Clouds play a major role in the climate system, but large uncertainties remain about their decadal variations. Here we report a widespread decrease in cloud cover since the 1970 s over the Mediterranean region, in particular during the 1970 s–1980 s, especially in the central and eastern areas and during springtime. Confidence in these findings is high due to the good agreement between the interannual variations of cloud cover provided by surface observations and several satellite-derived and reanalysis products, although some discrepancies exist in their trends. Climate model simulations of the historical experiment from the Coupled Model Intercomparison Project Phase 5 (CMIP5) also exhibit a decrease in cloud cover over the Mediterranean since the 1970 s, in agreement with surface observations, although the rate of decrease is slightly lower. The observed northward expansion of the Hadley cell is discussed as a possible cause of detected trends.

  14. Evaluation of Cloud-Resolving Model Intercomparison Simulations Using TWP-ICE Observations: Precipitation and Cloud Structure

    Energy Technology Data Exchange (ETDEWEB)

    Varble, Adam C.; Fridlind, Ann; Zipser, Ed; Ackerman, Andrew; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; McFarlane, Sally A.; Pinty, Jean-Pierre; Shipway, Ben

    2011-06-24

    The Tropical Warm Pool - International Cloud Experiment (TWP-ICE) provided high quality model forcing and observational datasets through which detailed model and observational intercomparisons could be performed. In this first of a two part study, precipitation and cloud structures within nine cloud-resolving model simulations are compared with scanning radar reflectivity and satellite infrared brightness temperature observations during an active monsoon period from 19 to 25 January 2006. Most simulations slightly overestimate volumetric convective rainfall. Overestimation of simulated convective area by 50% or more in several simulations is somewhat offset by underestimation of mean convective rain rates. Stratiform volumetric rainfall is underestimated by 13% to 53% despite overestimation of stratiform area by up to 65% because stratiform rain rates in every simulation are much lower than observed. Although simulations match the peaked convective radar reflectivity distribution at low levels, they do not reproduce the peaked distributions observed above the melting level. Simulated radar reflectivity aloft in convective regions is too high in most simulations. 29 In stratiform regions, there is a large spread in model results with none resembling 30 observed distributions. Above the melting level, observed radar reflectivity decreases 31 more gradually with height than simulated radar reflectivity. A few simulations produce 32 unrealistically uniform and cold 10.8-μm infrared brightness temperatures, but several 33 simulations produce distributions close to observed. Assumed ice particle size 34 distributions appear to play a larger role than ice water contents in producing incorrect 35 simulated radar reflectivity distributions aloft despite substantial differences in mean 36 graupel and snow water contents across models. 37

  15. Evaluation of Cloud-Resolving Model Intercomparison Simulations Using TWP-ICE Observations: Precipitation and Cloud Structure

    Energy Technology Data Exchange (ETDEWEB)

    Varble, Adam; Fridlind, Ann; Zipser, Edward J.; Ackerman, Andrew; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; McFarlane, Sally A.; Pinty, Jean-Pierre; Shipway, Ben

    2011-10-04

    The Tropical Warm Pool – International Cloud Experiment (TWP-ICE) provided high quality model forcing and observational datasets through which detailed model and observational intercomparisons could be performed. In this first of a two part study, precipitation and cloud structures within nine cloud-resolving model simulations are compared with scanning radar reflectivity and satellite infrared brightness temperature observations during an active monsoon period from 19 to 25 January 2006. Most simulations slightly overestimate volumetric convective rainfall. Overestimation of simulated convective area by 50% or more in several simulations is somewhat offset by underestimation of mean convective rain rates. Stratiform volumetric rainfall is underestimated by 13% to 53% despite overestimation of stratiform area by up to 65% because stratiform rain rates in every simulation are much lower than observed. Although simulations match the peaked convective radar reflectivity distribution at low levels, they do not reproduce the peaked distributions observed above the melting level. Simulated radar reflectivity aloft in convective regions is too high in most simulations. In stratiform regions, there is a large spread in model results with none resembling observed distributions. Above the melting level, observed radar reflectivity decreases more gradually with height than simulated radar reflectivity. A few simulations produce unrealistically uniform and cold 10.8-μm infrared brightness temperatures, but several simulations produce distributions close to observed. Assumed ice particle size distributions appear to play a larger role than ice water contents in producing incorrect simulated radar reflectivity distributions aloft despite substantial differences in mean graupel and snow water contents across models.

  16. Discrepancies between observational data and theoretical forecast in single field slow roll inflation

    CERN Document Server

    Amorós, Jaume

    2015-01-01

    The PLANCK collaboration has determined values for the spectral parameters of the CMB radiation, namely the spectral index $n_s$, its running $\\alpha_s$, the running of the running $\\beta_s$, using a growing body of measurements of CMB anisotropies by the Planck satellite and other missions. These values do not follow the hierarchy of sizes predicted by single field, slow roll inflationary theory, and are thus difficult to fit for such inflation models. In this work we present first a study of 49 single field, slow roll inflationary potentials in which we assess the likelyhood of these models fitting the spectral parameters to their currently most accurate determination given by the PLANCK collaboration. We check numerically with a MATLAB program the spectral parameters that each model can yield for a very broad, comprehensive list of possible parameter and field values. The comparison of spectral parameter values supported by the models with their determinations by the PLANCK collaboration leads to the concl...

  17. Analysis of Co-Located MODIS and CALIPSO Observations Near Clouds

    Science.gov (United States)

    Varnai, Tamas; Marshak, Alexander

    2011-01-01

    The purpose of this paper is to help researchers combine data from different satellites and thus gain new insights into two critical yet poorly understood aspects of anthropogenic climate change, aerosol-cloud interactions and aerosol radiative effects, For this, the paper explores whether cloud information from the Aqua satellite's MODIS instrument can help characterize systematic aerosol changes near clouds by refining earlier perceptions of these changes that were based on the CALIPSO satellite's CALIOP instrument. Similar to a radar but using visible and ncar-infrared light, CALIOP sends out laser pulses and provides aerosol and cloud information along a single line that tracks the satellite orbit by measuring the reflection of its pulses. In contrast, MODIS takes images of reflected sunlight and emitted infrared radiation at several wavelengths, and covers wide areas around the satellite track. This paper analyzes a year-long global dataset covering all ice-free oceans, and finds that MODIS can greatly help the interpretation of CALIOP observations, especially by detecting clouds that lie outside the line observed by CALlPSO. The paper also finds that complications such as differences in view direction or clouds drifting in the 72 seconds that elapse between MODIS and CALIOP observations have only a minor impact. The study also finds that MODIS data helps refine but does not qualitatively alter perceptions of the systematic aerosol changes that were detected in earlier studies using only CALIOP data. It then proposes a statistical approach to account for clouds lying outside the CALIOP track even when MODIS cannot as reliably detect low clouds, for example at night or over ice. Finally, the paper finds that, because of variations in cloud amount and type, the typical distance to clouds in maritime clear areas varies with season and location. The overall median distance to clouds in maritime clear areas around 4-5 km. The fact that half of all clear areas is

  18. The effect of sensor resolution on the number of cloud-free observations from space

    Directory of Open Access Journals (Sweden)

    J. M. Krijger

    2006-06-01

    Full Text Available Air quality and surface emission inversions are likely to be focal points for future satellite missions on atmospheric composition. Most important for these applications is sensitivity to the atmospheric composition in the lowest few kilometers of the troposphere. Reduced sensitivity by clouds needs to be minimized. In this study we have quantified the increase in number of useful footprints, i.e. footprints which are sufficient cloud-free, as a function of sensor resolution (footprint area. High resolution (1 km×1 km MODIS TERRA cloud mask observations are aggregated to lower resolutions. Statistics for different thresholds on cloudiness are applied. For each month in 2004 two days of MODIS data are analyzed. Globally the fraction of cloud-free observations drops from 16% at 100 km2 resolution to only 3% at 10 000 km2 if not a single MODIS observation within a footprint is allowed to be cloudy. If up to 5% or 20% of a footprint is allowed to be cloudy, the fraction of cloud-free observations is 9% or 17%, respectively, at 10 000 km2 resolution. The probability of finding cloud-free observations for different sensor resolutions is also quantified as a function of geolocation and season, showing examples over Europe and northern South America.

  19. Aerosol-Precipitation Responses Deduced from Ship tracks as Observed by CloudSat

    Science.gov (United States)

    Christensen, M.; Stephens, G. L.

    2011-12-01

    Ship tracks, produced from the exhaust plumes of ocean going vessels were analyzed using the 94-GHZ cloud profiling radar on the CloudSat satellite to examine the precipitation response of marine stratocumulus to changes in aerosol concentration. Ship tracks provide an ideal laboratory to study this response because the regions of clouds that are heavily contaminated by pollution can be separated from adjacent regions of clouds formed in the clean marine boundary layer. Several hundred ship tracks, coinciding with the radar and lidar observations from CloudSat and Calipso, were identified in MODIS imagery. The results demonstrate that, aerosol plumes from ships tend to decrease the spatial extent of rainfall (rain cover fraction) and intensity compared to the nearby pristine clouds. However, there were a substantial fraction of cases (30%), which exhibited increased rainfall. The sign and strength of the precipitation response was strongly tied to the mesoscale structure of the clouds. When the clouds exhibited closed cellular structures, liquid water amount, rainfall (-63%), and rain cover fraction significantly decreased (-55%). These reductions in rainfall were primarily associated with the decrease in rain cover fraction over the ship track domain. The opposite occurred in the open cell regime. Ship plumes ingested into this regime resulted in deeper, wetter, rainier, and brighter clouds, where rainfall increased by 88% primarily due to changes in intensity and to a lesser extent rain cover fraction. Microphysical changes almost always led to significantly smaller droplet radii in ship tracks, even when precipitation was increased. On the other hand, macrophysical changes (liquid water path) varied in magnitude and sign, and typically followed the direction of the precipitation response. The results presented here underline the need to consider the mesoscale structure of stratocumulus when examining the cloud dynamic response to changes in aerosol concentration.

  20. Combined vertical-velocity observations with Doppler lidar, cloud radar and wind profiler

    Directory of Open Access Journals (Sweden)

    J. Bühl

    2015-01-01

    Full Text Available Case studies of combined vertical-velocity measurements of Doppler lidar, cloud radar and wind profiler are presented. The measurements were taken at the Meteorological Observatory Lindenberg, Germany. Synergistic products are presented that are derived from the vertical-velocity measurements of the three instruments: A comprehensive classification mask of vertically moving atmospheric targets and the terminal fall velocity of water droplets and ice crystals corrected for vertical air motion. It is shown that the measurements of the Doppler lidar can extent the view of the cloud radar and the wind profiler, especially when observing clouds.

  1. Use of A-train satellite observations (CALIPSO-PARASOL) to evaluate tropical cloud properties in the LMDZ5 GCM

    Science.gov (United States)

    Konsta, D.; Dufresne, J.-L.; Chepfer, H.; Idelkadi, A.; Cesana, G.

    2016-08-01

    The evaluation of key cloud properties such as cloud cover, vertical profile and optical depth as well as the analysis of their intercorrelation lead to greater confidence in climate change projections. In addition, the comparison between observations and parameterizations of clouds in climate models is improved by using collocated and instantaneous data of cloud properties. Simultaneous and independent observations of the cloud cover and its three-dimensional structure at high spatial and temporal resolutions are made possible by the new space-borne multi-instruments observations collected with the A-train. The cloud cover and its vertical structure observed by CALIPSO and the visible directional reflectance (a surrogate for the cloud optical depth) observed by PARASOL, are used to evaluate the representation of cloudiness in two versions of the atmospheric component of the IPSL-CM5 climate model (LMDZ5). A model-to-satellite approach, applying the CFMIP Observation Simulation Package (COSP), is used to allow a quantitative comparison between model results and observations. The representation of clouds in the two model versions is first evaluated using monthly mean data. This classical approach reveals biases of different magnitudes in the two model versions. These biases consist of (1) an underestimation of cloud cover associated to an overestimation of cloud optical depth, (2) an underestimation of low- and mid-level tropical clouds and (3) an overestimation of high clouds. The difference in the magnitude of these biases between the two model versions clearly highlights the improvement of the amount of boundary layer clouds, the improvement of the properties of high-level clouds, and the improvement of the simulated mid-level clouds in the tropics in LMDZ5B compared to LMDZ5A, due to the new convective, boundary layer, and cloud parametrizations implemented in LMDZ5B. The correlation between instantaneous cloud properties allows for a process-oriented evaluation

  2. Precipitating Snow Retrievals from Combined Airborne Cloud Radar and Millimeter-Wave Radiometer Observations

    Science.gov (United States)

    Grecu, Mircea; Olson, William S.

    2008-01-01

    An algorithm for retrieving snow over oceans from combined cloud radar and millimeter-wave radiometer observations is developed. The algorithm involves the use of physical models to simulate cloud radar and millimeter-wave radiometer observations from basic atmospheric variables such as hydrometeor content, temperature, and relative humidity profiles and is based on an optimal estimation technique to retrieve these variables from actual observations. A high-resolution simulation of a lake-effect snowstorm by a cloud-resolving model is used to test the algorithm. That is, synthetic observations are generated from the output of the cloud numerical model, and the retrieval algorithm is applied to the synthetic data. The algorithm performance is assessed by comparing the retrievals with the reference variables used in synthesizing the observations. The synthetic observation experiment indicates good performance of the retrieval algorithm. The algorithm is also applied to real observations from the Wakasa Bay field experiment that took place over the Sea of Japan in January and February 2003. The application of the retrieval algorithm to data from the field experiment yields snow estimates that are consistent with both the cloud radar and radiometer observations.

  3. Magnetization of cloud cores and envelopes and other observational consequences of reconnection diffusion

    CERN Document Server

    Lazarian, A; Crutcher, R

    2012-01-01

    Recent observational results for magnetic fields in molecular clouds reviewed by Crutcher (2012) seem to be inconsistent with the predictions of the ambipolar diffusion theory of star formation. These include the measured decrease in mass to flux ratio between envelopes and cores, the failure to detect any self-gravitating magnetically subcritical clouds, the determination of the flat PDF of the total magnetic field strengths implying that there are many clouds with very weak magnetic fields, and the observed scaling $B \\propto \\rho^{2/3}$ that implies gravitational contraction with weak magnetic fields. We consider the problem of magnetic field evolution in turbulent molecular clouds and discuss the process of magnetic field diffusion mediated by magnetic reconnection. For this process that we termed "reconnection diffusion" we provide a simple physical model and explain that this process is inevitable in view of the present day understanding of MHD turbulence. We address the issue of the expected magnetizat...

  4. Evaluation of Cloud-Resolving Model Intercomparison Simulations Using TWP-ICE Observations: Precipitation and Cloud Structure

    Science.gov (United States)

    Varble, Adam; Fridlind, Ann M.; Zipser, Edward J.; Ackerman, Andrew S.; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; McFarlane, Sally A.; Pinty, Jean-Pierre; Shipway, Ben

    2011-01-01

    The Tropical Warm Pool.International Cloud Experiment (TWP ]ICE) provided extensive observational data sets designed to initialize, force, and constrain atmospheric model simulations. In this first of a two ]part study, precipitation and cloud structures within nine cloud ]resolving model simulations are compared with scanning radar reflectivity and satellite infrared brightness temperature observations during an active monsoon period from 19 to 25 January 2006. Seven of nine simulations overestimate convective area by 20% or more leading to general overestimation of convective rainfall. This is balanced by underestimation of stratiform rainfall by 5% to 50% despite overestimation of stratiform area by up to 65% because of a preponderance of very low stratiform rain rates in all simulations. All simulations fail to reproduce observed radar reflectivity distributions above the melting level in convective regions and throughout the troposphere in stratiform regions. Observed precipitation ]sized ice reaches higher altitudes than simulated precipitation ]sized ice despite some simulations that predict lower than observed top ]of ]atmosphere infrared brightness temperatures. For the simulations that overestimate radar reflectivity aloft, graupel is the cause with one ]moment microphysics schemes whereas snow is the cause with two ]moment microphysics schemes. Differences in simulated radar reflectivity are more highly correlated with differences in mass mean melted diameter (Dm) than differences in ice water content. Dm is largely dependent on the mass ]dimension relationship and gamma size distribution parameters such as size intercept (N0) and shape parameter (m). Having variable density, variable N0, or m greater than zero produces radar reflectivities closest to those observed.

  5. Evaluation of Cloud-Resolving Model Intercomparison Simulations Using TWP-ICE Observations: Precipitation and Cloud Structure

    Science.gov (United States)

    Varble, Adam; Fridlind, Ann M.; Zipser, Edward J.; Ackerman, Andrew S.; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; McFarlane, Sally A.; Pinty, Jean-Pierre; Shipway, Ben

    2011-01-01

    The Tropical Warm Pool.International Cloud Experiment (TWP ]ICE) provided extensive observational data sets designed to initialize, force, and constrain atmospheric model simulations. In this first of a two ]part study, precipitation and cloud structures within nine cloud ]resolving model simulations are compared with scanning radar reflectivity and satellite infrared brightness temperature observations during an active monsoon period from 19 to 25 January 2006. Seven of nine simulations overestimate convective area by 20% or more leading to general overestimation of convective rainfall. This is balanced by underestimation of stratiform rainfall by 5% to 50% despite overestimation of stratiform area by up to 65% because of a preponderance of very low stratiform rain rates in all simulations. All simulations fail to reproduce observed radar reflectivity distributions above the melting level in convective regions and throughout the troposphere in stratiform regions. Observed precipitation ]sized ice reaches higher altitudes than simulated precipitation ]sized ice despite some simulations that predict lower than observed top ]of ]atmosphere infrared brightness temperatures. For the simulations that overestimate radar reflectivity aloft, graupel is the cause with one ]moment microphysics schemes whereas snow is the cause with two ]moment microphysics schemes. Differences in simulated radar reflectivity are more highly correlated with differences in mass mean melted diameter (Dm) than differences in ice water content. Dm is largely dependent on the mass ]dimension relationship and gamma size distribution parameters such as size intercept (N0) and shape parameter (m). Having variable density, variable N0, or m greater than zero produces radar reflectivities closest to those observed.

  6. Cloud Structure and Cloud-Radiation Interaction: From Smallest Observable Scales (Less than 10 m) to GCM Grid Scales (More than 100 km)

    Science.gov (United States)

    Marshak, Alexander; Davis, A. B.; Wiscombe, W. J.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    In this presentation we review the fractal nature of internal cloud structure from cm- to km-scales as captured by in-situ probes during long horizontal penetrations by aircraft. We uncover the non-Poissonian spatial distribution of cloud droplets at submeter scales and confirm scale-invariant behavior for large scales. Based on these structural characteristics, we generate simple fractal cloud models that reproduce statistical scaling properties of real clouds. These stochastic models represent a link between nonlinear science, in general, and cloud-radiation interaction, in particular. Next we run three-dimensional radiative transfer computations on these synthetic fractal clouds and compare the structure of the resulting radiation fields with the known structure of the cloud model and with satellite images of real clouds. The different behaviors observed for small and large-scale variabilities will be discussed in detail. We find that while the large-scale fluctuations of the resulting radiation fields resemble those in the original scale-invariant cloud structure, the radiation at small scales is much smoother than its cloud liquid water counterpart. This violates scale-invariance and produces a scale-break at 0.2-0.5 km that is clearly observed in high-resolution satellite data such as from Landsat. Finally, we show how radiative transfer Green function theory in the photon diffusion limit explains (and predicts) the above phenomena of "radiative smoothing."

  7. Polar stratospheric clouds at the South Pole in 1990: Lidar observations and analysis

    Energy Technology Data Exchange (ETDEWEB)

    Collins, R.L.; Bowman, K.P.; Gardner, C.S. (Univ. of Illinois, Urbana-Champaign (United States))

    1993-01-20

    In December 1989 a Rayleigh/sodium lidar (589 nm) was installed at the Amundsen-Scott South Pole station, and was used to measure stratospheric aerosol, temperature, and mesospheric sodium profiles through October 1990. Observations of stratospheric aerosol and temperature are presented in this paper. Polar stratospheric clouds (PSCs) were first observed in late May at about 20 km. As the lower stratosphere cooled further, PSCs were observed throughout the 12-27 km altitude region, and remained there from mid-June until late August. Observations in early September detected no PSCs above 21 km. An isolated cloud was observed in mid-October. Throughout the winter the clouds had small backscatter ratios (< 10). Observations made at two wavelengths in July show that the clouds are predominately composed of nitric acid trihydrate with associated Angstrom coefficients between 0.2 and 3.7. Comparison of the lidar data and balloon borne frost point measurements in late August indicate that the nitric acid mixing ratio was less than 1.5 ppbv. Observations over periods of several hours show downward motions in the cloud layers similar to the phase progressions of upwardly-propagating gravity waves. The vertical phase velocities of these features ([approx] 4 cm/s) are significantly faster than the expected settling velocities of the cloud particles. Both the backscatter ratio profiles and the radiosonde horizontal wind profiles show 1-4 km vertical structures. This suggests that the kilometer-scale vertical structure of the PSCs is maintained by low frequency gravity waves propagating through the cloud layers. 24 refs., 9 figs., 4 tabs.

  8. Dynamics of molecular clouds: observations, simulations, and NIF experiments

    Science.gov (United States)

    Kane, Jave O.; Martinez, David A.; Pound, Marc W.; Heeter, Robert F.; Casner, Alexis; Mancini, Roberto C.

    2015-02-01

    For over fifteen years astronomers at the University of Maryland and theorists and experimentalists at LLNL have investigated the origin and dynamics of the famous Pillars of the Eagle Nebula, and similar parsec-scale structures at the boundaries of HII regions in molecular hydrogen clouds. Eagle Nebula was selected as one of the National Ignition Facility (NIF) Science programs, and has been awarded four NIF shots to study the cometary model of pillar formation. These experiments require a long-duration drive, 30 ns or longer, to drive deeply nonlinear ablative hydrodynamics. The NIF shots will feature a new long-duration x-ray source prototyped at the Omega EP laser, in which multiple hohlraums are driven with UV light in series for 10 ns each and reradiate the energy as an extended x-ray pulse. The new source will be used to illuminate a science package with directional radiation mimicking a cluster of stars. The scaled Omega EP shots tested whether a multi-hohlraum concept is viable — whether earlier time hohlraums would degrade later time hohlraums by preheat or by ejecting ablated plumes that would deflect the later beams. The Omega EP shots illuminated three 2.8 mm long by 1.4 mm diameter Cu hohlraums for 10 ns each with 4.3 kJ per hohlraum. At NIF each hohlraum will be 4 mm long by 3 mm in diameter and will be driven with 80 kJ per hohlraum.

  9. SPITZER SAGE Observations of Large Magellanic Cloud Planetary Nebulae

    CERN Document Server

    Hora, J L; Ellis, R G; Meixner, M; Blum, R D; Latter, W B; Whitney, B A; Meade, M R; Indebetouw, R; Gordon, K; For, B -Q; Block, M; Misselt, K; Vijh, U; Leitherer, C

    2007-01-01

    We present IRAC and MIPS images and photometry of a sample of previously known planetary nebulae (PNe) from the SAGE survey of the Large Magellanic Cloud (LMC) performed with the Spitzer Space Telescope. Of the 233 known PNe in the survey field, 185 objects were detected in at least two of the IRAC bands, and 161 detected in the MIPS 24 micron images. Color-color and color-magnitude diagrams are presented using several combinations of IRAC, MIPS, and 2MASS magnitudes. The location of an individual PN in the color-color diagrams is seen to depend on the relative contributions of the spectral components which include molecular hydrogen, polycyclic aromatic hydrocarbons (PAHs), infrared forbidden line emission from the ionized gas, warm dust continuum, and emission directly from the central star. The sample of LMC PNe is compared to a number of Galactic PNe and found to not significantly differ in their position in color-color space. We also explore the potential value of IR PNe luminosity functions (LFs) in the...

  10. Observational study of land-surface-cloud-atmosphere coupling on daily timescales

    Directory of Open Access Journals (Sweden)

    Alan K Betts

    2015-04-01

    Full Text Available Our aim is to provide an observational reference for the evaluation of the surface and boundary layer parameterizations used in large-scale models using the remarkable long-term Canadian Prairie hourly dataset. First we use shortwave and longwave data from the Baseline Surface Radiation Network (BSRN station at Bratt’s Lake, Saskatchewan, and clear sky radiative fluxes from ERA-Interim, to show the coupling between the diurnal cycle of temperature and relative humidity and effective cloud albedo and net longwave flux. Then we calibrate the nearby opaque cloud observations at Regina, Saskatchewan in terms of the BSRN radiation fluxes. We find that in the warm season, we can determine effective cloud albedo to ±0.08 from daytime opaque cloud, and net long-wave radiation to ±8 W/m2 from daily mean opaque cloud and relative humidity. This enables us to extend our analysis to the 55 years of hourly observations of opaque cloud cover, temperature, relative humidity, and daily precipitation from 11 climate stations across the Canadian Prairies. We show the land-surface-atmosphere coupling on daily timescales in summer by stratifying the Prairie data by opaque cloud, relative humidity, surface wind, day-night cloud asymmetry and monthly weighted precipitation anomalies. The multiple linear regression fits relating key diurnal climate variables, the diurnal temperature range, afternoon relative humidity and lifting condensation level, to daily mean net longwave flux, wind-speed and precipitation anomalies have R2 values between 0.61 and 0.69. These fits will be a useful guide for evaluating the fully coupled system in models.

  11. Observational Approach to Molecular Cloud Evolution with the Submillimeter CI Lines

    Science.gov (United States)

    Oka, T.; Yamamoto, S.; Mt. Fuji Submillimeter-Wave Telescope Group

    Neutral carbon atoms (CI) play important role both in chemistry and cooling processes of interstellar molecular clouds. It is thus crucial to explore its large area distribution to investigate formation processes and thermal balance of molecular clouds. We have constructed a 1.2 m submillimeter-wave telescope at the summit of Mt.Fuji. The telescope was designed for the exclusive use of surveying molecular clouds in two submillimeter CI lines, 3P1--3P0 (492 GHz) and 3P2--3P1 (809 GHz), of atomic carbon. It has been operated successfully during 4 observing seasons since July 1998 in a remote way from the Hongo campus of the University of Tokyo. We have already revealed large-scale CI 492 GHz distributions of many giant molecular clouds, including Orion MC, Taurus MC, DR15, DR21, NGC2264, M17, W3, W44, W51, Rosette MC, covering more than 40 square degrees of the sky. The distribution of CI 492 GHz emission is found to be different from those of the 13CO or C18O emission in some clouds. We found the spatial order of C+/CO/C from UV sources. This is the general property of the cloud illuminated by intense UV radiation, whereas it is apparently inconsistent with the standard photodissociation region (PDR) picture. We also found CI-rich areas (C/CO˜1) in several dark clouds without strong UV sources. These results are discussed in relation to formation processes of molecular clouds and dense cloud cores.

  12. Satellite observations of cirrus clouds in the Northern Hemisphere lowermost stratosphere

    Directory of Open Access Journals (Sweden)

    R. Spang

    2014-05-01

    Full Text Available Here we present observations of the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA of cirrus cloud and water vapour in August 1997 in the upper troposphere and lower stratosphere (UTLS region. The observations indicate a considerable flux of moisture from the upper tropical troposphere into the extra-tropical lowermost stratosphere (LMS, resulting in the occurrence of high altitude optically thin cirrus clouds in the LMS. The locations of the LMS cloud events observed by CRISTA are consistent with the tropopause height determined from coinciding radiosonde data. For a hemispheric analysis in tropopause relative coordinates an improved tropopause determination has been applied to the ECMWF temperature profiles. We found that a significant fraction of the cloud occurrences in the tropopause region are located in the LMS, even if a conservative overestimate of the cloud top height (CTH determination by CRISTA of 500 m is assumed. The results show rather high occurrence frequencies (∼5% up to high northern latitudes (70° N and altitudes well above the tropopause (>500 m at ∼350 K and above in large areas at mid and high latitudes. Comparisons with model runs of the Chemical Lagragian Model of the Stratosphere (CLaMS over the CRISTA period show a reasonable consistency for the retrieved cloud pattern. For this purpose a limb ray tracing approach was applied through the 3-D model fields to obtain integrated measurement information through the atmosphere along the limb path of the instrument. The simplified cirrus scheme implemented in CLaMS seems to cause a systematic underestimation in the CTH occurrence frequencies in the LMS with respect to the observations. The observations together with the model results demonstrate the importance of isentropic, quasi-horizontal transport of water vapour from the sub-tropics and the potential for the occurrence of cirrus clouds in the lowermost stratosphere and tropopause region.

  13. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    Directory of Open Access Journals (Sweden)

    K. Pistone

    2015-10-01

    Full Text Available There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood, as changes in atmospheric conditions due to aerosol may change the expected magnitude of indirect effects by altering cloud properties in unexpected ways. Here we describe several observed correlations between aerosol conditions and cloud and atmospheric properties in the Indian Ocean winter monsoon season. In the CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment field campaign conducted in February and March 2012 in the northern Indian Ocean, continuous measurements of atmospheric precipitable water vapor and the liquid water path (LWP of trade cumulus clouds were made, concurrent with measurements of water vapor flux, cloud and aerosol vertical profiles, meteorological data, and surface and total-column aerosol. Here we present evidence of a positive correlation between aerosol and cloud LWP which becomes clear after the data are filtered to control for the natural meteorological variability in the region. We then use the aircraft and ground observatory measurements to explore the mechanisms behind the observed aerosol–LWP correlation. We determine that increased boundary-layer humidity lowering the cloud base is responsible for the observed increase in cloud liquid water. Large-scale analysis indicates that high pollution cases originate with a highly-polluted boundary layer air mass approaching the observatory from a northwesterly direction. This polluted mass exhibits higher temperatures and humidity than the clean case, the former of which may be attributable to heating due to aerosol absorption of solar radiation over the subcontinent. While high temperature conditions dispersed along

  14. Combined observational and modeling efforts of aerosol-cloud-precipitation interactions over Southeast Asia

    Science.gov (United States)

    Loftus, Adrian; Tsay, Si-Chee; Nguyen, Xuan Anh

    2016-04-01

    droplet size and number concentration, but also the spectral width of the cloud droplet size distribution, the 3M scheme is well suited to simulate aerosol-cloud-precipitation interactions within a three-dimensional regional cloud model. Moreover, the additional variability predicted on the hydrometeor distributions provides beneficial input for forward models to link the simulated microphysical processes with observations as well as to assess both ground-based and satellite retrieval methods. In this presentation, we provide an overview of the 7 South East Asian Studies / Biomass-burning Aerosols and Stratocumulus Environment: Lifecycles and Interactions Experiment (7-SEAS/BASELInE) operations during the spring of 2013. Preliminary analyses of pre-monsoon Sc system lifecycles observed during the first-ever deployment of a ground-based cloud radar to northern Vietnam will be also be presented. Initial results from GCE model simulations of these Sc using double-moment and the new 3M bulk microphysics schemes under various aerosol loadings will be used to showcase the 3M scheme as well as provide insight into how the impact of aerosols on cloud and precipitation processes in stratocumulus over land may manifest themselves in simulated remote-sensing signals. Applications and future work involving ongoing 7-SEAS campaigns aimed at improving our understanding of aerosol-cloud-precipitation interactions of will also be discussed.

  15. Evaluation of a Cloud Resolving Model Using TRMM Observations for Multiscale Modeling Applications

    Science.gov (United States)

    Posselt, Derek J.; L'Ecuyer, Tristan; Tao, Wei-Kuo; Hou, Arthur Y.; Stephens, Graeme L.

    2007-01-01

    The climate change simulation community is moving toward use of global cloud resolving models (CRMs), however, current computational resources are not sufficient to run global CRMs over the hundreds of years necessary to produce climate change estimates. As an intermediate step between conventional general circulation models (GCMs) and global CRMs, many climate analysis centers are embedding a CRM in each grid cell of a conventional GCM. These Multiscale Modeling Frameworks (MMFs) represent a theoretical advance over the use of conventional GCM cloud and convection parameterizations, but have been shown to exhibit an overproduction of precipitation in the tropics during the northern hemisphere summer. In this study, simulations of clouds, precipitation, and radiation over the South China Sea using the CRM component of the NASA Goddard MMF are evaluated using retrievals derived from the instruments aboard the Tropical Rainfall Measuring Mission (TRMM) satellite platform for a 46-day time period that spans 5 May - 20 June 1998. The NASA Goddard Cumulus Ensemble (GCE) model is forced with observed largescale forcing derived from soundings taken during the intensive observing period of the South China Sea Monsoon Experiment. It is found that the GCE configuration used in the NASA Goddard MMF responds too vigorously to the imposed large-scale forcing, accumulating too much moisture and producing too much cloud cover during convective phases, and overdrying the atmosphere and suppressing clouds during monsoon break periods. Sensitivity experiments reveal that changes to ice cloud microphysical parameters have a relatively large effect on simulated clouds, precipitation, and radiation, while changes to grid spacing and domain length have little effect on simulation results. The results motivate a more detailed and quantitative exploration of the sources and magnitude of the uncertainty associated with specified cloud microphysical parameters in the CRM components of MMFs.

  16. Detection of global tropospheric clouds and polar stratospheric clouds over Antarctica using thermal infrared spectral data observed by TANSO-FTS/GOSAT

    Science.gov (United States)

    Someya, Yu; Imasu, Ryoichi; Ota, Yoshifumi; Saitoh, Naoko

    2014-05-01

    Global tropospheric cloud distribution was derived from thermal infrared band data observed by Thermal And Near infrared Sensor for carbon Observation - Fourier Transform Spectrometer (TANSO-FTS) onboard Greenhouse gases Observation SATellite (GOSAT). It is expected that this band has ability to detect optically thin clouds compared with Cloud and Aerosol Imager (CAI) which is the other sensor on GOSAT. In addition, polar stratospheric clouds (PSCs) which can be harder to detect than the tropospheric clouds because of high reflectivity or low temperature of the surface and their low optical thickness were also detected. We have modified CO2 slicing method which was developed as one of the cirrus cloud detection techniques using thermal infrared band data to detect thin clouds more stably. The pseudo spectral channels were defined as sets of several actual spectral channels between 700cm-1 and 750cm-1 which have weighting function peak height in a same height range for each 0.5km. These pseudo channels were optimized with simulation studies using a multi-scattering radiative transfer code, Polarized radiance System for Transfer of Atmospheric Radiation (Pstar) 3 for several temperature profile patterns prepared based on latitudes and temperature at 500hPa. GOSAT data was analyzed with the combination of these pseudo channels determined for each of observation points from these simulations and the results were compared with the observational results from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) / Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The comparisons about global cloud are based on the coincident observations in 2010. Monthly occurrences of Antarctic PSCs were compared for each grid area from June to September in 2010. As a result, the correlation coefficients in each month are 0.76, 0.71, 0.75, and 0.61 relatively. Though that is low value in September, it can be explained by decrease of occurrences.

  17. User Observed Estimates of Cloud Fraction for Modifying a Cloud-free UV Index for Use in an Educational Smart-phone Application on Erythema

    Science.gov (United States)

    Lantz, K. O.; Long, C. S.; Buller, D.; Berwick, M.; Buller, M.; Kane, I.; Shane, J.

    2012-12-01

    The UV Index (UVI) is a measure of the skin-damaging UV radiation levels at the Earth's surface. Clouds, haze, air pollution, total ozone, surface elevation, and ground reflectivity affect the levels of UV radiation reaching the ground. The global UV Index was developed as a simple tool to educate the public for taking precautions when exposed to UV radiation to avoid sun-burning, which has been linked to the development of skin cancer. The purpose of this study was to validate an algorithm to modify a cloud-free UV Index forecast for cloud conditions as observed by adults in real-time. The cloud attenuation algorithm is used in a smart-phone application to modify a clear-sky UV Index forecast. In the United States, the Climate Prediction Center of the National Oceanic and Atmospheric Administration's (NOAA) issues a daily UV Index Forecast. The NOAA UV Index is an hourly forecast for a 0.5 x 0.5 degree area and thus has a degree of uncertainty. Cloud cover varies temporally and spatially over short times and distances as weather conditions change and can have a large impact on the UV radiation. The smart-phone application uses the cloud-based UV Index forecast as the default but allows the user to modify a cloud-free UV Index forecast when the predicted sky conditions do not match observed conditions. Eighty four (n=84) adults were recruited to participate in the study through advertisements posted online and in a university e-newsletter. Adults were screened for eligibility (i.e., 18 or older, capable to traveling to test site, had a smart phone with a data plan to access online observation form). A sky observation measure was created to assess cloud fraction. The adult volunteers selected from among four photographs the image that best matched the cloud conditions they observed. Images depicted no clouds (clear sky), thin high clouds, partly cloudy sky, and thick clouds (sky completely overcast). When thin high clouds or partly cloudy images were selected

  18. A study of cloud microphysics and precipitation over the Tibetan Plateau by radar observations and cloud-resolving model simulations: Cloud Microphysics over Tibetan Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Wenhua [State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing China; Pacific Northwest National Laboratory, Richland Washington USA; Sui, Chung-Hsiung [Department of Atmospheric Sciences, National Taiwan University, Taipei Taiwan; Fan, Jiwen [Pacific Northwest National Laboratory, Richland Washington USA; Hu, Zhiqun [State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing China; Zhong, Lingzhi [State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing China

    2016-11-27

    Cloud microphysical properties and precipitation over the Tibetan Plateau (TP) are unique because of the high terrains, clean atmosphere, and sufficient water vapor. With dual-polarization precipitation radar and cloud radar measurements during the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-III), the simulated microphysics and precipitation by the Weather Research and Forecasting model (WRF) with the Chinese Academy of Meteorological Sciences (CAMS) microphysics and other microphysical schemes are investigated through a typical plateau rainfall event on 22 July 2014. Results show that the WRF-CAMS simulation reasonably reproduces the spatial distribution of 24-h accumulated precipitation, but has limitations in simulating time evolution of precipitation rates. The model-calculated polarimetric radar variables have biases as well, suggesting bias in modeled hydrometeor types. The raindrop sizes in convective region are larger than those in stratiform region indicated by the small intercept of raindrop size distribution in the former. The sensitivity experiments show that precipitation processes are sensitive to the changes of warm rain processes in condensation and nucleated droplet size (but less sensitive to evaporation process). Increasing droplet condensation produces the best area-averaged rain rate during weak convection period compared with the observation, suggesting a considerable bias in thermodynamics in the baseline simulation. Increasing the initial cloud droplet size causes the rain rate reduced by half, an opposite effect to that of increasing droplet condensation.

  19. Analysis of aerosol effects on warm clouds over the Yangtze River Delta from multi-sensor satellite observations

    Science.gov (United States)

    Liu, Yuqin; de Leeuw, Gerrit; Kerminen, Veli-Matti; Zhang, Jiahua; Zhou, Putian; Nie, Wei; Qi, Ximeng; Hong, Juan; Wang, Yonghong; Ding, Aijun; Guo, Huadong; Krüger, Olaf; Kulmala, Markku; Petäjä, Tuukka

    2017-05-01

    Aerosol effects on low warm clouds over the Yangtze River Delta (YRD, eastern China) are examined using co-located MODIS, CALIOP and CloudSat observations. By taking the vertical locations of aerosol and cloud layers into account, we use simultaneously observed aerosol and cloud data to investigate relationships between cloud properties and the amount of aerosol particles (using aerosol optical depth, AOD, as a proxy). Also, we investigate the impact of aerosol types on the variation of cloud properties with AOD. Finally, we explore how meteorological conditions affect these relationships using ERA-Interim reanalysis data. This study shows that the relation between cloud properties and AOD depends on the aerosol abundance, with a different behaviour for low and high AOD (i.e. AOD 0.35). This applies to cloud droplet effective radius (CDR) and cloud fraction (CF), but not to cloud optical thickness (COT) and cloud top pressure (CTP). COT is found to decrease when AOD increases, which may be due to radiative effects and retrieval artefacts caused by absorbing aerosol. Conversely, CTP tends to increase with elevated AOD, indicating that the aerosol is not always prone to expand the vertical extension. It also shows that the COT-CDR and CWP (cloud liquid water path)-CDR relationships are not unique, but affected by atmospheric aerosol loading. Furthermore, separation of cases with either polluted dust or smoke aerosol shows that aerosol-cloud interaction (ACI) is stronger for clouds mixed with smoke aerosol than for clouds mixed with dust, which is ascribed to the higher absorption efficiency of smoke than dust. The variation of cloud properties with AOD is analysed for various relative humidity and boundary layer thermodynamic and dynamic conditions, showing that high relative humidity favours larger cloud droplet particles and increases cloud formation, irrespective of vertical or horizontal level. Stable atmospheric conditions enhance cloud cover horizontally

  20. Engaging observers to look at clouds from both sides: connecting NASA mission science with authentic STEM experiences

    Science.gov (United States)

    Chambers, L. H.; Taylor, J.; Ellis, T. D.; McCrea, S.; Rogerson, T. M.; Falcon, P.

    2016-12-01

    In 1997, NASA's Clouds and the Earth's Radiant Energy System (CERES) team began engaging K-12 schools as ground truth observers of clouds. CERES seeks to understand cloud effects on Earth's energy budget; thus accurate detection and characterization of clouds is key. While satellite remote sensing provides global information about clouds, it is limited in time and resolution. Ground observers, on the other hand, can observe clouds at any time of day (and sometimes night), and can see small and thin clouds that are challenging to detect from space. In 2006, two active sensing satellites, CloudSat and CALIPSO, were launched into the A-Train, which already contained 2 CERES instruments on the Aqua spacecraft. The CloudSat team also engaged K-12 schools to observe clouds, through The GLOBE Program, with a specialized observation protocol customized for the narrow radar swath. While providing valuable data for satellite assessment, these activities also engage participants in accessible, authentic science that gets people outdoors, helps them develop observation skills, and is friendly to all ages. The effort has evolved substantially since 1997, adopting new technology to provide a more compelling experience to citizen observers. Those who report within 15 minutes of the passage of a wide range of satellites (Terra, Aqua, CloudSat, CALIPSO, NPP, as well as a number of geostationary satellites) are sent a satellite image centered on their location and are invited to extend the experience beyond simple observation to include analysis of the two different viewpoints. Over the years these projects have collected large amounts of cloud observations from every continent and ocean basin on Earth. A number of studies have been conducted comparing the ground observations to the satellite results. This presentation will provide an overview of those results and also describe plans for a coordinated, thematic cloud observation and data analysis activity going forward.

  1. Airborne hyperspectral observations of surface and cloud directional reflectivity using a commercial digital camera

    Directory of Open Access Journals (Sweden)

    A. Ehrlich

    2012-04-01

    Full Text Available Spectral radiance measurements by a digital single-lens reflex camera were used to derive the directional reflectivity of clouds and different surfaces in the Arctic. The camera has been calibrated radiometrically and spectrally to provide accurate radiance measurements with high angular resolution. A comparison with spectral radiance measurements with the Spectral Modular Airborne Radiation measurement sysTem (SMART-Albedometer showed an agreement within the uncertainties of both instruments (6% for both. The directional reflectivity in terms of the hemispherical directional reflectance factor (HDRF was obtained for sea ice, ice-free ocean and clouds. The sea ice, with an albedo of ρ = 0.96 (at 530 nm wavelength, showed an almost isotropic HDRF, while sun glint was observed for the ocean HDRF (ρ = 0.12. For the cloud observations with ρ = 0.62, the cloudbow – a backscatter feature typically for scattering by liquid water droplets – was covered by the camera. For measurements above heterogeneous stratocumulus clouds, the required number of images to obtain a mean HDRF that clearly exhibits the cloudbow has been estimated at about 50 images (10 min flight time. A representation of the HDRF as a function of the scattering angle only reduces the image number to about 10 (2 min flight time.

    The measured cloud and ocean HDRF have been compared to radiative transfer simulations. The ocean HDRF simulated with the observed surface wind speed of 9 m s−1 agreed best with the measurements. For the cloud HDRF, the best agreement was obtained by a broad and weak cloudbow simulated with a cloud droplet effective radius of Reff = 4 μm. This value agrees with the particle sizes derived from in situ measurements and retrieved from the spectral radiance of the SMART-Albedometer.

  2. Assessment of CCRS Cloud Detection Algorithm CLEAR Using AVHRR and MODIS Observations

    Science.gov (United States)

    Khlopenkov, K.; Trishchenko, A.

    2005-12-01

    The cloud/clear-sky detection algorithm CLEAR (CLoud Estimation using Aggregated Rating index) has been developed at the Canada Centre for Remote Sensing (CCRS) for the processing of the historical Advanced Very High Resolution Radiometer (AVHRR) observations made from the National Oceanic Atmospheric Administration satellites NOAA-6 to NOAA-17. The algorithm employs observations from 5 AVHRR channels and temperature fields from the North America Regional Reanalysis (NARR). The unique feature of the scene identification algorithm is the incorporation of several tests to produce an aggregated effective cloudiness index. This aggregated index has better reliability than a simple sequence of separate tests and allows for a distinction between the different levels of cloudiness. Other features of the algorithm are the dynamic correction for the sun glint for water pixels, the generation of snow/ice maps for cloud-free and thin-cloud pixels, and the calculation of a cloud shadow mask. The algorithm is implemented to operate for daytime and nighttime scenes during snow-free and snow seasons, over water and land areas. An assessment of the algorithm performance was conducted using supervised cloud/snow classification employing the Maximum Likelihood Classifier (MLC) routine available as a part of the multispectral analysis package of the Geomatica system (PCI Geomatics 2003). Comparison has been done for 12 scenes that covered Canada and US mid-latitude and polar regions and represented various seasons. Comparison showed very good consistency between automated processing using CLEAR scheme and the results of supervised classification. The agreement in the cloud detection was in the range of 89 percent to 91 percent for the summer scenes and around 84 percent to 88 percent for the winter. The consistency in the snow identification varied from 86 percent in winter to 94 percent during the warm season. The CLEAR algorithm has been also tuned to MODIS channels and applied for

  3. Analysis of Observation Data of Earth-Rockfill Dam Based on Cloud Probability Distribution Density Algorithm

    Directory of Open Access Journals (Sweden)

    Han Liwei

    2014-07-01

    Full Text Available Monitoring data on an earth-rockfill dam constitutes a form of spatial data. Such data include much uncertainty owing to the limitation of measurement information, material parameters, load, geometry size, initial conditions, boundary conditions and the calculation model. So the cloud probability density of the monitoring data must be addressed. In this paper, the cloud theory model was used to address the uncertainty transition between the qualitative concept and the quantitative description. Then an improved algorithm of cloud probability distribution density based on a backward cloud generator was proposed. This was used to effectively convert certain parcels of accurate data into concepts which can be described by proper qualitative linguistic values. Such qualitative description was addressed as cloud numerical characteristics-- {Ex, En, He}, which could represent the characteristics of all cloud drops. The algorithm was then applied to analyze the observation data of a piezometric tube in an earth-rockfill dam. And experiment results proved that the proposed algorithm was feasible, through which, we could reveal the changing regularity of piezometric tube’s water level. And the damage of the seepage in the body was able to be found out.

  4. Cloud-radiation-precipitation associations over the Asian monsoon region: an observational analysis

    Science.gov (United States)

    Li, Jiandong; Wang, Wei-Chyung; Dong, Xiquan; Mao, Jiangyu

    2017-01-01

    This study uses 2001-2014 satellite observations and reanalyses to investigate the seasonal characteristics of Cloud Radiative Effects (CREs) and their associations with cloud fraction (CF) and precipitation over the Asian monsoon region (AMR) covering Eastern China (EC) and South Asia (SA). The CREs exhibit strong seasonal variations but show distinctly different relationships with CFs and precipitation over the two regions. For EC, the CREs is dominated by shortwave (SW) cooling, with an annual mean value of - 40 W m- 2 for net CRE, and peak in summer while the presence of extensive and opaque low-level clouds contributes to large Top-Of-Atmosphere (TOA) albedo (>0.5) in winter. For SA, a weak net CRE exists throughout the year due to in-phase compensation of SWCRE by longwave (LW) CRE associated with the frequent occurrence of high clouds. For the entire AMR, SWCRE strongly correlates with the dominant types of CFs, although the cloud vertical structure plays important role particularly in summer. The relationships between CREs and precipitation are stronger in SA than in EC, indicating the dominant effect of monsoon circulation in the former region. SWCRE over EC is only partly related to precipitation and shows distinctive regional variations. Further studies need to pay more attention to vertical distributions of cloud micro- and macro-physical properties, and associated precipitation systems over the AMR.

  5. First observations of volcanic eruption clouds from L1 by DSCOVR/EPIC

    Science.gov (United States)

    Carn, S. A.; Krotkov, N. A.; Taylor, S.; Fisher, B. L.; Li, C.; Hughes, E. J.; Bhartia, P. K.; Prata, F.

    2016-12-01

    Volcanic emissions of sulfur dioxide (SO2) and ash have been measured by ultraviolet (UV) sensors on US and European polar-orbiting satellites since the late 1970s. Although successful, the main limitation of these UV observations from low-Earth orbit has been poor temporal resolution. Timeliness can be crucial when detecting hazardous volcanic eruption clouds that threaten aviation, and most operational geostationary satellites cannot detect SO2, a key tracer of volcanic plumes. In 2015, the launch of the Earth Polychromatic Imaging Camera (EPIC) aboard the Deep Space Climate Observatory (DSCOVR) provided the first opportunity to observe volcanic clouds from the L1 Lagrange point. EPIC is a 10-band spectroradiometer spanning UV to near-IR wavelengths with two UV channels sensitive to SO2, and a ground resolution of 25 km. The unique L1 vantage point provides continuous observations of the sunlit Earth disk, potentially offering multiple daily observations of volcanic SO2 and ash clouds in the EPIC field of view. When coupled with complementary retrievals from polar-orbiting UV and infrared (IR) sensors such as the Ozone Monitoring Instrument (OMI), the Ozone Mapping and Profiler Suite (OMPS), and the Atmospheric Infrared Sounder (AIRS), the increased observation frequency afforded by DSCOVR/EPIC will permit more timely volcanic eruption detection, improved trajectory modeling, and novel analyses of the temporal evolution of volcanic clouds. We demonstrate the sensitivity of EPIC UV radiances to volcanic clouds using examples from the first year of EPIC observations including the December 2015 paroxysmal eruption of Etna volcano (Italy). When combined with OMI and OMPS measurements, the EPIC SO2 data permit hourly tracking of the Etna eruption cloud as it drifts away from the volcano. We also describe ongoing efforts to adapt existing UV backscatter (BUV) algorithms to produce operational EPIC SO2 and Ash Index (AI) products.

  6. Jupiter's Deep Cloud Structure Revealed Using Keck Observations of Spectrally Resolved Line Shapes

    Science.gov (United States)

    Bjoraker, G. L.; Wong, M.H.; de Pater, I.; Adamkovics, M.

    2015-01-01

    Technique: We present a method to determine the pressure at which significant cloud opacity is present between 2 and 6 bars on Jupiter. We use: a) the strength of a Fraunhofer absorption line in a zone to determine the ratio of reflected sunlight to thermal emission, and b) pressure- broadened line profiles of deuterated methane (CH3D) at 4.66 meters to determine the location of clouds. We use radiative transfer models to constrain the altitude region of both the solar and thermal components of Jupiter's 5-meter spectrum. Results: For nearly all latitudes on Jupiter the thermal component is large enough to constrain the deep cloud structure even when upper clouds are present. We find that Hot Spots, belts, and high latitudes have broader line profiles than do zones. Radiative transfer models show that Hot Spots in the North and South Equatorial Belts (NEB, SEB) typically do not have opaque clouds at pressures greater than 2 bars. The South Tropical Zone (STZ) at 32 degrees South has an opaque cloud top between 4 and 5 bars. From thermochemical models this must be a water cloud. We measured the variation of the equivalent width of CH3D with latitude for comparison with Jupiter's belt-zone structure. We also constrained the vertical profile of H2O in an SEB Hot Spot and in the STZ. The Hot Spot is very dry for a probability less than 4.5 bars and then follows the H2O profile observed by the Galileo Probe. The STZ has a saturated H2O profile above its cloud top between 4 and 5 bars.

  7. Observations of cloud and rainfall enhancement over irrigated agriculture in an arid environment

    Science.gov (United States)

    Garcia-Carreras, Luis; Marsham, John H.; Spracklen, Dominick V.

    2017-04-01

    The impact of irrigated agriculture on clouds and rainfall remains uncertain, particularly in less studied arid regions. Irrigated crops account for 20% of global cropland area, and non-renewable groundwater accounts for 20% of global irrigation water demand. Quantifying the feedbacks between agriculture and the atmosphere are therefore not only necessary to better understand the climate impacts of land-use change, but are also crucial for predicting long-term water use in water-scarce regions. Here we use high spatial-resolution satellite data to show the impact of irrigated crops in the arid environment of northern Saudi Arabia on cloud cover and rainfall patterns. Land surface temperatures over the crops are 5-10 K lower than their surroundings, linked to evapotranspiration rates of up to 20 mm/ month. Daytime cloud cover is up to 30% higher over the cropland compared to its immediate surroundings, and this enhancement is highly correlated with the seasonal variability in leaf area index. The cloud enhancement is associated with a much more rapid cloud cloud development during the morning. Afternoon rainfall is 85% higher over, and just downwind, of the cropland during the growing season, although rainfall remains very low in absolute terms. The feedback sign we find is the opposite to what has been observed in tropical and semiarid regions, where temperature gradients promote convergence and clouds on the warmer side of land-surface type discontinuities. This suggests that different processes are responsible for the land-atmosphere feedback in very dry environments, where lack of moisture may be a stronger constraint. Increased cloud and rainfall, and associated increases in diffuse radiation and reductions in temperature, can affect vegetation growth thus producing an internal feedback. These effects will therefore need to be taken into account to properly assess the impact of climate change on crop productivity and water use, as well as how global land

  8. Rotation of a Magnetic Cloud: MESSENGER and STEREO-B Observations

    Science.gov (United States)

    Good, S. W.; Forsyth, R. J.

    2014-12-01

    Magnetic clouds are a magnetically well ordered subset of CMEs observed in interplanetary space. We report observations of the same magnetic cloud made by the MESSENGER spacecraft at Mercury (then at 0.44 AU) and later by STEREO-B at 1.09 AU, while the two spacecraft were radially aligned in November 2011. Observation with two radially aligned spacecraft allows sampling of approximately the same region of a magnetic cloud, and so allows any evolution that may have occurred within that region during propagation between the two spacecraft to be determined. The flux rope within the November 2011 cloud has been analysed using force-free fitting and minimum variance analysis: it has been estimated that the rope axis rotated from an inclination of approximately 25° relative to the solar equatorial plane at MESSENGER to lie within a few degrees of the plane at STEREO-B. We investigate the hypothesis that this rotation and alignment with the solar equatorial plane is driven by interactions of the cloud with the heliospheric current sheet.

  9. Copernicus observations of C I and CO in diffuse interstellar clouds

    Science.gov (United States)

    Jenkins, E. B.; Jura, M.; Loewenstein, M.

    1980-01-01

    Copernicus was used to observe absorption lines of C I in its ground state and excited fine structure levels and CO toward 29 stars. We use the C I data to infer densities and pressures within the observed clouds, and because our results are of higher precision than previous work, much more precise estimates of the physical conditions in clouds are obtained. In agreement with previous work, the interstellar thermal pressure appears to be variable, with most clouds having values of p/k between 1000/cu cm K and 10,000/cu cm K, but there are some clouds with p/k as high as 100,000/cu cm K. Our results are consistent with the view that the interstellar thermal pressure is so variable that the gas undergoes continuous dynamic evolution. Our observations provide useful constraints on the physical processes on the surfaces of grains. In particular, we find that grains are efficient catalysts of interstellar H2 in the sense that at least half of the hydrogen atoms that strike grains come off as part of H2. Results place strong constraints on models for the formation and destruction of interstellar CO. In many clouds, an order of magnitude less CO than predicted in some models was found.

  10. A cloud detection scheme for the Chinese Carbon Dioxide Observation Satellite (TANSAT)

    Science.gov (United States)

    Wang, Xi; Guo, Zheng; Huang, Yipeng; Fan, Hongjie; Li, Wanbiao

    2017-01-01

    Cloud detection is an essential preprocessing step for retrieving carbon dioxide from satellite observations of reflected sunlight. During the pre-launch study of the Chinese Carbon Dioxide Observation Satellite (TANSAT), a cloud-screening scheme was presented for the Cloud and Aerosol Polarization Imager (CAPI), which only performs measurements in five channels located in the visible to near-infrared regions of the spectrum. The scheme for CAPI, based on previous cloudscreening algorithms, defines a method to regroup individual threshold tests for each pixel in a scene according to the derived clear confidence level. This scheme is proven to be more effective for sensors with few channels. The work relies upon the radiance data from the Visible and Infrared Radiometer (VIRR) onboard the Chinese FengYun-3A Polar-orbiting Meteorological Satellite (FY-3A), which uses four wavebands similar to that of CAPI and can serve as a proxy for its measurements. The scheme has been applied to a number of the VIRR scenes over four target areas (desert, snow, ocean, forest) for all seasons. To assess the screening results, comparisons against the cloud-screening product from MODIS are made. The evaluation suggests that the proposed scheme inherits the advantages of schemes described in previous publications and shows improved cloud-screening results. A seasonal analysis reveals that this scheme provides better performance during warmer seasons, except for observations over oceans, where results are much better in colder seasons.

  11. Evaluation of cloud resolving model simulations of midlatitude cirrus with ARM and A-Train observations

    Science.gov (United States)

    Muehlbauer, A. D.; Ackerman, T. P.; Lawson, P.; Xie, S.; Zhang, Y.

    2015-12-01

    This paper evaluates cloud resolving model (CRM) and cloud system-resolving model (CSRM) simulations of a midlatitude cirrus case with comprehensive observations collected under the auspices of the Atmospheric Radiation Measurements (ARM) program and with spaceborne observations from the National Aeronautics and Space Administration (NASA) A-train satellites. Vertical profiles of temperature, relative humidity and wind speeds are reasonably well simulated by the CSRM and CRM but there are remaining biases in the temperature, wind speeds and relative humidity, which can be mitigated through nudging the model simulations toward the observed radiosonde profiles. Simulated vertical velocities are underestimated in all simulations except in the CRM simulations with grid spacings of 500m or finer, which suggests that turbulent vertical air motions in cirrus clouds need to be parameterized in GCMs and in CSRM simulations with horizontal grid spacings on the order of 1km. The simulated ice water content and ice number concentrations agree with the observations in the CSRM but are underestimated in the CRM simulations. The underestimation of ice number concentrations is consistent with the overestimation of radar reflectivity in the CRM simulations and suggests that the model produces too many large ice particles especially toward cloud base. Simulated cloud profiles are rather insensitive to perturbations in the initial conditions or the dimensionality of the model domain but the treatment of the forcing data has a considerable effect on the outcome of the model simulations. Despite considerable progress in observations and microphysical parameterizations, simulating the microphysical, macrophysical and radiative properties of cirrus remains challenging. Comparing model simulations with observations from multiple instruments and observational platforms is important for revealing model deficiencies and for providing rigorous benchmarks. However, there still is considerable

  12. NEW WESTERBORK OBSERVATIONS OF THE HI CLOUD NEAR NGC-4472

    NARCIS (Netherlands)

    HENNING, PA; SANCISI, R; MCNAMARA, BR

    1993-01-01

    The H I gas which hes between the giant Virgo elliptical NGC 4472 and the gas-deficient dwarf irregular UGC 7636 has been observed at high resolution and sensitivity with the Westerbork radio telescope. It is a concentration of gas at a projected distance halfway between the two galaxies, and at an

  13. Evaluating MODIS cloud retrievals with in situ observations from VOCALS-REx

    Directory of Open Access Journals (Sweden)

    N. J. King

    2012-09-01

    Full Text Available Microphysical measurements collected during eleven profiles through marine stratocumulus as part of the Variability of the American Monsoon Systems (VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx are compared to collocated overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS aboard the Aqua and Terra satellite platforms. The full depth of the cloud is sampled in each case using a Cloud Droplet Probe (CDP and a Two-Dimensional Stereo Probe (2DS together sizing cloud and precipitation droplets in the diameter range 2-1260 μm. This allows the total optical depth (τc of the cloud and effective radius (re of the droplet size distribution to be compared to MODIS cloud retrievals of the same quantities along with the secondarily derived total liquid water path. When compared to the effective radius at cloud top, the MODIS retrieved re using the 2.1 μm wavelength channel overestimates the in situ measurements on average by 13% with the largest overestimations coinciding with the detection by the 2DS of drizzle sized droplets. We show through consideration of the full vertical profile and penetration depths of the wavelengths used in the retrieval that the expected retrieved values are less than those at cloud top thus increasing the apparent bias in re retrievals particularly when using the 1.6 and 2.1 μm channels, with the 3.7 μm channel retrievals displaying the best agreement with in situ values. Retrievals of τc also tend to overestimate in situ values which, coupled with a high bias in re retrievals, lead to an overestimation of liquid water path. There is little apparent correlation between the variation of the three near-infrared re retrievals and the vertical structure of the cloud observed in situ. Retrievals are performed using measured profiles of water vapour and

  14. Sensitivity to deliberate sea salt seeding of marine cloudsobservations and model simulations

    Directory of Open Access Journals (Sweden)

    K. Alterskjær

    2011-10-01

    Full Text Available Sea salt seeding of marine clouds to increase their albedo is a proposed technique to counteract or slow global warming. In this study, we first investigate the susceptibility of marine clouds to sea salt injections, using observational data of cloud droplet number concentration, cloud optical depth, and liquid cloud fraction from the MODIS (Moderate Resolution Imaging Spectroradiometer instruments on board the Aqua and Terra satellites. We then compare the derived susceptibility function to a corresponding estimate from the Norwegian Earth System Model (NorESM. Results compare well between simulations and observations, showing that stratocumulus regions off the west coast of the major continents along with large regions in the Pacific and the Indian Oceans are susceptible.

    We then carry out geo-engineering experiments with a uniform increase of 10−9 kg m−2 s−1 in emissions of sea salt particles with a modal radius of 0.13 μm. The increased sea salt concentrations and the resulting change in marine cloud properties lead to a globally averaged forcing of −4.8 W m−2 at the top of the atmosphere, more than cancelling a doubling of CO2 concentrations. The forcing is large in areas found to be sensitive by using the susceptibility function, confirming its usefulness as an indicator of where to inject sea salt for maximum effect.

    Results also show that the effectiveness of sea salt seeding is reduced because the injected sea salt provide a large surface area for water vapor and gaseous sulphuric acid to condense on, thereby lowering the maximum supersaturation and suppressing the formation and lifetime of sulphate particles. In some areas, our simulations show an overall reduction in the CCN concentration and the number of activated cloud droplets decreases, resulting in a positive globally averaged forcing.

  15. Morphology of the cloud tops as observed by the Venus Express Monitoring Camera

    Science.gov (United States)

    Titov, Dmitrij V.; Markiewicz, Wojciech J.; Ignatiev, Nikolay I.; Song, Li; Limaye, Sanjay S.; Sanchez-Lavega, Agustin; Hesemann, Jonas; Almeida, Miguel; Roatsch, Thomas; Matz, Klaus-Dieter; Scholten, Frank; Crisp, David; Esposito, Larry W.; Hviid, Stubbe F.; Jaumann, Ralf; Keller, Horst U.; Moissl, Richard

    2012-02-01

    Since the discovery of ultraviolet markings on Venus, their observations have been a powerful tool to study the morphology, motions and dynamical state at the cloud top level. Here we present the results of investigation of the cloud top morphology performed by the Venus Monitoring Camera (VMC) during more than 3 years of the Venus Express mission. The camera acquires images in four narrow-band filters centered at 365, 513, 965 and 1010 nm with spatial resolution from 50 km at apocentre to a few hundred of meters at pericentre. The VMC experiment provides a significant improvement in the Venus imaging as compared to the capabilities of the earlier missions. The camera discovered new cloud features like bright "lace clouds" and cloud columns at the low latitudes, dark polar oval and narrow circular and spiral "grooves" in the polar regions, different types of waves at the high latitudes. The VMC observations revealed detailed structure of the sub-solar region and the afternoon convective wake, the bow-shape features and convective cells, the mid-latitude transition region and the "polar cap". The polar orbit of the satellite enables for the first time nadir viewing of the Southern polar regions and an opportunity to zoom in on the planet. The experiment returned numerous images of the Venus limb and documented global and local brightening events. VMC provided almost continuous monitoring of the planet with high temporal resolution that allowed one to follow changes in the cloud morphology at various scales. We present the in-flight performance of the instrument and focus in particular on the data from the ultraviolet channel, centered at the characteristic wavelength of the unknown UV absorber that yields the highest contrasts on the cloud top. Low latitudes are dominated by relatively dark clouds that have mottled and fragmented appearance clearly indicating convective activity in the sub-solar region. At ˜50° latitude this pattern gives way to streaky clouds

  16. Radiative effects of African dust and smoke observed from Clouds and the Earth's Radiant Energy System (CERES) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data

    Science.gov (United States)

    Yorks, John E.; McGill, Matt; Rodier, Sharon; Vaughan, Mark; Hu, Yongxiang; Hlavka, Dennis

    2009-09-01

    Cloud and aerosol effects have a significant impact on the atmospheric radiation budget in the tropical Atlantic because of the spatial and temporal extent of desert dust and smoke from biomass burning in the atmosphere. The influences of African dust and smoke aerosols on cloud radiative properties over the tropical Atlantic Ocean were analyzed for the month of July for 3 years (2006-2008) using colocated data collected by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Aqua satellites. Aerosol layer height and type can be accurately determined using CALIOP data through directly measured parameters such as optical depth, volume depolarization ratio, attenuated backscatter, and color ratio. On average, clouds below 5 km had a daytime instantaneous shortwave (SW) radiative flux of 270.2 ± 16.9 W/m2 and thin cirrus clouds had a SW radiative flux of 208.0 ± 12.7 W/m2. When dust aerosols interacted with clouds below 5 km, as determined from CALIPSO, the SW radiative flux decreased to 205.4 ± 13.0 W/m2. Similarly, smoke aerosols decreased the SW radiative flux of low clouds to a value of 240.0 ± 16.6 W/m2. These decreases in SW radiative flux were likely attributed to the aerosol layer height and changes in cloud microphysics. CALIOP lidar observations, which more accurately identify aerosol layer height than passive instruments, appear essential for better understanding of cloud-aerosol interactions, a major uncertainty in predicting the climate system.

  17. The Arctic clouds from model simulations and long-term observations at Barrow, Alaska

    Science.gov (United States)

    Zhao, Ming

    The Arctic is a region that is very sensitive to global climate change while also experiencing significant changes in its surface air temperature, sea-ice cover, atmospheric circulation, precipitation, snowfall, biogeochemical cycling, and land surface. Although previous studies have shown that the arctic clouds play an important role in the arctic climate changes, the arctic clouds are poorly understood and simulated in climate model due to limited observations. Furthermore, most of the studies were based on short-term experiments and typically only cover the warm seasons, which do not provide a full understanding of the seasonal cycle of arctic clouds. To address the above concerns and to improve our understanding of arctic clouds, six years of observational and retrieval data from 1999 to 2004 at the Atmospheric Radiation Management (ARM) Climate Research Facility (ACRF) North Slope of Alaska (NSA) Barrow site are used to understand the arctic clouds and related radiative processes. In particular, we focus on the liquid-ice mass partition in the mixed-phase cloud layer. Statistical results show that aerosol type and concentration are important factors that impact the mixed-phase stratus (MPS) cloud microphysical properties: liquid water path (LWP) and liquid water fraction (LWF) decrease with the increase of cloud condensation nuclei (CCN) number concentration; the high dust loading and dust occurrence in the spring are possible reasons for the much lower LWF than the other seasons. The importance of liquid-ice mass partition on surface radiation budgets was analyzed by comparing cloud longwave radiative forcings under the same LWP but different ice water path (IWP) ranges. Results show the ice phase enhance the surface cloud longwave (LW) forcing by 8˜9 W m-2 in the moderately thin MPS. This result provides an observational evidence on the aerosol glaciation effect in the moderately thin MPS, which is largely unknown so far. The above new insights are

  18. Herschel observations of extra-ordinary sources: Detecting spiral arm clouds by CH absorption lines

    CERN Document Server

    Qin, S -L; Comito, C; Möller, T; Rolffs, R; Müller, H S P; Belloche, A; Menten, K M; Lis, D C; Phillips, T G; Bergin, E A; Bell, T A; Crockett, N R; Blake, G A; Cabrit, S; Caux, E; Ceccarelli, C; Cernicharo, J; Daniel, F; Dubernet, M -L; Emprechtinger, M; Encrenaz, P; Falgarone, E; Gerin, M; Giesen, T F; Goicoechea, J R; Goldsmith, P F; Gupta, H; Herbst, E; Joblin, C; Johnstone, D; Langer, W D; Lord, S D; Maret, S; Martin, P G; Melnick, G J; Morris, P; Murphy, J A; Neufeld, D A; Ossenkopf, V; Pagani, L; Pearson, J C; Pérault, M; Plume, R; Salez, M; Schlemmer, S; Stutzki, J; Trappe, N; van der Tak, F F S; Vastel, C; Wang, S; Yorke, H W; Yu, S; Zmuidzinas, J; Boogert, A; Güsten, R; Hartogh, P; Honingh, N; Karpov, A; Kooi, J; Krieg, J M; Schieder, R; Diez-Gonzalez, M C; Bachille, R; Martin-Pintado, J; Baechtold, W; Olberg, M; Nordh, L H; Gill, J L; Chattopadhyay, G

    2010-01-01

    We have observed CH absorption lines ($J=3/2, N=1 \\leftarrow J=1/2, N=1$) against the continuum source Sgr~B2(M) using the \\textit{Herschel}/HIFI instrument. With the high spectral resolution and wide velocity coverage provided by HIFI, 31 CH absorption features with different radial velocities and line widths are detected and identified. The narrower line width and lower column density clouds show `spiral arm' cloud characteristics, while the absorption component with the broadest line width and highest column density corresponds to the gas from the Sgr~B2 envelope. The observations show that each `spiral arm' harbors multiple velocity components, indicating that the clouds are not uniform and that they have internal structure. This line-of-sight through almost the entire Galaxy offers unique possibilities to study the basic chemistry of simple molecules in diffuse clouds, as a variety of different cloud classes are sampled simultaneously. We find that the linear relationship between CH and H$_2$ column dens...

  19. Aerosol indirect effect on warm clouds over South-East Atlantic, from co-located MODIS and CALIPSO observations

    Directory of Open Access Journals (Sweden)

    L. Costantino

    2013-01-01

    Full Text Available In this study, we provide a comprehensive analysis of aerosol interaction with warm boundary layer clouds over the South-East Atlantic. We use aerosol and cloud parameters derived from MODIS observations, together with co-located CALIPSO estimates of the layer altitudes, to derive statistical relationships between aerosol concentration and cloud properties. The CALIPSO products are used to differentiate between cases of mixed cloud-aerosol layers from cases where the aerosol is located well-above the cloud top. This technique allows us to obtain more reliable estimates of the aerosol indirect effect than from simple relationships based on vertically integrated measurements of aerosol and cloud properties. Indeed, it permits us to somewhat distinguish the effects of aerosol and meteorology on the clouds, although it is not possible to fully ascertain the relative contribution of each on the derived statistics.

    Consistently with the results from previous studies, our statistics clearly show that aerosol affects cloud microphysics, decreasing the Cloud Droplet Radius (CDR. The same data indicate a concomitant strong decrease in cloud Liquid Water Path (LWP, which is inconsistent with the hypothesis of aerosol inhibition of precipitation (Albrecht, 1989. We hypothesise that the observed reduction in LWP is the consequence of dry air entrainment at cloud top. The combined effect of CDR decrease and LWP decrease leads to rather small sensitivity of the Cloud Optical Thickness (COT to an increase in aerosol concentration. The analysis of MODIS-CALIPSO coincidences also evidences an aerosol enhancement of low cloud cover. Surprisingly, the Cloud Fraction (CLF response to aerosol invigoration is much stronger when (absorbing particles are located above cloud top than in cases of physical interaction. This result suggests a relevant aerosol radiative effect on low cloud occurrence: absorbing particles above the cloud top may heat the

  20. The impact of European forests on cloud cover: an observation-based study

    Science.gov (United States)

    Teuling, Ryan; Melsen, Lieke; Vila-Guerau de Arellano, Jordi; van Heerwaarden, Chiel; Miralles, Diego; Taylor, Chris; Stegehuis, Annemiek; Fokke Meirink, Jan; Nabuurs, Gert-Jan

    2016-04-01

    The impact of temperate forests on their environment is still uncertain [1]. While forests generally have a lower albedo, the flux partitioning over forests and its relation to weather conditions is still poorly understood [2,3], complicating attempts to study impacts of forest cover on atmospheric conditions through modeling. Effects of land surface conditions on boundary-layer humidity and cloud formation can also be very non-linear [4]. Furthermore, the study of hydrological and climate impacts of temperate European forests is complicated because forests are strongly fragmented and often can be found on hilly terrain, making it impossible to attribute differences in for instance cloud cover or runoff directly to forest cover. Only few regions exist where forests can be found in absence of strong topography of a size large enough to result in near-equilibrium between the atmospheric boundary layer and local surface conditions. In this study, we analyse 10 years (2004-2013) of cloud cover observations from the Meteosat Second Generation satellite platform at a 15-minute temporal resolution. These observations come from a physically-based cloud product at the 6 km resolution [5], and a statistical cloud product based on the high-resolution visible imagery (1 km resolution). We focus on two regions in France where large forests are found which satisfy the following criteria: a) absence of strong topography, and b) presence of sharp contrast between forest and non-forest regions. Cloud occurrence is expressed by the fraction of the daytime that clouds are detected within a pixel. We find that in particular in summer and late summer, clouds are much more likely to occur over forest than over the surrounding non-forest land (difference in the order of 0.2). An opposite signal, but of much weaker magnitude, is found during springtime, when clouds are less likely to develop over forest. Difference in cloud occurrence is consistent with MODIS-derived differences in EVI

  1. DACCIWA Cloud-Aerosol Observations in West Africa Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, J Christine [Univ. of Reading (United Kingdom); Blanchard, Yann [Univ. of Reading (United Kingdom); Hill, Peter [Univ. of Reading (United Kingdom); Gregory, Laurie [Brookhaven National Lab. (BNL), Upton, NY (United States); Wagener, Richard [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2017-06-15

    Interactions between aerosols and clouds, and their effects on radiation, precipitation, and regional circulations, are one of the largest uncertainties in understanding climate. With reducing uncertainties in predictions of weather, climate, and climate impacts in mind, the Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa (DACCIWA) project, funded by the European Commission, set out to improve our understanding of cloud-aerosol interactions in southern West Africa. This region is ideal for studying cloud-aerosol interactions because of its rich mix of natural and anthropogenic aerosols and diverse clouds, and because of the strong dependence on the regional and global climate of the sensitive West African monsoon. The overview of DACCIWA is described in Knippertz et al. 2015. The interdisciplinary DACCIWA team includes not only several European and African universities, but also Met Centres in the UK, France, Germany, Switzerland, Benin, Ghana, and Nigeria. One of the crucial research activities in DACCIWA is the major field campaign in southern West Africa from June to July 2016, comprising a benchmark data set for assessing detailed processes on natural and anthropogenic emissions; atmospheric composition; air pollution and its impacts on human and ecosystem health; boundary layer processes; couplings between aerosols, clouds, and rainfall; weather systems; radiation; and the monsoon circulation. Details and highlights of the campaign can be found in Flamant et al. 2017. To provide aerosol/cloud microphysical and optical properties that are essential for model evaluations and for the linkage between ground-based, airborne, and spaceborne observations, the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility loaned two sun photometers to the DACCWIA team for the campaign from June 8 to July 29, 2016. The first sun photometer was deployed at Kumasi, Ghana (6.67962°N, 1.56019°W) by the University of Leeds

  2. Evolution in Cloud Population Statistics of the MJO. From AMIE Field Observations to Global-Cloud Permitting Models final report Version 1

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Min [Univ. of Wyoming, Laramie, WY (United States)

    2016-01-08

    Methods of convective/stratiform precipitation classification and surface rain rate estimation based on the Atmospheric Radiation Measurement (ARM) program cloud radar measurements were developed and evaluated. Simultaneous and collocated observations of the Ka-band ARM zenith radar (KAZR), two scanning precipitation radars (NCAR S-PolKa and Texas A&M University SMART-R), and surface precipitation during the DYNAMO/AMIE field campaign were used. The motivation of this study is to apply the unique long-term ARM cloud radar observations without accompanying precipitation radars to the study of cloud lifecycle and precipitation features under different weather and climate regimes.

  3. Radial Evolution of a Magnetic Cloud: MESSENGER, STEREO, and Venus Express Observations

    Science.gov (United States)

    Good, S. W.; Forsyth, R. J.; Raines, J. M.; Gershman, D. J.; Slavin, J. A.; Zurbuchen, T. H.

    2015-07-01

    The Solar Orbiter and Solar Probe Plus missions will provide observations of magnetic clouds closer to the Sun than ever before, and it will be good preparation for these missions to make full use of the most recent in situ data sets from the inner heliosphere—namely, those provided by MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) and Venus Express—for magnetic cloud studies. We present observations of the same magnetic cloud made by MESSENGER at Mercury and later by Solar TErrestrial RElations Observatory-B (STEREO-B), while the spacecraft were radially aligned in 2011 November. Few such radial observations of magnetic clouds have been previously reported. Estimates of the solar wind speed at MESSENGER are also presented, calculated through the application of a previously established technique. The cloud's flux rope has been analyzed using force-free fitting; the rope diameter increased from 0.18 to 0.41 AU (corresponding to an {r}{{H}}0.94 dependence on heliocentric distance, rH), and the axial magnetic field strength dropped from 46.0 to 8.7 nT (an {r}{{H}}-1.84 dependence) between the spacecraft, clear indications of an expanding structure. The axial magnetic flux was ˜0.50 nT AU2 at both spacecraft, suggesting that the rope underwent no significant erosion through magnetic reconnection between MESSENGER and STEREO-B. Further, we estimate the change in the cloud's angular width by assuming helicity conservation. It has also been found that the rope axis rotated by 30° between the spacecraft to lie close to the solar equatorial plane at STEREO-B. Such a rotation, if it is a common feature of coronal mass ejection propagation, would have important implications for space weather forecasting.

  4. Can CFMIP2 models reproduce the leading modes of cloud vertical structure in the CALIPSO-GOCCP observations?

    Science.gov (United States)

    Wang, Fang; Yang, Song

    2017-02-01

    Using principal component (PC) analysis, three leading modes of cloud vertical structure (CVS) are revealed by the GCM-Oriented CALIPSO Cloud Product (GOCCP), i.e. tropical high, subtropical anticyclonic and extratropical cyclonic cloud modes (THCM, SACM and ECCM, respectively). THCM mainly reflect the contrast between tropical high clouds and clouds in middle/high latitudes. SACM is closely associated with middle-high clouds in tropical convective cores, few-cloud regimes in subtropical anticyclonic clouds and stratocumulus over subtropical eastern oceans. ECCM mainly corresponds to clouds along extratropical cyclonic regions. Models of phase 2 of Cloud Feedback Model Intercomparison Project (CFMIP2) well reproduce the THCM, but SACM and ECCM are generally poorly simulated compared to GOCCP. Standardized PCs corresponding to CVS modes are generally captured, whereas original PCs (OPCs) are consistently underestimated (overestimated) for THCM (SACM and ECCM) by CFMIP2 models. The effects of CVS modes on relative cloud radiative forcing (RSCRF/RLCRF) (RSCRF being calculated at the surface while RLCRF at the top of atmosphere) are studied in terms of principal component regression method. Results show that CFMIP2 models tend to overestimate (underestimated or simulate the opposite sign) RSCRF/RLCRF radiative effects (REs) of ECCM (THCM and SACM) in unit global mean OPC compared to observations. These RE biases may be attributed to two factors, one of which is underestimation (overestimation) of low/middle clouds (high clouds) (also known as stronger (weaker) REs in unit low/middle (high) clouds) in simulated global mean cloud profiles, the other is eigenvector biases in CVS modes (especially for SACM and ECCM). It is suggested that much more attention should be paid on improvement of CVS, especially cloud parameterization associated with particular physical processes (e.g. downwelling regimes with the Hadley circulation, extratropical storm tracks and others), which

  5. The Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES): An Observational Campaign for Determining Role of Clouds, Aerosols and Radiation in Climate System

    Science.gov (United States)

    McFarquhar, G. M.; Wood, R.; Bretherton, C. S.; Alexander, S.; Jakob, C.; Marchand, R.; Protat, A.; Quinn, P.; Siems, S. T.; Weller, R. A.

    2014-12-01

    The Southern Ocean (SO) region is one of the cloudiest on Earth, and as such clouds determine its albedo and play a major role in climate. Evidence shows Earth's climate sensitivity and the Intertropical Convergence Zone location depend upon SO clouds. But, climate models are challenged by uncertainties and biases in the simulation of clouds, aerosols, and air-sea exchanges in this region which trace back to a poor process-level understanding. Due to the SO's remote location, there have been sparse observations of clouds, aerosols, precipitation, radiation and the air-sea interface apart from those from satellites. Plans for an upcoming observational program, SOCRATES, are outlined. Based on feedback on observational and modeling requirements from a 2014 workshop conducted at the University of Washington, a plan is described for obtaining a comprehensive dataset on the boundary-layer structure and associated vertical distributions of liquid and mixed-phase cloud and aerosol properties across a range of synoptic settings, especially in the cold sector of cyclonic storms. Four science themes are developed: improved climate model simulation of SO cloud and boundary layer structure in a rapidly varying synoptic setting; understanding seasonal and synoptic variability in SO cloud condensation and ice nucleus concentration and the role of local biogenic sources; understanding supercooled liquid and mixed-phase clouds and their impacts; and advancing retrievals of clouds, precipitation, aerosols, radiation and surface fluxes. Testable hypotheses for each theme are identified. The observational strategy consists of long-term ground-based observations from Macquarie Island and Davis, continuous data collection onboard Antarctic supply ships, satellite retrievals, and a dedicated field campaign covering 2 distinct seasons using in-situ and remote sensors on low- and high-altitude aircraft, UAVs, and a ship-borne platform. A timeline for these activities is proposed.

  6. Observation and Schmid factor analysis of multiple twins in a warm-rolled Mg–3Al–1Zn alloy

    DEFF Research Database (Denmark)

    Xin, Renlong; Wang, Maoyin; Huang, Xiaoxu

    2014-01-01

    This study aims to understand the features of twinning that occurred during warm-rolling of Mg–3Al–1Zn alloys. The rolling was performed at 150 °C with the c-axis of most grains nearly parallel to the transverse direction. Electron backscatter diffraction analysis was conducted to examine microst...

  7. WIND observations of plasma waves inside the magnetic cloud boundary layers

    Institute of Scientific and Technical Information of China (English)

    WEI Fengsi; ZHONG Dingkun; FENG Xueshang; YANG Fang; LIU Rui

    2005-01-01

    Based on the WIND observational data for the plasma waves from thermal noise receptor (TNR) working on the frequency 4―256 kHz and the solar wind and the magnetic fields, we analyze the plasma wave activities in the 60 magnetic cloud's boundary layers (BLs) and find that there are often various plasma wave activities in the BLs, which are different from those in the adjacent solar wind (SW) and the magnetic clouds (MC). The basic characteristics are that: (1) the enhancement of the Langmuir wave near the electronic plasma frequency (fpe) is a dominant wave activity, which occupies 75% investigated samples; (2) the events enhanced both in the langmuir and ion acustic (f < fpe) waves are about 60% of investigated samples; (3) broadband, continuous enhancement events in the plasma wave activities were observed in the whole frequency band of TNR, and about 30% of the 60 samples, however, were not observed in the SW and the MC investigated events; (4) although the ratio of the temperatures between the electon and proton, Te/Tp≤1, the ion caustic wave enhancement activities are still often observed in the BLs, which makes it difficult to ex-plain them by the traditional plasma theory. New results reported in this paper further show that the magnetic cloud's BL is an important dynamic structure, which could provide useful diagnosis for understanding the cloud's BL physics and could expand a space developing space plasma wave theory.

  8. Dual wavelength lidar observation of tropical high-altitude cirrus clouds during the ALBATROSS 1996 Campaign

    Science.gov (United States)

    Beyerle, G.; Schäfer, H.-J.; Neuber, R.; Schrems, O.; McDermid, I. S.

    Dual wavelength aerosol lidar observations of tropical high-altitude cirrus clouds were performed during the ALBATROSS 1996 campaign aboard the research vessel “POLARSTERN” on the Atlantic ocean in October-November 1996. On the basis of 57 hours of night-time observations between 23.5°N and 23.5°S we find in 72% of the altitude profiles indications of the presence of cirrus cloud layers. This percentage drops to 32% at subtropical latitudes (23.5°-30°) based on 15 hours of data. About one-half of the subtropical and tropical cirrus layers are subvisual with an optical depth of less than 0.03 at a wavelength of 532 nm. In general the clouds exhibit high spatial and temporal variability on scales of a few tens of meters vertically and a few hundred meters horizontally. No clouds are observed above the tropopause. An abrupt change in the relation between the color ratios of the parallel and perpendicular backscatter coefficients at about 240 K is interpreted in terms of changes of particle shape and/or size distribution. At temperatures between 195 and 255 K only a small fraction of the observations are consistent with the presence of small particles with dimensions of less than 0.1 µm.

  9. Estimating land-surface temperature under clouds using MSG/SEVIRI observations

    NARCIS (Netherlands)

    Lu, L.; Venus, V.; Skidmore, A.K.; Wang, T.; Luo, G.

    2011-01-01

    The retrieval of land-surface temperature (LST) from thermal infrared satellite sensor observations is known to suffer from cloud contamination. Hence few studies focus on LST retrieval under cloudy conditions. In this paper a temporal neighboring-pixel approach is presented that reconstructs the di

  10. Estimating land-surface temperature under clouds using MSG/SEVIRI observations

    NARCIS (Netherlands)

    Lu, L.; Venus, V.; Skidmore, A.K.; Wang, T.; Luo, G.

    2011-01-01

    The retrieval of land-surface temperature (LST) from thermal infrared satellite sensor observations is known to suffer from cloud contamination. Hence few studies focus on LST retrieval under cloudy conditions. In this paper a temporal neighboring-pixel approach is presented that reconstructs the

  11. Observational perspectives on cloud-atmosphere-surface coupling at Summit, Greenland

    Science.gov (United States)

    Cox, C. J.; Shupe, M.; Miller, N.; Noone, D.; Berkelhammer, M. B.; Raudzens Bailey, A.; O'Neill, M.; Persson, O. P. G.; Rowe, P. M.; Schneider, D. P.; Steen-Larsen, H. C.; Steffen, K.; Turner, D. D.; Walden, V. P.; White, J. W. C.

    2016-12-01

    The atmosphere modulates the surface mass and energy balances of the Greenland ice sheet, including the temperature of the snow and firn, thus facilitating surface melt. In the absence of clouds, infrared loss at the surface leads to the development of a stably-stratified boundary layer, which weakens turbulent mixing and limits surface mass loss through sublimation. This stable state is eroded by clouds, which are frequently observed throughout the year. Through precipitation clouds are a source of accumulation, but clouds also modify the surface energy budget substantially, providing an overall warming of the surface in all months (33 W m-2 annually) over the central plateau. Thus, variability in cloud cover can drive or facilitate many of the physical processes acting out at and near the surface. Here, recent research on the coupled surface-atmosphere dynamic, radiative, and mass relationships at Summit Station are discussed. The response of the surface energy and mass budgets to forcing caused by varying atmospheric and cloud conditions is quantified and contextualized with other Arctic locations. Some unique features of the Summit environment, such as its high elevation, low humidity, and seasonally persistent snow cover, are found to be important factors in the way that clouds and the atmosphere interact with the surface there compared to elsewhere. This work is supported by a recent critical mass of measurements pertaining to such interactions at Summit. Observations have been made by the Integrated Characterization of Energy, Clouds, Atmospheric state, and Precipitation at Summit (ICECAPS) program since 2010, including twice-daily temperature and humidity profiles from radiosoundings and cloud properties acquired from measurements made by lidar, radar, and passive spectral infrared and microwave radiometers. These measurements complement those of the surface radiation budget and meteorology made by the Swiss Federal Institute of Technology (ETH) and NOAA

  12. Evaluation of long-term surface-retrieved cloud droplet number concentration with in situ aircraft observations: ARM Cloud Droplet Number Concentration

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Kyo-Sun Sunny [Pacific Northwest National Laboratory, Richland Washington USA; Riihimaki, Laura [Pacific Northwest National Laboratory, Richland Washington USA; Comstock, Jennifer M. [Pacific Northwest National Laboratory, Richland Washington USA; Schmid, Beat [Pacific Northwest National Laboratory, Richland Washington USA; Sivaraman, Chitra [Pacific Northwest National Laboratory, Richland Washington USA; Shi, Yan [Pacific Northwest National Laboratory, Richland Washington USA; McFarquhar, Greg M. [Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana Illinois USA

    2016-03-06

    A new cloud-droplet number concentration (NDROP) value added product (VAP) has been produced at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site for the 13 years from January 1998 to January 2011. The retrieval is based on surface radiometer measurements of cloud optical depth from the multi-filter rotating shadow-band radiometer (MFRSR) and liquid water path from the microwave radiometer (MWR). It is only applicable for single-layered warm clouds. Validation with in situ aircraft measurements during the extended-term aircraft field campaign, Routine ARM Aerial Facility (AAF) CLOWD Optical Radiative Observations (RACORO), shows that the NDROP VAP robustly reproduces the primary mode of the in situ measured probability density function (PDF), but produces a too wide distribution, primarily caused by frequent high cloud-droplet number concentration. Our analysis shows that the error in the MWR retrievals at low liquid water paths is one possible reason for this deficiency. Modification through the diagnosed liquid water path from the coordinate solution improves not only the PDF of the NDROP VAP but also the relationship between the cloud-droplet number concentration and cloud-droplet effective radius. Consideration of entrainment effects rather than assuming an adiabatic cloud improves the values of the NDROP retrieval by reducing the magnitude of cloud-droplet number concentration. Aircraft measurements and retrieval comparisons suggest that retrieving the vertical distribution of cloud-droplet number concentration and effective radius is feasible with an improvement of the parameter representing the mixing effects between environment and clouds and with a better understanding of the effect of mixing degree on cloud properties.

  13. Observational evidence for human impact on aerosol cloud-mediated processes in the Baltic region

    Directory of Open Access Journals (Sweden)

    Olaf Krüger

    2014-03-01

    Full Text Available Knowledge about aerosol cloud-mediated processes is important for judging climate change in Europe during recent decades. Here, some observational evidence for anthropogenic influences is described and discussed. The emphasis is laid on the effects of the large emissions of sulphur dioxide and particulate matter during the 1980s in Europe and the subsequent strong decrease in the 1990s. In addition, an analysis of the dependence of aerosol cloud-mediated processes on atmospheric circulation patterns (Grosswetterlagen is presented.

  14. Observational evidence for human impact on aerosol cloud-mediated processes in the Baltic region

    Directory of Open Access Journals (Sweden)

    Olaf Krüger

    2014-01-01

    Full Text Available Knowledge about aerosol cloud-mediated processes is important for judging climate change in Europe during recent decades. Here, some observational evidence for anthropogenic influences is described and discussed. The emphasis is laid on the effects of the large emissions of sulphur dioxide and particulate matter during the 1980s in Europe and the subsequent strong decrease in the 1990s. In addition, an analysis of the dependence of aerosol cloud-mediated processes on atmospheric circulation patterns (Großwetterlagen is presented.

  15. C18O Observations of the Dark Molecular Cloud L134 and Gas Depletion onto Dust

    Institute of Scientific and Technical Information of China (English)

    Xin-Jie Mao; Xiao-Xia Sun

    2005-01-01

    We map the dark molecular cloud core of L134 in the C18O (J =1 -0) emission line using the PMO 13.7m telescope, and present a contour map of integrated intensity of C18O (J = 1 - 0) emission. The C18O cloud is inside the distribution of extinction AB, the visual extinction of blue light, as well as inside the 13CO cloud in the L134 region. The depletion factors in this C18O cloud are generally greater than unity, which means there is gas depletion onto dust. Since only a minimum AB = 9.7 mag is available, and our observations measure both undepleted and depleted regions along the line of sight, the depletion factors could very likely be larger in the central core than the calculated value. So we conclude that depletion does occur in the bulk of the C18O cloud through a comparison between the C18O and blue extinction maps in the L134 region. There is no direct evidence as yet for star formation in L134, and so cores on the verge of collapse will not be visible in CO and other gas molecules.

  16. The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. III. Perseus Observed with IRAC

    CERN Document Server

    Jørgensen, J K; Evans, N J; Huard, T L; Allen, L E; Porras, A; Blake, G A; Bourke, T L; Chapman, N; Cieza, L; Körner, D W; Lai, S P; Mundy, L G; Myers, P C; Padgett, D L; Rebull, L M; Sargent, A I; Spiesman, W; Stapelfeldt, K R; Van Dishoeck, E F; Wahhaj, Z; Young, K E; Jorgensen, Jes K.; Harvey, Paul M.; II, Neal J. Evans; Huard, Tracy L.; Allen, Lori E.; Porras, Alicia; Blake, Geoffrey A.; Bourke, Tyler L.; Chapman, Nicholas; Cieza, Lucas; Koerner, David W.; Lai, Shih-Ping; Mundy, Lee G.; Myers, Philip C.; Padgett, Deborah L.; Rebull, Luisa; Sargent, Anneila I.; Spiesman, William; Stapelfeldt, Karl R.; Dishoeck, Ewine F. van; Wahhaj, Zahed; Young, Kaisa E.

    2006-01-01

    We present observations of 3.86 sq. deg. of the Perseus molecular cloud complex with the Spitzer Space Telescope Infrared Array Camera (IRAC). The maps show strong extended emission arising from shocked H2 in outflows in the region and from polycyclic aromatic hydrocarbon features. More than 120,000 sources are extracted toward the cloud. Based on their IRAC colors and comparison to off-cloud and extragalactic fields, we identify 400 candidate young stellar objects. About two thirds of these are associated with the young clusters IC348 and NGC1333, while the last third is distributed over the remaining cloud. We classify the young stellar objects according to the traditional scheme based on the slope of their spectral energy distributions. Significant differences are found for the numbers of embedded Class I objects relative to more evolved Class II objects in IC348, NGC1333 and the remaining cloud with the embedded Class I and "flat spectrum" YSOs constituting 14%, 36% and 47% of the total number of YSOs ide...

  17. Lidar and Ceilometer Observations and Comparisons of Atmospheric Cloud Structure at Nagqu of Tibetan Plateau in 2014 Summer

    Directory of Open Access Journals (Sweden)

    Xiaoquan Song

    2017-01-01

    Full Text Available In the project of the Third Tibetan Plateau Experiment of Atmospheric Science (TIPEX III, the intensive observation of cloud and precipitation in Nagqu was conducted from 1 July to 31 August 2014. The CL31 ceilometer and a WAter vapor, Cloud and Aerosol Lidar (WACAL were deployed and focused on studying the cloud macroscopic characteristics and vertical distribution. The statistical result of CL31 ceilometer in continuous operation mode shows that the cloud occurrence is about 81% with a majority of simple one-layer cloud. The cloud base and top height are retrieved by improved differential zero-crossing method using lidar data. The results of cloud base height (CBH are compared with CL31 ceilometer, showing a good consistency with each other, however, in some cases, the CL31 ceilometer overestimates the CBH and is also validated by synchronous radiosonde data. The time snippet comparisons of cloud property between CL31 ceilometer and lidar imply that the cloud properties have obvious diurnal variations with “U” shape distribution. The cloud development including the time-spatial distribution features also has distinct diurnal variations based on the lidar measurement. The detection range of lidar goes beyond the maximum height of CL31 ceilometer, offering substantial observations to the analysis of cirrus cloud radiation characteristics and formation mechanism.

  18. Inferring spatial clouds statistics from limited field-of-view, zenith observations

    Energy Technology Data Exchange (ETDEWEB)

    Sun, C.H.; Thorne, L.R. [Sandia National Labs., Livermore, CA (United States)

    1996-04-01

    Many of the Cloud and Radiation Testbed (CART) measurements produce a time series of zenith observations, but spatial averages are often the desired data product. One possible approach to deriving spatial averages from temporal averages is to invoke Taylor`s hypothesis where and when it is valid. Taylor`s hypothesis states that when the turbulence is small compared with the mean flow, the covariance in time is related to the covariance in space by the speed of the mean flow. For clouds fields, Taylor`s hypothesis would apply when the {open_quotes}local{close_quotes} turbulence is small compared with advective flow (mean wind). The objective of this study is to determine under what conditions Taylor`s hypothesis holds or does not hold true for broken cloud fields.

  19. A process oriented characterization of tropical oceanic clouds for climate model evaluation, based on a statistical analysis of daytime A-train observations

    Energy Technology Data Exchange (ETDEWEB)

    Konsta, Dimitra [Ecole Polytechnique, LMD, Palaiseau (France); Academy of Athens, Research Center of Atmospheric Physics and Climatology, Athens (Greece); Chepfer, Helene [Universite Pierre et Marie Curie, LMD/IPSL, Paris (France); Dufresne, Jean-Louis [CNRS, Universite Pierre et Marie Curie, LMD/IPSL, Paris (France)

    2012-11-15

    This paper aims at characterizing how different key cloud properties (cloud fraction, cloud vertical distribution, cloud reflectance, a surrogate of the cloud optical depth) vary as a function of the others over the tropical oceans. The correlations between the different cloud properties are built from 2 years of collocated A-train observations (CALIPSO-GOCCP and MODIS) at a scale close to cloud processes; it results in a characterization of the physical processes in tropical clouds, that can be used to better understand cloud behaviors, and constitute a powerful tool to develop and evaluate cloud parameterizations in climate models. First, we examine a case study of shallow cumulus cloud observed simultaneously by the two sensors (CALIPSO, MODIS), and develop a methodology that allows to build global scale statistics by keeping the separation between clear and cloudy areas at the pixel level (250, 330 m). Then we build statistical instantaneous relationships between the cloud cover, the cloud vertical distribution and the cloud reflectance. The vertical cloud distribution indicates that the optically thin clouds (optical thickness <1.5) dominate the boundary layer over the trade wind regions. Optically thick clouds (optical thickness >3.4) are composed of high and mid-level clouds associated with deep convection along the ITCZ and SPCZ and over the warm pool, and by stratocumulus low level clouds located along the East coast of tropical oceans. The cloud properties are analyzed as a function of the large scale circulation regime. Optically thick high clouds are dominant in convective regions (CF > 80 %), while low level clouds with low optical thickness (<3.5) are present in regimes of subsidence but in convective regimes as well, associated principally to low cloud fractions (CF < 50 %). A focus on low-level clouds allows us to quantify how the cloud optical depth increases with cloud top altitude and with cloud fraction. (orig.)

  20. Observer Interface Analysis for Standardization to a Cloud Based Real-Time Space Situational Awareness (SSA)

    Science.gov (United States)

    Eilers, J.

    2013-09-01

    The interface analysis from an observer of space objects makes a standard necessary. This standardized dataset serves as input for a cloud based service, which aimed for a near real-time Space Situational Awareness (SSA) system. The system contains all advantages of a cloud based solution, like redundancy, scalability and an easy way to distribute information. For the standard based on the interface analysis of the observer, the information can be separated in three parts. One part is the information about the observer e.g. a ground station. The next part is the information about the sensors that are used by the observer. And the last part is the data from the detected object. Backbone of the SSA System is the cloud based service which includes the consistency check for the observed objects, a database for the objects, the algorithms and analysis as well as the visualization of the results. This paper also provides an approximation of the needed computational power, data storage and a financial approach to deliver this service to a broad community. In this context cloud means, neither the user nor the observer has to think about the infrastructure of the calculation environment. The decision if the IT-infrastructure will be built by a conglomerate of different nations or rented on the marked should be based on an efficiency analysis. Also combinations are possible like starting on a rented cloud and then go to a private cloud owned by the government. One of the advantages of a cloud solution is the scalability. There are about 3000 satellites in space, 900 of them are active, and in total there are about ~17.000 detected space objects orbiting earth. But for the computation it is not a N(active) to N problem it is more N(active) to N(apo peri) quantity of N(all). Instead of 15.3 million possible collisions to calculate a computation of only approx. 2.3 million possible collisions must be done. In general, this Space Situational Awareness System can be used as a

  1. Observations of rapid aerosol optical depth enhancements in the vicinity of polluted cumulus clouds

    Science.gov (United States)

    Eck, T. F.; Holben, B. N.; Reid, J. S.; Arola, A.; Ferrare, R. A.; Hostetler, C. A.; Crumeyrolle, S. N.; Berkoff, T. A.; Welton, E. J.; Lolli, S.; Lyapustin, A.; Wang, Y.; Schafer, J. S.; Giles, D. M.; Anderson, B. E.; Thornhill, K. L.; Minnis, P.; Pickering, K. E.; Loughner, C. P.; Smirnov, A.; Sinyuk, A.

    2014-11-01

    During the July 2011 Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field experiment in Maryland, significant enhancements in Aerosol Robotic Network (AERONET) sun-sky radiometer measured aerosol optical depth (AOD) were observed in the immediate vicinity of non-precipitating cumulus clouds on some days. Both measured Ångström exponents and aerosol size distribution retrievals made before, during and after cumulus development often suggest little change in fine mode particle size; therefore, implying possible new particle formation in addition to cloud processing and humidification of existing particles. In addition to sun-sky radiometer measurements of large enhancements of fine mode AOD, lidar measurements made from both ground-based and aircraft-based instruments during the experiment also measured large increases in aerosol signal at altitudes associated with the presence of fair weather cumulus clouds. These data show modifications of the aerosol vertical profile as a result of the aerosol enhancements at and below cloud altitudes. The airborne lidar data were utilized to estimate the spatial extent of these aerosol enhancements, finding increased AOD, backscatter and extinction out to 2.5 km distance from the cloud edge. Furthermore, in situ measurements made from aircraft vertical profiles over an AERONET site during the experiment also showed large increases in aerosol scattering and aerosol volume after cloud formation as compared to before. The 15-year AERONET database of AOD measurements at the Goddard Space Flight Center (GSFC), Maryland site, was investigated in order to obtain a climatological perspective of this phenomenon of AOD enhancement. Analysis of the diurnal cycle of AOD in summer showed significant increases in AOD from morning to late afternoon, corresponding to the diurnal cycle of cumulus development.

  2. Classification of Clouds and Deep Convection from GEOS-5 Using Satellite Observations

    Science.gov (United States)

    Putman, William; Suarez, Max

    2010-01-01

    With the increased resolution of global atmospheric models and the push toward global cloud resolving models, the resemblance of model output to satellite observations has become strikingly similar. As we progress with our adaptation of the Goddard Earth Observing System Model, Version 5 (GEOS-5) as a high resolution cloud system resolving model, evaluation of cloud properties and deep convection require in-depth analysis beyond a visual comparison. Outgoing long-wave radiation (OLR) provides a sufficient comparison with infrared (IR) satellite imagery to isolate areas of deep convection. We have adopted a binning technique to generate a series of histograms for OLR which classify the presence and fraction of clear sky versus deep convection in the tropics that can be compared with a similar analyses of IR imagery from composite Geostationary Operational Environmental Satellite (GOES) observations. We will present initial results that have been used to evaluate the amount of deep convective parameterization required within the model as we move toward cloud system resolving resolutions of 10- to 1-km globally.

  3. Analysis of a jet stream induced gravity wave associated with an observed ice cloud over Greenland

    Directory of Open Access Journals (Sweden)

    S. Buss

    2004-01-01

    Full Text Available A polar stratospheric ice cloud (PSC type II was observed by airborne lidar above Greenland on 14 January 2000. It was the unique observation of an ice cloud over Greenland during the SOLVE/THESEO 2000 campaign. Mesoscale simulations with the hydrostatic HRM model are presented which, in contrast to global analyses, are capable to produce a vertically propagating gravity wave that induces the low temperatures at the level of the PSC afforded for the ice formation. The simulated minimum temperature is ~8 K below the driving analyses and ~4.5 K below the frost point, exactly coinciding with the location of the observed ice cloud. Despite the high elevations of the Greenland orography the simulated gravity wave is not a mountain wave. Analyses of the horizontal wind divergence, of the background wind profiles, of backward gravity wave ray-tracing trajectories, of HRM experiments with reduced Greenland topography and of several diagnostics near the tropopause level provide evidence that the wave is emitted from an intense, rapidly evolving, anticyclonically curved jet stream. The precise physical process responsible for the wave emission could not be identified definitely, but geostrophic adjustment and shear instability are likely candidates. In order to evaluate the potential frequency of such non-orographic polar stratospheric cloud events, the non-linear balance equation diagnostic is performed for the winter 1999/2000. It indicates that ice-PSCs are only occasionally generated by gravity waves emanating from spontaneous adjustment.

  4. Ice phase in altocumulus clouds over Leipzig: remote sensing observations and detailed modeling

    Science.gov (United States)

    Simmel, M.; Bühl, J.; Ansmann, A.; Tegen, I.

    2015-09-01

    The present work combines remote sensing observations and detailed cloud modeling to investigate two altocumulus cloud cases observed over Leipzig, Germany. A suite of remote sensing instruments was able to detect primary ice at rather high temperatures of -6 °C. For comparison, a second mixed phase case at about -25 °C is introduced. To further look into the details of cloud microphysical processes, a simple dynamics model of the Asai-Kasahara (AK) type is combined with detailed spectral microphysics (SPECS) forming the model system AK-SPECS. Vertical velocities are prescribed to force the dynamics, as well as main cloud features, to be close to the observations. Subsequently, sensitivity studies with respect to ice microphysical parameters are carried out with the aim to quantify the most important sensitivities for the cases investigated. For the cases selected, the liquid phase is mainly determined by the model dynamics (location and strength of vertical velocity), whereas the ice phase is much more sensitive to the microphysical parameters (ice nucleating particle (INP) number, ice particle shape). The choice of ice particle shape may induce large uncertainties that are on the same order as those for the temperature-dependent INP number distribution.

  5. Ice phase in altocumulus clouds over Leipzig: remote sensing observations and detailed modelling

    Science.gov (United States)

    Simmel, M.; Bühl, J.; Ansmann, A.; Tegen, I.

    2015-01-01

    The present work combines remote sensing observations and detailed cloud modeling to investigate two altocumulus cloud cases observed over Leipzig, Germany. A suite of remote sensing instruments was able to detect primary ice at rather warm temperatures of -6 °C. For comparison, a second mixed phase case at about -25 °C is introduced. To further look into the details of cloud microphysical processes a simple dynamics model of the Asai-Kasahara type is combined with detailed spectral microphysics forming the model system AK-SPECS. Vertical velocities are prescribed to force the dynamics as well as main cloud features to be close to the observations. Subsequently, sensitivity studies with respect to ice microphysical parameters are carried out with the aim to quantify the most important sensitivities for the cases investigated. For the cases selected, the liquid phase is mainly determined by the model dynamics (location and strength of vertical velocity) whereas the ice phase is much more sensitive to the microphysical parameters (ice nuclei (IN) number, ice particle shape). The choice of ice particle shape may induce large uncertainties which are in the same order as those for the temperature-dependent IN number distribution.

  6. Arctic Low Cloud Changes as Observed by MISR and CALIOP: Implication for the Enhanced Autumnal Warming and Sea Ice Loss

    Science.gov (United States)

    Wu, Dong L.; Lee, Jae N.

    2012-01-01

    Retreat of Arctic sea ice extent has led to more evaporation over open water in summer and subsequent cloud changes in autumn. Studying recent satellite cloud data over the Arctic Ocean, we find that low (0.5-2 km) cloud cover in October has been increasing significantly during 2000-2010 over the Beaufort and East Siberian Sea (BESS). This change is consistent with the expected boundary-layer cloud response to the increasing Arctic evaporation accumulated during summer. Because low clouds have a net warming effect at the surface, October cloud increases may be responsible for the enhanced autumnal warming in surface air temperature, which effectively prolong the melt season and lead to a positive feedback to Arctic sea ice loss. Thus, the new satellite observations provide a critical support for the hypothesized positive feedback involving interactions between boundary-layer cloud, water vapor, temperature and sea ice in the Arctic Ocean.

  7. HoloGondel: in situ cloud observations on a cable car in the Swiss Alps using a holographic imager

    Science.gov (United States)

    Beck, Alexander; Henneberger, Jan; Schöpfer, Sarah; Fugal, Jacob; Lohmann, Ulrike

    2017-02-01

    In situ observations of cloud properties in complex alpine terrain where research aircraft cannot sample are commonly conducted at mountain-top research stations and limited to single-point measurements. The HoloGondel platform overcomes this limitation by using a cable car to obtain vertical profiles of the microphysical and meteorological cloud parameters. The main component of the HoloGondel platform is the HOLographic Imager for Microscopic Objects (HOLIMO 3G), which uses digital in-line holography to image cloud particles. Based on two-dimensional images the microphysical cloud parameters for the size range from small cloud particles to large precipitation particles are obtained for the liquid and ice phase. The low traveling velocity of a cable car on the order of 10 m s-1 allows measurements with high spatial resolution; however, at the same time it leads to an unstable air speed towards the HoloGondel platform. Holographic cloud imagers, which have a sample volume that is independent of the air speed, are therefore well suited for measurements on a cable car. Example measurements of the vertical profiles observed in a liquid cloud and a mixed-phase cloud at the Eggishorn in the Swiss Alps in the winters 2015 and 2016 are presented. The HoloGondel platform reliably observes cloud droplets larger than 6.5 µm, partitions between cloud droplets and ice crystals for a size larger than 25 µm and obtains a statistically significantly size distribution for every 5 m in vertical ascent.

  8. Detection of supercooled liquid water-topped mixed-phase clouds >from shortwave-infrared satellite observations

    Science.gov (United States)

    NOH, Y. J.; Miller, S. D.; Heidinger, A. K.

    2015-12-01

    Many studies have demonstrated the utility of multispectral information from satellite passive radiometers for detecting and retrieving the properties of cloud globally, which conventionally utilizes shortwave- and thermal-infrared bands. However, the satellite-derived cloud information comes mainly from cloud top or represents a vertically integrated property. This can produce a large bias in determining cloud phase characteristics, in particular for mixed-phase clouds which are often observed to have supercooled liquid water at cloud top but a predominantly ice phase residing below. The current satellite retrieval algorithms may report these clouds simply as supercooled liquid without any further information regarding the presence of a sub-cloud-top ice phase. More accurate characterization of these clouds is very important for climate models and aviation applications. In this study, we present a physical basis and preliminary results for the algorithm development of supercooled liquid-topped mixed-phase cloud detection using satellite radiometer observations. The detection algorithm is based on differential absorption properties between liquid and ice particles in the shortwave-infrared bands. Solar reflectance data in narrow bands at 1.6 μm and 2.25 μm are used to optically probe below clouds for distinction between supercooled liquid-topped clouds with and without an underlying mixed phase component. Varying solar/sensor geometry and cloud optical properties are also considered. The spectral band combination utilized for the algorithm is currently available on Suomi NPP Visible/Infrared Imaging Radiometer Suite (VIIRS), Himawari-8 Advanced Himawari Imager (AHI), and the future GOES-R Advance Baseline Imager (ABI). When tested on simulated cloud fields from WRF model and synthetic ABI data, favorable results were shown with reasonable threat scores (0.6-0.8) and false alarm rates (0.1-0.2). An ARM/NSA case study applied to VIIRS data also indicated promising

  9. Multispacecraft Observations of Magnetic Clouds and Their Solar Origins between 19 and 23 May 2007

    OpenAIRE

    Kilpua, E. K. J.; Liewer, P. C.; Farrugia, C.; Luhmann, J. G.; Möstl, C.; Li, Y.; Y. Liu; Lynch, B. J.; Russell, C. T.; Vourlidas, A.; ACUNA, M. H.; A. B. Galvin; D. Larson; Sauvaud, J. A.

    2009-01-01

    We analyze a series of complex interplanetary events and their solar origins that occurred between 19 and 23 May 2007 using observations by the STEREO and Wind satellites. The analyses demonstrate the new opportunities offered by the STEREO multispacecraft configuration for diagnosing the structure of in situ events and relating them to their solar sources. The investigated period was characterized by two high-speed solar wind streams and magnetic clouds observed in the vicinity of the sector...

  10. Sensitivity to deliberate sea salt seeding of marine cloudsobservations and model simulations

    Directory of Open Access Journals (Sweden)

    K. Alterskjær

    2012-03-01

    Full Text Available Sea salt seeding of marine clouds to increase their albedo is a proposed technique to counteract or slow global warming. In this study, we first investigate the susceptibility of marine clouds to sea salt injections, using observational data of cloud droplet number concentration, cloud optical depth, and liquid cloud fraction from the MODIS (Moderate Resolution Imaging Spectroradiometer instruments on board the Aqua and Terra satellites. We then compare the derived susceptibility function to a corresponding estimate from the Norwegian Earth System Model (NorESM. Results compare well between simulations and observations, showing that stratocumulus regions off the west coast of the major continents along with large regions over the Pacific and the Indian Oceans are susceptible. At low and mid latitudes the signal is dominated by the cloud fraction.

    We then carry out geo-engineering experiments with a uniform increase over ocean of 10−9 kg m−2 s−1 in emissions of sea salt particles with a dry modal radius of 0.13 μm, an emission strength and areal coverage much greater than proposed in earlier studies. The increased sea salt concentrations and the resulting change in marine cloud properties lead to a globally averaged forcing of −4.8 W m−2 at the top of the atmosphere, more than cancelling the forcing associated with a doubling of CO2 concentrations. The forcing is large in areas found to be sensitive by using the susceptibility function, confirming its usefulness as an indicator of where to inject sea salt for maximum effect.

    Results also show that the effectiveness of sea salt seeding is reduced because the injected sea salt provides a large surface area for water vapor and gaseous sulphuric acid to condense on, thereby lowering the maximum supersaturation and suppressing the formation and lifetime of sulphate particles. In some areas, our simulations show an

  11. The high-latitude cloud MBM 7. I. H I and CO observations

    Science.gov (United States)

    Minh, Y. C.; Park, Y. S.; Kim, K. T.; Irvine, W. M.; Brewer, M. K.; Turner, B. E.

    1996-01-01

    The high-latitude cloud (HLC) MBM 7 has been observed in the 21 cm H I line and the 12CO(1-0) and 13CO(1-0) lines with similar spatial resolutions. The data reveal a total mass approximately 30 M solar for MBM 7 and a complex morphology. The cloud consists of a cold dense core of 5 M solar surrounded by atomic and molecular gas with about 25 M solar, which is embedded in hotter and more diffuse H I gas. We derive a total column density N(H I + 2H2) of 1 x 10(21) cm-2 toward the center and 1 x 10(20) cm-3 toward the envelope of MBM 7. The CO line indicates the existence of dense cores [n(H2) > or = 2000 cm-3] of size (FWHM) approximately 0.5 pc. The morphology suggests shock compression from the southwest direction, which can form molecular cores along the direction perpendicular to the H I distribution. The H I cloud extends to the northeast, and the velocity gradient appears to be about 2.8 km s-1 pc-1 in this direction, which indicates a systematic outward motion which will disrupt the cloud in approximately 10(6) yr. The observed large line widths of approximately 2 km s-1 for CO suggest that turbulent motions exist in the cloud, and hydrodynamical turbulence may dominate the line broadening. Considering the energy and pressure of MBM 7, the dense cores appear not to be bound by gravity, and the whole cloud including the dense cores seem to be expanding. The distance to HLCs suggest that they belong to the galactic plane, since the scale height of the cloud is < or approximately equal to 100 pc. Compared to the more familiar dense dark clouds, HLCs may differ only in their small mass and low density, with their proximity reducing the filling factor and enhancing the contrast of the core and envelope structure.

  12. Tropical cloud and precipitation regimes as seen from near-simultaneous TRMM, CloudSat, and CALIPSO observations and comparison with ISCCP

    Science.gov (United States)

    Luo, Zhengzhao Johnny; Anderson, Ricardo C.; Rossow, William B.; Takahashi, Hanii

    2017-06-01

    Although Tropical Rainfall Measuring Mission (TRMM) and CloudSat/CALIPSO fly in different orbits, they frequently cross each other so that for the period between 2006 and 2010, a total of 15,986 intersect lines occurred within 20 min of each other from 30°S to 30°N, providing a rare opportunity to study tropical cloud and precipitation regimes and their internal vertical structure from near-simultaneous measurements by these active sensors. A k-means cluster analysis of TRMM and CloudSat matchups identifies three tropical cloud and precipitation regimes: the first two regimes correspond to, respectively, organized deep convection with heavy rain and cirrus anvils with moderate rain; the third regime is a convectively suppressed regime that can be further divided into three subregimes, which correspond to, respectively, stratocumulus clouds with drizzle, cirrus overlying low clouds, and nonprecipitating cumulus. Inclusion of CALIPSO data adds to the dynamic range of cloud properties and identifies one more cluster; subcluster analysis further identifies a thin, midlevel cloud regime associated with tropical mountain ranges. The radar-lidar cloud regimes are compared with the International Satellite Cloud Climatology Project (ISCCP) weather states (WSs) for the extended tropics. Focus is placed on the four convectively active WSs, namely, WS1-WS4. ISCCP WS1 and WS2 are found to be counterparts of Regime 1 and Regime 2 in radar-lidar observations, respectively. ISCCP WS3 and WS4, which are mainly isolated convection and broken, detached cirrus, do not have a strong association with any individual radar and lidar regimes, a likely effect of the different sampling strategies between ISCCP and active sensors and patchy cloudiness of these WSs.

  13. Airborne lidar observations of cirrus clouds in the Tropics, Mid-latitudes, and the Arctic

    Science.gov (United States)

    Ismail, S.; Browell, E.; Ferrare, R.; Grant, W.; Kooi, S.; Brackett, V.; Mahoney, M.

    2003-04-01

    Airborne lidar systems have demonstrated an unsurpassed capability to detect and profile optically thin cirrus. The airborne Lidar Atmospheric Sensing Experiment (LASE) has demonstrated a capability to detect thin cirrus at aerosol scattering levels of latitudes. LASE data from these field experiments have been used to characterize the cirrus as thin laminae, thick cirrus, deep convective cirrus, and cirrus anvils. In addition, characteristics including the cloud top height, optical depth, aerosol scattering ratio, lidar extinction-to-backscatter ratio have been derived for optically thin cirrus. During these field experiments, many data sets were available to interpret the cirrus cloud properties including data from satellites, in situ temperature and moisture instruments on aircraft, radiosondes, and during some field experiments, the Microwave Temperature Profiler (MTP). LASE data from long-range flights have been used to derive a relationship between the latitudinal variation of cloud top heights and tropopause locations. These measurements were also used to examine the relationship between relative humidity and the presence of cirrus. LASE observations of cirrus clouds and water vapor fields have also been used to identify dynamical processes like stratosphere-troposphere exchange and to study their characteristics. Examples of these observations and analyses are presented to demonstrate the advantage of using LASE measurements for conducting atmospheric science investigations.

  14. Observation of cloud-to-ground lightning channels with high-speed video camera

    CERN Document Server

    Buguet, M; Blanchet, P; Pédeboy, S; Barnéoud, P; Laroche, P

    2014-01-01

    Between May and October 2013 (period of sustained thunderstorm activity in France), several cloud-to-ground lightning flashes have been observed in Paris area with a high-speed video camera (14000 frames per second). The localization and the polarity of the recorded cloud-to-ground flashes have been obtained from the French lightning detection network M{\\'e}t{\\'e}orage which is equipped with the same low frequency sensors used by the US NLDN. In this paper we focused on 7 events (3 positive cloud-to-ground lightning flashes and 4 negative cloud-to-ground lightning flashes). The propagation velocity of the leaders and its temporal evolution have been estimated; the evolution of branching of the negative leaders have been observed during the propagation of the channel which get connected to ground and initiate the first return stroke. One aim of this preliminary study is to emphasize the differences between the characteristics of the positive and of the negative leaders.

  15. The Impact of Time Difference between Satellite Overpass and Ground Observation on Cloud Cover Performance Statistics

    Directory of Open Access Journals (Sweden)

    Jędrzej S. Bojanowski

    2014-12-01

    Full Text Available Cloud property data sets derived from passive sensors onboard the polar orbiting satellites (such as the NOAA’s Advanced Very High Resolution Radiometer have global coverage and now span a climatological time period. Synoptic surface observations (SYNOP are often used to characterize the accuracy of satellite-based cloud cover. Infrequent overpasses of polar orbiting satellites combined with the 3- or 6-h SYNOP frequency lead to collocation time differences of up to 3 h. The associated collocation error degrades the cloud cover performance statistics such as the Hanssen-Kuiper’s discriminant (HK by up to 45%. Limiting the time difference to 10 min, on the other hand, introduces a sampling error due to a lower number of corresponding satellite and SYNOP observations. This error depends on both the length of the validated time series and the SYNOP frequency. The trade-off between collocation and sampling error call for an optimum collocation time difference. It however depends on cloud cover characteristics and SYNOP frequency, and cannot be generalized. Instead, a method is presented to reconstruct the unbiased (true HK from HK affected by the collocation differences, which significantly (t-test p < 0.01 improves the validation results.

  16. Spectral observations of Ellerman bombs and fitting with a two-cloud model

    CERN Document Server

    Hong, Jie; Li, Ying; Fang, Cheng; Cao, Wenda

    2014-01-01

    We study the H$\\alpha$ and Ca II 8542 \\r{A} line spectra of four typical Ellerman bombs (EBs) in active region NOAA 11765 on 2013 June 6, observed with the Fast Imaging Solar Spectrograph installed at the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. Considering that EBs may occur in a restricted region in the lower atmosphere, and that their spectral lines show particular features, we propose a two-cloud model to fit the observed line profiles. The lower cloud can account for the wing emission, and the upper cloud is mainly responsible for the absorption at line center. After choosing carefully the free parameters, we get satisfactory fitting results. As expected, the lower cloud shows an increase of the source function, corresponding to a temperature increase of 400--1000 K in EBs relative to the quiet Sun. This is consistent with previous results deduced from semi-empirical models and confirms that a local heating occurs in the lower atmosphere during the appearance of EBs. We also find that...

  17. Southeast Atlantic Ocean aerosol direct radiative effects over clouds: Comparison of observations and simulations

    Science.gov (United States)

    de Graaf, M.; Haywood, J.; Bellouin, N.; Tilstra, L. G.; Stammes, P.

    2017-02-01

    Absorbing aerosols exert a warming or a cooling effect on the Earth's system, depending on the circumstances. The direct radiative effect (DRE) of absorbing aerosols is negative (cooling) at the top-of-the-atmosphere (TOA) over a dark surface like the ocean, as the aerosols increase the planetary albedo, but it is positive (warming) over bright backgrounds like clouds. Furthermore, radiation absorption by aerosols heat the atmosphere locally, and, through rapid adjustments of the atmospheric column and cloud dynamics, the net effect can be amplified considerably. We developed a technique to study the absorption of radiation of smoke over low lying clouds using satellite spectrometry. The TOA DRE of smoke over clouds is large and positive over the southeast Atlantic Ocean off the west coast of Africa, which can be explained by the large decrease of reflected radiation by a polluted cloud, especially in the UV. However, general circulation models (GCMs) fail to reproduce these strong positive DRE, and in general GCMs disagree on the magnitude and even sign of the aerosol DRE in the southeast Atlantic region. Our satellite-derived DRE measurements show clear seasonal and inter-annual variations, consistent with other satellite measurements, which are not reproduced by GCMs. A comparison with model results showed discrepancies with the Ångström exponent of the smoke aerosols, which is larger than assumed in simulations, and a sensitivity to emission scenarios. However, this was not enough to explain the discrepancies, and we suspect that the modeling of cloud distributions and microphysics will have the necessary larger impact on DRE that will explain the differences between observations and modeling.

  18. Observational Approach to Molecular Cloud Evolutation with the Submillimeter-Wave CI Lines

    Science.gov (United States)

    Oka, T.; Yamamoto, S.

    Neutral carbon atoms (CI) play important roles both in chemistry and cooling processes of interstellar molecular clouds. It is thus crucial to explore its large area distribution to obtain information on formation processes and thermal balance of molecular clouds. However, observations of the submillimeter-wave CI lines have been limited to small areas around some representative objects. We have constructed a 1.2 m submillimeter-wave telescope at the summit of Mt.Fuji. The telescope was designed for the exclusive use of surveying molecular clouds in two submillimeter-wave CI lines, 3 P1 -3 P0 (492GHz) and 3 P2 -3 P1 (809 GHz), of atomic carbon. A superconductor-insulator-superconductor (SIS) mixer receiver was equipped on the Nasmyth focus of the telescope. The receiver noise temperatures [Trx(DSB)] are 300 K and 1000 K for the 492 GHz and the 809 GHz mixers, respectively. The intermediate frequency is centered at 2 GHz, having a 700 MHz bandwidth. An acousto-optical spectrometer (AOS) with 1024 channel outputs is used as a receiver backend. The telescope was installed at Nishi-yasugawara (alt. 3725 m), which is 200 m north of the highest peak, Kengamine (3776 m), in July 1998. It has b en operatede successfully during 4 observing seasons in a remote way from the Hongo campus of the University of Tokyo. We have already observed more than 40 square degrees of the sky with the CI 492 GHz line. The distribution of CI emission is found to be different from those of the 13 CO or C1 8 O emission in some clouds. These differences are discussed in relation to formation processes of molecular clouds.

  19. Cloud parcel modelling of CCN activation in megacity air based on observations from Beijing and Guangzhou

    Science.gov (United States)

    Su, H.; Reutter, P.; Trentmann, J.; Rose, D.; Gunthe, S.; Simmel, M.; Nowak, A.; Wiedensohler, A.; Zhu, T.; Pöschl, U.

    2009-04-01

    The other team members are P. Achtert (3), M. Hu (4), M. Shao (4), and Y.H. Zhang (4). The activation of cloud condensation nuclei (CCN) determines the initial number of cloud droplets, and thus influences the evolution of the cloud and formation of precipitation. Characterizing the CCN activation process by parcel model studies with detailed cloud microphysics and dynamics provides useful information for parameterizing the activation process in meso-scale and global-scale models. During the CAREBEIJING 2006 campaign in Beijing and the PRIDE-PRD2006 campaign in Guangzhou, fast condensational growth of particles was frequently observed and the CCN size distribution was sometimes dominated by the growing nucleation mode (Aitken Mode) rather than by the accumulation mode. In this study we investigated the implications of the experimental findings using a cloud parcel model with detailed spectral cloud microphysics and with the ΰ-Köhler model approach for efficient and realistic description of the effective hygroscopicity and CCN activity of aerosol particles. The number of droplets formed at the cloud base was examined for a wide range of updraft velocities and aerosol particle number concentrations. Moreover, the impact of aerosol hygroscopicity, size distribution and giant CCN were also evaluated. References: Reutter, P., Trentmann, J., Su, H., Simmel M., Rose, D., Wernli, H., Andreae, M. O., and Pöschl, U.: Activation of aerosol particles as cloud condensation nuclei (CCN) under smoky and pyro-convective conditions, manuscript in preparation, 2009 Rose, D., Gunthe, S. S., Mikhailov, E., Frank, G. P., Dusek, U., Andreae, M. O., and Pöschl, U.: Calibration and measurement uncertainties of a continuous-flow cloud condensation nuclei counter (DMT-CCNC): CCN activation of ammonium sulfate and sodium chloride aerosol particles in theory and experiment, Atmos. Chem. Phys., 8, 1153-1179, 2008. Rose, D., Nowak, A., Achtert, P., Wiedensohler, A., Hu, M., Shao, M

  20. Evaluation of Aerosol-cloud Interaction in the GISS Model E Using ARM Observations

    Science.gov (United States)

    DeBoer, G.; Bauer, S. E.; Toto, T.; Menon, Surabi; Vogelmann, A. M.

    2013-01-01

    Observations from the US Department of Energy's Atmospheric Radiation Measurement (ARM) program are used to evaluate the ability of the NASA GISS ModelE global climate model in reproducing observed interactions between aerosols and clouds. Included in the evaluation are comparisons of basic meteorology and aerosol properties, droplet activation, effective radius parameterizations, and surface-based evaluations of aerosol-cloud interactions (ACI). Differences between the simulated and observed ACI are generally large, but these differences may result partially from vertical distribution of aerosol in the model, rather than the representation of physical processes governing the interactions between aerosols and clouds. Compared to the current observations, the ModelE often features elevated droplet concentrations for a given aerosol concentration, indicating that the activation parameterizations used may be too aggressive. Additionally, parameterizations for effective radius commonly used in models were tested using ARM observations, and there was no clear superior parameterization for the cases reviewed here. This lack of consensus is demonstrated to result in potentially large, statistically significant differences to surface radiative budgets, should one parameterization be chosen over another.

  1. Further seasonal changes in Uranus’ cloud structure observed by Gemini-North and UKIRT

    Science.gov (United States)

    Irwin, P. G. J.; Teanby, N. A.; Davis, G. R.; Fletcher, L. N.; Orton, G. S.; Calcutt, S. B.; Tice, D. S.; Hurley, J.

    2012-03-01

    Near-infrared observations of Uranus were made in October/November 2010 with the Gemini-North telescope in Hawaii, using NIFS, an integral field spectrograph, and the NIRI instrument in imaging mode. Observations were acquired using adaptive optics and have a spatial resolution of approximately 0.1-0.2″. The observed spectra along Uranus’ central meridian were analysed using a multiple-scattering retrieval algorithm to infer the vertical/latitudinal variation in cloud optical depth, which we compare with previous observations made by Gemini-North/NIFS in 2009 and UKIRT/UIST observations made between 2006 and 2008. Assuming a continuous distribution of small particles (r ∼ 1 μm, and refractive index of 1.4 + 0i) with the single scattering albedo set to 0.75 and using a Henyey-Greenstein phase function with asymmetry parameter set to 0.7 at all wavelengths and latitudes, the retrieved cloud density profiles show that the north polar zone at 45°N has continued to steadily brighten while the south polar zone at 45°S has continued to fade. As with our previous analyses we find that, assuming that the methane vertical profile is the same at all latitudes, the clouds forming these polar zones at 45°N and 45°S lie at slightly lower pressures than the clouds at more equatorial latitudes. However, we also find that the Gemini data can be reproduced by assuming that the main cloud remains fixed at ∼2 bar at all latitudes and adjusting the relative humidity of methane instead. In this case we find that the deep cloud is still more opaque at the equator and at the zones at 45°N and 45°S and shows the same seasonal trends as when the methane humidity remain fixed. However, with this approach the relative humidity of methane is seen to rise sharply from approximately 20% at polar latitudes to values closer to 80% for latitudes equatorward of 45°S and 45°N, consistent with the analysis of 2002 HST observations by Karkoschka and Tomasko (Karkoschka, E., Tomasko, M

  2. MAGNETIZATION OF CLOUD CORES AND ENVELOPES AND OTHER OBSERVATIONAL CONSEQUENCES OF RECONNECTION DIFFUSION

    Energy Technology Data Exchange (ETDEWEB)

    Lazarian, A. [Astronomy Department, University of Wisconsin, Madison, WI 53706 (United States); Esquivel, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, 04510 Mexico D.F. (Mexico); Crutcher, R. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W. Green Street, Urbana, IL 61801 (United States)

    2012-10-01

    Recent observational results for magnetic fields in molecular clouds reviewed by Crutcher seem to be inconsistent with the predictions of the ambipolar diffusion theory of star formation. These include the measured decrease in mass to flux ratio between envelopes and cores, the failure to detect any self-gravitating magnetically subcritical clouds, the determination of the flat probability distribution function (PDF) of the total magnetic field strengths implying that there are many clouds with very weak magnetic fields, and the observed scaling B{proportional_to}{rho}{sup 2/3} that implies gravitational contraction with weak magnetic fields. We consider the problem of magnetic field evolution in turbulent molecular clouds and discuss the process of magnetic field diffusion mediated by magnetic reconnection. For this process that we termed 'reconnection diffusion', we provide a simple physical model and explain that this process is inevitable in view of the present-day understanding of MHD turbulence. We address the issue of the expected magnetization of cores and envelopes in the process of star formation and show that reconnection diffusion provides an efficient removal of magnetic flux that depends only on the properties of MHD turbulence in the core and the envelope. We show that as the amplitude of turbulence as well as the scale of turbulent motions decrease from the envelope to the core of the cloud, the diffusion of the magnetic field is faster in the envelope. As a result, the magnetic flux trapped during the collapse in the envelope is being released faster than the flux trapped in the core, resulting in much weaker fields in envelopes than in cores, as observed. We provide simple semi-analytical model calculations which support this conclusion and qualitatively agree with the observational results. Magnetic reconnection is also consistent with the lack of subcritical self-gravitating clouds, with the observed flat PDF of field strengths, and

  3. Insights into aerosols, chemistry, and clouds from NETCARE: Observations from the Canadian Arctic in summer 2014

    Science.gov (United States)

    Abbatt, J.

    2015-12-01

    The Canadian Network on Aerosols and Climate: Addressing Key Uncertainties in Remote Canadian Regions (or NETCARE) was established in 2013 to study the interactions between aerosols, chemistry, clouds and climate. The network brings together Canadian academic and government researchers, along with key international collaborators. Attention is being given to observations and modeling of Arctic aerosol, with the goal to understand underlying processes and so improve predictions of aerosol climate forcing. Motivation to understand the summer Arctic atmosphere comes from the retreat of summer sea ice and associated increase in marine influence. To address these goals, a suite of measurements was conducted from two platforms in summer 2014 in the Canadian Arctic, i.e. an aircraft-based campaign on the Alfred Wegener Institute POLAR 6 and an ocean-based campaign from the CGCS Amundsen icebreaker. NETCARE-POLAR was based out of Resolute Bay, Nunavut during an initial period of little transport and cloud-free conditions and a later period characterized by more transport with potentially biomass burning influence. Measurements included particle and cloud droplet numbers and size distributions, aerosol composition, cloud nuclei, and levels of gaseous tracers. Ultrafine particle events were more frequently observed in the marine boundary layer than above, with particle growth observed in some cases to cloud condensation nucleus sizes. The influence of biological processes on atmospheric constituents was also assessed from the ship during NETCARE-AMUNDSEN, as indicated by high measured levels of gaseous ammonia, DMS and oxygenated VOCs, as well as isolated particle formation and growth episodes. The cruise took place in Baffin Bay and through the Canadian archipelago. Interpretation of the observations from both campaigns is enhanced through the use of chemical transport and particle dispersion models. This talk will provide an overview of NETCARE Arctic observational and

  4. Observations of boundary layer, mixed-phase and multi-layer Arctic clouds with different lidar systems during ASTAR 2007

    Directory of Open Access Journals (Sweden)

    A. Lampert

    2009-07-01

    Full Text Available During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR, which was conducted in Svalbard in March and April 2007, tropospheric Arctic clouds were observed with two ground-based backscatter lidar systems (micro pulse lidar and Raman lidar and with an airborne elastic lidar. An increase in low-level (cloud tops below 2.5 km cloud cover from 51% to 65% was observed above Ny-Ålesund during the time of the ASTAR campaign. Four different case studies of lidar cloud observations are analyzed: With the ground-based Raman lidar, a pre-condensation layer was observed at an altitude of 2 km. The layer consisted of small droplets with a high number concentration (around 300 cm−3 at low temperatures (−30°C. Observations of a boundary layer mixed-phase cloud by airborne lidar were evaluated with the measurements of concurrent airborne in situ and spectral solar radiation sensors. Two detailed observations of multiply layered clouds in the free troposphere are presented. The first case was composed of various ice layers with different optical properties detected with the Raman lidar, the other case showed a mixed-phase double layer and was observed by airborne lidar.

    The analysis of these four cases confirmed that lidar data provide information of the whole range from subvisible to optically thick clouds. Despite the attenuation of the laser signal in optically thick clouds and multiple scattering effects, information on the geometrical boundaries of liquid water clouds were obtained. Furthermore, the dominating phase of the clouds' particles in the layer closest to the lidar system could be retrieved.

  5. The Spitzer survey of interstellar clouds in the gould belt. VI. The Auriga-California molecular cloud observed with IRAC and MIPS

    Energy Technology Data Exchange (ETDEWEB)

    Broekhoven-Fiene, Hannah; Matthews, Brenda C. [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8W 3P6 (Canada); Harvey, Paul M. [Astronomy Department, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States); Gutermuth, Robert A. [Department of Astronomy, University of Massachusetts, Amherst, MA (United States); Huard, Tracy L.; Miller, Jennifer F. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Tothill, Nicholas F. H. [School of Computing, Engineering and Mathematics, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751 (Australia); Nutter, David [School of Physics and Astronomy, Cardiff University, Queen' s Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); Bourke, Tyler L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); DiFrancesco, James [National Research Council Herzberg Astronomy and Astrophysics, Victoria, BC, V9E 2E7 (Canada); Jørgensen, Jes K. [Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-DK-2100 Copenhagen Ø. (Denmark); Allen, Lori E. [National Optical Astronomy Observatories, Tucson, AZ (United States); Chapman, Nicholas L. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Dunham, Michael M. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States); Merín, Bruno [Herschel Science Centre, ESAC-ESA, P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain); Terebey, Susan [Department of Physics and Astronomy PS315, 5151 State University Drive, California State University at Los Angeles, Los Angeles, CA 90032 (United States); Peterson, Dawn E. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); and others

    2014-05-01

    We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70, and 160 μm observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 deg{sup 2} with IRAC and 10.47 deg{sup 2} with MIPS. This giant molecular cloud is one of two in the nearby Gould Belt of star-forming regions, the other being the Orion A Molecular Cloud (OMC). We compare source counts, colors, and magnitudes in our observed region to a subset of the SWIRE data that was processed through our pipeline. Using color-magnitude and color-color diagrams, we find evidence for a substantial population of 166 young stellar objects (YSOs) in the cloud, many of which were previously unknown. Most of this population is concentrated around the LkHα 101 cluster and the filament extending from it. We present a quantitative description of the degree of clustering and discuss the relative fraction of YSOs in earlier (Class I and F) and later (Class II) classes compared to other clouds. We perform simple SED modeling of the YSOs with disks to compare the mid-IR properties to disks in other clouds and identify 14 classical transition disk candidates. Although the AMC is similar in mass, size, and distance to the OMC, it is forming about 15-20 times fewer stars.

  6. Fitting density models to observational data - The local Schmidt law in molecular clouds

    CERN Document Server

    Lombardi, Marco; Alves, João

    2013-01-01

    We consider the general problem of fitting a parametric density model to discrete observations, taken to follow a non-homogeneous Poisson point process. This class of models is very common, and can be used to describe many astrophysical processes, including the distribution of protostars in molecular clouds. We give the expression for the likelihood of a given spatial density distribution of protostars and apply it to infer the most probable dependence of the protostellar surface density on the gas surface density. Finally, we apply this general technique to model the distribution of protostars in the Orion molecular cloud and robustly derive the local star formation scaling (Schmidt) law for a molecular cloud. We find that in this cloud the protostellar surface density, \\Sigma_YSO, is directly proportional to the square gas column density, here expressed as infrared extinction in the K-band, A_K: more precisely, \\Sigma_YSO = (1.65 +/- 0.19) A_K^(2.03 +/- 0.15) stars pc^-2.

  7. Gamma-ray observations of the Orion Molecular Clouds with the Fermi Large Area Telescope

    CERN Document Server

    Ackermann, M; Allafort, A; Antolini, E; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bottacini, E; Brandt, T J; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Cecchi, C; Chekhtman, A; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; D'Ammando, F; de Angelis, A; de Palma, F; Dermer, C D; Silva, E do Couto e; Drell, P S; Drlica-Wagner, A; Enoto, T; Falletti, L; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Fukazawa, Y; Fukui, Y; Fusco, P; Gargano, F; Gasparrini, D; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashida, M; Hayashi, K; Horan, D; Hou, X; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Kamae, T; Katagiri, H; Kataoka, J; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Larsson, S; Lee, S -H; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Makishima, K; Mazziotta, M N; Mehault, J; Mitthumsiri, W; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Naumann-Godo, M; Nishino, S; Norris, J P; Nuss, E; Ohno, M; Ohsugi, T; Okumura, A; Orienti, M; Orlando, E; Ormes, J F; Ozaki, M; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pesce-Rollins, M; Pierbattista, M; Piron, F; Pivato, G; Porter, T A; Rainò, S; Razzano, M; Reimer, A; Reimer, O; Roth, M; Sadrozinski, H F -W; Sgrò, C; Siskind, E J; Spandre, G; Spinelli, P; Strong, A W; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J G; Thayer, J B; Tibolla, O; Tinivella, M; Torres, D F; Tramacere, A; Troja, E; Uchiyama, Y; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Yang, Z; Zimmer, S

    2012-01-01

    We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between \\sim100 MeV and \\sim100 GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to \\sim10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity integrated CO intensity (WCO) at a 1{\\deg} \\times1{\\deg} pixel level. The correlation is found to be linear over a WCO range of ~10 fold when divided in 3 regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The Wco-to-mass conversion factor, Xco, is found to be \\sim2.3\\times1...

  8. The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds VIII. Serpens Observed with MIPS

    CERN Document Server

    Harvey, Paul M; Brooke, Tim; Spiesman, William J; Chapman, Nicholas; Huard, Tracy L; Evans, Neal J; Cieza, Lucas; Lai, Shih-Ping; Allen, Lori E; Mundy, Lee G; Padgett, Deborah L; Sargent, Anneila I; Stapelfeldt, Karl R; Myers, Philip C; van Dishoeck, Ewine F; Blake, Geoffrey A; Koerner, David W

    2007-01-01

    We present maps of 1.5 square degrees of the Serpens dark cloud at 24, 70, and 160\\micron observed with the Spitzer Space Telescope MIPS Camera. More than 2400 compact sources have been extracted at 24um, nearly 100 at 70um, and 4 at 160um. We estimate completeness limits for our 24um survey from Monte Carlo tests with artificial sources inserted into the Spitzer maps. We compare source counts, colors, and magnitudes in the Serpens cloud to two reference data sets, a 0.50 deg^2 set on a low-extinction region near the dark cloud, and a 5.3 deg^2 subset of the SWIRE ELAIS N1 data that was processed through our pipeline. These results show that there is an easily identifiable population of young stellar object candidates in the Serpens Cloud that is not present in either of the reference data sets. We also show a comparison of visual extinction and cool dust emission illustrating a close correlation between the two, and find that the most embedded YSO candidates are located in the areas of highest visual extinct...

  9. Implications of Observed High Supersaturation for TTL Cloud Formation and Dehydration

    Science.gov (United States)

    Jensen, Eric

    2004-01-01

    In situ measurements of water vapor concentration made during the CRYSTAL-FACE and Pre-AVE missions indicate higher than expected supersaturations in both clear and cloudy air near the cold tropical tropopause: (1) steady-state ice supersaturations of 20-30% were measured within cirrus at T supersaturations exceeding 100% (near water saturation) were observed under cloud-free conditions near 187 K. The in-cloud measurements challenge the conventional belief that any water vapor in excess of ice saturation should be depleted by crystal growth given sufficient time. The high clear-sky supersaturations imply that thresholds for ice nucleation due to homogeneous freezing of aerosols (or any other mechanism) are much higher than those inferred from laboratory measurements. We will use simulations of Tropical Tropopause Layer (TTL) transport and cloud formation throughout the tropics to show that these effects have important implications for TTL cloud frequency and freeze-drying of air crossing the tropical tropopause cold trap.

  10. Observational Evidence of Dynamic Star Formation Rate in Milky Way Giant Molecular Clouds

    CERN Document Server

    Lee, Eve J; Murray, Norman

    2016-01-01

    Star formation on galactic scales is known to be a slow process, but whether it is slow on smaller scales is uncertain. We cross-correlate 5469 giant molecular clouds (GMCs) from a new all-sky catalog with 256 star forming complexes (SFCs) to build a sample of 191 SFC-GMC complexes---collections of multiple clouds each matched to 191 SFCs. The total mass in stars harbored by these clouds is inferred from WMAP free-free fluxes. We measure the GMC mass, the virial parameter, the star formation efficiency $\\epsilon$ and the star formation rate per free-fall time $\\epsilon_{\\rm ff}$. Both $\\epsilon$ and $\\epsilon_{\\rm ff}$ range over 3--4 orders of magnitude. We find that 68.3% of the clouds fall within $\\sigma_{\\log\\epsilon}=0.79\\pm0.22\\,{\\rm dex}$ and $\\sigma_{\\log\\epsilon_{\\rm ff}}=0.91\\pm0.22\\,{\\rm dex}$ about the median. Compared to these observed scatters, a simple model with a time independent $\\epsilon_{\\rm ff}$ that depends on the host GMC properties predicts $\\sigma_{\\log\\epsilon_{\\rm ff}}=0.24$. Allowi...

  11. Rolling Deck to Repository (R2R): Transforming the Academic Fleet Into an Integrated Global Observing System

    Science.gov (United States)

    Carbotte, S. M.; Ferrini, V.; Arko, R. A.; Chandler, C. L.; Maffei, A. R.; Miller, S. P.; Stocks, K.; Smith, S. R.; Bourassa, M. A.

    2009-12-01

    NSF-supported oceanographic research expeditions support diverse scientific investigations across all disciplines of ocean sciences, targeting important questions ranging from the impacts of global change on ocean chemistry and ecosystems, to the structure and dynamics of ocean circulation and the nature of volcanic and earthquake processes at the global plate boundaries. Research vessels coordinated by the University-National Oceanographic Laboratory System (UNOLS) are the primary oceanographic research platforms, and operate as essential mobile observing platforms for ocean science. Ships ranging from “global” to “local” class are capable of operating throughout the deep oceans and within coastal and inland waterways. Each vessel is equipped with a suite of sensors, including geophysical, water column, and meteorological sensors, that are available for continuous operation during each expedition. The “underway” datasets obtained from these sensors provide characterization of basic environmental conditions for the oceans and are of high value for later reuse for building global syntheses, climatologies, and historical time series of ocean properties. The recently funded Rolling Deck to Repository (R2R) Project aims to develop a comprehensive plan for fleet-wide data management to ensure preservation and accessibility of our national oceanographic research data resources. The R2R Portal (www.rvdata.us) is being developed as a central shore-side data gateway through which underway data from oceanographic expeditions can be routinely cataloged and securely transmitted to the national long-term digital data archives including the National Geophysical Data Center (NGDC) and the National Oceanographic Data Center (NODC). R2R will provide essential data documentation services for every expedition along with new tools to improve documentation of the wide array of shipboard data collection activities typical of modern expeditions. Protocols will be developed

  12. High-resolution mapping of Martian water ice clouds using Mars Express OMEGA observations - Derivation of the diurnal cloud life cycle

    Science.gov (United States)

    Szantai, Andre; Audouard, Joachim; Madeleine, Jean-Baptiste; Forget, Francois; Pottier, Alizée; Millour, Ehouarn; Gondet, Brigitte; Langevin, Yves; Bibring, Jean-Pierre

    2016-10-01

    The mapping in space and time of water ice clouds can help to explain the Martian water cycle and atmospheric circulation. For this purpose, an ice cloud index (ICI) corresponding to the depth of a water ice absorption band at 3.4 microns is derived from a series of OMEGA images (spectels) covering 5 Martian years. The ICI values for the corresponding pixels are then binned on a high-resolution regular grid (1° longitude x 1° latitude x 5° Ls x 1 h local time) and averaged. Inside each bin, the cloud cover is calculated by dividing the number of pixels considered as cloudy (after comparison to a threshold) to the number of all (valid) pixelsWe compare the maps of clouds obtained around local time 14:00 with collocated TES cloud observations (which were only obtained around this time of the day). A good agreement is found.Averaged ICI compared to the water ice column variable from the Martian Climate Database (MCD) show a correct correlation (~0.5) , which increases when values limited to the tropics only are compared.The number of gridpoints containing ICI values is small ( ~1%), but by taking several neighbor gridpoints and over longer periods, we can observe a cloud life cycle during daytime. An example in the the tropics, around the northern summer solstice, shows a decrease of cloudiness in the morning followed by an increase in the afternoon.

  13. A ten-year global record of absorbing aerosols above clouds from OMI's near-UV observations

    Science.gov (United States)

    Jethva, Hiren; Torrres, Omar; Ahn, Changwoo

    2016-05-01

    Aerosol-cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of an adequate knowledge of the complex microphysical and radiative processes associated with the aerosolcloud system. The situations when aerosols and clouds are found in the same atmospheric column, for instance, when light-absorbing aerosols such as biomass burning generated carbonaceous particles or wind-blown dust overlay low-level cloud decks, are commonly found over several regional of the world. Contrary to the cloud-free scenario over dark surface, for which aerosols are known to produce a net cooling effect (negative radiative forcing) on climate, the overlapping situation of absorbing aerosols over cloud can potentially exert a significant level of atmospheric absorption and produces a positive radiative forcing at top-of-atmosphere. The magnitude of direct radiative effects of aerosols above cloud depends directly on the aerosol loading, microphysical-optical properties of the aerosol layer and the underlying cloud deck, and geometric cloud fraction. We help in addressing this problem by introducing a novel product of optical depth of absorbing aerosols above clouds retrieved from near-UV observations made by the Ozone Monitoring Instrument (OMI) on board NASA's Aura platform. The presence of absorbing aerosols above cloud reduces the upwelling radiation reflected by cloud and produces a strong `color ratio' effect in the near-UV region, which can be unambiguously detected in the OMI measurements. Physically based on this effect, the OMACA algorithm retrieves the optical depths of aerosols and clouds simultaneously under a prescribed state of atmosphere. The algorithm architecture and results from a ten-year global record including global climatology of frequency of occurrence and above-cloud aerosol optical depth, and a discussion on related future field campaigns are presented.

  14. Mapping Observations of DNC and HN^13C in Dark Cloud Cores

    OpenAIRE

    Hirota, T; M. Ikeda(Kyoto University); Yamamoto, S.

    2003-01-01

    We present results of mapping observations of the DNC, HN^13C, and H^13CO^+ lines (J=1-0) toward 4 nearby dark cloud cores, TMC-1, L1512, L1544, and L63, along with observations of the DNC and HN^13C lines (J=2-1) toward selected positions. By use of statistical equilibrium calculations based on the LVG model, the H_2 densities are derived to be (1.4-5.5)*10^5 cm^-3, and the [DNC]/[HN^13C] ratios are derived to be 1.25-5.44 with a typical uncertainty by a factor of 2. The observed [DNC]/[HNC]...

  15. Observational Analysis of Cloud and Precipitation in Midlatitude Cyclones: Northern Versus Southern Hemisphere Warm Fronts

    Science.gov (United States)

    Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

    2012-01-01

    Extratropical cyclones are responsible for most of the precipitation and wind damage in the midlatitudes during the cold season, but there are still uncertainties on how they will change in a warming climate. An ubiquitous problem amongst General Circulation Models (GCMs) is a lack of cloudiness over the southern oceans that may be in part caused by a lack of clouds in cyclones. We analyze CloudSat, CALIPSO and AMSR-E observations for 3 austral and boreal cold seasons and composite cloud frequency of occurrence and precipitation at the warm fronts for northern and southern hemisphere oceanic cyclones. We find that cloud frequency of occurrence and precipitation rate are similar in the early stage of the cyclone life cycle in both northern and southern hemispheres. As cyclones evolve and reach their mature stage, cloudiness and precipitation at the warm front increase in the northern hemisphere but decrease in the southern hemisphere. This is partly caused by lower amounts of precipitable water being available to southern hemisphere cyclones, and smaller increases in wind speed as the cyclones evolve. Southern hemisphere cloud occurrence at the warm front is found to be more sensitive to the amount of moisture in the warm sector than to wind speeds. This suggests that cloudiness in southern hemisphere storms may be more susceptible to changes in atmospheric water vapor content, and thus to changes in surface temperature than their northern hemisphere counterparts. These differences between northern and southern hemisphere cyclones are statistically robust, indicating A-Train-based analyses as useful tools for evaluation of GCMs in the next IPCC report.

  16. Tropical deep convective life cycle: Cb-anvil cloud microphysics from high-altitude aircraft observations

    Science.gov (United States)

    Frey, W.; Borrmann, S.; Fierli, F.; Weigel, R.; Mitev, V.; Matthey, R.; Ravegnani, F.; Sitnikov, N. M.; Ulanovsky, A.; Cairo, F.

    2014-12-01

    The case study presented here focuses on the life cycle of clouds in the anvil region of a tropical deep convective system. During the SCOUT-O3 campaign from Darwin, Northern Australia, the Hector storm system has been probed by the Geophysica high-altitude aircraft. Clouds were observed by in situ particle probes, a backscatter sonde, and a miniature lidar. Additionally, aerosol number concentrations have been measured. On 30 November 2005 a double flight took place and Hector was probed throughout its life cycle in its developing, mature, and dissipating stage. The two flights were four hours apart and focused on the anvil region of Hector in altitudes between 10.5 and 18.8 km (i.e. above 350 K potential temperature). Trajectory calculations, satellite imagery, and ozone measurements have been used to ensure that the same cloud air masses have been probed in both flights. The size distributions derived from the measurements show a change not only with increasing altitude but also with the evolution of Hector. Clearly different cloud to aerosol particle ratios as well as varying ice crystal morphology have been found for the different development stages of Hector, indicating different freezing mechanisms. The development phase exhibits the smallest ice particles (up to 300 μm) with a rather uniform morphology. This is indicative for rapid glaciation during Hector's development. Sizes of ice crystals are largest in the mature stage (larger than 1.6 mm) and even exceed those of some continental tropical deep convective clouds, also in their number concentrations. The backscatter properties and particle images show a change in ice crystal shape from the developing phase to rimed and aggregated particles in the mature and dissipating stages; the specific shape of particles in the developing phase cannot be distinguished from the measurements. Although optically thin, the clouds in the dissipating stage have a large vertical extent (roughly 6 km) and persist for at

  17. Satellite Cloud Data Validation through MAGIC Ground Observation and the S'COOL Project: Scientific Benefits grounded in Citizen Science

    Science.gov (United States)

    Crecelius, S.; Chambers, L. H.; Lewis, P. M.; Rogerson, T.

    2013-12-01

    The Students' Cloud Observation On-Line (S'COOL) Project was launched in 1997 as the Formal Education and Public Outreach arm of the Clouds and the Earth's Radiant Energy System (CERES) Mission. ROVER, the Citizen Scientist area of S'COOL, started in 2007 and allows participants to make 'roving' observations from any location as opposed to a fixed, registered classroom. The S'COOL Project aids the CERES Mission in trying to answer the research question: 'What is the Effect of Clouds on the Earth's Climate'. Participants from all 50 states, most U.S. Territories, and 63 countries have reported more than 100,500 observations to the S'COOL Project over the past 16 years. The Project is supported by an intuitive website that provides curriculum support and guidance through the observation steps; 1) Request satellite overpass schedule, 2) Observe clouds, and 3) Report cloud observations. The S'COOL Website also hosts a robust database housing all participants' observations as well as the matching satellite data. While the S'COOL observation parameters are based on the data collected by 5 satellite missions, ground observations provide a unique perspective to data validation. Specifically, low to mid level clouds can be obscured by overcast high-level clouds, or difficult to observe from a satellite's perspective due to surface cover or albedo. In these cases, ground observations play an important role in filling the data gaps and providing a better, global picture of our atmosphere and clouds. S'COOL participants, operating within the boundary layer, have an advantage when observing low-level clouds that affect the area we live in, regional weather patterns, and climate change. S'COOL's long-term data set provides a valuable resource to the scientific community in improving the "poorly characterized and poorly represented [clouds] in climate and weather prediction models'. The MAGIC Team contacted S'COOL in early 2012 about making cloud observations as part of the MAGIC

  18. Assessment of NASA GISS CMIP5 and Post-CMIP5 Simulated Clouds and TOA Radiation Budgets Using Satellite Observations. Part I: Cloud Fraction and Properties

    Science.gov (United States)

    Stanfield, Ryan E.; Dong, Xiquan; Xi, Baike; Kennedy, Aaron; Del Genio, Anthony D.; Minnia, Patrick; Jiang, Jonathan H.

    2014-01-01

    Although many improvements have been made in phase 5 of the Coupled Model Intercomparison Project (CMIP5), clouds remain a significant source of uncertainty in general circulation models (GCMs) because their structural and optical properties are strongly dependent upon interactions between aerosol/cloud microphysics and dynamics that are unresolved in such models. Recent changes to the planetary boundary layer (PBL) turbulence and moist convection parameterizations in the NASA GISS Model E2 atmospheric GCM(post-CMIP5, hereafter P5) have improved cloud simulations significantly compared to its CMIP5 (hereafter C5) predecessor. A study has been performed to evaluate these changes between the P5 and C5 versions of the GCM, both of which used prescribed sea surface temperatures. P5 and C5 simulated cloud fraction (CF), liquid water path (LWP), ice water path (IWP), cloud water path (CWP), precipitable water vapor (PWV), and relative humidity (RH) have been compared to multiple satellite observations including the Clouds and the Earth's Radiant Energy System-Moderate Resolution Imaging Spectroradiometer (CERES-MODIS, hereafter CM), CloudSat- Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO; hereafter CC), Atmospheric Infrared Sounder (AIRS), and Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). Although some improvements are observed in the P5 simulation on a global scale, large improvements have been found over the southern midlatitudes (SMLs), where correlations increased and both bias and root-mean-square error (RMSE) significantly decreased, in relation to the previous C5 simulation, when compared to observations. Changes to the PBL scheme have resulted in improved total column CFs, particularly over the SMLs where marine boundary layer (MBL) CFs have increased by nearly 20% relative to the previous C5 simulation. Globally, the P5 simulated CWPs are 25 gm22 lower than the previous C5 results. The P5 version of the

  19. A 15 year legacy of cloud and atmosphere observations in Barrow, Alaska

    Science.gov (United States)

    Shupe, M.

    2012-12-01

    For the past 15 years, the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program has operated the North Slope of Alaska (NSA) atmospheric observatory in Barrow, Alaska. Barrow offers many valuable perspectives on the Arctic environment that complement observations at lower latitudes. Unique features of the Arctic region include cold and dry atmospheric conditions, strong annual variability in sun light, a seasonally high-reflective surface, and persistent clouds that involve mixed-phase processes. ARM's ultimate objective with its flagship observatory at the northernmost point in U.S. territory is to provide measurements that can be used to improve the understanding of these atmospheric physical and radiative properties and processes such that they can be better represented in climate models. The NSA is the most detailed and long-lasting cloud-radiation-atmosphere observatory in the Arctic, providing continuous, sophisticated measurements of climate-relevant parameters. Instrument suites include active radars and lidars at various frequencies, passive radiometers monitoring radiation in microwave, infrared, visible and ultraviolet wavelengths, meteorological towers, and sounding systems. Together these measurements are used to characterize many of the important properties of clouds, aerosols, atmospheric radiation, dynamics, thermodynamics, and the surface. The coordinated nature of these measurements offers important multi-dimensional insight into many fundamental processes linking these different elements of the climate system. Moreover, the continuous operations of the facility support these observations over the full diurnal cycle and in all seasons of the year. This presentation will highlight a number of important studies and key findings that have been facilitated by the NSA observations during the first 15 years in operation. Some of these include: a thorough documentation of clouds, their occurrence frequency, phase, microphysical

  20. 3D MODELING OF GJ1214b's ATMOSPHERE: FORMATION OF INHOMOGENEOUS HIGH CLOUDS AND OBSERVATIONAL IMPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Charnay, B.; Meadows, V.; Misra, A.; Arney, G. [Astronomy Department, University of Washington, Seattle, WA 98125 (United States); Leconte, J., E-mail: bcharnay@uw.edu [Canadian Institute for Theoretical Astrophysics, 60 St George Street, University of Toronto, Toronto, ON M5S 3H8 (Canada)

    2015-11-01

    The warm sub-Neptune GJ1214b has a featureless transit spectrum that may be due to the presence of high and thick clouds or haze. Here, we simulate the atmosphere of GJ1214b with a 3D General Circulation Model for cloudy hydrogen-dominated atmospheres, including cloud radiative effects. We show that the atmospheric circulation is strong enough to transport micrometric cloud particles to the upper atmosphere and generally leads to a minimum of cloud at the equator. By scattering stellar light, clouds increase the planetary albedo to 0.4–0.6 and cool the atmosphere below 1 mbar. However, the heating by ZnS clouds leads to the formation of a stratospheric thermal inversion above 10 mbar, with temperatures potentially high enough on the dayside to evaporate KCl clouds. We show that flat transit spectra consistent with Hubble Space Telescope observations are possible if cloud particle radii are around 0.5 μm, and that such clouds should be optically thin at wavelengths >3 μm. Using simulated cloudy atmospheres that fit the observed spectra we generate transit, emission, and reflection spectra and phase curves for GJ1214b. We show that a stratospheric thermal inversion would be readily accessible in near- and mid-infrared atmospheric spectral windows. We find that the amplitude of the thermal phase curves is strongly dependent on metallicity, but only slightly impacted by clouds. Our results suggest that primary and secondary eclipses and phase curves observed by the James Webb Space Telescope in the near- to mid-infrared should provide strong constraints on the nature of GJ1214b's atmosphere and clouds.

  1. High-resolution HI and CO observations of high-latitude intermediate-velocity clouds

    CERN Document Server

    Röhser, T; Bekhti, N Ben; Winkel, B

    2016-01-01

    Intermediate-velocity clouds (IVCs) are HI halo clouds that are likely related to a Galactic fountain process. In-falling IVCs are candidates for the re-accretion of matter onto the Milky Way. We study the evolution of IVCs at the disk-halo interface, focussing on the transition from atomic to molecular IVCs. We compare an atomic IVC to a molecular IVC and characterise their structural differences in order to investigate how molecular IVCs form high above the Galactic plane. With high-resolution HI observations of the Westerbork Synthesis Radio Telescope and 12CO(1-0) and 13CO(1-0) observations with the IRAM 30m telescope, we analyse the small-scale structures within the two clouds. By correlating HI and far-infrared (FIR) dust continuum emission from the Planck satellite, the distribution of molecular hydrogen (H2) is estimated. We conduct a detailed comparison of the HI, FIR, and CO data and study variations of the $X_\\rm{CO}$ conversion factor. The atomic IVC does not disclose detectable CO emission. The a...

  2. Simultaneous radar and aircraft observations of mixed-phase cloud at the 100 m scale

    Science.gov (United States)

    Field, P. R.; Hogan, R. J.; Brown, P. R. A.; Illingworth, A. J.; Choularton, T. W.; Kaye, P. H.; Hirst, E.; Greenaway, R.

    2004-07-01

    Three UK C-130 aircraft flights performed in conjunction with the Chilbolton Advanced Meteorological Radar were carried out in mixed-phase clouds. The aircraft instrumentation included the Small Ice Detector (SID) and Nevzorov probe that are both capable of discriminating between liquid and ice phase. It was found that particle sphericity measured by the SID could be successfully used as a proxy for particle phase. Using a combination of the SID and other probes it is possible to determine whether a 100 m cloud segment is ice, liquid or mixed-phase. Regions as short as 100 m exhibited mixed-phase characteristics. There was generally good agreement between water phase indicated by the SID and Nevzorov probes, with any differences arising from the fact that the SID provides a number-weighted estimate of dominant phase, while the Nevzorov probe provides a mass-weighted estimate. The radar and aircraft observations show that when high values of differential reflectivity are observed the nearby presence of liquid water is indicated. When large ice crystals are present in deeper cloud they can suppress the differential reflectivity signal. Therefore the absence of a high differential reflectivity signal does not necessarily mean that liquid water is absent.

  3. The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds: VII. Ophiuchus Observed with MIPS

    CERN Document Server

    Padgett, Deborah L; Stapelfeldt, Karl R; Chapman, Nicholas L; Lai, Shih-Ping; Mundy, Lee G; Evans, Neal J; Brooke, Timothy Y; Cieza, Lucas A; Spiesman, William J; Noriega-Crespo, Alberto; McCabe, Caer-Eve; Allen, Lori E; Blake, Geoffrey A; Harvey, Paul M; Huard, Tracy L; Jorgensen, Jes K; Koerner, David W; Myers, Philip C; Sargent, Anneila I; Teuben, Peter; van Dishoeck, Ewine F; Wahhaj, Zahed; Young, Kaisa E

    2007-01-01

    We present maps of 14.4 deg^2 of the Ophiuchus dark clouds observed by the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS). These high quality maps depict both numerous point sources as well as extended dust emission within the star-forming and non-star-forming portions of these clouds. Using PSF-fitting photometry, we detect 5779 sources at 24 um and 81 sources at 70 um at the 10 sigma level of significance. Three hundred twenty-three candidate young stellar objects (YSOs) were identified according to their positions on the MIPS/2MASS K versus K$-$[24] color-magnitude diagrams as compared to 24 um detections in the SWIRE extragalactic survey. We find that more than half of the YSO candidates, and almost all the ones with protostellar Class I spectral energy distributions, are confined to the known cluster and aggregates.

  4. Cirrus cloud properties from combined IIR and lidar observations of CALIPSO

    Science.gov (United States)

    Garnier, Anne; Pelon, Jacques; Winker, Dave M.; Dubuisson, Philippe; Vaughan, Mark A.; Pascal, Nicolas

    2013-05-01

    Cirrus clouds are of particular importance for the understanding and the survey of climate change due to their impact on the Earth radiation budget. However, their optical and microphysical properties are still poorly known. The NASA-CNES CALIPSO mission provides new pieces of information by combining observations of active (lidar) and passive (radiometer) remote sensing instruments. Cirrus cloud optical depths derived in the thermal infrared (12 μm) from the IIR are found in excellent agreement with those retrieved in the visible spectrum (532 nm) from the CALIOP lidar, down to optical depths smaller than 0.05. The ice water paths derived from the two instruments use very different approaches, and show a highly correlated linear relationship. On average, CALIOP retrievals are 1.7 times larger than IIR estimates, requiring further studies.

  5. Observations of the gas cloud G2 in the Galactic Center

    CERN Document Server

    Gillessen, Stefan; Fritz, Tobias K; Eisenhauer, Frank; Pfuhl, Oliver; Ott, Thomas; Burkert, Andreas; Schartmann, Marc; Ballone, Alessandro

    2013-01-01

    In 2011, we discovered a compact gas cloud ("G2") with roughly three Earth masses that is falling on a near-radial orbit toward the massive black hole in the Galactic Center. The orbit is well constrained and pericenter passage is predicted for early 2014. Our data beautifully show that G2 gets tidally sheared apart due to the massive black hole's force. During the next months, we expect that in addition to the tidal effects, hydrodynamics get important, when G2 collides with the hot ambient gas around Sgr A*. Simulations show that ultimately, the cloud's material might fall into the massive black hole. Predictions for the accretion rate and luminosity evolution, however, are very difficult due to the many unknowns. Nevertheless, this might be a unique opportunity in the next years to observe how gas feeds a massive black hole in a galactic nucleus.

  6. Observations of the gas cloud G2 in the Galactic center

    Science.gov (United States)

    Gillessen, S.; Genzel, R.; Fritz, T. K.; Eisenhauer, F.; Pfuhl, O.; Ott, T.; Burkert, A.; Schartmann, M.; Ballone, A.

    2014-05-01

    In 2011, we discovered a compact gas cloud ("G2") with roughly three Earth masses that is falling on a near-radial orbit toward the massive black hole in the Galactic center. The orbit is well constrained and pericenter passage is predicted for early 2014. Our data beautifully show that G2 gets tidally sheared apart due to the massive black hole's force. During the next months, we expect that in addition to the tidal effects, hydrodynamics get important, when G2 collides with the hot ambient gas around Sgr A*. Simulations show that ultimately, the cloud's material might fall into the massive black hole. Predictions for the accretion rate and luminosity evolution, however, are very difficult due to the many unknowns. Nevertheless, this might be a unique opportunity in the next years to observe how gas feeds a massive black hole in a galactic nucleus.

  7. Size-resolved observations of refractory black carbon particles in cloud droplets at a marine boundary layer site

    Directory of Open Access Journals (Sweden)

    J. C. Schroder

    2014-05-01

    Full Text Available Size resolved observations of aerosol particles (including black carbon particles and cloud residuals were studied at a marine boundary layer site (251 m a.m.s.l. in La Jolla, CA during 2012. A counterflow virtual impactor was used to sample cloud residuals while a total inlet was used to sample both cloud residuals and interstitial particles. Two cloud events totaling ten hours of in-cloud sampling were analyzed. Since the CVI only sampled cloud droplets larger than ≈11 μm, less than 100% of the cloud droplets were sampled during the two cloud events (≈38% of the cloud droplets for the first cloud event and ≈24% of the cloud droplets for the second cloud were sampled. Back trajectories showed that air masses for both cloud events spent at least 96 h over the Pacific Ocean and traveled near, or over populated regions just before sampling. Based on bulk aerosol particle concentrations measured from the total inlet the two air masses sampled were classified as polluted marine air, a classification that was consistent with back trajectory analysis and the mass concentrations of refractory black carbon (rBC measured from the total inlet. The activated fraction of rBC, estimated from the measurements, ranged from 0.01 to 0.1 for core diameters ranging from 70 to 220 nm. Since the fraction of cloud droplets sampled by the CVI was less than 100%, the measured activated fractions of rBC should be considered as lower limits to the total fraction of rBC activated during the two cloud events. Size distributions of rBC sampled from the residual inlet show that sub-100 nm rBC cores were incorporated into the droplets in both clouds. The coating analysis shows that the rBC cores had average coating thicknesses of 75 nm for core diameters of 70 nm and 29 nm for core diameters of 220 nm. The presence of sub-100 nm rBC cores in the cloud residuals is consistent with kappa-Köhler theory and the measured coating thicknesses of the rBC cores.

  8. RACORO Extended-Term Aircraft Observations of Boundary-Layer Clouds

    Science.gov (United States)

    Vogelmann, Andrew M.; McFarquhar, Greg M.; Ogren, John A.; Turner, David D.; Comstock, Jennifer M.; Feingold, Graham; Long, Charles N.; Jonsson, Haflidi H.; Bucholtz, Anthony; Collins, Don R.; hide

    2012-01-01

    Small boundary-layer clouds are ubiquitous over many parts of the globe and strongly influence the Earths radiative energy balance. However, our understanding of these clouds is insufficient to solve pressing scientific problems. For example, cloud feedback represents the largest uncertainty amongst all climate feedbacks in general circulation models (GCM). Several issues complicate understanding boundary-layer clouds and simulating them in GCMs. The high spatial variability of boundary-layer clouds poses an enormous computational challenge, since their horizontal dimensions and internal variability occur at spatial scales much finer than the computational grids used in GCMs. Aerosol-cloud interactions further complicate boundary-layer cloud measurement and simulation. Additionally, aerosols influence processes such as precipitation and cloud lifetime. An added complication is that at small scales (order meters to 10s of meters) distinguishing cloud from aerosol is increasingly difficult, due to the effects of aerosol humidification, cloud fragments and photon scattering between clouds.

  9. Cloud object analysis of CERES Aqua observations of tropical and subtropical cloud regimes: Evolution of cloud object size distributions during the Madden-Julian Oscillation

    Science.gov (United States)

    Xu, Kuan-Man; Wong, Takmeng; Dong, Shengtao; Chen, Feng; Kato, Seiji; Taylor, Patrick C.

    2017-02-01

    In this study, we analyze cloud object data from the Aqua satellite between July 2006 and June 2010 that are matched with the real-time multivariate Madden-Julian Oscillation (MJO) index to examine the impact of MJO evolution on the evolutions of the size distributions of cloud object types. These types include deep convective (DC), cirrostratus, shallow cumulus, stratocumulus and overcast-stratus. A cloud object is a contiguous region of the earth with a single dominant cloud-system type. It is found that the cloud object size distributions of some phases depart greatly from the 8-phase combined distribution at large cloud-object diameters. The large-size group of cloud objects contributes to most of the temporal variations during the MJO evolution. For deep convective and cirrostratus cloud objects, there is a monotonic increase in both the number and footprint of large objects from the depressed to mature phases, which is attributed to the development and maturing of deep convection and anvils. The largest increase in the mean diameter during the mature phases that lasts to the early dissipating phase is related to growth of anvil clouds and is accompanied by moderate decreases in small-size objects. For shallow cumulus, the large objects decrease in number at the mature phases, but increase in number for both sizes before the mature phase. The opposite is true for the large overcast-stratus objects. The temporal evolution of large stratocumulus objects is similar to that of deep convective and cirrostratus object types except for peaking slightly earlier.

  10. Cirrus cloud occurrence as function of ambient relative humidity: a comparison of observations obtained during the INCA experiment

    Directory of Open Access Journals (Sweden)

    J. Ström

    2003-01-01

    Full Text Available Based on in-situ observations performed during the Interhemispheric differences in cirrus properties from anthropogenic emissions (INCA experiment, we introduce and discuss the cloud presence fraction (CPF defined as the ratio between the number of data points determined to represent cloud at a given ambient relative humidity over ice (RHI divided by the total number of data points at that value of RHI. The CPFs are measured with four different cloud probes. Within similar ranges of detected particle sizes and concentrations, it is shown that different cloud probes yield results that are in good agreement with each other. The CPFs taken at Southern Hemisphere (SH and Northern Hemisphere (NH midlatitudes differ from each other. Above ice saturation, clouds occurred more frequently during the NH campaign. Local minima in the CPF as a function of RHI are interpreted as a systematic underestimation of cloud presence when cloud particles become invisible to cloud probes. Based on this interpretation, we find that clouds during the SH campaign formed preferentially at RHIs between 140 and 155%, whereas clouds in the NH campaign formed at RHIs somewhat below 130%. The data show that interstitial aerosol and ice particles coexist down to RHIs of 70-90%, demonstrating that the ability to distinguish between different particle types in cirrus conditions depends on the sensors used to probe the aerosol/cirrus system. Observed distributions of cloud water content differ only slightly between the NH and SH campaigns and seem to be only weakly, if at all, affected by the freezing aerosols.

  11. Tropical deep convective life cycle: Cb-anvil cloud microphysics from high altitude aircraft observations

    Directory of Open Access Journals (Sweden)

    W. Frey

    2014-05-01

    Full Text Available The case study presented here focusses on the life cycle of clouds in a tropical deep convective system. During the SCOUT-O3 campaign from Darwin, Northern Australia, the Hector storm system has been probed by the Geophysica high altitude aircraft. Clouds were observed by in situ particle probes, a backscatter sonde, and a miniature lidar. Additionally, aerosol number concentrations have been measured. On 30 November 2005 a double flight took place and Hector was probed throughout its life cycle in its developing, mature, and dissipating stage. The two flights were four hours apart and focussed on the anvil region of Hector in altitudes between 10.5 km and 18.8 km (i.e. above 350 K potential temperature. Trajectory calculations and ozone measurements have been used to identify that the same cloud air masses have been probed in both flights. The size distributions derived from the measurements not only show a change with increasing altitude but also with the evolution of Hector. Clearly different aerosol to cloud particle ratios as well as varying ice crystal morphology have been found for the different development stages of Hector, indicating a change in freezing mechanisms. The development phase exhibits the smallest ice particles (up to 300 μm with a rather uniform morphology. This is indicative for rapid glaciation during Hector's development. Sizes of ice crystals are largest in the mature stage (larger 1.6 mm and even exceed those of some continental tropical deep convective clouds, also in their number concentrations. The backscatter properties and particle images show a change from frozen droplets in the developing phase to rimed and aggregated particles. The clouds in the dissipating stage have a large vertical extend (roughly 6 km though optically thin and persist for at least 6 h. This poses a high potential for affecting the tropical tropopause layer background conditions regarding humidity, e.g. through facilitating subvisible

  12. Tropical deep convective life cycle: Cb-anvil cloud microphysics from high altitude aircraft observations

    Science.gov (United States)

    Frey, W.; Borrmann, S.; Fierli, F.; Weigel, R.; Mitev, V.; Matthey, R.; Ravegnani, F.; Sitnikov, N. M.; Ulanovsky, A.; Cairo, F.

    2014-05-01

    The case study presented here focusses on the life cycle of clouds in a tropical deep convective system. During the SCOUT-O3 campaign from Darwin, Northern Australia, the Hector storm system has been probed by the Geophysica high altitude aircraft. Clouds were observed by in situ particle probes, a backscatter sonde, and a miniature lidar. Additionally, aerosol number concentrations have been measured. On 30 November 2005 a double flight took place and Hector was probed throughout its life cycle in its developing, mature, and dissipating stage. The two flights were four hours apart and focussed on the anvil region of Hector in altitudes between 10.5 km and 18.8 km (i.e. above 350 K potential temperature). Trajectory calculations and ozone measurements have been used to identify that the same cloud air masses have been probed in both flights. The size distributions derived from the measurements not only show a change with increasing altitude but also with the evolution of Hector. Clearly different aerosol to cloud particle ratios as well as varying ice crystal morphology have been found for the different development stages of Hector, indicating a change in freezing mechanisms. The development phase exhibits the smallest ice particles (up to 300 μm) with a rather uniform morphology. This is indicative for rapid glaciation during Hector's development. Sizes of ice crystals are largest in the mature stage (larger 1.6 mm) and even exceed those of some continental tropical deep convective clouds, also in their number concentrations. The backscatter properties and particle images show a change from frozen droplets in the developing phase to rimed and aggregated particles. The clouds in the dissipating stage have a large vertical extend (roughly 6 km) though optically thin and persist for at least 6 h. This poses a high potential for affecting the tropical tropopause layer background conditions regarding humidity, e.g. through facilitating subvisible cirrus formation, and

  13. Towards global Landsat burned area mapping: revisit time and availability of cloud free observations

    Science.gov (United States)

    Melchiorre, A.; Boschetti, L.

    2016-12-01

    Global, daily coarse resolution satellite data have been extensively used for systematic burned area mapping (Giglio et al. 2013; Mouillot et al. 2014). The adoption of similar approaches for producing moderate resolution (10 - 30 m) global burned area products would lead to very significant improvements for the wide variety of fire information users. It would meet a demand for accurate burned area perimeters needed for fire management, post-fire assessment and environmental restoration, and would lead to more accurate and precise atmospheric emission estimations, especially over heterogeneous areas (Mouillot et al. 2014; Randerson et al. 2012; van der Werf et al. 2010). The increased spatial resolution clearly benefits mapping accuracy: the reduction of mixed pixels directly translates in increased spectral separation compared to coarse resolution data. As a tradeoff, the lower temporal resolution (e.g. 16 days for Landsat), could potentially cause large omission errors in ecosystems with fast post-fire recovery. The spectral signal due to the fire effects is non-permanent, can be detected for a period ranging from a few weeks in savannas and grasslands, to over a year in forest ecosystems (Roy et al. 2010). Additionally, clouds, smoke, and other optically thick aerosols limit the number of available observations (Roy et al. 2008; Smith and Wooster 2005), exacerbating the issues related to mapping burned areas globally with moderate resolution sensors. This study presents a global analysis of the effect of cloud cover on Landsat data availability over burned areas, by analyzing the MODIS data record of burned area (MCD45) and cloud detections (MOD35), and combining it with the Landsat acquisition calendar and viewing geometry. For each pixel classified as burned in the MCD45 product, the MOD35 data are used to determine how many cloud free observations would have been available on Landsat overpass days, within the period of observability of the burned area

  14. A comparison of ground and satellite observations of cloud cover to saturation pressure differences during a cold air outbreak

    Energy Technology Data Exchange (ETDEWEB)

    Alliss, R.J.; Raman, S. [North Carolina State Univ., Raleigh, NC (United States)

    1996-04-01

    The role of clouds in the atmospheric general circulation and the global climate is twofold. First, clouds owe their origin to large-scale dynamical forcing, radiative cooling in the atmosphere, and turbulent transfer at the surface. In addition, they provide one of the most important mechanisms for the vertical redistribution of momentum and sensible and latent heat for the large scale, and they influence the coupling between the atmosphere and the surface as well as the radiative and dynamical-hydrological balance. In existing diagnostic cloudiness parameterization schemes, relative humidity is the most frequently used variable for estimating total cloud amount or stratiform cloud amount. However, the prediction of relative humidity in general circulation models (GCMs) is usually poor. Even for the most comprehensive GCMs, the predicted relative humidity may deviate greatly from that observed, as far as the frequency distribution of relative humidity is concerned. Recently, there has been an increased effort to improve the representation of clouds and cloud-radiation feedback in GCMs, but the verification of cloudiness parameterization schemes remains a severe problem because of the lack of observational data sets. In this study, saturation pressure differences (as opposed to relative humidity) and satellite-derived cloud heights and amounts are compared with ground determinations of cloud cover over the Gulf Stream Locale (GSL) during a cold air outbreak.

  15. CubeSat Constellation Cloud Winds(C3Winds) A New Wind Observing System to Study Mesoscale Cloud Dynamics and Processes

    Science.gov (United States)

    Wu, D. L.; Kelly, M.A.; Yee, J.-H.; Boldt, J.; Demajistre, R.; Reynolds, E. L.; Tripoli, G. J.; Oman, L. D.; Prive, N.; Heidinger, A. K.; hide

    2016-01-01

    The CubeSat Constellation Cloud Winds (C3Winds) is a NASA Earth Venture Instrument (EV-I) concept with the primary objective to better understand mesoscale dynamics and their structures in severe weather systems. With potential catastrophic damage and loss of life, strong extratropical and tropical cyclones (ETCs and TCs) have profound three-dimensional impacts on the atmospheric dynamic and thermodynamic structures, producing complex cloud precipitation patterns, strong low-level winds, extensive tropopause folds, and intense stratosphere-troposphere exchange. Employing a compact, stereo IR-visible imaging technique from two formation-flying CubeSats, C3Winds seeks to measure and map high-resolution (2 km) cloud motion vectors (CMVs) and cloud geometric height (CGH) accurately by tracking cloud features within 5-15 min. Complementary to lidar wind observations from space, the high-resolution wind fields from C3Winds will allow detailed investigations on strong low-level wind formation in an occluded ETC development, structural variations of TC inner-core rotation, and impacts of tropopause folding events on tropospheric ozone and air quality. Together with scatterometer ocean surface winds, C3Winds will provide a more comprehensive depiction of atmosphere-boundary-layer dynamics and interactive processes. Built upon mature imaging technologies and long history of stereoscopic remote sensing, C3Winds provides an innovative, cost-effective solution to global wind observations with potential of increased diurnal sampling via CubeSat constellation.

  16. Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 8

    Directory of Open Access Journals (Sweden)

    S. A. Buehler

    2012-02-01

    Full Text Available Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized "essential climate variable" ice water path (IWP and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8, which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

  17. Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 8

    Directory of Open Access Journals (Sweden)

    S. A. Buehler

    2012-07-01

    Full Text Available Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized "essential climate variable" ice water path (IWP and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8, which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

  18. A YOUNG GIANT MOLECULAR CLOUD FORMED AT THE INTERFACE OF TWO COLLIDING SUPERSHELLS: OBSERVATIONS MEET SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, J. R. [Department of Physics and Astronomy and MQ Research Centre in Astronomy, Astrophysics and Astrophotonics, Macquarie University, NSW 2109 (Australia); Ntormousi, E. [Service d' Astrophysique, CEA/DSM/IRFU Orme des Merisiers, Bat 709 Gif-sur-Yvette F-91191 (France); Fukui, Y.; Hayakawa, T. [Department of Physics and Astrophysics, Nagoya University, Chikusa-ku, Nagoya (Japan); Fierlinger, K., E-mail: joanne.dawson@mq.edu.au [University Observatory Munich, Scheinerstr. 1, D-81679 München (Germany)

    2015-01-20

    Dense, star-forming gas is believed to form at the stagnation points of large-scale interstellar medium flows, but observational examples of this process in action are rare. We here present a giant molecular cloud (GMC) sandwiched between two colliding Milky Way supershells, which we argue shows strong evidence of having formed from material accumulated at the collision zone. Combining {sup 12}CO, {sup 13}CO, and C{sup 18}O(J = 1-0) data with new high-resolution, three-dimensional hydrodynamical simulations of colliding supershells, we discuss the origin and nature of the GMC (G288.5+1.5), favoring a scenario in which the cloud was partially seeded by pre-existing denser material, but assembled into its current form by the action of the shells. This assembly includes the production of some new molecular gas. The GMC is well interpreted as non-self-gravitating, despite its high mass (M{sub H{sub 2}}∼1.7×10{sup 5} M{sub ⊙}), and is likely pressure confined by the colliding flows, implying that self-gravity was not a necessary ingredient for its formation. Much of the molecular gas is relatively diffuse, and the cloud as a whole shows little evidence of star formation activity, supporting a scenario in which it is young and recently formed. Drip-like formations along its lower edge may be explained by fluid dynamical instabilities in the cooled gas.

  19. The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds: VI. Perseus Observed with MIPS

    CERN Document Server

    Rebull, L M; II, N J E; Jørgensen, J K; Harvey, P M; Brooke, T Y; Bourke, T L; Padgett, D L; Chapman, N L; Lai, S P; Spiesmann, W J; Noreiga-Crespo, A; Merin, B; Huard, T; Allen, L E; Blake, G A; Jarrett, T; Körner, D W; Mundy, L G; Myers, P C; Sargent, A I; Van Dishoeck, E F; Wahhaj, Z; Young, K E

    2007-01-01

    We present observations of 10.6 square degrees of the Perseus molecular cloud at 24, 70, and 160 microns with the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS). The image mosaics show prominent, complex extended emission dominated by illuminating B stars on the East side of the cloud, and by cold filaments of 160 micron emission on the West side. Of 3950 point sources identified at 24 microns, 1141 have 2MASS counterparts. A quarter of these populate regions of the Ks vs. Ks-[24] diagram that are distinct from stellar photospheres and background galaxies, and thus are likely to be cloud members with infrared excess. Nearly half (46%) of these 24 micron excess sources are distributed outside the IC 348 and NGC 1333 clusters. NGC 1333 shows the highest fraction of stars with flat or rising spectral energy distributions (28%), while Class II SEDs are most common in IC 348. These results are consistent with previous relative age determinations for the two clusters. The intercluster regio...

  20. Configuration and Use of WRF as a Cloud Resolving Model in Evaluation against Observations

    Science.gov (United States)

    Endo, S.; Liu, Y.; Lin, W.; Liu, G.

    2010-12-01

    Cloud-resolving Models (CRM) and large-eddy simulations (LES) have been demonstrated to be an effective tool in evaluation and development of parameterizations of various fast processes in climate models, including microphysics and turbulence. The DOE FAst-physics System TEstbed and Research (FASTER) project proposes to utilize the Weather Research and Forecasting (WRF) model as a CRM/LES in model evaluation against ARM observations. Here we reconfigure the WRF-LES that uses doubly periodic lateral boundaries to implement additional functions for this purpose, including prescription of time-varying large-scale and surface forcings. This framework allows us to perform (1) cloud resolving simulations using large-scale forcings, (2) conventional CRM simulations with planetary boundary layer scheme, as well as (3) one-dimensional single column simulations with full parameterizations, under the same forcings. We will report results of using the newly configured WRF-CRM to simulate the well-tested continental cumulus case in GCSS model inter-comparison studies described in Brown et al (2002), and the cases collected during the ARM March 2000 Cloud IOP at the Southern Great Plains (SGP) site.

  1. Observational Diagnostics for Two-Fluid Turbulence in Molecular Clouds As Suggested by Simulations

    CERN Document Server

    Meyer, Chad D; Burkhart, Blakesely; Lazarian, Alex

    2013-01-01

    We present high resolution simulations of two-fluid (ion-neutral) MHD turbulence with resolutions as large as 512^3. The simulations are supersonic and mildly sub-Alfvenic, in keeping with the conditions present in molecular clouds. Such turbulence is thought to influence star formation processes in molecular clouds because typical cores form on length scales that are comparable to the dissipation scales of this turbulence in the ions. The simulations are motivated by the fact that recent studies of isophotologue lines in molecular clouds have found significant differences in the linewidth-size relationship for neutral and ion species. The goals of this paper are to explain those observations using simulations and analytic theory, present a new set of density-based diagnostics by drawing on similar diagnostics that have been obtained by studying single-fluid turbulence, and show that our two-fluid simulations play a vital role in reconciling alternative models of star formation. The velocity-dependent diagnos...

  2. Cloud mask via cumulative discriminant analysis applied to satellite infrared observations: scientific basis and initial evaluation

    Directory of Open Access Journals (Sweden)

    U. Amato

    2014-06-01

    Full Text Available We introduce a classification method (Cumulative Discriminant Analysis of the Discriminant Analysis type to discriminate between cloudy and clear sky satellite observations in the thermal infrared. The tool is intended for the high spectral resolution infrared sounder (IRS planned for the geostationary METEOSAT (Meteorological Satellite Third Generation platform and uses IASI (Infrared Atmospheric Sounding Interferometer data as a proxy. The Cumulative Discriminant Analysis does not introduce biases intrinsic with the approximation of the probability density functions and is flexible enough to adapt to different strategies to optimize the cloud mask. The methodology is based on nine statistics computed from IASI spectral radiances, which exploit the high spectral resolution of the instrument and which effectively summarize information contained within the IASI spectrum. A Principal Component Analysis prior step is also introduced which makes the problem more consistent with the statistical assumptions of the methodology. An initial assessment of the scheme is performed based on global and regional IASI real data sets and cloud masks obtained from AVHRR (Advanced Very High Resolution Radiometer and SEVIRI (Spinning Enhanced Visible and Infrared Imager imagers. The agreement with these independent cloud masks is generally well above 80%, except at high latitudes in their winter seasons.

  3. Cloud mask via cumulative discriminant analysis applied to satellite infrared observations: scientific basis and initial evaluation

    Science.gov (United States)

    Amato, U.; Lavanant, L.; Liuzzi, G.; Masiello, G.; Serio, C.; Stuhlmann, R.; Tjemkes, S. A.

    2014-10-01

    We introduce a classification method (cumulative discriminant analysis) of the discriminant analysis type to discriminate between cloudy and clear-sky satellite observations in the thermal infrared. The tool is intended for the high-spectral-resolution infrared sounder (IRS) planned for the geostationary METEOSAT (Meteorological Satellite) Third Generation platform and uses IASI (Infrared Atmospheric Sounding Interferometer) data as a proxy. The cumulative discriminant analysis does not introduce biases intrinsic with the approximation of the probability density functions and is flexible enough to adapt to different strategies to optimize the cloud mask. The methodology is based on nine statistics computed from IASI spectral radiances, which exploit the high spectral resolution of the instrument and which effectively summarize information contained within the IASI spectrum. A principal component analysis prior step is also introduced, which makes the problem more consistent with the statistical assumptions of the methodology. An initial assessment of the scheme is performed based on global and regional IASI real data sets and cloud masks obtained from AVHRR (Advanced Very High Resolution Radiometer) and SEVIRI (Spinning Enhanced Visible and Infrared Imager) imagers. The agreement with these independent cloud masks is generally well above 80 %, except at high latitudes in the winter seasons.

  4. The Three-Dimensional Spatial Structure of Cirrus Clouds Determined from Lidar Satellite Observations

    Science.gov (United States)

    Eloranta, E. W.; Wylie, D.; Wolf, W.

    1996-01-01

    Simultaneous imagery from the University of Wisconsin Volume Imaging Lidar (VIL) and meteorological satellites were used to quantify the spatial structure of cirrus clouds with 60 m resolution. This data was used to determine the spatial distributions of cloud base altitude, cloud top altitude, and mid-cloud altitude. Two dimensional auto-correlation functions describing the mean shape of cirrus clouds were computed. Because cirrus clouds seldom have distinct edges, these correlation functions are derived as a function of a threshold value which defines the cloud edge.

  5. Gamma-ray observations of the Orion Molecular Clouds with the Fermi Large Area Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; Ajello, M.; Allafort, A.; Antolini, E.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cecchi, C.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; D' Ammando, F.; de Angelis, A.; de Palma, F.; Dermer, C. D.; do Couto e Silva, E.; Drell, P. S.; Drlica-Wagner, A.; Enoto, T.; Falletti, L.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fukazawa, Y.; Fukui, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hayashi, K.; Horan, D.; Hou, X.; Hughes, R. E.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Lee, S. -H.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Makishima, K.; Mazziotta, M. N.; Mehault, J.; Mitthumsiri, W.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nishino, S.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Orienti, M.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Razzano, M.; Reimer, A.; Reimer, O.; Roth, M.; Sadrozinski, H. F. -W.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Strong, A. W.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibolla, O.; Tinivella, M.; Torres, D. F.; Tramacere, A.; Troja, E.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Zimmer, S.

    2012-08-08

    We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between ~100 MeV and ~100 GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to ~10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity-integrated CO intensity (W CO) at a 1° × 1° pixel level. The correlation is found to be linear over a W CO range of ~10-fold when divided in three regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The W CO-to-mass conversion factor, X CO, is found to be ~2.3 × 1020 cm-2(K km s–1)–1 for the high-longitude part of Orion A (l > 212°), ~1.7 times higher than ~1.3 × 1020 found for the rest of Orion A and B. We interpret the apparent high X CO in the high-longitude region of Orion A in the light of recent works proposing a nonlinear relation between H2 and CO densities in the diffuse molecular gas. W CO decreases faster than the H2 column density in the region making the gas "darker" to W CO.

  6. The earth's radiation budget and its relation to atmospheric hydrology. I - Observations of the clear sky greenhouse effect. II - Observations of cloud effects

    Science.gov (United States)

    Stephens, Graeme L.; Greenwald, Thomas J.

    1991-01-01

    The clear-sky components of the earth's radiation budget (ERB), the relationship of these components to the sea surface temperature (SST), and microwave-derived water-vapor amount are analyzed in an observational study along with the relationship between the cloudy-sky components of ERB and space/time coincident observations of SST, microwave-derived cloud liquid water, and cloud cover. The purpose of the study is to use these observations for establishing an understanding of the couplings between radiation and the atmosphere that are important to understanding climate feedback. A strategy for studying the greenhouse effect of earth by analyzing the emitted clear-sky longwave flux over the ocean is proposed. It is concluded that the largest observed influence of clouds on ERB is more consistent with macrophysical properties of clouds as opposed to microphysical properties. The analysis for clouds and the greenhouse effect of clouds is compared quantitatively with the clear sky results. Land-ocean differences and tropical-midlatitude differences are shown and explained in terms of the cloud macrostructure.

  7. Observation of the spectrally invariant properties of clouds in cloudy-to-clear transition zones during the MAGIC field campaign

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Weidong; Marshak, Alexander; McBride, Patrick J.; Chiu, J. Christine; Knyazikhin, Yuri; Schmidt, K. Sebastian; Flynn, Connor; Lewis, Ernie R.; Eloranta, Edwin W.

    2016-12-01

    We use the spectrally invariant method to study the variability of cloud optical thickness τ and droplet effective radius reff in transition zones (between the cloudy and clear sky columns) observed from Solar Spectral Flux Radiometer (SSFR) and Shortwave Array Spectroradiometer-Zenith (SASZe) during the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The measurements from the SSFR and the SASZe are different, however inter-instrument differences of self-normalized measurements (divided by their own spectra at a fixed time) are small. The spectrally invariant method approximates the spectra in the cloud transition zone as a linear combination of definitely clear and cloudy spectra, where the coefficients, slope and intercept, character-ize the spectrally invariant properties of the transition zone. Simulation results from the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model demonstrate that (1) the slope of the visible band is positively correlated with the cloud optical thickness τ while the intercept of the near-infrared band has high negative cor-relation with the cloud drop effective radius reff even without the exact knowledge of τ; (2) the above relations hold for all Solar Zenith Angle (SZA) and for cloud-contaminated skies. In observations using redundant measure-ments from SSFR and SASZe, we find that during cloudy-to-clear transitions, (a) the slopes of the visible band de-crease, and (b) the intercepts of the near-infrared band remain almost constant near cloud edges. The findings in simulations and observations suggest that, while the optical thickness decreases during the cloudy-to-clear transition, the cloud drop effective radius does not change when cloud edges are approached. These results sup-port the hypothesis that inhomogeneous mixing dominates near cloud edges in the studied cases.

  8. Observed microphysical changes in Arctic mixed-phase clouds when transitioning from sea ice to open ocean

    Science.gov (United States)

    Young, Gillian; Jones, Hazel M.; Choularton, Thomas W.; Crosier, Jonathan; Bower, Keith N.; Gallagher, Martin W.; Davies, Rhiannon S.; Renfrew, Ian A.; Elvidge, Andrew D.; Darbyshire, Eoghan; Marenco, Franco; Brown, Philip R. A.; Ricketts, Hugo M. A.; Connolly, Paul J.; Lloyd, Gary; Williams, Paul I.; Allan, James D.; Taylor, Jonathan W.; Liu, Dantong; Flynn, Michael J.

    2016-11-01

    In situ airborne observations of cloud microphysics, aerosol properties, and thermodynamic structure over the transition from sea ice to ocean are presented from the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) campaign. A case study from 23 March 2013 provides a unique view of the cloud microphysical changes over this transition under cold-air outbreak conditions. Cloud base lifted and cloud depth increased over the transition from sea ice to ocean. Mean droplet number concentrations, Ndrop, also increased from 110 ± 36 cm-3 over the sea ice to 145 ± 54 cm-3 over the marginal ice zone (MIZ). Downstream over the ocean, Ndrop decreased to 63 ± 30 cm-3. This reduction was attributed to enhanced collision-coalescence of droplets within the deep ocean cloud layer. The liquid water content increased almost four fold over the transition and this, in conjunction with the deeper cloud layer, allowed rimed snowflakes to develop and precipitate out of cloud base downstream over the ocean. The ice properties of the cloud remained approximately constant over the transition. Observed ice crystal number concentrations averaged approximately 0.5-1.5 L-1, suggesting only primary ice nucleation was active; however, there was evidence of crystal fragmentation at cloud base over the ocean. Little variation in aerosol particle number concentrations was observed between the different surface conditions; however, some variability with altitude was observed, with notably greater concentrations measured at higher altitudes ( > 800 m) over the sea ice. Near-surface boundary layer temperatures increased by 13 °C from sea ice to ocean, with corresponding increases in surface heat fluxes and turbulent kinetic energy. These significant thermodynamic changes were concluded to be the primary driver of the microphysical evolution of the cloud. This study represents the first investigation, using in situ airborne observations, of cloud microphysical changes with

  9. HST/WFC3 Observations of Uranus' 2014 storm clouds and comparison with VLT/SINFONI and IRTF/SpeX observations

    CERN Document Server

    Irwin, Patrick G J; Simon, Amy A; Orton, G S; Toledo, Daniel

    2016-01-01

    Observations of Uranus were made on the 8/9th November with HST/WFC3 at a time when a huge cloud complex was present at 30 - 40N. We imaged Uranus in seven filters spanning 467 - 924 nm, and analysed these observations with the NEMESIS radiative-transfer and retrieval code. The same system was also observed in the H-band with VLT/SINFONI ON 31st October and 11th November (Irwin et al., 2016). To constrain the background cloud particle sizes and scattering properties we conducted a limb-darkening analysis of the background cloud structure at 30-40N by simultaneously fitting: a) these HST/OPAL observations at a range of zenith angles; b) the VLT/SINFONI observations at a range of zenith angles; and c) IRTF/SpeX observations made in 2009 (Irwin et al., 2015). We find that the observations are well modelled with a three-component cloud comprised of: 1) a vertically thin, but optically thick 'deep' tropospheric cloud at a pressure of ~2 bars; 2) a methane-ice cloud at the methane-condensation level with variable v...

  10. CARMA LARGE AREA STAR FORMATION SURVEY: OBSERVATIONAL ANALYSIS OF FILAMENTS IN THE SERPENS SOUTH MOLECULAR CLOUD

    Energy Technology Data Exchange (ETDEWEB)

    Fernández-López, M.; Looney, L.; Lee, K.; Segura-Cox, D. [Department of Astronomy, University of Illinois at Urbana—Champaign, 1002 West Green Street, Urbana, IL 61801 (United States); Arce, H. G.; Plunkett, A. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Mundy, L. G.; Storm, S.; Teuben, P. J.; Pound, M. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Isella, A.; Kauffmann, J. [Astronomy Department, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Tobin, J. J. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Rosolowsky, E. [Departments of Physics and Statistics, University of British Columbia, Okanagan Campus, 3333 University Way, Kelowna, BC V1V 1V7 (Canada); Kwon, W. [SRON Netherlands Institute for Space Research, Landleven 12, 9747-AD Groningen (Netherlands); Ostriker, E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Tassis, K. [Department of Physics and Institute of Theoretical and Computational Physics, University of Crete, P.O. Box 2208, GR-710 03 Heraklion, Crete (Greece); Shirley, Y. L., E-mail: manferna@gmail.com [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2014-08-01

    We present the N{sub 2}H{sup +} (J = 1 → 0) map of the Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey. The observations cover 250 arcmin{sup 2} and fully sample structures from 3000 AU to 3 pc with a velocity resolution of 0.16 km s{sup –1}, and they can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N{sub 2}H{sup +} emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two or three quasi-parallel N{sub 2}H{sup +} filaments comprise a single observed dust continuum filament. The difference between the dust and gas filament widths casts doubt on Herschel ability to resolve the Serpens South filaments. Some molecular filaments show velocity gradients along their major axis, and two are characterized by a steep velocity gradient in the direction perpendicular to the filament axis. The observed velocity gradient along one of these filaments was previously postulated as evidence for mass infall toward the central cluster, but these kind of gradients can be interpreted as projection of large-scale turbulence.

  11. CARMA Large Area Star Formation Survey: Observational Analysis of Filaments in the Serpens South Molecular Cloud

    CERN Document Server

    Fernández-López, M; Looney, L; Mundy, L G; Storm, S; Teuben, P J; Lee, K; Segura-Cox, D; Isella, A; Tobin, J J; Rosolowsky, E; Plunkett, A; Kwon, W; Kauffmann, J; Ostriker, E; Tassis, K; Shirley, Y L; Pound, M

    2014-01-01

    We present the N2H+(J=1-0) map of the Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey (CLASSy). The observations cover 250 square arcminutes and fully sample structures from 3000 AU to 3 pc with a velocity resolution of 0.16 km/s, and they can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N2H+ emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two or three quasi-parallel N2H+ filaments comprise a single observed dust continuum filament. The difference between the dust and gas filament widths casts doubt on Herschel ability to resolve the Serpens South filaments. Some molecular filaments show velocity gradients along their major axis, and two are characterized by a steep velocity gradient in the direction perpendicular to the filament axis. The observed velocity gra...

  12. First Mapping Observations of Two Possible Cloud Collision Candidates IRAS 02459+6029 and 05363+3127

    Institute of Scientific and Technical Information of China (English)

    Bei Xin; Jun-Jie Wang

    2008-01-01

    The first mapping observations of the cold infrared sources IRAS 02459+6029 and 05363+3127 in the molecular lines 12CO(1-0), 13CO(1-0) and C18o(1-0) were made using the 13.7 m millimeter wave telescope in Qinghai. Both the integrated intensity maps and position-velocity diagrams show that each has two components adjacent in both space and velocity which means possible cloud-cloud collisions in the two regions. The near-infrared color-color diagram from the 2MASS database reveals that the density of YSOs in the colliding site is much higher than in the surrounding regions. The results appear to indicate that star forming activities have taken place in the two regions due to the cloud-cloud collision. We conclude that both sources are cloud collision candidates.

  13. HST/WFC3 observations of Uranus' 2014 storm clouds and comparison with VLT/SINFONI and IRTF/Spex observations

    Science.gov (United States)

    Irwin, Patrick G. J.; Wong, Michael H.; Simon, Amy A.; Orton, G. S.; Toledo, Daniel

    2017-05-01

    In November 2014 Uranus was observed with the Wide Field Camera 3 (WFC3) instrument of the Hubble Space Telescope as part of the Hubble 2020: Outer Planet Atmospheres Legacy program, OPAL. OPAL annually maps Jupiter, Uranus and Neptune (and will also map Saturn from 2018) in several visible/near-infrared wavelength filters. The Uranus 2014 OPAL observations were made on the 8/9th November at a time when a huge cloud complex, first observed by de Pater et al. (2015) and subsequently tracked by professional and amateur astronomers (Sayanagi et al., 2016), was present at 30-40°N. We imaged the entire visible atmosphere, including the storm system, in seven filters spanning 467-924 nm, capturing variations in the coloration of Uranus' clouds and also vertical distribution due to wavelength dependent changes in Rayleigh scattering and methane absorption optical depth. Here we analyse these new HST observations with the NEMESIS radiative-transfer and retrieval code in multiple-scattering mode to determine the vertical cloud structure in and around the storm cloud system. The same storm system was also observed in the H-band (1.4-1.8 μm) with the SINFONI Integral Field Unit Spectrometer on the Very Large Telescope (VLT) on 31st October and 11th November, reported by Irwin et al. (2016, 10.1016/j.icarus.2015.09.010). To constrain better the cloud particle sizes and scattering properties over a wide wavelength range we also conducted a limb-darkening analysis of the background cloud structure in the 30-40°N latitude band by simultaneously fitting: a) these HST/OPAL observations at a range of zenith angles; b) the VLT/SINFONI observations at a range of zenith angles; and c) IRTF/SpeX observations of this latitude band made in 2009 at a single zenith angle of 23°, spanning the wavelength range 0.8-1.8 μm (Irwin et al., 2015, 10.1016/j.icarus.2014.12.020). We find that the HST observations, and the combined HST/VLT/IRTF observations at all locations are well modelled with

  14. A new ice cloud parameterization for infrared radiative transfer simulation of cloudy radiances: Evaluation and optimization with IIR observations and ice cloud profile retrieval products

    Science.gov (United States)

    Vidot, Jérôme; Baran, Anthony J.; Brunel, Pascal

    2015-07-01

    A new ice cloud optical property database in the thermal infrared has been parameterized for the RTTOV radiative transfer model. The Self-Consistent Scattering Model (SCSM) database is based on an ensemble model of ice crystals and a parameterization of the particle size distribution. This convolution can predict the radiative properties of cirrus without the need of a priori information on the ice particle shape and an estimate of the ice crystal effective dimension. The ice cloud optical properties are estimated through linear parameterizations of ambient temperature and ice water content. We evaluate the new parameterization against existing parameterizations used in RTTOV. We compare infrared observations from Imaging Infrared Radiometer, on board CALIPSO, against RTTOV simulations of the observations. The simulations are performed using two different products of ice cloud profiles, retrieved from the synergy between space-based radar and lidar observations. These are the 2C-ICE and DARDAR products. We optimized the parameterization by testing different SCSM databases, derived from different shapes of the particle size distribution, and weighting the volume extinction coefficient of the ensemble model. By selecting a large global data set of ice cloud profiles of visible optical depths between 0.03 and 4, we found that the simulations, based on the optimized SCSM database parameterization, reproduces the observations with a mean bias of only 0.43 K and a standard deviation of 6.85 K. The optimized SCSM database parameterization can also be applied to any other radiative transfer model.

  15. Reanalysis of Uranus' cloud scattering properties from IRTF/SpeX observations using a self-consistent scattering cloud retrieval scheme

    CERN Document Server

    Irwin, P G J; Fletcher, L N; Barstow, J K; Teanby, N A; Orton, G S; Davis, G R

    2016-01-01

    We have developed a new retrieval approach to modelling near-infrared spectra of Uranus that represents a significant improvement over previous modelling methods. We reanalysed IRTF/SpeX observations of Uranus observed in 2009 covering the wavelength range 0.8 to 1.8 microns and reported by Tice et al. (2013). By retrieving the imaginary refractive index spectra of cloud particles we are able to consistently define the real part of the refractive index spectra, through a Kramers-Kronig analysis, and thus determine self-consistent extinction cross-section, single-scattering and phase-function spectra for the clouds and hazes in Uranus' atmosphere. We tested two different cloud-modelling schemes used in conjunction with the temperature/methane profile of Baines et al. (1995), a reanalysis of the Voyager-2 radio-occultation observations performed by Sromovsky, Fry and Tomasko (2011), and a recent determination from Spitzer (Orton et al., 2014). We find that both cloud-modelling schemes represent the observed cen...

  16. CLOUD AND HAZE IN THE WINTER POLAR REGION OF TITAN OBSERVED WITH VISUAL AND INFRARED MAPPING SPECTROMETER ON BOARD CASSINI

    Energy Technology Data Exchange (ETDEWEB)

    Rannou, P. [GSMA, UMR CNRS 7331, Universite de Reims Champagne-Ardenne (France); Le Mouelic, S. [LPGN, UMR CNRS 6112, Universite de Nantes (France); Sotin, C. [JPL, California Institute of Technology, PA (United States); Brown, R. H., E-mail: pascal.rannou@univ-reims.fr [LPL, University of Arizona, Tucson, AZ (United States)

    2012-03-20

    A large cloud in the north polar region of Titan was first observed by the Visual and Infrared Mapping Spectrometer (VIMS) in 2005 and then in 2006. This cloud, confined beyond the latitude 62 Degree-Sign N, is surrounded by a mixture of aerosol and mist probably lying in the low stratosphere and troposphere. Subsequent images of this region of Titan show a gradual vanishing of this cloud which was reported previously. In this paper, we characterize the physical properties of this cloud, haze, and mist as well as their time evolutions. We note several details on the images such as a secondary cloud above the main cloud and latitudes beyond 70 Degree-Sign N. We also show that the cloud disappearance leaves the polar region poorly loaded in aerosols, yielding an annular zone of aerosols between 50 Degree-Sign N and 65 Degree-Sign N. Our analysis suggests that this structure observed by VIMS in the near-IR is an annular structure observed by ISS on board Voyager one Titan year ago in 1980.

  17. Retrieval of ice cloud properties using an optimal estimation algorithm and MODIS infrared observations: 2. Retrieval evaluation

    Science.gov (United States)

    Wang, Chenxi; Platnick, Steven; Zhang, Zhibo; Meyer, Kerry; Wind, Gala; Yang, Ping

    2016-05-01

    An infrared-based optimal estimation (OE-IR) algorithm for retrieving ice cloud properties is evaluated. Specifically, the implementation of the algorithm with MODerate resolution Imaging Spectroradiometer (MODIS) observations is assessed in comparison with the operational retrieval products from MODIS on the Aqua satellite (MYD06), Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), and the Imaging Infrared Radiometer (IIR); the latter two instruments fly on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite in the Afternoon Constellation (A-Train) with Aqua. The results show that OE-IR cloud optical thickness (τ) and effective radius (reff) retrievals perform best for ice clouds having 0.5 1 km) occurs for τ < 0.5. Analysis of 1 month of the OE-IR retrievals shows large τ and reff uncertainties in storm track regions and the southern oceans where convective clouds are frequently observed, as well as in high-latitude regions where temperature differences between the surface and cloud top are more ambiguous. Generally, comparisons between the OE-IR and the operational products show consistent τ and h retrievals. However, obvious differences between the OE-IR and the MODIS Collection 6 reff are found.

  18. A development of cloud top height retrieval using thermal infrared spectra observed with GOSAT and comparison with CALIPSO data

    Science.gov (United States)

    Someya, Yu; Imasu, Ryoichi; Saitoh, Naoko; Ota, Yoshifumi; Shiomi, Kei

    2016-05-01

    An algorithm based on CO2 slicing, which has been used for cirrus cloud detection using thermal infrared data, was developed for high-resolution radiance spectra from satellites. The channels were reconstructed based on sensitivity height information of the original spectral channels to reduce the effects of measurement errors. Selection of the reconstructed channel pairs was optimized for several atmospheric profile patterns using simultaneous studies assuming a cloudy sky. That algorithm was applied to data by the Greenhouse gases Observing SATellite (GOSAT). Results were compared with those obtained from the space-borne lidar instrument on-board Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Monthly mean cloud amounts from the slicing generally agreed with those from CALIPSO observations despite some differences caused by surface temperature biases, optically very thin cirrus, multilayer structures of clouds, extremely low cloud tops, and specific atmospheric conditions. Comparison of coincident data showed good agreement, except for some cases, and revealed that the improved slicing method is more accurate than the traditional slicing method. Results also imply that improved slicing can detect low-level clouds with cloud top heights as low as approximately 1.5 km.

  19. Uncertainty in Observed and Modelled Cloud Fraction Over Greenland and its Impact on the Ice Sheet Energy Balance

    Science.gov (United States)

    Griggs, J.; Bamber, J.

    2006-12-01

    Clouds have an important controlling influence on the radiative balance, and as a consequence ablation rates, over the Greenland ice sheet. In addition, to derive reliable estimates of surface albedo, temperature and radiative fluxes from satellite data, it is necessary to adequately identify clouds in imagery. Energy balance models (EBM) for the ice sheet have been developed that use both parameterizations for cloud cover and numerical weather prediction re-analysis data. Little is known, however, about the true cloud cover characteristics over Greenland to assess the quality of these EBM inputs. Here, we attempt to address this knowledge gap by examining cloud characteristics, as determined by three different satellites sensors: AVHRR, ATSR-2 and MODIS. The first provides a multi-decadal time series of clouds, albedo and surface temperature and is available as a homogeneous, consistent data set from 1982. AVHRR data, however, is also the most challenging to cloud clear over snow-covered terrain, due to the limited spectral capabilities of the instrument, while ATSR-2 permits identification and classification using stereo- photogrammetric techniques and MODIS has enhanced spectral sampling in the visible. We compare spatial and seasonal cloud fractions from the three sensors against each other and with synoptic coastal and automatic weather station data. We then assess the cloud fractions, and inferred patterns of accumulation, from the two most commonly used re-analysis data sets: NCEP/NCAR and ERA-40. We find poor agreement between the two re-analysis data sets. In addition, they bear little similarity to the observed cloud fractions derived from the satellite observations. This implies that they likely produce poor accumulation estimates over the ice sheet, but also poor estimates of radiation balance. Using the re-analysis data to force an EBM, without appropriate downscaling and correction for the substantial biases present, would, therefore, produce serious

  20. Evaluation of the shortwave cloud radiative effect over the ocean by use of ship and satellite observations

    Directory of Open Access Journals (Sweden)

    T. Hanschmann

    2012-12-01

    Full Text Available In this study the shortwave cloud radiative effect (SWCRE over ocean calculated by the ECHAM 5 climate model is evaluated for the cloud property input derived from ship based measurements and satellite based estimates and compared to ship based radiation measurements. The ship observations yield cloud fraction, liquid water path from a microwave radiometer, cloud bottom height as well as temperature and humidity profiles from radiosonde ascents. Level-2 products of the Satellite Application Facility on Climate Monitoring (CM~SAF from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI have been used to characterize clouds. Within a closure study six different experiments have been defined to find the optimal set of measurements to calculate downward shortwave radiation (DSR and the SWCRE from the model, and their results have been evaluated under seven different synoptic situations. Four of these experiments are defined to investigate the advantage of including the satellite-based cloud droplet effective radius as additional cloud property. The modeled SWCRE based on satellite retrieved cloud properties has a comparable accuracy to the modeled SWCRE based on ship data. For several cases, an improvement through introducing the satellite-based estimate of effective radius as additional information to the ship based data was found. Due to their different measuring characteristics, however, each dataset shows best results for different atmospheric conditions.

  1. Observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

    Directory of Open Access Journals (Sweden)

    M. Schäfer

    2015-01-01

    Full Text Available Based on airborne spectral imaging observations three-dimensional (3-D radiative effects between Arctic boundary layer clouds and ice floes have been identified and quantified. A method is presented to discriminate sea ice and open water in case of clouds from imaging radiance measurements. This separation simultaneously reveals that in case of clouds the transition of radiance between open water and sea ice is not instantaneously but horizontally smoothed. In general, clouds reduce the nadir radiance above bright surfaces in the vicinity of sea ice – open water boundaries, while the nadir radiance above dark surfaces is enhanced compared to situations with clouds located above horizontal homogeneous surfaces. With help of the observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge. This affected distance Δ L was found to depend on both, cloud and sea ice properties. For a ground overlaying cloud in 0–200 m altitude, increasing the cloud optical thickness from τ = 1 to τ = 10 decreases Δ L from 600 to 250 m, while increasing cloud base altitude or cloud geometrical thickness can increase Δ L; Δ L(τ = 1/10 = 2200 m/1250 m for 500–1000 m cloud altitude. To quantify the effect for different shapes and sizes of the ice floes, various albedo fields (infinite straight ice edge, circles, squares, realistic ice floe field were modelled. Simulations show that Δ L increases by the radius of the ice floe and for sizes larger than 6 km (500–1000 m cloud altitude asymptotically reaches maximum values, which corresponds to an infinite straight ice edge. Furthermore, the impact of these 3-D-radiative effects on retrieval of cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 and 30% in retrievals of cloud optical thickness and effective radius reff, respectively. With help of

  2. Relationships Between Ice Cloud Properties and Radiative Effects from A-Train Observations and Global Climate Models

    Science.gov (United States)

    Berry, B. J.; Mace, G. G.

    2014-12-01

    Using data from the A-Train satellites, we investigate the distribution of clouds and their microphysical and radiative properties in Southeast Asia during the summer monsoon. We find an approximate balance in the top of the atmosphere (TOA) cloud radiative effect, which is largely due to commonly occurring cirrus layers that warm the atmosphere, and less frequent deep layer clouds, which produce a strong cooling at the surface. The distribution of cloud ice water path (IWP) in cirrus layers, obtained from the 2C-ICE CloudSat data product, is highly skewed with a mean value of 170 g m-2 and a median of 16 g m-2. We evaluate the fraction of the total IWP observed by CloudSat and CALIPSO individually and find that both instruments are necessary for describing the overall IWP statistics and particularly the values that are most important to cirrus radiative impact. In examining how cirrus cloud radiative effects at the TOA vary as a function of IWP, we find that cirrus with IWP less than 200 g m-2 produce a net warming. Weighting the distribution of radiative effect by the frequency of occurrence of IWP values, we find that cirrus with IWP around 20 g m-2 contribute most to heating at the TOA. We conclude that the mean IWP is a poor diagnostic of radiative impact. We suggest that climate model intercomparisons with data should focus on the median IWP because that statistic is more descriptive of the cirrus that contribute most to the radiative impacts of tropical ice clouds. Given these findings, we use the A-Train observations to address the issues of IWP occurrence and high cloud forcing in a global climate model (GCM). Our goal is to determine whether the clouds that heat the upper troposphere in the model are the same genre of clouds that heat the upper troposphere in the real atmosphere. First, we define a cloud radiative kernel that's a function of IWP to determine whether the modeled ice clouds produce similar shortwave and longwave radiative effects at the TOA

  3. Using Satellite Observations of Cloud Vertical Distribution to Improve Global Model Estimates of Cloud Radiative Effect on Key Tropospheric Oxidants

    Science.gov (United States)

    Liu, Hongyu; Crawford, James; Ham, Seung-Hee; Zhang, Bo; Kato, Seiji; Voulgarakis, Apostolos; Chen, Gao; Fairlie, Duncan; Duncan, Bryan; Yantosca, Robert

    2017-01-01

    Clouds directly affect tropospheric photochemistry through modification of solar radiation that determines photolysis frequencies. This effect is an important component of global tropospheric chemistry-climate interaction, and its understanding is thus essential for predicting the feedback of climate change on tropospheric chemistry.

  4. Observations of Three-Dimensional Radiative Effects that Influence Satellite Retrievals of Cloud Properties

    Science.gov (United States)

    Varnai, Tamas; Marshak, Alexander; Lau, William K. M. (Technical Monitor)

    2001-01-01

    This paper examines three-dimensional (3D) radiative effects, which arise from horizontal radiative interactions between areas that have different cloud properties. Earlier studies have argued that these effects can cause significant uncertainties in current satellite retrievals of cloud properties, because the retrievals rely on one-dimensional (1D) theory and do not consider the effects of horizontal changes in cloud properties. This study addresses two questions: which retrieved cloud properties are influenced by 3D radiative effects, and where 3D effects tend to occur? The influence of 3D effects is detected from the wayside illumination and shadowing make clouds appear asymmetric: Areas appear brighter if the cloud top surface is tilted toward, rather than away from, the Sun. The analysis of 30 images by the Moderate Resolution Imaging Spectroradiometer (MODIS) reveals that retrievals of cloud optical thickness and cloud water content are most influenced by 3D effects, whereas retrievals of cloud particle size are much less affected. The results also indicate that while 3D effects are strongest at cloud edges, cloud top variability in cloud interiors, even in overcast regions, also produces considerable 3D effects. Finally, significant 3D effects are found in a wide variety of situations, ranging from thin clouds to thick ones and from low clouds to high ones.

  5. The Spitzer Survey of Interstellar Clouds in the Gould Belt. VI. The Auriga-California Molecular Cloud observed with IRAC and MIPS

    CERN Document Server

    Broekhoven-Fiene, Hannah; Harvey, Paul M; Gutermuth, Robert A; Huard, Tracy L; Tothill, Nicholas F H; Nutter, David; Bourke, Tyler L; DiFrancesco, James; Jørgensen, Jes K; Allen, Lori E; Chapman, Nicholas L; Dunham, Michael M; Merın, Bruno; Miller, Jennifer F; Terebey, Susan; Peterson, Dawn E; Stapelfeldt, Karl R

    2014-01-01

    We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70 and 160 micron observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 sq-deg with IRAC and 10.47 sq-deg with MIPS. This giant molecular cloud is one of two in the nearby Gould Belt of star-forming regions, the other being the Orion A Molecular Cloud (OMC). We compare source counts, colors and magnitudes in our observed region to a subset of the SWIRE data that was processed through our pipeline. Using color-magnitude and color-color diagrams, we find evidence for a substantial population of 166 young stellar objects (YSOs) in the cloud, many of which were previously unknown. Most of this population is concentrated around the LkHalpha 101 cluster and the filament extending from it. We present a quantitative description of the degree of clustering and discuss the fraction of YSOs in the region with disks relative to an estimate of the diskless YS...

  6. The Spitzer Survey of Interstellar Clouds in the Gould Belt. VI. The Auriga-California Molecular Cloud Observed with IRAC and MIPS

    Science.gov (United States)

    Broekhoven-Fiene, Hannah; Matthews, Brenda C.; Harvey, Paul M.; Gutermuth, Robert A.; Huard, Tracy L.; Tothill, Nicholas F. H.; Nutter, David; Bourke, Tyler L.; DiFrancesco, James; Jorgensen, Jes K.; Allen, Lori E.; Chapman, Nicholas L.; Dunham, Michael M.; Merin, Bruno; Miller, Jennifer F.; Terebey, Susan; Peterson, Dawn E.; Stapelfeldt, Karl R.

    2014-01-01

    We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70 and 160 micrometers observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 deg(exp 2) with IRAC and 10.47 deg2 with MIPS. This giant molecular cloud is one of two in the nearby Gould Belt of star-forming regions, the other being the Orion A Molecular Cloud (OMC). We compare source counts, colors and magnitudes in our observed region to a subset of the SWIRE data that was processed through our pipeline. Using color-magnitude and color-color diagrams, we find evidence for a substantial population of 166 young stellar objects (YSOs) in the cloud, many of which were previously unknown. Most of this population is concentrated around the LkH(alpha) 101 cluster and the filament extending from it. We present a quantitative description of the degree of clustering and discuss the fraction of YSOs in the region with disks relative to an estimate of the diskless YSO population. Although the AMC is similar in mass, size and distance to the OMC, it is forming about 15 - 20 times fewer stars.

  7. Japan Data Exchange Network JDXnet and Cloud-type Data Relay Server for Earthquake Observation Data

    Science.gov (United States)

    Takano, K.; Urabe, T.; Tsuruoka, H.; Nakagawa, S.

    2015-12-01

    In Japan, high-sensitive seismic observation and broad-band seismic observation are carried out by several organization such as Japan Meteorological Agency (JMA) , National Research Institute for Earth Science and Disaster Prevention (NIED), nine National Universities, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) , etc. The total number of the observation station is about 1400 points. The total volume of the seismic waveform data collected from all these observation station is about 1MByte for 1 second (about 8 to 10Mbps) by using the WIN system(Urabe 1991). JDXnet is the Japan Data eXchange network for earthquake observation data. JDXnet was started from 2007 by cooperation of the researchers of each organization. All the seismic waveform data are available at the all organizations in real-time. The core of JDXnet is the broadcast type real-time data exchange by using the nationwide L2-VPN service offered in JGN-X of NICT and SINET4 of NII. Before the Tohoku earthquake, the nine national universities had collected seismic data to each data center and then exchanged with other universities and institutions by JDXnet. However, in this case, if the center of the university was stopped, all data of the university could not use even though there are some alive observation stations. Because of this problem, we have prepared the data relay server in the data center of SINET4 ie the cloud center. This data relay server collects data directly from the observation stations of the universities and delivers data to all universities and institutions by JDXnet. By using the relay server on cloud center, even if some universities are affected by a large disaster, it is eliminated that the data of the living station is lost. If the researchers set up seismometers and send data to the relay server, then data are available to all researchers. This mechanism promotes the joint use of the seismometers and joint research activities in nationwide researchers.

  8. An Intercomparison of Cloud-Resolving Models with the Atmospheric Radiation Measurement Summer 1997 Intensive Observation Period Data

    Science.gov (United States)

    Xu, Kuan-Man; Cederwall, Richard T.; Donner, Leo J.; Grabowski, Wojciech W.; Guichard, Francoise; Johnson, Daniel E.; Khairoutdinov, Marat; Krueger, Steven K.; Petch, Jon C.; Randall, David A.

    2002-01-01

    This paper reports an intercomparison study of midlatitude continental cumulus convection simulated by eight two-dimensional and two three-dimensional cloud-resolving models (CRMs), driven by observed large-scale advective temperature and moisture tendencies, surface turbulent fluxes, and radiative-heating profiles during three sub-periods of the summer 1997 Intensive Observation Period of the US Department of Energy's Atmospheric Radiation Measurement (ARM) program. Each sub-period includes two or three precipitation events of various intensities over a span of 4 or 5 days. The results can be summarized as follows. CRMs can reasonably simulate midlatitude continental summer convection observed at the ARM Cloud and Radiation Testbed site in terms of the intensity of convective activity, and the temperature and specific-humidity evolution. Delayed occurrences of the initial precipitation events are a common feature for all three sub-cases among the models. Cloud mass fluxes, condensate mixing ratios and hydrometeor fractions produced by all CRMs are similar. Some of the simulated cloud properties such as cloud liquid-water path and hydrometeor fraction are rather similar to available observations. All CRMs produce large downdraught mass fluxes with magnitudes similar to those of updraughts, in contrast to CRM results for tropical convection. Some inter-model differences in cloud properties are likely to be related to those in the parametrizations of microphysical processes. There is generally a good agreement between the CRMs and observations with CRMs being significantly better than single-column models (SCMs), suggesting that current results are suitable for use in improving parametrizations in SCMs. However, improvements can still be made in the CRM simulations; these include the proper initialization of the CRMs and a more proper method of diagnosing cloud boundaries in model outputs for comparison with satellite and radar cloud observations.

  9. Technical Note: The effect of sensor resolution on the number of cloud-free observations from space

    Directory of Open Access Journals (Sweden)

    J. M. Krijger

    2007-06-01

    Full Text Available Air quality and surface emission inversions are likely to be focal points for future satellite missions on atmospheric composition. Most important for these applications is sensitivity to the atmospheric composition in the lowest few kilometers of the troposphere. Reduced sensitivity by clouds needs to be minimized. In this study we have quantified the increase in number of useful footprints, i.e. footprints which are sufficient cloud-free, as a function of sensor resolution (footprint area. High resolution (1 km×1 km MODIS TERRA cloud mask observations are aggregated to lower resolutions. Statistics for different thresholds on cloudiness are applied. For each month in 2004 four days of MODIS data are analyzed. Globally the fraction of cloud-free observations drops from 16% at 100 km2 resolution to only 3% at 10 000 km2 if not a single MODIS observation within a footprint is allowed to be cloudy. If up to 5% or 20% of a footprint is allowed to be cloudy, the fraction of cloud-free observations is 9% or 17%, respectively, at 10 000 km2 resolution. The probability of finding cloud-free observations for different sensor resolutions is also quantified as a function of geolocation and season, showing examples over Europe and northern South America (ITCZ.

  10. In situ observation of texture and microstructure evolution during rolling and globularization of Ti-6Al-4V

    KAUST Repository

    Warwick, Jonnathan L W

    2013-03-01

    The evolution of texture in β-annealed Ti-6Al-4V during α-β rolling and so-called recrystallization annealing has been examined using synchrotron X-ray diffraction and ex situ characterization. During rolling, the initial α (0 0 0 2) texture softens and the colony α becomes kinked. During globularization, the texture strengthens as highly strained (and hence misoriented) areas of the laths disappear and this strengthening continues once coarsening of the primary α becomes dominant. At shorter heat treatment times the αs laths that form on cooling do so with a range of variant-related orientations to the β, but at longer annealing times this αs takes on the orientation of the surrounding αp. The implications for the mechanical performance of macrozone-containing bimodal Ti-6Al-4V material are discussed. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  11. Evaluation of cloud fraction and its radiative effect simulated by IPCC AR4 global models against ARM surface observations

    Directory of Open Access Journals (Sweden)

    Y. Qian

    2012-02-01

    Full Text Available Cloud Fraction (CF is the dominant modulator of radiative fluxes. In this study, we evaluate CF simulated in the IPCC AR4 GCMs against ARM long-term ground-based measurements, with a focus on the vertical structure, total amount of cloud and its effect on cloud shortwave transmissivity. Comparisons are performed for three climate regimes as represented by the Department of Energy Atmospheric Radiation Measurement (ARM sites: Southern Great Plains (SGP, Manus, Papua New Guinea and North Slope of Alaska (NSA. Our intercomparisons of three independent measurements of CF or sky-cover reveal that the relative differences are usually less than 10% (5% for multi-year monthly (annual mean values, while daily differences are quite significant. The total sky imager (TSI produces smaller total cloud fraction (TCF compared to a radar/lidar dataset for highly cloudy days (CF > 0.8, but produces a larger TCF value than the radar/lidar for less cloudy conditions (CF < 0.3. The compensating errors in lower and higher CF days result in small biases of TCF between the vertically pointing radar/lidar dataset and the hemispheric TSI measurements as multi-year data is averaged. The unique radar/lidar CF measurements enable us to evaluate seasonal variation of cloud vertical structures in the GCMs.

    Both inter-model deviation and model bias against observation are investigated in this study. Another unique aspect of this study is that we use simultaneous measurements of CF and surface radiative fluxes to diagnose potential discrepancies among the GCMs in representing other cloud optical properties than TCF. The results show that the model-observation and inter-model deviations have similar magnitudes for the TCF and the normalized cloud effect, and these deviations are larger than those in surface downward solar radiation and cloud transmissivity. This implies that other dimensions of cloud in addition to cloud amount, such as cloud optical thickness and

  12. Ship and satellite observations over the ocean for verification of the shortwave cloud radiative effect in climate models

    Directory of Open Access Journals (Sweden)

    T. Hanschmann

    2012-07-01

    Full Text Available In this study the accuracy of the radiative transfer scheme of the ECHAM-5 climate model for reproducing the shortwave cloud radiative effect (SWCRE at the sea surface has been investigated. A characterization of both the observed state of the atmosphere and the surface radiation budget from ship and satellite is used for this purpose. The ship observations yield cloud fraction, liquid water path from a microwave radiometer, cloud bottom height as well as temperature and humidity profiles from radiosonde ascents. Level-2 products of the Satellite Application Facility on Climate Monitoring (CM-SAF from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI have been used to characterize clouds. Within a closure study six different experiments have been defined to find the optimal set of measurements to calculate downward shortwave radiation (DSR and the SWCRE from the model, and their results have been evaluated under seven different synoptic situations. Four of these experiments are defined to investigate the advantage of including the satellite-based cloud droplet effective radius as additional cloud property. The modeled SWCRE based on satellite retrieved cloud properties has a comparable accuracy to the modeled SWCRE based on ship data. For several cases, an improvement through introducing the satellite-based estimate of effective radius as additional information to the ship based data was found. Due to their different measuring characteristics, however, each dataset shows best results for different atmospheric conditions.

  13. A molecular cloud complex above the galactic plane.. I. Extended CO observations of the NGC 281 region

    Science.gov (United States)

    Lee, Youngung; Jung, Jae-Hoon

    2003-03-01

    We have mapped the entire extent of the molecular cloud complex associated with NGC 281, both in 12CO ( J=1-0) and 13CO ( J=1-0), using the Taeduk Radio Astronomy Observatory (TRAO) 14 m telescope. We also observed a few selected fields with bright 13CO emission, in CS ( J=2-1) and HCO + ( J=1-0). This region is distinguished by its vertical height of ˜320 pc above the midplane of the Perseus spiral arm, at a distance of 2.9 kpc. The molecular gas in the mapped region is found to extend far beyond the H II region NGC 281 (Sh 184). The southern boundary of the CO emission closely follows the southern boundary of the 100 μm dust emission. The molecular cloud complex consists of two main clouds bisected by the H II region, as well as several other clouds distributed over a range of 90 pc along the galactic longitude direction. Except for one cloud at VLSR=-43.9 km s -1, all these clouds occupy a small, contiguous velocity range centered at VLSR=-30 km s -1. Although these clouds are weakly connected, they clearly show distinct, knotted features along the galactic longitude direction. We assigned names to each cloud (A-H), derive their various physical parameters, and discuss their physical properties. These clouds do not show any specific, systematic behavior in their velocity field, except for a small gradient along galactic longitude (for A-E). The brightest 12CO and 13CO emissions are detected toward cloud A, which is located farthest from the two main clouds. We found star formation to be ongoing in clouds A and B, though these are not as active as D and E. The associated newborn stars have FIR properties similar to those of Herbig Ae/Be stars, and several outflows are also seen. We estimated the cloud masses in three different ways, and discuss the discrepancies between the resulting values. We estimate the total mass of the mapped region to be ˜3.7×10 4 M ⊙, using a conversion factor from CO luminosity to gas mass. About half of the clouds seem to be

  14. A Comparison of TWP-ICE Observational Data with Cloud-Resolving Model Results

    Energy Technology Data Exchange (ETDEWEB)

    Fridlind, A. M.; Ackerman, Andrew; Chaboureau, Jean-Pierre; Fan, Jiwen; Grabowski, Wojciech W.; Hill, A.; Jones, T. R.; Khaiyer, M. M.; Liu, G.; Minnis, Patrick; Morrison, H.; Nguyen, L.; Park, S.; Petch, Jon C.; Pinty, Jean-Pierre; Schumacher, Courtney; Shipway, Ben; Varble, A. C.; Wu, Xiaoqing; Xie, Shaocheng; Zhang, Minghua

    2012-03-13

    Observations made during the TWP-ICE campaign are used to drive and evaluate thirteen cloud-resolving model simulations with periodic lateral boundary conditions. The simulations employ 2D and 3D dynamics, one- and two-moment microphysics, several variations on large-scale forcing, and the use of observationally derived aerosol properties to prognose droplet numbers. When domain means are averaged over a 6-day active monsoon period, all simulations reproduce observed surface precipitation rate but not its structural distribution. Simulated fractional areas covered by convective and stratiform rain are uncorrelated with one another, and are both variably overpredicted by up to a factor of {approx}2. Stratiform area fractions are strongly anticorrelated with outgoing longwave radiation (OLR) but are negligibly correlated with ice water path (IWP), indicating that ice spatial distribution controls OLR more than mean IWP. Overpredictions of OLR tend to be accompanied by underpredictions of reflected shortwave radiation (RSR). When there are two simulations differing only in microphysics scheme or large-scale forcing, the one with smaller stratiform area tends to exhibit greater OLR and lesser RSR by similar amounts. After {approx}10 days, simulations reach a suppressed monsoon period with a wide range of mean precipitable water vapor, attributable in part to varying overprediction of cloud-modulated radiative flux divergence compared with observationally derived values. Differences across the simulation ensemble arise from multiple sources, including dynamics, microphysics, and radiation treatments. Close agreement of spatial and temporal averages with observations may not be expected, but the wide spreads of predicted stratiform fraction and anticorrelated OLR indicate a need for more rigorous observation-based evaluation of the underlying micro- and macrophysical properties of convective and stratiform structures.

  15. Aircraft observations and model simulations of concentration and particle size distribution in the Eyjafjallajökull volcanic ash cloud

    OpenAIRE

    Dacre, H. F.; A. L. M. Grant; Johnson, B. T.

    2013-01-01

    The Eyjafjallajökull volcano in Iceland emitted a cloud of ash into the atmosphere during April and May 2010. Over the UK the ash cloud was observed by the FAAM BAe-146 Atmospheric Research Aircraft which was equipped with in-situ probes measuring the concentration of volcanic ash carried by particles of varying sizes. The UK Met Office Numerical Atmospheric-dispersion Modelling Environment (NAME) has been used to simulate the evolution of the ash cloud emitted by the Eyjafjallajökull volcano...

  16. Aircraft observations and model simulations of concentration and particle size distribution in the Eyjafjallajökull volcanic ash cloud

    OpenAIRE

    Dacre, H. F.; A. L. M. Grant; Johnson, B. T.

    2012-01-01

    The Eyjafjallajökull volcano in Iceland emitted a cloud of ash into the atmosphere during April and May 2010. Over the UK the ash cloud was observed by the FAAM BAe-146 Atmospheric Research Aircraft which was equipped with in-situ probes measuring the concentration of volcanic ash carried by particles of varying sizes. The UK Met Office Numerical Atmospheric-dispersion Modelling Environment (NAME) has been used to simulate the evolution of the ash cloud emitted by the Eyjafjallajökull volcano...

  17. OH AND CN ZEEMAN OBSERVATIONS OF MAGNETIC FIELDS IN MOLECULAR CLOUDS

    Directory of Open Access Journals (Sweden)

    R. M. Crutcher

    2009-01-01

    Full Text Available Observations of the Zeeman e ect in OH and CN provide valuable information about magnetic eld strengths and directions in molecular clouds in the density range 103 < n(cm-3 < 106 that these species sample. These data make it possible to test predictions of weak eld, turbulence driven star formation and strong eld, ambipolar di usion driven star formation. Here we discuss exactly what information Zeeman observations provide and how those data may be analyzed to yield meaningful results. The data imply that the mean mass-to-ux ratio in molecular cores is - 2 - 3 times critical, which means that magnetic elds are generally not strong enough to prevent gravitational collapse. However, this information about mean eld strengths is not de nitive in excluding one or the other of the two models of star formation. Present data do suggest that magnetic elds play a very signi cant role in the evolution of molecular clouds and in the star formation process. Finally, very preliminary results are discussed from two in-progress studies; these studies have the potential to be signi cantly more de nitive in testing the predictions of star formation theory, and perhaps in discriminating between the two theories.

  18. N2H+ and HC3N Observations of the Orion A Cloud

    CERN Document Server

    Tatematsu, K; Umemoto, T; Sekimoto, Y

    2008-01-01

    The ``integral-shaped filament'' of the Orion A giant molecular cloud was mapped in N2H+, and its northern end, the OMC-2/3 region was observed also in HC3N and CCS. The N2H+ distribution is similar to the dust continuum distribution, except for the central part of the Orion Nebula. The distribution of H13CO+ holds resemblance to that of dust continuum, but the N2H+ distribution looks more similar to dust continuum distribution. The N-bearing molecules, N2H+ and NH3 seem to be more intense in OMC-2, compared with the H13CO+ and CS distribution. We identified 34 cloud cores from N2H+ data. Over the Orion Nebula region, the N2H+ linewidth is large (1.1-2.1 km/s). In the OMC-2/3 region, it becomes moderate (0.5-1.3 km/s), and it is smaller (0.3-1.1 km/s) in the south of the Orion Nebula. On the other hand, the gas kinetic temperature of the quiescent cores observed in N2H+ is rather constant (~ 20 K) over the $\\int$-shaped filament. We detected no CCS emission in the OMC-2/3 region. In general, N2H+ and HC3N dis...

  19. On the Possibility of Observing H2 Emission from Primordial Molecular Cloud Kernels

    CERN Document Server

    Kamaya, H; Kamaya, Hideyuki; Silk, Joseph

    2002-01-01

    We study the prospects for observing H$_2$ emission during the assembly of primordial molecular cloud kernels. The primordial molecular cloud cores, which resemble those at the present epoch, can emerge around $1+z=20$ according to recent numerical simulations. The kernels form inside the cores, and the first stars will appear inside the kernels. A kernel typically contracts to form one of the first generation stars with an accretion rate that is as large as $\\sim 0.01 M_\\odot$ year$^{-1}$. This occurs due to the primordial abundances that result in a kernel temperature of order 1000K, and the collapsing kernel emits H$_2$ line radiation at a rate $\\sim 10^{35}$ erg sec$^{-1}$. Principally $J=5-3$ (v=0) rotational emission of H$_2$ is expected. At redshift $1+z=20$, the expected flux is $\\sim 0.01~\\mu$Jy for a single kernel. While an individual object is not observable by any facilities available in the near future, the expected assembly of primordial star clusters on sub-galactic scales can result in fluxes ...

  20. Advanced ocean color sensor observations for retrieval of cloud, aerosol and water vapor properties

    Science.gov (United States)

    Remer, L. A.

    2016-02-01

    While the next generation of ocean color sensors offers enhanced capability to retrieve ocean parameters and to advance ocean science, these sensors also offer enhanced capability for observing atmospheric parameters, as well. In particular advanced ocean color sensors are expected to broaden the spectral range to include bands from the UV to the SWIR, inclusive on a single instrument that will observe aquatic, terrestrial and atmospheric targets with the same geometry, same spatial resolution, and similar calibration strategies across the entire spectrum. This broad spectrum instrument is unprecedented, and unites atmospheric parameter retrieval algorithms from MODIS and OMI heritages, but for the first time providing UV data at moderate resolution and not the 13x24 km currently available from OMI. In addition the advanced ocean instruments will likely be hyperspectral, providing opportunity to apply retrieval techniques for aerosols, clouds and water vapor that have been developed for airborne spectrometers like AVIRIS, but now can be attempted from space. These spectral techniques are powerful and may overcome longstanding issues concerning aerosol and cloud layer height, gas corrections etc. Note, that the added capability of hyperspectral and broad spectrum imagers can push atmospheric science forward, over both land and ocean, and at the same time improve atmospheric correction over ocean.

  1. Observation of interstellar lithium in the low-metallicity Small Magellanic Cloud.

    Science.gov (United States)

    Howk, J Christopher; Lehner, Nicolas; Fields, Brian D; Mathews, Grant J

    2012-09-01

    The primordial abundances of light elements produced in the standard theory of Big Bang nucleosynthesis (BBN) depend only on the cosmic ratio of baryons to photons, a quantity inferred from observations of the microwave background. The predicted primordial (7)Li abundance is four times that measured in the atmospheres of Galactic halo stars. This discrepancy could be caused by modification of surface lithium abundances during the stars' lifetimes or by physics beyond the Standard Model that affects early nucleosynthesis. The lithium abundance of low-metallicity gas provides an alternative constraint on the primordial abundance and cosmic evolution of lithium that is not susceptible to the in situ modifications that may affect stellar atmospheres. Here we report observations of interstellar (7)Li in the low-metallicity gas of the Small Magellanic Cloud, a nearby galaxy with a quarter the Sun's metallicity. The present-day (7)Li abundance of the Small Magellanic Cloud is nearly equal to the BBN predictions, severely constraining the amount of possible subsequent enrichment of the gas by stellar and cosmic-ray nucleosynthesis. Our measurements can be reconciled with standard BBN with an extremely fine-tuned depletion of stellar Li with metallicity. They are also consistent with non-standard BBN.

  2. Molecular cloud formation as seen in synthetic Hi and molecular gas observations

    CERN Document Server

    Heiner, Jonathan S; Ballesteros-Paredes, Javier

    2014-01-01

    We present synthetic Hi and CO observations of a simulation of decaying turbulence in the thermally bistable neutral medium. We first present the simulation, with clouds initially consisting of clustered clumps. Self-gravity causes these clump clusters to form more homogeneous dense clouds. We apply a simple radiative transfer algorithm, and defining every cell with > 1 as molecular. We then produce maps of Hi, CO-free molecular gas, and CO, and investigate the following aspects: i) The spatial distribution of the warm, cold, and molecular gas, finding the well-known layered structure, with molecular gas surrounded by cold Hi, surrounded by warm Hi. ii) The velocity of the various components, with atomic gas generally flowing towards the molecular gas, and that this motion is reflected in the frequently observed bimodal shape of the Hi profiles. This conclusion is tentative, because we do not include feedback. iii) The production of Hi self-absorption (HISA) profiles, and the correlation of HISA with molecul...

  3. VLT/UVES Observations of Interstellar Molecules and Diffuse Bands in the Magellanic Clouds

    CERN Document Server

    Welty, D E; Gredel, R; Lambert, D L; Thorburn, J A

    2006-01-01

    We discuss the abundances of interstellar CH, CH+, and CN in the Magellanic Clouds (MC), derived from spectra of 7 SMC and 13 LMC stars obtained (mostly) with the VLT/UVES. CH and/or CH+ are detected toward 3 SMC and 9 LMC stars; CN is detected toward 2 stars. In the MC, the CH/H2 ratio is comparable to that found for diffuse Galactic molecular clouds in some sight lines, but is lower by factors up to 10-15 in others. The abundance of CH in the MC thus appears to depend on local physical conditions -- and not just on metallicity. The observed relationships between the column density of CH and those of CN, CH+, Na I, and K I in the MC are generally consistent with the trends observed in our Galaxy. Using existing data for the rotational populations of H2, we estimate temperatures, radiation field strengths, and local hydrogen densities for the diffuse molecular gas. Densities estimated from N(CH), assuming that CH is produced via steady-state gas-phase reactions, are considerably higher; much better agreement ...

  4. COLLABORATIVE RESEARCH:USING ARM OBSERVATIONS & ADVANCED STATISTICAL TECHNIQUES TO EVALUATE CAM3 CLOUDS FOR DEVELOPMENT OF STOCHASTIC CLOUD-RADIATION

    Energy Technology Data Exchange (ETDEWEB)

    Somerville, Richard

    2013-08-22

    The long-range goal of several past and current projects in our DOE-supported research has been the development of new and improved parameterizations of cloud-radiation effects and related processes, using ARM data, and the implementation and testing of these parameterizations in global models. The main objective of the present project being reported on here has been to develop and apply advanced statistical techniques, including Bayesian posterior estimates, to diagnose and evaluate features of both observed and simulated clouds. The research carried out under this project has been novel in two important ways. The first is that it is a key step in the development of practical stochastic cloud-radiation parameterizations, a new category of parameterizations that offers great promise for overcoming many shortcomings of conventional schemes. The second is that this work has brought powerful new tools to bear on the problem, because it has been a collaboration between a meteorologist with long experience in ARM research (Somerville) and a mathematician who is an expert on a class of advanced statistical techniques that are well-suited for diagnosing model cloud simulations using ARM observations (Shen).

  5. Atmospheric Waves and Dynamics Beneath Jupiters Clouds from Radio Wavelength Observations

    Science.gov (United States)

    Cosentino, Richard G.; Butler, Bryan; Sault, Bob; Morales-Juberias, Raul; Simon, Amy; De Pater, Imke

    2017-01-01

    We observed Jupiter at wavelengths near 2 cm with the Karl G. Jansky Very Large Array (VLA) in February 2015. These frequencies are mostly sensitive to variations in ammonia abundance and probe between approx. 0.5- 2.0 bars of pressure in Jupiters atmosphere; within and below the visible cloud deck which has its base near 0.7 bars. The resultant observed data were projected into a cylindrical map of the planet with spatial resolution of approx. 1500 km at the equator. We have examined the data for atmospheric waves and observed a prominent bright belt of radio hotspot features near 10 N, likely connected to the same equatorial wave associated with the 5-m hotspots. We conducted a passive tracer power spectral wave analysis for the entire map and latitude regions corresponding to eastward and westward jets and compare our results to previous studies. The power spectra analysis revealed that the atmosphere sampled in our observation (excluding the NEB region) is in a 2-D turbulent regime and its dynamics are predominately governed by the shallow water equations. The Great Red Spot (GRS) is also very prominent and has a noticeable meridional asymmetry and we compare it, and nearby storms, with optical images. We find that the meridional radio profile has a global north-south hemisphere distinction and find correlations of it to optical intensity banding and to shear zones of the zonal wind profile over select regions of latitude. Amateur optical images taken before and after our observation complemented the radio wave- length map to investigate dynamics of the equatorial region in Jupiters atmosphere. We find that two radio hotspots at 2 cm are well correlated with optical plumes in the NEB, additionally revealing they are not the same 5 m hotspot features correlated with optical dark patches between adjacent plumes. This analysis exploits the VLAs upgraded sensitivity and explores the opportunities now possible when studying gas giants, especially atmospheric

  6. Observed and simulated temperature dependence of the liquid water path of low clouds

    Energy Technology Data Exchange (ETDEWEB)

    Del Genio, A.D.; Wolf, A.B. [NASA Goddard Institute for Space Studies, New York, NY (United States)

    1996-04-01

    Data being acquired at the Atmospheric Radiation Measurement (ARM) Southern great Plains (SGP) Cloud and Radiation Testbed (CART) site can be used to examine the factors determining the temperature dependence of cloud optical thickness. We focus on cloud liquid water and physical thickness variations which can be derived from existing ARM measurements.

  7. Observational Diagnostics of Self-Gravitating MHD Turbulence in Giant Molecular Clouds

    CERN Document Server

    Burkhart, Blakesley; Lazarian, Alex

    2015-01-01

    We study the observable signatures of self-gravitating MHD turbulence by applying the probability density functions (PDFs) and the spatial density power spectrum to synthetic column density maps. We find that there exists three characterizable stages of the evolution of the collapsing cloud which we term "early," "intermediate," and "advanced." At early times, i.e. $t0.35t_{ff}$, the power spectral slope is positive valued, and a dramatic increase is observed in the PDF moments and the Tsallis incremental PDF parameters, which gives rise to deviations between PDF-sonic Mach number relations. Finally, we show that the imprint of gravity on the density power spectrum can be replicated in non-gravitating turbulence by introducing a delta-function with amplitude equivalent to the maximum valued point in a given self-gravitating map. We find that the turbulence power spectrum restored through spatial filtering of the high density material.

  8. Dispersion of Observed Angles of Submillimeter Polarization in Giant Molecular Clouds

    CERN Document Server

    Novak, G; Li, H

    2007-01-01

    We present submillimeter polarimetric observations of the Giant Molecular Cloud (GMC) NGC 6334, obtained using the Hertz instrument at the Caltech Submillimeter Observatory on Mauna Kea. We obtain constraints on GMC magnetic fields by interpreting these Hertz data together with (a) previously published larger-scale submillimeter polarization maps of the GMCs NGC 6334 and G333.6-0.2 obtained using the SPARO instrument at South Pole, and (b) simulated GMC polarization maps from published magnetohydrodynamic turbulence simulations. The agreement between observations and simulations is good only when the ratio R(F:U) of fluctuating to uniform field amplitudes lies in the range 0.6 < R(F:U) < 2.0, and when the ratio R(T:K) of total magnetic energy (including both uniform and fluctuating components) to turbulent kinetic energy lies in the range 0.9 < R(T:K) < 1.8. We also compare our results with those obtained by other investigators.

  9. Polar Mesospheric Clouds (PMCs) Observed by the Ozone Monitoring Instrument (OMI) on Aura

    Science.gov (United States)

    DeLand, Matthew T.; Shettle, Eric P.; Levelt, Pieternel F.; Kowalewski, Matthew G.

    2010-01-01

    Backscattered ultraviolet (BUV) instruments designed for measuring stratospheric ozone profiles have proven to be robust tools for observing polar mesospheric clouds (PMCs). These measurements are available for more than 30 years, and have been used to demonstrate the existence of long-term variations in PMC occurrence frequency and brightness. The Ozone Monitoring Instrument (OMI) on the EOS Aura satellite provides new and improved capabilities for PMC characterization. OMI uses smaller pixels than previous BUV instruments, which increases its ability to identify PMCs and discern more spatial structure, and its wide cross-track viewing swath provides full polar coverage up to 90 latitude every day in both hemispheres. This cross-track coverage allows the evolution of PMC regions to be followed over several consecutive orbits. Localized PMC variations determined from OMI measurements are consistent with coincident SBUV/2 measurements. Nine seasons of PMC observations from OMI are now available, and clearly demonstrate the advantages of these measurements for PMC analysis.

  10. A catalogue of Large Magellanic Cloud star clusters observed in the Washington photometric system

    CERN Document Server

    Palma, Tali; Clariá, Juan J; Lares, Marcelo; Geisler, Doug; Ahumada, Andrea V

    2016-01-01

    The main goal of this study is to compile a catalogue including the fundamental parameters of a complete sample of 277 star clusters (SCs) of the Large Magellanic Cloud (LMC) observed in the Washington photometric system, including 82 clusters very recently studied by us. All the clusters' parameters such as radii, deprojected distances, reddenings, ages and metallicities have been obtained by appyling essentially the same procedures which are briefly described here. We have used empirical cumulative distribution functions to examine age, metallicity and deprojected distance distributions for different cluster subsamples of the catalogue. Our new sample made up of 82 additional clusters recently studied by us represents about a 40% increase in the total number of LMC SCs observed up to now in the Washington photometric system. In particular, we report here the fundamental parameters obtained for the first time for 42 of these clusters. We found that single LMC SCs are typically older than multiple SCs. Both s...

  11. Observation of Electron Cloud Instabilities and Emittance Dilution at the Cornell Electron-Positron Storage Ring Test Accelerator

    Science.gov (United States)

    Holtzapple, R. L.; Billing, M. G.; Campbell, R. C.; Dugan, G. F.; Flanagan, J.; McArdle, K. E.; Miller, M. I.; Palmer, M. A.; Ramirez, G. A.; Sonnad, K. G.; Totten, M. M.; Tucker, S. L.; Williams, H. A.

    2016-04-01

    Electron cloud related emittance dilution and instabilities of bunch trains limit the performance of high intensity circular colliders. One of the key goals of the Cornell electron-positron storage ring Test Accelerator (CesrTA) research program is to improve our understanding of how the electron cloud alters the dynamics of bunches within the train. Single bunch beam diagnotics have been developed to measure the beam spectra, vertical beam size, two important dynamical effects of beams interacting with the electron cloud, for bunch trains on a turn-by-turn basis. Experiments have been performed at CesrTA to probe the interaction of the electron cloud with stored positron bunch trains. The purpose of these experiments was to characterize the dependence of beam-electron cloud interactions on the machine parameters such as bunch spacing, vertical chromaticity, and bunch current. The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 1) a gated beam position monitor (BPM) and spectrum analyzer to measure the bunch-by-bunch frequency spectrum of the bunch trains; 2) an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the observations from these experiments and analyze the effects of the electron cloud on the stability of bunches in a train under many different operational conditions.

  12. Satellite observations of lightning-generated NOx in volcanic eruption clouds

    Science.gov (United States)

    Carn, Simon; Krotkov, Nickolay; Pickering, Ken; Allen, Dale; Bucsela, Eric

    2016-04-01

    The generation of NO2 by lightning flashes is known to be an important source of NOx in the free troposphere, particularly in the tropics, with implications for ozone production. Although UV-visible satellite observations of lightning-generated NOx (LNOx) in thunderstorms have been previously reported, here we present the first satellite observations of LNOx generated by lightning in explosive volcanic eruption clouds (vLNOx) from the Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite. To date we have identified vLNOx in operational OMI NO2 measurements (OMNO2) during the high-latitude eruptions of Okmok (Aleutian Is; July 2008), Kasatochi (Aleutian Is; August 2008), Redoubt (Alaska; March 2009) and Grimsvötn (Iceland; May 2011), although analysis of OMNO2 data for other eruptions is underway. We use World Wide Lightning Location Network (WWLLN) observations to verify the occurrence and location of lightning flashes in the volcanic eruption clouds. All the vLNOx anomalies are associated with strong UV Aerosol Index (UVAI) signals due to volcanic ash. Preliminary analysis shows that the maximum vLNOx column detected by OMI decreases linearly with time since eruption, and suggests that the vLNOx signal is transient and can be detected up to ~5-6 hours after an eruption. Detection of vLNOx is hence only possible for eruptions occurring a few hours before the daytime OMI overpass. Based on the number of lightning flashes detected by WWLLN in each eruption cloud, we also estimate the vLNOx production efficiency (moles vLNOx per flash). Preliminary estimates for the 2008 Kasatochi eruption suggest that this is significantly higher than the production efficiency in thunderstorms, but may be biased high due to the low detection efficiency of WWLLN (aviation hazards due to volcanic ash. Furthermore, the vLNOx observations may provide information on air entrainment in volcanic eruption columns, which is required for some volcanic ash dispersion models. Although

  13. Coordinated observations of sprites and in-cloud lightning flash structure

    Science.gov (United States)

    Lu, Gaopeng; Cummer, Steven A.; Li, Jingbo; Zigoneanu, Lucian; Lyons, Walter A.; Stanley, Mark A.; Rison, William; Krehbiel, Paul R.; Edens, Harald E.; Thomas, Ronald J.; Beasley, William H.; Weiss, Stephanie A.; Blakeslee, Richard J.; Bruning, Eric C.; Macgorman, Donald R.; Meyer, Tiffany C.; Palivec, Kevin; Ashcraft, Thomas; Samaras, Tim

    2013-06-01

    The temporal and spatial development of sprite-producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system (MCS) on 29 June 2011 near the Oklahoma Lightning Mapping Array (LMA). Sprites produced by a total of 26 lightning flashes were observed simultaneously on video from Bennett, Colorado and Hawley, Texas, enabling a triangulation of sprites in comparison with temporal development of parent lightning (in particular, negatively charged stepped leaders) in three-dimensional space. In general, prompt sprites produced within 20 ms after the causative stroke are less horizontally displaced (typically 30 km). However, both prompt and delayed sprites are usually centered within 30 km of the geometric center of relevant LMA sources (with affinity to negative stepped leaders) during the prior 100 ms interval. Multiple sprites appearing as dancing/jumping events associated with a single lightning flash could be produced either by distinct strokes of the flash, by a single stroke through a series of current surges superposed on an intense continuing current, or by both. Our observations imply that sprites elongated in one direction are sometimes linked to in-cloud leader structure with the same elongation, and sprites that were more symmetric were produced above the progression of multiple negative leaders. This suggests that the large-scale structure of sprites could be affected by the in-cloud geometry of positive charge removal. Based on an expanded dataset of 39 sprite-parent flashes by including more sprites recorded by one single camera over the same MCS, the altitude (above mean sea level, MSL) of positively charged cloud region tapped by sprite-producing strokes declined gradually from ~10 km MSL (-35°C) to around 6 km MSL (-10°C) as the MCS evolved through the mature stage. On average, the positive charge removal by causative strokes of sprites observed on 29 June is centered at 3.6 km above the freezing

  14. Entrainment and mixing at the interface of shallow cumulus clouds: Results from a combination of observations and simulations

    Directory of Open Access Journals (Sweden)

    Fabian Hoffmann

    2014-09-01

    Full Text Available This study combines observations, large-eddy simulations (LES, and direct numerical simulations (DNS in order to analyze entrainment and mixing in shallow cumulus clouds at all relevant spatial scales and, additionally, to verify the results by the multiple methods used. The observations are based on three flights of the CARRIBA campaign which are similar to the classical BOMEX case used for LES. Virtual flights in the LES data are used to validate the observational method of line measurements. It is shown that line measurements overrepresent the cloud core, and it is quantified how derived statistics depend on small perturbations of the flight track, which has to be taken in account for the interpretation of airborne observations. A linear relation between fluctuations of temperature and liquid water content has been found in both LES and observations in a good quantitative agreement. However, the constant of proportionality deviates from purely adiabatic estimates, which can be attributed to cloud edge mixing. The cloud edge is compared in detail in observations and LES, which agree qualitatively although the LES cloud edge is smoother due to the model's resolution. The resulting typical amplitudes of the turbulence fields from this comparison are compared with the large-scale forcing model which is used in a series of DNS which study the mixing below the meter scale, which show that LES does not resolve the intermittency of small-scale turbulence.

  15. Cloud and aerosol classification for 2 1/2 years of MAX-DOAS observations in Wuxi (China and comparison to independent data sets

    Directory of Open Access Journals (Sweden)

    Y. Wang

    2015-05-01

    Full Text Available Multi-Axis-Differential Optical Absorption Spectroscopy (MAX-DOAS observations of trace gases can be strongly influenced by clouds and aerosols. Thus it is important to identify clouds and characterise their properties. In a recent study Wagner et al. (2014 developed a cloud classification scheme based on the MAX-DOAS measurements themselves with which different "sky conditions" (e.g. clear sky, continuous clouds, broken clouds can be distinguished. Here we apply this scheme to long term MAX-DOAS measurements from 2011 to 2013 in Wuxi, China (31.57° N, 120.31° E. The original algorithm has been modified, in particular in order to account for smaller solar zenith angles (SZA. Instrumental degradation is accounted for to avoid artificial trends of the cloud classification. We compared the results of the MAX-DOAS cloud classification scheme to several independent measurements: aerosol optical depth from a nearby AERONET station and from MODIS, visibility derived from a visibility meter; and various cloud parameters from different satellite instruments (MODIS, OMI, and GOME-2. The most important findings from these comparisons are: (1 most cases characterized as clear sky with low or high aerosol load were associated with the respective AOD ranges obtained by AERONET and MODIS, (2 the observed dependences of MAX-DOAS results on cloud optical thickness and effective cloud fraction from satellite indicate that the cloud classification scheme is sensitive to cloud (optical properties, (3 separation of cloudy scenes by cloud pressure shows that the MAX-DOAS cloud classification scheme is also capable of detecting high clouds, (4 some clear sky conditions, especially with high aerosol load, classified from MAX-DOAS observations corresponding to the optically thin and low clouds derived by satellite observations probably indicate that the satellite cloud products contain valuable information on aerosols.

  16. Mid-J CO Shock Tracing Observations of Infrared Dark Clouds III: SLED fitting

    CERN Document Server

    Pon, A; Johnstone, D; Caselli, P; Fontani, F; Butler, M J; Jiménez-Serra, I; Palau, A; Tan, J C

    2016-01-01

    Giant molecular clouds contain supersonic turbulence that can locally heat small fractions of gas to over 100 K. We run shock models for low-velocity, C-type shocks propagating into gas with densities between 10^3 and 10^5 cm^(-3) and find that CO lines are the most important cooling lines. Comparison to photodissociation region (PDR) models indicates that mid-J CO lines (J = 8-7 and higher) should be dominated by emission from shocked gas. In papers I and II we presented CO J = 3-2, 8-7, and 9-8 observations towards four primarily quiescent clumps within infrared dark clouds. Here, we fit PDR models to the combined spectral line energy distributions and show that the PDR models that best fit the low-J CO emission underpredict the mid-J CO emission by orders of magnitude, strongly hinting at a hot gas component within these clumps. The low-J CO data clearly show that the integrated intensity of both the CO J = 8-7 and 9-8 lines are anomalously high, such that the line ratio can be used to characterize the hot...

  17. Observations of Supernova Remnants associated with Molecular Clouds with H.E.S.S.

    Science.gov (United States)

    Fiasson, A.; Nukri, K.; Rowell, G.; Kosack, K.; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A.G.; Anton, G.; Barres de Almeida, U.; Bazer-Bachi, A.R.; Becherini, Y.; Behera, B.; Bernlöhr, K.; Bochow, A.; Boisson, C.; Bolmont, J.; Borrel, V.; Brucker, J.; Brun, F.; Brun, P.; Bühler, R.; Bulik, T.; Büsching, I.; Boutelier, T.; Chadwick, P.M.; Charbonnier, A.; Chaves, R.C.G.; Cheesebrough, A.; Conrad, J.; Chounet, L.-M.; Clapson, A.C.; Coignet, G.; Dalton, M.; Daniel, M.K.; Davids, I.D.; Degrange, B.; Deil, C.; Dickinson, H.J.; Djannati-Atai, A.; Domainko, W.; Drury, L.O'C.; Dubus, G.; Dykes, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M.V.; Förster, A.; Fontaine, G.; Füssling, M.; Gabici, S.; Gallant, Y.A.; Gerard, L.; Gerbig, F.; Giebels, B.; Glicenstein, J.F.; Glück, B.; Goret, P.; Göring, D.; Hampf, D.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J.A.; Hoffman, A.; Hofmann, W.; Hofverberg, P.; Holleran, M.; Hoppe, S.; Horns, D.; Jacholkowska, A.; de Jager, O.C.; Jahn, C.; Jung, I.; Katarzynski, K.; Kluzniak, W.; Kneiske, T.; Komin, Nu.; Kossakowski, R.; Lamanna, G.; Lenain, J.-P.; Lohse, T.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, D.; McComb, T.J.L.; Medina, M.C.; Mehault, J.; Moderski, R.; Moulin, E.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S.J.; Ohm, S.; Olive, J.-F.; de Ona Wilhelmi, E.; Opitz, B.; Orford, K.J.; Ostrowski, M.; Panter, M.; Paz Arribas, M.; Pedaletti, G.; Pelletier, G.; Petrucci, P.-O.; Pita, S.; Pöhlhofer, G.; Punch, M.; Quirrenbach, A.; Raubenheimer, B.C.; Raue, M.; Rayner, S.M.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rudak, B.; Rulten, C.B.; Ruppel, J.; Ryde, F.; Sahakian, V.; Santangelo, A.; Schlickeiser, R.; Schöck, F.M.; Schönwald, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Shalchi, A.; Sushch, I.; Sikora, M.; Skilton, J.L.; Sol, H.; Stawarz, L.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Szostek, A.; Tam, P.H.; Tavernet, J.-P.; Terrier, R.; Tibolla, O.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Venter, L.; Vialle, J.P.; Viana, A.; Vincent, P.; Vivier, M.; Völk, H.J.; Volpe, F.; Vorobiov, S.; Wagner, S.J.; Ward, M.; Zdziarski, A.A.; Zech, A.; Zechlin, H.-S.

    The bulk of the Galactic Cosmic Rays (with energies up to 1015 eV) is believed to be accelerated in the shock fronts of supernova remnants. Current Imaging Air Cherenkov Telescopes like H.E.S.S. with their high sensitivity and very good angular resolution are perfect instruments for the observation of these objects in Very High Energy (several 100 GeV up to 100 TeV) gamma-rays, radiation which is produced in the interactions of accelerated protons with ambient material. On this poster we will focus on the case of shell-type supernova remnants associated with molecular clouds. The presence of dense molecular clouds provides substantial target for high energy particles and can be thus used to probe the presence of accelerated hadrons. Several associations traced by 1720 MHz OH masers have been detected by H.E.S.S. and the VHE gamma-ray emission correlates with the matter distribution. High energy gamma-ray have been also detected by Fermi toward these associations. We will discuss the origin of the gamma-ray in terms of cosmic-rays acceleration within the remnants. We will as well estimate the detection potential by neutrino instruments. Traditionnal supernova remnants detected with H.E.S.S. are presented on a separate poster.

  18. Observational studies of pre-stellar cores and infrared dark clouds

    CERN Document Server

    Caselli, Paola

    2011-01-01

    Stars like our Sun and planets like our Earth form in dense regions within interstellar molecular clouds, called pre-stellar cores (PSCs). PSCs provide the initial conditions in the process of star and planet formation. In the past 15 years, detailed observations of (low-mass) PSCs in nearby molecular cloud complexes have allowed us to find that they are cold (T < 10 K) and quiescent (molecular line widths are close to thermal), with a chemistry profoundly affected by molecular freeze-out onto dust grains. In these conditions, deuterated molecules flourish, becoming the best tools to unveil the PSC physical and chemical structure. Despite their apparent simplicity, PSCs still offer puzzles to solve and they are far from being completely understood. For example, what is happening to the gas and dust in their nuclei (the future stellar cradles) is still a mystery that awaits for ALMA. Other important questions are: how do different environments and external conditions affect the PSC physical/chemical structu...

  19. The relationship between polar mesospheric clouds and their background atmosphere as observed by Odin-SMR and Odin-OSIRIS

    Science.gov (United States)

    Christensen, Ole Martin; Benze, Susanne; Eriksson, Patrick; Gumbel, Jörg; Megner, Linda; Murtagh, Donal P.

    2016-10-01

    In this study the properties of polar mesospheric clouds (PMCs) and the background atmosphere in which they exist are studied using measurements from two instruments, OSIRIS and SMR, on board the Odin satellite. The data comes from a set of tomographic measurements conducted by the satellite during 2010 and 2011. The expected ice mass density and cloud frequency for conditions of thermodynamic equilibrium, calculated using the temperature and water vapour as measured by SMR, are compared to the ice mass density and cloud frequency as measured by OSIRIS. We find that assuming thermodynamic equilibrium reproduces the seasonal, latitudinal and vertical variations in ice mass density and cloud frequency, but with a high bias of a factor of 2 in ice mass density. To investigate this bias, we use a simple ice particle growth model to estimate the time it would take for the observed clouds to sublimate completely and the time it takes for these clouds to reform. We find a difference in the median sublimation time (1.8 h) and the reformation time (3.2 h) at peak cloud altitudes (82-84 km). This difference implies that temperature variations on these timescales have a tendency to reduce the ice content of the clouds, possibly explaining the high bias of the equilibrium model. Finally, we detect and are, for the first time, able to positively identify cloud features with horizontal scales of 100 to 300 km extending far below the region of supersaturation ( > 2 km). Using the growth model, we conclude these features cannot be explained by sedimentation alone and suggest that these events may be an indication of strong vertical transport.

  20. Characterization of fast-growing convection from synergistic observations of CloudSat, MODIS and IIR

    Science.gov (United States)

    Luo, Z. J.; Anderson, R.

    2012-12-01

    We exploit the fact that Aqua leads CloudSat/CALIPSO by 1-2 min to identify fast-growing convection, whose cloud-top temperature (CTT) shows significant decrease from MODIS (onboard Aqua) to IIR (onboard CALIPSO). Assuming adiabatic ascent of convective clouds, we estimate cloud-top vertical velocity (w) from the decrease rate of CTT. Categorizing convective towers by cloud-top height (CTH) gives a means to study the vertical profiles of w - an important parameter for understanding convective dynamics. Our initial results show that the fastest-growing convection has CTH ~ 8- 10 km. They are likely deep convection in early life stage. Finally, we analyze CloudSat cloud-profiling radar (CPR) reflectivities which provide a glimpse into the internal vertical structure of these fast-growing convective towers.

  1. Shallow-cumulus cloud feedback: model uncertainties and perspectives of observational constraint

    Science.gov (United States)

    Bony, Sandrine

    2017-04-01

    Shallow-cumulus clouds constitute the most prominent cloud type on Earth, and their response to changing environmental conditions is critical for climate sensitivity. Research over the last decade has pointed out the importance of the interplay between clouds, convection, turbulence and circulation in controlling this response. Unfortunately, numerical models represent this interplay in diverse ways, which translates into different shallow-cumulus cloud feedbacks in climate change. Climate models predict that the cloud-base cloud fraction is very sensitive to changes in environmental conditions, while process models suggest that it is very resilient to such changes. To understand and solve this contradiction, a field campaign named EUREC4A (Elucidating the role of clouds-circulation coupling in climate) will be organized in the lower Atlantic trades in Jan-Fev 2020. The scientific objectives of this campaign will be presented, and the experimental strategy envisioned to reach these objectives will be discussed.

  2. Odin observations of ammonia in the Sgr A +50 km s-1 cloud and circumnuclear disk

    Science.gov (United States)

    Sandqvist, Aa.; Hjalmarson, Å.; Frisk, U.; Lundin, S.; Nordh, L.; Olberg, M.; Olofsson, G.

    2017-03-01

    Context. The Odin satellite is now into its sixteenth year of operation, much surpassing its design life of two years. One of the sources which Odin has observed in great detail is the Sgr A complex in the centre of the Milky Way. Aims: To study the presence of NH3 in the Galactic centre and spiral arms. Methods: Recently, Odin has made complementary observations of the 572 GHz NH3 line towards the Sgr A +50 km s-1 cloud and circumnuclear disk (CND). Results: Significant NH3 emission has been observed in both the +50 km s-1 cloud and the CND. Clear NH3 absorption has also been detected in many of the spiral arm features along the line of sight from the Sun to the core of our Galaxy. Conclusions: The very large velocity width (80 km s-1) of the NH3 emission associated with the shock region in the southwestern part of the CND may suggest a formation/desorption scenario similar to that of gas-phase H2O in shocks/outflows. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), the Centre National d'Études Spatiales (CNES), France, and the European Space Agency (ESA). The former Space division of the Swedish Space Corporation, today OHB Sweden, is the prime contractor, also responsible for Odin operations.The reduced spectra are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A135

  3. Mid-J CO Shock Tracing Observations of Infrared Dark Clouds. III. SLED Fitting

    Science.gov (United States)

    Pon, A.; Kaufman, M. J.; Johnstone, D.; Caselli, P.; Fontani, F.; Butler, M. J.; Jiménez-Serra, I.; Palau, A.; Tan, J. C.

    2016-08-01

    Giant molecular clouds contain supersonic turbulence that can locally heat small fractions of gas to over 100 K. We run shock models for low-velocity, C-type shocks propagating into gas with densities between 103 and 105 cm-3 and find that CO lines are the most important cooling lines. Comparison to photodissociation region (PDR) models indicates that mid-J CO lines (J = 8 \\to 7 and higher) should be dominated by emission from shocked gas. In Papers I and II we presented CO J = 3 \\to 2, 8 \\to 7, and 9 \\to 8 observations toward four primarily quiescent clumps within infrared dark clouds. Here we fit PDR models to the combined spectral line energy distributions and show that the PDR models that best fit the low-J CO emission underpredict the mid-J CO emission by orders of magnitude, strongly hinting at a hot gas component within these clumps. The low-J CO data clearly show that the integrated intensities of both the CO J = 8 \\to 7 and 9 \\to 8 lines are anomalously high, such that the line ratio can be used to characterize the hot gas component. Shock models are reasonably consistent with the observed mid-J CO emission, with models with densities near {10}4.5 cm-3 providing the best agreement. Where this mid-J CO is detected, the mean volume filling factor of the hot gas is 0.1%. Much of the observed mid-J CO emission, however, is also associated with known protostars and may be due to protostellar feedback.

  4. Airborne observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

    Directory of Open Access Journals (Sweden)

    M. Schäfer

    2015-07-01

    Full Text Available Based on airborne spectral imaging observations, three-dimensional (3-D radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces were identified and quantified. A method is presented to discriminate between sea ice and open water under cloudy conditions based on airborne nadir reflectivity γλ measurements in the visible spectral range. In cloudy cases the transition of γλ from open water to sea ice is not instantaneous but horizontally smoothed. In general, clouds reduce γλ above bright surfaces in the vicinity of open water, while γλ above open sea is enhanced. With the help of observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge (for a dark-ocean albedo of αwater = 0.042 and a sea-ice albedo of αice = 0.91 at 645 nm wavelength. The affected distance Δ L was found to depend on both cloud and sea ice properties. For a low-level cloud at 0–200 m altitude, as observed during the Arctic field campaign VERtical Distribution of Ice in Arctic clouds (VERDI in 2012, an increase in the cloud optical thickness τ from 1 to 10 leads to a decrease in Δ L from 600 to 250 m. An increase in the cloud base altitude or cloud geometrical thickness results in an increase in Δ L; for τ = 1/10 Δ L = 2200 m/1250 m in case of a cloud at 500–1000 m altitude. To quantify the effect for different shapes and sizes of ice floes, radiative transfer simulations were performed with various albedo fields (infinitely long straight ice edge, circular ice floes, squares, realistic ice floe field. The simulations show that Δ L increases with increasing radius of the ice floe and reaches maximum values for ice floes with radii larger than 6 km (500–1000 m cloud altitude, which matches the results found for an infinitely long, straight ice edge. Furthermore, the influence of these 3-D radiative effects on the retrieved cloud optical

  5. On microphysical processes of noctilucent clouds (NLC: observations and modeling of mean and width of the particle size-distribution

    Directory of Open Access Journals (Sweden)

    G. Baumgarten

    2010-07-01

    Full Text Available Noctilucent clouds (NLC in the polar summer mesopause region have been observed in Norway (69° N, 16° E between 1998 and 2009 by 3-color lidar technique. Assuming a mono-modal Gaussian size distribution we deduce mean and width of the particle sizes throughout the clouds. We observe a quasi linear relationship between distribution width and mean of the particle size at the top of the clouds and a deviation from this behavior for particle sizes larger than 40 nm, most often in the lower part of the layer. The vertically integrated particle properties show that 65% of the data follows the linear relationship with a slope of 0.42±0.02 for mean particle sizes up to 40 nm. For the vertically resolved particle properties (Δz = 0.15 km the slope is comparable and about 0.39±0.03. For particles larger than 40 nm the distribution width becomes nearly independent of particle size and even decreases in the lower part of the layer. We compare our observations to microphysical modeling of noctilucent clouds and find that the distribution width depends on turbulence, the time that turbulence can act (cloud age, and the sampling volume/time (atmospheric variability. The model results nicely reproduce the measurements and show that the observed slope can be explained by eddy diffusion profiles as observed from rocket measurements.

  6. Three dimensional characteristics of precipitating cloud systems observed during Indian summer monsoon

    Science.gov (United States)

    Kumar, Shailendra

    2016-09-01

    Ten year of TRMM PR data is used to study the properties of the precipitating cloud systems over Indian land and ocean areas. TRMM PR reflectivity information is often displayed in three dimensions, making it excellent for study the three dimensional characteristics of precipitating cloud systems. A cloud system (CS) is defined by connecting pixels of more than 17 dBZ, with at least one pixel must be higher than 40 dBZ. Within the CSs two types of cloud cells are defined, namely most vigorous cell (MVC) and reflectivity profile for cloud (RPC) for informing the vertical structure of precipitation. Most vigorous cell contains the maximum Ze at each altitude from the CSs, whereas the RPC consists of the vertical extension of Ze ⩾ 40 dBZ at any altitude. Area covered by different reflectivity thresholds (30, 35 and 40 dBZ), and analysis of three dimensional cloud vertical structure show the evolution characteristics of cloud systems. Vertical structure of precipitation shows higher regional differences compared to cloud area and evolution of clouds. Head of Bay consists higher number of precipitating cloud systems. Land areas show the intense cloud systems compared to oceanic areas and on an average, precipitation intensity is least over Arabian Sea and highest over central India. Probability of warm rain is higher over Western Ghats and Arabian Sea. Between 5 and 10 km altitude, reflectivity values show 5 dBZ difference in MVC and RPC. Western Ghats shows higher reflectivity value above 12 km altitude and matches with land dominated areas. Land dominated area shows higher fraction of deep clouds. Almost 50% MVCs cross 10 km altitude over land dominated areas whereas only 20% MVCs are crossing the 10 km altitude over Arabian Sea. Maximum height of 30 and 40 dBZ consist the lower mode over Arabian Sea and Bay of Bengal compared to land dominated areas. Small cloud systems consist higher area of intense precipitation (higher values of Ze) and as the area of cloud

  7. Microphysical and radiative characterization of a subvisible midlevel Arctic ice cloud by airborne observations – a case study

    Directory of Open Access Journals (Sweden)

    A. Lampert

    2009-04-01

    Full Text Available During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR campaign, which was conducted in March and April 2007, an optically thin ice cloud was observed south of Svalbard at around 3 km altitude. The microphysical and radiative properties of this particular subvisible midlevel cloud were investigated with complementary remote sensing and in situ instruments. Collocated airborne lidar remote sensing and spectral solar radiation measurements were performed at a flight altitude of 2300 m below the cloud base. Under almost stationary atmospheric conditions, the same subvisible midlevel cloud was probed with various in situ sensors roughly 30 min later.

    From individual ice crystal samples detected with the Cloud Particle Imager and the ensemble of particles measured with the Polar Nephelometer, microphysical properties were retrieved with a bi-modal inversion algorithm. The best agreement with the measurements was obtained for small ice spheres and deeply rough hexagonal ice crystals. Furthermore, the single-scattering albedo, the scattering phase function as well as the volume extinction coefficient and the effective diameter of the crystal population were determined. A lidar ratio of 21(±6 sr was deduced by three independent methods. These parameters in conjunction with the cloud optical thickness obtained from the lidar measurements were used to compute spectral and broadband radiances and irradiances with a radiative transfer code. The simulated results agreed with the observed spectral downwelling radiance within the range given by the measurement uncertainty. Furthermore, the broadband radiative simulations estimated a net (solar plus thermal infrared radiative forcing of the subvisible midlevel ice cloud of −0.4 W m−2 (−3.2 W m−2 in the solar and +2.8 W m−2 in the thermal infrared wavelength range.

  8. BOPPS Observations of Oort Cloud Comets Siding and PanSTARRS

    Science.gov (United States)

    Cheng, A. F.; Hibbitts, C.; Young, E. F.; Bernasconi, P. N.; Tibor, K.

    2014-12-01

    The Balloon Observation Platform for Planetary Science (BOPPS) mission is a stratospheric balloon mission to conduct planetary science observations during a one-day flight from Ft. Sumner, NM in late September, 2014. BOPPS will fly an 80-cm telescope with two instruments to detect and characterize two Oort Cloud comets, C/2013 A1 Siding Spring and C/2012 K1 PanSTARRS. The BOPPS instruments [1,2] are the BOPPS Infrared Camera (BIRC), imaging at R band and from 2.5 to 5 microns, and the UVvis camera which includes a fine pointing system to demonstrate sub-arc second pointing and ability to obtain high SNR imaging at wavelengths near 300 nm sensitive to OH emission (1). The BIRC will image the comets in nine filter pass bands at 1.16 arc second per pixel resolution and will measure the strengths of H2O and CO2 emissions at 2.7μ and 4.3μ respectively. These are the primary volatiles driving cometary activity, and there is no alternative way to make these measurements from Earth or from space. The BIRC observations of Comet Siding Spring will occur about three weeks prior to the close approach of the comet to Mars, which will also be observed by the full constellation of Mars spacecraft. We will report initial results of BOPPS comet observations. References: [1] Young EF et al. (2014), Fall AGU this session [2] Hibbitts et al., (2014), Fall AGU

  9. Rolling Uphill

    Science.gov (United States)

    Cross, Rod

    2017-01-01

    In a recent letter to this journal, Mungan noted that translational energy can be converted into gravitational potential energy when an object is projected vertically, but rotational energy is not usually converted in this manner. As an exception, he gave an example where "a ball initially rolling without slipping will travel higher up a…

  10. 1300 micron continuum observations of the Sagittarius B2 molecular cloud core

    Energy Technology Data Exchange (ETDEWEB)

    Goldsmith, P.F.; Snell, R.L.; Lis, D.C.

    1987-02-01

    Observations with 23-arcsec angular resolution are obtained of the continuum emission at 1300 microns wavelength from the central region of the Sgr B2 molecular cloud, which contains the north and middle high-mass star-forming regions and associated radio continuum and maser sources. The spatial resolution of the present data shows that the 1300-micron continuum emission peak is located at Sgr B2(N), in contrast to the midinfrared emission, which is centered on Sgr B2(M). Comparison with 53 micron data having comparable angular resolution suggests that there is optically thick foreground dust which prevents detection of Sgr B2(N) at wavelengths not greater than 100 microns. Within the about 1.5 x 3.5 pc region mapped, the total mass is 500,000 solar masses and the mean H2 density is 300,000/cu cm, somewhat larger than found in previous investigations. 27 references.

  11. Kinetic temperature and density of the Sagittarius B2 molecular cloud from observations of methyl cyanide

    Energy Technology Data Exchange (ETDEWEB)

    Cummins, S.E.; Green, S.; Thaddeus, P.; Linke, R.A.

    1983-03-01

    From observations with the Bell Laboratories 7 m telescope of the K components of the CH/sub 3/CH J = 4..-->..3 rotational transition at 73.6 GHz, 6..-->..5 transition at 110.4 GHz, and 7..-->..6 transition at 128.7 GHz, a mean kinetic temperature of 85 +- 10 K and a mean H/sub 2/ density of (1.1 +- 0.5) x 10/sup 5/ cm/sup -3/ are deduced for the central 2' of the Sgr B2 molecular cloud. Within the K = 0--4 ladders of CH/sub 3/CN in Sgr B2 the populations of the radiatively coupled J levels are relaxed, with a rotational temperature of approximately 16 K: similar to that of several linear molecules.

  12. New Insight into Polar Stratospheric Cloud Processes from A-Train Observations

    Science.gov (United States)

    Pitts, M. C.; Poole, L. R.

    2016-12-01

    Polar stratospheric clouds (PSCs) play essential roles in the chemical depletion of stratospheric ozone at high latitudes. Heterogeneous reactions occurring on PSC particles, primarily supercooled ternary (H2SO4-H2O-HNO3) solution (STS) droplets, convert stable chlorine reservoir species to highly reactive ozone-destructive forms. Also, sedimentation and evaporation of large nitric acid trihydrate (NAT) particles irreversibly redistributes odd nitrogen and prolongs ozone depletion by slowing the reformation of stable chlorine reservoirs. Even after three decades of research, significant gaps in our understanding of PSC processes still exist, particularly concerning NAT nucleation and the extent to which chlorine is activated on cold background aerosol prior to PSC formation. These uncertainties limit our ability to represent PSCs accurately in global models and call into question predictions of ozone recovery in a changing climate. PSC observations from the A-Train satellite constellation have stimulated a number of new research activities that have both extended and challenged our knowledge of PSC processes and modeling capabilities. Specifically, the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite is providing information on PSC morphology and composition in unprecedented detail, while the Microwave Limb Sounder (MLS) on the Aura satellite is providing nearly coincident measurements of gas-phase HNO3 and H2O, the major constituents of all PSC particles. The combined analyses of these datasets enable better PSC composition discrimination and provide valuable new insight into processes such as PSC-catalyzed chlorine activation and PSC particle growth kinetics. The more than ten years of CALIOP and MLS measurements have uniquely captured the primary aspects of the seasonal and multi-year variability of PSCs in the Arctic and Antarctic and are enabling the

  13. Mid-latitude mesospheric clouds and their environment from SOFIE observations

    Science.gov (United States)

    Hervig, Mark E.; Gerding, Michael; Stevens, Michael H.; Stockwell, Robert; Bailey, Scott M.; Russell, James M.; Stober, Gunter

    2016-11-01

    Observations from the Solar Occultation For Ice Experiment (SOFIE) on the Aeronomy of Ice in the Mesosphere (AIM) satellite are used to examine noctilucent clouds (NLC) and their environment at middle latitudes ( 56°N and 52°S). Because SOFIE is uniquely capable of measuring NLC, water vapor, and temperature simultaneously, the local cloud environment can be specified to examine what controls their formation at mid-latitudes. Compared to higher latitudes, mid-latitude NLCs are less frequent and have lower ice mass density, by roughly a factor of five. Compared to higher latitudes at NLC heights, mid-latitude water vapor is only 12% lower while temperatures are more than 10 K higher. As a result the reduced NLC mass and frequency at mid-latitudes can be attributed primarily to temperature. Middle and high latitude NLCs contain a similar amount of meteoric smoke, which was not anticipated because smoke abundance increases towards the equator in summer. SOFIE indicates that mid-latitude NLCs may or may not be associated with supersaturation with respect to ice. It is speculated that this situation is due in part to SOFIE uncertainties related to the limb measurement geometry combined with the non-uniform nature of NLCs. SOFIE is compared with concurrent NLC, temperature, and wind observations from Kühlungsborn, Germany (54°N) during the 2015 summer. The results indicate good agreement in temperature and NLC occurrence frequency, backscatter, and height. SOFIE indicates that NLCs were less frequent over Europe during 2015 compared to other longitudes, in contrast to previous years at higher latitudes that showed no clear longitude dependence. Comparisons of SOFIE and the Solar Backscatter Ultraviolet (SBUV) indicate good agreement in average ice water column (IWC), although differences in occurrence frequency were often large.

  14. Herschel observations of ortho- and para-oxidaniumyl (H2O+) in spiral arm clouds toward Sagittarius B2(M)

    NARCIS (Netherlands)

    Schilke, P.; Comito, C.; Müller, H. S. P.; Bergin, E. A.; Herbst, E.; Lis, D. C.; Neufeld, D. A.; Phillips, T. G.; Bell, T. A.; Blake, G. A.; Cabrit, S.; Caux, E.; Ceccarelli, C.; Cernicharo, J.; Crockett, N. R.; Daniel, F.; Dubernet, M.-L.; Emprechtinger, M.; Encrenaz, P.; Falgarone, E.; Gerin, M.; Giesen, T. F.; Goicoechea, J. R.; Goldsmith, P. F.; Gupta, H.; Joblin, C.; Johnstone, D.; Langer, W. D.; Latter, W. B.; Lord, S. D.; Maret, S.; Martin, P. G.; Melnick, G. J.; Menten, K. M.; Morris, P.; Murphy, J. A.; Ossenkopf, V.; Pagani, L.; Pearson, J. C.; Pérault, M.; Plume, R.; Qin, S.-L.; Salez, M.; Schlemmer, S.; Stutzki, J.; Trappe, N.; van der Tak, F. F. S.; Vastel, C.; Wang, S.; Yorke, H. W.; Yu, S.; Erickson, N.; Maiwald, F. W.; Kooi, J.; Karpov, A.; Zmuidzinas, J.; Boogert, A.; Schieder, R.; Zaal, P.

    2010-01-01

    H2O+ has been observed in its ortho- and para- states toward the massive star forming core Sgr B2(M), located close to the Galactic center. The observations show absorption in all spiral arm clouds between the Sun and Sgr B2. The average o/p ratio of H2O+ in most velocity intervals is 4.8, which cor

  15. Herschel observations of ortho- and para-oxidaniumyl (H2O+) in spiral arm clouds toward Sagittarius B2(M)

    NARCIS (Netherlands)

    Schilke, P.; Comito, C.; Mueller, H. S. P.; Bergin, E. A.; Herbst, E.; Lis, D. C.; Neufeld, D. A.; Phillips, T. G.; Bell, T. A.; Blake, G. A.; Cabrit, S.; Caux, E.; Ceccarelli, C.; Cernicharo, J.; Crockett, N. R.; Daniel, F.; Dubernet, M. -L.; Emprechtinger, M.; Encrenaz, P.; Falgarone, E.; Gerin, M.; Giesen, T. F.; Goicoechea, J. R.; Goldsmith, P. F.; Gupta, H.; Joblin, C.; Johnstone, D.; Langer, W. D.; Latter, W. B.; Lord, S. D.; Maret, S.; Martin, P. G.; Melnick, G. J.; Menten, K. M.; Morris, P.; Murphy, J. A.; Ossenkopf, Volker; Pagani, L.; Pearson, J. C.; Perault, M.; Plume, R.; Qin, S. -L.; Salez, M.; Schlemmer, S.; Stutzki, J.; Trappe, N.; van der Tak, F. F. S.; Vastel, C.; Wang, S.; Yorke, H. W.; Yu, S.; Erickson, N.; Maiwald, F. W.; Kooi, J.; Karpov, A.; Zmuidzinas, J.; Boogert, A.; Schieder, R.; Zaal, P.

    2010-01-01

    H2O+ has been observed in its ortho- and para- states toward the massive star forming core Sgr B2(M), located close to the Galactic center. The observations show absorption in all spiral arm clouds between the Sun and Sgr B2. The average o/p ratio of H2O+ in most velocity intervals is 4.8, which

  16. Planetary perturbations for Oort cloud comets: II. Implications for the origin of observable comets

    Science.gov (United States)

    Fouchard, M.; Rickman, H.; Froeschlé, Ch.; Valsecchi, G. B.

    2014-03-01

    We present Monte Carlo simulations of the dynamical history of the Oort cloud, where in addition to the main external perturbers (Galactic tides and stellar encounters) we include, as done in a companion paper (Fouchard, M., Rickman, H., Froeschlé, Ch., Valsecchi, G.B. [2013b]. Icarus, in press), the planetary perturbations experienced each time the comets penetrate to within 50 AU of the Sun. Each simulation involves an initial sample of four million comets and extends over a maximum of 5 Gyr. For better understanding of the outcomes, we supplement the full dynamical model by others, where one or more of the effects are left out. We concentrate on the production of observable comets, reaching for the first time a perihelion within 5 AU of the Sun. We distinguish between four categories, depending on whether the comet jumps across, or creeps through, the Jupiter-Saturn barrier (perihelion distances between 5 and 15 AU), and whether the orbit leading to the observable perihelion is preceded by a major planetary perturbation or not. For reasons explained in the paper, we call the strongly perturbed comets "Kaib-Quinn comets". We thus derive a synthetic picture of the Oort spike, from which we draw two main conclusions regarding the full dynamical model. One is that 2/3 of the observable comets are injected with the aid of a planetary perturbation at the previous perihelion passage, and about half of the observable comets are of the Kaib-Quinn type. The other is that the creepers dominate over the jumpers. Due to this fact, the spike peaks at only 31 000 AU, and the majority of new comets have semi-major axes less than this value. The creepers show a clear preference for retrograde orbits as a consequence of the need to avoid untimely, planetary ejection before becoming observable. Thus, the new comets should have a 60/40 preference for retrograde against prograde orbits in apparent conflict with observations. However, both these and other results depend on our model

  17. Photometry of pulsating stars in the Magellanic Clouds as observed in the MOA project

    CERN Document Server

    Hearnshaw, J B; Rattenbury, N J; Noda, S; Takeuti, M; Abe, F; Carter, B S; Dodd, R J; Honda, M; Juga Ku Jun; Kabe, S; Kilmartin, P M; Matsubara, Y; Masuda, K; Muraki, Y; Nakamura, T; Reid, M; Rumsey, N J; Saitô, T; Sato, H; Sekiguchi, M; Sullivan, D J; Sumi, T; Watase, Y; Yanagisawa, T; Yock, P C M; Yoshizawa, M; Koribalski, B S; Saito, To.

    1999-01-01

    A review of the MOA (Microlensing Observations in Astrophysics) project is presented. MOA is a collaboration of approximately 30 astronomers from New Zealand and Japan established with the aim of finding and detecting microlensing events towards the Magellanic Clouds and the Galactic bulge, which may be indicative of either dark matter or of planetary companions. The observing program commenced in 1995, using very wide band blue and red filters and a nine-chip mosaic CCD camera. As a by-product of these observations a large database of CCD photometry for 1.4 million stars towards both LMC and SMC has been established. In one preliminary analysis 576 bright variable stars were confirmed, nearly half of them being Cepheids. Another analysis has identified large numbers of blue variables, and 205 eclipsing binaries are included in this sample. In addition 351 red variables (AGB stars) have been found. Light curves have been obtained for all these stars. The observations are carried out on a 61-cm f/6.25 telescop...

  18. Mapping Observations of DNC and HN^13C in Dark Cloud Cores

    CERN Document Server

    Hirota, T; Yamamoto, S

    2003-01-01

    We present results of mapping observations of the DNC, HN^13C, and H^13CO^+ lines (J=1-0) toward 4 nearby dark cloud cores, TMC-1, L1512, L1544, and L63, along with observations of the DNC and HN^13C lines (J=2-1) toward selected positions. By use of statistical equilibrium calculations based on the LVG model, the H_2 densities are derived to be (1.4-5.5)*10^5 cm^-3, and the [DNC]/[HN^13C] ratios are derived to be 1.25-5.44 with a typical uncertainty by a factor of 2. The observed [DNC]/[HNC] ratios range from 0.02 to 0.09, assuming the [^12C]/[^13C] ratio of 60. Distributions of DNC and HN^13C are generally similar to each other, whereas the distribution of H^13CO^+ is more extended than those of DNC and HN^13C, indicating that they reside in an inner part of the cores than HCO^+. The [DNC]/[HN^13C] ratio is rather constant within each core, although a small systematic gradients are observed in TMC-1 and L63. Particularly, no such systematic gradient is found in L1512 and L1544, where a significant effect of...

  19. Marine boundary layer cloud property retrievals from high-resolution ASTER observations: case studies and comparison with Terra MODIS

    Science.gov (United States)

    Werner, Frank; Wind, Galina; Zhang, Zhibo; Platnick, Steven; Di Girolamo, Larry; Zhao, Guangyu; Amarasinghe, Nandana; Meyer, Kerry

    2016-12-01

    A research-level retrieval algorithm for cloud optical and microphysical properties is developed for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard the Terra satellite. It is based on the operational MODIS algorithm. This paper documents the technical details of this algorithm and evaluates the retrievals for selected marine boundary layer cloud scenes through comparisons with the operational MODIS Data Collection 6 (C6) cloud product. The newly developed, ASTER-specific cloud masking algorithm is evaluated through comparison with an independent algorithm reported in [Zhao and Di Girolamo(2006)]. To validate and evaluate the cloud optical thickness (τ) and cloud effective radius (reff) from ASTER, the high-spatial-resolution ASTER observations are first aggregated to the same 1000 m resolution as MODIS. Subsequently, τaA and reff, aA retrieved from the aggregated ASTER radiances are compared with the collocated MODIS retrievals. For overcast pixels, the two data sets agree very well with Pearson's product-moment correlation coefficients of R > 0.970. However, for partially cloudy pixels there are significant differences between reff, aA and the MODIS results which can exceed 10 µm. Moreover, it is shown that the numerous delicate cloud structures in the example marine boundary layer scenes, resolved by the high-resolution ASTER retrievals, are smoothed by the MODIS observations. The overall good agreement between the research-level ASTER results and the operational MODIS C6 products proves the feasibility of MODIS-like retrievals from ASTER reflectance measurements and provides the basis for future studies concerning the scale dependency of satellite observations and three-dimensional radiative effects.

  20. Airborne hyperspectral surface and cloud bi-directional reflectivity observations in the Arctic using a commercial, digital camera

    Directory of Open Access Journals (Sweden)

    A. Ehrlich

    2011-09-01

    Full Text Available Spectral radiance measurements by a digital single-lens reflex camera were used to derive the bi-directional reflectivity of clouds and different surfaces in the Arctic. The camera has been calibrated radiometrically and spectrally to provide accurate radiance measurements with high angular resolution. A comparison with spectral radiance measurements with the SMART-Albedometer showed an agreement within the uncertainties of both instruments. The bi-directional reflectivity in terms of the hemispherical directional reflectance factor HDRF was obtained for sea ice, ice free ocean and clouds. The sea ice, with an albedo of ρ = 0.96, showed an almost isotropic HDRF, while sun glint was observed for the ocean HDRF (ρ = 0.12. For the cloud observations with ρ = 0.62, the fog bow – a backscatter feature typically for scattering by liquid water droplets – was covered by the camera. For measurements above a heterogeneous stratocumulus clouds, the required number of images to obtain a mean HDRF which clearly exhibits the fog bow has been estimated with about 50 images (10 min flight time. A representation of the HDRF as function of the scattering angle only reduces the image number to about 10 (2 min flight time.

    The measured cloud and ocean HDRF have been compared to radiative transfer simulations. The ocean HDRF simulated with the observed surface wind speed of 9 m s−1 agreed best with the measurements. For the cloud HDRF, the best agreement was obtained by a broad and weak fog bow simulated with a cloud droplet effective radius of Reff = 4 μm. This value agrees with the particle sizes from in situ measurements and retrieved from the spectral radiance of the SMART-Albedometer.

  1. Linking atmospheric synoptic transport, cloud phase, surface energy fluxes, and sea-ice growth: observations of midwinter SHEBA conditions

    Science.gov (United States)

    Persson, P. Ola G.; Shupe, Matthew D.; Perovich, Don; Solomon, Amy

    2017-08-01

    Observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) project are used to describe a sequence of events linking midwinter long-range advection of atmospheric heat and moisture into the Arctic Basin, formation of supercooled liquid water clouds, enhancement of net surface energy fluxes through increased downwelling longwave radiation, and reduction in near-surface conductive heat flux loss due to a warming of the surface, thereby leading to a reduction in sea-ice bottom growth. The analyses provide details of two events during Jan. 1-12, 1998, one entering the Arctic through Fram Strait and the other from northeast Siberia; winter statistics extend the results. Both deep, precipitating frontal clouds and post-frontal stratocumulus clouds impact the surface radiation and energy budget. Cloud liquid water, occurring preferentially in stratocumulus clouds extending into the base of the inversion, provides the strongest impact on surface radiation and hence modulates the surface forcing, as found previously. The observations suggest a minimum water vapor threshold, likely case dependent, for producing liquid water clouds. Through responses to the radiative forcing and surface warming, this cloud liquid water also modulates the turbulent and conductive heat fluxes, and produces a thermal wave penetrating into the sea ice. About 20-33 % of the observed variations of bottom ice growth can be directly linked to variations in surface conductive heat flux, with retarded ice growth occurring several days after these moisture plumes reduce the surface conductive heat flux. This sequence of events modulate pack-ice wintertime environmental conditions and total ice growth, and has implications for the annual sea-ice evolution, especially for the current conditions of extensive thinner ice.

  2. Linking atmospheric synoptic transport, cloud phase, surface energy fluxes, and sea-ice growth: observations of midwinter SHEBA conditions

    Science.gov (United States)

    Persson, P. Ola G.; Shupe, Matthew D.; Perovich, Don; Solomon, Amy

    2016-10-01

    Observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) project are used to describe a sequence of events linking midwinter long-range advection of atmospheric heat and moisture into the Arctic Basin, formation of supercooled liquid water clouds, enhancement of net surface energy fluxes through increased downwelling longwave radiation, and reduction in near-surface conductive heat flux loss due to a warming of the surface, thereby leading to a reduction in sea-ice bottom growth. The analyses provide details of two events during Jan. 1-12, 1998, one entering the Arctic through Fram Strait and the other from northeast Siberia; winter statistics extend the results. Both deep, precipitating frontal clouds and post-frontal stratocumulus clouds impact the surface radiation and energy budget. Cloud liquid water, occurring preferentially in stratocumulus clouds extending into the base of the inversion, provides the strongest impact on surface radiation and hence modulates the surface forcing, as found previously. The observations suggest a minimum water vapor threshold, likely case dependent, for producing liquid water clouds. Through responses to the radiative forcing and surface warming, this cloud liquid water also modulates the turbulent and conductive heat fluxes, and produces a thermal wave penetrating into the sea ice. About 20-33 % of the observed variations of bottom ice growth can be directly linked to variations in surface conductive heat flux, with retarded ice growth occurring several days after these moisture plumes reduce the surface conductive heat flux. This sequence of events modulate pack-ice wintertime environmental conditions and total ice growth, and has implications for the annual sea-ice evolution, especially for the current conditions of extensive thinner ice.

  3. Comparing Herschel dust emission structures, magnetic fields observed by Planck, and dynamics: high-latitude star forming cloud L1642

    Science.gov (United States)

    Malinen, Johanna

    2016-01-01

    The nearby high-latitude cloud L1642 is one of only two known very high latitude (|b| > 30 deg) clouds actively forming stars. This cloud is a rare example of star formation in isolated conditions, and can reveal important details of star formation in general, e.g., of the effect of magnetic fields. We compare Herschel dust emission structures and magnetic field orientation revealed by Planck polarization maps in L1642, and also combine these with dynamic information from molecular line observations. The high-resolution Herschel data reveal a complex structure including a dense, compressed central blob with elongated extensions, low density striations, "fishbone" like structures with a spine and perpendicular striations, and a spiraling "tail". The Planck polarization data reveal an ordered magnetic field that pervades the cloud and is aligned with the surrounding low density striations. We show that there is a complex interplay between the cloud structure and large scale magnetic fields revealed by Planck polarization data at 10' resolution. This suggests that the magnetic field is closely linked to the formation and evolution of the cloud. We see a clear transition from aligned to perpendicular structures approximately at a column density of NH = 2x10^21 cm-2. We conclude that Planck polarization data revealing the large scale magnetic field orientation can be very useful even when comparing to the finest structures in higher resolution data, e.g. Herschel at ~18" resolution.

  4. New Approaches to Derive Aerosol-Cloud Sensitivity from Global Observations

    Science.gov (United States)

    Andersen, Hendrik; Cermak, Jan; Fuchs, Julia

    2017-04-01

    This contribution presents novel satellite-based approaches to analyze interactions between aerosols and marine liquid water clouds (ACI) on a global scale. Clouds play a central role in the Earth's radiative budget by increasing the albedo but also by interacting with outgoing thermal radiation, leading to a net cooling effect. Cloud properties are determined by environmental conditions, as cloud formation requires sufficiently saturated conditions as well as condensation nuclei on which the water vapor can condense. The ways in which aerosols influence the optical, micro- and macrophysical properties of clouds as condensation nuclei are among the largest remaining uncertainties in climate research. In particular, cloud droplet size is believed to be impacted, and subsequently cloud reflectivity, lifetime, and precipitation susceptibility may be modified. Advances in the understanding of the processes that govern liquid-water cloud properties are of great importance in order to increase accuracy of climate model predictions of a changing climate. Two methods that illustrate how global satellite retrievals may be combined with reanalysis data sets to enhance knowledge on global patterns of ACI are presented: 1. A novel change-point analysis is presented to detect aerosol loadings at which cloud droplet size shows the greatest sensitivity to changes in aerosol loading. The method is applied to Terra MODIS L3 data sets; patterns of the maximum aerosol-cloud sensitivity are analyzed. Results point towards the importance of water-vapor availability as the framework in which ACI take place. 2. In a multivariate approach to analyzing ACI on a system scale, global monthly aerosol, cloud and meteorology data sets are applied in artificial neural networks (ANN). The ability of ANNs to predict global cloud patterns is demonstrated and sensitivities are subsequently derived. On this basis, the magnitude of aerosol indirect effects is compared to other determinants, pointing

  5. Atmospheric waves and dynamics beneath Jupiter's clouds from radio wavelength observations

    Science.gov (United States)

    Cosentino, Richard G.; Butler, Bryan; Sault, Bob; Morales-Juberías, Raúl; Simon, Amy; de Pater, Imke

    2017-08-01

    We observed Jupiter at wavelengths near 2 cm with the Karl G. Jansky Very Large Array (VLA) in February 2015. These frequencies are mostly sensitive to variations in ammonia abundance and probe between ∼ 0.5 - 2.0 bars of pressure in Jupiter's atmosphere; within and below the visible cloud deck which has its base near 0.7 bars. The resultant observed data were projected into a cylindrical map of the planet with spatial resolution of ∼1500 km at the equator. We have examined the data for atmospheric waves and observed a prominent bright belt of radio hotspot features near 10°N, likely connected to the same equatorial wave associated with the 5-μm hotspots. We conducted a passive tracer power spectral wave analysis for the entire map and latitude regions corresponding to eastward and westward jets and compare our results to previous studies. The power spectra analysis revealed that the atmosphere sampled in our observation (excluding the NEB region) is in a 2-D turbulent regime and its dynamics are predominately governed by the shallow water equations. The Great Red Spot (GRS) is also very prominent and has a noticeable meridional asymmetry and we compare it, and nearby storms, with optical images. We find that the meridional radio profile has a global north-south hemisphere distinction and find correlations of it to optical intensity banding and to shear zones of the zonal wind profile over select regions of latitude. Amateur optical images taken before and after our observation complemented the radio wavelength map to investigate dynamics of the equatorial region in Jupiter's atmosphere. We find that two radio hotspots at 2 cm are well correlated with optical plumes in the NEB, additionally revealing they are not the same 5 μm hotspot features correlated with optical dark patches between adjacent plumes. This analysis exploits the VLA's upgraded sensitivity and explores the opportunities now possible when studying gas giants, especially atmospheric dynamics

  6. Abundances of Cloud-Related Gases in the Venus Atmosphere as Inferred from Observed Radio Opacity.

    Science.gov (United States)

    Steffes, Paul Gregory

    1982-03-01

    Various radio-analytical techniques have detected microwave opacity in the middle atmosphere of Venus, well above the main carbon dioxide opacity of the lower atmosphere. Consideration of the amount, distribution, and effects of the constituents which produce the main cloud layer at about 50 km altitude, indicate that such cloud-related gases, especially sulfuric acid vapor, are the predominant source of the observed opacity of the middle atmosphere. Theoretical and laboratory studies were made of the microwave absorption from three cloud-related gases: sulfur dioxide, sulfur trioxide, and gaseous sulfuric acid. While the measured absorption from sulfur dioxide under conditions for the middle atmosphere of Venus was found to be 50% larger than suggested by theory, the amount of sulfur dioxide required to explain the opacity as measured by radio occultation exceeded the abundance measured in situ by atmospheric probes, suggesting that there must be another important source of opacity. Sulfur trioxide was tested and found to be relatively transparent, but laboratory measurements of the microwave opacity of gaseous sulfuric acid under Venus atmospheric conditions indicate that it is an exceptionally strong absorber with absorptivity that has a surprisingly weak dependence on radio frequency. Initial theoretical studies also indicate a large absorptivity and weak frequency dependence, although the measured opacity is larger than the computed value, presumably due to deviations from Van Vleck-Weisskopf theory. The absorbing characteristics of sulfuric acid vapor appear to reconcile past inconsistencies among measurements and deductions concerning the constituents of the atmosphere of Venus, and radio occultation, radar reflection, and radio emission measurements of its opacity. The results of the current studies are used with previous data for the absorptivity of water vapor and carbon dioxide to model relative contributions to opacity as a function of height, in a way

  7. Venus upper clouds and the UV-absorber from MESSENGER/MASCS observations

    Science.gov (United States)

    Perez-Hoyos, Santiago; Sanchez-Lavega, Agustin; Garcia Munoz, Antonio; Irwin, Patrick; Peralta, Javier; Holsclaw, Greg; McClintock, William

    2014-11-01

    In June 2007, the MESSENGER spacecraft performed its second Venus flyby on its route to Mercury. The spacecraft’s MASCS instrument (VIRS channel) acquired numerous spectra of the sunlight reflected from the equatorial region of the planet at wavelengths from the near ultraviolet (300nm) to the near infrared (1450 nm). In this work we present an analysis of the data and their spectral and spatial variability following the mission footprint on the Venus disk. In order to reproduce the observed reflectivity and obtain information on the upper clouds and the unknown UV absorber, we use the NEMESIS retrieval code, including SO2 , CO2 and H2O absorption together with absorption and scattering by mode-1, -2 and -3 cloud particles. This spectral range provides sensitivity to the uppermost cloud levels, above 60 km. Vertical profiles of the mode-1 and mode-2 particles have been retrieved along the equatorial region of Venus, with average retrieved sounding levels of 70 +/- 2 km at 1 micron, in good agreement with previous investigations. This spectral range is also very interesting because of the existence of a mysterious absorber in the blue and UV side of the reflected spectra, whose origin remains as one of the key questions about the Venus atmosphere. Here we report a comparison with some of the previously proposed absorbers: (1) sulfur-related compounds (amorphous and liquid sulfur, S3, S4, S8, S2O); (2) chlorine related species (Cl2, FeCl3); (3) organics (C3O2, Croconic acid). Preliminary results show that the first group provides better fits to the data, although combinations of the proposed agents might be required in order to produce better results. Acknowledgements: This work was supported by the Spanish MICIIN projects AYA2009- 10701, AYA2012-38897-C02-01, and AYA2012-36666 with FEDER support, PRICIT-S2009/ESP-1496, Grupos Gobierno Vasco IT765-13, and UPV/EHU UFI11/55. S.P.-H. acknowledges support from the Jose Castillejo Program funded by Ministerio de Educaci

  8. Observations on the effects of grooved surfaces on the interfacial torque in highly loaded rolling and sliding tests

    DEFF Research Database (Denmark)

    Janakiraman, Shravan; Klit, Peder; Jensen, Niels Steenfeldt;

    2014-01-01

    Some efforts have been undertaken to study the effects of grooved surfaces on the interfacial film thickness and torque between two contacting non-conformal surfaces under heavy loads. Transverse grooves of micrometer scale depth were engraved on polished, flat ring surfaces using established...... industrial methods like laser engraving and wire cutting. The grooved surfaces were then run against a polished flat surface at loads corresponding to high normal Hertzian pressures. Experiments were conducted to study the effects of the following parameters on the interfacial torque-groove depth, groove...... wavelength, load, inlet speed and slide-roll ratio. Experimental results were then justified, in certain cases, based on a multigrid model predicting the interfacial pressure and film thickness....

  9. Evaluation of cloud fraction and its radiative effect simulated by IPCC AR4 global models against ARM surface observations

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Yun; Long, Charles N.; Wang, Hailong; Comstock, Jennifer M.; McFarlane, Sally A.; Xie, Shaocheng

    2012-02-17

    Cloud Fraction (CF) is the dominant modulator of radiative fluxes. In this study, we evaluate CF simulations in the IPCC AR4 GCMs against ARM ground measurements, with a focus on the vertical structure, total amount of cloud and its effect on cloud shortwave transmissivity, for both inter-model deviation and model-measurement discrepancy. Our intercomparisons of three CF or sky-cover related dataset reveal that the relative differences are usually less than 10% (5%) for multi-year monthly (annual) mean values, while daily differences are quite significant. The results also show that the model-observation and the inter-model deviations have a similar magnitude for the total CF (TCF) and the normalized cloud effect, and they are twice as large as the surface downward solar radiation and cloud transmissivity. This implies that the other cloud properties, such as cloud optical depth and height, have a similar magnitude of disparity to TCF among the GCMs, and suggests that a better agreement among the GCMs in solar radiative fluxes could be the result of compensating errors in either cloud vertical structure, cloud optical depth or cloud fraction. Similar deviation pattern between inter-model and model-measurement suggests that the climate models tend to generate larger bias against observations for those variables with larger inter-model deviation. The simulated TCF from IPCC AR4 GCMs are very scattered through all seasons over three ARM sites: Southern Great Plains (SGP), Manus, Papua New Guinea and North Slope of Alaska (NSA). The GCMs perform better at SGP than at Manus and NSA in simulating the seasonal variation and probability distribution of TCF; however, the TCF in these models is remarkably underpredicted and cloud transmissivity is less susceptible to the change of TCF than the observed at SGP. Much larger inter-model deviation and model bias are found over NSA than the other sites in estimating the TCF, cloud transmissivity and cloud-radiation interaction

  10. An Observational Diagnostic for Distinguishing between Clouds and Haze in Hot Exoplanet Atmospheres

    Science.gov (United States)

    Kempton, Eliza M.-R.; Bean, Jacob L.; Parmentier, Vivien

    2017-08-01

    The nature of aerosols in hot exoplanet atmospheres is one of the primary vexing questions facing the exoplanet field. The complex chemistry, multiple formation pathways, and lack of easily identifiable spectral features associated with aerosols make it especially challenging to constrain their key properties. We propose a transmission spectroscopy technique to identify the primary aerosol formation mechanism for the most highly irradiated hot Jupiters (HIHJs). The technique is based on the expectation that the two key types of aerosols—photochemically generated hazes and equilibrium condensate clouds—are expected to form and persist in different regions of a highly irradiated planet’s atmosphere. Haze can only be produced on the permanent daysides of tidally locked hot Jupiters, and will be carried downwind by atmospheric dynamics to the evening terminator (seen as the trailing limb during transit). Clouds can only form in cooler regions on the nightside and morning terminator of HIHJs (seen as the leading limb during transit). Because opposite limbs are expected to be impacted by different types of aerosols, ingress and egress spectra, which primarily probe opposing sides of the planet, will reveal the dominant aerosol formation mechanism. We show that the benchmark HIHJ, WASP-121b, has a transmission spectrum consistent with partial aerosol coverage and that ingress-egress spectroscopy would constrain the location and formation mechanism of those aerosols. In general, using this diagnostic we find that observations with the James Webb Space Telescope and potentially with the Hubble Space Telescope should be able to distinguish between clouds and haze for currently known HIHJs.

  11. Investigating Type I Polar Stratospheric Cloud Formation Mechanisms with POAM Satellite Observations

    Science.gov (United States)

    Strawa, Anthony W.; Drdla, K.; Fromm, M.; Hoppel, K.; Browell, E.; Hamill, P.; Dempsey, D.; Gore, Warren J. (Technical Monitor)

    2001-01-01

    Type Ia PSCs are believed to be composed of nitric acid hydrate particles. Recent results from the SOLVE/THESEO 2000 campaign showed evidence that this type of PSC was composed of a small number of very large particles capable of sedimentary denitrification of regions of the stratosphere. It is unknown whether homogeneous or heterogeneous nucleation is responsible for the formation of these PSCs. Arctic winters are tending to be colder in response to global tropospheric warming. The degree to which this influences ozone depletion will depend on the freezing mechanism of nitric acid hydrate particles. If nucleation is homogeneous it implies that the freezing process is an inherent property of the particle, while heterogeneous freezing means that the extent of PSCs will depend in part on the number of nuclei available. The Polar Ozone and Aerosol Measurement (POAM)II and III satellites have been making observations of stratospheric aerosols and Polar Stratospheric Clouds (PSCs) since 1994. Recently, we have developed a technique that can discriminate between Type Ia and Ib PSCs using these observations. A statistical approach is employed to demonstrate the robustness of this approach and results are compared with lidar measurements. The technique is used to analyze observations from POAM II and II during Northern Hemisphere winters where significant PSC formation occurred with the objective of exploring Type I PSC formation mechanisms. The different PSCs identified using this method exhibit different growth curve as expressed as extinction versus temperature.

  12. AzTEC 1.1 mm Observations of the MBM12 Molecular Cloud

    CERN Document Server

    Kim, M J; Youn, S; Yun, M S; Wilson, G W; Aretxaga, I; Williams, J P; Hughes, D H; Humphrey, A; Austermann, J E; Perera, T A; Mauskopf, P D; Magnani, L; Kang, Y -W

    2011-01-01

    We present 1.1 mm observations of the dust continuum emission from the MBM12 high-latitude molecular cloud observed with the Astronomical Thermal Emission Camera (AzTEC) mounted on the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. We surveyed a 6.34 deg$^2$ centered on MBM12, making this the largest area that has ever been surveyed in this region with submillimeter and millimeter telescopes. Eight secure individual sources were detected with a signal-to-noise ratio of over 4.4. These eight AzTEC sources can be considered to be real astronomical objects compared to the other candidates based on calculations of the false detection rate. The distribution of the detected 1.1 mm sources or compact 1.1 mm peaks is spatially anti-correlated with that of the 100 micronm emission and the $^{12}$CO emission. We detected the 1.1 mm dust continuum emitting sources associated with two classical T Tauri stars, LkHalpha262 and LkHalpha264. Observations of spectral energy distributions (SEDs) indicate that LkHalpha262 ...

  13. Mantle formation, coagulation and the origin of cloud/core-shine: II. Comparison with observations

    CERN Document Server

    Ysard, N; Jones, A P; Dartois, E; Godard, M; Gavilan, L

    2016-01-01

    Many dense interstellar clouds are observable in emission in the near-IR, commonly referred to as "Cloudshine", and in the mid-IR, the so-called "Coreshine". These C-shine observations have usually been explained with grain growth but no model has yet been able to self-consistently explain the dust spectral energy distribution from the near-IR to the submm. We want to demonstrate the ability of our new core/mantle evolutionary dust model THEMIS (The Heterogeneous dust Evolution Model at the IaS), which has been shown to be valid in the far-IR and submm, to reproduce the C-shine observations. Our starting point is a physically motivated core/mantle dust model. It consists of 3 dust populations: small aromatic-rich carbon grains; bigger core/mantle grains with mantles of aromatic-rich carbon and cores either made of amorphous aliphatic-rich carbon or amorphous silicate. We assume an evolutionary path where these grains, when entering denser regions, may first form a second aliphatic-rich carbon mantle (coagulat...

  14. Simultaneous infrared and optical observations of the transiting debris cloud around WD 1145+017

    CERN Document Server

    Zhou, G; Bailey, J; Marshall, J P; Bayliss, D D R; Stockade, C; Nelson, P; Tan, T G; Rodriguez, J E; Tinney, C G; Dragomir, D; Colon, K; Shporer, A; Bento, J; Sefako, R; Horne, K; Cochran, W

    2016-01-01

    We present multi-wavelength photometric monitoring of WD 1145+017, a white dwarf exhibiting periodic dimming events interpreted to be the transits of orbiting, disintegrating planetesimals. Our observations include the first set of near-infrared light curves for the object, obtained on multiple nights over the span of one month, and recorded multiple transit events with depths ranging from ~20% to 50%. Simultaneous near-infrared and optical observations of the deepest and longest duration transit event were obtained at two epochs with the Anglo-Australian Telescope and three optical facilities, over the wavelength range of 0.5-1.2 microns. These observations revealed no measurable difference in transit depths for multiple photometric pass bands, allowing us to place a 2 sigma lower limit of 0.8 microns on the grain size in the putative transiting debris cloud. The lack of small grains is consistent with the infrared excess about the white dwarf, and may point towards a collision-dominated debris disc.

  15. A deep XMM-Newton X-ray observation of the Chamaeleon I dark cloud

    CERN Document Server

    Robrade, J

    2006-01-01

    Methods. The northern-eastern fringe of the Chameleon I dark cloud was observed with XMM-Newton, revisiting a region observed with ROSAT 15 years ago. Centered on the extended X-ray source CHXR49 we are able to resolve it into three major contributing components and to analyse their spectral properties. Furthermore, the deep exposure allows not only the detection of numerous, previously unknown X-ray sources, but also the investigation of variability and the study of the X-ray properties for the brighter targets in the field. We use EPIC spectra, to determine X-ray brightness, coronal temperatures and emission measures for these sources, compare the properties of classical and weak-line T Tauri stars and make a comparison with results from the ROSAT observation. Results. X-ray properties of T Tauri stars in Cha I are presented. The XMM-Newton images resolve some previously blended X-ray sources, confirm several possible ones and detect many new X-ray targets, resulting in the most comprehensive list with 71 X...

  16. Observed microphysical changes in Arctic mixed-phase clouds when transitioning from sea-ice to open ocean

    Science.gov (United States)

    Young, Gillian; Jones, Hazel M.; Crosier, Jonathan; Bower, Keith N.; Darbyshire, Eoghan; Taylor, Jonathan W.; Liu, Dantong; Allan, James D.; Williams, Paul I.; Gallagher, Martin W.; Choularton, Thomas W.

    2016-04-01

    The Arctic sea-ice is intricately coupled to the atmosphere[1]. The decreasing sea-ice extent with the changing climate raises questions about how Arctic cloud structure will respond. Any effort to answer these questions is hindered by the scarcity of atmospheric observations in this region. Comprehensive cloud and aerosol measurements could allow for an improved understanding of the relationship between surface conditions and cloud structure; knowledge which could be key in validating weather model forecasts. Previous studies[2] have shown via remote sensing that cloudiness increases over the marginal ice zone (MIZ) and ocean with comparison to the sea-ice; however, to our knowledge, detailed in-situ data of this transition have not been previously presented. In 2013, the Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign was carried out in the vicinity of Svalbard, Norway to collect in-situ observations of the Arctic atmosphere and investigate this issue. Fitted with a suite of remote sensing, cloud and aerosol instrumentation, the FAAM BAe-146 aircraft was used during the spring segment of the campaign (Mar-Apr 2013). One case study (23rd Mar 2013) produced excellent coverage of the atmospheric changes when transitioning from sea-ice, through the MIZ, to the open ocean. Clear microphysical changes were observed, with the cloud liquid-water content increasing by almost four times over the transition. Cloud base, depth and droplet number also increased, whilst ice number concentrations decreased slightly. The surface warmed by ~13 K from sea-ice to ocean, with minor differences in aerosol particle number (of sizes corresponding to Cloud Condensation Nuclei or Ice Nucleating Particles) observed, suggesting that the primary driver of these microphysical changes was the increased heat fluxes and induced turbulence from the warm ocean surface as expected. References: [1] Kapsch, M.L., Graversen, R.G. and Tjernström, M. Springtime

  17. Exploring the differences in cloud properties observed by the Terra and Aqua MODIS Sensors

    Directory of Open Access Journals (Sweden)

    N. Meskhidze

    2009-05-01

    Full Text Available The aerosol-cloud interaction in different parts of the globe is examined here using multi-year statistics of remotely sensed data from two MODIS sensors aboard NASA's Terra (morning and Aqua (afternoon satellites. Simultaneous retrievals of aerosol loadings and cloud properties by the MODIS sensor allowed us to explore morning-to-afternoon variation of liquid cloud fraction (CF and optical thickness (COT for clean, moderately polluted and heavily polluted clouds in different seasons. Data analysis for seven-years of MODIS retrievals revealed strong temporal and spatial patterns in morning-to-afternoon variation of cloud fraction and optical thickness over different parts of the global oceans and the land. For the vast areas of stratocumulus cloud regions, the data shows that the days with elevated aerosol abundance were also associated with enhanced afternoon reduction of CF and COT pointing to the possible reduction of the indirect climate forcing. A positive correlation between aerosol optical depth and morning-to-afternoon variation of trade wind cumulus cloud cover was also found over the northern Indian Ocean, though no clear relationship between the concentration of Indo-Asian haze and morning-to-afternoon variation of COT was established. Over the Amazon region during wet conditions, aerosols are associated with an enhanced convective process in which morning shallow warm clouds are organized into afternoon deep convection with greater ice cloud coverage. Analysis presented here demonstrates that the new technique for exploring morning-to-afternoon variability in cloud properties by using the differences in data products from the two daily MODIS overpasses is capable of capturing some of the major features of diurnal variations in cloud properties and can be used for better understanding of aerosol radiative effects.

  18. Evaluation of cloud-resolving modeling of haboobs using in-situ and remotely sensed observations

    Science.gov (United States)

    Anisimov, Anatolii; Axisa, Duncan; Mostamandi, Suleiman; Kucera, Paul A.; Stenchikov, Georgiy

    2017-04-01

    Arabian Peninsula is one of the major dust generation regions that at present is severely under-sampled. In this study, we combine unique aircraft observations of aerosol and fine-resolution simulations to better quantify dust generation and transport in deep convective storms called haboobs. The aerosol observations were obtained during the "Kingdom of Saudi Arabia Assessment of Rainfall Augmentation" research program that was conducted in the Central and Southwest regions of Saudi Arabia for the years of 2006 through 2009. We ingest the observations from the first phase of the project conducted in the central Arabian Peninsula near Riyadh in April 2007 and focus on the observational cases when the aircraft sampled high concentrations of dust within haboobs. These data are indispensable for assessment of dust properties during periods of extreme aerosol loading. We perform cloud-resolving 2-km simulations using the coupled meteorology-chemistry WRF-Chem model with 8-bin MOSAIC aerosol microphysics scheme that accounts for direct and indirect aerosol effects. The model is validated using observations from surface weather stations, Doppler weather radar network, AERONET stations, MODIS and SEVIRI satellite aerosol sensors. We also compare the model results with recent MERRA-2 reanalysis that assimilates aerosols and chemical components. The model captures the spatiotemporal variability of atmospheric circulation and aerosol properties and calculates contributions of different aerosol species. We specifically compare the simulated aerosols with the aircraft measurements to evaluate the vertical extent and the structure of dust layers in haboobs. The simulated column-averaged dust size distribution compares reasonably well with AERONET and aircraft measurement. Despite total aerosol optical depth in simulations and MERRA2 reanalysis are quite similar, the vertical distribution and regional dust emission fluxes in the model and reanalysis differ significantly. The

  19. Evidence for an orographic forcing of SO2 observed above the clouds with SPICAV/Venus Express.

    Science.gov (United States)

    Bertaux, J.-L.; Marcq, E.; Hauchecorne, A.; Lebonnois, S.

    2014-04-01

    SPICAV UV spectrometer on board Venus Express(VEX) has routinely observed the quantity of SO2 above the clouds. A periodogram analysis of the signal shows a distinct peak at 117 days, the length of the Venus day. The same 117 day peak was found also in the zonal wind from Venus Monitoring Camera (VMC) [1]. It is argued that this is the result of a ground-altitude forcing of both phenomena, most likely with the quantity of SO2 observable above the clouds responding to increased vertical winds The role of orography interacting with the zonal wind and generating gravity waves propagating upward to above cloud level will be examined, as well as the LMD GCM model (containing orography) output for zonal velocity at a constant Local Time.

  20. Herschel far-infrared observations of the Carina Nebula Complex. - III: Detailed cloud structure and feedback effects

    CERN Document Server

    Roccatagliata, Veronica; Ratzka, Thorsten; Gaczkowski, Benjamin

    2013-01-01

    The Carina Nebula complex (CNC) represents one of the most massive star-forming regions in our Galaxy and shows strong feedback from the high massive stars. We use our Herschel FIR observations to study the properties of the clouds over the entire area of the CNC. The good angular resolution of the Herschel maps corresponds to physical scales of 0.1 - 0.4 pc, and allows us to analyze the small-scale structures of the clouds. The full extent of the CNC was mapped with PACS and SPIRE from 70 to 500 micron. We determine temperatures and column densities at each point in this maps by modeling the observed FIR SEDs. We also derive a map showing the strength of the UV field. We investigate the relation between the cloud properties and the spatial distribution of the high-mass stars, and compute total cloud masses for different density thresholds. Our Herschel maps resolve, for the first time, the small-scale structure of the dense clouds. Several particularly interesting regions, including the prominent pillars sou...

  1. Scent marking in Sunda clouded leopards (Neofelis diardi): novel observations close a key gap in understanding felid communication behaviours

    Science.gov (United States)

    Allen, Maximilian L.; Wittmer, Heiko U.; Setiawan, Endro; Jaffe, Sarah; Marshall, Andrew J.

    2016-01-01

    Intraspecific communication is integral to the behavioural ecology of solitary carnivores, but observing and quantifying their communication behaviours in natural environments is difficult. Our systematic literature review found that basic information on scent marking is completely lacking for 23% of all felid species, and information on 21% of other felid species comes solely from one study of captive animals. Here we present results of the first systematic investigation of the scent marking behaviours of Sunda clouded leopards in the wild. Our observations using motion-triggered video cameras in Indonesian Borneo are novel for clouded leopards, and contrary to previous descriptions of their behaviour. We found that clouded leopards displayed 10 distinct communication behaviours, with olfaction, scraping, and cheek rubbing the most frequently recorded. We also showed that males make repeated visits to areas they previously used for marking and that multiple males advertise and receive information at the same sites, potentially enhancing our ability to document and monitor clouded leopard populations. The behaviours we recorded are remarkably similar to those described in other solitary felids, despite tremendous variation in the environments they inhabit, and close a key gap in understanding and interpreting communication behaviours of clouded leopards and other solitary felids. PMID:27739507

  2. VLA Observations of the Magnetic Field of the Smith High Velocity Cloud

    Science.gov (United States)

    Betti, Sarah; Hill, Alex S.; Mao, Sui Ann; McClure-Griffiths, Naomi M.; Lockman, Felix J.; Benjamin, Robert A.; Gaensler, Bryan M.

    2017-01-01

    High velocity clouds (HVCs) are hydrogen gas clouds around galaxies with velocities inconsistent with Galactic rotation. HVCs may fuel future star formation and drive galaxy evolution. The Smith Cloud is an HVC with an orbit suggesting it has made at least one passage through the disk. A measured magnetic field suggests how it survived passage through the Galactic halo. The Faraday rotation measure (RM) provides information about the strength and direction of the magnetic field. We use the Karl G. Jansky Very Large Array (VLA) to obtain reliable RMs towards ~950 background point sources to measure the geometry of the magnetic field of the Smith Cloud. These RMs constrain the strength of the magnetic field at the head, tail, and body of the Smith Cloud while RMs directly behind the Smith Cloud suggest there is ionized gas associated with the cloud that has not previously been detected. The confirmation of the magnetic field of the Smith Cloud along with a detailed morphology of the magnetic field structure will constrain how HVCs pass through the Galactic halo without losing their gas and survive the passage through the intergalactic and interstellar media.

  3. The Plane-parallel Albedo Bias of Liquid Clouds from MODIS Observations

    Science.gov (United States)

    Oreopoulos, Lazaros; Cahalan, Robert F.; Platnick, Steven

    2007-01-01

    In our most advanced modeling tools for climate change prediction, namely General Circulation Models (GCMs), the schemes used to calculate the budget of solar and thermal radiation commonly assume that clouds are horizontally homogeneous at scales as large as a few hundred kilometers. However, this assumption, used for convenience, computational speed, and lack of knowledge on cloud small scale variability, leads to erroneous estimates of the radiation budget. This paper provides a global picture of the solar radiation errors at scales of approximately 100 km due to warm (liquid phase) clouds only. To achieve this, we use cloud retrievals from the instrument MODIS on the Terra and Aqua satellites, along with atmospheric and surface information, as input into a GCM-style radiative transfer algorithm. Since the MODIS product contains information on cloud variability below 100 km we can run the radiation algorithm both for the variable and the (assumed) homogeneous clouds. The difference between these calculations for reflected or transmitted solar radiation constitutes the bias that GCMs would commit if they were able to perfectly predict the properties of warm clouds, but then assumed they were homogeneous for radiation calculations. We find that the global average of this bias is approx.2-3 times larger in terms of energy than the additional amount of thermal energy that would be trapped if we were to double carbon dioxide from current concentrations. We should therefore make a greater effort to predict horizontal cloud variability in GCMs and account for its effects in radiation calculations.

  4. Influence of the liquid layer within mixed-phase clouds on radar observations

    NARCIS (Netherlands)

    Pfitzenmaier, L.; Dufournet, Y.; Unal, C.M.H.; Russchenberg, H.W.J.

    2014-01-01

    Mixed-phase clouds play an important role in the earth system. They affect earth radiative balance and the climate (Comstock et al., 2007; Solomon et al., 2007) as well as the formation of precipitation (de Boer et al., 2009; Fan et al., 2011; Lamb and Verlinde, 2011). Within such mixed-phase clouds

  5. Understanding Seasonal Variability in thin Cirrus Clouds from Continuous MPLNET Observations at GSFC in 2012

    Science.gov (United States)

    Lolli, Simone; Lewis, Jasper R.; Welton, Ellsworth J.; Campbell, James R.; Gu, Y.

    2016-06-01

    Optically thin cirrus cloud (optical depth effect can outweigh the infrared greenhouse effect, cooling the earthatmosphere system rather than warming it exclusively. As result, based on latitude, the net forcing of sub-visible cirrus clouds can be more accurately parameterized in climate models.

  6. Variation in Texture and Lankford Value of 1070 Aluminum Sheet Rolled by Cone-shaped Roll

    Institute of Scientific and Technical Information of China (English)

    Yasumasa Chino; Xinsheng Huang; Kazutaka Suzuki; Mamoru Mabuchi

    2013-01-01

    A rolling with cone-shaped roll,the diameter of which continuously varies along the axial direction,has been proposed as a new shear rolling for controlling the texture of an aluminum alloy sheet.In this study,variations in the texture and Lankford value of a 1070 aluminum sheet rolled by the cone-shaped roll were investigated.Rolling with the cone-shaped roll was found to impose intense shear strain at the edges of the specimen,specifically near the surface.The shear directions in the left and right portions of the specimen were opposite to each other.The surface and middle layer of the specimen rolled by the cone-shaped roll and the reference specimen were characterized by a shear texture and typical recrystallization texture components,respectively.Notably,the specimen rolled by the cone-shaped roll exhibited smaller texture intensity than the reference specimen,especially at the surface,and the shear texture-components were observed at relatively deeper positions.As a result of Lankford value measurements,the specimen rolled with the cone-shape roll exhibited a smaller planar anisotropy than the reference specimen and an average Lankford value close to unity,which are likely due to the texture modifications introduced during rolling with the cone-shaped roll.

  7. Alternative methods for specification of observed forcing in single-column models and cloud system models

    Science.gov (United States)

    Randall, David A.; Cripe, Douglas G.

    1999-10-01

    We discuss alternative methods for prescribing advective tendencies in single-column models (SCMs) and cloud system models. These include "revealed forcing," in which the total advective tendency is prescribed from observations; "horizontal advective forcing," in which the horizontal advective tendencies are prescribed, together with the observed vertical motion which is combined with the predicted sounding to determine the tendencies due to vertical advection; and "relaxation forcing," in which the horizontal advective tendencies are computed by relaxing the sounding toward the observed upstream sounding, with a relaxation timescale determined by the time required for the wind to carry parcels across the grid column. When relaxation forcing is used, the horizontal advective tendencies can be diagnosed from the model output and compared with the corresponding observed tendencies. We present SCM results to illustrate these three forcing methods, based on data from several field experiments in both the tropics and the midlatitudes. Each method is shown to have its strengths and weaknesses. Overall, the results presented here do not show unambiguous differences between revealed forcing and horizontal advective forcing. The two methods appear to be generally comparable. Revealed forcing may therefore be preferred for its simplicity. Relaxation forcing guarantees realistic soundings of the state variables but can produce large errors in parameterized processes which are driven by rates (e.g., fluxes) rather than states. In particular, relaxation forcing gives large errors in the precipitation rate in this model. We demonstrate that relaxation forcing leads to unrealistically high (low) precipitation in versions of the model which tend to produce unrealistically dry (humid) soundings. The observed horizontal advective tendencies in the tropics are so weak, especially for temperature, that small absolute errors in the diabatic tendencies diagnosed with relaxation forcing

  8. Fitting a Turbulent Cloud Model to CO Observations of Starless Bok Globules

    Science.gov (United States)

    Hegmann, M.; Hengel, C.; Röllig, M.; Kegel, W. H.

    We present observations of five starless Bok globules in transitions of 12CO (J=2-1 and {J=3-2}), 13CO (J=2-1), and C18O (J=2-1) which have been obtained at the Heinrich-Hertz-Telescope. For an analysis of the data we use the model of Kegel et al. (see e.g. Piehler & Kegel 1995, A&A 297, 841; Hegmann & Kegel 2000, A&A 359, 405) which describes an isothermal sphere stabilized by turbulent and thermal pressure. This approach deals with the full NLTE radiative transfer problem and accounts for a turbulent velocity field with finite correlation length. By a comparison of observed and calculated line profiles we are able not only to determine the kinetic temperature, hydrogen density and CO coloumn density of the globules, but also to study the properties of the turbulent velocity field, i.e. the variance of its one-point-distribution and its correlation length. We consider our model to be an alternative tool for the evaluation of molecular lines emitted by molecular clouds. The model assumptions are certainly closer to reality than the assumptions behind the standard evaluation models, as for example the LVG model. Our current study shows that that the results obtained from our model can differ significantly from those obtained from a LVG analysis.

  9. A multi-wavelength observation and investigation of six infrared dark clouds

    CERN Document Server

    Zhang, Chuan-Peng; Li, Guang-Xing; Zhou, Jian-Jun; Wang, Jun-Jie

    2016-01-01

    Context. Infrared dark clouds (IRDCs) are ubiquitous in the Milky Way, yet they play a crucial role in breeding newly-formed stars. Aims. With the aim of further understanding the dynamics, chemistry, and evolution of IRDCs, we carried out multi-wavelength observations on a small sample. Methods. We performed new observations with the IRAM 30 m and CSO 10.4 m telescopes, with tracers ${\\rm HCO^+}$, HCN, ${\\rm N_2H^+}$, ${\\rm C^{18}O}$, DCO$^+$, SiO, and DCN toward six IRDCs G031.97+00.07, G033.69-00.01, G034.43+00.24, G035.39-00.33, G038.95-00.47, and G053.11+00.05. Results. We investigated 44 cores including 37 cores reported in previous work and seven newly-identified cores. Toward the dense cores, we detected 6 DCO$^+$, and 5 DCN lines. Using pixel-by-pixel spectral energy distribution (SED) fits of the $\\textit{Herschel}$ 70 to 500 $\\mu$m, we obtained dust temperature and column density distributions of the IRDCs. We found that ${\\rm N_2H^+}$ emission has a strong correlation with the dust temperature and...

  10. Observations of cloud liquid water path over oceans: Optical and microwave remote sensing methods

    Science.gov (United States)

    Lin, Bing; Rossow, William B.

    1994-01-01

    Published estimates of cloud liquid water path (LWP) from satellite-measured microwave radiation show little agreement, even about the relative magnitudes of LWP in the tropics and midlatitudes. To understand these differences and to obtain more reliable estimate, optical and microwave LWP retrieval methods are compared using the International Satellite Cloud Climatology Project (ISCCP) and special sensor microwave/imager (SSM/I) data. Errors in microwave LWP retrieval associated with uncertainties in surface, atmosphere, and cloud properties are assessed. Sea surface temperature may not produce great LWP errors, if accurate contemporaneous measurements are used in the retrieval. An uncertainty of estimated near-surface wind speed as high as 2 m/s produces uncertainty in LWP of about 5 mg/sq cm. Cloud liquid water temperature has only a small effect on LWP retrievals (rms errors less than 2 mg/sq cm), if errors in the temperature are less than 5 C; however, such errors can produce spurious variations of LWP with latitude and season. Errors in atmospheric column water vapor (CWV) are strongly coupled with errors in LWP (for some retrieval methods) causing errors as large as 30 mg/sq cm. Because microwave radiation is much less sensitive to clouds with small LWP (less than 7 mg/sq cm) than visible wavelength radiation, the microwave results are very sensitive to the process used to separate clear and cloudy conditions. Different cloud detection sensitivities in different microwave retrieval methods bias estimated LWP values. Comparing ISCCP and SSM/I LWPs, we find that the two estimated values are consistent in global, zonal, and regional means for warm, nonprecipitating clouds, which have average LWP values of about 5 mg/sq cm and occur much more frequently than precipitating clouds. Ice water path (IWP) can be roughly estimated from the differences between ISCCP total water path and SSM/I LWP for cold, nonprecipitating clouds. IWP in the winter hemisphere is about

  11. AzTEC 1.1 mm OBSERVATIONS OF THE MBM12 MOLECULAR CLOUD

    Energy Technology Data Exchange (ETDEWEB)

    Kim, M. J.; Kim, S.; Youn, S.; Kang, Y.-W. [Department of Astronomy and Space Science, Sejong University, KwangJin-gu, KunJa-dong 98, Seoul 143-747 (Korea, Republic of); Yun, M. S.; Wilson, G. W. [Department of Astronomy, University of Massachusetts, 710 North Pleasant St., Amherst, MA 01003 (United States); Aretxaga, I.; Hughes, D. H.; Humphrey, A. [Instituto Nacional de Astrofisca, Optica y Electronica, Tonantzintla, Puebla (Mexico); Williams, J. P. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Austermann, J. E. [Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, Colorado 80309 (United States); Perera, T. A. [Department of Physics, Illinois Wesleyan University, Bloomington, IL 61701 (United States); Mauskopf, P. D. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Magnani, L., E-mail: sek@sejong.ac.kr [Department of Physics and Astronomy, The University of Georgia, Athens, GA 30602-2451 (United States)

    2012-02-10

    We present 1.1 mm observations of the dust continuum emission from the MBM12 high-latitude molecular cloud observed with the Astronomical Thermal Emission Camera (AzTEC) mounted on the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. We surveyed 6.34 deg{sup 2} centered on MBM12, making this the largest area that has ever been surveyed in this region with submillimeter and millimeter telescopes. Eight secure individual sources were detected with a signal-to-noise ratio of over 4.4. These eight AzTEC sources can be considered to be real astronomical objects compared to the other candidates based on calculations of the false detection rate. The distribution of the detected 1.1 mm sources or compact 1.1 mm peaks is spatially anti-correlated with that of the 100 {mu}m emission and the {sup 12}CO emission. We detected the 1.1 mm dust continuum emitting sources associated with two classical T Tauri stars, LkH{alpha}262 and LkH{alpha}264. Observations of spectral energy distributions (SEDs) indicate that LkH{alpha}262 is likely to be Class II (pre-main-sequence star), but there are also indications that it could be a late Class I (protostar). A flared disk and a bipolar cavity in the models of Class I sources lead to more complicated SEDs. From the present AzTEC observations of the MBM12 region, it appears that other sources detected with AzTEC are likely to be extragalactic and located behind MBM12. Some of these have radio counterparts and their star formation rates are derived from a fit of the SEDs to the photometric evolution of galaxies in which the effects of a dusty interstellar medium have been included.

  12. The First Observation of the Submillimeter Polarization Spectrum in a Low-AV Molecular Cloud

    Science.gov (United States)

    Campbell Ashton, Peter; Ade, Peter; Angilè, Francesco E.; Benton, Steven J.; Devlin, Mark J.; Dober, Bradley; Fissel, Laura M.; Fukui, Yasuo; Galitzki, Nicholas; Gandilo, Natalie; Klein, Jeffrey; Li, Zhi-Yun; Korotkov, Andrei; Martin, Peter G.; Matthews, Tristan; Moncelsi, Lorenzo; nakamura, fumitaka; Barth Netterfield, Calvin; Novak, Giles; Pascale, Enzo; Poidevin, Frédérick; Santos, Fabio P.; Savini, Giorgio; Scott, Douglas; Shariff, Jamil; Soler, Juan D.; Thomas, Nicholas; tucker, carole; Tucker, Gregory S.; Ward-Thompson, Derek; BLASTPol

    2017-01-01

    Polarized emission from aligned interstellar dust is both a crucial tool for studies of magnetism in the interstellar medium and a troublesome contaminant in studies of the polarized cosmic microwave background. In each case, an understanding of the significance of the dust polarization signal requires well-calibrated models that accurately describe dust grains’ physical properties and interactions with their environment. Despite decades of progress in both theory and observation, polarized dust emission models remain largely underconstrained. During its 2012 flight, BLASTPol (the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry) obtained simultaneous broad-band polarimetric maps at 250, 350, and 500 μm of a several degree-scale region containing several low-AV molecular clouds. Combining these data with polarimetric observations from the Planck 850 μm band, we have produced a submillimeter polarization spectrum for one of these objects for the first time. We find the polarization degree to be largely constant across the four submillimeter bands. This result introduces a new observable with the potential to place strong empirical constraints on polarized dust models of the ISM in a density regime that has not been accessible to previous experiments. Comparing with the work of Draine & Fraisse (2009), our result is inconsistent with two of their four models. In particular, the two models for which all polarization arises from the aligned silicate component yield submillimeter polarization spectra that rise steeply with wavelength, in disagreement with our observations. This line of investigation will continue in the near future, as new experiments like The Next-Generation BLAST Polarimeter (BLAST-TNG) use their enhanced sensitivities to characterize polarized dust emission in even more diffuse environments.

  13. Roll-pitch-yaw autopilot design for nonlinear time-varying missile using partial state observer based global fast terminal sliding mode control

    Institute of Scientific and Technical Information of China (English)

    Ahmed Awad; Wang Haoping

    2016-01-01

    The acceleration autopilot design for skid-to-turn (STT) missile faces a great challenge owing to coupling effect among planes, variation of missile velocity and its parameters, inexistence of a complete state vector, and nonlinear aerodynamics. Moreover, the autopilot should be designed for the entire flight envelope where fast variations exist. In this paper, a design of inte-grated roll-pitch-yaw autopilot based on global fast terminal sliding mode control (GFTSMC) with a partial state nonlinear observer (PSNLO) for STT nonlinear time-varying missile model, is employed to address these issues. GFTSMC with a novel sliding surface is proposed to nullify the integral error and the singularity problem without application of the sign function. The pro-posed autopilot consisting of two-loop structure, controls STT maneuver and stabilizes the rolling with a PSNLO in order to estimate the immeasurable states as an output while its inputs are missile measurable states and control signals. The missile model considers the velocity variation, gravity effect and parameters’ variation. Furthermore, the environmental conditions’ dynamics are mod-eled. PSNLO stability and the closed loop system stability are studied. Finally, numerical simula-tion is established to evaluate the proposed autopilot performance and to compare it with existing approaches in the literature.

  14. Roll-pitch-yaw autopilot design for nonlinear time-varying missile using partial state observer based global fast terminal sliding mode control

    Directory of Open Access Journals (Sweden)

    Awad Ahmed

    2016-10-01

    Full Text Available The acceleration autopilot design for skid-to-turn (STT missile faces a great challenge owing to coupling effect among planes, variation of missile velocity and its parameters, inexistence of a complete state vector, and nonlinear aerodynamics. Moreover, the autopilot should be designed for the entire flight envelope where fast variations exist. In this paper, a design of integrated roll-pitch-yaw autopilot based on global fast terminal sliding mode control (GFTSMC with a partial state nonlinear observer (PSNLO for STT nonlinear time-varying missile model, is employed to address these issues. GFTSMC with a novel sliding surface is proposed to nullify the integral error and the singularity problem without application of the sign function. The proposed autopilot consisting of two-loop structure, controls STT maneuver and stabilizes the rolling with a PSNLO in order to estimate the immeasurable states as an output while its inputs are missile measurable states and control signals. The missile model considers the velocity variation, gravity effect and parameters’ variation. Furthermore, the environmental conditions’ dynamics are modeled. PSNLO stability and the closed loop system stability are studied. Finally, numerical simulation is established to evaluate the proposed autopilot performance and to compare it with existing approaches in the literature.

  15. Observational and Numerical Studies of the Boundary Layer, Cloud, and Aerosol Variability in the Southeast Pacific Coastal Marine Stratocumulus

    Science.gov (United States)

    2012-05-01

    processes and cloud-top entrainment processes ( Turton and Nicholls 1987; Nieuwstadt and Businger 1984; Randall 1980). Observations (Bretherton et al...campaign VOCALS-REx in austral Spring 2008. Atmos. Chem. Phys., 11, 4977-5009, doi:10.5194/acp-11-4977-2011. Turton , J. D., and S. Nicholls, 1987: A

  16. Cloud Structure of Galactic OB Cluster-forming Regions from Combining Ground- and Space-based Bolometric Observations

    Science.gov (United States)

    Lin, Yuxin; Liu, Hauyu Baobab; Li, Di; Zhang, Zhi-Yu; Ginsburg, Adam; Pineda, Jaime E.; Qian, Lei; Galván-Madrid, Roberto; McLeod, Anna Faye; Rosolowsky, Erik; Dale, James E.; Immer, Katharina; Koch, Eric; Longmore, Steve; Walker, Daniel; Testi, Leonardo

    2016-09-01

    We have developed an iterative procedure to systematically combine the millimeter and submillimeter images of OB cluster-forming molecular clouds, which were taken by ground-based (CSO, JCMT, APEX, and IRAM-30 m) and space telescopes (Herschel and Planck). For the seven luminous (L\\gt {10}6 L ⊙) Galactic OB cluster-forming molecular clouds selected for our analyses, namely W49A, W43-Main, W43-South, W33, G10.6-0.4, G10.2-0.3, and G10.3-0.1, we have performed single-component, modified blackbody fits to each pixel of the combined (sub)millimeter images, and the Herschel PACS and SPIRE images at shorter wavelengths. The ˜10″ resolution dust column density and temperature maps of these sources revealed dramatically different morphologies, indicating very different modes of OB cluster-formation, or parent molecular cloud structures in different evolutionary stages. The molecular clouds W49A, W33, and G10.6-0.4 show centrally concentrated massive molecular clumps that are connected with approximately radially orientated molecular gas filaments. The W43-Main and W43-South molecular cloud complexes, which are located at the intersection of the Galactic near 3 kpc (or Scutum) arm and the Galactic bar, show a widely scattered distribution of dense molecular clumps/cores over the observed ˜10 pc spatial scale. The relatively evolved sources G10.2-0.3 and G10.3-0.1 appear to be affected by stellar feedback, and show a complicated cloud morphology embedded with abundant dense molecular clumps/cores. We find that with the high angular resolution we achieved, our visual classification of cloud morphology can be linked to the systematically derived statistical quantities (i.e., the enclosed mass profile, the column density probability distribution function (N-PDF), the two-point correlation function of column density, and the probability distribution function of clump/core separations). In particular, the massive molecular gas clumps located at the center of G10.6-0.4 and

  17. Direct Observation of Secondary Organic Aerosol Formation during Cloud Condensation-Evaporation Cycles (SOAaq) in Simulation Chamber Experiments

    Science.gov (United States)

    Doussin, J. F.; Bregonzio-Rozier, L.; Giorio, C.; Siekmann, F.; Gratien, A.; Temime-Roussel, B.; Ravier, S.; Pangui, E.; Tapparo, A.; Kalberer, M.; Monod, A.

    2014-12-01

    Biogenic volatile organic compounds (BVOCs) undergo many reactions in the atmosphere and form a wide range of oxidised and water-soluble compounds. These compounds can partition into atmospheric water droplets, and react within the aqueous phase producing higher molecular weight and/or less volatile compounds which can remain in the particle phase after water evaporation and thus increase the organic aerosol mass (Ervens et al., 2011; Altieri et al., 2008; Couvidat et al., 2013). While this hypothesis is frequently discussed in the literature, so far, almost no direct observations of such a process have been provided.The aim of the present work is to study SOA formation from isoprene photooxidation during cloud condensation-evaporation cycles.The experiments were performed during the CUMULUS project (CloUd MULtiphase chemistry of organic compoUndS in the troposphere), in the CESAM simulation chamber located at LISA. CESAM is a 4.2 m3 stainless steel chamber equipped with realistic irradiation sources and temperature and relative humidity (RH) controls (Wang et al., 2011). In each experiment, isoprene was allowed to oxidize during several hours in the presence on nitrogen oxides under dry conditions. Gas phase compounds were analyzed on-line by a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS), a Fourier Transform Infrared Spectrometer (FTIR), NOx and O3 analyzers. SOA formation was monitored on-line with a Scanning Mobility Particle Sizer (SMPS) and an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). The experimental protocol was optimised to generate cloud events in the simulation chamber, which allowed us to generate clouds lasting for ca. 10 minutes in the presence of light.In all experiments, we observed that during cloud formation, water-soluble gas-phase oxidation products (e.g., methylglyoxal, hydroxyacetone, acetaldehyde, formic acid, acetic acid and glycolaldehyde) readily partitioned into cloud

  18. The role of ensemble-based statistics in variational assimilation of cloud-affected observations from infrared imagers

    Science.gov (United States)

    Hacker, Joshua; Vandenberghe, Francois; Jung, Byoung-Jo; Snyder, Chris

    2017-04-01

    Effective assimilation of cloud-affected radiance observations from space-borne imagers, with the aim of improving cloud analysis and forecasting, has proven to be difficult. Large observation biases, nonlinear observation operators, and non-Gaussian innovation statistics present many challenges. Ensemble-variational data assimilation (EnVar) systems offer the benefits of flow-dependent background error statistics from an ensemble, and the ability of variational minimization to handle nonlinearity. The specific benefits of ensemble statistics, relative to static background errors more commonly used in variational systems, have not been quantified for the problem of assimilating cloudy radiances. A simple experiment framework is constructed with a regional NWP model and operational variational data assimilation system, to provide the basis understanding the importance of ensemble statistics in cloudy radiance assimilation. Restricting the observations to those corresponding to clouds in the background forecast leads to innovations that are more Gaussian. The number of large innovations is reduced compared to the more general case of all observations, but not eliminated. The Huber norm is investigated to handle the fat tails of the distributions, and allow more observations to be assimilated without the need for strict background checks that eliminate them. Comparing assimilation using only ensemble background error statistics with assimilation using only static background error statistics elucidates the importance of the ensemble statistics. Although the cost functions in both experiments converge to similar values after sufficient outer-loop iterations, the resulting cloud water, ice, and snow content are greater in the ensemble-based analysis. The subsequent forecasts from the ensemble-based analysis also retain more condensed water species, indicating that the local environment is more supportive of clouds. In this presentation we provide details that explain the

  19. Improvements to the OMI O2-O2 operational cloud algorithm and comparisons with ground-based radar-lidar observations

    Science.gov (United States)

    Pepijn Veefkind, J.; de Haan, Johan F.; Sneep, Maarten; Levelt, Pieternel F.

    2016-12-01

    The OMI (Ozone Monitoring Instrument on board NASA's Earth Observing System (EOS) Aura satellite) OMCLDO2 cloud product supports trace gas retrievals of for example ozone and nitrogen dioxide. The OMCLDO2 algorithm derives the effective cloud fraction and effective cloud pressure using a DOAS (differential optical absorption spectroscopy) fit of the O2-O2 absorption feature around 477 nm. A new version of the OMI OMCLDO2 cloud product is presented that contains several improvements, of which the introduction of a temperature correction on the O2-O2 slant columns and the updated look-up tables have the largest impact. Whereas the differences in the effective cloud fraction are on average limited to 0.01, the differences of the effective cloud pressure can be up to 200 hPa, especially at cloud fractions below 0.3. As expected, the temperature correction depends on latitude and season. The updated look-up tables have a systematic effect on the cloud pressure at low cloud fractions. The improvements at low cloud fractions are very important for the retrieval of trace gases in the lower troposphere, for example for nitrogen dioxide and formaldehyde. The cloud pressure retrievals of the improved algorithm are compared with ground-based radar-lidar observations for three sites at mid-latitudes. For low clouds that have a limited vertical extent the comparison yields good agreement. For higher clouds, which are vertically extensive and often contain several layers, the satellite retrievals give a lower cloud height. For high clouds, mixed results are obtained.

  20. CALIPSO Observations of Transatlantic Dust: Vertical Stratification and Effect of Clouds

    Science.gov (United States)

    Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Kalashnikova, Olga V.; Kostinski, Alexander B.

    2014-01-01

    We use CALIOP nighttime measurements of lidar backscatter, color and depolarization ratios, as well as particulate retrievals during the summer of 2007 to study transatlantic dust properties downwind of Saharan sources, and to examine the influence of nearby clouds on dust. Our analysis suggests that (1) under clear skies, while lidar backscatter and color ratio do not change much with altitude and longitude in the Saharan Air Layer (SAL), depolarization ratio increases with altitude and decreases westward in the SAL (2) the vertical lapse rate of dust depolarization ratio, introduced here, increases within SAL as plumes move westward (3) nearby clouds barely affect the backscatter and color ratio of dust volumes within SAL but not so below SAL. Moreover, the presence of nearby clouds tends to decrease the depolarization of dust volumes within SAL. Finally, (4) the odds of CALIOP finding dust below SAL next to clouds are about of those far away from clouds. This feature, together with an apparent increase in depolarization ratio near clouds, indicates that particles in some dust volumes loose asphericity in the humid air near clouds, and cannot be identified by CALIPSO as dust.

  1. High-accuracy diagnostic tool for electron cloud observation in the LHC based on synchronous phase measurements

    CERN Document Server

    Esteban Müller, J F; Shaposhnikova, E; Valuch, D; Mastoridis, T

    2014-01-01

    Electron cloud effects such as heat load in the cryogenic system, pressure rise and beam instabilities are among the main limitations for the LHC operation with 25 ns spaced bunches. A new observation tool was developed to monitor the e-cloud activity and has been successfully used in the LHC during Run 1 (2010-2012). The power loss of each bunch due to the e-cloud can be estimated using very precise bunch-by-bunch measurement of the synchronous phase shift. In order to achieve the required accuracy, corrections for reflection in the cables and some systematic errors need to be applied followed by a post-processing of the measurements. Results clearly show the e-cloud build-up along the bunch trains and its evolution during each LHC fill as well as from fill to fill. Measurements during the 2012 LHC scrubbing run reveal a progressive reduction in the e-cloud activity and therefore a decrease in the secondary electron yield (SEY). The total beam power loss can be computed as a sum of the contributions from all...

  2. High-accuracy diagnostic tool for electron cloud observation in the LHC based on synchronous phase measurements

    Science.gov (United States)

    Esteban Müller, J. F.; Baudrenghien, P.; Mastoridis, T.; Shaposhnikova, E.; Valuch, D.

    2015-11-01

    Electron cloud effects, which include heat load in the cryogenic system, pressure rise, and beam instabilities, are among the main intensity limitations for the LHC operation with 25 ns spaced bunches. A new observation tool was proposed and developed to monitor the e-cloud activity and it has already been used successfully during the LHC run 1 (2010-2012) and it is being intensively used in operation during the start of the LHC run 2 (2015-2018). It is based on the fact that the power loss of each bunch due to e-cloud can be estimated using bunch-by-bunch measurement of the synchronous phase. The measurements were done using the existing beam phase module of the low-level rf control system. In order to achieve the very high accuracy required, corrections for reflection in the cables and for systematic errors need to be applied followed by a post-processing of the measurements. Results clearly show the e-cloud buildup along the bunch trains and its time evolution during each LHC fill as well as from fill to fill. Measurements during the 2012 LHC scrubbing run reveal a progressive reduction in the e-cloud activity and therefore a decrease in the secondary electron yield. The total beam power loss can be computed as a sum of the contributions from all bunches and compared with the heat load deposited in the cryogenic system.

  3. Antarctic clouds

    OpenAIRE

    Lachlan-Cope, Tom

    2010-01-01

    Sensitivity studies with global climate models show that, by their influence on the radiation balance, Antarctic clouds play a major role in the climate system, both directly at high southern latitudes and indirectly globally, as the local circulation changes lead to global teleconnections. Unfortunately, observations of cloud distribution in the Antarctic are limited and often of low quality because of the practical difficulty in observing clouds in the harsh Antarctic environment. The best ...

  4. Aircraft observations and model simulations of concentration and particle size distribution in the Eyjafjallajökull volcanic ash cloud

    Science.gov (United States)

    Dacre, H. F.; Grant, A. L. M.; Johnson, B. T.

    2013-02-01

    The Eyjafjallajökull volcano in Iceland emitted a cloud of ash into the atmosphere during April and May 2010. Over the UK the ash cloud was observed by the FAAM BAe-146 Atmospheric Research Aircraft which was equipped with in-situ probes measuring the concentration of volcanic ash carried by particles of varying sizes. The UK Met Office Numerical Atmospheric-dispersion Modelling Environment (NAME) has been used to simulate the evolution of the ash cloud emitted by the Eyjafjallajökull volcano during the period 4-18 May 2010. In the NAME simulations the processes controlling the evolution of the concentration and particle size distribution include sedimentation and deposition of particles, horizontal dispersion and vertical wind shear. For travel times between 24 and 72 h, a 1/t relationship describes the evolution of the concentration at the centre of the ash cloud and the particle size distribution remains fairly constant. Although NAME does not represent the effects of microphysical processes, it can capture the observed decrease in concentration with travel time in this period. This suggests that, for this eruption, microphysical processes play a small role in determining the evolution of the distal ash cloud. Quantitative comparison with observations shows that NAME can simulate the observed column-integrated mass if around 4% of the total emitted mass is assumed to be transported as far as the UK by small particles (< 30 μm diameter). NAME can also simulate the observed particle size distribution if a distal particle size distribution that contains a large fraction of < 10 μm diameter particles is used, consistent with the idea that phraetomagmatic volcanoes, such as Eyjafjallajökull, emit very fine particles.

  5. Aircraft observations and model simulations of concentration and particle size distribution in the Eyjafjallajökull volcanic ash cloud

    Directory of Open Access Journals (Sweden)

    H. F. Dacre

    2013-02-01

    Full Text Available The Eyjafjallajökull volcano in Iceland e