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Sample records for cirrus clouds applied

  1. Measurement errors in cirrus cloud microphysical properties

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    H. Larsen

    Full Text Available The limited accuracy of current cloud microphysics sensors used in cirrus cloud studies imposes limitations on the use of the data to examine the cloud's broadband radiative behaviour, an important element of the global energy balance. We review the limitations of the instruments, PMS probes, most widely used for measuring the microphysical structure of cirrus clouds and show the effect of these limitations on descriptions of the cloud radiative properties. The analysis is applied to measurements made as part of the European Cloud and Radiation Experiment (EUCREX to determine mid-latitude cirrus microphysical and radiative properties.

    Key words. Atmospheric composition and structure (cloud physics and chemistry · Meteorology and atmospheric dynamics · Radiative processes · Instruments and techniques

  2. Spectral emissivity of cirrus clouds

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    Beck, Gordon H.; Davis, John M.; Cox, Stephen K.

    1993-01-01

    The inference of cirrus cloud properties has many important applications including global climate studies, radiation budget determination, remote sensing techniques and oceanic studies from satellites. Data taken at the Parsons Kansas site during the FIRE II project are used for this study. On November 26 there were initially clear sky conditions gradually giving way to a progressively thickening cirrus shield over a period of a few hours. Interferometer radiosonde and lidar data were taken throughout this event. Two techniques are used to infer the downward spectral emittance of the observed cirrus layer. One uses only measurements and the other involves measurements and FASCODE III calculations. FASCODE III is a line-by line radiance/transmittance model developed at the Air Force Geophysics Laboratory.

  3. Dust ice nuclei effects on cirrus clouds

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    M. Kuebbeler

    2013-04-01

    Full Text Available In order to study aerosol-cloud interactions in cirrus clouds we apply a new multiple-mode ice microphysical scheme to the general circulation model ECHAM5-HAM. The multiple-mode ice microphysical scheme allows to analyse the competition between homogeneous freezing of solution droplets, deposition nucleation of pure dust particles, immersion freezing of coated dust particles and pre-existing ice. We base the freezing efficiencies of coated and pure dust particles on most recent laboratory data. The effect of pre-existing ice, which was neglected in previous ice nucleation parameterizations, is to deplete water vapour by depositional growth and thus prevent homogeneous and heterogeneous freezing from occurring. In a first step, we extensively tested the model and validated the results against in-situ measurements from various aircraft campaigns. The results compare well with observations; properties like ice crystal size and number concentration as well as supersaturation are predicted within the observational spread. We find that heterogeneous nucleation on mineral dust particles and the consideration of pre-existing ice in the nucleation process may lead to significant effects: globally, ice crystal number and mass are reduced by 10% and 5%, whereas the ice crystals size is increased by 3%. The reductions in ice crystal number are most pronounced in the tropics and mid-latitudes on the Northern Hemisphere. While changes in the microphysical and radiative properties of cirrus clouds in the tropics are mostly driven by considering pre-existing ice, changes in the northern hemispheric mid-latitudes mainly result from heterogeneous nucleation. The so called negative Twomey-effect in cirrus clouds is represented in ECHAM5-HAM. The net change in the radiation budget is −0.94 W m−2, implying that both, heterogeneous nucleation on dust and pre-existing ice have the potential to modulate cirrus properties in climate simulations and thus should be

  4. Distribution and Radiative Forcing of Tropical Thin Cirrus Clouds

    Science.gov (United States)

    2009-12-01

    depths of thin cirrus clouds. 1. Introduction Numerous studies have demonstrated that thin cirrus clouds are frequently present near the tropical tropo ...Methodology a. Optical depth of tropical thin cirrus clouds Cirrus clouds are often present in the upper tropo - sphere or lower stratosphere, and more than

  5. Could cirrus clouds have warmed early Mars?

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    Ramirez, Ramses M.; Kasting, James F.

    2017-01-01

    The presence of the ancient valley networks on Mars indicates that the climate at 3.8 Ga was warm enough to allow substantial liquid water to flow on the martian surface for extended periods of time. However, the mechanism for producing this warming continues to be debated. One hypothesis is that Mars could have been kept warm by global cirrus cloud decks in a CO2sbnd H2O atmosphere containing at least 0.25 bar of CO2 (Urata and Toon, 2013). Initial warming from some other process, e.g., impacts, would be required to make this model work. Those results were generated using the CAM 3-D global climate model. Here, we use a single-column radioactive-convective climate model to further investigate the cirrus cloud warming hypothesis. Our calculations indicate that cirrus cloud decks could have produced global mean surface temperatures above freezing, but only if cirrus cloud cover approaches ∼75 - 100% and if other cloud properties (e.g., height, optical depth, particle size) are chosen favorably. However, at more realistic cirrus cloud fractions, or if cloud parameters are not optimal, cirrus clouds do not provide the necessary warming, suggesting that other greenhouse mechanisms are needed.

  6. Cirrus cloud iridescence: a rare case study

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    Sassen, Kenneth

    2003-01-01

    On the evening of 25 November 1998, a cirrus cloud revealing the pastel colors of the iridescence phenomenon was photographed and studied by a polarization lidar system at the University of Utah Facility for Atmospheric Remote Sensing (FARS). The diffraction of sunlight falling on relatively minute cloud particles, which display spatial gradients in size, is the cause of iridescence. According to the 14-year study of midlatitude cirrus clouds at FARS, cirrus rarely produce even poor iridescent patches, making this particularly long-lived and vivid occurrence unique. In this unusually high (13.2-14.4-km) and cold (-69.7 ° to -75.5°) tropopause-topped cirrus cloud, iridescence was noted from ~6.0° to ~13.5° from the Sun. On the basis of simple diffraction theory, this indicates the presence of particles of 2.5-5.5-μm effective diameter. The linear depolarization ratios of δ = 0.5 measured by the lidar verify that the cloud particles were nonspherical ice crystals. The demonstration that ice clouds can generate iridescence has led to the conclusion that iridescence is rarely seen in midlatitude cirrus clouds because populations of such small particles do not exist for long in the presence of the relatively high water-vapor supersaturations needed for ice-particle nucleation.

  7. Estimating cirrus cloud properties from MIPAS data

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    Mendrok, J.; Schreier, F.; Höpfner, M.

    2007-04-01

    High resolution mid-infrared limb emission spectra observed by the spaceborne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) showing evidence of cloud interference are analyzed. Using the new line-by-line multiple scattering [Approximate] Spherical Atmospheric Radiative Transfer code (SARTre), a sensitivity study with respect to cirrus cloud parameters, e.g., optical thickness and particle size distribution, is performed. Cirrus properties are estimated by fitting spectra in three distinct microwindows between 8 and 12 μm. For a cirrus with extremely low ice water path (IWP = 0.1 g/m2) and small effective particle size (D e = 10 μm) simulated spectra are in close agreement with observations in broadband signal and fine structures. We show that a multi-microwindow technique enhances reliability of MIPAS cirrus retrievals compared to single microwindow methods.

  8. Why cirrus cloud seeding cannot substantially cool the planet

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    Gasparini, Blaž; Lohmann, Ulrike

    2016-05-01

    The net warming effect of cirrus clouds has driven part of the geoengineering research toward the idea of decreasing their occurrence frequency by seeding them with efficient ice nucleating particles. We study responses of cirrus clouds to simplified global seeding strategies in terms of their radiative fluxes with the help of the ECHAM-HAM general circulation model. Our cirrus scheme takes into account the competition between homogeneous and heterogeneous freezing, preexisting ice crystals, and the full spectrum of updraft velocities. While we find that the cirrus cloud radiative effect evaluated from our model is positive and large enough (5.7 W/m2) to confirm their geoengineering potential, none of the seeding strategies achieves a significant cooling due to complex microphysical mechanisms limiting their climatic responses. After globally uniform seeding is applied, we observe an increase in cirrus cloud cover, a decrease in ice crystal number concentration, and a decrease in ice crystal radius. An analysis of their respective radiative contributions points to the ice crystal radius decrease as the main factor limiting seeding effectiveness.

  9. Could Cirrus Clouds Have Warmed Early Mars?

    CERN Document Server

    Ramirez, Ramses M

    2016-01-01

    The presence of the ancient valley networks on Mars indicates that the climate at 3.8 Ga was warm enough to allow substantial liquid water to flow on the martian surface for extended periods of time. However, the mechanism for producing this warming continues to be debated. One hypothesis is that Mars could have been kept warm by global cirrus cloud decks in a CO2-H2O atmosphere containing at least 0.25 bar of CO2 (Urata and Toon, 2013). Initial warming from some other process, e.g., impacts, would be required to make this model work. Those results were generated using the CAM 3-D global climate model. Here, we use a single-column radiative-convective climate model to further investigate the cirrus cloud warming hypothesis. Our calculations indicate that cirrus cloud decks could have produced global mean surface temperatures above freezing, but only if cirrus cloud cover approaches ~75 - 100% and if other cloud properties (e.g., height, optical depth, particle size) are chosen favorably. However, at more real...

  10. Lidar cirrus cloud retrieval - methodology and applications

    Science.gov (United States)

    Larroza, Eliane; Keckhut, Philippe; Nakaema, Walter; Brogniez, Gérard; Dubuisson, Philippe; Pelon, Jacques; Duflot, Valentin; Marquestaut, Nicolas; Payen, Guillaume

    2016-04-01

    In the last decades numerical modeling has experimented sensitive improvements on accuracy and capability for climate predictions. In the same time it has demanded the reduction of uncertainties related with the respective input parameters. In this context, high altitude clouds (cirrus) have attracted special attention for their role as radiative forcing. Also such clouds are associated with the vertical transport of water vapor from the surface to upper troposphere/lower stratosphere (URLS) in form of ice crystals with variability of concentration and morphology. Still cirrus formation can occur spatially and temporally in great part of the globe due to horizontal motion of air masses and circulations. Determining accurately the physical properties of cirrus clouds still represents a challenge. Especially the so-called subvisible cirrus clouds (optical depth inferior to 0.03) are invisible for space-based passive observations. On the other hand, ground based active remote sensing as lidar can be used to suppress such deficiency. Lidar signal can provide spatial and temporal high resolution to characterize physically (height, geometric thickness, mean temperature) and optically (optical depth, extinction-to-scattering ratio or lidar ratio, depolarization ratio) the cirrus clouds. This report describes the evolution of the methodology initially adopted to retrieval systematically the lidar ratio and the subsequent application on case studies and climatology on the tropical sites of the globe - São Paulo, Brazil (23.33 S, 46.44 W) and OPAR observatory at Ille de La Réunion (21.07 S, 55.38 W). Also is attempting a synergy between different instrumentations and lidar measurements: a infrared radiometer to estimate the kind of ice crystals compounding the clouds; CALIPSO satellite observations and trajectory model (HYSPLIT) for tracking air masses potentially responsible for the horizontal displacement of cirrus. This last approach is particularly interesting to

  11. Remote sensing of contrails and aircraft altered cirrus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Palikonda, R.; Nguyen, L.; Garber, D.P.; Smith, W.L. Jr [Analytical Services and Materials, Inc., Hampton, VA (United States); Minnis, P.; Young, D.F. [National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center

    1997-12-31

    Analyses of satellite imagery are used to show that contrails can develop into fully extended cirrus cloud systems. Contrails can be advective on great distances, but would appear to observers as natural cirrus clouds. The conversion of simple contrails into cirrus may help explain the apparent increase of cloudiness over populated areas since the beginning of commercial jet air travel. Statistics describing the typical growth, advection, and lifetime of contrail cirrus is needed to evaluate their effects on climate. (author) 4 refs.

  12. Can cirrus clouds warm early Mars?

    Science.gov (United States)

    Ramirez, R. M.

    2015-12-01

    The presence of the ancient valley networks on Mars indicates a climate 3.8 Ga that was warm enough to allow substantial liquid water to flow on the martian surface for extended periods of time. However, the origin of these enigmatic features is hotly debated and discussion of their formation has been focused on how warm such a climate may have been and for how long. Recent warm and wet solutions using single-column radiative convective models involve supplementing CO2-H2O atmospheres with other greenhouse gases, such as H2 (i.e. Ramirez et al., 2014; Batalha et al., 2015). An interesting recent proposal, using the CAM 3-D General Circulation model, argues that global cirrus cloud decks in CO2-H2O atmospheres with at least 0.25 bar of CO2 , consisting of 10-micron (and larger) sized particles, could have generated the above-freezing temperatures required to explain the early martian surface geology (Urata and Toon, 2013). Here, we use our single-column radiative convective climate model to check these 3-D results and analyze the likelihood that such warm atmospheres, with mean surface pressures of up to 3 bar, could have supported cirrus cloud decks at full and fractional cloud cover for sufficiently long durations to form the ancient valleys. Our results indicate that cirrus cloud decks could have provided the mean surface temperatures required, but only if cloud cover approaches 100%, in agreement with Urata and Toon (2013). However, even should cirrus cloud coverage approach 100%, we show that such atmospheres are likely to have been too short-lived to produce the volumes of water required to carve the ancient valleys. At more realistic early Mars cloud fractions (~50%, Forget et al., 2013), cirrus clouds do not provide the required warming. Batalha, N., Domagal-Goldman, S. D., Ramirez, R.M., & Kasting, J. F., 2015. Icarus, 258, 337-349. Forget, F., Wordsworth, R., Millour, E., Madeleine, J. B., Kerber, L., Leconte, J., ... & Haberle, R. M., 2013. Icarus, 222

  13. Cirrus cloud seeding has potential to cool climate

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    Storelvmo, T.; Kristjansson, J. E.; Muri, H.; Pfeffer, M.; Barahona, D.; Nenes, A.

    2013-01-01

    Cirrus clouds, thin ice clouds in the upper troposphere, have a net warming effect on Earth's climate. Consequently, a reduction in cirrus cloud amount or optical thickness would cool the climate. Recent research indicates that by seeding cirrus clouds with particles that promote ice nucleation, their lifetimes and coverage could be reduced. We have tested this hypothesis in a global climate model with a state-of-the-art representation of cirrus clouds and find that cirrus cloud seeding has the potential to cancel the entire warming caused by human activity from pre-industrial times to present day. However, the desired effect is only obtained for seeding particle concentrations that lie within an optimal range. With lower than optimal particle concentrations, a seeding exercise would have no effect. Moreover, a higher than optimal concentration results in an over-seeding that could have the deleterious effect of prolonging cirrus lifetime and contributing to global warming.

  14. Fractal properties and denoising of lidar signals from cirrus clouds

    NARCIS (Netherlands)

    Heuvel, J.C. van den; Driesenaar, M.L.; Lerou, R.J.L.

    2000-01-01

    Airborne lidar signals of cirrus clouds are analyzed to determine the cloud structure. Climate modeling and numerical weather prediction benefit from accurate modeling of cirrus clouds. Airborne lidar measurements of the European Lidar in Space Technology Experiment (ELITE) campaign were analyzed by

  15. On the distribution of relative humidity in cirrus clouds

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    P. Spichtinger

    2004-01-01

    Full Text Available We have analysed relative humidity statistics from measurements in cirrus clouds taken unintentionally during the Measurement of OZone by Airbus In-service airCraft project (MOZAIC. The shapes of the in-cloud humidity distributions change from nearly symmetric in relatively warm cirrus (warmer than −40° to considerably positively skew (i.e. towards high humidities in colder clouds. These results are in agreement to findings obtained recently from the INterhemispheric differences in Cirrus properties from Anthropogenic emissions (INCA campaign (Ovarlez et al., 2002. We interprete the temperature dependence of the shapes of the humidity distributions as an effect of the length of time a cirrus cloud needs from formation to a mature equilibrium stage, where the humidity is close to saturation. The duration of this transitional period increases with decreasing temperature. Hence cold cirrus clouds are more often met in the transitional stage than warm clouds.

  16. On the distribution of relative humidity in cirrus clouds

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    P. Spichtinger

    2004-01-01

    Full Text Available We have analysed relative humidity statistics from measurements in cirrus clouds taken unintentionally during the Measurement of OZone by Airbus In-service airCraft project (MOZAIC. The shapes of the in-cloud humidity distributions change from nearly symmetric in relatively warm cirrus (warmer than −40°C to considerably positively skew (i.e. towards high humidities in colder clouds. These results are in agreement to findings obtained recently from the INterhemispheric differences in Cirrus properties from Anthropogenic emissions (INCA campaign (Ovarlez et al., 2002. We interprete the temperature dependence of the shapes of the humidity distributions as an effect of the length of time a cirrus cloud needs from formation to a mature equilibrium stage, where the humidity is close to saturation. The duration of this transitional period increases with decreasing temperature. Hence cold cirrus clouds are more often met in the transitional stage than warm clouds.

  17. 3D reconstruction of tropospheric cirrus clouds

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    Kouahla, M. N.; Faivre, M.; Moreels, G.; Seridi, H.

    2016-10-01

    In this paper, we present a series of results from stereo-imagery of cirrus clouds in the troposphere. These clouds are either of natural origin or are created by aircraft exhausts. They are presently considered to be a major cause for the climate change. Two observation campaigns were conducted in France in 2013 and 2014. The observing sites were located in Marnay (47°17‧31.5″ N, 5°44‧58.8″ E; altitude 275 m) and in Mont Poupet (46°58‧31.5″ N, 5°52‧22.7″ E; altitude 600 m). The distance between both sites was 36 km. We used numeric CMOS photographic cameras. The image processing sequence included a contrast enhancement and a perspective inversion to obtain a satellite-type view. Finally, the triangulation procedure was used in an area that is a common part of both fields of view.

  18. 3D reconstruction of tropospheric cirrus clouds by stereovision system

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    Nadjib Kouahla, Mohamed; Moreels, Guy; Seridi, Hamid

    2016-07-01

    A stereo imaging method is applied to measure the altitude of cirrus clouds and provide a 3D map of the altitude of the layer centroid. They are located in the high troposphere and, sometimes in the lower stratosphere, between 6 and 10 km high. Two simultaneous images of the same scene are taken with Canon cameras (400D) in two sites distant of 37 Km. Each image processed in order to invert the perspective effect and provide a satellite-type view of the layer. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a correlation coefficient (ZNCC: Zero mean Normalized Cross-correlation or ZSSD: as Zero mean Sum of Squared Differences). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in June 2014 in France. The images were taken simultaneously at Marnay (47°17'31.5" N, 5°44'58.8" E; altitude 275 m) 25 km northwest of Besancon and in Mont poupet (46°58'31.5" N, 5°52'22.7" E; altitude 600 m) southwest of Besancon at 43 km. 3D maps of the Natural cirrus clouds and artificial like "aircraft trails" are retrieved. They are compared with pseudo-relief intensity maps of the same region. The mean altitude of the cirrus barycenter is located at 8.5 ± 1km on June 11.

  19. Cirrus clouds in a global climate model with a statistical cirrus cloud scheme

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    M. Wang

    2010-06-01

    Full Text Available A statistical cirrus cloud scheme that accounts for mesoscale temperature perturbations is implemented in a coupled aerosol and atmospheric circulation model to better represent both subgrid-scale supersaturation and cloud formation. This new scheme treats the effects of aerosol on cloud formation and ice freezing in an improved manner, and both homogeneous freezing and heterogeneous freezing are included. The scheme is able to better simulate the observed probability distribution of relative humidity compared to the scheme that was implemented in an older version of the model. Heterogeneous ice nuclei (IN are shown to decrease the frequency of occurrence of supersaturation, and improve the comparison with observations at 192 hPa. Homogeneous freezing alone can not reproduce observed ice crystal number concentrations at low temperatures (<205 K, but the addition of heterogeneous IN improves the comparison somewhat. Increases in heterogeneous IN affect both high level cirrus clouds and low level liquid clouds. Increases in cirrus clouds lead to a more cloudy and moist lower troposphere with less precipitation, effects which we associate with the decreased convective activity. The change in the net cloud forcing is not very sensitive to the change in ice crystal concentrations, but the change in the net radiative flux at the top of the atmosphere is still large because of changes in water vapor. Changes in the magnitude of the assumed mesoscale temperature perturbations by 25% alter the ice crystal number concentrations and the net radiative fluxes by an amount that is comparable to that from a factor of 10 change in the heterogeneous IN number concentrations. Further improvements on the representation of mesoscale temperature perturbations, heterogeneous IN and the competition between homogeneous freezing and heterogeneous freezing are needed.

  20. Aviation effects on already-existing cirrus clouds

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    Tesche, Matthias; Achtert, Peggy; Glantz, Paul; Noone, Kevin J.

    2016-06-01

    Determining the effects of the formation of contrails within natural cirrus clouds has proven to be challenging. Quantifying any such effects is necessary if we are to properly account for the influence of aviation on climate. Here we quantify the effect of aircraft on the optical thickness of already-existing cirrus clouds by matching actual aircraft flight tracks to satellite lidar measurements. We show that there is a systematic, statistically significant increase in normalized cirrus cloud optical thickness inside mid-latitude flight tracks compared with adjacent areas immediately outside the tracks.

  1. Cirrus cloud properties measurement using lidar in Beijing

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    Ji, Chengli; Tao, Zongming; Hu, Shunxing; Che, Huizheng; Yu, Jie; Feng, Caiyun; Xie, Chenbo; Liu, Dong; Zhong, Zhiqing; Yuan, Ke'e.; Cao, Kaifa; Huang, Jian; Zhou, Jun; Wang, Yingjian; Chen, Zhenyi

    2016-01-01

    Cirrus cloud has an important effect on the radiation balance between the earth's surface and the atmosphere. The vertical structures, optical depth and effective lidar ratio of cirrus cloud detected by Mie scattering-polarization-Raman lidar system in Beijing from April 11 to December 31, 2012 are analyzed. The results show that the cloud height in Beijing is lower in spring and higher in autumn, with a mean value of about 8km. The mean of cloud thickness is 0.74km. The mean of optical depth is 0.092, and most observed cirrus cloud is thin while optical depth is less than 0.3. The effective lidar ratio of cirrus is lower in summer and higher in winter, inversely related to local temperature, with a mean value of 32.29Sr.

  2. Towards an automatic Lidar cirrus cloud retrieval for climate studies

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    E. G. Larroza

    2013-04-01

    Full Text Available In the present study, a methodology to calculate lidar ratios for distinct cirrus clouds has been implemented for a site located in the Southern Hemisphere. The cirrus cloud lidar data processing has been developed to consider a large cloud variability with the final aim of cirrus cloud monitoring through a robust retrieval process. Among the many features lidar systems can extract for cirrus detection, we highlight: cloud geometrical information and extinction-to-backscatter ratio (also called lidar ratio – LR. LR's can, in general, provide important information on cirrus cloud microphysics due to the presence of ice crystals and their properties such as shape, size, composition and orientation of particles and their effect on LR values. Conditions for LR calculations and their resulting uncertainty have been improved as their analysis requires identifying cirrus cloud stationary periods through the use of a specific statistical approach well-established in the literature and employed here with good results, allowing for the study of specific cases with multi-layer cirrus cloud occurrence. The results from the measurements taken in the region of the Metropolitan City of São Paulo – MSP have been used to implement and test the methodology developed herein. In addition to the geometrical parameters extracted, improved values of LR's were calculated and showed significantly different values for the different layers inspected, varying between 19 ± 01 sr and 74 ± 13 sr. This large value interval allowed us to indirectly verify the presence of different ice crystal sizes and shapes and those associated with different air mass sources for the cirrus cloud formation.

  3. Towards Improved Cirrus Cloud Optical Depths from CALIPSO

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    Garnier, Anne; Vaughan, Mark; Pelon, Jacques; Winker, David; Trepte, Chip; Young, Stuart

    2016-06-01

    This paper reviews recent advances regarding the retrieval of optical depths of semi-transparent cirrus clouds using synergetic analyses of perfectly collocated observations from the CALIOP lidar and the IIR infrared radiometer aboard the CALIPSO satellite.

  4. Quantifying the Amount of Ice in Cold Tropical Cirrus Clouds

    Science.gov (United States)

    Avery, Melody A.; Winker, David M.; Garnier, Anne; Lawson, R. Paul; Heymsfield, Andrew J.; Mo, Qixu; Schoeberl, Mark R.; Woods, Sarah; Lance, Sara; Young, Stuart A.; Vaughan, Mark A.; Trepte, Charles R.

    2014-01-01

    How much ice is there in the Tropical Tropopause layer, globally? How does one begin to answer that question? Clouds are currently the largest source of uncertainty in climate models, and the ice water content (IWC) of cold cirrus clouds is needed to understand the total water and radiation budgets of the upper troposphere and lower stratosphere (UT/LS). The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, originally a "pathfinder" mission only expected to last for three years, has now been operational for more than eight years. Lidar data from CALIPSO can provide information about how IWC is vertically distributed in the UT/LS, and about inter-annual variability and seasonal changes in cloud ice. However, cloud IWC is difficult to measure accurately with either remote or in situ instruments because IWC from cold cirrus clouds is derived from the particle cross-sectional area or visible extinction coefficient. Assumptions must be made about the relationship between the area, volume and density of ice particles with various crystal habits. Recently there have been numerous aircraft field campaigns providing detailed information about cirrus ice water content from cloud probes. This presentation evaluates the assumptions made when creating the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) global IWC data set, using recently reanalyzed aircraft particle probe measurements of very cold, thin TTL cirrus from the 2006 CR-AVE.

  5. Modification of cirrus clouds to reduce global warming

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, David L; Finnegan, William, E-mail: david.mitchell@dri.ed [Desert Research Institute, Reno, NV 89512-1095 (United States)

    2009-10-15

    Greenhouse gases and cirrus clouds regulate outgoing longwave radiation (OLR) and cirrus cloud coverage is predicted to be sensitive to the ice fall speed which depends on ice crystal size. The higher the cirrus, the greater their impact is on OLR. Thus by changing ice crystal size in the coldest cirrus, OLR and climate might be modified. Fortunately the coldest cirrus have the highest ice supersaturation due to the dominance of homogeneous freezing nucleation. Seeding such cirrus with very efficient heterogeneous ice nuclei should produce larger ice crystals due to vapor competition effects, thus increasing OLR and surface cooling. Preliminary estimates of this global net cloud forcing are more negative than -2.8 W m{sup -2} and could neutralize the radiative forcing due to a CO{sub 2} doubling (3.7 W m{sup -2}). A potential delivery mechanism for the seeding material is already in place: the airline industry. Since seeding aerosol residence times in the troposphere are relatively short, the climate might return to its normal state within months after stopping the geoengineering experiment. The main known drawback to this approach is that it would not stop ocean acidification. It does not have many of the drawbacks that stratospheric injection of sulfur species has.

  6. Statistics of vertical backscatter profile of cirrus clouds

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    P. Veglio

    2011-09-01

    Full Text Available A nearly global statistical analysis of vertical backscatter and extinction profiles of cirrus clouds collected by the CALIOP lidar, on-board of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, is presented.

    Statistics on frequency of occurrence and distributions of bulk properties of cirrus clouds in general and, for the first time, of horizontally homogeneous (on a 5-km field of view cirrus clouds only are provided. Annual and seasonal backscatter profiles (BSP are computed for the horizontally homogeneous cirri. Differences found in the day/night cases and for midlatitudes and tropics are studied in terms of the mean physical parameters of the clouds from which they are derived.

    The relation between cloud physical parameters (optical depth, geometrical thickness and temperature and the shape of the BSP is investigated. It is found that cloud geometrical thickness is the main parameter affecting the shape of the mean CALIOP BSP. Specifically, cirrus clouds with small geometrical thicknesses show a maximum in mean BSP curve placed near cloud top. As the cloud geometrical thickness increases the BSP maximum shifts towards cloud base. Cloud optical depth and temperature have smaller effect on the shape of the CALIOP BSPs. In general a slight increase in the BSP maximum is observed as cloud temperature and optical depth increase.

    In order to fit mean BSPs, as functions of geometrical thickness and position within the cloud layer, polynomial functions are provided. The impact on satellite radiative transfer simulations in the infrared spectrum when using either a constant ice-content (IWC along the cloud vertical dimension or an IWC profile derived from the BSP fitting functions is evaluated. It is, in fact, demonstrated that, under realistic hypotheses, the mean BSP is linearly proportional to the IWC profile.

  7. Statistics of vertical backscatter profiles of cirrus clouds

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    P. Veglio

    2011-12-01

    Full Text Available A nearly global statistical analysis of vertical backscatter and extinction profiles of cirrus clouds collected by the CALIOP lidar, on-board of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, is presented.

    Statistics on frequency of occurrence and distribution of bulk properties of cirrus clouds in general and, for the first time, of horizontally homogeneous (on a 5-km field of view cirrus clouds only are provided. Annual and seasonal backscatter profiles (BSP are computed for the horizontally homogeneous cirri. Differences found in the day/night cases and for midlatitudes and tropics are studied in terms of the mean physical parameters of the clouds from which they are derived.

    The relationship between cloud physical parameters (optical depth, geometrical thickness and temperature and the shape of the BSP is investigated. It is found that cloud geometrical thickness is the main parameter affecting the shape of the mean CALIOP BSP. Specifically, cirrus clouds with small geometrical thicknesses show a maximum in mean BSP curve located near cloud top. As the cloud geometrical thickness increases the BSP maximum shifts towards cloud base. Cloud optical depth and temperature have smaller effects on the shape of the CALIOP BSPs. In general a slight increase in the BSP maximum is observed as cloud temperature and optical depth increase.

    In order to fit mean BSPs, as functions of geometrical thickness and position within the cloud layer, polynomial functions are provided. The impact on satellite radiative transfer simulations in the infrared spectrum when using either a constant ice-content (IWC along the cloud vertical dimension or an IWC profile derived from the BSP fitting functions is evaluated. It is, in fact, demonstrated that, under realistic hypotheses, the mean BSP is linearly proportional to the IWC profile.

  8. Evidence of impact of aviation on cirrus cloud formation

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    C. S. Zerefos

    2003-06-01

    Full Text Available This work examines changes in cirrus cloud cover in possible association with aviation activities at congested air corridors. The analysis is based on the latest version of the International Satellite Cloud Climatology Project D2 data set and covers the period 1984&ndash1998. Over areas with heavy air traffic, the effect of large-scale modes of natural climate variability such as ENSO, QBO and NAO as well as the possible influence of the tropopause variability, were first removed from the cloud data set in order to calculate long-term changes of observed cirrus cloudiness. The results show increasing trends in cirrus cloud coverage, between 1984 and 1998, over the high air traffic corridors of North America, North Atlantic and Europe, which in the summertime only over the North Atlantic are statistically significant at the 99.5% confidence level (2.6% per decade. In wintertime however, statistically significant changes at the 95% confidence level are found over North America, amounting to +2.1% per decade. Statistically significant increases at the 95% confidence level are also found for the annual mean cirrus cloud coverage over the North Atlantic air corridor (1.2% per decade. Over adjacent locations with lower air traffic, the calculated trends are statistically insignificant and in most cases negative both during winter and summer in regions studied. Moreover, it is shown that the longitudinal distribution of decadal changes in cirrus cloudiness along the latitude belt centered at the North Atlantic air corridor, parallels the spatial distribution of fuel consumption from highflying air traffic, providing an independent test of possible impact of aviation on contrail cirrus formation. Results from this study are compared with other studies and different periods of records and it appears as evidenced in this and in earlier studies that there exists general agreement on the aviation effect on high cloud trends.

  9. Seasonal and optical characterisation of cirrus clouds over Indian sub-continent using LIDAR

    Energy Technology Data Exchange (ETDEWEB)

    Jayeshlal, G. S., E-mail: drssatyanarayana.malladi@gmail.com; Satyanarayana, Malladi, E-mail: drssatyanarayana.malladi@gmail.com; Dhaman, Reji K., E-mail: drssatyanarayana.malladi@gmail.com; Motty, G. S., E-mail: drssatyanarayana.malladi@gmail.com [Department of Optoelectronics, University of Kerala, Karyavattom, Trivandrum-695 581, Kerala (India)

    2014-10-15

    Light Detection and Ranging (LIDAR) is an important remote sensing technique to study about the cirrus clouds. The subject of cirrus clouds and related climate is challenging one. The received scattered signal from Lidar contains information on the physical and optical properties of cirrus clouds. The Lidar profile of the cirrus cloud provides information on the optical characteristics like depolarisation ratio, lidar ratio and optical depth, which give knowledge about possible phase, structure and orientation of cloud particle that affect the radiative budgeting of cirrus clouds. The findings from the study are subjected to generate inputs for better climatic modelling.

  10. Cirrus microphysics and radiative transfer: Cloud field study on October 28, 1986

    Science.gov (United States)

    Kinne, Stefan; Ackerman, Thomas P.; Heymsfield, Andrew J.; Valero, Francisco P. J.; Sassen, Kenneth; Spinhirne, James D.

    1990-01-01

    The radiative properties of cirrus clouds present one of the unresolved problems in weather and climate research. Uncertainties in ice particle amount and size and, also, the general inability to model the single scattering properties of their usually complex particle shapes, prevent accurate model predictions. For an improved understanding of cirrus radiative effects, field experiments, as those of the Cirrus IFO of FIRE, are necessary. Simultaneous measurements of radiative fluxes and cirrus microphysics at multiple cirrus cloud altitudes allows the pitting of calculated versus measured vertical flux profiles; with the potential to judge current cirrus cloud modeling. Most of the problems in this study are linked to the inhomogeneity of the cloud field. Thus, only studies on more homogeneous cirrus cloud cases promises a possibility to improve current cirrus parameterizations. Still, the current inability to detect small ice particles will remain as a considerable handicap.

  11. Microphysical properties of contrails and natural cirrus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Strauss, B.; Wendling, P. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V., Oberpfaffenhofen (Germany)

    1997-12-31

    The radiative properties of a condensation trail (contrail) are determined by its microphysical properties. Therefore an understanding of the concentration, size distribution, and shapes of the particles is necessary for an estimation of the climatic impact of contrails. In-situ particle measurements by use of an ice replicator are presented for several contrail and cirrus events. Contrail particles aged about 2 minutes show shapes which are nearly spherical. Typical sizes are 5 to 10 {mu}m. Concentration values reach up to the order of 1000 cm{sup -3}. Aged contrail size distributions are within the variability of those found in natural cirrus clouds. (author) 2 refs.

  12. Can cirrus cloud seeding be used for geoengineering?

    Science.gov (United States)

    Penner, Joyce E.; Zhou, Cheng; Liu, Xiaohong

    2015-10-01

    Cirrus cloud seeding has been proposed as a possible technique that might thin cirrus clouds leading to reduced heating. The technique was shown to be viable in one model evaluation. Here we use an updated version of the Community Atmosphere Model version 5 (CAM5) and reevaluate whether seeding is a viable mechanism for cooling. We explore different model setups (with and without secondary organic aerosols acting as heterogeneous ice nuclei). None of the updated versions of the CAM5 lead to a significant amount of negative climate forcing and hence do not lead to cooling. We only calculate a net negative cloud forcing (-0.74 ± 0.25 W m-2) if we restrict the modeled subgrid-scale updraft velocity during nucleation to <0.2 m s-1 and if the deposition of water vapor onto preexisting ice crystals during nucleation is not included. Hence, we do not find that cirrus cloud seeding is a viable climate intervention technique.

  13. Modification of cirrus clouds to reduce global warming

    Science.gov (United States)

    Mitchell, D. L.

    2009-12-01

    Since both greenhouse gases and cirrus clouds strongly affect outgoing longwave radiation (OLR) with no affect or less affect on solar radiation, respectively, an attempt to delay global warming to buy time for emission reduction strategies to work might naturally target cirrus clouds. Cirrus having optical depths Seeding such cirrus with very efficient heterogeneous ice nuclei should produce larger ice crystals due to vapor competition effects, thus increasing OLR and surface cooling. Preliminary estimates of this global net cloud forcing via GCM simulations are more negative than -2.8 W m-2 and could neutralize the radiative forcing due to a CO2 doubling (3.7 W m-2). This cirrus engineered net forcing is due to (1) reduced cirrus coverage and (2) reduced upper tropospheric water vapor, due to enhanced ice sedimentation. The implementation of this climate engineering could use the airline industry to disperse the seeding material. Commercial airliners typically fly at temperatures between -40 and -60 deg. C (where homogeneous freezing nucleation dominates). Weather modification research has developed ice nucleating substances that are extremely effective at these cold temperatures, are non-toxic and are relatively inexpensive. The seeding material could be released in both clear and cloudy conditions to build up a background concentration of efficient ice nuclei so that non-contrail cirrus will experience these nuclei and grow larger ice crystals. Flight corridors are denser in the high- and mid-latitudes where global warming is more severe. A risk with any geoengineering experiment is that it could affect climate in unforeseen ways, causing more harm than good. Since seeding aerosol residence times in the troposphere are 1-2 weeks, the climate might return back to its normal state within a few months after stopping the geoengineering. A drawback to this approach is that it would not stop ocean acidification. It may not have many of the draw-backs that

  14. 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.

  15. Investigation of tropical cirrus cloud properties using ground based lidar measurements

    Science.gov (United States)

    Dhaman, Reji K.; Satyanarayana, Malladi; Krishnakumar, V.; Mahadevan Pillai, V. P.; Jayeshlal, G. S.; Raghunath, K.; Venkat Ratnam, M.

    2016-05-01

    Cirrus clouds play a significant role in the Earths radiation budget. Therefore, knowledge of geometrical and optical properties of cirrus cloud is essential for the climate modeling. In this paper, the cirrus clouds microphysical and optical properties are made by using a ground based lidar measurements over an inland tropical station Gadanki (13.5°N, 79.2°E), Andhra Pradesh, India. The variation of cirrus microphysical and optical properties with mid cloud temperature is also studied. The cirrus clouds mean height is generally observed in the range of 9-17km with a peak occurrence at 13- 14km. The cirrus mid cloud temperature ranges from -81°C to -46°C. The cirrus geometrical thickness ranges from 0.9- 4.5km. During the cirrus occurrence days sub-visual, thin and dense cirrus were at 37.5%, 50% and 12.5% respectively. The monthly cirrus optical depth ranges from 0.01-0.47, but most (extinction ranges from 2.8E-06 to 8E-05 and depolarization ratio and lidar ratio varies from 0.13 to 0.77 and 2 to 52 sr respectively. A positive correlation exists for both optical depth and extinction with the mid-cloud temperature. The lidar ratio shows a scattered behavior with mid-cloud temperature.

  16. 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.

  17. Interactions of radiation, microphysics, and turbulence in the evolution of cirrus clouds

    Science.gov (United States)

    Gu, Yu

    2000-12-01

    A two-dimensional cirrus cloud model has been developed to investigate the interaction and feedback of radiation, ice microphysics, and turbulence-scale turbulence, and their influence on the evolution of cirrus clouds. The new features of the model include a detailed ice microphysical module for the prediction of ice crystal size distributions, a radiation scheme which interacts with the ice crystal size distribution via ice water content (IWC) and a mean effective ice crystal size, the effects of radiation on the diffusional growth of ice crystals, and a second-order closure for turbulence. Simulation results show that initial cloud formation occurs through ice nucleation associated with dynamic and thermodynamic forcings. Radiative processes enhance both the growth of ice crystals at the cloud top by radiative cooling and the sublimation of ice crystals in the lower region by radiative heating. In addition, the radiation effect on individual ice crystals through diffusional growth is shown to be significant. Turbulence begins to play a substantial role in cloud evolution during the maintenance and dissipation period of the cirrus cloud life cycle. The inclusion of turbulence tends to generate more intermediate-to-large ice crystals, especially in the middle and lower parts of the cloud. A three-dimensional (3D) radiative transfer model has also been developed to simulate the transfer of solar and thermal infrared radiation in inhomogeneous cirrus clouds. The model utilizes a diffusion approximation approach for application to inhomogeneous media employing Cartesian coordinates. The extinction coefficient, single-scattering albedo, and asymmetry factor are parameterized in terms of the ice water content and mean effective ice crystal size. We employ the correlated k- distribution method for incorporation of gaseous absorption in multiple scattering atmospheres. Delta- function adjustment is used to account for the strong forward diffraction nature of the phase

  18. 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.

  19. Cirrus cloud retrieval from MSG/SEVIRI during day and night using artificial neural networks

    Science.gov (United States)

    Strandgren, Johan; Bugliaro, Luca

    2017-04-01

    By covering a large part of the Earth, cirrus clouds play an important role in climate as they reflect incoming solar radiation and absorb outgoing thermal radiation. Nevertheless, the cirrus clouds remain one of the largest uncertainties in atmospheric research and the understanding of the physical processes that govern their life cycle is still poorly understood, as is their representation in climate models. To monitor and better understand the properties and physical processes of cirrus clouds, it's essential that those tenuous clouds can be observed from geostationary spaceborne imagers like SEVIRI (Spinning Enhanced Visible and InfraRed Imager), that possess a high temporal resolution together with a large field of view and play an important role besides in-situ observations for the investigation of cirrus cloud processes. CiPS (Cirrus Properties from Seviri) is a new algorithm targeting thin cirrus clouds. CiPS is an artificial neural network trained with coincident SEVIRI and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) observations in order to retrieve a cirrus cloud mask along with the cloud top height (CTH), ice optical thickness (IOT) and ice water path (IWP) from SEVIRI. By utilizing only the thermal/IR channels of SEVIRI, CiPS can be used during day and night making it a powerful tool for the cirrus life cycle analysis. Despite the great challenge of detecting thin cirrus clouds and retrieving their properties from a geostationary imager using only the thermal/IR wavelengths, CiPS performs well. Among the cirrus clouds detected by CALIOP, CiPS detects 70 and 95 % of the clouds with an optical thickness of 0.1 and 1.0 respectively. Among the cirrus free pixels, CiPS classify 96 % correctly. For the CTH retrieval, CiPS has a mean absolute percentage error of 10 % or less with respect to CALIOP for cirrus clouds with a CTH greater than 8 km. For the IOT retrieval, CiPS has a mean absolute percentage error of 100 % or less with respect to

  20. Parameterization of cirrus optical depth and cloud fraction

    Energy Technology Data Exchange (ETDEWEB)

    Soden, B. [Princeton Univ., Princeton, NJ (United States)

    1995-09-01

    This research illustrates the utility of combining satellite observations and operational analysis for the evaluation of parameterizations. A parameterization based on ice water path (IWP) captures the observed spatial patterns of tropical cirrus optical depth. The strong temperature dependence of cirrus ice water path in both the observations and the parameterization is probably responsible for the good correlation where it exists. Poorer agreement is found in Southern Hemisphere mid-latitudes where the temperature dependence breaks down. Uncertainties in effective radius limit quantitative validation of the parameterization (and its inclusion into GCMs). Also, it is found that monthly mean cloud cover can be predicted within an RMS error of 10% using ECMWF relative humidity corrected by TOVS Upper Troposphere Humidity. 1 ref., 2 figs.

  1. A modelling study of moisture redistribution by thin cirrus clouds

    Directory of Open Access Journals (Sweden)

    T. Dinh

    2014-05-01

    Full Text Available A high resolution 2-dimensional numerical model is used to study the moisture redistribution following homogeneous ice nucleation induced by Kelvin waves in the tropical tropopause layer (TTL. We compare results for dry/moist initial conditions, and three levels of complexity for the representation of cloud processes: full bin microphysics and radiative effects of the ice, ditto but without radiative effects, and instantaneous removal of moisture in excess of saturation upon nucleation. Cloud evolution and the profiles of moisture redistribution are found to be sensitive to initial conditions and cloud processes. Ice sedimentation leads to a downward flux of water. On the other hand, the cloud radiative heating induces upward advection of the cloudy air. This results in an upward flux of water vapour if the cloudy air is moister (or drier than the environment, which is typically when the environment is subsaturated (or supersaturated. The numerical results show that only a small fraction (less than 25% of the cloud experiences nucleation. Sedimentation and reevaporation are important, and hydrated layers in observation may be as good an indicator as dehydrated layers for the occurrence of thin cirrus clouds. The calculation with instantaneous removal of condensates misses the hydration by construction, but also underestimates dehydration due to lack of moisture removal from sedimenting particles below the nucleation level, and due to nucleation before reaching the minimum saturation mixing ratio. The sensitivity to initial conditions and cloud processes suggests that it is difficult to reach generic, quantitative conclusions regarding the role of thin cirrus clouds for the moisture distribution in the TTL and stratosphere.

  2. 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.

  3. Polarization lidars with conical scanning for retrieving the microphysical characteristics of cirrus clouds

    Science.gov (United States)

    Konoshonkin, Alexander V.; Borovoi, Anatoli G.; Liu, Dong; Wang, Zhenzhu; Balin, Yuri S.; Kustova, Natalia V.; Kokhanenko, Grigorii; Penner, Iogannes; Nasonov, Sergey V.; Bryukhanov, Ilia D.; Doroshkevich, Anton A.

    2015-11-01

    The paper presents the first results of observations of cirrus clouds by polarization lidars with conical scanning, which were developed in Hefei (China) and in Tomsk (Russia). The light scattering matrix of ice crystal particles of cirrus clouds has been calculated for the first by the authors within the framework of the physical optics approximations in the case of conical scanning lidar. It is found that in this case the Mueller matrix consists of ten non-zero elements, four of which are small and can't be applied to interpret the azimuthal distribution of particle orientation. All the diagonal elements have a strong azimuthal dependence. Among the off-diagonal elements only one element M34 carries additional information for interpreting the azimuthal distribution.

  4. 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.

  5. Distinguishing cirrus cloud presence in autonomous lidar measurements

    Directory of Open Access Journals (Sweden)

    J. R. Campbell

    2014-07-01

    Full Text Available Level 2 Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP satellite-based cloud datasets from 2012 are investigated for metrics that help distinguish the cirrus cloud presence of in autonomous lidar measurements, using temperatures, heights, optical depth and phase. A thermal threshold, proposed by Sassen and Campbell (2001; SC2001 for cloud top temperature Ttop ≤ −37 °C, is evaluated vs. CALIOP algorithms that identify ice-phase cloud layers alone using depolarized backscatter. Global mean cloud top heights (11.15 vs. 10.07 km a.m.s.l., base heights (8.76 vs. 7.95 km a.m.s.l., temperatures (−58.48 °C vs. −52.18 °C and −42.40 °C vs. −38.13 °C, respectively for tops and bases and optical depths (1.18 vs. 1.23 reflect the sensitivity to these competing constraints. Over 99% of all Ttop ≤ −37 °C clouds are classified as ice by CALIOP Level 2 algorithms. Over 81% of all ice clouds correspond with Ttop ≤ −37 °C. For instruments lacking polarized measurements, and thus practical phase estimates, Ttop ≤ −37 °C proves stable for distinguishing cirrus, as opposed to the risks of glaciated liquid water cloud contamination occurring in a given sample from clouds identified at warmer temperatures. Uncertainties in temperature profiles use to collocate with lidar data (i.e., model reanalyses/sondes may justifiably relax the Ttop ≤ −37 °C threshold to include warmer cases. The ambiguity of "warm" (Ttop > −37 °C ice cloud genus cannot be reconciled completely with available measurements, however, conspicuously including phase. Cloud top heights and optical depths are evaluated as potential constraints, as functions of CALIOP-retrieved phase. However, these data provide, at best, additional constraint in regional samples, compared with temperature alone, and may exacerbate classification uncertainties overall globally.

  6. 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.

  7. 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...

  8. Evidence of impact of aviation on cirrus cloud formation

    Directory of Open Access Journals (Sweden)

    C. S. Zerefos

    2003-01-01

    Full Text Available This work examines changes in cirrus cloud cover (CCC in possible association with aviation activities at congested air corridors. The analysis is based on the latest version of the International Satellite Cloud Climatology Project D2 data set and covers the period 1984-1998. Over the studied areas, the effect of large-scale modes of natural climate variability such as ENSO, QBO and NAO as well as the possible influence of the tropopause variability, were first removed from the cloud data set in order to calculate long-term changes of observed cirrus cloudiness. The results show increasing trends in (CCC between 1984 and 1998 over the high air traffic corridors of North America, North Atlantic and Europe. Of these upward trends, only in the summertime over the North Atlantic and only in the wintertime over North America are statistically significant (exceeding +2.0% per decade. Over adjacent locations with low air traffic, the calculated trends are statistically insignificant and in most cases negative both during winter and summer in the regions studied. These negative trends, over low air traffic regions, are consistent with the observed large scale negative trends seen in (CCC over most of the northern middle latitudes and over the tropics. Moreover, further investigation of vertical velocities over high and low air traffic regions provide evidence that the trends of opposite signs in (CCC over these regions, do not seem to be caused by different trends in dynamics. It is also shown that the longitudinal distribution of decadal changes in (CCC along the latitude belt centered at the North Atlantic air corridor, parallels the spatial distribution of fuel consumption from highflying air traffic, providing an independent test of possible impact of aviation on contrail cirrus formation. The correlation between the fuel consumption and the longitudinal variability of (CCC is significant (+0.7 over the middle latitudes but not over the tropics

  9. Climatological and radiative properties of midlatitude cirrus clouds derived by automatic evaluation of lidar measurements

    Science.gov (United States)

    Kienast-Sjögren, Erika; Rolf, Christian; Seifert, Patric; Krieger, Ulrich K.; Luo, Bei P.; Krämer, Martina; Peter, Thomas

    2016-06-01

    Cirrus, i.e., high, thin clouds that are fully glaciated, play an important role in the Earth's radiation budget as they interact with both long- and shortwave radiation and affect the water vapor budget of the upper troposphere and stratosphere. Here, we present a climatology of midlatitude cirrus clouds measured with the same type of ground-based lidar at three midlatitude research stations: at the Swiss high alpine Jungfraujoch station (3580 m a.s.l.), in Zürich (Switzerland, 510 m a.s.l.), and in Jülich (Germany, 100 m a.s.l.). The analysis is based on 13 000 h of measurements from 2010 to 2014. To automatically evaluate this extensive data set, we have developed the Fast LIdar Cirrus Algorithm (FLICA), which combines a pixel-based cloud-detection scheme with the classic lidar evaluation techniques. We find mean cirrus optical depths of 0.12 on Jungfraujoch and of 0.14 and 0.17 in Zürich and Jülich, respectively. Above Jungfraujoch, subvisible cirrus clouds (τ change in cloud morphology at Jungfraujoch above ˜ 13 km, possibly because high particle number densities form in the observed cirrus clouds, when many ice crystals nucleate in the high supersaturations following rapid uplifts in lee waves above mountainous terrain. The retrieved optical properties are used as input for a radiative transfer model to estimate the net cloud radiative forcing, CRFNET, for the analyzed cirrus clouds. All cirrus detected here have a positive CRFNET. This confirms that these thin, high cirrus have a warming effect on the Earth's climate, whereas cooling clouds typically have cloud edges too low in altitude to satisfy the FLICA criterion of temperatures below -38 °C. We find CRFNET = 0.9 W m-2 for Jungfraujoch and 1.0 W m-2 (1.7 W m-2) for Zürich (Jülich). Further, we calculate that subvisible cirrus (τ < 0.03) contribute about 5 %, thin cirrus (0.03 < τ < 0.3) about 45 %, and opaque cirrus (0.3 < τ) about 50 % of the total cirrus radiative forcing.

  10. Properties of subvisible cirrus clouds formed by homogeneous freezing

    Directory of Open Access Journals (Sweden)

    B. Kärcher

    2002-04-01

    Full Text Available Number concentrations and mean sizes of ice crystals and derived microphysical and optical properties of subvisible cirrus clouds (SVCs formed by homogeneous freezing of supercooled aerosols are investigated as a function of temperature and updraft speed of adiabatically ascending air parcels. The properties of such clouds are insensitive to variations of the aerosol number and size distribution. Based on criteria constraining the optical extinction, sedimentation time, and existence time of SVCs, longer-lived (>10 min clouds, capable of exerting a measurable radiative or chemical impact, are generated within a narrow range of updraft speeds below 1 - 2 cm s -1 at temperatures below about 215K, with concentrations of ice crystals not exceeding 0.1 cm-3. The clouds do not reach an equilibrium state because the ice crystals sediment out of the formation layer typically before the supersaturation is removed. Given these results, it seems likely that a limited number (<0.1 cm-3 of effective heterogeneous freezing nuclei that nucleate ice below the homogeneous freezing threshold can control the formation and properties of SVCs, although homogeneous freezing nuclei are far more abundant.

  11. A combined atmospheric radiative transfer (CART) model and its applications for cirrus clouds simulations

    Science.gov (United States)

    Wei, Heli; Cao, Ya'nan; Chen, Xiuhong

    2012-11-01

    A fast atmospheric radiative transfer model called Combined Atmospheric Radiative Transfer model (CART) has been developed to rapidly calculate atmospheric transmittance and background radiance in the wavenumber range from 1 to 25000 cm-1 with spectral resolution of 1 cm-1. The spectral radiative properties of cirrus clouds at various effective sizes, optical thicknesses, and altitudes from visible to infrared wavelength region are simulated using the CART. The analyses show that the properties of cirrus clouds might be retrieved from the satellite-base spectral characteristics of cirrus clouds based on these simulations.

  12. Revisiting the iris effect of tropical cirrus clouds with TRMM and A-Train satellite data

    Science.gov (United States)

    Choi, Yong-Sang; Kim, WonMoo; Yeh, Sang-Wook; Masunaga, Hirohiko; Kwon, Min-Jae; Jo, Hyun-Su; Huang, Lei

    2017-06-01

    Just as the iris of human eye controls the light influx (iris effect), tropical anvil cirrus clouds may regulate the Earth's surface warming by controlling outgoing longwave radiation. This study examines this possible effect with monthly satellite observations such as Tropical Rainfall Measuring Mission (TRMM) precipitation, Moderate Resolution Imaging Spectroradiometer cirrus fraction, and Clouds and the Earth's Radiant Energy System top-of-the-atmosphere radiative fluxes averaged over different tropical domains from March 2000 to October 2014. To confirm that high-level cirrus is relevant to this study, Cloud-Aerosol Lidar with Orthogonal Polarization high cloud observations were also analyzed from June 2006 to December 2015. Our analysis revealed that the increase in sea surface temperature in the tropical western Pacific tends to concentrate convective cloud systems. This concentration effect very likely induces the significant reduction of both stratiform rain rate and cirrus fraction, without appreciable change in the convective rain rate. This reduction of stratiform rain rate and cirrus fraction cannot be found over its subregion or the tropical eastern Pacific, where the concentration effect of anvil cirrus is weak. Consistently, over the tropical western Pacific, the higher ratio of convective rain rate to total rain rate (i.e., precipitation efficiency) significantly correlates with warmer sea surface temperature and lower cirrus fraction. The reduced cirrus eventually increased outgoing longwave radiation to a greater degree than absorbed solar radiation. Finally, the negative relationship between precipitation efficiency and cirrus fraction tends to correspond to a low global equilibrium climate sensitivity in the models in the Coupled Model Intercomparison Project Phase 5. This suggests that tropical anvil cirrus clouds exert a negative climate feedback in strong association with precipitation efficiency.

  13. Study of Ice Crystal Orientation in Cirrus Clouds based on Satellite Polarized Radiance Measurements

    OpenAIRE

    Noel, Vincent; Chepfer, Hélène

    2004-01-01

    International audience; The goal of this paper is to retrieve information about ice particle orientation in cirrus clouds. This is achieved by comparing simulations of sunlight reflection on a cirrus cloud with measurements of polarized radiances from the spaceborne instrument Polarization and Directionality of the Earth's Reflectance (POLDER-1) on Advanced Earth Observing Satellite-1 (ADEOS-1). Results show that horizontal orientation of cr ystals can be spotted by the presence of a local ma...

  14. Cirrus Cloud Macrophysical and Optical Properties over North China from CALIOP Measurements

    Institute of Scientific and Technical Information of China (English)

    MIN Min; WANG Pucai; James R. CAMPBELL; ZONG Xuemei; XIA Junrong

    2011-01-01

    Two years of mid-latitude cirrus cloud macrophysical and optical properties over North China are described from Earth-orbiting Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite measurements. Global cloud climatological studies based on active remote sensing data sets benefit from more accurate resolution of vertical structure and more reliable detection of optically thin layers. The mean values for cirrus cases over North China are 0.19-0.18 for infrared emittance, 0.41±0.68 for visible optical depth,0.26±0.12 for integrated depolarization ratio, and 0.72±0.22 for integrated color ratio. When studied using reasonable assumptions for the relationship between extinction and ice crystal backscatter coefficients, our results show that most of the cirrus clouds profiled using the 0.532 μm channel data stream correspond with an optical depth of less than 1.0. The dependence of cirrus cloud properties on cirrus cloud mid-cloud temperature and geometry thickness are generally similar to the results derived from the ground-based lidar,which are mainly impacted by the adiabatic process on the ice cloud content. However, the differences in macrophysical parameter variability indicate the limits of spaceborne-lidar and dissimilarities in regional climate variability and the nature and source of cloud nuclei in different geographical regions.

  15. Cirrus Cloud Macrophysical and Optical Properties over North China from CALIOP Measurements

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Two years of mid-latitude cirrus cloud macrophysical and optical properties over North China are described from Earth-orbiting Cloud-Aerosol Lidar with Orthogonal Polarization(CALIOP) satellite measurements. Global cloud climatological studies based on active remote sensing data sets benefit from more accurate resolution of vertical structure and more reliable detection of optically thin layers.The mean values for cirrus cases over North China are 0.19±0.18 for infrared emittance,0.41±0.68 for visible optical depth, 0.26±0.12 for integrated depolarization ratio,and 0.72±0.22 for integrated color ratio.When studied using reasonable assumptions for the relationship between extinction and ice crystal backscatter coefficients,our results show that most of the cirrus clouds profiled using the 0.532μm channel data stream correspond with an optical depth of less than 1.0.The dependence of cirrus cloud properties on cirrus cloud mid-cloud temperature and geometry thickness are generally similar to the results derived from the ground-based lidar, which are mainly impacted by the adiabatic process on the ice cloud content.However,the differences in macrophysical parameter variability indicate the limits of spaceborne-lidar and dissimilarities in regional climate variability and the nature and source of cloud nuclei in different geographical regions.

  16. Freezing thresholds and cirrus cloud formation mechanisms inferred from in situ measurements of relative humidity

    Directory of Open Access Journals (Sweden)

    W. Haag

    2003-06-01

    Full Text Available Factors controlling the distribution of relative humidity above ice saturation in the upper troposphere and lower stratosphere in the presence of cirrus clouds are examined with the help of microphysical trajectory simulations using a box model. Our findings are related to results from recent field campaigns and global model studies. We suggest that the relative humidities at which ice crystals form in the atmosphere can be inferred from in situ measurements of water vapor and temperature close to, but outside of, cirrus clouds. The comparison with similar measurements performed inside cirrus clouds provides a clue to freezing mechanisms active in cirrus. The comparison with field data reveals distinct interhemispheric differences in cirrus cloud freezing thresholds. Combining the present findings with recent results addressing the frequency distributions of updraft speeds and cirrus ice crystal number densities (Kärcher and Ström, 2993} provides evidence for the existence of complex heterogeneous freezing mechanisms in cirrus, at least in the polluted northern hemisphere, and further emphasizes the key role of gravity wave-induced dynamical variability in vertical air motion at the mesoscale. The key features of distributions of upper tropospheric relative humidity simulated by a global climate model are shown to be in general agreement with both, microphysical simulations and field observations, delineating a feasible method to include and validate ice supersaturation in other large-scale models of the atmosphere, in particular chemistry-transport and weather forecast models.

  17. 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.

  18. 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.

  19. Particle backscatter and relative humidity measured across cirrus clouds and comparison with state-of-the-art cirrus modelling

    Directory of Open Access Journals (Sweden)

    M. Brabec

    2012-04-01

    Full Text Available Advanced measurement and modelling techniques are employed to determine the partitioning of atmospheric water between the gas phase and the condensed phase in and around cirrus clouds, and thus to identify in-cloud and out-of-cloud supersaturations with respect to ice. In November 2008 the newly developed balloon-borne backscatter sonde COBALD (Compact Optical Backscatter and AerosoL Detector was flown 14 times together with a CFH (Cryogenic Frost point Hygrometer from Lindenberg, Germany (52° N, 14° E. The case discussed here in detail shows two cirrus layers with in-cloud relative humidities with respect to ice between 50% and 130%. Global operational analysis data of ECMWF (roughly 1° × 1° horizontal and 1 km vertical resolution, 6-hourly stored fields fail to represent ice water contents and relative humidities. Conversely, regional COSMO-7 forecasts (6.6 km × 6.6 km, 5-min stored fields capture the measured humidities and cloud positions remarkably well. The main difference between ECMWF and COSMO data is the resolution of small-scale vertical features responsible for cirrus formation. Nevertheless, ice water contents in COSMO-7 are still off by factors 2–10, likely reflecting limitations in COSMO's ice phase bulk scheme. Significant improvements can be achieved by comprehensive size-resolved microphysical and optical modelling along backward trajectories based on COSMO-7 wind and temperature fields, which allow accurate computation of humidities, ice particle size distributions and backscatter ratios at the COBALD wavelengths. However, only by superimposing small-scale temperature fluctuations, which remain unresolved by the NWP models, can we obtain a satisfying agreement with the observations and reconcile the measured in-cloud non-equilibrium humidities with conventional ice cloud microphysics.

  20. 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.

  1. Corona-producing ice clouds: a case study of a cold mid-latitude cirrus layer.

    Science.gov (United States)

    Sassen, K; Mace, G G; Hallett, J; Poellot, M R

    1998-03-20

    A high (14.0-km), cold (-71.0 degrees C) cirrus cloud was studied by ground-based polarization lidar and millimeter radar and aircraft probes on the night of 19 April 1994 from the Cloud and Radiation Testbed site in northern Oklahoma. A rare cirrus cloud lunar corona was generated by this 1-2-km-deep cloud, thus providing an opportunity to measure the composition in situ, which had previously been assumed only on the basis of lidar depolarization data and simple diffraction theory for spheres. In this case, corona ring analysis indicated an effective particle diameter of ~22 mum. A variety of in situ data corroborates the approximate ice-particle size derived from the passive retrieval method, especially near the cloud top, where impacted cloud samples show simple solid crystals. The homogeneous freezing of sulfuric acid droplets of stratospheric origin is assumed to be the dominant ice-particle nucleation mode acting in corona-producing cirrus clouds. It is speculated that this process results in a previously unrecognized mode of acid-contaminated ice-particle growth and that such small-particle cold cirrus clouds are potentially a radiatively distinct type of cloud.

  2. Corona-producing ice clouds: A case study of a cold mid-latitude cirrus layer

    Energy Technology Data Exchange (ETDEWEB)

    Sassen, K.; Mace, G.G. [University of Utah, Salt Lake City, Utah 84112 (United States); Hallett, J. [Desert Research Institute, Reno, Nevada 89506 (United States); Poellot, M.R. [University of North Dakota, Grand Forks, North Dakota 58202 (United States)

    1998-03-01

    A high (14.0-km), cold ({minus}71.0thinsp{degree}C) cirrus cloud was studied by ground-based polarization lidar and millimeter radar and aircraft probes on the night of 19 April 1994 from the Cloud and Radiation Testbed site in northern Oklahoma. A rare cirrus cloud lunar corona was generated by this 1{endash}2-km-deep cloud, thus providing an opportunity to measure the composition {ital in situ}, which had previously been assumed only on the basis of lidar depolarization data and simple diffraction theory for spheres. In this case, corona ring analysis indicated an effective particle diameter of {approximately}22 {mu}m. A variety of {ital in situ} data corroborates the approximate ice-particle size derived from the passive retrieval method, especially near the cloud top, where impacted cloud samples show simple solid crystals. The homogeneous freezing of sulfuric acid droplets of stratospheric origin is assumed to be the dominant ice-particle nucleation mode acting in corona-producing cirrus clouds. It is speculated that this process results in a previously unrecognized mode of acid-contaminated ice-particle growth and that such small-particle cold cirrus clouds are potentially a radiatively distinct type of cloud. {copyright} 1998 Optical Society of America

  3. 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.

  4. Technical note: Fu-Liou-Gu and Corti-Peter model performance evaluation for radiative retrievals from cirrus clouds

    Science.gov (United States)

    Lolli, Simone; Campbell, James R.; Lewis, Jasper R.; Gu, Yu; Welton, Ellsworth J.

    2017-06-01

    We compare, for the first time, the performance of a simplified atmospheric radiative transfer algorithm package, the Corti-Peter (CP) model, versus the more complex Fu-Liou-Gu (FLG) model, for resolving top-of-the-atmosphere radiative forcing characteristics from single-layer cirrus clouds obtained from the NASA Micro-Pulse Lidar Network database in 2010 and 2011 at Singapore and in Greenbelt, Maryland, USA, in 2012. Specifically, CP simplifies calculation of both clear-sky longwave and shortwave radiation through regression analysis applied to radiative calculations, which contributes significantly to differences between the two. The results of the intercomparison show that differences in annual net top-of-the-atmosphere (TOA) cloud radiative forcing can reach 65 %. This is particularly true when land surface temperatures are warmer than 288 K, where the CP regression analysis becomes less accurate. CP proves useful for first-order estimates of TOA cirrus cloud forcing, but may not be suitable for quantitative accuracy, including the absolute sign of cirrus cloud daytime TOA forcing that can readily oscillate around zero globally.

  5. Technical note: Fu–Liou–Gu and Corti–Peter model performance evaluation for radiative retrievals from cirrus clouds

    Directory of Open Access Journals (Sweden)

    S. Lolli

    2017-06-01

    Full Text Available We compare, for the first time, the performance of a simplified atmospheric radiative transfer algorithm package, the Corti–Peter (CP model, versus the more complex Fu–Liou–Gu (FLG model, for resolving top-of-the-atmosphere radiative forcing characteristics from single-layer cirrus clouds obtained from the NASA Micro-Pulse Lidar Network database in 2010 and 2011 at Singapore and in Greenbelt, Maryland, USA, in 2012. Specifically, CP simplifies calculation of both clear-sky longwave and shortwave radiation through regression analysis applied to radiative calculations, which contributes significantly to differences between the two. The results of the intercomparison show that differences in annual net top-of-the-atmosphere (TOA cloud radiative forcing can reach 65 %. This is particularly true when land surface temperatures are warmer than 288 K, where the CP regression analysis becomes less accurate. CP proves useful for first-order estimates of TOA cirrus cloud forcing, but may not be suitable for quantitative accuracy, including the absolute sign of cirrus cloud daytime TOA forcing that can readily oscillate around zero globally.

  6. Midlatitude Cirrus Clouds and Multiple Tropopauses from a 2002-2006 Climatology over the SIRTA Observatory

    CERN Document Server

    Noel, Vincent

    2007-01-01

    This study present a comparison of lidar observations of midlatitude cirrus clouds over the SIRTA observatory between 2002 and 2006 with multiple tropopauses (MT) retrieved from radiosounding temperature profiles. The temporal variability of MT properties (frequency, thickness) are discussed. Results show a marked annual cycle, with MT frequency reaching its lowest point in May (~18% occurrence of MT) and slowly rising to more than 40% in DJF. The average thickness of the MT also follows an annual cycle, going from less than 1 km in spring to 1.5 km in late autumn. Comparison with lidar observations show that cirrus clouds show a preference for being located close below the 1st tropopause. When the cloud top is above the 1st tropopause (7% of observations), in 20% of cases the cloud base is above it as well, resulting in a cirrus cloud "sandwiched" between the two tropopauses. Compared to the general distribution of cirrus, cross-tropopause cirrus show a higher frequency of large optical depths, while inter-t...

  7. Optical and geometrical properties of cirrus clouds in Amazonia derived from 1 year of ground-based lidar measurements

    Science.gov (United States)

    Gouveia, Diego A.; Barja, Boris; Barbosa, Henrique M. J.; Seifert, Patric; Baars, Holger; Pauliquevis, Theotonio; Artaxo, Paulo

    2017-03-01

    Cirrus clouds cover a large fraction of tropical latitudes and play an important role in Earth's radiation budget. Their optical properties, altitude, vertical and horizontal coverage control their radiative forcing, and hence detailed cirrus measurements at different geographical locations are of utmost importance. Studies reporting cirrus properties over tropical rain forests like the Amazon, however, are scarce. Studies with satellite profilers do not give information on the diurnal cycle, and the satellite imagers do not report on the cloud vertical structure. At the same time, ground-based lidar studies are restricted to a few case studies. In this paper, we derive the first comprehensive statistics of optical and geometrical properties of upper-tropospheric cirrus clouds in Amazonia. We used 1 year (July 2011 to June 2012) of ground-based lidar atmospheric observations north of Manaus, Brazil. This dataset was processed by an automatic cloud detection and optical properties retrieval algorithm. Upper-tropospheric cirrus clouds were observed more frequently than reported previously for tropical regions. The frequency of occurrence was found to be as high as 88 % during the wet season and not lower than 50 % during the dry season. The diurnal cycle shows a minimum around local noon and maximum during late afternoon, associated with the diurnal cycle of precipitation. The mean values of cirrus cloud top and base heights, cloud thickness, and cloud optical depth were 14.3 ± 1.9 (SD) km, 12.9 ± 2.2 km, 1.4 ± 1.1 km, and 0.25 ± 0.46, respectively. Cirrus clouds were found at temperatures down to -90 °C. Frequently cirrus were observed within the tropical tropopause layer (TTL), which are likely associated to slow mesoscale uplifting or to the remnants of overshooting convection. The vertical distribution was not uniform, and thin and subvisible cirrus occurred more frequently closer to the tropopause. The mean lidar ratio was 23.3 ± 8.0 sr. However, for

  8. Impacts of cloud heterogeneities on cirrus optical properties retrieved from spatial thermal infrared radiometry

    Directory of Open Access Journals (Sweden)

    T. Fauchez

    2014-08-01

    Full Text Available This paper presents a study, based on simulations, of the impact of cirrus cloud heterogeneities on the retrieval of cloud parameters (optical thickness and effective diameter for the Imaging Infrared Radiometer (IIR on board CALIPSO. Cirrus clouds are generated by the stochastic model 3DCLOUD for two different cloud fields and for several averaged cloud parameters. One is obtained from a cirrus observed on the 25 May 2007 during the airborne campaign CIRCLE-2 and the other is a cirrus uncinus. The radiative transfer is simulated with the code 3DMCPOL. To assess the errors due to cloud heterogeneities, two related retrieval algorithms are used: (i The split window technique to retrieve the ice crystal effective diameter and (ii an algorithm similar to the IIR operational algorithm to retrieve the effective emissivity and the effective optical thickness. Differences between input parameters and retrieved parameters are compared as a function of different cloud properties such as the mean optical thickness, the heterogeneity parameter and the effective diameter. The optical thickness heterogeneity for each 1 km × 1 km observation pixel is represented by the optical thickness standard deviation computed using 100 m × 100 m subpixels. We show that optical thickness heterogeneity may have a strong impact on the retrieved parameters, mainly due to the Plane Parallel Approximation (PPA. In particular, for cirrus cloud with ice crystal size of approximately 10 μm, the averaged error on the retrieved effective diameter is about 2.5 μm (~ 25% and on the effective optical thickness of about −0.20 (~ 12%. Then, these biases decrease with the increase of the ice effective size due to a decrease of the cloud absorption and thus of the PPA bias. Cloud heterogeneity effects are much more higher than other possible sources of error. They become larger than the retrieval incertitude of the IIR algorithm from a standard deviation of the optical thickness

  9. Evaluation of Cirrus Cloud Simulations using ARM Data-Development of Case Study Data Set

    Science.gov (United States)

    Starr, David OC.; Demoz, Belay; Wang, Yansen; Lin, Ruei-Fong; Lare, Andrew; Mace, Jay; Poellot, Michael; Sassen, Kenneth; Brown, Philip

    2002-01-01

    Cloud-resolving models (CRMs) are being increasingly used to develop parametric treatments of clouds and related processes for use in global climate models (GCMs). CRMs represent the integrated knowledge of the physical processes acting to determine cloud system lifecycle and are well matched to typical observational data in terms of physical parameters/measurables and scale-resolved physical processes. Thus, they are suitable for direct comparison to field observations for model validation and improvement. The goal of this project is to improve state-of-the-art CRMs used for studies of cirrus clouds and to establish a relative calibration with GCMs through comparisons among CRMs, single column model (SCM) versions of the GCMs, and observations. The objective is to compare and evaluate a variety of CRMs and SCMs, under the auspices of the GEWEX Cloud Systems Study (GCSS) Working Group on Cirrus Cloud Systems (WG2), using ARM data acquired at the Southern Great Plains (SGP) site. This poster will report on progress in developing a suitable WG2 case study data set based on the September 26, 1996 ARM IOP case - the Hurricane Nora outflow case. Progress is assessing cloud and other environmental conditions will be described. Results of preliminary simulations using a regional cloud system model (MM5) and a CRM will be discussed. Focal science questions for the model comparison are strongly based on results of the idealized GCSS WG2 cirrus cloud model comparison projects (Idealized Cirrus Cloud Model Comparison Project and Cirrus Parcel Model Comparison Project), which will also be briefly summarized.

  10. Diagnosis of cirrus cloud occurrence using large-scale analysis data and a cloud-scale model

    Directory of Open Access Journals (Sweden)

    G. Cautenet

    Full Text Available The development of cirrus clouds is governed by large-scale synoptic movements such as updraft regions in convergence zones, but also by smaller scale features, for instance microphysical phenomena, entrainment, small-scale turbulence and radiative field, fall-out of the ice phase or wind shear. For this reason, the proper handling of cirrus life cycles is not an easy task using a large-scale model alone. We present some results from a small-scale cirrus cloud model initialized by ECMWF first-guess data, which prove more convenient for this task than the analyzed ones. This model is Starr's 2-D cirrus cloud model, where the rate of ice production/destruction is parametrized from environmental data. Comparison with satellite and local observations during the ICE89 experiment (North Sea shows that such an efficient model using large-scale data as input provides a reasonable diagnosis of cirrus occurrence in a given meteorological field. The main driving features are the updraft provided by the large-scale model, which enhances or inhibits the cloud development according to its sign, and the water vapour availability. The cloud fields retrieved are compared to satellite imagery. Finally, the use of a small-scale model in large-scale numerical studies is examined.

  11. A case study of formation and maintenance of a lower stratospheric cirrus cloud over the tropics

    Science.gov (United States)

    Sandhya, M.; Sridharan, S.; Indira Devi, M.; Niranjan, K.; Jayaraman, A.

    2015-05-01

    A rare occurrence of stratospheric cirrus at 18.6 km height persisting for about 5 days during 3-7 March 2014 is inferred from the ground-based Mie lidar observations over Gadanki (13.5° N, 79.2° E) and spaceborne observations. Due to the vertical transport by large updrafts on 3 March in the troposphere, triggered by a potential vorticity intrusion, the water vapour mixing ratio shows an increase around the height of 18.6 km. Relative humidity with respect to ice is ~ 150%, indicating that the cirrus cloud may be formed though homogeneous nucleation of sulfuric acid. The cirrus cloud persists due to the cold anomaly associated with the presence of a 4-day wave.

  12. Understanding Ice Supersaturation, Particle Growth, and Number Concentration in Cirrus Clouds

    Science.gov (United States)

    Comstock, Jennifer M.; Lin, Ruei-Fong; Starr, David O'C.; Yang, Ping

    2008-01-01

    Many factors control the ice supersaturation and microphysical properties in cirrus clouds. We explore the effects of dynamic forcing, ice nucleation mechanisms, and ice crystal growth rate on the evolution and distribution of water vapor and cloud properties in nighttime cirrus clouds using a one-dimensional cloud model with bin microphysics and remote sensing measurements obtained at the Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility located near Lamont, OK. We forced the model using both large-scale vertical ascent and, for the first time, mean mesoscale velocity derived from radar Doppler velocity measurements. Both heterogeneous and homogeneous nucleation processes are explored, where a classical theory heterogeneous scheme is compared with empirical representations. We evaluated model simulations by examining both bulk cloud properties and distributions of measured radar reflectivity, lidar extinction, and water vapor profiles, as well as retrieved cloud microphysical properties. Our results suggest that mesoscale variability is the primary mechanism needed to reproduce observed quantities. Model sensitivity to the ice growth rate is also investigated. The most realistic simulations as compared with observations are forced using mesoscale waves, include fast ice crystal growth, and initiate ice by either homogeneous or heterogeneous nucleation. Simulated ice crystal number concentrations (tens to hundreds particles per liter) are typically two orders of magnitude smaller than previously published results based on aircraft measurements in cirrus clouds, although higher concentrations are possible in isolated pockets within the nucleation zone.

  13. Aerosol Indirect Effects on Cirrus Clouds in Global Aerosol-Climate Models

    Science.gov (United States)

    Liu, X.; Zhang, K.; Wang, Y.; Neubauer, D.; Lohmann, U.; Ferrachat, S.; Zhou, C.; Penner, J.; Barahona, D.; Shi, X.

    2015-12-01

    Cirrus clouds play an important role in regulating the Earth's radiative budget and water vapor distribution in the upper troposphere. Aerosols can act as solution droplets or ice nuclei that promote ice nucleation in cirrus clouds. Anthropogenic emissions from fossil fuel and biomass burning activities have substantially perturbed and enhanced concentrations of aerosol particles in the atmosphere. Global aerosol-climate models (GCMs) have now been used to quantify the radiative forcing and effects of aerosols on cirrus clouds (IPCC AR5). However, the estimate uncertainty is very large due to the different representation of ice cloud formation and evolution processes in GCMs. In addition, large discrepancies have been found between model simulations in terms of the spatial distribution of ice-nucleating aerosols, relative humidity, and temperature fluctuations, which contribute to different estimates of the aerosol indirect effect through cirrus clouds. In this presentation, four GCMs with the start-of-the art representations of cloud microphysics and aerosol-cloud interactions are used to estimate the aerosol indirect effects on cirrus clouds and to identify the causes of the discrepancies. The estimated global and annual mean anthropogenic aerosol indirect effect through cirrus clouds ranges from 0.1 W m-2 to 0.3 W m-2 in terms of the top-of-the-atmosphere (TOA) net radiation flux, and 0.5-0.6 W m-2 for the TOA longwave flux. Despite the good agreement on global mean, large discrepancies are found at the regional scale. The physics behind the aerosol indirect effect is dramatically different. Our analysis suggests that burden of ice-nucleating aerosols in the upper troposphere, ice nucleation frequency, and relative role of ice formation processes (i.e., homogeneous versus heterogeneous nucleation) play key roles in determining the characteristics of the simulated aerosol indirect effects. In addition to the indirect effect estimate, we also use field campaign

  14. Evidence of High Ice Supersaturation in Cirrus Clouds Using ARM Raman Lidar Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Comstock, Jennifer M.; Ackerman, Thomas P.; Turner, David D.

    2004-06-05

    Water vapor amounts in the upper troposphere are crucial to understanding the radiative feedback of cirrus clouds on the Earth’s climate. We use a unique, year-long dataset of water vapor mixing ratio inferred from ground-based Raman lidar measurements to study the role of ice supersaturation in ice nucleation processes. We find that ice supersaturation occurs 31% of the time in over 300,000 data points. We also examine the distribution of ice supersaturation with height and find that in the uppermost portion of a cloud layer, the air is ice supersaturated 43% of the time. These measurements show that large ice supersaturation is common in cirrus clouds, which supports the theory of ice forming homogeneously. Given the continuous nature of these Raman lidar measurements, our results have important implications for studying ice nucleation processes using cloud microphysical models.

  15. ARM Raman Lidar Measurements of High Ice Supersaturation in Cirrus Clouds

    Energy Technology Data Exchange (ETDEWEB)

    Comstock, Jennifer M.; Ackerman, Thomas P.; Turner, David D.

    2004-09-01

    Water vapor amounts in the upper troposphere are crucial to understanding the radiative feedback of cirrus clouds on the Earth's climate. We use a unique, year-long dataset of water vapor mixing ratio inferred from ground-based Raman lidar measurements to study the role of ice supersaturation in ice nucleation processes. We find that ice supersaturation occurs 31% of the time in over 300,000 data points. We also examine the distribution of ice supersaturation with height and find that in the uppermost portion of a cloud layer, the air is ice supersaturated 43% of the time. These measurements show that large ice supersaturation is common in cirrus clouds, which supports the theory of ice forming homogeneously. Given the continuous nature of these Raman lidar measurements, our results have important implications for studying ice nucleation processes using cloud microphysical models.

  16. Retrieval of subvisual cirrus cloud optical thickness from limb-scatter measurements

    Directory of Open Access Journals (Sweden)

    J. T. Wiensz

    2013-01-01

    Full Text Available We present a technique for estimating the optical thickness of subvisual cirrus clouds detected by OSIRIS (Optical Spectrograph and Infrared Imaging System, a limb-viewing satellite instrument that measures scattered radiances from the UV to the near-IR. The measurement set is composed of a ratio of limb radiance profiles at two wavelengths that indicates the presence of cloud-scattering regions. Cross-sections and phase functions from an in situ database are used to simulate scattering by cloud-particles. With appropriate configurations discussed in this paper, the SASKTRAN successive-orders of scatter radiative transfer model is able to simulate accurately the in-cloud radiances from OSIRIS. Configured in this way, the model is used with a multiplicative algebraic reconstruction technique (MART to retrieve the cloud extinction profile for an assumed effective cloud particle size. The sensitivity of these retrievals to key auxiliary model parameters is shown, and it is shown that the retrieved extinction profile, for an assumed effective cloud particle size, models well the measured in-cloud radiances from OSIRIS. The greatest sensitivity of the retrieved optical thickness is to the effective cloud particle size. Since OSIRIS has an 11-yr record of subvisual cirrus cloud detections, the work described in this manuscript provides a very useful method for providing a long-term global record of the properties of these clouds.

  17. Retrieval of Cirrus Cloud Optical Depth under Day and Night Conditions from MODIS Collection 6 Cloud Property Data

    Directory of Open Access Journals (Sweden)

    Andrew K. Heidinger

    2015-06-01

    Full Text Available This paper presents a technique to generate cirrus optical depth and particle effective size estimates from the cloud emissivities at 8.5, 11 and 12 μm contained in the Collection-6 (C6 MYD06 cloud product. This technique employs the latest scattering models and scattering radiative transfer approximations to estimate cloud optical depth and particle effective size using efficient analytical formulae. Two scattering models are tested. The first is the same scattering model as that used in the C6 MYD06 solar reflectance products. The second model is an empirical model derived from radiometric consistency. Both models are shown to generate optical depths that compare well to those from constrained CALIPSO retrievals and MYD06. In terms of effective radius retrievals, the results from the radiometric empirical model agree more closely with MYD06 than those from the C6 model. This analysis is applied to AQUA/MODIS data collocated with CALIPSO/CALIOP during January 2010.

  18. Dual-wavelength millimeter-wave radar measurements of cirrus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Sekelsky, S.M.; Firda, J.M.; McIntosh, R.E. [Univ. of Massachusetts, Amherst, MA (United States)

    1996-04-01

    In April 1994, the University of Massachusetts` 33-GHz/95-GHz Cloud Profiling Radar System (CPRS) participated in the multi-sensor Remote Cloud Sensing (RCS) Intensive Operation Period (IOP), which was conducted at the Southern Great Plains Cloud and Radiation Testbed (CART). During the 3-week experiment, CPRS measured a variety of cloud types and severe weather. In the context of global warming, the most significant measurements are dual-frequency observations of cirrus clouds, which may eventually be used to estimate ice crystal size and shape. Much of the cirrus data collected with CPRS show differences between 33-GHz and 95-GHz reflectivity measurements that are correlated with Doppler estimates of fall velocity. Because of the small range of reflectivity differences, a precise calibration of the radar is required and differential attenuation must also be removed from the data. Depolarization, which is an indicator of crystal shape, was also observed in several clouds. In this abstract we present examples of Mie scattering from cirrus and estimates of differential attenuation due to water vapor and oxygen that were derived from CART radiosonde measurements.

  19. Correlations among the Optical Properties of Cirrus-Cloud Particles: Microphysical Interpretation

    Science.gov (United States)

    Reichardt, J.; Reichardt, S.; Hess, M.; McGee, T. J.; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    Cirrus measurements obtained with a ground-based polarization Raman lidar at 67.9 deg N in January 1997 reveal a strong positive correlation between the particle optical properties, specifically depolarization ratio delta(sub par) and extinction- to-backscatter (lidar) ratio S, for delta(sub par) less than approximately 40%, and an anti-correlation for delta(sub par) greater than approximately 40%. Over the length of the measurements the particle properties vary systematically. Initially, delta (sub par) approximately equals 60% and S approximately equals 10sr are observed. Then, with decreasing delta(sub par), S first increases to approximately 27sr (delta(sub par) approximately equals 40%) before decreasing to values around 10sr again (delta(sub par) approximately equals 20%). The analysis of lidar humidity and radiosonde temperature data shows that the measured optical properties stem from scattering by dry solid ice particles, while scattering by supercooled droplets, or by wetted or subliming ice particles can be excluded. For the microphysical interpretation of the lidar measurements, ray-tracing computations of particle scattering properties have been used. The comparison with the theoretical data suggests that the observed cirrus data can be interpreted in terms of size, shape, and, under the assumption that the lidar measurements of consecutive cloud segments can be mapped on the temporal development of a single cloud parcel moving along its trajectory, growth of the cirrus particles: Near the cloud top in the early stage of cirrus development, light scattering by nearly isometric particles that have the optical characteristics of hexagonal columns (short, column-like particles) is dominant. Over time the ice particles grow, and as the cloud base height extends to lower altitudes characterized by warmer temperatures they become morphologically diverse. For large S and depolarization values of approximately 40%, the scattering contributions of column- and

  20. Cirrus clouds triggered by radiation, a multiscale phenomenon

    OpenAIRE

    2010-01-01

    In this study, the influence of radiative cooling and small eddies on cirrus formation is investigated. For this purpose the non-hydrostatic, anelastic model EULAG is used with a recently developed and validated ice microphysics scheme (Spichtinger and Gierens, 2009a). Additionally, we implemented a fast radiation transfer code (Fu et al., 1998). Using idealized profiles with high ice supersaturations up to 144% and weakly stable stratifications with Brunt-Vaisala frequencies down to 0....

  1. Daytime Land Surface Temperature Extraction from MODIS Thermal Infrared Data under Cirrus Clouds

    Directory of Open Access Journals (Sweden)

    Xiwei Fan

    2015-04-01

    Full Text Available Simulated data showed that cirrus clouds could lead to a maximum land surface temperature (LST retrieval error of 11.0 K when using the generalized split-window (GSW algorithm with a cirrus optical depth (COD at 0.55 μm of 0.4 and in nadir view. A correction term in the COD linear function was added to the GSW algorithm to extend the GSW algorithm to cirrus cloudy conditions. The COD was acquired by a look up table of the isolated cirrus bidirectional reflectance at 0.55 μm. Additionally, the slope k of the linear function was expressed as a multiple linear model of the top of the atmospheric brightness temperatures of MODIS channels 31–34 and as the difference between split-window channel emissivities. The simulated data showed that the LST error could be reduced from 11.0 to 2.2 K. The sensitivity analysis indicated that the total errors from all the uncertainties of input parameters, extension algorithm accuracy, and GSW algorithm accuracy were less than 2.5 K in nadir view. Finally, the Great Lakes surface water temperatures measured by buoys showed that the retrieval accuracy of the GSW algorithm was improved by at least 1.5 K using the proposed extension algorithm for cirrus skies.

  2. Cirrus cloud radiative forcing on surface-level shortwave and longwave irradiances at regional and global scale

    Science.gov (United States)

    Dupont, J. C.; Haeffelin, M.; Long, C. N.

    2009-04-01

    Cirrus clouds not only play a major role in the energy budget of the Earth-Atmosphere system, but are also important in the hydrological cycle. According to satellite passive remote sensing high-altitude clouds cover as much as 40% of the earth's surface on average and can reach 70% of cloud cover over the Tropics. Hence, given their very large cloud cover, the relatively small instantaneous radiative effects of these cirrus clouds can engender a significant cumulative radiative forcing at the surface. Precise calculations of the cirrus cloud radiative forcing are obtained from the difference between measured radiative fluxes downwelling at the surface in the presence of cirrus clouds (broadband flux measurements) and computed clear sky references (parametric models with RMS error water vapor content obtained in studying the 4 observatories allows us to quantify the combined influence of aerosol optical thickness and integrated water vapor on CRFSW* : 10 to 20 % CRFSW* range for turbid and pristine atmosphere. Moreover, the sensitivity of the CRFLW to both cloud emissivity and cloud temperature (noted CRFLW*) is established and the influence of integrated water vapor on CRFLW* quantified: partial infrared opacity for arctic site (dry atmosphere) and quasi-total infrared opacity for tropical site (wet atmosphere), respectively 20% and 97% of opacity. Cirrus cloud radiative forcing parameterizations are hence developed starting from the ground-based collocated measurements. They relate CRFSW or CRFLW to cirrus cloud macrophysical properties, atmospheric humidity, aerosol content and solar zenith angle. Satellite measurements are used next as input parameters to the cirrus cloud radiative forcing parameterizations to calculate CRFSW and CRFLW at global scale. CALIOP provide aerosol and cirrus cloud properties and AIRS the integrated water vapor. Meridian distribution are shown and discussed. They reveal a positive cirrus cloud net radiative effect (CRFSW + CRFLW) from

  3. The accommodation coefficient of water molecules on ice – cirrus cloud studies at the AIDA simulation chamber

    Directory of Open Access Journals (Sweden)

    J. Skrotzki

    2013-04-01

    Full Text Available Cirrus clouds and their impact on the Earth's radiative budget are subjects of current research. The processes governing the growth of cirrus ice particles are central to the radiative properties of cirrus clouds. At temperatures relevant to cirrus clouds, the growth of ice crystals smaller than a few microns in size is strongly influenced by the accommodation coefficient of water molecules on ice, αice, making this parameter relevant for cirrus cloud modeling. However, the experimentally determined magnitude of αice for cirrus temperatures is afflicted with uncertainties of almost three orders of magnitude, and values for αice derived from cirrus cloud data lack significance so far. This has motivated dedicated experiments at the cloud chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere to determine αice in the cirrus-relevant temperature interval between 190 K and 235 K under realistic cirrus ice particle growth conditions. The experimental data sets have been evaluated independently with two model approaches: the first relying on the newly developed model SIGMA (Simple Ice Growth Model for determining Alpha, the second one on an established model, ACPIM (Aerosol-Cloud-Precipitation Interaction Model. Within both approaches a careful uncertainty analysis of the obtained αice values has been carried out for each AIDA experiment. The results show no significant dependence of αice on temperature between 190 K and 235 K. In addition, we find no evidence for a dependence of αice on ice particle size or on water vapor supersaturation for ice particles smaller than 20 μm and supersaturations of up to 70%. The temperature-averaged and combined result from both models is αice = 0.7−0.5+0.3, which implies that αice may only exert a minor impact on cirrus clouds and their characteristics when compared to the assumption of αice =1. Impact on prior calculations of cirrus cloud properties, e.g., in climate models, with

  4. Radiative Effects on the Diffusional Growth of Ice Particles in Cirrus Clouds.

    Science.gov (United States)

    Wu, Ting; Cotton, William R.; Cheng, William Y. Y.

    2000-09-01

    At Colorado State University the Regional Atmospheric Modeling System (RAMS) has been used to study the radiative effect on the diffusional growth of ice particles in cirrus clouds. Using soundings extracted from a mesoscale simulation of the 26 November 1991 cirrus event, the radiative effect was studied using a two-dimensional cloud-resolving model (CRM) version of RAMS, coupled to an explicit bin-resolving microphysics.The CRM simulations of the 26 November 1991 cirrus event demonstrate that the radiative impact on the diffusional growth (or sublimation) of ice crystals is significant. Even in a radiatively cooled atmospheric environment, ice particles may experience radiative warming because the net radiation received by an ice particle depends upon the emission from the particle, and the local upwelling and downwelling radiative fluxes.Model results show that radiative feedbacks on the diffusional growth of ice particles can be very complex. Radiative warming of an ice particle will restrict the particle's diffusional growth. In the case of radiative warming, ice particles larger than a certain size will experience so much radiative warming that surface ice saturation vapor pressures become large enough to cause sublimation of the larger crystals, while smaller crystals are growing by vapor deposition. However, ice mass production can be enhanced in the case of radiative cooling of an ice particle. For the 26 November 1991 cirrus event, radiative feedback results in significant reduction in the total ice mass, especially in the production of large ice crystals, and consequently, both radiative and dynamic properties of the cirrus cloud are significantly affected.

  5. 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.

  6. Utilizing the MODIS 1.38 micrometer Channel for Cirrus Cloud Optical Thickness Retrievals: Algorithm and Retrieval Uncertainties

    Science.gov (United States)

    Meyer, Kerry; Platnick, Steven

    2010-01-01

    The cloud products from the Moderate Resolution Imaging Spectroradiometers (MODIS) on Terra and Aqua have been widely used within the atmospheric research community. The retrieval algorithms, however, oftentimes have difficulty detecting and retrieving thin cirrus, due to sensitivities to surface reflectance. Conversely, the 1.38 micron channel, located within a strong water vapor absorption band, is quite useful for detecting thin cirrus clouds since the signal from the surface can be blocked or substantially attenuated by the absorption of atmospheric water vapor below cirrus. This channel, however, suffers from nonnegligible attenuation due to the water vapor located above and within the cloud layer. Here we provide details of a new technique pairing the 1.38 micron and 1.24 micron channels to estimate the above/in-cloud water vapor attenuation and to subsequently retrieve thin cirrus optical thickness (tau) from attenuation-corrected 1.38 p.m reflectance measurements. In selected oceanic cases, this approach is found to increase cirrus retrievals by up to 38% over MOD06. For these cases, baseline 1.38 micron retrieval uncertainties are estimated to be between 15 and 20% for moderately thick cirrus (tau > 1), with the largest error source being the unknown cloud effective particle radius, which is not retrieved with the described technique. Uncertainties increase to around 90% for the thinnest clouds (tau < 0.5) where instrument and surface uncertainties dominate.

  7. Comparisons of cirrus cloud microphysical properties between polluted and pristine air

    Science.gov (United States)

    Diao, Minghui; Schumann, Ulrich; Minikin, Andreas; Jensen, Jorgen

    2015-04-01

    Cirrus clouds occur in the upper troposphere at altitudes where atmospheric radiative forcing is most sensitive to perturbations of water vapor concentration and water phase. The formation of cirrus clouds influences the distributions of water in both vapor and ice forms. The radiative properties of cirrus depend strongly on particle sizes. Currently it is still unclear how the formation of cirrus clouds and their microphysical properties are influenced by anthropogenic emissions (e.g., industrial emission and biomass burning). If anthropogenic emissions influence cirrus formation in a significant manner, then one should expect a systematic difference in cirrus properties between pristine (clean) air and polluted air. Because of the pollution contrasts between the Southern (SH) and Northern Hemispheres (NH), cirrus properties could have hemispheric differences as well. Therefore, we study high-resolution (~200 m), in-situ observations from two global flight campaigns: 1) the HIAPER Pole-to-Pole Observations (HIPPO) global campaign in 2009-2011 funded by the US National Science Foundation (NSF), and 2) the Interhemispheric Differences In Cirrus Properties from Anthropogenic Emissions (INCA) campaign in 2000 funded by the European Union and participating research institutions. To investigate the changes of cirrus clouds by anthropogenic emissions, we compare ice crystal distributions in polluted and pristine air, in terms of their frequency occurrence, number concentration (Nc) and mean diameter (i.e., effective-mean Deff and volume-mean Dc). Total aerosol concentration is used to represent the combined influence of natural and anthropogenic aerosols. In addition, measured carbon monoxide (CO) mixing ratio is used to discriminate between polluted and pristine air masses. All analyses are restricted to temperatures ≤ -40°C to exclude mixed-phased clouds. The HIPPO campaign observations were obtained over the North America continent and the central Pacific Ocean

  8. 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.

  9. Aerosol Particles From Tropical Cirrus Clouds in the Lower Stratosphere

    Science.gov (United States)

    Kojima, T.; Buseck, P. R.; Wilson, J. C.; Reeves, J. M.

    2002-12-01

    Aerosol samples were collected from convective systems and cirrus layers over Florida during the July 2002 CRYSTAL-FACE Mission. Particles between 0.02 and 700 \\micron were deposited directly onto TEM grids. Here we report preliminary results of the TEM study of particles collected near and above the tropopause. Most particles are sulfate droplets that range from 0.8 to 5 \\micron in diameter on the TEM grids. All have a characteristic appearance that consists of a main central particle (0.3 -1 \\micron) surrounded by many smaller satellite droplets. Their appearance suggests that the droplets were sulfuric acid partially neutralized with ammonium at the time of collection, with ammonium sulfate and bisulfate constituting the central particles (Bigg, 1975, 1980). The degree of ammoniation in individual droplets, which is indicated by the size of central particles relative to satellite ring diameter, is fairly uniform. The ratio of central particle diameter to satellite ring diameter is generally around 0.3. Such ammoniated droplets with solid cores may be more efficient in nucleating cirrus than pure sulfuric acid droplets (Tabazadeh and Toon, 1998). Ammonium sulfate particles without satellites commonly coexist with the acid droplets. Minor particles consist of C-rich amorphous material, silicates, Na- and K-chlorides and sulfates, and Cr- and Ti-oxides. Some were coated with sulfate. Many of the C-rich particles contain significant amount of K, S, and O with lesser N. All silicate particles are flakes of clay minerals that have pseudohexagonal structures. They would work as effective ice nuclei (Pruppacher and Klett, 1997).

  10. Cloud chamber experiments on the origin of ice crystal complexity in cirrus clouds

    National Research Council Canada - National Science Library

    Valery N Shcherbakov; Carl G Schmitt; Andrew J Heymsfield

    2016-01-01

    ...) cloud chamber of the Karlsruhe Institute of Technology (KIT). A new experimental procedure was applied to grow and sublimate ice particles at defined super- and subsaturated ice conditions and for temperatures in the -40 to -60-°C range...

  11. Retrieving Microphysical Properties and Air Motion of Cirrus Clouds Based on the Doppler Moments Method Using Cloud Radar

    Institute of Scientific and Technical Information of China (English)

    ZHONG Lingzhi; LIU Liping; DENG Min; ZHOU Xiuji

    2012-01-01

    Radar parameters including radar reflectivity,Doppler velocity,and Doppler spectrum width were obtained from Doppler spectrum moments.The Doppler spectrum moment is the convolution of both the particle spectrum and the mean air vertical motion.Unlike strong precipitation,the motion of particles in cirrus clouds is quite close to the air motion around them.In this study,a method of Doppler moments was developed and used to retrieve cirrus cloud microphysical properties such as the mean air vertical velocity,mass-weighted diameter,effective particle size,and ice content. Ice content values were retrieved using both the Doppler spectrum method and classic Z-IWC (radar reflectivity-ice water content) relationships;however,the former is a more reasonable method.

  12. Cirrus microphysics and radiative transfer - Cloud field study on 28 October 1986

    Science.gov (United States)

    Kinne, Stefan; Ackerman, Thomas P.; Heymsfield, Andrew J.; Valero, Francisco P. J.; Sassen, Kenneth; Spinhirne, James D.

    1992-01-01

    An analysis of remote-sensing measurements which had detected an inhomogeneous cloud structure, at 6-11 km altitude, in the data acquired during the FIRE 86 experiment in a 75 x 50 km cirrus cloud field, has derived fluxes whose comparison with modeled fluxes imply a modeling-based underestimation of both solar reflectivity/attenuation and downward IR fluxes. Reconciliation of model results with measurements can be achieved either by adding large concentrations of ice crystals or by altering the backscattering properties of ice crystals.

  13. Influence of heterogeneous freezing on the microphysical and radiative properties of orographic cirrus clouds

    Directory of Open Access Journals (Sweden)

    H. Joos

    2013-07-01

    Full Text Available The influence of heterogeneous freezing on the microphysical and optical properties of orographic cirrus clouds has been simulated with the cloud resolving model EULAG. Idealized simulations with different concentrations of ice nuclei (IN in a dynamically dominated regime with high vertical velocities have been performed. Furthermore the temperature under which the cloud forms as well as the critical supersaturation which is needed for the initiation of heterogenoues freezing have been varied. The short wave, long wave and net cloud forcing has been calculated under the assumption that the clouds form between 06:00 and 12:00 LT or between 12:00 and 18:00 LT, respectively. In general it can be seen that the onset of homogeneous freezing is shifted in time depending on the IN concentration as part of the available water vapor is depleted before the critical threshold for homogeneous freezing is reached. Although the high vertical velocities in an orographic gravity wave lead to a strong adiabatic cooling followed by high ice supersaturations, a small number concentration of IN in the order of 5 L−1 is already able to strongly decrease the simulated ice crystal number burden (ICNB, ice water path (IWP and optical depth of the cloud. In general, the ICNB, IWP and optical depth strongly decrease when the IN concentrations are increased from 0 to 50 L−1. The absolute values of the short wave, long wave and net cloud forcing are also reduced with increasing IN concentrations. If a cloud produces a net warming or cooling depends on the IN concentration, the temperature and the time of day at which the cloud forms. The clouds that form between 06:00 and 12:00 LT are mainly cooling whereas the clouds with the same microphysical properties can lead to a warming when they form between 12:00 and 18:00 LT. In order to predict the radiative forcing of cirrus clouds it is therefore necessary to take the correct dynamical and thermodynamical processes as

  14. Comparisons of cirrus cloud formation and evolution lifetime between five field campaigns

    Science.gov (United States)

    Diao, M.; Zondlo, M. A.; DiGangi, J. P.; O'Brien, A.; Heymsfield, A.; Rogers, D. C.; Beaton, S. P.

    2013-12-01

    In order to understand the microphysical properties of cirrus clouds, it is important to understand the formation and evolution of the environments where ice crystals form and reside on the microscale (~100 m). Uncertainties remain in simulating/parameterizing the evolution of ice crystals, which require more analyses in the Lagrangian view. However, most in situ observations are in the Eulerian view and are restricted from examining the lifecycle of cirrus clouds. In this work, a new method of Diao et al. GRL (2013)* is used to separate out five phases of ice crystal evolution, using the horizontal spatial relationships between ice supersaturated regions (ISSRs) and ice crystal regions (ICRs). In-situ, aircraft-based observations from five flight campaigns are used to compare the evolution processes of ISSRs and ICRs, which include the National Science Foundation HIAPER Pole-to-Pole Observations (HIPPO) Global campaign (2009-2011 Arctic to Antarctic over the central Pacific Ocean), the Stratosphere Troposphere Analyses Regional Transport 2008 (START08) campaign (2008 North America), the Pre-Depression Investigation of Cloud-Systems in the Tropics (PREDICT) campaign (2010 tropical western Atlantic), the Tropical Ocean Troposphere Exchange of Reactive Halogen Species and Oxygenated VOC (2012 Costa Rica), and the Deep Convection, Clouds, and Chemistry (DC3) campaign (2011 Interior North America). To understand the evolution of ICRs and ISSRs on the microscale, we compare the microphysical evolution processes inside ISSRs and ICRs in terms of relative humidity with respect to ice (RHi), ice crystal mean diameter (Dc) and ice crystal number density (Nc) at different meteorological and dynamical backgrounds during these five campaigns. Different phases of ice nucleation and evolution are contrasted to understand how cirrus clouds evolve from clear-sky ISS into fully developed clouds, and finally into sedimentation/evaporation phase. The results show that the ratios of

  15. Vertical Sizing of Cirrus Clouds using the 1.38 μm Spectral Lines and MODIS Data

    Science.gov (United States)

    Wang, X.; Liou, K.; Ou, S.

    2006-12-01

    Atmospheric albedo and heating rates in cloudy conditions are dependent on the vertical inhomogeneity of clouds. For example, small ice crystal sizes aloft coupled with larger sizes at the cloud base would reflect more solar radiation as compared to the use of an averaged ice crystal size for the same cloud. Significant variability of the heating rate also occurs in association with vertical inhomogeneity. In situ measurements from the airborne optical probe, replicator, and cloud scope clearly illustrate the vertical distribution of ice crystal size and shape. We have developed an approach to infer the vertical profile of mean effective particle size on the basis of the spectral line reflectance of the 1.38 μm water vapor band. In it, seventeen narrow bands of various water vapor absorption strengths have been selected. The physical principle for this approach is based on the fact that the reflectance in strong absorptive wavelengths is most sensitive to cloud top properties, whereas the reflectance in less absorptive wavelengths senses the microphysical properties deeper into the cloud. To test this concept, we have prescribed several cloud vertical structures and used an adding-doubling radiative transfer program coupled with the correlated k-distribution method to calculate the look-up tables of reflectance for a variety of cloud settings. We show some success of hypothetical retrieval exercises by applying a χ2 minimization principle. The vertical sizing idea described above has been applied to the MODIS visible and three near-IR channels and we demonstrate that it is possible to derive two vertical ice crystal sizes from a combination of these channels. For validation purposes, we have selected a number of cirrus scenes over the ARM Southern Great Plain site and compared the retrieved vertical ice crystal sizes with the ground-based cloud radar retrieval values. The vertical sizing results determined from the 1.38 μm spectral lines and MODIS data will be

  16. 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

  17. Optical remote measurement of ozone in cirrus clouds; Optische Fernmessung von Ozon in Zirruswolken

    Energy Technology Data Exchange (ETDEWEB)

    Reichardt, J. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Physikalische und Chemische Analytik

    1998-12-31

    The subject of this thesis is theoretical and experimental investigations into the simultaneous optical remote measurement of atmospheric ozone concentration and particle properties. A lidar system was developed that combines the Raman-lidar and the polarization-lidar with the Raman-DIAL technique. An error analysis is given for ozone measurements in clouds. It turns out that the wavelength dependencies of photon multiple scattering and of the particle extinction coefficient necessitate a correction of the measured ozone concentration. To quantify the cloud influence, model calculations based on particle size distributions of spheres are carried out. The most important experimental result of this thesis is the measured evidence of pronounced minima in the ozone distribution in a humid upper troposphere shortly before and during cirrus observation. Good correlation between ozone-depleted altitude ranges and ice clouds is found. This finding is in contrast to ozone profiles measured in a dry and cloud-free troposphere. (orig.) 151 refs.

  18. A Simple Framework for the Dynamic Response of Cirrus Clouds to Local Diabatic Radiative Heating

    CERN Document Server

    Schmidt, C T

    2012-01-01

    This paper presents a simple analytical framework for the dynamic response of cirrus to a local radiative flux convergence, expressible in terms of three independent modes of cloud evolution. Horizontally narrow and tenuous clouds within a stable environment adjust to radiative heating by ascending gradually across isentropes while spreading sufficiently fast so as to keep isentropic surfaces nearly flat. More optically dense clouds experience very concentrated heating, and if they are also very broad, they develop a convecting mixed layer. Along isentropic spreading still occurs, but in the form of turbulent density currents rather than laminar flows. A third adjustment mode relates to evaporation, which erodes cloudy air as it lofts. The dominant mode is determined from two dimensionless numbers, whose predictive power is shown in comparisons with high resolution numerical cloud simulations. The power and simplicity of the approach hints that fast, sub-grid scale radiative-dynamic atmospheric interactions m...

  19. Ice nucleation and cloud microphysical properties in tropical tropopause layer cirrus

    Directory of Open Access Journals (Sweden)

    E. J. Jensen

    2009-10-01

    Full Text Available In past modeling studies, it has generally been assumed that the predominant mechanism for nucleation of ice in the uppermost troposphere is homogeneous freezing of aqueous aerosols. However, recent in situ and remote-sensing measurements of the properties of cirrus clouds at very low temperatures in the tropical tropopause layer (TTL are broadly inconsistent with theoretial predictions based on the homogeneous freezing assumption. The nearly ubiquitous occurence of gravity waves in the TTL makes the predictions from homogeneous nucleation theory particularly difficult to reconcile with measurements. These measured properties include ice number concentrations, which are much lower than theory predicts; ice crystal size distributions, which are much broader than theory predicts; and cloud extinctions, which are much lower than theory predicts. Although other explanations are possible, one way to limit ice concentrations is to have on the order of 50 L−1 effective ice nuclei (IN that could nucleate ice at relatively low supersaturations. We suggest that ammonium sulfate particles, which would be dry much of the time in the cold TTL, are a potential IN candidate for TTL cirrus. Possible implications of the observed cloud microphysical properties for ice sedimentation, dehydration, and cloud persistence are also discussed.

  20. Ice nucleation and cloud microphysical properties in tropical tropopause layer cirrus

    Directory of Open Access Journals (Sweden)

    E. J. Jensen

    2010-02-01

    Full Text Available In past modeling studies, it has generally been assumed that the predominant mechanism for nucleation of ice in the uppermost troposphere is homogeneous freezing of aqueous aerosols. However, recent in situ and remote-sensing measurements of the properties of cirrus clouds at very low temperatures in the tropical tropopause layer (TTL are broadly inconsistent with theoretial predictions based on the homogeneous freezing assumption. The nearly ubiquitous occurence of gravity waves in the TTL makes the predictions from homogeneous nucleation theory particularly difficult to reconcile with measurements. These measured properties include ice number concentrations, which are much lower than theory predicts; ice crystal size distributions, which are much broader than theory predicts; and cloud extinctions, which are much lower than theory predicts. Although other explanations are possible, one way to limit ice concentrations is to have on the order of 50 L−1 effective ice nuclei (IN that could nucleate ice at relatively low supersaturations. We suggest that ammonium sulfate particles, which would be dry much of the time in the cold TTL, are a potential IN candidate for TTL cirrus. However, this mechanism remains to be fully quantified for the size distribution of ammonium sulfate (possibly internally mixed with organics actually present in the upper troposphere. Possible implications of the observed cloud microphysical properties for ice sedimentation, dehydration, and cloud persistence are also discussed.

  1. On the origin of subvisible cirrus clouds in the tropical upper troposphere

    Directory of Open Access Journals (Sweden)

    M. Reverdy

    2012-12-01

    Full Text Available Spaceborne lidar observations have recently revealed a previously undetected significant population of Subvisible Cirrus (SVC. We show them to be colder than −74 °, with an optical depth below 0.0015 on average. The formation and persistence over time of this new cloud population could be related to several atmospheric phenomena. In this paper, we investigate if these clouds follow the same formation mechanisms as the general tropical cirrus population (including convection and in-situ ice nucleation, or if specific nucleation sites and trace species play a role in their formation. The importance of three scenarios in the formation of the global SVC population is investigated through different approaches that include comparisons with data imaging from several spaceborne instruments and back-trajectories that document the history and behavior of air masses leading to the point in time and space where subvisible cirrus were detected. In order to simplify the study of their formation, we singled out SVC with coherent temperature histories (mean variance lower than 4 K according to back-trajectories along 5, 10 or 15 days (respectively 58, 25 and 11% of SVC. Our results suggest that external processes, including local increases in liquid and hygroscopic aerosol concentration (either through biomass burning or volcanic injection forming sulfate-based aerosols in the troposphere or the stratosphere have very limited short-term or mid-term impact on the SVC population. On the other hand, we find that ~20% of air masses leading to SVC formation interacted with convective activity 5 days before they led to cloud formation and detection, a number that climbs to 60% over 15 days. SVC formation appears especially linked to convection over Africa and Central America, more so during JJA than DJF. These results support the view that the SVC population observed by CALIOP is an extension of the general upper tropospheric ice clouds population with its extreme

  2. The vertical distribution of aerosols, Saharan dust and cirrus clouds in Rome (Italy in the year 2001

    Directory of Open Access Journals (Sweden)

    G. P. Gobbi

    2004-01-01

    Full Text Available A set of 813 lidar profiles of tropospheric aerosol and cirrus clouds extinction and depolarization observed in Rome, Italy, between February 2001 and February 2002 is analyzed and discussed. The yearly record reveals a meaningful contribution of both cirrus clouds (38% and Saharan dust (12% to the total optical thickness (OT of 0.26, at 532nm. Seasonal analysis shows the planetary boundary layer (PBL aerosols to be confined below 2km in winter and 3.8km in summer, with relevant OT shifting from 0.08 to 0.16, respectively. Cirrus clouds maximise in spring and autumn, in both cases with average OT similar to the PBL aerosols one. With the exception of winter months, Saharan dust is found to represent an important third layer mostly residing between PBL aerosols and cirrus clouds, with yearly average OT0.03. Saharan dust and cirrus clouds were detected in 20% and in 45% of the observational days, respectively. Validation of the lidar OT retrievals against collocated sunphotometer observations show very good agreement. These results represent one of the few yearly records of tropospheric aerosol vertical profiles available in the literature.

  3. On the origin of subvisible cirrus clouds in the tropical upper troposphere

    Directory of Open Access Journals (Sweden)

    M. Reverdy

    2012-06-01

    Full Text Available Spaceborne lidar observations have recently revealed a previously undetected significant population of SubVisible Cirrus (SVC. We show them to be colder than −74 °C, with an optical depth below 0.0015 on average. The formation and persistence over time of this new cloud population could be related to several atmospheric phenomena. In this paper, we investigate the importance of external processes in the creation of this cloud population, vs. the traditional ice cloud formation theory through convection. The importance of three scenarios in the formation of the global SVC population is investigated through different approaches that include comparisons with data imaging from several spaceborne instruments and back-trajectories that document the history and behavior of air masses leading to a point in time and space where subvisible cirrus were detected. In order simplify the study of cloud formation processes, we singled out SVC with coherent temperature histories (mean variance lower than 4 K according to back-trajectories along 5, 10 or 15 days (respectively 58, 25 and 11% of SVC. Our results suggest that external processes, including local increases in liquid and hygroscopic aerosol concentration (either through biomass burning or volcanic injection forming sulfate-based aerosols in the troposphere or the stratosphere have no noticeable short-term or mid-term impact on the SVC population. On the other hand, we find that ~60% of air masses interacted with convective activity in the days before they led to cloud formation and detection, which correspond to 37 to 65% of SVC. These results put forward the important influence of classical cloud formation processes compared to external influences in forming SVC. They support the view that the SVC population observed by CALIOP is an extension of the general upper tropospheric ice clouds population with its extreme thinness as its only differentiating factor.

  4. Cloud chamber experiments on the origin of ice crystal complexity in cirrus clouds

    National Research Council Canada - National Science Library

    M. Schnaiter; E. Järvinen; P. Vochezer; A. Abdelmonem; R. Wagner; O. Jourdan; G. Mioche; V. N. Shcherbakov; C. G. Schmitt; U. Tricoli; Z. Ulanowski; A. J. Heymsfield

    2015-01-01

    ...) cloud chamber of the Karlsruhe Institute of Technology (KIT). A new experimental procedure was applied to grow and sublimate ice particles at defined super- and subsaturated ice conditions and for temperatures in the −40 to −60 °C range...

  5. Lidar Observations of Tropical High-altitude Cirrus Clouds: Results form Dual Wavelength Raman Lidar Measurements During the ALBATROSS Campaign 1996

    Science.gov (United States)

    Neuber, R.; Wegener, Alfred; Schrems, O.; McDermid, I. S.

    1997-01-01

    Results from dual wavelength Raman Lidar Observations of tropical high-altitude cirrus clouds are reported. Based on 107 hours of night-time measurements cirrus cloud were present in more than 50% of the observations at latitudes between 23.5 degress S and 23.5 degrees N and altitudes between 11 and 16km.

  6. Lidar Observations of Tropical High-altitude Cirrus Clouds: Results form Dual Wavelength Raman Lidar Measurements During the ALBATROSS Campaign 1996

    Science.gov (United States)

    Neuber, R.; Wegener, Alfred; Schrems, O.; McDermid, I. S.

    1997-01-01

    Results from dual wavelength Raman Lidar Observations of tropical high-altitude cirrus clouds are reported. Based on 107 hours of night-time measurements cirrus cloud were present in more than 50% of the observations at latitudes between 23.5 degress S and 23.5 degrees N and altitudes between 11 and 16km.

  7. Insights into the role of soot aerosols in cirrus cloud formation

    Directory of Open Access Journals (Sweden)

    B. Kärcher

    2007-08-01

    Full Text Available Cirrus cloud formation is believed to be dominated by homogeneous freezing of supercooled liquid aerosols in many instances. Heterogeneous ice nuclei such as mineral dust, metallic, and soot particles, and some crystalline solids within partially soluble aerosols are suspected to modulate cirrus properties. Among those, the role of ubiquitous soot particles is perhaps the least understood. Because aviation is a major source of upper tropospheric soot particles, we put emphasis on ice formation in dispersing aircraft plumes. The effect of aircraft soot on cirrus formation in the absence of contrails is highly complex and depends on a wide array of emission and environmental parameters. We use a microphysical-chemical model predicting the formation of internally mixed, soot-containing particles up to two days after emission, and suggest two principal scenarios: high concentrations of original soot emissions could slightly increase the number of ice crystals; low concentrations of particles originating from coagulation of emitted soot with background aerosols could lead to a significant reduction in ice crystal number. Both scenarios assume soot particles to be moderate ice nuclei relative to cirrus formation by homogeneous freezing in the presence of few efficient dust ice nuclei. A critical discussion of laboratory experiments reveals that the ice nucleation efficiency of soot particles depends strongly on their source, and, by inference, on atmospheric aging processes. Mass and chemistry of soluble surface coatings appear to be crucial factors. Immersed soot particles tend to be poor ice nuclei, some bare ones nucleate ice at low supersaturations. However, a fundamental understanding of these studies is lacking, rendering extrapolations to atmospheric conditions speculative. In particular, we cannot yet decide which indirect aircraft effect scenario is more plausible, and options suggested to mitigate the problem remain uncertain.

  8. Insights into the role of soot aerosols in cirrus cloud formation

    Directory of Open Access Journals (Sweden)

    B. Kärcher

    2007-06-01

    Full Text Available Cirrus cloud formation is believed to be domi-nated by homogeneous freezing of supercooled liquid aerosols in many instances. Heterogeneous ice nuclei such as mineral dust, metallic, and soot particles, and some crystalline solids within partially soluble aerosols are suspected to modulate cirrus properties. Among those, the role of ubiqui-tous soot particles is perhaps the least understood. Because aviation is a major source of upper tropospheric soot particles, we put emphasis on ice formation in dispersing aircraft plumes. The effect of aircraft soot on cirrus formation in the absence of contrails is highly complex and depends on a wide array of emission and environmental parameters. We use a microphysical-chemical model predicting the formation of internally mixed, soot-containing particles up to two days after emission, and suggest two principal scenarios, both assuming soot particles to be moderate ice nuclei relative to cirrus formation by homogeneous freezing in the presence of few efficient dust ice nuclei: high concentrations of original soot emissions could slightly increase the number of ice crystals; low concentrations of particles originating from coagulation of emitted soot with background aerosols could lead to a significant reduction in ice crystal number. A critical discussion of laboratory experiments reveals that the ice nucleation efficiency of soot particles depends strongly on their source, and, by inference, on atmospheric aging processes. Mass and chemistry of soluble surface coatings appear to be crucial factors. Immersed soot particles tend to be poor ice nuclei, some bare ones nucleate ice at low supersaturations. However, a fundamental understanding of these studies is lacking, rendering extrapolations to atmospheric conditions speculative. In particular, we cannot yet decide which indirect aircraft effect scenario is more plausible, and options suggested to mitigate the problem remain uncertain.

  9. A new retrieval method for the ice water content of cirrus using data from the CloudSat and CALIPSO

    Science.gov (United States)

    Pan, Honglin; Bu, Lingbing; Kumar, K. Raghavendra; Gao, Haiyang; Huang, Xingyou; Zhang, Wentao

    2017-08-01

    The CloudSat and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) are the members of satellite observation system of A-train to achieve the quasi-synchronization observation on the same orbit. With the help of active (CALIOP and CPR) and passive payloads from these two satellites, respectively, unprecedented detailed information of microphysical properties of ice cloud can be retrieved. The ice water content (IWC) is regarded as one of the most important microphysical characteristics of cirrus for its prominent role in cloud radiative forcing. In this paper, we proposed a new joint (Combination) retrieval method using the full advantages of different well established retrieval methods, namely the LIDAR method (for the region Lidar-only), the MWCR method (for the region Radar-only), and Wang method (for the region Lidar-Radar) proposed by Wang et al. (2002). In retrieval of cirrus IWC, empirical formulas of the exponential type were used for both thinner cirrus (detected by Lidar-only), thicker cirrus (detected by radar-only), and the part of cirrus detected by both, respectively. In the present study, the comparison of various methods verified that our proposed new joint method is more comprehensive, rational and reliable. Further, the retrieval information of cirrus is complete and accurate for the region that Lidar cannot penetrate and Radar is insensitive. On the whole, the retrieval results of IWC showed certain differences retrieved from the joint method, Ca&Cl, and ICARE which can be interpreted from the different hypothesis of microphysical characteristics and parameters used in the retrieval method. In addition, our joint method only uses the extinction coefficient and the radar reflectivity factor to calculate the IWC, which is simpler and reduces to some extent the accumulative error. In future studies, we will not only compare the value of IWC but also explore the detailed macrophysical and microphysical characteristics of

  10. The Polarization Signature of Cirrus Clouds At Mm and Sub-mm Wavelength: Effect of Particle Size, Shape, and Orientation

    Science.gov (United States)

    Miao, J.

    Cirrus clouds can be found globally from the tropics to polar regions in the upper troposphere and lower stratosphere. They are composed primarily of ice crystals in various shapes, with or without preferred orientation. Research shows that they have significant effects on the radiation budget of the Earth, on the water budget of the atmosphere, and therefore on the global climate. Information on the microphysical parameters of cirrus clouds is crucial to the understanding of the cirrus clouds impact on our climate. Recent work in both simulations and measurements has demonstrated the usefulness of passive millimeter and sub-millimeter radiometric measurements from space in determining cirrus cloud parameters such as the integrated ice water content (or ice water path) and the characteristic size of ice particles. However, these studies were mainly concerned with the information content of the radiometric inten- sity measurements, albeit some brief discussions on the potential of the polarization measurements were given in some literature. Frankly speaking, there is a shortage of systematic studies on the polarization signature from cirrus clouds at the millimeter and sub-millimeter wavelengths, i.e., how the polarization difference measured at two orthogonal polarizations is related to the ice particle size, the shape, and the orienta- tion. Here we present some results of a systematic analysis on the polarization effect of non-spherical ice particles. Three types of particles are considered: nearly spherical, cylindrical, and plate-like particles. Studies are carried out at the following 7 frequen- cies: 90, 157, 220, 340, 463, 683, and 874 GHz. Among these frequencies some (e.g. 90, 157, 220, and 340 GHz) have been tested in space-borne or air-borne sensors and some (e.g. 463, 683, and 874 GHz) are proved by simulations to be well suited for cirrus clouds measurements and therefore planned currently for a future satellite mis- sion.

  11. The Prevalence of the 22 deg Halo in Cirrus Clouds

    Science.gov (United States)

    Diedenhoven, vanBastiaan

    2014-01-01

    Halos at 22 deg from the sun attributed to randomly-orientated, pristine hexagonal crystals are frequently observed through ice clouds. These frequent sightings of halos formed by pristine crystals pose an apparent inconsistency with the dominance of distorted, nonpristine ice crystals indicated by in situ and remote sensing data. Furthermore, the 46 deg halo, which is associated with pristine hexagonal crystals as well, is observed far less frequently than the 22 deg halo. Considering that plausible mechanisms that could cause crystal distortion such as aggregation, sublimation, riming and collisions are stochastic processes that likely lead to distributions of crystals with varying distortion levels, here the presence of the 22 deg and 46 deg halo features in phase functions of mixtures of pristine and distorted hexagonal ice crystals is examined. We conclude that the 22 deg halo feature is generally present if the contribution by pristine crystals to the total scattering cross section is greater than only about 10% in the case of compact particles or columns, and greater than about 40% for plates. The 46 deg halo feature is present only if the mean distortion level is low and the contribution of pristine crystals to the total scattering cross section is above about 20%, 50% and 70%, in the case of compact crystals, plates and columns, respectively. These results indicate that frequent sightings of 22 deg halos are not inconsistent with the observed dominance of distorted, non-pristine ice crystals. Furthermore, the low mean distortion levels and large contributions by pristine crystals needed to produce the 461 halo features provide a potential explanation of the common sighting of the 22 deg halo without any detectable 46 deg halo.

  12. Investigation on the monthly variation of cirrus optical properties over the Indian subcontinent using cloud-aerosol lidar and infrared pathfinder satellite observation (Calipso)

    Science.gov (United States)

    Dhaman, Reji K.; Satyanarayana, Malladi; Jayeshlal, G. S.; Mahadevan Pillai, V. P.; Krishnakumar, V.

    2016-05-01

    Cirrus clouds have been identified as one of the atmospheric component which influence the radiative processes in the atmosphere and plays a key role in the Earth Radiation Budget. CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) is a joint NASA-CNES satellite mission designed to provide insight in understanding of the role of aerosols and clouds in the climate system. This paper reports the study on the variation of cirrus cloud optical properties of over the Indian sub - continent for a period of two years from January 2009 to December 2010, using cloud-aerosol lidar and infrared pathfinder satellite observations (Calipso). Indian Ocean and Indian continent is one of the regions where cirrus occurrence is maximum particularly during the monsoon periods. It is found that during the south-west monsoon periods there is a large cirrus cloud distribution over the southern Indian land masses. Also it is observed that the north-east monsoon periods had optical thick clouds hugging the coast line. The summer had large cloud formation in the Arabian Sea. It is also found that the land masses near to the sea had large cirrus presence. These cirrus clouds were of high altitude and optical depth. The dependence of cirrus cloud properties on cirrus cloud mid-cloud temperature and geometrical thickness are generally similar to the results derived from the ground-based lidar. However, the difference in macrophysical parameter variability shows the limits of space-borne-lidar and dissimilarities in regional climate variability and the nature and source of cloud nuclei in different geographical regions.

  13. Cirrus Crystal Terminal Velocities.

    Science.gov (United States)

    Heymsfield, Andrew J.; Iaquinta, Jean

    2000-04-01

    Cirrus crystal terminal velocities are of primary importance in determining the rate of transport of condensate from upper- to middle-tropospheric levels and profoundly influence the earth's radiation balance through their effect on the rate of buildup or decay of cirrus clouds. In this study, laboratory and field-based cirrus crystal drag coefficient data, as well as analytical descriptions of cirrus crystal shapes, are used to derive more physically based expressions for the velocities of cirrus crystals than have been available in the past.Polycrystals-often bullet rosettes-are shown to be the dominant crystal types in synoptically generated cirrus, with columns present in varying but relatively large percentages, depending on the cloud. The two critical parameters needed to calculate terminal velocity are the drag coefficient and the ratio of mass to cross-sectional area normal to their fall direction. Using measurements and calculations, it is shown that drag coefficients from theory and laboratory studies are applicable to crystals of the types found in cirrus. The ratio of the mass to area, which is shown to be relatively independent of the number of bullets in the rosette, is derived from an analytic model that represents bullet rosettes containing one to eight bullets in 19 primary geometric configurations. The ratio is also derived for columns. Using this information, a general set of equations is developed to calculate the terminal velocities and masses in terms of the aspect ratio (width divided by length), ice density, and rosette maximum dimension. Simple expressions for terminal velocity and mass as a function of bullet rosette maximum dimension are developed by incorporating new information on bullet aspect ratios.The general terminal velocity and mass relations are then applied to a case from the First International Satellite Cloud Climatology Project (ISCCP) Research Experiment (FIRE) 2, when size spectra from a balloon-borne ice crystal

  14. 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.

  15. Influence of aerosols and thin cirrus clouds on the GOSAT-observed CO2: a case study over Tsukuba

    Directory of Open Access Journals (Sweden)

    A. Bril

    2011-11-01

    Full Text Available Lidar observations of vertical profiles of aerosols and thin cirrus clouds were made at Tsukuba (36.1° N, 140.1° E, Japan, to investigate the influence of aerosols and thin cirrus clouds on the column-averaged dry-air mole fraction of carbon dioxide (XCO2 retrieved from observation data of the Thermal And Near-infrared Sensor for carbon Observation Fourier Transform Spectrometer, measured in the Short-Wavelength InfraRed band (TANSO-FTS SWIR, onboard the Greenhouse gases Observing SATellite (GOSAT. The lidar system measured the backscattering ratio, depolarization ratio, and/or the wavelength exponent of atmospheric particles. The lidar observations and ground-based high-resolution FTS measurements at the Tsukuba Total Carbon Column Observing Network (Tsukuba TCCON site were recorded simultaneously during passages of GOSAT over Tsukuba. GOSAT SWIR XCO2 data (version 01.xx released in August 2010 were compared with the lidar and Tsukuba TCCON data. High-altitude aerosols and thin cirrus clouds had a large impact on the GOSAT SWIR XCO2 results. By taking into account the observed aerosol/cirrus vertical profiles and using a more adequate solar irradiance database in the GOSAT SWIR retrieval, the difference between the GOSAT SWIR XCO2 data and the Tsukuba TCCON data was greatly reduced.

  16. Ice crystal characterization in cirrus clouds: a sun-tracking camera system and automated detection algorithm for halo displays

    Science.gov (United States)

    Forster, Linda; Seefeldner, Meinhard; Wiegner, Matthias; Mayer, Bernhard

    2017-07-01

    Halo displays in the sky contain valuable information about ice crystal shape and orientation: e.g., the 22° halo is produced by randomly oriented hexagonal prisms while parhelia (sundogs) indicate oriented plates. HaloCam, a novel sun-tracking camera system for the automated observation of halo displays is presented. An initial visual evaluation of the frequency of halo displays for the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign from October to mid-November 2014 showed that sundogs were observed more often than 22° halos. Thus, the majority of halo displays was produced by oriented ice crystals. During the campaign about 27 % of the cirrus clouds produced 22° halos, sundogs or upper tangent arcs. To evaluate the HaloCam observations collected from regular measurements in Munich between January 2014 and June 2016, an automated detection algorithm for 22° halos was developed, which can be extended to other halo types as well. This algorithm detected 22° halos about 2 % of the time for this dataset. The frequency of cirrus clouds during this time period was estimated by co-located ceilometer measurements using temperature thresholds of the cloud base. About 25 % of the detected cirrus clouds occurred together with a 22° halo, which implies that these clouds contained a certain fraction of smooth, hexagonal ice crystals. HaloCam observations complemented by radiative transfer simulations and measurements of aerosol and cirrus cloud optical thickness (AOT and COT) provide a possibility to retrieve more detailed information about ice crystal roughness. This paper demonstrates the feasibility of a completely automated method to collect and evaluate a long-term database of halo observations and shows the potential to characterize ice crystal properties.

  17. Ice crystal characterization in cirrus clouds: a sun-tracking camera system and automated detection algorithm for halo displays

    Directory of Open Access Journals (Sweden)

    L. Forster

    2017-07-01

    Full Text Available Halo displays in the sky contain valuable information about ice crystal shape and orientation: e.g., the 22° halo is produced by randomly oriented hexagonal prisms while parhelia (sundogs indicate oriented plates. HaloCam, a novel sun-tracking camera system for the automated observation of halo displays is presented. An initial visual evaluation of the frequency of halo displays for the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques field campaign from October to mid-November 2014 showed that sundogs were observed more often than 22° halos. Thus, the majority of halo displays was produced by oriented ice crystals. During the campaign about 27 % of the cirrus clouds produced 22° halos, sundogs or upper tangent arcs. To evaluate the HaloCam observations collected from regular measurements in Munich between January 2014 and June 2016, an automated detection algorithm for 22° halos was developed, which can be extended to other halo types as well. This algorithm detected 22° halos about 2 % of the time for this dataset. The frequency of cirrus clouds during this time period was estimated by co-located ceilometer measurements using temperature thresholds of the cloud base. About 25 % of the detected cirrus clouds occurred together with a 22° halo, which implies that these clouds contained a certain fraction of smooth, hexagonal ice crystals. HaloCam observations complemented by radiative transfer simulations and measurements of aerosol and cirrus cloud optical thickness (AOT and COT provide a possibility to retrieve more detailed information about ice crystal roughness. This paper demonstrates the feasibility of a completely automated method to collect and evaluate a long-term database of halo observations and shows the potential to characterize ice crystal properties.

  18. Development and Comparison of Ground and Satellite-based Retrievals of Cirrus Cloud Physical Properties

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, David L

    2009-10-14

    This report is the final update on ARM research conducted at DRI through May of 2006. A relatively minor amount of work was done after May, and last month (November), two journal papers partially funded by this project were published. The other investigator on this project, Dr. Bob d'Entremont, will be submitting his report in February 2007 when his no-cost extension expires. The main developments for this period, which concludes most of the DRI research on this project, are as follows: (1) Further development of a retrieval method for cirrus cloud ice particle effective diameter (De) and ice water path (IWP) using terrestrial radiances measured from satellites; (2) Revision and publication of the journal article 'Testing and Comparing the Modified Anomalous Diffraction Approximation'; and (3) Revision and publication of our radar retrieval method for IWC and snowfall rate.

  19. An automated cirrus classification

    Science.gov (United States)

    Gryspeerdt, Edward; Quaas, Johannes; Sourdeval, Odran; Goren, Tom

    2017-04-01

    Cirrus clouds play an important role in determining the radiation budget of the earth, but our understanding of the lifecycle and controls on cirrus clouds remains incomplete. Cirrus clouds can have very different properties and development depending on their environment, particularly during their formation. However, the relevant factors often cannot be distinguished using commonly retrieved satellite data products (such as cloud optical depth). In particular, the initial cloud phase has been identified as an important factor in cloud development, but although back-trajectory based methods can provide information on the initial cloud phase, they are computationally expensive and depend on the cloud parametrisations used in re-analysis products. In this work, a classification system (Identification and Classification of Cirrus, IC-CIR) is introduced. Using re-analysis and satellite data, cirrus clouds are separated in four main types: frontal, convective, orographic and in-situ. The properties of these classes show that this classification is able to provide useful information on the properties and initial phase of cirrus clouds, information that could not be provided by instantaneous satellite retrieved cloud properties alone. This classification is designed to be easily implemented in global climate models, helping to improve future comparisons between observations and models and reducing the uncertainty in cirrus clouds properties, leading to improved cloud parametrisations.

  20. Implications of the ISOCLOUD campaigns at the AIDA Cloud Chamber for ice growth in cold cirrus

    Science.gov (United States)

    Lamb, Kara; Clouser, Benjamin; Sarkozy, Laszlo; Wagner, Steven; Ebert, Volker; Kerstel, Erik; Saathoff, Harald; Möhler, Ottmar; Moyer, Elisabeth

    2015-04-01

    In-situ water vapor measurements in the upper troposphere and lower stratosphere (UTLS) have routinely observed anomalous supersaturations on the order of 10-20particles when temperatures were below 200 K, raising questions about the physics of how ice forms at cold temperatures in the atmosphere1,2,3,4. The ISOCLOUD campaigns in 2012-2013 at the AIDA Aerosol and Cloud Chamber sought to investigate ice growth at cold temperatures by simulating cirrus clouds at temperatures and pressures characteristic of the upper troposphere. Experiments tested both homogeneous nucleation of sulfate aerosols and heterogeneous nucleation with various ice nuclei, including mineral dust and organic aerosols with and without nitric acid coatings. Optical instruments, both in-situ (TDLAS) and extractive (TDLAS and OFCEAS), measured ice particle number density, water vapor, total water, and water vapor isotopic concentrations, with multiple instruments measuring water. In a series of cirrus formation experiments, we observed no evidence of anomalous saturation vapor pressure and no evidence of ice growth inhibition at low temperatures for the parameter space tested during the ISOCLOUD campaigns. That is, we see no evidence for temperature dependence in the deposition coefficient. In these experiments we determined the deposition coefficient from bulk parameters of the gas (vapor concentration and ice number density). The ISOCLOUD experiments were particularly suited to deposition coefficient measurements since they involved lower pressures and often lower temperatures than previous similar campaigns, producing lower error bars.5 These results can aid in the interpretation of data from aircraft campaigns in the UTLS by solidifying our understanding of the microphysics of ice formation at cold temperatures. [1] Gao, R. et al., Science, 303, no. 6567, 516-520, (2004). [2] Jensen, E. et al., Atmos. Chem. Phys., 5, 851-862, (2005). [3] Peter, T. et al., Science, 314, no. 5804, 1399

  1. Effects of Ice-Crystal Structure on Halo Formation: Cirrus Cloud Experimental and Ray-Tracing Modeling Studies

    Science.gov (United States)

    Sassen, Kenneth; Knight, Nancy C.; Takano, Yoshihide; Heymsfield, Andrew J.

    1994-01-01

    During the 1986 Project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) field campaign, four 22 deg halo-producing cirrus clouds were studied jointly from a ground-based polarization lidar and an instrumented aircraft. The lidar data show the vertical cloud structure and the relative position of the aircraft, which collected a total of 84 slides by impaction, preserving the ice crystals for later microscopic examination. Although many particles were too fragile to survive impaction intact, a large fraction of the identifiable crystals were columns and radial bullet rosettes, with both displaying internal cavitations and radial plate-column combinations. Particles that were solid or displayed only a slight amount of internal structure were relatively rare, which shows that the usual model postulated by halo theorists, i.e., the randomly oriented, solid hexagonal crystal, is inappropriate for typical cirrus clouds. With the aid of new ray-tracing simulations for hexagonal hollow-ended column and bullet-rosette models, we evaluate the effects of more realistic ice-crystal structures on halo formation and lidar depolarization and consider why the common halo is not more common in cirrus clouds.

  2. A Study of Global Cirrus Cloud Morphology with AIRS Cloud-clear Radiances (CCRs)

    Science.gov (United States)

    Wu, Dong L.; Gong, Jie

    2012-01-01

    Version 6 (V6) AIRS cloud-clear radiances (CCR) are used to derive cloud-induced radiance (Tcir=Tb-CCR) at the infrared frequencies of weighting functions peaked in the middle troposphere. The significantly improved V 6 CCR product allows a more accurate estimation of the expected clear-sky radiance as if clouds are absent. In the case where strong cloud scattering is present, the CCR becomes unreliable, which is reflected by its estimated uncertainty, and interpolation is employed to replace this CCR value. We find that Tcir derived from this CCR method are much better than other methods and detect more clouds in the upper and lower troposphere as well as in the polar regions where cloud detection is particularly challenging. The cloud morphology derived from the V6 test month, as well as some artifacts, will be shown.

  3. Influence of aerosols and thin cirrus clouds on the GOSAT-observed CO2: a case study over Tsukuba

    Directory of Open Access Journals (Sweden)

    A. Bril

    2012-04-01

    Full Text Available Lidar observations of vertical profiles of aerosols and thin cirrus clouds were made at Tsukuba (36.05° N, 140.12° E, Japan, to investigate the influence of aerosols and thin cirrus clouds on the column-averaged dry-air mole fraction of carbon dioxide (XCO2 retrieved from observation data of the Thermal And Near-infrared Sensor for carbon Observation Fourier Transform Spectrometer, measured in the Short-Wavelength InfraRed band (TANSO-FTS SWIR, onboard the Greenhouse gases Observing SATellite (GOSAT. The lidar system measured the backscattering ratio, depolarization ratio, and/or the wavelength exponent of atmospheric particles. The lidar observations and ground-based high-resolution FTS measurements at the Tsukuba Total Carbon Column Observing Network (Tsukuba TCCON site were recorded simultaneously during passages of GOSAT over Tsukuba. GOSAT SWIR XCO2 data (Version 01.xx released in August 2010 were compared with the lidar and Tsukuba TCCON data. High-altitude aerosols and thin cirrus clouds had a large impact on the GOSAT SWIR XCO2 results. By taking into account the observed aerosol/cirrus vertical profiles and using a more adequate solar irradiance database in the GOSAT SWIR retrieval, the difference between the GOSAT SWIR XCO2 data and the Tsukuba TCCON data was reduced. The 3-band retrieval approach where the aerosol and cirrus profiles were retrieved gave us the best results and the retrieved XCO2 data followed the seasonal cycle of ~8 ppm observed at Tsukuba TCCON site.

  4. Discovery and imaging of a Galactic cirrus cloud with the far ultraviolet space telescope

    Science.gov (United States)

    Haikala, Lauri K.; Mattila, Kalevi; Bowyer, Stuart; Sasseen, Timothy P.; Lampton, Michael; Knude, Jens

    1995-01-01

    We present new far-ultraviolet (1400-1800 A) data concerning a Galactic cirrus cloud G251.2+73.3 near the north Galactic pole obtained with the space-borne imaging telescope FAUST (Far Ultraviolet Space Telescope). We obtain a good correlation between the far-ultraviolet (FUV) and IRAS 100 micrometers surface brightnesses, their relation being I(sub FUV) = (128 +/- 3) I(sub 100 micrometers) - (264 +/- 9), where the I(sub FUV) flux is given in units of photon/s/sq cm/A/sr and I(sub 100 micrometers) in MJy/sr. Using uvbyH-beta photometry, we get a distance of 120 pc and a visual extinction in the center of the cloud of 0.39 mag corresponding to an extinction of 1.0 mag at 1565 A. We have performed a multiple scattering calculation for the scattered light using the Monte Carlo method. These calculations provide restrictions on the FUV scattering properties of the interstellar dust.

  5. Large scale and cloud scale dynamics and microphysics in the formation and evolution of a TTL cirrus : a case modelling study

    Science.gov (United States)

    Podglajen, Aurélien; Plougonven, Riwal; Hertzog, Albert; Legras, Bernard

    2015-04-01

    Cirrus clouds in the tropical tropopause layer (TTL) control dehydration of air masses entering the stratosphere and strongly contribute to the local radiative heating. In this study, we aim at understanding, through a real case simulation, the dynamics controlling the formation and life cycle of a cirrus cloud event in the TTL. We also aim at quantifying the chemical and radiative impacts of the clouds. To do this, we use the Weather Research and Forecast (WRF) model to simulate a large scale TTL cirrus event happening in January 2009 (27-29) over the Eastern Pacific, which has been extensively described through satellite observations (Taylor et al., 2011). Comparison of simulated and observed high clouds shows a fair agreement, and validates the reference simulation regarding cloud extension, location and life time. The simulation and Lagrangian trajectories within the simulation are then used to characterize the evolution of the cloud : displacement, Lagrangian life time and links with dynamics. The efficiency of dehydration by such clouds is also examined. Sensitivity tests were performed to evaluate the importance of different microphysics schemes and initial and boundary conditions to accurately simulate the cirrus. As expected, both were found to have strong impacts. In particular, there were substantial differences between simulations using different initial and boundary conditions from atmospheric analyses (NCEP CFSR and ECMWF). This illustrates the primordial role of accurate vapour and dynamics for realistic cirrus modelling, on top of the need for appropriate microphysics. Last, we examined the effects of cloud radiative heating. Long wave radiative heating in cirrus clouds has been invoked to induce a cloud scale circulation that would lengthen the cloud lifetime, and increase the size of its dehydration area (Dinh et al. 2010). To try to diagnose this, we have carried out simulations using different radiative schemes, including or suppressing the

  6. Likely seeding of cirrus clouds by stratospheric Kasatochi volcanic aerosol particles near a mid-latitude tropopause fold

    Science.gov (United States)

    Campbell, James R.; Welton, Ellsworth J.; Krotkov, Nickolay A.; Yang, Kai; Stewart, Sebastian A.; Fromm, Michael D.

    2012-01-01

    Following the explosive 7-8 August 2008 Mt. Kasatochi volcanic eruption in southwestern Alaska, a segment of the dispersing stratospheric aerosol layer was profiled beginning 16 August in continuous ground-based lidar measurements over the Mid-Atlantic coast of the eastern United States. On 17-18 August, the layer was displaced downward into the upper troposphere through turbulent mixing near a tropopause fold. Cirrus clouds and ice crystal fallstreaks were subsequently observed, having formed within the entrained layer. The likely seeding of these clouds by Kasatochi aerosol particles is discussed. Cloud formation is hypothesized as resulting from either preferential homogenous freezing of relatively large sulfate-based solution droplets deliquesced after mixing into the moist upper troposphere or through heterogeneous droplet activation by volcanic ash. Satellite-borne spectrometer measurements illustrate the evolution of elevated Kasatochi SO 2 mass concentrations regionally and the spatial extent of the cirrus cloud band induced by likely particle seeding. Satellite-borne polarization lidar observations confirm ice crystal presence within the clouds. Geostationary satellite-based water vapor channel imagery depicts strong regional subsidence, symptomatic of tropopause folding, along a deepening trough in the sub-tropical westerlies. Regional radiosonde profiling confirms both the position of the fold and depth of upper-tropospheric subsidence. These data represent the first unambiguous observations of likely cloud seeding by stratospheric volcanic aerosol particles after mixing back into the upper troposphere.

  7. Validation of the CALIPSO-CALIOP extinction coefficients from in situ observations in midlatitude cirrus clouds during the CIRCLE-2 experiment

    Science.gov (United States)

    Mioche, Guillaume; Josset, Damien; Gayet, Jean-FrançOis; Pelon, Jacques; Garnier, Anne; Minikin, Andreas; Schwarzenboeck, Alfons

    2010-01-01

    This paper presents a comparison of combined Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) extinction retrievals with airborne lidar and in situ cirrus cloud measurements. Specially oriented research flights were carried out in western Europe in May 2007 during the Cirrus Cloud Experiment (CIRCLE-2) with the German Deutsches Zentrum für Luft- und Raumfahrt (DLR) and the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon aircraft equipped for remote and in situ measurements, respectively. Four cirrus cloud situations including thin cirrus layers and outflow cirrus linked to midlatitude fronts and convective systems were chosen to perform experimental collocated observations along the satellite overpasses. The measurements were carried out with temperatures ranging between -38°C and -60°C and with extinction coefficients no larger than 2 km-1. Comparisons between CALIOP and airborne lidar (LEANDRE New Generation (LNG)) attenuated backscatter coefficients reveal much larger CALIOP values for one frontal cirrus situation which could be explained by oriented pristine ice crystals. During the four selected cases the CALIOP cirrus extinction profiles were compared with in situ extinction coefficients derived from the Polar Nephelometer. The results show a very good agreement for two situations (frontal and outflow cases) despite very different cloud conditions. The slope parameters of linear fittings of CALIOP extinction coefficients with respect to in situ measurements are 0.90 and 0.94, with correlation coefficients of 0.69 and only 0.36 for the latter case because of a small number of measurements. On the contrary, significant differences are evidenced for two other situations. In thin frontal cirrus at temperatures ranging between -58°C and -60°C, systematic larger CALIOP extinctions can be explained by horizontally

  8. 16 year climatology of cirrus clouds over a tropical station in southern India using ground and space-based lidar observations

    Directory of Open Access Journals (Sweden)

    A. K. Pandit

    2015-06-01

    Full Text Available 16 year (1998–2013 climatology of cirrus clouds and their macrophysical (base height, top height and geometrical thickness and optical properties (cloud optical thickness observed using a ground-based lidar over Gadanki (13.5° N, 79.2° E, India, is presented. The climatology obtained from the ground-based lidar is compared with the climatology obtained from seven and half years (June 2006–December 2013 of Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP observations. A very good agreement is found between the two climatologies in spite of their opposite viewing geometries and difference in sampling frequencies. Nearly 50–55% of cirrus clouds were found to possess geometrical thickness less than 2 km. Ground-based lidar is found to detect more number of sub-visible clouds than CALIOP which has implications for global warming studies as sub-visible cirrus clouds have significant positive radiative forcing. Cirrus clouds with mid-cloud temperatures between −50 to −70 °C have a mean geometrical thickness greater than 2 km in contrast to the earlier reported value of 1.7 km. Trend analyses reveal a statistically significant increase in the altitude of sub-visible cirrus clouds which is consistent with the recent climate model simulations. Also, the fraction of sub-visible cirrus cloud is found to be increasing during the last sixteen years (1998 to 2013 which has implications to the temperature and water vapour budget in the tropical tropopause layer.

  9. Lidar multiple scattering factors inferred from CALIPSO lidar and IIR retrievals of semi-transparent cirrus cloud optical depths over oceans

    Science.gov (United States)

    Garnier, A.; Pelon, J.; Vaughan, M. A.; Winker, D. M.; Trepte, C. R.; Dubuisson, P.

    2015-07-01

    Cirrus cloud absorption optical depths retrieved at 12.05 μm are compared to extinction optical depths retrieved at 0.532 μm from perfectly co-located observations of single-layered semi-transparent cirrus over ocean made by the Imaging Infrared Radiometer (IIR) and the Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP) flying on board the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite. IIR infrared absorption optical depths are compared to CALIOP visible extinction optical depths when the latter can be directly derived from the measured apparent two-way transmittance through the cloud. An evaluation of the CALIOP multiple scattering factor is inferred from these comparisons after assessing and correcting biases in IIR and CALIOP optical depths reported in version 3 data products. In particular, the blackbody radiance taken in the IIR version 3 algorithm is evaluated, and IIR retrievals are corrected accordingly. Numerical simulations and IIR retrievals of ice crystal sizes suggest that the ratios of CALIOP extinction and IIR absorption optical depths should remain roughly constant with respect to temperature. Instead, these ratios are found to increase quasi-linearly by about 40 % as the temperature at the layer centroid altitude decreases from 240 to 200 K. It is discussed that this behavior can be explained by variations of the multiple scattering factor ηT applied to correct the measured apparent two-way transmittance for contribution of forward-scattering. While the CALIOP version 3 retrievals hold ηT fixed at 0.6, this study shows that ηT varies with temperature (and hence cloud particle size) from ηT = 0.8 at 200 K to ηT = 0.5 at 240 K for single-layered semi-transparent cirrus clouds with optical depth larger than 0.3. The revised parameterization of ηT introduces a concomitant temperature dependence in the simultaneously derived CALIOP lidar ratios that is consistent with observed changes in CALIOP

  10. Sensitivity Studies of Dust Ice Nuclei Effect on Cirrus Clouds with the Community Atmosphere Model CAM5

    Science.gov (United States)

    Liu, Xiaohong; Zhang, Kai; Jensen, Eric J.; Gettelman, Andrew; Barahona, Donifan; Nenes, Athanasios; Lawson, Paul

    2012-01-01

    In this study the effect of dust aerosol on upper tropospheric cirrus clouds through heterogeneous ice nucleation is investigated in the Community Atmospheric Model version 5 (CAM5) with two ice nucleation parameterizations. Both parameterizations consider homogeneous and heterogeneous nucleation and the competition between the two mechanisms in cirrus clouds, but differ significantly in the number concentration of heterogeneous ice nuclei (IN) from dust. Heterogeneous nucleation on dust aerosol reduces the occurrence frequency of homogeneous nucleation and thus the ice crystal number concentration in the Northern Hemisphere (NH) cirrus clouds compared to simulations with pure homogeneous nucleation. Global and annual mean shortwave and longwave cloud forcing are reduced by up to 2.0+/-0.1Wm (sup-2) (1 uncertainty) and 2.4+/-0.1Wm (sup-2), respectively due to the presence of dust IN, with the net cloud forcing change of -0.40+/-0.20W m(sup-2). Comparison of model simulations with in situ aircraft data obtained in NH mid-latitudes suggests that homogeneous ice nucleation may play an important role in the ice nucleation at these regions with temperatures of 205-230 K. However, simulations overestimate observed ice crystal number concentrations in the tropical tropopause regions with temperatures of 190- 205 K, and overestimate the frequency of occurrence of high ice crystal number concentration (greater than 200 L(sup-1) and underestimate the frequency of low ice crystal number concentration (less than 30 L(sup-1) at NH mid-latitudes. These results highlight the importance of quantifying the number concentrations and properties of heterogeneous IN (including dust aerosol) in the upper troposphere from the global perspective.

  11. Lidar observations of tropical high-altitude cirrus clouds: results from dual-wavelength Raman lidar measurements during the ALBATROSS campaign 1996

    Science.gov (United States)

    Beyerle, Georg; Schaefer, H. J.; Schrems, Otto; Neuber, R.; Rairoux, P.; McDermid, I. S.

    1997-05-01

    Results from dual wavelength Raman lidar observations of tropical high-altitude cirrus clouds are reported. Based on 107 hours of night-time measurements cirrus clouds were present in more than 50% of the observations at latitudes between 23.5 degrees south and 23.5 degrees north and altitudes between 11 and 16 km. Volume depolarization is found to be a sensitive parameter for the detection of subvisible cloud layers. Using Mie scattering calculations estimates of the ice water content are derived.

  12. Evaluation of cloud-resolving model simulations of midlatitude cirrus with ARM and A-train observations

    Science.gov (United States)

    Muhlbauer, A.; Ackerman, T. P.; Lawson, R. P.; Xie, S.; Zhang, Y.

    2015-07-01

    Cirrus clouds are ubiquitous in the upper troposphere and still constitute one of the largest uncertainties in climate predictions. 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 A-train satellites. The CRM simulations are driven with periodic boundary conditions and ARM forcing data, whereas the CSRM simulations are driven by the ERA-Interim product. 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 500 m or finer, which suggests that turbulent vertical air motions in cirrus clouds need to be parameterized in general circulation models and in CSRM simulations with horizontal grid spacings on the order of 1 km. 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 the 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

  13. A decadal cirrus clouds climatology from ground-based and spaceborne lidars above the south of France (43.9° N–5.7° E

    Directory of Open Access Journals (Sweden)

    C. Hoareau

    2013-07-01

    Full Text Available This study provides an analysis of cirrus cloud properties at midlatitude in the southern part of France from ground-based and spaceborne lidars. A climatology of cirrus cloud properties and their evolution over more than 12 yr is presented and compared to other mid-latitude climatological studies. Cirrus clouds occur ~37% of the total observation time and remain quasi-constant across seasons with a variation within ~5% around the mean occurrence. Similar results are obtained from CALIOP and the ground-based lidar, with a mean difference in occurrence of ~5% between both instruments. From the ground-based lidar data, a slight decrease in occurrence of ~3% per decade is observed but found statistically insignificant. Based on a clustering analysis of cirrus cloud parameters, three distinct classes have been identified and investigations concerning their origin are discussed. Properties of these different classes are analysed, showing that thin cirrus in the upper troposphere represent ~50% of cloud cover detected in summer and fall, decreasing by 15–20% for other seasons.

  14. Depolarization properties of cirrus clouds from polarization lidar measurements over Hefei in spring

    Institute of Scientific and Technical Information of China (English)

    Zhenzhu Wang; Ruli Chi; Bo Liu; Jun Zhou

    2008-01-01

    @@ A new polarization lidar has been developed for detecting depolarization characteristics of aerosol and cirrus over Hefei (31.90°N, 117.16°E), China. The fundamental principle of polarization lidar is briefly introduced.

  15. Effects of air traffic on cirrus cloud formation in Europe. Final report of the development area environmental and climate research; Untersuchungen zum Einfluss des Flugverkehrs auf die Cirrus-Bewoelkung in Europa. Endbericht im Foerdergebiet Umwelt und Klimaforschung

    Energy Technology Data Exchange (ETDEWEB)

    Mannstein, H.; Wendling, P.

    2001-06-01

    The cloud cover over Europe caused by linear condensation trails has been investigated already in earlier studies. However, after quite a short period of time, these can no longer be distinguished from natural cirrus clouds. There were no data on the effect of air travel on cirrus formation. This study investigated the effects of air travel on cirrus cloud formation by investigating a time series of METEOSAT data and relating it to air travel data in high temporal and local resolution. (orig.) [German] Der Bedeckungsgrad an deutlich im Satellitenbild erkennbaren, linearen Kondensstreifen ueber Europa wurde bereits untersucht. Nach relativ kurzer Zeit sind Kondensstreifen jedoch mit den bisher bekannten Fernerkundungsmethoden nicht mehr von natuerlichen Cirren zu unterscheiden. In welchem Masse der Flugverkehr zur Cirrus-Bewoelkung beitraegt, war bisher nicht bekannt. In dieser Arbeit wurde mit hoher Signifikanz der Einfluss des Flugverkehrs auf die Cirrusbedeckung, wie sie sich ans METEOSAT-Daten ableiten laesst, nachgewiesen. Dazu wurde eine Zeitserie von METEOSAT-Daten im Vergleich zu zeitlich und raeumlich hochaufgeloesten Flugverkehrsdaten untersucht. (orig.)

  16. The SARTre model for radiative transfer in spherical atmospheres and its application to the derivation of cirrus cloud properties

    Energy Technology Data Exchange (ETDEWEB)

    Mendrock, J.

    2006-07-01

    Modeling of radiative transfer (RT) is one of the essentials of atmospheric remote sensing. It has been common to use separate models for the simulation of shortwave radiation dominated by scattering of sunlight and longwave radiation characterized by emission from trace gases. These days also shortwave instruments are operated in limb mode, which demand models taking the sphericity of the Earth and atmosphere into account. On the other hand, infrared and microwave sounders are increasingly being used for the observation of ice clouds, that necessitate the modeling of scattering by cloud particles. Both trends require RT models, that are capable of taking into account scattering as well as the sphericity of the atmosphere. This suggests a unified handling of short- and longwave radiation, which furthermore allows for a consistent evaluation of multispectral data. Focusing on these aspects, the RT-model SARTre ([Approximate] Spherical Atmospheric Radiative Transfer model) has been developed. To our knowledge, SARTre is the first model, that is capable of limb modeling in the ultraviolet, visible, near to far infrared, and microwave spectral region. Here, algorithm baseline, implementation, verification and validation of SARTre are presented. SARTre has been used to study effects of cirrus clouds on infrared limb emission spectra. An exemplary retrieval of cirrus parameters from MIPAS measurements is demonstrated, and the plausibility of the results is discussed. (orig.)

  17. Influence of aerosols and thin cirrus clouds on the GOSAT-observed CO2: a case study over Tsukuba

    OpenAIRE

    A. Bril; S. Oshchepkov; A. Uchiyama; A. Yamazaki; Shibata, T.; Shimizu, A.; T. Nagai; Y. Yoshida; Morino, I.; Sakai, T; N. Kikuchi; O. Uchino; Yokota, T

    2011-01-01

    Lidar observations of vertical profiles of aerosols and thin cirrus clouds were made at Tsukuba (36.1° N, 140.1° E), Japan, to investigate the influence of aerosols and thin cirrus clouds on the column-averaged dry-air mole fraction of carbon dioxide (XCO2) retrieved from observation data of the Thermal And Near-infrared Sensor for carbon Observation Fourier Transform Spectrometer, measured in the Short-Wavelength InfraRed band (TANSO-FTS SWIR), onboard the Greenhouse gases Observing ...

  18. Midlatitude cirrus classification at Rome Tor Vergata through a multichannel Raman-Mie-Rayleigh lidar

    Science.gov (United States)

    Dionisi, D.; Keckhut, P.; Liberti, G. L.; Cardillo, F.; Congeduti, F.

    2013-12-01

    A methodology to identify and characterize cirrus clouds has been developed and applied to the multichannel-multiwavelength Rayleigh-Mie-Raman (RMR) lidar in Rome Tor Vergata (RTV). A set of 167 cirrus cases, defined on the basis of quasi-stationary temporal period conditions, has been selected in a data set consisting of about 500 h of nighttime lidar sessions acquired between February 2007 and April 2010. The derived lidar parameters (effective height, geometrical and optical thickness and mean back-scattering ratio) and the cirrus mid-height temperature (estimated from the radiosonde data of Pratica di Mare, WMO, World Meteorological Organization, site no. 16245) of this sample have been analyzed by the means of a clustering multivariate analysis. This approach identified four cirrus classes above the RTV site: two thin cirrus clusters in mid- and upper troposphere and two thick cirrus clusters in mid-upper troposphere. These results, which are very similar to those derived through the same approach at the lidar site of the Observatoire de Haute-Provence (OHP), allows characterization of cirrus clouds over the RTV site and attests to the robustness of such classification. To acquire some indications about the cirrus generation methods for the different classes, analyses of the extinction-to-backscatter ratio (lidar ratio, LReff, in terms of frequency distribution functions and dependencies on the mid-height cirrus temperature, have been performed. A preliminary study relating some meteorological parameters (e.g., relative humidity, wind components) to cirrus clusters has also been conducted. The RTV cirrus results, recomputed through the cirrus classification by Sassen and Cho (1992), show good agreement with other midlatitude lidar cirrus observations for the relative occurrence of subvisible (SVC), thin and opaque cirrus classes (10%, 49% and 41%, respectively). The overall mean value of cirrus optical depth is 0.37 ± 0.18, while most retrieved LReff values

  19. Combining multiple remote sensors with reanalysis and a radiative transfer model to assess the microphysical impact of smoke on cirrus clouds

    Science.gov (United States)

    Kablick, G. P.

    2011-12-01

    A multi-spectral technique for retrieving properties of smoke contaminated ice clouds is evaluated. This method utilizes Earth orbiting active and passive remote sensors combined with atmospheric reanalysis and a multiple scattering, single column radiative transfer algorithm. This study focuses on a specific type of cirrus cloud that exhibits IR radiances, lidar backscatter values, color ratios and depolarization ratios comparable to thick cirrus as observed by MODIS and CALIPSO. However, the radar reflectivities as determined by CloudSat are significantly lower than expected for clouds with such large visible optical depths. This work also demonstrates the sensitivity of retrievals to a priori assumptions by using a few notable cases. Collocated data observed during the boreal fire season of 2010 is analyzed using this methodology as a first step to ascertain the impact that pyroconvection may have on ice cloud properties.

  20. Diversity on subtropical and polar cirrus clouds properties as derived from both ground-based lidars and CALIPSO/CALIOP measurements

    Science.gov (United States)

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

    2017-01-01

    Cirrus (Ci) cloud properties can change significantly from place to place over the globe as a result of weather processes, reflecting their likely different radiative and climate implications. In this work Cirrus clouds (Ci) features observed in late autumn/early winter season at both subtropical and polar latitudes are examined and compared to CALIPSO/CALIOP observations. Lidar measurements were carried out in three stations: São Paulo (MSP, Brazil) and Tenerife (SCO, Canary Islands, Spain), as subtropical sites, and the polar Belgrano II base (BEL, Argentina) in the Antarctic continent. The backscattering ratio (BSR) profiles and the top and base heights of the Ci layers together to their Cirrus Cloud Optical Depth (CCOD) and Lidar Ratio (LR) for Ci clouds were derived. In addition, temperatures at the top and base boundaries of the Ci clouds were also obtained from local radiosoundings to verify pure ice Ci clouds occurrence using a given temperature top threshold ( 70 km far), inferring the irregular extension and inhomogeneity of the Ci clouds over each study area. These considerations can be useful for assimilation of the Ci features into climate models and evaluation of future space-borne lidar observations of Ci clouds, especially for the future ESA/Copernicus-Sentinel and ESA/EarthCARE missions.

  1. Microphysical properties of cirrus clouds between 75°N and 25°S derived from extensive airborne in-situ observations

    Science.gov (United States)

    Krämer, Martina

    2016-04-01

    Numerous airborne field campaigns were performed in the last decades to record cirrus clouds microphysical properties. Beside the understanding of the processes of cirrus formation and evolution, an additional motivation for those studies is to provide a database to evaluate the representation of cirrus clouds in global climate models. This is of importance for an improved certainty of climate predictions, which are affected by the poor understanding of the microphysical processes of ice clouds (IPCC, 2013). To this end, the observations should ideally cover the complete respective parameter range and not be influenced by instrumental artifacts. However, due to the difficulties in measuring cirrus properties on fast-flying, high-altitude aircraft, some issues with respect to the measurements %evolved have arisen. In particular, concerns about the relative humidity in and around cirrus clouds and the ice crystal number concentrations were under discussion. Too high ice supersaturations as well as ice number concentrations were often reported. These issues have made more challenging the goal of compiling a large database using data from a suite of different instruments that were used on different campaigns. In this study, we have have addressed these challenges and compiled a large data set of cirrus clouds, sampled during eighteen field campaigns between 75°N and 25°S, representing measurements fulfilling the above mentioned requirements. The most recent campaigns were performed in 2014; namely, the ATTREX campaign with the research aircraft Global Hawk and the ML-CIRRUS and ACRIDICON campaigns with HALO. % The observations include ice water content (IWC: 130 hours of observations), ice crystal numbers (N_ice: 83 hours), ice crystal mean mass size (Rice: 83 hours) and relative humidity (RH_ice) in- and outside of cirrus clouds (78 and 140 hours). % We will present the parameters as PDFs versus temperature and derive medians and core ranges (including the most

  2. Optical depths of semi-transparent cirrus clouds over oceans from CALIPSO infrared radiometer and lidar measurements, and an evaluation of the lidar multiple scattering factor

    Directory of Open Access Journals (Sweden)

    A. Garnier

    2015-02-01

    Full Text Available This paper provides a detailed evaluation of cloud absorption optical depths retrieved at 12.05 μm and comparisons to extinction optical depths retrieved at 0.532 μm from perfectly co-located observations of single-layered semi-transparent cirrus over ocean made by the Imaging Infrared Radiometer (IIR and the Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP flying on-board the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations satellite. The blackbody radiance taken in the IIR Version 3 algorithm is evaluated, and IIR retrievals are corrected accordingly. IIR infrared absorption optical depths are then compared to CALIOP visible extinction optical depths when the latter can be directly derived from the measured apparent 2-way transmittance through the cloud. Numerical simulations and IIR retrievals of ice crystal sizes suggest that the ratios of CALIOP extinction and IIR absorption optical depths should remain roughly constant with respect to temperature. Instead, these ratios are found to increase quasi-linearly by about 40% as the temperature at the layer centroid altitude decreases from 240 to 200 K. This behavior is explained by variations of the multiple scattering factor ηT to be applied to correct the measured transmittance, which is taken equal to 0.6 in the CALIOP Version 3 algorithm, and which is found here to vary with temperature (and hence cloud particle size from ηT = 0.8 at 200 K to ηT = 0.5 at 240 K for clouds with optical depth larger than 0.3. The revised parameterization of ηT introduces a concomitant temperature dependence in the simultaneously derived CALIOP lidar ratios that is consistent with observed changes in CALIOP depolarization ratios and particle habits derived from IIR measurements.

  3. Inhomogeneities in cirrus clouds and their effects on solar radiative transfer; Inhomogenitaeten in Cirren und ihre Auswirkungen auf den solaren Strahlungstransport

    Energy Technology Data Exchange (ETDEWEB)

    Buschmann, N. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Atmosphaerenphysik

    2001-07-01

    Inhomogeneities in cirrus clouds have an important impact on radiative transfer calculations in climate models. Compared to homogeneous clouds, inhomogeneities within clouds decrease reflectivity and result in an increased transmission of solar radiation through the cloud towards the surface. A quantitative investigation of this effect is still to be done. In-situ and remote sensing data of 11 cirrus clouds are used to investigate horizontal inhomogeneities. The 3-dimensional radiative transfer model GRIMALDI is used to calculate radiative flux densities and absorption for a cloudy atmosphere. Comparisons between homogeneous and heterogeneous calculations show, that the homogeneous assumption can cause relative errors up to {+-} 30% for radiative flux densities and absorption especially for tropical cirrus clouds. Mid-latitude cirrus clouds with mean optical thickness smaller than 5 and minor inhomogeneity result in relative errors smaller than {+-} 10% for radiative flux density and absorption. A correction scheme is developed to account for horizontal inhomogeneity in optically thick cirrus clouds in homogeneous radiative transfer calculations. This way, for a known horizontal distribution of optical thickness, relative errors of radiative properties can be reduced to a maximum of {+-} 10%. (orig.) [German] Inhomogenitaeten in Cirrus-Wolken spielen insbesondere bei Strahlungstransportrechnungen in Klimamodellen eine bedeutende Rolle. Im Vergleich zur homogenen Wolkenbetrachtung verringern Inhomogenitaeten die Reflektivitaet der Wolken und fuehren zu einer hoeheren Transmission solarer Strahlung durch die Wolke zum Erdboden. Eine quantitative Untersuchung dieses Effekts steht allerdings bislang aus. Flugzeugmessungen sowie Fernerkundungsdaten von insgesamt 11 Cirrus-Wolken werden auf ihre horizontale Inhomogenitaet untersucht. Das 3-dimensionale Strahlungstransportmodell GRIMALDI wird fuer die Berechnung solarer Strahlungsflussdichten und Absorption in bewoelkter

  4. Origin and transport of tropical cirrus clouds observed over Paramaribo, Suriname (5.8°N, 55.2°W)

    Science.gov (United States)

    Fortuin, J. P. F.; Becker, C. R.; Fujiwara, M.; Immler, F.; Kelder, H. M.; Scheele, M. P.; Schrems, O.; Verver, G. H. L.

    2007-05-01

    The Intertropical Convergence Zone (ITCZ) passes twice a year over tropical Suriname, bringing two wet and two dry seasons. During a pilot study campaign in Suriname, cirrus clouds were observed with a mobile aerosol Raman lidar (MARL) and with balloon sondes containing a frost point hygrometer called Snow White, over the period October-November 2004. These observations are used to study the origin of cirrus clouds and the dynamical processes that determine their transport, using European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses. The height of cirrus occurrence is in phase with the height of the cold point tropopause, with maximum heights occurring during Northern Hemisphere winter that are about 2 km above the minimum values in summertime. The occurrence of cirrus often corresponds with a northerly meridional wind flow (in a layer underneath the tropopause), also when the ITCZ lies to the south in the period January-May. ECMWF analyses point out that inertial instability flow, in the form of vertically stacked meridional circulation cells in the upper troposphere (UT), can explain the transport of these cirrus events. Also evident is that radiative cooling of a moist layer transported in the UT leads to a thermal wind in the form of an easterly/westerly jet associated with the southward/northward transport of moist air. An interactive play between the inertial instability and thermal wind mechanisms explains many of the observed features of cirrus occurrence over Suriname. The observed cirrus mostly originates from the ITCZ or from deep convective centers to the south that form during the early summer monsoon.

  5. In-situ measurements of tropical cloud properties in the West African monsoon: upper tropospheric ice clouds, mesoscale convective system outflow, and subvisual cirrus

    Science.gov (United States)

    Frey, W.; Borrmann, S.; Kunkel, D.; Weigel, R.; de Reus, M.; Schlager, H.; Roiger, A.; Voigt, C.; Hoor, P.; Curtius, J.; Krämer, M.; Schiller, C.; Volk, C. M.; Homan, C. D.; Fierli, F.; di Donfrancesco, G.; Ulanovsky, A.; Ravegnani, F.; Sitnikov, N. M.; Viciani, S.; D'Amato, F.; Shur, G. N.; Belyaev, G. V.; Law, K. S.; Cairo, F.

    2011-01-01

    In-situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 ''Geophysica'' with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two or three modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionate more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3, and satellite images clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow (developing MCS) ice crystal number concentrations of up to 8.3 cm-3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m-3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm-3, an ice water content of 2.3 × 10-4 g m-3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm-3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10-4 g m-3. All known in-situ measurements of subvisual tropopause cirrus are compared and an

  6. In situ measurements of tropical cloud properties in the West African Monsoon: upper tropospheric ice clouds, Mesoscale Convective System outflow, and subvisual cirrus

    Science.gov (United States)

    Frey, W.; Borrmann, S.; Kunkel, D.; Weigel, R.; de Reus, M.; Schlager, H.; Roiger, A.; Voigt, C.; Hoor, P.; Curtius, J.; Krämer, M.; Schiller, C.; Volk, C. M.; Homan, C. D.; Fierli, F.; di Donfrancesco, G.; Ulanovsky, A.; Ravegnani, F.; Sitnikov, N. M.; Viciani, S.; D'Amato, F.; Shur, G. N.; Belyaev, G. V.; Law, K. S.; Cairo, F.

    2011-06-01

    In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3 ± 1.6) cm-3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m-3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm-3, an ice water content of 2.3 × 10-4 g m-3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm-3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10-4 g m-3. All known in situ measurements of subvisual tropopause cirrus are compared

  7. Cirrus clouds, humidity, and dehydration in the tropical tropopause layer observed at Paramaribo, Suriname (5.8°N, 55.2°W)

    Science.gov (United States)

    Immler, Franz; Krüger, Kirstin; Tegtmeier, Susann; Fujiwara, Masatomo; Fortuin, Paul; Verver, Gé; Schrems, Otto

    2007-02-01

    In the framework of the European Project STAR the Mobile Aerosol Raman Lidar (MARL) of the Alfred Wegener Institute (AWI) was operated in Paramaribo, Suriname (5.8°N, 55.2°W), and carried out extensive observations of tropical cirrus clouds during the local dry season from 28 September 2004 to 16 November 2004. The coverage with ice clouds was very high with 81% in the upper troposphere (above 12 km). The frequency of occurrence of subvisual clouds was found to be clearly enhanced compared to similar observations performed with the same instrument at a station in the midlatitudes. The extinction-to-backscatter ratio of thin tropical cirrus is with 26 ± 7 sr significantly higher than that of midlatitude cirrus (16 ± 9 sr). Subvisual cirrus clouds often occur in the tropical tropopause layer (TTL) above an upper tropospheric inversion. Our observations show that the ice-forming ability of the TTL is very high. The transport of air in this layer was investigated by means of a newly developed trajectory model. We found that the occurrence of clouds is highly correlated with the temperature and humidity history of the corresponding air parcel. Air that experienced a temperature minimum before the measurement took place was generally cloud free, while air that was at its temperature minimum during the observation and thus was saturated contained ice. We also detected extremely thin cloud layers slightly above the temperature minimum in subsaturated air. The solid particles of such clouds are likely to consist of nitric acid trihydrate (NAT) rather than ice.

  8. Derivation of Physical and Optical Properties of Midlatitude Cirrus Ice Crystals for a Size-Resolved Cloud Microphysics Model

    Science.gov (United States)

    Fridlind, Ann M.; Atlas, Rachel; Van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-01-01

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5-2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by approx. 0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from approx. 0:05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.

  9. Derivation of Physical and Optical Properties of Midlatitude Cirrus Ice Crystals for a Size-Resolved Cloud Microphysics Model

    Science.gov (United States)

    Fridlind, Ann M.; Atlas, Rachel; Van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-01-01

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5-2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by approx. 0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from approx. 0:05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.

  10. Comparisons of cirrus cloud properties between polluted and pristine air based on in-situ observations from the NSF HIPPO, EU INCA and NASA ATTREX campaigns

    Science.gov (United States)

    Diao, M.; Schumann, U.; Jensen, J. B.; Minikin, A.

    2015-12-01

    The radiative forcing of cirrus clouds is influenced by microphysical (e.g., ice crystal number concentration and size distribution) and macroscopic properties. Currently it is still unclear how the formation of cirrus clouds and their microphysical properties are influenced by anthropogenic emissions. In this work, we use airborne in-situ observations to compare cirrus cloud properties between polluted and pristine regions. Our dataset includes: the NSF HIAPER Pole-to-Pole Observations (HIPPO) Global campaign (2009-2011), the EU Interhemispheric Differences In Cirrus Properties from Anthropogenic Emissions (INCA) campaign (2000) and the NASA Airborne Tropical Tropopause Experiment (ATTREX) campaign (2014). The combined dataset include observations of both extratropical (HIPPO and INCA) and tropical (ATTREX) cirrus, over the Northern and Southern Hemispheres. We use the in-situ measured carbon monoxide (CO) mixing ratio as a pollution indicator, and compare ice microphysical properties (i.e., ice crystal number concentration (Nc) and number-weighted mean diameter (Dc)) between air masses with higher and lower CO. All analyses are restricted to T ≤ -40°C. By analyzing ice crystals (Fast-2DC, 87.5-1600 µm) in HIPPO, we found that Dc decreases with increasing CO concentration at multiple constant pressure levels. In addition, analysis of INCA data shows that Nc and extinction of small ice particles (FSSP 3-20 µm) increases with increasing CO. Particles < 87.5 µm in Fast-2DC data are not considered due to uncertainty in sample volume, and the FSSP measurements are subject to possible shattering. We further analyze the ice crystals (SPEC FCDP, 1-50 µm) in the tropical tropopause layer in ATTREX. At -70°C to -90°C, we found that the average Nc (Dc) increases (decreases) at higher CO. Overall, our results suggest that extratropical and tropical cirrus are likely to have more numerous small ice particles, when sampled in the more polluted background. Back

  11. Optical properties of the cirrus cloud ice crystals with preferred azimuthal orientation for polarization lidars with azimuthal scanning

    Science.gov (United States)

    Konoshonkin, Alexander V.; Kustova, Natalia V.; Nasonov, Sergey V.; Bryukhanov, Ilia D.; Shishko, Viktor A.; Timofeev, Dmitriy N.; Borovoi, Anatoly G.

    2016-10-01

    Optical properties of the cirrus cloud ice crystals with preferred azimuthal orientation are required for current numerical models of the Earth's radiation balance. Retrieving the orientation distributions function of the crystals from a vertically pointing polarization lidar measuring the full Mueller matrix is a very complicated problem because of lake of information. Lidars with zenith scanning can be used only to retrieve the properties of horizontally oriented particles. The paper shows that if the particles have preferred azimuthal orientation, the polarization lidars with azimuthal scanning should be used. It is also shown that all the elements of the Mueller matrix give no extra information compare to the depolarization ratio. Optical properties of preferred azimuthal oriented hexagonal ice columns with size from 10 to 1000 μm for wavelengths of 0.355, 0.532 and 1.064 μm were collected as a data bank.

  12. An intensified hydrological cycle in the simulation of geoengineering by cirrus cloud thinning using ice crystal fall speed changes

    Science.gov (United States)

    Jackson, L. S.; Crook, J. A.; Forster, P. M.

    2016-06-01

    Proposals to geoengineer Earth's climate by cirrus cloud thinning (CCT) potentially offer advantages over solar radiation management schemes: amplified cooling of the Arctic and smaller perturbations to global mean precipitation in particular. Using an idealized climate model implementation of CCT in which ice particle fall speeds were increased 2×, 4×, and 8× we examine the relationships between effective radiative forcing (ERF) at the top of atmosphere, near-surface temperature, and the response of the hydrological cycle. ERF was nonlinear with fall speed change and driven by the trade-off between opposing positive shortwave and negative longwave radiative forcings. ERF was -2.0 Wm-2 for both 4× and 8× fall speeds. Global mean temperature decreased linearly with ERF, while Arctic temperature reductions were amplified compared with the global mean change. The change in global mean precipitation involved a rapid adjustment (~ 1%/Wm2), which was linear with the change in the net atmospheric energy balance, and a feedback response (~2%/°C). Global mean precipitation and evaporation increased strongly in the first year of CCT. Intensification of the hydrological cycle was promoted by intensification of the vertical overturning circulation of the atmosphere, changes in boundary layer climate favorable for evaporation, and increased energy available at the surface for evaporation (from increased net shortwave radiation and reduced subsurface storage of heat). Such intensification of the hydrological cycle is a significant side effect to the cooling of climate by CCT. Any accompanying negative cirrus cloud feedback response would implicitly increase the costs and complexity of CCT deployment.

  13. Seasonal Variations of the Relative Optical Air Mass Function for Background Aerosol and Thin Cirrus Clouds at Arctic and Antarctic Sites

    Directory of Open Access Journals (Sweden)

    Claudio Tomasi

    2015-06-01

    Full Text Available New calculations of the relative optical air mass function are made over the 0°–87° range of apparent solar zenith angle θ, for various vertical profiles of background aerosol, diamond dust and thin cirrus cloud particle extinction coefficient in the Arctic and Antarctic atmospheres. The calculations were carried out by following the Tomasi and Petkov (2014 procedure, in which the above-mentioned vertical profiles derived from lidar observations were used as weighting functions. Different sets of lidar measurements were examined, recorded using: (i the Koldewey-Aerosol-Raman Lidar (KARL system (AWI, Germany at Ny-Ålesund (Spitsbergen, Svalbard in January, April, July and October 2013; (ii the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO satellite-based sensor over Barrow (Alaska, Eureka (Nunavut, Canada and Sodankylä (northern Finland, and Neumayer III, Mario Zucchelli and Mirny coastal stations in Antarctica in the local summer months of the last two years; (iii the National Institute of Optics (INO, National Council of Research (CNR Antarctic lidar at Dome C on the Antarctic Plateau for a typical “diamond dust” case; and (iv the KARL lidar at Ny-Ålesund and the University of Rome/National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA lidar at Thule (northwestern Greenland for some cirrus cloud layers in the middle and upper troposphere. The relative optical air mass calculations are compared with those obtained by Tomasi and Petkov (2014 to define the seasonal changes produced by aerosol particles, diamond dust and cirrus clouds. The results indicate that the corresponding air mass functions generally decrease as angle θ increases with rates that are proportional to the increase in the pure aerosol, diamond dust and cirrus cloud particle optical thickness.

  14. Cirrus feedback on interannual climate fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, C; Dessler, A E; Zelinka, M D; Yang, P; Wang, T

    2014-12-28

    Cirrus clouds are not only important in determining the current climate, but also play an important role in climate change and variability. Analysis of satellite observations shows that the amount and altitude of cirrus clouds (optical depth <3.6, cloud top pressure <440 hPa) increase in response to inter-annual surface warming. Thus, cirrus clouds are likely to act as a positive feedback on short-term climate fluctuations, by reducing the planet’s ability to radiate longwave radiation to space in response to planetary surface warming. Using cirrus cloud radiative kernels, the magnitude of cirrus feedback is estimated to be 0.20±0.21W/m2/°C, which is comparable to the surface albedo feedback. Most of the cirrus feedback comes from increasing cloud amount in the tropical tropopause layer (TTL) and subtropical upper troposphere.

  15. Polarimetric Retrievals of Surface and Cirrus Clouds Properties in the Region Affected by the Deepwater Horizon Oil Spill

    Science.gov (United States)

    Ottaviani, Matteo; Cairns, Brian; Chowdhary, Jacek; Van Diedenhoven, Bastiaan; Knobelspiesse, Kirk; Hostetler, Chris; Ferrare, Rich; Burton, Sharon; Hair, John; Obland, Michael D.; Rogers, Raymond

    2012-01-01

    prohibitive variability in atmospheric conditions (very inhomogeneous aerosol distribution and cloud cover). Although the results presented for the surface are essentially unaffected, we discuss the results obtained by typing algorithms in sorting the complex mix of aerosol types, and show evidence of oriented ice in cirrus clouds present in the area. In this context, polarization measurements at 1880 nm were used to infer ice habit and cirrus optical depth, which was found in the subvisual/threshold-visible regime, confirming the utility of the aforementioned RSP channel for the remote sensing of even thin cold clouds.

  16. Mid-latitude cirrus classification at Rome Tor Vergata through a multi-channel Raman–Mie–Rayleigh lidar

    Directory of Open Access Journals (Sweden)

    D. Dionisi

    2013-04-01

    Full Text Available A methodology to identify and characterize cirrus clouds has been developed and applied to the multichannel-multiwavelength Rayleigh–Mie–Raman (RMR lidar in Rome-Tor Vergata (RTV. A set of 167 cirrus cases, defined on the basis of quasi-stationary temporal period conditions, has been selected in a dataset consisting of about 500 h of nighttime lidar sessions acquired between February 2007 and April 2010. The derived lidar parameters (effective height, geometrical and optical thickness and mean back-scattering ratio and the cirrus mid-height temperature (estimated from the radiosoundings of Pratica di Mare, WMO site #16245 of this sample have been analyzed by the means of a clustering multivariate analysis. This approach identified four cirrus classes above the RTV site: two thin cirrus clusters in mid and upper troposphere and two thick cirrus clusters in mid-upper troposphere. These results, which are very similar to those derived through the same approach in the lidar site of the Observatoire of Haute Provence (OHP, allows characterizing cirrus clouds over RTV site and attests the robustness of such classification. To have some indications about the cirrus generation methods for the different classes, the analyses of the extinction-to-backscatter ratio (lidar ratio, LReff, in terms of the frequency distribution functions and depending on the mid-height cirrus temperature have been performed. This study suggests that smaller (larger ice crystals compose thin (thick cirrus classes. This information, together with the value of relative humidity over ice (110 ± 30%, calculated through the simultaneous WV Raman measurements for the mid-tropospheric thin class, indicates that this class could be formed by an heterogeneous nucleation mechanism. The RTV cirrus results, re-computed through the cirrus classification by Sassen and Cho (1992, shows good agreement to other mid-latitude lidar cirrus observation for the relative occurrence of

  17. “Using Statistical Comparisons between SPartICus Cirrus Microphysical Measurements, Detailed Cloud Models, and GCM Cloud Parameterizations to Understand Physical Processes Controlling Cirrus Properties and to Improve the Cloud Parameterizations”

    Energy Technology Data Exchange (ETDEWEB)

    Woods, Sarah [SPEC Inc., Boulder, CO (United States)

    2015-12-01

    The dual objectives of this project were improving our basic understanding of processes that control cirrus microphysical properties and improvement of the representation of these processes in the parameterizations. A major effort in the proposed research was to integrate, calibrate, and better understand the uncertainties in all of these measurements.

  18. In situ measurements of tropical cloud properties in the West African Monsoon: upper tropospheric ice clouds, Mesoscale Convective System outflow, and subvisual cirrus

    Directory of Open Access Journals (Sweden)

    W. Frey

    2011-06-01

    Full Text Available In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100 and a Cloud Imaging Probe (CIP operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS. Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3 ± 1.6 cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm.

    Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130

  19. In-situ measurements of tropical cloud properties in the West African monsoon: upper tropospheric ice clouds, mesoscale convective system outflow, and subvisual cirrus

    Directory of Open Access Journals (Sweden)

    W. Frey

    2011-01-01

    Full Text Available In-situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100 and a Cloud Imaging Probe (CIP operated aboard the Russian high altitude research aircraft M-55 ''Geophysica'' with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS. Two or three modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionate more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3, and satellite images clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow (developing MCS ice crystal number concentrations of up to 8.3 cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm.

    Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean

  20. Balloon-borne and Raman lidar observations of Asian dust and cirrus cloud properties over Tsukuba, Japan

    Science.gov (United States)

    Sakai, Tetsu; Orikasa, Narihiro; Nagai, Tomohiro; Murakami, Masataka; Tajiri, Takuya; Saito, Atsushi; Yamashita, Katsuya; Hashimoto, Akihiro

    2014-03-01

    The vertical distributions of the microphysical and optical properties of tropospheric aerosols and cirrus cloud were measured using an instrumented balloon and a ground-based Raman lidar over Tsukuba, Japan (36°N, 140°E), during the Asian dust events on 9 and 21 May 2007 to investigate the influence of Asian mineral dust on ice cloud formation in the upper troposphere. The instrumented balloon measured the particle size distribution, ice crystal images, dew/frost point, relative humidity, and temperature. The Raman lidar measured the particle backscattering and extinction coefficients and the depolarization ratio at a wavelength of 532 nm. The results of the balloon measurements showed that supermicrometer (0.7 to 2.8 µm in optical-equivalent radius) dust particles and ice crystals (10 to 400 µm in maximum dimension) were present in the upper troposphere (8 to 12 km in altitude), with number concentrations varying from 5 × 10-3 to 0.6 cm-3 for dust and from 5 × 10-3 to 0.15 cm-3 for ice crystals. The Raman lidar measurement indicated that the particle depolarization ratios were 15 to 35% in the altitude range of 6 to 12 km, indicating the predominance of nonspherical particles in the region. The temperature ranged from -33 to -63°C, and the relative humidity with respect to ice (RHi), estimated from the total (vapor plus condensate) water content obtained with the Snow White hygrometer in the cloud, was 130% at maximum on 9 May, which was close to the activation point of Asian mineral dust as ice nuclei to form ice crystals.

  1. LIDAR and Millimeter-Wave Cloud RADAR (MWCR) techniques for joint observations of cirrus in Shouxian (32.56°N, 116.78°E), China

    Science.gov (United States)

    Bu, Lingbing; Pan, Honglin; Kumar, K. Raghavendra; Huang, Xingyou; Gao, Haiyang; Qin, Yanqiu; Liu, Xinbo; Kim, Dukhyeon

    2016-10-01

    Cirrus plays an important role in the regulation of the Earth-atmosphere radiation budget. The joint observation using both the LIght Detection And Ranging (LIDAR) and Millimeter-Wave Cloud RADAR (MWCR) was implemented in this study to obtain properties of cirrus at Atmospheric Radiation Measurement (ARM) mobile facility in Shouxian (32.56°N, 116.78°E, 21 m above sea level), China during May-December 2008. We chose the simultaneous measurements of LIDAR and MWCR with effective data days, and the days must with cirrus. Hence, the cirrus properties based on 37 days of data between October 18th and December 13th, 2008 were studied in the present work. By comparing the LIDAR data with the MWCR data, we analyzed the detection capabilities of both instruments quantitatively for measuring the cirrus. The LIDAR cannot penetrate through the thicker cirrus with optical depth (τ) of more than 1.5, while the MWCR cannot sense the clouds with an optical depth of less than 0.3. Statistical analysis showed that the mean cloud base height (CBH) and cloud thickness (CT) of cirrus were 6.5±0.8 km and 2.1±1.1 km, respectively. Furthermore, we investigated three existing inversion methods for deriving the ice water content (IWC) by using the separate LIDAR, MWCR, and the combination of both, respectively. Based on the comparative analysis, a novel joint method was provided to obtain more accurate IWC. In this joint method, cirrus was divided into three different categories according to the optical depth (τ≤0.3, τ≥1.5, and 0.3<τ<1.5). Based on the joint method used in this study, the mean IWC was calculated by means of the statistics, which showed that the mean IWC of cirrus was 0.011±0.008 g m-3.

  2. Spectral reflectance and atmospheric energetics in cirrus-like clouds. Part II: Applications of a Fourier-Riccati approach to radiative transfer

    Energy Technology Data Exchange (ETDEWEB)

    Tsay, S.C.; King, M.D. [NASA/Goddard Space Flight Center, Greenbelt, MD (United States); Gabriel, P.M.; Stephens, G.L. [Colorado State Univ., Fort Collins, CO (United States)

    1996-12-01

    One of the major sources of uncertainty in climate studies is the detection of cirrus clouds and characterization of their radiative properties. Combinations of water vapor absorption channels (e.g., 1.38 {mu}m), ice-water absorption channels (e.g., 1.64 {mu}m), and atmospheric window channels (e.g., 11 {mu}m) in the imager, together with a lidar profiler on future EOS platforms, will contribute to enhancing present understanding of cirrus clouds. The aforementioned spectral channels are used in this study to explore the effects exerted by uncertainties in cloud microphysical properties (e.g., particle size distribution) and cloud morphology on the apparent radiative properties, such as spectral reflectance and heating and cooling rate profiles. As in Part I of the previous study, which establishes the foundations of the Fourier-Riccati method of radiative transfer in inhomogeneous media, cloud extinction and scattering functions are characterized by simple spatial variations with measured and hypothesized microphysics to facilitate the understanding of their radiative properties. Results of this study suggest that (i) while microphysical variations in the scattering and extinction functions of clouds affect the magnitudes of their spectral reflectances, cloud morphology significantly alters the shape of their angular distribution; (ii) spectral reflectances viewed near nadir are least affected by cloud variability; and (iii) cloud morphology can lead to spectral heating and cooling rate profiles that differ substantially from their plane-parallel averaged equivalents. Since there are no horizontal thermal gradients in plane-parallel clouds, it may be difficult to correct for this deficiency. 32 refs., 11 figs., 1 tab.

  3. Cirrus cloud occurrence as function of ambient relative humidity: A comparison of observations from the Southern and Northern Hemisphere midlatitudes obtained during the INCA experiment

    Directory of Open Access Journals (Sweden)

    J. Ström

    2003-06-01

    Full Text Available The occurrence frequency of cirrus clouds as function of ambient relative humidity over ice, based on in-situ observations performed during the INCA experiment, show a clear difference between the campaign carried out at Southern Hemisphere (SH midlatitudes and the campaign carried out at Northern Hemisphere (NH midlatitudes. At a given relative humidity above ice saturation, clouds are more frequent in the NH. At relative humidities near ice saturation, clouds defined as containing particles with sizes larger than 0.55 μm diameter and an integral number density above 0.2 cm−3 were present 70% of the time during the SH campaign, whereas clouds where present 95% of the time during the NH campaign. Using a size threshold of 1 μm diameter to define the presence of clouds result in a less frequent occurrence of 60% of the time in the SH campaign and 75% of the time in the NH campaign. The data show that the presence of particles is a common characteristic of cirrus clouds. Clouds at ice saturation defined as having crystal sizes of at least 5 μm diameter and a number density exceeding 0.001 cm−3 were present in about 80% of the time during the SH campaign, and almost 90% of the time during the NH campaign. The observations reveal a significant cloud presence fraction at humidities well below ice saturation. Local minima in the cloud presence fraction as a function of relative humidity are interpreted as systematic underestimation of cloud presence because cloud particles may become invisible to cloud probes. Based on this interpretation the data suggests that clouds in the SH form preferentially at relative humidities between 140 and 155%, whereas clouds in the NH formed at relative humidities less than 130%. A simple assumption about the probability to reach successively higher humidities in an ice supersaturated air parcel provides a model that explains the main trend of the cloud presence fraction as function of

  4. Nucleation and growth of crystals under cirrus and polar stratospheric cloud conditions

    Science.gov (United States)

    Hallett, John; Queen, Brian; Teets, Edward; Fahey, James

    1995-03-01

    Laboratory studies examine phase changes of hygroscopic substances which occur as aerosol in stratosphere and troposphere (sodium chloride, ammonium sulfate, ammonium bisulfate, nitric acid, sulfuric acid), under controlled conditions, in samples volume 1 to 10(exp -4) ml. Crystallization of salts from supersaturated solutions is examined by slowly evaporating a solution drop on a substrate, under controlled relative humidity, until self nucleation occurs; controlled nucleation of ice in a mm capillary U-tube gives a measured ice crystallization velocity at known supercooling. Two states of crystallization occur for regions where hydrates exist. It is inferred that all of the materials readily exist as supersaturated/supercooled solutions; the degree of metastability appears to be slightly enhanced by inclusion of aircraft produced soot. The crystallization velocity is taken as a measure of viscosity. Results suggest an approach to a glass transition at high molality, supersaturation and/or supercooling within the range of atmospheric interest. It is hypothesized that surface reactions occur more readily on solidified particles - either crystalline or glass, whereas volume reactions are more important on droplets with sufficiently low viscosity and volume diffusivity. Implications are examined for optical properties of such particles in the atmosphere. In a separate experiment, crystal growth was examined in a modified thermal vapor diffusion chamber over the range of cirrus temperature (-30 to -70 C) and under controlled supersaturation and air pressure. The crystals grew at a velocity of 1-2 microns/s, thickness 60-70 micron, in the form of thin column crystals. Design criteria are given for a system to investigate particle growth down to -100 C, (PSC temperatures) where nitric acid particles can be grown under similar control and in the form of hydrate crystals.

  5. Shallow cirrus convection – a source for ice supersaturation

    Directory of Open Access Journals (Sweden)

    Peter Spichtinger

    2014-09-01

    Full Text Available The origin and persistence of high ice supersaturation is still not well understood. In this study, the impact of local dynamics as source for ice supersaturation inside cirrus clouds is investigated. Nucleation and growth of ice crystals inside potentially unstable layers in the tropopause region might lead to shallow convection inside (layered cirrus clouds due to latent heat release. The intrinsic updraught inside convective cells constitutes a dominant but transient source for ice supersaturation. A realistic case of shallow cirrus convection is investigated using radiosonde data, meteorological analyses and large-eddy simulations of cirrus clouds. The simulations corroborate the existence of ice supersaturation inside cirrus clouds as a transient phenomenon. Ice supersaturation is frequent, but determined by the life cycle of convective cells in shallow cirrus convection. Cirrus clouds driven by shallow cirrus convection are mostly not in thermodynamic equilibrium; they are usually in a subsaturated or supersaturated state.

  6. Cirrus microphysics and radiative transfer: A case study

    Science.gov (United States)

    Kinne, Stefan A.; Ackerman, Thomas P.; Heymsfield, Andrew J.

    1990-01-01

    During the Cirrus Intensive Field Operations of FIRE, data collected by the NCAR King Air in the vicinity of Wausau, WI on October 28 were selected to study the influence of cirrus cloud microphysics on radiative transfer and the role of microphysical approximations in radiative transfer models. The instrumentation of the King Air provided, aside from temperature and wind data, up-and downwelling broadband solar and infrared fluxes as well as detailed microphysical data. The aircraft data, supplied every second, are averaged over the 7 legs to represent the properties for that altitude. The resulting vertical profiles, however, suffer from the fact that each leg represents a different cloud column path. Based on the measured microphysical data particle size distributions of equivalent spheres for each cloud level are developed. Accurate radiative transfer calculations are performed, incorporating atmospheric and radiative data from the ground and the stratosphere. Comparing calculated to the measured up- and downwelling fluxes at the seven cloud levels for both the averaged and the three crossover data will help to assess the validity of particle size and shape approximation as they are frequently used to model cirrus clouds. Once agreement is achieved the model results may be applied to determine, in comparison to a cloudfree case, the influence of this particular cirrus on the radiation budget of the earth atmosphere system.

  7. An improved cirrus detection algorithm MeCiDA2 for SEVIRI and its evaluation with MODIS

    Directory of Open Access Journals (Sweden)

    F. Ewald

    2013-02-01

    Full Text Available In this study, a substantially improved version of the Meteosat cirrus detection algorithm (MeCiDA2 will be presented, which now allows application to the full earth disc visible by the Meteosat satellite. As cirrus clouds have an influence on the radiation budget of the earth, their optical properties and their global coverage has to be monitored at the global scale using instruments aboard geostationary satellites. Since MeCiDA was optimised for the area of Europe only, various changes were necessary to handle the variable conditions found over the full Meteosat disc. Required changes include the consideration of the viewing angle dependency and of the sensitivity of the 9.7 μm channel to the ozone column. To this end, a correction is implemented that minimises the influence of the variability of the stratospheric ozone. The evaluation of the proposed improvements is carried out by using MeCiDA applied to MODIS (moderate resolution imaging spectrometer data to address viewing angle-dependent cirrus detection, and by additionally comparing it to the cloud optical properties MOD06 cirrus product. The new MeCiDA version detects less cirrus than the original one for latitudes larger than 40°, but almost the same amount elsewhere. MeCiDA's version for MODIS is more sensitive than that for SEVIRI (spinning enhanced visible and infrared imager with cirrus occurrences higher by 10%, and the new MeCiDA provides almost the same cirrus coverage (±0.1 as given by the cloud phase optical properties from MODIS for latitudes smaller than 50°. Finally, the influence of sub-pixel clouds on the SEVIRI cirrus detection has been examined: more than 60% of the undetected SEVIRI cirrus pixels have a cirrus coverage smaller than 0.5.

  8. Simultaneous retrieval of water vapour, temperature and cirrus clouds properties from measurements of far infrared spectral radiance over the Antarctic Plateau

    Science.gov (United States)

    Di Natale, Gianluca; Palchetti, Luca; Bianchini, Giovanni; Del Guasta, Massimo

    2017-03-01

    The possibility separating the contributions of the atmospheric state and ice clouds by using spectral infrared measurements is a fundamental step to quantifying the cloud effect in climate models. A simultaneous retrieval of cloud and atmospheric parameters from infrared wideband spectra will allow the disentanglement of the spectral interference between these variables. In this paper, we describe the development of a code for the simultaneous retrieval of atmospheric state and ice cloud parameters, and its application to the analysis of the spectral measurements acquired by the Radiation Explorer in the Far Infrared - Prototype for Applications and Development (REFIR-PAD) spectroradiometer, which has been in operation at Concordia Station on the Antarctic Plateau since 2012. The code performs the retrieval with a computational time that is comparable with the instrument acquisition time. Water vapour and temperature profiles and the cloud optical and microphysical properties, such as the generalised effective diameter and the ice water path, are retrieved by exploiting the 230-980 cm-1 spectral band. To simulate atmospheric radiative transfer, the Line-By-Line Radiative Transfer Model (LBLRTM) has been integrated with a specifically developed subroutine based on the δ-Eddington two-stream approximation, whereas the single-scattering properties of cirrus clouds have been derived from a database for hexagonal column habits. In order to detect ice clouds, a backscattering and depolarisation lidar, co-located with REFIR-PAD has been used, allowing us to infer the position and the cloud thickness to be used in the retrieval. A climatology of the vertical profiles of water vapour and temperature has been performed by using the daily radiosounding available at the station at 12:00 UTC. The climatology has been used to build an a priori profile correlation to constrain the fitting procedure. An optimal estimation method with the Levenberg-Marquardt approach has been

  9. Ready-to-Use Methods for the Detection of Clouds, Cirrus, Snow, Shadow, Water and Clear Sky Pixels in Sentinel-2 MSI Images

    Directory of Open Access Journals (Sweden)

    André Hollstein

    2016-08-01

    Full Text Available Classification of clouds, cirrus, snow, shadows and clear sky areas is a crucial step in the pre-processing of optical remote sensing images and is a valuable input for their atmospheric correction. The Multi-Spectral Imager on board the Sentinel-2’s of the Copernicus program offers optimized bands for this task and delivers unprecedented amounts of data regarding spatial sampling, global coverage, spectral coverage, and repetition rate. Efficient algorithms are needed to process, or possibly reprocess, those big amounts of data. Techniques based on top-of-atmosphere reflectance spectra for single-pixels without exploitation of external data or spatial context offer the largest potential for parallel data processing and highly optimized processing throughput. Such algorithms can be seen as a baseline for possible trade-offs in processing performance when the application of more sophisticated methods is discussed. We present several ready-to-use classification algorithms which are all based on a publicly available database of manually classified Sentinel-2A images. These algorithms are based on commonly used and newly developed machine learning techniques which drastically reduce the amount of time needed to update the algorithms when new images are added to the database. Several ready-to-use decision trees are presented which allow to correctly label about 91 % of the spectra within a validation dataset. While decision trees are simple to implement and easy to understand, they offer only limited classification skill. It improves to 98 % when the presented algorithm based on the classical Bayesian method is applied. This method has only recently been used for this task and shows excellent performance concerning classification skill and processing performance. A comparison of the presented algorithms with other commonly used techniques such as random forests, stochastic gradient descent, or support vector machines is also given. Especially

  10. The Dependence of Cirrus Gamma Size Distributions Expressed as Volumes in N(sub 0)-Lambda-Mu Phase Space and Bulk Cloud Properties on Environmental Conditions: Results from the Small Ice Particles in Cirrus Experiment (SPARTICUS)

    Science.gov (United States)

    Jackson, Robert C.; McFarquhar, Greg M.; Fridlind, Ann M.; Atlas, Rachel

    2015-01-01

    The variability of cirrus ice microphysical properties is investigated using observations obtained during the Small Particles in Cirrus (SPARTICUS) campaign. An existing approach that represents a size distribution (SD) as a single gamma function using an ellipsoid of equally realizable solutions in (N(sub 0), lambda, mu) phase space is modified to automatically identify multiple modes in SDs and characterize each mode by such an ellipsoid. The modified approach is applied to ice crystals with maximum dimension D greater than15 micrometers collected by the 2-D stereo and 2-D precipitation probes on the Stratton Park Engineering Company Learjet. The dependencies of N(sub 0), mu, and lambda from each mode, total number concentration, bulk extinction, ice water content (IWC), and mass median maximum dimension D(sub mm) as a function of temperature T and cirrus type are then analyzed. The changes in the observed codependencies between N(sub 0), mu, and lambda, bulk extinction, IWC, and D(sub mm) with environmental conditions indicate that particles were larger at higher T during SPARTICUS. At most two modes were observed in any SD during SPARTICUS, with the average boundary between them at 115 micrometers, similar to past studies not using probes with shatter mitigating tips and artifact removal algorithms. The bimodality of the SDs increased with T. This and the differences in N(sub 0), mu, and lambda between the modes suggest that particles with smaller D nucleated more recently than particles with larger D, which grew via vapor deposition and aggregation. Because smaller crystals, whose concentrations are uncertain, make marginal contributions to higher order moments, the use of higher moments for evaluating model fields is suggested.

  11. Sensitivity of Cirrus and Mixed-phase Clouds to the Ice Nuclei Spectra in McRAS-AC: Single Column Model Simulations

    Science.gov (United States)

    Betancourt, R. Morales; Lee, D.; Oreopoulos, L.; Sud, Y. C.; Barahona, D.; Nenes, A.

    2012-01-01

    The salient features of mixed-phase and ice clouds in a GCM cloud scheme are examined using the ice formation parameterizations of Liu and Penner (LP) and Barahona and Nenes (BN). The performance of LP and BN ice nucleation parameterizations were assessed in the GEOS-5 AGCM using the McRAS-AC cloud microphysics framework in single column mode. Four dimensional assimilated data from the intensive observation period of ARM TWP-ICE campaign was used to drive the fluxes and lateral forcing. Simulation experiments where established to test the impact of each parameterization in the resulting cloud fields. Three commonly used IN spectra were utilized in the BN parameterization to described the availability of IN for heterogeneous ice nucleation. The results show large similarities in the cirrus cloud regime between all the schemes tested, in which ice crystal concentrations were within a factor of 10 regardless of the parameterization used. In mixed-phase clouds there are some persistent differences in cloud particle number concentration and size, as well as in cloud fraction, ice water mixing ratio, and ice water path. Contact freezing in the simulated mixed-phase clouds contributed to transfer liquid to ice efficiently, so that on average, the clouds were fully glaciated at T approximately 260K, irrespective of the ice nucleation parameterization used. Comparison of simulated ice water path to available satellite derived observations were also performed, finding that all the schemes tested with the BN parameterization predicted 20 average values of IWP within plus or minus 15% of the observations.

  12. Sensitivity of cirrus and mixed-phase clouds to the ice nuclei spectra in McRAS-AC: single column model simulations

    Directory of Open Access Journals (Sweden)

    R. Morales Betancourt

    2012-06-01

    Full Text Available The salient features of mixed-phase and ice clouds in a GCM cloud scheme are examined using the ice formation parameterizations of Liu and Penner (LP and Barahona and Nenes (BN. The performance of LP and BN ice nucleation parameterizations were assessed in the GEOS-5 AGCM using the McRAS-AC cloud microphysics framework in single column mode. Four dimensional assimilated data from the intensive observation period of ARM TWP-ICE campaign was used to drive the fluxes and lateral forcing. Simulation experiments where established to test the impact of each parameterization in the resulting cloud fields. Three commonly used IN spectra were utilized in the BN parameterization to described the availability of IN for heterogeneous ice nucleation. The results show large similarities in the cirrus cloud regime between all the schemes tested, in which ice crystal concentrations were within a factor of 10 regardless of the parameterization used. In mixed-phase clouds there are some persistent differences in cloud particle number concentration and size, as well as in cloud fraction, ice water mixing ratio, and ice water path. Contact freezing in the simulated mixed-phase clouds contributed to transfer liquid to ice efficiently, so that on average, the clouds were fully glaciated at T~260 K, irrespective of the ice nucleation parameterization used. Comparison of simulated ice water path to available satellite derived observations were also performed, finding that all the schemes tested with the BN parameterization predicted average values of IWP within ±15% of the observations.

  13. Sensitivity of cirrus and mixed-phase clouds to the ice nuclei spectra in McRAS-AC: single column model simulations

    Directory of Open Access Journals (Sweden)

    R. Morales Betancourt

    2012-11-01

    Full Text Available The salient features of mixed-phase and ice clouds in a GCM cloud scheme are examined using the ice nucleation parameterizations of Liu and Penner (LP and Barahona and Nenes (BN. The performance of both parameterizations was assessed in the GEOS-5 AGCM using the McRAS-AC cloud microphysics framework in single column mode. Four dimensional assimilated data from the intensive observation period of ARM TWP-ICE campaign was used to drive the fluxes and lateral forcing. Simulation experiments were established to test the impact of each parameterization in the resulting cloud fields. Three commonly used IN spectra were utilized in the BN parameterization to describe the availability of IN for heterogeneous ice nucleation. The results showed large similarities in the cirrus cloud regime between all the schemes tested, in which ice crystal concentrations were within a factor of 10 regardless of the parameterization used. In mixed-phase clouds there were some persistent differences in cloud particle number concentration and size, as well as in cloud fraction, ice water mixing ratio, and ice water path. Contact freezing in the simulated mixed-phase clouds contributed to the effective transfer of liquid to ice, so that on average, the clouds were fully glaciated at T 260 K, irrespective of the ice nucleation parameterization used. Comparison of simulated ice water path to available satellite derived observations were also performed, finding that all the schemes tested with the BN parameterization predicted average values of IWP within ±15% of the observations.

  14. Characterization of 3D Cirrus Cloud and Radiation Fields Using ARS/AIRS/MODIS data and its Application to Climate Model

    Energy Technology Data Exchange (ETDEWEB)

    Liou, Kuo-Nan [Univ. of California, Los Angeles, CA (United States); Ou, S. C. [Univ. of California, Los Angeles, CA (United States); Gu, Y. [Univ. of California, Los Angeles, CA (United States); Takano, Y. [Univ. of California, Los Angeles, CA (United States)

    2016-02-22

    During the report period, we have made the following research accomplishments. First, we performed analysis for a number of MODIS scenes comprising of heavy dust events and ice clouds, covering regions of frequent dust outbreaks in East Asia, Middle East, and West Africa, as well as areas associated with long-range dust transports over the Equatorial Tropical Atlantic Ocean. These scenes contain both dust/aerosols and clouds. We collected suitable aerosol/ice-cloud data, correlated ice cloud and aerosol parameters by means of statistical analysis, and interpreted resulting correlation trends based on the physical principles governing cloud microphysics. Aerosol and cloud optical depths and cloud effective particle size inferred from MODIS for selected domains were analyzed from which the parameters including dust aerosol number concentration, ice cloud water path, and ice particle number concentration were subsequently derived. We illustrated that the Twomey (solar albedo) effect can be statistically quantified based on the slope of best-fit straight lines in the correlation study. Analysis of aerosol and cloud retrieval products revealed that for all cases, the region with a larger dust aerosol optical depth is always characterized by a smaller cloud particle size, consistent with the Twomey hypothesis for aerosol-cloud interactions. Second, we developed mean correlation curves with uncertainties associated with small ice-crystal concentration observations for the mean effective ice crystal size (De) and ice water content (IWC) by dividing the atmosphere into three characteristic regions: Tropics cirrus, Midlatitude cirrus, including a temperature classification to improve correlation, and Arctic ice clouds. We illustrated that De has a high correlation with IWC based on theoretical consideration and analysis of thousands of observed ice crystal data obtained from a number of ARM-DOE field campaigns and other experiments. The correlation has the form: ln(De) = a

  15. Molecular Hydrogen in Infrared Cirrus

    CERN Document Server

    Gillmon, K; Gillmon, Kristen

    2006-01-01

    We combine data from our recent FUSE survey of interstellar molecular hydrogen absorption toward 50 high-latitude AGN with COBE-corrected IRAS 100 micron emission maps to study the correlation of infrared cirrus with H2. A plot of the H2 column density vs. IR cirrus intensity shows the same transition in molecular fraction, f_H2, as seen with total hydrogen column density, N_H. This transition is usually attributed to H2 self-shielding, and it suggests that many diffuse cirrus clouds contain H2 in significant fractions, f_H2 = 1-30%. These clouds cover approximately 50% of the northern sky at latitudes b > 30 degrees, at temperature-corrected 100 micron intensities D_100 > 1.5 MJy/sr. The sheetlike cirrus clouds, with hydrogen densities n_H > 30 cm^-3, may be compressed by dynamical processes at the disk-halo interface, and they are conducive to H2 formation on grain surfaces. Exploiting the correlation between N(H2) and 100 micron intensity, we estimate that cirrus clouds at b > 30 contain approximately 3000...

  16. Contrails, contrail cirrus, and ship tracks

    OpenAIRE

    Gierens, Klaus Martin

    2007-01-01

    The following text is an enlarged version of the conference tutorial lecture on contrails, contrail cirrus, and ship tracks. I start with a general introduction into aerosol effects on clouds. Contrail formation and persistence, aviation’s share to cirrus trends and ship tracks are treated then.

  17. Laboratory measurements of HDO/H$_{2}$O isotopic fractionation during ice deposition in simulated cirrus clouds

    CERN Document Server

    Lamb, Kara; Bolot, Maximilien; Sarkozy, Laszlo; Saathoff, Harald; Möhler, Ottmar; Moyer, Elisabeth

    2015-01-01

    The stable isotopologues of water have been used in atmospheric and climatic studies for over fifty years, because the temperature-dependent preferential condensation of heavy isotopologues during phase changes makes them useful diagnostics of the hydrological cycle. However, the degree of preferential condensation has never been directly measured at temperatures below 233 K (-40$^{\\circ}$C), conditions of cirrus formation in the atmosphere and routinely observed at surface elevation in polar regions. (Models generally assume an extrapolation from the warmer experiments of Merlivat and Nief, 1967.) Non-equilibrium effects that should alter preferential partitioning have also not been well-characterized experimentally (Jouzel and Merlivat 1984). We present here the first direct experimental measurements of the HDO/H$_2$O equilibrium fractionation factor between vapour and ice ($\\alpha_{\\mathrm {eq}}$) at cirrus-relevant temperatures, and the first quantitative validation of the kinetic modification to equilibr...

  18. A tandem approach for collocated measurements of microphysical and radiative cirrus properties

    Science.gov (United States)

    Klingebiel, Marcus; Ehrlich, André; Finger, Fanny; Röschenthaler, Timo; Jakirlić, Suad; Voigt, Matthias; Müller, Stefan; Maser, Rolf; Wendisch, Manfred; Hoor, Peter; Spichtinger, Peter; Borrmann, Stephan

    2017-09-01

    Microphysical and radiation measurements were collected with the novel AIRcraft TOwed Sensor Shuttle (AIRTOSS) - Learjet tandem platform. The platform is a combination of an instrumented Learjet 35A research aircraft and an aerodynamic bird, which is detached from and retracted back to the aircraft during flight via a steel wire with a length of 4000 m. Both platforms are equipped with radiative, cloud microphysical, trace gas, and meteorological instruments. The purpose of the development of this tandem set-up is to study the inhomogeneity of cirrus as well as other stratiform clouds. Sophisticated numerical flow simulations were conducted in order to optimally integrate an axially asymmetric Cloud Combination Probe (CCP) inside AIRTOSS. The tandem platform was applied during measurements at altitudes up to 36 000 ft (10 970 m) in the framework of the AIRTOSS - Inhomogeneous Cirrus Experiment (AIRTOSS-ICE). Ten flights were performed above the North Sea and Baltic Sea to probe frontal and in situ formed cirrus, as well as anvil outflow cirrus. For one flight, cirrus microphysical and radiative properties displayed significant inhomogeneities resolved by both measurement platforms. The CCP data show that the maximum of the observed particle number size distributions shifts with decreasing altitude from 30 to 300 µm, which is typical for frontal, midlatitude cirrus. Theoretical considerations imply that cloud particle aggregation inside the studied cirrus is very unlikely. Consequently, diffusional growth was identified to be the dominant microphysical growth process. Measurements of solar downward and upward irradiances at 670 nm wavelength were conducted above, below, and in the cirrus on both the Learjet and AIRTOSS. The observed variability of the downward irradiance below the cirrus reflects the horizontal heterogeneity of the observed thin cirrus. Vertically resolved solar heating rates were derived by either using single-platform measurements at different

  19. Optical-Microphysical Cirrus Model

    Science.gov (United States)

    Reichardt, J.; Reichardt, S.; Lin, R.-F.; Hess, M.; McGee, T. J.; Starr, D. O.

    2008-01-01

    A model is presented that permits the simulation of the optical properties of cirrus clouds as measured with depolarization Raman lidars. It comprises a one-dimensional cirrus model with explicit microphysics and an optical module that transforms the microphysical model output to cloud and particle optical properties. The optical model takes into account scattering by randomly oriented or horizontally aligned planar and columnar monocrystals and polycrystals. Key cloud properties such as the fraction of plate-like particles and the number of basic crystals per polycrystal are parameterized in terms of the ambient temperature, the nucleation temperature, or the mass of the particles. The optical-microphysical model is used to simulate the lidar measurement of a synoptically forced cirrostratus in a first case study. It turns out that a cirrus cloud consisting of only monocrystals in random orientation is too simple a model scenario to explain the observations. However, good agreement between simulation and observation is reached when the formation of polycrystals or the horizontal alignment of monocrystals is permitted. Moreover, the model results show that plate fraction and morphological complexity are best parameterized in terms of particle mass, or ambient temperature which indicates that the ambient conditions affect cirrus optical properties more than those during particle formation. Furthermore, the modeled profiles of particle shape and size are in excellent agreement with in situ and laboratory studies, i.e., (partly oriented) polycrystalline particles with mainly planar basic crystals in the cloud bottom layer, and monocrystals above, with the fraction of columns increasing and the shape and size of the particles changing from large thin plates and long columns to small, more isometric crystals from cloud center to top. The findings of this case study corroborate the microphysical interpretation of cirrus measurements with lidar as suggested previously.

  20. Persistent Ice Supersaturation in Tropical Anvil Cirrus

    Science.gov (United States)

    Jensen, E.; Fridlind, A.; Ackerman, A.; Pfister, L.; Herman, R.; Bui, T.; Baumgardner, D.; Lawson, P.

    2003-12-01

    During the 2002 Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE), the NASA WB-57 spent many hours sampling cloud microphysical properties, temperature, turbulence, and water vapor concentration within subtropical anvil cirrus. These measurements indicate that air within the cirrus is often substantially supersaturated with respect to ice, with average ice supersaturations increasing from about 5 to 30% as cloud temperature decreases from 220 to 195 K. The persistence of large supersaturations in cirrus with high ice crystal surface areas is unexpected. In this study, we examine the dependence of the measured anvil supersaturations on parameters such as ice water content, turbulence, anvil age, and temperature. We also use a three-dimensional cloud model that resolves the size distributions of cloud particles to investigate the physical processes responsible for the maintenance of ice supersaturation in anvils. The effects of radiatively driven turbulence, wave-driven temperature oscillations, and entrainment of ambient air will be discussed.

  1. Characterization of 3D Cirrus Cloud and Radiation Fields Using ARS/AIRS/MODIS data and its Application to Climate Model

    Energy Technology Data Exchange (ETDEWEB)

    Liou, Kuo-Nan [Univ. of California, Los Angeles, CA (United States); Ou, S. C. [Univ. of California, Los Angeles, CA (United States); Gu, Y. [Univ. of California, Los Angeles, CA (United States); Takano, Y. [Univ. of California, Los Angeles, CA (United States)

    2016-02-22

    During the report period, we have made the following research accomplishments. First, we performed analysis for a number of MODIS scenes comprising of heavy dust events and ice clouds, covering regions of frequent dust outbreaks in East Asia, Middle East, and West Africa, as well as areas associated with long-range dust transports over the Equatorial Tropical Atlantic Ocean. These scenes contain both dust/aerosols and clouds. We collected suitable aerosol/ice-cloud data, correlated ice cloud and aerosol parameters by means of statistical analysis, and interpreted resulting correlation trends based on the physical principles governing cloud microphysics. Aerosol and cloud optical depths and cloud effective particle size inferred from MODIS for selected domains were analyzed from which the parameters including dust aerosol number concentration, ice cloud water path, and ice particle number concentration were subsequently derived. We illustrated that the Twomey (solar albedo) effect can be statistically quantified based on the slope of best-fit straight lines in the correlation study. Analysis of aerosol and cloud retrieval products revealed that for all cases, the region with a larger dust aerosol optical depth is always characterized by a smaller cloud particle size, consistent with the Twomey hypothesis for aerosol-cloud interactions. Second, we developed mean correlation curves with uncertainties associated with small ice-crystal concentration observations for the mean effective ice crystal size (De) and ice water content (IWC) by dividing the atmosphere into three characteristic regions: Tropics cirrus, Midlatitude cirrus, including a temperature classification to improve correlation, and Arctic ice clouds. We illustrated that De has a high correlation with IWC based on theoretical consideration and analysis of thousands of observed ice crystal data obtained from a number of ARM-DOE field campaigns and other experiments. The correlation has the form: ln(De) = a

  2. Orographic cirrus in the future climate

    Directory of Open Access Journals (Sweden)

    H. Joos

    2009-04-01

    Full Text Available A cloud resolving model (CRM is used to investigate the formation of orographic cirrus clouds in the current and future climate. The formation of cirrus clouds depends on a variety of dynamical and thermodynamical processes, which act on different scales. First, the capability of the CRM in realistically simulating orographic cirrus clouds has been tested by comparing the simulated results to aircraft measurements of an orographic cirrus cloud. The influence of a warmer climate on the microphysical and optical properties of cirrus clouds has been investigated by initializing the CRM with vertical profiles of horizontal wind, temperature and moisture from IPCC A1B simulations for the current climate and for the period 2090–2099 for two regions representative for North and South America. In a future climate, the increase in moisture dampens the vertical propagation of gravity waves and the occurring vertical velocities. Together with higher temperatures fewer ice crystals nucleate homogeneously. Assuming that the relative humidity does not change in a warmer climate the specific humidity in the model is increased. This increase in specific humidity in a warmer climate results in a higher ice water content. The net effect of a reduced ice crystal number concentration and a higher ice water content is an increased optical depth.

  3. A statistical comparison of cirrus particle size distributions measured using the 2-D stereo probe during the TC4, SPARTICUS, and MACPEX flight campaigns with historical cirrus datasets

    Science.gov (United States)

    Schwartz, M. Christian

    2017-08-01

    This paper addresses two straightforward questions. First, how similar are the statistics of cirrus particle size distribution (PSD) datasets collected using the Two-Dimensional Stereo (2D-S) probe to cirrus PSD datasets collected using older Particle Measuring Systems (PMS) 2-D Cloud (2DC) and 2-D Precipitation (2DP) probes? Second, how similar are the datasets when shatter-correcting post-processing is applied to the 2DC datasets? To answer these questions, a database of measured and parameterized cirrus PSDs - constructed from measurements taken during the Small Particles in Cirrus (SPARTICUS); Mid-latitude Airborne Cirrus Properties Experiment (MACPEX); and Tropical Composition, Cloud, and Climate Coupling (TC4) flight campaigns - is used.Bulk cloud quantities are computed from the 2D-S database in three ways: first, directly from the 2D-S data; second, by applying the 2D-S data to ice PSD parameterizations developed using sets of cirrus measurements collected using the older PMS probes; and third, by applying the 2D-S data to a similar parameterization developed using the 2D-S data themselves. This is done so that measurements of the same cloud volumes by parameterized versions of the 2DC and 2D-S can be compared with one another. It is thereby seen - given the same cloud field and given the same assumptions concerning ice crystal cross-sectional area, density, and radar cross section - that the parameterized 2D-S and the parameterized 2DC predict similar distributions of inferred shortwave extinction coefficient, ice water content, and 94 GHz radar reflectivity. However, the parameterization of the 2DC based on uncorrected data predicts a statistically significantly higher number of total ice crystals and a larger ratio of small ice crystals to large ice crystals than does the parameterized 2D-S. The 2DC parameterization based on shatter-corrected data also predicts statistically different numbers of ice crystals than does the parameterized 2D-S, but the

  4. Challenges in applying the ACPO principles in cloud forensic investigations

    Directory of Open Access Journals (Sweden)

    Harjinder Singh Lallie

    2012-03-01

    Full Text Available The numerous advantages offered by cloud computing has fuelled its growth and has made it one of the most significant of current computing trends. The same advantages have created complex issues for those conducting digital forensic investigations. Digital forensic investigators rely on the ACPO guidelines when conducting an investigation, however the guidelines make no reference to some of the issues presented by cloud investigations.This study investigates the impact of cloud computing on ACPO’s core principles and asks whether there is a need for the principles and guidelines to be reviewed to address the issues presented by cloud computing. Empirical research is conducted and data collected from key experts in the field of digital forensics.This research presents several key findings: there is a very real concern for how cloud computing will affect digital forensic investigations; the ACPO principles cannot easily be applied in all cloud investigations but are generally sufficient for cloud computing forensic investigations. However the advent of cloud computing is a significant development in technology and may in the near future warrant a review of the guidelines in particular to incorporate the involvement of third parties in cloud investigations.

  5. Estimation of cirrus parameters from multispectral measurements in the near-infrared and statements about multilayered clouds

    Science.gov (United States)

    Costanzo, Claudio; Bakan, Stephan

    1997-01-01

    During the aircraft campaign EUCREX 94 different missions with the multispectral sensor OVID were flown inside frontal ice cloud systems. This study present estimated effective radii and cloud optical depths from measurements around 1.05 and 1.6 micrometer under the assumption of different particle shapes. The best agreement with independent measurements of other instruments result from the assumption of an irregular polycrystal. The measured effective radii vary between 18 and 46 micrometer which is compatible with published particle size distributions of moderate ambient temperatures between minus 45 and minus 55 degrees Celsius. An additional consideration of spatial features allow the distinction of cloud layers in different altitudes in the atmosphere and perhaps the estimation of cloud parameters from individual layers. This study show an example of such a recognition and discuss the potential for an operational algorithm.

  6. Parameterization of convective clouds mesoscale convective systems, and convective-generated cirrus. Final report, September 15, 1990--October 31, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Cotton, W.R.

    1993-11-05

    The overall goal of this research is to develop a scheme to parameterize diabatic heating, moisture/water substance, and momentum transports, and precipitation from mesoscale convective systems (MCSs) for use in general circulation models (GCMs). Our approach is to perform explicit cloud-resolving simulations of MCSs in the spirit of the GEWEX Cloud Systems Study (GCSS), by using the Regional Atmospheric Modeling System (RAMS) developed at Colorado State University (CSU). We then perform statistical analyses (conditional sampling, ensemble-averages, trajectory analyses) of simulated MCSs to assist in fabricating a parameterization scheme, calibrating coefficients, and provide independent tests of the efficacy of the parameterization scheme. A cloud-resolving simulation of ordinary cumulonimbi forced by sea breeze fronts has been completed. Analysis of this case and comparison with parameterized convection simulations has resulted in a number of refinements in the scheme. Three three-dimensional, cloud-resolving simulations of MCSs have been completed. Statistical analyses of model-output data are being performed to assist in developing a parameterization scheme of MCSs in general circulation models.

  7. A comparison of radiometric fluxes influenced by parameterization cirrus clouds with observed fluxes at the Southern Great Plains (SGP) cloud and radiation testbed (CART) site

    Energy Technology Data Exchange (ETDEWEB)

    Mace, G.G.; Ackerman, T.P.; George, A.T. [Penn State Univ., University Park, PA (United States)

    1996-04-01

    The data from the Atmospheric Radiation Measurement (ARM) Program`s Southern Great plains Site (SCP) is a valuable resource. We have developed an operational data processing and analysis methodology that allows us to examine continuously the influence of clouds on the radiation field and to test new and existing cloud and radiation parameterizations.

  8. Microphysical Ice Crystal Properties in Mid-Latitude Frontal Cirrus

    Science.gov (United States)

    Schlage, Romy; Jurkat, Tina; Voigt, Christiane; Minikin, Andreas; Weigel, Ralf; Molleker, Sergej; Klingebiel, Marcus; Borrmann, Stephan; Luebke, Anna; Krämer, Martina; Kaufmann, Stefan; Schäfler, Andreas

    2015-04-01

    Cirrus clouds modulate the climate by reflection of shortwave solar radiation and trapping of longwave terrestrial radiation. Their net radiative effect can be positive or negative depending on atmospheric and cloud parameters including ice crystal number density, size and shape. Latter microphysical ice crystal properties have been measured during the mid-latitude cirrus mission ML-CIRRUS with a set of cloud instruments on the new research aircraft HALO. The mission took place in March/April 2014 with 16 flights in cirrus formed above Europe and the Atlantic. The ice clouds were encountered at altitudes from 7 to 14 km in the typical mid-latitude temperature range. A focus of the mission was the detection of frontal cirrus linked to warm conveyor belts (WCBs). Within WCBs, water vapor is transported in the warm sector of an extra-tropical cyclone from the humid boundary layer to the upper troposphere. Cirrus cloud formation can be triggered in the WCB outflow region at moderate updraft velocities and additionally at low updrafts within the high pressure system linked to the WCB. Due to their frequent occurrence, WCBs represent a major source for regions of ice supersaturation and cirrus formation in the mid-latitudes. Here, we use data from the Cloud and Aerosol Spectrometer with detection for POLarization (CAS-POL) and the Cloud Combination Probe (CCP), combining a Cloud Droplet Probe (CDP) and a greyscale Cloud Imaging Probe (CIPgs) to investigate the ice crystal distribution in the size range from 0.5 µm to 1 mm. We derive microphysical cirrus properties in mid-latitude warm front cirrus. Further, we investigate their variability and their dependence on temperature and relative humidity. Finally, we compare the microphysical properties of these frontal cirrus to cirrus clouds that formed at low updrafts within high pressure systems or at high updraft velocities in lee waves. We quantify statistically significant differences in cirrus properties formed in these

  9. Orographic cirrus in a future climate

    Directory of Open Access Journals (Sweden)

    H. Joos

    2009-10-01

    Full Text Available A cloud resolving model (CRM is used to investigate the formation of orographic cirrus clouds in the current and future climate. The formation of cirrus clouds depends on a variety of dynamical and thermodynamical processes, which act on different scales. First, the capability of the CRM in realistically simulating orographic cirrus clouds has been tested by comparing the simulated results to aircraft measurements of an orographic cirrus cloud. The influence of a warmer climate on the microphysical and optical properties of cirrus clouds has been investigated by initializing the CRM with vertical profiles of horizontal wind, potential temperature and equivalent potential temperature, respectively. The vertical profiles are extracted from IPCC A1B simulations for the current climate and for the period 2090–2099 for two regions representative for North and South America. The influence of additional moisture in a future climate on the propagation of gravity waves and the formation of orographic cirrus could be estimated. In a future climate, the increase in moisture dampens the vertical propagation of gravity waves and the occurring vertical velocities in the moist simulations. Together with higher temperatures fewer ice crystals nucleate homogeneously. Assuming that the relative humidity does not change in a warmer climate the specific humidity in the model is increased. This increase in specific humidity in a warmer climate results in a higher ice water content. The net effect of a reduced ice crystal number concentration and a higher ice water content is an increased optical depth. However, in some moist simulations dynamical changes contribute to changes in the ice water content, ice crystal number concentration and optical depth. For the corresponding dry simulations dynamical changes are more pronounced leading to a decreased optical depth in a future climate in some cases.

  10. Abundance of fluorescent biological aerosol particles at temperatures conducive to the formation of mixed-phase and cirrus clouds

    Science.gov (United States)

    Twohy, Cynthia H.; McMeeking, Gavin R.; DeMott, Paul J.; McCluskey, Christina S.; Hill, Thomas C. J.; Burrows, Susannah M.; Kulkarni, Gourihar R.; Tanarhte, Meryem; Kafle, Durga N.; Toohey, Darin W.

    2016-07-01

    Some types of biological particles are known to nucleate ice at warmer temperatures than mineral dust, with the potential to influence cloud microphysical properties and climate. However, the prevalence of these particle types above the atmospheric boundary layer is not well known. Many types of biological particles fluoresce when exposed to ultraviolet light, and the Wideband Integrated Bioaerosol Sensor takes advantage of this characteristic to perform real-time measurements of fluorescent biological aerosol particles (FBAPs). This instrument was flown on the National Center for Atmospheric Research Gulfstream V aircraft to measure concentrations of fluorescent biological particles from different potential sources and at various altitudes over the US western plains in early autumn. Clear-air number concentrations of FBAPs between 0.8 and 12 µm diameter usually decreased with height and generally were about 10-100 L-1 in the continental boundary layer but always much lower at temperatures colder than 255 K in the free troposphere. At intermediate temperatures where biological ice-nucleating particles may influence mixed-phase cloud formation (255 K ≤ T ≤ 270 K), concentrations of fluorescent particles were the most variable and were occasionally near boundary-layer concentrations. Predicted vertical distributions of ice-nucleating particle concentrations based on FBAP measurements in this temperature regime sometimes reached typical concentrations of primary ice in clouds but were often much lower. If convection was assumed to lift boundary-layer FBAPs without losses to the free troposphere, better agreement between predicted ice-nucleating particle concentrations and typical ice crystal concentrations was achieved. Ice-nucleating particle concentrations were also measured during one flight and showed a decrease with height, and concentrations were consistent with a relationship to FBAPs established previously at the forested surface site below. The vertical

  11. Abundance of fluorescent biological aerosol particles at temperatures conducive to the formation of mixed-phase and cirrus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Twohy, Cynthia H.; McMeeking, Gavin R.; DeMott, Paul J.; McCluskey, Christina S.; Hill, Thomas C. J.; Burrows, Susannah M.; Kulkarni, Gourihar R.; Tanarhte, Meryem; Kafle, Durga N.; Toohey, Darin W.

    2016-01-01

    Some types of biological particles are known to nucleate ice at warmer temperatures than mineral dust, with the potential to influence cloud microphysical properties and climate. However, the prevalence of these particle types above the atmospheric boundary layer is not well known. Many types of biological particles fluoresce when exposed to ultraviolet light, and the Wideband Integrated Bioaerosol Sensor takes advantage of this characteristic to perform real-time measurements of fluorescent biological aerosol particles (FBAPs). This instrument was flown on the National Center for Atmospheric Research Gulfstream V aircraft to measure concentrations of fluorescent biological particles from different potential sources and at various altitudes over the US western plains in early autumn. Clear-air number concentrations of FBAPs between 0.8 and 12 µm diameter usually decreased with height and generally were about 10–100 L-1 in the continental boundary layer but always much lower at temperatures colder than 255 K in the free troposphere. At intermediate temperatures where biological ice-nucleating particles may influence mixed-phase cloud formation (255 K ≤ T ≤ 270 K), concentrations of fluorescent particles were the most variable and were occasionally near boundary-layer concentrations. Predicted vertical distributions of ice-nucleating particle concentrations based on FBAP measurements in this temperature regime sometimes reached typical concentrations of primary ice in clouds but were often much lower. If convection was assumed to lift boundary-layer FBAPs without losses to the free troposphere, better agreement between predicted ice-nucleating particle concentrations and typical ice crystal concentrations was achieved. Ice-nucleating particle concentrations were also measured during one flight and showed a decrease with height, and concentrations were consistent with a relationship to FBAPs established previously at the forested surface

  12. Lifetime Extension of Cirrus Cloud Ice Particles upon Contamination with HCl and HNO3 under conditions of the Upper Troposphere and Lower Stratosphere

    Science.gov (United States)

    Rossi, Michel J.; Delval, Christophe

    2016-04-01

    Ice particles in the Upper Troposphere/Lower Stratosphere (UT/LS) are the seat of heterogeneous chemical processes that are important in polar ozone chemistry. Estimated evaporative lifetimes of typical pure ice particles of a few micrometers radius in Cirrus clouds are on the order of a minute or so at 80% relative humidity, too short to allow significant heterogeneous processing. We took this as a motivation to systematically measure absolute rates of evaporation and condensation of H2O in 1 to 2 micrometer thick ice films taken as proxies for small atmospheric ice particles under controlled conditions of HCl and HNO3 trace gas contamination. We have used a multidiagnostic reaction vessel equipped with residual gas mass spectrometry (MS), FTIR absorption spectroscopy in transmission and a quartz crystal microbalance (QCMB) in order to simultaneously observe both the gas and condensed phases under relevant atmospheric conditions. The rates (Rev(H2O)) or fluxes of evaporation (Jev(H2O)) of H2O from thin ice films contaminated by a measured amount of HCl in the range of 10% of a formal monolayer to 20 formal monolayers decreased by factors of between 2 and 50 depending on parameters such as temperature of deposition (Tdep), rate (RHCl) and dose (NHCl) of contaminant doping. Experiments with HCl fell into two categories as far as the decrease of Jev with the average mole fraction of contaminant (χHCl) in the remaining ice slab was concerned: one group where Jev(H2O) decreased gradually after pure ice evaporated, and another group where Jev(H2O) abruptly changes with χHCl after evaporation of excess ice. FTIR spectroscopy revealed an unknown, yet crystalline form of HCl hydrate upon HCl doping that does not correspond to a known crystalline hydrate. Of importance is the observation, that the equilibrium vapor pressure of these contaminated ices correspond to that of pure ice even after evaporation of excess ice at the characteristic rate of pure ice evaporation

  13. Aerosol-cirrus interactions: a number based phenomenon at all?

    Directory of Open Access Journals (Sweden)

    M. Seifert

    2004-01-01

    Full Text Available In situ measurements of the partitioning of aerosol particles within cirrus clouds were used to investigate aerosol-cloud interactions in ice clouds. The number density of interstitial aerosol particles (non-activated particles in between the cirrus crystals was compared to the number density of cirrus crystal residuals. The data was obtained during the two INCA (Interhemispheric Differences in Cirrus Properties from Anthropogenic Emissions campaigns, performed in the Southern Hemisphere (SH and Northern Hemisphere (NH midlatitudes. Different aerosol-cirrus interactions can be linked to the different stages of the cirrus lifecycle. Cloud formation is linked to positive correlations between the number density of interstitial aerosol (Nint and crystal residuals (Ncvi, whereas the correlations are smaller or even negative in a dissolving cloud. Unlike warm clouds, where the number density of cloud droplets is positively related to the aerosol number density, we observed a rather complex relationship when expressing Ncvi as a function of Nint for forming clouds. The data sets are similar in that they both show local maxima in the Nint range 100 to 200cm, where the SH- maximum is shifted towards the higher value. For lower number densities Nint and Ncvi are positively related. The slopes emerging from the data suggest that a tenfold increase in the aerosol number density corresponds to a 3 to 4 times increase in the crystal number density. As Nint increases beyond the ca. 100 to 200cm, the mean crystal number density decreases at about the same rate for both data sets. For much higher aerosol number densities, only present in the NH data set, the mean Ncvi remains low. The situation for dissolving clouds allows us to offer two possible, but at this point only speculative, alternative interactions between aerosols and cirrus: evaporating clouds might be associated with a source of aerosol particles, or air pollution (high aerosol number density might

  14. The cloud paradigm applied to e-Health.

    Science.gov (United States)

    Vilaplana, Jordi; Solsona, Francesc; Abella; Filgueira, Rosa; Rius, Josep

    2013-03-14

    Cloud computing is a new paradigm that is changing how enterprises, institutions and people understand, perceive and use current software systems. With this paradigm, the organizations have no need to maintain their own servers, nor host their own software. Instead, everything is moved to the cloud and provided on demand, saving energy, physical space and technical staff. Cloud-based system architectures provide many advantages in terms of scalability, maintainability and massive data processing. We present the design of an e-health cloud system, modelled by an M/M/m queue with QoS capabilities, i.e. maximum waiting time of requests. Detailed results for the model formed by a Jackson network of two M/M/m queues from the queueing theory perspective are presented. These results show a significant performance improvement when the number of servers increases. Platform scalability becomes a critical issue since we aim to provide the system with high Quality of Service (QoS). In this paper we define an architecture capable of adapting itself to different diseases and growing numbers of patients. This platform could be applied to the medical field to greatly enhance the results of those therapies that have an important psychological component, such as addictions and chronic diseases.

  15. Impact of Cirrus Crystal Shape on Solar Spectral Irradiance: A Case Study for Subtropical Cirrus

    Science.gov (United States)

    Wendisch, Manfred; Pilewskie, Peter; Pommier, John; Howard, Steve; Yang, Ping; Heymsfield, Andrew J.; Schmitt, Carl G.; Baumgardner, Darrel; Mayer, Barnhard

    2005-01-01

    Profiles of in situ measurements of ice crystal size distribution of subtropical cirrus were used to calculate solar spectral irradiances above and below the clouds. Spheres and nonspherical ice crystal habits (columns, hollows, plates, bullets, and aggregates) were assumed in the calculations. The simulation results were compared to irradiance measurements from the NASA Solar Spectral Flux Radiometer. The microphysical and radiation data were collected by three aircraft during CRYSTAL-FACE. Two cirrus cases (optical thickness of about 1 and 7) from two mission dates (26 and 23 July 2002) were investigated in detail. The measured downwelling and upwelling irradiance spectra above the cirrus could mostly be reproduced by the radiation model to within +/- 5-10% for most ice crystal habits. Below the cirrus the simulations disagreed with the measured irradiances due to surface albedo variability along the flight track, and nonoptimal colocation between the microphysical and irradiance measurements. The impact of shape characteristics of the crystals was important for the reflected irradiances above the optically thin cirrus, especially for small solar zenith angles, because in this case single-scattering dominated the solar radiation field. For the cirrus of moderate optical thickness the enhanced multiple scattering tended to diminish particular shape features caused by nonspherical single-scattering. Within the ice absorption bands the shape-related differences in the absorption characteristics of the individual nonspherical ice crystals were amplified if multiple scattering prevailed. Furthermore, it was found that below the cloud the shape sensitivity of the downwelling irradiance spectra is larger compared to the nonsphericity effects on reflected irradiances above the cirrus. Finally, it was shown that the calculated cirrus solar radiative forcing could vary by as much as 26% depending on the ice crystal habit.

  16. The optical properties of equatorial cirrus in the pilot radiation observation experiment

    Energy Technology Data Exchange (ETDEWEB)

    Platt, C.M.R.; Young, S.A.; Manson, P.; Patterson, G.R. [CSIRO, Victoria (Australia)] [and others

    1996-04-01

    The development of a sensitive filter radiometer for the Atmospheric Radiation Measurement (ARM) Program has been reported. The aim was to develop a reliable and fast instrument that could be used alongside a lidar to obtain near realtime optical properties of clouds, particularly high ice clouds, as they drifted over an ARM Cloud and Radiation Testbed (CART) site allowing calculation of the radiation divergence in the atmosphere over the site. Obtaining cloud optical properties by the lidar/radiometer, or LIRAD, method was described by Platt et al.; the latter paper also describes a year`s data on mid-latitude cirrus. The optical properties of equatorial cirrus (i.e., cirrus within a few degrees of the equator) have hardly been studied at all. The same is true of tropical cirrus, although a few observations have been reported by Davis and Platt et al.This paper describes obersvations performed on cirrus clouds, analysis methods used, and results.

  17. Factors controlling contrail cirrus optical depth

    Directory of Open Access Journals (Sweden)

    B. Kärcher

    2009-08-01

    Full Text Available Aircraft contrails develop into contrail cirrus by depositional growth and sedimentation of ice particles and horizontal spreading due to wind shear. Factors controlling this development include temperature, ice supersaturation, thickness of ice-supersaturated layers, and vertical gradients in the horizontal wind field. An analytical microphysical cloud model is presented and validated that captures these processes. Many individual contrail cirrus are simulated that develop differently owing to the variability in the controlling factors, resulting in large samples of cloud properties that are statistically analyzed. Contrail cirrus development is studied over the first four hours past formation, similar to the ages of line-shaped contrails that were tracked in satellite imagery on regional scales. On these time scales, contrail cirrus optical depth and microphysical variables exhibit a marked variability, expressed in terms of broad and skewed probability distribution functions. Simulated mean optical depths at a wavelength of 0.55 μm range from 0.05-0.5 and a substantial fraction 20-50% of contrail cirrus stay subvisible (optical depth <0.02, depending on meteorological conditions.

    A detailed analysis based on an observational case study over the continental USA suggests that previous satellite measurements of line-shaped persistent contrails have missed about 89%, 50%, and 11% of contrails with optical depths 0-0.05, 0.05-0.1, and 0.1-0.2, respectively, amounting to 65% of contrail coverage of all optical depths. When comparing observations with simulations and when estimating the contrail cirrus climate impact, not only mean values but also the variability in optical depth and microphysical properties need to be considered.

  18. Evaluations of cirrus contamination and screening in ground aerosol observations using collocated lidar systems

    Science.gov (United States)

    Huang, Jingfeng; Hsu, N. Christina; Tsay, Si-Chee; Holben, Brent N.; Welton, Ellsworth J.; Smirnov, Alexander; Jeong, Myeong-Jae; Hansell, Richard A.; Berkoff, Timothy A.; Liu, Zhaoyan; Liu, Gin-Rong; Campbell, James R.; Liew, Soo Chin; Barnes, John E.

    2012-08-01

    Cirrus clouds, particularly subvisual high thin cirrus with low optical thickness, are difficult to screen in operational aerosol retrieval algorithms. Collocated aerosol and cirrus observations from ground measurements, such as the Aerosol Robotic Network (AERONET) and the Micro-Pulse Lidar Network (MPLNET), provide us with an unprecedented opportunity to systematically examine the susceptibility of operational aerosol products to cirrus contamination. Quality assured aerosol optical thickness (AOT) measurements were also tested against the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) vertical feature mask (VFM) and the Moderate Resolution Imaging Spectroradiometer (MODIS) thin cirrus screening parameters for the purpose of evaluating cirrus contamination. Key results of this study include: (1) quantitative evaluations of data uncertainties in AERONET AOT retrievals are conducted; although AERONET cirrus screening schemes are successful in removing most cirrus contamination, strong residuals displaying strong spatial and seasonal variability still exist, particularly over thin cirrus prevalent regions during cirrus peak seasons; (2) challenges in matching up different data for analysis are highlighted and corresponding solutions proposed; and (3) estimates of the relative contributions from cirrus contamination to aerosol retrievals are discussed. The results are valuable for better understanding and further improving ground aerosol measurements that are critical for aerosol-related climate research.

  19. Cirrus Susceptibility to Changes in Ice Nuclei: Physical Processes, Model Uncertainties, and Measurement Needs

    Science.gov (United States)

    Jensen, Eric

    2017-01-01

    In this talk, I will begin by discussing the physical processes that govern the competition between heterogeneous and homogeneous ice nucleation in upper tropospheric cirrus clouds. Next, I will review the current knowledge of low-temperature ice nucleation from laboratory experiments and field measurements. I will then discuss the uncertainties and deficiencies in representations of cirrus processes in global models used to estimate the climate impacts of changes in cirrus clouds. Lastly, I will review the critical field measurements needed to advance our understanding of cirrus and their susceptibility to changes in aerosol properties.

  20. MST radar and polarization lidar observations of tropical cirrus

    Directory of Open Access Journals (Sweden)

    Y. Bhavani Kumar

    Full Text Available Significant gaps in our understanding of global cirrus effects on the climate system involve the role of frequently occurring tropical cirrus. Much of the cirrus in the atmosphere is largely due to frequent cumulus and convective activity in the tropics. In the Indian sub-tropical region, the deep convective activity is very prominent from April to December, which is a favorable period for the formation of deep cumulus clouds. The fibrous anvils of these clouds, laden with ice crystals, are one of the source mechanisms for much of the cirrus in the atmosphere. In the present study, several passages of tropical cirrus were investigated by simultaneously operating MST radar and a co-located polarization lidar at the National MST Radar Facility (NMRF, Gadanki (13.45° N, 79.18° E, India to understand its structure, the background wind field and the microphysics at the cloud boundaries. The lidar system used is capable of measuring the degree of depolarization in the laser backscatter. It has identified several different cirrus structures with a peak linear depolarization ratio (LDR in the range of 0.1 to 0.32. Simultaneous observations of tropical cirrus by the VHF Doppler radar indicated a clear enhancement of reflectivity detected in the vicinity of the cloud boundaries, as revealed by the lidar and are strongly dependent on observed cloud LDR. An inter-comparison of radar reflectivity observed for vertical and oblique beams reveals that the radar-enhanced reflectivity at the cloud boundaries is also accompanied by significant aspect sensitivity. These observations indicate the presence of anisotropic turbulence at the cloud boundaries. Radar velocity measurements show that boundaries of cirrus are associated with enhanced horizontal winds, significant vertical shear in the horizontal winds and reduced vertical velocity. Therefore, these measurements indicate that a circulation at the cloud boundaries suggest an entrainment taking place close to

  1. Cirrus and aerosol lidar profilometer - analysis and results

    Energy Technology Data Exchange (ETDEWEB)

    Spinhirne, J.D.; Scott, V.S. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Reagan, J.A.; Galbraith, A. [Univ. of Arizona, Tucson, AZ (United States)

    1996-04-01

    A cloud and aerosol lidar set from over a year of near continuous operation of a micro pulse lidar (MPL) instrument at the Cloud and Radiation Testbed (CART) site has been established. MPL instruments are to be included in the Ames Research Center (ARC) instrument compliments for the SW Pacific and Arctic ARM sites. Operational processing algorithms are in development for the data sets. The derived products are to be cloud presence and classification, base height, cirrus thickness, cirrus optical thickness, cirrus extinction profile, aerosol optical thickness and profile, and planetary boundary layer (PBL) height. A cloud presence and base height algorithm is in use, and a data set from the CART site is available. The scientific basis for the algorithm development of the higher level data products and plans for implementation are discussed.

  2. Cirrus microphysics and infrared radiative transfer: A case study

    Science.gov (United States)

    Ackerman, Thomas P.; Heymsfield, Andrew J.; Valero, Francisco P. J.; Kinne, Stefan

    1988-01-01

    Coincident measurements of cirrus cloud microphysical properties such as particle size distribution and particle shape and morphology, and measurements of infrared intensity and flux were made. Data was acquired nearly simultaneously in space and time by a KingAir in cloud and by an ER-2 at an altitude of 19 km. Upwelling infrared intensities and fluxes measured from the ER-2 and observations of cloud particle size distributions and particle phase and morphology made from the KingAir are discussed. Broad-band flux measurements were available both in and below the cirrus layer from the KingAir.

  3. Applied Ontology Engineering in Cloud Services, Networks and Management Systems

    CERN Document Server

    Serrano Orozco, J Martín

    2012-01-01

    Metadata standards in today’s ICT sector are proliferating at unprecedented levels, while automated information management systems collect and process exponentially increasing quantities of data. With interoperability and knowledge exchange identified as a core challenge in the sector, this book examines the role ontology engineering can play in providing solutions to the problems of information interoperability and linked data. At the same time as introducing basic concepts of ontology engineering, the book discusses methodological approaches to formal representation of data and information models, thus facilitating information interoperability between heterogeneous, complex and distributed communication systems. In doing so, the text advocates the advantages of using ontology engineering in telecommunications systems. In addition, it offers a wealth of guidance and best-practice techniques for instances in which ontology engineering is applied in cloud services, computer networks and management systems. �...

  4. Sub-visual cirrus LIDAR measurements for satellite masking improvement

    Science.gov (United States)

    Landulfo, Eduardo; Larroza, Eliane G.; Lopes, Fábio J. S.; de Jesus, Wellington C.; Bottino, Marcus; Nakaema, Walter M.; Steffens, Juliana

    2008-10-01

    Understanding the impact of cirrus cloud on modifying both the solar reflected and terrestrial emitted radiations is crucial for climate studies. Unlike most boundary layer stratus and stratocumulus clouds that have a net cooling effect on the climate, high-level thin cirrus clouds have a warming effect on our climate. However, the satellites as GOES from the NOAA series are limited to the cloud top and its reflectivity or brightness temperature, without assessing accurately the optical depth or physical thickness. Other more recent sensors as MODIS are able to determine optical depths for aerosols and clouds but when related to cirrus they are still inaccurate. Research programs as First ISCCP, FIRE, HOIST, ECLIPS and ARM have concentrated efforts in the research of cirrus, being based mainly on the observations of combined terrestrial remote sensing and airplanes instruments. LIDARs are able to detect sub-visual cirrus cloud (SVCs) in altitudes above 15 km and estimate exactly their height, thickness and optical depth, contributing with information for satellites sensors and radiative transfer models. In order to research characteristics of SVCs, the LIDAR system at Instituto de Pesquisas Energeticas e Nucleares has as objective to determine such parameters and implement a cirrus cloud mask that could be used in the satellite images processing as well as in the qualitative improvement of the radiative parameters for numerical models of climate changes. The first preliminary study shows where we compare the data lidar with Brightness temperature differences between the split-window data from GOES-10 (DSA/INPE) and CALIPSO.

  5. 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.

  6. 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.

  7. GCSS Idealized Cirrus Model Comparison Project

    Science.gov (United States)

    Starr, David OC.; Benedetti, Angela; Boehm, Matt; Brown, Philip R. A.; Gierens, Klaus; Girard, Eric; Giraud, Vincent; Jakob, Christian; Jensen, Eric; Khvorostyanov, Vitaly; hide

    2000-01-01

    The GCSS Working Group on Cirrus Cloud Systems (WG2) is conducting a systematic comparison and evaluation of cirrus cloud models. This fundamental activity seeks to support the improvement of models used for climate simulation and numerical weather prediction through assessment and improvement of the "process" models underlying parametric treatments of cirrus cloud processes in large-scale models. The WG2 Idealized Cirrus Model Comparison Project is an initial comparison of cirrus cloud simulations by a variety of cloud models for a series of idealized situations with relatively simple initial conditions and forcing. The models (16) represent the state-of-the-art and include 3-dimensional large eddy simulation (LES) models, two-dimensional cloud resolving models (CRMs), and single column model (SCM) versions of GCMs. The model microphysical components are similarly varied, ranging from single-moment bulk (relative humidity) schemes to fully size-resolved (bin) treatments where ice crystal growth is explicitly calculated. Radiative processes are included in the physics package of each model. The baseline simulations include "warm" and "cold" cirrus cases where cloud top initially occurs at about -47C and -66C, respectively. All simulations are for nighttime conditions (no solar radiation) where the cloud is generated in an ice supersaturated layer, about 1 km in depth, with an ice pseudoadiabatic thermal stratification (neutral). Continuing cloud formation is forced via an imposed diabatic cooling representing a 3 cm/s uplift over a 4-hour time span followed by a 2-hour dissipation stage with no cooling. Variations of these baseline cases include no-radiation and stable-thermal-stratification cases. Preliminary results indicated the great importance of ice crystal fallout in determining even the gross cloud characteristics, such as average vertically-integrated ice water path (IWP). Significant inter-model differences were found. Ice water fall speed is directly

  8. The Geospatial Data Cloud: An Implementation of Applying Cloud Computing in Geosciences

    Directory of Open Access Journals (Sweden)

    Xuezhi Wang

    2014-11-01

    Full Text Available The rapid growth in the volume of remote sensing data and its increasing computational requirements bring huge challenges for researchers as traditional systems cannot adequately satisfy the huge demand for service. Cloud computing has the advantage of high scalability and reliability, which can provide firm technical support. This paper proposes a highly scalable geospatial cloud platform named the Geospatial Data Cloud, which is constructed based on cloud computing. The architecture of the platform is first introduced, and then two subsystems, the cloud-based data management platform and the cloud-based data processing platform, are described.  ––– This paper was presented at the First Scientific Data Conference on Scientific Research, Big Data, and Data Science, organized by CODATA-China and held in Beijing on 24-25 February, 2014.

  9. Heavy rainfall prediction applying satellite-based cloud data assimilation over land

    Science.gov (United States)

    Seto, Rie; Koike, Toshio; Rasmy, Mohamed

    2016-08-01

    To optimize flood management, it is crucial to determine whether rain will fall within a river basin. This requires very fine precision in prediction of rainfall areas. Cloud data assimilation has great potential to improve the prediction of precipitation area because it can directly obtain information on locations of rain systems. Clouds can be observed globally by satellite-based microwave remote sensing. Microwave observation also includes information of latent heat and water vapor associated with cloud amount, which enables the assimilation of not only cloud itself but also the cloud-affected atmosphere. However, it is difficult to observe clouds over land using satellite microwave remote sensing, because their emissivity is much lower than that of the land surface. To overcome this challenge, we need appropriate representation of heterogeneous land emissivity. We developed a coupled atmosphere and land data assimilation system with the Weather Research and Forecasting Model (CALDAS-WRF), which can assimilate soil moisture, vertically integrated cloud water content over land, and heat and moisture within clouds simultaneously. We applied this system to heavy rain events in Japan. Results show that the system effectively assimilated cloud signals and produced very accurate cloud and precipitation distributions. The system also accurately formed a consistent atmospheric field around the cloud. Precipitation intensity was also substantially improved by appropriately representing the local atmospheric field. Furthermore, combination of the method and operationally analyzed dynamical and moisture fields improved prediction of precipitation duration. The results demonstrate the method's promise in dramatically improving predictions of heavy rain and consequent flooding.

  10. An extended lookup table of cloud detection for MTSAT-1R

    Science.gov (United States)

    Chen, Wuhan; Zhong, Bo; Li, Weisheng; Wu, Shanlong; Yu, Shanshan

    2014-11-01

    Cloud detection is a key work for the estimation of solar radiation from remote sensing. Particularly, the detection of thin cirrus cloud and the edges of thicker cloud is critical and difficult. To obtain accurate estimates of cloud cover of MTSAT-1R image, we propose an effective cloud detection algorithm for improving the detection of thin cirrus cloud and the edges of thicker cloud. Using the brightness temperature difference (BTD) and lookup table to identify cloud-free and cloud-filled pixels is not sufficient for MTSAT-1R data on the region of China. Therefore, a new lookup table (LUT) is made by extending the original one. On the basis of the exiting method, in order to apply to the MTSAT-1R satellite data in China region, we expand the scope of the latitude and extend the applicable scope of satellite zenith angle. We change the interpolation method from linear mode to nonlinear mode. The evaluation results indicate that our proposed method is effective for the cirrus and the edges of thicker cloud detection of MTSAT-1R in China region.

  11. Sensitivity of Cirrus Simulations in Idealized Situations: The WG2 Test Cases

    Science.gov (United States)

    Starr, David OC.

    1998-01-01

    GCSS Cirrus Cloud Systems Working Group (WG2) is presently conducting a comparison of cirrus cloud models for idealized initial conditions. The experiments involve binary (off/on) tests of model sensitivity to infrared radiative processes, and thermal stratification, and vertical wind shear for situations of weakly forced (3 cm/s uplift) cold (-60 to -70 C) and warm (-35 to -50 C) cirrus clouds. A range of model types are involved including parcel, SCM, 2-D CRM, 3-D CRM and LES models. The test cases will be described and results from 2-dimensional cirrus cloud models with bulk microphysics (implicit second moment scheme) and explicit bin microphysics will be compared. Vertical ice mass flux (particle fall speed) is a critical model component leading to significant intermodel differences. Efforts are ongoing to better quantify this aspect. Future plans of WG2 will also be briefly described and include model comparisons for a well-observed case of cold (ARM IOP) cirrus and of warm (EUCREX) cirrus, as well as, a joint activity with WG4 to consider the treatment of anvil cirrus in a variety of models.

  12. Applying a cloud computing approach to storage architectures for spacecraft

    Science.gov (United States)

    Baldor, Sue A.; Quiroz, Carlos; Wood, Paul

    As sensor technologies, processor speeds, and memory densities increase, spacecraft command, control, processing, and data storage systems have grown in complexity to take advantage of these improvements and expand the possible missions of spacecraft. Spacecraft systems engineers are increasingly looking for novel ways to address this growth in complexity and mitigate associated risks. Looking to conventional computing, many solutions have been executed to solve both the problem of complexity and heterogeneity in systems. In particular, the cloud-based paradigm provides a solution for distributing applications and storage capabilities across multiple platforms. In this paper, we propose utilizing a cloud-like architecture to provide a scalable mechanism for providing mass storage in spacecraft networks that can be reused on multiple spacecraft systems. By presenting a consistent interface to applications and devices that request data to be stored, complex systems designed by multiple organizations may be more readily integrated. Behind the abstraction, the cloud storage capability would manage wear-leveling, power consumption, and other attributes related to the physical memory devices, critical components in any mass storage solution for spacecraft. Our approach employs SpaceWire networks and SpaceWire-capable devices, although the concept could easily be extended to non-heterogeneous networks consisting of multiple spacecraft and potentially the ground segment.

  13. A modelling case study of a large-scale cirrus in the tropical tropopause layer

    Science.gov (United States)

    Podglajen, Aurélien; Plougonven, Riwal; Hertzog, Albert; Legras, Bernard

    2016-03-01

    We use the Weather Research and Forecast (WRF) model to simulate a large-scale tropical tropopause layer (TTL) cirrus in order to understand the formation and life cycle of the cloud. This cirrus event has been previously described through satellite observations by Taylor et al. (2011). Comparisons of the simulated and observed cirrus show a fair agreement and validate the reference simulation regarding cloud extension, location and life time. The validated simulation is used to understand the causes of cloud formation. It is shown that several cirrus clouds successively form in the region due to adiabatic cooling and large-scale uplift rather than from convective anvils. The structure of the uplift is tied to the equatorial response (equatorial wave excitation) to a potential vorticity intrusion from the midlatitudes. Sensitivity tests are then performed to assess the relative importance of the choice of the microphysics parameterization and of the initial and boundary conditions. The initial dynamical conditions (wind and temperature) essentially control the horizontal location and area of the cloud. However, the choice of the microphysics scheme influences the ice water content and the cloud vertical position. Last, the fair agreement with the observations allows to estimate the cloud impact in the TTL in the simulations. The cirrus clouds have a small but not negligible impact on the radiative budget of the local TTL. However, for this particular case, the cloud radiative heating does not significantly influence the simulated dynamics. This result is due to (1) the lifetime of air parcels in the cloud system, which is too short to significantly influence the dynamics, and (2) the fact that induced vertical motions would be comparable to or smaller than the typical mesoscale motions present. Finally, the simulation also provides an estimate of the vertical redistribution of water by the cloud and the results emphasize the importance in our case of both

  14. Applying Encryption Algorithm for Data Security and Privacy in Cloud Computing

    Directory of Open Access Journals (Sweden)

    Mohit Marwaha

    2013-01-01

    Full Text Available Cloud computing is the next big thing after internet in the field of information technology; some say its a metaphor for internet. It is an Internet-based computing technology, in which software, shared recourses and information, are provided to consumers and devices on-demand, and as per users requirement on a pay per use model. Even though the cloud continues to grow in popularity, Usability and respectability, Problems with data protection and data privacy and other Security issues play a major setback in the field of Cloud Computing. Privacy and security are the key issue for cloud storage. Encryption is a well known technology for protecting sensitive data. Use of the combination of Public and Private key encryption to hide the sensitive data of users, and cipher text retrieval. The paper analyzes the feasibility of the applying encryption algorithm for data security and privacy in cloud Storage.

  15. Applying Data Mining Techniques to Improve Information Security in the Cloud: A Single Cache System Approach

    Directory of Open Access Journals (Sweden)

    Amany AlShawi

    2016-01-01

    Full Text Available Presently, the popularity of cloud computing is gradually increasing day by day. The purpose of this research was to enhance the security of the cloud using techniques such as data mining with specific reference to the single cache system. From the findings of the research, it was observed that the security in the cloud could be enhanced with the single cache system. For future purposes, an Apriori algorithm can be applied to the single cache system. This can be applied by all cloud providers, vendors, data distributors, and others. Further, data objects entered into the single cache system can be extended into 12 components. Database and SPSS modelers can be used to implement the same.

  16. A modelling case study of a large-scale cirrus in the tropical tropopause layer

    Science.gov (United States)

    Podglajen, A.; Plougonven, R.; Hertzog, A.; Legras, B.

    2015-11-01

    We use the Weather Research and Forecast (WRF) model to simulate a large-scale tropical tropopause layer (TTL) cirrus, in order to understand the formation and life cycle of the cloud. This cirrus event has been previously described through satellite observations by Taylor et al. (2011). Comparisons of the simulated and observed cirrus show a fair agreement, and validate the reference simulation regarding cloud extension, location and life time. The validated simulation is used to understand the causes of cloud formation. It is shown that several cirrus clouds successively form in the region due to adiabatic cooling and large-scale uplift rather than from ice lofting from convective anvils. The equatorial response (equatorial wave excitation) to a midlatitude potential vorticity (PV) intrusion structures the uplift. Sensitivity tests are then performed to assess the relative importance of the choice of the microphysics parametrisation and of the initial and boundary conditions. The initial dynamical conditions (wind and temperature) essentially control the horizontal location and area of the cloud. On the other hand, the choice of the microphysics scheme influences the ice water content and the cloud vertical position. Last, the fair agreement with the observations allows to estimate the cloud impact in the TTL in the simulations. The cirrus clouds have a small but not negligible impact on the radiative budget of the local TTL. However, the cloud radiative heating does not significantly influence the simulated dynamics. The simulation also provides an estimate of the vertical redistribution of water by the cloud and the results emphasize the importance in our case of both re and dehydration in the vicinity of the cirrus.

  17. Cirrus Microphysical Properties from Stellar Aureole Measurements, Phase I

    Energy Technology Data Exchange (ETDEWEB)

    DeVore, J. G.; Kristl, J. A.; Rappaport, S. A.

    2012-04-20

    While knowledge of the impact of aerosols on climate change has improved significantly due to the routine, ground-based, sun photometer measurements of aerosols made at AERONET sites world-wide, the impact of cirrus clouds remains much less certain because they occur high in the atmosphere and are more difficult to measure. This report documents work performed on a Phase I SBIR project to retrieve microphysical properties of cirrus ice crystals from stellar aureole imagery. The Phase I work demonstrates that (1) we have clearly measured stellar aureole profiles; (2) we can follow the aureole profiles out to ~1/4 degree from stars (~1/2 degree from Jupiter); (3) the stellar aureoles from cirrus have very distinctive profiles, being flat out to a critical angle, followed by a steep power-law decline with a slope of ~-3; (4) the profiles are well modeled using exponential size distributions; and (5) the critical angle in the profiles is ~0.12 degrees, (6) indicating that the corresponding critical size ranges from ~150 to ~200 microns. The stage has been set for a Phase II project (1) to proceed to validating the use of stellar aureole measurements for retrieving cirrus particle size distributions using comparisons with optical property retrievals from other, ground-based instruments and (2) to develop an instrument for the routine, automatic measurement of thin cirrus microphysical properties.

  18. Impact of large-scale dynamics on the microphysical properties of midlatitude cirrus

    Energy Technology Data Exchange (ETDEWEB)

    Muhlbauer, Andreas; Ackerman, Thomas P.; Comstock, Jennifer M.; Diskin, G. S.; Evans, Stuart; Lawson, Paul; Marchand, Roger

    2014-04-16

    In situ microphysical observations 3 of mid-latitude cirrus collected during the Department of Energy Small Particles in Cirrus (SPAR-TICUS) field campaign are combined with an atmospheric state classification for the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site to understand statistical relationships between cirrus microphysics and the large-scale meteorology. The atmospheric state classification is informed about the large-scale meteorology and state of cloudiness at the ARM SGP site by combining ECMWF ERA-Interim reanalysis data with 14 years of continuous observations from the millimeter-wavelength cloud radar. Almost half of the cirrus cloud occurrences in the vicinity of the ARM SGP site during SPARTICUS can be explained by three distinct synoptic condi- tions, namely upper-level ridges, mid-latitude cyclones with frontal systems and subtropical flows. Probability density functions (PDFs) of cirrus micro- physical properties such as particle size distributions (PSDs), ice number con- centrations and ice water content (IWC) are examined and exhibit striking differences among the different synoptic regimes. Generally, narrower PSDs with lower IWC but higher ice number concentrations are found in cirrus sam- pled in upper-level ridges whereas cirrus sampled in subtropical flows, fronts and aged anvils show broader PSDs with considerably lower ice number con- centrations but higher IWC. Despite striking contrasts in the cirrus micro- physics for different large-scale environments, the PDFs of vertical velocity are not different, suggesting that vertical velocity PDFs are a poor predic-tor for explaining the microphysical variability in cirrus. Instead, cirrus mi- crophysical contrasts may be driven by differences in ice supersaturations or aerosols.

  19. Final Technical Report on Scaling Models of the Internal Variability of Clouds DoE Grant No. DE-FG02-04ER63773

    Energy Technology Data Exchange (ETDEWEB)

    Ivanova, Kristinka

    2008-04-24

    The purpose of this proposal is to gain a better understanding of the space-time correlations of atmospheric fluctuations in clouds through application of methods from statistical physics to high resolution, continuous data sets of cloud observations available at the Department of Energy Atmospheric Radiation Measurement Program archive. In this report we present the accomplishments achieved during the four year period. Starting with the most recent one, we report on two break-throughs in our research that make the fourth year of the project exceptionally successful and markedly outperforming the objectives. The first break-through is on characterization of the structure of cirrus radiative properties at large, intermediate and small, generating cells scales by applying the Fokker-Planck equation method and other methods to ARM millimeter wavelength radar observations collected at the Southern Great Plains site. The second break-through is that we show that different characterizations of the cirrus radiative properties are obtained for different synoptic scale environments. We outline a stochastic approach to investigate the internal structure of radiative properties of cirrus clouds based on empirical modeling and draw conclusions about cirrus dynamical properties in the context of the synoptic environment. Results on the structure of cirrus dynamical properties are consistent with the structure of cirrus based on aircraft in situ measurements, with results from ground-based Raman lidar, and with results from model studies. These achievements would not have been possible without the accomplishments from the previous years on a number of problems that involve application of methods of analysis such as the Fokker-Planck equation approach, Tsallis nonextensive statistical mechanics, detrended fluctuation analysis, and others. These include stochastic analysis of neutrally stratified cirrus layers, internal variability and turbulence in cirrus, dynamical model and

  20. Cirrus Parcel Model Comparison Project. Phase 1: The Critical Components to Simulate Cirrus Initiation Explicitly.

    Science.gov (United States)

    Lin, Ruei-Fong; O'C. Starr, David; Demott, Paul J.; Cotton, Richard; Sassen, Kenneth; Jensen, Eric; Kärcher, Bernd; Liu, Xiaohong

    2002-08-01

    The Cirrus Parcel Model Comparison Project, a project of the GCSS [Global Energy and Water Cycle Experiment (GEWEX) Cloud System Studies] Working Group on Cirrus Cloud Systems, involves the systematic comparison of current models of ice crystal nucleation and growth for specified, typical, cirrus cloud environments. In Phase 1 of the project reported here, simulated cirrus cloud microphysical properties from seven models are compared for `warm' (40°C) and `cold' (60°C) cirrus, each subject to updrafts of 0.04, 0.2, and 1 m s1. The models employ explicit microphysical schemes wherein the size distribution of each class of particles (aerosols and ice crystals) is resolved into bins or the evolution of each individual particle is traced. Simulations are made including both homogeneous and heterogeneous ice nucleation mechanisms (all-mode simulations). A single initial aerosol population of sulfuric acid particles is prescribed for all simulations. Heterogeneous nucleation is disabled for a second parallel set of simulations in order to isolate the treatment of the homogeneous freezing (of haze droplets) nucleation process. Analysis of these latter simulations is the primary focus of this paper.Qualitative agreement is found for the homogeneous-nucleation-only simulations; for example, the number density of nucleated ice crystals increases with the strength of the prescribed updraft. However, significant quantitative differences are found. Detailed analysis reveals that the homogeneous nucleation rate, haze particle solution concentration, and water vapor uptake rate by ice crystal growth (particularly as controlled by the deposition coefficient) are critical components that lead to differences in the predicted microphysics.Systematic differences exist between results based on a modified classical theory approach and models using an effective freezing temperature approach to the treatment of nucleation. Each method is constrained by critical freezing data from

  1. Contrail and Cirrus Observations over Europe from 6 Years of NOAA-AVHRR Data

    OpenAIRE

    R. Meyer; Mannstein, H.; Meerkötter, R.; Wendling, P.

    2002-01-01

    Thin ice cloudscirrus and contrails – are analysed in a long-term 1 km data set from the Advanced Very High Resolution Radiometer (AVHRR). Here twice daily data received at DLR Oberpfaffenhofen covering most of Europe over the full lifetime of the NOAA-14 satellite from January 1995 until October 2001 is taken into account to derive high resolution contrail and cirrus cloud maps. The data presented here is part of the ongoing European Cloud Climatology (ECC). For the detection of thin cirr...

  2. The Cloud Radar System

    Science.gov (United States)

    Racette, Paul; Heymsfield, Gerald; Li, Lihua; Tian, Lin; Zenker, Ed

    2003-01-01

    Improvement in our understanding of the radiative impact of clouds on the climate system requires a comprehensive view of clouds including their physical dimensions, dynamical generation processes, and detailed microphysical properties. To this end, millimeter vave radar is a powerful tool by which clouds can be remotely sensed. The NASA Goddard Space Flight Center has developed the Cloud Radar System (CRS). CRS is a highly sensitive 94 GHz (W-band) pulsed-Doppler polarimetric radar that is designed to fly on board the NASA high-altitude ER-2 aircraft. The instrument is currently the only millimeter wave radar capable of cloud and precipitation measurements from above most all clouds. Because it operates from high-altitude, the CRS provides a unique measurement perspective for cirrus cloud studies. The CRS emulates a satellite view of clouds and precipitation systems thus providing valuable measurements for the implementation and algorithm validation for the upcoming NASA CloudSat mission that is designed to measure ice cloud distributions on the global scale using a spaceborne 94 GHz radar. This paper describes the CRS instrument and preliminary data from the recent Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE). The radar design is discussed. Characteristics of the radar are given. A block diagram illustrating functional components of the radar is shown. The performance of the CRS during the CRYSTAL-FACE campaign is discussed.

  3. Cirrus, contrails, and ice supersaturated regions in high pressure systems at northern mid latitudes

    Science.gov (United States)

    Immler, F.; Treffeisen, R.; Engelbart, D.; Krüger, K.; Schrems, O.

    2008-03-01

    During the European heat wave summer 2003 with predominant high pressure conditions we performed a detailed study of upper tropospheric humidity and ice particles which yielded striking results concerning the occurrence of ice supersaturated regions (ISSR), cirrus, and contrails. Our study is based on lidar observations and meteorological data obtained at Lindenberg/Germany (52.2° N, 14.1° E) as well as the analysis of the European centre for medium range weather forecast (ECMWF). Cirrus clouds were detected in 55% of the lidar profiles and a large fraction of them were subvisible (optical depth <0.03). Thin ice clouds were particularly ubiquitous in high pressure systems. The radiosonde data showed that the upper troposphere was very often supersaturated with respect to ice. Relating the radiosonde profiles to concurrent lidar observations reveals that the ISSRs almost always contained ice particles. Persistent contrails observed with a camera were frequently embedded in these thin or subvisible cirrus clouds. The ECMWF cloud parametrisation reproduces the observed cirrus clouds consistently and a close correlation between the ice water path in the model and the measured optical depth of cirrus is demonstrated.

  4. Investigation of the Directional Structure of Horizontal Cloud Inhomogeneities Derived from Ground-Based and Airborne Spectral Imaging and Cloud Resolving Models

    Science.gov (United States)

    Schäfer, Michael; Bierwirth, Eike; Ehrlich, André; Jäkel, Evelyn; Loewe, Katharina; Werner, Frank; Hoose, Corinna; Wendisch, Manfred

    2017-04-01

    Clouds exhibit considerable horizontal inhomogeneities of their optical and microphysical properties. This complicates their realistic representation in weather and climate models. In order to investigate cloud inhomogeneities with respect to their horizontal structure, two-dimensional (2D) fields of optical thickness of subtropical cirrus and Arctic stratus are investigated. The applied 2D cloud optical thickness fields with a spatial resolution of less than 10 m are derived from (a) ground-based measured downward (transmitted) solar spectral radiance fields of four subtropical cirrus clouds, and (b) upward (reflected) radiances measured airborne above ten Arctic stratus clouds. The measurements were performed during the two field campaigns: (a) Clouds, Aerosol, Radiation, and tuRbulence in the trade wInd regime over BArbados (CARRIBA), and (b) VERtical Distribution of Ice in Arctic clouds (VERDI). One-dimensional (1D) inhomogeneity parameters and 2D autocorrelation functions are derived from the retrieved fields of cloud optical thickness. For each measurement case, the typical spatial scale of horizontal cloud inhomogeneities is quantified. The results reveal that considerable cloud inhomogeneities with prevailing directional structures are found in most of the investigated cloud cases; the cloud inhomogeneities favour a specific horizontal direction while across this direction the cloud is of homogeneous character. The investigations show that it is not sufficient to quantify horizontal cloud inhomogeneities by 1D inhomogeneity parameters; 2D parameters are strongly required. Additionally, the applied methods are used in conjunction with simulated fields of Arctic stratus obtained from cloud resolving models in order to (I) validate model results against measurements and (II) to increase the number of available cloud fields, which improves the statistics of investigated cloud cases.

  5. Applying analytic hierarchy process to assess healthcare-oriented cloud computing service systems.

    Science.gov (United States)

    Liao, Wen-Hwa; Qiu, Wan-Li

    2016-01-01

    Numerous differences exist between the healthcare industry and other industries. Difficulties in the business operation of the healthcare industry have continually increased because of the volatility and importance of health care, changes to and requirements of health insurance policies, and the statuses of healthcare providers, which are typically considered not-for-profit organizations. Moreover, because of the financial risks associated with constant changes in healthcare payment methods and constantly evolving information technology, healthcare organizations must continually adjust their business operation objectives; therefore, cloud computing presents both a challenge and an opportunity. As a response to aging populations and the prevalence of the Internet in fast-paced contemporary societies, cloud computing can be used to facilitate the task of balancing the quality and costs of health care. To evaluate cloud computing service systems for use in health care, providing decision makers with a comprehensive assessment method for prioritizing decision-making factors is highly beneficial. Hence, this study applied the analytic hierarchy process, compared items related to cloud computing and health care, executed a questionnaire survey, and then classified the critical factors influencing healthcare cloud computing service systems on the basis of statistical analyses of the questionnaire results. The results indicate that the primary factor affecting the design or implementation of optimal cloud computing healthcare service systems is cost effectiveness, with the secondary factors being practical considerations such as software design and system architecture.

  6. Tropical tropopause layer cirrus and its relation to tropopause

    Science.gov (United States)

    Tseng, H.-H.; Fu, Q.

    2017-02-01

    This study examines the spatial and temporal patterns of tropical tropopause layer (TTL) cirrus clouds (i.e., clouds with bases higher than 14.5 km) and their relationship to tropical tropopause including both cold point tropopause (CPT) and lapse rate tropopause (LRT). We use eight years (2006-2014) data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements. In addition to the CALIPSO cloud layer product, the clouds included in the current CALIPSO dataset as stratospheric features have been considered by separating clouds from aerosols, which are important in the TTL cloud analysis. It is also shown that the temporal variation of the stratospheric aerosols matches well with the volcanic eruption events. The TTL cloud fraction and the tropical tropopause temperature both have pronounced annual cycles and are strongly negatively correlated both temporally and spatially. The examination of the TTL cloud height relative to tropopause from collocated CALIPSO and COSMIC observations indicates that the tropopause plays a critical role in constraining the TTL cloud top height. We show that the probability density function of TTL cloud top height peaks just below the CPT while the occurrence of TTL clouds with cloud tops above the CPT could be largely explained by observed tropopause height uncertainty associated with the COSMIC vertical resolution.

  7. Above the cloud computing: applying cloud computing principles to create an orbital services model

    Science.gov (United States)

    Straub, Jeremy; Mohammad, Atif; Berk, Josh; Nervold, Anders K.

    2013-05-01

    Large satellites and exquisite planetary missions are generally self-contained. They have, onboard, all of the computational, communications and other capabilities required to perform their designated functions. Because of this, the satellite or spacecraft carries hardware that may be utilized only a fraction of the time; however, the full cost of development and launch are still bone by the program. Small satellites do not have this luxury. Due to mass and volume constraints, they cannot afford to carry numerous pieces of barely utilized equipment or large antennas. This paper proposes a cloud-computing model for exposing satellite services in an orbital environment. Under this approach, each satellite with available capabilities broadcasts a service description for each service that it can provide (e.g., general computing capacity, DSP capabilities, specialized sensing capabilities, transmission capabilities, etc.) and its orbital elements. Consumer spacecraft retain a cache of service providers and select one utilizing decision making heuristics (e.g., suitability of performance, opportunity to transmit instructions and receive results - based on the orbits of the two craft). The two craft negotiate service provisioning (e.g., when the service can be available and for how long) based on the operating rules prioritizing use of (and allowing access to) the service on the service provider craft, based on the credentials of the consumer. Service description, negotiation and sample service performance protocols are presented. The required components of each consumer or provider spacecraft are reviewed. These include fully autonomous control capabilities (for provider craft), a lightweight orbit determination routine (to determine when consumer and provider craft can see each other and, possibly, pointing requirements for craft with directional antennas) and an authentication and resource utilization priority-based access decision making subsystem (for provider craft

  8. 太赫兹波被动遥感卷云微物理参数的敏感性试验分析∗%Sensitivity analysis of terahertz wave passive remote sensing of cirrus microphysical parameters

    Institute of Scientific and Technical Information of China (English)

    李书磊; 刘磊; 高太长; 黄威; 胡帅

    2016-01-01

    Cirrus clouds play an important role in the energy budget and the hydrological cycle of the atmosphere. It is still one of the largest uncertainties in the global climate change studies. This is mainly attributable to the measurement dis-crepancies of cirrus parameters, especially the microphysical parameters, which are constrained by the existing methods. With THz wavelengths on the order of the size of typical cirrus cloud particles and therefore being sensitive to cirrus clouds, THz region is expected to have a promising prospect concerning measuring cirrus microphysical parameters (ice water path and effective particle size). In order to evaluate the effects of cirrus microphysical parameters on THz trans-mission characteristics and the sensitivity of cirrus in THz region, the THz radiation spectra at the top of atmosphere in the clear sky and the cloudy situations are simulated and calculated based on the atmospheric radiative transfer simulator. The effects of cirrus particle shape, particle size and ice water path on THz transmission characteristics are obtained by analyzing the brightness temperature difference between the two situations, and the sensitivity parameters that quantitatively describ the effects. The results indicate that cirrus particle shape, particle size and ice water path have different effects on the THz wave propagation. The cirrus effect varies also with channel frequency. Overall, in the low frequency channels, cirrus effects are enhanced with the increases of particle size and ice water path;in the high fre-quency channels, cirrus effects are more complicated and vary with particle size and ice water path. The effects are first enhanced and then turned into saturation. The THz wave is sensitive to cirrus cloud ice water path and effective particle size, and THz wave may be the best waveband for remote sensing of cirrus microphysical parameters in theory. For thin clouds, the sensitivity parameters are approximately constant

  9. Properties of small cirrus ice crystals from commercial aircraft measurements and implications for flight operations

    Directory of Open Access Journals (Sweden)

    Karl Beswick

    2015-10-01

    Full Text Available Measurements of cloud ice crystal size distributions have been made by a backscatter cloud probe (BCP mounted on five commercial airliners flying international routes that cross five continents. Bulk cloud parameters were also derived from the size distributions. As of 31 December 2014, a total of 4399 flights had accumulated data from 665 hours in more than 19 000 cirrus clouds larger than 5 km in length. The BCP measures the equivalent optical diameter (EOD of individual crystals in the 5–90 µm range from which size distributions are derived and recorded every 4 seconds. The cirrus cloud property database, an ongoing development stemming from these measurements, registers the total crystal number and mass concentration, effective and median volume diameters and extinction coefficients derived from the size distribution. This information is accompanied by the environmental temperature, pressure, aircraft position, date and time of each sample. The seasonal variations of the cirrus cloud properties measured from 2012 to 2014 are determined for six geographic regions in the tropics and extratropics. Number concentrations range from a few per litre for thin cirrus to several hundreds of thousands for heavy cirrus. Temperatures range from 205 to 250 K and effective radii from 12 to 20 µm. A comparison of the regional and seasonal number and mass size distributions, and the bulk microphysical properties derived from them, demonstrates that cirrus properties cannot be easily parameterised by temperature or by latitude. The seasonal changes in the size distributions from the extratropical Atlantic and Eurasian air routes are distinctly different, showing shifts from mono-modal to bi-modal spectra out of phase with one another. This phase difference may be linked to the timing of deep convection and cold fronts that lead to the cirrus formation. Likewise, the size spectra of cirrus over the tropical Atlantic and Eastern Brazil differ from each

  10. Correlation among Cirrus Ice Content, Water Vapor and Temperature in the TTL as Observed by CALIPSO and Aura-MLS

    Science.gov (United States)

    Flury, T.; Wu, D. L.; Read, W. G.

    2012-01-01

    Water vapor in the tropical tropopause layer (TTL) has a local radiative cooling effect. As a source for ice in cirrus clouds, however, it can also indirectly produce infrared heating. Using NASA A-Train satellite measurements of CALIPSO and Aura/MLS we calculated the correlation of water vapor, ice water content and temperature in the TTL. We find that temperature strongly controls water vapor (correlation r =0.94) and cirrus clouds at 100 hPa (r = -0.91). Moreover we observe that the cirrus seasonal cycle is highly (r =-0.9) anticorrelated with the water vapor variation in the TTL, showing higher cloud occurrence during December-January-February. We further investigate the anticorrelation on a regional scale and find that the strong anticorrelation occurs generally in the ITCZ (Intertropical Convergence Zone). The seasonal cycle of the cirrus ice water content is also highly anticorrelated to water vapor (r = -0.91) and our results support the hypothesis that the total water at 100 hPa is roughly constant. Temperature acts as a main regulator for balancing the partition between water vapor and cirrus clouds. Thus, to a large extent, the depleting water vapor in the TTL during DJF is a manifestation of cirrus formation.

  11. Contrail Cirrus Forecasts for the ML-CIRRUS Experiment and Some Comparison Results

    Science.gov (United States)

    Schumann, Ulrich; Graf, Kaspar; Bugliaro, Luca; Dörnbrack, Andreas; Giez, Andreas; Jurkat, Tina; Kaufmann, Stefan; Krämer, Martina; Minikin, Andreas; Schäfler, Andreas; Voigt, Christiane; Wirth, Martin; Zahn, Andreas; Ziereis, Helmut

    2015-04-01

    rerun with improved ECMWF-NWP data (at one-hour time resolution). The model results are included in the HALO mission data bank, and the results are available for comparison to in-situ data. The data are useful for identifying aircraft and other sources for measured air properties. The joint analysis of observations and model result has basically just started. Preliminary results from comparisons with lidar-measured extinction profiles, in-situ measured humidity, nitrogen oxides, and aerosol and ice particle concentrations, and with meteorological observations (wind, temperature etc.) illustrate the expected gain in insight. The contrail forecasts have been checked by comparison to available data including satellite data and HALO observations. During the campaign, it became obvious that predicted contrail cirrus cover compared qualitatively mostly well with what was found when HALO reached predicted cirrus regions. From the analysis of the measured data, some examples of significant correlation between model results and observations have been found. However, the quantitative agreement is not uniform. As expected, nature is far more variable than a model can predict. The observed optical properties of cirrus and contrails vary far more in time and space than predicted. Local values were often far higher or lower than mean values. A one-to-one correlation between local observations and model results is not to be expected. This inhomogeneity may have consequences for the climate impact of aviation induced cloud changes.

  12. On the Development of Above-Anvil Cirrus Plumes in Extratropical Convection

    Science.gov (United States)

    Homeyer, C. R.; McAuliffe, J. D.; Bedka, K. M.

    2016-12-01

    Expansive cirrus clouds present above the anvils of extratropical convection have been observed in satellite and aircraft-based imagery for several decades. Despite knowledge of their occurrence, the precise mechanisms and atmospheric conditions leading to their formation and maintenance are not entirely known. Here, we examine the formation of these cirrus "plumes" using a combination of satellite imagery, three-dimensional ground-based radar observations, assimilated atmospheric states from a state-of-the-art reanalysis, and idealized numerical simulations with explicitly resolved convection. Using data from ten recent cases (2013-Present), we find that all storms with above-anvil cirrus plumes reach altitudes 1 to 6 km above the tropopause. Thus, it is likely that these clouds represent the injection of cloud material into the lower stratosphere. Comparison of above-anvil cirrus plume cases with ten additional cases of observed tropopause-penetrating convection without plumes reveals that these clouds are associated with large vector differences between the motion of a storm and the environmental wind in the upper troposphere and lower stratosphere (UTLS), suggesting that gravity wave breaking and/or stretching of the tropopause-penetrating cloud are/is more prevalent in plume-producing storms. No relationship is found between above-anvil cirrus plume occurrence and the stability of the lower stratosphere (or tropopause structure) or the duration of stratospheric penetration. Idealized model simulations of tropopause-penetrating convection with small and large magnitudes of storm-relative wind in the UTLS are found to reproduce the established observational relationship and show that frequent gravity wave breaking is the primary mechanism responsible for above-anvil cirrus plume formation.

  13. Zooming in on cirrus with the Canadian Regional Climate Model

    Science.gov (United States)

    Stefanof, C.; Stefanof, A.; Beaulne, A.; Munoz Alpizar, R.; Szyrmer, W.; Blanchet, J.

    2004-05-01

    The Canadian Regional Climate Model plus a microphysical scheme: two-moments microphysics with three hydrometeor categories (cloud liquid water, pristine ice crystals and larger precipitation crystals) is used to test the simulation in forecast mode using ECMWF data at 0.4 X 0.4 degree. We are zooming in on cirrus at higher resolutions (9, 1.8, 0.36 km). We are currently using the data set measured in APEX-E3, measurements of radar, lidar, passive instruments and interpreted microphysics for some flights (G-II, C404, B200). The radar and lidar data are available for high level cirrus. The south west of Japon is the flight region. The dates are March 20, March 27 and April 2, 2003. We first focus on the March 27 frontal system. We did a rigorous synoptical analysis for the cases. The cirrus at 360 m resolution are simulated. The cloud structure and some similarities between model simulation and observations will be presented.

  14. Applying a one-dimensional PDR model to the Taurus molecular cloud and its atomic envelope

    CERN Document Server

    Heiner, J S

    2012-01-01

    In this contribution, we test our previously published one-dimensional PDR model for deriving total hydrogen volume densities from HI column density measurements in extragalactic regions by applying it to the Taurus molecular cloud, where its predictions can be compared to available data. Also, we make the first direct detailed comparison of our model to CO(1-0) and far-infrared emission. Using an incident UV flux G0 of 4.25 ({\\chi} = 5) throughout the main body of the cloud, we derive total hydrogen volume densities of \\approx 430 cm-3, consistent with the extensive literature available on Taurus. The distribution of the volume densities shows a log-normal shape with a hint of a power-law shape on the high density end. We convert our volume densities to H2 column densities assuming a cloud depth of 5 parsec and compare these column densities to observed CO emission. We find a slope equivalent to a CO conversion factor relation that is on the low end of reported values for this factor in the literature (0.9 x...

  15. Estimation of the Vertical Velocity Leading to the Formation of Cirrus Using Ultra-High Resolution Global Simulations

    Science.gov (United States)

    Barahona, D.; Molod, A.; Putman, W.; Suarez, M.

    2014-12-01

    Cirrus clouds significantly impact the radiative and transport processes of the upper troposphere and the lower stratosphere. State-of-the-art global models parameterize the formation of cirrus explicitly linking ice nucleation events to the aerosol properties and the cloud-scale dynamics. However most GCMs cannot resolve the scale at which cloud formation occurs. Thus subgrid scale dynamics is typically parameterized by relating the vertical velocity variance, σw, to grid-scale fields. These parameterizations are typically validated against field campaign data for specific locations. However an assessment of the global spatial distribution of σw is lacking, limiting the ability of GCMs to describe cirrus formation. Here the non-hydrostatic version of the NASA Goddard Earth Observing System model (GEOS-5) is used to estimate the variance of vertical velocity in GCMs. GEOS-5 was run at cloud-resolving resolutions (~7 km), allowing the explicit calculation of σw. Our results indicate that σw is determined by orographic drag and local convection, and higher over the continents than over the ocean. A recently developed parameterization of σw is also evaluated. Compared to the model results the parameterization is able to reproduce the global distribution of σw for warm cirrus clouds but tends to overestimate σw near the tropopause. Our work provides for the first time an assessment of the global variability in the subgrid scale dynamics leading to the formation of cirrus.

  16. Medium-Range Predictability of Contrail-Cirrus Demonstrated during Experiments Ml-Cirrus and Access-Ii

    Science.gov (United States)

    Schumann, U.

    2015-12-01

    The Contrail Cirrus Prediction model CoCiP (doi:10.5194/gmd-5-543-2012) has been applied quasi operationally to predict contrails for flight planning of ML-CIRRUS (C. Voigt, DLR, et al.) in Europe and for ACCESS II in California (B. Anderson, NASA, et al.) in March-May 2014. The model uses NWP data from ECMWF and past airtraffic data (actual traffic data are used for analysis). The forecasts provided a sequence of hourly forecast maps of contrail cirrus optical depth for 3.5 days, every 12 h. CoCiP has been compared to observations before, e.g. within a global climate-aerosol-contrail model (Schumann, Penner et al., ACPD, 2015, doi:10.5194/acpd-15-19553-2015). Good predictions would allow for climate optimal routing (see, e.g., US patent by Mannstein and Schumann, US 2012/0173147 A1). The predictions are tested by: 1) Local eyewitness reports and photos, 2) satellite observed cloudiness, 3) autocorrelation analysis of predictions for various forecast periods, 4) comparisons of computed with observed optical depth from COCS (doi:10.5194/amt-7-3233-2014, 2014) by IR METEOSAT-SEVIRI observations over Europe. The results demonstrate medium-range predictability of contrail cirrus to a useful degree for given traffic, soot emissions, and high-quality NWP data. A growing set of satellite, Lidar, and in-situ data from ML-CIRRUS and ACCENT are becoming available and will be used to further test the forecast quality. The autocorrelation of optical depth predictions is near 70% for 3-d forecasts for Europe (outside times with high Sahara dust loads), and only slightly smaller for continental USA. Contrail cirrus is abundant over Europe and USA. More than 1/3 of all cirrus measured with the research aircraft HALO during ML-CIRRUS was impacted by contrails. The radiative forcing (RF) is strongly daytime and ambience dependent. The net annual mean RF, based on our global studies, may reach up to 0.08 W/m2 globally, and may well exceed 1 W/m2 regionally, with maximum over Europe

  17. Ground Based Retrievals of Small Ice Crystals and Water Phase in Arctic Cirrus

    Science.gov (United States)

    Mishra, Subhashree; Mitchell, David L.; DeSlover, Daniel

    2009-03-01

    The microphysical properties of cirrus clouds are uncertain due to the problem of ice particles shattering at the probe inlet upon sampling. To facilitate better estimation of small ice crystal concentrations in cirrus clouds, a new ground-based remote sensing technique has been used in combination with in situ aircraft measurements. Data from the Mixed-Phase Arctic Cloud Experiment (M-PACE), conducted at the north slope of Alaska (winter 2004), have been used to test a new method for retrieving the liquid water path (LWP) and ice water path (IWP) in mixed phase clouds. The framework of the retrieval algorithm consists of the modified anomalous diffraction approximation or MADA (for mixed phase cloud optical properties), a radar reflectivity-ice microphysics relationship and a temperature-dependent ice particle size distribution (PSD) scheme. Cloud thermal emission measurements made by the ground-based Atmospheric Emitted Radiance Interferometer (AERI) yield information on the total water path (TWP) while reflectivity measurements from the Millimeter Cloud Radar (MMCR) are used to derive the IWP. The AERI is also used to indicate the concentration of small ice crystals (DBeer's law absorption. While this is still a work in progress, the anticipated products from this AERI-radar retrieval scheme are the IWP, LWP, small-to-large ice crystal number concentration ratio and effective diameter for cirrus, as well as the ice particle number concentration for a given ice water content (IWC).

  18. The role of boundary layer aerosol particles for the development of deep convective clouds: A high-resolution 3D model with detailed (bin) microphysics applied to CRYSTAL-FACE

    Science.gov (United States)

    Leroy, Delphine; Wobrock, Wolfram; Flossmann, Andrea I.

    2009-01-01

    This paper reproduces aircraft microphysical measurements using a three-dimensional model with bin resolved microphysics and is then used to analyze in particular the role of boundary layer aerosol particles in the anvil and the ice phase. The simulated case is a convective cloud which develops a large anvil of around 10 km height, which was sampled during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers — Florida Area Cirrus Experiment (CRYSTAL-FACE). The model couples the 3D dynamics of a cloud scale model with a detailed mixed phase microphysical code. The microphysical package considers the evolution of the wet aerosol particles, drop and ice crystal spectra on size grids with 39 bins. With this model hereafter called DESCAM 3D, we are able to simulate the cloud with features close to those observed and to provide explanations of the observed phenomena concerning cloud microphysics as well as cloud dynamics. The same CRYSTAL-FACE cloud has already been simulated by other groups using a similar model. They investigated the role of mid-tropospheric aerosol particles versus boundary layer aerosol on the microphysical properties of the anvil. Similar simulations with our DESCAM 3D lead to quite different results. Reducing the number of mid-tropospheric aerosol particles causes only minor changes in the cloud anvil. However, changing the aerosol particle spectrum in the boundary layer from clean to polluted conditions modifies strongly the dynamical evolution of the convective clouds and thus impacts significantly on the microphysical properties of the anvil. Possible reasons for the differences are discussed.

  19. Applying super-droplets as a compact representation of warm-rain microphysics for aerosol-cloud-aerosol interactions

    Science.gov (United States)

    Arabas, S.; Jaruga, A.; Pawlowska, H.; Grabowski, W. W.

    2012-12-01

    Clouds may influence aerosol characteristics of their environment. The relevant processes include wet deposition (rainout or washout) and cloud condensation nuclei (CCN) recycling through evaporation of cloud droplets and drizzle drops. Recycled CCN physicochemical properties may be altered if the evaporated droplets go through collisional growth or irreversible chemical reactions (e.g. SO2 oxidation). The key challenge of representing these processes in a numerical cloud model stems from the need to track properties of activated CCN throughout the cloud lifecycle. Lack of such "memory" characterises the so-called bulk, multi-moment as well as bin representations of cloud microphysics. In this study we apply the particle-based scheme of Shima et al. 2009. Each modelled particle (aka super-droplet) is a numerical proxy for a multiplicity of real-world CCN, cloud, drizzle or rain particles of the same size, nucleus type,and position. Tracking cloud nucleus properties is an inherent feature of the particle-based frameworks, making them suitable for studying aerosol-cloud-aerosol interactions. The super-droplet scheme is furthermore characterized by linear scalability in the number of computational particles, and no numerical diffusion in the condensational and in the Monte-Carlo type collisional growth schemes. The presentation will focus on processing of aerosol by a drizzling stratocumulus deck. The simulations are carried out using a 2D kinematic framework and a VOCALS experiment inspired set-up (see http://www.rap.ucar.edu/~gthompsn/workshop2012/case1/).

  20. Global tropospheric NO2 profiles obtained from a cloud-slicing technique applied to the Aura OMI observations

    Science.gov (United States)

    Choi, S.; Joiner, J.; Lamsal, L. N.; Marchenko, S. V.; Krotkov, N. A.

    2016-12-01

    Nitrogen dioxide (NO2) is an important trace species in the troposphere; it has adverse human health effects and also contributes to the formation of tropospheric ozone, a criteria pollutant and climate agent. We derive tropospheric NO2 volume mixing ratio (VMR) profiles by applying a cloud slicing technique to data from the Ozone Monitoring Instrument (OMI) on the Aura satellite. In the cloud-slicing approach, the slope of the above-cloud NO2 column versus the cloud scene pressure is proportional to the NO2 VMR. We apply this technique to OMI O2-O2 cloud scene pressures and above-cloud NO2 vertical column densities from a differential optical absorption spectroscopy (DOAS) algorithm. We derived a global seasonal climatology of tropospheric NO2 VMR profiles in cloudy conditions and compare the results with aircraft profiles measured during the NASA Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign in 2006. An analysis of our cloud slicing NO2 profiles indicates signatures of uplifted and transported anthropogenic NOx in the middle troposphere as well as lightning-generated NOx in the upper troposphere. We expect that this technique can be applied to future geostationary missions including the NASA Earth Ventures Instrument (EVI) 1 selected mission Tropospheric Emissions: Monitoring of Pollution (TEMPO) over North America, the Korean Geostationary Environment Monitoring Spectrometer (GEMS) over the Asia-Pacific region, and the European Space Agency (ESA) Sentinel-4 over Europe.

  1. To what extent can cirrus seeding counteract global warming?

    Science.gov (United States)

    Gasparini, Blaz; Lohmann, Ulrike

    2017-04-01

    The idea of modifying cirrus clouds to directly counteract greenhouse gas warming has gained a lot of momentum in recent years, despite large disputes over its physical feasibility. We use the ECHAM-HAM general circulation model to evaluate the temperature and precipitation responses to cirrus thinning by seeding with efficient ice nucleating particles and increasing ice crystal sedimentation velocities in a 1.5xCO2 world. The seeding scenario can counteract about 40% of the warming and precipitation increase induced by 1.5 x CO2 concentrations with respect to present day values. The idealized ice crystal sedimentation velocity increase scenario on the other hand fully restores the global annual temperature but counteracts only half of the precipitation increase. Moreover, we define a climate damage function, quadratic in temperature and precipitation anomalies to calculate the damage of the different scenarios in 21 selected land regions. Seeding can decrease about 55% of the CO2 induced damage, while the sedimentation velocity increase can counteract about 95% of the damage. A regional analysis shows the negative responses of seeding are minimal both in terms of precipitation and temperature, which makes cirrus seeding an attractive geoengineering method.

  2. A test of cirrus ice crystal scattering phase functions

    Science.gov (United States)

    Field, P. R.; Baran, A. J.; Kaye, P. H.; Hirst, E.; Greenaway, R.

    2003-07-01

    In-situ ice crystal scattering has been measured in cirrus cloud with the Small Ice Detector laser scattering probe. Using light scattered from single particles (maximum dimension ~<100 μm) at 4-10° and 20-40° we have tested ice crystal scattering phase functions for spheres, hexagonal columns, hexagonal plates, polycrystals an aggregate of columns and an analytic function. We find that phase functions that lack a pronounced 22° halo are the best representatives for the example data presented here. Spherical ice particle phase functions do not satisfy the measurements.

  3. Sensitivity of PARASOL multi-angle photo-polarimetric aerosol retrievals to cloud contamination

    Science.gov (United States)

    Stap, F. A.; Hasekamp, O.; Röckmann, T.

    2014-10-01

    An important problem in satellite remote sensing of aerosols is related to the need to perform an adequate cloud screening. If a cloud screening is applied that is not strict enough, the ground scene has the probability of residual cloud cover which causes large errors on the retrieved aerosol parameters. On the other hand, if the cloud screening procedure is too strict, too many clear sky cases, especially near-cloud scenes, will falsely be flagged cloudy. The detrimental effects of cloud contamination as well as the importance of aerosol cloud interactions that can be studied in these near-cloud scenes call for new approaches to cloud screening. Multi-angle, multi-wavelength photo-polarimetric measurements have a unique capability to distinguish between scattering by (liquid) cloud droplets and aerosol particles. In this paper the sensitivity of aerosol retrievals from multi-angle, photo-polarimetric measurements to cloud contamination is investigated and the ability to intrinsically filter the cloud contaminated scenes based on a goodness-of-fit criteria is evaluated. Hereto, an aerosol retrieval algorithm is applied to a partially clouded, synthetic data-set including partial cloud cover as well as non-cloud screened POLDER-3/PARASOL observations It is found that a goodness-of-fit filter, together with a filter on the coarse mode refractive index (mrcoarse > 1.335) and a cirrus screening adequately reject the cloud contaminated scenes. No bias nor larger SD are found in the retrieved parameters for this intrinsic cloud filter compared to the parameters retrieved in a priori cloud screened data-set (using MODIS/AQUA cloud masks) of PARASOL observations. Moreover, less high aerosol load scenes are misinterpreted as cloud contaminated. The retrieved aerosol optical thickness, single scattering albedo and Ångström exponent show good agreement with AERONET observations. Furthermore, the synthetic retrievals give confidence in the ability of the algorithm to

  4. On the importance of small ice crystals in tropical anvil cirrus

    Directory of Open Access Journals (Sweden)

    E. J. Jensen

    2009-08-01

    Full Text Available In situ measurements of ice crystal concentrations and sizes made with aircraft instrumentation over the past two decades have often indicated the presence of numerous relatively small (< 50 μm diameter crystals in cirrus clouds. Further, these measurements frequently indicate that small crystals account for a large fraction of the extinction in cirrus clouds. The fact that the instruments used to make these measurements, such as the Forward Scattering Spectrometer Probe (FSSP and the Cloud Aerosol Spectrometer (CAS, ingest ice crystals into the sample volume through inlets has led to suspicion that the indications of numerous small-crystals could be artifacts of large-crystal shattering on the instrument inlets. We present new aircraft measurements in anvil cirrus sampled during the Tropical Composition, Cloud, and Climate Coupling (TC4 campaign with the 2-Dimensional Stereo (2D-S probe, which detects particles as small as 10 μm. The 2D-S has detector "arms" instead of an inlet tube. Since the 2D-S probe surfaces are much further from the sample volume than is the case for the instruments with inlets, it is expected that 2D-S will be less susceptible to shattering artifacts. In addition, particle inter-arrival times are used to identify and remove shattering artifacts that occur even with the 2D-S probe. The number of shattering artifacts identified by the 2D-S interarrival time analysis ranges from a negligible contribution to an order of magnitude or more enhancement in apparent ice concentration over the natural ice concentration, depending on the abundance of large crystals and the natural small-crystal concentration. The 2D-S measurements in tropical anvil cirrus suggest that natural small-crystal concentrations are typically one to two orders of magnitude lower than those inferred from CAS. The strong correlation between the CAS/2D-S ratio of small-crystal concentrations and large-crystal concentration suggests that the discrepancy is

  5. Cloud computing architecture and applied research of enterprise"cloud"%云计算架构与企业“云”应用研究

    Institute of Scientific and Technical Information of China (English)

    康瑞锋

    2013-01-01

    云计算是物联时代的热点话题,国内外知名的大企业都在进行云计算架构的相关研究。谷歌、微软、华为均在部署并架构自己的云计算平台,云服务无疑将成IT企业未来的赢利模式。文中主要对云计算架构进行技术分析与应用研究,并对构建企业“云”应用所面临的挑战加以分析,提出了应对方法与实践过程,以便为物联时代企业构建可靠、高效的云服务提供技术支持。%Cloud computing is a hot topic in the IOT era. The large enterprises known at home and abroad are all making a research relative to cloud computing architecture. Google, Microsoft and Huawei are deploying and structuring their own cloud computing platform. The cloud service will become the IT companys’ proift mode in the future evidently. The technical analysis and applied research on the"cloud"computing architecture are performed in this paper emphatically. The challenge building enterprise"cloud"applications is analyzed, and corresponding methods to rise the challenge are proposed for providing a technical support for the enterprises to complete their reliable and efifcient cloud services in the IOT era.

  6. Sensitivity of PARASOL multi-angle photopolarimetric aerosol retrievals to cloud contamination

    Science.gov (United States)

    Stap, F. A.; Hasekamp, O. P.; Röckmann, T.

    2015-03-01

    An important problem in satellite remote sensing of aerosols is related to the need to perform an adequate cloud screening. If a cloud screening is applied that is not strict enough, the ground scene has the probability of residual cloud cover which causes large errors on the retrieved aerosol parameters. On the other hand, if the cloud-screening procedure is too strict, too many clear sky cases, especially near-cloud scenes, will falsely be flagged cloudy. The detrimental effects of cloud contamination as well as the importance of aerosol cloud interactions that can be studied in these near-cloud scenes call for new approaches to cloud screening. Multi-angle multi-wavelength photopolarimetric measurements have a unique capability to distinguish between scattering by (liquid) cloud droplets and aerosol particles. In this paper the sensitivity of aerosol retrievals from multi-angle photopolarimetric measurements to cloud contamination is investigated and the ability to intrinsically filter the cloud-contaminated scenes based on a goodness-of-fit criteria is evaluated. Hereto, an aerosol retrieval algorithm is applied to a partially clouded over-ocean synthetic data set as well as non-cloud-screened over-ocean POLDER-3/PARASOL observations. It is found that a goodness-of-fit filter, together with a filter on the coarse mode refractive index (mrcoarse > 1.335) and a cirrus screening, adequately rejects the cloud-contaminated scenes. No bias or larger SD are found in the retrieved parameters for this intrinsic cloud filter compared to the parameters retrieved in a priori cloud-screened data set (using MODIS/AQUA cloud masks) of PARASOL observations. Moreover, less high-aerosol load scenes are misinterpreted as cloud contaminated. The retrieved aerosol optical thickness, single scattering albedo and Ångström exponent show good agreement with AERONET observations. Furthermore, the synthetic retrievals give confidence in the ability of the algorithm to correctly

  7. Considerations for modeling thin cirrus effects via brightness temperature differences

    Science.gov (United States)

    Schmidt, E. O.; Arduini, R. F.; Wielicki, B. A.; Stone, R. S.; Tsay, S.-C.

    1995-01-01

    Brightness temperature difference (BTD) values are calculated for selected Geostationary Operational Environmental Satellite (GOES-6) channels (3.9, 12.7 micrometer) and Advanced Very High Resolution Radiometer channels (3.7, 12.0 micrometer). Daytime and nighttime discrimination of particle size information is possible given the infrared cloud extinction optical depth and the BTD value. BTD values are presented and compared for cirrus clouds composed of equivalent ice spheres (volume, surface area) versus randomly oriented hexagonal ice crystals. The effect of the hexagonal ice crystals is to increase the magnitude of the BTD values calculated relative to equivalent ice sphere (volume, surface area) BTDs. Equivalent spheres (volume or surface area) do not do a very good job of modeling hexagonal ice crystal effects on BTDs; however, the use of composite spheres improves the simulation and offers interesting prospects. Careful consideration of the number of Legendre polynomial coefficients used to fit the scattering phase functions is crucial to realistic modeling of cirrus BTDs. Surface and view-angle effects are incorporated to provide more realistic simulation.

  8. On the Quality of Point-Clouds Derived from Sfm-Photogrammetry Applied to UAS Imagery

    Science.gov (United States)

    Carbonneau, P.; James, T.

    2014-12-01

    Structure from Motion photogrammetry (SfM-photogrammetry) recently appeared in environmental sciences as an impressive tool allowing for the creation of topographic data from unstructured imagery. Several authors have tested the performance of SfM-photogrammetry vs that of TLS or dGPS. Whilst the initial results were very promising, there is currently a growing awareness that systematic deformations occur in DEMs and point-clouds derived from SfM-photogrammetry. Notably, some authors have identified a systematic doming manifest as an increasing error vs distance to the model centre. Simulation studies have confirmed that this error is due to errors in the calibration of camera distortions. This work aims to further investigate these effects in the presence of real data. We start with a dataset of 220 images acquired from a sUAS. After obtaining an initial self-calibration of the camera lens with Agisoft Photoscan, our method consists in applying systematic perturbations to 2 key lens parameters: Focal length and the k1 distortion parameter. For each perturbation, a point-cloud was produced and compared to LiDAR data. After deriving the mean and standard deviation of the error residuals (ɛ), a 2nd order polynomial surface was fitted to the errors point-cloud and the peak ɛ defined as the mathematical extrema of this surface. The results are presented in figure 1. This figure shows that lens perturbations can induce a range of errors with systematic behaviours. Peak ɛ is primarily controlled by K1 with a secondary control exerted by the focal length. These results allow us to state that: To limit the peak ɛ to 10cm, the K1 parameter must be calibrated to within 0.00025 and the focal length to within 2.5 pixels (≈10 µm). This level of calibration accuracy can only be achieved with proper design of image acquisition and control network geometry. Our main point is therefore that SfM is not a bypass to a rigorous and well-informed photogrammetric approach. Users

  9. A variational approach for retrieving ice cloud properties from infrared measurements: application in the context of two IIR validation campaigns

    Science.gov (United States)

    Sourdeval, O.; -Labonnote, L. C.; Brogniez, G.; Jourdan, O.; Pelon, J.; Garnier, A.

    2013-08-01

    Cirrus are cloud types that are recognized to have a strong impact on the Earth-atmosphere radiation balance. This impact is however still poorly understood, due to the difficulties in describing the large variability of their properties in global climate models. Consequently, numerous airborne and space-borne missions have been dedicated to their study in the last decades. The satellite constellation A-Train has for instance proven to be particularly helpful for the study of cirrus. More particularly, the Infrared Imaging Radiometer (IIR) carried onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite shows a great sensitivity to the radiative and microphysical properties of these clouds. Our study presents a novel methodology that uses the thermal infrared measurements of IIR to retrieve the ice crystal effective size and optical thickness of cirrus. This methodology is based on an optimal estimation scheme, which possesses the advantage of attributing precise uncertainties to the retrieved parameters. Two IIR airborne validation campaigns have been chosen as case studies for illustrating the results of our retrieval method. It is observed that optical thicknesses could be accurately retrieved but that large uncertainties may occur on the effective diameters. Strong agreements have also been found between the products of our method when separately applied to the measurements of IIR and of the airborne radiometer CLIMAT-AV, which consolidates the results of previous validation studies of IIR level-1 measurements. Comparisons with in situ observations and with operational products of IIR are also discussed and appear to be coherent with our results. However, we have found that the quality of our retrievals can be strongly impacted by uncertainties related to the choice of a pristine crystal model and by poor constraints on the properties of possible liquid cloud layers underneath cirrus. Simultaneous retrievals of liquid

  10. 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.

  11. Effective Ice Particle Densities for Cold Anvil Cirrus

    Science.gov (United States)

    Heymsfield, Andrew J.; Schmitt, Carl G.; Bansemer, Aaron; Baumgardner, Darrel; Weinstock, Elliot M.; Smith, Jessica

    2002-01-01

    This study derives effective ice particle densities from data collected from the NASA WB-57F aircraft near the tops of anvils during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) in southern Florida in July 2002. The effective density, defined as the ice particle mass divided by the volume of an equivalent diameter liquid sphere, is obtained for particle populations and single sizes containing mixed particle habits using measurements of condensed water content and particle size distributions. The mean effective densities for populations decrease with increasing slopes of the gamma size distributions fitted to the size distributions. The population-mean densities range from near 0.91 g/cu m to 0.15 g/cu m. Effective densities for single sizes obey a power-law with an exponent of about -0.55, somewhat less steep than found from earlier studies. Our interpretations apply to samples where particle sizes are generally below 200-300 microns in maximum dimension because of probe limitations.

  12. Radiative properties of ice clouds

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, D.L.; Koracin, D.; Carter, E. [Desert Research Institute, Reno, NV (United States)

    1996-04-01

    A new treatment of cirrus cloud radiative properties has been developed, based on anomalous diffraction theory (ADT), which does not parameterize size distributions in terms of an effective radius. Rather, is uses the size distribution parameters directly, and explicitly considers the ice particle shapes. There are three fundamental features which characterize this treatment: (1) the ice path radiation experiences as it travels through an ice crystal is parameterized, (2) only determines the amount of radiation scattered and absorbed, and (3) as in other treatments, the projected area of the size distribution is conserved. The first two features are unique to this treatment, since it does not convert the ice particles into equivalent volume or area spheres in order to apply Mie theory.

  13. Radiative Heating of the ISCCP Upper Level Cloud Regimes and its Impact on the Large-scale Tropical Circulation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wei; Schumacher, Courtney; McFarlane, Sally A.

    2013-01-31

    Radiative heating profiles of the International Satellite Cloud Climatology Project (ISCCP) cloud regimes (or weather states) were estimated by matching ISCCP observations with radiative properties derived from cloud radar and lidar measurements from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) sites at Manus, Papua New Guinea, and Darwin, Australia. Focus was placed on the ISCCP cloud regimes containing the majority of upper level clouds in the tropics, i.e., mesoscale convective systems (MCSs), deep cumulonimbus with cirrus, mixed shallow and deep convection, and thin cirrus. At upper levels, these regimes have average maximum cloud occurrences ranging from 30% to 55% near 12 km with variations depending on the location and cloud regime. The resulting radiative heating profiles have maxima of approximately 1 K/day near 12 km, with equal heating contributions from the longwave and shortwave components. Upper level minima occur near 15 km, with the MCS regime showing the strongest cooling of 0.2 K/day and the thin cirrus showing no cooling. The gradient of upper level heating ranges from 0.2 to 0.4 K/(day∙km), with the most convectively active regimes (i.e., MCSs and deep cumulonimbus with cirrus) having the largest gradient. When the above heating profiles were applied to the 25-year ISCCP data set, the tropics-wide average profile has a radiative heating maximum of 0.45Kday-1 near 250 hPa. Column-integrated radiative heating of upper level cloud accounts for about 20% of the latent heating estimated by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The ISCCP radiative heating of tropical upper level cloud only slightly modifies the response of an idealized primitive equation model forced with the tropics-wide TRMM PR latent heating, which suggests that the impact of upper level cloud is more important to large-scale tropical circulation variations because of convective feedbacks rather than direct forcing by

  14. Cirrus Dopant Nano-Composite Coatings

    Science.gov (United States)

    2014-11-01

    Inorganic Nano-particles • Ti • Zr • Al • Zn • Yr • Si Coatings • Au • Ag • Sn • Cu • Zn • Ni • NiB • NiCo • NiP cirrus Broadened...1000 1200 HARDNESS (HV) MICROHARDNESS - ELECTROLESS NIP STANDARD COATING TI DOPED COATING ZR DOPED COATING ↑74% Standard DC NiB Cirrus DC NiB 15

  15. Applying Chemical Imaging Analysis to Improve Our Understanding of Cold Cloud Formation

    Science.gov (United States)

    Laskin, A.; Knopf, D. A.; Wang, B.; Alpert, P. A.; Roedel, T.; Gilles, M. K.; Moffet, R.; Tivanski, A.

    2012-12-01

    The impact that atmospheric ice nucleation has on the global radiation budget is one of the least understood problems in atmospheric sciences. This is in part due to the incomplete understanding of various ice nucleation pathways that lead to ice crystal formation from pre-existing aerosol particles. Studies investigating the ice nucleation propensity of laboratory generated particles indicate that individual particle types are highly selective in their ice nucleating efficiency. This description of heterogeneous ice nucleation would present a challenge when applying to the atmosphere which contains a complex mixture of particles. Here, we employ a combination of micro-spectroscopic and optical single particle analytical methods to relate particle physical and chemical properties with observed water uptake and ice nucleation. Field-collected particles from urban environments impacted by anthropogenic and marine emissions and aging processes are investigated. Single particle characterization is provided by computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). A particle-on-substrate approach coupled to a vapor controlled cooling-stage and a microscope system is applied to determine the onsets of water uptake and ice nucleation including immersion freezing and deposition ice nucleation as a function of temperature (T) as low as 200 K and relative humidity (RH) up to water saturation. We observe for urban aerosol particles that for T > 230 K the oxidation level affects initial water uptake and that subsequent immersion freezing depends on particle mixing state, e.g. by the presence of insoluble particles. For T cloud formation. Initial results applying single particle IN analysis using CCSEM/EDX and STXM/NEXAFS reveal that a significant amount of IN are coated by organics and, thus, are similar to the

  16. Microphysical and optical properties of contrails and cirrus

    Energy Technology Data Exchange (ETDEWEB)

    Gayet, J.F.; Febvre, G. [Universite Blaise Pascal, Clermont-Ferand (France). Lab. de Meteorologie Physique; Brogniez, G. [Universite des Sciences et Techniques de Lille, (France). Lab. d`Optique Atmospherique; Wendling, P. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere; Larsen, H. [National Inst. for Water and Atmospheric Research, Wellington (New Zealand)

    1997-12-31

    Aircraft contrails have significantly different properties to natural cirrus clouds. Their local and global climate impact cannot be assessed without consideration of these differences. Microphysical data were obtained from the Merlin aircraft equipped with a PMS FSSP-100 for particle spectrum measurements over the 3 {mu}m to 45 {mu}m diameter range; a PMS 2D-C for particle size spectrum and particle shape over the size range from 25 {mu}m to 800 {mu}m and a Johnson-Williams cloud liquid-water probe. Radiative measurements were obtained from a Do228 aircraft which carried the upward looking ALEX-F Lidar operating at a wavelength of 1.06 {mu}m and a Barnes PRT-5 radiometer aligned parallel to the lidar and with a 9 to 11 {mu}m spectral range. The limitation in accuracy of cloud microphysical sensor used in contrail studies are also discussed with subsequent errors on description of cloud radiative properties. (R.P.) 9 refs.

  17. CALIPSO Observations of PSCs and Cirrus During the 2015-2016 Arctic Winter

    Science.gov (United States)

    Pitts, Michael; Poole, Lamont

    2016-04-01

    The POLSTRACC (POlar STRAtosphere in a Changing Climate) field campaign was conducted in the Arctic during December 2015 - March 2016 to investigate the chemical, microphysical, and dynamical processes of the Arctic lowermost stratosphere and upper troposphere. The primary measurement platform for POLSTRACC was the German HALO (High Altitude LOng range) research aircraft carrying a large suite of in situ and remote sensing instruments to measure key chemical species, tracers, as well as aerosol and cloud particles and meteorological parameters. Two primary science objectives of POLSTRACC are to improve our understanding of polar stratospheric cloud (PSC) particle characteristics and formation processes and investigate the impact of Arctic cirrus clouds on radiative forcing and chlorine activation. To complement the more focused measurements from the POLSTRACC field campaign, we have used spaceborne lidar measurements from CALIPSO to characterize PSC occurrence and composition, as well as the occurrence of Arctic cirrus during the 2015-2016 season on vortex-wide scales. In this paper, we present a general overview of the 2015-2016 winter, examine in detail the evolution of PSCs and cirrus during the season, and explore the unique aspects of this season in attempt to understand the underlying physical mechanisms.

  18. A multi-approach to the optical depth of a contrail cirrus cluster

    Science.gov (United States)

    Vazquez-Navarro, Margarita; Bugliaro, Luca; Schumann, Ulrich; Strandgren, Johan; Wirth, Martin; Voigt, Christiane

    2017-04-01

    Amongst the individual aviation emissions, contrail cirrus contribute the largest fraction to the aviation effects on climate. To investigate the optical depth from contrail cirrus, we selected a cirrus and contrail cloud outbreak on the 10th April 2014 between the North Sea and Switzerland detected during the ML-CIRRUS experiment (Voigt et al., 2017). The outbreak was not forecast by weather prediction models. We describe its origin and evolution using a combination of in-situ measurements, remote sensing approaches and contrail prediction model prognosis. The in-situ and lidar measurements were carried out with the HALO aircraft, where the cirrus was first identified. Model predictions from the contrail prediction model CoCiP (Schumann et al., 2012) point to an anthropogenic origin. The satellite pictures from the SEVIRI imager on MSG combined with the use of a contrail cluster tracking algorithm enable the automatic assessment of the origin, displacement and growth of the cloud and the correct labeling of cluster pixels. The evolution of the optical depth and particle size of the selected cluster pixels were derived using the CiPS algorithm, a neural network primarily based on SEVIRI images. The CoCiP forecast of the cluster compared to the actual cluster tracking show that the model correctly predicts the occurrence of the cluster and its advection direction although the cluster spreads faster than simulated. The optical depth derived from CiPS and from the airborne high spectral resolution lidar WALES are compared and show a remarkably good agreement. This confirms that the new CiPS algorithm is a very powerful tool for the assessment of the optical depth of even optically thinner cirrus clouds. References: Schumann, U.: A contrail cirrus prediction model, Geosci. Model Dev., 5, 543-580, doi: 10.5194/gmd-5-543-2012, 2012. Voigt, C., Schumann, U., Minikin, A., Abdelmonem, A., Afchine, A., Borrmann, S., Boettcher, M., Buchholz, B., Bugliaro, L., Costa, A

  19. Retrieval of Cirrus properties by Sunphotometry: A new perspective on an old issue

    Science.gov (United States)

    Segal-Rosenhaimer, M.; Russell, P. B.; Livingston, J. M.; Ramachandran, S.; Redemann, J.; Baum, B. A.

    2012-12-01

    Cirrus clouds are important modulators of the earth radiation budget and continue to be one of the most uncertain components in weather and climate modeling and in the estimations of cooling and warming effects. This is mainly due to the high uncertainty in the derivation of their optical thicknesses and ice crystal size, shape and amount. While sunphotometers are widely accepted as one of the most accurate platforms for measuring aerosol optical depth (AOD), such measurements under cirrus are still considered unreliable. The ease and the relatively widespread use of sunphotometers globally, both as airborne and ground-based platforms, can potentially contribute to our increased capability in quantifying some of the most important cirrus properties such as cloud optical thickness (COT) and ice crystal effective diameter. However, under cloudy conditions, the signal received at the sunphotometer FOV contains not only the direct attenuated solar irradiation, but also the forward scattered term, which interferes with the proper derivation of AOD via the simple Beer-Lambert relation. Solutions to this problem were previously suggested in the form of correction factors. In the present work we have proposed a new approach that utilizes the additional information content that lies within the total measured irradiance under a cloudy scene. Relatively thin cirrus clouds (i.e. COT<4.0) allow direct sun irradiation to reach the detector, and at the same time strongly scatter some of this radiation into the instrument FOV. This results in increased transmittance values due to both the direct and scattered components. This quantity was modeled for the spectral range of 400-2200 nm, for a range of COT (0-4), and a range of ice particle effective diameters using the explicit Baum and Yang cirrus optical properties data sets. This allowed the derivations of transmittance look-up tables that were used for the retrieval procedure. The new approach was tested on two cases; an

  20. Model of Quantum Computing in the Cloud: The Relativistic Vision Applied in Corporate Networks

    Directory of Open Access Journals (Sweden)

    Chau Sen Shia

    2016-08-01

    Full Text Available Cloud computing has is one of the subjects of interest to information technology professionals and to organizations when the subject covers financial economics and return on investment for companies. This work aims to present as a contribution proposing a model of quantum computing in the cloud using the relativistic physics concepts and foundations of quantum mechanics to propose a new vision in the use of virtualization environment in corporate networks. The model was based on simulation and testing of connection with providers in virtualization environments with Datacenters and implementing the basics of relativity and quantum mechanics in communication with networks of companies, to establish alliances and resource sharing between the organizations. The data were collected and then were performed calculations that demonstrate and identify connections and integrations that establish relations of cloud computing with the relativistic vision, in such a way that complement the approaches of physics and computing with the theories of the magnetic field and the propagation of light. The research is characterized as exploratory, because searches check physical connections with cloud computing, the network of companies and the adhesion of the proposed model. Were presented the relationship between the proposal and the practical application that makes it possible to describe the results of the main features, demonstrating the relativistic model integration with new technologies of virtualization of Datacenters, and optimize the resource with the propagation of light, electromagnetic waves, simultaneity, length contraction and time dilation.

  1. Submillimeter-Wave Cloud Ice Radiometry

    Science.gov (United States)

    Walter, Steven J.

    1999-01-01

    Submillimeter-wave cloud ice radiometry is a new and innovative technique for characterizing cirrus ice clouds. Cirrus clouds affect Earth's climate and hydrological cycle by reflecting incoming solar energy, trapping outgoing IR radiation, sublimating into vapor, and influencing atmospheric circulation. Since uncertainties in the global distribution of cloud ice restrict the accuracy of both climate and weather models, successful development of this technique could provide a valuable tool for investigating how clouds affect climate and weather. Cloud ice radiometry could fill an important gap in the observational capabilities of existing and planned Earth-observing systems. Using submillimeter-wave radiometry to retrieve properties of ice clouds can be understood with a simple model. There are a number of submillimeter-wavelength spectral regions where the upper troposphere is transparent. At lower tropospheric altitudes water vapor emits a relatively uniform flux of thermal radiation. When cirrus clouds are present, they scatter a portion of the upwelling flux of submillimeter-wavelength radiation back towards the Earth as shown in the diagram, thus reducing the upward flux o f energy. Hence, the power received by a down-looking radiometer decreases when a cirrus cloud passes through the field of view causing the cirrus cloud to appear radiatively cool against the warm lower atmospheric thermal emissions. The reduction in upwelling thermal flux is a function of both the total cloud ice content and mean crystal size. Radiometric measurements made at multiple widely spaced frequencies permit flux variations caused by changes in crystal size to be distinguished from changes in ice content, and polarized measurements can be used to constrain mean crystal shape. The goal of the cloud ice radiometry program is to further develop and validate this technique of characterizing cirrus. A multi-frequency radiometer is being designed to support airborne science and

  2. Technical note: A new day- and night-time Meteosat Second Generation Cirrus Detection Algorithm MeCiDA

    Directory of Open Access Journals (Sweden)

    W. Krebs

    2007-12-01

    Full Text Available A new cirrus detection algorithm for the Spinning Enhanced Visible and Infra-Red Imager (SEVIRI aboard the geostationary Meteosat Second Generation (MSG, MeCiDA, is presented. The algorithm uses the seven infrared channels of SEVIRI and thus provides a consistent scheme for cirrus detection at day and night. MeCiDA combines morphological and multi-spectral threshold tests and detects optically thick and thin ice clouds. The thresholds were determined by a comprehensive theoretical study using radiative transfer simulations for various atmospheric situations as well as by manually evaluating actual satellite observations. The cirrus detection has been optimized for mid- and high latitudes but it could be adapted to other regions as well. The retrieved cirrus masks have been validated by comparison with the Moderate Resolution Imaging Spectroradiometer (MODIS Cirrus Reflection Flag. To study possible seasonal variations in the performance of the algorithm, one scene per month of the year 2004 was randomly selected and compared with the MODIS flag. 81% of the pixels were classified identically by both algorithms. In a comparison of monthly mean values for Europe and the North-Atlantic MeCiDA detected 29.3% cirrus coverage, while the MODIS SWIR cirrus coverage was 38.1%. A lower detection efficiency is to be expected for MeCiDA, as the spatial resolution of MODIS is considerably better and as we used only the thermal infrared channels in contrast to the MODIS algorithm which uses infrared and visible radiances. The advantage of MeCiDA compared to retrievals for polar orbiting instruments or previous geostationary satellites is that it permits the derivation of quantitative data every 15 min, 24 h a day. This high temporal resolution allows the study of diurnal variations and life cycle aspects. MeCiDA is fast enough for near real-time applications.

  3. A collaborative computing framework of cloud network and WBSN applied to fall detection and 3-D motion reconstruction.

    Science.gov (United States)

    Lai, Chin-Feng; Chen, Min; Pan, Jeng-Shyang; Youn, Chan-Hyun; Chao, Han-Chieh

    2014-03-01

    As cloud computing and wireless body sensor network technologies become gradually developed, ubiquitous healthcare services prevent accidents instantly and effectively, as well as provides relevant information to reduce related processing time and cost. This study proposes a co-processing intermediary framework integrated cloud and wireless body sensor networks, which is mainly applied to fall detection and 3-D motion reconstruction. In this study, the main focuses includes distributed computing and resource allocation of processing sensing data over the computing architecture, network conditions and performance evaluation. Through this framework, the transmissions and computing time of sensing data are reduced to enhance overall performance for the services of fall events detection and 3-D motion reconstruction.

  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. 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.

  6. 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.

  7. Long-lived contrails and convective cirrus above the tropical tropopause

    Science.gov (United States)

    Schumann, Ulrich; Kiemle, Christoph; Schlager, Hans; Weigel, Ralf; Borrmann, Stephan; D'Amato, Francesco; Krämer, Martina; Matthey, Renaud; Protat, Alain; Voigt, Christiane; Volk, C. Michael

    2017-02-01

    This study has two objectives: (1) it characterizes contrails at very low temperatures and (2) it discusses convective cirrus in which the contrails occurred. (1) Long-lived contrails and cirrus from overshooting convection are investigated above the tropical tropopause at low temperatures down to -88 °C from measurements with the Russian high-altitude research aircraft M-55 Geophysica, as well as related observations during the SCOUT-O3 field experiment near Darwin, Australia, in 2005. A contrail was observed to persist below ice saturation at low temperatures and low turbulence in the stratosphere for nearly 1 h. The contrail occurred downwind of the decaying convective system Hector of 16 November 2005. The upper part of the contrail formed at 19 km altitude in the tropical lower stratosphere at ˜ 60 % relative humidity over ice at -82 °C. The ˜ 1 h lifetime is explained by engine water emissions, slightly enhanced humidity from Hector, low temperature, low turbulence, and possibly nitric acid hydrate formation. The long persistence suggests large contrail coverage in case of a potential future increase of air traffic in the lower stratosphere. (2) Cirrus observed above the strongly convective Hector cloud on 30 November 2005 was previously interpreted as cirrus from overshooting convection. Here we show that parts of the cirrus were caused by contrails or are mixtures of convective and contrail cirrus. The in situ data together with data from an upward-looking lidar on the German research aircraft Falcon, the CPOL radar near Darwin, and NOAA-AVHRR satellites provide a sufficiently complete picture to distinguish between contrail and convective cirrus parts. Plume positions are estimated based on measured or analyzed wind and parameterized wake vortex descent. Most of the non-volatile aerosol measured over Hector is traceable to aircraft emissions. Exhaust emission indices are derived from a self-match experiment of the Geophysica in the polar stratosphere

  8. Intercomparison of MAS, AVIRIS, and HIS data from FIRE cirrus 2

    Science.gov (United States)

    Gumley, Liam E.; King, Michael D.; Tsay, Si-Chee; Gao, Bo-Cai; Arnold, G. Thomas

    1993-01-01

    The NASA ER-2 flight on 5 Dec. 1991 is unique among the FIRE Cirrus 2 missions in that data were acquired simultaneously by the MODIS Airborne Simulator (MAS), the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), and the High Resolution Interferometer Sounder (HIS). These data represent a unique source of information about the spatial and spectral properties of cirrus clouds. The MAS is a new instrument which will aid in defining algorithms and building an understanding of the ability of the Moderate Resolution Imaging Spectroradiometer (MODIS) to remotely sense atmospheric conditions for assessing global change. In order to establish confidence in the absolute calibration accuracy of the MAS radiances, an inter-comparison of MAS radiances with AVIRIS and HIS has been undertaken.

  9. Cloud recognition from ground-based solar radiation measurements: preliminary results

    Science.gov (United States)

    Calbo, Josep; Gonzalez, Josep-Abel

    1998-12-01

    Despite cloud recognition techniques that can routinely identify cloud classes form satellite images, observation of clouds from the ground is still needed to acquire a complete description of cloud climatology. Solar radiation in a given site is one of the meteorological magnitudes that are most affected by cloud cover. Presently, the number of stations where both global and diffuse total solar radiation is measured is growing, due basically to energetic applications of solar radiation. Global and diffuse hourly irradiation, along with some measure of the temporal variability of solar radiation, are used in this paper to describe the sky condition, and to classify it into several cloud types. A classical maximum likelihood method is applied for clustering data. One year of solar radiation data and cloud observations at a site in Catalonia, Spain is used to illustrate the ability of solar radiation measurements to describe cloud types. Preliminary results of the above methodology show that three clusters appear using global and diffuse hourly irradiation only. Fog, stratus, and stratocumulus from the first group. A second group includes altocumulus alone or mixed with other clouds, as well as scattered cumulus congestus. In a third group, we find clear skies, cirrus and scattered cumulus. Especially in this third group, variability of solar radiation within an hour helps to separate different situations.

  10. Methods provided and applied in a research aircraft for the study of cloud physics and chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Maser, R. [Zentrum fuer Umweltforschung, J. W. Goethe-Univ., Frankfurt/Main (Germany); Franke, H. [Zentrum fuer Umweltforschung, J. W. Goethe-Univ., Frankfurt/Main (Germany); Preiss, M. [Zentrum fuer Umweltforschung, J. W. Goethe-Univ., Frankfurt/Main (Germany); Jaeschke, W. [Zentrum fuer Umweltforschung, J. W. Goethe-Univ., Frankfurt/Main (Germany)

    1994-11-01

    For the observation of gaseous, liquid, and solid pollutants in and in the vicinity of clouds a small aircraft (Piper Chieftain Navajo) was equipped with microphysical and chemical instruments. It was used to study the role of clouds in distributing atmospheric pollutants and to quantify the involved scavenging and oxidation processes. New devices for the isokinetic collection of cloud water and interstitial aerosol particles were developed. Analytical instruments for measuring S(IV) and H{sub 2}O{sub 2} in the liquid and in the gas phase were modified to allow the analysis during flight immediately after sampling the cloud water. During the field experiment CLEOPATRA 1992 (Meischner et al., 1993) the aircraft and its instrumentation proved well and enabled the simultaneous measurement of microphysical and chemical properties. In this contribution the aircraft and newly developed instrumentation are presented while first results of measurements performed aboard the Piper will be discussed by Preiss et al., 1994; Seyffer et al., 1994; Schaefer et al., 1994 and Wurzler et al., 1994. (orig.) [Deutsch] Zur Untersuchung der Rolle von Wolken bei der Verteilung und Umwandlung von Spurenstoffen in der Atmosphaere und zur Quantifizierung damit verbundener `scavenging`- und Oxidationsprozesse wurden Messungen innerhalb und in der Umgebung von Wolken durchgefuehrt. Dazu wurde ein Kleinflugzeug mit mikrophysikalischen und chemischen Messgeraeten ausgeruestet und im Rahmen des Feldexperimentes CLEOPATRA (Meischner et al., 1993) eingesetzt. Neben Neuentwicklungen zur Sammlung von Wolkenwasser und interstitiellem Aerosol wurden auch erprobte Messsysteme eingesetzt, die zuvor an die spezielle Aufgabenstellung angepasst wurden. So konnte z.B. das gesammelte Wolkenwasser direkt nach der Sammlung noch im Flugzeug durch modifizierte CFCL-Analysatoren auf ihren Gehalt an S(IV) und H{sub 2}O{sub 2} hin untersucht werden. Waehrend des Feldexperimentes konnte das Flugzeug und seine

  11. Infrared radiative transfer modelling in a 3D scattering cloudy atmosphere: Application to limb sounding measurements of cirrus

    Energy Technology Data Exchange (ETDEWEB)

    Ewen, G.B.L. [Department of Atmospheric, Oceanic and Planetary Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU (United Kingdom)]. E-mail: gewen@atm.ox.ac.uk; Grainger, R.G. [Department of Atmospheric, Oceanic and Planetary Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU (United Kingdom); Lambert, A. [National Center for Atmospheric Research (NCAR), Boulder, CO (United States); Baran, A.J. [Met Office, Exeter (United Kingdom)

    2005-11-15

    The Monte Carlo cloud scattering forward model (McClouds{sub F}M) has been developed to simulate limb radiative transfer in the presence of cirrus clouds, for the purposes of simulating cloud contaminated measurements made by an infrared limb sounding instrument, e.g. the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). A reverse method three-dimensional Monte Carlo transfer model is combined with a line-by-line model for radiative transfer through the non-cloudy atmosphere to explicitly account for the effects of multiple scattering by the clouds. The ice cloud microphysics are characterised by a size distribution of randomly oriented ice crystals, with the single scattering properties of the distribution determined by accurate calculations accounting for non-spherical habit. A comparison of McClouds{sub F}M simulations and real MIPAS spectra of cirrus shows good agreement. Of particular interest are several noticeable spectral features (i.e. H{sub 2}O absorption lines) in the data that are replicated in the simulations: these can only be explained by upwelling tropospheric radiation scattered into the line-of-sight by the cloud ice particles.

  12. Ice water content of arctic, midlatitude, and tropical cirrus – Part 2: Extension of the database and new statistical analysis

    Directory of Open Access Journals (Sweden)

    C. Rolf

    2012-11-01

    Full Text Available Ice clouds are known to be major contributors to radiative forcing in the Earth's atmosphere, yet describing their microphysical properties in climate models remains challenging. Among these properties, the ice water content (IWC of cirrus clouds is of particular interest both because it is measurable and because it can be directly related to a number of other radiatively important variables such as extinction and effective radius. This study expands upon the work of Schiller et al. (2008, extending a climatology of IWC by combining datasets from several European and US airborne campaigns and ground-based lidar measurements over Jülich, Germany. The relationship between IWC and temperature is further investigated using the new merged dataset and probability distribution functions (PDFs. A PDF-based formulation allows for representation of not only the mean values of IWC, but also the variability of IWC within a temperature band. The IWC-PDFs are found to be bimodal over the whole cirrus temperature range, which might be attributed to different cirrus formation mechanisms such as heterogeneous and homogeneous freezing. The PDFs of IWC are further compared to distributions of cirrus ice crystal number and mass mean radius, which show that the general relationship between IWC and temperature appears to be influenced much more by particle number than by particle size.

  13. Glassy aerosols with a range of compositions nucleate ice heterogeneously at cirrus temperatures

    Directory of Open Access Journals (Sweden)

    T. W. Wilson

    2012-09-01

    Full Text Available Atmospheric secondary organic aerosol (SOA is likely to exist in a semi-solid or glassy state, particularly at low temperatures and humidities. Previously, it has been shown that glassy aqueous citric acid aerosol is able to nucleate ice heterogeneously under conditions relevant to cirrus in the tropical tropopause layer (TTL. In this study we test if glassy aerosol distributions with a range of chemical compositions heterogeneously nucleate ice under cirrus conditions. Three single component aqueous solution aerosols (raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA and levoglucosan and one multi component aqueous solution aerosol (raffinose mixed with five dicarboxylic acids and ammonium sulphate were studied in both the liquid and glassy states at a large cloud simulation chamber. The investigated organic compounds have similar functionality to oxidised organic material found in atmospheric aerosol and have estimated temperature/humidity induced glass transition thresholds that fall within the range predicted for atmospheric SOA. A small fraction of aerosol particles of all compositions were found to nucleate ice heterogeneously in the deposition mode at temperatures relevant to the TTL (<200 K. Raffinose and HMMA, which form glasses at higher temperatures, nucleated ice heterogeneously at temperatures as high as 214.6 and 218.5 K respectively. We present the calculated ice active surface site density, ns, of the aerosols tested here and also of glassy citric acid aerosol as a function of relative humidity with respect to ice (RHi. We also propose a parameterisation which can be used to estimate heterogeneous ice nucleation by glassy aerosol for use in cirrus cloud models up to ~220 K. Finally, we show that heterogeneous nucleation by glassy aerosol may compete with ice nucleation on mineral dust particles in mid-latitudes cirrus.

  14. MOLECULAR LINE OBSERVATIONS OF MCLD 123.5+24.9 IN THE POLARIS CIRRUS

    Energy Technology Data Exchange (ETDEWEB)

    Shimoikura, Tomomi; Dobashi, Kazuhito; Sakurai, Tohko; Nishiura, Shingo [Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501 (Japan); Takano, Shuro [Nobeyama Radio Observatory, National Astronomical Observatory of Japan, 462-2 Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305 (Japan); Hirota, Tomoya, E-mail: ikura@u-gakugei.ac.jp [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

    2012-02-01

    In this paper, we present results of millimeter-wave observations with various molecular lines made toward MCLD 123.5+24.9 in the Polaris cirrus using the 45 m telescope at Nobeyama Radio Observatory. MCLD 123.5+24.9 is one of the rare dense cores forming in diffuse cirrus clouds where star formation may rarely take place. In order to investigate the structure, dynamics, the evolutionary stage of MCLD 123.5+24.9, we observed this core in 17 emission lines from 13 different molecular species. Emission lines of CS, CCS, and HC{sub 3}N are strongly detected all over the core, while those of SO and N{sub 2}H{sup +} are weak or remain undetected, indicating that MCLD 123.5+24.9 is in an early stage of core evolution in terms of chemical composition. Based on comparison of the fractional abundances of CCS and HC{sub 3}N, which are considered indicators of chemical age, with those of other cores with and without star formation as well as with model calculations in the literature, we suggest that MCLD 123.5+24.9 is in a phase prior to star formation. From the C{sup 18}O data obtained, we derived the total molecular mass of MCLD 123.5+24.9 to be {approx}3 M{sub Sun} at an assumed distance of 150 pc. There are three subcores in MCLD 123.5+24.9, called CS-A, CS-B, and CS-C. We derived their masses to be 0.2-0.6 M{sub Sun }. We also investigated the dynamical stability of MCLD 123.5+24.9 and the subcores by applying the virial theorem to find that MCLD 123.5+24.9 is not gravitationally bound as a whole, while the individual subcores are in the virial equilibrium and can collapse with a small increase of external pressure imposed on their surfaces.

  15. Parameterization of ice fall speeds in midlatitude cirrus: Results from SPartICus

    Science.gov (United States)

    Mishra, Subhashree; Mitchell, David L.; Turner, David D.; Lawson, R. P.

    2014-04-01

    The climate sensitivity predicted in general circulation models can be sensitive to the treatment of the ice particle fall velocity. In this study, the mass-weighted ice fall speed (Vm) and the number concentration ice fall speed (Vn) in midlatitude cirrus clouds are computed from in situ measurements of ice particle area and number concentration made by the two-dimensional stereo probe during the Small Particles In Cirrus field campaign. For single-moment ice microphysical schemes, Vm and the ice particle size distribution effective diameter De were parameterized in terms of cloud temperature (T) and ice water content (IWC). For two-moment schemes, Vm and Vn were related to De and the mean maximum dimension¯D, respectively. For single-moment schemes, although the correlations of Vm and De with T were higher than the correlations of Vm and De with IWC, it is demonstrated that Vm and De are better predicted by using both T and IWC. The parameterization relating Vm to T and IWC is compared with another scheme relating Vm to T and IWC, with the latter based on millimeter cloud radar measurements. Regarding two-moment ice microphysical schemes, a strong correlation was found between De and Vm and between¯D and Vn owing to their similar weightings by ice particle mass and number concentration, respectively. Estimating Vm from De makes Vm a function of IWC and projected area, realistically coupling Vm with both the cloud microphysics and radiative properties.

  16. A multi-diagnostic approach to cloud evaluation

    Directory of Open Access Journals (Sweden)

    K. D. Williams

    2017-07-01

    Full Text Available Most studies evaluating cloud in general circulation models present new diagnostic techniques or observational datasets, or apply a limited set of existing diagnostics to a number of models. In this study, we use a range of diagnostic techniques and observational datasets to provide a thorough evaluation of cloud, such as might be carried out during a model development process. The methodology is illustrated by analysing two configurations of the Met Office Unified Model – the currently operational configuration at the time of undertaking the study (Global Atmosphere 6, GA6, and the configuration which will underpin the United Kingdom's Earth System Model for CMIP6 (Coupled Model Intercomparison Project 6; GA7. By undertaking a more comprehensive analysis which includes compositing techniques, comparing against a set of quite different observational instruments and evaluating the model across a range of timescales, the risks of drawing the wrong conclusions due to compensating model errors are minimized and a more accurate overall picture of model performance can be drawn. Overall the two configurations analysed perform well, especially in terms of cloud amount. GA6 has excessive thin cirrus which is removed in GA7. The primary remaining errors in both configurations are the in-cloud albedos which are too high in most Northern Hemisphere cloud types and sub-tropical stratocumulus, whilst the stratocumulus on the cold-air side of Southern Hemisphere cyclones has in-cloud albedos which are too low.

  17. A multi-diagnostic approach to cloud evaluation

    Science.gov (United States)

    Williams, Keith D.; Bodas-Salcedo, Alejandro

    2017-07-01

    Most studies evaluating cloud in general circulation models present new diagnostic techniques or observational datasets, or apply a limited set of existing diagnostics to a number of models. In this study, we use a range of diagnostic techniques and observational datasets to provide a thorough evaluation of cloud, such as might be carried out during a model development process. The methodology is illustrated by analysing two configurations of the Met Office Unified Model - the currently operational configuration at the time of undertaking the study (Global Atmosphere 6, GA6), and the configuration which will underpin the United Kingdom's Earth System Model for CMIP6 (Coupled Model Intercomparison Project 6; GA7). By undertaking a more comprehensive analysis which includes compositing techniques, comparing against a set of quite different observational instruments and evaluating the model across a range of timescales, the risks of drawing the wrong conclusions due to compensating model errors are minimized and a more accurate overall picture of model performance can be drawn. Overall the two configurations analysed perform well, especially in terms of cloud amount. GA6 has excessive thin cirrus which is removed in GA7. The primary remaining errors in both configurations are the in-cloud albedos which are too high in most Northern Hemisphere cloud types and sub-tropical stratocumulus, whilst the stratocumulus on the cold-air side of Southern Hemisphere cyclones has in-cloud albedos which are too low.

  18. The radiation budget of a Cirrus layer deduced from simultaneous aircraft observations and model calculations

    Science.gov (United States)

    Ackerman, Thomas P.; Kinne, Stefan A.; Heymsfield, Andrew J.; Valero, Francisco P. J.

    1990-01-01

    Several aircraft were employed during the FIRE Cirrus IFO in order to make nearly simultaneous observations of cloud properties and fluxes. A segment of the flight data collected on 28 October 1988 during which the NASA Ames ER-2 overflew the NCAR King Air was analyzed. The ER-2 flew at high altitude making observations of visible and infrared radiances and infrared flux and cloud height and thickness. During this segment, the King Air flew just above the cloud base making observations of ice crystal size and shape, local meteorological variables, and infrared fluxes. While the two aircraft did not collect data exactly coincident in space and time, they did make observations within a few minutes of each other. For this case study, the infrared radiation balance of the cirrus layer is of primary concern. Observations of the upwelling 10 micron radiance, made from the ER-2, can be used to deduce the 10 micron optical depth of the layer. The upwelling broadband infrared flux is also measured from the ER-2. At the same time, the upwelling and downwelling infrared flux at the cloud base is obtained from the King Air measurements. Information on cloud microphysics is also available from the King Air. Using this data in conjunction with atmospheric temperature and humidity profiles from local radiosondes, the necessary inputs for an infrared radiative transfer model can be developed. Infrared radiative transfer calculations are performed with a multispectral two-stream model. The model fluxes at the cloud base and at 19 km are then compared with the aircraft observations to determine whether the model is performing well. Cloud layer heating rates can then be computed from the radiation exchange.

  19. Ground-based imaging remote sensing of ice clouds: uncertainties caused by sensor, method and atmosphere

    Science.gov (United States)

    Zinner, Tobias; Hausmann, Petra; Ewald, Florian; Bugliaro, Luca; Emde, Claudia; Mayer, Bernhard

    2016-09-01

    In this study a method is introduced for the retrieval of optical thickness and effective particle size of ice clouds over a wide range of optical thickness from ground-based transmitted radiance measurements. Low optical thickness of cirrus clouds and their complex microphysics present a challenge for cloud remote sensing. In transmittance, the relationship between optical depth and radiance is ambiguous. To resolve this ambiguity the retrieval utilizes the spectral slope of radiance between 485 and 560 nm in addition to the commonly employed combination of a visible and a short-wave infrared wavelength.An extensive test of retrieval sensitivity was conducted using synthetic test spectra in which all parameters introducing uncertainty into the retrieval were varied systematically: ice crystal habit and aerosol properties, instrument noise, calibration uncertainty and the interpolation in the lookup table required by the retrieval process. The most important source of errors identified are uncertainties due to habit assumption: Averaged over all test spectra, systematic biases in the effective radius retrieval of several micrometre can arise. The statistical uncertainties of any individual retrieval can easily exceed 10 µm. Optical thickness biases are mostly below 1, while statistical uncertainties are in the range of 1 to 2.5.For demonstration and comparison to satellite data the retrieval is applied to observations by the Munich hyperspectral imager specMACS (spectrometer of the Munich Aerosol and Cloud Scanner) at the Schneefernerhaus observatory (2650 m a.s.l.) during the ACRIDICON-Zugspitze campaign in September and October 2012. Results are compared to MODIS and SEVIRI satellite-based cirrus retrievals (ACRIDICON - Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems; MODIS - Moderate Resolution Imaging Spectroradiometer; SEVIRI - Spinning Enhanced Visible and Infrared Imager). Considering the identified

  20. Cirrus Airframe Parachute System and Odds of a Fatal Accident in Cirrus Aircraft Crashes.

    Science.gov (United States)

    Alaziz, Mustafa; Stolfi, Adrienne; Olson, Dean M

    2017-06-01

    General aviation (GA) accidents have continued to demonstrate high fatality rates. Recently, ballistic parachute recovery systems (BPRS) have been introduced as a safety feature in some GA aircraft. This study evaluates the effectiveness and associated factors of the Cirrus Airframe Parachute System (CAPS) at reducing the odds of a fatal accident in Cirrus aircraft crashes. Publicly available Cirrus aircraft crash reports were obtained from the National Transportation Safety Board (NTSB) database for the period of January 1, 2001-December 31, 2016. Accident metrics were evaluated through univariate and multivariate analyses regarding odds of a fatal accident and use of the parachute system. Included in the study were 268 accidents. For CAPS nondeployed accidents, 82 of 211 (38.9%) were fatal as compared to 8 of 57 (14.0%) for CAPS deployed accidents. After controlling for all other factors, the adjusted odds ratio for a fatal accident when CAPS was not deployed was 13.1. The substantial increased odds of a fatal accident when CAPS was not deployed demonstrated the effectiveness of CAPS at providing protection of occupants during an accident. Injuries were shifted from fatal to serious or minor with the use of CAPS and postcrash fires were significantly reduced. These results suggest that BPRS could play a significant role in the next major advance in improving GA accident survival.Alaziz M, Stolfi A, Olson DM. Cirrus Airframe Parachute System and odds of a fatal accident in Cirrus aircraft crashes. Aerosp Med Hum Perform. 2017; 88(6):556-564.

  1. Diagnosis of processes controlling water vapour in the tropical tropopause layer by a Lagrangian cirrus model

    Directory of Open Access Journals (Sweden)

    C. Ren

    2007-04-01

    Full Text Available We have developed a Lagrangian air-parcel cirrus model (LACM, to diagnose the processes controlling water in the tropical tropopause layer (TTL. LACM applies parameterised microphysics to air parcel trajectories. The parameterisation includes the homogeneous freezing of aerosol droplets, the growth/sublimation of ice particles, and sedimentation of ice particles, so capturing the main dehydration mechanism for air in the TTL. Rehydration is also considered by resetting the water vapour mixing ratio in an air parcel to the value at the point in the 4-D analysis/forecast data used to generate the trajectories, but only when certain conditions, indicative of convection, are satisfied. These conditions are imposed to confine what processes contribute to rehydration. The conditions act to restrict rehydration of the Lagrangian air parcels to regions where convective transport of water vapour from below is significant, at least to the extent that the analysis/forecast captures this process. The inclusion of hydration and dehydration mechanisms in LACM results in total water fields near tropical convection that have more of the "stripey" character of satellite observations of high cloud, than do either the ECMWF analysis or trajectories without microphysics.

    The mixing ratios of total water in the TTL, measured by a high-altitude aircraft over Brazil (during the TROCCINOX campaign, have been reconstructed by LACM using trajectories generated from ECMWF analysis. Two other Lagrangian reconstructions are also tested: linear interpolation of ECMWF analysed specific humidity onto the aircraft flight track, and instantaneous dehydration to the saturation vapour pressure over ice along trajectories. The reconstructed total water mixing ratios along aircraft flight tracks are compared with observations from the FISH total water hygrometer. Process-oriented analysis shows that modelled cirrus cloud events are responsible for dehydrating the air

  2. Diagnosis of processes controlling water vapour in the tropical tropopause layer by a Lagrangian cirrus model

    Directory of Open Access Journals (Sweden)

    C. Ren

    2007-10-01

    Full Text Available We have developed a Lagrangian air-parcel cirrus model (LACM, to diagnose the processes controlling water in the tropical tropopause layer (TTL. LACM applies parameterised microphysics to air parcel trajectories. The parameterisation includes the homogeneous freezing of aerosol droplets, the growth/sublimation of ice particles, and sedimentation of ice particles, so capturing the main dehydration mechanism for air in the TTL. Rehydration is also considered by resetting the water vapour mixing ratio in an air parcel to the value at the point in the 4-D analysis/forecast data used to generate the trajectories, but only when certain conditions, indicative of convection, are satisfied. The conditions act to restrict rehydration of the Lagrangian air parcels to regions where convective transport of water vapour from below is significant, at least to the extent that the analysis/forecast captures this process. The inclusion of hydration and dehydration mechanisms in LACM results in total water fields near tropical convection that have more of the "stripy" character of satellite observations of high cloud, than do either the ECMWF analysis or trajectories without microphysics.

    The mixing ratios of total water in the TTL, measured by a high-altitude aircraft over Brazil (during the TROCCINOX campaign, have been reconstructed by LACM using trajectories generated from ECMWF analysis. Two other Lagrangian reconstructions are also tested: linear interpolation of ECMWF analysed specific humidity onto the aircraft flight track, and instantaneous dehydration to the saturation vapour pressure over ice along trajectories. The reconstructed total water mixing ratios along aircraft flight tracks are compared with observations from the FISH total water hygrometer. Process-oriented analysis shows that modelled cirrus cloud events are responsible for dehydrating the air parcels coming from lower levels, resulting in total water mixing ratios as low as 2

  3. The Zodiacal Cloud Model applied to the Martian atmosphere. Diurnal variations in Meteoric ion layers

    Science.gov (United States)

    Diego Carrillo-Sánchez, Juan; Plane, John M. C.; Withers, Paul; Fallows, Kathryn; Nesvorný, David; Pokorný, Petr; Feng, Wuhu

    2016-04-01

    Sporadic metal layers have been detected in the Martian atmosphere by radio occultation measurements using the Mars Express Orbiter and Mars Global Surveyor spacecraft. More recently, metallic ion layers produced by the meteor storm event following the close encounter between Comet Siding Spring (C/2013 A1) and Mars were identified by the Imaging UltraViolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. However, the background metal layers produced by the influx of sporadic meteors have not yet been detected at Mars (contrary to the permanent metal layers identified in the Earth's atmosphere). The Zodiacal Dust Cloud (ZDC) model for particle populations released by asteroids (AST), and dust grains from Jupiter Family Comets (JFC) and Halley-Type Comets (HTC) has been combined with a Monte Carlo sampling method and the Chemical ABlation MODel (CABMOD) to predict the ablation rates of Na, K, Fe, Si, Mg, Ca and Al above 40 km altitude in the Martian atmosphere. CABMOD considers the standard treatment of meteor physics, including the balance of frictional heating by radiative losses and the absorption of heat energy through temperature increases, melting phase transitions and vaporization, as well as sputtering by inelastic collisions with the air molecules. These vertical profiles are input into the Leeds 1-D Mars atmospheric model which includes photo-ionization, and gas-phase ion-molecule and neutral chemistry, in order to explore the evolution of the resulting metallic ions and atoms. We conclude that the formation of the sporadic ion layers observed below 100 km with a plasma density exceeding 104 cm-3 requires the combination of the three different influx sources considered by the ZDC model, with a significant asteroidal contribution. Finally, we explore the changes of the neutral and ionized Mg and Fe layers over a diurnal cycle.

  4. Ice supersaturations exceeding 100% at the cold tropical tropopause: implications for cirrus formation and dehydration

    Directory of Open Access Journals (Sweden)

    E. J. Jensen

    2005-01-01

    Full Text Available Recent in situ measurements at tropical tropopause temperatures as low as 187 K indicate supersaturations with respect to ice exceeding 100% with little or no ice present. In contrast, models used to simulate cloud formation near the tropopause assume a supersaturation threshold for ice nucleation of about 65% based on laboratory measurements of aqueous aerosol freezing. The high supersaturations reported here, along with cloud simulations assuming a plausible range of temperature histories in the sampled air mass, indicate that the vast majority of aerosols in the air sampled on this flight must have had supersaturation thresholds for ice nucleation exceeding 100% (i.e. near liquid water saturation at these temperatures. Possible explanations for this high threshold are that (1 the expressions used for calculating vapor pressure over supercooled water at low temperatures give values are at least 20% too low, (2 organic films on the aerosol surfaces reduce their accommodation coefficient for uptake of water, resulting in aerosols with more concentrated solutions when moderate-rapid cooling occurs and correspondingly inhibited homogeneous freezing, and (3 if surface freezing dominates, organic coatings may increase the surface energy of the ice embryo/vapor interface resulting in suppressed ice nucleation. Simulations of in situ cloud formation in the tropical tropopause layer (TTL throughout the tropics indicate that if decreased accommodation coefficients and resulting high thresholds for ice nucleation prevailed throughout the tropics, then the calculated occurrence frequency and areal coverage of TTL cirrus would be significantly suppressed. However, the simulations also show that even if in situ TTL cirrus form only over a very small fraction of the tropics in the western Pacific, enough air passes through them due to rapid horizontal transport such that they can still effectively freeze-dry air entering the stratosphere. The TTL cirrus

  5. Applied Discovery on Cloud Computation of Sensory Mine Internet of Things%感知矿山物联网云计算应用探索

    Institute of Scientific and Technical Information of China (English)

    张申; 刘鹏; 张彭

    2012-01-01

    From the cloud computation conception, services mode and cloud computation advantage, some misunderstandings of the cloud computation were clarified. Based on the circumstances, the relationship between the 4 layer structures of the mine industrial internet of things and the cloud computation was provided. The cloud services in the mine internet of things as the definition would be mainly provid- ed by the professional service suppliers. According to the conceptions of the resource pool and services in the cloud computation, the ex- perts cloud would be one of the cloud service modes. In combination with the cloud computation applied site in the several mine internet of things, the necessity and rationality of the cloud computation in the sensory mine internet of things was discussed.%从云计算的概念、服务模式及云计算的优势出发,澄清一些对云计算的误解,在此基础上,给出矿山行业物联网的4层结构与云计算间的关系。明确在矿山物联网中云服务应主要由专业的服务商来提供。根据云计算中资源池与服务的概念,指出专家云是云服务的一种形式,结合几种矿山物联网中云计算的应用场景,讨论了感知矿山物联网中云计算的必要性与合理性。

  6. Sensitivity Studies For Cirrus Effective Ice Crystal Size Retrieval In The Infrared

    Science.gov (United States)

    Radel, G.; Stubenrauch, C.; Holz, R.; Mitchell, D.

    During the last years, much effort has been made to find a realistic description of the single-scattering properties of non-spherical ice crystals of cirrus clouds explicitely in dependence of ice crystal shape and size distribution. By using single scattering properties of non-spherical ice crystals instead of ice spheres, one observes that the spectral region between 8 and 12 micron offers a possibility of effective ice crystal size retrieval. The difference between cirrus emissivities at these wavelengths is sen- sitive to the mean ice crystal size of the cirrus cloud. At present, we use two different sets of ice crystal single scattering properties in the infrared: one for randomly oriented planar polycrystals and the other for hexagonal columns. For planar polycrystals, mod- ified Anomalous Diffraction Approximation (mADA) is used to describe absorption coefficients as analytical expressions of size distribution parameters, ice crystal shape, wavelength and refractive index, taking into account a parameterized correction for internal reflection and refraction. As scattering cannot be calculated through mADA, scattering contributions are obtained from different combinations of Improved Geo- metric Optics and Finite Difference Time Domain. For hexagonal columns the single scattering properties have been computed using the Finite Difference Time Domain method. Retrievals of mean effective ice crystal sizes in the infrared have the advan- tage that they are less dependent on the assumed shape of the ice crystals, in contrary to retrievals from differences between the visible and near-infrared radiation. Several satellite instruments measure now emitted and scattered radiation from different lev- els of the atmosphere. The longest time period is covered by the TOVS instruments aboard the NOAA Polar Orbiting Environmental Satellites (since 1979). These obser- vations have been converted into atmospheric temperature and water vapor profiles as well as cloud and

  7. Effect of particle nonsphericity on bidirectional reflectance of cirrus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Mishchenko, M.I.; Rossow, W.B.; Macke, A.; Lacis, A.A. [Goddard Institute for Space Studies, New York, NY (United States)

    1996-04-01

    This paper describes the use of the fractal ice particle method to study the differences in bidirectional reflectance caused by the differences in the single scattering phase functions of spherical water droplets and nonspherical ice crystals.

  8. Evaluation of the MOZAIC Capacitive Hygrometer during the airborne field study CIRRUS-III

    Science.gov (United States)

    Neis, P.; Smit, H. G. J.; Krämer, M.; Spelten, N.; Petzold, A.

    2015-03-01

    The MOZAIC Capacitive Hygrometer (MCH) is usually operated aboard passenger aircraft in the framework of MOZAIC (Measurement of Ozone by Airbus In-Service Aircraft) for measuring atmospheric relative humidity (RH). In order to evaluate the performance of the MCH, the instrument was operated aboard a Learjet 35A research aircraft as part of the CIRRUS-III field study together with a closed-cell Lyman-α fluorescence hygrometer (Fast in situ Stratospheric Hygrometer, or FISH) and an open-path tunable diode laser system (Open-path Jülich Stratospheric TDL ExpeRiment, or OJSTER) for water vapour measurement. After reducing the CIRRUS-III data set to data corresponding to MOZAIC aircraft operation conditions, the 1 Hz RH data cross correlation between the MCH and reference instruments FISH (clear sky) and OJSTER (in-cirrus) yielded a remarkably good agreement of R2 = 0.92 and slope m = 1.02 and provided a MCH uncertainty of 5% RH. Probability distribution functions of RH deduced from the MCH and reference instruments agreed well between 10 and 70% RH with respect to liquid water in the ambient temperature range of ca. -70 to -40 °C. The use of MCH data is limited to sensor temperatures above the calibration limit of Tsensor = -40 °C (corresponds to ambient temperature of Tambient = -70 °C at typical cruising speed of long-haul passenger aircraft). Good performance of the MCH for clear sky as well as for in-cirrus conditions demonstrated the sensor robustness also for operation inside ice clouds.

  9. A 6-year global cloud climatology from the Atmospheric InfraRed Sounder AIRS and a statistical analysis in synergy with CALIPSO and CloudSat

    Directory of Open Access Journals (Sweden)

    C. J. Stubenrauch

    2010-03-01

    Full Text Available We present a six-year global climatology of cloud properties, obtained from observations of the Atmospheric Infrared Sounder (AIRS onboard the NASA Aqua satellite. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO combined with CloudSat observations, both missions launched as part of the A-Train in 2006, provide a unique opportunity to evaluate the retrieved AIRS cloud properties such as cloud amount and height as well as to explore the vertical structure of different cloud types. AIRS-LMD cloud detection agrees with CALIPSO about 85% over ocean and about 75% over land. Global cloud amount has been estimated as about 66% to 74%, depending on the weighting of not cloudy AIRS footprints by partial cloud cover (0 or 0.3. 40% of all clouds are high clouds, and about 44% of all clouds are single layer low-level clouds. The "radiative" cloud height determined by the AIRS-LMD retrieval corresponds well to the height of the maximum backscatter signal and of the "apparent middle" of the cloud. Whereas the real cloud thickness of high opaque clouds often fills the whole troposphere, their "apparent" cloud thickness (at which optical depth reaches about 5 is on average only 2.5 km. The real geometrical thickness of optically thin cirrus as identified by AIRS-LMD is identical to the "apparent" cloud thickness with an average of about 2.5 km in the tropics and midlatitudes. High clouds in the tropics have slightly more diffusive cloud tops than at higher latitudes. In general, the depth of the maximum backscatter signal increases nearly linearly with increasing "apparent" cloud thickness. For the same "apparent" cloud thickness optically thin cirrus show a maximum backscatter about 10% deeper inside the cloud than optically thicker clouds. We also show that only the geometrically thickest opaque clouds and (the probably surrounding anvil cirrus penetrate the stratosphere in the tropics.

  10. A 6-year global cloud climatology from the Atmospheric InfraRed Sounder AIRS and a statistical analysis in synergy with CALIPSO and CloudSat

    Directory of Open Access Journals (Sweden)

    S. Cros

    2010-08-01

    Full Text Available We present a six-year global climatology of cloud properties, obtained from observations of the Atmospheric Infrared Sounder (AIRS onboard the NASA Aqua satellite. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO combined with CloudSat observations, both missions launched as part of the A-Train in 2006, provide a unique opportunity to evaluate the retrieved AIRS cloud properties such as cloud amount and height. In addition, they permit to explore the vertical structure of different cloud types. AIRS-LMD cloud detection agrees with CALIPSO about 85% over ocean and about 75% over land. Global cloud amount has been estimated from 66% to 74%, depending on the weighting of not cloudy AIRS footprints by partial cloud cover from 0 to 0.3. 42% of all clouds are high clouds, and about 42% of all clouds are single layer low-level clouds. The "radiative" cloud height determined by the AIRS-LMD retrieval corresponds well to the height of the maximum backscatter signal and of the "apparent middle" of the cloud. Whereas the real cloud thickness of high opaque clouds often fills the whole troposphere, their "apparent" cloud thickness (at which optical depth reaches about 5 is on average only 2.5 km. The real geometrical thickness of optically thin cirrus as identified by AIRS-LMD is identical to the "apparent" cloud thickness with an average of about 2.5 km in the tropics and midlatitudes. High clouds in the tropics have slightly more diffusive cloud tops than at higher latitudes. In general, the depth of the maximum backscatter signal increases nearly linearly with increasing "apparent" cloud thickness. For the same "apparent" cloud thickness optically thin cirrus show a maximum backscatter about 10% deeper inside the cloud than optically thicker clouds. We also show that only the geometrically thickest opaque clouds and (the probably surrounding anvil cirrus penetrate the stratosphere in the tropics.

  11. Thermal stability analysis of particles incorporated in cirrus crystals and of non-activated particles in between the cirrus crystals: comparing clean and polluted air masses

    Directory of Open Access Journals (Sweden)

    M. Seifert

    2004-01-01

    Full Text Available A thermal volatility technique is used to provide indirect information about the chemical composition of the aerosol involved in cirrus cloud formation. The fraction of particles that disappears after being heated to 125°C is termed volatile and the fraction that disappears between 125 and 250°C is termed semi-volatile. Particles that still remain after being heated to 250°C make up the non-volatile fraction. The thermal composition of residual particles remaining from evaporated cirrus crystals is presented and compared to interstitial aerosol particles (non-activated particles in between the cirrus crystals for two temperature regimes (cold: T< -38°C, warm: -38≤T< -23°C, based on in-situ observations. The observations were conducted in cirrus clouds in the Southern Hemisphere (SH and Northern Hemisphere (NH midlatitudes during the INCA project. In the cold temperature regime, the non-volatile fraction of the residual particles was typically in the range 10 to 30% in the NH and 30 to 40% in the SH. In the warm temperature regime, the non-volatile residual fraction was typically 10 to 30% (NH and 20 to 40% (SH. At high crystal number densities the non-volatile fraction in both temperature regimes was even higher: in the range of 30 to 40% (NH and 40 to 50% (SH. The semi-volatile fraction was typically less than 10% in both hemispheres, causing the volatile fraction to essentially be a complement to the non-volatile fraction. In terms of the fractioning into the three types of particles, the SH cold case is clearly different compared to the other three cases (the two warm cases and the cold NH case, which share many features. In the NH data the distribution of different particle types does not seem to be temperature dependent. In all the cases, the non-volatile fraction is enriched in the residual particles compared to the fractions observed for the interstitial particles. This enrichment corresponds to about 15 (NH and 30 (SH percent

  12. Thermal stability analysis of particles incorporated in cirrus crystals and of non-activated particles in between the cirrus crystals: Comparing clean and polluted air masses

    Directory of Open Access Journals (Sweden)

    M. Seifert

    2003-07-01

    Full Text Available A thermal volatility technique is used to provide indirect information about the chemical composition of the aerosol involved in cirrus cloud formation. The fraction of particles that disappears after being heated to 125°C is termed volatile and the fraction that disappears between 125 and 250°C is termed semi-volatile. Particles that still remain after being heated to 250°C make up the non-volatile fraction. The thermal composition of residual particles remaining from evaporated cirrus crystals is presented and compared to interstitial aerosol particles (non-activated particles in between the cirrus crystals for two temperature regimes (cold: T<235 K, warm: 235<T<250 K, based on in-situ observations. The observations were conducted in cirrus clouds in the Southern Hemisphere (SH and Northern Hemisphere (NH midlatitudes during the INCA project. In the cold temperature regime, the non-volatile fraction of the residual particles was typically in the range 10 to 30% in the NH and 30 to 40% in the SH. In the warm temperature regime, the non-volatile residual fraction was typically 10 to 30% (NH and 20 to 40% (SH. At high crystal number densities the non-volatile fraction in both temperature regimes was even higher: in the range of 30 to 40% (NH and 40 to 50% (SH. The semi-volatile fraction was typically less than 10% in both hemispheres, causing the volatile fraction to essentially be a complement to the non-volatile fraction. In terms of the fractioning into the three types of particles, the SH cold case is clearly different compared to the other three cases (the two warm cases and the cold NH case, which share many features. In the NH data the distribution of different particle types does not seem to be temperature dependent. In all the cases, the non-volatile fraction is enriched in the residual particles compared to the fractions observed for the interstitial particles. This enrichment corresponds to about 15 (NH and 30 (SH percent

  13. The origin of midlatitude ice clouds and the resulting influence on their microphysical properties

    Directory of Open Access Journals (Sweden)

    A. E. Luebke

    2015-12-01

    Full Text Available The radiative role of ice clouds in the atmosphere is known to be important, but uncertainties remain concerning the magnitude and net effects. However, through measurements of the microphysical properties of cirrus clouds, we can better characterize them, which can ultimately allow for their radiative properties to be more accurately ascertained. It has recently been proposed that there are two types of cirrus clouds – in situ and liquid origin. In this study, we present observational evidence to show that two distinct types of cirrus do exist. Airborne, in situ measurements of cloud ice water content (IWC, ice crystal concentration (Nice, and ice crystal size from the 2014 ML-CIRRUS campaign provide cloud samples that have been divided according to their origin type. The key features that set liquid origin cirrus apart from the in situ origin cirrus are a higher frequency of high IWC (> 100 ppmv, higher Nice values, and larger ice crystals. A vertical distribution of Nice shows that the in situ origin cirrus clouds exhibit a median value of around 0.1 cm−3, while the liquid origin concentrations are slightly, but notably higher. The median sizes of the crystals contributing the most mass are less than 200 μm for in situ origin cirrus, with some of the largest crystals reaching 550 μm in size. The liquid origin cirrus, on the other hand, were observed to have median diameters greater than 200 μm, and crystals that were up to 750 μm. An examination of these characteristics in relation to each other and their relationship to temperature provides strong evidence that these differences arise from the dynamics and conditions in which the ice crystals formed. Additionally, the existence of these two groups in cirrus cloud populations may explain why a bimodal distribution in the IWC-temperature relationship has been observed. We hypothesize that the low IWC mode is the result of in situ origin cirrus and the high IWC mode is the result of

  14. An Accuracy Assessment of Georeferenced Point Clouds Produced via Multi-View Stereo Techniques Applied to Imagery Acquired via Unmanned Aerial Vehicle

    Science.gov (United States)

    Harwin, S.; Lucieer, A.

    2012-08-01

    Low-cost Unmanned Aerial Vehicles (UAVs) are becoming viable environmental remote sensing tools. Sensor and battery technology is expanding the data capture opportunities. The UAV, as a close range remote sensing platform, can capture high resolution photography on-demand. This imagery can be used to produce dense point clouds using multi-view stereopsis techniques (MVS) combining computer vision and photogrammetry. This study examines point clouds produced using MVS techniques applied to UAV and terrestrial photography. A multi-rotor micro UAV acquired aerial imagery from a altitude of approximately 30-40 m. The point clouds produced are extremely dense (study area, a 70 m section of sheltered coastline in southeast Tasmania. Areas with little surface texture were not well captured, similarly, areas with complex geometry such as grass tussocks and woody scrub were not well mapped. The process fails to penetrate vegetation, but extracts very detailed terrain in unvegetated areas. Initially the point clouds are in an arbitrary coordinate system and need to be georeferenced. A Helmert transformation is applied based on matching ground control points (GCPs) identified in the point clouds to GCPs surveying with differential GPS. These point clouds can be used, alongside laser scanning and more traditional techniques, to provide very detailed and precise representations of a range of landscapes at key moments. There are many potential applications for the UAV-MVS technique, including coastal erosion and accretion monitoring, mine surveying and other environmental monitoring applications. For the generated point clouds to be used in spatial applications they need to be converted to surface models that reduce dataset size without loosing too much detail. Triangulated meshes are one option, another is Poisson Surface Reconstruction. This latter option makes use of point normal data and produces a surface representation at greater detail than previously obtainable. This

  15. Remote Sensing of chlorophyll fluorescence and the impact of clouds on the retrival

    Science.gov (United States)

    Köhler, Philipp; Guanter, Luis; Frankenberg, Christian

    2013-04-01

    are estimated from the same soundings. Especial attention will be given to the impact of optically-thin cirrus clouds on SIF retrievals, which is of particular interest over tropical rainforest areas. The detection of cirrus clouds is difficult due to their optical properties. Therefore the measurement of GOSAT in the 2 µm region is applicable to add a cirrus filter. Due to the strongly absorbing H2O-band in this spectral region, the signal in clear sky conditions should not be significantly higher than the noise level of the instrument. With the appearance of cirrus clouds, the light path is shortened and less absorption of H2O yields to a significant signal. Based on this principle, different thresholds for a cirrus filter are applied to study the impact of cirrus clouds on the retrieved SIF.

  16. Structure analysis of interstellar clouds: II. Applying the Delta-variance method to interstellar turbulence

    CERN Document Server

    Ossenkopf, V; Stutzki, J

    2008-01-01

    The Delta-variance analysis is an efficient tool for measuring the structural scaling behaviour of interstellar turbulence in astronomical maps. In paper I we proposed essential improvements to the Delta-variance analysis. In this paper we apply the improved Delta-variance analysis to i) a hydrodynamic turbulence simulation with prominent density and velocity structures, ii) an observed intensity map of rho Oph with irregular boundaries and variable uncertainties of the different data points, and iii) a map of the turbulent velocity structure in the Polaris Flare affected by the intensity dependence on the centroid velocity determination. The tests confirm the extended capabilities of the improved Delta-variance analysis. Prominent spatial scales were accurately identified and artifacts from a variable reliability of the data were removed. The analysis of the hydrodynamic simulations showed that the injection of a turbulent velocity structure creates the most prominent density structures are produced on a sca...

  17. The Effects of Water Vapor and Clouds on the Spectral Distribution of Solar Radiation at the...

    Science.gov (United States)

    Pilewskie, P.; Bergstrom, R.; Mariani, P.; Gore, Warren J. Y. (Technical Monitor)

    1997-01-01

    During the Subsonic Contrail and Cloud Effect Special Study (SUCCESS) a Solar Spectral Flux Radiometer was deployed at the surface in a zenith observing position. The instrument measured the solar spectral downwelling irradiance between 350 and 2500 nm with 10 nm resolution. From April 12 through April 29 approximately 18000 spectra were acquired, under a variety of meteorological conditions including cloud free, cirrus, Stearns, and cumulonimbus clouds. This study focuses on the effect of cirrus and cirrus contrails on the spectral distribution of solar irradiance at the surface and on inferring cirrus properties from their spectral transmittance. The observations have also proven to be useful for comparing the solar spectral irradiance measurements with model predictions, and in particular, for inferring the amount of solar radiation absorbed in the clear and cloudy atmosphere.

  18. 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.

  19. Fast cloud parameter retrievals of MIPAS/Envisat

    Directory of Open Access Journals (Sweden)

    R. Spang

    2012-08-01

    and tropospheric clouds similar to that of space- and ground-based lidars, with a tendency for higher cloud top heights and consequently higher sensitivity for some of the MIPAS detection methods. For the high cloud amount (HCA, pressure levels below 440 hPa on global scales the sensitivity of MIPAS is significantly greater than that of passive nadir viewers. This means that the high cloud fraction will be underestimated in the ISCCP dataset compared to the amount of high clouds deduced by MIPAS. Good correspondence in seasonal variability and geographical distribution of cloud occurrence and zonal means of cloud top height is found in a detailed comparison with a climatology for subvisible cirrus clouds from the Stratospheric Aerosol and Gas Experiment II (SAGE II limb sounder. Overall, validation with various sensors shows the need to consider differences in sensitivity, and especially the viewing geometries and field-of-view size, to make the datasets comparable (e.g. applying integration along the limb path through nadir cloud fields. The simulation of the limb path integration will be an important issue for comparisons with cloud-resolving global circulation or chemical transport models.

  20. The DC-8 Submillimeter-Wave Cloud Ice Radiometer

    Science.gov (United States)

    Walter, Steven J.; Batelaan, Paul; Siegel, Peter; Evans, K. Franklin; Evans, Aaron; Balachandra, Balu; Gannon, Jade; Guldalian, John; Raz, Guy; Shea, James

    2000-01-01

    An airborne radiometer is being developed to demonstrate the capability of radiometry at submillimeter-wavelengths to characterize cirrus clouds. At these wavelengths, cirrus clouds scatter upwelling radiation from water vapor in the lower troposphere. Radiometric measurements made at multiple widely spaced frequencies permit flux variations caused by changes in scattering due to crystal size to be distinguished from changes in cloud ice content. Measurements at dual polarizations can also be used to constrain the mean crystal shape. An airborne radiometer measuring the upwelling submillimeter-wave flux should then able to retrieve both bulk and microphysical cloud properties. The radiometer is being designed to make measurements at four frequencies (183 GHz, 325 GHz, 448 GHz, and 643 GHz) with dual-polarization capability at 643 GHz. The instrument is being developed for flight on NASA's DC-8 and will scan cross-track through an aircraft window. Measurements with this radiometer in combination with independent ground-based and airborne measurements will validate the submillimeter-wave radiometer retrieval techniques. The goal of this effort is to develop a technique to enable spaceborne characterization of cirrus, which will meet a key climate measurement need. The development of an airborne radiometer to validate cirrus retrieval techniques is a critical step toward development of spaced-based radiometers to investigate and monitor cirrus on a global scale. The radiometer development is a cooperative effort of the University of Colorado, Colorado State University, Swales Aerospace, and Jet Propulsion Laboratory and is funded by the NASA Instrument Incubator Program.

  1. Fast cloud parameter retrievals of MIPAS/Envisat

    Directory of Open Access Journals (Sweden)

    R. Spang

    2011-12-01

    similar to that of space- and ground-based lidars, with a tendency for higher cloud top heights and consequently higher sensitivity for some of the MIPAS detection methods. For the high cloud amount (HCA, pressure levels below 440 hPa on global scales the sensitivity of MIPAS is significantly greater than that of passive nadir viewers. This means that the high cloud fraction will be underestimated in the ISCCP dataset compared to the amount of high clouds deduced by MIPAS. Good correspondence in seasonal variability and geographical distribution of cloud occurrence and zonal means of cloud top height is found in a detailed comparison with a climatology for subvisible cirrus clouds from the Stratospheric Aerosol and Gas Experiment II (SAGE II limb sounder. Overall, validation with various sensors shows the need to consider differences in sensitivity, and especially the viewing geometries and field-of-view size, to make the datasets comparable (e.g. applying integration along the limb path through nadir cloud fields. The simulation of the limb path integration will be an important issue for comparisons with cloud-resolving global circulation or chemical transport models.

  2. Global free tropospheric NO2 abundances derived using a cloud slicing technique applied to satellite observations from the Aura Ozone Monitoring Instrument (OMI

    Directory of Open Access Journals (Sweden)

    S. Choi

    2014-01-01

    Full Text Available We derive free-tropospheric NO2 volume mixing ratios (VMRs and stratospheric column amounts of NO2 by applying a cloud slicing technique to data from the Ozone Monitoring Instrument (OMI on the Aura satellite. In the cloud-slicing approach, the slope of the above-cloud NO2 column vs. the cloud scene pressure is proportional to the NO2 VMR. In this work, we use a sample of nearby OMI pixel data from a single orbit for the linear fit. The OMI data include cloud scene pressures from the rotational-Raman algorithm and above-cloud NO2 vertical column density (VCD (defined as the NO2 column from the cloud scene pressure to the top-of-the-atmosphere from a differential optical absorption spectroscopy (DOAS algorithm. Estimates of stratospheric column NO2 are obtained by extrapolating the linear fits to the tropopause. We compare OMI-derived NO2 VMRs with in situ aircraft profiles measured during the NASA Intercontinental Chemical Transport Experiment Phase B (INTEX-B campaign in 2006. The agreement is generally within the estimated uncertainties when appropriate data screening is applied. We then derive a global seasonal climatology of free-tropospheric NO2 VMR in cloudy conditions. Enhanced NO2 in the free troposphere commonly appears near polluted urban locations where NO2 produced in the boundary layer may be transported vertically out of the boundary layer and then horizontally away from the source. Signatures of lightning NO2 are also shown throughout low and middle latitude regions in summer months. A profile analysis of our cloud slicing data indicates signatures of uplifted and transported anthropogenic NO2 in the middle troposphere as well as lightning-generated NO2 in the upper troposphere. Comparison of the climatology with simulations from the Global Modeling Initiative (GMI for cloudy conditions (cloud optical thicknesses > 10 shows similarities in the spatial patterns of continental pollution outflow. However, there are also some

  3. Global Free Tropospheric NO2 Abundances Derived Using a Cloud Slicing Technique Applied to Satellite Observations from the Aura Ozone Monitoring Instrument (OMI)

    Science.gov (United States)

    Choi, S.; Joiner, J.; Choi, Y.; Duncan, B. N.; Bucsela, E.

    2014-01-01

    We derive free-tropospheric NO2 volume mixing ratios (VMRs) and stratospheric column amounts of NO2 by applying a cloud slicing technique to data from the Ozone Monitoring Instrument (OMI) on the Aura satellite. In the cloud-slicing approach, the slope of the above-cloud NO2 column versus the cloud scene pressure is proportional to the NO2 VMR. In this work, we use a sample of nearby OMI pixel data from a single orbit for the linear fit. The OMI data include cloud scene pressures from the rotational-Raman algorithm and above-cloud NO2 vertical column density (VCD) (defined as the NO2 column from the cloud scene pressure to the top-of-the-atmosphere) from a differential optical absorption spectroscopy (DOAS) algorithm. Estimates of stratospheric column NO2 are obtained by extrapolating the linear fits to the tropopause. We compare OMI-derived NO2 VMRs with in situ aircraft profiles measured during the NASA Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign in 2006. The agreement is generally within the estimated uncertainties when appropriate data screening is applied. We then derive a global seasonal climatology of free-tropospheric NO2 VMR in cloudy conditions. Enhanced NO2 in the free troposphere commonly appears near polluted urban locations where NO2 produced in the boundary layer may be transported vertically out of the boundary layer and then horizontally away from the source. Signatures of lightning NO2 are also shown throughout low and middle latitude regions in summer months. A profile analysis of our cloud slicing data indicates signatures of uplifted and transported anthropogenic NO2 in the middle troposphere as well as lightning-generated NO2 in the upper troposphere. Comparison of the climatology with simulations from the Global Modeling Initiative (GMI) for cloudy conditions (cloud optical thicknesses > 10) shows similarities in the spatial patterns of continental pollution outflow. However, there are also some differences in

  4. Cloud Computing in Support of Applied Learning: A Baseline Study of Infrastructure Design at Southern Polytechnic State University

    Science.gov (United States)

    Conn, Samuel S.; Reichgelt, Han

    2013-01-01

    Cloud computing represents an architecture and paradigm of computing designed to deliver infrastructure, platforms, and software as constructible computing resources on demand to networked users. As campuses are challenged to better accommodate academic needs for applications and computing environments, cloud computing can provide an accommodating…

  5. Scale Dependence of Cirrus Horizontal Heterogeneity Effects on TOA Measurements. Part I; MODIS Brightness Temperatures in the Thermal Infrared

    Science.gov (United States)

    Fauchez, Thomas; Platnick, Steven; Meyer, Kerry; Cornet, Celine; Szczap, Frederic; Varnai, Tamas

    2017-01-01

    This paper presents a study on the impact of cirrus cloud heterogeneities on MODIS simulated thermal infrared (TIR) brightness temperatures (BTs) at the top of the atmosphere (TOA) as a function of spatial resolution from 50 meters to 10 kilometers. A realistic 3-D (three-dimensional) cirrus field is generated by the 3DCLOUD model (average optical thickness of 1.4, cloudtop and base altitudes at 10 and 12 kilometers, respectively, consisting of aggregate column crystals of D (sub eff) equals 20 microns), and 3-D thermal infrared radiative transfer (RT) is simulated with the 3DMCPOL (3-D Monte Carlo Polarized) code. According to previous studies, differences between 3-D BT computed from a heterogenous pixel and 1-D (one-dimensional) RT computed from a homogeneous pixel are considered dependent at nadir on two effects: (i) the optical thickness horizontal heterogeneity leading to the plane-parallel homogeneous bias (PPHB); and the (ii) horizontal radiative transport (HRT) leading to the independent pixel approximation error (IPAE). A single but realistic cirrus case is simulated and, as expected, the PPHB mainly impacts the low-spatial resolution results (above approximately 250 meters), with averaged values of up to 5-7 K (thousand), while the IPAE mainly impacts the high-spatial resolution results (below approximately 250 meters) with average values of up to 1-2 K (thousand). A sensitivity study has been performed in order to extend these results to various cirrus optical thicknesses and heterogeneities by sampling the cirrus in several ranges of parameters. For four optical thickness classes and four optical heterogeneity classes, we have found that, for nadir observations, the spatial resolution at which the combination of PPHB and HRT effects is the smallest, falls between 100 and 250 meters. These spatial resolutions thus appear to be the best choice to retrieve cirrus optical properties with the smallest cloud heterogeneity-related total bias in the thermal

  6. Development of Cloud and Precipitation Property Retrieval Algorithms and Measurement Simulators from ASR Data

    Energy Technology Data Exchange (ETDEWEB)

    Mace, Gerald G. [Univ. of Utah, Salt Lake City, UT (United States). Dept. of Atmospheric Sciences

    2016-02-10

    What has made the ASR program unique is the amount of information that is available. The suite of recently deployed instruments significantly expands the scope of the program (Mather and Voyles, 2013). The breadth of this information allows us to pose sophisticated process-level questions. Our ASR project, now entering its third year, has been about developing algorithms that use this information in ways that fully exploit the new capacity of the ARM data streams. Using optimal estimation (OE) and Markov Chain Monte Carlo (MCMC) inversion techniques, we have developed methodologies that allow us to use multiple radar frequency Doppler spectra along with lidar and passive constraints where data streams can be added or subtracted efficiently and algorithms can be reformulated for various combinations of hydrometeors by exchanging sets of empirical coefficients. These methodologies have been applied to boundary layer clouds, mixed phase snow cloud systems, and cirrus.

  7. A Fast Hybrid (3-D/1-D) Model for Thermal Radiative Transfer in Cirrus via Successive Orders of Scattering

    Science.gov (United States)

    Fauchez, Thomas; Davis, Anthony B.; Cornet, Celine; Szczap, Frederic; Platnick, Steven; Dubuisson, Philippe; Thieuleux, Francois

    2017-01-01

    We investigate the impact of cirrus cloud heterogeneity on the direct emission by cloud or surface and on the scattering by ice particles in the thermal infrared (TIR). Realistic 3-D cirri are modeled with the 3DCLOUD code, and top-of-atmosphere radiances are simulated by the 3-D Monte Carlo radiative transfer (RT) algorithm 3DMCPOL for two (8.65 micrometers and 12.05 micrometers) channels of the Imaging Infrared Radiometer on CALIPSO. At nadir, comparisons of 1-D and 3-D RT show that 3-D radiances are larger than their 1-D counterparts for direct emission but smaller for scattered radiation. For our cirrus cases, 99% of the 3-D total radiance is computed by the third scattering order, which corresponds to 90% of the total computational effort, but larger optical thicknesses need more scattering orders. To radically accelerate the 3-D RT computations (using only few percent of 3-D RT time with a Monte Carlo code), even in the presence of large optical depths, we develop a hybrid model based on exact 3-D direct emission, the first scattering order from 1-D in each homogenized column, and an empirical adjustment linearly dependent on the optical thickness to account for higher scattering orders. Good agreement is found between the hybrid model and the exact 3-D radiances for two very different cirrus models without changing the empirical parameters. We anticipate that a future deterministic implementation of the hybrid model will be fast enough to process multiangle thermal imagery in a practical tomographic reconstruction of 3-D cirrus fields.

  8. Introduction to MODIS Collection 6 'Deep Blue' aerosol products and strategy for cirrus-signal correction in AOD retrievals using 1.38 μm reflectance data

    Science.gov (United States)

    Lee, J.; Hsu, N. C.; Sayer, A. M.; Bettenhausen, C.

    2012-12-01

    This study shows the characteristics of the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6 Deep Blue aerosol products (hereafter, C006 DB products) and a strategy for correcting cirrus-signal in the aerosol optical depth (AOD) retrievals. The C006 DB products have several changes over the C005, including extended coverage, surface reflectance model, aerosol microphysical model, and cloud screening, etc. One of the new features is the inclusion of pixel-level uncertainty estimates on the retrieved AOD. These uncertainty estimates have been determined based on a validation against Aerosol Robotic Network (AERONET) direct-Sun AOD measurements, and are parameterized as a function of AOD, viewing geometry, and retrieval quality flag. This will provide users with a simple way to assess the uncertainty on Deep Blue AOD data for their particular application of interest. Preliminary results show strong agreement with AERONET, suggesting that the Deep Blue algorithm performs as well as other state-of-the-art satellite AOD datasets. In addition, a strategy for cirrus-signal correction in the retrieved AOD is presented. The cirrus reflectance at each wavelength to be used in the aerosol retrieval algorithms is determined by the relationships between reflectances at 1.38 μm and the aerosol bands and subtracted from the original TOA reflectance values assuming linear relationship for the optically thin case (ρ1.38 < 0.05). Since the 1.38 μm band is located in the strong water vapor absorption band, thus representing cirrus signal only, the slope between the 1.38 μm reflectance values and minimum reflectance values at each aerosol band for the corresponding values at 1.38 μm can be used to convert the 1.38 μm reflectance to the cirrus reflectance at each wavelength. Then, the cirrus-signal-corrected AOD can be retrieved by using the corrected reflectance data as input data into the aerosol retrieval algorithms. The retrieval results show that the AOD

  9. Retrieving Cirrus Microphysical Properties from Stellar Aureoles

    CERN Document Server

    DeVore, John G; Rappaport, Saul

    2013-01-01

    The aureoles around stars caused by thin cirrus limit nighttime measurement opportunities for ground-based astronomy but can provide information on high-altitude ice crystals for climate research. In this paper we attempt to demonstrate quantitatively how this works. Aureole profiles can be followed out to ~0.2 degrees from stars and ~0.5 degrees from Jupiter. Interpretation of diffracted starlight is similar to that for sunlight, but emphasizes larger particles. Stellar diffraction profiles are very distinctive, typically being approximately flat out to a critical angle followed by gradually steepening power-law falloff with slope less steep than -3. Using the relationship between the phase function for diffraction and the average Fourier transform of the projected area of complex ice crystals we show that defining particle size in terms of average projected area normal to the propagation direction of the starlight leads to a simple, analytic approximation representing large-particle diffraction that is near...

  10. Ice supersaturations exceeding 100% at the cold tropical tropopause: implications for cirrus formation and dehydration

    Directory of Open Access Journals (Sweden)

    E. Jensen

    2004-11-01

    Full Text Available Recent in situ measurements at tropical tropopause temperatures as low as 187 K indicate supersaturations with respect to ice exceeding 100% with little or no ice present. In contrast, models used to simulate cloud formation near the tropopause assume a supersaturation threshold for ice nucleation of about 65% based on laboratory measurements of sulfate aerosol freezing. The high supersaturations reported here, along with cloud simulations assuming a plausible range of temperature histories in the sampled air mass, indicate that the vast majority of aerosols in the air sampled on this flight must have had supersaturation thresholds for ice nucleation exceeding 100% (i.e. near liquid water saturation at these temperatures. Possible explanations for this high threshold are that (1 the expressions used for calculating vapor pressure over supercooled water at low temperatures give values at least 20% too low, (2 most of the available aerosols had a composition that makes them much more resistant to ice nucleation than aerosols used in laboratory experiments, and (3 organic films on the aerosol surfaces reduce their accommodation coefficient for uptake of water, resulting in aerosols with more concentrated solutions when moderate-rapid cooling occurs and correspondingly inhibited homogeneous freezing. Simulations of in situ cloud formation in the tropical tropopause layer (TTL throughout the tropics indicate that if these decreased accommodation coefficients and resulting high thresholds for ice nucleation prevailed throughout the tropics, then the calculated occurrence frequency and areal coverage of TTL cirrus would be significantly suppressed. However, the simulations also show that even if in situ TTL cirrus form only over a very small fraction of the tropics in the western Pacific, enough air passes through them due to rapid horizontal transport such that they can still effectively freeze-dry air entering the stratosphere.

  11. Improved cloud mask algorithm for FY-3A/VIRR data over the northwest region of China

    Science.gov (United States)

    Wang, X.; Li, W.; Zhu, Y.; Zhao, B.

    2013-03-01

    The existence of various land surfaces always leads to more difficulties in cloud detection based on satellite observations, especially over bright surfaces such as snow and deserts. To improve the cloud mask result over complex terrain, an unbiased, daytime cloud detection algorithm for the Visible and InfRared Radiometer (VIRR) on board the Chinese FengYun-3A polar-orbiting meteorological satellite is applied over the northwest region of China. The algorithm refers to the concept of the clear confidence level from Moderate Resolution Imaging Spectroradiometer (MODIS) and the unbiased structure of the CLoud and Aerosol Unbiased Decision Intellectual Algorithm (CLAUDIA). Six main channels of VIRR centered at the wavelengths of 0.455, 0.63, 0.865, 1.595, 1.36, and 10.8 μm are designed to estimate the degree of a pixel's cloud contamination judged by the clear confidence level. Based on the statistical data set during four months (January, April, July, and October) in 2010, seasonal thresholds are applied to improve the accuracy of the cloud detection results. Flags depicting snow and water are also generated by the specific threshold tests for special surfaces. As shown in image inspections, the cloud detection results over snow and deserts, adopting the proposed scheme, exhibit better correlations with true-color images than the VIRR official cloud mask results do. The performance of the proposed algorithm has been evaluated in detail for four seasons in 2011, using cloud mask products from MODIS and the ground-based observations. The evaluation is based on, overall, 47 scenes collocated with MODIS and 96 individual matchups between VIRR and the ground-based observations from two weather stations located in the research region. The quantitative validations suggest that the estimations of clear-sky regions have been greatly improved by the proposed algorithm, while a poor identification of the cirrus clouds occurs over deserts.

  12. Improved cloud mask algorithm for FY-3A/VIRR data over the northwest region of China

    Directory of Open Access Journals (Sweden)

    X. Wang

    2013-03-01

    Full Text Available The existence of various land surfaces always leads to more difficulties in cloud detection based on satellite observations, especially over bright surfaces such as snow and deserts. To improve the cloud mask result over complex terrain, an unbiased, daytime cloud detection algorithm for the Visible and InfRared Radiometer (VIRR on board the Chinese FengYun-3A polar-orbiting meteorological satellite is applied over the northwest region of China. The algorithm refers to the concept of the clear confidence level from Moderate Resolution Imaging Spectroradiometer (MODIS and the unbiased structure of the CLoud and Aerosol Unbiased Decision Intellectual Algorithm (CLAUDIA. Six main channels of VIRR centered at the wavelengths of 0.455, 0.63, 0.865, 1.595, 1.36, and 10.8 μm are designed to estimate the degree of a pixel's cloud contamination judged by the clear confidence level. Based on the statistical data set during four months (January, April, July, and October in 2010, seasonal thresholds are applied to improve the accuracy of the cloud detection results. Flags depicting snow and water are also generated by the specific threshold tests for special surfaces. As shown in image inspections, the cloud detection results over snow and deserts, adopting the proposed scheme, exhibit better correlations with true-color images than the VIRR official cloud mask results do. The performance of the proposed algorithm has been evaluated in detail for four seasons in 2011, using cloud mask products from MODIS and the ground-based observations. The evaluation is based on, overall, 47 scenes collocated with MODIS and 96 individual matchups between VIRR and the ground-based observations from two weather stations located in the research region. The quantitative validations suggest that the estimations of clear-sky regions have been greatly improved by the proposed algorithm, while a poor identification of the cirrus clouds occurs over deserts.

  13. Parameterizing Size Distribution in Ice Clouds

    Energy Technology Data Exchange (ETDEWEB)

    DeSlover, Daniel; Mitchell, David L.

    2009-09-25

    PARAMETERIZING SIZE DISTRIBUTIONS IN ICE CLOUDS David L. Mitchell and Daniel H. DeSlover ABSTRACT An outstanding problem that contributes considerable uncertainty to Global Climate Model (GCM) predictions of future climate is the characterization of ice particle sizes in cirrus clouds. Recent parameterizations of ice cloud effective diameter differ by a factor of three, which, for overcast conditions, often translate to changes in outgoing longwave radiation (OLR) of 55 W m-2 or more. Much of this uncertainty in cirrus particle sizes is related to the problem of ice particle shattering during in situ sampling of the ice particle size distribution (PSD). Ice particles often shatter into many smaller ice fragments upon collision with the rim of the probe inlet tube. These small ice artifacts are counted as real ice crystals, resulting in anomalously high concentrations of small ice crystals (D < 100 µm) and underestimates of the mean and effective size of the PSD. Half of the cirrus cloud optical depth calculated from these in situ measurements can be due to this shattering phenomenon. Another challenge is the determination of ice and liquid water amounts in mixed phase clouds. Mixed phase clouds in the Arctic contain mostly liquid water, and the presence of ice is important for determining their lifecycle. Colder high clouds between -20 and -36 oC may also be mixed phase but in this case their condensate is mostly ice with low levels of liquid water. Rather than affecting their lifecycle, the presence of liquid dramatically affects the cloud optical properties, which affects cloud-climate feedback processes in GCMs. This project has made advancements in solving both of these problems. Regarding the first problem, PSD in ice clouds are uncertain due to the inability to reliably measure the concentrations of the smallest crystals (D < 100 µm), known as the “small mode”. Rather than using in situ probe measurements aboard aircraft, we employed a treatment of ice

  14. Tropical Warm Pool International Cloud Experiment TWP-ICE Cloud and rain characteristics in the Australian Monsoon

    Energy Technology Data Exchange (ETDEWEB)

    May, P.T., Jakob, C., and Mather, J.H.

    2004-05-31

    The impact of oceanic convection on its environment and the relationship between the characteristics of the convection and the resulting cirrus characteristics is still not understood. An intense airborne measurement campaign combined with an extensive network of ground-based observations is being planned for the region near Darwin, Northern Australia, during January-February, 2006, to address these questions. The Tropical Warm Pool International Cloud Experiment (TWP-ICE) will be the first field program in the tropics that attempts to describe the evolution of tropical convection, including the large scale heat, moisture, and momentum budgets, while at the same time obtaining detailed observations of cloud properties and the impact of the clouds on the environment. The emphasis will be on cirrus for the cloud properties component of the experiment. Cirrus clouds are ubiquitous in the tropics and have a large impact on their environment but the properties of these clouds are poorly understood. A crucial product from this experiment will be a dataset suitable to provide the forcing and testing required by cloud-resolving models and parameterizations in global climate models. This dataset will provide the necessary link between cloud properties and the models that are attempting to simulate them.

  15. The Herschel Virgo Cluster Survey. XX. Dust and gas in the foreground Galactic cirrus

    Science.gov (United States)

    Bianchi, S.; Giovanardi, C.; Smith, M. W. L.; Fritz, J.; Davies, J. I.; Haynes, M. P.; Giovanelli, R.; Baes, M.; Bocchio, M.; Boissier, S.; Boquien, M.; Boselli, A.; Casasola, V.; Clark, C. J. R.; De Looze, I.; di Serego Alighieri, S.; Grossi, M.; Jones, A. P.; Hughes, T. M.; Hunt, L. K.; Madden, S.; Magrini, L.; Pappalardo, C.; Ysard, N.; Zibetti, S.

    2017-01-01

    We study the correlation between far-infrared/submm dust emission and atomic gas column density in order to derive the properties of the high Galactic latitude, low density, Milky Way cirrus in the foreground of the Virgo cluster of galaxies. Dust emission maps from 60 to 850 μm are obtained from observations with the Spectral and Photometric Imaging Receiver (SPIRE) and carried out within the Herschel Virgo Cluster Survey (HeViCS); these are complemented by IRAS and Planck maps. Data from the Arecibo legacy Fast ALFA Survey is used to derive atomic gas column densities for two broad velocity components: low and intermediate velocity clouds. Dust emissivities are derived for each gas component and each far-infrared/submm band. For the low velocity clouds, we measure an average emissivity ɛLVCν = (0.79 ± 0.08) × 10-20 MJy sr-1 cm2 at 250 μm. After fitting a modified blackbody to the available bands, we estimated a dust absorption cross section of τLVCν/NH i = (0.49 ± 0.13) × 10-25 cm2 H-1 at 250 μm (with dust temperature T = 20.4 ± 1.5 K and spectral index β = 1.53 ± 0.17). The results are in excellent agreement with those obtained by Planck over a much larger coverage of the high Galactic latitude cirrus (50% of the sky versus 0.2% in our work). For dust associated with intermediate velocity gas, we confirm earlier Planck results and find a higher temperature and lower emissivity and cross section. After subtracting the modeled components, we find regions at scales smaller than 20' in which the residuals deviate significantly from the average scatter, which is dominated by cosmic infrared background. These large residuals are most likely due to local variations in the cirrus dust properties or to high-latitude molecular clouds with average NH2 ≲ 1020 cm-2. We find no conclusive evidence for intracluster dust emission in Virgo. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and

  16. a Brief Climatology of Cirrus LIDAR Ratios Measured by High Spectral Resolution LIDAR

    Science.gov (United States)

    Kuehn, R.; Holz, R.; Hair, J. W.; Vaughan, M. A.; Eloranta, E. W.

    2015-12-01

    Our ability to detect and probe the vertical extent of cirrus was hugely improved with the launch of the NASA-CNES CALIPSO mission in April 2006. However, our skill at retrieving the optical properties of the cirrus detected by the CALIPSO lidar is not yet commensurate with our detection abilities. As with any new observing system, CALIPSO faces challenges and uncertainties in the retrieval of the geophysical parameters from its fundamental measurements. Specifically, extinction and optical depth retrievals for elastic backscatter lidars like CALIPSO typically rely on a priori assumptions about layer-mean extinction-to-backscatter ratios (AKA lidar ratios), which can vary regionally and for which uncertainties are high. To improve CALIPSO optical properties retrievals, we show High Spectral Resolution Lidar (HSRL) measurements acquired with systems from the University of Wisconsin and NASA Langley. HSRLs can directly determine ice cloud extinction and lidar ratio by separately measuring the molecular and particulate components of the total backscattered signal, thus largely eliminating many of the uncertainties inherent in elastic backscatter retrievals. These measurements were acquired during the SEAC4RS (Huntsville, AL, USA and Singapore), and FRAPPE/DISCOVER-AQ 2014 (BAO tower near Boulder, CO, USA) field campaigns, and an intensive operations period in Hampton, VA, USA.

  17. Applied research on cloud computing in AIS%云计算在AIS中的应用研究

    Institute of Scientific and Technical Information of China (English)

    韩光强

    2012-01-01

    云计算可以帮助企业用户更方便快捷地进行财务应用管理,减少企业AIS系统投入成本,提高企业IT设备资源的使用效率,但云计算本身固有的不足也阻碍了它在AIS中的推广应用.本文分析了云计算在AIS中的应用及存在问题,提出了推广促进云计算在AIS中应用发展的途径.%Cloud computing has become China's academic and industrial hot research spot. It helps enterpriser to do more convenient and quicker financial application management, reduces the cost of enterprise AI5 system, and improves enterprise's IT equipment efficiency in the use of resources. However, cloud computing has its insufficiency in preventing IT from the popularization and application of AIS. An analysis is made of the cloud computing in the application and problems of AIS, and ways are proposed to promote the application of cloud computing in AIS.

  18. In Situ Balloon-Borne Ice Particle Imaging in High-Latitude Cirrus

    Science.gov (United States)

    Kuhn, Thomas; Heymsfield, Andrew J.

    2016-09-01

    Cirrus clouds reflect incoming solar radiation, creating a cooling effect. At the same time, these clouds absorb the infrared radiation from the Earth, creating a greenhouse effect. The net effect, crucial for radiative transfer, depends on the cirrus microphysical properties, such as particle size distributions and particle shapes. Knowledge of these cloud properties is also needed for calibrating and validating passive and active remote sensors. Ice particles of sizes below 100 µm are inherently difficult to measure with aircraft-mounted probes due to issues with resolution, sizing, and size-dependent sampling volume. Furthermore, artefacts are produced by shattering of particles on the leading surfaces of the aircraft probes when particles several hundred microns or larger are present. Here, we report on a series of balloon-borne in situ measurements that were carried out at a high-latitude location, Kiruna in northern Sweden (68N 21E). The method used here avoids these issues experienced with the aircraft probes. Furthermore, with a balloon-borne instrument, data are collected as vertical profiles, more useful for calibrating or evaluating remote sensing measurements than data collected along horizontal traverses. Particles are collected on an oil-coated film at a sampling speed given directly by the ascending rate of the balloon, 4 m s-1. The collecting film is advanced uniformly inside the instrument so that an always unused section of the film is exposed to ice particles, which are measured by imaging shortly after sampling. The high optical resolution of about 4 µm together with a pixel resolution of 1.65 µm allows particle detection at sizes of 10 µm and larger. For particles that are 20 µm (12 pixel) in size or larger, the shape can be recognized. The sampling volume, 130 cm3 s-1, is well defined and independent of particle size. With the encountered number concentrations of between 4 and 400 L-1, this required about 90- to 4-s sampling times to

  19. Convective formation of pileus cloud near the tropopause

    Directory of Open Access Journals (Sweden)

    T. J. Garrett

    2006-01-01

    Full Text Available Pileus clouds form where humid, vertically stratified air is mechanically displaced ahead of rising convection. This paper describes convective formation of pileus cloud in the tropopause transition layer (TTL, and explores a possible link to the formation of long-lasting cirrus at cold temperatures. The study examines in detail in-situ measurements from off the coast of Honduras during the July 2002 CRYSTAL-FACE experiment that showed an example of TTL cirrus associated with, and penetrated by, deep convection. The TTL cirrus was enriched with total water compared to its surroundings, but was composed of extremely small ice crystals with effective radii between 2 and 4 μm. Through gravity wave analysis, and intercomparison of measured and simulated cloud microphysics, it is argued that the TTL cirrus originated neither from convectively-forced gravity wave motions nor environmental mixing alone. Rather, it is hypothesized that a combination of these two processes was involved in which, first, a pulse of convection forced pileus cloud to form from TTL air; second, the pileus layer was punctured by the convective pulse and received larger ice crystals through interfacial mixing; third, the addition of this condensate inhibited evaporation of the original pileus ice crystals where a convectively forced gravity wave entered its warm phase; fourth, through successive pulses of convection, a sheet of TTL cirrus formed. While the general incidence and longevity of pileus cloud remains unknown, in-situ measurements, and satellite-based Microwave Limb Sounder retrievals, suggest that much of the tropical TTL is sufficiently humid to be susceptible to its formation. Where these clouds form and persist, there is potential for an irreversible repartition from water vapor to ice at cold temperatures.

  20. Small Particles in Cirrus (SPartICus) and Storm Peak Lab Validation Experiment (StormVEx) Science Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Mace, Gerald [Univ. of Utah, Salt Lake City, UT (United States)

    2016-10-28

    The Small Particles in Cirrus (SPartICus) campaign took place from January through June, 2011 and the Storm Peak Lab Cloud Property Validation Experiment (StormVEx) took place from November, 2011 through April, 2012. The PI of this project, Dr. Gerald Mace, had the privilege to be the lead on both of these campaigns. The essence of the project that we report on here was to conduct preliminary work that was necessary to bring the field data sets to a point where they could be used for their intended science purposes

  1. Classification of Particle Shapes from Lidar Depolarization Ratios in Convective Ice Clouds Compared to in situ Observations During CRYSTAL-FACE

    Science.gov (United States)

    Noel, Vincent; Winker, David; McGill, Matthew; Lawson, Paul

    2004-01-01

    This manuscript describes a method to class@ cirrus cloud ice particle shape using lidar depolarization measurements as a basis for segregating different particle shape regimes. Measurements from the ER-2 Cloud Physics Lidar (CPL) system during CRYSTAL-FACE provide the basis for this work. While the CPL onboard the ER-2 aircraft was providing remote sensing measurements of cirrus clouds, the Cloud Particle Imager (CPI) onboard the WB-57 aircraft was flying inside those same clouds to sample particle sizes. The results of classifying particle shapes using the CPL data are compared to the in situ measurements made using the CPI , and there is found to be good agreement between the particle shape inferred from the CPL data and that actually measured by the CPI. If proven practical, application of this technique to spaceborne observations could lead to large-scale classification of cirrus cloud particle shapes.

  2. Study of Multi-Scale Cloud Processes Over the Tropical Western Pacific Using Cloud-Resolving Models Constrained by Satellite Data

    Energy Technology Data Exchange (ETDEWEB)

    Dudhia, Jimy

    2013-03-12

    Clouds in the tropical western Pacific are an integral part of the large scale environment. An improved understanding of the multi-scale structure of clouds and their interactions with the environment is critical to the ARM (Atmospheric Radiation Measurement) program for developing and evaluating cloud parameterizations, understanding the consequences of model biases, and providing a context for interpreting the observational data collected over the ARM Tropical Western Pacific (TWP) sites. Three-dimensional cloud resolving models (CRMs) are powerful tools for developing and evaluating cloud parameterizations. However, a significant challenge in using CRMs in the TWP is that the region lacks conventional data, so large uncertainty exists in defining the large-scale environment for clouds. This project links several aspects of the ARM program, from measurements to providing improved analyses, and from cloud-resolving modeling to climate-scale modeling and parameterization development, with the overall objective to improve the representations of clouds in climate models and to simulate and quantify resolved cloud effects on the large-scale environment. Our objectives will be achieved through a series of tasks focusing on the use of the Weather Research and Forecasting (WRF) model and ARM data. Our approach includes: -- Perform assimilation of COSMIC GPS radio occultation and other satellites products using the WRF Ensemble Kalman Filter assimilation system to represent the tropical large-scale environment at 36 km grid resolution. This high-resolution analysis can be used by the community to derive forcing products for single-column models or cloud-resolving models. -- Perform cloud-resolving simulations using WRF and its nesting capabilities, driven by the improved regional analysis and evaluate the simulations against ARM datasets such as from TWP-ICE to optimize the microphysics parameters for this region. A cirrus study (Mace and co-authors) already exists for

  3. Microphysics of Pyrocumulonimbus Clouds

    Science.gov (United States)

    Jensen, Eric; Ackerman, Andrew S.; Fridlind, Ann

    2004-01-01

    The intense heat from forest fires can generate explosive deep convective cloud systems that inject pollutants to high altitudes. Both satellite and high-altitude aircraft measurements have documented cases in which these pyrocumulonimbus clouds inject large amounts of smoke well into the stratosphere (Fromm and Servranckx 2003; Jost et al. 2004). This smoke can remain in the stratosphere, be transported large distances, and affect lower stratospheric chemistry. In addition recent in situ measurements in pyrocumulus updrafts have shown that the high concentrations of smoke particles have significant impacts on cloud microphysical properties. Very high droplet number densities result in delayed precipitation and may enhance lightning (Andrew et al. 2004). Presumably, the smoke particles will also lead to changes in the properties of anvil cirrus produces by the deep convection, with resulting influences on cloud radiative forcing. In situ sampling near the tops of mature pyrocumulonimbus is difficult due to the high altitude and violence of the storms. In this study, we use large eddy simulations (LES) with size-resolved microphysics to elucidate physical processes in pyrocumulonimbus clouds.

  4. Microphysics of Pyrocumulonimbus Clouds

    Science.gov (United States)

    Jensen, Eric; Ackerman, Andrew S.; Fridlind, Ann

    2004-01-01

    The intense heat from forest fires can generate explosive deep convective cloud systems that inject pollutants to high altitudes. Both satellite and high-altitude aircraft measurements have documented cases in which these pyrocumulonimbus clouds inject large amounts of smoke well into the stratosphere (Fromm and Servranckx 2003; Jost et al. 2004). This smoke can remain in the stratosphere, be transported large distances, and affect lower stratospheric chemistry. In addition recent in situ measurements in pyrocumulus updrafts have shown that the high concentrations of smoke particles have significant impacts on cloud microphysical properties. Very high droplet number densities result in delayed precipitation and may enhance lightning (Andrew et al. 2004). Presumably, the smoke particles will also lead to changes in the properties of anvil cirrus produces by the deep convection, with resulting influences on cloud radiative forcing. In situ sampling near the tops of mature pyrocumulonimbus is difficult due to the high altitude and violence of the storms. In this study, we use large eddy simulations (LES) with size-resolved microphysics to elucidate physical processes in pyrocumulonimbus clouds.

  5. A Study of Cirrus Ice Particle Size Distribution Using TC4 Observations

    Science.gov (United States)

    Tian, Lin; Heymsfield, Gerald M.; Li, Lihua; Heymsfield, Andrew J.; Bansemer, Aaron; Twohy, Cynthia H.; Srivastava, Ramesh C.

    2010-01-01

    An analysis of two days of in situ observations of ice particle size spectra, in convectively generated cirrus, obtained during NASA s Tropical Composition, Cloud, and Climate Coupling (TC4) mission is presented. The observed spectra are examined for their fit to the exponential, gamma, and lognormal function distributions. Characteristic particle size and concentration density scales are determined using two (for the exponential) or three (for the gamma and lognormal functions) moments of the spectra. It is shown that transformed exponential, gamma, and lognormal distributions should collapse onto standard curves. An examination of the transformed spectra, and of deviations of the transformed spectra from the standard curves, shows that the lognormal function provides a better fit to the observed spectra.

  6. Quantifying uncertainties in radar forward models through a comparison between CloudSat and SPartICus reflectivity factors

    Science.gov (United States)

    Mascio, Jeana; Mace, Gerald G.

    2017-02-01

    Interpretations of remote sensing measurements collected in sample volumes containing ice-phase hydrometeors are very sensitive to assumptions regarding the distributions of mass with ice crystal dimension, otherwise known as mass-dimensional or m-D relationships. How these microphysical characteristics vary in nature is highly uncertain, resulting in significant uncertainty in algorithms that attempt to derive bulk microphysical properties from remote sensing measurements. This uncertainty extends to radar reflectivity factors forward calculated from model output because the statistics of the actual m-D in nature is not known. To investigate the variability in m-D relationships in cirrus clouds, reflectivity factors measured by CloudSat are combined with particle size distributions (PSDs) collected by coincident in situ aircraft by using an optimal estimation-based (OE) retrieval of the m-D power law. The PSDs were collected by 12 flights of the Stratton Park Engineering Company Learjet during the Small Particles in Cirrus campaign. We find that no specific habit emerges as preferred, and instead, we find that the microphysical characteristics of ice crystal populations tend to be distributed over a continuum-defying simple categorization. With the uncertainties derived from the OE algorithm, the uncertainties in forward-modeled backscatter cross section and, in turn, radar reflectivity is calculated by using a bootstrapping technique, allowing us to infer the uncertainties in forward-modeled radar reflectivity that would be appropriately applied to remote sensing simulator algorithms.

  7. Comparison of different cloud types from surface and satellite cloud classification products over China

    Science.gov (United States)

    Wang, Minyan; Zeng, Le; Wang, Shengjie; Gu, Junxia; Yang, Runzhi

    2016-04-01

    Different cloud types usually have different cloud dynamic process and micro-physical characteristics, and the relative cloud radiation forcing effects vary much. In recent years, the focus of cloud classification is the algorithm development, as well as the analysis on total cloud amount, high/middle/low cloud amount. While, research on the different cloud types (like cirrus, stratus, and cumulonimbus) is not enough. In this research, we use multi-resources cloud classification products including FY-2, Cloudsat and surface observation to obtain the temporal-spatial distribution characteristics and evolvement of different cloud types in different regions of China, analyze the quantitative difference of multi-source products and the reasons. According to the temporal and spatial scales of cloud, and temporal-spatial representation of cloud classification products based on CloudSat, etc, the scaling is necessary to explore in temporal-spatial matching/validation research. This research have important scientific significances on understanding the regional characteristics of different cloud types in China, improving the remote sensing retrieve algorithms on cloud classification, temporal-spatial matching/validation techniques of satellite data, and cloud vertical structure parameterized methods in numerical models.

  8. The 94 GHz Cloud Radar System on a NASA ER-2 Aircraft

    Science.gov (United States)

    Li, Lihua; Heymsfield, Gerald M.; Racette, Paul E.; Tian, Lin; Zenker, Ed

    2003-01-01

    The 94-GHz (W-band) Cloud Radar System (CRS) has been developed and flown on a NASA ER-2 high-altitude (20 km) aircraft. The CRS is a fully coherent, polarimeteric Doppler radar that is capable of detecting clouds and precipitation from the surface up to the aircraft altitude in the lower stratosphere. The radar is especially well suited for cirrus cloud studies because of its high sensitivity and fine spatial resolution. This paper describes the CRS motivation, instrument design, specifications, calibration, and preliminary data &om NASA s Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE) field campaign. The unique combination of CRS with other sensors on the ER-2 provides an unprecedented opportunity to study cloud radiative effects on the global energy budget. CRS observations are being used to improve our knowledge of atmospheric scattering and attenuation characteristics at 94 GHz, and to provide datasets for algorithm implementation and validation for the upcoming NASA CloudSat mission that will use a 94-GHz spaceborne cloud radar to provide the first direct global survey of the vertical structure of cloud systems.

  9. Robots and sensor clouds

    CERN Document Server

    Shakshuki, Elhadi

    2016-01-01

    This book comprises four chapters that address some of the latest research in clouds robotics and sensor clouds. The first part of the book includes two chapters on cloud robotics. The first chapter introduces a novel resource allocation framework for cloud robotics and proposes a Stackelberg game model and the corresponding task oriented pricing mechanism for resource allocation. In the second chapter, the authors apply Cloud Computing for building a Cloud-Based 3D Point Cloud extractor for stereo images. Their objective is to have a dynamically scalable and applicable to near real-time scenarios.  .

  10. 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.

  11. Validation of VIIRS Cloud Base Heights at Night Using Ground and Satellite Measurements over Alaska

    Science.gov (United States)

    NOH, Y. J.; Miller, S. D.; Seaman, C.; Forsythe, J. M.; Brummer, R.; Lindsey, D. T.; Walther, A.; Heidinger, A. K.; Li, Y.

    2016-12-01

    Knowledge of Cloud Base Height (CBH) is critical to describing cloud radiative feedbacks in numerical models and is of practical significance to aviation communities. We have developed a new CBH algorithm constrained by Cloud Top Height (CTH) and Cloud Water Path (CWP) by performing a statistical analysis of A-Train satellite data. It includes an extinction-based method for thin cirrus. In the algorithm, cloud geometric thickness is derived with upstream CTH and CWP input and subtracted from CTH to generate the topmost layer CBH. The CBH information is a key parameter for an improved Cloud Cover/Layers product. The algorithm has been applied to the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi NPP spacecraft. Nighttime cloud optical properties for CWP are retrieved from the nighttime lunar cloud optical and microphysical properties (NLCOMP) algorithm based on a lunar reflectance model for the VIIRS Day/Night Band (DNB) measuring nighttime visible light such as moonlight. The DNB has innovative capabilities to fill the polar winter and nighttime gap of cloud observations which has been an important shortfall from conventional radiometers. The CBH products have been intensively evaluated against CloudSat data. The results showed the new algorithm yields significantly improved performance over the original VIIRS CBH algorithm. However, since CloudSat is now operational during daytime only due to a battery anomaly, the nighttime performance has not been fully assessed. This presentation will show our approach to assess the performance of the CBH algorithm at night. VIIRS CBHs are retrieved over the Alaska region from October 2015 to April 2016 using the Clouds from AVHRR Extended (CLAVR-x) processing system. Ground-based measurements from ceilometer and micropulse lidar at the Atmospheric Radiation Measurement (ARM) site on the North Slope of Alaska are used for the analysis. Local weather conditions are checked using temperature and precipitation

  12. Mobile Laser Scanning along Dieppe coastal cliffs: reliability of the acquired point clouds applied to rockfall assessments

    Science.gov (United States)

    Michoud, Clément; Carrea, Dario; Augereau, Emmanuel; Cancouët, Romain; Costa, Stéphane; Davidson, Robert; Delacourt, Chirstophe; Derron, Marc-Henri; Jaboyedoff, Michel; Letortu, Pauline; Maquaire, Olivier

    2013-04-01

    Dieppe coastal cliffs, in Normandy, France, are mainly formed by sub-horizontal deposits of chalk and flintstone. Largely destabilized by an intense weathering and the Channel sea erosion, small and large rockfalls are regularly observed and contribute to retrogressive cliff processes. During autumn 2012, cliff and intertidal topographies have been acquired with a Terrestrial Laser Scanner (TLS) and a Mobile Laser Scanner (MLS), coupled with seafloor bathymetries realized with a multibeam echosounder (MBES). MLS is a recent development of laser scanning based on the same theoretical principles of aerial LiDAR, but using smaller, cheaper and portable devices. The MLS system, which is composed by an accurate dynamic positioning and orientation (INS) devices and a long range LiDAR, is mounted on a marine vessel; it is then possible to quickly acquire in motion georeferenced LiDAR point clouds with a resolution of about 15 cm. For example, it takes about 1 h to scan of shoreline of 2 km long. MLS is becoming a promising technique supporting erosion and rockfall assessments along the shores of lakes, fjords or seas. In this study, the MLS system used to acquire cliffs and intertidal areas of the Cap d'Ailly was composed by the INS Applanix POS-MV 320 V4 and the LiDAR Optech Ilirs LR. On the same day, three MLS scans with large overlaps (J1, J21 and J3) have been performed at ranges from 600 m at 4 knots (low tide) up to 200 m at 2.2 knots (up tide) with a calm sea at 2.5 Beaufort (small wavelets). Mean scan resolutions go from 26 cm for far scan (J1) to about 8.1 cm for close scan (J3). Moreover, one TLS point cloud on this test site has been acquired with a mean resolution of about 2.3 cm, using a Riegl LMS Z390i. In order to quantify the reliability of the methodology, comparisons between scans have been realized with the software Polyworks™, calculating shortest distances between points of one cloud and the interpolated surface of the reference point cloud. A Mat

  13. A voting-based statistical cylinder detection framework applied to fallen tree mapping in terrestrial laser scanning point clouds

    Science.gov (United States)

    Polewski, Przemyslaw; Yao, Wei; Heurich, Marco; Krzystek, Peter; Stilla, Uwe

    2017-07-01

    This paper introduces a statistical framework for detecting cylindrical shapes in dense point clouds. We target the application of mapping fallen trees in datasets obtained through terrestrial laser scanning. This is a challenging task due to the presence of ground vegetation, standing trees, DTM artifacts, as well as the fragmentation of dead trees into non-collinear segments. Our method shares the concept of voting in parameter space with the generalized Hough transform, however two of its significant drawbacks are improved upon. First, the need to generate samples on the shape's surface is eliminated. Instead, pairs of nearby input points lying on the surface cast a vote for the cylinder's parameters based on the intrinsic geometric properties of cylindrical shapes. Second, no discretization of the parameter space is required: the voting is carried out in continuous space by means of constructing a kernel density estimator and obtaining its local maxima, using automatic, data-driven kernel bandwidth selection. Furthermore, we show how the detected cylindrical primitives can be efficiently merged to obtain object-level (entire tree) semantic information using graph-cut segmentation and a tailored dynamic algorithm for eliminating cylinder redundancy. Experiments were performed on 3 plots from the Bavarian Forest National Park, with ground truth obtained through visual inspection of the point clouds. It was found that relative to sample consensus (SAC) cylinder fitting, the proposed voting framework can improve the detection completeness by up to 10 percentage points while maintaining the correctness rate.

  14. Cirrus and water vapor transport in the tropical tropopause layer – Part 1: A specific case modeling study

    Directory of Open Access Journals (Sweden)

    T. Dinh

    2012-10-01

    Full Text Available In a simulation of a tropical-tropopause-layer (TTL cirrus forced by a large-scale equatorial Kelvin wave, the radiatively induced mesoscale dynamics of the cloud actively contributes to the transport of water vapor in the vertical direction.

    In a typical TTL cirrus, the heating that results from absorption of radiation by ice crystals induces a mesoscale circulation. Advection of water vapor by the radiatively induced circulation leads to upward advection of the cloudy air. Upward advection of the cloudy air is equivalent to upward transport of water vapor when the air above the cloud is drier than the cloudy air. On the other hand, ice nucleation and depositional growth, followed by sedimentation and sublimation lead to downward transport of water vapor.

    Under the conditions specific to our simulation, the upward transport of water vapor by the mesoscale circulation dominates the downward transport by microphysical processes. The net result is upward transport of water vapor, which is equivalent to hydration of the lower stratosphere. Sensitivity to model conditions and parameters will be discussed in a follow-up paper.

  15. Measurements of the Ice Water Content of Cirrus in the Tropics and Subtropics. I; Instrument Details and Validation

    Science.gov (United States)

    Weinstock, E. M.; Smith, J. B.; Sayres, D.; Pittman, J. V.; Allen, N.; Demusz, J.; Greenberg, M.; Rivero, M.; Anderson, J. G.

    2003-01-01

    We describe an instrument mounted in a pallet on the NASA WB-57 aircraft that is designed to measure the sum of gas phase and solid phase water, or total water, in cirrus clouds. Using an isokinetic inlet, a 600-watt heater mounted directly in the flow, and Lyman-alpha photofragment fluorescence technique for detection, accurate measurements of total water have been made over almost three orders of magnitude. Isokinetic flow is achieved with an actively controlled roots pump by referencing aircraft pressure, temperature, and true air speed, together with instrument flow velocity, temperature, and pressure. During CRYSTAL FACE, the instrument operated at duct temperatures sufficiently warm to completely evaporate particles up to 150 microns diameter. In flight diagnostics, intercomparison with water measured by absorption in flight, as well as intercomparisons in clear air with water vapor measured by the Harvard water vapor instrument and the JPL infrared tunable diode laser hygrometer validate the detection sensitivity of the instrument and illustrate minimal hysteresis from instrument surfaces. The simultaneous measurement of total water and water vapor in cirrus clouds yields their ice water content.

  16. Serendipity observations of far infrared cirrus emission in the Spitzer Infrared Nearby Galaxies Survey: Analysis of far-infrared correlations

    CERN Document Server

    Bot, Caroline; Boulanger, Francois; Lagache, Guilaine; Miville-Deschenes, Marc-Antoine; Draine, Bruce; Martin, Peter

    2009-01-01

    We present an analysis of far-infrared dust emission from diffuse cirrus clouds. This study is based on serendipitous observations at 160 microns at high galactic latitude with the Multiband Imaging Photometer (MIPS) onboard the Spitzer Space Telescope by the Spitzer Infrared Nearby Galaxies Survey (SINGS). These observations are complemented with IRIS data at 100 and 60 microns and constitute one of the most sensitive and unbiased samples of far infrared observations at small scale of diffuse interstellar clouds. Outside regions dominated by the cosmic infrared background fluctuations, we observe a substantial scatter in the 160/100 colors from cirrus emission. We compared the 160/100 color variations to 60/100 colors in the same fields and find a trend of decreasing 60/100 with increasing 160/100. This trend can not be accounted for by current dust models by changing solely the interstellar radiation field. It requires a significant change of dust properties such as grain size distribution or emissivity or ...

  17. Improved cloud mask algorithm for FY-3A/VIRR data over the northwest region of China

    Directory of Open Access Journals (Sweden)

    X. Wang

    2012-11-01

    Full Text Available The existence of various land surfaces has always been a difficult problem for researchers who study cloud detection using satellite observations, especially over bright surfaces such as snow and desert. To improve the cloud mask result over complex terrain, an unbiased daytime cloud detection algorithm for the Visible and InfRared Radiometer (VIRR on board the Chinese FengYun-3A polar-orbiting meteorological satellite is applied over the northwest region of China. Based on the statistical seasonal threshold tests, the algorithm consists of six main channels centered on the wavelengths of 0.63, 0.865, 10.8, 1.595, 0.455, and 1.36 μm. The combination of the unbiased algorithm and the specific threshold tests for special surfaces has effectively improved the cloud mask results over complex terrain and decreased the false identifications of clouds. The visual images over snow and desert adopting the proposed scheme exhibit better correlations with true-color images than do the VIRR official cloud mask results. The validation with the Moderate Resolution Imaging Spectroradiometer (MODIS cloud mask product shows that the probability of detection for clear-sky regions over snow of the new scheme has increased nearly five times over the official method, and the false-alarm ratio for cloudy areas over desert has reduced by half compared with the official result. With regard to comparisons between ground measurements and cloud mask results, this approach also provides acceptable correspondence with the ground observations except for some cases, which are mainly obscured by cirrus clouds.

  18. The SDSS High Latitude Cloud Survey

    Science.gov (United States)

    McGehee, P. M.

    2009-01-01

    The high latitude clouds (|b| > 30) are primarily translucent molecular clouds and diffuse Galactic cirrus with the majority of them seen at high latitude simply due to their proximity to the Sun. The rare exceptions are those, like the Draco and other intermediate or high velocity clouds, found significantly above or below the Galactic plane. To date, star formation has only been verified in MBM 12 and MBM 20, which are two of the densest high latitude molecular clouds. We present results from an ongoing study of high latitude clouds based on the Sloan Digital Sky Survey (SDSS) and the Two Micron All-Sky Survey (2MASS). This study consists of two major efforts, the first (described here) to provide a 3-D mapping of the interstellar dust using a color-excess technique, the second to identify candidate low-mass Classical T Tauri stars in the field.

  19. 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

  20. 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.

  1. Modeling of Cloud/Radiation Processes for Large-Scale Clouds and Tropical Anvils

    Science.gov (United States)

    1994-05-31

    The radiative effet of ice 0 W sin (25 pAm), IR heating/cooling rates of about 30 K day-’ ditrlbdm take place close to the bottom and top of the cloud...montre que le forqage radiatif net A la partic suptrieure de I’atmosph~re charg6e de cirrus est positif, de sorte que I’effet infrarouge de serre d~passe

  2. An objective classification of Saturn cloud features from Cassini ISS images

    Science.gov (United States)

    Del Genio, Anthony D.; Barbara, John M.

    2016-06-01

    A k-means clustering algorithm is applied to Cassini Imaging Science Subsystem continuum and methane band images of Saturn's northern hemisphere to objectively classify regional albedo features and aid in their dynamical interpretation. The procedure is based on a technique applied previously to visible-infrared images of Earth. It provides a new perspective on giant planet cloud morphology and its relationship to the dynamics and a meteorological context for the analysis of other types of simultaneous Saturn observations. The method identifies 6 clusters that exhibit distinct morphology, vertical structure, and preferred latitudes of occurrence. These correspond to areas dominated by deep convective cells; low contrast areas, some including thinner and thicker clouds possibly associated with baroclinic instability; regions with possible isolated thin cirrus clouds; darker areas due to thinner low level clouds or clearer skies due to downwelling, or due to absorbing particles; and fields of relatively shallow cumulus clouds. The spatial associations among these cloud types suggest that dynamically, there are three distinct types of latitude bands on Saturn: deep convectively disturbed latitudes in cyclonic shear regions poleward of the eastward jets; convectively suppressed regions near and surrounding the westward jets; and baroclinically unstable latitudes near eastward jet cores and in the anti-cyclonic regions equatorward of them. These are roughly analogous to some of the features of Earth's tropics, subtropics, and midlatitudes, respectively. This classification may be more useful for dynamics purposes than the traditional belt-zone partitioning. Temporal variations of feature contrast and cluster occurrence suggest that the upper tropospheric haze in the northern hemisphere may have thickened by 2014. The results suggest that routine use of clustering may be a worthwhile complement to many different types of planetary atmospheric data analysis.

  3. An Objective Classification of Saturn Cloud Features from Cassini ISS Images

    Science.gov (United States)

    Del Genio, Anthony D.; Barbara, John M.

    2016-01-01

    A k -means clustering algorithm is applied to Cassini Imaging Science Subsystem continuum and methane band images of Saturn's northern hemisphere to objectively classify regional albedo features and aid in their dynamical interpretation. The procedure is based on a technique applied previously to visible- infrared images of Earth. It provides a new perspective on giant planet cloud morphology and its relationship to the dynamics and a meteorological context for the analysis of other types of simultaneous Saturn observations. The method identifies 6 clusters that exhibit distinct morphology, vertical structure, and preferred latitudes of occurrence. These correspond to areas dominated by deep convective cells; low contrast areas, some including thinner and thicker clouds possibly associated with baroclinic instability; regions with possible isolated thin cirrus clouds; darker areas due to thinner low level clouds or clearer skies due to downwelling, or due to absorbing particles; and fields of relatively shallow cumulus clouds. The spatial associations among these cloud types suggest that dynamically, there are three distinct types of latitude bands on Saturn: deep convectively disturbed latitudes in cyclonic shear regions poleward of the eastward jets; convectively suppressed regions near and surrounding the westward jets; and baro-clinically unstable latitudes near eastward jet cores and in the anti-cyclonic regions equatorward of them. These are roughly analogous to some of the features of Earth's tropics, subtropics, and midlatitudes, respectively. This classification may be more useful for dynamics purposes than the traditional belt-zone partitioning. Temporal variations of feature contrast and cluster occurrence suggest that the upper tropospheric haze in the northern hemisphere may have thickened by 2014. The results suggest that routine use of clustering may be a worthwhile complement to many different types of planetary atmospheric data analysis.

  4. A Framework for Applying Point Clouds Grabbed by Multi-Beam LIDAR in Perceiving the Driving Environment

    Directory of Open Access Journals (Sweden)

    Jian Liu

    2015-08-01

    Full Text Available The quick and accurate understanding of the ambient environment, which is composed of road curbs, vehicles, pedestrians, etc., is critical for developing intelligent vehicles. The road elements included in this work are road curbs and dynamic road obstacles that directly affect the drivable area. A framework for the online modeling of the driving environment using a multi-beam LIDAR, i.e., a Velodyne HDL-64E LIDAR, which describes the 3D environment in the form of a point cloud, is reported in this article. First, ground segmentation is performed via multi-feature extraction of the raw data grabbed by the Velodyne LIDAR to satisfy the requirement of online environment modeling. Curbs and dynamic road obstacles are detected and tracked in different manners. Curves are fitted for curb points, and points are clustered into bundles whose form and kinematics parameters are calculated. The Kalman filter is used to track dynamic obstacles, whereas the snake model is employed for curbs. Results indicate that the proposed framework is robust under various environments and satisfies the requirements for online processing.

  5. A Framework for Applying Point Clouds Grabbed by Multi-Beam LIDAR in Perceiving the Driving Environment

    Science.gov (United States)

    Liu, Jian; Liang, Huawei; Wang, Zhiling; Chen, Xiangcheng

    2015-01-01

    The quick and accurate understanding of the ambient environment, which is composed of road curbs, vehicles, pedestrians, etc., is critical for developing intelligent vehicles. The road elements included in this work are road curbs and dynamic road obstacles that directly affect the drivable area. A framework for the online modeling of the driving environment using a multi-beam LIDAR, i.e., a Velodyne HDL-64E LIDAR, which describes the 3D environment in the form of a point cloud, is reported in this article. First, ground segmentation is performed via multi-feature extraction of the raw data grabbed by the Velodyne LIDAR to satisfy the requirement of online environment modeling. Curbs and dynamic road obstacles are detected and tracked in different manners. Curves are fitted for curb points, and points are clustered into bundles whose form and kinematics parameters are calculated. The Kalman filter is used to track dynamic obstacles, whereas the snake model is employed for curbs. Results indicate that the proposed framework is robust under various environments and satisfies the requirements for online processing. PMID:26404290

  6. A Framework for Applying Point Clouds Grabbed by Multi-Beam LIDAR in Perceiving the Driving Environment.

    Science.gov (United States)

    Liu, Jian; Liang, Huawei; Wang, Zhiling; Chen, Xiangcheng

    2015-08-31

    The quick and accurate understanding of the ambient environment, which is composed of road curbs, vehicles, pedestrians, etc., is critical for developing intelligent vehicles. The road elements included in this work are road curbs and dynamic road obstacles that directly affect the drivable area. A framework for the online modeling of the driving environment using a multi-beam LIDAR, i.e., a Velodyne HDL-64E LIDAR, which describes the 3D environment in the form of a point cloud, is reported in this article. First, ground segmentation is performed via multi-feature extraction of the raw data grabbed by the Velodyne LIDAR to satisfy the requirement of online environment modeling. Curbs and dynamic road obstacles are detected and tracked in different manners. Curves are fitted for curb points, and points are clustered into bundles whose form and kinematics parameters are calculated. The Kalman filter is used to track dynamic obstacles, whereas the snake model is employed for curbs. Results indicate that the proposed framework is robust under various environments and satisfies the requirements for online processing.

  7. Cloud computing strategies

    CERN Document Server

    Chorafas, Dimitris N

    2011-01-01

    A guide to managing cloud projects, Cloud Computing Strategies provides the understanding required to evaluate the technology and determine how it can be best applied to improve business and enhance your overall corporate strategy. Based on extensive research, it examines the opportunities and challenges that loom in the cloud. It explains exactly what cloud computing is, what it has to offer, and calls attention to the important issues management needs to consider before passing the point of no return regarding financial commitments.

  8. The Herschel Virgo Cluster Survey. XX. Dust and gas in the foreground Galactic cirrus

    CERN Document Server

    Bianchi, S; Smith, M W L; Fritz, J; Davies, J I; Haynes, M P; Giovanelli, R; Baes, M; Bocchio, M; Boissier, S; Boquien, M; Boselli, A; Casasola, V; Clark, C J R; De Looze, I; Alighieri, S di Serego; Grossi, M; Jones, A P; Hughes, T M; Hunt, L K; Madden, S; Magrini, L; Pappalardo, C; Ysard, N; Zibetti, S

    2016-01-01

    We study the correlation between far-infared/submm dust emission and atomic gas column density in order to derive the properties of the high Galactic latitude, low density, Milky Way cirrus in the foreground of the Virgo cluster of galaxies. Dust emission maps from 60 to 850 um are obtained from SPIRE observations carried out within the Herschel Virgo Cluster Survey, complemented by IRAS-IRIS and Planck-HFI maps. Data from the Arecibo legacy Fast ALFA Survey is used to derive atomic gas column densities for two broad velocity components, low and intermediate velocity clouds. Dust emissivities are derived for each gas component and each far-infared/submm band. For the low velocity clouds, we measure an average emissivity 0.79 +/- 0.08 times 1E-20 MJy sr^-1 cm^2 at 250 um. After fitting a modified blackbody to the available bands, we estimated a dust absorption cross-section 0.49 +/- 0.13 times 1E-25 cm^2 H^-1 at 250 um (with dust temperature T = 20.4 +/- 1.5 K and spectral index beta = 1.53 +/- 0.17). The resu...

  9. CloudSat Image of Tropical Thunderstorms Over Africa

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] Figure 1 CloudSat image of a horizontal cross-section of tropical clouds and thunderstorms over east Africa. The red colors are indicative of highly reflective particles such as water (rain) or ice crystals, which the blue indicates thinner clouds (such as cirrus). The flat green/blue lines across the bottom represent the ground signal. The vertical scale on the CloudS at Cloud Profiling Radar image is approximately 30 kilometers (19 miles). The brown line below the image indicates the relative elevation of the land surface. The inset image shows the CloudSat track relative to a Moderate Resolution Imaging Spectroradiometer (MODIS) visible image taken at nearly the same time.

  10. Detecting Super-Thin Clouds With Polarized Light

    Science.gov (United States)

    Sun, Wenbo; Videen, Gorden; Mishchenko, Michael I.

    2014-01-01

    We report a novel method for detecting cloud particles in the atmosphere. Solar radiation backscattered from clouds is studied with both satellite data and a radiative transfer model. A distinct feature is found in the angle of linear polarization of solar radiation that is backscattered from clouds. The dominant backscattered electric field from the clear-sky Earth-atmosphere system is nearly parallel to the Earth surface. However, when clouds are present, this electric field can rotate significantly away from the parallel direction. Model results demonstrate that this polarization feature can be used to detect super-thin cirrus clouds having an optical depth of only 0.06 and super-thin liquid water clouds having an optical depth of only 0.01. Such clouds are too thin to be sensed using any current passive satellite instruments.

  11. Sensitivity analysis of upwelling thermal radiance in presence of clouds

    Science.gov (United States)

    Subramanian, S. V.; Tiwari, S. N.; Suttles, J. T.

    1981-01-01

    Total upwelling radiance at the top of the atmosphere is evaluated theoretically in the presence of clouds. The influence of cloud heights, thicknesses and different cloud covers on the upwelling radiance is also investigated. The characteristics of the two cloud types considered in this study closely correspond to altocumulus and cirrus with the cloud emissivity as a function of its liquid water (or ice) content. For calculation of the integrated transmittance of atmospheric gases such as, H2O, CO2, O3, and N2O, the Quasi Random Band (QRB) model approach is adopted. Results are obtained in three different spectral ranges and are compared with the clearsky radiance results. It is found that the difference between the clearsky and cloudy radiance increases with increasing cloud height and liquid water content. This difference also decreases as the surface temperature approaches the value of the cloud top temperature.

  12. Cloud-type discrimination via multispectral textural analysis

    Science.gov (United States)

    Lamei, Niloufar; Hutchison, Keith D.; Crawford, Melba M.; Khazenie, Nahid

    1994-04-01

    In recent years, with the development of satellite and computer technology, Earth observation and atmospheric research have become highly dependent on digital imagery. One of the primary interests in digital image processing is the development of robust methods to perform feature detection, extraction, and classification. Until recently, classification methods for cloud discrimination were mainly based on the spectral information of the imagery. However, because of the spectral similarities of certain features (such as ice clouds and snow) and the effects of atmospheric attenuation, multispectral rule-based classifications do not necessarily produce accurate feature discrimination. Spectral homogeneity of two different features within a scene can lead to misclassification. Furthermore, the opposite problem can occur when one feature exhibits different spectral signatures locally but is homogeneous in its cyclic spatial variation. The exploration of spatial information is often advantageous in these discrimination problems. A texture- based method for feature identification has been investigated. This method uses a set of localized spatial filters known as 2-D Gabor functions. Gabor filters can be described as a sinusoidal plane wave within a 2-D Gaussian envelope. The frequency and orientation of the sine plane and the width of the Gaussian envelope are determine by the Gabor parameters. These tunable channels yield joint optimal information both in the spatial and the frequency domains. The new method has been applied to the thermal channels of the NOAA Advanced Very High Resolution Radiometer data for cloud-type discrimination. Results show that additional texture information improves discrimination between cloud types (especially thin cirrus).

  13. A Raman lidar at La Reunion (20.8° S, 55.5° E for monitoring water vapour and cirrus distributions in the subtropical upper troposphere: preliminary analyses and description of a future system

    Directory of Open Access Journals (Sweden)

    C. Hoareau

    2012-06-01

    Full Text Available A ground-based Rayleigh lidar has provided continuous observations of tropospheric water vapour profiles and cirrus cloud using a preliminary Raman channels setup on an existing Rayleigh lidar above La Reunion over the period 2002–2005. With this instrument, we performed a first measurement campaign of 350 independent water vapour profiles. A statistical study of the distribution of water vapour profiles is presented and some investigations concerning the calibration are discussed. Analysis regarding the cirrus clouds is presented and a classification has been performed showing 3 distinct classes. Based on these results, the characteristics and the design of a future lidar system, to be implemented at the new Reunion Island altitude observatory (2200 m for long-term monitoring, is presented and numerical simulations of system performance have been realised to compare both instruments.

  14. An explanation for some fallstreak clouds

    Directory of Open Access Journals (Sweden)

    R. M. Worthington

    Full Text Available Fallstreak cirrus clouds are associated with super-saturated air, together with waves, instabilities and/or turbulence; however, their precise cause is usually uncertain. This paper uses already-published satellite, radiosonde and radar data, reanalysed to study some large fallstreaks which had been previously overlooked. The fallstreaks – up to 60 km long with a parent cloud 20 km wide – are caused by lifting and/or turbulence from a mountain wave, rather than, for example, Kelvin-Helmholtz instabilities. If turbulent breaking of mountain waves affects ice particle formation, this may be relevant for the seeder-feeder effect on orographic rain, and the efficiency of mountain-wave polar stratospheric clouds for ozone depletion.

    Key words. Meteorology and atmospheric dynamics (turbulence; waves and tides – Atmospheric composition and structure (cloud physics and chemistry

  15. Extraction of Profile Information from Cloud Contaminated Radiances. Appendixes 2

    Science.gov (United States)

    Smith, W. L.; Zhou, D. K.; Huang, H.-L.; Li, Jun; Liu, X.; Larar, A. M.

    2003-01-01

    Clouds act to reduce the signal level and may produce noise dependence on the complexity of the cloud properties and the manner in which they are treated in the profile retrieval process. There are essentially three ways to extract profile information from cloud contaminated radiances: (1) cloud-clearing using spatially adjacent cloud contaminated radiance measurements, (2) retrieval based upon the assumption of opaque cloud conditions, and (3) retrieval or radiance assimilation using a physically correct cloud radiative transfer model which accounts for the absorption and scattering of the radiance observed. Cloud clearing extracts the radiance arising from the clear air portion of partly clouded fields of view permitting soundings to the surface or the assimilation of radiances as in the clear field of view case. However, the accuracy of the clear air radiance signal depends upon the cloud height and optical property uniformity across the two fields of view used in the cloud clearing process. The assumption of opaque clouds within the field of view permits relatively accurate profiles to be retrieved down to near cloud top levels, the accuracy near the cloud top level being dependent upon the actual microphysical properties of the cloud. The use of a physically correct cloud radiative transfer model enables accurate retrievals down to cloud top levels and below semi-transparent cloud layers (e.g., cirrus). It should also be possible to assimilate cloudy radiances directly into the model given a physically correct cloud radiative transfer model using geometric and microphysical cloud parameters retrieved from the radiance spectra as initial cloud variables in the radiance assimilation process. This presentation reviews the above three ways to extract profile information from cloud contaminated radiances. NPOESS Airborne Sounder Testbed-Interferometer radiance spectra and Aqua satellite AIRS radiance spectra are used to illustrate how cloudy radiances can be used

  16. The Atmospheric Infrared Sounder Version 6 cloud products

    Directory of Open Access Journals (Sweden)

    B. H. Kahn

    2013-06-01

    Full Text Available The Version 6 cloud products of the Atmospheric Infrared Sounder (AIRS and Advanced Microwave Sounding Unit (AMSU instrument suite are described. The cloud top temperature, pressure, and height and effective cloud fraction are now reported at the AIRS field of view (FOV resolution. Significant improvements in cloud height assignment over Version 5 are shown with pixel-scale comparisons to cloud vertical structure observed by the CloudSat 94 GHz radar and the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP. Cloud thermodynamic phase (ice, liquid, and unknown phase, ice cloud effective diameter (De, and ice cloud optical thickness (τ are derived using an optimal estimation methodology for AIRS FOVs, and global distributions for January 2007 are presented. The largest values of τ are found in the storm tracks and near convection in the Tropics, while De is largest on the equatorial side of the midlatitude storm tracks in both hemispheres, and lowest in tropical thin cirrus and the winter polar atmosphere. Over the Maritime Continent the diurnal cycle of τ is significantly larger than for the total cloud fraction, ice cloud frequency, and De, and is anchored to the island archipelago morphology. Important differences are described between northern and southern hemispheric midlatitude cyclones using storm center composites. The infrared-based cloud retrievals of AIRS provide unique, decadal-scale and global observations of clouds over the diurnal and annual cycles, and captures variability within the mesoscale and synoptic scales at all latitudes.

  17. Monitoring of the Polar Stratospheric Clouds formation and evolution in Antarctica in August 2007 during IPY with the MATCH method applied to lidar data

    Science.gov (United States)

    Montoux, Nadege; David, Christine; Klekociuk, Andrew; Pitts, Michael; di Liberto, Luca; Snels, Marcel; Jumelet, Julien; Bekki, Slimane; Larsen, Niels

    2010-05-01

    The project ORACLE-O3 ("Ozone layer and UV RAdiation in a changing CLimate Evaluated during IPY") is one of the coordinated international proposals selected for the International Polar Year (IPY). As part of this global project, LOLITA-PSC ("Lagrangian Observations with Lidar Investigations and Trajectories in Antarctica and Arctic, of PSC") is devoted to Polar Stratospheric Clouds (PSC) studies. Indeed, understanding the formation and evolution of PSC is an important issue to quantify the impact of climate changes on their frequency of formation and, further, on chlorine activation and subsequent ozone depletion. In this framework, three lidar stations performed PSC observations in Antarctica during the 2006, 2007, and 2008 winters: Davis (68.58°S, 77.97°E), McMurdo (77.86°S, 166.48°E) and Dumont D'Urville (66.67°S, 140.01°E). The data are completed with the lidar data from CALIOP ("Cloud-Aerosol Lidar with Orthogonal Polarization") onboard the CALIPSO ("Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation") satellite. Lagrangian trajectory calculations are used to identify air masses with PSCs sounded by several ground-based lidar stations with the same method, called MATCH, applied for the first time in Arctic to study the ozone depletion with radiosoundings. The evolution of the optical properties of the PSCs and thus the type of PSCs formed (supercooled ternary solution, nitric acid trihydrate particles or ice particles) could thus be linked to the thermodynamical evolution of the air mass deduced from the trajectories. A modeling with the microphysical model of the Danish Meteorological Institute allows assessing our ability to predict PSCs for various environmental conditions. Indeed, from pressure and temperature evolution, the model allows retrieving the types of particles formed as well as their mean radii, their concentrations and could also simulate the lidar signals. In a first step, a case in August 2007 around 17-18 km, involving

  18. Climatic Effects of Contrail Cirrus over the Western United States: A Regional Climate Model Investigation

    Science.gov (United States)

    Liou, K.; Ou, S. S.; Kim, J.; Gu, Y.; Yang, P.; Friedl, R. R.

    2009-12-01

    We investigate the impact of contrails and contrail induced cirrus clouds (CICC) on regional energy and water cycles over the Western United States (WUS), a region of both heavy air traffic and high climate sensitivity. Mountain snowpack in the WUS is a major source of warm-season water supply for Southern California and is highly sensitive to seasonal insolation variation, which can be significantly affected by the frequent presence of contrails/CICC. A regional climate model with an 18-km horizontal resolution based on the Weather Research and Forecast (WRF) model has been developed, which includes improved parameterizations of the optical properties of ice clouds and contrails in the Fu-Liou broadband radiative transfer model. The large-scale forcing data for driving regional climate simulations has been obtained from the NCEP/DOE re-analysis-2. We conduct multiple-year perpetual-spring climate runs to simulate the current climate conditions of the WUS and to investigate the climatic impact of contrails/CICC on radiative forcing, surface temperature, precipitation, and snowpack coverage. As a first approximation, we develop a linear correlation between available aviation emission data and contrail cover using the existing GCM results as proxy. Additionally, we use the ice crystal size spectrum and shape determined from the Subsonic Aircraft Contrail and Cloud Effects Special Study (SUCCESS) for calculations of the optical properties of contrails/CICC for input to the regional climate model. Preliminary simulation results and uncertainty analysis are presented in association with the effects of contrails/CICC cover and ice crystal size/shape on surface radiative forcing, surface temperature, and snow cover over the WUS in spring.

  19. 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.

  20. IBM Cloud Computing Powering a Smarter Planet

    Science.gov (United States)

    Zhu, Jinzy; Fang, Xing; Guo, Zhe; Niu, Meng Hua; Cao, Fan; Yue, Shuang; Liu, Qin Yu

    With increasing need for intelligent systems supporting the world's businesses, Cloud Computing has emerged as a dominant trend to provide a dynamic infrastructure to make such intelligence possible. The article introduced how to build a smarter planet with cloud computing technology. First, it introduced why we need cloud, and the evolution of cloud technology. Secondly, it analyzed the value of cloud computing and how to apply cloud technology. Finally, it predicted the future of cloud in the smarter planet.

  1. 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.

  2. Satellite retrieval of cloud condensation nuclei concentrations by using clouds as CCN chambers

    Science.gov (United States)

    Rosenfeld, Daniel; Zheng, Youtong; Hashimshoni, Eyal; Pöhlker, Mira L.; Jefferson, Anne; Pöhlker, Christopher; Yu, Xing; Zhu, Yannian; Liu, Guihua; Yue, Zhiguo; Fischman, Baruch; Li, Zhanqing; Giguzin, David; Goren, Tom; Artaxo, Paulo; Pöschl, Ulrich

    2016-01-01

    Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Validation against ground-based CCN instruments at Oklahoma, at Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25° restricts the satellite coverage to ∼25% of the world area in a single day. PMID:26944081

  3. Directional, horizontal inhomogeneities of cloud optical thickness fields retrieved from ground-based and airbornespectral imaging

    Science.gov (United States)

    Schäfer, Michael; Bierwirth, Eike; Ehrlich, André; Jäkel, Evelyn; Werner, Frank; Wendisch, Manfred

    2017-02-01

    Clouds exhibit distinct horizontal inhomogeneities of their optical and microphysical properties, which complicate their realistic representation in weather and climate models. In order to investigate the horizontal structure of cloud inhomogeneities, 2-D horizontal fields of optical thickness (τ) of subtropical cirrus and Arctic stratus are investigated with a spatial resolution of less than 10 m. The 2-D τ-fields are derived from (a) downward (transmitted) solar spectral radiance measurements from the ground beneath four subtropical cirrus and (b) upward (reflected) radiances measured from aircraft above 10 Arctic stratus. The data were collected during two field campaigns: (a) Clouds, Aerosol, Radiation, and tuRbulence in the trade wind regime over BArbados (CARRIBA) and (b) VERtical Distribution of Ice in Arctic clouds (VERDI). One-dimensional and 2-D autocorrelation functions, as well as power spectral densities, are derived from the retrieved τ-fields. The typical spatial scale of cloud inhomogeneities is quantified for each cloud case. Similarly, the scales at which 3-D radiative effects influence the radiance field are identified. In most of the investigated cloud cases considerable cloud inhomogeneities with a prevailing directional structure are found. In these cases, the cloud inhomogeneities favour a specific horizontal direction, while across this direction the cloud is of homogeneous character. The investigations reveal that it is not sufficient to quantify horizontal cloud inhomogeneities using 1-D inhomogeneity parameters; 2-D parameters are necessary.

  4. Automatic cloud classification of whole sky images

    Directory of Open Access Journals (Sweden)

    A. Heinle

    2010-05-01

    Full Text Available The recently increasing development of whole sky imagers enables temporal and spatial high-resolution sky observations. One application already performed in most cases is the estimation of fractional sky cover. A distinction between different cloud types, however, is still in progress. Here, an automatic cloud classification algorithm is presented, based on a set of mainly statistical features describing the color as well as the texture of an image. The k-nearest-neighbour classifier is used due to its high performance in solving complex issues, simplicity of implementation and low computational complexity. Seven different sky conditions are distinguished: high thin clouds (cirrus and cirrostratus, high patched cumuliform clouds (cirrocumulus and altocumulus, stratocumulus clouds, low cumuliform clouds, thick clouds (cumulonimbus and nimbostratus, stratiform clouds and clear sky. Based on the Leave-One-Out Cross-Validation the algorithm achieves an accuracy of about 97%. In addition, a test run of random images is presented, still outperforming previous algorithms by yielding a success rate of about 75%, or up to 88% if only "serious" errors with respect to radiation impact are considered. Reasons for the decrement in accuracy are discussed, and ideas to further improve the classification results, especially in problematic cases, are investigated.

  5. Characterizing the Height Structure and Composition of a Boreal Forest Using an Individual Tree Crown Approach Applied to Photogrammetric Point Clouds

    Directory of Open Access Journals (Sweden)

    Benoît St-Onge

    2015-10-01

    Full Text Available Photogrammetric point clouds (PPC obtained by stereomatching of aerial photographs now have a resolution sufficient to discern individual trees. We have produced such PPCs of a boreal forest and delineated individual tree crowns using a segmentation algorithm applied to the canopy height model derived from the PPC and a lidar terrain model. The crowns were characterized in terms of height and species (spruce, fir, and deciduous. Species classification used the 3D shape of the single crowns and their reflectance properties. The same was performed on a lidar dataset. Results show that the quality of PPC data generally approaches that of airborne lidar. For pixel-based canopy height models, viewing geometry in aerial images, forest structure (dense vs. open canopies, and composition (deciduous vs. conifers influenced the quality of the 3D reconstruction of PPCs relative to lidar. Nevertheless, when individual tree height distributions were analyzed, PPC-based results were very similar to those extracted from lidar. The random forest classification (RF of individual trees performed better in the lidar case when only 3D metrics were used (83% accuracy for lidar, 79% for PPC. However, when 3D and intensity or multispectral data were used together, the accuracy of PPCs (89% surpassed that of lidar (86%.

  6. SSH-2 measurements of cirrus at 18-28 micrometers from the King Air during FIRE 2

    Science.gov (United States)

    Griffin, Michael K.

    1993-01-01

    In November of 1991, the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) Phase II cirrus study took place at Coffeyville, Kansas. The field experiment incorporated instrumentation from surface, aircraft, and satellite to attempt to define the optical, radiative, and microphysical characteristics of these high altitude, predominantly ice clouds. The NCAR King Air research aircraft was outfitted with a variety of radiative and microphysical instrumentation for the FIRE II project. Included for this project was the SSH-2, a 16-channel passive radiometer. The SSH-2 was originally designed as a space-qualified infrared (IR) temperature and water vapor sounder for deployment onboard the Defense Meteorological Satellite Program (DMSP) series of environmental satellites. For this experiment, only those channels associated with the water vapor profiling function have been examined although downwelling radiance measurements were taken at all channels during the project. With supporting information from the aircraft telemetry observations it may be possible to relate these SSH-2 measurements to cloud radiative and microphysical properties. The following sections will describe the spectral characteristics of the instrument, the calibration scheme used to convert the raw measured counts into calibrated radiances, and the case studies that will be covered in this paper. This will be followed by a discussion of the results of this preliminary investigation and a description of future work to be done.

  7. 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.

  8. Determination of Cloud Base Height, Wind Velocity, and Short-Range Cloud Structure Using Multiple Sky Imagers Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Dong [NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Schwartz, Stephen E. [Brookhaven National Lab. (BNL), Upton, NY (United States); Yu, Dantong [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-07-01

    Clouds are a central focus of the U.S. Department of Energy (DOE)’s Atmospheric System Research (ASR) program and Atmospheric Radiation Measurement (ARM) Climate Research Facility, and more broadly are the subject of much investigation because of their important effects on atmospheric radiation and, through feedbacks, on climate sensitivity. Significant progress has been made by moving from a vertically pointing (“soda-straw”) to a three-dimensional (3D) view of clouds by investing in scanning cloud radars through the American Recovery and Reinvestment Act of 2009. Yet, because of the physical nature of radars, there are key gaps in ARM's cloud observational capabilities. For example, cloud radars often fail to detect small shallow cumulus and thin cirrus clouds that are nonetheless radiatively important. Furthermore, it takes five to twenty minutes for a cloud radar to complete a 3D volume scan and clouds can evolve substantially during this period. Ground-based stereo-imaging is a promising technique to complement existing ARM cloud observation capabilities. It enables the estimation of cloud coverage, height, horizontal motion, morphology, and spatial arrangement over an extended area of up to 30 by 30 km at refresh rates greater than 1 Hz (Peng et al. 2015). With fine spatial and temporal resolution of modern sky cameras, the stereo-imaging technique allows for the tracking of a small cumulus cloud or a thin cirrus cloud that cannot be detected by a cloud radar. With support from the DOE SunShot Initiative, the Principal Investigator (PI)’s team at Brookhaven National Laboratory (BNL) has developed some initial capability for cloud tracking using multiple distinctly located hemispheric cameras (Peng et al. 2015). To validate the ground-based cloud stereo-imaging technique, the cloud stereo-imaging field campaign was conducted at the ARM Facility’s Southern Great Plains (SGP) site in Oklahoma from July 15 to December 24. As shown in Figure 1, the

  9. CLOUD COMPUTING SECURITY

    Directory of Open Access Journals (Sweden)

    Ştefan IOVAN

    2016-05-01

    Full Text Available Cloud computing reprentes the software applications offered as a service online, but also the software and hardware components from the data center.In the case of wide offerd services for any type of client, we are dealing with a public cloud. In the other case, in wich a cloud is exclusively available for an organization and is not available to the open public, this is consider a private cloud [1]. There is also a third type, called hibrid in which case an user or an organization might use both services available in the public and private cloud. One of the main challenges of cloud computing are to build the trust and ofer information privacy in every aspect of service offerd by cloud computingle. The variety of existing standards, just like the lack of clarity in sustenability certificationis not a real help in building trust. Also appear some questions marks regarding the efficiency of traditionsecurity means that are applied in the cloud domain. Beside the economic and technology advantages offered by cloud, also are some advantages in security area if the information is migrated to cloud. Shared resources available in cloud includes the survey, use of the "best practices" and technology for advance security level, above all the solutions offered by the majority of medium and small businesses, big companies and even some guvermental organizations [2].

  10. Direct Estimate of Cirrus Noise in Herschel Hi-GAL Images

    CERN Document Server

    Martin, P G; Roy, A; Bernard, J -P; Molinari, S; Billot, N; Brunt, C; Calzoletti, L; DiGiorgio, A M; Elia, D; Faustini, F; Joncas, G; Mottram, J C; Natoli, P; Noriega-Crespo, A; Paladini, R; Robitaille, J F; Strafella, F; Traficante, A; Veneziani, M

    2010-01-01

    In Herschel images of the Galactic plane and many star forming regions, a major factor limiting our ability to extract faint compact sources is cirrus confusion noise, operationally defined as the "statistical error to be expected in photometric measurements due to confusion in a background of fluctuating surface brightness". The histogram of the flux densities of extracted sources shows a distinctive faint-end cutoff below which the catalog suffers from incompleteness and the flux densities become unreliable. This empirical cutoff should be closely related to the estimated cirrus noise and we show that this is the case. We compute the cirrus noise directly, both on Herschel images from which the bright sources have been removed and on simulated images of cirrus with statistically similar fluctuations. We connect these direct estimates with those from power spectrum analysis, which has been used extensively to predict the cirrus noise and provides insight into how it depends on various statistical properties ...

  11. CO Signatures in Subtropical Convective Clouds and Anvils During CRYSTAL-FACE: An Analysis of Convective Transport and Entertainment Using Observations and a Cloud-Resolving Model

    Science.gov (United States)

    Lopez, Jimena P.; Fridlind, Ann M.; Jost, Hans-Jurg; Loewenstein, Max; Ackerman, Andrew S.; Campos, Teresa L.; Weinstock, Elliot M.; Sayres, David S.; Smith, Jessica B.; Pittman, Jasna V.; hide

    2006-01-01

    Convective systems are an important mechanism in the transport of boundary layer air into the upper troposphere. The Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) campaign, in July 2002, was developed as a comprehensive atmospheric mission to improve knowledge of subtropical cirrus systems and their roles in regional and global climate. In situ measurements of carbon monoxide (CO), water vapor (H20v), and total water (H20t) aboard NASA's . WB-57F aircraft and CO aboard the U.S. Navy's Twin Otter aircraft were obtained to study the role of convective transport. Three flights sampled convective outflow on 11, 16 and 29 July found varying degrees of CO enhancement relative to the fiee troposphere. A cloud-resolving model used the in situ observations and meteorological fields to study these three systems. Several methods of filtering the observations were devised here using ice water content, relative humidity with respect to ice, and particle number concentration as a means to statistically sample the model results to represent the flight tracks. A weighted histogram based on ice water content observations was then used to sample the simulations for the three flights. In addition, because the observations occurred in the convective outflow cirrus and not in the storm cores, the model was used to estimate the maximum CO within the convective systems. In general, anvil-level air parcels contained an estimated 20-40% boundary layer air in the analyzed storms.

  12. CO Signatures in Subtropical Convective Clouds and Anvils during CRYSTAL-FACE: An Analysis of Convective Transport and Entrainment using Observations and a Cloud-Resolving Model

    Science.gov (United States)

    Lopez, Jimena P.; Fridlind, Ann M.; Jost, Hans-Juerg; Loewenstein, Max; Ackerman, Andrew S.; Campos, Teresa L.; Weinstock, Elliot M.; Sayres, David S.; Smith, Jessica B.; Pittman, Jasna V.

    2006-01-01

    Convective systems are an important mechanism in the transport of boundary layer air into the upper troposphere. The Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) campaign, in July 2002, was developed as a comprehensive atmospheric mission to improve knowledge of subtropical cirrus systems and their roles in regional and global climate. In situ measurements of carbon monoxide (CO), water vapor (H2Ov), and total water (H2Ot) aboard NASA's WB-57F aircraft and CO aboard the U.S. Navy's Twin Otter aircraft were obtained to study the role of convective transport. Three flights sampled convective outflow on 11, 16 and 29 July found varying degrees of CO enhancement relative to the free troposphere. A cloud-resolving model used the in situ observations and meteorological fields to study these three systems. Several methods of filtering the observations were devised here using ice water content, relative humidity with respect to ice, and particle number concentration as a means to statistically sample the model results to represent the flight tracks. A weighted histogram based on ice water content observations was then used to sample the simulations for the three flights. In addition, because the observations occurred in the convective outflow cirrus and not in the storm cores, the model was used to estimate the maximum CO within the convective systems. In general, anvil-level air parcels contained an estimated 20-40% boundary layer air in the analyzed storms.

  13. Deep convective clouds at the tropopause

    Directory of Open Access Journals (Sweden)

    H. H. Aumann

    2010-07-01

    Full Text Available Data from the Advanced Infrared Sounder (AIRS on the EOS Aqua spacecraft identify thousands of cloud tops colder than 225 K, loosely referred to as Deep Convective Clouds (DCC. Many of these cloud tops have "inverted" spectra, i.e. areas of strong water vapor, CO2 and ozone opacity, normally seen in absorption, are now seen in emission. We refer to these inverted spectra as DCCi. They are found in about 0.4% of all spectra from the tropical oceans excluding the Western Tropical Pacific (WTP, 1.1% in the WTP. The cold clouds are the anvils capping thunderstorms and consist of optically thick cirrus ice clouds. The precipitation rate associated with DCCi suggests that imbedded in these clouds, protruding above them, and not spatially resolved by the AIRS 15 km FOV, are even colder bubbles, where strong convection pushes clouds to within 5 hPa of the pressure level of the tropopause cold point. Associated with DCCi is a local upward displacement of the tropopause, a cold "bulge", which can be seen directly in the brightness temperatures of AIRS and AMSU channels with weighting function peaking between 40 and 2 hPa, without the need for a formal temperature retrieval. The bulge is not resolved by the analysis in numerical weather prediction models. The locally cold cloud tops relative to the analysis give the appearance (in the sense of an "illusion" of clouds overshooting the tropopause and penetrating into the stratosphere. Based on a simple model of optically thick cirrus clouds, the spectral inversions seen in the AIRS data do not require these clouds to penetrate into the stratosphere. However, the contents of the cold bulge may be left in the lower stratosphere as soon as the strong convection subsides. The heavy precipitation and the distortion of the temperature structure near the tropopause indicate that DCCi are associated with intense storms. Significant long-term trends in the statistical properties of DCCi could be

  14. Search Cloud

    Science.gov (United States)

    ... of this page: https://medlineplus.gov/cloud.html Search Cloud To use the sharing features on this ... of Top 110 zoster vaccine Share the MedlinePlus search cloud with your users by embedding our search ...

  15. DIGITAL ERA: UTILIZE OF CLOUD COMPUTING TECHNOLOGY IN DIGITAL LIBRARY

    OpenAIRE

    T. RAGHUNADHA REDDY

    2012-01-01

    With the purpose of applying cloud computing to digital library, the paper initially describes cloud computing and analyzes current status of cloud computing in digital library. Then it proposes the architecture of cloud computing in digital library and summarises the application of cloud computing in digital library. Finally the author brings out the future improvement in digital library using cloud computing technology.

  16. Alpine cloud climatology using long-term NOAA-AVHRR satellite data

    Energy Technology Data Exchange (ETDEWEB)

    Kaestner, M.; Kriebel, K.T.

    2000-07-01

    Three different climates have been identified by our evaluation of AVHRR (advanced very high resolution radiometer) data using APOLLO (AVHRR processing scheme over land, clouds and ocean) for a five-years cloud climatology of the Alpine region. The cloud cover data from four layers were spatially averaged in boxes of 15 km by 14 km. The study area only comprises 540 km by 560 km, but contains regions with moderate, Alpine and Mediterranean climate. Data from the period July 1989 until December 1996 have been considered. The temporal resolution is one scene per day, the early afternoon pass, yielding monthly means of satellite derived cloud coverages 5% to 10% above the daily mean compared to conventional surface observation. At nonvegetated sites the cloudiness is sometimes significantly overestimated. Averaging high resolution cloud data seems to be superior to low resolution measurements of cloud properties and averaging is favourable in topographical homogeneous regions only. The annual course of cloud cover reveals typical regional features as foehn or temporal singularities as the so-called Christmas thaw. The cloud cover maps in spatially high resolution show local luff/lee features which outline the orography. Less cloud cover is found over the Alps than over the forelands in winter, an accumulation of thick cirrus is found over the High Alps and an accumulation of thin cirrus north of the Alps. (orig.)

  17. Ubiquity and impact of thin mid-level clouds in the tropics.

    Science.gov (United States)

    Bourgeois, Quentin; Ekman, Annica M L; Igel, Matthew R; Krejci, Radovan

    2016-08-17

    Clouds are crucial for Earth's climate and radiation budget. Great attention has been paid to low, high and vertically thick tropospheric clouds such as stratus, cirrus and deep convective clouds. However, much less is known about tropospheric mid-level clouds as these clouds are challenging to observe in situ and difficult to detect by remote sensing techniques. Here we use Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite observations to show that thin mid-level clouds (TMLCs) are ubiquitous in the tropics. Supported by high-resolution regional model simulations, we find that TMLCs are formed by detrainment from convective clouds near the zero-degree isotherm. Calculations using a radiative transfer model indicate that tropical TMLCs have a cooling effect on climate that could be as large in magnitude as the warming effect of cirrus. We conclude that more effort has to be made to understand TMLCs, as their influence on cloud feedbacks, heat and moisture transport, and climate sensitivity could be substantial.

  18. Two-moment Bulk Stratiform Cloud Microphysics in the Grid-point Atmospheric Model of IAP LASG (GAMIL)

    Institute of Scientific and Technical Information of China (English)

    SHI Xiangjun; WANG Bin; Xiaohong LIU; Minghuai WANG

    2013-01-01

    A two-moment bulk stratiform microphysics scheme,including recently developed physically-based droplet activation/ice nucleation parameterizations has been implemented into the Grid-point Atmospheric Model of IAP LASG (GAMIL) as an effort to enhance the model's capability to simulate aerosol indirect effects.Unlike the previous one-moment cloud microphysics scheme,the new scheme produces a reasonable representation of cloud particle size and number concentration.This scheme captures the observed spatial variations in cloud droplet number concentrations.Simulated ice crystal number concentrations in cirrus clouds qualitatively agree with in situ observations.The longwave and shortwave cloud forcings are in better agreement with observations.Sensitivity tests show that the column cloud droplet number concentrations calculated from two different droplet activation parameterizations are similar.However,ice crystal number concentration in mixed-phased clouds is sensitive to different heterogeneous ice nucleation formulations.The simulation with high ice crystal number concentration in mixed-phase clouds has less liquid water path and weaker cloud forcing.Furthermore,ice crystal number concentration in cirrus clouds is sensitive to different ice nucleation parameterizations.Sensitivity tests also suggest that the impact of pre-existing ice crystals on homogeneous freezing in old clouds should be taken into account.

  19. Applied Research and Design of the Cloud Media Platform%云媒体平台的应用研究与设计

    Institute of Scientific and Technical Information of China (English)

    孔彬

    2012-01-01

    三网融合为广电业务与云计算结合提供了良好的应用场景。介绍了适合云媒体平台开展的增值业务类型,分析了云媒体平台的系统架构,根据应用环境,给出了平台的整体设计,并实现了云媒体平台视频系统的数据流程,最后设计出云媒体平台的资源调度核心模块。%Triple play for the broadcasting business and cloud computing provides a good scenario. This article briefly describes the cloud media platform to carry out value-added type of business, and then analyze the sys- tem architecture of the cloud media platform, followed by the targeted application environment, given the over- all design of the platform, and cloud media platform video data processes, it is finally to design a cloud media platform for resource scheduling in the core module.

  20. A method for determination of cirrus extinction-to-backscatter ratio from CALIOP data

    Directory of Open Access Journals (Sweden)

    Zhang Jingbin

    2016-01-01

    Full Text Available We are presenting an empirical equation to retrieve cirrus lidar ratio by using CALIOP 532 nm level 1 data for nighttime cases. Retrieval results have non-relationship with cirrus multiple scattering effects and not affected by the error of transmission. The average CALIPSO 532 nm cirrus lidar ratio over Longitude 120+/- 10 and Latitude 25+/-10 for whole year of 2008 are 21.66±0.06sr for the year of 2008 respectively, with the maximum bias of 9.25% for the year 2008, the results is fairly stable and reasonable.

  1. Satellite-based 3D structure of cloud and aerosols over the Indian Monsoon region: implications for aerosol-cloud interaction

    Science.gov (United States)

    Dey, Sagnik; Sengupta, Kamalaika; Basil, George; Das, Sushant; Nidhi, Nidhi; Dash, S. K.; Sarkar, Arjya; Srivastava, Parul; Singh, Ajit; Agarwal, P.

    2012-11-01

    Accurate knowledge of vertical distributions of aerosol and cloud fields and their space-time variations are required to reduce the uncertainty in estimated climate forcing. Here, multi-sensor (both passive and active) data were used to construct the climatology of 3-D cloud and aerosol fields over the Indian monsoon region. Multilayer clouds are found to persist throughout the year, among which cumulus and stratocumulus dominate the low clouds and cirrus dominates the high clouds. A combination of passive stereo-technique (MISR) and radiometric technique (ISCPP) captures the multilayer cloud structure as revealed by active sensor CALIOP. Coexistence of low clouds throughout the year with high aerosol concentration beneath and above leads to a transition from increasing to decreasing cloud fraction with an increase in aerosol optical depth. Such transition is rapid in the monsoon season due to convergence of low clouds to form high clouds facilitated by high aerosol loading. Further, the regional climate model RegCM 4.1 has been used to examine aerosol-cloud interaction. The aerosol-induced changes of low cloud amount are under-estimated by the model. The observation-based seasonal climatology of aerosol and cloud fields presented here may help in improving the model simulations of cloud variability and associated rainfall.

  2. A methodology for in-situ and remote sensing of microphysical and radiative properties of contrails as they evolve into cirrus

    Directory of Open Access Journals (Sweden)

    H. M. Jones

    2012-03-01

    Full Text Available Contrails and especially their evolution into cirrus-like clouds are thought to have very important effects on local and global radiation budgets, though are generally not well represented in global climate models. Lack of contrail parameterisations is due to the limited availability of in situ contrail measurements which are difficult to obtain. Here we present a methodology for successful sampling and interpretation of contrail microphysical and radiative data using both in situ and remote sensing instrumentation on board the FAAM BAe146 UK research aircraft as part of the COntrails Spreading Into Cirrus (COSIC study.

    Forecast models were utilised to determine flight regions suitable for contrail formation and sampling; regions that were both free of cloud but showed a high probability of occurrence of air mass being supersaturated with respect to ice. The FAAM research aircraft, fitted with cloud microphysics probes and remote sensing instruments, formed a distinctive spiral-shaped contrail in the predicted area by flying in an orbit over the same ground position as the wind advected the contrails to the east. Parts of these contrails were sampled during the completion of four orbits, with sampled contrail regions being between 7 and 30 min old. Lidar measurements were useful for in-flight determination of the location and spatial extent of the contrails, and also to report extinction values that agreed well with those calculated from the microphysical data. A shortwave spectrometer was also able to detect the contrails, though the signal was weak due to the dispersion and evaporation of the contrails. Post-flight the UK Met Office NAME III dispersion model was successfully used as a tool for modelling the dispersion of the persistent contrail; determining its location and age, and determining when there was interference from other measured other aircraft contrails or when cirrus encroached on the area later in the flight.

  3. Cloud Interactions

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] Released 1 July 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth. Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms. This image was acquired during mid-spring near the North Pole. The linear water-ice clouds are now regional in extent and often interact with neighboring cloud system, as seen in this image. The bottom of the image shows how the interaction can destroy the linear nature. While the surface is still visible through most of the clouds, there is evidence that dust is also starting to enter the atmosphere. Image information: VIS instrument. Latitude 68.4, Longitude 258.8 East (101.2 West). 38 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara

  4. 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.

  5. Vertical microphysical profiles of convective clouds as a tool for obtaining aerosol cloud-mediated climate forcings

    Energy Technology Data Exchange (ETDEWEB)

    Rosenfeld, Daniel [Hebrew Univ. of Jerusalem (Israel)

    2015-12-23

    Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Developing and validating this methodology was possible thanks to the ASR/ARM measurements of CCN and vertical updraft profiles. Validation against ground-based CCN instruments at the ARM sites in Oklahoma, Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25º restricts the satellite coverage to ~25% of the world area in a single day. This methodology will likely allow overcoming the challenge of quantifying the aerosol indirect effect and facilitate a substantial reduction of the uncertainty in anthropogenic climate forcing.

  6. A combined spectral and object-based approach to transparent cloud removal in an operational setting for Landsat ETM+

    Science.gov (United States)

    Watmough, Gary R.; Atkinson, Peter M.; Hutton, Craig W.

    2011-04-01

    The automated cloud cover assessment (ACCA) algorithm has provided automated estimates of cloud cover for the Landsat ETM+ mission since 2001. However, due to the lack of a band around 1.375 μm, cloud edges and transparent clouds such as cirrus cannot be detected. Use of Landsat ETM+ imagery for terrestrial land analysis is further hampered by the relatively long revisit period due to a nadir only viewing sensor. In this study, the ACCA threshold parameters were altered to minimise omission errors in the cloud masks. Object-based analysis was used to reduce the commission errors from the extended cloud filters. The method resulted in the removal of optically thin cirrus cloud and cloud edges which are often missed by other methods in sub-tropical areas. Although not fully automated, the principles of the method developed here provide an opportunity for using otherwise sub-optimal or completely unusable Landsat ETM+ imagery for operational applications. Where specific images are required for particular research goals the method can be used to remove cloud and transparent cloud helping to reduce bias in subsequent land cover classifications.

  7. Terahertz Remote Sensing of Ice Clouds - Sensitivity on Ice Dielectric Properties

    Science.gov (United States)

    Mendrok, J.; Baron, P.; Kasai, Y.

    2007-12-01

    Initiated by current developments in terahertz sensor technology the application of instruments operating in the spectral region between 0.1 - 30 THz is considered for a number of remote sensing issues. Accounting for more than 50 percent of the outgoing longwave radiation and with the major component of cirrus radiative forcing in the far-infrared, satellite measurements in this spectral region will significantly support the determination of the radiation budget of the Earth. Furthermore, spanning the whole range of particle sizes found in tropospheric ice clouds, the Terahertz region bears the potential to complement existing methods and improve our knowlegde and understanding of those clouds. Both, determination of the Earth's radiation budget as well as retrieving ice cloud properties require appropriately accurate calculations of radiative transfer. Hence, a good knowledge of the input parameters to the radiative transfer models is needed. In particular, this includes spectrally dependent properties of the molecular as well as particulate atmospheric matter, i.e., spectroscopic parameters of the molecular absorption lines and continua as well as the dielectric properties of aerosol and cloud particle material. Due to the lack of Terahertz light source and receiver technology in the past, measurements of these parameters have been sparse and the knowledge about them is rather poor. In preparation to evaluate the feasibility of monitoring tropospheric ice clouds using passive Terahertz observations, we study the modeling uncertainties due to the unconfident knowledge of the complex refractive index of ice. We give an overview of the consistency and discrepancies, respectively, of the existing measurements and models for ice refractive index in the Terahertz region. Using calculations of particle optical properties according to Mie theory as well as the radiative transfer models Moliere and SARTre, we estimate the deviations in particle optical properties and

  8. An improved ice cloud formation parameterization in the EMAC model

    Science.gov (United States)

    Bacer, Sara; Pozzer, Andrea; Karydis, Vlassis; Tsimpidi, Alexandra; Tost, Holger; Sullivan, Sylvia; Nenes, Athanasios; Barahona, Donifan; Lelieveld, Jos

    2017-04-01

    Cirrus clouds cover about 30% of the Earth's surface and are an important modulator of the radiative energy budget of the atmosphere. Despite their importance in the global climate system, there are still large uncertainties in understanding the microphysical properties and interactions with aerosols. Ice crystal formation is quite complex and a variety of mechanisms exists for ice nucleation, depending on aerosol characteristics and environmental conditions. Ice crystals can be formed via homogeneous nucleation or heterogeneous nucleation of ice-nucleating particles in different ways (contact, immersion, condensation, deposition). We have implemented the computationally efficient cirrus cloud formation parameterization by Barahona and Nenes (2009) into the EMAC (ECHAM5/MESSy Atmospheric Chemistry) model in order to improve the representation of ice clouds and aerosol-cloud interactions. The parameterization computes the ice crystal number concentration from precursor aerosols and ice-nucleating particles accounting for the competition between homogeneous and heterogeneous nucleation and among different freezing modes. Our work shows the differences and the improvements obtained after the implementation with respect to the previous version of EMAC.

  9. Martian Clouds

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] Released 28 June 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth. Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms. This image was acquired during early spring near the North Pole. The linear 'ripples' are transparent water-ice clouds. This linear form is typical for polar clouds. The black regions on the margins of this image are areas of saturation caused by the build up of scattered light from the bright polar material during the long image exposure. Image information: VIS instrument. Latitude 68.1, Longitude 147.9 East (212.1 West). 38 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip

  10. Particles and cirrus clouds (PAZI-2). Final report (2004-2007)

    Energy Technology Data Exchange (ETDEWEB)

    Kaercher, B. (ed.)

    2008-06-27

    Led by the DLR Institute for Atmospheric Physics, several DLR institutes in Stuttgart and Cologne studied effects of aircraft soot emissions and aviation-induced contrails on climate in concert with partners from the Helmholtz Society (HGF) and from universities and industry. The complex issues have been tackled on the one hand with laboratory and aircraft-based measurements as well as investigations using the high pressure combustion test rig (HBKS). On the other hand, the formation of soot from fuel combustion and the evolution of climate have been studied by means of comprehensive numerical simulations using the DLR-Theta and ECHAM4/DLR codes, respectively. The present report recalls the structure and major milestones and summarizes and assesses the main results of the project. New developments emerging from the project work are outlined. A list of references demonstrates the international visibility of the project in the atmospheric and soot-related research communities. (orig.)

  11. Cluster analysis of midlatitude oceanic cloud regimes: mean properties and temperature sensitivity

    Directory of Open Access Journals (Sweden)

    N. D. Gordon

    2010-07-01

    temperature advection in the warm and cold subsets to have near-median values in three layers of the troposphere. Across all of the seven clusters, we find that cloud fraction is smaller and cloud optical thickness is mostly larger for the warm subset. Cloud-top pressure is higher for the three low-level cloud regimes and lower for the cirrus regime. The net upwelling radiation flux at the top of the atmosphere is larger for the warm subset in every cluster except cirrus, and larger when averaged over all clusters. This implies that the direct response of midlatitude oceanic clouds to increasing temperature acts as a negative feedback on the climate system. Note that the cloud response to atmospheric dynamical changes produced by global warming, which we do not consider in this study, may differ, and the total cloud feedback may be positive.

  12. Cloud Computing Services Accounting

    Directory of Open Access Journals (Sweden)

    Igor Ruiz-Agundez

    2012-06-01

    Full Text Available Cloud computing provides a new promising parading to offer services. It brings the opportunity to develop new business models in the Internet. Classic accounting solutions fail to full fill the new requirements of these services due to their structural design. To understand these new constrains, we study the different actors and processes that interact in the Internet Economics. Specifically, we focus on cloud computing introducing a methodology that allows the deployment of cloud services. Further, we present an Infrastructure as a Service (IaaS use case that applies the proposed system.

  13. Tropical Warm Pool International Cloud Experiment (TWP-ICE): Cloud and Rain Characteristics in the Australian Monsoon

    Energy Technology Data Exchange (ETDEWEB)

    PT May; C Jakob; JH Mather

    2004-05-30

    The impact of oceanic convection on its environment and the relationship between the characteristics of the convection and the resulting cirrus characteristics is still not understood. An intense airborne measurement campaign combined with an extensive network of ground-based observations is being planned for the region near Darwin, Northern Australia, during January-February, 2006, to address these questions. The Tropical Warm Pool – International Cloud Experiment (TWP-ICE) will be the first field program in the tropics that attempts to describe the evolution of tropical convection, including the large scale heat, moisture, and momentum budgets, while at the same time obtaining detailed observations of cloud properties and the impact of the clouds on the environment. The emphasis will be on cirrus for the cloud properties component of the experiment. Cirrus clouds are ubiquitous in the tropics and have a large impact on their environment but the properties of these clouds are poorly understood. A crucial product from this experiment will be a dataset suitable to provide the forcing and testing required by cloud-resolving models and parameterizations in global climate models. This dataset will provide the necessary link between cloud properties and the models that are attempting to simulate them. The experiment is a collaboration between the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program, the Bureau of Meteorology (BoM), the National Aeronautics and Space Administration (NASA), the European Commission DG RTD-1.2, and several United States, Australian, Canadian, and European Universities. This experiment will be undertaken over a 4-week period in early 2006. January and February corresponds to the wet phase of the Australia monsoon. This season has been selected because, despite Darwin’s coastal location, the convection that occurs over and near Darwin at this time is largely of maritime origin with a large fetch over water

  14. Cloud Governance

    DEFF Research Database (Denmark)

    Berthing, Hans Henrik

    Denne præsentation beskriver fordele og værdier ved anvendelse af Cloud Computing. Endvidere inddrager resultater fra en række internationale analyser fra ISACA om Cloud Computing.......Denne præsentation beskriver fordele og værdier ved anvendelse af Cloud Computing. Endvidere inddrager resultater fra en række internationale analyser fra ISACA om Cloud Computing....

  15. 云计算在广播电视频率规划方面的应用构想%A Discussion on Applying Cloud Computing to Radio and Television Frequency Planning

    Institute of Scientific and Technical Information of China (English)

    陈颖; 孟瀑

    2016-01-01

    云计算作为一种可以将计算资源变为公用服务的技术理念,具有改变传统软件系统使用模式的潜力。然而云计算技术需要与实际业务应用相结合才能得到更充分的发挥。本文以广播电视频率规划工作为例,就云计算技术在特定业务领域的落地应用做一些探讨。%Nowadays, Cloud computing has become into a technical concept of providing computing resources as public service, which has such potential abilities to change the usage of traditional software system model. However, the advantages of Cloud computing techniques need to be combined with practical business applications to be maxi-mized. This paper aims to take radio and television frequency planning operation as an example to critically discuss the idea of applying cloud computing techniques to a certain practice process.

  16. Tracers and traceability: implementing the cirrus parameterisation from LACM in the TOMCAT/SLIMCAT chemistry transport model as an example of the application of quality assurance to legacy models

    Directory of Open Access Journals (Sweden)

    A. M. Horseman

    2010-03-01

    Full Text Available A new modelling tool for the investigation of large-scale behaviour of cirrus clouds has been developed. This combines two existing models, the TOMCAT/SLIMCAT chemistry transport model (nupdate library version 0.80, script mpc346_l and cirrus parameterisation of Ren and MacKenzie (LACM implementation not versioned. The development process employed a subset of best-practice software engineering and quality assurance processes, selected to be viable for small-scale projects whilst maintaining the same traceability objectives. The application of the software engineering and quality control processes during the development has been shown to be not a great overhead, and their use has been of benefit to the developers as well as the end users of the results. We provide a step-by-step guide to the implementation of traceability tailored to the production of geo-scientific research software, as distinct from commercial and operational software. Our recommendations include: maintaining a living "requirements list"; explicit consideration of unit, integration and acceptance testing; and automated revision/configuration control, including control of analysis tool scripts and programs.

    Initial testing of the resulting model against satellite and in-situ measurements has been promising. The model produces representative results for both spatial distribution of the frequency of occurrence of cirrus ice, and the drying of air as it moves across the tropical tropopause. The model is now ready for more rigorous quantitative testing, but will require the addition of a vertical wind velocity downscaling scheme to better represent extra-tropical continental cirrus.

  17. Tracers and traceability: implementing the cirrus parameterisation from LACM in the TOMCAT/SLIMCAT chemistry transport model as an example of the application of quality assurance to legacy models

    Directory of Open Access Journals (Sweden)

    A. M. Horseman

    2009-11-01

    Full Text Available A new modelling tool for the investigation of large-scale behaviour of cirrus clouds has been developed. This combines two existing models, the TOMCAT/SLIMCAT chemistry transport model (nupdate library version 0.80, script mpc346_l and cirrus parameterisation of Ren and MacKenzie (LACM implementation not versioned. The development process employed a subset of best-practice software engineering and quality assurance processes, selected to be viable for small-scale projects whilst maintaining the same traceability objectives. The application of the software engineering and quality control processes during the development has been shown to be not a great overhead, and their use has been of benefit to the developers as well as the end users of the results. We provide a step-by-step guide to the implementation of traceability tailored to the production of geo-scientific research software, as distinct from commercial and operational software. Our recommendations include: maintaining a living "requirements list"; explicit consideration of unit, integration and acceptance testing; and automated revision/configuration control, including control of analysis tool scripts and programs.

    Initial testing of the resulting model against satellite and in-situ measurements has been promising. The model produces representative results for both spatial distribution of the frequency of occurrence of cirrus ice, and the drying of air as it moves across the tropical tropopause. The model is now ready for more rigorous quantitative testing, but will require the addition of a vertical wind velocity downscaling scheme to better represent extra-tropical continental cirrus.

  18. Applied Research on the Enterprise Information Technology of Cloud Computing%云计算在企业信息化的应用

    Institute of Scientific and Technical Information of China (English)

    王石玉

    2012-01-01

    企业信息化管理和建设是提高企业综合实力的有效途径。云计算作为科学管理模式对加强企业的信息化建设愈显重要,在一定程度上减少了企业的运行成本、降低了经营风险、缩短了运行周期、改善了企业的信息化管理和建设、提高了企业整体效益,弥补了企业发展的缺陷。文中从云计算出发,阐述了云计算的概念、特点和技术,并对与计算的优势和缺陷进行探讨及分析,为云计算和企业的共同发展提供参考。%Enterprise information management and construction is an effective way to improve the enterprise's comprehensive strength. Cloud computing, an advanced scientific management mode, is becoming increasingly im-portant to the strengthening of the enterprise's information construction. To some extent, it reduces enterprise risk, shortens the cycle of business operation, improves enterprise information management and construction, improves their overall effectiveness, and makes up for the defects of the enterprise development, This paper introduces the concept, features and technologies of cloud calculation and analyzes the strengths and weaknesses of the calculation It serves as a reference for the common development of cloud computing and enterprises.

  19. Cloud optics

    CERN Document Server

    Kokhanovsky, A

    2006-01-01

    Clouds affect the climate of the Earth, and they are an important factor in the weather. Therefore, their radiative properties must be understood in great detail. This book summarizes current knowledge on cloud optical properties, for example their ability to absorb, transmit, and reflect light, which depends on the clouds' geometrical and microphysical characteristics such as sizes of droplets and crystals, their shapes, and structures. In addition, problems related to the image transfer through clouds and cloud remote sensing are addressed in this book in great detail. This book can be an im

  20. Lean computing for the cloud

    CERN Document Server

    Bauer, Eric

    2016-01-01

    Applies lean manufacturing principles across the cloud service delivery chain to enable application and infrastructure service providers to sustainably achieve the shortest lead time, best quality, and value This book focuses on lean in the context of cloud computing capacity management of applications and the physical and virtual cloud resources that support them. Lean Computing for the Cloud considers business, architectural and operational aspects of efficiently delivering valuable services to end users via cloud-based applications hosted on shared cloud infrastructure. The work also focuses on overall optimization of the service delivery chain to enable both application service and infrastructure service providers to adopt leaner, demand driven operations to serve end users more efficiently. The book’s early chapters analyze how capacity management morphs with cloud computing into interlocked physical infrastructure capacity management, virtual resou ce capacity management, and application capacity ma...

  1. Ice nucleation activity of diesel soot particles at Cirrus relevant conditions: Effects of hydration, secondary organics coating, hydration, soot morphology, and coagulation

    Energy Technology Data Exchange (ETDEWEB)

    Kulkarni, Gourihar R.; China, Swarup; Liu, Shang; Nandasiri, Manjula I.; Sharma, Noopur; Wilson, Jacqueline M.; Aiken, A. C.; Chand, Duli; Laskin, Alexander; Mazzoleni, Claudio; Pekour, Mikhail S.; Shilling, John E.; Shutthanandan, V.; Zelenyuk, Alla; Zaveri, Rahul A.

    2016-04-16

    The role of atmospheric relevant soot particles that are processed in the atmosphere toward ice nucleation at cirrus cloud condition is poorly understood. In this study, the ice nucleating properties of diesel soot particles subjected to various physical and chemical aging treatments were investigated at temperatures ranging from -40 to -50 °C. We show that bare soot particles nucleate ice in deposition mode, but coating with secondary organics suppresses the heterogeneous ice nucleation potential of soot particles requiring homogeneous freezing threshold conditions. However, the ice nucleation efficiency of soot particles coated with an aqueous organic layer was similar to bare soot particles. Hydration of bare soot particles slightly enhanced the ice nucleation efficiency, and the IN abilities of compact soot particles (roundness = ~ 0.6) were similar to bare lacey soot particles (roundness = ~ 0.4). These results indicate that ice nucleation properties are sensitive to the various aging treatments.

  2. Cloud Computing Technology Applied in the Human Resource Management System%云计算技术在人力资源管理系统中的应用

    Institute of Scientific and Technical Information of China (English)

    王燕

    2013-01-01

      随着科技的发展和知识经济时代的来临,企业管理者逐步认识到人力资源管理的信息化将成为未来发展的必然趋势。云计算技术作为新一代的资源共享利用模式,具有需求服务自助化、服务可计量化的特点。将云计算技术引入人力资源管理系统,可对人才招聘、绩效管理和薪酬管理等方面产生重大影响,人力资源管理工作将更加流程化、标准化和透明化。%With the development of technology and the knowledge economy era coming,enterprise managers gradually realize that human resource management information technology will become a trend.As one of the next generation of resource sharing modes,cloud computing technology has the feature that demand service is on self and can be measured.Putting the cloud computing technology into human resource management system,it will have significant impact on talent recruitment,performance management and compensation management so that human resources management will be more streamlined,standardized and transparent.

  3. 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

  4. 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.

  5. 应用于云计算中心的虚拟主机安全防护系统%A Virtual Host Protection System Applying to Cloud Computing Center

    Institute of Scientific and Technical Information of China (English)

    王茜; 朱志祥; 葛新; 杜迟

    2014-01-01

    A virtual host protection system applying to cloud computing center is constructed in this paper to guarantee the security of cloud computing. Virtualization calculation has the characteristics of being no boundary. According to this,the virtual host protection sys-tem provides a unified security for cloud computing by taking security-as-a-service as a starting point,the virtual machine as the core, and the virtual cluster as a unit. Customized security services are provided for different applications,multi-tenancy,and virtual hosts on the cloud computing platform. The security template is tailored to satisfy the different security needs. The security protection measures are realized by software,the security function is achieved by components,the deployment method becomes dynamic,the configuration man-agement becomes automatic,and the security disposal means are updated constantly. Then the adaptive security protection system integra-ting with a variety of security measures for cloud computing platform is built.%针对云计算环境下的安全防护问题,文中提出了一种云计算中心虚拟主机安全防护系统。系统以“安全即服务冶为出发点,以虚拟机为核心,针对虚拟化计算无边界的特点,以虚拟机群为单位,提供统一的安全防护。为云平台下的不同应用、租户、虚拟主机提供定制化的安全服务,以安全防护模板的形式对不同的安全性需求进行量身定制,将安全防护措施软件化、安全功能组件化、部署方式动态化、配置管理自动化,使安全处置手段不断更新,从而建立起了集各种安全措施为一体的自适应云平台安全防护体系。

  6. Comparative Study on Cloud Parameter Estimation Among GOSAT/CAI, MODIS, CALIPSO/CALIOP and Landsat-8/OLI with Laser Radar: Lidar as Truth Data

    Directory of Open Access Journals (Sweden)

    Kohei Arai

    2016-10-01

    Full Text Available A comparative study on cloud parameter estimation among GOSAT/CAI, MODIS, CALIPSO/CALIOP and Landsat-8/OLI is carried out using Laser Radar: Lidar as a truth data. Optical depth, size distribution, as well as cirrus type of clouds are cloud parameters. In particular, cirrus cloud detection is tough issue. 1.38 µm channel is required for its detection. Although MODIS and Landsat-8/OLI have such channel, the other mission instruments, CAI and CALIPSO/CALIOP do not have such channel. As a truth data of cloud parameter, ground based Lidar is used in this comparative study. From the Lidar, backscattered echo signal and depolarization coefficient are obtained as a function of altitude. Therefore, cloud type, vertical profile can be derived from the Lidar data. CALIPSO/CALIOP is satellite based Lidar which allows observation of clouds from space. Although the directions of laser light emissions between CALIPSO/CALIOP and the ground based Lidar are different, their principles are same. Therefore, it is expected that CALIPSO/CALIOP data derived cloud parameters are similar to the ground based Lidar data derived cloud parameters. The experimental results show the aforementioned facts and are useful for improvement of cloud parameter estimation accuracy with several sensor data combinations.

  7. Icing Characteristics of Low Altitude, Supercooled Layer Clouds. Revision

    Science.gov (United States)

    1980-05-01

    Buffalo (BUF), NY, the upper layer appeared to be cirrus or cirro- stratus which provided about 30% sky cover in the two northern quadrants at this time...Aircraft still below cloud base at this altitude and position 13 mi south of BUF at the completion of the final data run for the day. Aircraft starL - ing...Otherwise the sky was cloudless with good ve;tical and horizontal visibility during the transit into Ohio. At about 1530 E.S.T., near Belleaire, Ohio, the

  8. 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 ...

  9. Cloud Computing

    CERN Document Server

    Antonopoulos, Nick

    2010-01-01

    Cloud computing has recently emerged as a subject of substantial industrial and academic interest, though its meaning and scope is hotly debated. For some researchers, clouds are a natural evolution towards the full commercialisation of grid systems, while others dismiss the term as a mere re-branding of existing pay-per-use technologies. From either perspective, 'cloud' is now the label of choice for accountable pay-per-use access to third party applications and computational resources on a massive scale. Clouds support patterns of less predictable resource use for applications and services a

  10. How to govern the cloud?

    NARCIS (Netherlands)

    Prüfer, J.; Diamond, S.; Wainwright, N.

    2013-01-01

    This paper applies economic governance theory to the cloud computing industry. We analyze which governance institution may be best suited to solve the problems stemming from asymmetric information about the true level of data protection, security, and accountability offered by cloud service provider

  11. Stereoscopic, thermal, and true deep cumulus cloud top heights

    Science.gov (United States)

    Llewellyn-Jones, D. T.; Corlett, G. K.; Lawrence, S. P.; Remedios, J. J.; Sherwood, S. C.; Chae, J.; Minnis, P.; McGill, M.

    2004-05-01

    We compare cloud-top height estimates from several sensors: thermal tops from GOES-8 and MODIS, stereoscopic tops from MISR, and directly measured heights from the Goddard Cloud Physics Lidar on board the ER-2, all collected during the CRYSTAL-FACE field campaign. Comparisons reveal a persistent 1-2 km underestimation of cloud-top heights by thermal imagery, even when the finite optical extinctions near cloud top and in thin overlying cirrus are taken into account. The most severe underestimates occur for the tallest clouds. The MISR "best-sinds" and lidar estimates disagree in very similar ways with thermally estimated tops, which we take as evidence of excellent performance by MISR. Encouraged by this, we use MISR to examine variations in cloud penetration and thermal top height errors in several locations of tropical deep convection over multiple seasons. The goals of this are, first, to learn how cloud penetration depends on the near-tropopause environment; and second, to gain further insight into the mysterious underestimation of tops by thermal imagery.

  12. Managing Clouds in Cloud Platforms

    CERN Document Server

    Ahmat, Kamal A

    2010-01-01

    Managing cloud services is a fundamental challenge in todays virtualized environments. These challenges equally face both providers and consumers of cloud services. The issue becomes even more challenging in virtualized environments that support mobile clouds. Cloud computing platforms such as Amazon EC2 provide customers with flexible, on demand resources at low cost. However, they fail to provide seamless infrastructure management and monitoring capabilities that many customers may need. For instance, Amazon EC2 doesn't fully support cloud services automated discovery and it requires a private set of authentication credentials. Salesforce.com, on the other hand, do not provide monitoring access to their underlying systems. Moreover, these systems fail to provide infrastructure monitoring of heterogenous and legacy systems that don't support agents. In this work, we explore how to build a cloud management system that combines heterogeneous management of virtual resources with comprehensive management of phys...

  13. Cloud computing theory and practice

    CERN Document Server

    Marinescu, Dan C

    2013-01-01

    Cloud Computing: Theory and Practice provides students and IT professionals with an in-depth analysis of the cloud from the ground up. Beginning with a discussion of parallel computing and architectures and distributed systems, the book turns to contemporary cloud infrastructures, how they are being deployed at leading companies such as Amazon, Google and Apple, and how they can be applied in fields such as healthcare, banking and science. The volume also examines how to successfully deploy a cloud application across the enterprise using virtualization, resource management and the ri

  14. Cloud Control

    Science.gov (United States)

    Ramaswami, Rama; Raths, David; Schaffhauser, Dian; Skelly, Jennifer

    2011-01-01

    For many IT shops, the cloud offers an opportunity not only to improve operations but also to align themselves more closely with their schools' strategic goals. The cloud is not a plug-and-play proposition, however--it is a complex, evolving landscape that demands one's full attention. Security, privacy, contracts, and contingency planning are all…

  15. Cloud Cover

    Science.gov (United States)

    Schaffhauser, Dian

    2012-01-01

    This article features a major statewide initiative in North Carolina that is showing how a consortium model can minimize risks for districts and help them exploit the advantages of cloud computing. Edgecombe County Public Schools in Tarboro, North Carolina, intends to exploit a major cloud initiative being refined in the state and involving every…

  16. Cloud Computing

    CERN Document Server

    Mirashe, Shivaji P

    2010-01-01

    Computing as you know it is about to change, your applications and documents are going to move from the desktop into the cloud. I'm talking about cloud computing, where applications and files are hosted on a "cloud" consisting of thousands of computers and servers, all linked together and accessible via the Internet. With cloud computing, everything you do is now web based instead of being desktop based. You can access all your programs and documents from any computer that's connected to the Internet. How will cloud computing change the way you work? For one thing, you're no longer tied to a single computer. You can take your work anywhere because it's always accessible via the web. In addition, cloud computing facilitates group collaboration, as all group members can access the same programs and documents from wherever they happen to be located. Cloud computing might sound far-fetched, but chances are you're already using some cloud applications. If you're using a web-based email program, such as Gmail or Ho...

  17. Comprehensive Evaluation Cloud Model for Ship Navigation Adaptability

    OpenAIRE

    Man Zhu; Y.Q. Wen; Zhou, C. H.; C.S. Xiao

    2014-01-01

    In this paper, using cloud model and Delphi, we build a comprehensive evaluation cloud model to solve the problems of qualitative description and quantitative transformation in ship navigation adaptability comprehensive evaluation. In the model, the normal cloud generator is used to find optimal cloud models of reviews and evaluation factors. The weight of each evaluation factor is determined by cloud model and Delphi. The floating cloud algorithm is applied to aggregate the bottom level’s ev...

  18. DIGITAL ERA: UTILIZE OF CLOUD COMPUTING TECHNOLOGY IN DIGITAL LIBRARY

    Directory of Open Access Journals (Sweden)

    T. RAGHUNADHA REDDY

    2012-09-01

    Full Text Available With the purpose of applying cloud computing to digital library, the paper initially describes cloud computing and analyzes current status of cloud computing in digital library. Then it proposes the architecture of cloud computing in digital library and summarises the application of cloud computing in digital library. Finally the author brings out the future improvement in digital library using cloud computing technology.

  19. Improvements in Representations of Cloud Microphysics for BBHRP and Models using Data Collected during M-PACE and TWP-ICE

    Energy Technology Data Exchange (ETDEWEB)

    Greg M. McFarquhar

    2010-02-22

    In our research we proposed to use data collected during the 2004 Mixed-Phase Arctic Cloud Experiment (MPACE) and the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE) to improve retrievals of ice and mixed-phase clouds, to improve our understanding of how cloud and radiative processes affect cloud life cycles, and to develop and test methods for using ARM data more effectively in model. In particular, we proposed to: 1) use MPACE in-situ data to determine how liquid water fraction and cloud ice and liquid effective radius (r{sub ei} and r{sub ew}) vary with temperature, normalized cloud altitude and other variables for Arctic mixed-phase clouds, and to use these data to evaluate the performance of model parameterization schemes and remote sensing retrieval algorithms; 2) calculate rei and size/shape distributions using TWP-ICE in-situ data, investigate their dependence on cirrus type (oceanic or continental anvils or cirrus not directly traced to convection), and develop and test representations for MICROBASE; 3) conduct fundamental research enhancing our understanding of cloud/radiative interactions, concentrating on effects of small crystals and particle shapes and sizes on radiation; and 4) improve representations of microphysical processes for models (fall-out, effective density, mean scattering properties, rei and rew) and provide them to ARM PIs. In the course of our research, we made substantial progress on all four goals.

  20. Turbulence in high latitude molecular clouds

    Science.gov (United States)

    Shore, S. N.; Larosa, T. N.; Magnani, L.; Chastain, R. J.; Costagliola, F.

    We summarize a continuing investigation of turbulence in high-latitude translucent molecular clouds. These low mass (~ 50 M(solar), nearby (~ 100 pc), non-star forming clouds appear to be condensing out of the atomic cirrus and must be forced by external dynamical processes, since they lack internal sources, for which we can distinguish the injection scale for the turbulence. We have now mapped three clouds -- MBM 3, MBM 16, and MBM 40 -- with high spatial (0.03 pc) and velocity resolution (<0.08 km/s) in 12CO(1-0) 13CO(1-0) (NRAO 12m and FCRAO). All three clouds show evidence for large-shear flows and we propose that the turbulent motions are powered by shear-flow instability. The densest gas is structured into filaments but the velocity profiles do not change in going across a filament indicating that shocks are not compressing the gas. The density field is more likely the result of thermal instability. The velocity-size relationship, a commonly used diagnostic of ISM turbulence, does not hold in these clouds: the linewidth does not increase with region size. The centroid velocity probability distribution function (PDF) is a more precise measure of turbulence. In these clouds the PDFs exhibit broad wings, consistent with a Lorentzian distribution and showing evidence non-Gaussian correlated processes. This is a clear signature of intermittency. We have also begun a mapping survey of CS (1-0), CS (2-1), H2CO, and HCO+ at Arecibo and OSO and willdiscuss results for the Polaris flare and L1512. We will also discusssome implications of these studies for the turbulent dissipation in these systems.

  1. Screaming Clouds

    Science.gov (United States)

    Fikke, Svein; Egill Kristjánsson, Jón; Nordli, Øyvind

    2017-04-01

    "Mother-of-pearl clouds" appear irregularly in the winter stratosphere at high northern latitudes, about 20-30 km above the surface of the Earth. The size range of the cloud particles is near that of visible light, which explains their extraordinary beautiful colours. We argue that the Norwegian painter Edvard Munch could well have been terrified when the sky all of a sudden turned "bloodish red" after sunset, when darkness was expected. Hence, there is a high probability that it was an event of mother-of-pearl clouds which was the background for Munch's experience in nature, and for his iconic Scream. Currently, the leading hypothesis for explaining the dramatic colours of the sky in Munch's famous painting is that the artist was captivated by colourful sunsets following the enormous Krakatoa eruption in 1883. After carefully considering the historical accounts of some of Munch's contemporaries, especially the physicist Carl Störmer, we suggest an alternative hypothesis, namely that Munch was inspired by spectacular occurrences of mother-of-pearl clouds. Such clouds, which have a wave-like structure akin to that seen in the Scream were first observed and described only a few years before the first version of this motive was released in 1892. Unlike clouds related to conventional weather systems in the troposphere, mother-of-pearl clouds appear in the stratosphere, where significantly different physical conditions prevail. This result in droplet sizes within the range of visible light, creating the spectacular colour patterns these clouds are famous for. Carl Störmer observed such clouds, and described them in minute details at the age of 16, but already with a profound interest in science. He later noted that "..these mother-of-pearl clouds was a vision of indescribable beauty!" The authors find it logical that the same vision could appear scaring in the sensible mind of a young artist unknown to such phenomena.

  2. An assessment of cloud top thermodynamic phase products obtained from A-Train passive and active sensors

    Directory of Open Access Journals (Sweden)

    S. Zeng

    2013-09-01

    Full Text Available The A-Train observations provide an unprecedented opportunity for the production of high quality dataset describing cloud properties. We illustrate in this study the use of one year of coincident POLDER (Polarization and Directionality of the Earth Reflectance, MODIS (MODerate Resolution Imaging Spectroradiometer and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization observations to establish a reference dataset for the description of cloud top thermodynamic phase at global scale. We present the results of an extensive comparison between POLDER and MODIS cloud top phase products and discuss those in view of cloud vertical structure and optical properties derived simultaneously from collocated CALIOP active measurements. These results allow to identify and quantify potential biases present in the 3 considered dataset. Among those, we discuss the impacts of observation geometry, thin cirrus in multilayered and single layered cloud systems, supercooled liquid droplets, aerosols, fractional cloud cover and snow/ice or bright surfaces on global statistics of cloud phase derived from POLDER and MODIS passive measurements. Based on these analysis we define criteria for the selection of high confidence cloud phase retrievals which in turn can serve for the establishment of a reference cloud phase product. This high confidence joint product derived from POLDER/PARASOL and MODIS/Aqua can be used in the future as a benchmark for the evaluation of other cloud climatologies, for the assessment of cloud phase representation in models and the development of better cloud phase parametrization in the general circulation models (GCMs.

  3. The retrieval of cloud microphysical properties using satellite measurements and an in situ database

    Directory of Open Access Journals (Sweden)

    Christophe Poix

    Full Text Available By combining AVHRR data from the NOAA satellites with information from a database of in situ measurements, large-scale maps can be generated of the microphysical parameters most immediately significant for the modelling of global circulation and climate. From the satellite data, the clouds can be classified into cumuliform, stratiform and cirrus classes and then into further sub-classes by cloud top temperature. At the same time a database of in situ measurements made by research aircraft is classified into the same sub-classes and a statistical analysis is used to derive relationships between the sub-classes and the cloud microphysical properties. These two analyses are then linked to give estimates of the microphysical properties of the satellite observed clouds. Examples are given of the application of this technique to derive maps of the probability of occurrence of precipitating clouds and of precipitating water content derived from a case study within the International Cirrus Experiment (ICE held in 1989 over the North Sea.

  4. Securing Cloud from Cloud Drain

    Directory of Open Access Journals (Sweden)

    Niva Das

    2014-09-01

    Full Text Available Today, in the world of communication, connected systems is growing at a rapid pace. To accommodate this growth the need for computational power and storage is also increasing at a similar rate. Companies are investing a large amount of resources in buying, maintaining and ensuring availability of the system to their customers. To mitigate these issues, cloud computing is playing a major role [1]. The underlying concept of cloud computing dates back to the ‘50s but the term entering into widespread usage can be traced to 2006 when Amazon.com announced the Elastic Compute Cloud. In this paper, we will discuss about cloud security approaches. We have used the term “CloudDrain” to define data leakage in case of security compromise.

  5. 75 FR 20516 - Special Conditions: Cirrus Design Corporation, Model SF50; Fire Extinguishing for Upper Aft...

    Science.gov (United States)

    2010-04-20

    ...; Fire Extinguishing for Upper Aft Fuselage Mounted Engine AGENCY: Federal Aviation Administration (FAA... the postcard and mail it back to you. Background On September 9, 2008, Cirrus Design Corporation... protect such installed engines from fires, were not envisioned in the development of the part 23...

  6. Statistical properties of the ice particle distribution in stratiform clouds

    Science.gov (United States)

    Delanoe, J.; Tinel, C.; Testud, J.

    2003-04-01

    This paper presents an extensive analysis of several microphysical data bases CEPEX, EUCREX, CLARE and CARL to determine statistical properties of the Particle Size Distribution (PSD). The data base covers different type of stratiform clouds : tropical cirrus (CEPEX), mid-latitude cirrus (EUCREX) and mid-latitude cirrus and stratus (CARL,CLARE) The approach for analysis uses the concept of normalisation of the PSD developed by Testud et al. (2001). The normalization aims at isolating three independent characteristics of the PSD : its "intrinsic" shape, the "average size" of the spectrum and the ice water content IWC, "average size" is meant the mean mass weighted diameter. It is shown that concentration should be normalized by N_0^* proportional to IWC/D_m^4. The "intrinsic" shape is defined as F(Deq/D_m)=N(Deq)/N_0^* where Deq is the equivalent melted diameter. The "intrinsic" shape is found to be very stable in the range 001.5, more scatter is observed, but future analysis should decide if it is representative of real physical variation or statistical "error" due to counting problem. Considering an overall statistics over the full data base, a large scatter of the N_0^* against Dm plot is found. But in the case of a particular event or a particular leg of a flight, the N_0^* vs. Dm plot is much less scattered and shows a systematic trend for decaying of N_0^* when Dm increases. This trend is interpreted as the manifestation of the predominance of the aggregation process. Finally an important point for cloud remote sensing is investigated : the normalised relationships IWC/N_0^* against Z/N_0^* is much less scattered that the classical IWC against Z the radar reflectivity factor.

  7. Cloud migration

    CERN Document Server

    Höllwarth, Tobias

    2012-01-01

    This book is designed for managers and entrepreneurs, who are considering improving the economics and flexibility of their IT solutions and infrastructures. The book is also for readers who wish to learn more about the Cloud, but do not want to become specialists.This book discusses the technical, legal, fiscal, economic, organisational and environmental aspects of Cloud services. If you are looking for practical advice on vendor selection and certification, as well as real world Cloud project case studies, this is the book to consult.It is the result of a highly cooper

  8. Cloud Computing

    CERN Document Server

    Baun, Christian; Nimis, Jens; Tai, Stefan

    2011-01-01

    Cloud computing is a buzz-word in today's information technology (IT) that nobody can escape. But what is really behind it? There are many interpretations of this term, but no standardized or even uniform definition. Instead, as a result of the multi-faceted viewpoints and the diverse interests expressed by the various stakeholders, cloud computing is perceived as a rather fuzzy concept. With this book, the authors deliver an overview of cloud computing architecture, services, and applications. Their aim is to bring readers up to date on this technology and thus to provide a common basis for d

  9. Numerical simulations of altocumulus with a cloud resolving model

    Energy Technology Data Exchange (ETDEWEB)

    Liu, S.; Krueger, S.K. [Univ. of Utah, Salt Lake City, UT (United States)

    1996-04-01

    Altocumulus and altostratus clouds together cover approximately 22% of the earth`s surface. They play an important role in the earth`s energy budget through their effect on solar and infrared radiation. However, there has been little altocumulus cloud investigation by either modelers or observational programs. Starr and Cox (SC) (1985a,b) simulated an altostratus case as part of the same study in which they modeled a thin layer of cirrus. Although this calculation was originally described as representing altostratus, it probably better represents altocumulus stratiformis. In this paper, we simulate altocumulus cloud with a cloud resolving model (CRM). We simply describe the CRM first. We calculate the same middle-level cloud case as SC to compare our results with theirs. We will look at the role of cloud-scale processes in response to large-scale forcing. We will also discuss radiative effects by simulating diurnal and nocturnal cases. Finally, we discuss the utility of a 1D model by comparing 1D simulations and 2D simulations.

  10. Aerosol Microphysical and Macrophysical Effects on Deep Convective Clouds

    Science.gov (United States)

    Yuan, T.; Li, Z.; Wilcox, E. M.; Oreopoulos, L.; Remer, L. A.; Yu, H.; Platnick, S. E.; Posselt, D. J.; Zhang, Z.; Martins, J. V.

    2014-12-01

    We illustrate a conceptual model of hydrometeor vertical development inside a convective cloud and its utility in studying of aerosol-DCC interactions. Both case studies and ensemble means are used to investigate aerosol-DCC interactions. We identify a few scenarios where possible signal of aerosol effect on DCC may be extracted. The results show a consistent and physically sound picture of aerosols affecting DCC microphysics as well as macrophysical properties. Specifically, pollutions and smokes are shown to consistently decrease ice particle size. On the contrary, dust particles close to source regions are shown to make cloud ice particle size more maritime like. We postulate that dust may achieve this by acting as either heterogeneous ice nuclei or giant cloud condensation nuclei. This contrast between smoke or pollution and dust also exists for their effects on cloud glaciation temperature. Smoke and pollution aerosols are shown to decrease glaciation temperature while dust particles do the opposite. Possible Implications of our results for studying aerosol indirect forcing, cirrus cloud properties, troposphere-stratosphere water vapor exchange and cloud latent heating are discussed.

  11. Star Formation and Molecular Clouds at High Galactic L