WorldWideScience

Sample records for volcanic aerosol cloud

  1. Strong Constraints on Aerosol-Cloud Interactions from Volcanic Eruptions

    Science.gov (United States)

    Malavelle, Florent F.; Haywood, Jim M.; Jones, Andy; Gettelman, Andrew; Clarisse, Lieven; Bauduin, Sophie; Allan, Richard P.; Karset, Inger Helene H.; Kristjansson, Jon Egill; Oreopoulos, Lazaros; hide

    2017-01-01

    Aerosols have a potentially large effect on climate, particularly through their interactions with clouds, but the magnitude of this effect is highly uncertain. Large volcanic eruptions produce sulfur dioxide, which in turn produces aerosols; these eruptions thus represent a natural experiment through which to quantify aerosol-cloud interactions. Here we show that the massive 2014-2015 fissure eruption in Holuhraun, Iceland, reduced the size of liquid cloud droplets - consistent with expectations - but had no discernible effect on other cloud properties. The reduction in droplet size led to cloud brightening and global-mean radiative forcing of around minus 0.2 watts per square metre for September to October 2014. Changes in cloud amount or cloud liquid water path, however, were undetectable, indicating that these indirect effects, and cloud systems in general, are well buffered against aerosol changes. This result will reduce uncertainties in future climate projections, because we are now able to reject results from climate models with an excessive liquid-water-path response.

  2. Cloud, Aerosol, and Volcanic Ash Retrievals Using ASTR and SLSTR with ORAC

    Science.gov (United States)

    McGarragh, Gregory; Poulsen, Caroline; Povey, Adam; Thomas, Gareth; Christensen, Matt; Sus, Oliver; Schlundt, Cornelia; Stapelberg, Stefan; Stengel, Martin; Grainger, Don

    2015-12-01

    The Optimal Retrieval of Aerosol and Cloud (ORAC) is a generalized optimal estimation system that retrieves cloud, aerosol and volcanic ash parameters using satellite imager measurements in the visible to infrared. Use of the same algorithm for different sensors and parameters leads to consistency that facilitates inter-comparison and interaction studies. ORAC currently supports ATSR, AVHRR, MODIS and SEVIRI. In this proceeding we discuss the ORAC retrieval algorithm applied to ATSR data including the retrieval methodology, the forward model, uncertainty characterization and discrimination/classification techniques. Application of ORAC to SLSTR data is discussed including the additional features that SLSTR provides relative to the ATSR heritage. The ORAC level 2 and level 3 results are discussed and an application of level 3 results to the study of cloud/aerosol interactions is presented.

  3. 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.

  4. Water-soluble material on aerosols collected within volcanic eruption clouds ( Fuego, Pacaya, Santiaguito, Guatamala).

    Science.gov (United States)

    Smith, D.B.; Zielinski, R.A.; Rose, W.I.; Huebert, B.J.

    1982-01-01

    In Feb. and March of 1978, filter samplers mounted on an aircraft were used to collect the aerosol fraction of the eruption clouds from three active Guatemalan volcanoes (Fuego, Pacaya, and Santiaguito). The elements dissolved in the aqueous extracts represent components of water-soluble material either formed directly in the eruption cloud or derived from interaction of ash particles and aerosol components of the plume. Calculations of enrichment factors, based upon concentration ratios, showed the elements most enriched in the extracts relative to bulk ash composition were Cd, Cu, V, F, Cl, Zn, and Pb.-from Authors

  5. Cloud radiative properties and aerosol - cloud interaction

    Science.gov (United States)

    Viviana Vladutescu, Daniela; Gross, Barry; Li, Clement; Han, Zaw

    2015-04-01

    The presented research discusses different techniques for improvement of cloud properties measurements and analysis. The need for these measurements and analysis arises from the high errors noticed in existing methods that are currently used in retrieving cloud properties and implicitly cloud radiative forcing. The properties investigated are cloud fraction (cf) and cloud optical thickness (COT) measured with a suite of collocated remote sensing instruments. The novel approach makes use of a ground based "poor man's camera" to detect cloud and sky radiation in red, green, and blue with a high spatial resolution of 30 mm at 1km. The surface-based high resolution photography provides a new and interesting view of clouds. As the cloud fraction cannot be uniquely defined or measured, it depends on threshold and resolution. However as resolution decreases, cloud fraction tends to increase if the threshold is below the mean, and vice versa. Additionally cloud fractal dimension also depends on threshold. Therefore these findings raise concerns over the ability to characterize clouds by cloud fraction or fractal dimension. Our analysis indicate that Principal Component analysis may lead to a robust means of quantifying cloud contribution to radiance. The cloud images are analyzed in conjunction with a collocated CIMEL sky radiometer, Microwave Radiometer and LIDAR to determine homogeneity and heterogeneity. Additionally, MFRSR measurements are used to determine the cloud radiative properties as a validation tool to the results obtained from the other instruments and methods. The cloud properties to be further studied are aerosol- cloud interaction, cloud particle radii, and vertical homogeneity.

  6. A Model Simulation of Pinatubo Volcanic Aerosols in the Stratosphere

    Science.gov (United States)

    Zhao , Jing-xia; Turco, Richard P.; Toon, Owen B.

    1995-01-01

    A one-dimensional, time-dependent model is used to study the chemical, microphysical, and radiative properties of volcanic aerosols produced by the Mount Pinatubo eruption on June 15, 1991. Our model treats gas-phase sulfur photochemistry, gas-to-particle conversion of sulfur, and the microphysics of sulfate aerosols and ash particles under stratospheric conditions. The dilution and diffusion of the volcanic eruption clouds are also accounted for in these conditions. Heteromolecular homogeneous and heterogeneous binary H2SO4/H2O nucleation, acid and water condensational growth, coagulation, and gravitational sedimentation are treated in detail in the model. Simulations suggested that after several weeks, the volcanic cloud was composed mainly of sulfuric acid/water droplets produced in situ from the SO2 emissions. The large amounts of SO2 (around 20 Mt) injected into the stratosphere by the Pinatubo eruption initiated homogeneous nucleation which generated a high concentration of small H2SO4/H2O droplets. These newly formed particles grew rapidly by condensation and coagulation in the first few months and then reach their stabilized sizes with effective radii in a range between 0.3 and 0.5 micron approximately one-half year after the eruption. The predicted volcanic cloud parameters reasonably agree with measurements in term of the vertical distribution and lifetime of the volcanic aerosols, their basic microphysical structures (e.g., size distribution, concentration, mass ratio, and surface area) and radiative properties. The persistent volcanic aerosols can produce significant anomalies in the radiation field, which have important climatic consequences. The large enhancement in aerosol surface area can result in measurable global stratospheric ozone depletion.

  7. Real Time Volcanic Cloud Products and Predictions for Aviation Alerts

    Science.gov (United States)

    Krotkov, Nickolay A.; Habib, Shahid; da Silva, Arlindo; Hughes, Eric; Yang, Kai; Brentzel, Kelvin; Seftor, Colin; Li, Jason Y.; Schneider, David; Guffanti, Marianne; Hoffman, Robert L.; Myers, Tim; Tamminen, Johanna; Hassinen, Seppo

    2014-01-01

    Volcanic eruptions can inject significant amounts of sulfur dioxide (SO2) and volcanic ash into the atmosphere, posing a substantial risk to aviation safety. Ingesting near-real time and Direct Readout satellite volcanic cloud data is vital for improving reliability of volcanic ash forecasts and mitigating the effects of volcanic eruptions on aviation and the economy. NASA volcanic products from the Ozone Monitoring Insrument (OMI) aboard the Aura satellite have been incorporated into Decision Support Systems of many operational agencies. With the Aura mission approaching its 10th anniversary, there is an urgent need to replace OMI data with those from the next generation operational NASA/NOAA Suomi National Polar Partnership (SNPP) satellite. The data provided from these instruments are being incorporated into forecasting models to provide quantitative ash forecasts for air traffic management. This study demonstrates the feasibility of the volcanic near-real time and Direct Readout data products from the new Ozone Monitoring and Profiling Suite (OMPS) ultraviolet sensor onboard SNPP for monitoring and forecasting volcanic clouds. The transition of NASA data production to our operational partners is outlined. Satellite observations are used to constrain volcanic cloud simulations and improve estimates of eruption parameters, resulting in more accurate forecasts. This is demonstrated for the 2012 eruption of Copahue. Volcanic eruptions are modeled using the Goddard Earth Observing System, Version 5 (GEOS-5) and the Goddard Chemistry Aerosol and Radiation Transport (GOCART) model. A hindcast of the disruptive eruption from Iceland's Eyjafjallajokull is used to estimate aviation re-routing costs using Metron Aviation's ATM Tools.

  8. Particle sedimentation and diffusive convection in volcanic ash-clouds

    Science.gov (United States)

    Carazzo, G.; Jellinek, A. M.

    2013-04-01

    Understanding the longevity of volcanic ash-clouds generated by powerful explosive eruptions is a long standing problem for assessing volcanic hazards and the nature and time scale of volcanic forcings on climate change. It is well known that the lateral spreading and longevity of these clouds is influenced by stratospheric winds, particle settling and turbulent diffusion. Observations of the recent 2010 Eyjafjallajökull and 2011 Grimsvötn umbrella clouds, as well as the structure of atmospheric aerosol clouds from the 1991 Mt Pinatubo event, suggest that an additional key process governing the cloud dynamics is the production of internal layering. Here, we use analog experiments on turbulent particle-laden umbrella clouds to show that this layering occurs where natural convection driven by particle sedimentation and the differential diffusion of primarily heat and fine particles give rise to a large scale instability. Where umbrella clouds are particularly enriched in fine ash, this "particle diffusive convection" strongly influences the cloud longevity. More generally, cloud residence time will depend on fluxes due to both individual settling and diffusive convection. We develop a new sedimentation model that includes both sedimentation processes, and which is found to capture real-time measurements of the rate of change of particle concentration in the 1982 El Chichon, 1991 Mt Pinatubo and 1992 Mt Spurr ash-clouds. A key result is that these combined sedimentation processes enhance the fallout of fine particles relative to expectations from individual settling suggesting that particle aggregation is not the only mechanism required to explain volcanic umbrella longevity.

  9. CALIPSO Observations of Aerosol Properties Near Clouds

    Science.gov (United States)

    Marshak, Alexander; Varnai, Tamas; Yang, Weidong

    2010-01-01

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

  10. Global simulations of aerosol processing in clouds

    Directory of Open Access Journals (Sweden)

    C. Hoose

    2008-12-01

    Full Text Available An explicit and detailed representation of in-droplet and in-crystal aerosol particles in stratiform clouds has been introduced in the global aerosol-climate model ECHAM5-HAM. The new scheme allows an evaluation of the cloud cycling of aerosols and an estimation of the relative contributions of nucleation and collision scavenging, as opposed to evaporation of hydrometeors in the global aerosol processing by clouds. On average an aerosol particle is cycled through stratiform clouds 0.5 times. The new scheme leads to important changes in the simulated fraction of aerosol scavenged in clouds, and consequently in the aerosol wet deposition. In general, less aerosol is scavenged into clouds with the new prognostic treatment than what is prescribed in standard ECHAM5-HAM. Aerosol concentrations, size distributions, scavenged fractions and cloud droplet concentrations are evaluated and compared to different observations. While the scavenged fraction and the aerosol number concentrations in the marine boundary layer are well represented in the new model, aerosol optical thickness, cloud droplet number concentrations in the marine boundary layer and the aerosol volume in the accumulation and coarse modes over the oceans are overestimated. Sensitivity studies suggest that a better representation of below-cloud scavenging, higher in-cloud collision coefficients, or a reduced water uptake by seasalt aerosols could reduce these biases.

  11. Global simulations of aerosol processing in clouds

    Directory of Open Access Journals (Sweden)

    C. Hoose

    2008-07-01

    Full Text Available An explicit and detailed representation of in-droplet and in-crystal aerosol particles in stratiform clouds has been introduced in the global aerosol-climate model ECHAM5-HAM. The new scheme allows an evaluation of the cloud cycling of aerosols and an estimation of the relative contributions of nucleation and collision scavenging, as opposed to evaporation of hydrometeors in the global aerosol processing by clouds. On average an aerosol particle is cycled through stratiform clouds 0.5 times. The new scheme leads to important changes in the simulated fraction of aerosol scavenged in clouds, and consequently in the aerosol wet deposition. In general, less aerosol is scavenged into clouds with the new prognostic treatment than what is prescribed in standard ECHAM5-HAM. Aerosol concentrations, size distributions, scavenged fractions and cloud droplet concentrations are evaluated and compared to different observations. While the scavenged fraction and the aerosol number concentrations in the marine boundary layer are well represented in the new model, aerosol optical thickness, cloud droplet number concentrations in the marine boundary layer and the aerosol volume in the accumulation and coarse modes over the oceans are overestimated. Sensitivity studies suggest that a better representation of below-cloud scavenging, higher in-cloud collision coefficients, or a reduced water uptake by seasalt aerosols could reduce these biases.

  12. Comparison of TOMS and AVHRR imagery of volcanic clouds

    Science.gov (United States)

    Rose, William I.

    1994-01-01

    This project consisted of merging volcanic cloud data from initial studies from TOMS and AVHRR sensors. Because of the different data acquisition platforms and processing algorithms and formats, the combination of the two data required special consideration. Once the registration technique was perfected, several eruptions with data from both sensors were studied. The conclusion showed that, from the initial work, the positions of the volcanic clouds as detected by the two sensors are very similar. Because the AVHRR algorithm is now capable of retrieving masses of ash and sulfate aerosol, the capability of comparing data from the two sensors now allows changes in SO2, H2SO4, and silicated ash in drifting clouds to be described. The results of this study culminated in several presentations, and a master's thesis, which in turn was converted into a paper submitted to the Journal of Geophysical Research. Abstracts of two presentations are attached.

  13. Importance of tropospheric volcanic aerosol for indirect radiative forcing of climate

    Directory of Open Access Journals (Sweden)

    A. Schmidt

    2012-03-01

    Full Text Available Observations and models have shown that continuously degassing volcanoes have a potentially large effect on the natural background aerosol loading and the radiative state of the atmosphere. Here, we use a global aerosol microphysics model to quantify the impact of these volcanic emissions on the cloud albedo radiative forcing under pre-industrial (PI and present-day (PD conditions. We find that volcanic degassing increases global annual mean cloud droplet number concentrations by 40% under PI conditions, but by only 10% under PD conditions. Consequently, volcanic degassing causes a global annual mean cloud albedo effect of −1.06 W m−2 in the PI era but only −0.56 W m−2 in the PD era. This non-equal effect is explained partly by the lower background aerosol concentrations in the PI era, but also because more aerosol particles are produced per unit of volcanic sulphur emission in the PI atmosphere. The higher sensitivity of the PI atmosphere to volcanic emissions has an important consequence for the anthropogenic cloud radiative forcing because the large uncertainty in volcanic emissions translates into an uncertainty in the PI baseline cloud radiative state. Assuming a −50/+100% uncertainty range in the volcanic sulphur flux, we estimate the annual mean anthropogenic cloud albedo forcing to lie between −1.16 W m−2 and −0.86 W m−2. Therefore, the volcanically induced uncertainty in the PI baseline cloud radiative state substantially adds to the already large uncertainty in the magnitude of the indirect radiative forcing of climate.

  14. The Aerosol/Cloud/Ecosystems Mission (ACE)

    Science.gov (United States)

    Schoeberl, Mark

    2008-01-01

    The goals and measurement strategy of the Aerosol/Cloud/Ecosystems Mission (ACE) are described. ACE will help to answer fundamental science questions associated with aerosols, clouds, air quality and global ocean ecosystems. Specifically, the goals of ACE are: 1) to quantify aerosol-cloud interactions and to assess the impact of aerosols on the hydrological cycle and 2) determine Ocean Carbon Cycling and other ocean biological processes. It is expected that ACE will: narrow the uncertainty in aerosol-cloud-precipitation interaction and quantify the role of aerosols in climate change; measure the ocean ecosystem changes and precisely quantify ocean carbon uptake; and, improve air quality forecasting by determining the height and type of aerosols being transported long distances. Overviews are provided of the aerosol-cloud community measurement strategy, aerosol and cloud observations over South Asia, and ocean biology research goals. Instruments used in the measurement strategy of the ACE mission are also highlighted, including: multi-beam lidar, multiwavelength high spectra resolution lidar, the ocean color instrument (ORCA)--a spectroradiometer for ocean remote sensing, dual frequency cloud radar and high- and low-frequency micron-wave radiometer. Future steps for the ACE mission include refining measurement requirements and carrying out additional instrument and payload studies.

  15. Global Analysis of Aerosol Properties Above Clouds

    Science.gov (United States)

    Waquet, F.; Peers, F.; Ducos, F.; Goloub, P.; Platnick, S. E.; Riedi, J.; Tanre, D.; Thieuleux, F.

    2013-01-01

    The seasonal and spatial varability of Aerosol Above Cloud (AAC) properties are derived from passive satellite data for the year 2008. A significant amount of aerosols are transported above liquid water clouds on the global scale. For particles in the fine mode (i.e., radius smaller than 0.3 m), including both clear sky and AAC retrievals increases the global mean aerosol optical thickness by 25(+/- 6%). The two main regions with man-made AAC are the tropical Southeast Atlantic, for biomass burning aerosols, and the North Pacific, mainly for pollutants. Man-made AAC are also detected over the Arctic during the spring. Mineral dust particles are detected above clouds within the so-called dust belt region (5-40 N). AAC may cause a warming effect and bias the retrieval of the cloud properties. This study will then help to better quantify the impacts of aerosols on clouds and climate.

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

    Science.gov (United States)

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

    2017-04-01

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

  17. Volcanic aerosols: Chemistry, evolution, and effects

    Science.gov (United States)

    Turco, Richard

    1991-01-01

    Stratospheric aerosols have been the subject of scientific speculation since the 1880s, when the powerful eruption of Krakatoa attracted worldwide attention to the upper atmosphere through spectacular optical displays. The presence of a permanent tenuous dust layer in the lower stratosphere was postulated in the 1920s following studies of the twilight glow. Junge collected the first samples of these 'dust' particles and demonstrated that they were actually composed of sulfates, most likely concentrated sulfuric acid (Junge and Manson, 1961; Junge, 1963). Subsequent research has been spurred by the realization that stratospheric particles can influence the surface climate of earth through their effects on atmospheric radiation. Such aerosols can also influence, through chemical and physical effects, the trace composition of the atmosphere, ozone concentrations, and atmospheric electrical properties. The properties of stratospheric aerosols (both the background particles and those enhanced by volcanic eruptions) were measured in situ by balloon ascents and high altitude aircraft sorties. The aerosols were also observed remotely from the ground and from satellites using both active (lidar) and passive (solar occultation) techniques (remote sensing instruments were carried on aircraft and balloon platforms as well). In connection with the experimental work, models were developed to test theories of particle formation and evolution, to guide measurement strategies, to provide a means of connecting laboratory and field data, and to apply the knowledge gained to answer practical questions about global changes in climate, depletion of the ozone layer, and related environmental problems.

  18. Microphysical, Macrophysical and Radiative Signatures of Volcanic Aerosols in Trade Wind Cumulus Observed by the A-Train

    Science.gov (United States)

    Yuan, T.; Remer, L. A.; Yu, H.

    2011-01-01

    Increased aerosol concentrations can raise planetary albedo not only by reflecting sunlight and increasing cloud albedo, but also by changing cloud amount. However, detecting aerosol effect on cloud amount has been elusive to both observations and modeling due to potential buffering mechanisms and convolution of meteorology. Here through a natural experiment provided by long-tem1 degassing of a low-lying volcano and use of A-Train satellite observations, we show modifications of trade cumulus cloud fields including decreased droplet size, decreased precipitation efficiency and increased cloud amount are associated with volcanic aerosols. In addition we find significantly higher cloud tops for polluted clouds. We demonstrate that the observed microphysical and macrophysical changes cannot be explained by synoptic meteorology or the orographic effect of the Hawaiian Islands. The "total shortwave aerosol forcin", resulting from direct and indirect forcings including both cloud albedo and cloud amount. is almost an order of magnitude higher than aerosol direct forcing alone. Furthermore, the precipitation reduction associated with enhanced aerosol leads to large changes in the energetics of air-sea exchange and trade wind boundary layer. Our results represent the first observational evidence of large-scale increase of cloud amount due to aerosols in a trade cumulus regime, which can be used to constrain the representation of aerosol-cloud interactions in climate models. The findings also have implications for volcano-climate interactions and climate mitigation research.

  19. Microphysical, macrophysical and radiative signatures of volcanic aerosols in trade wind cumulus observed by the A-Train

    Directory of Open Access Journals (Sweden)

    T. Yuan

    2011-07-01

    Full Text Available Increased aerosol concentrations can raise planetary albedo not only by reflecting sunlight and increasing cloud albedo, but also by changing cloud amount. However, detecting aerosol effect on cloud amount has been elusive to both observations and modeling due to potential buffering mechanisms and convolution of meteorology. Here through a natural experiment provided by long-term degassing of a low-lying volcano and use of A-Train satellite observations, we show modifications of trade cumulus cloud fields including decreased droplet size, decreased precipitation efficiency and increased cloud amount are associated with volcanic aerosols. In addition we find significantly higher cloud tops for polluted clouds. We demonstrate that the observed microphysical and macrophysical changes cannot be explained by synoptic meteorology or the orographic effect of the Hawaiian Islands. The "total shortwave aerosol forcin", resulting from direct and indirect forcings including both cloud albedo and cloud amount, is almost an order of magnitude higher than aerosol direct forcing alone. Furthermore, the precipitation reduction associated with enhanced aerosol leads to large changes in the energetics of air-sea exchange and trade wind boundary layer. Our results represent the first observational evidence of large-scale increase of cloud amount due to aerosols in a trade cumulus regime, which can be used to constrain the representation of aerosol-cloud interactions in climate models. The findings also have implications for volcano-climate interactions and climate mitigation research.

  20. Self-limiting physical and chemical effects in volcanic eruption clouds

    Science.gov (United States)

    Pinto, Joseph P.; Toon, Owen B.; Turco, Richard P.

    1989-01-01

    One-dimensional aerosol microphysical and photochemical models are used to study the chemistry of stratospheric volcanic clouds. The results indicate that the aerosol microphysical processes of condensation and coagulation produce larger particles as the SO2 injection rate is increased. Larger particles have a smaller optical depth per unit mass and settle out of the stratosphere at a faster rate than smaller ones, restricting the total number of particles in the stratosphere. The microphysical processes moderate the impact of volcanic clouds on the earth's radiation budget and climate, suggesting that volcanic effects may be self limiting. It is noted that the injection of HCl into the stratosphere, which could lead to large ozone changes, is limited by a cold trap effect in which HCl and water vapor condense on ash particles in the rising volcanic plume and fall out as ice.

  1. The Influence of Volcanic Aerosols on Planetary Habitability

    Science.gov (United States)

    Chen, Howard; Horton, Daniel Ethan

    2017-01-01

    On rocky planetary bodies such as Proxima Centuri b, the detection of sulphate aerosols may indicate volcanism and tectonic activity; ingredients hypothesized to be necessary for planetary habitability. However, due to the effect of atmospheric aerosols on a planet’s energy balance, coupled with eruption constituent and frequency uncertainties, the potential impact of volcanic activity on planetary habitability remains unresolved. Here, we employ multi-column climate models in conjunction with a parameter space approach to test the effect of volcanic aerosols on planetary climate with various climate sensitivities. Preliminary results indicate that volcanic activity could provide a means of extending the inner edge of the habitable zone (IHZ), depending on eruption constituents and frequency. Previous work using transit spectra simulations have demonstrated the possibility of detecting transient aerosols of volcanic origin. Our work investigates the range of habitability implications detection of such aerosols would imply.

  2. Aerosols, clouds and their climatic impacts

    Energy Technology Data Exchange (ETDEWEB)

    Kulmala, M.; Laaksonen, A.; Korhonen, P. [Helsinki Univ. (Finland). Dept. of Physics

    1995-12-31

    The increasing atmospheric concentrations of greenhouse gases such as carbon dioxide and methane may drive a significant warming of the earth`s climate. However, a topic of more recent attention is the possibility that increased atmospheric concentrations of aerosol particles might drive a cooling of the planet. There are two distinct cooling mechanisms related to the enhanced concentrations of aerosol particles: the increase in the direct reflection of solar radiation (the direct effect), and the increase in cloud reflectivity caused by greater numbers of cloud condensation nuclei available (the indirect effect). Aerosols and clouds play a major role in the scattering and absorption of radiation in the Earth`s atmosphere. Locally the net effect can vary because of different kinds of surfaces. But according to measurements, the global net effect of clouds (and aerosols) on the atmosphere is net cooling and thus in opposition to the effect of greenhouse gases. The prediction of the future evolution of the climate involves substantial uncertainties. Clouds have a major effect on the radiation balance of the Earth and the prediction of amount and radiative properties of clouds is very difficult. Also the formation mechanisms and residence times of aerosol particles in the atmosphere involve large uncertainties. Thus the most serious difficulties arise in the area of the physics of clouds and aerosols

  3. The Aerosol, Clouds and Ecosystem (ACE) Mission

    Science.gov (United States)

    Schoeberl, M.; Remer, L.; Kahn, R.; Starr, D.; Hildebrand, P.; Colarco, P.; Diner, D.; Vane, D.; Im, E.; Behrenfeld, M.; Stephens, G.; Maring, H.; Bontempi, P.; Martins, J. V.

    2008-12-01

    The Aerosol, Clouds and Ecosystem (ACE) Mission is a second tier Decadal Survey mission designed to characterize the role of aerosols in climate forcing, especially their impact on precipitation and cloud formation. ACE also includes ocean biosphere measurements (chlorophyll and dissolved organic materials) which will be greatly improved by simultaneous measurements of aerosols. The nominal ACE payload includes lidar and multiangle spectropolarimetric polarimetric measurements of aerosols, radar measurements of clouds and multi-band spectrometer for the measurement of ocean ecosystems. An enhancement to ACE payload under consideration includes µ-wave radiometer measurements of cloud ice and water outside the nadir path of the radar/lidar beams. This talk will cover ACE instrument and science options, updates on the science team definition activity and science potential.

  4. New capabilities for space-based cloud and aerosols measurements: The Cloud-Aerosol Transport System (CATS)

    Science.gov (United States)

    Yorks, J. E.; McGill, M. J.; Hlavka, D. L.; Palm, S. P.; Hart, W. D.; Nowottnick, E. P.; Vaughan, M.; Rodier, S. D.; Colarco, P. R.; da Silva, A.; Buchard-Marchant, V.

    2013-12-01

    Current uncertainties in cloud and aerosol properties limit our ability to accurately model the Earth's climate system and predict climate change. These limitations are due primarily to difficulties in adequately measuring aerosols and clouds on a global scale. NASA's A-Train satellites provide an unprecedented opportunity to address these uncertainties. In particular, the Cloud-Aerosol Lidar Infrared Pathfinder Spaceborne Observations (CALIPSO) satellite provides vertical profiles of cloud and aerosol properties. The CALIOP lidar onboard CALIPSO has reached its seventh year of operation, well past its expected lifetime. The ATLID lidar on EarthCARE is not expected to launch until 2016 or later. If the CALIOP lidar fails before a new mission is operational, there will be a gap in global lidar measurements. The Cloud-Aerosol Transport System (CATS), built at NASA Goddard Space Flight Center as a payload for the International Space Station (ISS), is set to launch in the summer of 2014. CATS is an elastic backscatter lidar with three wavelengths (1064, 532, 355 nm) and HSRL capability at 532 nm. Depolarization measurements will be made at all three wavelengths. The ISS orbit is a 51 degree inclination orbit at an altitude of about 405 km. This orbit provides more comprehensive coverage of the tropics and mid-latitudes than sun-synchronous orbiting sensors, with nearly a three day repeat cycle. Thus, science applications of CATS include cloud and aerosol climate studies, air quality monitoring, and smoke/volcanic plume tracking. The primary science objectives of CATS include: continuing the CALIPSO aerosol and cloud vertical profile data record, providing near real time data to support operational applications such as air quality modeling, and advancing technology in support of future mission development using the HSRL channel. Furthermore, the vertical profiles of cloud and aerosol properties provided by CATS will complement current and future passive satellite

  5. A framework for cloud - Aerosol interaction study

    NARCIS (Netherlands)

    Sarna, K.; Russchenberg, H.W.J.

    2012-01-01

    Aerosols can indirectly influence climate either by cloud albedo or lifetime effect. In order to have better understanding of these processes it is crucial to measure detailed vertical profiles of the radiative transfer and the microphysical evolution of clouds. Best results can be achieved by using

  6. A framework for cloud - Aerosol interaction study

    NARCIS (Netherlands)

    Sarna, K.; Russchenberg, H.W.J.

    2012-01-01

    Aerosols can indirectly influence climate either by cloud albedo or lifetime effect. In order to have better understanding of these processes it is crucial to measure detailed vertical profiles of the radiative transfer and the microphysical evolution of clouds. Best results can be achieved by using

  7. Cloud albedo increase from carbonaceous aerosol

    Directory of Open Access Journals (Sweden)

    W. R. Leaitch

    2010-08-01

    Full Text Available Airborne measurements from two consecutive days, analysed with the aid of an aerosol-adiabatic cloud parcel model, are used to study the effect of carbonaceous aerosol particles on the reflectivity of sunlight by water clouds. The measurements, including aerosol chemistry, aerosol microphysics, cloud microphysics, cloud gust velocities and cloud light extinction, were made below, in and above stratocumulus over the northwest Atlantic Ocean. On the first day, the history of the below-cloud fine particle aerosol was marine and the fine particle sulphate and organic carbon mass concentrations measured at cloud base were 2.4 μg m−3 and 0.9 μg m−3 respectively. On the second day, the below-cloud aerosol was continentally influenced and the fine particle sulphate and organic carbon mass concentrations were 2.3 μg m−3 and 2.6 μg m−3 respectively. Over the range 0.06–0.8 μm diameter, the shapes of the below-cloud size distributions were similar on both days and the number concentrations were approximately a factor of two higher on the second day. The cloud droplet number concentrations (CDNC on the second day were approximately three times higher than the CDNC measured on the first day. Using the parcel model to separate the influence of the differences in gust velocities, we estimate from the vertically integrated cloud light scattering measurements a 6% increase in the cloud albedo principally due to the increase in the carbonaceous components on the second day. Assuming no additional absorption by this aerosol, a 6% albedo increase translates to a local daytime radiative cooling of ∼12 W m−2. This result provides observational evidence that the role of anthropogenic carbonaceous components in the cloud albedo effect can be much larger than that of anthropogenic sulphate, as some global simulations have indicated.

  8. The effect of volcanic aerosols on the thermal infrared budget of the lower stratosphere

    Science.gov (United States)

    Charlock, T. P.

    1983-01-01

    The thermal IR heating of the stratosphere due to volcanic aerosols such as those released by the eruption of El Chichon is investigated by means of clear-sky model computations using a LOWTRAN5 radiance code (Kneizys et al., 1980) modified by Charlock (1983) to increase its vertical resolution. The results are presented graphically for 4-km-thick aerosol layers at altitudes 18, 22, and 25 km and at latitudes 0 deg and 35 deg N, and the effects of tropospheric cloud height (0-10 km) are taken into account. The aerosol-induced IR divergence is shown to depend on aerosol height and to be highly and nonlinearly sensitive to the location of underlying water clouds.

  9. Small volcanic eruptions and the stratospheric sulfate aerosol burden

    Science.gov (United States)

    Pyle, David M.

    2012-09-01

    Understanding of volcanic activity and its impacts on the atmosphere has evolved in discrete steps, associated with defining eruptions. The eruption of Krakatau, Indonesia, in August 1883 was the first whose global reach was recorded through observations of atmospheric phenomena around the world (Symons 1888). The rapid equatorial spread of Krakatau's ash cloud revealed new details of atmospheric circulation, while the vivid twilights and other optical phenomena were soon causally linked to the effects of particles and gases released from the volcano (e.g. Stothers 1996, Schroder 1999, Hamilton 2012). Later, eruptions of Agung, Bali (1963), El Chichón, Mexico (1982) and Pinatubo, Philippines (1991) led to a fuller understanding of how volcanic SO2 is transformed to a long-lived stratospheric sulfate aerosol, and its consequences (e.g. Meinel and Meinel 1967, Rampino and Self 1982, Hoffman and Rosen 1983, Bekki and Pyle 1994, McCormick et al 1995). While our ability to track the dispersal of volcanic emissions has been transformed since Pinatubo, with the launch of fleets of Earth-observing satellites (e.g. NASA's A-Train; ESA's MetOp) and burgeoning networks of ground-based remote-sensing instruments (e.g. lidar and sun-photometers; infrasound and lightning detection systems), there have been relatively few significant eruptions. Thus, there have been limited opportunities to test emerging hypotheses including, for example, the vexed question of the role of 'smaller' explosive eruptions in perturbations of the atmosphere—those that may just be large enough to reach the stratosphere (of size 'VEI 3', Newhall and Self 1982, Pyle 2000). Geological evidence, from ice-cores and historical eruptions, suggests that small explosive volcanic eruptions with the potential to transport material into the stratosphere should be frequent (5-10 per decade), and responsible for a significant proportion of the long-term time-averaged flux of volcanic sulfur into the stratosphere

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

    Science.gov (United States)

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

    2012-01-01

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

  11. Detection of volcanic sulfate aerosol with Envisat MIPAS shown for the Kasatochi, Sarychev, and Nabro eruptions

    Science.gov (United States)

    Griessbach, Sabine; Hoffmann, Lars; Spang, Reinhold; von Hobe, Marc; Müller, Rolf; Riese, Martin

    2013-04-01

    Stratospheric sulfate aerosol is known to have a strong impact on climate. Transport pathways of sulfur dioxide and sulfate aerosol to the stratosphere are still discussed. It is known that volcanic eruptions can inject significant amounts of sulfur directly into the stratosphere. Most sulfur, however, is injected into the troposphere and only a fraction of it can make its way into the stratosphere. Global and altitude resolved time series of observations are a valuable source of information for sulfur dioxide and sulfate aerosol detection. Here we present a new aerosol detection method for the infrared limb sounder Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the results for the Kasatochi, Sarychev, and Nabro eruptions. The new detection method utilizes three infrared window regions that are located around 830, 960, and 1224 cm-1. The combination of these three windows allows for a better detection of enhanced aerosol events in the troposphere as well as the discrimination from ice clouds. With this new method the 10 year record of MIPAS measurements was analyzed. The most remarkable sulfate aerosol events follow the Kasatochi, Sarychev, and Nabro eruptions. After these eruptions enhanced aerosol is detected in the upper troposphere and lower stratosphere (UTLS) region. Within one to two months it spreads over most of the northern hemisphere. In the tropics the aerosol reaches altitudes up to around 20 km and in the Arctic up to 15 km. The enhanced aerosol signal can be observed for about 5, 7, and up to 10 month for the Kasatochi, Sarychev, and Nabro eruptions, respectively. During this period the enhanced aerosol detections decrease in number, strength, and observation altitude. After the Nabro eruption on 13 June 2011 volcanic aerosol is detected in the UTLS region two days after the initial eruption. The following days the aerosol moves around the northern edge of the Asian monsoon region, is then transported southwards and later

  12. Global volcanic aerosol properties derived from emissions, 1990-2014, using CESM1(WACCM): VOLCANIC AEROSOLS DERIVED FROM EMISSIONS

    Energy Technology Data Exchange (ETDEWEB)

    Mills, Michael J. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Schmidt, Anja [School of Earth and Environment, University of Leeds, Leeds UK; Easter, Richard [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Solomon, Susan [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge Massachusetts USA; Kinnison, Douglas E. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Ghan, Steven J. [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Neely, Ryan R. [School of Earth and Environment, University of Leeds, Leeds UK; National Centre for Atmospheric Science, University of Leeds, Leeds UK; Marsh, Daniel R. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Conley, Andrew [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Bardeen, Charles G. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Gettelman, Andrew [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA

    2016-03-06

    Accurate representation of global stratospheric aerosol properties from volcanic and non-volcanic sulfur emissions is key to understanding the cooling effects and ozone-loss enhancements of recent volcanic activity. Attribution of climate and ozone variability to volcanic activity is of particular interest in relation to the post-2000 slowing in the apparent rate of global average temperature increases, and variable recovery of the Antarctic ozone hole. We have developed a climatology of global aerosol properties from 1990 to 2014 calculated based on volcanic and non-volcanic emissions of sulfur sources. We have complied a database of volcanic SO2 emissions and plume altitudes for eruptions between 1990 and 2014, and a new prognostic capability for simulating stratospheric sulfate aerosols in version 5 of the Whole Atmosphere Community Climate Model, a component of the Community Earth System Model. Our climatology shows remarkable agreement with ground-based lidar observations of stratospheric aerosol optical depth (SAOD), and with in situ measurements of aerosol surface area density (SAD). These properties are key parameters in calculating the radiative and chemical effects of stratospheric aerosols. Our SAOD climatology represents a significant improvement over satellite-based analyses, which ignore aerosol extinction below 15 km, a region that can contain the vast majority of stratospheric aerosol extinction at mid- and high-latitudes. Our SAD climatology significantly improves on that provided for the Chemistry-Climate Model Initiative, which misses 60% of the SAD measured in situ. Our climatology of aerosol properties is publicly available on the Earth System Grid.

  13. Smoke and Pollution Aerosol Effect on Cloud Cover

    Science.gov (United States)

    Kaufman, Yoram J.; Koren, Ilan

    2006-01-01

    Pollution and smoke aerosols can increase or decrease the cloud cover. This duality in the effects of aerosols forms one of the largest uncertainties in climate research. Using solar measurements from Aerosol Robotic Network sites around the globe, we show an increase in cloud cover with an increase in the aerosol column concentration and an inverse dependence on the aerosol absorption of sunlight. The emerging rule appears to be independent of geographical location or aerosol type, thus increasing our confidence in the understanding of these aerosol effects on the clouds and climate. Preliminary estimates suggest an increase of 5% in cloud cover.

  14. Dispersion of the Volcanic Sulfate Cloud from the Mount Pinatubo Eruption

    Science.gov (United States)

    Aquila, Valentina; Oman, Luke D.; Stolarski, Richard S.; Colarco, Peter R.; Newman, Paul A.

    2012-01-01

    We simulate the transport of the volcanic cloud from the 1991 eruption of Mount Pinatubo with the GEOS-5 general circulation model. Our simulations are in good agreement with observational data. We tested the importance of initial condition corresponding to the specific meteorological situation at the time of the eruption by employing reanalysis from MERRA. We found no significant difference in the transport of the cloud. We show how the inclusion of the interaction between volcanic sulfate aerosol and radiation is essential for a reliable simulation of the transport of the volcanic cloud. The absorption of long wave radiation by the volcanic sulfate induces a rising of the volcanic cloud up to the middle stratosphere, combined with divergent motion from the latitude of the eruption to the tropics. Our simulations indicate that the cloud diffuses to the northern hemisphere through a lower stratospheric pathway, and to mid- and high latitudes of the southern hemisphere through a middle stratospheric pathway, centered at about 30 hPa. The direction of the middle stratospheric pathway depends on the season. We did not detect any significant change of the mixing between tropics and mid- and high latitudes in the southern hemisphere.

  15. What do we need to know to model the microphysical evolution of volcanic clouds and how can we make these measurements?

    Science.gov (United States)

    English, J. M.; Toon, O. B.; Mills, M. J.

    2015-12-01

    Large volcanic eruptions can inject millions of tons of ash, sulfate and gaseous precursors into the stratosphere. The magnitude and duration of the volcanic cloud on Earth's temperatures, circulation, clouds, and stratospheric ozone is strongly affected by the microphysical properties of the aerosol size distribution, which can evolve in complex ways. This presentation will cover the impacts and uncertainties associated with microphysical aerosol measurements and modeling of the 1991 Mount Pinatubo eruption, and valuable future measurements after the next large volcanic eruption. These additional measurements can help improve our understanding of stratospheric processes as well as possible consequences of large volcanic eruptions and hypothetical geoengineering scenarios on radiative forcing and chemistry.

  16. Improved SAGE II cloud/aerosol categorization and observations of the Asian tropopause aerosol layer: 1989–2005

    Directory of Open Access Journals (Sweden)

    L. W. Thomason

    2013-05-01

    Full Text Available We describe the challenges associated with the interpretation of extinction coefficient measurements by the Stratospheric Aerosol and Gas Experiment (SAGE II in the presence of clouds. In particular, we have found that tropospheric aerosol analyses are highly dependent on a robust method for identifying when clouds affect the measured extinction coefficient. Herein, we describe an improved cloud identification method that appears to capture cloud/aerosol events more effectively than early methods. In addition, we summarize additional challenges to observing the Asian Tropopause Aerosol Layer (ATAL using SAGE II observations. Using this new approach, we perform analyses of the upper troposphere, focusing on periods in which the UTLS (upper troposphere/lower stratosphere is relatively free of volcanic material (1989–1990 and after 1996. Of particular interest is the Asian monsoon anticyclone where CALIPSO (Cloud-Aerosol Lidar Pathfinder Satellite Observations has observed an aerosol enhancement. This enhancement, called the ATAL, has a similar morphology to observed enhancements in long-lived trace gas species like CO. Since the CALIPSO record begins in 2006, the question of how long this aerosol feature has been present requires a new look at the long-lived SAGE II data sets despite significant hurdles to its use in the subtropical upper troposphere. We find that there is no evidence of ATAL in the SAGE II data prior to 1998. After 1998, it is clear that aerosol in the upper troposphere in the ATAL region is substantially enhanced relative to the period before that time. In addition, the data generally supports the presence of the ATAL beginning in 1999 and continuing through the end of the mission, though some years (e.g., 2003 are complicated by the presence of episodic enhancements most likely of volcanic origin.

  17. Microphysical processing of aerosol particles in orographic clouds

    Directory of Open Access Journals (Sweden)

    S. Pousse-Nottelmann

    2015-01-01

    Full Text Available An explicit and detailed treatment of cloud-borne particles allowing for the consideration of aerosol cycling in clouds has been implemented in the regional weather forecast and climate model COSMO. The effects of aerosol scavenging, cloud microphysical processing and regeneration upon cloud evaporation on the aerosol population and on subsequent cloud formation are investigated. For this, two-dimensional idealized simulations of moist flow over two bell-shaped mountains were carried out varying the treatment of aerosol scavenging and regeneration processes for a warm-phase and a mixed-phase orographic cloud. The results allowed to identify different aerosol cycling mechanisms. In the simulated non-precipitating warm-phase cloud, aerosol mass is incorporated into cloud droplets by activation scavenging and released back to the atmosphere upon cloud droplet evaporation. In the mixed-phase cloud, a first cycle comprises cloud droplet activation and evaporation via the Wegener-Bergeron-Findeisen process. A second cycle includes below-cloud scavenging by precipitating snow particles and snow sublimation and is connected to the first cycle via the riming process which transfers aerosol mass from cloud droplets to snow flakes. In the simulated mixed-phase cloud, only a negligible part of the total aerosol mass is incorporated into ice crystals. Sedimenting snow flakes reaching the surface remove aerosol mass from the atmosphere. The results show that aerosol processing and regeneration lead to a vertical redistribution of aerosol mass and number. However, the processes not only impact the total aerosol number and mass, but also the shape of the aerosol size distributions by enhancing the internally mixed/soluble accumulation mode and generating coarse mode particles. Concerning subsequent cloud formation at the second mountain, accounting for aerosol processing and regeneration increases the cloud droplet number concentration with possible

  18. Warming effect of dust aerosols modulated by overlapping clouds below

    Science.gov (United States)

    Xu, Hui; Guo, Jianping; Wang, Yuan; Zhao, Chuanfeng; Zhang, Zhibo; Min, Min; Miao, Yucong; Liu, Huan; He, Jing; Zhou, Shunwu; Zhai, Panmao

    2017-10-01

    Due to the substantial warming effect of dust aerosols overlying clouds and its poor representation in climate models, it is imperative to accurately quantify the direct radiative forcing (DRF) of above-cloud dust aerosols. When absorbing aerosol layers are located above clouds, the warming effect of aerosols strongly depends on the cloud macro- and micro-physical properties underneath, such as cloud optical depth and cloud fraction at visible wavelength. A larger aerosol-cloud overlap is believed to cause a larger warming effect of absorbing aerosols, but the influence of overlapping cloud fraction and cloud optical depth remains to be explored. In this study, the impact of overlapping cloud properties on the shortwave all-sky DRF due to springtime above-cloud dust aerosols is quantified over northern Pacific Ocean based on 10-year satellite measurements. On average, the DRF is roughly 0.62 Wm-2. Furthermore, the warming effect of dust aerosols linearly increases with both overlapping cloud fraction and cloud optical depth. An increase of 1% in overlapping cloud fraction will amplify this warming effect by 1.11 Wm-2τ-1. For the springtime northern Pacific Ocean, top-of-atmosphere cooling by dust aerosols turns into warming when overlapping cloud fraction is beyond 0.20. The variation of critical cloud optical depth beyond which dust aerosols switch from exerting a net cooling to a net warming effect depends on the concurrent overlapping cloud fraction. When the overlapping cloud coverage range increases from 0.2 to -0.4 to 0.6-0.8, the corresponding critical cloud optical depth reduces from 6.92 to 1.16. Our results demonstrate the importance of overlapping cloud properties for determining the springtime warming effect of dust aerosols.

  19. Microphysical processing of aerosol particles in orographic clouds

    Directory of Open Access Journals (Sweden)

    S. Pousse-Nottelmann

    2015-08-01

    aerosol cycling in clouds has been implemented into COSMO-Model, the regional weather forecast and climate model of the Consortium for Small-scale Modeling (COSMO. The effects of aerosol scavenging, cloud microphysical processing and regeneration upon cloud evaporation on the aerosol population and on subsequent cloud formation are investigated. For this, two-dimensional idealized simulations of moist flow over two bell-shaped mountains were carried out varying the treatment of aerosol scavenging and regeneration processes for a warm-phase and a mixed-phase orographic cloud. The results allowed us to identify different aerosol cycling mechanisms. In the simulated non-precipitating warm-phase cloud, aerosol mass is incorporated into cloud droplets by activation scavenging and released back to the atmosphere upon cloud droplet evaporation. In the mixed-phase cloud, a first cycle comprises cloud droplet activation and evaporation via the Wegener–Bergeron–Findeisen (WBF process. A second cycle includes below-cloud scavenging by precipitating snow particles and snow sublimation and is connected to the first cycle via the riming process which transfers aerosol mass from cloud droplets to snowflakes. In the simulated mixed-phase cloud, only a negligible part of the total aerosol mass is incorporated into ice crystals. Sedimenting snowflakes reaching the surface remove aerosol mass from the atmosphere. The results show that aerosol processing and regeneration lead to a vertical redistribution of aerosol mass and number. Thereby, the processes impact the total aerosol number and mass and additionally alter the shape of the aerosol size distributions by enhancing the internally mixed/soluble Aitken and accumulation mode and generating coarse-mode particles. Concerning subsequent cloud formation at the second mountain, accounting for aerosol processing and regeneration increases the cloud droplet number concentration with possible implications for the ice crystal number

  20. The Cloud-Aerosol Transport System (CATS): A New Lidar for Aerosol and Cloud Profiling from the International Space Station

    Science.gov (United States)

    Welton, Ellsworth J.; McGill, Mathew J.; Yorks. John E.; Hlavka, Dennis L.; Hart, William D.; Palm, Stephen P.; Colarco, Peter R.

    2012-01-01

    Spaceborne lidar profiling of aerosol and cloud layers has been successfully implemented during a number of prior missions, including LITE, ICESat, and CALIPSO. Each successive mission has added increased capability and further expanded the role of these unique measurements in wide variety of applications ranging from climate, to air quality, to special event monitoring (ie, volcanic plumes). Many researchers have come to rely on the availability of profile data from CALIPSO, especially data coincident with measurements from other A-Train sensors. The CALIOP lidar on CALIPSO continues to operate well as it enters its fifth year of operations. However, active instruments have more limited lifetimes than their passive counterparts, and we are faced with a potential gap in lidar profiling from space if the CALIOP lidar fails before a new mission is operational. The ATLID lidar on EarthCARE is not expected to launch until 2015 or later, and the lidar component of NASA's proposed Aerosols, Clouds, and Ecosystems (ACE) mission would not be until after 2020. Here we present a new aerosol and cloud lidar that was recently selected to provide profiling data from the International Space Station (ISS) starting in 2013. The Cloud-Aerosol Transport System (CATS) is a three wavelength (1064,532,355 nm) elastic backscatter lidar with HSRL capability at 532 nm. Depolarization measurements will be made at all wavelengths. The primary objective of CATS is to continue the CALIPSO aerosol and cloud profile data record, ideally with overlap between both missions and EarthCARE. In addition, the near real time (NRT) data capability ofthe ISS will enable CATS to support operational applications such as aerosol and air quality forecasting and special event monitoring. The HSRL channel will provide a demonstration of technology and a data testbed for direct extinction retrievals in support of ACE mission development. An overview of the instrument and mission will be provided, along with a

  1. Dark Targets, Aerosols, Clouds and Toys

    Science.gov (United States)

    Remer, L. A.

    2015-12-01

    Today if you use the Thomson-Reuters Science Citations Index to search for "aerosol*", across all scientific disciplines and years, with no constraints, and you sort by number of citations, you will find a 2005 paper published in the Journal of the Atmospheric Sciences in the top 20. This is the "The MODIS Aerosol Algorithm, Products and Validation". Although I am the first author, there are in total 12 co-authors who each made a significant intellectual contribution to the paper or to the algorithm, products and validation described. This paper, that algorithm, those people lie at the heart of a lineage of scientists whose collaborations and linked individual pursuits have made a significant contribution to our understanding of radiative transfer and climate, of aerosol properties and the global aerosol system, of cloud physics and aerosol-cloud interaction, and how to measure these parameters and maximize the science that can be obtained from those measurements. The 'lineage' had its origins across the globe, from Soviet Russia to France, from the U.S. to Israel, from the Himalayas, the Sahel, the metropolises of Sao Paulo, Taipei, and the cities of east and south Asia. It came together in the 1990s and 2000s at the NASA Goddard Space Flight Center, using cultural diversity as a strength to form a common culture of scientific creativity that continues to this day. The original algorithm has spawned daughter algorithms that are being applied to new satellite and airborne sensors. The original MODIS products have been fundamental to analyses as diverse as air quality monitoring and aerosol-cloud forcing. AERONET, designed originally for the need of validation, is now its own thriving institution, and the lineage continues to push forward to provide new technology for the coming generations.

  2. Distribution of sulfur aerosol precursors in the SPCZ released by continuous volcanic degassing at Ambrym, Vanuatu

    Science.gov (United States)

    Lefèvre, Jérôme; Menkes, Christophe; Bani, Philipson; Marchesiello, Patrick; Curci, Gabriele; Grell, Georg A.; Frouin, Robert

    2016-08-01

    The Melanesian Volcanic Arc (MVA) emits about 12 kT d- 1 of sulfur dioxide (SO2) to the atmosphere from continuous passive (non-explosive) volcanic degassing, which contributes 20% of the global SO2 emission from volcanoes. Here we assess, from up-to-date and long-term observations, the SO2 emission of the Ambrym volcano, one of the dominant volcanoes in the MVA, and we investigate its role as sulfate precursor on the regional distribution of aerosols, using both satellite observations and model results at 1° × 1° spatial resolution from WRF-Chem/GOCART. Without considering aerosol forcing on clouds, our model parameterizations for convection, vertical mixing and cloud properties provide a reliable chemical weather representation, making possible a cross-examination of model solution and observations. This preliminary work enables the identification of biases and limitations affecting both the model (missing sources) and satellite sensors and algorithms (for aerosol detection and classification) and leads to the implementation of improved transport and aerosol processes in the modeling system. On the one hand, the model confirms a 50% underestimation of SO2 emissions due to satellite swath sampling of the Ozone Monitoring Instrument (OMI), consistent with field studies. The OMI irregular sampling also produces a level of noise that impairs its monitoring capacity during short-term volcanic events. On the other hand, the model reveals a large sensitivity on aerosol composition and Aerosol Optical Depth (AOD) due to choices of both the source function in WRF-Chem and size parameters for sea-salt in FlexAOD, the post-processor used to compute offline the simulated AOD. We then proceed to diagnosing the role of SO2 volcanic emission in the regional aerosol composition. The model shows that both dynamics and cloud properties associated with the South Pacific Convergence Zone (SPCZ) have a large influence on the oxidation of SO2 and on the transport pathways of

  3. A cloud-resolving model study of aerosol-cloud correlation in a pristine maritime environment

    Science.gov (United States)

    Nishant, Nidhi; Sherwood, Steven C.

    2017-06-01

    In convective clouds, satellite-observed deepening or increased amount of clouds with increasing aerosol concentration has been reported and is sometimes interpreted as aerosol-induced invigoration of the clouds. However, such correlations can be affected by meteorological factors that affect both aerosol and clouds, as well as observational issues. In this study, we examine the behavior in a 660 × 660 km2 region of the South Pacific during June 2007, previously found by Koren et al. (2014) to show strong correlation between cloud fraction, cloud top pressure, and aerosols, using a cloud-resolving model with meteorological boundary conditions specified from a reanalysis. The model assumes constant aerosol loading, yet reproduces vigorous clouds at times of high real-world aerosol concentrations. Days with high- and low-aerosol loading exhibit deep-convective and shallow clouds, respectively, in both observations and the simulation. Synoptic analysis shows that vigorous clouds occur at times of strong surface troughs, which are associated with high winds and advection of boundary layer air from the Southern Ocean where sea-salt aerosol is abundant, thus accounting for the high correlation. Our model results show that aerosol-cloud relationships can be explained by coexisting but independent wind-aerosol and wind-cloud relationships and that no cloud condensation nuclei effect is required.

  4. Sulfur aerosol in the clouds of Venus

    Science.gov (United States)

    Krasnopolsky, Vladimir A.

    2016-08-01

    The photochemical model for the middle atmosphere of Venus (Krasnopolsky, V.A. [2012] Icarus, 218, 230-246) predicts sulfur aerosol as a product of the OCS photolysis at 55-60 km. The calculated mass loading is much smaller than that of the mode 1 particles in the upper cloud layer. The chemical kinetic model for the lower atmosphere (Krasnopolsky, V.A. [2013], Icarus, 225, 570-580) results in a constant mixing ratio of 20 ppm for OCS + XSX. This means the S8 mixing ratio of 2.5 ppm near the model upper boundary at 47 km. Using this abundance, the calculated profile of the sulfur aerosol has a bottom that coincides with the lower boundary of modes 2 and 3 and constitutes ∼10% of the total mass loading in the lower cloud layer. Sulfur aerosol cannot be the near UV absorber because its abundance is too low at the cloud tops and disagrees with the profile of the absorber observed by Venera 14.

  5. Global CALIPSO Observations of Aerosol Changes Near Clouds

    Science.gov (United States)

    Varnai, Tamas; Marshak, Alexander

    2011-01-01

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

  6. Climate impact of volcanic aerosol in the stratosphere and upper troposphere - CALIPSO observations from 2006-2015

    Science.gov (United States)

    Friberg, Johan; Martinsson, Bengt G.; Andersson, Sandra M.; Sandvik, Oscar S.; Hermann, Markus; van Velthoven, Peter F. J.; Zahn, Andreas

    2017-04-01

    We have investigated the climate impact of volcanic eruptions in the period 2006-2015, and found that the volcanic perturbations of the stratospheric aerosol is stronger and lasts longer than previously thought. Recent studies (Ridley et al., 2014, Andersson et al., 2015) show that a large portion of volcanic climate impact stems from aerosol in the LMS (lowermost stratosphere). Although the LMS holds >40% of the stratospheric mass (Appenzeller et al., 1996) it is generally neglected in estimations of the stratospheric AOD (aerosol optical depth). In the past decade the stratospheric aerosol load was perturbed by a number of volcanic eruptions. We cover that period by using the CALIPSO level 1b night-time data to study the volcanic influence on the global and regional climate. CALIPSO data were averaged to a resolution of 180 m vertically and 1×1° horizontally, cleaned from ice clouds by means of the depolarization ratio (Vernier et al., 2009), and a method was developed to remove polar stratospheric clouds (PSC). This approach enables identification of aerosol also at low altitudes (currently using 4 km minimum altitude) and in the Antarctic region (60 to 90°S) where PSCs are frequent during winter. In the current study, we estimate the total stratospheric AOD and radiative forcing and find that significant fractions of volcanic aerosol were located below the static tropopause after volcanic eruptions. Volcanic aerosol was generally observed down to the dynamic tropopause, and detected down to potential vorticities of 1.5-2 PVU (almost 1 km below the static tropopause). Hence, the dynamic tropopause was found to better enclose the volcanic aerosol. Furthermore, large concentrations of aerosol from the Kasatochi eruption (Aug 2008) is found to linger in the extratropical UT (upper troposphere) for several months after the eruption. Sulphate-rich volcanic aerosol transported from the LMS may influence cirrus clouds in the extratropical UT, inducing an indirect

  7. Some Technical Aspects of a CALIOP and MODIS Data Analysis that Examines Near-Cloud Aerosol Properties as a Function of Cloud Fraction

    Science.gov (United States)

    Varnai, Tamas; Yang, Weidong; Marshak, Alexander

    2016-01-01

    CALIOP shows stronger near-cloud changes in aerosol properties at higher cloud fractions. Cloud fraction variations explain a third of near-cloud changes in overall aerosol statistics. Cloud fraction and aerosol particle size distribution have a complex relationship.

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

    Science.gov (United States)

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

    2015-01-01

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

  9. Constraining the instantaneous aerosol influence on cloud albedo.

    Science.gov (United States)

    Gryspeerdt, Edward; Quaas, Johannes; Ferrachat, Sylvaine; Gettelman, Andrew; Ghan, Steven; Lohmann, Ulrike; Morrison, Hugh; Neubauer, David; Partridge, Daniel G; Stier, Philip; Takemura, Toshihiko; Wang, Hailong; Wang, Minghuai; Zhang, Kai

    2017-05-09

    Much of the uncertainty in estimates of the anthropogenic forcing of climate change comes from uncertainties in the instantaneous effect of aerosols on cloud albedo, known as the Twomey effect or the radiative forcing from aerosol-cloud interactions (RFaci), a component of the total or effective radiative forcing. Because aerosols serving as cloud condensation nuclei can have a strong influence on the cloud droplet number concentration (Nd ), previous studies have used the sensitivity of the Nd to aerosol properties as a constraint on the strength of the RFaci. However, recent studies have suggested that relationships between aerosol and cloud properties in the present-day climate may not be suitable for determining the sensitivity of the Nd to anthropogenic aerosol perturbations. Using an ensemble of global aerosol-climate models, this study demonstrates how joint histograms between Nd and aerosol properties can account for many of the issues raised by previous studies. It shows that if the anthropogenic contribution to the aerosol is known, the RFaci can be diagnosed to within 20% of its actual value. The accuracy of different aerosol proxies for diagnosing the RFaci is investigated, confirming that using the aerosol optical depth significantly underestimates the strength of the aerosol-cloud interactions in satellite data.

  10. Estimating the frequency of volcanic ash clouds over northern Europe

    Science.gov (United States)

    Watson, E. J.; Swindles, G. T.; Savov, I. P.; Lawson, I. T.; Connor, C. B.; Wilson, J. A.

    2017-02-01

    Fine ash produced during explosive volcanic eruptions can be dispersed over a vast area, where it poses a threat to aviation, human health and infrastructure. Here, we focus on northern Europe, which lies in the principal transport direction for volcanic ash from Iceland, one of the most active volcanic regions in the world. We interrogate existing and newly produced geological and written records of past ash fallout over northern Europe in the last 1000 years and estimate the mean return (repose) interval of a volcanic ash cloud over the region to be 44 ± 7 years. We compare tephra records from mainland northern Europe, Great Britain, Ireland and the Faroe Islands, with records of proximal Icelandic volcanism and suggest that an Icelandic eruption with a Volcanic Explosivity Index rating (VEI) ≥ 4 and a silicic magma composition presents the greatest risk of producing volcanic ash that can reach northern Europe. None of the ash clouds in the European record which have a known source eruption are linked to a source eruption with VEI < 4. Our results suggest that ash clouds are more common over northern Europe than previously proposed and indicate the continued threat of ash deposition across northern Europe from eruptions of both Icelandic and North American volcanoes.

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

    Science.gov (United States)

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

    2016-11-01

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

  12. Large Eddy Simulation Study on Arctic Marine Clouds: the Effect of Aerosol-Cloud Interactions

    Science.gov (United States)

    Raatikainen, T.; Ahola, J.; Tonttila, J.; Romakkaniemi, S.; Laaksonen, A.; Korhonen, H.

    2016-12-01

    Dynamics of marine stratocumulus clouds depend on radiative cooling from cloud tops, turbulent transport of moisture and heat from the sea surface, and the availability of atmospheric aerosols to act as cloud condensation nuclei (CCN). These processes and especially aerosol-cloud interactions can be examined with a recently developed Large Eddy Simulation (LES) model UCLALES-SALSA (Tonttila et al., Geosci. Model Dev. Discuss., 2016). Unlike most other LES models, UCLALES-SALSA has fully interactive sectional description for aerosols and liquid and frozen cloud species. UCLALES-SALSA simulations are initialized using atmospheric observations from the Arctic Summer Cloud Ocean Study (ASCOS). First, the model is used to examine the effects of initial total aerosol number concentration on cloud properties. In agreement with several observations, lowering aerosol number concentration decreases cloud lifetime by increasing drizzle and precipitation rates, which further decreases aerosol number concentration. The second test includes comparison between model versions with different microphysics. The new sectional approach seems to produce thicker and more persistent clouds than a two moment model version (Stevens et al., J. Atmos. Sci., 1999) even when the models are tuned to have equal cloud droplet number concentrations. The third part of the study is focused on the effect of ice on cloud properties. Preliminary results indicate that the current cloud case is so warm that the liquid phase dominates, but further studies are ongoing. In general, the results show that cloud evolution depends on aerosol-cloud interactions.

  13. Discrimination of water, ice and aerosols by light polarisation in the CLOUD experiment

    Directory of Open Access Journals (Sweden)

    L. Nichman

    2015-11-01

    Full Text Available Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather and General Circulation Models (GCMs. The simultaneous detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud-particle size range below 50 μm, remains challenging in mixed phase, often unstable ice-water phase environments. The Cloud Aerosol Spectrometer with Polarisation (CASPOL is an airborne instrument that has the ability to detect such small cloud particles and measure their effects on the backscatter polarisation state. Here we operate the versatile Cosmics-Leaving-OUtdoor-Droplets (CLOUD chamber facility at the European Organisation for Nuclear Research (CERN to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water and ice particles. In this paper, optical property measurements of mixed phase clouds and viscous Secondary Organic Aerosol (SOA are presented. We report observations of significant liquid – viscous SOA particle polarisation transitions under dry conditions using CASPOL. Cluster analysis techniques were subsequently used to classify different types of particles according to their polarisation ratios during phase transition. A classification map is presented for water droplets, organic aerosol (e.g., SOA and oxalic acid, crystalline substances such as ammonium sulphate, and volcanic ash. Finally, we discuss the benefits and limitations of this classification approach for atmospherically relevant concentration and mixtures with respect to the CLOUD 8–9 campaigns and its potential contribution to Tropical Troposphere Layer (TTL analysis.

  14. Cloud Scavenging Effects on Aerosol Radiative and Cloud-nucleating Properties - Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

    2009-03-05

    The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

  15. Impact of cloud-borne aerosol representation on aerosol direct and indirect effects

    Directory of Open Access Journals (Sweden)

    S. J. Ghan

    2006-01-01

    Full Text Available Aerosol particles attached to cloud droplets are much more likely to be removed from the atmosphere and are much less efficient at scattering sunlight than if unattached. Models used to estimate direct and indirect effects of aerosols employ a variety of representations of such cloud-borne particles. Here we use a global aerosol model with a relatively complete treatment of cloud-borne particles to estimate the sensitivity of simulated aerosol, cloud and radiation fields to various approximations to the representation of cloud-borne particles. We find that neglecting transport of cloud-borne particles introduces little error, but that diagnosing cloud-borne particles produces global mean biases of 20% and local errors of up to 40% for aerosol, droplet number, and direct and indirect radiative forcing. Aerosol number, aerosol optical depth and droplet number are significantly underestimated in regions and seasons where and when wet removal is primarily by stratiform rather than convective clouds (polar regions during winter, but direct and indirect effects are less biased because of the limited sunlight there and then. A treatment that predicts the total mass concentration of cloud-borne particles for each mode yields smaller errors and runs 20% faster than the complete treatment. The errors are much smaller than current estimates of uncertainty in direct and indirect effects of aerosols, which suggests that the treatment of cloud-borne aerosol is not a significant source of uncertainty in estimates of direct and indirect effects.

  16. Aerosol cloud precipitation interactions. Part 1. The nature and sources of cloud-active aerosols

    Science.gov (United States)

    Andreae, M. O.; Rosenfeld, D.

    2008-07-01

    Atmospheric aerosol particles serve as condensation nuclei for the formation of both, cloud droplets and atmospheric ice particles. As a result, they exert a substantial influence on the microphysical properties of water and ice clouds, which in turn affect the processes that lead to the formation of rain, snow, hail, and other forms of precipitation. In recent years, considerable progress has been made in understanding the chemical composition of aerosols, their microphysical properties, and the factors that enable them to act as cloud condensation nuclei (CCN) and ice nuclei (IN). The first part of this review article will focus on the nature and sources of CCN and IN. We discuss the fundamentals of the cloud droplet and ice nucleation processes, and the role that the chemical composition and particle size play in this process. We show that, in many instances, the influence of chemical composition can be represented by a simple parameterization, which leaves particle size as the main variable controlling CCN efficiency. Aerosol particles are produced either directly by anthropogenic and natural sources (dust, sea salt, soot, biological particles, etc.), or they are formed in the atmosphere by condensation of low-volatility compounds (e.g., sulfuric acid or oxidized organic compounds). We discuss the magnitude of these sources, and the CCN and IN characteristics of the particles they produce. In contrast to previous assessments, which focused on the aerosol mass, we are emphasizing the number of particles being produced, as this is the key variable in cloud microphysics. Large uncertainties still exist for many aerosol sources, e.g., the submicron part of the seaspray aerosol, the particles produced by the biosphere, and the secondary organic aerosol. We conclude with a discussion on what particle concentrations may have been in the pristine atmosphere, before the onset on anthropogenic pollution. Model calculations and observations in remote continental regions

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

    Science.gov (United States)

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

    2016-12-01

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

  18. Transient Sulfate Aerosols as a Signature of Exoplanet Volcanism

    CERN Document Server

    Misra, Amit; Koehler, Matthew C; Sholes, Steven

    2015-01-01

    Geological activity is thought to be important for the origin of life and for maintaining planetary habitability. We show that transient sulfate aerosols could be a signature of exoplanet volcanism, and therefore a geologically active world. A detection of transient aerosols, if linked to volcanism, could thus aid in habitability evaluations of the exoplanet. On Earth, subduction-induced explosive eruptions inject SO2 directly into the stratosphere, leading to the formation of sulfate aerosols with lifetimes of months to years. We demonstrate that the rapid increase and gradual decrease in sulfate aerosol loading associated with these eruptions may be detectable in transit transmission spectra with future large-aperture telescopes, such as the James Webb Space Telescope (JWST) and European Extremely-Large Telescope (E-ELT) for a planetary system at a distance of 10 pc, assuming an Earth-like atmosphere, bulk composition, and size. Specifically, we find that a S/N of 12.1 and 7.1 could be achieved with E-ELT (...

  19. Aerosol Effects on Instability, Circulations, Clouds, and Precipitation

    Directory of Open Access Journals (Sweden)

    Seoung-Soo Lee

    2014-01-01

    Full Text Available It is well known that increasing aerosol and associated changes in aerosol-cloud interactions and precipitation since industrialization have been playing an important role in climate change, but this role has not been well understood. This prevents us from predicting future climate with a good confidence. This review paper presents recent studies on the changes in the aerosol-cloud interactions and precipitation particularly in deep convective clouds. In addition, this review paper discusses how to improve our understanding of these changes by considering feedbacks among aerosol, cloud dynamics, cloud and its embedded circulations, and microphysics. Environmental instability basically determines the dynamic intensity of clouds and thus acts as one of the most important controls on these feedbacks. As a first step to the improvement of the understanding, this paper specifically elaborates on how to link the instability to the feedbacks.

  20. Constraining the instantaneous aerosol influence on cloud albedo

    Energy Technology Data Exchange (ETDEWEB)

    Gryspeerdt, Edward; Quaas, Johannes; Ferrachat, Sylvaine; Gettelman, Andrew; Ghan, Steven; Lohmann, Ulrike; Morrison, Hugh; Neubauer, David; Partridge, Daniel G.; Stier, Philip; Takemura, Toshihiko; Wang, Hailong; Wang, Minghuai; Zhang, Kai

    2017-04-26

    Much of the uncertainty in estimates of the anthropogenic forcing of climate change comes from uncertainties in the instantaneous effect of aerosols on cloud albedo, known as the Twomey effect or the radiative forcing from aerosol–cloud interactions (RFaci), a component of the total or effective radiative forcing. Because aerosols serving as cloud condensation nuclei can have a strong influence on the cloud droplet number concentration (Nd), previous studies have used the sensitivity of the Nd to aerosol properties as a constraint on the strength of the RFaci. However, recent studies have suggested that relationships between aerosol and cloud properties in the present-day climate may not be suitable for determining the sensitivity of the Nd to anthropogenic aerosol perturbations. Using an ensemble of global aerosol–climate models, this study demonstrates how joint histograms between Nd and aerosol properties can account for many of the issues raised by previous studies. It shows that if the anthropogenic contribution to the aerosol is known, the RFaci can be diagnosed to within 20% of its actual value. The accuracy of different aerosol proxies for diagnosing the RFaci is investigated, confirming that using the aerosol optical depth significantly underestimates the strength of the aerosol–cloud interactions in satellite data.

  1. Aerosol-Cloud-Precipitation Interactions in the Climate System

    Science.gov (United States)

    Andreae, M. O.

    2015-12-01

    Aerosols serve as cloud condensation nuclei (CCN) and thus have a powerful effect on cloud properties. Increased aerosol concentrations resulting from pollution lead to higher cloud droplet concentrations, but smaller droplet sizes. This in turn affects the physical processes inside clouds that lead to the initiation of precipitation. Depending on a number of factors, including aerosol composition, atmospheric stability, and cloud water content, increasing CCN concentrations may either decrease or increase rainfall. In convective clouds, early rain formation is suppressed, which makes more water and energy available to rise higher in the atmosphere and form ice particles. This may invigorate the dynamics of convection, encourage the formation of hail and lightning, and enhance the transport of materials to the upper troposphere. In turn, cloud processing also affects the concentrations, composition, and distribution of atmospheric aerosols. In order to understand and quantify the effects of air pollution on climate, and precipitation in particular, knowledge of natural abundance and characteristics of aerosols is as essential as the observation of perturbed conditions. I will present recent advances in the conceptual understanding of aerosol-precipitation interactions, as well as results of measurements on aerosol and cloud characteristics in pristine and polluted conditions.

  2. Aerosol processing in stratiform clouds in ECHAM6-HAM

    Science.gov (United States)

    Neubauer, David; Lohmann, Ulrike; Hoose, Corinna

    2013-04-01

    Aerosol processing in stratiform clouds by uptake into cloud particles, collision-coalescence, chemical processing inside the cloud particles and release back into the atmosphere has important effects on aerosol concentration, size distribution, chemical composition and mixing state. Aerosol particles can act as cloud condensation nuclei. Cloud droplets can take up further aerosol particles by collisions. Atmospheric gases may also be transferred into the cloud droplets and undergo chemical reactions, e.g. the production of atmospheric sulphate. Aerosol particles are also processed in ice crystals. They may be taken up by homogeneous freezing of cloud droplets below -38° C or by heterogeneous freezing above -38° C. This includes immersion freezing of already immersed aerosol particles in the droplets and contact freezing of particles colliding with a droplet. Many clouds do not form precipitation and also much of the precipitation evaporates before it reaches the ground. The water soluble part of the aerosol particles concentrates in the hydrometeors and together with the insoluble part forms a single, mixed, larger particle, which is released. We have implemented aerosol processing into the current version of the general circulation model ECHAM6 (Stevens et al., 2013) coupled to the aerosol module HAM (Stier et al., 2005). ECHAM6-HAM solves prognostic equations for the cloud droplet number and ice crystal number concentrations. In the standard version of HAM, seven modes are used to describe the total aerosol. The modes are divided into soluble/mixed and insoluble modes and the number concentrations and masses of different chemical components (sulphate, black carbon, organic carbon, sea salt and mineral dust) are prognostic variables. We extended this by an explicit representation of aerosol particles in cloud droplets and ice crystals in stratiform clouds similar to Hoose et al. (2008a,b). Aerosol particles in cloud droplets are represented by 5 tracers for the

  3. Cloud Cover Increase with Increasing Aerosol Absorptivity: A Counterexample to the Conventional Semidirect Aerosol Effect

    Science.gov (United States)

    Perlwitz, Jan; Miller, Ron L.

    2010-01-01

    We reexamine the aerosol semidirect effect using a general circulation model and four cases of the single-scattering albedo of dust aerosols. Contrary to the expected decrease in low cloud cover due to heating by tropospheric aerosols, we find a significant increase with increasing absorptivity of soil dust particles in regions with high dust load, except during Northern Hemisphere winter. The strongest sensitivity of cloud cover to dust absorption is found over land during Northern Hemisphere summer. Here even medium and high cloud cover increase where the dust load is highest. The cloud cover change is directly linked to the change in relative humidity in the troposphere as a result of contrasting changes in specific humidity and temperature. More absorption by aerosols leads to larger diabatic heating and increased warming of the column, decreasing relative humidity. However, a corresponding increase in the specific humidity exceeds the temperature effect on relative humidity. The net effect is more low cloud cover with increasing aerosol absorption. The higher specific humidity where cloud cover strongly increases is attributed to an enhanced convergence of moisture driven by dust radiative heating. Although in some areas our model exhibits a reduction of low cloud cover due to aerosol heating consistent with the conventional description of the semidirect effect, we conclude that the link between aerosols and clouds is more varied, depending also on changes in the atmospheric circulation and the specific humidity induced by the aerosols. Other absorbing aerosols such as black carbon are expected to have a similar effect.

  4. Aviation response to a widely dispersed volcanic ash and gas cloud from the August 2008 eruption of Kasatochi, Alaska, USA

    Science.gov (United States)

    Guffanti, Marianne; Schneider, David J.; Wallace, Kristi L.; Hall, Tony; Bensimon, Dov R.; Salinas, Leonard J.

    2010-01-01

    The extensive volcanic cloud from Kasatochi's 2008 eruption caused widespread disruptions to aviation operations along Pacific oceanic, Canadian, and U.S. air routes. Based on aviation hazard warnings issued by the National Oceanic and Atmospheric Administration, U.S. Geological Survey, the Federal Aviation Administration, and Meteorological Service of Canada, air carriers largely avoided the volcanic cloud over a 5 day period by route modifications and flight cancellations. Comparison of time coincident GOES thermal infrared (TIR) data for ash detection with Ozone Monitoring Instrument (OMI) ultraviolet data for SO2 detection shows congruent areas of ash and gas in the volcanic cloud in the 2 days following onset of ash production. After about 2.5 days, the area of SO2 detected by OMI was more extensive than the area of ash indicated by TIR data, indicating significant ash depletion by fall out had occurred. Pilot reports of visible haze at cruise altitudes over Canada and the northern United States suggested that SO2 gas had converted to sulfate aerosols. Uncertain about the hazard potential of the aging cloud, airlines coped by flying over, under, or around the observed haze layer. Samples from a nondamaging aircraft encounter with Kasatochi's nearly 3 day old cloud contained volcanic silicate particles, confirming that some fine ash is present in predominantly gas clouds. The aircraft's exposure to ash was insufficient to cause engine damage; however, slightly damaging encounters with volcanic clouds from eruptions of Reventador in 2002 and Hekla in 2000 indicate the possibility of lingering hazards associated with old and/or diffuse volcanic clouds.

  5. Opportunities for understanding of aerosol cloud interactions in the context of Marine Cloud Brightening Experiments

    Science.gov (United States)

    Rasch, Philip J.; Wood, Robert; Ackerman, Thomas P.

    2017-04-01

    Anthropogenic aerosol impacts on clouds constitute the largest source of uncertainty in radiative forcing of climate, confounding estimates of climate sensitivity to increases in greenhouse gases. Projections of future warming are also thus strongly dependent on estimates of aerosol effects on clouds. I will discuss the opportunities for improving estimates of aerosol effects on clouds from controlled field experiments where aerosol with well understood size, composition, amount, and injection altitude could be introduced to deliberately change cloud properties. This would allow scientific investigation to be performed in a manner much closer to a lab environment, and facilitate the use of models to predict cloud responses ahead of time, testing our understanding of aerosol cloud interactions.

  6. Evaluating aerosol indirect effect through marine stratocumulus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Kogan, Z.N.; Kogan, Y.L.; Lilly, D.K. [Univ. of Oklahoma, Norman, OK (United States)

    1996-04-01

    During the last decade much attention has been focused on anthropogenic aerosols and their radiative influence on the global climate. Charlson et al. and Penner et al. have demonstrated that tropospheric aerosols and particularly anthropogenic sulfate aerosols may significantly contribute to the radiative forcing exerting a cooling influence on climate (-1 to -2 W/m{sup 2}) which is comparable in magnitude to greenhouse forcing, but opposite in sign. Aerosol particles affect the earth`s radiative budget either directly by scattering and absorption of solar radiation by themselves or indirectly by altering the cloud radiative properties through changes in cloud microstructure. Marine stratocumulus cloud layers and their possible cooling influence on the atmosphere as a result of pollution are of special interest because of their high reflectivity, durability, and large global cover. We present an estimate of thet aerosol indirect effect, or, forcing due to anthropogenic sulfate aerosols.

  7. A Multi-Sensor Approach for Volcanic Ash Cloud Retrieval and Eruption Characterization: The 23 November 2013 Etna Lava Fountain

    Directory of Open Access Journals (Sweden)

    Stefano Corradini

    2016-01-01

    Full Text Available Volcanic activity is observed worldwide with a variety of ground and space-based remote sensing instruments, each with advantages and drawbacks. No single system can give a comprehensive description of eruptive activity, and so, a multi-sensor approach is required. This work integrates infrared and microwave volcanic ash retrievals obtained from the geostationary Meteosat Second Generation (MSG-Spinning Enhanced Visible and Infrared Imager (SEVIRI, the polar-orbiting Aqua-MODIS and ground-based weather radar. The expected outcomes are improvements in satellite volcanic ash cloud retrieval (altitude, mass, aerosol optical depth and effective radius, the generation of new satellite products (ash concentration and particle number density in the thermal infrared and better characterization of volcanic eruptions (plume altitude, total ash mass erupted and particle number density from thermal infrared to microwave. This approach is the core of the multi-platform volcanic ash cloud estimation procedure being developed within the European FP7-APhoRISM project. The Mt. Etna (Sicily, Italy volcano lava fountaining event of 23 November 2013 was considered as a test case. The results of the integration show the presence of two volcanic cloud layers at different altitudes. The improvement of the volcanic ash cloud altitude leads to a mean difference between the SEVIRI ash mass estimations, before and after the integration, of about the 30%. Moreover, the percentage of the airborne “fine” ash retrieved from the satellite is estimated to be about 1%–2% of the total ash emitted during the eruption. Finally, all of the estimated parameters (volcanic ash cloud altitude, thickness and total mass were also validated with ground-based visible camera measurements, HYSPLIT forward trajectories, Infrared Atmospheric Sounding Interferometer (IASI satellite data and tephra deposits.

  8. Improved prediction and tracking of volcanic ash clouds

    Science.gov (United States)

    Webley, P.; Mastin, L.

    2009-01-01

    During the past 30??years, more than 100 airplanes have inadvertently flown through clouds of volcanic ash from erupting volcanoes. Such encounters have caused millions of dollars in damage to the aircraft and have endangered the lives of tens of thousands of passengers. In a few severe cases, total engine failure resulted when ash was ingested into turbines and coating turbine blades. These incidents have prompted the establishment of cooperative efforts by the International Civil Aviation Organization and the volcanological community to provide rapid notification of eruptive activity, and to monitor and forecast the trajectories of ash clouds so that they can be avoided by air traffic. Ash-cloud properties such as plume height, ash concentration, and three-dimensional ash distribution have been monitored through non-conventional remote sensing techniques that are under active development. Forecasting the trajectories of ash clouds has required the development of volcanic ash transport and dispersion models that can calculate the path of an ash cloud over the scale of a continent or a hemisphere. Volcanological inputs to these models, such as plume height, mass eruption rate, eruption duration, ash distribution with altitude, and grain-size distribution, must be assigned in real time during an event, often with limited observations. Databases and protocols are currently being developed that allow for rapid assignment of such source parameters. In this paper, we summarize how an interdisciplinary working group on eruption source parameters has been instigating research to improve upon the current understanding of volcanic ash cloud characterization and predictions. Improved predictions of ash cloud movement and air fall will aid in making better hazard assessments for aviation and for public health and air quality. ?? 2008 Elsevier B.V.

  9. An aggregation model for ash particles in volcanic clouds

    Science.gov (United States)

    Costa, A.; Folch, A.; Macedonio, G.; Durant, A.

    2009-12-01

    A large fraction of fine ash particles injected into the atmosphere during explosive eruptions aggregate through complex interactions of surface liquid layers, electrostatic forces, and differences in particle settling velocities. The aggregates formed have a different size and density compared to primary particles formed during eruption which dramatically changes the dynamics of sedimentation from the volcanic cloud. Consequently, the lifetime of ash particles in the atmosphere is reduced and a distal mass deposition maximum is often generated in resulting tephra deposits. A complete and rigorous description of volcanic ash fallout requires the full coupling of models of volcanic cloud dynamics and dispersion, and ash particle transport, aggregation and sedimentation. Furthermore, volcanic ash transport models should include an aggregation model that accounts for the interaction of all particle size classes. The problem with this approach is that simulations would require excessively long computational times thereby prohibiting its application in an operational setting during an explosive volcanic eruption. Here we present a simplified model for ash particle transport and aggregation that includes the effects of water in the volcanic cloud and surrounding atmosphere. The aggregation model assumes a fractal relationship for the number of primary particles in aggregates, average sticking efficiency factors, and collision frequency functions that account for Brownian motion, laminar and turbulent fluid shear, and differential settling velocity. A parametric study on the key parameters of the model was performed. We implemented the aggregation model in the WRF+FALL3D coupled modelling system and applied it to different eruptions where aggregation has been recognized to play an important role, including the August and September 1992 Crater Peak eruptions and the 1980 Mt St Helens eruption. In these cases, mass deposited as a function of deposit area and the particle

  10. Importance of Raman Lidar Aerosol Extinction Measurements for Aerosol-Cloud Interaction Studies

    Directory of Open Access Journals (Sweden)

    Han Zaw

    2016-01-01

    Full Text Available Using a UV Raman Lidar for aerosol extinction, and combining Microwave Radiometer derived Liquid Water Path (LWP with Multifilter Rotating Shadowband Radiometer derived Cloud Optical depth, to get cloud effective radius (Reff, we observe under certain specialized conditions, clear signatures of the Twomey Aerosol Indirect effect on cloud droplet properties which are consistent with the theoretical bounds. We also show that the measurement is very sensitive to how far the aerosol layer is from the cloud base and demonstrate that surface PM25 is far less useful. Measurements from both the DOE ARM site and new results at CCNY are presented.

  11. Global cloud condensation nuclei influenced by carbonaceous combustion aerosol

    Directory of Open Access Journals (Sweden)

    D. V. Spracklen

    2011-09-01

    Full Text Available Black carbon in carbonaceous combustion aerosol warms the climate by absorbing solar radiation, meaning reductions in black carbon emissions are often perceived as an attractive global warming mitigation option. However, carbonaceous combustion aerosol can also act as cloud condensation nuclei (CCN so they also cool the climate by increasing cloud albedo. The net radiative effect of carbonaceous combustion aerosol is uncertain because their contribution to CCN has not been evaluated on the global scale. By combining extensive observations of CCN concentrations with the GLOMAP global aerosol model, we find that the model is biased low (normalised mean bias = −77 % unless carbonaceous combustion aerosol act as CCN. We show that carbonaceous combustion aerosol accounts for more than half (52–64 % of global CCN with the range due to uncertainty in the emitted size distribution of carbonaceous combustion particles. The model predicts that wildfire and pollution (fossil fuel and biofuel carbonaceous combustion aerosol causes a global mean cloud albedo aerosol indirect effect of −0.34 W m−2, with stronger cooling if we assume smaller particle emission size. We calculate that carbonaceous combustion aerosol from pollution sources cause a global mean aerosol indirect effect of −0.23 W m−2. The small size of carbonaceous combustion particles from fossil fuel sources means that whilst pollution sources account for only one-third of the emitted mass they cause two-thirds of the cloud albedo aerosol indirect effect that is due to carbonaceous combustion aerosol. This cooling effect must be accounted for, along with other cloud effects not studied here, to ensure that black carbon emissions controls that reduce the high number concentrations of fossil fuel particles have the desired net effect on climate.

  12. Global estimation of above-cloud aerosols using spaceborne LIDAR

    Science.gov (United States)

    Chand, D.; Wood, R.; Anderson, T. L.; Satheesh, S. K.; Leahy, L.

    2008-12-01

    Estimates of global mean direct climate forcing by absorbing aerosols located above boundary layer clouds are large, uncertain, and almost entirely unconstrained by observations. Spaceborne lidar offers a new opportunity of estimating the aerosols at global scale. Here we use two recently available techniques quantifying the above-cloud aerosols using liquid water clouds as lidar targets from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) [Chand et al., 2008]. Both methods can quantify aerosols above clouds and are based on their self-calibrating techniques. We used one year of global data between 70N-70S to show that day time calibration constants are different than night time calibrations constants. A clear latitudinal dependence is observed in the calibrations constants in CALIPSO observations. Using these 'self-calibration' constants, aerosol optical depth (AOD) and angstrom exponent (AE) of 'above- cloud' aerosols are quantified. Biomass burning is a major source of fine mode aerosols in different regions of world. For example, it is observed that June is the onset of the biomass burning fires in Southern Africa, peaking in August and September and then slowly decreasing until November, with a corresponding signature in aerosol optical depth. Layers with aerosol optical depth greater than 0.3 are commonly observed up to several thousand kilometers away from Africa over the Atlantic Ocean. The 'above-cloud' AOD as high as 1.5 is observed in the peak months. Despite of large variations is AOD, mean AE of these aerosols is about 1.6, without any systematic variability away from the source region. The results estimating the aerosols above clouds, including other regions at global scale, will be presented in the AGU meeting. Chand, D., T. L. Anderson, R. Wood, R. J. Charlson, Y. Hu, Z. Liu, and M. Vaughan (2008), Quantifying above-cloud aerosol using spaceborne lidar for improved understanding of cloudy-sky direct climate forcing, J

  13. Aerosol Interactions with Extensive Stratus Cloud During VOCALS

    Science.gov (United States)

    Clarke, A. D.; McNaughton, C. S.; Freitag, S.; Howell, S.; Kapustin, V.; Snider, J.; Campos, T. L.; Leon, D.; Shank, L.; Wood, R.

    2009-12-01

    The 2008 VOCALS experiment over the Pacific and off the north coast of Chile provided numerous opportunities to examine aerosol-stratus interactions over 1000km flight legs and processes associated with their breakup into pockets of open cells (POC’s). Our HiGEAR (Hawaii Group for Environmental Aerosol Research) measurements on the NCAR C-130 aircraft included the aerosol size-distribution, size-resolved volatile and non-volatile components, ionic and organic chemistry (AMS), black carbon (BC, as measured by Single Particle Soot Photometer - SP2) and associated optical properties. We are exploring these observations in conjunction with meteorological data, trace gas data (eg. O3, CO) and cloud condensation nuclei (CCN) to resolve features related to the source, removal and evolution of aerosol active as CCN. Stratus clouds decks along the coast were heavily impacted by anthropogenic combustion sources along the coast. Offshore in the marine boundary layer (MBL) below cloud these influences diminished and transitioned to clean central Pacific aerosol west of about 75W. Periods with smallest aerosol sizes tended to show subsidence around the South Pacific high pressure system while larger sizes had spent more time in the MBL. However, at various altitudes in the free troposphere (FT) above cloud, relatively low concentrations of biomass burning (BB) aerosol occurred in patches and “rivers” of flow. These BB aerosol were often near cloud top or within a day of subsiding to cloud top for estimated rates of about 0.4 cm/s. The BB aerosol was generally associated with elevated CO, organic, non-volatile aerosol, and BC. POC’s were lowest in CO compared to both adjacent cloudy air and FT air, indicating less prior influence from combustion aerosol than cloudy regions. POC regions manifested dramatic aerosol reduction through precipitation and drizzle resulting in low concentrations with diameters often less than about 40nm. Offshore, drizzling cloudy regions

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

    Science.gov (United States)

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

    2013-10-01

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

  15. Aerosol-cloud relationships in continental shallow cumulus

    OpenAIRE

    Lu, Miao-Ling; Feingold, Graham; Jonsson, Haflidi; Chuang, Patrick Y.; Gates, Harmony; Flagan, Richard C.; Seinfeld, John H.

    2008-01-01

    The article of record as published may be located at http://dx.doi.org/10.1029/2007JD009354 Aerosol-cloud relationships are derived from 14 warm continental cumuli cases sampled during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) by the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. Cloud droplet number concentration is clearly proportional to the subcloud accumulation mode aerosol number concentration...

  16. Aerosol effects on deep convective clouds: impact of changes in aerosol size distribution and aerosol activation parameterization

    Science.gov (United States)

    Ekman, A. M. L.; Engström, A.; Söderberg, A.

    2010-03-01

    A cloud-resolving model including explicit aerosol physics and chemistry is used to study the impact of aerosols on deep convective strength. More specifically, by conducting six sensitivity series we examine how the complexity of the aerosol model, the size of the aerosols and the aerosol activation parameterization influence the aerosol-induced deep convective cloud sensitivity. Only aerosol effects on liquid droplet formation are considered. We find that an increased aerosol concentration generally results in stronger convection, which for the simulated case is in agreement with the conceptual model presented by Rosenfeld et al. (2008). However, there are two sensitivity series that do not display a monotonic increase in updraft velocity with increasing aerosol concentration. These exceptions illustrate the need to: 1) account for changes in evaporation processes and subsequent cooling when assessing aerosol effects on deep convective strength, 2) better understand graupel impaction scavenging of aerosols which may limit the number of CCN at a critical stage of cloud development and thereby dampen the convection, 3) increase our knowledge of aerosol recycling due to evaporation of cloud droplets. Furthermore, we find a significant difference in the aerosol-induced deep convective cloud sensitivity when using different complexities of the aerosol model and different aerosol activation parameterizations. For the simulated case, a 100% increase in aerosol concentration results in a difference in average updraft between the various sensitivity series which is as large as the average updraft increase itself. The model simulations also show that the change in graupel and rain formation is not necessarily directly proportional to the change in updraft velocity. For example, several of the sensitivity series display a decrease of the rain amount at the lowest model level with increasing updraft velocity. Finally, an increased number of aerosols in the Aitken mode (here

  17. Aerosol effects on deep convective clouds: impact of changes in aerosol size distribution and aerosol activation parameterization

    Directory of Open Access Journals (Sweden)

    A. M. L. Ekman

    2010-03-01

    Full Text Available A cloud-resolving model including explicit aerosol physics and chemistry is used to study the impact of aerosols on deep convective strength. More specifically, by conducting six sensitivity series we examine how the complexity of the aerosol model, the size of the aerosols and the aerosol activation parameterization influence the aerosol-induced deep convective cloud sensitivity. Only aerosol effects on liquid droplet formation are considered. We find that an increased aerosol concentration generally results in stronger convection, which for the simulated case is in agreement with the conceptual model presented by Rosenfeld et al. (2008. However, there are two sensitivity series that do not display a monotonic increase in updraft velocity with increasing aerosol concentration. These exceptions illustrate the need to: 1 account for changes in evaporation processes and subsequent cooling when assessing aerosol effects on deep convective strength, 2 better understand graupel impaction scavenging of aerosols which may limit the number of CCN at a critical stage of cloud development and thereby dampen the convection, 3 increase our knowledge of aerosol recycling due to evaporation of cloud droplets. Furthermore, we find a significant difference in the aerosol-induced deep convective cloud sensitivity when using different complexities of the aerosol model and different aerosol activation parameterizations. For the simulated case, a 100% increase in aerosol concentration results in a difference in average updraft between the various sensitivity series which is as large as the average updraft increase itself. The model simulations also show that the change in graupel and rain formation is not necessarily directly proportional to the change in updraft velocity. For example, several of the sensitivity series display a decrease of the rain amount at the lowest model level with increasing updraft velocity. Finally, an increased number of aerosols in the

  18. Meteorological and aerosol effects on marine cloud microphysical properties

    Science.gov (United States)

    Sanchez, K. J.; Russell, L. M.; Modini, R. L.; Frossard, A. A.; Ahlm, L.; Corrigan, C. E.; Roberts, G. C.; Hawkins, L. N.; Schroder, J. C.; Bertram, A. K.; Zhao, R.; Lee, A. K. Y.; Lin, J. J.; Nenes, A.; Wang, Z.; Wonaschütz, A.; Sorooshian, A.; Noone, K. J.; Jonsson, H.; Toom, D.; Macdonald, A. M.; Leaitch, W. R.; Seinfeld, J. H.

    2016-04-01

    Meteorology and microphysics affect cloud formation, cloud droplet distributions, and shortwave reflectance. The Eastern Pacific Emitted Aerosol Cloud Experiment and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets studies provided measurements in six case studies of cloud thermodynamic properties, initial particle number distribution and composition, and cloud drop distribution. In this study, we use simulations from a chemical and microphysical aerosol-cloud parcel (ACP) model with explicit kinetic drop activation to reproduce observed cloud droplet distributions of the case studies. Four cases had subadiabatic lapse rates, resulting in fewer activated droplets, lower liquid water content, and higher cloud base height than an adiabatic lapse rate. A weighted ensemble of simulations that reflect measured variation in updraft velocity and cloud base height was used to reproduce observed droplet distributions. Simulations show that organic hygroscopicity in internally mixed cases causes small effects on cloud reflectivity (CR) (modal peak near 0.1 µm). Differences in simulated droplet spectral widths (k) caused larger differences in CR than organic hygroscopicity in cases with organic mass fractions of 60% or less for the cases shown. Finally, simulations from a numerical parameterization of cloud droplet activation suitable for general circulation models compared well with the ACP model, except under high organic mass fraction.

  19. 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.

  20. Super-droplet method as a versatile numerical approach for representing aerosol-cloud-aerosol interactions.

    Science.gov (United States)

    Jaruga, Anna; Arabas, Sylwester; Pawlowska, Hanna

    2013-04-01

    Aerosol interacts with clouds by serving as cloud condensation nuclei (CCN). Its physical and chemical properties are one of the factors defining cloud droplet size distribution. On the other hand, clouds process atmospheric aerosol taking part in its wet deposition and CCN regeneration through evaporation of cloud droplets and drizzle. Physical and chemical properties of the regenerated CCN may be altered if the evaporated droplets go through collisional growth or irreversible chemical reactions. The main challenge of representing these aerosol-cloud interactions in a numerical cloud model stems from the need to track the properties of the drop nuclei throughout the cloud lifecycle. A class of methods allowing such studies is the Lagrangian particle-based simulation technique. In a simulation of cloud, each modeled particle represents a multiplicity of particles of the same nucleus type, position and size. During the simulation particle sizes change in a continuous way from CCN-sized to rain drop particles. Tracking microphysical properties of modeled particles is an inherent feature of the particle-based frameworks, making them suitable for studying aerosol-cloud-aerosol interactions. Super-droplet method is a Lagrangian technique introduced by Shima et al. (2009) featuring an efficient Monte-Carlo type solver for particle coalescence. In this study a new implementation of the super-droplet method, using the kappa-Koehler parametrisation of aerosol composition and an aqueous chemistry module for representing irreversible oxidation, will be presented. Components of the developed model will be discussed using a single-eddy prescribed-flow framework, focusing solely on the microphysical aspects of simulations. Example case will mimic a Stratocumulus cloud and depict cloud-aerosol interactions resolved by the model.

  1. Four-dimensional distribution of the 2010 Eyjafjallajökull volcanic cloud over Europe observed by EARLINET

    Directory of Open Access Journals (Sweden)

    G. Pappalardo

    2012-11-01

    Full Text Available The eruption of the Icelandic volcano Eyjafjallajökull in April/May 2010 represents a "natural experiment" to study the impact of volcanic emissions on a continental scale. For the first time, quantitative data about the presence, altitude, and layering of the volcanic cloud, in conjunction with optical information, are available for most parts of Europe derived from the observations by the European Aerosol Research Lidar NETwork (EARLINET. Based on multi-wavelength Raman lidar systems EARLINET is the only instrument worldwide that is able to provide dense time series of high-quality optical data to be used for aerosol typing and for the retrieval of particle microphysical properties as a function of altitude.

    In this work we show the four-dimensional (4-D distribution of the Eyjafjallajökull volcanic cloud over Europe as observed by EARLINET during the entire volcanic event (15 April–26 May 2010. All optical properties directly measured (backscatter, extinction, and particle linear depolarization ratio are stored in the EARLINET database available at http://www.earlinet.org. A specific relational database providing the volcanic mask over Europe, realized ad hoc for this specific event, has been developed and is available on request at http://www.earlinet.org.

    During the first days after the eruption, volcanic particles were detected over Central Europe within a wide range of altitudes, from the lower stratosphere down to the local Planetary Boundary Layer (PBL. After 19 April 2010, volcanic particles were detected over South and South Eastern Europe. During the first half of May (5–15 May, material emitted by the Eyjafjallajökull volcano was detected over Spain and Portugal and then over the Mediterranean and the Balkans. Last observations of the event were recorded until 25 May in Central Europe and in the Eastern

  2. Evaluating Global Aerosol Models and Aerosol and Water Vapor Properties Near Clouds

    Energy Technology Data Exchange (ETDEWEB)

    Richard A. Ferrare; David D. Turner

    2011-09-01

    Project goals: (1) Use the routine surface and airborne measurements at the ARM SGP site, and the routine surface measurements at the NSA site, to continue our evaluations of model aerosol simulations; (2) Determine the degree to which the Raman lidar measurements of water vapor and aerosol scattering and extinction can be used to remotely characterize the aerosol humidification factor; (3) Use the high temporal resolution CARL data to examine how aerosol properties vary near clouds; and (4) Use the high temporal resolution CARL and Atmospheric Emitted Radiance Interferometer (AERI) data to quantify entrainment in optically thin continental cumulus clouds.

  3. Satellite observations of lightning-generated NOx in volcanic eruption clouds

    Science.gov (United States)

    Carn, Simon; Krotkov, Nickolay; Pickering, Ken; Allen, Dale; Bucsela, Eric

    2016-04-01

    The generation of NO2 by lightning flashes is known to be an important source of NOx in the free troposphere, particularly in the tropics, with implications for ozone production. Although UV-visible satellite observations of lightning-generated NOx (LNOx) in thunderstorms have been previously reported, here we present the first satellite observations of LNOx generated by lightning in explosive volcanic eruption clouds (vLNOx) from the Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite. To date we have identified vLNOx in operational OMI NO2 measurements (OMNO2) during the high-latitude eruptions of Okmok (Aleutian Is; July 2008), Kasatochi (Aleutian Is; August 2008), Redoubt (Alaska; March 2009) and Grimsvötn (Iceland; May 2011), although analysis of OMNO2 data for other eruptions is underway. We use World Wide Lightning Location Network (WWLLN) observations to verify the occurrence and location of lightning flashes in the volcanic eruption clouds. All the vLNOx anomalies are associated with strong UV Aerosol Index (UVAI) signals due to volcanic ash. Preliminary analysis shows that the maximum vLNOx column detected by OMI decreases linearly with time since eruption, and suggests that the vLNOx signal is transient and can be detected up to ~5-6 hours after an eruption. Detection of vLNOx is hence only possible for eruptions occurring a few hours before the daytime OMI overpass. Based on the number of lightning flashes detected by WWLLN in each eruption cloud, we also estimate the vLNOx production efficiency (moles vLNOx per flash). Preliminary estimates for the 2008 Kasatochi eruption suggest that this is significantly higher than the production efficiency in thunderstorms, but may be biased high due to the low detection efficiency of WWLLN (aviation hazards due to volcanic ash. Furthermore, the vLNOx observations may provide information on air entrainment in volcanic eruption columns, which is required for some volcanic ash dispersion models. Although

  4. Stratocumulus cloud thickening beneath layers of absorbing smoke aerosol

    Science.gov (United States)

    Wilcox, E. M.

    2010-12-01

    Marine stratocumulus cloud properties, and the free-tropospheric environment above them, are examined in NASA A-Train satellite data for cases where smoke from seasonal burning of the West African savannah overlay the persistent southeast Atlantic stratocumulus cloud deck. CALIPSO space-borne lidar observations show that features identified as layers of aerosol occur predominantly between 2 km and 4 km. Layers identified as cloud features occur predominantly below 1.5 km altitude and beneath the layer of elevated smoke aerosol. The diurnal mean shortwave heating rates attributable to the absorption of solar energy in the aerosol layer is nearly 1.5 K d-1 for an aerosol optical thickness value of 1, and increases to 1.8 K d-1 when the smoke resides above clouds owing to the additional component of upward solar radiation reflected by the cloud. As a consequence of this heating, the 700 hPa air temperature above the cloud deck is warmer by approximately 1 K on average for cases where smoke is present above the cloud compared to cases without smoke above cloud. The warmer conditions in the free-troposphere above the cloud during smoke events coincide with cloud liquid water path values that are greater by 20 g m-2 and cloud tops that are lower for overcast conditions compared to periods with low amounts of smoke. The observed thickening and subsidence of the cloud layer are consistent with published results of large-eddy simulations showing that solar absorption by smoke above stratocumulus clouds increases the buoyancy of free-tropospheric air above the temperature inversion capping the boundary layer. Increased buoyancy inhibits the entrainment of dry air through the cloud-top, thereby helping to preserve humidity and cloud cover in the boundary layer. The direct radiative effect of absorbing aerosols residing over a bright cloud deck is a positive radiative forcing (warming) at the top of the atmosphere. However, the greater liquid water path for cases of smoke

  5. On the aerosol-cloud relationship at a high-alpine site

    Energy Technology Data Exchange (ETDEWEB)

    Baltensperger, U.; Schwikowski, M.; Jost, D.T.; Nyeki, S.; Gaeggeler, H.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Field experiments at the Jungfraujoch showed that during the presence of a cloud, most of the aerosol mass is transferred into the cloud phase. This results in smaller cloud droplets for increasing aerosol concentration, which increases the albedo of clouds (known as the indirect effect of climate forcing by aerosol particles). (author) 1 fig., 4 refs.

  6. Cloud-Aerosol-Radiation (CAR ensemble modeling system

    Directory of Open Access Journals (Sweden)

    X.-Z. Liang

    2013-04-01

    Full Text Available A Cloud-Aerosol-Radiation (CAR ensemble modeling system has been developed to incorporate the largest choices of alternative parameterizations for cloud properties (cover, water, radius, optics, geometry, aerosol properties (type, profile, optics, radiation transfers (solar, infrared, and their interactions. These schemes form the most comprehensive collection currently available in the literature, including those used by the world leading general circulation models (GCMs. The CAR provides a unique framework to determine (via intercomparison across all schemes, reduce (via optimized ensemble simulations, and attribute specific key factors for (via physical process sensitivity analyses the model discrepancies and uncertainties in representing greenhouse gas, aerosol and cloud radiative forcing effects. This study presents a general description of the CAR system and illustrates its capabilities for climate modeling applications, especially in the context of estimating climate sensitivity and uncertainty range caused by cloud-aerosol-radiation interactions. For demonstration purpose, the evaluation is based on several CAR standalone and coupled climate model experiments, each comparing a limited subset of the full system ensemble with up to 896 members. It is shown that the quantification of radiative forcings and climate impacts strongly depends on the choices of the cloud, aerosol and radiation schemes. The prevailing schemes used in current GCMs are likely insufficient in variety and physically biased in a significant way. There exists large room for improvement by optimally combining radiation transfer with cloud property schemes.

  7. Aerosol-cloud interactions from urban, regional to global scales

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuan [California Institute of Technology, Pasadena, CA (United States). Seismological Lab.

    2015-10-01

    The studies in this dissertation aim at advancing our scientific understandings about physical processes involved in the aerosol-cloud-precipitation interaction and quantitatively assessing the impacts of aerosols on the cloud systems with diverse scales over the globe on the basis of the observational data analysis and various modeling studies. As recognized in the Fifth Assessment Report by the Inter-government Panel on Climate Change, the magnitude of radiative forcing by atmospheric aerosols is highly uncertain, representing the largest uncertainty in projections of future climate by anthropogenic activities. By using a newly implemented cloud microphysical scheme in the cloud-resolving model, the thesis assesses aerosol-cloud interaction for distinct weather systems, ranging from individual cumulus to mesoscale convective systems. This thesis also introduces a novel hierarchical modeling approach that solves a long outstanding mismatch between simulations by regional weather models and global climate models in the climate modeling community. More importantly, the thesis provides key scientific solutions to several challenging questions in climate science, including the global impacts of the Asian pollution. As scientists wrestle with the complexities of climate change in response to varied anthropogenic forcing, perhaps no problem is more challenging than the understanding of the impacts of atmospheric aerosols from air pollution on clouds and the global circulation.

  8. Aerosol activation and cloud processing in the global aerosol-climate model ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    G. J. Roelofs

    2006-01-01

    Full Text Available A parameterization for cloud processing is presented that calculates activation of aerosol particles to cloud drops, cloud drop size, and pH-dependent aqueous phase sulfur chemistry. The parameterization is implemented in the global aerosol-climate model ECHAM5-HAM. The cloud processing parameterization uses updraft speed, temperature, and aerosol size and chemical parameters simulated by ECHAM5-HAM to estimate the maximum supersaturation at the cloud base, and subsequently the cloud drop number concentration (CDNC due to activation. In-cloud sulfate production occurs through oxidation of dissolved SO2 by ozone and hydrogen peroxide. The model simulates realistic distributions for annually averaged CDNC although it is underestimated especially in remote marine regions. On average, CDNC is dominated by cloud droplets growing on particles from the accumulation mode, with smaller contributions from the Aitken and coarse modes. The simulations indicate that in-cloud sulfate production is a potentially important source of accumulation mode sized cloud condensation nuclei, due to chemical growth of activated Aitken particles and to enhanced coalescence of processed particles. The strength of this source depends on the distribution of produced sulfate over the activated modes. This distribution is affected by uncertainties in many parameters that play a direct role in particle activation, such as the updraft velocity, the aerosol chemical composition and the organic solubility, and the simulated CDNC is found to be relatively sensitive to these uncertainties.

  9. Aerosol and Cloud Microphysical Characteristics of Rifts and Gradients in Maritime Stratocumulus Clouds

    Science.gov (United States)

    Sharon, Tarah M.; Albrecht, Bruce A.; Jonsson, Haflidi H.; Minnis, Patrick; Khaiyer, Mandana M.; Van Reken, Timothy; Seinfeld, John; Flagan, Rick

    2008-01-01

    A cloud rift is characterized as a large-scale, persistent area of broken, low reflectivity stratocumulus clouds usually surrounded by a solid deck of stratocumulus. A rift observed off the coast of Monterey Bay, California on 16 July 1999 was studied to compare the aerosol and cloud microphysical properties in the rift with those of the surrounding solid stratus deck. Variables measured from an instrumented aircraft included temperature, water vapor, and cloud liquid water. These measurements characterized the thermodynamic properties of the solid deck and rift areas. Microphysical measurements made included aerosol, cloud drop and drizzle drop concentrations and cloud condensation nuclei (CCN) concentrations. The microphysical characteristics in a solid stratus deck differ substantially from those of a broken, cellular rift where cloud droplet concentrations are a factor of 2 lower than those in the solid cloud. Further, CCN concentrations were found to be about 3 times greater in the solid cloud area compared with those in the rift and aerosol concentrations showed a similar difference as well. Although drizzle was observed near cloud top in parts of the solid stratus cloud, the largest drizzle rates were associated with the broken clouds within the rift area. In addition to marked differences in particle concentrations, evidence of a mesoscale circulation near the solid cloud rift boundary is presented. This mesoscale circulation provides a mechanism for maintaining a rift, but further study is required to understand the initiation of a rift and the conditions that may cause it to fill.

  10. Sensitivities of Amazonian clouds to aerosols and updraft speed

    Science.gov (United States)

    Cecchini, Micael A.; Machado, Luiz A. T.; Andreae, Meinrat O.; Martin, Scot T.; Albrecht, Rachel I.; Artaxo, Paulo; Barbosa, Henrique M. J.; Borrmann, Stephan; Fütterer, Daniel; Jurkat, Tina; Mahnke, Christoph; Minikin, Andreas; Molleker, Sergej; Pöhlker, Mira L.; Pöschl, Ulrich; Rosenfeld, Daniel; Voigt, Christiane; Weinzierl, Bernadett; Wendisch, Manfred

    2017-08-01

    The effects of aerosol particles and updraft speed on warm-phase cloud microphysical properties are studied in the Amazon region as part of the ACRIDICON-CHUVA experiment. Here we expand the sensitivity analysis usually found in the literature by concomitantly considering cloud evolution, putting the sensitivity quantifications into perspective in relation to in-cloud processing, and by considering the effects on droplet size distribution (DSD) shape. Our in situ aircraft measurements over the Amazon Basin cover a wide range of particle concentration and thermodynamic conditions, from the pristine regions over coastal and forested areas to the southern Amazon, which is highly polluted from biomass burning. The quantitative results show that particle concentration is the primary driver for the vertical profiles of effective diameter and droplet concentration in the warm phase of Amazonian convective clouds, while updraft speeds have a modulating role in the latter and in total condensed water. The cloud microphysical properties were found to be highly variable with altitude above cloud base, which we used as a proxy for cloud evolution since it is a measure of the time droplets that were subject to cloud processing. We show that DSD shape is crucial in understanding cloud sensitivities. The aerosol effect on DSD shape was found to vary with altitude, which can help models to better constrain the indirect aerosol effect on climate.

  11. The NASA Decadal Survey Aerosol, Cloud, Ecosystems Mission

    Science.gov (United States)

    McClain, Charles R.; Bontempi, Paula; Maring, Hal

    2011-01-01

    In 2007, the National Academy of Sciences delivered a Decadal Survey (Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond) for NASA, NOAA, and USGS, which is a prioritization of future satellite Earth observations. The recommendations included 15 missions (13 for NASA, two for NOAA), which were prioritized into three groups or tiers. One of the second tier missions is the Aerosol, Cloud, (ocean) Ecosystems (ACE) mission, which focuses on climate forcing, cloud and aerosol properties and interactions, and ocean ecology, carbon cycle science, and fluxes. The baseline instruments recommended for ACE are a cloud radar, an aerosol/cloud lidar, an aerosol/cloud polarimeter, and an ocean radiometer. The instrumental heritage for these measurements are derived from the Cloudsat, CALIPSO, Glory, SeaWiFS and Aqua (MODIS) missions. In 2008, NASA HQ, lead by Hal Maring and Paula Bontempi, organized an interdisciplinary science working group to help formulate the ACE mission by refining the science objectives and approaches, identifying measurement (satellite and field) and mission (e.g., orbit, data processing) requirements, technology requirements, and mission costs. Originally, the disciplines included the cloud, aerosol, and ocean biogeochemistry communities. Subsequently, an ocean-aerosol interaction science working group was formed to ensure the mission addresses the broadest range of science questions possible given the baseline measurements, The ACE mission is a unique opportunity for ocean scientists to work closely with the aerosol and cloud communities. The science working groups are collaborating on science objectives and are defining joint field studies and modeling activities. The presentation will outline the present status of the ACE mission, the science questions each discipline has defined, the measurement requirements identified to date, the current ACE schedule, and future opportunities for broader community

  12. 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

  13. Indirect and Semi-Direct Aerosol Campaign: The Impact of Arctic Aerosols on Clouds

    Energy Technology Data Exchange (ETDEWEB)

    McFarquhar, Greg; Ghan, Steven J.; Verlinde, J.; Korolev, Alexei; Strapp, J. Walter; Schmid, Beat; Tomlinson, Jason M.; Wolde, Mengistu; Brooks, Sarah D.; Cziczo, Daniel J.; Dubey, Manvendra K.; Fan, Jiwen; Flynn, Connor J.; Gultepe, Ismail; Hubbe, John M.; Gilles, Mary K.; Laskin, Alexander; Lawson, Paul; Leaitch, W. R.; Liu, Peter S.; Liu, Xiaohong; Lubin, Dan; Mazzoleni, Claudio; Macdonald, A. M.; Moffet, Ryan C.; Morrison, H.; Ovchinnikov, Mikhail; Shupe, Matthew D.; Turner, David D.; Xie, Shaocheng; Zelenyuk, Alla; Bae, Kenny; Freer, Matthew; Glen, Andrew

    2011-02-01

    A comprehensive dataset of microphysical and radiative properties of aerosols and clouds in the arctic boundary layer in the vicinity of Barrow, Alaska was collected in April 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) sponsored by the Department of Energy Atmospheric Radiation Measurement (ARM) and Atmospheric Science Programs. The primary aim of ISDAC was to examine indirect effects of aerosols on clouds that contain both liquid and ice water. The experiment utilized the ARM permanent observational facilities at the North Slope of Alaska (NSA) in Barrow. These include a cloud radar, a polarized micropulse lidar, and an atmospheric emitted radiance interferometer as well as instruments specially deployed for ISDAC measuring aerosol, ice fog, precipitation and spectral shortwave radiation. The National Research Council of Canada Convair-580 flew 27 sorties during ISDAC, collecting data using an unprecedented 42 cloud and aerosol instruments for more than 100 hours on 12 different days. Data were obtained above, below and within single-layer stratus on 8 April and 26 April 2008. These data enable a process-oriented understanding of how aerosols affect the microphysical and radiative properties of arctic clouds influenced by different surface conditions. Observations acquired on a heavily polluted day, 19 April 2008, are enhancing this understanding. Data acquired in cirrus on transit flights between Fairbanks and Barrow are improving our understanding of the performance of cloud probes in ice. Ultimately the ISDAC data will be used to improve the representation of cloud and aerosol processes in models covering a variety of spatial and temporal scales, and to determine the extent to which long-term surface-based measurements can provide retrievals of aerosols, clouds, precipitation and radiative heating in the Arctic.

  14. Testing exposure of a jet engine to a dilute volcanic-ash cloud

    Science.gov (United States)

    Guffanti, M.; Mastin, L. G.; Schneider, D. J.; Holliday, C. R.; Murray, J. J.

    2013-12-01

    An experiment to test the effects of volcanic-ash ingestion by a jet engine is being planned for 2014 by a consortium of U.S. Government agencies and engine manufacturers, under the auspices of NASA's Vehicle Integrated Propulsion Research Program. The experiment, using a 757-type engine, will be an on-ground, on-wing test carried out at Edwards Air Force Base, California. The experiment will involve the use of advanced jet-engine sensor technology for detecting and diagnosing engine health. A primary test objective is to determine the effect on the engine of many hours of exposure to ash concentrations (1 and 10 mg/cu m) representative of ash clouds many 100's to >1000 km from a volcanic source, an aviation environment of great interest since the 2010 Eyjafjallajökull, Iceland, eruption. A natural volcanic ash will be used; candidate sources are being evaluated. Data from previous ash/aircraft encounters, as well as published airborne measurements of the Eyjafjallajökull ash cloud, suggest the ash used should be composed primarily of glassy particles of andesitic to rhyolitic composition (SiO2 of 57-77%), with some mineral crystals, and a few tens of microns in size. Collected ash will be commercially processed less than 63 microns in size with the expectation that the ash particles will be further pulverized to smaller sizes in the engine during the test. For a nominally planned 80 hour test at multiple ash-concentration levels, the test will require roughly 500 kg of processed (appropriately sized) ash to be introduced into the engine core. Although volcanic ash clouds commonly contain volcanic gases such as sulfur dioxide, testing will not include volcanic gas or aerosol interactions as these present complex processes beyond the scope of the planned experiment. The viscous behavior of ash particles in the engine is a key issue in the experiment. The small glassy ash particles are expected to soften in the engine's hot combustion chamber, then stick to cooler

  15. Aerosol activation and cloud processing in the global aerosol-climate model ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    G. J. Roelofs

    2006-01-01

    Full Text Available A parameterization for cloud processing is presented that calculates activation of aerosol particles to cloud drops, cloud drop size, and pH-dependent aqueous phase sulfur chemistry. The parameterization is implemented in the global aerosol-climate model ECHAM5-HAM. The cloud processing parameterization uses updraft speed, temperature, and aerosol size and chemical parameters simulated by ECHAM5-HAM to estimate the maximum supersaturation at the cloud base, and subsequently the cloud drop number concentration (CDNC due to activation. In-cloud sulfate production occurs through oxidation of dissolved SO2 by ozone and hydrogen peroxide. The model simulates realistic distributions for annually averaged CDNC although it is underestimated especially in remote marine regions. On average, CDNC is dominated by particles from the accumulation mode, with smaller contributions from the Aitken and coarse modes. The simulations indicate that in-cloud sulfate production is a potentially important source of accumulation mode sized cloud condensation nuclei, due to chemical growth of activated Aitken particles and to enhanced coalescence of processed particles. The strength of this source depends on the distribution of produced sulfate over the activated modes. This distribution is affected by uncertainties in many parameters that play a direct role in particle activation, such as the updraft velocity, the aerosol chemical composition and the organic solubility, and the simulated CDNC is found to be relatively sensitive to these uncertainties.

  16. The impact of stratospheric volcanic aerosol on decadal-scale climate predictions

    Science.gov (United States)

    Timmreck, Claudia; Pohlmann, Holger; Illing, Sebastian; Kadow, Christopher

    2016-04-01

    The possibility of a large future volcanic eruption provides arguably the largest uncertainty concerning the evolution of the climate system on the time scale of a few years; but also the greatest opportunity to learn about the behavior of the climate system, and our models thereof. So the question emerges how large will the uncertainty be for future decadal climate predictions if no volcanic aerosol is taken into account? And how strong has volcanic aerosol affected decadal prediction skill on annual and multi-year seasonal scales over the CMIP5 hindcast period? To understand the impact of volcanic aerosol on multi-year seasonal and decadal climate predictions we performed CMIP5-type hindcasts without volcanic aerosol using the German MiKlip prediction system system baseline 1 from 1961 to 1991 and compared them to the corresponding simulations including aerosols. Our results show that volcanic aerosol significantly affects the prediction skill for global mean surface air temperature in the first five years after strong volcanic eruptions. Also on the regional scale a volcanic imprint on decadal-scale variability is detectable. Neglecting volcanic aerosol leads to a reduced prediction skill over the tropical and subtropical Atlantic, Indic and West Pacific but to an improvement over the tropical East-Pacific, where the model has in general no skill. Multi-seasonal differences in the skill for seasonal-mean temperatures are evident over Continental Europe with significant skill loss due to neglection of volcanic aerosol in boreal winter over central Europe, Scandinavia and over south-eastern Europe and the East-Mediterranean in boreal summer.

  17. Spectral signatures of polar stratospheric clouds and sulfate aerosol

    Energy Technology Data Exchange (ETDEWEB)

    Massie, S.T.; Bailey, P.L.; Gille, J.C. [National Center for Atmospheric Research, Boulder, CO (United States); Lee, E.C. [Princeton Univ., NJ (United States); Mergenthaler, J.L.; Roche, A.E.; Kumer, J.B. [Lockheed Palo Alto Research Lab., CA (United States); Fishbein, E.F.; Waters, J.W. [California Institute of Technology, Pasadena, CA (United States); Lahoz, W.A. [Univ. of Reading (United Kingdom)

    1994-10-15

    Multiwavelength observations of Antarctic and midlatitude aerosol by the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment on the Upper Atmosphere Research Satellite are used to demonstrate a technique that identifies the location of polar stratospheric clouds. The technique discussed uses the normalized area of the triangle formed by the aerosol extinctions at 925, 1257, and 1605 cm{sup {minus}1} (10.8, 8.0, and 6.2 {mu}m) to derive a spectral aerosol measure M of the aerosol spectrum. Mie calculations for spherical particles and T-matrix calculations for spheroidal particles are used to generate theoretical spectral extinction curves for sulfate and polar stratospheric cloud particles. The values of the spectral aerosol measure M for the sulfate and polar stratospheric cloud particles are shown to be different. Aerosol extinction data, corresponding to temperatures between 180 and 220 K at a pressure of 46 hPa (near 21-km altitude) for 18 August 1992, are used to demonstrate the technique. Thermodynamic calculations, based upon frost-point calculation and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles. 47 refs., 22 figs., 3 tabs.

  18. BAECC Biogenic Aerosols - Effects on Clouds and Climate

    Energy Technology Data Exchange (ETDEWEB)

    Petäjä, Tuukka [Univ. of Helsinki (Finland); Moisseev, Dmitri [Univ. of Helsinki (Finland); Sinclair, Victoria [Univ. of Helsinki (Finland); O' Connor, Ewan J. [Finnish Meteorological Institute, Helsinki (Finland); Manninen, Antti J. [Univ. of Helsinki (Finland); Levula, Janne [Univ. of Helsinki (Finland); Väänänen, Riikka [Univ. of Helsinki (Finland); Heikkinen, Liine [Univ. of Helsinki (Finland); Äijälä, Mikko [Univ. of Helsinki (Finland); Aalto, Juho [Univ. of Helsinki (Finland); Bäck, Jaana [University of Helsinki, Finland

    2015-11-01

    “Biogenic Aerosols - Effects on Clouds and Climate (BAECC)”, featured the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Program’s 2nd Mobile Facility (AMF2) in Hyytiälä, Finland. It operated for an 8-month intensive measurement campaign from February to September 2014. The main research goal was to understand the role of biogenic aerosols in cloud formation. One of the reasons to perform BAECC study in Hyytiälä was the fact that it hosts SMEAR-II (Station for Measuring Forest Ecosystem-Atmosphere Relations), which is one of the world’s most comprehensive surface in-situ observation sites in a boreal forest environment. The station has been measuring atmospheric aerosols, biogenic emissions and an extensive suite of parameters relevant to atmosphere-biosphere interactions continuously since 1996. The BAECC enables combining vertical profiles from AMF2 with surface-based in-situ SMEAR-II observations and allows the processes at the surface to be directly related to processes occurring throughout the entire tropospheric column. With the inclusion of extensive surface precipitation measurements, and intensive observation periods involving aircraft flights and novel radiosonde launches, the complementary observations of AMF2 and SMEAR-II provide a unique opportunity for investigating aerosol-cloud interactions, and cloud-to-precipitation processes. The BAECC dataset will initiate new opportunities for evaluating and improving models of aerosol sources and transport, cloud microphysical processes, and boundary-layer structures.

  19. 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.

  20. Meteorological and Aerosol effects on Marine Cloud Microphysical Properties

    Science.gov (United States)

    Sanchez, K. J.; Russell, L. M.; Modini, R. L.; Frossard, A. A.; Ahlm, L.; Roberts, G.; Hawkins, L. N.; Schroder, J. C.; Wang, Z.; Lee, A.; Abbatt, J.; Lin, J.; Nenes, A.; Wonaschuetz, A.; Sorooshian, A.; Noone, K.; Jonsson, H.; Albrecht, B. A.; Desiree, T. S.; Macdonald, A. M.; Seinfeld, J.; Zhao, R.

    2015-12-01

    Both meteorology and microphysics affect cloud formation and consequently their droplet distributions and shortwave reflectance. The Eastern Pacific Emitted Aerosol Cloud Experiment (EPEACE) and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) studies provide detailed measurements in 6 case studies of both cloud thermodynamic properties and initial particle number distribution and composition, as well as the resulting cloud drop distribution and composition. This study uses simulations of a detailed chemical and microphysical aerosol-cloud parcel (ACP) model with explicit kinetic drop activation to reproduce the observed cloud droplet distribution and composition. Four of the cases examined had a sub-adiabatic lapse rate, which was shown to have fewer droplets due to decreased maximum supersaturation, lower LWC and higher cloud base height, consistent with previous findings. These detailed case studies provided measured thermodynamics and microphysics that constrained the simulated droplet size distribution sufficiently to match the droplet number within 6% and the size within 19% for 4 of the 6 cases, demonstrating "closure" or consistency of the measured composition with the measured CCN spectra and the inferred and modeled supersaturation. The contribution of organic components to droplet formation shows small effects on the droplet number and size in the 4 marine cases that had background aerosol conditions with varying amounts of coastal, ship or other non-biogenic sources. In contrast, the organic fraction and hygroscopicity increased the droplet number and size in the cases with generated smoke and cargo ship plumes that were freshly emitted and not yet internally mixed with the background particles. The simulation results show organic hygroscopicity causes small effects on cloud reflectivity (smoke plume which increased absolute cloud reflectivity fraction by 0.02 and 0.20 respectively. In addition, the ACP model

  1. Assessment of aerosol-cloud interactions during southern African biomass burning activity, employing cloud parameterizations

    Science.gov (United States)

    Wiston, Modise; McFiggans, Gordon; Schultz, David

    2015-04-01

    In this study, we perform a simulation of the spatial distributions of particle and gas concentrations from a significantly large source of pollution event during a dry season in southern Africa and their interactions with cloud processes. Specific focus is on the extent to which cloud-aerosol interactions are affected by various inputs (i.e. emissions) and parameterizations and feedback mechanisms in a coupled mesoscale chemistry-meteorology model -herein Weather Research and Forecasting model with chemistry (WRF-Chem). The southern African dry season (May-Sep) is characterised by biomass burning (BB) type of pollution. During this period, BB particles are frequently observed over the subcontinent, at the same time a persistent deck of stratocumulus covers the south West African coast, favouring long-range transport over the Atlantic Ocean of aerosols above clouds. While anthropogenic pollutants tend to spread more over the entire domain, biomass pollutants are concentrated around the burning areas, especially the savannah and tropical rainforest of the Congo Basin. BB is linked to agricultural practice at latitudes south of 10° N. During an intense burning event, there is a clear signal of strong interactions of aerosols and cloud microphysics. These species interfere with the radiative budget, and directly affect the amount of solar radiation reflected and scattered back to space and partly absorbed by the atmosphere. Aerosols also affect cloud microphysics by acting as cloud condensation nuclei (CCN), modifying precipitation pattern and the cloud albedo. Key area is to understand the role of pollution on convective cloud processes and its impacts on cloud dynamics. The hypothesis is that an environment of potentially high pollution enables the probability of interactions between co-located aerosols and cloud layers. To investigate this hypothesis, we outline an approach to integrate three elements: i) focusing on regime(s) where there are strong indications of

  2. The relationship between aerosol and cloud drop number concentrations in a global aerosol microphysics model

    Directory of Open Access Journals (Sweden)

    K. J. Pringle

    2009-01-01

    Full Text Available Empirical relationships that link cloud droplet number (CDN to aerosol number or mass are commonly used to calculate global fields of CDN for climate forcing assessments. In this work we use a sectional global model of sulfate and sea-salt aerosol coupled to a mechanistic aerosol activation scheme to explore the limitations of this approach. We find that a given aerosol number concentration produces a wide range of CDN concentrations due to variations in the shape of the aerosol size distribution. On a global scale, the dependence of CDN on the size distribution results in regional biases in predicted CDN (for a given aerosol number. Empirical relationships between aerosol number and CDN are often derived from regional data but applied to the entire globe. In an analogous process, we derive regional "correlation-relations" between aerosol number and CDN and apply these regional relations to calculations of CDN on the global scale. The global mean percentage error in CDN caused by using regionally derived CDN-aerosol relations is 20 to 26%, which is about half the global mean percentage change in CDN caused by doubling the updraft velocity. However, the error is as much as 25–75% in the Southern Ocean, the Arctic and regions of persistent stratocumulus when an aerosol-CDN correlation relation from the North Atlantic is used. These regions produce much higher CDN concentrations (for a given aerosol number than predicted by the globally uniform empirical relations. CDN-aerosol number relations from different regions also show very different sensitivity to changing aerosol. The magnitude of the rate of change of CDN with particle number, a measure of the aerosol efficacy, varies by a factor 4. CDN in cloud processed regions of persistent stratocumulus is particularly sensitive to changing aerosol number. It is therefore likely that the indirect effect will be underestimated in these important regions.

  3. The relationship between aerosol and cloud drop number concentrations in a global aerosol microphysics model

    Directory of Open Access Journals (Sweden)

    K. J. Pringle

    2009-06-01

    Full Text Available Empirical relationships that link cloud droplet number (CDN to aerosol number or mass are commonly used to calculate global fields of CDN for climate forcing assessments. In this work we use a sectional global model of sulfate and sea-salt aerosol coupled to a mechanistic aerosol activation scheme to explore the limitations of this approach. We find that a given aerosol number concentration produces a wide range of CDN concentrations due to variations in the shape of the aerosol size distribution. On a global scale, the dependence of CDN on the size distribution results in regional biases in predicted CDN (for a given aerosol number. Empirical relationships between aerosol number and CDN are often derived from regional data but applied to the entire globe. In an analogous process, we derive regional "correlation-relations" between aerosol number and CDN and apply these regional relations to calculations of CDN on the global scale. The global mean percentage error in CDN caused by using regionally derived CDN-aerosol relations is 20 to 26%, which is about half the global mean percentage change in CDN caused by doubling the updraft velocity. However, the error is as much as 25–75% in the Southern Ocean, the Arctic and regions of persistent stratocumulus when an aerosol-CDN correlation relation from the North Atlantic is used. These regions produce much higher CDN concentrations (for a given aerosol number than predicted by the globally uniform empirical relations. CDN-aerosol number relations from different regions also show very different sensitivity to changing aerosol. The magnitude of the rate of change of CDN with particle number, a measure of the aerosol efficacy, varies by a factor 4. CDN in cloud processed regions of persistent stratocumulus is particularly sensitive to changing aerosol number. It is therefore likely that the indirect effect will be underestimated in these important regions.

  4. Temporal variations of flux and altitude of sulfur dioxide emissions during volcanic eruptions: implications for long-range dispersal of volcanic clouds

    Directory of Open Access Journals (Sweden)

    M. Boichu

    2015-07-01

    exploiting the high spectral resolution of IASI. The validity of the modelled SO2 altitude is further confirmed by the detection of a layer of particles at the same altitude by the spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP. Analysis of CALIOP colour and depolarization ratios suggests that these particles consist of sulfate aerosols formed from precursory volcanic SO2. The reconstruction of emission altitude, through inversion procedures which assimilate volcanic SO2 column amounts, requires specific meteorological conditions, especially sufficient wind shear so that gas parcels emitted at different altitudes follow distinct trajectories. We consequently explore the possibility and limits of assimilating in inverse schemes infrared (IR imagery of the volcanic SO2 cloud altitude which will render the inversion procedure independent of the wind shear prerequisite.

  5. Aerosol Effect on the Phase of Low-Level Clouds in the Arctic

    Science.gov (United States)

    Filioglou, M.; Mielonen, T.; Giannakaki, E.; Arola, A. T.; Komppula, M.; Romakkaniemi, S.

    2016-12-01

    Cloud phase (liquid or ice) affects the cloud's persistence and optical properties, and thus the atmospheric radiation balance. In the warming Arctic, the transition from ice to liquid clouds has a potential to enhance the warming rate, however, changes in aerosol properties can affect the cloud phase even more substantially. Here, a characterization of low level clouds and their dependence on dust aerosols, which are assumed to be the most important ice nuclei (IN) over the Arctic area, is presented based on measurements from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The level 2 aerosol and cloud layer products with 5 km horizontal resolution from the CALIOP lidar (Cloud-Aerosol Lidar with Orthogonal Polarization) were employed for the period June 2006 to December 2015. The three available cloud phases (ice, water, unknown) were linked with the coinciding aerosol type characterization (dust, polluted dust, smoke and background aerosols). Based on the ice cloud fraction calculations done in this study, clouds freeze in warmer temperatures in the presence of dust particles than with other aerosol types. A difference in the cloud freezing temperature as high as 7o C was observed. Thus, dust aerosols have a high potential to affect the properties of Arctic clouds. Furthermore, possible increments in efficient IN due to long-range transported aerosols or new local aerosol sources due to anthropogenic activities may lead to optically thinner clouds modifying the radiation balance over Arctic.

  6. Phosphorus-bearing Aerosol Particles From Volcanic Plumes

    Science.gov (United States)

    Obenholzner, J. H.; Schroettner, H.; Poelt, P.; Delgado, H.; Caltabiano, T.

    2003-12-01

    Particles rich in P or bulk geochemical data of volcanic aerosol particles showing high P contents are known from many volcanic plumes (Stanton, 1994; Obenholzner et al., 2003). FESEM/EDS analysis of individual particles obtained from the passively degassing plume of Popocatepetl volcano, Mx. (1997) and from the plume of Stromboli (May 2003) show P frequently. Even at the high resolution of the FESEM, euhedral apatite crystals could not be observed. At Popocatepetl (1997) spherical Ca-P-O particles are common. Fluffy, fractal or botryoidal particles also can contain EDS-detectable amounts of P. The EDS spectrum of such particles can comprise various elements. However most particles show P, S and Cl. P-S and P-S-metal species are known in chemistry but do they occur in volcanic plumes? Stoichiometric considerations had been made in the past suggesting the existence of P-S species in plumes (Stanton 1994), gas sampling and remote gas monitoring systems have not detected yet such molecules in plumes. The particle spectrum of the reawakened Popocateptel volcano might be related to accumulation of volatiles at the top of a magma chamber during the phase of dormancy. P-Fe rich, Ca-free aggregates are also known from the eruption of El Chichon 1982 (SEM/EDS by M. Sheridan, per. comm. 08-24-2003). Persistently active volcanoes (i.e. Stromboli) represent a different category according to continuous degassing and aerosol particle formation. A particle collector ( ca. 90 ml/min) accompanied a COSPEC helicopter flight at Stromboli (May 15, 2003) after one of the rare types of sub-plinian events on April 5 2003. P-bearing particles are very common. For instance, an Fe oxide grain (diam. = 2 æm) is partially covered by fluffy and euhedral P-bearing matter. The elements detected are P, Cl, Na, Mg, Al, Si, K, Ca, Ti and (Fe). The fluffy and the euhedral (rhombohedral?) matter show in SE-BSE-mix image almost identical grey colors. At Stromboli and Popocatepetl particles on which

  7. 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.

  8. Regional radiative impact of volcanic aerosol from the 2009 eruption of Redoubt volcano

    Directory of Open Access Journals (Sweden)

    C. L. Young

    2011-09-01

    Full Text Available High northern latitude eruptions have the potential to release volcanic aerosol into the Arctic environment, perturbing the Arctic's climate system. In this study, we present assessments of shortwave (SW, longwave (LW and net direct aerosol radiative forcings (DARFs and atmospheric heating/cooling rates caused by volcanic aerosol from the 2009 eruption of Redoubt Volcano by performing radiative transfer modeling constrained by NASA A-Train satellite data. The Ozone Monitoring Instrument (OMI, the Moderate Resolution Imaging Spectroradiometer (MODIS, and the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT model for volcanic ash were used to characterize aerosol across the region. A representative range of aerosol optical depths (AODs at 550 nm were obtained from MODIS, and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO was used to determine the altitude and thickness of the plumes. The optical properties of volcanic aerosol were calculated using a compositionally resolved microphysical model developed for both ash and sulfates. Two compositions of volcanic aerosol were considered in order to examine a fresh, ash rich plume and an older, ash poor plume. Optical models were incorporated into a modified version of the Santa Barbara Disort Atmospheric Radiative Transfer (SBDART model. Radiative transfer calculations were made for a range of surface albedos and solar zenith angles (SZA representative of the region. We find that the total DARF caused by a fresh, thin plume (~2.5–7 km at an AOD (550 nm range of 0.16–0.58 and SZA = 55° is –46 W m−2AOD−1 at the top of the atmosphere (TOA, 110 W m−2AOD−1 in the aerosol layer, and – 150 W m−2AOD−1 at the surface over seawater. However, the total DARF for the same plume over snow and at the same SZA at TOA, in the layer, and at the surface is 170, 170, and −2 W m−2

  9. Evaluating Global Aerosol Models and Aerosol and Water Vapor Properties Near Clouds

    Energy Technology Data Exchange (ETDEWEB)

    Turner, David, D.; Ferrare, Richard, A.

    2011-07-06

    The 'Evaluating Global Aerosol Models and Aerosol and Water Vapor Properties Near Clouds' project focused extensively on the analysis and utilization of water vapor and aerosol profiles derived from the ARM Raman lidar at the Southern Great Plains ARM site. A wide range of different tasks were performed during this project, all of which improved quality of the data products derived from the lidar or advanced the understanding of atmospheric processes over the site. These activities included: upgrading the Raman lidar to improve its sensitivity; participating in field experiments to validate the lidar aerosol and water vapor retrievals; using the lidar aerosol profiles to evaluate the accuracy of the vertical distribution of aerosols in global aerosol model simulations; examining the correlation between relative humidity and aerosol extinction, and how these change, due to horizontal distance away from cumulus clouds; inferring boundary layer turbulence structure in convective boundary layers from the high-time-resolution lidar water vapor measurements; retrieving cumulus entrainment rates in boundary layer cumulus clouds; and participating in a field experiment that provided data to help validate both the entrainment rate retrievals and the turbulent profiles derived from lidar observations.

  10. Aerosol-Cloud Interactions during Tropical Deep Convection: Evidence for the Importance of Free Tropospheric Aerosols

    Science.gov (United States)

    Ackerman, A.; Jensen, E.; Stevens, D.; Wang, D.; Heymsfield, A.; Miloshevich, L.; Twohy, C.; Poellot, M.; VanReken, T.; Fridland, Ann

    2003-01-01

    NASA's 2002 CRYSTAL-FACE field experiment focused on the formation and evolution of tropical cirrus cloud systems in southern Florida. Multiple aircraft extensively sampled cumulonimbus dynamical and microphysical properties, as well as characterizing ambient aerosol populations both inside and outside the full depth of the convective column. On July 18, unique measurements were taken when a powerful updraft was traversed directly by aircraft, providing a window into the primary source region of cumulonimbus anvil crystals. Observations of the updraft, entered at approximately l0 km altitude and -34 C, indicated more than 200 cloud particles per mL at vertical velocities exceeding 20 m/s and the presence of significant condensation nuclei and liquid water within the core. In this work, aerosol and cloud phase observations are integrated by simulating the updraft conditions using a large-eddy resolving model with 3 explicit multiphase microphysics, including treatment of size-resolved aerosol fields, aerosol activation and freezing, and evaporation of cloud particles back to the aerosol phase. Simulations were initialized with observed thermodynamic and aerosol size distributions profiles and convection was driven by surface fluxes assimilated from the ARPS forecast model. Model results are consistent with the conclusions that most crystals are homogeneously frozen droplets and that entrained free tropospheric aerosols may contribute a significant fraction of the crystals. Thus most anvil crystals appear to be formed aloft in updraft cores, well above cloud base. These conclusions are supported by observations of hydrometeor size distribution made while traversing the dore, as well as aerosol and cloud particle size distributions generally observed by aircraft below 4km and crystal properties generally observed by aircraft above 12km.

  11. Effects of Ocean Ecosystem on Marine Aerosol-Cloud Interaction

    Directory of Open Access Journals (Sweden)

    Nicholas Meskhidze

    2010-01-01

    Full Text Available Using satellite data for the surface ocean, aerosol optical depth (AOD, and cloud microphysical parameters, we show that statistically significant positive correlations exist between ocean ecosystem productivity, the abundance of submicron aerosols, and cloud microphysical properties over different parts of the remote oceans. The correlation coefficient for remotely sensed surface chlorophyll a concentration ([Chl-a] and liquid cloud effective radii over productive areas of the oceans varies between −0.2 and −0.6. Special attention is given to identifying (and addressing problems from correlation analysis used in the previous studies that can lead to erroneous conclusions. A new approach (using the difference between retrieved AOD and predicted sea salt aerosol optical depth, AODdiff is developed to explore causal links between ocean physical and biological systems and the abundance of cloud condensation nuclei (CCN in the remote marine atmosphere. We have found that over multiple time periods, 550 nm AODdiff (sensitive to accumulation mode aerosol, which is the prime contributor to CCN correlates well with [Chl-a] over the productive waters of the Southern Ocean. Since [Chl-a] can be used as a proxy of ocean biological productivity, our analysis demonstrates the role of ocean ecology in contributing CCN, thus shaping the microphysical properties of low-level marine clouds.

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

    Science.gov (United States)

    Loeb, Norman G.; Schuster, Gregory L.

    2008-01-01

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

  13. Model-based aviation advice on distal volcanic ash clouds by assimilating aircraft in situ measurements

    NARCIS (Netherlands)

    Fu, G.; Heemink, A.; Lu, S.; Segers, A.; Weber, K.; Lin, H.X.

    2016-01-01

    The forecast accuracy of distal volcanic ash clouds is important for providing valid aviation advice during volcanic ash eruption. However, because the distal part of volcanic ash plume is far from the volcano, the influence of eruption information on this part becomes rather indirect and uncertain,

  14. Glass shards, pumice fragments and volcanic aerosol particles - diagenesis a recorder of volcanic activity?

    Science.gov (United States)

    Obenholzner, J. H.; Schroettner, H.; Poelt, P.; Delgado, H.

    2003-04-01

    Detailed SEM/EDS studies of Triassic (Southern Alps, A, I, Sl) and Miocene (Mixteca Alta, Mexico) tuffs revealed that volcanic glass shards can be replaced by zeolites (analcite), chlorites and smectites preserving the shape of primary shards (1). The Triassic pyroclastic deposits have been incorporated in the pre-Alpine burial diagenesis, the Miocene pyroclastic deposits are bentonites. The volcanologist is impressed by the circumstances that million years old pyroclast relict textures can be sized. Shape parameters obtained by image analysis can be compared with much younger pyroclastic deposits (2). Both deposits have not been effected by shearing. The alteration of pumice fragments of Triassic age is not a simple replacement process. Intergrowth of different illites and chlorites and probably vesicle filling by SiO2 and subsequent overgrowth make a reconstruction sometimes difficult. These processes are accompanied by the formation of REE-, Y- and Zr-bearing minerals as well as with the alteration of zircons. Studies of recently erupted ash from Popocatepetl volcano reveal the presence of a variety of µm-sized contact-metamorphosed clasts being a part of the volcanic ash (3). Such clasts should be present in many older pyroclastic deposits, especially where volcanoes had been situated on massive sedimentary units providing contact metamorphism in the realm of a magma chamber or during magma ascent. Volcanic aerosol particles collected in 1997 from the passively degassing plume of Popocatepetl volcano revealed in FESEM/EDS analysis (H. Schroettner and P. Poelt) a wide spectrum of fluffy, spherical and coagulated spherical particles (µm-sized). Under pre-vacuum conditions they remained stable for ca. 3 years (3). In nature the fate of these particles in the atmosphere is unknown. Are there relicts in marine, lacustrine sediments and ice cores, which could be used as proxies of volcanic activity? (1) Obenholzner &Heiken,1999. Ann.Naturhist.Mus.Wien, 100 A, 13

  15. Cloud condensation nuclei (CCN) activity of aliphatic amine secondary aerosol

    Science.gov (United States)

    Tang, X.; Price, D.; Praske, E.; Vu, D. N.; Purvis-Roberts, K.; Silva, P. J.; Cocker, D. R., III; Asa-Awuku, A.

    2014-06-01

    Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g., hydroxyl radical and nitrate radical). The particle can contain both secondary organic aerosol (SOA) and inorganic salts. The ratio of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ, ≤ 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3) contains less volatile compounds than the primary aliphatic amine (BA) aerosol. As relative humidity (RH) increases, inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. The humid BA + N2O5 aerosol products were found to be very sensitive to the temperature at which the measurements were made within the streamwise continuous-flow thermal gradient CCN counter; κ ranges from 0.4 to 0.7 dependent on the instrument supersaturation (ss) settings. The variance of the measured aerosol κ values indicates that simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems' κ ranges within 0.2 systems.

  16. Influences of in-cloud aerosol scavenging parameterizations on aerosol concentrations and wet deposition in ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    B. Croft

    2009-10-01

    Full Text Available A diagnostic nucleation scavenging scheme, which determines stratiform cloud scavenging ratios for both aerosol mass and number distributions, based on cloud droplet, and ice crystal number concentrations, is introduced into the ECHAM5-HAM global climate model. This is coupled with a size-dependent in-cloud impaction scavenging parameterization for both cloud droplet-aerosol, and ice crystal-aerosol collisions. Sensitivity studies are presented, which compare aerosol concentrations, and deposition between a variety of in-cloud scavenging approaches, including prescribed fractions, several diagnostic schemes, and a prognostic aerosol cloud processing treatment that passes aerosol in-droplet and in-ice crystal concentrations between model time steps. For one sensitivity study, assuming 100% of the in-cloud aerosol is scavenged into the cloud droplets and ice crystals, the annual global mean accumulation mode number burden is decreased by 65%, relative to a simulation with prognostic aerosol cloud processing. Diagnosing separate nucleation scavenging ratios for aerosol number and mass distributions, as opposed to equating the aerosol mass scavenging to the number scavenging ratios, reduces the annual global mean sulfate burden by near to 10%. The annual global mean sea salt burden is 30% lower for the diagnostic approach, which does not carry aerosol in-droplet and in-crystal concentrations between model time-steps as compared to the prognostic scheme. Implementation of in-cloud impaction scavenging reduced the annual, global mean black carbon burden by 30% for the prognostic aerosol cloud processing scheme. Better agreement with observations of black carbon profiles from aircraft (changes near to one order of magnitude for mixed phase clouds, 210Pb surface layer concentrations and wet deposition, and the geographic distribution of aerosol optical depth are found for the new diagnostic scavenging as compared to prescribed ratio

  17. Aerosol-Cloud-Precipitation Interactions over Indo-Gangetic Basin

    Science.gov (United States)

    Tsay, S.-C.; Lau, K. .; Holben, B. N.; Hsu, N. C.; Bhartia, P. K.

    2005-01-01

    About 60% of world population reside in Asia, in term of which sheer population density presents a major environmental stress. Economic expansion in this region is, in fact, accompanied by increases in bio-fuel burning, industrial pollution, and land cover and land use changes. With a growth rate of approx. 8%/yr for Indian economy, more than 600 million people from Lahore, Pakistan to Calcutta, India over the Indo-Gangetic Basin have particularly witnessed increased frequencies of floods and droughts as well as a dramatic increase in atmospheric loading of aerosols (i.e., anthropogenic and natural aerosol) in recent decades. This regional change (e.g., aerosol, cloud, precipitation, etc.) will constitute a vital part of the global change in the 21st century. Better understanding of the impacts of aerosols in affecting monsoon climate and water cycles is crucial in providing the physical basis to improve monsoon climate prediction and for disaster mitigation. Based on climate model simulations, absorbing aerosols (dust and black carbon) play a critical role in affecting interannual and intraseasonal variability of the Indian monsoon. An initiative on the integrated (aerosols, clouds, and precipitation) measurements approach over the Indo-Gangetic Basin will be discussed. An array of ground-based (e.g., AERONET, MPLNET, SMART-COMMIT, etc.) and satellite (e.g., Terra, A-Train, etc.) sensors will be utilized to acquire aerosol characteristics, sources/sinks, and transport processes during the pre-monsoon (April-May, aerosol forcing) season, and to obtain cloud and precipitation properties during the monsoon (May-June, water cycle response) season. Close collaboration with other international programs, such as ABC, CLIVAR, GEWEX, and CEOP in the region is anticipated.

  18. PSC and volcanic aerosol routine observations in Antarctica by UV-visible ground-based spectrometry

    Science.gov (United States)

    Sarkissian, A.; Pommereau, J. P.; Goutail, F.

    1994-01-01

    Polar statospheric clouds (PSC) and stratospheric aerosol can be observed by ground-based UV-visible spectrometry by looking at the variation of the color of the sky during twilight. A radiative transfer model shows that reddenings are caused by high altitude (22-28 km) thin layers of scatterers, while low altitude (12-20 km) thick ones result in blueings. The color index method applied on 4 years of observations at Dumont d'Urville (67 deg S), from 1988 to 1991, shows that probably because the station is located at the edge of the vortex, dense PSC are uncommon. More unexpected is the existence of a systematic seasonal variation of the color of the twilight sky - bluer at spring - which reveals the formation of a dense scattering layer at or just above the tropopause at the end of the winter. Large scattering layers are reported above the station in 1991, first in August around 12-14 km, later in September at 22-24 km. They are attributed to volcanic aerosol from Mt Hudson and Mt Pinatubo respectively, which erupted in 1991. Inspection of the data shows that the lowest entered rapidly into the polar vortex but not the highest which remained outside, demonstrating that the vortex was isolated at 22-26 km.

  19. 卫星遥感技术在火山灰云监测中的应用%APPLICATION OF SATELLITE REMOTE SENSING IN VOLCANIC ASH CLOUD MONITORING

    Institute of Scientific and Technical Information of China (English)

    尹京苑; 沈迪; 李成范

    2013-01-01

    A large volcanic eruption can produce large amounts of volcanic ash,water vapor and heat,and form the volcanic ash cloud.The volcanic ash cloud is mainly composed of volcanic ash debris in diameter less than 2mm and gases including SO2,H2S,CO2,the mixture of the two can form acidic aerosols which can stay in the atmosphere for a long time.It not only destructs the balance of earth's surface solar radiation and causes the depletion of the ozone layer,the greenhouse effect,air pollution,acid rain,anomalies of air temperature and precipitation,and other major global climate and environmental changes,but also damages and corrodes the structure of an aircraft,reduces the visibility and jams the radio communication system.The most serious problem is that the volcanic ash debris particles are capable of cooling and adhering to the aircraft engine blades after high-temperature melting,resulting in the flameout of aircraft engine.Under the background of globalization and the boom of air-transport industry,the volcanic ash cloud is a serious threat to aviation safety.Remote sensing technology can quickly and accurately obtain the information of the surface's and the atmosphere's changes,therefore it is playing an important role in monitoring volcanic activity.In recent years,with the advancement of sensor technology,the thermal infrared remote sensing technology has become an important means of monitoring the volcanic ash cloud.Currently,there have been a variety of remote sensors for volcanic ash cloud monitoring.Meanwhile,based on that,a series of volcanic ash cloud monitoring algorithms have also been developed for different remote sensors.However,most of the volcanic ash cloud monitoring algorithms have limitations of a low accuracy and a narrow scope.This paper tries to conduct a more comprehensive overview of the different types of remote sensors and the different algorithms for volcanic ash cloud monitoring.First,the damage of volcanic ash cloud to the natural

  20. Cloud-Aerosol Interactions: Retrieving Aerosol Ångström Exponents from Calipso Measurements of Opaque Water Clouds

    Directory of Open Access Journals (Sweden)

    Vaughan Mark

    2016-01-01

    Full Text Available Backscatter and extinction from water clouds are well-understood, both theoretically and experimentally, and thus changes to the expected measurement of layer-integrated attenuated backscatter can be used to infer the optical properties of overlying layers. In this paper we offer a first look at a new retrieval technique that uses CALIPSO measurements of opaque water clouds to derive optical depths and Ångström exponents for overlying aerosol layers.

  1. ARM Cloud-Aerosol-Precipitation Experiment (ACAPEX) Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Leung, L Ruby [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-03-01

    The U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) Climate Research Facility’s ARM Cloud-Aerosol-Precipitation Experiment (ACAPEX) field campaign contributes to CalWater 2015, a multi-agency field campaign that aims to improve understanding of atmospheric rivers and aerosol sources and transport that influence cloud and precipitation processes. The ultimate goal is to reduce uncertainties in weather predictions and climate projections of droughts and floods in California. With the DOE G-1 aircraft and ARM Mobile Facility 2 (AMF2) well equipped for making aerosol and cloud measurements, ACAPEX focuses specifically on understanding how aerosols from local pollution and long-range transport affect the amount and phase of precipitation associated with atmospheric rivers. ACAPEX took place between January 12, 2015 and March 8, 2015 as part of CalWater 2015, which included four aircraft (DOE G-1, National Oceanic and Atmospheric Administration [NOAA] G-IV and P-3, and National Aeronautics and Space Administration [NASA] ER-2), the NOAA research ship Ron Brown, carrying onboard the AMF2, National Science Foundation (NSF)-sponsored aerosol and precipitation measurements at Bodega Bay, and the California Department of Water Resources extreme precipitation network.

  2. Aerosol Impacts on the Growth of Cumulus Congestus Clouds

    Science.gov (United States)

    Sheffield, A. M.; van den Heever, S. C.; Saleeby, S. M.

    2012-12-01

    Tropical convection has been observed to contain three modes of convection, the middle mode of which is cumulus congestus clouds. This study investigates the impacts of aerosol, specifically those aerosols that can serve as cloud condensation nuclei, on the growth and development of congestus clouds observed within idealized cloud-resolving model (CRM) simulations conducted under a state of radiative-convective equilibrium (RCE). The model employed here is the Regional Atmospheric Modeling System (RAMS). RAMS CRM simulations were completed using a large two-dimensional domain (7200 km) at fine resolution (1 km) and long duration (100 days). Results indicate that congestus in more polluted conditions extend to greater heights more frequently than those developing in clean cases. Greater cloud water mass and ice mass forms in more polluted conditions, though ice forms at a fraction of the rate of the cloud mass. The importance of vapor diffusional growth of cloud droplets in the more polluted conditions is highlighted as one such process contributing to congestus development through latent heat release.

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

    Science.gov (United States)

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

    2016-07-01

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

  4. Aerosol-Cloud-Precipitation Interactions during VOCALS-REx (Invited)

    Science.gov (United States)

    Feingold, G.; Wang, H.; Kazil, J.

    2009-12-01

    Satellite imagery of marine stratocumulus regions often reveals the existence of cellular structures that appear to be manifestations of self-organizing properties of the cloud field. These striking features present themselves in visible satellite imagery as either bright cloudy cells ringed by darker edges (closed cells) or dark cellular regions ringed by bright cloudy edges (open cells). The starkly different reflectance patterns associated with these cellular structures are of great interest from the perspective of planetary albedo. Observations have implicated precipitation as one of the controls on the preferred state of stratocumulus: Non-precipitating clouds that typically exist in regions of higher background aerosol and/or thinner cloud prefer the closed cell state, while cleaner and/or thicker precipitating clouds favor the open cell structure. Precipitation appears to be prevalent in open cells, but is not a sufficient condition for open cell formation. We will present large eddy simulations over large domains (order 100 km) that explore the processes associated with the formation and growth of open cells observed during the VOCALS-REx field experiment off the coast of Chile (October-November 2008). The simulations will include treatment of the lifecycle of aerosol. We will examine the boundary region between clean and polluted regions and show how aerosol gradients can generate mesoscale circulations that play a major role in determining cloud microphysics and morphology. Finally, we will use these results to test conceptual models of the structure of open- and closed- cell boundary layers.

  5. Multistatic aerosol-cloud lidar in space: A theoretical perspective

    Science.gov (United States)

    Mishchenko, Michael I.; Alexandrov, Mikhail D.; Cairns, Brian; Travis, Larry D.

    2016-11-01

    Accurate aerosol and cloud retrievals from space remain quite challenging and typically involve solving a severely ill-posed inverse scattering problem. In this Perspective, we formulate in general terms an aerosol and aerosol-cloud interaction space mission concept intended to provide detailed horizontal and vertical profiles of aerosol physical characteristics as well as identify mutually induced changes in the properties of aerosols and clouds. We argue that a natural and feasible way of addressing the ill-posedness of the inverse scattering problem while having an exquisite vertical-profiling capability is to fly a multistatic (including bistatic) lidar system. We analyze theoretically the capabilities of a formation-flying constellation of a primary satellite equipped with a conventional monostatic (backscattering) lidar and one or more additional platforms each hosting a receiver of the scattered laser light. If successfully implemented, this concept would combine the measurement capabilities of a passive multi-angle multi-spectral polarimeter with the vertical profiling capability of a lidar; address the ill-posedness of the inverse problem caused by the highly limited information content of monostatic lidar measurements; address the ill-posedness of the inverse problem caused by vertical integration and surface reflection in passive photopolarimetric measurements; help relax polarization accuracy requirements; eliminate the need for exquisite radiative-transfer modeling of the atmosphere-surface system in data analyses; yield the day-and-night observation capability; provide direct characterization of ground-level aerosols as atmospheric pollutants; and yield direct measurements of polarized bidirectional surface reflectance. We demonstrate, in particular, that supplementing the conventional backscattering lidar with just one additional receiver flown in formation at a scattering angle close to 170° can dramatically increase the information content of the

  6. Volcanic ash and meteorological clouds detection by neural networks

    Science.gov (United States)

    Picchiani, Matteo; Del Frate, Fabio; Stefano, Corradini; Piscini, Alessandro; Merucci, Luca; Chini, Marco

    2014-05-01

    interpreted considering the information of the visible and infrared channels. The comparison shows that the proposed methodology achieves very promising performances, indeed an overall accuracy greater than 87% can be iteratively obtained classifying new images without human interactions. References: Corradini, S., Spinetti, C., Carboni, E., Tirelli, C., Buongiorno, M. F., Pugnaghi, S., and Gangale, G..; "Mt. Etna tropospheric ash retrieval and sensitivity analysis using Moderate Resolution Imaging Spectroradiometer measurements". J, Atmosph. Rem. Sens., 2, 023550, DOI:10.1117/12.823215, 2008. Prata A. J., "Infrared radiative transfer calculations for volcanic ash clouds", Geophys. Res. Lett., Vol. 16, No. 11, pp. 1293-1296, 1989. Picchiani, M., Chini, M., Corradini, S., Merucci, L., Sellitto, P., Del Frate, F. and Stramondo, S., "Volcanic ash detection and retrievals from MODIS data by means of Neural Networks", Atmos. Meas. Tech., 4, 2619-2631, doi:10.5194/amt-4-2619-2011, 2011.

  7. Mapping the Twilight Zone—What We Are Missing between Clouds and Aerosols

    Directory of Open Access Journals (Sweden)

    Katharina Schwarz

    2017-06-01

    Full Text Available Scientific understanding of aerosol-cloud interactions can profit from an analysis of the transition regions between pure aerosol and pure clouds as detected in satellite data. This study identifies and evaluates pixels in this region by analysing the residual areas of aerosol and cloud products from the Moderate Resolution Imaging Radiometer (MODIS satellite sensor. These pixels are expected to represent the “twilight zone” or transition zone between aerosols and clouds. In the analysis period (February and August, 2007–2011, about 20% of all pixels are discarded by both MODIS aerosol and cloud retrievals (“Lost Pixels”. The reflective properties and spatial distribution of Lost Pixels are predominantly in between pure aerosol and cloud. The high amount of discarded pixels underlines the relevance of analyzing the transition zone as a relevant part of the Earth’s radiation budget and the importance of considering them in research on aerosol-cloud interactions.

  8. Arctic Aerosol-­Cloud Interactions during ASCOS

    Science.gov (United States)

    Stevens, R.; Hill, A. A.; Shipway, B. J.; Field, P.; Carslaw, K. S.

    2015-12-01

    A decrease in Arctic sea ice extent and thickness has been observed within recent decades. Further decreases are expected to increase the fluxes aerosol and precursor gases from the open ocean surface within the Arctic. The resulting increase in cloud condensation nuclei (CCN) concentrations would be expected to result in increased cloud albedo (Struthers et al, 2011), leading to potentially large changes in radiative forcings.However, Browse et al. (2014) have shown that these increases in condensable material could also result in the growth of existing particles to sizes where they are more efficiently removed by wet deposition in drizzling stratocumulus clouds, ultimately decreasing CCN concentrations in the high Arctic. The study of Browse et al (2014) was limited in that it did not simulate alterations of dynamics or cloud properties due to either changes in heat and moisture fluxes following sea­-ice loss or changing aerosol concentrations.Taken together, the results of Struthers et al (2011) and Browse et al (2014) show that significant uncertainties remain in trying to quantify aerosol­-cloud processes in the poorly understood Arctic system. It is likely that the CCN response to sea-­ice loss is controlled by many interrelated processes and unlikely that the current representation of these processes in global climate models include is sufficient to realistically simulate long­-term changes.Using the Met Office Unified Model (UM) including Cloud AeroSol Interactions Microphysics (CASIM), we perform a case study of summertime high Arctic (>80N) clouds in order to better understand the processes currently governing Arctic clouds, and how they may change in the future. We compare our results with observations obtained during the 2008 ASCOS campaign. We then perform sensitivity studies to assess the changes in cloud properties to reductions in sea­-ice, through either changes in fluxes of surface heat and moisture or changes in fluxes of aerosol and

  9. Aerosol-Cloud-Drizzle-Turbulence Interactions in Boundary Layer Clouds

    Science.gov (United States)

    2013-09-30

    prevent sticking. They were dispersed using a mechanism that auger fed particles into fluidized bed of grit before emitting them to the outside in a...objectives are to: 1) document the structure and characteristics of entrainment circulations in marine stratocumulus and fair-weather-cumuli, 2...characterize the vertical distribution of drizzle and how it relates to cloud and mesoscale circulations ; 3) investigate the relative role of cloud

  10. The Invigoration of Deep Convective Clouds Over the Atlantic: Aerosol Effect, Meteorology or Retrieval Artifact?

    Science.gov (United States)

    Koren, Ilan; Feingold, Graham; Remer, Lorraine A.

    2010-01-01

    Associations between cloud properties and aerosol loading are frequently observed in products derived from satellite measurements. These observed trends between clouds and aerosol optical depth suggest aerosol modification of cloud dynamics, yet there are uncertainties involved in satellite retrievals that have the potential to lead to incorrect conclusions. Two of the most challenging problems are addressed here: the potential for retrieved aerosol optical depth to be cloud-contaminated, and as a result, artificially correlated with cloud parameters; and the potential for correlations between aerosol and cloud parameters to be erroneously considered to be causal. Here these issues are tackled directly by studying the effects of the aerosol on convective clouds in the tropical Atlantic Ocean using satellite remote sensing, a chemical transport model, and a reanalysis of meteorological fields. Results show that there is a robust positive correlation between cloud fraction or cloud top height and the aerosol optical depth, regardless of whether a stringent filtering of aerosol measurements in the vicinity of clouds is applied, or not. These same positive correlations emerge when replacing the observed aerosol field with that derived from a chemical transport model. Model-reanalysis data is used to address the causality question by providing meteorological context for the satellite observations. A correlation exercise between the full suite of meteorological fields derived from model reanalysis and satellite-derived cloud fields shows that observed cloud top height and cloud fraction correlate best with model pressure updraft velocity and relative humidity. Observed aerosol optical depth does correlate with meteorological parameters but usually different parameters from those that correlate with observed cloud fields. The result is a near-orthogonal influence of aerosol and meteorological fields on cloud top height and cloud fraction. The results strengthen the case

  11. Aerosols upwind of Mexico City during the MILAGRO campaign: regional scale biomass burning, dust and volcanic ash from aircraft measurements

    Science.gov (United States)

    Junkermann, W.; Steinbrecher, R.

    2009-04-01

    During the MILAGRO Campaign March/April 2006 a series of aircraft flights with the FZK microlight D-MIFU were performed in the area southeast of Mexico City starting from Puebla airport, circling the national park area of Ixtachiuatl and Popocatepetl and scanning the Chalco valley down to Cuautla in the Cuernavaca province. All flights were combined with vertical profiles up to 4500 m a.s.l. in several locations, typically north of volcano Ixtachiuatl on the Puebla side, above Chalco or Tenago del Aire and south of volcano Popocatepetl, either at Cuautla or Atlixco. In Tenango del Aire a ceilometer was additionally operated continuously for characterization of the planetary boundary layer. The aircraft carried a set of aerosol instrumentation, fine and coarse particles and size distributions as well as a 7 wavelength aethalometer. Additionally meteorological parameters, temperature and dewpoint, global radiation and actinic radiation balance, respectively photolysis rates, and ozone concentrations were measured. The instrumentation allowed to characterize the aerosol according to their sources and also their impact on radiation transfer. Biomass burning aerosol, windblown dust and volcanic ash were identified within the upwind area of Mexico City with large differences between the dry season in the first weeks of the campaign and the by far cleaner situation after beginning thunderstorm activity towards the end of the campaign. Also the aerosol characteristics inside and outside the Mexico City basin were often completely different. With wind speeds of ~ 5 m/sec from southerly directions in the Chalco valley the aerosol mixture can reach the City within ~ 2 h. Rural aerosol mixtures from the Cuernavaca plain were mixed during the transport with dust from the MC basin. Very high intensity biomass burning plumes normally reached higher altitudes and produced pyrocumulus clouds. These aerosols were injected mainly into the free troposphere. Within the MC basin a large

  12. Marine Aerosols: Hygroscopocity and Aerosol-Cloud Relationships

    Science.gov (United States)

    2012-09-30

    large eddy simulation (LES) and field measurements, the latter including Twin Otter missions such as MASE I and MASE II and those involving other...continuous spectral aerosol-droplet microphysics model is presented and implemented into the Weather Research and Forecasting (WRF) model for large- eddy ...Dey, A. Sorooshian, F. J. Brechtel, Z. Wang, A. Metcalf , M. Coggon, J. Mulmenstadt, L. M. Russell, H. H. Jonsson, and J. H. Seinfeld, Atmos. Meas

  13. Influence of African Dust and Volcanic Ash on the Chemical Composition of Cloud/Rain Water Collected in a Tropical Montane Cloud Forest in Puerto Rico

    Science.gov (United States)

    Reyes-Rodríguez, G. J.; Gioda, A.; Mayol-Bracero, O. L.; Collett, J.

    2007-12-01

    Some organic compounds present in aerosols are surface active and their presence in cloud condensation nuclei can affect the surface tension of cloud droplets. The nature of these surface active compounds in clouds and rainwater is not well understood and there is very little information about their content in remote tropical environments. Therefore, our study focuses on the chemical characterization of the organic component of cloud and rainwater samples collected in a tropical montane cloud forest on the island of Puerto Rico. Samples were collected during periods of varying air mass origin, including periods of influence by African dust and by volcanic ash. Cloud samples were collected using a compact version of the single-stage Caltech Active Strand Cloudwater Collector. Rain samples were collected using a passive collector. The organic fraction of collected samples was characterized using a total organic carbon and total nitrogen analyzer (TOC/TN) and nuclear magnetic resonance (1H-NMR) spectroscopy. Elemental and organic carbon (EC, OC) were determined for suspended particles contained in collected cloud and rainwater samples. These particles were also analyzed using scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) to determine their elemental compositions. Preliminary results indicate that average concentrations of cloud water TOC ranged from 0.9 to 1.2 mg/L. Lower concentrations were observed in rainwater, 0.3 to 0.7 mg/L. TN concentrations were higher than TOC in cloud water samples when air masses came from the African continent. The suspended aerosol particles had a content of 2.0 µg of OC per mL of cloud water, but EC was not detected. Suspended particle analysis by SEM-EDS showed Si, Al, and Fe, which have crustal origin, as the predominant species. The 1H-NMR spectra showed alcohols in large quantities, suggesting the presence of biogenic material or polyols when air masses arrived from the African continent. A more complete set

  14. Aerosol and Trace Gas Processing by Clouds During the Cumulus Humilis Aerosol Processing Study (CHAPS)

    Science.gov (United States)

    Yu, X.; Berg, L.; Berkowitz, C.; Alexander, L.; Lee, Y.; Ogren, J.; Andrews, B.

    2008-12-01

    Clouds play an active role in the processing and cycling of atmospheric constituents. Gases and particles can partition to cloud droplets by absorption and condensation as well as activation and pact scavenging. The Cumulus Humilis Aerosol Processing Study (CHAPS) aimed at characterizing freshly emitted aerosols above, within and below fields of cumulus humilis (or fair-weather cumulus) in the vicinity of Oklahoma City. The experiment took place in June 2007. Evolution of aerosol and cloud properties downwind of the Oklahoma City is of particular interest in this project. These observations of a mid-size and mid-latitude city can be used in the development and evaluation of regional-scale and global climate model cumulus parameterizations that describes the transport and transformations of these aerosols by fair-weather cumulus. The Department of Energy (DOE) G-1 aircraft was one of the main platforms used in CHAPS. It carried a suite of instruments to measure properties of interstitial aerosols behind an isokinetic inlet and a set of duplicate instruments to determine properties of activated particles behind a counter-flow virtual impactor (CVI). The sampling line to the Aerodyne Aerosol Mass Spectrometer was switched between the isokinetic inlet and the CVI to allow characterization of interstitial particles out of clouds in contrast to particles activated in clouds. Trace gases including ozone, carbon monoxide, sulfur dioxide, and a series of volatile organic compounds (VOCs) were also measured as were key meteorological state parameters including liquid water content, cloud drop size, and dew point temperature were measured. This presentation will focus on results related to the transformation and transport of aerosols and trace gases observed in fair-weather cumulus and compare these results with concurrent observations made outside these clouds. Our interest will focus on the differences in particle size and composition under varying conditions. The role of

  15. Statistical Comparison of Cloud and Aerosol Vertical Properties between Two Eastern China Regions Based on CloudSat/CALIPSO Data

    Directory of Open Access Journals (Sweden)

    Yujun Qiu

    2017-01-01

    Full Text Available The relationship between cloud and aerosol properties was investigated over two 4° × 4° adjacent regions in the south (R1 and in the north (R2 in eastern China. The CloudSat/CALIPSO data were used to extract the cloud and aerosol profiles properties. The mean value of cloud occurrence probability (COP was the highest in the mixed cloud layer (−40°C~0°C and the lowest in the warm cloud layer (>0°C. The atmospheric humidity was more statistically relevant to COP in the warm cloud layer than aerosol condition. The differences in COP between the two regions in the mixed cloud layer and ice cloud layer (<−40°C had good correlations with those in the aerosol extinction coefficient. A radar reflectivity factor greater than −10 dBZ occurred mainly in warm cloud layers and mixed cloud layers. A high-COP zone appeared in the above-0°C layer with cloud thicknesses of 2-3 km in both regions and in all the four seasons, but the distribution of the zonal layer in R2 was more continuous than that in R1, which was consistent with the higher aerosol optical thickness in R2 than in R1 in the above-0°C layer, indicating a positive correlation between aerosol and cloud probability.

  16. New spectral methods in cloud and aerosol remote sensing applications

    Science.gov (United States)

    Schmidt, K. Sebastian; McBride, Patrick; Pilewskie, Peter; Feingold, Graham; Jiang, Hongli

    2010-05-01

    We present new remote sensing techniques that rely on spectral observations of clouds and aerosols in the solar wavelength range. As a first example, we show how the effects of heterogeneous clouds, aerosols of changing optical properties, and the surface within one pixel can be distinguished by means of their spectral signatures. This example is based on data from the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS, Houston, Texas, 2006), Large Eddy Simulations (LES) of polluted boundary layer clouds, and 3-dimensional radiative transfer calculations. In a second example, we show that the uncertainty of cloud retrievals can be improved considerably by exploiting the spectral information around liquid water absorption features in the near-infrared wavelength range. This is illustrated with spectral transmittance data from the NOAA International Chemistry Experiment in the Arctic LOwer Troposphere (ICEALOT, 2008). In contrast to reflected radiance, transmitted radiance is only weakly sensitive to cloud effective drop radius, and only cloud optical thickness can be obtained from the standard dual-channel technique. We show that effective radius and liquid water path can also be retrieved with the new spectral approach, and validate our results with microwave liquid water path measurements.

  17. Characterization of aerosol and cloud water at a mountain site during WACS 2010: secondary organic aerosol formation through oxidative cloud processing

    Directory of Open Access Journals (Sweden)

    A. K. Y. Lee

    2012-08-01

    Full Text Available The water-soluble fractions of aerosol filter samples and cloud water collected during the Whistler Aerosol and Cloud Study (WACS 2010 were analyzed using an Aerodyne aerosol mass spectrometer (AMS. This is the first study to report AMS organic spectra of re-aerosolized cloud water, and to make direct comparison between the AMS spectra of cloud water and aerosol samples collected at the same location. In general, the mass spectra of aerosol were very similar to those of less volatile cloud organics. By using a photochemical reactor to oxidize both aerosol filter extracts and cloud water, we find evidence that fragmentation of water-soluble organics in aerosol increases their volatility during photochemical oxidation. By contrast, enhancement of AMS-measurable organic mass by up to 30% was observed during the initial stage of oxidation of cloud water organics, which was followed by a decline at the later stages of oxidation. These observations are in support of the general hypothesis that cloud water oxidation is a viable route for SOA formation. In particular, we propose that additional SOA material was produced by functionalizing dissolved organics via OH oxidation, where these dissolved organics are sufficiently volatile that they are not usually part of the aerosol. This work demonstrates that water-soluble organic compounds of intermediate volatility (IVOC, such as cis-pinonic acid, produced via gas-phase oxidation of monoterpenes, can be important aqueous-phase SOA precursors in a biogenic-rich environment.

  18. Retrieval of the aerosol direct radiative effect over clouds from spaceborne spectrometry

    Science.gov (United States)

    Graaf, M.; Tilstra, L. G.; Wang, P.; Stammes, P.

    2012-04-01

    The solar radiative absorption by an aerosol layer above clouds is quantified using passive satellite spectrometry from the ultraviolet (UV) to the shortwave infrared (SWIR). UV-absorbing aerosols have a strong signature that can be detected using UV reflectance measurements, even when above clouds. Since the aerosol extinction optical thickness decreases rapidly with increasing wavelength for biomass burning aerosols, the properties of the clouds below the aerosol layer can be retrieved in the SWIR, where aerosol extinction optical thickness is sufficiently small. Using radiative transfer computations, the contribution of the clouds to the reflected radiation can be modeled for the entire solar spectrum. In this way, cloud and aerosol effects can be separated for a scene with aerosols above clouds. Aerosol microphysical assumptions and retrievals are avoided by modeling only the pure (aerosol-free) cloud spectra. An algorithm was developed using the spaceborne spectrometer Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). The aerosol direct radiative effect (DRE) over clouds over the South Atlantic Ocean west of Africa, averaged through August 2006 was found to be 23 ± 8 Wm-2 with a mean variation over the region in this month of 22 Wm-2. The largest aerosol DRE over clouds found in that month was 132 ± 8 Wm-2. The algorithm can be applied to any instrument, or a combination of instruments, that measures UV, visible and SWIR reflectances at the top of the atmosphere (TOA) simultaneously.

  19. 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

  20. Effects of aerosol on evaporation, freezing and precipitation in a multiple cloud system

    Science.gov (United States)

    Lee, Seoung Soo; Kim, Byung-Gon; Yum, Seong Soo; Seo, Kyong-Hwan; Jung, Chang-Hoon; Um, Jun Shik; Li, Zhanqing; Hong, JinKyu; Chang, Ki-Ho; Jeong, Jin-Yim

    2017-02-01

    Aerosol effects on clouds and precipitation account for a large portion of uncertainties in the prediction of the future course of global hydrologic circulations and climate. As a process of a better understanding of interactions between aerosol, clouds and precipitation, simulations are performed for a mixed-phase convective multiple-cloud system over the tropics. Studies on single-cloud systems have shown that aerosol-induced increases in freezing, associated increases in parcel buoyancy and thus the intensity of clouds (or updrafts) are a main mechanism which controls aerosol-cloud-precipitation interactions in convective clouds. However, in the multiple-cloud system that plays much more important roles in global hydrologic circulations and thus climate than single-cloud systems, aerosol effects on condensation play the most important role in aerosol-induced changes in the intensity of clouds and the effects on freezing play a negligible role in those changes. Aerosol-induced enhancement in evaporation intensifies gust fronts and increases the number of subsequently developing clouds, which leads to the substantial increases in condensation and associated intensity of convection. Although aerosol-induced enhancement in freezing takes part in the increases in condensation by inducing stronger convergence around cloud bottom, the increases in condensation are one order of magnitude larger than those in freezing. It is found that while aerosol-induced increases in freezing create intermittent extremely heavy precipitation, aerosol-induced increases in evaporation enhance light and medium precipitation in the multiple-cloud system here. This increase in light and medium precipitation makes it possible that cumulative precipitation increases with increasing aerosol concentration, although the increase is small. It is interesting that the altitude of the maximum of the time- and domain-averaged hydrometeor mass densities is quite robust to increases in aerosol

  1. The Role of Aerosol Composition in Arctic Cloud Formation

    Science.gov (United States)

    Brooks, S. D.; Hiranuma, N.; Moffet, R.; Laskin, A.; Gilles, M. K.; Glen, A.

    2010-12-01

    While it has been shown that aerosol size has a direct correlation with its ability to act as an ice nucleus, the role of the composition of freshly emitted and evolving aerosol in nucleation is poorly understood. Here we use combined measurements of ice nucleation and high resolution single particle composition to provide insight on the connection between aerosol composition in ice nucleation. These measurements were collected during the Indirect and Semidirect Aerosols Campaign (ISDAC) over Barrow, AK in the springtime of 2008. In-situ ice nucleation measurements were conducted using the Texas Continuous Flow Diffusion Chamber (CFDC). The composition of ambient particles as well as residuals of cloud droplets and ice crystals were studied on a particle by particle basis using computer controlled scanning electron microscopy with energy dispersive X-ray analysis (CCSEM/EDX) and scanning transmission X-Ray microscopy coupled with near edge X-ray absorption spectroscopy (STXM/NEXAFAS). Observed IN concentrations varied from frequent values of 0.01 per liter to more than 10 per liters, depending on conditions and the availability of ice-nucleating aerosols. Ice crystals residuals collected in a fully glaciated cloud demonstrate that both particle chemistry and size requirement must be met for a particle to be an efficient ice nucleus. According to the STXM/NEXAFAS spectral maps, ice crystals residuals are characterized by insoluble cores of either large brown or black carbon (BBC) or carbonates coated by water soluble organics. In contrast, in ambient air samples collected from a biomass burning plume, many organic particles were also observed, but these were smaller and did not have insoluble cores. In-situ ice nucleation measurements show that these biomass particles have inferior ice nuclei ability, relative to those collected in the glaciated cloud. Taken together our measurements suggest that two key elements, a critical size (provided by BBC and/or carbonate

  2. Total Volcanic Stratospheric Aerosol Optical Depths and Implications for Global Climate Change

    Science.gov (United States)

    Ridley, D. A.; Solomon, S.; Barnes, J. E.; Burlakov, V. D.; Deshler, T.; Dolgii, S. I.; Herber, A. B.; Nagai, T.; Neely, R. R., III; Nevzorov, A. V.; Ritter, C.; Sakai, T.; Santer, B. D.; Sato, M.; Schmidt, A.; Uchino, O.; Vernier, J. P.

    2014-01-01

    Understanding the cooling effect of recent volcanoes is of particular interest in the context of the post-2000 slowing of the rate of global warming. Satellite observations of aerosol optical depth above 15 km have demonstrated that small-magnitude volcanic eruptions substantially perturb incoming solar radiation. Here we use lidar, Aerosol Robotic Network, and balloon-borne observations to provide evidence that currently available satellite databases neglect substantial amounts of volcanic aerosol between the tropopause and 15 km at middle to high latitudes and therefore underestimate total radiative forcing resulting from the recent eruptions. Incorporating these estimates into a simple climate model, we determine the global volcanic aerosol forcing since 2000 to be 0.19 +/- 0.09W/sq m. This translates into an estimated global cooling of 0.05 to 0.12 C. We conclude that recent volcanic events are responsible for more post-2000 cooling than is implied by satellite databases that neglect volcanic aerosol effects below 15 km.

  3. Influences of in-cloud aerosol scavenging parameterizations on aerosol concentrations and wet deposition in ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    B. Croft

    2010-02-01

    Full Text Available A diagnostic cloud nucleation scavenging scheme, which determines stratiform cloud scavenging ratios for both aerosol mass and number distributions, based on cloud droplet, and ice crystal number concentrations, is introduced into the ECHAM5-HAM global climate model. This scheme is coupled with a size-dependent in-cloud impaction scavenging parameterization for both cloud droplet-aerosol, and ice crystal-aerosol collisions. The aerosol mass scavenged in stratiform clouds is found to be primarily (>90% scavenged by cloud nucleation processes for all aerosol species, except for dust (50%. The aerosol number scavenged is primarily (>90% attributed to impaction. 99% of this impaction scavenging occurs in clouds with temperatures less than 273 K. Sensitivity studies are presented, which compare aerosol concentrations, burdens, and deposition for a variety of in-cloud scavenging approaches: prescribed fractions, a more computationally expensive prognostic aerosol cloud processing treatment, and the new diagnostic scheme, also with modified assumptions about in-cloud impaction and nucleation scavenging. Our results show that while uncertainties in the representation of in-cloud scavenging processes can lead to differences in the range of 20–30% for the predicted annual, global mean aerosol mass burdens, and near to 50% for accumulation mode aerosol number burden, the differences in predicted aerosol mass concentrations can be up to one order of magnitude, particularly for regions of the middle troposphere with temperatures below 273 K where mixed and ice phase clouds exist. Different parameterizations for impaction scavenging changed the predicted global, annual mean number removal attributed to ice clouds by seven-fold, and the global, annual dust mass removal attributed to impaction by two orders of magnitude. Closer agreement with observations of black carbon profiles from aircraft (increases near to one order of magnitude for mixed phase clouds

  4. 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

  5. The effect of aerosol representation on cloud microphysical properties in Northeast Asia

    Science.gov (United States)

    Choi, In-Jin; Iguchi, Takamichi; Kim, Sang-Woo; Nakajima, Teruyuki; Yoon, Soon-Chang

    2014-02-01

    This study performed a three-dimensional regional-scale simulation of aerosol and cloud fields using a meso-scale non-hydrostatic model with a bin-based cloud microphysics. The representation of aerosols in the model has been improved to account for more realistic multi-modal size distribution and multiple chemical compositions. Two case studies for shallow stratocumulus over Northeast Asia in March 2005 were conducted with different aerosol conditions to evaluate model performance. Improved condensation nuclei (CN) and cloud condensation nuclei (CCN) are attributable to the newly constructed aerosol size distribution. The simulated results of cloud microphysical properties (cloud droplet effective radius, liquid water path, and optical thickness) with improved CN/CCN number are close to the retrievals from satellite-based observation. The effects of aerosol on the microphysical properties of shallow stratocumulus are investigated by model simulation, in terms of columnar aerosol number concentration. Enhanced aerosol number concentration results in increased liquid water path in humid case, but invariant liquid water path in dry case primarily due to precipitation occurrence. The changes of cloud microphysical properties are more predominant for small aerosol burden than for large aerosol burden with the retarded changes in cloud mass and size due to inactive condensation and collision-coalescence processes. Quantitative evaluation of sensitivity factor between aerosol and cloud microphysical properties indicates a strong aerosol-cloud interaction in Northeast Asian region.

  6. Impact of aerosols on precipitation from deep convective clouds in eastern China

    Science.gov (United States)

    Jiang, Mengjiao; Li, Zhanqing; Wan, Bingcheng; Cribb, Maureen

    2016-08-01

    We analyzed the impact of aerosols on precipitation based on 3 years of 3-hourly observations made in heavily polluted eastern China. The probability of precipitation from different cloud types was calculated using International Satellite Cloud Climatology Project cloud data and gauge-based hourly precipitation data. Because deep convective clouds have the largest precipitation probability, the influence of aerosols on the precipitation from such clouds was studied in particular. Aerosol properties were taken from the Modern-Era Retrospective Analysis for Research and Applications Aerosol Reanalysis data set. As aerosol optical depth increased, rainfall amounts from deep convective clouds increased at first and then decreased. The descending part of the trend is likely due to the aerosol radiative effect. Downwelling solar radiative fluxes at the surface decreased as aerosol optical depth increased. The decrease in solar radiation led to a decrease in ground heat fluxes and convective available potential energy, which is unfavorable for development of convective clouds and precipitation. The tendencies for lower cloud top temperatures, lower cloud top pressures, and higher cloud optical depths as a response to larger aerosol optical depths suggest the invigoration effect. Vertical velocity, relative humidity, and air temperature from the National Centers for Environmental Prediction Climate Forecast System Reanalysis were sorted to help investigate if the trends are dependent on any environmental conditions. How dynamic and microphysical factors strengthen or mitigate the impact of aerosols on clouds and precipitation and more details about their interplay should be studied further using more observations and model simulations.

  7. Cloud-Driven Changes in Aerosol Optical Properties - Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

    2007-09-30

    The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

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

    OpenAIRE

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

    2013-01-01

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

  9. Temporal variations of flux and altitude of sulfur dioxide emissions during volcanic eruptions: implications for long-range dispersal of volcanic clouds

    Directory of Open Access Journals (Sweden)

    M. Boichu

    2015-02-01

    of the modeled SO2 altitude is further confirmed by the detection of a layer of particles at the same altitude by the spaceborne CALIOP LiDAR. Analysis of CALIOP color and depolarization ratios suggests that these particles consist of sulfate aerosols formed from precursory volcanic SO2. The reconstruction of emission altitude, through inversion procedures which assimilate volcanic SO2 column amounts, requires specific meteorological conditions, especially sufficient wind shear so that gas parcels emitted at different altitudes follow distinct trajectories. We consequently explore the possibility and limits of assimilating in inverse schemes infrared (IR imagery of the volcanic SO2 cloud altitude which will render the inversion procedure independent of the wind shear prerequisite.

  10. Volcanic ash cloud detection from MODIS image based on CPIWS method

    Science.gov (United States)

    Liu, Lan; Li, Chengfan; Lei, Yongmei; Yin, Jingyuan; Zhao, Junjuan

    2017-02-01

    Volcanic ash cloud detection has been a difficult problem in moderate-resolution imaging spectroradiometer (MODIS) multispectral remote sensing application. Principal component analysis (PCA) and independent component analysis (ICA) are effective feature extraction methods based on second-order and higher order statistical analysis, and the support vector machine (SVM) can realize the nonlinear classification in low-dimensional space. Based on the characteristics of MODIS multispectral remote sensing image, via presenting a new volcanic ash cloud detection method, named combined PCA-ICA-weighted and SVM (CPIWS), the current study tested the real volcanic ash cloud detection cases, i.e., Sangeang Api volcanic ash cloud of 30 May 2014. Our experiments suggest that the overall accuracy and Kappa coefficient of the proposed CPIWS method reach 87.20 and 0.7958%, respectively, under certain conditions with the suitable weighted values; this has certain feasibility and practical significance.

  11. Eastern Pacific Emitted Aerosol Cloud Experiment

    OpenAIRE

    Russell, Lynn M.; Sorooshian, Armin; Seinfeld, John H.; Albrecht, Bruce A.; Nenes, Athanasios; Ahlm, Lars; Chen, Yi-Chun; Coggon, Matthew; Craven, Jill S.; Flagan, Richard C.; Frossard, Amanda A.; Jonsson, Haflidi; Jung, Eunsil; Lin, Jack J.; Metcalf, Andrew R.

    2013-01-01

    Aerosol–cloud–radiation interactions are widely held to be the largest single source of uncertainty in climate model projections of future radiative forcing due to increasing anthropogenic emissions. The underlying causes of this uncertainty among modeled predictions of climate are the gaps in our fundamental understanding of cloud processes. There has been significant progress with both observations and models in addressing these important questions but quantifying them correctly is nontrivi...

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

    NARCIS (Netherlands)

    Stap, F. A.; Hasekamp, O. P.; Roeckmann, Thomas

    2015-01-01

    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 param

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

    NARCIS (Netherlands)

    Stap, F. A.; Hasekamp, O. P.; Roeckmann, Thomas

    2015-01-01

    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

  14. Quantifying Above-Cloud Aerosols through Integrating Multi-Sensor Measurements from A-Train Satellites

    Science.gov (United States)

    Zhang, Yan

    2012-01-01

    Quantifying above-cloud aerosols can help improve the assessment of aerosol intercontinental transport and climate impacts. Large-scale measurements of aerosol above low-level clouds had been generally unexplored until very recently when CALIPSO lidar started to acquire aerosol and cloud profiles in June 2006. Despite CALIPSO s unique capability of measuring above-cloud aerosol optical depth (AOD), such observations are substantially limited in spatial coverage because of the lidar s near-zero swath. We developed an approach that integrates measurements from A-Train satellite sensors (including CALIPSO lidar, OMI, and MODIS) to extend CALIPSO above-cloud AOD observations to substantially larger areas. We first examine relationships between collocated CALIPSO above-cloud AOD and OMI absorbing aerosol index (AI, a qualitative measure of AOD for elevated dust and smoke aerosol) as a function of MODIS cloud optical depth (COD) by using 8-month data in the Saharan dust outflow and southwest African smoke outflow regions. The analysis shows that for a given cloud albedo, above-cloud AOD correlates positively with AI in a linear manner. We then apply the derived relationships with MODIS COD and OMI AI measurements to derive above-cloud AOD over the whole outflow regions. In this talk, we will present spatial and day-to-day variations of the above-cloud AOD and the estimated direct radiative forcing by the above-cloud aerosols.

  15. The Deep South Clouds & Aerosols project: Improving the modelling of clouds in the Southern Ocean region

    Science.gov (United States)

    Morgenstern, Olaf; McDonald, Adrian; Harvey, Mike; Davies, Roger; Katurji, Marwan; Varma, Vidya; Williams, Jonny

    2016-04-01

    Southern-Hemisphere climate projections are subject to persistent climate model biases affecting the large majority of contemporary climate models, which degrade the reliability of these projections, particularly at the regional scale. Southern-Hemisphere specific problems include the fact that satellite-based observations comparisons with model output indicate that cloud occurrence above the Southern Ocean is substantially underestimated, with consequences for the radiation balance, sea surface temperatures, sea ice, and the position of storm tracks. The Southern-Ocean and Antarctic region is generally characterized by an acute paucity of surface-based and airborne observations, further complicating the situation. In recognition of this and other Southern-Hemisphere specific problems with climate modelling, the New Zealand Government has launched the Deep South National Science Challenge, whose purpose is to develop a new Earth System Model which reduces these very large radiative forcing problems associated with erroneous clouds. The plan is to conduct a campaign of targeted observations in the Southern Ocean region, leveraging off international measurement campaigns in this area, and using these and existing measurements of cloud and aerosol properties to improve the representation of clouds in the nascent New Zealand Earth System Model. Observations and model development will target aerosol physics and chemistry, particularly sulphate, sea salt, and non-sulphate organic aerosol, its interactions with clouds, and cloud microphysics. The hypothesis is that the cloud schemes in most GCMs are trained on Northern-Hemisphere data characterized by substantial anthropogenic or terrestrial aerosol-related influences which are almost completely absent in the Deep South.

  16. Cloud, Aerosol, and Complex Terrain Interactions (CACTI) Preliminary Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Varble, Adam [Univ. of Utah, Salt Lake City, UT (United States); Nesbitt, Steve [Univ. of Illinois, Urbana-Champaign, IL (United States); Salio, Paola [Univ. of Buenos Aires (Argentina); Zipser, Edward [Univ. of Utah, Salt Lake City, UT (United States); van den Heever, Susan [Colorado State Univ., Fort Collins, CO (United States); McFarquhar, Greg [Univ. of Illinois, Urbana-Champaign, IL (United States); Kollias, Pavlos [Stony Brook Univ., NY (United States); Kreidenweis, Sonia [Colorado State Univ., Fort Collins, CO (United States); DeMott, Paul [Colorado State Univ., Fort Collins, CO (United States); Jensen, Michael [Brookhaven National Lab. (BNL), Upton, NY (United States); Houze, Jr., Robert [Univ. of Washington, Seattle, WA (United States); Rasmussen, Kristen [Colorado State Univ., Fort Collins, CO (United States); Leung, Ruby [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Romps, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Gochis, David [National Center for Atmospheric Research, Boulder, CO (United States); Avila, Eldo [National Univ. of Cordoba (Argentina); Williams, Christopher [Univ. of Colorado, Boulder, CO (United States); National Center for Atmospheric Research, Boulder, CO (United States)

    2017-02-01

    General circulation models and downscaled regional models exhibit persistent biases in deep convective initiation location and timing, cloud top height, stratiform area and precipitation fraction, and anvil coverage. Despite important impacts on the distribution of atmospheric heating, moistening, and momentum, nearly all climate models fail to represent convective organization, while system evolution is not represented at all. Improving representation of convective systems in models requires characterization of their predictability as a function of environmental conditions, and this characterization depends on observing many cases of convective initiation, non-initiation, organization, and non-organization. The Cloud, Aerosol, and Complex Terrain Interactions (CACTI) experiment in the Sierras de Córdoba mountain range of north-central Argentina is designed to improve understanding of cloud life cycle and organization in relation to environmental conditions so that cumulus, microphysics, and aerosol parameterizations in multi-scale models can be improved. The Sierras de Córdoba range has a high frequency of orographic boundary-layer clouds, many reaching congestus depths, many initiating into deep convection, and some organizing into mesoscale systems uniquely observable from a single fixed site. Some systems even grow upscale to become among the deepest, largest, and longest-lived in the world. These systems likely contribute to an observed regional trend of increasing extreme rainfall, and poor prediction of them likely contributes to a warm, dry bias in climate models downstream of the Sierras de Córdoba range in a key agricultural region. Many environmental factors influence the convective lifecycle in this region including orographic, low-level jet, and frontal circulations, surface fluxes, synoptic vertical motions influenced by the Andes, cloud detrainment, and aerosol properties. Local and long-range transport of smoke resulting from biomass burning as

  17. On COBACC (COntinental Biosphere-Aerosol-Cloud-Climate) feedback

    Science.gov (United States)

    Kulmala, Markku

    2016-04-01

    Anthropogenic emissions of GHGs have increased substantially during the past century. Elevated concentrations of CO2 and methane are the most important forcing agents causing global warming. However, it is not straightforward to attribute or predict the climate change in detail, as the internal variability of climate is only partially understood, aerosol forcings are still highly uncertain, and there are many feedback mechanisms that are difficult to quantify. It has been recognized for decades that the biosphere plays an important role in climate. For example, Kulmala et al. (2004) suggested a negative climate feedback mechanism whereby higher temperatures and CO2-levels boost continental biomass production, leading to increased biogenic secondary organic aerosol (BSOA) and cloud condensation nuclei (CCN) concentrations, tending to cause cooling. This COBACC (COntinental Biosphere-Aerosol-Cloud-Climate) feedback is similar to the so-called CLAW-hypothesis by Charlson et al. (1987) which connects the ocean biochemistry and climate via a negative feedback loop involving CCN production due to sulphur emissions from plankton. The first quantification of the COBACC feedback loop (Kulmala et al. 2014) was based on continuous comprehensive observations at SMEAR II (Station for Measuring Forest Ecosystem-Atmosphere Relations) station in Hyytiälä, Finland, and showed that a 10 ppm increase in atmospheric CO2 concentration leads to a significant (several percent) increase in both carbon sink and aerosol source. These effects operate through changes in gross primary production, volatile organic compound (VOC) emissions and secondary aerosol formation associated with atmospheric oxidation of VOCs. Here we will describe the present knowledge from processes level understanding to whole COBACC feedback including some hints on biogenic and anthropogenic contributions to global aerosol number load. References: Charlson, R. J. et al. Nature 326, 655 1987 Kulmala, M. et al. Atmos

  18. Determination of cloud and aerosol layers using CALIPSO and image processing

    Science.gov (United States)

    Alias, A. N.; MatJafri, M. Z.; Lim, H. S.; Abdullah, K.; Saleh, N. Mohd.

    2008-10-01

    The height of cloud and aerosol layers in the atmosphere is believed to affect climate change and air pollution because both of them have important direct effects on the radiation balance of the earth. In this paper, we study the ability of Cloud Aerosol LIDAR and Infrared Pathfinder Satellite Observation (CALIPSO) data to detect, locate and distinguish between cloud and aerosol layers in the atmosphere over Peninsula Malaysia. We also used image processing technique to differentiate between cloud and aerosol layers from the CALIPSO images. The cloud and aerosol layers mostly are seen at troposphere (>10 km) and lower stratosphere (>15km). The results shows that CALIPSO can be used to determine cloud and aerosol layers and image processing technique has successfully distinguished them in the atmosphere.

  19. Arctic aerosol and cloud measurements performed during IAOOS 2014

    Science.gov (United States)

    Mariage, Vincent; Pelon, Jacques; Blouzon, Frédéric; Geyskens, Nicolas; Amarouche, Nadir; Drezen, Christine; Calzas, Michel; Victori, Stéphane; Garracio, Magali; Desautez, Alain; Pascal, Nicolas; Foujols, Thomas; Sarkissian, Alain; Pommereau, Jean-Pierre; Sennechael, Nathalie; Provost, Christine

    2015-04-01

    Better understanding of atmosphere-ice-ocean interactions and in particular of the role of aerosols and clouds in this Earth system is of prime importance in the Arctic. In the frame of the French IAOOS Equipex project, a new observational network is planned to be developed for ocean-ice-atmosphere climate survey over the Arctic, starting in 2015, to complement satellite observations. Eye-safe lidar measurements will allow us to profile aerosols and clouds for the atmospheric part, with the objective to perform regular measurements and characterize the vertical structure and optical properties. Radiation and meteorological parameters will be measured at the surface. A first buoy has been prototyped and deployed in April 2014 at the Barneo site set by the Russian teams at the North Pole. Measurements with the first autonomous backscatter lidar ever deployed in the arctic have been taken from April to end of November 2014 before the buoy was lost. Four profiles a day have been performed allowing a good sampling of cloud variability. Observations have shown that the occurrence of low level clouds was higher than 90% during summer. The project is presented, instrument performance is described and first results are discussed.

  20. Effects of El Chichon volcanic effluents on stratospheric aerosol dynamics

    Science.gov (United States)

    Pueschel, R. F.; Snetsinger, K. G.; Russell, P. B.; Oberbeck, V. R.; Livingston, J. M.

    1988-01-01

    The effects of El Chichon's April 1982 eruption on stratospheric aerosol dynamics are presently discussed in terms of log-normal size distributions over 15-20 km sample altitudes between 30 and 45 deg N over the contiguous U.S. After collection, samples were studied by SEM, and log-normal size distributions were fitted to the data-points obtained. It is found that stratospheric aerosol behavior is explainable by the laws of aerosol mechanics more easily than has been the case for tropospheric aerosol, for which the source-sink relationship is much more complex.

  1. Formation of highly porous aerosol particles by atmospheric freeze-drying in ice clouds.

    Science.gov (United States)

    Adler, Gabriela; Koop, Thomas; Haspel, Carynelisa; Taraniuk, Ilya; Moise, Tamar; Koren, Ilan; Heiblum, Reuven H; Rudich, Yinon

    2013-12-17

    The cycling of atmospheric aerosols through clouds can change their chemical and physical properties and thus modify how aerosols affect cloud microphysics and, subsequently, precipitation and climate. Current knowledge about aerosol processing by clouds is rather limited to chemical reactions within water droplets in warm low-altitude clouds. However, in cold high-altitude cirrus clouds and anvils of high convective clouds in the tropics and midlatitudes, humidified aerosols freeze to form ice, which upon exposure to subsaturation conditions with respect to ice can sublimate, leaving behind residual modified aerosols. This freeze-drying process can occur in various types of clouds. Here we simulate an atmospheric freeze-drying cycle of aerosols in laboratory experiments using proxies for atmospheric aerosols. We find that aerosols that contain organic material that undergo such a process can form highly porous aerosol particles with a larger diameter and a lower density than the initial homogeneous aerosol. We attribute this morphology change to phase separation upon freezing followed by a glass transition of the organic material that can preserve a porous structure after ice sublimation. A porous structure may explain the previously observed enhancement in ice nucleation efficiency of glassy organic particles. We find that highly porous aerosol particles scatter solar light less efficiently than nonporous aerosol particles. Using a combination of satellite and radiosonde data, we show that highly porous aerosol formation can readily occur in highly convective clouds, which are widespread in the tropics and midlatitudes. These observations may have implications for subsequent cloud formation cycles and aerosol albedo near cloud edges.

  2. Lidar Observations of Stratospheric Aerosol Layer After the Mt. Pinatubo Volcanic Eruption

    Science.gov (United States)

    Nagai, Tomohiro; Uchino, Osamu; Fujimoto, Toshifumi

    1992-01-01

    The volcano Mt. Pinatubo located on the Luzon Island, Philippines, had explosively erupted on June 15, 1991. The volcanic eruptions such as volcanic ash, SO2 and H2O reached into the stratosphere over 30 km altitude by the NOAA-11 satellite observation and this is considered one of the biggest volcanic eruptions in this century. A grandiose volcanic eruption influences the atmosphere seriously and causes many climatic effects globally. There had been many impacts on radiation, atmospheric temperature and stratospheric ozone after some past volcanic eruptions. The main cause of volcanic influence depends on stratospheric aerosol, that stay long enough to change climate and other meteorological conditions. Therefore it is very important to watch stratospheric aerosol layers carefully and continuously. Standing on this respect, we do not only continue stratospheric aerosol observation at Tsukuba but also have urgently developed another lidar observational point at Naha in Okinawa Island. This observational station could be thought valuable since there is no lidar observational station in this latitudinal zone and it is much nearer to Mt. Pinatubo. Especially, there is advantage to link up these two stations on studying the transportation mechanism in the stratosphere. In this paper, we present the results of lidar observations at Tsukuba and Naha by lidar systems with Nd:YAG laser.

  3. Cloud condensation nucleus activation properties of biogenic secondary organic aerosol

    Science.gov (United States)

    Vanreken, Timothy M.; Ng, Nga L.; Flagan, Richard C.; Seinfeld, John H.

    2005-04-01

    Organic aerosols in general and secondary organic aerosol (SOA) in particular are known to contribute significantly to the atmospheric population of cloud condensation nuclei (CCN). However, current knowledge is limited with respect to the nature of this contribution. This study presents a series of experiments wherein the potential for biogenically derived SOA to act as CCN is explored. Five compounds were studied: four monoterpenes (α-pinene, β-pinene, limonene, and Δ3-carene) and one terpenoid alcohol (terpinene-4-ol). In each case the aerosol formation was driven by the reaction of ozone with the biogenic precursor. The SOA produced in each experiment was allowed to age for several hours, during which CCN concentrations were periodically measured at four supersaturations: S = 0.27%, 0.32%, 0.54%, and 0.80%. The calculated relationships between particle dry diameter and critical supersaturation were found to fall in the range of previously reported data for single-component organic aerosols; of the systems studied, α-pinene SOA was the least CCN active, while limonene SOA exhibited the strongest CCN activity. Interestingly, the inferred critical supersaturation of the SOA products was considerably more sensitive to particle diameter than was found in previous studies. Furthermore, the relationships between particle size and critical supersaturation for the monoterpene SOA shifted considerably over the course of the experiments, with the aerosol becoming less hygroscopic over time. These results are consistent with the progressive oligomerization of the SOA.

  4. Influence of galactic cosmic rays and solar variability on aerosols, clouds and climate: Results from the CLOUD experiment at CERN

    Energy Technology Data Exchange (ETDEWEB)

    Curtius, Joachim [Institute for Atmosph. and Envir. Sciences, Univ. of Frankfurt am Main (Germany)

    2013-07-01

    The potential influence of ions produced from galactic cosmic rays on the formation of new aerosol particles in the atmosphere may play an important role relevant for aerosol properties, cloud formation and climate. Variability of galactic cosmic rays due to modulating influences from the sun therefore may affect (regional) climate on various time scales. A quantitative understanding of the role of ions for atmospheric aerosol formation has not been reached, but also the dependence of aerosol formation on the concentration of the nucleating substances such as gaseous sulfuric acid, ammonia and amines is missing. Here results from the CLOUD experiment at CERN are presented. CLOUD is a new aerosol and cloud chamber facility at CERN. The chamber can be exposed to a pion beam from CERN to simulate various levels of atmospheric ionization. CLOUD has been set up to investigate aerosol and cloud processes under well-controlled laboratory conditions. We find that cosmic ray ionization substantially increases the nucleation rate of pure sulfuric acid/water particles while charge effects are much less pronounced for ternary systems including ammonia or dimethylamine. The results from the CLOUD experiments have been used to develop a new parameterization of aerosol nucleation which has been included in a global climate model. Impacts of our findings for cloud formation and climate are discussed.

  5. Aerosol-Cloud-Precipitation Interactions in WRF Model:Sensitivity to Autoconversion Parameterization

    Institute of Scientific and Technical Information of China (English)

    解小宁; 刘晓东

    2015-01-01

    Cloud-to-rain autoconversion process is an important player in aerosol loading, cloud morphology, and precipitation variations because it can modulate cloud microphysical characteristics depending on the par-ticipation of aerosols, and aff ects the spatio-temporal distribution and total amount of precipitation. By applying the Kessler, the Khairoutdinov-Kogan (KK), and the Dispersion autoconversion parameterization schemes in a set of sensitivity experiments, the indirect eff ects of aerosols on clouds and precipitation are investigated for a deep convective cloud system in Beijing under various aerosol concentration backgrounds from 50 to 10000 cm−3. Numerical experiments show that aerosol-induced precipitation change is strongly dependent on autoconversion parameterization schemes. For the Kessler scheme, the average cumulative precipitation is enhanced slightly with increasing aerosols, whereas surface precipitation is reduced signifi-cantly with increasing aerosols for the KK scheme. Moreover, precipitation varies non-monotonically for the Dispersion scheme, increasing with aerosols at lower concentrations and decreasing at higher concentrations. These diff erent trends of aerosol-induced precipitation change are mainly ascribed to diff erences in rain wa-ter content under these three autoconversion parameterization schemes. Therefore, this study suggests that accurate parameterization of cloud microphysical processes, particularly the cloud-to-rain autoconversion process, is needed for improving the scientifi c understanding of aerosol-cloud-precipitation interactions.

  6. Volcanic aerosol and ozone depletion within the Antarctic polar vortex during the austral spring of 1991

    Energy Technology Data Exchange (ETDEWEB)

    Deshler, T.; Adriani, A.; Gobbi, G.P.; Hofmann, D.J.; Donfrancesco, G. di; Johnson, B.J. (Wyoming Univ., Laramie (United States) CNR, Ist. de Fisica dell' Atmosfera, Frascati (Italy) NOAA, Climate Monitoring and Diagnostics Lab., Boulder, CO (United States) ENEA, Centro Ricerche Energia Casaccia, Rome (Italy))

    1992-09-01

    In the spring of 1991 the Antarctic lower stratosphere was characterized by a layer of volcanic aerosol from the Cerro Hudson eruption. This aerosol layer was observed from McMurdo Station, Antarctica, with both lidar and balloonborne particle counters beginning around 10 September. After 20 September the aerosol was observed daily between 9 and 13 km. In this layer homogeneous nucleation of new aerosol was observed with concentrations greater than 6000/cu cm. Comparisons of scattering ratio calculated from measured particle size distributions agree best with the lidar measurements when a real index of refraction near 1.5 is used. In the past 5 years of measurements, ozone below 13 km has been relatively unchanged during the annual Antartic ozone depletion; however, in 1991 ozone below 13 km decreased at a rate of 4 - 8 ppb/day over 30 days. This change began shortly after the appearance of the volcanic aerosol, providing direct measurements correlating volcanic aerosol and ozone depletion. 16 refs.

  7. Quantifying compositional impacts of ambient aerosol on cloud droplet formation

    Science.gov (United States)

    Lance, Sara

    It has been historically assumed that most of the uncertainty associated with the aerosol indirect effect on climate can be attributed to the unpredictability of updrafts. In Chapter 1, we analyze the sensitivity of cloud droplet number density, to realistic variations in aerosol chemical properties and to variable updraft velocities using a 1-dimensional cloud parcel model in three important environmental cases (continental, polluted and remote marine). The results suggest that aerosol chemical variability may be as important to the aerosol indirect effect as the effect of unresolved cloud dynamics, especially in polluted environments. We next used a continuous flow streamwise thermal gradient Cloud Condensation Nuclei counter (CCNc) to study the water-uptake properties of the ambient aerosol, by exposing an aerosol sample to a controlled water vapor supersaturation and counting the resulting number of droplets. In Chapter 2, we modeled and experimentally characterized the heat transfer properties and droplet growth within the CCNc. Chapter 3 describes results from the MIRAGE field campaign, in which the CCNc and a Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) were deployed at a ground-based site during March, 2006. Size-resolved CCN activation spectra and growth factor distributions of the ambient aerosol in Mexico City were obtained, and an analytical technique was developed to quantify a probability distribution of solute volume fractions for the CCN in addition to the aerosol mixing-state. The CCN were shown to be much less CCN active than ammonium sulfate, with water uptake properties more consistent with low molecular weight organic compounds. The pollution outflow from Mexico City was shown to have CCN with an even lower fraction of soluble material. "Chemical Closure" was attained for the CCN, by comparing the inferred solute volume fraction with that from direct chemical measurements. A clear diurnal pattern was observed for the CCN solute

  8. CCN Properties of Organic Aerosol Collected Below and within Marine Stratocumulus Clouds near Monterey, California

    Directory of Open Access Journals (Sweden)

    Akua Asa-Awuku

    2015-10-01

    Full Text Available The composition of aerosol from cloud droplets differs from that below cloud. Its implications for the Cloud Condensation Nuclei (CCN activity are the focus of this study. Water-soluble organic matter from below cloud, and cloud droplet residuals off the coast of Monterey, California were collected; offline chemical composition, CCN activity and surface tension measurements coupled with Köhler Theory Analysis are used to infer the molar volume and surfactant characteristics of organics in both samples. Based on the surface tension depression of the samples, it is unlikely that the aerosol contains strong surfactants. The activation kinetics for all samples examined are consistent with rapid (NH42SO4 calibration aerosol. This is consistent with our current understanding of droplet kinetics for ambient CCN. However, the carbonaceous material in cloud drop residuals is far more hygroscopic than in sub-cloud aerosol, suggestive of the impact of cloud chemistry on the hygroscopic properties of organic matter.

  9. Impacts of Aerosol, Surface and Meteorological Conditions on Polar Cloud Properties: Use of In-Situ Cloud Probe Data

    Science.gov (United States)

    McFarquhar, Greg; Wu, Wei; Maahn, Maximilian

    2017-04-01

    Over the Southern Oceans, models from the Coupled Model Intercomparison Project 5 (CMIP5) almost universally underestimate sunlight reflected by near surface cloud in the Austral summer compared to Clouds and the Earth's Radiant Energy System (CERES) data. These and other biases in radiative fluxes over the Arctic are believed to be associated with the poorly modeled properties of low-level clouds that are frequently composed of supercooled water. Because changes in cloud macrophysical (heights, coverage) and microphysical (sizes, shapes and phases of particles) can alter the radiative impact of clouds, it is important to understand the processes that control cloud properties. In this presentation, in-situ microphysical observations obtained in prior arctic field campaigns (e.g., the Indirect and Semi-Direct Aerosol Campaign ISDAC, the Mixed-Phase Arctic Cloud Experiment M-PACE, and the Atmospheric Radiation Measurement Carbon Measurements Program-V ACME-V) are discussed. Strategies for comparing data collected in campaigns with different probes and processed with varying algorithms are introduced, along with procedures for using cloud probe data to refine assumptions about cloud properties in model schemes (e.g., size distributions, mass-dimension, and velocity-dimension relations) that affect rates at which mass and number are transferred between hydrometeor categories and hence estimates of latent and radiative heating, which feeds back on dynamics and hence cloud properties. Such observations from past arctic field experiments have enhanced our understanding of aerosol-cloud interactions acting in single-layer mixed phase clouds that are ubiquitous in the Arctic. But, it is still unknown what controls the amount of supercooled water in polar clouds (especially in frequently occurring complex multi-layer clouds), how probability distributions of cloud properties vary with aerosol loading and composition in different surface and meteorological conditions, and how

  10. Aerosol-induced changes of convective cloud anvils produce strong climate warming

    Directory of Open Access Journals (Sweden)

    I. Koren

    2010-01-01

    Full Text Available The effect of aerosol on clouds poses one of the largest uncertainties in estimating the anthropogenic contribution to climate change. In contrast, even small human-induced perturbations in cloud coverage, lifetime, height or optical properties can change the instantaneous radiative energy flux by hundreds of watts per unit area, and this forcing can be either warming or cooling. Clouds and aerosols form a complex coupled system that, unlike greenhouse gases, have relatively short lifetime (hours to days and inhomogeneous distribution. This and the inherent complexity of cloud microphysics and dynamics, and the strong coupling with meteorology explain why the estimation of the overall effect of aerosol on climate is so challenging.

    Here we focus on the effect of aerosol on cloud top properties of deep convective clouds over the tropical Atlantic. The tops of these vertically developed clouds consist of mostly ice and can reach high levels of the atmosphere, overshooting the lower stratosphere and reaching altitudes greater than 16 km. We show a link between aerosol, clouds and the free atmosphere wind profile that can change the magnitude and sign of the overall climate radiative forcing.

    This study demonstrates the deep link between cloud shape and aerosol loading and that the overall aerosol effect in regions of deep convective clouds might be warming. Moreover we show how averaging the cloud height and optical properties over large regions may lead to a false cooling estimation.

  11. Systematic variations of cloud top temperature and precipitation rate with aerosols over the global tropics

    Directory of Open Access Journals (Sweden)

    Feng Niu

    2012-09-01

    Full Text Available Aerosols may modify cloud properties and precipitation via a variety of mechanisms with varying and contradicting consequences. Using a large ensemble of satellite data acquired by the Moderate Resolution Imaging Spectroradiometer onboard the Earth Observing System's Aqua platform, the CloudSat cloud profiling radar and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO satellite over the tropical oceans, we identified two distinct correlations of clouds and precipitation with aerosol loading. Cloud-top temperatures are significantly negatively correlated with increasing aerosol index (AI over oceans and aerosol optical depth (AOT over land for deep mixed-phase clouds with liquid droplets near the warm bases and ice crystals near the cold tops; no significant changes were found for uniformly liquid clouds. Precipitation rates are positively correlated with the AI for mixed-phase clouds, but negatively correlated for liquid clouds. These distinct correlations might be a manifestation of two potential mechanisms: the invigoration effect (which enhances convection and precipitation and the microphysical effect (which suppresses precipitation. We note that the highly limited information garnered from satellite products cannot unequivocally support the causal relationships between cloud-top temperature/precipitation rate and aerosol loading. But if aerosols are indeed the causes for the observed relationships, they may change the overall distribution of precipitation, leading to a more extreme and unfavorable rainfall pattern of suppressing light rains and fostering heavy rains.

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

    Science.gov (United States)

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

    2016-12-01

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

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

    OpenAIRE

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

    2014-01-01

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

  14. Using High-Resolution Airborne Remote Sensing to Study Aerosol Near Clouds

    Science.gov (United States)

    Levy, Robert; Munchak, Leigh; Mattoo, Shana; Marshak, Alexander; Wilcox, Eric; Gao, Lan; Yorks, John; Platnick, Steven

    2016-01-01

    The horizontal space in between clear and cloudy air is very complex. This so-called twilight zone includes activated aerosols that are not quite clouds, thin cloud fragments that are not easily observable, and dying clouds that have not quite disappeared. This is a huge challenge for satellite remote sensing, specifically for retrieval of aerosol properties. Identifying what is cloud versus what is not cloud is critically important for attributing radiative effects and forcings to aerosols. At the same time, the radiative interactions between clouds and the surrounding media (molecules, surface and aerosols themselves) will contaminate retrieval of aerosol properties, even in clear skies. Most studies on aerosol cloud interactions are relevant to moderate resolution imagery (e.g. 500 m) from sensors such as MODIS. Since standard aerosol retrieval algorithms tend to keep a distance (e.g. 1 km) from the nearest detected cloud, it is impossible to evaluate what happens closer to the cloud. During Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS), the NASA ER-2 flew with the enhanced MODIS Airborne Simulator (eMAS), providing MODIS-like spectral observations at high (50 m) spatial resolution. We have applied MODIS-like aerosol retrieval for the eMAS data, providing new detail to characterization of aerosol near clouds. Interpretation and evaluation of these eMAS aerosol retrievals is aided by independent MODIS-like cloud retrievals, as well as profiles from the co-flying Cloud Physics Lidar (CPL). Understanding aerosolcloud retrieval at high resolution will lead to better characterization and interpretation of long-term, global products from lower resolution (e.g.MODIS) satellite retrievals.

  15. 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.

  16. The role of aerosols in cloud drop parameterizations and its applications in global climate models

    Energy Technology Data Exchange (ETDEWEB)

    Chuang, C.C.; Penner, J.E. [Lawrence Livermore National Lab., CA (United States)

    1996-04-01

    The characteristics of the cloud drop size distribution near cloud base are initially determined by aerosols that serve as cloud condensation nuclei and the updraft velocity. We have developed parameterizations relating cloud drop number concentration to aerosol number and sulfate mass concentrations and used them in a coupled global aerosol/general circulation model (GCM) to estimate the indirect aerosol forcing. The global aerosol model made use of our detailed emissions inventories for the amount of particulate matter from biomass burning sources and from fossil fuel sources as well as emissions inventories of the gas-phase anthropogenic SO{sub 2}. This work is aimed at validating the coupled model with the Atmospheric Radiation Measurement (ARM) Program measurements and assessing the possible magnitude of the aerosol-induced cloud effects on climate.

  17. Use of Lidar Derived Optical Extinction and Backscattering Coefficients Near Cloud Base to Explore Aerosol-Cloud Interactions

    Science.gov (United States)

    Han, Zaw; Wu, Yonhgua; Gross, Barry; Moshary, Fred

    2016-06-01

    Combination of microwave radiometer (MWR) and mutlifilter rotating shadowband radiometer (MFRSR) measurement data together with SBDART radiative transfer model to compute cloud optical depth (COD) and cloud droplet effective radius (Reff). Quantify the first aerosol indirect effect using calculated Reff and aerosol extinction from Raman lidar measurement in urban coastal region. Illustrate comparison between ground-based and satellite retrievals. Demonstrate relationship between surface aerosol (PM2.5) loading and Reff. We also explain the sensitivity of aerosol-cloud-index (ACI) depend on the aerosol layer from cloud base height. Potential used of less noisy elastic backscattering to calculate the ACI instead of using Raman extinction. We also present comparison of elastic backscattering and Raman extinction correlation to Reff.

  18. Separating Real and Apparent Effects of Cloud, Humidity, and Dynamics on Aerosol Optical Thickness near Cloud Edges

    Science.gov (United States)

    Jeong, Myeong-Jae; Li, Zhanqing

    2010-01-01

    Aerosol optical thickness (AOT) is one of aerosol parameters that can be measured on a routine basis with reasonable accuracy from Sun-photometric observations at the surface. However, AOT-derived near clouds is fraught with various real effects and artifacts, posing a big challenge for studying aerosol and cloud interactions. Recently, several studies have reported correlations between AOT and cloud cover, pointing to potential cloud contamination and the aerosol humidification effect; however, not many quantitative assessments have been made. In this study, various potential causes of apparent correlations are investigated in order to separate the real effects from the artifacts, using well-maintained observations from the Aerosol Robotic Network, Total Sky Imager, airborne nephelometer, etc., over the Southern Great Plains site operated by the U.S. Department of Energy's Atmospheric Radiation Measurement Program. It was found that aerosol humidification effects can explain about one fourth of the correlation between the cloud cover and AOT. New particle genesis, cloud-processed particles, atmospheric dynamics, and aerosol indirect effects are likely to be contributing to as much as the remaining three fourth of the relationship between cloud cover and AOT.

  19. Natural Aerosols Explain Seasonal and Spatial Patterns of Southern Ocean Cloud Albedo

    Energy Technology Data Exchange (ETDEWEB)

    McCoy, Daniel; Burrows, Susannah M.; Wood, R.; Grosvenor, Daniel P.; Elliott, Scott; Ma, Po-Lun; Rasch, Philip J.; Hartmann, Dennis L.

    2015-07-17

    Small particles called aerosols act as nucleation sites for cloud drop formation, affecting clouds and cloud properties – ultimately influencing the cloud dynamics, lifetime, water path and areal extent that determine the reflectivity (albedo) of clouds. The concentration Nd of droplets in clouds that influences planetary albedo is sensitive to the availability of aerosol particles on which the droplets form. Natural aerosol concentrations not only affect cloud properties themselves, but also modulate the sensitivity of clouds to changes in anthropogenic aerosols. Here, it is shown that modeled natural aerosols, principally marine biogenic primary and secondary aerosol sources, explain more than half of the spatiotemporal variability in satellite-observed Nd. Enhanced Nd over regions of high biological activity is found to be driven primarily by high concentrations of sulfate aerosol at lower Southern Ocean latitudes (35-45°S) and by organic matter in sea spray aerosol at higher latitudes (45-55°S). Biogenic sources are estimated to increase the summertime mean reflected solar radiation in excess of 10 W m-2 over parts of the Southern Ocean, which is comparable to the annual mean increases expected from anthropogenic aerosols over heavily polluted regions of the Northern Hemisphere.

  20. Impact of aerosol on post-frontal convective clouds over Germany

    Directory of Open Access Journals (Sweden)

    Daniel Rieger

    2014-07-01

    Full Text Available We carried out simulations with predefined and simulated aerosol distributions in order to investigate the improvement in the forecasting capabilities of an operational weather forecast model by the use of an improved aerosol representation. This study focuses on convective cumulus clouds developing after the passage of a cold front on 25 April 2008 over Germany. The northerly flow after the cold front leads to increased sea salt aerosol concentrations compared to prefrontal conditions. High aerosol number concentrations are simulated in the interactive scenario representing typically polluted conditions. Nevertheless, due to the presence of sea salt particles, effective radii of cloud droplets reach values typical of pristine clouds (between 7 µm and 13 µm at the same time. Compared to the predefined continental and maritime aerosol scenarios, the simulated aerosol distribution leads to a significant change in cloud properties such as cloud droplet radii and number concentrations. Averaged over the domain covered by the convective cumuli clouds, we found a systematic decrease in precipitation with increasing aerosol number concentrations. Differences in cloud cover, short wave radiation and cloud top heights are buffered by systematic differences in precipitation and the related diabatic effects. Comparisons with measured precipitation show good agreement for the interactive aerosol scenario as well as for the extreme maritime aerosol scenario.

  1. Aerosol-cloud-precipitation interactions: A challenging problem in regional environment and climate research

    Institute of Scientific and Technical Information of China (English)

    P.C.S.Devara; M.G.Manoj

    2013-01-01

    Aerosols affect clouds in two broad ways:(i) presence of more number of aerosols leads to formation of more smaller droplets,and reduces coalescence,resulting in brighter clouds that reflect more solar energy back to space,hence they contribute to cooling of the Earth's surface and (ii) numerous smaller cloud droplets tend to reduce precipitation and change the extent of cloud cover and increase cloud lifetime and albedo.One of our recent studies on aerosols over the Indo-Gangetic Plains (IGP) relative to the pristine oceans to the south of Indian Ocean showed that highly absorbing aerosols could potentially lead to the revival of active condition preceded by long break.The absorption of solar radiation by aerosols such as black carbon and desert dust produces surface cooling and local stabilization of lower atmosphere.This stability effect is overcome by the enhanced moisture convergence due to the meridional gradient of aerosol-induced heating.In some other studies,we showed association between cloud thickness and cloud to sub-cloud ratio (SCR),aerosol variability (in terms of aerosol optical depth and aerosol index) and monsoon precipitation and climate over regional scale.This paper provides an overview of some salient results that have been obtained from the studies conducted,using the ground-and space-based active and passive remote sensing techniques,at the Indian Institute of Tropical Meteorology (IITM),Pune,India in the recent decade.

  2. Massive Volcanic SO2 Oxidation and Sulphate Aerosol Deposition in Cenozoic North America

    Science.gov (United States)

    Volcanic eruptions release a large amount of sulphur dioxide (SO2) into the atmosphere. SO2 is oxidized to sulphate and can subsequently form sulphate aerosol, which can affect the Earth's radiation balance, biologic productivity and high-altitude ozone co...

  3. Microphysical effects determine macrophysical response for aerosol impacts on deep convective clouds.

    Science.gov (United States)

    Fan, Jiwen; Leung, L Ruby; Rosenfeld, Daniel; Chen, Qian; Li, Zhanqing; Zhang, Jinqiang; Yan, Hongru

    2013-11-26

    Deep convective clouds (DCCs) play a crucial role in the general circulation, energy, and hydrological cycle of our climate system. Aerosol particles can influence DCCs by altering cloud properties, precipitation regimes, and radiation balance. Previous studies reported both invigoration and suppression of DCCs by aerosols, but few were concerned with the whole life cycle of DCC. By conducting multiple monthlong cloud-resolving simulations with spectral-bin cloud microphysics that capture the observed macrophysical and microphysical properties of summer convective clouds and precipitation in the tropics and midlatitudes, this study provides a comprehensive view of how aerosols affect cloud cover, cloud top height, and radiative forcing. We found that although the widely accepted theory of DCC invigoration due to aerosol's thermodynamic effect (additional latent heat release from freezing of greater amount of cloud water) may work during the growing stage, it is microphysical effect influenced by aerosols that drives the dramatic increase in cloud cover, cloud top height, and cloud thickness at the mature and dissipation stages by inducing larger amounts of smaller but longer-lasting ice particles in the stratiform/anvils of DCCs, even when thermodynamic invigoration of convection is absent. The thermodynamic invigoration effect contributes up to ~27% of total increase in cloud cover. The overall aerosol indirect effect is an atmospheric radiative warming (3-5 W m(-2)) and a surface cooling (-5 to -8 W m(-2)). The modeling findings are confirmed by the analyses of ample measurements made at three sites of distinctly different environments.

  4. Model-based aviation advice on distal volcanic ash clouds by assimilating aircraft in situ measurements

    Science.gov (United States)

    Fu, Guangliang; Heemink, Arnold; Lu, Sha; Segers, Arjo; Weber, Konradin; Lin, Hai-Xiang

    2016-07-01

    The forecast accuracy of distal volcanic ash clouds is important for providing valid aviation advice during volcanic ash eruption. However, because the distal part of volcanic ash plume is far from the volcano, the influence of eruption information on this part becomes rather indirect and uncertain, resulting in inaccurate volcanic ash forecasts in these distal areas. In our approach, we use real-life aircraft in situ observations, measured in the northwestern part of Germany during the 2010 Eyjafjallajökull eruption, in an ensemble-based data assimilation system combined with a volcanic ash transport model to investigate the potential improvement on the forecast accuracy with regard to the distal volcanic ash plume. We show that the error of the analyzed volcanic ash state can be significantly reduced through assimilating real-life in situ measurements. After a continuous assimilation, it is shown that the aviation advice for Germany, the Netherlands and Luxembourg can be significantly improved. We suggest that with suitable aircrafts measuring once per day across the distal volcanic ash plume, the description and prediction of volcanic ash clouds in these areas can be greatly improved.

  5. Sensitivity of cloud albedo to aerosol concentration and spectral dispersion of cloud droplet size distribution

    Energy Technology Data Exchange (ETDEWEB)

    Iorga, G. [Faculty of Chemistry, University of Bucharest, Bucharest (Romania)]. E-mail: giorga@gw-chimie.math.unibuc.ro; Stefan, S. [Faculty of Physics, University of Bucharest, Bucharest (Romania)

    2007-07-15

    Both the enhancement of the aerosol number concentration and the relative dispersion of the cloud droplet size distribution (spectral dispersion) on a regional scale can modify the cloud reflectivity. This work is focused on the role that pre-cloud aerosol plays in cloud reflectivity. Log-normal aerosol size distributions were used to describe two aerosol types: marine and rural. The number of aerosols that activate to droplets was obtained based on Abdul-Razzak and Ghan's (2000) activation parameterization. The cloud albedo taking into account the spectral dispersion effect in the parameterization of cloud effective radius and in the scattering asymmetry factor has been estimated. Two different scaling factors to account for dispersion were used. The sensitivity of cloud albedo to spectral dispersion-cloud droplet number concentration relationship in connection to the changes in liquid water content (LWC), and the cloud droplet effective radius has been also investigated. We obtained higher values of effective radius when dispersion is taken into account, with respect to the base case (without considering dispersion). The inferred absolute differences in effective radius values between calculations with each of the scaling factors are below 0.8 {mu}m as LWC ranges between 0.1 and 1.0 g m-3. The optical depth decreased by up to 14% (marine), and up to 29% (continental) when dispersion is considered in both effective radius and asymmetry factor ({beta}LDR scaling factor). Correspondingly, the relative change in cloud albedo is up to 6% (marine) and up to 11% (continental) clouds. For continental clouds, the calculated effective radius when dispersion is considered fits well within the measured range of effective radius in SCAR-B project. The calculated cloud albedo when dispersion is considered shows better agreement with the estimated cloud albedo from measured effective radius in SCAR-B project than the cloud albedo calculated without dispersion. In cleaner

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

    Science.gov (United States)

    L'Ecuyer, T. S.

    2016-12-01

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

  7. 17 years of aerosol and clouds from the ATSR Series of Instruments

    Science.gov (United States)

    Poulsen, C. A.

    2015-12-01

    Aerosols play a significant role in Earth's climate by scattering and absorbing incoming sunlight and affecting the formation and radiative properties of clouds. The extent to which aerosols affect cloud remains one of the largest sources of uncertainty amongst all influences on climate change. Now, a new comprehensive datasets has been developed under the ESA Climate Change Initiative (CCI) programme to quantify how changes in aerosol levels affect these clouds. The unique dataset is constructed from the Optimal Retrieval of Aerosol and Cloud (ORAC) algorithm used in (A)ATSR (Along Track Scanning Radiometer) retrievals of aerosols generated in the Aerosol CCI and the CC4CL ( Community Code for CLimate) for cloud retrieval in the Cloud CCI. The ATSR instrument is a dual viewing instrument with on board visible and infra red calibration systems making it an ideal instrument to study trends of Aerosol and Clouds and their interactions. The data set begins in 1995 and ends in 2012. A new instrument in the series SLSTR(Sea and Land Surface Temperature Radiometer) will be launch in 2015. The Aerosol and Clouds are retreived using similar algorithms to maximise the consistency of the results These state-of-the-art retrievals have been merged together to quantify the susceptibility of cloud properties to changes in aerosol concentration. Aerosol-cloud susceptibilities are calculated from several thousand samples in each 1x1 degree globally gridded region. Two-D histograms of the aerosol and cloud properties are also included to facilitate seamless comparisons between other satellite and modelling data sets. The analysis of these two long term records will be discussed individually and the initial comparisons between these new joint products and models will be presented.

  8. Study of Aerosol/Cloud/Radiation Interactions over the ARM SGP Site

    Energy Technology Data Exchange (ETDEWEB)

    Chuang, C; Chin, S

    2006-03-14

    While considerable advances in the understanding of atmospheric processes and feedbacks in the climate system have led to a better representation of these mechanisms in general circulation models (GCMs), the greatest uncertainty in predictability of future climate arises from clouds and their interactions with radiation. To explore this uncertainty, cloud resolving model has been evolved as one of the main tools for understanding and testing cloud feedback processes in climate models, whereas the indirect effects of aerosols are closely linked with cloud feedback processes. In this study we incorporated an existing parameterization of cloud drop concentration (Chuang et al., 2002a) together with aerosol prediction from a global chemistry/aerosol model (IMPACT) (Rotman et al., 2004; Chuang et al., 2002b; Chuang et al., 2005) into LLNL cloud resolving model (Chin, 1994; Chin et al., 1995; Chin and Wilhelmson, 1998) to investigate the effects of aerosols on cloud/precipitation properties and the resulting radiation fields over the Southern Great Plains.

  9. Aerosol removal and cloud collapse accelerated by supersaturation fluctuations in turbulence

    Science.gov (United States)

    Chandrakar, K. K.; Cantrell, W.; Ciochetto, D.; Karki, S.; Kinney, G.; Shaw, R. A.

    2017-05-01

    Prior observations have documented the process of cloud cleansing, through which cloudy, polluted air from a continent is slowly transformed into cloudy, clean air typical of a maritime environment. During that process, cloud albedo changes gradually, followed by a sudden reduction in cloud fraction and albedo as drizzle forms and convection changes from closed to open cellular. Experiments in a cloud chamber that generates a turbulent environment show a similar cloud cleansing process followed by rapid cloud collapse. Observations of (1) cloud droplet size distribution, (2) interstitial aerosol size distribution, (3) cloud droplet residual size distribution, and (4) water vapor supersaturation are all consistent with the hypothesis that turbulent fluctuations of supersaturation accelerate the cloud cleansing process and eventual cloud collapse. Decay of the interstitial aerosol concentration occurs slowly at first then more rapidly. The accelerated cleansing occurs when the cloud phase relaxation time exceeds the turbulence correlation time.

  10. Clouds-Aerosols-Precipitation Satellite Analysis Tool (CAPSAT

    Directory of Open Access Journals (Sweden)

    I. M. Lensky

    2008-03-01

    Full Text Available A methodology for representing much of the physical information content of the METEOSAT Second Generation (MSG geostationary satellite using red-green-blue (RGB composites of the computed physical values of the picture elements is presented. The physical values are the solar reflectance in the solar channels and brightness temperature in the thermal channels. The main RGB compositions are (1 "Day Natural Colors", presenting vegetation in green, bare surface in brown, sea surface in black, water clouds as white, ice as magenta; (2 "Day Microphysical", presenting cloud microstructure using the solar reflectance component of the 3.9 μm, visible and thermal IR channels; (3 "Night Microphysical", also presenting clouds microstructure using the brightness temperature differences between 10.8 and 3.9 μm; (4 "Day and Night", using only thermal channels for presenting surface and cloud properties, desert dust and volcanic emissions; (5 "Air Mass", presenting mid and upper tropospheric features using thermal water vapor and ozone channels. The scientific basis for these rendering schemes is provided, with examples for the applications. The expanding use of these rendering schemes requires their proper documentation and setting as standards, which is the main objective of this publication.

  11. Investigation of Aerosol Effects on Cumulus Cloud Microphysics and Precipitation in Houston, Texas

    Science.gov (United States)

    Fan, J.; Zhang, R.; Tao, W.

    2006-05-01

    The effect of aerosols on clouds is of significant uncertainty. Aerosols in polluted air may influence the cloud microphysical processes and precipitation by serving as cloud condensation nuclei (CCN), potentially forming smaller cloud droplets and higher concentrations. The aerosol concentration and properties (composition, solubility, etc) have an important effect on cloud droplet activation, which determine the number-size distribution of cloud droplets, the precipitation rate, and the lifetime of a cloud. We investigate the effect of aerosol concentrations and properties on a convective cloud case in Houston, Texas, using a cloud resolving model (CRM) developed at the NASA-GSFC, which incorporates a spectral-bin microphysics Hebrew University Cloud Model (HUCM). The CRM simulations are compared to measurements of radar reflectivity and accumulated precipitation. Sensitivity studies are performed to examine the effects of aerosol number concentration, chemical compositions, and other environmental parameters such relative humidity on cloud droplet number concentration, droplet size, precipitation rate, convective intensity, etc. The implications of the present results on assessment of aerosol indirect effect are discussed.

  12. Contrasting influences of aerosols on cloud properties during deficient and abundant monsoon years.

    Science.gov (United States)

    Patil, Nitin; Dave, Prashant; Venkataraman, Chandra

    2017-03-24

    Direct aerosol radiative forcing facilitates the onset of Indian monsoon rainfall, based on synoptic scale fast responses acting over timescales of days to a month. Here, we examine relationships between aerosols and coincident clouds over the Indian subcontinent, using observational data from 2000 to 2009, from the core monsoon region. Season mean and daily timescales were considered. The correlation analyses of cloud properties with aerosol optical depth revealed that deficient monsoon years were characterized by more frequent and larger decreases in cloud drop size and ice water path, but increases in cloud top pressure, with increases in aerosol abundance. The opposite was observed during abundant monsoon years. The correlations of greater aerosol abundance, with smaller cloud drop size, lower evidence of ice processes and shallower cloud height, during deficient rainfall years, imply cloud inhibition; while those with larger cloud drop size, greater ice processes and a greater cloud vertical extent, during abundant rainfall years, suggest cloud invigoration. The study establishes that continental aerosols over India alter cloud properties in diametrically opposite ways during contrasting monsoon years. The mechanisms underlying these effects need further analysis.

  13. Encounters of aircraft with volcanic ash clouds; A compilation of known incidents, 1953-2009

    Science.gov (United States)

    Guffanti, Marianne; Casadevall, Thomas J.; Budding, Karin

    2010-01-01

    Information about reported encounters of aircraft with volcanic ash clouds from 1953 through 2009 has been compiled to document the nature and scope of risks to aviation from volcanic activity. The information, gleaned from a variety of published and other sources, is presented in database and spreadsheet formats; the compilation will be updated as additional encounters occur and as new data and corrections come to light. The effects observed by flight crews and extent of aircraft damage vary greatly among incidents, and each incident in the compilation is rated according to a severity index. Of the 129 reported incidents, 94 incidents are confirmed ash encounters, with 79 of those having various degrees of airframe or engine damage; 20 are low-severity events that involve suspected ash or gas clouds; and 15 have data that are insufficient to assess severity. Twenty-six of the damaging encounters involved significant to very severe damage to engines and (or) airframes, including nine encounters with engine shutdown during flight. The average annual rate of damaging encounters since 1976, when reporting picked up, has been approximately 2 per year. Most of the damaging encounters occurred within 24 hours of the onset of ash production or at distances less than 1,000 kilometers from the source volcanoes. The compilation covers only events of relatively short duration for which aircraft were checked for damage soon thereafter; documenting instances of long-term repeated exposure to ash (or sulfate aerosols) will require further investigation. Of 38 source volcanoes, 8 have caused 5 or more encounters, of which the majority were damaging: Augustine (United States), Chaiten (Chile), Mount St. Helens (United States), Pacaya (Guatemala), Pinatubo (Philippines), Redoubt (United States), Sakura-jima (Japan), and Soufriere Hills (Montserrat, Lesser Antilles, United Kingdom). Aircraft have been damaged by eruptions ranging from small, recurring episodes to very large

  14. The effect of smoke, dust, and pollution aerosol on shallow cloud development over the Atlantic Ocean.

    Science.gov (United States)

    Kaufman, Yoram J; Koren, Ilan; Remer, Lorraine A; Rosenfeld, Daniel; Rudich, Yinon

    2005-08-09

    Clouds developing in a polluted environment tend to have more numerous but smaller droplets. This property may lead to suppression of precipitation and longer cloud lifetime. Absorption of incoming solar radiation by aerosols, however, can reduce the cloud cover. The net aerosol effect on clouds is currently the largest uncertainty in evaluating climate forcing. Using large statistics of 1-km resolution MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data, we study the aerosol effect on shallow water clouds, separately in four regions of the Atlantic Ocean, for June through August 2002: marine aerosol (30 degrees S-20 degrees S), smoke (20 degrees S-5 degrees N), mineral dust (5 degrees N-25 degrees N), and pollution aerosols (30 degrees N- 60 degrees N). All four aerosol types affect the cloud droplet size. We also find that the coverage of shallow clouds increases in all of the cases by 0.2-0.4 from clean to polluted, smoky, or dusty conditions. Covariability analysis with meteorological parameters associates most of this change to aerosol, for each of the four regions and 3 months studied. In our opinion, there is low probability that the net aerosol effect can be explained by coincidental, unresolved, changes in meteorological conditions that also accumulate aerosol, or errors in the data, although further in situ measurements and model developments are needed to fully understand the processes. The radiative effect at the top of the atmosphere incurred by the aerosol effect on the shallow clouds and solar radiation is -11 +/- 3 W/m2 for the 3 months studied; 2/3 of it is due to the aerosol-induced cloud changes, and 1/3 is due to aerosol direct radiative effect.

  15. Simultaneous Retrieval of Aerosol and Cloud Properties During the MILAGRO Field Campaign

    Science.gov (United States)

    Knobelspiesse, K.; Cairns, B.; Redemann, J.; Bergstrom, R. W.; Stohl, A.

    2011-01-01

    Estimation of Direct Climate Forcing (DCF) due to aerosols in cloudy areas has historically been a difficult task, mainly because of a lack of appropriate measurements. Recently, passive remote sensing instruments have been developed that have the potential to retrieve both cloud and aerosol properties using polarimetric, multiple view angle, and multi spectral observations, and therefore determine DCF from aerosols above clouds. One such instrument is the Research Scanning Polarimeter (RSP), an airborne prototype of a sensor on the NASA Glory satellite, which unfortunately failed to reach orbit during its launch in March of 2011. In the spring of 2006, the RSP was deployed on an aircraft based in Veracruz, Mexico, as part of the Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign. On 13 March, the RSP over flew an aerosol layer lofted above a low altitude marine stratocumulus cloud close to shore in the Gulf of Mexico. We investigate the feasibility of retrieving aerosol properties over clouds using these data. Our approach is to first determine cloud droplet size distribution using the angular location of the cloud bow and other features in the polarized reflectance. The selected cloud was then used in a multiple scattering radiative transfer model optimization to determine the aerosol optical properties and fine tune the cloud size distribution. In this scene, we were able to retrieve aerosol optical depth, the fine mode aerosol size distribution parameters and the cloud droplet size distribution parameters to a degree of accuracy required for climate modeling. This required assumptions about the aerosol vertical distribution and the optical properties of the coarse aerosol size mode. A sensitivity study was also performed to place this study in the context of future systematic scanning polarimeter observations, which found that the aerosol complex refractive index can also be observed accurately if the aerosol optical depth is

  16. Aerosol-induced changes of convective cloud anvils produce strong climate warming

    Directory of Open Access Journals (Sweden)

    I. Koren

    2010-05-01

    Full Text Available The effect of aerosol on clouds poses one of the largest uncertainties in estimating the anthropogenic contribution to climate change. Small human-induced perturbations to cloud characteristics via aerosol pathways can create a change in the top-of-atmosphere radiative forcing of hundreds of Wm−2. Here we focus on links between aerosol and deep convective clouds of the Atlantic and Pacific Intertropical Convergence Zones, noting that the aerosol environment in each region is entirely different. The tops of these vertically developed clouds consisting of mostly ice can reach high levels of the atmosphere, overshooting the lower stratosphere and reaching altitudes greater than 16 km. We show a link between aerosol, clouds and the free atmosphere wind profile that can change the magnitude and sign of the overall climate radiative forcing.

    We find that increased aerosol loading is associated with taller cloud towers and anvils. The taller clouds reach levels of enhanced wind speeds that act to spread and thin the anvil clouds, increasing areal coverage and decreasing cloud optical depth. The radiative effect of this transition is to create a positive radiative forcing (warming at top-of-atmosphere.

    Furthermore we introduce the cloud optical depth (τ, cloud height (Z forcing space and show that underestimation of radiative forcing is likely to occur in cases of non homogenous clouds. Specifically, the mean radiative forcing of towers and anvils in the same scene can be several times greater than simply calculating the forcing from the mean cloud optical depth in the scene.

    Limitations of the method are discussed, alternative sources of aerosol loading are tested and meteorological variance is restricted, but the trend of taller clouds, increased and thinner anvils associated with increased aerosol loading remains robust through all the different tests and perturbations.

  17. Impact of Asian aerosols on air quality over the United States: A perspective from aerosol-cloud-radiation coupling

    Science.gov (United States)

    Tao, Z.; Yu, H.; Chin, M.

    2013-12-01

    It has well been established, through satellite/ground observations, that dust and aerosols from various Asian sources can travel across the Pacific and reach North America (NA) at least on episode bases. Once reaching NA, these inflow aerosols would compete with local emissions to influence atmospheric composition and air quality over the United States (US). The previous studies, typically based on one or multiple satellite measurements in combination with global/regional model simulations, suggest that the impact of Asian dust/aerosols on US air quality tend to be small since most inflow aerosols stay aloft. On the other hand, aerosols affect many key meteorological processes that will ultimately channel down to impact air quality. Aerosols absorb and scatter solar radiation that change the atmospheric stability, thus temperature, wind, and planetary boundary layer structure that would directly alter air quality. Aerosols can serve as cloud condensation nuclei and ice nuclei to modify cloud properties and precipitation that would also affect aerosol removal and concentration. This indirect impact of Asian aerosol inflow on US air quality may be substantial and need to be investigated. This study employs the NASA Unified WRF (NU-WRF) to address the question from the aerosol-radiation-cloud interaction perspective. The simulation period was selected from April to June of 2010 during which the Asian dust continuously reached NA based on CALIPSO satellite observation. The preliminary results show that the directly-transported Asian aerosol increases surface PM2.5 concentration by less than 2 μg/m3 over the west coast areas of US, and the aerosol-radiation-cloud feedback has a profound effect on air quality over the central to eastern US. A more detailed analysis links this finding to a series of meteorological conditions modified by aerosol effects.

  18. Microphysical, macrophysical and radiative signatures of volcanic aerosols in trade wind cumulus observed by the A-Train

    Directory of Open Access Journals (Sweden)

    T. Yuan

    2011-02-01

    Full Text Available Increased aerosol concentrations can raise planetary albedo not only by reflecting sunlight and increasing cloud albedo, but also by changing cloud amount. However, detecting aerosol effect on cloud amount has been elusive to both observations and modeling due to potential buffering mechanisms and convolution of meteorology. Here through a natural experiment provided by long-term degassing of a low-lying volcano and use of A-Train satellite observations, we show aerosols are associated strongly with modification of trade cumulus cloud fields including decreased droplet size, decreased precipitation efficiency and increased cloud amount. We also demonstrate that the observed microphysical and macrophysical changes cannot be explained by synoptic meteorology or the orographic effect of the Hawaiian Islands. The "total shortwave aerosol forcing", resulting from direct and indirect forcings including both cloud albedo and cloud amount, is almost an order of magnitude higher than aerosol direct forcing alone. The precipitation reduction associated with enhanced aerosol leads to large changes in the energetics of air-sea exchange. Our results represent the first observational evidence of large-scale increase of cloud amount due to aerosols in a trade cumulus regime, which can be used to constrain the representation of aerosol-cloud interactions in climate models. The findings also have implications for volcano-climate interactions and climate mitigation research.

  19. Cloud Condensation Nuclei Activity of Aerosols during GoAmazon 2014/15 Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Martin, S. T. [Harvard Univ., Cambridge, MA (United States); Kleinman, L. [Brookhaven National Lab. (BNL), Upton, NY (United States); Thalman, R. M. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-03-01

    Aerosol indirect effects, which represent the impact of aerosols on climate through influencing the properties of clouds, remain one of the main uncertainties in climate predictions (Stocker et al. 2013). Reducing this large uncertainty requires both improved understanding and representation of aerosol properties and processes in climate models, including the cloud activation properties of aerosols. The Atmospheric System Research (ASR) science program plan of January 2010 states that: “A key requirement for simulating aerosol-cloud interactions is the ability to calculate cloud condensation nuclei and ice nuclei (CCN and IN, respectively) concentrations as a function of supersaturation from the chemical and microphysical properties of the aerosol.” The Observations and Modeling of the Green Ocean Amazon (GoAmazon 2014/15) study seeks to understand how aerosol and cloud life cycles are influenced by pollutant outflow from a tropical megacity (Manaus)—in particular, the differences in cloud-aerosol-precipitation interactions between polluted and pristine conditions. One key question of GoAmazon2014/5 is: “What is the influence of the Manaus pollution plume on the cloud condensation nuclei (CCN) activities of the aerosol particles and the secondary organic material in the particles?” To address this question, we measured size-resolved CCN spectra, a critical measurement for GoAmazon2014/5.

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

    Science.gov (United States)

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

    2017-04-01

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

  1. Influence of 3D effects on 1D aerosol retrievals in synthetic, partially clouded scenes

    NARCIS (Netherlands)

    Stap, F. A.; Hasekamp, O. P.; Emde, C.; Roeckmann, Thomas|info:eu-repo/dai/nl/304838233

    2016-01-01

    An important challenge in aerosol remote sensing is to retrieve aerosol properties in the vicinity of clouds and in cloud contaminated scenes. Satellite based multi-wavelength, multi-angular, photo-polarimetric instruments are particularly suited for this task as they have the ability to separate

  2. Physical and Radiative Properties of Aerosol Particles in the Caribbean: Influence of African Dust and Soufriere Volcanic Ash

    Science.gov (United States)

    Villanueva-Birriel, C. M.; Mayol-Bracero, O. L.; Sheridan, P.; Ogren, J. A.

    2007-12-01

    Atmospheric particles such as dust and volcanic ash have the potential of influencing the earth's radiative budget directly by scattering or absorbing solar radiation in the atmosphere and indirectly by affecting cloud condensation nuclei (CCN) concentrations and, therefore, cloud albedo. The radiatively-important properties of atmospheric particles are determined at the most fundamental level by their chemical composition and size distributions; therefore, the importance of studying the chemical, physical, and optical aerosol properties. Over the summer months, the island of Puerto Rico receives African dust incursions that reduce visibility and have an impact on public health, ecosystem, and climate. Visibility is also negatively affected when the island receives south-east winds and the Soufriere volcano (Montserrat Island) has been active. Here we present preliminary results of measurements performed during 2006 and 2007 at Cape San Juan, a ground-based station located at the northeastern tip of Puerto Rico. The cases investigated showed three possible types of air masses: clean (C), with African Dust (AD), and with volcanic ash (VA) from the Soufriere. We used a condensation particle counter to determine the particle number concentration, a sunphotometer (part of the AERONET) to determine volume size distributions and aerosol optical thickness (AOT), a 3-wavelength nephelometer to determine the scattering coefficients, and a 3-wavelength particle/soot absorption photometer (PSAP) for the absorption coefficients. The particle number concentrations were higher for AD and VA periods (up to about 700 cm-3 on average for both cases) in contrast to ~400 cm-3 for the C period. Volume size distributions showed bimodal distributions for the three cases with a greater influence of the coarse fraction for the C and VA periods and an increase in the fine particles for the AD period. The total scattering coefficient showed higher values for the AD (30 Mm-1) and the VA (26

  3. A State-of-the-Art Experimental Laboratory for Cloud and Cloud-Aerosol Interaction Research

    Science.gov (United States)

    Fremaux, Charles M.; Bushnell, Dennis M.

    2011-01-01

    The state of the art for predicting climate changes due to increasing greenhouse gasses in the atmosphere with high accuracy is problematic. Confidence intervals on current long-term predictions (on the order of 100 years) are so large that the ability to make informed decisions with regard to optimum strategies for mitigating both the causes of climate change and its effects is in doubt. There is ample evidence in the literature that large sources of uncertainty in current climate models are various aerosol effects. One approach to furthering discovery as well as modeling, and verification and validation (V&V) for cloud-aerosol interactions is use of a large "cloud chamber" in a complimentary role to in-situ and remote sensing measurement approaches. Reproducing all of the complex interactions is not feasible, but it is suggested that the physics of certain key processes can be established in a laboratory setting so that relevant fluid-dynamic and cloud-aerosol phenomena can be experimentally simulated and studied in a controlled environment. This report presents a high-level argument for significantly improved laboratory capability, and is meant to serve as a starting point for stimulating discussion within the climate science and other interested communities.

  4. Variations of atmospheric aerosols inside and outside cloud air

    Science.gov (United States)

    Kandalgaonkar, Suvarna; Tinmaker, M. I. R.

    2000-08-01

    Aitken Nuclei are present in the size range of 0.001 to 0.1 μm in appreciable concentrations in the continental and maritime environments. The main sources of these nuclei are mainly trace gases and they form out of gas to particle conversion which can occur through the nucleation of aerosol from the supersaturated gases and by the photochemical reactions associated with the absorption of solar radiation by molecules. Gas to particle conversions may be enhanced by high relative humidity and the presence of liquid water. During the summer monsoon months of 1980-1982 warm cloud modification experiment was conducted by IITM at Pune. During this experiment Aitken nuclei observations were made inside and outside the stratocumulus and cumulus clouds at the same altitude during three monsoon seasons. The results of the study suggested that observed higher concentration of Aitken nuclei inside the cloud may be due to more active gas-to-particle conversion process than in the cloud free air.

  5. Raman Lidar Measurements of Aerosol and Cloud Optical Properties in the Troposphere

    Institute of Scientific and Technical Information of China (English)

    WU Yonghua; HU Shunxing; QI Fudi; XU Jisheng; ZHOU Jun; HU Huanling

    2002-01-01

    A Raman lidar has been developed with photon counting technique. Aerosol and cloud extinction coefficients are derived by nitrogen (N2) molecular Raman scatter returns in the troposphere. Both backscatter coefficients and extinction-backscatter-ratios of aerosol and cloud are presented by simultaneously combining N2 Raman and Mie-Rayleigh returns of aerosol and molecule. Ratios of extinction to backscatter between 20 sr and 70 sr are usually found for aerosol, but less than 15 sr for mid-high altitude cloud in the troposphere.

  6. 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/).

  7. Implementation of aerosol-cloud interactions in the regional atmosphere-aerosol model COSMO-MUSCAT(5.0) and evaluation using satellite data

    Science.gov (United States)

    Dipu, Sudhakar; Quaas, Johannes; Wolke, Ralf; Stoll, Jens; Mühlbauer, Andreas; Sourdeval, Odran; Salzmann, Marc; Heinold, Bernd; Tegen, Ina

    2017-06-01

    The regional atmospheric model Consortium for Small-scale Modeling (COSMO) coupled to the Multi-Scale Chemistry Aerosol Transport model (MUSCAT) is extended in this work to represent aerosol-cloud interactions. Previously, only one-way interactions (scavenging of aerosol and in-cloud chemistry) and aerosol-radiation interactions were included in this model. The new version allows for a microphysical aerosol effect on clouds. For this, we use the optional two-moment cloud microphysical scheme in COSMO and the online-computed aerosol information for cloud condensation nuclei concentrations (Cccn), replacing the constant Cccn profile. In the radiation scheme, we have implemented a droplet-size-dependent cloud optical depth, allowing now for aerosol-cloud-radiation interactions. To evaluate the models with satellite data, the Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP) has been implemented. A case study has been carried out to understand the effects of the modifications, where the modified modeling system is applied over the European domain with a horizontal resolution of 0.25° × 0.25°. To reduce the complexity in aerosol-cloud interactions, only warm-phase clouds are considered. We found that the online-coupled aerosol introduces significant changes for some cloud microphysical properties. The cloud effective radius shows an increase of 9.5 %, and the cloud droplet number concentration is reduced by 21.5 %.

  8. Aerosol indirect effects on the nighttime Arctic Ocean surface from thin, predominantly liquid clouds

    Science.gov (United States)

    Zamora, Lauren M.; Kahn, Ralph A.; Eckhardt, Sabine; McComiskey, Allison; Sawamura, Patricia; Moore, Richard; Stohl, Andreas

    2017-06-01

    Aerosol indirect effects have potentially large impacts on the Arctic Ocean surface energy budget, but model estimates of regional-scale aerosol indirect effects are highly uncertain and poorly validated by observations. Here we demonstrate a new way to quantitatively estimate aerosol indirect effects on a regional scale from remote sensing observations. In this study, we focus on nighttime, optically thin, predominantly liquid clouds. The method is based on differences in cloud physical and microphysical characteristics in carefully selected clean, average, and aerosol-impacted conditions. The cloud subset of focus covers just ˜ 5 % of cloudy Arctic Ocean regions, warming the Arctic Ocean surface by ˜ 1-1.4 W m-2 regionally during polar night. However, within this cloud subset, aerosol and cloud conditions can be determined with high confidence using CALIPSO and CloudSat data and model output. This cloud subset is generally susceptible to aerosols, with a polar nighttime estimated maximum regionally integrated indirect cooling effect of ˜ -0.11 W m-2 at the Arctic sea ice surface (˜ 8 % of the clean background cloud effect), excluding cloud fraction changes. Aerosol presence is related to reduced precipitation, cloud thickness, and radar reflectivity, and in some cases, an increased likelihood of cloud presence in the liquid phase. These observations are inconsistent with a glaciation indirect effect and are consistent with either a deactivation effect or less-efficient secondary ice formation related to smaller liquid cloud droplets. However, this cloud subset shows large differences in surface and meteorological forcing in shallow and higher-altitude clouds and between sea ice and open-ocean regions. For example, optically thin, predominantly liquid clouds are much more likely to overlay another cloud over the open ocean, which may reduce aerosol indirect effects on the surface. Also, shallow clouds over open ocean do not appear to respond to aerosols as

  9. Aerosol indirect effects on the nighttime Arctic Ocean surface from thin, predominantly liquid clouds

    Directory of Open Access Journals (Sweden)

    L. M. Zamora

    2017-06-01

    Full Text Available Aerosol indirect effects have potentially large impacts on the Arctic Ocean surface energy budget, but model estimates of regional-scale aerosol indirect effects are highly uncertain and poorly validated by observations. Here we demonstrate a new way to quantitatively estimate aerosol indirect effects on a regional scale from remote sensing observations. In this study, we focus on nighttime, optically thin, predominantly liquid clouds. The method is based on differences in cloud physical and microphysical characteristics in carefully selected clean, average, and aerosol-impacted conditions. The cloud subset of focus covers just ∼ 5 % of cloudy Arctic Ocean regions, warming the Arctic Ocean surface by ∼ 1–1.4 W m−2 regionally during polar night. However, within this cloud subset, aerosol and cloud conditions can be determined with high confidence using CALIPSO and CloudSat data and model output. This cloud subset is generally susceptible to aerosols, with a polar nighttime estimated maximum regionally integrated indirect cooling effect of ∼ −0.11 W m−2 at the Arctic sea ice surface (∼ 8 % of the clean background cloud effect, excluding cloud fraction changes. Aerosol presence is related to reduced precipitation, cloud thickness, and radar reflectivity, and in some cases, an increased likelihood of cloud presence in the liquid phase. These observations are inconsistent with a glaciation indirect effect and are consistent with either a deactivation effect or less-efficient secondary ice formation related to smaller liquid cloud droplets. However, this cloud subset shows large differences in surface and meteorological forcing in shallow and higher-altitude clouds and between sea ice and open-ocean regions. For example, optically thin, predominantly liquid clouds are much more likely to overlay another cloud over the open ocean, which may reduce aerosol indirect effects on the surface. Also, shallow clouds over

  10. Global anthropogenic aerosol effects on convective clouds in ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    U. Lohmann

    2008-04-01

    Full Text Available Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei and may have an influence on the hydrological cycle. Here we investigate aerosol effects on convective clouds by extending the double-moment cloud microphysics scheme developed for stratiform clouds, which is coupled to the HAM double-moment aerosol scheme, to convective clouds in the ECHAM5 general circulation model. This enables us to investigate whether more, and smaller cloud droplets suppress the warm rain formation in the lower parts of convective clouds and thus release more latent heat upon freezing, which would then result in more vigorous convection and more precipitation. In ECHAM5, including aerosol effects in large-scale and convective clouds (simulation ECHAM5-conv reduces the sensitivity of the liquid water path increase with increasing aerosol optical depth in better agreement with observations and large-eddy simulation studies. In simulation ECHAM5-conv with increases in greenhouse gas and aerosol emissions since pre-industrial times, the geographical distribution of the changes in precipitation better matches the observed increase in precipitation than neglecting microphysics in convective clouds. In this simulation the convective precipitation increases the most suggesting that the convection has indeed become more vigorous.

  11. ARM Cloud Aerosol Precipitation Experiment (ACAPEX) Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Leung, L. R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Prather, K. [Scripps Institution of Oceanography, La Jolla, CA (United States); Ralph, R. [National Oceanic and Atmospheric Administration, Washington, DC (United States); Rosenfeld, D. [The Hebrew University of Jerusalem (Israel); Spackman, R. [Science and Technology Corporation (STC), Hampton, VA (United States); DeMott, P. [Colorado State Univ., Fort Collins, CO (United States); Fairall, C. [National Oceanic and Atmospheric Administration, Washington, DC (United States); Fan, J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hagos, S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hughes, M. [National Oceanic and Atmospheric Administration, Washington, DC (United States); Long, C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rutledge, S. [Colorado State Univ., Fort Collins, CO (United States); Waliser, D. [National Aeronautics and Space Administration (NASA), Washington, DC (United States); Wang, H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-09-01

    The western U.S. receives precipitation predominantly during the cold season when storms approach from the Pacific Ocean. The snowpack that accumulates during winter storms provides about 70-90% of water supply for the region. Understanding and modeling the fundamental processes that govern the large precipitation variability and extremes in the western U.S. is a critical test for the ability of climate models to predict the regional water cycle, including floods and droughts. Two elements of significant importance in predicting precipitation variability in the western U.S. are atmospheric rivers and aerosols. Atmospheric rivers (ARs) are narrow bands of enhanced water vapor associated with the warm sector of extratropical cyclones over the Pacific and Atlantic oceans. Because of the large lower-tropospheric water vapor content, strong atmospheric winds and neutral moist static stability, some ARs can produce heavy precipitation by orographic enhancement during landfall on the U.S. West Coast. While ARs are responsible for a large fraction of heavy precipitation in that region during winter, much of the rest of the orographic precipitation occurs in post-frontal clouds, which are typically quite shallow, with tops just high enough to pass the mountain barrier. Such clouds are inherently quite susceptible to aerosol effects on both warm rain and ice precipitation-forming processes.

  12. Connecting Chemistry and Climate through Aerosol Particles : Laboratory and Field Studies of Cloud Condensation Nuclei /

    OpenAIRE

    Collins, Douglas Bradford

    2014-01-01

    The influence of aerosol particles on the Earth's climate is a major driver of scientific uncertainty in assessing future conditions. The importance of aerosols in their role as cloud condensation nuclei (CCN) and ice nuclei (IN), known as the Aerosol Indirect Effect, is most poorly understood. The number concentration of CCN available to nucleate droplets can have important influences on cloud albedo, lifetime, and propensity to form precipitation. Natural sources are of particular importanc...

  13. Simultaneous retrieval of aerosol and cloud properties during the MILAGRO field campaign

    Directory of Open Access Journals (Sweden)

    K. Knobelspiesse

    2011-02-01

    Full Text Available Estimation of Direct Climate Forcing (DCF due to aerosols in cloudy areas has historically been a difficult task, mainly because of a lack of appropriate measurements. The Aerosol Polarimetry Sensor (APS, on the upcoming NASA Glory mission, has the potential to retrieve both cloud and aerosol properties because of its polarimetric, multiple view angle, and multi spectral observations. The APS airborne prototype is the Research Scanning Polarimeter (RSP, which has similar characteristics and can be used to demonstrate APS capabilities. In the spring of 2006, the RSP was deployed on an aircraft based in Veracruz, Mexico, as part of the Megacity Initiative: Local and Global Research Observations (MILAGRO field campaign. On March 13th, the RSP over flew an aerosol layer lofted above a low altitude marine stratocumulus cloud close to shore in the Gulf of Mexico. We investigate the feasibility of retrieving aerosol properties over clouds using these data. Our approach is to first determine cloud droplet size distribution using the angular location of the cloud bow and other features in the polarized reflectance. The selected cloud was then used in a multiple scattering radiative transfer model optimization to determine the aerosol optical properties and fine tune the cloud size distribution. In this scene, we were able to retrieve aerosol optical depth, the fine mode aerosol size distribution and the cloud droplet size distribution to a degree of accuracy required for climate modeling. This required assumptions about the aerosol vertical distribution and the optical properties of the coarse aerosol size mode. A sensitivity study was also performed to place this case study in the context of the potential for future systematic APS observations of this kind, which found that the aerosol complex refractive index can also be observed accurately if the aerosol optical depth is larger than roughly 0.8 at a wavelength of 0.555 μm.

  14. Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions.

    Science.gov (United States)

    Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; Ciochetto, David; Niedermeier, Dennis; Ovchinnikov, Mikhail; Shaw, Raymond A; Yang, Fan

    2016-12-13

    The influence of aerosol concentration on the cloud-droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud-droplet growth and fallout. As aerosol concentration is increased, the cloud-droplet mean diameter decreases, as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics ([Formula: see text]) for high aerosol concentration, and slow microphysics ([Formula: see text]) for low aerosol concentration; here, [Formula: see text] is the phase-relaxation time and [Formula: see text] is the turbulence-correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as [Formula: see text], and the measurements are in excellent agreement with this finding. The result underscores the importance of droplet size dispersion for aerosol indirect effects: increasing aerosol concentration changes the albedo and suppresses precipitation formation not only through reduction of the mean droplet diameter but also by narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol/slow microphysics limit are likely of leading importance for precipitation formation.

  15. Analytical Studies of the Cloud Droplet Spectral Dispersion Influence on the First Indirect Aerosol Effect

    Institute of Scientific and Technical Information of China (English)

    XIE Xiaoning; LIU Xiaodong

    2013-01-01

    Atmospheric aerosols (acting as cloud condensation nuclei) can enhance the cloud droplet number concentration and reduce the cloud droplet size,and in turn affect the cloud optical depth,as well as the cloud albedo,and thereby exert a radiative influence on climate (the first indirect aerosol effect).In this paper,based on various relationships between cloud droplet spectral dispersion (ε) and cloud droplet number concentration (Nc),we analytically derive the corresponding expressions of the cloud radiative forcing induced by changes in the cloud droplet number concentration.Further quantitative evaluation indicates that the cloud radiative forcing induced by aerosols for the different ε-Nc relationships varies from-29.1% to 25.2%,compared to the case without considering spectral dispersion (ε =0).Our results suggest that an accurate description of ε-Nc relationships helps to reduce the uncertainty of the first indirect aerosol effect and advances our scientific understanding of aerosol-cloud-radiation interactions.

  16. New Approaches to Derive Aerosol-Cloud Sensitivity from Global Observations

    Science.gov (United States)

    Andersen, Hendrik; Cermak, Jan; Fuchs, Julia

    2017-04-01

    This contribution presents novel satellite-based approaches to analyze interactions between aerosols and marine liquid water clouds (ACI) on a global scale. Clouds play a central role in the Earth's radiative budget by increasing the albedo but also by interacting with outgoing thermal radiation, leading to a net cooling effect. Cloud properties are determined by environmental conditions, as cloud formation requires sufficiently saturated conditions as well as condensation nuclei on which the water vapor can condense. The ways in which aerosols influence the optical, micro- and macrophysical properties of clouds as condensation nuclei are among the largest remaining uncertainties in climate research. In particular, cloud droplet size is believed to be impacted, and subsequently cloud reflectivity, lifetime, and precipitation susceptibility may be modified. Advances in the understanding of the processes that govern liquid-water cloud properties are of great importance in order to increase accuracy of climate model predictions of a changing climate. Two methods that illustrate how global satellite retrievals may be combined with reanalysis data sets to enhance knowledge on global patterns of ACI are presented: 1. A novel change-point analysis is presented to detect aerosol loadings at which cloud droplet size shows the greatest sensitivity to changes in aerosol loading. The method is applied to Terra MODIS L3 data sets; patterns of the maximum aerosol-cloud sensitivity are analyzed. Results point towards the importance of water-vapor availability as the framework in which ACI take place. 2. In a multivariate approach to analyzing ACI on a system scale, global monthly aerosol, cloud and meteorology data sets are applied in artificial neural networks (ANN). The ability of ANNs to predict global cloud patterns is demonstrated and sensitivities are subsequently derived. On this basis, the magnitude of aerosol indirect effects is compared to other determinants, pointing

  17. Small fraction of marine cloud condensation nuclei made up of sea spray aerosol

    Science.gov (United States)

    Quinn, P. K.; Coffman, D. J.; Johnson, J. E.; Upchurch, L. M.; Bates, T. S.

    2017-09-01

    Sea spray aerosols impact Earth's radiation balance by directly scattering solar radiation. They also act as cloud condensation nuclei, thereby altering cloud properties including reflectivity, lifetime and extent. The influence of sea spray aerosol on cloud properties is thought to be particularly strong over remote ocean regions devoid of continental particles. Yet the contribution of sea spray aerosol to the population of cloud condensation nuclei in the marine boundary layer remains poorly understood. Here, using a lognormal-mode-fitting procedure, we isolate sea spray aerosols from measurements of particle size and abundance over the Pacific, Southern, Arctic and Atlantic oceans to determine the contribution of sea spray aerosol to the population of cloud condensation nuclei in the marine boundary layer. On a global basis, with the exception of the high southern latitudes, sea spray aerosol makes a contribution of less than 30% to the cloud condensation nuclei population for air that is supersaturated at 0.1 to 1.0%--the supersaturation range typical of marine boundary layer clouds. Instead, the cloud condensation nuclei population between 70° S and 80° N is composed primarily of non-sea-salt sulfate aerosols, due to large-scale meteorological features that result in entrainment of particles from the free troposphere.

  18. Investigation of the seasonal variations of aerosol physicochemical properties and their impact on cloud condensation nuclei number concentration

    Science.gov (United States)

    Logan, Timothy S.

    strongly absorbing carbonaceous particles generated from the flaming combustion mode. The cases represented complex mixtures of the flaming and smoldering combustion phases. Lastly, SQ3 is addressed by using a multi-platform dataset from the Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) Graciosa, Azores, 2009-2010 field campaign. The seasonal aerosol particle volume and number size distributions, AOD, and AEAOD during the CAP-MBL campaign have shown that a low overall mean AOD440 of 0.12 denoted a clean environment over this region that typically contains MBL sea salt. In terms of aerosol volume, a bimodal signal was prominent where the coarse mode influence (r ≥ 1 μm) dominated that of the fine mode (r < 1 μm) throughout the year. However, there are considerable continental fine mode aerosols advected to the Azores region during summer months, including Saharan mineral dust, volcanic ash, biomass smoke, and pollution from North American as identified by HYSPLIT backward trajectories. These aerosol types have been shown to have impacts on MBL cloud condensation nuclei (CCN) that are likely different from coarse mode marine aerosols (e.g., sea salt) (Remillard et al. 2014; Wood et al. 2014). The alternating presence of dominant clean air masses with periodic episodes of polluted air masses will provide a substantial variety in aerosol properties during the summer. This will provide a great opportunity to investigate the interactions between aerosol and cloud properties in terms of the aerosol indirect effect (AIE).

  19. The influence of eruption season on the global aerosol evolution and radiative impact of tropical volcanic eruptions

    Directory of Open Access Journals (Sweden)

    M. Toohey

    2011-08-01

    Full Text Available Simulations of tropical volcanic eruptions using a general circulation model with coupled aerosol microphysics are used to assess the influence of season of eruption on the aerosol evolution and radiative impacts at the Earth's surface. This analysis is presented for eruptions with SO2 injection magnitudes of 17 and 700 Tg, the former consistent with estimates of the 1991 Mt. Pinatubo eruption, the later a near-"super eruption". For each eruption magnitude, simulations are performed with eruptions at 15° N, at four equally spaced times of year, and sensitivity to eruption season is quantified as the difference between the maximum and minimum cumulative anomalies.

    Eruption season has a significant influence on aerosol optical depth (AOD and clear-sky shortwave (SW radiative flux anomalies for both eruption magnitudes. The sensitivity to eruption season for both fields is generally weak in the tropics, but increases in the mid- and high latitudes, reaching maximum values of ~80 %. Global mean AOD and clear-sky SW anomalies show sensitivity to eruption season on the order of 15–20 %, which results from differences in aerosol effective radius for the different eruption seasons. Smallest aerosol size and largest cumulative impact result from a January eruption for the Pinatubo-magnitude, and from a July eruption for the near-super eruption. In contrast to AOD and clear-sky SW anomalies, all-sky SW anomalies are found to be insensitive to season of eruption for the Pinatubo-magnitude eruption experiment, due to the reflection of solar radiation by clouds in the mid- to high latitudes. However, differences in all-sky SW anomalies between eruptions in different seasons are significant for the larger eruption magnitude, and the ~15 % sensitivity to eruption season of the global mean all-sky SW anomalies is comparable to the sensitivity of global mean AOD and clear-sky SW anomalies. Our estimates of sensitivity to eruption season

  20. The influence of eruption season on the global aerosol evolution and radiative impact of tropical volcanic eruptions

    Directory of Open Access Journals (Sweden)

    M. Toohey

    2011-12-01

    Full Text Available Simulations of tropical volcanic eruptions using a general circulation model with coupled aerosol microphysics are used to assess the influence of season of eruption on the aerosol evolution and radiative impacts at the Earth's surface. This analysis is presented for eruptions with SO2 injection magnitudes of 17 and 700 Tg, the former consistent with estimates of the 1991 Mt. Pinatubo eruption, the later a near-"super eruption". For each eruption magnitude, simulations are performed with eruptions at 15° N, at four equally spaced times of year. Sensitivity to eruption season of aerosol optical depth (AOD, clear-sky and all-sky shortwave (SW radiative flux is quantified by first integrating each field for four years after the eruption, then calculating for each cumulative field the absolute or percent difference between the maximum and minimum response from the four eruption seasons. Eruption season has a significant influence on AOD and clear-sky SW radiative flux anomalies for both eruption magnitudes. The sensitivity to eruption season for both fields is generally weak in the tropics, but increases in the mid- and high latitudes, reaching maximum values of ~75 %. Global mean AOD and clear-sky SW anomalies show sensitivity to eruption season on the order of 15–20 %, which results from differences in aerosol effective radius for the different eruption seasons. Smallest aerosol size and largest cumulative impact result from a January eruption for Pinatubo-magnitude eruption, and from a July eruption for the near-super eruption. In contrast to AOD and clear-sky SW anomalies, all-sky SW anomalies are found to be insensitive to season of eruption for the Pinatubo-magnitude eruption experiment, due to the reflection of solar radiation by clouds in the mid- to high latitudes. However, differences in all-sky SW anomalies between eruptions in different seasons are significant for the larger eruption magnitude, and the ~15 % sensitivity to

  1. A long-term satellite study of aerosol effects on convective clouds in Nordic background air

    Directory of Open Access Journals (Sweden)

    M. K. Sporre

    2013-05-01

    Full Text Available Aerosol-cloud interactions constitute a~major uncertainty in future climate predictions. This study combines 10 yr of ground-based aerosol particle measurements from 2 Nordic background stations (Vavihill and Hyytiälä with MODIS (Moderate Resolution Imaging Spectroradiometer satellite data of convective clouds. The merged data are used to examine the indirect aerosol effects on convective clouds over the Nordic countries. From the satellite scenes, vertical profiles of cloud droplet effective radius (re are created by plotting re against cloud top temperature. The profiles have been divided according to aerosol loading but also modeled meteorological parameters from the ECMWF (European Centre for Medium-Range Forecasts. Furthermore, weather radar data from the BALTEX (Baltic Sea Experiment and ground based precipitation measurements from several ground-based meteorological measurement stations have been investigated to determine whether aerosols affect precipitation intensity and amount. Higher aerosol number concentrations result in smaller re throughout the entire profiles at both stations. Profiles associated with no or little precipitation have smaller droplets than those associated with more precipitation. Furthermore, an increase in aerosol loadings results in a suppression of precipitation rates, when the vertical extent of the clouds has been taken into account. Clouds with greater vertical extent have the highest precipitation rates and are most sensitive to aerosol perturbations. Nevertheless, meteorological parameters such as the vertical extent of the clouds, the atmospheric instability and the relative humidity in the lower atmosphere affect the amount of precipitation that reaches the ground more than the aerosols do. The combination of these ground-based and remote sensing datasets provides a unique long-term study of the effects of aerosols on convective clouds over the Nordic countries.

  2. Boreal forests, aerosols and the impacts on clouds and climate.

    Science.gov (United States)

    Spracklen, Dominick V; Bonn, Boris; Carslaw, Kenneth S

    2008-12-28

    Previous studies have concluded that boreal forests warm the climate because the cooling from storage of carbon in vegetation and soils is cancelled out by the warming due to the absorption of the Sun's heat by the dark forest canopy. However, these studies ignored the impacts of forests on atmospheric aerosol. We use a global atmospheric model to show that, through emission of organic vapours and the resulting condensational growth of newly formed particles, boreal forests double regional cloud condensation nuclei concentrations (from approx. 100 to approx. 200 cm(-3)). Using a simple radiative model, we estimate that the resulting change in cloud albedo causes a radiative forcing of between -1.8 and -6.7 W m(-2) of forest. This forcing may be sufficiently large to result in boreal forests having an overall cooling impact on climate. We propose that the combination of climate forcings related to boreal forests may result in an important global homeostasis. In cold climatic conditions, the snow-vegetation albedo effect dominates and boreal forests warm the climate, whereas in warmer climates they may emit sufficiently large amounts of organic vapour modifying cloud albedo and acting to cool climate.

  3. Impact of aerosol composition on cloud condensation nuclei activity

    Directory of Open Access Journals (Sweden)

    Q. Zhang

    2012-04-01

    Full Text Available The impact of aerosol composition on cloud condensation nuclei (CCN activity were analyzed in this study based on field experiments carried out at downtown Tianjin, China in September 2010. In the experiments, the CCN measurements were performed at supersaturation (SS of 0.1%, 0.2% and 0.4% using a thermal-gradient diffusion chamber (DMT CCNC, whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS, respectively. The results show that the influence of aerosol composition on CCN activity is notable under low SS (0.1%, and their influence decreased with increasing SS. For example, under SS of 0.1%, the CCN activity increases from 4.5±2.6% to 12.8±6.1% when organics fraction decrease from 30–40% to 10–20%. The rate of increase reached up to 184%. While under SS of 0.4%, the CCN activity increases only from 35.7±19.0% to 46.5±12.3% correspondingly. The calculated NCCN based on the size-resolved activation ratio and aerosol number size distribution correlated well with observed NCCN at high SS (0.4%, but this consistence decreased with the falling of SS. The slopes of linear fitted lines between calculated and observed NCCN are 0.708, 0.947, and 0.995 at SS of 0.1%, 0.2% and 0.4% respectively. Moreover, the stand deviation (SD of calculated NCCN increased with the decreasing of SS. A case study of CCN closure analyses indicated that the calculated error of NCCN could reach up to 34% at SS of 0.1% if aerosol composition were not included, and the calculated error decreased with the raising of SS. It is decreased to 9% at SS of 0.2%, and further decreased to 4% at SS of 0.4%.

  4. Impact of aerosol composition on cloud condensation nuclei activity

    Directory of Open Access Journals (Sweden)

    Q. Zhang

    2012-01-01

    Full Text Available The impact of aerosol composition on cloud condensation nuclei (CCN activity was analyzed in this study based on field experiments carried out at downtown Tianjin, China, in September 2010. In the experiments, the CCN measurements were performed at supersaturation (SS of 0.1%, 0.2% and 0.4% using a thermal-gradient diffusion chamber (DMT CCNC, whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS, respectively. The results show that the influence of aerosol composition on CCN activity is notable under low SS (0.1%, and their influence decreased with increasing SS. For example, under SS of 0.1%, the CCN activity increases from 4.5 ± 2.6% to 12.8 ± 6.1% when organics fraction decrease from 30–40% to 10–20%. The rate of increase reaches up to 184%. While under SS of 0.4%, the CCN activity increases only from 35.7 ± 19.0% to 46.5 ± 12.3%, correspondingly. The calculated NCCN based on the size-resolved activation ratio and aerosol number size distribution correlates well with observed NCCN at high SS (0.4%, but this correlation decreases with the falling of SS. The slopes of linear fitted lines between calculated and observed NCCN are 0.708, 0.947, and 0.995 at SS of 0.1%, 0.2% and 0.4%, respectively. Moreover, the standard deviation (SD of calculated NCCN increases with the decreasing of SS. A case study of CCN closure analyses indicates that the calculated error of NCCN can reach up to 34% at SS of 0.1% if aerosol composition is not included, and the calculated error decreases with the raising of SS. It decreases to 9% at SS of 0.2%, and further decreases to 4% at SS of 0.4%.

  5. Sensitivity of remote aerosol distributions to representation of cloud-aerosol interactions in a global climate model

    Directory of Open Access Journals (Sweden)

    H. Wang

    2013-01-01

    Full Text Available Many global aerosol and climate models, including the widely used Community Atmosphere Model version 5 (CAM5, have large biases in predicting aerosols in remote regions such as upper troposphere and high latitudes. In this study, we conduct CAM5 sensitivity simulations to understand the role of key processes associated with aerosol transformation and wet removal affecting the vertical and horizontal long-range transport of aerosols to the remote regions. Improvements are made to processes that are currently not well represented in CAM5, which are guided by surface and aircraft measurements together with results from a multi-scale aerosol-climate model (PNNL-MMF that explicitly represents convection and aerosol-cloud interactions at cloud-resolving scales. We pay particular attention to black carbon (BC due to its importance in the Earth system and the availability of measurements. We introduce into CAM5 a new unified scheme for convective transport and aerosol wet removal with explicit aerosol activation above convective cloud base. This new implementation reduces the excessive BC aloft to better simulate observed BC profiles that show decreasing mixing ratios in the mid- to upper-troposphere. After implementing this new unified convective scheme, we examine wet removal of submicron aerosols that occurs primarily through cloud processes. The wet removal depends strongly on the sub-grid scale liquid cloud fraction and the rate of conversion of liquid water to precipitation. These processes lead to very strong wet removal of BC and other aerosols over mid- to high latitudes during winter months. With our improvements, the Arctic BC burden has a10-fold (5-fold increase in the winter (summer months, resulting in a much better simulation of the BC seasonal cycle as well. Arctic sulphate and other aerosol species also increase but to a lesser extent. An explicit treatment of BC aging with slower aging assumptions produces an additional 30-fold (5-fold

  6. 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.

  7. Aerosol and Cloud Experiments in Eastern North Atlantic (ACE-ENA) Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jian [Brookhaven National Lab. (BNL), Upton, NY (United States); Dong, Xiquan [Univ. of North Dakota, Grand Forks, ND (United States); Wood, Robert [Univ. of Washington, Seattle, WA (United States)

    2016-04-01

    With their extensive coverage, low clouds greatly impact global climate. Presently, low clouds are poorly represented in global climate models (GCMs), and the response of low clouds to changes in atmospheric greenhouse gases and aerosols remains the major source of uncertainty in climate simulations. The poor representations of low clouds in GCMs are in part due to inadequate observations of their microphysical and macrophysical structures, radiative effects, and the associated aerosol distribution and budget in regions where the aerosol impact is the greatest. The Eastern North Atlantic (ENA) is a region of persistent but diverse subtropical marine boundary-layer (MBL) clouds, whose albedo and precipitation are highly susceptible to perturbations in aerosol properties. Boundary-layer aerosol in the ENA region is influenced by a variety of sources, leading to strong variations in cloud condensation nuclei (CCN) concentration and aerosol optical properties. Recently a permanent ENA site was established by the U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) Climate Research Facility on Graciosa Island in the Azores, providing invaluable information on MBL aerosol and low clouds. At the same time, the vertical structures and horizontal variabilities of aerosol, trace gases, cloud, drizzle, and atmospheric thermodynamics are critically needed for understanding and quantifying the budget of MBL aerosol, the radiative properties, precipitation efficiency, and lifecycle of MBL clouds, and the cloud response to aerosol perturbations. Much of this data can be obtained only through aircraft-based measurements. In addition, the interconnected aerosol and cloud processes are best investigated by a study involving simultaneous in situ aerosol, cloud, and thermodynamics measurements. Furthermore, in situ measurements are also necessary for validating and improving ground-based retrieval algorithms at the ENA site. This project is motivated by the need

  8. Challenges for cloud modeling in the context of aerosol-cloud-precipitation interactions

    Energy Technology Data Exchange (ETDEWEB)

    Lebo, Zachary J.; Shipway, Ben; Fan, Jiwen; Geresdi, Istyan; Hill, Adrian; Miltenberger, Annette; Morrison, H.; Rosenberg, Philip; Varble, A. C.; Xue, L.

    2017-09-06

    The International Cloud Modeling Workshop (CMW) has been a longstanding tradition in the cloud microphysics modeling community and is typically held the week prior to the International Conference on Clouds and Precipitation (ICCP). For the Ninth CMW, more than 40 participants from 10 countries convened at the Met Office in Exeter, United Kingdom. The workshop included 4 detailed case studies (described in more detail below) rooted in recent field campaigns. The overarching objective of these cases was to utilize new observations to better understand inter-model differences and model deficiencies, explore new modeling techniques, and gain physical insight into the behavior of clouds. As was the case at the Eighth CMW, there was a general theme of understanding the role of aerosol impacts in the context of cloud-precipitation interactions. However, an additional objective was the focal point of several cases at the most recent workshop: microphysical-dynamical interactions. Many of the cases focused less on idealized small-domain simulations (as was the general focus of previous workshops) and more on large-scale nested configurations examining effects at various scales.

  9. Aerosol and cloud typing with an automated 24/7 aerosol lidar

    Science.gov (United States)

    Baars, Holger; Seifert, Patric; Wandinger, Ulla

    2015-04-01

    Modern sophisticated multi-wavelength Raman polarization lidars have the ability to measure autonomous and unattended in 24/7 mode. These aerosol lidars can deliver backscatter, extinction, and depolarization profiles of the atmosphere which can be used for a target categorization, i.e. the determination of different aerosol and cloud types. However, to derive the optical particle properties a calibration of the lidar signals in the free atmosphere, where only Rayleigh scattering occurs, is needed. This calibration is usually done manually case by case and thus prohibits automatic data analysis and particle typing. To overcome this limitation, the mobile EARLINET lidar PollyXT of TROPOS was deployed continuously without changes in the instrumental setup during two field campaigns in the framework of the German HD(CP)2 project to obtain temporally stable lidar signals. The temporal stability together with the high performance and good characterization of the lidar lead to the possibility of an absolute lidar calibration. The corresponding calibration constant was derived in two ways: first by using manually Raman and Klett retrievals for selected periods and second by using the aerosol optical depth (AOD) from co-located AERONET sun photometer measurements. The derived calibration constants show a high temporal stability and a good agreement between both methods and thus allowed the continuous calibration of the lidar and the retrieval of the attenuated backscatter coefficient at three wavelengths. In addition, the calibrated volume depolarization ratio, obtained following EARLINET recommendations, is continuously available. After correction for the molecular contribution, these four quantities were used for an aerosol and cloud typing in terms of particle size and shape. The final categorization leads to 11 categories, e.g. clean atmosphere, small spherical particles, large non-spherical particles, water droplets, ice crystals and corresponding mixtures. In this

  10. Cloud condensation nuclei closure study on summer arctic aerosol

    Directory of Open Access Journals (Sweden)

    M. Martin

    2011-11-01

    Full Text Available We present an aerosolcloud condensation nuclei (CCN closure study on summer high Arctic aerosol based on measurements that were carried out in 2008 during the Arctic Summer Cloud Ocean Study (ASCOS on board the Swedish ice breaker Oden. The data presented here were collected during a three-week time period in the pack ice (>85° N when the icebreaker Oden was moored to an ice floe and drifted passively during the most biological active period into autumn freeze up conditions.

    CCN number concentrations were obtained using two CCN counters measuring at different supersaturations. The directly measured CCN number concentration was then compared with a CCN number concentration calculated using both bulk aerosol mass composition data from an aerosol mass spectrometer (AMS and aerosol number size distributions obtained from a differential mobility particle sizer, assuming κ-Köhler theory, surface tension of water and an internally mixed aerosol. The last assumption was supported by measurements made with a hygroscopic tandem differential mobility analyzer (HTDMA for particles >70 nm.

    For the two highest measured supersaturations, 0.73 and 0.41%, closure could not be achieved with the investigated settings concerning hygroscopicity and density. The calculated CCN number concentration was always higher than the measured one for those two supersaturations. This might be caused by a relative larger insoluble organic mass fraction of the smaller particles that activate at these supersaturations, which are thus less good CCN than the larger particles. On average, 36% of the mass measured with the AMS was organic mass. At 0.20, 0.15 and 0.10% supersaturation, closure could be achieved with different combinations of hygroscopic parameters and densities within the uncertainty range of the fit. The best agreement of the calculated CCN number concentration with the observed one was achieved when the organic fraction of the

  11. Ocean Emission Effects on Aerosol-Cloud Interactions: Insights from Two Case Studies

    Directory of Open Access Journals (Sweden)

    Armin Sorooshian

    2010-01-01

    Full Text Available Two case studies are discussed that evaluate the effect of ocean emissions on aerosol-cloud interactions. A review of the first case study from the eastern Pacific Ocean shows that simultaneous aircraft and space-borne observations are valuable in detecting links between ocean biota emissions and marine aerosols, but that the effect of the former on cloud microphysics is less clear owing to interference from background anthropogenic pollution and the difficulty with field experiments in obtaining a wide range of aerosol conditions to robustly quantify ocean effects on aerosol-cloud interactions. To address these limitations, a second case was investigated using remote sensing data over the less polluted Southern Ocean region. The results indicate that cloud drop size is reduced more for a fixed increase in aerosol particles during periods of higher ocean chlorophyll A. Potential biases in the results owing to statistical issues in the data analysis are discussed.

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

    Directory of Open Access Journals (Sweden)

    L. Costantino

    2013-01-01

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

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-08-15

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

  14. Development and testing of an aerosol-stratus cloud parameterization scheme for middle and high latitudes

    Energy Technology Data Exchange (ETDEWEB)

    Olsson, P.Q.; Meyers, M.P.; Kreidenweis, S.; Cotton, W.R. [Colorado State Univ., Fort Collins, CO (United States)

    1996-04-01

    The aim of this new project is to develop an aerosol/cloud microphysics parameterization of mixed-phase stratus and boundary layer clouds. Our approach is to create, test, and implement a bulk-microphysics/aerosol model using data from Atmospheric Radiation Measurement (ARM) Cloud and Radiation Testbed (CART) sites and large-eddy simulation (LES) explicit bin-resolving aerosol/microphysics models. The primary objectives of this work are twofold. First, we need the prediction of number concentrations of activated aerosol which are transferred to the droplet spectrum, so that the aerosol population directly affects the cloud formation and microphysics. Second, we plan to couple the aerosol model to the gas and aqueous-chemistry module that will drive the aerosol formation and growth. We begin by exploring the feasibility of performing cloud-resolving simulations of Arctic stratus clouds over the North Slope CART site. These simulations using Colorado State University`s regional atmospheric modeling system (RAMS) will be useful in designing the structure of the cloud-resolving model and in interpreting data acquired at the North Slope site.

  15. Clouds, Aerosols, and Precipitation in the Marine Boundary Layer: An Arm Mobile Facility Deployment

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Robert; Wyant, Matthew; Bretherton, Christopher S.; Rémillard, Jasmine; Kollias, Pavlos; Fletcher, Jennifer; Stemmler, Jayson; de Szoeke, Simone; Yuter, Sandra; Miller, Matthew; Mechem, David; Tselioudis, George; Chiu, J. Christine; Mann, Julian A. L.; O’Connor, Ewan J.; Hogan, Robin J.; Dong, Xiquan; Miller, Mark; Ghate, Virendra; Jefferson, Anne; Min, Qilong; Minnis, Patrick; Palikonda, Rabindra; Albrecht, Bruce; Luke, Ed; Hannay, Cecile; Lin, Yanluan

    2015-03-01

    The Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) 38 deployment at Graciosa Island in the Azores generated a 21 month (April 2009-December 2010) 39 comprehensive dataset documenting clouds, aerosols and precipitation using the Atmospheric 40 Radiation Measurement (ARM) Mobile Facility (AMF). The scientific aim of the deployment is 41 to gain improved understanding of the interactions of clouds, aerosols and precipitation in the 42 marine boundary layer. 43 Graciosa Island straddles the boundary between the subtropics and midlatitudes in the 44 Northeast Atlantic Ocean, and consequently experiences a great diversity of meteorological and 45 cloudiness conditions. Low clouds are the dominant cloud type, with stratocumulus and cumulus 46 occurring regularly. Approximately half of all clouds contained precipitation detectable as radar 47 echoes below the cloud base. Radar and satellite observations show that clouds with tops from 1-48 11 km contribute more or less equally to surface-measured precipitation at Graciosa. A wide 49 range of aerosol conditions was sampled during the deployment consistent with the diversity of 50 sources as indicated by back trajectory analysis. Preliminary findings suggest important two-way 51 interactions between aerosols and clouds at Graciosa, with aerosols affecting light precipitation 52 and cloud radiative properties while being controlled in part by precipitation scavenging. 53 The data from at Graciosa are being compared with short-range forecasts made a variety 54 of models. A pilot analysis with two climate and two weather forecast models shows that they 55 reproduce the observed time-varying vertical structure of lower-tropospheric cloud fairly well, 56 but the cloud-nucleating aerosol concentrations less well. The Graciosa site has been chosen to 57 be a long-term ARM site that became operational in October 2013.

  16. On the iron chloride aerosol in the clouds of Venus

    Science.gov (United States)

    Krasnopolsky, Vladimir A.

    2017-04-01

    Iron chloride in the Venus clouds is under discussion for three decades, and the saturated vapor pressure of this species is of crucial importance for its modeling. There is a great scatter in the published data, and the preferable results are by Rustad and Gregory (1983, J. Chem. Eng. Data 28, 151-155) and those based on thermodynamic parameters by Chase (1998, J. Phys. Chem. Ref. Data Monograph 9). Using these data, loss by coagulation with sulfuric acid, transport by eddy diffusion, and the Stokes precipitation, the model confirms conclusions of our early study (Krasnopolsky 1985, Planet. Space Sci. 33, 109-117) that FeCl3 in the Venus clouds (1) agrees with the near UV and blue reflectivity of Venus (Zasova et al. 1981, Adv. Space Res. 1, #9, 13-16), (2) was observed by the direct X-ray fluorescent spectroscopy, (3) explains the altitude profiles of the mode 1 aerosol in the middle and lower cloud layers and (4) the decrease in the NUV absorption below 60 km. Here we add to these conclusions that (5) the delivery of FeCl3 into the upper cloud layer and the production of sulfuric acid are just in proportion of 1: 100 by mass that is required to fit the observed NUV albedo. Furthermore, (6) the mode 1 and 2 particle sizes fit this proportion as well. Finally, (7) the required Fe2Cl6 mixing ratio is 17 ppbv in the atmosphere and the FeCl3 mole fraction is 19 ppbv in the Venus surface rocks.

  17. Sensitivity of Remote Aerosol Distributions to Representation of Cloud-Aerosol Interactions in a Global Climate Model

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hailong; Easter, Richard C.; Rasch, Philip J.; Wang, Minghuai; Liu, Xiaohong; Ghan, Steven J.; Qian, Yun; Yoon, Jin-Ho; Ma, Po-Lun; Vinoj, V.

    2013-06-05

    Many global aerosol and climate models, including the widely used Community Atmosphere Model version 5 (CAM5), have large biases in predicting aerosols in remote regions such as upper troposphere and high latitudes. In this study, we conduct CAM5 sensitivity simulations to understand the role of key processes associated with aerosol transformation and wet removal affecting the vertical and horizontal long-range transport of aerosols to the remote regions. Improvements are made to processes that are currently not well represented in CAM5, which are guided by surface and aircraft measurements together with results from a multi-scale aerosol-climate model (PNNL-MMF) that explicitly represents convection and aerosol-cloud interactions at cloud-resolving scales. We pay particular attention to black carbon (BC) due to its importance in the Earth system and the availability of measurements. We introduce into CAM5 a new unified scheme for convective transport and aerosol wet removal with explicit aerosol activation above convective cloud base. This new implementation reduces the excessive BC aloft to better simulate observed BC profiles that show decreasing mixing ratios in the mid- to upper-troposphere. After implementing this new unified convective scheme, we examine wet removal of submicron aerosols that occurs primarily through cloud processes. The wet removal depends strongly on the sub-grid scale liquid cloud fraction and the rate of conversion of liquid water to precipitation. These processes lead to very strong wet removal of BC and other aerosols over mid- to high latitudes during winter months. With our improvements, the Arctic BC burden has a10-fold (5-fold) increase in the winter (summer) months, resulting in a much better simulation of the BC seasonal cycle as well. Arctic sulphate and other aerosol species also increase but to a lesser extent. An explicit treatment of BC aging with slower aging assumptions produces an additional 30-fold (5-fold) increase in

  18. The effects of mineral dust particles, aerosol regeneration and ice nucleation parameterizations on clouds and precipitation

    Directory of Open Access Journals (Sweden)

    A. Teller

    2012-03-01

    Full Text Available This study focuses on the effects of aerosol particles on the formation of convective clouds and precipitation in the Eastern Mediterranean sea with a special emphasis on the role of mineral dust particles in these processes. We used a new detailed numerical cloud microphysics scheme that has been implemented in the Weather Research and Forecast (WRF model in order to study aerosol-cloud interaction in 3-D configuration based on realistic meteorological data. Using a number of case studies we tested the contribution of mineral dust particles and different ice nucleation parameterizations to precipitation development. In this study we also investigated the importance of recycled (regenerated aerosols that had been released to the atmosphere following the evaporation of cloud droplets.

    The results showed that increased aerosol concentration due to the presence of mineral dust enhanced the formation of ice crystals. The dynamic evolution of the cloud system sets the time periods and regions in which heavy or light precipitation occurred in the domain. The precipitation rate, the time and duration of precipitation were affected by the aerosol properties only at small area scales (with areas of about 20 km2. Changes of the ice nucleation scheme from ice supersaturation dependent parameterization to a recent approach of aerosol concentration and temperature dependent parameterization modified the ice crystals concentrations but did not affect the total precipitation in the domain. Aerosol regeneration modified the concentration of cloud droplets at cloud base by dynamic recirculation of the aerosols but also had only a minor effect on precipitation.

    The major conclusion from this study is that the effect of mineral dust particles on clouds and total precipitation is limited by the properties of the atmospheric dynamics and the only effect of aerosol on precipitation may come from significant increase in the concentration

  19. Aerosol effects on the development of cumulus clouds over the Tibetan Plateau

    Science.gov (United States)

    Zhou, Xu; Bei, Naifang; Liu, Hongli; Cao, Junji; Xing, Li; Lei, Wenfang; Molina, Luisa T.; Li, Guohui

    2017-06-01

    The aerosol-cloud interaction over the Tibetan Plateau has been investigated using a cloud-resolving weather research and forecasting model with a two-moment bulk microphysical scheme including aerosol effects on cloud condensation nuclei and ice nuclei. Two types of cumulus clouds with a similar convective available potential energy, occurring over the Tibetan Plateau (Cu-TP) and North China Plain (Cu-NCP) in August 2014, are simulated to explore the response of convective clouds to aerosols. A set of aerosol profiles is used in the simulations, with the surface aerosol number concentration varying from 20 to 9000 cm-3 and the sulfate mass concentration varying from 0.02 to 9.0 µg cm-3. Increasing aerosol concentrations generally enhances the cloud core updraft and maximum updraft, intensifying convections in Cu-TP and Cu-NCP. However, the core updraft is much stronger in Cu-TP than Cu-NCP, because of the early occurrence of the glaciation process in Cu-TP that is triggered at an elevation above 4000 m. The precipitation increases steadily with aerosol concentrations in Cu-NCP, caused by the suppression of the warm rain but occurrence of efficient mix-phased precipitation due to the reduced cloud droplet size. The precipitation in Cu-TP also increases with aerosol concentrations, but the precipitation enhancement is not substantial compared to that in Cu-NCP with high aerosol concentrations. The aerosol-induced intensification of convections in Cu-TP not only facilitates the precipitation but also transports more ice-phase hydrometeors into the upper troposphere to decrease the precipitation efficiency. Considering the very clean atmosphere over the Tibetan Plateau, elevated aerosol concentrations can remarkably enhance convections due to its specific topography, which not only warms the middle troposphere to influence the Asian summer monsoon but also delivers hydrometeors into the upper troposphere to allow more water vapor to travel into the lower stratosphere.

  20. Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: single particle analysis during the Cloud and Aerosol Characterization Experiment (CLACE 6

    Directory of Open Access Journals (Sweden)

    M. Kamphus

    2009-07-01

    Full Text Available Two different single particle mass spectrometers were operated in parallel at the Swiss High Alpine Research Station Jungfraujoch (JFJ, 3580 m a.s.l. during the Cloud and Aerosol Characterization Experiment (CLACE 6 in February and March 2007. During mixed phase cloud events ice crystals from 5 μm up to 20 μm were separated from large ice aggregates, non-activated, interstitial aerosol particles and supercooled droplets using an Ice-Counterflow Virtual Impactor (Ice-CVI. During one cloud period supercooled droplets were additionally sampled and analyzed by changing the Ice-CVI setup. The small ice particles and droplets were evaporated by injection into dry air inside the Ice-CVI. The resulting ice and droplet residues (IR and DR were analyzed for size and composition by two single particle mass spectrometers: a custom-built Single Particle Laser-Ablation Time-of-Flight Mass Spectrometer (SPLAT and a commercial Aerosol Time of Flight Mass Spectrometer (ATOFMS, TSI Model 3800. During CLACE 6 the SPLAT instrument characterized 355 individual ice residues that produced a mass spectrum for at least one polarity and the ATOFMS measured 152 particles. The mass spectra were binned in classes, based on the combination of dominating substances, such as mineral dust, sulfate, potassium and elemental carbon or organic material. The derived chemical information from the ice residues is compared to the JFJ ambient aerosol that was sampled while the measurement station was out of clouds (several thousand particles analyzed by SPLAT and ATOFMS and to the composition of the residues of supercooled cloud droplets (SPLAT: 162 cloud droplet residues analyzed, ATOFMS: 1094. The measurements showed that mineral dust particles were strongly enhanced in the ice particle residues. 57% of the SPLAT spectra from ice residues were dominated by signatures from mineral compounds, and 78% of the ATOFMS spectra. Sulfate and nitrate containing particles were strongly

  1. Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Fast, JD [Pacific Northwest National Laboratory; Berg, LK [Pacific Northwest National Laboratory

    2015-12-01

    Cumulus convection is an important component in the atmospheric radiation budget and hydrologic cycle over the Southern Great Plains and over many regions of the world, particularly during the summertime growing season when intense turbulence induced by surface radiation couples the land surface to clouds. Current convective cloud parameterizations contain uncertainties resulting in part from insufficient coincident data that couples cloud macrophysical and microphysical properties to inhomogeneities in boundary layer and aerosol properties. The Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) campaign is designed to provide a detailed set of measurements that are needed to obtain a more complete understanding of the life cycle of shallow clouds by coupling cloud macrophysical and microphysical properties to land surface properties, ecosystems, and aerosols. HI-SCALE consists of 2, 4-week intensive observational periods, one in the spring and the other in the late summer, to take advantage of different stages and distribution of “greenness” for various types of vegetation in the vicinity of the Atmospheric Radiation and Measurement (ARM) Climate Research Facility’s Southern Great Plains (SGP) site as well as aerosol properties that vary during the growing season. Most of the proposed instrumentation will be deployed on the ARM Aerial Facility (AAF) Gulfstream 1 (G-1) aircraft, including those that measure atmospheric turbulence, cloud water content and drop size distributions, aerosol precursor gases, aerosol chemical composition and size distributions, and cloud condensation nuclei concentrations. Routine ARM aerosol measurements made at the surface will be supplemented with aerosol microphysical properties measurements. The G-1 aircraft will complete transects over the SGP Central Facility at multiple altitudes within the boundary layer, within clouds, and above clouds.

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

    Science.gov (United States)

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

    2017-05-01

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

  3. General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales

    DEFF Research Database (Denmark)

    Kulmala, M.; Asmi, A.; Lappalainen, H. K.;

    2011-01-01

    of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol...

  4. Inverse modeling of cloud-aerosol interactions -- Part 2: Sensitivity tests on liquid phase clouds using a Markov Chain Monte Carlo based simulation approach

    NARCIS (Netherlands)

    Partridge, D.G.; Vrugt, J.A.; Tunved, P.; Ekman, A.M.L.; Struthers, H.; Sooroshian, A.

    2012-01-01

    This paper presents a novel approach to investigate cloud-aerosol interactions by coupling a Markov chain Monte Carlo (MCMC) algorithm to an adiabatic cloud parcel model. Despite the number of numerical cloud-aerosol sensitivity studies previously conducted few have used statistical analysis tools t

  5. Intercomparison between CMIP5 model and MODIS satellite-retrieved data of aerosol optical depth, cloud fraction, and cloud-aerosol interactions

    Science.gov (United States)

    Sockol, Alyssa; Small Griswold, Jennifer D.

    2017-08-01

    Aerosols are a critical component of the Earth's atmosphere and can affect the climate of the Earth through their interactions with solar radiation and clouds. Cloud fraction (CF) and aerosol optical depth (AOD) at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used with analogous cloud and aerosol properties from Historical Phase 5 of the Coupled Model Intercomparison Project (CMIP5) model runs that explicitly include anthropogenic aerosols and parameterized cloud-aerosol interactions. The models underestimate AOD by approximately 15% and underestimate CF by approximately 10% overall on a global scale. A regional analysis is then used to evaluate model performance in two regions with known biomass burning activity and absorbing aerosol (South America (SAM) and South Africa (SAF)). In SAM, the models overestimate AOD by 4.8% and underestimate CF by 14%. In SAF, the models underestimate AOD by 35% and overestimate CF by 13.4%. Average annual cycles show that the monthly timing of AOD peaks closely match satellite data in both SAM and SAF for all except the Community Atmosphere Model 5 and Geophysical Fluid Dynamics Laboratory (GFDL) models. Monthly timing of CF peaks closely match for all models (except GFDL) for SAM and SAF. Sorting monthly averaged 2° × 2.5° model or MODIS CF as a function of AOD does not result in the previously observed "boomerang"-shaped CF versus AOD relationship characteristic of regions with absorbing aerosols from biomass burning. Cloud-aerosol interactions, as observed using daily (or higher) temporal resolution data, are not reproducible at the spatial or temporal resolution provided by the CMIP5 models.

  6. The impact of humidity above stratiform clouds on indirect aerosol climate forcing.

    Science.gov (United States)

    Ackerman, Andrew S; Kirkpatrick, Michael P; Stevens, David E; Toon, Owen B

    2004-12-23

    Some of the global warming from anthropogenic greenhouse gases is offset by increased reflection of solar radiation by clouds with smaller droplets that form in air polluted with aerosol particles that serve as cloud condensation nuclei. The resulting cooling tendency, termed the indirect aerosol forcing, is thought to be comparable in magnitude to the forcing by anthropogenic CO2, but it is difficult to estimate because the physical processes that determine global aerosol and cloud populations are poorly understood. Smaller cloud droplets not only reflect sunlight more effectively, but also inhibit precipitation, which is expected to result in increased cloud water. Such an increase in cloud water would result in even more reflective clouds, further increasing the indirect forcing. Marine boundary-layer clouds polluted by aerosol particles, however, are not generally observed to hold more water. Here we simulate stratocumulus clouds with a fluid dynamics model that includes detailed treatments of cloud microphysics and radiative transfer. Our simulations show that the response of cloud water to suppression of precipitation from increased droplet concentrations is determined by a competition between moistening from decreased surface precipitation and drying from increased entrainment of overlying air. Only when the overlying air is humid or droplet concentrations are very low does sufficient precipitation reach the surface to allow cloud water to increase with droplet concentrations. Otherwise, the response of cloud water to aerosol-induced suppression of precipitation is dominated by enhanced entrainment of overlying dry air. In this scenario, cloud water is reduced as droplet concentrations increase, which diminishes the indirect climate forcing.

  7. EDITORIAL: Aerosol cloud interactions—a challenge for measurements and modeling at the cutting edge of cloud climate interactions

    Science.gov (United States)

    Spichtinger, Peter; Cziczo, Daniel J.

    2008-04-01

    Research in aerosol properties and cloud characteristics have historically been considered two separate disciplines within the field of atmospheric science. As such, it has been uncommon for a single researcher, or even research group, to have considerable expertise in both subject areas. The recent attention paid to global climate change has shown that clouds can have a considerable effect on the Earth's climate and that one of the most uncertain aspects in their formation, persistence, and ultimate dissipation is the role played by aerosols. This highlights the need for researchers in both disciplines to interact more closely than they have in the past. This is the vision behind this focus issue of Environmental Research Letters. Certain interactions between aerosols and clouds are relatively well studied and understood. For example, it is known that an increase in the aerosol concentration will increase the number of droplets in warm clouds, decrease their average size, reduce the rate of precipitation, and extend the lifetime. Other effects are not as well known. For example, persistent ice super-saturated conditions are observed in the upper troposphere that appear to exceed our understanding of the conditions required for cirrus cloud formation. Further, the interplay of dynamics versus effects purely attributed to aerosols remains highly uncertain. The purpose of this focus issue is to consider the current state of knowledge of aerosol/cloud interactions, to define the contemporary uncertainties, and to outline research foci as we strive to better understand the Earth's climate system. This focus issue brings together laboratory experiments, field data, and model studies. The authors address issues associated with warm liquid water, cold ice, and intermediate temperature mixed-phase clouds. The topics include the uncertainty associated with the effect of black carbon and organics, aerosol types of anthropogenic interest, on droplet and ice formation. Phases

  8. Analysis of aerosol-cloud-precipitation interactions based on MODIS data

    Science.gov (United States)

    Cheng, Feng; Zhang, Jiahua; He, Junliang; Zha, Yong; Li, Qiannan; Li, Yunmei

    2017-01-01

    Aerosols exert an indirect impact on climate change via its impact on clouds by altering its radiative and optical properties which, in turn, changes the process of precipitation. Over recent years how to study the indirect climate effect of aerosols has become an important research topic. In this study we attempted to understand the complex mutual interactions among aerosols, clouds and precipitation through analysis of the spatial correlation between aerosol optical depth (AOD), cloud effective radius (CER) and precipitation during 2000-2012 in central-eastern China that has one of the highest concentrations of aerosols globally. With the assistance of moderate resolution imaging spectroradiometer (MODIS)-derived aerosol and cloud product data, this analysis focuses on regional differentiation and seasonal variation of the correlation in which in situ observed precipitation was incorporated. On the basis of the achieved results, we proposed four patterns depicting the mutual interactions between aerosols, clouds and precipitation. They characterize the indirect effects of aerosols on the regional scale. These effects can be summarized as complex seasonal variations and north-south regional differentiation over the study area. The relationship between AOD and CER is predominated mostly by the first indirect effect (the negative correlation between AOD and CER) in the north of the study area in the winter and spring seasons, and over the entire study area in the summer season. The relationship between CER and precipitation is dominated chiefly by the second indirect effect (the positive correlation between CER and precipitation) in the northern area in summer and over the entire study area in autumn. It must be noted that aerosols are not the factor affecting clouds and rainfall singularly. It is the joint effect of aerosols with other factors such as atmospheric dynamics that governs the variation in clouds and rainfall.

  9. Aerosol-droplet relations in Arctic clouds: insight from the Indirect and Semi-Direct Aerosol Campaign (ISDAC)

    Science.gov (United States)

    Earle, M. E.; Liu, P.; Strapp, J. W.; Zelenyuk, A.; Ovchinnikov, M.; MacDonald, A.; Shantz, N. C.; Leaitch, W. R.; Ghan, S. J.

    2010-12-01

    The relationships between atmospheric aerosol particles and Arctic cloud microphysics are investigated through a droplet number closure study using aircraft observational data from the US Department of Energy ISDAC study conducted in Alaska in April, 2008. In-situ measurements of aerosol physicochemical properties and atmospheric state are used to simulate droplet activation and growth in an adiabatic cloud parcel model. Size distributed aerosol particle concentration and composition measurements were obtained below-cloud using a Passive Cavity Aerosol Spectrometer Probe (PCASP; size range ~ 0.12 - 3 µm) and SPLAT II, a single particle mass spectrometer. The updraft velocity defines the development of supersaturation, and so dictates the onset of droplet nucleation. For model simulations in the present work, the updraft velocity was determined from a combination of gust probe observations and updraft trajectories computed using a large eddy simulation cloud-resolving model (LES-CRM). The simulated droplet concentrations are compared against in situ measurements from a DMT Cloud Droplet Probe (CDP; size range 2 - 50 µm) and/or Forward-Scattering Spectrometer Probe (FSSP-100X; size range 3 - 45 µm). The sensitivity of the comparison of simulated and observed cloud droplet number concentrations is examined for reasonable variations of the aerosol physicochemical properties (e.g. mass accommodation coefficient) and updraft velocity. Droplet closure analysis is presented for selected cases during ISDAC, comprising both clean and polluted air masses with respect to aerosol particle number concentration and composition. The applicability of the results to model parameterizations is considered, with emphasis on the description of the updraft velocity. The findings increase our knowledge of factors affecting the lifetime and radiative properties of Arctic clouds, which are critical to our understanding of the role of climate change in the Arctic.

  10. Impact of aerosols on marine cloud microphysics over the Indian Ocean using satellite data.

    Science.gov (United States)

    Rao, Sofiya; Dey, Sagnik

    2017-04-01

    Aerosol-cloud interaction is the one of the least understood and largest sources of uncertainty in quantifying climate forcing. Despite progress, the problem remains unresolved because of the buffering effect of meteorology and therefore it is suggested to separate the meteorological forcing from aerosol forcing focusing on different cloud types (Stevens and Feingold 2009). However, most of the previous studies on aerosol-cloud interaction over the Indian Ocean (including INDOEX) are limited to either one particular season or short period. We examine relationships between aerosol and cloud parameters using MODIS data sets for 15 years (2000-2015) period over Indian Ocean. We separated the meteorological forcing from aerosol forcing. In both the Arabian Sea (AS) and Bay of Bengal (BOB), the meteorological forcing is largest in the monsoon. In all the four seasons, cloud microphysical properties are more sensitive to aerosol optical depth (AOD) over the AS compared to BOB. Further analysis reveals presence of semi-direct effect in the winter season. Influence of aerosols on liquid water path (LWP) - cloud effective radius (Reff) relation is quantified. Cloud albedo (Rc) dependency on LWP and Reff is examined in view of changing aerosol load. Cloud drop growth is facilitated in presence of high moisture content. This is evident from the fact that Reff is found to broadly increase with an increase in LWP in every season over Arabian Sea as well as over Bay of Bengal. It is also noted that Reff is larger across a wide range of LWP in 'clean' condition (AOD polluted' condition (0.2 polluted' condition and (AOD > 0.4). This clearly demonstrate that in more polluted conditions, growth of cloud drops are restricted. This is the evidence of classic aerosol indirect effect. However, we notice a saturation in the decrease in Reff with an increase in AOD beyond 0.4. The results provide robust observational evidence of aerosol-cloud interaction in the Indian Ocean region that

  11. Characterizing uncertainty in the motion, future location and ash concentrations of volcanic plumes and ash clouds

    Science.gov (United States)

    Webley, P.; Patra, A. K.; Bursik, M. I.; Pitman, E. B.; Dehn, J.; Singh, T.; Singla, P.; Stefanescu, E. R.; Madankan, R.; Pouget, S.; Jones, M.; Morton, D.; Pavolonis, M. J.

    2013-12-01

    Forecasting the location and airborne concentrations of volcanic ash plumes and their dispersing clouds is complex and knowledge of the uncertainty in these forecasts is critical to assess and mitigate the hazards that could exist. We show the results from an interdisciplinary project that brings together scientists drawn from the atmospheric sciences, computer science, engineering, mathematics, and geology. The project provides a novel integration of computational and statistical modeling with a widely-used volcanic particle dispersion code, to provide quantitative measures of confidence in predictions of the motion of ash clouds caused by volcanic eruptions. We combine high performance computing and stochastic analysis, resulting in real time predictions of ash cloud motion that account for varying wind conditions and a range of model variables. We show how coupling a real-time model for ash dispersal, PUFF, with a volcanic eruption model, BENT, allows for the definition of the variability in the dispersal model inputs and hence classify the uncertainty that can then propagate for the ash cloud location and downwind concentrations. We additionally analyze the uncertainty in the numerical weather prediction forecast data used by the dispersal model by using ensemble forecasts and assess how this affects the downwind concentrations. These are all coupled together and by combining polynomical chaos quadrature with stochastic integration techniques, we provide a quantitative measure of the reliability (i.e. error) of those predictions. We show comparisons of the downwind height calculations and mass loadings with observations of ash clouds available from satellite remote sensing data. The aim is to provide a probabilistic forecast of location and ash concentration that can be generated in real-time and used by those end users in the operational ash cloud hazard assessment environment.

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

    Science.gov (United States)

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

    2016-04-01

    Low-level stratocumulus (Sc) clouds cover more of the Earth's surface than any other cloud type rendering them critical for Earth's energy balance, primarily via reflection of solar radiation, as well as their role in the global hydrological cycle. Stratocumuli are particularly sensitive to changes in aerosol loading on both microphysical and macrophysical scales, yet the complex feedbacks involved in aerosol-cloud-precipitation interactions remain poorly understood. Moreover, research on these clouds has largely been confined to marine environments, with far fewer studies over land where major sources of anthropogenic aerosols exist. The aerosol burden over Southeast Asia (SEA) in boreal spring, attributed to biomass burning (BB), exhibits highly consistent spatiotemporal distribution patterns, with major variability due to changes in aerosol loading mediated by processes ranging from large-scale climate factors to diurnal meteorological events. Downwind from source regions, the transported BB aerosols often overlap with low-level Sc cloud decks associated with the development of the region's pre-monsoon system, providing a unique, natural laboratory for further exploring their complex micro- and macro-scale relationships. Compared to other locations worldwide, studies of springtime biomass-burning aerosols and the predominately Sc cloud systems over SEA and their ensuing interactions are underrepresented in scientific literature. Measurements of aerosol and cloud properties, whether ground-based or from satellites, generally lack information on microphysical processes; thus cloud-resolving models are often employed to simulate the underlying physical processes in aerosol-cloud-precipitation interactions. The Goddard Cumulus Ensemble (GCE) cloud model has recently been enhanced with a triple-moment (3M) bulk microphysics scheme as well as the Regional Atmospheric Modeling System (RAMS) version 6 aerosol module. Because the aerosol burden not only affects cloud

  13. Lidar Observation of the 2014 Kelut Volcanic Stratospheric Aerosols at Kototabang, Indonesia

    Science.gov (United States)

    Abo, Makoto; Shibata, Yasukuni; Nagasawa, Chikao

    2016-06-01

    The Kelut (Kelud) volcano (7.9S, 112.3E) in the Java island of Indonesia erupted on 13 February 2014. The CALIOP observed that the eruption cloud reached 26km above sea level. We have observed this stratospheric aerosol from 28 February 2014 at equatorial lidar site located in the Sumatra island of Indonesia (0.2S, 100.3E). We observed the depolarization maximum to be up to 2km below the backscatter maximum in April 2014. We also observed the vertical transportation process of stratospheric aerosol to troposphere by equatorial Kelvin wave.

  14. Observation and Model Comparison on Precipitation response to Volcanic Aerosols in the Asian Monsoon Region

    Science.gov (United States)

    Zhuo, Z.; Gao, C.

    2014-12-01

    Disagreement between observation and models were shown on the volcanic sulfate aerosols' effect on precipitation in Asia monsoon region. Here, we investigate it by classifying two groups of historical volcanism between AD 1300 and AD 1850 to 2, 1, and 0.5 times Pinatubo sulfate injection into the northern hemisphere (NH) stratosphere based on IVI2 and Crowley2013 volcanic reconstructions, then comparing precipitation response of BCC-CSM1 and CCSM4 model outputs under past1000 scenario to IVI2 volcanic group, and that of MIROC-ESM and MPI-ESM-P to Crowley2013 group with tree-ring reconstruction data MADA. In both groups, Superposed Epoch Analysis (SEA) of MADA and four model outputs show a drying trend over Asia monsoon regions after the NH injections and drier with larger sulfate magnitude, with a 1 or 2 year time lag in MADA comparing to the model outputs, this may result from the biological response of tree ring data that lag behind the meteorological forcing of model outputs. On the other hand, different responses to Southern Hemisphere (SH) only injections were found between the two groups as well as MADA and model outputs. Most of the results were found significant at 90% or even 95% significance level with a 10,000 Monte Carlo resampling procedure. Spatial variation of MADA show a significant drying effect in central Asia in year 1, and then move westward in year 2 and 3 after 2, 1×Pinatubo eruptions of IVI2, while a significant wetting effect in northwest Asia but drying effect in south Asia were shown in Crowley2013 group. However, model outputs did not show spatial variation, with a pattern drier in northwest than in southeast Asia along the years after the eruptions in both volcanic groups. Thus, observation and model outputs are well consistent on precipitation response to NH aerosol injections, but models may need large improvement on the response to SH aerosol injection as well as the spatial variation. Besides, opposite precipitation response to SH

  15. Climate Response to Warm Cloud-Aerosol Interactions: Comparisons With Direct Aerosol and Long-Lived Greenhouse Gas Impacts

    Science.gov (United States)

    Ramaswamy, V.; Ming, Y.

    2006-12-01

    We employ the NOAA/ GFDL global atmospheric model coupled to a mixed-layer ocean to investigate the mechanisms and quantitative aspects underlying the radiative perturbations and climate response arising due to cloud-aerosol interactions in low-lying clouds. The aerosol species considered include sulfate, sea-salt and carbonaceous species, whose space-time distributions are determined offline by the MOZART 2 chemistry- transport model based on emissions data. The model's prognostic cloud scheme of liquid water and amount is expanded to include cloud droplet concentration in a way that importantly allows them to be computed using the same large-scale and convective updraft velocity field. The equilibrium response of the model's global climate system to the change in aerosols from pre- industrial to present-day is evaluated, in terms of the forcing applied and the role of the large- and cloud-scale feedback mechanisms. The cloud characteristics simulated are compared against observations, while the model's response is compared with that obtained from using a diagnostic aerosol-cloud relationship to highlight the significance of specific cloud microphysical processes. The spatial distributions of the thermal and hydrologic responses are also compared with those resulting from simulations performed for the pre-industrial to present-day direct aerosol effect. The temperature responses in the low and high latitudes, including changes in the large-scale precipitation pattern, are contrasted with those due to the well-mixed greenhouse gases. The forcing-response relationship is examined for the radiative perturbations investigated, with surface radiative forcing included in these considerations. We finally investigate the concept of linear additivity of the responses in various climate variables for the set of radiative perturbations considered above, extending from the global- and zonal-mean to continental scales.

  16. Black carbon mixing state impacts on cloud microphysical properties: effects of aerosol plume and environmental conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ching, Ping Pui; Riemer, Nicole; West, Matthew

    2016-05-27

    Black carbon (BC) is usually mixed with other aerosol species within individual aerosol particles. This mixture, along with the particles' size and morphology, determines the particles' optical and cloud condensation nuclei properties, and hence black carbon's climate impacts. In this study the particle-resolved aerosol model PartMC-MOSAIC was used to quantify the importance of black carbon mixing state for predicting cloud microphysical quantities. Based on a set of about 100 cloud parcel simulations a process level analysis framework was developed to attribute the response in cloud microphysical properties to changes in the underlying aerosol population ("plume effect") and the cloud parcel cooling rate ("parcel effect"). It shows that the response of cloud droplet number concentration to changes in BC emissions depends on the BC mixing state. When the aerosol population contains mainly aged BC particles an increase in BC emission results in increasing cloud droplet number concentrations ("additive effect"). In contrast, when the aerosol population contains mainly fresh BC particles they act as sinks for condensable gaseous species, resulting in a decrease in cloud droplet number concentration as BC emissions are increased ("competition effect"). Additionally, we quantified the error in cloud microphysical quantities when neglecting the information on BC mixing state, which is often done in aerosol models. The errors ranged from -12% to +45% for the cloud droplet number fraction, from 0% to +1022% for the nucleation-scavenged black carbon (BC) mass fraction, from -12% to +4% for the effective radius, and from -30% to +60% for the relative dispersion.

  17. Secondary organic aerosols. Chemical aging, hygroscopicity, and cloud droplet activation

    Energy Technology Data Exchange (ETDEWEB)

    Buchholz, Angela

    2011-07-06

    Atmospheric aerosols have an important impact on the radiation balance, and thus, on the climate of the Earth. Aerosol particles scatter and absorb incoming solar and terrestrial radiation. Apart from this direct effect, aerosol particles act as cloud condensation nuclei (CCN), thereby greatly influencing the microphysics of clouds. Secondary organic aerosols (SOA) are an important fraction of the total aerosol mass. In many environments these organic compounds are mainly products of the oxidation of biogenic volatile organic compounds (VOC). In this study the hygroscopic growth and CCN activation of biogenic SOA were investigated which was formed by the oxidation of VOC with O{sub 3} and photochemically formed OH radicals under low NO{sub x} conditions. For this purpose, a complex mixture of VOC emitted by boreal tree species as gas-phase precursors was used in the Juelich Plant Atmosphere Chamber (JPAC). In long-term studies in the atmosphere simulation chamber SAPHIR {alpha}-pinene or a defined mixture of {alpha}-pinene, {beta}-pinene, limonene, ocimene, {delta}-3-carene served as precursors. Initial precursor concentrations between 40 and 1000 ppbC were investigated. The observed SOA particles were slightly hygroscopic with an average hygroscopicity parameter {kappa}(CCN) = 0.10 {+-} 0.02 and {kappa}(90%RH) = 0.05 {+-} 0.01. Closure between hygroscopic growth and CCN activation data could be achieved allowing either surface tension reduction, limited solubility, or non-ideality of the solution in the droplet. The SOA solutions in equilibrium with RH <95% are possible highly non-ideal. Therefore the organic-water interaction were investigated by applying the UNIFAC model. Calculations for surrogate compounds exhibited the same strong concentration (i.e. RH) dependence of {kappa} at sub-saturation. The growth curves could be fitted and CCN activation predicted by assuming a binary mixture of water and one hypothetical organic compound. The occurrence of

  18. Near-Cloud Aerosol Properties from the 1 Km Resolution MODIS Ocean Product

    Science.gov (United States)

    Varnai, Tamas; Marshak, Alexander

    2014-01-01

    This study examines aerosol properties in the vicinity of clouds by analyzing high-resolution atmospheric correction parameters provided in the MODIS (Moderate Resolution Imaging Spectroradiometer) ocean color product. The study analyzes data from a 2 week long period of September in 10 years, covering a large area in the northeast Atlantic Ocean. The results indicate that on the one hand, the Quality Assessment (QA) flags of the ocean color product successfully eliminate cloud-related uncertainties in ocean parameters such as chlorophyll content, but on the other hand, using the flags introduces a sampling bias in atmospheric products such as aerosol optical thickness (AOT) and Angstrom exponent. Therefore, researchers need to select QA flags by balancing the risks of increased retrieval uncertainties and sampling biases. Using an optimal set of QA flags, the results reveal substantial increases in optical thickness near clouds-on average the increase is 50% for the roughly half of pixels within 5 km from clouds and is accompanied by a roughly matching increase in particle size. Theoretical simulations show that the 50% increase in 550nm AOT changes instantaneous direct aerosol radiative forcing by up to 8W/m2 and that the radiative impact is significantly larger if observed near-cloud changes are attributed to aerosol particles as opposed to undetected cloud particles. These results underline that accounting for near-cloud areas and understanding the causes of near-cloud particle changes are critical for accurate calculations of direct aerosol radiative forcing.

  19. “Lidar Investigations of Aerosol, Cloud, and Boundary Layer Properties Over the ARM ACRF Sites”

    Energy Technology Data Exchange (ETDEWEB)

    Ferrare, Richard [NASA Langley Research Center, Hampton, VA (United States); Turner, David [National Oceanic and Atmospheric Administration (NOAA) National Severe Storms Lab., Norman, OK (United States)

    2015-01-13

    Project goals; Characterize the aerosol and ice vertical distributions over the ARM NSA site, and in particular to discriminate between elevated aerosol layers and ice clouds in optically thin scattering layers; Characterize the water vapor and aerosol vertical distributions over the ARM Darwin site, how these distributions vary seasonally, and quantify the amount of water vapor and aerosol that is above the boundary layer; Use the high temporal resolution Raman lidar data to examine how aerosol properties vary near clouds; Use the high temporal resolution Raman lidar and Atmospheric Emitted Radiance Interferometer (AERI) data to quantify entrainment in optically thin continental cumulus clouds; and Use the high temporal Raman lidar data to continue to characterize the turbulence within the convective boundary layer and how the turbulence statistics (e.g., variance, skewness) is correlated with larger scale variables predicted by models.

  20. Letter to the Editor Aerosol radiative forcing over land: effect of surface and cloud reflection

    Directory of Open Access Journals (Sweden)

    S. K. Satheesh

    Full Text Available It is now clearly understood that atmospheric aerosols have a significant impact on climate due to their important role in modifying the incoming solar and outgoing infrared radiation. The question of whether aerosol cools (negative forcing or warms (positive forcing the planet depends on the relative dominance of absorbing aerosols. Recent investigations over the tropical Indian Ocean have shown that, irrespective of the comparatively small percentage contribution in optical depth ( ~ 11%, soot has an important role in the overall radiative forcing. However, when the amount of absorbing aerosols such as soot are significant, aerosol optical depth and chemical composition are not the only determinants of aerosol climate effects, but the altitude of the aerosol layer and the altitude and type of clouds are also important. In this paper, the aerosol forcing in the presence of clouds and the effect of different surface types (ocean, soil, vegetation, and different combinations of soil and vegetation are examined based on model simulations, demonstrating that aerosol forcing changes sign from negative (cooling to positive (warming when reflection from below (either due to land or clouds is high.Key words. Atmospheric composition and structure (aerosols and particles History of Geophysics (atmospheric sciences Hydrology (anthropogenic effects

  1. The Effect of Aerosol-Cloud-Vegetation Interactions and Intraseasonal Meteorological Variability on Warm Cloud Development during the Amazonian Biomass Burning Season

    Science.gov (United States)

    Ten Hoeve, J. E.; Remer, L. A.; Jacobson, M. Z.

    2009-12-01

    The effect of aerosols on the hydrological cycle remains one of the largest uncertainties in our climate system. Biomass burning, from both deforestation and annual agricultural burning, is the largest anthropogenic source of these aerosols in the Southern Hemisphere. Biomass burning aerosols have competing effects on clouds: Depending on the level of aerosol loading and the background cloud characteristics, biomass burning aerosols have been shown in observational studies to invigorate or inhibit cloud formation and/or growth through microphysical and absorptive pathways, respectively. Many of these previous studies have employed all days during the Amazonian burning season months of August through October to formulate aerosol-cloud correlations, assuming relatively constant meteorological conditions exist throughout these months. This study investigates how intraseasonal trends of precipitable water vapor and aerosol loading between August and October impact these aerosol-cloud correlations. Other factors affecting aerosol-cloud relationships, such as atmospheric stability, are also investigated. This study is focused on a small 3 degree NE x 4 degree WE region in Rondonia, Brazil that encompasses extensive, contiguous areas of both forested and deforested land. High resolution aerosol, cloud, water vapor, and atmospheric profile data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra and Aqua satellites, as well as aerosol and water vapor data from the Aerosol Robotic Network (AERONET), are used collectively to explore the effect of aerosols on water vapor loading and warm cloud development over the Amazon. The difference in aerosol effects on the local hydrological cycle over forested and deforested areas is also examined. This final exercise provides insight into the relationship between aerosols, land-atmosphere processes, and warm clouds.

  2. Potential impacts from biological aerosols on ensembles of continental clouds simulated numerically

    Directory of Open Access Journals (Sweden)

    V. T. J. Phillips

    2009-06-01

    Full Text Available An aerosol-cloud modeling framework is described to simulate the activation of ice particles and droplets by biological aerosol particles, such as airborne ice-nucleation active (INA bacteria. It includes the empirical parameterisation of heterogeneous ice nucleation and a semi-prognostic aerosol component, which have been incorporated into a cloud-system resolving model (CSRM with double-moment bulk microphysics. The formation of cloud liquid by soluble material coated on these partially insoluble organic aerosols is represented. It determines their partial removal from deep convective clouds by accretion onto precipitation in the cloud model. This "aerosol-cloud model" is validated for diverse cases of deep convection with contrasting aerosol conditions, against satellite, ground-based and aircraft observations.

    Simulations are performed with the aerosol-cloud model for a month-long period of summertime convective activity over Oklahoma. It includes three cases of continental deep convection simulated previously by Phillips and Donner (2006. Elevated concentrations of insoluble organic aerosol, boosted by a factor of 100 beyond their usual values for this continental region, are found to influence significantly the following quantities: (1 the average numbers and sizes of ice crystals and droplets in the clouds; (2 the horizontal cloud coverage in the free troposphere; (3 precipitation at the ground; and (4 incident solar insolation at the surface. This factor of 100 is plausible for natural fluctuations of the concentration of insoluble organic aerosol, in view of variability of cell concentrations for airborne bacteria seen by Lindemann et al. (1982.

    In nature, such boosting of the insoluble organic aerosol loading could arise from enhanced emissions of biological aerosol particles from a land surface. Surface wetness and solar insolation at the ground are meteorological quantities known to influence rates of growth of

  3. Coupling spectral-bin cloud microphysics with the MOSAIC aerosol model in WRF-Chem: Methodology and results for marine stratocumulus clouds

    Science.gov (United States)

    Gao, Wenhua; Fan, Jiwen; Easter, R. C.; Yang, Qing; Zhao, Chun; Ghan, Steven J.

    2016-09-01

    Aerosol-cloud interaction processes can be represented more physically with bin cloud microphysics relative to bulk microphysical parameterizations. However, due to computational power limitations in the past, bin cloud microphysics was often run with very simple aerosol treatments. The purpose of this study is to represent better aerosol-cloud interaction processes in the Chemistry version of Weather Research and Forecast model (WRF-Chem) at convection-permitting scales by coupling spectral-bin cloud microphysics (SBM) with the MOSAIC sectional aerosol model. A flexible interface is built that exchanges cloud and aerosol information between them. The interface contains a new bin aerosol activation approach, which replaces the treatments in the original SBM. It also includes the modified aerosol resuspension and in-cloud wet removal processes with the droplet loss tendencies and precipitation fluxes from SBM. The newly coupled system is evaluated for two marine stratocumulus cases over the Southeast Pacific Ocean with either a simplified aerosol setup or full-chemistry. We compare the aerosol activation process in the newly coupled SBM-MOSAIC against the SBM simulation without chemistry using a simplified aerosol setup, and the results show consistent activation rates. A longer time simulation reinforces that aerosol resuspension through cloud drop evaporation plays an important role in replenishing aerosols and impacts cloud and precipitation in marine stratocumulus clouds. Evaluation of the coupled SBM-MOSAIC with full-chemistry using aircraft measurements suggests that the new model works realistically for the marine stratocumulus clouds, and improves the simulation of cloud microphysical properties compared to a simulation using MOSAIC coupled with the Morrison two-moment microphysics.

  4. Coupling Spectral-bin Cloud Microphysics with the MOSAIC Aerosol Model in WRF-Chem: Methodology and Results for Marine Stratocumulus Clouds

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Wenhua; Fan, Jiwen; Easter, Richard C.; Yang, Qing; Zhao, Chun; Ghan, Steven J.

    2016-08-23

    Aerosol-cloud interaction processes can be represented more physically with bin cloud microphysics relative to bulk microphysical parameterizations. However, due to computational power limitations in the past, bin cloud microphysics was often run with very simple aerosol treatments. The purpose of this study is to represent better aerosol-cloud interaction processes in the Chemistry version of Weather Research and Forecast model (WRF-Chem) at convection-permitting scales by coupling spectral-bin cloud microphysics (SBM) with the MOSAIC sectional aerosol model. A flexible interface is built that exchanges cloud and aerosol information between them. The interface contains a new bin aerosol activation approach, which replaces the treatments in the original SBM. It also includes the modified aerosol resuspension and in-cloud wet removal processes with the droplet loss tendencies and precipitation fluxes from SBM. The newly coupled system is evaluated for two marine stratocumulus cases over the Southeast Pacific Ocean with either a simplified aerosol setup or full-chemistry. We compare the aerosol activation process in the newly-coupled SBM-MOSAIC against the SBM simulation without chemistry using a simplified aerosol setup, and the results show consistent activation rates. A longer time simulation reinforces that aerosol resuspension through cloud drop evaporation plays an important role in replenishing aerosols and impacts cloud and precipitation in marine stratocumulus clouds. Evaluation of the coupled SBM-MOSAIC with full-chemistry using aircraft measurements suggests that the new model works realistically for the marine stratocumulus clouds, and improves the simulation of cloud microphysical properties compared to a simulation using MOSAIC coupled with the Morrison two-moment microphysics.

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

    Science.gov (United States)

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

    2014-12-01

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

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

    Directory of Open Access Journals (Sweden)

    L. Costantino

    2012-06-01

    Full Text Available In this study, we provide a comprehensive analysis of aerosol interaction with warm boundary layer clouds, over South-East Atlantic. We use MODIS retrievals to derive statistical relationships between aerosol concentration and cloud properties, together with co-located CALIPSO estimates of cloud and aerosol layer altitudes. The latter are used to differentiate between cases of mixed and interacting cloud-aerosol layers from cases where the aerosol is located well-above the cloud top. This strategy allows, to a certain extent, to isolate real aerosol-induced effect from meteorology.

    Similar to previous studies, statistics clearly show that aerosol affects cloud microphysics, decreasing the Cloud Droplet Radius (CDR. The same data indicate a concomitant strong decrease in cloud Liquid Water Path (LWP, in evident contrast with the hypothesis of aerosol inhibition of precipitation (Albrecht, 1989. Because of this water loss, probably due to the entrainment of dry air at cloud top, Cloud Optical Thickness (COT is found to be almost insensitive to changes in aerosol concentration. The analysis of MODIS-CALIPSO coincidences also evidenced an aerosol enhancement of low cloud cover. Surprising, the Cloud Fraction (CLF response to aerosol invigoration is much stronger when (absorbing particles are located above cloud top, than in cases of physical interaction, This result suggests a relevant aerosol radiative effect on low cloud occurrence. Heating the atmosphere above the inversion, absorbing particles above cloud top may decrease the vertical temperature gradient, increase the low tropospheric stability and provide favorable conditions for low cloud formation.

    We also focus on the impact of anthropogenic aerosols on precipitation, through the statistical analysis of CDR-COT co-variations. A COT value of 10 is found to be the threshold beyond which precipitation mostly forms, in both clean and polluted environments. For larger COT

  7. Imaginary refractive index and other microphysical properties of volcanic ash, Sarahan dust, and other mineral aerosols

    Science.gov (United States)

    Rocha Lima, A.; Martins, J.; Krotkov, N. A.; Artaxo, P.; Todd, M.; Ben Ami, Y.; Dolgos, G.; Espinosa, R.

    2013-12-01

    Aerosol properties are essential to support remote sensing measurements, atmospheric circulation and climate models. This research aims to improve the understanding of the optical and microphysical properties of different types of aerosols particles. Samples of volcanic ash, Saharan dust and other mineral aerosols particles were analyzed by different techniques. Ground samples were sieved down to 45um, de-agglomerated and resuspended in the laboratory using a Fluidized Bed Aerosol Generator (FBAG). Particles were collected on Nuclepore filters into PM10, PM2.5, or PM1.0. and analyzed by different techniques, such as Scanning Electron Microscopy (SEM) for determination of size distribution and shape, spectral reflectance for determination of the optical absorption properties as a function of the wavelength, material density, and X-Ray fluorescence for the elemental composition. The spectral imaginary part of refractive index from the UV to the short wave infrared (SWIR) wavelength was derived empirically from the measurements of the spectral mass absorption coefficient, size distribution and density of the material. Some selected samples were also analyzed with the Polarized Imaging Nephelometer (PI-Neph) instrument for the characterization of the aerosol polarized phase function. This work compares results of the spectral refractive index of different materials obtained by our methodology with those available in the literature. In some cases there are significant differences both in magnitude and spectral dependence of the imaginary refractive index. These differences are evaluated and discussed in this work.

  8. Clouds, aerosols and biogeochemical cycles. Risks of non-linear climate change

    Energy Technology Data Exchange (ETDEWEB)

    Van Ham, J.; Van Beers, R.J.; Builtjes, P.J.H.; Roemer, M.G.M. [TNO Institute of Environmental Sciences, Delft (Netherlands); Koennen, G.P. [Royal Netherlands Meteorological Institute KNMI, De Bilt (Netherlands); Oerlemans, J. [Institute for Meteorological and Atmospheric Research, University of Utrecht, Utrecht (Netherlands)

    1995-12-31

    Part of the results of an investigation into risks for climate change, which are presently not adequately covered in General Circulation Models, is described. The investigation included the interaction with biogeochemical cycles, the effects of clouds and aerosols, ice flow instability, albedo instability and modified ocean circulation. In this paper our results for clouds and aerosols and for bio-geochemical cycles are reported. 1 tab., 21 refs.

  9. Artificial cloud test confirms volcanic ash detection using infrared spectral imaging

    Science.gov (United States)

    Prata, A. J.; Dezitter, F.; Davies, I.; Weber, K.; Birnfeld, M.; Moriano, D.; Bernardo, C.; Vogel, A.; Prata, G. S.; Mather, T. A.; Thomas, H. E.; Cammas, J.; Weber, M.

    2016-05-01

    Airborne volcanic ash particles are a known hazard to aviation. Currently, there are no means available to detect ash in flight as the particles are too fine (radii < 30 μm) for on-board radar detection and, even in good visibility, ash clouds are difficult or impossible to detect by eye. The economic cost and societal impact of the April/May 2010 Icelandic eruption of Eyjafjallajökull generated renewed interest in finding ways to identify airborne volcanic ash in order to keep airspace open and avoid aircraft groundings. We have designed and built a bi-spectral, fast-sampling, uncooled infrared camera device (AVOID) to examine its ability to detect volcanic ash from commercial jet aircraft at distances of more than 50 km ahead. Here we report results of an experiment conducted over the Atlantic Ocean, off the coast of France, confirming the ability of the device to detect and quantify volcanic ash in an artificial ash cloud created by dispersal of volcanic ash from a second aircraft. A third aircraft was used to measure the ash in situ using optical particle counters. The cloud was composed of very fine ash (mean radii ~10 μm) collected from Iceland immediately after the Eyjafjallajökull eruption and had a vertical thickness of ~200 m, a width of ~2 km and length of between 2 and 12 km. Concentrations of ~200 μg m-3 were identified by AVOID at distances from ~20 km to ~70 km. For the first time, airborne remote detection of volcanic ash has been successfully demonstrated from a long-range flight test aircraft.

  10. Artificial cloud test confirms volcanic ash detection using infrared spectral imaging.

    Science.gov (United States)

    Prata, A J; Dezitter, F; Davies, I; Weber, K; Birnfeld, M; Moriano, D; Bernardo, C; Vogel, A; Prata, G S; Mather, T A; Thomas, H E; Cammas, J; Weber, M

    2016-05-09

    Airborne volcanic ash particles are a known hazard to aviation. Currently, there are no means available to detect ash in flight as the particles are too fine (radii ash clouds are difficult or impossible to detect by eye. The economic cost and societal impact of the April/May 2010 Icelandic eruption of Eyjafjallajökull generated renewed interest in finding ways to identify airborne volcanic ash in order to keep airspace open and avoid aircraft groundings. We have designed and built a bi-spectral, fast-sampling, uncooled infrared camera device (AVOID) to examine its ability to detect volcanic ash from commercial jet aircraft at distances of more than 50 km ahead. Here we report results of an experiment conducted over the Atlantic Ocean, off the coast of France, confirming the ability of the device to detect and quantify volcanic ash in an artificial ash cloud created by dispersal of volcanic ash from a second aircraft. A third aircraft was used to measure the ash in situ using optical particle counters. The cloud was composed of very fine ash (mean radii ~10 μm) collected from Iceland immediately after the Eyjafjallajökull eruption and had a vertical thickness of ~200 m, a width of ~2 km and length of between 2 and 12 km. Concentrations of ~200 μg m(-3) were identified by AVOID at distances from ~20 km to ~70 km. For the first time, airborne remote detection of volcanic ash has been successfully demonstrated from a long-range flight test aircraft.

  11. Aerosol direct effect retrieval over clouds from space-borne passive hyperspectral measurements (Invited)

    Science.gov (United States)

    de Graaf, M.; Tilstra, L.; Stammes, P.

    2013-12-01

    A novel approach for the retrieval of the aerosol direct radiative effect (DRE) over clouds will be presented, which is independent of aerosol parameters estimates. The direct effect at the top of the atmosphere (TOA) of aerosols over clouds can be estimated using hyperspectral reflectance measurements from space-borne spectrometers, when the equivalent aerosol-unpolluted cloud scene reflectance spectrum is known. For smoke over clouds the cloud parameters can be estimated from the shortwave infrared (SWIR), where the absorption of the small smoke particles becomes sufficiently small. Using precomputed tables of cloud reflectance spectra, the unpolluted cloud scene spectrum can then be simulated and compared to the real measured polluted cloud scene reflectance spectrum. The UV-radiation absorption by the smoke will lead to a difference between the measured and simulated spectra, which is proportional to the aerosol DRE at TOA. Aerosol microphysical assumptions and retrievals are avoided by modeling only the aerosol-free scene spectra, all the aerosol effects are in the reflectance measurements. The method works especially well for cloud scenes, which can be simulated relatively accurately. An algorithm was developed to derive the aerosol DRE over marine clouds, using the space-borne spectrometer SCIAMACHY, which produced shortwave reflectance spectra (from 240 to 1700 nm contiguously) from 2002 till 2012. These are ideally suited to study the effect of aerosols on the shortwave spectrum. However, since aerosols in general do not have high resolution spectral features, the algorithm can be adapted to suit data from any combination of instruments that measures UV, visible and SWIR reflectances simultaneously. Examples include OMI and MODIS, flying in the A-Train constellation, and TROPOMI, on the future Sentinel 5 precursor mission, combined with NOAA's NPP VIIRS. This would produce aerosol DRE estimates with unprecedented accuracy and spatial resolution. The

  12. Software to analyze the relationship between aerosol, clouds, and precipitation: SAMAC

    Science.gov (United States)

    Gagné, S.; MacDonald, L. P.; Leaitch, W. R.; Pierce, J. R.

    2016-02-01

    The analysis of aircraft-based measurements of clouds is critical for studies of aerosol and of clouds. Many such measurements have been taken, but it is difficult to compare such data across instruments, flights and campaigns. We present a new open-source software program, SAMAC (Software for Airborne Measurements of Aerosol and Clouds), that may enable a more systematic and comparable approach to the analysis of aerosol-cloud-precipitation data. The software offers a cooperative and reproducible approach to the analysis of aircraft measurements of clouds across campaigns. SAMAC is an object-oriented software program in which a cloud is an object; all the data related to a cloud is contained in the cloud object. The cloud objects come with built-in methods and functions that allow for the quick generation of basic plots and calculations, SAMAC provides a quick view of the data set and may be used to compare clouds and to filter for specific characteristics. Other researchers can readily use already submitted algorithms once their data is placed in the cloud structure provided, and they can contribute their own algorithms to the software for others to see and use. This approach would improve comparability, reproducibility and transparency by allowing others to replicate results and test the same algorithms on different data. SAMAC can be downloaded at https://github.com/StephGagne/SAMAC/releases.

  13. The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

    Directory of Open Access Journals (Sweden)

    M. Toohey

    2014-06-01

    Full Text Available Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol–climate model simulations. For all forcings, we find that temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high latitude effects result from robust enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. While there is significant ensemble variability in the high latitude response to each aerosol forcing set, the mean response is sensitive to the forcing set used. Significant differences, for example, are found in the NH polar stratosphere temperature and zonal wind response to two different forcing data sets constructed from different versions of SAGE II aerosol observations. Significant strengthening of the polar vortex, in rough agreement with the expected response, is achieved only using aerosol forcing extracted from prior coupled aerosol–climate model simulations. Differences in the dynamical response to the different forcing sets used

  14. Quantification of the aerosol direct radiative effect from smoke over clouds using passive space-borne spectrometry

    Science.gov (United States)

    de Graaf, M.; Stammes, P.; Tilstra, L. G.

    2013-05-01

    The solar radiative absorption by smoke layers above clouds is quantified, using the unique broad spectral range of the space-borne spectrometer Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) from the ultraviolet (UV) to the shortwave infrared (SWIR). Aerosol radiative effects in the UV are separated from cloud radiative effects in the shortwave infrared (SWIR). In the UV, aerosol absorption from smoke is strong, creating a strong signal in the measured reflectance. In the SWIR, absorbing and scattering effects from smoke are negligible, allowing the retrieval of cloud parameters from the measured spectrum using existing retrieval techniques. The spectral signature of the cloud can be modelled using a radiative transfer model (RTM) and the cloud parameters retrieved in the SWIR. In this way, the aerosol effects can be determined from the measured aerosol-polluted cloud shortwave spectrum and the modelled aerosol-unpolluted cloud shortwave spectrum. This can be used to derive the aerosol direct radiative effect (DRE) over marine clouds, independent of aerosol parameter retrievals, significantly improving the current accuracy of aerosol DRE estimates. Only cloud parameters are needed to model the aerosolunpolluted cloud reflectance, while the effects of the aerosol absorption are in the aerosol-polluted cloud reflectance measurements. In this paper we present a case study of the above method using SCIAMACHY data over the South Atlantic Ocean west of Africa on 13 August 2006, when a huge plume of smoke was present over persistent cloud fields. The aerosol DRE over clouds was as high as 128 ± 8 Wm-2 for this case, while the aerosol DRE over clouds averaged through August 2006 was found to be 23 ± 8 Wm-2 with a mean variation over the region in this month of 22 Wm-2.

  15. Aircraft measurements of cloud-aerosol interaction over East Inner Mongolia

    Science.gov (United States)

    Lü, Yuhuan; Lei, Hengchi; Yang, Jiefan

    2017-08-01

    To investigate the potential effects of aerosols on the microphysical properties of warm clouds, airborne observational data collected from 2009 to 2011 in Tongliao, Inner Mongolia, China, were statistically analyzed in this study. The results demonstrated that the vertical distribution of the aerosol number concentration ( N a) was similar to that of the clean rural continent. The average aerosol effective diameter ( D e) was maintained at approximately 0.4 μm at all levels. The data obtained during cloud penetrations showed that there was a progressive increase in the cloud droplet concentration ( N c) and liquid water content (LWC) from outside to inside the clouds, while the N a was negatively related to the N c and LWC at the same height. The fluctuation of the N a, N c and LWC during cloud penetration was more obvious under polluted conditions (Type 1) than under clean conditions (Type 2). Moreover, the wet scavenging of cloud droplets had a significant impact on the accumulation mode of aerosols, especially on particles with diameters less than 0.4 μm. The minimum wet scavenging coefficient within the cloud was close to 0.02 under Type 1 conditions, while it increased to 0.1 under Type 2 conditions, which proved that the cloud wet scavenging effect under Type 1 conditions was stronger than that under Type 2 conditions. Additionally, cloud droplet spectra under Type 1 conditions were narrower, and their horizontal distributions were more homogeneous than those under Type 2 conditions.

  16. Consistency of aerosols above clouds characterization from A-Train active and passive measurements

    Science.gov (United States)

    Deaconu, Lucia T.; Waquet, Fabien; Josset, Damien; Ferlay, Nicolas; Peers, Fanny; Thieuleux, François; Ducos, Fabrice; Pascal, Nicolas; Tanré, Didier; Pelon, Jacques; Goloub, Philippe

    2017-09-01

    This study presents a comparison between the retrieval of optical properties of aerosol above clouds (AAC) from different techniques developed for the A-Train sensors CALIOP/CALIPSO and POLDER/PARASOL. The main objective is to analyse the consistency between the results derived from the active and the passive measurements. We compare the aerosol optical thickness (AOT) above optically thick clouds (cloud optical thickness (COT) larger than 3) and their Ångström exponent (AE). These parameters are retrieved with the CALIOP operational method, the POLDER operational polarization method and the CALIOP-based depolarization ratio method (DRM) - for which we also propose a calibrated version (denominated DRMSODA, where SODA is the Synergized Optical Depth of Aerosols). We analyse 6 months of data over three distinctive regions characterized by different types of aerosols and clouds. Additionally, for these regions, we select three case studies: a biomass-burning event over the South Atlantic Ocean, a Saharan dust case over the North Atlantic Ocean and a Siberian biomass-burning event over the North Pacific Ocean. Four and a half years of data are studied over the entire globe for distinct situations where aerosol and cloud layers are in contact or vertically separated. Overall, the regional analysis shows a good correlation between the POLDER and the DRMSODA AOTs when the microphysics of aerosols is dominated by fine-mode particles of biomass-burning aerosols from southern Africa (correlation coefficient (R2) of 0.83) or coarse-mode aerosols of Saharan dust (R2 of 0.82). A good correlation between these methods (R2 of 0.68) is also observed in the global treatment, when the aerosol and cloud layers are separated well. The analysis of detached layers also shows a mean difference in AOT of 0.07 at 532 nm between POLDER and DRMSODA at a global scale. The correlation between the retrievals decreases when a complex mixture of aerosols is expected (R2 of 0.37) - as in the

  17. Understanding the Effect of Aerosol Properties on Cloud Droplet Formation during TCAP Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Cziczo, Daniel [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

    2016-05-01

    The formation of clouds is an essential element in understanding the Earth’s radiative budget. Liquid water clouds form when the relative humidity exceeds saturation and condensedphase water nucleates on atmospheric particulate matter. The effect of aerosol properties such as size, morphology, and composition on cloud droplet formation has been studied theoretically as well as in the laboratory and field. Almost without exception these studies have been limited to parallel measurements of aerosol properties and cloud formation or collection of material after the cloud has formed, at which point nucleation information has been lost. Studies of this sort are adequate when a large fraction of the aerosol activates, but correlations and resulting model parameterizations are much more uncertain at lower supersaturations and activated fractions.

  18. Importance of including ammonium sulfate ((NH42SO4 aerosols for ice cloud parameterization in GCMs

    Directory of Open Access Journals (Sweden)

    R. Yang

    2010-02-01

    Full Text Available A common deficiency of many cloud-physics parameterizations including the NASA's microphysics of clouds with aerosol-cloud interactions (hereafter called McRAS-AC is that they simulate lesser (larger than the observed ice cloud particle number (size. A single column model (SCM of McRAS-AC physics of the GEOS4 Global Circulation Model (GCM together with an adiabatic parcel model (APM for ice-cloud nucleation (IN of aerosols were used to systematically examine the influence of introducing ammonium sulfate (NH42SO4 aerosols in McRAS-AC and its influence on the optical properties of both liquid and ice clouds. First an (NH42SO4 parameterization was included in the APM to assess its effect on clouds vis-à-vis that of the other aerosols. Subsequently, several evaluation tests were conducted over the ARM Southern Great Plain (SGP and thirteen other locations (sorted into pristine and polluted conditions distributed over marine and continental sites with the SCM. The statistics of the simulated cloud climatology were evaluated against the available ground and satellite data. The results showed that inclusion of (NH42SO4 into McRAS-AC of the SCM made a remarkable improvement in the simulated effective radius of ice cloud particulates. However, the corresponding ice-cloud optical thickness increased even more than the observed. This can be caused by lack of horizontal cloud advection not performed in the SCM. Adjusting the other tunable parameters such as precipitation efficiency can mitigate this deficiency. Inclusion of ice cloud particle splintering invoked empirically further reduced simulation biases. Overall, these changes make a substantial improvement in simulated cloud optical properties and cloud distribution particularly over the Intertropical Convergence Zone (ITCZ in the GCM.

  19. Entrainment and mixing of biomass burning aerosol into the Namibian stratocumulus cloud deck

    Science.gov (United States)

    Diamond, M. S.; Wood, R.; LeBlanc, S. E.

    2016-12-01

    Interactions between the seasonal biomass burning (BB) smoke plume and the semi-permanent stratocumulus cloud deck in the southeast Atlantic Ocean (SEA) remain poorly understood due to lack of direct observations, despite the importance of this region for the global energy budget. In particular, the extent to which BB aerosol is entrained and mixed into the cloud deck is poorly constrained. Although CALIOP lidar data shows that the smoke layer is clearly separated from the cloud deck near the Namibian/Angolan coast and subsides as it moves westward, the lidar may underestimate the geometric extent of the smoke layer in cases of strong attenuation. As a result, the longitude at which mixing first occurs is uncertain. Large Eddy Simulation (LES) studies suggest that the net radiative forcing of BB aerosol above cloud is negative, in large part due to the Twomey indirect effect. Thus, the extent of BB aerosol mixing is of prime climatic importance in this region. NASA's ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) field campaign will investigate multiple facets of the aerosol-cloud-marine boundary layer system in the SEA between August 2016 and October 2018. We present evidence from the campaign, from A-train satellite sensors, and from radiative transfer calculations to constrain the longitude of first mixing and identify a seasonal cycle in the extent of aerosol mixing.

  20. Improving Our Fundamental Understanding of the Role of Aerosol-Cloud Interactions in the Climate System

    Energy Technology Data Exchange (ETDEWEB)

    Seinfeld, John H.; Bretherton, Christopher S.; Carslaw, K. S.; Coe, H.; DeMott, Paul J.; Dunlea, Edward J.; Feingold, G.; Ghan, Steven J.; Guenther, Alex B.; Kahn, Ralph; Kraucunas, Ian P.; Kreidenweis, Sonia M.; Molina, Mario J.; Nenes, Athanasios; Penner, J.; Prather, Kimberly; Ramanathan, Veerabhadran; Ramaswamy, V.; Rasch, Philip J.; Ravishankara, A. R.; Rosenfeld, Daniel; Stephens, Graeme; Wood, R.

    2016-05-24

    The effect of an increase in atmospheric aerosol concentrations on the distribution and radiative properties of Earth’s clouds is the most uncertain component of the overall global radiative forcing from pre-industrial time. General Circulation Models (GCMs) are the tool for predicting future climate, but the treatment of aerosols, clouds, and aerosol-cloud radiative effects carries large uncertainties that directly affect GCM predictions, such as climate sensitivity. Predictions are hampered by the large range of scales of interaction between various components that need to be captured. Observation systems (remote sensing, in situ) are increasingly being used to constrain predictions but significant challenges exist, to some extent because of the large range of scales and the fact that the various measuring systems tend to address different scales. Fine-scale models represent clouds, aerosols, and aerosol-cloud interactions with high fidelity but do not include interactions with the larger scale and are therefore limited from a climatic point of view. We suggest strategies for improving estimates of aerosol-cloud relationships in climate models, for new remote sensing and in situ measurements, and for quantifying and reducing model uncertainty.

  1. CloudAerosol interaction during lightning activity over land and ocean: Precipitation pattern assessment

    Science.gov (United States)

    Pal, Jayanti; Chaudhuri, Sutapa; Chowdhury, Arumita Roy; Bandyopadhyay, Tanuka

    2016-06-01

    The present study attempts to identify the land - ocean contrast in cloud - aerosol relation during lightning and non-lightning days and its effect on subsequent precipitation pattern. The thermal hypothesis in view of Convective Available Potential Energy (CAPE) behind the land - ocean contrast is observed to be insignificant in the present study region. The result shows that the lightning activities are significantly and positively correlated with aerosols over both land and ocean in case of low aerosol loading whereas for high aerosol loading the correlation is significant but, only over land. The study attempts to comprehend the mechanism through which the aerosol and lightning interact using the concept of aerosol indirect effect that includes the study of cloud effective radius, cloud fraction and precipitation rate. The result shows that the increase in lightning activity over ocean might have been caused due to the first aerosol indirect effect, while over land the aerosol indirect effect might have been suppressed due to lightning. Thus, depending on the region and relation between cloud parameters it is observed that the precipitation rate decreases (increases) over ocean during lightning (non-lightning) days. On the other hand during non-lightning days, the precipitation rate decreases over land.

  2. Ozone Depletion at Mid-Latitudes: Coupling of Volcanic Aerosols and Temperature Variability to Anthropogenic Chlorine

    Science.gov (United States)

    Solomon, S.; Portmann, R. W.; Garcia, R. R.; Randel, W.; Wu, F.; Nagatani, R.; Gleason, J.; Thomason, L.; Poole, L. R.; McCormick, M. P.

    1998-01-01

    Satellite observations of total ozone at 40-60 deg N are presented from a variety of instruments over the time period 1979-1997. These reveal record low values in 1992-3 (after Pinatubo) followed by partial but incomplete recovery. The largest post-Pinatubo reductions and longer-term trends occur in spring, providing a critical test for chemical theories of ozone depletion. The observations are shown to be consistent with current understanding of the chemistry of ozone depletion when changes in reactive chlorine and stratospheric aerosol abundances are considered along with estimates of wave-driven fluctuations in stratospheric temperatures derived from global temperature analyses. Temperature fluctuations are shown to make significant contributions to model calculated northern mid-latitude ozone depletion due to heterogeneous chlorine activation on liquid sulfate aerosols at temperatures near 200-210 K (depending upon water vapor pressure), particularly after major volcanic eruptions. Future mid-latitude ozone recovery will hence depend not only on chlorine recovery but also on temperature trends and/or variability, volcanic activity, and any trends in stratospheric sulfate aerosol.

  3. Role of volcanic and anthropogenic aerosols in the recent global surface warming slowdown

    Science.gov (United States)

    Smith, Doug M.; Booth, Ben B. B.; Dunstone, Nick J.; Eade, Rosie; Hermanson, Leon; Jones, Gareth S.; Scaife, Adam A.; Sheen, Katy L.; Thompson, Vikki

    2016-10-01

    The rate of global mean surface temperature (GMST) warming has slowed this century despite the increasing concentrations of greenhouse gases. Climate model experiments show that this slowdown was largely driven by a negative phase of the Pacific Decadal Oscillation (PDO), with a smaller external contribution from solar variability, and volcanic and anthropogenic aerosols. The prevailing view is that this negative PDO occurred through internal variability. However, here we show that coupled models from the Fifth Coupled Model Intercomparison Project robustly simulate a negative PDO in response to anthropogenic aerosols implying a potentially important role for external human influences. The recovery from the eruption of Mount Pinatubo in 1991 also contributed to the slowdown in GMST trends. Our results suggest that a slowdown in GMST trends could have been predicted in advance, and that future reduction of anthropogenic aerosol emissions, particularly from China, would promote a positive PDO and increased GMST trends over the coming years. Furthermore, the overestimation of the magnitude of recent warming by models is substantially reduced by using detection and attribution analysis to rescale their response to external factors, especially cooling following volcanic eruptions. Improved understanding of external influences on climate is therefore crucial to constrain near-term climate predictions.

  4. Impact of aerosol on post-frontal convective clouds over Germany

    OpenAIRE

    Rieger, D; M. Bangert; Kottmeier, C; Vogel, H.; Vogel, B.

    2014-01-01

    We carried out simulations with predefined and simulated aerosol distributions in order to investigate the improvement in the forecasting capabilities of an operational weather forecast model by the use of an improved aerosol representation. This study focuses on convective cumulus clouds developing after the passage of a cold front on 25 April 2008 over Germany. The northerly flow after the cold front leads to increased sea salt aerosol concentrations compared to prefrontal conditions. High ...

  5. Hygroscopic growth of atmospheric aerosol particles and its relation to nucleation scavenging in clouds

    Energy Technology Data Exchange (ETDEWEB)

    Svenningsson, B.

    1997-11-01

    Aerosol particles in the atmosphere are important in several aspects. Some major aerosol constituents that are deposited in ecosystems are acidic or fertilizers and some minor or trace constituents are toxic. Aerosol particles are also involved in the earth`s radiation balance, both directly by scattering the sunlight and indirectly by influencing the clouds. All these effects are influenced by the interaction between the aerosol particles and water vapour. A tandem differential mobility analyser (TDMA) has been designed to measure hygroscopic growth, i.e. the particle diameter change due to uptake of water at well defined relative humidities below 100%. Tests of the instrument performance have been made using aerosol particles of pure inorganic salts. Three field experiments have been performed as parts of large fog and cloud experiments. Bimodal hygroscopic growth spectra were found: less-hygroscopic particles containing a few percent and more-hygroscopic particles around 50% by volume of hygroscopically active material. In general the fraction of less-hygroscopic particles decreases with particle size and it is larger in polluted continental aerosols than in remote background aerosols. This external mixing cannot be fully understood using present views on the formation of aerosols. Evidence or the importance of the external mixing on the cloud nucleating properties of the particles are found in comparisons between hygroscopic growth spectra for the total aerosol, the interstitial aerosol in clouds, and cloud drop residuals. Cloud condensation nuclei spectra, calculated using aerosol particle size distributions and hygroscopic growth spectra, in combination with information on the major inorganic ions are presented. These CCN spectra reveal for instance that the influence of less-hygroscopic particles on the cloud droplets increases with increasing peak supersaturation. The fraction of the particles that were scavenged to cloud drops, as a function of particle

  6. Near-cloud aerosol properties from the 1 km resolution MODIS ocean product

    Science.gov (United States)

    Várnai, Tamás.; Marshak, Alexander

    2014-02-01

    This study examines aerosol properties in the vicinity of clouds by analyzing high-resolution atmospheric correction parameters provided in the MODIS (Moderate Resolution Imaging Spectroradiometer) ocean color product. The study analyzes data from a 2 week long period of September in 10 years, covering a large area in the northeast Atlantic Ocean. The results indicate that on the one hand, the Quality Assessment (QA) flags of the ocean color product successfully eliminate cloud-related uncertainties in ocean parameters such as chlorophyll content, but on the other hand, using the flags introduces a sampling bias in atmospheric products such as aerosol optical thickness (AOT) and Angstrom exponent. Therefore, researchers need to select QA flags by balancing the risks of increased retrieval uncertainties and sampling biases. Using an optimal set of QA flags, the results reveal substantial increases in optical thickness near clouds—on average the increase is 50% for the roughly half of pixels within 5 km from clouds and is accompanied by a roughly matching increase in particle size. Theoretical simulations show that the 50% increase in 550 nm AOT changes instantaneous direct aerosol radiative forcing by up to 8 W/m2 and that the radiative impact is significantly larger if observed near-cloud changes are attributed to aerosol particles as opposed to undetected cloud particles. These results underline that accounting for near-cloud areas and understanding the causes of near-cloud particle changes are critical for accurate calculations of direct aerosol radiative forcing.

  7. Consistency of aerosols above clouds characterization from A-Train active and passive measurements

    Directory of Open Access Journals (Sweden)

    L. T. Deaconu

    2017-09-01

    Full Text Available This study presents a comparison between the retrieval of optical properties of aerosol above clouds (AAC from different techniques developed for the A-Train sensors CALIOP/CALIPSO and POLDER/PARASOL. The main objective is to analyse the consistency between the results derived from the active and the passive measurements. We compare the aerosol optical thickness (AOT above optically thick clouds (cloud optical thickness (COT larger than 3 and their Ångström exponent (AE. These parameters are retrieved with the CALIOP operational method, the POLDER operational polarization method and the CALIOP-based depolarization ratio method (DRM – for which we also propose a calibrated version (denominated DRMSODA, where SODA is the Synergized Optical Depth of Aerosols. We analyse 6 months of data over three distinctive regions characterized by different types of aerosols and clouds. Additionally, for these regions, we select three case studies: a biomass-burning event over the South Atlantic Ocean, a Saharan dust case over the North Atlantic Ocean and a Siberian biomass-burning event over the North Pacific Ocean. Four and a half years of data are studied over the entire globe for distinct situations where aerosol and cloud layers are in contact or vertically separated. Overall, the regional analysis shows a good correlation between the POLDER and the DRMSODA AOTs when the microphysics of aerosols is dominated by fine-mode particles of biomass-burning aerosols from southern Africa (correlation coefficient (R2 of 0.83 or coarse-mode aerosols of Saharan dust (R2 of 0.82. A good correlation between these methods (R2 of 0.68 is also observed in the global treatment, when the aerosol and cloud layers are separated well. The analysis of detached layers also shows a mean difference in AOT of 0.07 at 532 nm between POLDER and DRMSODA at a global scale. The correlation between the retrievals decreases when a complex mixture of aerosols is expected (R2 of 0.37

  8. Aerosol patterns and aerosol-cloud-interactions off the West African Coast based on the A-train formation

    Science.gov (United States)

    Fuchs, Julia; Bendix, Jörg; Cermak, Jan

    2013-04-01

    In this study, spatial and temporal aerosol patterns off the Western African coast are characterized and related to cloud properties, based on satellite data Atmospheric aerosols play a key role in atmospheric processes and influence our environmental system in a complex way. Their identification, characterization, transport patterns as well as their interactions with clouds pose major challenges. Especially the last aspect reveals major uncertainties in terms of the Earth's radiation budget as reported in the IPCC's Fourth Assessment Report (IPCC, 2007). Western and Southern Africa are dominated by two well-known source types of atmospheric aerosols. First, the Saharan Desert is the world's largest aeolian dust emitting source region. Second, biomass burning aerosol is commonly transported off-shore further south (Kaufman et al., 2005). Both aerosol types influence Earth's climate in different manners and can be detected by the MODIS (MODerate resolution Imaging Spectrometer) sensor onboard the EOS platforms as they propagate to the Central and Southern Atlantic. The motivation of this study was to reveal the seasonal pattern of the Saharan dust transport based on an observation period of 11 years and trying to explain the meteorological mechanisms. North African dust plumes are transported along a latitude of 19°N in July and 6°N in January. The seasonally fluctuating intensities adapt to the annual cycle of wind and precipitation regimes. A strong relationship is found between the spatial shift of the Azores High and the Saharan dust load over the middle Atlantic Ocean. Monthly Aerosol Optical Thickness products of Terra MODIS and NCEP-DOE (National Centers for Environmental Predictions) Reanalysis II data are used for this purpose. The relationship between aerosol and cloud droplet parameters is blurred by high sensitivities to aerosol size and composition (Feingold, 2003; McFiggans et al., 2006) as well as meteorological context (Ackerman et al., 2004

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

    Science.gov (United States)

    Jethva, Hiren; Torrres, Omar; Ahn, Changwoo

    2016-05-01

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

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

    Science.gov (United States)

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

    2014-11-01

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

  11. Velocity profiles inside volcanic clouds from three-dimensional scanning microwave dual-polarization Doppler radars

    Science.gov (United States)

    Montopoli, Mario

    2016-07-01

    In this work, velocity profiles within a volcanic tephra cloud obtained by dual-polarization Doppler radar acquisitions with three-dimensional (3-D) mechanical scanning capability are analyzed. A method for segmenting the radar volumes into three velocity regimes: vertical updraft, vertical fallout, and horizontal wind advection within a volcanic tephra cloud using dual-polarization Doppler radar moments is proposed. The horizontal and vertical velocity components within the regimes are retrieved using a novel procedure that makes assumptions concerning the characteristics of the winds inside these regimes. The vertical velocities retrieved are combined with 1-D simulations to derive additional parameters including particle fallout, mass flux, and particle sizes. The explosive event occurred on 23 November 2013 at the Mount Etna volcano (Sicily, Italy), is considered a demonstrative case in which to analyze the radar Doppler signal inside the tephra column. The X-band radar (3 cm wavelength) in the Catania, Italy, airport observed the 3-D scenes of the Etna tephra cloud ~32 km from the volcano vent every 10 min. From the radar-derived vertical velocity profiles of updraft, particle fallout, and horizontal transportation, an exit velocity of 150 m/s, mass flux rate of 1.37 • 107 kg/s, particle fallout velocity of 18 m/s, and diameters of precipitating tephra particles equal to 0.8 cm are estimated on average. These numbers are shown to be consistent with theoretical 1-D simulations of plume dynamics and local reports at the ground, respectively. A thickness of 3 ± 0.36 km for the downwind ash cloud is also inferred by differentiating the radar-derived cloud top and the height of transition between the convective and buoyancy regions, the latter being inferred by the estimated vertical updraft velocity profile. The unique nature of the case study as well as the novelty of the segmentation and retrieval methods presented potentially give new insights into the

  12. A Study of Cloud Processing of Organic Aerosols Using Models and CHAPS Data

    Energy Technology Data Exchange (ETDEWEB)

    Ervens, Barbara [Univ. of Colorado, Boulder, CO (United States)

    2012-01-17

    The main theme of our work has been the identification of parameters that mostly affect the formation and modification of aerosol particles and their interaction with water vapor. Our detailed process model studies led to simplifications/parameterizations of these effects that bridge detailed aerosol information from laboratory and field studies and the need for computationally efficient expressions in complex atmospheric models. One focus of our studies has been organic aerosol mass that is formed in the atmosphere by physical and/or chemical processes (secondary organic aerosol, SOA) and represents a large fraction of atmospheric particulate matter. Most current models only describe SOA formation by condensation of low volatility (or semivolatile) gas phase products and neglect processes in the aqueous phase of particles or cloud droplets that differently affect aerosol size and vertical distribution and chemical composition (hygroscopicity). We developed and applied models of aqueous phase SOA formation in cloud droplets and aerosol particles (aqSOA). Placing our model results into the context of laboratory, model and field studies suggests a potentially significant contribution of aqSOA to the global organic mass loading. The second focus of our work has been the analysis of ambient data of particles that might act as cloud condensation nuclei (CCN) at different locations and emission scenarios. Our model studies showed that the description of particle chemical composition and mixing state can often be greatly simplified, in particular in aged aerosol. While over the past years many CCN studies have been successful performed by using such simplified composition/mixing state assumptions, much more uncertainty exists in aerosol-cloud interactions in cold clouds (ice or mixed-phase). Therefore we extended our parcel model that describes warm cloud formation by ice microphysics and explored microphysical parameters that determine the phase state and lifetime of

  13. Spectrally Enhanced Cloud Objects—A generalized framework for automated detection of volcanic ash and dust clouds using passive satellite measurements: 1. Multispectral analysis

    Science.gov (United States)

    Pavolonis, Michael J.; Sieglaff, Justin; Cintineo, John

    2015-08-01

    While satellites are a proven resource for detecting and tracking volcanic ash and dust clouds, existing algorithms for automatically detecting volcanic ash and dust either exhibit poor overall skill or can only be applied to a limited number of sensors and/or geographic regions. As such, existing techniques are not optimized for use in real-time applications like volcanic eruption alerting and data assimilation. In an effort to significantly improve upon existing capabilities, the Spectrally Enhanced Cloud Objects (SECO) algorithm was developed. The SECO algorithm utilizes a combination of radiative transfer theory, a statistical model, and image processing techniques to identify volcanic ash and dust clouds in satellite imagery with a very low false alarm rate. This fully automated technique is globally applicable (day and night) and can be adapted to a wide range of low earth orbit and geostationary satellite sensors or even combinations of satellite sensors. The SECO algorithm consists of four primary components: conversion of satellite measurements into robust spectral metrics, application of a Bayesian method to estimate the probability that a given satellite pixel contains volcanic ash and/or dust, construction of cloud objects, and the selection of cloud objects deemed to have the physical attributes consistent with volcanic ash and/or dust clouds. The first two components of the SECO algorithm are described in this paper, while the final two components are described in a companion paper.

  14. Aerosol-Cloud Interactions Over the North Pacific Ocean: an Integrated Assessment Using Aircraft, Satellites and a Global Model

    Science.gov (United States)

    Wilcox, E. M.; Mauger, G.; Lariviere, O.; Roberts, G.; Ramanathan, V.; Ming, Y.

    2004-12-01

    Interactions between aerosols and the cloud systems of the North Pacific Ocean were observed by aircraft during the Cloud Indirect Forcing Experiment (CIFEX) in April 2004. The CIFEX project seeks to determine the impact of aerosol indirect effects on the radiative forcing of highly reflective North Pacific clouds under the influence of aerosols traveling across the ocean basin from Asia. Toward this end, CIFEX aircraft observations from the Northeast Pacific of aerosol and cloud microphysics are blended with coincident satellite observations of cloud properties from MODIS and cloud radiative forcing from CERES. The satellite observations are then compared with global model simulations of aerosol indirect forcing over the entire North Pacific basin. During April 2004 the U. Wyoming King Air research aircraft sampled aerosol and cloud microphysical parameters including aerosol and cloud particle sizes and concentrations, cloud liquid water amounts, and cloud structure using the Wyoming Cloud Radar. A range of clean and polluted conditions were observed by the aircraft during the period, in addition to two major Asian dust storm events. CN concentrations below stratus clouds varied from 25 to 300 cm-3. A variety of cloud systems were sampled as well, ranging from shallow stratus and stratocumulus clouds to mixed-phase precipitating cumulus. Under pristine conditions, many shallow clouds were observed to be drizzling, suggesting that Northern Pacific Ocean cloud systems may be highly susceptible to the influence of aerosols. Clouds in this region are responsible for a large cooling of the ocean surface. The magnitude of shortwave cloud radiative cooling exceeded -80 W m-2 over much of the North Pacific during the experiment. Stratus cloud drop concentrations varied from 25 to 150 cm-3 and are correlated with the concentration of accumulation mode aerosols below cloud base. Mean cloud albedos vary from 0.3 to 0.5 for these same clouds, and MODIS observations of cloud

  15. Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions

    Energy Technology Data Exchange (ETDEWEB)

    Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; Ciochetto, David; Niedermeier, Dennis; Ovchinnikov, Mikhail; Shaw, Raymond A.; Yang, Fan

    2016-11-28

    The influence of aerosol concentration on cloud droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud droplet growth and fallout. As aerosol concentration is increased the cloud droplet mean diameter decreases as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics (τc < τt) for high aerosol concentration, and slow microphysics (τc > τt) for low aerosol concentration; here, τc is the phase relaxation time and τt is the turbulence correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as τs-1c-1 + τt-1, and the measurements are in excellent agreement with this finding. This finding underscores the importance of droplet size dispersion for the aerosol indirect effect: increasing aerosol concentration not only suppresses precipitation formation through reduction of the mean droplet diameter, but perhaps more importantly, through narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol / slow microphysics limit are likely of leading importance for precipitation formation.

  16. Study on the volcanic ash cloud with Feng Yun-3 meteorological satellite data

    Science.gov (United States)

    Gong, Cai-lan T.; Jiang, Shan; Hu, Yong; Meng, Peng

    2013-09-01

    Volcano eruption can produce a mass of volcanic ash floating in the air for a long period, which will seriously threaten the aerial planes safety, and cause the air pollution, it could do harm to people's living environment and their health. Take the Iceland Eyjafjallajokull volcano as an example which erupted in April to May 2010, the volcano ash cloud were derived with the visible and infrared scanning radiometer of FengYun-3(FY-3 VIRR) meteorological satellite data. The medium wave infrared (MWIR) and the thermal infrared split windows (THIR-SW) data were used separately. the MODIS THIR-SW data were also be used to retrieve ash cloud to test the results derived from FY-3 VIRR data. It showed that the MWIR was more applicable for the ash cloud retrieving than the THIR-SW with FY-3 VIRR data, and the threshold value should be adjusted to around negative 1 rather than 0 for VIRR THIR-SW data. And the threshold should be adjusted with the THIR-SW of FY-3. The ash cloud radiation and bright temperature(BT), spatial distribution characteristics were also analyzed quantitatively with the two channels data. The study could provide parameters for the prediction of volcanic ash cloud dispersion simulate. When the real temperature of lava flow were high enough, the sensor will show a false bright temperature, how to retrieve the real temperature of the higher lava flow is a problem need to be studied in the future.

  17. Inverse modeling of cloud-aerosol interactions -- Part 1: Detailed response surface analysis

    NARCIS (Netherlands)

    Partridge, D.G.; Vrugt, J.A.; Tunved, P.; Ekman, A.M.L.; Gorea, D.; Sooroshian, A.

    2011-01-01

    New methodologies are required to probe the sensitivity of parameters describing cloud droplet activation. This paper presents an inverse modeling-based method for exploring cloud-aerosol interactions via response surfaces. The objective function, containing the difference between the measured and

  18. Aerosol-cloud-precipitation system as a predator-prey problem.

    Science.gov (United States)

    Koren, Ilan; Feingold, Graham

    2011-07-26

    We show that the aerosol-cloud-precipitation system exhibits characteristics of the predator-prey problem in the field of population dynamics. Both a detailed large eddy simulation of the dynamics and microphysics of a precipitating shallow boundary layer cloud system and a simpler model built upon basic physical principles, reproduce predator-prey behavior with rain acting as the predator and cloud as the prey. The aerosol is shown to modulate the predator-prey response. Steady-state solution to the proposed model shows the known existence of bistability in cloudiness. Three regimes are identified in the time-dependent solutions: (i) the weakly precipitating regime where cloud and rain coexist in a quasi steady state; (ii) the moderately drizzling regime where limit-cycle behavior in the cloud and rain fields is produced; and (iii) the heavily precipitating clouds where collapse of the boundary layer is predicted. The manifestation of predator-prey behavior in the aerosol-cloud-precipitation system is a further example of the self-organizing properties of the system and suggests that exploiting principles of population dynamics may help reduce complex aerosol-cloud-rain interactions to a more tractable problem.

  19. Ground-based remote sensing scheme for monitoring aerosol-cloud interactions

    NARCIS (Netherlands)

    Sarna, K.; Russchenberg, H.W.J.

    2016-01-01

    A new method for continuous observation of aerosol–cloud interactions with ground-based remote sensing instruments is presented. The main goal of this method is to enable the monitoring of the change of the cloud droplet size due to the change in the aerosol concentration. We use high-resolution mea

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

    Directory of Open Access Journals (Sweden)

    K. Pistone

    2015-10-01

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

  1. Cloud condensation nuclei activation of limited solubility organic aerosol

    Science.gov (United States)

    Huff Hartz, Kara E.; Tischuk, Joshua E.; Chan, Man Nin; Chan, Chak K.; Donahue, Neil M.; Pandis, Spyros N.

    The cloud condensation nuclei (CCN) activation of 19 organic species with water solubilities ( Csat) ranging from 10 -4 to 10 2 g solute 100 g -1 H 2O was measured. The organic particles were generated by nebulization of an aqueous or an alcohol solution. Use of alcohols as solvents enables the measurement of low solubility, non-volatile organic CCN activity and reduces the likelihood of residual water in the aerosol. The activation diameter of organic species with very low solubility in water ( Csat<0.3 g 100 g -1 H 2O) is in agreement with Köhler theory using the bulk solubility (limited solubility case) of the organic in water. Many species, including 2-acetylbenzoic acid, aspartic acid, azelaic acid, glutamic acid, homophthalic acid, phthalic acid, cis-pinonic acid, and salicylic acid are highly CCN active in spite of their low solubility (0.3 g 100 g -1 H 2O< Csat<1 g 100 g -1 H 2O), and activate almost as if completely water soluble. The CCN activity of most species is reduced, if the particles are produced using non-aqueous solvents. The existence of the particles in a metastable state at low RH can explain the observed enhancement in CCN activity beyond the levels suggested by their solubility.

  2. Pre-Cloud Aerosol, Cloud Droplet Concentration, and Cloud Condensation Nuclei from the VAMOS Ocean-Cloud-Atmosphere Land Study (VOCALS) Field Campaign First Quarter 2010 ASR Program Metric Report

    Energy Technology Data Exchange (ETDEWEB)

    Kleinman, LI; Springston, SR; Daum, PH; Lee, Y-N; Sedlacek, AJ; Senum, G; Wang, J

    2011-08-31

    In this, the first of a series of Program Metric Reports, we (1) describe archived data from the DOE G-1 aircraft, (2) illustrate several relations between sub-cloud aerosol, CCN, and cloud droplets pertinent to determining the effects of pollutant sources on cloud properties, and (3) post to the data archive an Excel spreadsheet that contains cloud and corresponding sub-cloud data.

  3. Absorption of aerosols above clouds from POLDER/PARASOL measurements and estimation of their Direct Radiative Effect

    Directory of Open Access Journals (Sweden)

    F. Peers

    2014-10-01

    Full Text Available The albedo of clouds and the aerosol absorption are key parameters to evaluate the direct radiative effect of an aerosol layer above clouds. While most of the retrievals of above clouds aerosol characteristics rely on assumptions on the aerosol properties, this study offers a new method to evaluate aerosol and cloud optical properties simultaneously (i.e. aerosol and cloud optical thickness, aerosol single scattering albedo and angström exponent. It is based on multi-angle total and polarized radiances both provided by the A-train satellite instrument POLDER – Polarization and Directionality of Earth Reflectances. The sensitivities brought by each kind of measurements are used in a complementary way. Polarization mostly translates scattering processes and is thus used to estimate the scattering aerosol optical thickness and the aerosol size. On the other hand, total radiances, together with the scattering properties of aerosols, are used to evaluate the absorption optical thickness of aerosols and the cloud optical thickness. In addition, a procedure has been developed to process the shortwave direct radiative effect of aerosols above clouds based on exact modeling. Besides the three case studies (i.e. biomass burning aerosols from Africa and Siberia and Saharan dust, both algorithms have been applied on the South East Atlantic Ocean and results have been averaged through August 2006. The mean direct radiative effect is found to be 33.5 W m−2. Finally, the effect of the heterogeneity of clouds has been investigated and reveals that it affects mostly the retrieval of the cloud optical thickness and not much the aerosols properties. The homogenous cloud assumption used in both the properties retrieval and the DRE processing leads to a slight underestimation of the DRE.

  4. Aerosol Impacts on Microphysical and Radiative Properties of Stratocumulus Clouds in the Southeast Pacific

    Science.gov (United States)

    Twohy, C. H.; Toohey, D. W.; Andrejczuk, M.; Anderson, J. R.; Adams, A.; Lytle, M.; George, R.; Wood, R.; Zuidema, P.; Leon, D.

    2011-12-01

    The southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, cloud droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties along an E-W track from near the Chilean coast to remote areas offshore. Mean statistics from seven flights were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. The effect extends ~800 to 1000 km from shore. The additional particles are mainly sulfates from anthropogenic sources. Liquid water content and drizzle concentration tended to increase with distance from shore, but exhibited much greater variability. Analysis of the droplet residual measurements showed that not only were there more residual nuclei near shore, but that they tended to be larger than those offshore. Single particle analysis over a broad particle size range was used to reveal types and sources of CCN, which were primarily sulfates near shore. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed due to the preferential activation of large aerosol particles. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, which initiate drizzle, contain the largest aerosol particles. However, the scavenging efficiency is not sharp as expected from a simple parcel activation model. A wide range of

  5. Multi-sensor cloud and aerosol retrieval simulator and remote sensing from model parameters - Part 2: Aerosols

    Science.gov (United States)

    Wind, Galina; da Silva, Arlindo M.; Norris, Peter M.; Platnick, Steven; Mattoo, Shana; Levy, Robert C.

    2016-07-01

    The Multi-sensor Cloud Retrieval Simulator (MCRS) produces a "simulated radiance" product from any high-resolution general circulation model with interactive aerosol as if a specific sensor such as the Moderate Resolution Imaging Spectroradiometer (MODIS) were viewing a combination of the atmospheric column and land-ocean surface at a specific location. Previously the MCRS code only included contributions from atmosphere and clouds in its radiance calculations and did not incorporate properties of aerosols. In this paper we added a new aerosol properties module to the MCRS code that allows users to insert a mixture of up to 15 different aerosol species in any of 36 vertical layers.This new MCRS code is now known as MCARS (Multi-sensor Cloud and Aerosol Retrieval Simulator). Inclusion of an aerosol module into MCARS not only allows for extensive, tightly controlled testing of various aspects of satellite operational cloud and aerosol properties retrieval algorithms, but also provides a platform for comparing cloud and aerosol models against satellite measurements. This kind of two-way platform can improve the efficacy of model parameterizations of measured satellite radiances, allowing the assessment of model skill consistently with the retrieval algorithm. The MCARS code provides dynamic controls for appearance of cloud and aerosol layers. Thereby detailed quantitative studies of the impacts of various atmospheric components can be controlled.In this paper we illustrate the operation of MCARS by deriving simulated radiances from various data field output by the Goddard Earth Observing System version 5 (GEOS-5) model. The model aerosol fields are prepared for translation to simulated radiance using the same model subgrid variability parameterizations as are used for cloud and atmospheric properties profiles, namely the ICA technique. After MCARS computes modeled sensor radiances equivalent to their observed counterparts, these radiances are presented as input to

  6. Multi-Sensor Cloud and Aerosol Retrieval Simulator and Remote Sensing from Model Parameters . Part 2; Aerosols

    Science.gov (United States)

    Wind, Galina; Da Silva, Arlindo M.; Norris, Peter M.; Platnick, Steven; Mattoo, Shana; Levy, Robert C.

    2016-01-01

    The Multi-sensor Cloud Retrieval Simulator (MCRS) produces a simulated radiance product from any high-resolution general circulation model with interactive aerosol as if a specific sensor such as the Moderate Resolution Imaging Spectroradiometer (MODIS) were viewing a combination of the atmospheric column and land ocean surface at a specific location. Previously the MCRS code only included contributions from atmosphere and clouds in its radiance calculations and did not incorporate properties of aerosols. In this paper we added a new aerosol properties module to the MCRS code that allows users to insert a mixture of up to 15 different aerosol species in any of 36 vertical layers. This new MCRS code is now known as MCARS (Multi-sensor Cloud and Aerosol Retrieval Simulator). Inclusion of an aerosol module into MCARS not only allows for extensive, tightly controlled testing of various aspects of satellite operational cloud and aerosol properties retrieval algorithms, but also provides a platform for comparing cloud and aerosol models against satellite measurements. This kind of two-way platform can improve the efficacy of model parameterizations of measured satellite radiances, allowing the assessment of model skill consistently with the retrieval algorithm. The MCARS code provides dynamic controls for appearance of cloud and aerosol layers. Thereby detailed quantitative studies of the impacts of various atmospheric components can be controlled. In this paper we illustrate the operation of MCARS by deriving simulated radiances from various data field output by the Goddard Earth Observing System version 5 (GEOS-5) model. The model aerosol fields are prepared for translation to simulated radiance using the same model sub grid variability parameterizations as are used for cloud and atmospheric properties profiles, namely the ICA technique. After MCARS computes modeled sensor radiances equivalent to their observed counterparts, these radiances are presented as input to

  7. Cloud Coverage Enhancement and Nocturnal Drizzle Suppression in Stratocumulus by Aerosols

    Science.gov (United States)

    Ackerman, Andrew S.; Toon, Owen B.; Stevens, David E.; Coakley, James A., Jr.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    Recent satellite observations of ship tracks surprisingly indicate that cloud water decreases with increasing droplet concentrations. However, we find by analyzing detailed simulations of stratocumulus that the reported trend is likely an artifact of sampling, only overcast clouds. The simulations instead show cloud coverage increasing with droplet concentrations, accounting for 25% of cloud albedo increase at moderate droplet concentrations. Our simulations also show that increases in cloud water from drizzle suppression (by increasing droplet concentrations) are favored only at night or at extremely low droplet concentrations, suggesting that the indirect aerosol forcing is overestimated in climate change projections by many general circulation models.

  8. Cloud Coverage Enhancement and Nocturnal Drizzle Suppression in Stratocumulus by Aerosols

    Science.gov (United States)

    Ackerman, Andrew S.; Toon, Owen B.; Stevens, David E.; Coakley, James A., Jr.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    Recent satellite observations of ship tracks surprisingly indicate that cloud water decreases with increasing droplet concentrations. However, we find by analyzing detailed simulations of stratocumulus that the reported trend is likely an artifact of sampling, only overcast clouds. The simulations instead show cloud coverage increasing with droplet concentrations, accounting for 25% of cloud albedo increase at moderate droplet concentrations. Our simulations also show that increases in cloud water from drizzle suppression (by increasing droplet concentrations) are favored only at night or at extremely low droplet concentrations, suggesting that the indirect aerosol forcing is overestimated in climate change projections by many general circulation models.

  9. Retrieval of aerosol microphysical and optical properties above liquid clouds from POLDER/PARASOL polarization measurements

    Directory of Open Access Journals (Sweden)

    F. Waquet

    2013-04-01

    Full Text Available Most of the current aerosol retrievals from passive sensors are restricted to cloud-free scenes, which strongly reduces our ability to monitor the aerosol properties at a global scale and to estimate their radiative forcing. The presence of aerosol above clouds (AAC affects the polarized light reflected by the cloud layer, as shown by the spaceborne measurements provided by the POlarization and Directionality of Earth Reflectances (POLDER instrument on the PARASOL satellite. In a previous work, a first retrieval method was developed for AAC scenes and evaluated for biomass-burning aerosols transported over stratocumulus clouds. The method was restricted to the use of observations acquired at forward scattering angles (90–120° where polarized measurements are highly sensitive to fine-mode particle scattering. Non-spherical particles in the coarse mode, such as mineral dust particles, do not much polarize light and cannot be handled with this method. In this paper, we present new developments that allow retrieving also the properties of mineral dust particles above clouds. These particles do not much polarize light but strongly reduce the polarized cloud bow generated by the liquid cloud layer beneath and observed for scattering angles around 140°. The spectral attenuation can be used to qualitatively identify the nature of the particles (i.e. accumulation mode versus coarse mode, i.e. mineral dust particles versus biomass-burning aerosols, whereas the magnitude of the attenuation is related to the optical thickness of the aerosol layer. We also use the polarized measurements acquired in the cloud bow to improve the retrieval of both the biomass-burning aerosol properties and the cloud microphysical properties. We provide accurate polarized radiance calculations for AAC scenes and evaluate the contribution of the POLDER polarization measurements for the simultaneous retrieval of the aerosol and cloud properties. We investigate various scenes

  10. APhoRISM FP7 project: the Multi-platform volcanic Ash Cloud Estimation (MACE) infrastructure

    Science.gov (United States)

    Merucci, Luca; Corradini, Stefano; Bignami, Christian; Stramondo, Salvatore

    2014-05-01

    APHORISM is an FP7 project that aims to develop innovative products to support the management and mitigation of the volcanic and the seismic crisis. Satellite and ground measurements will be managed in a novel manner to provide new and improved products in terms of accuracy and quality of information. The Multi-platform volcanic Ash Cloud Estimation (MACE) infrastructure will exploit the complementarity between geostationary, and polar satellite sensors and ground measurements to improve the ash detection and retrieval and to fully characterize the volcanic ash clouds from source to the atmosphere. The basic idea behind the proposed method consists to manage in a novel manner, the volcanic ash retrievals at the space-time scale of typical geostationary observations using both the polar satellite estimations and in-situ measurements. The typical ash thermal infrared (TIR) retrieval will be integrated by using a wider spectral range from visible (VIS) to microwave (MW) and the ash detection will be extended also in case of cloudy atmosphere or steam plumes. All the MACE ash products will be tested on three recent eruptions representative of different eruption styles in different clear or cloudy atmospheric conditions: Eyjafjallajokull (Iceland) 2010, Grimsvotn (Iceland) 2011 and Etna (Italy) 2011-2012. The MACE infrastructure will be suitable to be implemented in the next generation of ESA Sentinels satellite missions.

  11. Direct and semi-direct radiative forcing of smoke aerosols over clouds

    Science.gov (United States)

    Wilcox, E. M.

    2012-01-01

    Observations from Earth observing satellites indicate that dark carbonaceous aerosols that absorb solar radiation are widespread in the tropics and subtropics. When these aerosols mix with clouds, there is generally a reduction of cloudiness owing to absorption of solar energy in the aerosol layer. Over the subtropical South Atlantic Ocean, where smoke from savannah burning in southern Africa resides above a persistent deck of marine stratocumulus clouds, radiative heating of the smoke layer leads to a thickening of the cloud layer. Here, satellite observations of the albedo of overcast scenes of 25 km2 size or larger are combined with additional satellite observations of clouds and aerosols to estimate the top-of-atmosphere direct radiative forcing attributable to presence of dark aerosol above bright cloud, and the negative semi-direct forcing attributable to the thickening of the cloud layer. The average positive direct radiative forcing by smoke over an overcast scene is 9.2±6.6 W m-2 for cases with an unambiguous signal of absorbing aerosol over cloud in passive ultraviolet remote sensing observations. However, cloud liquid water path is enhanced by 16.3±7.7 g m-2 across the range of values for sea surface temperature for cases of smoke over cloud. The negative radiative forcing associated with this semi-direct effect of smoke over clouds is estimated to be -5.9±3.5 W m-2. Therefore, the cooling associated with the semi-direct cloud thickening effect compensates for greater than 60 % of the direct radiative effect. Accounting for the frequency of occurrence of significant absorbing aerosol above overcast scenes leads to an estimate of the average direct forcing of 1.0±0.7 W m-2 contributed by these scenes averaged over the subtropical southeast Atlantic Ocean during austral winter. The regional average of the negative semi-direct forcing is -0.7±0.4 W m-2. Therefore, smoke aerosols overlaying the decks of overcast marine stratocumulus clouds considered

  12. Explicit simulation of aerosol physics in a cloud-resolving model

    Directory of Open Access Journals (Sweden)

    A. M. L. Ekman

    2004-02-01

    Full Text Available The role of convection in introducing aerosols and promoting the formation of new particles to the upper troposphere has been examined using a cloud-resolving model coupled with an interactive explicit aerosol module. A baseline simulation suggests good agreement in the upper troposphere between modeled and observed results including concentrations of aerosols in different size ranges, mole fractions of key chemical species, and concentrations of ice particles. In addition, a set of 34 sensitivity simulations has been carried out to investigate the sensitivity of modeled results to the treatment of various aerosol physical and chemical processes in the model. The size distribution of aerosols is proved to be an important factor in determining the aerosols' fate within the convective cloud. Nucleation mode aerosols (0<−d<−5.84 nm are quickly transferred to the larger modes as they grow through coagulation and condensation of H2SO4. Accumulation mode aerosols (d>−31.0 nm are almost completely removed by nucleation (activation of cloud droplets and impact scavenging. However, a substantial part (up to 10% of the boundary layer concentration of the Aitken mode aerosol population (5.84 nm<−d<−31.0 nm reaches the top of the cloud and the free troposphere. These particles may continually survive in the upper troposphere, or over time form ice crystals, both that could impact the atmospheric radiative budget. The sensitivity simulations performed indicate that critical processes in the model causing a substantial change in the upper tropospheric Aitken mode number concentration are coagulation, condensation, nucleation scavenging, nucleation of aerosols and the transfer of aerosol mass and number between different aerosol bins. In particular, for aerosols in the Aitken mode to grow to CCN size, coagulation appears to be more important than condensation. Less important processes are dry deposition, impact scavenging

  13. Enhanced PM2.5 pollution in China due to aerosol-cloud interactions.

    Science.gov (United States)

    Zhao, Bin; Liou, Kuo-Nan; Gu, Yu; Li, Qinbin; Jiang, Jonathan H; Su, Hui; He, Cenlin; Tseng, Hsien-Liang R; Wang, Shuxiao; Liu, Run; Qi, Ling; Lee, Wei-Liang; Hao, Jiming

    2017-06-30

    Aerosol-cloud interactions (aerosol indirect effects) play an important role in regional meteorological variations, which could further induce feedback on regional air quality. While the impact of aerosol-cloud interactions on meteorology and climate has been extensively studied, their feedback on air quality remains unclear. Using a fully coupled meteorology-chemistry model, we find that increased aerosol loading due to anthropogenic activities in China substantially increases column cloud droplet number concentration and liquid water path (LWP), which further leads to a reduction in the downward shortwave radiation at surface, surface air temperature and planetary boundary layer (PBL) height. The shallower PBL and accelerated cloud chemistry due to larger LWP in turn enhance the concentrations of particulate matter with diameter less than 2.5 μm (PM2.5) by up to 33.2 μg m(-3) (25.1%) and 11.0 μg m(-3) (12.5%) in January and July, respectively. Such a positive feedback amplifies the changes in PM2.5 concentrations, indicating an additional air quality benefit under effective pollution control policies but a penalty for a region with a deterioration in PM2.5 pollution. Additionally, we show that the cloud processing of aerosols, including wet scavenging and cloud chemistry, could also have substantial effects on PM2.5 concentrations.

  14. Validation of MODIS aerosol retrievals and evaluation of potential cloud contamination in East Asia

    Institute of Scientific and Technical Information of China (English)

    XIA Xiang-ao; CHEN Hong-bin; WANG Pu-cai

    2004-01-01

    MODIS aerosol retrievals onboard Terra/Aqua and ground truth data obtained from AERONET(Aerosol Robtic Network) solar direct radiance measurements are collocated to evaluate the quality of the former in East Asia. AERONET stations in East Asia are separated into two groups according to their locations and the preliminary validation results for each station. The validation results showed that the accuracy of MODIS aerosol retrievals in East Asia is a little worse than that obtained in other regions such as Eastern U.S., Western Europe, Brazil and so on. The primary reason is due to the improper aerosol model used in MODIS aerosol retrieval algorithm, so it is of significance to characterize aerosol properties properly according to long term ground-based remote sensing or other relevant in situ observations in order to improve MODIS retrievals in East Asia. Cloud contamination is proved to be one of large errors, which is demonstrated by the significant relation between MODIS aerosol retrievals versus cloud fraction, as well as notable improvement of linear relation between satellite and ground aerosol data after potential cloud contamination screened. Hence, it is suggested that more stringent clear sky condition be set in use of MODIS aerosol data. It should be pointed out that the improvement might be offset by other error sources in some cases because of complex relation between different errors. Large seasonal variation of surface reflection and uncertainties associated with it result in large intercepts and random error in MODIS aerosol retrievals in northern inland of East Asia. It remains to be a big problem to retrieve aerosols accurately in inland characterized by relatively larger surface reflection than the requirement in MODIS aerosol retrieval algorithm.

  15. Effects of atmospheric dynamics and aerosols on the fraction of supercooled water clouds

    Science.gov (United States)

    Li, Jiming; Lv, Qiaoyi; Zhang, Min; Wang, Tianhe; Kawamoto, Kazuaki; Chen, Siyu; Zhang, Beidou

    2017-02-01

    Based on 8 years of (January 2008-December 2015) cloud phase information from the GCM-Oriented Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud Product (GOCCP), aerosol products from CALIPSO and meteorological parameters from the ERA-Interim products, the present study investigates the effects of atmospheric dynamics on the supercooled liquid cloud fraction (SCF) during nighttime under different aerosol loadings at global scale to better understand the conditions of supercooled liquid water gradually transforming to ice phase. Statistical results indicate that aerosols' effect on nucleation cannot fully explain all SCF changes, especially in those regions where aerosols' effect on nucleation is not a first-order influence (e.g., due to low ice nuclei aerosol frequency). By performing the temporal and spatial correlations between SCFs and different meteorological factors, this study presents specifically the relationship between SCF and different meteorological parameters under different aerosol loadings on a global scale. We find that the SCFs almost decrease with increasing of aerosol loading, and the SCF variation is closely related to the meteorological parameters but their temporal relationship is not stable and varies with the different regions, seasons and isotherm levels. Obviously negative temporal correlations between SCFs versus vertical velocity and relative humidity indicate that the higher vertical velocity and relative humidity the smaller SCFs. However, the patterns of temporal correlation for lower-tropospheric static stability, skin temperature and horizontal wind are relatively more complex than those of vertical velocity and humidity. For example, their close correlations are predominantly located in middle and high latitudes and vary with latitude or surface type. Although these statistical correlations have not been used to establish a certain causal relationship, our results may provide a unique point of view

  16. Role of aerosols in modulating cloud properties during active-break cycle of Indian summer monsoon

    Science.gov (United States)

    Bhattacharya, A.; Chakraborty, A.; Venugopal, V.

    2016-11-01

    In this study, the weather research and forecast model coupled with chemistry (WRF-Chem), is used to understand the impact of aerosol-cloud interaction during the active-break cycles of the Indian summer monsoon. Two sets of simulations are performed, one with a fixed aerosol concentration (ConstantAero) and the other with an observation-based prescription of the rate of change of aerosol concentration as a function of precipitation (VaryingAero). This prescription is derived based on satellite-retrieved daily rainrate and concurrent observations of aerosol optical depth from aerosol robotic network. The proposed modification is necessitated by the lack of realistic emission estimates over the Indian region as well as the presence of inherent biases in monsoon simulation in WRF-Chem. In the VaryingAero simulation, unlike in the ConstantAero run, we find that the break-to-active monsoon phase has more cloud liquid water (CLW) and less rain efficiency than in the active-to-break phase. This is primarily due to the indirect effect of increased aerosol loading in the break phase. This result is in accordance with the observed behaviour of CLW estimtes from microwave imager (TRMM 2A12) and radar reflectivity (TRMM precipitation radar). We also find that the proposed interactive aerosol loading results in higher spatial variability in CLW and enhances the likelihood of increased cloud cover via formation of larger clouds. The modification also alters the diurnal cycle of clouds in break and break-to-active phases as compared to other phases due to aerosol loading, with a stronger diurnal cycle of upper level clouds in these phases in the VaryingAero model as compared to ConstantAero model.

  17. Role of aerosols in modulating cloud properties during active-break cycle of Indian summer monsoon

    Science.gov (United States)

    Bhattacharya, A.; Chakraborty, A.; Venugopal, V.

    2017-09-01

    In this study, the weather research and forecast model coupled with chemistry (WRF-Chem), is used to understand the impact of aerosol-cloud interaction during the active-break cycles of the Indian summer monsoon. Two sets of simulations are performed, one with a fixed aerosol concentration ( ConstantAero) and the other with an observation-based prescription of the rate of change of aerosol concentration as a function of precipitation ( VaryingAero). This prescription is derived based on satellite-retrieved daily rainrate and concurrent observations of aerosol optical depth from aerosol robotic network. The proposed modification is necessitated by the lack of realistic emission estimates over the Indian region as well as the presence of inherent biases in monsoon simulation in WRF-Chem. In the VaryingAero simulation, unlike in the ConstantAero run, we find that the break-to-active monsoon phase has more cloud liquid water (CLW) and less rain efficiency than in the active-to-break phase. This is primarily due to the indirect effect of increased aerosol loading in the break phase. This result is in accordance with the observed behaviour of CLW estimtes from microwave imager (TRMM 2A12) and radar reflectivity (TRMM precipitation radar). We also find that the proposed interactive aerosol loading results in higher spatial variability in CLW and enhances the likelihood of increased cloud cover via formation of larger clouds. The modification also alters the diurnal cycle of clouds in break and break-to-active phases as compared to other phases due to aerosol loading, with a stronger diurnal cycle of upper level clouds in these phases in the VaryingAero model as compared to ConstantAero model.

  18. Study of Mechanisms of Aerosol Indirect Effects on Glaciated Clouds: Progress during the Project Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Vaughan T. J.

    2013-10-18

    This 3-year project has studied how aerosol pollution influences glaciated clouds. The tool applied has been an 'aerosol-cloud model'. It is a type of Cloud-System Resolving Model (CSRM) modified to include 2-moment bulk microphysics and 7 aerosol species, as described by Phillips et al. (2009, 2013). The study has been done by, first, improving the model and then performing sensitivity studies with validated simulations of a couple of observed cases from ARM. These are namely the Tropical Warm Pool International Cloud Experiment (TWP-ICE) over the tropical west Pacific and the Cloud and Land Surface Interaction Campaign (CLASIC) over Oklahoma. During the project, sensitivity tests with the model showed that in continental clouds, extra liquid aerosols (soluble aerosol material) from pollution inhibited warm rain processes for precipitation production. This promoted homogeneous freezing of cloud droplets and aerosols. Mass and number concentrations of cloud-ice particles were boosted. The mean sizes of cloud-ice particles were reduced by the pollution. Hence, the lifetime of glaciated clouds, especially ice-only clouds, was augmented due to inhibition of sedimentation and ice-ice aggregation. Latent heat released from extra homogeneous freezing invigorated convective updrafts, and raised their maximum cloud-tops, when aerosol pollution was included. In the particular cases simulated in the project, the aerosol indirect effect of glaciated clouds was twice than of (warm) water clouds. This was because glaciated clouds are higher in the troposphere than water clouds and have the first interaction with incoming solar radiation. Ice-only clouds caused solar cooling by becoming more extensive as a result of aerosol pollution. This 'lifetime indirect effect' of ice-only clouds was due to higher numbers of homogeneously nucleated ice crystals causing a reduction in their mean size, slowing the ice-crystal process of snow production and slowing

  19. The Impact of humidity above stratiform clouds on indirect aerosol climate forcing

    Energy Technology Data Exchange (ETDEWEB)

    Ackerman, A S; Kirkpatrick, M P; Stevens, D E; Toon, O B

    2004-12-20

    Some of the global warming effect of anthropogenic greenhouse gases is offset by increased solar reflection from clouds with smaller droplets that form on increased numbers of cloud condensation nuclei in polluted air. The global magnitude of the resulting indirect aerosol climate forcing is estimated to be comparable (and opposed) to the anthropogenic carbon dioxide forcing, but estimates are highly uncertain because of complexities in characterizing the physical process that determine global aerosol and cloud populations and their interactions. Beyond reflecting sunlight more effectively, smaller droplets are less efficient at producing precipitation, and decreased precipitation is expected to result in increased cloud water and cloud cover, further increasing the indirect forcing. Yet polluted marine boundary-layer clouds are not generally observed to hold more water. Here we use model simulations of stratocumulus clouds to show that suppression of precipitation from increased droplet concentrations leads to increased cloud water only when sufficient precipitation reaches the surface, a condition favored when the overlying air is moist. Otherwise, aerosol induced suppression of precipitation enhances entrainment of overlying dry air, thereby reducing cloud water and diminishing the indirect climate forcing.

  20. Model simulations of aerosol effects on clouds and precipitation in comparison with ARM data

    Energy Technology Data Exchange (ETDEWEB)

    Penner, Joyce E. [Univ. of Michigan, Ann Arbor, MI (United States); Zhou, Cheng [Univ. of Michigan, Ann Arbor, MI (United States)

    2017-01-12

    Observation-based studies have shown that the aerosol cloud lifetime effect or the increase of cloud liquid water path (LWP) with increased aerosol loading may have been overestimated in climate models. Here, we simulate shallow warm clouds on 05/27/2011 at the Southern Great Plains (SGP) measurement site established by Department of Energy's Atmospheric Radiation Measurement (ARM) Program using a single column version of a global climate model (Community Atmosphere Model or CAM) and a cloud resolving model (CRM). The LWP simulated by CAM increases substantially with aerosol loading while that in the CRM does not. The increase of LWP in CAM is caused by a large decrease of the autoconversion rate when cloud droplet number increases. In the CRM, the autoconversion rate is also reduced, but this is offset or even outweighed by the increased evaporation of cloud droplets near cloud top, resulting in an overall decrease in LWP. Our results suggest that climate models need to include the dependence of cloud top growth and the evaporation/condensation process on cloud droplet number concentrations.

  1. Indirect radiative forcing of aerosols via water vapor above non-precipitating maritime cumulus clouds

    Directory of Open Access Journals (Sweden)

    M. A. Pfeffer

    2011-10-01

    Full Text Available Aerosol-cloud-water vapor interactions in clean maritime air have been described for different aerosol sources using the WRF-Chem atmospheric model. The simulations were made over the Lesser Antilles in the region of the RICO measurement campaign where the clouds are low, patchy, typical trade-wind cumuli. In this very clean air, sea salt and DMS are found to have greater effects than anthropogenic pollution on the cloud droplets' effective radii and longwave and shortwave outgoing top of atmosphere radiation. The changes in radiation due to each aerosol source are a function of how each source influences aerosol concentration, cloud droplet number concentration, cloud droplet sizes, and water vapor concentration. Changes in outgoing shortwave radiation are due predominantly to changes in the clouds, followed by the direct aerosol effect which is about 2/3 as important, followed by the effects of water vapor which is in turn about 2/3 as important as the direct effect. Changes in outgoing longwave radiation are due predominantly to changes in the clouds, with changes in water vapor being about 1/10 as important. The simulated changes in water vapor concentration are due to the competing effects of aerosol particles being able to both enhance condensation of available water vapor and enhance evaporation of smaller droplets. These changes are independent of precipitation effects as there is essentially no drizzle in the domain. It is expected that the indirect radiative forcing of aerosols via water vapor may be stronger in dirtier and more strongly convective conditions.

  2. Aerosol nucleation and its role for clouds and Earth's radiative forcing in the aerosol-climate model ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    J. Kazil

    2010-05-01

    Full Text Available Nucleation from the gas phase is an important source of aerosol particles in the Earth's atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosol-climate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms for clouds and the Earth's radiative budget. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual nucleation processes to total absorbed solar short-wave radiation via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are −1.15 W/m2 for charged H2SO4/H2O nucleation, −0.235 W/m2 for cluster activation, and −0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is −2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks and interactions in the model. Aerosol nucleation contributes over the oceans with −2.18 W/m2 to total absorbed solar short-wave radiation, compared to −0.37 W/m2 over land. We explain the higher effect of aerosol nucleation on Earth's radiative budget over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of

  3. Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) Final Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Wood, R. [Univ. of Washington, Seattle, WA (United States)

    2016-01-01

    The extensive coverage of low clouds over the subtropical eastern oceans greatly impacts the current climate. In addition, the response of low clouds to changes in atmospheric greenhouse gases and aerosols is a major source of uncertainty, which thwarts accurate prediction of future climate change. Low clouds are poorly simulated in climate models, partly due to inadequate long-term simultaneous observations of their macrophysical and microphysical structure, radiative effects, and associated aerosol distribution in regions where their impact is greatest. The thickness and extent of subtropical low clouds is dependent on tight couplings between surface fluxes of heat and moisture, radiative cooling, boundary layer turbulence, and precipitation (much of which evaporates before reaching the ocean surface and is closely connected to the abundance of cloud condensation nuclei). These couplings have been documented as a result of past field programs and model studies. However, extensive research is still required to achieve a quantitative understanding sufficient for developing parameterizations, which adequately predict aerosol indirect effects and low cloud response to climate perturbations. This is especially true of the interactions between clouds, aerosol, and precipitation. These processes take place in an ever-changing synoptic environment that can confound interpretation of short time period observations.

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

    Science.gov (United States)

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

    2009-09-01

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

  5. Remote Sensing of Aerosols from Satellites: Why Has It Been Do Difficult to Quantify Aerosol-Cloud Interactions for Climate Assessment, and How Can We Make Progress?

    Science.gov (United States)

    Kahn, Ralph A.

    2015-01-01

    The organizers of the National Academy of Sciences Arthur M. Sackler Colloquia Series on Improving Our Fundamental Understanding of the Role of Aerosol-Cloud Interactions in the Climate System would like to post Ralph Kahn's presentation entitled Remote Sensing of Aerosols from Satellites: Why has it been so difficult to quantify aerosol-cloud interactions for climate assessment, and how can we make progress? to their public website.

  6. MIPAS detection of cloud and aerosol particle occurrence in the UTLS with comparison to HIRDLS and CALIOP

    Directory of Open Access Journals (Sweden)

    H. Sembhi

    2012-10-01

    detection of particle distributions in the UTLS, with extinction detection limits above 13 km often better than 10−4 km−1, with values approaching 10−5 km−1 in some cases.

    Comparisons of the new MIPAS results with cloud data from HIRDLS and CALIOP, outside of the poles, establish a good agreement in distributions (cloud and aerosol top heights and occurrence frequencies with an offset between MIPAS and the other instruments of 0.5 km to 1 km between 12 km and 20 km, consistent with vertical oversampling of extended cloud layers within the MIPAS field of view. We conclude that infrared limb sounders provide a very consistent picture of particles in the UTLS, allowing detection limits which are consistent with the lidar observations. Investigations of MIPAS data for the Mount Kasatochi volcanic eruption on the Aleutian Islands and the Black Saturday fires in Australia are used to exemplify how useful MIPAS limb sounding data were for monitoring aerosol injections into the UTLS. It is shown that the new thresholds allowed such events to be much more effectively derived from MIPAS with detection limits for these case studies of 1 × 10−5 km−1 at a wavelength of 12 μm.

  7. Estimating particle sizes, concentrations, and total mass of ash in volcanic clouds using weather radar

    Science.gov (United States)

    Harris, D. M.; Rose, W. I., Jr.

    1983-12-01

    Radar observations of the March 19, 1982 ash eruption of Mount St. Helens were used to estimate the volume of the ash cloud (2000 + or - 500 cu km), the concentration of ash (0.2-0.6 g/cu m), and the total mass of ash erupted (3-10 x 10 to the 11th g). Previously published ashfall data for the May 18, 1980 Mount St. Helens eruption were studied using an inversion technique to estimate 6-hr mean particle concentration (3 g/cu m), the size distribution, the total ashfall mass (5 x 10 to the 14th g), and radar reflectivity factors for the ash cloud. Because volcanic ash clouds with particle concentrations of at least 0.2 g/cu m are produced in very small (in terms of total ashfall mass) eruptions of duration less than 1 min, volcanic ash clouds must be considered an extremely serious hazard to in-flight aircraft, regardless of the eruption magnitude.

  8. Primary marine aerosol-cloud interactions off the coast of California

    Science.gov (United States)

    Modini, R. L.; Frossard, A. A.; Ahlm, L.; Russell, L. M.; Corrigan, C. E.; Roberts, G. C.; Hawkins, L. N.; Schroder, J. C.; Bertram, A. K.; Zhao, R.; Lee, A. K. Y.; Abbatt, J. P. D.; Lin, J.; Nenes, A.; Wang, Z.; Wonaschütz, A.; Sorooshian, A.; Noone, K. J.; Jonsson, H.; Seinfeld, J. H.; Toom-Sauntry, D.; MacDonald, A. M.; Leaitch, W. R.

    2015-05-01

    Primary marine aerosol (PMA)-cloud interactions off the coast of California were investigated using observations of marine aerosol, cloud condensation nuclei (CCN), and stratocumulus clouds during the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) studies. Based on recently reported measurements of PMA size distributions, a constrained lognormal-mode-fitting procedure was devised to isolate PMA number size distributions from total aerosol size distributions and applied to E-PEACE measurements. During the 12 day E-PEACE cruise on the R/V Point Sur, PMA typically contributed less than 15% of total particle concentrations. PMA number concentrations averaged 12 cm-3 during a relatively calmer period (average wind speed 12 m/s1) lasting 8 days, and 71 cm-3 during a period of higher wind speeds (average 16 m/s1) lasting 5 days. On average, PMA contributed less than 10% of total CCN at supersaturations up to 0.9% during the calmer period; however, during the higher wind speed period, PMA comprised 5-63% of CCN (average 16-28%) at supersaturations less than 0.3%. Sea salt was measured directly in the dried residuals of cloud droplets during the SOLEDAD study. The mass fractions of sea salt in the residuals averaged 12 to 24% during three cloud events. Comparing the marine stratocumulus clouds sampled in the two campaigns, measured peak supersaturations were 0.2 ± 0.04% during E-PEACE and 0.05-0.1% during SOLEDAD. The available measurements show that cloud droplet number concentrations increased with >100 nm particles in E-PEACE but decreased in the three SOLEDAD cloud events.

  9. Modeling aerosol-cloud interactions with a self-consistent cloud scheme in a general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Ming, Y; Ramaswamy, V; Donner, L J; Phillips, V T; Klein, S A; Ginoux, P A; Horowitz, L H

    2005-05-02

    This paper describes a self-consistent prognostic cloud scheme that is able to predict cloud liquid water, amount and droplet number (N{sub d}) from the same updraft velocity field, and is suitable for modeling aerosol-cloud interactions in general circulation models (GCMs). In the scheme, the evolution of droplets fully interacts with the model meteorology. An explicit treatment of cloud condensation nuclei (CCN) activation allows the scheme to take into account the contributions to N{sub d} of multiple types of aerosol (i.e., sulfate, organic and sea-salt aerosols) and kinetic limitations of the activation process. An implementation of the prognostic scheme in the Geophysical Fluid Dynamics Laboratory (GFDL) AM2 GCM yields a vertical distribution of N{sub d} characteristic of maxima in the lower troposphere differing from that obtained through diagnosing N{sub d} empirically from sulfate mass concentrations. As a result, the agreement of model-predicted present-day cloud parameters with satellite measurements is improved compared to using diagnosed N{sub d}. The simulations with pre-industrial and present-day aerosols show that the combined first and second indirect effects of anthropogenic sulfate and organic aerosols give rise to a global annual mean flux change of -1.8 W m{sup -2} consisting of -2.0 W m{sup -2} in shortwave and 0.2 W m{sup -2} in longwave, as model response alters cloud field, and subsequently longwave radiation. Liquid water path (LWP) and total cloud amount increase by 19% and 0.6%, respectively. Largely owing to high sulfate concentrations from fossil fuel burning, the Northern Hemisphere mid-latitude land and oceans experience strong cooling. So does the tropical land which is dominated by biomass burning organic aerosol. The Northern/Southern Hemisphere and land/ocean ratios are 3.1 and 1.4, respectively. The calculated annual zonal mean flux changes are determined to be statistically significant, exceeding the model's natural

  10. Cosmic rays, aerosol formation and cloud-condensation nuclei: sensitivities to model uncertainties

    Directory of Open Access Journals (Sweden)

    E. J. Snow-Kropla

    2011-01-01

    Full Text Available The flux of cosmic rays to the atmosphere has been observed to correlate with cloud and aerosol properties. One proposed mechanism for these correlations is the "ion-aerosol clear-air" mechanism where the cosmic rays modulate atmospheric ion concentrations, ion-induced nucleation of aerosols and cloud condensation nuclei (CCN concentrations. We use a global chemical transport model with online aerosol microphysics to explore the dependence of CCN concentrations on the cosmic-ray flux. Expanding upon previous work, we test the sensitivity of the cosmic-ray/CCN connection to several uncertain parameters in the model including primary emissions, Secondary Organic Aerosol (SOA condensation and charge-enhanced condensational growth. The sensitivity of CCN to cosmic rays increases when simulations are run with decreased primary emissions, but show location-dependent behavior from increased amounts of secondary organic aerosol and charge-enhanced growth. For all test cases, the change in the concentration of particles larger than 80 nm between solar minimum (high cosmic ray flux and solar maximum (low cosmic ray flux simulations is less than 0.2%. The change in the total number of particles larger than 10 nm was larger, but always less than 1%. The simulated change in the column-integrated Ångström exponent was negligible for all test cases. Additionally, we test the predicted aerosol sensitivity to week-long Forbush decreases of cosmic rays and find that the maximum change in aerosol properties for these cases is similar to steady-state aerosol differences between the solar maximum and solar minimum. These results provide evidence that the effect of cosmic rays on CCN and clouds through the ion-aerosol clear-sky mechanism is limited by dampening from aerosol processes.

  11. Cosmic rays, aerosol formation and cloud-condensation nuclei: sensitivities to model uncertainties

    Directory of Open Access Journals (Sweden)

    E. J. Snow-Kropla

    2011-04-01

    Full Text Available The flux of cosmic rays to the atmosphere has been reported to correlate with cloud and aerosol properties. One proposed mechanism for these correlations is the "ion-aerosol clear-air" mechanism where the cosmic rays modulate atmospheric ion concentrations, ion-induced nucleation of aerosols and cloud condensation nuclei (CCN concentrations. We use a global chemical transport model with online aerosol microphysics to explore the dependence of CCN concentrations on the cosmic-ray flux. Expanding upon previous work, we test the sensitivity of the cosmic-ray/CCN connection to several uncertain parameters in the model including primary emissions, Secondary Organic Aerosol (SOA condensation and charge-enhanced condensational growth. The sensitivity of CCN to cosmic rays increases when simulations are run with decreased primary emissions, but show location-dependent behavior from increased amounts of secondary organic aerosol and charge-enhanced growth. For all test cases, the change in the concentration of particles larger than 80 nm between solar minimum (high cosmic ray flux and solar maximum (low cosmic ray flux simulations is less than 0.2 %. The change in the total number of particles larger than 10 nm was larger, but always less than 1 %. The simulated change in the column-integrated Ångström exponent was negligible for all test cases. Additionally, we test the predicted aerosol sensitivity to week-long Forbush decreases of cosmic rays and find that the maximum change in aerosol properties for these cases is similar to steady-state aerosol differences between the solar maximum and solar minimum. These results provide evidence that the effect of cosmic rays on CCN and clouds through the ion-aerosol clear-sky mechanism is limited by dampening from aerosol processes.

  12. Integrated approach towards understanding interactions of mineral dust aerosol with warm clouds

    Science.gov (United States)

    Kumar, Prashant

    2011-12-01

    Mineral dust is ubiquitous in the atmosphere and represents a dominant type of particulate matter by mass. Dust particles can serve as cloud condensation nuclei (CCN), giant CCN (GCCN), or ice nuclei (IN), thereby, affecting cloud microphysics, albedo, and lifetime. Despite its well-recognized importance, assessments of dust impacts on clouds and climate remain highly uncertain. This thesis addresses the role of dust as CCN and GCCN with the goal of improving our understanding of dust-warm cloud interactions and their representation in climate models. Most studies to date focus on the soluble fraction of aerosol particles when describing cloud droplet nucleation, and overlook the interactions of the hydrophilic insoluble fraction with water vapor. A new approach to include such interactions (expressed by the process of water vapor adsorption) is explored, by combining multilayer Frenkel-Halsey-Hill (FHH) physical adsorption isotherm and curvature (Kelvin) effects. The importance of adsorption activation theory (FHH-AT) is corroborated by measurements of CCN activity of mineral aerosols generated from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. A new aerosol generation setup for CCN measurements was developed based on a dry generation technique capable of reproducing natural dust aerosol emission. Based on the dependence of critical supersaturation with particle dry diameter, it is found that the FHH-AT is a better framework for describing fresh (and unprocessed) dust CCN activity than the classical Kohler theory (KT). Ion Chromatography (IC) measurements performed on fresh regional dust samples indicate negligible soluble fraction, and support that water vapor adsorption is the prime source of CCN activity in the dust. CCN measurements with the commonly used wet generated mineral aerosol (from atomization of a dust aqueous suspension) are also carried out. Results indicate that the method is subject

  13. Ceilometer for aerosol profiling: comparison with the multiwavelength in the frame of INTERACT (INTERcomparison of Aerosol and Cloud Tracking)

    Science.gov (United States)

    Madonna, Fabio; Vande Hey, Joshua; Rosoldi, Marco; Amato, Francesco; Pappalardo, Gelsomina

    2015-04-01

    Observations of cloud base height are important for meteorology, observations of aerosols are important for air quality applications, observations of cloud cover and aerosols address key uncertainties in climate study. To improve parameterization and uncertainties of numerical models, observations provided by high resolution networks of ground-based instruments are needed. In order to achieve broad, high resolution coverage, low-cost instruments are preferable, though it is essential that the sensitivity, stability, biases and uncertainties of these instruments are well-understood. Despite of their differences from more advanced and more powerful lidars, low construction and operation cost of ceilometer, originally designed for cloud base height monitoring, has fostered their use for the quantitative study of aerosol properties. The large number of ceilometers available worldwide represent a strong motivation to investigate to which extent they can be used to fill the geographical gaps between advanced lidar stations and how their continuous data flow can be linked to existing networks of the advanced lidars, like EARLINET (European Aerosol research LIdar NETwork). In order to make the best use of existing and future ceilometer deployments, ceilometer must be better characterized. This is the purpose of the INTERACT campaign carried out in the frame of ACTRIS Transnational Access activities at CNR-IMAA Atmospheric Observatory (CIAO - 760 m a.s.l., 40.60 N, 15.72 E). In this paper, an overview of the results achieved during the campaign is provided. In particular multi-wavelength Raman lidar measurements are used to investigate the capability of ceilometers to provide reliable information about atmospheric aerosol content through the INTERACT (INTERcomparison of Aerosol and Cloud Tracking) campaign carried out at the CNR-IMAA Atmospheric Observatory (760 m a.s.l., 40.60N, 15.72E), in the framework of ACTRIS (Aerosol Clouds Trace gases Research InfraStructure) FP7

  14. Extending 'Deep Blue' aerosol retrieval coverage to cases of absorbing aerosols above clouds: sensitivity analysis and first case studies

    Energy Technology Data Exchange (ETDEWEB)

    Sayer, Andrew M.; Hsu, C.; Bettenhausen, Corey; Lee, Jae N.; Redemann, Jens; Schmid, Beat; Shinozuka, Yohei

    2016-05-07

    Cases of absorbing aerosols above clouds (AAC), such as smoke or mineral dust, are omitted from most routinely-processed space-based aerosol optical depth (AOD) data products, including those from the Moderate Resolution Imaging Spectroradiometer (MODIS). This study presents a sensitivity analysis and preliminary algorithm to retrieve above-cloud AOD and liquid cloud optical depth (COD) for AAC cases from MODIS or similar

  15. Aerosol properties and meteorological conditions in the city of Buenos Aires, Argentina, during the resuspension of volcanic ash from the Puyehue-Cordón Caulle eruption

    Science.gov (United States)

    Graciela Ulke, Ana; Torres Brizuela, Marcela M.; Raga, Graciela B.; Baumgardner, Darrel

    2016-09-01

    The eruption in June 2011 of the Puyehue-Cordón Caulle Volcanic Complex in Chile impacted air traffic around the Southern Hemisphere for several months after the initial ash emissions. The ash deposited in vast areas of the Patagonian Steppe was subjected to the strong wind conditions prevalent during the austral winter and spring experiencing resuspension over various regions of Argentina. In this study we analyze the meteorological conditions that led to the episode of volcanic ash resuspension which impacted the city of Buenos Aires and resulted in the closure of the two main airports in Buenos Aires area (Ezeiza and Aeroparque) on 16 October 2011. A relevant result is that resuspended material (volcanic ash plus dust) imprints a distinguishable feature within the atmospheric thermodynamic vertical profiles. The thermodynamic soundings show the signature of "pulses of drying" in layers associated with the presence of hygroscopic ash in the atmosphere that has already been reported in similar episodes after volcanic eruptions in other parts of the world. This particular footprint can be used to detect the probable existence of volcanic ash layers. This study also illustrates the utility of ceilometers to detect not only cloud base at airports but also volcanic ash plumes at the boundary layer and up to 7 km altitude. Aerosol properties measured in the city during the resuspension episode indicate the presence of enhanced concentrations of aerosol particles in the boundary layer along with spectral signatures in the measurements at the Buenos Aires AERONET site typical of ash plus dust advected towards the city. The mandatory aviation reports from the National Weather Service about airborne and deposited volcanic ash at the airport near the measurement site (Aeroparque) correlate in time with the enhanced concentrations. The presence of the resuspended material was detected by the CALIOP lidar overpassing the region. Since the dynamics of ash resuspension and

  16. Software and database structure to analyze the relationship between aerosol, clouds and precipitation: SAMAC

    Directory of Open Access Journals (Sweden)

    S. Gagné

    2014-04-01

    Full Text Available The analysis of aircraft-based measurements of clouds are critical for studies of aerosol and clouds. Many such measurements have been taken, but it is difficult to compare such data across instruments, flights and campaigns. We present a new open-source software program, SAMAC (Software for Airborne Measurements of Aerosol and Clouds, that may enable a more generic approach to the analysis of aerosol-cloud-precipitation data. The software offers a faster and standardized approach to the analysis of aircraft measurements of clouds across campaigns. SAMAC is an object-oriented software program in which a cloud is an object. The cloud objects come with built-in methods and properties that allow for the quick generation of basic plots and calculations, which provide a quick view of the data set and may be used to compare clouds and to filter for specific characteristics. Other researchers are encouraged to apply the software to their data and to contribute to its improvement. SAMAC can be downloaded at https://github.com/StephGagne/SAMAC/releases.

  17. Aerosol and cloud microphysics covariability in the northeast Pacific boundary layer estimated with ship-based and satellite remote sensing observations: NE Pacific Aerosol-Cloud Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Painemal, David [Science Systems and Applications, Inc., Hampton Virginia USA; NASA Langley Research Center, Hampton Virginia USA; Chiu, J. -Y. Christine [Department of Meteorology, University of Reading, Reading UK; Minnis, Patrick [NASA Langley Research Center, Hampton Virginia USA; Yost, Christopher [Science Systems and Applications, Inc., Hampton Virginia USA; Zhou, Xiaoli [Department of Atmospheric and Oceanic Sciences, McGill University, Montreal Quebec Canada; Cadeddu, Maria [Environmental Science Division, Argonne National Laboratory, Lemont Illinois USA; Eloranta, Edwin [Space Science and Engineering Center, University of Wisconsin-Madison, Madison Wisconsin USA; Lewis, Ernie R. [Brookhaven National Laboratory, Upton New York USA; Ferrare, Richard [NASA Langley Research Center, Hampton Virginia USA; Kollias, Pavlos [School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook New York USA

    2017-02-27

    Ship measurements collected over the northeast Pacific along transects between the port of Los Angeles (33.7°N, 118.2°W) and Honolulu (21.3°N, 157.8°W) during May to August 2013 were utilized to investigate the covariability between marine low cloud microphysical and aerosol properties. Ship-based retrievals of cloud optical depth (τ) from a Sun photometer and liquid water path (LWP) from a microwave radiometer were combined to derive cloud droplet number concentration Nd and compute a cloud-aerosol interaction (ACI) metric defined as ACICCN = ∂ ln(Nd)/∂ ln(CCN), with CCN denoting the cloud condensation nuclei concentration measured at 0.4% (CCN0.4) and 0.3% (CCN0.3) supersaturation. Analysis of CCN0.4, accumulation mode aerosol concentration (Na), and extinction coefficient (σext) indicates that Na and σext can be used as CCN0.4 proxies for estimating ACI. ACICCN derived from 10 min averaged Nd and CCN0.4 and CCN0.3, and CCN0.4 regressions using Na and σext, produce high ACICCN: near 1.0, that is, a fractional change in aerosols is associated with an equivalent fractional change in Nd. ACICCN computed in deep boundary layers was small (ACICCN = 0.60), indicating that surface aerosol measurements inadequately represent the aerosol variability below clouds. Satellite cloud retrievals from MODerate-resolution Imaging Spectroradiometer and GOES-15 data were compared against ship-based retrievals and further analyzed to compute a satellite-based ACICCN. Satellite data correlated well with their ship-based counterparts with linear correlation coefficients equal to or greater than 0.78. Combined satellite Nd and ship-based CCN0.4 and Na yielded a maximum ACICCN = 0.88–0.92, a value slightly less than the ship-based ACICCN, but still consistent with aircraft-based studies in the eastern Pacific.

  18. Top-down and bottom-up aerosol-cloud closure: towards understanding sources of uncertainty in deriving cloud shortwave radiative flux

    Science.gov (United States)

    Sanchez, Kevin J.; Roberts, Gregory C.; Calmer, Radiance; Nicoll, Keri; Hashimshoni, Eyal; Rosenfeld, Daniel; Ovadnevaite, Jurgita; Preissler, Jana; Ceburnis, Darius; O'Dowd, Colin; Russell, Lynn M.

    2017-08-01

    Top-down and bottom-up aerosol-cloud shortwave radiative flux closures were conducted at the Mace Head Atmospheric Research Station in Galway, Ireland, in August 2015. This study is part of the BACCHUS (Impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) European collaborative project, with the goal of understanding key processes affecting aerosol-cloud shortwave radiative flux closures to improve future climate predictions and develop sustainable policies for Europe. Instrument platforms include ground-based unmanned aerial vehicles (UAVs)1 and satellite measurements of aerosols, clouds and meteorological variables. The ground-based and airborne measurements of aerosol size distributions and cloud condensation nuclei (CCN) concentration were used to initiate a 1-D microphysical aerosol-cloud parcel model (ACPM). UAVs were equipped for a specific science mission, with an optical particle counter for aerosol distribution profiles, a cloud sensor to measure cloud extinction or a five-hole probe for 3-D wind vectors. UAV cloud measurements are rare and have only become possible in recent years through the miniaturization of instrumentation. These are the first UAV measurements at Mace Head. ACPM simulations are compared to in situ cloud extinction measurements from UAVs to quantify closure in terms of cloud shortwave radiative flux. Two out of seven cases exhibit sub-adiabatic vertical temperature profiles within the cloud, which suggests that entrainment processes affect cloud microphysical properties and lead to an overestimate of simulated cloud shortwave radiative flux. Including an entrainment parameterization and explicitly calculating the entrainment fraction in the ACPM simulations both improved cloud-top radiative closure. Entrainment reduced the difference between simulated and observation-derived cloud-top shortwave radiative flux (δRF) by between 25 and 60 W m-2. After accounting for entrainment

  19. Clear-Sky Remote Sensing in the Vicinity of Clouds: What Can Be Learned About Aerosol Changes?

    Science.gov (United States)

    Marshak, Alexander; Varnai, Tamas; Wen, Guoyong

    2010-01-01

    Studies on aerosol direct and indirect effects require a precise separation of cloud-free and cloudy air. However, separation between cloud-free and cloudy areas from remotely-sensed measurements is ambiguous. The transition zone in the regions around clouds often stretches out tens of km, which are neither precisely clear nor precisely cloudy. We study the transition zone between cloud-free and cloudy air using MODerate-resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements. Both instruments show enhanced clear-sky reflectance (MODIS) and clear-sky backscatterer (CALIPSO) near clouds. Analyzing a large dataset of MODIS observations we examine the effect of three-dimensional (3D) radiative interactions between clouds and cloud-free areas, also known as a cloud adjacency effect. Comparing with CALIPSO clear-sky backscatterer measurements, we show that the cloud adjacency effect may be responsible for a large portion of the enhanced clear sky reflectance observed by MODIS. While aerosol particles are responsible for a large part of the near-cloud enhancements in CALIPSO observations, misidentified or undetected cloud particles are also likely to contribute. As a result, both the nature of these particles (cloud vs. aerosol) and the processes creating them need to be clarified using a quantitative assessment of remote sensing limitations in particle detection and identification. "The width and ubiquity of the transition zone near clouds imply that studies of-aerosol-cloud -interactions and aerosol direct radiative effects need to account for aerosol changes near clouds. Not accounted, these changes can cause systematic biases toward smaller aerosol radiative forcing. On the other hand, including aerosol products near clouds despite their uncertainties may overestimate aerosol radiative forcing. Therefore, there is an urgent need for developing methods that can assess and account for

  20. A model study of Fuego volcanic aerosol dispersion in the lower stratosphere

    Science.gov (United States)

    Remsberg, E. E.; Turner, R. E.; Butler, C. F.

    1982-01-01

    A zonally averaged time-dependent primitive equation model is used to simulate the dispersion of both a carbon 14 injection and the volcanic aerosol from the 1974 Fuego eruption. It is noted that both injections occurred at low latitudes to midlatitudes in the Northern Hemisphere. The eddy flux terms, which account for the major portion of the transport in the lower stratosphere of this model, are specified in a manner similar to that of Harwood and Pyle (1975). Comparisons with data underline the ability of the model to simulate the vertical character of the tracer while maintaining reasonable meridional transport times. For the aerosol study, the simulated 1/e decay time at 37 deg N and for the 16- to 21-km altitude region is 9 months, whereas lidar measurements at the same latitude give a decay time of 8 months. The simulated vertical width at half-maximum for the aerosol tracer at 37 deg N and 19 deg N and for 6 months after the event possesses values of 5.0 km and 3.6 km, respectively, whereas the observed lidar values are 4.4 km and 3.0 km, respectively. The tracer transport to the Southern Hemisphere also is in qualitative agreement with the limited data that are available.

  1. Process-model simulations of cloud albedo enhancement by aerosols in the Arctic

    Science.gov (United States)

    Kravitz, Ben; Wang, Hailong; Rasch, Philip J.; Morrison, Hugh; Solomon, Amy B.

    2014-01-01

    A cloud-resolving model is used to simulate the effectiveness of Arctic marine cloud brightening via injection of cloud condensation nuclei (CCN), either through geoengineering or other increased sources of Arctic aerosols. An updated cloud microphysical scheme is employed, with prognostic CCN and cloud particle numbers in both liquid and mixed-phase marine low clouds. Injection of CCN into the marine boundary layer can delay the collapse of the boundary layer and increase low-cloud albedo. Albedo increases are stronger for pure liquid clouds than mixed-phase clouds. Liquid precipitation can be suppressed by CCN injection, whereas ice precipitation (snow) is affected less; thus, the effectiveness of brightening mixed-phase clouds is lower than for liquid-only clouds. CCN injection into a clean regime results in a greater albedo increase than injection into a polluted regime, consistent with current knowledge about aerosol–cloud interactions. Unlike previous studies investigating warm clouds, dynamical changes in circulation owing to precipitation changes are small. According to these results, which are dependent upon the representation of ice nucleation processes in the employed microphysical scheme, Arctic geoengineering is unlikely to be effective as the sole means of altering the global radiation budget but could have substantial local radiative effects. PMID:25404677

  2. In-situ Measurements of Aerosol-Cloud-Precipitation Interactions During the 2011 E-PEACE Campaign: Case Studies of Clouds Perturbed by Ship Emissions

    Science.gov (United States)

    Metcalf, A. R.; Sorooshian, A.; Craven, J. S.; Coggon, M.; Lin, J. J.; Wang, Z.; Shingler, T.; Song, S.; Jung, E.; Albrecht, B. A.; Jonsson, H.; Nenes, A.; Seinfeld, J.

    2011-12-01

    The Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter probed aerosol-cloud-precipitation interactions during the 2011 Eastern-Pacific Emitted Aerosol Cloud Experiment (E-PEACE) off the central coast of California. During the project, ship exhaust in a major north-south shipping lane used by large cargo and tanker ships off the coast of Monterey, CA was probed in order to study its effect on the marine stratocumulus commonly found in the summer months. During the course of a single experiment, fresh ship exhaust was sampled near the ship and followed downwind for approximately 20 miles before ascending to sample the plume at multiple heights in cloud. The chemical and physical properties of the ship exhaust was characterized below cloud by an Aerosol Mass Spectrometer (AMS), a Cloud Condensation Nuclei Counter (CCNC), multiple Condensation Particle Counters (CPCs), parallel Differential Mobility Analyzers (DMAs), a Passive Cavity Aerosol Spectrometer Probe, a Single Particle Soot Photometer (SP2), and a Photoacoustic Soot Spectrometer (PASS3). An upward-facing Doppler cloud radar (3 mm wavelength) captured the vertical microphysical and velocity structure of the clouds. The cloud droplet number and size distributions were characterized within the cloud with a Cloud, Aerosol, and Precipitation Spectrometer, a Forward Scattering Spectrometer Probe, and a Phase Doppler Interferometer, as were the cloud droplet nuclei chemistry and physical properties by several instruments (AMS, DMA, PASS3, SP2, CCNC, and CPC) sampling behind a Counterflow Virtual Impactor inlet. This presentation provides an overview of our findings.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-06-15

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

  4. A new WRF-Chem treatment for studying regional scale impacts of cloud-aerosol interactions in parameterized cumuli

    Science.gov (United States)

    Berg, L. K.; Shrivastava, M.; Easter, R. C.; Fast, J. D.; Chapman, E. G.; Liu, Y.

    2014-04-01

    A new treatment of cloud-aerosol interactions within parameterized shallow and deep convection has been implemented in WRF-Chem that can be used to better understand the aerosol lifecycle over regional to synoptic scales. The modifications to the model to represent cloud-aerosol interactions include treatment of the cloud droplet number mixing ratio; key cloud microphysical and macrophysical parameters (including the updraft fractional area, updraft and downdraft mass fluxes, and entrainment) averaged over the population of shallow clouds, or a single deep convective cloud; and vertical transport, activation/resuspension, aqueous chemistry, and wet removal of aerosol and trace gases in warm clouds. These changes have been implemented in both the WRF-Chem chemistry packages as well as the Kain-Fritsch cumulus parameterization that has been modified to better represent shallow convective clouds. Preliminary testing of the modified WRF-Chem has been completed using observations from the Cumulus Humilis Aerosol Processing Study (CHAPS) as well as a high-resolution simulation that does not include parameterized convection. The simulation results are used to investigate the impact of cloud-aerosol interactions on regional scale transport of black carbon (BC), organic aerosol (OA), and sulfate aerosol. Based on the simulations presented here, changes in the column integrated BC can be as large as -50% when cloud-aerosol interactions are considered (due largely to wet removal), or as large as +40% for sulfate in non-precipitating conditions due to the sulfate production in the parameterized clouds. The modifications to WRF-Chem version 3.2.1 are found to account for changes in the cloud drop number concentration (CDNC) and changes in the chemical composition of cloud-drop residuals in a way that is consistent with observations collected during CHAPS. Efforts are currently underway to port the changes described here to WRF-Chem version 3.5, and it is anticipated that they

  5. CHASER: An Innovative Satellite Mission Concept to Measure the Effects of Aerosols on Clouds and Climate

    Science.gov (United States)

    Renno, N.; Williams, E.; Rosenfeld, D.; Fischer, D.; Fischer, J.; Kremic, T.; Agrawal, A.; Andreae, M.; Bierbaum, R.; Blakeslee, R.; Boerner, A.; Bowles, N.; Christian, H.; Dunion, J.; Horvath, A.; Huang, X.; Khain, A.; Kinne, S.; Lemos, M.-C.; Penner, J.

    2012-04-01

    The formation of cloud droplets on aerosol particles, technically known as the activation of cloud condensation nuclei (CCN), is the fundamental process driving the interactions of aerosols with clouds and precipitation. Knowledge of these interactions is foundational to our understanding of weather and climate. The Intergovernmental Panel on Climate Change (IPCC) and the Decadal Survey (NRC 2007) indicate that the uncertainty in how clouds adjust to aerosol perturbations dominates the uncertainty in the overall quantification of the radiative forcing attributable to human activities. The Clouds, Hazards, and Aerosols Survey for Earth Researchers (CHASER) mission concept responds to the IPCC and Decadal Survey concerns by studying the activation of CCN and their interactions with clouds and storms. CHASER proposes to revolutionize our understanding of the interactions of aerosols with clouds by making the first global measurements of the fundamental physical entity linking them: activated cloud condensation nuclei. The CHASER mission was conceptualized to measure all quantities necessary for determining the interactions of aerosols with clouds and storms. Measurements by current satellites allow the determination of crude profiles of cloud particle size but not of the activated CCN that seed them. CHASER uses a new technique (Freud et al. 2011; Rosenfeld et al. 2012) and high-heritage instruments to produce the first global maps of activated CCN and the properties of the clouds associated with them. CHASER measures the CCN concentration and cloud thermodynamic forcing simultaneously, allowing their effects to be distinguished. Changes in the behavior of a group of weather systems in which only one of the quantities varies (a partial derivative of the intensity with the desirable quantity) allow the determination of each effect statistically. The high uncertainties of current climate predictions limit their much-needed use in decision-making. CHASER mitigates this

  6. Extending "Deep Blue" aerosol retrieval coverage to cases of absorbing aerosols above clouds: Sensitivity analysis and first case studies

    Science.gov (United States)

    Sayer, A. M.; Hsu, N. C.; Bettenhausen, C.; Lee, J.; Redemann, J.; Schmid, B.; Shinozuka, Y.

    2016-05-01

    Cases of absorbing aerosols above clouds (AACs), such as smoke or mineral dust, are omitted from most routinely processed space-based aerosol optical depth (AOD) data products, including those from the Moderate Resolution Imaging Spectroradiometer (MODIS). This study presents a sensitivity analysis and preliminary algorithm to retrieve above-cloud AOD and liquid cloud optical depth (COD) for AAC cases from MODIS or similar sensors, for incorporation into a future version of the "Deep Blue" AOD data product. Detailed retrieval simulations suggest that these sensors should be able to determine AAC AOD with a typical level of uncertainty ˜25-50% (with lower uncertainties for more strongly absorbing aerosol types) and COD with an uncertainty ˜10-20%, if an appropriate aerosol optical model is known beforehand. Errors are larger, particularly if the aerosols are only weakly absorbing, if the aerosol optical properties are not known, and the appropriate model to use must also be retrieved. Actual retrieval errors are also compared to uncertainty envelopes obtained through the optimal estimation (OE) technique; OE-based uncertainties are found to be generally reasonable for COD but larger than actual retrieval errors for AOD, due in part to difficulties in quantifying the degree of spectral correlation of forward model error. The algorithm is also applied to two MODIS scenes (one smoke and one dust) for which near-coincident NASA Ames Airborne Tracking Sun photometer (AATS) data were available to use as a ground truth AOD data source, and found to be in good agreement, demonstrating the validity of the technique with real observations.

  7. Extending "Deep Blue" Aerosol Retrieval Coverage to Cases of Absorbing Aerosols Above Clouds: Sensitivity Analysis and First Case Studies

    Science.gov (United States)

    Sayer, A. M.; Hsu, N. C.; Bettenhausen, C.; Lee, J.; Redemann, J.; Schmid, B.; Shinozuka, Y.

    2016-01-01

    Cases of absorbing aerosols above clouds (AACs), such as smoke or mineral dust, are omitted from most routinely processed space-based aerosol optical depth (AOD) data products, including those from the Moderate Resolution Imaging Spectroradiometer (MODIS). This study presents a sensitivity analysis and preliminary algorithm to retrieve above-cloud AOD and liquid cloud optical depth (COD) for AAC cases from MODIS or similar sensors, for incorporation into a future version of the "Deep Blue" AOD data product. Detailed retrieval simulations suggest that these sensors should be able to determine AAC AOD with a typical level of uncertainty approximately 25-50 percent (with lower uncertainties for more strongly absorbing aerosol types) and COD with an uncertainty approximately10-20 percent, if an appropriate aerosol optical model is known beforehand. Errors are larger, particularly if the aerosols are only weakly absorbing, if the aerosol optical properties are not known, and the appropriate model to use must also be retrieved. Actual retrieval errors are also compared to uncertainty envelopes obtained through the optimal estimation (OE) technique; OE-based uncertainties are found to be generally reasonable for COD but larger than actual retrieval errors for AOD, due in part to difficulties in quantifying the degree of spectral correlation of forward model error. The algorithm is also applied to two MODIS scenes (one smoke and one dust) for which near-coincident NASA Ames Airborne Tracking Sun photometer (AATS) data were available to use as a ground truth AOD data source, and found to be in good agreement, demonstrating the validity of the technique with real observations.

  8. Investigating relationships between aerosol optical depth and cloud fraction using satellite, aerosol reanalysis and general circulation model data

    Directory of Open Access Journals (Sweden)

    B. S. Grandey

    2013-03-01

    Full Text Available Strong positive relationships between cloud fraction (fc and aerosol optical depth (τ have been reported. Data retrieved from the MODerate resolution Imaging Spectroradiometer (MODIS instrument show positive fc–τ relationships across most of the globe. A global mean fc increase of approximately 0.2 between low and high τ conditions is found for both ocean and land. However, these relationships are not necessarily due to cloud–aerosol interactions. Using state-of-the-art Monitoring Atmospheric Composition and Climate (MACC reanalysis-forecast τ data, which should be less affected by retrieval artefacts, it is demonstrated that a large part of the observed fc–τ signal may be due to cloud contamination of satellite-retrieved τ. For longer MACC forecast time steps of 24 h, which likely contain less cloud contamination, some negative fc–τ relationships are found. The global mean fc increase between low and high τ conditions is reduced to 0.1, suggesting that cloud contamination may account for approximately one half of the satellite-retrieved increase in fc. ECHAM5-HAM general circulation model (GCM simulations further demonstrate that positive fc–τ relationships may arise due to covariation with relative humidity. Widespread negative simulated fc–τ relationships in the tropics are shown to arise due to scavenging of aerosol by convective precipitation. Wet scavenging events are likely poorly sampled in satellite-retrieved data, because the properties of aerosol below clouds cannot be retrieved. Quantifying the role of wet scavenging, and assessing GCM representations of this important process, remains a challenge for future observational studies of aerosol–cloud–precipitation interactions.

  9. Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Fast, J. D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Berg, L. K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Burleyson, C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Fan, J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Feng, Z. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hagos, S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Huang, M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Guenther, A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Laskin, A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Ovchinnikov, M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shilling, J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shrivastava, M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Xiao, H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zaveri, R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zelenyuk-Imre, A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kuang, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wang, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Smith, J. [University of California-Irvine; Turner, D. [National Severe Storms Laboratory; Gentine, P. [Columbia Univ., New York, NY (United States)

    2017-05-01

    Cumulus convection is an important component in the atmospheric radiation budget and hydrologic cycle over the southern Great Plains and over many regions of the world, particularly during the summertime growing season when intense turbulence induced by surface radiation couples the land surface to clouds. Current convective cloud parameterizations contain uncertainties resulting in part from insufficient coincident data that couples cloud macrophysical and microphysical properties to inhomogeneities in land surface, boundary layer, and aerosol properties. The Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) campaign was designed to provide a detailed set of measurements that are needed to obtain a more complete understanding of the lifecycle of shallow clouds by coupling cloud macrophysical and microphysical properties to land surface properties, ecosystems, and aerosols. Some of the land-atmosphere-cloud interactions that can be studied using HI-SCALE data are shown in Figure 1. HI-SCALE consisted of two 4-week intensive operation periods (IOPs), one in the spring (April 24-May 21) and the other in the late summer (August 28-September 24) of 2016, to take advantage of different stages of the plant lifecycle, the distribution of “greenness” for various types of vegetation in the vicinity of the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility Southern Great Plains (SGP) site, and aerosol properties that vary during the growing season. As expected, satellite measurements indicated that the Normalized Difference Vegetation Index (NDVI) was much “greener” in the vicinity of the SGP site during the spring IOP than the late summer IOP as a result of winter wheat maturing in the spring and being harvested in the early summer. As shown in Figure 2, temperatures were cooler than average and soil moisture was high during the spring IOP, while temperatures were warmer than average and

  10. Improvement of Representation of the Cloud-Aerosol Interaction in Large-Scale Models

    Energy Technology Data Exchange (ETDEWEB)

    Khain, Alexander [Hebrew Univ. of Jerusalem (Israel); Phillips, Vaughan [Lund Univ. (Sweden); Pinsky, Mark [Hebrew Univ. of Jerusalem (Israel); Lynn, Barry [Hebrew Univ. of Jerusalem (Israel)

    2016-12-20

    The main achievements reached under the DOE award DE-SC0006788 are described. It is shown that the plan of the Project is completed. Unique results concerning cloud-aerosol interaction are obtained. It is shown that aerosols affect intensity of hurricanes. The effects of small aerosols on formation of ice in anvils of deep convective clouds are discovered, for the first time the mechanisms of drizzle formation are found and described quantitatively. Mechanisms of formation of warm rain are clarified and the dominating role of adiabatic processes and turbulence are stressed. Important results concerning the effects of sea spray on intensity of clouds and tropical cyclones are obtained. A novel methods of calculation of hail formation has been developed and implemented.

  11. 3D Cloud Radiative Effects on Aerosol Optical Thickness Retrievals in Cumulus Cloud Fields in the Biomass Burning Region in Brazil

    Science.gov (United States)

    Wen, Guo-Yong; Marshak, Alexander; Cahalan, Robert F.

    2004-01-01

    Aerosol amount in clear regions of a cloudy atmosphere is a critical parameter in studying the interaction between aerosols and clouds. Since the global cloud cover is about 50%, cloudy scenes are often encountered in any satellite images. Aerosols are more or less transparent, while clouds are extremely reflective in the visible spectrum of solar radiation. The radiative transfer in clear-cloudy condition is highly three- dimensional (3D). This paper focuses on estimating the 3D effects on aerosol optical thickness retrievals using Monte Carlo simulations. An ASTER image of cumulus cloud fields in the biomass burning region in Brazil is simulated in this study. The MODIS products (i-e., cloud optical thickness, particle effective radius, cloud top pressure, surface reflectance, etc.) are used to construct the cloud property and surface reflectance fields. To estimate the cloud 3-D effects, we assume a plane-parallel stratification of aerosol properties in the 60 km x 60 km ASTER image. The simulated solar radiation at the top of the atmosphere is compared with plane-parallel calculations. Furthermore, the 3D cloud radiative effects on aerosol optical thickness retrieval are estimated.

  12. Influence of meteorological conditions on correlation between aerosol and cloud in summer

    Science.gov (United States)

    Shi, Lamei; Zhang, Jiahua; Yao, Fengmei; Han, Xinlei; Igbawua, Tertsea; Liu, Yuqin; Zhang, Da

    2017-04-01

    Aerosols can affect the atmospheric radiation balance through direct and indirect effects. The formation and development of cloud and precipitation influenced by aerosols differ significantly from each other in different meteorological conditions. In this work, we used the MODIS's daily Aerosol Optical Depth (AOD), Cloud Effective Radius (CER), Cloud Top Temperature (CTT), Cloud Water Path (CWP) and ECMWF's Relative Humidity (RH), Vertical Velocity (VV) and Horizontal Wind (HW) (from 2005 to 2008) to reveal the influence of meteorological factors on the distribution of aerosols, and also the correlation between aerosols and clouds. The study was designed in such a way that, the RH, VV, Upwind (UW), Downwind (DW) and CWP were divided into several intervals, to quantify the relationship between AOD and CER by controlling one single variable or two comprehensive variables over the mountains and plains. At the same time, the effect of wind speed and direction on polluted conditions was analyzed through the superposed spatial distribution map of wind and AOD. The conclusions are as follows: (1) The wind coming from mountains dispelled aerosols while the sea breeze invigorated aerosols, and the upwind showed a markedly negative relevance with AOD. (2) The strong upwind contributed to the positive relationship between AOD and CER, and the correlation rose by 38% after excluding the condition where CWP < 34 g/m2. (3) For the horizontal wind, only the zonal wind over the plains had obvious effects on the correlation, while the meridonal wind did not show evident influence. (4) For the plains, when CWP values were within the interval of 0-34 g/m2 and 74-150 g/m2, the correlation was positive, while in 34-74 g/m2, it was negative. However, it is generally positive either over the mountains or in clean conditions. Moreover, the influence of RH on the correlation was consistent with that of CWP.

  13. Investigating marine stratocumulus with a fully coupled cloud-aerosol scheme in a WRF/Chem Large Eddy Simulation

    Science.gov (United States)

    Kazil, J.; Wang, H.; Feingold, G.

    2009-12-01

    Drizzle in stratocumulus clouds is triggered by low concentrations of cloud condensation nuclei (CCN), and concurrently acts as a sink of CCN. The progression of this cloud-aerosol feedback may result in a transition in marine boundary layer dynamics and cloud structure; Closed cell circulation, characterized by a solid stratocumulus layer, may transition into an open cellular mode featuring low cloud fraction. Aerosol sources may balance the loss of CCN from drizzle, and delay or prevent the emergence of open cell circulation. Such sources include particle emissions from the sea surface, entrainment of aerosol from the free troposphere into the cloud deck, advection from land sources, and aerosol nucleation. In order to investigate the role of aerosol sources and processes in the transition between these two states, we have coupled in detail aerosol processes, cloud microphysics, and gas and aqueous chemistry in the WRF/Chem model. We operate WRF/Chem in Large Eddy Simulation mode. Aerosol nucleation is described with a sulfuric acid/water scheme based on laboratory measurements of the nucleation process. Here we present first results on the role of aerosol nucleation for cloud properties and drizzle formation in pristine conditions of the South-East Pacific region, and in polluted conditions.

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

    Science.gov (United States)

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

    2017-02-01

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

  15. Aerosol and Cloud-Nucleating Particle Observations during an Atmospheric River Event

    Science.gov (United States)

    DeMott, P. J.; McCluskey, C. S.; Petters, M.; Suski, K. J.; Levin, E. J.; Hill, T. C. J.; Atwood, S. A.; Schill, G. P.; Rocci, K.; Boose, Y.; Martin, A.; Cornwell, G.; Al-Mashat, H.; Moore, K.; Prather, K. A.; Rothfuss, N.; Taylor, H.; Leung, L. R.; Tomlinson, J. M.; Mei, F.; Hubbe, J. M.; Rosenfeld, D.; Spackman, J. R.; Fairall, C. W.; Creamean, J.; White, A. B.; Kreidenweis, S. M.

    2015-12-01

    The multi-agency CalWater 2015 project occurred over North Central CA and the Eastern Pacific during January to March 2015 (Spackman et al., this session). The goals of the campaign were to document the structure of atmospheric rivers (ARs) that deliver much of the water vapor associated with major winter storms along the U.S. West Coast and to investigate the modulating effect of aerosols on precipitation. Aerosol sources that may influence orographic cloud properties for air lifted over the mountains in California in winter include pollution, biomass burning, soil dusts and marine aerosols, but their roles will also be influenced by transport, vertical stratification, and scavenging processes. We present results from a comprehensive study of aerosol distributions, compositions, and cloud nucleating properties during an intense winter storm during February 2015, including data from an NSF-supported measurement site at Bodega Bay, from the DOE-ARM Cloud Aerosol Precipitation Experiment that included sampling on the NOAA RV Ron Brown offshore and the G-1 aircraft over ocean and land, and with context provided by other NOAA aircraft and remote sensing facilities. With a special focus on the coastal site, we discuss changes in aerosol distributions, aerosol hygroscopicity, and number concentrations of fluorescent particles, cloud condensation nuclei (CCN), and ice nucleating particles (INPs) during the AR event. We compare with periods preceding and following the event. For example, total aerosol number and surface area concentrations at below 0.5 μm diameter decreased from typical values of a few thousand cm-3 and 100 μm2 cm-3, respectively, to a few hundred cm-3 and 10 μm2cm-3 at Bodega Bay during the AR event. CCN concentrations were similarly lower, but hygroscopicity parameter (kappa) increased from typical values of 0.2 to values > 0.5 during the AR.INP and fluorescent particle number concentrations were generally lower during the AR event than at any other

  16. Comparison of aerosol optical properties above clouds between POLDER and AeroCom models over the South East Atlantic Ocean during the fire season

    OpenAIRE

    F. Peers; Bellouin, Nicolas; F. Waquet; F. Ducos; P. Goloub; Mollard, J.; Myhre, G; R. B. Skeie; T. Takemura; Tanré, D.; F. Thieuleux; Zhang, K

    2016-01-01

    Aerosol properties above clouds have been retrieved over the South East Atlantic Ocean during the fire season 2006 using satellite observations from POLDER (Polarization and Directionality of Earth Reflectances). From June to October, POLDER has observed a mean Above-Cloud Aerosol Optical Thickness (ACAOT) of 0.28 and a mean Above-Clouds Single Scattering Albedo (ACSSA) of 0.87 at 550nm. These results have been used to evaluate the simulation of aerosols above clouds in five Aerosol Compariso...

  17. Lidar profiling of aerosols and clouds for regional climate and pollution research

    Science.gov (United States)

    Devara, Panuganti C. S.; Raj, Pulidindi E.; Pandithurai, G.; Dani, Kundan K.; Saha, Sanjoy K.; Sonbawne, Sunil M.

    2006-12-01

    The space-time variability of aerosol inhomogeneities provides unique information on atmospheric behavior needed for climate and environmental research and operational programs. An additional indirect forcing from aerosols results from their involvement in nucleation and growth of cloud droplets, reducing droplet size and thereby potentially influencing cloud albedo. These studies have particular significance over tropics where the convective and dynamical processes associated with high-altitude thunderstorms greatly affect the vertical distributions of aerosols and pre-cursor gases. As the anthropogenic share of the total aerosol loading is quite substantial over many parts of the world, it is essential to monitor the aerosol features systematically over longer time scales. Such observations are very important for understanding the coupling processes that exist between physico-chemical, radiative, dynamical and biological phenomena in the Earth's environment, and provide valuable input information for modeling and simulation studies of climate and air quality. The multi-year aerosol number density data acquired during October 1986-September 2000 with a computer-controlled lidar at the Indian Institute of Tropical Meteorology (IITM), Pune, an urban station in India have been utilized to investigate (i) climate variability, (ii) cloud macro-physical parameters and (iii) environmental pollution. The results reveal a long-term trend in aerosol loading, single and multiple layer clouds with low cloud-base during the south-west monsoon months, and high pollution potential during winter late evenings. The trends in aerosol loading and air quality are found to be changing from year to year depending upon meteorological parameters (precipitation in particular). Some of these parameters have also been compared with co-located complementary facilities such as solar radiometers. In order to enlarge the scope of these studies, a dual polarization micro pulse lidar (DPMPL) has

  18. Dimethyl sulfide control of the clean summertime Arctic aerosol and cloud

    Directory of Open Access Journals (Sweden)

    W. Richard Leaitch

    2013-12-01

    Full Text Available Abstract One year of aerosol particle observations from Alert, Nunavut shows that new particle formation (NPF is common during clean periods of the summertime Arctic associated with attendant low condensation sinks and with the presence of methane sulfonic acid (MSA, a product of the atmospheric oxidation of dimethyl sulfide (DMS. The clean aerosol time periods, defined using the distribution of refractory black carbon number concentrations, increase in frequency from June through August as the anthropogenic influence dwindles. During the clean periods, the number concentrations of particles that can act as cloud condensation nuclei (CCN increase from June through August suggesting that DMS, and possibly other oceanic organic precursors, exert significant control on the Arctic summertime submicron aerosol, a proposition supported by simulations from the GEOS-Chem-TOMAS global chemical transport model with particle microphysics. The CCN increase for the clean periods across the summer is estimated to be able to increase cloud droplet number concentrations (CDNC by 23–44 cm-3, comparable to the mean CDNC increase needed to yield the current global cloud albedo forcing from industrial aerosols. These results suggest that DMS may contribute significantly to modification of the Arctic summer shortwave cloud albedo, and they offer a reference for future changes in the Arctic summer aerosol.

  19. Performance of McRAS-AC in the GEOS-5 AGCM: aerosol-cloud-microphysics, precipitation, cloud radiative effects, and circulation

    Directory of Open Access Journals (Sweden)

    Y. C. Sud

    2012-06-01

    Full Text Available A revised version of the Microphysics of clouds with Relaxed Arakawa-Schubert and Aerosol-Cloud interaction scheme (McRAS-AC including, among others, the Barahona and Nenes ice nucleation parameterization, is implemented in the GEOS-5 AGCM. Various fields from a 10-yr long integration of the AGCM with McRAS-AC were compared with their counterparts from an integration of the baseline GEOS-5 AGCM using satellite data as observations. Generally McRAS-AC simulations have smaller biases in cloud fields and cloud radiative effects over most of the regions of the Earth than the baseline GEOS-5 AGCM. Two systematic biases are identified in the McRAS-AC runs: one under-prediction of cloud particles around 40° S–60° S, and one over-prediction of cloud water path during Northern Hemisphere summer over the Gulf Stream and North Pacific. Sensitivity analyses show that these biases potentially originate from biases in the aerosol input. The first bias is largely eliminated in a sensitivity test using 50% smaller sea-salt aerosol particles, while the second bias is much reduced when interactive aerosol chemistry was turned on. The main drawback of McRAS-AC is dearth of low-level marine stratus clouds, probably due to lack of boundary-layer clouds that is an outcome of explicit dry-convection not yet implemented into the cloud model. Nevertheless, McRAS-AC simulates realistic clouds and their optical properties that can further improve with better aerosol-input. Thereby, McRAS-AC has the potential to be a valuable tool for climate modeling research because of its superior simulation capabilities that physically couple aerosols, cloud microphysics, cloud macrophysics, and cloud-radiation interaction for all clouds.

  20. Coupling aerosol-cloud-radiative processes in the WRF-Chem model: investigating the radiative impact of elevated point sources

    Directory of Open Access Journals (Sweden)

    E. G. Chapman

    2008-08-01

    Full Text Available The local and regional influence of elevated point sources on summertime aerosol forcing and cloud-aerosol interactions in northeastern North America was investigated using the WRF-Chem community model. The direct effects of aerosols on incoming solar radiation were simulated using existing modules to relate aerosol sizes and chemical composition to aerosol optical properties. Indirect effects were simulated by adding a prognostic treatment of cloud droplet number and adding modules that activate aerosol particles to form cloud droplets, simulate aqueous-phase chemistry, and tie a two-moment treatment of cloud water (cloud water mass and cloud droplet number to an existing radiation scheme. Fully interactive feedbacks thus were created within the modified model, with aerosols affecting cloud droplet number and cloud radiative properties, and clouds altering aerosol size and composition via aqueous processes, wet scavenging, and gas-phase-related photolytic processes. Comparisons of a baseline simulation with observations show that the model captured the general temporal cycle of aerosol optical depths (AODs and produced clouds of comparable thickness to observations at approximately the proper times and places. The model overpredicted SO2 mixing ratios and PM2.5 mass, but reproduced the range of observed SO2 to sulfate aerosol ratios, suggesting that atmospheric oxidation processes leading to aerosol sulfate formation are captured in the model. The baseline simulation was compared to a sensitivity simulation in which all emissions at model levels above the surface layer were set to zero, thus removing stack emissions. Instantaneous, site-specific differences for aerosol and cloud related properties between the two simulations could be quite large, as removing above-surface emission sources influenced when and where clouds formed within the modeling domain. When summed spatially over the finest resolution model

  1. The effects of timing and rate of marine cloud brightening aerosol injection on albedo changes during the diurnal cycle of marine stratocumulus clouds

    Directory of Open Access Journals (Sweden)

    A. K. L. Jenkins

    2012-09-01

    Full Text Available The marine-cloud brightening geoengineering technique has been suggested as a~possible means of counteracting the positive radiative forcing associated with anthropogenic atmospheric CO2 increases. The focus of this study is to quantify the albedo response to aerosols injected into marine stratocumulus cloud from a point source at different times of day. We use a cloud-resolving model to investigate both weakly precipitating and non-precipitating regimes. Injection into both regimes induces a first indirect aerosol effect. Additionally, the weakly precipitating regime shows evidence of the second indirect aerosol effect and leads to cloud changes indicative of a regime change to more persistent cloud. This results in a cloud albedo increase up to six times larger than in the non-precipitating case. These indirect effects show considerable variation with injection at different times in the diurnal cycle. For the weakly precipitating case, aerosol injection results in average increases in cloud albedo of 0.28 and 0.17 in the early and mid morning (03:00:00 local time (LT and 08:00:00 LT, respectively and 0.01 in the evening (18:00:00 LT. No cloud develops when injecting into the cloud-free day (13:00:00 LT. However, the all-sky albedo increases (which include both the indirect and direct aerosol effects are highest for early morning injection (0.11. Mid-morning and daytime injections produce increases of 0.06, with the direct aerosol effect compensating for the lack of cloud albedo perturbation during the cloud-free day. Evening injection results in an increase of 0.04. Penetration and accumulation of aerosols above the cloud top may lead to a reduction of all-sky albedo that tempers the cloud albedo increases. The apparent direct aerosol tempering effect increases with injection rate, although not enough to overcome the increase in all-sky planetary albedo resulting from increases in cloud albedo. For the weakly precipitating case

  2. Cloud condensation nuclei activity of aliphatic amine secondary aerosol

    Science.gov (United States)

    Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g. hydroxyl radical and nitrate radical). The resulting particle composition can contain both secondary organic aerosol (SOA) and inorganic salts. The fraction of organic to inorganic materials in the particulate ...

  3. Investigation of the aerosol-cloud-rainfall association over the Indian summer monsoon region

    Science.gov (United States)

    Sarangi, Chandan; Nand Tripathi, Sachchida; Kanawade, Vijay P.; Koren, Ilan; Sivanand Pai, D.

    2017-04-01

    Monsoonal rainfall is the primary source of surface water in India. Using 12 years of in situ and satellite observations, we examined the association of aerosol loading with cloud fraction, cloud top pressure, cloud top temperature, and daily surface rainfall over the Indian summer monsoon region (ISMR). Our results showed positive correlations between aerosol loading and cloud properties as well as rainfall. A decrease in outgoing longwave radiation and an increase in reflected shortwave radiation at the top of the atmosphere with an increase in aerosol loading further indicates a possible seminal role of aerosols in the deepening of cloud systems. Significant perturbation in liquid- and ice-phase microphysics was also evident over the ISMR. For the polluted cases, delay in the onset of collision-coalescence processes and an enhancement in the condensation efficiency allows for more condensate mass to be lifted up to the mixed colder phases. This results in the higher mass concentration of larger-sized ice-phase hydrometeors and, therefore, implies that the delayed rain processes eventually lead to more surface rainfall. A numerical simulation of a typical rainfall event case over the ISMR using a spectral bin microphysical scheme coupled with the Weather Research Forecasting (WRF-SBM) model was also performed. Simulated microphysics also illustrated that the initial suppression of warm rain coupled with an increase in updraft velocity under high aerosol loading leads to enhanced super-cooled liquid droplets above freezing level and ice-phase hydrometeors, resulting in increased accumulated surface rainfall. Thus, both observational and numerical analysis suggest that high aerosol loading may induce cloud invigoration, thereby increasing surface rainfall over the ISMR. While the meteorological variability influences the strength of the observed positive association, our results suggest that the persistent aerosol-associated deepening of cloud systems and an

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

    Directory of Open Access Journals (Sweden)

    Olaf Krüger

    2014-03-01

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

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

    Directory of Open Access Journals (Sweden)

    Olaf Krüger

    2014-01-01

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

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

    Science.gov (United States)

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

    2013-01-01

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

  7. Establishing the Impact of Model Surfactants on Cloud Condensation Nuclei Activation of Sea Spray Aerosols

    Science.gov (United States)

    Forestieri, S.; Cappa, C. D.; Ruehl, C. R.

    2016-12-01

    Aerosol impacts on cloud properties, also known as indirect effects, remain a major source of uncertainty in modeling global radiative forcing. To reduce this uncertainty necessitates better understanding of how aerosol chemical composition impacts the cloud-forming ability of aerosols. It is well established that both size and hygroscopicity impact the cloud condensation nuclei (CCN) activity of aerosols. Previous studies demonstrate that the presence of surface-active organic material in aerosols can also reduce the surface tension of activating droplets, thereby enhancing CCN activity. We quantified surface tension of microscopic droplets using a continuous-flow stream-wise thermal gradient chamber at humidities close to activation for multi-component lab-generated sea spray aerosol (SSA) proxies. The SSA proxies used were atomized NaCl or synthetic sea salt coated with one to many various fatty acids found in nascent SSA particles. Observed surface tension values near the point of activation as a function of chemical composition for various SSA proxies will be presented.

  8. Partial Collapse of Plinian Volcanic Jets and the Production of Multiply Layered Ash Clouds

    Science.gov (United States)

    Gilchrist, J. T.; Jellinek, M.

    2014-12-01

    Powerful explosive volcanic eruptions inject ash high into the atmosphere, which spreads as an intrusion to form characteristic umbrella-shaped clouds. An enigmatic feature of a number of recent eruption clouds (e.g. Popocatepetl, 2012; Soufriere Hills, 2010; Mt. St. Helens, 1980 and Puyehue, 2011) is that they are constructed of multiple layers (Figure 1, left). How such layering emerges within an advancing gravity current of initially well-mixed ash is unclear. Potential major controls include the strength and structure of the atmospheric density stratification, the particle size distribution within the ash cloud and the entrainment of ambient atmosphere into the rising plume. Accordingly, we conduct analog experiments in which saltwater jets with mono- and bi-disperse suspensions of fine and coarse silica particles are injected into a saltwater tank with a linear density stratification. Whereas classical umbrella clouds are produced for strong jets (low source Richardson number, -Ri0) under all particle-loading conditions, multiply layered clouds emerge for weak jets (high -Ri0) and relatively concentrated bi-disperse and coarse mono-disperse suspensions. In particular, at high -Ri0 coarse particles inhibit entrainment and enhance the partial collapse of rising jets to form gravity currents that intermittently descend along the jet margin and spread at varying neutral buoyancy heights to form layers. For high concentrations of coarse sand gravity currents can reach the tank floor. Collapse and compaction of this material to form a deposit expels buoyant interstitial fluid that rises to form additional layers below and within the overlying multiply layered cloud. One layer and multiply layered clouds have distinct depositional patterns and present unique risks to air traffic.

  9. Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France

    Directory of Open Access Journals (Sweden)

    M. Hervo

    2012-02-01

    Full Text Available During the Eyjafjallajökull eruption (14 April to 24 May 2010, the volcanic aerosol cloud was observed across Europe by several airborne in situ and ground-based remote-sensing instruments. On 18 and 19 May, layers of depolarizing particles (i.e. non-spherical particles were detected in the free troposphere above the Puy de Dôme station, (PdD, France with a Rayleigh-Mie LIDAR emitting at a wavelength of 355 nm, with parallel and crossed polarization channels. These layers in the free troposphere (FT were also well captured by simulations with the Lagrangian particle dispersion model FLEXPART, which furthermore showed that the ash was eventually entrained into the planetary boundary layer (PBL. Indeed, the ash cloud was then detected and characterized with a comprehensive set of in situ instruments at the Puy de Dôme station (PdD. In agreement with the FLEXPART simulation, up to 65 μg m−3 of particle mass and 2.2 ppb of SO2 were measured at PdD, corresponding to concentrations higher than the 95 percentile of 2 yr of measurements at PdD. Moreover, the number concentration of particles increased to 24 000 cm−3, mainly in the submicronic mode, but a supermicronic mode was also detected with a modal diameter of 2 μm. The resulting optical properties of the ash aerosol were characterized by a low scattering Ångström exponent (0.98, showing the presence of supermicronic particles. For the first time to our knowledge, the combination of in situ optical and physical characterization of the volcanic ash allowed the calculation of the mass-to-extinction ratio (η with no assumptions on the aerosol density. The mass-to-extinction ratio was found to be significantly different from the background boundary layer aerosol (max: 1.57 g m−2 as opposed to 0.33 ± 0.03 g m−2. Using this ratio, ash mass concentration in the volcanic plume derived from LIDAR measurements was found to be 655 ± 23

  10. Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France

    Science.gov (United States)

    Hervo, M.; Quennehen, B.; Kristiansen, N. I.; Boulon, J.; Stohl, A.; Fréville, P.; Pichon, J.-M.; Picard, D.; Labazuy, P.; Gouhier, M.; Roger, J.-C.; Colomb, A.; Schwarzenboeck, A.; Sellegri, K.

    2012-02-01

    During the Eyjafjallajökull eruption (14 April to 24 May 2010), the volcanic aerosol cloud was observed across Europe by several airborne in situ and ground-based remote-sensing instruments. On 18 and 19 May, layers of depolarizing particles (i.e. non-spherical particles) were detected in the free troposphere above the Puy de Dôme station, (PdD, France) with a Rayleigh-Mie LIDAR emitting at a wavelength of 355 nm, with parallel and crossed polarization channels. These layers in the free troposphere (FT) were also well captured by simulations with the Lagrangian particle dispersion model FLEXPART, which furthermore showed that the ash was eventually entrained into the planetary boundary layer (PBL). Indeed, the ash cloud was then detected and characterized with a comprehensive set of in situ instruments at the Puy de Dôme station (PdD). In agreement with the FLEXPART simulation, up to 65 μg m-3 of particle mass and 2.2 ppb of SO2 were measured at PdD, corresponding to concentrations higher than the 95 percentile of 2 yr of measurements at PdD. Moreover, the number concentration of particles increased to 24 000 cm-3, mainly in the submicronic mode, but a supermicronic mode was also detected with a modal diameter of 2 μm. The resulting optical properties of the ash aerosol were characterized by a low scattering Ångström exponent (0.98), showing the presence of supermicronic particles. For the first time to our knowledge, the combination of in situ optical and physical characterization of the volcanic ash allowed the calculation of the mass-to-extinction ratio (η) with no assumptions on the aerosol density. The mass-to-extinction ratio was found to be significantly different from the background boundary layer aerosol (max: 1.57 g m-2 as opposed to 0.33 ± 0.03 g m-2). Using this ratio, ash mass concentration in the volcanic plume derived from LIDAR measurements was found to be 655 ± 23 μg m-3 when the plume was located in the FT (3000 m above the sea level

  11. Dust aerosol impact on North Africa climate: a GCM investigation of aerosol-cloud-radiation interactions using A-Train satellite data

    Directory of Open Access Journals (Sweden)

    Y. Gu

    2012-02-01

    Full Text Available The climatic effects of dust aerosols in North Africa have been investigated using the atmospheric general circulation model (AGCM developed at the University of California, Los Angeles (UCLA. The model includes an efficient and physically based radiation parameterization scheme developed specifically for application to clouds and aerosols. Parameterization of the effective ice particle size in association with the aerosol first indirect effect based on ice cloud and aerosol data retrieved from A-Train satellite observations have been employed in climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols at the top of the atmosphere (TOA generally increase with increasing aerosol optical depth. When the dust semi-direct effect is included with the presence of ice clouds, positive IR radiative forcing is enhanced since ice clouds trap substantial IR radiation, while the positive solar forcing with dust aerosols alone has been changed to negative values due to the strong reflection of solar radiation by clouds, indicating that cloud forcing associated with aerosol semi-direct effect could exceed direct aerosol forcing. With the aerosol first indirect effect, the net cloud forcing is generally reduced in the case for an ice water path (IWP larger than 20 g m−2. The magnitude of the reduction increases with IWP.

    AGCM simulations show that the reduced ice crystal mean effective size due to the aerosol first indirect effect results in less OLR and net solar flux at TOA over the cloudy area of the North Africa region because ice clouds with smaller size trap more IR radiation and reflect more solar radiation. The precipitation in the same area, however, increases due to the aerosol indirect effect on ice clouds, corresponding to the enhanced convection as indicated by reduced OLR. Adding the aerosol direct effect into the model simulation reduces the precipitation in the

  12. Lidar System for Airborne Measurement of Clouds and Aerosols

    Science.gov (United States)

    McGill, Matthew; Scott, V. Stanley; Izquierdo, Luis Ramos; Marzouk, Joe

    2008-01-01

    A lidar system for measuring optical properties of clouds and aerosols at three wavelengths is depicted. The laser transmitter is based on a Nd:YVO4 laser crystal pumped by light coupled to the crystal via optical fibers from laser diodes that are located away from the crystal to aid in dissipating the heat generated in the diodes and their drive circuits. The output of the Nd:YVO4 crystal has a wavelength of 1064 nm, and is made to pass through frequency-doubling and frequency-tripling crystals. As a result, the net laser output is a collinear superposition of beams at wavelengths of 1064, 532, and 355 nm. The laser operates at a pulse-repetition rate of 5 kHz, emitting per-pulse energies of 50 microJ at 1064 nm, 25 microJ at 532 nm and 50 microJ at 355 nm. An important feature of this system is an integrating sphere located between the laser output and the laser beam expander lenses. The integrating sphere collects light scattered from the lenses. Three energy-monitor detectors are located at ports inside the integrating sphere. Each of these detectors is equipped with filters such that the laser output energy is measured independently for each wavelength. The laser output energy is measured on each pulse to enable the most accurate calibration possible. The 1064-nm and 532-nm photodetectors are, more specifically, single photon-counting modules (SPCMs). When used at 1064 nm, these detectors have approximately 3% quantum efficiency and low thermal noise (fewer than 200 counts per second). When used at 532 nm, the SPCMs have quantum efficiency of about 60%. The photodetector for the 355-nm channel is a photon-counting photomultiplier tube having a quantum efficiency of about 20%. The use of photon-counting detectors is made feasible by the low laser pulse energy. The main advantage of photon-counting is ease of inversion of data without need for complicated calibration schemes like those necessary for analog detectors. The disadvantage of photon-counting detectors

  13. Long-Term Evolution of the Aerosol Debris Cloud Produced by the 2009 Impact on Jupiter

    Science.gov (United States)

    Sanchez-Lavega, A.; Orton, G. S.; Hueso, R.; Perez-Hoyos, S.; Fletcher, L. N.; Garcia-Melendo, E.; Gomez-Forrellad, J. M.; de Pater, I.; Wong, M.; Hammel. H. B.; Yanamandra-Fisher, P.; Simon-Miller, A.; Barrado-Izagirre, N.; Marchis, F.; Mousis, O.; Oritz, J. L.; Garcia-Rojas, J.; Cecconi, M.; Clarke, J. T.; Noll, K.; Pedraz, S.; Wesley, A.; Kalas, P.; McConnell, N.; Golisch, W.

    2011-01-01

    We present a study of the long-term evolution of the cloud of aerosols produced in the atmosphere of Jupiter by the impact of an object on 19 July 2009. The work is based on images obtained during 5 months from the impact to 31 December 2009 taken in visible continuum wavelengths and from 20 July 2009 to 28 May 2010 taken in near-infrared deep hydrogen-methane absorption bands at 2.1-2.3 micron. The impact cloud expanded zonally from approximately 5000 km (July 19) to 225,000 km (29 October, about 180 deg in longitude), remaining meridionally localized within a latitude band from 53.5 deg S to 61.5 deg S planetographic latitude. During the first two months after its formation the site showed heterogeneous structure with 500-1000 km sized embedded spots. Later the reflectivity of the debris field became more homogeneous due to clump mergers. The cloud was mainly dispersed in longitude by the dominant zonal winds and their meridional shear, during the initial stages, localized motions may have been induced by thermal perturbation caused by the impact's energy deposition. The tracking of individual spots within the impact cloud shows that the westward jet at 56.5 deg S latitude increases its eastward velocity with altitude above the tropopause by 5- 10 m/s. The corresponding vertical wind shear is low, about 1 m/s per scale height in agreement with previous thermal wind estimations. We found evidence for discrete localized meridional motions with speeds of 1-2 m/s. Two numerical models are used to simulate the observed cloud dispersion. One is a pure advection of the aerosols by the winds and their shears. The other uses the EPIC code, a nonlinear calculation of the evolution of the potential vorticity field generated by a heat pulse that simulates the impact. Both models reproduce the observed global structure of the cloud and the dominant zonal dispersion of the aerosols, but not the details of the cloud morphology. The reflectivity of the impact cloud decreased

  14. Fingerprinting Volcanic and Anthropogenic Sulfur Dioxide in the Air: A 25 Year Record of Sulfate Aerosols from the South Pole Snowpit, Antarctica

    Science.gov (United States)

    Shaheen, R.; Abaunza-Quintero, M.; Jackson, T. L.; McCabe, J.; Savarino, J. P.; Thiemens, M. H.

    2012-12-01

    Sulfate aerosols, unlike greenhouse gases, cause cooling effect (-0.4 ± 0.2 W.m-2) by scattering incoming solar radiation and by acting as cloud condensation nuclei (IPCC 2007). Volcanic eruptions with explosivity Indices >5 inject large amounts of SO2 and particles into the stratosphere causing a significant decrease in temperature. For example a 0.7oC decrease in Earth's temperature was observed following the Pinatubo eruption in 1991. Stratospheric injection of sulfate aerosols has been suggested as a geoengineering effort to mitigate global warming caused by a significant increase in greenhouse gases. To understand the impact of volcanic events on the stratospheric sulfate aerosol layer and subsequent changes in the dynamics of the upper atmosphere, a long term and high temporal resolution record of sulfate aerosol is needed. Here we present a 25 year (1978 to 2003) high resolution record of sulfate aerosols which covers largest volcanic eruptions of the 20th century namely, El-Chichón 1982 and Pinatubo 1991. Sulfate aerosol samples were obtained from a 1x1m snowpit at the South Pole, Antarctica with approximately 6 month time steps. Sulfate concentrations vary from 30 to 70 ppb depending on the season with exceptions during volcanic events which contributed a three to four folds increase in sulfate concentration Sulfate concentrations of120 ppb following El Chichón and 190 ppb after Pinatubo eruptions were observed. The oxygen isotopic anomaly varied from 0.7‰ to 3.9‰ with the highest anomaly occurring after the Pinatubo eruption. The positive Δ17O of sulfate derives from aqueous phase oxidation of SO2 by H2O2 and O3 oxidation and involves transfer of the isotopic anomaly from the oxidant to the product sulfate. Coupled with kinetic analysis the relative reaction rates the relative proportions of oxidation can be calculated. All other sulfate sources such as sea salt sulfates, primary sulfates from fossil fuel combustion, metal catalyzed oxidation of S

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

    Science.gov (United States)

    Christensen, M.; Stephens, G. L.

    2011-12-01

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

  16. Rate of non-linearity in DMS aerosol-cloud-climate interactions

    Directory of Open Access Journals (Sweden)

    M. A. Thomas

    2011-11-01

    Full Text Available The degree of non-linearity in DMS-cloud-climate interactions is assessed using the ECHAM5-HAMMOZ model by taking into account end-to-end aerosol chemistry-cloud microphysics link. The evaluation is made over the Southern oceans in austral summer, a region of minimal anthropogenic influence. In this study, we compare the DMS-derived changes in the aerosol and cloud microphysical properties between a baseline simulation with the ocean DMS emissions from a prescribed climatology, and a scenario where the DMS emissions are doubled. Our results show that doubling the DMS emissions in the current climate results in a non-linear response in atmospheric DMS burden and subsequently, in SO2 and H2SO4 burdens due to inadequate OH oxidation. The aerosol optical depth increases by only ~20 % in the 30° S–75° S belt in the SH summer months. This increases the vertically integrated cloud droplet number concentrations (CDNC by 25 %. Since the vertically integrated liquid water vapor is constant in our model simulations, an increase in CDNC leads to a reduction in cloud droplet radius of 3.4 % over the Southern oceans in summer. The equivalent increase in cloud liquid water path is 10.7 %. The above changes in cloud microphysical properties result in a change in global annual mean radiative forcing at the TOA of −1.4 W m−2. The results suggest that the DMS-cloud microphysics link is highly non-linear. This has implications for future studies investigating the DMS-cloud climate feedbacks in a warming world and for studies evaluating geoengineering options to counteract warming by modulating low level marine clouds.

  17. Cloud-Aerosol-Radiation (CAR) Ensemble Modeling System:Overall Accuracy and Efficiency

    Institute of Scientific and Technical Information of China (English)

    Feng ZHANG; Xin-Zhong LIANG; ZENG Qingcun; Yu GU; Shenjian SU

    2013-01-01

    The Cloud-Aerosol-Radiation (CAR) ensemble modeling system has recently been built to better understand cloud/aerosol/radiation processes and determine the uncertainties caused by different treatments of cloud/aerosol/radiation in climate models.The CAR system comprises a large scheme collection of cloud,aerosol,and radiation processes available in the literature,including those commonly used by the world's leading GCMs.In this study,detailed analyses of the overall accuracy and efficiency of the CAR system were performed.Despite the different observations used,the overall accuracies of the CAR ensemble means were found to be very good for both shortwave (SW) and longwave (LW) radiation calculations.Taking the percentage errors for July 2004 compared to ISCCP (International Satellite Cloud Climatology Project)data over (60°N,60°S) as an example,even among the 448 CAR members selected here,those errors of the CAR ensemble means were only about-0.67% (-0.6 W m-2) and-0.82% (-2.0 W m-2) for SW and LW upward fluxes at the top of atmosphere,and 0.06% (0.1 W m-2) and-2.12% (-7.8 W m-2) for SW and LW downward fluxes at the surface,respectively.Furthermore,model SW frequency distributions in July 2004 covered the observational ranges entirely,with ensemble means located in the middle of the ranges.Moreover,it was found that the accuracy of radiative transfer calculations can be significantly enhanced by using certain combinations of cloud schemes for the cloud cover fraction,particle effective size,water path,and optical properties,along with better explicit treatments for unresolved cloud structures.

  18. Science Plan Biogenic Aerosols – Effects on Clouds and Climate (BAECC)

    Energy Technology Data Exchange (ETDEWEB)

    Petäjä, T

    2013-12-01

    Atmospheric aerosol particles impact human health in urban environments, while on regional and global scales they can affect climate patterns, the hydrological cycle, and the intensity of radiation that reaches the Earth’s surface. In spite of recent advances in the understanding of aerosol formation processes and the links between aerosol dynamics and biosphere-atmosphere-climate interactions, great challenges remain in the analysis of related processes on a global scale. Boreal forests, situated in a circumpolar belt in the northern latitudes throughout the United States, Canada, Russia and Scandinavia, are among the most active areas of atmospheric aerosol formation among all biomes. The formation of aerosol particles and their growth to the sizes of cloud condensation nuclei in these areas are associated with biogenic volatile organic emissions from vegetation and soil.

  19. Assimilating Aircraft-based measurements to improve the State of Distal Volcanic Ash Cloud

    Science.gov (United States)

    Fu, Guangliang; Lin, Hai Xiang; Heemink, Arnold; Segers, Arjo; Lu, Sha; Palsson, Thorgeir

    2015-04-01

    The sudden eruption at the 1666 m high, ice-capped Eyjafjallajökull volcano, in south Iceland during 14 April to 23 May 2010, had caused an unprecedented closure of the European and North Atlantic airspace resulting in global economic losses of US5 billion. This has initiated a lot of research on how to improve aviation advice after eruption onset. Good estimation of both the state of volcanic ash cloud and the emission of volcano are crucial for providing a successful aviation advice. Currently most of the approaches, employing satellite-based and ground-based measurements, are in the focus of improving the definition of Eruption Source Parameters (ESPs) such as plume height and mass eruption rate, which are certainly very important for estimating volcano emission and state of volcanic ash cloud near to the volcano. However, for ash cloud state in a far field, these approaches can hardly make improvements. This is mainly because the influence of ESPs on the ash plume becomes weaker as the distance to the volcano is getting farther, thus for a distal plume the information of ESPs will have little influence. This study aims to find an efficient way to improve the state of distal volcanic ash cloud. We use real-life aircraft-based observations, measured along Dutch border between Borken and Twist during the 2010 Eyjafjallajökull eruption, in an data assimilation system combining with a transport model to identify the potential benefit of this kind of observations and the influence on the ash state around Dutch border. We show that assimilating aircraft-based measurements can significantly improve the state of distal ash clouds, and further provide an improved aviation advice on distal ash plume. We compare the performances of different sequential data assimilation methods. The results show standard Ensemble Kalman Filter (EnKF) works better than others, which is because of the strong nonlinearity of the dynamics and the EnKF's resampling Gaussianity nature

  20. Aerosol effect on the evolution of the thermodynamic properties of warm convective cloud fields

    Science.gov (United States)

    Dagan, Guy; Koren, Ilan; Altaratz, Orit; Heiblum, Reuven H.

    2016-12-01

    Convective cloud formation and evolution strongly depend on environmental temperature and humidity profiles. The forming clouds change the profiles that created them by redistributing heat and moisture. Here we show that the evolution of the field’s thermodynamic properties depends heavily on the concentration of aerosol, liquid or solid particles suspended in the atmosphere. Under polluted conditions, rain formation is suppressed and the non-precipitating clouds act to warm the lower part of the cloudy layer (where there is net condensation) and cool and moisten the upper part of the cloudy layer (where there is net evaporation), thereby destabilizing the layer. Under clean conditions, precipitation causes net warming of the cloudy layer and net cooling of the sub-cloud layer (driven by rain evaporation), which together act to stabilize the atmosphere with time. Previous studies have examined different aspects of the effects of clouds on their environment. Here, we offer a complete analysis of the cloudy atmosphere, spanning the aerosol effect from instability-consumption to enhancement, below, inside and above warm clouds, showing the temporal evolution of the effects. We propose a direct measure for the magnitude and sign of the aerosol effect on thermodynamic instability.

  1. Lidar investigation of tropical nocturnal boundary layer aerosols and cloud macrophysics

    Science.gov (United States)

    Manoj, M. G.; Devara, P. C. S.; Taraphdar, S.

    2013-10-01

    Observational evidence of two-way association between nocturnal boundary layer aerosols and cloud macrophysical properties over a tropical urban site is reported in this paper. The study has been conducted during 2008-09 employing a high space-time resolution polarimetric micro-pulse lidar over a tropical urban station in India. Firstly, the study highlights the crucial role of boundary layer aerosols and background meteorology on the formation and structure of low-level stratiform clouds in the backdrop of different atmospheric stability conditions. Turbulent mixing induced by the wind shear at the station, which is associated with a complex terrain, is found to play a pivotal role in the formation and structural evolution of nocturnal boundary layer clouds. Secondly, it is shown that the trapping of energy in the form of outgoing terrestrial radiation by the overlying low-level clouds can enhance the aerosol mixing height associated with the nocturnal boundary layer. To substantiate this, the long-wave heating associated with cloud capping has been quantitatively estimated in an indirect way by employing an Advanced Research Weather Research and Forecasting (WRF-ARW) model developed by National Center for Atmospheric Research (NCAR), Colorado, USA, and supplementary data sets; and differentiated against other heating mechanisms. The present investigation as well establishes the potential of lidar remote-sensing technique in exploring some of the intriguing aspects of the cloud-environment relationship.

  2. The Impacts of Chihuahua Desert Aerosol Intrusions on Convective Clouds and Regional Precipitation

    Science.gov (United States)

    Apodaca, Karina

    Growing up in a desert region influenced by a monsoon system and experiencing, first-hand, dust storms produced by convective thunderstorms stimulated my interest in the study of the impacts of aerosols on clouds. Contrary to other studies which focus more on anthropogenic aerosols, I chose to investigate the role of natural aerosols in the deserts of North America. Moreover, the role played by aerosols in desert regions within the North American Monsoon domain has not received as much attention as in other monsoon regions around the world. This dissertation describes my investigation of the connection between mineral aerosols (dust storms) and monsoon rainfall in the deserts of the Southwestern United States and Northwestern Mexico. To develop the context for the study of the role of mineral dust in summer-time convection on a regional scale, large-scale dynamical processes and their impact on the inter-annual variability of monsoon rainfall were analyzed. I developed the climatology of monsoonal rainfall and dust storms using surface observations to determine which mesoscale features influence North American Monsoon rainfall in the Paso Del Norte region. The strongest correlations were found between sea surface temperatures over the Gulf of California, Gulf of California moisture surges and monsoon rainfall in the Paso Del Norte region. A connection to ENSO could not be clearly established despite analyzing twenty-one years of data. However, by breaking the data into segments, a strong correlation was found for periods of intense rainfall. Twenty-one case studies were identified in which dust storms were produced in conjunction with thunderstorms during the 2005 - 2007 monsoon seasons. However, in some cases all the conditions were there for rainfall to occur but it did not precipitate. I concluded that strong thunderstorm outflow was triggering dust storms. The Weather Research and Forecasting model coupled with Chemistry (WRF-Chem V3.1.1) was used to evaluate

  3. Dissolution process of atmospheric aerosol particles into cloud droplets; Processus de dissolution des aerosols atmospheriques au sein des gouttes d'eau nuageuses

    Energy Technology Data Exchange (ETDEWEB)

    Desboeufs, K.

    2001-01-15

    Clouds affect both climate via the role they play in the Earth's radiation balance and tropospheric chemistry since they are efficient reaction media for chemical transformation of soluble species. Cloud droplets are formed in the atmosphere by condensation of water vapour onto aerosol particles, the cloud condensation nuclei (CCN). The water soluble fraction of these CCN governs the cloud micro-physics, which is the paramount factor playing on the radiative properties of clouds. Moreover, this soluble fraction is the source of species imply in the oxidation/reduction reactions in the aqueous phase. Thus, it is of particular importance to understand the process controlling the solubilization of aerosols in the cloud droplets. The main purpose of this work is to investigate experimentally and theoretically the dissolution of particles incorporated in the aqueous phase. From the studies conducted up to now, we have identify several factors playing on the dissolution reaction of aerosols. However, the quantification of the effects of these factors is difficult since the current means of study are not adapted to the complexity of cloud systems. First, this work consisted to perform a experimental system, compound by an open flow reactor, enabling to follow the kinetic of dissolution in conditions representative of cloud. This experimental device is used to a systematic characterisation of the known factors playing on the dissolution, i.e. pH, aerosol nature, aerosol weathering... and also for the identification and the quantification of the effects of other factors: ionic strength, acid nature, clouds processes. These experiments gave quantitative results, which are used to elaborate a simple model of aerosol dissolution in the aqueous phase. This model considers the main factors playing on the dissolution and results in a general mechanism of aerosol dissolution extrapolated to the cloud droplets. (author)

  4. The response of clouds and aerosols to cosmic ray decreases

    Science.gov (United States)

    Svensmark, J.; Enghoff, M. B.; Shaviv, N. J.; Svensmark, H.

    2016-09-01

    A method is developed to rank Forbush decreases (FDs) in the galactic cosmic ray radiation according to their expected impact on the ionization of the lower atmosphere. Then a Monte Carlo bootstrap-based statistical test is formulated to estimate the significance of the apparent response in physical and microphysical cloud parameters to FDs. The test is subsequently applied to one ground-based and three satellite-based data sets. Responses (>95%) to FDs are found in the following parameters of the analyzed data sets. AERONET: Ångström exponent (cloud condensation nuclei changes), SSM/I: liquid water content, International Satellite Cloud Climate Project (ISCCP): total, high, and middle, IR-detected clouds over the oceans, Moderate Resolution Imaging Spectroradiometer (MODIS): cloud effective emissivity, cloud optical thickness, liquid water, cloud fraction, liquid water path, and liquid cloud effective radius. Moreover, the responses in MODIS are found to correlate positively with the strength of the FDs, and the signs and magnitudes of the responses agree with model-based expectations. The effect is mainly seen in liquid clouds. An impact through changes in UV-driven photo chemistry is shown to be negligible and an impact via UV absorption in the stratosphere is found to have no effect on clouds. The total solar irradiance has a relative decrease in connection with FDs of the order of 10-3, which is too small to have a thermodynamic impact on timescales of a few days. The results demonstrate that there is a real influence of FDs on clouds probably through ions.

  5. Real time retrieval of volcanic cloud particles and SO2 by satellite using an improved simplified approach

    Science.gov (United States)

    Pugnaghi, Sergio; Guerrieri, Lorenzo; Corradini, Stefano; Merucci, Luca

    2016-07-01

    Volcanic plume removal (VPR) is a pr