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Sample records for cloud particle microphysics

  1. Microphysical processing of aerosol particles in orographic clouds

    NASA Astrophysics Data System (ADS)

    Pousse-Nottelmann, S.; Zubler, E. M.; Lohmann, U.

    2015-01-01

    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 implications for the ice

  2. Microphysical processing of aerosol particles in orographic clouds

    NASA Astrophysics Data System (ADS)

    Pousse-Nottelmann, S.; Zubler, E. M.; Lohmann, U.

    2015-08-01

    An explicit and detailed treatment of cloud-borne particles allowing for the consideration of 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

  3. Microphysics of Pyrocumulonimbus Clouds

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  4. Microphysics of Pyrocumulonimbus Clouds

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  5. Retrievals of Aerosol and Cloud Particle Microphysics Using Polarization and Depolarization Techniques

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael; Hansen, James E. (Technical Monitor)

    2001-01-01

    The recent availability of theoretical techniques for computing single and multiple scattering of light by realistic polydispersions of spherical and nonspherical particles and the strong dependence of the Stokes scattering matrix on particle size, shape, and refractive index make polarization and depolarization measurements a powerful particle characterization tool. In this presentation I will describe recent applications of photopolarimetric and lidar depolarization measurements to remote sensing characterization of tropospheric aerosols, polar stratospheric clouds (PSCs), and contrails. The talk will include (1) a short theoretical overview of the effects of particle microphysics on particle single-scattering characteristics; (2) the use of multi-angle multi-spectral photopolarimetry to retrieve the optical thickness, size distribution, refractive index, and number concentration of tropospheric aerosols over the ocean surface; and (3) the application of the T-matrix method to constraining the PSC and contrail particle microphysics using multi-spectral measurements of lidar backscatter and depolarization.

  6. Retrievals of Aerosol and Cloud Particle Microphysics Using Polarization and Depolarization Techniques

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael; Hansen, James E. (Technical Monitor)

    2001-01-01

    The recent availability of theoretical techniques for computing single and multiple scattering of light by realistic polydispersions of spherical and nonspherical particles and the strong dependence of the Stokes scattering matrix on particle size, shape, and refractive index make polarization and depolarization measurements a powerful particle characterization tool. In this presentation I will describe recent applications of photopolarimetric and lidar depolarization measurements to remote sensing characterization of tropospheric aerosols, polar stratospheric clouds (PSCs), and contrails. The talk will include (1) a short theoretical overview of the effects of particle microphysics on particle single-scattering characteristics; (2) the use of multi-angle multi-spectral photopolarimetry to retrieve the optical thickness, size distribution, refractive index, and number concentration of tropospheric aerosols over the ocean surface; and (3) the application of the T-matrix method to constraining the PSC and contrail particle microphysics using multi-spectral measurements of lidar backscatter and depolarization.

  7. Effect of cloud microphysics on particle growth under mixed phase conditions

    NASA Astrophysics Data System (ADS)

    Pfitzenmaier, Lukas; Dufournet, Yann; Unal, Christine; Russchenberg, Herman; Myagkov, Alexander; Seifert, Patric

    2015-04-01

    Mixed phase clouds contain both ice particles and super-cooled cloud water droplets in the same volume of air. Currently, one of the main challenges is to observe and understand how ice particles grow by interacting with liquid water within the mixed-phase clouds. In the mid latitudes this process is one of the most efficient processes for precipitation formation. It is particularly important to understand under which conditions growth processes are most efficient within such clouds. The observation of microphysical cloud properties from the ground is one possible approach to study the liquid-ice interaction that play a role on the ice crystal growth processes. The study presented here is based on a ground-based multi-sensor technique. Dataset of this study was taken during the ACCEPT campaign (Analysis of the Composition of mixed-phase Clouds with Extended Polarization Techniques) at Cabauw The Netherlands, autumn 2014. Measurements with the Transportable Atmospheric RAdar (TARA), S-band precipitation radar profiler, from the Delft Technical University, and Ka-band cloud radar systems were performed in cooperation with the Leibniz Institute for Tropospheric Research (TROPOS), Leipzig, Germany. All the radar systems had full Doppler capabilities. In addition , TARA and one of the Ka-band radar systems had full polarimetric capabilities as well, in order to get information of the ice phase within mixed-phase cloud systems. Lidar, microwave radiometer and radiosonde measurements were combined to describe the liquid phase within such clouds. So a whole characterisation of microphysical processes within mixed-phase cloud systems could be done. This study shows how such a combination of instruments is used to: - Detect the liquid layer within the ice clouds - Describe the microphysical conditions for ice particle growth within mixed phase clouds based on cloud hydrometeor shape, size, number concentration obtained from measurements The project aims to observe

  8. Ice particle morphology and microphysical properties of cirrus clouds inferred from combined CALIOP-IIR measurements

    NASA Astrophysics Data System (ADS)

    Saito, Masanori; Iwabuchi, Hironobu; Yang, Ping; Tang, Guanglin; King, Michael D.; Sekiguchi, Miho

    2017-04-01

    Ice particle morphology and microphysical properties of cirrus clouds are essential for assessing radiative forcing associated with these clouds. We develop an optimal estimation-based algorithm to infer cirrus cloud optical thickness (COT), cloud effective radius (CER), plate fraction including quasi-horizontally oriented plates (HOPs), and the degree of surface roughness from the Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) and the Infrared Imaging Radiometer (IIR) on the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) platform. A simple but realistic ice particle model is used, and the relevant bulk optical properties are computed using state-of-the-art light-scattering computational capabilities. Rigorous estimation of uncertainties related to surface properties, atmospheric gases, and cloud heterogeneity is performed. The results based on the present method show that COTs are quite consistent with other satellite products and CERs essentially agree with the other counterparts. A 1 month global analysis for April 2007, in which CALIPSO off-nadir angle is 0.3°, shows that the HOP has significant temperature-dependence and is critical to the lidar ratio when cloud temperature is warmer than -40°C. The lidar ratio is calculated from the bulk optical properties based on the inferred parameters, showing robust temperature dependence. The median lidar ratio of cirrus clouds is 27-31 sr over the globe.

  9. Retrieval of Polar Stratospheric Cloud Microphysical Properties from Lidar Measurements: Dependence on Particle Shape Assumptions

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    A retrieval algorithm has been developed for the microphysical analysis of polar stratospheric cloud (PSC) optical data obtained using lidar instrumentation. The parameterization scheme of the PSC microphysical properties allows for coexistence of up to three different particle types with size-dependent shapes. The finite difference time domain (FDTD) method has been used to calculate optical properties of particles with maximum dimensions equal to or less than 2 mu m and with shapes that can be considered more representative of PSCs on the scale of individual crystals than the commonly assumed spheroids. Specifically. these are irregular and hexagonal crystals. Selection of the optical parameters that are input to the inversion algorithm is based on a potential data set such as that gathered by two of the lidars on board the NASA DC-8 during the Stratospheric Aerosol and Gas Experiment 0 p (SAGE) Ozone Loss Validation experiment (SOLVE) campaign in winter 1999/2000: the Airborne Raman Ozone and Temperature Lidar (AROTEL) and the NASA Langley Differential Absorption Lidar (DIAL). The 0 microphysical retrieval algorithm has been applied to study how particle shape assumptions affect the inversion of lidar data measured in leewave PSCs. The model simulations show that under the assumption of spheroidal particle shapes, PSC surface and volume density are systematically smaller than the FDTD-based values by, respectively, approximately 10-30% and approximately 5-23%.

  10. Simulation of particle size distributions in Polar Mesospheric Clouds from Microphysical Models

    NASA Astrophysics Data System (ADS)

    Thomas, G. E.; Merkel, A.; Bardeen, C.; Rusch, D. W.; Lumpe, J. D.

    2009-12-01

    The size distribution of ice particles is perhaps the most important observable aspect of microphysical processes in Polar Mesospheric Cloud (PMC) formation and evolution. A conventional technique to derive such information is from optical observation of scattering, either passive solar scattering from photometric or spectrometric techniques, or active backscattering by lidar. We present simulated size distributions from two state-of-the-art models using CARMA sectional microphysics: WACCM/CARMA, in which CARMA is interactively coupled with WACCM3 (Bardeen et al, 2009), and stand-alone CARMA forced by WACCM3 meteorology (Merkel et al, this meeting). Both models provide well-resolved size distributions of ice particles as a function of height, location and time for realistic high-latitude summertime conditions. In this paper we present calculations of the UV scattered brightness at multiple scattering angles as viewed by the AIM Cloud Imaging and Particle Size (CIPS) satellite experiment. These simulations are then considered discretely-sampled “data” for the scattering phase function, which are inverted using a technique (Lumpe et al, this meeting) to retrieve particle size information. We employ a T-matrix scattering code which applies to a wide range of non-sphericity of the ice particles, using the conventional idealized prolate/oblate spheroidal shape. This end-to-end test of the relatively new scattering phase function technique provides insight into both the retrieval accuracy and the information content in passive remote sensing of PMC.

  11. Retrieval of Polar Stratospheric Cloud Microphysical Properties From Lidar Measurements: Dependence on Particle Shape Assumptions

    NASA Technical Reports Server (NTRS)

    Reichardt, Susanne; Reichardt, Jens; Yang, Ping; McGee, Thomas J.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Knowledge of particle sizes and number densities of polar stratospheric clouds (PSCs) is highly important, because they are critical parameters for the modeling of the ozone chemistry of the stratosphere. In situ measurements of PSC particles are rare. the main instrument for the accumulation of PSC data are lidar systems. Therefore the derivation of some microphysical properties of PSCS from the optical parameters measured by lidars would be highly beneficial for ozone research. Inversion of lidar data obtained in the presence of PSCs formed from crystalline particles type 11 and the various nitric acid tri Ydrrate (NAT) types cannot be easily accomplished, because a suitable scattering theory for small faceted crystals has not been readily available tip to now. As a consequence, the T-matrix method is commonly used for the interpretation of these PSC lidar data. Here the assumption is made that the optical properties of an ensemble of spheroids resemble those of crystalline PSCs, and microphysical properties of the PSC are inferred from the optical signatures of the PSC at two or more wavelengths. The problem with the T-matrix approach is that the assumption of spheroidal instead of faceted particles can lead to dramatically wrong results: Usually cloud particle properties are deduced from analysis of lidar profiles of backscatter ratio and depolarization ratio. The particle contribution to the backscatter ratio is given by the product of the particle number density and the backscattering cross section. The latter is proportional to the value of the particle's scattering phase function at 180 degrees scattering angle. At 180 degrees however, the phase functions of rough, faceted crystals and of spheroids with same maximum dimension differ by a factor of 6. From this it follows that for a PSC consisting of faceted crystals, the particle number density is underestimated by roughly the same factor if spheroidal particles are unrealistically assumed. We are currently

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  13. Retrieving fall streaks signatures in radar data to study microphysical changes of particle populations within a mixed phase clouds

    NASA Astrophysics Data System (ADS)

    Pfitzenmaier, Lukas; Dufournet, Yann; Unal, Christine; Russchenberg, Herman

    2016-04-01

    Within mixed-phase clouds the interaction of ice crystals with super-cooled liquid water leads to an enhanced growth of the ice particles. The growth of ice particles from mixed-phase interactions is an important process for precipitation formation in the mid-latitudes. However, such a process is still not clearly understood, nowerdays. To understand the ice particle growth within these clouds the microphysical changes of a single particle population falling through the cloud have to be analysed. Using the 3 beam configuration of the Transportable Atmospheric Radar (TARA) we retrieve the full 3-D Doppler velocity vector. This retrieved dynamical information is used to retrieve the path of a single particle population through the measured cloud system - the so called fall streak - so that microphysical changes along those path can be studied. A way to study changes in ice particle microphysics is to analyse radar Doppler spectra. Microphysical changes along the path of a population of ice particles through a mixed-phase cloud can be correlated to changes in the retrieved radar spectrograms. The instrumental synergy setup during the ACCEPT campaign (Analysis of the Composition of Clouds with Extended Polarization Techniques campaign), fall 2014, Cabauw the Netherlands, allows to detect liquid water layers within mixed-phase clouds. Therefore, identified changes within the retrieved spectrograms can be linked to the presence of super-cooled liquid layers. In this work we will explain the backtracking methodology and its use for the interpretation of velocity spectra. The application of this new methodology for ice particle growth process studies within mixed-phase clouds will be discussed.

  14. Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    there. Thus, larger scale forcings that impact cloud macrophysical properties, as well as enhanced aerosol particles, are important in determining cloud droplet size and cloud albedo. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, some of which may initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.

  15. Microphysics of Exoplanet Clouds and Hazes

    NASA Astrophysics Data System (ADS)

    Gao, Peter; Benneke, Björn; Knutson, Heather A.; Yung, Yuk L.

    2015-11-01

    Clouds and hazes are ubiquitous in the atmospheres of exoplanets. However, as most of these planets have temperatures between 600 and 2000 K, their clouds and hazes are likely composed of exotic condensates such as silicates, metals, and salts. We currently lack a satisfactory understanding of the microphysical processes that govern the distribution of these clouds and hazes, thus creating a gulf between the cloud properties retrieved from observations and the cloud composition predictions from condensation equilibrium models. In this work we present a 1D microphysical cloud model that calculates, from first principles, the rates of condensation, evaporation, coagulation, and vertical transport of chemically mixed cloud and haze particles in warm and hot exoplanet atmospheres. The model outputs the equilibrium number density of cloud particles with altitude, the particle size distribution, and the chemical makeup of the cloud particles as a function of altitude and particle mass. The model aims to (1) explain the observed variability in “cloudiness” of individual exoplanets, (2) assess whether the proposed cloud materials are capable of forming the observed particle distributions, and (3) examine the role clouds have in the transport of (cloud-forming) heavy elements in exoplanet atmospheres.

  16. Microphysics of Exoplanet Clouds and Hazes

    NASA Astrophysics Data System (ADS)

    Gao, Peter; Benneke, Björn; Knutson, Heather; Yung, Yuk

    2016-01-01

    Clouds and hazes are ubiquitous in the atmospheres of exoplanets. However, as most of these planets have temperatures between 600 and 2000 K, their clouds and hazes are likely composed of exotic condensates such as silicates, metals, and salts. We currently lack a satisfactory understanding of the microphysical processes that govern the distribution of these clouds and hazes, thus creating a gulf between the cloud properties retrieved from observations and the cloud composition predictions from condensation equilibrium models. In this work we present a 1D microphysical cloud model that calculates, from first principles, the rates of condensation, evaporation, coagulation, and vertical transport of chemically mixed cloud and haze particles in warm and hot exoplanet atmospheres. The model outputs the equilibrium number density of cloud particles with altitude, the particle size distribution, and the chemical makeup of the cloud particles as a function of altitude and particle mass. The model aims to (1) explain the observed variability in "cloudiness" of individual exoplanets, (2) assess whether the proposed cloud materials are capable of forming the observed particle distributions, and (3) examine the role clouds have in the transport of (cloud-forming) heavy elements in exoplanet atmospheres.

  17. Microphysics of Exoplanet Clouds and Hazes

    NASA Astrophysics Data System (ADS)

    Gao, Peter; Benneke, Björn; Knutson, Heather; Yung, Yuk

    2015-12-01

    Clouds and hazes are ubiquitous in the atmospheres of exoplanets. However, as most of these planets have temperatures between 600 and 2000 K, their clouds and hazes are likely composed of exotic condensates such as silicates, metals, and salts. We currently lack a satisfactory understanding of the microphysical processes that govern the distribution of these clouds and hazes, thus creating a gulf between the cloud properties retrieved from observations and the cloud composition predictions from condensation equilibrium models. In this work we present a 1D microphysical cloud model that calculates, from first principles, the rates of condensation, evaporation, coagulation, and vertical transport of chemically mixed cloud and haze particles in warm and hot exoplanet atmospheres. The model outputs the equilibrium number density of cloud particles with altitude, the particle size distribution, and the chemical makeup of the cloud particles as a function of altitude and particle mass. The model aims to (1) explain the observed variability in “cloudiness” of individual exoplanets, (2) assess whether the proposed cloud materials are capable of forming the observed particle distributions, and (3) examine the role clouds have in the transport of (cloud-forming) heavy elements in exoplanet atmospheres.

  18. Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the Southeast Pacific ocean

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    distribution of droplet residual particles and ambient aerosol particles were observed. 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. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.

  19. Cloud Microphysics and Absorption Validation

    NASA Technical Reports Server (NTRS)

    Ackerman, Steven

    2002-01-01

    Vertical distributions of particle size and habit were developed from in-situ data collected from three midlatitude cirrus field campaigns (FIRE-1, FIRE-2, and ARM IOP). These new midlatitude microphysical models were used to develop new cirrus scattering models at a number of wavelengths appropriate for use with the MODIS imager (Nasiri et al. 2002). This was the first successful collaborative effort between all the investigators on this proposal. Recent efforts have extended the midlatitude cirrus cloud analyses to tropical cirrus, using in-situ data collected during the Tropical Rainfall Measurement Mission (TRMM) Kwajalein field campaign in 1999. We note that there are critical aspects to the work: a) Improvement in computing the scattering and radiative properties of ice crystals; b) Requirement for copious amounts of cirrus in-situ data, presented in terms of both particle size and habit distributions; c) Development of cirrus microphysical and optical models for various satellite, aircraft, and ground-based instruments based on the theoretical calculations and in-situ measurements; d) Application to satellite data.

  20. The Role of African Dust Particles on Cloud Chemistry and Microphysics in a Tropical Montane Cloud Forest in the Caribbean

    NASA Astrophysics Data System (ADS)

    Torres-Delgado, E.; Valle-Diaz, C. J.; Baumgardner, D.; McDowell, W. H.; Gonzalez, G.; Mayol-Bracero, O. L.

    2015-12-01

    Huge amounts of African dust travels thousands of kilometers from the Sahara and Sahel regions to the Caribbean, northern South America and southern North America. However, not much is understood about how the aging process that takes place during transport changes dust properties, and how it affects cloud's composition and microphysics. In order to improve our understanding of the role of long-range transported African dust (LRTAD) in cloud formation processes we had field campaigns measuring dust physical and chemical properties in summers of 2013, 2014 and 2015, as part of the Puerto Rico African Dust and Cloud Study (PRADACS), and of the Luquillo Critical Zone Observatory (LCZO). Measurements were performed at the tropical montane cloud forest (TMCF) of Pico del Este (PE, 1051 masl) and at the nature reserve of Cabezas de San Juan (CSJ, 60 masl). In both ground stations we monitored meteorological parameters (e.g., temperature, wind speed, wind direction). At CSJ, we measured light absorption and scattering at three wavelengths (467, 528 and 652 nm). At PE we collected cloud and rainwater for chemical analyses and monitored cloud microphysical properties (e.g., liquid water content, droplet size distribution, droplet number concentration, effective diameter and median volume diameter). Summer 2015 was the first attempt to characterize microphysical properties of the summer period (June to August) at PE, where dust is in its higher concentrations of the year. Samples were classified using data from models and satellites together with CSJ measurements as low or high dust influenced. Soluble ions, insoluble trace metals, pH, conductivity, total and dissolved organic carbon and total and dissolved nitrogen were measured for cloud and rainwater. Enrichment factor analysis was used to determine sea and crustal contribution of species by sample, as well as the neutralization factor and fractional acidity. Some preliminary results show cloud water conductivity for low

  1. Analysis of Cirrus Cloud Microphysical Data

    NASA Technical Reports Server (NTRS)

    Poellot, Michael R.; Grainger, Cedric A.

    1999-01-01

    The First International Satellite Cloud Climatology Regional Experiment (FIRE) program has the goal of improving our capabilities to understand, model and detect the properties of climatically-important clouds. This is being undertaken through a three-pronged effort of modeling, long-term observations and short-term intensive field studies. Through examination of satellite and other data it is apparent that stratus and cirrus cloud types have the greatest impact on climate due to their radiative effects and ubiquitous nature. As a result, the FIRE program has developed two paths of investigation, each having its own subset of research objectives and measurement programs. The work conducted under this grant was directed toward furthering our understanding of cirrus cloud systems. While it is known that cirrus are climatically important, the magnitude and even sign of the impact is unclear. Cirrus clouds affect the transfer of radiation according to their physical depth and location in the atmosphere and their microphysical composition. However, significant uncertainties still exist in how cirrus clouds form and how they are maintained, what their physical properties are and how they can be parameterized in numerical models. Better remote sensing techniques for monitoring cirrus cloud systems and improved modeling of radiative transfer through ice particles are also needed. A critical element in resolving these issues is a better understanding of cirrus cloud microphysical properties and how they vary. The focus of the research to be conducted under this grant was th data collected in situ by the University of North Dakota Citation aircraft. The goals of this research were to add to the body of knowledge of cirrus cloud microphysics, particularly at the small end of the size spectrum; and analyze the spatial variation of cirrus clouds.

  2. Chemistry and microphysics of polar stratospheric clouds and cirrus clouds.

    PubMed

    Zondlo, M A; Hudson, P K; Prenni, A J; Tolbert, M A

    2000-01-01

    Ice particles found within polar stratospheric clouds (PSCs) and upper tropospheric cirrus clouds can dramatically impact the chemistry and climate of the Earth's atmosphere. The formation of PSCs and the subsequent chemical reactions that occur on their surfaces are key components of the massive ozone hole observed each spring over Antarctica. Cirrus clouds also provide surfaces for heterogeneous reactions and significantly modify the Earth's climate by changing the visible and infrared radiation fluxes. Although the role of ice particles in climate and chemistry is well recognized, the exact mechanisms of cloud formation are still unknown, and thus it is difficult to predict how anthropogenic activities will change cloud abundances in the future. This article focuses on the nucleation, chemistry, and microphysical properties of ice particles composing PSCs and cirrus clouds. A general overview of the current state of research is presented along with some unresolved issues facing scientists in the future.

  3. Studying Effects of Cloud Area Structure on Entrainment-Mixing Processes, Droplet Clustering, and Microphysics with a New Particle-Resolved Direct Numerical Simulation Model

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Gao, Z.; Lin, X.

    2016-12-01

    A new particle-resolved three dimensional direct numerical simulation (DNS) model is developed that combines Lagrangian droplet tracking with the Eulerian field representation. Six numerical experiments, each of which represents a different combination of three initial cloudy area structure and two turbulence scenarios (decaying and forced turbulence) are performed to investigate the processes of entrainment of clear air and sub-sequent mixing with cloudy air and their interactions with cloud microphysics under different environments (e.g., cloud-top mixing, lateral mixing, and inside clouds). The results show that even with the same cloud water fraction, the thermodynamic and microphysical properties are highly different with different settings, especially for the decaying cases, highlighting the role of the initial shape of cloud filaments in the study of cloud entrainment and mixing. Further investigated are the effects of droplet sedimentation on droplet clustering and preferential concentration. Also explored are the potentials of using the DNS to develop understanding and parameterization of such sub-LES turbulent processes and their interactions with cloud microphysics.

  4. Cloud Processed CCN Affect Cloud Microphysics

    NASA Astrophysics Data System (ADS)

    Hudson, J. G.; Noble, S. R., Jr.; Tabor, S. S.

    2015-12-01

    Variations in the bimodality/monomodality of CCN spectra (Hudson et al. 2015) exert opposite effects on cloud microphysics in two aircraft field projects. The figure shows two examples, droplet concentration, Nc, and drizzle liquid water content, Ld, against classification of CCN spectral modality. Low ratings go to balanced separated bimodal spectra, high ratings go to single mode spectra, strictly monomodal 8. Intermediate ratings go merged modes, e.g., one mode a shoulder of another. Bimodality is caused by mass or hygroscopicity increases that go only to CCN that made activated cloud droplets. In the Ice in Clouds Experiment-Tropical (ICE-T) small cumuli with lower Nc, greater droplet mean diameters, MD, effective radii, re, spectral widths, σ, cloud liquid water contents, Lc, and Ld were closer to more bimodal (lower modal ratings) below cloud CCN spectra whereas clouds with higher Nc, smaller MD, re, σ, and Ld were closer to more monomodal CCN (higher modal ratings). In polluted stratus clouds of the MArine Stratus/Stratocumulus Experiment (MASE) clouds that had greater Nc, and smaller MD, re, σ, Lc, and Ld were closer to more bimodal CCN spectra whereas clouds with lower Nc, and greater MD, re, σ, Lc, and Ld were closer to more monomodal CCN. These relationships are opposite because the dominant ICE-T cloud processing was coalescence whereas chemical transformations (e.g., SO2 to SO4) were dominant in MASE. Coalescence reduces Nc and thus also CCN concentrations (NCCN) when droplets evaporate. In subsequent clouds the reduced competition increases MD and σ, which further enhance coalescence and drizzle. Chemical transformations do not change Nc but added sulfate enhances droplet and CCN solubility. Thus, lower critical supersaturation (S) CCN can produce more cloud droplets in subsequent cloud cycles, especially for the low W and effective S of stratus. The increased competition reduces MD, re, and σ, which inhibit coalescence and thus reduce drizzle

  5. Formation and growth of nucleated particles into cloud condensation nuclei: Comparison of a global microphysics model with observations

    NASA Astrophysics Data System (ADS)

    Westervelt, D. M.; Adams, P. J.; Riipininen, I.; Pierce, J. R.; Trivitayanurak, W.

    2012-04-01

    Aerosol nucleation occurs frequently in the atmosphere and is an important source of particle number. Observations suggest that nucleated particles are capable of growing to sufficiently large sizes that they act as cloud condensation nuclei (CCN), but some global models have reported that CCN concentrations are only modestly sensitive to large changes in nucleation rates. The connection between nucleation and CCN represents a key uncertainty in understanding the CCN budget and its implications for Earth's radiative balance. Here we present a novel approach for evaluating, in observations and models, the impact of single-day nucleation and growth events on the regional CCN budget. We also compare model-predicted nucleation rates, diameter growth rates, condensation and coagulation sinks, and survival probabilities to observations. This work uses the TwO-Moment Aerosol Sectional algorithm (TOMAS) hosted by the global chemical transport model GEOS-Chem to simulate nucleation events predicted by ternary (with a 10-5 tuning factor) or activation nucleation over one year. To evaluate model performance, we compare GEOS-Chem-TOMAS output in 30-minute intervals against a full year of size distribution datasets measured at the five following locations: Pittsburgh, Hyytiälä, Atlanta, St. Louis, and Po Valley. Results show that GEOS-Chem-TOMAS does not understate the importance of nucleation to CCN concentrations, as most metrics are within a 50% error in the model-measurement agreement and tend to be biased high. Median survival probabilities to 100 nm within one day for the model and measurements range from less than 1% to 9% across the five locations we considered. The strength of the coagulation sink and the infrequency of strong growth events (greater than 10 nm h-1) are mainly responsible for these relatively low single-day survival probabilies. Additionally, both observations and models suggest that single-day nucleation and growth events contribute less than 5% to

  6. Evaluating uncertainty in convective cloud microphysics using statistical emulation

    NASA Astrophysics Data System (ADS)

    Johnson, J. S.; Cui, Z.; Lee, L. A.; Gosling, J. P.; Blyth, A. M.; Carslaw, K. S.

    2015-03-01

    The microphysical properties of convective clouds determine their radiative effects on climate, the amount and intensity of precipitation as well as dynamical features. Realistic simulation of these cloud properties presents a major challenge. In particular, because models are complex and slow to run, we have little understanding of how the considerable uncertainties in parameterized processes feed through to uncertainty in the cloud responses. Here we use statistical emulation to enable a Monte Carlo sampling of a convective cloud model to quantify the sensitivity of 12 cloud properties to aerosol concentrations and nine model parameters representing the main microphysical processes. We examine the response of liquid and ice-phase hydrometeor concentrations, precipitation, and cloud dynamics for a deep convective cloud in a continental environment. Across all cloud responses, the concentration of the Aitken and accumulation aerosol modes and the collection efficiency of droplets by graupel particles have the most influence on the uncertainty. However, except at very high aerosol concentrations, uncertainties in precipitation intensity and amount are affected more by interactions between drops and graupel than by large variations in aerosol. The uncertainties in ice crystal mass and number are controlled primarily by the shape of the crystals, ice nucleation rates, and aerosol concentrations. Overall, although aerosol particle concentrations are an important factor in deep convective clouds, uncertainties in several processes significantly affect the reliability of complex microphysical models. The results suggest that our understanding of aerosol-cloud interaction could be greatly advanced by extending the emulator approach to models of cloud systems.

  7. Cloud Microphysical Characteristics over East Asia

    NASA Astrophysics Data System (ADS)

    Yin, J.; Wang, D.; Zhai, G.

    2012-04-01

    A survey of the existing literature on in-situ measurements of cloud-precipitation microphysical properties was undertaken. Then, a database was established to contain microphysical properties for raindrop, cloud droplet, fog, ice nuclei (IN), snow crystal, as well as the relationship between radar reflectivity (Z) and rainfall rate (R). The time span of the in-situ probe measurements ranges from 1960 to 2008 over East Asia and from 1940 to 2008 in the other regions (which is defined as those include the Americas, Europe, and Australia). From the datasets, dividing the data coverage into East Asia and the other regions, several parameters are presented, including mean concentration of hydrometeor particles, liquid water content (LWC), as well as functional fit parameters of particles size distributions. The main properties of hydrometeor particles were presented, and the functional fitted parameters of particle size distributions over East Asia have been compared with those over the other regions. Note that the all measurements taken in other regions do not mean that all cloud systems in the other regions are similar. Our main method of the present study is to put all measurement results taken in different regions over the world together. If the cloud systems over East Asia have their own characteristics, it will be grouped together. Thus, the difference between East Asia and other regions is readily discernible. The results show that there are differences, sometimes even large differences, between East Asia and the other regions in terms of these cloud-precipitation microphysical characteristics. More specific conclusions are as follows: (1) Both exponential- and gamma-size distributions are used to fit RSD of rains originating from stratiform clouds. Average intercept N0 of exponential-size distribution over East Asia is one order of magnitude smaller than that over the other regions, and average slope λ is slight smaller. As for gamma-size distributions, the

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

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

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

  9. Salt-dust storms and their effect on cloud microphysics

    NASA Astrophysics Data System (ADS)

    Rudich, Y.; Rosenfled, D.

    2002-12-01

    It was recently shown that urban pollution, biomass burning smoke and desert dust reduce the size of cloud droplets, increase cloud albedo and suppress precipitation formation. In contrast, cloud simulations suggest that even low concentrations of large soluble aerosols should promote droplets' growth and rainfall. Until now, though, no observational evidence of such microphysical effects in natural circumstance has been presented due to the low concnetration of large soluble partciles in the atmosphere. By using NOAA-AVHRR retrievals on cases where salt-dust storms from the Aral Sea interacts with clouds we show that large salt-containing dust particles increase cloud drops to sizes that promote precipitation formation processes. The effects has also been observed after 24-36 hourse transport of the aerosols. These findings are in line with the findings of the microphysical models and recent results from hygroscopic cloud seeding experiments for rain enhancement.

  10. Evidence of Mineral Dust Altering Cloud Microphysics and Precipitation

    NASA Technical Reports Server (NTRS)

    Min, Qilong; Li, Rui; Lin, Bing; Joseph, Everette; Wang, Shuyu; Hu, Yongxiang; Morris, Vernon; Chang, F.

    2008-01-01

    Multi-platform and multi-sensor observations are employed to investigate the impact of mineral dust on cloud microphysical and precipitation processes in mesoscale convective systems. It is clearly evident that for a given convection strength,small hydrometeors were more prevalent in the stratiform rain regions with dust than in those regions that were dust free. Evidence of abundant cloud ice particles in the dust sector, particularly at altitudes where heterogeneous nucleation process of mineral dust prevails, further supports the observed changes of precipitation. The consequences of the microphysical effects of the dust aerosols were to shift the precipitation size spectrum from heavy precipitation to light precipitation and ultimately suppressing precipitation.

  11. Cloud microphysics - Analysis of the clouds of Earth, Venus, Mars, and Jupiter

    NASA Technical Reports Server (NTRS)

    Rossow, W. B.

    1978-01-01

    The probable microphysics of a cloud is deduced by a described method which requires information on cloud particle mean size, composition, number density, and atmospheric structure, but does not require any additional information. The analysis is applied to the sulfuric acid clouds of Venus, the water ice and dust clouds of Mars, and the ammonia-water and ammonia ice clouds of Jupiter. The Venus cloud layer is found to have some resemblance to smog and haze layers on earth. The water ice clouds on Mars resemble tenuous nonprecipitating cirrus clouds on earth. Precipitation, vertical distribution of gases, and vertical transport of heat in the clouds on Jupiter are considered.

  12. Effects of ice-phase cloud microphysics in simulating wintertime precipitation

    SciTech Connect

    Kim, Jinwon; Cho, Han-Ru; Soong, Sy-Tzai

    1995-11-01

    We compare two numerical experiments to investigate the effects of ice-phase cloud microphysical processes on simulations of wintertime precipitation in the southwestern United States. Results of these simulations, one with and the other without ice-phase microphysics, suggest that an inclusion of ice-phase microphysics plays a crucial role in simulating wintertime precipitation. The simulation that employs both the ice and water-phase microphysics better reproduced the observed spatial distribution of precipitation compared to the one without ice-phase microphysics. The most significant effect of ice-phase microphysics appeared in local production of precipitating particles by collection processes, rather than in local condensation.

  13. Cloud Susceptibilities to Ice Nuclei: Microphysical Effects and Dynamical Feedbacks

    NASA Astrophysics Data System (ADS)

    Paukert, Marco; Hoose, Corinna

    2015-04-01

    The impact of aerosols on cloud properties is currently not well established. This is largely attributed to the interdependencies of aerosols and cloud microphysical processes, among which primary ice formation contributes to considerable uncertainties. Although it is known that in a large range of thermodynamic conditions aerosol particles are required to initiate ice formation, identifying and characterizing the effect of specific ice nuclei is among current scientific efforts. Here we attempt to quantify the change of cloud properties with varying aerosol background concentrations. We adapt the concept of susceptibilities for mixed-phase and ice clouds, defining the susceptibility as the derivation of a macrophysical quantity with respect to ice nucleating aerosol concentrations. A focus of our study is the use of different model approaches in order to identify the distinct contributions of both cloud microphysics and cloud-dynamical feedbacks to the overall susceptibility. The classical method is the direct comparison of two independent model runs, where the whole range of microphysical and cloud-dynamical feedbacks contributes to different cloud properties in a perturbed simulation. Our alternative method relies on a single simulation which incorporates multiple executions of the microphysical scheme within the same time step, each "perturbed microphysics" scheme with varying aerosol concentrations and an additional set of cloud particle tracers. Since in the latter case the model dynamics are held constant and only microphysical feedbacks contribute to the properties of perturbed clouds, we can distinguish between the pure microphysical effect and the dynamical enhancement or suppression. For a persistent Arctic mixed-phase stratocumulus cloud layer which is expected to be particularly sensitive to feedback cycles, we show an enhancement of the cloud susceptibility to ice nucleating particles by dynamics of around 50%, but a decay of the enhancement with time

  14. Large ice particles associated with small ice water content observed by AIM CIPS imagery of polar mesospheric clouds: Evidence for microphysical coupling with small-scale dynamics

    NASA Astrophysics Data System (ADS)

    Rusch, D.; Thomas, G.; Merkel, A.; Olivero, J.; Chandran, A.; Lumpe, J.; Carstans, J.; Randall, C.; Bailey, S.; Russell, J.

    2017-09-01

    Observations by the Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite have demonstrated the existence of Polar Mesospheric Cloud (PMC) regions populated by particles whose mean sizes range between 60 and 100 nm (radii of equivalent volume spheres). It is known from numerous satellite experiments that typical mean PMC particle sizes are of the order of 40-50 nm. Determination of particle size by CIPS is accomplished by measuring the scattering of solar radiation at various scattering angles at a spatial resolution of 25 km2. In this size range we find a robust anti-correlation between mean particle size and albedo. These very-large particle-low-ice (VLP-LI) clouds occur over spatially coherent areas. The surprising result is that VLP-LI are frequently present either in the troughs of gravity wave-like features or at the edges of PMC voids. We postulate that an association with gravity waves exists in the low-temperature summertime mesopause region, and illustrate the mechanism by a gravity wave simulation through use of the 2D Community Aerosol and Radiation Model for Atmospheres (CARMA). The model results are consistent with a VLP-LI population in the cold troughs of monochromatic gravity waves. In addition, we find such events in Whole Earth Community Climate Model/CARMA simulations, suggesting the possible importance of sporadic downward winds in heating the upper cloud regions. This newly-discovered association enhances our understanding of the interaction of ice microphysics with dynamical processes in the upper mesosphere.

  15. Are Climate Models Sensitive to the Microphysics of Clouds?

    NASA Astrophysics Data System (ADS)

    Somerville, R. C.

    2001-12-01

    Parameterization transplant experiments with general circulation models (GCMs) demonstrate that details of cloud-radiation interactions can have large potential effects on the simulated climate. However, in order to determine which aspects of sub-grid physics are important and which parameterizations are most realistic, detailed comparisons with observations are essential. One useful diagnostic tool for making such comparisons is the single-column model (SCM), which consists of one isolated column of an atmospheric GCM. When an SCM is forced with observed horizontal advection terms, the parameterizations within the SCM produce time-dependent vertical profiles of fields which can be compared directly with measurements. In the case of cloud microphysical schemes, these fields include cloud altitude, cloud amount, liquid and ice content, particle size spectra, and radiative fluxes at the surface and the top of the atmosphere. Comparisons with data from the Atmospheric Radiation Measurement (ARM) Program show conclusively that prognostic cloud algorithms with detailed microphysics are far more realistic than simpler diagnostic approaches. These results also demonstrate the critical need for more and better in situ observations of cloud microphysical variables.

  16. Microphysical Timescales in Clouds and their Application in Cloud-Resolving Modeling

    NASA Technical Reports Server (NTRS)

    Zeng, Xiping; Tao, Wei-Kuo; Simpson, Joanne

    2007-01-01

    Independent prognostic variables in cloud-resolving modeling are chosen on the basis of the analysis of microphysical timescales in clouds versus a time step for numerical integration. Two of them are the moist entropy and the total mixing ratio of airborne water with no contributions from precipitating particles. As a result, temperature can be diagnosed easily from those prognostic variables, and cloud microphysics be separated (or modularized) from moist thermodynamics. Numerical comparison experiments show that those prognostic variables can work well while a large time step (e.g., 10 s) is used for numerical integration.

  17. Ice cloud microphysical properties in tropical Pacific regions derived from CloudSat and CALIPSO measurements

    NASA Astrophysics Data System (ADS)

    Takahashi, Naoya; Hayasaka, Tadahiro; Okamoto, Hajime

    2017-02-01

    We revealed the difference in tropical ice cloud microphysical properties between the western Pacific (WP) and the eastern Pacific (EP), based on satellite retrievals. Vertical profile of effective particle radius of ice cloud (re) was estimated from active sensors on board CloudSat and CALIPSO satellites. In this study, we focused only on ice cloud which is defined as clouds with the cloud top temperature lower than 0°C. To investigate the relationship between cloud optical properties and cloud vertical structures, these ice clouds were classified into five types based on cloud optical thickness values. Compared the vertical profile of re in WP with that in the EP, re around the freezing level within convective cloud in EP slightly larger than that in WP. This analysis also shows that re of optically thick cloud is larger than that of optically thin cloud. The difference in re may be caused by differences in moisture convergence, upward motion, aerosols.

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

    NASA Technical Reports Server (NTRS)

    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.

  19. Influence of particle size and shape on the backscattering linear depolarisation ratio of small ice crystals - cloud chamber measurements in the context of contrail and cirrus microphysics

    NASA Astrophysics Data System (ADS)

    Schnaiter, M.; Büttner, S.; Möhler, O.; Skrotzki, J.; Vragel, M.; Wagner, R.

    2012-11-01

    The article presents the laser scattering and depolarisation instrument SIMONE that is installed at the large aerosol and cloud chamber facility AIDA of the Karlsruhe Institute of Technology. SIMONE uses a 488 nm cw laser to probe simulated atmospheric clouds by measuring the scattered light from the 1.8° and 178.2° directions. At 178.2°, the scattered light is analysed for the linear polarisation state to deduce the particle linear depolarisation ratio δp which is a common measurement parameter of atmospheric lidar applications. The optical setup and the mathematical formalism of the depolarisation detection concept are given. SIMONE depolarisation measurements in spheroidal hematite aerosol and supercooled liquid clouds are used to validate the instrument. SIMONE data from a series of AIDA ice nucleation experiments at temperatures between 195 and 225 K were analysed in terms of the impact of the ice particle microphysics on δp. We found strong depolarisation values of up to 0.4 in case of small growing and sublimating ice particles with volume equivalent diameters of only a few micrometers. Modelling runs with the T-matrix method showed that the measured depolarisation ratios can be accurately reproduced assuming spheroidal and cylindrical particles with a size distribution that has been constrained by IR extinction spectroscopy. Based on the T-matrix modelling runs, we demonstrate that in case of small ice crystals the SIMONE depolarisation results are representative for the lidar depolarisation ratio which is measured at exact backscattering direction of 180°. The relevance of our results for the interpretation of recent lidar observations in cirrus and contrails is discussed. In view of our results, the high depolarisation ratios observed by the spaceborne lidar CALIOP in the tropical upper troposphere might be a hint for the presence of small (sublimating) ice particles in the outflows of deep convective systems.

  20. Microphysical Characteristics of Tropical Clouds

    NASA Technical Reports Server (NTRS)

    Grainger, Cedric A.; Anderson, Nicholas

    2004-01-01

    This report summarizes the analysis of data collected by the University of North Dakota Citation II measurement platform during three TRMM Field measurement campaigns. The Citation II made cloud measurements during TEFLUN B in Florida, the LBA program in Brazil, and KWAJEX in Kwajalein. The work performed can be divided into two parts. The first part consisted of reformatting the Citation data into a form more easily used to compare to the satellite information. The second part consisted of examination of the cloud data in order to characterize the properties of the tropical clouds. The reformatting of the Citation data was quite labor intensive and, due to the fact that the aircraft was involved in three of the field campaigns, it required a substantial number of person-hours to complete. Much of the analysis done on the second part was done in conjunction with the thesis work of Nicholas Anderson, then a graduate student at the University of North Dakota.

  1. Clouds Microphysics Analysis and Modeling.

    DTIC Science & Technology

    1986-07-01

    mesoscale cloud models and analyze data in support of such models. Results Of the BIGH-ILL and CCOPE experiment model runs and the transfer and implementation...model of cumulus clouds. the SNOW\\-11s’’.s’n analysi, STRATEX data analysis. UND data analysis of aircraft flight tapes, and program, for th4e anal...8217 (i\\ f P\\lS-’iU) mc Image Data . 20. OiSTRIBUTIONIAVAILABILiTY OF ABSTRACT 21 ABSTRACT SECURITY CLASSIFICATION UNCLASSIFIEO/UNLIMITEO [:(SAME AS RPT OTIC

  2. Depolarization Lidar Determination Of Cloud-Base Microphysical Properties

    NASA Astrophysics Data System (ADS)

    Donovan, D. P.; Klein Baltink, H.; Henzing, J. S.; de Roode, S.; Siebesma, A. P.

    2016-06-01

    The links between multiple-scattering induced depolarization and cloud microphysical properties (e.g. cloud particle number density, effective radius, water content) have long been recognised. Previous efforts to use depolarization information in a quantitative manner to retrieve cloud microphysical cloud properties have also been undertaken but with limited scope and, arguably, success. In this work we present a retrieval procedure applicable to liquid stratus clouds with (quasi-)linear LWC profiles and (quasi-)constant number density profiles in the cloud-base region. This set of assumptions allows us to employ a fast and robust inversion procedure based on a lookup-table approach applied to extensive lidar Monte-Carlo multiple-scattering calculations. An example validation case is presented where the results of the inversion procedure are compared with simultaneous cloud radar observations. In non-drizzling conditions it was found, in general, that the lidar- only inversion results can be used to predict the radar reflectivity within the radar calibration uncertainty (2-3 dBZ). Results of a comparison between ground-based aerosol number concentration and lidar-derived cloud base number considerations are also presented. The observed relationship between the two quantities is seen to be consistent with the results of previous studies based on aircraft-based in situ measurements.

  3. Influence of particle size and shape on the backscattering linear depolarisation ratio of small ice crystals - cloud chamber measurements in the context of contrail and cirrus microphysics

    NASA Astrophysics Data System (ADS)

    Schnaiter, M.; Büttner, S.; Möhler, O.; Skrotzki, J.; Vragel, M.; Wagner, R.

    2012-06-01

    The article presents the laser scattering and depolarisation instrument SIMONE that is installed at the large aerosol and cloud chamber facility AIDA of the Karlsruhe Institute of Technology. SIMONE uses a 488 nm cw laser to probe simulated atmospheric clouds by measuring the scattered light from the 1.8° and 178.2° directions. At 178.2°, the scattered light is analysed for the linear polarisation state to deduce the linear depolarisation ratio δl which is a common measurement parameter of atmospheric LIDAR applications. The optical setup and the mathematical formalism of the depolarisation detection concept are given. SIMONE depolarisation measurements in spheroidal hematite aerosol and supercooled liquid clouds are used to validate the instrument. SIMONE data from a series of AIDA ice nucleation experiments at temperatures between 195 and 225 K were analysed in terms of the impact of the ice particle microphysics on δl. We found strong depolarisation values of up to 0.4 in case of small growing and sublimating ice particles with volume equivalent diameters of only a few micrometers. Modelling runs with the T-matrix method showed that the measured depolarisation ratios can be accurately reproduced assuming spheroidal and cylindrical particles with a size distribution that has been constrained by IR extinction spectroscopy. Based on the T-matrix modelling runs, we demonstrate that in case of small ice crystals the SIMONE depolarisation results are representative for the LIDAR depolarisation ratio which is measured at exact backscattering direction of 180°. The relevance of our results for the interpretation of recent LIDAR observations in cirrus and contrails is discussed. In view of our results, the high depolarisation ratios observed by the spaceborne LIDAR CALIOP in the tropical upper troposphere might be a hint for the presence of small (sublimating) ice particles in the outflows of deep convective systems.

  4. Microphysics and Southern Ocean Cloud Feedback

    NASA Astrophysics Data System (ADS)

    McCoy, Daniel T.

    Global climate models (GCMs) change their cloud properties in the Southern Ocean (SO) with warming in a qualitatively consistent fashion. Cloud albedo increases in the mid-latitudes and cloud fraction decreases in the subtropics. This creates a distinctive 'dipole' structure in the SW cloud feedback. However, the shape of the dipole varies from model to model. In this thesis we discuss the microphysical mechanisms underlying the SW cloud feedback over the mid-latitude SO. We will focus on the negative lobe of the dipole. The negative SW cloud feedback in the mid-latitudes is created by transitions from ice to liquid in models. If ice transitions to liquid in mixed-phase clouds the cloud albedo increases because ice crystals are larger than liquid droplets and therefore more reflective for a constant mass of water. Decreases in precipitation efficiency further enhance this effect by decreasing sinks of cloud water. This transition is dependent on the mixed-phase cloud parameterization. Parameterizations vary wildly between models and GCMs disagree by up to 35 K on the temperature where ice and liquid are equally prevalent. This results in a wide spread in the model predictions of the increase in liquid water path (LWP, where the path is the vertically integrated mass of water) with warming that drives the negative optical depth cloud feedback. It is found that this disagreement also results in a wide array of climate mean-states as models that create liquid at lower temperatures have a higher mean-state LWP, lower ice water path (IWP), and higher condensed (ice and liquid) water path (CWP). This presents a problem in climate models. GCMs need to have a reasonable planetary albedo in their climate mean-state. We show evidence that GCMs have tuned cloud fraction to compensate for the variation in mid-latitude cloud albedo driven by the mixed-phase cloud parameterization. This tuning results in mid-latitude clouds that are both too few and too bright as well as a

  5. Cloud microphysical relationships in California marine stratus

    SciTech Connect

    Hudson, J.G.; Svensson, G.

    1995-12-01

    Cloud microphysical measurements off the southern California coast are presented and compared with in situ airborne measurements of cloud condensation nuclei (CCN) spectra. Large-scale variations in cloud droplet concentrations were due to CCN variations, some medium-scale variations may be a result of the conversion of droplets to drops by coalescence, while small-scale variations were due to different proportions of the CCN spectra being activated because of variations in updraft velocity at cloud base. This latter internal mixing process produces an inverse relationship between droplet concentration and mean size and an increase in droplet spectral width with mean droplet size. Drizzle drop concentrations are strongly associated with lower droplet concentrations, larger droplets, and greater droplet spectral width. 29 refs., 9 figs., 3 tabs.

  6. The Influence of Microphysical Cloud Parameterization on Microwave Brightness Temperatures

    NASA Technical Reports Server (NTRS)

    Skofronick-Jackson, Gail M.; Gasiewski, Albin J.; Wang, James R.; Zukor, Dorothy J. (Technical Monitor)

    2000-01-01

    The microphysical parameterization of clouds and rain-cells plays a central role in atmospheric forward radiative transfer models used in calculating passive microwave brightness temperatures. The absorption and scattering properties of a hydrometeor-laden atmosphere are governed by particle phase, size distribution, aggregate density., shape, and dielectric constant. This study identifies the sensitivity of brightness temperatures with respect to the microphysical cloud parameterization. Cloud parameterizations for wideband (6-410 GHz observations of baseline brightness temperatures were studied for four evolutionary stages of an oceanic convective storm using a five-phase hydrometeor model in a planar-stratified scattering-based radiative transfer model. Five other microphysical cloud parameterizations were compared to the baseline calculations to evaluate brightness temperature sensitivity to gross changes in the hydrometeor size distributions and the ice-air-water ratios in the frozen or partly frozen phase. The comparison shows that, enlarging the rain drop size or adding water to the partly Frozen hydrometeor mix warms brightness temperatures by up to .55 K at 6 GHz. The cooling signature caused by ice scattering intensifies with increasing ice concentrations and at higher frequencies. An additional comparison to measured Convection and Moisture LA Experiment (CAMEX 3) brightness temperatures shows that in general all but, two parameterizations produce calculated T(sub B)'s that fall within the observed clear-air minima and maxima. The exceptions are for parameterizations that, enhance the scattering characteristics of frozen hydrometeors.

  7. Meteorological and aerosol effects on marine cloud microphysical properties

    NASA Astrophysics Data System (ADS)

    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) (<0.01), except for cargo ship and smoke plumes, which increased CR by 0.02 and 0.07, respectively, owing to their high organic mass fraction. Organic hygroscopicity had larger effects on droplet concentrations for cases with higher aerosol concentrations near the critical diameter (namely, polluted cases with a 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.

  8. Cloud Microphysics by Thermal Wave Methods

    NASA Technical Reports Server (NTRS)

    Anderson, B. J.; Bowdle, D. A.; Reischel, M.

    1985-01-01

    This experiments series is the first application of a low-gravity experimental technique to the study of cloud microphysics. The low-gravity environment is provided by the parabolic maneuver of NASA's KC-135 aircraft. The primary objective is to compare experimental observations of cloud droplet growth and evaporation in a convection free environment with a numerical model of the process. Beyond that, the work also involves the development and testing of low-gravity research techniques. In particular, passive methods of thermal control have been devised and used effectively. The study to date has shown that the method is particularly suitable for looking at interactions between adjoining portions of the cloud drop field and interactions of the drop field with a solid interface. After final analysis of the data, it is expected the results will shed light on the development of cloud droplet size spectra in natural clouds as well as the performance of certain types of cloud physics instrumentation, particularly continuous flow diffusion chambers and loud condensation nuclei counters.

  9. Comparison of cloud microphysical parameters derived from surface and satellite measurements during FIRE phase 2

    NASA Technical Reports Server (NTRS)

    Young, David F.; Minnis, Patrick; Snider, Jack; Uttal, Taneil; Intrieri, Janet M.; Matrosov, Sergey

    1993-01-01

    Cloud microphysical properties are an important component in climate model parameterizations of water transport, cloud radiative exchange, and latent heat processes. Estimation of effective cloud particle size, liquid or ice water content, and optical depth from satellite-based instrumentation is needed to develop a climatology of cloud microphysical properties and to better understand and model cloud processes in atmospheric circulation. These parameters are estimated from two different surface data sets taken at Coffeyville, Kansas, during the First ISCCP Regional Experiment (FIRE) Phase-2 Intensive Field Observation (IFO) period (November 13 - December 7, 1991). Satellite data can also provide information about optical depth and effective particle size. This paper explores the combination of the FIRE-2 surface and satellite data to determine each of the cloud microphysical properties.

  10. Meteorological and Aerosol effects on Marine Cloud Microphysical Properties

    NASA Astrophysics Data System (ADS)

    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 (<0.7%) with the exception of the cargo ship plume and smoke plume which increased absolute cloud reflectivity fraction by 0

  11. Laboratory experiments on the microphysical formation process of Noctilucent Clouds

    NASA Astrophysics Data System (ADS)

    Nachbar, Mario; Duft, Denis; Wilms, Henrike; Kitajima, Kensei; Leisner, Thomas

    2017-04-01

    Ablated meteoric material condensates in the upper atmosphere to nanometer sized meteoric smoke particles (MSPs). These particles are believed to be the major kind of nuclei for the formation of so called NoctiLucent Clouds (NLCs) in the polar summer mesosphere. However, describing the formation process of these clouds is flawed with large uncertainties mainly due to a lack of experimental data on their microphysical formation process. To investigate these processes, we produce single charged nanometer sized (1-3 nm) MSP analogues in a microwave plasma particle source. The particles are suspended in a carrier gas and transferred to a vacuum setup where they are stored in a linear ion trap (MICE). The trap allows us to apply realistic mesopause conditions in terms of temperature, background pressure and water vapor concentration. By using a time-of-flight mass spectrometer, we are able to observe adsorption and, if nucleation occurs, subsequent deposition of water vapor on the MSP analogues as a function of saturation and residence time in MICE. From these experiments, we determine critical saturations needed to activate cloud formation. However, NLCs occur during polar summer and therefore are exposed to sunlight. At the low pressures of the mesopause, MSPs may heat up with respect to the background gas temperature which significantly influences the critical saturation needed to activate cloud formation. We expose the MSP analogues trapped in MICE to laser light of a known radiation profile in order to determine the heat up of the particles as well as the resulting influence on the nucleation process. The results of our experiments describe the microphysical H2O nucleation process on MSPs at realistic mesopause conditions and therefore can be used in models to describe the formation of NLCs and countercheck the results with observational cloud properties.

  12. Reformulating Aerosol Thermodynamics and Cloud Microphysics

    NASA Astrophysics Data System (ADS)

    Metzger, S.

    2006-12-01

    Modeling aerosol composition and cloud microphysics is rather complex due to the required thermodynamics, even if chemical and thermodynamical equilibrium is assumed. We show, however, that for deliquescent atmospheric aerosols thermodynamics can be considerably simplified, if we reformulate chemical equilibrium to include water purely based on thermodynamic principles. In chemical and thermodynamical equilibrium, the relative humidity (RH) fixes the molality of atmospheric aerosols. Although this fact is in theory well known, it has hardly been utilized in aerosol modeling nor has been the fact that for the same reason also the aerosol activity (including activity coefficients) and water content are fixed (by RH) for a given aerosol concentration and type. The only model that successfully utilizes this fact is the computationally very efficient EQuilibrium Simplified thermodynamic gas/Aerosol partitioning Model, EQSAM (Metzger et al., 2002a), EQSAM2 (Metzger et al., 2006). In both versions the entire gas/liquid/solid aerosol equilibrium partitioning is solved analytically and hence non-iteratively a substantial advantage in aerosol composition modeling. Here we briefly present the theoretical framework of EQSAM2, which differs from EQSAM in a way that the calculation of the water activity of saturated binary or mixed inorganic/organic salt solutions of multi-component aerosols has been generalized by including the Kelvin-term, thus allowing for any solute activity above the deliquescence relative humidity, including supersaturation. With application of our new concept to a numerical whether prediction (NWP) model, we demonstrate its wide implications for the computation of various aerosol and cloud properties, as our new concept allows to consistently and efficiently link the modeling of aerosol thermodynamics and cloud microphysics through the aerosol water mass, which therefore deserves special attention in atmospheric chemistry, air pollution, NWP and climate

  13. The microphysical properties of small ice particles measured during MACPEX

    NASA Astrophysics Data System (ADS)

    Schmitt, C. G.; Schnaiter, M.; Heymsfield, A.; Bansemer, A.; Hirst, E.

    2012-12-01

    During the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) field campaign, the Small Ice Detector version 3 (SID-3) and the NCAR Video Ice Particle Sampler (VIPS) probes were operated onboard the NASA WB-57 aircraft to measure the microphysical properties of small ice particles in midlatitude cirrus clouds. The VIPS was optimized to measure the particle size distribution and projected area properties of ice particles between 20 and 200 microns and measurements agreed well with other microphysical probes. SID-3 measures the forward light scattering pattern from ice particles in the 1 to 100 micron size range. Forward scattering patterns can be used to characterize ice particle shape as well as surface roughness. Scattering patterns appear to be 'speckled' when particles have surface roughness and/or are polycrystalline. Scattering patterns can be used to identify quasi-spherical ice particles as well as particles which are sublimating. Sublimating crystals, spherical ice particles, and particles with surface roughness were all observed by SID-3 during MACPEX. Observed particle properties will be correlated to concurrent atmospheric observations. Measurements from the controlled environment of the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber will be related to atmospheric particle measurements.

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

    SciTech Connect

    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.

  15. Factors controlling cloud microphysics, precipitation rate, and brightness temperature of tropical convective and stratiform clouds

    NASA Astrophysics Data System (ADS)

    Hashino, T.; Casella, D.; Mugnai, A.; Sano, P.; Smith, E. A.; Tripoli, G.

    2008-12-01

    This paper discusses factors controlling cloud microphysics, precipitation rate and brightness temperature of tropical convective and stratiform clouds. Tropical convective and stratiform clouds are important in radiative forcing of climates and distribution of precipitation over the ocean. The possible effects of climate change on these clouds are still not well understood. Recent studies show that the higher CCN concentration in a convective cloud can lead to more vigorous updrafts and a higher evaporation/precipitation ratio. The stronger updraft often means stronger downdraft and gust fronts, which can trigger convection nearby. This implies that increases in CCN concentration can result in an increase in area coverage and persistence of tropical cirrus and stratiform clouds. The increased cloudiness would then be expected to lower sensible and latent heat flux from the ocean by lowering sea surface temperature, affecting the future development of convective clouds. The sea surface temperature may also change in a local area due to change of ocean circulation in climate change scenarios. Satellite remote sensing is a powerful tool to study tropical and global precipitation distribution. Many physically-based passive-microwave (MW) satellite precipitation algorithms make use of cloud radiation databases (CRDs), which typically consist of microphysical profiles from cloud resolving model (CRMs) and simulated MW brightness temperature (Tb). Thus, it is important to validate Tb simulated by a CRM against the observed Tb. Also, it is important to study how any changes in the tropical clouds due to aerosols and sea surface temperature translate into the precipitation and brightness temperature. The case study chosen is KWAJEX campaign that took place from 23 July to 14 September 1999. Authors have developed microphysical physical framework (Advanced Microphysics Prediction System) to predict ice particle properties explicitly in a CRM (University of Wisconsin

  16. Macrophysical cloud properties simulated by two-moment microphysics

    NASA Astrophysics Data System (ADS)

    Baba, Y.

    2016-12-01

    Cloud-resolving model (CRM) is becoming useful tool for climate. Recently, two-moment cloud microphysics which additionally predicts number concentration of water species and thus realizes more flexible representation for cloud properties has been widely used in CRM. The two-moment representation is also suitable for long-range CRM simulation, since cloud-radiation interaction is affected by number concentration of cloud droplet through aerosol indirect effects. In spite of the advancement in microphysical modeling, cloud properties simulated by CRM is dependent on microphysical parameterization and the resulting properties remains unknown until model's sensitivity has been confirmed. In order to clarify dependence of microphysical parametezation on cloud macrophysical outcome, especially focusing on two-moment representation of cloud microphysics, sensitivity experiments were performed in two idealized experiments, i.e., squall line and radiative convective quasi-equilibrium. The former experiment showed that predicting number concentration of large ice water species was necessary for simulating more realistic precipitation trends. A distinct difference between strong convective and weak stratiform precipitations in squall line was found to be dependent on the microphysical parameterization. The latter experiments showed a consistent trends with that of the former experiment, i.e., prediction of number concentration of large ice water species affects long-range, macrophysical cloud properties such as resulting heat and water budget in cloud-radiation interaction, and the budgets were greatly controlled by the behaviors of large ice water species. The vertical profiles of cloud mass flux were different and it was found to be derived from production rate of ice water species which was affected by number concentration of ice water species. The present results indicate that macrophysics of cloud properties depend on behaviors of ice water species rather than liquid

  17. Re-formulation and Validation of Cloud Microphysics Schemes

    NASA Astrophysics Data System (ADS)

    Wang, J.; Georgakakos, K. P.

    2007-12-01

    The research focuses on improving quantitative precipitation forecasts by removing significant uncertainties in current cloud microphysics schemes embedded in models such as WRF and MM5 and cloud-resolving models such as GCE. Reformulation of several production terms in these microphysics schemes was found necessary. When estimating four graupel production terms involved in the accretion between rain, snow and graupel, current microphysics schemes assumes that all raindrops and snow particles are falling at their appropriate mass-weighted mean terminal velocities and thus analytic solutions are able to be found for these production terms. Initial analysis and tests showed that these approximate analytic solutions give significant and systematic overestimates of these terms, and, thus, become one of major error sources of the graupel overproduction and associated extreme radar reflectivity in simulations. These results are corroborated by several reports. For example, the analytic solution overestimates the graupel production by collisions between raindrops and snow by up to 230%. The structure of "pure" snow (not rimed) and "pure graupel" (completely rimed) in current microphysics schemes excludes intermediate forms between "pure" snow and "pure" graupel and thus becomes a significant reason of graupel overproduction in hydrometeor simulations. In addition, the generation of the same density graupel by both the freezing of supercooled water and the riming of snow may cause underestimation of graupel production by freezing. A parameterization scheme of the riming degree of snow is proposed and then a dynamic fallspeed-diameter relationship and density- diameter relationship of rimed snow is assigned to graupel based on the diagnosed riming degree. To test if these new treatments can improve quantitative precipitation forecast, the Hurricane Katrina and a severe winter snowfall event in the Sierra Nevada Range are selected as case studies. A series of control

  18. Impacts of cloud microphysics on trade wind cumulus: which cloud microphysics processes contribute to the diversity in a large eddy simulation?

    NASA Astrophysics Data System (ADS)

    Sato, Yousuke; Nishizawa, Seiya; Yashiro, Hisashi; Miyamoto, Yoshiaki; Kajikawa, Yoshiyuki; Tomita, Hirofumi

    2015-12-01

    This study investigated the impact of several cloud microphysical schemes on the trade wind cumulus in the large eddy simulation model. To highlight the differences due to the cloud microphysical component, we developed a fully compressible large eddy simulation model, which excluded the implicit scheme and approximations as much as possible. The three microphysical schemes, the one-moment bulk, two-moment bulk, and spectral bin schemes were used for sensitivity experiments in which the other components were fixed. Our new large eddy simulation model using a spectral bin scheme successfully reproduced trade wind cumuli, and reliable model performance was confirmed. Results of the sensitivity experiments indicated that precipitation simulated by the one-moment bulk scheme started earlier, and its total amount was larger than that of the other models. By contrast, precipitation simulated by the two-moment scheme started late, and its total amount was small. These results support those of a previous study. The analyses revealed that the expression of two processes, (1) the generation of cloud particles and (2) the conversion from small droplets to raindrops, were crucial to the results. The fast conversion from cloud to rain and the large amount of newly generated cloud particles at the cloud base led to evaporative cooling and subsequent stabilization in the sub-cloud layer. The latent heat released at higher layers by the condensation of cloud particles resulted in the development of the boundary layer top height.

  19. Cloud Microphysics Budget in the Tropical Deep Convective Regime

    NASA Technical Reports Server (NTRS)

    Li, Xiao-Fan; Sui, C.-H.; Lau, K.-M.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Cloud microphysics budgets in the tropical deep convective regime are analyzed based on a 2-D cloud resolving simulation. The model is forced by the large-scale vertical velocity and zonal wind and large-scale horizontal advections derived from TOGA COARE for a 20-day period. The role of cloud microphysics is first examined by analyzing mass-weighted mean heat budget and column-integrated moisture budget. Hourly budgets show that local changes of mass-weighted mean temperature and column-integrated moisture are mainly determined by the residuals between vertical thermal advection and latent heat of condensation and between vertical moisture advection and condensation respectively. Thus, atmospheric thermodynamics depends on how cloud microphysical processes are parameterized. Cloud microphysics budgets are then analyzed for raining conditions. For cloud-vapor exchange between cloud system and its embedded environment, rainfall and evaporation of raindrop are compensated by the condensation and deposition of supersaturated vapor. Inside the cloud system, the condensation of supersaturated vapor balances conversion from cloud water to raindrop, snow, and graupel through collection and accretion processes. The deposition of supersaturated vapor balances conversion from cloud ice to snow through conversion and riming processes. The conversion and riming of cloud ice and the accretion of cloud water balance conversion from snow to graupel through accretion process. Finally, the collection of cloud water and the melting of graupel increase raindrop to compensate the loss of raindrop due to rainfall and the evaporation of raindrop.

  20. A Comparison of Cloud Microphysical and Optical Properties during TOGA-COARE

    NASA Technical Reports Server (NTRS)

    Strawa, A. W.; Pueschel, R. F.; Pilewskie, P.; Valero, F. P. J.; Gore, Warren J. (Technical Monitor)

    1996-01-01

    The impact of cirrus clouds on climate is an issue of research interest currently. Whether cirrus clouds heat or cool the Earth-atmosphere system depends on the cloud shortwave albedo and infrared reflectance and absorptance. These in turn are determined by the size distribution, phase, and composition of particles in the clouds. The TOGA-COARE campaign presented an excellent opportunity to study cirrus clouds and their influence on climate. In this campaign, a microphysics instrument package was flown aboard the DC-8 aircraft at medium altitudes in cirrus clouds. This package included a 2D Greyscale Cloud Particle Probe, a Forward Scattering Spectrometer Aerosol Probe, and an ice crystal replicator. At the same time the ER-2 equipped with a radiation measurement system flew coordinated flight tracks above the DC-8 at very high altitude. The radiation measurement made were short and long wave fluxes, as well as narrowband fluxes, both upwelling and downwelling. In addition LIDAR data is available. The existence of these data sets allows for a the comparison of radiation measurement with microphysical measurements. For example, the optical depth and effective radius retrieved from the ER-2 radiation measurements can be compared to the microphysical data. Conversely, the optical properties and fluxes produced by the clouds can be calculated from the microphysical measurements and compared to those measured aboard the ER-2. The assumptions required to make these comparisons are discussed. Typical microphysical results show a prevalence of micron-sized particles, in addition to the cloud particles that exceed 100 mm. The large number of small particles or "haze" cause the effective cloud radii to shift to smaller sizes, leading to changes in optical parameters.

  1. Evaluation of Microphysics Parameterization for Convective Clouds in the NCAR Community Atmosphere Model CAM5

    NASA Astrophysics Data System (ADS)

    Song, X.; Zhang, G. J.; Li, J. F.

    2012-12-01

    A physically-based two-moment microphysics parameterization scheme for convective clouds is implemented in the NCAR CAM5 to improve the representation of convective clouds and their interaction with large-scale clouds and aerosols. The explicit treatment of mass mixing ratio and number concentration of cloud and precipitation particles enables the scheme to account for the impact of aerosols on convection. The scheme is linked to aerosols through cloud droplet activation and ice nucleation processes, and to stratiform cloud parameterization through convective detrainment of cloud liquid/ice water content (LWC/IWC) and droplet/crystal number concentration (DNC/CNC). A 5-yr simulation with the new convective microphysics scheme shows that both cloud LWC/IWC and DNC/CNC are in good agreement with observations, indicating the scheme describes microphysical processes in convection well. Moreover, the microphysics scheme is able to represent the aerosol effects on convective clouds such as the suppression of warm rain formation and enhancement of freezing when aerosol loading is increased. With more realistic simulations of convective cloud microphysical properties and their detrainment, the mid- and low-level cloud fraction is increased significantly over the ITCZ/SPCZ and subtropical oceans, making it much closer to the observations. Correspondingly the serious negative bias in cloud liquid water path over subtropical oceans observed in the standard CAM5 is reduced markedly. The large-scale precipitation is increased and precipitation distribution is improved as well. The longstanding precipitation bias in the western Pacific is significantly alleviated due to microphysics-thermodynamics-circulation feedbacks.

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

    PubMed

    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.

  3. Cloud microphysical background for the Israel-4 cloud seeding experiment

    NASA Astrophysics Data System (ADS)

    Freud, Eyal; Koussevitzky, Hagai; Goren, Tom; Rosenfeld, Daniel

    2015-05-01

    The modest amount of rainfall in Israel occurs in winter storms that bring convective clouds from the Mediterranean Sea when the cold post frontal air interacts with its relatively warm surface. These clouds were seeded in the Israel-1 and Israel-2 cloud glaciogenic seeding experiments, which have shown statistically significant positive effect of added rainfall of at least 13% in northern Israel, whereas the Israel-3 experiment showed no added rainfall in the south. This was followed by operational seeding in the north since 1975. The lack of physical evidence for the causes of the positive effects in the north caused a lack of confidence in the statistical results and led to the Israel-4 randomized seeding experiment in northern Israel. This experiment started in the winter of 2013/14. The main difference from the previous experiments is the focus on the orographic clouds in the catchment of the Sea of Galilee. The decision to commence the experiment was partially based on evidence supporting the existence of seeding potential, which is reported here. Aircraft and satellite microphysical and dynamic measurements of the clouds document the critical roles of aerosols, especially sea spray, on cloud microstructure and precipitation forming processes. It was found that the convective clouds over sea and coastal areas are naturally seeded hygroscopically by sea spray and develop precipitation efficiently. The diminution of the large sea spray aerosols farther inland along with the increase in aerosol concentrations causes the clouds to develop precipitation more slowly. The short time available for the precipitation forming processes in super-cooled orographic clouds over the Golan Heights farthest inland represents the best glaciogenic seeding potential.

  4. Simulation of the Upper Clouds and Hazes of Venus Using a Microphysical Cloud Model

    NASA Astrophysics Data System (ADS)

    McGouldrick, K.

    2012-12-01

    Several different microphysical and chemical models of the clouds of Venus have been developed in attempts to reproduce the in situ observations of the Venus clouds made by Pioneer Venus, Venera, and Vega descent probes (Turco et al., 1983 (Icarus 53:18-25), James et al, 1997 (Icarus 129:147-171), Imamura and Hashimoto, 2001 (J. Atm. Sci. 58:3597-3612), and McGouldrick and Toon, 2007 (Icarus 191:1-24)). The model of McGouldrick and Toon has successfully reproduced observations within the condensational middle and lower cloud decks of Venus (between about 48 and 57 km altitude, experiencing conditions similar to Earth's troposphere) and it now being extended to also simulate the microphysics occurring in the upper cloud deck (between altitudes of about 57 km and 70 km, experiencing conditions similar to Earth's stratosphere). In the upper clouds, aerosols composed of a solution of sulfuric acid in water are generated from the reservoir of available water vapor and sulfuric acid vapor that is photochemically produced. The manner of particle creation (e.g., activation of cloud condensation nuclei, or homogeneous or heterogeneous nucleation) is still incompletely understood, and the atmospheric environment has been measured to be not inconsistent with frozen aerosol particles (either sulfuric acid monohydrate or water ice). The material phase, viscosity, and surface tension of the aerosols (which are strongly dependent up on the local temperature and water vapor concentration) can affect the coagulation efficiencies of the aerosol, leading to variations in the size distributions, and other microphysical and radiative properties. Here, I present recent work exploring the effects of nucleation rates and coalescence efficiencies on the simulated Venus upper clouds.

  5. Alterations of Cloud Microphysics Due to Cloud Processed CCN

    NASA Astrophysics Data System (ADS)

    Hudson, J. G.; Tabor, S. S.; Noble, S. R., Jr.

    2015-12-01

    High-resolution CCN spectra have revealed bimodality (Hudson et al. 2015) similar to aerosol size spectra (e.g., Hoppel et al. 1985). Bimodality is caused by chemical and physical cloud processes that increase mass or hygroscopicity of only CCN that produced activated cloud droplets. Bimodality is categorized by relative CCN concentrations (NCCN) within the two modes, Nu-Np; i.e., NCCN within the higher critical supersaturation, Sc, mode that did not undergo cloud processing minus NCCN within the lower Sc mode that was cloud processed. Lower, especially negative, Nu-Np designates greater processing. The table shows regressions between Nu-Np and characteristics of clouds nearest the CCN measurements. ICE-T MASE parameter R SL R SL Nc 0.17 93.24 -0.26 98.65 MD -0.31 99.69 0.33 99.78 σ -0.27 99.04 0.48 100.00 Ld -0.31 99.61 0.38 99.96 Table. Correlation coefficients, R, and one-tailed significance levels in percent, SL, for Nu-Np with microphysics of the clouds closest to each CCN measurement, 75 ICE-T and 74 MASE cases. Nc is cloud droplet concentration, MD is cloud droplet mean diameter, σ is standard deviation of cloud droplet spectra, Ldis drizzle drop LWC. Two aircraft field campaigns, Ice in Clouds Experiment-Tropical (ICE-T) and Marine Stratus/Stratocumulus Experiment (MASE) show opposite R signs because coalescence dominated cloud processing in low altitude ICE-T cumuli whereas chemical transformations predominated in MASE low altitude polluted stratus. Coalescence reduces Nc and NCCN, which thus increases MD, and σ, which promote Ld. Chemical transformations, e.g., SO2 to SO4, increase CCN hygroscopicity, thus reducing Sc, but not affecting Nc or NCCN. Lower Sc CCN are capable of producing greater Nc in subsequent cloud cycles, which leads to lower MD and σ which reduce Ld (figure). These observations are consistent with cloud droplet growth models for the higher vertical wind (W) of cumuli and lower W of stratus. Coalescence thus reduces the indirect

  6. Advancements in the Representation of Cloud-Aerosol Microphysics in the GEOS-5 AGCM

    NASA Technical Reports Server (NTRS)

    Lee, D.; Oreopoulos, L.; Sud, Y.; Barahona, D.; Nemes, A.; Bhattacharjee, P.

    2011-01-01

    Despite numerous challenges, the physical parameterization of cloud-aerosol interactions in atmospheric GCMs has become a top priority for advancement because of our need to simulate and understand past, current, and future indirect effects of aerosols on clouds. The challenges stem from the involvement of wide range of cloud-scale dynamics and aerosol activation physical processes. Cloud dynamics modulate cloud areal extent and condensate, while aerosol activation depends on aerosol mass load, size distribution, internal mixing state, and nucleating properties, and ultimately determines cloud optical properties via particle sizes. Both macro- and micro-scale processes are obviously important for cloud-radiation interactions. We will present the main features of cloud microphysical properties in the GEOS- 5 Atmospheric GCM (AGCM) as simulated by the McRAS-AC (Microphysics of Clouds with Relaxed Arakawa-Schubert and Aerosol-Cloud interaction) scheme. McRAS-AC uses Fountoukis and Nenes (2005) aerosol activation for liquid clouds, and has an option for either Liu and Penner (2005) or Barahona and Nenes (2008, 2009) aerosol activation for ice clouds. Aerosol loading (on-line or climatological) comes from GOCART, with an assumed log-normal size distribution. Other features of McRAS-AC are level-by-level cloud-scale thermodynamics, and Seifert-Beheng (2001)-type precipitation microphysics, particularly from moist convection. Results from Single-Column Model simulations will be shown to demonstrate how cloud radiative properties, lifetimes, and precipitation are influenced by different parameterization assumptions. Corresponding fields from year-long simulations of the full AGCM will also be presented with geographical distributions of cloud effective particle sizes compared to satellite retrievals. While the primary emphasis will be on current climate, simulation results with perturbed aerosol loadings will also be shown to expose the radiative sensitivity of the

  7. Microphysical properties of low-level clouds and fogs in a mountain area of South Korea

    NASA Astrophysics Data System (ADS)

    Jeong, Jin-Yim; Lee, Chulkyu; Jung, Hyun-Sook; Nam, Jae-Chul

    2013-05-01

    Measurements of microphysical properties in low-level clouds and fogs were carried out at Daegwallyeong in the northeastern mountainous region of South Korea. The microphysical characteristics are presented through analyzing the number concentration, mean diameter, liquid water contents and size distribution of cloud particles sampled with the groundbased Forward Scattering Spectrometer Probe (FSSP). The aim of this study is to analyze the influence of the proposed cloud condensation nuclei (CCN) type on the size and the number of cloud droplets. Observational cases are classified 5 sectors according to backward air mass trajectories from the NOAA/ARL HYSPLIT model. Clean maritime cloud is characterized by sector 1 trajectories and clean continental cloud is by sector 2. Contaminated maritime cloud is by sector 3 and contaminated continental cloud is by sector 4. Sector 5 trajectories are undefined air masses. On average, the droplet number concentrations in marine clouds were lower than for continental clouds, while the mean diameters and liquid water contents for marine clouds were larger than for continental clouds. Our observed values of microphysical properties are similar to the reported values from previous studies.

  8. Airborne In-Situ Measurements of Aerosol and Cloud Microphysical Properties in Mixed-Phase Clouds Under Varying Conditions

    NASA Astrophysics Data System (ADS)

    Comstock, J. M.; Fan, J.; Tomlinson, J. M.; Mei, F.; Hubbe, J. M.; Schmid, B.

    2014-12-01

    Cloud microphysical properties impact the interaction of clouds and radiation in the atmosphere, and can influence atmospheric circulations through changes in cloud phase. Characterizing the conditions that control phase changes and the microphysical properties of mixed-phase clouds is important for improving understanding of physical processes that influence cloud phase. We characterize the aerosol and cloud microphysical properties in relation to the atmospheric dynamic and thermodynamic conditions observed in mixed-phase clouds during several aircraft-based field experiments. The Department of Energy Atmospheric Radiation Measurement program's Gulfstream-1 aircraft was used to sample aerosol and cloud properties in warm and cold clouds during several recent field experiments. We analyze in-situ observations from the CalWater and TCAP field campaigns to examine the variability of cloud properties (phase, hydrometeor size, ice and liquid water content, particle habit) with changes in aerosol, vertical velocity, and temperature. These measurements indicate that in addition to aerosol concentration, vertical velocity strength has important influence on cloud phase in mixed-phase cloud regimes.

  9. Microphysical Effects Determine Macrophysical Response for Aerosol Impacts on Deep Convective Clouds

    SciTech Connect

    Fan, Jiwen; Leung, Lai-Yung R.; 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 and energy and hydrological cycle of our climate system. Anthropogenic and natural aerosol particles can influence DCCs through changes in cloud properties, precipitation regimes, and radiation balance. Modeling studies have reported both invigoration and suppression of DCCs by aerosols, but none has fully quantified aerosol impacts on convection life cycle and radiative forcing. By conducting multiple month-long cloud-resolving simulations with spectral-bin cloud microphysics that capture the observed macro- and micro-physical properties of summer convective clouds in the tropics and mid-latitudes, this study provides the first comprehensive look at how aerosols affect cloud cover, cloud top height (CTH), and radiative forcing. Observations validate these simulation results. We find that microphysical aerosol effects contribute predominantly to increased cloud cover and CTH by inducing larger amount of smaller but longer lasting ice particles in the stratiform/anvils of DCCs with dynamical aerosol effects contributing at most ~ 1/4 of the total increase of cloud cover. The overall effect is a radiative warming in the atmosphere (3 to 5 W m-2) with strong surface cooling (-5 to -8 W m-2). Herein we clearly identified mechanisms more important than and additional to the invigoration effects hypothesized previously that explain the consistent signatures of increased cloud tops area and height by aerosols in DCCs revealed by observations.

  10. Variability of Microphysical Properties in High-Altitude Ice Clouds: Results of the Remote Sensing Method

    SciTech Connect

    S. Y. Matrosov

    1997-06-01

    (A260/OAK) Ice cloud microphysical parameters are estimated from the ground using combined radar and radiometer techniques. The remote sensing method for retrieving vertical profiles of microphysical parameters in ice clouds from ground-based measurements taken by the Doppler radar and IR radiometer was applied to several cloud cases observed during different field experiments including FIRE-II, ASTEX, and the Arizona Program. The measurements were performed with the NOAA Environmental Technology Laboratory instrumentation. The observed ice clouds were mostly cirrus clouds located in the upper troposphere above 5.6 km. Their geometrical thicknesses varied from a few hundred meters to 3 km. Characteristic cloud particle sizes expressed in median mass diameters of equal-volume spheres varied from about 25 {micro}m to more than 400 {micro}m. Typically, characteristic particle sizes were increasing toward the cloud base, with the exception of the lowest range gates where particles were quickly sublimating. Highest particle concentrations were usually observed near the cloud tops. The vertical variability of particle sizes inside an individual cloud could reach one order of magnitude. The standard deviation of the mean profile for a typical cloud is usually factor of 2 or 3 smaller than mean values of particle characteristic size. Typical values of retrieved cloud ice water content varied from 1 to 100 mg m{sup -3}; however, individual variations were as high as four orders of magnitude. There was no consistent pattern in the vertical distribution of ice water content except for the rapid decrease in the vicinity of the cloud base. The relationships between retrieved cloud parameters and measured radar reflectivities were considered. The uncertainty of estimating cloud parameters from the power-law regressions is discussed. The parameters of these regressions varied from cloud to cloud and were comparable to the parameters in corresponding regressions obtained from

  11. Microphysical properties of the Shuttle exhaust cloud

    NASA Technical Reports Server (NTRS)

    Keller, V. W.; Anderson, B. J.

    1983-01-01

    A data base describing the properties of the exhaust cloud produced by the launch of the STS has been developed based on data from a series of ground and aircraft based measurements made during the launches of STS 2, 3, and 4. Aircraft observations were performed during the STS-3 launch with a NOAA WP-3D Orion hurricane research aircraft which contained instrumentation for cloud condensation nucleus and ice nucleus counting, Aitken particle counting, and pH determination. Ground observations were conducted at 50 different sites, as well as in the direct exhaust from the solid rocket booster flame trench at all three launches. The data is analyzed in order to determine any possible adverse impacts of the exhaust products on human health and/or the environment. Analyses of the exhaust cloud measurements indicate that in the case of the ground cloud where plenty of large water drops are present and considerable scavenging and fallout of aerosol takes place, possible adverse impacts of the remaining aerosols (CCN and IN) on natural precipitation processes which may occur in the launch area hours after the launch are remote. However, it is determined that under certain atmospheric conditions there could be short term adverse effects on visibility.

  12. 3-D model simulations of dynamical and microphysical interactions in pyroconvective clouds under idealized conditions

    NASA Astrophysics Data System (ADS)

    Reutter, P.; Trentmann, J.; Seifert, A.; Neis, P.; Su, H.; Chang, D.; Herzog, M.; Wernli, H.; Andreae, M. O.; Pöschl, U.

    2014-07-01

    Dynamical and microphysical processes in pyroconvective clouds in mid-latitude conditions are investigated using idealized three-dimensional simulations with the Active Tracer High resolution Atmospheric Model (ATHAM). A state-of-the-art two-moment microphysical scheme building upon a realistic parameterization of cloud condensation nuclei (CCN) activation has been implemented in order to study the influence of aerosol concentration on cloud development. The results show that aerosol concentration influences the formation of precipitation. For low aerosol concentrations (NCN = 200 cm-3), rain droplets are rapidly formed by autoconversion of cloud droplets. This also triggers the formation of large graupel and hail particles, resulting in an early onset of precipitation. With increasing aerosol concentration (NCN = 1000 cm-3 and NCN = 20 000 cm-3) the formation of rain droplets is delayed due to more but smaller cloud droplets. Therefore, the formation of ice crystals and snowflakes becomes more important for the eventual formation of graupel and hail, which is delayed at higher aerosol concentrations. This results in a delay of the onset of precipitation and a reduction of its intensity with increasing aerosol concentration. This study is the first detailed investigation of the interaction between cloud microphysics and the dynamics of a pyroconvective cloud using the combination of a high-resolution atmospheric model and a detailed microphysical scheme.

  13. Observations of cloud microphysics and ice formation during COPE

    NASA Astrophysics Data System (ADS)

    Taylor, J. W.; Choularton, T. W.; Blyth, A. M.; Liu, Z.; Bower, K. N.; Crosier, J.; Gallagher, M. W.; Williams, P. I.; Dorsey, J. R.; Flynn, M. J.; Bennett, L. J.; Huang, Y.; French, J.; Korolev, A.; Brown, P. R. A.

    2016-01-01

    We present microphysical observations of cumulus clouds measured over the southwest peninsula of the UK during the COnvective Precipitation Experiment (COPE) in August 2013, which are framed into a wider context using ground-based and airborne radar measurements. Two lines of cumulus clouds formed in the early afternoon along convergence lines aligned with the peninsula. The lines became longer and broader during the afternoon due to new cell formation and stratiform regions forming downwind of the convective cells. Ice concentrations up to 350 L-1, well in excess of the expected ice nuclei (IN) concentrations, were measured in the mature stratiform regions, suggesting that secondary ice production was active. Detailed sampling focused on an isolated liquid cloud that glaciated as it matured to merge with a band of cloud downwind. In the initial cell, drizzle concentrations increased from ˜ 0.5 to ˜ 20 L-1 in around 20 min. Ice concentrations developed up to a few per litre, which is around the level expected of primary IN. The ice images were most consistent with freezing drizzle, rather than smaller cloud drops or interstitial IN forming the first ice. As new cells emerged in and around the cloud, ice concentrations up to 2 orders of magnitude higher than the predicted IN concentrations developed, and the cloud glaciated over a period of 12-15 min. Almost all of the first ice particles to be observed were frozen drops, while vapour-grown ice crystals were dominant in the latter stages. Our observations are consistent with the production of large numbers of small secondary ice crystals/fragments, by a mechanism such as Hallett-Mossop or droplets shattering upon freezing. Some of the small ice froze drizzle drops on contact, while others grew more slowly by vapour deposition. Graupel and columns were seen in cloud penetrations up to the -12 °C level, though many ice particles were mixed habit due to riming and growth by vapour deposition at multiple temperatures

  14. High Resolution Cloud Microphysics and Radiation Studies

    DTIC Science & Technology

    2011-06-16

    characteristics of mid level altocumulus clouds and upper level visible and subvisual cirrus clouds The MPL lidar provided information about the temporal...balloon, lidar, and radar study of cirrus and altocumulus clouds to further investigate the presence of multi- cloud and nearly cloud -free layers...data set of the clouds and thermodynanuc structure to build a mesoscale and LF.S test-bed for cirrus and altocumulus cloud layers. The project was

  15. MAD-VenLA: a microphysical modal representation of clouds for the IPSL Venus GCM

    NASA Astrophysics Data System (ADS)

    Guilbon, Sabrina; Määttänen, Anni; Burgalat, Jérémie; Montmessin, Franck; Stolzenbach, Aurélien; Bekki, Slimane

    2016-10-01

    Venus is enshrouded by 20km-thick clouds, which are composed of sulfuric acid-water solution droplets. Clouds play a crucial role on the climate of the planet. Our goal is to study the formation and evolution of Venusian clouds with microphysical models. The goal of this work is to develop the first full 3D microphysical model of Venus coupled with the IPSL Venus GCM and the photochemical model included (Lebonnois et al. 2010, Stolzenbach et al. 2016).Two particle size distribution representations are generally used in cloud modeling: sectional and modal. The term 'sectional' means that the continuous particle size distribution is divided into a discrete set of size intervals called bins. In the modal approach, the particle size distribution is approximated by a continuous parametric function, typically a log-normal, and prognostic variables are distribution or distribution-integrated parameters (Seigneur et al. 1986, Burgalat et al. 2014). These two representations need to be compared to choose the optimal trade-off between precision and computational efficiency. At high radius resolution, sectional models are computationally too demanding to be integrated in GCMs. That is why, in other GCMs, such as the IPSL Titan GCM, the modal scheme is used (Burgalat et al. 2014).The Venus Liquid Aerosol cloud model (VenLA) and the Modal Dynamics of Venusian Liquid Aerosol cloud model (MAD-VenLA) are respectively the sectional and the modal model discussed here and used for defining the microphysical cloud module to be integrated in the IPSL Venus GCM. We will compare the two models with the key microphysical processes in 0D setting: homogeneous and heterogeneous nucleation, condensation/evaporation and coagulation. Then, MAD-VenLA will be coupled with the IPSL VGCM. The first results of the complete VGCM with microphysics coupled with chemistry will be presented.

  16. Microphysics of KCl and ZnS Clouds on GJ 1214 b

    NASA Astrophysics Data System (ADS)

    Gao, Peter; Benneke, Björn

    2016-10-01

    Clouds are ubiquitous in the atmospheres of exoplanets. However, as most of these planets have temperatures between 600 and 2000 K, their clouds are likely composed of exotic condensates such as salts, sulfides, silicates, and metals. Treatment of these clouds in current exoplanet atmosphere models do not consider the microphysical processes that govern their formation, evolution, and distribution, such as nucleation and condensation/evaporation, thus creating a gulf between the cloud properties retrieved from observations and the cloud composition predictions from condensation equilibrium models. In this work, we apply a 1D microphysical cloud model to GJ 1214 b and investigate the properties of potassium chloride (KCl) and zinc sulfide (ZnS) clouds as a function of atmospheric metallicity, the intensity of vertical mixing, and the mode of nucleation. Our cloud model has been widely applied to planets in our own Solar System, and as such our work bridges a gap between planetary science and exoplanets. Using model background atmospheres calculated by the SCARLET code, we find that (1) the cloud distribution is not significantly affected by metallicity unless [Fe/H] > 2, (2) higher intensities of vertical mixing leads to more extended cloud decks, more cloud particles at all altitudes, and smaller mean particle radii, (3) the high surface energy of solid ZnS prevents the homogeneous nucleation of pure ZnS cloud particles, such that KCl clouds dominate; solid ZnS can only manifest by nucleating onto pre-existing surfaces (heterogeneous nucleation), such as KCl cloud particles, resulting in mixed clouds, and (4) formation of KCl clouds results in a KCl vapor abundance above the cloud deck ~5 orders of magnitude less than that calculated from equilibrium chemistry. We also examine the transmission spectra that would result from these different cases. Extension of this model to other planets and condensates will shed light on the observed continuum in the "cloudiness

  17. A low-cost digital holographic imager for calibration and validation of cloud microphysics remote sensing

    NASA Astrophysics Data System (ADS)

    Chambers, Thomas E.; Hamilton, Murray W.; Reid, Iain M.

    2016-10-01

    Clouds cover approximately 70% of the Earth's surface and therefore play a crucial rule in governing both the climate system and the hydrological cycle. The microphysical properties of clouds such as the cloud particle size distribution, shape distribution and spatial homogeneity contribute significantly to the net radiative effect of clouds and these properties must therefore be measured and understood to determine the exact contribution of clouds to the climate system. Significant discrepancies are observed between meteorological models and observations, particularly in polar regions that are most sensitive to changes in climate, suggesting a lack of understanding of these complex microphysical processes. Remote sensing techniques such as polarimetric LIDAR and radar allow microphysical cloud measurements with high temporal and spatial resolution however these instruments must be calibrated and validated by direct in situ measurements. To this end a low cost, light weight holographic imaging device has been developed and experimentally tested that is suitable for deployment on a weather balloon or tower structure to significantly increase the availability of in situ microphysics retrievals.

  18. Aerosols-Cloud-Microphysics Interactions in Tropical Cyclone Earl

    NASA Astrophysics Data System (ADS)

    Luna-Cruz, Yaitza

    Aerosols-cloud-microphysical processes are largely unknown in their influence on tropical cyclone evolution and intensification; aerosols possess the largest uncertainty. For example: What is the link between aerosols and cloud microphysics quantities? How efficient are the aerosols (i.e. dust from the Saharan Air Layer -SAL) as cloud condensation nuclei (CCN) and ice nuclei (IN)? Does aerosols affect the vertical velocity, precipitation rates, cloud structure and lifetime? What are the dominant factors and in which sectors of the tropical cyclone? To address some of the questions in-situ microphysics measurements from the NASA DC-8 aircraft were obtained during the Genesis and Rapid Intensification Processes (GRIP) 2010 field campaign. A total of four named storms (Earl, Gaston, Karl and Mathew) were sampled. Earl presented the excellent opportunity to study aerosols-cloud-microphysics interactions because Saharan dust was present and it underwent rapid intensification. This thesis seeks to explore hurricane Earl to develop a better understanding of the relationship between the SAL aerosols and cloud microphysics evolution. To assist in the interpretation of the microphysics observations, high resolution numerical simulations of hurricane Earl were performed using the Weather Research and Forecasting (WRF-ARW) model with the new Aerosol-Aware bulk microphysics scheme. This new version of Thompson scheme includes explicit activation of cloud condensation nuclei (CCN) from a major CCN source (i.e. sulfates and sea salt) and explicit ice nucleation (IN) from mineral dust. Three simulations are performed: (1) the Control case with the old Thompson scheme and initial conditions from GFS model, (2) the Aerosol-Aware first baseline case with GOCART aerosol module as an input conditions, and (3) the Aerosol-Aware increase case in which the GOCART aerosols concentrations were increased significantly. Overall, results of model simulations along with aircraft observations

  19. The role of cloud microphysical processes in climate: An assessment from a one-dimensional perspective

    NASA Astrophysics Data System (ADS)

    Liou, Kuo-Nan; Ou, Szu-Cheng

    1989-06-01

    The potential link between cloud microphysical processes and climate is investigated and theorized. We base our theory on results simulated from a one-dimensional climate model with an interactive cloud formation and precipitation program. This cloud program includes temperature-dependent parameterization equations for condensation, evaporation, and precipitation derived from growth equations for water droplets. We show that the cloud liquid water content is directly related to precipitation processes, which are governed by the mean cloud particle radius. In particular, we illustrate that the rate of precipitation generation is directly proportional to the fourth power of this radius. A doubling of CO2 is used as the radiative forcing. If the perturbed mean cloud particle radii for model high, middle, and low clouds are less than the climatological mean values, precipitation decreases because of the presence of smaller cloud particles, leading to an increase in the cloud liquid water content. Cloud solar albedo effects are enhanced, resulting in a reduction of temperature increases due to CO2 doubling (negative feedback). If, however, the perturbed mean cloud particle radii are larger than the climatological mean values, the availability of larger cloud particles would increase precipitation, leading to a decrease in the cloud liquid water content. The temperature increase in the case of CO2 doubling is amplified because of a reduction of cloud solar albedo effects (positive feedback). In the model the particle sizes are not directly related to radiative transfer, but they are indirectly related through precipitation and condensation processes, which determine the cloud liquid water content. We hypothesize that there are uncertainties in cloud microphysical processes and that a possible key to climate stability due to external radiative perturbations is the availability of larger or smaller cloud droplets (in reference to the climatological mean values). Smaller

  20. Indian summer monsoon precipitating clouds: role of microphysical process rates

    NASA Astrophysics Data System (ADS)

    Hazra, Anupam; Chaudhari, Hemantkumar S.; Pokhrel, Samir; Saha, Subodh K.

    2016-04-01

    The budget analysis of microphysical process rates based on Modern Era Retrospective-analysis for Research and Applications (MERRA) products are presented in the study. The relative importance of different microphysical process rates, which is crucial for GCMs, is investigated. The autoconversion and accretion processes are found to be vital for Indian Summer Monsoon (ISM). The map-to-map correlations are examined between observed precipitation and MERRA reanalysis. The pattern correlations connote the fidelity of the MERRA datasets used here. Results of other microphysical parameters (e.g. ice water content from CloudSat, high cloud fraction from CALIPSO and MODIS, latent heating from TRMM, cloud ice mixing ratio from MERRA) are presented in this study. The tropospheric temperature from reanalysis product of MERRA and NCEP are also analyzed. Furthermore, the linkages between cloud microphysics production rates and dynamics, which are important for North-South tropospheric temperature gradient for maintaining the ISM circulation, are also discussed. The study demonstrates the microphysical process rates, which are actually responsible for the cloud hydrometeors and precipitation formation on the monsoon intraseasonal oscillations timescale. Cloud to rain water auto-conversion and snow accretion rates are the dominant processes followed by the rain accretion. All these tendency terms replicates the similar spatial patterns as that of precipitation. The quantification of microphysical process rates and precipitation over different regions are shown here. The freezing rate is also imperative for the formation of cloud ice as revealed by the observation. Freezing rates at upper level and snow accretion at middle level may have effect on latent heating release. Further it can modulate the north-south temperature gradient which can influence the large-scale monsoon dynamics. The rain water evaporation is also considered as a key aspect for controlling the low level

  1. The Microphysics of Antarctic Clouds - Part two Modelling.

    NASA Astrophysics Data System (ADS)

    Listowski, Constantino; Lachlan-Cope, Tom

    2016-04-01

    We compare different cloud microphysical schemes implemented in the Weather Research & Forecasting model (WRF, v3.5.1) to investigate their ability to simulate clouds over the Antarctic Peninsula. We also discuss first results obtained over the Weddell Sea. Comparisons are made to cloud in-situ measurements performed with the British Antarctic Survey's instrumented Twin Otter aircraft. We discuss the performance of the microphysical scheme currently used by the operational model Antarctic Mesoscale Prediction System (AMPS), which uses the Polar version of WRF, by contrasting its results with the ones of more sophisticated WRF schemes. We also evaluate the reliability of Ice Nuclei and Cloud Condensation Nuclei parameterizations used by the schemes, which are almost exclusively based on mid-latitudes measurements.

  2. Minimalist Model of Ice Microphysics in Mixed-phase Stratiform Clouds

    SciTech Connect

    Yang, F.; Ovchinnikov, Mikhail; Shaw, Raymond A.

    2013-07-28

    The question of whether persistent ice crystal precipitation from super cooled layer clouds can be explained by time-dependent, stochastic ice nucleation is explored using an approximate, analytical model, and a large-eddy simulation (LES) cloud model. The updraft velocity in the cloud defines an accumulation zone, where small ice particles cannot fall out until they are large enough, which will increase the residence time of ice particles in the cloud. Ice particles reach a quasi-steady state between growth by vapor deposition and fall speed at cloud base. The analytical model predicts that ice water content (wi) has a 2.5 power law relationship with ice number concentration ni. wi and ni from a LES cloud model with stochastic ice nucleation also confirm the 2.5 power law relationship. The prefactor of the power law is proportional to the ice nucleation rate, and therefore provides a quantitative link to observations of ice microphysical properties.

  3. Testing of Cloud Microphysics Scheme with Snow Events

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Shi, Jainn Jong; Matsui, Toshihisa; Hou, Arthur; Lang, Stephen; Cifelli, Robert; Peters-Lidar, C.; Jackson, Gail; Rutledge, Steve; Petersen, Walter

    2008-01-01

    One of the grand challenges of the Global Precipitation Measurement (GPM) mission is to improve precipitation measurements in mid- and high-latitudes during cold seasons through the use of high-frequency passive microwave radiometry. For this, the Weather Research Forecast (WRF) model with the Goddard microphysics scheme is coupled with the Satellite Data Simulation Unit (WRF-SDSU) that has been developed to facilitate the over-snowfall retrieval algorithm by providing virtual cloud library and microwave brightness temperature (To) measurements consistent to the GPM Microwave Imager (GMI). This study tested the Goddard cloud microphysics scheme in WRF in snowstorm events (January 20-22, 2007) over the Canadian CloudSat/CALIPSO Validation Project (C3VP) site up in Ontario, Canada. In this meeting, we will present the performance of the Goddard cloud microphysics scheme both with 2ice (ice and snow) and 3ice (ice, snow and graupel) as well as other WRF microphysics schemes. Results will be compared with the King Radar data. We will also use the WRF model outputs to drive the Goddard SDSU to calculate radiances and backscattering signals consistent to satellite direct observations. These simulated radiance are evaluated against the measurement from A-Train satellites.

  4. Parameterizations of Cloud Microphysics and Indirect Aerosol Effects

    SciTech Connect

    Tao, Wei-Kuo

    2014-05-19

    , 2005]. Recently, a detailed spectral-bin microphysical scheme was implemented into the Goddard Cumulus Ensemble (GCE) model. Atmospheric aerosols are also described using number density size-distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep tropical clouds in the west Pacific warm pool region and summertime convection over a mid-latitude continent with different concentrations of CCN: a low "clean" concentration and a high "dirty" concentration. The impact of atmospheric aerosol concentration on cloud and precipitation will be investigated. 2. MODEL DESCRIPTION AND CASE STUDIES 2.1 GCE MODEL The model used in this study is the 2D version of the GCE model. Modeled flow is anelastic. Second- or higher-order advection schemes can produce negative values in the solution. Thus, a Multi-dimensional Positive Definite Advection Transport Algorithm (MPDATA) has been implemented into the model. All scalar variables (potential temperature, water vapor, turbulent coefficient and all five hydrometeor classes) use forward time differencing and the MPDATA for advection. Dynamic variables, u, v and w, use a second-order accurate advection scheme and a leapfrog time integration (kinetic energy semi-conserving method). Short-wave (solar) and long-wave radiation as well as a subgrid-scale TKE turbulence scheme are also included in the model. Details of the model can be found in Tao and Simpson (1993) and Tao et al. (2003). 2.2 Microphysics (Bin Model) The formulation of the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (cloud droplets and raindrops), and six types of ice particles: pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops

  5. Retrieval of radiative and microphysical properties of clouds from multispectral infrared measurements

    NASA Astrophysics Data System (ADS)

    Iwabuchi, Hironobu; Saito, Masanori; Tokoro, Yuka; Putri, Nurfiena Sagita; Sekiguchi, Miho

    2016-12-01

    Satellite remote sensing of the macroscopic, microphysical, and optical properties of clouds are useful for studying spatial and temporal variations of clouds at various scales and constraining cloud physical processes in climate and weather prediction models. Instead of using separate independent algorithms for different cloud properties, a unified, optimal estimation-based cloud retrieval algorithm is developed and applied to moderate resolution imaging spectroradiometer (MODIS) observations using ten thermal infrared bands. The model considers sensor configurations, background surface and atmospheric profile, and microphysical and optical models of ice and liquid cloud particles and radiative transfer in a plane-parallel, multilayered atmosphere. Measurement and model errors are thoroughly quantified from direct comparisons of clear-sky observations over the ocean with model calculations. Performance tests by retrieval simulations show that ice cloud properties are retrieved with high accuracy when cloud optical thickness (COT) is between 0.1 and 10. Cloud-top pressure is inferred with uncertainty lower than 10 % when COT is larger than 0.3. Applying the method to a tropical cloud system and comparing the results with the MODIS Collection 6 cloud product shows good agreement for ice cloud optical thickness when COT is less than about 5. Cloud-top height agrees well with estimates obtained by the CO2 slicing method used in the MODIS product. The present algorithm can detect optically thin parts at the edges of high clouds well in comparison with the MODIS product, in which these parts are recognized as low clouds by the infrared window method. The cloud thermodynamic phase in the present algorithm is constrained by cloud-top temperature, which tends not to produce results with an ice cloud that is too warm and liquid cloud that is too cold.

  6. Microphysical Parameters of Precipitating Shallow Marine Clouds over Graciosa Island, Azores

    NASA Astrophysics Data System (ADS)

    West, T.; Mace, J.

    2013-12-01

    Cloud microphysical parameters of marine boundary layer (MBL) clouds over the Atmospheric Radiation Measurement Program (ARM) mobile site at Graciosa Island, Azores are examined. Hourly averaged raw variables of cloud fraction, column summed dBZ, liquid water path, first cloud base height, boundary layer static stability, and mid-tropospheric static stability are clustered together using a K-means clustering algorithm. From this analysis, six characteristic cloud type regimes are inferred that describe the spectrum of warm boundary layer clouds that occurred over this site during the deployment. These cloud regimes range from non-precipitating stratus to precipitating cumulus congestus to broad synoptic scale frontal systems. Using NCEP/NCAR reanalysis, the typical meteorological environments for MBL clouds are also derived. MBL cloud microphysical properties are then derived using a new retrieval algorithm that assumes the presence of both cloud and precipitation particle modes within a radar resolution volume. Compared to a traditional single mode particle size distribution (PSD), this bimodal PSD is more inline with observations and is expected to provide improved statistics and understanding of the cloud microphysical parameters such as number concentration (Nd), precipitation rate (R), and effective droplet sizes. The information content of the measurements and the expected uncertainties of the retrievals will be explored using statistical approaches such as optimal estimation and formal information content theory. The relationships between Nd and R will be quantified as the precipitation susceptibility factor (So) and the comparison of So across different North Atlantic meteorological environments will result in a better understanding of the precipitation processes of shallow marine clouds in this region.

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

    PubMed Central

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

    2013-01-01

    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. PMID:24218569

  8. The Microbase Value-Added Product: A Baseline Retrieval of Cloud Microphysical Properties

    SciTech Connect

    Dunn, M; Johnson, K; Jensen, M

    2011-05-31

    This report describes the Atmospheric Radiation Measurement (ARM) Climate Research Facility baseline cloud microphysical properties (MICROBASE) value-added product (VAP). MICROBASE uses a combination of millimeter-wavelength cloud radar, microwave radiometer, and radiosonde observations to estimate the vertical profiles of the primary microphysical parameters of clouds including the liquid/ice water content and liquid/ice cloud particle effective radius. MICROBASE is a baseline algorithm designed to apply to most conditions and locations using a single set of parameterizations and a simple determination of water phase based on temperature. This document provides the user of this product with guidelines to assist in determining the accuracy of the product under certain conditions. Quality control flags are designed to identify outliers and indicate instances where the retrieval assumptions may not be met. The overall methodology is described in this report through a detailed description of the input variables, algorithms, and output products.

  9. Evaluation of Cloud Microphysics in JMA-NHM Simulations Using Bin or Bulk Microphysical Schemes through Comparison with Cloud Radar Observations

    NASA Technical Reports Server (NTRS)

    Iguchi, Takamichi; Nakajima, Teruyuki; Khain, Alexander P.; Saito, Kazuo; Takemura, Toshihiko; Okamoto, Hajime; Nishizawa, Tomoaki; Tao, Wei-Kuo

    2012-01-01

    Numerical weather prediction (NWP) simulations using the Japan Meteorological Agency NonhydrostaticModel (JMA-NHM) are conducted for three precipitation events observed by shipborne or spaceborneW-band cloud radars. Spectral bin and single-moment bulk cloud microphysics schemes are employed separatelyfor an intercomparative study. A radar product simulator that is compatible with both microphysicsschemes is developed to enable a direct comparison between simulation and observation with respect to theequivalent radar reflectivity factor Ze, Doppler velocity (DV), and path-integrated attenuation (PIA). Ingeneral, the bin model simulation shows better agreement with the observed data than the bulk modelsimulation. The correction of the terminal fall velocities of snowflakes using those of hail further improves theresult of the bin model simulation. The results indicate that there are substantial uncertainties in the masssizeand sizeterminal fall velocity relations of snowflakes or in the calculation of terminal fall velocity of snowaloft. For the bulk microphysics, the overestimation of Ze is observed as a result of a significant predominanceof snow over cloud ice due to substantial deposition growth directly to snow. The DV comparison shows thata correction for the fall velocity of hydrometeors considering a change of particle size should be introducedeven in single-moment bulk cloud microphysics.

  10. Relationship between Ice Cloud Microphysics and Supersaturation from Spaceborne Cloud Radar, Lidar and Infrared Sounder

    NASA Astrophysics Data System (ADS)

    Tanaka, K.; Okamoto, H.; Sato, K.; Ishimoto, H.

    2014-12-01

    We examined the relationship between ice cloud microphysics retrieved from cloud radar on CloudSat and CALIOP on CALIPSO and super saturation inferred from AIRS on AQUA. Ice microphysics such as ice water content (IWC) and effective radius was estimated by CloudSat and CALIPSO data. Unique features of the algorithm is that it has been designed to use depolarization ratio from CALIOP addition to radar reflectivity factor from CloudSat and attenuated backscattering coefficient from CALIOP in order to take into account the variation of ice particle shapes and their orientations [Okamoto et al., 2010]. Water vapor density and temperature were retrieved with much finer resolution by the application of Ishimoto's algorithm [2009] compared with standard AIRS products where horizontal resolution is 45km. The algorithm allows retrievals of water vapor density and temperature every 13.5km in horizontal direction with 1km in vertical. The retrievals are carried out when there is no cloud with its cloud top pressure <200hPa. That is, it is possible to report water vapor information above low-level clouds. Then we sampled the amount of water vapor and temperature estimated from AIRS data to match the CloudSat and CALIPSO foot-print and the data were interpolated to have the same space and time resolution of the merged data sets of CloudSat and CALIPSO, i.e., 1.1km and 240m for horizontal and vertical resolutions. In the new AIRS products, ice super saturation often reached 150% while standard AIRS products showed less frequent super saturation. The ECMWF results generally showed smaller fraction of ice super saturation compared with the new AIRS products. In order to quantitatively compare the water vapor amount and retrieved IWC, we estimated the excess of water amount respect to ice saturation by using ice super saturation. The occurrences of ice clouds inferred from CloudSat and CALIOP agreed with the occurrences of ice-supersaturation reported in the new AIRS products. The

  11. Microphysical Consequences of the Spatial Distribution of Ice Nucleation in Mixed-Phase Stratiform Clouds

    SciTech Connect

    Yang, Fan; Ovchinnikov, Mikhail; Shaw, Raymond A.

    2014-07-28

    Mixed-phase stratiform clouds can persist even with steady ice precipitation fluxes, and the origin and microphysical properties of the ice crystals are of interest. Vapor deposition growth and sedimentation of ice particles along with a uniform volume source of ice nucleation, leads to a power law relation between ice water content wi and ice number concentration ni with exponent 2.5. The result is independent of assumptions about the vertical velocity structure of the cloud and is therefore more general than the related expression of Yang et al. [2013]. The sensitivity of the wi-ni relationship to the spatial distribution of ice nucleation is confirmed by Lagrangian tracking and ice growth with cloud-volume, cloud-top, and cloud-base sources of ice particles through a time-dependent cloud field. Based on observed wi and ni from ISDAC, a lower bound of 0.006 m^3/s is obtained for the ice crystal formation rate.

  12. Impact of volcanic ash plume aerosol on cloud microphysics

    NASA Astrophysics Data System (ADS)

    Martucci, G.; Ovadnevaite, J.; Ceburnis, D.; Berresheim, H.; Varghese, S.; Martin, D.; Flanagan, R.; O'Dowd, C. D.

    2012-03-01

    This study focuses on the dispersion of the Eyjafjallajökull volcanic ash plume over the west of Ireland, at the Mace Head Supersite, and its influence on cloud formation and microphysics during one significant event spanning May 16th and May 17th, 2010. Ground-based remote sensing of cloud microphysics was performed using a K a-band Doppler cloud RADAR, a LIDAR-ceilometer and a multi-channel microwave-radiometer combined with the synergistic analysis scheme SYRSOC ( Synergistic Remote Sensing Of Cloud). For this case study of volcanic aerosol interaction with clouds, cloud droplet number concentration (CDNC), liquid water content (LWC), and droplet effective radius ( reff) and the relative dispersion were retrieved. A unique cloud type formed over Mace Head characterized by layer-averaged maximum, mean and standard deviation values of the CDNC, reff and LWC: Nmax = 948 cm -3, N¯=297cm, σ=250cm, reff max = 35.5 μm, r¯=4.8μm, σ=4.4μm, LWC=0.23gm, LWC¯=0.055gm, σ=0.054gm, respectively. The high CDNC, for marine clean air, were associated with large accumulation mode diameter (395 nm) and a hygroscopic growth factor consistent with sulphuric acid aerosol, despite being almost exclusively internally mixed in submicron sizes. Additionally, the Condensation Nuclei (CN, d > 10 nm) to Cloud Condensation Nuclei (CCN) ratio, CCN:CN ˜1 at the moderately low supersaturation of 0.25%. This case study illustrates the influence of volcanic aerosols on cloud formation and microphysics and shows that volcanic aerosol can be an efficient CCN.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  14. Cloud microphysics and surface properties in climate

    SciTech Connect

    Stamnes, K.

    1995-09-01

    Cloud optical thickness is determined from ground-based measurements of broadband incoming solar irradiance using a radiation model in which the cloud optical depth is adjusted until computed irradiance agrees with the measured value. From spectral measurements it would be feasible to determine both optical thickness and mean drop size, which apart from cloud structure and morphology, are the most important climatic parameters of clouds. A radiative convective model is used to study the sensitivity of climate to cloud liquid water amount and cloud drop size. This is illustrated in Figure 21.1 which shows that for medium thick clouds a 10 % increase in drop size yields a surface warming of 1.5{degrees}C, which is the same as that due to a doubling of carbon dioxide. For thick clouds, a 5% decrease in drop size is sufficient to offset the warming due to doubling of carbon dioxide. A radiative transfer model for the coupled atmosphere/sea ice/ocean system is used to study the partitioning of radiative energy between the three strata, and the potential for testing such a model in terms of planned experiments in the Arctic is discussed.

  15. Satellite Determination of Stratus Cloud Microphysical Properties.

    NASA Astrophysics Data System (ADS)

    Zuidema, Paquita; Hartmann, Dennis L.

    1995-06-01

    Satellite measurements of liquid water path from SSM/I, broadband albedo from ERBE, and cloud characteristics from ISCCP are used to study stratus regions. An average cloud liquid water path of 0.120 ± 0.032 kg m2 is derived by dividing the average liquid water path for stratus areas by the fractional area coverage of cloud in the region. The diurnal range in this average cloud liquid water path is about 25%. Stratus cloud liquid water is positively correlated with cloud amount and is negatively correlated with low cloud-top temperature.Cloud liquid water path (LWP) and cloud albedo measurements are used to derive an effective droplet radius using the plane-parallel cloud albedo model of Slingo. The 2.5;dg by 2.5;dg grid boxes are first screened for completely overcast scenes in an attempt to justify the plane-parallel assumption. The mean effective droplet radius for this sample is 10.1 ± 4.4 m. This serves as an upper bound since small-scale LWP variability is estimated to affect the average albedo by up to 0.07, corresponding to an overestimate in the derived droplet size of up to almost 6 m. The authors find larger droplet sizes in the evening than in the morning, along with smaller LWPs and lower albedos. No correlation is seen between effective radius and liquid water path, reinforcing the independence of these two parameters. Small droplet sizes are only derived in conjunction with high albedos, but this may simply reflect the effect of LWP inhomogeneity on the albedo and hence the derived droplet size. Individual case studies both support the validity of the methodology given high spatial homogeneity and yet demonstrate the common occurrence of nonhomogeneous conditions within stratus regions.

  16. Satellite determination of stratus cloud microphysical properties

    SciTech Connect

    Zuidema, P.; Hartmann, D.L.

    1995-06-01

    Satellite measurements of liquid water path from SSM/I, broadband albedo from ERBE, and cloud characteristics from ISCCP are used to study stratus regions. An average cloud liquid water path of 0.120{+-}0.032 kg m{sup {minus}2} is derived by dividing the average liquid water path for stratus areas by the fractional area coverage of cloud in the region. The diurnal range in this average cloud liquid water path is about 25%. Stratus cloud liquid water is positively correlated with cloud amount and is negatively correlated with low cloud-top temperature. Cloud liquid water path (LWP) and cloud albedo measurements are used to derive an effective droplet radius using the plane-parallel cloud albedo model of Slingo. The 2.5{degrees} by 2.5{degrees} grid boxes are first screened for completely overcast scenes in an attempt to justify the plane-parallel assumption. The mean effective droplet radius for this sample is 10.1{+-}4.4{mu}m. This serves as an upper bound since small-scale LWP variability is estimated to affect the average albedo by up to 0.07, corresponding to an overestimate in the derived droplet size of up to almost 6{mu}m. The authors find larger droplet sizes in the evening than in the morning, along with smaller LWP`s and lower albedos. No correlation is seen between effective radius and liquid water path, reinforcing the independence of these two parameters. Small droplet sizes are only derived in conjunction with high albedos, but this may simply reflect the effect of LWP inhomogeneity on the albedo and hence the derived droplet size. Individual case studies both support the validity of the methodology given high spatial homogeneity and yet demonstrate the common occurrence of nonhomogeneous conditions within stratus regions. 63 refs., 18 figs., 3 tabs.

  17. Effect of cloud microphysics on Indian summer monsoon precipitating clouds: A coupled climate modeling study

    NASA Astrophysics Data System (ADS)

    Hazra, Anupam; Chaudhari, Hemantkumar S.; Saha, Subodh K.; Pokhrel, Samir

    2017-04-01

    The quest for one of the most dominant processes controlling the large-scale circulations in the tropics is unraveled. The impact of cloud microphysical processes is known to have effects on rainfall and local atmospheric thermodynamics; however, its effect on the prevailing mean circulations is not yet studied. Two sets of coupled global climate model experiments (ICE and NO ICE microphysics) reveal that ice microphysics improves the strength of the Hadley circulation with respect to observation. Results pinpoint that ICE simulation enhances high cloud fraction (global tropics: 59%, India: 51%) and stratiform rain (global tropics: 5%, India: 15%) contribution. ICE and NO ICE cloud microphysics impacts differently on the outgoing longwave radiation (OLR), tropospheric temperature, and surface shortwave and longwave radiation. The effect of ice microphysics reduces OLR, which signifies deeper convection in the ICE run. The global annual average of the net radiation flux (shortwave and longwave) at the surface in ICE run (108.1 W/m2) is close to the observation (106 W/m2), which is overestimated in NO ICE run (112 W/m2). The result of apparent heat source term over the land and ocean surface eventually modifies regional Hadley circulation. Thus, the effect of ice microphysics in the global coupled model is important not only because of microphysics but also due to the radiation feedbacks. Therefore, better ice-phase microphysics is required in the new generation of climate forecast model, which may lead to improvements in the simulation of monsoon.

  18. A Cloud Microphysics Model for the Gas Giant Planets

    NASA Astrophysics Data System (ADS)

    Palotai, Csaba J.; Le Beau, Raymond P.; Shankar, Ramanakumar; Flom, Abigail; Lashley, Jacob; McCabe, Tyler

    2016-10-01

    Recent studies have significantly increased the quality and the number of observed meteorological features on the jovian planets, revealing banded cloud structures and discrete features. Our current understanding of the formation and decay of those clouds also defines the conceptual modes about the underlying atmospheric dynamics. The full interpretation of the new observational data set and the related theories requires modeling these features in a general circulation model (GCM). Here, we present details of our bulk cloud microphysics model that was designed to simulate clouds in the Explicit Planetary Hybrid-Isentropic Coordinate (EPIC) GCM for the jovian planets. The cloud module includes hydrological cycles for each condensable species that consist of interactive vapor, cloud and precipitation phases and it also accounts for latent heating and cooling throughout the transfer processes (Palotai and Dowling, 2008. Icarus, 194, 303-326). Previously, the self-organizing clouds in our simulations successfully reproduced the vertical and horizontal ammonia cloud structure in the vicinity of Jupiter's Great Red Spot and Oval BA (Palotai et al. 2014, Icarus, 232, 141-156). In our recent work, we extended this model to include water clouds on Jupiter and Saturn, ammonia clouds on Saturn, and methane clouds on Uranus and Neptune. Details of our cloud parameterization scheme, our initial results and their comparison with observations will be shown. The latest version of EPIC model is available as open source software from NASA's PDS Atmospheres Node.

  19. Atmospheric State, Cloud Microphysics and Radiative Flux

    DOE Data Explorer

    Mace, Gerald

    2008-01-15

    Atmospheric thermodynamics, cloud properties, radiative fluxes and radiative heating rates for the ARM Southern Great Plains (SGP) site. The data represent a characterization of the physical state of the atmospheric column compiled on a five-minute temporal and 90m vertical grid. Sources for this information include raw measurements, cloud property and radiative retrievals, retrievals and derived variables from other third-party sources, and radiative calculations using the derived quantities.

  20. a Three-Dimensional Model of Cloud Dynamics, Microphysics and Chemistry

    NASA Astrophysics Data System (ADS)

    Wang, Chien

    1992-01-01

    A three-dimensional, comprehensive cloud modeling system with detailed descriptions of dynamics, microphysics, and chemistry has been developed. This system can be used to study not only the evolution of dynamical and microphysical processes, but also those of chemical processes and the interactions or relationships among them. The primary objective of this model is the simulation of deep convective events and severe storms. The physical component of this model starts with a pseudo-elastic form of the continuity equation. The overall model is a self-consistent, time -dependent system which is easier to solve. Seven different water categories in three phases are considered in this model. Both the mass mixing ratio and concentration of each liquid or solid phase category are predicted so that a semi-spectra microphysical parameterization scheme can be formulated. More than 40 microphysical processes have been parameterized based on the spectrum-integration and the behavior of the individual particles in the microphysical interactions. Concentrations of seven chemical groups in air and in 6 liquid- or solid-phase water carriers are predicted by our chemical model. Their evolution in this model came from not only the dynamical and subgrid-scale transports, but also the chemical reactions and microphysics -related conversions. A strong convective storm, the 1 August 1981 case of CCOPE project, has been modeled by using our three-dimensional modeling system. The modeled precipitation feature and three-dimensional radar reflectivity factors are close to the observed data. The modeled main chemical parameters are also reasonable. The evolution of dynamical and thermodynamical structure of the storm, the formation and the evolution of precipitation, the redistribution of chemical species, the evolution of cloud and precipitation chemical features, and the relationships among dynamical, microphysical, and chemical processes have been studied through the case study. Some

  1. Constraints on PSC Particle Microphysics Derived From Lidar Observations

    NASA Technical Reports Server (NTRS)

    Liu, Li; Mishchenko, Michael I.

    2001-01-01

    Based on extensive T-matrix computations of light scattering by polydispersions of randomly oriented, rotationally symmetric nonspherical particles, we analyze existing lidar observations of polar stratospheric clouds (PSCs) and derive several constraints on PSC particle microphysical properties. We show that sharp-edged nonspherical particles (finite circular cylinders) exhibit less variability of lidar backscattering characteristics with particle size and aspect ratio than particles with smooth surfaces (spheroids). For PSC particles significantly smaller than the wavelength, the backscatter color index Alpha and the depolarization color index Beta are essentially shape-independent. Observations for type Ia PSCs can be reproduced by spheroids with aspect ratios larger than 1.2, oblate cylinders with diameter-to-length ratios greater than 1.6, and prolate cylinders with length-to-diameter ratios greater than 1.4. The effective equal-volume-sphere radius for type la PSCs is about 0.8 microns or larger. Type Ib PSCs are likely to be composed of spheres or nearly spherical particles with effective radii smaller than 0.8 microns. Observations for type II PSCs are consistent with large ice crystals (effective radius greater than 1 micron modeled as cylinders or prolate spheroids.

  2. An Aircraft And Radar Based Analysis Of Cloud And Precipitation Microphysics In Mid-Latitude Continental Clouds

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Kumjian, M.; Bansemer, A.; Giangrande, S. E.; Ryzhkov, A.; Toto, T.

    2014-12-01

    An observational analysis of precipitation microphysics was conducted using data obtained during the Midlatitude Continental Convective Clouds Experiment (MC3E) that took place around the Atmospheric Radiation Measurement (ARM) site in Lamont, Oklahoma from April 22- June 6, 2011. MC3E was a collaborative campaign led by the National Aeronautic and Space Administration's (NASA's) Global Precipitation Measurement (GPM) mission and the U.S. Department of Energy ARM program. MC3E provided a unique opportunity to compare in-situ data from aircraft based microphysical probes with data from polarimetric radars in the radar bright band region or melting layer. One of the primary objectives of this study was to understand how riming and aggregation affect polarimetric signatures. In depth case study analysis of cloud and precipitation microphysics was performed for two specific cases, April 27th, 2011 (A27) and May 20th, 2011 (M20). Both these cases provided coincident aircraft and radar data in extensive stratiform cloud regions. Measurements from the University of North Dakota (UND) Citation aircraft and polarimetric data from the ARM CSAPR data reveal interesting details of cloud scale processes. Observations based on data from cloud probes (2DC, CIP and HVPS) along with in-situ observations of environmental variables provide remarkable details of particle growth and cloud dynamics for both case studies. For the A27 case study, UND aircraft measurements from two successive spiral profiles through the stratiform cloud region showed a transition from a riming dominated region to an aggregation dominated region. This is supported by polarimetric data from the C-Band ARM Precipitation Radar (CSAPR ). An extensive region of trailing stratiform precipitation was sampled in the M20 case study, where the aggregation, melting, and evaporation processes were measured in detail with the in-situ microphysical instruments. Latest findings from MC3E based on this combined aircraft

  3. A comparison of cloud microphysical quantities with forecasts from cloud prediction models

    SciTech Connect

    Dunn, M.; Jensen, M.; Hogan, R.; O’Connor, E.; Huang, D.

    2010-03-15

    Numerical weather prediction models (ECMWF, NCEP) are evaluated using ARM observational data collected at the Southern Great Plains (SGP) site. Cloud forecasts generated by the models are compared with cloud microphysical quantities, retrieved using a variety of parameterizations. Information gained from this comparison will be utilized during the FASTER project, as models are evaluated for their ability to reproduce fast physical processes detected in the observations. Here the model performance is quantified against the observations through a statistical analysis. Observations from remote sensing instruments (radar, lidar, radiometer and radiosonde) are used to derive the cloud microphysical quantities: ice water content, liquid water content, ice effective radius and liquid effective radius. Unfortunately, discrepancies in the derived quantities arise when different retrieval schemes are applied to the observations. The uncertainty inherent in retrieving the microphysical quantities using various retrievals is estimated from the range of output microphysical values. ARM microphysical retrieval schemes (Microbase, Mace) are examined along with the CloudNet retrieval processing of data from the ARM sites for this purpose. Through the interfacing of CloudNet and “ARM” processing schemes an ARMNET product is produced and employed as accepted observations in the assessment of cloud model predictions.

  4. Microphysical properties of the November 26 cirrus cloud retrieved by Doppler radar/IR radiometer technique

    NASA Technical Reports Server (NTRS)

    Matrosov, Sergey Y.; Kropfli, Robert A.; Orr, Brad W.; Snider, Jack B.

    1993-01-01

    Gaining information about cirrus cloud microphysics requires development of remote sensing techniques. In an earlier paper. Matrosov et al. (1992) proposed a method to estimate ice water path (IWP) (i.e., vertically integrated ice mass content IMC) and characteristic particle size averaged through the cloud from combined groundbased measurements of radar reflectivities and IR brightness temperatures of the downwelling thermal radiation in the transparency region of 10-12 mu m. For some applications, the vertically averaged characteristic particle sizes and IWP could be the appropriate information to use. However, vertical profiles of cloud microphysical parameters can provide a better understanding of cloud structure and development. Here we describe a further development of the previous method by Matrosov et al. (1992) for retrieving vertical profiles of cirrus particle sizes and IMC rather than their vertically averaged values. In addition to measurements of radar reflectivities, the measurements of Doppler velocities are used in the new method. This provides us with two vertical profiles of measurements to infer two vertical profiles of unknowns, i.e., particle characteristic sizes and IMC. Simultaneous measurements of the IR brightness temperatures are still needed to resolve an ambiguity in particle size-fall velocity relationships.

  5. Microphysical Timescales in Clouds and their Application in Cloud-Resolving Modeling

    NASA Technical Reports Server (NTRS)

    Zeng, Xi-Ping; Tao, Wei-Kuo; Simpson, Joanne

    2004-01-01

    Computational phenomena (i.e., spurious supersaturation and negative mixing ratio of cloud water) usually exist in cloud-resolving models when the time step for explicit integration is larger than a microphysical timescale in clouds. In this paper, the microphysical timescales in clouds are studied, showing that the timescale of water vapor condensation (or cloud water evaporation) is smaller than 10 s - the order of a typical time step for cloud-resolving models. To avoid spurious computational phenomena in cloud-resolving modeling, it is suggested that moist entropy be used as a prognostic thermodynamic variable, and temperature be diagnosed from that and other prognostic variables. A simple numerical model with moist entropy as a prognostic variable, for example, is presented to show that spurious computational phenomena are removed when moist entropy is used as a prognostic variable.

  6. Aerosol characteristics observed in southeast Queensland and implications for cloud microphysics

    NASA Astrophysics Data System (ADS)

    Tessendorf, Sarah A.; Weeks, Courtney E.; Axisa, Duncan; Bruintjes, Roelof T.

    2013-04-01

    Regular cloud base aerosol measurements were collected by a research aircraft over a 4 month period during the wet season in southeast Queensland, near Brisbane, Australia. In situ cloud microphysical measurements were also collected in many of these clouds. Brisbane is situated on the east coast of Australia and, depending on the synoptic weather conditions, can experience influences from inland or from the adjacent ocean. In situ aerosol measurements were used to compile a climatology of the aerosol conditions in the region and a back trajectory model was run for 120 h from each measurement to determine the possible air mass influences on each measurement. The most influential factor on the measured aerosol concentrations was the time the trajectory spent over land beneath 2 km (a proxy for the boundary layer). Using this criterion, the measurements were divided into two regimes: maritime for those with minimal time histories over land and continental for the remainder. Other influential factors on the aerosol concentration were also diagnosed and quantified with a regression model, including the proximity of the trajectory to the city of Brisbane and the number of fires along the trajectory. Thermodynamic, aerosol, and cloud microphysical characteristics are presented for each regime. The maritime regime tended to have more coarse mode (larger) aerosol particles and a tail of larger drops in the cloud base droplet spectra, which could be due to nucleation on the larger aerosol particles. The city influence on maritime regime trajectories yielded enhanced nucleation (fine) particle concentrations.

  7. Synergetic radar and lidar algorithm for the retrieval of radiative and microphysical properties in ice clouds

    NASA Astrophysics Data System (ADS)

    Tinel, Claire; Testud, Jacques; Protat, Alain; Pelon, Jacques R.

    2003-04-01

    To appreciate the radiative impact of clouds in the dynamics of the global atmosphere, it is important to deploy from space, from aircraft, or from ground, instruments able to describe the cloud layering and to document the cloud characteristics (namely liquid and/or ice water content, and the effective particle radius). In the framework of EarthCARE (ESA), that plans to associate a cloud radar and a lidar on the same spatial platform, RALI (RAdar-LIdar) airborne system is an interesting demonstrator. RALI combines the 95 GHz radar of the CETP and the 0.5 μm wavelength backscattering lidar of the SA. In order to derive the radiative and microphysical properties of clouds, a synergetic algorithm has been developed. It combines the apparent backscatter coefficient, βa, from the lidar and the apparent reflectivity, Za, from the radar to infer properties of the particle size distribution. The principle of this algorithm is to apply in parallel the Hitschfeld-Bordan algorithm to the radar and the Klett algorithm to the lidar. Taken separately, these two algorithms are unstable, but by considering a mutual constraint, it is shown that a stable solution can be established. This solution formulates the retrieval of the true reflectivity and backscattering coefficient, to access microphysical and radiative parameters of clouds. This algorithm allows also to retrieve the variable N0* parameter, which is a normalization parameter of the particle size distribution. This synergetic algorithm has been tested with simulated cases, and results of the algorithm applied on real data are validated by microphysical in-situ measurements.

  8. An Intercomparison of Microphysical Retrieval Algorithms for Upper Tropospheric Ice Clouds

    NASA Technical Reports Server (NTRS)

    Comstock, Jennifer M.; d'Entremont, Robert; DeSlover, Daniel; Mace, Gerald G.; Matrosov, Sergey Y.; McFarlane, Sally A.; Minnis, Patrick; Mitchell, David; Sassen, Kenneth; Shupe, Matthew D.; hide

    2006-01-01

    The large horizontal extent, location in the cold upper troposphere, and ice composition make cirrus clouds important modulators of the earth's radiation budget and climate. Cirrus cloud microphysical properties are difficult to measure and model because they are inhomogeneous in nature and their ice crystal size distribution and habit are not well characterized. Accurate retrievals of cloud properties are crucial for improving the representation of cloud scale processes in large-scale models and for accurately predicting the earth's future climate. A number of passive and active remote sensing retrieval algorithms exist for estimating the microphysical properties of upper tropospheric clouds. We believe significant progress has been made in the evolution of these retrieval algorithms in the last decade, however, there is room for improvement. Members of the Atmospheric Radiation measurement program (ARM) Cloud properties Working Group are involved in an intercomparison of optical depth(tau), ice water path, and characteristic particle size in clouds retrieved using ground-based instruments. The goals of this intercomparison are to evaluate the accuracy of state-of-the-art algorithms, quantify the uncertainties, and make recommendations for improvement.

  9. Investigation of warm-cloud microphysics using a multi-component cloud model: Interactive effects of the aerosol spectrum. Master's thesis

    SciTech Connect

    Zahn, S.G.

    1993-12-01

    Clouds, especially low, warm, boundary-layer clouds, play an important role in regulating the earth's climate due to their significant contribution to the global albedo. The radiative effects of individual clouds are controlled largely by cloud microstructure, which is itself sensitive to the concentration and spectral distribution of the atmospheric aerosol. Increases in aerosol particle concentrations from anthropogenic activity could result in increased cloud albedo and global cloudiness, increasing the amount of reflected solar radiation. However, the effects of increased aerosol particle concentrations could be offset by the presence of giant or ultragiant aerosol particles. A one-dimensional, multi-component microphysical cloud model has been used to demonstrate the effects of aerosol particle spectral variations on the microstructure of warm clouds. Simulations performed with this model demonstrate that the introduction of increased concentrations of giant aerosol particles has a destabilizing effect on the cloud microstructure. Also, it is shown that warm-cloud microphysical processes modify the aerosol particle spectrum, favoring the generation of the largest sized particles via the collision-coalescence process. These simulations provide further evidence that the effect of aerosol particles on cloud microstructure must be addressed when considering global climate forecasts.

  10. Evaluation of Retrieval Algorithms for Ice Microphysics Using CALIPSO/CloudSat and Earthcare

    NASA Astrophysics Data System (ADS)

    Okamoto, Hajime; Sato, Kaori; Hagihara, Yuichiro; Ishimoto, Hiroshi; Borovoi, Anatoli; Konoshonkin, Alexander; Kustova, Natalia

    2016-06-01

    We developed lidar-radar algorithms that can be applied to Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar and CloudSat data to retrieve ice microphysics. The algorithms were the extended version of previously reported algorithm [1] and can treat both of nadir pointing of CALIPSO lidar period and 3°-off-nadir pointing one. We used the scattering data bank produced by the physical optics methods [2] and created lidar look-up tables of quasi-horizontally oriented ice plates (Q2D-plate) for nadir- and off-nadir lidar pointing periods. Then LUTs were implemented in the ice retrieval algorithms. We performed several sensitivity studies to evaluate uncertainties in the retrieved ice microphysics due to ice particle orientation and shape. It was found that the implementation of orientation of horizontally oriented ice plate model in the algorithm drastically improved the retrieval results in both for nadir- and off-nadir lidar pointing periods. Differences in the retrieved microphysics between only randomly oriented ice model (3D-ice) and mixture of 3D-ice and Q2Dplate model were large especially in off-nadir period, e.g., 100% in effective radius and one order in ice water content, respectively. And differences in the retrieved ice microphysics among different mixture models were smaller than about 50% for effective radius in nadir period.

  11. The potential effects of volcanic aerosols on cirrus cloud microphysics

    NASA Technical Reports Server (NTRS)

    Jensen, Eric J.; Toon, Owen B.

    1992-01-01

    The potential impact of volcanic aerosols on nucleation of ice crystals in upper tropospheric cirrus clouds is examined from a microphysical perspective. The sulfuric acid aerosols which form in the stratosphere are presumably transported into the troposphere by sedimentation and tropopause folding. The tropospheric volcanic aerosol size distribution is estimated from 10-micron lidar backscatter and in situ measurements. Microphysical simulations suggest that at temperatures below about -50 C the concentration of ice crystals which nucleate may be as much as a factor of 5 larger when volcanic aerosols are present. The simulations suggest that the presence of volcanic aerosols may increase the net radiative forcing (surface warming) of certain types of cirrus near the tropopause by as much as 8 W/sq m. Further observations are required to determine whether these effects actually occur, and their global impact.

  12. Quantifying the importance of galactic cosmic rays in cloud microphysical processes

    NASA Astrophysics Data System (ADS)

    Rawal, Akhilesh.; Tripathi, Sachchida Nand.; Michael, Marykutty.; Srivastava, Atul K.; Harrison, Richard G.

    2013-09-01

    Galactic Cosmic Rays are one of the major sources of ion production in the troposphere and stratosphere. Recent studies have shown that ions form electrically charged clusters which may grow to become cloud droplets. Aerosol particles charge by the attachment of ions and electrons. The collision efficiency between a particle and a water droplet increases, if the particle is electrically charged, and thus aerosol-cloud interactions can be enhanced. Because these microphysical processes may change radiative properties of cloud and impact Earth's climate it is important to evaluate these processes' quantitative effects. Five different models developed independently have been coupled to investigate this. The first model estimates cloud height from dew point temperature and the temperature profile. The second model simulates the cloud droplet growth from aerosol particles using the cloud parcel concept. In the third model, the scavenging rate of the aerosol particles is calculated using the collision efficiency between charged particles and droplets. The fourth model calculates electric field and charge distribution on water droplets and aerosols within cloud. The fifth model simulates the global electric circuit (GEC), which computes the conductivity and ionic concentration in the atmosphere in altitude range 0-45 km. The first four models are initially coupled to calculate the height of cloud, boundary condition of cloud, followed by growth of droplets, charge distribution calculation on aerosols and cloud droplets and finally scavenging. These models are incorporated with the GEC model. The simulations are verified with experimental data of charged aerosol for various altitudes. Our calculations showed an effect of aerosol charging on the CCN concentration within the cloud, due to charging of aerosols increase the scavenging of particles in the size range 0.1 μm to 1 μm.

  13. Cloud microphysical properties of convective clouds sampled during the Convective Precipitation Experiment (COPE) experiment.

    NASA Astrophysics Data System (ADS)

    Jackson, R.; French, J.; Leon, D.; Plummer, D. M.; Lasher-Trapp, S.; Blyth, A. M.

    2015-12-01

    The COnvective Precipitation Experiment (COPE), occurring in the southwest UK during Summer 2013, was motivated to improve quantitative precipitation forecasting, in part, with the aim to increase understanding of the warm and cold precipitation processes that can produce heavy convective rainfall in the southwest UK. In particular, we examine the creation of graupel embryos, the Hallett-Mossop process, and the effect of entrainment on these processes. To characterize the evolution of cloud microphysical properties of maturing thunderstorms, the University of Wyoming King Air sampled the tops of fresh turrets between -15 and 0. Data sampled by the Cloud Droplet Probe, Cloud Imaging grayscale Probe (CIP-Grey) and 2D Precipitation Probe during four missions are examined. Here we characterize the variability of the cloud liquid and ice particle size distributions and liquid water contents (LWC) inside updraft cores, as a function of temperature, T, and vertical velocity, w. On one of the days, the number concentration of particles with maximum dimension D > 300 μm, N>300, was less than 1 L-1, with very few ice hydrometeors observed. However, on the other missions, N>300 ranged from 1 L-1 to 250 L-1. The CIP-Grey detected liquid drops at T > -5 and a mixture of graupel and rimed columns at T < -5 for these missions, consistent with the warm rain process providing the frozen drops necessary to form graupel embryos that initiate secondary production. In general, LWC relative to adiabatic decreased from 0.75 to 0.2 with height and was lowest when N>300 > 1 L-1, consistent with precipitation growth by collision-coalescence and accretion. Finally, ice precipitation was primarily present at w < 7 m s-1 and greatest when w < 3 m s-1, suggesting that w influences the number of ice particles generated in the updraft cores sampled during COPE-MED.

  14. The global atmospheric electric circuit and its effects on cloud microphysics

    NASA Astrophysics Data System (ADS)

    Tinsley, B. A.

    2008-06-01

    This review is an overview of progress in understanding the theory and observation of the global atmospheric electric circuit, with the focus on its dc aspects, and its short and long term variability. The effects of the downward ionosphere-earth current density, Jz, on cloud microphysics, with its variability as an explanation for small observed changes in weather and climate, will also be reviewed. The global circuit shows responses to external as well as internal forcing. External forcing arises from changes in the distribution of conductivity due to changes in the cosmic ray flux and other energetic space particle fluxes, and at high magnetic latitudes from solar wind electric fields. Internal forcing arises from changes in the generators and changes in volcanic and anthropogenic aerosols in the troposphere and stratosphere. All these result in spatial and temporal variation in Jz. Variations in Jz affect the production of space charge in layer clouds, with the charges being transferred to droplets and aerosol particles. New observations and new analyses are consistent with non-negligible effects of the charges on the microphysics of such clouds. Observed effects are small, but of high statistical significance for cloud cover and precipitation changes, with resulting atmospheric temperature, pressure and dynamics changes. These effects are detectable on the day-to-day timescale for repeated Jz changes of order 10%, and are thus second order electrical effects. The implicit first order effects have not, as yet, been incorporated into basic cloud and aerosol physics. Long term (multidecadal through millennial) global circuit changes, due to solar activity modulating the galactic cosmic ray flux, are an order of magnitude greater at high latitudes and in the stratosphere, as can be inferred from geological cosmogenic isotope records. Proxies for climate change in the same stratified depositories show strong correlations of climate with the inferred global circuit

  15. Impact of nucleation schemes on cirrus cloud formation in a GCM with sectional microphysics

    NASA Astrophysics Data System (ADS)

    Bardeen, C.; Gettelman, A.; Jensen, E. J.; Heymsfield, A.; Delanoe, J.; Deng, M.

    2012-12-01

    We have implemented a sectional microphysics scheme for ice clouds based upon the Community Aerosol and Radiation Model for Atmospheres (CARMA) in the Community Atmosphere Model version 5 (CAM5), which allows for a size resolved treatment of ice particle nucleation, condensational growth, coagulation, sedimentation and detrainment. Detrained and in situ formed ice particles are tracked separately in the model allowing for different microphysical assumptions and separate analysis. Cloud ice from CAM5/CARMA simulations compare better with satellite observations than those with the standard CAM5 two-moment microphysics. CAM5/CARMA has a prognostic treatment for snow, which results in improved ice mass and representation of a melting layer that is absent in CAM5. Here we explore the sensitivity of the simulations to different nucleation schemes including: homogeneous freezing based on Koop et al. (2000), homogeneous freezing based upon Aerosols Interaction and Dynamics in the Atmosphere (AIDA) chamber measurement (Möhler et al., 2010), heterogeneous nucleation with dust aerosols, and heterogeous nucleation with glassy aerosols (Murray et al. 2010). The initial size for detrained ice particles in CAM5/CARMA is temperature dependent based upon a fits to observations from Heymsfield et al. (2010). We explore the sensitivity of the model to different choices for these fits. Results from these simulations are compared to retrievals of water vapor from the Microwave Limb Sounder (MLS) and the Atmospheric Infrared Sounder (AIRS), ice cloud properties from CloudSat-CALIPSO observations (Delanoë and Hogan, 2010; Deng et al. 2010) and to aircraft observations from several field campaigns including: the Costa Rica Aura Validation Experiment (CR-AVE), the Tropical Composition, Cloud and Climate Coupling (TC4), the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) and the Airborne Tropical Tropopause Experiment (ATTREX).

  16. Soot microphysical effects on liquid clouds, a multi-model investigation

    SciTech Connect

    Koch, D; Balkanski, Y; Bauer, S; Easter, Richard C; Ferrachat, S; Ghan, Steven J; Hoose, C; Iversen, T; Kirkevag, A; Kristjansson, J E; Liu, Xiaohong; Lohmann, U; Menon, Surabi; Quaas, J; Schulz, M; Seland, O; Takemura, T; Yan, N

    2011-02-10

    We use global models to explore the microphysical effects of carbonaceous aerosols on liquid clouds. Although absorption of solar radiation by soot warms the atmosphere, soot may cause climate cooling due to its contribution to cloud condensation nuclei (CCN) and therefore cloud brightness. Six global models conducted three soot experiments; four of the models had detailed aerosol microphysical schemes. The average cloud radiative response to biofuel soot (black and organic carbon), including both indirect and semi-direct effects, is -0.11Wm-2, comparable in size but opposite in sign to the respective direct effect. In a more idealized fossil fuel black carbon experiment, some models calculated a positive cloud response because soot provides a deposition sink for sulfuric and nitric acids and secondary organics, decreasing nucleation and evolution of viable CCN. Biofuel soot particles were also typically assumed to be larger and more hygroscopic than for fossil fuel soot and therefore caused more negative forcing, as also found in previous studies. Diesel soot (black and organic carbon) experiments had relatively smaller cloud impacts with five Correspondence to: D. Koch (dorothy.koch@science.doe.gov) of the models <±0.06Wm-2 from clouds. The results are subject to the caveats that variability among models, and regional and interrannual variability for each model, are large. This comparison together with previously published results stresses the need to further constrain aerosol microphysical schemes. The non-linearities resulting from the competition of opposing effects on the CCN population make it difficult to extrapolate from idealized experimen

  17. Soot microphysical effects on liquid clouds, a multi-model investigation

    NASA Astrophysics Data System (ADS)

    Koch, D.; Balkanski, Y.; Bauer, S. E.; Easter, R. C.; Ferrachat, S.; Ghan, S. J.; Hoose, C.; Iversen, T.; Kirkevâg, A.; Kristjansson, J. E.; Liu, X.; Lohmann, U.; Menon, S.; Quaas, J.; Schulz, M.; Seland, Ø.; Takemura, T.; Yan, N.

    2010-10-01

    We use global models to explore the microphysical effects of carbonaceous aerosols on clouds. Although absorption of solar radiation by soot warms the atmosphere, soot may cause climate cooling due to its contribution to cloud condensation nuclei (CCN) and therefore cloud brightness. Six global models conducted three soot experiments; four of the models had detailed aerosol microphysical schemes. The average cloud radiative response to biofuel soot (black and organic carbon), including both indirect and semi-direct effects, is -0.11 Wm-2, comparable in size but opposite in sign to the respective direct effect. In a more idealized fossil fuel black carbon experiment, some models calculated a~positive cloud response because soot provides a deposition sink for sulfuric and nitric acids and secondary organics, decreasing nucleation and evolution of viable CCN. Biofuel soot particles were also typically assumed to be larger and more hygroscopic than for fossil fuel soot and therefore caused more negative forcing, as also found in previous studies. Diesel soot (black and organic carbon) experiments had relatively smaller cloud impacts with five of the models <±0.06 Wm-2 from clouds. The results are subject to the caveats that variability among models, and regional and interrannual variability for each model, are large. This comparison together with previously published results stresses the need to further constrain aerosol microphysical schemes. The non-linearities resulting from the competition of opposing effects on the CCN population make it difficult to extrapolate from idealized experiments to likely impacts of realistic potential emission changes.

  18. Soot microphysical effects on liquid clouds, a multi-model investigation

    NASA Astrophysics Data System (ADS)

    Koch, D.; Balkanski, Y.; Bauer, S. E.; Easter, R. C.; Ferrachat, S.; Ghan, S. J.; Hoose, C.; Iversen, T.; Kirkevåg, A.; Kristjansson, J. E.; Liu, X.; Lohmann, U.; Menon, S.; Quaas, J.; Schulz, M.; Seland, Ø.; Takemura, T.; Yan, N.

    2011-02-01

    We use global models to explore the microphysical effects of carbonaceous aerosols on liquid clouds. Although absorption of solar radiation by soot warms the atmosphere, soot may cause climate cooling due to its contribution to cloud condensation nuclei (CCN) and therefore cloud brightness. Six global models conducted three soot experiments; four of the models had detailed aerosol microphysical schemes. The average cloud radiative response to biofuel soot (black and organic carbon), including both indirect and semi-direct effects, is -0.11 Wm-2, comparable in size but opposite in sign to the respective direct effect. In a more idealized fossil fuel black carbon experiment, some models calculated a positive cloud response because soot provides a deposition sink for sulfuric and nitric acids and secondary organics, decreasing nucleation and evolution of viable CCN. Biofuel soot particles were also typically assumed to be larger and more hygroscopic than for fossil fuel soot and therefore caused more negative forcing, as also found in previous studies. Diesel soot (black and organic carbon) experiments had relatively smaller cloud impacts with five of the models <±0.06 Wm-2 from clouds. The results are subject to the caveats that variability among models, and regional and interrannual variability for each model, are large. This comparison together with previously published results stresses the need to further constrain aerosol microphysical schemes. The non-linearities resulting from the competition of opposing effects on the CCN population make it difficult to extrapolate from idealized experiments to likely impacts of realistic potential emission changes.

  19. Observed microphysical and radiative structure of mid- level, mixed-phase clouds

    NASA Astrophysics Data System (ADS)

    Fleishauer, Robert Paul

    Airborne measurements of six mid-level clouds observed over the Great Plains of the United States in late 1999 and early 2000 are analyzed extensively. All cloud fields are associated with a 500-mb low-pressure center or a potential vorticity maximum, with additional lift provided by upper-level jet streams. Data show that these innocuous looking clouds display complicated microphysical and thermodynamic structures. Five of six cases include mixed-phase conditions in temperatures ranging from near freezing to -31°C, at altitudes of 2400 to 7200 in. Four of the cases consist of a single cloud layer, while the other two are multi- layered systems. Of particular note, in single-layered clouds, there is an increase of liquid water content with height versus a decrease in ice water content over the same depth. This is in contrast to multi-layered systems, where the liquid water content has the same basic shape, but the ice water content is distributed more uniformly throughout all layers. We attribute these structural differences to a seeder-feeder mechanism operating in the multi-layered systems. A lack of temperature inversions in these mid-level clouds is a major difference from the thermodynamic structure of most stratocumulus systems. We found the virtual potential temperature to be the best discriminator of cloud interfaces for mid-level clouds, with 1-2°C differences between ambient and cloud air. A noteworthy contribution to this observational study was the use of the Cloud Particle Imager (CPI) instrument for the qualitative analysis of the particle sizes, shapes, habits, and distributions through the cloud. An analysis of the liquid water budget of a Lagrangian cloud sample revealed that large-scale subsidence was the main mechanism responsible for its dissipation. Heating rates and fluxes are computed for each cloud using a single-column radiative transfer model. Sensitivity studies included the radiative effects of doubling and halving liquid and ice water

  20. Microphysics of condensational clouds of Venus and observation strategy

    NASA Astrophysics Data System (ADS)

    Imamura, T.; Hashimoto, G.

    The variability of Venusian clouds in the tropics was studied by simultaneously solving advection and cloud microphysics equations, using a one-dimensional model that includes a weak upwelling representing the rising branch of Hadley circulation and also strong temporal winds. Cloud droplets in the upper cloud region are formed by the photochemical production of H2 SO4 vapor and eventually removed from the tropical atmosphere by Hadley circulation, whereas in the middle and lower cloud regions dynamical processes supply H2 SO4 vapor from below such that resultant droplets are large and fall against the upwelling. Within the latter condensational clouds, transient strong winds govern droplet growth and produce a variety of size distributions similar to those observed. Specifically, in an updraft, adiabatic expansion abruptly cools H2 SO4 vapor, thereby forcing the saturation pressure over condensation nuclei to transiently fall below the ambient H2 SO4 vapor pressure. Bare condensation nuclei may then overcome the Kelvin barrier and form middle-size droplets, that gradually merge into pre-existing larger size mode with a time constant of several hours. Such a temporal change in droplet size associated with each transient event would be detected if successive nightside images are acquired with short time intervals (<1 hr) at several wavelengths in the near-infrared window, since a near-infrared spectrum of Venus nightside is sensitive to the dominant droplet size. A Venus orbiter with high-apoapsis orbit will be suitable for such an observation.

  1. An Intercomparison of Microphysical Retrieval Algorithms for Upper-Tropospheric Ice Clouds

    SciTech Connect

    Comstock, Jennifer M.; d'Entremont, Robert; DeSlover, Daniel; Mace, Gerald G.; Matrosov, S. Y.; McFarlane, Sally A.; Minnis, Patrick; Mitchell, David; Sassen, Kenneth; Shupe, Matthew D.; Turner, David D.; Wang, Zhien

    2007-02-01

    The large horizontal extent, location in the cold upper troposphere, and ice composition make cirrus clouds important modulators of the earth’s radiation budget and climate. Cirrus cloud microphysical properties are difficult to measure and model because they are inhomogeneous in nature and their ice crystal size distribution and habit are not well characterized. Accurate retrievals of cloud properties are crucial for improving the representation of cloud scale processes in large-scale models and for accurately predicting the earth’s future climate. A number of passive and active remote sensing retrievals exist for estimating the microphysical properties of upper tropospheric clouds. We believe significant progress has been made in the evolution of these retrieval algorithms in the last decade; however, there is room for improvement. Members of the Atmospheric Radiation Measurement program (ARM) Cloud Properties Working Group are involved in an intercomparison of optical depth (tau), ice water path, and characteristic particle size in ice clouds retrieved using ground-based instruments. The goals of this intercomparison are to evaluate the accuracy of state-of-the-art algorithms, quantify the uncertainties, and make recommendations for improvement. Currently, there is significant scatter in the algorithms for difficult clouds with very small optical depths (tau<0.3) and thick ice clouds (tau>1). The good news is that for thin cirrus (0.3cloud properties with aircraft and satellite measurements, and perform a radiative closure experiment to begin gauging the accuracy of these retrieval algorithms.

  2. Use of Field Observations for Understanding Controls of Polar Low Cloud Microphysical Properties

    NASA Astrophysics Data System (ADS)

    McFarquhar, G. M.

    2016-12-01

    Although arctic clouds have a net warming effect on the Arctic surface, their radiative effect is sensitive to cloud microphysical properties, namely the sizes, phases and shapes of cloud particles. Such cloud properties are influenced by the numbers, compositions and sizes of aerosols, meteorological conditions, and surface characteristics. Uncertainty in representing cloud-aerosol interactions in varying environmental conditions and associated feedbacks is a major cause in our lack of understanding of why the Arctic is warming faster than the rest of the Earth. Here, the understanding of cloud-aerosol interactions gained from past arctic field experiments is reviewed. Such studies have characterized the structure of single-layer mixed phase clouds that are ubiquitous in the Arctic and investigated different aerosol indirect effect mechanisms acting in these clouds. But, it is still unknown what controls the amount of supercooled water in arctic clouds (especially in complex frequently occurring multi-layer clouds), how probability distributions of cloud properties and radiative heating and their subsequent impact on temperature profiles and underlying snow and sea ice cover vary with aerosol loading and composition in different surface and meteorological conditions, how the composition and concentration of arctic aerosols and cloud microphysical properties vary annually and interannually, and how cloud-aerosol-radiative interactions can be better represented in models with varying temporal and spatial scales. These needs can be addressed in two ways. First, there is a need for comprehensive and routine aircraft, UAV and tethered balloon measurements in the presence of ground, air or space-based remote sensors over a variety of surface and meteorological conditions. Second, planned observational campaigns (the Measurements of Aerosols Radiation and Clouds over the Southern Oceans MARCUS and the Southern Oceans Cloud Radiation Transport Experimental Study SOCRATES

  3. UV Raman lidar measurements of relative humidity for the characterization of cirrus cloud microphysical properties

    NASA Astrophysics Data System (ADS)

    di Girolamo, P.; Summa, D.; Lin, R.-F.; Maestri, T.; Rizzi, R.; Masiello, G.

    2009-11-01

    Raman lidar measurements performed in Potenza by the Raman lidar system BASIL in the presence of cirrus clouds are discussed. Measurements were performed on 6 September 2004 in the frame of the Italian phase of the EAQUATE Experiment. The major feature of BASIL is represented by its capability to perform high-resolution and accurate measurements of atmospheric temperature and water vapour, and consequently relative humidity, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. BASIL is also capable to provide measurements of the particle backscatter and extinction coefficient, and consequently lidar ratio (at the time of these measurements, only at one wavelength), which are fundamental to infer geometrical and microphysical properties of clouds. A case study is discussed in order to assess the capability of Raman lidars to measure humidity in presence of cirrus clouds, both below and inside the cloud. While air inside the cloud layers is observed to be always under-saturated with respect to water, both ice super-saturation and under-saturation conditions are found inside these clouds. Upper tropospheric moistening is observed below the lower cloud layer. The synergic use of the data derived from the ground based Raman Lidar and of spectral radiances measured by the NAST-I Airborne Spectrometer allows the determination of the temporal evolution of the atmospheric cooling/heating rates due to the presence of the cirrus cloud. Lidar measurements beneath the cirrus cloud layer have been interpreted using a 1-D cirrus cloud model with explicit microphysics. The 1-D simulations indicate that sedimentation-moistening has contributed significantly to the moist anomaly, but other mechanisms are also contributing. This result supports the hypothesis that the observed mid-tropospheric humidification is a real feature which is strongly influenced by the sublimation of precipitating ice crystals. Results

  4. UV Raman lidar measurements of relative humidity for the characterization of cirrus cloud microphysical properties

    NASA Astrophysics Data System (ADS)

    di Girolamo, P.; Summa, D.; Lin, R.-F.; Maestri, T.; Rizzi, R.; Masiello, G.

    2009-07-01

    Raman lidar measurements performed in Potenza by the Raman lidar system BASIL in the presence of cirrus clouds are discussed. Measurements were performed on 6 September 2004 in the frame of Italian phase of the EAQUATE Experiment. The major feature of BASIL is represented by its capability to perform high-resolution and accurate measurements of atmospheric temperature and water vapour, and consequently relative humidity, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. BASIL is also capable to provide measurements of the particle backscatter and extinction coefficient, and consequently lidar ratio (at the time of these measurements only at one wavelength), which are fundamental to infer geometrical and microphysical properties of clouds. A case study is discussed in order to assess the capability of Raman lidars to measure humidity in presence of cirrus clouds, both below and inside the cloud. While air inside the cloud layers is observed to be always under-saturated with respect to water, both ice super-saturation and under-saturation conditions are found inside these clouds. Upper tropospheric moistening is observed below the lower cloud layer. The synergic use of the data derived from the ground based Raman Lidar and of spectral radiances measured by the NAST-I Airborne Spectrometer allows to determine the temporal evolution of the atmospheric cooling/heating rates due to the presence of the cirrus cloud anvil. Lidar measurements beneath the cirrus cloud layer have been interpreted using a 1-D cirrus cloud model with explicit microphysics. The 1-D simulations indicates that sedimentation-moistening has contributed significantly to the moist anomaly, but other mechanisms are also contributing. This result supports the hypothesis that the observed mid-tropospheric humidification is a real feature which is strongly influenced by the sublimation of precipitating ice crystals. Results

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    We present detailed airborne in situ measurements of cloud microphysics in two midlatitude cirrus clouds, collected as part of the Cirrus Coupled Cloud-Radiation Experiment. A new habit recognition algorithm for sorting cloud particle images using a neural network is introduced. Both flights observed clouds that were related to frontal systems, but one was actively developing while the other dissipated as it was sampled. The two clouds showed distinct differences in particle number, habit, and size. However, a number of common features were observed in the 2-D stereo data set, including a distinct bimodal size distribution within the higher-temperature regions of the clouds. This may result from a combination of local heterogeneous nucleation and large particles sedimenting from aloft. Both clouds had small ice crystals (<100 µm) present at all levels However, this small ice mode is not present in observations from a holographic probe. This raises the possibility that the small ice observed by optical array probes may at least be in part an instrument artifact due to the counting of out-of-focus large particles as small ice. The concentrations of ice crystals were a factor 10 higher in the actively growing cloud with the stronger updrafts, with a mean concentration of 261 L-1 compared to 29 L-1 in the decaying case. Particles larger than 700 µm were largely absent from the decaying cirrus case. A comparison with ice-nucleating particle parameterizations suggests that for the developing case the ice concentrations at the lowest temperatures are best explained by homogenous nucleation.

  6. Exploring the Effects of Cloud Vertical Structure on Cloud Microphysical Retrievals based on Polarized Reflectances

    NASA Astrophysics Data System (ADS)

    Miller, D. J.; Zhang, Z.; Platnick, S. E.; Ackerman, A. S.; Cornet, C.; Baum, B. A.

    2013-12-01

    A polarized cloud reflectance simulator was developed by coupling an LES cloud model with a polarized radiative transfer model to assess the capabilities of polarimetric cloud retrievals. With future remote sensing campaigns like NASA's Aerosols/Clouds/Ecosystems (ACE) planning to feature advanced polarimetric instruments it is important for the cloud remote sensing community to understand the retrievable information available and the related systematic/methodical limitations. The cloud retrieval simulator we have developed allows us to probe these important questions in a realistically relevant test bed. Our simulator utilizes a polarized adding-doubling radiative transfer model and an LES cloud field from a DHARMA simulation (Ackerman et al. 2004) with cloud properties based on the stratocumulus clouds observed during the DYCOMS-II field campaign. In this study we will focus on how the vertical structure of cloud microphysics can influence polarized cloud effective radius retrievals. Numerous previous studies have explored how retrievals based on total reflectance are affected by cloud vertical structure (Platnick 2000, Chang and Li 2002) but no such studies about the effects of vertical structure on polarized retrievals exist. Unlike the total cloud reflectance, which is predominantly multiply scattered light, the polarized reflectance is primarily the result of singly scattered photons. Thus the polarized reflectance is sensitive to only the uppermost region of the cloud (tau~<1) where photons can scatter once and still escape before being scattered again. This means that retrievals based on polarized reflectance have the potential to reveal behaviors specific to the cloud top. For example cloud top entrainment of dry air, a major influencer on the microphysical development of cloud droplets, can be potentially studied with polarimetric retrievals.

  7. Improving the representation of mixed-phase cloud microphysics in the ICON-LEM

    NASA Astrophysics Data System (ADS)

    Tonttila, Juha; Hoose, Corinna; Milbrandt, Jason; Morrison, Hugh

    2017-04-01

    The representation of ice-phase cloud microphysics in ICON-LEM (the Large-Eddy Model configuration of the ICOsahedral Nonhydrostatic model) is improved by implementing the recently published Predicted Particle Properties (P3) scheme into the model. In the typical two-moment microphysical schemes, such as that previously used in ICON-LEM, ice-phase particles must be partitioned into several prescribed categories. It is inherently difficult to distinguish between categories such as graupel and hail based on just the particle size, yet this partitioning may significantly affect the simulation of convective clouds. The P3 scheme avoids the problems associated with predefined ice-phase categories that are inherent in traditional microphysics schemes by introducing the concept of "free" ice-phase categories, whereby the prognostic variables enable the prediction of a wide range of smoothly varying physical properties and hence particle types. To our knowledge, this is the first application of the P3 scheme in a large-eddy model with horizontal grid spacings on the order of 100 m. We will present results from ICON-LEM simulations with the new P3 scheme comprising idealized stratiform and convective cloud cases. We will also present real-case limited-area simulations focusing on the HOPE (HD(CP)2 Observational Prototype Experiment) intensive observation campaign. The results are compared with a matching set of simulations employing the two-moment scheme and the performance of the model is also evaluated against observations in the context of the HOPE simulations, comprising data from ground based remote sensing instruments.

  8. Studies of Radiation and Microphysics in Cirrus and Marine Stratocumulus Clouds

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Two tasks were completed during this period. In the first, we examined the polarization of millimeter-wavelength radar beams scattered by ice crystals. Because of their non-spherical shape and size, ice crystals depolarize the incident polarized radar beam. In principle, this depolarization can be used to identify ice from liquid water, as well as provide some information on size. However, the amount of de-polarization is small, producing only a weak signal at the receiver. Our task was to determine the magnitude of such a signal and decide if our radar would be capable of measuring it under typical cirrus conditions. The theoretical study was carried out by Henrietta Lemke, a visiting graduate student from Germany. She had prior experience using a discrete dipole code to compute scattering depolarization. Dr. Kultegin Aydin of the Penn State Electrical Engineering Department, who is also expert in this area, consulted with us on this project at no cost to the project. Our conclusion was that the depolarization signal is too weak to be usefully measured by our system. Therefore we proceeded no further in this study. The second task involved the study of the effect of stratus microphysics on surface cloud forcing. Manajit Sengupta, a graduate student, and the project PI jointly carried out this task. The study used data culled from over a year of continuous radar and radiometer observations at the Atmospheric Radiation Measurement (ARM) site in Oklahoma. The study compared solar radiation calculations made using constant microphysics with calculations made using a retrieved mean particle size. The results showed that on average the constant microphysics produced the correct forcing when compared with the observed forcing. We conclude, therefore, that there is little impetus on radiation grounds alone to include explicit microphysics in climate models. The question of pollutant particle emission impacts on microphysics remains to be resolved. A manuscript is in

  9. A Microphysics Guide to Cirrus Clouds - Part I: Cirrus Types

    NASA Astrophysics Data System (ADS)

    Krämer, Martina; Rolf, Christian; Anna, Luebke; Armin, Afchine; Nicole, Spelten; Anja, Costa; Jessica, Meyer; Martin, Zöger; Jessica, Smith; Robert, Herman; Bernhard, Buchholz; Volker, Ebert; Darrel, Baumgardner; Stephan, Borrmann; Marcus, Klingebiel; Linnea, Avallone

    2016-04-01

    The microphysical and radiative properties of cirrus clouds continue to be beyond understanding and thus still represent one of the largest uncertainties in the prediction of the Earth's climate (IPCC, 2013). Our study provides a guide to cirrus microphysics, which is compiled from an extensive set of model simulations, covering the broad range of atmospheric conditions for cirrus formation and evolution (Krämer et al., 2015, ACPD). The model results are portrayed in the same parameter space as field measurements, i.e. in the Ice Water Content-Temperature (IWC-T) parameter space. We validate this cirrus analysis approach by evaluating cirrus data sets from seventeen aircraft campaigns, conducted in the last fifteen years, spending about 94 h in cirrus over Europe, Australia, Brazil as well as Southern and Northern America. Altogether, the approach of this study is to track cirrus IWC development with temperature by means of model simulations, compare with observations and then assign, to a certain degree, cirrus microphysics to the observations. Indeed, the field observations show characteristics expected from the simulated cirrus guide. For example, high/low IWCs are found together with high/low ice crystal concentrations. An important finding from our study is the classification of two types of cirrus with differing formation mechanisms and microphysical properties: the first cirrus type is rather thin with lower IWCs and forms directly as ice (in-situ origin cirrus). The second type consists predominantly of thick cirrus originating from mixed phase clouds (i.e. via freezing of liquid droplets - liquid origin cirrus), which are completely glaciated while lifting to the cirrus formation temperature region (< 235 K). In the European field campaigns, in-situ origin cirrus occur frequently at slow updrafts in low and high pressure systems, but also in conjunction with faster updrafts. Also, liquid origin cirrus mostly related to warm conveyor belts are found. In

  10. Development of a detailed microphysical model for Martian dust and ice clouds

    NASA Astrophysics Data System (ADS)

    Daerden, F.; Verhoeven, C.; Larsen, N.; Mateshvili, N.; Fussen, D.; Akingunola, D.; McConell, J. C.; Kaminski, J. W.

    2007-08-01

    Although water vapor is a minor constituent in the composition of the Martian atmosphere, water ice clouds have been observed for more than thirty years. They seem to play an important role in the atmospheric transport of water and dust. A careful and detailed modeling study of these clouds is therefore important to better understand the Martian climate. Marsbox is a new microphysical boxmodel for the dust and water ice clouds on Mars. This model has been adapted from PSCbox, a detailed model for polar stratospheric clouds in the Earth's atmosphere which has been developed at the Danish Meteorological Institute [1, 2]. Marsbox takes into account the following processes: • heterogeneous nucleation of ice particles by water vapor deposition on dust particles, • condensation and evaporation of water vapor to and from the ice particles, causing growth and shrinking of the particles, • gravitational sedimentation of the cloud particles, • eddy diffusion, which describes the vertical mixing of the cloud particles and the water vapor. Each particle type is described by a binned size distribution for the number density and composition. The model calculates the evolution in time of these size distributions, of the mixing ratio of water vapor, and of the mass of condensed water. The model uses the ambient air temperature and pressure and the partial pressure of water vapor as input. The initial size distribution of the cloud particles is assumed to follow a lognormal distribution. The model has a variable internal timestep because the microphysical processes may require computational timescales much smaller than the driver's timestep. We present the first simulations with this new model using input fields from GEMMars (or GM3), a recently developed global circulations model (GCM) for the Martian atmosphere which has been developed at York University, Toronto, Canada [3]. These first results will be compared to cloud retrievals from the SPICAM instrument on Mars

  11. Retrieving microphysical properties and air motion of cirrus clouds based on the doppler moments method using cloud radar

    NASA Astrophysics Data System (ADS)

    Zhong, Lingzhi; Liu, Liping; Deng, Min; Zhou, Xiuji

    2012-05-01

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

  12. Bin-Resolved Microphysical Modeling of Water Vapor Isotopic Composition During Ice Nucleation and Growth in Mixed-Phase Clouds

    NASA Astrophysics Data System (ADS)

    Aho, S.; Weinhold, F.; Peter, T.; Moyer, E. J.

    2011-12-01

    Because any phase change in water is accompanied by isotopic fractionation, ice nucleation and growth in mixed-phase and cirrus clouds should be accompanied by large isotopic changes, and isotopic composition can be a useful tracer for understanding microphysics in these contexts. However, detailed microphysical modeling that includes isotopologues of water has not previously been done. We present here initial studies with the BRIMM ("Bin-Resolved Isotopic Microphysical Model") model, developed at ETH Zurich, a bin-resolved model that incorporates isotopic accounting during evaporation and condensation. Explicit resolution of particle sizes is especially important for isotopic microphysics because particle sizes affect isotopic evolution: in particular, heating via the latent heat of condensation has strong effects on isotopic fractionation and can be misrepresented by a bulk microphysical model. We show here the range of isotopic evolution produced by changes in physical parameters and processes, focusing especially on latent heat effects in the Bergeron process, as water is transferred from liquid to solid particles through the vapor phase. These isotopic studies can form the foundations for interpretation of eventual in-situ measurements of isotopic compositions in cirrus and mixed-phase clouds.

  13. Effects of drop freezing on microphysics of an ascending cloud parcel under biomass burning conditions

    NASA Astrophysics Data System (ADS)

    Diehl, K.; Simmel, M.; Wurzler, S.

    There is some evidence that the initiation of warm rain is suppressed in clouds over regions with vegetation fires. Thus, the ice phase becomes important as another possibility to initiate precipitation. Numerical simulations were performed to investigate heterogeneous drop freezing for a biomass-burning situation. An air parcel model with a sectional two-dimensional description of the cloud microphysics was employed with parameterizations for immersion and contact freezing which consider the different ice nucleating efficiencies of various ice nuclei. Three scenarios were simulated resulting to mixed-phase or completely glaciated clouds. According to the high insoluble fraction of the biomass-burning particles drop freezing via immersion and contact modes was very efficient. The preferential freezing of large drops followed by riming (i.e. the deposition of liquid drops on ice particles) and the evaporation of the liquid drops (Bergeron-Findeisen process) caused a further decrease of the liquid drops' effective radius in higher altitudes. In turn ice particle sizes increased so that they could serve as germs for graupel or hailstone formation. The effects of ice initiation on the vertical cloud dynamics were fairly significant leading to a development of the cloud to much higher altitudes than in a warm cloud without ice formation.

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

    NASA Astrophysics Data System (ADS)

    Gu, Yu

    2000-12-01

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

  15. Effects of aerosols on retrieval of the microphysical properties of water clouds from the airborne solar spectral reflectance measurements

    NASA Astrophysics Data System (ADS)

    Asano, Shoji; Uchiyama, Akihiro; Yamazaki, Akihiro; Tanizono, Masayo

    2001-02-01

    We have investigated effects of the temperature dependence of water absorption indexes and of absorbing aerosols on the retrieval of cloud microphysical properties from the multi- spectral solar reflectance measurement by the airborne Multi- channel Cloud Pyranometer (MCP) system through collocated two- aircraft validation flights. For the clean liquid-water clouds, the reasonable cloud parameters were successfully retrieved by taking into account the temperature dependence of the complex refractive index of water by Kou et al. For the water cloud contaminated by absorbing aerosols, the present MCP-retrieval, under the assumption of pure liquid-water clouds, underestimated the visible optical thickness and overestimated the effective particle radius. The result suggests that new remote sensing techniques should be developed to discriminate and evaluate the effects of cloud particles and aerosols.

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

    SciTech Connect

    Gao, Wenhua; Sui, Chung-Hsiung; Fan, Jiwen; Hu, Zhiqun; Zhong, Lingzhi

    2016-11-27

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

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

    NASA Astrophysics Data System (ADS)

    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

    particle sizes, down to at least 55 nm in size, act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show this can occur without invoking differences in chemical composition. Aerosol number concentration in the >0.05 and >0.1 μm size ranges was correlated with droplet number concentration, and anti-correlated with droplet effective radius, and the effect is statistically significant. The impact of aerosol pollutants was to increase droplet number and decrease droplet size within a region extending about 1000 km offshore. Cloud droplets were more numerous and smaller near shore, and there was less drizzle. However, MODIS satellite measurements were used to show that despite the smaller droplets near shore, cloud albedo is not higher near shore than offshore. This is due to the generally thinner clouds and lower liquid water path near shore.

  18. A New Two-Moment Bulk Stratiform Cloud Microphysics Scheme in the Community Atmosphere Model, Version 3 (CAM3). Part II: Single-Column and Global Results

    SciTech Connect

    Gettelman, A.; Morrison, H.; Ghan, Steven J.

    2008-08-11

    The global performance of a new 2-moment cloud microphysics scheme for a General Circulation Model (GCM) is presented and evaluated relative to observations. The scheme produces reasonable representations of cloud particle size and number concentration when compared to observations, and represents expected and observed spatial variations in cloud microphysical quantities. The scheme has smaller particles and higher number concentrations over land than the standard bulk microphysics in the GCM, and is able to balance the radiation budget of the planet with 60% the liquid water of the standard scheme, in better agreement with observations. The new scheme treats both the mixing ratio and number concentration of rain and snow, and is therefore able to differentiate the two key regimes, consisting of drizzle in shallow warm clouds and larger rain drops in deeper cloud systems. The modeled rain and snow size distributions are consistent with observations.

  19. Towards More Consistent Retrievals of Ice Cloud Optical and Microphysical Properties from Polar Orbiting Sensors

    NASA Astrophysics Data System (ADS)

    Baum, B. A.; Heymsfield, A.; Yang, P.

    2011-12-01

    Differences exist in the ice cloud optical thickness and effective particle size products provided by teams working with data from AVHRR (Advanced Very High Resolution Radiometer), MODIS (MODerate resolution Imaging Spectroradiometer), POLDER (Polarization and Directionality of the Earth Reflectance), Imaging Infrared Radiometer (IIR), and CALIOP (Cloud Aerosol LIdar with Orthogonal Polarization). The issue is in large part due to the assumed ice cloud single-scattering properties that each team uses in their retrievals. To gain insight into this problem, we are developing ice cloud single-scattering properties consistently from solar through far-infrared wavelengths by merging ice cloud microphysical data from in situ measurements with the very latest light scattering calculations for ice habits that include droxtals, solid/hollow columns, plates, solid/hollow bullet rosettes, aggregates of columns, and small/large aggregates of plates. The in-situ measurements are from a variety of field campaigns, including ARM-IOP, CRYSTAL-FACE, ACTIVE, SCOUT, MidCiX, pre-AVE, TC-4, and MACPEX. Among other advances, the light scattering calculations include the full phase matrix (i.e., polarization), incorporate a new treatment of forward scattering, and three levels of surface roughness from smooth to severely roughened. This talk will focus on improvements to our methodology for building both spectral and narrowband bulk scattering optical models appropriate for satellite imagers and hyperspectral infrared sensors. The new models provide a basis for investigating retrieval differences in the products from the sensor teams. We will discuss recent work towards improving the consistency of ice cloud microphysical/optical property retrievals between solar, polarimetric, and infrared retrieval approaches. It will be demonstrated that severely roughened ice particles correspond best in comparisons to polarization measurements. Further discussion will provide insight as to the

  20. The Microphysics of Antarctic Clouds - Part one Observations.

    NASA Astrophysics Data System (ADS)

    Lachlan-Cope, Tom; Listowski, Constantino; O'Shea, Sebastian; Bower, Keith

    2016-04-01

    During the Antarctic summer of 2010 and 2011 in-situ measurements of clouds were made over the Antarctic Peninsula and in 2015 similar measurements were made over the eastern Weddell Sea using the British Antarctic Surveys instrumented Twin Otter aircraft. This paper contrasts the clouds found on either side of the Antarctic Peninsula with the clouds over the eastern Weddell Sea, paying particular attention to the total number of ice and water particles found in the clouds. The differences found between the clouds are considered in relation to the sources of cloud condensation nuclei and ice nuclei that are expected to be active in the different cases. In particular it was found that the number of ice nuclei was very low over the Weddell Sea when compared to other regions.

  1. Continuous Profiles of Cloud Microphysical Properties for the Fixed Atmospheric Radiation Measurement Sites

    SciTech Connect

    Jensen, M; Jensen, K

    2006-06-01

    The Atmospheric Radiation Measurement (ARM) Program defined a specific metric for the third quarter of Fiscal Year 2006 to produce and refine a one-year continuous time series of cloud microphysical properties based on cloud radar measurements for each of the fixed ARM sites. To accomplish this metric, we used a combination of recently developed algorithms that interpret radar reflectivity profiles, lidar backscatter profiles, and microwave brightness temperatures into the context of the underlying cloud microphysical structure.

  2. Two-moment Bulk Stratiform Cloud Microphysics in the Grid-point Atmospheric Model of IAP LASG (GAMIL)

    SciTech Connect

    Shi, Xiangjun; Wang, Bin; Liu, Xiaohong; Wang, Minghuai

    2013-05-01

    A two-moment bulk stratiform microphysics scheme, including recently developed physically-based droplet activation/ice nucleation parameterizations has been implemented into the Grid-point Atmospheric Model of IAP LASG (GAMIL) as an effort to enhance the model capability for studying aerosol indirect effects. Unlike the previous one-moment cloud microphysics scheme, the new scheme produces reasonable representation of cloud particle size and number concentration. This scheme captures the observed spatial variations in cloud droplet number concentrations. Simulated ice crystal number concentrations in cirrus clouds qualitatively agree with in-situ observations. The longwave and shortwave cloud forcing are in better agreement with observations. Sensitivity tests show that the column cloud droplet number concentrations calculated from two different droplet activation parameterizations are similar. However, ice crystal number concentration in mixed-phased clouds is sensitive to different heterogeneous freezing formulations. The simulation with high ice crystal number concentration in mixed-phase clouds has less liquid water path and weaker cloud forcing. Furthermore, ice crystal number concentration in cirrus clouds is sensitive to different ice nucleation parameterizations. Sensitivity tests also suggest that impact of pre-existing ice crystals on homogeneous freezing in old clouds should be taken into account.

  3. Retrievals of ice cloud microphysical properties of deep convective systems using radar measurements: Convective Cloud Microphysical Retrieval

    SciTech Connect

    Tian, Jingjing; Dong, Xiquan; Xi, Baike; Wang, Jingyu; Homeyer, Cameron R.; McFarquhar, Greg M.; Fan, Jiwen

    2016-09-23

    This study presents new algorithms for retrieving ice cloud microphysical properties (ice water content (IWC) and median mass diameter (Dm)) for the stratiform and thick anvil regions of Deep Convective Systems (DCSs) using Next-Generation Radar (NEXRAD) reflectivity and recently developed empirical relationships from aircraft in situ measurements during the Midlatitude Continental Convective Clouds Experiment (MC3E). A classic DCS case on 20 May 2011 is used to compare the retrieved IWC profiles with other retrieval and cloud-resolving model simulations. The mean values of each retrieved and simulated IWC fall within one standard derivation of the other two. The statistical results from six selected cases during MC3E show that the aircraft in situ derived IWC and Dm are 0.47 ± 0.29 g m-3 and 2.02 ± 1.3 mm, while the mean values of retrievals have a positive bias of 0.16 g m-3 (34%) and a negative bias of 0.39 mm (19%). To validate the newly developed retrieval algorithms from this study, IWC and Dm are performed with other DCS cases during Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) field campaign using composite gridded NEXRAD reflectivity and compared with in situ IWC and Dm from aircraft. A total of 64 1-min collocated aircraft and radar samples are available for comparisons, and the averages of radar retrieved and aircraft in situ measured IWCs are 1.22 g m-3 and 1.26 g m-3 with a correlation of 0.5, and their averaged Dm values are 2.15 and 1.80 mm. These comparisons have shown that the retrieval algorithms 45 developed during MC3E can retrieve similar ice cloud microphysical properties of DCS to aircraft in situ measurements during BAMEX with median errors of ~40% and ~25% for IWC and Dm retrievals, respectively. This is indicating our retrieval algorithms are suitable for other midlatitude continental DCS ice clouds, especially at stratiform rain and thick anvil regions. In addition, based on the averaged IWC and Dm values during MC3E and

  4. Multi-year analysis of ice microphysics derived from CloudSat and CALIPSO

    NASA Astrophysics Data System (ADS)

    Okamoto, H.; Sato, K.; Hagihara, Y.

    2012-12-01

    We conducted multi-year analys of ice microphysics using CloudSat and CALIPSO data. Inter-annual variability, land-ocean differences and seasonal changes of ice microphysical properties were reported for the observation periods from 2006 to 2009. CALIPSO changed the laser tilt angle from 0.3 degrees to 3 degrees off nadir direction on November 2007 and the zonal mean properties of backscattering coefficient and depolarization ratio were significantly decreased and increased, respectively, for low altitude after November 2007. This could be explained by the different backscattering behavior of horizontally oriented ice crystals for the different laser tilt angles. On the other hand, inter-annual variability of zonal mean properties of reflectivity factor observed by CloudSat showed the very similar characteristics during the four years. In addition, the lidar observables were similar when the monthly mean properties were compared for different years before November 2007 and also the same was true for the comparisons after November 2007. These analyses of observables suggested that the inter-annual variability of zonal mean properties of ice microphysics could be considered to be similar. Application of the radar-lidar algorithm showed that the change of the laser tilt angle introduced the large gap between the ice microphysical properties before and after November 2007, if the proper treatment of the oriented ice crystals were not conducted in the retrievals. Global analysis of cloud particle types showed that the frequent occurrence of oriented ice crystals were identified in the temperature range between -10 to -20 degrees C. It is also noted that the significant overestimation of ice water content and significant underestimation of ice effective radius were found if the scattering properties of the horizontally oriented ice particles were not considered. Therefore it is highly demanded that the realistic ice orientation model is implemented in the look up tables

  5. Effect Of Black Carbon Radiative Heating On Cloud Microphysics Over Indo-Gangetic Basin

    NASA Astrophysics Data System (ADS)

    Ghosh, A.; Tripathi, S. N.

    2008-12-01

    Airborne black carbon (BC), the most significant particulate absorber of solar radiation in the atmosphere, is an important contributor to both global and regional-scale climate forcing (Tripathi et al., 2005). In context of cloud microphysics, freshly emitted pure BC particles are hydrophobic (i.e., bad cloud condensation nuclei (CCN)). However, exposure in the atmosphere may transform BC to a hydrophilic state if these particles are coated with additional materials, such as sulfate and organic carbon (OC). In a recent study, Conant et al. (2002) has examined the effect of radiative heating of BC on the critical supersaturation spectrum of internally mixed aerosols. Two main uncertainties introduced in this work are due to lack of knowledge of actual state of mixing and realistic distributions of different aerosol species. Indo-Gangetic Basin (IGB) in the northern India is one of the most polluted regions in the world. The cloud microphysical processes in IGB are very complex and it requires an in depth investigation for understanding of the aerosol-cloud interaction in the region (Tripathi, et al., 2007). In the present work, an attempt has been made to study the effect of radiative heating due to BC particles coated with hydrophilic materials on cloud microphysics over IGB. For this purpose, we have used (a) a two-layer radiative parameter model based on Mie theory (Toon and Ackerman, 1981) to calculate the particle (monodisperse) absorption cross section; (b) a three-dimensional (3D) radiative transfer model, the spherical harmonics discrete ordinate method (SHDOM) (Evans,1998), which assumes a tropical continental atmosphere, to simulate the 3D spectral actinic flux over the study region; and (c) Extended Köhler theory (Conant et al., 2002) to simulate the effect the BC radiative heating on cloud droplet activation. The solar wavelength spectrum used ranges from 0.2 to 5 micrometer. Following the in situ measurements and modeling studies on mixing state (Dey

  6. Modeling the influence of aerosols on cloud microphysical properties in the east Asia region using a mesoscale model coupled with a bin-based cloud microphysics scheme

    NASA Astrophysics Data System (ADS)

    Iguchi, Takamichi; Nakajima, Teruyuki; Khain, Alexander P.; Saito, Kazuo; Takemura, Toshihiko; Suzuki, Kentaroh

    2008-07-01

    A bin-based microphysics scheme for cloud is implemented into a three-dimensional nonhydrostatic model and off-line coupled with a global aerosol transport model to reproduce realistic and inhomogeneous condensation nuclei (CN) fields. This coupling makes it possible to calculate cloud microphysical properties over a larger area under more realistic environmental conditions. Using the model, nested grid simulations are performed for two precipitation events associated with transitional synoptic-scale forcing during the spring over an area of the East China Sea. The nested grid simulations reproduce the general features of the horizontal distributions of variables such as effective droplet radius derived from satellite data retrieval. Comparison of the relationships among simulated cloud variables with those among satellite-derived variables reveals that the implementation of an inhomogeneous CN field results in a more accurate simulation of the distribution of cloud microphysical properties. Sensitivity tests with respect to CN concentration show that the simulated area and amount of precipitation are slightly affected by the CN concentration. Comparative simulations using bin-based and bulk microphysical schemes indicate that the difference in cloud microphysics has little effect on precipitation except over the areas of elevated pollution (i.e., elevated CN). Comparison with previous reports indicates that the precipitation response to aerosols is dependent on the environmental conditions and the type of the cloud system.

  7. A new single-moment microphysics scheme for cloud-resolving models using observed dependence of ice concentration on temperature.

    NASA Astrophysics Data System (ADS)

    Khairoutdinov, M.

    2015-12-01

    The representation of microphysics, especially ice microphysics, remains one of the major uncertainties in cloud-resolving models (CRMs). Most of the cloud schemes use the so-called bulk microphysics approach, in which a few moments of such distributions are used as the prognostic variables. The System for Atmospheric Modeling (SAM) is the CRM that employs two such schemes. The single-moment scheme, which uses only mass for each of the water phases, and the two-moment scheme, which adds the particle concentration for each of the hydrometeor category. Of the two, the single-moment scheme is much more computationally efficient as it uses only two prognostic microphysics variables compared to ten variables used by the two-moment scheme. The efficiency comes from a rather considerable oversimplification of the microphysical processes. For instance, only a sum of the liquid and icy cloud water is predicted with the temperature used to diagnose the mixing ratios of different hydrometeors. The main motivation for using such simplified microphysics has been computational efficiency, especially in the applications of SAM as the super-parameterization in global climate models. Recently, we have extended the single-moment microphysics by adding only one additional prognostic variable, which has, nevertheless, allowed us to separate the cloud ice from liquid water. We made use of some of the recent observations of ice microphysics collected at various parts of the world to parameterize several aspects of ice microphysics that have not been explicitly represented before in our sing-moment scheme. For example, we use the observed broad dependence of ice concentration on temperature to diagnose the ice concentration in addition to prognostic mass. Also, there is no artificial separation between the pristine ice and snow, often used by bulk models. Instead we prescribed the ice size spectrum as the gamma distribution, with the distribution shape parameter controlled by the

  8. Effect of Cloud Microphysics on Storm Dynamics: PRE-STORM Case Study

    NASA Astrophysics Data System (ADS)

    Li, X.; Tao, W.; Khain, A.; Simpson, J.

    2007-05-01

    A 2D cloud-resolving model, the Goddard Cloud Ensemble (GCE) model, is used to simulate a mid-latitude summertime squall line during the PRE-STORM field campaign on June 10-11, 1985. Two microphysical schemes, a simple bulk scheme and a detailed spectral bin scheme, using identical environmental conditions and initialization, produce storms with different characteristics in terms of storm structures and temporal variations. During the mature stage of the squall line, the bulk scheme produces a multi-cell storm with convective cells, which are remnants of previous leading cells, embedded well into its stratiform region. The leading cell simulated by the bulk scheme has a distinct lifecycle with each new leading cell generated as an independent entity. In contrast, the bin scheme produces a uni-cell storm with a homogeneous stratiform region. The single convective cell at the leading edge has a weak evolution mode with little temporal variation. These characteristics have been observed in storms formed in different environmental conditions, but are simulated here by two self-consistent microphysical schemes. This indicates the significance of cloud microphysics in shaping the storm structure and dynamics. Sensitivity tests using the simple bulk microphysical scheme reveal two major contributors to the sensitivities simulated by the control bulk and bin scheme, that is, the artificial enhancement of the rain evaporation rate simulated in the bulk scheme, and the different partitioning of precipitable ice particles in these two schemes. Strong rain evaporation in the bulk scheme results in a strong near surface cool pool, which overwhelms the horizontal vorticity generated by the near surface wind shear and causes the leading convection to lean backward. The excessive backward tilting is the reason for the splitting and rearward traveling of the leading convection. Reduced rain evaporation in the bulk scheme produces an upright leading convection with little temporal

  9. Ground based in situ measurements of arctic cloud microphysical and optical properties at Mount Zeppelin (Ny-Alesund Svalbard)

    NASA Astrophysics Data System (ADS)

    Guyot, Gwennolé; Jourdan, Olivier; Olofson, Frans; Schwarzenboeck, Alfons; Gourbeyre, Christophe; Febvre, Guy; Dupuy, Régis; Bernard, Christophe; Tunved, Peter; Ancellet, Gérard; Law, Kathy; Wobrock, Wolfram; Shcherbakov, Valery

    2015-04-01

    The high sensitivity of the polar regions to climate perturbation, due to complex feedback mechanisms existing in this region, was shown by many studies (Solomon et al., 2007; Verlinde et al., 2007; IPCC, 2007). In particular, climate simulations suggest that cloud feedback plays an important role in the arctic warming (Vavrus 2004; Hassol, 2005). Moreover, the high seasonal variability of arctic aerosol properties (Engwall et al., 2008; Tunveld et al., 2013) is expected to significantly impact the cloud properties during the winter-summer transition. Field measurements are needed for improved understanding and representation of cloud-aerosol interactions in climate models. Within the CLIMSLIP project (CLimate IMpacts of Short-LIved Pollutants and methane in the arctic), a two months (March-April 2012) ground-based cloud measurement campaign was performed at Mt Zeppelin station, Ny-Alesund, Svalbard. The experimental set-up comprised a wide variety of instruments. A CPI (Cloud Particle Imager) was used for the microphysical and morphological characterization of ice particles. Measurements of sized-resolved liquid cloud parameters were performed by the FSSP-100 (Forward Scattering Spectrometer Probe). The Nevzorov Probe measured the bulk properties (LWC and IWC) of clouds. The Polar Nephelometer (PN) was used to assess the single scattering properties of an ensemble of cloud particles. This cloud instrumentation combined with the aerosol properties (size distribution and total concentration) continuously measured at the station allowed us to study the variability of the microphysical and optical properties of low level Mixed Phase Clouds (MPC) as well as the aerosol-cloud interaction in the Arctic. Typical properties of MPC, snow precipitation and blowing snow will be presented. First results suggest that liquid water is ubiquitous in arctic low level clouds. Precipitations are characterized by large (typically 1 mm sized) stellar and pristine shape particles

  10. Impact of cloud microphysics on the CSU GCM atmospheric moisture budget

    SciTech Connect

    Fowler, L.D.; Randall, D.A.

    1993-12-31

    In this article, we present the first maps of the global distribution of the cloud liquid and ice water contents of the atmosphere. It is shown that the cloud microphysics package produces realistic distributions of both moisture variables. We axe presently adapting the present model so that long-term simulations with the CSU GCM may be made. In the near future, we plan to couple the cloud liquid and ice water contents prognosed by the cloud microphysics package with the cloud fraction and cloud optical properties.

  11. Indian Summer Monsoon Drought 2009: Role of Aerosol and Cloud Microphysics

    SciTech Connect

    Hazra, Anupam; Taraphdar, Sourav; Halder, Madhuparna; Pokhrel, S.; Chaudhari, H. S.; Salunke, K.; Mukhopadhyay, P.; Rao, S. A.

    2013-07-01

    Cloud dynamics played a fundamental role in defining Indian summer monsoon (ISM) rainfall during drought in 2009. The anomalously negative precipitation was consistent with cloud properties. Although, aerosols inhibited the growth of cloud effective radius in the background of sparse water vapor, their role is secondary. The primary role, however, is played by the interactive feedback between cloud microphysics and dynamics owing to reduced efficient cloud droplet growth, lesser latent heating release and shortage of water content. Cloud microphysical processes were instrumental for the occurrence of ISM drought 2009.

  12. Role of vertical structure of cloud microphysical properties on cloud radiative forcing over the Asian monsoon region

    NASA Astrophysics Data System (ADS)

    Ravi Kiran, V.; Rajeevan, M.; Gadhavi, H.; Rao, S. Vijaya Bhaskara; Jayaraman, A.

    2015-12-01

    Five years (2006-2010) of clouds and earth's radiant energy system (CERES) and CloudSat data have been analyzed to examine the role of vertical structure of cloud microphysical properties on cloud radiative forcing (CRF) parameters at the top-of-the atmosphere over the Asian monsoon region during the summer monsoon season (June-September) and the Pacific warm pool region during April. Vertical profile of cloud properties (optical depth, cloud liquid water content and cloud ice water content) derived from CloudSat data has been used for the present analysis. Shortwave, longwave and net CRF derived from the CERES data have been used. The results suggest an imbalance between shortwave cloud radiative forcing and longwave cloud radiative forcing over the Asian monsoon region consistent with the results reported earlier. The present analysis suggests that over the Bay-of-Bengal (BoB), vertical profile of cloud microphysical properties determine more than 50 % of variance in CRF. However, over the Pacific warm pool region, cloud microphysical property profiles does not contribute significantly to variance in net CRF (<10 %). Over the BoB, large asymmetry between shortwave and longwave CRF is caused by large amounts of cloud liquid water content in the layer between the surface and 9 km. The present study highlights the importance of accurate representation of cloud microphysical properties in determining the influence of clouds on the radiative balance over the top-of-the atmosphere.

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

    SciTech Connect

    Turner, David D.

    2003-06-01

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

  14. Impact of cloud microphysics on cloud-radiation interactions in the CSU general circulation model

    SciTech Connect

    Fowler, L.D.; Randall, D.A.

    1995-04-01

    Our ability to study and quantify the impact of cloud-radiation interactions in studying global scale climate variations strongly relies upon the ability of general circulation models (GCMs) to simulate the coupling between the spatial and temporal variations of the model-generated cloudiness and atmospheric moisture budget components. In particular, the ability of GCMs to reproduce the geographical distribution of the sources and sinks of the planetary radiation balance depends upon their representation of the formation and dissipation of cloudiness in conjunction with cloud microphysics processes, and the fractional amount and optical characteristics of cloudiness in conjunction with the mass of condensate stored in the atmosphere. A cloud microphysics package which encompasses five prognostic variables for the mass of water vapor, cloud water, cloud ice, rain, and snow has been implemented in the Colorado State University General Circulation Model (CSU GCM) to simulate large-scale condensation processes. Convection interacts with the large-scale environment through the detrainment of cloud water and cloud ice at the top of cumulus towers. The cloud infrared emissivity and cloud optical depth of the model-generated cloudiness are interactive and depend upon the mass of cloud water and cloud ice suspended in the atmosphere. The global atmospheric moisture budget and planetary radiation budget of the CSU GCM obtained from a perpetual January simulation are discussed. Geographical distributions of the atmospheric moisture species are presented. Global maps of the top-of-atmosphere outgoing longwave radiation and planetary albedo are compared against Earth Radiation Budget Experiment (ERBE) satellite data.

  15. Retrievals of the Deep Convective System Ice Cloud Microphysical Properties using Nexrad and Aircraft In-situ Measurements

    NASA Astrophysics Data System (ADS)

    Tian, J.; Dong, X.; Xi, B.; Wang, J.; Hong, G.

    2014-12-01

    This study presents a newly developed algorithm for retrieving deep convective system (DCS) ice cloud microphysical properties using Next-Generation Radar (NEXRAD) reflectivity during the Midlatitude Continental Convective Clouds Experiment (MC3E) at the Atmospheric Radiation Measurement (ARM) Southern Great Plain (SGP) site during April-June 2011. The fundamental problems to retrieve the ice cloud microphysical properties of DCS using radar reflectivity are the attenuation of cloud radar reflectivity by heavy precipitation, unknown particle size distributions (PSDs) and the habit of the ice particles in sample volume. In this study, NEXRAD (precipitation radars) reflectivity, with no/little attenuation in heavy precipitation and intense spatial coverage, has been used in retrieval, although it has lower vertical resolution than cloud radars. The aircraft in-situ measurements observed PSDs were fit to analytic function (gamma function) to compare observations made in different meteorological conditions (stratiform rain /anvil regions of DCS) and to best reproduce the true PSD for retrievals. The aircraft in-situ cloud particle imager (CPI) measurements show the habit of the ice particles (aggregates). The relationship between backscatter cross section (σ) and particle dimension (D) is parameterized for the ice crystal habit (aggregates) with the aid of scattering database. Results of the vertical profiles of ice water content (IWC) and median mass diameter (Dm) in ice cloud of DCS, which have been retrieved from NEXRAD reflectivity assuming gamma distribution and σ-D relationship during the MC3E, will be presented. The retrieved microphysical properties are also validated by aircraft in-situ best-estimated IWC and Dm.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  17. An Automated System for Measuring Microphysical and Radiative Cloud Characteristics from a Tethered Balloon

    SciTech Connect

    Dr. Paul Lawson

    2004-03-15

    OAK-B135 The rate of climate change in polar regions is now felt to be a harbinger of possible global warming. Long-lived, relatively thin stratus clouds play a predominant role in transmitting solar radiation and trapping long wave radiation emitted from open water and melt ponds. In situ measurements of microphysical and radiative properties of Arctic and Antarctic stratus clouds are needed to validate retrievals from remote measurements and simulations using numerical models. While research aircraft can collect comprehensive microphysical and radiative data in clouds, the duration of these aircraft is relatively short (up to about 12 hours). During the course of the Phase II research, a tethered balloon system was developed that supports miniaturized meteorological, microphysical and radiation sensors that can collect data in stratus clouds for days at a time. The tethered balloon system uses a 43 cubic meter balloon to loft a 17 kg sensor package to altitudes u p to 2 km. Power is supplied to the instrument package via two copper conductors in the custom tether. Meteorological, microphysical and radiation data are recorded by the sensor package. Meteorological measurements include pressure, temperature, humidity, wind speed and wind direction. Radiation measurements are made using a 4-pi radiometer that measures actinic flux at 500 and 800 nm. Position is recorded using a GPS receiver. Microphysical data are obtained using a miniaturized version of an airborne cloud particle imager (CPI). The miniaturized CPI measures the size distribution of water drops and ice crystals from 9 microns to 1.4 mm. Data are recorded onboard the sensor package and also telemetered via a 802.11b wireless communications link. Command signals can also be sent to the computer in the sensor package via the wireless link. In the event of a broken tether, a GMRS radio link to the balloon package is used to heat a wire that burns 15 cm opening in the top of the balloon. The balloon and

  18. Studyng the Influence of Aerosols in the Evolution of Cloud Microphysics Procesess Associated with Tropical Cyclone Earl Using Airborne Measurements from the NASA Grip Field Campaing 2010

    NASA Astrophysics Data System (ADS)

    Luna-Cruz, Y.; Heymsfield, A.; Jenkins, G. S.; Bansemer, A.

    2011-12-01

    Cloud microphysics processes are strongly related to tropical cyclones evolution. Although there have been three decades of research dedicated to understand the role of cloud microphysics in tropical cyclogenesis, there are still questions unanswered. With the intention of fulfill the gaps and to better understand the processes involves in tropical storms formation the NASA Genesis and Rapid Intensification Processes (GRIP) field campaign was conducted during the months of August and September of 2010. In-situ microphysical measurements, including particle size distributions, shapes, liquid/ice water content and supercooled liquid water were obtained from the DC-8 aircraft. A total of 139 hrs of flying science modules were performed including sampling of four named storms (Earl, Gaston, Karl and Matthew). One tropical cyclone, Earl, was one of the major hurricanes of the season reaching a category 4 in the Saffir-Simpson scale. Earl emerged from the West Africa on August 22 as an easterly wave, moved westward and became a tropical storm on August 25 before undergoing rapid intensification. This project seeks to explore the lifecycle of hurricane Earl including the genesis and rapid intensification from a microphysics perspective; to develop a better understanding of the relationship between dust from the Saharan Air Layer and cloud microphysics evolution and to develop a better understanding of how cloud microphysics processes interacts and serve as precursor for thermodynamics processes. An overview of the microphysics measurements as well as preliminary results will be presented.

  19. New RAMS cloud microphysics parameterization. Part II: The two-moment scheme

    NASA Astrophysics Data System (ADS)

    Meyers, Michael P.; Walko, Robert L.; Harrington, Jerry Y.; Cotton, William R.

    This paper is the second in a series of articles describing the new microphysics scheme in the Regional Atmospheric Modeling System (RAMS). In this part, a new two-moment microphysical parameterization is described. The proposed scheme predicts the mixing ratio and number concentration of rain, pristine ice crystals, snow, aggregates, graupel and hail. The general gamma distribution is the basis function used for hydrometeor size in each category. Additional features include: use of stochastic collection for number concentration tendency; breakup of rain droplets formulated into the collection efficiency; diagnosis of ice crystal habit dependent on temperature and saturation; evaporation and melting of each species assuming that the smallest particles completely disappear first; and more complex shedding formulations which take into account the amount of water mass on the coalesced hydrometeor. Preliminary sensitivity testing of the new microphysical scheme in an idealized convective simulation shows that the two-moment prediction scheme allows more flexibility of the size distribution enabling the mean diameter to evolve in contrast to the one-moment scheme. Sensitivity to the prescribed input parameters such as cloud droplet concentrations and the shape parameter v is demonstrated in the model results.

  20. METHANE-NITROGEN BINARY NUCLEATION: A NEW MICROPHYSICAL MECHANISM FOR CLOUD FORMATION IN TITAN'S ATMOSPHERE

    SciTech Connect

    Tsai, I-Chun; Chen, Jen-Ping; Liang, Mao-Chang

    2012-03-01

    It is known that clouds are present in the troposphere of Titan; however, their formation mechanism, particle size, and chemical composition remain poorly understood. In this study, a two-component (CH{sub 4} and N{sub 2}) bin-microphysics model is developed and applied to simulate cloud formation in the troposphere of Titan. A new process, binary nucleation of particles from CH{sub 4} and N{sub 2} gases, is considered. The model is validated and calibrated by recent laboratory experiments that synthesize particle formation in Titan-like environments. Our model simulations show that cloud layers can be formed at about 20 km with a particle size ranging from one to several hundred {mu}m and number concentration 10{sup -2} to over 100 cm{sup -3} depending on the strength of the vertical updraft. The particles are formed by binary nucleation and grow via the condensation of both CH{sub 4} and N{sub 2} gases, with their N{sub 2} mole fraction varying from <10% in the nucleation stage to >30% in the condensation growth stage. The locally occurring CH{sub 4}-N{sub 2} binary nucleation mechanism is strong and could potentially be more important than the falling condensation nuclei mechanism assumed in many current models.

  1. Investigations of cloud microphysical response to mixing using digital holography

    NASA Astrophysics Data System (ADS)

    Beals, Matthew Jacob

    Cloud edge mixing plays an important role in the life cycle and development of clouds. Entrainment of subsaturated air affects the cloud at the microscale, altering the number density and size distribution of its droplets. The resulting effect is determined by two timescales: the time required for the mixing event to complete, and the time required for the droplets to adjust to their new environment. If mixing is rapid, evaporation of droplets is uniform and said to be homogeneous in nature. In contrast, slow mixing (compared to the adjustment timescale) results in the droplets adjusting to the transient state of the mixture, producing an inhomogeneous result. Studying this process in real clouds involves the use of airborne optical instruments capable of measuring clouds at the 'single particle' level. Single particle resolution allows for direct measurement of the droplet size distribution. This is in contrast to other 'bulk' methods (i.e. hot-wire probes, lidar, radar) which measure a higher order moment of the distribution and require assumptions about the distribution shape to compute a size distribution. The sampling strategy of current optical instruments requires them to integrate over a path tens to hundreds of meters to form a single size distribution. This is much larger than typical mixing scales (which can extend down to the order of centimeters), resulting in difficulties resolving mixing signatures. The Holodec is an optical particle instrument that uses digital holography to record discrete, local volumes of droplets. This method allows for statistically significant size distributions to be calculated for centimeter scale volumes, allowing for full resolution at the scales important to the mixing process. The hologram also records the three dimensional position of all particles within the volume, allowing for the spatial structure of the cloud volume to be studied. Both of these features represent a new and unique view into the mixing problem. In

  2. Cirrus cloud model parameterizations: Incorporating realistic ice particle generation

    NASA Technical Reports Server (NTRS)

    Sassen, Kenneth; Dodd, G. C.; Starr, David OC.

    1990-01-01

    Recent cirrus cloud modeling studies have involved the application of a time-dependent, two dimensional Eulerian model, with generalized cloud microphysical parameterizations drawn from experimental findings. For computing the ice versus vapor phase changes, the ice mass content is linked to the maintenance of a relative humidity with respect to ice (RHI) of 105 percent; ice growth occurs both with regard to the introduction of new particles and the growth of existing particles. In a simplified cloud model designed to investigate the basic role of various physical processes in the growth and maintenance of cirrus clouds, these parametric relations are justifiable. In comparison, the one dimensional cloud microphysical model recently applied to evaluating the nucleation and growth of ice crystals in cirrus clouds explicitly treated populations of haze and cloud droplets, and ice crystals. Although these two modeling approaches are clearly incompatible, the goal of the present numerical study is to develop a parametric treatment of new ice particle generation, on the basis of detailed microphysical model findings, for incorporation into improved cirrus growth models. For example, the relation between temperature and the relative humidity required to generate ice crystals from ammonium sulfate haze droplets, whose probability of freezing through the homogeneous nucleation mode are a combined function of time and droplet molality, volume, and temperature. As an example of this approach, the results of cloud microphysical simulations are presented showing the rather narrow domain in the temperature/humidity field where new ice crystals can be generated. The microphysical simulations point out the need for detailed CCN studies at cirrus altitudes and haze droplet measurements within cirrus clouds, but also suggest that a relatively simple treatment of ice particle generation, which includes cloud chemistry, can be incorporated into cirrus cloud growth.

  3. Influence of Atmospheric Organic Compounds on Cloud Microphysics.

    NASA Astrophysics Data System (ADS)

    Shulman, Michelle Lee

    With the knowledge that polar organic constituents such as difunctional organic oxygenates contribute significantly to particulate matter in the atmosphere, the motivation for this research was to understand the influence of polar organic matter on cloud microphysical processes that affect both the equilibrium thermodynamics and kinetics of nucleating cloud droplets. To understand the equilibrium condition of polar organics in growing, diluting droplets, solubility and surface tension measurements were made for a group of difunctional organic oxygenates that have been detected consistently in the atmosphere. The organics chosen as models included short chain dicarboxylic acids (C _2-C_6), phthalic acid, cis-pinonic acid. The dicarboxylic acids and phthalic acid are generated from the incomplete combustion of fossil fuels, and cis-pinonic acid originates from the oxidation of alpha-pinene emitted from coniferous trees. From the solubility information, the dissolution behavior is shown to alter the growth characteristics of a nucleating cloud droplet. From the surface tension studies, the growth characteristics are also shown to be further influenced by the organic. To understand the affect of difunctional organic oxygenates on the transport of water at the air/water interface of single droplets, the evaporation rate of aqueous systems containing the model organics were measured. Light scattering techniques were used to measure the droplet size as a function of time for electrodynamically levitated single microdroplets under conditions of controlled humidity and temperature. The evaporation rates are compared to that of pure water and are found to be reduced by up to an order of magnitude. In addition, the evaporation rates are found to be correlated with the surface tension of the aqueous solution containing the organic. Due to the complex nature of the atmosphere, the arena of observation and experimentation was limited to the laboratory for this thesis work.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Case study on microphysical properties of boundary layer mixed-phase cloud observed at Ny-Ålesund, Svalbard: Observed cloud microphysics and calculated optical properties on 9 June 2011

    NASA Astrophysics Data System (ADS)

    Uchiyama, Akihiro; Yamazaki, Akihiro; Shiobara, Masataka; Kobayashi, Hiroshi

    2014-06-01

    Cloud radiation interactions are important in the global climate system. However, an understanding of mixed-phase boundary layer clouds in the Arctic remains poor. During May-June 2011, ground-based in situ measurements were made at Zeppelin Station, operated by the Norwegian Polar Institute (altitude 474 m) in Ny-Ålesund (78.9°N, 11.9°E), Svalbard. The instruments used comprised a Cloud, Aerosol and Precipitation Spectrometer (CAPS), and a Cloud Particle Microscope imager. The CAPS incorporated a Cloud and Aerosol Spectrometer and Cloud Imaging Probe (CIP). During the observation period, clouds associated with cyclonic disturbances and those associated with outbreaks of westerly cold air masses from the sea were observed. Atmospheric temperature during all measurements ranged from 0 to -5 °C. In every case, columns were the major type of ice particle measured by the CAPS-CIP. Cloud microphysical properties were observed continuously on 9 June 2011. Size spectra, liquid/ice water content, and particle effective size changed depending on progress stages. Based on the observed microphysics, optical properties were calculated and investigated. Optical properties were determined mainly by those of liquid water particles, even during periods when the relative contribution of ice particles to total water content was at the maximum. It was confirmed that the wavelength region of 1.6 and 2.2 μm can be used in remote sensing. This study shows that it is possible to measure detailed changes of cloud properties in the Arctic region by using instruments installed at a ground-based mountain station.

  6. Comparison of LES model produced and in-situ measured stratocumulus cloud microphysics

    NASA Astrophysics Data System (ADS)

    Choi, K.; Yeom, J. M.; Yum, S. S.

    2015-12-01

    Large Eddy Simulation (LES) models are known to be a valuable tool that can be used to study microphysical, dynamical and radiative properties and their complex interactions in stratocumulus clouds since they can generate stratocumulus clouds realistically. These model generated properties were often compared with observations usually focusing on macroscopic features such as cloud depth and LWP. In this study we try to examine how good LES models are in re-producing cloud microphysical characteristics of stratocumulus clouds. After all if microphysics is not right, macroscopic, dynamic and radiative characteristics represented by the model cannot be fully trusted. The observation data are obtained from the G-1 aircraft measurements of marine stratocumulus clouds over the southeast Pacific near the coast of Chile during the Variability of the American Monsoon Systems Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). Two LES models are used to simulate these clouds: one is CIMMS (Cooperative Institute for Mesoscale Meteorological Studies) LES and the other is WRF (Weather Research and Forecasting Model) LES. Both models are run in 3-D setting and employ bin microphysics to be appropriate for detailed cloud microphysics calculation. Comparison between observation and LES models could reveal intrinsic problems of the LES models in representing entrainment and mixing processes. The difference between the two LES models may reveal the intrinsic differences between the two models in representing large eddies and microphysical processes. Some preliminary results indicate that the CIMMS LES model tends to produce cloud microphysical relationships that are expected to occur when homogeneous mixing is dominant. More detail will be presented at the conference.

  7. A Cloud-Resolving Modeling Intercomparison Study on Properties of Cloud Microphysics, Convection, and Precipitation for a Squall Line Cas

    NASA Astrophysics Data System (ADS)

    Fan, J.; Han, B.; Morrison, H.; Varble, A.; Mansell, E.; Milbrandt, J.; Wang, Y.; Lin, Y.; Dong, X.; Giangrande, S. E.; Jensen, M. P.; Collis, S. M.; North, K.; Kollias, P.

    2015-12-01

    The large spread in CRM model simulations of deep convection and aerosol effects on deep convective clouds (DCCs) makes it difficult (1) to further our understanding of deep convection and (2) to define "benchmarks" and recommendations for their use in parameterization developments. Past model intercomparison studies used different models with different complexities of dynamic-microphysics interactions, making it hard to isolate the causes of differences between simulations. In this intercomparison study, we employed a much more constrained approach - with the same model and same experiment setups for simulations with different cloud microphysics schemes (one-moment, two-moment, and bin models). Both the piggybacking and interactive approaches are employed to explore the major microphysical processes that control the model differences and the significance of their feedback to dynamics through latent heating/cooling and cold pool characteristics. Real-case simulations are conducted for the squall line case 20 May 2011 from the MC3E field campaign. Results from the piggybacking approach show substantially different responses of the microphysics schemes to the same dynamical fields. Although the interactive microphysics-dynamics simulations buffer some differences compared with those from the piggyback runs, large differences still exist and are mainly contributed by ice microphysical processes parameterizations. The presentation will include in-depth analyses of the major microphysical processes for the squall line case, the significance of the feedback of the processes to dynamics, and how those results differ in different cloud microphysics schemes.

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

    NASA Astrophysics Data System (ADS)

    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/).

  9. Recent Ice Ages on Mars: The role of radiatively active clouds and cloud microphysics

    NASA Astrophysics Data System (ADS)

    Madeleine, J.-B.; Head, J. W.; Forget, F.; Navarro, T.; Millour, E.; Spiga, A.; Colaïtis, A.; Määttänen, A.; Montmessin, F.; Dickson, J. L.

    2014-07-01

    Global climate models (GCMs) have been successfully employed to explain the origin of many glacial deposits on Mars. However, the latitude-dependent mantle (LDM), a dust-ice mantling deposit that is thought to represent a recent "Ice Age," remains poorly explained by GCMs. We reexamine this question by considering the effect of radiatively active water-ice clouds (RACs) and cloud microphysics. We find that when obliquity is set to 35°, as often occurred in the past 2 million years, warming of the atmosphere and polar caps by clouds modifies the water cycle and leads to the formation of a several centimeter-thick ice mantle poleward of 30° in each hemisphere during winter. This mantle can be preserved over the summer if increased atmospheric dust content obscures the surface and provides dust nuclei to low-altitude clouds. We outline a scenario for its deposition and preservation that compares favorably with the characteristics of the LDM.

  10. Studying the influence of temperature and pressure on microphysical properties of mixed-phase clouds using airborne measurements

    NASA Astrophysics Data System (ADS)

    Andreea, Boscornea; Sabina, Stefan; Sorin-Nicolae, Vajaiac; Mihai, Cimpuieru

    2015-04-01

    One cloud type for which the formation and evolution process is not well-understood is the mixed-phase type. In general mixed-phase clouds consist of liquid droplets and ice crystals. The temperature interval within both liquid droplets and ice crystals can potentially coexist is limited to 0 °C and - 40 °C. Mixed-phase clouds account for 20% to 30% of the global cloud coverage. The need to understand the microphysical characteristics of mixed-phase clouds to improve numerical forecast modeling and radiative transfer calculation is of major interest in the atmospheric community. In the past, studies of cloud phase composition have been significantly limited by a lack of aircraft instruments capable of discriminating between the ice and liquid phase for a wide range of particle sizes. Presently, in situ airborne measurements provide the most accurate information about cloud microphysical characteristics. This information can be used for verification of both numerical models and cloud remote-sensing techniques. The knowledge of the temperature and pressure variation during the airborne measurements is crucial in order to understand their influence on the cloud dynamics and also their role in the cloud formation processes like accretion and coalescence. Therefore, in this paper is presented a comprehensive study of cloud microphysical properties in mixed-phase clouds in focus of the influence of temperature and pressure variation on both, cloud dynamics and the cloud formation processes, using measurements performed with the ATMOSLAB - Airborne Laboratory for Environmental Atmospheric Research in property of the National Institute for Aerospace Research "Elie Carafoli" (INCAS). The airborne laboratory equipped for special research missions is based on a Hawker Beechcraft - King Air C90 GTx aircraft and is equipped with a sensors system CAPS - Cloud, Aerosol and Precipitation Spectrometer (30 bins, 0.51-50 µm) and a HAWKEYE cloud probe. The analyzed data in this

  11. Next generation aerosol-cloud microphysics for advanced high-resolution climate predictions

    SciTech Connect

    Bennartz, Ralf; Hamilton, Kevin P; Phillips, Vaughan T.J.; Wang, Yuqing; Brenguier, Jean-Louis

    2013-01-14

    The three top-level project goals are: -We proposed to develop, test, and run a new, physically based, scale-independent microphysical scheme for those cloud processes that most strongly affect greenhouse gas scenarios, i.e. warm cloud microphysics. In particular, we propsed to address cloud droplet activation, autoconversion, and accretion. -The new, unified scheme was proposed to be derived and tested using the University of Hawaii's IPRC Regional Atmospheric Model (iRAM). -The impact of the new parameterizations on climate change scenarios will be studied. In particular, the sensitivity of cloud response to climate forcing from increased greenhouse gas concentrations will be assessed.

  12. Radiative and microphysical properties of cirrus cloud inferred from the MODIS infrared split-window measurements

    NASA Astrophysics Data System (ADS)

    Iwabuchi, H.; Yamada, S.; Katagiri, S.; Yang, P.; Okamoto, H.

    2013-12-01

    An optimal estimation-based algorithm is developed for retrieval of radiative and microphysical properties of cirrus cloud from the measurements made by the Moderate Resolution Imaging Spectroradiometer (MODIS) at three infrared (IR) split-window bands with center wavelengths at 8.5, 11 and 12 μm. Prior information of cloud top and underlying surface temperatures are from the MODIS operational products. A fast forward model is based on semi-analytical equations for the brightness temperature assuming a single-layer homogeneous ice cloud with prescribed particle habit and size distributions. Modeling errors in the brightness temperature from the present approximate treatment of radiative transfer are insignificant, but relatively more substantial errors occur due to the uncertainties in model parameters including surface emissivity, precipitable water, and cloud bottom temperature. The total measurement-model errors are well correlated for the three bands, which is considered properly in the optimal estimation framework. Retrieval errors of cloud optical thickness and effective particle radius are mainly from uncertainties in a priori cloud top and surface temperatures and model parameters. The three-band IR method is suitable for retrieving optical thickness and effective particle radius for opaque and moderately thick cirrus clouds (with cloud optical thicknesses within a range of 0.5-6). The efficient retrieval algorithm enables global-scale remote sensing at a 1-km2 resolution. A tropical region case study demonstrates advantages of the method; particularly, the ability to be applied to more pixels in optically-thin cirrus in comparison with a solar-reflection based method, and the ability of the optimal estimation framework to produce useful diagnostics of retrieval uncertainties and the retrieval cost that denote the quantitative consistency between measurement and model calculation with several assumptions. The IR retrieval shows smaller optical thickness

  13. Spatio-temporal variability in cloud microphysical properties over the South East Atlantic

    NASA Astrophysics Data System (ADS)

    Gupta, S.; McFarquhar, G. M.; Poellot, M.; O'Brien, J.; Delene, D. J.

    2016-12-01

    The ObseRvations of Aerosols above Clouds and their intEractionS (ORACLES) project will provide in-situ measurements and remotely sensed retrievals of aerosol and cloud properties over the South East Atlantic off the coast of Namibia during August-September 2016. Biomass burning aerosol from Southern Africa is advected toward the South East Atlantic at elevated altitudes and overlies the ubiquitous stratocumulus cloud deck over the ocean. The aerosols subside farther from the coast so that the vertical displacement between the clouds and aerosols varies, and whose effect on aerosol-cloud interaction is poorly known. A NASA P-3 aircraft will be equipped with a Cloud Droplet Probe CDP sizing particles between 2 and 50μm, a Cloud and Aerosol Spectrometer CAS sizing between 0.51 and 50μm, a 2D-stereo probe 2DS, nominally sizing between 10 and 1280μm, a Cloud Imaging Probe CIP, from 25 to 1600μm, and a High Volume Precipitation Sampler HVPS-3, from 150μm to 1.92cm for measuring number distribution functions (n(D)) along with a King probe and hot wire probe for measuring the total liquid water content, LWC. A Passive Cavity Aerosol Spectrometer Probe PCASP will measure aerosol particles between 0.1 to 3μm. By examining consistency between n(D) measured by probes in the overlap ranges and by conducting closure tests whereby the bulk LWC is compared against that derived from n(D), a probe-independent product will be generated to provide the best estimate of the following cloud parameters: total concentration, extinction, n(D), effective radius and LWC. The resulting database will be used to determine how cloud properties vary with distance away from the coast of Africa and with aerosol concentrations measured in the accumulation mode by the PCASP above and below cloud. The impact of the changing separation between the cloud and aerosol layers will be examined and potential impacts of the variation of cloud microphysical properties with aerosol concentrations on

  14. Microphysical and Dynamical Influences on Cirrus Cloud Optical Depth Distributions

    SciTech Connect

    Kay, J.; Baker, M.; Hegg, D.

    2005-03-18

    Cirrus cloud inhomogeneity occurs at scales greater than the cirrus radiative smoothing scale ({approx}100 m), but less than typical global climate model (GCM) resolutions ({approx}300 km). Therefore, calculating cirrus radiative impacts in GCMs requires an optical depth distribution parameterization. Radiative transfer calculations are sensitive to optical depth distribution assumptions (Fu et al. 2000; Carlin et al. 2002). Using raman lidar observations, we quantify cirrus timescales and optical depth distributions at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in Lamont, OK (USA). We demonstrate the sensitivity of outgoing longwave radiation (OLR) calculations to assumed optical depth distributions and to the temporal resolution of optical depth measurements. Recent work has highlighted the importance of dynamics and nucleation for cirrus evolution (Haag and Karcher 2004; Karcher and Strom 2003). We need to understand the main controls on cirrus optical depth distributions to incorporate cirrus variability into model radiative transfer calculations. With an explicit ice microphysics parcel model, we aim to understand the influence of ice nucleation mechanism and imposed dynamics on cirrus optical depth distributions.

  15. The microphysics of clouds over the Antarctic Peninsula - Part 2: modelling aspects within Polar WRF

    NASA Astrophysics Data System (ADS)

    Listowski, Constantino; Lachlan-Cope, Tom

    2017-08-01

    supercooled liquid clouds compared to the other schemes. However, our investigation shows that all the schemes fail at simulating the supercooled liquid mass at some temperatures (altitudes) where observations show evidence of its persistence. An ice nuclei parameterization relying on both temperature and aerosol content like DeMott et al. (2010) (not currently used in WRF cloud schemes) is in best agreement with the observations, at temperatures and aerosol concentration characteristic of the Antarctic Peninsula where the primary ice production occurs (part 1), compared to parameterization only relying on the atmospheric temperature (used by the WRF cloud schemes). Overall, a realistic double-moment ice microphysics implementation is needed for the correct representation of the supercooled liquid phase in Antarctic clouds. Moreover, a more realistic ice-nucleating particle alone is not enough to improve the cloud modelling, and water vapour and temperature biases also need to be further investigated and reduced.

  16. Numerical Analysis Using WRF-SBM for the Cloud Microphysical Structures in the C3VP Field Campaign: Impacts of Supercooled Droplets and Resultant Riming on Snow Microphysics

    NASA Technical Reports Server (NTRS)

    Iguchi, Takamichi; Matsui, Toshihisa; Shi, Jainn J.; Tao, Wei-Kuo; Khain, Alexander P.; Hao, Arthur; Cifelli, Robert; Heymsfield, Andrew; Tokay, Ali

    2012-01-01

    Two distinct snowfall events are observed over the region near the Great Lakes during 19-23 January 2007 under the intensive measurement campaign of the Canadian CloudSat/CALIPSO validation project (C3VP). These events are numerically investigated using the Weather Research and Forecasting model coupled with a spectral bin microphysics (WRF-SBM) scheme that allows a smooth calculation of riming process by predicting the rimed mass fraction on snow aggregates. The fundamental structures of the observed two snowfall systems are distinctly characterized by a localized intense lake-effect snowstorm in one case and a widely distributed moderate snowfall by the synoptic-scale system in another case. Furthermore, the observed microphysical structures are distinguished by differences in bulk density of solid-phase particles, which are probably linked to the presence or absence of supercooled droplets. The WRF-SBM coupled with Goddard Satellite Data Simulator Unit (G-SDSU) has successfully simulated these distinctive structures in the three-dimensional weather prediction run with a horizontal resolution of 1 km. In particular, riming on snow aggregates by supercooled droplets is considered to be of importance in reproducing the specialized microphysical structures in the case studies. Additional sensitivity tests for the lake-effect snowstorm case are conducted utilizing different planetary boundary layer (PBL) models or the same SBM but without the riming process. The PBL process has a large impact on determining the cloud microphysical structure of the lake-effect snowstorm as well as the surface precipitation pattern, whereas the riming process has little influence on the surface precipitation because of the small height of the system.

  17. Radiative and microphysical properties of Arctic stratus clouds from multiangle downwelling infrared radiances

    NASA Astrophysics Data System (ADS)

    Rathke, Carsten; Neshyba, Steven; Shupe, Matthew D.; Rowe, Penny; Rivers, Aaron

    2002-12-01

    The information content of multiangle downwelling infrared radiance spectra of stratus clouds is investigated. As an example, 76 sets of spectra were measured at angles of 0, 15, 30 and 45° from zenith, using an interferometer based at the Surface Heat Budget of the Arctic Ocean (SHEBA) drifting ice camp. Exploiting the angular variation of radiance in infrared microwindows, a "geometric" algorithm is used to determine cloud temperature and optical depth without auxiliary information. For comparison, a spectral method allows us to infer cloud microphysical properties for each angle; each multiangle set therefore constitutes a microphysical characterization of horizontal inhomogeneity of the cloudy scene. We show that cloud temperatures determined with both approaches agree with temperatures obtained from lidar/radiosonde data. The multiangle radiance observations can also be used to calculate the longwave flux reaching the surface. We find that up to 14 W m-2 of the overcast fluxes can be attributed to horizontal variations in cloud microphysical properties.

  18. Microphysical Properties of Warm Clouds During The Aircraft Take-Off and Landing Over Bucharest, Romania

    NASA Astrophysics Data System (ADS)

    Stefan, Sabina; Nicolae Vajaiac, Sorin; Boscornea, Andreea

    2016-06-01

    This paper is focused on airborne measurements of microphysical parameters into warm clouds when the aircraft penetrates the cloud, both during take-off and landing. The experiment was conducted during the aircraft flight between Bucharest and Craiova, in the southern part of Romania. The duration of the experimental flight was 2 hours and 35 minutes in October 7th, 2014, but the present study is dealing solely with the analysis of cloud microphysical properties at the beginning of the experiment (during the aircraft take-off) and at the end, when it got finalized by the aircraft landing procedure. The processing and interpretation of the measurements showed the differences between microphysical parameters, emphasizing that the type of cloud over Bucharest changed, as it was expected. In addition, the results showed that it is important to take into account both the synoptic context and the cloud perturbation due to the velocity of the aircraft, in such cases.

  19. Parameterization of the Vertical Variability of Tropical Cirrus Cloud Microphysical and Optical Properties

    NASA Technical Reports Server (NTRS)

    Gerber, Hermann E.

    2004-01-01

    Cloud Integrating Nephelometers (CIN) were flown on the U. North Dakota Citation aircraft and the NASA WB-57 aircraft for the purpose of measuring in-situ the optical extinction coefficient and the asymmetry parameter (g) at a wavelength of 635 nm of primarily ice particles encountered during the NASA CRYSTAL-FACE study of large cumulus clouds (Cu) and their anvils found in the southern Florida region. The probes performance was largely successful and produced archived data for vertical profiles of extinction, asymmetry parameter, and effective radius (Re), the latter being obtained by combining CIN and CVI (total water; Oregon State U.) measurements. Composites of the CIN and CVI data describing the average microphysical and optical behavior of the Cu and their anvils showed the following: The extinction increases with height as a result of the size of the particles also decreasing with height as shown by the Re measurements; near the top of anvils the size of the primary ice particles is about 10-um radius; and the value of g does not vary significantly with height and has a mean value of about 0.73 consistent with the idea that ambient ice crystals are primarily of complex shape and reflect solar radiation more efficiently than particles of pristine crystal shape. Other observations include: The g measurements were found to be an indicator of the phase of the cloud permitting identification of the clouds with water droplets, rain, and ice; visual ranges as small as several tens of meters were occasionally found in "extinction cores" that coincided with strong updraft cores; and comparison of the cloud probes on the Citation showed significant disagreement.

  20. Cloud Macro- and Microphysical Properties Derived from GOES over the ARM SGP Domain

    NASA Technical Reports Server (NTRS)

    Minnis, P.; Smith, W. L., Jr.; Young, D. F.

    2001-01-01

    Cloud macrophysical properties like fractional coverage and height Z(sub c) and microphysical parameters such as cloud liquid water path (LWP), effective droplet radius r(sub e), and cloud phase, are key factors affecting both the radiation budget and the hydrological cycle. Satellite data have been used to complement surface observations from Atmospheric Radiation Measurements (ARM) by providing additional spatial coverage and top-of-atmosphere boundary conditions of these key parameters. Since 1994, the Geostationary Operational Environmental Satellite (GOES) has been used for deriving at each half-hour over the ARM Southern Great Plains (SGP) domain: cloud amounts, altitudes, temperatures, and optical depths as well as broadband shortwave (SW) albedo and outgoing longwave radiation at the top of the atmosphere. A new operational algorithm has been implemented to increase the number of value-added products to include cloud particle phase and effective size (r(sub e) or effective ice diameter D(sub e)) as well as LWP and ice water path. Similar analyses have been performed on the data from the Visible Infrared Scanner (VIRS) on the Tropical Rainfall Measuring Mission satellite as part of the Clouds and Earth's Radiant Energy System project. This larger suite of cloud properties will enhance our knowledge of cloud processes and further constrain the mesoscale and single column models using ARM data as a validation/initialization resource. This paper presents the results of applying this new algorithm to GOES-8 data taken during 1998 and 2000. The global VIRS results are compared to the GOES SGP results to provide appropriate context and to test consistency.

  1. Development of Two-Moment Cloud Microphysics for Liquid and Ice Within the NASA Goddard Earth Observing System Model (GEOS-5)

    NASA Technical Reports Server (NTRS)

    Barahona, Donifan; Molod, Andrea M.; Bacmeister, Julio; Nenes, Athanasios; Gettelman, Andrew; Morrison, Hugh; Phillips, Vaughan,; Eichmann, Andrew F.

    2013-01-01

    This work presents the development of a two-moment cloud microphysics scheme within the version 5 of the NASA Goddard Earth Observing System (GEOS-5). The scheme includes the implementation of a comprehensive stratiform microphysics module, a new cloud coverage scheme that allows ice supersaturation and a new microphysics module embedded within the moist convection parameterization of GEOS-5. Comprehensive physically-based descriptions of ice nucleation, including homogeneous and heterogeneous freezing, and liquid droplet activation are implemented to describe the formation of cloud particles in stratiform clouds and convective cumulus. The effect of preexisting ice crystals on the formation of cirrus clouds is also accounted for. A new parameterization of the subgrid scale vertical velocity distribution accounting for turbulence and gravity wave motion is developed. The implementation of the new microphysics significantly improves the representation of liquid water and ice in GEOS-5. Evaluation of the model shows agreement of the simulated droplet and ice crystal effective and volumetric radius with satellite retrievals and in situ observations. The simulated global distribution of supersaturation is also in agreement with observations. It was found that when using the new microphysics the fraction of condensate that remains as liquid follows a sigmoidal increase with temperature which differs from the linear increase assumed in most models and is in better agreement with available observations. The performance of the new microphysics in reproducing the observed total cloud fraction, longwave and shortwave cloud forcing, and total precipitation is similar to the operational version of GEOS-5 and in agreement with satellite retrievals. However the new microphysics tends to underestimate the coverage of persistent low level stratocumulus. Sensitivity studies showed that the simulated cloud properties are robust to moderate variation in cloud microphysical parameters

  2. A Hierarchical Modeling Study of the Interactions Among Turbulence, Cloud Microphysics, and Radiative Transfer in the Evolution of Cirrus Clouds

    NASA Technical Reports Server (NTRS)

    Curry, Judith; Khvorostyanov, V. I.

    2005-01-01

    This project used a hierarchy of cloud resolving models to address the following science issues of relevance to CRYSTAL-FACE: What ice crystal nucleation mechanisms are active in the different types of cirrus clouds in the Florida area and how do these different nucleation processes influence the evolution of the cloud system and the upper tropospheric humidity? How does the feedback between supersaturation and nucleation impact the evolution of the cloud? What is the relative importance of the large-scale vertical motion and the turbulent motions in the evolution of the crystal size spectra? How does the size spectra impact the life-cycle of the cloud, stratospheric dehydration, and cloud radiative forcing? What is the nature of the turbulence and waves in the upper troposphere generated by precipitating deep convective cloud systems? How do cirrus microphysical and optical properties vary with the small-scale dynamics? How do turbulence and waves in the upper troposphere influence the cross-tropopause mixing and stratospheric and upper tropospheric humidity? The models used in this study were: 2-D hydrostatic model with explicit microphysics that can account for 30 size bins for both the droplet and crystal size spectra. Notably, a new ice crystal nucleation scheme has been incorporated into the model. Parcel model with explicit microphysics, for developing and evaluating microphysical parameterizations. Single column model for testing bulk microphysics parameterizations

  3. Ice Cloud Optical and Microphysical Properties from the CALIPSO Imaging Infrared Radiometer

    NASA Astrophysics Data System (ADS)

    Garnier, A.; Pelon, J.; Dubuisson, P.; Yang, P.; Vaughan, M.; Avery, M. A.; Winker, D. M.

    2013-12-01

    We will present cirrus cloud optical and microphysical properties as retrieved from the operational analysis of the Imaging Infrared Radiometer (IIR) data in synergy with the CALIOP lidar co-located observations collected in the framework of the CALIPSO mission. The IIR data provides nighttime and daytime independent retrievals of optical depth and effective diameter, from which the cloud layer ice water path is inferred. The technique takes advantage of the vertical information provided by CALIOP to select suitable scenes and compute effective emissivity and optical depth. Effective diameters are retrieved through microphysical indices defined as the ratio of the effective infrared optical depths in the two pairs of channels 10.6-12.05 μm and 8.65-12.05 μm, and are related to the ice crystal effective diameter and shape through pre-computed Look-Up Tables. Sources of uncertainty are discussed and possible biases are assessed through internal consistency checks. Comparisons of IIR and CALIOP cirrus optical depths show the very good sensitivity of the IIR retrievals, down to 0.05 visible optical depth. It is shown that particle effective diameter and cloud layer ice water path of single-layered cirrus clouds can be retrieved over ocean, land, as well as over low opaque clouds, for thin to dense clouds of visible optical depth ranging between 0.1 and 6 and of ice water path found typically between 1 and 150 g.m-2. Taking advantage of the cloud boundaries simultaneously derived by CALIOP, IIR power law relationships between mean ice water content (IWC, in g.m-3) and mean extinction coefficient (α, in m-1) are established for cloud temperatures between 190 and 233 K. An average global power law relationship IWC = 75. α1.23 is obtained, which compares well with parameterizations derived from in-situ observations at mid-latitude and in the tropics. However, the IWCs reported in our study are lower by about 40% than those derived from the power law relationship used

  4. Evaluating Microphysics in Cloud-Resolving Models using TRMM and Ground-based Precipitation Radar Observations

    NASA Astrophysics Data System (ADS)

    Krueger, S. K.; Zulauf, M. A.; Li, Y.; Zipser, E. J.

    2005-05-01

    Global satellite datasets such as those produced by ISCCP, ERBE, and CERES provide strong observational constraints on cloud radiative properties. Such observations have been widely used for model evaluation, tuning, and improvement. Cloud radiative properties depend primarily on small, non-precipitating cloud droplets and ice crystals, yet the dynamical, microphysical and radiative processes which produce these small particles often involve large, precipitating hydrometeors. There now exists a global dataset of tropical cloud system precipitation feature (PF) properties, collected by TRMM and produced by Steve Nesbitt, that provides additional observational constraints on cloud system properties. We are using the TRMM PF dataset to evaluate the precipitation microphysics of two simulations of deep, precipitating, convective cloud systems: one is a 29-day summertime, continental case (ARM Summer 1997 SCM IOP, at the Southern Great Plains site); the second is a tropical maritime case: the Kwajalein MCS of 11-12 August 1999 (part of a 52-day simulation). Both simulations employed the same bulk, three-ice category microphysical parameterization (Krueger et al. 1995). The ARM simulation was executed using the UCLA/Utah 2D CRM, while the KWAJEX simulation was produced using the 3D CSU CRM (SAM). The KWAJEX simulation described above is compared with both the actual radar data and the TRMM statistics. For the Kwajalein MCS of 11 to 12 August 1999, there are research radar data available for the lifetime of the system. This particular MCS was large in size and rained heavily, but it was weak to average in measures of convective intensity, against the 5-year TRMM sample of 108. For the Kwajalein MCS simulation, the 20 dBZ contour is at 15.7 km and the 40 dBZ contour at 14.5 km! Of all 108 MCSs observed by TRMM, the highest value for the 40 dBZ contour is 8 km. Clearly, the high reflectivity cores are off scale compared with observed cloud systems in this area. A similar

  5. Global analysis of ice microphysics from CloudSat and CALIPSO: Incorporation of specular reflection in lidar signals

    NASA Astrophysics Data System (ADS)

    Okamoto, Hajime; Sato, Kaori; Hagihara, Yuichiro

    2010-11-01

    We developed a new radar-lidar algorithm that can be applied to CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data to retrieve ice microphysics. The algorithm analyzes the specular reflection of lidar signals often observed by CALIPSO with large backscattering coefficients and small depolarization ratios. Analyses of CloudSat and CALIPSO data by our former radar-lidar algorithm showed problems retrieving ice cloud microphysics when specular reflection was present. We implemented additional look-up tables for horizontally oriented plates. A specular reflection mode in the radar-lidar algorithm could drastically improve retrieval results. The new radar-lidar algorithm requires depolarization ratios measured by CALIPSO, in addition to the radar reflectivity factor and backscattering coefficient at 532 nm. We performed several sensitivity studies to retrieval results. Nonsphericity turned out to be the largest source of uncertainties. Global analyses of ice microphysics for CloudSat-CALIPSO overlap regions were performed. The effective radius decreased as the altitude increased. The effective radius in the specular reflection ranged from 100 to 300 μm. The ice water content (IWC) ranged from 10-4 to several tenths of a gram per cubic meter. Both effective radius and IWC increased as the altitude (temperature) decreased (increased). The largest mixing ratio of oriented particles occurred between -20 and -5°C. The IWC had two maxima in the tropics above 15 km and around 5 km. We also examined the differences in ice microphysics over land and ocean. The effective radius was similar over land and ocean, but the IWC tended to be larger over land.

  6. Lidar multiple scattering as a tool for cloud microphysical parameters

    NASA Astrophysics Data System (ADS)

    Werner, Christian; Oppel, Ulrich G.

    1995-09-01

    Lidar was applied to identify atmospheric inhomogeneities by different scattering behavior of the aerosol particles. Aerosol is a general term, it includes also the aggregation to clouds. In the stratosphere there exist droplets of sulfuric acid (from volcanic eruptions), nitric acids and water vapor in mixed phases. In the polar region polar stratospheric (aerosol) clouds form during winter at temperatures around 195K. Usually the nucleation of nitric acid trihydrate (NAT) and nitric acids dihydrate (NAD) happens in a complicated mechanism. A lidar can identify the result of the nucleation process, not the gas phases. It can distinguish between droplets (as Mie particles) and crystal (frozen droplets of NAT and NAD) by polarization. Because the aerosols are driven with the wind and have a tendency to sediment, the orientation of the lidar to the aerosol particles is an important factor. Improvement of lidar measurements to distinguish between stratospheric aerosols and polar stratospheric clouds (i.e. by the given definition the frozen aggregation) was focused: 1) on the use of multiple wavelength lidar with a polarization channel, 2) on a theoretical study on the possibility to use multiple scattering as an additional discriminant and, 3) on scanning. Points 2 and 3 require a better detection and signal processing system. Statistical problems arise for the comparison of measurements, for example if one compares ground-based and airborne measurements of the same cloud. Airborne measurements can contribute to the problem because one can reduce the distance to the object and therefore the 1/R2-dependency leads to larger signals. Averaging with respect to ensemble statistics are covered in this report. It is accepted that ground-based lidar systems especially with a Raman channel measure with a high pulse repetition rate over a few minutes to get a signal which can be processed.

  7. Understanding the Covariance of Microphysics, Thermodynamics, and Dynamics in Mixed Phase Clouds using Airborne Measurements

    NASA Astrophysics Data System (ADS)

    Comstock, J. M.; Fan, J.; Tomlinson, J. M.; Hubbe, J.; Kluzek, C.; Schmid, B.

    2013-12-01

    The physical processes responsible for cloud initiation and lifecycle are complex and involve the interaction between the microphysics, thermodynamics, and dynamics of the atmosphere. Representation of these processes in models requires understanding of the covariance of important parameters at scales that are difficult to resolve in models. We utilize aircraft based measurements in mixed phase clouds to examine the relationship of ice phase partitioning and microphysics with thermodynamic properties and vertical motion. Results are compiled from observational data obtained in convective mixed phase clouds during the Calwater and Two Column Aerosol Project (TCAP) field campaigns conducted using the Department of Energy Gulfstream-1 aircraft. Our results provide a basis for building statistical relationships between microphysical, thermodynamic, and dynamic properties in clouds that are useful for model development and evaluation.

  8. Measuring CCN to Characterize Warm Cloud Microphysics Over The Caribbean

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Hudson, J. G.

    2006-12-01

    Cloud Condensation Nuclei (CCN) are embryos for cloud droplets and are suspected to play a vital role in the production of initial collision drops that explain the classical problem of warm rain initiation. They may also be instrumental in modifying the droplet spectra to promote warm rain initiation. Although the giant nuclei hypothesis seems to be the simplest solution to the problem of warm rain initiation, modeling studies by Johnson 1982 and Ochs and Semonin 1978, suggest that the importance of UGN for precipitation formation diminishes when the CCN concentrations are low as in clear maritime air. Measurement of CCN is essential to verify all hypotheses that investigate precipitation processes. Thus, a detailed analysis of the complete CCN spectra in relation to other cloud parameters is crucial for understanding warm rain initiation. During the RICO field project, aerosol measurements were made by the two DRI instantaneous CCN spectrometers to analyze their distribution and properties. Use of two instruments ensured redundancy and enabled in-flight calibrations without interrupting ambient measurements. These measurements include more than 180 flight hours from 19 flights over a two month period in the western Atlantic near the northeastern corner of the Antilles (Antigua and Barbuda) in December and January (2004-05). During 17 of these flights there were two hours of subcloud measurements at constant altitudes, which enabled evaluation of aerosol characteristics since they allowed long observation times in clear air with very few cloud penetrations. Average and standard deviations of the total particle (CN) and cumulative CCN concentrations during the low altitude horizontal legs showed major variations in the total concentrations and standard deviations. This implies that even in clean maritime air there is some significant day-to-day variability in concentrations, which seems to be related either to wind velocity or to cloudiness. Higher concentrations at

  9. What are the Microphysical Properties of Clouds in an Atmosphere without Human-Induced Pollution?

    NASA Astrophysics Data System (ADS)

    Feichter, J.; O'Donnell, D.

    2009-04-01

    The composition of the atmosphere without any man-made emissions is controlled by biogenic and volcanic emissions and wind-driven particle emissions from the pedosphere and the ocean. Biogenic sources include phytoplankton, emission of volatile organic carbon (VOC) compounds by plants and reduced sulfur emissions from vegetation and soils. Besides mineral dust and biomass burning emissions, organics formed from biogenic VOC was likely the dominating aerosol over continents. The different chemical composition of present-day and past climate aerosol loading might affect the subset of aerosols acting as cloud condensation nuclei and subsequently the microphysical properties of clouds. We will present some exploratory model simulations contrasting the climate system in the absence of human-induced aerosol and VOC emissions with that in the presence of such emissions. In particular, cloud properties will be simulated for present-day emissions and contrasted to a scenario where anthropogenic emissions are switched off. The atmospheric general circulation model ECHAM5 used for this study includes the aerosol model HAM and has been extended by an emission model and a module for secondary organic aerosol (SOA). The updated model treats SOA formed from the anthropogenic precursors toluene, xylene and benzene and from the biogenic precursors isoprene and monoterpenes. SOA-specific modelled processes are precursor emissions, gas-phase formation of SOA and gas-aerosol phase partitioning of SOA. Aerosol microphysical and sink processes (dry and wet removal) are treated with minor modifications to the existing model. The VOC emissions from plants are calculated dependent on surface temperature and photosynthetically active radiation flux.

  10. Observational constraints on the sub-grid variability of cloud and rain: Implications for microphysical parameterization

    NASA Astrophysics Data System (ADS)

    Lebsock, M. D.; Morrison, H.; Gettelman, A.

    2012-12-01

    The transition of cloud water to rain water through the autoconversion and accretion processes are highly non-linear. Furthermore, accretion is sensitive to the covariance of cloud and rain water. Accurately representing these process in global models therefore requires assumptions regarding the sub-grid variability and co-variability of cloud and rain hydrometeors. In addition, recent results suggest that model estimates of the aerosol indirect effect are largely determined by the balance between accretion and autoconversion. We present a multi-sensor analysis of the covariance parameters that govern these processes derived from Aqua-MODIS and CloudSat observations for marine boundary layer clouds. These observational results provide critical constraints on the sub-grid variability and co-variability that are assumed in microphysical parameterizations. These results reiterate a substantial dependence of the sub-grid cloud water on cloud regime, which scales well with cloud fraction and cloud water path. A power-law dependence of the rain water content on the cloud water content is found that permits straightforward integration into existing cloud microphysics parameterizations. The power-law covariance scaling between cloud and rain shows only minor variation with cloud regime. However, the interaction of this covariance with the sub-grid cloud variability results in significant regime dependence in the derived accretion rates. In particular, a significant enhancement of accretion rates can be inferred in shallow convection regimes relative to stratocumulus cloud regimes. This result is particularly relevant to modelling efforts that seek to unify microphysical representation across cloud regimes that have traditionally been treated by independent parameterization schemes. Initial implementation of the observational constraints in the Community Atmosphere Model (CAM) suggest that obtaining the correct balance between autoconversion and accretion requires careful

  11. Study of the microphysical properties in stratus clouds on the Romanian Black Sea coast

    NASA Astrophysics Data System (ADS)

    Boscornea, Andreea; Stefan, Sabina; Sorin Vajaiac, Nicolae

    2016-04-01

    Stratocumulus clouds play a critical role in the Earth's climate system due to their spatial and temporal large extent. For this reason, this study aims to highlight the significant differences of microphysical properties of maritime and continental stratus clouds and By using the ATMOSLAB research aircraft were examined aerosol and microphysical properties, as well as the thermodynamics of the marine boundary layer in and around the Black Sea (between Mangalia, N: 43 48' 34,6'', E: 28̊ 35' 25,12'' and Navodari City N: 44̊ 19' 02'', E: 28̊ 36' 55,24''). More than 10 h measurements obtained by a Cloud Aerosol and Precipitation Spectrometer and the HAWKEYE included aerosol, CCN, cloud droplet and drizzle drop concentrations, air temperatures, liquid water content, real time cloud droplet and ice crystals images and marine aerosol measurements above the sea surface. The over 15 flight legs in clouds (minimum altitude 250 m and maximum altitude 4000 m) and the 4 flight legs performed directly above the sea surface (altitude 120 m) from the three flight 30 October 2015 and 23 November 2015 conducted to results that provide evidence of indirect aerosol effects associated with natural variability in the cloud and aerosol characteristics. For a complete understanding of the large-scale context processes maintaining and dissipating the continental and marine stratocumulus clouds information from a Sun Photometer (Eforie, N: 44̊ 04' 30'', E: 28̊ 37' 55'', altitude 40 m) and satellite data were used. The interpretation performed on the in situ (into cloud and below cloud) measured data have shown, as it was expected, differences between microphysical parameters for maritime and continental clouds and their dependence on aerosol concentrations. These presented results of in situ measurements of clouds above the Romanian Black Sea Coast are the first reported, so that more data is needed for an enhanced understanding of the maritime/continental microphysical contrasts in

  12. Dominant cloud microphysical processes of a torrential rainfall event in Sichuan, China

    NASA Astrophysics Data System (ADS)

    Huang, Yongjie; Cui, Xiaopeng

    2015-03-01

    High-resolution numerical simulation data of a rainstorm triggering debris flow in Sichuan Province of China simulated by the Weather Research and Forecasting (WRF) Model were used to study the dominant cloud microphysical processes of the torrential rainfall. The results showed that: (1) In the strong precipitation period, particle sizes of all hydrometeors increased, and mean-mass diameters of graupel increased the most significantly, as compared with those in the weak precipitation period; (2) The terminal velocity of raindrops was the strongest among all hydrometeors, followed by graupel's, which was much smaller than that of raindrops. Differences between various hydrometeors' terminal velocities in the strong precipitation period were larger than those in the weak precipitation period, which favored relative motion, collection interaction and transformation between the particles. Absolute terminal velocity values of raindrops and graupel were significantly greater than those of air upward velocity, and the stronger the precipitation was, the greater the differences between them were; (3) The orders of magnitudes of the various hydrometeors' sources and sinks in the strong precipitation period were larger than those in the weak precipitation period, causing a difference in the intensity of precipitation. Water vapor, cloud water, raindrops, graupel and their exchange processes played a major role in the production of the torrential rainfall, and there were two main processes via which raindrops were generated: abundant water vapor condensed into cloud water and, on the one hand, accretion of cloud water by rain water formed rain water, while on the other hand, accretion of cloud water by graupel formed graupel, and then the melting of graupel formed rain water.

  13. LACIS-T - A humid wind tunnel for investigating the Interactions between Cloud Microphysics and Turbulence

    NASA Astrophysics Data System (ADS)

    Voigtländer, Jens; Niedermeier, Dennis; Siebert, Holger; Shaw, Raymond; Schumacher, Jörg; Stratmann, Frank

    2017-04-01

    To improve the fundamental and quantitative understanding of the interactions between cloud microphysical and turbulent processes, the Leibniz Institute for Tropospheric Research (TROPOS) has built up a new humid wind tunnel (LACIS-T). LACIS-T allows for the investigation of cloud microphysical processes, such as cloud droplet activation and freezing, under-well defined thermodynamic and turbulent flow conditions. It therewith allows for the straight forward continuation, extension, and completion of the cloud microphysics related investigations carried out at the Leipzig Aerosol Cloud Interaction Simulator (LACIS) under laminar flow conditions. Characterization of the wind tunnel with respect to flow, thermodynamics, and droplet microphysics is carried out with probes mounted inside (pitot tube and hot-wire anemometer for mean velocity and fluctuations, Pt100 sensor for mean temperature, cold-wire sensor for temperature fluctuations is in progress, as well as a dew-point mirror for mean water vapor concentration, a Lyman-alpha sensor for water vapor fluctuations is in progress) the measurement section, and from outside with optical detection methods (a laser light sheet is available for cloud droplet visualization, a digital holography system for detection of cloud droplet size distributions will be installed for tests in February 2017), respectively. Computational fluid dynamics (CFD) simulations have been carried out for defining suitable experimental conditions and assisting the interpretation of the experimental data. In this work, LACIS-T, its fundamental operating principle, and first preliminary results from ongoing characterization efforts will be presented.

  14. MODIS Microphysical Regimes for Examining Apparent Aerosol Effects on Clouds and Precipitation

    NASA Astrophysics Data System (ADS)

    Oreopoulos, L.; Cho, N.; Lee, D.; Kato, S.; Lebsock, M. D.; Yuan, T.; Huffman, G. J.

    2014-12-01

    We use a 10-year record of MODIS Terra and Aqua Level-3 joint histograms of cloud optical thickness (COT) and cloud effective radius (CER) to derive so-called cloud microphysical regimes by means of clustering analysis. The regimes reveal the dominant modes of COT and CER co-variations around the globe for both liquid and ice phases. The clustering analysis is capable of separating regimes so that each is dominated by one of the two water phases and can be associated with previously derived "dynamical" regimes. The microphysical regimes serve as an appropriate basis to study possible effects of aerosols on cloud microphysical changes and precipitation. To this end, we employ MODIS aerosol loading measurements either in terms of aerosol index or aerosol optical depth and spatiotemporally matched precipitation (from either GPCP, TRMM or CloudSat) to examine intra-regime variability, regime transitions from morning (Terra) to afternoon (Aqua), and regime precipitation characteristics for locally low, average, and high aerosol loadings. Breakdowns by ocean/land and geographical zone (e.g., tropics vs. midlatitudes) are essential for physical interpretation of the results. The analysis conducted so far reveals notable differences in apparent characteristics of low- and high-cloud dominated microphysical regimes when in different aerosol environments. The presentation will attempt to examine whether the picture painted by our work is consistent with prevailing expectations, rooted to either modeling or prior observational studies, on how clouds and precipitation respond to distinct aerosol environments.

  15. Uncertainties in synthetic Meteosat SEVIRI infrared brightness temperatures in the presence of cirrus clouds and implications for evaluation of cloud microphysics

    NASA Astrophysics Data System (ADS)

    Senf, Fabian; Deneke, Hartwig

    2017-01-01

    Synthetic brightness temperatures of five infrared Meteosat SEVIRI channels are investigated for their sensitivities on cirrus radiative properties. The operational SynSat scheme of the regional German weather prediction model COSMO-DE is contrasted to a revised scheme with a special emphasis on consistency between the model-internal ice-microphysics and infrared radiation in convective situations. In particular, the formulation of generalized effective diameters of ice, snow and graupel as well as subgrid-scale cloud cover has been improved. Based on the applied modifications, we first show that changed assumptions on the cirrus radiative properties can lead to 10 K warmer brightness temperatures. Second, we demonstrate that prescribed relative changes of 20% in cloud cover and particle size induce maximum changes of around 4 to 5 K. The maximum sensitivity appears for semi-transparent cirrus having brightness temperatures around 240 and 260 K and total frozen water path around 30 gm- 2 for viewing geometries over Central Europe. We further consider the known COSMO-DE cold bias to discuss the problem of inconsistencies in model-internal and external formulations of cloud microphysical and radiative properties. We demonstrate that between 35% and 70% of the cold bias can be attributed to the radiative representation of cirrus clouds. We additionally discuss the use of window-channel brightness temperature differences for evaluation of model microphysics and hypothesize that the amount of COSMO-DE ice is overestimated in convective situations.

  16. Effects of aerosols on cloud microphysics simulations with Weather Research Forecasting (WRF) model in East Asia

    NASA Astrophysics Data System (ADS)

    Bae, S.; Park, R.; Lim, K.; Hong, S.

    2011-12-01

    Aerosols in the atmosphere play an important role in cloud formation as cloud condensation nuclei (CCN). Chemical composition and number size distribution of aerosols significantly modify cloud properties by altering droplet number concentration, droplet effective radius, cloud albedo, cloud liquid water content, and cloud lifetime. However, a mechanistic simulation of aerosol effects in cloud microphysics is relatively scarce in regional meteorological forecasting models. We examine the effect of dynamically varying aerosols on CCN activation and cloud formation in the WRF model by employing the updated Twomey equation and our improvement in the cloud microphysics scheme in particular for the CCN activation process. First, we use the Community Multiscale Air Quality (CMAQ) model to obtain spatially and temporally varying aerosol concentrations in East Asia, which are provided as input data in the WRF simulations. The baseline and sensitivity simulations are conducted using the WRF. The latter includes explicit calculation of CCN activation with aerosol concentrations from the CMAQ. A comparison of simulated precipitation with Tropical Rainfall Measuring Mission observation shows better agreement of sensitivity results with observed data. We also find that the simulated precipitation in the sensitivity model shows a clear weekly variability such as increases in precipitation during the weekdays whereas the decrease during the weekends. This simulated weekly variability is consistent with that of observed precipitation in Korea over the past decades and can be attributed to the indirect effect of anthropogenic aerosols coined as "weekend effect", indicating the importance of an explicit consideration of aerosols for cloud microphysics simulations of regional meteorological models.

  17. Aerosol-Cloud microphysical closure in warm tropical cumulus during CRYSTAL-FACE

    NASA Astrophysics Data System (ADS)

    Conant, W. C.; Lu, M.; Vanreken, T.; Rissman, T.; Varutbangkul, V.; Jonsson, H. H.; Nenes, A.; Jimenez, J. L.; Delia, A. E.; Bahreini, R.; Roberts, G. C.; Flagan, R. C.; Seinfeld, J. H.

    2002-12-01

    We present a closure study between aerosol and warm-cloud microphysics using field data collected during the NASA CRYSTAL-FACE campaign. CRYSTAL-FACE was conducted in continental and marine environments near southern Florida in July, 2002. Detailed profiles of thirteen cumulus clouds were made by the CIRPAS Twin Otter aircraft, which was equipped with four aerosol sizing systems, two CCN counters operated at 0.4% and 0.7% supersaturation, an Aerodyne aerosol mass spectrometer, a MOUDI filter sampler system, two cloud drop sizing probes, and two turbulence probes. A wide range of CCN (300 to >3500 cm-3) and cloud drop concentrations (200 to >1600 cm-3) provides an ideal case study for aerosol-cloud interactions and the first and second indirect effects. Vertical characterization of the young and mature cumulus clouds are obtained from multiple horizontal passes from below cloud base to cloud top. A detailed adiabatic cloud activation model accurately predicts the cloud drop concentration 100 m above cloud base. The model is constrained by observed updraft velocity and below-cloud aerosol properties (i.e. concentration, size distribution, composition, and supersaturation spectrum). Each cloud contains a core often exceeding 500 m in height in which the equivalent potential temperature follows a moist-adiabatic vertical profile. Effective radius most often follows an adiabatic profile, even in regions where liquid water content and/or equivalent potential temperature are sub-adiabatic. Large cloud-to-cloud variations in the vertical profile of effective radius are primarily driven by below-cloud aerosol concentration and to a lesser degree by cloud dynamics (i.e. vertical velocity). Six of the thirteen clouds are simulated using the RAMS large-eddy-simulation model. RAMS is integrated with bulk and bin microphysical models and is coupled to an offline 3-D radiative transfer model to study the aerosol effects on cloud microphysics and radiative properties. More

  18. Probing the impact of different aerosol sources on cloud microphysics and precipitation through in-situ measurements of chemical mixing state

    NASA Astrophysics Data System (ADS)

    Prather, K. A.; Suski, K.; Cazorla, A.; Cahill, J. F.; Creamean, J.; Collins, D. B.; Heymsfield, A.; Roberts, G. C.; DeMott, P. J.; Sullivan, R. C.; Rosenfeld, D.; Comstock, J. M.; Tomlinson, J. M.

    2011-12-01

    Aerosol particles play a crucial role in affecting cloud processes by serving as cloud nuclei. However, our understanding of which particles actually form cloud and ice nuclei limits our ability to treat aerosols properly in climate models. In recent years, it has become possible to measure the chemical composition of individual cloud nuclei within the clouds using on-line mass spectrometry. In-situ high time resolution chemistry can now be compared with cloud physics measurements to directly probe the impact of aerosol chemistry on cloud microphysics. This presentation will describe results from two recent field campaigns, CalWater in northern California and ICE-T in the western Caribbean region. Ground-based and aircraft measurements will be presented of aerosol mixing state, cloud microphysics, and meteorology. Results from single particle mass spectrometry will show the sources of the cloud seeds, including dust, biomass burning, sea spray, and biological particles. Details will be provided on how we are now able to probe the sources and cycling of atmospheric aerosols by measuring individual aerosols, cloud nuclei, and precipitation chemistry. The important role of dust, both Asian and African, and bioparticles in forming ice nuclei will be discussed. Finally, a summary will be provided discussing how these new in-situ measurements are being used to advance our understanding of complex atmospheric processes, and improve our understanding of aerosol impacts on climate.

  19. Determining Best Estimates and Uncertainties in Cloud Microphysical Parameters from ARM Field Data: Implications for Models, Retrieval Schemes and Aerosol-Cloud-Radiation Interactions

    SciTech Connect

    McFarquhar, Greg

    2015-12-28

    We proposed to analyze in-situ cloud data collected during ARM/ASR field campaigns to create databases of cloud microphysical properties and their uncertainties as needed for the development of improved cloud parameterizations for models and remote sensing retrievals, and for evaluation of model simulations and retrievals. In particular, we proposed to analyze data collected over the Southern Great Plains (SGP) during the Mid-latitude Continental Convective Clouds Experiment (MC3E), the Storm Peak Laboratory Cloud Property Validation Experiment (STORMVEX), the Small Particles in Cirrus (SPARTICUS) Experiment and the Routine AAF Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) field campaign, over the North Slope of Alaska during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) and the Mixed-Phase Arctic Cloud Experiment (M-PACE), and over the Tropical Western Pacific (TWP) during The Tropical Warm Pool International Cloud Experiment (TWP-ICE), to meet the following 3 objectives; derive statistical databases of single ice particle properties (aspect ratio AR, dominant habit, mass, projected area) and distributions of ice crystals (size distributions SDs, mass-dimension m-D, area-dimension A-D relations, mass-weighted fall speeds, single-scattering properties, total concentrations N, ice mass contents IWC), complete with uncertainty estimates; assess processes by which aerosols modulate cloud properties in arctic stratus and mid-latitude cumuli, and quantify aerosol’s influence in context of varying meteorological and surface conditions; and determine how ice cloud microphysical, single-scattering and fall-out properties and contributions of small ice crystals to such properties vary according to location, environment, surface, meteorological and aerosol conditions, and develop parameterizations of such effects.In this report we describe the accomplishments that we made on all 3 research objectives.

  20. Implementation of an Aerosol-Cloud Microphysics-Radiation Coupling into the NASA Unified WRF: Simulation Results for the 6-7 August 2006 AMMA Special Observing Period

    NASA Technical Reports Server (NTRS)

    Shi, J. J.; Matsui, T.; Tao, W.-K.; Tan, Q.; Peters-Lidard, C.; Chin, M.; Pickering, K.; Guy, N.; Lang, S.; Kemp, E. M.

    2014-01-01

    Aerosols affect the Earth's radiation balance directly and cloud microphysical processes indirectly via the activation of cloud condensation and ice nuclei. These two effects have often been considered separately and independently, hence the need to assess their combined impact given the differing nature of their effects on convective clouds. To study both effects, an aerosol-microphysics-radiation coupling, including Goddard microphysics and radiation schemes, was implemented into the NASA Unified Weather Research and Forecasting model (NU-WRF). Fully coupled NU-WRF simulations were conducted for a mesoscale convective system (MCS) that passed through the Niamey, Niger area on 6-7 August 2006 during an African Monsoon Multidisciplinary Analysis (AMMA) special observing period. The results suggest that rainfall is reduced when aerosol indirect effects are included, regardless of the aerosol direct effect. Daily mean radiation heating profiles in the area traversed by the MCS showed the aerosol (mainly mineral dust) direct effect had the largest impact near cloud tops just above 200 hectopascals where short-wave heating increased by about 0.8 Kelvin per day; the weakest long-wave cooling was at around 250 hectopascals. It was also found that more condensation and ice nuclei as a result of higher aerosol/dust concentrations led to increased amounts of all cloud hydrometeors because of the microphysical indirect effect, and the radiation direct effect acts to reduce precipitating cloud particles (rain, snow and graupel) in the middle and lower cloud layers while increasing the non-precipitating particles (ice) in the cirrus anvil. However, when the aerosol direct effect was activated, regardless of the indirect effect, the onset of MCS precipitation was delayed about 2 hours, in conjunction with the delay in the activation of cloud condensation and ice nuclei. Overall, for this particular environment, model set-up and physics configuration, the effect of aerosol

  1. Global climate modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds

    NASA Astrophysics Data System (ADS)

    Navarro, T.; Madeleine, J.-B.; Forget, F.; Spiga, A.; Millour, E.; Montmessin, F.; Määttänen, A.

    2014-07-01

    Water ice clouds play a key role in the radiative transfer of the Martian atmosphere, impacting its thermal structure, its circulation, and, in turn, the water cycle. Recent studies including the radiative effects of clouds in global climate models (GCMs) have found that the corresponding feedbacks amplify the model defaults. In particular, it prevents models with simple microphysics from reproducing even the basic characteristics of the water cycle. Within that context, we propose a new implementation of the water cycle in GCMs, including a detailed cloud microphysics taking into account nucleation on dust particles, ice particle growth, and scavenging of dust particles due to the condensation of ice. We implement these new methods in the Laboratoire de Météorologie Dynamique GCM and find satisfying agreement with the Thermal Emission Spectrometer observations of both water vapor and cloud opacities, with a significant improvement when compared to GCMs taking into account radiative effects of water ice clouds without this implementation. However, a lack of water vapor in the tropics after Ls = 180° is persistent in simulations compared to observations, as a consequence of aphelion cloud radiative effects strengthening the Hadley cell. Our improvements also allow us to explore questions raised by recent observations of the Martian atmosphere. Supersaturation above the hygropause is predicted in line with Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars observations. The model also suggests for the first time that the scavenging of dust by water ice clouds alone fails to fully account for the detached dust layers observed by the Mars Climate Sounder.

  2. Electric Fields, Cloud Microphysics, and Reflectivity in Anvils of Florida Thunderstorms

    NASA Technical Reports Server (NTRS)

    Dye, J. E.; Bateman, M. G.; Christian, H. J.; Grainger, C. A.; Hall, W. D.; Krider, E. P.; Lewis, S. A.; Mach, D. M.; Merceret, F. J.; Willett, J. C.; Willis, P. T.

    2006-01-01

    A coordinated aircraft - radar project that investigated the electric fields, cloud microphysics and radar reflectivity of thunderstorm anvils near Kennedy Space Center is described. Measurements from two cases illustrate the extensive nature of the microphysics and electric field observations. As the aircraft flew from the edges of anvils into the interior, electric fields very frequently increased abruptly from approx.1 to >10 kV/m even though the particle concentrations and radar reflectivity increased smoothly. The abrupt increase in field usually occurred when the aircraft entered regions with a reflectivity of 10 to 15 dBZ. It is suggested that the abrupt increase in electric field may be because the charge advection from the storm core did not occur across the entire breadth of the anvil and was not constant in time. Screening layers were not detected near the edges of the anvils. Some long-lived anvils showed subsequent enhancement of electric field and reflectivity and growth of particles, which if localized, might be a factor in explaining the abrupt change of field in some cases. Comparisons of electric field magnitude with particle concentration or reflectivity for a combined data set that included all anvil measurements showed a threshold behavior. When the average reflectivity, such as in a 3-km cube, was less than approximately 5 dBZ, the electric field magnitude was <3 kV/m. Based on these findings, the Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) is now being used by NASA, the Air Force and Federal Aviation Administration in new Lightning Launch Commit Criteria as a diagnostic for high electric fields in anvils.

  3. Electric Fields, Cloud Microphysics, and Reflectivity in Anvils of Florida Thunderstorms

    NASA Technical Reports Server (NTRS)

    Dye, J. E.; Bateman, M. G.; Christian, H. J.; Defer, E.; Grainger, C. A.; Hall, W. D.; Krider, E. P.; Lewis, S. A.; Mach, D. M.; Merceret, F. J.; hide

    2007-01-01

    A coordinated aircraft - radar project that investigated the electric fields, cloud microphysics and radar reflectivity of thunderstorm anvils near Kennedy Space Center is described. Measurements from two cases illustrate the extensive nature of the microphysics and electric field observations. As the aircraft flew from the edges of anvils into the interior, electric fields very frequently increased abruptly from approximately 1 to more than 10 kV m(exp -1) even though the particle concentration and radar reflectivity increased smoothly. The abrupt increase in field usually occurred when the aircraft entered regions with a reflectivity of 10 to 15 dBZ. It is suggested that the abrupt increase in electric field may be because the charge advection from the storm core did not occur across the entire breadth of the anvil and was not constant in time. Screening layers were not detected near the edges of the anvils. Some long-lived anvils showed subsequent enhancement of electric field and reflectivity and growth of particles, which if localized, might be a factor in explaining the abrupt change of field in some cases. Comparisons of electric field magnitude with particle concentration or reflectivity for a combined data set that included all anvil measurements showed a threshold behavior. When the average reflectivity, such as in a 3-km cube, was less than approximately 5 dBZ, the electric field magnitude was les than kV m(exp -1). Based on these findings, the Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) is now being used by NASA, the Air Force and Federal Aviation Administration in new Lightning Launch Commit Criteria as a diagnostic for high electric fields in anvils.

  4. Impact of Cloud Model Microphysics on Passive Microwave Retrievals of Cloud Properties. Part I: Model Comparison Using EOF Analyses

    NASA Astrophysics Data System (ADS)

    Biggerstaff, Michael I.; Seo, Eun-Kyoung; Hristova-Veleva, Svetla M.; Kim, Kwang-Yul

    2006-07-01

    The impact of model microphysics on the relationships among hydrometeor profiles, latent heating, and derived satellite microwave brightness temperatures TB have been examined using a nonhydrostatic, adaptive-grid cloud model to simulate a mesoscale convective system over water. Two microphysical schemes (each employing three-ice bulk parameterizations) were tested for two different assumptions in the number of ice crystals assumed to be activated at 0°C to produce simulations with differing amounts of supercooled cloud water. The model output was examined using empirical orthogonal function (EOF) analysis, which provided a quantitative framework in which to compare the simulations. Differences in the structure of the vertical anomaly patterns were related to physical processes and attributed to different approaches in cloud microphysical parameterizations in the two schemes. Correlations between the first EOF coefficients of cloud properties and TB at frequencies associated with the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) showed additional differences between the two parameterization schemes that affected the relationship between hydrometeors and TB. Classified in terms of TB, the microphysical schemes produced significantly different mean vertical profiles of cloud water, cloud ice, snow, vertical velocity, and latent heating. The impact of supercooled cloud water on the 85-GHz TB led to a 15% variation in mean convective rain mass at the surface. The variability in mean profiles produced by the four simulations indicates that the retrievals of cloud properties, especially latent heating, based on TMI frequencies are dependent on the particular microphysical parameterizations used to construct the retrieval database.

  5. The effect of cloud microphysics on climate sensitivity. Progress report, July 15, 1990--July 14, 1992

    SciTech Connect

    Stamnes, K.

    1992-12-31

    Clouds play an important role in the climate system through radiative energy redistribution. The cloud radiative properties change if the cloud droplet size spectrum changes. This research shows that the climate is very sensitive to cloud water path and equivalent radius. To explore this issue, an accurate parameterization of cloud radiative properties for the purpose of climate modeling has been developed. A one-dimensional radiative convective model with a comprehensive radiative transfer scheme using the new parameterization of cloud radiative properties has also been developed to investigate the climate sensitivity to changes in cloud microphysics. By looking at clouds with different size distributions, we find that for clouds with the same cloud water amount and equivalent radius, the cloud radiative properties are essentially the same. Thus cloud radiative properties depend primarily on equivalent radius and are independent of the details of the size distribution. Our parameterization allows these two parameters to change independently. A sensitivity study has been performed, to consider cloud droplet size. First, we looked at cloud radiative forcing. The results show that the cloud radiative forcing is indeed very sensitive to the changes in cloud equivalent radius. Secondly, we have looked at the response of equilibrium temperature to changes in cloud equivalent radius. This sensitivity study suggests that in climate models, an interactive cloud parameterization is needed, in which cloud water amount and equivalent radius are predicted independently.

  6. A microphysical parameterization of aqSOA and sulfate formation in clouds

    NASA Astrophysics Data System (ADS)

    McVay, Renee; Ervens, Barbara

    2017-07-01

    Sulfate and secondary organic aerosol (cloud aqSOA) can be chemically formed in cloud water. Model implementation of these processes represents a computational burden due to the large number of microphysical and chemical parameters. Chemical mechanisms have been condensed by reducing the number of chemical parameters. Here an alternative is presented to reduce the number of microphysical parameters (number of cloud droplet size classes). In-cloud mass formation is surface and volume dependent due to surface-limited oxidant uptake and/or size-dependent pH. Box and parcel model simulations show that using the effective cloud droplet diameter (proportional to total volume-to-surface ratio) reproduces sulfate and aqSOA formation rates within ≤30% as compared to full droplet distributions; other single diameters lead to much greater deviations. This single-class approach reduces computing time significantly and can be included in models when total liquid water content and effective diameter are available.

  7. Cloud Microphysics in Hurricane Outflows: Observations in 'Bonnie' (1998) at 12 km Altitude

    NASA Technical Reports Server (NTRS)

    Pueschel, Rudolf F.; Hallett, J.; Strawa, A. W.; Ferry, G. V.; Bui, T. P.; Condon, Estelle P. (Technical Monitor)

    2000-01-01

    The water balance of a hurricane is controlled by boundary layer inflow, near vertical motion in the eyewall causing coalescence precipitation at above and residual ice precipitation at below freezing temperatures, and cirrus outflow at below -40 C aloft. In this paper we address the question of efficiency of water removal by this cirrus outflow which is important for the release of latent heat at high altitudes and its role in the dynamic flow at that level. During NASA's 1998 Convection and Moisture Experiment campaign we acquired microphysical outflow data in order to (1) determine the release and redistribution of latent heat near the top of hurricanes, (2) aid in TRMM algorithm development for remote sensing of precipitation, and (3) determine the optical/radiative characteristics of hurricane outflow. The data were acquired with Particle Measuring Systems two dimensional imaging spectrometers. On 23 August and again during the hurricane's landfall on 26 August, 1998, the NASA DC-8 aircraft penetrated hurricane 'Bonnie' four times each near 200 hPa pressure altitude. The eye crossing times were determined by (1) zero counts of cloud particles, (2) approximately 5 C increases in static and potential temperatures, and (3) minima in speeds and changes of direction of horizontal winds. The vertical winds showed shear between -6 m per second and +4 m per second and tangential winds approached 30 m per second in the eyewall. The particle volumes in the eyewall (determined by the pixels the particles shadowed in the direction of flight [x-direction] and normally to it by the number of diodes that they shadowed [y-direction]) ranged between 0.5 and 5.0 cubic centimeters per cubic meter. With a particle density near 0.2 g per cubic centimeter (determined from in situ melting and evaporation on a surface collector), the 1.0 g per meter corresponding mass of cloud ice ranged between 0.27 and 2.7 g per kilograms yielding horizontal fluxes between 8.1 and 81 g per square

  8. Cloud Microphysics in Hurricane Outflows: Observations in 'Bonnie' (1998) at 12 km Altitude

    NASA Technical Reports Server (NTRS)

    Pueschel, Rudolf F.; Hallett, J.; Strawa, A. W.; Ferry, G. V.; Bui, T. P.; Condon, Estelle P. (Technical Monitor)

    2000-01-01

    The water balance of a hurricane is controlled by boundary layer inflow, near vertical motion in the eyewall causing coalescence precipitation at above and residual ice precipitation at below freezing temperatures, and cirrus outflow at below -40 C aloft. In this paper we address the question of efficiency of water removal by this cirrus outflow which is important for the release of latent heat at high altitudes and its role in the dynamic flow at that level. During NASA's 1998 Convection and Moisture Experiment campaign we acquired microphysical outflow data in order to (1) determine the release and redistribution of latent heat near the top of hurricanes, (2) aid in TRMM algorithm development for remote sensing of precipitation, and (3) determine the optical/radiative characteristics of hurricane outflow. The data were acquired with Particle Measuring Systems two dimensional imaging spectrometers. On 23 August and again during the hurricane's landfall on 26 August, 1998, the NASA DC-8 aircraft penetrated hurricane 'Bonnie' four times each near 200 hPa pressure altitude. The eye crossing times were determined by (1) zero counts of cloud particles, (2) approximately 5 C increases in static and potential temperatures, and (3) minima in speeds and changes of direction of horizontal winds. The vertical winds showed shear between -6 m per second and +4 m per second and tangential winds approached 30 m per second in the eyewall. The particle volumes in the eyewall (determined by the pixels the particles shadowed in the direction of flight [x-direction] and normally to it by the number of diodes that they shadowed [y-direction]) ranged between 0.5 and 5.0 cubic centimeters per cubic meter. With a particle density near 0.2 g per cubic centimeter (determined from in situ melting and evaporation on a surface collector), the 1.0 g per meter corresponding mass of cloud ice ranged between 0.27 and 2.7 g per kilograms yielding horizontal fluxes between 8.1 and 81 g per square

  9. Understanding the Relationships Between Lightning, Cloud Microphysics, and Airborne Radar-derived Storm Structure During Hurricane Karl (2010)

    NASA Technical Reports Server (NTRS)

    Reinhart, Brad; Fuelberg, Henry; Blakeslee, Richard; Mach, Douglas; Heymsfield, Andrew; Bansemer, Aaron; Durden, Stephen L.; Tanelli, Simone; Heymsfield, Gerald; Lambrigtsen, Bjorn

    2013-01-01

    This study explores relationships between lightning, cloud microphysics, and tropical cyclone (TC) storm structure in Hurricane Karl (16 September 2010) using data collected by the NASA DC-8 and Global Hawk (GH) aircraft during NASA's Genesis and Rapid Intensification Processes (GRIP) experiment. The research capitalizes on the unique opportunity provided by GRIP to synthesize multiple datasets from two aircraft and analyze the microphysical and kinematic properties of an electrified TC. Five coordinated flight legs through Karl by the DC-8 and GH are investigated, focusing on the inner-core region (within 50km of the storm center) where the lightning was concentrated and the aircraft were well coordinated. GRIP datasets are used to compare properties of electrified and nonelectrified inner-core regions that are related to the noninductive charging mechanism, which is widely accepted to explain the observed electric fields within thunderstorms. Three common characteristics of Karl's electrified regions are identified: 1) strong updrafts of 10-20ms21, 2) deep mixed-phase layers indicated by reflectivities.30 dBZ extending several kilometers above the freezing level, and 3) microphysical environments consisting of graupel, very small ice particles, and the inferred presence of supercooled water. These characteristics describe an environment favorable for in situ noninductive charging and, hence, TC electrification. The electrified regions in Karl's inner core are attributable to a microphysical environment that was conducive to electrification because of occasional, strong convective updrafts in the eyewall.

  10. Investigation of the cloud microphysics and albedo susceptibility of the Southeast Pacific stratocumulus cloud deck

    NASA Astrophysics Data System (ADS)

    Painemal, David

    2011-12-01

    This thesis investigates the interactions between aerosols, cloud microphysics, regional circulation, and radiative response in the Southeast Pacific stratocumulus cloud deck, one of the largest and most persistent cloud regimes in the planet. Synoptic and satellite-derived cloud property variations for the Southeast Pacific region associated with changes in coastal satellite-derived cloud droplet number concentration (Nd) are analyzed through a composite technique. MAX and MIN Nd composites are defined by the top and bottom terciles of daily area-mean Nd values over the Arica Bight, the region with the largest mean oceanic Nd, for the five October months of 2001, 2005, 2006, 2007, and 2008. The MAX-Nd composite is characterized by a weaker subtropical anticyclone and weaker winds than the MIN-Nd composite. Additionally, the MAX-Nd composite clouds over the Arica Bight are thinner than the MIN-Nd composite clouds, have lower cloud tops, lower near-coastal cloud albedos, and occur below warmer and drier free tropospheres. At 85W, the top-of-atmosphere shortwave fluxes are significantly higher (50%) for the MAX-Nd, with thicker, lower clouds and higher cloud fractions than for the MIN-Nd. The change in Nd at this location is small, suggesting that the MAX-MIN Nd composite differences in radiative properties primarily reflects synoptic changes. The ability of MODIS level 2 retrievals to represent the cloud microphysics is assessed with in-situ measurements of droplet size distributions, collected during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). The MODIS cloud optical thickness (tau) correlates well with the in-situ values with a positive bias (1.42). In contrast, the standard 2.1 micron-derived MODIS cloud effective radius (re) is found to systematically exceed the in-situ cloud-top re, with a mean bias of 2.08 mum. Three sources of errors that could contribute to the MODIS re positive bias are investigated further: the spread of

  11. Modeling the microphysics of CO2 ice clouds within wave-induced cold pockets in the martian mesosphere

    NASA Astrophysics Data System (ADS)

    Listowski, C.; Määttänen, A.; Montmessin, F.; Spiga, A.; Lefèvre, F.

    2014-07-01

    Mesospheric CO2 ice clouds on Mars are simulated with a 1D microphysical model, which includes a crystal growth rate adapted to high supersaturations encountered in the martian mesosphere. Observational constraints (crystal radius and opacity) exist for these clouds observed during the day around the equator at ∼60-80 km altitude. Nighttime mesospheric clouds interpreted as CO2 ice clouds have also been characterized at low southern latitudes, at ∼90-100 km altitude. From modeling and observational evidence, it is believed that mesospheric clouds are formed within temperature minima created by thermal tides, where gravity wave propagation allows for the creation of supersaturated layers (cold pockets). Thus, temperature profiles perturbed by gravity waves are used in the model to initiate nucleation and maintain growth of CO2 ice crystals. We show that it is possible to reproduce the observed effective radii for daytime and nighttime clouds. Crystal sizes are mainly governed by the altitude where the cloud forms, and by the amplitude of supersaturation. The temporal and spatial behavior of the cloud is controlled by the extent and lifetime of the cold pocket. The cloud evaporates fast after the cold pocket has vanished, implying a strong correlation between gravity wave activity and CO2 cloud formation. Simulated opacities remain far below the observed ones as long as typical dust conditions are used. In the case of the lower daytime clouds, the enhanced mesospheric dust loading typically reached during dust storm conditions, allows for greater cloud opacities, close to observed values, by supplying the atmosphere with condensation nuclei. However, CO2 ice clouds are not detected during the dust storm season, and, because of fast sedimentation of dust particles, an exogenous supply (meteoritic flux) appears necessary to explain opacities of both daytime and nighttime mesospheric CO2 ice clouds along their whole period of observation.

  12. A study of cloud microphysics and precipitation over the Tibetan Plateau by radar observations and cloud-resolving model simulations

    NASA Astrophysics Data System (ADS)

    Gao, Wenhua; Sui, Chung-Hsiung; Fan, Jiwen; Hu, Zhiqun; Zhong, Lingzhi

    2016-11-01

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

  13. Factors influencing the microphysics and radiative properties of liquid-dominated Arctic clouds: insight from observations of aerosol and clouds during ISDAC

    SciTech Connect

    Earle, Michael; Liu, Peter S.; Strapp, J. Walter; Zelenyuk, Alla; Imre, D.; McFarquhar, Greg; Shantz, Nicole C.; Leaitch, W. R.

    2011-11-04

    Aircraft measurements during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in April 2008 are used to investigate aerosol indirect effects in Arctic clouds. Two aerosol-cloud regimes are considered in this analysis: single-layer stratocumulus cloud with below-cloud aerosol concentrations (N{sub a}) below 300 cm{sup -3} on April 8 and April 26-27 (clean cases); and inhomogeneous layered cloud with N{sub a} > 500 cm{sup -3} below cloud base on April 19-20, concurrent with a biomass burning episode (polluted cases). Vertical profiles through cloud in each regime are used to determine average cloud microphysical and optical properties. Positive correlations between the cloud droplet effective radius (Re) and cloud optical depth ({tau}) are observed for both clean and polluted cases, which are characteristic of optically-thin, non-precipitating clouds. Average Re values for each case are {approx} 6.2 {mu}m, despite significantly higher droplet number concentrations (Nd) in the polluted cases. The apparent independence of Re and Nd simplifies the description of indirect effects, such that {tau} and the cloud albedo (A) can be described by relatively simple functions of the cloud liquid water path. Adiabatic cloud parcel model simulations show that the marked differences in Na between the regimes account largely for differences in droplet activation, but that the properties of precursor aerosol also play a role, particularly for polluted cases where competition for vapour amongst the more numerous particles limits activation to larger and/or more hygroscopic particles. The similarity of Re for clean and polluted cases is attributed to compensating droplet growth processes for different initial droplet size distributions.

  14. Parametric studies of contrail ice particle formation in jet regime using microphysical parcel modeling

    NASA Astrophysics Data System (ADS)

    Wong, H.-W.; Miake-Lye, R. C.

    2010-04-01

    Condensation trails (contrails) formed from water vapor emissions behind aircraft engines are the most uncertain components of the aviation impacts on climate change. To gain improved knowledge of contrail and contrail-induced cirrus cloud formation, understanding of contrail ice particle formation immediately after aircraft engines is needed. Despite many efforts spent in modeling the microphysics of ice crystal formation in jet regime (with a plume age <5 s), systematic understanding of parametric effects of variables affecting contrail ice particle formation is still limited. In this work, we apply a microphysical parcel modeling approach to study contrail ice particle formation in near-field aircraft plumes up to 1000 m downstream of an aircraft engine in the soot-rich regime (soot number emission index >1×1015 (kg-fuel)-1) at cruise. The effects of dilution history, ion-mediated nucleation, ambient relative humidity, fuel sulfur contents, and initial soot emissions were investigated. Our simulation results suggest that ice particles are mainly formed by water condensation on emitted soot particles. The growth of ice coated soot particles is driven by water vapor emissions in the first 1000 m and by ambient relative humidity afterwards. The presence of chemi-ions does not significantly contribute to the formation of ice particles in the soot-rich regime, and the effect of fuel sulfur contents is small over the range typical of standard jet fuels. The initial properties of soot emissions play the most critical role, and our calculations suggest that higher number concentration and smaller size of contrail particle nuclei may be able to effectively suppress the formation of contrail ice particles. Further modeling and experimental studies are needed to verify if our findings can provide a possible approach for contrail mitigation.

  15. Retrieval of cloud microphysical parameters from INSAT-3D: a feasibility study using radiative transfer simulations

    NASA Astrophysics Data System (ADS)

    Jinya, John; Bipasha, Paul S.

    2016-05-01

    Clouds strongly modulate the Earths energy balance and its atmosphere through their interaction with the solar and terrestrial radiation. They interact with radiation in various ways like scattering, emission and absorption. By observing these changes in radiation at different wavelength, cloud properties can be estimated. Cloud properties are of utmost importance in studying different weather and climate phenomena. At present, no satellite provides cloud microphysical parameters over the Indian region with high temporal resolution. INSAT-3D imager observations in 6 spectral channels from geostationary platform offer opportunity to study continuous cloud properties over Indian region. Visible (0.65 μm) and shortwave-infrared (1.67 μm) channel radiances can be used to retrieve cloud microphysical parameters such as cloud optical thickness (COT) and cloud effective radius (CER). In this paper, we have carried out a feasibility study with the objective of cloud microphysics retrieval. For this, an inter-comparison of 15 globally available radiative transfer models (RTM) were carried out with the aim of generating a Look-up- Table (LUT). SBDART model was chosen for the simulations. The sensitivity of each spectral channel to different cloud properties was investigated. The inputs to the RT model were configured over our study region (50°S - 50°N and 20°E - 130°E) and a large number of simulations were carried out using random input vectors to generate the LUT. The determination of cloud optical thickness and cloud effective radius from spectral reflectance measurements constitutes the inverse problem and is typically solved by comparing the measured reflectances with entries in LUT and searching for the combination of COT and CER that gives the best fit. The products are available on the website www.mosdac.gov.in

  16. Improving estimates of aerosol radiative forcing through a particle-based aerosol microphysical scheme

    NASA Astrophysics Data System (ADS)

    Fierce, L.; McGraw, R. L.

    2016-12-01

    Forcing by atmospheric aerosols remains a large source of uncertainty in assessing human influences on the climate. Although global models have moved toward including more detailed representations of aerosol populations, aerosol microphysical schemes have been evaluated against benchmark models in only limited cases. Here we introduce a new framework for simulating atmospheric aerosols based on the Quadrature Method of Moments. This new aerosol model has been designed to reproduce key features of benchmark populations simulated by the particle-resolved model PartMC-MOSAIC, while tracking as little information about aerosol distributions as is necessary. The quadrature-based model simulates the aerosol evolution using a small number of weighted particles and is, therefore, decided as a reduced particle-based model. By applying principles of maximum entropy, the quadrature-based model efficiently reproduces distributions with respect to key aerosol properties, such as critical supersaturation for cloud condensation nuclei activation and optical cross sections, with high accuracy. In addition to providing an optimized aerosol model, the present study also describes how multi-scale modeling can be used as a tool for development of advanced aerosol microphysical schemes.

  17. Cirrus Clouds Optical, Microphysical and Radiative Properties Observed During Crystal-Face Experiment: I. A Radar-Lidar Retrieval System

    NASA Technical Reports Server (NTRS)

    Mitrescu, C.; Haynes, J. M.; Stephens, G. L.; Heymsfield, G. M.; McGill, M. J.

    2004-01-01

    A method of retrieving cloud microphysical properties using combined observations from both cloud radar and lidar is introduced. This retrieval makes use of an improvement to the traditional optimal estimation retrieval method, whereby a series of corrections are applied to the state vector during the search for an iterative solution. This allows faster convergence to a solution and is less processor intensive. The method is first applied to a synthetic cloud t o demonstrate its validity, and it is shown that the retrieval reliably reproduces vertical profiles of ice water content. The retrieval method is then applied to radar and lidar observations from the CRYSTAL-FACE experiment, and vertical profiles of ice crystal diameter, number concentration, and ice water content are retrieved for a cirrus cloud layers observed one day of that experiment. The validity of the relationship between visible extinction coefficient and radar reflectivity was examined. While synthetic tests showed such a functional relationship, the measured data only partially supported such a conclusion. This is due to errors in the forward model (as explained above) as well as errors in the data sets, including possible mismatch between lidar and radar profiles or errors in the optical depth. Empirical relationships between number concentrations and mean particle diameter were also examined. The results indicate that a distinct and robust relationship exists between these retrieved quantities and it is argued that such a relationship is more than an artifact of the retrieval process offering insight into the nature of the microphysical processes taking place in cirrus.

  18. Cirrus Clouds Optical, Microphysical and Radiative Properties Observed During Crystal-Face Experiment: I. A Radar-Lidar Retrieval System

    NASA Technical Reports Server (NTRS)

    Mitrescu, C.; Haynes, J. M.; Stephens, G. L.; Heymsfield, G. M.; McGill, M. J.

    2004-01-01

    A method of retrieving cloud microphysical properties using combined observations from both cloud radar and lidar is introduced. This retrieval makes use of an improvement to the traditional optimal estimation retrieval method, whereby a series of corrections are applied to the state vector during the search for an iterative solution. This allows faster convergence to a solution and is less processor intensive. The method is first applied to a synthetic cloud t o demonstrate its validity, and it is shown that the retrieval reliably reproduces vertical profiles of ice water content. The retrieval method is then applied to radar and lidar observations from the CRYSTAL-FACE experiment, and vertical profiles of ice crystal diameter, number concentration, and ice water content are retrieved for a cirrus cloud layers observed one day of that experiment. The validity of the relationship between visible extinction coefficient and radar reflectivity was examined. While synthetic tests showed such a functional relationship, the measured data only partially supported such a conclusion. This is due to errors in the forward model (as explained above) as well as errors in the data sets, including possible mismatch between lidar and radar profiles or errors in the optical depth. Empirical relationships between number concentrations and mean particle diameter were also examined. The results indicate that a distinct and robust relationship exists between these retrieved quantities and it is argued that such a relationship is more than an artifact of the retrieval process offering insight into the nature of the microphysical processes taking place in cirrus.

  19. Compute unified device architecture (CUDA)-based parallelization of WRF Kessler cloud microphysics scheme

    NASA Astrophysics Data System (ADS)

    Mielikainen, Jarno; Huang, Bormin; Wang, Jun; Allen Huang, H.-L.; Goldberg, Mitchell D.

    2013-03-01

    In recent years, graphics processing units (GPUs) have emerged as a low-cost, low-power and a very high performance alternative to conventional central processing units (CPUs). The latest GPUs offer a speedup of two-to-three orders of magnitude over CPU for various science and engineering applications. The Weather Research and Forecasting (WRF) model is the latest-generation numerical weather prediction model. It has been designed to serve both operational forecasting and atmospheric research needs. It proves useful for a broad spectrum of applications for domain scales ranging from meters to hundreds of kilometers. WRF computes an approximate solution to the differential equations which govern the air motion of the whole atmosphere. Kessler microphysics module in WRF is a simple warm cloud scheme that includes water vapor, cloud water and rain. Microphysics processes which are modeled are rain production, fall and evaporation. The accretion and auto-conversion of cloud water processes are also included along with the production of cloud water from condensation. In this paper, we develop an efficient WRF Kessler microphysics scheme which runs on Graphics Processing Units (GPUs) using the NVIDIA Compute Unified Device Architecture (CUDA). The GPU-based implementation of Kessler microphysics scheme achieves a significant speedup of 70× over its CPU based single-threaded counterpart. When a 4 GPU system is used, we achieve an overall speedup of 132× as compared to the single thread CPU version.

  20. FINAL REPORT: An Investigation of the Microphysical, Radiative, and Dynamical Properties of Mixed-Phase Clouds

    SciTech Connect

    Shupe, Matthew D

    2007-10-01

    This final report summarizes the major accomplishments and products resulting from a three-year grant funded by the DOE, Office of Science, Atmospheric Radiation Measurement Program titled: An Investigation of the Microphysical, Radiative, and Dynamical Properties of Mixed-Phase Clouds. Accomplishments are listed under the following subcategories: Mixed-phase cloud retrieval method development; Mixed-phase cloud characterization; ARM mixed-phase cloud retrieval review; and New ARM MICROBASE product. In addition, lists are provided of service to the Atmospheric Radiation Measurement Program, data products provided to the broader research community, and publications resulting from this grant.

  1. Deriving Arctic Cloud Microphysics at Barrow, Alaska. Algorithms, Results, and Radiative Closure

    SciTech Connect

    Shupe, Matthew D.; Turner, David D.; Zwink, Alexander; Thieman, Mandana M.; Mlawer, Eli J.; Shippert, Timothy

    2015-07-01

    Cloud phase and microphysical properties control the radiative effects of clouds in the climate system and are therefore crucial to characterize in a variety of conditions and locations. An Arctic-specific, ground-based, multi-sensor cloud retrieval system is described here and applied to two years of observations from Barrow, Alaska. Over these two years, clouds occurred 75% of the time, with cloud ice and liquid each occurring nearly 60% of the time. Liquid water occurred at least 25% of the time even in the winter, and existed up to heights of 8 km. The vertically integrated mass of liquid was typically larger than that of ice. While it is generally difficult to evaluate the overall uncertainty of a comprehensive cloud retrieval system of this type, radiative flux closure analyses were performed where flux calculations using the derived microphysical properties were compared to measurements at the surface and top-of-atmosphere. Radiative closure biases were generally smaller for cloudy scenes relative to clear skies, while the variability of flux closure results was only moderately larger than under clear skies. The best closure at the surface was obtained for liquid-containing clouds. Radiative closure results were compared to those based on a similar, yet simpler, cloud retrieval system. These comparisons demonstrated the importance of accurate cloud phase classification, and specifically the identification of liquid water, for determining radiative fluxes. Enhanced retrievals of liquid water path for thin clouds were also shown to improve radiative flux calculations.

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

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

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

  3. A microphysical pathway analysis to investigate aerosol effects on convective clouds

    NASA Astrophysics Data System (ADS)

    Heikenfeld, Max; White, Bethan; Labbouz, Laurent; Stier, Philip

    2017-04-01

    The impact of aerosols on ice- and mixed-phase processes in convective clouds remains highly uncertain, which has strong implications for estimates of the role of aerosol-cloud interactions in the climate system. The wide range of interacting microphysical processes are still poorly understood and generally not resolved in global climate models. To understand and visualise these processes and to conduct a detailed pathway analysis, we have added diagnostic output of all individual process rates for number and mass mixing ratios to two commonly-used cloud microphysics schemes (Thompson and Morrison) in WRF. This allows us to investigate the response of individual processes to changes in aerosol conditions and the propagation of perturbations throughout the development of convective clouds. Aerosol effects on cloud microphysics could strongly depend on the representation of these interactions in the model. We use different model complexities with regard to aerosol-cloud interactions ranging from simulations with different levels of fixed cloud droplet number concentration (CDNC) as a proxy for aerosol, to prognostic CDNC with fixed modal aerosol distributions. Furthermore, we have implemented the HAM aerosol model in WRF-chem to also perform simulations with a fully interactive aerosol scheme. We employ a hierarchy of simulation types to understand the evolution of cloud microphysical perturbations in atmospheric convection. Idealised supercell simulations are chosen to present and test the analysis methods for a strongly confined and well-studied case. We then extend the analysis to large case study simulations of tropical convection over the Amazon rainforest. For both cases we apply our analyses to individually tracked convective cells. Our results show the impact of model uncertainties on the understanding of aerosol-convection interactions and have implications for improving process representation in models.

  4. Microphysical Simulations of Polar Stratospheric Clouds Compared with Calipso and MLS Observations

    NASA Astrophysics Data System (ADS)

    Zhu, Y.; Toon, O. B.; Kinnison, D. E.; Lambert, A.; Brakebusch, M.

    2014-12-01

    Polar stratospheric clouds (PSCs) form in the lower stratosphere during the polar night due to the cold temperature inside the polar vortex. PSCs are important to understand because they are responsible for the formation of the Antarctic ozone hole and the ozone depletion over the Arctic. In this work, we explore the formation and evolution of STS particles (Super-cooled Ternary Solution) and NAT (Nitric-acid Trihydrate) particles using the SD-WACCM/CARMA model. SD-WACCM/CARMA couples the Whole Atmosphere Community Climate Model using Specific Dynamics with the microphysics model (CARMA). The 2010-2011 Arctic winter has been simulated because the Arctic vortex remained cold enough for PSCs from December until the end of March (Manney et al., 2011). The unusual length of this cold period and the presence of PSCs caused strong ozone depletion. This model simulates the growth and evaporation of the STS particles instead of considering them as being in equilibrium as other models do (Carslaw et al., 1995). This work also explores the homogeneous nucleation of NAT particles and derives a scheme for NAT formation based on the observed denitrification during the winter 2010-2011. The simulated microphysical features (particle volumes, size distributions, etc.) of both STS (Supercooled Ternary Solutions) and NAT particles show a consistent comparison with historical observations. The modeled evolution of PSCs and gas phase ozone related chemicals inside the vortex such as HCl and ClONO2 are compared with the observations from MLS, MIPAS and CALIPSO over this winter. The denitrification history indicate the surface nucleation rate from Tabazadeh et al. (2002) removes too much HNO3 over the winter. With a small modification of the free energy term of the equation, the denitification and the PSC backscattering features are much closer to the observations. H2O, HCl, O3 and ClONO2 are very close to MLS and MIPAS observations inside the vortex. The model underestimates ozone

  5. Retrieve Optically Thick Ice Cloud Microphysical Properties by Using Airborne Dual-Wavelength Radar Measurements

    NASA Technical Reports Server (NTRS)

    Wang, Zhien; Heymsfield, Gerald M.; Li, Lihua; Heymsfield, Andrew J.

    2005-01-01

    An algorithm to retrieve optically thick ice cloud microphysical property profiles is developed by using the GSFC 9.6 GHz ER-2 Doppler Radar (EDOP) and the 94 GHz Cloud Radar System (CRS) measurements aboard the high-altitude ER-2 aircraft. In situ size distribution and total water content data from the CRYSTAL-FACE field campaign are used for the algorithm development. To reduce uncertainty in calculated radar reflectivity factors (Ze) at these wavelengths, coincident radar measurements and size distribution data are used to guide the selection of mass-length relationships and to deal with the density and non-spherical effects of ice crystals on the Ze calculations. The algorithm is able to retrieve microphysical property profiles of optically thick ice clouds, such as, deep convective and anvil clouds, which are very challenging for single frequency radar and lidar. Examples of retrieved microphysical properties for a deep convective clouds are presented, which show that EDOP and CRS measurements provide rich information to study cloud structure and evolution. Good agreement between IWPs derived from an independent submillimeter-wave radiometer, CoSSIR, and dual-wavelength radar measurements indicates accuracy of the IWC retrieved from the two-frequency radar algorithm.

  6. Sensitivity Study of Cloud Cover and Ozone Modeling to Microphysics Parameterization

    NASA Astrophysics Data System (ADS)

    Wałaszek, Kinga; Kryza, Maciej; Szymanowski, Mariusz; Werner, Małgorzata; Ojrzyńska, Hanna

    2017-02-01

    Cloud cover is a significant meteorological parameter influencing the amount of solar radiation reaching the ground surface, and therefore affecting the formation of photochemical pollutants, most of all tropospheric ozone (O3). Because cloud amount and type in meteorological models are resolved by microphysics schemes, adjusting this parameterization is a major factor determining the accuracy of the results. However, verification of cloud cover simulations based on surface data is difficult and yields significant errors. Current meteorological satellite programs provide many high-resolution cloud products, which can be used to verify numerical models. In this study, the Weather Research and Forecasting model (WRF) has been applied for the area of Poland for an episode of June 17th-July 4th, 2008, when high ground-level ozone concentrations were observed. Four simulations were performed, each with a different microphysics parameterization: Purdue Lin, Eta Ferrier, WRF Single-Moment 6-class, and Morrison Double-Moment scheme. The results were then evaluated based on cloud mask satellite images derived from SEVIRI data. Meteorological variables and O3 concentrations were also evaluated. The results show that the simulation using Morrison Double-Moment microphysics provides the most and Purdue Lin the least accurate information on cloud cover and surface meteorological variables for the selected high ozone episode. Those two configurations were used for WRF-Chem runs, which showed significantly higher O3 concentrations and better model-measurements agreement of the latter.

  7. The Influence of Thermodynamic Phase on the Retrieval of Mixed-Phase Cloud Microphysical and Optical Properties in the Visible and Near Infrared Region

    NASA Technical Reports Server (NTRS)

    Lee, Joonsuk; Yang, Ping; Dessler, Andrew E.; Baum, Bryan A.; Platnick, Steven

    2005-01-01

    Cloud microphysical and optical properties are inferred from the bidirectional reflectances simulated for a single-layered cloud consisting of an external mixture of ice particles and liquid droplets. The reflectances are calculated with a rigorous discrete ordinates radiative transfer model and are functions of the cloud effective particle size, the cloud optical thickness, and the values of the ice fraction in the cloud (i.e., the ratio of ice water content to total water content). In the present light scattering and radiative transfer simulations, the ice fraction is assumed to be vertically homogeneous; the habit (shape) percentage as a function of ice particle size is consistent with that used for the Moderate Resolution Imaging Spectroradiometer (MODIS) operational (Collection 4 and earlier) cloud products; and the surface is assumed to be Lambertian with an albedo of 0.03. Furthermore, error analyses pertaining to the inference of the effective particle sizes and optical thicknesses of mixed-phase clouds are performed. Errors are calculated with respect to the assumption of a cloud containing solely liquid or ice phase particles. The analyses suggest that the effective particle size inferred for a mixed-phase cloud can be underestimated (or overestimated) if pure liquid phase (or pure ice phase) is assumed for the cloud, whereas the corresponding cloud optical thickness can be overestimated (or underestimated).

  8. Sensitivity of Cloud Microphysics to Choice of Physics Parameterizations : a Crm Study

    NASA Astrophysics Data System (ADS)

    Sarangi, C.; Tripathi, S. N.

    2013-12-01

    Weather Research and Forecasting regional meteorological model coupled with chemistry (WRF-Chem) is being used widely to study direct and indirect effect of aerosols. The results of a numerical study on the impacts of aerosols on meteorology and microphysics depend on the accuracy with which the model parameterizes any weather conditions. This study investigates the sensitivity of simulated hydrometeors at 3 km resolution over Northern India, to different types of microphysics parameterizations, such as ETA microphysics (only warm rain processes are parameterized), LIN microphysics (single moment including ice processes) and Morrison microphysics (double moment including ice processes) and planetary boundary layer parameterizations (Yonsei and MYJ). WRF's ability to simulate the vertical and horizontal distribution of hydrometeors using cloud resolving mode is evaluated using in-situ aircraft measurements of hydrometeors during CAIPEEX campaign and cloud products from MODIS satellite. The results suggest that the model underestimates the mass concentration of hydrometeors, but can reasonably simulate the distribution of hydrometeors at most places, except a few places where the hydrometeors are modeled simulated at higher altitude than observed. Ongoing work includes aerosol impact on these simulated hydrometeors distribution.

  9. Ten Years of Cloud Optical and Microphysical Retrievals from MODIS

    NASA Technical Reports Server (NTRS)

    Platnick, Steven; King, Michael D.; Wind, Galina; Hubanks, Paul; Arnold, G. Thomas; Amarasinghe, Nandana

    2010-01-01

    The MODIS cloud optical properties algorithm (MOD06/MYD06 for Terra and Aqua MODIS, respectively) has undergone extensive improvements and enhancements since the launch of Terra. These changes have included: improvements in the cloud thermodynamic phase algorithm; substantial changes in the ice cloud light scattering look up tables (LUTs); a clear-sky restoral algorithm for flagging heavy aerosol and sunglint; greatly improved spectral surface albedo maps, including the spectral albedo of snow by ecosystem; inclusion of pixel-level uncertainty estimates for cloud optical thickness, effective radius, and water path derived for three error sources that includes the sensitivity of the retrievals to solar and viewing geometries. To improve overall retrieval quality, we have also implemented cloud edge removal and partly cloudy detection (using MOD35 cloud mask 250m tests), added a supplementary cloud optical thickness and effective radius algorithm over snow and sea ice surfaces and over the ocean, which enables comparison with the "standard" 2.1 11m effective radius retrieval, and added a multi-layer cloud detection algorithm. We will discuss the status of the MOD06 algorithm and show examples of pixellevel (Level-2) cloud retrievals for selected data granules, as well as gridded (Level-3) statistics, notably monthly means and histograms (lD and 2D, with the latter giving correlations between cloud optical thickness and effective radius, and other cloud product pairs).

  10. Ten Years of Cloud Optical and Microphysical Retrievals from MODIS

    NASA Technical Reports Server (NTRS)

    Platnick, Steven; King, Michael D.; Wind, Galina; Hubanks, Paul; Arnold, G. Thomas; Amarasinghe, Nandana

    2010-01-01

    The MODIS cloud optical properties algorithm (MOD06/MYD06 for Terra and Aqua MODIS, respectively) has undergone extensive improvements and enhancements since the launch of Terra. These changes have included: improvements in the cloud thermodynamic phase algorithm; substantial changes in the ice cloud light scattering look up tables (LUTs); a clear-sky restoral algorithm for flagging heavy aerosol and sunglint; greatly improved spectral surface albedo maps, including the spectral albedo of snow by ecosystem; inclusion of pixel-level uncertainty estimates for cloud optical thickness, effective radius, and water path derived for three error sources that includes the sensitivity of the retrievals to solar and viewing geometries. To improve overall retrieval quality, we have also implemented cloud edge removal and partly cloudy detection (using MOD35 cloud mask 250m tests), added a supplementary cloud optical thickness and effective radius algorithm over snow and sea ice surfaces and over the ocean, which enables comparison with the "standard" 2.1 11m effective radius retrieval, and added a multi-layer cloud detection algorithm. We will discuss the status of the MOD06 algorithm and show examples of pixellevel (Level-2) cloud retrievals for selected data granules, as well as gridded (Level-3) statistics, notably monthly means and histograms (lD and 2D, with the latter giving correlations between cloud optical thickness and effective radius, and other cloud product pairs).

  11. Microphysical Characteristics of Clouds During the TRMM Field Campaign

    NASA Technical Reports Server (NTRS)

    Stith, Jeffrey L.

    2003-01-01

    Further analysis of the TRMM field campaign data was conducted to examine the growth of precipitation in updraft regions of the TRMM field campaign tropical clouds and to extend the earlier results to cover the whole TRMM data set collected by the University of North Dakota (UND). The results have been submitted for publication. In this paper, composite vertical profiles of liquid water, small particle concentration, and updraft/downdraft magnitudes were presented from each of the campaigns. They exhibited similar peak values for the two TRMM regions of LBA and Kwajalein. Updrafts were found to be favored locations for precipitation embryos in the form of liquid or frozen drizzle-sized droplets. Although liquid water concentrations decreased to undetectable levels between -5 and -18 C in most glaciating updrafts, occasional traces of liquid water were found in updrafts at colder temperatures, probably due to the persistence of liquid drizzle droplets. The updraft magnitudes where the traces of liquid water were observed at cold temperatures do not appear to be stronger than updrafts without liquid water at similar temperatures, however.

  12. Microphysical Characteristics of Clouds During the TRMM Field Campaign

    NASA Technical Reports Server (NTRS)

    Stith, Jeffrey L.

    2003-01-01

    Further analysis of the TRMM field campaign data was conducted to examine the growth of precipitation in updraft regions of the TRMM field campaign tropical clouds and to extend the earlier results to cover the whole TRMM data set collected by the University of North Dakota (UND). The results have been submitted for publication. In this paper, composite vertical profiles of liquid water, small particle concentration, and updraft/downdraft magnitudes were presented from each of the campaigns. They exhibited similar peak values for the two TRMM regions of LBA and Kwajalein. Updrafts were found to be favored locations for precipitation embryos in the form of liquid or frozen drizzle-sized droplets. Although liquid water concentrations decreased to undetectable levels between -5 and -18 C in most glaciating updrafts, occasional traces of liquid water were found in updrafts at colder temperatures, probably due to the persistence of liquid drizzle droplets. The updraft magnitudes where the traces of liquid water were observed at cold temperatures do not appear to be stronger than updrafts without liquid water at similar temperatures, however.

  13. Parameterizations of the Vertical Variability of Tropical Cirrus Cloud Microphysical and Optical Properties

    NASA Technical Reports Server (NTRS)

    Twohy, Cynthia; Heymsfield, Andrew; Gerber, Hermann

    2005-01-01

    Our multi-investigator effort was targeted at the following areas of interest to CRYSTAL-FACE: (1) the water budgets of anvils, (2) parameterizations of the particle size distributions and related microphysical and optical properties (3) characterizations of the primary ice particle habits, (4) the relationship of the optical properties to the microphysics and particle habits, and (5) investigation of the ice-nuclei types and mechanisms in anvil cirrus. Dr. Twohy's effort focused on (l), (2), and (5), with the measurement and analysis of ice water content and cirrus residual nuclei using the counterflow virtual impactor (CVI).

  14. Development of Theoretical Models and Analyses of the Micro-Physics of Cloud and Precipitation Systems.

    DTIC Science & Technology

    1983-05-31

    AND ANALYSES OF THE MICRO-PHYSICS OF CLOUD AND PRECIPITATION SYSTEMS I C LAWRENCE E. BELSKY FREDRICK B. KAPLAN * f JAMES P. LALLY D. KEITH ROBERTS...NUMBER(S) Lawrence E. Belsky Peter Miller Fredrick B. Kaplan John FoleyF19628-81-C-0141 James P.Lally Ter nne F ITo nl 9. PERFORMING ORGANIZATION NAME...THEORETICAL MODELS AND ANALYSES OF THE 213 MICRO-PHYSICS OF CL..(Ii) DIGITAL PROGRAMMING SERVICES INC WALTHAM MA L E BELSKY ET AL. 31 MAY 83 NCASIFIED AFGL-TR

  15. Effects of 1D and 3D Thermal Radiation on Cloud Dynamics and Microphysics

    NASA Astrophysics Data System (ADS)

    Klinger, C.; Mayer, B. C.; Jakub, F.; Zinner, T.

    2016-12-01

    Radiation is a key driver for the development of clouds. Solar radiation heats the surface and causes updrafts to rise, thus initializing cloud formation. In the very moment that a cloud forms, absorption and emission of thermal radiation at the cloud itself cause heating and cooling rates of several hundred K/d at the interface between cloud and cloudless sky. The magnitude of the cooling rates, compared to the commonly known clear sky cooling of 1-2 K/d, can alter cloud dynamics and microphysics and thus cloud development or lifetime. In cloud resolving numerical simulations, radiation is, if considered at all, usually applied as a 1D approximation, omitting horizontal transport of radiation through the modeling domain. However, it is obvious that radiation is a three dimensional problem. Applying 3D radiative transfer in cloud resolving simulations causes, in addition to cloud top cooling and cloud bottom warming, an additional cooling at cloud sides which is completely neglected by common 1D radiative transfer solutions. Here, we examine the effects of 1D and 3D thermal radiative transfer in cloud resolving simulation, by applying the newly developed "Neighboring Column Approximation" (NCA) - a fast 3D approximation for thermal radiative transfer in cloud resolving simulations. The NCA accurately represents 3D effects at moderate computational cost which make it an ideal tool to explore how 1D and 3D radiative transfer modify cloud development in numerical models. Thermal radiation can modify clouds in terms of cloud lifetime, cloud size and cloud circulation. These effects on cloud development will be analyzed in a set of cumulus cloud simulations.

  16. An investigation of the effect of sulfate on cloud microphysics using a chemistry/transport model

    SciTech Connect

    Wei, H.D.; Green, R.; Schwartz, S.E.; Benkovitz, C.M.

    2001-01-14

    Here the authors have used the output of a chemistry/transport model to identify a situation in which sulfate aerosol from industrial sources may be expected to exert a strong influence on cloud microphysical and radiative properties in an oceanic area that is well displaced from source regions. Pertinent cloud microphysical properties (optical depth and cloud drop radius) are inferred from radiance data obtained from satellite remote sensing. Comparison of these quantities in situations where the model indicates the presence or absence of industrial sulfate has allowed identification of the expected signature of one aerosol indirect effect--an increase in droplet number concentration and concomitant decrease in droplet radii, on a synoptic scale. Although the information obtained on changes in cloud optical depth is too meager to draw conclusions regarding radiative forcing, there is no doubt that the cloud microphysical properties are influenced by the incursion of continental sulfate aerosol in a way that is consistent with that expected by the Twomey indirect forcing mechanism.

  17. Particle cloud mixing in microgravity

    NASA Technical Reports Server (NTRS)

    Ross, H.; Facca, L.; Tangirala, V.; Berlad, A. L.

    1989-01-01

    Quasi-steady flame propagation through clouds of combustible particles requires quasi-steady transport properties and quasi-steady particle number density. Microgravity conditions may be employed to help achieve the conditions of quiescent, uniform clouds needed for such combustion studies. Joint experimental and theoretical NASA-UCSD studies were concerned with the use of acoustic, electrostatic, and other methods of dispersion of fuel particulates. Results of these studies are presented for particle clouds in long cylindrical tubes.

  18. A numerical study of aerosol effects on the dynamics and microphysics of a deep convective cloud in a continental environment

    NASA Astrophysics Data System (ADS)

    Cui, Zhiqiang; Carslaw, Kenneth S.; Yin, Yan; Davies, Stewart

    2006-03-01

    The effects of aerosols on a deep convective cloud in a midlatitude continental environment are studied using an axisymmetric cloud model with a sectional treatment of aerosol and hydrometeor microphysical processes. Simulations are conducted using observations from the Cooperative Convective Precipitation Experiments (CCOPE). The isolated cloud occurred in an environment with low wind shear and with relatively dry air in the midtroposphere and upper troposphere. By varying the concentration of aerosol particles in the accumulation mode within realistic limits for a continental environment, the simulated cloud exhibited different properties. The overall impact as the aerosol concentration increased is that (1) the cloud development was inhibited; (2) the precipitation was suppressed; (3) the maximum values of liquid water content decreased, but the maximum values of droplet number concentration increased before the dissipating stage; (4) a clear tendency was found for ice crystals to be larger and less numerous in the anvil cloud; and (5) there was a significant reduction of the inflow in the lower 2 km of the atmosphere. In the relatively dry environment in the midtroposphere, the latent heat changes associated with the Wegener-Bergeron-Findeisen mechanism played an important role in the upper part of the cloud at altitudes below the homogeneous freezing level. In particular, immersion freezing and latent heat release were much more rapid in the base simulation than in the increased aerosol simulation. Less latent heat release and insufficient inflow together impeded the development of the cloud with the higher aerosol loading. Our simulations suggest that continental clouds existing below the homogeneous freezing level could show an opposite response of cloud top height and anvil crystal concentrations to changes in aerosol to what has previously been reported for clouds ascending to higher levels.

  19. Use of microphysical relationships to discern growth/decay mechanisms of cloud droplets with focus on Z-LWC relationships.

    SciTech Connect

    Liu,Y.; Daum, P.H.; Yum, S.S.; Wang, J.

    2008-05-01

    Cloud droplet size distributions hence the key microphysical quantities (e.g., radar reflectivity, droplet concentration, liquid water content, relative dispersion, and mean-volume radius) are determined by different physical mechanisms, including pre-cloud aerosols as CCNs, cloud updraft, and various turbulent entrainment-mixing processes. Therefore, different relationships among these microphysical properties are expected in response to these various mechanisms. The effect of turbulent entrainment-mixing processes is particularly vexing, with different entrainment-mixing processes likely leading to different microphysical relationships. Cloud radar has been widely used to infer the cloud liquid water content (L) from the measurement of radar reflectivity (Z) using a Z-L relationship. Existing Z-L expressions have been often obtained empirically, and differ substantially (Khain et al. 2008). The discrepancy among Z-L relations, which has been hindering the application of cloud radar in measuring cloud properties, likely stems from the different relationships between the relevant microphysical properties caused by different physical processes. This study first analyzes the Z-L relationship theoretically, and identify the key microphysical properties that affect this relationship, and then address the effects of various processes on the Z-L relationship by discerning the characteristics of the relationships between the relative dispersion, droplet concentration, liquid water content, and mean-volume radius calculated from in-situ measurements of cloud droplet size distributions. Effort is also made to further relate the microphysical relationships to physical processes such as turbulent entrainment-mixing.

  20. MLS and CALIOP Cloud Ice Measurements in the Upper Troposphere: A Constraint from Microwave on Cloud Microphysics

    NASA Technical Reports Server (NTRS)

    Wu, Dong L.; Lambert, Alyn; Read, William G.; Eriksson, Patrick; Gong, Jie

    2014-01-01

    This study examines the consistency and microphysics assumptions among satellite ice water content (IWC) retrievals in the upper troposphere with collocated A-Train radiances from Microwave Limb Sounder (MLS) and lidar backscatters from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). For the cases in which IWC values are small (less than 10mg m(exp-23)), the cloud ice retrievals are constrained by both MLS 240- and 640- GHz radiances and CALIOP 532-nm backscatter beta(532). From the observed relationships between MLS cloud-induced radiance T(sub cir) and the CALIOP backscatter integrated gamma532 along the MLS line of sight, an empirical linear relation between cloud ice and the lidar backscatter is found: IWC/beta532=0.58+/-0.11. This lidar cloud ice relation is required to satisfy the cloud ice emission signals simultaneously observed at microwave frequencies, in which ice permittivity is relatively well known. This empirical relationship also produces IWC values that agree well with the CALIOP, version 3.0, retrieval at values, less than 10mg m(exp-3). Because the microphysics assumption is critical in satellite cloud ice retrievals, the agreement found in the IWC-beta532 relationships increase fidelity of the assumptions used by the lidar and microwave techniques for upper-tropospheric clouds.

  1. Laboratory study of microphysical and scattering properties of corona-producing cirrus clouds.

    PubMed

    Järvinen, E; Vochezer, P; Möhler, O; Schnaiter, M

    2014-11-01

    Corona-producing cirrus clouds were generated and measured under chamber conditions at the AIDA cloud chamber in Karlsruhe. We were able to measure the scattering properties as well as microphysical properties of these clouds under well-defined laboratory conditions in contrast with previous studies of corona-producing clouds, where the measurements were conducted by means of lidar and in situ aircraft measurements. Our results are in agreement with those of previous studies, confirming that corona-producing cirrus clouds consist of a narrow distribution of small (median Dp=19-32  μm) and compact ice crystals. We showed that the ice crystals in these clouds are most likely formed in homogeneous freezing processes. As a result of the homogeneous freezing process, the ice crystals grow uniformly in size; furthermore, the majority of the ice crystals have rough surface features.

  2. Observations of Particle Size and Phase in Tropical Cyclones: Implications for Mesoscale Modeling of Microphysical Processes.

    NASA Astrophysics Data System (ADS)

    McFarquhar, Greg M.; Black, Robert A.

    2004-02-01

    Mesoscale model simulations of tropical cyclones are sensitive to representations of microphysical processes, such as fall velocities of frozen hydrometeors. The majority of microphysical parameterizations are based on observations obtained in clouds not associated with tropical cyclones, and hence their suitability for use in simulations of tropical cyclones is not known. Here, representations of mass-weighted fall speed Vm for snow and graupel are examined to show that parameters describing the exponential size distributions and fall speeds of individual hydrometeors [through use of relations such as V(D) = aDb] are identically important for determining Vm. The a and b coefficients are determined by the composition and shape of snow and graupel particles; past modeling studies have not adequately considered the possible spread of a and b values. Step variations in these coefficients, associated with different fall velocity regimes, however, do not have a large impact on Vm for observed size distributions in tropical cyclones and the values of a and b used here, provided that coefficients are chosen in accordance with the sizes where the majority of mass occurs. New parameterizations for Vm are developed such that there are no inconsistencies between the diameters used to define the mass, number concentration, and fall speeds of individual hydrometeors. Effects due to previous inconsistencies in defined diameters on mass conversion rates between different hydrometeor classes (e.g., snow, graupel, cloud ice) are shown to be significant.In situ microphysical data obtained in Hurricane Norbert (1984) and Hurricane Emily (1987) with two-dimensional cloud and precipitation probes are examined to determine typical size distributions of snow and graupel particles near the melting layer. Although well represented by exponential functions, there are substantial differences in how the intercept and slope of these distributions vary with mass content when compared to

  3. Aerosol Impacts on Clouds and Precipitation in Eastern China: Results from Bin and Bulk Microphysics

    SciTech Connect

    Fan, Jiwen; Leung, Lai-Yung R.; Li, Zhanqing; Morrison, H.; Chen, Hongbin; Zhou, Yuquan; Qian, Yun; Wang, Yuan

    2012-01-19

    Using the Weather Research and Forecasting (WRF) model coupled with a 3 spectral-bin microphysics ('SBM') and measurements from the Atmospheric Radiation 4 Measurement (ARM) Mobile Facility field campaign in China (AMF-China), the authors 5 examine aerosol indirect effects (AIE) in the typical cloud regimes of the warm and cold 6 seasons in Southeast China: deep convective clouds (DCC) and stratus clouds (SC), 7 respectively. Comparisons with a two-moment bulk microphysics ('Bulk') are performed 8 to gain insights for improving bulk schemes in estimating AIE in weather and climate 9 simulations. For the first time, measurements of aerosol and cloud properties acquired in 10 China are used to evaluate model simulations to better understand AIE in China. It is 11 found that changes in cloud condensation nuclei (CCN) concentration significantly 12 change the timing of storms, the spatial and temporal distributions of precipitation, the 13 frequency distribution of precipitation rate, as well as cloud base and top heights for the 14 DCC, but not for the SC. CCN increase cloud droplet number (Nc) and mass 15 concentrations, decrease raindrop number concentration (Nr), and delay the onset of 16 precipitation. It is indicated much higher Nc and the opposite CCN effects on convection 17 and heavy rain with Bulk compared to SBM stem from the fixed CCN prescribed in Bulk. 18 CCN have a significant effect on ice microphysical properties with SBM but not Bulk 19 and different condensation/deposition freezing parameterizations employed could be the 20 main reason. This study provided insights to further improve the bulk scheme to better 21 account for aerosol-cloud interactions in regional and global climate simulations, which 22 will be the focus for a follow-on paper.

  4. Aerosol impacts on radiative and microphysical properties of clouds and precipitation formation

    NASA Astrophysics Data System (ADS)

    Alizadeh-Choobari, O.; Gharaylou, M.

    2017-03-01

    Through modifying the number concentration and size of cloud droplets, aerosols have intricate impacts on radiative and microphysical properties of clouds, which together influence precipitation processes. Aerosol-cloud interactions for a mid-latitude convective cloud system are investigated using a two-moment aerosol-aware bulk microphysical scheme implemented into the Weather Research and Forecasting (WRF) model. Three sensitivity experiments with initial identical dynamic and thermodynamic conditions, but different cloud-nucleating aerosol concentrations were conducted. Increased aerosol number concentration has resulted in more numerous cloud droplets of overall smaller sizes, through which the optical properties of clouds have been changed. While the shortwave cloud forcing is significantly increased in more polluted experiments, changes in the aerosol number concentration have negligible impacts on the longwave cloud forcing. For the first time, it is found that polluted clouds have higher cloud base heights, the feature that is caused by more surface cooling due to a higher shortwave cloud forcing, as well as a drier boundary layer in the polluted experiment compared to the clean. The polluted experiment was also associated with a higher liquid water content (LWC), caused by an increase in the number of condensation of water vapor due to higher concentration of hygroscopic aerosols acting as condensation nuclei. The domain-averaged accumulated precipitation is little changed under both polluted and clean atmosphere. Nevertheless, changes in the rate of precipitation are identified, such that under polluted atmosphere light rain is reduced, while both moderate and heavy rain are intensified, confirming the fact that if an ample influx of water vapor exists, an increment of hygroscopic aerosols can increase the amount of precipitation.

  5. Microphysical characterization of winter cloud systems during a research flight campaign

    NASA Astrophysics Data System (ADS)

    Fernández-González, Sergio; Sánchez, José Luis; Valero, Francisco; Gascón, Estíbaliz; Merino, Andrés; Hermida, Lucía; López, Laura; Marcos, José Luis; García-Ortega, Eduardo

    2015-04-01

    The lack of accuracy in the knowledge of cloud microphysics leads to aviation risks, which have caused numerous crashes, mainly owing to aircraft icing (e.g., an EMB-120 crashed in Detroit, Michigan in 1997, and an ATR-72 crashed near Roselawn, Indiana in 1994). Further, this lack is a source of uncertainty in numerical weather forecasting models, since commonly used parameterizations often overestimate ice water content and underestimate supercooled liquid water. This makes the collection of data on cloud microphysical characteristics very useful toward improving the forecasting of icing conditions. Ten research flights were conducted during the winters of 2011/12 and 2012/13. Their goal was to determine dominant microphysical conditions of winter cloud systems traversing the Guadarrama Mountains in the central Iberian Peninsula. The aircraft was a C-212-200, equipped with a Cloud, Aerosol, and Precipitation Spectrometer (CAPS) under the left wing. Data of temperature and Liquid Water Content (LWC), registered by the CAPS probe, were used in the study. Furthermore, we thoroughly analyzed images taken by a Cloud Imaging Probe Grayscale (CIP-GS), capable of measuring hydrometeors between 25 and 1,550 µm in size, and representing them in a 2D image. The various types of hydrometeors observed during these flights are described, along with microphysical processes inferred from the CIP-GS images. ACKNOWLEDGEMENTS S. Fernández-González acknowledges grant support from the FPU program (AP 2010-2093). This study was also supported by grants from GRANIMETRO (CGL2010-15930) and MICROMETEO (IPT-310000-2010-22). The authors thank INTA for the research flights.

  6. The Dependence on Grid Resolution of Numerically Simulated Convective Cloud Systems Using Ice Microphysics

    NASA Technical Reports Server (NTRS)

    Braun, Scott A.; Tao, Wei-Kuo; Lang, Stephen E.; Ferrier, Bradley S.

    1999-01-01

    Mesoscale research and forecast models are increasingly being used at horizontal resolutions of 1-8 km to simulate a variety of precipitating systems. When the model is used to simulate convective systems, it is uncertain to what extent the dynamics and microphysics of convective updrafts can be resolved with grids larger than 1 km. In this study, two- and three-dimensional versions of the Goddard Cumulus Ensemble model are used to determine the impact of horizontal grid resolution on the behavior of the simulated storms and on the characteristics of the cloud microphysical fields. It will be shown that as resolution decreases from about 1 km to greater than 3 km, there is a fairly rapid degradation of the storm structure in the form of reduced convective mass fluxes, updraft tilts, and cloud microphysics. A high-resolution simulation of hurricane outer rainbands using the MM5 mesoscale model shows also that there can be a substantial modification of the key microphysical processes that contribute to rainfall as a result of reducing the horizontal resolution.

  7. Meteoric smoke particles; a model study of microphysical properties and global distribution

    NASA Astrophysics Data System (ADS)

    Megner, L.; Rapp, M.; Siskind, D.; Gumbel, J.

    2005-12-01

    Meteoric material reaching the Earth ablates in the 80-100 km region and is believed to be the major source of so-called "smoke particles". These are thought to play a major role in a host of atmospheric phenomena such as noctilucent clouds, polar mesosphere summer echoes, metal atom layers, and heterogeneous chemistry controlling key atmospheric species such as water vapour. Despite their obvious scientific importance, only little is known about their actual properties. Motivated by the recent first experimental proof of the existence of these particles in the course of the MAGIC project (MAGIC = Mesospheric Aerosol: Genesis, Interaction and Composition), we here present a systematic model study of the properties of mesospheric smoke particles. We investigate the sensitivity of particle properties and their spatial distribution on parameters such as the magnitude of the meteoric influx, microphysical parameters controlling particle coagulation, and vertical transport. The study is carried out using the 1D CARMA model (CARMA = Community Aerosol and radiation Model for Atmospheres). Current work involves combining the CARMA model with a 2D chemical transport model (CHEM2D) to study transport of smoke particles by the meridional circulation. The global smoke distribution is particulary interesting in the light of recent experimental findings. Preliminary results from this work will also be presented"

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

    NASA Astrophysics Data System (ADS)

    Young, Gillian; Jones, Hazel M.; Crosier, Jonathan; Bower, Keith N.; Darbyshire, Eoghan; Taylor, Jonathan W.; Liu, Dantong; Allan, James D.; Williams, Paul I.; Gallagher, Martin W.; Choularton, Thomas W.

    2016-04-01

    The Arctic sea-ice is intricately coupled to the atmosphere[1]. The decreasing sea-ice extent with the changing climate raises questions about how Arctic cloud structure will respond. Any effort to answer these questions is hindered by the scarcity of atmospheric observations in this region. Comprehensive cloud and aerosol measurements could allow for an improved understanding of the relationship between surface conditions and cloud structure; knowledge which could be key in validating weather model forecasts. Previous studies[2] have shown via remote sensing that cloudiness increases over the marginal ice zone (MIZ) and ocean with comparison to the sea-ice; however, to our knowledge, detailed in-situ data of this transition have not been previously presented. In 2013, the Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign was carried out in the vicinity of Svalbard, Norway to collect in-situ observations of the Arctic atmosphere and investigate this issue. Fitted with a suite of remote sensing, cloud and aerosol instrumentation, the FAAM BAe-146 aircraft was used during the spring segment of the campaign (Mar-Apr 2013). One case study (23rd Mar 2013) produced excellent coverage of the atmospheric changes when transitioning from sea-ice, through the MIZ, to the open ocean. Clear microphysical changes were observed, with the cloud liquid-water content increasing by almost four times over the transition. Cloud base, depth and droplet number also increased, whilst ice number concentrations decreased slightly. The surface warmed by ~13 K from sea-ice to ocean, with minor differences in aerosol particle number (of sizes corresponding to Cloud Condensation Nuclei or Ice Nucleating Particles) observed, suggesting that the primary driver of these microphysical changes was the increased heat fluxes and induced turbulence from the warm ocean surface as expected. References: [1] Kapsch, M.L., Graversen, R.G. and Tjernström, M. Springtime

  9. The Operational MODIS Cloud Optical and Microphysical Property Product: Overview of the Collection 6 Algorithm and Preliminary Results

    NASA Technical Reports Server (NTRS)

    Platnick, Steven; King, Michael D.; Wind, Galina; Amarasinghe, Nandana; Marchant, Benjamin; Arnold, G. Thomas

    2012-01-01

    Operational Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals of cloud optical and microphysical properties (part of the archived products MOD06 and MYD06, for MODIS Terra and Aqua, respectively) are currently being reprocessed along with other MODIS Atmosphere Team products. The latest "Collection 6" processing stream, which is expected to begin production by summer 2012, includes updates to the previous cloud retrieval algorithm along with new capabilities. The 1 km retrievals, based on well-known solar reflectance techniques, include cloud optical thickness, effective particle radius, and water path, as well as thermodynamic phase derived from a combination of solar and infrared tests. Being both global and of high spatial resolution requires an algorithm that is computationally efficient and can perform over all surface types. Collection 6 additions and enhancements include: (i) absolute effective particle radius retrievals derived separately from the 1.6 and 3.7 !-lm bands (instead of differences relative to the standard 2.1 !-lm retrieval), (ii) comprehensive look-up tables for cloud reflectance and emissivity (no asymptotic theory) with a wind-speed interpolated Cox-Munk BRDF for ocean surfaces, (iii) retrievals for both liquid water and ice phases for each pixel, and a subsequent determination of the phase based, in part, on effective radius retrieval outcomes for the two phases, (iv) new ice cloud radiative models using roughened particles with a specified habit, (v) updated spatially-complete global spectral surface albedo maps derived from MODIS Collection 5, (vi) enhanced pixel-level uncertainty calculations incorporating additional radiative error sources including the MODIS L1 B uncertainty index for assessing band and scene-dependent radiometric uncertainties, (v) and use of a new 1 km cloud top pressure/temperature algorithm (also part of MOD06) for atmospheric corrections and low cloud non-unity emissivity temperature adjustments.

  10. Double-moment cloud microphysics scheme for the deep convection parameterization in the GFDL AM3

    NASA Astrophysics Data System (ADS)

    Belochitski, A.; Donner, L.

    2014-12-01

    A double-moment cloud microphysical scheme originally developed by Morrision and Gettelman (2008) for the stratiform clouds and later adopted for the deep convection by Song and Zhang (2011) has been implemented in to the Geophysical Fluid Dynamics Laboratory's atmospheric general circulation model AM3. The scheme treats cloud drop, cloud ice, rain, and snow number concentrations and mixing ratios as diagnostic variables and incorporates processes of autoconversion, self-collection, collection between hydrometeor species, sedimentation, ice nucleation, drop activation, homogeneous and heterogeneous freezing, and the Bergeron-Findeisen process. Such detailed representation of microphysical processes makes the scheme suitable for studying the interactions between aerosols and convection, as well as aerosols' indirect effects on clouds and their roles in climate change. The scheme is first tested in the single column version of the GFDL AM3 using forcing data obtained at the U.S. Department of Energy Atmospheric Radiation Measurment project's Southern Great Planes site. Scheme's impact on SCM simulations is discussed. As the next step, runs of the full atmospheric GCM incorporating the new parameterization are compared to the unmodified version of GFDL AM3. Global climatological fields and their variability are contrasted with those of the original version of the GCM. Impact on cloud radiative forcing and climate sensitivity is investigated.

  11. Cirrus cloud radiative forcing at the top of atmosphere using the nighttime global distribution with the microphysical parameters derived from AVHRR

    NASA Astrophysics Data System (ADS)

    Katagiri, Shuichiro; Sekiguchi, Miho; Hayasaka, Tadahiro; Nakajima, Teruyuki

    2013-05-01

    The radiative effect of cirrus clouds is particularly ambiguous in the climate research. We calculated the global cirrus cloud radiative forcing (CRFci) distributions at the top of the atmosphere (TOA) using the cloud microphysical parameters of effective radius (Re), optical thickness (COT) and the cloud top temperature (CTT) derived from AVHRR nighttime data. The results indicate that cirrus clouds warm the atmosphere, and in particular produce a large warming effect in the tropics. We also computed the dependence of radiative forcing on the effective radius of cloud particles, the optical thickness of the cloud, and the cloud-top temperature (CTT) and determined that cooling effects occur with clouds when their optical thickness is greater than 4.0˜4.5 with a cloud top temperature of 220K and 2.5˜3.0 with a cloud top temperature of 235K. Cloud radiative forcing in April 1987 (El Niño year) and April 1990 (neutral year) were computed, and found that a larger amount of cirrus clouds appeared in the tropics off Peru in 1987 than in 1990. But the globally averaged net cloud radiative forcing was smaller by 0.55W/m2 in 1987 than in 1990. Consequently, the temperature distribution of the oceans has a global effect on atmospheric warming and cooling.

  12. MODIS Cloud Microphysics Product (MOD_PR06OD) Data Collection 6 Updates

    NASA Technical Reports Server (NTRS)

    Wind, Gala; Platnick, Steven; King, Michael D.

    2014-01-01

    The MODIS Cloud Optical and Microphysical Product (MOD_PR060D) for Data Collection 6 has entered full scale production. Aqua reprocessing is almost completed and Terra reprocessing will begin shortly. Unlike previous collections, the CHIMAERA code base allows for simultaneous processing for multiple sensors and the operational CHIMAERA 6.0.76 stream is also available for VIIRS and SEVIRI sensors and for our E-MAS airborne platform.

  13. Rain chemistry and cloud composition and microphysics in a Caribbean tropical montane cloud forest under the influence of African dust

    NASA Astrophysics Data System (ADS)

    Torres-Delgado, Elvis; Valle-Diaz, Carlos J.; Baumgardner, Darrel; McDowell, William H.; González, Grizelle; Mayol-Bracero, Olga L.

    2015-04-01

    It is known that huge amounts of mineral dust travels thousands of kilometers from the Sahara and Sahel regions in Africa over the Atlantic Ocean reaching the Caribbean, northern South America and southern North America; however, not much is understood about how the aging process that takes place during transport changes dust properties, and how the presence of this dust affects cloud's composition and microphysics. This African dust reaches the Caribbean region mostly in the summer time. In order to improve our understanding of the role of long-range transported African dust (LRTAD) in cloud formation processes in a tropical montane cloud forest (TMCF) in the Caribbean region we had field campaigns measuring dust physical and chemical properties in summer 2013, as part of the Puerto Rico African Dust and Cloud Study (PRADACS), and in summer 2014, as a part of the Luquillo Critical Zone Observatory (LCZO) and in collaboration with the Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE). Measurements were performed at the TMCF of Pico del Este (PE, 1051 masl) and at the nature reserve of Cabezas de San Juan (CSJ, 60 masl). In both stations we monitored meteorological parameters (e.g., temperature, wind speed, wind direction). At CSJ, we measured light absorption and scattering at three wavelengths (467, 528 and 652 nm). At PE we collected cloud and rainwater and monitored cloud microphysical properties (e.g., liquid water content, droplet size distribution, droplet number concentration, effective diameter and median volume diameter). Data from aerosol models, satellites, and back-trajectories were used together with CSJ measurements to classify air masses and samples collected at PE in the presence or absence of dust. Soluble ions, insoluble trace metals, pH and conductivity were measured for cloud and rainwater. Preliminary results for summer 2013 showed that in the presence of LRTAD (1) the average conductivity of cloud water

  14. Aerosol particles scavenging by a droplet: Microphysical modeling in the Greenfield gap

    NASA Astrophysics Data System (ADS)

    Cherrier, Gaël; Belut, Emmanuel; Gerardin, Fabien; Tanière, Anne; Rimbert, Nicolas

    2017-10-01

    Studying the scavenging of aerosol particle by drops has been a key topic of atmospheric science since the late seventies, given its relationships with atmospheric depollution, with the physics of clouds and precipitations and with global warming. However, the efficiency with which falling droplets capture aerosol particles is still imprecisely known for a wide range of drop Reynolds number, Weber numbers, aerosol particles inertia and Brownian Schmidt number. In this paper, microphysical modeling is used to compute precisely the drop collection efficiency for aerosol particles around the Greenfield gap which are submitted to both drag force and Brownian motion, for droplets falling in quiescent air at moderate Reynolds number (Red ≤ 100). Depending on the impactional or diffusional parameters, the collection regions on the drop surface are highlighted. The results are then compressed by a correlation which extends the field of use of the theoretical model of Wang et al. (1978) by taking inertial capture into account. The proposed correlation is suitable to estimate the aerosol scavenging efficiency for a non-evaporating, non-deforming drop with Red ≤ 100 and particle Stokes number Stp ∈ [ 0 ; + ∞ ] . In case of evaporating or condensing droplets, the effect of thermophoresis and diffusiophoresis are also taken into account through an extension of the formulation proposed by Wang et al. (1978) and hence with similar accuracy.

  15. Interactions between aerosol absorption, thermodynamics, dynamics, and microphysics and their impacts on a multiple-cloud system

    NASA Astrophysics Data System (ADS)

    Lee, Seoung Soo; Li, Zhanqing; Mok, Jungbin; Ahn, Myoung-Hwan; Kim, Byung-Gon; Choi, Yong-Sang; Jung, Chang-Hoon; Yoo, Hye Lim

    2017-02-01

    This study investigates how the increasing concentration of black carbon aerosols, which act as radiation absorbers as well as agents for the cloud-particle nucleation, affects stability, dynamics and microphysics in a multiple-cloud system using simulations. Simulations show that despite increases in stability due to increasing concentrations of black carbon aerosols, there are increases in the averaged updraft mass fluxes (over the whole simulation domain and period). This is because aerosol-enhanced evaporative cooling intensifies convergence near the surface. This increase in the intensity of convergence induces an increase in the frequency of updrafts with the low range of speeds, leading to the increase in the averaged updraft mass fluxes. The increase in the frequency of updrafts induces that in the number of condensation entities and this leads to more condensation and cloud liquid that acts to be a source of the accretion of cloud liquid by precipitation. Hence, eventually, there is more accretion that offsets suppressed autoconversion, which results in negligible changes in cumulative precipitation as aerosol concentrations increase. The increase in the frequency of updrafts with the low range of speeds alters the cloud-system organization (represented by cloud-depth spatiotemporal distributions and cloud-cell population) by supporting more low-depth clouds. The altered organization in turn alters precipitation spatiotemporal distributions by generating more weak precipitation events. Aerosol-induced reduction in solar radiation that reaches the surface induces more occurrences of small-value surface heat fluxes, which in turn supports the more low-depth clouds and weak precipitation together with the greater occurrence of low-speed updrafts.

  16. Sensitivity of Precipitation Processes to Microphysics and Resolution in a Cloud-Resolving Model

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2003-01-01

    The Goddard Cumulus Ensemble (GCE) model is used to examine the impact of various microphysical schemes, and vertical and horizontal resolution on the development, intensity and rainfall associated with mesoscale convective systems, idealized hurricanes and an ensemble of clouds. The model variables include horizontal and vertical velocities, potential temperature, perturbation pressure, turbulent kinetic energy, and mixing ratios of all water phases (vapor, liquid, and ice). The major characteristics of the GCE model are the explicit representation of warm rain and ice microphysical processes, and their complex interactions with solar and infrared radiative transfer processes, and with surface processes. For idealized hurricane, an axisymmetric version of the GCE model was developed and used successfully to simulate the tropical cyclogenesis process using both a Rankin vortex and saturated air within a specified radius as initial conditions. For mesoscale convective systems, the 3-D version of the GCE model was used to simulate squall lines that developed in the western Pacific, eastern Atlantic and central US. For the cloud ensemble, the GCE model was integrated for several days in order to have good sampling of cloud statistics. In this paper, the sensitivities of hurricane intensity to various microphysical processes and model grid resolution will be examined.

  17. Sensitivity of Tropical Cyclone Intensification to Cloud Microphysics Parameterizations: WRF Simulations of Hurricane Dennis (2005)

    NASA Astrophysics Data System (ADS)

    Schneider, E.; Jewett, B. F.; McFarquhar, G. M.; Gilmore, M.; Hood, R.; Heymsfield, G.

    2006-12-01

    The Weather Research and Forecasting model (WRF) is used to simulate Hurricane Dennis (2005) as it transitioned from a tropical storm to a category 1 hurricane, from a category 1 to a category 2 hurricane and as it re-intensified to a category 4 hurricane after moving off Cuba. The simulations have a fixed, 3 km innermost horizontal grid, use 54 vertical layers and utilize state-of-the art microphysics parameterizations. Advanced Microwave Precipitation Radiometer (AMPR) and EDOP radar data collected during the Tropical Cloud Systems and Processes field campaign on three separate days over Hurricane Dennis offer a unique set of remotely retrieved cloud and precipitation properties for evaluating the simulations. Frequency diagrams of simulated brightness temperature and contoured frequency by altitude diagrams (CFADs) of equivalent reflectivity and Doppler velocity are compared against similar quantities derived from modeled fields to determine if the model simulations capture changes in cloud properties observed during the three stages of intensification of Hurricane Dennis. This hence offers insight into the role microphysical processes play during hurricane intensification. A particular focus is also placed on whether WRF simulations of Dennis overproduce graupel compared to observations when using the default microphysics parameters, a trend noted in some simulations of previous hurricanes.

  18. Long-term in situ measurements of the cloud-precipitation microphysical properties over East Asia

    NASA Astrophysics Data System (ADS)

    Yin, Jinfang; Wang, Donghai; Zhai, Guoqing

    2011-10-01

    A database of cloud-precipitation microphysical characteristics is established, using in situ data during 1960-2008. Main features of aerosol, ice nuclei (IN), cloud droplet, fog, ice crystal, snow crystal, and raindrop are presented based on the analyses of the database. In addition, a statistical analysis has been performed. The results show that the overall average aerosol concentration in diameter greater than 0.3 μm is 166.9 cm -3 and the average maximum values of IN concentration can reach 78.9 L -1 at - 20 °C, with an overall average of 22.9 L -1. In addition, cumuliform clouds have higher overall average cloud droplet number concentration (N c) of 907.7 cm -3, and that of stratiform clouds, is 120.9 cm -3; cumuliform clouds (stratiform clouds) have an average liquid water content (LWC) of 0.875 (0.140) g m -3, with a peak value of 2.000 (0.520) g m -3. The gamma size distributions are shown to be suitable for most of the observed spectra in stratiform clouds. Both the exponential and gamma size distributions are applicable to fit the raindrops originating from stratiform clouds. Good agreement is obtained when the gamma size distribution is applied to fit the raindrops originating from both convective and mixing (stratiform and cumuliform) clouds. The exponential size distributions are suitable for both ice crystal and snow crystal fitting.

  19. Unique manifestations of mixed-phase cloud microphysics over Ross Island and the Ross Ice Shelf, Antarctica

    NASA Astrophysics Data System (ADS)

    Scott, Ryan C.; Lubin, Dan

    2016-03-01

    Spaceborne radar and lidar observations from the CloudSat and CALIPSO satellites are used to compare seasonal variations in the microphysical and radiative properties of clouds over Ross Island, Antarctica, with two contrasting Arctic atmospheric observatories located in Barrow, Alaska, and Summit, Greenland. At Ross Island, downstream from recurrent intrusions of marine air over the West Antarctic Ice Sheet and eastern Ross Ice Shelf, clouds exhibit a tendency toward the greatest geometrical thickness and coldest temperatures in summer, the largest average ice water content, IWC, at low altitude during summer and autumn, the most abundant IWC at cold mixed-phase temperatures (-40°C Clouds over Barrow form and evolve in a contrastingly warm and moist atmosphere and on average contain the largest liquid water content and ice and liquid water effective particle radii, re, year round. In contrast, clouds observed atop the central Greenland Ice Sheet are relatively tenuous, containing the smallest IWC and ice re of all sites.

  20. Microphysical and optical properties of precipitating drizzle and ice particles obtained from alternated lidar and in situ measurements

    NASA Astrophysics Data System (ADS)

    Gayet, J.-F.; Stachlewska, I. S.; Jourdan, O.; Shcherbakov, V.; Schwarzenboeck, A.; Neuber, R.

    2007-07-01

    During the international ASTAR experiment (Arctic Study of Aerosols, Clouds and Radiation) carried out from Longyearbyen (Spitsbergen) from 10 May to 11 June 2004, the AWI (Alfred Wegener Institute) Polar 2 aircraft was equipped with a unique combination of remote and in situ instruments. The airborne AMALi lidar provided downward backscatter and Depolarisation ratio profiles at 532 nm wavelength. The in situ instrumental setup comprised a Polar Nephelometer, a Cloud Particle Imager (CPI) as well as a Nevzorov and standard PMS probes to measure cloud particle properties in terms of scattering characteristics, particle morphology and size, and in-cloud partitioning of ice/water content. The objective of the paper is to present the results of a case study related to observations with ice crystals precipitating down to supercooled boundary-layer stratocumulus. The flight pattern was predefined in a way that firstly the AMALi lidar probed the cloud tops to guide the in situ measurements into a particular cloud formation. Three kinds of clouds with different microphysical and optical properties have therefore been quasi-simultaneously observed: (i) water droplets stratiform-layer, (ii) drizzle-drops fallstreak and (iii) precipitating ice-crystals from a cirrus cloud above. The signatures of these clouds are clearly evidenced from the in situ measurements and from the lidar profiles in term of backscatter and Depolarisation ratio. Accordingly, typical lidar ratios, i.e., extinction-to-backscatter ratios, are derived from the measured scattering phase function combined with subsequent particle shapes and size distributions. The backscatter profiles can therefore be retrieved under favourable conditions of low optical density. From these profiles extinction values in different cloud types can be obtained and compared with the direct in situ measurements.

  1. Microphysical Properties of Single Secondary Organic Aerosol (SOA) Particles

    NASA Astrophysics Data System (ADS)

    Rovelli, Grazia; Song, Young-Chul; Pereira, Kelly; Hamilton, Jacqueline; Topping, David; Reid, Jonathan

    2017-04-01

    Secondary Organic Aerosols (SOA) deriving from the oxidation of volatile organic compounds (VOCs) can account for a substantial fraction of the overall atmospheric aerosol mass.[1] Therefore, the investigation of SOA microphysical properties is crucial to better comprehend their role in the atmospheric processes they are involved in. This works describes a single particle approach to accurately characterise the hygroscopic response, the optical properties and the gas-particle partitioning kinetics of water and semivolatile components for laboratory generated SOA. SOA was generated from the oxidation of different VOCs precursors (e.g. α-pinene, toluene) in a photo-chemical flow reactor, which consists of a temperature and relative humidity controlled 300 L polyvinyl fluoride bag. Known VOC, NOx and ozone concentrations are introduced in the chamber and UV irradiation is performed by means of a Hg pen-ray. SOA samples were collected with an electrical low pressure impactor, wrapped in aluminium foil and kept refrigerated at -20°C. SOA samples were extracted in a 1:1 water/methanol mixture. Single charged SOA particles were generated from the obtained solution using a microdispenser and confined within an electrodynamic balance (EDB), where they sit in a T (250-320 K) and RH (0-95%) controlled nitrogen flow. Suspended droplets are irradiated with a 532 nm laser and the evolving angularly resolved scattered light is used to keep track of changes in droplet size. One of the key features of this experimental approach is that very little SOA solution is required because of the small volumes needed to load the dispensers (<20 μL). A number of diverse experiments were performed in order to characterise different microphysical properties of SOA. The equilibrium hygroscopic response of SOA was determined with comparative evaporation kinetics experiments (CK-EDB) of suspended probe and sample droplets.[2] The variation of the refractive index of SOA droplets following to

  2. Exploring the Impact of Land Use Change on an Idealized Convective Boundary Layer and the Microphysics of Shallow Cumulus Clouds

    NASA Astrophysics Data System (ADS)

    Pennypacker, S.; O, K. T.; Wood, R.; Swann, A. L. S.

    2016-12-01

    Continental shallow cumulus clouds are important players in the surface energy budget and exchange between the boundary layer and free atmosphere despite being less routinely studied than their marine counterparts. One of the primary mechanisms through which humans are thought to perturb clouds is through aerosol effects on cloud microphysics. However, the cloud microphysical parameters most important for understanding cloud radiative properties are also partially controlled by the convective dynamics of the cloud, particularly the updraft speed. Shallow cumulus clouds are rooted in convective boundary layer dynamics, which are in turn sensitive to energy fluxes at the land surface. Therefore, land use changes that alter the surface energy budget open up new pathways for anthropogenic perturbations to boundary layer cloud properties. We determine the effects of several land use change scenarios on boundary layer convective velocity scales in a coupled land surface-mixed layer model, and perform experiments under both current and projected future CO2 levels. Representative observations provide initialization conditions and validation of the mixed layer model. The kinematics of these convective conditions are then used to force a one-dimensional adiabatic cloud parcel model to determine effects of land surface changes on supersaturation evolution and initial microphysical properties of idealized, forced shallow cumuli. We employ several sub-cloud aerosol concentrations and size distributions within the parcel model to further examine the sensitivity of shallow cumulus microphysics to land cover changes over a range of realizable continental aerosol conditions.

  3. Application of a new scheme of cloud base droplet nucleation in a spectral (bin) microphysics cloud model: sensitivity to aerosol size distribution

    NASA Astrophysics Data System (ADS)

    Ilotoviz, Eyal; Khain, Alexander

    2016-11-01

    A new scheme of droplet nucleation at cloud base is implemented into the Hebrew University Cloud Model (HUCM) with spectral (bin) microphysics. In this scheme, supersaturation maximum Smax near cloud base is calculated using theoretical results according to which Smax ˜ w3/4Nd-1/2, where w is the vertical velocity at cloud base and Nd is droplet concentration. Microphysical cloud structure obtained in the simulations of a midlatitude hail storm using the new scheme is compared with that obtained in the standard approach, in which droplet nucleation is calculated using supersaturation calculated in grid points. The simulations were performed with different concentrations of cloud condensational nuclei (CCN) and with different shapes of CCN size spectra. It is shown that the new nucleation scheme substantially improves the vertical profile of droplet concentration shifting the concentration maximum to cloud base. It is shown that the effect of the CCN size distribution shape on cloud microphysics is not less important than the effect of the total CCN concentration. It is shown that the smallest CCN with diameters less than about 0.015 µm have a substantial effect on mixed-phase and ice microphysics of deep convective clouds. Such CCN are not measured by standard CCN probes, which hinders understanding of cold microphysical processes.

  4. Sensitivity of Precipitation Processes of Microphysics and Resolution in a Cloud-Resolving Model

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2003-01-01

    The Goddard Cumulus Ensemble (GCE) model is used to examine the impact of various microphysical schemes, and vertical and horizontal resolution ion the development, intensity and rainfall associated with mesoscale convective systems, idealized hurricanes and an ensemble f clouds. The model variables include horizontal and vertical velocities, potential temperatures, perturbation pressure, turbulent kinetic energy, and mixing ratios of all water phases (vapor, liquid, and ice). The major characteristics of the GCE model are the explicit representation of warm rain and ice microphysical processes, and their complex interactions with solar and infrared radiative transfer processes, and with surface processes. For idealized hurricane, an axisymmetric version of the GCE model was developed and used successfully to simulate the tropical cyclogenesis process using both a Rankin vortex and saturated air within a specified radius as initial conditions. For mesoscale convective systems, the 3-D version of the GCE model was used to simulated squall lines that developed in the western Pacific, eastern Atlantic and central US. For the cloud ensemble, the GCE model was integrated for several days in order to have good sampling of cloud statistics. In this paper, the sensitivities of hurricane intensity to various microphysical processes and model grid resolution will be examined. This will be mainly achieved by performing sensitivity tests using various horizontal (from 1- to 5-km) and vertical resolutions (from 20- to 200-m in the lower troposphere to 200- to 500-m in the middle and upper troposphere). Sensitivity tests using various microphysical schemes (warm rain only, and three ice with either graupel or hail) will also be performed. The thermodynamic and water budget associated with various types of precipitation systems will also be evaluated. The budgets will be calculated for different regions (i.e., convective and stratiform regions).

  5. Sensitivity of Precipitation Processes to Microphysics and Resolution in a Cloud-Resolving Model

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kao

    2003-01-01

    The Goddard Cumulus Ensemble (GCE) model is used to examine the impact of various microphysical schemes, and vertical and horizontal resolution on the development, intensity and rainfall associated with mesoscale convective systems, idealized hurricanes and an ensemble of clouds. The model variables include horizontal and vertical velocities, potential temperature, perturbation pressure, turbulent kinetic energy, and mixing ratios of all water phases (vapor, liquid, and ice). The major characteristics of the GCE model are the explicit representation of warm rain and ice microphysical processes, and their complex interactions with solar and infrared radiative transfer processes, and with surface processes. For idealized hurricane, an axisymmetric version of the GCE model was developed and used successfully to simulate the tropical cyclogenesis process using both a Rankin vortex and saturated air within a specified radius as initial conditions. For mesoscale convective systems, the 3-D version of the GCE model was used to simulate squall lines that developed in the western Pacific, South China Sea, eastern Atlantic, South America and central U.S. For the cloud ensemble, the GCE model was integrated for several days in order to have good sampling of cloud statistics. In this paper, the sensitivities of hurricane intensity to various microphysical processes and model grid resolution will be examined. This will be mainly achieved by performing sensitivity tests using various horizontal (from 1- to 5-kilometers) and vertical resolutions (from 20- to 200-meters in the lower troposphere to 200- to 500-m in the middle and upper troposphere). Sensitivity tests using various microphysical schemes (warm rain only, and three ice with either graupel or hail) will also be performed. The PBL and diurnal variation of precipitation processes will also be evaluated. The budgets will be calculated for different regions (i.e., convective and stratiform regions).

  6. Sensitivity of Precipitation Processes to Microphysics and Resolution in a Cloud Resolving Model

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2003-01-01

    The Goddard Cumulus Ensemble (GCE) model examines the impact of various microphysical schemes, and vertical and horizontal resolution in the development, intensity and rainfall associated with mesoscale convective systems, idealized hurricanes and an ensemble of clouds. The model variables include horizontal and vertical velocities, potential temperature, perturbation pressure, turbulent kinetic energy, and mixing rations of all water phases (vapor, liquid and ice). The major characteristics of the GCE model are the explicit representation of warm rain and ice microphysical processes, and their complex interactions with solar and infrared radiative transfer processes and with surface processes. For idealized hurricanes, an axisymmetric version of the GCE model was developed and used to simulate the tropical cyclogenesis process using both a Rankin vortex and saturated air within a specified radius as initial conditions. For mesoscale convective systems, the 3-D version of the GCE model was use to simulate squall lines that developed in the western Pacific, South China Sea, eastern Atlantic, South America and central U.S. FOr the cloud ensemble, the GCE model was integrated for several days in order to have a good sampling of cloud statistics. In this paper, the sensitivities of hurricane intensity to various microphysical processes and model grid resolutio will be examined. This will be mainly achieved by performing sensitivity tests using various horizontal (from 1-to 5-km) and vertical resolutions (from 20- to 200-m in the lower troposphere to 200- to 500m in the middle and upper troposphere). Sensitivity test using various microphysical schemes (warm rain only, and three ice with either graupel or hail) will also be performed. The thermodynamic and water budget associated with various types of precipitation systems will also be evaluated. The budgets will be calculated for different regions (i.e., convective and stratiform regions).

  7. Simulation of the effects of aerosol on mixed-phase orographic clouds using the WRF model with a detailed bin microphysics scheme

    NASA Astrophysics Data System (ADS)

    Xiao, Hui; Yin, Yan; Jin, Lianji; Chen, Qian; Chen, Jinghua

    2015-08-01

    The Weather Research Forecast (WRF) mesoscale model coupled with a detailed bin microphysics scheme is used to investigate the impact of aerosol particles serving as cloud condensation nuclei and ice nuclei on orographic clouds and precipitation. A mixed-phase orographic cloud developed under two scenarios of aerosol (a typical continental background and a relatively polluted urban condition) and ice nuclei over an idealized mountain is simulated. The results show that, when the initial aerosol condition is changed from the relatively clean case to the polluted scenario, more droplets are activated, leading to a delay in precipitation, but the precipitation amount over the terrain is increased by about 10%. A detailed analysis of the microphysical processes indicates that ice-phase particles play an important role in cloud development, and their contribution to precipitation becomes more important with increasing aerosol particle concentrations. The growth of ice-phase particles through riming and Wegener-Bergeron-Findeisen regime is more effective under more polluted conditions, mainly due to the increased number of droplets with a diameter of 10-30 µm. Sensitivity tests also show that a tenfold increase in the concentration of ice crystals formed from ice nucleation leads to about 7% increase in precipitation, and the sensitivity of the precipitation to changes in the concentration and size distribution of aerosol particles is becoming less pronounced when the concentration of ice crystals is also increased.

  8. The Microphysics of clouds over the Weddell Sea during the Austral Summer

    NASA Astrophysics Data System (ADS)

    Lachlan-Cope, Tom; Listowski, Contantino; Kirchgaessner, Amélie; Ladkin, Russ; Fleming, Zoe; O'Shea, Sebastian; Choularton, Tom; Flynn, Michael; Gallagher, Martin; Bower, Keith

    2017-04-01

    Three airborne campaigns have been carried out over the Weddell Sea during the austral summer - two during 2010 and 2011 in the west close to the Antarctic Peninsula and one in the east close to the Brunt Ice shelf. The cloud microphysics at both locations are compared and the source of aerosols that are active as cloud nuclei are considered. It is found that the difference between the two sides of the Weddell Sea is small despite the obvious difference in potential sources of cloud nuclei. It is found that in both areas a major source of cloud nuclei are air masses that have passed close to the surface of the sea ice leading to the suggestion that the sea ice is a source of nuclei.

  9. Statistical retrieval of thin liquid cloud microphysical properties using ground-based infrared and microwave observations

    NASA Astrophysics Data System (ADS)

    Marke, Tobias; Ebell, Kerstin; Löhnert, Ulrich; Turner, David D.

    2016-12-01

    In this article, liquid water cloud microphysical properties are retrieved by a combination of microwave and infrared ground-based observations. Clouds containing liquid water are frequently occurring in most climate regimes and play a significant role in terms of interaction with radiation. Small perturbations in the amount of liquid water contained in the cloud can cause large variations in the radiative fluxes. This effect is enhanced for thin clouds (liquid water path, LWP <100 g/m2), which makes accurate retrieval information of the cloud properties crucial. Due to large relative errors in retrieving low LWP values from observations in the microwave domain and a high sensitivity for infrared methods when the LWP is low, a synergistic retrieval based on a neural network approach is built to estimate both LWP and cloud effective radius (reff). These statistical retrievals can be applied without high computational demand but imply constraints like prior information on cloud phase and cloud layering. The neural network retrievals are able to retrieve LWP and reff for thin clouds with a mean relative error of 9% and 17%, respectively. This is demonstrated using synthetic observations of a microwave radiometer (MWR) and a spectrally highly resolved infrared interferometer. The accuracy and robustness of the synergistic retrievals is confirmed by a low bias in a radiative closure study for the downwelling shortwave flux, even for marginally invalid scenes. Also, broadband infrared radiance observations, in combination with the MWR, have the potential to retrieve LWP with a higher accuracy than a MWR-only retrieval.

  10. Theoretical Studies of Microphysics of Marine Boundary-Layer Clouds

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.

    2002-01-01

    This project is aimed at better understanding the role that aerosols play in altering the properties of stratus clouds. This interaction, termed the indirect effect of aerosols on climate, is a major subject a of study since the radiative forcing involved may rival that of greenhouse gases, but may be of the opposite sign. Our goal was to create numerical models of the phenomena, test them with data, and thereby gain insight into the physical processes occurring. Below we list the papers that we have produced during this grant. We then discuss these papers.

  11. Unified Very Low Stratus Cloud/Subcloud Microphysics Model

    DTIC Science & Technology

    1992-04-01

    radiation effect in the cloud and is an unknown function of z, Ac = F(z) (22d) (Turb) is the turbulence effect, after Priestley (1953), k2(T - T’) (22e...equations, "horizontal" entrainment or the Priestley (1953) turbulence effect tends to increase the magnitude of dT/dz when dT/dz is negative, but... Priestley . As was done in section 4.3, we allow either entrainment or Priestley turbulence to be activated in equation (35), but not both. If

  12. Impacts of nanoparticle events on cloud condensation nuclei and cloud microphysical properties

    NASA Astrophysics Data System (ADS)

    O'Halloran, Thomas Liam

    This dissertation examines aerosol properties above a forested site in the Piedmont of central Virginia and evaluates the effects of those aerosols on convective cloud properties using a cloud resolving model. During the measurement period between October and December, 2006, aerosol size distributions and hygroscopicity varied among air mass source regions. In stagnant air masses, aerosol concentrations and surface area were relatively high and hygroscopicity was enhanced in particles with dry diameter less than 0.100 mm (average growth factor increase = 0.05). Aerosol nucleation was a frequent source of new particles in the atmosphere, as inferred from nanoparticle growth events, which were observed on 35% of all days. These events occurred preferentially (50% of all observed events) in relatively cool, dry air masses (median values: Tair = 6°C; relative humidity (RH) = 49%) from the northwest, in the climatologically dominant flow regime. Preexisting aerosol surface area (a competing sink for nucleating vapors) were lowest in this relatively clean flow (mean total surface area = 142 mum2 cm-3). Temporal trends in aerosol size distributions, concentration, growth rates, and the relationship between solubility and concentration, indirectly suggest that biogenic hydrocarbons had a decreasing influence on aerosol properties in time as canopy defoliation progressed. The observed diurnal cycle in aerosol hygroscopicity had the largest amplitude of any previously reported values. Calculated aerosol soluble mass fraction increased by up to 80% between 0800 local time (LT) and 1700 LT. We observed an association of activation diameter and hygroscopicity of a growing population of recently formed particles. These changes in aerosol solubility were independently confirmed (also for the first time) to affect the aerosol activation diameter 4 (Dp50) into cloud condensation nuclei (CCN). During a case study the CCN activation diameter varied from 40 nm to 57 nm at 0

  13. A 1D microphysical cloud model for Earth, and Earth-like exoplanets: Liquid water and water ice clouds in the convective troposphere

    NASA Astrophysics Data System (ADS)

    Zsom, Andras; Kaltenegger, Lisa; Goldblatt, Colin

    2012-11-01

    One significant difference between the atmospheres of stars and exoplanets is the presence of condensed particles (clouds or hazes) in the atmosphere of the latter. In current 1D models clouds and hazes are treated in an approximate way by raising the surface albedo, or adopting measured Earth cloud properties. The former method introduces errors to the modeled spectra of the exoplanet, as clouds shield the lower atmosphere and thus modify the spectral features. The latter method works only for an exact Earth-analog, but it is challenging to extend to other planets. The main goal of this paper is to develop a self-consistent microphysical cloud model for 1D atmospheric codes, which can reproduce some observed properties of Earth, such as the average albedo, surface temperature, and global energy budget. The cloud model is designed to be computationally efficient, simple to implement, and applicable for a wide range of atmospheric parameters for planets in the habitable zone. We use a 1D, cloud-free, radiative-convective, and photochemical equilibrium code originally developed by Kasting, Pavlov, Segura, and collaborators as basis for our cloudy atmosphere model. The cloud model is based on models used by the meteorology community for Earth’s clouds. The free parameters of the model are the relative humidity and number density of condensation nuclei, and the precipitation efficiency. In a 1D model, the cloud coverage cannot be self-consistently determined, thus we treat it as a free parameter. We apply this model to Earth (aerosol number density 100 cm-3, relative humidity 77%, liquid cloud fraction 40%, and ice cloud fraction 25%) and find that a precipitation efficiency of 0.8 is needed to reproduce the albedo, average surface temperature and global energy budget of Earth. We perform simulations to determine how the albedo and the climate of a planet is influenced by the free parameters of the cloud model. We find that the planetary climate is most sensitive to

  14. Cloud microphysical relationships and their implication on entrainment and mixing mechanism for the stratocumulus clouds measured during the VOCALS project

    DOE PAGES

    Yum, Seong Soo; Wang, Jian; Liu, Yangang; ...

    2015-05-27

    Cloud microphysical data obtained from G-1 aircraft flights over the southeastern pacific during the VOCALS-Rex field campaign were analyzed for evidence of entrainment mixing of dry air from above cloud top. Mixing diagram analysis was made for the horizontal flight data recorded at 1 Hz and 40 Hz. The dominant observed feature, a positive relationship between cloud droplet mean volume (V) and liquid water content (L), suggested occurrence of homogeneous mixing. On the other hand, estimation of the relevant scale parameters (i.e., transition length scale and transition scale number) consistently indicated inhomogeneous mixing. Importantly, the flight altitudes of the measurementsmore » were significantly below cloud top. We speculate that mixing of the entrained air near the cloud top may have indeed been inhomogeneous; but due to vertical circulation mixing, the correlation between V and L became positive at the measurement altitudes in mid-level of clouds, because during their descent, cloud droplets evaporate, faster in more diluted cloud parcels, leading to a positive correlation between V and L regardless of the mixing mechanism near the cloud top.« less

  15. Cloud microphysical relationships and their implication on entrainment and mixing mechanism for the stratocumulus clouds measured during the VOCALS project

    SciTech Connect

    Yum, Seong Soo; Wang, Jian; Liu, Yangang; Senum, Gunnar; Springston, Stephen; McGraw, Robert; Yeom, Jae Min

    2015-05-27

    Cloud microphysical data obtained from G-1 aircraft flights over the southeastern pacific during the VOCALS-Rex field campaign were analyzed for evidence of entrainment mixing of dry air from above cloud top. Mixing diagram analysis was made for the horizontal flight data recorded at 1 Hz and 40 Hz. The dominant observed feature, a positive relationship between cloud droplet mean volume (V) and liquid water content (L), suggested occurrence of homogeneous mixing. On the other hand, estimation of the relevant scale parameters (i.e., transition length scale and transition scale number) consistently indicated inhomogeneous mixing. Importantly, the flight altitudes of the measurements were significantly below cloud top. We speculate that mixing of the entrained air near the cloud top may have indeed been inhomogeneous; but due to vertical circulation mixing, the correlation between V and L became positive at the measurement altitudes in mid-level of clouds, because during their descent, cloud droplets evaporate, faster in more diluted cloud parcels, leading to a positive correlation between V and L regardless of the mixing mechanism near the cloud top.

  16. Sensitivity of a Cloud-Resolving Model to Bulk and Explicit Bin Microphysical Schemes. Part 2; Cloud Microphysics and Storm Dynamics Interactions

    NASA Technical Reports Server (NTRS)

    Li, Xiaowen; Tao, Wei-Kuo; Khain, Alexander P.; Simpson, Joanne; Johnson, Daniel E.

    2009-01-01

    Part I of this paper compares two simulations, one using a bulk and the other a detailed bin microphysical scheme, of a long-lasting, continental mesoscale convective system with leading convection and trailing stratiform region. Diagnostic studies and sensitivity tests are carried out in Part II to explain the simulated contrasts in the spatial and temporal variations by the two microphysical schemes and to understand the interactions between cloud microphysics and storm dynamics. It is found that the fixed raindrop size distribution in the bulk scheme artificially enhances rain evaporation rate and produces a stronger near surface cool pool compared with the bin simulation. In the bulk simulation, cool pool circulation dominates the near-surface environmental wind shear in contrast to the near-balance between cool pool and wind shear in the bin simulation. This is the main reason for the contrasting quasi-steady states simulated in Part I. Sensitivity tests also show that large amounts of fast-falling hail produced in the original bulk scheme not only result in a narrow trailing stratiform region but also act to further exacerbate the strong cool pool simulated in the bulk parameterization. An empirical formula for a correction factor, r(q(sub r)) = 0.11q(sub r)(exp -1.27) + 0.98, is developed to correct the overestimation of rain evaporation in the bulk model, where r is the ratio of the rain evaporation rate between the bulk and bin simulations and q(sub r)(g per kilogram) is the rain mixing ratio. This formula offers a practical fix for the simple bulk scheme in rain evaporation parameterization.

  17. Impacts of cloud microphysics and radiation on the cloud and precipitation in a simulated Meiyu-frontal system

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Wang, Y.

    2009-04-01

    Meiyu frontal system that formed and moved over the Huai River basin of China on 7-8 July 2007 is investigated using weather radar observations, Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar and CloudSat Cloud Profiling Radar measurements, and brightness temperatures from the MTSAT-1R satellite. These results are used to evaluate cloud-resolving simulations performed using the Weather Research and Forecasting (WRF) model. Sensitivity experiments are conducted to explore impacts of cloud microphysics and radiation on the cloud and precipitation structure. At its mature stage, the observed convective system consisted of a west-east oriented leading convective line with stratiform precipitating and non-precipitating cloud regions trailing off to the north and east. While the cloud system extending hundreds kilometers from west to east, the widths of the convective and stratiform raining regions are of 10-20 km and 100-200 km, respectively. During the system's development stage, newer convection occurred on the western edge of the convective line. The convective centers progressed through a period of rapid growth when propagated eastward, with echo tops penetrating to maximum heights of 16-km, then decreasing to height of 13-km, which corresponds to the height of the stratiform precipitating cloud top with which the convective elements merged at the end of their lifetimes. Results from four simulations are analyzed: CONTROL, Lin, Thompson, and noRad. The three sensitivity experiments are identical to CONTROL except that the Lin and Thompson simulations employ the 1-moment microphysics schemes of Lin and Thompson, respectively, rather than the 2-moment microphysics scheme of Morrison as in CONTROL, and the noRad simulation turns off the radiative cooling/warming effect. The CONTROL reasonably reproduces not only the magnitude and spatial distribution of the accumulated surface precipitation, but also the evolution of the leading convective lines and

  18. A Comparison Of Cloud Microphysical Properties Derived Using VIRS 3.7 Micron and 1.6 Micron Data

    NASA Technical Reports Server (NTRS)

    Young, David F.; Minnis, Patrick; Arduini, Robert F.

    1999-01-01

    One of the main objectives of the Clouds and the Earth's Radiant Energy System (CERES) project is the retrieval of cloud physical and microphysical properties simultaneously with observations of broadband radiative fluxes. These cloud parameter sare used for three main purposes: 1) to provide data for radiation-cloud climate feedback studies; 2) to provide scene identification data for the construction and application of angular distribution models; and 3) to be used as input to radiative transfer calculations of intra-atmospheric fluxes

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

    SciTech Connect

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Retrievals of Ice Cloud Microphysical Properties of Deep Convective Systems using Radar Measurements

    NASA Astrophysics Data System (ADS)

    Tian, J.; Dong, X.; Xi, B.; Wang, J.; Homeyer, C. R.

    2015-12-01

    This study presents innovative algorithms for retrieving ice cloud microphysical properties of Deep Convective Systems (DCSs) using Next-Generation Radar (NEXRAD) reflectivity and newly derived empirical relationships from aircraft in situ measurements in Wang et al. (2015) during the Midlatitude Continental Convective Clouds Experiment (MC3E). With composite gridded NEXRAD radar reflectivity, four-dimensional (space-time) ice cloud microphysical properties of DCSs are retrieved, which is not possible from either in situ sampling at a single altitude or from vertical pointing radar measurements. For this study, aircraft in situ measurements provide the best-estimated ice cloud microphysical properties for validating the radar retrievals. Two statistical comparisons between retrieved and aircraft in situ measured ice microphysical properties are conducted from six selected cases during MC3E. For the temporal-averaged method, the averaged ice water content (IWC) and median mass diameter (Dm) from aircraft in situ measurements are 0.50 g m-3 and 1.51 mm, while the retrievals from radar reflectivity have negative biases of 0.12 g m-3 (24%) and 0.02 mm (1.3%) with correlations of 0.71 and 0.48, respectively. For the spatial-averaged method, the IWC retrievals are closer to the aircraft results (0.51 vs. 0.47 g m-3) with a positive bias of 8.5%, whereas the Dm retrievals are larger than the aircraft results (1.65 mm vs. 1.51 mm) with a positive bias of 9.3%. The retrieved IWCs decrease from ~0.6 g m-3 at 5 km to ~0.15 g m-3 at 13 km, and Dm values decrease from ~2 mm to ~0.7 mm at the same levels. In general, the aircraft in situ measured IWC and Dm values at each level are within one standard derivation of retrieved properties. Good agreements between microphysical properties measured from aircraft and retrieved from radar reflectivity measurements indicate the reasonable accuracy of our retrievals.

  2. Microphysical and radiative properties of stratocumulus clouds: the EUCREX mission 206 case study

    NASA Astrophysics Data System (ADS)

    Pawlowska, Hanna; Brenguier, Jean-Louis; Fouquart, Yves; Armbruster, Wolfgang; Bakan, Stephan; Descloitres, Jacques; Fischer, Jürgen; Flamant, Cyril; Fouilloux, Anne; Gayet, Jean-François; Gosh, Sat; Jonas, Peter; Parol, Frederic; Pelon, Jacques; Schüller, Lothar

    In this conclusion paper, remote sensing retrievals of cloud optical thickness performed during the EUCREX mission 206 are analyzed. The comparison with estimates derived from in situ measurements demonstrates that the adiabatic model of cloud microphysics is more realistic than the vertically uniform plane parallel model (VUPPM) for parameterization of optical thickness. The analysis of the frequency distributions of optical thickness in the cloud layer then shows that the adiabatic model provides a good prediction when the cloud layer is thick and homogeneous, while it overestimates significantly the optical thickness when the layer is thin and broken. Finally, it is shown that the effective optical thickness over the whole sampled cloud is smaller than the adiabatic prediction based on the mean geometrical thickness of the cloud layer. The high sensitivity of the optical thickness on cloud geometrical thickness suggests that the effect of aerosol and droplet concentration on precipitation efficiency, and therefore on cloud extent and lifetime, is likely to be more significant than the Twomey effect.

  3. Jovian clouds and haze

    NASA Astrophysics Data System (ADS)

    West, Robert A.; Baines, Kevin H.; Friedson, A. James; Banfield, Don; Ragent, Boris; Taylor, Fred W.

    Tropospheric clouds: thermochemical equilibrium theory and cloud microphysical theory, condensate cloud microphysics, tropospheric cloud and haze distribution - observations, results from the Galileo probe experiments, Galileo NIMS observations and results, Galileo SSE observations and results, recent analyses of ground-based and HST data; Tropospheric clouds and haze: optical and physical properties: partical composition, particle optical properties, size and shape, chromophores; Stratospheric haze: particle distribution, optical properties, size and shape, particle formation.

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

    NASA Astrophysics Data System (ADS)

    Luebke, Anna E.; Afchine, Armin; Costa, Anja; Grooß, Jens-Uwe; Meyer, Jessica; Rolf, Christian; Spelten, Nicole; Avallone, Linnea M.; Baumgardner, Darrel; Krämer, Martina

    2016-05-01

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

  5. Retrieval of cloud and drizzle microphysical properties using ground-based radar, lidar, and microwave radiometer

    NASA Astrophysics Data System (ADS)

    Rusli, Stephanie; Donovan, David; Russchenberg, Herman

    2017-04-01

    Owing to their large aerial extent, low-level liquid water clouds have a strong impact on the Earth's energy balance. Observations of these clouds to characterize the microphysical and radiative processes are therefore needed for climate studies. In such clouds, drizzle is recognized to be a common occurence and an accurate retrieval of the cloud physical properties has to account for its possible presence. We develop a retrieval technique that exploits the synergy of different remote sensing systems to simultaneously profile the cloud and drizzle properties using ground-based measurements of radar reflectivity, lidar attenuated backscatter and microwave brightness temperatures. This technique first identifies the presence of drizzle above the cloud base in an optimized and a physically-consistent manner. Subsequently, physical forward models, coupled to cloud and drizzle structure parametrization are used in an optimal-estimation type framework to derive the best-estimate for the cloud and drizzle properties as a function of height. The cloud retrieval is evaluated using simulated signals generated from large-eddy simulation output, from which it is found that the cloud properties can be retrieved within 5% of the mean truth. The full cloud-drizzle retrieval method is then applied to a selected ACCEPT campaign that took place in the Fall of 2014 in Cabauw, the Netherlands. One-to-one comparisons with three independent cloud-only or drizzle-only retrieval methods from the literature show that the results of our method are generally consistent with what is derived using the three independent methods.

  6. Arctic Cloud Fraction and Microphysical Characteristics from 8-year Space-based Lidar and Radar Measurements

    NASA Astrophysics Data System (ADS)

    Kim, S. W.; Yeo, H.; Jeong, J. H.; Kim, M. H.; Son, S. W.; Kim, B. M.; Kim, S. J.

    2015-12-01

    Arctic clouds are a key factor in determining the energy budget both at the top of the atmosphere and at the suface by modulating the long-wave and short-wave radiative fluxes, which affect the surface temperature and may effect on the growth or retreat of sea ice extent and thickness. In this work, we exmine three-dimensional geometric and microphysical properties of Arctic clouds mainly from 8-year space-borne lidar Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR). Cloud Frations (CFs) from CALIOP-CPR and MODIS show similar seasonal and inter-annual variations, but shows significant different in CF over the opened sea area (i.e., Barents and Kara Sea) and over the sea ice. High occurrences of cloud top height are found below 2 km. But comparably high presences of mid- and high-level clouds are also found, especially in winter-time. This suggests that both low- and high-level clouds over the Arctic may influence on the long-wave radiation budget both at the surface and top of the atmosphere. On the other hand, the top height of winter-time clouds looks consistent with tropopause height. Cloud Optical Depth (COD) over the Arctic shows high in summer and low in winter, which would be contrary to the seasonal/monthly variations of CF. High COD during summer can be explained by enhanced level of liquid cloud droplet number concentrations. The number concentration and effective radius (in parenthesis) of liquid cloud droplet during summner was in the range of about 30 to 80 cm-3 (about 6 ~ 16 mm).

  7. Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurements

    NASA Astrophysics Data System (ADS)

    Gong, Jie; Wu, Dong L.

    2017-02-01

    Scattering differences induced by frozen particle microphysical properties are investigated, using the vertically (V) and horizontally (H) polarized radiances from the Global Precipitation Measurement (GPM) Microwave Imager (GMI) 89 and 166 GHz channels. It is the first study on frozen particle microphysical properties on a global scale that uses the dual-frequency microwave polarimetric signals.From the ice cloud scenes identified by the 183.3 ± 3 GHz channel brightness temperature (Tb), we find that the scattering by frozen particles is highly polarized, with V-H polarimetric differences (PDs) being positive throughout the tropics and the winter hemisphere mid-latitude jet regions, including PDs from the GMI 89 and 166 GHz TBs, as well as the PD at 640 GHz from the ER-2 Compact Scanning Submillimeter-wave Imaging Radiometer (CoSSIR) during the TC4 campaign. Large polarization dominantly occurs mostly near convective outflow regions (i.e., anvils or stratiform precipitation), while the polarization signal is small inside deep convective cores as well as at the remote cirrus region. Neglecting the polarimetric signal would easily result in as large as 30 % error in ice water path retrievals. There is a universal bell curve in the PD-TBV relationship, where the PD amplitude peaks at ˜ 10 K for all three channels in the tropics and increases slightly with latitude (2-4 K). Moreover, the 166 GHz PD tends to increase in the case where a melting layer is beneath the frozen particles aloft in the atmosphere, while 89 GHz PD is less sensitive than 166 GHz to the melting layer. This property creates a unique PD feature for the identification of the melting layer and stratiform rain with passive sensors.Horizontally oriented non-spherical frozen particles are thought to produce the observed PD because of different ice scattering properties in the V and H polarizations. On the other hand, turbulent mixing within deep convective cores inevitably promotes the random

  8. How do changes in warm-phase microphysics affect deep convective clouds?

    NASA Astrophysics Data System (ADS)

    Chen, Qian; Koren, Ilan; Altaratz, Orit; Heiblum, Reuven H.; Dagan, Guy; Pinto, Lital

    2017-08-01

    Understanding aerosol effects on deep convective clouds and the derived effects on the radiation budget and rain patterns can largely contribute to estimations of climate uncertainties. The challenge is difficult in part because key microphysical processes in the mixed and cold phases are still not well understood. For deep convective clouds with a warm base, understanding aerosol effects on the warm processes is extremely important as they set the initial and boundary conditions for the cold processes. Therefore, the focus of this study is the warm phase, which can be better resolved. The main question is: How do aerosol-derived changes in the warm phase affect the properties of deep convective cloud systems? To explore this question, we used a weather research and forecasting (WRF) model with spectral bin microphysics to simulate a deep convective cloud system over the Marshall Islands during the Kwajalein Experiment (KWAJEX). The model results were validated against observations, showing similarities in the vertical profile of radar reflectivity and the surface rain rate. Simulations with larger aerosol loading resulted in a larger total cloud mass, a larger cloud fraction in the upper levels, and a larger frequency of strong updrafts and rain rates. Enlarged mass both below and above the zero temperature level (ZTL) contributed to the increase in cloud total mass (water and ice) in the polluted runs. Increased condensation efficiency of cloud droplets governed the gain in mass below the ZTL, while both enhanced condensational and depositional growth led to increased mass above it. The enhanced mass loading above the ZTL acted to reduce the cloud buoyancy, while the thermal buoyancy (driven by the enhanced latent heat release) increased in the polluted runs. The overall effect showed an increased upward transport (across the ZTL) of liquid water driven by both larger updrafts and larger droplet mobility. These aerosol effects were reflected in the larger

  9. Retrieval of ice cloud microphysical parameters using the CloudSat millimeter-wave radar and temperature

    NASA Astrophysics Data System (ADS)

    Austin, Richard T.; Heymsfield, Andrew J.; Stephens, Graeme L.

    2009-04-01

    A new remote sensing retrieval of ice cloud microphysics has been developed for use with millimeter-wave radar from ground-, air-, or space-based sensors. Developed from an earlier retrieval that used measurements of radar reflectivity factor together with a priori information about the likely cloud targets, the new retrieval includes temperature information as well to assist in determining the correct region of state space, particularly for those size distribution parameters that are less constrained by the radar measurements. These algorithms have served as the ice cloud retrieval algorithms in Releases 3 and 4 of the CloudSat 2B-CWC-RO Standard Data Product. Several comparison studies have been performed on the previous and current retrieval algorithms: some involving tests of the algorithms on simulated radar data (based on actual cloud probe data or cloud resolving models) and others featuring statistical comparisons of the R04 2B-CWC-RO product (current algorithm) to ice cloud mass retrievals by other spaceborne, airborne, and ground-based instruments or alternative algorithms using the same CloudSat radar data. Comparisons involving simulated radar data based on a database of cloud probe data showed generally good performance, with ice water content (IWC) bias errors estimated to be less than 40%. Comparisons to ice water content and ice water path estimates by other instruments are mixed. When the comparison is restricted to different retrieval approaches using the same CloudSat radar measurements, CloudSat R04 results generally agree with alternative IWC retrievals for IWC < 1000 mg m-3 at altitudes below 12 km but differ at higher ice contents and altitudes, either exceeding other retrievals or falling within a spread of retrieval values. Validation and reconciliation of all these approaches will continue to be a topic for further research.

  10. Microphysical characterization of long-range transported biomass burning particles from North America at three EARLINET stations

    NASA Astrophysics Data System (ADS)

    Ortiz-Amezcua, Pablo; Guerrero-Rascado, Juan Luis; José Granados-Muñoz, María; Benavent-Oltra, José Antonio; Böckmann, Christine; Samaras, Stefanos; Stachlewska, Iwona S.; Janicka, Łucja; Baars, Holger; Bohlmann, Stephanie; Alados-Arboledas, Lucas

    2017-05-01

    Strong events of long-range transported biomass burning aerosol were detected during July 2013 at three EARLINET (European Aerosol Research Lidar Network) stations, namely Granada (Spain), Leipzig (Germany) and Warsaw (Poland). Satellite observations from MODIS (Moderate Resolution Imaging Spectroradiometer) and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) instruments, as well as modeling tools such as HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) and NAAPS (Navy Aerosol Analysis and Prediction System), have been used to estimate the sources and transport paths of those North American forest fire smoke particles. A multiwavelength Raman lidar technique was applied to obtain vertically resolved particle optical properties, and further inversion of those properties with a regularization algorithm allowed for retrieving microphysical information on the studied particles. The results highlight the presence of smoke layers of 1-2 km thickness, located at about 5 km a.s.l. altitude over Granada and Leipzig and around 2.5 km a.s.l. at Warsaw. These layers were intense, as they accounted for more than 30 % of the total AOD (aerosol optical depth) in all cases, and presented optical and microphysical features typical for different aging degrees: color ratio of lidar ratios (LR532 / LR355) around 2, α-related ångström exponents of less than 1, effective radii of 0.3 µm and large values of single scattering albedos (SSA), nearly spectrally independent. The intensive microphysical properties were compared with columnar retrievals form co-located AERONET (Aerosol Robotic Network) stations. The intensity of the layers was also characterized in terms of particle volume concentration, and then an experimental relationship between this magnitude and the particle extinction coefficient was established.

  11. Sensitivity of Precipitation Processes to Microphysics and Resolution in a Cloud-resolving Model

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2003-01-01

    The Goddard Cumulus Ensemble (GCE) model is used to examine the impact of various microphysical schemes, and vertical and horizontal resolution on the development, intensity and rainfall associated with mesoscale convective systems, idealized hurricanes and an ensemble of clouds. The model variables include horizontal and vertical velocities, potential temperature, perturbation pressure, turbulent kinetic energy, and mixing ratios of all water phases (vapor, liquid, and ice). The major characteristics of the GCE model are the explicit representation of warm rain and ice microphysical processes, and their complex interactions with solar and infrared radiative transfer processes. For idealized hurricane, an axisymmetric version of the GCE model was developed and used successfully to simulate the tropical cyclogenesis process using both a Rankin vortex and saturated air within a specified radius as initial conditions. For mesoscale convective systems, the 3-D version of the GCE model was used to simulate squall lines that developed in the western Pacific, South China Sea, eastern Atlantic, South America and central US. For the cloud ensemble, the GCE model was integrated for several days in order to have a good sampling of cloud statistics.

  12. Final Report for "Improved Representations of Cloud Microphysics for Model and Remote Sensing Evaluation using Data Collected during ISDAC, TWP-ICE and RACORO

    SciTech Connect

    McFarquhar, Greg M.

    2003-06-11

    We were funded by ASR to use data collected during ISDAC and TWP-ICE to evaluate models with a variety of temporal and spatial scales, to evaluate ground-based remote sensing retrievals and to develop cloud parameterizations with the end goal of improving the modeling of cloud processes and properties and their impact on atmospheric radiation. In particular, we proposed to: 1) Calculate distributions of microphysical properties observed in arctic stratus during ISDAC for initializing and evaluating LES and GCMs, and for developing parameterizations of effective particle sizes, mean fall velocities, and mean single-scattering properties for such models; 2) Improve representations of particle sizes, fall velocities and scattering properties for tropical and arctic cirrus using TWP-ICE, ISDAC and M-PACE data, and to determine the contributions that small ice crystals, with maximum dimensions D less than 50 μm, make to mass and radiative properties; 3) Study fundamental interactions between clouds and radiation by improving representations of small quasi-spherical particles and their scattering properties. We were additionally funded 1-year by ASR to use RACORO data to develop an integrated product of cloud microphysical properties. We accomplished all of our goals.

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

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  16. Microphysical Modelling of Polar Stratospheric Clouds During the 1999-2000 Winter

    NASA Technical Reports Server (NTRS)

    Drdla, Katja; Schoeberl, Mark; Rosenfield, Joan; Gore, Warren J. (Technical Monitor)

    2000-01-01

    The evolution of the 1999-2000 Arctic winter has been examined using a microphysical/photochemical model run along diabatic trajectories. A large number of trajectories have been generated, filling the vortex throughout the region of polar stratospheric cloud (PSC) formation, and extending from November until the vortex breakup, in order to provide representative sampling of the evolution of PSCs and their effect on stratospheric chemistry. The 1999-2000 winter was particularly cold, allowing extensive PSC formation. Many trajectories have ten-day periods continuously below the Type I PSC threshold; significant periods of Type II PSCs are also indicated. The model has been used to test the extent and severity of denitrification and dehydration predicted using a range of different microphysical schemes. Scenarios in which freezing only occurs below the ice frost point (causing explicit coupling of denitrification and dehydration) have been tested, as well as scenarios with partial freezing at warmer temperatures (in which denitrification can occur independently of dehydration). The sensitivity to parameters such as aerosol freezing rates and heterogeneous freezing have been explored. Several scenarios cause sufficient denitrification to affect chlorine partitioning, and in turn, model-predicted ozone depletion, demonstrating that an improved understanding of the microphysics responsible for denitrification is necessary for understanding ozone loss rates.

  17. Microphysical Modelling of Polar Stratospheric Clouds During the 1999-2000 Winter

    NASA Technical Reports Server (NTRS)

    Drdla, Katja; Schoeberl, Mark; Rosenfield, Joan; Gore, Warren J. (Technical Monitor)

    2000-01-01

    The evolution of the 1999-2000 Arctic winter has been examined using a microphysical/photochemical model run along diabatic trajectories. A large number of trajectories have been generated, filling the vortex throughout the region of polar stratospheric cloud (PSC) formation, and extending from November until the vortex breakup, in order to provide representative sampling of the evolution of PSCs and their effect on stratospheric chemistry. The 1999-2000 winter was particularly cold, allowing extensive PSC formation. Many trajectories have ten-day periods continuously below the Type I PSC threshold; significant periods of Type II PSCs are also indicated. The model has been used to test the extent and severity of denitrification and dehydration predicted using a range of different microphysical schemes. Scenarios in which freezing only occurs below the ice frost point (causing explicit coupling of denitrification and dehydration) have been tested, as well as scenarios with partial freezing at warmer temperatures (in which denitrification can occur independently of dehydration). The sensitivity to parameters such as aerosol freezing rates and heterogeneous freezing have been explored. Several scenarios cause sufficient denitrification to affect chlorine partitioning, and in turn, model-predicted ozone depletion, demonstrating that an improved understanding of the microphysics responsible for denitrification is necessary for understanding ozone loss rates.

  18. Formation of Bidisperse Particle Clouds

    NASA Astrophysics Data System (ADS)

    Er, Jenn Wei; Zhao, Bing; Law, Adrian W. K.; Adams, E. Eric

    2014-11-01

    When a group of dense particles is released instantaneously into water, their motion has been conceptualized as a circulating particle thermal (Ruggerber 2000). However, Wen and Nacamuli (1996) observed the formation of particle clumps characterized by a narrow, fast moving core shedding particles into wakes. They observed the clump formation even for particles in the non-cohesive range as long as the source Rayleigh number was large (Ra > 1E3) or equivalently the source cloud number (Nc) was small (Nc < 3.2E2). This physical phenomenon has been investigated by Zhao et al. (2014) through physical experiments. They proposed the theoretical support for Nc dependence and categorized the formation processes into cloud formation, transitional regime and clump formation. Previous works focused mainly on the behavior of monodisperse particles. The present study further extends the experimental investigation to the formation process of bidisperse particles. Experiments are conducted in a glass tank with a water depth of 90 cm. Finite amounts of sediments with various weight proportions between coarser and finer particles are released from a cylindrical tube. The Nc being tested ranges from 6E-3 to 9.9E-2, which covers all the three formation regimes. The experimental results showed that the introduction of coarse particles promotes cloud formation and reduce the losses of finer particles into the wake. More quantitative descriptions of the effects of source conditions on the formation processes will be presented during the conference.

  19. Numerical Simulation of Hurricane Bonnie (1998). Part II: Sensitivity to Varying Cloud Microphysical Processes.

    NASA Astrophysics Data System (ADS)

    Zhu, Tong; Zhang, Da-Lin

    2006-01-01

    In this study, the effects of various cloud microphysics processes on the hurricane intensity, precipitation, and inner-core structures are examined with a series of 5-day explicit simulations of Hurricane Bonnie (1998), using the results presented in Part I as a control run. It is found that varying cloud microphysics processes produces little sensitivity in hurricane track, except for very weak and shallow storms, but it produces pronounced departures in hurricane intensity and inner-core structures.Specifically, removing ice microphysics produces the weakest (15-hPa underdeepening) and shallowest storm with widespread cloud water but little rainwater in the upper troposphere. Removing graupel from the control run generates a weaker hurricane with a wider area of precipitation and more cloud coverage in the eyewall due to the enhanced horizontal advection of hydrometeors relative to the vertical fallouts (or increased water loading). Turning off the evaporation of cloud water and rainwater leads to the most rapid deepening storm (i.e., 90 hPa in 48 h) with the smallest radius but a wider eyewall and the strongest eyewall updrafts. The second strongest storm, but with the most amount of rainfall, is obtained when the melting effect is ignored. It is found that the cooling due to melting is more pronounced in the eyewall where more frozen hydrometeors, especially graupel, are available, whereas the evaporative cooling occurs more markedly when the storm environment is more unsaturated.It is shown that stronger storms tend to show more compact eyewalls with heavier precipitation and more symmetric structures in the warm-cored eye and in the eyewall. It is also shown that although the eyewall replacement scenarios occur as the simulated storms move into weak-sheared environments, the associated inner-core structural changes, timing, and location differ markedly, depending on the hurricane intensity. That is, the eyewall convection in weak storms tends to diminish

  20. Optical and Microphysical Retrievals of Marine Stratocumulus Clouds off the Coast of Namibia from Satellite and Aircraft

    NASA Technical Reports Server (NTRS)

    Platnick, Steven E.

    2010-01-01

    Though the emphasis of the Southern Africa Regional Science Initiative 2000 (SAFARI-2000) dry season campaign was largely on emission sources and transport, the assemblage of aircraft (including the high altitude NASA ER-2 remote sensing platform and the University of Washington CV-580, UK MRF C-130, and South African Weather Bureau JRA in situ aircrafts) provided a unique opportunity for cloud studies. Therefore, as part of the SAFARI initiative, investigations were undertaken to assess regional aerosol-cloud interactions and cloud remote sensing algorithms. In particular, the latter part of the experiment concentrated on marine boundary layer stratocumulus clouds off the southwest coast of Africa. Associated with cold water upwelling along the Benguela current, the Namibian stratocumulus regime has received limited attention but appears to be unique for several reasons. During the dry season, outflow of continental fires and industrial pollution over this area can be extreme. From below, upwelling provides a rich nutrient source for phytoplankton (a source of atmospheric sulfur through DMS production as well as from decay processes). The impact of these natural and anthropogenic sources on the microphysical and optical properties of the stratocumulus is unknown. Continental and Indian Ocean cloud systems of opportunity were also studied during the campaign. SAFARI 2000 aircraft flights off the coast of Namibia were coordinated with NASA Terra Satellite overpasses for synergy with the Moderate Resolution Imaging Spectroradiometer (MODIS) and other Terra instruments. MODIS was developed by NASA and launched onboard the Terra spacecraft on December 18, 1999 (and Aqua spacecraft on May 4, 2002). Among the remote sensing algorithms developed and applied to this sensor are cloud optical and microphysical properties that include cloud thermodynamic phase, optical thickness, and effective particle radius of both liquid water and ice clouds. The archived products from

  1. Observations of monsoon convective cloud microphysics over India and role of entrainment-mixing

    NASA Astrophysics Data System (ADS)

    Bera, Sudarsan; Prabha, Thara V.; Grabowski, Wojciech W.

    2016-08-01

    Microphysical characteristics of premonsoon and monsoon deep cumuli over India observed by an instrumented aircraft are contrasted focusing on influences of environmental conditions and entrainment-mixing processes. Differences in the lower tropospheric temperature and moisture profiles lead to contrasting undiluted cloud buoyancy profiles around the cloud base, larger in the premonsoon case. It is argued that this affects the variation of the mean and maximum cloud droplet number concentrations and the droplet radius within the lowest several hundred meters above the cloud base. The conserved-variable thermodynamic diagram analysis suggests that entrained parcels originate from levels close to the observational level. Mixing processes and their impact on the droplet size distribution (DSD) are investigated contrasting 1 Hz and 10 Hz observations. Inhomogeneous-type mixing, likely because of unresolved small-scale structures associated with active turbulent stirring, is noted at cloud edge volumes where dilution is significant and DSDs shift toward smaller sizes with reduced droplet number concentrations due to complete evaporation of smaller droplets and partial evaporation of larger droplets. DSDs within cloud core volumes suggest that the largest droplets are formed in the least diluted volumes where raindrops can form at higher levels; no superadiabatic droplet growth is observed. The typical diluted parcel size is approximately 100-200 m for cloud edge volumes, and it is much smaller, 10-20 m, for cloud core volumes. Time scale analysis indicates the possibility of inhomogeneous type mixing within the diluted cloud edge volumes at spatial scales of a 100 m or more.

  2. Influence of the Entrainment Interface Layer on Cloud Microphysical Properties near Stratocumulus Top

    NASA Astrophysics Data System (ADS)

    Chuang, P. Y.; Carman, J. K.; Rossiter, D. L.

    2010-12-01

    Entrainment across the stratocumulus-topped boundary layer is a key process governing the cloud properties and evolution. This process is not well-represented even in high-resolution large-eddy simulations, in part due to the sharp gradients in temperature, buoyancy and (usually) humidity that occur at the top of the boundary layer. In summer 2008, the Physics of Stratocumulus Top (POST) field campaign conduct extensive measurements in the vicinity of cloud top, including the so-called entrainment interface layer or EIL that separates boundary layer and free tropospheric air. Roughly half of the fifteen flights occurred during the day (near solar noon) while the remaining flights occurred during late evening-to-night when solar input was minimal. A wide diversity of EIL properties has been revealed over the course of the campaign. EIL vertical thickness diagnosed using total water varies from fairly thin (~20 m) to very thick (>100 m). The thickness and intensity of the turbulent layer in this interfacial region also varies substantially, with the top of the significantly turbulent region ranging from 10 m to 50 m above cloud top. Shear in the vicinity of cloud top also varied strongly from day-to-day. While almost all cases exhibited strong jumps in potential temperature, there are a number of cases where the jump in total water was very small-to-none, and one case where total water was higher in the free troposphere by 1.4 g/kg. POST thus demonstrates that the cloud-top interfacial region exhibits a rich and diverse range of properties. This study focuses on how this EIL diversity affects the stratocumulus cloud itself. We build on our study of the EIL dynamic and thermodynamic properties to investigate the influence of the EIL on the microphysical properties of the stratocumulus in the vicinity of cloud top. Entrainment of the overlying warmer and (usually) drier air can strongly impact the amount of liquid water as well as the size and concentration of cloud

  3. Impact of particle shape on the morphology of noctilucent clouds

    NASA Astrophysics Data System (ADS)

    Kiliani, J.; Baumgarten, G.; Lübken, F.-J.; Berger, U.

    2015-11-01

    Noctilucent clouds (NLCs) occur during summer in the polar region at altitudes around 83 km. They consist of ice particles with a typical size around 50 nm. The shape of NLC particles is less well known but is important both for interpreting optical measurements and modeling ice cloud characteristics. In this paper, NLC modeling of microphysics and optics is adapted to use cylindrical instead of spherical particle shape. The optical properties of the resulting ice clouds are compared directly to NLC three-color measurements by the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) Rayleigh/Mie/Raman (RMR) lidar between 1998 and 2014. Shape distributions including both needle- and disc-shaped particles are consistent with lidar measurements. The best agreement occurs if disc shapes are 60 % more common than needles, with a mean axis ratio of 2.8. Cylindrical particles cause stronger ice clouds on average than spherical shapes with an increase of backscatter at 532 nm by ≈ 30 % and about 20 % in ice mass density. This difference is less pronounced for bright than for weak ice clouds. Cylindrical shapes also cause NLCs to have larger but a smaller number of ice particles than for spherical shapes.

  4. HOLIMO II: a digital holographic instrument for ground-based in-situ observations of microphysical properties of mixed-phase clouds

    NASA Astrophysics Data System (ADS)

    Henneberger, J.; Fugal, J. P.; Stetzer, O.; Lohmann, U.

    2013-05-01

    Measurements of the microphysical properties of mixed-phase clouds with high spatial resolution are important to understand the processes inside these clouds. This work describes the design and characterization of the newly developed ground-based field instrument HOLIMO II (HOLographic Imager for Microscopic Objects II). HOLIMO II uses digital in-line holography to in-situ image cloud particles in a well defined sample volume. By an automated algorithm, two-dimensional images of single cloud particles between 6 and 250 μm in diameter are obtained and the size spectrum, the concentration and water content of clouds are calculated. By testing the sizing algorithm with monosized beads a systematic overestimation near the resolution limit was found, which has been used to correct the measurements. Field measurements from the high altitude research station Jungfraujoch, Switzerland, are presented. The measured number size distributions are in good agreement with parallel measurements by a fog monitor (FM-100, DMT, Boulder USA). The field data shows that HOLIMO II is capable of measuring the number size distribution with a high spatial resolution and determines ice crystal shape, thus providing a method of quantifying variations in microphysical properties. A case study over a period of 8 h has been analyzed, exploring the transition from a liquid to a mixed-phase cloud, which is the longest observation of a cloud with a holographic device. During the measurement period, the cloud does not completely glaciate, contradicting earlier assumptions of the dominance of the Wegener-Bergeron-Findeisen (WBF) process.

  5. HOLIMO II: a digital holographic instrument for ground-based in situ observations of microphysical properties of mixed-phase clouds

    NASA Astrophysics Data System (ADS)

    Henneberger, J.; Fugal, J. P.; Stetzer, O.; Lohmann, U.

    2013-11-01

    Measurements of the microphysical properties of mixed-phase clouds with high spatial resolution are important to understand the processes inside these clouds. This work describes the design and characterization of the newly developed ground-based field instrument HOLIMO II (HOLographic Imager for Microscopic Objects II). HOLIMO II uses digital in-line holography to in situ image cloud particles in a well-defined sample volume. By an automated algorithm, two-dimensional images of single cloud particles between 6 and 250 μm in diameter are obtained and the size spectrum, the concentration and water content of clouds are calculated. By testing the sizing algorithm with monosized beads a systematic overestimation near the resolution limit was found, which has been used to correct the measurements. Field measurements from the high altitude research station Jungfraujoch, Switzerland, are presented. The measured number size distributions are in good agreement with parallel measurements by a fog monitor (FM-100, DMT, Boulder USA). The field data shows that HOLIMO II is capable of measuring the number size distribution with a high spatial resolution and determines ice crystal shape, thus providing a method of quantifying variations in microphysical properties. A case study over a period of 8 h has been analyzed, exploring the transition from a liquid to a mixed-phase cloud, which is the longest observation of a cloud with a holographic device. During the measurement period, the cloud does not completely glaciate, contradicting earlier assumptions of the dominance of the Wegener-Bergeron-Findeisen (WBF) process.

  6. Performance of McRAS-AC in the GEOS-5 AGCM: Part 1, Aerosol-Activated Cloud Microphysics, Precipitation, Radiative Effects, and Circulation

    NASA Technical Reports Server (NTRS)

    Sud, Y. C.; Lee, D.; Oreopoulos, L.; Barahona, D.; Nenes, A.; Suarez, M. J.

    2012-01-01

    A revised version of the Microphysics of clouds with Relaxed Arakawa-Schubert and Aerosol-Cloud interaction (McRAS-AC), including, among others, the Barahona and Nenes ice nucleation parameterization, is implemented in the GEOS-5 AGCM. Various fields from a 10-year long integration of the AGCM with McRAS-AC were compared with their counterparts from an integration of the baseline GEOS-5 AGCM, and with satellite data as observations. Generally using McRAS-AC reduced biases in cloud fields and cloud radiative effects are much better over most of the regions of the Earth. Two weaknesses are identified in the McRAS-AC runs, namely, too few cloud particles around 40S-60S, and too high cloud water path during northern hemisphere summer over the Gulf Stream and North Pacific. Sensitivity analyses showed that these biases potentially originated from biases in the aerosol input. The first bias is largely eliminated in a sensitivity test using 50% smaller 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 dry-convection, not yet implemented into the cloud scheme. Despite these biases, McRAS-AC does simulate realistic clouds and their optical properties that can improve with better aerosol-input and thereby has the potential to be a valuable tool for climate modeling research because of its aerosol indirect effect simulation capabilities involving prediction of cloud particle number concentration and effective particle size for both convective and stratiform clouds is quite realistic.

  7. Cloud-radiative and microphysical impacts from precipitating hydrometeors in South Asian summer monsoon

    NASA Astrophysics Data System (ADS)

    Wu, Wanchen

    A sensitivity test was performed to examine the radiative and microphysical feed- back of large hydrometeors (LHR) to both large-scale environment (LSE) and convec- tive systems in South Asian Summer Monsoon by Weather Research and Forecasting Advanced Research Model (WRF-ARW) equipped with Single-moment 6-class Mi- crophysics Scheme (WSM6) and new Goddard radiative transfer model. The cloud processes are fully represented and featured by WSM6. The results show ignoring LHR-radiative feedback can result in an average of SW gain around 20˜30 W/m2 at surface and LW loss around 5˜20 W/m2 at TOA over BoB, which are slightly larger than 3 ˜5 W/m2 estimated by Waliser at. el. (2011) for both surface SW gain and TOA LW loss. The absent of LHR-radiative effects only have slight difference in magnitude of monthly mean state compared to control run, while the exclusion of LHR can have a north shift of convective area which results in a huge bias in the monthly mean state. The results indicate the bias from exclusion of LHR is mainly from instantaneous fallout of LHR instead of neglect of LHR-radiative feedback. This study reveals the importance of LHR in microphysical parameterization. The MD cir- culation and convective structure could be changed substantially due to the absent of LHR. The cloud water and ice in convective systems as well as precipitation are greatly increased due to the absent of LHR, while the downdraft area is largely re- duced because of the incomplete microphysical processes. Overall, the overestimated the intensity, frequency and lifetime of MDs have substantial and profound influences on LSE and monthly mean state, which serves as an upper bound of the bias due to instantaneous fallout of LHR in GCM.

  8. Cloud microphysical and radiative properties measured by combined lidar, radar, and infrared radiometer

    SciTech Connect

    Eberhard, W.L.; Intrieri, J.M.; Chan, K.P.; Feingold, G.

    1995-04-01

    The goal of our research in the Instrument Development Program (IDP) is to provide experimental descriptions of the bulk, microphysical, and radiative parameters of clouds (especially cirrus) and the relationships between these properties, for use in developing and validating climate models. The strategy of the Atmospheric Lidar Division of our laboratory is to develop remote sensing techniques to simultaneously measure important cloud parameters and to apply these new methods and older ones in case studies and statistical investigations. Our division participated with the University of Utah on technique development during the first three years of IDP including field tests locally and at FIRE II. The Atmospheric Radiation Measurement (ARM) Program also helped fund demonstration of new technology at the Atlantic Stratocumulus Transition EXperiment (ASTEX). Our current research under a new, independent grant comprises four tasks, which are summarized.

  9. FINAL REPORT FOR THE DOE/ARM PROJECT TITLED Representation of the Microphysical and Radiative Properties of Ice Clouds in SCMs and GCMs

    SciTech Connect

    Mitchell, David L.

    2005-08-08

    The broad goal of this research is to improve climate prediction through better representation of cirrus cloud microphysical and radiative properties in global climate models (GCMs). Clouds still represent the greatest source of uncertainty in climate prediction, and the representation of ice clouds is considerably more challenging than liquid water clouds. While about 40% of cloud condensate may be in the form of ice by some estimates, there have been no credible means of representing the ice particle size distribution and mass removal rates from ice clouds in GCMs. Both factors introduce large uncertainties regarding the global net flux, the latter factor alone producing a change of 10 W/m2 in the global net flux due to plausible changes in effective ice particle fallspeed. In addition, the radiative properties of ice crystals themselves are in question. This research provides GCMs with a credible means of representing the full (bimodal) ice particle size distribution (PSD) in ice clouds, including estimates of the small crystal (D < 65 microns) mode of the PSD. It also provides realistic estimates of mass sedimentation rates from ice clouds, which have a strong impact on their ice contents and radiative properties. This can be done through proper analysis of ice cloud microphysical data from ARM and other field campaigns. In addition, this research tests the ice cloud radiation treatment developed under two previous ARM projects by comparing it against laboratory measurements of ice cloud extinction efficiency and by comparing it with explicit theoretical calculations of ice crystal optical properties. The outcome of this project includes two PSD schemes for ice clouds; one appropriate for mid-latitude cirrus clouds and another for tropical anvil cirrus. Cloud temperature and ice water content (IWC) are the inputs for these PSD schemes, which are based on numerous PSD observations. The temperature dependence of the small crystal mode of the PSD for tropical

  10. A regime-by-regime analysis of the microphysical properties and warm rain characteristics of marine-boundary-layer clouds using collocated CloudSat and MODIS data

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Cho, H.; Lebsock, M. D.; Platnick, S.

    2012-12-01

    Marine boundary layer (MBL) clouds play a critical role in the climate system, through their strong radiative forcing, and interactions with aerosols and precipitation. Recently, significant progresses have been made in modeling MBL clouds and aerosol-cloud-precipitation interactions in climate models. Physically-based cloud microphysics parameterization schemes have been developed and implemented in several popular climate models. The new schemes allow simulation of the influence of aerosol on cloud microphysics, in particular cloud droplet size, which is an essential step toward simulation of aerosol- cloud interaction. Despite the progress in modeling, systematic evaluations of the microphysical properties of MBL clouds and the warm rain characteristics on global scale using satellite observations are still lacking. As a result, cloud microphysics, which is the central component of aerosol-cloud-precipitation interaction, is still largely unconstrained in climate models. Recent studies found that MBL cloud droplet effective radii simulated in several GCMs are systematically smaller than MODIS operational retrievals. Further investigations of model issues based on these studies are, however, hampered by several issues, including the lack of constraint on precipitation in model-satellite comparison and inherent satellite retrieval uncertainties. Cloud observations from the instruments on NASA's A-Train satellite constellation, in particular CloudSat and MODIS, have provided an unprecedented opportunity for solving these issues and evaluating MBL clouds in climate models. In this study, we will classify MBL clouds into three different regimes based on collocated CloudSat and MODIS observations. After cloud regime classification, we will study the geographical location of each regime, derive statistics of key cloud properties and warm rain characteristics for each regime, which include MODIS cloud re, cloud τ, cloud liquid-water path (LWP) retrievals and Cloud

  11. Cloud properties and bulk microphysical properties of semi-transparent cirrus from IR Sounders

    NASA Astrophysics Data System (ADS)

    Stubenrauch, Claudia; Feofilov, Artem; Armante, Raymond; Guignard, Anthony

    2013-04-01

    Satellite observations provide a continuous survey of the atmosphere over the whole globe. IR sounders have been observing our planet since 1979. The spectral resolution has improved from TIROS-N Operational Vertical Sounders (TOVS) to the Atmospheric InfraRed Sounder (AIRS), and to the InfraRed Atmospheric Sounding Interferometer (IASI); resolution within the CO2 absorption band makes these passive sounders most sensitive to semi-transparent cirrus (about 30% of all clouds), day and night. The LMD cloud property retrieval method developed for TOVS, has been adapted to the second generation of IR sounders like AIRS and, recently, IASI. It is based on a weighted χ2 method using different channels within the 15 micron CO2 absorption band. Once the cloud physical properties (cloud pressure and IR emissivity) are retrieved, cirrus bulk microphysical properties (De and IWP) are determined from spectral emissivity differences between 8 and 12 μm. The emissivities are determined using the retrieved cloud pressure and are then compared to those simulated by the radiative transfer model. For IASI, we use the latest version of the radiative transfer model 4A (http://4aop.noveltis.com), which has been coupled with the DISORT algorithm to take into account multiple scattering of ice crystals. The code incorporates single scattering properties of column-like or aggregate-like ice crystals provided by MetOffice (Baran et al. (2001); Baran and Francis (2004)). The synergy of AIRS and two active instruments of the A-Train (lidar and radar of the CALIPSO and CloudSat missions), which provide accurate information on vertical cloud structure, allowed the evaluation of cloud properties retrieved by the weighted χ2 method. We present first results for cloud properties obtained with IASI/ Metop-A and compare them with those of AIRS and other cloud climatologies having participated in the GEWEX cloud assessment. The combination of IASI observations at 9:30 AM and 9:30 PM complement

  12. Impacts from Time-dependent Freezing of Rain and Wet Hail on Deep Convection Simulated by a Cloud Model with Spectral Bin Microphysics

    NASA Astrophysics Data System (ADS)

    Phillips, V. T.; Khain, A.; Ilotoviz, E.; BenMoshe, N.

    2014-12-01

    Any hydrometeor containing some supercooled liquid can only freeze it as fast as latent heat is dissipated to the ambient air. Consequently, at sub-zero temperatures any given particle in a cloud can contain both ice and liquid water. Wet growth of hail occurs when supercooled cloud-liquid is accreted faster than it can freeze immediately on impact. Equally, raindrops in clear air can take up to a few mins to freeze. A new theory of time-dependent freezing is proposed in this presentation. First, wet growth of hail is represented by treating inhomogeneities of liquid coverage and temperature over the surface of the particle. Radial heat fluxes from the sponge layer through the liquid skin to the air are predicted, as well as heat fluxes between its wet and dry parts. Gradual internal freezing of liquid that soaks the interior of the hail or graupel particle during dry growth ('riming') is represented. The microphysical recycling with alternating episodes of wet and dry growth is predicted. Second, the time-dependent process of raindrop freezing is represented by including thermodynamic effects from accretion of cloud-liquid and -ice. Freezing drops larger than about 0.1 mm are represented as a new microphysical species in a cloud model with spectral bin microphysics. The freezing drops consist of interior water covered by ice initially. Possibilities of both dry and wet growth of freezing drops are represented. Schemes of time-dependent freezing for rain and wet growth of hail and graupel were implemented in a spectral bin microphysics cloud model. The model predicted that accretion of liquid produces giant freezing drops of 0.5-2 cm in diameter, due to downdraft-updraft recirculation and wet growth of freezing drops. Appreciable contents of freezing drops reach a height level of 7 km (-30 degC) in the simulated storm. The critical diameter separating wet and dry growth regimes is predicted to increase with height for freezing drops. It is more vertically uniform

  13. Liquid and Ice Cloud Microphysics in the CSU General Circulation Model. Part III: Sensitivity to Modeling Assumptions.

    NASA Astrophysics Data System (ADS)

    Fowler, Laura D.; Randall, David A.

    1996-03-01

    The inclusion of cloud microphysical processes in general circulation models makes it possible to study the multiple interactions among clouds, the hydrological cycle, and radiation. The gaps between the temporal and spatial scales at which such cloud microphysical processes work and those at which general circulation models presently function force climate modelers to crudely parameterize and simplify the various interactions among the different water species (namely, water vapor, cloud water, cloud ice, rain, and snow) and to use adjustable parameters to which large-scale models can be highly sensitive. Accordingly, the authors have investigated the sensitivity of the climate, simulated with the Colorado State University general circulation model, to various aspects of the parameterization of cloud microphysical processes and its interactions with the cumulus convection and radiative transfer parameterizations.The results of 120-day sensitivity experiments corresponding to perpetual January conditions have been compared with those of a control simulation in order to 1 ) determine the importance of advecting cloud water, cloud ice, rain, and snow at the temporal and spatial scale resolutions presently used in the model; 2) study the importance of the formation of extended stratiform anvils at the tops of cumulus towers, 3) analyze the role of mixed-phase clouds in determining the partitioning among cloud water, cloud ice, rain, and snow and, hence, their impacts on the simulated cloud optical properties; 4) evaluate the sensitivity of the atmospheric moisture budget and precipitation rates to a change in the fall velocities of rain and snow; 5) determine the model's sensitivity to the prescribed thresholds of autoconversion of cloud water to rain and cloud ice to snow; and 6) study the impact of the collection of supercooled cloud water by snow, as well as accounting for the cloud optical properties of snow.Results are presented in terms of 30-day mean differences

  14. Improvements in Representations of Cloud Microphysics for BBHRP and Models using Data Collected during M-PACE and TWP-ICE

    SciTech Connect

    Greg M. McFarquhar

    2010-02-22

    In our research we proposed to use data collected during the 2004 Mixed-Phase Arctic Cloud Experiment (MPACE) and the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE) to improve retrievals of ice and mixed-phase clouds, to improve our understanding of how cloud and radiative processes affect cloud life cycles, and to develop and test methods for using ARM data more effectively in model. In particular, we proposed to: 1) use MPACE in-situ data to determine how liquid water fraction and cloud ice and liquid effective radius (r{sub ei} and r{sub ew}) vary with temperature, normalized cloud altitude and other variables for Arctic mixed-phase clouds, and to use these data to evaluate the performance of model parameterization schemes and remote sensing retrieval algorithms; 2) calculate rei and size/shape distributions using TWP-ICE in-situ data, investigate their dependence on cirrus type (oceanic or continental anvils or cirrus not directly traced to convection), and develop and test representations for MICROBASE; 3) conduct fundamental research enhancing our understanding of cloud/radiative interactions, concentrating on effects of small crystals and particle shapes and sizes on radiation; and 4) improve representations of microphysical processes for models (fall-out, effective density, mean scattering properties, rei and rew) and provide them to ARM PIs. In the course of our research, we made substantial progress on all four goals.

  15. Effects of Cloud-Microphysics on Tropical Atmospheric Hydrologic Processes in the GEOS GCM

    NASA Technical Reports Server (NTRS)

    Lau, K. M.; Wu, H. T.; Sud, Y. C.; Walker, G. K.

    2004-01-01

    The sensitivity of tropical atmospheric hydrologic processes to cloud-microphysics is investigated using the NASA GEOS GCM. Results show that a faster autoconversion - rate produces more warm rain and less clouds at all levels. Fewer clouds enhances longwave cooling and reduces shortwave heating in the upper troposphere, while more warm rain produces increased condensation heating in the lower troposphere. This vertical heating differential destablizes the tropical atmosphere, producing a positive feedback resulting in more rain over the tropics. The feedback is maintained via a two-cell secondary circulation. The lower cell is capped by horizontal divergence and maximum cloud detrainment near the melting/freezing, with rising motion in the warm rain region connected to descending motion in the cold rain region. The upper cell is found above the freezing/melting level, with longwave-induced subsidence in the warm rain and dry regions, coupled to forced ascent in the deep convection region. The tropical large scale circulation is found to be very sensitive to the radiative-dynamic effects induced by changes in autoconversion rate. Reduced cloud-radiation processes feedback due to a faster autoconversion rate results in intermittent but more energetic eastward propagating Madden and Julian Oscillations (MJO). Conversely,-a slower autconversion rate, with increased cloud radiation produces MJO's with more realistic westward propagating transients, resembling a supercloud cluster structure. Results suggests that warm rain and associated low and mid level clouds, i.e., cumulus congestus, may play a critical role in regulating the time-intervals of deep convections and hence the fundamental time scales of the MJO.

  16. Volcanic particle aggregation in explosive eruption columns. Part I: Parameterization of the microphysics of hydrometeors and ash

    NASA Astrophysics Data System (ADS)

    Textor, C.; Graf, H. F.; Herzog, M.; Oberhuber, J. M.; Rose, William I.; Ernst, G. G. J.

    2006-02-01

    The aggregation of volcanic ash particles within the eruption column of explosive eruptions has been observed at many volcanoes. It influences the residence time of ash in the atmosphere and the radiative properties of the umbrella cloud. However, the information on the processes leading to aggregate formation are still either lacking or very incomplete. We examine the fate of ash particles through numerical experiments with the plume model ATHAM (Active Tracer High resolution Atmospheric Model) in order to determine the conditions that promote ash particle aggregation. In this paper we describe the microphysics and parameterization of ash and hydrometeors. In a companion paper (this issue) we use this information in a series of numerical experiments. The parameterization includes the condensation of water vapor in the rising eruption column. The formation of liquid and solid hydrometeors and the effect of latent heat release on the eruption column dynamics are considered. The interactions of hydrometeors and volcanic ash within the eruption column that lead to aggregate formation are simulated for the first time within a rising eruption column. The microphysical parameterization follows a modal approach. The hydrometeors are described by two size classes, each of which is divided into a liquid and a frozen category. By analogy with the hydrometeor classification, we specify four categories of volcanic ash particles. We imply that volcanic particles are active as condensation nuclei for water and ice formation. Ash can be contained in all categories of hydrometeors, thus forming mixed particles of any composition reaching from mud rain to accretionary lapilli. Collisions are caused by gravitational capture of particles with different fall velocity. Coalescence of hydrometeor-ash aggregates is assumed to be a function of the hydrometeor mass fraction within the mixed particles. The parameterization also includes simplified descriptions of electrostatics and salinity

  17. A Mechanistic Understanding of North American Monsoon and Microphysical Properties of Ice Particles

    NASA Astrophysics Data System (ADS)

    Erfani, Ehsan

    A mechanistic understanding of the North American Monsoon (NAM) is suggested by incorporating local- and synoptic-scale processes. The local-scale mechanism describes the effect sea surface temperature (SST) in Gulf of California (GC) and how it contributes to the low-level moisture during the 2004 NAM. Before NAM onset, the strong low-level temperature inversion exists over the GC, but this inversion weakens with increasing GC SST and generally disappears once SSTs exceed 29.5°C, allowing the moist air, trapped in the MBL, to mix with free tropospheric air. This leads to a deep, moist layer that can be transported toward the NAM regions to produce thunderstorms. The synoptic scale mechanism is based on climatologies from 1983 to 2010 and explains that the warmest SSTs moving up the coast contributes to NAM convection and atmospheric heating, and consequently advancing the position of the anticyclone and the region of descent northward. In order to improve microphysical properties of ice clouds, this study develops self-consistent second order polynomial mass- and projected area-dimension (m-D and A-D) expressions that are valid over a much larger size range, compared to traditional power laws. Such expressions can easily be reduced to power laws for the size range of interest, in order to use in cloud and climate models. This was done by combining field measurements of individual ice particle m and D with airborne optical probe measurements of D, A and estimates of m. The resulting m-D and A-D expressions are functions of temperature and cloud type (synoptic vs. anvil), and are in good agreement with m-D power laws developed from recent field studies. These expressions also appear representative for heavily rimed dendrites occurring over the Sierra Nevada Mountains. By using the m-D field measurements of rimed and unrimed particles, and by developing theoretical methods, an approach was suggested for calculating rimed m and A, which has the benefit of accounting

  18. Impacts of Asian Dust on Cloud Microphysics and Precipitation during an Atmospheric River

    NASA Astrophysics Data System (ADS)

    Ault, A. P.; Creamean, J. M.; Williams, C. R.; Gaston, C. J.; Ralph, F. M.; Prather, K. A.

    2009-12-01

    Atmospheric rivers constitute a significant source of precipitation in the mid-latitudes of the northern hemisphere over relatively short time periods, but questions remain about the influence of external factors, such as aerosols, on precipitation locally and regionally. During the CalWater Early Start Campaign (Feb-Mar 2009) sampling aerosol measurements (aerosol time-of-flight mass spectrometry - ATOFMS, aerosol number concentration, CCN concentrations, aerosol size distributions, and PM2.5 mass concentrations) were combined with S-band profiling radar, meteorological, and disdrometer measurements at a remote site in the Central California Sierra Nevada to characterize atmospheric rivers. Aerosol measurements were made of clear air at the site, while rainwater samples were collected. The rainwater samples were then aerosolized and characterized on site using an ATOFMS. S-band radar measured the microphysics of the precipitating cloud and disdrometer measurements characterized the subsequent hydrometeors. During the study an atmospheric river and transported dust interacted, altering cloud properties and shifting the chemical composition of the aerosolized precipitation to markers indicative of transported Asia dust. In contrast, an atmospheric river characterized 8 days earlier was not impacted by Asian dust, leading to different cloud properties and rain water chemical composition. This study examined the impacts of long range transport on precipitation in the Sierras. A greater understanding of the impact of Asian dust on these processes is necessary to properly evaluate long term climate change in the middle latitudes and properly account for transported aerosols in cloud and precipitation models.

  19. Cloud Microphysical Properties in Mesoscale Convective Systems: An Intercomparison of Three Tropical Locations

    NASA Astrophysics Data System (ADS)

    Fontaine, Emmanuel; Leroy, Delphine; Schwarzenboeck, Alfons; Coutris, Pierre; Delanoë, Julien; Protat, Alain; Dezitter, Fabien; Grandin, Alice; Strapp, John W.; Lilie, Lyle E.

    2017-04-01

    Mesoscale Convective Systems are complex cloud systems which are primarily the result of specific synoptic conditions associated with mesoscale instabilities leading to the development of cumulonimbus type clouds (Houze, 2004). These systems can last several hours and can affect human societies in various ways. In general, weather and climate models use simplistic schemes to describe ice hydrometeors' properties. However, MCS are complex cloud systems where the dynamic, radiative and precipitation processes depend on spatiotemporal location in the MCS (Houze, 2004). As a consequence, hydrometeor growth processes in MCS vary in space and time, thereby impacting shape and concentration of ice crystals and finally CWC. As a consequence, differences in the representation of ice properties in models (Li et al., 2007, 2005) lead to significant disagreements in the quantification of ice cloud effects on climate evolution (Intergovernmental Panel on Climate Change Fourth Assessment Report). An accurate estimation of the spatiotemporal CWC distribution is therefore a key parameter for evaluating and improving numerical weather prediction (Stephens et al., 2002). The main purpose of this study is to show ice microphysical properties of MCS observed in three different locations in the tropical atmosphere: West-African continent, Indian Ocean, and Northern Australia. An intercomparison study is performed in order to quantify how similar or different are the ice hydrometeors' properties in these three regions related to radar reflectivity factors and temperatures observed in respective MCS.

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

    NASA Astrophysics Data System (ADS)

    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 < 0.2) and it decreases in the 'moderately polluted' condition (0.2 < AOD < 0.4) and decreases further in the 'highly 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

  1. Influence of the Kuwait oil fires plume (1991) on the microphysical development of clouds

    NASA Astrophysics Data System (ADS)

    Rudich, Yinon; Sagi, Ayelet; Rosenfeld, Daniel

    2003-08-01

    Applications of new retrieval methods to old satellite data allowed us to study the effects of smoke from the Kuwait oil fires in 1991 on clouds and precipitation. The properties of smoke-affected and smoke-free clouds were compared on the background of the dust-laden desert atmosphere. Several effects were observed: (1) clouds typically developed at the top of the smoke plume, probably because of solar heating and induced convection by the strongly absorbing aerosols; (2) large salt particles from the burning mix of oil and brines formed giant cloud condensation nuclei (CCN) close to the source, which initiated coalescence in the highly polluted clouds; (3) farther away from the smoke source, the giant CCN were deposited, and the extremely high concentrations of medium and small CCN dominated cloud development by strongly suppressing drop coalescence and growth with altitude; and (4) the smaller cloud droplets in the smoke-affected clouds froze at colder temperatures and suppressed both the water and ice precipitation forming processes. These observations imply that over land the smoke particles are not washed out efficiently and can be transported to long distances, extending the observed effects to large areas. The absorption of solar radiation by the smoke induces convection above the smoke plumes and consequently leads to formation of clouds with roots at the top of the smoke layer. This process dominates over the semidirect effect of cloud evaporation due to the smoke-induced enhanced solar heating, at least in the case of the Kuwait fires.

  2. Impact of Cloud Model Microphysics on Passive Microwave Retrievals of Cloud Properties. Part II: Uncertainty in Rain, Hydrometeor Structure, and Latent Heating Retrievals

    NASA Astrophysics Data System (ADS)

    Seo, Eun-Kyoung; Biggerstaff, Michael I.

    2006-07-01

    The impact of model microphysics on the retrieval of cloud properties based on passive microwave observations was examined using a three-dimensional, nonhydrostatic, adaptive-grid cloud model to simulate a mesoscale convective system over ocean. Two microphysical schemes, based on similar bulk two-class liquid and three-class ice parameterizations, were used to simulate storms with differing amounts of supercooled cloud water typical of both the tropical oceanic environment, in which there is little supercooled cloud water, and midlatitude continental environments in which supercooled cloud water is more plentiful. For convective surface-level rain rates, the uncertainty varied between 20% and 60% depending on which combination of passive and active microwave observations was used in the retrieval. The uncertainty in surface rain rate did not depend on the microphysical scheme or the parameter settings except for retrievals over stratiform regions based on 85-GHz brightness temperatures TB alone or 85-GHz TB and radar reflectivity combined. In contrast, systematic differences in the treatment of the production of cloud water, cloud ice, and snow between the parameterization schemes coupled with the low correlation between those properties and the passive microwave TB examined here led to significant differences in the uncertainty in retrievals of those cloud properties and latent heating. The variability in uncertainty of hydrometeor structure and latent heating associated with the different microphysical parameterizations exceeded the inherent variability in TB cloud property relations. This was true at the finescales of the cloud model as well as at scales consistent with satellite footprints in which the inherent variability in TB cloud property relations are reduced by area averaging.

  3. The Effects of Saharan Dust on Cloud Microphysics and its Impacts on the Caribbean Mid-Summer Drought

    NASA Astrophysics Data System (ADS)

    Comarazamy, D. E.; Gonzalez, J.; Glenn, E.

    2012-12-01

    Long-term atmospheric particle concentration data obtained from all Caribbean locations available in the Aerosol Robotic Network (AERONET) record show an increase in fine mode particle concentration during the summer months, leading to believe that this is evidence of the passing of Saharan Dust through the region. The annual precipitation pattern in the Caribbean basin shows a distinct bimodal behavior, where the first mode is called the Early Rainfall Season (ERS, April-July), and the second mode the Late Rainfall Season (LRS, August-November). The brief, relatively low-precipitation, period in July is usually referred to as the mid-summer drought (MSD). It has been hypothesized that the passing of Saharan Dust across the Caribbean may result in this observed precipitation pattern. A cloud-resolving regional atmospheric model driven with the AERONET observations was used to investigate the possible effects of different AP concentrations on cloud formation and rain development over the Caribbean Island of Puerto Rico. The modeling system was also used to investigate the role of aerosols in originating and controlling the Caribbean MSD. Results indicate that cloud microphysics play an important role in producing the bimodal precipitation pattern, while variations in large-scale atmospheric dynamics (e.g., VWS) help explain variations in the strength of the yearly bimodal events. In recent years the aerosol observing network in Puerto Rico has been enhanced to include AERONET sites upwind of San Juan, PR, and lidar locations downwind of the city, namely at the Arecibo Observatory and the University of Puerto Rico - Mayagüez. This configuration will help discriminate urban aerosols from large-scale transport. To further complement the lidar efforts in the island, a comprehensive surface observation data analysis and planetary boundary layer characterization of the Intra-Americas Region was performed using historical data from COOP stations as archived by the NCDC, 2

  4. Effect of Amazon smoke on cloud microphysics and albedo - analysis from satellite imagery

    SciTech Connect

    Kaufman, Y.J. ); Nakajima, Teruyuki )

    1993-04-01

    NOAA Advanced Very High Resolution Radiometer images taken over the Brazilian Amazon Basin during the biomass burning season of 1987 are used to study the effect of smoke aerosol particles on the properties of low cumulus and stratocumulus clouds. The reflectance at a wavelength of 0.64 [mu]m and the drop size, derived from the cloud reflectance at 3.75 [mu]m, are studied for tens of thousands of clouds. The opacity of the smoke layer adjacent to each cloud is also monitored simultaneously. Satellite data can be used to generate large-scale statistics of the properties of clouds and surrounding aerosol from which the interaction of aerosol with clouds can be surmised. To minimize the effect of variations in the precipitable water vapor and in other smoke and cloud properties, biomass burning in the tropics is chosen as the study topic. The results are averaged for numerous clouds with the same ambient smoke optical thickness. It is shown that the presence of dense smoke can reduce the remotely sensed drop size of continental cloud drops from 15 to 9 [mu]m. Due to the high initial reflectance of clouds in the visible part of the spectrum and the presence of graphitic carbon, the average cloud reflectance at 0.64 [mu]m is reduced from 0.71 to 0.68 for an increase in smoke optical thickness from 0.1 to 2.0. The measurements are compared to results from other years. A high concentration of aerosol particles causes a decrease in the cloud-drop size and that smoke darkens the bright Amazonian clouds. Comparison with theoretical computations based on Twomey's model show that it is possible to explain the reduction in the cloud reflectance at 0.64 [mu]m for smoke imagery index of -0.02 to -0.03. Smoke particles are hygroscopic and have a similar size distribution to maritime and anthropogenic sulfuric aerosol particles. These results may also be representative of the interaction of sulfuric particles with clouds. 65 refs., 10 figs., 3 tabs.

  5. Simulation study of the remote sensing of optical and microphysical properties of cirrus clouds from satellite IR measurements.

    PubMed

    Xu, L; Zhang, J

    1995-05-20

    Improved ray-optics theory and Mie theory for single scattering and an adding-doubling method for multiple scattering have been used to study the interaction of radiation in NASA's Visible and Infrared Spin-Scan Radiometer Atmospheric Sounder Satellite (VAS) IR channels and the microphysics of inhomogeneous cirrus clouds. The simulation study shows that crystal shape has remarkable effects on scattering and on the radiative-transfer properties of cirrus clouds in IR spectra. The sensitivity of the brightness temperature, as observed with VAS-IR channels, to the hexagonal columns and plates in cirrus clouds is noticeable. A method that permits one to infer the optical thickness, crystal shape, ice-water content,and emittance of cirrus clouds by using a multi-IR window channel with a scanning observation technique is developed. Detailed error analyses are carried out, and the characteristics of VAS-IR window channels are investigated through the examination of the effects of sea-surface reflection and variations in the temperature and water-vapor profiles on the VAS measurements. It is shown that these effects are large and need to be considered. Some uncertainties that have risen from the theoretical model are studied; they demonstrate that the Mie-scattering theory should not be used to retrieve the microphysical and optical properties of cirrus clouds. A suitable cloud-microphysics model and a suitable scattering model are needed instead.

  6. On the acceleration of Eta Ferrier Cloud Microphysics Scheme in the Weather Research and Forecasting (WRF) model using a GPU

    NASA Astrophysics Data System (ADS)

    Huang, Melin; Mielikainen, Jarno; Huang, Bormin; Huang, H.-L. A.; Goldberg, Mitchell D.

    2012-10-01

    The Eta Ferrier cloud microphysics scheme is a sophisticated cloud microphysics module in the Weather Research and Forecasting (WRF) model. In this paper, we present the approach and the results of accelerating the Eta Ferrier microphysics scheme on NVIDIA Graphics Processing Units (GPUs). We discuss how our GPU implementation takes advantage of the parallelism in Eta Ferrier scheme, leading to a highly efficient GPU acceleration. We implement the Eta Ferrier microphysics scheme on NVidia GTX 590 GPU. Our 1-GPU implementation achieves an overall speedup of 37 as compared with a single thread CPU. Since Eta Ferrier microphysics scheme is only an intermediate module of the entire WRF model, the GPU I/O should not occur, i.e. its input data should be already available in the GPU global memory from previous modules and its output data should reside at the GPU global memory for later usage by other modules. The speedup without the host-device data transfer time is 272 with respect to its serial version running on 3.20GHz Intel® CoreTM i7 970 CPU.

  7. Study of Midlatitude and Arctic Aerosol-Cloud-Radiation Feedbacks Based on LES Model with Explicit Ice and Liquid Phase Microphysics.

    DTIC Science & Technology

    2007-11-02

    validate the CIMMS LES model and to improve our understanding of the interaction between the microphysical, radiative, and thermodynamical processes...modeling part of the research will be based on the CIMMS 3-D LES model of a stratocumulus cloud layer that includes an explicit formulation of aerosol...and cloud drop size resolving microphysics and radiation. The study of mixed phase clouds will use the new version of the CIMMS model which includes

  8. A statistical data analysis and plotting program for cloud microphysics experiments

    NASA Technical Reports Server (NTRS)

    Jordan, A. J.

    1981-01-01

    The analysis software developed for atmospheric cloud microphysics experiments conducted in the laboratory as well as aboard a KC-135 aircraft is described. A group of four programs was developed and implemented on a Hewlett Packard 1000 series F minicomputer running under HP's RTE-IVB operating system. The programs control and read data from a MEMODYNE Model 3765-8BV cassette recorder, format the data on the Hewlett Packard disk subsystem, and generate statistical data (mean, variance, standard deviation) and voltage and engineering unit plots on a user selected plotting device. The programs are written in HP FORTRAN IV and HP ASSEMBLY Language with the graphics software using the HP 1000 Graphics. The supported plotting devices are the HP 2647A graphics terminal, the HP 9872B four color pen plotter, and the HP 2608A matrix line printer.

  9. Influence of Ice Cloud Microphysics on Imager-Based Estimates of Earth's Radiation Budget

    NASA Astrophysics Data System (ADS)

    Loeb, N. G.; Kato, S.; Minnis, P.; Yang, P.; Sun-Mack, S.; Rose, F. G.; Hong, G.; Ham, S. H.

    2016-12-01

    A central objective of the Clouds and the Earth's Radiant Energy System (CERES) is to produce a long-term global climate data record of Earth's radiation budget from the TOA down to the surface along with the associated atmospheric and surface properties that influence it. CERES relies on a number of data sources, including broadband radiometers measuring incoming and reflected solar radiation and OLR, high-resolution spectral imagers, meteorological, aerosol and ozone assimilation data, and snow/sea-ice maps based on microwave radiometer data. While the TOA radiation budget is largely determined directly from accurate broadband radiometer measurements, the surface radiation budget is derived indirectly through radiative transfer model calculations initialized using imager-based cloud and aerosol retrievals and meteorological assimilation data. Because ice cloud particles exhibit a wide range of shapes, sizes and habits that cannot be independently retrieved a priori from passive visible/infrared imager measurements, assumptions about the scattering properties of ice clouds are necessary in order to retrieve ice cloud optical properties (e.g., optical depth) from imager radiances and to compute broadband radiative fluxes. This presentation will examine how the choice of an ice cloud particle model impacts computed shortwave (SW) radiative fluxes at the top-of-atmosphere (TOA) and surface. The ice cloud particle models considered correspond to those from prior, current and future CERES data product versions. During the CERES Edition2 (and Edition3) processing, ice cloud particles were assumed to be smooth hexagonal columns. In the Edition4, roughened hexagonal columns are assumed. The CERES team is now working on implementing in a future version an ice cloud particle model comprised of a two-habit ice cloud model consisting of roughened hexagonal columns and aggregates of roughened columnar elements. In each case, we use the same ice particle model in both the

  10. Determining the Polar Cosmic Ray Effect on Cloud Microphysics and the Earth's Ozone Layer

    NASA Astrophysics Data System (ADS)

    Beckie, Charlene Radons

    water content and effective radius, or altitude specific studies concerning the stratosphere. Continued results from laboratory studies at the CERN facility may lead to a deeper understanding of cosmic ray, cloud microphysics and ozone relationships in nature.

  11. Implication of observed cloud variability for parameterizations of microphysical and radiative transfer processes in climate models

    NASA Astrophysics Data System (ADS)

    Huang, D.; Liu, Y.

    2014-12-01

    The effects of subgrid cloud variability on grid-average microphysical rates and radiative fluxes are examined by use of long-term retrieval products at the Tropical West Pacific (TWP), Southern Great Plains (SGP), and North Slope of Alaska (NSA) sites of the Department of Energy's Atmospheric Radiation Measurement (ARM) Program. Four commonly used distribution functions, the truncated Gaussian, Gamma, lognormal, and Weibull distributions, are constrained to have the same mean and standard deviation as observed cloud liquid water content. The PDFs are then used to upscale relevant physical processes to obtain grid-average process rates. It is found that the truncated Gaussian representation results in up to 30% mean bias in autoconversion rate whereas the mean bias for the lognormal representation is about 10%. The Gamma and Weibull distribution function performs the best for the grid-average autoconversion rate with the mean relative bias less than 5%. For radiative fluxes, the lognormal and truncated Gaussian representations perform better than the Gamma and Weibull representations. The results show that the optimal choice of subgrid cloud distribution function depends on the nonlinearity of the process of interest and thus there is no single distribution function that works best for all parameterizations. Examination of the scale (window size) dependence of the mean bias indicates that the bias in grid-average process rates monotonically increases with increasing window sizes, suggesting the increasing importance of subgrid variability with increasing grid sizes.

  12. Application of TRMM PR and TMI Measurements to Assess Cloud Microphysical Schemes in the MM5 Model for a Winter Storm

    NASA Technical Reports Server (NTRS)

    Han, Mei; Braun, Scott A.; Olson, William S.; Persson, P. Ola G.; Bao, Jian-Wen

    2009-01-01

    Seen by the human eye, precipitation particles are commonly drops of rain, flakes of snow, or lumps of hail that reach the ground. Remote sensors and numerical models usually deal with information about large collections of rain, snow, and hail (or graupel --also called soft hail ) in a volume of air. Therefore, the size and number of the precipitation particles and how particles interact, evolve, and fall within the volume of air need to be represented using physical laws and mathematical tools, which are often implemented as cloud and precipitation microphysical parameterizations in numerical models. To account for the complexity of the precipitation physical processes, scientists have developed various types of such schemes in models. The accuracy of numerical weather forecasting may vary dramatically when different types of these schemes are employed. Therefore, systematic evaluations of cloud and precipitation schemes are of great importance for improvement of weather forecasts. This study is one such endeavor; it pursues quantitative assessment of all the available cloud and precipitation microphysical schemes in a weather model (MM5) through comparison with the observations obtained by National Aeronautics and Space Administration (NASA) s and Japan Aerospace Exploration Agency (JAXA) s Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and microwave imager (TMI). When satellite sensors (like PR or TMI) detect information from precipitation particles, they cannot directly observe the microphysical quantities (e.g., water species phase, density, size, and amount etc.). Instead, they tell how much radiation is absorbed by rain, reflected away from the sensor by snow or graupel, or reflected back to the satellite. On the other hand, the microphysical quantities in the model are usually well represented in microphysical schemes and can be converted to radiative properties that can be directly compared to the corresponding PR and TMI observations

  13. Microphysical and radiative changes in cirrus clouds by geoengineering the stratosphere

    NASA Astrophysics Data System (ADS)

    Cirisan, A.; Spichtinger, P.; Luo, B. P.; Weisenstein, D. K.; Wernli, H.; Lohmann, U.; Peter, T.

    2013-05-01

    In the absence of tangible progress in reducing greenhouse gas emissions, the implementation of solar radiation management has been suggested as measure to stop global warming. Here we investigate the impacts on northern midlatitude cirrus from continuous SO2emissions of 2-10 Mt/a in the tropical stratosphere. Transport of geoengineering aerosols into the troposphere was calculated along trajectories based on ERA Interim reanalyses using ozone concentrations to quantify the degree of mixing of stratospheric and tropospheric air termed "troposphericity". Modeled size distributions of the geoengineered H2SO4-H2O droplets have been fed into a cirrus box model with spectral microphysics. The geoengineering is predicted to cause changes in ice number density by up to 50%, depending on troposphericity and cooling rate. We estimate the resulting cloud radiative effects from a radiation transfer model. Complex interplay between the few large stratospheric and many small tropospheric H2SO4-H2O droplets gives rise to partly counteracting radiative effects: local increases in cloud radiative forcing up to +2 W/m2for low troposphericities and slow cooling rates, and decreases up to -7.5 W/m2for high troposphericities and fast cooling rates. The resulting mean impact on the northern midlatitudes by changes in cirrus is predicted to be low, namely <1% of the intended radiative forcing by the stratospheric aerosols. This suggests that stratospheric sulphate geoengineering is unlikely to have large microphysical effects on the mean cirrus radiative forcing. However, this study disregards feedbacks, such as temperature and humidity changes in the upper troposphere, which must be examined separately.

  14. Tropical Convective Responses to Microphysical and Radiative Processes: A Sensitivity Study With a 2D Cloud Resolving Model

    NASA Technical Reports Server (NTRS)

    Li, Xiao-Fan; Sui, C.-H.; Lau, K.-M.; Tao, W.-K.

    2004-01-01

    Prognostic cloud schemes are increasingly used in weather and climate models in order to better treat cloud-radiation processes. Simplifications are often made in such schemes for computational efficiency, like the scheme being used in the National Centers for Environment Prediction models that excludes some microphysical processes and precipitation-radiation interaction. In this study, sensitivity tests with a 2D cloud resolving model are carried out to examine effects of the excluded microphysical processes and precipitation-radiation interaction on tropical thermodynamics and cloud properties. The model is integrated for 10 days with the imposed vertical velocity derived from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. The experiment excluding the depositional growth of snow from cloud ice shows anomalous growth of cloud ice and more than 20% increase of fractional cloud cover, indicating that the lack of the depositional snow growth causes unrealistically large mixing ratio of cloud ice. The experiment excluding the precipitation-radiation interaction displays a significant cooling and drying bias. The analysis of heat and moisture budgets shows that the simulation without the interaction produces more stable upper troposphere and more unstable mid and lower troposphere than does the simulation with the interaction. Thus, the suppressed growth of ice clouds in upper troposphere and stronger radiative cooling in mid and lower troposphere are responsible for the cooling bias, and less evaporation of rain associated with the large-scale subsidence induces the drying in mid and lower troposphere.

  15. Modeling cloud microphysics using a two-moments hybrid bulk/bin scheme for use in Titan’s climate models: Application to the annual and diurnal cycles

    NASA Astrophysics Data System (ADS)

    Burgalat, J.; Rannou, P.; Cours, T.; Rivière, E. D.

    2014-03-01

    Microphysical models describe the way aerosols and clouds behave in the atmosphere. Two approaches are generally used to model these processes. While the first approach discretizes processes and aerosols size distributions on a radius grid (bin scheme), the second uses bulk parameters of the size distribution law (its mathematical moments) to represent the evolution of the particle population (moment scheme). However, with the latter approach, one needs to have an a priori knowledge of the size distributions. Moments scheme for Cloud microphysics modeling have been used and enhanced since decades for climate studies of the Earth. Most of the tools are based on Log-Normal law which are suitable for Earth, Mars or Venus. On Titan, due to the fractal structure of the aerosols, the size distributions do not follow a log-normal law. Then using a moment scheme in that case implies to define the description of the size distribution and to review the equations that are widely published in the literature. Our objective is to enable the use of a fully described microphysical model using a moment scheme within a Titan's Global Climate Model. As a first step in this direction, we present here a moment scheme dedicated to clouds microphysics adapted for Titan's atmosphere conditions. We perform comparisons between the two kinds of schemes (bin and moments) using an annual and a diurnal cycle, to check the validity of our moment description. The various forcing produce a time-variable cloud layer in relation with the temperature cycle. We compare the column opacities and the temperature for the two schemes, for each cycles. We also compare more detailed quantities as the opacity distribution of the cloud events at different periods of these cycles. Results show that differences between the two approaches have a small impact on the temperature (less than 1 K) and range between 1% and 10% for haze and clouds opacities. Both models behave in similar way when forced by an annual and

  16. Effect of Long-Range Aerosol Transport on the Microphysical Properties of Low-Level Clouds in the Arctic

    NASA Astrophysics Data System (ADS)

    Coopman, Q.; Garrett, T. J.; Riedi, J.; Finch, D.

    2015-12-01

    The Arctic region is influenced by elevated concentration of aerosols from mid-latitudes. By acting as Cloud Condensation Nuclei (CCN) and/or Ice Nuclei (IN), these aerosols influence cloud presence and formation, and in turn cloud radiative properties and forcing. We analyze the impact of pollution plumes on cloud microphysical properties, including droplet effective radius and cloud optical depth, by calculating an indirect effect (IE) parameter. This IE parameter is defined by the ratio of relative change in cloud microphysical properties to relative variations in pollution concentrations. We also study the impact of aerosols on the cloud thermodynamic phase. In our study we used three sets of data: (i) A combination of POLDER-3/PARASOL and MODIS/AQUA satellite measurements to retrieve cloud properties, (ii) an atmospheric chemistry transport model GEOS-Chem carbon monoxide tracer for concentrations of biomass burning and anthropogenic pollution plumes, (iii) and reanalysis data from ECMWF for the meteorological state. The pollution plumes from biomass burning sources appear to be good IN, whereas pollution from anthropogenic sources appears to act as better CCN. We extend the analysis to different specific humidity and stability regimes to find that the specific humidity and lower tropospheric stability increase the cloud microphysical sensitivity to pollution loading. For example, for low specific humidity situations the IE parameter is close to zero whereas for the highest values of specific humidity - greater than 5 g kg-1 - the impact of aerosols is a maximum: The IE parameter is up to 0.1 and 0.2 for the effective radius and the optical depth respectively. When the lower tropospheric stability is greater than 25˚K, the IE parameter is approximately 0.3 for the optical depth. We hypothesize that the observed correlation between IE and stability is because cloud formation in the Arctic region is dominated by radiative cooling.

  17. Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

    NASA Astrophysics Data System (ADS)

    Coopman, Q.; Garrett, T. J.; Riedi, J.; Eckhardt, S.; Stohl, A.

    2015-11-01

    The properties of clouds in the Arctic can be altered by long-range aerosol transport to the region. The goal of this study is to use satellite, tracer transport model, and meteorological data sets to determine the effects of pollution on cloud microphysics due only to pollution itself and not to the meteorological state. Here, A-Train, POLDER-3 and MODIS satellite instruments are used to retrieve low-level liquid cloud microphysical properties over the Arctic between 2008 and 2010. Cloud retrievals are co-located with simulated pollution represented by carbon-monoxide concentrations from the FLEXPART tracer transport model. The sensitivity of clouds to pollution plumes - including aerosols - is constrained for cloud liquid water path, temperature, altitude, specific humidity, and lower tropospheric stability (LTS). We define an Indirect Effect (IE) parameter from the ratio of relative changes in cloud microphysical properties to relative variations in pollution concentrations. Retrievals indicate that, depending on the meteorological regime, IE parameters range between 0 and 0.34 for the cloud droplet effective radius, and between -0.10 and 0.35 for the optical depth, with average values of 0.12 ± 0.02 and 0.15 ± 0.02 respectively. The IE parameter increases with increasing specific humidity and LTS. Further, the results suggest that for a given set of meteorological conditions, the liquid water path of arctic clouds does not respond strongly to pollution. Or, not constraining sufficiently for meteorology may lead to artifacts that exaggerate the magnitude of the aerosol indirect effect. The converse is that the response of arctic clouds to pollution does depend on the meteorologic state. Finally, we find that IE values are highest when pollution concentrations are low, and that they depend on the source of pollution.

  18. Retrieval of cloud microphysical parameters using the NOAA/PSD W-band cloud radar from R/V Ronald H. Brown during the VOCALS-REx field program

    NASA Astrophysics Data System (ADS)

    Fairall, C. W.; Deszoeke, S. P.; Moran, K.; Pezoa, S.; Wolfe, D. E.; Zuidema, P.

    2009-12-01

    The NOAA Physical Science Division deployed a new pitch-roll stabilized, vertically pointing W-band (94 GHz) Doppler cloud radar on the NOAA research vessel Ronald H. Brown during the VOCALS-Rex field program in fall 2008 in the stratocumulus region off the coast of Chile. The radar operated at full sensitivity on Leg-2 (November 8-30, 2008). The radar produced profiles of full Doppler spectra and the first three moments of the spectral peak at 0.3 s time intervals; the vertical resolution is 25 m. Pitch-roll stabilization allows Doppler measurement of vertical motion without tilt-contamination by horizontal winds; ship heave is measured independently and subtracted from the radar vertical velocity to yield very accurate particle vertical motions. In this paper we describe the results of processing the radar moments in one-hour blocks to retrieve cloud and drizzle microphysical parameters using the method of Frisch, Fairall, and Snider, JAS1995. Additional inputs from a lidar ceilometer and a microwave radiometer are used. For cloud, profiles of liquid water and mean cloud drop radius are obtained; for drizzle profiles of liquid water, mean drizzle drop radius, and rainrate are obtained. Cloud microphysics processing is only possible in non-drizzling cases. The results are compared to analyses from the EPIC2001 field program in the same location.

  19. Investigation of the effects of the macrophysical and microphysical properties of cirrus clouds on the retrieval of optical properties: Results for FIRE 2

    NASA Technical Reports Server (NTRS)

    Stackhouse, Paul W., Jr.; Stephens, Graeme L.

    1993-01-01

    Due to the prevalence and persistence of cirrus cloudiness across the globe, cirrus clouds are believed to have an important effect on the climate. Stephens et al., (1990) among others have shown that the important factor determining how cirrus clouds modulate the climate is the balance between the albedo and emittance effect of the cloud systems. This factor was shown to depend in part upon the effective sizes of the cirrus cloud particles. Since effective sizes of cirrus cloud microphysical distributions are used as a basis of parameterizations in climate models, it is crucial that the relationships between effective sizes and radiative properties be clearly established. In this preliminary study, the retrieval of cirrus cloud effective sizes are examined using a two dimensional radiative transfer model for a cirrus cloud case sampled during FIRE Cirrus 11. The purpose of this paper is to present preliminary results from the SHSG model demonstrating the sensitivity of the bispectral relationships of reflected radiances and thus the retrieval of effective sizes to phase function and dimensionality.

  20. Radiative and cloud microphysical effects of forest fire smoke over North America and Siberia

    NASA Astrophysics Data System (ADS)

    vant-Hull, Brian

    Siberia, as expected from the higher sulfate load with greater activity as cloud condensation nuclei (CCN). The aerosol indirect effect on cloud microphysics increases with aerosol loading in both regions, but much more so in Canada. This is attributed to a large sulfate background in Siberia, so the addition of smoke makes a smaller percentage change to the amount of cloud CCN.

  1. Optical-Microphysical Cirrus Model

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  2. Characterization of optical and micro-physical properties of cirrus clouds using a wideband thermal infrared spectrometer

    NASA Astrophysics Data System (ADS)

    Palchetti, Luca; Di Natale, Gianluca; Bianchini, Giovanni

    2014-05-01

    High-altitude ice clouds such as cirrus clouds play a key role in the Earth's radiation budget since they cover permanently about 20-30% of the surface of the planet, reaching even to 60-70% in the tropics. The modulation of the incoming solar radiation and the outgoing Earth's thermal emission due to cirrus can contribute to heat or to cool the atmosphere, according to their optical properties, which must be characterised with great accuracy and over the whole spectral range involved in the scattering and emission processes. Here we present the infrared measurements over the wide spectral range from 9 to 50 micron performed by the Fourier transform spectrometer REFIR-PAD (Radiation Explorer in Far InfraRed - Prototype for Application and Development) during many field campaigns that have taken place since 2007 from different high-altitude ground-based stations: Testa Grigia Station, Cervinia-Italy, (3480 m asl), Cerro Toco, Atacama-Chile, (5380 m asl), Concordia Base, Dome C-Antarctica (3230 m asl). These measurements show for the first time the spectral effect of cirrus clouds in the long-wave part of the emission spectrum above 15 micron of wavelength. To characterise these measurements over the wide spectral range as a function of the optical properties of ice particles, a model of the radiative transfer, that integrates the well known numerical code LBLRTM, which simulates the radiative transfer in the atmosphere, with a specific code which simulates the propagation of the radiation through the cloud, was developed. The optical properties of clouds have been modelled using the δ-scaled Eddington approximation for a single layer and the Ping Yang's database for the single-scattering properties of ice crystals. The preliminary results of the fit procedure used for the determination of the micro-physical parameters of ice crystals, such as the effective diameter, ice water path, effective temperature and optical thickness will be shown in the presentation. The

  3. Radiative-dynamical and microphysical processes of thin cirrus clouds controlling humidity of air entering the stratosphere

    NASA Astrophysics Data System (ADS)

    Dinh, Tra; Fueglistaler, Stephan

    2016-04-01

    Thin cirrus clouds in the tropical tropopause layer (TTL) are of great interest due to their role in the control of water vapor and temperature in the TTL. Previous research on TTL cirrus clouds has focussed mainly on microphysical processes, specifically the ice nucleation mechanism and dehydration efficiency. Here, we use a cloud resolving model to analyse the sensitivity of TTL cirrus characteristics and impacts with respect to microphysical and radiative processes. A steady-state TTL cirrus cloud field is obtained in the model forced with dynamical conditions typical for the TTL (2-dimensional setup with a Kelvin-wave temperature perturbation). Our model results show that the dehydration efficiency (as given by the domain average relative humidity in the layer of cloud occurrence) is relatively insensitive to the ice nucleation mechanism, i.e. homogeneous versus heterogeneous nucleation. Rather, TTL cirrus affect the water vapor entering the stratosphere via an indirect effect associated with the cloud radiative heating and dynamics. Resolving the cloud radiative heating and the radiatively induced circulations approximately doubles the domain average ice mass. The cloud radiative heating is proportional to the domain average ice mass, and the observed increase in domain average ice mass induces a domain average temperature increase of a few Kelvin. The corresponding increase in water vapor entering the stratosphere is estimated to be about 30 to 40%.

  4. A one-dimensional radiative convective model with detailed cloud microphysics

    SciTech Connect

    Simmons, J.; Lie-Svendsen, O.; Stamnes, K.

    1995-04-01

    The Arctic is a key element in determining the radiation budget of the earth. Within the polar regions, the net radiation (incoming solar radiation minus outgoing infrared radiation) is negative. To understand the role this energy deficit plays in the overall radiation budget, one must examine the prevalent atmospheric features of the Arctic. One such feature is a persistent layer of low-altitude, stratiform clouds found over the central Arctic predominantly from April to September. These Arctic stratus clouds (ASC) modulate the earth`s radiation budget by contributing to the vertical transport of heat. It is, therefore, crucial to understand the radiative properties of Arctic stratus clouds. We believe that the radiative properties of ASC are strongly coupled with their cloud microphysics. Our aim is to develop a model that will determine if this coupling is sufficient to describe the observed characteristic properties, such as lifetime and the multi-layered structure, of ASC. In addition, we hope to provide useful input to measurement programs at the Atmospheric Radiation Measurement Program`s North Slope of Alaska site by isolating the measurable parameters that influence the overall radiative properties of ASC. Several features of ASC have been integrated directly into the one-dimensional model currently being developed. Generally, ASC cover large areas and exhibit reasonable horizontal homogeneity but extensive vertical inhomogeneities. Therefore, in our model, we have assumed radiative processes are important in determining vertical structure while not considering horizontal transport. In addition, ASC occur in defined, multi-layered structures. This feature of the ASC, in conjunction with their horizontal homogeneity, justifies the use of radiative transfer theory for plane-parallel geometry with multiple scattering. Finally, ASC are generally long-lived and precipitate little during their lifetimes.

  5. Microphysical Processes Affecting the Pinatubo Volcanic Plume

    NASA Technical Reports Server (NTRS)

    Hamill, Patrick; Houben, Howard; Young, Richard; Turco, Richard; Zhao, Jingxia

    1996-01-01

    In this paper we consider microphysical processes which affect the formation of sulfate particles and their size distribution in a dispersing cloud. A model for the dispersion of the Mt. Pinatubo volcanic cloud is described. We then consider a single point in the dispersing cloud and study the effects of nucleation, condensation and coagulation on the time evolution of the particle size distribution at that point.

  6. Microphysical Processes Affecting the Pinatubo Volcanic Plume

    NASA Technical Reports Server (NTRS)

    Hamill, Patrick; Houben, Howard; Young, Richard; Turco, Richard; Zhao, Jingxia

    1996-01-01

    In this paper we consider microphysical processes which affect the formation of sulfate particles and their size distribution in a dispersing cloud. A model for the dispersion of the Mt. Pinatubo volcanic cloud is described. We then consider a single point in the dispersing cloud and study the effects of nucleation, condensation and coagulation on the time evolution of the particle size distribution at that point.

  7. Vertical profiles of optical and microphysical particle properties above the northern Indian Ocean during CARDEX 2012

    NASA Astrophysics Data System (ADS)

    Höpner, F.; Bender, F. A.-M.; Ekman, A. M. L.; Praveen, P. S.; Bosch, C.; Ogren, J. A.; Andersson, A.; Gustafsson, Ö.; Ramanathan, V.

    2016-01-01

    A detailed analysis of optical and microphysical properties of aerosol particles during the dry winter monsoon season above the northern Indian Ocean is presented. The Cloud Aerosol Radiative Forcing Experiment (CARDEX), conducted from 16 February to 30 March 2012 at the Maldives Climate Observatory on Hanimaadhoo island (MCOH) in the Republic of the Maldives, used autonomous unmanned aerial vehicles (AUAV) to perform vertical in situ measurements of particle number concentration, particle number size distribution as well as particle absorption coefficients. These measurements were used together with surface- based Mini Micro Pulse Lidar (MiniMPL) observations and aerosol in situ and off-line measurements to investigate the vertical distribution of aerosol particles.Air masses were mainly advected over the Indian subcontinent and the Arabian Peninsula. The mean surface aerosol number concentration was 1717 ± 604 cm-3 and the highest values were found in air masses from the Bay of Bengal and Indo-Gangetic Plain (2247 ± 370 cm-3). Investigations of the free tropospheric air showed that elevated aerosol layers with up to 3 times higher aerosol number concentrations than at the surface occurred mainly during periods with air masses originating from the Bay of Bengal and the Indo-Gangetic Plain. This feature is different compared to what was observed during the Indian Ocean Experiment (INDOEX) conducted in winter 1999, where aerosol number concentrations generally decreased with height. In contrast, lower particle absorption at the surface (σabs(520 nm) = 8.5 ± 4.2 Wm-1) was found during CARDEX compared to INDOEX 1999.Layers with source region specific single-scattering albedo (SSA) values were derived by combining vertical in situ particle absorption coefficients and scattering coefficients calculated with Mie theory. These SSA layers were utilized to calculate vertical particle absorption profiles from MiniMPL profiles. SSA surface values for 550 nm for dry

  8. ISDAC Microphysics

    DOE Data Explorer

    McFarquhar, Greg

    2011-07-25

    Best estimate of cloud microphysical parameters derived using data collected by the cloud microphysical probes installed on the National Research Council (NRC) of Canada Convair-580 during ISDAC. These files contain phase, liquid and ice crystal size distributions (Nw(D) and Ni(D) respectively), liquid water content (LWC), ice water content (IWC), extinction of liquid drops (bw), extinction of ice crystals (bi), effective radius of water drops (rew) and of ice crystals (rei) and median mass diameter of liquid drops (Dmml) and of ice crystals (Dmmi) at 30 second resolution.

  9. Estimation of atmospheric aging time of black carbon particles in the polluted atmosphere over central-eastern China using microphysical process analysis in regional chemical transport model

    NASA Astrophysics Data System (ADS)

    Chen, Xueshun; Wang, Zifa; Yu, Fangqun; Pan, Xiaole; Li, Jie; Ge, Baozhu; Wang, Zhe; Hu, Min; Yang, Wenyi; Chen, Huansheng

    2017-08-01

    Mixing state of black carbon (BC) particles has significant impacts on their radiative forcing, visibility impairment and the ability in modifying cloud formation. In this study, an aging scheme of BC particles using prognostic variables based on aerosol microphysics was incorporated into a regional atmospheric chemistry model, Nested Air Quality Prediction Modeling System with Advanced Particle Microphysics (NAQPMS + APM), to investigate the temporal and spatial variations in aging time scale of BC particles in polluted atmosphere over central-eastern China. The model results show that the aging time scale has a clear diurnal variation with a lower value in the daytime and a higher value in the nighttime. The shorter aging time scale in the daytime is due to condensation aging associated with intense photochemical reaction while the longer aging time scale in the nighttime is due to coagulation aging, which is much slower than that due to condensation. In Beijing, the aging time scale is 2 h or less in the surface layer in daytime, which is far below the fixed 1.2 days used in many models. As a result, the fraction of hydrophilic BC particles by the new scheme is larger than that by the scheme with fixed aging time scale though the mean aging time scale by the new scheme is much larger than 1.2 days. Hydrophilic fraction of BC particles increases with the increase of height. Over central-eastern China, the averaged aging time scale calculated by the new scheme is in the range from 12 h to 7 days, with higher values in regions far from the source areas. Hydrophilic fraction of BC particles is more than 90% at the higher levels in polluted atmosphere. Difference of simulated BC concentration with internal mixing and microphysical aging is within 5%, indicating that the assumption of internal mixing for BC particles to respond to in-cloud scavenging is more appropriate than the external mixing assumption in polluted atmosphere over central-eastern China.

  10. Microphysical Model of the Venus clouds between 40km and 80km

    NASA Astrophysics Data System (ADS)

    McGouldrick, Kevin

    2013-10-01

    I am continuing to adapt the Community Aerosol and Radiation Model for Atmospheres (CARMA) to successfully simulate the multi-layered clouds of Venus. The present version of the one-dimensional model now includes a simple parameterization of the photochemicial production of sulfuric acid around altitudes of 62km, and its thermochemical destruction below cloud base. Photochemical production in the model is limited by the availability of water vapor and insolation. Upper cloud particles are introduced into the model via binary homogeneous nucleation, while the lower and middle cloud particles are created via activation of involatile cloud condensation nuclei. Growth by condensation and coagulation and coalescence are also treated. Mass loadings and particle sizes compare favorably with the in situ observations by the Pioneer Venus Large Probe Particle Size Spectrometer, and mixing ratios of volatiles compare favorably with remotely sensed observations of water vapor and sulfuric acid vapor. This work was supported by the NASA Planetary Atmospheres Program, grant number NNX11AD79G.

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  13. A Model for Particle Microphysics,Turbulent Mixing, and Radiative Transfer in the Stratocumulus-Topped Marine Boundary Layer and Comparisons with Measurements

    NASA Technical Reports Server (NTRS)

    Ackerman, Andrew S.; Toon, Owen B.; Hobbs, Peter V.

    1995-01-01

    A detailed 1D model of the stratocumulus-topped marine boundary layer is described. The model has three coupled components: a microphysics module that resolves the size distributions of aerosols and cloud droplets, a turbulence module that treats vertical mixing between layers, and a multiple wavelength radiative transfer module that calculates radiative heating rates and cloud optical properties. The results of a 12-h model simulation reproduce reasonably well the bulk thermodynamics, microphysical properties, and radiative fluxes measured in an approx. 500-m thick, summertime marine stratocumulus cloud layer by Nicholls. However, in this case, the model predictions of turbulent fluxes between the cloud and subcloud layers exceed the measurements. Results of model simulations are also compared to measurements of a marine stratus layer made under gate conditions and with measurements of a high, thin marine stratocumulus layer. The variations in cloud properties are generally reproduced by the model, although it underpredicts the entrainment of overlying air at cloud top under gale conditions. Sensitivities of the model results are explored. The vertical profile of cloud droplet concentration is sensitive to the lower size cutoff of the droplet size distribution due to the presence of unactivated haze particles in the lower region of the modeled cloud. Increases in total droplet concentrations do not always produce less drizzle and more cloud water in the model. The radius of the mean droplet volume does not correlate consistently with drizzle, but the effective droplet radius does. The greatest impacts on cloud properties predicted by the model are produced by halving the width of the size distribution of input condensation nuclei and by omitting the effect of cloud-top radiative cooling on the condensational growth of cloud droplets. The omission of infrared scattering produces noticeable changes in cloud properties. The collection efficiencies for droplets less

  14. A Model for Particle Microphysics, Turbulent Mixing, and Radiative Transfer in the Stratocumulus-Topped Marine Boundary Layer and Comparisons with Measurements

    NASA Technical Reports Server (NTRS)

    Ackerman, Andrew S.; Toon, Owen B.; Hobbs, Peter V.

    1995-01-01

    A detailed 1D model of the stratocumulus-topped marine boundary layer is described. The model has three coupled components: a microphysics module that resolves the size distributions of aerosols and cloud droplets, a turbulence module that treats vertical mixing between layers, and a multiple wavelength radiative transfer module that calculates radiative heating rates and cloud optical properties. The results of a 12-h model simulation reproduce reasonably well the bulk thermodynamics, microphysical properties, and radiative fluxes measured in an approx. 500-m thick, summertime marine stratocumulus cloud layer by Nicholls. However, in this case, the model predictions of turbulent fluxes between the cloud and subcloud layers exceed the measurements. Results of model simulations are also compared to measurements of a marine stratus layer made under gale conditions and with measurements of a high, thin marine stratocumulus layer. The variations in cloud properties are generally reproduced by the model, although it underpredicts the entrainment of overlying air at cloud top under gale conditions. Sensitivities of the model results are explored. The vertical profile of cloud droplet concentration is sensitive to the lower size cutoff of the droplet size distribution due to the presence of unactivated haze particles in the lower region of the modeled cloud. Increases in total droplet concentrations do not always produce less drizzle and more cloud water in the model. The radius of the mean droplet volume does not correlate consistently with drizzle, but the effective droplet radius does. The greatest impacts on cloud properties predicted by the model are produced by halving the width of the size distribution of input condensation nuclei and by omitting the effect of cloud-top radiative cooling on the condensational growth of cloud droplets. The omission of infrared scattering produces noticeable changes in cloud properties. The collection efficiencies for droplets less

  15. The Shortwave Spectroradiometer as a Versatile Sensor for Observation of Cloud Optical and Microphysical Properties

    NASA Astrophysics Data System (ADS)

    Lubin, D.; Vogelmann, A. M.; Flynn, C. J.

    2013-12-01

    Recent years have seen the advent of shortwave spectroradiometers covering the ultraviolet through near-infrared parts of the spectrum. With multiple linear-array detectors, spectral coverage as wide as 350-2200 nanometers is possible. In this wide spectral interval, the downwelling irradiance is sensitive - in contrasting atmospheric windows - to surface albedo, cloud optical depth, cloud thermodynamic phase, and effective droplet/particle size. For climatological studies relevant to climate model improvement, a shortwave spectroradiometer offers four significant advantages. First, full spectral observations can be made at high time resolution, often in one-minute averages. This enables study of cloud formation, evolution, and dissipation, in response to meteorological and aerosol forcing. Second, with shortwave spectral data cloud properties can be derived for a wide range of liquid water content; in contrast to the middle-infrared window where only optically thin clouds can be studied. Third, commercial technology is now available - including some instruments nearly entirely ready for atmospheric application - that make the acquisition cost of a spectroradiometer relatively modest compared to other types of advanced atmospheric instrumentation. This offers the possibility of developing ground-based networks for geographically distributed measurements. Fourth, measurement of the downwelling spectral irradiance enables direct empirical interpretation of cloud properties' influence on the surface radiation budget. We have experience with shortwave spectroradiometer deployment in the high Arctic, at the US Department of Energy Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP) site, and at Ross Island, Antarctica. These measurements reveal a great diversity in cloud properties, including extensive Arctic mixed-phase cloud during springtime, rapidly evolving liquid water cloud at SGP, and ice-dominated cloud in response to moisture traversing

  16. In search of the best match: probing a multi-dimensional cloud microphysical parameter space to better understand what controls cloud thermodynamic phase

    NASA Astrophysics Data System (ADS)

    Tan, Ivy; Storelvmo, Trude

    2015-04-01

    Substantial improvements have been made to the cloud microphysical schemes used in the latest generation of global climate models (GCMs), however, an outstanding weakness of these schemes lies in the arbitrariness of their tuning parameters, which are also notoriously fraught with uncertainties. Despite the growing effort in improving the cloud microphysical schemes in GCMs, most of this effort has neglected to focus on improving the ability of GCMs to accurately simulate the present-day global distribution of thermodynamic phase partitioning in mixed-phase clouds. Liquid droplets and ice crystals not only influence the Earth's radiative budget and hence climate sensitivity via their contrasting optical properties, but also through the effects of their lifetimes in the atmosphere. The current study employs NCAR's CAM5.1, and uses observations of cloud phase obtained by NASA's CALIOP lidar over a 79-month period (November 2007 to June 2014) guide the accurate simulation of the global distribution of mixed-phase clouds in 20∘ latitudinal bands at the -10∘ C, -20∘C and -30∘C isotherms, by adjusting six relevant cloud microphysical tuning parameters in the CAM5.1 via Quasi-Monte Carlo sampling. Among the parameters include those that control the Wegener-Bergeron-Findeisen (WBF) timescale for the conversion of supercooled liquid droplets to ice and snow in mixed-phase clouds, the fraction of ice nuclei that nucleate ice in the atmosphere, ice crystal sedimentation speed, and wet scavenging in stratiform and convective clouds. Using a Generalized Linear Model as a variance-based sensitivity analysis, the relative contributions of each of the six parameters are quantified to gain a better understanding of the importance of their individual and two-way interaction effects on the liquid to ice proportion in mixed-phase clouds. Thus, the methodology implemented in the current study aims to search for the combination of cloud microphysical parameters in a GCM that

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

    NASA Astrophysics Data System (ADS)

    Luebke, Anna; Rolf, Christian; Costa, Anja; Afchine, Armin; Avallone, Linnea; Borrmann, Stephan; Baumgardner, Darrel; Klingebiel, Marcus; Kraemer, Martina

    2015-04-01

    Ice clouds are known to play an important role in the radiative balance of the atmosphere. The nature of this role is determined by the macrophysical and microphysical properties of a cloud. Thus, it is crucial that we have an accurate understanding of properties such as the ice water content (IWC), ice crystal concentration (Ni), and ice crystal size (Ri). However, these properties are difficult to parameterize due to their large variability and the fact that they are influenced by a number of other factors such as temperature, vertical velocity, relative humidity with respect to ice (RHice), and the available ice nuclei. The combination of those factors ultimately establishes whether heterogeneous or homogeneous nucleation will lead to ice crystal formation. The aforementioned factors are largely determined by the dynamics of the environment in which the ice cloud forms, collectively contained in a meteorological situation. Ice clouds have been observed in a variety of situations such as frontal systems, jet streams, gravity waves, and convective systems. Most recently, the concept of the influence of large-scale dynamics on midlatitude cirrus properties has been demonstrated in the work of Muehlbauer et al. (2014). In the work presented here, we explore this concept further by examining how differences in dynamics are translated into the differences in IWC, Ni, and Ri that are found within and between datasets. Data from two American-based campaigns, the 2004 Midlatitude Cirrus Experiment (MidCiX) and the 2011 Midlatitude Airborne Cirrus Properties Experiment (MACPEX), as well as some European-based campaigns, the 2004 and 2006 CIRRUS campaigns, the 2013 AIRTOSS-ICE campaign, and the 2014 ML-CIRRUS campaign are combined to form a large, and more latitudinally comprehensive database of Northern Hemisphere in-situ, midlatitude ice cloud observations. We have divided the data by meteorological situation and explored the differences and similarities between

  18. Inter-comparison of CALIPSO and CloudSat retrieved profiles of aerosol and cloud microphysical parameters with aircraft profiles over a tropical region

    NASA Astrophysics Data System (ADS)

    Padmakumari, B.; Harikishan, G.; Maheskumar, R. S.

    2016-05-01

    Satellites play a major role in understanding the spatial and vertical distribution of aerosols and cloud microphysical parameters over a large area. However, the inherent limitations in satellite retrievals can be improved through inter-comparisons with airborne platforms. Over the Indian sub-continent, the vertical profiles retrieved from space-borne lidar such as CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) on board the satellite CALIPSO and Cloud Profiling Radar (CPR) on board the satellite CloudSat were inter- compared with the aircraft observations conducted during Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX). In the absence of high clouds, both aircraft and CALIOP showed similar features of aerosol layering and water-ice cloud signatures. As CALIOP could not penetrate the thick clouds, the aerosol information below the cloud is missed. While the aircraft could measure high concentrations below the cloud base and above the low clouds in the presence of high clouds. The aircraft derived liquid water content (LWC) and droplet effective radii (Re) showed steady increase from cloud base to cloud top with a variable cloud droplet number concentration (CDNC). While the CloudSat derived LWC, CDNC and Re showed increase from the cloud top to cloud base in contradiction to the aircraft measurements. The CloudSat profiles are underestimated as compared to the corresponding aircraft profiles. Validation of satellite retrieved vertical profiles with aircraft measurements is very much essential over the tropics to improve the retrieval algorithms and to constrain the uncertainties in the regional cloud parameterization schemes.

  19. Final Report on the Development of an Improved Cloud Microphysical Product for Model and Remote Sensing Evaluation using RACORO Observations

    SciTech Connect

    McFarquhar, Greg

    2012-09-19

    We proposed to analyze data collected during the Routine Aerial Facilities (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) in order to develop an integrated product of cloud microphysical properties (number concentration of drops in different size bins, total liquid drop concentration integrated over all bin sizes, liquid water content LWC, extinction of liquid clouds bw, effective radius of water drops re, and radar reflectivity factor) that could be used to evaluate large-eddy simulations (LES), general circulation models (GCMs) and ground-based remote sensing retrievals, and to develop cloud parameterizations with the end goal of improving the modeling of cloud processes and properties and their impact on atmospheric radiation. We have completed the development of this microphysical database and have submitted it to ARM for consideration of its inclusion on the ARM database as a PI product. This report describes the development of this database, and also describes research that has been conducted on cloud-aerosol interactions using the data obtained during RACORO. A list of conference proceedings and publications is also included.

  20. Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments

    NASA Astrophysics Data System (ADS)

    Nichman, Leonid; Fuchs, Claudia; Järvinen, Emma; Ignatius, Karoliina; Florian Höppel, Niko; Dias, Antonio; Heinritzi, Martin; Simon, Mario; Tröstl, Jasmin; Wagner, Andrea Christine; Wagner, Robert; Williamson, Christina; Yan, Chao; Connolly, Paul James; Dorsey, James Robert; Duplissy, Jonathan; Ehrhart, Sebastian; Frege, Carla; Gordon, Hamish; Hoyle, Christopher Robert; Bjerring Kristensen, Thomas; Steiner, Gerhard; McPherson Donahue, Neil; Flagan, Richard; Gallagher, Martin William; Kirkby, Jasper; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Stratmann, Frank; Tomé, António

    2016-03-01

    Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The 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 environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization 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 polarization transitions under dry conditions using CASPOL. Cluster analysis techniques were subsequently used to classify different types of particles according to their polarization 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 sulfate, and volcanic ash. Finally, we discuss the benefits and limitations of this classification approach for atmospherically relevant concentrations and mixtures with respect to the CLOUD 8-9 campaigns and its potential contribution to tropical troposphere layer analysis.

  1. Ignition of Aluminum Particles and Clouds

    SciTech Connect

    Kuhl, A L; Boiko, V M

    2010-04-07

    Here we review experimental data and models of the ignition of aluminum (Al) particles and clouds in explosion fields. The review considers: (i) ignition temperatures measured for single Al particles in torch experiments; (ii) thermal explosion models of the ignition of single Al particles; and (iii) the unsteady ignition Al particles clouds in reflected shock environments. These are used to develop an empirical ignition model appropriate for numerical simulations of Al particle combustion in shock dispersed fuel explosions.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  3. Parameterizations of Depositional Growth of Cloud Ice in a Bulk Microphysical Scheme

    NASA Technical Reports Server (NTRS)

    Braun, Scott A.; Ferrier, Brad S.; Tao, Wei-Kuo

    1999-01-01

    Two aspects of the cloud ice parameterization in the Goddard Cumulus Ensemble Model cloud physics parameterization are examined: the conversion of cloud ice to snow by depositional growth, designated PSFI, and the saturation adjustment scheme. The original formulation of PSFI is shown to produce excessive conversion of cloud ice to snow because of an implicit assumption that the relative humidity is 100% with respect to water even though the air may actually be quite less humid. Two possible corrections to this problem are proposed, the first involving application of a relative humidity dependent correction factor to the original formulation of PSFI, and the second involving a new formulation of PSFI based on the equation for depositional growth of cloud ice. The sensitivity of these formulations of PSFI to the assumed masses of the ice particles is examined. Possible problems associated with using a saturation adjustment scheme for cloud ice are discussed and simulations of a squall line with and without application of the adjustment scheme for ice are compared.

  4. Challenges in Analyzing and Representing Cloud Microphysical Data Measured with Airborne Cloud Probes

    NASA Astrophysics Data System (ADS)

    Baumgardner, D.; Freer, M.; McFarquhar, G. M.; Heymsfield, A.; Cziczo, D. J.

    2014-12-01

    There are a variety of in-situ instruments that are deployed on aircraft for measuring cloud properties, some of which provide data which are used to produce number and mass concentrations of water droplets and ice crystals and their size and shape distributions. Each of these instruments has its strengths and limitations that must be recognized and taken into account during analysis of the data. Various processing techniques have been developed by different groups and techniques implemented to partially correct for the known uncertainties and limitations. The cloud measurement community has in general acknowledged the various issues associated with these instruments and numerous studies have published processing algorithms that seek to improve data quality; however, there has not been a forum in which these various algorithms and processing techniques have been discussed and consensus reached both on optimum analysis strategy and on quantification of uncertainties on the derived data products. Prior to the 2014 AMS Cloud Physics Conference, a study was conducted in which many data sets taken from various aircraft (NCAR-130, North Dakota Citation, Wyoming King Air and FAAM BAE-146) and many instruments (FSSP, CDP, SID, 2D-C/P, CIP/PIP, 2D-S, CPI, Nevzorov Probe and King Hot-wire LWC sensor) were processed by more than 20 individuals or groups to produce a large number of derived products (size distributions, ice fraction, number and mass concentrations, CCN/IN concentrations and median volume diameter). Each person or group that processed a selected data set used their own software and algorithm to produce a secondary data file with derived parameters whose name was encoded to conceal the source of the file so that this was a blind comparison. The workshop that was convened July 5 and 6, 2014, presented the results of the evaluation of the derived products with respect to individual instruments as well as the types of conditions under which the measurements were

  5. Parallel implementation of WRF double moment 5-class cloud microphysics scheme on multiple GPUs

    NASA Astrophysics Data System (ADS)

    Huang, Melin; Huang, Bormin; Huang, Allen H.-L.

    2015-05-01

    The Weather Research and Forecast (WRF) Double Moment 5-class (WDM5) mixed ice microphysics scheme predicts the mixing ratio of hydrometeors and their number concentrations for warm rain species including clouds and rain. WDM5 can be computed in parallel in the horizontal domain using multi-core GPUs. In order to obtain a better GPU performance, we manually rewrite the original WDM5 Fortran module into a highly parallel CUDA C program. We explore the usage of coalesced memory access and asynchronous data transfer. Our GPU-based WDM5 module is scalable to run on multiple GPUs. By employing one NVIDIA Tesla K40 GPU, our GPU optimization effort on this scheme achieves a speedup of 252x with respect to its CPU counterpart Fortran code running on one CPU core of Intel Xeon E5-2603, whereas the speedup for one CPU socket (4 cores) with respect to one CPU core is only 4.2x. We can even boost the speedup of this scheme to 468x with respect to one CPU core when two NVIDIA Tesla K40 GPUs are applied.

  6. The Role of Initial Cloud Condensation Nuclei Concentration in Hail Using the WRF NSSL 2-moment Microphysics Scheme

    NASA Astrophysics Data System (ADS)

    Li, Xiaofei; Zhang, Qinghong; Xue, Huiwen

    2017-04-01

    The effects of the initial cloud condensation nuclei (CCN) concentrations (100-3000 mg-1) on hail properties were investigated in an idealized hail storm experiment using the Weather Research and Forecasting (WRF) model, with the National Severe Storms Laboratory two-moment microphysics scheme. The initial CCN concentration had obvious non-monotonic effects on the mixing ratio, number concentrations, and radius of hail, both in clouds and at the surface, with a threshold CCN concentration between 300 and 500 mg-1. An increasing CCN concentration is conducive (suppressive) to the amount of surface hail precipitation below (above) the threshold. The non-monotonic effects were due to both the thermodynamics and microphysics. Below the threshold, the mixing ratios of cloud droplets and ice crystals increased dramatically with the increasing CCN concentration, resulting in more latent heat being released from vapor condensation and intensified updraft volume. The extent of the riming process, which is the primary process for hail production, increased dramatically. Above the threshold, the mixing ratio of cloud droplets and ice crystals increased continuously, but the maximum updraft volume was weakened because of reduced latent heating, which was related to the reduced riming rate in the storm core area. The smaller ice crystals reduced the formation of hail and smaller clouds, with decreased rain water reducing riming efficiency so that graupel and hail also decreased with increasing CCN concentration, which is unfavorable for hail growth.

  7. The role of initial cloud condensation nuclei concentration in hail using the WRF NSSL 2-moment microphysics scheme

    NASA Astrophysics Data System (ADS)

    Li, Xiaofei; Zhang, Qinghong; Xue, Huiwen

    2017-09-01

    The effects of the initial cloud condensation nuclei (CCN) concentrations (100-3000 mg-1) on hail properties were investigated in an idealized non-severe hail storm experiment using theWeather Research and Forecasting (WRF) model, with the National Severe Storms Laboratory 2-moment microphysics scheme. The initial CCN concentration (CCNC) had obvious non-monotonic effects on the mixing ratio, number concentrations, and radius of hail, both in clouds and at the surface, with a CCNC threshold between 300 and 500 mg-1. An increasing CCNC is conducive (suppressive) to the amount of surface hail precipitation below (above) the CCNC threshold. The non-monotonic effects were due to both the thermodynamics and microphysics. Below the CCNC threshold, the mixing ratios of cloud droplets and ice crystals increased dramatically with the increasing CCNC, resulting in more latent heat released from condensation and frozen between 4 and 8 km and intensified updraft volume. The extent of the riming process, which is the primary process for hail production, increased dramatically. Above the CCNC threshold, the mixing ratio of cloud droplets and ice crystals increased continuously, but the maximum updraft volume was weakened because of reduced frozen latent heating at low level. The smaller ice crystals reduced the formation of hail and smaller clouds, with decreased rain water reducing riming efficiency so that graupel and hail also decreased with increasing CCNC, which is unfavorable for hail growth.

  8. Contrasting microphysical characteristics of the clouds measured during the dry and wet seasons in Amazon and their implication on entrainment and mixing processes

    NASA Astrophysics Data System (ADS)

    Yum, S. S.; Yeom, J. M.; Mei, F.; Schmid, B.; Comstock, J. M.; Machado, L.; Cecchini, M. A.

    2016-12-01

    Cloud microphysical properties can be modulated by entrainment and mixing of clear air, and how this occurs critically determines colloidal stability and optical properties of clouds. Our recent study showed predominant homogeneous mixing (HM) traits although relevant scale parameter analyses indicated dominance of inhomogeneous mixing (IM), for the marine stratocumulus clouds over the southeast Pacific. We speculated that entrainment and mixing at the cloud top may have been indeed inhomogeneous as the scale parameters suggested but the vertical circulation mixing in the cloud may have changed the cloud microphysical relationships to suggest HM at the altitudes of horizontal penetration. Meanwhile, continental stratocumulus clouds over the Southern Great Plains of the US showed even stronger HM traits. We do similar analyses for the Amazonian clouds measured onboard the US DOE G-1 aircraft during the Green Ocean Amazon (GOAmazon) project. Aerosol, thermodynamic, and cloud microphysical characteristics of the dry and wet seasons were contrastingly different. Mixing diagram analysis and cloud microphysical relationships suggested strong HM traits for both dry and wet seasons except that in the dry season secondary droplet activation during entrainment and mixing processes seemed to have an effect on the results. With the availability of 1 Hz and 10 Hz datasets, scale dependence of the results were also examined.

  9. Particle Cloud Flames in Acoustic Fields

    NASA Technical Reports Server (NTRS)

    Berlad, A. L.; Tangirala, V.; Ross, H.; Facca, L.

    1990-01-01

    Results are presented on a study of flames supported by clouds of particles suspended in air, at pressures about 100 times lower than normal. In the experiment, an acoustic driver (4-in speaker) placed at one end of a closed tube, 0.75-m long and 0.05 m in diameter, disperses a cloud of lycopodium particles during a 0.5-sec powerful acoustic burst. Properties of the particle cloud and the flame were recorded by high-speed motion pictures and optical transmission detectors. Novel flame structures were observed, which owe their features to partial confinement, which encourages flame-acoustic interactions, segregation of particle clouds into laminae, and penetration of the flame's radiative flux density into the unburned particle-cloud regimes. Results of these experiments imply that, for particles in confined spaces, uncontrolled fire and explosion may be a threat even if the Phi(0) values are below some apparent lean limit.

  10. Influence of different microphysical schemes on the prediction of dissolution of nonreactive gases by cloud droplets and raindrops

    SciTech Connect

    Huret, N.; Chaumerliac, N.; Isaka, H.; Nickerson, E.C. |

    1994-09-01

    Three microphysical formulations are closely compared to evaluate their impact upon gas scavenging and wet deposition processes. They range from a classical bulk approach to a fully spectral representation, including an intermediate semispectral parameterization. Detailed comparisons among the microphysical rates provided by these three parameterizations are performed with special emphasis on evaporation rate calculations. This comparative study is carried out in the context of a mountain wave simulation. Major differences are essentially found in the contrasted spreading of the microphysical fields on the downwind side of the mountain. A detailed chemical module including the dissolution of the species and their transfer between phases (air, cloud, and rain) is coupled with the three microphysical parameterizations in the framework of the dynamical mesoscale model. An assessment of the accuracy of each scheme is then proposed by comparing their ability to represent the drop size dependency of chemical wet processes. The impact of evaporation (partial versus total) upon the partition of species between gas and aqueous phases is also studied in detail.

  11. A study of the formation and evolution of aerosols and contrails in aircraft wakes: Development, validation and application of an advanced particle microphysics (APM) model

    NASA Astrophysics Data System (ADS)

    Yu, Fangqun

    1998-10-01

    The aerosols generated by current and future fleets of subsonic and supersonic aircraft may affect stratosphere ozone abundances by enhancing the particulate surface area on which heterogeneous chemical reactions can occur, and may affect global climate by modifying high-level clouds. A reliable assessment of aviation impacts requires a thorough understanding of the mechanisms that control the production and physical properties of the emitted particles. This dissertation discusses the development of an advanced particle microphysics (APM) model, and the application of this model to investigate the formation mechanisms and physical properties of the aviation- generated aerosols. In the model, the composition and size distributions of various categories of particles (electrically charged and uncharged, volatile and nonvolatile, and liquid and solid) are tracked through the different phases of plume evolution, including the condensation and evaporation of contrails when ambient conditions favor ice formation. The APM model is modularized and highly efficient, and may be applied to study a variety of aerosol-related problems. Here, the model is applied to analyze in-situ plume particle observations obtained in several field campaigns. The simulations-constrained by measurements-reveal that the largest volatile particles-those most likely to contribute to the background abundance of condensation nuclei-are dominated by ``ion-mode'' aerosols, which are formed on the chemiions emitted by the aircraft engines. The population of ion-mode aerosols is controlled by the abundance of chemiions which is determined by combustion chemistry and is relatively invariant. The theory of chemiion effects on aircraft plume microphysics is developed here, and the first quantitative calculations of chemiion-influenced plume aerosols are presented. In this work, a molecular kinetic model is used for the first time to interpret in-situ aircraft particle measurements, showing that the

  12. Boundary layer regulation in the southeast Atlantic cloud microphysics during the biomass burning season as seen by the A-train satellite constellation

    NASA Astrophysics Data System (ADS)

    Painemal, David; Kato, Seiji; Minnis, Patrick

    2014-10-01

    Solar radiation absorption by biomass burning aerosols has a strong warming effect over the southeast Atlantic. Interactions between the overlying smoke aerosols and low-level cloud microphysics and the subsequent albedo perturbation are, however, generally ignored in biomass burning radiative assessments. In this study, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) are combined with Aqua satellite observations from Moderate Resolution Imaging Spectroradiometer (MODIS), Advanced Microwave Scanning Radiometer-EOS (AMSR-E), and Clouds and the Earth's Radiant Energy System (CERES) to assess the effect of variations in the boundary layer height and the separation distance between the cloud and aerosol layers on the cloud microphysics. The merged data analyzed at a daily temporal resolution suggest that overlying smoke aerosols modify cloud properties by decreasing cloud droplet size despite an increase in the cloud liquid water as boundary layer deepens, north of 5°S. These changes are controlled by the proximity of the aerosol layer to the cloud top rather than increases in the column aerosol load. The correlations are unlikely driven by meteorological factors, as three predictors of cloud variability, lower tropospheric stability, surface winds, and mixing ratio suggest that cloud effective radius, cloud top height, and liquid water path should correlate positively. Because cloud effective radius anticorrelates with cloud liquid water over the region with large microphysical changes—north of 5°S—the overall radiative consequence at the top of the atmosphere is a strong albedo susceptibility, equivalent to a 3% albedo increase due to a 10% decrease in cloud effective radius. This albedo enhancement partially offsets the aerosol solar absorption. Our analysis emphasizes the importance of accounting for the indirect effect of smoke aerosols in the cloud microphysics when estimating the radiative impact of the biomass burning at the

  13. Final Report: Operational Retrieval of Cloud Microphysical Properties Using Combined Measurements by Diverse Instruments

    SciTech Connect

    Richard T. Austin

    2008-06-30

    The report on the final phase of the project describes improvements in the ice and liquid cloud retrieval algorithms due to the use of three-parameter particle size distributions in which all three parameters may vary with height, testing of the improved retrievals by comparisons of measured and calculated fluxes, and further improvement in liquid retrievals obtained by adding liquid water path information from the microwave radiometer to radar and visible optical depth information.

  14. Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

    NASA Astrophysics Data System (ADS)

    Coopman, Quentin; Garrett, Timothy J.; Riedi, Jérôme; Eckhardt, Sabine; Stohl, Andreas

    2016-04-01

    The properties of low-level liquid clouds in the Arctic can be altered by long-range pollution transport to the region. Satellite, tracer transport model, and meteorological data sets are used here to determine a net aerosol-cloud interaction (ACInet) parameter that expresses the ratio of relative changes in cloud microphysical properties to relative variations in pollution concentrations while accounting for dry or wet scavenging of aerosols en route to the Arctic. For a period between 2008 and 2010, ACInet is calculated as a function of the cloud liquid water path, temperature, altitude, specific humidity, and lower tropospheric stability. For all data, ACInet averages 0.12 ± 0.02 for cloud-droplet effective radius and 0.16 ± 0.02 for cloud optical depth. It increases with specific humidity and lower tropospheric stability and is highest when pollution concentrations are low. Carefully controlling for meteorological conditions we find that the liquid water path of arctic clouds does not respond strongly to aerosols within pollution plumes. Or, not stratifying the data according to meteorological state can lead to artificially exaggerated calculations of the magnitude of the impacts of pollution on arctic clouds.

  15. Microphysical aerosol parameters of spheroidal particles via regularized inversion of lidar data

    NASA Astrophysics Data System (ADS)

    Samaras, Stefanos; Böckmann, Christine

    2015-04-01

    One of the main topics in understanding the aerosol impact on climate requires the investigation of the spatial and temporal variability of microphysical properties of particles, e.g., the complex refractive index, the effective radius, the volume and surface-area concentration, and the single-scattering albedo. Remote sensing is a technique used to monitor aerosols in global coverage and fill in the observational gap. This research topic involves using multi-wavelength Raman lidar systems to extract the microphysical properties of aerosol particles, along with depolarization signals to account for the non-sphericity of the latter. Given, the optical parameters (measured by a lidar), the kernel functions, which summarize the size, shape and composition of particles, we solve for the size distribution of the particles modeled by a Fredholm integral system and further calculate the refractive index. This model works well for spherical particles (e.g. smoke); the kernel functions are derived from relatively simplified formulas (Mie scattering theory) and research has led to successful retrievals for particles which at least resemble a spherical geometry (small depolarization ratio). Obviously, more complicated atmospheric structures (e.g dust) require employment of non-spherical kernels and/or more complicated models which are investigated in this paper. The new model is now a two-dimensional one including the aspect ratio of spheroidal particles. The spheroidal kernel functions are able to be calculated via T-Matrix; a technique used for computing electromagnetic scattering by single, homogeneous, arbitrarily shaped particles. In order to speed up the process and massively perform simulation tests, we created a software interface using different regularization methods and parameter choice rules. The following methods have been used: Truncated singular value decomposition and Pade iteration with the discrepancy principle, and Tikhonov regularization with the L

  16. LIMA (v1.0): A quasi two-moment microphysical scheme driven by a multimodal population of cloud condensation and ice freezing nuclei

    NASA Astrophysics Data System (ADS)

    Vié, B.; Pinty, J.-P.; Berthet, S.; Leriche, M.

    2016-02-01

    The paper describes the LIMA (Liquid Ice Multiple Aerosols) quasi two-moment microphysical scheme, which relies on the prognostic evolution of an aerosol population, and the careful description of the nucleating properties that enable cloud droplets and pristine ice crystals to form from aerosols. Several modes of cloud condensation nuclei (CCN) and ice freezing nuclei (IFN) are considered individually. A special class of partially soluble IFN is also introduced. These "aged" IFN act first as CCN and then as IFN by immersion nucleation at low temperatures. All the CCN modes are in competition with each other, as expressed by the single equation of maximum supersaturation. The IFN are insoluble aerosols that nucleate ice in several ways (condensation, deposition and immersion freezing) assuming the singular hypothesis. The scheme also includes the homogeneous freezing of cloud droplets, the Hallett-Mossop ice multiplication process and the freezing of haze at very low temperatures. LIMA assumes that water vapour is in thermodynamic equilibrium with the population of cloud droplets (adjustment to saturation in warm clouds). In ice clouds, the prediction of the number concentration of the pristine ice crystals is used to compute explicit deposition and sublimation rates (leading to free under/supersaturation over ice). The autoconversion, accretion and self-collection processes shape the raindrop spectra. The initiation of the large crystals and aggregates category is the result of the depositional growth of large crystals beyond a critical size. Aggregation and riming are computed explicitly. Heavily rimed crystals (graupel) can experience a dry or wet growth mode. An advanced version of the scheme includes a separate hail category of particles forming and growing exclusively in the wet growth mode. The sedimentation of all particle types is included. The LIMA scheme is inserted into the Meso-NH cloud-resolving mesoscale model. The flexibility of LIMA is illustrated

  17. Ice nucleation active particles are efficiently removed by precipitating clouds

    PubMed Central

    Stopelli, Emiliano; Conen, Franz; Morris, Cindy E.; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine

    2015-01-01

    Ice nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of ice nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ18O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs active at temperatures ≥ −10 °C (INPs−10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs active at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space. PMID:26553559

  18. Ice nucleation active particles are efficiently removed by precipitating clouds.

    PubMed

    Stopelli, Emiliano; Conen, Franz; Morris, Cindy E; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine

    2015-11-10

    Ice nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of ice nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ(18)O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs active at temperatures ≥ -10 °C (INPs-10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs active at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space.

  19. Revisiting Intel Xeon Phi optimization of Thompson cloud microphysics scheme in Weather Research and Forecasting (WRF) model

    NASA Astrophysics Data System (ADS)

    Mielikainen, Jarno; Huang, Bormin; Huang, Allen

    2015-10-01

    The Thompson cloud microphysics scheme is a sophisticated cloud microphysics scheme in the Weather Research and Forecasting (WRF) model. The scheme is very suitable for massively parallel computation as there are no interactions among horizontal grid points. Compared to the earlier microphysics schemes, the Thompson scheme incorporates a large number of improvements. Thus, we have optimized the speed of this important part of WRF. Intel Many Integrated Core (MIC) ushers in a new era of supercomputing speed, performance, and compatibility. It allows the developers to run code at trillions of calculations per second using the familiar programming model. In this paper, we present our results of optimizing the Thompson microphysics scheme on Intel Many Integrated Core Architecture (MIC) hardware. The Intel Xeon Phi coprocessor is the first product based on Intel MIC architecture, and it consists of up to 61 cores connected by a high performance on-die bidirectional interconnect. The coprocessor supports all important Intel development tools. Thus, the development environment is familiar one to a vast number of CPU developers. Although, getting a maximum performance out of MICs will require using some novel optimization techniques. New optimizations for an updated Thompson scheme are discusses in this paper. The optimizations improved the performance of the original Thompson code on Xeon Phi 7120P by a factor of 1.8x. Furthermore, the same optimizations improved the performance of the Thompson on a dual socket configuration of eight core Intel Xeon E5-2670 CPUs by a factor of 1.8x compared to the original Thompson code.

  20. A New Characterization of Sticking Efficiencies for Graupel-Ice and Snow-Ice Collisions: Derivation and Implementation in a Cloud Model with Hybrid Bin/Bulk Microphysics.

    NASA Astrophysics Data System (ADS)

    Formenton, Marco; Phillips, Vaughan; Kudzotsa, Innocent

    2014-05-01

    The collision-adhesion process of ice crystals to form snowflakes and graupel pellets is one of the important processes in the growth of precipitation particles in clouds. The collision-rebound of ice particles in presence of supercooled droplets affects deeply the charge separation processes in the convective clouds. An empirical parametrization of the sticking efficiency for graupel-ice and snow-ice collisions processes is presented. The parametrization infers the sticking efficiency as function of the temperature, collision kinetic energy and surface area. It has been derived from experimental measurements of aggregation efficiency using a 0D simple bin model to interpret the data. We compared our parametrization of sticking efficiency with experimental results to check the robustness of the scheme. The sticking efficiency scheme has been implemented in a cloud model with hybrid bin/bulk microphysics and an electrification scheme. A simulation of a thunderstorm over the US High Plains has been validated against aircraft, ground-based and electrical observations (e.g. lightning flash rate). We then performed several sensitivity tests on the effects from inclusion of realistic sticking efficiencies on the simulated electrical activity. Moreoever, the role of sticking efficiencies in modifying the response of simulated lightning activity to extra aerosols has been investigated with more sensitivity tests.

  1. Separating dynamical and microphysical impacts of aerosols on deep convection applying piggybacking methodology

    NASA Astrophysics Data System (ADS)

    Grabowski, Wojciech W.

    2016-04-01

    Formation and growth of cloud and precipitation particles ("cloud microphysics") affect cloud dynamics and such macroscopic cloud field properties as the mean surface rainfall, cloud cover, and liquid/ice water paths. Traditional approaches to investigate the impacts involve parallel simulations with different microphysical schemes or with different scheme parameters (such as the assumed droplet/ice concentration for single-moment bulk schemes or the assumed CCN/IN concentration for double-moment schemes). Such methodologies are not reliable because of the natural variability of a cloud field that is affected by the feedback between cloud microphysics and cloud dynamics. In a nutshell, changing the cloud microphysics leads to a different realization of the cloud-scale flow, and separating dynamical and microphysical impacts is cumbersome. A novel modeling methodology, referred to as the microphysical piggybacking, was recently developed to separate purely microphysical effects from the impact on the dynamics. The main idea is to use two sets of thermodynamic variables driven by two microphysical schemes or by the same scheme with different scheme parameters. One set is coupled to the dynamics and drives the simulation, and the other set piggybacks the simulated flow, that is, it responds to the simulated flow but does not affect it. By switching the sets (i.e., the set driving the simulation becomes the piggybacking one, and vice versa), the impact on the cloud dynamics can be isolated from purely microphysical effects. Application of this methodology to the daytime deep convection development over land based on the observations during the Large-scale Biosphere-Atmosphere (LBA) field project in Amazonia will be discussed applying single-moment and double-moment bulk microphysics schemes. We show that the new methodology documents a small indirect aerosol impact on convective dynamics, and a strong microphysical effect. These results question the postulated strong

  2. Remote sensing of cirrus cloud microphysical properties using spectral measurements over the full range of their thermal emission

    NASA Astrophysics Data System (ADS)

    Palchetti, L.; Di Natale, G.; Bianchini, G.

    2016-09-01

    The thermal emission of cirrus clouds, spectrally resolved in the 100-1400 cm-1 range (100-7.1 μm), has been modeled and compared with measurements performed during two field campaigns from the ground-based site of Testa Grigia on the Italian Alps at 3480 m of altitude. The analysis of cirrus microphysics, through spectral fitting, shows the importance of using also the far infrared portion of the emitted spectrum at wave numbers below the 667 cm-1 carbon dioxide absorption band, where only a few measurements exist because of the high opacity of the atmosphere caused by the strong water vapor absorption. The resulted distribution of the fitted cloud parameters is in good agreement with the typical statistical distribution of the midlatitude cirrus cloud parameters.

  3. Numerical simulation of precipitation formation in the case orographically induced convective cloud: Comparison of the results of bin and bulk microphysical schemes

    NASA Astrophysics Data System (ADS)

    Sarkadi, N.; Geresdi, I.; Thompson, G.

    2016-11-01

    In this study, results of bulk and bin microphysical schemes are compared in the case of idealized simulations of pre-frontal orographic clouds with enhanced embedded convection. The description graupel formation by intensive riming of snowflakes was improved compared to prior versions of each scheme. Two methods of graupel melting coincident with collisions with water drops were considered: (1) all simulated melting and collected water drops increase the amount of melted water on the surface of graupel particles with no shedding permitted; (2) also no shedding permitted due to melting, but the collision with the water drops can induce shedding from the surface of the graupel particles. The results of the numerical experiments show: (i) The bin schemes generate graupel particles more efficiently by riming than the bulk scheme does; the intense riming of snowflakes was the most dominant process for the graupel formation. (ii) The collision-induced shedding significantly affects the evolution of the size distribution of graupel particles and water drops below the melting level. (iii) The three microphysical schemes gave similar values for the domain integrated surface precipitation, but the patterns reveal meaningful differences. (iv) Sensitivity tests using the bulk scheme show that the depth of the melting layer is sensitive to the description of the terminal velocity of the melting snow. (v) Comparisons against Convair-580 flight measurements suggest that the bin schemes simulate well the evolution of the pristine ice particles and liquid drops, while some inaccuracy can occur in the description of snowflakes riming. (vi) The bin scheme with collision-induced shedding reproduced well the quantitative characteristics of the observed bright band.

  4. Micro-physical properties of carbonaceous aerosol particles generated by laser ablation of a graphite target

    NASA Astrophysics Data System (ADS)

    Ajtai, T.; Utry, N.; Pintér, M.; Tápai, Cs.; Kecskeméti, G.; Smausz, T.; Hopp, B.; Bozóki, Z.; Szabó, G.

    2014-09-01

    In this work the authors propose laser ablation as a highly versatile tool for carbonaceous aerosol generation. The generated carbonaceous particles can be used as a model aerosol for atmospheric black carbon. Various microphysical properties including mass concentration, size distribution and morphology of aerosol particles generated by laser ablation of a high purity graphite sample were investigated in detail. These measurements proved that the proposed method can be used to generate both primary particles and fractal aggregates with a high yield. As a further advantage of the method the size distribution of the generated aerosol can cover a wide range, and can be tuned accurately with laser fluence, the ambient composition or with the volumetric flow rate of the carrier gas.

  5. Stratospheric ion and aerosol chemistry and possible links with cirrus cloud microphysics - A critical assessment

    NASA Technical Reports Server (NTRS)

    Mohnen, Volker A.

    1990-01-01

    Aspects of stratospheric ion chemistry and physics are assessed as they relate to aerosol formation and the transport of aerosols to upper tropospheric regions to create conditions favorable for cirrus cloud formation. It is found that ion-induced nucleation and other known phase transitions involving ions and sulfuric acid vapor are probably not efficient processes for stratospheric aerosol formation, and cannot compete with condensation of sulfuric acid on preexisting particles of volcanic or meteoritic origin which are larger than about 0.15 micron in radius. Thus, galactic cosmic rays cannot have a significant impact on stratospheric aerosol population. Changes in the stratospheric aerosol burden due to volcanos are up to two orders of magnitude larger than changes in ion densities. Thus, volcanic activity may modulate the radiative properties of cirrus clouds.

  6. Japan's research on particle clouds and sprays

    NASA Technical Reports Server (NTRS)

    Sato, Jun'ichi

    1995-01-01

    Most of energy used by us is generated by combustion of liquid and solid fuels. These fuels are burned in combustors mainly as liquid sprays and pulverized solids, respectively. A knowledge of the combustion processes in combustors is needed to achieve proper designs that have stable operation, high efficiency, and low emission levels. However, current understanding of liquid and solid particle cloud combustion is far from complete. If combustion experiments for these fuels are performed under a normal gravity field, some experimental difficulties are encountered. These difficulties encountered include, that since the particles fall by the force of gravity it is impossible to stop the particles in the air, the falling speeds of particles are different from each other, and are depend on the particle size, the flame is lifted up and deformed by the buoyancy force, and natural convection makes the flow field more complex. Since these experimental difficulties are attributable to the gravity force, a microgravity field can eliminate the above problems. This means that the flame propagation experiments in static homogeneous liquid and solid particle clouds can be carried out under a microgravity field. This will provide much information for the basic questions related to combustion processes of particle clouds and sprays. In Japan, flame propagation processes in the combustible liquid and solid particle clouds have been studied experimentally by using a microgravity field generated by a 4.5 s dropshaft, a 10 s dropshaft, and by parabolic flight. Described in this presentation are the recent results of flame propagations studies in a homogeneous liquid particle cloud, in a mixture of liquid particles/gas fuel/air, in a PMMA particle cloud, and in a pulverized coal particle cloud.

  7. Improving representation of convective transport for scale-aware parameterization: 1. Convection and cloud properties simulated with spectral bin and bulk microphysics

    NASA Astrophysics Data System (ADS)

    Fan, Jiwen; Liu, Yi-Chin; Xu, Kuan-Man; North, Kirk; Collis, Scott; Dong, Xiquan; Zhang, Guang J.; Chen, Qian; Kollias, Pavlos; Ghan, Steven J.

    2015-04-01

    The ultimate goal of this study is to improve the representation of convective transport by cumulus parameterization for mesoscale and climate models. As Part 1 of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in midlatitude continent and tropical regions using the Weather Research and Forecasting model with spectral bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation and vertical velocity of convective cores than MOR and MY2 and therefore will be used for analysis of scale dependence of eddy transport in Part 2. The common features of the simulations for all convective systems are (1) the model tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates Ze in convective cores, especially for the weak updraft velocity; and (3) the model performs better for midlatitude convective systems than the tropical system. The modeled mass fluxes of the midlatitude systems are not sensitive to microphysics schemes but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow, and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes.

  8. Improving representation of convective transport for scale-aware parameterization: 1. Convection and cloud properties simulated with spectral bin and bulk microphysics

    SciTech Connect

    Fan, Jiwen; Liu, Yi-Chin; Xu, Kuan-Man; North, Kirk; Collis, Scott; Dong, Xiquan; Zhang, Guang J; Qian, Chen; Kollias, Pavlos; Ghan, Steven

    2015-04-27

    The ultimate goal of this study is to improve the representation of convective transport by cumulus parameterization for mesoscale and climate models. As Part 1 of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in midlatitude continent and tropical regions using the Weather Research and Forecasting model with spectral bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation and vertical velocity of convective cores than MOR and MY2 and therefore will be used for analysis of scale dependence of eddy transport in Part 2. The common features of the simulations for all convective systems are (1) themodel tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates Ze in convective cores, especially for the weak updraft velocity; and (3) the model performs better for midlatitude convective systems than the tropical system. The modeled mass fluxes of the midlatitude systems are not sensitive to microphysics schemes but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow, and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes

  9. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    DOE PAGES

    Fridlind, Ann M.; Atlas, Rachel; van Diedenhoven, Bastiaan; ...

    2016-06-10

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

  10. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  11. Physical and Optical/Radiative Characteristics of Aerosol and Cloud Particles in Tropical Cirrus: Importance in Radiation Balance

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Howard, S. D.; Foster, T. C.; Hallett, J.; Arnott, W. P.; Condon, Estelle P. (Technical Monitor)

    1996-01-01

    Whether cirrus clouds heat or cool the Earth-atmosphere system depends on the relative importance of the cloud shortwave albedo effect and the cloud thermal greenhouse effect. Both are determined by the distribution of ice condensate with cloud particle size. The microphysics instrument package flown aboard the NASA DC-8 in TOGA/COARE included an ice crystal replicator, a 2D Greyscale Cloud Particle Probe and a Forward Scattering Spectrometer Aerosol Probe. In combination, the electro-optical instruments permitted particle size measurements between