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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.

    2015-08-01

    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

  2. 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.

  3. Optical and microphysical properties of a cold cirrus cloud - Evidence for regions of small ice particles

    NASA Technical Reports Server (NTRS)

    Platt, C. M. R.; Spinhirne, J. D.; Hart, W. D.

    1989-01-01

    An airborne lidar and a scanning radiometer aboard an ER-2 aircraft were used to observe a cold cirrus cloud, and a Forward Scattering Spectrometer Probe (FSSP) was used to obtain simultaneous in situ microphysical observations at two altitudes within the cloud. Lidar depolarization ratio data show that the clouds were composed predominantly of ice crystals. At an altitude where the temperature was -62.7 C, the lidar and radiometer analysis gave a visible extinction to infrared absorption ratio (alpha) of 2.3, while the cloud microphysics data provided an alpha value of 3.77. The discrepancy is attributed to undersizing of particles by the FSSP. Direct and remote measurements showed better agreement for a lower layer where the temperature was -47.3 C.

  4. 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

  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. 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%.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. On microphysical processes of noctilucent clouds (NLC): observations and modeling of mean and width of the particle size-distribution

    NASA Astrophysics Data System (ADS)

    Baumgarten, G.; Fiedler, J.; Rapp, M.

    2010-07-01

    Noctilucent clouds (NLC) in the polar summer mesopause region have been observed in Norway (69° N, 16° E) between 1998 and 2009 by 3-color lidar technique. Assuming a mono-modal Gaussian size distribution we deduce mean and width of the particle sizes throughout the clouds. We observe a quasi linear relationship between distribution width and mean of the particle size at the top of the clouds and a deviation from this behavior for particle sizes larger than 40 nm, most often in the lower part of the layer. The vertically integrated particle properties show that 65% of the data follows the linear relationship with a slope of 0.42±0.02 for mean particle sizes up to 40 nm. For the vertically resolved particle properties (Δz = 0.15 km) the slope is comparable and about 0.39±0.03. For particles larger than 40 nm the distribution width becomes nearly independent of particle size and even decreases in the lower part of the layer. We compare our observations to microphysical modeling of noctilucent clouds and find that the distribution width depends on turbulence, the time that turbulence can act (cloud age), and the sampling volume/time (atmospheric variability). The model results nicely reproduce the measurements and show that the observed slope can be explained by eddy diffusion profiles as observed from rocket measurements.

  16. 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.

  17. 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

  18. On microphysical processes of noctilucent clouds (NLC): observations and modeling of mean and width of the particle size-distribution

    NASA Astrophysics Data System (ADS)

    Baumgarten, G.; Fiedler, J.; Rapp, M.

    2010-02-01

    Noctilucent clouds (NLC) in the polar summer mesopause region have been observed in Norway (69° N, 16° E) between 1998 and 2009 by 3-color lidar technique. Assuming a mono-modal Gaussian size distribution we deduce mean and width of the particle sizes throughout the clouds. We observe a quasi linear relationship between distribution width and mean of the particle size at the top of the clouds and a deviation from this behavior for particle sizes larger than 40 nm, most often in the lower part of the layer. The vertically integrated particle properties show that 65% of the data follows the linear relationship with a slope of 0.42±0.02. For the vertically resolved particle properties (Δz=0.15 km) the slope is smaller and only 0.39±0.03. We compare our observations to microphysical modeling of noctilucent clouds and find that the distribution width depends on turbulence, the time that turbulence can act (cloud age), and the sampling volume/time (atmospheric variability). The model results nicely reproduce the measurements and show that the observed slope can be explained by eddy diffusion profiles as observed from rocket measurements.

  19. Measurements of the Microphysics and Size Distributed Composition of Aerosol Particles at the Kosan Supersite, Jeju Island, Korea During ACE-ASIA and Their Influence on Cloud Microphysics

    NASA Astrophysics Data System (ADS)

    Bower, K. N.; Alfarra, R.; Allan, J. D.; Williams, P. I.; McFiggans, G. B.; Flynn, M.; Coe, H.; Gallagher, M. W.; Choularton, T. W.; Fuzzi, S.; Facchini, C.; Berner, A.; Jayne, J. T.; Canagaratne, M. R.; Jimenez, J. L.; Worsnop, D.; Topping, D.; Burgess, R. A.

    2002-12-01

    Measurements of particle number, size distribution and chemical composition of aerosol were made at the Kosan supersite on the island of Jeju during the ACE-ASIA experiment. The measurements of chemical composition included those from an Aerodyne Aerosol Mass Spectrometer, which can deliver quantitative information of the mass of a range of volatile and semi-volatile aerosol components in near real time. These include sulfate, nitrate, ammonium, and the total organic fraction. The instrument also delivers measurements of the size-distributed mass of these components. In addition to the AMS, multi stage Berner impactors were also run for both mass collection on aluminium foil substrates and chemical analysis using Teflon substrates. The substrates were chemically analysed for a range of inorganic species, carbonate, a range of simple organic ions and also the water soluble organic fraction. The latter were subdivided by functionality: neutrals, mono and di carboxylix acids, and poly-carboxylic acids. A second sampling location on the mountain-side of Jeju was used to sample cloud microphysical parameters during the experiment. Measurements were made of liquid water content and cloud droplet number as a function of size during cloud events sampled during the experiment. We will show that the largest contributor to the accumulation mode particle mass is sulfate, with a variable contribution from the organic fraction. The organic is observed to be internally mixed with the sulfate in a mass mode centred at around 400 nm and using AMS data and the analyses from the impactors is oxidised and water soluble. The largest constituents of this component of the aerosol were di and poly carboxylic acids. There was little evidence for a mode of organic particles, typical of urban outflow at Jeju, indicating the particulate had been significantly processed between source and arrival at the sampling site. Little nitrate was observed in the sub micron aerosol at Jeju, but

  20. Possible evidence of new particle formation and its impact on cloud microphysics from airborne measurements over Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Deshpande, C. G.; Bhalwankar, Rohini; Padmakumari, B.; Maheskumar, R. S.; Axisa, Duncan; Kulkarni, J. R.

    2014-04-01

    Airborne measurements conducted under a special mission over Bay of Bengal (BoB) during the CAIPEEX (Cloud Aerosol Interaction and Precipitation Enhancement EXperiment) in 2011 were analyzed in the present study. Research flights were carried out on 19 and 20 October, 2011 (referred as RF1 and RF2), in the region over BoB, which was influenced by a depression to evaluate the aerosol-cloud interactions over marine environment. The increased concentration of aitken/accumulation mode particles was observed at 500 m above sea surface level over the ocean after the passage of the depression. The source of these particles and their subsequent growth during RF1 at about 200 km from coastline has been attributed to (i) increased production of aerosols due to oxidation of dimethyl sulfide (DMS) because of upwelling of the deep ocean water during the depression and (ii) anthropogenic aerosols transported from inland. Moreover, measurements of accumulation and coarse mode particles with diameter ranging from 0.1 to 3 μm and cloud droplets in the range 3 to 47 μm show systematic growth associated with cloud microphysical/rain formation process. On the other hand, no such evidence of increasing particle concentration and growth has been observed at about 60 km from coastline towards southeast during RF2. Evidently, the rain event observed during the night hours of 19 October caused the washout and scavenging of aerosols which contributed towards the decreased aerosol concentration observed near the coast.

  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. PMID:11031290

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. Microphysical properties of synoptic-scale polar stratospheric clouds: in situ measurements of unexpectedly large HNO3-containing particles in the Arctic vortex

    NASA Astrophysics Data System (ADS)

    Molleker, S.; Borrmann, S.; Schlager, H.; Luo, B.; Frey, W.; Klingebiel, M.; Weigel, R.; Ebert, M.; Mitev, V.; Matthey, R.; Woiwode, W.; Oelhaf, H.; Dörnbrack, A.; Stratmann, G.; Grooß, J.-U.; Günther, G.; Vogel, B.; Müller, R.; Krämer, M.; Meyer, J.; Cairo, F.

    2014-10-01

    , with respect to the denitrification by sedimentation of large HNO3-containing particles, generally considered to be NAT, our new measurements raise questions concerning composition, shape and nucleation pathways. Answering these would improve the numerical simulation of PSC microphysical processes like cloud particle formation, growth and denitrification, which is necessary for better predictions of future polar ozone losses, especially under changing global climate conditions. Generally, it seems that the occurrence of large NAT particles - sometimes termed "NAT rocks" - are a regular feature of synoptic-scale PSCs in the Arctic.

  11. Microphysical Model Studies of Venus Clouds

    NASA Astrophysics Data System (ADS)

    Meade, P. E.; Bullock, M. A.; Grinspoon, D. H.

    2004-11-01

    We have adapted a standard cloud microphysics model to construct a self-consistent microphysical model of Venus' cloud layer which reproduces and extends previous studies (e.g. James et al. 1997). Our model is based on the Community Aerosol and Radiation Model Atmosphere (CARMA), which is a widely used computer code for terrestrial cloud microphysics, derived from the work of Toon et al. (1988). The standard code has been adapted to treat H2O and H2SO4 as co-condensing vapor species onto aqueous H2SO4 cloud droplets, as well as the nucleation of condensation nuclei to droplets. Vapor condensation and evaporation follows the method of James et al. (1997). Microphysical processes included in this model include nucleation of condensation nuclei, condensation and evaporation of H2O and H2SO4 vapor, and droplet coagulation. Vertical transport occurs though advection, eddy diffusion, sedimentation for both droplets and condensation nuclei. The cloud model is used to explore the sensitivity of Venus' cloud layer to environmental changes. Observations of the Venus' lower cloud from the Pioneer Venus, Venera, and Galileo spacecraft have suggested that the properties of the lower cloud may be time-variable, and at times may be entirely absent (Carlson et al. 1993, Grinspoon et al. 1993, Esposito et al. 1997). Our model explores the dependence of such behavior on environment factors such as variations in water or SO2 abundance. We have also calculated the optical properties of the model atmosphere using both the conventional optical constants for H2SO4 (Palmer and Williams, 1975), and the new data of Tisdale et al. (1998). This work has been supported by NASA's Exobiology Program. References Carlson, R.W., et al., 1993. Planetary and Space Science, 41, 477-486. Esposito, L.W., et al., 1997. In Venus II, eds. S.W. Bougher et al., pp. 415-458, University of Arizona Press, Tucson. Grinspoon, D.H., et al., 1993. Planetary and Space Science, 41 (July 1993), 515-542. James, E. P

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Microphysical properties of low clouds over the North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Maruyama, Takumi; Hayasaka, Tadahiro

    2012-11-01

    Low clouds are widespread over the North Pacific Ocean during summer. Past ship observations, which were carried out in the western region of the North Pacific Ocean, suggested that low clouds (stratus and fog) are likely to occur when sea surface temperature (SST) is lower than surface air temperature (SAT). In this study, we investigated the SST-SAT relationship and microphysical properties of low clouds for the first step of understanding the mechanism of cloud occurrence, maintenance and disappearance by using MODIS satellite observations, JAMSTEC ship observations and MERRA reanalysis data. We divided the North Pacific into four regions according to meteorological condition and made basic statistical analysis about cloud properties in each region by using monthly mean data for July 2011. The statistical analysis indicates that in the central region of the North Pacific where SST-SAT value is negative and the difference is the largest, cloud effective particle radius (re) is larger than those in other regions. We also used ship observation data and simultaneous satellite observation data to examine the relationship between SST-SAT and cloud microphysical properties in detail. This analysis indicates that re in the positive SST-SAT area is larger than that in the negative SSTSAT area. This feature is opposite to the monthly mean results. It suggests that other factors such as humidity and aerosols as well as SST-SAT have to be taken into account, although the SST-SAT relationship can be one of the important factors determining cloud microphysical properties in the summer North Pacific region.

  19. Simulation of cloud microphysical and chemical processes using a multicomponent framework. Part 2: Microphysical evolution of a wintertime orographic cloud

    SciTech Connect

    Chen, J.P. . Dept. of Atmospheric Sciences); Lamb, D. . Dept. of Meteorology)

    1999-07-15

    A detailed microphysical model is used to simulate the formation of wintertime orographic clouds in a two-dimensional domain under steady-state conditions. Mass contents and number concentrations of both liquid- and ice-phase cloud particles are calculated to be in reasonable agreement with observations. The ice particles in the cloud, as well as those precipitated to the surface, are classified into small cloud ice, planar crystals, columnar crystals, heavily rimed crystals, and crystal aggregates. Detailed examination of the results reveals that contact nucleation and rime splintering are the major ice-production mechanisms functioning in the warmer part of the cloud, whereas deposition/condensation-freezing nucleation is dominant at the upper levels. Surface precipitation, either in the form of rain or snow, develops mainly through riming and aggregation, removing over 17% of the total water vapor that entered the cloud. The spectral distributions of cloud particles in a multicomponent framework provide information not only on particle sizes but also on their solute contents and, for ice particles, their shapes. Examination of these multicomponent distributions reveals the mechanisms of particle formation and interaction, as well as the adaptation of crystal habits to the ambient conditions. Additional simulations were done to test the sensitivity of cloud and precipitation formation to the size distribution of aerosol particles. It is found that the size distribution of aerosol particles has significant influence on not only the warm-cloud processes, but also the cold-cloud processes. A reduction in aerosol particle concentration not only causes an earlier precipitation development but also an increase in the amount of total precipitation from the orographic clouds.

  20. 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.

  1. 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.

  2. A Microphysics Guide to Cirrus Clouds

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Cirrus clouds still represent one of the largest uncertainties in the prediction of the Earth's climate (IPCC, 2013) since their microphysical and radiative properties remain poorly or only partially characterized. One major reason is that it is difficult to measure these properties on fast-flying, high altitude aircraft. Another problem is that aircraft measurements cannot capture the evolution of the cirrus clouds properties with time. The most common parameters that are measured in cirrus clouds -besides the meteorological variables- are ice water content (IWC), number of ice crystals (Nice) and relative humidity (with respect to ice, RHice), and sometimes vertical velocity. However, it is difficult to deduce on the history of ice nucleation and development of microphysical properties from these observations. Our study aims to provide 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. The model results are portrayed in the same parameter space as the field measurements, i.e. in the temperature - IWC parameter space. From this representation of simulated cirrus, we can relate the formation mechanism and history to specific combinations of IWC, Nice and RHice inside of cirrus as a function of temperature. We validate this analysis approach by evaluating measurements of about 60h in cirrus during fifteen aircraft campaigns conducted in the last fifteen years over Europe, Australia and Southern and Northern America. It can be shown that the field observations indeed show the characteristics expected from the cirrus guide. For example, high/low IWCs are found together with high/low Nice. As a result it is now possible to track, to a certain degree, the formation mechanism and history of the observed cirrus clouds only from the measurement of IWC and RHice. Important findings from our study are that (i) a substantial part of thick cirrus

  3. Aerosol Microphysical and Macrophysical Effects on Deep Convective Clouds

    NASA Astrophysics Data System (ADS)

    Yuan, T.; Li, Z.; Wilcox, E. M.; Oreopoulos, L.; Remer, L. A.; Yu, H.; Platnick, S. E.; Posselt, D. J.; Zhang, Z.; Martins, J. V.

    2014-12-01

    We illustrate a conceptual model of hydrometeor vertical development inside a convective cloud and its utility in studying of aerosol-DCC interactions. Both case studies and ensemble means are used to investigate aerosol-DCC interactions. We identify a few scenarios where possible signal of aerosol effect on DCC may be extracted. The results show a consistent and physically sound picture of aerosols affecting DCC microphysics as well as macrophysical properties. Specifically, pollutions and smokes are shown to consistently decrease ice particle size. On the contrary, dust particles close to source regions are shown to make cloud ice particle size more maritime like. We postulate that dust may achieve this by acting as either heterogeneous ice nuclei or giant cloud condensation nuclei. This contrast between smoke or pollution and dust also exists for their effects on cloud glaciation temperature. Smoke and pollution aerosols are shown to decrease glaciation temperature while dust particles do the opposite. Possible Implications of our results for studying aerosol indirect forcing, cirrus cloud properties, troposphere-stratosphere water vapor exchange and cloud latent heating are discussed.

  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. Contrasting ice microphysical properties of wintertime frontal clouds and summertime convective clouds

    NASA Astrophysics Data System (ADS)

    Wu, W.; McFarquhar, G. M.

    2015-12-01

    The microphysical and optical properties of ice clouds were derived from measurements collected during the Colorado Airborne Multi-phase Cloud Study (CAMPS) and the Storm Peak Laboratory Cloud Property Validation Experiment (STORMVEX) conducted in the winter of 2010-2011 over the Rocky Mountains and during the Midlatitude Continental Convective Clouds Experiment (MC3E) conducted in the summer of 2011 over Oklahoma. A two-dimensional cloud (2DC) probe, two-dimensional precipitation (2DP) probe and Fast 2DC probe were installed on the University of Wyoming King Air aircraft during CAMPS and a Cloud Imaging Probe (CIP) and Precipitation Imaging Probe were operated on the ground at the Storm Peak Laboratory during STORMVEX. A 2DC, CIP and a high volume precipitation spectrometer were installed in the University of North Dakota Citation aircraft during MC3E. The distributions of particle habits, number distribution functions, total number concentrations, ice water contents, precipitation rates, extinction and effective radius from four cases of wintertime frontal clouds sampled during CAMPS/STORMVEX and from four cases of the stratiform region of summer convective systems from MC3E are compared. It is found that there is higher percentage of pristine ice particles, such as dendrites and columns, in the wintertime frontal clouds than in the summertime convective clouds, where the dominant habits are rimed particles. The number distribution functions are generally broader in the summertime clouds than in the wintertime frontal clouds. In addition, the number concentrations and ice water contents are generally lower in the wintertime frontal clouds than in the summertime convective clouds when comparing the same temperature ranges. Implications about the potential microphysical processes that are acting in these two types of ice clouds are discussed. The results in this study are also compared with previous studies using data from other field campaigns.

  6. Cloud radar Doppler spectra in drizzling stratiform clouds: 2. Observations and microphysical modeling of drizzle evolution

    SciTech Connect

    Kollias, P.; Luke, E.; Szyrmer, W.; Rémillard, J.

    2011-07-02

    In part I, the influence of cloud microphysics and dynamics on the shape of cloud radar Doppler spectra in warm stratiform clouds was discussed. The traditional analysis of radar Doppler moments was extended to include skewness and kurtosis as additional descriptors of the Doppler spectrum. Here, a short climatology of observed Doppler spectra moments as a function of the radar reflectivity at continental and maritime ARM sites is presented. The evolution of the Doppler spectra moments is consistent with the onset and growth of drizzle particles and can be used to assist modeling studies of drizzle onset and growth. Time-height radar observations are used to exhibit the coherency of the Doppler spectra shape parameters and demonstrate their potential to improve the interpretation and use of radar observations. In addition, a simplified microphysical approach to modeling the vertical evolution of the drizzle particle size distribution in warm stratiform clouds is described and used to analyze the observations. The formation rate of embryonic drizzle droplets due to the autoconversion process is not calculated explicitly; however, accretion and evaporation processes are explicitly modeled. The microphysical model is used as input to a radar Doppler spectrum forward model, and synthetic radar Doppler spectra moments are generated. Three areas of interest are studied in detail: early drizzle growth near the cloud top, growth by accretion of the well-developed drizzle, and drizzle depletion below the cloud base due to evaporation. The modeling results are in good agreement with the continental and maritime observations. This demonstrates that steady state one-dimensional explicit microphysical models coupled with a forward model and comprehensive radar Doppler spectra observations offer a powerful method to explore the vertical evolution of the drizzle particle size distribution.

  7. 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.

  8. A Comparison between Airborne and Mountaintop Cloud Microphysics

    NASA Astrophysics Data System (ADS)

    David, R.; Lowenthal, D. H.; Hallar, A. G.; McCubbin, I.; Avallone, L. M.; Mace, G. G.; Wang, Z.

    2014-12-01

    Complex terrain has a large impact on cloud dynamics and microphysics. Several studies have examined the microphysical details of orographically-enhanced clouds from either an aircraft or from a mountain top location. However, further research is needed to characterize the relationships between mountain top and airborne microphysical properties. During the winter of 2011, an airborne study, the Colorado Airborne Mixed-Phase Cloud Study (CAMPS), and a ground-based field campaign, the Storm Peak Lab (SPL) Cloud Property Validation Experiment (StormVEx) were conducted in the Park Range of the Colorado Rockies. The CAMPS study utilized the University of Wyoming King Air (UWKA) to provide airborne cloud microphysical and meteorological data on 29 flights totaling 98 flight hours over the Park Range from December 15, 2010 to February 28, 2011. The UWKA was equipped with instruments that measured both cloud droplet and ice crystal size distributions, liquid water content, total water content (vapor, liquid, and ice), and 3-dimensional wind speed and direction. The Wyoming Cloud Radar and Lidar were also deployed during the campaign. These measurements are used to characterize cloud structure upwind and above the Park Range. StormVEx measured cloud droplet, ice crystal, and aerosol size distributions at SPL, located on the west summit of Mt. Werner at 3220m MSL. The observations from SPL are used to determine mountain top cloud microphysical properties at elevations lower than the UWKA was able to sample in-situ. Comparisons showed that cloud microphysics aloft and at the surface were consistent with respect to snow growth processes while small crystal concentrations were routinely higher at the surface, suggesting ice nucleation near cloud base. The effects of aerosol concentrations and upwind stability on mountain top and downwind microphysics are considered.

  9. 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.

    2015-06-01

    Intense rainfall generated by convective clouds causes flash flooding in many parts of the world. Understanding the microphysical processes leading to the formation of precipitation is one of the main challenges to improving our capability to make quantitative precipitation forecasts. Here, we present microphysics 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 as a result of new cell formation and stratiform regions forming downwind of the convective cells. Aircraft penetrations at -5 °C showed that all the required conditions of the Hallett-Mossop (H-M) ice multiplication process were met in developing regions, and ice concentrations up to 350 L-1 were measured in the mature stratiform regions, indicating 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, a few drizzle drops were measured, some of which froze to form graupel; the ice images are most consistent with freezing drizzle, rather than smaller cloud drops forming the first ice. As new cells developed in and around the cloud, ice concentrations up to two orders of magnitude higher than the predicted ice nuclei concentrations began to be observed and the cloud glaciated over a period of 12-15 min. Ice splinters were captured by supercooled drizzle drops causing them to freeze to form instant-rimers. Graupel and columns were observed in cloud penetrations up to the -12 °C level, though many ice particles were mixed-habit due to riming and growth by vapour diffusion at multiple temperatures. Frozen drizzle

  10. 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.

  11. 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.

  12. A Step Towards an Advanced Parameterization of Cloud Microphysical Processes

    NASA Astrophysics Data System (ADS)

    Beheng, K. D.

    2002-12-01

    Consideration of cloud microphysical properties and processes in atmospheric models usually requires reliable and accurate parameterizations. For describing all hydrometeor types by size distribution functions and corresponding budget equations comprising a multitude of processes in an adapted manner is by far too costly. An alternative is to only deal with certain integrals (i.e. moments of the size spectra as, e.g., water contents) and their tendency equations. Moreover, the parameter formulae should comply with the natural situation of having smaller (cloud) and larger (precipitation) particles which interact by collisions in a complex way. Many years ago this idea has been elaborated by Kessler (1969) for liquid (warm) clouds. Kessler presented a rate equation for the transformation of cloud water content to rainwater mass (autoconversion) which relies on high intuition and another one for accretion, i.e. for the increase of rainwater content by mutual collection of cloud droplets by raindrops, which is based on a simplistic evaluation of the collection integrals of the spectral budget equation for drops. This first approach to parameterize the evolution of rain water from cloud water is a very important one since almost all clouds start as liquid clouds. For a long time and also to date these so-called Kessler formulae were the only parameterization available for warm cloud processes. In adopting this idea corresponding formulations have also been derived and extensively applied for mixed and ice cloud microphysics. The drawback of Kesslers formulation is that it only uses (cloud and rain) water contents such that a differentiation between continental and maritime clouds exhibiting very different size spectra but identical water contents is not possible. To overcome this deficiency and to include typical cloud characteristics several authors extended Kessler's idea by formulating - in addition to the rates of change of mass contents - rates for the

  13. 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.

  14. 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. PMID:24218569

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. Observational and simulated cloud microphysical features of rain formation in the mixed phase clouds observed during CAIPEEX

    NASA Astrophysics Data System (ADS)

    Patade, Sachin; Shete, Sonali; Malap, Neelam; Kulkarni, Gayatri; Prabha, T. V.

    2016-03-01

    Cloud microphysical observations of rain formation in mixed phase monsoon clouds (from 10 to - 9 °C) using instrumented aircraft during Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) are presented. The drop size and particle size distributions are broader in the mixed phase region, indicating efficient growth of liquid as well as ice phase. Aircraft observations noticed higher ice particle concentrations in Hallet-Mossop zone (- 3 to - 8 °C) with existence of smaller and larger cloud droplets, rimed needles columns, and graupel particles. Observations strongly suggested the active presence of Hallet-Mossop (1974) process in this cloud. The higher correlations found between slope and intercept parameters of exponential size distributions can be attributed to the efficient secondary ice production as well as to the aggregation growth of ice particles. Large Eddy Simulation (LES) of these clouds are compared with observed cloud microphysical properties, also illustrated the important role of Hallet-Mossop (HM) process and its link with warm rain and graupel formation. The raindrop freezing plays a crucial role in graupel formation in early stage of ice development. The observed mean values of microphysical parameters including liquid water content, ice water content, ice number concentrations, and reflectivity showed good agreement with model simulations. Primary ice nuclei have only a minor role in the total ice mass in these clouds.

  20. In-situ measurements of cloud-precipitation microphysics in the East Asian monsoon region since 1960

    NASA Astrophysics Data System (ADS)

    Wang, Donghai; Yin, Jinfang; Zhai, Guoqing

    2015-04-01

    A large number of in-situ measurements of cloud-precipitation microphysical properties have been made since 1960, including measurements of particle size distribution, particle concentration, and liquid water content of clouds and rain. These measurements have contributed to considerable progress in understanding microphysical processes in clouds and precipitation and significant improvements in parameterizations of cloud microphysics in numerical models. This work reviews key findings regarding cloud-precipitation microphysics over China. The total number concentrations of various particles vary significantly, with certain characteristic spatial scales. The size distributions of cloud droplets in stratiform clouds can generally be fit with gamma distributions, but the fit parameters cover a wide range. Raindrop size distributions (RSDs) associated with stratiform clouds can be fit with either exponential or gamma distributions, while RSDs associated with convective or mixed stratiform-cumuliform clouds are best fit with gamma distributions. Concentrations of ice nuclei (IN) over China are higher than those observed over other regions, and increase exponentially as temperature decreases. The particle size distributions of ice crystals, snow crystals, and hailstones sampled at a variety of locations can be reliably approximated by using exponential distributions, while aerosol particle size distributions are best described as the sum of a modified gamma distribution and a Junge power-law distribution. These results are helpful for evaluating and improving the fidelity of physical processes and hydrometeor fields simulated by microphysical parameterizations. The comprehensive summary and analysis of previous work presented here also provide useful guidelines for the design of future observational programs.

  1. 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

  2. Microphysical sensitivities of cloud-resolving model simulations of KWAJEX

    NASA Astrophysics Data System (ADS)

    Blossey, P. N.; Bretherton, C. S.

    2005-05-01

    Cloud-resolving model simulations of the conditions around Kwajalein Island during the Tropical Rainfall Measuring Mission (TRMM) Kwajalein Experiment (KWAJEX), July 24--September 15, 1999, are performed to understand the sensitivities of the results to changes in the model's microphysics and radiation parameterizations. An extensive set of observations were collected during KWAJEX, including high quality estimates of precipitation by an S-band ground validation radar. Large-scale forcings for the simulations --- which use cyclic boundary conditions --- have been derived from the observations by Minghua Zhang. The cloud-resolving model used here is the System for Atmospheric Modeling (SAM), developed by Marat Khairoutdinov at Colorado State University, to which the authors have added a second microphysical package (Fu et al 1995) and radiation scheme (from CAM3.0). While the alternate microphysics represents all hydrometeor interactions and has prognostic equations for water vapor, rain, snow, graupel, cloud water and cloud ice, SAM's default microphysics uses temperature to partition the condensate and precipitate among the phases and has prognostic equations only for total water (vapor+cloud) and precipitating water. The simulations are able to track the observed conditions over the full 52 day period without nudging. The different versions of the model generally reproduce the observed precipitation rate, temperature and relative humidity profiles, with mean temperature biases of less than 2K below the tropopause. However, detailed comparisons of simulated ISCCP cloud amounts and radar reflectivities with observations from ISCCP and the ground validation radar reveal important differences that are also reflected in the top-of-atmosphere radiative fluxes. Such discrepancies are strongest in the suppressed periods during KWAJEX, and these are explored in detail to reveal factors that contribute to model biases. The different microphysical and radiation

  3. 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

  4. Comparison of microphysical cloud properties from the FSSP and CDP during the CAMPS field campaign

    NASA Astrophysics Data System (ADS)

    Pina, A. J.; Hallar, A. G.; Salazar, V.; Chirokova, G.

    2011-12-01

    Understanding and accurately sampling microphysical cloud properties for orographic-forced mixed-phase is of crucial importance for an enhanced representation of mixed-phase clouds in global climate models. The Forward Scattering Spectrometer Probe (FSSP) has been the most widely used instrument to measure cloud microphysical characteristics for over three decades. The Cloud Droplet Probe (CDP) is a new instrument that was introduced to address mechanical issues the FSSP experienced (e.g. ice shattering). In current work, in-situ cloud data from 9 January 2011 of the Colorado Airborne Multi-Phase Cloud Study (CAMPS) field campaign were used to compare measurements by the FSSP and CDP. For all cloud penetrations considered, the FSSP measured a mean cloud droplet concentration of 131.66 cm-3 while the CDP measured a mean concentration of 110.89 cm-3. From calibration data, the CDP showed to undersize cloud particles. Results show concentrations measured by the FSSP and CDP, in general, do not agree in clouds comprised mostly of ice. In conclusion, on the considered day, data from the FSSP were significantly affected by ice particle shattering while the CDP undersized particles by 2-3.5 μm.

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Microphysical fundamentals governing cirrus cloud growth: Modeling studies

    NASA Technical Reports Server (NTRS)

    Sassen, Kenneth; Dodd, Gregory C.; Starr, David

    1990-01-01

    For application to Global Climate Models, large scale numerical models of cirrus cloud formation and maintenance need to be refined to more reliably simulate the effects and feedbacks of high level clouds. A key aspect is how ice crystal growth is initiated in cirrus, which has started a cloud microphysical controversy between camps either believing that heterogeneous or homogeneous drop freezing is predominantly responsible for cold cirrus ice crystal nucleation. In view of convincing evidence for the existence of highly supercooled cloud droplets in the middle and upper troposphere, however, it is concluded that active ice nuclei are rather scarce at cirrus cloud altitudes, and so a new understanding of cirrus cloud formation is needed. This understanding is sought through an examination of cirrus cloud growth models.

  12. In Situ Measurements of Microphysical and Radiative Properties of Cirrus and Anvil Clouds

    NASA Astrophysics Data System (ADS)

    Lawson, P.; Baker, B.; Pilson, B.

    2003-12-01

    In situ microphysical and radiative properties of mid-latitude cirrus, anvil and tropical anvil clouds, based on research flights conducted with the SPEC Learjet, the NASA WB-57 and DC-8, and the University of North Dakota Citation research aircraft, are presented. The measurements were collected in Colorado, Utah, Oklahoma, Florida and Kwajalein. All of the research aircraft were equipped with a standard complement of microphysical sensors and optical probes, plus a cloud particle imager (CPI), which produces high-definition (2.3 micron pixel) digital images of ice particles. The CPI data provide improved measurements of particle shape and size, facilitating better calculations of radiative properties of cirrus and anvil clouds. Based on the measurements, average mid-latitude cirrus, and mid-latitude and tropical cirrus microphysical properties of particle size distribution, crystal habit, ice water content, extinction coefficient, effective radius and optical depth are derived. The data show a distinct difference between particle characteristics in mid-latitude cirrus and anvil clouds. In cirrus, the predominate crystal type (weighted by area or mass) is the bullet rosette, a polycrystalline structure typical of crystal formation at temperatures colder than -30 C. Conversely, although anvils occur at temperatures similar to cirrus, bullet rosettes are very rare in anvils. Instead crystal types in anvils are typical of those formed at temperatures warmer than - 30 C. There is also a notable difference in microphysical and radiative characteristics between mid-latitude, Florida, and tropical (Kwajalein) anvils. Tropical anvils are comprised mainly of single crystals, mostly irregular blocky-shapes. In mid-latitude and Florida anvils, there are more aggregates and often chains of small particles that may be formed as a result of the higher electric fields in continental clouds. The impact of crystal type on calculations of radiative transfer are also considered.

  13. Numerical framework and performance of the new multiple-phase cloud microphysics scheme in RegCM4.5: precipitation, cloud microphysics, and cloud radiative effects

    NASA Astrophysics Data System (ADS)

    Nogherotto, Rita; Tompkins, Adrian Mark; Giuliani, Graziano; Coppola, Erika; Giorgi, Filippo

    2016-07-01

    We implement and evaluate a new parameterization scheme for stratiform cloud microphysics and precipitation within regional climate model RegCM4. This new parameterization is based on a multiple-phase one-moment cloud microphysics scheme built upon the implicit numerical framework recently developed and implemented in the ECMWF operational forecasting model. The parameterization solves five prognostic equations for water vapour, cloud liquid water, rain, cloud ice, and snow mixing ratios. Compared to the pre-existing scheme, it allows a proper treatment of mixed-phase clouds and a more physically realistic representation of cloud microphysics and precipitation. Various fields from a 10-year long integration of RegCM4 run in tropical band mode with the new scheme are compared with their counterparts using the previous cloud scheme and are evaluated against satellite observations. In addition, an assessment using the Cloud Feedback Model Intercomparison Project (CFMIP) Observational Simulator Package (COSP) for a 1-year sub-period provides additional information for evaluating the cloud optical properties against satellite data. The new microphysics parameterization yields an improved simulation of cloud fields, and in particular it removes the overestimation of upper level cloud characteristics of the previous scheme, increasing the agreement with observations and leading to an amelioration of a long-standing problem in the RegCM system. The vertical cloud profile produced by the new scheme leads to a considerably improvement of the representation of the longwave and shortwave components of the cloud radiative forcing.

  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

    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.

  16. 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.

  17. 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.

  18. 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.

  19. Cirrus Cloud Optical and Microphysical Property Measurements with Raman Lidar

    NASA Astrophysics Data System (ADS)

    Demoz, B.; Wang, Z.; Whiteman, D.

    2006-12-01

    To improve our understanding of the impact of cirrus clouds on the current and future climate, improved knowledge of cirrus cloud optical and microphysical properties is needed. However, long-term studies of the problem indicate that accurate cirrus cloud measurements are challenging, especially in the low ice water content regime most frequent in the tropical cirrus layers. Recent advances in Raman lidar techniques have demonstrated that Raman lidar is an excellent tool to provide reliable cirrus cloud optical and microphysical properties, which are important to study cirrus clouds as well as to validate satellite cirrus cloud measurements. Based on elastic and nitrogen Raman signals, cirrus cloud optical depth and extinction to backscatter ratio can be quantified. By utilizing the Raman scattered intensities from ice crystals, a new method to remotely sense cirrus ice water content and general effective radius profiles has been demonstrated with NASA/GSFC Scanning Raman Lidar (SRL) measurements. Since the intensity of Raman scattering is fundamentally proportional to the number of molecules involved, this method provides a more direct way of measuring the ice water content compared with other schemes. Based on the SRL measurements, these Raman lidar capabilities will be illustrated.

  20. Assessing global microphysics of warm cloud and light precipitation from active sensors

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Synergetic uses of radar and lidar are potentially useful for deriving vertically resolved microphysical properties of aerosols, clouds and precipitation. The Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) mission, carrying Doppler Cloud Profiling Radar (CPR) and a high spectral resolution lidar (ATLID) is expected to bring qualitative estimate of these quantities together with cloud vertical velocity information. The standard algorithm for warm cloud microphysics developed under the first Jaxa EarthCARE Research announcement enables us to tackle bimodal problems on retrieving size and number concentration of cloud particles and drizzles coexisting within a vertical grid, by practically incorporating backward Monte-Carlo calculations of the polarized lidar returns in the inversion scheme with sufficient processing speed adapted to global data. In the present study, the developed algorithm has been applied to similar set of measurements from A-train, especially from CloudSat and CALIPSO, to derive global views of cloud and drizzle vertical distributions to be further used to examine the performance of their parameterizations in climate and cloud resolving models.

  1. 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

  2. Aerosols, cloud microphysics, and fractional cloudiness.

    PubMed

    Albrecht, B A

    1989-09-15

    Increases in aerosol concentrations over the oceans may increase the amount of low-level cloudiness through a reduction in drizzle-a process that regulates the liquid-water content and the energetics of shallow marine clouds. The resulting increase in the global albedo would be in addition to the increase due to enhancement in reflectivity associated with a decrease in droplet size and would contribute to a cooling of the earth's surface. PMID:17747885

  3. SeReNA Project: studying aerosol interactions with cloud microphysics in the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Correia, A. L.; Catandi, P. B.; Frigeri, F. F.; Ferreira, W. C.; Martins, J.; Artaxo, P.

    2012-12-01

    Cloud microphysics and its interaction with aerosols is a key atmospheric process for weather and climate. Interactions between clouds and aerosols can impact Earth's radiative balance, its hydrological and energetic cycles, and are responsible for a large fraction of the uncertainty in climatic models. On a planetary scale, the Amazon Basin is one of the most significant land sources of moisture and latent heat energy. Moreover, every year this region undergoes mearked seasonal shifts in its atmospheric state, transitioning from clean to heavily polluted conditions due to the occurrence of seasonal biomass burning fires, that emit large amounts of smoke to the atmosphere. These conditions make the Amazon Basin a special place to study aerosol-cloud interactions. The SeReNA Project ("Remote sensing of clouds and their interaction with aerosols", from the acronym in Portuguese, @SerenaProject on Twitter) is an ongoing effort to experimentally investigate the impact of aerosols upon cloud microphysics in Amazonia. Vertical profiles of droplet effective radius of water and ice particles, in single convective clouds, can be derived from measurements of the emerging radiation on cloud sides. Aerosol optical depth, cloud top properties, and meteorological parameters retrieved from satellites will be correlated with microphysical properties derived for single clouds. Maps of cloud brightness temperature will allow building temperature vs. effective radius profiles for hydrometeors in single clouds. Figure 1 shows an example extracted from Martins et al. (2011), illustrating a proof-of-concept for the kind of result expected within the framework for the SeReNA Project. The results to be obtained will help foster the quantitative knowledge about interactions between aerosols and clouds in a microphysical level. These interactions are a fundamental process in the context of global climatic changes, they are key to understanding basic processes within clouds and how aerosols

  4. On Depolarization Lidar-Based Method for The Determination of Liquid-Cloud Microphysical Properties

    NASA Astrophysics Data System (ADS)

    Roy, Gilles; Cao, Xiaoying; Tremblay, Grégoire; Bernier, Robert

    2016-06-01

    Under single scattering conditions, water droplets clouds do not depolarize the backscattered light. However, backscattered light from multiple scattering will be depolarized. The level of depolarization is a function of the droplets size, the cloud extinction coefficient value and profile; it has also an important dependency on the lidar field-of-view (FOV). The use of depolarization information to retrieve cloud microphysical properties, using Multiple-FOV has been the object of studies, [1], [2]. Recently the use of the depolarization, at a single FOV, has been studied for cloud with linear liquid water content profiles, [3], [4]. In this paper we present the mechanism leading to depolarization and identify the FOV values for which the information on particle size is high. Also Monte Carlo simulations for cloud with constant and ramp up profiles are presented. The degree of linear depolarization as a function of cloud penetration is significantly different for both cloud profiles. This suggests that the use of the degree of linear depolarization at a single FOV should be used with caution to determine clouds micro-physical parameters.

  5. 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.

  6. 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.

  7. Microphysical relationships of clouds observed during March 2000 Cloud IOP at SGP Site and important implications

    SciTech Connect

    Lu, C.; Liu, Y.

    2010-03-15

    Cloud droplet size distributions ---- hence the key microphysical quantities of climate importance (e.g., the total droplet concentration, liquid water content, relative dispersion, mean-volume radius, radar reflectivity, and effective radius) are determined by different physical mechanisms such as pre-cloud aerosols, cloud updraft and turbulent entrainment-mixing processes. Therefore, the relationships among these microphysical properties are expected to behave differently in response to aerosols, cloud updrafts and turbulent entrainment-mixing processes. Identifying and quantifying the influences on these microphysical relationships of the various mechanisms is critical for accurately representing cloud microphysics in climate models and for reducing the uncertainty in estimates of aerosol indirect effects. This study first examines the characteristics of the relationships between relative dispersion, droplet concentration, liquid water content, mean-volume radius, effective radius and radar reflectivity calculated from in-situ measurements of cloud droplet size distributions collected during the March 2000 Cloud IOP at the SGP site. The relationships are further analyzed to dissect the effects from different mechanisms/factors (aerosols, updraft, and different turbulent entrainment-mixing processes). Potential applications to improve radar retrievals of cloud properties will be explored as well.

  8. 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.

  9. Remote measurement of cloud microphysics and its influence in predicting high impact weather events

    NASA Astrophysics Data System (ADS)

    Bipasha, Paul S.; Jinya, John

    2016-05-01

    Understanding the cloud microphysical processes and precise retrieval of parameters governing the same are crucial for weather and climate prediction. Advanced remote sensing sensors and techniques offer an opportunity for monitoring micro-level developments in cloud structure. . Using the observations from a visible and near-infrared lidar onboard CALIPSO satellite (part of A-train) , the spatial variation of cloud structure has been studied over the Tropical monsoon region . It is found that there is large variability in the cloud microphysical parameters manifesting in distinct precipitation regimes. In particular, the severe storms over this region are driven by processes which range from the synoptic to the microphysical scale. Using INSAT-3D data, retrieval of cloud microphysical parameters like effective radius (CER) and optical depth (COD) were carried out for tropical cyclone Phailine. It was observed that there is a general increase of CER in a top-down direction, characterizing the progressively increasing number and size of precipitation hydrometeors while approaching the cloud base. The distribution of CER relative to cloud top temperature for growing convective clouds has been investigated to reveal the evolution of the particles composing the clouds. It is seen that the relatively high concentration of large particles in the downdraft zone is closely related to the precipitation efficiency of the system. Similar study was also carried using MODIS observations for cyclones over Indian Ocean (2010-2013), in which we find that that the mean effective radius is 24 microns with standard deviation 4.56, mean optical depth is 21 with standard deviation 13.98, mean cloud fraction is 0.92 with standard deviation 0.13 and mainly ice phase is dominant. Thus the remote observations of microstructure of convective storms provide very crucial information about the maintenance and potential devastation likely to be associated with it. With the synergistic

  10. A two-habit model for the microphysical and optical properties of ice clouds

    NASA Astrophysics Data System (ADS)

    Liu, C.; Yang, P.; Minnis, P.; Loeb, N.; Kato, S.; Heymsfield, A.; Schmitt, C.

    2014-12-01

    To provide a better representation of natural ice clouds, a novel ice cloud model is developed by assuming an ice cloud to consist of an ensemble of hexagonal columns and 20-element aggregates with specific habit fractions at each particle size bin. The microphysical and optical properties of this two-habit model (THM) are compared with both laboratory and in situ measurements, and its performance in downstream satellite remote sensing applications is assessed. The ice water contents and median mass diameters calculated based on the THM closely agree with in situ measurements made during 11 field campaigns. In this study, the scattering, absorption, and polarization properties of ice crystals are calculated with a combination of the invariant imbedding T matrix, pseudo-spectral time domain, and improved geometric-optics methods over an entire practical range of particle sizes. The phase functions, calculated based on the THM, show close agreement with counterparts from laboratory and in situ measurements and from satellite-based retrievals. When the THM is applied to the retrievals of cloud microphysical and optical properties from MODIS (the Moderate Resolution Imaging Spectroradiometer) observations, excellent spectral consistency is achieved; specifically, the retrieved cloud optical thicknesses based on the visible/near infrared bands and the thermal infrared bands agree quite well. Furthermore, a comparison between the polarized reflectivities observed by the PARASOL satellite and from theoretical simulations illustrates that the THM can be used to represent ice cloud polarization properties.

  11. 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.; Turner, David D.; Wang, Zhien

    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.

  12. A microphysics guide to cirrus clouds - Part 1: Cirrus types

    NASA Astrophysics Data System (ADS)

    Krämer, M.; Rolf, C.; Luebke, A.; Afchine, A.; Spelten, N.; Costa, A.; Zöger, M.; Smith, J.; Herman, R.; Buchholz, B.; Ebert, V.; Baumgardner, D.; Borrmann, S.; Klingebiel, M.; Avallone, L.

    2015-11-01

    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 aims to provide 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. 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 Nice. 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 the US and tropical

  13. 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.

  14. Effect of microphysics scheme in cloud resolving models in passive microwave remote sensing of precipitation over ocean

    NASA Astrophysics Data System (ADS)

    Kim, Ju-Hye; Shin, Dong-Bin; Kummerow, Christian

    2014-05-01

    particles and the other case is precipitation with mid cloud top (MCT) having less ice particles. Two rainfall databases (DBs) are constructed that simulated component of the first is new WRF rainfall simulations and the second is CRM simulations used in GPROF algorithm. The cloud microphysics in CRM is important factor in rainfall estimations of deep convection in HCT case, because this system has ice phase particles in the upper atmosphere which brings scattering at high frequency TBs. On the other hand, high resolution channel of 85 GHz (7 km x 5 km) gives little information in MCT case and it brings underestimation of rain rate compare to radar measurement. In other words, dependency of CRM and its microphysics is not significant in estimation of rainfall by radiometer for warm type precipitation.

  15. 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.

  16. 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.

  17. Microphysical Analysis using Airborne 2-D Cloud and Precipitation Imaging Probe Data

    NASA Astrophysics Data System (ADS)

    Guy, N.; Jorgensen, D.; Witte, M.; Chuang, P. Y.; Black, R. A.

    2013-12-01

    The NOAA P-3 instrumented aircraft provided in-situ cloud and precipitation microphysical observations during the DYNAMO (Dynamics of the Madden-Julian Oscillation) field experiment. The Particle Measuring System 2D cloud (2D-C) and precipitation (2D-P) probes collected data for particles between 12.5 μm - 1.55 mm (25 μm resolution) and 100 μm - 6.2 mm (100 μm resolution), respectively. Spectra from each instrument were combined to provide a broad distribution of precipitation particle sizes. The 'method of moments' technique was used to analyze drop size distribution (DSD) spectra, which were modeled by fitting a three-parameter (slope, shape, and intercept) gamma distribution to the spectra. The characteristic shape of the mean spectrum compares to previous maritime measurements. DSD variability will be presented with respect to the temporal evolution of cloud populations during a Madden-Julian Oscillation (MJO) event, as well as in-situ aircraft vertical wind velocity measurements. Using the third and sixth moments, rainfall rate (R) and equivalent radar reflectivity factor (Z), respectively, were computed for each DSD. Linear regression was applied to establish a Z-R relationship for the data for the estimation of precipitation. The study indicated unique characteristics of microphysical processes for this region. These results are important to continue to define the cloud population characteristics in the climatological MJO region. Improved representation of the cloud characteristics on the microphysical scale will serve as a check to model parameterizations, helping to improve numerical simulations.

  18. 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).

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. Microphysical and macrophysical responses of marine stratocumulus polluted by underlying ships: Evidence of cloud deepening

    NASA Astrophysics Data System (ADS)

    Christensen, Matthew W.; Stephens, Graeme L.

    2011-02-01

    Ship tracks observed by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) were analyzed to determine the extent to which aerosol plumes from ships passing below marine stratocumulus alter the microphysical and macrophysical properties of the clouds. Moderate Resolution Imaging Spectroradiometer (MODIS) imagery was used to distinguish ship tracks embedded in closed, open, and undefined mesoscale cellular cloud structures. The impact of aerosol on the microphysical cloud properties in both the closed and open cell regimes were consistent with the changes predicted by the Twomey hypothesis. For the macrophysical changes, differences were observed between regimes. In the open cell regime, polluted clouds had significantly higher cloud tops (16%) and more liquid water (39%) than nearby unpolluted clouds. However, in the closed cell regime, polluted clouds exhibited no change in cloud top height and had less liquid water (-6%). Both microphysical (effective radius) and macrophysical (liquid water path) cloud properties contribute to a fractional change in cloud optical depth; in the closed cell regime the microphysical contribution was 3 times larger than the macrophysical contribution. However, the opposite was true in the open cell regime where the macrophysical contribution was nearly 2 times larger than the microphysical contribution because the aerosol probably increased cloud coverage. The results presented here demonstrate key differences aerosols have on the microphysical and macrophysical responses of boundary layer clouds between mesoscale stratocumulus convective regimes.

  4. Evaluation of cloud microphysical schemes on aerosol indirect effects from different scale models

    NASA Astrophysics Data System (ADS)

    Shiu, C. J.; Chen, Y. H.; Hashino, T.; Tsai, I. C.; Chen, W. T.; Chen, J. P.; Hsu, H. H.

    2014-12-01

    Quantification of aerosol indirect effects in climate modeling remain unresolved and of large uncertainties. The complicated aerosol-cloud-precipitation interactions in climate model are suggested to be quite sensitive to some tunable microphysical parameters such as the threshold radius associated with autoconversion of cloud droplets to rain droplets. More fundamental studies regarding to different microphysical processes used in various cloud microphysical schemes should be devoted, evaluated and investigated. In this study, we apply a synergy of different scale models with the same cloud and aerosol microphysical schemes (Chen and Liu, 2004; Cheng et al., 2007; and Chen et al., 2013) to understand and evaluate how cloud microphysical processes can be influenced by different microphysical schemes and their interaction with aerosols and radiation. These models include Kinematic Driver (KiD), Single Column Model of Community Atmosphere Model (SCAM), Large Eddy Simulation (LES), and NCAR CESM model. Simulation results from these models will be further validated and compared to either field campaign or satellite observations depending on the scale of the models. Off-line satellite simulator approach (i.e. Joint-Simulator) will also be applied for evaluating cloud microphysics against CloudSat and CALIPSO. Such type of synergy of models can be very useful for improvement, development and evaluation of physical parameterizations for global climate prediction and weather forecast in the near future especially for processes related to cloud macrophysics and microphysics.

  5. A General Uncertainty Quantification Methodology for Cloud Microphysical Property Retrievals

    NASA Astrophysics Data System (ADS)

    Tang, Q.; Xie, S.; Chen, X.; Zhao, C.

    2014-12-01

    The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program provides long-term (~20 years) ground-based cloud remote sensing observations. However, there are large uncertainties in the retrieval products of cloud microphysical properties based on the active and/or passive remote-sensing measurements. To address this uncertainty issue, a DOE Atmospheric System Research scientific focus study, Quantification of Uncertainties in Cloud Retrievals (QUICR), has been formed. In addition to an overview of recent progress of QUICR, we will demonstrate the capacity of an observation-based general uncertainty quantification (UQ) methodology via the ARM Climate Research Facility baseline cloud microphysical properties (MICROBASE) product. This UQ method utilizes the Karhunen-Loéve expansion (KLE) and Central Limit Theorems (CLT) to quantify the retrieval uncertainties from observations and algorithm parameters. The input perturbations are imposed on major modes to take into account the cross correlations between input data, which greatly reduces the dimension of random variables (up to a factor of 50) and quantifies vertically resolved full probability distribution functions of retrieved quantities. Moreover, this KLE/CLT approach has the capability of attributing the uncertainties in the retrieval output to individual uncertainty source and thus sheds light on improving the retrieval algorithm and observations. We will present the results of a case study for the ice water content at the Southern Great Plains during an intensive observing period on March 9, 2000. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  6. 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

  7. 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

  8. 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

  9. A microphysics guide to cirrus clouds - Part 1: Cirrus types

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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 aims to provide 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. 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 17 aircraft campaigns, conducted in the last 15 years, spending about 94 h in cirrus over Europe, Australia, Brazil as well as South and North 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 Nice. 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 forms directly as ice (in situ origin cirrus) and splits in two subclasses, depending on the prevailing strength of the updraft: in slow updrafts these cirrus are rather thin with lower IWCs, while in fast updrafts thicker cirrus with higher IWCs can form. 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, slow updraft in situ origin cirrus occur frequently in low- and high

  10. Exploiting Cloud Radar Doppler Spectra of Mixed-Phase Clouds during ACCEPT Field Experiment to Identify Microphysical Processes

    NASA Astrophysics Data System (ADS)

    Kalesse, H.; Myagkov, A.; Seifert, P.; Buehl, J.

    2015-12-01

    Cloud radar Doppler spectra offer much information about cloud processes. By analyzing millimeter radar Doppler spectra from cloud-top to -base in mixed-phase clouds in which super-cooled liquid-layers are present we try to tell the microphysical evolution story of particles that are present by disentangling the contributions of the solid and liquid particles to the total radar returns. Instead of considering vertical profiles, dynamical effects are taken into account by following the particle population evolution along slanted paths which are caused by horizontal advection of the cloud. The goal is to identify regions in which different microphysical processes such as new particle formation (nucleation), water vapor deposition, aggregation, riming, or sublimation occurr. Cloud radar measurements are supplemented by Doppler lidar and Raman lidar observations as well as observations with MWR, wind profiler, and radio sondes. The presence of super-cooled liquid layers is identified by positive liquid water paths in MWR measurements, the vertical location of liquid layers (in non-raining systems and below lidar extinction) is derived from regions of high-backscatter and low depolarization in Raman lidar observations. In collocated cloud radar measurements, we try to identify cloud phase in the cloud radar Doppler spectrum via location of the Doppler peak(s), the existence of multi-modalities or the spectral skewness. Additionally, within the super-cooled liquid layers, the radar-identified liquid droplets are used as air motion tracer to correct the radar Doppler spectrum for vertical air motion w. These radar-derived estimates of w are validated by independent estimates of w from collocated Doppler lidar measurements. A 35 GHz vertically pointing cloud Doppler radar (METEK MIRA-35) in linear depolarization (LDR) mode is used. Data is from the deployment of the Leipzig Aerosol and Cloud Remote Observations System (LACROS) during the Analysis of the Composition of

  11. 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

  12. Cloud-microphysical sensors intercomparison at the Puy-de-Dôme Observatory, France

    NASA Astrophysics Data System (ADS)

    Guyot, G.; Gourbeyre, C.; Febvre, G.; Shcherbakov, V.; Burnet, F.; Dupont, J. C.; Sellegri, K.; Jourdan, O.

    2015-06-01

    Clouds play an important role on the radiative budget of the earth (Boucher et al., 2013). Since the late 70s, several instrumental developments have been made in order to quantify the microphysical and optical properties of clouds, for both airborne and ground-based applications. However, the cloud properties derived from these different instrumentations have rarely been compared. In this work, we discuss the results of an intercomparison campaign, performed at the Puy de Dôme during May 2013. During this campaign, a unique set of cloud instruments were compared. Two Particle Volume Monitors (PVM-100), a Forward Scattering Spectrometer Probe (FSSP), a Fog Monitor (FM-100) and a Present Weather Detector (PWD) were sampling on the roof of the station. Within a wind tunnel located underneath the roof, two Cloud Droplet Probes (CDP) and a modified FSSP (SPP-100) were operating. The main objectives of this paper are to study the effects of wind direction and speed on ground based cloud observations, to quantify the cloud parameters discrepancies observed by the different instruments, and to develop methods to improve the quantification of the measurements. The results reveal that all instruments, except one PVM, show a good agreement in their sizing abilities, both in term of amplitudes and variability. However, some of them, especially the FM-100, the FSSP and the SPP, display large discrepancies in their capability to assess the cloud droplet number concentrations. As a result, the total liquid water content can differ by up to a factor of 5 between the probes. The use of a standardization procedure, based on data of integrating probes (PVM-100 or visibilimeter) and extinction coefficient comparison, substantially enhances the instrumental agreement. During the intercomparison campaign, the total concentration agreed in variations with the visibilimeter, except for the FSSP, so corrective factor can be applied and range from 0.43 to 2.2. This intercomparison study

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. Two-moment bulk stratiform cloud microphysics in the grid-point atmospheric model of IAP LASG (GAMIL)

    NASA Astrophysics Data System (ADS)

    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's capability to simulate aerosol indirect effects. Unlike the previous one-moment cloud microphysics scheme, the new scheme produces a reasonable representation of cloud particle size and number concentration. This scheme captures the observed spatial variations in cloud droplet number concentrations. Simulated ice crystal number concentrations in cirrus clouds qualitatively agree with in situ observations. The longwave and shortwave cloud forcings are in better agreement with observations. Sensitivity tests show that the column cloud droplet number concentrations calculated from two different droplet activation parameterizations are similar. However, ice crystal number concentration in mixed-phased clouds is sensitive to different heterogeneous ice nucleation formulations. The simulation with high ice crystal number concentration in mixed-phase clouds has less liquid water path and weaker cloud forcing. Furthermore, ice crystal number concentration in cirrus clouds is sensitive to different ice nucleation parameterizations. Sensitivity tests also suggest that the impact of pre-existing ice crystals on homogeneous freezing in old clouds should be taken into account.

  20. 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.

  1. 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

  2. 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

  3. Synergy between ground-based remote sensing systems in microphysical analysis of cirrus clouds

    NASA Astrophysics Data System (ADS)

    Wolf, V.; Reichardt, J.; Görsdorf, Ulrich; Reigert, Andrew; Leinweber, R.; Lehmann, Volker

    2014-10-01

    A broad suite of ground-based remote sensing instruments of the Meteorological Observatory Lindenberg, Germany, is combined for the first time to synergistically analyze cirrus cloud microphysics, including a Raman lidar, a Ka band cloud radar and a 5ff tilted ceilometer. 84 days of cirrus cloud measurements have been selected to study the correlation between, and the dependences of, the different measured variables. The presented study investigates the effect of the spatial orientation and the shape of solid cloud particles on particle optical properties and their relation to wind and turbulence parameters. A sensitive indicator of particle spatial orientation is the particle depolarization ratio (PDR). When ice crystals are horizontally aligned, mirror reflections can occur, which is evidenced by low PDR if observed with a vertically pointing Raman lidar. Observations are grouped according to the prevailing weather condition. It is found that on some days PDR is constant for long time periods. Interestingly, during warm fronts the PDR is generally small (<0.2), while during cold fronts it is high (> 0.4). Moreover, the mean lidar ratio of cirrus with high PDR is about 20 sr, two times larger than of cirrus with low PDR. Similar dependences on PDR have been found for the particle extinction coefficient, and for the backscatter coefficient from the tilted ceilometer, but for the Raman lidar backscatter coefficient in perpendicular polarization the opposite behavior is observed.

  4. Microphysical properties of synoptic scale polar stratospheric clouds: in situ measurements of unexpectedly large HNO3 containing particles in the Arctic vortex

    NASA Astrophysics Data System (ADS)

    Molleker, S.; Borrmann, S.; Schlager, H.; Luo, B.; Frey, W.; Klingebiel, M.; Weigel, R.; Ebert, M.; Mitev, V.; Matthey, R.; Woiwode, W.; Oelhaf, H.; Dörnbrack, A.; Stratmann, G.; Grooß, J.-U.; Günther, G.; Vogel, B.; Müller, R.; Krämer, M.; Meyer, J.; Cairo, F.

    2014-05-01

    In January 2010 and December 2011 synoptic scale PSC fields were probed during seven flights of the high altitude research aircraft M-55 Geophysica within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interaction.) and the ESSenCe (ESSenCe: ESA Sounder Campaign) projects. Particle size distributions in a diameter range between 0.46 μm and 40 μm were recorded simultaneously by up to four different optical in situ instruments. Three of these particle instruments are based on the detection of forward scattered light by single particles. The fourth instrument is a grey scale optical array imaging probe. Optical particle diameters of up to 35 μm were detected with particle number densities and total particle volumes exceeding previous Arctic measurements. Also, gas phase and particle bound NOy were measured, as well as water vapor concentrations, and other variables. Two remote sensing particle instruments, the Miniature Aerosol Lidar (MAL) and the backscatter sonde (MAS, Multiwavelenght Aerosol Scatterometer) showed the synoptic scale of the encountered PSCs. The particle mode below 2 μm in size diameter has been identified as supercooled ternary solution droplets (STS). The PSC particles in the size range above 2 μm in diameter are considered to consist of nitric acid hydrates or ice, and the particles' high HNO3 content was confirmed by the NOy instrument. Assuming a particle composition of nitric acid trihydrate (NAT), the optically measured size distributions result in particle-phase HNO3 mixing ratios exceeding available stratospheric values. In particular, with respect to the denitrification by sedimentation of large HNO3-contaning particles, generally considered as NAT, our new measurements raise questions concerning composition, shape and nucleation pathways. Measurement uncertainties are discussed concerning probable overestimations of measured particle sizes

  5. 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

  6. 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.

  7. New Miniaturized Cloud Microphysical Instrumentation for Small UAV's

    NASA Astrophysics Data System (ADS)

    O'Connor, D.; Lawson, P.; Zmarzly, P.; Evans, F.

    2007-12-01

    A new micro-sensor and data acquisition system that measures the cloud particle size distribution from 1 to 50 microns and records high-resolution (2.3 micron pixel) digital images of cloud particles has been developed. The new sensor, called a micro-CPI (cloud particle imager) weighs less than 2 kg and consumes about 10 W of electrical power. A single-board Linux processor controls a large field programmable gate array (FPGA) and stores data on a flash disk. A forward scattering optical system that sizes particles from 1 to 50 microns is also part of the particle detection system used to pulse the high-power imaging laser diode. Test flights on an Aerosonde UAV are scheduled for the spring of 2008. A new miniaturized version of a dual-wavelength in situ lidar (ISL) is also being developed for application on small UAV's. The micro-ISL pulses two high-power laser diodes, one at a wavelength that is non-absorbing and a second at a wavelength that is slightly absorbing in water clouds. The time of flight of multiply-scattered photons is measured by off-axis photo detectors. The micro-ISL measures the volumetric extinction, liquid water content and effective drop radius of water clouds within several tens of meters around the UAV. The micro-ISL is based on a principle that has been successfully documented using a large, high-power Nd:YAG laser on a Learjet.

  8. 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.

  9. 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

  10. Ice Formation in Arctic Mixed-Phase Clouds: Insights from a 3-D Cloud-Resolving Model with Size-Resolved Aerosol and Cloud Microphysics

    SciTech Connect

    Fan, Jiwen; Ovtchinnikov, Mikhail; Comstock, Jennifer M.; McFarlane, Sally A.; Khain, Alexander

    2009-02-27

    The single-layer mixed-phase clouds observed during the Atmospheric Radiation Measurement (ARM) program’s Mixed-Phase Arctic Cloud Experiment (MPACE) are simulated with a 3-dimensional cloud-resolving model the System for Atmospheric Modeling (SAM) coupled with an explicit bin microphysics scheme and a radar-lidar simulator. Two possible ice enhancement mechanisms – activation of droplet evaporation residues by condensation-followed-by-freezing and droplet freezing by contact freezing inside-out, are scrutinized by extensive comparisons with aircraft and radar and lidar measurements. The locations of ice initiation associated with each mechanism and the role of ice nuclei (IN) in the evolution of mixed-phase clouds are mainly addressed. Simulations with either mechanism agree well with the in-situ and remote sensing measurements on ice microphysical properties but liquid water content is slightly underpredicted. These two mechanisms give very similar cloud microphysical, macrophysical, dynamical, and radiative properties, although the ice nucleation properties (rate, frequency and location) are completely different. Ice nucleation from activation of evaporation nuclei is most efficient near cloud top areas concentrated on the edges of updrafts, while ice initiation from the drop freezing process has no significant location preference (occurs anywhere that droplet evaporation is significant). Both enhanced nucleation mechanisms contribute dramatically to ice formation with ice particle concentration of 10-15 times higher relative to the simulation without either of them. The contribution of ice nuclei (IN) recycling from ice particle evaporation to IN and ice particle concentration is found to be very significant in this case. Cloud can be very sensitive to IN initially and form a nonquilibrium transition condition, but become much less sensitive as cloud evolves to a steady mixed-phase condition. The parameterization of Meyers et al. [1992] with the observed

  11. 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.

  12. 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.

  13. Examining the Sensitivity of Regional Scale Cloud Properties to Convective Microphysics

    NASA Astrophysics Data System (ADS)

    Storer, R. L.; Zhang, G. J.; Song, X.

    2014-12-01

    A two-moment microphysics scheme for deep convection was implemented in the NCAR Community Atmosphere Model version 5 (CAM5) by Song et al. (2012). The new scheme improved hydrometeor profiles in deep convective clouds and increased deep convective detrainment, reducing the negative biases in low and mid-level cloud fraction and liquid water path compared to observations. Here, we examine in more detail the impacts of this improved microphysical representation on regional scale water and radiation budgets. As the primary source of cloud water for stratus clouds is detrainment from deep and shallow convection, the enhanced convective activity leads to larger stratus cloud fractions, higher cloud water content, and more stratiform precipitation in all oceanic regions examined, particularly in the subtropics. This can be seen also in increased values of net cloud radiative forcing. Over land regions, cloud amounts are reduced, leading to weaker cloud forcing and increased OLR. The magnitude and, occasionally, the sign of the changes in cloud properties can differ if scaled by the precipitation produced in a region, and much of the changes occur in the mixed phase region of the atmosphere. This indicates that the complex interactions between liquid and ice phase microphysics can effect changes in regional scale circulations. We will present details of the large scale water and radiation budgets and the microphysical budgets of cloud liquid and ice for several regions. Results will be compared to cloud resolving model simulations.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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/).

  19. 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.

  20. Microphysical processes affecting stratospheric aerosol particles

    NASA Technical Reports Server (NTRS)

    Hamill, P.; Toon, O. B.; Kiang, C. S.

    1977-01-01

    Physical processes which affect stratospheric aerosol particles include nucleation, condensation, evaporation, coagulation and sedimentation. Quantitative studies of these mechanisms to determine if they can account for some of the observed properties of the aerosol are carried out. It is shown that the altitude range in which nucleation of sulfuric acid-water solution droplets can take place corresponds to that region of the stratosphere where the aerosol is generally found. Since heterogeneous nucleation is the dominant nucleation mechanism, the stratospheric solution droplets are mainly formed on particles which have been mixed up from the troposphere or injected into the stratosphere by volcanoes or meteorites. Particle growth by heteromolecular condensation can account for the observed increase in mixing ratio of large particles in the stratosphere. Coagulation is important in reducing the number of particles smaller than 0.05 micron radius. Growth by condensation, applied to the mixed nature of the particles, shows that available information is consistent with ammonium sulfate being formed by liquid phase chemical reactions in the aerosol particles. The upper altitude limit of the aerosol layer is probably due to the evaporation of sulfuric acid aerosol particles, while the lower limit is due to mixing across the tropopause.

  1. An overview of microphysical properties of Arctic clouds observed in May and July 1998 during FIRE ACE

    NASA Astrophysics Data System (ADS)

    Lawson, R. Paul; Baker, Brad A.; Schmitt, Carl G.; Jensen, T. L.

    2001-07-01

    Microphysical data were collected by the NCAR C-130 research aircraft during the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment Arctic Cloud Experiment (FIRE ACE). Boundary layer clouds 100 to 400 m thick were observed on 11 of the 16 missions. The all-water clouds varied from being adiabatic and homogeneous with monomodal drop spectra to subadiabatic and inhomogeneous with bimodal drop spectra and drizzle. The subadiabatic clouds were observed to be actively mixing near cloud top. The adiabatic clouds provided a test of the performance of the liquid water content (LWC) probes but only in low LWC conditions. A mixed-phase boundary layer cloud displayed striking variability in the hydrometeor fields on a horizontal scale of 10 km and a vertical scale of 100 m. Cloud Particle Imager (CPI) data showed separate regions with small supercooled cloud drops, supercooled drizzle (at -25°C) and graupel particles. A deep stratus cloud with its base at 2 km (+2°C) and top at 6 km (-25°C) contained drizzle near cloud top and (lower in the cloud) very high (2500 to 4000 L-1) concentrations of ice particles in conditions that did not meet all the Hallett-Mossop criteria. CPI data showed that an Arctic cirrus cloud was composed of very high (˜100,000 L-1) concentrations of small ice particles interspersed with single, large (mostly bullet rosette) crystals. The data showed that the cirrus cloud was inhomogeneous on scales down to tens of meters. The average ice particle concentrations measured in the cirrus by the FSSP and CPI probes were several hundred to a few thousand per liter, much higher than commonly found in the literature.

  2. Cloud microphysical and optical properties from 'cloud-mode' observations during the ARM MAGIC campaign

    NASA Astrophysics Data System (ADS)

    Chiu, J. C.; Gregory, L.; Wagener, R.

    2013-12-01

    To better represent marine boundary layer clouds in climate models and to understand their feedback processes, the Atmospheric Radiation Measurement (ARM) Climate Research Facility conducted the MAGIC field campaign to observe the transition from the stratocumulus to shallow trade-wind cumulus along the transect between Los Angeles, California and Honolulu, Hawaii in 2012-2013. These clouds pose great challenges for remote sensing techniques because of their highly inhomogeneous and fast evolving nature. To appropriately measure properties for such clouds at their time scale, we introduce the first marine 'cloud-mode' operation that measures zenith radiance from a sunphotometer, which has demonstrated a robust performance over lands in the worldwide sites of the Aerosol Robotic Network (AERONET). Using cloud-mode observations, we will provide novel retrievals of cloud microphysical and optical properties, and contrast them between cloud regimes and between various retrieval techniques. This cloud-mode operation is a pathfinder not just for seagoing deployments, but also for many future deployments.

  3. 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.

  4. 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.

  5. The great Indian haze revisited: aerosol distribution effects on microphysical and optical properties of warm clouds over peninsular India

    NASA Astrophysics Data System (ADS)

    Ghanti, R.; Ghosh, S.

    2010-03-01

    The Indian subcontinent is undergoing a phase of rapid urbanisation. Inevitable fallout of this process is a concomitant increase in air pollution much of which can be attributed to the infamous great Indian haze phenomena. One observes that the aerosol size distributions vary considerably along the Bay of Bengal (BOB), Arabian Sea (AS) and the Indian Ocean (IO), although, the dynamical attributes are very similar, particularly over the BOB and the AS during this season. Unlike major European studies (e.g. Aerosol Characterization Experiment-2, Ghosh et al., 2005), there are no cloud microphysical modelling studies to complement these observational results for the Indian sub-continent. Ours is the first modelling study over this important region where a time-tested model (O'Dowd et al., 1999a; Ghosh et al., 2007; Rap et al., 2009) is used to obtain cloud microphysical and optical properties from observed aerosol size distributions. Un-activated aerosol particles and very small cloud droplets have to be treated specially to account for non-ideal effects-our model does this effectively yielding realistic estimate of cloud droplet number concentrations (Nc). Empirical relationships linking aerosol concentration to (Nc) yield a disproportionately higher Nc suggesting that such empirical formulations should be used with caution. Our modelling study reveals that the cloud's microphysical and optical properties are very similar along the AS and the BOB despite them having disparate dry aerosol spectral distributions. This is non-intuitive, as one would expect changes in microphysical development with widely different aerosol distributions. There is some increase in cloud droplet numbers with increased haze concentrations but much less than a simple proportion would indicate.

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. Microphysics Parameterization in Convection and its Effects on Cloud Simulation in the NCAR CAM5

    NASA Astrophysics Data System (ADS)

    Zhang, G. J.; Song, X.

    2010-12-01

    Microphysical processes in convection are important to convection-cloud-climate interactions and atmospheric hydrological cycle. They are also essential to understanding aerosol-cloud interaction. However, their parameterization in GCMs is crude. As part of an effort to improve the convection parameterization scheme for the NCAR CAM using observations, we incorporate a cloud microphysics parameterization into the Zhang-McFarlane convection scheme. The scheme is then evaluated against observations of cloud ice and water from the TWP-ICE experiment and other sources using the NCAR SCAM. It is found that this physically-based treatment of convective microphysics yields more realistic vertical profiles of convective cloud ice and liquid water contents. Cloud water and ice budgets are calculated to estimate the role of cloud water and ice detrainment from convection as water and ice sources for large-scale clouds. The new microphysics treatment is further implemented into CAM5 to test its effect on GCM simulations of clouds. Results will be presented at the meeting, and the implications on the simulation of hydrological cycle will be discussed.

  11. 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

  12. 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

  13. 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

  14. 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.

  15. Microphysical and radiative characteristics of convective clouds during COHMEX

    NASA Technical Reports Server (NTRS)

    Fulton, Richard; Heymsfield, Gerald M.

    1990-01-01

    The microphysical structure and the evolution of two strong isolated thunderstorms that occurred on July 11, 1986 in northern Alabama were investigated using data obtained during the Cooperative Huntsville Meteorological Experiment by CP-2 multiparameter radar, together with passive microwave measurements from ER-2 aircraft. A correlation was found between the magnitude of the microwave T(B) depression and the storm intensity, although a clear relationship was not always obvious between radar-deduced microphysical characteristics and passive microwave radiative observations.

  16. 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

  17. In-Situ Microphysical Measurements In Rocket Plumes With The Cloud And Aerosol Spectrometer (CAS)

    NASA Astrophysics Data System (ADS)

    Kok, G.; Baumgardner, D.; Avallone, L.; Kalnajs, L.; Herman, R.; Ross, M.; Thompson, T.; Toohey, D.

    2005-12-01

    High resolution, single particle measurements have been made in rocket plumes using an optical particle spectrometer that measures diameters from 0.5 to 44 um. The Cloud and Aerosol Spectrometer (CAS) measures the light scattered in two directions from individual particles that pass through a focused, 680 nm laser beam and we derive the diameter, shape and composition from this information. The CAS was mounted on the NASA WB57-F aircraft as part of the Plume Ultrafast Measurements Acquisition (PUMA) project, an experiment funded by NSF and NASA to study the chemistry and microphysics of rocket plumes. Measurements were first made in a plume generated by an Atlas IIAS rocket in May, 2004 and again in July, 2005 in the plume formed from the exhaust of the solid state boosters used to launch the space shuttle Discovery into orbit. The microstructure of the two plumes and the characteristics of their particles were distinctly different. The two cases had similar maximum concentrations of 300 cm-3, but the space shuttle particles were on average larger and a greater percentage of them were irregular in shape. An analysis of the distance between particles suggests clustering because of the non-Poisson shape of the frequency distribution of inter-arrival times.

  18. Properties of jet engine combustion particles during the PartEmis experiment: Microphysics and Chemistry

    NASA Astrophysics Data System (ADS)

    Petzold, A.; Stein, C.; Nyeki, S.; Gysel, M.; Weingartner, E.; Baltensperger, U.; Giebl, H.; Hitzenberger, R.; Döpelheuer, A.; Vrchoticky, S.; Puxbaum, H.; Johnson, M.; Hurley, C. D.; Marsh, R.; Wilson, C. W.

    2003-07-01

    The particles emitted from an aircraft engine combustor were investigated in the European project PartEmis. Measured aerosol properties were mass and number concentration, size distribution, mixing state, thermal stability of internally mixed particles, hygroscopicity, and cloud condensation nuclei (CCN) activation potential. The combustor operation conditions corresponded to modern and older engine gas path temperatures at cruise altitude, with fuel sulphur contents (FSC) of 50, 410, and 1270 μg g-1. Operation conditions and FSC showed only a weak influence on the microphysical aerosol properties, except for hygroscopic and CCN properties. Particles of size D >= 30 nm were almost entirely internally mixed. Particles of sizes D < 20 nm showed a considerable volume fraction of compounds that volatilise at 390 K (10-15%) and 573 K (4-10%), while respective fractions decreased to <5% for particles of size D >= 50 nm.

  19. Application of Cloud Vertical Structure to Investigate the Microphysical and Optical Properties of Cirriform, Anvil, and Deep Convective Clouds

    NASA Astrophysics Data System (ADS)

    Bates, J. J.; Young, A. H.; Curry, J. A.

    2012-12-01

    This study uses cloud vertical structure (CVS) to evaluate the optical and microphysical properties of high clouds including cirriform, anvil, and deep convection (DC) over the region between 35°S-35°N for a 1-yr period from January-December 2007. The analyses are based on integrated multisensory pixel-level observations of CVS from CloudSat/CALIPSO and Level 2 cloud data from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua satellite. Cloud products evaluated include mean cloud optical thickness, cloud effective radius, cloud-top temperature, cloud-top pressure, cloud brightness temperature, and cloud effective emissivity. Unlike other studies, high clouds investigated in this study are not determined by the International Satellite Cloud Climatology Project (ISCCP) cloud classification scheme. Instead it relies on the CloudSat 2B-CLDCLASS product which uses radar reflectivity data and also considers the spatial and horizontal cloud structure to classify cirriform, anvil, and DC clouds. Results of the study are used to evaluate the capabilities of MODIS to estimate cloud properties and identify the impacts of using CVS to classify various types of high level clouds rather than the ISCCP cloud classification scheme. Applications of the study's results include potential improvements to precipitation retrievals and the representation of cloud systems in general circulation models.

  20. 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.

  1. Implications of microphysics for cloud-radiation parameterizations: Lessons from TOGA COARE

    SciTech Connect

    Iacobellis, S.F.; Somerville, R.C.J.

    2000-01-15

    A single-column model (SCM) and observational data collected during TOGA COARE were used to investigate the sensitivity of model-produced cloud properties and radiative fluxes to the representation of cloud microphysics in the cloud-radiation parameterizations. Four 78-day SCM numerical experiments were conducted for the atmospheric column overlying the COARE Intensive Flux Array. Each SCM experiment used a different cloud-radiation parameterization with a different representation of cloud microphysics. All the SCM experiments successfully reproduced most of the observed temporal variability in precipitation, cloud fraction, shortwave and longwave cloud forcing, and downwelling surface shortwave flux. The magnitude and temporal variability of the downward surface longwave flux was overestimated by all the SCM experiments. This bias is probably due to clouds forming too low in the model atmosphere. Time-averaged model results were used to examine the sensitivity of model performance to the differences between the four cloud-radiation parameterization packages. The SCM versions that calculated cloud amount as a function of cloud liquid water, instead of using a relative humidity-based cloud scheme, produced smaller amounts of both low and deep convective clouds. Additionally, larger high (cirrus) cloud emissivities were obtained with interactive cloud liquid water schemes than with the relative humidity-based scheme. Surprisingly, calculating cloud optical properties as a function of cloud liquid water amount, instead of parameterizing them based on temperature, humidity, and pressure, resulted in relatively little change in radiative fluxes. However, model radiative fluxes were sensitive to the specification of the effective cloud droplet radius. Optically thicker low clouds and optically thinner high clouds were produced when an interactive effective cloud droplet radius scheme was used instead of specifying a constant value. Comparison of model results to both

  2. 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

  3. Dual-field-of-view Raman lidar measurements for the retrieval of cloud microphysical properties.

    PubMed

    Schmidt, Jörg; Wandinger, Ulla; Malinka, Aleksey

    2013-04-10

    Dual-field-of-view Raman lidar measurements, detecting Raman-scattered light with two fields of view simultaneously, are used for the first time to retrieve cloud microphysical properties. The measurements are performed with the Multiwavelength Atmospheric Raman Lidar for Temperature, Humidity, and Aerosol Profiling (MARTHA) at the Leibniz Institute for Tropospheric Research in Leipzig, Germany. Light that is scattered in forward direction by cloud droplets and inelastically backscattered by N2 molecules is detected. A forward iterative algorithm uses the measured signals to derive profiles of the effective cloud droplet radius, extinction coefficient, and liquid-water content of the investigated clouds. The setup, algorithm, error analysis, and a measurement example are presented. The obtained liquid-water path is validated by observations with a microwave radiometer. With the capability to retrieve aerosol properties as well as cloud microphysical properties, the Raman lidar MARTHA is an ideal tool for studies of the aerosol indirect effect. PMID:23670751

  4. 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.

  5. 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.; Willett, J. C.; Willis, P. T.

    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.

  6. 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.

  7. 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.

  8. Simulation of cirrus clouds with a quasi 2-moment microphysical scheme: a 1D case study

    NASA Astrophysics Data System (ADS)

    Pinty, J.-P.

    2003-04-01

    Cirrus clouds are receiving a great scientific interest because of their importance on the climate system through their impact on the radiation budget and on the physico-chemical balance of the upper troposphere. In this presentation, we concentrate on the application of a mixed-phase 2-moment microphysical scheme to simulate cirrus cloud properties with various ice nucleation modes. The complete scheme is implemented in the multi-purpose mesoscale model MésoNH with several capabilities (3D real vs. academic flows, grid-nesting, etc.). The 1D FIRE and subvisible test cases of Jensen et al. (1994 and 1996 both in JGR) are selected in the present study. The simulations are performed with a similar a thermo-dynamical and dynamical framework and microphysical results are analysed. Additional variations of some critical input parameters (CCN and IN concentrations, vertical velocity and ice characteristics) are explored to test the sensitivity of the microphysical scheme.

  9. 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.

  10. Simulating Feedbacks Between Stratocumulus Cloud Dynamics, Microphysics and Aerosols Over Large Scales.

    NASA Astrophysics Data System (ADS)

    Grosvenor, D. P.; Field, P.; Hill, A. A.; Shipway, B. J.

    2014-12-01

    The response of a stratocumulus cloud deck to aerosols involves a complex interplay between cloud microphysics, precipitation, cold pool dynamical interactions between neighboring cells, cloud top entrainment and the boundary layer structure over larger scales. Such feedbacks are thought to be involved in, for example, the formation of Pockets of Open Cells (POCs), which represent a large albedo change relative to the closed cell regime. However, they are not represented in GCM parameterizations and have also so far have not been simulated adequately in mesoscale models, which is a necessary step in order to develop parameterizations. We will show results from high resolution (<1 km) mesoscale simulations of stratocumulus using a new multi-moment microphysics scheme coupled to the UK Met Office Unified Model. The new scheme represents the processing of aerosol by clouds, allowing examination of the feedbacks between cloud dynamics, microphysics and aerosol. Results will be shown for domains of order 1000km that are driven by meteorological analysis, allowing realistic forcing and large scale interactions, in contrast to idealized LES simulations. Additionally, a representation of sub-grid vertical velocities based on resolved motions has been implemented, which will allow consistent droplet activation across a range of horizontal model resolutions. A cloud scheme to account for sub-grid humidity variability was also added and was found to be necessary in order to simulate realistic clouds.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Coupling of the microphysical and optical properties of an Arctic nimbostratus cloud during the ASTAR 2004 experiment: Implications for light-scattering modeling

    NASA Astrophysics Data System (ADS)

    Jourdan, Olivier; Mioche, Guillaume; Garrett, Timothy J.; SchwarzenböCk, Alfons; Vidot, JéRôMe; Xie, Yu; Shcherbakov, Valery; Yang, Ping; Gayet, Jean-FrançOis

    2010-12-01

    Airborne measurements in an Arctic mixed-phase nimbostratus cloud were conducted in Spitsbergen on 21 May 2004 during the international Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign. The in situ instrument suite aboard the Alfred Wegener Institute Polar 2 aircraft included a polar nephelometer (PN), a cloud particle imager (CPI), a Nevzorov probe, and a standard PMS 2DC probe to measure the cloud particle single-scattering properties (at a wavelength of 0.8 μm), and the particle morphology and size, as well as the in-cloud partitioning of ice/water content. The main objective of this work is to present a technique based on principal component analysis and light-scattering modeling to link the microphysical properties of cloud particles to their optical characteristics. The technique is applied to the data collected during the 21 May case study where a wide variety of ice crystal shapes and liquid water fractions were observed at temperatures ranging from -1°C to -12°C. CPI measurements highlight the presence of large supercooled water droplets with diameters close to 500 μm. Although the majority of ice particles were found to have irregular shapes, columns and needles were the prevailing regular habits between -3°C and -6°C while stellars and plates were observed at temperatures below -8°C. The implementation of the principal component analysis of the PN scattering phase function measurements revealed representative optical patterns that were consistent with the particle habit classification derived from the CPI. This indicates that the synergy between the CPI and the PN can be exploited to link the microphysical and shape properties of cloud particles to their single-scattering characteristics. Using light-scattering modeling, we have established equivalent microphysical models based on a limited set of free parameters (roughness, mixture of idealized particle habits, and aspect ratio of ice crystals) that reproduce the main

  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. 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

    2016-01-01

    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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Platnick, S. E.; King, M. D.; Wind, G.; Hubanks, P.; Arnold, G. T.; Amarasinghe, N.

    2009-12-01

    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 µm effective radius retrieval, and added a multi-layer cloud detection algorithm. We will discuss the status of the MOD06 algorithm and show examples of pixel-level (Level-2) cloud retrievals for selected data granules, as well as gridded (Level-3) statistics, notably monthly means and histograms (1D and 2D, with the latter giving correlations between cloud optical thickness and effective radius, and other cloud product pairs).

  1. 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).

  2. Cloud microphysical relationships and their implication on the mixing processes in the stratocumulus clouds measured during the VOCALS-REx

    NASA Astrophysics Data System (ADS)

    Yum, S. S.; Wang, J.; Liu, Y.; Senum, G.; Springston, S. R.; McGraw, R. L.; Yeom, J.

    2014-12-01

    Understanding the nature of marine stratocumulus clouds (MSCs) have been recognize as crucially important in climate change prediction due to their important roles in modulating radiation budget on a very wide spatial scale. However, despite the seemingly simple shape of MSCs, microphysical and dynamical characteristics of these clouds are very complex. MSCs are usually topped by much warmer and drier air and entrainment and mixing at the top of these clouds modulate the cloud microphysics and dynamics. The important point is that depending on how entrained air mixes with the cloudy air, further development of the cloud can turn out to be different. Here we examine this problem for the MSCs observed over the Southeastern Pacific. The airborne data we used were obtained from the G-1 aircraft during Vamos Ocean Cloud Atmosphere Land Study-Regional Experiment (VOCALS-REx). The data were recorded at various rates but the ones presented in this study are the 1Hz and 40Hz data. Cloud microphysics data obtained from horizontal penetrations through the clouds are analyzed to find the evidence for the dominant mixing mechanism of the entrained dry air from above the cloud top. We find that the dominant feature is the positive relationship between cloud droplet mean volume (V) and liquid water content (L). Despite this apparent trait of homogeneous mixing, relevant scale parameters (i.e., transition length scale and transition scale number) consistently suggest that inhomogeneous mixing would be dominant for the VOCALS MSCs. Here we propose that this clear discrepancy can be explained by vertical circulation mixing that can modulate the V-L relationship to suggest homogeneous mixing at the measurement altitudes, which was on average 10.2 mb down from the cloud top where actual mixing may have occurred inhomogeneously.

  3. 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.

  4. Microphysical Simulation of Polar Stratospheric Clouds Within the Community Earth System Model

    NASA Astrophysics Data System (ADS)

    Zhu, Yunqian

    Polar stratospheric clouds (PSCs) are critical elements for polar ozone depletion. A new PSC model coupling stratospheric chemistry, microphysics and climate is constructed and the formation of STS (Super-cooled Ternary Solution) and NAT (Nitric-Acid Trihydrate) PSCs are explored. STS particle properties are dominated by thermodynamics. Simulations of particle volumes and size distributions are generally within the observational error bars. STS particles are not in equilibrium with their environment when the particle surface area is smaller than 4 mum2/cm 3. A new nucleation rate equation for NAT is derived based on observed denitrification in the 2010-2011 Arctic winter. The homogeneous nucleation scheme leads to supermicron NAT particles as observed. The simulated the lidar backscatter, and denitrification are generally within observational error bars. However, the simulations are very sensitive to temperature. Using the same STS and NAT schemes, as well as a prognostic treatment for ice PSC formation and dehydration, the PSCs are simulated during the Antarctic winter of 2010. The current model correctly simulates large NAT particles and denitrification, but cannot produce NAT with high backscattering ratio/number density sometimes observed by CALIPSO. However, our simulated ice has similar backscatter and depolarization which is often attributed to NAT by CALIPSO. Possibly the CALIPSO algorithm misclassifies ice as NAT when the stratosphere is denitrified or dehydrated. STS and NAT form near the pole in May and June, but form a ring outside 80?S later in the winter when polar HNO3 is depleted. Ice always forms in the coldest area, but becomes less abundant later in the winter. The model is missing some processes forming NAT such as gravity waves or evaporating ice. These processes should be added to the model in the future.

  5. 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).

  6. 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).

  7. 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.

  8. A two-moment cloud microphysics parameterization for mixed-phase clouds. Part 2: Maritime vs. continental deep convective storms

    NASA Astrophysics Data System (ADS)

    Seifert, A.; Beheng, K. D.

    2006-02-01

    A systematic modeling study investigates the effects of cloud condensation nuclei (CCNs) on the evolution of mixed-phase deep convective storms. Following previous studies the environmental conditions like buoyancy and vertical wind shear are varied to simulate different storm types like ordinary single cells, multicells and supercells. In addition, the CCN characteristics are changed from maritime to continental conditions. The results reveal very different effects of continentality on the cloud microphysics and dynamics of the different storms. While a negative feedback on total precipitation and maximum updraft velocity is found for ordinary single cells and supercell storms, a positive feedback exists for multicell cloud systems. The most important link between CCN properties, microphysics and dynamics is the release of latent heat of freezing.

  9. 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.

  10. 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.

  11. 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. PMID:25402925

  12. Cloud microphysical relationships and their implication on entrainment and mixing mechanisms for marine and continental stratocumulus clouds

    NASA Astrophysics Data System (ADS)

    Yum, S. S.; Yeom, J. M.; Wang, J.; Liu, Y.; Senum, G.; Springston, S. R.; McGraw, R. L.; Lu, C.

    2015-12-01

    Cloud microphysical data obtained from aircraft measurements of stratocumulus clouds over the southeastern pacific during the VOCALS-Rex field campaign and over the Great Plains region in Oklahoma during the RACORO field campaign were analyzed for evidence of entrainment mixing of air from above cloud top. Mixing diagram analysis was made for the horizontal flight data recorded at various rates (1 Hz, 10 Hz and 40 Hz). For the maritime stratocumulus clouds, 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. For the continental stratocumulus clouds, the positive relationship between V and L was even more pronounced while the scale parameters were less indicative of inhomogeneous mixing. Finding evidence for vertical circulation mixing was difficult for these clouds because flight plans in this campaign were not designed to investigate such process.

  13. 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.

  14. Large-Scale Analysis of Cirrus Clouds from AVHRR Data: Assessment of Both a Microphysical Index and the Cloud-Top Temperature.

    NASA Astrophysics Data System (ADS)

    Giraud, V.; Buriez, J. C.; Fouquart, Y.; Parol, F.; Seze, G.

    1997-06-01

    An algorithm that allows an automatic analysis of cirrus properties from Advanced Very High Resolution Radiometer (AVHRR) observations is presented. Further investigations of the information content and physical meaning of the brightness temperature differences (BTD) between channels 4 (11 m) and 5 (12 m) of the radiometer have led to the development of an automatic procedure to provide global estimates both of the cirrus cloud temperature and of the ratio of the equivalent absorption coefficients in the two channels, accounting for scattering effects. The ratio is useful since its variations are related to differences in microphysical properties. Assuming that cirrus clouds are composed of ice spheres, the effective diameter of the particle size distribution can be deduced from this microphysical index.The automatic procedure includes first, a cloud classification and a selection of the pixels corresponding to the envelope of the BTD diagram observed at a scale of typically 100 × 100 pixels. The classification, which uses dynamic cluster analysis, takes into account spectral and spatial properties of the AVHRR pixels. The selection is made through a series of tests, which also guarantees that the BTD diagram contains the necessary information, such as the presence of both cirrus-free pixels and pixels totally covered by opaque cirrus in the same area. Finally, the cloud temperature and the equivalent absorption coefficient ratio are found by fitting the envelope of the BTD diagram with a theoretical curve. Note that the method leads to the retrieval of the maximum value of the equivalent absorption coefficient ratio in the scene under consideration. This, in turn, corresponds to the minimum value of the effective diameter of the size distribution of equivalent Mie particles.The automatic analysis has been applied to a series of 21 AVHRR images acquired during the International Cirrus Experiment (ICE'89). Although the dataset is obviously much too limited to draw

  15. 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.

  16. Optimizing Weather and Research Forecast (WRF) Thompson cloud microphysics on Intel Many Integrated Core (MIC)

    NASA Astrophysics Data System (ADS)

    Mielikainen, Jarno; Huang, Bormin; Huang, Allen

    2014-05-01

    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. Those optimization techniques are discusses in this paper. The results show that the optimization improved MIC performance by 3.4x. Furthermore, the optimized MIC code is 7.0x faster than the optimized multi-threaded code on the four CPU cores of a single socket Intel Xeon E5-2603 running at 1.8 GHz.

  17. 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.

  18. 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

  19. Using Directional Emissivity as a Probe of Particle Microphysical Properties

    NASA Astrophysics Data System (ADS)

    Pitman, K. M.; Wolff, M. J.; Bandfield, J. L.; Clayton, G. C.

    2002-09-01

    Real surfaces are not expected to be diffuse emitters, thus observed emissivity values are a function of viewing geometry. This fact has strong implications for analyses of the MGS/TES emission phase function (EPF) sequences and the upcoming Mars Exploration Rover mini-TES dataset. As reviewed previously [1], in the absence of strong thermal gradients, directional emissivity may be obtained via a combination of reciprocity and Kirchhoff's Law. Here we focus on the potential utility of directional emissivity as a direct probe of surface particle microphysical properties. We explore the effects of particle size and composition on observed radiances in the TES spectral regime using a combination of multiple scattering radiative transfer and Mie scattering algorithms. Comparisons of these simulated spectra to TES EPF observations of typical surface units (e.g., high and low albedo regions) will also be made. This work is supported through NASA grant NAGS-9820 (MJW) and LSU Board of Regents (KMP). [1] Pitman, K.M., et al. (2001), AAS-DPS meeting # 33, # 36.01.

  20. Total Storm Currents and their Relationship to Microphysical and Dynamical Cloud Properties

    NASA Astrophysics Data System (ADS)

    Kalb, C. P.; Deierling, W.; Mach, D. M.; Liu, C.

    2013-12-01

    Electrified clouds are thought to play a major role in the global electric circuit (GEC). These clouds produce total storm currents from the top of thunderstorms which help maintain the potential difference between earth's surface and the upper atmosphere. Total storm currents for different types of electrified clouds were recently derived from overflights of the NASA ER-2 aircraft spanning several field campaigns between 1992 and 2005. In this study, total storm current measurements are compared with radar derived dynamical and microphysical properties to investigate whether these storm properties can be used to describe the current variability of different electrified clouds. When applied globally, such relationships may be used to improve modeling of the GEC via quantification and improved parameterization of the conduction current contribution from different cloud types in a model framework.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Hail formation and growth in a 3D cloud model with hail-bin microphysics

    NASA Astrophysics Data System (ADS)

    Guo, Xueliang; Huang, Meiyuan

    The hailstorm of 22 July 1976 in Colorado was studied using a three-dimensional compressible nonhydrostatic cloud model with hail-bin microphysics and parameterized bulk hail microphysics. Results show that observed storm features, such as long-lasting, transient weak-echo vaults and a pronounced forward overhang structure can be better simulated in the model with hail-bin microphysics. The role of a feeder updraft in forming and transferring graupel into a main updraft is analyzed using three-dimensional information on hail and graupel locations and corresponding wind field data from the simulations with hail-bin microphysics. It is found that the formation of a feeder cell with weaker updraft along the side of a main cell has two important roles in forming of hail in the simulated multicellular hailstorm. One is to efficiently transfer graupel descended along the edge of the main updraft or from a massive forward overhang region into the main updraft by preventing the rapid fall of graupel to the surface, and by lifting the low-level inflow by which graupel can be advected into the main updraft. Second, to evolve as a daughter cell in which hail from the decaying old cell can continue their growth. Based on the study, the primary role of a feeder cell is to transfer hail embryos originally formed in a main cell to reenter the main cell rather than to generate initial hail embryos as proposed by previous studies.

  8. 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.

  9. Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM

    NASA Astrophysics Data System (ADS)

    Lohmann, U.; Stier, P.; Hoose, C.; Ferrachat, S.; Kloster, S.; Roeckner, E.; Zhang, J.

    2007-07-01

    The double-moment cloud microphysics scheme from ECHAM4 that predicts both the mass mixing ratios and number concentrations of cloud droplets and ice crystals has been coupled to the size-resolved aerosol scheme ECHAM5-HAM. ECHAM5-HAM predicts the aerosol mass, number concentrations and mixing state. The simulated liquid, ice and total water content and the cloud droplet and ice crystal number concentrations as a function of temperature in stratiform mixed-phase clouds between 0 and -35° C agree much better with aircraft observations in the ECHAM5 simulations. ECHAM5 performs better because more realistic aerosol concentrations are available for cloud droplet nucleation and because the Bergeron-Findeisen process is parameterized as being more efficient. The total anthropogenic aerosol effect includes the direct, semi-direct and indirect effects and is defined as the difference in the top-of-the-atmosphere net radiation between present-day and pre-industrial times. It amounts to -1.9 W m-2 in ECHAM5, when a relative humidity dependent cloud cover scheme and aerosol emissions representative for the years 1750 and 2000 from the AeroCom emission inventory are used. The contribution of the cloud albedo effect amounts to -0.7 W m-2. The total anthropogenic aerosol effect is larger when either a statistical cloud cover scheme or a different aerosol emission inventory are employed because the cloud lifetime effect increases.

  10. 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.

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

    DOE PAGESBeta

    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 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

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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).

  17. Statistical Retrieval of Thin Liquid Cloud Microphysical Properties Using Ground-Based Infrared and Microwave Observations

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    In this study, liquid water cloud microphysical properties are retrieved by exploiting passive remote sensing techniques in the microwave and infrared spectral regime. Liquid water clouds are highly frequent in various 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 enhances for thin clouds with a low liquid water path (LWP), which requires accurate retrieval information on the cloud properties. Retrieving low LWP values using the microwave spectral regime reveals large relative errors, whereas the potential for infrared methods is high. Therefore robust and computationally low demanding synergistic retrievals based on a multivariate regression and a neural network are derived to estimate LWP and cloud effective radius. While the regression-type synergy retrievals are strongly influenced by the nonlinearities of saturating signals in the infrared regime for higher LWP, the neural network retrieval is able to retrieve LWP and cloud effective radius with a higher accuracy than the single instrument retrievals. This is achieved by examining synthetic observations in the low LWP range. Furthermore, the performance of the retrievals is assessed in a radiative closure study for the downwelling shortwave flux, using measurements of a microwave radiometer, a broadband infrared radiometer and a spectrally highly resolved Atmospheric Emitted Radiance Interferometer (AERI).

  18. Ascent dynamics of large phreatomagmatic eruption clouds: The role of microphysics

    NASA Astrophysics Data System (ADS)

    van Eaton, A. R.; Herzog, M.; Wilson, C. J. N.; McGregor, J.

    2012-03-01

    We examine the impact of abundant surface water interaction on the development of volcanic clouds from large-scale (>108 kg s-1 magma) phreatomagmatic eruptions, presenting the first 2-D large-eddy simulations of "wet" volcanic plumes that incorporate the effects of microphysics. The Active Tracer High-Resolution Atmospheric Model was forced with field-derived inputs from an exceptionally large phreatomagmatic eruption: the 27 ka Oruanui supereruption (Taupo volcano, New Zealand). Surface water contents were varied from 0 to 40 wt% for eruptions with equivalent magma eruption rates of ˜1.3 × 108 and 1.1 × 109 kg s-1. Our findings confirm that increased surface water has a pronounced impact on column stability, leading to transitional column behavior and hybrid clouds resulting from simultaneous ascent of material from stable columns and pyroclastic density currents (PDCs). Contrary to the suggestion of previous workers, however, abundant surface water does not systematically lower the spreading level or maximum height of volcanic clouds, owing to vigorous microphysics-assisted lofting of PDCs. The simulated behavior and ash cloud dimensions provide a close match to field evidence from the Oruanui case study. Cloud heights from the collapsing eruption columns also show a notable sensitivity to changes in the altitude of the tropopause, while ambient humidity primarily impacts the abundance of airborne hydrometeors (particularly ice) associated with the volcanic clouds. General relationships between eruption style, meteorological conditions, and the resulting vertical profiles of volcanic emissions outlined here could also be adapted for use in operational volcanic ash forecasting and deposit reconstruction techniques already in existence.

  19. Quantitative evaluation of seven optical sensors for cloud microphysical measurements at the Puy-de-Dôme Observatory, France

    NASA Astrophysics Data System (ADS)

    Guyot, G.; Gourbeyre, C.; Febvre, G.; Shcherbakov, V.; Burnet, F.; Dupont, J.-C.; Sellegri, K.; Jourdan, O.

    2015-10-01

    Clouds have an important role in Earth's radiative budget. Since the late 1970s, considerable instrumental developments have been made in order to quantify cloud microphysical and optical properties, for both airborne and ground-based applications. Intercomparison studies have been carried out in the past to assess the reliability of cloud microphysical properties inferred from various measurement techniques. However, observational uncertainties still exist, especially for droplet size distribution measurements and need to be reduced. In this work, we discuss results from an intercomparison campaign, performed at the Puy de Dôme in May 2013. During this campaign, a unique set of cloud instruments was operating simultaneously in ambient air conditions and in a wind tunnel. A Particle Volume Monitor (PVM-100), a Forward Scattering Spectrometer Probe (FSSP), a Fog Monitor (FM-100), and a Present Weather Detector (PWD) were sampling on the roof of the station. Within a wind tunnel located underneath the roof, two Cloud Droplet Probes (CDPs) and a modified FSSP (SPP-100) were operating. The main objectives of this paper are (1) to study the effects of wind direction and speed on ground-based cloud observations, (2) to quantify the cloud parameters discrepancies observed by the different instruments, and (3) to develop methods to improve the quantification of the measurements. The results revealed that all instruments showed a good agreement in their sizing abilities, both in terms of amplitude and variability. However, some of them, especially the FM-100, the FSSP and the SPP, displayed large discrepancies in their capability to assess the magnitude of the total number concentration of the cloud droplets. As a result, the total liquid water content can differ by up to a factor of 5 between the probes. The use of a standardization procedure, based on data of integrating probes (PVM-100 or visibilimeter) and extinction coefficient comparison substantially enhanced the

  20. The influence of entrainment-induced variability of cloud microphysics on the chemical composition of cloudwater

    NASA Astrophysics Data System (ADS)

    Walcek, Chris J.; Brankov, Elvira

    We propose a mechanism by which condensed water within clouds becomes chemically heterogeneous due to the turbulent nature of entrainment of noncloudy air into a rising cloudy parcel. We hypothesize that the observed small-scale variability of cloud microphysics, temperature and vertical velocity results from the formation of turbulent-scale sub-regions composed of varying proportions of undiluted cloudy air mixed with dry, cloud-free air above cloud base. Cloudy regions that are exposed to a higher degree of entrainment will contain lower condensed water contents, lower temperatures, lower droplet number concentrations at smaller sizes, and lower vertical velocities as a result of entrainment-induced dilution and evaporation. Greater entrainment will also increase concentrations of sulfate, nitrate and ammonium in cloudwater, and will lead to a size-dependent chemical composition of cloudwater across the range of entrainment mixtures. We find significant discrepancies between calculated SO 2 oxidation rates that account for turbulent-scale variability, relative to simpler calculations that ignore turbulent-induced variability. The more exact description of a cloud composed of a heterogeneous mix of parcels yields higher sulfur oxidation rates and lower dissolved concentrations of highly soluble sulfate, nitrate and ammonia. Most current measurements and models of cloudwater chemical composition cannot resolve the fine structure of entrainment-induced fluctuations in cloud microphysics, and therefore implicitly "average out" small-scale fluctuations of momentum, heat, buoyancy and water substance within the measurement volume or numerical grid. This averaging can lead to erroneous interpretations of measurements, and may yield biased calculations of SO 2 oxidation within clouds. Using measured concentrations of pertinent air quality concentrations in conjunction with a relatively simple regional-scale atmospheric chemistry model, we find that during most of the

  1. Cloud Resolving Simulations of Convection during AMIE/DYNAMO: Microphysics and Heat / Moisture Budget

    NASA Astrophysics Data System (ADS)

    Janiga, M. A.; Li, X.; Hagos, S.; Feng, Z.; Wang, S.; Rowe, A.; Tao, W. K.; Zhang, C.

    2014-12-01

    This study compares simulations of convection during the AMIE/DYNAMO field campaign performed using three doubly-periodic cloud-resolving models (CRMs) and one regional CRM. A variety of microphysics parameterizations are used in these simulations. The target of these simulations is the second MJO event of the campaign, including suppressed periods before and after the passage of the convective envelope. The properties of convection in the CRM simulations are compared to observations of reflectivity and hydrometeor type from the dual-polarimetric SPOL radar. Contrasts in the properties of convection between the various simulations are related to their effect on the heat and moisture budgets.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Sensitivity of a Cloud-Resolving Model to the Bulk and Explicit Bin Microphysical Schemes

    NASA Technical Reports Server (NTRS)

    Li, Xiao-Wen; Tao, Wei-Kuo; Khain, Alexander P.; Simpson, Joanne

    2004-01-01

    A cloud-resolving model is used to study sensitivities of two different microphysical schemes, one is the traditional bulk type, and the other is an explicit bin scheme, in simulating a mid-latitude squall line case (PRE-STORM, June 10-1 1,1985). Simulations using different microphysical schemes are compared with each other and also with the observations. Both the bulk and bin models reproduce the general features during the developing and mature stage of the system. Furthermore, the observations and the well-proven bulk scheme simulation serve as validations for the newly incorporated bin scheme. However, it is also shown that the bulk and bin simulations have distinct differences, most notably in the stratiform region of the squall line system. Weak convective cells exist in the stratiform region in the bulk simulation, but not in the bin simulation. These weak convective cells in the stratiform region simulated in the bulk scheme model are remnants of the stronger convections previously at the leading edge of the system, sustained by horizontal vorticity generated by its own cool pool near the surface. The bin simulation, on the other hand, has a horizontally homogeneous stratiform cloud structure, which agrees better with the observations. Examinations of the downdraft core strength, the potential temperature perturbation, and the evaporative cooling rate show that the differences between the bulk and bin models are due mainly to the stronger low-level evaporative cooling in the convective zone simulated in the bulk microphysical scheme, which is unrealistic because of the assumptions made in raindrop size distribution. Further sensitivity tests that reduce the evaporation rate in bulk scheme artificially produce more upright convective core and less weak cores in stratiform region. However, they produce weaker upper level outflow and consequently less stratiform rain area. The addition of a more realistic raindrop breakup scheme in the bin scheme results more

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  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. 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.

  16. 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.

  17. 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. PMID:21052418

  18. Simulation study of the remote sensing of optical and microphysical properties of cirrus clouds from satellite IR measurements

    NASA Astrophysics Data System (ADS)

    Xu, Lisheng; Zhang, Jianyun

    1995-05-01

    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.

  19. Benefits of a 4th Ice Class in the Simulation of Convective Systems with a Cloud-resolving Model using One-moment Bulk Microphysics

    NASA Astrophysics Data System (ADS)

    Lang, S. E.; Tao, W.; Wu, D.; Li, X.

    2012-12-01

    A fourth class of ice (i.e., hail) was recently added to an improved version of the 3-class ice (i.e., cloud ice, snow, and graupel), one-moment, bulk microphysics scheme developed for the Goddard Cumulus Ensemble model (or GCE), a cloud-resolving model. The scheme was originally derived from Rutledge and Hobbs (1983, 1984). The additional hail processes are taken from a comparable scheme based on Lin et al. (1983). The following hail processes were kept unchanged: riming, melting, shedding, and accretion of rain. To prevent the overly efficient collection of frozen particles by hail, dry growth was eliminated; however, wet growth was retained and slightly expanded to allow cloud ice and snow particles to be efficiently collected when hail is at or near wet growth conditions. The two 3-class schemes were merged by treating frozen rain as hail and rimed snow as graupel. In addition to hail, a snow density mapping and rain evaporation correction were added, and depositional growth was used to migrate graupel and hail particles to snow at colder temperatures. The saturation adjustment scheme was also modified to allow cloud particles to subsist in sub-saturated conditions. The new scheme is applied to convective cases from the Midlatitude Continental Convective Clouds Experiment (MC3E) and results in notable improvements to the synthetic radar signatures.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. Aerosol indirect effects in the ECHAM5-HAM2 climate model with subgrid cloud microphysics in a stochastic framework

    NASA Astrophysics Data System (ADS)

    Tonttila, Juha; Räisänen, Petri; Järvinen, Heikki

    2015-04-01

    Representing cloud properties in global climate models remains a challenging topic, which to a large extent is due to cloud processes acting on spatial scales much smaller than the typical model grid resolution. Several attempts have been made to alleviate this problem. One such method was introduced in the ECHAM5-HAM2 climate model by Tonttila et al. (2013), where cloud microphysical properties, along with the processes of cloud droplet activation and autoconversion, were computed using an ensemble of stochastic subcolumns within the climate model grid columns. Moreover, the subcolumns were sampled for radiative transfer using the Monte Carlo Independent Column Approximation approach. The same model version is used in this work (Tonttila et al. 2014), where 5-year nudged integrations are performed with a series of different model configurations. Each run is performed twice, once with pre-industrial (PI, year 1750) aerosol emission conditions and once with present-day (PD, year 2000) conditions, based on the AEROCOM emission inventories. The differences between PI and PD simulations are used to estimate the impact of anthropogenic aerosols on clouds and the aerosol indirect effect (AIE). One of the key results is that when both cloud activation and autoconversion are computed in the subcolumn space, the aerosol-induced PI-to-PD change in the global-mean liquid water path is up to 19 % smaller than in the reference with grid-scale computations. Together with similar changes in the cloud droplet number concentration, this influences the cloud radiative effects and thus the AIE, which is estimated as the difference in the net cloud radiative effect between PI and PD conditions. Accordingly, the AIE is reduced by 14 %, from 1.59 W m-2 in the reference model version to 1.37 W m-2 in the experimental model configuration. The results of this work explicitly show that careful consideration of the subgrid variability in cloud microphysical properties and consistent

  7. 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.

  8. Evaluation of a New Mixed-Phase Cloud Microphysics Parameterization with a Single Column Model, CAPT Forecasts and M-PACE Observations

    NASA Astrophysics Data System (ADS)

    Liu, X.; Xie, S.; Boyle, J.; Klein, S.; Ghan, S.

    2007-12-01

    Most global climate models generally prescribe the partitioning of condensed water into liquid droplets and ice crystals in mixed-phase clouds according to a temperature-dependent function, which affects modeled cloud phase, cloud lifetime and radiative properties. In this study we evaluate a new mixed-phase cloud microphysics parameterization (for ice nucleation and water vapor deposition) against the Atmospheric Radiation Measurement (ARM) Mixed-phase Arctic Cloud Experiment (M-PACE) observations using the NCAR Community Atmospheric Model Version 3 (CAM3) running in the single column mode (SCAM) and in the CCPP-ARM Parameterization Testbed (CAPT) forecasts. It is found that SCAM with the new physically-based cloud microphysical scheme produces a more realistic simulation of the cloud phase structure and the partitioning of condensed water into liquid droplets against observations during the M-PACE than the standard CAM with an oversimplified cloud microphysics. CAM3 in the CAPT forecasts significantly underestimates the observed boundary layer mixed- phase cloud fraction. The simulation of the boundary layer mixed-phase clouds and their microphysical properties is considerably improved in CAM3 when the new scheme is used. The new scheme also leads to an improved simulation of the surface and top of the atmosphere longwave radiative fluxes. Both SCAM simulations and CAPT forecasts suggest that the ice number concentration could play an important role in the simulated mixed-phase cloud microphysics, and thereby needs to be realistically represented in global climate models.

  9. 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%.

  10. 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.

  11. 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

  12. Forecasting and understanding cirrus clouds with the large scale Lagrangian microphysical model CLaMS-Ice

    NASA Astrophysics Data System (ADS)

    Rolf, Christian; Grooß, Jens-Uwe; Spichtinger, Peter; Costa, Anja; Krämer, Martina

    2015-04-01

    Cirrus clouds play an important role by influencing the Earth's radiation budget and the global climate (Heintzenberg and Charlson, 2009). This is shown in the recent IPCC reports, where the large error bars relating to the cloud radiative forcing underline the poor scientific knowledge of the underlying processes. The formation and further evolution of cirrus clouds is determined by the interplay of temperature, ice nuclei (IN) properties, relative humidity, cooling rates and ice crystal sedimentation. For that reason, a Lagrangian approach using meteorological wind fields is the most realistic way to simulate cirrus clouds. In addition, to represent complete cirrus systems as e.g. frontal cirrus, three dimensional cloud modeling on a large scale is desirable. To this end, we coupled the two momentum microphysical ice model of Spichtinger and Gierens (2009) with the 3D Lagrangian model CLaMS (McKenna et al., 2002). The new CLaMS-Ice module simulates cirrus formation by including heterogeneous and homogeneous freezing as well as ice crystal sedimentation. The boxmodel is operated along CLaMS trajectories and individually initialized with the ECMWF meteorological fields. In addition, temperature fluctuations are superimposed directly to the trajectory temperature and pressure by the parametrization of Gary et al. (2006). For a typical cirrus scenario with latitude/longitude coverage of 49° x 42° on three pressure levels, 6100 trajectories are simulated over 24 hours in time. To achieve the model results in an acceptable time, the box model is accelerated by about a factor of 10 before coupling to CLaMS. Now, CLaMS-Ice needs only about 30-40 minutes for such a simulation. During the first HALO cloud field campaign (ML-Cirrus), CLaMS-Ice has been successfully deployed as a forecast tool. Here, we give an overview about the capabilities of CLaMS-Ice for forecasting, modeling and understanding of cirrus clouds in general. In addition, examples from the recent ML

  13. ISDAC Microphysics

    SciTech Connect

    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.

  14. 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.

  15. Sensitivity of a Cloud-Resolving Model to the Bulk and Explicit Bin Microphysical Schemes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Li, X.; Khain, A. P.; Simpson, J.

    2004-01-01

    A cloud-resolving model is used to study sensitivities of two different microphysical schemes, one is the bulk type, and the other is an explicit bin scheme, in simulating a mid-latitude squall line case. Simulations using different microphysical schemes are compared with each other and also with the observations. Both the bulk and bin models reproduce the general features during the developing and mature stage of the system. The leading convective zone, the trailing stratiform region, the horizontal wind flow patterns, pressure perturbation associated with the storm dynamics, and the cool pool in front of the system all agree well with the observations. Both the observations and the bulk scheme simulation serve as validations for the newly incorporated bin scheme. However, it is also shown that the bulk and bin simulations have distinct differences, most notably in the stratiform region. Weak convective cells exist in the stratiform region in the bulk simulation, but not in the bin simulation. These weak convective cells in the stratiform region are remnants of the previous stronger convections at the leading edge of the system. The bin simulation, on the other hand, has a horizontally homogeneous stratiform rain structure, which agrees better with the observations. Further analysis of the downdraft core strength, the potential temperature perturbation, and the evaporative cooling rate shows that the differences between the bulk and bin models are due mainly to the stronger low-level evaporative cooling simulated in the bulk model. Further quantitative analysis and sensitivity tests for this case using both the bulk and bin models will be presented in the talk.

  16. 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.

  17. Real-time Measurements of Biological Aerosol Particles in Clouds

    NASA Astrophysics Data System (ADS)

    Twohy, C. H.; McMeeking, G. R.; DeMott, P. J.; Toohey, D. W.; Kok, G.; McCluskey, C.; Hill, T. C.

    2013-12-01

    Some types of biological particles are known to efficiently nucleate ice at relatively warm temperatures in the atmosphere, with the potential to influence cloud microphysical properties and climate. However, the prevalence (or lack thereof) of these particle types in different parts of the atmosphere and in clouds is a matter of debate. Current techniques are mostly limited to near-ground sampling or to limited aircraft sampling with complex instrumentation. Many types of biological particles fluoresce when exposed to ultraviolet light, and the Wideband Integrated Bioaerosol Sensor (WIBS-4A) takes advantage of this characteristic to perform real-time measurements of biological particles. During the IDEAS-2013 test campaign based in Colorado (USA), the WIBS-4A was flown behind a counterflow virtual impactor (CVI) to measure concentrations of biological particles in clouds of different types, temperatures, and altitudes. Preliminary results from this first-ever combination of instruments on the high-performance Gulfstream-V research aircraft will be presented. Concentrations of fluorescent particles measured by the WIBS will also be related to ice nuclei concentrations and properties of particles collected simultaneously on filters.

  18. 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.

  19. Polar stratospheric clouds in the 1998-2003 Antarctic vortex: Microphysical modeling and Polar Ozone and Aerosol Measurement (POAM) III observations

    NASA Astrophysics Data System (ADS)

    Benson, C. M.; Drdla, K.; Nedoluha, G. E.; Shettle, E. P.; Alfred, J.; Hoppel, K. W.

    2006-09-01

    The Integrated Microphysics and Aerosol Chemistry on Trajectories (IMPACT) model is used to study polar stratospheric cloud (PSC) formation and evolution in the Antarctic vortex. The model is applied to individual air parcel trajectories driven by UK Met Office (UKMO) wind and temperature fields. The IMPACT model calculates the parcel microphysics, including the formation and sedimentation of ice, nitric acid trihydrate (NAT), sulfuric acid tetrahydrate (SAT), and supercooled ternary solution (STS) aerosols. Model results are validated by comparison with data obtained by the Polar Ozone and Aerosol Measurement (POAM) III solar occultation instrument and are examined for 6 years of POAM data (1998-2003). Comparisons of POAM water vapor and aerosol extinction measurements to the model results help to constrain three microphysical parameters influencing the formation and growth of both type I and type II PSCs. Principally, measurements of aerosol extinction prove to be valuable in differentiating model runs; the relationship of aerosol extinction to temperature is determined by the various particle types as they form and grow. Comparison of IMPACT calculations of this relationship to POAM measurements suggests that the initial fraction of nuclei available for heterogeneous NAT freezing is approximately 0.02% of all aerosols. Constraints are also placed on the accommodation coefficient of ice and the NAT-ice lattice compatibility. However, these two parameters have similar effects on the extinction-temperature relationship, and thus a range of values are permissible for each.

  20. Simulation of the aerosol effect on the microphysical properties of shallow stratocumulus clouds over East Asia using a bin-based meso-scale cloud model

    NASA Astrophysics Data System (ADS)

    Choi, I.-J.; Iguchi, T.; Kim, S.-W.; Yoon, S.-C.; Nakajima, T.

    2010-10-01

    A bin-based meso-scale cloud model has been employed to explore the aerosol influence on the cloud microphysical properties and precipitation efficiency of shallow stratocumulus in East Asia in March 2005. We newly constructed aerosol size distributions and hygroscopicity parameters for five aerosol species that reproduced observed aerosol and cloud condensation nuclei (CCN) number concentrations in the target period, and thereby used in model simulation of the cloud microphysical properties and precipitation efficiency. It is found that the simulated results were satisfactorily close to the satellite-based observation. Significant effects of aerosols as well as of the meteorological condition were found in the simulated cloud properties and precipitation as confirmed by comparing maritime and polluted aerosol cases and by a sensitivity test with interchanging the aerosol conditions for two cases. Cloud droplets in the polluted condition tended to exhibit relatively narrower cloud drop spectral widths with a bias toward smaller droplet sizes than those in maritime condition, supporting the dispersion effect. The polluted aerosol condition also had a tendency of thinner and higher cloud layers than maritime aerosol condition under relatively humid meteorological condition, possibly due to enhanced updraft. In our cases, vertical structures of cloud droplet number and size were affected predominantly by the change in aerosol conditions, whereas in the structures of liquid water content and cloud fraction were influenced by both meteorological and aerosol conditions. Aerosol change made little differences in cloud liquid water, vertical cloud structure, and updraft/downdraft velocities between the maritime and polluted conditions under dry atmospheric condition. Quantitative evaluations of the sensitivity factor between aerosol and cloud parameters revealed a large sensitivity values in the target area compared to the previously reported values, indicating the strong

  1. 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.

    2015-02-01

    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 in February and 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. 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. 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. Compared to the Indian Ocean Experiment (INDOEX) conducted in winter 1999, elevated aerosol layers with increased aerosol number concentration were observed more frequently in 2012. However, lower particle absorption at the surface (σabs(520 nm)=8.5±4.2 Wm-1) was found during CARDEX compared to INDOEX 1999. By combining vertical in-situ measured particle absorption with scattering calculated with Mie-theory, layers with single-scattering albedo (SSA) values of specific source regions were derived and utilized to calculate vertical particle absorption profiles from MiniMPL profiles. SSA surface values for dry conditions were found to be 0.94±0.02 and 0.91±0.02 for air masses from the Arabian Sea (and

  2. 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

  3. 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

  4. 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

  5. Microphysical and macrophysical responses of marine stratocumulus polluted by underlying ships: 2. Impacts of haze on precipitating clouds

    NASA Astrophysics Data System (ADS)

    Christensen, Matthew W.; Stephens, Graeme L.

    2012-06-01

    The 94-GHz cloud profiling radar on the CloudSat satellite was used to examine the precipitation response of marine stratocumulus clouds to the increased aerosol burden from oceangoing vessels. Aerosol plumes generated by ships sometimes influence cloud microphysics and, to a largely undetermined extent, precipitation. To assess this response, the locations of over one thousand ship tracks coinciding with the radar were meticulously logged by hand from the Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. Although precipitation detectable by the radar was infrequent, drizzle rates were often suppressed (72% of cases) and lighter in the ship tracks compared to the clouds adjacent to them. Ship plumes primarily decreased average rain rates through reducing the spatial coverage of precipitation. However, larger liquid water paths in ship tracks seldom coincided with the reduced cloud water sink from the suppression of precipitation (in less than 20% of cases). The sign and strength of the precipitation response was primarily tied to the mesoscale convective structure of the clouds. When closed cellular clouds were identified, significant decreases in the relative average liquid water path, rain rate (an average relative decrease of 68%), and rain cover fraction were observed in ship tracks compared to the surrounding clouds. The opposite occurred in the open cell regime where it was more common to find enhanced precipitation in the perturbed clouds. Ship plumes ingested into this regime resulted in significantly deeper and brighter clouds with higher liquid water amounts and rain rates (an average relative increase of 89%).

  6. 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.

  7. 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.

  8. Dynamical, convective, and microphysical control on wintertime distributions of water vapor and clouds in the tropical tropopause layer

    NASA Astrophysics Data System (ADS)

    Ueyama, Rei; Jensen, Eric J.; Pfister, Leonhard; Kim, Ji-Eun

    2015-10-01

    Processes that influence the humidity and cirrus cloud abundance in the Tropical Tropopause Layer (TTL) during boreal winter 2006-2007 are investigated in simulations of clouds along backward trajectories of parcels ending at the 372 K potential temperature (100 hPa) level in the tropics. Trajectories are calculated using offline calculations of seasonal mean tropical radiative heating rates along with reanalysis temperature and wind data with enhanced wave-driven variability in the TTL. The one-dimensional (vertical) time-dependent cloud microphysical model is initialized with water vapor measurements from the Microwave Limb Sounder and the evolution of clouds along each trajectory is simulated using temperature profiles extracted from reanalysis data and convective cloud top heights estimated from 3-hourly geostationary satellite imagery. Averaged over the tropics, waves dehydrate the 100 hPa level by 0.5 ppmv, while convection and cloud microphysical processes moisten by 0.3 and 0.7 ppmv, respectively. The tropical mean cloud occurrence frequencies in the middle to upper TTL agree well with those based on satellite observations (spatial correlation of 0.8). Waves and convection enhance cloud occurrence at the cold point tropopause by 4% and 2%, respectively. Temporal variability of the heating rates as indicated by the ERA-Interim 6-hourly heating rate fields dehydrates the TTL by 0.4 ppmv and decreases the cloud occurrence by 4% because parcels are more likely to encounter the coldest temperatures and dehydrate near the cold point, limiting cloud formation above. The final dehydration locations of parcels, concentrated near the dateline in the tropical Pacific, are insensitive to various model parameters.

  9. 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

  10. 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

  11. 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

  12. Particle nonuniformity effects on particle cloud flames in low gravity

    NASA Technical Reports Server (NTRS)

    Berlad, A. L.; Tangirala, V.; Seshadri, K.; Facca, L. T.; Ogrin, J.; Ross, H.

    1991-01-01

    Experimental and analytical studies of particle cloud combustion at reduced gravity reveal the substantial roles that particle cloud nonuniformities may play in particle cloud combustion. Macroscopically uniform, quiescent particle cloud systems (at very low gravitational levels and above) sustain processes which can render them nonuniform on both macroscopic and microscopic scales. It is found that a given macroscopically uniform, quiescent particle cloud flame system can display a range of microscopically nonuniform features which lead to a range of combustion features. Microscopically nonuniform particle cloud distributions are difficult experimentally to detect and characterize. A uniformly distributed lycopodium cloud of particle-enriched microscopic nonuniformities in reduced gravity displays a range of burning velocities for any given overall stoichiometry. The range of observed and calculated burning velocities corresponds to the range of particle enriched concentrations within a characteristic microscopic nonuniformity. Sedimentation effects (even in reduced gravity) are also examined.

  13. 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.

  14. 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

  15. Evaluation of a new mixed-phase cloud microphysics parameterization with CAM3 single-column model and M-PACE observations

    NASA Astrophysics Data System (ADS)

    Liu, Xiaohong; Xie, Shaocheng; Ghan, Steven J.

    2007-12-01

    Most global climate models generally prescribe the partitioning of condensed water into cloud droplets and cloud ice in mixed-phase clouds according to a temperature-dependent function, which affects modeled cloud phase, cloud lifetime and radiative properties. This study evaluates a new mixed-phase cloud microphysics parameterization (for ice nucleation and water vapor deposition) against the Atmospheric Radiation Measurement (ARM) Mixed-phase Arctic Cloud Experiment (M-PACE) observations using the NCAR Community Atmospheric Model Version 3 (CAM3) single column model (SCAM). It is shown that SCAM with the new scheme produces a more realistic simulation of the cloud phase structure and the partitioning of condensed water into liquid droplets against observations during the M-PACE than the standard SCAM. A sensitivity test indicates that ice number concentration could play an important role in the simulated mixed-phase cloud microphysics, and therefore needs to be realistically represented in global climate models.

  16. 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.

  17. Sulphuric acid clouds on Venus: an improved nucleation parameterization and a new microphysical model

    NASA Astrophysics Data System (ADS)

    Määttänen, A.; Bekki, S.; Vehkamäki, H.; Julin, J.; Montmessin, F.; Ortega, I. K.; Lebonnois, S.

    2013-09-01

    Both the clouds of Venus and aerosols found in the Earth's stratosphere are mainly composed of sulphuric acid droplets. On the Earth, the sulphur in the stratosphere originates from surface emissions of long-lived sulphur species, transported to the stratosphere by the general circulation, and from volcanic eruptions that can inject material above the tropopause. On Venus, the source of sulphur is most likely volcanism, but the question is still open. The clouds on Venus are organised in three quite distinct layers with differing properties in terms of particle size distributions and possibly composition. Some early observations hint to species other than sulphuric acid present in the clouds, but recent missions have not been able to verify their existence. The clouds are optically very thick in the visible, inhibiting visual observation of the surface. The lowest cloud layers are very dynamic and the reason for the observed multimodal size distributions could be partly explained by mixing and distinct altitudes of nucleation. However, the possibility of mixed phase clouds and different chemical compositions of the droplets have not yet been excluded.

  18. Characterization of cloud microphysical parameters using airborne measurements by the research scanning polarimeter

    NASA Astrophysics Data System (ADS)

    Alexandrov, Mikhail D.; Cairns, Brian; Mishchenko, Michael I.; Ackerman, Andrew S.; Emde, Claudia

    2013-05-01

    We present the retrievals of cloud droplet size distribution parameters (effective radius and variance) from the Research Scanning Polarimeter (RSP) measurements made during the recent field campaign Development and Evaluation of satellite Validation Tools by Experimenters (DEVOTE, 2011). The RSP is an airborne prototype for the Aerosol Polarimetery Sensor (APS), which was built for the NASA Glory Mission project. This instrument measures both polarized and total reflectances in 9 spectral channels with wavelengths ranging from 410 to 2250 nm. For cloud droplet size retrievals we utilize the polarized reflectances in the scattering range between 135° and 165° where they exhibit the rainbow, the shape of which is determined mainly by single-scattering properties of the cloud particles. Two different retrieval methods were used: standard fitting of the observations with a model based on pre-assumed gamma distribution shape, and a novel non-parametric technique Rainbow Fourier Transform (RFT), which does not require any a priori assumptions about the droplet size distribution. The RSP measurements over cumulus clouds also allow for estimation of their geometry (cloud length, top and base heights), which, combined with the droplet size, can provide further insight into cloud processes.

  19. 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.

  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. 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.

    2014-05-01

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

  2. LIMA (v1.0): a 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.

    2015-09-01

    The paper describes the 2-moment microphysical scheme LIMA (Liquid Ice Multiple Aerosols), which relies on the prognostic evolution of a three-dimensional (3-D) aerosol population, and the careful description of the nucleating properties that enable cloud droplets and pristine ice crystals to form. LIMA uses the aerosol nucleating properties to form cloud droplets and pristine ice crystals. 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 temperature. 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 formation of hydrometeors is standard. 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

  3. 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.

  4. Laboratory and Cloud Chamber Studies of Formation Processes and Properties of Atmospheric Ice Particles

    NASA Astrophysics Data System (ADS)

    Leisner, T.; Abdelmonem, A.; Benz, S.; Brinkmann, M.; Möhler, O.; Rzesanke, D.; Saathoff, H.; Schnaiter, M.; Wagner, R.

    2009-04-01

    The formation of ice in tropospheric clouds controls the evolution of precipitation and thereby influences climate and weather via a complex network of dynamical and microphysical processes. At higher altitudes, ice particles in cirrus clouds or contrails modify the radiative energy budget by direct interaction with the shortwave and longwave radiation. In order to improve the parameterisation of the complex microphysical and dynamical processes leading to and controlling the evolution of tropospheric ice, laboratory experiments are performed at the IMK Karlsruhe both on a single particle level and in the aerosol and cloud chamber AIDA. Single particle experiments in electrodynamic levitation lend themselves to the study of the interaction between cloud droplets and aerosol particles under extremely well characterized and static conditions in order to obtain microphysical parameters as freezing nucleation rates for homogeneous and heterogeneous ice formation. They also allow the observation of the freezing dynamics and of secondary ice formation and multiplication processes under controlled conditions and with very high spatial and temporal resolution. The inherent droplet charge in these experiments can be varied over a wide range in order to assess the influence of the electrical state of the cloud on its microphysics. In the AIDA chamber on the other hand, these processes are observable under the realistic dynamic conditions of an expanding and cooling cloud- parcel with interacting particles and are probed simultaneously by a comprehensive set of analytical instruments. By this means, microphysical processes can be studied in their complex interplay with dynamical processes as for example coagulation or particle evaporation and growth via the Bergeron - Findeisen process. Shortwave scattering and longwave absorption properties of the nucleating and growing ice crystals are probed by in situ polarised laser light scattering measurements and infrared extinction

  5. 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.

  6. 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.

  7. Mesoscale Modeling of Springtime Arctic Mixed-Phase Stratiform Clouds Using a New Two-Moment Bulk Microphysics Scheme.

    NASA Astrophysics Data System (ADS)

    Morrison, H.; Pinto, J. O.

    2005-10-01

    A new two-moment bulk microphysics scheme is implemented into the polar version of the fifth-generation Pennsylvania State University NCAR Mesoscale Model (MM5) to simulate arctic mixed-phase boundary layer stratiform clouds observed during Surface Heat Budget of the Arctic (SHEBA) First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) Arctic Cloud Experiment (ACE). The microphysics scheme predicts the number concentrations and mixing ratios of four hydrometeor species (cloud droplets, small ice, rain, snow) and includes detailed treatments of droplet activation and ice nucleation from a prescribed distribution of aerosol obtained from observations. The model is able to reproduce many features of the observed mixed-phase cloud, including a near-adiabatic liquid water content profile located near the top of a well-mixed boundary layer, droplet number concentrations of about 200 250 cm-3 that were distributed fairly uniformly through the depth of the cloud, and continuous light snow falling from the cloud base to the surface. The impacts of droplet and ice nucleation, radiative transfer, turbulence, large-scale dynamics, and vertical resolution on the simulated mixed-phase stratiform cloud are examined. The cloud layer is largely self-maintained through strong cloud-top radiative cooling that exceeds 40 K day-1. It persists through extended periods of downward large-scale motion that tend to thin the layer and reduce water contents. Droplet activation rates are highest near cloud base, associated with subgrid vertical motion that is diagnosed from the predicted turbulence kinetic energy. A sensitivity test neglecting subgrid vertical velocity produces only weak activation and small droplet number concentrations (<90 cm-3). These results highlight the importance of parameterizing the impact of subgrid vertical velocity to generate local supersaturation for aerosol-droplet closure. The primary ice nucleation mode in the simulated

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. A numerical model of aerosol scavenging: Part 1, Microphysics parameterization

    SciTech Connect

    Molenkamp, C.R.; Bradley, M.M.

    1991-09-01

    We have developed a three-dimensional numerical model (OCTET) to simulate the dynamics and microphysics of clouds and the transport, diffusion and precipitation scavenging of aerosol particles. In this paper we describe the cloud microphysics and scavenging parameterizations. The representation of cloud microphysics is a bulk- water parameterization which includes water vapor and five types of hydrometeors (cloud droplets, rain drops, ice crystals, snow, and graupel). A parallel parameterization represents the scavenging interactions between pollutant particles and hydrometeors including collection of particles because of condensation nucleation, Brownian and phoretic attachment, and inertial capture, resuspension because of evaporation and sublimation; and transfer interactions where particles collected by one type of hydrometeor are transferred to another type of freezing, melting, accretion, riming and autoconversion.

  13. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    DOE PAGESBeta

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

    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

  14. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    DOE PAGESBeta

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

    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. Furthermore, 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

  15. 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.

  16. 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

  17. Impacts of the Manaus pollution plume on the microphysical properties of Amazonian warm-phase clouds in the wet season

    DOE PAGESBeta

    Cecchini, Micael A.; Machado, Luiz A. T.; Comstock, Jennifer M.; Mei, Fan; Wang, Jian; Fan, Jiwen; Tomlinson, Jason M.; Schmid, Beat; Albrecht, Rachel; Martin, Scot T.; et al

    2016-06-09

    The remote atmosphere over the Amazon can be similar to oceanic regions in terms of aerosol conditions and cloud type formations. This is especially true during the wet season. The main aerosol-related disturbances over the Amazon have both natural sources, such as dust transport from Africa, and anthropogenic sources, such as biomass burning or urban pollution. The present work considers the impacts of the latter on the microphysical properties of warm-phase clouds by analyzing observations of the interactions between the Manaus pollution plume and its surroundings, as part of the GoAmazon2014/5 Experiment. The analyzed period corresponds to the wet seasonmore » (specifically from February to March 2014 and corresponding to the first Intensive Operating Period (IOP1) of GoAmazon2014/5). The droplet size distributions reported are in the range 1 µm ≤ D ≤ 50 µm in order to capture the processes leading up to the precipitation formation. The wet season largely presents a clean background atmosphere characterized by frequent rain showers. As such, the contrast between background clouds and those affected by the Manaus pollution can be observed and detailed. The focus is on the characteristics of the initial microphysical properties in cumulus clouds predominantly at their early stages. The pollution-affected clouds are found to have smaller effective diameters and higher droplet number concentrations. The differences range from 10 to 40 % for the effective diameter and are as high as 1000% for droplet concentration for the same vertical levels. The growth rates of droplets with altitude are slower for pollution-affected clouds (2.90 compared to 5.59 µm km–1), as explained by the absence of bigger droplets at the onset of cloud development. Clouds under background conditions have higher concentrations of larger droplets (> 20 µm) near the cloud base, which would contribute significantly to the growth rates through the collision–coalescence process. The

  18. Impacts of the Manaus pollution plume on the microphysical properties of Amazonian warm-phase clouds in the wet season

    NASA Astrophysics Data System (ADS)

    Cecchini, Micael A.; Machado, Luiz A. T.; Comstock, Jennifer M.; Mei, Fan; Wang, Jian; Fan, Jiwen; Tomlinson, Jason M.; Schmid, Beat; Albrecht, Rachel; Martin, Scot T.; Artaxo, Paulo

    2016-06-01

    The remote atmosphere over the Amazon can be similar to oceanic regions in terms of aerosol conditions and cloud type formations. This is especially true during the wet season. The main aerosol-related disturbances over the Amazon have both natural sources, such as dust transport from Africa, and anthropogenic sources, such as biomass burning or urban pollution. The present work considers the impacts of the latter on the microphysical properties of warm-phase clouds by analysing observations of the interactions between the Manaus pollution plume and its surroundings, as part of the GoAmazon2014/5 Experiment. The analysed period corresponds to the wet season (specifically from February to March 2014 and corresponding to the first Intensive Operating Period (IOP1) of GoAmazon2014/5). The droplet size distributions reported are in the range 1 µm ≤ D ≤ 50 µm in order to capture the processes leading up to the precipitation formation. The wet season largely presents a clean background atmosphere characterized by frequent rain showers. As such, the contrast between background clouds and those affected by the Manaus pollution can be observed and detailed. The focus is on the characteristics of the initial microphysical properties in cumulus clouds predominantly at their early stages. The pollution-affected clouds are found to have smaller effective diameters and higher droplet number concentrations. The differences range from 10 to 40 % for the effective diameter and are as high as 1000 % for droplet concentration for the same vertical levels. The growth rates of droplets with altitude are slower for pollution-affected clouds (2.90 compared to 5.59 µm km-1), as explained by the absence of bigger droplets at the onset of cloud development. Clouds under background conditions have higher concentrations of larger droplets (> 20 µm) near the cloud base, which would contribute significantly to the growth rates through the collision-coalescence process. The overall shape

  19. Sensitivity of summer ensembles of super-parameterized US mesoscale convective systems to cloud resolving model microphysics and resolution

    NASA Astrophysics Data System (ADS)

    Elliott, E.; Yu, S.; Kooperman, G. J.; Morrison, H.; Wang, M.; Pritchard, M. S.

    2014-12-01

    Microphysical and resolution sensitivities of explicitly resolved convection within mesoscale convective systems (MCSs) in the central United States are well documented in the context of single case studies simulated by cloud resolving models (CRMs) under tight boundary and initial condition constraints. While such an experimental design allows researchers to causatively isolate the effects of CRM microphysical and resolution parameterizations on modeled MCSs, it is still challenging to produce conclusions generalizable to multiple storms. The uncertainty associated with the results of such experiments comes both from the necessary physical constraints imposed by the limited CRM domain as well as the inability to evaluate or control model internal variability. A computationally practical method to minimize these uncertainties is the use of super-parameterized (SP) global climate models (GCMs), in which CRMs are embedded within GCMs to allow their free interaction with one another as orchestrated by large-scale global dynamics. This study uses NCAR's SP Community Atmosphere Model 5 (SP-CAM5) to evaluate microphysical and horizontal resolution sensitivities in summer ensembles of nocturnal MCSs in the central United States. Storm events within each run were identified using an objective empirical orthogonal function (EOF) algorithm, then further calibrated to harmonize individual storm signals and account for the temporal and spatial heterogeneity between them. Three summers of control data from a baseline simulation are used to assess model internal interannual variability to measure its magnitude relative to sensitivities in a number of distinct experimental runs with varying CRM parameters. Results comparing sensitivities of convective intensity to changes in fall speed assumptions about dense rimed species, one- vs. two-moment microphysics, and CRM horizontal resolution will be discussed.

  20. Tropical Anvil Cirrus Microphysics

    NASA Astrophysics Data System (ADS)

    Heymsfield, A.; Bansemer, A.; Schmitt, C.; Baumgardner, D.; Poellot, M.; Twohy, C.; Weinstock, E. M.; Smith, J. T.; Sayres, D.; Avallone, L.; Hallar, G.

    2003-12-01

    This study synthesizes data collected during a number of field campaigns by in-situ aircraft to characterize the microphysical properties of tropical, convectively-generated cirrus. The field campaigns include the Tropical Rain Measuring Mission KWAJEX campaign near Kwajalein, M. I., KAMP (the Keys Area Microphysics Project) and the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE), both over southern Florida, and CAMEX-4 (the fourth convection and moisture experiment), studying hurricanes off the east coast of Florida. The measurements include particle size distribution and particle shape information, direct measurements of the condensed water content (CRYSTAL-FACE), and radar imagery. We examine the temperature dependence and vertical variability of the ice water content (IWC), extinction, and effective radii, and deduce the ensemble-mean ice particle densities. Data obtained in quiescent regions outside of convection are compared to observations within convective cells. The relationship between the properties of the particle size distributions and proximity to convection are examined. The IWCs show a strong temperature dependence and dependence on distance below cloud top. The IWCs are larger in the convective regions than in the quiescent regions, and the particle size distributions are markedly broader. Ensemble-mean ice particle densities are a strong function of the breadth of the particle size distributions.

  1. A Climatology of Midlatitude Continental Clouds from the ARM SGP Site. Part I; Low-Level Cloud Macrophysical, Microphysical, and Radiative Properties

    NASA Technical Reports Server (NTRS)

    Dong, Xiquan; Minnis, Patrick; Xi, Baike

    2005-01-01

    A record of single-layer and overcast low cloud (stratus) properties has been generated using approximately 4000 hours of data collected from January 1997 to December 2002 at the Atmospheric Radiation Measurement (ARM) Southern Great Plains Central Facility (SCF). The cloud properties include liquid-phase and liquid-dominant, mixed-phase, low cloud macrophysical, microphysical, and radiative properties including cloud-base and -top heights and temperatures, and cloud physical thickness derived from a ground-based radar and lidar pair, and rawinsonde sounding; cloud liquid water path (LWP) and content (LWC), and cloud-droplet effective radius (r(sub e)) and number concentration (N) derived from the macrophysical properties and radiometer data; and cloud optical depth (tau), effective solar transmission (gamma), and cloud/top-of-atmosphere albedos (R(sub cldy)/R(sub TOA)) derived from Eppley precision spectral pyranometer measurements. The cloud properties were analyzed in terms of their seasonal, monthly, and hourly variations. In general, more stratus clouds occur during winter and spring than in summer. Cloud-layer altitudes and physical thicknesses were higher and greater in summer than in winter with averaged physical thicknesses of 0.85 km and 0.73 km for day and night, respectively. The seasonal variations of LWP, LWC, N. tau, R(sub cldy), and R(sub TOA) basically follow the same pattern with maxima and minima during winter and summer, respectively. There is no significant variation in mean r(sub e), however, despite a summertime peak in aerosol loading, Although a considerable degree of variability exists, the 6-yr average values of LWP, LWC, r(sub e), N, tau, gamma, R(sub cldy) and R(sub TOA) are 150 gm(exp -2) (138), 0.245 gm(exp -3) (0.268), 8.7 micrometers (8.5), 213 cm(exp -3) (238), 26.8 (24.8), 0.331, 0.672, 0.563 for daytime (nighttime). A new conceptual model of midlatitude continental low clouds at the ARM SGP site has been developed from this study

  2. The microphysical and radiative properties of tropical cirrus from the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE)

    NASA Astrophysics Data System (ADS)

    Um, Jun Shik

    During the 2006 Tropical Warm Pool International Cloud Experiment conducted in the region near Darwin, Australia, the Scaled Composites Proteus aircraft executed spiral profiles and flew horizontal legs through aging cirrus, fresh anvils, and cirrus of unknown origin. Data from 27 Jan., 29 Jan., and 2 Feb., when all the microphysical probes a Cloud and Aerosol Spectrometer (CAS), a Cloud Droplet Probe (CDP), a Cloud Imaging Probe (CIP), and a Cloud Particle Imager (CPI) were working, are used to investigate whether a single parameterization can be used to characterize tropical cirrus in terms of prognostic variables used in large-scale models, to calculate the single-scattering properties (scattering phase function P11 and asymmetry parameter g) of aggregates and small ice crystals that more closely match observed ice crystals, and to quantify the influences of small ice crystals on the bulk scattering properties of tropical cirrus. A combination of CDP (D < 50 mum), fits (50 < D < 125 microm), and CIP (D > 125 mum) distributions is used to represent ice crystal size distributions. The CDP measurements are used for small ice crystals because comparison between the CAS and CDP suggested the CAS was artificially amplifying small ice crystal concentrations by detecting remnants of shattered large ice crystals. Artifacts in CIP images are removed or corrected and then CIP measurements are used to represent large ice crystals. Because of the uncertainties in both the CPI and CIP for 50 < D < 125 mum, the incomplete gamma fitting method with the CDP (D < 50 mum) and CIP (D > 125 mum) measurements as input is used to characterize these distributions. A new quasi-automatic habit classification scheme is developed. For all days, small quasi-spheres dominated the contributions from all ice crystal sizes (D > 0 mum, by number) for all 3 days. The areal fraction (D > 200 mum) from bullet rosettes and their aggregates was 48% and 60% for 27 and 29 Jan., respectively, but only 7

  3. 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 0.5 micrometer and 2.6 millimeter diameter. Ice crystal replicas were used to validate signals from the electrooptical instruments. Both optical and scanning electron microscopy were utilized to analyze aerosol and ice particle replicas between 0.1 micrometer and several 100 micrometer diameter. In first approximation, the combined aerosol-cloud particle spectrum in several clouds followed a power law N alpha D(sup -2.5). Thus, large cloud particles carried most of the condensate mass, while small cloud and aerosol particles determined the surface area. The mechanism of formation of small particles is growth of (hygroscopic, possibly ocean-derived) aerosol particles along the Kohler curves. The concentration of small particles is higher and less variable in space and time, and their tropospheric residence time is longer, than those of large cloud particles because of lower sedimentation velocities. Small particles shift effective cloud particle radii to sizes much smaller than the mean diameter of the cloud particles. This causes an increase in shortwave reflectivity and IR emissivity, and a decrease in transmissivity. Occasionally, the cloud reflectivity increased with altitude (decreasing temperature) stronger than did cloud emissivity, yielding enhanced radiative cooling at higher altitudes. Thus, cirrus produced by deep convection in the tropics may be critical in controlling processes whereby energy from warm

  4. Investigating the Microphysics of Arctic Mixed-Phase Clouds using Large Eddy Simulations: The Importance of Liquid-Dependent Ice Nucleation

    NASA Astrophysics Data System (ADS)

    Young, Gillian; Connolly, Paul J.; Jones, Hazel M.; Choularton, Thomas W.; Gallagher, Martin W.; Crosier, Jonathan; Lloyd, Gary; Bower, Keith N.

    2015-04-01

    Our ability to comprehend and accurately model the Arctic climate is currently hindered by a lack of observations of the atmospheric processes unique to this region. A significant source of uncertainty in such models may be found in our representation of aerosol-cloud interactions [1]: for example, there are unanswered questions concerning the relationship between the ice-nucleating Arctic aerosol and the unique cloud microphysics observed in this region [2]. In an effort to address this issue, the Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign of 2013 was conducted in the vicinity of the Svalbard archipelago, carrying out in-situ airborne observations of the mixed-phase clouds in this region. This campaign was split into two segments - one in spring, the other in summer - with airborne- and surface-based measurement platforms utilised in each. During the spring campaign, a range of microphysics and remote-sensing instruments were active on board the Facility for Airborne Atmospheric Measurements' (FAAM) BAe146 aircraft to produce a detailed record of the observed Arctic atmosphere. These data were used to conduct a modelling investigation with a focus on ice nucleation: the Large Eddy Model (LEM) - a cloud-resolving model developed by the UK Met Office - was initialised from these observations and simulations were performed to allow the resultant cloud evolution, structure and microphysics to be examined. Models on various scales notoriously have issues with reproducing persistent, mixed-phase Arctic clouds [2,3] and, upon first inspection, the LEM was no different: the modelled cloud dissipated quickly, thus inaccurately replicating the long-lived, mixed-phase clouds observed. However, by considering the discrepancies between the model output and aircraft observations, the treatment of cloud microphysics within the LEM has been developed to improve the simulation of the observed clouds. A long-lived, mixed-phase cloud of similar

  5. A New Approach to Modeling Aerosol Effects on East Asian Climate: Parametric Uncertainties Associated with Emissions, Cloud Microphysics and their Interactions

    SciTech Connect

    Yan, Huiping; Qian, Yun; Zhao, Chun; Wang, Hailong; Wang, Minghuai; Yang, Ben; Liu, Xiaohong; Fu, Qiang

    2015-09-16

    In this study, we adopt a parametric sensitivity analysis framework that integrates the quasi-Monte Carlo parameter sampling approach and a surrogate model to examine aerosol effects on the East Asian Monsoon climate simulated in the Community Atmosphere Model (CAM5). A total number of 256 CAM5 simulations are conducted to quantify the model responses to the uncertain parameters associated with cloud microphysics parameterizations and aerosol (e.g., sulfate, black carbon (BC), and dust) emission factors and their interactions. Results show that the interaction terms among parameters are important for quantifying the sensitivity of fields of interest, especially precipitation, to the parameters. The relative importance of cloud-microphysics parameters and emission factors (strength) depends on evaluation metrics or the model fields we focused on, and the presence of uncertainty in cloud microphysics imposes an additional challenge in quantifying the impact of aerosols on cloud and climate. Due to their different optical and microphysical properties and spatial distributions, sulfate, BC, and dust aerosols have very different impacts on East Asian Monsoon through aerosol-cloud-radiation interactions. The climatic effects of aerosol do not always have a monotonic response to the change of emission factors. The spatial patterns of both sign and magnitude of aerosol-induced changes in radiative fluxes, cloud, and precipitation could be different, depending on the aerosol types, when parameters are sampled in different ranges of values. We also identify the different cloud microphysical parameters that show the most significant impact on climatic effect induced by sulfate, BC and dust, respectively, in East Asia.

  6. Determination of optical and microphysical properties of thin warm clouds using ground based hyper-spectral analysis

    NASA Astrophysics Data System (ADS)

    Hirsch, E.; Agassi, E.; Koren, I.

    2012-04-01

    proposed methodology can be used to study the spatial microphysical behaviour of these edges. (4) A spatial-temporal analysis can be used to study mixing processes in clouds' entrainment zone.

  7. Determination of optical and microphysical properties of thin warm clouds using ground based hyper-spectral analysis

    NASA Astrophysics Data System (ADS)

    Hirsch, E.; Agassi, E.; Koren, I.

    2011-12-01

    , the proposed methodology can be used to study the spatial microphysical behaviour of these edges. (4) A spatial-temporal analysis can be used to study mixing processes in clouds' entrainment zone.

  8. Microphysics of Clouds Initiated from a 1000 MW Dry Heat Source in Comparison with Environmental Clods--A Statistical Study.

    NASA Astrophysics Data System (ADS)

    van Dinh, Pham; Bénech, Bruno; Radke, Lawrence F.

    1986-08-01

    To evaluate potential atmospheric impacts of wate heat released by dry cooling towers, studies have been made of an oil burning system (the `Météotron'), which emits sensible heat at a rate of 1000 MW and large quantities of aerosol particles into the atmosphere. Out of the 15 `burns' made during 1979, 12 times the rising column of smoke was capped with a cloud formation. The structures of these clouds were investigated with an instrumented aircraft. The clouds capping the Météotron (A) and the natural clouds unaffected by it (N) were compared by means of the Student's t applied to the mean liquid water content (LWC), droplet mean diameter (Dm) and droplet concentration (conc.) The N-clouds consisted essentially of stratus, cumulus and stratocumulus, developing sometimes up to 2000 m (AGL). Compared to the N-clouds, the volume of the A-clouds were similar or smaller, despite the fact that their condensation levels were sometimes lower and their tops generally higher. Generally, for both A- and N-clouds, the conc decreased with height while Dm and LWC increased; the increase of LWC is associated with the increase of Dm and the decrease of conc. In most cases, the A-clouds contained more droplets but with smaller mean diameter than the N-clouds (statistically significant at the 95% confidence level). This led to generally lower LWC in the A-clouds than in the N-clouds. This result is particularly noticeable when comparing cloud properties at the same height. The higher droplet concentration apparently did not result from a higher concentration of cloud condensation nuclei. The A-cloud characteristics were similar to those of freshly formed clouds. Their differences from N-clouds seem largely due to the heart released; the effect of the aerosol from Météotron is comparatively small.

  9. Evaluation of A New Mixed-Phase Cloud Microphysics Parameterization with the NCAR Climate Atmospheric Model (CAM3) and ARM Observations Fourth Quarter 2007 ARM Metric Report

    SciTech Connect

    X Liu; SJ Ghan; S Xie; J Boyle; SA Klein

    2007-09-30

    Mixed-phase clouds are composed of a mixture of cloud droplets and ice crystals. The cloud microphysics in mixed-phase clouds can significantly impact cloud optical depth, cloud radiative forcing, and cloud coverage. However, the treatment of mixed-phase clouds in most current climate models is crude and the partitioning of condensed water into liquid droplets and ice crystals is prescribed as temperature dependent functions. In our previous 2007 ARM metric reports a new mixed-phase cloud microphysics parameterization (for ice nucleation and water vapor deposition) was documented and implemented in the NCAR Community Atmospheric Model Version 3 (CAM3). The new scheme was tested against the Atmospheric Radiation Measurement (ARM) Mixed-phase Arctic Cloud Experiment (M-PACE) observations using the single column modeling and short-range weather forecast approaches. In this report this new parameterization is further tested with CAM3 in its climate simulations. It is shown that the predicted ice water content from CAM3 with the new parameterization is in better agreement with the ARM measurements at the Southern Great Plain (SGP) site for the mixed-phase clouds.

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

    SciTech Connect

    Comstock, Jennifer M.; Lin, Ruei-Fong; Starr, David O.; Yang, P.

    2008-12-10

    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 cirrus clouds using a detailed microphysical model and remote sensing measurements obtained at the Department of Energy’s Atmospheric Radiation Measurement (ARM) Climate Research Facility located near Lamont, OK. To help understand dynamic scales important in cirrus formation, we force the model using both large-scale forcing derived using ARM variational analysis, and mean mesoscale velocity derived from radar Doppler velocity measurements. Both heterogeneous and homogeneous nucleation processes are explored, where we have implemented a rigorous classical theory heterogeneous nucleation scheme to compare with empirical representations. We evaluate 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. This approach allows for independent verification of both the large and small particle modes of the particle size distribution. Our results suggest that mesoscale variability is the primary mechanism needed to reproduce observed quantities, while nucleation mechanism is secondary. Slow ice crystal growth tends to overestimate the number of small ice crystals, but does not seem to influence bulk properties such as ice water path and cloud thickness. 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. Ice crystal number concentrations on the order of 10-100 L-1 produce results consistent with both lidar and radar observations during a cirrus event observed on 7 December 1999, which has an optical depth range typical of

  11. Arctic Mixed-phase Clouds Simulated by a Cloud-Resolving Model: Comparison with ARM Observations and Sensitivity to Microphysics Parameterizations

    NASA Technical Reports Server (NTRS)

    Xu, Kuan-Man; Luo, Yali; Morrison, Hugh; Mcfarquhar, G.M.

    2008-01-01

    Single-layer mixed-phase stratiform (MPS) Arctic clouds, which formed under conditions of large surface heat flux combined with general subsidence during a subperiod of the Atmospheric Radiation Measurement (ARM) Program Mixed-Phase Arctic Cloud Experiment (M-PACE), are simulated with a cloud resolving model (CRM). The CRM is implemented with either an advanced two-moment (M05) or a commonly used one-moment (L83) bulk microphysics scheme and a state-of-the-art radiative transfer scheme. The CONTROL simulation, that uses the M05 scheme and observed aerosol size distribution and ice nulei (IN) number concentration, reproduces the magnitudes and vertical structures of cloud liquid water content (LWC), total ice water content (IWC), number concentration and effective radius of cloud droplets as suggested by the M-PACE observations. It underestimates ice crystal number concentrations by an order of magnitude and overestimates effective radius of ice crystals by a factor of 2-3. The OneM experiment, that uses the L83 scheme, produces values of liquid water path (LWP) and ice plus snow water path (ISWP) that were about 30% and 4 times, respectively, of those produced by the CONTROL. Its vertical profile of IWC exhibits a bimodal distribution in contrast to the constant distribution of IWC produced in the CONTROL and observations.

  12. Statistical study of global cloud microphysics using A-Train satellites

    NASA Astrophysics Data System (ADS)

    Zeng, S.; Trepte, C. R.; Winker, D. M.; Riedi, J.; Hu, Y.

    2012-12-01

    Observations from A-train provide valuable new information on the vertical structure of clouds and their properties over the globe. Advanced cloud retrievals have been developed using combined measurements using active remote sensing instruments from CALIPSO (lidar) and CloudSat (radar) and passive visible and infrared sensors from MODIS, PARASOL, and CALIPSO to provide improved estimates of cloud extinction coefficients, cloud liquid/ice water content, cloud droplet number concentrations and other water cloud physical properties. One of the surprise discoveries from these new and innovative A-Train cloud retrievals is that the droplet number concentrations for water clouds over the open ocean are very low (around 20 per cc) in contrast to values closer to 100 per cc used in many weather and climate models. These lower droplet concentrations can have profound implications on the ability to form clouds in the marine boundary layer and their precipitation rates. In this study, we will introduce the basic concept of cloud droplet number concentration retrievals using CALIPSO and A-train measurements, evaluate their uncertainties, and present new global statistics of on the their distribution and temporal variation. We will also explore examples of possible aerosol/cloud interactions using these observations together with back-trajectory analysis.

  13. The Impact of Microphysical Schemes and Parameter Choices on MM5 Simulations of Warm-Season High Latitude Cloud and Precipitation Systems

    NASA Astrophysics Data System (ADS)

    Tilley, J. S.; Kramm, G.

    2002-12-01

    Recently, an increasing variety of schemes to represent cloud microphysical processes have been incorporated into mesoscale models. These schemes, which are usually "bulk" approaches to the microphysics in order to reduce computational cost, range from the rather simple to relatively complex in terms of the processes represented and their formulation. The schemes are based upon various theoretical, laboratory, field measurement, and cloud modeling studies that have appeared in the literature over the past forty years, studies that have focused almost exclusively on mid-latitude and tropical areas. While significant effort has been exercised to validate such microphysical schemes in mid-latitude and tropical environments, relatively little systematic work has been done to consider how such schemes would behave in high latitudes. This is particularly the case for sophisticated regional models such as the Penn State/NCAR MM5, where the microphysical scheme used must interact with other physical schemes in complex and nonlinear ways. This issue is an important one to consider from the perspectives of aviation weather, quantitative precipitation forecasts and radiative transfer, the latter having importance to regional and global climate modeling applications. In this paper we examine the impacts of different cloud microphysical treatments on MM5 simulations of warm season high latitude cloud and precipitation systems. We examine the sensitivity of simulated mesoscale cloud, precipitation and dynamic fields to (1) the choice of the various microphysical schemes routinely available with the MM5 system, and (2) modifications to key parameters (baseline ice nuclei concentrations, temperature thresholds and supersaturation thresholds) within individual parameterization schemes. Our experiments focus on a period during mid-June 1998 during the Surface Heat Budget of the Arctic (SHEBA) Experiment. Through the period there is considerable cloud property data available over the

  14. 3D Cloud Tomography, Followed by Mean Optical and Microphysical Properties, with Multi-Angle/Multi-Pixel Data

    NASA Astrophysics Data System (ADS)

    Davis, A. B.; von Allmen, P. A.; Marshak, A.; Bal, G.

    2010-12-01

    The geometrical assumption in all operational cloud remote sensing algorithms is that clouds are plane-parallel slabs, which applies relatively well to the most uniform stratus layers. Its benefit is to justify using classic 1D radiative transfer (RT) theory, where angular details (solar, viewing, azimuthal) are fully accounted for and precise phase functions can be used, to generate the look-up tables used in the retrievals. Unsurprisingly, these algorithms catastrophically fail when applied to cumulus-type clouds, which are highly 3D. This is unfortunate for the cloud-process modeling community that may thrive on in situ airborne data, but would very much like to use satellite data for more than illustrations in their presentations and publications. So, how can we obtain quantitative information from space-based observations of finite aspect ratio clouds? Cloud base/top heights, vertically projected area, mean liquid water content (LWC), and volume-averaged droplet size would be a good start. Motivated by this science need, we present a new approach suitable for sparse cumulus fields where we turn the tables on the standard procedure in cloud remote sensing. We make no a priori assumption about cloud shape, save an approximately flat base, but use brutal approximations about the RT that is necessarily 3D. Indeed, the first order of business is to roughly determine the cloud's outer shape in one of two ways, which we will frame as competing initial guesses for the next phase of shape refinement and volume-averaged microphysical parameter estimation. Both steps use multi-pixel/multi-angle techniques amenable to MISR data, the latter adding a bi-spectral dimension using collocated MODIS data. One approach to rough cloud shape determination is to fit the multi-pixel/multi-angle data with a geometric primitive such as a scalene hemi-ellipsoid with 7 parameters (translation in 3D space, 3 semi-axes, 1 azimuthal orientation); for the radiometry, a simple radiosity

  15. Testing cloud microphysics parameterizations in NCAR CAM5 with ISDAC and M-PACE observations

    SciTech Connect

    Liu X.; Lin W.; Xie, S.; Boyle, J.; Klein, S. A.; Shi, X.; Wang, Z.; Ghan, S. J.; Earle, M.; Liu, P. S. K.; Zelenyuk, A.

    2011-12-24

    Arctic clouds simulated by the National Center for Atmospheric Research (NCAR) Community Atmospheric Model version 5 (CAM5) are evaluated with observations from the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Indirect and Semi-Direct Aerosol Campaign (ISDAC) and Mixed-Phase Arctic Cloud Experiment (M-PACE), which were conducted at its North Slope of Alaska site in April 2008 and October 2004, respectively. Model forecasts for the Arctic spring and fall seasons performed under the Cloud-Associated Parameterizations Testbed framework generally reproduce the spatial distributions of cloud fraction for single-layer boundary-layer mixed-phase stratocumulus and multilayer or deep frontal clouds. However, for low-level stratocumulus, the model significantly underestimates the observed cloud liquid water content in both seasons. As a result, CAM5 significantly underestimates the surface downward longwave radiative fluxes by 20-40 W m{sup -2}. Introducing a new ice nucleation parameterization slightly improves the model performance for low-level mixed-phase clouds by increasing cloud liquid water content through the reduction of the conversion rate from cloud liquid to ice by the Wegener-Bergeron-Findeisen process. The CAM5 single-column model testing shows that changing the instantaneous freezing temperature of rain to form snow from -5 C to -40 C causes a large increase in modeled cloud liquid water content through the slowing down of cloud liquid and rain-related processes (e.g., autoconversion of cloud liquid to rain). The underestimation of aerosol concentrations in CAM5 in the Arctic also plays an important role in the low bias of cloud liquid water in the single-layer mixed-phase clouds. In addition, numerical issues related to the coupling of model physics and time stepping in CAM5 are responsible for the model biases and will be explored in future studies.

  16. Testing Cloud Microphysics Parameterizations in NCAR CAM5 with ISDAC and M-PACE Observations

    SciTech Connect

    Liu, Xiaohong; Xie, Shaocheng; Boyle, James; Klein, Stephen A.; Shi, Xiangjun; Wang, Zhien; Lin, Wuyin; Ghan, Steven J.; Earle, Michael; Liu, Peter; Zelenyuk, Alla

    2011-12-24

    Arctic clouds simulated by the NCAR Community Atmospheric Model version 5 (CAM5) are evaluated with observations from the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Indirect and Semi-Direct Aerosol Campaign (ISDAC) and Mixed-Phase Arctic Cloud Experiment (M-PACE), which were conducted at its North Slope of Alaska site in April 2008 and October 2004, respectively. Model forecasts for the Arctic Spring and Fall seasons performed under the Cloud- Associated Parameterizations Testbed (CAPT) framework generally reproduce the spatial distributions of cloud fraction for single-layer boundary layer mixed-phase stratocumulus, and multilayer or deep frontal clouds. However, for low-level clouds, the model significantly underestimates the observed cloud liquid water content in both seasons and cloud fraction in the Spring season. As a result, CAM5 significantly underestimates the surface downward longwave (LW) radiative fluxes by 20-40 W m-2. The model with a new ice nucleation parameterization moderately improves the model simulations by increasing cloud liquid water content in mixed-phase clouds through the reduction of the conversion rate from cloud liquid to ice by the Wegener-Bergeron- Findeisen (WBF) process. The CAM5 single column model testing shows that change in the homogeneous freezing temperature of rain to form snow from -5 C to -40 C has a substantial impact on the modeled liquid water content through the slowing-down of liquid and rain-related processes. In contrast, collections of cloud ice by snow and cloud liquid by rain are of minor importance for single-layer boundary layer mixed-phase clouds in the Arctic.

  17. Statistical characteristics of cloud variability. Part 2: Implication for parameterizations of microphysical and radiative transfer processes in climate models

    SciTech Connect

    Huang, Dong; Liu, Yangang

    2014-09-17

    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, Southern Great Plains, and North Slope of Alaska sites of the Department of Energy's Atmospheric Radiation Measurement 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 probability density functions 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.

  18. Evaluation of cloud-resolving and limited area model intercomparison simulations using TWP-ICE observations: 2. Precipitation microphysics

    NASA Astrophysics Data System (ADS)

    Varble, Adam; Zipser, Edward J.; Fridlind, Ann M.; Zhu, Ping; Ackerman, Andrew S.; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; Shipway, Ben; Williams, Christopher

    2014-12-01

    Ten 3-D cloud-resolving model (CRM) simulations and four 3-D limited area model (LAM) simulations of an intense mesoscale convective system observed on 23-24 January 2006 during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) are compared with each other and with observations and retrievals from a scanning polarimetric radar, colocated UHF and VHF vertical profilers, and a Joss-Waldvogel disdrometer in an attempt to explain a low bias in simulated stratiform rainfall. Despite different forcing methodologies, similar precipitation microphysics errors appear in CRMs and LAMs with differences that depend on the details of the bulk microphysics scheme used. One-moment schemes produce too many small raindrops, which biases Doppler velocities low, but produces rainwater contents (RWCs) that are similar to observed. Two-moment rain schemes with a gamma shape parameter (μ) of 0 produce excessive size sorting, which leads to larger Doppler velocities than those produced in one-moment schemes but lower RWCs. Two-moment schemes also produce a convective median volume diameter distribution that is too broad relative to observations and, thus, may have issues balancing raindrop formation, collision-coalescence, and raindrop breakup. Assuming a μ of 2.5 rather than 0 for the raindrop size distribution improves one-moment scheme biases, and allowing μ to have values greater than 0 may improve excessive size sorting in two-moment schemes. Underpredicted stratiform rain rates are associated with underpredicted ice water contents at the melting level rather than excessive rain evaporation, in turn likely associated with convective detrainment that is too high in the troposphere and mesoscale circulations that are too weak. A limited domain size also prevents a large, well-developed stratiform region like the one observed from developing in CRMs, although LAMs also fail to produce such a region.

  19. Evaluation of Cloud-resolving and Limited Area Model Intercomparison Simulations using TWP-ICE Observations. Part 2: Rain Microphysics

    SciTech Connect

    Varble, Adam; Zipser, Edward J.; Fridlind, Ann; Zhu, Ping; Ackerman, Andrew; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; Shipway, Ben; Williams, Christopher R.

    2014-12-27

    Ten 3D cloud-resolving model (CRM) simulations and four 3D limited area model (LAM) simulations of an intense mesoscale convective system observed on January 23-24, 2006 during the Tropical Warm Pool – International Cloud Experiment (TWP-ICE) are compared with each other and with observations and retrievals from a scanning polarimetric radar, co-located UHF and VHF vertical profilers, and a Joss-Waldvogel disdrometer in an attempt to explain published results showing a low bias in simulated stratiform rainfall. Despite different forcing methodologies, similar precipitation microphysics errors appear in CRMs and LAMs with differences that depend on the details of the bulk microphysics scheme used. One-moment schemes produce too many small raindrops, which biases Doppler velocities low, but produces rain water contents (RWCs) that are similar to observed. Two-moment rain schemes with a gamma shape parameter (μ) of 0 produce excessive size sorting, which leads to larger Doppler velocities than those produced in one-moment schemes, but lower RWCs than observed. Two moment schemes also produce a convective median volume diameter distribution that is too broad relative to observations and thus, may have issues balancing raindrop formation, collision coalescence, and raindrop breakup. Assuming a μ of 2.5 rather than 0 for the raindrop size distribution improves one-moment scheme biases, and allowing μ to have values greater than 0 may improve two-moment schemes. Under-predicted stratiform rain rates are associated with under-predicted ice water contents at the melting level rather than excessive rain evaporation, in turn likely associated with convective detrainment that is too high in the troposphere and mesoscale circulations that are too weak. In addition to stronger convective updrafts than observed, limited domain size prevents a large, well-developed stratiform region from developing in CRMs, while a dry bias in ECMWF analyses does the same to the LAMs.

  20. Evaluation of Cloud-Resolving and Limited Area Model Intercomparison Simulations Using TWP-ICE Observations. Part 2 ; Precipitation Microphysics

    NASA Technical Reports Server (NTRS)

    Varble, Adam; Zipser, Edward J.; Fridland, Ann M.; Zhu, Ping; Ackerman, Andrew S.; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; Shipway, Ben; Williams, Christopher

    2014-01-01

    Ten 3-D cloud-resolving model (CRM) simulations and four 3-D limited area model (LAM) simulations of an intense mesoscale convective system observed on 23-24 January 2006 during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) are compared with each other and with observations and retrievals from a scanning polarimetric radar, colocated UHF and VHF vertical profilers, and a Joss-Waldvogel disdrometer in an attempt to explain a low bias in simulated stratiform rainfall. Despite different forcing methodologies, similar precipitation microphysics errors appear in CRMs and LAMs with differences that depend on the details of the bulk microphysics scheme used. One-moment schemes produce too many small raindrops, which biases Doppler velocities low, but produces rainwater contents (RWCs) that are similar to observed. Two-moment rain schemes with a gamma shape parameter (mu) of 0 produce excessive size sorting, which leads to larger Doppler velocities than those produced in one-moment schemes but lower RWCs. Two-moment schemes also produce a convective median volume diameter distribution that is too broad relative to observations and, thus, may have issues balancing raindrop formation, collision-coalescence, and raindrop breakup. Assuming a mu of 2.5 rather than 0 for the raindrop size distribution improves one-moment scheme biases, and allowing mu to have values greater than 0 may improve excessive size sorting in two-moment schemes. Underpredicted stratiform rain rates are associated with underpredicted ice water contents at the melting level rather than excessive rain evaporation, in turn likely associated with convective detrainment that is too high in the troposphere and mesoscale circulations that are too weak. A limited domain size also prevents a large, well-developed stratiform region like the one observed from developing in CRMs, although LAMs also fail to produce such a region.

  1. Investigation of ice cloud microphysical properties of DCSs using aircraft in situ measurements during MC3E over the ARM SGP site

    NASA Astrophysics Data System (ADS)

    Wang, Jingyu; Dong, Xiquan; Xi, Baike

    2015-04-01

    Six deep convective systems (DCSs) with a total of 5589 five-second samples and a range of temperatures from -41°C to 0°C during the Midlatitude Continental Convective Clouds Experiment (MC3E) were selected to investigate the ice cloud microphysical properties of DCSs over the Department of Energy Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site. The ice cloud measurements of the DCS cases were made by the University of North Dakota Citation II research aircraft, and the ice cloud properties were derived through the following processes. First, the instances of supercooled liquid water in the ice-dominated cloud layers of DCSs have been eliminated using multisensor detection, including the Rosemount Icing Detector, King and Cloud Droplet Probes, as well as 2DC and Cloud Imaging Probe images. Then the Nevzorov-measured ice water contents (IWCs) at maximum diameter Dmax < 4000 µm are used as the best estimation to determine a new mass-dimensional relationship. Finally, the newly derived mass-dimensional relationship (a = 0.00365, b = 2.1) has been applied to a full spectrum of particle size distributions (PSDs, 120-30,000 µm) constructed from both 2DC and High-Volume Precipitation Spectrometer measurements to calculate the best-estimated IWCs of DCSs during MC3E. The averages of the total number concentrations (Nt), median mass diameter (Dm), maximum diameter (Dmax), and IWC from six selected cases are 0.035 cm-3, 1666 µm, 8841 µm, and 0.45 g m-3, respectively. The gamma-type-size distributions are then generated matching the observed PSDs (120-30,000 µm), and the fitted gamma parameters are compared with the observed PSDs through multimoment assessments including first moment (Dm), third moment (IWC), and sixth moment (equivalent radar reflectivity, Ze). For application of observed PSDs to the remote sensing community, a series of empirical relationships between fitted parameters and Ze values has been derived, and the bullet rosette

  2. Haze Particles and Condensation in Pluto's Atmosphere Explored through Microphysical Modeling

    NASA Astrophysics Data System (ADS)

    Barth, E. L.

    2014-12-01

    To explore scenarios involving condensation in Pluto's atmosphere, a 1-D microphysics model based on the Community Aerosol and Radiation Model for Atmospheres (CARMA) has been developed. CARMA has been used successfully many times to explore the vertical distribution, size, shape, and composition of particles in Titan's atmosphere, and in particular, to predict the appearance of methane condensate layers which were observed at the Huygens' landing site. Physical processes in CARMA include nucleation, condensation, evaporation, sedimentation, and coagulation. In Pluto's atmosphere, most of the condensation would require the presence of a troposphere with at least a few kilometers vertical extent. However, if photochemical production proceeds similarly to the case of Titan's atmosphere, there are possibilities for condensation at higher altitudes as well. A number of sensitivity tests will be presented, including variations in the abundance, size, and shape of haze particles; evaluating the onset of homogeneous methane nucleation; exploring the size distribution of the resulting methane ice particles; and the effects of condensation of other photochemically produced trace species as well.

  3. Improving Representation of Convective Transport for Scale-Aware Parameterization – Part I: 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 M.; Dong, Xiquan; Zhang, Guang J.; Chen, Qian; Ghan, Steven J.

    2015-04-27

    The ultimate goal of this study is to improve representation of convective transport by cumulus parameterization for meso-scale and climate models. As Part I of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in mid-latitude continent and tropical regions using the Weather Research and Forecasting (WRF) 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, vertical velocity of convective cores, and the vertically decreasing trend of radar reflectivity than MOR and MY2, and therefore will be used for analysis of scale-dependence of eddy transport in Part II. 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 radar reflectivity in convective cores (SBM predicts smaller radar reflectivity but does not remove the large overestimation); and (3) the model performs better for mid-latitude convective systems than tropical system. The modeled mass fluxes of the mid latitude 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.

  4. Development and testing of parameterizations for continental and tropical ice cloud microphysical and radiative properties in GCM and mesoscale models. Final report

    SciTech Connect

    Heymsfield, A.

    1997-09-01

    The overall purpose of this research was to exploit measurements in clouds sampled during several field programs, especially from experiments in tropical regions, in a four-component study to develop and validate cloud parameterizations for general circulation models, emphasizing ice clouds. The components were: (1) parameterization of basic properties of mid- and upper-tropospheric clouds, such as condensed water content, primarily with respect to cirrus from tropical areas; (2) the second component was to develop parameterizations which express cloud radiative properties in terms of basic cloud microphysical properties, dealing primarily with tropical oceanic cirrus clouds and continental thunderstorm anvils, but also including altocumulus clouds; (3) the third component was to validate the parameterizations through use of ground-based measurements calibrated using existing and planned in-situ measurements of cloud microphysical properties and bulk radiative properties, as well as time-resolved data collected over extended periods of time; (4) the fourth component was to implement the parameterizations in the National Center for Atmospheric Research (NCAR) community climate model (CCM) II or in the NOAA-GFDL model (by L. Donner GFDL) and to perform sensitivity studies.

  5. Vertical microphysical profiles of convective clouds as a tool for obtaining aerosol cloud-mediated climate forcings

    SciTech Connect

    Rosenfeld, Daniel

    2015-12-23

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

  6. Microphysical particle properties derived from inversion algorithms developed in the framework of EARLINET

    NASA Astrophysics Data System (ADS)

    Müller, D.; Böckmann, C.; Kolgotin, A.; Schneidenbach, L.; Chemyakin, E.; Rosemann, J.; Znak, P.; Romanov, A.

    2015-12-01

    We present a summary on the current status of two inversion algorithms that are used in EARLINET for the inversion of data collected with EARLINET multiwavelength Raman lidars. These instruments measure backscatter coefficients at 355, 532, and 1064 nm, and extinction coefficients at 355 and 532 nm. Development of these two algorithms started in 2000 when EARLINET was founded. The algorithms are based on manually controlled inversion of optical data which allows for detailed sensitivity studies and thus provides us with comparably high quality of the derived data products. The algorithms allow us to derive particle effective radius, and volume and surface-area concentration with comparably high confidence. The retrieval of the real and imaginary parts of the complex refractive index still is a challenge in view of the accuracy required for these parameters in climate change studies in which light-absorption needs to be known with high accuracy. Single-scattering albedo can be computed from the retrieved microphysical parameters and allows us to categorize aerosols into high and low absorbing aerosols. We discuss the current status of these manually operated algorithms, the potentially achievable accuracy of data products, and the goals for future work on the basis of a few exemplary simulations with synthetic optical data. The optical data used in our study cover a range of Ångström exponents and extinction-to-backscatter (lidar) ratios that are found from lidar measurements of various aerosol types. We also tested aerosol scenarios that are considered highly unlikely, e.g., the lidar ratios fall outside the commonly accepted range of values measured with Raman lidar, even though the underlying microphysical particle properties are not uncommon. The goal of this part of the study is to test robustness of the algorithms toward their ability to identify aerosol types that have not been measured so far, but cannot be ruled out based on our current knowledge of

  7. Sensitivity and dependence of mesoscale downscaled prediction results on different parameterizations of convection and cloud microphysics

    NASA Astrophysics Data System (ADS)

    Remesan, R.; Bellerby, T.

    2012-04-01

    These days as operational real-time flood forecasting and warning systems rely more on high resolution mesoscale models employed with coupling system of hydrological models. So it is inevitable to assess prediction sensitivity or disparity in collection with selection of different cumulus and microphysical parameterization schemes, to assess the possible uncertainties associated with mesoscale downscaling. This study investigates the role of physical parameterization in mesoscale model simulations on simulation of unprecedented heavy rainfall over Yorkshire-Humberside in United Kingdom during 1-14th March, 1999. The study has used a popular mesoscale numerical weather prediction model named Advanced Research Weather Research Forecast model (version 3.3) which was developed at the National Center for Atmospheric Research (NCAR) in the USA. This study has performed a comprehensive evaluation of four cumulus parameterization schemes (CPSs) [Kian-Fritsch (KF), Betts-Miller-Janjic (BMJ) and Grell-Devenyi ensemble (GD)] and five microphysical schemes Lin et al scheme, older Thompson scheme, new Thompson scheme, WRF Single Moment - 6 class scheme, and WRF Single Moment - 5 class scheme] to identify how their inclusion influences the mesoscale model's meteorological parameter estimation capabilities and related uncertainties in prediction. The case study was carried out at the Upper River Derwent catchment in Northern Yorkshire, England using both the ERA-40 reanalysis data and the land based observation data.

  8. UV contrasts and microphysical properties of the upper clouds of Venus from the UV and NIR VMC/VEx images

    NASA Astrophysics Data System (ADS)

    Petrova, Elena V.; Shalygina, Oksana S.; Markiewicz, Wojciech J.

    2015-11-01

    The nature of UV contrasts observed on the upper cloud deck of Venus is still not known. To constrain better the properties of particles that may cause the UV contrasts, the phase dependences of brightness of the venusian clouds measured by the ultraviolet and near-infrared channels of the Venus Express Venus Monitoring Camera (VMC) in the UV dark and bright regions are jointly analyzed. The range of small phase angles, where the glory phenomenon is observed, is of key importance, since the properties of cloud particles can be reliably estimated from the shape and position of glory. However, from more than 2500 orbits of the mission, only in ten orbits the images were taken simultaneously in UV and near-IR channels at small phase angles. Their analysis have yielded the following results. In the UV dark and bright clouds of the equatorial region near the local noon, the derived radii of cloud particles turned out to be the same and rather large, 1.3-1.6 μm. No unambiguous connection between the UV contrasts and the brightness in the near-IR channel was found. In some cases, the regions that appear contrasting in UV show no difference in the near-IR brightness. This means that the properties of 1-μm mode particles are the same in these regions and only the contribution of small submicron particles differs, because the near-IR channel is weakly sensitive to the presence of particles smaller than ≈0.3 μm in radius. The difference in the composition of 10% of the number of submicron particles (if sulfur and sulfuric acid compositions are considered as probable for the submicron mode) is enough to produce the observed UV contrasts. In the other cases, the UV contrasts are accompanied by the differences in near-IR brightness. This suggests that the cloud particles of the 1-μm mode contribute to these contrasts as well. However, the modeling showed that exactly the variations in the composition of submicron particles in the clouds produce a key effect on the UV

  9. Modeling of microphysics and optics of aerosol particles in the marine environments

    NASA Astrophysics Data System (ADS)

    Kaloshin, Gennady

    2013-05-01

    We present a microphysical model for the surface layer marine and coastal atmospheric aerosols that is based on long-term observations of size distributions for 0.01-100 μm particles. The fundamental feature of the model is a parameterization of amplitudes and widths for aerosol modes of the aerosol size distribution function (ASDF) as functions of fetch and wind speed. The shape of ASDF and its dependence on meteorological parameters, height above sea level (H), fetch (X), wind speed (U) and relative humidity (RH), are investigated. At present, the model covers the ranges H = 0 - 25 m, U = 3 - 18 km s-1, X ≤ 120 km and RH = 40 - 98%. The latest version of the Marine Aerosol Extinction Profiles model (MaexPro) is described and applied for the computation and analysis of the spectral profiles of aerosol extinction coefficients α(λ) in the wavelength band λ = 0.2-12 μm. MaexPro is based on the aforementioned aerosol model assuming spherically shaped aerosol particles and the well-known Mie theory. The spectral profiles of α(λ) calculated by MaexPro are in good agreement with observational data and the numerical results. Moreover, MaexPro was found to be an accurate and reliable tool for investigating the optical properties of atmospheric aerosols.

  10. Final Report fir DE-SC0005507 (A1618): The Development of an Improved Cloud Microphysical Product for Model and Remote Sensing Evaluation using RACORO Observations

    SciTech Connect

    McFarquhar, Greg M.

    2012-09-21

    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, effective radius of water drops, 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. we investigated the differences in the size distributions measured by the Cloud and Aerosol Spectrometer (CAS) and the Forward Scattering Probe (FSSP), between the one dimensional cloud imaging probe (1DC) and the two-dimensional cloud imaging probe (2DC), and between the bulk LWCs measured by the Gerber probe against those derived from the size resolved probes.

  11. Hybrid fine scale climatology and microphysics of in-cloud icing: From 32 km reanalysis to 5 km mesoscale modeling

    NASA Astrophysics Data System (ADS)

    Lamraoui, Fayçal; Benoit, Robert; Perron, Jean; Fortin, Guy; Masson, Christian

    2015-03-01

    In-cloud icing can impose safety concerns and economic challenges for various industries. Icing climate representations proved beneficial for optimal designs and careful planning. The current study investigates in-cloud icing, its related cloud microphysics and introduces a 15-year time period climatology of icing events. The model was initially driven by reanalysis data from North American Regional Reanalysis and downscaled through a two-level nesting of 10 km and 5 km, using a limited-area version of the Global Environment Multiscale Model of the Canadian Meteorological Center. In addition, a hybrid approach is used to reduce time consuming calculations. The simulation realized exclusively on significant icing days, was combined with non-significant icing days as represented by data from NARR. A proof of concept is presented here for a 1000 km area around Gaspé during January for those 15 years. An increase in the number and intensity of icing events has been identified during the last 15 years. From GEM-LAM simulations and within the atmospheric layer between 10 m and 200 m AGL, supercooled liquid water contents indicated a maximum of 0.4 g m- 3, and 50% of the values are less than 0.05 g m- 3. All values of median volume diameters (MVD) are approximately capped by 70 μm and the typical values are around 15 μm. Supercooled Large Droplets represent approximately 5%. The vertical profile of icing climatology demonstrates a steady duration of icing events until the level of 60 m. The altitudes of 60 m and 100 m indicate substantial icing intensification toward higher elevations. GEM-LAM demonstrated a substantial improvement in the calculation of in-cloud icing, reducing significantly the challenge posed by complex terrains.

  12. Regional assessment of microphysical properties of marine boundary layer cloud using the PATMOS-x dataset

    NASA Astrophysics Data System (ADS)

    Rausch, John; Heidinger, Andrew; Bennartz, Ralf

    2010-12-01

    Cloud droplet number concentration and geometrical thickness of marine boundary layer clouds are inferred from 25 years of National Oceanic and Atmospheric Administration's AVHRR Pathfinder Atmospheres-Extended (PATMOS-x) Level 2b retrievals of optical thickness and cloud droplet effective radius over the period 1982 through 2009. A novel approach to addressing nonphysical values of cloud droplet number concentration N owing to satellite orbital drift is applied by normalizing estimated droplet number concentrations with respect to local observation time. Cloud geometrical thickness H is also normalized to a common reference time by scaling H against diurnal values from a passive microwave liquid water path climatology. The effectiveness of the methods applied to correct N and H are evaluated. Both quantities are spatially and temporally characterized in several subtropical subsidence regions for likely drizzle-free observations. Estimated liquid water path from PATMOS-x is further validated against 20 years of liquid water path values from the Special Sensor Microwave/Imager (SSM/I). Good agreement between SSM/I and PATMOS-x is found in coastal regions. Cloud droplet number concentrations in excess of 300 cm-3 are found along the western boundaries of the American and African continents, with greatly lower values found further out to sea with no observed long-term trends in cloud properties.

  13. Estimation of Microphysical and Radiative Parameters of Precipitating Cloud Systems Using mm-Wavelength Radars

    NASA Astrophysics Data System (ADS)

    Matrosov, Sergey Y.

    2009-03-01

    A remote sensing approach is described to retrieve cloud and rainfall parameters within the same precipitating system. This approach is based on mm-wavelength radar signal attenuation effects which are observed in a layer of liquid precipitation containing clouds and rainfall. The parameters of ice clouds in the upper part of startiform precipitating systems are then retrieved using the absolute measurements of radar reflectivity. In case of the ground-based radar location, these measurements are corrected for attenuation in the intervening layer of liquid hydrometers.

  14. Simulations of aerosol, microphysical and coastal influences on Arctic mixed-phase clouds

    NASA Astrophysics Data System (ADS)

    Avramov, Alexander Elkov

    Mixed-phase stratus clouds are the prevalent cloud type in the Arctic during the winter and transition seasons. Despite their important role in various climate feedback mechanisms they are still not well understood and are difficult to represent accurately in large-scale models. In this study the role of ice nucleation mechanisms, the influence of the coastally-generated circulations and parameterized ice crystal habit on the longevity and structure of Arctic mixed-phase clouds were examined using detailed mesoscale, cloud- and eddy-resolving model simulations. The structure and the lifetime of simulated Arctic mixed-phase clouds were found to be highly sensitive to the concentration of ice-nuclei (IN) acting in deposition/condensation-freezing nucleation mode. Contact nucleation could not produce significant ice amounts unless the contact IN concentrations were increased to unrealistically high values. Local, coastally induced circulations were found to be responsible for maintaining the continuous ice precipitation along the coastline through transport of deposition/condensation-freezing IN from above the cloud layer. It was demonstrated that incorrect partitioning of the liquid and ice phase can produce errors in the surface radiative budget of up to 90 Wm-2. Simulated IN sensitivity and liquid/ice phase partitioning were found to depend critically on the assumed ice crystal habit. It was demonstrated that a large range of liquid or ice water path can be produced by reasonable changes in ice crystal habit mass-dimensional and terminal fall-speed relations based on data reported in the literature. The changes in ice crystal habit were shown to be related to liquid layer formation, splitting of liquid layers, and cloud dissipation mechanisms in multi-layered Arctic mixed-phase clouds. These results suggest that predicting changes in crystal habit is of significant importance for correct model representation of mixed-phase clouds. Three additional ice nucleation

  15. Clouds and climate: Ability of atmospheric particles to uptake water

    NASA Astrophysics Data System (ADS)

    Farnham, Gabriella Joy Engelhart

    Atmospheric aerosols have significant impacts on human health, visibility and climate. Their interactions with water alter deposition within the human respiratory system, change particle optical properties, and change cloud microphysics by serving as cloud condensation nuclei (CCN). These clouds have a considerable influence on climate by reflecting incoming solar radiation, which provides a negative forcing, or cooling effect on earth's climate due to increased reflectivity. Our current understanding of the interactions of aerosols with clouds and climate is limited; the parameterizations needed for modeling predictions of climate can be aided by constraints from laboratory and in-situ experiments. Much of the uncertainty regarding the water uptake by atmospheric particles resides in organic aerosols. This thesis utilizes smog chamber techniques to study the CCN activity of biogenic secondary organic aerosol (SOA) including isoprene, monoterpene and sesquiterpene precursors. Particular emphasis is placed on comparison to Kohler theory, surface tension, solubility, droplet growth kinetics and volatility. The work also studies the CCN activity of a less controlled mixture of primary aerosol from biomass burning and the potential for transformation in the atmosphere via oxidation. Finally, this dissertation utilizes a dry-ambient aerosol size spectrometer (DAASS) to study the water content of aged atmospheric particles in a remote environment. We find monoterpene and isoprene SOA serve as good CCN. The water soluble component of sesquiterpene SOA has similar properties to those observed for monoterpene SOA meaning that a predictive understanding of SOA CCN may require knowledge of the water soluble fraction, but not its exact speciation. Sesquiterpene SOA CCN activity is particularly sensitive to temperature, suggesting that the CCN active fraction of the SOA is semi-volatile. Biomass burning experiments reveal that the CCN characteristics of primary aerosols

  16. Correlation Between Cirrus Particle Optical Properties: Microphysics and Implications for Spaceborne Remote Sensing

    NASA Technical Reports Server (NTRS)

    Reichardt, Jens; Hess, M.; Reichardt, S.; Behrendt, A.; McGee, T. J.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Cirrus measurements obtained with a ground-based polarization Raman lidar at 67.9 deg N in arctic winter reveal a strong correlation between the particle optical properties, specifically depolarization ratio and extinction-to-backscatter ratio, for ambient cloud temperatures above approximately -45 C, and an anti-correlation for colder temperatures. Similar correlations are evident in a 2-year midlatitude (53.4 deg N) cirrus data set. Scattering calculations show that the observed dependences can be interpreted in terms of the shapes and sizes of the cirrus ice particles. These findings suggest a retrieval method for determining cirrus extinction profiles from spaceborne lidar polarization data.

  17. 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; Einaudi, Franco (Technical Monitor)

    2001-01-01

    The conversion of cloud ice to snow by depositional growth, designated P(sub SFI), in the Goddard Cumulus Ensemble Model cloud physics parameterization is examined. The original formulation of P(sub SFI) 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 P(sub SFI), and the second involving a new formulation of P(sub SFI) based on the equation for depositional growth of cloud ice.

  18. Microphysical Properties of Clouds with Low Liquid Water Paths: An Update from Clouds with Low Optical (Water) Depth

    SciTech Connect

    Turner, D.D.; Flynn, C.; Long, C.; McFarlane, S.; Vogelmann, A.; Johnson, K.; Miller, M.; Chiu, C.; Marshak, A.; Wiscombe, W.; Clough, S.A.; Heck, P.; Minnis, P.; Liljegren, J.; Min, Q.; O'Hirok, W.; Wang, Z.

    2005-03-18

    Clouds play a critical role in the modulation of the radiative transfer in the atmosphere, and how clouds interact with radiation is one of the primary uncertainties in global climate models (GCMs). To reduce this uncertainty, the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program collects an immense amount of data from its Climate Research Facilities (CRFs); these data include observations of radiative fluxes, cloud properties from active and passive remote sensors, upper atmospheric soundings, and other observations. The program's goal is to use these coincident, longterm observations to improve the parameterization of radiative transfer in clear and cloudy atmospheres in GCMs.

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

    PubMed

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

    2013-12-17

    The cycling of atmospheric aerosols through clouds can change their chemical and physical properties and thus modify how aerosols affect cloud microphysics and, subsequently, precipitation and climate. Current knowledge about aerosol processing by clouds is rather limited to chemical reactions within water droplets in warm low-altitude clouds. However, in cold high-altitude cirrus clouds and anvils of high convective clouds in the tropics and midlatitudes, humidified aerosols freeze to form ice, which upon exposure to subsaturation conditions with respect to ice can sublimate, leaving behind residual modified aerosols. This freeze-drying process can occur in various types of clouds. Here we simulate an atmospheric freeze-drying cycle of aerosols in laboratory experiments using proxies for atmospheric aerosols. We find that aerosols that contain organic material that undergo such a process can form highly porous aerosol particles with a larger diameter and a lower density than the initial homogeneous aerosol. We attribute this morphology change to phase separation upon freezing followed by a glass transition of the organic material that can preserve a porous structure after ice sublimation. A porous structure may explain the previously observed enhancement in ice nucleation efficiency of glassy organic particles. We find that highly porous aerosol particles scatter solar light less efficiently than nonporous aerosol particles. Using a combination of satellite and radiosonde data, we show that highly porous aerosol formation can readily occur in highly convective clouds, which are widespread in the tropics and midlatitudes. These observations may have implications for subsequent cloud formation cycles and aerosol albedo near cloud edges. PMID:24297908

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

    PubMed Central

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

    2013-01-01

    The cycling of atmospheric aerosols through clouds can change their chemical and physical properties and thus modify how aerosols affect cloud microphysics and, subsequently, precipitation and climate. Current knowledge about aerosol processing by clouds is rather limited to chemical reactions within water droplets in warm low-altitude clouds. However, in cold high-altitude cirrus clouds and anvils of high convective clouds in the tropics and midlatitudes, humidified aerosols freeze to form ice, which upon exposure to subsaturation conditions with respect to ice can sublimate, leaving behind residual modified aerosols. This freeze-drying process can occur in various types of clouds. Here we simulate an atmospheric freeze-drying cycle of aerosols in laboratory experiments using proxies for atmospheric aerosols. We find that aerosols that contain organic material that undergo such a process can form highly porous aerosol particles with a larger diameter and a lower density than the initial homogeneous aerosol. We attribute this morphology change to phase separation upon freezing followed by a glass transition of the organic material that can preserve a porous structure after ice sublimation. A porous structure may explain the previously observed enhancement in ice nucleation efficiency of glassy organic particles. We find that highly porous aerosol particles scatter solar light less efficiently than nonporous aerosol particles. Using a combination of satellite and radiosonde data, we show that highly porous aerosol formation can readily occur in highly convective clouds, which are widespread in the tropics and midlatitudes. These observations may have implications for subsequent cloud formation cycles and aerosol albedo near cloud edges. PMID:24297908

  1. Cloud Properties Simulated by a Single-Column Model. Part II: Evaluation of Cumulus Detrainment and Ice-phase Microphysics Using a Cloud Resolving Model

    NASA Technical Reports Server (NTRS)

    Luo, Yali; Krueger, Steven K.; Xu, Kuan-Man

    2005-01-01

    This paper is the second in a series in which kilometer-scale-resolving observations from the Atmospheric Radiation Measurement program and a cloud-resolving model (CRM) are used to evaluate the single-column model (SCM) version of the National Centers for Environmental Prediction Global Forecast System model. Part I demonstrated that kilometer-scale cirrus properties simulated by the SCM significantly differ from the cloud radar observations while the CRM simulation reproduced most of the cirrus properties as revealed by the observations. The present study describes an evaluation, through a comparison with the CRM, of the SCM's representation of detrainment from deep cumulus and ice-phase microphysics in an effort to better understand the findings of Part I. It is found that detrainment occurs too infrequently at a single level at a time in the SCM, although the detrainment rate averaged over the entire simulation period is somewhat comparable to that of the CRM simulation. Relatively too much detrained ice is sublimated when first detrained. Snow falls over too deep of a layer due to the assumption that snow source and sink terms exactly balance within one time step in the SCM. These characteristics in the SCM parameterizations may explain many of the differences in the cirrus properties between the SCM and the observations (or between the SCM and the CRM). A possible improvement for the SCM consists of the inclusion of multiple cumulus cloud types as in the original Arakawa-Schubert scheme, prognostically determining the stratiform cloud fraction and snow mixing ratio. This would allow better representation of the detrainment from deep convection, better coupling of the volume of detrained air with cloud fraction, and better representation of snow field.

  2. Improvements in modeling the microphysical and radiative properties of cirrus clouds using the Regional Atmospheric Modeling System (RAMS). Final report

    SciTech Connect

    Mitchell, D.L.; Koracin, D.; Edwards, J.M.

    1998-08-01

    The main work activity during this period was the refinement and GCM parameterization of the treatment of ice cloud radiative properties, developed for this project. The treatment has now been rigorously tested and improved, and can now be used with confidence in radiation transfer schemes. The ice Cloud radiation scheme has also proven useful in satellite remote sensing. The radiation scheme differs from others in the thermal infrared, where it is assumed that photon tunneling does not occur for real ice particles (tunneling can be viewed as a process by which photons outside a particle`s area-cross section can still be absorbed). Single particle T-matrix and Mie calculations suggest that a particle`s ability to capture energy through tunneling depends on surface morphology, with more tunneling the more circular (or less angular) a surface is. This assumption leads to retrievals of mean particle size which are similar to those observed in tropical cirrus by optical imaging probes, whereas retrieved sizes using Mie theory are about 1/3 those predicted by this scheme. The retrieval method requires channels in the 8--9 {micro}m and 11--12 {micro}m ranges. This assumption about tunneling, as well as treating size distributions in the radiation scheme as bimodal, allows retrievals over a broader range of mean particle size than previous schemes permitted, making such size retrievals applicable to most types of cirrus clouds.

  3. Using Nadir and Directional Emissivity as a Probe of Particle Microphysical Properties

    NASA Astrophysics Data System (ADS)

    Pitman, Karly M.; Wolff, Michael J.; Bandfield, Joshua L.; Clayton, Geoffrey C.

    Real surfaces are not expected to be diffuse emitters, thus observed emissivity values of surface dust deposits are a function of viewing geometry. Attempts to model infrared emission spectral profiles of surface dust deposits at nadir have not yet matured to match the sophistication of astrophysical dust radiative transfer codes. In the absence of strong thermal gradients, directional emissivity may be obtained theoretically via a combination of reciprocity and Kirchhoff's Law. Owing to a lack of laboratory data on directional emissivity for comparison, theorists have not explored the potential utility of directional emissivity as a direct probe of surface dust microphysical properties. Motivated by future analyses of MGS/TES emission phase function (EPF) sequences and the upcoming Mars Exploration Rover mini-TES dataset, we explore the effects of dust particle size and composition on observed radiances at nadir and off-nadir geometries in the TES spectral regime using a combination of multiple scattering radiative transfer and Mie scattering algorithms. Comparisons of these simulated spectra to laboratory spectra of standard mineral assemblages will also be made. This work is supported through NASA grant NAGS-9820 (MJW) and LSU Board of Regents (KMP).

  4. Particle Size Distributions in Atmospheric Clouds

    NASA Technical Reports Server (NTRS)

    Paoli, Roberto; Shariff, Karim

    2003-01-01

    In this note, we derive a transport equation for a spatially integrated distribution function of particles size that is suitable for sparse particle systems, such as in atmospheric clouds. This is done by integrating a Boltzmann equation for a (local) distribution function over an arbitrary but finite volume. A methodology for evolving the moments of the integrated distribution is presented. These moments can be either tracked for a finite number of discrete populations ('clusters') or treated as continuum variables.

  5. Analysis of Organic matter from cloud particles

    NASA Astrophysics Data System (ADS)

    Bank, Shelton; Castillo, Raymond

    1987-03-01

    Organic matter collected from filtration of two separate cloud events was analysed by Fourier Transform Infrared Spectroscopy. Particles collected from different size filters were separated by color and each type of particle gave rise to a characteristic spectrum. The major constituents were identified as complex proteins and cellulose. Additionally, some degraded material (likely protein) and an unidentified orange-brown material were present. Finally some trace components were identified as wax, oil, silicon oil, polyvinyl chloride, calcium carbonate, clay, sand and polyethylene.

  6. Comparison of CERES-MODIS cloud microphysical properties with surface observations over Loess Plateau

    NASA Astrophysics Data System (ADS)

    Yan, Hongru; Huang, Jianping; Minnis, Patrick; Yi, Yuhong; Sun-Mack, Sunny; Wang, Tianhe; Nakajima, Takashi Y.

    2015-03-01

    To enhance the utility of satellite-derived cloud properties for studying the role of clouds in climate change and the hydrological cycle in semi-arid areas, it is necessary to know their uncertainties. This paper estimates the uncertainties of several cloud properties by comparing those derived over the China Loess Plateau from the MODerate-resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua by the Clouds and Earth's Radiant Energy System (CERES) with surface observations at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL). The comparisons use data from January 2008 to June 2010 limited to single layer and overcast stratus conditions during daytime. Cloud optical depths (τ) and liquid water paths (LWP) from both Terra and Aqua generally track the variation of the surface counterparts with modest correlation, while cloud effective radius (re) is only weakly correlated with the surface retrievals. The mean differences between Terra and the SACOL retrievals are -4.7±12.9, 2.1±3.2 μm and 30.2±85.3 g m-2 for τ, re and LWP, respectively. The corresponding differences for Aqua are 2.1±8.4, 1.2±2.9 μm and 47.4±79.6 g m-2, respectively. Possible causes for biases of satellite retrievals are discussed through statistical analysis and case studies. Generally, the CERES-MODIS cloud properties have a bit larger biases over the Loess Plateau than those in previous studies over other locations.

  7. a 33GHZ and 95GHZ Cloud Profiling Radar System (cprs): Preliminary Estimates of Particle Size in Precipitation and Clouds.

    NASA Astrophysics Data System (ADS)

    Sekelsky, Stephen Michael

    1995-11-01

    The Microwave Remote Sensing Laboratory (MIRSL) st the University of Massachusetts has developed a unique single antenna, dual-frequency polarimetric Cloud Profiling Radar System (CPRS). This project was funded by the Department of Energy's Atmospheric Radiation Measurement (ARM) program, and was intended to help fill the void of ground-based remote sensors capable of characterizing cloud microphysical properties. CPRS is unique in that it can simultaneously measure the complex power backscattered from clouds at 33 GHz and 95 GHz through the same aperture. Both the 33 GHz and 95 GHz channels can transmit pulse-to-pulse selectable vertical or horizontal polarization, and simultaneously record both the copolarized and crosspolarized backscatter. CPRS Doppler, polarimetric and dual-wavelength reflectivity measurements combined with in situ cloud measurements should lead to the development of empirical models that can more accurately classify cloud-particle phase and habit, and make better quantitative estimates of particle size distribution parameters. This dissertation describes the CPRS hardware, and presents colocated 33 GHz and 95 GHz measurements that illustrate the use of dual-frequency measurements to estimate particle size when Mie scattering, is observed in backscatter from rain and ice-phase clouds. Polarimetric measurements are presented as a means of discriminating cloud phase (ice-water) and estimating crystal shape in cirrus clouds. Polarimetric and dual-wavelength observations of insects are also presented with a brief discussion of their impact on the interpretation of precipitation and liquid cloud measurements. In precipitation, Diermendjian's equations for Mie backscatter (1) and the Marshal-Palmer drop-size distribution are used to develop models relating differences in the reflectivity and mean velocity at 33 GHz and 95 GHz to the microphysical parameters of rain. These models are then used to estimate mean droplet size from CPRS measurements of

  8. Vertical velocities within a Cirrus cloud from Doppler lidar and aircraft measurements during FIRE: Implications for particle growth

    NASA Technical Reports Server (NTRS)

    Gultepe, Ismail; Heymsfield, Andrew J.

    1990-01-01

    A large and comprehensive data set taken by the NOAA CO2 Doppler lidar, the NCAR King Air, and rawinsondes on 31 October 1986 during the FIRE (First ISCCP Regional Experiment) field program which took place in Wisconsin are presented. Vertical velocities are determined from the Doppler lidar data, and are compared with velocities derived from the aircraft microphysical data. The data are used for discussion of particle growth and dynamical processes operative within the cloud.

  9. Design, Evaluation and GCM-Performance of a New Parameterization for Microphysics of Clouds with Relaxed Arakawa-Schubert Scheme (McRas)

    NASA Technical Reports Server (NTRS)

    Sud, Y. C.; Walker, G. K.

    1998-01-01

    A prognostic cloud scheme named McRAS (Microphysics of clouds with Relaxed Arakawa-Schubert Scheme) was developed with the aim of improving cloud-microphysics, and cloud-radiation interactions in GCMs. McRAS distinguishes convective, stratiform, and boundary-layer clouds. The convective clouds merge into stratiform clouds on an hourly time-scale, while the boundary-layer clouds do so instantly. The cloud condensate transforms into precipitation following the auto-conversion relations of Sundqvist that contain a parametric adaptation for the Bergeron-Findeisen process of ice crystal growth and collection of cloud condensate by precipitation. All clouds convect, advect, and diffuse both horizontally and vertically with a fully active cloud-microphysics throughout its life-cycle, while the optical properties of clouds are derived from the statistical distribution of hydrometeors and idealized cloud geometry. An evaluation of McRAS in a single column model (SCM) with the GATE Phase III data has shown that McRAS can simulate the observed temperature, humidity, and precipitation without discernible systematic errors. An evaluation with the ARM-CART SCM data in a cloud model intercomparison exercise shows reasonable but not an outstanding accurate simulation. Such a discrepancy is common to almost all models and is related, in part, to the input data quality. McRAS was implemented in the GEOS II GCM. A 50 month integration that was initialized with the ECMWF analysis of observations for January 1, 1987 and forced with the observed sea-surface temperatures and sea-ice distribution and vegetation properties (biomes, and soils), with prognostic soil moisture, snow-cover, and hydrology showed a very realistic simulation of cloud process, incloud water and ice, and cloud-radiative forcing (CRF). The simulated ITCZ showed a realistic time-mean structure and seasonal cycle, while the simulated CRF showed sensitivity to vertical distribution of cloud water which can be easily

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  11. Retrievals of cloud microphysical properties from the Research Scanning Polarimeter measurements made during PODEX field campaign

    NASA Astrophysics Data System (ADS)

    Alexandrov, M. D.; Cairns, B.; Sinclair, K.

    2013-12-01

    We present the retrievals of cloud droplet size distribution parameters (effective radius and variance) from the Research Scanning Polarimeter (RSP) measurements made during NASA's POlarimeter Definition EXperiment (PODEX), which was based in Palmdale, California in January - February 2013. The RSP is an airborne prototype for the Aerosol Polarimetery Sensor (APS), which was built for the NASA Glory Mission project. This instrument measures both polarized and total reflectances in 9 spectral channels with center wavelengths of 410, 470, 555, 670, 865, 960, 1590, 1880 and 2250 nm. The RSP is a push broom scanner making samples at 0.8 degree intervals within 60 degrees from nadir in both forward and backward directions. The data from actual RSP scans is aggregated into "virtual" scans, each consisting of all reflectances (at a variety of scattering angles) from a single point on the ground or at the cloud top. In the case of water clouds the rainbow is observed in the polarized reflectances in the scattering angle range between 135 and 170 degrees. It has a unique signature that is being used to accurately determine the droplet size and is not affected by cloud morphology. Simple parametric fitting algorithm applied to these polarized reflectances provides retrievals of the droplet effective radius and variance assuming a prescribed size distribution shape (gamma distribution). In addition to this, we use a non-parametric method, Rainbow Fourier Transform (RFT), which allows to retrieve the droplet size distribution a parametric model. Of particular interest is the information contained in droplet size distribution width, which is indicative of cloud life cycle. The absorbing band method is also applied to RSP total reflectance observations. The difference in the retrieved droplet size between polarized and absorbing band techniques is expected to reflect the strength of the vertical gradient in cloud liquid water content. In addition to established retrieval

  12. Comparison of Satellite and Aircraft Measurements of Cloud Microphysical Properties in Icing Conditions During ATREC/AIRS-II

    NASA Technical Reports Server (NTRS)

    Nguyen, Louis; Minnis, Patrick; Spangenberg, Douglas A.; Nordeen, Michele L.; Palikonda, Rabindra; Khaiyer, Mandana M.; Gultepe, Ismail; Reehorst, Andrew L.

    2004-01-01

    Satellites are ideal for continuous monitoring of aircraft icing conditions in many situations over extensive areas. The satellite imager data are used to diagnose a number of cloud properties that can be used to develop icing intensity indices. Developing and validating these indices requires comparison with objective "cloud truth" data in addition to conventional pilot reports (PIREPS) of icing conditions. Minnis et al. examined the relationships between PIREPS icing and satellite-derived cloud properties. The Atlantic-THORPEX Regional Campaign (ATReC) and the second Alliance Icing Research Study (AIRS-II) field programs were conducted over the northeastern USA and southeastern Canada during late 2003 and early 2004. The aircraft and surface measurements are concerned primarily with the icing characteristics of clouds and, thus, are ideal for providing some validation information for the satellite remote sensing product. This paper starts the process of comparing cloud properties and icing indices derived from the Geostationary Operational Environmental Satellite (GOES) with the aircraft in situ measurements of several cloud properties during campaigns and some of the The comparisons include cloud phase, particle size, icing intensity, base and top altitudes, temperatures, and liquid water path. The results of this study are crucial for developing a more reliable and objective icing product from satellite data. This icing product, currently being derived from GOES data over the USA, is an important complement to more conventional products based on forecasts, and PIREPS.

  13. Exploring the Effects of Waves on the Middle and Lower Cloud Decks of Venus with a Microphysical Model Including a Radiative-Dynamical Feedback.

    NASA Astrophysics Data System (ADS)

    McGouldrick, Kevin; Toon, O. B.

    2006-09-01

    Allen and Crawford (1984) discovered regions with unexpectedly high brightness temperatures on the nightside of Venus in the near infrared. It was soon realized that variability in the optical thickness of the middle and lower cloud decks was directly responsible for the variability of these high brightness temperature features. The middle and lower cloud deck is sustained by a radiative-dynamical feedback whereby heating of the cloud base by radiation from the lower atmosphere destabilizes the lapse rate within the cloud region. We have developed a model from the CU/NASA Ames Community Aerosol and Radiation Model for Atmospheres (CARMA) which accurately simulates the middle and lower cloud deck by means of a combined microphysical, radiative transfer, and turbulent dynamical model. Breaking waves which dump energy and momentum at the cloud base might be responsible for the break-up of the Venus cloud. We demonstrate the sensitivity of our simulated Venus cloud to changes in the static stability and to changes in the temperature profile. We also explore the effects of breaking waves on the simulated Venus cloud. We find that a loss of mixing can produce cloud optical thickness consistent with observations on a timescale of several weeks. Changes in temperature act far more quickly but warmings of approximately 10 K are required to significantly reduce the cloud optical thickness.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  15. libcloudph++ 1.0: a single-moment bulk, double-moment bulk, and particle-based warm-rain microphysics library in C++

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    This paper introduces a library of algorithms for representing cloud microphysics in numerical models. The library is written in C++, hence the name libcloudph++. In the current release, the library covers three warm-rain schemes: the single- and double-moment bulk schemes, and the particle-based scheme with Monte Carlo coalescence. The three schemes are intended for modelling frameworks of different dimensionalities and complexities ranging from parcel models to multi-dimensional cloud-resolving (e.g. large-eddy) simulations. A two-dimensional (2-D) prescribed-flow framework is used in the paper to illustrate the library features. The libcloudph++ and all its mandatory dependencies are free and open-source software. The Boost.units library is used for zero-overhead dimensional analysis of the code at compile time. The particle-based scheme is implemented using the Thrust library that allows one to leverage the power of graphics processing units (GPU), retaining the possibility of compiling the unchanged code for execution on single or multiple standard processors (CPUs). The paper includes a complete description of the programming interface (API) of the library and a performance analysis including comparison of GPU and CPU set-ups.

  16. Studying Precipitation Processes in WRF with Goddard Bulk Microphysics in Comparison with Other Microphysical Schemes

    NASA Technical Reports Server (NTRS)

    Tao, W.K.; Shi, J.J.; Braun, S.; Simpson, J.; Chen, S.S.; Lang, S.; Hong, S.Y.; Thompson, G.; Peters-Lidard, C.

    2009-01-01

    A Goddard bulk microphysical parameterization is implemented into the Weather Research and Forecasting (WRF) model. This bulk microphysical scheme has three different options, 2ICE (cloud ice & snow), 3ICE-graupel (cloud ice, snow & graupel) and 3ICE-hail (cloud ice, snow & hail). High-resolution model simulations are conducted to examine the impact of microphysical schemes on different weather events: a midlatitude linear convective system and an Atlantic hurricane. The results suggest that microphysics has a major impact on the organization and precipitation processes associated with a summer midlatitude convective line system. The Goddard 3ICE scheme with the cloud ice-snow-hail configuration agreed better with observations ill of rainfall intensity and having a narrow convective line than did simulations with the cloud ice-snow-graupel and cloud ice-snow (i.e., 2ICE) configurations. This is because the Goddard 3ICE-hail configuration has denser precipitating ice particles (hail) with very fast fall speeds (over 10 m/s) For an Atlantic hurricane case, the Goddard microphysical scheme (with 3ICE-hail, 3ICE-graupel and 2ICE configurations) had no significant impact on the track forecast but did affect the intensity slightly. The Goddard scheme is also compared with WRF's three other 3ICE bulk microphysical schemes: WSM6, Purdue-Lin and Thompson. For the summer midlatitude convective line system, all of the schemes resulted in simulated precipitation events that were elongated in southwest-northeast direction in qualitative agreement with the observed feature. However, the Goddard 3ICE-hail and Thompson schemes were closest to the observed rainfall intensities although the Goddard scheme simulated more heavy rainfall (over 48 mm/h). For the Atlantic hurricane case, none of the schemes had a significant impact on the track forecast; however, the simulated intensity using the Purdue-Lin scheme was much stronger than the other schemes. The vertical distributions of

  17. Flame propagation and extinction in particle clouds

    NASA Technical Reports Server (NTRS)

    Berlad, A. L.; Joshi, N. D.

    1986-01-01

    Two phase flame propagation and extinction theory required to support the corresponding experiments planned for the space shuttle is being developed. Also being planned are specialized collaborative, experimental and theoretical NASA UCSD studies needed to support the ongoing definition of needed experimental hardware, experimental procedures, data acquisition philosophy, and other ground based support activities required to assure the success of space shuttle based experiments concerned with combustion of clouds of particulates at reduced gravitational conditions. The further development of relations delineating premixed particle cloud and premixed gaseous systems as well as burner stabilized and freely propagating flame systems is considered.

  18. Testing ice microphysics parameterizations in the NCAR Community Atmospheric Model Version 3 using Tropical Warm Pool-International Cloud Experiment data

    DOE PAGESBeta

    Wang, Weiguo; Liu, Xiaohong; Xie, Shaocheng; Boyle, Jim; McFarlane, Sally A.

    2009-07-23

    Here, cloud properties have been simulated with a new double-moment microphysics scheme under the framework of the single-column version of NCAR Community Atmospheric Model version 3 (CAM3). For comparison, the same simulation was made with the standard single-moment microphysics scheme of CAM3. Results from both simulations compared favorably with observations during the Tropical Warm Pool–International Cloud Experiment by the U.S. Department of Energy Atmospheric Radiation Measurement Program in terms of the temporal variation and vertical distribution of cloud fraction and cloud condensate. Major differences between the two simulations are in the magnitude and distribution of ice water content within themore » mixed-phase cloud during the monsoon period, though the total frozen water (snow plus ice) contents are similar. The ice mass content in the mixed-phase cloud from the new scheme is larger than that from the standard scheme, and ice water content extends 2 km further downward, which is in better agreement with observations. The dependence of the frozen water mass fraction on temperature from the new scheme is also in better agreement with available observations. Outgoing longwave radiation (OLR) at the top of the atmosphere (TOA) from the simulation with the new scheme is, in general, larger than that with the standard scheme, while the surface downward longwave radiation is similar. Sensitivity tests suggest that different treatments of the ice crystal effective radius contribute significantly to the difference in the calculations of TOA OLR, in addition to cloud water path. Numerical experiments show that cloud properties in the new scheme can respond reasonably to changes in the concentration of aerosols and emphasize the importance of correctly simulating aerosol effects in climate models for aerosol-cloud interactions. Further evaluation, especially for ice cloud properties based on in-situ data, is needed.« less

  19. Testing ice microphysics parameterizations in the NCAR Community Atmospheric Model Version 3 using Tropical Warm Pool-International Cloud Experiment data

    SciTech Connect

    Wang, Weiguo; Liu, Xiaohong; Xie, Shaocheng; Boyle, Jim; McFarlane, Sally A.

    2009-07-23

    Here, cloud properties have been simulated with a new double-moment microphysics scheme under the framework of the single-column version of NCAR Community Atmospheric Model version 3 (CAM3). For comparison, the same simulation was made with the standard single-moment microphysics scheme of CAM3. Results from both simulations compared favorably with observations during the Tropical Warm Pool–International Cloud Experiment by the U.S. Department of Energy Atmospheric Radiation Measurement Program in terms of the temporal variation and vertical distribution of cloud fraction and cloud condensate. Major differences between the two simulations are in the magnitude and distribution of ice water content within the mixed-phase cloud during the monsoon period, though the total frozen water (snow plus ice) contents are similar. The ice mass content in the mixed-phase cloud from the new scheme is larger than that from the standard scheme, and ice water content extends 2 km further downward, which is in better agreement with observations. The dependence of the frozen water mass fraction on temperature from the new scheme is also in better agreement with available observations. Outgoing longwave radiation (OLR) at the top of the atmosphere (TOA) from the simulation with the new scheme is, in general, larger than that with the standard scheme, while the surface downward longwave radiation is similar. Sensitivity tests suggest that different treatments of the ice crystal effective radius contribute significantly to the difference in the calculations of TOA OLR, in addition to cloud water path. Numerical experiments show that cloud properties in the new scheme can respond reasonably to changes in the concentration of aerosols and emphasize the importance of correctly simulating aerosol effects in climate models for aerosol-cloud interactions. Further evaluation, especially for ice cloud properties based on in-situ data, is needed.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  1. Climatic implications of ice microphysics

    SciTech Connect

    Liou, K.N.

    1995-09-01

    Based on aircraft measurements of mid-latitude cirrus clouds, ice crystal size distribution and ice water content (IWC) are shown to be dependent on temperature. This dependence is also evident from the theoretical consideration of ice crystal growth. Using simple models of the diffusion and accretion growth of ice particles, the computed mean ice crystal size and IWC compare reasonably well with the measured mean values. The temperature dependence of ice crystal size and IWC has important climatic implications in that the temperature field perturbed by external radiative forcings, such as greenhouse warming, can alter the composition of ice crystal clouds. Through radiative transfer, ice microphysics can in turn affect the temperature field. Higher IWC would increase cloud solar albedo and infrared emissivity, while for a given IWC, larger crystals would reduce cloud albedo and emissivity. The competing effects produced by greenhouse temperature perturbations via ice micro-physics and radiation interactions and feedbacks are assessed by a one-dimensional radiative-convective climate model that includes an advanced radiation parameterization program. 3 figs.

  2. Energetics of Mixed Phase Cloud Particle Interactions

    NASA Astrophysics Data System (ADS)

    Vidaurre, G.; Hallett, J.

    2005-12-01

    The ratio of the kinetic to surface energy of a crystal or a drop on impact gives a measure of the available energy for break-up and splash. Such a break-up process may influence particle collision and also particle observations at aircraft speed. The detail physical processes of the impact determines how the kinetic energy is distributed: 1) part retained by bouncing particles, 2) to create new surfaces during break-up, 3) to dislocate or melt part of the crystal, and 4) converted to thermal energy through viscous dissipation of deforming liquid or displacing air on impact. Extensive break-up of 2% of the crystal or melting of 6% is enough to explain the crystal kinetic energy losses during the encounter at aircraft speed. Ice crystals from convective and stratiform clouds and continental clouds were collected in formvar solution by continuous replicator and also were video-recorded following impact on optical flat of a Cloudscope. Particle sizes were classified in bins, the expected number of fragments being given by an exponential function for ice particles with effective diameter between 5 μm and 2500 μm, and 70% standard deviation. Regions of crystals broken into a few fragments account for 0.6% of the kinetic energy loss; in other parts severe break-up makes it impossible to measure the fracture length. Knowledge regarding ice and water interaction in Mixed-Phase clouds and also with the aircraft instruments provides basic underpinning for characterization of ice particle impact. Further, detail of the fracture process may also be of importance in relation to electrical properties of the particle after impaction or break-up. These conclusions are of major operational importance for prediction of the icing process itself, having implications for both aircraft icing and particle measurement instrumentation.

  3. Microphysical response of cloud droplets in a fluctuating updraft. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Harding, D. D.

    1977-01-01

    The effect of a fluctuating updraft upon a distribution of cloud droplets is examined. Computations are performed for fourteen vertical velocity patterns; each allows a closed parcel of cloud air to undergo downward as well as upward motion. Droplet solution and curvature effects are included. The classical equations for the growth rate of an individual droplet by vapor condensation relies on simplifying assumptions. Those assumptions are isolated and examined. A unique approach is presented in which all energy sources and sinks of a droplet may be considered and is termed the explicit model. It is speculated that the explicit model may enhance the growth of large droplets at greater heights. Such a model is beneficial to the studies of pollution scavenging and acid rain.

  4. Cloud life cycle investigated via high resolution and full microphysics simulations in the surroundings of Manaus, Central Amazonia

    NASA Astrophysics Data System (ADS)

    Pauliquevis, T.; Gomes, H. B.; Barbosa, H. M.

    2014-12-01

    In this study we evaluate the skill of WRF model to simulate the actual diurnal cycle of convection in the Amazon basin. Models tipically are not capable to simulate the well documented cycle of 1) shallow cumulus in the morning; 2) towering process around noon; 3) shallow-to-deep convection and rain around 14h (LT). The fail in models is explained by the typical size of shallow cumulus (~0.5 - 2.0 km) and the coarse resolution of models using convection parameterisation (> 20 km). In this study we employed high spatial resolution (Dx = 0.625 km) to reach the shallow cumulus scale. . The simulations corresponds to a dynamical downscaling of ERA-Interim from 25 to 28 February 2013 with 40 vertical levels, 30 minutes outputs,and three nested grids (10 km, 2.5 km, 0.625 km). Improved vegetation (USGS + PROVEG), albedo and greenfrac (computed from MODIS-NDVI + LEAF-2 land surface parameterization), as well as pseudo analysis of soil moisture were used as input data sets, resulting in more realistic precipitation fields when compared to observations in sensitivity tests. Convective parameterization was switched off for the 2.5/0.625 km grids, where cloud formation was solely resolved by the microphysics module (WSM6 scheme, which provided better results). Results showed a significant improved capability of the model to simulate diurnal cycle. Shallow cumulus begin to appear in the first hours in the morning. They were followed by a towering process that culminates with precipitation in the early afternoon, which is a behavior well described by observations but rarely obtained in models. Rain volumes were also realistic (~20 mm for single events) when compared to typical events during the period, which is in the core of the wet season. Cloud fields evolution also differed with respect to Amazonas River bank, which is a clear evidence of the interaction between river breeze and large scale circulation.

  5. Scale Dependency of Convective Momentum Transport as Diagnosed from Cloud-Resolving Model Simulation with Spectral-bin Microphysics

    NASA Astrophysics Data System (ADS)

    Liu, Y. C.; Fan, J.; Zhang, G. J.; Xu, K. M.; Ghan, S. J.

    2014-12-01

    Convective momentum transport (CMT) has been demonstrated to have a large impact on global atmospheric circulation in both observational and numerical studies. In General Circulation Models (GCMs) CMT is often parameterized in a simple way by assuming that in-cloud horizontal momentum depends only on lateral entrainment and detrainment rates [Schneider and Lindzen, 1976]. In addition to lateral entrainment and detrainment rates the effect of perturbation pressure gradient force induced by convection (Pc) on momentum transport is significant. Because it is the most complicated term to be parameterized, a very simple form of products among a constant coefficient, mass flux, and environment vertical wind shear was employed to parameterize it [Gregory et al., 1997]. In addition, none of these CMT parameterizations deal with the scale problems. Thus, the goal of this study is to evaluate the past CMT parameterizations and explore the scale dependencies of Pc and CMT using Cloud Resolving Model (CRM) simulations from the Weather Research and Forecasting (WRF) coupled with the most sophisticated spectral-bin microphysics. Our preliminary results show that the parameterized CMT from the top-hat approach is underestimated especially at the gray zone scale (~4-50 km); using the simplified 3-updraft and 1-downdraft formulation proposed in our previous study for eddy transport of moisture, the CMT can be represented well. The formulation also produced a more accurate mass flux compared to the top-hat approach, which can potentially improve the parameterization of Pc. We investigate the relative contributions from linear and nonlinear forcing to Pc at different model grid spacing (dx). Our results show that the assumption that non-linear forcing is much smaller than linear force is valid only at dx > 128 km and dx < 8 km. At the dx = 32~16 km, linear and nonlinear forcings become compatible, suggesting a more sophisticated formula for Pc might be needed.

  6. Classification of particle effective shape ratios in cirrus clouds based on the lidar depolarization ratio.

    PubMed

    Noel, Vincent; Chepfer, Helene; Ledanois, Guy; Delaval, Arnaud; Flamant, Pierre H

    2002-07-20

    A shape classification technique for cirrus clouds that could be applied to future spaceborne lidars is presented. A ray-tracing code has been developed to simulate backscattered and depolarized lidar signals from cirrus clouds made of hexagonal-based crystals with various compositions and optical depth, taking into account multiple scattering. This code was used first to study the sensitivity of the linear depolarization rate to cloud optical and microphysical properties, then to classify particle shapes in cirrus clouds based on depolarization ratio measurements. As an example this technique has been applied to lidar measurements from 15 mid-latitude cirrus cloud cases taken in Palaiseau, France. Results show a majority of near-unity shape ratios as well as a strong correlation between shape ratios and temperature: The lowest temperatures lead to high shape ratios. The application of this technique to space-borne measurements would allow a large-scale classification of shape ratios in cirrus clouds, leading to better knowledge of the vertical variability of shapes, their dependence on temperature, and the formation processes of clouds. PMID:12148751

  7. In situ exhaust cloud measurements. [particle size distribution and cloud physics of rocket exhaust clouds

    NASA Technical Reports Server (NTRS)

    Wornom, D.

    1980-01-01

    Airborne in situ exhaust cloud measurements were conducted to obtain definitions of cloud particle size range, Cl2 content, and HCl partitioning. Particle size distribution data and Cl2 measurements were made during the May, August, and September 1977 Titan launches. The measurements of three basic effluents - HCl, NO sub X, and particles - against minutes after launch are plotted. The maximum observed HCl concentration to the maximum Cl2 concentration are compared and the ratios of the Cl2 to the HCl is calculated.

  8. Evaluation of Cloud Microphysics Simulated using a Meso-Scale Model Coupled with a Spectral Bin Microphysical Scheme through Comparison with Observation Data by Ship-Borne Doppler and Space-Borne W-Band Radars

    NASA Technical Reports Server (NTRS)

    Iguchi, T.; Nakajima, T.; Khain, A. P.; Saito, K.; Takemura, T.; Okamoto, H.; Nishizawa, T.; Tao, W.-K.

    2012-01-01

    Equivalent radar reflectivity factors (Ze) measured by W-band radars are directly compared with the corresponding values calculated from a three-dimensional non-hydrostatic meso-scale model coupled with a spectral-bin-microphysical (SBM) scheme for cloud. Three case studies are the objects of this research: one targets a part of ship-borne observation using 95 GHz Doppler radar over the Pacific Ocean near Japan in May 2001; other two are aimed at two short segments of space-borne observation by the cloud profiling radar on CloudSat in November 2006. The numerical weather prediction (NWP) simulations reproduce general features of vertical structures of Ze and Doppler velocity. A main problem in the reproducibility is an overestimation of Ze in ice cloud layers. A frequency analysis shows a strong correlation between ice water contents (IWC) and Ze in the simulation; this characteristic is similar to those shown in prior on-site studies. From comparing with the empirical correlations by the prior studies, the simulated Ze is overestimated than the corresponding values in the studies at the same IWC. Whereas the comparison of Doppler velocities suggests that large-size snowflakes are necessary for producing large velocities under the freezing level and hence rules out the possibility that an overestimation of snow size causes the overestimation of Ze. Based on the results of several sensitivity tests, we conclude that the source of the overestimation is a bias in the microphysical calculation of Ze or an overestimation of IWC. To identify the source of the problems needs further validation research with other follow-up observations.

  9. A microphysical connection among biomass burning, cumulus clouds, and stratospheric moisture.

    PubMed

    Sherwood, Steven

    2002-02-15

    A likely causal chain is established here that connects humidity in the stratosphere, relative humidity near the tropical tropopause, ice crystal size in towering cumulus clouds, and aerosols associated with tropical biomass burning. The connections are revealed in satellite-observed fluctuations of each quantity on monthly to yearly time scales. More aerosols lead to smaller ice crystals and more water vapor entering the stratosphere. The connections are consistent with physical reasoning, probably hold on longer time scales, and may help to explain why stratospheric water vapor appears to have been increasing for the past five decades. PMID:11847336

  10. Statistical properties of the ice particle distribution in stratiform clouds

    NASA Astrophysics Data System (ADS)

    Delanoe, J.; Tinel, C.; Testud, J.

    2003-04-01

    This paper presents an extensive analysis of several microphysical data bases CEPEX, EUCREX, CLARE and CARL to determine statistical properties of the Particle Size Distribution (PSD). The data base covers different type of stratiform clouds : tropical cirrus (CEPEX), mid-latitude cirrus (EUCREX) and mid-latitude cirrus and stratus (CARL,CLARE) The approach for analysis uses the concept of normalisation of the PSD developed by Testud et al. (2001). The normalization aims at isolating three independent characteristics of the PSD : its "intrinsic" shape, the "average size" of the spectrum and the ice water content IWC, "average size" is meant the mean mass weighted diameter. It is shown that concentration should be normalized by N_0^* proportional to IWC/D_m^4. The "intrinsic" shape is defined as F(Deq/D_m)=N(Deq)/N_0^* where Deq is the equivalent melted diameter. The "intrinsic" shape is found to be very stable in the range 001.5, more scatter is observed, but future analysis should decide if it is representative of real physical variation or statistical "error" due to counting problem. Considering an overall statistics over the full data base, a large scatter of the N_0^* against Dm plot is found. But in the case of a particular event or a particular leg of a flight, the N_0^* vs. Dm plot is much less scattered and shows a systematic trend for decaying of N_0^* when Dm increases. This trend is interpreted as the manifestation of the predominance of the aggregation process. Finally an important point for cloud remote sensing is investigated : the normalised relationships IWC/N_0^* against Z/N_0^* is much less scattered that the classical IWC against Z the radar reflectivity factor.

  11. Particle cloud combustion in reduced gravity

    NASA Technical Reports Server (NTRS)

    Berlad, A. L.

    1988-01-01

    The prinicipal objectives of this microgravity experiment program are to obtain flame propagation rate and flame extinction limit data for several important premixed, quiescent particle cloud combustion systems under near zero-gravity conditions. The data resulting from these experiments are needed for utilization with currently available and tractable flame propagation and extinction theory. These data are also expected to provide standards for the evaluation of fire hazards in particle suspensions in both Earth-based and space-based applications. Both terrestrial and space-based fire safety criteria require the identification of the critical concentrations of particulate fuels and inerts at the flame extinction conditions.

  12. On the Sensitivity of Atmospheric Ensembles to Cloud Microphysics in Long-Term Cloud-Resolving Model Simulations

    NASA Technical Reports Server (NTRS)

    Zeng, Xiping; Tao, Wei-Kuo; Lang, Stephen; Hou, Arthur Y.; Zhang, Minghua; Simpson, Joanne

    2008-01-01

    Month-long large-scale forcing data from two field campaigns are used to drive a cloud-resolving model (CRM) and produce ensemble simulations of clouds and precipitation. Observational data are then used to evaluate the model results. To improve the model results, a new parameterization of the Bergeron process is proposed that incorporates the number concentration of ice nuclei (IN). Numerical simulations reveal that atmospheric ensembles are sensitive to IN concentration and ice crystal multiplication. Two- (2D) and three-dimensional (3D) simulations are carried out to address the sensitivity of atmospheric ensembles to model dimensionality. It is found that the ensembles with high IN concentration are more sensitive to dimensionality than those with low IN concentration. Both the analytic solutions of linear dry models and the CRM output show that there are more convective cores with stronger updrafts in 3D simulations than in 2D, which explains the differing sensitivity of the ensembles to dimensionality at different IN concentrations.

  13. Aerosol Mass Loading, Mixing State, Size and Number in Present Day (2000) and Future (2100): Study with the Advanced Particle Microphysics (APM) module in the Community Earth System Model (CESM)

    NASA Astrophysics Data System (ADS)

    Luo, G.; Yu, F.

    2014-12-01

    Aerosols affect the global energy budget by scattering and absorbing sunlight (direct effects) and by changing the microphysical properties, lifetime, and coverage of clouds (indirect effects). One of the key challenges in quantifying the aerosol direct and indirect effects is to deep our understanding about the size distribution, size-resolved composition, and mixing state of aerosols. However, detailed information on size distribution and mixing state is often not available or incomplete in current climate models. Here, we incorporated APM into CESM. APM is a multi-type, multi-component (sulfate, nitrate, ammonium, SOA, BC, OC, dust, and sea salt), size-resolved particle microphysics model. Online chemistry, up-to-date nucleation, oxidation aging of medium-volatile and semi-volatile organic gases, aerosol-cloud interaction with stratiform cloud, shallow convection cloud, and deep convection cloud are considered. The amounts of secondary species coated on primary particles, through condensation, coagulation, equilibrium uptake, and aqueous chemistry, are also tracked. Model results are compared with aerosol mass observed by IMPROVE/EMEP, vertical structure of global particle number from aircraft-based field campaigns, particle and cloud condensation nuclei number at ground-based stations, aerosol optical properties retrieved by several satellites. Model results can capture the major characteristics shown in these observations. With this model system, we find that global burdens of sulfate, nitrate, ammonium, BC, OC from 2000 to 2100, under scenario RCP 4.5 where total radiative forcing is stabilized before 2100, are decreased by 44%, 50%, 43%, 40%, 40%, respectively. Dust and sea salt increase slightly. Global burdens of secondary species coated on BCOC, dust, and sea salt are deceased by 34%, 30% and 60%, respectively. Global averaged aerosol number in the lower troposphere (from surface to 3 km) is significantly decreased, especially for particles smaller than

  14. Combined sphere-spheroid particle model for the retrieval of the microphysical aerosol parameters via regularized inversion of lidar data

    NASA Astrophysics Data System (ADS)

    Samaras, Stefanos; Böckmann, Christine; Nicolae, Doina

    2016-06-01

    In this work we propose a two-step advancement of the Mie spherical-particle model accounting for particle non-sphericity. First, a naturally two-dimensional (2D) generalized model (GM) is made, which further triggers analogous 2D re-definitions of microphysical parameters. We consider a spheroidal-particle approach where the size distribution is additionally dependent on aspect ratio. Second, we incorporate the notion of a sphere-spheroid particle mixture (PM) weighted by a non-sphericity percentage. The efficiency of these two models is investigated running synthetic data retrievals with two different regularization methods to account for the inherent instability of the inversion procedure. Our preliminary studies show that a retrieval with the PM model improves the fitting errors and the microphysical parameter retrieval and it has at least the same efficiency as the GM. While the general trend of the initial size distributions is captured in our numerical experiments, the reconstructions are subject to artifacts. Finally, our approach is applied to a measurement case yielding acceptable results.

  15. The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.

    2005-01-01

    Cloud microphysics are inevitable affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds, Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effect of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, a detailed spectral-bin microphysical scheme was implemented into the the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral-bim microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e., pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e., 33 bins). Atmospheric aerosols are also described using number density size-distribution functions.

  16. Cirrus microphysics and radiative transfer: A case study

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  17. Cirrus cloud optical and microphysical properties determined from AIRS infrared spectra

    NASA Astrophysics Data System (ADS)

    Yue, Qing; Liou, K. N.

    2009-03-01

    We developed an efficient thermal infrared radiative transfer model on the basis of the delta-four-stream approximation to facilitate high-spectral-resolution remote sensing applications under cirrus cloudy conditions in the Atmospheric Infrared Sounder (AIRS) data. Numerical experiments demonstrated that sensitivity in the 800-1130 cm-1 thermal infrared window spectral region is sufficiently distinct for the inference of cirrus optical depth and ice crystal mean effective size and shape factor. We analyzed 312 nighttime cirrus pixels in two AIRS granules over ARM TWP sites and applied the radiative transfer model to these cases to determine cirrus optical depth and ice crystal mean effective size, based on a look-up table approach. The retrieval program has been evaluated through an error budget analysis and validation effort by comparing AIRS-retrieved results with those determined from ground-based millimeter-wave cloud radar data at ARM TWP sites, for five AIRS pixels that were collocated and coincident with ground-based measurements.

  18. Macroscopic impacts of cloud and precipitation processes on maritime shallow convection as simulated by a large eddy simulation model with bin microphysics

    NASA Astrophysics Data System (ADS)

    Grabowski, W. W.; Wang, L.-P.; Prabha, T. V.

    2015-01-01

    This paper discusses impacts of cloud and precipitation processes on macrophysical properties of shallow convective clouds as simulated by a large eddy model applying warm-rain bin microphysics. Simulations with and without collision-coalescence are considered with cloud condensation nuclei (CCN) concentrations of 30, 60, 120, and 240 mg-1. Simulations with collision-coalescence include either the standard gravitational collision kernel or a novel kernel that includes enhancements due to the small-scale cloud turbulence. Simulations with droplet collisions were discussed in Wyszogrodzki et al. (2013) focusing on the impact of the turbulent collision kernel. The current paper expands that analysis and puts model results in the context of previous studies. Despite a significant increase of the drizzle/rain with the decrease of CCN concentration, enhanced by the effects of the small-scale turbulence, impacts on the macroscopic cloud field characteristics are relatively minor. Model results show a systematic shift in the cloud-top height distributions, with an increasing contribution of deeper clouds for stronger precipitating cases. We show that this is consistent with the explanation suggested in Wyszogrodzki et al. (2013); namely, the increase of drizzle/rain leads to a more efficient condensate offloading in the upper parts of the cloud field. A second effect involves suppression of the cloud droplet evaporation near cloud edges in low-CCN simulations, as documented in previous studies (e.g., Xue and Feingold, 2006). We pose the question whether the effects of cloud turbulence on drizzle/rain formation in shallow cumuli can be corroborated by remote sensing observations, for instance, from space. Although a clear signal is extracted from model results, we argue that the answer is negative due to uncertainties caused by the temporal variability of the shallow convective cloud field, sampling and spatial resolution of the satellite data, and overall accuracy of

  19. Collaborative Research: The Influence of Cloud Microphysics and Radiation on the Response of Water Vapor and Clouds to Climate Change

    SciTech Connect

    Dr. Kerry Emanuel; Michael J. Iacono

    2011-06-28

    Uncertainties in representing the atmospheric water cycle are major obstacles to an accurate prediction of future climate. This project focused on addressing some of these uncertainties by implementing new physics for convection and radiation into the NCAR climate model. To better understand and eventually better represent these processes, we modified CAM3.5 to use the convection and cloud schemes developed by the Massachusetts Institute of Technology (MIT) and the RRTMG rapid radiation code for global models developed by Atmospheric and Environmental Research, Inc. (AER). The impact of the new physics on the CAM3.5 simulation of convection on diurnal and intra-seasonal scales, intra-seasonal oscillations and the distribution of water vapor has been investigated. The effect of the MIT and AER physics also has been tested in the Weather Research and Forecasting (WRF) regional forecast model. It has been found that the application of the AER radiation and MIT convection produces significant improvements in the modeled diurnal cycle of convection, especially over land, in the NCAR climate model. However, both the standard CAM3.5 (hereinafter STD) and the modified CAM3.5 with the new physics (hereinafter MOD) are still unable to capture the proper spectrum and propagating characteristics of the intra-seasonal oscillations (ISOs). The new physics methods modify, but do not substantially improve, the distribution of upper tropospheric water vapor relative to satellite measurements.

  20. Multiparameter radar and aircraft based studies of microphysical, kinematic, and electrical structure of convective clouds during CaPE

    NASA Astrophysics Data System (ADS)

    Bringi, V. N.

    1994-03-01

    Two storms from the 9 August, 1991 CaPE case were analyzed in-depth focusing on multiparameter radar signature evolution over 60 min. in coordination with 24 aircraft penetrations which provided particle image and electric field data together with vertical air motion, cloud water and other state parameters. A total of five discrete 'cells' were identified in the two storms and their life cycle fully documented. Collaboration with South Dakota School of Mines and University of Alabama at Huntsville has resulted in a full integration of aircraft image and field mill data (from SDSM&T T-28 aircraft) with vertical air motion from dual-Doppler wind synthesis (UAH). The cellular evolution starts with a warm rain phase where updrafts and a very low concentration of large drops dominate the cloud. As the supercooled drops rise in the updraft they freeze and acquire a water-coat possibly by collisions with other liquid drops. The multi-parameter radar signatures clearly identify this mixed-phase zone. The cloud thereafter gets electrified which may intensify to produce lightning depending on cloud vertical growth, and generation of updraft/ downdrafts.

  1. Raman lidar observations of a Saharan dust outbreak event: Characterization of the dust optical properties and determination of particle size and microphysical parameters

    NASA Astrophysics Data System (ADS)

    Di Girolamo, Paolo; Summa, Donato; Bhawar, Rohini; Di Iorio, Tatiana; Cacciani, Marco; Veselovskii, Igor; Dubovik, Oleg; Kolgotin, Alexey

    2012-04-01

    The Raman lidar system BASIL was operational in Achern (Black Forest) between 25 May and 30 August 2007 in the framework of the Convective and Orographically-induced Precipitation Study (COPS). The system performed continuous measurements over a period of approx. 36 h from 06:22 UTC on 1 August to 18:28 UTC on 2 August 2007, capturing the signature of a severe Saharan dust outbreak episode. The data clearly reveal the presence of two almost separate aerosol layers: a lower layer located between 1.5 and 3.5 km above ground level (a.g.l.) and an upper layer extending between 3.0 and 6.0 km a.g.l. The time evolution of the dust cloud is illustrated and discussed in the paper in terms of several optical parameters (particle backscatter ratio at 532 and 1064 nm, the colour ratio and the backscatter Angström parameter). An inversion algorithm was used to retrieve particle size and microphysical parameters, i.e., mean and effective radius, number, surface area, volume concentration, and complex refractive index, as well as the parameters of a bimodal particle size distribution (PSD), from the multi-wavelength lidar data of particle backscattering, extinction and depolarization. The retrieval scheme employs Tikhonov's inversion with regularization and makes use of kernel functions for randomly oriented spheroids. Size and microphysical parameters of dust particles are estimated as a function of altitude at different times during the dust outbreak event. Retrieval results reveal the presence of a fine mode with radii of 0.1-0.2 μm and a coarse mode with radii of 3-5 μm both in the lower and upper dust layers, and the dominance in the upper dust layer of a coarse mode with radii of 4-5 μm. Effective radius varies with altitude in the range 0.1-1.5 μm, while volume concentration is found to not exceed 92 μm3 cm-3. The real and imaginary part of the complex refractive index vary in the range 1.4-1.6 and 0.004-0.008, respectively.

  2. Impact of uncertainties in parameterized cloud-microphysical processes on the simulated development of an idealized 2-D squall line

    NASA Astrophysics Data System (ADS)

    Michelson, Sara; Bao, Jian-Wen; Grell, Evelyn

    2016-04-01

    In this study, numerical model simulations of an idealized 2-D squall line are investigated using microphysics budget analysis. Four commonly-used microphysics schemes of various complexity are used in the simulations. Diagnoses of the source and sink terms of the hydrometeor budget equations reveal that the differences related to the assumptions of hydrometeor size-distributions between the schemes lead to the differences in the simulations due to the net effect of various microphysical processes on the interaction between latent heating/evaporative cooling and flow dynamics as the squall line develops. Results from this study also highlight the possibility that the advantage of double-moment formulations can be overshadowed by the uncertainties in the spectral definition of individual hydrometeor categories and spectrum-dependent microphysical processes.

  3. The Influence of Cloud Microphysics and Radiation on the Response of Water Vapor and Clouds to Climate Change

    SciTech Connect

    Emanuel, Kerry; Iacono, Michael J.

    2010-11-11

    Uncertainties in representing the atmospheric water cycle are major obstacles to the accurate prediction of future climate. This project focused on addressing some of these uncertainties by implementing new physics for convection and radiation into the NCAR Community Atmosphere Model (CAM). To better understand and eventually better represent these processes in this major national climate model, we modified CAM3.5 to use the convection and cloud schemes developed by the Massachusetts Institute of Technology (MIT) and the RRTMG rapid radiation code for global climate models developed by Atmospheric and Environmental Research, Inc. (AER). The impact of the new physics on the CAM3.5 simulation of convection on diurnal and intra-seasonal scales, on intra-seasonal oscillations and on the distribution of water vapor has been investigated. In addition, the MIT and AER physics packages have been incorporated and tested in combination within the Weather Research and Forecasting (WRF) regional forecast model for the purpose of evaluating and improving convective and radiative processes on time scales appropriate to weather simulations. It has been found that the application of the AER radiation and MIT convection produces significant improvements in the modeled diurnal cycle of convection, especially over land, in the NCAR climate model. However, both the standard CAM3.5 and the modified CAM3.5 with the new physics are unable to capture the proper spectrum and propagating characteristics of dynamical intra-seasonal oscillations such as the Madden-Julian Oscillation. In addition, it has been shown that the new physics methods modify, but do not substantially improve, the distribution of upper tropospheric water vapor in CAM as established through the comparison of modeled and observed satellite radiances. This suggests that continuing regional discrepancies in water vapor amounts in the climate model may not be solely related to convective or radiative processes. The major

  4. Performance of the Goddard Multiscale Modeling Framework with Goddard Ice Microphysical Schemes

    NASA Astrophysics Data System (ADS)

    Chern, J. D.; Tao, W. K.; Lang, S. E.; Matsui, T.; Li, J. L. F.; Mohr, K. I.

    2015-12-01

    The multiscale modeling framework (MMF), which replaces traditional cloud parameterizations with cloud-resolving models (CRMs) within a host atmospheric general circulation model (GCM), has become a new approach for climate modeling. The embedded CRMs make it possible to apply CRM-based cloud microphysics directly within a GCM. However, most such schemes have never been tested in a global environment for long-term climate simulation. The benefits of using an MMF to evaluate rigorously and improve microphysics schemes are here demonstrated. Four one-moment microphysical schemes are implemented into the Goddard MMF and their results validated against three CloudSat/CALIPSO cloud ice products, CloudSat/CALIPSO cloud fractions, and other satellite data. The new four-class (cloud ice, snow, graupel, and frozen drops/hail) ice scheme produces a better overall spatial distribution of cloud ice amount and total cloud radiative forcing than earlier three-class ice schemes, with biases within the observational uncertainties. Sensitivity experiments are conducted to examine the impact of recently upgraded microphysical processes on global hydrometeor distributions. Five processes dominate the global distributions of cloud ice and snow amount in long-term simulations: (1) allowing for ice supersaturation in the saturation adjustment, (2) three additional correction terms in the depositional growth of cloud ice to snow, (3) accounting for cloud ice fall speeds, (4) limiting cloud ice particle size, and (5) new size-mapping schemes for snow/graupel as functions of temperature and mixing ratio. Despite the cloud microphysics improvements, systematic errors associated with sub-grid processes and cyclic lateral boundaries in the embedded CRMs remain and will require future improvement.

  5. Acid rain: Microphysical model

    NASA Technical Reports Server (NTRS)

    Dingle, A. N.

    1980-01-01

    A microphysical model was used to simulate the case of a ground cloud without dilution by entrainment and without precipitation. The numerical integration techniques of the model are presented. The droplet size spectra versus time and the droplet molalities for each value of time are discussed.

  6. Evaluation of microphysics and precipitation-type frequencies in long-term three-dimensional cloud-resolving model simulations using passive and active microwave sensors from the TRMM satellite

    NASA Astrophysics Data System (ADS)

    Matsui, T.; Zeng, X.; Tao, W.; Lang, S.; Zhang, M.; Masunaga, H.

    2007-12-01

    With significant improvements in computational power over the last decades, cloud-resolving model (CRM) simulations can now be conducted on larger scales for longer time periods to better understand cloud- precipitation systems. However, even after the decadal development of CRMs, there are many uncertainties in cloud microphysics processes and cloud-precipitation structures due to the lack of routine observations. Therefore, we need to establish a practical CRM evaluation framework using frequent observations from satellites. This evaluation framework consists of i) multi-satellite simulators and ii) the construction of statistical composites that can be used to effectively evaluate cloud-precipitation systems. First, simulated cloud- precipitation structures and microphysics processes are converted to satellite-consistent radar reflectivity and microwave brightness temperature using microwave and radar simulators in the Satellite Data Simulator Unit (SDSU). Second, the CRM-computed and satellite-observed radar reflectivities and microwave brightness temperatures are used to construct two statistical composites. One combines TRMM (Tropical Rainfall Measuring Mission) PR (precipitation radar) 13.8-GHz radar echo-top heights and TRMM VIRS (visible/infrared scanner) 10.8-micron brightness temperatures. This composite categorizes precipitating clouds into shallow warm, cumulus congestus, deep stratiform, and deep convective clouds. The other composite combines multi- frequency TMI (TRMM microwave imager) brightness temperatures. The combination of low- and high-frequency channels reveals the performance of the model cloud microphysics in terms of liquid and ice precipitation amounts. In this study, long-term CRM simulations are performed using the Goddard Cumulus Ensemble (GCE) model for three cases: ARM TWP-ICE (Tropical Warm Pool International Cloud Experiment), SCSMEX (South China Sea Monsoon Experiment), and KWAJEX (Kwajalein Experiment). Results from the proposed

  7. The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-resolving Model Simulations

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.; Johnson, D.; Remer, L.

    2004-01-01

    Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, r d a U production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensembe1 (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and platelike), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e. 33 bins). 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 in the mid-latitude continent with different concentrations of CCN: a low "c1ean"concentration and a high "dirty" concentration. In addition, differences and similarities between bulk microphysics and spectral-bin microphysical schemes will be examined and discussed.

  8. The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.; Johnson, D.; Remer, L.

    2004-01-01

    Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensembel (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e. 33 bins). 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 in the mid-latitude continent with different concentrations of CCN: a low "c1ean"concentration and a high "dirty" concentration. In addition, differences and similarities between bulk microphysics and spectral-bin microphysical schemes will be examined and discussed.

  9. Performance of the Goddard Multiscale Modeling Framework with Goddard Ice Microphysical Schemes

    NASA Technical Reports Server (NTRS)

    Chern, Jiun-Dar; Tao, Wei-Kuo; Lang, Stephen E.; Matsui, Toshihisa; Li, J.-L.; Mohr, Karen I.; Skofronick-Jackson, Gail M.; Peters-Lidard, Christa D.

    2016-01-01

    The multiscale modeling framework (MMF), which replaces traditional cloud parameterizations with cloud-resolving models (CRMs) within a host atmospheric general circulation model (GCM), has become a new approach for climate modeling. The embedded CRMs make it possible to apply CRM-based cloud microphysics directly within a GCM. However, most such schemes have never been tested in a global environment for long-term climate simulation. The benefits of using an MMF to evaluate rigorously and improve microphysics schemes are here demonstrated. Four one-moment microphysical schemes are implemented into the Goddard MMF and their results validated against three CloudSat/CALIPSO cloud ice products and other satellite data. The new four-class (cloud ice, snow, graupel, and frozen drops/hail) ice scheme produces a better overall spatial distribution of cloud ice amount, total cloud fractions, net radiation, and total cloud radiative forcing than earlier three-class ice schemes, with biases within the observational uncertainties. Sensitivity experiments are conducted to examine the impact of recently upgraded microphysical processes on global hydrometeor distributions. Five processes dominate the global distributions of cloud ice and snow amount in long-term simulations: (1) allowing for ice supersaturation in the saturation adjustment, (2) three additional correction terms in the depositional growth of cloud ice to snow, (3) accounting for cloud ice fall speeds, (4) limiting cloud ice particle size, and (5) new size-mapping schemes for snow and graupel. Despite the cloud microphysics improvements, systematic errors associated with subgrid processes, cyclic lateral boundaries in the embedded CRMs, and momentum transport remain and will require future improvement.

  10. Performance of the Goddard multiscale modeling framework with Goddard ice microphysical schemes

    NASA Astrophysics Data System (ADS)

    Chern, Jiun-Dar; Tao, Wei-Kuo; Lang, Stephen E.; Matsui, Toshihisa; Li, J.-L. F.; Mohr, Karen I.; Skofronick-Jackson, Gail M.; Peters-Lidard, Christa D.

    2016-03-01

    The multiscale modeling framework (MMF), which replaces traditional cloud parameterizations with cloud-resolving models (CRMs) within a host atmospheric general circulation model (GCM), has become a new approach for climate modeling. The embedded CRMs make it possible to apply CRM-based cloud microphysics directly within a GCM. However, most such schemes have never been tested in a global environment for long-term climate simulation. The benefits of using an MMF to evaluate rigorously and improve microphysics schemes are here demonstrated. Four one-moment microphysical schemes are implemented into the Goddard MMF and their results validated against three CloudSat/CALIPSO cloud ice products and other satellite data. The new four-class (cloud ice, snow, graupel, and frozen drops/hail) ice scheme produces a better overall spatial distribution of cloud ice amount, total cloud fractions, net radiation, and total cloud radiative forcing than earlier three-class ice schemes, with biases within the observational uncertainties. Sensitivity experiments are conducted to examine the impact of recently upgraded microphysical processes on global hydrometeor distributions. Five processes dominate the global distributions of cloud ice and snow amount in long-term simulations: (1) allowing for ice supersaturation in the saturation adjustment, (2) three additional correction terms in the depositional growth of cloud ice to snow, (3) accounting for cloud ice fall speeds, (4) limiting cloud ice particle size, and (5) new size-mapping schemes for snow and graupel. Despite the cloud microphysics improvements, systematic errors associated with subgrid processes, cyclic lateral boundaries in the embedded CRMs, and momentum transport remain and will require future improvement.

  11. Analysis of TRMM Microphysical Measurements: Tropical Rainfall Measuring Mission (TRMM)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    SPEC Incorporated participated in three of the four TRMM field campaigns (TEFLUN-A, TEFLUN-B and KWAJEX), installing and operating a cloud particle imager (CPI) and a high volume precipitation spectrometer (HVPS) on the SPEC Learjet in TEFLUN-A, the University of North Dakota Citation in TEFLUN-B and KWAJEX, and a CPI on the NASA DC-8 in KWAJEX. This report presents and discusses new software tools and algorithms that were developed to analyze microphysical data collected during these field campaigns, as well as scientific interpretations of the data themselves. Software algorithms were developed to improve the analysis of microphysical measurements collected by the TRMM aircraft during the field campaigns. Particular attention was paid to developing and/or improving algorithms used to compute particle size distributions and ice water content. Software was also developed in support of production of the TRMM Common Microphysical Product (CMP) data files. CMP data files for TEFLUN-A field campaign were produced and submitted to the DAAC. Typical microphysical properties of convective and stratiform regions from TEFLUN-A and KWAJEX clouds were produced. In general, it was found that in the upper cloud region near -20 to -25 C, stratiform clouds contain very high (greater than 1 per cubic centimeter) concentrations of small ice particles, which are suspected to be a residual from homogeneous freezing and sedimentation of small drops in a convective updraft. In the upper cloud region near -20 to -25 C, convective clouds contain aggregates, which are not found lower in the cloud. Stratiform clouds contain aggregates at all levels, with the majority in the lowest levels. Convective cloud regions contain much higher LWC and drop concentrations than stratiform regions at all levels, and higher LWC in the middle and upper regions. Stratiform clouds contain higher IWC than convective clouds only at the lowest level. Irregular shaped ice particles are found in very high

  12. Effects of nuclei concentrations, ice nucleation mechanisms and crystal habits on the dynamics and microphysics of Arctic mixed-phase clouds

    NASA Astrophysics Data System (ADS)

    Komurcu, Muge

    There is a significant warming in the Arctic that is evident in both observations and in the future climate predictions. The Arctic warming is greater than any other region on Earth, however, the degree of warming is inconsistent among the climate models even for the same emission scenarios. Clouds, especially low-level clouds, are a prevailing feature of the Arctic atmosphere. They strongly affect the surface radiative and energy budgets, which make them a key component of the Arctic climate. Recent inter-comparison studies using regional climate models show that models are incapable of reproducing the supercooled liquid water observed in clouds during the cold season. Large discrepancies exist in the partitioning of phase between ice and liquid water among different models. It is currently thought that these discrepancies are due to the uncertainties in ice nuclei concentrations, ice nucleation, and ice crystal habits used in models. Predicting these physical processes controls the partitioning between liquid and ice, and hence the impact of mixed-phase clouds on the surface energy budget. There is a need to improve model cloud predictions in the Arctic, however, the microphysical uncertainties mentioned above are tied directly to the cloud dynamics that help maintain persistent mixed-phase clouds. Therefore, this dissertation analyzes and inter-compares the impacts of different ice nuclei concentrations, ice nucleation mechanisms and ice crystal habits on mixedphase cloud dynamics. Separate simulations using different ice nuclei concentrations, ice nucleation mechanisms, and crystal habits are performed. It is found that the choice of habits in models alters the water paths and cloud dynamics strongly. Next, the relative importance of and interactions among the processes that influence the dynamics of the cloud, such as the radiative cooling at cloud top, and the ice precipitation induced cloudbase stabilization are investigated. To examine these processes in

  13. Measurement of Aerosol and Cloud Particles with PACS and HARP Hyperangular Imaging Polarimeters

    NASA Astrophysics Data System (ADS)

    Martins, J.; Fernandez-Borda, R.; Remer, L. A.; Sparr, L.; Buczkowski, S.; Munchak, L. A.

    2013-12-01

    PACS is new hyper-angular imaging polarimeter for aeorosol and cloud measurerents designed to meet the requirements of the proposed ACE decadal survey mission. The full PACS system consists of three wide field of view (110deg cross track) telescopes covering the UV, VNIR, and SWIR spectral ranges with angular coverage between +55 deg forward to -55deg backwards. The angular density can be selected to cover up to 100 different viewing angles at selected wavelengths. PACS_VNIR is a prototype airborne instrument designed to demonstrate PACS capability by deploying just one of the three wavelength modules of the full PACS. With wavelengths at 470, 550, 675, 760 and 875nm, PACS_VNIR flew for the first time during the PODEX experiment in January/February 2013 aboard the NASA ER-2 aircraft. PACS SWIR (1.64, 1.88, 2.1, and 2.25um) is currently under construction and should be operational in the lab by Fall/2013. PACS_ UV has been fully designed, but is not yet under construction. During the PODEX flights PACS_VNIR collected data for aerosol and clouds over variable surface types including, water, vegetation, urban areas, and snow. The data is currently being calibrated, geolocated and prepared for the inversion of geophysical parameters including water cloud size distribution and aerosol microphysical parameters. The large density of angles in PACS allows for the characterization of cloudbow features in relatively high spatial resolution in a pixel to pixel basis. This avoids the need for assumptions of cloud homogeneity over any distance. The hyperangle capability also allows detailed observation of cloud ice particles, surface characterization, and optimum selection of the number of angles desired for aerosol retrievals. The aerosol and cloud retrieval algorithms under development for the retrieval of particle microphysical properties from the PACS data will be discussed in this presentation. As an extension of the PACS concept we are currently developing the HARP (Hyper

  14. Modelling of contrail cirrus in a climate model: microphysical and optical properties

    NASA Astrophysics Data System (ADS)

    Bock, Lisa; Burkhardt, Ulrike; Kärcher, Bernd

    2014-05-01

    Contrail cirrus is the largest climate forcing component of aviation. Current estimates using a climate model rely on an approach parameterizing contrail microphysical processes based on ice water content alone. A microphysical two-moment-scheme (prognostic ice water content and ice particle number density) allows a more realistic representation of the microphysical and optical properties of contrail cirrus. That implies a better estimate of their radiative forcing and its sensitivity to changes in ice particle number concentration. We modify the cloud scheme in ECHAM5-HAM by changing the nucleation parameterization consistent with a fractional coverage. Afterwards the contrail cirrus module (Burkhardt and Kärcher, 2009) developed for one-moment microphysics is implemented in ECHAM5 and extended with a two-moment-scheme. An exact description of contrail cirrus volume is important for a realistic characterization of the microphysical and optical properties of contrail cirrus. Therefore, parameterizations for the growth of the contrail cirrus volume due to diffusion, wind shear and sedimentation are implemented. The fields of ice water content, ice particle number concentration, cloud coverage and the frequency of ice supersaturated regions are validated and microphysical and optical properties of contrail cirrus are studied. In an idealized experiment the relative importance of microphysical processes is evaluated. As a consequence of the improved parameterization of microphysical processes the optical depth of contrail cirrus is higher in regions with high flight density than it was in earlier studies (Burkhardt and Kärcher, 2011) due to the high ice particle number concentrations on the main flight routes. Microphysical and optical properties of contrail cirrus turn out to be strongly dependent on the initial ice particle number. Reducing the latter leads to an overall decrease of contrail cirrus optical depth and visible coverage.

  15. Impact of cloud microphysics and cumulus parameterization on simulation of heavy rainfall event during 7-9 October 2007 over Bangladesh

    NASA Astrophysics Data System (ADS)

    Mahbub Alam, M.

    2014-03-01

    In the present study, the Advanced Research WRF (ARW) version 3.2.1 has been used to simulate the heavy rainfall event that occurred between 7 and 9 October 2007 in the southern part of Bangladesh. Weather Research and Forecast (WRF-ARW version) modelling system with six different microphysics (MP) schemes and two different cumulus parameterization (CP) schemes in a nested configuration was chosen for simulating the event. The model domains consist of outer and inner domains having 9 and 3 km horizontal resolution, respectively with 28 vertical sigma levels. The impacts of cloud microphysical processes by means of precipitation, wind and reflectivity, kinematic and thermodynamic characteristics of the event have been studied. Sensitivity experiments have been conducted with the WRF model to test the impact of microphysical and cumulus parameterization schemes in capturing the extreme weather event. NCEP FNL data were used for the initial and boundary condition. The model ran for 72 h using initial data at 0000 UTC of 7 October 2007. The simulated rainfall shows that WSM6-KF combination gives better results for all combinations and after that Lin-KF combination. WSM3-KF has simulated, less area average rainfall out of all MP schemes that were coupled with KF scheme. The sharp peak of relative humidity up to 300 hPa has been simulated along the vertical line where maximum updraft has been found for all MPs coupled with KF and BMJ schemes. The simulated rain water and cloud water mixing ratio were maximum at the position where the vertical velocity and reflectivity has also been maximum. The production of rain water mixing ratio depends on MP schemes as well as CP schemes. Rainfall depends on rain water mixing ratio between 950 and 500 hPa. Rain water mixing ratio above 500 hPa level has no effect on surface rain.

  16. Analysis of In situ Observations of Cloud Microphysics from M-PACE Final Report, DOE Grant Agreement No. DE-FG02-06ER64168

    SciTech Connect

    Michael R. Poellot

    2009-01-09

    This report summarizes the findings and accomplishments of work performed under DOE Grant Agreement No. DE-FG02-06ER64168. The focus of the work was the analysis of in situ observations collected by the University of North Dakota Citation research aircraft during the Mixed-Phase Arctic Cloud Experiment (M-PACE). This project was conducted in 2004 along the North Slope of Alaska. The objectives of the research were: to characterize certain microphysical properties of clouds sampled during M-PACE, including spatial variability, precipitation formation, ice multiplication; to examine instrument performance and certain data processing algorithms; and to collaborate with other M-PACE investigators on case study analyses. A summary of the findings of the first two objectives is given here in parts 1 and 2; full results are contained in reports listed in part 3 of this report. The collaborative efforts are described in the publications listed in part 3.

  17. Why do particle clouds generate electric charges?

    NASA Astrophysics Data System (ADS)

    Pähtz, T.; Herrmann, H. J.; Shinbrot, T.

    2010-05-01

    Grains in desert sandstorms spontaneously generate strong electrical charges; likewise volcanic dust plumes produce spectacular lightning displays. Charged particle clouds also cause devastating explosions in food, drug and coal processing industries. Despite the wide-ranging importance of granular charging in both nature and industry, even the simplest aspects of its causes remain elusive, because it is difficult to understand how inert grains in contact with little more than other inert grains can generate the large charges observed. Here, we present a simple yet predictive explanation for the charging of granular materials in collisional flows. We argue from very basic considerations that charge transfer can be expected in collisions of identical dielectric grains in the presence of an electric field, and we confirm the model's predictions using discrete-element simulations and a tabletop granular experiment.

  18. Incorporation of New Convective Ice Microphysics into the NASA GISS GCM and Impacts on Cloud Ice Water Path (IWP) Simulation

    NASA Technical Reports Server (NTRS)

    Elsaesser, Greg; Del Genio, Anthony

    2015-01-01

    The CMIP5 configurations of the GISS Model-E2 GCM simulated a mid- and high latitude ice IWP that decreased by 50 relative to that simulated for CMIP3 (Jiang et al. 2012; JGR). Tropical IWP increased by 15 in CMIP5. While the tropical IWP was still within the published upper-bounds of IWP uncertainty derived using NASA A-Train satellite observations, it was found that the upper troposphere (200 mb) ice water content (IWC) exceeded the published upper-bound by a factor of 2. This was largely driven by IWC in deep-convecting regions of the tropics.Recent advances in the model-E2 convective parameterization have been found to have a substantial impact on tropical IWC. These advances include the development of both a cold pool parameterization (Del Genio et al. 2015) and new convective ice parameterization. In this presentation, we focus on the new parameterization of convective cloud ice that was developed using data from the NASA TC4 Mission. Ice particle terminal velocity formulations now include information from a number of NASA field campaigns. The new parameterization predicts both an ice water mass weighted-average particle diameter and a particle cross sectional area weighted-average size diameter as a function of temperature and ice water content. By assuming a gamma-distribution functional form for the particle size distribution, these two diameter estimates are all that are needed to explicitly predict the distribution of ice particles as a function of particle diameter.GCM simulations with the improved convective parameterization yield a 50 decrease in upper tropospheric IWC, bringing the tropical and global mean IWP climatologies into even closer agreement with the A-Train satellite observation best estimates.

  19. The role of organic compounds in cloud formation: Relative importance of entrainment, co-condensation and particle-phase properties

    NASA Astrophysics Data System (ADS)

    Lowe, Samuel; Partridge, Daniel; Topping, David; Riipinen, Ilona

    2016-04-01

    The organic fraction of atmospheric aerosols is widely acknowledged to affect the cloud nucleating potential of aerosols. Cloud droplet formation through activation of non-volatile CCN is considered to be relatively well understood, however, there are fewer systematic studies on the activation of aerosols containing semi-volatile organic compounds that co-condense alongside water vapour, thus enhancing CCN activity. Although the significance of co-condensation of organic vapours for cloud droplet number concentration predictions has recently been identified, it remains uncertain how this process may interact with atmospheric dynamics. In addition to co-condensation of existing in-cloud material, additional semi-volatile mass can be entrained from the surrounding environment. Reduced cloud droplet number concentrations are expected as the parcel is diluted with clean air; however, additional soluble mass in the particle phase promotes droplet activation. The extent of increased droplet activation due to co-condensation relies also on the physiochemical properties of the organic compounds, as seen in several other phase partitioning sensitivity studies. In this work we study the simultaneous impact of entrainment and co-condensation, the relative importance of these two processes at different atmospheric conditions, their interactions with each other, and the particle-phase chemistry in terms of cloud microphysical properties and their parametric sensitivities. To assess the importance of the entrainment of semi-volatile materials as compared with their co-condensation and chemical properties, a pseudo-adiabatic cloud parcel model with a detailed description of bin microphysics is employed. We have added the co-condensation process to the model such that it is coupled with the parametric entrainment representation. The effects of entrainment and co-condensation are benchmarked independently and simultaneously against a control simulation. Furthermore, we probe the

  20. Individual aerosol particles in ambient and updraft conditions below convective cloud bases in the Oman mountain region

    NASA Astrophysics Data System (ADS)

    Semeniuk, T. A.; Bruintjes, R. T.; Salazar, V.; Breed, D. W.; Jensen, T. L.; Buseck, P. R.

    2014-03-01

    An airborne study of cloud microphysics provided an opportunity to collect aerosol particles in ambient and updraft conditions of natural convection systems for transmission electron microscopy (TEM). Particles were collected simultaneously on lacey carbon and calcium-coated carbon (Ca-C) TEM grids, providing information on particle morphology and chemistry and a unique record of the particle's physical state on impact. In total, 22 particle categories were identified, including single, coated, aggregate, and droplet types. The fine fraction comprised up to 90% mixed cation sulfate (MCS) droplets, while the coarse fraction comprised up to 80% mineral-containing aggregates. Insoluble (dry), partially soluble (wet), and fully soluble particles (droplets) were recorded on Ca-C grids. Dry particles were typically silicate grains; wet particles were mineral aggregates with chloride, nitrate, or sulfate components; and droplets were mainly aqueous NaCl and MCS. Higher numbers of droplets were present in updrafts (80% relative humidity (RH)) compared with ambient conditions (60% RH), and almost all particles activated at cloud base (100% RH). Greatest changes in size and shape were observed in NaCl-containing aggregates (>0.3 µm diameter) along updraft trajectories. Their abundance was associated with high numbers of cloud condensation nuclei (CCN) and cloud droplets, as well as large droplet sizes in updrafts. Thus, compositional dependence was observed in activation behavior recorded for coarse and fine fractions. Soluble salts from local pollution and natural sources clearly affected aerosol-cloud interactions, enhancing the spectrum of particles forming CCN and by forming giant CCN from aggregates, thus, making cloud seeding with hygroscopic flares ineffective in this region.

  1. A model for particle microphysics, turbulent mixing, and radiative transfer in the stratocumulus-topped marine boundary layer and comparisons with measurements

    SciTech Connect

    Ackerman, A.S.; Hobbs, P.V.; Toon, O.B.

    1995-04-15

    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 collection efficiencies for droplets <30-{mu}m radius, and the value of the accommodation coefficient for condensational droplet growth, have noticeable effects on cloud properties. The divergence of the horizontal wind also has a significant effect on a 12-h model simulation of cloud structure. Conclusions drawn from the model are tentative because of the limitations of the 1D model framework. A principal simplification is that the model assumes horizontal homogeneity, and, therefore, does not resolve updrafts and downdrafts. Likely consequences of this simplification include overprediction of the growth of droplets by condensation in the upper region of the cloud, underprediction of droplet condensational growth in the lower region of the cloud, and underprediction of peak supersaturations. 64 refs., 11 figs., 3 tabs.

  2. New Particle Formation in and Around Ice Clouds

    NASA Astrophysics Data System (ADS)

    Axisa, D.; Reeves, J. M.; Wilson, J. C.; Lawson, P.; Sargent, M. R.; Sayres, D. S.; Smith, J. B.; Schiller, C.; Kraemer, M.

    2012-12-01

    The MACPEX mission permitted observation of aerosol size distributions in the 4 to 1000 nm diameter range, cloud particles and water vapor in and around clouds in the mid-latitude upper troposphere. The NMASS consists of 5 condensation particle counters (cpcs) operating in parallel. The 5 cpcs have lower detection limits of approximately 4 nm, 8 nm, 16 nm, 32 nm and 50 nm. The FCAS measures the optical size of particles in the 100 nm to 1000 nm range. The data from these instruments are combined to provide size distributions from 4 to 1000 nm. Size distributions that show a local maximum in the smallest size range are evidence for recent new particle formation since the lifetime of particles in this size range is short due to coagulation. Size distributions showing evidence of new particle formation were observed inside and near clouds in the altitude range from 10 to 14 km. The cloud particles in these high clouds are expected to be ice. Care was taken to avoid interpreting shattering of ice on the aerosol inlets as new particles. The size distributions showing new particle formation are contrasted with size distributions that do not show new particle formation in and out of the clouds. Temperature, relative humidity and trace gas abundances in air parcels exhibiting new particle formation are contrasted with those in air parcels not showing new particle formation.

  3. Parameterization of effective ice particle size for high-latitude clouds

    NASA Astrophysics Data System (ADS)

    Boudala, Faisal S.; Isaac, George A.; Fu, Qiang; Cober, Stewart G.

    2002-08-01

    A parameterization has been developed for mean effective size Dge in terms of ice water content (IWC) and temperature using in situ measurements of ice crystal spectra, cloud particle shapes and particle cross-sectional area A from four research projects conducted in latitudes north of 45° N. The cloud microphysical measurements were made using PMS 2D optical probes, a PMS forward scattering spectrometer probe (FSSP), and Nevzorov total water and liquid water content probes. The IWCs derived from particle spectra using three different methods were compared with IWC measured with the Nevzorov probe (IWCNev). The contribution of small particles to the total mass was estimated by integrating a gamma distribution function that was fitted to match the measured FSSP concentrations. The Dge was calculated from the derived IWC and total cross-sectional area per unit volume Ac. This analysis indicates that there are significant differences among the schemes used to derive the IWC. It was found that the IWC derived based on the Cunningham scheme and IWCNev have the highest correlation: r2 = 0.78. After considering small particles, the derived IWC almost matched the IWCNev. The average estimated contribution of small particles to the Ac was 43%. The average estimated contribution of small particles to the total IWC, however, was 20%. Since Dge is directly proportional to the ratio IWC/Ac, the addition of small particles reduced the derived Dge considerably. The largest changes in Dge associated with small particles, however, occur at the coldest temperature and at low IWC, reaching up to 45% for temperatures less than -25° C. Generally, Dge and IWC increase with increasing temperature. Good agreement between the parameterized Dge and derived Dge from measurements were found when small particles were included.

  4. Microphysical And Macrophysical Characteristics Of Non-Precipitating Morning Shallow Clouds In Central Amazonia Using One-Year Of Data From GOAMAZON 2014/15 Experiment

    NASA Astrophysics Data System (ADS)

    Pauliquevis, T.; Barbosa, H. M.; Rosario, N. M. E. D.; Rizzo, L. V.; Correia, A. L.; Adams, D. K.; Calheiros, A. J. P.; Alves, C. F.

    2015-12-01

    Shallow cumulus cloud fields in Amazonia are typical of the morning hours. They play a critical role in the mean observed diurnal cycle of precipitation in the Amazon Basin, which is characterized by the occurrence of heavy precipitation events in the afternoon. Shallow clouds act both to reduce incident shortwave radiation at the surface and in the transport of humidity from the lowest portions of the troposphere to higher levels. These two processes are poorly represented in numerical models, but are critical in the transition to deep convection and associated precipitation. Numerical models have problems in properly representing shallow cumulus fields and their transition to deep precipitating convection, the net result of which is producing rainfall to early in the diurnal cycle. Due to their importance, detailed characterization of morning shallow clouds is critical for understanding the shallow-to-deep transition as well as providing for model validation purposes. In this study we report 16 month data of observations of shallow cumulus with respect to cloud cover (CC), cloud base height (CBH), liquid water path (LWP), precipitable water vapor (PWV) and GOES (Visible and IR)analysis. Results showed a consistent pattern of evolution in the cloud field throughout the morning period. After sunrise the cloud field starts to move from a random cloud field to an organized shallow clouds field. In fact, there is an absence of any pattern in CBH from 6LT to 7LT. Once some amount of radiation reaches the surface shallow convection is established around 8:00LT, when a mode of CBH at 100 m is established and rises to 900 m at noon. During this time interval, CC grows up to 50% (mean), however with significant variability and oscillations. With respect to microphysical properties, both LWP and PWV were remarkably stable for single mornings and for shallow clouds, with LWP/PWV ~ 6.10-4. All of these results are being compared with GOES observations of cloud fields (Visible

  5. Intercomparison of four cloud microphysics schemes in the Weather Research and Forecasting (WRF) model for the simulation of summer monsoon precipitation in the Langtang Valley, Himalayas

    NASA Astrophysics Data System (ADS)

    Orr, Andrew; Couttet, Margaux; Collier, Emily; Immerzeel, Walter

    2016-04-01

    Better understanding of regional-scale precipitation patterns in the Himalayan region, and how these are affecting snow and ice, is critically required to increase our knowledge of the impacts of climate change on glaciers and snowpacks. This study examines how 4 different cloud microphysical schemes (Thompson, Morrison, WRF Single-Moment 5-class (WSM5; which is the WRF default scheme), and WRF Double-Moment 6-class (WDM6)) simulated precipitation in the Langtang Valley, Himalayas during the summer monsoon in the Weather Research and Forecasting (WRF) model. The precipitation is simulated for a ten-day period during July 2012 at high spatial-resolution (1.1 km) so as to simulate the local conditions in great detail. The model results are validated through a comparison with precipitation and radiation measurements made at two observation sites located on the main Langtang Valley floor and the mountain slopes. Analysis of water vapour and hydrometeors from each of the 4 schemes are also investigated to elucidate the main microphysics processes. The results show that the choice of microphysics scheme has a strong influence on precipitation in the Langtang Valley, with the simulated precipitation exhibiting large inter-model differences and significantly different day-to-day variability compared to measurements. The inter-model differences in simulated radiation were less marked, although under cloudy conditions all schemes demonstrated a significant positive bias in incoming radiation. However, overall the Morrison scheme showed the best agreement in terms of both precipitation and radiation over the ten-day period, while the poorest performing scheme is WDM6. Analysis of microphysics outputs suggested that 'cold-rain processes' is a key precipitation formation mechanism. The good performance of the Morrison scheme is consistent with its double-moment prediction of every ice-phase hydrometeor, which is ideally suited to represent this mechanism. By contrast, WDM6 is

  6. Interactions of mineral dust with pollution and clouds: An individual-particle TEM study of atmospheric aerosol from Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Pósfai, Mihály; Axisa, Duncan; Tompa, Éva; Freney, Evelyn; Bruintjes, Roelof; Buseck, Peter R.

    2013-03-01

    Aerosol particles from desert dust interact with clouds and influence climate on regional and global scales. The Riyadh (Saudi Arabia) aerosol campaign was initiated to study the effects of dust particles on cloud droplet nucleation and cloud properties. Here we report the results of individual-particle studies of samples that were collected from an aircraft in April 2007. We used analytical transmission electron microscopy, including energy-dispersive X-ray spectrometry, electron diffraction, and imaging techniques for the morphological, chemical, and structural characterization of the particles. Dust storms and regional background conditions were encountered during four days of sampling. Under dusty conditions, the coarse (supermicrometer) fraction resembles freshly crushed rock. The particles are almost exclusively mineral dust grains and include common rock-forming minerals, among which clay minerals, particularly smectites, are most abundant. Unaltered calcite grains also occur, indicating no significant atmospheric processing. The particles have no visible coatings but some contain traces of sulfur. The fine (submicrometer) fraction is dominated by particles of anthropogenic origin, primarily ammonium sulfate (with variable organic coating and some with soot inclusions) and combustion-derived particles (mostly soot). In addition, submicrometer, iron-bearing clay particles also occur, many of which are internally mixed with ammonium sulfate, soot, or both. We studied the relationships between the properties of the aerosol and the droplet microphysics of cumulus clouds that formed above the aerosol layer. Under dusty conditions, when a large concentration of coarse-fraction mineral particles was in the aerosol, cloud drop concentrations were lower and droplet diameters larger than under regional background conditions, when the aerosol was dominated by submicrometer sulfate particles.

  7. Tests of WRF Microphysics in GFS

    NASA Astrophysics Data System (ADS)

    Sun, R.; Han, J.

    2014-12-01

    Zhao and Carr microphysics scheme has been implemented into the NCEP Global Forecasting System (GFS) for many years. It predicts total cloud condensate (cloud water or ice). The scheme has significantly improved the forecast skills compared with its previous diagnostic cloud scheme. However, it has become too simple in several aspects as the computing power and resolution increase. Many microphysical processes are simplified or neglected for computing efficiency. Precipitation is diagnosed and falls to the surface instantaneously. Studies have shown that more sophisticated microphysics schemes generally give better results compared with observations. We are testing several sophisticated microphysics schemes from the Weather Research and Forecasting Model (WRF) in the GFS. These schemes have more cloud species and more physically-based parameterized processes. We will adjust or modify the schemes for the GFS. Partial cloud and cloud overlapping will be added to these schemes. The comparison will be focus on the precipitation skills and cloud properties and their effects.

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

    NASA Astrophysics Data System (ADS)

    Krämer, Martina

    2016-04-01

    Numerous airborne field campaigns were per