DOE Office of Scientific and Technical Information (OSTI.GOV)

Donner, Leo J.; O'Brien, Travis A.; Rieger, Daniel

Both climate forcing and climate sensitivity persist as stubborn uncertainties limiting the extent to which climate models can provide actionable scientific scenarios for climate change. A key, explicit control on cloud-aerosol interactions, the largest uncertainty in climate forcing, is the vertical velocity of cloud-scale updrafts. Model-based studies of climate sensitivity indicate that convective entrainment, which is closely related to updraft speeds, is an important control on climate sensitivity. Updraft vertical velocities also drive many physical processes essential to numerical weather prediction. Vertical velocities and their role in atmospheric physical processes have been given very limited attention in models for climatemore » and numerical weather prediction. The relevant physical scales range down to tens of meters and are thus frequently sub-grid and require parameterization. Many state-of-science convection parameterizations provide mass fluxes without specifying vertical velocities, and parameterizations which do provide vertical velocities have been subject to limited evaluation against what have until recently been scant observations. Atmospheric observations imply that the distribution of vertical velocities depends on the areas over which the vertical velocities are averaged. Distributions of vertical velocities in climate models may capture this behavior, but it has not been accounted for when parameterizing cloud and precipitation processes in current models. New observations of convective vertical velocities offer a potentially promising path toward developing process-level cloud models and parameterizations for climate and numerical weather prediction. Taking account of scale-dependence of resolved vertical velocities offers a path to matching cloud-scale physical processes and their driving dynamics more realistically, with a prospect of reduced uncertainty in both climate forcing and sensitivity.« less

The Cloud Top Distribution and Diurnal Variation of Clouds Over East Asia: Preliminary Results From Advanced Himawari Imager

NASA Astrophysics Data System (ADS)

Chen, Dandan; Guo, Jianping; Wang, Hongqing; Li, Jian; Min, Min; Zhao, Wenhui; Yao, Dan

2018-04-01

Clouds, as one of the most uncertain factors in climate system, have been intensively studied as satellites with advanced instruments emerged in recent years. However, few studies examine the vertical distributions of cloud top and their temporal variations over East Asia based on geostationary satellite data. In this study, the vertical structures of cloud top and its diurnal variations in summer of 2016 are analyzed using the Advanced Himawari Imager/Himawari-8 cloud products. Results show that clouds occur most frequently over the southern Tibetan Plateau and the Bay of Bengal. We find a steep gradient of cloud occurrence frequency extending from southwest to northeast China and low-value centers over the eastern Pacific and the Inner Mongolia Plateau. The vertical structures of cloud top are highly dependent on latitude, in addition to the nonnegligible roles of both terrain and land-sea thermal contrast. In terms of the diurnal cycle, clouds tend to occur more often in the afternoon, peaking around 1700 local time over land and ocean. The amplitude of cloud diurnal variation over ocean is much smaller than that over land, and complex terrain tends to be linked to larger amplitude. In vertical, the diurnal cycle of cloud frequency exhibits bimodal pattern over both land and ocean. The high-level peaks occur at almost the same altitude over land and ocean. In contrast, the low-level peaks over ocean mainly reside in the boundary layer, much lower than those over land, which could be indicative of the frequent occurrence of marine boundary layer clouds.

Use of In Situ Cloud Condensation Nuclei, Extinction, and Aerosol Size Distribution Measurements to Test a Method for Retrieving Cloud Condensation Nuclei Profiles From Surface Measurements

NASA Technical Reports Server (NTRS)

Ghan, Stephen J.; Rissman, Tracey A.; Ellman, Robert; Ferrare, Richard A.; Turner, David; Flynn, Connor; Wang, Jian; Ogren, John; Hudson, James; Jonsson, Haflidi H.;

Verification of NWP Cloud Properties using A-Train Satellite Observations

NASA Astrophysics Data System (ADS)

Kucera, P. A.; Weeks, C.; Wolff, C.; Bullock, R.; Brown, B.

2011-12-01

Recently, the NCAR Model Evaluation Tools (MET) has been enhanced to incorporate satellite observations for the verification of Numerical Weather Prediction (NWP) cloud products. We have developed tools that match fields spatially (both in the vertical and horizontal dimensions) to compare NWP products with satellite observations. These matched fields provide diagnostic evaluation of cloud macro attributes such as vertical distribution of clouds, cloud top height, and the spatial and seasonal distribution of cloud fields. For this research study, we have focused on using CloudSat, CALIPSO, and MODIS observations to evaluate cloud fields for a variety of NWP fields and derived products. We have selected cases ranging from large, mid-latitude synoptic systems to well-organized tropical cyclones. For each case, we matched the observed cloud field with gridded model and/or derived product fields. CloudSat and CALIPSO observations and model fields were matched and compared in the vertical along the orbit track. MODIS data and model fields were matched and compared in the horizontal. We then use MET to compute the verification statistics to quantify the performance of the models in representing the cloud fields. In this presentation we will give a summary of our comparison and show verification results for both synoptic and tropical cyclone cases.

MPL-net at ARM Sites

NASA Technical Reports Server (NTRS)

Spinhirne, J. D.; Welton, E. J.; Campbell, J. R.; Berkoff, T. A.; Starr, David OC. (Technical Monitor)

2002-01-01

The NASA MPL-net project goal is consistent data products of the vertical distribution of clouds and aerosol from globally distributed lidar observation sites. The four ARM micro pulse lidars are a basis of the network to consist of over twelve sites. The science objective is ground truth for global satellite retrievals and accurate vertical distribution information in combination with surface radiation measurements for aerosol and cloud models. The project involves improvement in instruments and data processing and cooperation with ARM and other partners.

Formation of Silicate and Titanium Clouds on Hot Jupiters

NASA Astrophysics Data System (ADS)

Powell, Diana; Zhang, Xi; Gao, Peter; Parmentier, Vivien

2018-06-01

We present the first application of a bin-scheme microphysical and vertical transport model to determine the size distribution of titanium and silicate cloud particles in the atmospheres of hot Jupiters. We predict particle size distributions from first principles for a grid of planets at four representative equatorial longitudes, and investigate how observed cloud properties depend on the atmospheric thermal structure and vertical mixing. The predicted size distributions are frequently bimodal and irregular in shape. There is a negative correlation between the total cloud mass and equilibrium temperature as well as a positive correlation between the total cloud mass and atmospheric mixing. The cloud properties on the east and west limbs show distinct differences that increase with increasing equilibrium temperature. Cloud opacities are roughly constant across a broad wavelength range, with the exception of features in the mid-infrared. Forward-scattering is found to be important across the same wavelength range. Using the fully resolved size distribution of cloud particles as opposed to a mean particle size has a distinct impact on the resultant cloud opacities. The particle size that contributes the most to the cloud opacity depends strongly on the cloud particle size distribution. We predict that it is unlikely that silicate or titanium clouds are responsible for the optical Rayleigh scattering slope seen in many hot Jupiters. We suggest that cloud opacities in emission may serve as sensitive tracers of the thermal state of a planet’s deep interior through the existence or lack of a cold trap in the deep atmosphere.

A 10-Year Climatology of Cloud Cover and Vertical Distribution Derived from Both Surface and GOES Observations Over the DOE ARM SGP Site

NASA Technical Reports Server (NTRS)

Xi, Baike; Dong, Xiquan; Minnis, P.; Khaiyer, M.

2010-01-01

Analysis of a decade of ARM radar-lidar and GOES observations at the SGP site reveal that 0.5 and 4-hr averages of the surface cloud fraction correspond closely to 0.5deg and 2.5deg averages of GOES cloudiness, respectively. The long-term averaged surface and GOES cloud fractions agree to within 0.5%. Cloud frequency increases and cloud amount decreases as the temporal and spatial averaging scales increase. Clouds occurred most often during winter and spring. Single-layered clouds account for 61.5% of the total cloud frequency. There are distinct bimodal vertical distributions of clouds with a lower peak around 1 km and an upper one that varies from 7.5 to 10.8 km between winter and summer, respectively. The frequency of occurrence for nighttime GOES high-cloud tops agree well with the surface observations, but are underestimated during the day.

In situ observations of snow particle size distributions over a cold frontal rainband within an extratropical cyclone

NASA Astrophysics Data System (ADS)

Yang, Jiefan; Lei, Hengchi

2016-02-01

Cloud microphysical properties of a mixed phase cloud generated by a typical extratropical cyclone in the Tongliao area, Inner Mongolia on 3 May 2014, are analyzed primarily using in situ flight observation data. This study is mainly focused on ice crystal concentration, supercooled cloud water content, and vertical distributions of fit parameters of snow particle size distributions (PSDs). The results showed several discrepancies of microphysical properties obtained during two penetrations. During penetration within precipitating cloud, the maximum ice particle concentration, liquid water content, and ice water content were increased by a factor of 2-3 compared with their counterpart obtained during penetration of a nonprecipitating cloud. The heavy rimed and irregular ice crystals obtained by 2D imagery probe as well as vertical distributions of fitting parameters within precipitating cloud show that the ice particles grow during falling via riming and aggregation process, whereas the lightly rimed and pristine ice particles as well as fitting parameters within non-precipitating cloud indicate the domination of sublimation process. During the two cloud penetrations, the PSDs were generally better represented by gamma distributions than the exponential form in terms of the determining coefficient ( R 2). The correlations between parameters of exponential /gamma form within two penetrations showed no obvious differences compared with previous studies.

Climate Impacts of CALIPSO-Guided Corrections to Black Carbon Aerosol Vertical Distributions in a Global Climate Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kovilakam, Mahesh; Mahajan, Salil; Saravanan, R.

Here, we alleviate the bias in the tropospheric vertical distribution of black carbon aerosols (BC) in the Community Atmosphere Model (CAM4) using the Cloud-Aerosol and Infrared Pathfinder Satellite Observations (CALIPSO)-derived vertical profiles. A suite of sensitivity experiments are conducted with 1x, 5x, and 10x the present-day model estimated BC concentration climatology, with (corrected, CC) and without (uncorrected, UC) CALIPSO-corrected BC vertical distribution. The globally averaged top of the atmosphere radiative flux perturbation of CC experiments is ~8–50% smaller compared to uncorrected (UC) BC experiments largely due to an increase in low-level clouds. The global average surface temperature increases, the globalmore » average precipitation decreases, and the ITCZ moves northward with the increase in BC radiative forcing, irrespective of the vertical distribution of BC. Further, tropical expansion metrics for the poleward extent of the Northern Hemisphere Hadley cell (HC) indicate that simulated HC expansion is not sensitive to existing model biases in BC vertical distribution.« less

Climate Impacts of CALIPSO-Guided Corrections to Black Carbon Aerosol Vertical Distributions in a Global Climate Model

DOE PAGES

Kovilakam, Mahesh; Mahajan, Salil; Saravanan, R.; ...

2017-09-13

Here, we alleviate the bias in the tropospheric vertical distribution of black carbon aerosols (BC) in the Community Atmosphere Model (CAM4) using the Cloud-Aerosol and Infrared Pathfinder Satellite Observations (CALIPSO)-derived vertical profiles. A suite of sensitivity experiments are conducted with 1x, 5x, and 10x the present-day model estimated BC concentration climatology, with (corrected, CC) and without (uncorrected, UC) CALIPSO-corrected BC vertical distribution. The globally averaged top of the atmosphere radiative flux perturbation of CC experiments is ~8–50% smaller compared to uncorrected (UC) BC experiments largely due to an increase in low-level clouds. The global average surface temperature increases, the globalmore » average precipitation decreases, and the ITCZ moves northward with the increase in BC radiative forcing, irrespective of the vertical distribution of BC. Further, tropical expansion metrics for the poleward extent of the Northern Hemisphere Hadley cell (HC) indicate that simulated HC expansion is not sensitive to existing model biases in BC vertical distribution.« less

Are Atmospheric Updrafts a Key to Unlocking Climate Forcing and Sensitivity?

DOE PAGES

Donner, Leo J.; O'Brien, Travis A.; Rieger, Daniel; ...

2016-06-08

Both climate forcing and climate sensitivity persist as stubborn uncertainties limiting the extent to which climate models can provide actionable scientific scenarios for climate change. A key, explicit control on cloud-aerosol interactions, the largest uncertainty in climate forcing, is the vertical velocity of cloud-scale updrafts. Model-based studies of climate sensitivity indicate that convective entrainment, which is closely related to updraft speeds, is an important control on climate sensitivity. Updraft vertical velocities also drive many physical processes essential to numerical weather prediction. Vertical velocities and their role in atmospheric physical processes have been given very limited attention in models for climatemore » and numerical weather prediction. The relevant physical scales range down to tens of meters and are thus frequently sub-grid and require parameterization. Many state-of-science convection parameterizations provide mass fluxes without specifying vertical velocities, and parameterizations which do provide vertical velocities have been subject to limited evaluation against what have until recently been scant observations. Atmospheric observations imply that the distribution of vertical velocities depends on the areas over which the vertical velocities are averaged. Distributions of vertical velocities in climate models may capture this behavior, but it has not been accounted for when parameterizing cloud and precipitation processes in current models. New observations of convective vertical velocities offer a potentially promising path toward developing process-level cloud models and parameterizations for climate and numerical weather prediction. Taking account of scale-dependence of resolved vertical velocities offers a path to matching cloud-scale physical processes and their driving dynamics more realistically, with a prospect of reduced uncertainty in both climate forcing and sensitivity.« less

Vertical distribution of clouds over Hampton, Virginia observed by lidar under the ECLIPS and FIRE ETO programs

NASA Technical Reports Server (NTRS)

Vaughan, M. A.; Winker, D. M.

1994-01-01

Intensive cloud lidar observations have been made by NASA Langley Research Center during the two observation phases of the ECLIPS project. Less intensive but longer term observations have been conducted as part of the FIRE extended time observation (ETO) program since 1987. We present a preliminary analysis of the vertical distribution of clouds based on these observations. A mean cirrus thickness of just under 1 km has been observed with a mean altitude of about 80 percent of the tropopause height. Based on the lidar data, cirrus coverage was estimated to be just under 20 percent, representing roughly 50 percent of all clouds studied. Cirrus was observed to have less seasonal variation than lower clouds. Mid-level clouds are found to occur primarily in association with frontal activity.

A method for estimating vertical distibution of the SAGE II opaque cloud frequency

NASA Technical Reports Server (NTRS)

Wang, Pi-Huan; Mccormick, M. Patrick; Minnis, Patrick; Kent, Geoffrey S.; Yue, Glenn K.; Skeens, Kristi M.

1995-01-01

A method is developed to infer the vertical distribution of the occurrence frequency of clouds that are opaque to the Stratospheric Aerosol and Gas Experiment (SAGE) II instrument. An application of the method to the 1986 SAGE II observations is included in this paper. The 1986 SAGE II results are compared with the 1952-1981 cloud climatology of Warren et al. (1986, 1988)

Vertical wind velocity measurements using a five-hole probe with remotely piloted aircraft to study aerosol-cloud interactions

NASA Astrophysics Data System (ADS)

Calmer, Radiance; Roberts, Gregory C.; Preissler, Jana; Sanchez, Kevin J.; Derrien, Solène; O'Dowd, Colin

2018-05-01

The importance of vertical wind velocities (in particular positive vertical wind velocities or updrafts) in atmospheric science has motivated the need to deploy multi-hole probes developed for manned aircraft in small remotely piloted aircraft (RPA). In atmospheric research, lightweight RPAs ( < 2.5 kg) are now able to accurately measure atmospheric wind vectors, even in a cloud, which provides essential observing tools for understanding aerosol-cloud interactions. The European project BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) focuses on these specific interactions. In particular, vertical wind velocity at cloud base is a key parameter for studying aerosol-cloud interactions. To measure the three components of wind, a RPA is equipped with a five-hole probe, pressure sensors, and an inertial navigation system (INS). The five-hole probe is calibrated on a multi-axis platform, and the probe-INS system is validated in a wind tunnel. Once mounted on a RPA, power spectral density (PSD) functions and turbulent kinetic energy (TKE) derived from the five-hole probe are compared with sonic anemometers on a meteorological mast. During a BACCHUS field campaign at Mace Head Atmospheric Research Station (Ireland), a fleet of RPAs was deployed to profile the atmosphere and complement ground-based and satellite observations of physical and chemical properties of aerosols, clouds, and meteorological state parameters. The five-hole probe was flown on straight-and-level legs to measure vertical wind velocities within clouds. The vertical velocity measurements from the RPA are validated with vertical velocities derived from a ground-based cloud radar by showing that both measurements yield model-simulated cloud droplet number concentrations within 10 %. The updraft velocity distributions illustrate distinct relationships between vertical cloud fields in different meteorological conditions.

Interpretation of multi-wavelength-retrieved cloud droplet effective radii in terms of cloud vertical inhomogeneity based on water cloud simulations using a spectral-bin microphysics cloud model

NASA Astrophysics Data System (ADS)

Matsui, T. N.; Suzuki, K.; Nakajima, T. Y.; Matsumae, Y.

2011-12-01

Clouds play an import role in energy balance and climate changes of the Earth. IPCC AR4, however, pointed out that cloud feedback is still the large source of uncertainty in climate estimates. In the recent decade, the new satellites with the active instruments (e.g. Cloudsat) represented a new epoch in earth observations. The active remote sensing is powerful for illustrating the vertical structures of clouds, but the passive remote sensing from satellite images also contribute to better understating of cloud system. For instance, Nakajima et al. (2010a) and Suzuki et al. (2010) illustrated transition of cloud growth, from cloud droplet to drizzle to rain, using the combine analysis of the cloud droplet size retrieved from passive images (MODIS) and the reflectivity profiles from Cloudsat. Furthermore, EarthCARE that is a new satellite launched years later is composed of not only the active but also passive instruments for the combined analysis. On the other hands, the methods to retrieve the advanced information of cloud properties are also required because many imagers have been operated and are now planned (e.g. GCOM-C/SGLI), and have the advantages such as wide observation width and more observation channels. Cloud droplet effective radius (CDR) and cloud optical thickness (COT) can be retrieved using a non-water-absorbing band (e.g. 0.86μm) and a water-absorbing band (1.6, 2.1, 3.7μm) of imagers under the assumptions such as the log-normal droplet size distribution and the plane-parallel cloud structure. However, the differences between three retrieved CDRs using 1.6, 2.1 or 3.7μm (R16, R21 and R37) are found in the satellite observations. Several studies pointed out that vertical/horizontal inhomogeneity of cloud structure, difference of penetration depth of water-absorbing bands, multi-modal droplet distribution and/or 3-D radiative transfer effect cause the CDR differences. In other words, the advanced information of clouds may lie hidden in the differences. Nakajima et al. (2010b) investigated the impact of the differences sensitivities to particle size and the penetration depth in an attempt to explain the CDR differences found in by using a simple two-layer cloud model with the bi-modal size distribution functions. Their results showed the sensitivity differences between 1.6, 2.1 and 3.7μm bands to droplet sizes and their vertical stratification. In this study, we further investigate the impact of the vertical inhomogeneity structure including the drizzle by using a spectral-bin microphysics cloud model. We apply the 1-D radiative transfer computation to the numerical cloud fields generated by the cloud model, and retrieve the CDRs from the reflectances thus simulated at each band. We then compare the statistics of these retrieved CDRs with the CDRs obtained from MODIS observations and derive the sensitivity functions of the retrieved CDRs to the particle size and the optical depth from the sets of the droplet distribution functions predicted by the model and the retrieved CDRs. This study is an attempt to interpret the CDR differences in terms of the cloud vertical structure and the cloud particle growth processes.

The GCM-Oriented CALIPSO Cloud Product (CALIPSO-GOCCP)

NASA Astrophysics Data System (ADS)

Chepfer, H.; Bony, S.; Winker, D.; Cesana, G.; Dufresne, J. L.; Minnis, P.; Stubenrauch, C. J.; Zeng, S.

2010-01-01

This article presents the GCM-Oriented Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud Product (GOCCP) designed to evaluate the cloudiness simulated by general circulation models (GCMs). For this purpose, Cloud-Aerosol Lidar with Orthogonal Polarization L1 data are processed following the same steps as in a lidar simulator used to diagnose the model cloud cover that CALIPSO would observe from space if the satellite was flying above an atmosphere similar to that predicted by the GCM. Instantaneous profiles of the lidar scattering ratio (SR) are first computed at the highest horizontal resolution of the data but at the vertical resolution typical of current GCMs, and then cloud diagnostics are inferred from these profiles: vertical distribution of cloud fraction, horizontal distribution of low, middle, high, and total cloud fractions, instantaneous SR profiles, and SR histograms as a function of height. Results are presented for different seasons (January-March 2007-2008 and June-August 2006-2008), and their sensitivity to parameters of the lidar simulator is investigated. It is shown that the choice of the vertical resolution and of the SR threshold value used for cloud detection can modify the cloud fraction by up to 0.20, particularly in the shallow cumulus regions. The tropical marine low-level cloud fraction is larger during nighttime (by up to 0.15) than during daytime. The histograms of SR characterize the cloud types encountered in different regions. The GOCCP high-level cloud amount is similar to that from the TIROS Operational Vertical Sounder (TOVS) and the Atmospheric Infrared Sounder (AIRS). The low-level and middle-level cloud fractions are larger than those derived from passive remote sensing (International Satellite Cloud Climatology Project, Moderate-Resolution Imaging Spectroradiometer-Cloud and Earth Radiant Energy System Polarization and Directionality of Earth Reflectances, TOVS Path B, AIRS-Laboratoire de Météorologie Dynamique) because the latter only provide information on the uppermost cloud layer.

Development of dual-wavelength Mie polarization Raman lidar for aerosol and cloud vertical structure probing

NASA Astrophysics Data System (ADS)

Wang, Zhenzhu; Liu, Dong; Wang, Yingjian; Wang, Bangxin; Zhong, Zhiqing; Xie, Chenbo; Wu, Decheng; Bo, Guangyu; Shao, Jie

2014-11-01

A Dual-wavelength Mie Polarization Raman Lidar has been developed for cloud and aerosol optical properties measurement. This idar system has built in Hefei and passed the performance assessment in 2012, and then moved to Jinhua city to carry out the long-term continuous measurements of vertical distribution of regional cloud and aerosol. A double wavelengths (532 and 1064 nm) Nd-YAG laser is employed as emitting source and four channels are used for detecting back-scattering signals from atmosphere aerosol and cloud including 1064 nm Mie, 607 nm N2 Raman, two 532 nm Orthogonal Polarization channels. The temporal and spatial resolutions for this system, which is operating with a continuing mode (24/7) automatically, are 30s and 7.5m, respectively. The measured data are used for investigating the aerosol and cloud vertical structure and cloud phase from combining of cloud signal intensity, polarization ratio and color ratio.

Influence of Arctic Sea Ice Extent on Polar Cloud Fraction and Vertical Structure and Implications for Regional Climate

NASA Technical Reports Server (NTRS)

Palm, Stephen P.; Strey, Sara T.; Spinhirne, James; Markus, Thorsten

2010-01-01

Recent satellite lidar measurements of cloud properties spanning a period of 5 years are used to examine a possible connection between Arctic sea ice amount and polar cloud fraction and vertical distribution. We find an anticorrelation between sea ice extent and cloud fraction with maximum cloudiness occurring over areas with little or no sea ice. We also find that over ice!free regions, there is greater low cloud frequency and average optical depth. Most of the optical depth increase is due to the presence of geometrically thicker clouds over water. In addition, our analysis indicates that over the last 5 years, October and March average polar cloud fraction has increased by about 7% and 10%, respectively, as year average sea ice extent has decreased by 5% 7%. The observed cloud changes are likely due to a number of effects including, but not limited to, the observed decrease in sea ice extent and thickness. Increasing cloud amount and changes in vertical distribution and optical properties have the potential to affect the radiative balance of the Arctic region by decreasing both the upwelling terrestrial longwave radiation and the downward shortwave solar radiation. Because longwave radiation dominates in the long polar winter, the overall effect of increasing low cloud cover is likely a warming of the Arctic and thus a positive climate feedback, possibly accelerating the melting of Arctic sea ice.

Aerosol effects on clouds and precipitation over the eastern China

NASA Astrophysics Data System (ADS)

Wang, W. C.; Chen, G.; Song, Y.

2017-12-01

Anthropogenic aerosols (sulfates, nitrates and black carbons) can act as cloud condensation nuclei to regulate cloud droplet number and size, thereby changing cloud radiative properties and atmospheric short- and long-wave radiation. These together with aerosol direct radiative effects in turn alter the circulation with likely effects on the spatial distribution of cloud and precipitation. We conduct WRF model simulations over the eastern China to investigate the aerosol-cloud-climate interactions. In general, more aerosols yield more but smaller cloud droplets and larger cloud water content, whereas the changes of vertical distribution of cloud cover exhibit strong regional variations. For example, the low-cloud fraction and water content increase by more than 10% over the west part of the Yangtze-Huai River Valley (YHRV) and the southeast coastal region, but decrease over the east part of the YHRV, and high-cloud fraction decreases in South and North China but increases in the YHRV. The radiative forcing of aerosols and cloud changes are compared, with focus on the effects of changes of vertical distribution of cloud properties (microphysics and fraction). The precipitation changes are found to be closely associated with the circulation change, which favors more (and longer duration) rainfall over the YHRV but less (and shorter) rainfall over other regions. Details of the circulation change and its associations with clouds and precipitation will be presented.

Very high elevation water ice clouds on Mars: Their morphology and temporal behavior

NASA Technical Reports Server (NTRS)

Jaquin, Fred

1988-01-01

Quantitative analysis of Viking images of the martian planetary limb has uncovered the existence and temporal behavior of water ice clouds that form between 50 and 90 km elevation. These clouds show a seasonal behavior that may be correlated with lower atmosphere dynamics. Enhanced vertical mixing of the atmosphere as Mars nears perihelion is hypothesized as the cause of the seasonal dependence, and the diurnal dependence is explained by the temporal behavior of the martian diurnal thermal tide. Viking images also provide a data set of the vertical distribution of aerosols in the martian atmosphere. The temporal and spatial distribution of aerosols are characterized.

Effects of cloud condensate vertical alignment on radiative transfer calculations in deep convective regions

NASA Astrophysics Data System (ADS)

Wang, Xiaocong

2017-04-01

Effects of cloud condensate vertical alignment on radiative transfer process were investigated using cloud resolving model explicit simulations, which provide a surrogate for subgrid cloud geometry. Diagnostic results showed that the decorrelation length Lcw varies in the vertical dimension, with larger Lcw occurring in convective clouds and smaller Lcw in cirrus clouds. A new parameterization of Lcw is proposed that takes into account such varying features and gives rise to improvements in simulations of cloud radiative forcing (CRF) and radiative heating, i.e., the peak of bias is respectively reduced by 8 W m- 2 for SWCF and 2 W m- 2 for LWCF in comparison with Lcw = 1 km. The role of Lcw in modulating CRFs is twofold. On the one hand, larger Lcw tends to increase the standard deviation of optical depth στ, as dense and tenuous parts of the clouds would be increasingly aligned in the vertical dimension, thereby broadening the probability distribution. On the other hand, larger στ causes a decrease in the solar albedo and thermal emissivity, as implied in their convex functions on τ. As a result, increasing (decreasing) Lcwleads to decreased (increased) CRFs, as revealed by comparisons among Lcw = 0, Lcw = 1 km andLcw = ∞. It also affects the vertical structure of radiative flux and thus influences the radiative heating. A better representation of στ in the vertical dimension yields an improved simulation of radiative heating. Although the importance of vertical alignment of cloud condensate is found to be less than that of cloud cover in regards to their impacts on CRFs, it still has enough of an effect on modulating the cloud radiative transfer process.

What does Reflection from Cloud Sides tell us about Vertical Distribution of Cloud Droplet Sizes?

NASA Technical Reports Server (NTRS)

Marshak, A.; Martins, J. V.; Zubko, V.; Kaufman, Y. J.

2006-01-01

Cloud development, the onset of precipitation and the effect of aerosol on clouds depend on the structure of the cloud profiles of droplet size and phase. Aircraft measurements of cloud profiles are limited in their temporal and spatial extent. Satellites were used to observe cloud tops not cloud profiles with vertical profiles of precipitation-sized droplets anticipated from CloudSat. The recently proposed CLAIM-3D satellite mission (cloud aerosol interaction mission in 3-D) suggests to measure profiles of cloud microphysical properties by retrieving them from the solar and infrared radiation reflected or emitted from cloud sides. Inversion of measurements from the cloud sides requires rigorous understanding of the 3-dimentional(3-D) properties of clouds. Here we discuss the reflected sunlight from the cloud sides and top at two wavelengths: one nonabsorbing to solar radiation (0.67 microns) and one with liquid water efficient absorption of solar radiation (2.1 microns). In contrast to the plane-parallel approximation, a conventional approach to all current operational retrievals, 3-D radiative transfer is used for interpreting the observed reflectances. General properties of the radiation reflected from the sides of an isolated cloud are discussed. As a proof of concept, the paper shows a few examples of radiation reflected from cloud fields generated by a simple stochastic cloud model with the prescribed vertically resolved microphysics. To retrieve the information about droplet sizes, we propose to use the probability density function of the droplet size distribution and its first two moments instead of the assumption about fixed values of the droplet effective radius. The retrieval algorithm is based on the Bayesian theorem that combines prior information about cloud structure and microphysics with radiative transfer calculations.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrare, Richard; Turner, David

2015-01-13

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

What Does Reflection from Cloud Sides Tell Us About Vertical Distribution of Cloud Droplet Sizes?

NASA Technical Reports Server (NTRS)

Marshak, Alexander; Martins, J. Vanderlei; Zubko, Victor; Kaufman, Yoram, J.

2005-01-01

Cloud development, the onset of precipitation and the effect of aerosol on clouds depend on the structure of the cloud profiles of droplet size and phase. Aircraft measurements of cloud profiles are limited in their temporal and spatial extent. Satellites were used to observe cloud tops not cloud profiles with vertical profiles of precipitation-sized droplets anticipated from Cloudsat. The recently proposed CLAIM-3D satellite mission (cloud aerosol interaction mission in 3D) suggests to measure profiles of cloud microphysical properties by retrieving them from the solar and infrared radiation reflected or emitted from cloud sides. Inversion of measurements from the cloud sides requires rigorous understanding of the 3-dimensional (3D) properties of clouds. Here we discuss the reflected sunlight from the cloud sides and top at two wavelengths: one nonabsorbing to solar radiation (0.67 micrometers) and one with liquid water efficient absorption of solar radiation (2.1 micrometers). In contrast to the plane-parallel approximation, a conventional approach to all current operational retrievals, 3D radiative transfer is used for interpreting the observed reflectances. General properties of the radiation reflected from the sides of an isolated cloud are discussed. As a proof of concept, the paper shows a few examples of radiation reflected from cloud fields generated by a simple stochastic cloud model with the prescribed vertically resolved microphysics. To retrieve the information about droplet sizes, we propose to use the probability density function of the droplet size distribution and its first two moments instead of the assumption about fixed values of the droplet effective radius. The retrieval algorithm is based on the Bayesian theorem that combines prior information about cloud structure and microphysics with radiative transfer calculations.

The Impact of Assimilating Precipitation-affected Radiance on Cloud and Precipitation in Goddard WRF-EDAS Analyses

NASA Technical Reports Server (NTRS)

Lin, Xin; Zhang, Sara Q.; Zupanski, M.; Hou, Arthur Y.; Zhang, J.

2015-01-01

High-frequency TMI and AMSR-E radiances, which are sensitive to precipitation over land, are assimilated into the Goddard Weather Research and Forecasting Model- Ensemble Data Assimilation System (WRF-EDAS) for a few heavy rain events over the continental US. Independent observations from surface rainfall, satellite IR brightness temperatures, as well as ground-radar reflectivity profiles are used to evaluate the impact of assimilating rain-sensitive radiances on cloud and precipitation within WRF-EDAS. The evaluations go beyond comparisons of forecast skills and domain-mean statistics, and focus on studying the cloud and precipitation features in the jointed rainradiance and rain-cloud space, with particular attentions on vertical distributions of height-dependent cloud types and collective effect of cloud hydrometers. Such a methodology is very helpful to understand limitations and sources of errors in rainaffected radiance assimilations. It is found that the assimilation of rain-sensitive radiances can reduce the mismatch between model analyses and observations by reasonably enhancing/reducing convective intensity over areas where the observation indicates precipitation, and suppressing convection over areas where the model forecast indicates rain but the observation does not. It is also noted that instead of generating sufficient low-level warmrain clouds as in observations, the model analysis tends to produce many spurious upperlevel clouds containing small amount of ice water content. This discrepancy is associated with insufficient information in ice-water-sensitive radiances to address the vertical distribution of clouds with small amount of ice water content. Such a problem will likely be mitigated when multi-channel multi-frequency radiances/reflectivity are assimilated over land along with sufficiently accurate surface emissivity information to better constrain the vertical distribution of cloud hydrometers.

Spatial distribution of cloud droplets in a turbulent cloud-chamber flow

NASA Astrophysics Data System (ADS)

Jaczewski, A.; Malinowski, S. P.

2005-07-01

We present the results of a laboratory study of the spatial distribution of cloud droplets in a turbulent environment. An artificial, weakly turbulent cloud, consisting of droplets of diameter around 14 m, is observed in a laboratory chamber. Droplets on a vertical cross-section through the cloud interior are imaged using laser sheet photography. Images are digitized and numerically processed in order to retrieve droplet positions in a vertical plane. The spatial distribution of droplets in the range of scales, l, from 4 to 80 mm is characterized by: the clustering index CI(l), the volume averaged pair correlation function eta;(l) and a local density defined on a basis of correlation analysis. The results indicate that, even in weak turbulence in the chamber that is less intense and less intermittent than turbulence observed in clouds, droplets are not spread according to the Poisson distribution. The importance of this deviation from the Poisson distribution is unclear when looking at CI(l) and (l). The local density indicates that in small scales each droplet has, on average, more neighbours than expected from the average droplet concentration and gives a qualitative and intuitive measure of clustering.

Sedimentation Efficiency of Condensation Clouds in Substellar Atmospheres

NASA Astrophysics Data System (ADS)

Gao, Peter; Marley, Mark S.; Ackerman, Andrew S.

2018-03-01

Condensation clouds in substellar atmospheres have been widely inferred from spectra and photometric variability. Up until now, their horizontally averaged vertical distribution and mean particle size have been largely characterized using models, one of which is the eddy diffusion–sedimentation model from Ackerman and Marley that relies on a sedimentation efficiency parameter, f sed, to determine the vertical extent of clouds in the atmosphere. However, the physical processes controlling the vertical structure of clouds in substellar atmospheres are not well understood. In this work, we derive trends in f sed across a large range of eddy diffusivities (K zz ), gravities, material properties, and cloud formation pathways by fitting cloud distributions calculated by a more detailed cloud microphysics model. We find that f sed is dependent on K zz , but not gravity, when K zz is held constant. f sed is most sensitive to the nucleation rate of cloud particles, as determined by material properties like surface energy and molecular weight. High surface energy materials form fewer, larger cloud particles, leading to large f sed (>1), and vice versa for materials with low surface energy. For cloud formation via heterogeneous nucleation, f sed is sensitive to the condensation nuclei flux and radius, connecting cloud formation in substellar atmospheres to the objects’ formation environments and other atmospheric aerosols. These insights could lead to improved cloud models that help us better understand substellar atmospheres. For example, we demonstrate that f sed could increase with increasing cloud base depth in an atmosphere, shedding light on the nature of the brown dwarf L/T transition.

CALIPSO Satellite Lidar Identification Of Elevated Dust Over Australia Compared With Air Quality Model PM60 Forecasts

NASA Technical Reports Server (NTRS)

Young, Stuart A.; Vaughan, Mark; Omar, Ali; Liu, Zhaoyan; Lee, Sunhee; Hu, Youngxiang; Cope, Martin

2008-01-01

Global measurements of the vertical distribution of clouds and aerosols have been recorded by the lidar on board the CALIPSO (Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations) satellite since June 2006. Such extensive, height-resolved measurements provide a rare and valuable opportunity for developing, testing and validating various atmospheric models, including global climate, numerical weather prediction, chemical transport and air quality models. Here we report on the initial results of an investigation into the performance of the Australian Air Quality Forecast System (AAQFS) model in forecasting the distribution of elevated dust over the Australian region. The model forecasts of PM60 dust distribution are compared with the CALIPSO lidar Vertical Feature Mask (VFM) data product. The VFM classifies contiguous atmospheric regions of enhanced backscatter as either cloud or aerosols. Aerosols are further classified into six subtypes. By comparing forecast PM60 concentration profiles to the spatial distribution of dust reported in the CALIPSO VFM, we can assess the model s ability to predict the occurrence and the vertical and horizontal extents of dust events within the study area.

Precipitation growth in convective clouds. [hail

NASA Technical Reports Server (NTRS)

Srivastava, R. C.

1981-01-01

Analytical solutions to the equations of both the growth and motion of hailstones in updrafts and of cloud water contents which vary linearly with height were used to investigate hail growth in a model cloud. A strong correlation was found between the hail embyro starting position and its trajectory and final size. A simple model of the evolution of particle size distribution by coalescence and spontaneous and binary disintegrations was formulated. Solutions for the mean mass of the distribution and the equilibrium size distribution were obtained for the case of constant collection kernel and disintegration parameters. Azimuthal scans of Doppler velocity at a number of elevation angles were used to calculate high resolution vertical profiles of particle speed and horizontal divergence (the vertical air velocity) in a region of widespread precipitation trailing a mid-latitude squall line.

The Influence of Arctic Sea Ice Extent on Polar Cloud Fraction and Vertical Structure and Implications for Regional Climate

NASA Technical Reports Server (NTRS)

Palm, Stephen P.; Strey, Sara T.; Spinhirne, James; Markus, Thorsten

2010-01-01

Recent satellite lidar measurements of cloud properties spanning a period of five years are used to examine a possible connection between Arctic sea ice amount and polar cloud fraction and vertical distribution. We find an anti-correlation between sea ice extent and cloud fraction with maximum cloudiness occurring over areas with little or no sea ice. We also find that over ice free regions, there is greater low cloud frequency and average optical depth. Most of the optical depth increase is due to the presence of geometrically thicker clouds over water. In addition, our analysis indicates that over the last 5 years, October and March average polar cloud fraction has increased by about 7 and 10 percent, respectively, as year average sea ice extent has decreased by 5 to 7 percent. The observed cloud changes are likely due to a number of effects including, but not limited to, the observed decrease in sea ice extent and thickness. Increasing cloud amount and changes in vertical distribution and optical properties have the potential to affect the radiative balance of the Arctic region by decreasing both the upwelling terrestrial longwave radiation and the downward shortwave solar radiation. Since longwave radiation dominates in the long polar winter, the overall effect of increasing low cloud cover is likely a warming of the Arctic and thus a positive climate feedback, possibly accelerating the melting of Arctic sea ice.

A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riihimaki, Laura D.; Comstock, Jennifer M.; Luke, Edward

To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement (ARM) site are used to classify cloud phase within a deep convective cloud in a shallow to deep convection transitional case. The cloud cannot be fully observed by a lidar due to signal attenuation. Thus we develop an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectramore » from vertically pointing Ka band cloud radar. This approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid, indicating complexity to how ice growth and diabatic heating occurs in the vertical structure of the cloud.« less

Assessing cloud radiative effects on tropospheric photolysis rates and key oxidants during aircraft campaigns using satellite cloud observations and a global chemical transport model

NASA Astrophysics Data System (ADS)

Zhang, B.; Liu, H.; Crawford, J. H.; Chen, G.; Voulgarakis, A.; Fairlie, T. D.; Duncan, B. N.; Ham, S. H.; Kato, S.; Payer Sulprizio, M.; Yantosca, R.

2017-12-01

Clouds affect tropospheric photochemistry through modifying solar radiation that determines photolysis rates. Observational and modeling studies have indicated that photolysis rates are enhanced above and in the upper portion of cloud layers and are reduced below optically thick clouds due to their dominant backscattering effect. However, large uncertainties exist in the representation of cloud spatiotemporal (especially vertical) distributions in global models, which makes understanding of cloud radiative effects on tropospheric chemistry challenging. Our previous study using a global 3-D chemical transport model (GEOS-Chem) driven by various meteorological data sets showed that the radiative effects of clouds on photochemistry are more sensitive to the differences in the vertical distribution of clouds than to those in the magnitude of column cloud optical depths. In this work, we evaluate monthly mean cloud optical properties and distributions in the MERRA-2 reanalysis with those in C3M, a 3-D cloud data product developed at NASA Langley Research Center and merged from multiple A-Train satellite (CERES, CloudSat, CALIPSO, and MODIS) observations. We conduct tropospheric chemistry simulations for the periods of several aircraft campaigns, including ARCTAS (April, June-July, 2008), DC3 (May-June, 2012), and SEAC4RS (August-September, 2013) with GEOS-Chem driven by MERRA-2. We compare model simulations with and without constraints of cloud optical properties and distributions from C3M, and evaluate model photolysis rates (J[O1D] and J[NO2]) and key oxidants (e.g., OH and ozone) with aircraft profile measurements. We will assess whether the constraints provided by C3M improve model simulations of photolysis rates and oxidants as well as their variabilities.

Near Real Time Vertical Profiles of Clouds and Aerosols from the Cloud-Aerosol Transport System (CATS) on the International Space Station

NASA Astrophysics Data System (ADS)

Yorks, J. E.; McGill, M. J.; Nowottnick, E. P.

2015-12-01

Plumes from hazardous events, such as ash from volcanic eruptions and smoke from wildfires, can have a profound impact on the climate system, human health and the economy. Global aerosol transport models are very useful for tracking hazardous plumes and predicting the transport of these plumes. However aerosol vertical distributions and optical properties are a major weakness of global aerosol transport models, yet a key component of tracking and forecasting smoke and ash. The Cloud-Aerosol Transport System (CATS) is an elastic backscatter lidar designed to provide vertical profiles of clouds and aerosols while also demonstrating new in-space technologies for future Earth Science missions. CATS has been operating on the Japanese Experiment Module - Exposed Facility (JEM-EF) of the International Space Station (ISS) since early February 2015. The ISS orbit provides more comprehensive coverage of the tropics and mid-latitudes than sun-synchronous orbiting sensors, with nearly a three-day repeat cycle. The ISS orbit also provides CATS with excellent coverage over the primary aerosol transport tracks, mid-latitude storm tracks, and tropical convection. Data from CATS is used to derive properties of clouds and aerosols including: layer height, layer thickness, backscatter, optical depth, extinction, and depolarization-based discrimination of particle type. The measurements of atmospheric clouds and aerosols provided by the CATS payload have demonstrated several science benefits. CATS provides near-real-time observations of cloud and aerosol vertical distributions that can be used as inputs to global models. The infrastructure of the ISS allows CATS data to be captured, transmitted, and received at the CATS ground station within several minutes of data collection. The CATS backscatter and vertical feature mask are part of a customized near real time (NRT) product that the CATS processing team produces within 6 hours of collection. The continuous near real time CATS data availability is an extraordinary capability and permits vertical profiles of aerosols to flow directly into any aerosol transport model.

Comparing the cloud vertical structure derived from several methods based on measured atmospheric profiles and active surface measurements

NASA Astrophysics Data System (ADS)

Costa-Surós, M.; Calbó, J.; González, J. A.; Long, C. N.

2013-06-01

The cloud vertical distribution and especially the cloud base height, which is linked to cloud type, is an important characteristic in order to describe the impact of clouds in a changing climate. In this work several methods to estimate the cloud vertical structure (CVS) based on atmospheric sounding profiles are compared, considering number and position of cloud layers, with a ground based system which is taken as a reference: the Active Remote Sensing of Clouds (ARSCL). All methods establish some conditions on the relative humidity, and differ on the use of other variables, the thresholds applied, or the vertical resolution of the profile. In this study these methods are applied to 125 radiosonde profiles acquired at the ARM Southern Great Plains site during all seasons of year 2009 and endorsed by GOES images, to confirm that the cloudiness conditions are homogeneous enough across their trajectory. The overall agreement for the methods ranges between 44-88%; four methods produce total agreements around 85%. Further tests and improvements are applied on one of these methods. In addition, we attempt to make this method suitable for low resolution vertical profiles, which could be useful in atmospheric modeling. The total agreement, even when using low resolution profiles, can be improved up to 91% if the thresholds for a moist layer to become a cloud layer are modified to minimize false negatives with the current data set, thus improving overall agreement.

Detection of Multi-Layer and Vertically-Extended Clouds Using A-Train Sensors

NASA Technical Reports Server (NTRS)

Joiner, J.; Vasilkov, A. P.; Bhartia, P. K.; Wind, G.; Platnick, S.; Menzel, W. P.

2010-01-01

The detection of mUltiple cloud layers using satellite observations is important for retrieval algorithms as well as climate applications. In this paper, we describe a relatively simple algorithm to detect multiple cloud layers and distinguish them from vertically-extended clouds. The algorithm can be applied to coincident passive sensors that derive both cloud-top pressure from the thermal infrared observations and an estimate of solar photon pathlength from UV, visible, or near-IR measurements. Here, we use data from the A-train afternoon constellation of satellites: cloud-top pressure, cloud optical thickness, the multi-layer flag from the Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) and the optical centroid cloud pressure from the Aura Ozone Monitoring Instrument (OMI). For the first time, we use data from the CloudSat radar to evaluate the results of a multi-layer cloud detection scheme. The cloud classification algorithms applied with different passive sensor configurations compare well with each other as well as with data from CloudSat. We compute monthly mean fractions of pixels containing multi-layer and vertically-extended clouds for January and July 2007 at the OMI spatial resolution (l2kmx24km at nadir) and at the 5kmx5km MODIS resolution used for infrared cloud retrievals. There are seasonal variations in the spatial distribution of the different cloud types. The fraction of cloudy pixels containing distinct multi-layer cloud is a strong function of the pixel size. Globally averaged, these fractions are approximately 20% and 10% for OMI and MODIS, respectively. These fractions may be significantly higher or lower depending upon location. There is a much smaller resolution dependence for fractions of pixels containing vertically-extended clouds (approx.20% for OMI and slightly less for MODIS globally), suggesting larger spatial scales for these clouds. We also find higher fractions of vertically-extended clouds over land as compared with ocean, particularly in the tropics and summer hemisphere.

Aerosol Activation Properties within and above Mixing Layer in the North China Plain

NASA Astrophysics Data System (ADS)

Deng, Z.; Ran, L.

2013-12-01

Aerosol particles, serving as cloud condensation nuclei (CCN), may modify the properties of clouds and have an impact on climate. The vertical distribution of aerosols and their activation properties is critical to quantify the effect of aerosols on clouds. An intensive field campaign, Vertical Observations of trace Gases and Aerosols in the North China Plain (VOGA-NCP 2013), was conducted in the North China Plain during the late July and early August 2013 to measure the vertical profiles of atmospheric components in this polluted region and estimate their effects on atmospheric environment and climate. Aerosols were measured with in-situ instruments and Lidar. Particularly, the aerosols were collected at 1000 m height with a 1 m3 bag sampler attached to a tethered balloon, and subsequently measured with combined scanning mobility particle sizer (SMPS) and CCN counter. Comparisons of size-resolved activation ratios at ground level and 1000 m height showed that aerosols in upper atmosphere were not only less concentrated, but also less CCN-active than those at the surface. The difference in aerosol properties between upper atmosphere and the ground indicates that the analysis of impacts of aerosols on cloud might be misleading in heavily polluted region based on the relationship of cloud properties and surface aerosols or column without considering the vertical distribution of aerosol activation abilities.

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

NASA Technical Reports Server (NTRS)

Hence, Deanna A.; Houze, Robert A.

2011-01-01

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

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

NASA Technical Reports Server (NTRS)

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

2011-01-01

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

Comparison between SAGE II and ISCCP high-level clouds. 2: Locating clouds tops

NASA Technical Reports Server (NTRS)

Liao, Xiaohan; Rossow, William B.; Rind, David

1995-01-01

A comparison is made of the vertical distribution of high-level cloud tops derived from the Stratospheric Aerosol and Gas Experiment II (SAGE II) occultation measurements and from the International Satellite Cloud Climatology Project (ISCCP) for all Julys and Januarys in 1985 to 1990. The results suggest that ISCCP overestimates the pressure of high-level clouds by up to 50-150 mbar, particularly at low latitudes. This is caused by the frequent presence of clouds with diffuse tops (greater than 50% time when cloudy events are observed). The averaged vertical extent of the diffuse top is about 1.5 km. At midlatitudes where the SAGE II and ISCCP cloud top pressure agree best, clouds with distinct tops reach a maximum relative proportion of the total level cloud amount (about 30-40%), and diffuse-topped clouds are reduced to their minimum (30-40%). The ISCCP-defined cloud top pressure should be regarded not as the material physical height of the clouds but as the level which emits the same infrared radiance as observed. SAGE II and ISCCP cloud top pressures agree for clouds with distinct tops. There is also an indication that the cloud top pressures of optically thin clouds not overlying thicker clouds are poorly estimated by ISCCP at middle latitudes. The average vertical extent of these thin clouds is about 2.5 km.

Methods for estimating 2D cloud size distributions from 1D observations

DOE PAGES

Romps, David M.; Vogelmann, Andrew M.

2017-08-04

The two-dimensional (2D) size distribution of clouds in the horizontal plane plays a central role in the calculation of cloud cover, cloud radiative forcing, convective entrainment rates, and the likelihood of precipitation. Here, a simple method is proposed for calculating the area-weighted mean cloud size and for approximating the 2D size distribution from the 1D cloud chord lengths measured by aircraft and vertically pointing lidar and radar. This simple method (which is exact for square clouds) compares favorably against the inverse Abel transform (which is exact for circular clouds) in the context of theoretical size distributions. Both methods also performmore » well when used to predict the size distribution of real clouds from a Landsat scene. When applied to a large number of Landsat scenes, the simple method is able to accurately estimate the mean cloud size. Finally, as a demonstration, the methods are applied to aircraft measurements of shallow cumuli during the RACORO campaign, which then allow for an estimate of the true area-weighted mean cloud size.« less

Methods for estimating 2D cloud size distributions from 1D observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romps, David M.; Vogelmann, Andrew M.

The two-dimensional (2D) size distribution of clouds in the horizontal plane plays a central role in the calculation of cloud cover, cloud radiative forcing, convective entrainment rates, and the likelihood of precipitation. Here, a simple method is proposed for calculating the area-weighted mean cloud size and for approximating the 2D size distribution from the 1D cloud chord lengths measured by aircraft and vertically pointing lidar and radar. This simple method (which is exact for square clouds) compares favorably against the inverse Abel transform (which is exact for circular clouds) in the context of theoretical size distributions. Both methods also performmore » well when used to predict the size distribution of real clouds from a Landsat scene. When applied to a large number of Landsat scenes, the simple method is able to accurately estimate the mean cloud size. Finally, as a demonstration, the methods are applied to aircraft measurements of shallow cumuli during the RACORO campaign, which then allow for an estimate of the true area-weighted mean cloud size.« less

Coupling the Mars Dust and Water Cycles: Investigating the Role of Clouds in Controlling the Vertical Distribution of Dust During N. H. Summer

NASA Technical Reports Server (NTRS)

Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.; Wilson, R. J.

2014-01-01

The dust cycle is critically important for the current climate of Mars. The radiative effects of dust impact the thermal and dynamical state of the atmosphere (Gierasch and Goody, 1968; Haberle et al., 1982; Zurek et al., 1992). Although dust is present in the Martian atmosphere throughout the year, the level of dustiness varies with season. The atmosphere is generally the dustiest during northern fall and winter and the least dusty during northern spring and summer (Smith, 2004). Dust particles are lifted into the atmosphere by dust storms that range in size from meters to thousands of kilometers across (Cantor et al., 2001). During some years, regional storms combine to produce hemispheric or planet encircling dust clouds that obscure the surface and raise atmospheric temperatures by as much as 40 K (Smith et al., 2002). Key recent observations of the vertical distribution of dust indicate that elevated layers of dust exist in the tropics and sub-tropics throughout much of the year (Heavens et al., 2011). These observations have brought particular focus on the processes that control the vertical distribution of dust in the Martian atmosphere. The goal of this work is to further our understanding of how clouds in particular control the vertical distribution of dust, particularly during N. H. spring and summer

Use of MISR measurements to study the radiative transfer of an isolated convective cloud: Implications for cloud optical thickness retrieval

NASA Astrophysics Data System (ADS)

Cornet, C.; Davies, R.

2008-02-01

Radiative transfer simulations of an isolated deep convective cloud reconstructed with stereo-techniques from the Multiangle Imaging Spectroradiometer (MISR) are compared with the reflectances measured at the nine MISR viewing angles. The simulations were done using a three dimensional Monte Carlo model, in which ocean reflectance, aerosol and Rayleigh scattering were prescribed to match the surrounding clear-sky MISR measurements. Making reasonable assumptions regarding the vertical and horizontal distribution of the volume extinction coefficient, we were able to reproduce the MISR measurements with the 3D radiative calculations. While the uniqueness of the these distributions cannot be proven, they all lead to retrievals of much larger cloud optical thickness and cloud water content than for a 1D retrieval. Averaged over the cloud, the difference was a factor of about 3, rising to 9 locally. This is a consequence of horizontal photon transport that serves to highlight the inadequacy of 1D retrievals for the case of deep convective cloud. Concerning the internal cloud properties, we noticed the angular distribution of modeled radiances did not match the measured radiances when an ice crystal phase function was applied. Better estimates of the optical depths and water contents of deep convective clouds appear to be obtainable by integrating an estimate of the extinction coefficient over the vertical cloud extent (when this can assessed) than by attempting to invert the radiance measured from a single-angle view using 1D theory.

Comparative Study of Aerosol and Cloud Detected by CALIPSO and OMI

NASA Technical Reports Server (NTRS)

Chen, Zhong; Torres, Omar; McCormick, M. Patrick; Smith, William; Ahn, Changwoo

2012-01-01

The Ozone Monitoring Instrument (OMI) on the Aura Satellite detects the presence of desert dust and smoke particles (also known as aerosols) in terms of a parameter known as the UV Aerosol Index (UV AI). The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission measures the vertical distribution of aerosols and clouds. Aerosols and clouds play important roles in the atmosphere and climate system. Accurately detecting their presence, altitude, and properties using satellite radiance measurements is a very important task. This paper presents a comparative analysis of the CALIPSO Version 2 Vertical Feature Mask (VFM) product with the (OMI) UV Aerosol Index (UV AI) and reflectivity datasets for a full year of 2007. The comparison is done at regional and global scales. Based on CALIPSO arid OMI observations, the vertical and horizontal extent of clouds and aerosols are determined and the effects of aerosol type selection, load, cloud fraction on aerosol identification are discussed. It was found that the spatial-temporal correlation found between CALIPSO and OMI observations, is strongly dependent on aerosol types and cloud contamination. CALIPSO is more sensitivity to cloud and often misidentifies desert dust aerosols as cloud, while some small scale aerosol layers as well as some pollution aerosols are unidentified by OMI UV AI. Large differences in aerosol distribution patterns between CALIPSO and OMI are observed, especially for the smoke and pollution aerosol dominated areas. In addition, the results found a significant correlation between CALIPSO lidar 1064 nm backscatter and the OMI UV AI over the study regions.

The actinic UV-radiation budget during the ESCOMPTE campaign 2001: results of airborne measurements with the microlight research aircraft D-MIFU

NASA Astrophysics Data System (ADS)

Junkermann, Wolfgang

2005-03-01

During the ESCOMPTE campaign 2001, the vertical distribution of ultraviolet actinic radiation was investigated with concurrent measurements of ozone, aerosol size distributions, and scattering coefficients using a microlight aircraft as airborne platform. Three-dimensional (3D) measurements were performed on a regional scale in the area between Avignon, Aix-en-Provence, and Marseille up to an altitude of 4000 m a.s.l. The results show a pronounced dependence of the vertical actinic flux distribution on aerosol load and stratification while horizontally no significant variability was observed. Furthermore, investigations under cloudy conditions and in the vicinity of cumulus clouds were performed allowing comparisons with one-dimensional and recently published three-dimensional model results. Cloud effects of scattered convective clouds were often found to be masked by aerosols and the aerosol content was generally the dominating factor controlling radiation transfer.

Overlap Properties of Clouds Generated by a Cloud Resolving Model

NASA Technical Reports Server (NTRS)

Oreopoulos, L.; Khairoutdinov, M.

2002-01-01

In order for General Circulation Models (GCMs), one of our most important tools to predict future climate, to correctly describe the propagation of solar and thermal radiation through the cloudy atmosphere a realistic description of the vertical distribution of cloud amount is needed. Actually, one needs not only the cloud amounts at different levels of the atmosphere, but also how these cloud amounts are related, in other words, how they overlap. Currently GCMs make some idealized assumptions about cloud overlap, for example that contiguous cloud layers overlap maximally and non-contiguous cloud layers overlap in a random fashion. Since there are difficulties in obtaining the vertical profile of cloud amount from observations, the realism of the overlap assumptions made in GCMs has not been yet rigorously investigated. Recently however, cloud observations from a relatively new type of ground radar have been used to examine the vertical distribution of cloudiness. These observations suggest that the GCM overlap assumptions are dubious. Our study uses cloud fields from sophisticated models dedicated to simulate cloud formation, maintenance, and dissipation called Cloud Resolving Models . These models are generally considered capable of producing realistic three-dimensional representation of cloudiness. Using numerous cloud fields produced by such a CRM we show that the degree of overlap between cloud layers is a function of their separation distance, and is in general described by a combination of the maximum and random overlap assumption, with random overlap dominating as separation distances increase. We show that it is possible to parameterize this behavior in a way that can eventually be incorporated in GCMs. Our results seem to have a significant resemblance to the results from the radar observations despite the completely different nature of the datasets. This consistency is encouraging and will promote development of new radiative transfer codes that will estimate the radiation effects of multi-layer cloud fields more accurately.

Using Satellite Observations of Cloud Vertical Distribution to Improve Global Model Estimates of Cloud Radiative Effect on Key Tropospheric Oxidants

NASA Technical Reports Server (NTRS)

Liu, Hongyu; Crawford, James; Ham, Seung-Hee; Zhang, Bo; Kato, Seiji; Voulgarakis, Apostolos; Chen, Gao; Fairlie, Duncan; Duncan, Bryan; Yantosca, Robert

2017-01-01

Clouds directly affect tropospheric photochemistry through modification of solar radiation that determines photolysis frequencies. This effect is an important component of global tropospheric chemistry-climate interaction, and its understanding is thus essential for predicting the feedback of climate change on tropospheric chemistry.

Measurement Comparisons Towards Improving the Understanding of Aerosol-Cloud Processing

NASA Astrophysics Data System (ADS)

Noble, Stephen R.

Cloud processing of aerosol is an aerosol-cloud interaction that is not heavily researched but could have implications on climate. The three types of cloud processing are chemical processing, collision and coalescence processing, and Brownian capture of interstitial particles. All types improve cloud condensation nuclei (CCN) in size or hygroscopicity (kappa). These improved CCN affect subsequent clouds. This dissertation focuses on measurement comparisons to improve our observations and understanding of aerosol-cloud processing. Particle size distributions measured at the continental Southern Great Plains (SGP) site were compared with ground based measurements of cloud fraction (CF) and cloud base altitude (CBA). Particle size distributions were described by a new objective shape parameter to define bimodality rather than an old subjective one. Cloudy conditions at SGP were found to be correlated with lagged shape parameter. Horizontal wind speed and regional CF explained 42%+ of this lag time. Many of these surface particle size distributions were influenced by aerosol-cloud processing. Thus, cloud processing may be more widespread with more implications than previously thought. Particle size distributions measured during two aircraft field campaigns (MArine Stratus/stratocumulus Experiment; MASE; and Ice in Cloud Experiment-Tropical; ICE-T) were compared to CCN distributions. Tuning particle size to critical supersaturation revealed hygroscopicity expressed as ? when the distributions were overlain. Distributions near cumulus clouds (ICE-T) had a higher frequency of the same ?s (48% in ICE-T to 42% in MASE) between the accumulation (processed) and Aitken (unprocessed) modes. This suggested physical processing domination in ICE-T. More MASE (stratus cloud) kappa differences between modes pointed to chemical cloud processing. Chemistry measurements made in MASE showed increases in sulfates and nitrates with distributions that were more processed. This supported chemical cloud processing in MASE. This new method to determine kappa provides the needed information without interrupting ambient measurements. MODIS derived cloud optical thickness (COT), cloud liquid water path (LWP), and cloud effective radius (re) were compared to the same in situ derived variables from cloud probe measurements of two stratus/stratocumulus cloud campaigns (MASE and Physics Of Stratocumulus Tops; POST). In situ data were from complete vertical cloud penetrations, while MODIS data were from pixels along the aircraft penetration path. Comparisons were well correlated except that MODIS LWP (14-36%) and re (20-30%) were biased high. The LWP bias was from re bias and was not improved by using the vertically stratified assumption. MODIS re bias was almost removed when compared to cloud top maximum in situ re, but, that does not describe re for the full depth of the cloud. COT is validated by in situ COT. High correlations suggest that MODIS variables are useful in self-comparisons such as gradient changes in stratus cloud re during aerosol-cloud processing.

a Point Cloud Classification Approach Based on Vertical Structures of Ground Objects

NASA Astrophysics Data System (ADS)

Zhao, Y.; Hu, Q.; Hu, W.

2018-04-01

This paper proposes a novel method for point cloud classification using vertical structural characteristics of ground objects. Since urbanization develops rapidly nowadays, urban ground objects also change frequently. Conventional photogrammetric methods cannot satisfy the requirements of updating the ground objects' information efficiently, so LiDAR (Light Detection and Ranging) technology is employed to accomplish this task. LiDAR data, namely point cloud data, can obtain detailed three-dimensional coordinates of ground objects, but this kind of data is discrete and unorganized. To accomplish ground objects classification with point cloud, we first construct horizontal grids and vertical layers to organize point cloud data, and then calculate vertical characteristics, including density and measures of dispersion, and form characteristic curves for each grids. With the help of PCA processing and K-means algorithm, we analyze the similarities and differences of characteristic curves. Curves that have similar features will be classified into the same class and point cloud correspond to these curves will be classified as well. The whole process is simple but effective, and this approach does not need assistance of other data sources. In this study, point cloud data are classified into three classes, which are vegetation, buildings, and roads. When horizontal grid spacing and vertical layer spacing are 3 m and 1 m respectively, vertical characteristic is set as density, and the number of dimensions after PCA processing is 11, the overall precision of classification result is about 86.31 %. The result can help us quickly understand the distribution of various ground objects.

Characteristics of vertical air motion in isolated convective clouds

DOE PAGES

Yang, Jing; Wang, Zhien; Heymsfield, Andrew J.; ...

2016-08-11

The vertical velocity and air mass flux in isolated convective clouds are statistically analyzed using aircraft in situ data collected from three field campaigns: High-Plains Cumulus (HiCu) conducted over the midlatitude High Plains, COnvective Precipitation Experiment (COPE) conducted in a midlatitude coastal area, and Ice in Clouds Experiment-Tropical (ICE-T) conducted over a tropical ocean. The results show that small-scale updrafts and downdrafts (<  500 m in diameter) are frequently observed in the three field campaigns, and they make important contributions to the total air mass flux. The probability density functions (PDFs) and profiles of the observed vertical velocity are provided. The PDFsmore » are exponentially distributed. The updrafts generally strengthen with height. Relatively strong updrafts (>  20 m s −1) were sampled in COPE and ICE-T. The observed downdrafts are stronger in HiCu and COPE than in ICE-T. The PDFs of the air mass flux are exponentially distributed as well. The observed maximum air mass flux in updrafts is of the order 10 4 kg m −1 s −1. The observed air mass flux in the downdrafts is typically a few times smaller in magnitude than that in the updrafts. Since this study only deals with isolated convective clouds, and there are many limitations and sampling issues in aircraft in situ measurements, more observations are needed to better explore the vertical air motion in convective clouds.« less

Comparing the cloud vertical structure derived from several methods based on radiosonde profiles and ground-based remote sensing measurements

NASA Astrophysics Data System (ADS)

Costa-Surós, M.; Calbó, J.; González, J. A.; Long, C. N.

2014-08-01

The cloud vertical distribution and especially the cloud base height, which is linked to cloud type, are important characteristics in order to describe the impact of clouds on climate. In this work, several methods for estimating the cloud vertical structure (CVS) based on atmospheric sounding profiles are compared, considering the number and position of cloud layers, with a ground-based system that is taken as a reference: the Active Remote Sensing of Clouds (ARSCL). All methods establish some conditions on the relative humidity, and differ in the use of other variables, the thresholds applied, or the vertical resolution of the profile. In this study, these methods are applied to 193 radiosonde profiles acquired at the Atmospheric Radiation Measurement (ARM) Southern Great Plains site during all seasons of the year 2009 and endorsed by Geostationary Operational Environmental Satellite (GOES) images, to confirm that the cloudiness conditions are homogeneous enough across their trajectory. The perfect agreement (i.e., when the whole CVS is estimated correctly) for the methods ranges between 26 and 64%; the methods show additional approximate agreement (i.e., when at least one cloud layer is assessed correctly) from 15 to 41%. Further tests and improvements are applied to one of these methods. In addition, we attempt to make this method suitable for low-resolution vertical profiles, like those from the outputs of reanalysis methods or from the World Meteorological Organization's (WMO) Global Telecommunication System. The perfect agreement, even when using low-resolution profiles, can be improved by up to 67% (plus 25% of the approximate agreement) if the thresholds for a moist layer to become a cloud layer are modified to minimize false negatives with the current data set, thus improving overall agreement.

Comparing the cloud vertical structure derived from several methods based on measured atmospheric profiles and active surface measurements

NASA Astrophysics Data System (ADS)

Costa-Surós, M.; Calbó, J.; González, J. A.; Long, C. N.

2014-04-01

The cloud vertical distribution and especially the cloud base height, which is linked to cloud type, is an important characteristic in order to describe the impact of clouds on climate. In this work several methods to estimate the cloud vertical structure (CVS) based on atmospheric sounding profiles are compared, considering number and position of cloud layers, with a ground based system which is taken as a reference: the Active Remote Sensing of Clouds (ARSCL). All methods establish some conditions on the relative humidity, and differ on the use of other variables, the thresholds applied, or the vertical resolution of the profile. In this study these methods are applied to 193 radiosonde profiles acquired at the ARM Southern Great Plains site during all seasons of year 2009 and endorsed by GOES images, to confirm that the cloudiness conditions are homogeneous enough across their trajectory. The perfect agreement (i.e. when the whole CVS is correctly estimated) for the methods ranges between 26-64%; the methods show additional approximate agreement (i.e. when at least one cloud layer is correctly assessed) from 15-41%. Further tests and improvements are applied on one of these methods. In addition, we attempt to make this method suitable for low resolution vertical profiles, like those from the outputs of reanalysis methods or from the WMO's Global Telecommunication System. The perfect agreement, even when using low resolution profiles, can be improved up to 67% (plus 25% of approximate agreement) if the thresholds for a moist layer to become a cloud layer are modified to minimize false negatives with the current data set, thus improving overall agreement.

Cloud Simulations in Response to Turbulence Parameterizations in the GISS Model E GCM

NASA Technical Reports Server (NTRS)

Yao, Mao-Sung; Cheng, Ye

2013-01-01

The response of cloud simulations to turbulence parameterizations is studied systematically using the GISS general circulation model (GCM) E2 employed in the Intergovernmental Panel on Climate Change's (IPCC) Fifth Assessment Report (AR5).Without the turbulence parameterization, the relative humidity (RH) and the low cloud cover peak unrealistically close to the surface; with the dry convection or with only the local turbulence parameterization, these two quantities improve their vertical structures, but the vertical transport of water vapor is still weak in the planetary boundary layers (PBLs); with both local and nonlocal turbulence parameterizations, the RH and low cloud cover have better vertical structures in all latitudes due to more significant vertical transport of water vapor in the PBL. The study also compares the cloud and radiation climatologies obtained from an experiment using a newer version of turbulence parameterization being developed at GISS with those obtained from the AR5 version. This newer scheme differs from the AR5 version in computing nonlocal transports, turbulent length scale, and PBL height and shows significant improvements in cloud and radiation simulations, especially over the subtropical eastern oceans and the southern oceans. The diagnosed PBL heights appear to correlate well with the low cloud distribution over oceans. This suggests that a cloud-producing scheme needs to be constructed in a framework that also takes the turbulence into consideration.

Vertical structure of tropospheric winds on gas giants

NASA Astrophysics Data System (ADS)

Scott, R. K.; Dunkerton, T. J.

2017-04-01

Zonal mean zonal velocity profiles from cloud-tracking observations on Jupiter and Saturn are used to infer latitudinal variations of potential temperature consistent with a shear stable potential vorticity distribution. Immediately below the cloud tops, density stratification is weaker on the poleward and stronger on the equatorward flanks of midlatitude jets, while at greater depth the opposite relation holds. Thermal wind balance then yields the associated vertical shears of midlatitude jets in an altitude range bounded above by the cloud tops and bounded below by the level where the latitudinal gradient of static stability changes sign. The inferred vertical shear below the cloud tops is consistent with existing thermal profiling of the upper troposphere. The sense of the associated mean meridional circulation in the upper troposphere is discussed, and expected magnitudes are given based on existing estimates of the radiative timescale on each planet.

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.

Lidar characterizations of atmospheric aerosols and clouds

NASA Astrophysics Data System (ADS)

Ferrare, R. A.; Hostetler, C. A.; Hair, J. W.; Burton, S. P.

2017-12-01

Knowledge of the vertical profile, composition, concentration, and size distribution of aerosols is required to quantify the impacts of aerosols on human health, global and regional climate, clouds and precipitation. In particular, radiative forcing due to anthropogenic aerosols is the most uncertain part of anthropogenic radiative forcing, with aerosol-cloud interactions (ACI) as the largest source of uncertainty in current estimates of global radiative forcing. Improving aerosol transport model predictions of the vertical profile of aerosol optical and microphysical characteristics is crucial for improving assessments of aerosol radiative forcing. Understanding how aerosols and clouds interact is essential for investigating the aerosol indirect effect and ACI. Through its ability to provide vertical profiles of aerosol and cloud distributions as well as important information regarding the optical and physical properties of aerosols and clouds, lidar is a crucial tool for addressing these science questions. This presentation describes how surface, airborne, and satellite lidar measurements have been used to address these questions, and in particular how High Spectral Resolution Lidar (HSRL) measurements provide profiles of aerosol properties (backscatter, extinction, depolarization, concentration, size) important for characterizing radiative forcing. By providing a direct measurement of aerosol extinction, HSRL provides more accurate aerosol measurement profiles and more accurate constraints for models than standard retrievals from elastic backscatter lidar, which loses accuracy and precision at lower altitudes due to attenuation from overlying layers. Information regarding particle size and abundance from advanced lidar retrievals provides better proxies for cloud-condensation-nuclei (CCN), which are required for assessing aerosol-cloud interactions. When combined with data from other sensors, advanced lidar measurements can provide information on aerosol and cloud properties for addressing both direct and indirect radiative forcing.

4-D cloud properties from passive satellite data and applications to resolve the flight icing threat to aircraft

NASA Astrophysics Data System (ADS)

Smith, William L., Jr.

The threat for aircraft icing in clouds is a significant hazard that routinely impacts aviation operations. Accurate diagnoses and forecasts of aircraft icing conditions requires identifying the location and vertical distribution of clouds with super-cooled liquid water (SLW) droplets, as well as the characteristics of the droplet size distribution. Traditional forecasting methods rely on guidance from numerical models and conventional observations, neither of which currently resolve cloud properties adequately on the optimal scales needed for aviation. Satellite imagers provide measurements over large areas with high spatial resolution that can be interpreted to identify the locations and characteristics of clouds, including features associated with adverse weather and storms. This thesis develops new techniques for interpreting cloud products derived from satellite data to infer the flight icing threat to aircraft in a wide range of cloud conditions. For unobscured low clouds, the icing threat is determined using empirical relationships developed from correlations between satellite imager retrievals of liquid water path and droplet size with icing conditions reported by pilots (PIREPS). For deep ice over water cloud systems, ice and liquid water content profiles are derived by using the imager cloud properties to constrain climatological information on cloud vertical structure and water phase obtained apriori from radar and lidar observations, and from cloud model analyses. Retrievals of the SLW content embedded within overlapping clouds are mapped to the icing threat using guidance from an airfoil modeling study. Compared to PIREPS, the satellite icing detection and intensity accuracies are found to be about 90% and 70%, respectively. Mean differences between the imager IWC retrievals with those from CloudSat and Calipso are less than 30%. This level of closure in the cloud water budget can only be achieved by correcting for errors in the imager retrievals due to the simplifying but poor assumption that deep optically thick clouds are single-phase and vertically homogeneous. When applied to geostationary satellite data, the profiling method provides a real-time characterization of clouds in 4-D. This research should improve the utility of satellite imager data for quantitatively diagnosing and predicting clouds and their effects in weather and climate applications.

Height Distribution Between Cloud and Aerosol Layers from the GLAS Spaceborne Lidar in the Indian Ocean Region

NASA Technical Reports Server (NTRS)

Hart, William D.; Spinhirne, James D.; Palm, Steven P.; Hlavka, Dennis L.

2005-01-01

The Geoscience Laser Altimeter System (GLAS), a nadir pointing lidar on the Ice Cloud and land Elevation Satellite (ICESat) launched in 2003, now provides important new global measurements of the relationship between the height distribution of cloud and aerosol layers. GLAS data have the capability to detect, locate, and distinguish between cloud and aerosol layers in the atmosphere up to 40 km altitude. The data product algorithm tests the product of the maximum attenuated backscatter coefficient b'(r) and the vertical gradient of b'(r) within a layer against a predetermined threshold. An initial case result for the critical Indian Ocean region is presented. From the results the relative height distribution between collocated aerosol and cloud shows extensive regions where cloud formation is well within dense aerosol scattering layers at the surface. Citation: Hart, W. D., J. D. Spinhime, S. P. Palm, and D. L. Hlavka (2005), Height distribution between cloud and aerosol layers from the GLAS spaceborne lidar in the Indian Ocean region,

Subtropical Low Cloud Responses to Central and Eastern Pacific El Nino Events

NASA Astrophysics Data System (ADS)

Rapp, A. D.; Bennartz, R.; Jiang, J. H.; Kato, S.; Olson, W. S.; Pinker, R. T.; Su, H.; Taylor, P. C.

2014-12-01

The eastern Pacific El Niño event in 2006-2007 and the central Pacific El Niño event during 2009-2010 exhibit opposite responses in the top of atmosphere (TOA) cloud radiative effects. These responses are driven by differences in large-scale circulation that result in significant low cloud anomalies in the subtropical southeastern Pacific. Both the vertical profile of cloud fraction and cloud water content are reduced during the eastern Pacific El Niño; however, the shift in the distribution of cloud characteristics and the physical processes underlying these changes need further analysis. The NASA Energy and Water Cycle Study (NEWS) Clouds and Radiation Working Group will use a synthesis of NEWS data products, A-Train satellite measurements, reanalysis, and modeling approaches to further explore the differences in the low cloud response to changes in the large-scale forcing, as well as try to understand the physical mechanism driving the observed changes in the low clouds for the 2006/07 and 2009/10 distinct El Niño events. The distributions of cloud macrophysical, microphysical, and radiative properties over the southeast Pacific will first be compared for these two events using a combination of MODIS, CloudSat/CALIPSO, and CERES data. Satellite and reanalysis estimates of changes in the vertical temperature and moisture profiles, lower tropospheric stability, winds, and surface heat fluxes are then used to identify the drivers for observed differences in the clouds and TOA radiative effects.

Remote Sensing the Vertical Profile of Cloud Droplet Effective Radius, Thermodynamic Phase, and Temperature

NASA Technical Reports Server (NTRS)

Martins, J. V.; Marshak, A.; Remer, L. A.; Rosenfeld, D.; Kaufman, Y. J.; Fernandez-Borda, R.; Koren, I.; Correia, A. L.; Zubko, V.; Artaxo, P.

2011-01-01

Cloud-aerosol interaction is a key issue in the climate system, affecting the water cycle, the weather, and the total energy balance including the spatial and temporal distribution of latent heat release. Information on the vertical distribution of cloud droplet microphysics and thermodynamic phase as a function of temperature or height, can be correlated with details of the aerosol field to provide insight on how these particles are affecting cloud properties and their consequences to cloud lifetime, precipitation, water cycle, and general energy balance. Unfortunately, today's experimental methods still lack the observational tools that can characterize the true evolution of the cloud microphysical, spatial and temporal structure in the cloud droplet scale, and then link these characteristics to environmental factors and properties of the cloud condensation nuclei. Here we propose and demonstrate a new experimental approach (the cloud scanner instrument) that provides the microphysical information missed in current experiments and remote sensing options. Cloud scanner measurements can be performed from aircraft, ground, or satellite by scanning the side of the clouds from the base to the top, providing us with the unique opportunity of obtaining snapshots of the cloud droplet microphysical and thermodynamic states as a function of height and brightness temperature in clouds at several development stages. The brightness temperature profile of the cloud side can be directly associated with the thermodynamic phase of the droplets to provide information on the glaciation temperature as a function of different ambient conditions, aerosol concentration, and type. An aircraft prototype of the cloud scanner was built and flew in a field campaign in Brazil.

A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

NASA Astrophysics Data System (ADS)

Riihimaki, L. D.; Comstock, J. M.; Luke, E.; Thorsen, T. J.; Fu, Q.

2017-07-01

To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, ground-based vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement site are used to classify cloud phase within a deep convective cloud. The cloud cannot be fully observed by a lidar due to signal attenuation. Therefore, we developed an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectra from vertically pointing Ka-band cloud radar. This approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid. Diffusional growth calculations show that the conditions for the Wegener-Bergeron-Findeisen process exist within one of these mixed-phase microstructures.

Radiative Effect of Clouds on Tropospheric Chemistry in a Global Three-Dimensional Chemical Transport Model

NASA Technical Reports Server (NTRS)

Liu, Hongyu; Crawford, James H.; Pierce, Robert B.; Norris, Peter; Platnick, Steven E.; Chen, Gao; Logan, Jennifer A.; Yantosca, Robert M.; Evans, Mat J.; Kittaka, Chieko;

Characteristics of cloud occurrence using ceilometer measurements and its relationship to precipitation over Seoul

NASA Astrophysics Data System (ADS)

Lee, Sanghee; Hwang, Seung-On; Kim, Jhoon; Ahn, Myoung-Hwan

2018-03-01

Clouds are an important component of the atmosphere that affects both climate and weather, however, their contributions can be very difficult to determine. Ceilometer measurements can provide high resolution information on atmospheric conditions such as cloud base height (CBH) and vertical frequency of cloud occurrence (CVF). This study presents the first comprehensive analysis of CBH and CVF derived using Vaisala CL51 ceilometers at two urban stations in Seoul, Korea, during a three-year period from January 2014 to December 2016. The average frequency of cloud occurrence detected by the ceilometers is 54.3%. It is found that the CL51 is better able to capture CBH as compared to another ceilometer CL31 at a nearby meteorological station because it could detect high clouds more accurately. Frequency distributions for CBH up to 13,000 m providing detailed vertical features with 500-m interval show 55% of CBHs below 2 km for aggregated CBHs. A bimodal frequency distribution was observed for three-layers CBHs. A monthly variation of CVF reveals that frequency concentration of lower clouds is found in summer and winter, and higher clouds more often detected in spring and autumn. Monthly distribution features of cloud occurrence and precipitation are depending on seasons and it might be easy to define their relationship due to higher degree of variability of precipitation than cloud occurrence. However, a fluctuation of cloud occurrence frequency in summer is similar to precipitation in trend, whereas clouds in winter are relatively frequent but precipitation is not accompanied. In addition, recent decrease of summer precipitation could be mostly explained by a decrease of cloud occurrence. Anomalous precipitation recorded sometimes is considerably related to corresponding cloud occurrence. The diurnal and daily variations of CBH and CVF from ceilometer observations and the analysis of microwave radiometer measurements for two typical cloudiness cases are also reviewed in parallel. This analysis in finer temporal scale exhibits that utilization of ground-based observations together could help to analyze the cloud behaviors.

Vertical overlap of probability density functions of cloud and precipitation hydrometeors: CLOUD AND PRECIPITATION PDF OVERLAP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ovchinnikov, Mikhail; Lim, Kyo-Sun Sunny; Larson, Vincent E.

Coarse-resolution climate models increasingly rely on probability density functions (PDFs) to represent subgrid-scale variability of prognostic variables. While PDFs characterize the horizontal variability, a separate treatment is needed to account for the vertical structure of clouds and precipitation. When sub-columns are drawn from these PDFs for microphysics or radiation parameterizations, appropriate vertical correlations must be enforced via PDF overlap specifications. This study evaluates the representation of PDF overlap in the Subgrid Importance Latin Hypercube Sampler (SILHS) employed in the assumed PDF turbulence and cloud scheme called the Cloud Layers Unified By Binormals (CLUBB). PDF overlap in CLUBB-SILHS simulations of continentalmore » and tropical oceanic deep convection is compared with overlap of PDF of various microphysics variables in cloud-resolving model (CRM) simulations of the same cases that explicitly predict the 3D structure of cloud and precipitation fields. CRM results show that PDF overlap varies significantly between different hydrometeor types, as well as between PDFs of mass and number mixing ratios for each species, - a distinction that the current SILHS implementation does not make. In CRM simulations that explicitly resolve cloud and precipitation structures, faster falling species, such as rain and graupel, exhibit significantly higher coherence in their vertical distributions than slow falling cloud liquid and ice. These results suggest that to improve the overlap treatment in the sub-column generator, the PDF correlations need to depend on hydrometeor properties, such as fall speeds, in addition to the currently implemented dependency on the turbulent convective length scale.« less

Clouds vertical properties over the Northern Hemisphere monsoon regions from CloudSat-CALIPSO measurements

NASA Astrophysics Data System (ADS)

Das, Subrata Kumar; Golhait, R. B.; Uma, K. N.

2017-01-01

The CloudSat spaceborne radar and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) space-borne lidar measurements, provide opportunities to understand the intriguing behavior of the vertical structure of monsoon clouds. The combined CloudSat-CALIPSO data products have been used for the summer season (June-August) of 2006-2010 to present the statistics of cloud macrophysical (such as cloud occurrence frequency, distribution of cloud top and base heights, geometrical thickness and cloud types base on occurrence height), and microphysical (such as ice water content, ice water path, and ice effective radius) properties of the Northern Hemisphere (NH) monsoon region. The monsoon regions considered in this work are the North American (NAM), North African (NAF), Indian (IND), East Asian (EAS), and Western North Pacific (WNP). The total cloud fraction over the IND (mostly multiple-layered cloud) appeared to be more frequent as compared to the other monsoon regions. Three distinctive modes of cloud top height distribution are observed over all the monsoon regions. The high-level cloud fraction is comparatively high over the WNP and IND. The ice water content and ice water path over the IND are maximum compared to the other monsoon regions. We found that the ice water content has little variations over the NAM, NAF, IND, and WNP as compared to their macrophysical properties and thus give an impression that the regional differences in dynamics and thermodynamics properties primarily cause changes in the cloud frequency or coverage and only secondary in the cloud ice properties. The background atmospheric dynamics using wind and relative humidity from the ERA-Interim reanalysis data have also been investigated which helps in understanding the variability of the cloud properties over the different monsoon regions.

Regional and vertical distribution of semitransparent cirrus clouds over the tropical Indian region derived from CALIPSO data

NASA Astrophysics Data System (ADS)

Meenu, S.; Rajeev, K.; Parameswaran, K.

2011-08-01

Monthly mean spatial and vertical distributions of the frequency of occurrence (FSTC) of semitransparent cirrus (STC) and their physical and optical properties over the Indian region are investigated using multiyear CALIPSO data. Over the Bay of Bengal (BoB), FSTC above the lapse-rate tropopause is >30% during the summer monsoon season, most of which has optical depth <0.03. Based on spatial variations of the observed STC properties away from deep convective regions, we propose that the presence of high-altitude clouds below STCs over the BoB and Indian regions during summer monsoon reduces dissipation of STCs, resulting in their longer lifetime (˜1-2 days).

The Impacts of an Observationally-Based Cloud Fraction and Condensate Overlap Parameterization on a GCM's Cloud Radiative Effect

NASA Technical Reports Server (NTRS)

Oreopoulos, Lazaros; Lee, Dongmin; Norris, Peter; Yuan, Tianle

2011-01-01

It has been shown that the details of how cloud fraction overlap is treated in GCMs has substantial impact on shortwave and longwave fluxes. Because cloud condensate is also horizontally heterogeneous at GCM grid scales, another aspect of cloud overlap should in principle also be assessed, namely the vertical overlap of hydrometeor distributions. This type of overlap is usually examined in terms of rank correlations, i.e., linear correlations between hydrometeor amount ranks of the overlapping parts of cloud layers at specific separation distances. The cloud fraction overlap parameter and the rank correlation of hydrometeor amounts can be both expressed as inverse exponential functions of separation distance characterized by their respective decorrelation lengths (e-folding distances). Larger decorrelation lengths mean that hydrometeor fractions and probability distribution functions have high levels of vertical alignment. An analysis of CloudSat and CALIPSO data reveals that the two aspects of cloud overlap are related and their respective decorrelation lengths have a distinct dependence on latitude that can be parameterized and included in a GCM. In our presentation we will contrast the Cloud Radiative Effect (CRE) of the GEOS-5 atmospheric GCM (AGCM) when the observationally-based parameterization of decorrelation lengths is used to represent overlap versus the simpler cases of maximum-random overlap and globally constant decorrelation lengths. The effects of specific overlap representations will be examined for both diagnostic and interactive radiation runs in GEOS-5 and comparisons will be made with observed CREs from CERES and CloudSat (2B-FLXHR product). Since the radiative effects of overlap depend on the cloud property distributions of the AGCM, the availability of two different cloud schemes in GEOS-5 will give us the opportunity to assess a wide range of potential cloud overlap consequences on the model's climate.

Evaluation of multi-layer cloud detection based on MODIS CO2-slicing algorithm with CALIPSO-CloudSat measurements.

NASA Astrophysics Data System (ADS)

Viudez-Mora, A.; Kato, S.; Smith, W. L., Jr.; Chang, F. L.

2016-12-01

Knowledge of the vertical cloud distribution is important for a variety of climate and weather applications. The cloud overlapping variations greatly influence the atmospheric heating/cooling rates, with implications for the surface-troposphere radiative balance, global circulation and precipitation. Additionally, an accurate knowledge of the multi-layer cloud distribution in real-time can be used in applications such safety condition for aviation through storms and adverse weather conditions. In this study, we evaluate a multi-layered cloud algorithm (Chang et al. 2005) based on MODIS measurements aboard Aqua satellite (MCF). This algorithm uses the CO2-slicing technique combined with cloud properties determined from VIS, IR and NIR channels to locate high thin clouds over low-level clouds, and retrieve the τ of each layer. We use CALIPSO (Winker et. al, 2010) and CloudSat (Stephens et. al, 2002) (CLCS) derived cloud vertical profiles included in the C3M data product (Kato et al. 2010) to evaluate MCF derived multi-layer cloud properties. We focus on 2 layer overlapping and 1-layer clouds identified by the active sensors and investigate how well these systems are identified by the MODIS multi-layer technique. The results show that for these multi-layered clouds identified by CLCS, the MCF correctly identifies about 83% of the cases as multi-layer. However, it is found that the upper CTH is underestimated by about 2.6±0.4 km, because the CO2-slicing technique is not as sensitive to the cloud physical top as the CLCS. The lower CTH agree better with differences found to be about 1.2±0.5 km. Another outstanding issue for the MCF approach is the large number of multi-layer false alarms that occur in single-layer conditions. References: Chang, F.-L., and Z. Li, 2005: A new method for detection of cirrus overlapping water clouds and determination of their optical properties. J. Atmos. Sci., 62. Kato, S., et al. (2010), Relationships among cloud occurrence frequency, overlap, and effective thickness derived from CALIPSO and CloudSat merged cloud vertical profiles, J. Geophys. Res., 115. Stephens, G. L., et al. (2002), The CloudSat mission and A-Train, Bull. Am. Meteorol. Soc., 83. Winker, D. M., et al., 2010: The CALIPSO Mission: A global 3D view of aerosols and clouds. Bull. Amer. Meteor. Soc., 91.

Observations of Dust Using the NASA Geoscience Laser Altimeter System (GLAS): New New Measurements of Aerosol Vertical Distribution From Space

NASA Technical Reports Server (NTRS)

Welton, Ellsworth; Spinhirne, James D.; Palm, Steven P.; Hlavka, Dennis; Hart, William

2003-01-01

On January 12, 2003 NASA launched the first satellite-based lidar, the Geoscience Laser -Altimeter System (GLAS), onboard the ICESat spacecraft. The GLAS atmospheric measurements introduce a fundamentally new and important tool for understanding the atmosphere and climate. In the past, aerosols have only been studied from space using images gathered by passive sensors. Analysis of this passive data has lead to an improved understanding of aerosol properties, spatial distribution, and their effect on the earth's climate. However, these images do not show the aerosol's vertical distribution. As a result, a key piece of information has been missing. The measurements now obtained by GLAS will provide information on the vertical distribution of aerosols and clouds, and improve our ability to study their transport processes and aerosol-cloud interactions. Here we show an overview of GLAS, provide an update of its current status, and present initial observations of dust profiles. In particular, a strategy of characterizing the height profile of dust plumes over source regions will be presented.

Microphysical Modeling of Mineral Clouds in GJ1214 b and GJ436 b: Predicting Upper Limits on the Cloud-top Height

NASA Astrophysics Data System (ADS)

Ohno, Kazumasa; Okuzumi, Satoshi

2018-05-01

The ubiquity of clouds in the atmospheres of exoplanets, especially of super-Earths, is one of the outstanding issues for the transmission spectra survey. Understanding the formation process of clouds in super-Earths is necessary to interpret the observed spectra correctly. In this study, we investigate the vertical distributions of particle size and mass density of mineral clouds in super-Earths using a microphysical model that takes into account the vertical transport and growth of cloud particles in a self-consistent manner. We demonstrate that the vertical profiles of mineral clouds significantly vary with the concentration of cloud condensation nuclei and atmospheric metallicity. We find that the height of the cloud top increases with increasing metallicity as long as the metallicity is lower than the threshold. If the metallicity is larger than the threshold, the cloud-top height no longer increases appreciably with metallicity because coalescence yields larger particles of higher settling velocities. We apply our cloud model to GJ1214 b and GJ436 b, for which recent transmission observations suggest the presence of high-altitude opaque clouds. For GJ436 b, we show that KCl particles can ascend high enough to explain the observation. For GJ1214 b, by contrast, the height of KCl clouds predicted from our model is too low to explain its flat transmission spectrum. Clouds made of highly porous KCl particles could explain the observations if the atmosphere is highly metal-rich, and hence the particle microstructure might be a key to interpret the flat spectrum of GJ1214 b.

Further developments in cloud statistics for computer simulations

NASA Technical Reports Server (NTRS)

Chang, D. T.; Willand, J. H.

1972-01-01

This study is a part of NASA's continued program to provide global statistics of cloud parameters for computer simulation. The primary emphasis was on the development of the data bank of the global statistical distributions of cloud types and cloud layers and their applications in the simulation of the vertical distributions of in-cloud parameters such as liquid water content. These statistics were compiled from actual surface observations as recorded in Standard WBAN forms. Data for a total of 19 stations were obtained and reduced. These stations were selected to be representative of the 19 primary cloud climatological regions defined in previous studies of cloud statistics. Using the data compiled in this study, a limited study was conducted of the hemogeneity of cloud regions, the latitudinal dependence of cloud-type distributions, the dependence of these statistics on sample size, and other factors in the statistics which are of significance to the problem of simulation. The application of the statistics in cloud simulation was investigated. In particular, the inclusion of the new statistics in an expanded multi-step Monte Carlo simulation scheme is suggested and briefly outlined.

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

NASA Astrophysics Data System (ADS)

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

2017-02-01

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

The Characteristics of Ice Cloud Properties in China Derived from DARDAR data

NASA Astrophysics Data System (ADS)

Lin, T.; Zheng, Y.

2017-12-01

Ice clouds play an important role in modulating the Earth radiation budget and global hydrological cycle.Thus,study the properties of ice clouds has the vital significance on the interaction between the atmospheric models,cloud,radiation and climate .The world has explore the combination of two or several kinds of sensor data to solve the complementary strengths and error reduction to improve accuracy of ice cloud at the present , but for China ,has be lack of research on combination sensor data to analysis properties of ice cloud.To reach a wider range of ice cloud, a combination of the CloudSat radar and the CALIPSO lidar is used to derive ice cloud properties. These products include the radar/lidar product (DARDAR) developed at the University of Reading.The China probability distribution of ice cloud occurrence frequency, ice water path, ice water content and ice cloud effective radius were presented based on DARDAR data from 2012 to 2016,the distribution and vertical sturctures was discussed.The results indicate that the ice cloud occurrence frequency distribution takes on ascend trend in the last 4 years and has obvious seasonal variation, the high concentration area in the northeastern part of the Tibetan Plateau,ice cloud occurrence frequency is relatively high in northwest area.the increased of ice cloud occurrence frequency play an integral role of the climate warming in these four years; the general trend for the ice water path is southeast area bigger than northwest area, in winter the IWP is the smallest, biggest in summer; the IWC is the biggest in summer, and the vertical height distribution higher than other seasons; ice cloud effective radius and ice water content had similar trend..There were slight declines in ice cloud effective radius with increase height of China,in the summer ice effective radius is generally larger.The ice cloud impact Earth radiation via their albedo an greenhouse effects, that is, cooling the Earth by reflecting solar incident radiation and at the same time.Thus,thorough research of the characteristics of ice cloud properties can explain the complicated relationship between ice cloud and global warming,and this kind of data analysis can comprehend the climate effect of mainland China .

A critical look at spatial scale choices in satellite-based aerosol indirect effect studies

NASA Astrophysics Data System (ADS)

Grandey, B. S.; Stier, P.

2010-06-01

Analysing satellite datasets over large regions may introduce spurious relationships between aerosol and cloud properties due to spatial variations in aerosol type, cloud regime and synoptic regime climatologies. Using MODerate resolution Imaging Spectroradiometer data, we calculate relationships between aerosol optical depth τa, derived liquid cloud droplet effective number concentration Ne and liquid cloud droplet effective radius re at different spatial scales. Generally, positive values of dlnNe dlnτa are found for ocean regions, whilst negative values occur for many land regions. The spatial distribution of dlnre dlnτa shows approximately the opposite pattern, with generally postive values for land regions and negative values for ocean regions. We find that for region sizes larger than 4°×4°, spurious spatial variations in retrieved cloud and aerosol properties can introduce widespread significant errors to calculations of dlnNe dlnτa and dlnre dlnτa . For regions on the scale of 60°×60°, these methodological errors may lead to an overestimate in global cloud albedo effect radiative forcing of order 80%.

Observed linkages between the northern annular mode/North Atlantic Oscillation, cloud incidence, and cloud radiative forcing

NASA Astrophysics Data System (ADS)

Li, Ying; Thompson, David W. J.; Huang, Yi; Zhang, Minghong

2014-03-01

The signature of the northern annular mode/North Atlantic Oscillation (NAM/NAO) in the vertical and horizontal distribution of tropospheric cloudiness is investigated in CloudSat and CALIPSO data from June 2006 to April 2011. During the Northern Hemisphere winter, the positive polarity of the NAM/NAO is marked by increases in zonally averaged cloud incidence north of ~60°N, decreases between ~25 and 50°N, and increases in the subtropics. The tripolar-like anomalies in cloud incidence associated with the NAM/NAO are largest over the North Atlantic Ocean basin/Middle East and are physically consistent with the NAM/NAO-related anomalies in vertical motion. Importantly, the NAM/NAO-related anomalies in tropospheric cloud incidence lead to significant top of atmosphere cloud radiative forcing anomalies that are comparable in amplitude to those associated with the NAM/NAO-related temperature anomalies. The results provide observational evidence that the most prominent pattern of Northern Hemisphere climate variability is significantly linked to variations in cloud radiative forcing. Implications for two-way feedback between extratropical dynamics and cloud radiative forcing are discussed.

Nearly a Decade of CALIPSO Observations of Asian and Saharan Dust Properties Near Source and Transport Regions

NASA Technical Reports Server (NTRS)

Omar, Ali H.; Liu, Z.; Tackett, J.; Vaughan, M.; Trepte, C.; Winker, D.; H. Yu,

2015-01-01

The lidar on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, makes robust measurements of dust and has generated a length of record that is significant both seasonally and inter-annually. We exploit this record to determine a multi-year climatology of the properties of Asian and Saharan dust, in particular seasonal optical depths, layer frequencies, and layer heights of dust gridded in accordance with the Level 3 data products protocol, between 2006-2015. The data are screened using standard CALIPSO quality assurance flags, cloud aerosol discrimination (CAD) scores, overlying features and layer properties. To evaluate the effects of transport on the morphology, vertical extent and size of the dust layers, we compare probability distribution functions of the layer integrated volume depolarization ratios, geometric depths and integrated attenuated color ratios near the source to the same distributions in the far field or transport region. CALIPSO is collaboration between NASA and Centre National D'études Spatiales (CNES), was launched in April 2006 to provide vertically resolved measurements of cloud and aerosol distributions. The primary instrument on the CALIPSO satellite is the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), a near-nadir viewing two-wavelength polarization-sensitive instrument. The unique nature of CALIOP measurements make it quite challenging to validate backscatter profiles, aerosol type, and cloud phase, all of which are used to retrieve extinction and optical depth. To evaluate the uncertainty in the lidar ratios, we compare the values computed from dust layers overlying opaque water clouds, considered nominal, with the constant lidar ratio value used in the CALIOP algorithms for dust. We also explore the effects of noise on the CALIOP retrievals at daytime by comparing the distributions of the properties at daytime to the nighttime distributions.

Short-range precipitation forecasts using assimilation of simulated satellite water vapor profiles and column cloud liquid water amounts

NASA Technical Reports Server (NTRS)

Wu, Xiaohua; Diak, George R.; Hayden, Cristopher M.; Young, John A.

1995-01-01

These observing system simulation experiments investigate the assimilation of satellite-observed water vapor and cloud liquid water data in the initialization of a limited-area primitive equations model with the goal of improving short-range precipitation forecasts. The assimilation procedure presented includes two aspects: specification of an initial cloud liquid water vertical distribution and diabatic initialization. The satellite data is simulated for the next generation of polar-orbiting satellite instruments, the Advanced Microwave Sounding Unit (AMSU) and the High-Resolution Infrared Sounder (HIRS), which are scheduled to be launched on the NOAA-K satellite in the mid-1990s. Based on cloud-top height and total column cloud liquid water amounts simulated for satellite data a diagnostic method is used to specify an initial cloud water vertical distribution and to modify the initial moisture distribution in cloudy areas. Using a diabatic initialization procedure, the associated latent heating profiles are directly assimilated into the numerical model. The initial heating is estimated by time averaging the latent heat release from convective and large-scale condensation during the early forecast stage after insertion of satellite-observed temperature, water vapor, and cloud water formation. The assimilation of satellite-observed moisture and cloud water, together withy three-mode diabatic initialization, significantly alleviates the model precipitation spinup problem, especially in the first 3 h of the forecast. Experimental forecasts indicate that the impact of satellite-observed temperature and water vapor profiles and cloud water alone in the initialization procedure shortens the spinup time for precipitation rates by 1-2 h and for regeneration of the areal coverage by 3 h. The diabatic initialization further reduces the precipitation spinup time (compared to adiabatic initialization) by 1 h.

Infrared radiative properties of tropical cirrus clouds inferred with aircraft measurements

NASA Technical Reports Server (NTRS)

Griffith, K. T.; Cox, S. K.; Knollenberg, R. G.

1980-01-01

Longwave emissivities and the vertical profile of cooling rates of tropical cirrus clouds are determined using broadband hemispheric irradiance data. Additionally, a broadband mass absorption coefficient is defined and used to relate emissivity to water content. The data used were collected by the National Center for Atmospheric Research (NCAR) Sabreliner during the GARP Atlantic Tropical Experiment (GATE) in the summer of 1974. Three case studies are analyzed showing that these tropical cirrus clouds approached an emissivity of 1.0 within a vertical distance of 1.0 km. Broadband mass absorption coefficients ranging from 0.076 to 0.096 sq m per g are derived. A comparison of these results with other work suggests that tropical cirrus cloud emissivities may be significantly larger than heretofore believed. Ice water content of the clouds were deduced from data collected by a one-dimensional particle spectrometer. Analyses of the ice water content and the observed particle size distributions are presented.

Microphysical modeling of cirrus. 2: Sensitivity studies

NASA Technical Reports Server (NTRS)

Jensen, Eric J.; Toon, Owen B.; Westphal, Douglas L.; Kinne, Stefan; Heymsfield, Andrew J.

1994-01-01

The one-dimensional cirrus model described in part 1 of this issue has been used to study the sensitivity of simulated cirrus microphysical and radiative properties to poorly known model parameters, poorly understood physical processes, and environmental conditions. Model parameters and physical processes investigated include nucleation rate, mode of nucleation (e.g., homogeneous freezing of aerosols and liquid droplets or heterogeneous deposition), ice crystal shape, and coagulation. These studies suggest that the leading sources of uncertainty in the model are the phase change (liquid-solid) energy barrier and the ice-water surface energy which dominate the homogeneous freezing nucleation rate and the coagulation sticking efficiency at low temperatures which controls the production of large ice crystals (radii greater than 100 mcirons). Environmental conditions considered in sensitivity tests were CN size distribution, vertical wind speed, and cloud height. We found that (unlike stratus clouds) variations in the total number of condensation nuclei (NC) have little effect on cirrus microphysical and radiative properties, since nucleation occurs only on the largest CN at the tail of the size distribution. The total number of ice crystals which nucleate has little or no relationship to the number of CN present and depends primarily on the temperature and the cooling rate. Stronger updrafts (more rapid cooling) generate higher ice number densities, ice water content, cloud optical depth, and net radiative forcing. Increasing the height of the clouds in the model leads to an increase in ice number density, a decrease in effective radius, and a decrease in ice water content. The most prominent effect of increasing cloud height was a rapid increase in the net cloud radiative forcing which can be attributed to the change in cloud temperature as well as change in cloud ice size distributions. It has long been recognized that changes in cloud height or cloud area have the greatest potential for causing feedbacks on climate change. Our results suggest that variations in vertical velocity or cloud microphysical changes associatd with cloud height changes may also be important.

Observations of Aerosol-Cloud Interactions with Varying Vertical Separation between Biomass-Burning Aerosols and Stratocumulus Clouds over the South East Atlantic

NASA Astrophysics Data System (ADS)

Gupta, S.; McFarquhar, G. M.; Poellot, M.; O'Brien, J.; Delene, D. J.; Thornhill, K. L., II

2017-12-01

The ObseRvations of Aerosols above Clouds and their intEractionS (ORACLES) 2016 project provided in-situ measurements and remotely sensed retrievals of aerosol and cloud properties over the South East Atlantic during September, 2016 with a second deployment scheduled for August, 2017. Biomass burning aerosol from Southern Africa is advected toward the South East Atlantic at elevated altitudes and overlies the ubiquitous stratocumulus cloud deck over the ocean. The aerosols subside farther from the coast so that the vertical displacement between the clouds and aerosols varies, and whose effect on aerosol-cloud interaction is poorly known. A NASA P-3 aircraft was equipped with a Cloud Droplet Probe CDP sizing particles between 2 and 50μm, a Cloud and Aerosol Spectrometer CAS sizing between 0.51 and 50 μm and a 2D-stereo probe 2DS, nominally sizing between 10 and 1280 μm a Cloud Imaging Probe CIP, from 25 to 1600μm, and a High Volume Precipitation Sampler HVPS-3, from 150μm to 1.92cm for measuring number distribution functions (n(D)) along with a King probe for measuring liquid water content, LWC. A Passive Cavity Aerosol Spectrometer Probe PCASP measured aerosol particles between 0.1 to 3μm. Cloud legs from three research flights are classified into different regimes based on the aerosol concentration measured in the accumulation mode by the PCASP (Na) and its location above clouds. These legs include vertical transects through clouds and sawtooths (ramped legs starting above or below the cloud layer, completing a vertical transect through the cloud and repeating this pattern for several legs). The regimes; clean, mixing and separated, correspond to conditions with Na less than 100 cm-3 above cloud top, Na greater than 100 cm-3 within 100 m above cloud top and Na greater than 100 cm-3 separated from the cloud top by more than 100 m. During the mixing regime, measurements from CAS and 2DS show that droplet concentrations and cloud optical depths increased and effective radii decreased, relative to other regimes. Drizzle suppression with lower probability of occurrence of drizzle drops (diameter greater than 50 um) and entrainment of dry air with decreased droplet concentrations near cloud tops was also observed. Similar LWC was observed across regimes with similar vertical velocities during the cloud legs.

Precipitating Condensation Clouds in Substellar Atmospheres

NASA Technical Reports Server (NTRS)

Ackerman, Andrew S.; Marley, Mark S.; Gore, Warren J. (Technical Monitor)

2000-01-01

We present a method to calculate vertical profiles of particle size distributions in condensation clouds of giant planets and brown dwarfs. The method assumes a balance between turbulent diffusion and precipitation in horizontally uniform cloud decks. Calculations for the Jovian ammonia cloud are compared with previous methods. An adjustable parameter describing the efficiency of precipitation allows the new model to span the range of predictions from previous models. Calculations for the Jovian ammonia cloud are found to be consistent with observational constraints. Example calculations are provided for water, silicate, and iron clouds on brown dwarfs and on a cool extrasolar giant planet.

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

NASA Astrophysics Data System (ADS)

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

2017-03-01

Cirrus clouds cover a large fraction of tropical latitudes and play an important role in Earth's radiation budget. Their optical properties, altitude, vertical and horizontal coverage control their radiative forcing, and hence detailed cirrus measurements at different geographical locations are of utmost importance. Studies reporting cirrus properties over tropical rain forests like the Amazon, however, are scarce. Studies with satellite profilers do not give information on the diurnal cycle, and the satellite imagers do not report on the cloud vertical structure. At the same time, ground-based lidar studies are restricted to a few case studies. In this paper, we derive the first comprehensive statistics of optical and geometrical properties of upper-tropospheric cirrus clouds in Amazonia. We used 1 year (July 2011 to June 2012) of ground-based lidar atmospheric observations north of Manaus, Brazil. This dataset was processed by an automatic cloud detection and optical properties retrieval algorithm. Upper-tropospheric cirrus clouds were observed more frequently than reported previously for tropical regions. The frequency of occurrence was found to be as high as 88 % during the wet season and not lower than 50 % during the dry season. The diurnal cycle shows a minimum around local noon and maximum during late afternoon, associated with the diurnal cycle of precipitation. The mean values of cirrus cloud top and base heights, cloud thickness, and cloud optical depth were 14.3 ± 1.9 (SD) km, 12.9 ± 2.2 km, 1.4 ± 1.1 km, and 0.25 ± 0.46, respectively. Cirrus clouds were found at temperatures down to -90 °C. Frequently cirrus were observed within the tropical tropopause layer (TTL), which are likely associated to slow mesoscale uplifting or to the remnants of overshooting convection. The vertical distribution was not uniform, and thin and subvisible cirrus occurred more frequently closer to the tropopause. The mean lidar ratio was 23.3 ± 8.0 sr. However, for subvisible cirrus clouds a bimodal distribution with a secondary peak at about 44 sr was found suggesting a mixed composition. A dependence of the lidar ratio with cloud temperature (altitude) was not found, indicating that the clouds are vertically well mixed. The frequency of occurrence of cirrus clouds classified as subvisible (τ < 0. 03) were 41.6 %, whilst 37.8 % were thin cirrus (0. 03 < τ < 0. 3) and 20.5 % opaque cirrus (τ > 0. 3). Hence, in central Amazonia not only a high frequency of cirrus clouds occurs, but also a large fraction of subvisible cirrus clouds. This high frequency of subvisible cirrus clouds may contaminate aerosol optical depth measured by sun photometers and satellite sensors to an unknown extent.

Quantifying the effect of aerosol on vertical velocity and effective terminal velocity in warm convective clouds

NASA Astrophysics Data System (ADS)

Dagan, Guy; Koren, Ilan; Altaratz, Orit

2018-05-01

Better representation of cloud-aerosol interactions is crucial for an improved understanding of natural and anthropogenic effects on climate. Recent studies have shown that the overall aerosol effect on warm convective clouds is non-monotonic. Here, we reduce the system's dimensions to its center of gravity (COG), enabling distillation and simplification of the overall trend and its temporal evolution. Within the COG framework, we show that the aerosol effects are nicely reflected by the interplay of the system's characteristic vertical velocities, namely the updraft (w) and the effective terminal velocity (η). The system's vertical velocities can be regarded as a sensitive measure for the evolution of the overall trends with time. Using a bin-microphysics cloud-scale model, we analyze and follow the trends of the aerosol effect on the magnitude and timing of w and η, and therefore the overall vertical COG velocity. Large eddy simulation (LES) model runs are used to upscale the analyzed trends to the cloud-field scale and study how the aerosol effects on the temporal evolution of the field's thermodynamic properties are reflected by the interplay between the two velocities. Our results suggest that aerosol effects on air vertical motion and droplet mobility imply an effect on the way in which water is distributed along the atmospheric column. Moreover, the interplay between w and η predicts the overall trend of the field's thermodynamic instability. These factors have an important effect on the local energy balance.

A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

DOE PAGES

Riihimaki, Laura D.; Comstock, J. M.; Luke, E.; ...

2017-07-12

To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, ground-based vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement site are used to classify cloud phase within a deep convective cloud. The cloud cannot be fully observed by a lidar due to signal attenuation. Therefore, we developed an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectra from vertically pointing Ka-band cloud radar. Furthermore, thismore » approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid. Diffusional growth calculations show that the conditions for the Wegener-Bergeron-Findeisen process exist within one of these mixed-phase microstructures.« less

A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riihimaki, Laura D.; Comstock, J. M.; Luke, E.

To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, ground-based vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement site are used to classify cloud phase within a deep convective cloud. The cloud cannot be fully observed by a lidar due to signal attenuation. Therefore, we developed an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectra from vertically pointing Ka-band cloud radar. Furthermore, thismore » approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid. Diffusional growth calculations show that the conditions for the Wegener-Bergeron-Findeisen process exist within one of these mixed-phase microstructures.« less

Evaluation of the Cloud Fields in the UK Met Office HadGEM3-UKCA Model Using the CCCM Satellite Data Product to Advance Our Understanding of the Influence of Clouds on Tropospheric Composition and Chemistry

NASA Technical Reports Server (NTRS)

Varma, Sunil; Voulgarakis, Apostolos; Liu, Hongyu; Crawford, James H.; White, James

2016-01-01

To determine the role of clouds in driving inter-annual and inter-seasonal variability of trace gases in the troposphere and lower stratosphere with a particular focus on the importance of cloud modification of photolysis. To evaluate the cloud fields and their vertical distribution in the HadGEM3 model utilizing CCCM, a unique 3-D cloud data product merged from multiple A-Train satellites (CERES, CloudSat, CALIPSO, and MODIS) developed at the NASA Langley Research Center.

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

NASA Astrophysics Data System (ADS)

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

2016-07-01

Shallow marine cumulus clouds are by far the most frequently observed cloud type over the Earth's oceans; but they are poorly understood and have not been investigated as extensively as stratocumulus clouds. This study describes and discusses the properties and variations of aerosol, cloud, and precipitation associated with shallow marine cumulus clouds observed in the North Atlantic trades during a field campaign (Barbados Aerosol Cloud Experiment- BACEX, March-April 2010), which took place off Barbados where African dust periodically affects the region. The principal observing platform was the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter (TO) research aircraft, which was equipped with standard meteorological instruments, a zenith pointing cloud radar and probes that measured aerosol, cloud, and precipitation characteristics.The temporal variation and vertical distribution of aerosols observed from the 15 flights, which included the most intense African dust event during all of 2010 in Barbados, showed a wide range of aerosol conditions. During dusty periods, aerosol concentrations increased substantially in the size range between 0.5 and 10 µm (diameter), particles that are large enough to be effective giant cloud condensation nuclei (CCN). The 10-day back trajectories showed three distinct air masses with distinct vertical structures associated with air masses originating in the Atlantic (typical maritime air mass with relatively low aerosol concentrations in the marine boundary layer), Africa (Saharan air layer), and mid-latitudes (continental pollution plumes). Despite the large differences in the total mass loading and the origin of the aerosols, the overall shapes of the aerosol particle size distributions were consistent, with the exception of the transition period.The TO was able to sample many clouds at various phases of growth. Maximum cloud depth observed was less than ˜ 3 km, while most clouds were less than 1 km deep. Clouds tend to precipitate when the cloud is thicker than 500-600 m. Distributions of cloud field characteristics (depth, radar reflectivity, Doppler velocity, precipitation) were well identified in the reflectivity-velocity diagram from the cloud radar observations. Two types of precipitation features were observed for shallow marine cumulus clouds that may impact boundary layer differently: first, a classic cloud-base precipitation where precipitation shafts were observed to emanate from the cloud base; second, cloud-top precipitation where precipitation shafts emanated mainly near the cloud tops, sometimes accompanied by precipitation near the cloud base. The second type of precipitation was more frequently observed during the experiment. Only 42-44 % of the clouds sampled were non-precipitating throughout the entire cloud layer and the rest of the clouds showed precipitation somewhere in the cloud, predominantly closer to the cloud top.

Behavior of predicted convective clouds and precipitation in the high-resolution Unified Model over the Indian summer monsoon region

NASA Astrophysics Data System (ADS)

Jayakumar, A.; Sethunadh, Jisesh; Rakhi, R.; Arulalan, T.; Mohandas, Saji; Iyengar, Gopal R.; Rajagopal, E. N.

2017-05-01

National Centre for Medium Range Weather Forecasting high-resolution regional convective-scale Unified Model with latest tropical science settings is used to evaluate vertical structure of cloud and precipitation over two prominent monsoon regions: Western Ghats (WG) and Monsoon Core Zone (MCZ). Model radar reflectivity generated using Cloud Feedback Model Intercomparison Project Observation Simulator Package along with CloudSat profiling radar reflectivity is sampled for an active synoptic situation based on a new method using Budyko's index of turbulence (BT). Regime classification based on BT-precipitation relationship is more predominant during the active monsoon period when convective-scale model's resolution increases from 4 km to 1.5 km. Model predicted precipitation and vertical distribution of hydrometeors are found to be generally in agreement with Global Precipitation Measurement products and BT-based CloudSat observation, respectively. Frequency of occurrence of radar reflectivity from model implies that the low-level clouds below freezing level is underestimated compared to the observations over both regions. In addition, high-level clouds in the model predictions are much lesser over WG than MCZ.

The clouds are hazes of Venus

NASA Technical Reports Server (NTRS)

Esposito, L. W.; Knollenberg, R. G.; Marov, M. IA.; Toon, O. B.; Turco, R. P.

1983-01-01

Pioneer Venus and Venera probe data for the clouds of Venus are considered. These clouds consist of a main cloud deck at 45-70 km altitude, with thinner hazes above and below, although the microphysical properties of the main cloud are further subdivided into upper, middle and lower cloud levels. Much of the cloud exhibits a multimodal particle size distribution, with the mode most visible from the earth being H2SO4 droplets having 2-3 micron diameters. Despite variations, the vertical structure of the clouds indicates persistent features at sites separated by years and by great distances. The clouds are more strongly affected by radiation than by latent heat release, and the small particle size and weak convective activity observed are incompatible with lightning of cloud origin.

Water Ice Cloud Opacities and Temperatures Derived from the Viking IRTM Data Set

NASA Technical Reports Server (NTRS)

TamppariL. K.; Zurek, R. W.; Paige, D. A.

1999-01-01

The degree to which water ice clouds play a role in the Mars climate is unknown. Latent heating of water ice clouds is small and since most hazes appeared to be thin (tau less than or = 1) their radiative effects have been neglected. Condensation likely limits the vertical extent of water vapor in the water column and a lowering of the condensation altitude, as seen in the northern spring and summer, could increase the seasonal exchange of water between the atmosphere and the surface. It has been suggested that water ice cloud formation is more frequent and widespread in the aphelic hemisphere (currently the northern). This may limit water to the northern hemisphere through greater exchange with the regolith and through restricted southward transport of water vapor by the Mars Hadley circulation. In addition, it has been suggested that water ice cloud formation also controls the vertical distribution of atmospheric dust in some seasons. This scavenging of dust may Continuing from the IRTM cloud maps, derived cloud opacities and cloud temperatures for several locations and seasons will be presented. Sensitivities to cloud particle sizes, surface temperature, and dust opacity will be discussed.

Airship measurements of aerosol size distributions, cloud droplet spectra, and trace gas concentrations in the marine boundary layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frick, G.M.; Hoppel, W.A.

1993-11-01

The use of an airship as a platform to conduct atmospheric chemistry, aerosol, and cloud microphysical research is described, and results from demonstration flights made off the Oregon coast are presented. The slow speed of the airship makes it an ideal platform to do high-spatial resolution profiling both vertically and horizontally, and to measure large aerosol and cloud droplet distributions without the difficulties caused by high-speed aircraft sampling. A unique set of data obtained during the demonstration flights show the effect that processing marine boundary layer aerosol through stratus clouds has on the aerosol size distribution. Evidence of new particlemore » formation (nucleation of particles) was also observed on about half the days on which flights were made. 11 refs., 9 figs., 1 tab.« less

Transmission of electric fields due to distributed cloud charges in the atmosphere-ionosphere system

NASA Astrophysics Data System (ADS)

Paul, Suman; De, S. S.; Haldar, D. K.; Guha, G.

2017-10-01

The transmission of electric fields in the lower atmosphere by thunder clouds with a suitable charge distribution profile has been modeled. The electromagnetic responses of the atmosphere are presented through Maxwell's equations together with a time-varying source charge distribution. The conductivities are taken to be exponentially graded function of altitude. The radial and vertical electric field components are derived for isotropic, anisotropic and thundercloud regions. The analytical solutions for the total Maxwell's current which flows from the cloud into the ionosphere under DC and quasi-static conditions are obtained for isotropic region. We found that the effect of charge distribution in thunderclouds produced by lightning discharges diminishes rapidly with increasing altitudes. Also, it is found that time to reach Maxwell's currents a maximum is higher for higher altitudes.

Clouds on Neptune: Motions, Evolution, and Structure

NASA Technical Reports Server (NTRS)

Sromovsky, Larry A.; Morgan, Thomas (Technical Monitor)

2001-01-01

The aims of our original proposal were these: (1) improving measurements of Neptune's circulation, (2) understanding the spatial distribution of cloud features, (3) discovery of new cloud features and understanding their evolutionary process, (4) understanding the vertical structure of zonal cloud patterns, (5) defining the structure of discrete cloud features, and (6) defining the near IR albedo and light curve of Triton. Towards these aims we proposed analysis of existing 1996 groundbased NSFCAM/IRTF observations and nearly simultaneous WFPC2 observations from the Hubble Space Telescope. We also proposed to acquire new observations from both HST and the IRTF.

Comparison of Cloud Detection Using the CERES-MODIS Ed4 and LaRC AVHRR Cloud Masks and CALIPSO Vertical Feature Mask

NASA Astrophysics Data System (ADS)

Trepte, Q. Z.; Minnis, P.; Palikonda, R.; Bedka, K. M.; Sun-Mack, S.

2011-12-01

Accurate detection of cloud amount and distribution using satellite observations is crucial in determining cloud radiative forcing and earth energy budget. The CERES-MODIS (CM) Edition 4 cloud mask is a global cloud detection algorithm for application to Terra and Aqua MODIS data with the aid of other ancillary data sets. It is used operationally for the NASA's Cloud and Earth's Radiant Energy System (CERES) project. The LaRC AVHRR cloud mask, which uses only five spectral channels, is based on a subset of the CM cloud mask which employs twelve MODIS channels. The LaRC mask is applied to AVHRR data for the NOAA Climate Data Record Program. Comparisons among the CM Ed4, and LaRC AVHRR cloud masks and the CALIPSO Vertical Feature Mask (VFM) constitute a powerful means for validating and improving cloud detection globally. They also help us understand the strengths and limitations of the various cloud retrievals which use either active and passive satellite sensors. In this paper, individual comparisons will be presented for different types of clouds over various surfaces, including daytime and nighttime, and polar and non-polar regions. Additionally, the statistics of the global, regional, and zonal cloud occurrence and amount from the CERES Ed4, AVHRR cloud masks and CALIPSO VFM will be discussed.

DC-8 scanning lidar characterization of aircraft contrails and cirrus clouds

NASA Technical Reports Server (NTRS)

Nielsen, Norman B.; Uthe, Edward E. (Principal Investigator)

1996-01-01

A Subsonic Assessment (SASS) element of the overall Atmospheric Effects of Aviation Project (AEAP) was initiated by NASA to assess the atmospheric impact of subsonic aircraft. SRI was awarded a project to develop and test a scanning backscatter lidar for installation on the NASA DC-8 (year 1), participate in the Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) field program (year 2), and conduct a comprehensive analysis of field data (year 3). A scanning mirror pod attached to the DC-8 aircraft provides for scanning lidar observations ahead of the DC-8 and fixed-angle upward or downward observations. The lidar system installed within the DC-8 transmits 275 MJ at 1.06 gm wavelength or about 130 mJ at 1.06 and 0.53 gm simultaneously. Range-resolved aerosol backscatter is displayed in real time in terms of cloud/contrail spatial distributions. The objectives of the project are to map contrail/cloud vertical distributions ahead of DC-8; provide DC-8 guidance into enhanced scattering layers; document DC-8 flight path intersection of contrail and cloud geometries (in-situ measurement positions relative to cloud/contrail shape and an extension of in-situ measurements into the vertical -- integrated contrail/cloud properties); analyze contrail/cloud radiative properties with LIRAD (combined lidar and radiometry) technique; evaluate mean particle sizes of aircraft emissions from two-wavelength observations; study contrail/cloud interactions, diffusion, and mass decay/growth; and make observations in the near-field of aircraft engine emissions. The scanning mirror pod may also provide a scanning capability for other remote sensing instruments.

Explicit and Observation-based Aerosol Treatment in Tropospheric NO2 Retrieval over China from the Ozone Monitoring Instrument

NASA Astrophysics Data System (ADS)

Liu, M.; Lin, J.; Boersma, F.; Pinardi, G.; Wang, Y.; Chimot, J.; Wagner, T.; Xie, P.; Eskes, H.; Van Roozendael, M.; Hendrick, F.

2017-12-01

Satellite retrieval of vertical column densities (VCDs) of tropospheric nitrogen dioxide (NO2) is influenced by aerosols substantially. Aerosols affect the retrieval of "effective cloud fraction (CF)" and "effective cloud top pressure (CP)" that are used in the subsequent NO2 retrieval to account for the presentence of clouds. And aerosol properties and vertical distributions directly affect the NO2 air mass factor (AMF) calculations. Our published POMINO algorithm uses a parallelized LIDORT-driven AMFv6 code to derive CF, CP and NO2 VCD. Daily information on aerosol optical properties are taken from GEOS-Chem simulations, with aerosol optical depth (AOD) further constrained by monthly MODIS AOD. However, the published algorithm does not include an observation-based constraint of aerosol vertical distribution. Here we construct a monthly climatological observation dataset of aerosol extinction profiles, based on Level-2 CALIOP data over 2007-2015, to further constrain aerosol vertical distributions. GEOS-Chem captures the temporal variations of CALIOP aerosol layer heights (ALH) but has an overall underestimate by about 0.3 km. It tends to overestimate the aerosol extinction by 10% below 2 km but with an underestimate by 30% above 2 km, leading to a low bias by 10-30% in the retrieved tropospheric NO2 VCD. After adjusting GEOS-Chem aerosol extinction profiles by the CALIOP monthly ALH climatology, the retrieved NO2 VCDs increase by 4-16% over China on a monthly basis in 2012. The improved NO2 VCDs are better correlated to independent MAX-DOAS observations at three sites than POMINO and DOMINO are - especially for the polluted cases, R2 reaches 0.76 for the adjusted POMINO, much higher than that for the published POMINO (0.68) and DOMINO (0.38). The newly retrieved CP increases by 60 hPa on average, because of a stronger aerosol screening effect. Compared to the CF used in DOMINO, which implicitly includes aerosol information, our improved CF is much lower and can reach a value of zero on actual cloud-free days. Overall, constraining aerosol vertical profiles greatly improves the retrievals of clouds and NO2 VCDs from satellite remote sensing. Our algorithm can be applied, with minimum modifications, to formaldehyde, sulfur dioxide and other species with similar retrieval methodologies.

Use of a W-band polarimeter to measure microphysical characteristics of clouds

NASA Astrophysics Data System (ADS)

Galloway, John Charles

1997-08-01

This dissertation presents W-Band measurements of the copolar correlation co-efficient and Doppler spectrum taken from the University of Wyoming King Air research airplane. These measurements demonstrate the utility of making W-Band polarimetric and Doppler spectrum measurements from an airborne platform in investigations of cloud microphysical properties. Comparison of copolar correlation coefficient measurements with aircraft in situ probe measurements verifies that polarimetric measurements indicate phase transitions, and hydrometeor alignment in ice clouds. Melting layers in clouds were measured by the W-Band system on board the King Air during 1992 and 1994. Both measurements established the use of the linear depolarization ratio, LDR, to locate the melting layer using an airborne W-Band system. The measurement during 1994 allowed direct comparison of the magnitude of the copolar correlation coefficient with the values of LDR. The relation between the measurements corresponds with a predicted relationship between the two parameters for observation of particles exhibiting isotropy in the plane of polarization. Measurements of needle crystals at horizontal and vertical incidence provided further evidence that the copolar correlation coefficient values agreed with the expected response from hydrometeors possessing a preferred alignment for the side looking case, and hydrometeors without a preferred alignment for the vertical incidence case. Observation of significant specific differential phase at vertical incidence, the first reported at W-Band, corresponded to a significant increase in differential reflectivity overhead, which was most likely produced by hydrometeor alignment driven by cloud electrification. Comparison of the drop size distributions estimated using the Doppler spectra with those measured by the wingtip probes on the King Air reveals that the radar system is better suited under some liquid cloud conditions to provide microphysical measurements of the cloud or precipitation than the probes. The radiometric calibration of the radar system determines the accuracy of the drop size distribution estimate. The results presented here indicate that the procedure used to absolutely calibrate the W-Band radar system successfully characterized the reflectivity measurements to the extent required to obtain close correspondence between the radar and probe measurements of the drop size distribution.

A critical look at spatial scale choices in satellite-based aerosol indirect effect studies

NASA Astrophysics Data System (ADS)

Grandey, B. S.; Stier, P.

2010-12-01

Analysing satellite datasets over large regions may introduce spurious relationships between aerosol and cloud properties due to spatial variations in aerosol type, cloud regime and synoptic regime climatologies. Using MODerate resolution Imaging Spectroradiometer data, we calculate relationships between aerosol optical depth τa derived liquid cloud droplet effective number concentration Ne and liquid cloud droplet effective radius re at different spatial scales. Generally, positive values of dlnNedlnτa are found for ocean regions, whilst negative values occur for many land regions. The spatial distribution of dlnredlnτa shows approximately the opposite pattern, with generally postive values for land regions and negative values for ocean regions. We find that for region sizes larger than 4° × 4°, spurious spatial variations in retrieved cloud and aerosol properties can introduce widespread significant errors to calculations of dlnNedlnτa and dlnredlnτa. For regions on the scale of 60° × 60°, these methodological errors may lead to an overestimate in global cloud albedo effect radiative forcing of order 80% relative to that calculated for regions on the scale of 1° × 1°.

Infrared experiments for spaceborne planetary atmospheres research. Full report

NASA Technical Reports Server (NTRS)

1981-01-01

The role of infrared sensing in atmospheric science is discussed and existing infrared measurement techniques are reviewed. Proposed techniques for measuring planetary atmospheres are criticized and recommended instrument developments for spaceborne investigations are summarized for the following phenomena: global and local radiative budget; radiative flux profiles; winds; temperature; pressure; transient and marginal atmospheres; planetary rotation and global atmospheric activity; abundances of stable constituents; vertical, lateral, and temporal distribution of abundances; composition of clouds and aerosols; radiative properties of clouds and aerosols; cloud microstructure; cloud macrostructure; and non-LTE phenomena.

Using LIDAR and UAV-derived point clouds to evaluate surface roughness in a gravel-bed braided river (Vénéon river, French Alps)

NASA Astrophysics Data System (ADS)

Vázquez Tarrío, Daniel; Borgniet, Laurent; Recking, Alain; Liebault, Frédéric; Vivier, Marie

2016-04-01

The present research is focused on the Vénéon river at Plan du Lac (Massif des Ecrins, France), an alpine braided gravel bed stream with a glacio-nival hydrological regime. It drains a catchment area of 316 km2. The present research is focused in a 2.5 km braided reach placed immediately upstream of a small hydropower dam. An airbone LIDAR survey was accomplished in October, 2014 by EDF (the company managing the small hydropower dam), and data coming from this LIDAR survey were available for the present research. Point density of the LIDAR-derived 3D-point cloud was between 20-50 points/m2, with a vertical precision of 2-3 cm over flat surfaces. Moreover, between April and Juin, 2015, we carried out a photogrammetrical campaign based in aerial images taken with an UAV-drone. The UAV-derived point-cloud has a point density of 200-300 points/m2, and a vertical precision over flat control surfaces comparable to that of the LIDAR point cloud (2-3 cm). Simultaneously to the UAV campaign, we took several Wolman samples with the aim of characterizing the grain size distribution of bed sediment. Wolman samples were taken following a geomorphological criterion (unit bars, head/tail of compound bars). Furthermore, some of the Wolman samples were repeated with the aim of defining the uncertainty of our sampling protocol. LIDAR and UAV-derived point clouds were treated in order to check whether both point-clouds were correctly co-aligned. After that, we estimated bed roughness using the detrended standard deviation of heights, in a 40-cm window. For all this data treatment we used CloudCompare. Then, we measured the distribution of roughness in the same geomorphological units where we took the Wolman samples, and we compared with the grain size distributions measured in the field: differences between UAV-point cloud roughness distributions and measured-grain size distribution (~1-2 cm) are in the same order of magnitude of the differences found between the repeated Wolman samples (~0.5-1.5 cm). Differences with LIDAR-derived roughness distributions are only slightly higher, which could be due to the lower point density of the LIDAR point clouds.

Cloud condensation nuclei near marine cumulus

NASA Technical Reports Server (NTRS)

Hudson, James G.

1993-01-01

Extensive airborne measurements of cloud condensation nucleus (CCN) spectra and condensation nuclei below, in, between, and above the cumulus clouds near Hawaii point to important aerosol-cloud interactions. Consistent particle concentrations of 200/cu cm were found above the marine boundary layer and within the noncloudy marine boundary layer. Lower and more variable CCN concentrations within the cloudy boundary layer, especially very close to the clouds, appear to be a result of cloud scavenging processes. Gravitational coagulation of cloud droplets may be the principal cause of this difference in the vertical distribution of CCN. The results suggest a reservoir of CCN in the free troposphere which can act as a source for the marine boundary layer.

What Controls the Vertical Distribution of Aerosol? Relationships Between Process Sensitivity in HadGEM3-UKCA and Inter-Model Variation from AeroCom Phase II

NASA Technical Reports Server (NTRS)

Kipling, Zak; Stier, Philip; Johnson, Colin E.; Mann, Graham W.; Bellouin, Nicolas; Bauer, Susanne E.; Bergman, Tommi; Chin, Mian; Diehl, Thomas; Ghan, Steven J.;

Martian Atmosphere Profiles

NASA Image and Video Library

2010-08-26

The Mars Climate Sounder instrument on NASA Mars Reconnaissance Orbiter maps the vertical distribution of temperatures, dust, water vapor and ice clouds in the Martian atmosphere as the orbiter flies a near-polar orbit.

Parameterization of Cirrus Cloud Vertical Profiles and Geometrical Thickness Using CALIPSO and CloudSat Data

NASA Astrophysics Data System (ADS)

Khatri, P.; Iwabuchi, H.; Saito, M.

2017-12-01

High-level cirrus clouds, which normally occur over more than 20% of the globe, are known to have profound impacts on energy budget and climate change. The scientific knowledge regarding the vertical structure of such high-level cirrus clouds and their geometrical thickness are relatively poorer compared to low-level water clouds. Knowledge regarding cloud vertical structure is especially important in passive remote sensing of cloud properties using infrared channels or channels strongly influenced by gaseous absorption when clouds are geometrically thick and optically thin. Such information is also very useful for validating cloud resolving numerical models. This study analyzes global scale data of ice clouds identified by Cloud profiling Radar (CPR) onboard CloudSat and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard CALIPSO to parameterize (i) vertical profiles of ice water content (IWC), cloud-particle effective radius (CER), and ice-particle number concentration for varying ice water path (IWP) values and (ii) the relation of cloud geometrical thickness (CGT) with IWP and CER for varying cloud top temperature (CTT) values. It is found that the maxima in IWC and CER profile shifts towards cloud base with the increase of IWP. Similarly, if the cloud properties remain same, CGT shows an increasing trend with the decrease of CTT. The implementation of such cloud vertical inhomogeneity parameterization in the forward model used in the Integrated Cloud Analysis System ICAS (Iwabuchi et al., 2016) generally shows increase of brightness temperatures in infrared channels compared to vertically homogeneous cloud assumption. The cloud vertical inhomogeneity is found to bring noticeable changes in retrieved cloud properties. Retrieved CER and cloud top height become larger for optically thick cloud. We will show results of comparison of cloud properties retrieved from infrared measurements and active remote sensing.

A Study of the Vertical Structure of Tropical (20 deg S-20 deg N) Optically Thin Clouds from SAGE II Observations

NASA Technical Reports Server (NTRS)

Wang, Pi-Huan; Minnis, Patrick; McCormick, M. Patrick; Kent, Geoffrey S.; Yue, Glenn K.; Young, David F.; Skeens, Kristi M.

1998-01-01

The tropical cloud data obtained by the satellite instrument of the Stratospheric Aerosol and Gas Experiment (SAGE) II from October 1984 to May 1991 have been used to study cloud vertical distribution, including thickness and multilayer structure, and to estimate cloud optical depth. The results indicate that the SAGE-II-observed clouds are generally optically thin clouds, corresponding to a range of optical depth between approximately 8 x 10(exp -4) and 3 x 10(exp -1) with a mean of about 0.035. Two-thirds are classified as subvisual cirrus and one-third thin cirrus. Clouds between 2- to 3-km thick occur most frequently. Approximately 30% of the SAGE II cloud measurements are isolated single-layer clouds, while 65% are high clouds contiguous with an underlying opaque cloud that terminates the SAGE II profile. Thin clouds above detached opaque clouds at altitudes greater than 6.5 km occur less often. Only about 3% of the SAGE II single-layer clouds are located above the tropopause, while 58% of the cloud layers never reach the tropopause. More than one-third of the clouds appear at the tropopause. This study also shows that clouds occur more frequently and extend higher above the tropopause over the western Pacific than than over the eastern Pacific, especially during northern winter. The uncertainty of the derived results due to the SAGE II sampling constraints, data processing, and cloud characteristics is discussed.

Aerosols and polar stratospheric clouds measurements during the EASOE campaign

NASA Technical Reports Server (NTRS)

Haner, D.; Godin, S.; Megie, G.; David, C.; Mitev, V.

1992-01-01

Preliminary results of observations performed using two different lidar systems during the EASOE (European Arctic Stratospheric Ozone Experiment), which has taken place in the winter of 1991-1992 in the northern hemisphere lattitude regions, are presented. The first system is a ground based multiwavelength lidar intended to perform measurements of the ozone vertical distribution in the 5 km to 40 km altitude range. It was located in Sodankyla (67 degrees N, 27 degrees E) as part of the ELSA experiment. The objectives of the ELSA cooperative project is to study the relation between polar stratospheric cloud events and ozone depletion with high vertical resolution and temporal continuity, and the evolution of the ozone distribution in relation to the position of the polar vortex. The second system is an airborne backscatter lidar (Leandre) which allows for the study of the 3-D structure and the optical properties of polar stratospheric clouds. The Leandre instrument is a dual-polarization lidar system, emitting at 532 nm, which allows for the determination of the type of clouds observed, according to the usual classification of polar stratospheric clouds. More than 60 hours of flight were performed in Dec. 1991, and Jan. and Feb. 1992 in Kiruna, Sweden. The operation of the Leandre instrument has led to the observation of the short scale variability of the Pinatubo volcanic cloud in the high latitude regions and to several episodes of polar stratospheric clouds. Preliminary analysis of the data is presented.

Observations and Parameterizations of Particle Size Distributions in Deep Tropical Cirrus and Stratiform Precipitation Clouds: Results from In-Situ Observations in TRMM Field Campaigns

NASA Technical Reports Server (NTRS)

Heymsfield, Andrew J.; Bansemer, Aaron; Field, Paul R.; Durden, Stephen L.; Stith, Jeffrey L.; Dye, James E.; Hall, William; Grainger, Cedric A.

2002-01-01

In this study, we report on the evolution of particle size distributions (PSDs) and habits as measured during slow, Lagrangian-type spiral descents through deep subtropical and tropical cloud layers in Florida, Brazil, and Kwajalein, Marshall Islands, most of which were precipitating. The objective of the flight patterns was to learn more about how the PSDs evolved in the vertical and to obtain information of the vertical structure of microphysical properties. New instrumentation yielding better information on the concentrations of particles in the size (D) range between 0.2 and 2 cm, as well as improved particle imagery, produced more comprehensive observations for tropical stratiform precipitation regions and anvils than have been available previously. Collocated radar observations provided additional information on the vertical structure of the cloud layers sampled. Most of the spirals began at cloud top, with temperatures (T) as low as -50 C, and ended at cloud base or below the melting layer (ML). The PSDs broadened from cloud top towards cloud base, with the largest particles increasing in size from several millimeters at cloud top to one centimeter or larger towards cloud base. Some continued growth was noted in the upper part of the ML. Concentrations of particles less than 1 mm in size decreased with decreasing height. The result was a consistent change in the PSDs in the vertical. Similarly, systematic changes in the size dependence of the particle cross-sectional area was noted with decreasing height. Aggregation-as ascertained from both the changes in the PSDs and evolution of particle habits as observed in high detail with the cloud particle imager (CPI) probe-was responsible for these trends. The PSDs were generally well-represented by gamma distributions of the form N = N0 gamma D microns e- lambda gamma D that were fitted to the PSDs over 1-km horizontal intervals throughout the spirals. The intercept (N0 gamma), slope (lambda gamma), and dispersion (microns) values were derived for each PSD. Exponential curves (N = N0e- lambdaD; micron = 0) were also fitted to the distributions. The lambda gamma values for given spirals varied systematically with temperature as did the values of lambda (exponential), and the data generally conformed to values found in previous studies involving exponential fits to size distributions in mid-latitude frontal and cirrus layers. Considerable variability often noted in the PSD properties during the loops of individual spirals was manifested primarily in large changes in N0 gamma and N0, but micron, lambda gamma and lambda remained fairly stable. Temperature is not found to be the sole factor controlling lambda gamma or lambda but is a primary one. Direct relationships were found between lambda gamma and N0 gamma or lambda gamma and micron for the gamma distributions and lambda and N0 for the exponential. The latter relationship was not found as distinctly in earlier studies; observed PSDs in this study had better fidelity with less scatter. The micron values changed monotonically with T over the range of temperatures and were directly related to N0 gamma or lambda gamma, thereby reducing the number of variables in the PSD functional equation to two. In the upper part of the ML, N0 and lambda continued to decrease, and in the lower part these values began to increase as the largest particles melted. We developed general expressions relating various bulk microphysical, radar, and radiative transfer-related variables to N0 gamma and lambda gamma, useful for both tropical and mid-latitude clouds. These relationships facilitate the specification of a number of bulk properties in cloud and climate models. The results presented in this paper apply best to temperatures between 0 and -40 C, for which the measured radar reflectivities fall in the range of 0 to 25 dBZe.

Correlated k-distribution method for radiative transfer in climate models: Application to effect of cirrus clouds on climate

NASA Technical Reports Server (NTRS)

Lacis, A. A.; Wang, W. C.; Hansen, J. E.

1979-01-01

A radiative transfer method appropriate for use in simple climate models and three dimensional global climate models was developed. It is fully interactive with climate changes, such as in the temperature-pressure profile, cloud distribution, and atmospheric composition, and it is accurate throughout the troposphere and stratosphere. The vertical inhomogeneity of the atmosphere is accounted for by assuming a correlation of gaseous k-distributions of different pressures and temperatures. Line-by-line calculations are made to demonstrate that The method is remarkably accurate. The method is then used in a one-dimensional radiative-convective climate model to study the effect of cirrus clouds on surface temperature. It is shown that an increase in cirrus cloud cover can cause a significant warming of the troposphere and the Earth's surface, by the mechanism of an enhanced green-house effect. The dependence of this phenomenon on cloud optical thickness, altitude, and latitude is investigated.

Microwave (SSM/I) Estimates of the Precipitation Rate to Improve Numerical Atmospheric Model Forecasts

NASA Technical Reports Server (NTRS)

Raymond, William H.; Olson, William S.

1990-01-01

Delay in the spin-up of precipitation early in numerical atmospheric forecasts is a deficiency correctable by diabatic initialization combined with diabatic forcing. For either to be effective requires some knowledge of the magnitude and vertical placement of the latent heating fields. Until recently the best source of cloud and rain water data was the remotely sensed vertical integrated precipitation rate or liquid water content. Vertical placement of the condensation remains unknown. Some information about the vertical distribution of the heating rates and precipitating liquid water and ice can be obtained from retrieval techniques that use a physical model of precipitating clouds to refine and improve the interpretation of the remotely sensed data. A description of this procedure and an examination of its 3-D liquid water products, along with improved modeling methods that enhance or speed-up storm development is discussed.

The Diagnosis and application of a convective vorticity vector associated with convective systems

NASA Astrophysics Data System (ADS)

Gao, S.; Zhou, Y.; Tao, W.

2005-05-01

Although dry/moist potential vorticity is a very useful and powerful physical quantity in the large scale dynamics, it is not a quite ideal dynamical tool for the study of convective systems or severe storms. A new convective vorticity vector (CVV) is introduced in this study to identify the development of convective systems or severe storms. The daily Aviation (AVN) Model Data is used to diagnose the distribution of the CVV associated with rain storms occurred in the period of Meiyu in 1998. The results have clearly demonstrated that the CVV is an effective vector for indicating the convective actions along the Meiyu front. The CVV also is used to diagnose a 2-D cloud-resolving simulation data associated with 2-D tropical convection. The cloud model is forced by the vertical velocity, zonal wind, horizontal advection, and sea surface temperature obtained from the Tropical cean-Global tmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) and is integrated for a selected 10-day period. The CVV has zonal and vertical components in the 2-D x-z frame. Analysis of zonally averaged and mass-integrated quantities shows that the correlation coefficient between the vertical component of the CVV and the sum of the cloud hydrometeor mixing ratios is 0.81, whereas the correlation coefficient between the zonal component and the sum of the mixing ratios is only 0.18. This indicates that the vertical component of the CVV is closely associated with tropical convection. The tendency equation for the vertical component of the CVV is derived and the zonally averaged and mass-integrated tendency budgets are analyzed. The tendency of the vertical component of the CVV is determined by the interaction between the vorticity and the zonal gradient of cloud heating. The results demonstrate that the vertical component of the CVV is a cloud-linked parameter and can be used to study tropical convection.

A Method for Obtaining High Frequency, Global, IR-Based Convective Cloud Tops for Studies of the TTL

NASA Technical Reports Server (NTRS)

Pfister, Leonhard; Ueyama, Rei; Jensen, Eric; Schoeberl, Mark

2017-01-01

Models of varying complexity that simulate water vapor and clouds in the Tropical Tropopause Layer (TTL) show that including convection directly is essential to properly simulating the water vapor and cloud distribution. In boreal winter, for example, simulations without convection yield a water vapor distribution that is too uniform with longitude, as well as minimal cloud distributions. Two things are important for convective simulations. First, it is important to get the convective cloud top potential temperature correctly, since unrealistically high values (reaching above the cold point tropopause too frequently) will cause excessive hydration of the stratosphere. Second, one must capture the time variation as well, since hydration by convection depends on the local relative humidity (temperature), which has substantial variation on synoptic time scales in the TTL. This paper describes a method for obtaining high frequency (3-hourly) global convective cloud top distributions which can be used in trajectory models. The method uses rainfall thresholds, standard IR brightness temperatures, meteorological temperature analyses, and physically realistic and documented corrections IR brightness temperature corrections to derive cloud top altitudes and potential temperatures. The cloud top altitudes compare well with combined CLOUDSAT and CALIPSO data, both in time-averaged overall vertical and horizontal distributions and in individual cases (correlations of .65-.7). An important finding is that there is significant uncertainty (nearly .5 km) in evaluating the statistical distribution of convective cloud tops even using lidar. Deep convection whose tops are in regions of high relative humidity (such as much of the TTL), will cause clouds to form above the actual convection. It is often difficult to distinguish these clouds from the actual convective cloud due to the uncertainties of evaluating ice water content from lidar measurements. Comparison with models show that calculated cloud top altitudes are generally higher than those calculated by global analyses (e.g., MERRA). Interannual variability in the distribution of convective cloud top altitudes is also investigated.

Global Measurements of Optically Thin Ice Clouds Using CALIOP

NASA Technical Reports Server (NTRS)

Ryan, R.; Avery, M.; Tackett, J.

2017-01-01

Optically thin ice clouds have been shown to have a net warming effect on the globe but, because passive instruments are not sensitive to optically thin clouds, the occurrence frequency of this class of clouds is greatly underestimated in historical passive sensor cloud climatology. One major strength of CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization), onboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) spacecraft, is its ability to detect these thin clouds, thus filling an important missing piece in the historical data record. This poster examines the full mission of CALIPSO Level 2 data, focusing on those CALIOP retrievals identified as thin ice clouds according to the definition shown to the right. Using this definition, thin ice clouds are identified and counted globally and vertically for each season. By examining the spatial and seasonal distributions of these thin clouds we hope to gain a better understanding these thin ice clouds and how their global distribution has changed over the mission. This poster showcases when and where CALIOP detects thin ice clouds and examines a case study of the eastern pacific and the effects seen from the El Nino-Southern Oscillation (ENSO).

Insights on the Martian water cycle through the SPICAM/MEx retrievals of the H _{2}O vertical distribution

NASA Astrophysics Data System (ADS)

Maltagliati, Luca; Montmessin, Franck; Fedorova, Anna; Bertaux, Jean-Loup; Korablev, Oleg

In pre-Mars Express era only very sparse measurements of the vertical profile of water vapor existed, with limited temporal and spatial coverage. Thus, knowledge of the H2 O distribution along the atmosphere relied almost exclusively on General Circulation Models. The vertical distribution of water vapor nonetheless allows to get otherwise unobtainable information on important characteristics of the Martian water cycle, such as the role of sources and sinks, phase changes, and the influence of clouds. Several other potentially significant phenomena, as the presence of supersaturation, the deposition of water vapor in the layer just below the saturation height, the formation of ice particles and water ice clouds, can be observed and studied in detail for the first time. The infrared channel of the SPICAM spectrometer onboard Mars Express, used in solar oc-cultation mode, allows to retrieve simultaneously the vertical profile of H2 O, CO2 , and aerosol properties. This dataset is thus perfectly suited to enhance our vertical knowledge of the at-mosphere of Mars, covering more than three full Martian years with good temporal and spatial distribution. We present the main results from the analysis of water vapor profiles, and their implication for the behavior of the water cycle on Mars. A comparison with the output from the state-of-the-art General Circulation Model developed at the Laboratoire de Météorologie Dynamique ee in Paris (LMD-GCM), is performed, in order to understand the consequences of this dataset on the current knowledge of physics and microphysics of water on Martian atmosphere. In particular, the currently accepted assumption that the distribution of water in the atmosphere is controlled by saturation physics is tested, and the consequences of the departure from this assumption are analysed in detail.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 icemore » 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.« less

Robust relations between CCN and the vertical evolution of cloud drop size distribution in deep convective clouds

NASA Astrophysics Data System (ADS)

Freud, E.; Rosenfeld, D.; Andreae, M. O.; Costa, A. A.; Artaxo, P.

2008-03-01

In-situ measurements in convective clouds (up to the freezing level) over the Amazon basin show that smoke from deforestation fires prevents clouds from precipitating until they acquire a vertical development of at least 4 km, compared to only 1-2 km in clean clouds. The average cloud depth required for the onset of warm rain increased by ~350 m for each additional 100 cloud condensation nuclei per cm3 at a super-saturation of 0.5% (CCN0.5%). In polluted clouds, the diameter of modal liquid water content grows much slower with cloud depth (at least by a factor of ~2), due to the large number of droplets that compete for available water and to the suppressed coalescence processes. Contrary to what other studies have suggested, we did not observe this effect to reach saturation at 3000 or more accumulation mode particles per cm3. The CCN0.5% concentration was found to be a very good predictor for the cloud depth required for the onset of warm precipitation and other microphysical factors, leaving only a secondary role for the updraft velocities in determining the cloud drop size distributions. The effective radius of the cloud droplets (re) was found to be a quite robust parameter for a given environment and cloud depth, showing only a small effect of partial droplet evaporation from the cloud's mixing with its drier environment. This supports one of the basic assumptions of satellite analysis of cloud microphysical processes: the ability to look at different cloud top heights in the same region and regard their re as if they had been measured inside one well developed cloud. The dependence of re on the adiabatic fraction decreased higher in the clouds, especially for cleaner conditions, and disappeared at re≥~10 μm. We propose that droplet coalescence, which is at its peak when warm rain is formed in the cloud at re=~10 μm, continues to be significant during the cloud's mixing with the entrained air, cancelling out the decrease in re due to evaporation.

Robust relations between CCN and the vertical evolution of cloud drop size distribution in deep convective clouds

NASA Astrophysics Data System (ADS)

Freud, E.; Rosenfeld, D.; Andreae, M. O.; Costa, A. A.; Artaxo, P.

2005-10-01

In-situ measurements in convective clouds (up to the freezing level) over the Amazon basin show that smoke from deforestation fires prevents clouds from precipitating until they acquire a vertical development of at least 4 km, compared to only 1-2 km in clean clouds. The average cloud depth required for the onset of warm rain increased by ~350 m for each additional 100 cloud condensation nuclei per cm3 at a super-saturation of 0.5% (CCN0.5%). In polluted clouds, the diameter of modal liquid water content grows much slower with cloud depth (at least by a factor of ~2), due to the large number of droplets that compete for available water and to the suppressed coalescence processes. Contrary to what other studies have suggested, we did not observe this effect to reach saturation at 3000 or more accumulation mode particles per cm3. The CCN0.5% concentration was found to be a very good predictor for the cloud depth required for the onset of warm precipitation and other microphysical factors, leaving only a secondary role for the updraft velocities in determining the cloud drop size distributions. The effective radius of the cloud droplets (re) was found to be a quite robust parameter for a given environment and cloud depth, showing only a small effect of partial droplet evaporation from the cloud's mixing with its drier environment. This supports one of the basic assumptions of satellite analysis of cloud microphysical processes: the ability to look at different cloud top heights in the same region and regard their re as if they had been measured inside one well developed cloud. The dependence of re on the adiabatic fraction decreased higher in the clouds, especially for cleaner conditions, and disappeared at re≥~10 µm. We propose that droplet coalescence, which is at its peak when warm rain is formed in the cloud at re~10 µm, continues to be significant during the cloud's mixing with the entrained air, canceling out the decrease in re due to evaporation.

OMMYDCLD: a New A-train Cloud Product that Co-locates OMI and MODIS Cloud and Radiance Parameters onto the OMI Footprint

NASA Technical Reports Server (NTRS)

Fisher, Brad; Joiner, Joanna; Vasilkov, Alexander; Veefkind, Pepijn; Platnick, Steven; Wind, Galina

2014-01-01

Clouds cover approximately 60% of the earth's surface. When obscuring the satellite's field of view (FOV), clouds complicate the retrieval of ozone, trace gases and aerosols from data collected by earth observing satellites. Cloud properties associated with optical thickness, cloud pressure, water phase, drop size distribution (DSD), cloud fraction, vertical and areal extent can also change significantly over short spatio-temporal scales. The radiative transfer models used to retrieve column estimates of atmospheric constituents typically do not account for all these properties and their variations. The OMI science team is preparing to release a new data product, OMMYDCLD, which combines the cloud information from sensors on board two earth observing satellites in the NASA A-Train: Aura/OMI and Aqua/MODIS. OMMYDCLD co-locates high resolution cloud and radiance information from MODIS onto the much larger OMI pixel and combines it with parameters derived from the two other OMI cloud products: OMCLDRR and OMCLDO2. The product includes histograms for MODIS scientific data sets (SDS) provided at 1 km resolution. The statistics of key data fields - such as effective particle radius, cloud optical thickness and cloud water path - are further separated into liquid and ice categories using the optical and IR phase information. OMMYDCLD offers users of OMI data cloud information that will be useful for carrying out OMI calibration work, multi-year studies of cloud vertical structure and in the identification and classification of multi-layer clouds.

Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

NASA Astrophysics Data System (ADS)

Krisna, Trismono C.; Wendisch, Manfred; Ehrlich, André; Jäkel, Evelyn; Werner, Frank; Weigel, Ralf; Borrmann, Stephan; Mahnke, Christoph; Pöschl, Ulrich; Andreae, Meinrat O.; Voigt, Christiane; Machado, Luiz A. T.

2018-04-01

Solar radiation reflected by cirrus and deep convective clouds (DCCs) was measured by the Spectral Modular Airborne Radiation Measurement System (SMART) installed on the German High Altitude and Long Range Research Aircraft (HALO) during the Mid-Latitude Cirrus (ML-CIRRUS) and the Aerosol, Cloud, Precipitation, and Radiation Interaction and Dynamic of Convective Clouds System - Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modelling and to the Global Precipitation Measurement (ACRIDICON-CHUVA) campaigns. On particular flights, HALO performed measurements closely collocated with overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite. A cirrus cloud located above liquid water clouds and a DCC topped by an anvil cirrus are analyzed in this paper. Based on the nadir spectral upward radiance measured above the two clouds, the optical thickness τ and particle effective radius reff of the cirrus and DCC are retrieved using a radiance ratio technique, which considers the cloud thermodynamic phase, the vertical profile of cloud microphysical properties, the presence of multilayer clouds, and the heterogeneity of the surface albedo. For the cirrus case, the comparison of τ and reff retrieved on the basis of SMART and MODIS measurements yields a normalized mean absolute deviation of up to 1.2 % for τ and 2.1 % for reff. For the DCC case, deviations of up to 3.6 % for τ and 6.2 % for reff are obtained. The larger deviations in the DCC case are mainly attributed to the fast cloud evolution and three-dimensional (3-D) radiative effects. Measurements of spectral upward radiance at near-infrared wavelengths are employed to investigate the vertical profile of reff in the cirrus. The retrieved values of reff are compared with corresponding in situ measurements using a vertical weighting method. Compared to the MODIS observations, measurements of SMART provide more information on the vertical distribution of particle sizes, which allow reconstructing the profile of reff close to the cloud top. The comparison between retrieved and in situ reff yields a normalized mean absolute deviation, which ranges between 1.5 and 10.3 %, and a robust correlation coefficient of 0.82.

Tropical Oceanic Precipitation Processes over Warm Pool: 2D and 3D Cloud Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, W.- K.; Johnson, D.

1998-01-01

Rainfall is a key link in the hydrologic cycle as well as the primary heat source for the atmosphere, The vertical distribution of convective latent-heat release modulates the large-scale circulations of the tropics, Furthermore, changes in the moisture distribution at middle and upper levels of the troposphere can affect cloud distributions and cloud liquid water and ice contents. How the incoming solar and outgoing longwave radiation respond to these changes in clouds is a major factor in assessing climate change. Present large-scale weather and climate models simulate cloud processes only crudely, reducing confidence in their predictions on both global and regional scales. One of the most promising methods to test physical parameterizations used in General Circulation Models (GCMS) and climate models is to use field observations together with Cloud Resolving Models (CRMs). The CRMs use more sophisticated and physically realistic parameterizations of cloud microphysical processes, and allow for their complex interactions with solar and infrared radiative transfer processes. The CRMs can reasonably well resolve the evolution, structure, and life cycles of individual clouds and cloud systems, The major objective of this paper is to investigate the latent heating, moisture and momenti,im budgets associated with several convective systems developed during the TOGA COARE IFA - westerly wind burst event (late December, 1992). The tool for this study is the Goddard Cumulus Ensemble (CCE) model which includes a 3-class ice-phase microphysical scheme, The model domain contains 256 x 256 grid points (using 2 km resolution) in the horizontal and 38 grid points (to a depth of 22 km depth) in the vertical, The 2D domain has 1024 grid points. The simulations are performed over a 7 day time period. We will examine (1) the precipitation processes (i.e., condensation/evaporation) and their interaction with warm pool; (2) the heating and moisture budgets in the convective and stratiform regions; (3) the cloud (upward-downward) mass fluxes in convective and stratiform regions; (4) characteristics of clouds (such as cloud size, updraft intensity and cloud lifetime) and the comparison of clouds with Radar observations. Differences and similarities in organization of convection between simulated 2D and 3D cloud systems. Preliminary results indicated that there is major differences between 2D and 3D simulated stratiform rainfall amount and convective updraft and downdraft mass fluxes.

Spectral band passes for a high precision satellite sounder

NASA Technical Reports Server (NTRS)

Kaplan, L. D.; Chahine, M. T.; Susskind, J.; Searl, J. E.

1977-01-01

Atmospheric temperature soundings with significantly improved vertical resolution can be obtained from carefully chosen narrow band-pass measurements in the 4.3-micron band of CO2 by taking advantage of the variation of the absorption coefficients, and thereby the weighting functions, with pressure and temperature. A set of channels has been found in the 4.2-micron region that is capable of yielding about 2-km vertical resolution in the troposphere. The concept of a complete system is presented for obtaining high resolution retrievals of temperature and water vapor distribution, as well as surface and cloud top temperatures, even in the presence of broken clouds.

Contaminant transport from point source on water surface in open channel flow with bed absorption

NASA Astrophysics Data System (ADS)

Guo, Jinlan; Wu, Xudong; Jiang, Weiquan; Chen, Guoqian

2018-06-01

Studying solute dispersion in channel flows is of significance for environmental and industrial applications. Two-dimensional concentration distribution for a most typical case of a point source release on the free water surface in a channel flow with bed absorption is presented by means of Chatwin's long-time asymptotic technique. Five basic characteristics of Taylor dispersion and vertical mean concentration distribution with skewness and kurtosis modifications are also analyzed. The results reveal that bed absorption affects both the longitudinal and vertical concentration distributions and causes the contaminant cloud to concentrate in the upper layer. Additionally, the cross-sectional concentration distribution shows an asymptotic Gaussian distribution at large time which is unaffected by the bed absorption. The vertical concentration distribution is found to be nonuniform even at large time. The obtained results are essential for practical implements with strict environmental standards.

Vertical stratification of forest canopy for segmentation of understory trees within small-footprint airborne LiDAR point clouds

NASA Astrophysics Data System (ADS)

Hamraz, Hamid; Contreras, Marco A.; Zhang, Jun

2017-08-01

Airborne LiDAR point cloud representing a forest contains 3D data, from which vertical stand structure even of understory layers can be derived. This paper presents a tree segmentation approach for multi-story stands that stratifies the point cloud to canopy layers and segments individual tree crowns within each layer using a digital surface model based tree segmentation method. The novelty of the approach is the stratification procedure that separates the point cloud to an overstory and multiple understory tree canopy layers by analyzing vertical distributions of LiDAR points within overlapping locales. The procedure does not make a priori assumptions about the shape and size of the tree crowns and can, independent of the tree segmentation method, be utilized to vertically stratify tree crowns of forest canopies. We applied the proposed approach to the University of Kentucky Robinson Forest - a natural deciduous forest with complex and highly variable terrain and vegetation structure. The segmentation results showed that using the stratification procedure strongly improved detecting understory trees (from 46% to 68%) at the cost of introducing a fair number of over-segmented understory trees (increased from 1% to 16%), while barely affecting the overall segmentation quality of overstory trees. Results of vertical stratification of the canopy showed that the point density of understory canopy layers were suboptimal for performing a reasonable tree segmentation, suggesting that acquiring denser LiDAR point clouds would allow more improvements in segmenting understory trees. As shown by inspecting correlations of the results with forest structure, the segmentation approach is applicable to a variety of forest types.

Cloud Optical Depth Retrievals from Solar Background "signal" of Micropulse Lidars

NASA Technical Reports Server (NTRS)

Chiu, J. Christine; Marshak, A.; Wiscombe, W.; Valencia, S.; Welton, E. J.

2007-01-01

Pulsed lidars are commonly used to retrieve vertical distributions of cloud and aerosol layers. It is widely believed that lidar cloud retrievals (other than cloud base altitude) are limited to optically thin clouds. Here we demonstrate that lidars can retrieve optical depths of thick clouds using solar background light as a signal, rather than (as now) merely a noise to be subtracted. Validations against other instruments show that retrieved cloud optical depths agree within 10-15% for overcast stratus and broken clouds. In fact, for broken cloud situations one can retrieve not only the aerosol properties in clear-sky periods using lidar signals, but also the optical depth of thick clouds in cloudy periods using solar background signals. This indicates that, in general, it may be possible to retrieve both aerosol and cloud properties using a single lidar. Thus, lidar observations have great untapped potential to study interactions between clouds and aerosols.

Comparison of Aerosol Classification Results from Airborne High Spectral Resolution Lidar (HSRL) Measurements and the Calipso Vertical Feature Mask

NASA Technical Reports Server (NTRS)

Burton, S. P.; Ferrare, R. A.; Hostetler, C. A.; Hair, J. W.; Rogers, R. R.; Obland, M. D.; Butler, C. F.; Cook, A. L.; Harper, D. B.; Froyd, K. D.;

Relationships among cloud occurrence frequency, overlap, and effective thickness derived from CALIPSO and CloudSat merged cloud vertical profiles

NASA Astrophysics Data System (ADS)

Kato, Seiji; Sun-Mack, Sunny; Miller, Walter F.; Rose, Fred G.; Chen, Yan; Minnis, Patrick; Wielicki, Bruce A.

2010-01-01

A cloud frequency of occurrence matrix is generated using merged cloud vertical profiles derived from the satellite-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and cloud profiling radar. The matrix contains vertical profiles of cloud occurrence frequency as a function of the uppermost cloud top. It is shown that the cloud fraction and uppermost cloud top vertical profiles can be related by a cloud overlap matrix when the correlation length of cloud occurrence, which is interpreted as an effective cloud thickness, is introduced. The underlying assumption in establishing the above relation is that cloud overlap approaches random overlap with increasing distance separating cloud layers and that the probability of deviating from random overlap decreases exponentially with distance. One month of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat data (July 2006) support these assumptions, although the correlation length sometimes increases with separation distance when the cloud top height is large. The data also show that the correlation length depends on cloud top hight and the maximum occurs when the cloud top height is 8 to 10 km. The cloud correlation length is equivalent to the decorrelation distance introduced by Hogan and Illingworth (2000) when cloud fractions of both layers in a two-cloud layer system are the same. The simple relationships derived in this study can be used to estimate the top-of-atmosphere irradiance difference caused by cloud fraction, uppermost cloud top, and cloud thickness vertical profile differences.

Vertical Structure of Ice Cloud Layers From CloudSat and CALIPSO Measurements and Comparison to NICAM Simulations

NASA Technical Reports Server (NTRS)

Ham, Seung-Hee; Sohn, Byung-Ju; Kato, Seiji; Satoh, Masaki

2013-01-01

The shape of the vertical profile of ice cloud layers is examined using 4 months of CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) global measurements taken on January, April, July, and October 2007. Ice clouds are selected using temperature profiles when the cloud base is located above the 253K temperature level. The obtained ice water content (IWC), effective radius, or extinction coefficient profiles are normalized by their layer mean values and are expressed in the normalized vertical coordinate, which is defined as 0 and 1 at the cloud base and top heights, respectively. Both CloudSat and CALIPSO observations show that the maximum in the IWC and extinction profiles shifts toward the cloud bottom, as the cloud depth increases. In addition, clouds with a base reaching the surface in a high-latitude region show that the maximum peak of the IWC and extinction profiles occurs near the surface, which is presumably due to snow precipitation. CloudSat measurements show that the seasonal difference in normalized cloud vertical profiles is not significant, whereas the normalized cloud vertical profile significantly varies depending on the cloud type and the presence of precipitation. It is further examined if the 7 day Nonhydrostatic Icosahedral Atmospheric Model (NICAM) simulation results from 25 December 2006 to 1 January 2007 generate similar cloud profile shapes. NICAM IWC profiles also show maximum peaks near the cloud bottom for thick cloud layers and maximum peaks at the cloud bottom for low-level clouds near the surface. It is inferred that oversized snow particles in the NICAM cloud scheme produce a more vertically inhomogeneous IWC profile than observations due to quick sedimentation.

Lightning Nitrogen Oxides (LNOx) Vertical Profile Quantification and 10 Year Trend Analysis using Ozone Monitoring Instrument (OMI) Satellite Measurements, Air Quality Station (AQS) Surface Measurements, The National Lightning Detection Network (NLDN), and Simulated by Cloud Resolving Chemical Transport Model (REAM Cloud)

NASA Astrophysics Data System (ADS)

Smeltzer, C. D.; Wang, Y.; Koshak, W. J.

2014-12-01

Vertical profiles and emission lifetimes of lightning nitrogen oxides (LNOx) are derived using the Ozone Monitoring Instrument (OMI). Approximately 200 million flashes, over a 10 year climate period, from the United States National Lighting Detection Network (NLDN), are aggregated with OMI cloud top height to determine the vertical LNOx structure. LNOx lifetime is determined as function of LNOx signal in a 36 kilometer vertical column from the time of the last known flash to depletion of the LNOx signal. Environmental Protection Agency (EPA) Air Quality Station (AQS) surface data further support these results by demonstrating as much as a 200% increase in surface level NO2 during strong thunderstorm events and a lag as long as 5 to 8 hours from the lightning event to the peak surface event, indicating a evolutional process. Analysis of cloud resolving chemical transport model (REAM Cloud) demonstrates that C-shaped LNOx profiles, which agree with OMI vertical profile observations, evolve due to micro-scale convective meteorology given inverted C-shaped LNOx emission profiles as determined from lightning radio telemetry. It is shown, both in simulations and in observations, that the extent to which the LNOx vertical distribution is C-shaped and the lifetime of LNOx is proportional to the shear-strength of the thunderstorm. Micro-scale convective meteorology is not adequately parameterized in global scale and regional scale chemical transport models (CTM). Therefore, these larger scale CTMs ought to use a C-shape emissions profile to best reproduce observations until convective parameterizations are updated. These findings are used to simulate decadal LNOx and lightning ozone climatology over the Continental United States (CONUS) from 2004-2014.

Measurements of the Vertical Structure of Aerosols and Clouds Over the Ocean Using Micro-Pulse LIDAR Systems

NASA Technical Reports Server (NTRS)

Welton, Ellsworth J.; Spinhirne, James D.; Campbell, James R.; Berkoff, Timothy A.; Bates, David; Starr, David OC. (Technical Monitor)

2001-01-01

The determination of the vertical distribution of aerosols and clouds over the ocean is needed for accurate retrievals of ocean color from satellites observations. The presence of absorbing aerosol layers, especially at altitudes above the boundary layer, has been shown to influence the calculation of ocean color. Also, satellite data must be correctly screened for the presence of clouds, particularly cirrus, in order to measure ocean color. One instrument capable of providing this information is a lidar, which uses pulses of laser light to profile the vertical distribution of aerosol and cloud layers in the atmosphere. However, lidar systems prior to the 1990s were large, expensive, and not eye-safe which made them unsuitable for cruise deployments. During the 1990s the first small, autonomous, and eye-safe lidar system became available: the micro-pulse lidar, or MPL. The MPL is a compact and eye-safe lidar system capable of determining the range of aerosols and clouds by firing a short pulse of laser light (523 nm) and measuring the time-of-flight from pulse transmission to reception of a returned signal. The returned signal is a function of time, converted into range using the speed of light, and is proportional to the amount of light backscattered by atmospheric molecules (Rayleigh scattering), aerosols, and clouds. The MPL achieves ANSI eye-safe standards by sending laser pulses at low energy (micro-J) and expanding the beam to 20.32 cm in diameter. A fast pulse-repetition-frequency (2500 Hz) is used to achieve a good signal-to-noise, despite the low output energy. The MPL has a small field-of-view (< 100 micro-rad) and signals received with the instrument do not contain multiple scattering effects. The MPL has been used successfully at a number of long-term sites and also in several field experiments around the world.

HST/WFC3 Observations of Uranus' 2014 Storm Clouds

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

Relation of Cloud Occurrence Frequency, Overlap, and Effective Thickness Derived from CALIPSO and CloudSat Merged Cloud Vertical Profiles

NASA Technical Reports Server (NTRS)

Kato, Seiji; Sun-Mack, Sunny; Miller, Walter F.; Rose, Fred G.; Chen, Yan; Minnis, Patrick; Wielicki, Bruce A.

2009-01-01

A cloud frequency of occurrence matrix is generated using merged cloud vertical profile derived from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR). The matrix contains vertical profiles of cloud occurrence frequency as a function of the uppermost cloud top. It is shown that the cloud fraction and uppermost cloud top vertical pro les can be related by a set of equations when the correlation distance of cloud occurrence, which is interpreted as an effective cloud thickness, is introduced. The underlying assumption in establishing the above relation is that cloud overlap approaches the random overlap with increasing distance separating cloud layers and that the probability of deviating from the random overlap decreases exponentially with distance. One month of CALIPSO and CloudSat data support these assumptions. However, the correlation distance sometimes becomes large, which might be an indication of precipitation. The cloud correlation distance is equivalent to the de-correlation distance introduced by Hogan and Illingworth [2000] when cloud fractions of both layers in a two-cloud layer system are the same.

What controls the vertical distribution of aerosol? Relationships between process sensitivity in HadGEM3–UKCA and inter-model variation from AeroCom Phase II

DOE PAGES

Kipling, Zak; Stier, Philip; Johnson, Colin E.; ...

2016-02-26

The vertical profile of aerosol is important for its radiative effects, but weakly constrained by observations on the global scale, and highly variable among different models. To investigate the controlling factors in one particular model, we investigate the effects of individual processes in HadGEM3–UKCA and compare the resulting diversity of aerosol vertical profiles with the inter-model diversity from the AeroCom Phase II control experiment. In this way we show that (in this model at least) the vertical profile is controlled by a relatively small number of processes, although these vary among aerosol components and particle sizes. We also show that sufficientlymore » coarse variations in these processes can produce a similar diversity to that among different models in terms of the global-mean profile and, to a lesser extent, the zonal-mean vertical position. However, there are features of certain models' profiles that cannot be reproduced, suggesting the influence of further structural differences between models. In HadGEM3–UKCA, convective transport is found to be very important in controlling the vertical profile of all aerosol components by mass. In-cloud scavenging is very important for all except mineral dust. Growth by condensation is important for sulfate and carbonaceous aerosol (along with aqueous oxidation for the former and ageing by soluble material for the latter). The vertical extent of biomass-burning emissions into the free troposphere is also important for the profile of carbonaceous aerosol. Boundary-layer mixing plays a dominant role for sea salt and mineral dust, which are emitted only from the surface. Dry deposition and below-cloud scavenging are important for the profile of mineral dust only. In this model, the microphysical processes of nucleation, condensation and coagulation dominate the vertical profile of the smallest particles by number (e.g. total CN > 3 nm), while the profiles of larger particles (e.g. CN > 100 nm) are controlled by the same processes as the component mass profiles, plus the size distribution of primary emissions. Here, we also show that the processes that affect the AOD-normalised radiative forcing in the model are predominantly those that affect the vertical mass distribution, in particular convective transport, in-cloud scavenging, aqueous oxidation, ageing and the vertical extent of biomass-burning emissions.« less

DC-8 Scanning Lidar Characterization of Aircraft Contrails and Cirrus Clouds

NASA Technical Reports Server (NTRS)

Uthe, Edward E.; Nielsen, Norman B.; Oseberg, Terje E.

1998-01-01

An angular-scanning large-aperture (36 cm) backscatter lidar was developed and deployed on the NASA DC-8 research aircraft as part of the SUCCESS (Subsonic Aircraft: Contrail and Cloud Effects Special Study) program. The lidar viewing direction could be scanned continuously during aircraft flight from vertically upward to forward to vertically downward, or the viewing could be at fixed angles. Real-time pictorial displays generated from the lidar signatures were broadcast on the DC-8 video network and used to locate clouds and contrails above, ahead of, and below the DC-8 to depict their spatial structure and to help select DC-8 altitudes for achieving optimum sampling by onboard in situ sensors. Several lidar receiver systems and real-time data displays were evaluated to help extend in situ data into vertical dimensions and to help establish possible lidar configurations and applications on future missions. Digital lidar signatures were recorded on 8 mm Exabyte tape and generated real-time displays were recorded on 8mm video tape. The digital records were transcribed in a common format to compact disks to facilitate data analysis and delivery to SUCCESS participants. Data selected from the real-time display video recordings were processed for publication-quality displays incorporating several standard lidar data corrections. Data examples are presented that illustrate: (1) correlation with particulate, gas, and radiometric measurements made by onboard sensors, (2) discrimination and identification between contrails observed by onboard sensors, (3) high-altitude (13 km) scattering layer that exhibits greatly enhanced vertical backscatter relative to off-vertical backscatter, and (4) mapping of vertical distributions of individual precipitating ice crystals and their capture by cloud layers. An angular scan plotting program was developed that accounts for DC-8 pitch and velocity.

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 than 30-micron 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 under-prediction of peak supersaturations.

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 than 30-micrometers 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.

Satellite-Observed Vertical Structures of Clouds over the Amazon Basin

NASA Astrophysics Data System (ADS)

Wu, M.; Lee, J. E.

2017-12-01

The long wet season of the Amazon basin currently plays a critical role in the terrestrial ecosystem, regulating carbon balance and supporting high biodiversity. It has been argued that the land surface processes are important in maintaining high precipitation; yet, how the land-atmosphere interactions modulate the atmospheric processes are not completely understood. As a first step toward solving this problem, here we examine the vertical structures of clouds and the thermodynamics of the atmosphere over the entire basin at the different time of the year. We combine the vertical distribution of cloud water content from CloudSat, and the atmospheric thermodynamic conditions from the ECMWF ERA-interim reanalysis to compare and contrast the atmospheric condition at different time of the year-the wet, dry, and dry-to-wet transition seasons-and in different regions-ever-wet evergreen broadleaf forests, wet evergreen broadleaf forests with a dry season, and dry wooded grasslands/woodlands-following water stress gradient. In the ever-wet and wet regions, a large amount of cloud ice water is present in the upper atmosphere (above 11km) and convective available potential energy (CAPE) is high during the transition season, supporting the claim that the convective activity is strongest during the transition season. In the dry region, there are more cloud water above 8km over woodlands than over wooded grasslands during the dry and transition seasons, indicating the influence of the land cover. We also classified our data following the large-scale circulation pattern, and the CloudSat data support more deep convective activities in the wet and dry regions when the wind blows from the east during the wet and transition seasons. As a next step, we will focus more on linking the cloud structure to the large-scale circulation and surface processes.

Post-midnight equatorial irregularity distributions and vertical drift velocity variations during solstices

NASA Astrophysics Data System (ADS)

Su, S.-Y.; Liu, C. H.; Chao, C.-K.

2018-04-01

Longitudinal distributions of post-midnight equatorial ionospheric irregularity occurrences observed by ROCSAT-1 (1st satellite of the Republic of China) during moderate to high solar activity years in two solstices are studied with respect to the vertical drift velocity and density variations. The post-midnight irregularity distributions are found to be similar to the well-documented pre-midnight ones, but are different from some published distributions taken during solar minimum years. Even though the post-midnight ionosphere is sinking in general, longitudes of frequent positive vertical drift and high density seems to coincide with the longitudes of high irregularity occurrences. Large scatters found in the vertical drift velocity and density around the dip equator in different ROCSAT-1 orbits indicate the existence of large and frequent variations in the vertical drift velocity and density that seem to be able to provide sufficient perturbations for the Rayleigh-Taylor (RT) instability to cause the irregularity occurrences. The need of seeding agents such as gravity waves from atmospheric convective clouds to initiate the Rayleigh-Taylor instability may not be necessary.

Stratus Cloud Radiative Effects from Cloud Processed Bimodal CCN Distributions

NASA Astrophysics Data System (ADS)

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

2016-12-01

Inability to understand cloud processes is a large component of climate uncertainty. Increases in cloud condensation nuclei (CCN) concentrations are known to increase cloud droplet number concentrations (Nc). This aerosol-cloud interaction (ACI) produces greater Nc at smaller sizes, which brightens clouds. A lesser understood ACI is cloud processing of CCN. This improves CCN that then more easily activate at lower cloud supersaturations (S). Bimodal CCN distributions thus ensue from these evaporated cloud droplets. Hudson et al. (2015) related CCN bimodality to Nc. In stratus clouds, bimodal CCN created greater Nc whereas in cumulus less Nc. Thus, CCN distribution shape influences cloud properties; microphysics and radiative properties. Measured uni- and bimodal CCN distributions were input into an adiabatic droplet growth model using various specified vertical wind speeds (W). Bimodal CCN produced greater Nc (Fig. 1a) and smaller mean diameters (MD; Fig. 1b) at lower W typical of stratus clouds (<70 cm/s). Improved CCN (low critical S) were more easily activated at the lower S of stratus from low W, thus, creating greater Nc. Competition for condensate thus reduced MD and drizzle. At greater W, typical of cumulus clouds (>70 cm/s), bimodal CCN made lower Nc with larger MD thus enhancing drizzle whereas unimodal CCN made greater Nc with smaller MD, thus reducing drizzle. Thus, theoretical predictions of Nc and MD for uni- and bimodal CCN agree with the sense of the observations. Radiative effects were determined using a cloud grown to a 250-meter thickness. Bimodal CCN at low W reduced cloud effective radius (re), made greater cloud optical thickness (COT), and made greater cloud albedo (Fig. 1c). At very low W changes were as much as +9% for albedo, +17% for COT, and -12% for re. Stratus clouds typically have low W and cover large areas. Thus, these changes in cloud radiative properties at low W impact climate. Stratus cloud susceptibility to CCN distribution thus requires further investigation to determine their impact on ACI. Hudson et al. (2015), JGRA, 120, 3436-3452.

Supersaturation, droplet spectra, and turbulent mixing in clouds

NASA Technical Reports Server (NTRS)

Gerber, H.

1990-01-01

Much effort has recently gone into explaining the observed broad precoalescence size distribution of droplets in cloud and fogs, because this differs from the results of condensational growth calculations which lead to much narrower distributions. A good example of droplet size-distribution broadening was observed on flight 17 (25 July) of the NRL tethered balloon during the 1987 FIRE San Nicolas Island IFO. These observations caused the interactions between cloud microphysics and turbulent mixing to be re-examined. The findings of Broadwell and Breidenthal (1982) who conducted laboratory and theoretical studies of mixing in shear flow, and those of Baker et al. (1984) who applied the earlier work to mixing in clouds, were used. Rather than looking at the 25 July case at SNI, earlier fog observations made at SUNY (6 Oct. 1982) which also indicated that shear-induced mixing was taking place, and which had a better collection of microphysical measurements including more precise supersaturation measurements and detailed vertical profiles of meteorological parameters were chosen instead.

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

NASA Technical Reports Server (NTRS)

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

2017-01-01

In November 2014 Uranus was observed with the Wide Field Camera 3 (WFC3) instrument of the Hubble Space Telescope as part of the Hubble 2020: Outer Planet Atmospheres Legacy program, OPAL. OPAL annually maps Jupiter, Uranus and Neptune (and will also map Saturn from 2018) in several visible near- infrared wavelength filters. The Uranus 2014 OPAL observations were made on the 89th November at a time when a huge cloud complex, first observed by de Pater et al. (2015) and subsequently tracked by professional and amateur astronomers (Sayanagi et al., 2016), was present at 30-40deg N. We imaged the entire visible atmosphere, including the storm system, in seven filters spanning 467924 nm, capturing variations in the coloration of Uranus clouds and also vertical distribution due to wavelength dependent changes in Rayleigh scattering and methane absorption optical depth. Here we analyse these new HST observations with the NEMESIS radiative-transfer and retrieval code in multiple-scattering mode to determine the vertical cloud structure in and around the storm cloud system. The same storm system was also observed in the H-band (1.4-1.8 micrometers) with the SINFONI Integral Field Unit Spectrometer on the Very Large Telescope (VLT) on 31st October and 11th November, reported by Irwin et al. (2016, 10.1016j.icarus.2015.09.010). To constrain better the cloud particle sizes and scattering properties over a wide wavelength range we also conducted a limb-darkening analysis of the background cloud structure in the 30-40deg N latitude band by simultaneously fitting: a) these HSTOPAL observations at a range of zenith angles; b) the VLTSINFONI observations at a range of zenith angles; and c) IRTFSpeX observations of this latitude band made in 2009 at a single zenith angle of 23deg, spanning the wavelength range 0.8-1.8 micrometers (Irwin et al., 2015, 10.1016j.icarus.2014.12.020). We find that the HST observations, and the combined HSTVLTIRTF observations at all locations are well modelled with a three-component cloud comprised of: 1) a vertically thin, but optically thick deep tropospheric cloud at a pressure of approximately 2 bars; 2) a methane-ice cloud based at the methane-condensation level of approximately 1.23 bar, with variable vertical extent; and 3) a vertically extended tropospheric haze, also based at the methane-condensation level of 1.23 bar. We find that modelling both haze and tropospheric cloud with particles having an effective radius of approximately 0.1 micron provides a good fit the observations, although for the tropospheric cloud, particles with an effective radius as large as 1.0 micron provide a similarly good fit. We find that the particles in both the tropospheric cloud and haze are more scattering at short wave- lengths, giving them a blue color, but are more absorbing at longer wavelengths, especially for the tropospheric haze. We find that the spectra of the storm clouds are well modelled by localized thickening and vertical extension of the methane-ice cloud. For the particles in the storm clouds, which we assume to be composed of methane ice particles, we find that their mean radii must lie somewhere in the range 0. 1 1. 0 m. We find that the high clouds have low integrated opacity, and that streamers reminiscent of convective thunderstorm anvils are confined to levels deeper than 1 bar. These results argue against vigorous moist convective origins for the cloud features.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newsom, R. K.; Sivaraman, C.; Shippert, T. R.

Accurate height-resolved measurements of higher-order statistical moments of vertical velocity fluctuations are crucial for improved understanding of turbulent mixing and diffusion, convective initiation, and cloud life cycles. The Atmospheric Radiation Measurement (ARM) Climate Research Facility operates coherent Doppler lidar systems at several sites around the globe. These instruments provide measurements of clear-air vertical velocity profiles in the lower troposphere with a nominal temporal resolution of 1 sec and height resolution of 30 m. The purpose of the Doppler lidar vertical velocity statistics (DLWSTATS) value-added product (VAP) is to produce height- and time-resolved estimates of vertical velocity variance, skewness, and kurtosismore » from these raw measurements. The VAP also produces estimates of cloud properties, including cloud-base height (CBH), cloud frequency, cloud-base vertical velocity, and cloud-base updraft fraction.« less

Large Scale Ice Water Path and 3-D Ice Water Content

DOE Data Explorer

Liu, Guosheng

2008-01-15

Cloud ice water concentration is one of the most important, yet poorly observed, cloud properties. Developing physical parameterizations used in general circulation models through single-column modeling is one of the key foci of the ARM program. In addition to the vertical profiles of temperature, water vapor and condensed water at the model grids, large-scale horizontal advective tendencies of these variables are also required as forcing terms in the single-column models. Observed horizontal advection of condensed water has not been available because the radar/lidar/radiometer observations at the ARM site are single-point measurement, therefore, do not provide horizontal distribution of condensed water. The intention of this product is to provide large-scale distribution of cloud ice water by merging available surface and satellite measurements. The satellite cloud ice water algorithm uses ARM ground-based measurements as baseline, produces datasets for 3-D cloud ice water distributions in a 10 deg x 10 deg area near ARM site. The approach of the study is to expand a (surface) point measurement to an (satellite) areal measurement. That is, this study takes the advantage of the high quality cloud measurements at the point of ARM site. We use the cloud characteristics derived from the point measurement to guide/constrain satellite retrieval, then use the satellite algorithm to derive the cloud ice water distributions within an area, i.e., 10 deg x 10 deg centered at ARM site.

A New Cloud and Aerosol Layer Detection Method Based on Micropulse Lidar Measurements

NASA Astrophysics Data System (ADS)

Wang, Q.; Zhao, C.; Wang, Y.; Li, Z.; Wang, Z.; Liu, D.

2014-12-01

A new algorithm is developed to detect aerosols and clouds based on micropulse lidar (MPL) measurements. In this method, a semi-discretization processing (SDP) technique is first used to inhibit the impact of increasing noise with distance, then a value distribution equalization (VDE) method is introduced to reduce the magnitude of signal variations with distance. Combined with empirical threshold values, clouds and aerosols are detected and separated. This method can detect clouds and aerosols with high accuracy, although classification of aerosols and clouds is sensitive to the thresholds selected. Compared with the existing Atmospheric Radiation Measurement (ARM) program lidar-based cloud product, the new method detects more high clouds. The algorithm was applied to a year of observations at both the U.S. Southern Great Plains (SGP) and China Taihu site. At SGP, the cloud frequency shows a clear seasonal variation with maximum values in winter and spring, and shows bi-modal vertical distributions with maximum frequency at around 3-6 km and 8-12 km. The annual averaged cloud frequency is about 50%. By contrast, the cloud frequency at Taihu shows no clear seasonal variation and the maximum frequency is at around 1 km. The annual averaged cloud frequency is about 15% higher than that at SGP.

Final Technical Report for Grant # DE-FG02-06ER64169

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dr. Beat Schmid, PI

2007-07-13

The Atmospheric Radiation Measurement (ARM) program is funding this project to improve the methodology of ground-based remote sensing of the vertical distribution of aerosol and cloud optical properties, and their effect on atmospheric radiative transfer. Remotely-sensed and in situ observed aerosol, cloud physical, and optical properties collected during the May 2003 Aerosol Intensive Operational Period (AIOP) and the Aerosol Lidar Validation Experiment (ALIVE), conducted from September 11-22, 2005, are the basis for the investigation. We have used ground-based lidar, airborne sunphotometer and in situ measurements and other data to evaluate the vertical profile of aerosol properties. We have been pursuingmore » research in the following three areas: (1) Aerosol Best Estimate Product--Sensitivity Study: ARM is developing an Aerosol Best Estimate (ABE) Value Added Product (VAP) to provide aerosol optical properties at all times and heights above its sites. The ABE is used as input for the Broadband Heating Rate Profile (BBHRP) VAP, whose output will be used to evaluate the radiative treatment of aerosols and clouds in climate models. ARM has a need to assess how much detail is required for the ABE and if a useful ABE can be derived for the tropical and arctic climate research facilities (CRFs) where only limited aerosol information in the vertical is available. We have been determining the sensitivity of BBHRP to the vertical profile of aerosol optical properties used in ABE. (2) Vertically Resolved Aerosol and Cloud Radiative Properties over the Southern Great Plains (SGP): The AIOP delivered an unprecedented airborne radiometric and in situ data set related to aerosols and clouds. The Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS's) Twin Otter aircraft carried solar pointing, up- and down-looking radiometers (spectral and broadband, visible, and infrared) with the uplooking radiometers mounted on a stabilized platform. We are performing an integrated analysis of the largely unexploited radiometric data set to provide observation-based quantification of the effect of aerosols and clouds on the radiation field. We will link aerosol and cloud properties measured in situ with the observed radiative fluxes using radiative transfer models. This over-determined dataset will provide validation of the BBHRP VAP. (3) Integrated Analysis of Data from the Aerosol Lidar Validation Experiment: The ABE VAP relies on continuous lidar observations to provide the vertical distribution of the aerosols above the ARM sites. The goal of ALIVE, conducted in September 2005, was the validation of the aerosol extinction profiles obtained from the SGP Raman lidar, which has been recently refurbished/updated, and the Micro Pulse Lidar, for which a new algorithm to retrieve aerosol profiles has recently been developed, using the National Aeronautics and Space Administration (NASA) Ames Airborne Tracking 14 channel Sun photometer. We are performing and publishing the integrated analysis of the ALIVE data set.« less

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 altered by the choice of time constant and incloud critical cloud water amount regulators for auto-conversion. The CRF and its feedbacks also have a profound effect on the ITCZ. Even though somewhat weaker than observed, the McRAS-GCM simulation produces robust 30-60 day oscillations in the 200 hPa velocity potential. Two ensembles of 4-summer (July, August, September) simulations, one each for 1987 and 1988 show that the McRAS-GCM simulates realistic and statistically significant precipitation differences over India, Central America, and tropical Africa. Several seasonal simulations were performed with McRAS-GEOS II GCM for the summer (June-July- August) and winter (December-January-February) periods to determine how the simulated clouds and CRFs would be affected by: i) advection of clouds; ii) cloud top entrainment instability, iii) cloud water inhomogeneity correction, and (iv) cloud production and dissipation in different cloud-processes. The results show that each of these processes contributes to the simulated cloud-fraction and CRF.

Effects of cumulus entrainment and multiple cloud types on a January global climate model simulation

NASA Technical Reports Server (NTRS)

Yao, Mao-Sung; Del Genio, Anthony D.

1989-01-01

An improved version of the GISS Model II cumulus parameterization designed for long-term climate integrations is used to study the effects of entrainment and multiple cloud types on the January climate simulation. Instead of prescribing convective mass as a fixed fraction of the cloud base grid-box mass, it is calculated based on the closure assumption that the cumulus convection restores the atmosphere to a neutral moist convective state at cloud base. This change alone significantly improves the distribution of precipitation, convective mass exchanges, and frequencies in the January climate. The vertical structure of the tropical atmosphere exhibits quasi-equilibrium behavior when this closure is used, even though there is no explicit constraint applied above cloud base.

Preliminary Results from the First Deployment of a Tethered-Balloon Cloud Particle Imager Instrument Package in Arctic Stratus Clouds at Ny-Alesund

NASA Astrophysics Data System (ADS)

Lawson, P.; Stamnes, K.; Stamnes, J.; Zmarzly, P.; O'Connor, D.; Koskulics, J.; Hamre, B.

2008-12-01

A tethered balloon system specifically designed to collect microphysical data in mixed-phase clouds was deployed in Arctic stratus clouds during May 2008 near Ny-Alesund, Svalbard, at 79 degrees North Latitude. This is the first time a tethered balloon system with a cloud particle imager (CPI) that records high-resolution digital images of cloud drops and ice particles has been operated in cloud. The custom tether supplies electrical power to the instrument package, which in addition to the CPI houses a 4-pi short-wavelength radiometer and a met package that measures temperature, humidity, pressure, GPS position, wind speed and direction. The instrument package was profiled vertically through cloud up to altitudes of 1.6 km. Since power was supplied to the instrument package from the ground, it was possible to keep the balloon package aloft for extended periods of time, up to 9 hours at Ny- Ålesund, which was limited only by crew fatigue. CPI images of cloud drops and the sizes, shapes and degree of riming of ice particles are shown throughout vertical profiles of Arctic stratus clouds. The images show large regions of mixed-phase cloud from -8 to -2 C. The predominant ice crystal habits in these regions are needles and aggregates of needles. The amount of ice in the mixed-phase clouds varied considerably and did not appear to be a function of temperature. On some occasions, ice was observed near cloud base at -2 C with supercooled cloud above to - 8 C that was devoid of ice. Measurements of shortwave radiation are also presented. Correlations between particle distributions and radiative measurements will be analyzed to determine the effect of these Arctic stratus clouds on radiative forcing.

Analysis of Meteorological Data Obtained During Flight in a Supercooled Stratiform Cloud of High Liquid-Water Content

NASA Technical Reports Server (NTRS)

Perkins, Porter J.; Kline, Dwight B.

1951-01-01

Flight icing-rate data obtained in a dense and. abnormally deep supercooled stratiform cloud system indicated the existence of liquid-water contents generally exceeding values in amount and extent previously reported over the midwestern sections of the United States. Additional information obtained during descent through a part of the cloud system indicated liquid-water contents that significantly exceeded theoretical values, especially near the middle of the cloud layer.. The growth of cloud droplets to sizes that resulted in sedimentation from the upper portions of the cloud is considered to be a possible cause of the high water contents near the center of the cloud layer. Flight measurements of the vertical temperature distribution in the cloud layer indicated a rate of change of temperature with altitude exceeding that of the moist adiabatic lapse rate. This excessive rate of change is considered to have contributed to the severity of the condition.

Production of Lightning NO(x) and its Vertical Distribution Calculated from 3-D Cloud-scale Chemical Transport Model Simulations

NASA Technical Reports Server (NTRS)

Ott, Lesley; Pickering, Kenneth; Stenchikov, Georgiy; Allen, Dale; DeCaria, Alex; Ridley, Brian; Lin, Ruei-Fong; Lang, Steve; Tao, Wei-Kuo

2009-01-01

A 3-D cloud scale chemical transport model that includes a parameterized source of lightning NO(x), based on observed flash rates has been used to simulate six midlatitude and subtropical thunderstorms observed during four field projects. Production per intracloud (P(sub IC) and cloud-to-ground (P(sub CG)) flash is estimated by assuming various values of P(sub IC) and P(sub CG) for each storm and determining which production scenario yields NO(x) mixing ratios that compare most favorably with in-cloud aircraft observations. We obtain a mean P(sub CG) value of 500 moles NO (7 kg N) per flash. The results of this analysis also suggest that on average, P(sub IC) may be nearly equal to P(sub CG), which is contrary to the common assumption that intracloud flashes are significantly less productive of NO than are cloud-to-ground flashes. This study also presents vertical profiles of the mass of lightning NO(x), after convection based on 3-D cloud-scale model simulations. The results suggest that following convection, a large percentage of lightning NO(x), remains in the middle and upper troposphere where it originated, while only a small percentage is found near the surface. The results of this work differ from profiles calculated from 2-D cloud-scale model simulations with a simpler lightning parameterization that were peaked near the surface and in the upper troposphere (referred to as a "C-shaped" profile). The new model results (a backward C-shaped profile) suggest that chemical transport models that assume a C-shaped vertical profile of lightning NO(x) mass may place too much mass neat the surface and too little in the middle troposphere.

StatisticAl Characteristics of Cloud over Beijing, China Obtained FRom Ka band Doppler Radar Observation

NASA Astrophysics Data System (ADS)

LIU, J.; Bi, Y.; Duan, S.; Lu, D.

2017-12-01

It is well-known that cloud characteristics, such as top and base heights and their layering structure of micro-physical parameters, spatial coverage and temporal duration are very important factors influencing both radiation budget and its vertical partitioning as well as hydrological cycle through precipitation data. Also, cloud structure and their statistical distribution and typical values will have respective characteristics with geographical and seasonal variation. Ka band radar is a powerful tool to obtain above parameters around the world, such as ARM cloud radar at the Oklahoma US, Since 2006, Cloudsat is one of NASA's A-Train satellite constellation, continuously observe the cloud structure with global coverage, but only twice a day it monitor clouds over same local site at same local time.By using IAP Ka band Doppler radar which has been operating continuously since early 2013 over the roof of IAP building in Beijing, we obtained the statistical characteristic of clouds, including cloud layering, cloud top and base heights, as well as the thickness of each cloud layer and their distribution, and were analyzed monthly and seasonal and diurnal variation, statistical analysis of cloud reflectivity profiles is also made. The analysis covers both non-precipitating clouds and precipitating clouds. Also, some preliminary comparison of the results with Cloudsat/Calipso products for same period and same area are made.

Vertical distribution of aerosol number concentration in the troposphere over Siberia derived from airborne in-situ measurements

NASA Astrophysics Data System (ADS)

Arshinov, Mikhail Yu.; Belan, Boris D.; Paris, Jean-Daniel; Machida, Toshinobu; Kozlov, Alexandr; Malyskin, Sergei; Simonenkov, Denis; Davydov, Denis; Fofonov, Alexandr

2016-04-01

Knowledge of the vertical distribution of aerosols particles is very important when estimating aerosol radiative effects. To date there are a lot of research programs aimed to study aerosol vertical distribution, but only a few ones exist in such insufficiently explored region as Siberia. Monthly research flights and several extensive airborne campaigns carried out in recent years in Siberian troposphere allowed the vertical distribution of aerosol number concentration to be summarized. In-situ aerosol measurements were performed in a wide range of particle sizes by means of improved version of the Novosibirsk-type diffusional particle sizer and GRIMM aerosol spectrometer Model 1.109. The data on aerosol vertical distribution enabled input parameters for the empirical equation of Jaenicke (1993) to be derived for Siberian troposphere up to 7 km. Vertical distributions of aerosol number concentration in different size ranges averaged for the main seasons of the year will be presented. This work was supported by Interdisciplinary integration projects of the Siberian Branch of the Russian Academy of Science No. 35, No. 70 and No. 131; the Branch of Geology, Geophysics and Mining Sciences of RAS (Program No. 5); and Russian Foundation for Basic Research (grant No. 14-05-00526). Jaenicke R. Tropospheric aerosols, in Aerosol-Cloud-Climate Interactions, edited by P.V. Hobs. -Academic Press, San Diego, CA, 1993.- P. 1-31.

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

NASA Astrophysics Data System (ADS)

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

2015-09-01

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

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

NASA Astrophysics Data System (ADS)

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

2015-01-01

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

Modeling the Hydrological Cycle in the Atmosphere of Mars: Influence of a Bimodal Size Distribution of Aerosol Nucleation Particles

NASA Astrophysics Data System (ADS)

Shaposhnikov, Dmitry S.; Rodin, Alexander V.; Medvedev, Alexander S.; Fedorova, Anna A.; Kuroda, Takeshi; Hartogh, Paul

2018-02-01

We present a new implementation of the hydrological cycle scheme into a general circulation model of the Martian atmosphere. The model includes a semi-Lagrangian transport scheme for water vapor and ice and accounts for microphysics of phase transitions between them. The hydrological scheme includes processes of saturation, nucleation, particle growth, sublimation, and sedimentation under the assumption of a variable size distribution. The scheme has been implemented into the Max Planck Institute Martian general circulation model and tested assuming monomodal and bimodal lognormal distributions of ice condensation nuclei. We present a comparison of the simulated annual variations, horizontal and vertical distributions of water vapor, and ice clouds with the available observations from instruments on board Mars orbiters. The accounting for bimodality of aerosol particle distribution improves the simulations of the annual hydrological cycle, including predicted ice clouds mass, opacity, number density, and particle radii. The increased number density and lower nucleation rates bring the simulated cloud opacities closer to observations. Simulations show a weak effect of the excess of small aerosol particles on the simulated water vapor distributions.

Microphysical and Optical Properties of Saharan Dust Measured during the ICE-D Aircraft Campaign

NASA Astrophysics Data System (ADS)

Ryder, Claire; Marenco, Franco; Brooke, Jennifer; Cotton, Richard; Taylor, Jonathan

2017-04-01

During August 2015, the UK FAAM BAe146 research aircraft was stationed in Cape Verde off the coast of West Africa. Measurements of Saharan dust, and ice and liquid water clouds, were taken for the ICE-D (Ice in Clouds Experiment - Dust) project - a multidisciplinary project aimed at further understanding aerosol-cloud interactions. Six flights formed part of a sub-project, AER-D, solely focussing on measurements of Saharan dust within the African dust plume. Dust loadings observed during these flights varied (aerosol optical depths of 0.2 to 1.3), as did the vertical structure of the dust, the size distributions and the optical properties. The BAe146 was fully equipped to measure size distributions covering aerosol accumulation, coarse and giant modes. Initial results of size distribution and optical properties of dust from the AER-D flights will be presented, showing that a substantial coarse mode was present, in agreement with previous airborne measurements. Optical properties of dust relating to the measured size distributions will also be presented.

Microphysics of Clouds with the Relaxed Arakawa-Schubert Scheme (McRAS). Part I: Design and Evaluation with GATE Phase III Data.

NASA Astrophysics Data System (ADS)

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

1999-09-01

A prognostic cloud scheme named McRAS (Microphysics of Clouds with Relaxed Arakawa-Schubert Scheme) has been designed and developed with the aim of improving moist processes, microphysics of clouds, and cloud-radiation interactions in GCMs. McRAS distinguishes three types of clouds: convective, stratiform, and boundary layer. The convective clouds transform and merge into stratiform clouds on an hourly timescale, while the boundary layer clouds merge into the stratiform clouds instantly. The cloud condensate converts into precipitation following the autoconversion equations 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, as well as diffuse both horizontally and vertically with a fully interactive cloud microphysics throughout the life cycle of the cloud, 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 Global Atmospheric Research Program Atlantic Tropical Experiment (GATE) Phase III data has shown that, together with the rest of the model physics, McRAS can simulate the observed temperature, humidity, and precipitation without discernible systematic errors. The time history and time mean in-cloud water and ice distribution, fractional cloudiness, cloud optical thickness, origin of precipitation in the convective anvils and towers, and the convective updraft and downdraft velocities and mass fluxes all simulate a realistic behavior. Some of these diagnostics are not verifiable with data on hand. These SCM sensitivity tests show that (i) without clouds the simulated GATE-SCM atmosphere is cooler than observed; (ii) the model's convective scheme, RAS, is an important subparameterization of McRAS; and (iii) advection of cloud water substance is helpful in simulating better cloud distribution and cloud-radiation interaction. An evaluation of the performance of McRAS in the Goddard Earth Observing System II GCM is given in a companion paper (Part II).

Mixed-phase altocumulus clouds over Leipzig: Remote sensing measurements and spectral cloud microphysics simulations

NASA Astrophysics Data System (ADS)

Simmel, Martin; Bühl, Johannes; Ansmann, Albert; Tegen, Ina

2015-04-01

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

Parameterized approximation of lacunarity functions derived from airborne laser scanning point clouds of forested areas

NASA Astrophysics Data System (ADS)

Székely, Balázs; Kania, Adam; Varga, Katalin; Heilmeier, Hermann

2017-04-01

Lacunarity, a measure of the spatial distribution of the empty space is found to be a useful descriptive quantity of the forest structure. Its calculation, based on laser-scanned point clouds, results in a four-dimensional data set. The evaluation of results needs sophisticated tools and visualization techniques. To simplify the evaluation, it is straightforward to use approximation functions fitted to the results. The lacunarity function L(r), being a measure of scale-independent structural properties, has a power-law character. Previous studies showed that log(log(L(r))) transformation is suitable for analysis of spatial patterns. Accordingly, transformed lacunarity functions can be approximated by appropriate functions either in the original or in the transformed domain. As input data we have used a number of laser-scanned point clouds of various forests. The lacunarity distribution has been calculated along a regular horizontal grid at various (relative) elevations. The lacunarity data cube then has been logarithm-transformed and the resulting values became the input of parameter estimation at each point (point of interest, POI). This way at each POI a parameter set is generated that is suitable for spatial analysis. The expectation is that the horizontal variation and vertical layering of the vegetation can be characterized by this procedure. The results show that the transformed L(r) functions can be typically approximated by exponentials individually, and the residual values remain low in most cases. However, (1) in most cases the residuals may vary considerably, and (2) neighbouring POIs often give rather differing estimates both in horizontal and in vertical directions, of them the vertical variation seems to be more characteristic. In the vertical sense, the distribution of estimates shows abrupt changes at places, presumably related to the vertical structure of the forest. In low relief areas horizontal similarity is more typical, in higher relief areas horizontal similarity fades out in short distances. Some of the input data have been acquired in the framework of the ChangeHabitats2 project financed by the European Union. BS contributed as an Alexander von Humboldt Research Fellow.

Radiative Impacts of Cloud Heterogeneity and Overlap in an Atmospheric General Circulation Model

NASA Technical Reports Server (NTRS)

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

2012-01-01

The radiative impacts of introducing horizontal heterogeneity of layer cloud condensate, and vertical overlap of condensate and cloud fraction are examined with the aid of a new radiation package operating in the GEOS-5 Atmospheric General Circulation Model. The impacts are examined in terms of diagnostic top-of-the-atmosphere shortwave (SW) and longwave (LW) cloud radiative effect (CRE) calculations for a range of assumptions and parameter specifications about the overlap. The investigation is conducted for two distinct cloud schemes, the one that comes with the standard GEOS-5 distribution, and another which has been recently used experimentally for its enhanced GEOS-5 distribution, and another which has been recently used experimentally for its enhanced cloud microphysical capabilities; both are coupled to a cloud generator allowing arbitrary cloud overlap specification. We find that cloud overlap radiative impacts are significantly stronger for the operational cloud scheme for which a change of cloud fraction overlap from maximum-random to generalized results to global changes of SW and LW CRE of approximately 4 Watts per square meter, and zonal changes of up to approximately 10 Watts per square meter. This is because of fewer occurrences compared to the other scheme of large layer cloud fractions and of multi-layer situations with large numbers of atmospheric being simultaneously cloudy, conditions that make overlap details more important. The impact on CRE of the details of condensate distribution overlap is much weaker. Once generalized overlap is adopted, both cloud schemes are only modestly sensitive to the exact values of the overlap parameters. We also find that if one of the CRE components is overestimated and the other underestimated, both cannot be driven towards observed values by adjustments to cloud condensate heterogeneity and overlap alone.

Statistical Analyses of Satellite Cloud Object Data from CERES. Part II; Tropical Convective Cloud Objects During 1998 El Nino and Validation of the Fixed Anvil Temperature Hypothesis

NASA Technical Reports Server (NTRS)

Xu, Kuan-Man; Wong, Takmeng; Wielicki, Bruce a.; Parker, Lindsay; Lin, Bing; Eitzen, Zachary A.; Branson, Mark

2006-01-01

Characteristics of tropical deep convective cloud objects observed over the tropical Pacific during January-August 1998 are examined using the Tropical Rainfall Measuring Mission/ Clouds and the Earth s Radiant Energy System single scanner footprint (SSF) data. These characteristics include the frequencies of occurrence and statistical distributions of cloud physical properties. Their variations with cloud-object size, sea surface temperature (SST), and satellite precessing cycle are analyzed in detail. A cloud object is defined as a contiguous patch of the Earth composed of satellite footprints within a single dominant cloud-system type. It is found that statistical distributions of cloud physical properties are significantly different among three size categories of cloud objects with equivalent diameters of 100 - 150 km (small), 150 - 300 km (medium), and > 300 km (large), respectively, except for the distributions of ice particle size. The distributions for the larger-size category of cloud objects are more skewed towards high SSTs, high cloud tops, low cloud-top temperature, large ice water path, high cloud optical depth, low outgoing longwave (LW) radiation, and high albedo than the smaller-size category. As SST varied from one satellite precessing cycle to another, the changes in macrophysical properties of cloud objects over the entire tropical Pacific were small for the large-size category of cloud objects, relative to those of the small- and medium-size categories. This result suggests that the fixed anvil temperature hypothesis of Hartmann and Larson may be valid for the large-size category. Combining with the result that a higher percentage of the large-size category of cloud objects occurs during higher SST subperiods, this implies that macrophysical properties of cloud objects would be less sensitive to further warming of the climate. On the other hand, when cloud objects are classified according to SSTs where large-scale dynamics plays important roles, statistical characteristics of cloud microphysical properties, optical depth and albedo are not sensitive to the SST, but those of cloud macrophysical properties are strongly dependent upon the SST. Frequency distributions of vertical velocity from the European Center for Medium-range Weather Forecasts model that is matched to each cloud object are used to interpret some of the findings in this study.

Improving microphysics in a convective parameterization: possibilities and limitations

NASA Astrophysics Data System (ADS)

Labbouz, Laurent; Heikenfeld, Max; Stier, Philip; Morrison, Hugh; Milbrandt, Jason; Protat, Alain; Kipling, Zak

2017-04-01

The convective cloud field model (CCFM) is a convective parameterization implemented in the climate model ECHAM6.1-HAM2.2. It represents a population of clouds within each ECHAM-HAM model column, simulating up to 10 different convective cloud types with individual radius, vertical velocities and microphysical properties. Comparisons between CCFM and radar data at Darwin, Australia, show that in order to reproduce both the convective cloud top height distribution and the vertical velocity profile, the effect of aerodynamic drag on the rising parcel has to be considered, along with a reduced entrainment parameter. A new double-moment microphysics (the Predicted Particle Properties scheme, P3) has been implemented in the latest version of CCFM and is compared to the standard single-moment microphysics and the radar retrievals at Darwin. The microphysical process rates (autoconversion, accretion, deposition, freezing, …) and their response to changes in CDNC are investigated and compared to high resolution CRM WRF simulations over the Amazon region. The results shed light on the possibilities and limitations of microphysics improvements in the framework of CCFM and in convective parameterizations in general.

Seasonal Differences in Tropical Western Pacific Cloud Ice, Water Vapor and Aerosols Observed From Space During ATTREX-III and POSIDON

NASA Astrophysics Data System (ADS)

Avery, M. A.; Rosenlof, K. H.; Vaughan, M.; Getzewich, B. J.; Thornberry, T. D.; Gao, R. S.; Rollins, A. W.; Woods, S.; Yorks, J. E.; Jensen, E. J.

2017-12-01

Recent aircraft missions sampling the tropical tropopause layer (TTL) in the tropical Western Pacific have provided a wealth of detailed cloud microphysical and associated aerosol, water vapor and temperature data for understanding processes that regulate stratospheric composition and hydration. This presentation seeks to provide a regional context for these measurements by comparing and contrasting active space-based observations from these time periods (Feb-Mar 2014 for ATTREX-III and Oct 2016 for POSIDON), primarily from the Clouds and Aerosol Lidar with Orthogonal Polarization (CALIOP), with the addition of Cloud Profiling Radar (CPR) and the Cloud-Aerosol Transport System (CATS) where these data sets are available. While the ATTREX III and POSIDON aircraft field missions both took place from Guam in the Western Pacific, there were striking differences between the amount, geographical distribution and properties of cirrus clouds and aerosols in the Tropical TTL. In addition to cloud and aerosol amount and location, we present geometric properties, including cloud top heights, transparent cloud and aerosol layer thicknesses and location of the 532 nm backscatter centroid, which is roughly equivalent to the layer vertical center of mass. We also present differences in the distribution of cirrus cloud extinction coefficients and ice water content, and aerosol optical depths, as detected from space, and compare these with in situ measurements and with temperature and water vapor distributions from the Microwave Limb Sounder (MLS). We find that there is more intense convection reaching the tropical tropopause during the POSIDON mission, and consequently more associated cloud ice observed during POSIDON than during ATTREX-III.

Cloud-Scale Vertical Velocity and Turbulent Dissipation Rate Retrievals

DOE Data Explorer

Shupe, Matthew

2013-05-22

Time-height fields of retrieved in-cloud vertical wind velocity and turbulent dissipation rate, both retrieved primarily from vertically-pointing, Ka-band cloud radar measurements. Files are available for manually-selected, stratiform, mixed-phase cloud cases observed at the North Slope of Alaska (NSA) site during periods covering the Mixed-Phase Arctic Cloud Experiment (MPACE, late September through early November 2004) and the Indirect and Semi-Direct Aerosol Campaign (ISDAC, April-early May 2008). These time periods will be expanded in a future submission.

Eleven quick tips for architecting biomedical informatics workflows with cloud computing.

PubMed

Cole, Brian S; Moore, Jason H

2018-03-01

Cloud computing has revolutionized the development and operations of hardware and software across diverse technological arenas, yet academic biomedical research has lagged behind despite the numerous and weighty advantages that cloud computing offers. Biomedical researchers who embrace cloud computing can reap rewards in cost reduction, decreased development and maintenance workload, increased reproducibility, ease of sharing data and software, enhanced security, horizontal and vertical scalability, high availability, a thriving technology partner ecosystem, and much more. Despite these advantages that cloud-based workflows offer, the majority of scientific software developed in academia does not utilize cloud computing and must be migrated to the cloud by the user. In this article, we present 11 quick tips for architecting biomedical informatics workflows on compute clouds, distilling knowledge gained from experience developing, operating, maintaining, and distributing software and virtualized appliances on the world's largest cloud. Researchers who follow these tips stand to benefit immediately by migrating their workflows to cloud computing and embracing the paradigm of abstraction.

Eleven quick tips for architecting biomedical informatics workflows with cloud computing

PubMed Central

Moore, Jason H.

2018-01-01

Cloud computing has revolutionized the development and operations of hardware and software across diverse technological arenas, yet academic biomedical research has lagged behind despite the numerous and weighty advantages that cloud computing offers. Biomedical researchers who embrace cloud computing can reap rewards in cost reduction, decreased development and maintenance workload, increased reproducibility, ease of sharing data and software, enhanced security, horizontal and vertical scalability, high availability, a thriving technology partner ecosystem, and much more. Despite these advantages that cloud-based workflows offer, the majority of scientific software developed in academia does not utilize cloud computing and must be migrated to the cloud by the user. In this article, we present 11 quick tips for architecting biomedical informatics workflows on compute clouds, distilling knowledge gained from experience developing, operating, maintaining, and distributing software and virtualized appliances on the world’s largest cloud. Researchers who follow these tips stand to benefit immediately by migrating their workflows to cloud computing and embracing the paradigm of abstraction. PMID:29596416

New insights about cloud vertical structure from CloudSat and CALIPSO observations

NASA Astrophysics Data System (ADS)

Oreopoulos, Lazaros; Cho, Nayeong; Lee, Dongmin

2017-09-01

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

Cloudsat tropical cyclone database

NASA Astrophysics Data System (ADS)

Tourville, Natalie D.

CloudSat (CS), the first 94 GHz spaceborne cloud profiling radar (CPR), launched in 2006 to study the vertical distribution of clouds. Not only are CS observations revealing inner vertical cloud details of water and ice globally but CS overpasses of tropical cyclones (TC's) are providing a new and exciting opportunity to study the vertical structure of these storm systems. CS TC observations are providing first time vertical views of TC's and demonstrate a unique way to observe TC structure remotely from space. Since December 2009, CS has intersected every globally named TC (within 1000 km of storm center) for a total of 5,278 unique overpasses of tropical systems (disturbance, tropical depression, tropical storm and hurricane/typhoon/cyclone (HTC)). In conjunction with the Naval Research Laboratory (NRL), each CS TC overpass is processed into a data file containing observational data from the afternoon constellation of satellites (A-TRAIN), Navy's Operational Global Atmospheric Prediction System Model (NOGAPS), European Center for Medium range Weather Forecasting (ECMWF) model and best track storm data. This study will describe the components and statistics of the CS TC database, present case studies of CS TC overpasses with complementary A-TRAIN observations and compare average reflectivity stratifications of TC's across different atmospheric regimes (wind shear, SST, latitude, maximum wind speed and basin). Average reflectivity stratifications reveal that characteristics in each basin vary from year to year and are dependent upon eye overpasses of HTC strength storms and ENSO phase. West Pacific (WPAC) basin storms are generally larger in size (horizontally and vertically) and have greater values of reflectivity at a predefined height than all other basins. Storm structure at higher latitudes expands horizontally. Higher vertical wind shear (≥ 9.5 m/s) reduces cloud top height (CTH) and the intensity of precipitation cores, especially in HTC strength storms. Average zero and ten dBZ height thresholds confirm WPAC storms loft precipitation sized particles higher into the atmosphere than in other basins. Two CS eye overpasses (32 hours apart) of a weakening Typhoon Nida in 2009 reveal the collapse of precipitation cores, warm core anomaly and upper tropospheric ice water content (IWC) under steady moderate shear conditions.

Evolution of Precipitation Particle Size Distributions within MC3E Systems and its Impact on Aerosol-Cloud-Precipitation Interactions: Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kollias, Pavlos

2017-08-08

This is a multi-institutional, collaborative project using observations and modeling to study the evolution (e.g. formation and growth) of hydrometeors in continental convective clouds. Our contribution was in data analysis for the generation of high-value cloud and precipitation products and derive cloud statistics for model validation. There are two areas in data analysis that we contributed: i) the development of novel, state-of-the-art dual-wavelength radar algorithms for the retrieval of cloud microphysical properties and ii) the evaluation of large domain, high-resolution models using comprehensive multi-sensor observations. Our research group developed statistical summaries from numerous sensors and developed retrievals of vertical airmore » motion in deep convection.« less

Contaminant transport in wetland flows with bulk degradation and bed absorption

NASA Astrophysics Data System (ADS)

Wang, Ping; Chen, G. Q.

2017-09-01

Ecological degradation and absorption are ubiquitous and exert considerable influence on the contaminant transport in natural and constructed wetland flows. It creates an increased demand on models to accurately characterize the spatial concentration distribution of the transport process. This work extends a method of spatial concentration moments by considering the non-uniform longitudinal solute displacements along the vertical direction, and analytically determines the spatial concentration distribution in the very initial stage since source release with effects of bulk degradation and bed absorption. The present method is demonstrated to bear a more accurate prediction especially in the initial stage through convergence analysis of Hermite polynomials. Results reveal that contaminant cloud shows to be more contracted and reformed by bed absorption with increasing damping factor of wetland flows. Tremendous vertical concentration variation especially in the downstream of the contaminant cloud remains great even at asymptotic large times. Spatial concentration evolution by the extended method other than the mean by previous studies is potential for various implements associated with contaminant transport with strict environmental standards.

Characterization of residuals from ice particles and droplets sampled in mid-latitude natural and aviation-influenced cirrus and in tropical deep convective cloud systems during ML-CIRRUS and ACRIDICON

NASA Astrophysics Data System (ADS)

Mertes, Stephan; Kästner, Udo; Schulz, Christiane; Klimach, Thomas; Krüger, Mira; Schneider, Johannes

2015-04-01

Airborne sampling of cloud particles inside different cirrus cloud types and inside deep convective clouds was conducted during the HALO missions ML-CIRRUS over Europe in March/April 2014 and ACRIDICON over Amazonia in September 2014. ML-CIRRUS aims at the investigation of the for-mation, evolution, microphysical state and radiative effects of different natural and aviation-induced cirrus clouds in the mid-latitudes. The main objectives of ACRIDICON are the microphysical vertical profiling, vertical aerosol transport and the cloud processing of aerosol particles (compari-son in- and outflow) of tropical deep convective cloud systems in clean and polluted air masses and over forested and deforested regions. The hydrometeors (drops and ice particles) are sampled by a counterflow virtual impactor (CVI) which has to be installed in the front part of the upper fuselage of the HALO aircraft. Such an intake position implies a size dependent abundance of cloud particles with respect to ambient conditions that was studied by particle trajectory simulations (Katrin Witte, HALO Technical Note 2008-003-A). On the other hand, this sampling location avoids that large ice crystals which could potentially bias the cloud particle sampling by shattering and break-up at the inlet shroud and tip enter the inlet. Both aspects as well as the flight conditions of HALO were taken into account for an optimized CVI design for HALO (HALO-CVI). Interstitial particles are pre-segregated and the condensed phase is evaporated/sublimated by the CVI, such that the residuals from cloud droplets and ice particles (CDR and IPR) can be microphysically and chemically analyzed by respective aerosol sensors located in the cabin. Although an even more comprehensive characterization of CDR and IPR was carried out, we like to report on the following measurements of certain aerosol properties. Particle number concentra-tion and size distribution are measured by a condensation particle counter (CPC) and an ultra-high sensitivity aerosol spectrometer (UHSAS). The absorption coefficient and thus a measure for the black carbon mass concentration is derived from the particle soot absorption photometer (PSAP). In the lower warm parts of the probed convective clouds during the ACRIDICON mission the mean charge of droplets was inferred by means of electrometer measurements. For the determination of the chemical properties of CDR and IPR, the Aircraft-based Laser Ablation Aerosol Mass Spec-trometer (ALABAMA) and a Compact-Time-of-Flight-Aerosol-Mass-Spectrometer (C-ToF-AMS) was operated during ML-CIRRUS and ACRIDICON, respectively, to obtain the mixing state and chemical composition of the cloud particle residues. During ML-CIRRUS, differences in IPR concentration, size distribution, and chemical composition between natural and aviation influenced cirrus clouds could be observed as well as between dif-ferent natural cirrus types and between young and aged contrail cirrus. During ACRIDICON, CDR concentration, size distribution, and chemical composition are found to be different for convective cloud systems evolving from more clean air masses compared to systems evolving from more polluted air masses. Droplet charges change from negative to positive values with height in all vertical cloud profiles. The measured IPR concentration strongly vary in the anvil outflow regions.

A new cloud and aerosol layer detection method based on micropulse lidar measurements

NASA Astrophysics Data System (ADS)

Zhao, Chuanfeng; Wang, Yuzhao; Wang, Qianqian; Li, Zhanqing; Wang, Zhien; Liu, Dong

2014-06-01

This paper introduces a new algorithm to detect aerosols and clouds based on micropulse lidar measurements. A semidiscretization processing technique is first used to inhibit the impact of increasing noise with distance. The value distribution equalization method which reduces the magnitude of signal variations with distance is then introduced. Combined with empirical threshold values, we determine if the signal waves indicate clouds or aerosols. This method can separate clouds and aerosols with high accuracy, although differentiation between aerosols and clouds are subject to more uncertainties depending on the thresholds selected. Compared with the existing Atmospheric Radiation Measurement program lidar-based cloud product, the new method appears more reliable and detects more clouds with high bases. The algorithm is applied to a year of observations at both the U.S. Southern Great Plains (SGP) and China Taihu sites. At the SGP site, the cloud frequency shows a clear seasonal variation with maximum values in winter and spring and shows bimodal vertical distributions with maximum occurrences at around 3-6 km and 8-12 km. The annual averaged cloud frequency is about 50%. The dominant clouds are stratiform in winter and convective in summer. By contrast, the cloud frequency at the Taihu site shows no clear seasonal variation and the maximum occurrence is at around 1 km. The annual averaged cloud frequency is about 15% higher than that at the SGP site. A seasonal analysis of cloud base occurrence frequency suggests that stratiform clouds dominate at the Taihu site.

Simulating the Effects of Semivolatile Compounds on Cloud Processing of Aerosol

NASA Astrophysics Data System (ADS)

Kokkola, H.; Kudzotsa, I.; Tonttila, J.; Raatikainen, T.; Romakkaniemi, S.

2017-12-01

Aerosol removal processes largely dictate how well aerosol is transported in the atmosphere and thus the aerosol load over remote regions depends on how effectively aerosol is removed during its transport from the source regions. This means that in order to model the global distribution aerosol, both in vertical and horizontal, wet deposition processes have to be properly modelled. However, in large scale models, the description of wet removal and the vertical redistribution of aerosol by cloud processes is often extremely simplified.Here we present a novel aerosol-cloud model SALSA, where the aerosol properties are tracked through different cloud processes. These processes include: cloud droplet activation, precipitation formation, ice nucleation, melting, and evaporation. It is a sectional model that includes separate size sections for non-activated aerosol, cloud droplets, precipitation droplets, and ice crystals. The aerosol-cloud model was coupled to a large eddy model UCLALES which simulates the boundary-layer dynamics. In this study, the model has been applied in studying the wet removal as well as interactions between aerosol, clouds, and semi-volatile compounds, ammonia and nitric acid. These semi-volative compounds are special in the sense that they co-condense together with water during cloud activation and have been suggested to form droplets that can be considered cloud-droplet-like already in subsaturated conditions. In our model, we calculate the kinetic partitioning of ammonia and sulfate thus explicitly taking into account the effect of ammonia and nitric acid in the cloud formation. Our simulations indicate that especially in polluted conditions, these compounds significantly affect the properties of cloud droplets thus significantly affecting the lifecycle of different aerosol compounds.

The detection of the electric field vertical distribution underneath thundercloud: Principle and applications

NASA Technical Reports Server (NTRS)

Soula, Serge; Chauzy, Serge

1991-01-01

During the Florida 89 experiment at Kennedy Space Center, a new system was used in order to obtain the vertical distribution of the electric field underneath thunderstorms. It consists of a standard shutter field mill at ground level and five other field sensors suspended from a cable fastened to a tethered balloon located at an altitude of about 1000 meters. It also includes a reception station for telemetered information transmitted by sensors, a processing system in order to store data, and real time display on a screen to show the simultaneous field variations at each level along with the instantaneous electric field profile. The first results obtained show the great importance of the electric field vertical distribution. The field detected at a height of 600m reaches 65 kV/m while that at the surface does not exceed 5 kV/m. The field intensity in altitude is a better criterion for determining the right moment to launch a rocket devoted to flash triggering. Using Gauss's law, the simultaneous field variations at several levels are used in order to evaluate charge densities. Average values close to 1nC.m(-3) are calculated in layers up to 600 m. The calculation of different average charge densities leads to the characterization of the layer between cloud and ground just before the leader propagation in the case of cloud to ground flash.

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

NASA Technical Reports Server (NTRS)

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

2011-01-01

Estimation of Direct Climate Forcing (DCF) due to aerosols in cloudy areas has historically been a difficult task, mainly because of a lack of appropriate measurements. Recently, passive remote sensing instruments have been developed that have the potential to retrieve both cloud and aerosol properties using polarimetric, multiple view angle, and multi spectral observations, and therefore determine DCF from aerosols above clouds. One such instrument is the Research Scanning Polarimeter (RSP), an airborne prototype of a sensor on the NASA Glory satellite, which unfortunately failed to reach orbit during its launch in March of 2011. In the spring of 2006, the RSP was deployed on an aircraft based in Veracruz, Mexico, as part of the Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign. On 13 March, the RSP over flew an aerosol layer lofted above a low altitude marine stratocumulus cloud close to shore in the Gulf of Mexico. We investigate the feasibility of retrieving aerosol properties over clouds using these data. Our approach is to first determine cloud droplet size distribution using the angular location of the cloud bow and other features in the polarized reflectance. The selected cloud was then used in a multiple scattering radiative transfer model optimization to determine the aerosol optical properties and fine tune the cloud size distribution. In this scene, we were able to retrieve aerosol optical depth, the fine mode aerosol size distribution parameters and the cloud droplet size distribution parameters to a degree of accuracy required for climate modeling. This required assumptions about the aerosol vertical distribution and the optical properties of the coarse aerosol size mode. A sensitivity study was also performed to place this study in the context of future systematic scanning polarimeter observations, which found that the aerosol complex refractive index can also be observed accurately if the aerosol optical depth is larger than roughly 0.8 at a wavelength of (0.555 m).

Thermodynamics in the Suppressed Phase of the Madden-Julian Oscillation Using a Multiplatform Strategy

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Robertson, Franklin R.; Clayson, Carol Anne; Taylor, Patrick

2014-01-01

The Madden-Julian Oscillation (MJO) represents a prominent mode of intraseasonal tropical variability. It is manifest by coherent large-scale changes in atmospheric circulation, convection, and thermodynamic processes. Preconditioning of the environment prior to the active phase of the MJO has been noted, but the balance of theorized mechanisms to accomplish this process remains unresolved. Further, there is a lack of consensus on the means by which primary initiation of an MJO event occurs. Observational and modeling efforts have recently been undertaken to advance our understanding of the physical underpinnings governing MJO development. However these intensive studies are often limited in space and/or time and are potentially subject to model deficiencies. Satellite observations, especially those providing vertical resolution of temperature and moisture, provide an opportunity to expand our knowledge of processes critical to MJO initiation and preconditioning. This work will provide an analysis of suppressed phase thermodynamics with an emphasis on the use of a complementary suite of satellite observations including AIRS/AMSU-A profiles, CERES radiative fluxes, and cloud properties observed by MODIS. Emphasis of this work will regard the distribution of cloud regimes, their radiative-convective effects, and their relationship to moist static energy during the recharge and suppressed stages of MJO initiation and eastward propagation. The analyses will make use of cloud regimes from MODIS observations to provide a compositing technique that enables the identification of systematic connections between different cloud regimes and the larger scale environment. Within these cloud regimes, the relationship between the associated cloud-radiative effects observed by CERES, vertically-resolved and vertically-integrated thermodynamics using AIRS/AMSU-A observations, and atmospheric boundary layer fluxes will be demonstrated.

Tropical Oceanic Precipitation Processes Over Warm Pool: 2D and 3D Cloud Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, W.-K.; Johnson, D.; Simpson, J.; Einaudi, Franco (Technical Monitor)

2001-01-01

Rainfall is a key link in the hydrologic cycle as well as the primary heat source for the atmosphere. The vertical distribution of convective latent-heat release modulates the large-scale circulations of the topics. Furthermore, changes in the moisture distribution at middle and upper levels of the troposphere can affect cloud distributions and cloud liquid water and ice contents. How the incoming solar and outgoing longwave radiation respond to these changes in clouds is a major factor in assessing climate change. Present large-scale weather and climate model simulate processes only crudely, reducing confidence in their predictions on both global and regional scales. One of the most promising methods to test physical parameterizations used in General Circulation Models (GCMs) and climate models is to use field observations together with Cloud Resolving Models (CRMs). The CRMs use more sophisticated and physically realistic parameterizations of cloud microphysical processes, and allow for their complex interactions with solar and infrared radiative transfer processes. The CRMs can reasonably well resolve the evolution, structure, and life cycles of individual clouds and clouds systems. The major objective of this paper is to investigate the latent heating, moisture and momentum budgets associated with several convective systems developed during the TOGA COARE IFA - westerly wind burst event (late December, 1992). The tool for this study is the Goddard Cumulus Ensemble (GCE) model which includes a 3-class ice-phase microphysics scheme.

Lidar Penetration Depth Observations for Constraining Cloud Longwave Feedbacks

NASA Astrophysics Data System (ADS)

Vaillant de Guelis, T.; Chepfer, H.; Noel, V.; Guzman, R.; Winker, D. M.; Kay, J. E.; Bonazzola, M.

2017-12-01

Satellite-borne active remote sensing Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations [CALIPSO; Winker et al., 2010] and CloudSat [Stephens et al., 2002] provide direct measurements of the cloud vertical distribution, with a very high vertical resolution. The penetration depth of the laser of the lidar Z_Opaque is directly linked to the LongWave (LW) Cloud Radiative Effect (CRE) at Top Of Atmosphere (TOA) [Vaillant de Guélis et al., in review]. In addition, this measurement is extremely stable in time making it an excellent observational candidate to verify and constrain the cloud LW feedback mechanism [Chepfer et al., 2014]. In this work, we present a method to decompose the variations of the LW CRE at TOA using cloud properties observed by lidar [GOCCP v3.0; Guzman et al., 2017]. We decompose these variations into contributions due to changes in five cloud properties: opaque cloud cover, opaque cloud altitude, thin cloud cover, thin cloud altitude, and thin cloud emissivity [Vaillant de Guélis et al., in review]. We apply this method, in the real world, to the CRE variations of CALIPSO 2008-2015 record, and, in climate model, to LMDZ6 and CESM simulations of the CRE variations of 2008-2015 period and of the CRE difference between a warm climate and the current climate. In climate model simulations, the same cloud properties as those observed by CALIOP are extracted from the CFMIP Observation Simulator Package (COSP) [Bodas-Salcedo et al., 2011] lidar simulator [Chepfer et al., 2008], which mimics the observations that would be performed by the lidar on board CALIPSO satellite. This method, when applied on multi-model simulations of current and future climate, could reveal the altitude of cloud opacity level observed by lidar as a strong constrain for cloud LW feedback, since the altitude feedback mechanism is physically explainable and the altitude of cloud opacity accurately observed by lidar.

Cloud chemistry on Jupiter

NASA Technical Reports Server (NTRS)

Carlson, Barbara E.; Prather, Michael J.; Rossow, William B.

1987-01-01

Chemical equilibrium models used currently to interpret observations of Jupiter are reexamined using new data defining thermal profiles, which are substantially different from those used in the previous models. A model is developed for the chemical reactions controlling the composition of the upper troposphere on Jupiter, specifically the cloud-forming region from 10 bar to 0.1 bar, which includes, for the first time, the effects of aqueous chemistry on the composition and the vertical distribution of many measurable species in the atmosphere, identifying the factors influencing their abundances above the H2O cloud. The thermodynamic data for potential condensates on Jupiter, i.e., NH3(s), NH4SH(s), (NH4)2S(s), and H2S(s), are reexamined, recognizing the lack of data on sulfides for the temperature range of interest on Jupiter. Vertical profiles of mixing ratios for CO2, H2S, NH3, and H2, obtained for several assumed bulk abundances with respect to solar, are presented.

Impact of aerosol vertical distribution on aerosol direct radiative effect and heating rate in the Mediterranean region

NASA Astrophysics Data System (ADS)

Pappas, Vasileios; Hatzianastassiou, Nikolaos; Matsoukas, Christos; Koras Carracca, Mario; Kinne, Stefan; Vardavas, Ilias

2015-04-01

It is now well-established that aerosols cause an overall cooling effect at the surface and a warming effect within the atmosphere. At the top of the atmosphere (TOA), both positive and negative forcing can be found, depending on a number of other factors, such as surface albedo and relative position of clouds and aerosols. Whilst aerosol surface cooling is important due to its relation with surface temperature and other bio-environmental reasons, atmospheric heating is of special interest as well having significant impacts on atmospheric dynamics, such as formation of clouds and subsequent precipitation. The actual position of aerosols and their altitude relative to clouds is of major importance as certain types of aerosol, such as black carbon (BC) above clouds can have a significant impact on planetary albedo. The vertical distribution of aerosols and clouds has recently drawn the attention of the aerosol community, because partially can account for the differences between simulated aerosol radiative forcing with various models, and therefore decrease the level of our uncertainty regarding aerosol forcing, which is one of our priorities set by IPCC. The vertical profiles of aerosol optical and physical properties have been studied by various research groups around the world, following different methodologies and using various indices in order to present the impact of aerosols on radiation on different altitudes above the surface. However, there is still variability between the published results as to the actual effect of aerosols on shortwave radiation and on heating rate within the atmosphere. This study uses vertical information on aerosols from the Max Planck Aerosol Climatology (MAC-v1) global dataset, which is a combination of model output with quality ground-based measurements, in order to provide useful insight into the vertical profile of atmospheric heating for the Mediterranean region. MAC-v1 and the science behind this aerosol dataset have already been presented and its validity has been tested against satellite-based retrievals. A detailed spectral radiative transfer model (RTM), already used in a number of planetary and regional studies, has been used in the present study to calculate the vertically distributed aerosol direct radiative effects (DREs) and the associated aerosol heating/cooling profiles within the troposphere. Specific emphasis is given to assessment of the crucial issue of the differences between modeling the aerosol DREs using either columnar aerosol optical properties, as usually done, or vertically layered information on those properties, which is the state of the art and ideal practice. To address this problem, the following experiment has been performed: the same RTM has been used twice with the same meteorological conditions but in the first run (set1) columnar values for aerosol optical depth (AOD) have been used while using vertically distributed AOD in the second run (set2). In the second run vertically layered information for AOD is considered for 20 layers extending from the surface to 20 km a.m.s.l.. The vertical profile of AOD has been mainly based on ECHAM model. The aerosol DREs are computed at the Earth's surface, at TOA and at various levels in the atmosphere. Apart from AOD, the model also requires single-scattering albedo (SSA) and asymmetry parameter (ASY) in 18 different wavelengths, which are obtained by linear interpolation from the available wavelengths in HAC. The comparison between the obtained two sets of DRE (set1 and set2) reveal small, but notable differences which vary from one place to another. Within the atmosphere, the difference -averaged over the four seasons - ranges from -0.3 to 1.7 Wm-2 with a mean value of 0.32 Wm-2. Given the fact that the average column-integrated DREAtm values for the entire Mediterranean region based on columnar aerosol optical properties is 11.44 Wm-2, there is an average variance of 3.7 %, which locally could get to 14.9 %. Differences between the columnar and the vertically layered versions of the model also exist for DRE(TOA) and DRE(NetSurface) calculations.

New Satellite Estimates of Mixed-Phase Cloud Properties: A Synergistic Approach for Application to Global Satellite Imager Data

NASA Astrophysics Data System (ADS)

Smith, W. L., Jr.; Spangenberg, D.; Fleeger, C.; Sun-Mack, S.; Chen, Y.; Minnis, P.

2016-12-01

Determining accurate cloud properties horizontally and vertically over a full range of time and space scales is currently next to impossible using data from either active or passive remote sensors or from modeling systems. Passive satellite imagers provide horizontal and temporal resolution of clouds, but little direct information on vertical structure. Active sensors provide vertical resolution but limited spatial and temporal coverage. Cloud models embedded in NWP can produce realistic clouds but often not at the right time or location. Thus, empirical techniques that integrate information from multiple observing and modeling systems are needed to more accurately characterize clouds and their impacts. Such a strategy is employed here in a new cloud water content profiling technique developed for application to satellite imager cloud retrievals based on VIS, IR and NIR radiances. Parameterizations are developed to relate imager retrievals of cloud top phase, optical depth, effective radius and temperature to ice and liquid water content profiles. The vertical structure information contained in the parameterizations is characterized climatologically from cloud model analyses, aircraft observations, ground-based remote sensing data, and from CloudSat and CALIPSO. Thus, realistic cloud-type dependent vertical structure information (including guidance on cloud phase partitioning) circumvents poor assumptions regarding vertical homogeneity that plague current passive satellite retrievals. This paper addresses mixed phase cloud conditions for clouds with glaciated tops including those associated with convection and mid-latitude storm systems. Novel outcomes of our approach include (1) simultaneous retrievals of ice and liquid water content and path, which are validated with active sensor, microwave and in-situ data, and yield improved global cloud climatologies, and (2) new estimates of super-cooled LWC, which are demonstrated in aviation safety applications and validated with icing PIREPS. The initial validation is encouraging for single-layer cloud conditions. More work is needed to test and refine the method for global application in a wider range of cloud conditions. A brief overview of our current method, applications, verification, and plans for future work will be presented.

The effect of cloud screening on MAX-DOAS aerosol retrievals.

NASA Astrophysics Data System (ADS)

Gielen, Clio; Van Roozendael, Michel; Hendrik, Francois; Fayt, Caroline; Hermans, Christian; Pinardi, Gaia; De Backer, Hugo; De Bock, Veerle; Laffineur, Quentin; Vlemmix, Tim

2014-05-01

In recent years, ground-based multi-axis differential absorption spectroscopy (MAX-DOAS) has shown to be ideally suited for the retrieval of tropospheric trace gases and deriving information on the aerosol properties. These measurements are invaluable to our understanding of the physics and chemistry of the atmospheric system, and the impact on the Earth's climate. Unfortunately, MAX-DOAS measurements are often performed under strong non-clear-sky conditions, causing strong data quality degradation and uncertainties on the retrievals. Here we present the result of our cloud-screening method, using the colour index (CI), on aerosol retrievals from MAX-DOAS measurements (AOD and vertical profiles). We focus on two large data sets, from the Brussels and Beijing area. Using the CI we define 3 different sky conditions: bad (=full thick cloud cover/extreme aerosols), mediocre (=thin clouds/aerosols) and good (=clear sky). We also flag the presence of broken/scattered clouds. We further compare our cloud-screening method with results from cloud-cover fractions derived from thermic infrared measurements. In general, our method shows good results to qualify the sky and cloud conditions of MAX-DOAS measurements, without the need for other external cloud-detection systems. Removing data under bad-sky and broken-cloud conditions results in a strongly improved agreement, in both correlation and slope, between the MAX-DOAS aerosol retrievals and data from other instruments (e.g. AERONET, Brewer). With the improved AOD retrievals, the seasonal and diurnal variations of the aerosol content and vertical distribution at both sites can be investigated in further detail. By combining with additional information derived by other instruments (Brewer, lidar, ...) operated at the stations, we will further study the observed aerosol characteristics, and their influence on and by meteorological conditions such as clouds and/or the boundary layer height.

The 27-28 October 1986 FIRE IFO Cirrus Case Study: Cloud Optical Properties Determined by High Spectral Resolution Lidar

NASA Technical Reports Server (NTRS)

Grund, C. J.; Eloranta, E. W.

1996-01-01

During the First ISCCP Region Experiment (FIRE) cirrus intensive field observation (IFO) the High Spectral Resolution Lidar was operated from a roof top site on the University of Wisconsin-Madison campus. Because the HSRL technique separately measures the molecular and cloud particle backscatter components of the lidar return, the optical thickness is determined independent of particle backscatter. This is accomplished by comparing the known molecular density distribution to the observed decrease in molecular backscatter signal with altitude. The particle to molecular backscatter ratio yields calibrated measurements of backscatter cross sections that can be plotted ro reveal cloud morphology without distortion due to attenuation. Changes in cloud particle size, shape, and phase affect the backscatter to extinction ratio (backscatter-phase function). The HSRL independently measures cloud particle backscatter phase function. This paper presents a quantitative analysis of the HSRL cirrus cloud data acquired over an approximate 33 hour period of continuous near zenith observations. Correlations between small scale wind structure and cirrus cloud morphology have been observed. These correlations can bias the range averaging inherent in wind profiling lidars of modest vertical resolution, leading to increased measurement errors at cirrus altitudes. Extended periods of low intensity backscatter were noted between more strongly organized cirrus cloud activity. Optical thicknesses ranging from 0.01-1.4, backscatter phase functions between 0.02-0.065 sr (exp -1) and backscatter cross sections spanning 4 orders of magnitude were observed. the altitude relationship between cloud top and bottom boundaries and the cloud optical center altitude was dependent on the type of formation observed Cirrus features were observed with characteristic wind drift estimated horizontal sizes of 5-400 km. The clouds frequently exhibited cellular structure with vertical to horizontal dimension ratios of 1:5-1:1.

Insights from a Regime Decomposition Approach on CERES and CloudSat-inferred Cloud Radiative Effects

NASA Astrophysics Data System (ADS)

Oreopoulos, L.; Cho, N.; Lee, D.

2015-12-01

Our knowledge of the Cloud Radiative Effect (CRE) not only at the Top-of-the-Atmosphere (TOA), but also (with the help of some modeling) at the surface (SFC) and within the atmospheric column (ATM) has been steadily growing in recent years. Not only do we have global values for these CREs, but we can now also plot global maps of their geographical distribution. The next step in our effort to advance our knowledge of CRE is to systematically assess the contributions of prevailing cloud systems to the global values. The presentation addresses this issue directly. We identify the world's prevailing cloud systems, which we call "Cloud Regimes" (CRs) via clustering analysis of MODIS (Aqua-Terra) daily joint histograms of Cloud Top Pressure and Cloud Optical Thickness (TAU) at 1 degree scales. We then composite CERES diurnal values of CRE (TOA, SFC, ATM) separately for each CR by averaging these values for each CR occurrence, and thus find the contribution of each CR to the global value of CRE. But we can do more. We can actually decompose vertical profiles of inferred instantaneous CRE from CloudSat/CALIPSO (2B-FLXHR-LIDAR product) by averaging over Aqua CR occurrences (since A-Train formation flying allows collocation). Such an analysis greatly enhances our understanding of the radiative importance of prevailing cloud mixtures at different atmospheric levels. We can, for example, in addition to examining whether the CERES findings on which CRs contribute to radiative cooling and warming of the atmospheric column are consistent with CloudSat, also gain insight on why and where exactly this happens from the shape of the full instantaneous CRE vertical profiles.

Monte Carlo Bayesian Inference on a Statistical Model of Sub-Gridcolumn Moisture Variability using High-Resolution Cloud Observations

NASA Astrophysics Data System (ADS)

Norris, P. M.; da Silva, A. M., Jr.

2016-12-01

Norris and da Silva recently published a method to constrain a statistical model of sub-gridcolumn moisture variability using high-resolution satellite cloud data. The method can be used for large-scale model parameter estimation or cloud data assimilation (CDA). The gridcolumn model includes assumed-PDF intra-layer horizontal variability and a copula-based inter-layer correlation model. The observables used are MODIS cloud-top pressure, brightness temperature and cloud optical thickness, but the method should be extensible to direct cloudy radiance assimilation for a small number of channels. The algorithm is a form of Bayesian inference with a Markov chain Monte Carlo (MCMC) approach to characterizing the posterior distribution. This approach is especially useful in cases where the background state is clear but cloudy observations exist. In traditional linearized data assimilation methods, a subsaturated background cannot produce clouds via any infinitesimal equilibrium perturbation, but the Monte Carlo approach is not gradient-based and allows jumps into regions of non-zero cloud probability. In the example provided, the method is able to restore marine stratocumulus near the Californian coast where the background state has a clear swath. The new approach not only significantly reduces mean and standard deviation biases with respect to the assimilated observables, but also improves the simulated rotational-Ramman scattering cloud optical centroid pressure against independent (non-assimilated) retrievals from the OMI instrument. One obvious difficulty for the method, and other CDA methods, is the lack of information content in passive cloud observables on cloud vertical structure, beyond cloud-top and thickness, thus necessitating strong dependence on the background vertical moisture structure. It is found that a simple flow-dependent correlation modification due to Riishojgaard is helpful, better honoring inversion structures in the background state.

The abundance and distribution of water vapor in the Jovian troposphere as inferred from Voyager IRIS observations

NASA Technical Reports Server (NTRS)

Carlson, Barbara E.; Lacis, Andrew A.; Rossow, William B.

1992-01-01

The Voyager IRIS spectra of the Jovian North Equatorial Belt (NEB) hot spots are reanalyzed using a radiative transfer model which includes the full effects of anisotropic multiple scattering by clouds. The atmospheric model includes the three thermochemically predicted cloud layers, NH3, NH4SH, and H2O. Spectrally dependent cloud extinction is modeled using Mie theory and the refractive indices of NH3 ice, NH4SH ice, water, and H2O ice. The upper tropospheric temperature profile, gas abundances, height-dependent parahydrogen profile, and vertical distribution of NH3 cloud opacity are retrieved from an analysis of the far-infrared (180-1200/cm) IRIS observations. With these properties constrained, the 5-micron (1800-2300/cm) observations are analyzed to determine the atmospheric and cloud structure of the deeper atmosphere (P of greater than 1.5 bars). The results show that the abundance of water is at least 1.5 times solar with 2 times solar (0.00276 mixing ratio relative to H2) providing the best-fit to the Voyager IRIS hot spot observations.

Capability of the CALIPSO lidar observations to detect the dust source regions

NASA Astrophysics Data System (ADS)

Kaskaoutis, D. G.; Kharol, Shailesh Kumar; Kambezidis, H. D.; Nastos, P. T.; Rani Sharma, Anu; Kvs, Badarinath

Two dust events with high aerosol optical depth (AOD) values have been observed over Athens on 4 and 6-7 February 2009. These dust events were well captured by the satellite obser-vations and are investigated in the present study by means of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations, ceilometer vertical profiles and DREAM model predictions. The CALIPSO provides new insight to study the role of clouds and atmospheric aerosols in regulating Earth's weather, climate, and air quality. CALIPSO has a 98o-inclination orbit and flies at an altitude of 705 km providing daily global maps of the ver-tical distribution of aerosols and clouds. The CALIPSO satellite carries a polarization-sensitive lidar, the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), which provides profiles of backscatter coefficient at 532 and 1064 nm. The ceilometer used in the present study is a Vaisala CL31 model. It is equipped with an InGaAs MOCVD pulsed laser, emitting at 930 nm and having an energy per pulse of 1.2 J. The emission frequency is 10 kHz while the pulse duration is 100 ns. The vertical profiles of the aerosol backscatter coefficient were obtained from 5 m up to 7.5 km at 930 nm. The CL31 is installed at the Actinometric station of the National Observatory of Athens. The CALIPSO-derived total attenuated backscatter at 532 and 1064 nm is used to identify the position of dust along the overpass trajectory. A typical example of the vertical distribution of the dust plume over the study region during nighttime on 5 Febru-ary 2009 is provided. Limiting the analysis over Libya, eastern Mediterranean and Greece (24o -37o N, 15o-19o E), the dust aerosol layer exhibits a high total attenuated backscatter at 532 nm, reaching to 0.05-0.06 km-1sr-1. CALIPSO observations clearly show that the dust plume was generated over the Sahara desert at about 24oN, 15oE near the borders of Libya, Chad and Niger. After its exposure it was uplifted to about 3-km in depth and moved northwards. As the dust layer moved towards Greece its intensity seems to decrease while its vertical extent was limited to lower altitudes within the first 2 km. The ceilometer also detected an elevated aerosol layer due to dust transport within the first 3 km, while the vertical profiles of dust predicted by DREAM were in close agreement with those of the ceilometer. The main goal of this study is the investigation via satellite vertical-profiling instrumentation not only the vertical extent and the transport of dust, but also its source region. Keywords: Dust, CALIPSO, DREAM model and AOD

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

NASA Astrophysics Data System (ADS)

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

2017-05-01

In November 2014 Uranus was observed with the Wide Field Camera 3 (WFC3) instrument of the Hubble Space Telescope as part of the Hubble 2020: Outer Planet Atmospheres Legacy program, OPAL. OPAL annually maps Jupiter, Uranus and Neptune (and will also map Saturn from 2018) in several visible/near-infrared wavelength filters. The Uranus 2014 OPAL observations were made on the 8/9th November at a time when a huge cloud complex, first observed by de Pater et al. (2015) and subsequently tracked by professional and amateur astronomers (Sayanagi et al., 2016), was present at 30-40°N. We imaged the entire visible atmosphere, including the storm system, in seven filters spanning 467-924 nm, capturing variations in the coloration of Uranus' clouds and also vertical distribution due to wavelength dependent changes in Rayleigh scattering and methane absorption optical depth. Here we analyse these new HST observations with the NEMESIS radiative-transfer and retrieval code in multiple-scattering mode to determine the vertical cloud structure in and around the storm cloud system. The same storm system was also observed in the H-band (1.4-1.8 μm) with the SINFONI Integral Field Unit Spectrometer on the Very Large Telescope (VLT) on 31st October and 11th November, reported by Irwin et al. (2016, 10.1016/j.icarus.2015.09.010). To constrain better the cloud particle sizes and scattering properties over a wide wavelength range we also conducted a limb-darkening analysis of the background cloud structure in the 30-40°N latitude band by simultaneously fitting: a) these HST/OPAL observations at a range of zenith angles; b) the VLT/SINFONI observations at a range of zenith angles; and c) IRTF/SpeX observations of this latitude band made in 2009 at a single zenith angle of 23°, spanning the wavelength range 0.8-1.8 μm (Irwin et al., 2015, 10.1016/j.icarus.2014.12.020). We find that the HST observations, and the combined HST/VLT/IRTF observations at all locations are well modelled with a three-component cloud comprised of: 1) a vertically thin, but optically thick 'deep' tropospheric cloud at a pressure of ∼ 2 bars; 2) a methane-ice cloud based at the methane-condensation level of 1.23 bar, with variable vertical extent; and 3) a vertically extended tropospheric haze, also based at the methane-condensation level of ∼ 1.23 bar. We find that modelling both haze and tropospheric cloud with particles having an effective radius of ∼ 0.1 μm provides a good fit the observations, although for the tropospheric cloud, particles with an effective radius as large as 1.0 μm provide a similarly good fit. We find that the particles in both the tropospheric cloud and haze are more scattering at short wavelengths, giving them a blue colour, but are more absorbing at longer wavelengths, especially for the tropospheric haze. We find that the spectra of the storm clouds are well modelled by localised thickening and vertical extension of the methane-ice cloud. For the particles in the storm clouds, which we assume to be composed of methane ice particles, we find that their mean radii must lie somewhere in the range 0.1 - 1.0 μ m. We find that the high clouds have low integrated opacity, and that "streamers" reminiscent of convective thunderstorm anvils are confined to levels deeper than 1 bar. These results argue against vigorous moist convective origins for the cloud features.

The impact of cloud vertical profile on liquid water path retrieval based on the bispectral method: A theoretical study based on large-eddy simulations of shallow marine boundary layer clouds.

PubMed

Miller, Daniel J; Zhang, Zhibo; Ackerman, Andrew S; Platnick, Steven; Baum, Bryan A

2016-04-27

Passive optical retrievals of cloud liquid water path (LWP), like those implemented for Moderate Resolution Imaging Spectroradiometer (MODIS), rely on cloud vertical profile assumptions to relate optical thickness ( τ ) and effective radius ( r e ) retrievals to LWP. These techniques typically assume that shallow clouds are vertically homogeneous; however, an adiabatic cloud model is plausibly more realistic for shallow marine boundary layer cloud regimes. In this study a satellite retrieval simulator is used to perform MODIS-like satellite retrievals, which in turn are compared directly to the large-eddy simulation (LES) output. This satellite simulator creates a framework for rigorous quantification of the impact that vertical profile features have on LWP retrievals, and it accomplishes this while also avoiding sources of bias present in previous observational studies. The cloud vertical profiles from the LES are often more complex than either of the two standard assumptions, and the favored assumption was found to be sensitive to cloud regime (cumuliform/stratiform). Confirming previous studies, drizzle and cloud top entrainment of dry air are identified as physical features that bias LWP retrievals away from adiabatic and toward homogeneous assumptions. The mean bias induced by drizzle-influenced profiles was shown to be on the order of 5-10 g/m 2 . In contrast, the influence of cloud top entrainment was found to be smaller by about a factor of 2. A theoretical framework is developed to explain variability in LWP retrievals by introducing modifications to the adiabatic r e profile. In addition to analyzing bispectral retrievals, we also compare results with the vertical profile sensitivity of passive polarimetric retrieval techniques.

The impact of cloud vertical profile on liquid water path retrieval based on the bispectral method: A theoretical study based on large-eddy simulations of shallow marine boundary layer clouds

PubMed Central

Miller, Daniel J.; Zhang, Zhibo; Ackerman, Andrew S.; Platnick, Steven; Baum, Bryan A.

2018-01-01

Passive optical retrievals of cloud liquid water path (LWP), like those implemented for Moderate Resolution Imaging Spectroradiometer (MODIS), rely on cloud vertical profile assumptions to relate optical thickness (τ) and effective radius (re) retrievals to LWP. These techniques typically assume that shallow clouds are vertically homogeneous; however, an adiabatic cloud model is plausibly more realistic for shallow marine boundary layer cloud regimes. In this study a satellite retrieval simulator is used to perform MODIS-like satellite retrievals, which in turn are compared directly to the large-eddy simulation (LES) output. This satellite simulator creates a framework for rigorous quantification of the impact that vertical profile features have on LWP retrievals, and it accomplishes this while also avoiding sources of bias present in previous observational studies. The cloud vertical profiles from the LES are often more complex than either of the two standard assumptions, and the favored assumption was found to be sensitive to cloud regime (cumuliform/stratiform). Confirming previous studies, drizzle and cloud top entrainment of dry air are identified as physical features that bias LWP retrievals away from adiabatic and toward homogeneous assumptions. The mean bias induced by drizzle-influenced profiles was shown to be on the order of 5–10 g/m2. In contrast, the influence of cloud top entrainment was found to be smaller by about a factor of 2. A theoretical framework is developed to explain variability in LWP retrievals by introducing modifications to the adiabatic re profile. In addition to analyzing bispectral retrievals, we also compare results with the vertical profile sensitivity of passive polarimetric retrieval techniques. PMID:29637042

Boundary Layer Thermodynamics and Cloud Microphysics for a Mixed Stratocumulus and Cumulus Cloud Field Observed during ACE-ENA

NASA Astrophysics Data System (ADS)

Jensen, M. P.; Miller, M. A.; Wang, J.

2017-12-01

The first Intensive Observation Period of the DOE Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) took place from 21 June through 20 July 2017 involving the deployment of the ARM Gulfstream-159 (G-1) aircraft with a suite of in situ cloud and aerosol instrumentation in the vicinity of the ARM Climate Research Facility Eastern North Atlantic (ENA) site on Graciosa Island, Azores. Here we present preliminary analysis of the thermodynamic characteristics of the marine boundary layer and the variability of cloud properties for a mixed cloud field including both stratiform cloud layers and deeper cumulus elements. Analysis combines in situ atmospheric state observations from the G-1 with radiosonde profiles and surface meteorology from the ENA site in order to characterize the thermodynamic structure of the marine boundary layer including the coupling state and stability. Cloud/drizzle droplet size distributions measured in situ are combined with remote sensing observations from a scanning cloud radar, and vertically pointing cloud radar and lidar provide quantification of the macrophysical and microphysical properties of the mixed cloud field.

CATS Version 2 Aerosol Feature Detection and Applications for Data Assimilation

NASA Technical Reports Server (NTRS)

Nowottnick, E. P.; Yorks, J. E.; Selmer, P. A.; Palm, S. P.; Hlavka, D. L.; Pauly, R. M.; Ozog, S.; McGill, M. J.; Da Silva, A.

2017-01-01

The Cloud Aerosol Transport System (CATS) lidar has been operating onboard the International Space Station (ISS) since February 2015 and provides vertical observations of clouds and aerosols using total attenuated backscatter and depolarization measurements. From February March 2015, CATS operated in Mode 1, providing backscatter and depolarization measurements at 532 and 1064 nm. CATS began operation in Mode 2 in March 2015, providing backscatter and depolarization measurements at 1064 nm and has continued to operate to the present in this mode. CATS level 2 products are derived from these measurements, including feature detection, cloud aerosol discrimination, cloud and aerosol typing, and optical properties of cloud and aerosol layers. Here, we present changes to our level 2 algorithms, which were aimed at reducing several biases in our version 1 level 2 data products. These changes will be incorporated into our upcoming version 2 level 2 data release in summer 2017. Additionally, owing to the near real time (NRT) data downlinking capabilities of the ISS, CATS provides expedited NRT data products within 6 hours of observation time. This capability provides a unique opportunity for supporting field campaigns and for developing data assimilation techniques to improve simulated cloud and aerosol vertical distributions in models. We additionally present preliminary work toward assimilating CATS observations into the NASA Goddard Earth Observing System version 5 (GEOS-5) global atmospheric model and data assimilation system.

Case Study Analyses of the SUCCESS DC-8 Scanning Lidar Database

NASA Technical Reports Server (NTRS)

Uthe, Edward E.

2000-01-01

Under project SUCCESS (Subsonic Aircraft Contrail and Cloud Effects Special Study) funded by the Atmospheric Effects of Aviation Program, SRI International (SRI) developed an angular scanning backscatter lidar for operation on the NASA DC-8 research aircraft and deployed the scanning lidar during the SUCCESS field campaign. The primary purpose of the lidar was to generate real-time video displays of clouds and contrails above, ahead of, and below the DC-8 as a means to help position the aircraft for optimum cloud and contrail sampling by onboard in situ sensors, and to help extend the geometrical domain of the in situ sampling records. A large, relatively complex lidar database was collected and several data examples were processed to illustrate the value of the lidar data for interpreting the other data records collected during SUCCESS. These data examples were used to develop a journal publication for the special SUCCESS Geophysical Research Letters issue. The data examples justified data analyses of a larger part of the DC-8 lidar database and is the objective of the current study. Efficient processing of the SUCCESS DC-8 scanning lidar database required substantial effort to enhance hardware and software components of the data system that was used for the initial analyses. MATLAB instructions are used to generate altitude and distance color-coded lidar displays corrected for effects introduced by aircraft pitch and forward movement during an angular scan time interval. Onboard in situ sensor atmospheric measurements are propagated to distances ahead of the DC-8 using recorded aircraft velocity so that they can be plotted on the lidar displays for comparison with lidar remotely observed aerosol distributions. Resulting lidar and in situ sensor polar scan displays over extended sampling intervals are integrated into a time series movie format for 36 case studies. Contrails and clouds were detected to ranges of 15 km by the forward-viewing angular scanning lidar and were progressively mapped as the aircraft approached and penetrated them. Near aircraft lidar observations were much better correlated with in situ sensor observations than lidar observations at greater distances ahead of the aircraft. The major cause of this difference was thought to be the about 2 deg. offset of the lidar viewing direction from the flight direction. Contrail spatial distributions were not of the quality obtainable from ground-based lidar observations. This results because contrails tend to become horizontally stratified, vertical distance between angular lidar observations increases with increased distance from the aircraft, and erratic aircraft motions during an angular scan. The most useful lidar observations were made with lidar viewing directions of vertically upward or vertically downward. These provided real-time information on aircraft altitudes to achieve optimum in situ cloud and contrail sampling. At sampling altitudes, the forward viewing angular scanning observations were useful for fine-tuning the aircraft altitude for cloud and contrail penetration. Best information on cloud and contrail properties were obtained from vertically directed lidar observations as the aircraft performed a series of upward and downward penetrations of contrails. This operational mode was especially well suited for lidar and radiometric evaluation of cloud and contrail optical and radiative properties. The vertical viewing lidar detected ice crystals thought to be precipitating from an aircraft contrail and their scavenging by a cirrus cloud layer. The lidar display indicates that the crystals are effective for increasing cirrus cloud density. Vertical angular scanning observations can evaluate the sharp decrease in lidar backscatter for small off-vertical viewing directions that result from horizontally aligned ice crystals and perhaps can provide additional information on crystal shapes. The about 2 deg. offset of the lidar viewing direction from the flight direction is thought to have greatly degraded the forward-viewing angular scanning observations and this mode of operation was not fully evaluated. However, the reasoning for this capability remains valid and the angular scan presentations collected during this program justifies modification of the lidar pod for true forward direction lidar viewing during future cloud and contrail studies.

Characterization of Convective Systems in Africa in Terms of their Vertical Structure, Electrification and Dynamics

NASA Astrophysics Data System (ADS)

Tadesse, A.; Anagnostou, E. N.

2007-05-01

Mesoscale Convective Systems (MCS) are cloud systems that occur from an ensemble of thunder storms and result in a precipitation that covers a huge contiguous area. They are long-lived storm system having dimensions much larger than an individual storm. Storm systems associated with MCSs over the Africa are tracked for the period July to December 2004 and their properties at different stages of their life are investigated in terms of the vertical reflectivity profile, electrification and dynamics of clouds. The research is facilitated by remote sensing data, which include instantaneous vertical reflectivity fields derived from the TRMM precipitation radar (PR), coincident 1/2-hourly observations of long-range lightning accumulation and Global IR fields. Results show a strong indication of the magnitude and intensity of electrification of a thunderstorm with the stage of its life. More vigorous dynamic conditions with intense electrification are observed during the growing stage of the storm and more or less stable situation uniform distribution of electrification has been distributed to most of the pixels in the storm during its maturity stage and less rainfall and electrification during its decaying stage was a general observation during the period. The vertical reflectivity has been found to be strongly related to the electrification and the stage of the convective life cycle in such away that the reflectivity decrease as the storm matures and decays. A good correlation is observed between the strength of vertical profile of reflectivity, which is a proxy for the ice concentration, and lightning activity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cecchini, Micael A.; Machado, Luiz A. T.; Comstock, Jennifer M.

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 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 overall shape of the droplet size distribution (DSD) does not appear to be predominantly determined by updraught strength, especially beyond the 20 µm range. The aerosol conditions play a major role in that case. However, the updraughts modulate the DSD concentrations and are responsible for the vertical transport of water in the cloud. The larger droplets found in background clouds are associated with weak water vapour competition and a bimodal distribution of droplet sizes in the lower levels of the cloud, which enables an earlier initiation of the collision–coalescence process. This study shows that the pollution produced by Manaus significantly affects warm-phase microphysical properties of the surrounding clouds by changing the initial DSD formation. The corresponding effects on ice-phase processes and precipitation formation will be the focus of future endeavours.« less

Ice Cloud Formation and Dehydration in the Tropical Tropopause Layer

NASA Technical Reports Server (NTRS)

Jensen, Eric; Gore, Warren J. (Technical Monitor)

2002-01-01

Stratospheric water vapor is important not only for its greenhouse forcing, but also because it plays a significant role in stratospheric chemistry. Several recent studies have focused on the potential for dehydration due to ice cloud formation in air rising slowly through the tropical tropopause layer (TTL). Holton and Gettelman showed that temperature variations associated with horizontal transport of air in the TTL can drive ice cloud formation and dehydration, and Gettelman et al. recently examined the cloud formation and dehydration along kinematic trajectories using simple assumptions about the cloud properties. In this study, a Lagrangian, one-dimensional cloud model has been used to further investigate cloud formation and dehydration as air is transported horizontally and vertically through the TTL. Time-height curtains of temperature are extracted from meteorological analyses. The model tracks the growth, advection, and sedimentation of individual cloud particles. The regional distribution of clouds simulated in the model is comparable to the subvisible cirrus distribution indicated by SAGE II. The simulated cloud properties and cloud frequencies depend strongly on the assumed supersaturation threshold for ice nucleation. The clouds typically do not dehydrate the air along trajectories down to the temperature minimum saturation mixing ratio. Rather the water vapor mixing ratio crossing the tropopause along trajectories is 10-50% larger than the saturation mixing ratio. I will also discuss the impacts of Kelvin waves and gravity waves on cloud properties and dehydration efficiency. These simulations can be used to determine whether observed lower stratospheric water vapor mixing ratios can be explained by dehydration associated with in situ TTL cloud formation alone.

The vertical structure of convectively-driven cloud microphysics and its dependency on atmospheric conditions: An investigation through observations and modeling

NASA Astrophysics Data System (ADS)

van Diedenhoven, B.; Fridlind, A. M.; Sinclair, K.; Ackerman, A. S.

2016-12-01

It is generally observed that ice crystal sizes decrease as a function of altitude within clouds. This dependency is often explained as resulting from size sorting owing to the greater fall speeds of larger particles, but may also be related to dependence of ice diffusional growth on available water vapor and temperature, or other factors. Furthermore, the vertical variation of ice sizes is expected to be affected by the glaciation temperature of convectively-driven clouds. Realistic modeling of ice formation, growth and sedimentation is crucial to reliably represent vertical structures of ice clouds and cloud evolution in general. In this presentation we use remote sensing observations of glaciation temperature and ice effective radius obtained with airborne instruments to explore how their vertical dependencies vary with atmospheric conditions, such as humidity and wind profiles. Our focus will be on convectively-driven clouds. Subsequently, we test the ability of a quasi-idealized cloud permitting model to reproduce these dependencies of ice formation and size to atmospheric conditions, applying various ice growth and multiplication assumptions. The goal of this study is to identify variables that determine the vertical structure of cold clouds that can be used to evaluate model simulations.

Overview: Precipitation characteristics and sensitivities to environmental conditions during GoAmazon2014/5 and ACRIDICON-CHUVA

NASA Astrophysics Data System (ADS)

Machado, Luiz A. T.; Calheiros, Alan J. P.; Biscaro, Thiago; Giangrande, Scott; Silva Dias, Maria A. F.; Cecchini, Micael A.; Albrecht, Rachel; Andreae, Meinrat O.; Araujo, Wagner F.; Artaxo, Paulo; Borrmann, Stephan; Braga, Ramon; Burleyson, Casey; Eichholz, Cristiano W.; Fan, Jiwen; Feng, Zhe; Fisch, Gilberto F.; Jensen, Michael P.; Martin, Scot T.; Pöschl, Ulrich; Pöhlker, Christopher; Pöhlker, Mira L.; Ribaud, Jean-François; Rosenfeld, Daniel; Saraiva, Jaci M. B.; Schumacher, Courtney; Thalman, Ryan; Walter, David; Wendisch, Manfred

2018-05-01

This study provides an overview of precipitation processes and their sensitivities to environmental conditions in the Central Amazon Basin near Manaus during the GoAmazon2014/5 and ACRIDICON-CHUVA experiments. This study takes advantage of the numerous measurement platforms and instrument systems operating during both campaigns to sample cloud structure and environmental conditions during 2014 and 2015; the rainfall variability among seasons, aerosol loading, land surface type, and topography has been carefully characterized using these data. Differences between the wet and dry seasons were examined from a variety of perspectives. The rainfall rates distribution, total amount of rainfall, and raindrop size distribution (the mass-weighted mean diameter) were quantified over both seasons. The dry season generally exhibited higher rainfall rates than the wet season and included more intense rainfall periods. However, the cumulative rainfall during the wet season was 4 times greater than that during the total dry season rainfall, as shown in the total rainfall accumulation data. The typical size and life cycle of Amazon cloud clusters (observed by satellite) and rain cells (observed by radar) were examined, as were differences in these systems between the seasons. Moreover, monthly mean thermodynamic and dynamic variables were analysed using radiosondes to elucidate the differences in rainfall characteristics during the wet and dry seasons. The sensitivity of rainfall to atmospheric aerosol loading was discussed with regard to mass-weighted mean diameter and rain rate. This topic was evaluated only during the wet season due to the insignificant statistics of rainfall events for different aerosol loading ranges and the low frequency of precipitation events during the dry season. The impacts of aerosols on cloud droplet diameter varied based on droplet size. For the wet season, we observed no dependence between land surface type and rain rate. However, during the dry season, urban areas exhibited the largest rainfall rate tail distribution, and deforested regions exhibited the lowest mean rainfall rate. Airplane measurements were taken to characterize and contrast cloud microphysical properties and processes over forested and deforested regions. Vertical motion was not correlated with cloud droplet sizes, but cloud droplet concentration correlated linearly with vertical motion. Clouds over forested areas contained larger droplets than clouds over pastures at all altitudes. Finally, the connections between topography and rain rate were evaluated, with higher rainfall rates identified at higher elevations during the dry season.

Production of NOx by Lightning and its Effects on Atmospheric Chemistry

NASA Technical Reports Server (NTRS)

Pickering, Kenneth E.

2009-01-01

Production of NO(x) by lightning remains the NO(x) source with the greatest uncertainty. Current estimates of the global source strength range over a factor of four (from 2 to 8 TgN/year). Ongoing efforts to reduce this uncertainty through field programs, cloud-resolved modeling, global modeling, and satellite data analysis will be described in this seminar. Representation of the lightning source in global or regional chemical transport models requires three types of information: the distribution of lightning flashes as a function of time and space, the production of NO(x) per flash, and the effective vertical distribution of the lightning-injected NO(x). Methods of specifying these items in a model will be discussed. For example, the current method of specifying flash rates in NASA's Global Modeling Initiative (GMI) chemical transport model will be discussed, as well as work underway in developing algorithms for use in the regional models CMAQ and WRF-Chem. A number of methods have been employed to estimate either production per lightning flash or the production per unit flash length. Such estimates derived from cloud-resolved chemistry simulations and from satellite NO2 retrievals will be presented as well as the methodologies employed. Cloud-resolved model output has also been used in developing vertical profiles of lightning NO(x) for use in global models. Effects of lightning NO(x) on O3 and HO(x) distributions will be illustrated regionally and globally.

PRECP: the Department of Energy's program on the nonlinearity of acid precipitation processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanner, R.L.; Tichler, J.; Brown, R.

During the period of 1 April to 3 May 1985, staff from Argonne National Laboratory (ANL), Brookhaven National Laboratory (BNL), and Pacific Northwest Laboratory (PNL), participated in a multifaceted, coordinated set of field studies from an aircraft logistical base in Columbus, OH, and a surface precipitation and air chemistry network in the Philadelphia area. The general goals of these activities, conducted within the DOE-sponsored PRocessing of Emissions by Clouds and Precipitation (PRECP) program were to obtain information concerning scavenging ratios and the vertical distribution of cloud and precipitation chemistry for sulfur and nitrogen oxides and oxyacids, and for oxidant speciesmore » in the vicinity of precipitating and nonprecipitating clouds. Profiling of pollutant concentrations and phase distributions, and studies of scavenging processes were accomplished principally by airborne measurements of aerosol and gaseous species in pre-cloud and below-cloud air and of aqueous-phase species in clouds and precipitation, accompanied by documentation of meteorological and cloud physics parameters in the sampled regimes. Studies in the Midwest utilized only limited surface precipitation collection and chemical measurements, whereas a more extensive ground precipitation network was deployed in the Philadelphia area studies together with surface air chemistry measurements at a single nonurban site.« less

The Sensitivity of Numerical Simulations of Cloud-Topped Boundary Layers to Cross-Grid Flow

NASA Astrophysics Data System (ADS)

Wyant, Matthew C.; Bretherton, Christopher S.; Blossey, Peter N.

2018-02-01

In mesoscale and global atmospheric simulations with large horizontal domains, strong horizontal flow across the grid is often unavoidable, but its effects on cloud-topped boundary layers have received comparatively little study. Here the effects of cross-grid flow on large-eddy simulations of stratocumulus and trade-cumulus marine boundary layers are studied across a range of grid resolutions (horizontal × vertical) between 500 m × 20 m and 35 m × 5 m. Three cases are simulated: DYCOMS nocturnal stratocumulus, BOMEX trade cumulus, and a GCSS stratocumulus-to-trade cumulus case. Simulations are performed with a stationary grid (with 4-8 m s-1 horizontal winds blowing through the cyclic domain) and a moving grid (equivalent to subtracting off a fixed vertically uniform horizontal wind) approximately matching the mean boundary-layer wind speed. For stratocumulus clouds, cross-grid flow produces two primary effects on stratocumulus clouds: a filtering of fine-scale resolved turbulent eddies, which reduces stratocumulus cloud-top entrainment, and a vertical broadening of the stratocumulus-top inversion which enhances cloud-top entrainment. With a coarse (20 m) vertical grid, the former effect dominates and leads to strong increases in cloud cover and LWP, especially as horizontal resolution is coarsened. With a finer (5 m) vertical grid, the latter effect is stronger and leads to small reductions in cloud cover and LWP. For the BOMEX trade cumulus case, cross-grid flow tends to produce fewer and larger clouds with higher LWP, especially for coarser vertical grid spacing. The results presented are robust to choice of scalar advection scheme and Courant number.

LIVAS: a 3-D multi-wavelength aerosol/cloud database based on CALIPSO and EARLINET

NASA Astrophysics Data System (ADS)

Amiridis, V.; Marinou, E.; Tsekeri, A.; Wandinger, U.; Schwarz, A.; Giannakaki, E.; Mamouri, R.; Kokkalis, P.; Binietoglou, I.; Solomos, S.; Herekakis, T.; Kazadzis, S.; Gerasopoulos, E.; Proestakis, E.; Kottas, M.; Balis, D.; Papayannis, A.; Kontoes, C.; Kourtidis, K.; Papagiannopoulos, N.; Mona, L.; Pappalardo, G.; Le Rille, O.; Ansmann, A.

2015-07-01

We present LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies), a 3-D multi-wavelength global aerosol and cloud optical database, optimized to be used for future space-based lidar end-to-end simulations of realistic atmospheric scenarios as well as retrieval algorithm testing activities. The LIVAS database provides averaged profiles of aerosol optical properties for the potential spaceborne laser operating wavelengths of 355, 532, 1064, 1570 and 2050 nm and of cloud optical properties at the wavelength of 532 nm. The global database is based on CALIPSO observations at 532 and 1064 nm and on aerosol-type-dependent backscatter- and extinction-related Ångström exponents, derived from EARLINET (European Aerosol Research Lidar Network) ground-based measurements for the UV and scattering calculations for the IR wavelengths, using a combination of input data from AERONET, suitable aerosol models and recent literature. The required spectral conversions are calculated for each of the CALIPSO aerosol types and are applied to CALIPSO backscatter and extinction data corresponding to the aerosol type retrieved by the CALIPSO aerosol classification scheme. A cloud optical database based on CALIPSO measurements at 532 nm is also provided, neglecting wavelength conversion due to approximately neutral scattering behavior of clouds along the spectral range of LIVAS. Averages of particle linear depolarization ratio profiles at 532 nm are provided as well. Finally, vertical distributions for a set of selected scenes of specific atmospheric phenomena (e.g., dust outbreaks, volcanic eruptions, wild fires, polar stratospheric clouds) are analyzed and spectrally converted so as to be used as case studies for spaceborne lidar performance assessments. The final global data set includes 4-year (1 January 2008-31 December 2011) time-averaged CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) data on a uniform grid of 1° × 1° with the original high vertical resolution of CALIPSO in order to ensure realistic simulations of the atmospheric variability in lidar end-to-end simulations.

Estimates of the aerosol indirect effect over the Baltic Sea region derived from 12 years of MODIS observations

NASA Astrophysics Data System (ADS)

Saponaro, Giulia; Kolmonen, Pekka; Sogacheva, Larisa; Rodriguez, Edith; Virtanen, Timo; de Leeuw, Gerrit

2017-02-01

Retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) on-board the Aqua satellite, 12 years (2003-2014) of aerosol and cloud properties were used to statistically quantify aerosol-cloud interaction (ACI) over the Baltic Sea region, including the relatively clean Fennoscandia and the more polluted central-eastern Europe. These areas allowed us to study the effects of different aerosol types and concentrations on macro- and microphysical properties of clouds: cloud effective radius (CER), cloud fraction (CF), cloud optical thickness (COT), cloud liquid water path (LWP) and cloud-top height (CTH). Aerosol properties used are aerosol optical depth (AOD), Ångström exponent (AE) and aerosol index (AI). The study was limited to low-level water clouds in the summer. The vertical distributions of the relationships between cloud properties and aerosols show an effect of aerosols on low-level water clouds. CF, COT, LWP and CTH tend to increase with aerosol loading, indicating changes in the cloud structure, while the effective radius of cloud droplets decreases. The ACI is larger at relatively low cloud-top levels, between 900 and 700 hPa. Most of the studied cloud variables were unaffected by the lower-tropospheric stability (LTS), except for the cloud fraction. The spatial distribution of aerosol and cloud parameters and ACI, here defined as the change in CER as a function of aerosol concentration for a fixed LWP, shows positive and statistically significant ACI over the Baltic Sea and Fennoscandia, with the former having the largest values. Small negative ACI values are observed in central-eastern Europe, suggesting that large aerosol concentrations saturate the ACI.

Multistatic aerosol-cloud lidar in space: A theoretical perspective

NASA Astrophysics Data System (ADS)

Mishchenko, M. I.; Alexandrov, M. D.; Brian, C.; Travis, L. D.

2016-12-01

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

Multistatic Aerosol Cloud Lidar in Space: A Theoretical Perspective

NASA Technical Reports Server (NTRS)

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

2016-01-01

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

Temporal Analysis and Automatic Calibration of the Velodyne HDL-32E LiDAR System

NASA Astrophysics Data System (ADS)

Chan, T. O.; Lichti, D. D.; Belton, D.

2013-10-01

At the end of the first quarter of 2012, more than 600 Velodyne LiDAR systems had been sold worldwide for various robotic and high-accuracy survey applications. The ultra-compact Velodyne HDL-32E LiDAR has become a predominant sensor for many applications that require lower sensor size/weight and cost. For high accuracy applications, cost-effective calibration methods with minimal manual intervention are always desired by users. However, the calibrations are complicated by the Velodyne LiDAR's narrow vertical field of view and the very highly time-variant nature of its measurements. In the paper, the temporal stability of the HDL-32E is first analysed as the motivation for developing a new, automated calibration method. This is followed by a detailed description of the calibration method that is driven by a novel segmentation method for extracting vertical cylindrical features from the Velodyne point clouds. The proposed segmentation method utilizes the Velodyne point cloud's slice-like nature and first decomposes the point clouds into 2D layers. Then the layers are treated as 2D images and are processed with the Generalized Hough Transform which extracts the points distributed in circular patterns from the point cloud layers. Subsequently, the vertical cylindrical features can be readily extracted from the whole point clouds based on the previously extracted points. The points are passed to the calibration that estimates the cylinder parameters and the LiDAR's additional parameters simultaneously by constraining the segmented points to fit to the cylindrical geometric model in such a way the weighted sum of the adjustment residuals are minimized. The proposed calibration is highly automatic and this allows end users to obtain the time-variant additional parameters instantly and frequently whenever there are vertical cylindrical features presenting in scenes. The methods were verified with two different real datasets, and the results suggest that up to 78.43% accuracy improvement for the HDL-32E can be achieved using the proposed calibration method.

Azores 2017 Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wehner, Birgit; Chevallier, Karine; Weinhold, Kay

Aerosol particles play an important role for the regional and global climate. Therefore, a network of measurement sites has been established worldwide, but only a small fraction of them is capturing the marine boundary layer (MBL) while approximately 70% of the Earth’s surface is covered with water. The main focus of this project is to improve the knowledge of sources and exchange processes of aerosol particles in general (German Research Foundation [DFG] project WE 2757/2-1) and of cloud condensation nuclei in particular (DFG project HE 6770/2-1) in the MBL in the northeastern Atlantic Ocean where the influence of local anthropogenicmore » sources is negligible. The main hypothesis of the project is that long-range transport of aerosols from North America as well as new particle formation in the free troposphere (FT) and at cloud edges followed by vertical transport contribute significantly to the aerosol budget in the MBL. The knowledge of sources and sinks of aerosol particles in combination with vertical exchange between FT and MBL is a prerequisite to predict aerosol particle number concentrations in the lowest regions of the MBL and its influence on the formation of clouds. These processes are not sufficiently quantified over the ocean up to now. To verify the hypothesis stated above, vertical exchange processes and particle sources over the Azores will be quantified using data of 17 measurement flights with high spatial resolution using a helicopter-borne platform developed at the Leibniz Institute for Tropospheric Research (TROPOS). Here, aerosol particle number concentration and vertical wind speed have been measured with a temporal resolution allowing the direct estimate of the vertical turbulent flux of aerosol particles in different heights for the first time. In addition, aerosol particle number size distributions, number concentrations of cloud condensation nuclei (CCN), cloud droplet number concentration (CDNC), and particle absorption at three different wavelengths have been determined. The data analysis is ongoing and final results are not available yet. The detailed analysis of these data will be used to conclude sources and origin of the investigated aerosol particles.« less

The Role of Aerosols on Precipitation Processes: Cloud Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Matsui, T.

2012-01-01

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, a detailed spectral-bin microphysical scheme was implemented into the Goddard Cumulus Ensemble (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. The model is tested by studying the evolution of deep cloud systems in the west Pacific warm pool region, the sub-tropics (Florida) and midlatitudes using identical thermodynamic conditions but with different concentrations of CCN: a low "clean" concentration and a high "dirty" concentration. Results indicate that the low CCN concentration case produces rainfall at the surface sooner than the high CeN case but has less cloud water mass aloft. Because the spectral-bin model explicitly calculates and allows for the examination of both the mass and number concentration of species in each size category, a detailed analysis of the instantaneous size spectrum can be obtained for these cases. It is shown that since the low (CN case produces fewer droplets, larger sizes develop due to greater condensational and collection growth, leading to a broader size spectrum in comparison to the high CCN case. Sensitivity tests were performed to identify the impact of ice processes, radiation and large-scale influence on cloud-aerosol interactive processes, especially regarding surface rainfall amounts and characteristics (i.e., heavy or convective versus light or stratiform types). In addition, an inert tracer was included to follow the vertical redistribution of aerosols by cloud processes. We will also give a brief review from observational evidence on the role of aerosol on precipitation processes.

A Multi-Model Analysis of the Cloud Phase Transition in 16 GCMs Using Satellite Observations (CALIPSO/GPCP) and Reanalysis Data (ECMWF/MERRA).

NASA Astrophysics Data System (ADS)

Cesana, G.; Waliser, D. E.; Jiang, X.; Li, J. L. F.

2014-12-01

The ubiquitous presence of clouds within the troposphere contributes to modulate the radiative balance of the earth-atmosphere system. Depending on their cloud phase, clouds may have different microphysical and macrophysical properties, and hence, different radiative effects. In this study, we took advantage of climate runs from the GASS-YoTC and AMIP multi-model experiments to document the differences associated to the cloud phase parameterizations of 16 GCMs. A particular emphasize has been put on the vertical structure of the transition between liquid and ice in clouds. A way to intercompare the models regardless of their cloud fraction is to study the ratio of the ice mass to the total mass of the condensed water. To address the challenge of evaluating the modeled cloud phase, we profited from the cloud phase climatology so called CALIPSO-GOCCP, which separates liquid clouds from ice clouds at global scale, with a high vertical resolution (480m), above all surfaces. We also used reanalysis data and GPCP satellite observations to investigate the influence of the temperature, the relative humidity, the vertical wind speed and the precipitations on the cloud phase transition. In 12 (of 16) models, there are too few super cooled liquid in clouds compared to observations, mostly in the high troposphere. We exhibited evidences of the link between the cloud phase transition and the humidity, the vertical wind speed as well as the precipitations. Some cloud phase schemes are more affected by the humidity and the vertical velocity and some other by the precipitations. Although a few models can reproduce the observe relation between cloud phase and temperature, humidity, vertical velocity or precipitations, none of them perform well for all the parameters. An important result of this study is that the T-dependent phase parameterizations do not allow simulating the complexity of the observed cloud phase transition. Unfortunately, more complex microphysics schemes do not succeed to reproduce all the processes neither. Finally, thanks to the combined use of CALIPSO-GOCCP and ECMWF water vapor pressure, we showed an updated version of the Clausius-Clapeyron water vapor phase diagram. This diagram represents a new tool to improve the simulation of the cloud phase transition in climate models.

Overview of the CERES Edition-4 Multilayer Cloud Property Datasets

NASA Astrophysics Data System (ADS)

Chang, F. L.; Minnis, P.; Sun-Mack, S.; Chen, Y.; Smith, R. A.; Brown, R. R.

2014-12-01

Knowledge of the cloud vertical distribution is important for understanding the role of clouds on earth's radiation budget and climate change. Since high-level cirrus clouds with low emission temperatures and small optical depths can provide a positive feedback to a climate system and low-level stratus clouds with high emission temperatures and large optical depths can provide a negative feedback effect, the retrieval of multilayer cloud properties using satellite observations, like Terra and Aqua MODIS, is critically important for a variety of cloud and climate applications. For the objective of the Clouds and the Earth's Radiant Energy System (CERES), new algorithms have been developed using Terra and Aqua MODIS data to allow separate retrievals of cirrus and stratus cloud properties when the two dominant cloud types are simultaneously present in a multilayer system. In this paper, we will present an overview of the new CERES Edition-4 multilayer cloud property datasets derived from Terra as well as Aqua. Assessment of the new CERES multilayer cloud datasets will include high-level cirrus and low-level stratus cloud heights, pressures, and temperatures as well as their optical depths, emissivities, and microphysical properties.

Cloud draft structure and trace gas transport

NASA Technical Reports Server (NTRS)

Scala, John R.; Tao, Wei-Kuo; Thompson, Anne M.; Simpson, Joanne; Garstang, Michael; Pickering, Kenneth E.; Browell, Edward V.; Sachse, Glen W.; Gregory, Gerald L.; Torres, Arnold L.

1990-01-01

During the second Amazon Boundary Layer Experiment (ABLE 2B), meteorological observations, chemical measurements, and model simulations are utilized in order to interpret convective cloud draft structure and to analyze its role in transport and vertical distribution of trace gases. One-dimensional photochemical model results suggest that the observed poststorm changes in ozone concentration can be attributed to convective transports rather than photochemical production and the results of a two-dimensional time-dependent cloud model simulation are presented for the May 6, 1987 squall system. The mesoscale convective system exhibited evidence of significant midlevel detrainment in addition to transports to anvil heights. Chemical measurements of O3 and CO obtained in the convective environment are used to predict photochemical production within the troposphere and to corroborate the cloud model results.

A Convective Vorticity Vector Associated With Tropical Convection: A 2D Cloud-Resolving Modeling Study

NASA Technical Reports Server (NTRS)

Gao, Shou-Ting; Ping, Fan; Li, Xiao-Fan; Tao, Wei-Kuo

2004-01-01

Although dry/moist potential vorticity is a useful physical quantity for meteorological analysis, it cannot be applied to the analysis of 2D simulations. A convective vorticity vector (CVV) is introduced in this study to analyze 2D cloud-resolving simulation data associated with 2D tropical convection. The cloud model is forced by the vertical velocity, zonal wind, horizontal advection, and sea surface temperature obtained from the TOGA COARE, and is integrated for a selected 10-day period. The CVV has zonal and vertical components in the 2D x-z frame. Analysis of zonally-averaged and mass-integrated quantities shows that the correlation coefficient between the vertical component of the CVV and the sum of the cloud hydrometeor mixing ratios is 0.81, whereas the correlation coefficient between the zonal component and the sum of the mixing ratios is only 0.18. This indicates that the vertical component of the CVV is closely associated with tropical convection. The tendency equation for the vertical component of the CVV is derived and the zonally-averaged and mass-integrated tendency budgets are analyzed. The tendency of the vertical component of the CVV is determined by the interaction between the vorticity and the zonal gradient of cloud heating. The results demonstrate that the vertical component of the CVV is a cloud-linked parameter and can be used to study tropical convection.

Radiative characteristics of Clouds embedded in and occurring beneath Smoke analyzed using airborne multiangular measurements

NASA Astrophysics Data System (ADS)

Gautam, R.; Gatebe, C. K.; Varnai, T.; Singh, M.; Poudyal, R.

2016-12-01

Clouds in the presence of absorbing aerosols results in their apparent darkening, observed at the Top of Atmosphere (TOA), which is associated with the radiative effects of aerosol absorption. Owing to the warming/darkening effect and potential impacts on regional climate via semidirect and thermodynamic pathways, above-cloud aerosols have been characterized in recent satellite-based studies. While satellite data are particularly useful in showing the radiative impact of above-cloud aerosols at the TOA, retrievals of aerosol and cloud properties are affected by large uncertainties when they co-occur. In this study, we present radiative characteristics of clouds in the presence of wildfire smoke using airborne data primarily from NASA's Cloud Absorption Radiometer (CAR), collected during the ARCTAS and SAFARI campaigns in Canada and southern Africa, respectively. Scattered cumulus clouds embedded in dense smoke over land (Canada) as well as smoke aerosols above marine stratocumulus clouds (southeast Atlantic) show characteristic spectral gradient across the UV-visible-NIR spectrum using CAR data. In general, clouds in the presence of smoke are impacted by absorbing aerosol-induced darkening at the shorter wavelengths (e.g. UV and blue bands), as opposed to an (expected) negative gradient for cloud-free smoke and a flat spectrum for smoke-free cloud cover. The circular and spiral flights not only allowed the complete characterization of the angular distribution of smoke-cloud radiative interactions, but also provided the vertical distribution of smoke and clouds. Overall, the observational-based smoke-cloud radiative interactions were found to be physically consistent with theoretical 1D and 3D radiation calculations. These airborne observations are also complemented by satellite data from MODIS reflectances and CERES shortwave fluxes, providing a synergistic radiative impact assessment of clouds in the presence of smoke. http://car.gsfc.nasa.gov/

Design and Performance of McRas in SCMs and GEOS I/II GCMs

NASA Technical Reports Server (NTRS)

Sud, Yogesh C.; Einaudi, Franco (Technical Monitor)

2000-01-01

The design of a prognostic cloud scheme named McRAS (Microphysics of clouds with Relaxed Arakawa-Schubert Scheme) for general circulation models (GCMs) will be discussed. McRAS distinguishes three types of clouds: (1) convective, (2) stratiform, and (3) boundary-layer types. The convective clouds transform and merge into stratiform clouds on an hourly time-scale, while the boundary-layer clouds merge into the stratiform clouds instantly. The cloud condensate converts into precipitation following the auto-conversion equations 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, as well as diffuse both horizontally and vertically with a fully interactive cloud-microphysics throughout the life-cycle of the cloud, 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 and 5-ARN CART datasets has shown that together with the rest of the model physics, McRAS can simulate the observed temperature, humidity, and precipitation without many systematic errors. The time history and time mean incloud water and ice distribution, fractional cloudiness, cloud optical thickness, origin of precipitation in the convective anvil and towers, and the convective updraft and downdraft velocities and mass fluxes all show a realistic behavior. Performance of McRAS in GEOS 11 GCM shows several satisfactory features but some of the remaining deficiencies suggest need for additional research involving convective triggers and inhibitors, provision for continuously detraining updraft, a realistic scheme for cumulus gravity wave drag, and refinements to physical conditions for ascertaining cloud detrainment level.

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

NASA Astrophysics Data System (ADS)

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

2013-12-01

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

Parameterization of cloud glaciation by atmospheric dust

NASA Astrophysics Data System (ADS)

Nickovic, Slobodan; Cvetkovic, Bojan; Madonna, Fabio; Pejanovic, Goran; Petkovic, Slavko

2016-04-01

The exponential growth of research interest on ice nucleation (IN) is motivated, inter alias, by needs to improve generally unsatisfactory representation of cold cloud formation in atmospheric models, and therefore to increase the accuracy of weather and climate predictions, including better forecasting of precipitation. Research shows that mineral dust significantly contributes to cloud ice nucleation. Samples of residual particles in cloud ice crystals collected by aircraft measurements performed in the upper tropopause of regions distant from desert sources indicate that dust particles dominate over other known ice nuclei such as soot and biological particles. In the nucleation process, dust chemical aging had minor effects. The observational evidence on IN processes has substantially improved over the last decade and clearly shows that there is a significant correlation between IN concentrations and the concentrations of coarser aerosol at a given temperature and moisture. Most recently, due to recognition of the dominant role of dust as ice nuclei, parameterizations for immersion and deposition icing specifically due to dust have been developed. Based on these achievements, we have developed a real-time forecasting coupled atmosphere-dust modelling system capable to operationally predict occurrence of cold clouds generated by dust. We have been thoroughly validated model simulations against available remote sensing observations. We have used the CNR-IMAA Potenza lidar and cloud radar observations to explore the model capability to represent vertical features of the cloud and aerosol vertical profiles. We also utilized the MSG-SEVIRI and MODIS satellite data to examine the accuracy of the simulated horizontal distribution of cold clouds. Based on the obtained encouraging verification scores, operational experimental prediction of ice clouds nucleated by dust has been introduced in the Serbian Hydrometeorological Service as a public available product.

Vertical distribution of microphysical properties of Arctic springtime low-level mixed-phase clouds over the Greenland and Norwegian seas

NASA Astrophysics Data System (ADS)

Mioche, Guillaume; Jourdan, Olivier; Delanoë, Julien; Gourbeyre, Christophe; Febvre, Guy; Dupuy, Régis; Monier, Marie; Szczap, Frédéric; Schwarzenboeck, Alfons; Gayet, Jean-François

2017-10-01

This study aims to characterize the microphysical and optical properties of ice crystals and supercooled liquid droplets within low-level Arctic mixed-phase clouds (MPCs). We compiled and analyzed cloud in situ measurements from four airborne spring campaigns (representing 18 flights and 71 vertical profiles in MPCs) over the Greenland and Norwegian seas mainly in the vicinity of the Svalbard archipelago. Cloud phase discrimination and representative vertical profiles of the number, size, mass and shape of ice crystals and liquid droplets are established. The results show that the liquid phase dominates the upper part of the MPCs. High concentrations (120 cm-3 on average) of small droplets (mean values of 15 µm), with an averaged liquid water content (LWC) of 0.2 g m-3 are measured at cloud top. The ice phase dominates the microphysical properties in the lower part of the cloud and beneath it in the precipitation region (mean values of 100 µm, 3 L-1 and 0.025 g m-3 for diameter, particle concentration and ice water content (IWC), respectively). The analysis of the ice crystal morphology shows that the majority of ice particles are irregularly shaped or rimed particles; the prevailing regular habits found are stellars and plates. We hypothesize that riming and diffusional growth processes, including the Wegener-Bergeron-Findeisen (WBF) mechanism, are the main growth mechanisms involved in the observed MPCs. The impact of larger-scale meteorological conditions on the vertical profiles of MPC properties was also investigated. Large values of LWC and high concentration of smaller droplets are possibly linked to polluted situations and air mass origins from the south, which can lead to very low values of ice crystal size and IWC. On the contrary, clean situations with low temperatures exhibit larger values of ice crystal size and IWC. Several parameterizations relevant for remote sensing or modeling studies are also determined, such as IWC (and LWC) - extinction relationship, ice and liquid integrated water paths, ice concentration and liquid water fraction according to temperature.

Simulation of Asia Dust and Cloud Interaction Over Pacific Ocean During Pacdex

NASA Astrophysics Data System (ADS)

Long, X.; Huang, J.; Cheng, C.; Wang, W.

2007-12-01

The effect of dust plume on the Pacific cloud systems and the associated radiative forcing is an outstanding problem for understanding climate change. Many studies showing that dust aerosol might be a good absorber for solar radiation, at the same time dust aerosols could affect the cloud's formation and precipitation by its capability as cloud condensation nuclei (CCN) and ice forming nuclei (IFN). But the role of aerosols in clouds and precipitation is very complex. Simulation of interaction between cloud and dust aerosols requires recognition that the aerosol cloud system comprises coupled components of dynamics, aerosol and cloud microphysics, radiation processes. In this study, we investigated the interaction between dust aerosols and cloud with WRF which coupled with detailed cloud microphysics processes and dust process. The observed data of SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) and PACDEX (Pacific Dust Experiment) is used as the initialization which include the vertical distributions and concentration of dust particles. Our results show that dust aerosol not only impacts cloud microphysical processes but also cloud microstructure; Dust aerosols can act as effective ice nuclei and intensify the ice-forming processes.

The Geoscience Laser Altimeter System (GLAS) for the ICESAT Mission

NASA Technical Reports Server (NTRS)

Abshire, James B.; Sun, Xia-Li; Ketchum, Eleanor A.; Afzal, Robert S.; Millar, Pamela S.; Smith, David E. (Technical Monitor)

2000-01-01

The Laser In space Technology Experiment, Shuttle Laser Altimeter and the Mars Observer Laser Altimeter have demonstrated accurate measurements of atmospheric backscatter and Surface heights from space. The recent MOLA measurements of the Mars surface have 40 cm vertical resolution and have reduced the global uncertainty in Mars topography from a few km to about 5 m. The Geoscience Laser Altimeter System (GLAS) is a next generation lidar for Earth orbit being developed as part of NASA's Icesat Mission. The GLAS design combines a 10 cm precision surface lidar with a sensitive dual wavelength cloud and aerosol lidar. GLAS will precisely measure the heights of the Earth's polar ice sheets, establish a grid of accurate height profiles of the Earth's land topography, and profile the vertical backscatter of clouds and aerosols on a global scale. GLAS is being developed to fly on a small dedicated spacecraft in a polar orbit with a 590 630 km altitude at inclination of 94 degrees. GLAS is scheduled to launch in the summer 2001 and to operate continuously for a minimum of 3 years with a goal of 5 years. The primary mission for GLAS is to measure the seasonal and annual changes in the heights of the Greenland and Antarctic ice sheets. GLAS will continuously measure the vertical distance from orbit to the Earth's surface with 1064 nm pulses from a ND:YAG laser at a 40 Hz rate. Each 5 nsec wide laser pulse is used to produce a single range measurement, and the laser spots have 66 m diameter and about 170 m center-center spacings. When over land GLAS will profile the heights of the topography and vegetation. The GLAS receiver uses a 1 m diameter telescope and a Si APD detector. The detector signal is sampled by an all digital receiver which records each surface echo waveform with I nsec resolution and a stored echo record lengths of either 200, 400, or 600 samples. Analysis of the echo waveforms within the instrument permits discrimination between cloud and surface echoes. Ground based echo analysis permits precise ranging, determining the roughness or slopes of the surface as well as the vertical distributions of vegetation illuminated by the laser. Accurate knowledge of the laser beam's pointing angle is needed to prevent height biases when over sloped surfaces. For surfaces with 2 deg. slopes, knowledge of pointing angle of the beam's centroid to about 8 urad is needed to achieve 10 cm height accuracy. GLAS uses a stellar reference system (SRS) to determine the pointing angle of each laser firing relative to inertial space. The SRS uses a high precision star camera oriented toward local zenith and a gyroscope to determine the inertial orientation of the SRS optical bench. The far field pattern of each laser is measured pulse relative to the star camera with a laser reference system (LRS). Optically measuring each laser far field pattern relative to the orientation of the star camera and gyroscope permits the precise pointing angle of each laser pulse to be determined. GLAS will also determine the vertical distributions of clouds and aerosols by measuring the vertical profile of laser energy backscattered by the atmosphere at both 1064 and 532 nm. The 1064 nm measurements use the Si APD detector and profile the height and vertical structure of thicker clouds. The measurements at 532 nm use new highly sensitive photon counting, detectors, and measure the height distributions of very thin Clouds and aerosol layers. With averaging these can be used to determine the height of the planetary boundary layer. The instrument design and expected performance will be discussed.

First UAV Measurements of Entrainment Layer Fluxes with Coupled Cloud Property Measurements

NASA Astrophysics Data System (ADS)

Thomas, R. M.; Praveen, P. S.; Wilcox, E. M.; Pistone, K.; Bender, F.; Ramanathan, V.

2012-12-01

This study details entrainment flux measurements made from a lightweight unmanned aerial vehicle (UAV) containing turbulent water vapor flux instrumentation (Thomas et al., 2012). The system was flown for 26 flights during the Cloud, Aerosol, Radiative forcing, Dynamics EXperiment (CARDEX) in the Maldives in March 2012 to study interrelationships between entrainment, aerosols, water budget, cloud microphysics and radiative fluxes in a trade wind cumulus cloud regime. A major advantage of using this lightweight, precision autopiloted UAV system with scientific telemetry is the ability to target small-scale features in the boundary layer, such as an entrainment layer, with minimal aircraft induced disruption. Results are presented from two UAVs flown in stacked formation: one UAV situated in-cloud measuring cloud-droplet size distribution spectra and liquid water content, and another co-located 100m above measuring turbulent properties and entrainment latent heat flux (λEE). We also show latent heat flux and turbulence measurements routinely made at the entrainment layer base and altitudes from the surface up to 4kft. Ratios of λEE to corresponding surface tower values (λES) display a bimodal frequency distribution with ranges 0.22-0.53 and 0.79-1.5, with occasional events >7. Reasons for this distribution are discussed drawing upon boundary layer and free tropospheric dynamics and meteorology, turbulence length scales, surface conditions, and cloud interactions. Latent heat flux profiles are combined with in-cloud UAV Liquid Water Content (LWC) data and surface based Liquid Water Path (LWP) and Precipitable Water Vapor (PWV) measurements to produce observationally constrained vertical water budgets, providing insights into diurnal coupling of λEE and λES. Observed λEE, λES, water budgets, and cloud microphysical responses to entrainment are then contextualized with respect to measured aerosol loading profiles and airmass history.

Features of clouds and convection during the pre- and post-onset periods of the Asian summer monsoon

NASA Astrophysics Data System (ADS)

Wang, Yi; Wang, Chenghai

2016-02-01

The statistical characteristics of the vertical structure of clouds in the Asian summer monsoon region are investigated using two CloudSat standard products (Geometrical Profiling Product (GEOPROF) and GEOPROF-lidar) during the pre- and post-onset periods of the Asian summer monsoon, from April to August in 2007-2010. The characteristics of the vertical structure of clouds are analyzed and compared for different underlying surfaces in four subregions during this period. Also analyzed are the evolution of precipitation and hydrometeors with the northward advance of the Asian summer monsoon, and different hydrometeor characteristics attributed to the underlying surface features. The results indicate that the vertical cloud amounts increase significantly after the summer monsoon onset; this increase occurs first in the upper troposphere and then at lower altitudes over tropical regions (South Asian and tropical Northwest Pacific regions). The heights of the cloud top ascend, and the vertical height between the top and the base of the whole cloud increases. Single-layer (SL) and double-layer (DL) hydrometeors contribute over half and one third of the cloudiness in these 5 months (April to August), respectively. The multilayer frequencies increase in four different regions, and cloud layer depths (CLD) increase after the summer monsoon onset. These changes are stronger in tropical regions than in subtropical regions, while the vertical distance between cloud layers (VDCL) deceases in tropical regions and increases in subtropical regions.

a Comparitive Study Using Geometric and Vertical Profile Features Derived from Airborne LIDAR for Classifying Tree Genera

NASA Astrophysics Data System (ADS)

Ko, C.; Sohn, G.; Remmel, T. K.

2012-07-01

We present a comparative study between two different approaches for tree genera classification using descriptors derived from tree geometry and those derived from the vertical profile analysis of LiDAR point data. The different methods provide two perspectives for processing LiDAR point clouds for tree genera identification. The geometric perspective analyzes individual tree crowns in relation to valuable information related to characteristics of clusters and line segments derived within crowns and overall tree shapes to highlight the spatial distribution of LiDAR points within the crown. Conversely, analyzing vertical profiles retrieves information about the point distributions with respect to height percentiles; this perspective emphasizes of the importance that point distributions at specific heights express, accommodating for the decreased point density with respect to depth of canopy penetration by LiDAR pulses. The targeted species include white birch, maple, oak, poplar, white pine and jack pine at a study site northeast of Sault Ste. Marie, Ontario, Canada.

Monitoring Cirrus Clouds Using Lamp Observations in Association with Balloon-Borne Radiosonde Over Nainital: Few Case Studies

NASA Astrophysics Data System (ADS)

Solanki, R.; Singh, N.

2012-12-01

Upper tropospheric clouds such as cirrus have been identified as one of the important regulator of the radiation balance of the earth atmospheric-system. Though the satellite observation provide valuable information on cirrus clouds, they have limitations on spectral, temporal and spatial coverage, hence the need for local remote sensing, such as LiDAR a leading technique for studying the characteristics and properties of cirrus clouds. The upgraded version of a micro pulse LiDAR popularly known as LiDAR for Atmospheric Measurements and Probing (LAMP) developed by National Atmospheric Research Laboratory (NARL) is operational since October 2011, at ARIES Nainital (29.4oN, 79.5oE, ~2 km above the mean sea level) a high altitude location in the central Himalayas. Regular observations are being carried out in order to study the vertical distribution of aerosols, clouds and boundary layer structure etc. Altitude profiles of range corrected photon count and derived aerosol back scatter coefficients have depicted the occurrence of high altitude cirrus clouds/ ice clouds in an altitude range of 7 to 11 Km. Among the total observations in 27% of the cases the occurrence of cirrus clouds were detected. The corresponding cloud parameters such as temperature (-59 0C), horizontal wind speed (26 m/s), vertical wind speed (24 m/s), Relative Humidity (61%), at a height (~9 Km) were measured with Radiosonde observations. The prevailing region for cirrus cloud is found to be highly turbulent, indicating the region of divergence followed by a convergence, showing the favorable conditions for cirrus cloud formation. Optical and geometrical characteristics of Cirrus clouds have been analyzed using LiDAR and radiosonde measurements. The temperature and thickness dependence of optical properties have also been studied. The results will be further substantiated with CALIPSO satellite and details will be discussed during the presentation.

W-band spaceborne radar observations of atmospheric river events

NASA Astrophysics Data System (ADS)

Matrosov, S. Y.

2010-12-01

While the main objective of the world first W-band radar aboard the CloudSat satellite is to provide vertically resolved information on clouds, it proved to be a valuable tool for observing precipitation. The CloudSat radar is generally able to resolve precipitating cloud systems in their vertical entirety. Although measurements from the liquid hydrometer layer containing rainfall are strongly attenuated, special retrieval approaches can be used to estimate rainfall parameters. These approaches are based on vertical gradients of observed radar reflectivity factor rather than on absolute estimates of reflectivity. Concurrent independent estimations of ice cloud parameters in the same vertical column allow characterization of precipitating systems and provide information on coupling between clouds and rainfall they produce. The potential of CloudSat for observations atmospheric river events affecting the West Coast of North America is evaluated. It is shown that spaceborne radar measurements can provide high resolution information on the height of the freezing level thus separating areas of rainfall and snowfall. CloudSat precipitation rate estimates complement information from the surface-based radars. Observations of atmospheric rivers at different locations above the ocean and during landfall help to understand evolutions of atmospheric rivers and their structures.

Role of Gravity Waves in Determining Cirrus Cloud Properties

NASA Technical Reports Server (NTRS)

OCStarr, David; Singleton, Tamara; Lin, Ruei-Fong

2008-01-01

Cirrus clouds are important in the Earth's radiation budget. They typically exhibit variable physical properties within a given cloud system and from system to system. Ambient vertical motion is a key factor in determining the cloud properties in most cases. The obvious exception is convectively generated cirrus (anvils), but even in this case, the subsequent cloud evolution is strongly influenced by the ambient vertical motion field. It is well know that gravity waves are ubiquitous in the atmosphere and occur over a wide range of scales and amplitudes. Moreover, researchers have found that inclusion of statistical account of gravity wave effects can markedly improve the realism of simulations of persisting large-scale cirrus cloud features. Here, we use a 1 -dimensional (z) cirrus cloud model, to systematically examine the effects of gravity waves on cirrus cloud properties. The model includes a detailed representation of cloud microphysical processes (bin microphysics and aerosols) and is run at relatively fine vertical resolution so as to adequately resolve nucleation events, and over an extended time span so as to incorporate the passage of multiple gravity waves. The prescribed gravity waves "propagate" at 15 m s (sup -1), with wavelengths from 5 to 100 km, amplitudes range up to 1 m s (sup -1)'. Despite the fact that the net gravity wave vertical motion forcing is zero, it will be shown that the bulk cloud properties, e.g., vertically-integrated ice water path, can differ quite significantly from simulations without gravity waves and that the effects do depend on the wave characteristics. We conclude that account of gravity wave effects is important if large-scale models are to generate realistic cirrus cloud property climatology (statistics).

Towards a Three-Dimensional Near-Real Time Cloud Product for Aviation Safety and Weather Diagnoses

NASA Technical Reports Server (NTRS)

Minnis, Patrick; Nguyen, Louis; Palikonda, Rabindra; Spangeberg, Douglas; Nordeen, Michele L.; Yi, Yu-Hong; Ayers, J. Kirk

2004-01-01

Satellite data have long been used for determining the extent of cloud cover and for estimating the properties at the cloud tops. The derived properties can also be used to estimate aircraft icing potential to improve the safety of air traffic in the region. Currently, cloud properties and icing potential are derived in near-real time over the United States of America (USA) from the Geostationary Operational Environmental Satellite GOES) imagers at 75 W and 135 W. Traditionally, the results have been given in two dimensions because of the lack of knowledge about the vertical extent of clouds and the occurrence of overlapping clouds. Aircraft fly in a three-dimensional space and require vertical as well as horizontal information about clouds, their intensity, and their potential for icing. To improve the vertical component of the derived cloud and icing parameters, this paper explores various methods and datasets for filling in the three-dimensional space over the USA with cloud water.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cecchini, Micael A.; Machado, Luiz A. T.; Comstock, Jennifer M.

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 overall shape of the droplet size distribution (DSD) does not appear to be predominantly determined by updraught strength, especially beyond the 20 µm range. The aerosol conditions play a major role in that case. However, the updraughts modulate the DSD concentrations and are responsible for the vertical transport of water in the cloud. The larger droplets found in background clouds are associated with weak water vapour competition and a bimodal distribution of droplet sizes in the lower levels of the cloud, which enables an earlier initiation of the collision–coalescence process. This paper shows that the pollution produced by Manaus significantly affects warm-phase microphysical properties of the surrounding clouds by changing the initial DSD formation. The corresponding effects on ice-phase processes and precipitation formation will be the focus of future endeavors.« less

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

DOE PAGES

Cecchini, Micael A.; Machado, Luiz A. T.; Comstock, Jennifer M.; ...

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 overall shape of the droplet size distribution (DSD) does not appear to be predominantly determined by updraught strength, especially beyond the 20 µm range. The aerosol conditions play a major role in that case. However, the updraughts modulate the DSD concentrations and are responsible for the vertical transport of water in the cloud. The larger droplets found in background clouds are associated with weak water vapour competition and a bimodal distribution of droplet sizes in the lower levels of the cloud, which enables an earlier initiation of the collision–coalescence process. This paper shows that the pollution produced by Manaus significantly affects warm-phase microphysical properties of the surrounding clouds by changing the initial DSD formation. The corresponding effects on ice-phase processes and precipitation formation will be the focus of future endeavors.« less

Investigating ice nucleation in cirrus clouds with an aerosol-enabled Multiscale Modeling Framework

DOE PAGES

Zhang, Chengzhu; Wang, Minghuai; Morrison, H.; ...

2014-11-06

In this study, an aerosol-dependent ice nucleation scheme [Liu and Penner, 2005] has been implemented in an aerosol-enabled multi-scale modeling framework (PNNL MMF) to study ice formation in upper troposphere cirrus clouds through both homogeneous and heterogeneous nucleation. The MMF model represents cloud scale processes by embedding a cloud-resolving model (CRM) within each vertical column of a GCM grid. By explicitly linking ice nucleation to aerosol number concentration, CRM-scale temperature, relative humidity and vertical velocity, the new MMF model simulates the persistent high ice supersaturation and low ice number concentration (10 to 100/L) at cirrus temperatures. The low ice numbermore » is attributed to the dominance of heterogeneous nucleation in ice formation. The new model simulates the observed shift of the ice supersaturation PDF towards higher values at low temperatures following homogeneous nucleation threshold. The MMF models predict a higher frequency of midlatitude supersaturation in the Southern hemisphere and winter hemisphere, which is consistent with previous satellite and in-situ observations. It is shown that compared to a conventional GCM, the MMF is a more powerful model to emulate parameters that evolve over short time scales such as supersaturation. Sensitivity tests suggest that the simulated global distribution of ice clouds is sensitive to the ice nucleation schemes and the distribution of sulfate and dust aerosols. Simulations are also performed to test empirical parameters related to auto-conversion of ice crystals to snow. Results show that with a value of 250 μm for the critical diameter, Dcs, that distinguishes ice crystals from snow, the model can produce good agreement to the satellite retrieved products in terms of cloud ice water path and ice water content, while the total ice water is not sensitive to the specification of Dcs value.« less

Atmospheric CO2 Concentration Measurements with Clouds from an Airborne Lidar

NASA Astrophysics Data System (ADS)

Mao, J.; Abshire, J. B.; Kawa, S. R.; Riris, H.; Allan, G. R.; Hasselbrack, W. E.; Numata, K.; Chen, J. R.; Sun, X.; DiGangi, J. P.; Choi, Y.

2017-12-01

Globally distributed atmospheric CO2 concentration measurements with high precision, low bias and full seasonal sampling are crucial to advance carbon cycle sciences. However, two thirds of the Earth's surface is typically covered by clouds, and passive remote sensing approaches from space are limited to cloud-free scenes. NASA Goddard is developing a pulsed, integrated-path differential absorption (IPDA) lidar approach to measure atmospheric column CO2 concentrations, XCO2, from space as a candidate for NASA's ASCENDS mission. Measurements of time-resolved laser backscatter profiles from the atmosphere also allow this technique to estimate XCO2 and range to cloud tops in addition to those to the ground with precise knowledge of the photon path-length. We demonstrate this measurement capability using airborne lidar measurements from summer 2017 ASCENDS airborne science campaign in Alaska. We show retrievals of XCO2 to ground and to a variety of cloud tops. We will also demonstrate how the partial column XCO2 to cloud tops and cloud slicing approach help resolving vertical and horizontal gradient of CO2 in cloudy conditions. The XCO2 retrievals from the lidar are validated against in situ measurements and compared to the Goddard Parameterized Chemistry Transport Model (PCTM) simulations. Adding this measurement capability to the future lidar mission for XCO2 will provide full global and seasonal data coverage and some information about vertical structure of CO2. This unique facility is expected to benefit atmospheric transport process studies, carbon data assimilation in models, and global and regional carbon flux estimation.

Detection of carbon monoxide pollution from cities and wildfires on regional and urban scales: the benefit of CO column retrievals from SCIAMACHY 2.3 µm measurements under cloudy conditions

NASA Astrophysics Data System (ADS)

Borsdorff, Tobias; Andrasec, Josip; aan de Brugh, Joost; Hu, Haili; Aben, Ilse; Landgraf, Jochen

2018-05-01

In the perspective of the upcoming TROPOMI Sentinel-5 Precursor carbon monoxide data product, we discuss the benefit of using CO total column retrievals from cloud-contaminated SCIAMACHY 2.3 µm shortwave infrared spectra to detect atmospheric CO enhancements on regional and urban scales due to emissions from cities and wildfires. The study uses the operational Sentinel-5 Precursor algorithm SICOR, which infers the vertically integrated CO column together with effective cloud parameters. We investigate its capability to detect localized CO enhancements distinguishing between clear-sky observations and observations with low (< 1.5 km) and medium-high clouds (1.5-5 km). As an example, we analyse CO enhancements over the cities Paris, Los Angeles and Tehran as well as the wildfire events in Mexico-Guatemala 2005 and Alaska-Canada 2004. The CO average of the SCIAMACHY full-mission data set of clear-sky observations can detect weak CO enhancements of less than 10 ppb due to air pollution in these cities. For low-cloud conditions, the CO data product performs similarly well. For medium-high clouds, the observations show a reduced CO signal both over Tehran and Los Angeles, while for Paris no significant CO enhancement can be detected. This indicates that information about the vertical distribution of CO can be obtained from the SCIAMACHY measurements. Moreover, for the Mexico-Guatemala fires, the low-cloud CO data captures a strong outflow of CO over the Gulf of Mexico and the Pacific Ocean and so provides complementary information to clear-sky retrievals, which can only be obtained over land. For both burning events, enhanced CO values are even detectable with medium-high-cloud retrievals, confirming a distinct vertical extension of the pollution. The larger number of additional measurements, and hence the better spatial coverage, significantly improve the detection of wildfire pollution using both the clear-sky and cloudy CO retrievals. Due to the improved instrument performance of the TROPOMI instrument with respect to its precursor SCIAMACHY, the upcoming Sentinel-5 Precursor CO data product will allow improved detection of CO emissions and their vertical extension over cities and fires, making new research applications possible.

Vertical profiling of aerosol particles and trace gases over the central Arctic Ocean during summer

NASA Astrophysics Data System (ADS)

Kupiszewski, P.; Leck, C.; Tjernström, M.; Sjogren, S.; Sedlar, J.; Graus, M.; Müller, M.; Brooks, B.; Swietlicki, E.; Norris, S.; Hansel, A.

2013-12-01

Unique measurements of vertical size-resolved aerosol particle concentrations, trace gas concentrations and meteorological data were obtained during the Arctic Summer Cloud Ocean Study (ASCOS, www.ascos.se), an International Polar Year project aimed at establishing the processes responsible for formation and evolution of low-level clouds over the high Arctic summer pack ice. The experiment was conducted from on board the Swedish icebreaker Oden, and provided both ship- and helicopter-based measurements. This study focuses on the vertical helicopter profiles and onboard measurements obtained during a three-week period when Oden was anchored to a drifting ice floe, and sheds light on the characteristics of Arctic aerosol particles and their distribution throughout the lower atmosphere. Distinct differences in aerosol particle characteristics within defined atmospheric layers are identified. Within the lowermost couple hundred metres, transport from the marginal ice zone (MIZ), condensational growth and cloud processing develop the aerosol population. During two of the four representative periods defined in this study, such influence is shown. At altitudes above about 1 km, long-range transport occurs frequently. However, only infrequently does large-scale subsidence descend such air masses to become entrained into the mixed layer in the high Arctic, and therefore long-range transport plumes are unlikely to directly influence low-level stratiform cloud formation. Nonetheless, such plumes can influence the radiative balance of the planetary boundary layer (PBL) by influencing formation and evolution of higher clouds, as well as through precipitation transport of particles downwards. New particle formation was occasionally observed, particularly in the near-surface layer. We hypothesize that the origin of these ultrafine particles could be in biological processes, both primary and secondary, within the open leads between the pack ice and/or along the MIZ. In general, local sources, in combination with upstream boundary-layer transport of precursor gases from the MIZ, are considered to constitute the origin of cloud condensation nuclei (CCN) particles and thus be of importance for the formation of interior Arctic low-level clouds during summer, and subsequently, through cloud influences, for the melting and freezing of sea ice.

Characteristic Vertical Profiles of Cloud Water Composition in Marine Stratocumulus Clouds and Relationships With Precipitation

NASA Astrophysics Data System (ADS)

MacDonald, Alexander B.; Dadashazar, Hossein; Chuang, Patrick Y.; Crosbie, Ewan; Wang, Hailong; Wang, Zhen; Jonsson, Haflidi H.; Flagan, Richard C.; Seinfeld, John H.; Sorooshian, Armin

2018-04-01

This study uses airborne cloud water composition measurements to characterize the vertical structure of air-equivalent mass concentrations of water-soluble species in marine stratocumulus clouds off the California coast. A total of 385 cloud water samples were collected in the months of July and August between 2011 and 2016 and analyzed for water-soluble ionic and elemental composition. Three characteristic profiles emerge: (i) a reduction of concentration with in-cloud altitude for particulate species directly emitted from sources below cloud without in-cloud sources (e.g., Cl- and Na+), (ii) an increase of concentration with in-cloud altitude (e.g., NO2- and formate), and (iii) species exhibiting a peak in concentration in the middle of cloud (e.g., non-sea-salt SO42-, NO3-, and organic acids). Vertical profiles of rainout parameters such as loss frequency, lifetime, and change in concentration with respect to time show that the scavenging efficiency throughout the cloud depth depends strongly on the thickness of the cloud. Thin clouds exhibit a greater scavenging loss frequency at cloud top, while thick clouds have a greater scavenging loss frequency at cloud base. The implications of these results for treatment of wet scavenging in models are discussed.

Characteristic Vertical Profiles of Cloud Water Composition in Marine Stratocumulus Clouds and Relationships With Precipitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, Alexander B.; Dadashazar, Hossein; Chuang, Patrick Y.

This study uses airborne cloud water composition measurements to characterize the vertical structure of air-equivalent mass concentrations of water-soluble species in marine stratocumulus clouds off the California coast. A total of 385 cloud water samples were collected in the months of July and August between 2011 and 2016 and analyzed for water-soluble ionic and elemental composition. Three characteristic profiles emerge: (i) a reduction of concentration with in-cloud altitude for particulate species directly emitted from sources below cloud without in-cloud sources (e.g., Cl-, Na+); (ii) an increase of concentration with in-cloud altitude (e.g., NO2-, formate); and (iii) species exhibiting a peakmore » in concentration in the middle of cloud (e.g., non-sea salt SO42-, NO3-, organic acids). Vertical profiles of rainout parameters such as loss frequency, lifetime, and change in concentration with respect to time show that the scavenging efficiency throughout the cloud depth depends strongly on the thickness of the cloud. Thin clouds exhibit a greater scavenging loss frequency at cloud top, while thick clouds have a greater scavenging loss frequency at cloud base. The implications of these results for treatment of wet scavenging in models are discussed.« less

Origin, Transport, and Vertical Distribution of Atmospheric Polluntants over the Northern Sourth China Sea During the 7-SEAS-Dongsha Experiment

NASA Technical Reports Server (NTRS)

Wang, Sheng-Hsiang; Tsay, Si-Chee; Lin, Neng-Huei; Chang, Shuenn-Chin; Li, Can; Welton, Ellsworth J.; Holben, Brent N.; Hsu, N. Christina; Lau, William K. M.; Lolli, Simone;

Sensitivity of Cirrus Bidirectional Reflectance at MODIS Bands to Vertical Inhomogeneity of Ice Crystal Habits and Size Distribution

NASA Technical Reports Server (NTRS)

Yang, P.; Gao, B.-C.; Baum, B. A.; Wiscombe, W.; Hu, Y.; Nasiri, S. L.; Soulen, P. F.; Heymsfield, A. J.; McFarquhar, G. M.; Miloshevich, L. M.

2000-01-01

A common assumption in satellite imager-based cirrus retrieval algorithms is that the radiative properties of a cirrus cloud may be represented by those associated with a specific ice crystal shape (or habit) and a single particle size distribution. However, observations of cirrus clouds have shown that the shapes and sizes of ice crystals may vary substantially with height within the clouds. In this study we investigate the sensitivity of the top-of-atmosphere bidirectional reflectances at two MODIS bands centered at 0.65 micron and 2.11 micron to the cirrus models assumed to be either a single homogeneous layer or three distinct but contiguous, layers. First, we define the single- and three-layer cirrus cloud models with respect to ice crystal habit and size distribution on the basis of in situ replicator data acquired during the First ISCCP Regional Experiment (FIRE-II), held in Kansas during the fall of 1991. Subsequently, fundamental light scattering and radiative transfer theory is employed to determine the single scattering and the bulk radiative properties of the cirrus cloud. Regarding the radiative transfer computations, we present a discrete form of the adding/doubling principle by introducing a direct transmission function, which is computationally straightforward and efficient an improvement over previous methods. For the 0.65 micron band, at which absorption by ice is negligible, there is little difference between the bidirectional reflectances calculated for the one- and three-layer cirrus models, suggesting that the vertical inhomogeneity effect is relatively unimportant. At the 2.11 micron band, the bidirectional reflectances computed for both optically thin (tau = 1) and thick (tau = 10) cirrus clouds show significant differences between the results for the one- and three-layer models. The reflectances computed for the three-layer cirrus model are substantially larger than those computed for the single-layer cirrus. Finally, we find that cloud reflectance is very sensitive to the optical properties of the small crystals that predominate in the top layer of the three-layer cirrus model. It is critical to define the most realistic geometric shape for the small "quasi-spherical" ice crystals in the top layer for obtaining reliable single-scattering parameters and bulk radiative properties of cirrus.

Observing microphysical structures and hydrometeor phase in convection with ARM active sensors

NASA Astrophysics Data System (ADS)

Riihimaki, L.; Comstock, J. M.; Luke, E. P.; Thorsen, T. J.; Fu, Q.

2016-12-01

The existence and distribution of super-cooled liquid water within convective clouds impacts the microphysical processes responsible for cloud radiative and lifetime effects. Yet few observations of cloud phase are available within convection and associated stratiform anvils. Here we identify super-cooled liquid layers within convection and associated stratiform clouds using measured radar Doppler spectra from vertically pointing Ka-band cloud radar and Raman Lidar, capitalizing on the strengths of both instruments. Observations from these sensors are used to show that liquid exists in patches within the cloud, rather than in uniform layers, impacting the growth and formation of ice. While a depolarization lidar like the Raman Lidar is a trusted measurement for identifying super-cooled liquid, the lidar attenuates at an optical depth of around three, limiting its ability to probe the full cloud. The use of the radar Doppler spectra is particularly valuable for this purpose because it allows observations within optically thicker clouds. We demonstrate a new method for identifying super-cooled liquid objectively from the radar Doppler spectra using machine-learning techniques.

CLouds, and Aerosols Radiative Impacts and Forcing: Year 2016 (CLARIFY-2016)

NASA Astrophysics Data System (ADS)

Haywood, J. M.; Bellouin, N.; Carslaw, K. S.; Coe, H.; Field, P.; Highwood, E. J.; Redemann, J.; Stier, P.; Wood, R.; Zuidema, P.

2013-12-01

Strongly absorbing biomass burning aerosols (BBAs) exist above highly reflectant stratocumulus clouds in the SE Atlantic with implications on the direct (e.g. Haywood et al., 2003), semi-direct (e.g. Johnson et al., 2006), and indirect effect of aerosols, implications on the remote sensing of cloud optical properties, development of clouds and feedback processes. Here, we present an analysis of modelled estimates of the direct effect using twelve models from the AEROCOM project (Myhre et al., 2013) to show that estimates of the direct effect in SE Atlantic range from strongly negative to strongly positive. Furthermore, we evaluate the performance of the HadGEM2 model and show it cannot replicate the extreme values of positive forcing inferred from high spectral resolution satellite retrievals. By examining patterns of deposition, we infer that the indirect effect from biomass burning aerosols is very limited in the model, but without detailed measurements we are unsure of the validity of this inference. We conclude that the SE Atlantic is therefore of key importance in determining the radiative forcing of biomass burning aerosols and provides a very stringent test for global climate models as they need to accurately represent the geographic distribution of the aerosol optical depth, the wavelength dependent aerosol single scattering albedo, the vertical profile of the aerosol, the geographic distribution of the cloud, the cloud fraction, the cloud liquid water content, the cloud droplet effective radii, and the vertical profile of the cloud. These results are used as scientific rationale to justify a new measurement campaign: CLouds and Aerosol Radiative Impacts and Forcing: Year-2016 (CLARIFY-2016). Haywood, J.M., Osborne, S.R. Francis, P.N., Keil, A., Formenti, P., Andreae, M.O., and Kaye, P.H., The mean physical and optical properties of regional haze dominated by biomass burning aerosol measured from the C-130 aircraft during SAFARI 2000, J. Geophys. Res., 108(D13), 8473, doi:10.1029/2002JD002226, 2003. Johnson, B.T., K.P. Shine, and P.M. Forster, The semi-direct aerosol effect: Impact of absorbing aerosols on marine stratocumulus, QJRMS, DOI: 10.1256/qj.03.61, 2006. Myhre, G. et al. Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations, Atmos. Chem. Phys., 13, 1853-1877, doi:10.5194/acp-13-1853-2013, 2013

The Geoscience Laser Altimeter System (GLAS) for the ICESAT Mission

NASA Technical Reports Server (NTRS)

Abshire, James B.; Sun, Xiao-Li; Ketchum, Eleanor A.; Afzal, Robert S.; Millar, Pamela S.

1999-01-01

Accurate measurements of surface heights and atmospheric backscatter have been demonstrated with the SLA, MOLA and LITE space lidar. Recent MOLA measurements of the Mars surface have 40 cm resolution and have reduced the global uncertainty in Mars topography from a few km to approx. 10 m. GLAS is a next generation lidar being developed as part of NASA's Icesat Mission for Earth orbit . The GLAS design combines a 10 cm precision surface lidar with a sensitive dual wavelength cloud and aerosol lidar. GLAS will precisely measure the heights of the Earth's polar ice sheets, determine the height profiles of the Earth's land topography, and profile the vertical backscatter of clouds and aerosols on a global scale. GLAS will fly on a small dedicated spacecraft in a polar orbit at 598 km altitude with an inclination of 94 degrees. GLAS is scheduled to launch in summer 2001 and to operate continuously for a minimum of 3 years with a goal of 5 years. The primary mission for GLAS is to measure the seasonal and annual changes in the heights of the Greenland and Antarctic ice sheets. GLAS will measure the vertical distance to the ice sheet from orbit with 1064 nm pulses from a Nd:Yag laser at 40 Hz. Each 5 nsec wide laser pulse is used for a single range measurement. When over land GLAS will profile the heights of the topography and vegetation. The GLAS receiver uses a I m diameter telescope and a Si APD detector. The detector signal is sampled by an all digital receiver which records each surface echo waveform with I nsec resolution and a stored echo record lengths of either 200, 400, or 600 samples. Analysis of the echo waveforms within the instrument permits discrimination between cloud and surface echoes. Ground based echo analysis permits precise ranging, determining the roughness or slopes of the surface as well as the vertical distributions of vegetation illuminated by the laser, Errors in knowledge of the laser beam pointing angle can bias height measurements of sloped surfaces. For surfaces with 2 deg. slopes, knowledge of pointing angle of the beam centroid to about 8 urad is required to achieve 10 cm height accuracy. GLAS uses a stellar reference system (SRS) to determine the pointing angle of each laser firing relative to inertial space. The SRS uses a high precision star camera oriented toward local zenith whose measurements are combined with a gyroscope to determine the inertial orientation of the SRS optical bench. The far field pattern of each laser pulse is measured with a laser reference system (LRS). Optically measuring each laser far field pattern relative to the star camera and gyroscope permits the angular offsets of each laser pulse to be determined. GLAS will also determine the vertical distributions of clouds and aerosols by measuring atmospheric backscatter profiles at both 1064 and 532 nm. The 1064 nm measurements use an analog detector and profile the height and vertical structure of thicker clouds. Measurements at 532 nm use new highly sensitive photon counting detectors, and measure the height distributions of very thin clouds and aerosol layers. With averaging these can be used to determine the height of the planetary boundary layer. The instrument design and expected performance will be discussed.

Measurement of the Vertical Distribution of Aerosol by Globally Distributed MP Lidar Network Sites

NASA Technical Reports Server (NTRS)

Spinhirne, James; Welton, Judd; Campbell, James; Starr, David OC. (Technical Monitor)

2001-01-01

The global distribution of aerosol has an important influence on climate through the scattering and absorption of shortwave radiation and through modification of cloud optical properties. Current satellite and other data already provide a great amount of information on aerosol distribution. However there are critical parameters that can only be obtained by active optical profiling. For aerosol, no passive technique can adequately resolve the height profile of aerosol. The aerosol height distribution is required for any model for aerosol transport and the height resolved radiative heating/cooling effect of aerosol. The Geoscience Laser Altimeter System (GLAS) is an orbital lidar to be launched by 2002. GLAS will provide global measurements of the height distribution of aerosol. The sampling will be limited by nadir only coverage. There is a need for local sites to address sampling, and accuracy factors. Full time measurements of the vertical distribution of aerosol are now being acquired at a number of globally distributed MP (micro pulse) lidar sites. The MP lidar systems provide profiling of all significant cloud and aerosol to the limit of signal attenuation from compact, eye safe instruments. There are currently six sites in operation and over a dozen planned. At all sites there are a complement of passive aerosol and radiation measurements supporting the lidar data. Four of the installations are at Atmospheric Radiation Measurement program sites. The aerosol measurements, retrievals and data products from the network sites will be discussed. The current and planned application of data to supplement satellite aerosol measurements is covered.

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.

Ortho-para-hydrogen equilibration on Jupiter

NASA Technical Reports Server (NTRS)

Carlson, Barbara E.; Lacis, Andrew A.; Rossow, William B.

1992-01-01

Voyager IRIS observations reveal that the Jovian para-hydrogen fraction is not in thermodynamic equilibrium near the NH3 cloud top, implying that a vertical gradient exists between the high-temperature equilibrium value of 0.25 at depth and the cloud top values. The height-dependent para-hydrogen profile is obtained using an anisotropic multiple-scattering radiative transfer model. A vertical correlation is found to exist between the location of the para-hydrogen gradient and the NH3 cloud, strongly suggesting that paramagnetic conversion on NH3 cloud particle surfaces is the dominant equilibration mechanism. Below the NH3 cloud layer, the para fraction is constant with depth and equal to the high-temperature equilibrium value of 0.25. The degree of cloud-top equilibration appears to depend on the optical depth of the NH3 cloud layer. Belt-zone variations in the para-hydrogen profile seem to be due to differences in the strength of the vertical mixing.

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

NASA Astrophysics Data System (ADS)

Brabec, M.; Wienhold, F. G.; Luo, B.; Vömel, H.; Immler, F.; Steiner, P.; Peter, T.

2012-04-01

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

Characterization of Individual Aerosol Particles Associated with Clouds (CRYSTAL-FACE)

NASA Technical Reports Server (NTRS)

Buseck, Peter R.

2004-01-01

The aim of our research was to obtain data on the chemical and physical properties of individual aerosol particles from near the bottoms and tops of the deep convective systems that lead to the generation of tropical cirrus clouds and to provide insights into the particles that serve as CCN or IN. We used analytical transmission electron microscopy (ATEM), including energy-dispersive X-ray spectrometry (EDS) and electron energy-loss spectroscopy (EELS), and field-emission electron microscopy (FESEM) to compare the compositions, concentrations, size distributions, shapes, surface coatings, and degrees of aggregation of individual particles from cloud bases and the anvils near the tropopause. Aggregates of sea salt and mineral dust, ammonium sulfate, and soot particles are abundant in in-cloud samples. Cirrus samples contain many H2SO4 droplets, but acidic sulfate particles are rare at the cloud bases. H2SO4 probably formed at higher altitudes through oxidation of SO2 in cloud droplets. The relatively high extent of ammoniation in the upper troposphere in-cloud samples appears to have resulted from vertical transport by strong convection. The morphology of H2SO4 droplets indicates that they had been at least yartiy ammoniated at the time of collection. They are internally mixed with organic materials, metal sulfates, and solid particles of various compositions. Ammoniation and internal mixing of result in freezing at higher temperature than in pure H2SO4 aerosols. K- and S-bearing organic particles and Si-Al-rich particles are common throughout. Sea salt and mineral dust were incorporated into the convective systems from the cloud bases and worked as ice nuclei while being vertically transported. The nonsulfate particles originated from the lower troposphere and were transported to the upper troposphere and lower stratosphere.

The impact of aerosol vertical distribution on aerosol optical depth retrieval using CALIPSO and MODIS data: Case study over dust and smoke regions

NASA Astrophysics Data System (ADS)

Wu, Yerong; de Graaf, Martin; Menenti, Massimo

2017-08-01

Global quantitative aerosol information has been derived from MODerate Resolution Imaging SpectroRadiometer (MODIS) observations for decades since early 2000 and widely used for air quality and climate change research. However, the operational MODIS Aerosol Optical Depth (AOD) products Collection 6 (C6) can still be biased, because of uncertainty in assumed aerosol optical properties and aerosol vertical distribution. This study investigates the impact of aerosol vertical distribution on the AOD retrieval. We developed a new algorithm by considering dynamic vertical profiles, which is an adaptation of MODIS C6 Dark Target (C6_DT) algorithm over land. The new algorithm makes use of the aerosol vertical profile extracted from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements to generate an accurate top of the atmosphere (TOA) reflectance for the AOD retrieval, where the profile is assumed to be a single layer and represented as a Gaussian function with the mean height as single variable. To test the impact, a comparison was made between MODIS DT and Aerosol Robotic Network (AERONET) AOD, over dust and smoke regions. The results show that the aerosol vertical distribution has a strong impact on the AOD retrieval. The assumed aerosol layers close to the ground can negatively bias the retrievals in C6_DT. Regarding the evaluated smoke and dust layers, the new algorithm can improve the retrieval by reducing the negative biases by 3-5%.

Cloud Coverage and Height Distribution from the GLAS Polar Orbiting Lidar: Comparison to Passive Cloud Retrievals

NASA Technical Reports Server (NTRS)

Spinhime, J. D.; Palm, S. P.; Hlavka, D. L.; Hart, W. D.; Mahesh, A.

2004-01-01

The Geoscience Laser Altimeter System (GLAS) began full on orbit operations in September 2003. A main application of the two-wavelength GLAS lidar is highly accurate detection and profiling of global cloud cover. Initial analysis indicates that cloud and aerosol layers are consistently detected on a global basis to cross-sections down to 10(exp -6) per meter. Images of the lidar data dramatically and accurately show the vertical structure of cloud and aerosol to the limit of signal attenuation. The GLAS lidar has made the most accurate measurement of global cloud coverage and height to date. In addition to the calibrated lidar signal, GLAS data products include multi level boundaries and optical depth of all transmissive layers. Processing includes a multi-variable separation of cloud and aerosol layers. An initial application of the data results is to compare monthly cloud means from several months of GLAS observations in 2003 to existing cloud climatologies from other satellite measurement. In some cases direct comparison to passive cloud retrievals is possible. A limitation of the lidar measurements is nadir only sampling. However monthly means exhibit reasonably good global statistics and coverage results, at other than polar regions, compare well with other measurements but show significant differences in height distribution. For polar regions where passive cloud retrievals are problematic and where orbit track density is greatest, the GLAS results are particularly an advance in cloud cover information. Direct comparison to MODIS retrievals show a better than 90% agreement in cloud detection for daytime, but less than 60% at night. Height retrievals are in much less agreement. GLAS is a part of the NASA EOS project and data products are thus openly available to the science community (see http://glo.gsfc.nasa.gov).

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Kyo-Sun Sunny; Riihimaki, Laura; Comstock, Jennifer M.

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

Raman lidar measurement of water vapor and ice clouds associated with Asian dust layer over Tsukuba, Japan

NASA Astrophysics Data System (ADS)

Sakai, Tetsu; Nagai, Tomohiro; Nakazato, Masahisa; Matsumura, Takatsugu

2004-03-01

The vertical distributions of particle extinction, backscattering, depolarization, and water vapor mixing ratio were measured using a Raman lidar over Tsukuba (36.1°N, 140.1°E), Japan, on 23-24 April 2001. Ice clouds associated with the Asian dust layer were observed at an altitude of ~6-9 km. The relative humidities in the cloud layer were close to the ice saturation values and the temperature at the top of the cloud layer was ~-35°C, suggesting that the Asian dust acted as ice nuclei at the high temperatures. The meteorological analysis suggested that the ice-saturated region was formed near the top of the dust layer where the moist air ascended in slantwise fashion above the cold-frontal zone associated with extratropical cyclone.

Characteristics of Moderately Deep Tropical Convection Observed by Dual-Polarimetric Radar

NASA Astrophysics Data System (ADS)

Powell, Scott

2017-04-01

Moderately deep cumulonimbus clouds (often erroneously called congestus) over the tropical warm pool play an important role in large-scale dynamics by moistening the free troposphere, thus allowing for the upscale growth of convection into mesoscale convective systems. Direct observational analysis of such convection has been limited despite a wealth of radar data collected during several field experiments in the tropics. In this study, the structure of isolated cumulonimbus clouds, particularly those in the moderately deep mode with heights of up to 8 km, as observed by RHI scans obtained with the S-PolKa radar during DYNAMO is explored. Such elements are first identified following the algorithm of Powell et al (2016); small contiguous regions of echo are considered isolated convection. Within isolated echo objects, echoes are further subdivided into core echoes, which feature vertical profiles reflectivity and differential reflectivity that is similar to convection embedded in larger cloud complexes, and fringe echoes, which contain vertical profiles of differential reflectivity that are more similar to stratiform regions. Between the surface and 4 km, reflectivities of 30-40 (10-20) dBZ are most commonly observed in isolated convective core (fringe) echoes. Convective cores in echo objects too wide to be considered isolated have a ZDR profile that peaks near the surface (with values of 0.5-1 dB common), and decays linearly to about 0.3 dB at and above an altitude of 6 km. Stratiform echoes have a minimum ZDR below of 0-0.5 dB below the bright band and a constant distribution centered on 0.5 dB above the bright band. The isolated convective core and fringe respectively possess composite vertical profiles of ZDR that resemble convective and stratiform echoes. The mode of the distribution of aspect ratios of isolated convection is approximately 2.3, but the long axis of isolated echo objects demonstrates no preferred orientation. An early attempt at illustrating composite radial velocity profiles within isolated convection is made. When the mean flow (determined from sounding data) is subtracted, a clear picture of radial velocities inside a composite representation of convection is obtained. As expected, Doppler radar data shows convergence in the lowest 1-2 km of isolated convective elements and divergence in the upper portions of the clouds. The composite velocity profiles can be used to compute crude profiles of horizontal divergence. Because the analysis uses data along radar rays (with gate size of 150 m) instead of data interpolated to a Cartesian grid, features in composited clouds can be observed at high vertical and horizontal resolution.

Analysis of Impact of Tropical Cyclone Blance on Rainfall at Kupang Region Based on Atmospheric Condition and Satellite Imagery

NASA Astrophysics Data System (ADS)

Roguna, S.; Saragih, I. J. A.; Siregar, P. S.; Julius, A. M.

2018-04-01

The Tropical Depression previously identified on March 3, 2017, at Arafuru Sea has grown to Tropical Cyclone Blance on March 5, 2017. The existence of Tropical Cyclone Blance gave impacts like increasing rainfall for some regions in Indonesia until March 7, 2017, such as Kupang. The increase of rainfall cannot be separated from the atmospheric dynamics related to convection processes and the formation of clouds. Analysis of weather parameters is made such as vorticity to observe vertical motion over the study area, vertical velocity to see the speed of lift force in the atmosphere, wind to see patterns of air mass distribution and rainfall to see the increase of rainfall compared to several days before the cyclone. Analysis of satellite imagery data is used as supporting analysis to see clouds imagery and movement direction of the cyclone. The results of weather parameters analysis show strong vorticity and lift force of air mass support the growth of Cumulonimbus clouds, cyclonic patterns on wind streamline and significant increase of rainfall compared to previous days. The results of satellite imagery analysis show the convective clouds over Kupang and surrounding areas when this phenomena and cyclone pattern moved down from Arafuru Sea towards the western part of Australia.

Development status of the EarthCARE Mission and its atmospheric Lidar

NASA Astrophysics Data System (ADS)

Hélière, A.; Wallace, K.; Pereira Do Carmo, J.; Lefebvre, A.; Eisinger, M.; Wehr, T.

2016-09-01

The European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) are co-operating to develop as part of ESA's Living Planet Programme, the third Earth Explorer Core Mission, EarthCARE, with the fundamental objective of improving the understanding of the processes involving clouds, aerosols and radiation in the Earth's atmosphere. EarthCARE payload consists of two active and two passive instruments: an ATmospheric LIDar (ATLID), a Cloud Profiling Radar (CPR), a Multi-Spectral Imager (MSI) and a Broad-Band Radiometer (BBR). The four instruments data are processed individually and in a synergetic manner to produce a large range of products, which include vertical profiles of aerosols, liquid water and ice, observations of cloud distribution and vertical motion within clouds, and will allow the retrieval of profiles of atmospheric radiative heating and cooling. Operating in the UV range at 355 nm, ATLID provides atmospheric echoes with a vertical resolution up to 100 m from ground to an altitude of 40 km. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol (Mie) and molecular (Rayleigh) scattering, which gives access to aerosol optical depth. Co-polarised and cross-polarised components of the Mie scattering contribution are also separated and measured on dedicated channels. This paper gives an overview of the mission science objective, the satellite configuration with its four instruments and details more specifically the implementation and development status of the Atmospheric Lidar. Manufacturing status and first equipment qualification test results, in particular for what concerns the laser transmitter development are presented.

ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, Vertical Air Motion (williams-vertair)

DOE Data Explorer

Williams, Christopher; Jensen, Mike

2012-11-06

This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

Vertical Photon Transport in Cloud Remote Sensing Problems

NASA Technical Reports Server (NTRS)

Platnick, S.

1999-01-01

Photon transport in plane-parallel, vertically inhomogeneous clouds is investigated and applied to cloud remote sensing techniques that use solar reflectance or transmittance measurements for retrieving droplet effective radius. Transport is couched in terms of weighting functions which approximate the relative contribution of individual layers to the overall retrieval. Two vertical weightings are investigated, including one based on the average number of scatterings encountered by reflected and transmitted photons in any given layer. A simpler vertical weighting based on the maximum penetration of reflected photons proves useful for solar reflectance measurements. These weighting functions are highly dependent on droplet absorption and solar/viewing geometry. A superposition technique, using adding/doubling radiative transfer procedures, is derived to accurately determine both weightings, avoiding time consuming Monte Carlo methods. Superposition calculations are made for a variety of geometries and cloud models, and selected results are compared with Monte Carlo calculations. Effective radius retrievals from modeled vertically inhomogeneous liquid water clouds are then made using the standard near-infrared bands, and compared with size estimates based on the proposed weighting functions. Agreement between the two methods is generally within several tenths of a micrometer, much better than expected retrieval accuracy. Though the emphasis is on photon transport in clouds, the derived weightings can be applied to any multiple scattering plane-parallel radiative transfer problem, including arbitrary combinations of cloud, aerosol, and gas layers.

Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Fan; Kollias, Pavlos; Shaw, Raymond A.

Cloud droplet size distributions (CDSDs), which are related to cloud albedo and lifetime, are usually broader in warm clouds than predicted from adiabatic parcel calculations. We investigate a mechanism for the CDSD broadening using a Lagrangian bin-microphysics cloud parcel model that considers the condensational growth of cloud droplets formed on polydisperse, sub-micrometer aerosols in an adiabatic cloud parcel that undergoes vertical oscillations, such as those due to cloud circulations or turbulence. Results show that the CDSD can be broadened during condensational growth as a result of Ostwald ripening amplified by droplet deactivation and reactivation, which is consistent with Korolev (1995).more » The relative roles of the solute effect, curvature effect, deactivation and reactivation on CDSD broadening are investigated. Deactivation of smaller cloud droplets, which is due to the combination of curvature and solute effects in the downdraft region, enhances the growth of larger cloud droplets and thus contributes particles to the larger size end of the CDSD. Droplet reactivation, which occurs in the updraft region, contributes particles to the smaller size end of the CDSD. In addition, we find that growth of the largest cloud droplets strongly depends on the residence time of cloud droplet in the cloud rather than the magnitude of local variability in the supersaturation fluctuation. This is because the environmental saturation ratio is strongly buffered by smaller cloud droplets. Two necessary conditions for this CDSD broadening, which generally occur in the atmosphere, are: (1) droplets form on polydisperse aerosols of varying hygroscopicity and (2) the cloud parcel experiences upwards and downwards motions. Therefore we expect that this mechanism for CDSD broadening is possible in real clouds. Our results also suggest it is important to consider both curvature and solute effects before and after cloud droplet activation in a cloud model. The importance of this mechanism compared with other mechanisms on cloud properties should be investigated through in-situ measurements and 3-D dynamic models.« less

Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation

DOE PAGES

Yang, Fan; Kollias, Pavlos; Shaw, Raymond A.; ...

2017-12-06

Cloud droplet size distributions (CDSDs), which are related to cloud albedo and lifetime, are usually broader in warm clouds than predicted from adiabatic parcel calculations. We investigate a mechanism for the CDSD broadening using a Lagrangian bin-microphysics cloud parcel model that considers the condensational growth of cloud droplets formed on polydisperse, sub-micrometer aerosols in an adiabatic cloud parcel that undergoes vertical oscillations, such as those due to cloud circulations or turbulence. Results show that the CDSD can be broadened during condensational growth as a result of Ostwald ripening amplified by droplet deactivation and reactivation, which is consistent with Korolev (1995).more » The relative roles of the solute effect, curvature effect, deactivation and reactivation on CDSD broadening are investigated. Deactivation of smaller cloud droplets, which is due to the combination of curvature and solute effects in the downdraft region, enhances the growth of larger cloud droplets and thus contributes particles to the larger size end of the CDSD. Droplet reactivation, which occurs in the updraft region, contributes particles to the smaller size end of the CDSD. In addition, we find that growth of the largest cloud droplets strongly depends on the residence time of cloud droplet in the cloud rather than the magnitude of local variability in the supersaturation fluctuation. This is because the environmental saturation ratio is strongly buffered by smaller cloud droplets. Two necessary conditions for this CDSD broadening, which generally occur in the atmosphere, are: (1) droplets form on polydisperse aerosols of varying hygroscopicity and (2) the cloud parcel experiences upwards and downwards motions. Therefore we expect that this mechanism for CDSD broadening is possible in real clouds. Our results also suggest it is important to consider both curvature and solute effects before and after cloud droplet activation in a cloud model. The importance of this mechanism compared with other mechanisms on cloud properties should be investigated through in-situ measurements and 3-D dynamic models.« less

Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation

NASA Astrophysics Data System (ADS)

Yang, Fan; Kollias, Pavlos; Shaw, Raymond A.; Vogelmann, Andrew M.

2018-05-01

Cloud droplet size distributions (CDSDs), which are related to cloud albedo and rain formation, are usually broader in warm clouds than predicted from adiabatic parcel calculations. We investigate a mechanism for the CDSD broadening using a moving-size-grid cloud parcel model that considers the condensational growth of cloud droplets formed on polydisperse, submicrometer aerosols in an adiabatic cloud parcel that undergoes vertical oscillations, such as those due to cloud circulations or turbulence. Results show that the CDSD can be broadened during condensational growth as a result of Ostwald ripening amplified by droplet deactivation and reactivation, which is consistent with early work. The relative roles of the solute effect, curvature effect, deactivation and reactivation on CDSD broadening are investigated. Deactivation of smaller cloud droplets, which is due to the combination of curvature and solute effects in the downdraft region, enhances the growth of larger cloud droplets and thus contributes particles to the larger size end of the CDSD. Droplet reactivation, which occurs in the updraft region, contributes particles to the smaller size end of the CDSD. In addition, we find that growth of the largest cloud droplets strongly depends on the residence time of cloud droplet in the cloud rather than the magnitude of local variability in the supersaturation fluctuation. This is because the environmental saturation ratio is strongly buffered by numerous smaller cloud droplets. Two necessary conditions for this CDSD broadening, which generally occur in the atmosphere, are as follows: (1) droplets form on aerosols of different sizes, and (2) the cloud parcel experiences upwards and downwards motions. Therefore we expect that this mechanism for CDSD broadening is possible in real clouds. Our results also suggest it is important to consider both curvature and solute effects before and after cloud droplet activation in a cloud model. The importance of this mechanism compared with other mechanisms on cloud properties should be investigated through in situ measurements and 3-D dynamic models.

Ice Cloud Formation and Dehydration in the Tropical Tropopause Layer

NASA Technical Reports Server (NTRS)

Jensen, Eric; Pfister, Leonhard; Gore, Warren J. (Technical Monitor)

2002-01-01

Stratospheric water vapor is important not only for its greenhouse forcing, but also because it plays a significant role in stratospheric chemistry. several recent studies have focused on the potential for dehydration due to ice cloud formation in air rising slowly through the tropical tropopause layer. Holton and Gettelman showed that temperature variations associated with horizontal transport of air in the tropopause layer can drive ice cloud formation and dehydration, and Gettelman et al. recently examined the cloud formation and dehydration along kinematic trajectories using simple assumptions about the cloud properties. In this study, we use a Lagrangian, one-dimensional cloud model to further investigate cloud formation and dehydration as air is transported horizontally and vertically through the tropical tropopause layer. Time-height curtains of temperature are extracted from meteorological analyses. The model tracks the growth and sedimentation of individual cloud particles. The regional distribution of clouds simulated in the model is comparable to the subvisible cirrus distribution indicated by SAGE II. The simulated cloud properties depend strongly on the assumed ice supersaturation threshold for ice nucleation. with effective nuclei present (low supersaturation threshold), ice number densities are high (0.1--10 cm(circumflex)-3), and ice crystals do not grow large enough to fall very far, resulting in limited dehydration. With higher supersaturation thresholds, ice number densities are much lower (less than 0.01 cm(circumflex)-3), and ice crystals grow large enough to fall substantially; however, supersaturated air often crosses the tropopause without cloud formation. The clouds typically do not dehydrate the air along trajectories down to the temperature minimum saturation mixing ratio. Rather the water vapor mixing ratio crossing the tropopause along trajectories is typically 10-50% larger than the saturation mixing ratio.

On the Vertical Nature of Biomass Burning Plumes by the California Coast and Their Relationship with Marine Boundary Layer Clouds

NASA Astrophysics Data System (ADS)

Hu, L.; Montzka, S. A.; Godwin, D.; Andrews, A. E.; Thoning, K. W.; Miller, B. R.; Sweeney, C.; Miller, J. B.; Lehman, S.; Siso, C.; Mondeel, D. J.; Hall, B. D.; Nance, J. D.; Tans, P. P.; Elkins, J. W.

2016-12-01

Biomass burning (BB) plumes can significantly impact stratocumulus clouds (Sc), the dominant cloud type by global area, by altering their microphysical properties. The California (CA) coast is home to one of the three major semi-permanent stratocumulus (Sc) cloud decks in the world and BB emissions are of growing concern in the western United States, owing to both a warmer climate and fire-control strategies over recent decades. The thickness and vertical position of BB plumes, especially relative to clouds, is critical to understand how the aerosol will affect the thermodynamic structure of the atmosphere, cloud properties, and radiative forcing. This study reports on the characterization of the vertical, spatial, and temporal nature of BB aerosol over coastal CA, based on airborne data collected in the months of July and August for 2013 and 2016. Results from over 100 soundings indicate that multiple BB plume layers exist above clouds, with the thickness of BB plumes and their vertical position relative to cloud top varying significantly as a function of distance from coastline. Comparison of soundings at a given location at two different times of day reveals significant variation in BB characteristics. Intercomparisons for BB plume characteristics are explored between the field data, NAAPS, and CALIPSO.

On the Vertical Nature of Biomass Burning Plumes by the California Coast and Their Relationship with Marine Boundary Layer Clouds

NASA Astrophysics Data System (ADS)

Hossein Mardi, A.; MacDonald, A. B.; Dadashazar, H.; Crosbie, E.; WANG, Z.; Lynch, P.; Campbell, J. R.; Jonsson, H.; Sorooshian, A.

2017-12-01

Biomass burning (BB) plumes can significantly impact stratocumulus clouds (Sc), the dominant cloud type by global area, by altering their microphysical properties. The California (CA) coast is home to one of the three major semi-permanent stratocumulus (Sc) cloud decks in the world and BB emissions are of growing concern in the western United States, owing to both a warmer climate and fire-control strategies over recent decades. The thickness and vertical position of BB plumes, especially relative to clouds, is critical to understand how the aerosol will affect the thermodynamic structure of the atmosphere, cloud properties, and radiative forcing. This study reports on the characterization of the vertical, spatial, and temporal nature of BB aerosol over coastal CA, based on airborne data collected in the months of July and August for 2013 and 2016. Results from over 100 soundings indicate that multiple BB plume layers exist above clouds, with the thickness of BB plumes and their vertical position relative to cloud top varying significantly as a function of distance from coastline. Comparison of soundings at a given location at two different times of day reveals significant variation in BB characteristics. Intercomparisons for BB plume characteristics are explored between the field data, NAAPS, and CALIPSO.

Extended field observations of cirrus clouds using a ground-based cloud observing system

NASA Technical Reports Server (NTRS)

Ackerman, Thomas P.

1994-01-01

The evolution of synoptic-scale dynamics associated with a middle and upper tropospheric cloud event that occurred on 26 November 1991 is examined. The case under consideration occurred during the FIRE CIRRUS-II Intensive Field Observing Period held in Coffeyville, KS during Nov. and Dec., 1991. Using data from the wind profiler demonstration network and a temporally and spatially augmented radiosonde array, emphasis is given to explaining the evolution of the kinematically-derived ageostrophic vertical circulations and correlating the circulation with the forcing of an extensively sampled cloud field. This is facilitated by decomposing the horizontal divergence into its component parts through a natural coordinate representation of the flow. Ageostrophic vertical circulations are inferred and compared to the circulation forcing arising from geostrophic confluence and shearing deformation derived from the Sawyer-Eliassen Equation. It is found that a thermodynamically indirect vertical circulation existed in association with a jet streak exit region. The circulation was displaced to the cyclonic side of the jet axis due to the orientation of the jet exit between a deepening diffluent trough and building ridge. The cloud line formed in the ascending branch of the vertical circulation with the most concentrated cloud development occurring in conjunction with the maximum large-scale vertical motion. The relationship between the large scale dynamics and the parameterization of middle and upper tropospheric clouds in large-scale models is discussed and an example of ice water contents derived from a parameterization forced by the diagnosed vertical motions and observed water vapor contents is presented.

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.

Application of the NASA A-Train to Evaluate Clouds Simulated by the Weather Research and Forecast Model

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.; Jedlovec, Gary J.; Lapenta, William M.

2008-01-01

The CloudSat Mission, part of the NASA A-Train, is providing the first global survey of cloud profiles and cloud physical properties, observing seasonal and geographical variations that are pertinent to evaluating the way clouds are parameterized in weather and climate forecast models. CloudSat measures the vertical structure of clouds and precipitation from space through the Cloud Profiling Radar (CPR), a 94 GHz nadir-looking radar measuring the power backscattered by clouds as a function of distance from the radar. One of the goals of the CloudSat mission is to evaluate the representation of clouds in forecast models, thereby contributing to improved predictions of weather, climate and the cloud-climate feedback problem. This paper highlights potential limitations in cloud microphysical schemes currently employed in the Weather Research and Forecast (WRF) modeling system. The horizontal and vertical structure of explicitly simulated cloud fields produced by the WRF model at 4-km resolution are being evaluated using CloudSat observations in concert with products derived from MODIS and AIRS. A radiative transfer model is used to produce simulated profiles of radar reflectivity given WRF input profiles of hydrometeor mixing ratios and ambient atmospheric conditions. The preliminary results presented in the paper will compare simulated and observed reflectivity fields corresponding to horizontal and vertical cloud structures associated with midlatitude cyclone events.

Overview: Precipitation characteristics and sensitivities to environmental conditions during GoAmazon2014/5 and ACRIDICON-CHUVA

DOE PAGES

Machado, Luiz A. T.; Calheiros, Alan J. P.; Biscaro, Thiago; ...

2018-05-07

This study provides an overview of precipitation processes and their sensitivities to environmental conditions in the Central Amazon Basin near Manaus during the GoAmazon2014/5 and ACRIDICON-CHUVA experiments. Here, this study takes advantage of the numerous measurement platforms and instrument systems operating during both campaigns to sample cloud structure and environmental conditions during 2014 and 2015; the rainfall variability among seasons, aerosol loading, land surface type, and topography has been carefully characterized using these data. Differences between the wet and dry seasons were examined from a variety of perspectives. The rainfall rates distribution, total amount of rainfall, and raindrop size distribution (the mass-weightedmore » mean diameter) were quantified over both seasons. The dry season generally exhibited higher rainfall rates than the wet season and included more intense rainfall periods. However, the cumulative rainfall during the wet season was 4 times greater than that during the total dry season rainfall, as shown in the total rainfall accumulation data. The typical size and life cycle of Amazon cloud clusters (observed by satellite) and rain cells (observed by radar) were examined, as were differences in these systems between the seasons. Moreover, monthly mean thermodynamic and dynamic variables were analysed using radiosondes to elucidate the differences in rainfall characteristics during the wet and dry seasons. The sensitivity of rainfall to atmospheric aerosol loading was discussed with regard to mass-weighted mean diameter and rain rate. This topic was evaluated only during the wet season due to the insignificant statistics of rainfall events for different aerosol loading ranges and the low frequency of precipitation events during the dry season. The impacts of aerosols on cloud droplet diameter varied based on droplet size. For the wet season, we observed no dependence between land surface type and rain rate. However, during the dry season, urban areas exhibited the largest rainfall rate tail distribution, and deforested regions exhibited the lowest mean rainfall rate. Airplane measurements were taken to characterize and contrast cloud microphysical properties and processes over forested and deforested regions. Vertical motion was not correlated with cloud droplet sizes, but cloud droplet concentration correlated linearly with vertical motion. Clouds over forested areas contained larger droplets than clouds over pastures at all altitudes. Finally, the connections between topography and rain rate were evaluated, with higher rainfall rates identified at higher elevations during the dry season.« less

Overview: Precipitation characteristics and sensitivities to environmental conditions during GoAmazon2014/5 and ACRIDICON-CHUVA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Machado, Luiz A. T.; Calheiros, Alan J. P.; Biscaro, Thiago

This study provides an overview of precipitation processes and their sensitivities to environmental conditions in the Central Amazon Basin near Manaus during the GoAmazon2014/5 and ACRIDICON-CHUVA experiments. Here, this study takes advantage of the numerous measurement platforms and instrument systems operating during both campaigns to sample cloud structure and environmental conditions during 2014 and 2015; the rainfall variability among seasons, aerosol loading, land surface type, and topography has been carefully characterized using these data. Differences between the wet and dry seasons were examined from a variety of perspectives. The rainfall rates distribution, total amount of rainfall, and raindrop size distribution (the mass-weightedmore » mean diameter) were quantified over both seasons. The dry season generally exhibited higher rainfall rates than the wet season and included more intense rainfall periods. However, the cumulative rainfall during the wet season was 4 times greater than that during the total dry season rainfall, as shown in the total rainfall accumulation data. The typical size and life cycle of Amazon cloud clusters (observed by satellite) and rain cells (observed by radar) were examined, as were differences in these systems between the seasons. Moreover, monthly mean thermodynamic and dynamic variables were analysed using radiosondes to elucidate the differences in rainfall characteristics during the wet and dry seasons. The sensitivity of rainfall to atmospheric aerosol loading was discussed with regard to mass-weighted mean diameter and rain rate. This topic was evaluated only during the wet season due to the insignificant statistics of rainfall events for different aerosol loading ranges and the low frequency of precipitation events during the dry season. The impacts of aerosols on cloud droplet diameter varied based on droplet size. For the wet season, we observed no dependence between land surface type and rain rate. However, during the dry season, urban areas exhibited the largest rainfall rate tail distribution, and deforested regions exhibited the lowest mean rainfall rate. Airplane measurements were taken to characterize and contrast cloud microphysical properties and processes over forested and deforested regions. Vertical motion was not correlated with cloud droplet sizes, but cloud droplet concentration correlated linearly with vertical motion. Clouds over forested areas contained larger droplets than clouds over pastures at all altitudes. Finally, the connections between topography and rain rate were evaluated, with higher rainfall rates identified at higher elevations during the dry season.« less

Forecasting the Northern African Dust Outbreak Towards Europe in April 2011: A Model Intercomparison

NASA Technical Reports Server (NTRS)

Huneeus, N.; Basart, S.; Fiedler, S.; Morcrette, J.-J.; Benedetti, A.; Mulcahy, J.; Terradellas, E.; Pérez García-Pando, C.; Pejanovic, G.; Nickovic, S.

2016-01-01

In the framework of the World Meteorological Organisation's Sand and Dust Storm Warning Advisory and Assessment System, we evaluated the predictions of five state-of-the-art dust forecast models during an intense Saharan dust outbreak affecting western and northern Europe in April 2011. We assessed the capacity of the models to predict the evolution of the dust cloud with lead times of up to 72 hours using observations of aerosol optical depth (AOD) from the AErosol RObotic NETwork (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS) and dust surface concentrations from a ground-based measurement network. In addition, the predicted vertical dust distribution was evaluated with vertical extinction profiles from the Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP). To assess the diversity in forecast capability among the models, the analysis was extended to wind field (both surface and profile), synoptic conditions, emissions and deposition fluxes. Models predict the onset and evolution of the AOD for all analysed lead times. On average, differences among the models are larger than differences among lead times for each individual model. In spite of large differences in emission and deposition, the models present comparable skill for AOD. In general, models are better in predicting AOD than near-surface dust concentration over the Iberian Peninsula. Models tend to underestimate the long-range transport towards northern Europe. Our analysis suggests that this is partly due to difficulties in simulating the vertical distribution dust and horizontal wind. Differences in the size distribution and wet scavenging efficiency may also account for model diversity in long-range transport.

Comparisons of Modeled and Observed Reflectivities and Fall Speeds for Snowfall of Varied Riming Degree During Winter Storms on Long Island, New York

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.; Colle, Brian A.; Yuter, Sandra E.; Stark, David

2016-01-01

Derived radar reflectivity and fall speed for four Weather Research and Forecasting model bulk microphysical parameterizations (BMPs) run at 1.33 km grid spacing are compared with ground-based, vertically-pointing Ku-band radar, scanning S- band radar, and in situ measurements at Stony Brook, NY. Simulations were partitioned into periods of observed riming degree as determined manually using a stereo microscope and camera during nine winter storms. Simulations were examined to determine whether the selected BMPs captured the effects of varying riming intensities, provided a reasonable match to the vertical structure of radar reflectivity or fall speed, and whether they produced reasonable surface fall speed distributions. Schemes assuming non spherical mass-diameter relationships yielded reflectivity distributions closer to observed values. All four schemes examined in this study provided a better match to the observed, vertical structure of reflectivity during moderate riming than light riming periods. The comparison of observed and simulated snow fall speeds had mixed results. One BMP produced episodes of excessive cloud water at times, resulting in fall speeds that were too large. However, most schemes had frequent periods of little or no cloud water during moderate riming periods and thus underpredicted the snow fall speeds at lower levels. Short, 1-4 hour periods with relatively steady snow conditions were used to compare BMP and observed size and fall speed distributions. These limited data suggest the examined BMPs underpredict fall speeds of cold-type snow habits and underrepresent aggregates larger than 4 mm diameter.

Diabatic forcing and intialization with assimilation of cloud water and rainwater in a forecast model

NASA Technical Reports Server (NTRS)

Raymond, William H.; Olson, William S.; Callan, Geary

1995-01-01

In this study, diabatic forcing, and liquid water assimilation techniques are tested in a semi-implicit hydrostatic regional forecast model containing explicit representations of grid-scale cloud water and rainwater. Diabatic forcing, in conjunction with diabatic contributions in the initialization, is found to help the forecast retain the diabatic signal found in the liquid water or heating rate data, consequently reducing the spinup time associated with grid-scale precipitation processes. Both observational Special Sensor Microwave/Imager (SSM/I) and model-generated data are used. A physical retrieval method incorporating SSM/I radiance data is utilized to estimate the 3D distribution of precipitating storms. In the retrieval method the relationship between precipitation distributions and upwelling microwave radiances is parameterized, based upon cloud ensemble-radiative model simulations. Regression formulae relating vertically integrated liquid and ice-phase precipitation amounts to latent heating rates are also derived from the cloud ensemble simulations. Thus, retrieved SSM/I precipitation structures can be used in conjunction with the regression-formulas to infer the 3D distribution of latent heating rates. These heating rates are used directly in the forecast model to help initiate Tropical Storm Emily (21 September 1987). The 14-h forecast of Emily's development yields atmospheric precipitation water contents that compare favorably with coincident SSM/I estimates.

Intercomparison of vertical structure of storms revealed by ground-based (NMQ) and spaceborne radars (CloudSat-CPR and TRMM-PR).

PubMed

Fall, Veronica M; Cao, Qing; Hong, Yang

2013-01-01

Spaceborne radars provide great opportunities to investigate the vertical structure of clouds and precipitation. Two typical spaceborne radars for such a study are the W-band Cloud Profiling Radar (CPR) and Ku-band Precipitation Radar (PR), which are onboard NASA's CloudSat and TRMM satellites, respectively. Compared to S-band ground-based radars, they have distinct scattering characteristics for different hydrometeors in clouds and precipitation. The combination of spaceborne and ground-based radar observations can help in the identification of hydrometeors and improve the radar-based quantitative precipitation estimation (QPE). This study analyzes the vertical structure of the 18 January, 2009 storm using data from the CloudSat CPR, TRMM PR, and a NEXRAD-based National Mosaic and Multisensor QPE (NMQ) system. Microphysics above, within, and below the melting layer are studied through an intercomparison of multifrequency measurements. Hydrometeors' type and their radar scattering characteristics are analyzed. Additionally, the study of the vertical profile of reflectivity (VPR) reveals the brightband properties in the cold-season precipitation and its effect on the radar-based QPE. In all, the joint analysis of spaceborne and ground-based radar data increases the understanding of the vertical structure of storm systems and provides a good insight into the microphysical modeling for weather forecasts.

Intercomparison of Vertical Structure of Storms Revealed by Ground-Based (NMQ) and Spaceborne Radars (CloudSat-CPR and TRMM-PR)

PubMed Central

Fall, Veronica M.; Hong, Yang

2013-01-01

Spaceborne radars provide great opportunities to investigate the vertical structure of clouds and precipitation. Two typical spaceborne radars for such a study are the W-band Cloud Profiling Radar (CPR) and Ku-band Precipitation Radar (PR), which are onboard NASA's CloudSat and TRMM satellites, respectively. Compared to S-band ground-based radars, they have distinct scattering characteristics for different hydrometeors in clouds and precipitation. The combination of spaceborne and ground-based radar observations can help in the identification of hydrometeors and improve the radar-based quantitative precipitation estimation (QPE). This study analyzes the vertical structure of the 18 January, 2009 storm using data from the CloudSat CPR, TRMM PR, and a NEXRAD-based National Mosaic and Multisensor QPE (NMQ) system. Microphysics above, within, and below the melting layer are studied through an intercomparison of multifrequency measurements. Hydrometeors' type and their radar scattering characteristics are analyzed. Additionally, the study of the vertical profile of reflectivity (VPR) reveals the brightband properties in the cold-season precipitation and its effect on the radar-based QPE. In all, the joint analysis of spaceborne and ground-based radar data increases the understanding of the vertical structure of storm systems and provides a good insight into the microphysical modeling for weather forecasts. PMID:24459424

Outcome of the third cloud retrieval evaluation workshop

NASA Astrophysics Data System (ADS)

Roebeling, Rob; Baum, Bryan; Bennartz, Ralf; Hamann, Ulrich; Heidinger, Andy; Thoss, Anke; Walther, Andi

2013-05-01

Accurate measurements of global distributions of cloud parameters and their diurnal, seasonal, and interannual variations are needed to improve understanding of the role of clouds in the weather and climate system, and to monitor their time-space variations. Cloud properties retrieved from satellite observations, such as cloud vertical placement, cloud water path and cloud particle size, play an important role for such studies. In order to give climate and weather researchers more confidence in the quality of these retrievals their validity needs to be determined and their error characteristics must be quantified. The purpose of the Cloud Retrieval Evaluation Workshop (CREW), held from 15-18 Nov. 2011 in Madison, Wisconsin, USA, is to enhance knowledge on state-of-art cloud properties retrievals from passive imaging satellites, and pave the path towards optimizing these retrievals for climate monitoring as well as for the analysis of cloud parameterizations in climate and weather models. CREW also seeks to observe and understand methods used to prepare daily and monthly cloud parameter climatologies. An important workshop component is discussion on results of the algorithm and sensor comparisons and validation studies. Hereto a common database with about 12 different cloud properties retrievals from passive imagers (MSG, MODIS, AVHRR, POLDER and/or AIRS), complemented with cloud measurements that serve as a reference (CLOUDSAT, CALIPSO, AMSU, MISR), was prepared for a number of "golden days". The passive imager cloud property retrievals were inter-compared and validated against Cloudsat, Calipso and AMSU observations. In our presentation we summarize the outcome of the inter-comparison and validation work done in the framework of CREW, and elaborate on reasons for observed differences. More in depth discussions were held on retrieval principles and validation, and utilization of cloud parameters for climate research. This was done in parallel breakout sessions on cloud vertical placement, cloud physical properties, and cloud climatologies. We present the recommendations of these sessions, propose a way forward to establish international partnerships on cloud research, and summarize actions defined to tailor CREW activities to missions of international programs, such as the Global Energy and Water Cycle Experiment (GEWEX) and Sustained, Co-Ordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM). Finally, attention is given to increase the traceability and uniformity of different longterm and homogeneous records of cloud parameters.

Biomass Burning Organic Aerosol as a Modulator of Droplet Number in the Southern Atlantic

NASA Astrophysics Data System (ADS)

Kacarab, M.; Howell, S. G.; Small Griswold, J. D.; Thornhill, K. L., II; Wood, R.; Redemann, J.; Nenes, A.

2017-12-01

Aerosols play a significant yet highly variable role in local and global air quality and climate. They act as cloud condensation nuclei (CCN) and both scatter and absorb radiation, lending a large source of uncertainty to climate predictions. Biomass burning organic aerosol (BBOA) can drastically elevate CCN concentrations, but the response in cloud droplet number may be suppressed or even reversed due to low supersaturations that develop from strong competition for water vapor. Constraining droplet response to BBOA is a key factor to understanding aerosol-cloud interactions. The southeastern Atlantic (SEA) cloud deck off the west coast of central Africa is a prime opportunity to study these cloud-BBOA interactions for marine stratocumulus as during winter in the southern hemisphere the SEA cloud deck is overlain by a large, optically thick BBOA plume. The NASA ObseRvations of Aerosols above Clouds and their intEractionS (ORACLES) study focuses on increasing the understanding of how these BBOA affect the SEA cloud deck. Measurements of CCN concentration, aerosol size distribution and composition, updraft velocities, and cloud droplet number in and around the SEA cloud deck and associated BBOA plume were taken aboard the NASA P-3 aircraft during the first two years of the ORACLES campaign in September 2016 and August 2017. Here we evaluate the predicted and observed droplet number sensitivity to the aerosol fluctuations and quantify, using the data, the drivers of droplet number variability (vertical velocity or aerosol properties) as a function of biomass burning plume characteristics. Over the course of the campaign, different levels of BBOA influence in the marine boundary layer (MBL) were observed, allowing for comparison of cloud droplet number, hygroscopicity parameter (κ), and maximum in-cloud supersaturation over a range of "clean" and "dirty" conditions. Droplet number sensitivity to aerosol concentration, κ, and vertical updraft velocities are also evaluated. Generally, an increase in BBOA led to increased droplet number along with decreased κ and maximum in-cloud supersaturation (leading to an increase in competition for water vapor). This work seeks to contribute to an increased understanding of how CCN and aerosol properties affect the radiative and hydrological properties and impact of the cloud.

Further evidence for CCN aerosol concentrations determining the height of warm rain and ice initiation in convective clouds over the Amazon basin

NASA Astrophysics Data System (ADS)

Campos Braga, Ramon; Rosenfeld, Daniel; Weigel, Ralf; Jurkat, Tina; Andreae, Meinrat O.; Wendisch, Manfred; Pöschl, Ulrich; Voigt, Christiane; Mahnke, Christoph; Borrmann, Stephan; Albrecht, Rachel I.; Molleker, Sergej; Vila, Daniel A.; Machado, Luiz A. T.; Grulich, Lucas

2017-12-01

We have investigated how aerosols affect the height above cloud base of rain and ice hydrometeor initiation and the subsequent vertical evolution of cloud droplet size and number concentrations in growing convective cumulus. For this purpose we used in situ data of hydrometeor size distributions measured with instruments mounted on HALO aircraft during the ACRIDICON-CHUVA campaign over the Amazon during September 2014. The results show that the height of rain initiation by collision and coalescence processes (Dr, in units of meters above cloud base) is linearly correlated with the number concentration of droplets (Nd in cm-3) nucleated at cloud base (Dr ≈ 5 ṡ Nd). Additional cloud processes associated with Dr, such as GCCN, cloud, and mixing with ambient air and other processes, produce deviations of ˜ 21 % in the linear relationship, but it does not mask the clear relationship between Dr and Nd, which was also found at different regions around the globe (e.g., Israel and India). When Nd exceeded values of about 1000 cm-3, Dr became greater than 5000 m, and the first observed precipitation particles were ice hydrometeors. Therefore, no liquid water raindrops were observed within growing convective cumulus during polluted conditions. Furthermore, the formation of ice particles also took place at higher altitudes in the clouds in polluted conditions because the resulting smaller cloud droplets froze at colder temperatures compared to the larger drops in the unpolluted cases. The measured vertical profiles of droplet effective radius (re) were close to those estimated by assuming adiabatic conditions (rea), supporting the hypothesis that the entrainment and mixing of air into convective clouds is nearly inhomogeneous. Additional CCN activation on aerosol particles from biomass burning and air pollution reduced re below rea, which further inhibited the formation of raindrops and ice particles and resulted in even higher altitudes for rain and ice initiation.

Normalized vertical ice mass flux profiles from vertically pointing 8-mm-wavelength Doppler radar

NASA Technical Reports Server (NTRS)

Orr, Brad W.; Kropfli, Robert A.

1993-01-01

During the FIRE 2 (First International Satellite Cloud Climatology Project Regional Experiment) project, NOAA's Wave Propagation Laboratory (WPL) operated its 8-mm wavelength Doppler radar extensively in the vertically pointing mode. This allowed for the calculation of a number of important cirrus cloud parameters, including cloud boundary statistics, cloud particle characteristic sizes and concentrations, and ice mass content (imc). The flux of imc, or, alternatively, ice mass flux (imf), is also an important parameter of a cirrus cloud system. Ice mass flux is important in the vertical redistribution of water substance and thus, in part, determines the cloud evolution. It is important for the development of cloud parameterizations to be able to define the essential physical characteristics of large populations of clouds in the simplest possible way. One method would be to normalize profiles of observed cloud properties, such as those mentioned above, in ways similar to those used in the convective boundary layer. The height then scales from 0.0 at cloud base to 1.0 at cloud top, and the measured cloud parameter scales by its maximum value so that all normalized profiles have 1.0 as their maximum value. The goal is that there will be a 'universal' shape to profiles of the normalized data. This idea was applied to estimates of imf calculated from data obtained by the WPL cloud radar during FIRE II. Other quantities such as median particle diameter, concentration, and ice mass content can also be estimated with this radar, and we expect to also examine normalized profiles of these quantities in time for the 1993 FIRE II meeting.

Vertical profiling of aerosol particles and trace gases over the central Arctic Ocean during summer

NASA Astrophysics Data System (ADS)

Kupiszewski, P.; Leck, C.; Tjernström, M.; Sjogren, S.; Sedlar, J.; Graus, M.; Müller, M.; Brooks, B.; Swietlicki, E.; Norris, S.; Hansel, A.

2013-04-01

Unique measurements of vertical size resolved aerosol particle concentrations, trace gas concentrations and meteorological data were obtained during the Arctic Summer Cloud Ocean Study (ASCOS, http://www.ascos.se), an International Polar Year project aimed at establishing the processes responsible for formation and evolution of low-level clouds over the high Arctic summer pack ice. The experiment was conducted from onboard the Swedish icebreaker Oden, and provided both ship- and helicopter-based measurements. This study focuses on the vertical helicopter profiles and onboard measurements obtained during a three-week period when Oden was anchored to a drifting ice floe, and sheds light on the characteristics of Arctic aerosol particles and their distribution throughout the lower atmosphere. Distinct differences in aerosol particle characteristics within defined atmospheric layers are identified. Near the surface (lowermost couple hundred meters), transport from the marginal ice zone (MIZ), if sufficiently short (less than ca. 2 days), condensational growth and cloud-processing develop the aerosol population. During two of the four representative periods defined in this study, such influence is shown. At altitudes above about 1 km, long-range transport occurs frequently. However, only infrequently does large-scale subsidence descend such air masses to become entrained into the mixed layer in the high Arctic, and therefore they are unlikely to directly influence low-level stratiform cloud formation. Nonetheless, long-range transport plumes can influence the radiative balance of the PBL by influencing formation and evolution of higher clouds, as well as through precipitation transport of particles downwards. New particle formation was occasionally observed, particularly in the near-surface layer. We hypothesize that the origin of these ultrafine particles can be from biological processes, both primary and secondary, within the open leads between the pack ice and/or along the MIZ. In general, local sources, in combination with upstream boundary layer transport of precursor gases from the MIZ, are suggested to constitute the origin of CCN particles and thus be of importance for the formation of interior Arctic low level clouds during summer, and subsequently, through cloud influences, on the melting and freezing of sea ice.

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

DOE PAGES

Muhlbauer, A.; Ackerman, T. P.; Lawson, R. P.; ...

2015-07-14

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

Geoscience Laser Altimeter System (GLAS) for the ICESat Mission

NASA Technical Reports Server (NTRS)

Abshire, James B.; Sun, Xiaoli; Ketchum, Eleanor A.; Millar, Pamela S.; Riris, Haris

2002-01-01

The Geoscience Laser Altimeter System (GLAS) is a new generation lidar and is the primary science payload for NASA's ICESat Mission. The GLAS design combines a 10 cm precision surface lidar with a sensitive dual wavelength cloud and aerosol lidar. GLAS will precisely measure the heights of the Earth's polar ice sheets, establish a grid of accurate height profiles of the Earth's land topography, and profile the vertical distribution of clouds and aerosols on a global scale. GLAS will be integrated onto a small spacecraft built by Ball Aerospace, and will be launched into a polar orbit with a 590-630 km altitude at an inclination of 94 degrees. ICESat is is currently planned to launch in winter 2002/03 and GLAS is designed to operate continuously in space for a minimum of 3 years. GLAS will measure the vertical distance from orbit to the Earth's surface with pulses from a ND:YAG laser at a 40 Hz rate. Each 6 nsec wide 1064 nm laser pulse is used to produce a single range measurement. On the surface, the laser footprints have 66 m diameter and approx. 170 m center-center spacings. The GLAS receiver uses a I m diameter telescope to detect laser backscatter and a Si APD to detect the 1064 nm signals. The detector's output is sampled by a digital ranging receiver, which records each transmitted pulse and surface echo waveform with 1 nsec (15 cm) resolution. Each echo pulse is digitized and is reported to ground with a record length of from 200 to 544 samples, depending on the spacecraft's location . The GLAS location and epoch times are measured by a precision GPS receiver carried on the ICESat spacecraft. Initial processing of the echo waveforms within GLAS permits discrimination between cloud and surface echoes for selecting appropriate waveform samples. This selection is guided by an on-board DEM which is used to set the boundaries for the echo pulse search algorithm. Subsequent ground-based echo pulse analysis, along with GPS-based clock frequency estimates, permit final determination of the range to the surface, degree of pulse spreading, and vertical distribution of any vegetation illuminated by the laser. Accurate knowledge of the laser beam's pointing angle is needed to prevent height biases when measuring over tilted surfaces, such as near the boundaries of ice sheets. For surfaces with 2 deg. slopes, knowledge of pointing angle of the beam's centroid angle to better than 10 urad is needed. GLAS uses a stellar reference system (SRS) to measure the pointing angle of each laser firing relative to inertial space. The SRS uses a high precision star camera oriented toward local zenith and a gyroscope to determine the inertial orientation of the SRS optical bench. The far field pattern of each laser is measured pulse relative to the star camera with a laser reference system (LRS). GLAS will also measure the vertical distributions of clouds and aerosols by recording the vertical profiles of laser pulse backscatter at both 1064 and 532 nm. The 1064 rim measurements use the Si APD detector and will be used to measure the height and echo pulse shape from thicker clouds. The lidar receiver at 532 nm uses a narrow bandwidth etalon filter and highly sensitive photon counting detectors. The 532 nm backscatter profiles will be used to measure the vertical extent of thinner clouds and the atmospheric boundary layer. The GLAS instrument component development is complete and the instrument is undergoing final testing and qualification at NASA-Goddard. The GLAS "as-built" characteristics and its expected measurement performance will be discussed.

Earth cloud, aerosol, and radiation explorer optical payload development status

NASA Astrophysics Data System (ADS)

Hélière, A.; Wallace, K.; Pereira do Carmo, J.; Lefebvre, A.

2017-09-01

The European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) are co-operating to develop as part of ESA's Living Planet Programme, the third Earth Explorer Core Mission, EarthCARE, with the ojective of improving the understanding of the processes involving clouds, aerosols and radiation in the Earth's atmosphere. EarthCARE payload consists of two active and two passive instruments: an ATmospheric LIDar (ATLID), a Cloud Profiling Radar (CPR), a Multi-Spectral Imager (MSI) and a Broad-Band Radiometer (BBR). The four instruments data are processed individually and in a synergetic manner to produce a large range of products, which include vertical profiles of aerosols, liquid water and ice, observations of cloud distribution and vertical motion within clouds, and will allow the retrieval of profiles of atmospheric radiative heating and cooling. MSI is a compact instrument with a 150 km swath providing 500 m pixel data in seven channels, whose retrieved data will give context to the active instrument measurements, as well as providing cloud and aerosol information. BBR measures reflected solar and emitted thermal radiation from the scene. Operating in the UV range at 355 nm, ATLID provides atmospheric echoes from ground to an altitude of 40 km. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol and molecular scattering, which gives access to aerosol optical depth. Co-polarised and cross-polarised components of the Mie scattering contribution are measured on dedicated channels. This paper will provide a description of the optical payload implementation, the design and characterisation of the instruments.

Vertical distributions of fluorescent aerosol over the Eastern U.S.

NASA Astrophysics Data System (ADS)

Perring, A. E.; Robinson, E. S.; Schwarz, J. P.; Gao, R. S.

2016-12-01

The prevalence of bioaerosol in the atmosphere is relevant to atmospheric chemistry, microbial ecology and climate. These particles can act as effective cloud condensation nuclei (CCN) and ice nuclei (IN), representing a potential feedback between vegetation and precipitation. As bioaerosol frequently account for a substantial fraction of coarse mode aerosol in the boundary layer, they may have significant impacts on mixed-phase and/or cirrus cloud formation and climate. Very few measurements are available, however, to constrain loadings of bioaerosol in the free troposphere. Here we present vertical profiles of fluorescent aerosol concentration as a proxy for bioaerosol. The data were obtained over the eastern U.S. during the summer of 2016 using a Wide Band Integrated Bioaerosol Sensor (WIBS) installed aboard a NOAA Twin Otter research aircraft. The airspeed and inlet configuration were chosen to permit efficient sampling of aerosol with diameters of up to 10 μm. Vertical profiles extend from 1000 to 17,500 feet AGL, spanning a temperature range relevant to ice formation. 100 hours of data cover a latitude range from 30N to 46N and target a variety of potential bioaerosol source regions including forests, croplands, the Gulf of Mexico, and Lake Michigan. Observed vertical profiles are compared to expected loadings based on current model parameterizations and implications are discussed.

Lidar cloud studies for FIRE and ECLIPS

NASA Technical Reports Server (NTRS)

Sassen, Kenneth; Grund, Christian J.; Spinhirne, James D.; Hardesty, Michael; Alvarez, James

1990-01-01

Optical remote sensing measurements of cirrus cloud properties were collected by one airborne and four ground-based lidar systems over a 32 h period during this case study from the First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment (FIRE) Intensive Field Observation (IFO) program. The lidar systems were variously equipped to collect linear depolarization, intrinsically calibrated backscatter, and Doppler velocity information. Data presented describe the temporal evolution and spatial distribution of cirrus clouds over an area encompassing southern and central Wisconsin. The cirrus cloud types include: dissipating subvisual and thin fibrous cirrus cloud bands, an isolated mesoscale uncinus complex (MUC), a large-scale deep cloud that developed into an organized cirrus structure within the lidar array, and a series of intensifying mesoscale cirrus cloud masses. Although the cirrus frequently developed in the vertical from particle fall-streaks emanating from generating regions at or near cloud tops, glaciating supercooled (-30 to -35 C) altocumulus clouds contributed to the production of ice mass at the base of the deep cirrus cloud, apparently even through riming, and other mechanisms involving evaporation, wave motions, and radiative effects are indicated. The generating regions ranged in scale from approximately 1.0 km cirrus uncinus cells, to organized MUC structures up to approximately 120 km across.

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. However significant sensitivity in ice cloud properties was found to variation in the dispersion of the ice crystal size distribution and the critical size for ice autoconversion. The implementation of the new microphysics leads to a more realistic representation of cloud processes in GEOS-5 and allows the linkage of cloud properties to aerosol emissions.

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

NASA Technical Reports Server (NTRS)

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

2003-01-01

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

Revised cloud processes to improve the mean and intraseasonal variability of Indian summer monsoon in climate forecast system: Part 1

NASA Astrophysics Data System (ADS)

Abhik, S.; Krishna, R. P. M.; Mahakur, M.; Ganai, Malay; Mukhopadhyay, P.; Dudhia, J.

2017-06-01

The National Centre for Environmental Prediction (NCEP) Climate Forecast System (CFS) is being used for operational monsoon prediction over the Indian region. Recent studies indicate that the moist convective process in CFS is one of the major sources of uncertainty in monsoon predictions. In this study, the existing simple cloud microphysics of CFS is replaced by the six-class Weather Research Forecasting (WRF) single moment (WSM6) microphysical scheme. Additionally, a revised convective parameterization is employed to improve the performance of the model in simulating the boreal summer mean climate and intraseasonal variability over the Indian summer monsoon (ISM) region. The revised version of the model (CFSCR) exhibits a potential to improve shortcomings in the seasonal mean precipitation distribution relative to the standard CFS (CTRL), especially over the ISM region. Consistently, notable improvements are also evident in other observed ISM characteristics. These improvements are found to be associated with a better simulation of spatial and vertical distributions of cloud hydrometeors in CFSCR. A reasonable representation of the subgrid-scale convective parameterization along with cloud hydrometeors helps to improve the convective and large-scale precipitation distribution in the model. As a consequence, the simulated low-frequency boreal summer intraseasonal oscillation (BSISO) exhibits realistic propagation and the observed northwest-southeast rainband is well reproduced in CFSCR. Additionally, both the high and low-frequency BSISOs are better captured in CFSCR. The improvement of low and high-frequency BSISOs in CFSCR is shown to be related to a realistic phase relationship of clouds.