Monte Carlo radiative transfer calculations for inhomogeneous mixed phase clouds

1999 ◽  
Vol 24 (3) ◽  
pp. 237-241 ◽  
Author(s):  
A. Macke ◽  
D.L. Mitchell ◽  
L.V. Bremen
Keyword(s):  
Monte Carlo ◽  
Radiative Transfer ◽  
Mixed Phase ◽  
Mixed Phase Clouds

AMSU-B Observations of Mixed-Phase Clouds over Land

2005 ◽  
Vol 44 (1) ◽  
pp. 72-85 ◽  
Author(s):  
M. N. Deeter ◽  
J. Vivekanandan
Keyword(s):  
Water Vapor ◽  
Radiative Transfer ◽  
Mixed Phase ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Radiative Effects ◽  
Liquid Water Path ◽  
Water Path ◽  
Cloud Properties ◽  
Mixed Phase Clouds

Abstract Measurements from passive microwave satellite instruments such as the Advanced Microwave Sounding Unit B (AMSU-B) are sensitive to both liquid and ice cloud particles. Radiative transfer modeling is exploited to simulate the response of the AMSU-B instrument to mixed-phase clouds over land. The plane-parallel radiative transfer model employed for the study accounts for scattering and absorption from cloud ice as well as absorption and emission from trace gases and cloud liquid. The radiative effects of mixed-phase clouds on AMSU-B window channels (i.e., 89 and 150 GHz) and water vapor line channels (i.e., 183 ± 1, 3, and 7 GHz) are studied. Sensitivities to noncloud parameters, including surface temperature, surface emissivity, and atmospheric temperature and water vapor profiles, are also quantified. Modeling results indicate that both cloud phases generally have significant radiative effects and that the 150- and 183 ± 7-GHz channels are typically the most sensitive channels to integrated cloud properties (i.e., liquid water path and ice water path). However, results also indicate that AMSU-B measurements alone are probably insufficient for retrieving all mixed-phase cloud properties of interest. These results are supported by comparisons of AMSU-B observations of a mixed-phase cloud over the Atmospheric Radiation Measurement (ARM) Program’s Southern Great Plains (SGP) site with corresponding calculated clear-sky values.

scholarly journals Study of Horizontally Oriented Ice Crystals with CALIPSO Observations and Comparison with Monte Carlo Radiative Transfer Simulations

2012 ◽  
Vol 51 (7) ◽  
pp. 1426-1439 ◽  
Author(s):  
Chen Zhou ◽  
Ping Yang ◽  
Andrew E. Dessler ◽  
Yongxiang Hu ◽  
Bryan A. Baum
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Model ◽  
Incident Beam ◽  
Mixed Phase ◽  
Ice Crystals ◽  
Orthogonal Polarization ◽  
Depolarization Ratio ◽  
Ice Clouds ◽  
Lidar Measurements ◽  
Mixed Phase Clouds

AbstractData from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) indicate that horizontally oriented ice crystals (HOIC) occur frequently in both ice and mixed-phase clouds. When compared with the case for clouds consisting of randomly oriented ice crystals (ROIC), lidar measurements from clouds with HOIC, such as horizontally oriented hexagonal plates or columns, have stronger backscatter signals and smaller depolarization ratio values. In this study, a 3D Monte Carlo model is developed for simulating the CALIOP signals from clouds consisting of a mixture of quasi HOIC and ROIC. With CALIOP’s initial orientation with a pointing angle of 0.3° off nadir, the integrated attenuated backscatter is linearly related to the percentage of HOIC but is negatively related to the depolarization ratio. At a later time in the CALIOP mission, the pointing angle of the incident beam was changed to 3° off nadir to minimize the signal from HOIC. In this configuration, both the backscatter and the depolarization ratio are similar for clouds containing HOIC and ROIC. Horizontally oriented columns with two opposing prism facets perpendicular to the lidar beam and horizontally oriented plates show similar backscattering features, but the effect of columns is negligible in comparison with that of plates because the plates have relatively much larger surfaces facing the incident lidar beam. From the comparison between the CALIOP simulations and observations, it is estimated that the percentage of quasi-horizontally oriented plates ranges from 0% to 6% in optically thick mixed-phase clouds, from 0% to 3% in warm ice clouds (>−35°C), and from 0% to 0.5% in cold ice clouds.

scholarly journals Sensitivity Study on the Influence of Cloud Microphysical Parameters on Mixed-Phase Cloud Thermodynamic Phase Partitioning in CAM5

2016 ◽  
Vol 73 (2) ◽  
pp. 709-728 ◽  
Author(s):  
Ivy Tan ◽  
Trude Storelvmo
Keyword(s):  
Sensitivity Analysis ◽  
Monte Carlo ◽  
Time Scale ◽  
Monte Carlo Sampling ◽  
Sensitivity Study ◽  
Mixed Phase ◽  
Phase Partitioning ◽  
Quasi Monte Carlo ◽  
Microphysical Parameters ◽  
Mixed Phase Clouds

Abstract The influence of six CAM5.1 cloud microphysical parameters on the variance of phase partitioning in mixed-phase clouds is determined by application of a variance-based sensitivity analysis. The sensitivity analysis is based on a generalized linear model that assumes a polynomial relationship between the six parameters and the two-way interactions between them. The parameters, bounded such that they yield realistic cloud phase values, were selected by adopting a quasi–Monte Carlo sampling approach. The sensitivity analysis is applied globally, and to 20°-latitude-wide bands, and over the Southern Ocean at various mixed-phase cloud isotherms and reveals that the Wegener–Bergeron–Findeisen (WBF) time scale for the growth of ice crystals single-handedly accounts for the vast majority of the variance in cloud phase partitioning in mixed-phase clouds, while its interaction with the WBF time scale for the growth of snowflakes plays a secondary role. The fraction of dust aerosols active as ice nuclei in latitude bands, and the parameter related to the ice crystal fall speed and their interactions with the WBF time scale for ice are also significant. All other investigated parameters and their interactions with each other are negligible (<3%). Further analysis comparing three of the quasi–Monte Carlo–sampled simulations with spaceborne lidar observations by CALIOP suggests that the WBF process in CAM5.1 is currently parameterized such that it occurs too rapidly due to failure to account for subgrid-scale variability of liquid and ice partitioning in mixed-phase clouds.

scholarly journals A Modeling Case Study of Mixed-Phase Clouds over the Southern Ocean and Tasmania

2010 ◽  
Vol 138 (3) ◽  
pp. 839-862 ◽  
Author(s):  
Anthony E. Morrison ◽  
Steven T. Siems ◽  
Michael J. Manton ◽  
Alex Nazarov
Keyword(s):  
Southern Ocean ◽  
Supercooled Liquid ◽  
Mixed Phase ◽  
Weather Research And Forecasting ◽  
Marine Stratocumulus ◽  
Cloud Structure ◽  
In Situ Observations ◽  
Cloud Tops ◽  
Mixed Phase Clouds

Abstract The cloud structure associated with two frontal passages over the Southern Ocean and Tasmania is investigated. The first event, during August 2006, is characterized by large quantities of supercooled liquid water and little ice. The second case, during October 2007, is more mixed phase. The Weather Research and Forecasting model (WRFV2.2.1) is evaluated using remote sensed and in situ observations within the post frontal air mass. The Thompson microphysics module is used to describe in-cloud processes, where ice is initiated using the Cooper parameterization at temperatures lower than −8°C or at ice supersaturations greater than 8%. The evaluated cases are then used to numerically investigate the prevalence of supercooled and mixed-phase clouds over Tasmania and the ocean to the west. The simulations produce marine stratocumulus-like clouds with maximum heights of between 3 and 5 km. These are capped by weak temperature and strong moisture inversions. When the inversion is at temperatures warmer than −10°C, WRF produces widespread supercooled cloud fields with little glaciation. This is consistent with the limited in situ observations. When the inversion is at higher altitudes, allowing cooler cloud tops, glaciated (and to a lesser extent mixed phase) clouds are more common. The simulations are further explored to evaluate any orographic signature within the cloud structure over Tasmania. No consistent signature is found between the two cases.

scholarly journals Processes that generate and deplete liquid water and snow in thin midlevel mixed-phase clouds

2009 ◽  
Vol 114 (D12) ◽  
Author(s):  
Adam J. Smith ◽  
Vincent E. Larson ◽  
Jianguo Niu ◽  
J. Adam Kankiewicz ◽  
Lawrence D. Carey
Keyword(s):  
Liquid Water ◽  
Mixed Phase ◽  
Mixed Phase Clouds
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