HR: 1330h
AN: A43A-07    [Abstracts]
TI: Evaluation of Mid-Latitude Ice Clouds Properties Using MM5 Mesoscale Model and Remote-Sensing Measurements at SIRTA Atmospheric Observatory
AU: * chiriaco, m
EM: chiriaco@lmd.polytechnique.fr
AF: LMD/IPSL, Ecole Polytechnique, Palaiseau, France
AU: Chepfer, H
EM: chepfer@lmd.polytechnique.fr
AF: LMD/IPSL, Ecole Polytechnique, Palaiseau, France
AU: Vautard, R
EM: vautard@lmd.polytechnique.fr
AF: LMD/IPSL, Ecole Polytechnique, Palaiseau, France
AU: Haeffelin, M
EM: haeffelin@lmd.polytechnique.fr
AF: LMD/IPSL, Ecole Polytechnique, Palaiseau, France
AU: Minnis, P
EM: p.minnis@nasa.gov
AF: LARC, NASA Langley Research Center, United States
AU: Dudhia, J
EM: dudhia@ucar.edu
AF: NCAR, Boulder, United States
AB: The mid-latitude ice clouds properties are evaluated by using MM5 mesoscale model and remote-sensing measurements. The first part of the study uses the model to observation approach: model outputs are compared to long-term meteorological measurements by active remote-sensing (radar and lidar) and passive remote-sensing (infrared and visible fluxes) at SIRTA atmospheric observatory near Paris. The ambition of this first part is to understand which of four available microphysical schemes is best suited to simulate mid-latitude ice clouds. The methodology consists in directly simulating instrument observables from the model outputs without any profile inversion, which allows us to use of fewer assumptions on microphysical and optical properties of ice particles. Results show that when a proper parameterization of the terminal velocity is used, the microphysics schemes allow the MM5 model to simulate the presence of mid-latitude ice clouds in more than 65% of our selection of observed cloud cases. In 35% of the cases, simulated clouds are too persistent whatever the microphysical scheme and tend to produce too much solid water (ice and snow) and not enough liquid water. Among the four schemes compared in the current study, the best observation-to-simulations scores are obtained when the terminal velocity formulation does not directly depends on particle size, and when clouds have medium optical thickness (about 3). The second part of the study uses the observation to model approach. Using several algorithms developed on the SIRTA, it is possible to retrieve a large panel of ice cloud properties with SIRTA remote-sensing instruments: cloud particle size and shape, cloud altitude, temperature and phase, vertical velocity within the cloud, ground shortwave and longwave fluxes (Fground). Cloud microphysical and macrophysical properties are also available using CERES algorithms applied to MSG from June 2004 to now, including the fluxes at the top of the atmosphere (FTOA). All those cloud parameters are also computed using MM5 model with the most performed microphysical scheme (first part study) for all the observation period. Using observation and measurements, the synoptical situations over SIRTA are separated onto four categories that correspond to four categories of FTOA/Fground values. Those four categories are then studied independently: we link all the available parameters using MM5/SIRTA/MSG, in order to understand how microphysical properties vary with the macrophysical ones, and inversely. This allows a better knowledge of the cloud process, and it will be possible to improve the microphysical scheme in mesoscale model.
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly