HR: 11:50h
AN: A32A-09    [Abstracts]
TI: Using Spectral (Bin) Microphysics in a Mesoscale Model to Investigate the Effect of Aerosols on Regional Precipitation.
AU: * Lynn, B H
EM: bhl7@columbia.edu
AF: Barry Lynn, Hebrew University of Jerusalem, Department of Earth Sciences, Jerusalem, 91904 Israel
AU: Khain, A
EM: khain@vms.huji.ac.il
AF: Barry Lynn, Hebrew University of Jerusalem, Department of Earth Sciences, Jerusalem, 91904 Israel
AU: Rosenfeld, D
EM: Rosenfeld@vms.huji.ac.il
AF: Barry Lynn, Hebrew University of Jerusalem, Department of Earth Sciences, Jerusalem, 91904 Israel
AB: A growing body of observational data suggests that the formation of precipitation is sensitive to aerosol concentration. For example, the effect of aerosols on precipitation has been noted downwind of urban centers along the California Coast and in Israel. The simulation of both orographic and convective precipitation along mountainous areas often involves both liquid and mixed precipitation processes that depend on the initial drop distribution. Spectral (bin) microphysics (SBM) embedded in a mesoscale model presents an ideal (if not the only) simulation platform to study the effect of aerosols on regional climate. The SBM is based on solving a system of equations for size distribution functions for water drops, three types of ice crystals (plates, columns, and dendrites) as well as snowflakes, graupel, and hail/frozen drops. A budget for aerosols is used to obtain the spectrum of condensation nuclei, which is used to obtain the initial drop spectrum. Primary and secondary ice nucleation are included in the model. Hydrometeors evolve through both diffusion and collisions. Breakup of large drops is also included. The SBM has been coupled with the three-dimensional mesoscale model, MM5, which allows SBM to simulate microphysics within a realistic, time-varying mesoscale environment. The new model has been used to simulate both convective and orographic precipitation. Results with MM5 SBM are compared to those obtained with MM5 using bulk parameterization. The MM5 SBM appears to better reproduce precipitation amounts, radar reflectivity, cloud structure, and cloud particle type than model simulations with bulk parameterization. We identify and discuss microphysical processes that are crucial to simulating the realistic development of both liquid and mixed precipitation. We explain why these processes cannot be well represented with bulk parameterization.
DE: 3329 Mesoscale meteorology
DE: 3354 Precipitation (1854)
DE: 3364 Synoptic-scale meteorology
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting