The 13–14 December 2001 IMPROVE-2 Event. Part III: Simulated Microphysical Budgets and Sensitivity Studies

Abstract
This paper investigates the microphysical pathways and sensitivities within the Reisner-2 bulk microphysical parameterization (BMP) of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) for the Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE)-2 field experiment on 13–14 December 2001. A microphysical budget over the windward slope at 1.33-km horizontal grid spacing was calculated, in which the importance of each microphysical process was quantified relative to the water vapor loss (WVL) rate. Over the windward Cascades, the largest water vapor loss was associated with condensation (73% of WVL) and snow deposition (24%), and the windward surface precipitation resulted primarily from accretion of cloud water by rain (27% of WVL), graupel fallout and melt (19%), and snowmelt (6%). Two-thirds of the snow generated aloft spilled over into the lee in an area of model overpredic... Abstract This paper investigates the microphysical pathways and sensitivities within the Reisner-2 bulk microphysical parameterization (BMP) of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) for the Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE)-2 field experiment on 13–14 December 2001. A microphysical budget over the windward slope at 1.33-km horizontal grid spacing was calculated, in which the importance of each microphysical process was quantified relative to the water vapor loss (WVL) rate. Over the windward Cascades, the largest water vapor loss was associated with condensation (73% of WVL) and snow deposition (24%), and the windward surface precipitation resulted primarily from accretion of cloud water by rain (27% of WVL), graupel fallout and melt (19%), and snowmelt (6%). Two-thirds of the snow generated aloft spilled over into the lee in an area of model overpredic...

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