Research Focus FY08:
I continue to investigate the impact of cloud microphysical parameterizations on simulations of organized convective systems while participating in a study that will focus on comparisons of partitioning of various microphysical processes among the Lin, 6-class graupel-phase microphysical model (WSM6), and Thompson microphysical schemes.
Colorado Headwaters Program
(Collaborators: Changhai Liu, Mitch Moncrieff, Roy Rasmussen, Xianfan Ma, Aijuan Bai, John Tuttle & others)
The Colorado Headwaters Program is a key project of NCAR's Water System Program in this fiscal year. Its major objective is to assess the projected Upper Colorado Snowpack and Runoff by global climate models using a very high resolution regional climate model. We started from the present-day cold season simulations in this region to evaluate the sensitivity of the simulated snowfall and snowpack to both the horizontal and vertical grid spacings as well as the various physical parameterizations. We have performed a series of 2~30-km resolution experiments over two multi-day periods (i.e., November 19 -- December 8, 2002; February 1--16, 2008) with the WRF model. North American Regional Reanalysis (NARR) data are used to provide the initial and boundary conditions in our simulations. The Snow Telemetry network (SNOTEL) and PRISM observations are used to evaluate the simulated snowfall. The preliminary analysis indicates that 1) the high-resolution simulations with 2~4-km grid spacing can well capture the heavy snowfall episodes during the two periods; 2) the simulated snowfall has little dependence on the choice of the PBL and land-surface schemes, but shows considerable sensitivity to the choice of microphysics parameterizations; and 3) the model performance gradually degrades when the grid spacing is coarser and coarser.
Ikeda, K., R. M. Rasmussen, C.-H. Liu, G. Thompson, L. Xue, 2008: Investigation of the dependence of squall line structure and dynamics on microphysical parameterization. 15th Intl. Conf. on Clouds and Precipitation, Cancun, MX, International Association of Meteorology and Atmospheric Science.
Ikeda, K., R. M. Rasmussen, E. A. Brandes, F. McDonough, 2008: Freezing drizzle detection with WSR-88D radars. J. Appl. Meteor. Climat., doi: 10.1175/2008JAMC1939.1.
Cao, Q., G. Zhang, E. A. Brandes, T. Schuur, . Ryzhkov, K. Ikeda, 2007: Analysis of video disdrometer and polarimetric radar data to characterize rain microphysics in Oklahoma. J. Appl. Meteor. Climat., 47, 2238-2255.
Brandes, E. A., K. Ikeda, G. Zhang, M. Schonhuber, R. M. Rasmussen, 2007: A statistical and physical description of hydrometeor distributions in Colorado snowstorms using a video disdrometer. J. Appl. Meteor. Climat., 46, 634-650, doi: 10.1175/JAM2489.1. (Accepted)