Numerical experiment of lake-effect snowstorm using the WRF model coupled with spectral bin microphysics for cloud

Global Precipitation Measurement (GPM) mission is in the formulation stage; the core satellite will be launched with the GPM Microwave Imager (GMI) and Dual-frequency Precipitation Radar (DPR) in July 2013. The GPM will offer a global view of precipitation systems including over mid- and high-latitudes, and enable measurement of frozen precipitation and light rainfall, which are difficult to be observed by the Tropical Rainfall Measurement Mission (TRMM) sensors in operation. A main target of GPM is an observation of snowfall events over land in mid- and high-latitude areas. Development of a retrieval algorithm for the satellite observation is an important subject prior to the mission start.

A virtual cloud library (VCL) will be offered by the meso-scale modeling group to support development of the retrieval algorithm. The VCL is a set of a basic output of the prognostic variables and a virtual output of a sensor calculated using a satellite simulator model applied to the simulation result. The satellite retrieval algorithm can be cross-checked with a physical-based approach by using the VCL as a priori database in the ground validation. Components of the VCL need to be sufficiently adjusted to the in-site observation data.

The first experiment for making VCL is planned for a snowfall event during the Canadian CloudSAT/CALIPSO Validation Project (C3VP) field campaign. This campaign was took place at the site located between the Lakes Huron and Ontario in south central Ontario, Canada. A cold wind passing over the lakes causes a snowstorm specific to areas over the lee side during winter season. Shi et al. [2010] showed a numerical simulation of the lake-effect snowstorm on Jan. 20, 2007 using the Weather and Research Forecasting (WRF) model with newly implemented the Goddard microphysics scheme (1-moment bulk for 2-water, 3-ice classes). The simulation reasonably represented the locally intensive frozen precipitation in agreement with King-city C-band radar observation. The structures of ice clouds were generally consistent with those in CloudSat and AMSU-B observations also.

This study is aimed at a follow-up study of their research using the WRF in conjunction with the spectral bin microphysics for clouds (WRF-SBM), especially targeted to cloud microphysics of the snowfall event. This SBM (1-moment 33 bins for 1-water, 6-ice classes) is based on the Hebrew University Cloud Model (HUCM) [e.g., Khain et al., 2000; Iguchi et al., 2008, Appendix A].

Our simulation with the WRF-SBM showed accumulated snowfall similar to that in Shi et al. The intensive snowfall in the simulation was off to the west side of that shown in the radar observation, and the spread of ice clouds to the lee side was not well enough. We will offer a discussion of ice cloud microphysics on a lake-effect snowstorm with sensitivity tests to improve the reproducibility and with reference to aircraft and ground measurements.