An improvement of the SBU-YLIN microphysics scheme in squall line simulation

TL;DR

This paper enhances the SBU-YLIN microphysics scheme in WRF to better simulate cold pools in squall line events by incorporating density factors, modifying rain evaporation, and correcting saturation adjustments, validated across multiple cases.

Contribution

It introduces specific modifications to the SBU-YLIN scheme that significantly improve cold pool simulation accuracy in squall line modeling.

Findings

Improved scheme produces more realistic cold pools.

Modifications validated across multiple squall line cases.

Rain evaporation scheme change is most impactful.

Abstract

The default SBU-YLIN scheme in Weather Research and Forecasting Model (WRF) is proved having a limited capability of producing a reasonable cold pool in squall line simulations. With the help of wealthy observation data of a squall line, we finally improve it by: adding a density factor to the precipitating ice; modify the rain evaporation scheme and correct the saturation adjustment process. The improved SBU-YLIN scheme could produce a reasonable cold pool. Simulation of another two squall line cases in northern and eastern China confirm our modifications are effective. In addition, further analysis reveals that the modification of rain evaporation scheme is the most important among them.