  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.
