Sensitivity studies on convective schemes and model resolutions in the simulations of wintertime circulation and precipitation over the Western Himalayas

The present study examines the performance of
convective parameterization schemes at two different horizontal
resolutions (90 and 30 km) in simulating winter (December–February;
DJF) circulation and associated precipitation over the
Western Himalayas using the regional climate model RegCM4.
The model integrations are carried out in a one-way nested mode
for three distinct precipitation years (excess, normal and deficit)
using four combinations of cumulus schemes. The National Center
for Environment Prediction—Department of Energy Reanalysis-2
project utilized gridded data, observed precipitation data from the
India Meteorological Department and station data from the Snow
and Avalanche Study Establishment were used to evaluate model
performance. The seasonal mean circulation patterns and precipitation
distribution are well demonstrated by all of the cumulus
convection schemes. However, model performance varies using
different schemes. Statistical analysis confirms that the root mean
square error is reduced by about 2–3 times and the correlation
coefficient (CC) increases in the fine resolution (30 km) simulations
compared to coarse resolution (90 km) simulations. A
statistically significant CC (at a 10 % significance level) is found
only in the fine resolution simulations. The Grell cumulus model
with a Fritsch–Chappell closure (Grell-FC) is better at simulating
seasonal mean patterns and inter-annual variability of two contrasting
winter seasons than the other scheme combinations.