Performance of a limited area model for the simulation of western disturbances

Abstract

A non-hydrostatic version of PSU /NCAR mesoscale model is used to simulate the characteristic features of the Western Disturbances (WDs) occurring over the Indian region during winter. For this study, four cases of very active WDs are selected. The model is integrated with 60 km resolution in simulating the WD features. Results showed that in all the four cases, the rate of movement of the system is in general, a little slower in the simulations. Examination of the differences between the predicted and analyzed zonal component of the wind reveal that the model simulated zonal winds are generally weaker/underestimated in the location of the upper trough at 500 hPa or aloft and even in the position of the WDs at lower levels. These results suggest that the model has a systematic bias, though the magnitude is small. In other words the advection simulated in the model is not strong enough to advect the system with the observed speed.