Modeling and Prediction of Wintertime Precipitation over Northwest India: Search for an Explicit Solution

Abstract:

The northwest part of India (NWI) known as the “wheat bowl” of the country, receives 40% - 45% of its annual precipitation during winter season. This precipitation is very important for the wheat crop, as it supplements the moisture and maintains low temperature during the reproductive stages. Most of the winter precipitation in the region is in the form of snowfall over western Himalayas. This precipitation, in turn, helps in maintaining the glaciers, which serve as the vast storehouse of freshwater supply to millions of people downstream throughout the year through rivers of western Himalayan origin. Therefore, for a country like India that gets more than 80% of its wheat production and fresh water from NWI region, the question arises whether strategies of winter-time precipitation prediction that have proved useful elsewhere can be adapted to the exceptionally complex terrain of Himalayas as well?

It has been found that present day coupled general circulation models (GCMs) provide seasonal-scale prediction in advance, however this prediction is in coarse resolution and skill is not satisfactory even with multi-model ensemble techniques. Thus, it is necessary to reproduce the information of the GCMs at higher resolution with improved skill using downscaling approaches. Therefore ultimate goal of the present study is to use output of the GCMs without statistical correction, and apply this output to regional climate model in a way that allows realistic simulation of precipitation and temperature over NWI. In particular we discuss (a) requirement for assessing the fidelity of the coupled general circulation models, (b) the role of various idealized experiments (for e.g. cumulus schemes, resolution, orography and land surface change) and (c) development of novel statistical downscaling technique for seasonal-scale prediction over NWI. We also highlight the benefits and current issues associated with the proposed "explicit" approach.