Variability, Teleconnections and Lrf of NW India Winter Precipitation

In this book, interannual variability of North-West India winter precipitation (NWIWP) has been examined. It has been found that the simultaneous relationship with ENSO and equatorial Indian Ocean SST relationship has strengthened and the North Atlantic Oscillation (NAO) relationship has weakened in the recent decades. The convective heating anomalies of the tropical atmosphere due to increased SST over equatorial Pacific and Indian Oceans during the excess NWIWP years increase the meridional temperature gradient, which in turn intensifies and shifts the sub-tropical westerly jet-stream to lower latitudes. The jet-stream over northern India plays an important role in modulating NWIWP. While, NAO intensifies subtropical high over North Atlantic and adjoining areas. This contributes to the synoptic forcing that helps to develop the trough over Caspian Sea and hence, excess NWIWP. Also, the simultaneous relationship between NWIWP and convective maximum over warm-pool region, increases the seasonal predictability of NWIWP. Of the three empirical seasonal forecast models developed for NWIWP, the Artificial Neural Network model with 6 predictors showed better skill.