Objective methods for monitoring Indian Summer Monsoon using NWP products

Indian Summer monsoon (ISM) is one of the spectacular features of the global atmospheric general circulation. The inter-annual variations is one of the strongest signals of the earths climate variability, particularly its interaction with ENSO as been greatest interest to the climate research community. The development of objective criteria to characterize main features of the ISM can greatly facilitate empirical studies of the relationships between monsoon variability and its forcing. It can also aid objective assessment of the capability of NWP models in reproducing monsoon variability. In this study an attempt is made for developing an objective methods for identifying onset, withdrawal and also active and break phases. The above criteria are tested on the ERA-40 data for the period 1958-2001. Also climatological characteristics of different phases of the Indian summer monsoon has been studied using the developed technique.. These methods are able to determine the above phases retrospectively and can be modified to use in forecasts based on numerical models.