Atmospheric water budget over the western Himalayas in a regional climate model

Abstract

During winter months (December, January, February – DJF), the western Himalayas (WH) receive precipitation from eastward moving extratropical cyclones, called western disturbances (WDs) in Indian parlance. Winter precipitation–moisture convergence–evaporation (P–C–E) cycle is analyzed for a period of 22 years (1981–2002: 1980(D)–1981(J, F) to 2001(D)–2002(J, F)) with observed and modelled (RegCM3) climatological estimates over WH. Remarkable model skills have been observed in depicting the hydrological cycle over WH. Although precipitation biases exist, similar spatial precipitation with well marked two maxima is simulated by the model. As season advances, temporal distribution shows higher precipitation in simulation than the observed. However, P–C–E cycle shows similar peaks of moisture convergence and evaporation in daily climatologies though with varying maxima/minima. In the first half of winter, evaporation over WH is mainly driven by ground surface and 2 m air temperature. Lowest temperatures during mid-winter correspond to lowest evaporation to precipitation ratio as well.