Climate change over the Yarlung Zangbo–Brahmaputra River Basin in the 21st century as simulated by a high resolution regional climate model

Abstract

Future climate changes over the Yarlung Zangbo-Brahmaputra River Basin (YAB) in the 21st century under the IPCC SRES A1B scenario are investigated based on a high-resolution regional climate model (RegCM3) simulation over East Asia. The model simulation extends from 1948 to 2100 at a horizontal grid spacing of 25 km, and it is one-way nested within a global model of MIROC3.2_hires. This is the first time that such a high resolution regional climate model was run consecutively over the East Asia domain. The simulated present day and future climate by RegCM3 and the driving MIROC3.2_hires are presented and compared. Results show better performances of RegCM3 in reproducing the observed temperature and precipitation over YAB. Significant warming in the 21st century is simulated by both models. However, differences exist concerning the spatial distribution and magnitude of the warming. Changes of precipitation in DJF (December–January–February) show similar pattern in the two models, whereas substantial differences are found in JJA (June–July–August) and the annual mean. While MIROC3.2_hires projects a prevailing increase of precipitation over the region, RegCM3 shows little change and a slight decrease. Changes of the difference between precipitation and evapotranspiration are also presented.