Hydrological Cycle over South and Southeast Asian River Basins as Simulated by PCMDI/CMIP3 Experiments

TL;DR

This study evaluates climate model simulations of the hydrological cycle over major Asian river basins across the 20th to 22nd centuries, highlighting biases and future variability projections.

Contribution

It provides a comprehensive assessment of CMIP3 climate models' ability to simulate water cycle components over Asian basins and their future projections.

Findings

Models underestimate precipitation and P - E, especially in the 20th century.

Inter-model agreement is modest, mainly on evaporation and variability.

Future projections show increased variability in Ganges and Mekong basins.

Abstract

We investigate how the climate models contributing to the PCMDI/CMIP3 dataset describe the hydrological cycle over four major South and Southeast Asian river basins (Indus, Ganges, Brahmaputra and Mekong) for the 20th, 21st (13 models) and 22nd (10 models) centuries. For the 20th century, some models do not seem to conserve water at the river basin scale up to a good degree of approximation. The simulated precipitation minus evaporation (P - E), total runoff (R) and precipitation (P) quantities are neither consistent with the observations nor among the models themselves. Most of the models underestimate P - E for all four river basins, which is mainly associated with the underestimation of precipitation. This is in agreement with the recent results on the biases of the representation of monsoonal dynamics by GCMs. Overall, a modest inter-model agreement is found only for the evaporation and inter-annual variability of P - E. For the 21st and 22nd centuries, models agree on the negative (positive) changes of P - E for the Indus basin (Ganges, Brahmaputra and Mekong basins). Most of the models foresee an increase in the inter-annual variability of P - E for the Ganges and Mekong basins, thus suggesting an increase in large low-frequency dry/wet events. Instead, no considerable future change in the inter-annual variability of P - E is found for the Indus and Brahmaputra basins.