High Resolution Climate Change Information for the Lower Mekong River Basin of Southeast Asia

Regional climate projections are derived for Southeast Asia with the goal to estimate future agricultural productivity and to derive adaptive land use strategies for the future. Therefore, the regional non-hydrostatic Weather Research and Forecasting (WRF) model is used to dynamically downscale large-scale coupled atmosphere–ocean general circulation model information. WRF is driven by ECHAM5 data for the control period 1960–2000 as well as for the period 2001–2050 using the two different SRES scenario A1B and B1. In addition to these long-term climate simulations, a 30-year WRF simulation using ERA40 reanalysis data (1971–2000) is performed to validate the performance of the WRF simulations for this region and to enable calibration of climate impact models. In total, around 1.7 Mio CPUh were used to finalize the climate simulations at the Steinbuch Centre for Computing (KIT, SCC). Trend analysis of the past reveals significant positive trends up to 0.04 K/year for the northern part of the Lower Mekong River Basin. Except for relatively small regions, precipitation shows positive trends with a magnitude of approximately + 10 mm/year. Temperature, in general, is expected to be increased in the future following both the A1B and the B1 scenario. The magnitude of increase, however, strongly depends on the scenario. For the period 2021–2050 the magnitude ranges between + 3. 5 K to + 1. 5 K on average for the A1B and the B1 scenario, respectively. For precipitation, however, the signal is not that clear. While for the B1 scenario an increase of precipitation is expected for almost the whole basin, both positive and negative signals are found for A1B.