Regional climate projections in two alpine river basins: Upper Danube and Upper Brahmaputra

Abstract

Abstract. Projections from coarse-grid global circulation models are not suitable for regional estimates of water balance or trends of extreme precipitation and temperature, especially not in complex terrain. Thus, downscaling of global to regionally resolved projections is necessary to provide input to integrated water resources management approaches for river basins like the Upper Danube River Basin (UDRB) and the Upper Brahmaputra River Basin (UBRB).This paper discusses the application of the regional climate model COSMO-CLM as a dynamical downscaling tool. To provide accurate data the COSMO-CLM model output was post-processed by statistical means. This downscaling chain performs well in the baseline period 1971 to 2000. However, COSMO-CLM performs better in the UDRB than in the UBRB because of a longer application experience and a less complex climate in Europe.Different climate change scenarios were downscaled for the time period 1960-2100. The projections show an increase of temperature in both basins and for all seasons. The values are generally higher in the UBRB with the highest values occurring in the region of the Tibetan Plateau. Annual precipitation shows no substantial change. However, seasonal amounts show clear trends, for instance an increasing amount of spring precipitation in the UDRB. Again, the largest trends for different precipitation statistics are projected in the region of the Tibetan Plateau. Here, the projections show up to 50% longer dry periods in the months June to September with a simultaneous increase of about 10% for the maximum amount of precipitation on five consecutive days. For the Assam region in India, the projections also show an increase of 25% in the number of consecutive dry days during the monsoon season leading to prolonged monsoon breaks.

Impact of climate change on the hydrological regime of the Indus, Ganges and Brahmaputra river basins: a review of the literature

“…By the end of the century, the average temperature of the basin is projected to increase by 3.5 and 2.3 8C for the A2 and B2 scenarios, respectively. Dobler, Yaoming, Sharma, Kienberger, and Ahrens (2011), using the COSMO-CLM RCM for the A1B, B1 and A2 scenarios, also projected an increase in temperature in all seasons, with greater increases at higher elevation, consistent with the projections by Immerzeel (2008).…”

Understanding the hydrological system dynamics of a glaciated alpine catchment in the Himalayan region using the J2000 hydrological model

“…The rise in the temperature in the modelling context means increase in maximum, minimum and average temperatures. A similar range of rise in temperature has been reported in the region in different studies including some based on Regional Climate Model results (Nepal, ; Kumar et al ., ; New et al ., ; IPCC, ; Dobler et al ., ; Gao et al ., ). The focus of this analysis is given on the effect of assumed increase in temperature on the resultant snowmelt runoff pattern.…”

Analysis of lake level changes in Nam Co in central Tibet utilizing synergistic satellite altimetry and optical imagery

“…The water budget of the lake was analysed by Krause et al (2010). Their modelling effort based on downscaled ECHAM5 data (Dobler et al, 2011) suffers with high uncertainty due to insufficient availability of measured climate data. ECHAM5 which is a Global Climate Model developed by the Max Planck Institute for Meteorology (Hagemann et al, 2006).…”