Use of regional climate model simulations as input for hydrological models for the Hindukush-Karakorum-Himalaya region

摘要

The most important climatological inputs required for the calibration andvalidation of hydrological models are temperature and precipitation that canbe derived from observational records or alternatively from regional climatemodels (RCMs). In this paper, meteorological station observations andresults of the PRECIS (Providing REgional Climate for Impact Studies) RCMdriven by the outputs of reanalysis ERA 40 data and HadAM3P generalcirculation model (GCM) results are used as input in the hydrological model.The objective is to investigate the effect of precipitation and temperaturesimulated with the PRECIS RCM nested in these two data sets on dischargesimulated with the HBV model for three river basins in theHindukush-Karakorum-Himalaya (HKH) region. Six HBV model experiments aredesigned: HBV-Met, HBV-ERA and HBV-Had, HBV-Met_{CRU-corrected},HBV-ERA_Benchmark and HBV-Had_Benchmark where HBV is driven bymeteorological stations data, data from PRECIS nested in ERA-40 and HadAM3P,meteorological stations CRU corrected data, ERA-40 reanalysis and HadAM3PGCM data, respectively. Present day PRECIS simulations possess strongcapacity to simulate spatial patterns of present day climatecharacteristics. However, also some quantitative biases exist in the HKHregion, where PRECIS RCM simulations underestimate temperature andoverestimate precipitation with respect to CRU observations. The calibrationand validation results of the HBV model experiments show that theperformance of HBV-Met is better than the HBV models driven by other datasources. However, using input data series from sources different from thedata used in the model calibration shows that HBV-Had is more efficient thanother models and HBV-Met has the least absolute relative error with respectto all other models. The uncertainties are higher in least efficient models(i.e. HBV-Met_{CRU-corrected} and HBV-ERA_Benchmark) where the modelparameters are also unrealistic. In terms of both robustness and uncertaintyranges the HBV models calibrated with PRECIS output performed better thanother calibrated models except for HBV-Met which has shown a higherrobustness. This suggests that in data sparse regions such as the HKH regiondata from regional climate models may be used as input in hydrologicalmodels for climate scenarios studies.