Abstract
In this study, a linear scaling method, precipitation extended linear scaling (PELS), is proposed to correct precipitation simulated by GCMs. In this method, monthly scaling factors were extended to daily scaling factors (DSFs) to improve the daily variation in precipitation. In addition, DSFs were also checked for outliers and smoothed with a smoothing filter to reduce the effect of noisy DSFs before correcting the GCM’s precipitation. This method was evaluated using the observed precipitation of 21 climate stations and five GCMs in the Jhelum River basin, Pakistan and India, for the period of 1986–2000 and also compared with the original linear scaling (OLS) method. The evaluation results showed substantial improvement in the corrected GCM precipitation, especially in case of mean and standard deviation values. Although PELS and OLS showed comparable results, the overall performance of PELS was better than OLS. After Evaluation, PELS was applied to the future precipitation from five GCMs for the period of 2041–2070 under RCP8.5 and RCP2.6 in the Jhelum basin, and the future changes in precipitation were calculated with respect to 1971–2000. According to average all GCMs, annual precipitation was projected to decrease by 4% and 6% in the basin under RCP8.5 and RCP2.6, respectively. Although two seasons, spring and fall, showed some increasing precipitation, the monsoon season showed severe decrease in precipitation, with 22% (RCP8.5) and 29% (RCP2.6), and even more reduction in July and August, up to 34% (RCP8.5) and 36% (RCP2.6). This means if the climate of the world follows the RCP8.5 and RCP2.6, then there will be a severe reduction in precipitation in the Jhelum basin during peak months. It was also observed that decline in precipitation was higher under RCP2.6 than RCP8.5.
Highlights
Global Climate Models (GCMs) are the most advanced numerical tools to understand the global climate system encompassing the atmosphere, oceans, and sea-ice [1,2] in order to project the global climate; and to investigate the potential changes in climate
We proposed a linear scaling technique, precipitation extended linear scaling (PELS), to correct the simulated future precipitation of GCMs
These values were increased after the correction with original linear scaling (OLS) for some GCMs: MIROC
Summary
Global Climate Models (GCMs) are the most advanced numerical tools to understand the global climate system encompassing the atmosphere, oceans, and sea-ice [1,2] in order to project the global climate; and to investigate the potential changes in climate. These models simulate outputs on a large grid size, ranging from 100 to 300 km horizontally, [3] which restrict their direct applications in the studies related environmental and hydrological assessment on local scale or basin scales [4]. The computational increases required to run an experiment as the resolution and domain size increases confines the study areas and the number of experiments to generate climate scenarios [1,9]
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