Skill of CMIP5 climate models to reproduce the stability indices in identifying thunderstorms over the Gangetic West Bengal

摘要

The skills of present generation Global Climate Models (GCMs) have been evaluated in reproducing the climatology of stability indices for the identification of thunderstorm over the Gangetic West Bengal (GWB) region. Three different stability Indices viz., K-Index (KI), Boyden Index (BI), and Total Totals Index (TT) have been used in this study. Estimated values of TT and BI from reanalysis data have shown significant (at 10%) declining trends in pre-monsoon season however, they have a similar month-to-month variation of trends as simulated by the GCMs. Similar declining trends as reanalysis data were also noticed in March. On the other hand, most GCMs were able to reproduce the mean climatology of BI and TT but failed to show better skill for KI. The values of correlation between GCMs simulated TT and KI have shown decreasing trends from March to May months which was almost similar to the reanalysis data. In general, the frequency of occurrence of different types of thunderstorms was more in May and less in March as per the analysis of KI and TT indices from the reanalysis data. It was found that few GCMs were able to discriminate the occurrences of thunderstormon-thunderstorm like the reanalysis data. Over the study region, either of KI or TT or a combination of both may be used to study the occurrence of thunderstormon-thunderstorms. However, based on the analysis of climatological mean, trend, and threshold values, TT has shown better performance than KI. It is concluded that the present generation of GCMs has shown a mixed response in simulating the stability indices to identify thunderstormon-thunderstorms over the GWB.