Fidelity of the latest high-resolution CORDEX-CORE regional climate model simulations in the representation of the Indian summer monsoon precipitation characteristics

This study evaluates the fidelity of the latest high-resolution CORDEX-CORE individual model (i.e., REMO2015, COSMO-crCLIM-v1-1, and RegCM4.7) simulations and their multi-model mean (MMM) in simulating the spatio-temporal characteristics of the Indian summer monsoon (ISM) precipitation during 1980-2015. The present study focuses on the mean, extreme, onset date, and intraseasonal variability and its propagation characteristics of the ISM. In addition, the evaluation of the recent IMDAA reanalysis is also presented. The results show that the MMM produced a more realistic representation of the spatio-temporal distribution of seasonal mean precipitation and wet-day frequency/intensity than any individual CORDEX model. It is noted that all simulations (except for the REGCM model) largely captured the observed spatial patterns of extreme precipitation indices (i.e., R99p and Rx1day) with some variation in precipitation spatial variability. The skill of simulations in representing the observed frequency of most severe precipitation events is relatively low, although their performance for precipitation intensity is considerable. On the other hand, the IMDAA reanalysis has shown good skill with overestimation of observed precipitation over the regions of northeast India and Indo-Gangetic plains, which may be associated with the increased atmospheric instability due to orographic lift. Furthermore, the observed intraseasonal variability of the summer monsoon (i.e., active and break spells) and it's northward and eastward propagation characteristics have been well captured by the IMDAA as well as the CORDEX models (except for the REGCM). The REGCM has shown a northward rather than a westward stretch of monsoon precipitation during the active and break phases and hence the propagation characteristics are also unclear in the REGCM. It has been observed that the low-pressure system (with a slightly northward gradient) is confined to the region of central India in the REGCM which explains the northward shift of monsoon trough activity and precipitation. The observed variability of monsoon onset has been well reproduced by the IMDAA. Overall, the IMDAA has shown better performance than the CORDEX models in all cases/aspects, and the COSMO model has been found to be the best performing model among the three CORDEX models and is in line with the skills of IMDAA and MMM, although COSMO has an early onset of monsoon.