Evaluating spatial patterns of Asian meteorological drought variations and associated SST anomalies in CMIP6 models

Abstract

This study evaluates the spatial patterns of the Asian summer drought variations and the associated sea surface temperature (SST) anomalies in 42 Coupled Model Intercomparison Project (CMIP6) models during 1950–2014. The analysis is focused on the meteorological drought measured using the standardized precipitation index (SPI). The evaluation is conducted for short-term, medium-term, and long-term droughts represented by 3-month, 9-month, and 24-month SPI, respectively. Most of the 42 models are able to capture the observed leading spatial pattern of short-term and medium-term drought variations, characterized by a north-south dipole structure. In contrast, most models fail to simulate the observed leading spatial pattern of long-term drought variations, featuring a southwest-northeast oriented tripole distribution. Further analysis shows that most models can represent the spatial pattern of interannual variation of long-term drought with a north-south dipole structure, but cannot produce the spatial pattern of interdecadal variation and trend of long-term drought. In most of the models, the dipole pattern of short-term and medium-term drought variations is associated with an El Niño–type SST anomaly pattern in the tropical Indo-Pacific region, which is similar to the observations, so is the dipole pattern of interannual variation of long-term droughts. This is attributed to the ability of most models to capture the tropica Indo-Pacific SST-related large-scale atmospheric circulation anomaly pattern.