Indian summer monsoon precipitation dominates the reproduction of Circumglobal teleconnection pattern: A comparison of CMIP5 and CMIP6 models

Abstract

Abstract The zonal wavenumber-5 circumglobal teleconnection pattern (CGT) is one of the most critical atmospheric teleconnection patterns during boreal summer over the Northern Hemisphere (NH). CGT can exert significant climatic impact across NH including Europe, East Asia and North America but how reliable coupled climate models simulate the characteristics of CGT is poorly understood. Here, twenty coupled models with their respective versions in Coupled Model Intercomparison Project Phase 5 (CMIP5) and CMIP6 are selected to evaluate their performance on CGT simulation. We find that while both CMIP5 and CMIP6 models are able to capture the basic features of CGT in multi-model mean (MMM), there are large inter-model discrepancies in the simulation of CGT pattern among CMIP5 and CMIP6 models. High-skill models exhibit strong action center over west-central Asia, coinciding with the pattern derived from reanalysis, while the corresponding action center in low-skill models are weaker. Further analyses demonstrate that high-skill models are capable of simulating more realistic Indian Summer Monsoon (ISM) precipitation anomalies related to CGT. The resultant anomalous upper-tropospheric divergence over west-central Asia, acting as a Rossby wave source, can therefore excite the above-mentioned action center. This high- and low-skill model difference on CGT-ISM relationship is consistent in both CMIP5 and CMIP6. It is also found that high-skill models tend to simulate more realistic CGT-ENSO relationship. The relationship between simulation skills of CGT-ENSO correlation and CGT spatial pattern is attributed to the remote impact of ENSO on CGT wavetrain through affecting ISM precipitation anomalies.