Interdecadal Changes of the South Asian High in CMIP5/6 and Projection of Its Future Changes

Abstract

Abstract Different from the significantly lifted geopotential height (H) that exhibits an enhanced South Asian high (SAH) under global warming, the eddy geopotential height (H′) can objectively reflect the decadal decline of SAH in the late 1970s. In this study, the capability of CMIP5/6 models for simulating the decadal decline of the SAH is assessed. Both the CMIP5 and CMIP6 models can yield better simulations of H′ compared to H simulations with smaller model spreads. CMIP6 models demonstrate better performances than CMIP5 in the simulation of variability and decadal changes of the SAH, which is attributed to the more reasonable simulations of upper-tropospheric eddy temperature (T′) by CMIP6. There is a large uncertainty of the SAH projection, since the SAH displays obviously different variations between SSP1-2.6 and SSP5-8.5. The internal climate variability may play a more important role in influencing the decadal variations of SAH compared to the anthropogenic forcing in the future twenty-first century, although both the external forcing and internal climate variability are important for the historical decadal changes of SAH.