Ocean–atmosphere coupling modulates the parametric impacts of cloud and convective processes on the East Asian summer monsoon precipitation simulations

Abstract

The simulations of East Asian summer monsoon (EASM) precipitation are highly uncertain in climate models due to cloud and convection parametrizations. The parameter‐perturbed ensemble (PPE) is an effective approach to quantify these uncertainties, yet previous studies mainly focused on atmosphere‐only PPEs (APPEs), neglecting the impacts of ocean–atmosphere interactions. This study compares two sets of long‐term PPE simulations using atmosphere‐only and ocean–atmosphere coupled climate models, revealing that the parametric sensitivity and associated mechanisms are quite different between the two PPEs. Convective parameters dominate precipitation uncertainty in the APPE, but their relative contribution is substantially reduced in the ocean–atmosphere coupled PPE (CPPE). The effects of convective parameters are weakened in the CPPE because the systematic cold bias in sea‐surface temperature (SST) reduces convection–circulation interactions. In contrast, the effect of the low‐cloud parameter is enhanced, with its precipitation response reversing from slightly negative in the APPE to strongly positive in the CPPE. This reversal arises because perturbations in the low‐cloud parameter modify the global SST pattern, which further alters atmospheric circulation and moisture transport to the EASM region. These changes jointly reduce the relative contribution of convective parameters and increase that of the low‐cloud parameter. Because the effect of convective parameters is a function of SST, their influences can also be modulated by the low‐cloud parameter in coupled simulations. These findings highlight the critical role of ocean–atmosphere coupling and associated SST bias induced by coupling in shaping parametric sensitivity.