Key process diagnostics for monsoon intraseasonal oscillation over the Indian Ocean in coupled CMIP6 models

Abstract The simulations of the monsoon intraseasonal oscillation (MISO) during Indian summer (ISM) are evaluated with 19 atmosphere–ocean coupled general circulation models (CGCMs) from phase 6 Coupled Model Inter-comparison Project (CMIP6). focus is on northward propagation MISO. CMIP6 have great improvement in simulating mean rainfall, as 17 out can reasonably simulate rainfall. However, many fail to reproduce realistic patterns rainfall and MISO amplitude, particularly over land region. underestimation amplitude still a notable model bias CMIP6. Moreover, 9 cannot generate features, some even stationary pattern. Process diagnostics based seasonal vertical zonal wind shear, low-level moisture, vortex tilting also examined. It found that accuracy strongly associated In contrast, fidelity not dependent simulation skill for state. addition, decomposition analysis illustrates meridional shear velocity crucial simulation. poor tiling caused by weak convection, absence downdraft north convection center. coupling between moisture boundary layer free troposphere may be responsible capturing motions. summary, useful metric evaluating