The surroundings of the Bay of Bengal (BoB) suffer a lot from the extreme rainfall events during Indian summer monsoon (ISM), controlled by monsoon intraseasonal oscillation (MISO). However, the simulation of ISM precipitation is still a challenge in state-of-the-art models, particularly at the intraseasonal timescale. Previous studies suggested that the sea-air interaction is an important factor for the monsoon precipitation. In this study, the performances of sea-air interaction related to MISO during the ISM in the 6th Couple Model Intercomparison Project (CMIP6) models are evaluated. The results show that the intraseasonal sea surface temperature (SST) anomalies are well captured by most models, but the latent heat flux is not always consistent with the variation of intraseasonal SST. Such bias is attributed to the weak intraseasonal wind anomalies. In addition to the turbulent heat fluxes, the turbulent momentum flux plays an important role in the north-propagation of MISO. The underestimated simulation of boundary layer convergence leads to the decrease of vertical moisture flux, weakening the MISO and precipitation in models. Thus, a better simulation of air-sea interaction benefits to the improvement of monsoonal precipitation.

Bay of Bengal, ocean-atmosphere interaction, CMIP6, latent heat flux, intraseasonal variability