High resolution regional climate simulation over CORDEX East Asia phase II domain using the COAWST Ocean-atmosphere coupled model

This study reveals the simulation results of a regional ocean-atmosphere coupled model (Coupled Ocean-Atmosphere-Wave Sediment Transport Modeling System, COAWST) for the Coordinated Regional Climate Downscaling Experiment (CORDEX) East Asia Phase II, which covers a period of 21 years (1989–2009) at a horizontal resolution of 25 km. The coupled simulation (CPL) and the uncoupled atmospheric simulation (UNCPL) are compared with observations to assess their capability of capturing the climatology characteristics over East Asia. The simulated sea surface temperature (SST) in CPL is generally overestimated (underestimated) in summer (winter) over most CORDEX-EA-II regions. Both CPL and UNCPL can capture the spatial patterns of seasonal air temperature over East Asia well. However, they both simulate cold biases of the winter temperature over most regions of China. CPL can reduce the cold biases over certain regions, which may be related to the increased cloud cover reflecting more longwave radiation to the ground. Additionally, CPL improves the simulation results of summer precipitation, diminishing the dry biases over northern Bay of Bengal and South China Sea. This improvement may be related to the better description of moisture transportation and precipitable water. Furthermore, The CPL experiment can better simulate the inter-annual variability of summer precipitation and the relationship between SST and precipitation, especially over the South China Sea and Philippines Sea. CPL also captures the northward propagation and amplitude of boreal summer intra-seasonal oscillation precipitation anomalies more accurately. These findings highlight the importance of ocean-atmosphere coupling processes to simulate multiscale climate changes in the CORDEX-EA-II regions.