East Asian presummer precipitation in the CMIP5 at high versus low horizontal resolution

Abstract

ABSTRACTInevitable drawbacks occur when the Asian monsoon is simulated at a horizontal resolution that is too low to resolve topographic effects and sub‐grid processes. By comparing the Coupled Model Intercomparison Project (CMIP) phase 5 simulations conducted at higher (∼1°) and lower (∼3°) horizontal resolutions, this study attempted to extend understanding of potential resolution limits in simulating the East Asian presummer climate. April–May is found to have considerable resolution‐dependent contrasts in position and strength of precipitation (spring rains and pre–Meiyu) among the simulations. The low‐resolution models cannot simulate ascending vertical motion over the mountainous regions in the southern Tibetan Plateau and subtropical East Asia, which coincides with the overestimation of the strength of the lower‐tropospheric westerly in 90°–105°E and of the downstream southerly in 110°–130°E. Because of the southerly wind bias, the East Asian presummer precipitation simulated in the low‐resolution models is lower in amount and located farther north compared with the observed and high‐resolution models. Despite distinct large‐scale climatology between April and late May, the East Asian precipitation contrasts in these two periods are similar between the high‐ and low‐resolution models, which could be possibly explained as a systematic response to resolution. Systematically less precipitation in the high‐resolution model compared with the low‐resolution model is also observable over the Maritime Continent, whereas a further connection to the East Asian precipitation simulation remains unclear. Regarding projected changes, the resolution‐dependent contrasts are also considerable; the contrasts further suggest potential regional interactions such as between the subtropical South and East Asia (10°–20°N).