资源环境科技发展态势分析平台

A 23-year integration of a Regional-Coupled Ocean-Atmosphere Model (RCOAM) centred over the Indian monsoon region is validated with observations and analysis for its seasonal climatology, evolution, and variability at intraseasonal and interannual scales. The RCOAM has the Regional Spectral Model (RSM) as its atmospheric component and Regional Ocean Model System (ROMS) as its oceanic component. They are both coupled at 15 km grid spacing with identical grids, without applying any form of flux correction and are forced with global fields of atmospheric and oceanic reanalysis. The verification indicates that the RCOAM simulation simulates the mean Indian SummerMonsoon (ISM) rainfall climatology and SST in the neighbouring oceans reasonably well with finer details apparent along the orography (e.g. Western Ghats, Himalaya) and along the upwelling regions of the coastal oceans. In addition the evolution of the ISM at its onset and its devolution around the time of demise in the RCOAM simulation both in the atmosphere and the ocean conform to its well known features and reinforce the coupled ocean-atmosphere phenomenon of the ISM. The intraseasonal variations in the RCOAM simulation also adhere to the observed composite of dry and wet spells of the ISM, with the low-level flow in the latter (former) counteracting (enhancing) the low-level atmospheric ISM climatological flow. The interannual variations in relation to the remote ENSO variations are also validated with respect to the observations. It is also shown that the variations of the length of the ISM to the seasonal anomalies of the ISM both in the RCOAM simulation and observations is largely a result of the ENSO teleconnection. However, significant systematic bias in surface fluxes, cloud fraction, SST, and precipitation of the RCOAM simulation of the ISM is also noted.