Comparison on the Circulation Background of Tropical Cyclone Affecting the South China Sea Based upon Different Reanalysis Datasets

China Meteorological Administration launched China's Global atmospheric reanalysis program in November 2013, and the global atmospheric reanalysis product (CMA-RA) has been successfully developed. The performance of CMA-RA on describing the circulation background of tropical cyclone activity affecting the South China Sea is analyzed and compared with ERA5 and NCEP-Ⅰ, exploring the applicability of CMA-RA in tropical cyclone activity analysis, based on the tropical cyclone best track dataset compiled by Shanghai Typhoon Research Institute of China Meteorological Administration, CMA-RA, the fifth generation ECMWF atmospheric reanalysis dataset (ERA5) and the first generation atmospheric monthly reanalysis dataset of National Center for Environmental Prediction(NCEP) and National Center for Atmospheric Research(NCAR) from 1981 to 2020. The results are shown as follows. Three reanalysis datasets can basically depict the anomaly circulation characteristics of the key influence regions closely related to tropical cyclone activity affecting the South China Sea from July to October, including the Southern Oscillation, low-level zonal wind field in the Philippines to the eastern sea of the South China Sea, reverse distribution pattern of low-level zonal wind filed in the tropics, low-level vorticity from the Philippines to the central and eastern part of the South China Sea, environmental vertical wind shear in the tropical western Pacific, and mid-level humidity field from the South China Sea to the eastern sea of the Philippines. All datasets are highly similar in describing the Southern Oscillation, low-level zonal wind field and mid-level humidity field of key regions. CMA-RA and ERA5 have high agreement on the Southern Oscillation, low-level zonal wind characteristics and their relationship with tropical cyclone activity, which are closer than NCEP-Ⅰ. However, their characterization of low-level meridional wind field, relative vorticity and vertical wind shear are relatively different. Some circulations in the tropical Indian Ocean are relatively different with each other too. All datasets have similar ability to depict the key regions circulations in the extreme years of tropical cyclone activity, but they are different in area and intensity. They are highly consistent in the sea level pressure and low-level zonal wind characteristics, with CMA-RA and ERA5 being the most similar. The mid-level humidity of CMA-RA is consistent with ERA5, and they are both lower than NCEP-Ⅰ. But the characteristics of low-level relative vorticity and vertical wind shear are significantly different. CMA-RA has comparable performance with ERA5 and NCEP-Ⅰ in describing the circulation background of tropical cyclone activity affecting the South China Sea, and it's highly consistent with ERA5 on the whole. Therefore, it can provide an alternative atmospheric reanalysis dataset for the research of tropical cyclone activity in the South China Sea.