Interannual Variability of August Precipitation in China Associated With the Antarctic Sea Ice Anomaly

Abstract

Through observational analysis and atmospheric simulation experiments, the relationship between sea ice in the region of South Pole and August precipitation in China was determined. Results indicate that the leading mode of August precipitation in China is significantly correlated with July sea ice concentration (SIC) in South Pole, specifically in eastern Indian Ocean (EIO) region. Typically, the SIC growth is followed by positive rainfall anomalies in the middle and lower reaches of Yangtze River Basin (YRB) and Northeast China (NEC), while South China (SC) is under the control of negative rainfall anomalies. Precisely, owing to the temporal persistence of sea ice in the South Polar region from May to August, sea ice anomalies exert a strong influence on August atmospheric stability in EIO of Southern Hemisphere via regulating turbulent heat flux and air temperature anomalies. As SIC increases, the atmospheric circulation in horizontal exhibits the characteristics of the Antarctic Oscillation (AAO) positive phase, affecting the zonal wind anomalies. Subsequently, the anomalous circulation with a barotropic structure propagates to Australia and the East Asian via the strengthened vertical meridional cells and zonal winds. Moreover, numerical simulations confirm that due to the growth of South Polar sea ice in EIO, abnormal cyclone and anticyclone appear over North China and SC respectively, together with the moisture converging anomalies in the middle and lower reaches of YRB, and diverging anomalies in SC. Accordingly, these atmospheric circulation anomalies triggered by Antarctic sea ice conducive to a wet (dry) August in northern (southern) China.

Interdecadal change in the relationship between the South China late rainy season rainfall and equatorial Pacific SSTs

“…Accordingly, anomalous cyclonic circulations over the WNP would lead to SC rainfall surplus in JA , Li et al 2021b. The related cyclonic/anticyclonic circulations can be influenced by multiple climate systems and external forcings, such as subtropical westerly jet, sea ice over the East Siberian Sea and Antarctic, SST anomalies over the North Atlantic, Maritime Continent and equatorial Pacific , Ge et al 2022, Zhou et al 2022, Wang et al 2023a, Xiao et al 2024. Particularly, suggested that the enhanced JA SC rainfall and related cyclonic circulation anomalies can be excited by warm SST anomalies over the central equatorial Pacific (CEP).…”