The Impacts of Moisture Transport of East Asian Monsoon on Summer Precipitation in Northeast China

By using the ECMWF reanalysis daily data and daily precipitation data of 80 stations in Northeast China from 1961 to 2002, the impacts of moisture transport of East Asian summer monsoon on the summer precipitation anomaly in Northeast China, and the relationship between the variation of moisture budget and the establishment of East Asian summer monsoon in this region are studied. The results demonstrate that the moisture of summer precipitation in Northeast China mainly originates from subtropical, South China Sea, and South Asia monsoon areas. East China and its near coastal area are the convergent region of the monsoonal moisture currents and the transfer station for the currents continually moving northward. The monsoonal moisture transport, as an important link or bridge, connects the interaction between middle and low latitude systems. In summer half year, there is a moisture sink in Northeast China where the moisture influx is greater than outflux. The advance transport and accumulation of moisture are of special importance to pentad time scale summer precipitation. The onset, retreat, and intensity change of the monsoonal rainy season over Northeast China are mainly signified by the moisture input condition along the southern border of this area. The establishment of East Asian summer monsoon in this area ranges from about 10 July to 20 August and the onset in the west is earlier than that in the east. The latitude that the monsoon can reach is gradually northward from west to east, reaching 50°N within longitude 120°-135°E. In summer, the difference of air mass transport between summers with high and low rainfall mainly lies in whether more air masses originating from lower latitudes move northward through East China and its coastal areas, consequently transporting large amounts of hot and humid air into Northeast China.

Polar WRF V4.1.1.simulation and evaluation for the Antarctic and Southern Ocean

A recent version of the Polar Weather Research and Forecasting model(Polar WRF)has been upgraded to the version 4.X era with an improved NoahMP Land Surface Model(LSM).To assess the model performance over the Antarctic and Southern Ocean,downscaling simulations with different LSM(NoahMP,Noah),WRF versions(Polar WRF 4.1.1 and earlier version 4.0.3,WRF 4.1.1),and driving data(ERA-Interim,ERA5)are examined with two simulation modes:the short-term that consists of a series of 48 h segments initialized daily at 0000 UTC with the first 24 h selected for model spin-up,whereas the long-term component used to evaluate long-term prediction consists of a series of 38-41 day segments initialized using the first 10 days for spin-up of the hydrological cycle and planetary boundary layer structure.Simulations using short-term mode driven by ERA-Interim with NoahMP and Noah are selected for benchmark experiments.The results show that Polar WRF 4.1.1 has good skills over the Antarctic and Southern Ocean and better performance than earlier simulations.The reduced downward shortwave radiation bias released with WRF 4.1.1 performed well with PWRF411.Although NoahMP and Noah led to very similar conclusions,NoahMP is slightly better than Noah,particularly for the 2 m temperature and surface radiation because the minimum albedo is set at 0.8 over the ice sheet.Moreover,a suitable nudging setting plays an important role in long-term forecasts,such as reducing the surface temperature diurnal cycle near the coast.The characteristics investigated in this study provide a benchmark to improve the model and guidance for further application of Polar WRF in the Antarctic.