The paper investigates the vertical circulation structure of the western Pacific subtropical high (STH) and its interannual variation features in relation tO East Asian subtropical summer monsoon and external thermal ...The paper investigates the vertical circulation structure of the western Pacific subtropical high (STH) and its interannual variation features in relation tO East Asian subtropical summer monsoon and external thermal forcing by using the high-resolution and good-quality observations from the 1998 South China Sea Summer Monsoon Experiment (SCSMEX), the NCEP 40-year reanalysis data and relevant SST and the STH parameters. It is found that the vertical circulation structures differ greatly in features between quasi-Stationary and transient components of the western Pacific STH. When rainstorms happen in the rainband of East Asian subtropical monsoon on the STH north side, the downdrafts are distinct around the ridge at a related meridian. The sinking at high (low) levels comes from the north (south) side of the STH, thereby revealing that the high is a tie between tropical and extratropical systems. The analyses of this paper suggest that the latent heat release associated with subtropical monsoon precipitation, the offshore SST and East Asian land-sea thermal contrast have a significant effect on the STH interannual anomaly. Our numerical experiment shows that the offshore SSTA-caused sensible heating may excite an anomalous anticyclonic circulation on the west side, which affects the intensity (area) and meridional position of the western Pacific STH.展开更多
The influence of eddy viscosity on the distribution of subtropical quasi-stationary planetary waves in summer is analysed theoretically.It is found that since the basic flow is very weak,the eddy viscosity may play an...The influence of eddy viscosity on the distribution of subtropical quasi-stationary planetary waves in summer is analysed theoretically.It is found that since the basic flow is very weak,the eddy viscosity may play an impor- tant role for the subtropical planetary-scale motion in summer. A linear,quasi-geostrophic,34-level spherical coordinate model is also utilized to calculate the differences of quasi-stationary planetary waves and of quasi-stationary disturbance pattern responding to forcing by topography and heat sources under the different eddy viscosities.The computed results show that the coefficient of eddy viscosity considerably influences the strength of the subtropical planetary-scale circulation in summer.展开更多
基金The National Natural Science Foundation of China (No.49635170)The program of Study on Regional Climate Variation and Mechani
文摘The paper investigates the vertical circulation structure of the western Pacific subtropical high (STH) and its interannual variation features in relation tO East Asian subtropical summer monsoon and external thermal forcing by using the high-resolution and good-quality observations from the 1998 South China Sea Summer Monsoon Experiment (SCSMEX), the NCEP 40-year reanalysis data and relevant SST and the STH parameters. It is found that the vertical circulation structures differ greatly in features between quasi-Stationary and transient components of the western Pacific STH. When rainstorms happen in the rainband of East Asian subtropical monsoon on the STH north side, the downdrafts are distinct around the ridge at a related meridian. The sinking at high (low) levels comes from the north (south) side of the STH, thereby revealing that the high is a tie between tropical and extratropical systems. The analyses of this paper suggest that the latent heat release associated with subtropical monsoon precipitation, the offshore SST and East Asian land-sea thermal contrast have a significant effect on the STH interannual anomaly. Our numerical experiment shows that the offshore SSTA-caused sensible heating may excite an anomalous anticyclonic circulation on the west side, which affects the intensity (area) and meridional position of the western Pacific STH.
文摘The influence of eddy viscosity on the distribution of subtropical quasi-stationary planetary waves in summer is analysed theoretically.It is found that since the basic flow is very weak,the eddy viscosity may play an impor- tant role for the subtropical planetary-scale motion in summer. A linear,quasi-geostrophic,34-level spherical coordinate model is also utilized to calculate the differences of quasi-stationary planetary waves and of quasi-stationary disturbance pattern responding to forcing by topography and heat sources under the different eddy viscosities.The computed results show that the coefficient of eddy viscosity considerably influences the strength of the subtropical planetary-scale circulation in summer.
