华南春季降水和水汽输送的年代际变化特征

The characteristics of spring precipitation and water vapor transport in South China were analyzed by using observational data and the National Centers for Environmental Prediction （NCEP） reanalysis data. The results show that, during the spring, each component of the water cycle （precipitation, wind field, specific humidity, water vapor transport, etc.） in South China exhibits a notable interdecadal variability. An abrupt increase in spring precipitation occurred in the early 1970s. During the dry period from 1958 to 1971, a water vapor flux divergence （positive divQ） existed in South China, which may have led to the deficiency in rainfall. However, during the wet period from 1973 to 1989, there was a remarkable water vapor flux convergence （negative divQ） in South China, which may have resulted in the higher rainfall. The interdecadal variability of water vapor transport is closely related to the interdecadal variability of wind fields, although the interdecadal variability of specific humidity also plays a role to some extent, and the interdecadal variability of the zonal water vapor transport contributes much more to the interdecadal variability of spring precipitation than the meridional water vapor transport.

Interdecadal Variability of Spring Precipitation Over South China and Its Associated Atmospheric Water Vapor Transport

The characteristics of spring precipitation and water vapor transport, as well as the related atmospheric circulation in South China are analyzed by using the data of observational and NCEP reanalysis data. The results show that spring precipitation in South China account for 32% of annual total, the water cycle (precipitation, wind field, water vapor transport, etc.) and the related atmospheric circulation in spring together show a notable interdecadal variability. The spring precipitation has an abrupt change in the turning point year of about 1972, which has undergone a significant increase since the early 1970s. In the period of relatively droughty years, the related atmospheric circulation is conductive to the formation of the south wind in eastern China, so there has anomalous south wind in the northern boundary of South China that make a huge outflows of water vapor, and existed a water vapor flux divergence (positive div ) in this region, causing deficient rainfall. In the period of relatively wet years, the related atmospheric circulation is conductive to the formation of the south wind in eastern China, so there has anomalous north wind in the northern boundary of South China that make a little outflows of water vapor, and existed a water vapor flux convergence (negative div ) in this region, causing sufficient rainfall.