洞庭湖流域旱涝异常的时空分布及其与大气环流和水汽输送的关系

Based on the monthly precipitation data of 103 meteorological stations in the Dongting Lake Basin from 1960 to 2017 and NCEP/NCAR reanalysis data, combining the Z-index and the droughts-floods region index, in order to enhance the understanding of seasonal droughts-floods abnormality and possible direct influence factors, the spatial-temporal distribution characteristics of seasonal droughts-floods abnormality, the synchronic atmospheric circulation and water vapor transport feature in typical droughts-floods years in the basin over 57 years were analysed. The results showed that in the statistical sense, it was unlikely that the droughts/floods abnormality appeared for two consecutive years, and the frequency of coexistence of droughts-floods abnormality in spring and summer was higher than that in autumn and winter in the basin. The dry and wet evolution showed interannual characteristic and obvious spatial distribution in spring and autumn, showing interdecadal transition and wetting tendency in winter and summer. In addition, each season showed that flood was heavier than drought in statistical sense. The synchronic atmospheric circulation feature would exert significant impacts on the droughts-floods abnormality in the basin. When the meridional (zonal) circulation was strong, the droughts were more likely to occur in winter (summer) and spring (autumn). When the subtropical high ridge was northward, the droughts tended to occur in summer and autumn; when the subtropical high was strong and westward, the floods were more likely to occur in winter. The Z-index was significantly positively correlated with the net meridional water vapor flux in each season, and the net water vapor budget in spring, summer and autumn, and may be more closely correlated with precipitation dynamic condition in winter.