Analysis of Characteristics of Late Spring Cold and Atmospheric Environment Field of Extreme Types in the Centre of Yunnan-Guizhou Plateau
Based on the data of 45 conventional daily average temperature data,and reanalysis data(2.5° × 2.5°)in the centre of Yunnan-Guizhou Plateau from 1981 to 2021,using the calculation and classification of late spring cold index,composite analysis and so on,we analyzed the interannual and interdecadal variation characteristics of cold late spring in the central Yunnan-Guizhou Plateau,selected the extremely heavy grade and non-grade late of spring cold years as extreme types,then made contrastive analysis of the circulation characteristics in order to explore forecast indicators.Results showed that:(1)The regional annual standardization index of late spring cold in the centre of Yunnan-Guizhou Plateau showed a downward trend from 1981 to 2021,and it had a very obvious mutation of late spring cold index around 1998(α=0.01).The extremely heavy grade and the heavy grade of late spring cold years basically occurred in the 1980s and 1990s,respectively.The light grade and no grade late spring cold years mainly occurred in the 21st.(2)The polar vortex was above-normal on 500 hPa in extremely heavy grade years.It presented an abnormal circulation pattern with high in the west and low in the east.It was helpful for increasing the circulation radial degree in East Asia.The temperature in the south of 50° N was basically negative anomaly distribution,indicating that the cold air activity was extremely active,resulting in a strong quasi-static front on the ground.At the same time,it was controlled by the easterly airflow at the east side of the anomalous cyclonic circulation on Yunnan-Guizhou Plateau at 700 hPa,and it converged with the easterly airflow at the bottom of the anomalous anti-cyclonic circulation in North China over the Yunnan-Guizhou Plateau,it was helpful for transferring water vapor from the South China Sea and the East China Sea to the Yunnan-Guizhou Plateau,thus facilitating the formation of low temperature and precipitation weather.While the above situation was opposite in the year of non-grade late spring cold years.(3)It was all the eastern type of El Nino phenomenon in the early summer,autumn,winter and the same period of spring in the extremely heavy grade late spring cold year,while it was all the central type of El Nino phenomenon in the early summer,autumn,winter and the same period of spring in the non-grade late spring cold year.
standardized index of late spring coldextreme typeYunnan-Guizhou quasi-stationary frontcirculationsea surface temperature
万方数据
维普
