关键词: 内蒙古中西部, 2022年7月, 涝-旱转折, 气象干旱, 海温异常

Abstract:

The rainfall in July of 2022 in the central and western regions of Inner Mongolia was obviously less and showed a phased characteristic of more in the early stage and less in the late stage. The analysis of circulation distribution and configuration in different stages is of great significance for further improving precipitation forecast ability in flood season in this region. Daily precipitation of 116 national meteorological stations in Inner Mongolia, 130 climate indexes from the National Climate Center, daily reanalysis data from National Center for Environmental Prediction/National Center for Atmospheric Science (NCEP/NCAR) and monthly sea surface temperature (SST) data from the National Oceanic and Atmospheric Administration (NOAA) were used to analyze the causes of the flood-drought transition event in the central and western regions of Inner Mongolia in July 2022. The results are as follows: (1) In July 2022, the rainfall in the central and western regions of Inner Mongolia was seriously less, which was the least in the same period since 1991 in this region, and the meteorological drought was relatively serious. (2) From July 1 to 11, the precipitation was relatively more, the cold air path was northward and the intensity was weak, the Western Pacific Subtropical high was weak and its location was northward and westward, and the warm and cold air intermingled in the central and western regions of Inner Mongolia. In addition, the position of upper westerly jet was northward during this period, and the central and western regions of Inner Mongolia were located in the south of the jet axis, which was conducive to upper level divergence and the development of upward movement. While from July 12 to 31, the precipitation was obviously less, the meridian of circulation increased, the cold air activity path was more southerly and the intensity increased, the Western Pacific subtropical high was obviously stronger and the location was southward, which was not conducive to water vapor transport. In addition, the location of upper westerly jet was southward, and the central and western part of Inner Mongolia was located in the north of the jet axis, which was not conducive to upper level divergence and the development of upward movement. The stronger disturbance of the upper westerly jet in mid and late July was conducive to stimulating the meridional teleconnection wave train from East Asia to the Northwest Pacific, which led to the position of the Western Pacific subtropical high southward and less precipitation. (3) The abnormal SST from the Sea of Japan to the northwest of the North Pacific was one of the important external forcing signals that affect the amount of precipitation in central and western regions of Inner Mongolia. In July 2022, the SST in the region was abnormally high, and the cyclonic circulation triggered by the abnormal SST over the region weakened the meridional transport of warm and humid water vapor in the south, which was one of the reasons for the change of precipitation from flood to drought in central and western regions of Inner Mongolia.

Key words: the central and western part of Inner Mongolia, July of 2022, flood-drought alternation, meteorological drought, abnormal sea surface temperature