Differences of the Low Level Easterly Jet over Tarim in Rainstorm and Non-Rainstorm Processes in Southern Xinjiang

Herein, the relation between the easterly jet in Tarim and the precipitation in southern Xinjiang was analyzed based on the precipitation data of the southern Xinjiang station from 1981 to 2020 and the ERA5 reanalysis data of the European Center. Results show that: (1) The low-level easterly jet in Tarim played an important role in the southern Xinjiang rainstorm. The stronger the precipitation grade and the wider the heavy precipitation range, the higher the proportion of the Tarim low-level easterly jet. More than half of the heavy rain and rainstorm days in southern Xinjiang were accompanied by the Tarim low-level easterly jet. Furthermore, the occurrence rate of the Tarim low-level easterly jet in a large-scale rainstorm process in southern Xinjiang was as high as 85.0%. (2) The Tarim low-level easterly jet advanced farther westward, with the easterly layer being thicker in the heavy rain in southern Xinjiang, and formed a lasting east–west wind convergence zone with the westward airflow in western southern Xinjiang. Inthe non-rainstorm process of the low-level jet , a strong northerly airflow appeared in the central Tarim Basin, which cut off the westward extension of the Tarim easterly low-level jet and maintained it mainly in the eastern part of southern Xinjiang. The thickness of the easterly layer was also slightly lower than that in the rainstorm in southern Xinjiang. (3) Unlike the low-level jet without a rainstorm in the monsoon region of China, the Tarim low-level jet without a rainstorm exhibited considerable instability similar to the Tarim easterly jet in the rainstorm process in southern Xinjiang. (4) The easterly water vapor transport path associated with the Tarim easterly low-level jet was the main water vapor transport channel in the rainstorm process in southern Xinjiang, while the westward path was the main water vapor transport channel in the non-rainstorm process of the low-level jet. (5) During the non-rainstorm process of the low-level jet, the moisture conditions are better in the western part of Southern Xinjiang, but the vertical upward motion is weaker. In the eastern part of Southern Xinjiang, the vertical upward motion is stronger, but the moisture conditions are poorer. Consequently, both circumstances hinder the occurrence of heavy rainfall.