Abstract:

Select daily precipitation, temperature, conventional ground and upper-air observation data, the national center for environmental prediction reanalysis data collected from seven national meteorological observatories in the Tacheng area of Xinjiang, China, from November 2000 to March 2019 to determine the warm snowstorm weather process in the Tacheng area over the past 20 years. The analysis results show the following: (1) The warm-area blizzards in the Tacheng area occurred in Tacheng Station, Yumin Station, and Emin Station in the Tacheng-Emin Basin, and Tacheng Station had the most frequent occurrences; in terms of time distribution, the frequency of warm-area blizzards occurred in November and December and was primarily concentrated in mid-November to early December, followed by January and the least in February. (2) The blizzard in the warm area of Tacheng is divided into three types: low trough front type, horizontal trough bottom type, and northwest jet type. The surface low pressure is primarily in the west and northwest path. The low trough front type is the most typical warm-area blizzard situation, which primarily occurs from November to early December and occurs in the confluence area of the frontal area of the low trough in West Siberia and the mid-latitude short-wave trough of the southern branch; the surface low pressure has a northwest path. The horizontal trough bottom type occurs primarily from November to January of the following year and occurs in the strong frontal area in which the westward airflow at the bottom of the polar frontal area and the warm and humid southwesterly airflow at the mid-latitude converge; the surface low pressure follows a westward path. The northwest jet type primarily occurs from November to December. It occurs in the northwesterly airflow in the polar frontal area, and the surface low pressure has a northwest path. (3) The superimposed area of 500-300 hPa strong northwest or westward jet, 700 hPa westward low-level jet, and 850 hPa warm shear is consistent with the blizzard fall area in the warm area. The low trough front type and the northwest jet type produce blizzards in the frontal warm area, and the horizontal trough bottom type produces blizzards in the low-pressure right warm front. (4) The water vapor in the low trough front type and the horizontal trough bottom type is in a westward path. The water vapor from the Mediterranean Sea and the Arabian Sea is improved by the Caspian Sea, Aral Sea, and then transported to the blizzard area. The northwest jet type has two water vapor types in the west and northwest. The water vapor from the high-latitude Barents Sea and the water vapor from the mid- and low-latitude Caspian Sea, Aral Sea, the Mediterranean Sea, and the Arabian Sea converge near Lake Balkhash and are transported to the blizzard area. The strong convergence center is located between 850 hPa and 700 hPa.

Key words: blizzard in warm area, temporal and spatial distribution characteristics, synoptic classification, three-dimensional configuration of weather system