Abstract:

The probability of a rainstorm in southern Xinjiang is small, and it is challenging to forecast and give an early warning of such events. Rainstorms in southern Xinjiang have a short duration and heavy intensity, accompanied by short-term heavy rainfall events. Other heavy rainfall events are relatively long, without short-term heavy rainfall events. To explore the differences between the two rainstorm types in southern Xinjiang, hourly precipitation data from 2013 to 2019 of 426 automatic weather stations were used to compare and analyze the fine observation differences in short-term heavy rainstorms and those without short-term heavy rainfall events. Results showed that heavy short-term rainfall occurred majorly during summer in southern Xinjiang, and more than 70% of the stations experienced heavy short-term rainfall during rainstorms. Heavy short-term rainfall occurred majorly in July, which accounted for approximately 95% of heavy rain days. Rainstorms with heavy short-term rainfall in southern Xinjiang are mainly distributed in areas with an altitude lower than 2000 m. Those without heavy short-term rainfall events are mainly distributed in areas with an altitude higher than 2000 m. The rainfall characteristics at night of the two types of rainstorms are evident in southern Xinjiang. The diurnal variation characteristics of cumulative precipitation, precipitation frequency, and average precipitation intensity are similar between the entire rainstorm days and the rainstorm days with heavy short-term rainfall events in southern Xinjiang. However, they are different from the rainstorm days without heavy short-term rainfall events. The peak periods of accumulated precipitation, precipitation frequency, and average precipitation intensity for rainstorm days without heavy short-term rainfall events appear in the morning. The peak periods of accumulated precipitation and average precipitation intensity for rainstorm days with heavy short-term rainfall events appear in the evening and the first half of the night. Also, the peak periods of accumulated precipitation frequency mainly appear from the second half of the night to the morning. The relationship between precipitation intensity and accumulated precipitation during rainstorm days with heavy short-term rainfall events is closer than precipitation frequency. The highest proportion of rainstorms occurred at stations with an altitude of 2000-2500 m in southern Xinjiang, and the lowest occurred at stations with an altitude of less than 1000 m. There were significant differences in the observable characteristics of rainstorms with heavy short-term rainfall events and those without heavy short-term rainfall events in southern Xinjiang. The precipitation formation mechanism of the two is not the same and requires further research.

Key words: rainstorm, rainstorms with short-term heavy rainfall events, altitude, fine-scale characteristics, southern Xinjiang