Extreme precipitation weather events in the Qinghai Tibet Plateau and its surrounding areas and weather background classification based on self-organizing feature mapping
This paper makes a statistical analysis of the 6-hour extreme precipitation weather events on the Qinghai Tibet Plateau and its surrounding areas based on self-organizing feature mapping,by using precipitation products from observations of China automatic stations and CMORPH and NCEP reanalysis data during 2008-2014.It is found that the high value and frequency of 6-hour extreme precipitation are mainly distributed in the Southwest and Southeast of the plateau,the Sichuan Basin on the southeast side of the plateau and the area along the Himalayas to Hengduan Mountains on the south side of the plateau.The 6-hour extreme precipitation mostly occurred at 14:00 BST in the southwest of the plateau,at 20:00 BST in the southeast of the plateau,and at 08:00 BST in the Sichuan Basin and on the south side of the plateau.Using the self-organizing feature mapping method,the weather background in 6-hour interval over the plateau and its surrounding areas from 2008 to 2014 is divided into five types.The weather background types from Ⅰ to Ⅴ reflect the gradual change from summer to spring/autumn to winter,and the occurrence rate of 6-hour extreme precipitation weather events decreases as the weather type number increases.The total 6-hour extreme precipitation on the plateau mainly comes from that of type Ⅰ,and the area of 6-hour extreme precipitation decreases gradully from type Ⅱ to higher type number and tends to be scattered along the Gangdise mountain.Comparison of the weathe types shows that the dynamic forcing becomes stronger from type Ⅰ to higher type number,while the favorable thermal conditions of warm center,humidity and convective available potential energy are significantly reduced,this results in the obvious reduction of extreme precipitation areas on the plateau type by type.The distribution of favorable thermal conditions has a good relationship with the larger area of 6-hour extreme precipitation.As the thermal conditions weaken,the stronger dynamic conditions interacting with the complex terrain are important for the scattered extreme precipitation on the plateau.The convective available potential energy in the Sichuan Basin and on the south side of the plateau is significantly higher than that in the plateau.It is easy for the uplift forcing induced by the plateau to trigger convective instability,release more convective available potential energy and form stronger and more frequent extreme precipitation weather events.
Qinghai Tibet Plateauextreme precipitationweather typeself-organizing map
万方数据
维普
