The Features of the Summertime Deep Atmospheric Boundary Layer over the Taklimakan Desert and Its Influence on the Regional Circulation

In order to investigate the features of the summertime deep atmospheric boundary layer (ABL) over the Taklimakan Desert (TD) and its influence, the paper utilizes the sounding data in the hinterland and the surrounding areas of the TD in July 2016 to study the structure of the deep ABL over the desert and its features of temporal and spatial variations. The differences, causes and the internal physical mechanism of the regional circulation under different land surface thermal conditions over the TD are also investigated. We show that: (1) Deep ABL occurred frequently in the hinterland and the surrounding areas of the TD in July 2016. The number of days when the ABL height reached 4,000 m at Tazhong, Minfeng, Korla, Ruoqiang and Kashgar are 8, 9, 5, 4, and 2 respectively; and the number of days when the ABL height exceeded 3,000 m at the above locations are 20, 22, 13, 15 and 5 respectively. (2) The ABL height reached 5,000 m over the TD on July 1, 2016. The diurnal variation of the ABL appears in such a manner that it gathers strength gradually from the southeast to the northwest direction. The middle of the desert witnesses the big values of the ABL heights. The desert ABL height is obviously higher than that of the surrounding mountains and the oases. (3) On July 1, 2016, the deep ABL process is accompanied with the strong eastward low level jet on the following night, which triggers significant air accumulation and dynamic convergence in the lower level atmosphere over the middle and the west of the TD and hence intensifies the divergence and the anticyclonic circulation at 500 hPa middle level atmosphere. (4) The influence of the deep ABL process on July 1 on the regional circulation occurs mainly below 400 hPa, while its influence is quite small above 400 hPa. This kind of influence is also regional, mainly over the TD and its surrounding areas. The study helps deepen the understanding of the deep ABL process over the TD and its influence. It can also provide scientific evidence for the parameterization of the ABL in the regional numerical model.