Features of the deep atmospheric boundary layer over the Taklimakan Desert in the summertime and its influence on regional circulation

To investigate the features of the extremely deep atmospheric boundary layer (ABL) over the Taklimakan Desert (TD) and its influence, this paper utilizes sounding data obtained from a month-long intensive field campaign carried out in July 2016 over the TD to study the structure of the 5,000-m-depth ABL over the desert and the features of its temporal and spatial variations. The differences and causes of the regional circulation are analyzed for both the deep ABL and shallow ABL over the TD. We show that (1) deep ABLs occurred frequently in the hinterland and the surrounding areas of the TD in July 2016. The numbers 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 numbers 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 1 July 2016. The diurnal variation of the ABL appears in such a manner that it develops and intensifies gradually from southeast to northwest direction. The middle of the desert witnesses large values of ABL heights. The ABL height in the desert is obviously higher than those in the surrounding oases and in the northern part of Xinjiang. (3) On 1 July 2016, a deep ABL process is accompanied by a strong easterly low-level jet on the following night, which triggers significant air accumulation and dynamic convergence in the lower-level atmosphere over the middle and west of the TD, thus intensifying the divergence and anticyclonic circulation at the 500-hPa middle-level atmosphere. (4) The influence of the deep ABL process on 1 July on the regional circulation mainly occurs below 400 hPa, while its influence is relatively small above 400 hPa. This type of influence is also regional, as it mainly occurs over the TD and its surrounding areas. This study enriches the understanding of the deep ABL process over the TD and its influence.