Abstract: Using the daily meteorological data of the ground and sounding observation of 16 stations, and the tenminute observational data of the mobile boundary layer wind profile radar(Airda K/LLX802J)in July 2013 in Ningxia Province, China, the atmospheric boundary layer structural characteristics of the sunny and rainy days in summer at Hetao arid region are analyzed with the statistical methods. The results show as follows: (1)The atmospheric boundary layer height is generally from 1644.3 to 3024.5m in the summer sunny days, with an average of 2309.4m. In contrast, it is from 494.2 to 2187.5m in the summer rainy days, with an average of 1457.2m. The maximum atmospheric boundary layer thickness of Hetao arid region in the summer sunny day is 3024.5m, which is 900m smaller than that of Dunhuang Gobi region.(2)In the summer sunny days, the potential temperature of Hetao arid region increases obviously with the rise of height in the atmospheric boundary layer below 700m, which average increasing rate is 0.76℃·(100m)^-1. Meanwhile, the multi-layer temperature inversion frequently occurs in the atmospheric boundary layer from 50 to 1500m in the summer rainy days. The average increasing rate of potential temperature with height-rising is 0.51℃·(100m)^-1 in the summer rainy days. Below the 700m atmospheric boundary layer, the potential temperature increasing rate of the sunny days is bigger than that of the rainy days. But above the 700m atmospheric boundary layer, the potential temperature increasing rate of sunny days is smaller than that of the rainy days.(3)The atmospheric boundary layer specific humidity decreases with the rising of height both in the sunny and rainy days in Hetao arid region in summer. The summer boundary layer mean specific humidity of Hetao arid region is generally 4.88-9.13g·kg^-1 in the sunny days, and 6.64- 12.35g·kg^-1 in the rainy days. At the meantime, it is more prone to appear multi-layer humidity inversion below the 1500m atmospheric boundary layers in the summer rainy days.(4)The atmospheric boundary layer average wind speed of Hetao arid region is 3.0m·s^-1 in summer sunny days, but 3.85m·s^-1 in the summer rainy days. The average wind speed increasing rate of the atmospheric surface layer at the region is 1.30m·s^-1·(100m)^-1 with the altitude in summer sunny days, but 1.35m·s^-1·(100m)^-1 in summer rainy days. In summer, the atmospheric boundary layer above 500m mainly prevail the easterly and southerly winds at Hetao arid region. At the same time, the wind speed and direction shear often occurs in the atmospheric boundary layer below 100m in the summer sunny days, and below 400m in the summer rainy days. The results of the paper are helpful to reveal and understand the summer atmospheric boundary layer structural characteristics and changes at Hetao arid region, and also have a positive significance to promote the development of the boundary layer parameterization scheme in weather numerical model at Hetao arid area.

Key words: Hetao arid region, atmospheric boundary layer, summer sunny day, summer rainy day, wind profile radar