In recent years, Ningxia relies on unique natural resources to develop vigorously starry sky tourism industry, but the starry sky tourism is greatly affected by meteorological conditions. Based on the meteorological observation data at 25 weather stations of Ningxia, reanalysis data from European Centre for Medium-Range Weather Forecasts and radiance data of satellite from National Oceanic and Atmospheric Administration, the composite evaluation model of climate resources suitability of starry sky tourism in Ningxia is established from five aspects, such as cloud cover, light pollution, visibility, seeing and human body comfort degree, and the climate suitability of starry sky tourism in Ningxia is evaluated in different seasons. The results show that the starry sky tourism is suitable or very suitable in most areas of Ningxia all year round, while the suitability in urban area of cities (counties and districts) is relatively lower. The very suitable area to starry sky tourism is the largest in summer, and mostly in the plain area, followed by autumn and winter, and that is the smallest in spring.

In order to explore the characteristics and influence factors of atmospheric boundary layer inversion in Yinchuan City and their relationship with winter PM_2.5 pollution, based on the sounding and surface meteorological observation data at Yinchuan meteorological station and the air quality monitoring data in Yinchuan City from 2015 to 2020, the characteristics of atmospheric boundary layer inversion and surface meteorological elements are analyzed. And on this basis that the influence of inversion and surface meteorological elements on PM_2.5 pollution weathers in winter is explored. The results are as follows: (1) The inversions in atmospheric boundary layer are more easily to occur in the early morning than in the evening in Yinchuan City, and most of the inversions are ground inversions, they are stronger and thinner than suspension inversions. The inversion frequency and thickness are the largest in winter and the smallest in summer, while the inversion intensity is the strongest in autumn and the weakest in summer. (2) In winter, the inversions are easily to occur on a sunny day with average surface wind speed from 1.0 to 1.5 m·s^-1 and relative humidity from 30% to 60%. (3) Ground inversion is one of the main meteorological factors affecting PM_2.5 pollution weathers in winter. When the inversion thickness exceeds 596 m and the intensity exceeds 1.4 ℃·(100 m)^-1, PM_2.5 pollution weathers are easily to occur, and the pollution is aggravated with the increase of inversion thickness and intensity. (4) Under PM_2.5 pollution weathers in winter, the sky is mostly sunny in the early morning, the average surface wind speed is usually less than 1.3 m·s^-1, the relative humidity is greater than 54%, and the pollution is aggravated with the increase of humidity. (5) The boundary layer height is significantly negatively correlated with PM_2.5 mass concentration, and the lower boundary layer height is, the heavier PM_2.5 pollution is.