Statistical Analysis of the Meteorological Conditions for Astronomical Observation at Mount Dashanbao in the Zhaotong City

This paper statistically analyzes the meteorological conditions of Mt.Dashanbao by using the meteorological data from the year 1960 to the year 1988, which were collected by the Meteorologic Bureau of the Zhaoyang District, Zhaotong City, Yunnan Province. We focus on meteorological parameters particularly relevant to the selection of an excellent solar observation site. We investigate the annual variation patterns of the parameters with wavelet analysis. We have found that the monthly relative humidity, average sunshine time, and average temperature all have nearly-fixed variation cycles of about one year, which is very important for ground-based solar observation. In addition, these parameters show two distinct steady stages in each year, and we call them the dry season (from November to April of next year) and wet season (from May to October). In the dry season, the monthly relative humidity, mean temperature, and average cloud amount are low, while the montly average sunshine-time and wind-speed values are relatively large. The average wind speed over a long time is still low, even though at some occasions high wind speed can influence observation. In addition, the wind direction is very stable there, so we can easily overcome the drawback of the occurrences of high wind speeds. In the wet season, the site does not fit well for solar observation due to the poor meteorological conditions. However, we do not rule out short-lasting meteorological conditions for observation in the wet season. Moreover, the site on Mt.Dashanbao is not far from the Yunnan Observatory, Chinese Academy of Sciences, Kunming, China. The convenient transportation can save a significant amount of financial resources in the installation, operation, and maintenance of telescope(s). Based on our statistical results, we conclude that Mt.Dashanbao is a potentially excellent solar observation site in the west China. In summary the site has long sunshine time, low coverage of clouds, low wind speed, steady wind direction, good seeing, nearly-fixed periodical change of the climate, and convenient transportation.