The preliminary analysis of sunshine durations with meteorological data for the Chinese Giant Solar Telescope site survey

Abstract

Using meteorological data is fundamental in any site survey for astronomical instruments. As a first step, the analyses of sunshine duration for candidate sites are crucial for remote site survey for solar observing instruments. In western China, some ground-based meteorological stations have collected daily sunshine data from only partial-sky area since they had to be constructed in valley. One aim of this study is to demonstrate the geographical properties of those meteorological stations. Our goal is to investigate the true sunshine durations obtained if the stations are installed at the top of nearby mountain without screen effect. We make use of the three-dimensional geographical data from the Google Earth software and the statistical meteorological data from the National Meteorology Administration and the meteorological stations. All the 76 national basic meteorological observing stations with altitude over 3000 m located in western China are measured. Since astronomical instruments tend to be installed at the top of a mountain, we need to take into account the loss of the sunshine durations in making the remote site survey. Our results, after the compensation, show that the condition of sunshine duration in the Hengduan-Shan Mountains (HSM) area can meet the basic requirement of at least 2500 h yr(-1) for the Chinese Giant Solar Telescope (CGST) site survey.