Measurement and study of daytime optical turbulence and precipitable water vapor in the northwestern area of China

A comprehensive site testing campaign was carried on in the northwestern area of China from July to November 2022. We conduct the study focusing on the daytime optical turbulence and precipitable water vapor long-term variation in this area, which are essential for time-domain astronomy and site scheduling. A relatively quiet and dry atmosphere situation that benefits observation can be more easily found in September and October. The so-called ’conversion time’, an excellent condition for observation at dawn and dusk, behaved differently in different months. Meanwhile, better observation conditions can be found at dawn in July, August and September but at dusk in October and November in the daytime.