Abstract: Dew is an important source of water for plant growth in arid areas. Therefore, exploring its generation process is of great significance for the construction of ecological restoration projects in arid areas. To clarify the characteristics and influencing factors of dew occurrence in the middle reaches of the Yarlung Zangbo River valley, an in situ dew observation experiment at 0.2 and 1 m height above ground using leaf wetness sensors was carried out in Qushui County, Lhasa City from September 2023 to August 2024. The results showed that: (1) During the monitoring period, the cumulative dew at 0.2 and 1 m height was 14.21 and 20.84 mm, respectively. Dew occurred mainly in autumn, followed by summer. Its main occurrence period was from 23:00 to 08:00 in the next morning, with the peak occurring from 06:30 to 08:00 in the early morning. (2) When the relative humidity was greater than 60% at 0.2 m height, the temperature dew point difference was less than 8 ℃, the wind speed at 2 m was less than 2.8 m·s^-1, and the wind direction was southeast, these conditions were conducive to dew formation. (3) At 0.2 and 1 m, the highest monthly ratio of dew to rain were found all in September, which was up to 152.02% and 226.26%, respectively. (4) When the daily dew amount reached its peak, soil moisture increased in the range of 1.23% to 3.57% at soil surface and 0.19% to 3.1% at the 5 cm depth. These results could provide a theoretical basis for the collection and utilization of dew and ecological restoration in arid areas.

Key words: dew, condensation characteristics, influencing factor, middle reaches of the Yarlung Tsangpo River valley