Observational analysis of rime condensation on plants over the Gurbantunggut Dsert in China

There are long winter seasons with stable snow cover and frequently rime phenomena in the Gurbantunggut Desert in China.Based on the rime observations from November 2007 to March 2008 at the experimental sites on the southern margin of the Gurbantunggut Desert,we find that the average water equivalent of rime condensation on desert shrub crowns is 5.8 mm,about 5 times more than that on snow surfaces,and accounts for 21.8% of the total winter precipitation.The values of rime-fall on plants on the top and foot of longitudinal dunes are 3.8 mm and 9.1mm respectively,which amount to 14.4% and 34.3% of the total winter precipitation,respectively.The rime condensation provides an important moisture input to the shrub cover regions of the Gurbantunggut Dsert during the winter seasons.The maximum wind speed for rime formation is usually less than 3m/s.The most frequent temperature for rime formation range between -15℃ and -20℃,which accounts for 24.3% of the total rime events.The rime-fall significantly reduces when the air temperature falls below -30℃.The rime days are 41% of the rime days occurred in winter when the maximum relative humidity is less than 80%.Low temperatures,high humilities,and low wind speeds,as well as the small diameter of the Haloxylon ammodendron crown branches and needle-like leaves are the important reasons for rime formation and condensation on desert shrubs over the Gurbantunggut Desert.