Experimental Study On Snow Evaporation And Condensation In Gurbantunggut Desert Of China

Gurbantonggut desert, which is located in northwest of China, is the only one desert that existence steady snow cover in winter. Snow evaporation-condensation characteristic researches are the important content of hydrological process, and the foundation of snow conservation efficiency and snowmelt utilization ratio of plants studies in desert. The studies are also of important values to further apprehend the water cycle characteristic and effective utilization of precipitation within winter period in arid-area. Furthermore, these studies provide a basis data for reveal the causes that plants have the characteristic features of diversity and stability in desert.Based on the data of field experimental observation and the weather data in the southern part of Gurbantunggut desert from November 2007 to March 2008, the snow evaporation-condensation, rime accumulations and the infiltration characteristics of seasonal frozen soils in desert were analyzed. Main results are concluded as follow:(1) Snow evaporation-condensation. The daily snow evaporation is 0.015mm for inter-dune clearing and 0.02mm for oases, the days of net condensation, which is mainly in February and January, represent 31.9% in total measured days. The maxest snow evaporation rate is 0.3mm/d for inter-dune and 0.46mm/d for oases; the total winter snow evaporation is 1.73mm and 1.95mm; this represents 6.51% and 7.37% of the winter precipitation, respectively. Snow evaporation in openings is higher than under H.ammodendron stands, there is a net condensation 0.41mm under stands and evaporation 0.86mm in openings during Dec.2007 to Feb.2008. The results of correlation analysis show that snow evaporation in the area of Gurbantunggut Desert mainly depends on the air temperature; the evaporation in desert is lower than in Tianshan Mountains and other arid-areas in the world, the reasons of lower snow evaporation are low air temperature and foggy weather conditions in desert.(2) Rime buildup on plant crowns. Field experimental observation indicated that water equivalent of rime caught on crowns is 4.1mm for desert; it represents 15.5% of the winter precipitation. Snow surface condensation at night is 3mm, rime accumulation on crowns is 5.2mm in winter in oases, and this represents 19.6% of the winter precipitation. It is obvious that the water equivalent of rime caught in entire winter is an important supplement to water input in the area. The conditions of riming, main meteorological elements in riming and the shape of plants were analyzed, results showed that the lower of air temperature, the lower humidity riming need; rime accumulations are grower with heights in power functions and have a positive linear correlation with branch lengths.(3) Infiltration characteristics of seasonal frozen soils. There was a higher infiltration capacity of seasonal frozen soils in desert district; results indicated that infiltration rate into seasonal frozen soil decreases along with increasing initial soil moisture content. The stable infiltration rate of frozen sandy soils in desert was about 0.26-0.30mm/min which is about 1/10 of unfrozen soil, but it is still 10-20 times for frozen loamy soil in farmland. Higher infiltration rate of frozen sandy soils ensure the snowmelt infiltration into soil layer rapidly and create favorable conditions for effective storage of snowmelt water. From November 2007 to March 2008, there is 92.1% of the snowfall water infiltrated into soils. The low initial moisture content and macropore texture of sandy soils are the major reasons for higher infiltration capacity of frozen sandy soils.(4) The experiment results of snow evaporation, rime accumulations and infiltration of sandy soils showed that the lower snow evaporation, more condensation and higher infiltration capacity of sangy soils in Gurbantonggut desert can provide advantage for effective conservation of winter precipitation and effective store of snowmelt in spring, occult precipition shch as rime is an important supplement to water input in local areas of desert. In Junggar basin desert vegetation rehabilitation and reconstruction process, we should take full account of this part of the winter natural water resources, and this can reduce the use of runoff and groundwater resources.