Observation of Ground Temperature at Shallow Layer of Different Dune Types in the Tazhong Area

Abstract

Land surface temperature affects the capability of long wave radiation,and it is an important parameter for studying climate change. The variation of air temperature and precipitation was often stressed in studying climate change in the Taklimakan Desert in the previous studies,but ground temperature in the desert was infrequently studied. In this paper,MicroLite 16K LITE5016 was used to examine the spatial distribution and temporal variation of ground temperature at shallow layer of different dune types in the Tazhong area located in the central Taklimakan Desert,where oceanic airstream is difficult to arrive. The Tazhong area is characterized by a typical continental climate with frequently and intensely wind-blown sand movement. The area of mobile dunes in Tazhong occupies more than 80% of the total area of the Taklimakan Desert. Temperature variation here is drastic,the maximum temperature is as high as 45.6 ℃,and the diurnal-nocturnal temperature difference is over 40 ℃. The annual sunshine duration in this area is 2 700 hours,accumulated temperature ≥0 ℃ is over 4 000 ℃,and the total solar radiation is 5 700-6 000 MJ/m2. Precipitation in this area is low,the annual precipitation is no more than 50 mm and only 4-5 mm in minimum,and it is extremely arid climate. The values of ground temperature at different depths (0 cm,10 cm and 20 cm) over a mobile dune and an artificially-fixed dune in the Tazhong area were measured during the period from August 3rd to 10th,2009. The results are as follows:(1) Daily range of ground surface temperature was high in summer both for mobile dune and artificially-fixed dune,it was decreased with the increase of depth,and it was the lowest at depth of 20 cm; furthermore,the maximum ground temperature occurred 2 hours later from noon,and the minimum one occurred at dawn; (2) The ground temperature of artificially-fixed dune was lower than that of mobile dune; (3) The difference between ground temperature and air temperature was the highest in summer; (4) Wind speed affected significantly the ground surface temperature regardless of mobile dune or artificially-fixed dune.