Analysis On The Climate Characteristics And Their Comparisons Of The Land Surface Process Over Arid Regions And Semi-arid Regions

By utilizing the integrated data of land-surface processes observed in Dunhuang arid region in northwest China from Sep.2000 to Aug.2001, observed the middle of arid region in Hexi Corridor in Zhangye from Nov.2005 to Oct.2006, observed Dingxi Synthetical Experimental Observatory of Land Surface Process in the Semi-arid Region in the Loess Plateau from Nov.2004 to Oct.2005, in and observed at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) from Nov.2008 to Oct.2009, the annual and daily variation characteristics and the mechanism of influence of soil temperature, soil moisture, precipitation, surface albedo, surface radiation components and energy balance components in each climate region are systematically analyzed. As well as, the relationship between surface albedo and soil moisture, also and precipitation are researched. Then the characteristics of land surface process in the four different climate regions are compared and contrasted. The following conclusions are obtained.1. In Dunhuang the extreme arid region in northwest China, the annual range of ground surface temperature exceeds 42℃. The annual range of surface albedo is quite large. The net radiation in summer is four times more than in winter. The daily variation of upward and downward long-wave radiation lag about 1 hour hours to the net radiation.2. In the arid region in Hexi Corridor, the response of soil moisture to the precipitation in winter delays 1 or 2 months. Surface albedo increases with the soil moisture decreasing, and their correlation coefficient reaches 0.7346. The soil heat flux is exported from soil to the air in winter while imported from air to the soil in summer. The import is lager than export. The diurnal maximum of soil heat moisture is the latest in winter and earliest in summer.3. In Yuzhong the semi-arid region in the Loess Plateau, the 10cm soil moisture is the biggest. There is a moisture inversion layer between 5 and 10 cm below the ground, as well as between 20 and 40cm. The surface albedo decreases with soil moisture increasing, while increasing with snow precipitation increasing. The latent heat flux in autumn is about 6 times as large as in winter. The downward transfer velocity of soil temperature daily waveform is about 1.5h-3h/10cm. The daily integral of net radiation is only 33%of global radiation, and the soil heat flux do not reach 1%of net radiation. The surface albedo in the morning is bigger than in the afternoon in the typical sunny day. The surface albedo varies gently when it rains, and its value is small. The surface albedo increases significantly when it snows, and the fluctuation is big.4. In Dingxi the semi-arid region in the Loess Plateau, the downward transfer velocity of soil temperature daily waveform is about 2.5h-3.5h/10cm. The correlation coefficient of surface albedo with soil moisture is 0.5338. While the correlation coefficient with snow precipitation is 0.6645. It takes 1 hour for solar radiation to heat the surface and atmosphere. Latent heat flux in summer is five times more than in winter. There are two obvious peak value of sensible heat flux. The daily peak values of latent heat flux, sensible heat flux, and soil heat flux lag 30 minutes-1 hour to the net radiation.5. The annual variation of soil temperature in the arid region is stronger than in the semi-arid region. On the whole, the soil moisture in semi-arid region is much greater than in arid region. The mean surface albedo of Dunhuang is the largest, and the smallest of Zhangye. The annual range of radiation components in Dunhuang is the most obvious, except the net radiation, and they are quite small in semi-arid regions. The annual range of net radiation in semi-arid region is lager than in arid region, and the one in Dingxi exceeds 50%more than in Dunhuang. It's drier in Yuzhong than in Dingxi by the Bowen ratio. The daily fluctuation of surface albedo is less obvious in Dingxi than in Yuzhong. The daily integral of net radiation of global radiation in Yuzhong is smallest, while it's 16.8%more than in Dingxi, and it's smallest in Zhangye. The Bowen ratio is less than 1 all day in Dingxi.