Hydrothermal Characteristics of the Land-Atmospheric System in an Alpine Area of West Nyainqentanglha Mountains
XIE Jian1,2,LIU Jingshi1,DU Mingyuan3,KANG Shichang1,JIA Shugang1,WANG Zhongyan1,2 (1. Institute of Tibetan Plateau Research,CAS,Beijing 100085,China; 2. Graduate University of Chinese Academy of Sciences,Beijing 100080,China; 3. Department of Agro-Meteorology,National Institute for Agro-Environmental Sciences,Tsukuba 3050053,Japan)
A preliminary study was carried out on the hydrothermal characteristics in the Nyainqentanglha mountainous region,using one-year observation data of air temperature,three layers of soil temperature and moisture from two sites at 4800 m a.s.l. and 5333 m a.s.l. on the southern slope,and one site at 5400 m a.s.l. on the northern slope. The results indicated that the differences between soil and air temperatures were greater in winter than in summer,and they were generally larger compared to the nearby areas. The soil thermal gradient could be inverse between higher and lower elevations. The soil at the higher elevation was slightly wetter than at the lower one. The soil moisture at the studied sites was dominated by the freeze-thaw cycle during dry season and by Indian monsoon precipitation during the wet season,respectively. The freezing period at the higher elevation was 3 to 4 months longer than at the lower place. The soil moisture at the lower depth (50 cm) for the higher elevation showed mutation near the phase changing point. The soil temperature differences for the same horizon between the southern and northern slopes of the Nyainqentanglha Mts. were within 0 -8℃. The soil temperatures on the southern slope was on average 3-4℃ greater than the northern counterpart. The southern slope showed latter freeze but earlier thaw compared to the northern one. The soil at the upper depth (5 cm) for the southern slope was drier than that for the northern counterpart. In contrast,the soil at the lower depth (50 cm) on the southern slope was wetter for than the northern slope. The hydrothermal characteristics showed differences between the two parts of the Nyainqentanglha Mts.