The Comparison and Analysis of ABL observational data between the East of Tibetan Plateau and Chengdu Plain(I)

Two atmospheric boundary layer(ABL) sites in Litang area situated on the east edge of Tibetan Plateau and in Wenjiang area situated in Chengdu Plain are briefly introduced.These two sites are both built by IPM,CMA.Diurnal variations and structure of profiles of wind speed,air temperature and humidity,characteristics of soil temperature and moisture,and radiation flux variation are analyzed and compared by using the surface-layer observational data in two sites from Feb.to Apr.in 2007.Some significant results are as follows:(1) Diurnal variations of wind speed,air temperature and relative humidity are marked both in two sites.The occurrence time of maximum and minimum wind speed in Litang site is later than that in Wenjiang site by two hours.Temperature gradient in Litang site shows relatively consistent while higher in the nighttime than that in the daytime in Wenjiang site.Humidity gradient is higher in the nighttime than that in the daytime in both two sites.(2) Wind speed profiles generally accord with the logarithm law in two sites.Temperature inversion phenomenon occurs from18:00 to 6:00 in Litang site and from 18:00 to 8:00 in Wenjiang site,and the biggest value of temperature difference of adjacent two levels is up to 0.54 ℃ and 1.02 ℃,respectively.Humidity inversion happens in the height of 8 m and 24 m from 8:00 to 18:00 in Litang site,in the height of 9.05 m and 18.25 m from 10:00 to 14:00 in Wenjiang site,and the biggest value of humidity difference of adjacent two levels is 0.1 g/kg and 0.04 g/kg,respectively.(3) Soil temperature in shallow layers(0 cm and 5 cm) presents evident diurnal variation,while varying little below 10 cm in Litang site.Soil temperature in the depth of 4 cm,10 cm and 20 cm shows diurnal variation remarkably in Wenjiang site.Vertical variation of soil temperature in Litang site is smaller than in Wenjiang site.Diurnal variation of soil moisture is not obvious in two sites.(4) Each radiation flux component has evident diurnal variation except downward long wave radiation flux in Wenjiang site.Downward and upward short wave radiation fluxes in Litang site are much stronger than those in Wenjiang site.