STUDY ON CLIMATIC FEATURES OF SURFACE TURBULENT HEAT EXCHANGE COEFFICIENTS AND SURFACE THERMAL SOURCES OVER THE QINGHAI-XIZANG PLATEAU

Using monthly mean of surface turbulent heat exchange coefficients calculated based on data from four automatic weather stations(AWS)for thermal equilibrium observation in July 1993— September 1996 and of surface conventional measurements,an empirical expression is established for such coefficients.With the expression,the heat exchange coefficients and the components of surface thermal source are computed in terms of 1961—1990 monthly mean conventional data from 148 stations over the Qinghai-Xizang(Tibetan)Plateau(QXP)and its adjoining areas,and the 1961—1990 climatic means are examined. Evidence suggests that the empirical expression is capable of showing the variation of the heat exchange coefficient in a climatic context.The monthly variation of the coefficients averaged over the QXP is in a range of 4×10^(-3)-5×10^(-3).The wintertime values are bigger in the mountains than in the valleys and reversal in summer.Surface effective radiation and sensible heat are the dominant factors of surface total heat.In spring surface sensible heat is enhanced quickly, resulting in two innegligible regions of sensible heat,one in the west QXP and the other in northern Tibet.with their maximums emerging in different months.In spring and summer sensible heat and surface effective radiation are higher in the west than in the east.The effective radiation peaks for the east in October—December and the whole QXP and in June and October for the west.The surface total heat of the plateau maximizes in May.minimizes in December and January,and shows seasonal variation more remarkable in the SW compared to the eastern part.In the SW plateau the total heat is much more intense than the eastern counterpart in all the seasons except winter.Under the effect of the sensible heat,the total heat on the SW plateau starts to considerably intensify in February,which leads to a predominant heating region in the west,with its center experiencing a noticeable westward migration early in summer and twice pronounced weakening in July and after October.However,the weakening courses are owing to different causes.The total heat over the north of QXP is greatly strengthened in March.thus generating another significant thermal region in the plateau.

Near ground air temperature calculation model based on heat transfer of vertical turbulent and horizontal air flow

In order to calculate the air temperature of the near surface layer in urban environment,the surface layer air was divided into several sections in the vertical direction,and some energy balance equations were developed for each air layer,in which the heat exchange due to vertical turbulence and horizontal air flow was taken into account.Then,the vertical temperature distribution of the surface layer air was obtained through the coupled calculation using the energy balance equations of underlying surfaces and building walls.Moreover,the measured air temperatures in a small area(with a horizontal scale of less than 500 m) and a large area(with a horizontal scale of more than 1 000 m) in Guangzhou in summer were used to validate the proposed model.The calculated results accord well with the measured ones,with a maximum relative error of 4.18%.It is thus concluded that the proposed model is a high-accuracy method to theoretically analyze the urban heat island and the thermal environment.