STUDY OF AERODYNAMIC PARAMETERS FOR DIFFERENT UNDERLING SURFACES

Zeroplane displacement (d), roughness length (z0), friction velocit y (u*) for the heavy grazing site, moderate grazing site, light grazing site, no grazing s ite, dune, interdune, grassland, paddy field site, wheat site, soybean site, a n d maize site etc underlying surfaces have been computed based on the Monin Obuk hovsimilarity theory by utilizing the micrometeorological observation data of th e dune and vegetation underlying surfaces in the semiarid area in Naiman city, Inner Mongolia of China, conducted jointly by the Institute of Desert Research o f CAS and the National Institute of AgroEnvironmental Sciences of Japan in 199 0 -1994, and their relationships with horizontal wind speed and Richardson number analyzed, and the aerodynamic characteristics for different underlying surfaces under the conditions of different anthropogenically disturbed grassland ecosyste ms also compared. Results show that the vegetation coverage and aboveground biomass decrease with the increase in the anthropogenically disturbed extent of gra ssland ecosystem. The roughness length for different anthropogenically disturbed underlying surfaces is close related with biomass, vegetation height, and groun d surface undulation, and Richardson number Ri is also its influence facto r. The friction velocity is positively proportional to wind speed and roughness length, but to different extent for different underlying surfaces. The aerodynamic param eters of the same underling surface are different, too, in different growth seas ons. The above results indicate that grassland and vegetation are of significanc e in preventing the desertification, especially in the arid and semiarid land ecosystem region. And the results of this paper are also important for constructi ng the land surface process as well as regional climate model.