A Study Of Wind Shear In Tower Layer Over Urban Land Surface

Wind Shear of the urban boundary layer has been analyzed with the observational data during 2002 of wind speed from the Beijing 325 m meteorological tower .and consequently, the study is useful to understand the dispersion of pollutants and the character of wind profile.First ,the study were taken by the distribution of different Frequency intensity that Wind Shear occured in tower layer.we have obtained the following results about Wind Shear over the urban boundary layer. (1) Wind Shear is a common phenomenon in atmosphere . In this paper we can get that serious Wind Shear take the whole tower layer and the high frequency that serious Wind Shear occured in tower layer can be selected between 80m and 200m . (2) The distribution of the Wind Shear is so complex that we can not classify tower layer by the average of Wind Shear.(3)When studying Wind Shear of the urban boundary layer,we should take the whole tower layer as the target.The daily variation and seasonly variation of Wind Shear over the urban boundary layer have been discussed .A Few Results were got as bellow :(1) there is a maximum of Wind Shear between 8:00am and 10:00am and the same was between 19:00 pm and 21:00pm ;(2) The number of Wind Shear was frist increase and then decrease and increase in the end .The seasonly variation of Wind Shear over the urban boundary layer was not remarkable in general.