The Research Of Atmospheric Stability In Beijing City During 2013-2015 Based On The Field Measurement

With the increasing of high-rise buildings and large span buildings,the research of wind field characteristics and wind load is becoming more and more important.Among them,the endogenous wind field characteristics of atmospheric boundary layer is the basis of studying the wind resistance performance of the structure.Atmospheric stability and landscape category are the main factors influencing the atmospheric motion.Due to the urban heat island effect,the changing rule of atmospheric stability in big city is markedly different from the one in flat open landscape.The atmospheric stability in wind field is needed to be analyzed firstly to determine the wind field characteristics of big cities.This paper has researched the atmospheric stabilities statistical property of the Beijing city by using the data gotten from the 11 ultrasonic anemometers fixed on the meteorological observation 325m tower in Beijing during 2013-2015 to lay a good foundation for further studying the characteristics of wind field in Beijing.The content of the paper is as follows:1)Statistical analysis of wind speed and direction is carried out.The distributions of its wind speed and direction have obvious seasonal characteristics,there is more possibility to appear large wind speed during spring and winter.The dominant wind directions of Beijing deduced from this paper are N and NNE.The geomorphic parameters in Beijing are calculated which are the roughness length 1.03m and the zero displacement 32.2m.2)The parameters and standards for the classification of stability in Beijing urban area are selected.The Richardson number and the M-O length were compared and analyzed.The M-O length is eventually chosen as the parameter to calculate the stability of the Beijing area,and the W.R.Wood method is also decided as the classification standard.3)The atmospheric stability is analyzed.The change of the stabilities distribution is not obvious within the small wind range while it is obvious within the large wind range.There is more neural stability during spring and winter and there is least neutral stability during summer.However,summer has the most unstable atmosphere.The atmospheric stabilities of day and night is respectively lean to stable and unstable.The frequency of stable atmosphere grow obviously with the grow of height especially at the higher height during summer.The frequency of neural atmosphere decreases obviously during winter.