峨眉山地区近地层微气象特征研究

基于2019年12月至2020年11月峨眉山站梯度塔资料、辐射观测资料和地表通量资料,采用涡动相关法对峨眉山地区近地层的地表通量和蒸散发量的变化进行分析,并估算了零平面位移、空气动力粗糙度、空气热力粗糙度、动量通量输送系数和感热通量输送系数等重要的空气动力学和热力学参数。研究表明:近地面风速呈现高层高、低层低的特征,且高层日变化较低层明显;垂直风廓线在冠层内与冠层上存在明显不同的相关关系及拐点现象,拐点以下风速随高度的增速明显比拐点以上的小;零平面位移d年平均值为10.45 m;空气动力学粗糙度Z_0m和空气热力学粗糙度Z_0h年均值分别为1.65 m和9.95 m;动量通量输送系数C_D和感热通量输送系数C_H的年平均值分别为1.58×10^-2和3.79×10^-3;近地层降水发生次数和降水量多寡有明显的季节变化,7月降水日和降水量都较多,近地层降水日变化明显,表现出川西盆地典型的夜雨特征;感热通量和潜热通量白天的主导地位随季节变化,夏季潜热通量占主导地位,冬季感热输送占主导地位;各天的蒸散发主要发生在08:00(北京时,下同)-17:00,在11:00-14:00达到最大值,且季节差异明显。

Study on Micrometeorological Characteristics of Near Surface Layer in Emeishan Area

The land surface process of the Qinghai-Xizang(Tibet)Plateau has an important impact on China's weather and climate.Mount Emei is in the southeast edge of the Qinghai-Xizang(Tibet)Plateau.It is necessary place for the eastward movement of the plateau system,and the place where the southwest vortex begins to develop.Based on the atmospheric boundary layer gradient tower data,radiation observation data and surface flux data of Emeishan station on the eastern edge of Qinghai-Xizang(Tibet)Plateau from December 2019 to November 2020,this paper uses the eddy correlation method to analyze the changes of surface flux and evapotranspiration near the surface layer in Emeishan area,and estimates the zero plane displacement,aerodynamic roughness,aerothermal roughness Kinetic and thermodynamic parameters such as momentum flux transport coefficient and sensible heat flux transport coefficient.The main conclusions are as follows:The temperature in the canopy is higher than that in the canopy during the day,but the opposite at night.The relative humidity in the canopy is higher than that on the canopy,and the diurnal variation of wind speed near the ground is more obvious in the upper layer than that in the lower layer.The seasonal variation characteristics of near ground temperature,relative humidity and wind speed are obvious.The vertical wind profile has significantly different correlation and inflection point phenomenon in the canopy and above the canopy.The growth rate of wind speed below the inflection point with height is significantly smaller than that above the inflection point.The annual average value of zero plane displacement d is 10.45 m;The annual mean values of aerodynamic roughness Z_0m and thermodynamic roughness roughness Z_0h are 1.65 m and 9.95 m respectively.The annual average values of momentum flux transport coefficient C_D and sensible heat flux transport coefficient C_H are 1.58×10^-2 and 3.79×10^-3 respectively.Aerodynamic roughness fluctuates greatly with season,while aerothermodynamic roughness is opposite.The occurrence times and amount of precipitation have obvious seasonal changes.There are more precipitation days and precipitation in July,and the daily change of precipitation is obvious,showing the typical characteristics of night rain in Western Sichuan Basin.The daily variation amplitude of sensible heat flux and latent heat flux is large.The latent heat flux is dominant in summer and sensible heat transport is dominant in winter.The evapotranspiration of each day mainly occurs from 08:00(Beijing Time the same as after)to 17:00,and reaches the maximum from 11:00 to 14:00,and the seasonal difference is obvious.