摘要
利用北京325 m气象塔上安装的7层CO_2涡动相关系统在2014年12月到2015年11月的观测资料,分析了北京城区不同高度上CO_2浓度、通量时空分布及湍流谱的特征。结果表明:城市CO_2浓度日变化除了冬季都呈现双峰型,冬季由于人为碳源排放的大幅增加,双峰型不明显。每层的CO_2浓度、通量都有明显的季节变化:冬季最高,春末、夏季最低。CO_2浓度整体随高度的增加而降低。北京城区是CO_2源,CO_2通量的日变化不如CO_2浓度日变化规律明显。CO_2通量在47 m以下为负,47 m以上为正。通量在140 m以下随高度的增加而增加;140m以上随高度的增加而减少。根据对CO_2时空分布的分析可知:边界层CO_2浓度、通量强烈受到碳源、下垫面植被、大气稳定度、环境温度和天气过程等因素的影响。各变量谱与Kaimal等的研究结果接近:归一化速度谱和CO_2谱在惯性子区有-2/3的斜率,在低频区与稳定度参数(Z/L)有一定的关系。这说明复杂地形的城市下垫面的湍流谱结构与平坦地形相比没有太大的实质性差异。
Using the turbulence data measured by the open path eddy covariance system deployed at the Beijing 325-m meteorological tower,the concentration and flux and spectrum of CO2 at seven different height levels are calculated for the period from December 2014 to November 2015.Analysis of the results indicate that the CO2 concentration displays diurnal variation with double peaks except in the winter.Human activities must be considered in the winter since they reduce the diurnal variation of CO2 concentration and lead to a relatively flat pattern.At all observational heights,the CO2 concentration and flux show obvious seasonal variations with the maximum values appearing in the winter and the minimum values occurring at the end of the spring and summer.The CO2 concentration decreases with height as a whole.Beijing is a carbon dioxide source.Daily changes in the CO2 flux are not as obvious as daily changes in the CO2 concentration.The CO2 flux is negative below 47 m and positive above 47 m.The CO2 flux decreases with height below 140 m and increases with height above 140 m.According to the analysis of spatial and temporal distribution of CO2,it is found that the CO2 concentration and flux in urban boundary layer are strongly affected by surface carbon emission source,underlying surface vegetation,atmospheric stability,environment temperature and weather process and so on.The results of turbulence spectra in the present study are very close to the results of Kaimal,i.e.,the normalized velocity spectrum and the CO2 spectrum have a slope of?2/3 in the inertial subregion and they both have relationships with the stability parameter(Z/L)in the low frequency zone.This indicates that the turbulence spectra of the city with complex topography are not quite different from those with flat topography.
作者
段月
程雪玲
华维
徐佳男
冯冬蕾
DUAN Yue;CHENG Xueling;HUA Wei;XU Jianan;FENG Donglei(Chengdu University of Information Technology,Chengdu 610225;State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,Institute of Atmospheric Physics,Chinese Academy of Science,Beijing 100029;Huanren Manchu Autonomous County Meteorological Bureau,Benxi,Liaoning Province 117200)
出处
《气候与环境研究》
CSCD
北大核心
2018年第6期725-736,共12页
Climatic and Environmental Research
基金
中国科学院战略先导科技专项“应对气候变化的碳收支认证及相关问题”(XDA05040301)。
关键词
涡动系统
二氧化碳浓度
二氧化碳通量
湍流能谱
城市边界层
Eddy covariance system
Carbon dioxide concentration
Carbon dioxide flux
Spectrum
Urban boundary layer