城、郊能量及辐射平衡特征观测分析

城市化发展导致城、郊能量平衡及辐射平衡存在明显差异。利用城、郊夏季涡度相关系统观测数据，分析了南京城、郊在晴天条件下的辐射平衡、能量平衡、反照率以及储热项变化特征。结果表明：（1）夏季晴天条件下，城、郊辐射收支分配有显著不同。城市辐射陷阱作用导致城区向上短波辐射日均值小于郊区，城、郊分别为246 W/m2和395 W/m2，城市辐射陷阱效应导致截留的短波辐射日平均值可达237 W/m2。同时城市地表向上长波辐射日均值大于郊区自然地表，城、郊分别为5051 W/m2和4883 W/m2，这与城、郊地区不同的地表温度直接相关；（2）城、郊能量平衡分配的方式有显著不同，城市地表储热及感热为能量分配的主要方式，感热全天为正，始终处于不稳定层结。郊区潜热为能量分配的主要方式，夜间存在稳定层结条件；（3）城区总体日平均反照率为011，郊区草地日平均反照率为017，城区水泥楼顶日平均反照率为023。城区铁塔上日均反照率代表整体城市下垫面反照率的特征，城市辐射陷阱作用导致其小于郊区反照率。而水泥楼顶的反照率代表水泥板单一下垫面城市特征，因此大于前2者的反照率日均值。另外，郊区日平均反照率的日变化比城区表现出更明显的不对称性；（4）白天城区储热项占净辐射的56%，而郊区仅占净辐射的7%，并与已有试验中夏季白天储热项数据进行了比较，城市储热项特征与观测所处站点的水泥（硬地）面积所占比重以及是否考虑人为热的影响密切相关

CHARACTERISTICS ANALYSIS OF RADIATION AND ENERGY BUDGET OVER URBAN AND SUBURBAN

With the development of urbanization，the radiation and energy budget over different urban and suburban underlying surface become increasingly different.Based on the radiation,turbulence flux and fluctuation wind velocity observed by the eddy correlation method on the urban and suburban sites in Nanjing from 27 July to 2 August 2010,the characteristics of the radiation and energy budget over different urban and suburban underlying surface on clear day in summer were analyzed and compared.In order to provide some fundamental characteristics of the radiation and energy budget over different urban and suburban underlying surface,the data observed by Eddy Covariance (EC) observations was studied by using classical statistics.The results show as follows.(1) The radiation over urban and suburban was significantly different on clear day.The average of upward long wave radiation were 5051 W/m2 and 4883 W/m2,and the average of upward short wave radiation were 246 W/m2 and 395 W/m2 over urban and suburban.The result was related with surface temperature and radiation trap.（2）The energy budget over urban and suburban was significantly different on clear day.Heat storage and sensible heat flux played major roles in urban energy budget.The sensible heat flux in urban was positive all day.The stratification of the atmosphere over urban was always unstable. In suburban,latent heat flux played major role in urban energy budget.The stratification of the atmosphere was stable in night.(3) The average of the diurnal albedo of the urban（33m above the tower）and suburban（2m over the grass）were 011 and 017.The urban albedo was representative characteristic of entirety urban levels of the hundreds meters diameter.In addition，the suburban albedo showed more serious asymmetry than the urban.(4)The heat storage of urban and suburban were 56% and 7% of the net radiation flux in daytime.Compared with the heat storage of some others investigations,the characteristic of the heat storage had close correlations with the proportion of hard ground in the observation site and the influence of approved anthropogenic heat.（5）The height of the turbulence flux of the radiation and energy budget observed by the eddy correlation method on the urban was 33 m above the tower on an urban building.The quality of urban turbulence flux datum was good and its reliability was high.Because many factors for the datum like three dimensional urban buildings were of vital importance,the instrument used to observe turbulence flux in urban should be set up in a high position of urban canopy