Characterization of Energy Flux Partitioning in Urban Environments: Links with Surface Seasonal Properties
Characterization of Energy Flux Partitioning in Urban Environments: Links with Surface Seasonal Properties
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DOI：
10.1175/jamc-d-11-038.1
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发表时间：
2012-02
影响因子：
3
通讯作者：
Thomas Loridan;C. Grimmond
中科院分区：
文献类型：
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作者：
Thomas Loridan;C. Grimmond
更好地了解城市环境的性质与大气交换之间的联系是广泛应用的核心。城市地区地表能量平衡数据的大量测量使得能够对不同环境中观测到的通量进行相互比较。本研究以两种新的方式分析大型数据库。首先，而不是使用净全波辐射归一化通量，仅使用入射辐射通量，以从分母中去除表面属性。第二，由于现在全年都有数据，因此制定了指数来描述积极参与能量交换的地表（建筑物;植被）的比例。这些帐户内的城市街道和植被物候季节性变化的阴影模式，其对传入辐射的分区的影响进行了分析。来自北美，欧洲，非洲和亚洲的19个站点的数据（包括6年的观测活动）用于推导广义表面通量关系。正午期间传出的辐射分数随总活跃表面指数的增加而减少，存储的能量分数随活跃的建筑指数而增加，潜热分数随活跃的植被指数而增加。作为表面指数的函数的这些能量交换比率的参数化[即，通量比-活性指数表面交换（FRAISE）方案]。这些被用来定义四个城市区域，其特征能源分区的基础上，其活跃的表面指数。一个独立的评估FRAISE，使用三个额外的网站从巴塞尔城市边界层实验（气泡），在每个位置产生准确的预测中午通量分区。
A better understanding of links between the properties of the urban environment and the exchange to the atmosphere is central to a wide range of applications. The numerous measurements of surface energy balance data in urban areas enable intercomparison of observed fluxes from distinct environments. This study analyzes a large database in two new ways. First, instead of normalizing fluxes using net all-wave radiation only the incoming radiative fluxes are used, to remove the surface attributes from the denominator. Second, because data are now available year-round, indices are developed to characterize the fraction of the surface (built; vegetation) actively engaged in energy exchanges. These account for shading patterns within city streets and seasonal changes in vegetation phenology; their impact on the partitioning of the incoming radiation is analyzed. Data from 19 sites in North America, Europe, Africa, and Asia (including 6-yr-long observation campaigns) are used to derive generalized surface‐flux relations. The midday-period outgoing radiative fraction decreases with an increasing total active surface index, the stored energy fraction increases with an active built index, and the latent heat fraction increases with an active vegetated index. Parameterizations of these energy exchange ratios as a function of the surface indices [i.e., the Flux Ratio‐Active Index Surface Exchange (FRAISE) scheme] are developed. These are used to define four urban zones that characterize energy partitioning on the basis of their active surface indices. An independent evaluation of FRAISE, using three additional sites from the Basel Urban Boundary Layer Experiment (BUBBLE), yields accurate predictions of the midday flux partitioning at each location.