The Bulk Aerodynamic Method for Heat Flux Based on Surface Radiation Temperature

[摘要]地表辐射温度是大多数大型野外项目中唯一可用的地表温度，因此用于估计体气动关系中的垂直温差。在许多数值模式中，垂直温差是根据地表能量平衡计算的地表辐射温度来估计的。这两种应用通常都保留了现有的相似理论，即使这种相似理论只适用于粗糙度高度的温度。最近的几项研究表明，表面辐射温度与现有的相似理论相结合可能导致较大的误差、反梯度通量和/或热的粗糙度高度值小得离谱。本文通过对现有相似理论的修正，结合表面辐射温度与气动表面温度的关系，提出了改善这些问题的方法。在这些发展之前，必须用表面辐射温度的微尺度分布函数来代替表面辐射温度的值。例如，对部分被蒸腾植被覆盖的干热地面的温度进行适当加权，应消除反梯度热输运的情况。提出了几种代表地表辐射温度微尺度分布的模型和测量方案。数据分析将利用现有塔台和飞机的观测数据，这些观测数据来自多个实地项目。此外，将与NCAR ASTER系统的通量测量一起，对地表辐射温度的微尺度分布进行更集中的测量。根据表面辐射温度的改进表示，将重新评估整体空气动力学公式。将特别注意与自由对流的情况下几乎消失的平均流量和情况下的空间平均通量在弱风条件下有关的问题。

Jielun Sun & L. Mahrt/Abstract ATM-9417959 The surface radiative temperature is the only available surface temperature in most large scale field programs and is therefore used to estimate the vertical temperature difference in the bulk aerodynamic relationship. In many numerical models, the vertical temperature difference is estimated in terms of radiative surface temperature computed from the surface energy balance. Both of these applications generally retain existing similarity theory even though such similarity theory is appropriate only for the temperature at the roughness height. Several recent studies have shown that the combination of surface radiative temperature with existing similarity theory can lead to large errors, counter gradient fluxes and/or absurdly small values of the roughness height for heat. This document research proposes to ameliorate these problems by considering modification of existing similarity theory and relationships between the surface radiation temperature and the aerodynamic surface temperature. These developments must be preceded by replacing the value of the surface radiative temperature with a function of the microscale distribution of the surface radiative temperature. As one example, appropriate weighting of the temperature of hot dry ground, partially covered by transpiring vegetation, should eliminate cases of countergradient heat transport. Several models and measurement schemes or representing the microscale distribution of surface radiation temperature are proposed. The data analysis will take advantage of existing tower and aircraft observations from a number of field programs. In addition, more focused measurements of the microscale distribution of surface radiative temperature will be implemented along with flux measurements from the NCAR ASTER System. The bulk aerodynamic formulation will be re-evaluated in terms of the improved representation of the surface radiation temperature. Special attention will be given to problems associated with the free convection case of nearly vanishing mean flow and the case of spatially- averaged fluxes under weak wind conditions.