地表土壤熱通量及蒸發散量之研究

Abstract

在生物圈與大氣之間的交互作用中，地表的動量通量、熱通量、水汽通量以及二氧化碳通量為相當重要的參數。本論文分別討論了推估土壤熱通量與蒸發散量的方法。第一部份，利用只需要單一層土壤溫度即可推估土壤熱通量的兩種方法(the traditional sinusoidally analytical method and the half-order time derivative method ,Wang and Bras, 1999)進行長期的土壤熱通量推估。研究結果發現，由於傳統解析解方法的假設使得土壤熱通量呈正弦函數變化，所以利用傳統解析解方法推估土壤熱通量的結果不太良好﹔然而，利用實際量測到的土壤熱通量與half-order method推估結果比較，顯示出此方法用於長期土壤熱通量推估可得到非常良好的結果。第二部份，本研究提出一個二維的Lagrangian analytical dispersion模式，利用此模式以及下風處某個位置量測到的水汽濃度剖面可以推求得地表的蒸發散量。研究的結果顯示出此模式可以在local advection的狀況下，推求得地表蒸發散量隨下風處距離增加的變化情形。

Surface fluxes of momentum, heat, water vapor, carbon dioxide and other scalars (e.g., CH4) are important parameters for understanding of the biosphere-atmosphere interactions. This study focuses on quantifying two of these important parameters: the soil heat flux and water vapor flux. In the first part of this study, long-term estimation of soil heat flux from single layer soil temperature was carried out by the traditional sinusoidally analytical method and the half-order time derivative method of Wang and Bras (1999). Our results pointed that the analytical method did not predict the soil heat flux well due to the sinusoidal assumption for soil heat flux’s temporal variation was not valid. While good agreement between soil heat flux measurements and predictions by the half-order time derivative method was found. In the second part of this study, a two-dimensional Lagrangian analytical dispersion model in conjunction with an inverse approach was proposed for inferring surface evapotranspiration rate from the mean humidity profile under local advection conditions. Our results showed that this approach was able to reproduce the measured downwind evolution of surface evapotranspiration rate (water vapor flux) under local advection conditions.