以通量變化法估計地表之可感熱、潛熱、以及二氧化碳通量

Abstract

使用通量變化法(flux-variance method)估計地表通量只需單點之濃度資料，因此近年來此法廣為使用。本研究針對三種不同的地表類型：草地、水稻田、以及森林，評估通量變化法在其可感熱、潛熱以及二氧化碳通量推估上的應用，並與渦流相關法(eddy-covariance method)的實際量測值做比較。研究發現，可感熱通量及潛熱通量的推估均有不錯之準確性。然二氧化碳通量則因為受到複雜的二氧化碳源與匯分布影響，而造成預測結果不佳；此外，若能由量測到之可感熱通量去推估潛熱及二氧化碳通量，將可提高約15％之準確度。比較結果顯示，在通量推估計算前，若能先由渦流相關法的量測資料中找出最適合之相似係數再進行預測，將得到較準確的結果。

This study predicted sensible heat (H), latent heat (LE), and CO2 fluxes (FCO2) by the Flux-Variance Method (FVM) and examined the performance of this method by eddy-correlation measured flux data at three different surface types: grassland, paddy rice field, and forest. The H and LE estimations were in good agreement with the measurements over the three ecosystems. However, the CO2 flux predictions were not good; this is attributed to the complicated CO2 sources and sinks distribution. Nevertheless, the prediction accuracy of LE and FCO2 could be improved by around 15 percent if the predictions were obtained with the measured sensible heat flux. Based on our results, we suggest that it is necessary to determine the adequate similarity constants for varied scalars and sites (ecosystems) before applying FVM for predicting surface fluxes.