地表溫度模擬之表面層數值厚度之決定及參數比較

在大氣模式中有關地表溫度之模擬，發現當使用有限差分法對地表作切割時，地表表面層數值厚度之大小，會影響所模擬之日夜溫差。本研究首先推導出能模擬實際日夜溫差之表面層數值厚度，並比較目前使用在UCLA GCM及ECMWF GCM之地表溫度之計算參數。以一水泥地面之實際案例作測試，發現在使用UCLA之參數，令表面層數值厚度為√(D/ω)能模擬出實際之日夜溫差，而ECMWF之參數其表層厚度則與底層地溫有關，一般而言，使用0.885√(D/ω)較為理想。其中D為熱擴散係數，ω為地球自轉之角速度。至於UCLA及ECMWF兩參數之比較，則各有優劣。UCLA參數由於不需底層之地溫、數值穩定且計算速度較快，為本研究所建議。將UCLA之公式應用於台中火力發電廠及宜蘭幸福水泥之草坪時，發現其模擬值與觀測值之相關性（γ^2）高達0.9，而標準誤差只有1℃左右。

關鍵字

地表溫度；地表參數；水泥地面；草；台中；宜蘭

並列摘要

Using the finite difference scheme to simulate land surface temperature, it is found that the magnitude of the diurnal temperature fluctuation of land surface will vary with the discretization of the land. The thicker the surface layer, the smaller the temperature fluctuation is. The purpose of this study is to determine the proper thickness of the land surface layer for temperature simulation. In addition, schemes for land temperature simulation used in the UCLA GCM and in the ECMWF GCM are compared. Using a concrete surface as a case study, it is found that in the UCLA GCM, the thickness has to be equal to √(D/ω) to simulate the diurnal fluctuation, but in the ECMWF GCM, it varies with the temperature of the deeper layer. Generally speaking, a value of 0.885 √(D/ω) is a better choice, where D is heat diffusivity of land, and ω is the angular rotation speed of the Earth. In respect to the comparison between the UCLA scheme and the ECMWF scheme, both schemes have advantages and disadvantages. Since UCLA scheme is very stable, no Tc1 value needed for input and less computational time, therefore, UCLA Scheme is recommended for land surface temperature computation by authors. By applying the UCLA scheme to grass overlayed surface in Taichung and in Ilan, the correlation γ^2 between calculated and observed land surface temperature is as high as 0.9 and the standard error is only 1°C.

並列關鍵字

ground surface temperature ； land surface parameterization ； concrete surface ； grass ； Taichung ； Ilan

國際替代計量

地表溫度模擬之表面層數值厚度之決定及參數比較

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