台灣土壤溫度分析和土壤熱擴散系數推估

Soil Temperature and Thermal Diffusivity Analyses for Eight Ground Stations in Taiwan

吳清吉(Ching-Chi Wu) ； 許武榮(Wu-Ron Hsu)

《大氣科學》 31卷2期 (2003/06) Pp. 115-130

摘要

土壤溫度是氣-地交互過程一個很重要的變數，大氣和地表的溫差決定地表熱通量的大小，進而影響大氣邊界層的發展。土壤熱擴散系數為土壤溫度變化的一個重要因素。本文利用氣象局8個測站(新竹、台中、嘉義、恒春、台東、成功、花蓮和宜蘭)的歷年土壤溫度觀資料，分析台灣土壤溫度年變化特性，並推估阻尼深度和土壤熱擴散系數。分析結果顯示，各測店土壤溫度年變化呈正弦變化，且土壤溫度振富隨深度呈指數減少，時間落後則隨深度而增加，這些結果符合土壤傳導方程式解析解的性質。
分析結果也顯示，表面土壤溫度振富大小隨測站緯度增加而增加，在恒春(22°00’N)為4.5°C，到了新竹(24°49’N)為7.4°C。土壤溫度的標準差和平均的比值，隨土壤深度呈指數的減少。除了恒春以外，各層土壤溫度第一個調和波佔土壤溫度變化的96%以上。由土壤溫度振富隨深度變他推估的阻尼深度和由時間落後隨深度變推估的阻尼深度相比較，兩考大致接近。8個測站推估的阻尼深度分布在2.1m和3.6m之間，由此結果得到的土熱擴散系數在4.69x10(superscript -7m (superscript)2 S(superscript)-1))和1.28x10(superscript-6)m(superscript2) S(superscript-1)之間。

關鍵字

土壤溫度 ； 熱擴散系數 ； 阻尼深度

並列摘要

Soil temperature is an important variable for the process of land –air interaction. The temperature difference between air and land determines the surface sensible heat flux, which controls the growth of the atmospheric boundary layer. Soil thermal diffusivity is a key factor that affects the soil temperature. We used the past soil temperature records (until 1997) at eight ground station of Central Weather Bureau to analyze their annual variations, damping depths, and thermal diffusivities. The results show that annual soil temperature is nearly sinusoidal in time with amplitudes decreasing exponentially with the soil depth. In addition, the time lags in soil temperature are proportional to the soil depth.
The wave amplitude of the surface soil temperature increases with latitude . For example, the amplitude is 4.5°C at Hengchun (22°00’N), and 7.4°C at hisnchu (24°49’N). The ratios of the standard deviation to the mean of soil temperature also decrease exponentially with depth. Except for Hengchun, the contribution of the first harmonic to the vairiance is more than 96%. The values of the damping depth estimated by the soil temperature amplitudes are consistant with those by the time lags. The estimated damping depths are between 2.1 m and 3.6 m. The estimated thermal diffusivities are between 4.69x10(superscript -7m (superscript)2 S(superscript)-1))和1.28x10(superscript-6)m(superscript2) S(superscript-1

並列關鍵字

Soil temperature ； Thermal diffusivity ； Damping Depth