| Summary: | 碩士 === 國立中興大學 === 水土保持學系所 === 97 === This study measured the daily soil temperature of different depth during March 2004 to January 2005 from the isolated area of two experimental plots of Huafan University in Taipei. Temperatures were collected by data logger at 30-minute intervals from thermistor probes installed at surface, 5, 10, 20 and 30cm depths. For eliminating influence of gravitational water, the soil temperature was taken on by non-raining days. The thermal diffusivity of non-raining days was estimated first and then the mean monthly thermal diffusivity was calculated by two methods; one was calculated by mean thermal diffusivity of monthly non-raining days, and the other was estimated from mean monthly temperature. Finally, the properties of thermal diffusivity in different depths were discussed and estimating the relation between measured and predicted soil temperature by monthly mean thermal diffusivity were compared.
The results indicated that the amplitude of the temperature sine curve led to an decrease due to the soil depth increase and the value of the amplitude in summer was higher than in winter. The time of achieving the peak temperature also decrease with soil depth increase. To estimate the thermal diffusivity calculated from the different soil depth showed the values of thermal diffusivity led to decrease in 10-20cm depth and increase in 30cm depth. Monthly percentage of mean variation between measured and predicted soil temperature, estimated from two methods were used to analyze the mean monthly thermal diffusivity, showed that temperature calculated with mean daily of thermal diffusivity had better result.
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