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Degree
Days VIEW SAMPLE (GIF 56kb)
Case I The minimum air temperature (Tmin) above the base temperature (Tbase). In this case there are no degreedays below the base temperature and the degreedays above are given by 1/2(Tmax + Tmin)  Tbase. Case II The maximum air temperature (Tmax) below the base temperature. In this case there are no degreedays above the base temperature and the degreedays below are given by Tbase  1/2(Tmax + Tmin). Case III The maximum air temperature above and the daily minimum air temperature below the base temperature but the mean temperature which equals 1/2(Tmax + Tmin), greater than the base temperature. In this case degreedays above are given by 1/2(Tmax  Tbase)  1/4(Tbase  Tmin) and degreedays below by 1/4(Tbase  Tmin). Case IV The maximum air temperature above and the minimum air temperature below the base temperature but the mean temperature which equals 1/2(Tmax + Tmin), less than the base temperature. In this case degreedays above are given by 1/4(Tmax  Tbase) and degreedays below are given by 1/2(Tbase  Tmin)  1/4(Tmax  Tbase). If the mean temperature is equal to the base temperature the same results obtain using either the formula for Case 111 or Case IV 

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