Campbell Scientific VisualWeather Software - Manual (Page 73)

Appendix E. Chill Hours
E.1 Chill Hours
Chill hours represent the number of hours the temperature stayed at or below a
certain base (or reference) temperature provided by the user.
E.1.1 Method
1. The hourly average temperature value, Ta, is compared to the base
temperature.
2. If Ta < = BaseTemp, then the number of chill hours = 1, and
If Ta > BaseTemp, then the number of chill hours = 0
3. A value of either 1 (if the hourly average temperature stayed at or below
the base temperature) or 0 (if the hourly average temperature stayed above
the base temperature) is assigned to each hour of the day.
4. These values are summed at the end of each 24-hour period. The total
value represents the number of chill hours; i.e., the number of hours the
temperature remained at or below the base temperature.
E-1