This function calculates winter chill for temperate trees according to the Utah Model.
Vector of hourly temperatures.
Boolean parameter indicating whether calculated metrics should be provided as cumulative values over the entire record (TRUE) or as the actual accumulation for each hour (FALSE).
Units of the Utah Model are calculated as suggested by Richardson et al. (1974) (different weights for different temperature ranges, and negation of chilling by warm temperatures).
Vector of length length(HourTemp) containing the cumulative Utah Chill Units over the entire duration of HourTemp.
After doing extensive model comparisons, and reviewing a lot of relevant literature, I do not recommend using the Utah Model, especially in warm climates! The Dynamic Model (Chill Portions), though far from perfect, seems much more reliable.
Utah Model reference:
Richardson EA, Seeley SD, Walker DR (1974) A model for estimating the completion of rest for Redhaven and Elberta peach trees. HortScience 9(4), 331-332
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