MAXIMUM-MINIMUM TEMPERATURES AS A BASIS FOR EVALUATING THERMOPERIODIC RESPONSE1

Since hourly temperatures are not commonly recorded at many locations, a procedure is tested involving the use of daily maximum-minimum temperatures in estimating the number of hours per day above certain temperature thresholds. The procedure assumes that the daily temperature curve may be approximated by a triangle. The number of hours per day, X, above base temperature, b, is estimated as: X=[24(Max-b)]/[Max-Min] Correlation-regression analyses of data from five diverse locations show close relationship between actual and estimated hours. Results indicate that simple computations involving only daily maximum-minimum temperatures may be used for evaluating thermoperiodic response when variations in temperature exposure of less than 2.5 hours per day are not critical.