Estimating Winter Design Temperatures from Daily Minimum Temperatures

Abstract

A methodology has been developed to estimate winter design temperatures (temperatures exceeded a specific number of hours during the December through February winter season-an important design parameter in building construction) from synthetic distributions of hourly temperatures for locations where only daily maximum and minimum temperatures are observed. Cumulative distributions of hourly temperatures and daily minimum temperatures were examined at seven different locations in Colorado having 10 or more consecutive years of complete hourly data. A consistent relationship between the two distributions was found for these stations by representing the lower half of each distribution with a best-fit power curve and relating the fitting coefficients. From these relationships an equation was derived that generated the shape of the lower half of the cumulative distribution of hourly temperatures. The only required input parameters are the regression coefficients resulting from the power curve fitting of the observed distribution of daily minimum temperatures. The method was tested in Colorado stations having both hourly and daily temperature data. Excellent results were obtained for Colorado. Synthesized temperatures at probabilities of up to 0.50 were generally within 0.7°C of the observed values. The method has now been employed to calculate winter design temperatures for dozens of Colorado cities where such information has previously been unavailable.