ADJUSTING TEMPERATURE PARAMETERS TO REFLECT WELL-WATERED CONDITIONS

Adjustment coefficients for air temperature and dew point temperature measurements at dry weather sites are determined for predicting reference evapotranspirations (ETo) for irrigated conditions. Seasonal and regional variation in changes in temperature parameters versus the ratio of effective precipitation to ETo are analyzed. The determined adjustment coefficients are tested for validity using weather data from reference weather stations, and paired reference and dry stations. The effects of adjusting air temperature and dew point temperature for site aridity are analyzed using the FAO Penman-Monteith and the Hargreaves equations. Maximum reductions in ETo caused by adjustments of temperature data for aridity effects was as high as 25%.