Weather Data Integrity

This appendix reviews general procedures for assessing the integrity and representativeness of weather data used for reference evapotranspiration (${\mathit{ET}}_{\mathit{ref}}$) calculation. Most modern automated weather stations measure the primary variables affecting ET—solar radiation, air temperature, wind speed, and humidity—and therefore provide somewhat complete data for estimating ET as compared with the older, manually operated weather stations that measured only air temperature. Meteorological data acquired to estimate ${\mathit{ET}}_{\mathit{ref}}$ should be subjected to several quality control checks prior to use. The first and most important quality control check involves gathering information about the origin of the weather data and conditions affecting measurements. The appendix describes procedures recommended by the American Society of Civil Engineers for assessing the integrity of meteorological data sets used in the computation of ${\mathit{ET}}_{\mathit{ref}}$.