EVAPORATION FROM ATMOMETERS AND PANS

Daily measurements of evaporation from the porous disk and Bellani plate atmometers, the Class A evaporation pan, and the Experimental Farms buried tank were compared and related to daily measurements of temperature, radiation, wind, and vapor pressure. Simple correlation coefficients indicated highly significant relationships among evaporation measurements (dependent variables) and the meteorological factors (independent variables) with the exception of wind.Multiple regression analyses showed highly significant correlations between each of the evaporimeters and the four meteorological variables studied. A linear combination of the four independent variables accounted for 70 to 86% of the variation in evaporation from the four evaporimeters, but the standard errors of estimate were also large. These four meteorological variables were of about equal importance in their influence on evaporation on the Canadian Prairies. Advected energy played a more important role than it has in more humid climates.