Evaporation‐maps of the United States

The monthly and annual numbers of Climatological Data of the United States contain monthly evaporation‐data at United States Weather Bureau Class‐A evaporation‐stations. A four‐foot diameter circular evaporation‐pan ten inches deep is used. The pan stands on a wooden grillage with the rim about 14 inches above ground. Water is maintained at a depth of one to two inches below the rim of the pan. These records were compiled for over 100 stations having records varying from three to 25 years' duration. South of latitude 37° north the records are mostly maintained throughout the entire year. For stations with full yearly records the means of the evaporation were separately determined for the six months of summer, May to October, the six months of winter, November to April, and also for the year. These original data, together with information regarding the stations, is given in columns (1) to (11), inclusive, of Table 1.