REGIONAL MODELS OF POTENTIAL EVAPORATION AND REFERENCE EVAPOTRANSPIRATION FOR THE NORTHEAST USA

Multivariate regression models of average monthly reference crop evapo transpiration, E(t)(tau), and potential evaporation, E(p)(tau), are de veloped for the northeast USA. Average monthly values of daily E(t) an d E(p) are estimated from the Penman-Monteith equation using monthly c limate data from 34 National Oceanic and Atmospheric Administration (N OAA) First Order weather observatories and specific reference vegetati on characteristics. The periodic seasonal behavior of E(t)(tau) and E( p)(tau) and average monthly temperature are approximated by Fourier se ries functions. Regional regression relationships are then developed w hich relate the E(t)(tau) and E(p)(tau) Fourier series coefficients wi th the average monthly temperature Fourier coefficients, station longi tude and station elevation. The regional E(t)(tau) model is shown to b e an improvement over the Linacre method (Linacre, 1977, Agric. Meteor ol., 18: 409-424) and the Hargreaves and Samani method (Hargreaves and Samani, 1985, Appl. Eng. Agric., 1(2): 96-99), and the regional E(p)( tau) model is shown to be an improvement over the Linacre method.