ON THE PROPER EMPLOYMENT OF PICHE EVAPORIMETERS IN ESTIMATING EVAPOTRANSPIRATION

Daily meteorological measurements taken in Athens during the period 19 51-1984 are used to investigate the feasibility of calculating Penman- Monteith's evapotranspiration estimates when wind measurements are not available. Dairy sheltered Piche data (from a large meteorological sc reen) are shown to be satisfactorily related to the second term in Pen man-Monteith's equation on a daily basis. Furthermore, daily conventio nal Penman-Monteith evapotranspiration estimates are compared with the ones obtained from the adjusted Piche readings and the results show t hat daily, monthly or yearly evapotranspiration estimates, acquired ov er long periods, can be successfully estimated by using the substantia l backlogs of Piche evaporimeter data. The analysis suggests monthly r elationships to be justified for adjusting Piche data, although even o ne annual relationship seems to be able to estimate evapotranspiration in most of the months, or in a whole year period, satisfactorily. (C) 1998 Royal Meteorological Society.