Estimating daytime latent heat flux and evapotranspiration in Jamaica

The suitability of the two-parameter scheme of De Bruin and Holtslag (1982) to estimate daytime latent heat flux and evapotranspiration in Jamaica was examined using meteorological data collected over fields of short grass. T he study covered three different periods, January to February of 1994, Janu ary to February of 1990, and August to September of 1989. The fields were i rrigated regularly (three times a week) to provide enough water to evaporat e. The daytime (07:00-18:00 hours) 20 min and hourly latent heat flux value s, average evaporation for the earlier mentioned three periods and evaporat ion on individual days were estimated using De Bruin and Holtslag scheme fo r two situations. One was with the parameter alpha'=0.95 and beta=20 W m(-2 ) and the other was with alpha'=1.05 and beta=20 W m(-2). The analysis of t he latent heat flux and evaporation led to the following results. (i) The v alues of latent heat flux and evaporation estimated using alpha'=0.95 and b eta=20 W m(-2) compare well with the corresponding measured values for time steps of the order of 20 min to several days. (ii) The level of agreement between estimated and measured hourly values of latent heat flux seen in ou r work was very close to that reported in the study of De Bruin and Holtsla g, implying the consistency of the skill of that scheme at higher average l atent heat flux levels in Jamaica. (iii) The choice of 1.05 for alpha' appl ies better for our data. These results indicate that the scheme of De Bruin and Holtslag with alpha'=0.95 and beta=20 W m(-2) can satisfactorily be us ed to estimate daytime latent heat flux and evaporation from well watered g rass surfaces in regions having environmental conditions similar to those e ncountered in Jamaica, but appears better with alpha'=1.05. (C) 2000 Elsevi er Science B.V. All rights reserved.