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. The study covered three different periods, January to February of 1994, January to February of 1990, and August to September of 1989. The fields were irrigated regularly (three times a week) to provide enough water to evaporate. The daytime (07:00-18:00 hours) 20 min and hourly latent heat flux values, average evaporation for the earlier mentioned three periods and evaporation on individual days were estimated using De Bruin and Holtslag scheme for 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 the latent heat flux and evaporation led to the following results. (i) The values of latent heat flux and evaporation estimated using alpha'=0.95 and beta=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 our work was very close to that reported in the study of De Bruin and Holtslag, implying the consistency of the skill of that scheme at higher average latent heat flux levels in Jamaica. (iii) The choice of 1.05 for alpha' applies 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 used to estimate daytime latent heat flux and evaporation from well watered grass surfaces in regions having environmental conditions similar to those encountered in Jamaica, but appears better with alpha'=1.05. (C) 2000 Elsevier Science B.V. All rights reserved.