ETo image data (2-km spatial resolution), calculated using three methods, are available here for download, from August 26, 2013, through yesterday. The three ETo methods include: Penman-Monteith, Priestly-Taylor and Hargreaves-Samani. Other climate parameters are also available (i.e., min, max and avg. air temperature, saturated and actual vapor pressure, and solar and net radiation).
FOR DAILY IMAGES CLICK HERE
DISCLAIMER: The information is provided “as is”. The authors and publishers of this information disclaim any loss or liability, either directly or indirectly as a consequence of applying the information provided herein, or in regard to the use and application of said information. No guarantee is given, either expressed or implied, in regard to the accuracy, or acceptability of the information.
YESTERDAY’S REFERENCE EVAPOTRANSPIRATION FOR JAMAICA
The methodology used to estimate ETo for Puerto Rico was applied in this study to estimate ETo over the island of Jamaica. A detailed description of the methodology is provided in the following paper:
Harmsen, E. W., J. Mecikalski, M. J. Cardona-Soto, A. Rojas Gonzalez and R. Vasquez, 2009. Estimating daily evapotranspiration in Puerto Rico using satellite remote sensing. WSEAS Transactions on Environment and Development. Vol. 6(5):456-465.
The algorithm for ETo is a preliminary step in the development of a water and energy balance algorithm for Jamaica. Currently, an investigation is underway to obtain daily values of measured or modeled weather parameters that can be used to improve our algorithm. The current algorithm uses the following simplified estimates of weather parameters:
1. Wind speed at a 2-m height is assumed to be the world-wide average of 2 m/s, recommended by the United Nations Food and Agriculture Organization: FAO Irrigation and Drainage Paper No. 56.
2. Average, minimum and maximum daily air temperatures are estimated using a lapse rate approached developed for Puerto Rico (Goyal et al., 1988).
3. The dew point temperature (used to estimate the actual vapor pressure) is assumed to be equal to the daily minimum temperature (Allen et al., 1998).
4. Solar radiation (the most important variable in the ETo calculation) is derived from a physical model for estimating incident solar radiation at the surface from GOES satellite data, first proposed by Gautier et al. (1980) (see also Diak et al. 1996; Okin et al. 2005; and Sumner et al., 2008). The ground level, 2-km resolution solar radiation product became available for the Northern Caribbean Region in March of 2010.
Practical Application of Reference Evapotranspiration for Irrigation Scheduling
At the following link a simple methodology is presented for scheduling irrigation, which can be applied to Jamaica to save water, fuel and money: Simple web-based irrigation scheduling procedure. See also the following presentation which illustrates the procedure through a specific example problem: An Agricultural Application of GOES-PRWEB .
The following publications provide additional useful information
Allen, R. G., L. S. Pereira, Dirk Raes and M. Smith, Crop Evapotranspiration Guidelines for Computing Crop Water Requirements. FAO
Irrigation and Drainage Paper 56, Food and Agriculture Organization of the United Nations, Rome. 1998, pp. 300
Diak, G. R., W.L. Bland, and J. Mecikalski, 1996: A note on first estimates of surface insolation from GOES-8 visible satellite data. Agric. For. Meteorol., 82, 219-226.
Gautier, C., G. R. Diak, and S. Masse, 1980: A simple physical model to estimate incident solar radiation at the surface from GOES satellite data. J. Appl. Meteor.,19, 1007–1012.
Goyal, M. R., E. A. González, C. Chao de Báez, 1988. Temperature versus elevation relationships for Puerto Rico. J. Agric. UPR 72(3):449-67.
Harmsen, E. W., J. Mecikalski, A. Mercado and P. Tosado Cruz, 2010. Estimating evapotranspiration in the Caribbean Region using satellite remote sensing. Proceedings of the AWRA Summer Specialty Conference, Tropical Hydrology and Sustainable Water Resources in a Changing Climate. San Juan, Puerto Rico. August 30-September 1, 2010.
Otkin, A. J., M. C. Anerso, J. R. Mecikalski and G. R. Diak, 2005. Validation of GOES-Based Insolation Estimates Using Data from the U.S. Climate Reference Network. J. of Hydrometeorology, Vol. 6, August:460-475.
Sumner, D. M, C. S. Pathak, J. R. Mecikalski, S. fJ. Paech, Q. Wu, and T. Sangoyomi, 2008. Calibration of GOES-derived Solar Radiation Data Using Network of Surface Measurements in Florida, USA. Proceedings of the ASCE World Environmental and Water Resources Congress 2008 Ahupua’a.
ACKNOWLEDGEMENTS: This research received partial funding from the following sources: NOAA-CREST (grant NA06OAR4810162) and USDA Hatch Project (Hatch-402). Special thanks to Dr. John Mecikalski for providing the solar radiation data, and Alejandra Rojas for providing various GIS maps used in this research. I would like to thank my student, Victor Reventos, who made this possible through his Python programming skills.
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