Abstract

The Food and Agriculture Organization (FAO) missing data procedure was employed in this study to verify its suitability under the climatic environment of Malawi. The performance of the procedure was analysed by regressing ETo estimated from the world wide recommended FAO penman Monteith (FPM) model with full data set versus FPM value computed with limited data. The coefficients of determination (r²), standard errors of estimates (SEE) and estimates rates (Rate) were used for evaluating the model performance in five production sites in Malawi including Karonga, Chitedze, Kasungu, Chileka and Ngabu. The study shows the suitability of the FAO procedure to estimate other climatic variables which are required in FPM model when only temperature data is available under the semiarid environment of Malawi. However in areas of high wind speed like Karonga and Chileka, care must be taken while applying the procedure when both wind and relative humidity are missing. Additionally, it is observed that the model performances improved while seasonal based estimation is applied. Therefore, the seasonal based consideration should be recommended accounting for the climatic variation between the seasons. The missing data estimation procedure may help to solve part of the irrigation planning and management problem due to the meteorological data unavailability in some areas of Malawi.

Key words: Evapotranspiration, missing data, seasonal based, irrigation management, wind speed, semiarid environment.