A daily resolution evapoclimatonomy model applied to surface water balance calculations at the HAPEX-Sahel supersites

Abstract

This paper describes the results of Lettau's evapoclimatonomy model at daily time scales as applied to the Central East and Southern supersites of the HAPEX-Sahel region in Niger, West Africa. A revised version of the evapoclimatonomy model has been applied to the millet and bush fallow ( Guiera senegalensis) fields at both supersites during the intensive observation period (IOP; 20 August–12 October, 1992), using daily means of precipitation, potential evapotranspiration, solar radiation, normalized difference vegetation index (NDVI) from the HAPEX-Sahel observations, as well as vegetation and soil parameters for the region. Soil moisture and immediate and delayed evapotranspiration and runoff are predicted. It has been found that the model predicts the soil moisture at the Central Eastern supersite quite well. However, it overestimates soil moisture at the Southern supersite even though its variability is captured by the model. Model results also indicate that soil moisture estimates are very sensitive to the NDVI-evaporivity relationship, which is robust at monthly scales but needs more revision for application at the daily scale. Overall the model performance when applied to the IOP observations is sufficiently good to indicate the suitability of the climatonomy for water balance studies on daily time scales.