Temporal extension of meteorological records for hydrological modelling of Lake Chad Basin (Africa) using satellite rainfall data and reanalysis datasets

Abstract

The inability to estimate reliable meteorological data for the hydrological modelling of the Lake Chad Basin (LCB) over the present decade hinders the use and evaluation of a wide range of hydrological information that can be extracted from satellite altimetry, gravitometry, and imagery. This is mainly due to the sparse distribution of gauging stations and difficulty in data assessment. Therefore, two key chronological records of rainfall and potential evapotranspiration (PET) were constructed for flow simulation modelling in the LCB. Rainfall estimates were extracted from two satellite-based precipitation products for the period 1998-2007 and combined with available chronological rainfall data. Similarly, PET records were derived over the period 1948-2007 using the meteorological variables extracted from reanalysis datasets, and the Hargreaves method. Subsequently, they were evaluated, first by pairwise comparison against available gridded datasets, and second by analyzing the error propagated through a distributed hydrological model. The satellite products strongly agree with the rain gauges. Compared to gridded rainfall estimates from the Climate Research Unit (CRU), satellite products tend to underestimate the values in the southern and eastern mountainous regions of the LCB and overestimate them within the central part of the LCB. Furthermore, flows simulated using the satellite products are in closer agreement with observed discharges than those modelled using CRU data. Concerning PET, the estimates from the Hargreaves method were compared with two gridded PET datasets: Penman PET data derived using climate data of the CRU, and climatological PET data from the Food and Agriculture Organization. © 2011 Royal Meteorological Society.