The Performances of the Helioclim Databases in Mozambique

Abstract

This paper deals with the solar irradiance observed at ground level on horizontal surfaces and integrated over the whole spectrum (total irradiance), also called surface solar irradiance (SSI). The HelioClim project is an initiative of MINES ParisTech / Armines launched in 1997, to increase knowledge on SSI and to offer SSI values for any site, any instant within a large geographical area and large period of time, to a wide audience. It covers Europe, Africa and the Atlantic Ocean. The HelioClim-1 database, abbreviated in HC-1, offers daily values of SSI for the period 1985-2005. It has been created from archives of images of the Meteosat First Generation (MFG). The HelioClim-3 database, abbreviated in HC-3, began in 2004 and is updtaed daily. It exploits the enhanced capabilities of the series of satellites Meteosat Second Generation (MSG) to deliver values of SSI every 15 min with a spatial resolution of 3 km at nadir. These databases are available on the SoDa Service (www.soda-is.com). Their performances have been already assessed by a comparison with SSI measurements made at a number of meteorological stations. However, most of these stations are located in Europe, a very few are available in Africa and very often for a limited period of time. This communication focuses on the specific case of Mozambique. Owing to the World Radiation Data Center, data from several stations are available though the period of measurements is often limited to a few years. We discuss the quality of the ground-based measured daily means of SSI. Then, we perform a comparison between these measurements and the HC values, using standard procedure and performance parameters. We quantify the quality of the SSI retrieved from HC-1 and HC-3. We conclude that the HelioClim databases are a good means to assess the SSI in Mozambique and that the close-to 30-years period covered by HelioClim helps in depicting the change in SSI.