Abstract
Abstract. Solar radiation plays a key role in the Earth's energy balance and is used as an essential input data in radiation-based evapotranspiration (ET) models. Accurate gridded solar radiation data at high spatial and temporal resolution are needed to retrieve ET over large domains. In this work we present an evaluation at hourly, daily and monthly time steps and regional scale (Catalonia, NE Iberian Peninsula) of a satellite-based solar radiation product developed by the Land Surface Analysis Satellite Application Facility (LSA SAF) using data from the Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI). Product performance and accuracy were evaluated for datasets segmented into two terrain classes (flat and hilly areas) and two atmospheric conditions (clear and cloudy sky), as well as for the full dataset as a whole. Evaluation against measurements made with ground-based pyranometers yielded good results in flat areas with an averaged model RMSE of 65 W m−2 (19%), 34 W m−2 (9.7%) and 21 W m−2 (5.6%), for hourly, daily and monthly-averaged solar radiation and including clear and cloudy sky conditions and snow or ice cover. Hilly areas yielded intermediate results with an averaged model RMSE (root mean square error) of 89 W m−2 (27%), 48 W m−2 (14.5%) and 32 W m−2 (9.3%), for hourly, daily and monthly time steps, suggesting the need of further improvements (e.g., terrain corrections) required for retrieving localized variability in solar radiation in these areas. According to the literature, the LSA SAF solar radiation product appears to have sufficient accuracy to serve as a useful and operative input to evaporative flux retrieval models.
Highlights
Knowledge of spatiotemporal distributions in solar radiation (Rs) is essential in many disciplines such as ecology, agronomy and hydrology, and plays a key role in the modeling of evapotranspiration (ET), both actual and potential, as well as air temperature
In this work we present a regional-scale evaluation of the Land Surface Analysis Satellite Application Facility (LSA SAF) Rs product, generated using Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) images from 2008 to 2011
The RMSE variability for all sky conditions from 2008 to 2010 is low in both terrain classes, not exceeding more than 10 W m−2 in flat sites and 2 W m−2 in hilly sites
Summary
Knowledge of spatiotemporal distributions in solar radiation (Rs) is essential in many disciplines such as ecology, agronomy and hydrology, and plays a key role in the modeling of evapotranspiration (ET), both actual and potential, as well as air temperature. ET algorithms operating at regional to global scales can benefit from Rs surfaces retrieved using satellite imaging Most of these ET methods have been validated in homogeneous covers (crops or natural vegetation) and flat areas, using a single value of Rs from a meteorological station record to describe a large area. Rs is typically estimated using one of three different methodologies: empirical models, based on statistical correlations between Rs and other parameters; parametric models, based on the physics of interactions of Rs with the atmosphere (Martınez-Durbaran et al, 2009); and hybrid models that combine both approaches Some of these models use GIS-based techniques and a digital elevation model, DEM, (Pons and Ninyerola, 2008) to compute Rs at regional and global scales in both simple and complex areas offering high accuracy and high spatial resolution, but relying on a well developed meteorological station network. The Rs product use as an input to evaporative flux retrievals is briefly discussed, as reported in the current literature
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