Estimating downwelling solar irradiance at the surface of the tropical Atlantic Ocean: A comparison of PIRATA measurements against several re-analyses and satellite-derived data sets

Abstract

Abstract. 15This paper assesses the merits and drawbacks of several data sets of the solar downwelling radiation received at the surface of the tropical Atlantic Ocean where the field of solar radiation is hardly known. The data sets are compared to qualified measurements of hourly irradiance made at five buoys of the PIRATA network for the period 2012-2013. The data sets comprise the re-analyses MERRA-2 and ERA-5 and three satellite-derived data sets: HelioClim 3v5, SARAH 2 and CAMS Radiation Service v2. The re-analyses often report cloud-free conditions while actual conditions are cloudy and reciprocally, 20 actual cloudless conditions as cloudy. The medium and high level clouds exhibit more bias than the low level clouds. The reanalyses poorly correlate with the optical state of the atmosphere derived from the measurements. The actual irradiance field is spatially distorted by re-analyses, especially for MERRA-2. Performances are similar between the three satellite-derived data sets. They correlate well with the optical state of the atmosphere and reproduce well the dynamics of the solar irradiance. The three data sets exhibit overestimation with the lowest biases reached by CAMS Radiation Service v2. The 25 bias of HelioClim 3v5 is fairly similar from one location to the other which means that the actual spatial gradients are well reproduced.Ocean Sci. Discuss., https://doi

Comparison of several satellite-derived databases of surface solar radiation against ground measurement in Morocco

“…Bell et al (2009), Bengulescu et al (2016Bengulescu et al ( , 2018, Blanc et al (2011Blanc et al ( , 2015, Lefèvre et al (2007), Wahab et al (2009). Solar radiation is also a crucial factor which influences life on Earth for animals, plants (Bois et al, 2008;Colombo et al, 2009;Wagner et al, 2012) and humans (Juzeniene et al, 2011). The energy received from the Sun and impinging on a horizontal surface of unit surface located at ground level is called the surface solar downward irradiation and is abbreviated as SSI.…”

“…For example, meteorological reanalyses offer estimates of SSI covering the whole world that span several decades back in time. Boilley and Wald (2015), Bengulescu et al (2017) and Trolliet et al (2017) have analyzed the quality of several reanalyses: ERA-Interim, ERA-5, MERRA, and MERRA-2, against ground measurements of SSI. These authors reported that re- Table 1.…”

“…Instrument description and measured data for each station (from Schüler et al, 2016 analyses often exhibit cloudy conditions while actual conditions are cloud-free and vice versa. Satellite images are another means to getting a synoptic view of the SSI and may supplement radiometric measurements (Lefèvre et al, 2014;Wagner et al, 2012). Several databases have been constructed from images acquired by the Meteosat series of satellites.…”

Deriving Photosynthetically Active Radiation at ground level in cloud-free conditions from Copernicus Atmospheric Monitoring Service (CAMS) products

“…There is a practical advantage to this approach as broadband radiation is accurately estimable from satellite images (Blanc et al, 2011;Lefèvre et al, 2014). Alternate sources of data on broadband radiation are meteorological analyses or forecasts though their quality is poorer than that of satellite-derived data (Boilley and Wald, 2015;Bengulescu et al, 2017;Trolliet et al, 2017).…”

Monthly solar radiation in the tropical Atlantic Ocean: Can its spatial variations be captured by the current configuration of the PIRATA moorings?

“…Too many stations may result in an over-investment with a negligible scientific gain; too few stations may lead to a misrepresentation of the spatial variability of the variables of interest, with possible biases in analyses and interpretation of the measurements. Techniques have been proposed for the optimal design of networks of measuring stations at ground (Bogárdi et al, 1985;Bras and Rodríguez-Iturbe, 1976;Stauffer et al, 2000;Vinnikov et al, 1999). They are often based on the analysis of a priori knowledge of the spatial correlation and more generally of the geostatistical properties of the variables of interest and the space and timescales to study.…”