Observed patterns of surface solar irradiance under cloudy and clear‐sky conditions

Mol, Wouter; Heusinkveld, Bert; Mangan, Mary Rose; Hartogensis, Oscar; Veerman, Menno; van Heerwaarden, Chiel

doi:10.1002/qj.4712

Cited by 4 publications

(1 citation statement)

References 65 publications

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“…GHI exceeding clear-sky GHI, occurs at multiple moments throughout this day. From surface observations, it is known that especially for altocumulus, cloud enhancement can be prominent, with GHI even exceeding its clear-sky value by up to 40 % at sub-minute timescales (Mol et al, 2024). Here, the observed cloud enhancement is smaller since, in this study, 5-minute averaged observations of GHI are considered and the effects of cloud enhancements are more pronounced at smaller timescales.…”

Section: Example Casesmentioning

confidence: 90%

Validating global horizontal irradiance retrievals from Meteosat SEVIRI at increased spatial resolution against a dense network of ground-based observations

Wiltink,

Deneke,

Saint-Drenan

et al. 2024

Preprint

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Abstract. Accurate and detailed retrieval of global horizontal irradiance (GHI) has many benefits, for instance, in support of the energy transition towards an energy supply with a high share of renewable energy sources and for validating high-resolution weather and climate models. In this study, we apply a downscaling algorithm that combines the High-Resolution Visible and standard-resolution channels onboard MSG-SEVIRI to obtain cloud physical properties and GHI at an increased nadir spatial resolution of 1 x 1 km2 instead of 3 x 3 km2. We validate the change in accuracy of the high-resolution GHI in comparison to the standard-resolution product against ground observations from a unique network of 99 pyranometers deployed during the HOPE field campaign in Jülich, Germany, from 18 April to 22 July 2013. Over the entire duration of the field campaign, a small but statistically significant reduction in root-mean-square error (RMSE) by 2.8 W m-2 is found for the high-resolution GHI at 5-minute scale. The added value of the increased spatial resolution is largest on days when GHI fluctuates strongly: for the ten most variable days a significant reduction of the RMSE by 7.9 W m-2 is obtained with high- versus standard-resolution retrievals. In contrast, we do not find significant differences between both resolutions for clear-sky and fully overcast days. The sensitivity of these results to temporal and spatial averaging scales is studied in detail. Our findings highlight the benefits of spatially dense network observations as well as a cloud-regime resolved approach for the validation of GHI retrievals. We also conclude that more research is needed to optimally exploit the instrumental capabilities of current advanced geostationary satellites in terms of spatial resolution for GHI retrieval.

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Section: Example Casesmentioning

confidence: 90%

Validating global horizontal irradiance retrievals from Meteosat SEVIRI at increased spatial resolution against a dense network of ground-based observations

Wiltink,

Deneke,

Saint-Drenan

et al. 2024

Preprint

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Combining observations and simulations to investigate the small-scale variability of surface solar irradiance under continental cumulus clouds

He,

Libois,

Villefranque

et al. 2024

Atmos. Chem. Phys.

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Abstract. The amount of solar radiation reaching the Earth surface (surface solar irradiance, SSI) is critical for a variety of applications, ranging from surface–atmosphere interactions to solar energy. SSI is characterized by a large spatiotemporal variability, in particular in the presence of cumulus clouds. This results in complex spatial patterns of shadows and sunlight directly related to clouds' geometry and physical properties. Although key in many respects, the instantaneous spatial distribution of SSI remains largely unexplored. Here, we use unique observations from a dense network of pyranometers deployed during the HOPE field campaign to investigate the SSI spatial distribution. For cumulus scenes, bimodal distributions are found, with one mode corresponding to cloud shadows and the other to sunlit areas with enhanced SSI exceeding clear-sky values. Combining large-eddy simulations of cumulus clouds with Monte Carlo ray tracing, we demonstrate the capability of advanced numerical tools to reproduce the observed distributions and quantify the impact of cloud geometrical and physical properties on both modes. In particular, cloud cover strongly modulates their amplitudes, in addition to their position and width, which are also sensitive to cloud height, geometrical depth, and liquid water content. Combining observations and simulations, we also explore sampling strategies to estimate the SSI spatial distribution with a limited number of sensors, suggesting that 10 pyranometers integrated over 10 min can capture most details of the full distribution. Such a strategy could be used for future campaigns to further investigate SSI distributions and their impact on land–atmosphere exchanges or photovoltaic farm management.

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Regional validation of the solar irradiance tool SolaRes in clear-sky conditions, with a focus on the aerosol module

Elias,

Ferlay,

Chesnoiu

et al. 2024

Atmos. Meas. Tech.

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Abstract. The Solar Resource estimate (SolaRes) tool based on the Speed-up Monte Carlo Advanced Radiative Transfer code using GPU (SMART-G) has the ambition to fulfil both research and industrial applications by providing accurate, precise, and high-time-resolution simulations of the solar resource. We investigate the capacity of SolaRes to reproduce the radiation field, relying on 2 years of ground-based measurements by pyrheliometers and pyranometers acquired in northern France (Lille and Palaiseau). Our main objective is to provide, as a first step in clear-sky conditions, a thorough regional validation of SolaRes, allowing us to investigate aerosol impacts on solar resource. We perform comparisons between SolaRes-simulated and clear-sky-measured global horizontal irradiance (GHI), direct normal irradiance (DNI), diffuse horizontal irradiance (DifHI), and global and diffuse irradiance on a tilted plane (GTI, DifTI), and we even consider the circumsolar contributions. Using spectral aerosol optical thickness (AOT) data sets as input, which are delivered by the AErosol RObotic NETwork (AERONET) and the Copernicus Atmosphere Monitoring Service (CAMS), we examine the influence of aerosol input data sets in SolaRes on the comparison scores. Two aerosol models are mixed to compute aerosol optical properties. We also perform a sensitivity study on the aerosol parametrisation and investigate the influence of applying more or less strict cloud-screening methods to derive ground-based proof data sets of clear-sky moments. SolaRes is validated with the (relative) root mean square difference (RMSD) in GHI as low as 1 % and a negligible mean bias difference (MBD). The impact of the cloud-screening method in GHI is 0.5 % of RMSD and 0.3 % of MBD. SolaRes also estimates the circumsolar contribution, which improves MBD in DNI and DifHI by 1 % and 4 %, respectively, and RMSD by ∼ 0.5 %. MBD in DNI is around −1 % and RMSD around 2 %, and MBD in DifHI is 2 % and RMSD around 9 %. RMSD and MBD in both DNI and DifHI are larger than in GHI because they are more sensitive to the aerosol and surface properties. DifTI measured on a vertical plane facing south is simulated by SolaRes with an RMSD of 8 %, comparable to that obtained for DifHI. Our results suggest a strong influence of reflection by not only ground surface but also surrounding buildings. The sensitivity studies on the aerosol parameterisation show that the spectral AOT contains enough information for high performance in DNI simulations, with low influence of the choice of the aerosol models on the RMSD. However, choosing a model with smaller aerosol single scattering albedo significantly decreases SolaRes DifHI and GHI. The best combination in Lille and Palaiseau consists of continental clean mixed with desert dust. Also, complementary information on angular scattering and aerosol absorption provided by the AERONET-inverted model further improves simulated clear-sky GHI by reducing RMSD by ∼ 0.5 % and MBD by ∼ 0.8 %. Eventually, the choice of the data source has a significant influence. Indeed, using CAMS AOT instead of AERONET AOT increases the RMSD in GHI by ∼ 1 % and MBD by ∼ 0.4 % and RMSD in DNI by 5 %. The RMSD in GHI remains slightly smaller than state-of-the-art methods.

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Observed patterns of surface solar irradiance under cloudy and clear‐sky conditions

Cited by 4 publications

References 65 publications

Validating global horizontal irradiance retrievals from Meteosat SEVIRI at increased spatial resolution against a dense network of ground-based observations

Validating global horizontal irradiance retrievals from Meteosat SEVIRI at increased spatial resolution against a dense network of ground-based observations

Combining observations and simulations to investigate the small-scale variability of surface solar irradiance under continental cumulus clouds

Regional validation of the solar irradiance tool SolaRes in clear-sky conditions, with a focus on the aerosol module

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