DSCOVR/EPIC-derived global hourly and daily downward shortwave and photosynthetically active radiation data at 0.1° × 0.1° resolution

Abstract

Abstract. Downward shortwave radiation (SW) and photosynthetically active radiation (PAR) play crucial roles in Earth system dynamics. Spaceborne remote sensing techniques provide a unique means for mapping accurate spatiotemporally continuous SW–PAR, globally. However, any individual polar-orbiting or geostationary satellite cannot satisfy the desired high temporal resolution (sub-daily) and global coverage simultaneously, while integrating and fusing multisource data from complementary satellites/sensors is challenging because of co-registration, intercalibration, near real-time data delivery and the effects of discrepancies in orbital geometry. The Earth Polychromatic Imaging Camera (EPIC) on board the Deep Space Climate Observatory (DSCOVR), launched in February 2015, offers an unprecedented possibility to bridge the gap between high temporal resolution and global coverage and characterize the diurnal cycles of SW–PAR globally. In this study, we adopted a suite of well-validated data-driven machine-learning models to generate the first global land products of SW–PAR, from June 2015 to June 2019, based on DSCOVR/EPIC data. The derived products have high temporal resolution (hourly) and medium spatial resolution (0.1∘×0.1∘), and they include estimates of the direct and diffuse components of SW–PAR. We used independently widely distributed ground station data from the Baseline Surface Radiation Network (BSRN), the Surface Radiation Budget Network (SURFRAD), NOAA's Global Monitoring Division and the U.S. Department of Energy's Atmospheric System Research (ASR) program to evaluate the performance of our products, and we further analyzed and compared the spatiotemporal characteristics of the derived products with the benchmarking Clouds and the Earth's Radiant Energy System Synoptic (CERES) data. We found both the hourly and daily products to be consistent with ground-based observations (e.g., hourly and daily total SWs have low biases of −3.96 and −0.71 W m−2 and root-mean-square errors (RMSEs) of 103.50 and 35.40 W m−2, respectively). The developed products capture the complex spatiotemporal patterns well and accurately track substantial diurnal, monthly, and seasonal variations in SW–PAR when compared to CERES data. They provide a reliable and valuable alternative for solar photovoltaic applications worldwide and can be used to improve our understanding of the diurnal and seasonal variabilities of the terrestrial water, carbon and energy fluxes at various spatial scales. The products are freely available at https://doi.org/10.25584/1595069 (Hao et al., 2020).

WRF-GC (v2.0): online two-way coupling of WRF (v3.9.1.1) and GEOS-Chem (v12.7.2) for modeling regional atmospheric chemistry–meteorology interactions

“…Zhang et al, 2011;Zhao et al, 2018). Over southern China, the observed effective radii of liquid cloud droplets in summer vary from 7.3 ± 1.7 to 7.9 ± 3.0 µm (Hao et al, 2017;. Our simulated effective radii of liquid cloud droplets are consistent with these observed sizes of liquid cloud droplets and reflect the spatial difference between northern and southern China.…”

“…Meteorology-dependent emissions, including the emissions of biogenic volatile organic compounds (Guenther et al, 2012), sea salt (Gong, 2003), dust (Zender et al, 2003), soil NO x (Hudman et al, 2012), and lightning NO x (Murray et al, 2012), are calculated online in the HEMCO module (Keller et al, 2014) in GEOS-Chem. Imaging Camera (EPIC)-derived products over land at 0.1 • resolution (Hao et al, 2020). The EPIC-derived total downward shortwave radiation is consistent with the ground-based observations with a low global bias of −0.71 W m −2 over land.…”

“…For January 2015, due to the lack of EPIC-derived products, we use the monthly gridded product from the Clouds and the Earth's Radiant Energy System (CERES) edition 4.1 at 1 • resolution (Rutan et al, 2015). The spatiotemporal variations of the surface downward shortwave radiation observed by the EPIC and CERES instruments are generally consistent (Hao et al, 2020).…”

Comment on gmd-2020-441

“…The EPIC-derived total downward shortwave radiation is consistent with the ground-based observations with a low global bias of -0.71 Wm −2 over land. The spatiotemporal variations in the EPICderived surface downward shortwave radiation agrees well with the Clouds and the Earth's Radiant Energy System Synoptic (CERES) data (Hao et al, 2020).…”

“…We validate the surface downward shortwave radiation simulated by WRF-GC using the latest Earth Polychromatic Imaging Camera (EPIC)-derived products over land at 0.1 • spatial resolution (Hao et al (2020), https://doi.org/10.25584/1595069).…”