Abstract
The use of regional climate models (RCMs) can partly reduce the biases in global radiative flux (Eg↓) that are found in reanalysis products and global models, as they allow for a finer spatial resolution and a finer parametrisation of surface and atmospheric processes. In this study, we assess the ability of the MAR («Modèle Atmosphérique Régional») RCM to reproduce observed changes in Eg↓, and we investigate the added value of MAR with respect to reanalyses. Simulations were performed at a horizontal resolution of 5 km for the period 1959–2010 by forcing MAR with different reanalysis products: ERA40/ERA-interim, NCEP/NCAR-v1, ERA-20C, and 20CRV2C. Measurements of Eg↓ from the Global Energy Balance Archive (GEBA) and from the Royal Meteorological Institute of Belgium (RMIB), as well as cloud cover observations from Belgocontrol and RMIB, were used for the evaluation of the MAR model and the forcing reanalyses. Results show that MAR enables largely reducing the mean biases that are present in the reanalyses. The trend analysis shows that only MAR forced by ERA40/ERA-interim shows historical trends, which is probably because the ERA40/ERA-interim has a better horizontal resolution and assimilates more observations than the other reanalyses that are used in this study. The results suggest that the solar brightening observed since the 1980s in Belgium has mainly been due to decreasing cloud cover.
Highlights
The amount of solar radiation reaching the Earth’s surface or global radiative flux governs a wide range of processes that support life on Earth
The regional climate models (RCMs) used in this study is the Modèle Atmosphérique Régional (MAR) model coupled to the one-dimensional (1D) surface transfer scheme SISVAT (Soil–Ice–Snow–Vegetation–Atmosphere–Transfer)
We find differences between ERA40 (1962–1978) and ERA-interim (1979–2010), while this value reaches +64.3 W m−2 in NCEP/NCAR-v1, which is in agreement with the findings of which are not observed in the associated MAR simulation (MAR-ERA) (Figure 2)
Summary
The amount of solar radiation reaching the Earth’s surface or global radiative flux (hereafter referred to as Eg↓ ) governs a wide range of processes that support life on Earth. It generates changes in the water cycle and carbon cycle, and causes droughts or heat waves [1]. Worldwide monitoring of Eg↓ from ground-based stations began in the late 1950s These ground-based measurements suggest that the period 1950–1980 was marked by a decrease in Eg↓ that is better known as “global dimming” [3,4,5,6].
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