Evaluation of the radiation budget with a regional climate model over Europe and inspection of dimming and brightening

Abstract

Shortwave (SW) and longwave (LW) components of the radiation budget at the surface and top of atmosphere (TOA) are evaluated in the regional climate model RegCM version 4 driven by European Centre for Medium-Range Weather Forecasts Reanalysis over Europe. The simulated radiative components were evaluated with those from satellite-based products and reanalysis. At the surface the model overestimated the absorbed solar radiation but was compensated by a greater loss of thermal energy while both SW and LW TOA net fluxes were underestimated representing too little solar energy absorbed and too little outgoing thermal energy. Averaged biases in radiative parameters were generally within 25 W m À2 , were dependent on differences by as much as 0.2 in cloud fraction, surface, and planetary albedo and less dependent on surface temperature associated with the surface longwave parameters, and are in line with other studies. Clear-sky fluxes showed better results when cloud cover differences had no influence. We also found a clear distinction between land versus water with smaller biases over land at the surface and over water at the TOA due to differences in cloud fraction and albedo. Finally, we inspected dimming and brightening for the period 1979-2010 with an indication for dimming early in the time series (i.e., 1979-1987) and brightening after, which agrees with surface-based observations. After 2000, however, a decrease in the brightening by more than 1 order of magnitude was evident which is in contrast to the continued brightening found in surface records and satellite-derived estimates.

Modelled and observed changes in aerosols and surface solar radiation over Europe between 1960 and 2009

“…Without ARE the simulated trend in SSR is underestimated (0.09 ± 0.14 W m −2 yr −1 ), suggesting that changes in aerosol concentrations are a dominant driver of SSR trends during this period. The simulated positive trend in SSR including ARE presented here is in agreement with other studies over this period Allen et al, 2013;SanchezLorenzo et al, 2013;Chiacchio et al, 2015).…”

“…Folini and Wild (2011) performed transient simulations with ECHAM5-HAM over Europe (with interactive aerosols) and found that simulated reductions in SSR occurred too early in the model, whereas the increase in SSR was correctly timed. Using a regional climate model over Europe driven by reanalysis data, Chiacchio et al (2015) overestimated SSR, simulated a premature onset of dimming and demonstrated that only simulations including aerosols were able to reproduce the observed brightening trend. In addition, Koch et al (2011) simulated the correct interdecadal variability in SSR but underestimated the magnitude of observed SSR.…”

More homogeneous wind conditions under strong climate change decrease the potential for inter-state balancing of electricity in Europe

“…Assessing changes in solar power generation is arguably more difficult due to, among other things, unresolved processes in relatively coarse climate models and uncertain parameterizations (e.g., Chiacchio et al, 2015;Herwehe et al, 2014). Acknowledging this difficulty and associated uncertainties, an evaluation of the EURO-CORDEX data finds limited impacts of climate change on solar photovoltaic (PV) potentials .…”

A Satellite-Based Sunshine Duration Climate Data Record for Europe and Africa

“…The significance of satellite-based solar radiation data for the evaluation of climate models has been recognized over the last few years (e.g., [12][13][14][15]). Compared to global radiation, there are many more stations worldwide that provide sunshine duration measurements.…”