Thesis of Gabriel Chenoiu

Defense of thesis Gabriel Chenoiu - laboratory LOA

Solar environment and atmopheric pollution particles in the Hauts-de-France region: recent evolution and future scenarios

Abstract :

The solar radiation incident at the surface, primary source of energy for life on Earth and for photovoltaic resources, exhibits strong spatiotemporal variabilities, mainly due to the influence of atmospheric properties.

The main objective of this thesis is to analyze the recent variability and future evolution of the solar environment in the Hauts-de-France region (HdF), which is characterized by a strong influence of cloudy conditions and significant levels of particulate pollution.

We first use continuous coincident measurements of aerosol optical properties and incident solar radiation at the surface conducted in Lille between 2010 and 2022. The development of a classification of sunshine conditions into three categories (clear sky, cloudy sky with visible or non-visible sun) allows us to obtain solar environment climatologies for the different situations. Furthermore, the use of a multivariate decomposition based on radiative transfer simulations allows us to analyze the influence of cloud and atmospheric aerosol variability on the measured solar environment in Lille. Spring and summer, two key seasons in terms of solar resource, are marked by less cloudy conditions and high aerosol concentrations. In spring, the aerosol direct radiative effect is maximum, with an average reduction of the incident global irradiance of about -9 W/m² (-23 W/m² in the absence of clouds in the direction of the Sun). Aerosols significantly alter the partition between direct and diffuse solar radiation, increasing the proportion of diffuse irradiance by a factor of 2 on average under clear skies. In Lille, our analysis also highlights a trend over the study period of increasing global and direct solar flux (approximately +4 W/m²/year) for these two seasons, in connection with a decrease in the frequency of cloudy conditions.

To spatially extend the study conducted in Lille to the entire HdF region and its surroundings, we use climate simulations from the ALADIN-Climat regional model, which includes the TACTIC aerosol scheme. Analysis of a first set of HINDCAST simulations for the period 2010-2020 shows satisfactory comparisons with flux and aerosol measurements from several sites in our study area. This approach also highlights maximum sunshine and global flux in spring and summer, especially in the southern part of the study region, the English Channel, and the North Sea, as well as particularly high levels of aerosols over the Benelux and the HdF region. Furthermore, the recent increasing trend of the global irradiance measured in Lille due to the decrease in the frequency of cloudy conditions is confirmed by ALADIN-Climat over a large part of the region. Finally, using three additional sets of ALADIN-Climat simulations in climate mode, we analyze the possible future evolution, in spring and summer, of the solar environment in 2050 and 2100 compared to the period 2005-2014 for two contrasting CMIP6 climate scenarios. For the relatively optimistic SSP1-1.9 scenario, ALADIN-Climat projects an increase in global flux in spring and summer in 2100, especially over England and the eastern part of the study area, in connection with a coincident decrease in cloud cover and aerosols. For the more pessimistic SSP3-7.0 scenario, ALADIN-Climat simulates, on the contrary, a significant decrease in global flux across the entire region for both seasons, in connection with an increase in aerosols and water vapor. In summer, ALADIN-Climat simulates a decrease in cloud cover that compensates for these initial effects, more so in 2050 than in 2100. In spring, the simulations project an increase in cloud cover, which amplifies the decrease in global flux as early as 2050.

Keywords : Solar Radiation,Pollution,Energy balance,Climate change,Climate plannification,Solar Energy