Changes in the spectral composition of surface solar radiation under the presence of stratospheric aerosols: a case study for the Pinatubo eruption

The presence of aerosols in the stratosphere alters the spectral shape, the amount and the spatial distribution of the solar light that reaches the Earth surface. Such changes in surface solar radiation have been discussed in a few studies, but the role of the underlying tropospheric aerosol layer in the presence of stratospheric aerosols has not been considered. In this study we investigate the changes in the direct and global spectral surface solar irradiances following the extremely intense volcanic eruption (VEI=6) of Mount Pinatubo (15°N, 120°E) in June 1991. The eruption of Mount Pinatubo ejected massive loads of sulphate and ash particles into the stratosphere, which covered the entire globe after three weeks and then remained in the stratosphere for several months. In the aftermath, major perturbations of the stratospheric ozone layer and the near-surface temperature have been documented. Here, we provide model-derived stratospheric aerosol optical properties, constrained by ground-based and airborne remote sensing and in-situ data, to the radiative transfer model libRadtran to calculate the spectral surface solar irradiance in the wavelength range 350 – 750 nm. Radiative transfer simulations have been performed for two European sites where in situ measurements of the aerosol extinction profile were available a few months after the eruption, assuming different concentrations and types of tropospheric aerosols present in the atmosphere along with the overlying stratospheric volcanic layers, as well as different solar zenith angles. Changes in the spectral composition and the distribution of surface solar radiation in the considered spectral range play a key role in many biological processes (e.g., photosynthesis), as well as in solar energy production. Thus, our results provide insights on how such processes could be impacted after future volcanic eruptions or under solar radiation modification scenarios.

Acknowledgements: This work has been supported by the action titled “Support for upgrading the operation of the National Network for Climate Change (CLIMPACT II)”, funded by the Public Investment Program of Greece, General Secretary of Research and Technology/Ministry of Development and Investments.