Velle Toll will defend his doctoral thesis titled "Direct radiative impacts of atmospheric aerosols on meteorological conditions over Europe" on 9. September 2016 at 14.15 at W. Ostwaldi 1, room B103.
Piia Post, Institute of Physics, University of Tartu
Aarne Männik, Institute of Physics, University of Tartu
Sami Niemelä, Finnish Meteorological Institute
Anu Reinart, Tartu Observatory
The most important applications of modern-day atmospheric physics are numerical weather prediction and projections of the future climate. Accurate weather forecasts provide great economic benefits and help to protect human lives and property. Climate modelling helps to determine anthropogenic influences on climate and it forms the basis for climate change mitigation and adaptation strategies. Atmospheric aerosols, tiny solid and liquid particles suspended in the air, influence both short-term weather conditions and the Earth's climate. It is very important to study aerosol impacts on meteorological conditions because in the projections of future climate the largest uncertainty is related to aerosol impacts. Aerosols influence the shortwave and longwave radiative transfer in the atmosphere and the properties of clouds and the formation of precipitation because aerosol particles serve as cloud condensation nuclei. The net effect of aerosols on the Earth's radiative budget is negative and they offset part of the warming induced by greenhouse gases. In this thesis, increasing of the accuracy of short-term numerical weather forecasts over Europe was investigated by improving the representation of the direct radiative effect of aerosols in an atmospheric model. It was found that aerosols have a considerable influence on the energy budget at the Earth's surface and temperature and humidity distributions in the lower atmosphere over Europe and it is necessary to account for the aerosol impacts in order to provide accurate numerical weather forecasts. Including a better representation of the direct radiative effect of aerosols leads to more accurate forecasts of the surface shortwave fluxes which are also necessary for solar energy applications. During periods with very high aerosol concentrations in the atmosphere, the influence of realistic aerosols should be accounted for. In addition, the weakening of a severe convective storm due to the influence of aerosols was demonstrated in this thesis.