Abstract:
Temperature changes in the Arctic due to anthropogenic climate change are larger in magnitude than those at lower latitudes, with sea ice extent and thickness diminishing since the dawn of the satellite era. Aerosols may play a vital role in determining the changes to the Arctic. Specifically, the ability of absorbing aerosols to change the vertical structure of the atmosphere and sulfate aerosols to act as cloud condensation nuclei play important parts in the maintenance of Arctic stratiform clouds. However, there are still large uncertainties in the impact of aerosols on the changes in Arctic surface temperature, particularly during the diurnal cycle. This study attempts to address these changes using the Weather, Research, and Forecasting Chemistry (WRF-CHEM) model. The study investigates the changes in surface temperature, as well as the variables which affect surface temperature, due to aerosol effects in the Arctic. A suite of ensemble runs are used to develop a filtering mechanism based upon the t-test to eliminate the effects of meteorological variability. The total aerosol effect is then separated into the changes caused by the aerosol direct effect, the aerosol semi-direct effect, and the aerosol indirect effects through the use of additional WRF-CHEM runs. The study shows that aerosol indirect effects are the dominant influence on surface temperature changes throughout the diurnal cycle. While much has been speculated about the cooling role of indirect aerosol effects, this study shows that the indirect effects have both a warming and cooling effect, depending upon the time of day, underlying surface properties, and aerosol size distribution/concentration.
