Aerosols and clouds affecting the radiation budget at Pituffik (Thule), northern Greenland: Insights on the installed and newly developed ground-based instruments at the Thule High Arctic Atmospheric Observatory (THAAO)

The relevance of the Arctic has become apparent in the last decades, and it is today widely agreed that this area is affected by fast and unavoidable changes taking place at the global and local scale. The Arctic environment is interesting from geopolitical, economic, and scientific perspectives, and the study of the natural components characterising the area, such as aerosols and clouds, their evolution and their response to external forcing, is of primary importance. This Dissertation contains a scientific contribution to the field of atmospheric physics focusing on satellite measurements and ground-based instruments available at the Thule High Arctic Atmospheric Observatory (THAAO, www.thuleatmos-it.it, 76.5° N, 68.8° W, 220 m a.s.l) located near Pituffik Space Base, PSB (formerly known as Thule Air Base (TAB)), in northern Greenland. In particular, aerosols produced by Canadian wildfires in 2017 strongly affected the Arctic and reached the Pituffik area. The combined analysis of surface measurements and satellite observations allowed us to estimate and extend the local radiative impact to a broader area. Clouds are another critical component of the Earth system from which most of the uncertainties in climate models and forecasts originate. This research exploited zenith spectral measurements conducted at THAAO to develop a retrieval algorithm for cloud optical thickness, especially when dealing with surfaces presenting high albedo, such as snow. The results have been compared to other methods based on different ground-based instruments and satellites.