While calibrating our ground based air quality monitoring station at the weather station in Resolute, my colleague, Ralf Staebler, showed me the horizon and pointed to an "inverse" mirage of distant cliffs of Somerset Island that was forming in the sky! This is called a Fata Morgana (or an inverse mirage).
We know that the cliffs of Somerset Island are 220m high. Based on this, it looks like the mirage starts around an elevation of 400m. So a first guess for the height of the strongest inversion layer is about 300m. This optical phenomenon occurs when rays of light are bent passing through air layers of different temperatures in a steep thermal inversion. A thermal inversion occurs when warmer air exists in a well-defined layer above a layer of significantly cooler air. This temperature inversion is the opposite of what is normally the case. Air is usually warmer close to the surface, and cooler higher up, the reason behind usual mirages forming on the ground in deserts.
In separate but related project, we measure surface air quality (PM2.5, NOx, SO2, and O3) to detect local pollution and also shipping pollution in remote Canadian Arctic sites (Cape Dorset and Resolute). The stations have been running and providing data with 1 minute resolution since last year.
-Amir A. Aliabadi & Ralf Staebler, Environment Canada, NETCARE Collaborators