How do temperature inversions control aerosol vertical distribution in the Arctic?

Once transported into the Arctic, the final fate of the aerosols and their overall impact on the atmosphere and surface depends heavily on local meteorological conditions. This is one of the research areas where comparatively little is known about the Arctic, due to the lack of suitable observations. Temperature inversions, both surface and elevated, are very commonly observed meteorological phenomena in the Arctic especially during winter and early spring. Characterizing co-variability of temperature inversions and aerosol distribution would shed light not only on the transport pathways into the Arctic, depending on if aerosol accumulation occurs above the inversion layer or below, but, also help in better understanding aerosol radiative effects. Furthermore, such co-variability provides observationally anchored constraints to evaluate the coupling of local meteorology and aerosol distribution in chemistry transport and global climate models.

Here, we characterized co-variability between aerosol vertical distribution and temperature inversion, using 10 years of simultaneous measurements of aerosol extinctions from CALIOP and temperature profiles from AIRS, both part of NASA's A-Train payloads. We investigated aerosol vertical distribution under different stability regimes that are defined based on temperature inversion strength. We found that as the atmosphere becomes more stable, more aerosols are trapped below inversions over the majority of the Arctic (except in the Pacific sector) during winter. During spring, the accumulation of aerosols over the inversion layers is dominant, except in the Atlantic sector. We argue that different pollution pathways into the Arctic can explain the observed contrasting relationships. In this study, satellite observations are, for the first time, used as sole evidence to support the hypothesis that low level transport dominates in winter and free tropospheric transport dominates in spring.