Assessment of the capability of the Infrared Atmospheric Sounding Interferometer (IASI), the Atmospheric Infrared Sounder (AIRS), and the ERA5 reanalysis to detect specific humidity inversions at an Arctic site

Specific humidity inversions are extremely frequent in the Arctic atmosphere, and they are strongly intertwined with the energy budget, by affecting downward longwave radiation and cloud processes. Despite their importance, they have been the focus of a limited number of studies, and our knowledge of their characteristics is limited because of the lack of in situ data in the region, and the presence of large errors in moisture variables in reanalyses. Retrievals from satellite infrared sounders could fill this knowledge gap. In this thesis, the capability of two benchmark satellite sounders, the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric Infrared Sounder (AIRS), to detect specific humidity inversions at an Arctic site, Ny-Ålesund, is systematically assessed for the first time. Additionally, an accurate characterization of specific humidity inversions above Ny-Ålesund is performed employing radiosonde data, and the capability to detect Arctic specific humidity inversions of the next-generation reanalysis ERA5 is also assessed. The assessment is performed by comparing specific humidity inversion statistics from radiosondes to analogous statistics obtained from co-located IASI and AIRS retrievals, as well as ERA5 fields. Results show that ERA5 provides a good representation of specific humidity inversion characteristics, while IASI and AIRS retrievals display strong limitations in capturing Arctic specific humidity inversions.