17 May 2022
17 May 2022
Status: this preprint is currently under review for the journal AMT.

Can state-of-the-art infrared satellite sounders and reanalyses detect moisture inversions in the Arctic?

Giovanni Chellini and Kerstin Ebell Giovanni Chellini and Kerstin Ebell
  • Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany

Abstract. Moisture inversions, i.e. layers in the troposphere where specific humidity increases with height, are extremely frequent in the Arctic. They are strongly intertwined with cloud processes, as well as the energy budget, by affecting the downward longwave radiation. In this study, the capability of two benchmark satellite sounders, the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric Infrared Sounder (AIRS), to detect moisture inversions is systematically assessed based on radiosonde data from the Arctic site Ny-Ålesund. In particular for IASI, such an analysis has not been done before. The frequency of occurrence of moisture inversions at Ny-Ålesund based on radiosoundings is above 95 % in all seasons, with multiple inversions in the same profile occurring most of the time (in 82 % of the profiles). We first performed a sensitivity analysis which revealed that the chosen vertical grid of the specific humidity profiles has a distinct impact on the inversion frequency: in general, the lower the grid resolution, the lower also the detected inversion frequency. However, even when reducing the vertical resolution of the radiosonde profiles used in the comparison to match that of the IASI and AIRS retrievals, a large underestimation in both inversion frequency and inversion strength can be found in the satellite products. While observed inversion frequency in any 100-hPa-deep layer between 1000 and 400 hPa is typically between 10 and 20 % (50 and 80 %) in the regridded (original) radiosonde data, inversion frequency in satellite data is in most cases below 10 %. A better agreement has been found for IASI below the 900-hPa level and in particular for winter, while AIRS does not detect any inversions below the 700-hPa level in this season. In addition to satellite data, reanalysis data also have the potential to provide an Arctic-wide view on moisture inversion characteristics. Here, we thus also assessed the capability of the latest reanalysis developed by ECMWF, ERA5, to detect moisture inversions at Ny-Ålesund, by performing a similar comparison with radiosoundings. We found that ERA5 represents Arctic moisture inversion characteristics very well, if the radiosonde profile resolution is reduced to that of the reanalysis.

Giovanni Chellini and Kerstin Ebell

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-22', Anonymous Referee #2, 02 Jun 2022
  • RC2: 'Comment on amt-2022-22', Anonymous Referee #1, 16 Jun 2022
  • RC3: 'Comment on amt-2022-22', Anonymous Referee #3, 23 Jun 2022
  • EC1: 'Comment on amt-2022-22', Martin Riese, 28 Jun 2022

Giovanni Chellini and Kerstin Ebell

Giovanni Chellini and Kerstin Ebell


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Short summary
Moisture inversions (MIs), i.e. atmospheric layers where specific humidity increases with height, are frequent in the Arctic. This study assesses the capability of two satellite instruments, IASI and AIRS, and one reanalysis, ERA5, to detect MIs at an Arctic site. The comparison with radiosonde data shows that humidity profiles from IASI and AIRS severely underestimate the occurrence of MIs. On the other hand, MI characteristics in ERA5 are comparable to those in the radiosonde data.