Preprints
https://doi.org/10.5194/amt-2021-302
https://doi.org/10.5194/amt-2021-302

  27 Oct 2021

27 Oct 2021

Review status: this preprint is currently under review for the journal AMT.

Time evolution of temperature profiles retrieved from 13 years of IASI data using an artificial neural network

Marie Bouillon1, Sarah Safieddine1, Simon Whitburn2, Lieven Clarisse2, Filipe Aires3, Victor Pellet3, Olivier Lezeaux4, Noëlle A. Scott5, Marie Doutriaux-Boucher6, and Cathy Clerbaux1,2 Marie Bouillon et al.
  • 1LATMOS/IPSL, Sorbonne Université/UVSQ/CNRS, Paris, France
  • 2Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), Université Livre de Bruxelles (ULB), Brussels, Belgium
  • 3LERMA, CNRS, Paris, France
  • 4SPASCIA, Ramonville-Saint-Agne, France
  • 5Laboratoire de Météorologie Dynamique, IPSL/CNRS/Ecole Polytechnique/Université Paris-Saclay, Palaiseau, France
  • 6European Organisation for the Exploitation of Meteorological Satellites, Darmstadt, Germany

Abstract. The three IASI instruments, launched in 2006, 2012, and 2018, are key instruments to weather forecasting, and most meteorological centers assimilate IASI nadir radiance data into atmospheric models to feed their forecasts. The EUropean organisation for the exploitation of METeorological SATellites (EUMETSAT) recently released a reprocessed homogeneous radiance record for the whole IASI observation period, from which thirteen years (2008–2020) of temperature profiles can be obtained. In this work, atmospheric temperatures at different altitudes are retrieved from IASI radiances measured in the carbon dioxide absorption bands (654–800 cm−1 and 2250–2400 cm−1) by selecting the channels that are the most sensitive to the temperature at different altitudes. We rely on an Artificial Neural Network (ANN) to retrieve atmospheric temperatures from a selected set of IASI radiances. We trained the ANN with IASI radiances as input and the European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis version 5 (ERA5) as output. The retrieved temperatures were validated with ERA5, with in-situ radiosonde temperatures from the Analysed RadioSoundings Archive (ARSA) network and with EUMETSAT temperatures retrieved from IASI radiances using a different method. Between 750 and 7 hPa, where IASI is most sensitive to temperature, a good agreement is observed between the three datasets: the differences between IASI on one hand, and ERA5, ARSA or EUMETSAT on the other hand are usually less than 0.5 K at these altitudes. At 2 hPa, as the IASI sensitivity decreases, we found differences up to 2 K between IASI and the three validation datasets. We then computed atmospheric temperature linear trends from atmospheric temperatures between 750 and 2 hPa. We found that in the past thirteen years, there is a general warming trend of the troposphere, that is more important at the poles than at the equator (0.7 K/decade at the equator, 1 K/decade at the North Pole). The stratosphere is globally cooling on average, except at the South Pole as a result of the ozone layer recovery. The cooling is most pronounced in the equatorial upper stratosphere (−1 K/decade). This work shows that ANN can be a powerful and simple tool to retrieve IASI temperatures at different altitudes in the upper troposphere and in the stratosphere, allowing us to construct a homogeneous and consistent temperature data record adapted to trend analyis.

Marie Bouillon et al.

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-2021-302', Anonymous Referee #1, 11 Nov 2021
  • RC2: 'Comment on amt-2021-302', Anonymous Referee #2, 01 Dec 2021

Marie Bouillon et al.

Data sets

Atmospheric Temperature Profiles (ATP) Bouillon, Marie https://doi.org/10.21413/IASI-FT_METOPA_ATP_L3_LATMOS-ULB

ERA5 hourly data on pressure levels from 1979 to present Copernicus https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-pressure-levels?tab=overview

https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-pressure-levels?tab=overview Scott, Noëlle https://ara.lmd.polytechnique.fr/index.php?page=arsa

IASI Level 1C Climate Data REcord Release 1 - Metop-A EUMETSAT https://doi.org/10.15770/EUM_SEC_CLM_0014

IASI-A and -B climate data record of all sky temperature and humidity profiles Release 1 Doutriaux-Boucher, Marie and August, Thomas https://doi.org/10.15770/EUM_SEC_CLM_0027

Marie Bouillon et al.

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Short summary
The IASI instruments have been observing Earth since 2007. We use a neural network to retrieve atmopsheric temperatures. This new temperature data record is validated against other datasets and shows good agreement. We use this new dataset to compute trends over the 2008–2020 period. We found a warming of the troposphere, more important at the poles. In the stratosphere, we found that temperatures decrease everywhere except at the South pole. The cooling is more pronounced at the South pole.