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A flexible and robust IASI-NH3 retrieval algorithm

Abstract

In recent years, infrared sounders on board satellites have demonstrated their capabilities to detect and measure atmospheric ammonia (NH3). The retrieval of NH3 total columns from satellite-based measurements remains, however, challenging due to the large variability both in terms of NH3 columns and measurements sensitivity. We present here a new flexible and robust NH3 retrieval algorithm from the measurements of IASI. The method is an extension of the method presented recently in Van Damme et al. (2014), based on the calculation of a spectral index (HRI) from the level1C radiances. The difference lies in the conversion of the HRI to a NH3 column. Indeed, instead of using two-dimensional look-up tables (LUT), the conversion of the HRI relies now on a neural network (NN), offering therefore a lot more flexibility since a neural network can easily cope with hundreds of input parameters. We describe the major improvements of the NN-based method over the other retrieval methods developed so-far. We next derive the first global distributions and compare the impact of different averaging procedures on these distributions. We assess the impact of the use of variable NH3 vertical distribution on the retrieved total column (this is a unique feature of the new retrieval method) on a global scale. We will show with different example applications and comparison with models how the NN-based HRI method will provide a further step in a better assessment of the NH3 atmospheric budget, its spatial distributions and long-term trends.
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Dates and versions

insu-01306806 , version 1 (25-04-2016)

Identifiers

  • HAL Id : insu-01306806 , version 1

Cite

Simon Whitburn, Martin van Damme, Lieven Clarisse, Colette Heald, Cathy Clerbaux, et al.. A flexible and robust IASI-NH3 retrieval algorithm. 4th IASI International Conference, Apr 2016, Antibes Juan-Les-Pins, France. ⟨insu-01306806⟩
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