Standard daily IASI/Metop-A ULB-LATMOS ammonia (NH3) L2 product (total column)

Abstract

The standard IASI/Metop-A daily ammonia (NH3) total column dataset (ANNI-NH3-v2.2), described in [Van Damme et al.](https://www.atmos-meas-tech.net/10/4905/2017/) (2017) includes the results of a flexible and robust NH3 retrieval algorithm from measurements of the Infrared Atmospheric Sounding Interferometer (IASI). The method is based on the calculation of a spectral hyperspectral range index (HRI) and subsequent conversion to NH3 columns via a neural network. With this method: (1) complete temperature and humidity vertical profiles can be accounted for, (2) third‐party NH3 vertical profile information can be used, and (3) a full measurement uncertainty characterization is provided. Separate neural networks were trained for land and sea observations. Recommendations for post-filtering the data and for averaging data in time or space are formulated in [Van Damme et al.](https://www.atmos-meas-tech.net/10/4905/2017/) (2017). ANNI-NH3-v2.2 relies on near real time meteorological parameters provided by Eumetsat (L2 data from IASI PPF). The dataset is available on a global scale from October 2007 till December 2017. Current Version: V2.2.0, available since 2018-06-15 - The main change from V2.1.0 to V2.2.0 is a first-order correction that had to be applied on the entire HRI/Metop-B time-series and on HRI/Metop-A after 7 June 2017 due to a change in the Level 1 information treatment in 2017 for Metop-A. Version history: V2.1.0, available from 2017-09-30 to 2018-06-15 Disclaimer: The Eumetsat IASI PPF L2 data processing chain has been updated several times since IASI launch, inducing discontinuities in the retrieved NH3 time-series. A second dataset (ANNI-NH3-v2.2R-I) which relies on ERA-Interim ECMWF meteorological input data, along with surface temperature retrieved from a dedicated network, rather than the operationally provided Eumetsat IASI Level 2 (L2) data used for the standard version is also available on AERIS Website [NH3_R-I](https://en.aeris-data.fr/metadata/?871d9366-22d7-4d8d-997e-02e7721f7e94). For inter-annual comparisons and trends analyses, only the reanalysed dataset should be used.