Preprints
https://doi.org/10.5194/acp-2021-473
https://doi.org/10.5194/acp-2021-473

  22 Jul 2021

22 Jul 2021

Review status: a revised version of this preprint is currently under review for the journal ACP.

Data assimilation of CrIS-NH3 satellite observations for improving spatiotemporal NH3 distributions in LOTOS-EUROS

Shelley van der Graaf1,2, Enrico Dammers2, Arjo Segers2, Richard Kranenburg2, Martijn Schaap2,3, Mark Shephard4, and Jan Willem Erisman5 Shelley van der Graaf et al.
  • 1Vrije Universiteit Amsterdam, Earth and Climate Cluster, The Netherlands
  • 2TNO, Climate Air and Sustainability, Utrecht, The Netherlands
  • 3Freie Universität Berlin, Institute of Meteorology, Berlin, Germany
  • 4Environment and Climate Change Canada, Toronto, Ontario, Canada
  • 5Universiteit Leiden, Institute of Environmental Sciences, Leiden, The Netherlands

Abstract. Atmospheric levels of ammonia (NH3) have substantially increased during the last century, posing a hazard to both human health and environmental quality. The atmospheric budget of NH3, however, is still highly uncertain due to an overall lack of observations. Satellite observations of atmospheric NH3 may help us in the current observational and knowledge gaps. Recent observations of the Cross-track Infrared Sounder (CrIS) provide us with daily, global distributions of NH3. In this study, the CrIS-NH3 product is assimilated into the LOTOS-EUROS chemistry transport model using two different methods aimed at improving the modelled spatio-temporal NH3 distributions. In the first method NH3 surface concentrations from CrIS are used to fit spatially varying NH3 emission time factors to redistribute model input NH3 emissions over the year. The second method uses the CrIS-NH3 column data to adjust the NH3 emissions using a Local Ensemble Transform Kalman Filter (LETKF) in a top-down approach. The two methods are tested separately and combined, focusing on a region in western Europe (Germany, Belgium, and the Netherlands). In this region, the mean CrIS-NH3 total columns were up to a factor 2 higher than the simulated NH3 columns between 2014 and 2018, which, after assimilating the CrIS-NH3 columns using the LETKF algorithm, led to an increase of the total NH3 emissions of up to approximately 30%. Our results illustrate that CrIS-NH3 observations can be used successfully to estimate spatially variable NH3 time factors, and improve NH3 emission distributions temporally, especially in spring (March to May). Moreover, the use of the CrIS-based NH3 time factors resulted in an improved comparison with the onset and duration of the NH3 spring peak observed at observation sites at hourly resolution in the Netherlands. Assimilation of the CrIS-NH3 columns with the LETKF algorithm is mainly advantageous for improving the spatial concentration distribution of the modelled NH3 fields. Compared to in-situ observations, a combination of both methods led to the most significant improvements in modelled monthly NH3 surface concentration and NH4+ wet deposition fields, illustrating the usefulness of the CrIS-NH3 products to improve the temporal representativity of the model and better constrain the budget in agricultural areas.

Shelley van der Graaf 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 acp-2021-473', Anonymous Referee #1, 11 Aug 2021
  • RC2: 'Comment on acp-2021-473', Anonymous Referee #2, 13 Aug 2021
  • AC1: 'Comment on acp-2021-473', Shelley C. van der Graaf, 10 Oct 2021

Shelley van der Graaf et al.

Shelley van der Graaf et al.

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Short summary
CrIS-NH3 satellite observations are assimilated into the LOTOS-EUROS model using two different methods. In the first method the data is used to fit spatially varying NH3 emission time factors. In the second method a Local Ensemble Transform Kalman Filter is used. Compared to in-situ observations, combining both methods led to the most significant improvements in the modelled concentrations and deposition, illustrating the usefulness of CrIS-NH3 to improve the spatio-temporal distribution of NH3.
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