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Validation of IASI satellite ammonia observations at the pixel scale using in situ vertical profiles

Xuehui Guo 1 Lieven Clarisse 2 Rui Wang 1 Martin van Damme 2 Simon Whitburn 2 Pierre-François Coheur 2 Cathy Clerbaux 3, 2 Bruno Franco 2 Da Pan 1 Levi M. Golston 4, 1 Lars Wendt 1, 5 Kang Sun 1, 6 Lei Tao 7, 1 David Miller 8, 1 Tomas Mikoviny 9, 10, 11 Markus Müller 12, 13 Armin Wisthaler 12, 11 Alexandra G. Tevlin 14, 15 Jennifer G. Murphy 14 John B. Nowak 9, 16 Joseph R. Roscioli 16 Rainer Volkamer 17, 18, 19 Natalie Kille 17, 18, 19 J. Andrew Neuman 18, 20 Scott J. Eilerman 21 James H. Crawford 9 Tara I. Yacovitch 16 John D. Barrick 9 Amy Jo Scarino 9 Mark A. Zondlo 1 
Abstract : Satellite ammonia (NH3) observations provide unprecedented insights into NH3 emissions, spatiotemporal variabilities and trends, but validation with in‐situ measurements remains lacking. Here, total columns from the Infrared Atmospheric Sounding Interferometer (IASI) were intercompared to boundary layer NH3 profiles derived from aircraft‐ and surface‐based measurements primarily in Colorado, USA, in the summer of 2014. IASI‐NH3 version 3 near real‐time dataset compared well to in‐situ derived columns (windows ±15 km around centroid, ±1 hour around overpass time) with a correlation of 0.58, a slope of 0.78±0.14, and an intercept of 2.1×1015±1.5×1015 molecules cm‐2. Agreement degrades at larger spatiotemporal windows, consistent with the short atmospheric lifetime of NH3. We also examined IASI version 3R data, which relies on temperature retrievals from the ERA Reanalysis, and a third product generated using aircraft‐measured temperature profiles. The overall agreement improves slightly for both cases, and neither is biased within their combined measurement errors. Thus, spatiotemporal averaging of IASI over large windows can be used to reduce retrieval noise. Nonetheless, sampling artifacts of airborne NH3 instruments result in significant uncertainties of the in‐situ‐derived columns. For example, large validation differences exist between ascent and descent profiles, and the assumptions of the free tropospheric NH3 profiles used above the aircraft ceiling significantly impact the validation. Because short‐lived species like NH3 largely reside within the boundary layer with complex vertical structures, more comprehensive validation is needed across a wide range of environments. More accurate and widespread in‐situ NH3 datasets are therefore required for improved validations of satellite products.
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Submitted on : Wednesday, January 20, 2021 - 1:38:43 PM
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Xuehui Guo, Lieven Clarisse, Rui Wang, Martin van Damme, Simon Whitburn, et al.. Validation of IASI satellite ammonia observations at the pixel scale using in situ vertical profiles. Journal of Geophysical Research: Atmospheres, American Geophysical Union, 2021, 126 (9), pp.e2020JD033475. ⟨10.1029/2020JD033475⟩. ⟨insu-03115077⟩



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