The increasing amounts of reactive nitrogen in the stratosphere necessitateaccurate global measurements of stratospheric nitrogen dioxide (NO). Overthe past decade, the SCIAMACHY (SCanning Imaging Absorption spectroMeter forAtmospheric CHartographY) instrument on ENVISAT (European EnvironmentalSatellite) has been providing global coverage of stratospheric NO every 6days. In this study, the vertical distributions of NO retrieved fromSCIAMACHY limb measurements of the scattered solar light are validated bycomparison with NO products from three different satellite instruments(SAGE II, HALOE and ACE-FTS). The retrieval algorithm based on the informationoperator approach is discussed, and the sensitivity of the SCIAMACHY NOlimb retrievals is investigated. The photochemical corrections needed to makethis validation feasible, and the chosen collocation criteria are described.For each instrument, a time period of two years is analyzed with severalhundreds of collocation pairs for each year. As NO is highly variable, thecomparisons are performed for five latitudinal bins and four seasons. In the 20to 40 km altitude range, mean relative differences between SCIAMACHY and otherinstruments are found to be typically within 20 to 30%. The mean partialNO columns in this altitude range agree typically within 15% (both globalmonthly and zonal annual means). Larger differences are seen for SAGE IIcomparisons, which is consistent with the results presented by other authors.For SAGE II and ACE-FTS, the observed differences can be partially attributedto the diurnal effect error.
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