Abstract
Abstract. This paper presents a validation study of SCanning Imaging Absorption SpectroMeter for Atmospheric CartograpHY (SCIAMACHY) carbon monoxide (CO) total column measurements from the Iterative Maximum Likelihood Method (IMLM) algorithm using vertically integrated profile aircraft measurements obtained within the MOZAIC project for the six year time period of 2003–2008. Overall we find a good agreement between SCIAMACHY and airborne measurements for both mean values – also on a year-to-year basis – as well as seasonal variations. Several locations show large biases that are attributed to local effects like orography and proximity of large emission sources. Differences were detected for individual years: 2003, 2004 and 2006 have larger biases than 2005, 2007 and 2008, which appear to be related to SCIAMACHY instrumental issues but require more research. Results from this study are consistent with, and complementary to, findings from a previous validation study using ground-based measurements (de Laat et al., 2010b). According to this study, the SCIAMACHY data, if individual measurements are of sufficient quality – good signal-to-noise, can be used to determine the spatial distribution and seasonal cycles of CO total columns over clean areas. Biases found over areas with strong emissions (Africa, China) could be explained by low sensitivity of the instrument in the boundary layer and users are recommended to avoid using the SCIAMACHY data while trying to quantify CO burden and/or retrieve CO emissions in such areas.
Highlights
De Laat et al (2010b) found that overall there was a good agreement between SCIAMACHY and ground-based spectrometer (GBS) observations for both mean values as well as seasonal variations
CO we present a brief validation study using Measurements of OZone, water vapour, carbon monoxide and nitrogen oxides by in-service AIrbus aircraft (MOZAIC) (Marenco et al, 1998)
The comparison shows a very good agreement between SCIAMACHY and MOZAIC, apart from three outliers which were already identified in Sect. 3.1 (Lagos, Teheran and Beijing). Disregarding these three locations by removing points for which the bias is larger than the arbitrary value of 1.0 × 1018 molecules cm−2, we find a correlation of 0.92 for the comparison
Summary
The SCIAMACHY instrument (SCanning Imaging Absorption SpectroMeter for Atmospheric CartograpHY; launchedMarch 2002) onboard of the ENVISAT satellite (Bovensmann et al, 1999) has been providing carbon monoxide (CO)measurements based on reflected sunlight measurements in the short-wave infrared around 2.3 μm from 2003 onwards.As of this moment, from the perspective of instrument characteristics six years of reliable data is available (2003–2008).Initially, several algorithms were developed by different research groups and some initial evaluation was presented, indicating that SCIAMACHY was able to measure CO (Buchwitz et al, 2004, 2006, 2007; Dils et al., 2006; Sussmann and Buchwitz, 2005; Warneke et al, 2005; Gloudemans et al, 2006). Measurements based on reflected sunlight measurements in the short-wave infrared around 2.3 μm from 2003 onwards. As of this moment, from the perspective of instrument characteristics six years of reliable data is available (2003–2008). Several algorithms were developed by different research groups and some initial evaluation was presented, indicating that SCIAMACHY was able to measure CO (Buchwitz et al, 2004, 2006, 2007; Dils et al., 2006; Sussmann and Buchwitz, 2005; Warneke et al, 2005; Gloudemans et al, 2006). De Laat et al (2010b) presented an extensive validation of (IMLM) retrieval algorithm by comparing the SCIAMACHY measurements with ground-based spectrometer (GBS) observations for the five year period 2003–2007. Validation results were robust with regard to the choices of the instrument-noise error filter, sampling area, and time
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