Abstract
Abstract. We present in this paper an alternative retrieval algorithm for the Atmospheric Infrared Sounder (AIRS) tropospheric Carbon Monoxide (CO) products using the Optimal Estimation (OE) technique, which is different from the AIRS operational algorithm. The primary objective for this study was to compare AIRS CO, as well as the other retrieval properties such as the Averaging Kernels (AKs), the Degrees of Freedom for Signal (DOFS), and the error covariance matrix, against the Tropospheric Emission Spectrometer (TES) and the Measurement of Pollution in the Troposphere (MOPITT) CO, which were also derived using the OE technique. We also demonstrate that AIRS OE CO results are much more realistic than AIRS V5 operational CO, especially in the lower troposphere and in the Southern Hemisphere (SH). These products are validated with in situ profiles obtained by the Differential Absorption Carbon Monoxide Measurements (DACOM), which took place as part of NASA's Intercontinental Chemical Transport Experiment (INTEX-B) field mission that was conducted over the northern Pacific in Spring 2006. To demonstrate the differences existing in the current operational products we first show a detailed direct comparison between AIRS V5 and TES operational V3 CO for the global datasets from December 2005 to July 2008. We then present global CO comparisons between AIRS OE, TES V3, and MOPITT V4 at selected pressure levels as well as for the total column amounts. We conclude that the tropospheric CO retrievals from AIRS OE and TES V3 agree to within 5–10 ppbv or 5% on average globally and throughout the free troposphere. The agreements in total column CO amounts between AIRS OE and MOPITT V4 have improved significantly compared to AIRS V5 with global relative RMS differences now being 12.7%.
Highlights
Satellite measurements of atmospheric chemical constituents have enhanced our understanding of how natural and human activities affect climate and air quality in the earth system
In an attempt to understand the implications of the above differences, we show in Fig. 3b the SDVs for Atmospheric Infrared Sounder (AIRS) V5 and Optimal Estimation (OE) Carbon Monoxide (CO) retrievals within 200 km radius www.atmos-chem-phys.net/10/9521/2010/
We have developed an offline retrieval algorithm for AIRS CO using the OE technique, similar to that used for Measurement of Pollution in the Troposphere (MOPITT) and Tropospheric Emission Spectrometer (TES)
Summary
Satellite measurements of atmospheric chemical constituents have enhanced our understanding of how natural and human activities affect climate and air quality in the earth system. Warner et al (2007) summarized AIRS version 4 (V4) CO validation results against NASA Intercontinental Chemical Transport Experiment-North America (INTEXNA) field campaign data (Singh et al, 2004) and concluded that in the mid-troposphere AIRS operational V4 CO products agree with in situ measurements to within 20 parts per billion volume (ppbv) or 10% over the US They further concluded that the performance of AIRS CO profile retrievals in the Northern Hemisphere (NH) mid-troposphere is comparable with MOPITT V3 CO profiles in the same region. To understand the CO retrievals from multiple instruments we need to understand the factors affecting retrievals, such as the Averaging Kernels (AKs), Degree of Freedom for Signal (DOFS), error covariance matrix, etc Because these quantities in the AIRS operational algorithm are obtained using a formulation (Maddy et al, 2008) that is different from that used in the OE method, a proper comparison of the sensors requires that we use the same retrieval method. We present the global CO comparisons between AIRS, MOPITT, and TES at the selected levels and for the total column amounts before summarizing our results
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
