Comparison of carbon monoxide measurements by TES and MOPITT: Influence of a priori data and instrument characteristics on nadir atmospheric species retrievals (original) (raw)
Related papers
A comparison of OEM CO retrievals from the IASI and MOPITT instruments
Atmospheric Measurement Techniques, 2011
Observations of atmospheric CO can only be made on global and regional scales by remote sensing instruments situated in space. One such instrument is the Infrared Atmospheric Sounding Interferometer (IASI), producing spectrally resolved, top-ofatmosphere radiance measurements from which CO vertical layers and total columns 5 can be retrieved. This paper presents the first intercomparison between an IASI CO data set, in this case that produced by the University of Leicester IASI Retrieval Scheme (ULIRS), and the V3 and V4 operationally retrieved CO products from the Measurements Of Pollution In The Troposphere (MOPITT) instrument. The comparison is performed for a localised region of Africa. By comparing both the standard data 10 and a special version of MOPITT data retrieved using the ULIRS a priori for CO, it is shown that standard intercomparisons of CO are strongly affected by the differing a priori data of the retrievals, and by the differing sensitivities of the two instruments. In particular, the differing a priori profiles for MOPITT V3 and V4 data result in systematic retrieved profile changes as expected. Application of averaging kernels is used to 15 derive a difference quantity which is much less affected by smoothing error and hence more sensitive to systematic error. This technique is used to show that the systematic bias between MOPITT V4 and ULIRS IASI data, at MOPITT vertical resolution, is less than 7%. These conclusions are confirmed by simulations with model profiles for the same region. 20
NAST-I tropospheric CO retrieval validation during INTEX-NA and EAQUATE
Quarterly Journal of the Royal Meteorological Society, 2007
Troposphere carbon monoxide (CO), as well as other trace species retrieved with advanced ultraspectral remote sensors of Earth observing satellites, is critical in air quality observation, modelling, and forecasting. The retrieval algorithm and the accuracy of the parameters retrieved from passive satellite remote sounders must be validated. The Intercontinental Chemical Transport Experiment -North America (INTEXNA) and the European Aqua Thermodynamic Experiment (EAQUATE) provide important validation of satellite observations with ongoing satellite measurement programmes such as Terra, Aura, and Aqua. One of the experimental objectives is to validate chemical species observed from ultraspectral sounders with aircraft in situ measurements, such as the NPOESS Airborne Sounder Testbed-Interferometer (NAST-I). Detailed intercomparisons between aircraft in situ measured and NAST-I retrieved CO profiles were performed to assess the retrieval capability of a passive infrared spectral remote sounder. Validation results illustrate that the CO vertical structure can be obtained by the NAST-I. The thermal radiances are most sensitive to CO emissions from the free troposphere. However, the profile retrieval accuracy depends on the CO uncertainty in the terrestrial boundary layer. It is shown here that the CO distribution in the terrestrial boundary layer over the sea cannot be obtained with reliable accuracy where there is little contrast between the surface air and surface skin temperature. . (a) NAST-I spectra simulated with the retrieved and in situ measured CO profile of 18 September 2004. (b) Spectral difference between retrieved and in situ measured CO profile (dashed black), difference due to free tropospheric CO (light grey), and difference due to TBL CO (dark grey).
Retrieval of MetOp-A/IASI CO profiles and validation with MOZAIC data
Atmospheric Measurement Techniques, 2012
The IASI (Infrared Atmospheric Sounding Interferometer) nadir-looking thermal infrared sounder onboard MetOp-A enables the monitoring of atmospheric constituents on a global scale. This paper presents a quality assessment of IASI CO profiles retrieved by the two different retrieval algorithms SOFRID and FORLI, by an intercomparison with airborne in-situ CO profiles from the MOZAIC program for the 2008-2009 period. Lower (surface-480 hPa) and upper tropospheric partial column (480-225 hPa) comparisons as well as profile comparisons are made. The retrieval errors of the IASI products are less than 21 % in the lower troposphere and less than 10 % in the upper troposphere. A statistical analysis shows similar correlation coefficients for the two retrieval algorithms and smoothed MOZAIC of r ∼ 0.8 and r ∼ 0.7 in the lower and upper troposphere respectively. Comparison with smoothed MOZAIC data of the temporal variation of the CO profiles at the airports of Frankfurt and Windhoek demonstrates that the IASI products are able to capture the seasonal variability at these sites. At Frankfurt SOFRID (respectively FORLI) is positively biased by 10.5 % (13.0 %) compared to smoothed MOZAIC in the upper (lower) troposphere, and the limited sensitivity of the IASI instrument to the boundary layer when thermal contrast is low is identified. At Windhoek, the impact of the vegetation fires in Southern Africa from July to November is captured by both SOFRID and FORLI, with an overestimation of the CO background values (fire maxima) by SOFRID (FORLI) by 12.8 % (10 %). Profile comparisons at Frankfurt and Windhoek show that the largest discrepancies are found between the two IASI products and MOZAIC for the nighttime retrievals.
Atmospheric Chemistry and Physics, 2010
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 AIRS operational algorithm. The primary objective for this study was to compare AIRS CO, as well as the other retrieval 5 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 OE technique. We also demonstrate that AIRS OE CO results are much more realistic than AIRS V5 operational CO, especially in the lower 10 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 prod-15 ucts 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 levels as well as for the total column amounts.
Comparisons between SCIAMACHY and ground-based FTIR data for total columns of CO, CH4, CO2 and N2O
Atmospheric Chemistry and Physics, 2006
Total column amounts of CO, CH 4 , CO 2 and N 2 O retrieved from SCIAMACHY nadir observations in its near-infrared channels have been compared to data from a groundbased quasi-global network of Fourier-transform infrared (FTIR) spectrometers. The SCIAMACHY data considered here have been produced by three different retrieval al-5 gorithms, WFM-DOAS (version 0.4, 0.41 for CH 4 ), IMAP-DOAS (version 0.9) and IMLM (version 5.5) and cover the January to December 2003 time period. Comparisons have been made for individual data, as well as for monthly averages. To maximize the number of reliable coincidences that satisfy the temporal and spatial collocation criteria, the SCIAMACHY data have been compared with a temporal 3rd order polynomial interpo-10 lation of the ground-based data. Particular attention has been given to the question whether SCIAMACHY observes correctly the seasonal and latitudinal variability of the target species. The ensemble of comparisons, discussed in this paper, demonstrate the capability of SCIAMACHY, using any of the three algorithms, to deliver products for the target species under consideration, which are already useful for qualitative geo-15 physical studies on a global scale. It is expected that the remaining uncertainties in the data products will decrease in future versions of the algorithm to also allow more quantitative investigations on a regional scale. 25 the first satellite instruments that can measure greenhouse gases in the troposphere 2679 ACPD
The three "carbon gases" carbon monoxide (CO), methane (CH4) and carbon dioxide (CO2) are important atmospheric constituents affecting air quality and climate. The near-infrared nadir spectra of reflected solar radiation measured by SCIAMACHY on-board ENVISAT contain information on the vertical columns of these gases which we retrieve using the scientific algorithm WFM-DOAS. For CH4 and CO2 our main data products are dry air column averaged mixing ratios (XCH4 in ppbv and XCO2 in ppmv) determined by simultaneous measurements of the dry air mass obtained from oxygen (O2) for CO2 and CO2 for methane. Our CO data product is the CO vertical column in molecules/cm 2 . Our previous activities focussed on the year 2003. The year 2003 data set (WFM-DOAS version 0.5 CO and XCH4; version 0.4 XCO2) has been extensively validated by comparison with a network of ground-based FTIR stations. We shortly summarize the main results of this validation effort which also resulted in the identi...
A Comparison of MOPITT and IASI Retrieved CO Profiles Using Similar Algorithms
In the following we compare collocated IASI CO profile retrievals and MOPITT Version 4 CO profile retrievals for a subset of orbits obtained from each satellite instrument on March 3, 2011. We use a δr = 200km, δt = ±2hr matchup window for the collocations and demand successfull retrievals from both instruments.