Carbon monoxide distributions from the IASI/METOP mission: evaluation with other space-borne remote sensors

Abstract

Abstract. The Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp satellite measures carbon monoxide (CO) on a global scale, twice a day. CO total columns and vertical profiles are retrieved in near real time from the nadir radiance spectra measured by the instrument in the thermal infrared (TIR) spectral range. This paper describes the measurement vertical sensitivity and provides a first assessment of the capabilities of IASI to measure CO distributions. On the global scale, 0.8 to 2.4 independent pieces of information are available for the retrieval. At mid latitudes, the information ranges between 1.5 and 2, which enables the lower and upper troposphere to be distinguished, especially when thermal contrast is significant. Northern Hemisphere and in the equatorial region. However when strong CO concentrations are present, such as during fire events, these discrepancies can climb as high as 17%. Instrument specifications of IASI versus other missions are also discussed.

Decadal record of satellite carbon monoxide observations

“…The AIRS data show a clear high bias with respect to the other instruments in the SH and a smaller seasonal amplitude in the NH. These biases with MOPITT, TES and IASI have been documented previously by George et al (2009) and Warner et al (2010), and are due to differences in instrument spectral resolution and retrieval methods. In particular, the high bias in SH AIRS V5 data is most likely due to the use of a single global first guess profile (Warner et al, 2010).…”

“…Total column results are less sensitive than profile retrievals to differences in vertical sensitivity that are due to instrument parameters, such as spectral resolution, and the choice of constraints in the retrieval algorithms. However there are differences in the instrument column averaging kernels, as shown in George et al (2009), that would give slightly different results if applied to the same atmospheric distribution.…”

“…Since thermal contrast is generally better for daytime observations and over land (e.g., Deeter et al, 2007;Clerbaux et al, 2009), we restrict this study to daytime observations only. Correlations, biases and measurement differences for the nadir viewing TIR instruments are provided in George et al (2009). As of this study, MOPITT, AIRS and IASI are performing nominal operations.…”

“…TIR measurements generally have good sensitivity to CO in the middle troposphere, broadly peaking around 500 hPa Luo et al, 2007b;Warner et al, 2007;George et al, 2009), with sensitivity into the lower troposphere when there is sufficient thermal contrast, i.e., the difference in temperature between the surface and lower troposphere. Since thermal contrast is generally better for daytime observations and over land (e.g., Deeter et al, 2007;Clerbaux et al, 2009), we restrict this study to daytime observations only.…”

Impact of biomass burning on pollutants surface concentrations in megacities of the Gulf of Guinea

“…The IASI CO total columns retrievals by the FORLI algorithm (Hurtmans et al, 2012;George et al, 2009;Clerbaux et al, 2009) The IASI data show the increase of CO concentrations over Central Africa and the Eastern Atlantic, from May to July (subdomains SW and SE): under the influence of biomass burning emissions, the CO concentrations are increased by 100%, from ≈ 1.5 10 18 to ≈ 3 10 18 molecules cm −3 .…”