Atmospheric Infrared Sounder Carbon Monoxide Research Articles

Ground-based and AIRS carbon monoxide behavior at El Arenosillo observatory (Southwestern Europe)

Carbon monoxide (CO) observations registered at El Arenosillo observatory (Southwestern Europe), during three years (2019–2022) were used to explore levels, temporal variations and patterns. The seasonal mean hourly oscillated between 127 ± 21 and 97 ± 14 ppb, with extreme peaks measured under wildfire plume arrival. A remarkable monthly evolution was observed with peaks in cold months (135 ± 20 ppb in January) and minimum in summer (90 ± 11 ppb in June). Seasonal daily patterns showed a different nocturnal behavior depending on the season, with a clear maximum at 7:00–9:00 UTC, a decrease during diurnal time, and a minimum at 17:00–18:00 UTC. To determine the potential trends from 2002 to 2022, the observations of the AIRS (Atmospheric Infrared Sounder) instrument and the emissions from the global emission inventory of CAMS (Copernicus Atmosphere Monitoring Service) were used. A downward trend for emissions of −31% decade−1 was found, whereas the decrease from AIRS was −9.8% decade−1. The effort to reduce CO emissions is being countered by other processes. The CO behavior was investigated under weather conditions governed by the synoptic and mesoscale processes. Background levels (∼90 ppb) were obtained under Atlantic airflows, while an increase of ∼40% was observed with the impact of urban plumes from continental areas. CO even lower than 90 ppb was obtained under non-pure sea-land breezes, whereas, with pure breezes, reached peaks above 120 ppb, affecting the atmosphere at the surface and up to 1–1.2 km in the air. The extreme level was registered under wildfire plume arrival, with peaks exceeding 350 ppb. Climate change is modifying weather patterns and modulating breezes; in addition, it is also increasing the frequency and intensity of wildfires. These processes could be counteracting the efforts carried out to reduce emissions.

Anthropogenic emissions and space-borne observations of carbon monoxide over South Asia

The focus of this study is to understand anthropogenic emissions, spatiotemporal variability and trends of carbon monoxide (CO) over South Asia by using datasets from MACCity (Monitoring Atmospheric Composition and Climate, MACC and megaCITY – Zoom for the Environment, CityZEN), REAS (Regional Emission inventory in Asia), AIRS (Atmospheric Infrared Sounder) and SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY). MACCity anthropogenic emissions show an overall increase of 16.5% during 2000–2010. Elevated levels of MACCity CO are found in Indo-Gangetic Basin (IGB), eastern mining region of India, Bangladesh and large urban areas. Some of the major contributors of these emissions have been identified as agricultural waste burning, land transport, industrial production, and energy generation and distribution. An area averaged mean value of AIRS CO at 600hPa is found to be 114±2ppbv (slope −0.48±0.2ppbvyr−1, y-intercept 117±1ppbv and r=0.68) with a minor declining trend at −0.41±0.18%yr−1 over the region during 2003–2015. A strong seasonality in AIRS CO concentration is observed with spring season peak in March 129±1.9ppbv, whereas low values have been observed in summer monsoon with sturdy dip in July 99.6±1.94ppbv. AIRS CO and SCIAMACHY CO Total Column (CO TC) over the study region show spatial patterns similar to MACCity and REAS emissions. An analysis of SCIAMACHY CO TC tendencies has been performed which indicates minor rising trends over some parts of the region. Background CO, Recent Emissions (RE), and spatial anomalies in RE over high anthropogenic activity zones of Indus Basin, Ganges Basin and Eastern Region were analyzed using AIRS and SCIAMACHY CO data.

Global carbon monoxide products from combined AIRS, TES and MLS measurements on A-train satellites

Abstract. This study tests a novel methodology to add value to satellite data sets. This methodology, data fusion, is similar to data assimilation, except that the background model-based field is replaced by a satellite data set, in this case AIRS (Atmospheric Infrared Sounder) carbon monoxide (CO) measurements. The observational information comes from CO measurements with lower spatial coverage than AIRS, namely, from TES (Tropospheric Emission Spectrometer) and MLS (Microwave Limb Sounder). We show that combining these data sets with data fusion uses the higher spectral resolution of TES to extend AIRS CO observational sensitivity to the lower troposphere, a region especially important for air quality studies. We also show that combined CO measurements from AIRS and MLS provide enhanced information in the UTLS (upper troposphere/lower stratosphere) region compared to each product individually. The combined AIRS–TES and AIRS–MLS CO products are validated against DACOM (differential absorption mid-IR diode laser spectrometer) in situ CO measurements from the INTEX-B (Intercontinental Chemical Transport Experiment: MILAGRO and Pacific phases) field campaign and in situ data from HIPPO (HIAPER Pole-to-Pole Observations) flights. The data fusion results show improved sensitivities in the lower and upper troposphere (20–30% and above 20%, respectively) as compared with AIRS-only version 5 CO retrievals, and improved daily coverage compared with TES and MLS CO data.

Tropospheric carbon monoxide variability from AIRS under clear and cloudy conditions

Abstract. We study the carbon monoxide (CO) variability in the last decade measured by NASA's Atmospheric InfraRed Sounder (AIRS) on the Earth Observing System (EOS)/Aqua satellite. The focus of this study is to analyze CO variability and short-term trends separately for background CO and fresh CO emissions based on a new statistical approach. The AIRS Level 2 (L2) retrieval algorithm utilizes cloud clearing to treat cloud contaminations in the signals, and this increases the data coverage significantly to a yield of more than 50% of the total measurements. We first study if the cloud clearing affects CO retrievals and the subsequent trend studies by using the collocated Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask to identify AIRS clear sky scenes. We then carry out a science analysis using AIRS CO data individually for the clear and cloud-cleared scenes to identify any potential effects due to cloud clearing. We also introduce a new technique to separate background and recently emitted CO observations, which aims to constrain emissions using only satellite CO data. We validate the CO variability of the recent emissions estimated from AIRS against other emission inventory databases (i.e., Global Fire Emissions Database – GFED3 and the MACC/CityZEN UE – MACCity) and calculate that the correlation coefficients between the AIRS CO recently emitted and the emission inventory databases are 0.726 for the Northern Hemisphere (NH) and 0.915 for the Southern Hemisphere (SH). The high degree of agreement between emissions identified using only AIRS CO and independent inventory sources demonstrates the validity of this approach to separate recent emissions from the background CO using one satellite data set.

Improvements to the OMI near-UV aerosol algorithm using A-train CALIOP and AIRS observations

Abstract. The height of desert dust and carbonaceous aerosols layers and, to a lesser extent, the difficulty in determining the predominant size mode of these absorbing aerosol types, are sources of uncertainty in the retrieval of aerosol properties from near-UV satellite observations. The availability of independent, near-simultaneous measurements of aerosol layer height, and aerosol-type related parameters derived from observations by other A-train sensors, makes possible the use of this information as input to the OMI (ozone monitoring instrument) near-UV aerosol retrieval algorithm (OMAERUV). A monthly climatology of aerosol layer height derived from observations by the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) sensor, and real-time AIRS (Atmospheric Infrared Sounder) carbon monoxide (CO) observations are used in an upgraded version of the OMAERUV algorithm. AIRS CO measurements are used as an adequate tracer of carbonaceous aerosols, which allows the identification of smoke layers in regions and seasons when the dust-smoke differentiation is difficult in the near-UV. The use of CO measurements also enables the identification of high levels of boundary layer pollution undetectable by near-UV observations alone. In this paper we discuss the combined use of OMI, CALIOP and AIRS observations for the characterization of aerosol properties, and show an improvement in OMI aerosol retrieval capabilities.

Validating the AIRS Version 5 CO Retrieval With DACOM In Situ Measurements During INTEX-A and -B

Herein we provide a description of the atmospheric infrared sounder (AIRS) version 5 (v5) carbon monoxide (CO) retrieval algorithm and its validation with the DACOM in situ measurements during the INTEX-A and -B campaigns. All standard and support products in the AIRS v5 CO retrieval algorithm are documented. Building on prior publications, we describe the convolution of in situ measurements with the AIRS v5 CO averaging kernel and first-guess CO profile as required for proper validation. Validation is accomplished through comparison of AIRS CO retrievals with convolved in situ CO profiles acquired during the NASA Intercontinental Chemical Transport Experiments (INTEX) in 2004 and 2006. From 143 profiles in the northern mid-latitudes during these two experiments, we find AIRS v5 CO retrievals are biased high by 6%-10% between 900 and 300 hPa with a root-mean-square error of 8%-12%. No significant differences were found between validation using spiral profiles coincident with AIRS overpasses and in-transit profiles under the satellite track but up to 13 h off in time. Similarly, no significant differences in validation results were found for ocean versus land, day versus night, or with respect to retrieved cloud top pressure or cloud fraction.

Improved agreement of AIRS tropospheric carbon monoxide products with other EOS sensors using optimal estimation retrievals

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%.

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

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. Global distributions of column CO are evaluated with correlative observations available from other nadir looking TIR missions currently in operation: the Measurements of Pollution in the Troposphere (MOPITT) onboard TERRA, the Atmospheric Infrared Sounder (AIRS) onboard AQUA and the Tropospheric Emission Spectrometer (TES) onboard AURA. The IASI CO columns are compared with MOPITT, AIRS and TES CO columns, adjusted with the a priori, for three different months: August 2008, November 2008 and February 2009. On average, total column discrepancies of about 7% are found between IASI and the three other sounders in the 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.

AIRS views transport from 12 to 22 July 2004 Alaskan/Canadian fires: Correlation of AIRS CO and MODIS AOD with forward trajectories and comparison of AIRS CO retrievals with DC‐8 in situ measurements during INTEX‐A/ICARTT

We present observations of transport of tropospheric carbon monoxide (CO) obtained by the Atmospheric Infrared Sounder (AIRS) on board NASA's Aqua satellite during the Intercontinental Chemical Transport Experiment–North America (INTEX‐A) field campaign in the summer of 2004, part of the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT). In situ measurements from NASA's DC‐8 provide crucial assessment of AIRS midtropospheric (400–500 mbar) CO retrievals. For the nine best INTEX‐A profiles, convolution of the in situ profiles with AIRS verticality functions demonstrates version 4 AIRS CO retrievals between 400 and 500 mbar are biased high by approximately 8% with a standard deviation slightly less than 5%. The 400–500 mbar region is the only portion of the version 4 AIRS CO retrievals that can be validated as presented here. In some cases, AIRS CO retrievals may be sensitive to CO in the lower to midtroposphere (800–500 mbar). Focusing on one major episode, we investigate transport of CO from a large fire outbreak in the Alaskan/Canadian Yukon region from 11 to 14 July 2004 and follow it downwind to the southeastern United States and Europe by 22 July 2004. Comparison of AIRS CO maps and forward trajectories from fire locations reveals substantial variations in fire emissions especially emission injection height. Any useful forecast model must control for such fire emission variabilities to predict correctly the downwind impact. To match the forward trajectory analyses with AIRS CO observations requires some fires to have directly injected emissions to at least 500 mbar and perhaps as high as 300 mbar. Ground‐based lidar observations show smoke plume altitudes from 3 to 11 km over Wisconsin and from 1 to 4 km over Maryland in agreement with the forward trajectories. The Wisconsin lidar profiles on the afternoon of 18 July 2004 constrain the altitude of CO‐rich smoke observed by AIRS and MODIS to lie between 2 and 5.5 km above the surface, roughly 800 to 500 mbar. We find that changes in the correlation between AIRS CO and MODIS AOD reflect changes in the CO vertical distribution during this event. This finding is confirmed by in situ measurements, meteorological analyses, and forward trajectory analyses.

Daily global maps of carbon monoxide from NASA's Atmospheric Infrared Sounder

We present the first observations of tropospheric carbon monoxide (CO) by the Atmospheric Infrared Sounder (AIRS) onboard NASA's Aqua satellite. AIRS daily coverage of ∼70% of the planet represents a significant evolutionary advance in satellite trace gas remote sensing. Tropospheric CO abundances are retrieved from AIRS 4.55 μm spectral region using the full AIRS retrieval algorithm run in a research mode. The presented AIRS daily global CO maps from 22–29 September 2002 show large‐scale, long‐range transport of CO from anthropogenic and natural sources, most notably from biomass burning. The sequence of daily maps reveal CO advection from Brazil to the South Atlantic in qualitative agreement with previous observations. Forward trajectory analysis confirms this scenario and indicates much longer range transport into the southern Indian Ocean. Preliminary comparisons to in situ aircraft profiles indicate AIRS CO retrievals are approaching the 15% accuracy target set by pre‐launch simulations.