Abstract
Abstract. In this paper, we analyze the performance of the Infrared Atmospheric Sounding Interferometer (IASI), launched in October 2006 on board METOP-A, for the monitoring of carbon monoxide (CO) during extreme fire events, focusing on the record-breaking fires which devastated thousands of square kilometers of forest in Greece during the last week (23–30) of August 2007. After an assessment of the quality of the profiles retrieved using the Fast Optimal Retrievals on Layers for IASI (FORLI) algorithm, the information provided on fire emissions and subsequent pollution outflow is discussed. Large CO plumes were observed above the Mediterranean Basin and North Africa, with total CO columns exceeding 24×1018 molecules/cm2 and absolute volume mixing ratios up to 4 ppmv on the 25 August. Up to 30×1018 molecules/cm2 and 22 ppmv in the lower troposphere are retrieved close to the fires above the Peloponnese, but with larger uncertainty. The average root-mean-square (RMS) difference between simulated and observed spectra is close to the estimated radiometric noise level, slightly increasing (by ~14%) in the fresh fire plumes. CO profiles are retrieved with a vertical resolution of about 8 km, with ~1.7 pieces of independent information on the vertical in the region considered and a maximum sensitivity in the free troposphere (~4–5 km). Using the integrated total amount, the increase in CO burden due to these fires is estimated to 0.321 Tg, ~40% of the total annual anthropogenic emissions in Greece. The patterns of these CO enhancements are in good agreement with the aerosol optical depth (AOD) retrieved from the MODIS measurements, highlighting a rapid transport of trace gases and aerosols across the Mediterranean Basin (less than one day). While the coarse vertical resolution will not allow the location of the exact plume height, the large CO enhancements observed in the lower troposphere are consistent with the maximum aerosol backscatter coefficient at ~2 km detected by the CALIPSO lidar in space (CALIOP).
Highlights
In addition to being devastating for local ecosystems and economies, wildfires significantly alter air quality, sometimes on regional to hemispheric scales, and are an important component of the climate system
After a general description of the Fast Optimal Retrievals on Layers for Infrared Atmospheric Sounding Interferometer (IASI) (FORLI) algorithm, we evaluate its performance for the study of fire plume events
These results are consistent with previous analysis by McMillan et al (2008) which show that correlations are larger downwind from the emission region, probably due to the lack of sensitivity of thermal IR instruments to the surface layers which results in a low bias close to the emissions
Summary
In addition to being devastating for local ecosystems and economies, wildfires significantly alter air quality, sometimes on regional to hemispheric scales, and are an important component of the climate system. Giglio et al, 2006), the corresponding emissions are difficult to evaluate accurately (e.g. Kasischke and Penner, 2004) and the vertical transport processes above these large sources are not well understood These are all critical parameters for the simulation of the impact of wildfires by chemistry and transport models that need to be better understood (e.g. Turquety et al, 2007; Damoah et al, 2006; Fromm and Servranckx, 2003). We explore the correlations between CO and aerosols in these plumes based on the MODIS aerosol optical depth (AOD), widely used for the monitoring of fire smoke, and the vertical soundings from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) These comparisons will allow a combined analysis of the transport pathways of trace gases and aerosols, as well as an evaluation of the information provided by IASI on plume height. This study will be a first step towards an analysis of the interactions between aerosols and photochemistry
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