Abstract
Abstract. Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern Hemispheres along with regional trends for Eastern China, Eastern USA, Europe and India. We find that all the satellite observations are consistent with a modest decreasing trend ~ −1 % yr−1 in total column CO over the Northern Hemisphere for this time period and a less significant, but still decreasing trend in the Southern Hemisphere. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China that, to our knowledge, has not been reported previously. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.
Highlights
Carbon monoxide (CO) is measured from space by several instruments due to its important role in atmospheric chemistry and climate
MOPITT V3 and V4 CO profiles and columns were validated with respect to NOAA aircraft in situ CO profile measurements (Emmons et al, 2009; Deeter et al, 2010) and we show a similar comparison for the MOPITT V5T total column with respect to validation data in Fig. 1, along with the latest comparison for V4
TES CO profiles and total column amounts have been validated with respect to in situ measurements (Luo et al, 2007a) and compared to MOPITT V3 data (Luo et al, 2007b) and to MOPITT data processed with the TES a priori profiles and covariances (Ho et al, 2009)
Summary
Carbon monoxide (CO) is measured from space by several instruments due to its important role in atmospheric chemistry and climate. Because CO has a medium lifetime (weeks to months), it can be transported globally, but does not become evenly mixed in the troposphere This makes CO an ideal tracer of transport processes from pollution sources which often produce significant enhancements over background values (e.g., Edwards et al, 2004; 2006). While limb-viewing instruments such as AuraMLS (Microwave Limb Sounder) (Livesey et al, 2008) and ACE-FTS (Atmospheric Chemistry Experiment-Fourier Transform Spectrometer) (Clerbaux et al, 2008b) measure CO abundance in the upper troposphere and stratosphere, they do not sample enough of the middle and lower troposphere to provide CO total columns. We use CO total columns derived from thermal-infrared (TIR) observations using CO absorption lines around 4.6 μm from TerraMOPITT (Measurements of Pollution in the Troposphere), Aqua-AIRS (Atmospheric InfraRed Sounder), Aura-TES (Tropospheric Emission Spectrometer) and MetOp-IASI (Infrared Atmospheric Sounding Interferometer).
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