Winter- and summertime continental influences on tropospheric O 3 and CO observed by TES over the western North Atlantic Ocean

• Published in: Atmospheric Chemistry and Physics
• Main Authors: R. Talbot, H. Mao, J. Hegarty
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2010
• Subjects: Physics; QC1-999; Chemistry; QD1-999; North Atlantic
• Online Access: https://doi.org/10.5194/acp-10-3723-2010; https://doaj.org/article/036ee5580ae3435b9305f851611484da

The distributions of tropospheric ozone (O 3 ) and carbon monoxide (CO), and the synoptic factors regulating these distributions over the western North Atlantic Ocean during winter and summer were investigated using profile retrievals from the Tropospheric Emission Spectrometer (TES) for 2004–2006. Seasonal composites of TES retrievals, reprocessed to remove the influence of the a priori on geographical and seasonal structure, exhibited strong seasonal differences. At the 681 hPa level during winter months of December, January and February (DJF) the composite O 3 mixing ratios were uniformly low (~45 ppbv), but continental export was evident in a channel of enhanced CO (100–110 ppbv) flowing eastward from the US coast. In summer months June, July, and August (JJA) O 3 mixing ratios were variable (45–65 ppbv) and generally higher due to increased photochemical production. The summer distribution also featured a channel of enhanced CO (95–105 ppbv) flowing northeastward around an anticyclone and exiting the continent over the Canadian Maritimes around 50° N. Offshore O 3 -CO slopes were generally 0.15–0.20 mol mol −1 in JJA, indicative of photochemical O 3 production. Composites for 4 predominant synoptic patterns or map types in DJF suggested that export to the lower free troposphere (681 hPa level) was enhanced by the warm conveyor belt airstream of mid-latitude cyclones while stratospheric intrusions increased TES O 3 levels at 316 hPa. A major finding in the DJF data was that offshore 681 hPa CO mixing ratios behind cold fronts could be enhanced up to >150 ppbv likely by lofting from the surface via shallow convection resulting from rapid destabilization of cold air flowing over much warmer ocean waters. In JJA composites for 3 map types showed that the general export pattern of the seasonal composites was associated with a synoptic pattern featuring the Bermuda High. However, weak cyclones and frontal troughs could enhance offshore 681 hPa CO mixing ratios to >110 ppbv with O 3 -CO slopes >0.50 mol ...