Bimodal distribution of free tropospheric ozone over the tropical western Pacific revealed by airborne observations

A recent airborne field campaign over the remote western Pacific obtained the first intensive in situ ozone sampling over the warm pool region from oceanic surface to 15 km altitude (near 360 K potential temperature level). The new data set quantifies ozone in the tropical tropopause layer under significant influence of convective outflow. The analysis further reveals a bimodal distribution of free tropospheric ozone mixing ratio. A primary mode, narrowly distributed around 20 ppbv, dominates the troposphere from the surface to 15 km. A secondary mode, broadly distributed with a 60 ppbv modal value, is prominent between 3 and 8 km (320 K to 340 K potential temperature levels). The latter mode occurs as persistent layers of ozone-rich drier air and is characterized by relative humidity under 45%. Possible controlling mechanisms are discussed. These findings provide new insight into the physical interpretation of the "S"-shaped mean ozone profiles in the tropics.

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Copyright 2015 American Geophysical Union.


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Author Pan, Laura
Honomichl, Shawn
Randel, William
Apel, Eric
Atlas, E.
Beaton, Stuart
Bresch, James
Hornbrook, Rebecca
Kinnison, Douglas
Lamarque, Jean-Francois
Saiz-Lopez, A.
Salawitch, R.
Weinheimer, Andrew
Publisher UCAR/NCAR - Library
Publication Date 2015-09-28T00:00:00
Digital Object Identifier (DOI) Not Assigned
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Topic Category geoscientificInformation
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Metadata Date 2023-08-18T19:05:03.708688
Metadata Record Identifier edu.ucar.opensky::articles:16943
Metadata Language eng; USA
Suggested Citation Pan, Laura, Honomichl, Shawn, Randel, William, Apel, Eric, Atlas, E., Beaton, Stuart, Bresch, James, Hornbrook, Rebecca, Kinnison, Douglas, Lamarque, Jean-Francois, Saiz-Lopez, A., Salawitch, R., Weinheimer, Andrew. (2015). Bimodal distribution of free tropospheric ozone over the tropical western Pacific revealed by airborne observations. UCAR/NCAR - Library. http://n2t.net/ark:/85065/d76h4jmc. Accessed 15 February 2025.

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