Bimodal distribution of free tropospheric ozone over the tropical western Pacific revealed by airborne observations. Issue 18 (30th September 2015)

• Record Type: Journal Article
• Authors: Pan, L. L.; Honomichl, S. B.; Randel, W. J.; Apel, E. C.; Atlas, E. L.; Beaton, S. P.; Bresch, J. F.; Hornbrook, R.; Kinnison, D. E.; Lamarque, J.‐F.; Saiz‐Lopez, A.; Salawitch, R. J.; Weinheimer, A. J.
• Is Part Of: Geophysical research letters. Volume 42:Issue 18(2015:Sep.)
• Page Start: 7844
• Page End: 7851
• Publication Date: 2015-09-30
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2015GL065562
• Languages: English
• ISSNs: 0094-8276

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>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.</p> </abstract>