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

L. L. Pan, S. B. Honomichl, W. J. Randel, E. C. Apel, E. L. Atlas, S. P. Beaton, J. F. Bresch, R. Hornbrook, D. E. Kinnison, J. F. Lamarque, A. Saiz-Lopez, R. J. Salawitch, A. J. Weinheimer

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)7844-7851
Number of pages8
JournalGeophysical Research Letters
Volume42
Issue number18
DOIs
StatePublished - Sep 28 2015

Keywords

  • convective transport
  • dry intrusions
  • ozone and water vapor relationship
  • tropospheric ozone

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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    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. (2015). Bimodal distribution of free tropospheric ozone over the tropical western Pacific revealed by airborne observations. Geophysical Research Letters, 42(18), 7844-7851. https://doi.org/10.1002/2015GL065562