Methane mole fraction and δ13C above and below the trade wind inversion at Ascension Island in air sampled by aerial robotics

Research output: Contribution to journalArticle

Authors

  • R. Brownlow
  • D. Lowry
  • R. E. Fisher
  • J. L. France
  • M. Cain
  • T. S. Richardson
  • C. Greatwood
  • J. Freer
  • J. A. Pyle
  • E. G. Nisbet

External organisations

  • Dep. of Physics, Royal Holloway, University of London, Egham TW20 0EX, UK
  • Royal Holloway, University of London
  • University of East Anglia
  • University of Cambridge
  • BRISTOL UNIVERSITY

Abstract

Ascension Island is a remote South Atlantic equatorial site, ideal for monitoring tropical background CH4. In September 2014 and July 2015, octocopters were used to collect air samples in Tedlar bags from different heights above and below the well-defined Trade Wind Inversion (TWI), sampling a maximum altitude of 2700 m above mean sea level. Sampling captured both remote air in the marine boundary layer below the TWI and also air masses above the TWI that had been lofted by convective systems in the African tropics. Air above the TWI was characterized by higher CH4, but no distinct shift in δ13C was observed compared to the air below. Back trajectories indicate that lofted CH4 emissions from Southern Hemisphere Africa have bulk δ13CCH4 signatures similar to background, suggesting mixed emissions from wetlands, agriculture, and biomass burning. The campaigns illustrate the usefulness of unmanned aerial system sampling and Ascension's value for atmospheric measurement in an understudied region.

Details

Original languageEnglish
Pages (from-to)11,893-11,902
JournalGeophysical Research Letters
Volume43
Issue number22
Early online date5 Nov 2016
Publication statusPublished - 28 Nov 2016

Keywords

  • Ascension Island, global carbon cycle, greenhouse gas, methane, stable carbon isotope, UAS