Articles | Volume 17, issue 10
Research article
24 May 2017
Research article |  | 24 May 2017

Spatial variability in tropospheric peroxyacetyl nitrate in the tropics from infrared satellite observations in 2005 and 2006

Vivienne H. Payne, Emily V. Fischer, John R. Worden, Zhe Jiang, Liye Zhu, Thomas P. Kurosu, and Susan S. Kulawik

Abstract. Peroxyacetyl nitrate (PAN) plays a fundamental role in the global ozone budget and is the primary reservoir of tropospheric reactive nitrogen over much of the globe. However, large uncertainties exist in how surface emissions, transport and lightning affect the global distribution, particularly in the tropics. We present new satellite observations of free-tropospheric PAN in the tropics from the Aura Tropospheric Emission Spectrometer. This dataset allows us to test expected spatiotemporal distributions that have been predicted by models but previously not well observed. We compare here with the GEOS-Chem model with updates specifically for PAN. We observe an austral springtime maximum over the tropical Atlantic, a feature that model predictions attribute primarily to lightning. Over northern central Africa in December, observations show strong interannual variability, despite low variation in fire emissions, that we attribute to the combined effects of changes in biogenic emissions and lightning. We observe small enhancements in free-tropospheric PAN corresponding to the extreme burning event over Indonesia associated with the 2006 El Niño.

Short summary
Peroxyacetyl nitrate (PAN) plays a key role in atmospheric chemistry and long-range transport of pollution. In this paper, we present measurements of PAN from the Tropospheric Emission Spectrometer, an instrument on board the NASA Aura satellite since 2004. We focus on measurements of PAN in tropical regions, where data from ground-based and aircraft campaigns are particularly sparse. We observe temporal changes in PAN associated with changes in fires, convection and emissions.
Final-revised paper