Global distributions of acetone in the upper troposphere from MIPAS spectra

D P Moore,A M Waterfall,J J Remedios

doi:10.5194/acp-12-757-2012

Abstract

Abstract. This study reports the first global measurements of acetone (C3H6O) in the upper troposphere (UT). Profiles were obtained between 9 km and 15 km from measurements made by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard Envisat in August 2003. Errors per profile are lower than 40 % between 180 hPa and 350 hPa. We report strong hemispheric differences in the acetone volume mixing ratios (VMRs), with average concentrations highest in the Northern Hemisphere (NH) mid-latitude UT, between 1000 pptv and 1600 pptv with maxima up to 2300 pptv. Our results show a strong enhancement of acetone relative to CO, particularly over Europe (7 pptv ppbv−1), confirming aircraft studies. Ten-day backward trajectories from these high European values show strong contributions from air flows over North America (56 %) and 25 % from Southernmost Asia. Enhanced acetone is also observed over Greenland, Siberia and biomass burning regions of Africa. Zonal distributions show that acetone VMRs decrease rapidly with increasing altitude (decreasing pressure), particularly in the NH. Poleward of 45° S, acetone VMRs remain fairly consistent with average VMRs between 400 pptv and 500 pptv. In 5-day averages at 9 km, NH VMRs poleward of 45° N are consistently higher than Southern Hemisphere observations poleward of 45° S, by between 750 pptv and 1100 pptv. The results show a clear influence of mid-latitude and transport processes on the acetone summertime distribution.

Highlights

Within the last few years, more regular montoring of acetone in the atmosphere has been achieved by the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrumental Container) program (Brenninkmeijer et al, 2007)
Hemispheric difference between the higher volume mixing ratios (VMRs) in the Northern Hemisphere (NH) compared to lower VMRs in the Southern Hemisphere (SH) at both 277 hPa and 185 hPa
The gas is a major source of hydrogen oxide radicals and peroxyacetyl nitrate (PAN) in the upper troposphere

Summary

Introduction

Acetone (C3H6O) is present ubiquitously in the troposphere with concentrations in the range 0.2 ppb to 3 ppb as determined from sporadic aircraft measurements (Jacob et al, 2002; Arnold et al, 1997; Knop and Arnold, 1987) and is a major source of hydrogen oxide radicals (HOx) and peroxyacetyl nitrate (PAN) in the upper troposphere (UT) (Singh et al, 1995; Jaegle et al, 1997, 2001; McKeen et al, 1997; Wennberg et al, 1998; Collins et al, 1999; Muller and Brasseur, 1999). The advent of spaceborne limb-viewing Fourier transform spectrometers, with high spectral resolution, has allowed the possibility to distinguish lines of weakly absorbing species from stronger absorbers such as carbon dioxide in the upper troposphere and lower stratosphere (UTLS). One such instrument, which measures limb-emission, is the Michelson Interferometer for Passive Atmospheric sounding (MIPAS) onboard the ENVIronmental SATellite (Envisat) (Fischer et al, 2008; Fischer and Oelhaf, 1996). We present results investigating the global relationship between acetone and carbon monoxide (CO)

Measurements

Radiance simulations

Error analysis

Findings

Conclusions