Tropospheric carbon monoxide measurements from the Scanning High‐Resolution Interferometer Sounder on 7 September 2000 in southern Africa during SAFARI 2000

Abstract

Retrieved tropospheric carbon monoxide (CO) column densities are presented for more than 9000 spectra obtained by the University of Wisconsin‐Madison (UWis) Scanning High‐Resolution Interferometer Sounder (SHIS) during a flight on the NASA ER‐2 on 7 September 2000 as part of the Southern African Regional Science Initiative (SAFARI 2000) dry season field campaign. Enhancements in tropospheric column CO were detected in the vicinity of a controlled biomass burn in the Timbavati Game Reserve in northeastern South Africa and over the edge of the river of smoke in south central Mozambique. Relatively clean air was observed over the far southern coast of Mozambique. Quantitative comparisons are presented with in situ measurements from five different instruments flying on two other aircraft: the University of Washington Convair‐580 (CV) and the South African Aerocommander JRB in the vicinity of the Timbavati fire. Measured tropospheric CO columns (extrapolated from 337 to 100 mb) of 2.1 × 1018 cm−2 in background air and up to 1.5 × 1019 cm−2 in the smoke plume agree well with SHIS retrieved tropospheric CO columns of (2.3 ± 0.25) × 1018 cm−2 over background air near the fire and (1.5 ± 0.35) × 1019 cm−2 over the smoke plume. Qualitative comparisons are presented with three other in situ CO profiles obtained by the South African JRA aircraft over Mozambique and northern South Africa showing the influence of the river of smoke.

Trace gas measurements in nascent, aged, and cloud‐processed smoke from African savanna fires by airborne Fourier transform infrared spectroscopy (AFTIR)

“…To provide a context for this study, we describe a few typical trace gas profiles up to 5.5 km during S2K. (The location of many vertical profiles is given elsewhere (Appendix A by P. V. Hobbs in the work of Sinha et al [2003a]) and one profile is discussed by McMillan et al [2003].) Most of southern Africa was dominated during the dry season of 2000 by a well‐mixed haze layer that extended to 3–6 km in altitude and contained aged emissions from savanna fires, cooking fires, vegetation and industry.…”

“…The accuracy, as determined by testing with calibration standards, for several molecules was: CO 2 , CO and CH 4 (1–2%); NO, NO 2 , and CH 3 OH (1–5%); and NH 3 (variable as discussed below). The CO values obtained by AFTIR were not significantly different from those obtained on a nearby aircraft using a CMDL flask‐sampling system [ McMillan et al , 2003].…”

Carbon monoxide mixing ratios over Oklahoma between 2002 and 2009 retrieved from Atmospheric Emitted Radiance Interferometer spectra

“…The basic AERI CO retrieval procedure was originally developed and validated for retrievals from space-and airborne IR spectra (McMillan et al, 1996(McMillan et al, , 1997(McMillan et al, , 2003 and subsequently modified for retrievals from the AERI spectra He et al, 2001). It is a oneparameter (CO column) retrieval algorithm based on temperature and water vapour profiles already retrieved from other portions of the same AERI spectra and archived.…”

Infrared Absorption Spectroscopy

“…Since in practice one cannot measure out to + retardation, FTIR instruments have finite spectral resolution determined by the practical mirror travel. Examples of resolution employed are 0 001 cm −1 in ground-based and some larger airborne instruments (Worden et al, 1997), through to 0 06 cm −1 (airborne or ground-based, Coffey et al, 2003), 0 5 cm −1 (airborne or ground-based, Yokelson et al, 1999), and 1 cm −1 for airborne measurements (McMillan et al, 2003). Individual vibrational-rotational lines of molecules have pressure-broadened absorption halfwidths of ∼0 1 cm −1 at atmospheric pressure and < 0 01 cm −1 at stratospheric pressures of ∼50 torr.…”