Carbon monoxide in the upper troposphere over the western Pacific between 1993 and 1996

Abstract

Abstract. Air samples at 8.5-13 km were collected regularly using a commercial airliner between Australia and Japan, and they were measured for CO mixing ratios to obtain time series data from April 1993 to July 1996. When averaged over 12 latitudinal bands between 30øN and 30øS, two overall features emerge from these data. First, CO levels in the upper troposphere decreased in all latitudinal bands. Second, the seasonal cycle showed significant differences between the northern and southern hemispheres. In the southern hemisphere a strong maximum in the CO mixing ratio (up to around 90 ppb) was found in October-November. The most likely source for this enhanced CO is tropical biomass burning. Methane oxidation and transport of industrial CO from the northern hemisphere were estimated as relatively minor sources during the austral spring. Air mass trajectories indicate that an extremely high CO level of -•130 ppb observed in November 1994 between 100 and 20øS was due to enhanced biomass burning in Southeast Asia and/or northern Australia. On the other hand, air mass trajectories for the 20 ø 30øS region indicate that CO-rich air from biomass burnings over southern Africa or South America was transported across the South Indian Ocean within •-1 week by the strong westerly winds around the subtropical jet. Tnus it is concluded that a rapid horizontal transport coupled with deep convection plays an important role in the appearance of the CO spring peak in the upper troposphere over the western South Pacific.

Pacific Exploratory Mission‐Tropics carbon monoxide measurements in historical context

“…The same measurements showed that the amplitude of the seasonal cycle increased with altitude. Measurements from commercial jets between Narita, Japan, and Sydney, Australia, at 9.5-13 km altitude also showed a CO seasonal cycle in the upper troposphere, with a maximum at 25øS-30øS [Matsueda et al, 1998]. Comparison of the surface measurements [Novelli et al, 1998b] with those in the upper troposphere [Matsueda et al, 1998] indicated that meridional variations are smaller in the marine boundary layer.…”

“…For example, whereas CO content in the Southern Hemisphere always is maximum in September-October, its magnitude varies significantly from place to place and from year to year [Novelli et al, 1998b;Rinsland et al, 1998b;Matsueda et al, 1998]. …”

Evaluation of a new JMA aircraft flask sampling system and laboratory trace gas analysis system

“…Each aircraft value is an average of four flask measurements. The mean standard deviations (SD) of four measurements were ±0.09 ppm for CO 2 , ±2.1 ppb for CH 4 , and ±2.2 ppb for CO, due mainly to the overall flask sample analytical errors of less than ±0.1 ppm for CO 2 , ±2 ppb for CH 4 , and ±2 ppb for CO at MRI (Matsueda and Inoue, 1996;Matsueda et al, 1998;Matsueda et al, 2002). The averaged aircraft data show distinct seasonal variations, as well as short-term variations, that are quite similar to those from the surface hourly mean data (Fig.…”

“…Thus, the flask air samples collected were returned to the MRI for analysis of CO 2 by an NDIR, and CH 4 and CO by a GC/FID (Matsueda and Inoue, 1996;Matsueda et al, 1998). In total, 6 flights were made each month during JulyDecember in 2010.…”

“…The internal surface of the flask is smoothed by electrochemical polishing, and is coated with amorphous silicon with a thickness of less than 1 µm (Smith et al, 2006) to minimize the drift of trace gas mole fractions in the sampled air during storage. This was done to reduce or eliminate the possibility of a gradual increase of CO mole fraction in metal cylinders and flasks (e.g., Novelli et al, 2003;Matsueda et al, 1998). At both ends of each flask, stainless-steel bellows valves (SS-4H, Swagelok) are attached.…”