[1] The Biomass Burning and Lightning Experiment phase A (BIBLE-A) aircraft observation campaign was conducted from 24 September to 10 October 1998, during a La Niña period. During this campaign, distributions of ozone and its precursors (NO, CO, and nonmethane hydrocarbons (NMHCs)) were observed over the tropical Pacific Ocean, Indonesia, and northern Australia. Mixing ratios of ozone and its precursors were very low at altitudes between 0 and 13.5 km over the tropical Pacific Ocean. The mixing ratios of ozone precursors above 8 km over Indonesia were often significantly higher than those over the tropical Pacific Ocean, even though the prevailing easterlies carried the air from the tropical Pacific Ocean to over Indonesia within several days. For example, median NO and CO mixing ratios in the upper troposphere were 12 parts per trillion ( pptv) and 72 parts per billion ( ppbv) over the tropical Pacific Ocean and were 83 pptv and 85 ppbv over western Indonesia, respectively. Meteorological analyses and high ethene (C 2 H 4 ) mixing ratios indicate that the increase of the ozone precursors was caused by active convection over Indonesia through upward transport of polluted air, mixing, and lightning all within the few days prior to observation. Sources of ozone precursors are discussed by comparing correlations of some NMHCs and CH 3 Cl concentrations with CO between the lower and upper troposphere. Biomass burning in Indonesia was nearly inactive during BIBLE-A and was not a dominant source of the ozone precursors, but urban pollution and lightning contributed importantly to their increases. The increase in ozone precursors raised net ozone production rates over western Indonesia in the upper troposphere, as shown by a photochemical model calculation. However, the ozone mixing ratio ($20 ppbv) did not increase significantly over Indonesia because photochemical production of ozone did not have sufficient time since the augmentation of ozone precursors. Backward trajectories show that many air masses sampled over the ocean south of Indonesia and over northern Australia passed over western Indonesia 4-9 days prior to being measured. In these air masses the mixing ratios of ozone precursors, except for short-lived species, were similar to those over western Indonesia. In contrast, the ozone mixing ratio was higher by about 10 ppbv than that over Indonesia, indicating that photochemical production of ozone occurred during transport from Indonesia. The average rate of ozone increase (1.8 ppbv/d) during this transport is similar to the net ozone formation rate calculated by the photochemical model. This study shows that active convection over Indonesia carried polluted air upward from the surface and had a discernable influence on the distribution of ozone in the upper troposphere over the Indian Ocean, northern Australia, and the south subtropical Pacific Ocean, combined with NO production by lightning. Citation: Kita, K., et al., Photochemical production of ozone in the upper troposphere in association with cumulus c...
Measurements of a suite of atmospheric trace constituents made from the NASA DC-8 aircraft, while it was making vertical profiles during the Pacific Exploratory Mission A (PEM-West A) to the westem Pacific in September-October 1991 have revealed a layered structure in much of the region. Ozone, water vapor, carbon monoxide, and methane were available continuously and are the primary constituents used to define the layers; nonmethane hydrocarbons, carbon dioxide, hydrogen peroxide and methylhydroperoxide were available less frequently but were also used. From 105 vertical profiles, sampled at vertical speeds of about 6 rn s -1, over 500 layers were identified using 03 and H20; their mean thickness was about 400 m. When these layers could be identified from lidar along-track cross sections of 03 made from the aircraft, they were found to extend over distances of 100-200 km or more. Combinations of several constituent deviations from vertical nmning means were used to identify possible layer sources; examples are high 03, low H20, CO, and CI-!4, corresponding to the extrusion of stratospheric air into the troposphere; low 03 and high H20, originating from convection from the tropical boundary layer; high 03, CO mad CH4, low H20, coming from convection from the continental boundary layer and transport in the upper troposphere, sometimes from distant sources. The layers show no clear relationship with wind velocity profiles measured simultaneously on the aircraft; there is some relationship with temperature and potential temperature, with some layers which show a stratospheric signature lying on isentropes that are in the lower stratosphere at higher latitudes. Potential vorticity (PV) is used as an additional tracer to check the conclusions about the different types of layers. While PV is often used as an indicator of stratospheric air, its use as an indicator of convection is also illustrated here. in fact, is usually ignored for all practical applications.One good way to find out about the vertical fine structure of the atmosphere is to fly spiral ascents or descents at a reasonably slow vertical velocity with an aircraft equipped with fast response instruments that sample atmospheric trace constituents which can be expected to vary distinctively through these features. Another way is to examine some of these constituents with a lidar carried on an aircraft. These procedures were carried out using instmments mounted on a DC-8 aircraft during the NASA Pacific Exploratory Mission-West A (PEM-West A) based in the western Pacific in September-October 1991 (see overview paper by Hoell et al. [this issue]).When several different atmospheric trace substances are measured simultaneously, the vertical layer structure carries information about the recent source of the air masses involved. For example, if a layer is detected in the middle tropical troposphere which contains a much higher water vapor mixing ratio than air immediately above or below, and concomitantly much lower ozone, then we might deduce from the water vapor ...
The DC-8 mission of September 27, 1991, was designed to sample air flowing into Typhoon Mireille in the boundary layer, air in the upper tropospheric eye region, and air emerging from the typhoon and ahead of the system, also in the upper troposphere. The objective was to find how a typhoon redistributes trace constituents in the West Pacific region and whether any such redistribution is important on the global scale. The boundary layer air (300 m), in a region to the SE of the eye, contained low mixing ratios of the tracer species 03, CO, C2H6, C2H2, C3H8, C6H6 and CS2 but high values of dimethylsulfide (DMS). The eye region relative to the boundary layer, showed somewhat elevated levels of CO, substantially increased levels of 03, CS2 and all nonmethane hydrocarbons (NMHCs), and somewhat reduced levels of DMS. Ahead of the eye, CO and the NMHCs remained unchanged, 03 and CS2 showed a modest decrease, and DMS showed a substantial decrease. There was no evidence from lidar cross sections of ozone for the downward entrainment of stratospheric air into the eye region; these sections show that low ozone values were measured in the troposphere. The DMS data suggest substantial entrainment of boundary layer air into the system, particularly into the eye wall region. Estimates of the DMS sulphur flux between the boundary layer and the free troposphere, based on computations of velocity potential and divergent winds, gave values of about 69 gg S m -2 d-•averaged over a 17.5 ø grid square encompassing the typhoon. A few hours a•er sampling with the DC-8, Mireille passed over Oki Island, just to the north of Japan, producing surface values of ozone of 5.5 ppbv. These 03 levels are consistent with the low tropospheric values found by lidar and are more typical of equatorial regions. We suggest that the central eye region may act like a Taylor column which has moved poleward from low latitudes. The high-altitude photochemical environment within Typhoon Mireille was found to be quite active as evidenced by significant levels of measured gas phase H202 and CH300H and model-computed levels of OH.
In situ aircraft measurements of ozone (O3) and its precursors were made over northern Australia in August–September 1999 during the Biomass Burning and Lightning Experiment Phase B (BIBLE‐B). A clear positive correlation of O3 with carbon monoxide (CO) was found in biomass burning plumes in the boundary layer (<3 km). The ΔO3/ΔCO ratio (linear regression slope of O3‐CO correlation) is found to be 0.12 ppbv/ppbv, which is comparable to the ratio of 0.15 ppbv/ppbv observed at 0–4 km over the Amazon and Africa in previous studies. The net flux of O3 exported from northern Australia during BIBLE‐B is estimated to be 0.3 Gmol O3/day. In the biomass burning region, large enhancements of O3 were coincident with the locations of biomass burning hot spots, suggesting that major O3 production occurred near fires (horizontal scale <50 km).
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