Pollution events observed during CARIBIC flights in the upper troposphere between South China and the Philippines

Abstract

Abstract.A strong pollution episode in the upper troposphere between South China and the Philippines was observed during CARIBIC flights in April 2007. Five pollution events were observed, where enhancements in aerosol and trace gas concentrations including CO, CO 2 , CH 4 , nonmethane hydrocarbons (NMHCs) and halocarbons were observed along the flight tracks during four sequential flights. The importance of the contribution of biomass/biofuel burning was investigated using chemical tracers, emission factor analysis, back-trajectory analysis and satellite images. The Indochinese peninsula was identified as the probable source region of biomass/biofuel burning. However, enhancements in the urban/industrial tracer C 2 Cl 4 during the events also indicate a substantial contribution from urban anthropogenic emissions. An estimation of the contribution of fossil fuel versus biomass/biofuel to the CO enhancement was made, indicating a biomass/biofuel burning contribution of ∼54 to ∼92% of the observed CO enhancements. Biomass/biofuel burning was found to be the most important source category during the sampling period.

Acetone variability in the upper troposphere: analysis of CARIBIC observations and LMDz-INCA chemistry-climate model simulations

“…Acquisition is performed during all seasons, for a large range of solar insolation conditions, and along four main routes. In 2006 and 2007, most flights were to Manila, with two flights to South America (February (Köppe et al, 2009), season, and aircraft position relatively to the tropopause (Sprung and Zahn, 2010), and due to pollution events (Lai et al, 2010). First we briefly summarise some key results from these studies.…”

“…Globally, maximal values in August 2003 were found to reach 3000 pptv between 300 and 500 hPa and to reach 2000 pptv above 200 hPa (Moore et al, 2010). Lai et al (2010) showed the impact on acetone vmr of pollution events observed in the UT in April 2007. Polluted air masses crossing the flight trajectory over China led to enhancements from 350 to 1800 pptv for acetone, from 70 to 150 ppbv for CO with O 3 remaining below 100 ppbv.…”

“…Polluted air masses crossing the flight trajectory over China led to enhancements from 350 to 1800 pptv for acetone, from 70 to 150 ppbv for CO with O 3 remaining below 100 ppbv. Back trajectories located the air mass origin over the Indochinese Peninsula, bringing pollution from biomass/biofuel burning activities (Lai et al, 2010). To ensure consistency in the data set, small-scale variability due to changes in acquisition altitude are avoided by only using measurements when the aircraft cruises at constant altitude, i.e.…”

Temporal variations of atmospheric CO<sub>2</sub> and CO at Ahmedabad in western India

“…The observed ratios are similar to the air mass influenced by both fossil fuel and biofuel emissions as discussed by Lin et al (2015) over Pondicherry. Using CARIBIC observations, Lai et al (2010) also reported the CO / CO 2 ratio in the range of 15.6-29.3 ppb ppm −1 from the air mass influenced by both biofuel and fossil fuel burning in the Indochinese Peninsula. Further, the CO / CO 2 ratio is also observed at about 13 ppb ppm −1 in the south-eastern Asian outflow during February-April 2001 during the TRACE-P cam- paign and it suggests the combined influence of fossil fuel and biofuel burning (Russo et al, 2003).…”

Analysis of <sup>13</sup>C and <sup>18</sup>O isotope data of CO<sub>2</sub> in CARIBIC aircraft samples as tracers of upper troposphere/lower stratosphere mixing and the global carbon cycle

“…Low values indicate more pronounced effects from respiration, fossil fuel and biomass burning. At times fresh plumes are intersected; for instance the data across biomass burning plumes over China (Lai et al, 2010) demonstrate some correlations between increases in CO and CO 2 and negative shifts in δ 13 C(CO 2 ) (data not plotted). Monsoon plumes were also crossed which were identified by increases in methane and some (negative) δ 18 O(CO 2 ) shifts.…”