Abstract
Abstract. The large bush fires which occurred in southeast Australia in February 2009 were unusually destructive. However, they were also unusual in the amounts of various combustion products which were injected directly into the stratosphere. We report the observations by the Microwave Limb Sounder (MLS) instrument on the Aura satellite of some of these combustion products. The highest quality observations are of CO; these clearly show a large region of enhanced mixing ratios to the north of New Zealand which remains in that region for about ten days before drifting westwards and finally dissipating over the Atlantic about a month after the fire. The region of enhanced CO ascends from the tropopause to 46 hPa during this period. Back trajectories run from the points where MLS observes enhanced CO pass close to the site of the fire. The MLS observations of CH3CN and HCN resemble those of CO except for their poorer vertical resolution and more limited vertical range. An apparent enhancement in ClO is also observed by MLS, but detailed analysis of the measured radiances reveals this feature to be a signature of CH3OH, which is not currently retrieved by the MLS data processing system. The fires of February 2009 are the only event of this type and magnitude in the 7-yr MLS record.
Highlights
Biomass burning releases a wide variety of chemicals into the atmosphere (Andreae and Merlet, 2001)
In this paper we report on the gaseous combustion products as observed by the Microwave Limb Sounder (MLS) instrument on NASA’s Aura platform
In February/March 2009 MLS observed an unusual airmass in the lower stratosphere containing high concentrations of several biomass-burning products
Summary
In this paper we report on the gaseous combustion products as observed by the Microwave Limb Sounder (MLS) instrument on NASA’s Aura platform. The random error on a single profile is around 0.025 ppbv (about 10 %) at 31 hPa and higher altitudes, worsening rapidly to 0.08 ppbv (about 40 %) at 100 hPa. Two separate CH3CN products are produced: one from the 190 GHz region and one from the 640 GHz region; there are systematic differences between the products and both have large biases in the lower stratosphere when compared to earlier measurements Version was released after this paper was written.) As the CO is the most reliable of these three MLS measurements of biomass-burning products, we used it to obtain an overview of the Black Saturday event
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