A54E-01
Simulating the Black Saturday 2009 UTLS Smoke Plume with an Interactive Composition-Climate Model

Friday, 18 December 2015: 16:00
3002 (Moscone West)
Robert D Field1,2, Ming Luo3, Michael D Fromm4, Apostolos Voulgarakis5, Stephane Mangeon5 and John R Worden3, (1)Columbia University, Department of Applied Physics and Applied Mathematics, New York, NY, United States, (2)NASA Goddard Institute for Space Studies, New York, NY, United States, (3)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (4)US Naval Research Laboratory, Washington, DC, United States, (5)Imperial College London, London, United Kingdom
Abstract:
Pyroconvective smoke plumes from large fires can be injected directly into the geostrophic flow and dry air at high altitudes. As a result, they are usually longer-lived, can be transported thousands of kilometers, and can cross the tropopause into the lower stratosphere. Because the emissions pulses are so abrupt relative to other non-volcanic sources, their evolution and decay can be easily separated from background levels of aerosols and trace gases. This makes them interesting natural experiments against which to evaluate models, and understand the fate and effects of surface emissions pulses.

We have simulated the well-observed February 2009 Black Saturday smoke plume from southeast Australia using the NASA GISS Earth System Model. To the best of our knowledge, this represents the first simulation of a high altitude smoke plume with a full-complexity composition-climate model. We compared simulated CO to a joint retrieval from the Aura Tropospheric Emission Spectrometer and Microwave Limb Sounder instruments.

Using an upper tropospheric injection height, we were able to simulate the plume’s eastward transport and ascent over New Zealand, anticyclonic circulation and ascent over the Coral Sea, westward transport in the lower tropical stratosphere, and arrival over Africa at the end of February. Simulations were improved by taking into account hourly variability in emissions associated with extreme fire behavior observed by fire management agencies. We considered a range of emissions amounts, based on different assumptions about which of the Black Saturday fires were explosive enough to inject smoke to high altitudes, and accounting for emissions factor uncertainty. The best agreement between plume concentrations at the end of February was found for the highest emissions scenario. Three days after the fire, there was a linear relationship between emissions amount and plume concentration. Three weeks after the fire, the relationship was non-linear; we discuss diabatic self-lofting as a possible cause of the non-linearity.

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