030415ChattanoogaEvent: Kansas Smoke Impact on Chattanooga
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Event Evidence Analysis
In the GA/TN petition, April 15 was identified as an exceptional smoke event at Chattanooga, caused by the agricultural grassland fires in Kansas. In order to set a temporal context for the event, the chemical and other data are examined for April 12 as well as April 15, 2003. On April 12, 2003, the concentration of SmokeBioMass was moderate at Chattanooga (5-10 ug/m3). However, the concentration of SmokeBioMass at Kansas City was over 30 ug/m3 indicating the presence of smoke. On April 15, 2003, the SmokeBioMass concentration at Chattanooga area was unusually high 15-20 ug/m3. Furthermore, on April 15, 2003, the SmokeBioMass fraction of PM2.5 was 44% compared to the 25% seasonal average value. Hence, the chemical data, in particular the higher SmokeBioMass/PM2.5 ratio, support a statement that on April 15, 2003, the PM2.5 concentration at Chattanooga was enhanced by SmokeBioMass.
Fire and Transport:
The existence of grassland fires in Kansas is well supported by satellite-derived and ground-based observations. The GA/TN petition well documents the grassland fires and their anthropogenic causes. The trajectory data show that on April 12-15, 2003, the direction of the smoke transport was toward the southeast, from Kansas to northern Alabama. On the April 15, 2003 the trajectories curved northward from Alabama to eastern Tennessee. Hence, both the smoke source in and around Kansas, as well as the regional scale transport of smoke from Kansas through Alabama to Chattanooga is consistent with the statement that on April 15, 2003 Chattanooga was influenced to some extent by smoke emissions in Kansas.
On April 12, 2003 the spatial pattern of PM2.5 concentration shows a pronounced aerosol plume (>30 ug/m3) stretching from Kansas towards the Southeast. Also, on April 15, 2003 a significant aerosol bulge (>30 ug/m3) covered much of Alabama and eastern Tennessee. It is also instructive to examine the satellite AOT which clearly shows the Kansas smoke plume stretching over MO, TN, and AL on April 13, 2003. The heavy aerosol bulge over Alabama-Eastern Tennessee is also evident on April 15, 2003. A further interesting observation is that on April 12, 2003 the SeaWifs AOT indicates direct easterly transport from Kansas toward Kentucky. However, the surface PM2.5 concentration on April 12, 2003 do not show high values of PM2.5 over Kentucky. This leads to the inference that the KS smoke drifting eastward on April 12, was elevated from the ground and it did not impact the surface concentrations along its path.
Based on the PM2.5 concentration time series at Chattanooga and nearby sites, there is a distinct aerosol peak (>35 ug/m3) on April 15, 2003.
During the April 12-15, 2003 period, there was a significant smoke source from grass burning in Kansas. Surface PM2.5 concentrations, satellite AOT and trajectory data indicate smoke transport eastward in elevated layers (April 12) as well as in surface-based layers on April 15, 2003. On April 15, 2003 about 44% of PM2.5 mass at Chattanooga was due to SmokeBioMass, compared to the 25% seasonal average value. The 'excess' SmokeBioMass at Chattanooga (44-25%=19% or 7ug/m3) on April 15, 2003 is attributable to exceptional smoke.