Georgia/Florida fires and air quality – April/May 2007

During April and May 2007, several hundred fires burned uncontrollably in Georgia and Florida. The smoke from these fire events was visible throughout the southeastern United States and had a major impact on particulate matter (PM) air quality. In this study, we show the strength of polar orbiting and geostationary satellite data in capturing the spatial distribution and diurnal variability of smoke from these fires. We quantitatively evaluate PM air quality from satellites and ground-based monitors, near and far away (>300 km) from fire source regions. We also show the changes in organic carbon concentrations (a tracer for smoke aerosols) before, during and after these fire events. Finally, we use fire locations and emissions retrieved and estimated from satellite observations as input to a regional mesoscale transport model to forecast the spatial distribution of aerosols and their impact on PM air quality.

During the fire events, total column 550nm aerosol optical thickness (AOT) exceeded 1.0 on several days and ground-based PM2.5 mass (particles less than 2.5 ?m in aerodynamic diameter) reached unhealthy levels (> 65.5 ugm^-3) near the source regions. Since the aerosols were reasonably well mixed in the first 1-2km (as estimated from meteorology), the column AOT values derived from both geostationary and polar orbiting satellites and the surface PM2.5 were well correlated (r>0.7). Several hundred miles away in Birmingham, AL the impact of the fires were also seen through the high AOT and PM2.5 values. Correspondingly, PM2.5 mass due to organic carbon obtained from ground-based monitors showed a three fold increase during fire events when compared to background values. Satellite data were especially useful in capturing PM2.5 air quality in areas where there were no ground-based monitors. Although the mesoscale transport model captured the timing and location of aerosols, the emissions could be underestimated by nearly 70%. Newly developed algorithms from space-borne sensors are becoming a vital tool for assessing extreme events such as fires, smoke, and particulate matter air quality.

Figure 1. MODIS true color image taken on April 29, 2007 showing smoke/fires over Georgia and Florida.

Figure 2.  Inter-comparison of MODIS AOD and surface measured PM2.5 mass concentration over south east region during April-May 2007.

Figure 3. Time series of PM2.5, MODIS AOD and GOES AOD over stations near the fire and away from the fires.

Reference

Christopher, S.A., P. Gupta, U. Nair, T.A. Jones, S. Kondragunta, Y. Wu, J. Hand, X. Zhang, Satellite Remote Sensing and Mesoscale Modeling of the 2007 Florida/Georgia Fires, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (JSTARS-2009-00020)