Morris, GA, Hersey, S, Thompson, AM, Pawson, S, Nielsen, JE, Colarco, PR, McMillan, WW, Stohl, A, Turquety, S, Warner, J, Johnson, BJ, Kucsera, TL, Larko, DE, Oltmans, SJ, Witte, JC (2006). "Alaskan and Canadian forest fires exacerbate ozone pollution over Houston, Texas, on 19 and 20 July 2004". JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 111(D24), D24S03.

On Monday, 19 July, and Tuesday, 20 July 2004, the air over Houston, Texas, appeared abnormally hazy. Transport model results and data from the Atmospheric Infrared Sounder ( AIRS), the Moderate Resolution Imaging Spectrometer ( MODIS), the Measurement of Ozone by Airbus In- service airCraft ( MOZAIC) experiment, and the Total Ozone Mapping Spectrometer ( TOMS) indicate that an air mass originating on 12 July 2004 over forest fires in eastern Alaska and western Canada arrived in Houston about 1 week later. Ozonesonde data from Houston on 19 and 20 July show elevated ozone at the surface (> 125 ppbv) and even higher concentrations aloft ( similar to 150 ppbv of ozone found 2 km above the surface) as compared to more typical profiles. Integrated ozone columns from the surface to 5 km increased from 17 - 22 DU ( measured in the absence of the polluted air mass) to 34 - 36 DU on 19 and 20 July. The average on 20 July 2004 of the 8- hour maximum ozone values recorded by surface monitors across the Houston area was the highest of any July day during the 2001 - 2005 period. The combination of the ozone observations, satellite data, and model results implicates the biomass burning effluence originating in Alaska and Canada a week earlier in exacerbating pollution levels seen in Houston.