Catastrophic fires in California
22 October 2007 00:00 UTC
The October 2007 California wildfires were a series of wildfires that began burning across Southern California on 20 and 21 October.
04 May 2023
22 October 2007
By Jochen Kerkmann, Alexander Jacob, Helmut Bauch (EUMETSAT) and Patrick Dills (COMET/UCAR)
According to Wikipedia, at least 1,500 homes were destroyed and over 2,000km² of land burned from Santa Barbara County to the US-Mexico border. Nine people died as a direct result of the fire, 85 others were injured, including at least 61 fire fighters.
Major contributing factors to the extreme fire conditions were drought in Southern California, hot weather, and unusually strong Santa Ana winds with gusts reaching 140km/h. Several fires were triggered by power lines damaged by the high winds. The last fire was fully contained on 9 November 2007, 19 days after the series of fires started.
The Metop-A AVHRR image below shows the situation on 22 October 2007 when large smoke plumes were visible over the Pacific Ocean. As smoke is more reflective at shorter wavelengths (VIS0.6 channel) than in the near infrared (NIR1.6 channel), the smoke clouds over the Pacific have a light blue colour.
It should be noted that, because of the strong Santa Ana winds, large dust clouds were also generated and blown out over the eastern Pacific. In the AVHRR composite image below, the dust clouds can be distinguished from the smoke clouds by the different colour (see Interpretation). This is because for dust clouds the difference between VIS0.6, VIS0.8, NIR1.6 images is not as strong as for smoke clouds (see MSG and MODIS examples, author: D. Rosenfeld).
The results discussed above are confirmed by MODIS images and products (see images and the AVHRR/MODIS Comparison). The method behind NRL's MODIS dust RGB (which discriminates smoke from dust very well) is to use the differential absorption sensitivity for dust and smoke in the VIS channels ((0.469 and 0.853 micron channels) over water.
Over land, because of the similar appearance of dust and especially desert surfaces, the product is enhanced with the split window IR channels which are sensitive to the fact that an elevated dust layer is generally cooler than the surface during daytime, and sensitive to the differential absorption present in the split window region (11 v 12 microns). A similar product could be generated from AVHRR or MSG data, eg by combining the Natural Colours RGB (over water) with the Dust RGB (over land).
Additional content
Metop-A AVHRR RGB Composite (23 October, 17:55 UTC)
Metop-A AVHRR Channel 3b image showing hot spots (24 October, 04:07 UTC)
Aqua MODIS RGB True Colour (source: NRL)
Aqua MODIS RGB Dust Product (source: NRL)
