September 24, 1999

 

SATELLITE DETECTION OF SMOKE AEROSOLS OVER A

SNOW/ICE SURFACE BY TOMS

Deposits of carbon have been found in ice cores obtained in Greenland that appear to have been caused by forest fires originating in Canada. Recently, data from TOMS have been used to confirm these speculations by showing that smoke frequently drifts over Greenland from the annual boreal fires in Canada. The main finding in this paper is that the TOMS technique can be reliably used to detect smoke over the bright background caused by ice and snow. TOMS uses a two-wavelength technique that is not as sensitive to knowing the reflective properties of the underlying surface compared to techniques using a single wavelength in the visible or infrared portions of the spectrum.

To demonstrate the UV two-wavelength technique, data was used from two different satellites, TOMS and GOME (Global Ozone Monitoring Experiment), taken during an August 1998 event. In this event, smoke generated by Canadian forest fires drifted more than a thousand miles to cross over Greenland. As the smoke moved over the permanent Greenland ice sheet it caused considerable darkening in the scene as observed from space. There is a difference in the amount of darkening in each of the two wavelengths that depends on the properties of the smoke (e.g., amount of absorption, height, particle size, etc.). The observed differences were used to deduce the amount of smoke and its frequency of appearance over Greenland based on 20 years of TOMS data.

Reference: N.C. Hsu, J.R. Herman, J.F. Gleason, O. Torres, and C.J. Seftor, Geophys. Res. Lett. 26, 1165-1168