Infrared Extinction Measurements of Stratospheric Smoke from Boreal Forest Fires

There have been a large number of extinction measurements of stratospheric smoke layers from POAM and SAGE at ultraviolet through near-infrared (IR) wavelengths (355 to 1060 nm). Here we will discuss a number of HALOE measurements of stratospheric smoke at mid-wave IR (2.45 to 5.26 micron). The spectral dependence of smoke across this part can easily be distinguished from that of the background stratospheric aerosols or thin ice clouds. The background stratospheric aerosols (sulfuric acid solution) have a unique IR signature in this spectral region, because the aerosol attenuation changes from being predominately due to scattering at wavelengths less than 2.5 microns to predominately due to absorption at wavelengths greater than 3.4 microns (the exact cross-over point depending on the characteristic particle size). This results in the 3.4, 3.45, and 5.26 micron HALOE channels having significantly larger extinction than the2.45 micron channel, whereas the smoke attenuation shows a decrease with increasing wavelength. We will focus on results from the 1998 and 2001 seasons when there was wide spread smoke in the Northern Hemisphere especially at the higher latitudes. There were also a number of coincident measurements between HALOE and either POAM or SAGE during these seasons which will be discussed.