RADIATIVELY DRIVEN DYNAMICS OF THE PLUME FROM 1991 KUWAIT OIL FIRES

Optical properties of the aerosol from the 1991 Kuwait oil fires are c alculated using measured aerosol size distributions and a spectral ref ractive index based on the measured chemical composition of the partic ulate matter. At a wavelength of 538 nm the calculated light-scatterin g coefficient agrees well with measurements, but the calculated single -scattering albedo is systematically higher by about 18% than the meas ured value. Radiative transfer calculations indicate maximum net dayti me heating rates of 94 and 56 K d(-1) for smoke 1 and 3 hours downwind of the fires, respectively. In the upper regions of the plume, where the calculated heating rates decrease with height, a radiative-convect ive mixed layer developed. There was no significant temperature invers ion at the top of this layer, which allowed rapid entrainment of air i nto the top of the plume, causing it to thicken at an observed rate of similar to 0.1 m s(-1) In addition, radiative heating of the plume as a whole caused it to lift as a unit at a measured rate of similar to 0.1 m s(-1) during the first few hours of plume evolution. A theory, b ased on mixed layer modeling and a scale analysis of the equations of motion, is presented that successfully reproduces the two rates of ver tical transport. This model of the dynamics of a radiatively heated pl ume can be used to predict the evolution and lofting of large composit e smoke plumes, such as those from forest fires; it also has implicati ons for the transport, lifetime, and climatic importance of smoke gene rated on continental scales.