Radiative properties, dynamics, and chemical evolution of the smoke from the 1991 Kuwait oil fires
[Thesis]
J. A. Herring
P. V. Hobbs
University of Washington
1994
201
Ph.D.
University of Washington
1994
The oil fields in Kuwait were the scene of a massive conflagration during much of 1991 that was started by Iraqi forces during the Gulf War. At this time, approximately 4 to 5 million barrels of oil were burning each day. The climatic impacts of the fires were limited by the fact that the smoke was generally confined to the lower 6 km of the atmosphere, where its removal by precipitation processes limited its lifetime. The optical properties of the smoke were such that it was an efficient absorber of solar radiation, with a single-scattering albedo of usd{\sim}usd0.6. This led to rapid warming of the plume during the daytime. Instantaneous heating rates were calculated to be up to usd{\sim}usd90 K day. Because of the vertical distribution of the heating in the plume, the upper part of the plume became unstable and a turbulent mixed-layer developed. Conversely, the lower part of the plume became stably stratified due to the heating. This led to a general decoupling of the lower boundary layer, preventing the heating experienced by the plume from reaching the ground. The general warming of the plume led to mesoscale vertical transport of the plume as a whole. This mode of vertical transport was limited because of the large horizontal extent of the region of buoyant smoke. The mesoscale vertical transport occurred at roughly the same rate as the upward mixing of smoke due to smaller-scale turbulent motions. This vertical transport, however, did not occur rapidly enough to loft the smoke into the upper troposphere before it was dispersed by wind shear and the mixing caused by solar heating of the smoke. The chemical evolution of the plume was generally somewhat slow, due to the lack of ultraviolet radiation to initiate photochemistry within the smoke plume and to the generally low concentrations of nitrogen oxides, which act as catalysts for photochemical chain reactions. Heterogeneous chemical reactions between gases and black carbon particles produced by the fires were also not important. There was evidence, however, of rapid removal of sulfur dioxide and nitrogen oxides through heterogeneous chemical reactions (typically usd{\sim}usd7% h and 10% h, respectively) on the surfaces of alkaline soil dust particles.