High spectral resolution solar absorption measurements of ethylene [formula omitted] in a forest fire smoke plume using HITRAN parameters: Tropospheric vertical profile retrieval

Abstract

The tropospheric mixing ratio profile of ethylene ( C 2 H 4 ) has been retrieved from a high spectral resolution ground-based infrared solar absorption spectrum. The spectrum was recorded during intense fires in New South Wales, Australia on January 1, 2002, and was analyzed with the C 2 H 4 spectral parameters added to the 2000 HITRAN compilation. Absorption by C 2 H 4 in the smoke-affected spectrum extends over a broad spectral range in a region with observable rotational fine structure. The fine structure occurs in addition to the 949.5 cm - 1 ν 7 band Q branch that is traditionally used to quantify C 2 H 4 amounts from infrared atmospheric measurements assuming room temperature laboratory absorption coefficients. The measured spectrum is fitted to near the noise level with a retrieved vertical column of ( 3.8 ± 0.2 ) × 10 17 molecules per square centimeter. The retrieved vertical C 2 H 4 profile increases with altitude near the surface reaching a maximum of 37 parts per billion ( 10 - 9 ) near 1 km, decreasing above.