Disaggregating global commercial aviation emissions by background static-stability in the upper-troposphere and lower-stratosphere

In 2006 commercial aircraft burned 188 Tg of jet fuel which resulted in the emission of 162 Tg of carbon dioxide among other combustion products. Many of the constituents of burned jet fuel are thought to have significant effects on climate, particularly because they are released in the upper-troposphere and lower-stratosphere (UTLS) where the vertical mixing is slow. The exact radiative effect, however, is difficult to quantify because the UTLS is a complicated dynamical zone where chemical transport time-scales can range from years (e.g. global scale stratosphere-troposphere exchange) to hours (e.g. tropopause folding processes) and horizontal scales can range from thousands of kilometers (e.g. eddy mixing along isentropic surfaces) to a single kilometer (e.g. the width of a tropopause fold). Furthermore, there are steep vertical gradients in the dynamical and chemical properties of the atmosphere near the tropopause which are only visible in tropopause relative coordinates because the tropopause height varies significantly from month to month and day to day. Therefore, since a third of global commercial aviation emissions occur near the tropopause, within a chemically defined transition layer, disaggregating aviation emissions by background atmospheric properties represents a step toward a more complete understanding of the potential impact aviation emissions have on climate and surface air quality. This study disaggregates global commercial aviation emissions in tropopause relative coordinates with respect to background static-stability and chemical composition. Furthermore, the data are regionally and temporally disaggregated and statistics are derived. The static-stability is derived from high resolution temperature profiles obtained from the Challenging Minisatellite Payload (CHAMP) and the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. The daily thermal tropopause height is also obtained from the Atmospheric Infrared Sounder (AIRS) on the NASA AQUA satellite. These data sets are collocated in time and space with an emission data set obtained from the Volpe National Transportation Systems Center, computed using the Federal Aviation Administration's Aviation Environmental Design Tool. It is of particular interest to find that 75% of global commercial aviation emissions in 2006 were emitted below the thermal tropopause. Of this 75%, 30% occurred below 5km, 40% occurred above 5km but into a region of low static-stability [Brunt-Vaisala Frequency, N2 < 1.0e-4 s-1], and 20% occurred in a region of moderate static stability [1.0e-4 s-1 < N2 < 2.0e-4 s-1]. The remaining global emissions, about a third of the total, were emitted near or above the tropopause in a region of higher static-stability [N2 > 2.0e-4s-1]. Overall, emissions occurred in less stable air in the tropics and increasingly stable air with increasing latitude. This is illustrated by the fact that, between 60o and 90o N, 70% of the total emissions occurred above the tropopause in very stable air.