OCTOBER 2001: Satellite observations of tropospheric NO₂ during TRACE-P

Tropospheric slant column concentrations of nitrogen dioxide (NO₂) measured by the GOME (Global Ozone Monitoring Experiment) satellite instrument during the March 16 - April 15 2001 period of the NASA TRACE-P aircraft experiment. The TRACE-P aircraft experiment was directed at quantifying Asian outflow over the western Pacific; Daniel Jacob was mission scientist. Analysis of TRACE-P observations to better understand Asian emissions and their chemical evolution is presently a major activity in the Harvard Atmospheric Chemistry Modeling Group. Nitrogen dioxide is emitted to the troposphere by high-temperature combustion, and is also produced in the stratosphere by oxidation of nitrous oxide (N₂O). It has a short lifetime against oxidation in the atmosphere (~1 day), therefore the tropospheric column concentration provides a mapping of emissions (see Martin et al. [2001]). The slant columns of NO₂ shown here were fitted from the GOME spectra by Randall Martin and the stratospheric component of the column was removed as described by Martin et al. [2001]. Here "slant" refers to the optical path followed by the backscattered solar photons detected by GOME; conversion to true (vertical) tropospheric columns requires scaling by an air mass factor (AMF) as described by Martin et al. [2001] and still needs to be done for the TRACE-P period. The GOME data show high NO₂ column concentrations over the highly populated and industrial areas of northeastern China and central Japan, and over the Yellow Sea (major outflow region). Biomass burning regions of southeast Asia show only slight enhancements, reflecting lower flame temperatures than for fossil fuel combustion.