Quantitative analysis of NOx emissions from Global Ozone Monitoring Experiment satellite image sequences

Nitric oxides (NOx) play a very important role among the anthropogenic trac e gases. They affect human health and have an impact on ozone chemistry and climatic change. Here we describe a new method for the quantification of t he global NOx budget from image sequences of the Global Ozone Monitoring Ex periment (GOME) spectrometer on board the ERS 2 satellite. In contrast to m easurements using ground-based or balloon- or aircraft-borne sensors, this instrument provides, for the first time, the possibility of observing globa l maps of NO2 column densities. As part of this work, algorithms were devel oped to analyze GOME spectra numerically and to extract physically relevant parameters from the resulting maps using image-processing techniques. Colu mn densities of NO, were determined using differential optical absorption s pectroscopy (DOAS) [Platt, 1994]. By the combined use of an efficient B-spl ine interpolation and an inversion algorithm based on Householder transform ations, the numerical algorithms accelerate the retrievals by a factor of 2 6 with respect to previous methods. Moreover, techniques are presented for separating tropospheric and stratospheric NO2 colums and estimating the lif etime of NO2 in the troposphere. This allows determination of regional NOx source strengths. Independent of traditional methods, a global source stren gth of (43 +/- 20) Tg N yr(-1) is estimated. The accurarcy of this method i s comparable to that of established statistical approaches.