We show in this study that the non-linearity of NOx
chemistry implies that the local derivative (of a first-order Taylor expansion) is better suited in the inverse modelling of NOx
emissions over eastern China. We used single-grid-cell-based perturbation sensitivity calculation. The method leads to smaller NOx
emission over highly polluted regions and higher NOx
emission over rural regions. There are also more consistent results from using two different satellite instruments.