New algorithm for satellite NO2 retrievals: Tropospheric results

Nitrogen dioxide (NO2) is an atmospheric trace gas, important in the chemistries of both stratospheric ozone and tropospheric pollution. We describe a new technique for retrieving NO2 vertical columns from nadir-viewing satellite instruments and apply it to the measurements from the Dutch-Finnish Ozone Monitoring Instrument (OMI) on board NASA Aura satellite. The algorithm, now operational at NASA, is a significant advance over the previous version, and includes a greatly improved stratospheric-tropospheric partition estimation that uses minimal model inputs, as well as seasonally dependent a priori NO2 profile shapes for better air mass factor calculations. These improvements greatly reduce biases noted in previous validation studies. We show a comparison of the new tropospheric NO2 columns against other satellite retrievals and present validation results, including a re-analysis of the Intercontinental Chemical Transport Experiment (INTEX-B).