Preliminary results for HCHO and BrO from the EOS-Aura Ozone Monitoring Instrument

The Ozone Monitoring Instrument (OMI), a nadir-viewing near-UV/Visible CCD spectrometer, was launched on NASA's EOS-Aura satellite platform on 15 July 2004 into a sun-synchronous, polar orbit with an equator crossing time of 13:45h (ascending node). OMI measurements cover the spectral region of 270-500 nm with a spectral resolution between 0.42 nm and 0.63 nm and a nominal ground footprint of 13x24 km2 at nadir. Global coverage is achieved in one day. The very high spatial resolution of OMI measurements set a new standard for trace gas and air quality monitoring from space. Combined with daily global coverage, this significantly advances our ability to answer outstanding questions on air chemistry, including the determination of BrO sources in mid and low latitudes, BrO-O3 anti-correlations as a function of latitude, and the production of formaldehyde in cities of the developing world. We give an overview of the OMI instrument and introduce the operational trace gas retrieval scheme for BrO, HCHO, and OClO that is based on a direct, non-linear fitting approach of observed radiances, including corrections for spectral undersampling. We present first results for tropospheric BrO and HCHO, an important element in air quality monitoring. Only limited results are currently available for OClO, an element in the destruction cycle of polar stratospheric ozone, due to the lack of OMI observations at a time of the year where OClO loading is significantly above the detection limit from space.

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