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.
The Ontar Corporation (www.Ontar.com) is well known for its products for atmospheric remote sensing to calculate radiative transport, atmospheric transmission, and sensor performance in both the normal atmosphere and the atmosphere disturbed by battlefield conditions of smoke, dust, explosives and turbulence. This paper will describe new research activities at Ontar to enhance both the user capabilities and the model functionality. Ontar has incorporated new models into our software products and has initiated an ambitious IR&D effort to further enhance the models. This paper will discuss these efforts. We will also discuss new software products and updates to existing software products that we are distributing. This includes a new release of NVTherm; updates to PcModWin and PcLnWin; and a high resolution gas absorbance spectral database from the Pacific Northwest National Laboratory's (PNNL) spectral data library.
We present detection methods for polar stratospheric clouds (PSCs) from the Environment Agency of Japan's Improved Limb Atmospheric Spectrometer (ILAS) instrument during the arctic winter of 1996/1997. The PSC detection methods are based on ILAS visible channel measurements in and around the oxygen A absorption band. They involve either full nonlinear or simple linear fitting of the spectra to obtain aerosol optical thickness as a function of tangent height. PSC optical thickness is determined from a subsequent linear fit to aerosol optical thickness as a function of altitude. Results for PSC optical thickness from the two methods agree reasonably well for all cases considered in this study, but only the nonlinear fitting approach allows the definitive identification of PSC events. Comparisons with operational ILAS data products show denitrification, removal of water vapor, and generally low temperatures over the vertical region of the PSC. Finally, we present a fast and simple method for the identification of possible PSC candidates from ILAS measurements.
The Global Ozone Monitoring Experiment (GOME) was launched on the European Space Agency's ERS-2 satellite in April 20, 1995. GOME measures the Earth's atmosphere in the nadir geometry, using a set of spectrometers that cover the UV and visible (240 - 790 nm) at moderate resolution (0.2 nm in the UV, 0.4 nm in the visible), employing silicon diode array detectors. GOME takes some 30,000 spectra per day, obtaining full global coverage in three days. We directly fit GOME radiance spectra using nonlinear least-squares analysis to obtain column amounts of several trace species with significant tropospheric concentrations, including ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and formaldehyde (HCHO). Measurements of HCHO due to biogenic activity in the troposphere are presented here.
The GOME was launched on the European Space Agency's ERS-2 satellite on April 20, 1995. GOME measures the Earth's atmosphere in the nadir geometry, using four spectrometers that cover the UV and visible at moderate resolution, employing silicon diode array detectors. GOME takes some 30,000 spectra per day, obtaining full global coverage at 40 X 320 km2 resolution in three days. It provides measurements of ozone, NO2, SO2, H2CO, H2O, BrO, ClO, and OClO. We directly fit GOME radiance spectra using nonlinear least-squares analysis to obtain column amounts of several trace species, including ClO, BrO, SO2, and H2CO. The use of recent improvements in the underlying physical and spectroscopy permits the fitting of radiances to very high precision, approaching 2 X 10-4 in favorable case, for standard 1.5s integration time GOME measurements. Examples of the fitting of BrO and SO2 are presented here.
The Global Ozone Monitoring Experiment (GOME) on board the ERS-2 satellite is an across-track nadir-viewing spectrometer which measures solar light reflected from the Earth's atmosphere and surface in the UV visible. The cloud retrieval algorithm presented here combines spectral threshold test on GOME's broad-band radiances with the fitting of reflectances to GOME's moderately high resolution spectra in and around the O2 A band to retrieve cloud- cover fraction, cloud-top height and cloud optical thickness. The algorithm utilizes the latest O2 spectroscopic data and features dynamical updating procedures to provide global threshold sets of GOME reflectances. Auxiliary information is obtained from GOME measurements of the Ring effect and the degree of polarization of the Earth's radiation field.