Detected oil spills are usually classified according to confidence levels. Such levels are supposed to describe the probability that an observed dark feature in the satellite image is related to the actual presence of an oil spill. The Synthetic Aperture Radar (SAR) derived oil spill detection probability estimation has been explored as an intrinsic aspect of oil spill classification, which fundamentally computes the likelihood that the detected dark area is related to an oil spill. However, the SAR based probability estimation should be integrated with additional criteria in order to become a more effective tool for the End Users. As example, the key information for the final users is not the confidence level of the detection “per se” but the alert (i.e. the potential impact of the pollution and the possibility to catch the polluter red-handed) that such detection generates. This topic was deeply discussed in the framework of the R and D European Group of Experts on remote sensing Monitoring of marine Pollution (EGEMP) and a paper was published in 2010. The newly established EMSA CleanSeaNet service (2nd generation) provides the alert level connected to the detection of a potential oil spill in a satellite image based on the likelihood of being an oil spill in combination with impact and culprit information.
MIPAS-B2 is a cryogenic limb-sounder dedicated to stratospheric trace gas research. The balloon borne instrument is a precursor of the MIPAS instrument on the ESA ENVISAT satellite. In consequence, the main instrumental specifications and parameters are similar. The instrument has been flown several times successfully in the frame of European atmospheric research campaigns (SESAME and THESEO) and a satellite validation campaign (ILAS). The heart of the instrument is a Fourier spectrometer working in the mid- infrared range (4 to 14 micrometer), which is cooled before launch to its operating temperature of 210 K with solid carbon dioxide. The spectral coverage is split into four spectral channels to improve sensitivity in particular in the short wavelength region. We employ liquid helium cooled Si:As-BIB- detectors to achieve optimum detectivity. A further important part of the instrument is the line of sight (LOS) stabilization system, which is based on an inertial navigation system and can be cross-examined with the help of an additional star reference system. The instrument was flown eight times from balloon launch sites in Sweden and France. The recorded data allowed the retrieval of many trace gases. One major scientific advantage of the instrument is the simultaneous detection of whole trace gas families in the stratosphere. All relevant night-time NOy species (NO2, N2O5, HNO3, ClONO2 and HO2NO2) together with the source gas N2O were successfully analyzed.
The balloon borne IR-Fourier transform spectrometer (FTS) MIPAS-B2 has been designed for a low self-emission from each of the instrument ports leading to low noise signals and a radiometrically balanced interferometer. The radiometric accuracy depends strongly on the quality of the phase correction of interferograms and of the calibration measurements and algorithms. It could be observed that the classically derived phases of the complex spectra are in correlation with line structures in the spectrum and cause disturbed calibrated spectra. These phase functions cannot be explained by the instrumental phase due to the beamsplitter nor by sampling shifts but by the emission of the beamsplitter itself. The determination of the instrumental phase function requires to invent an unconventional technique. According to the low radiance received from the stratosphere noise has also to be taken into account, especially in case of single non- coadded spectra. Therefore an advanced statistical method was investigated to derive the phase of the interferogram by minimizing the correlation of the real and imaginary part of the spectrum as well as the variance of the imaginary part (the beamsplitter spectrum). The complete processing and calibration scheme of the FTS-emission sounder will be presented focusing on a detailed description of phase behavior due to the beamsplitter emission and of the correction process.
Embedded in the ILAS validation campaign a balloon flight was carried out with the limb emission sounder MIPAS-B in the early night of March 24, 1997. MIPAS-B is capable is capable of simultaneously measuring profiles of all molecules ILAS was covering. Key reservoir molecules like ClONO2 and N2O25 which are not or hard to measure with ILAS complement the ILAS set of target species and allow the partitioning and budge to NOy to be studied. The balloon was launched from Kiruna/Sweden. The distance of the mean location of tangent points between the satellite and the balloonborne observation was less than 150 km and the time was offset by less then 4 hours for the most adjacent overpass of ADEOS. The balloon observations covered the altitude range of 11.0 to 29.5 km. Vertical profiles of N2O, CH4, H2O, HNO3 NO2 and aerosol extinction obtained with MIPAS-B have been compared to those obtained with ILAS based on the three most adjacent ADEOS overpasses. Model calculations with the 3D chemical transport model KASIMA were used to account for nay deviations in the dynamical and chemical properties of the airmasses observed at the different times and locations of observation. The paper demonstrates the progress made in the consistency of the data sets when going from Version 3.0 to Version 3.1 of the ILAS data processing software. Excellent agreement between balloon and satellite observation has been found for HNO3 on the basis of the Version 3.1 results. The same holds for NO2 above 20 km provided the diurnal variation is taken into account. Discrepancies still exist with the Version 3.1 results in the lowermost part of the stratospheric for most gases and generally in the case of N2O.
To investigate the ozone changes and their causes in the Arctic our FTIR spectrometers were operated in winter 1991/92 during the European Arctic stratospheric ozone experiment (EASOE): one at Esrange, Sweden, and the other one at Sondre Stromfjord, Greenland. The evaluation of the recorded spectra yields zenith column amounts (ZCA) of several trace gases like H2O, HDO, CH4, N2O, CFC-11, -12, -22, O3, HNO3, ClONO2, HCl and HF. This paper focuses on HCl, HF and ClONO2. The ratio HCl to HF is rather low inside the vortex indicating a perturbed chemistry. ClONO2 is increasing towards the end of the winter and is very high in the late polar vortex.
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