23-27 November 2004CONAE Workshop, Cordoba, Argentina1 Infrared methods for deriving volcanogenic sulphur dioxide Dr Fred Prata 1 Adjunct Professor Michigan Technological University 1 On leave from CSIRO Atmospheric Research, Melbourne, Australia 23-27 November 2004CONAE Workshop, Cordoba, Argentina2 Synopsis of Lecture Remote sensing of SO 2 clouds - basics Some theory Examples of detection - TOVS and MODIS Comparisons and validation New tools - AIRS Questions and Answers 23-27 November 2004CONAE Workshop, Cordoba, Argentina3 SO 2 Budgets Source SO 2 SO 4 Fossil-fuel combustion +industry702.2 Biomass burning Oceans40320 Plants+soils24 Volcanoes7824 Units: Tg(S) yr -1 Source: Berresheim et al. (1995) 23-27 November 2004CONAE Workshop, Cordoba, Argentina4 14 MODIS Bands 23-27 November 2004CONAE Workshop, Cordoba, Argentina5 23-27 November 2004CONAE Workshop, Cordoba, Argentina6 23-27 November 2004CONAE Workshop, Cordoba, Argentina7 23-27 November 2004CONAE Workshop, Cordoba, Argentina8 ~2300 AIRS channels 23-27 November 2004CONAE Workshop, Cordoba, Argentina9 M27M28 M29M30M31M32 M33 ~2300 AIRS channels 23-27 November 2004CONAE Workshop, Cordoba, Argentina10 Ulawun + Plumes can be identified in satellite data using spectral discrimination - e.g. MODIS data New Britain, PNG 23-27 November 2004CONAE Workshop, Cordoba, Argentina11 Ulawun m - 12 m temperature difference 23-27 November 2004CONAE Workshop, Cordoba, Argentina12 23-27 November 2004CONAE Workshop, Cordoba, Argentina13 T IROS O perational V ertical S ounder HIRS instrument with 20 channels ~18x18 km 2 pixels at nadir NOAA satellites Continuous since 1979 Same platform as AVHRR Day/night operation 23-27 November 2004CONAE Workshop, Cordoba, Argentina14 23-27 November 2004CONAE Workshop, Cordoba, Argentina15 The Physics of infrared SO 2 sensing Detector IR radiation SO 2 gas ++ absorption emission scattering 23-27 November 2004CONAE Workshop, Cordoba, Argentina16 Satellite (or airborne) detector z a b I 23-27 November 2004CONAE Workshop, Cordoba, Argentina17 Emission from layer modified by SO 2 absorption Emission to space from SO 2 -free atmosphere Emission above SO 2 layer Emission from SO 2 modified by atmosphere 23-27 November 2004CONAE Workshop, Cordoba, Argentina18 Weighting functions for some TOVS channels The weighting function is: t/z. 23-27 November 2004CONAE Workshop, Cordoba, Argentina19 Simplifying assumptions 1.We assume that the SO 2 layer lies above the peak of the weighting function for H 2 O in the 7.3 m channels, so that the absorption coefficient a (z) is zero for z > a. This is a significant assumption because H 2 O absorbs strongly at 7.3 m and the weighting function peaks relatively high in the atmosphere. 2.The SO 2 layer is assumed to be isothermal and therefore can be characterized by a single temperature T s. Clearly this assumption is questionable when the SO 2 layer is very deep. 23-27 November 2004CONAE Workshop, Cordoba, Argentina20 The radiance equation can be linearized by expansion in terms of the derivative of the Planck function (B/T). We denote this as: u*. In terms of measured top-of-atmosphere brightness temperatures we arrive at: Let u = I-I a In practice I, I a are averages over the filter response function of the channel. We write this as u. * 23-27 November 2004CONAE Workshop, Cordoba, Argentina21 23-27 November 2004CONAE Workshop, Cordoba, Argentina22 23-27 November 2004CONAE Workshop, Cordoba, Argentina23 23-27 November 2004CONAE Workshop, Cordoba, Argentina24 23-27 November 2004CONAE Workshop, Cordoba, Argentina25 23-27 November 2004CONAE Workshop, Cordoba, Argentina26 23-27 November 2004CONAE Workshop, Cordoba, Argentina27 23-27 November 2004CONAE Workshop, Cordoba, Argentina28 TOVS retrievals 23-27 November 2004CONAE Workshop, Cordoba, Argentina29 SO 2 from TOVS AGU Book Chapman, 2003 23-27 November 2004CONAE Workshop, Cordoba, Argentina30 TOVSTOMS 23-27 November 2004CONAE Workshop, Cordoba, Argentina31 Eruption of Cerro Hudson, southern Chile 7-27 August, 1991 23-27 November 2004CONAE Workshop, Cordoba, Argentina32 23-27 November 2004CONAE Workshop, Cordoba, Argentina33 23-27 November 2004CONAE Workshop, Cordoba, Argentina34 Pinatubo 15 June - 15 July, 1991 23-27 November 2004CONAE Workshop, Cordoba, Argentina35 23-27 November 2004CONAE Workshop, Cordoba, Argentina36 23-27 November 2004CONAE Workshop, Cordoba, Argentina37 Pinatubo SO 2 cloud seen from TOVS - 3 separate instrumnets provide unprecedented temporal resolution 23-27 November 2004CONAE Workshop, Cordoba, Argentina38 23-27 November 2004CONAE Workshop, Cordoba, Argentina39 23-27 November 2004CONAE Workshop, Cordoba, Argentina40 From: Carn, S., Prata, A. J., and Karlsdottir, S. (In prep.) 23-27 November 2004CONAE Workshop, Cordoba, Argentina41 23-27 November 2004CONAE Workshop, Cordoba, Argentina42 SO 2 from AIRS Atmospheric Infrared Sounder (AIRS) New research spectrometer (>2300 channels) EOS- Aqua platform Many new possibilities to study volcanic gases 23-27 November 2004CONAE Workshop, Cordoba, Argentina43 23-27 November 2004CONAE Workshop, Cordoba, Argentina44 AIRS Spectra 23-27 November 2004CONAE Workshop, Cordoba, Argentina45 AIRS - volcanic ash 10.7 m-11.8 m difference Positive slope =water vapour or cloud 23-27 November 2004CONAE Workshop, Cordoba, Argentina46 AIRS can be used to select optimal broad channels for specific applications 11 m -12 m 10.6 m m 23-27 November 2004CONAE Workshop, Cordoba, Argentina47 AIRS SO 2 for Anatahan 7.3 m SO 2 feature SO 2 cloud 7.3 m image Theoretical calculation using Modtran 23-27 November 2004CONAE Workshop, Cordoba, Argentina48 Compared with MODIS 23-27 November 2004CONAE Workshop, Cordoba, Argentina49 23-27 November 2004CONAE Workshop, Cordoba, Argentina50 23-27 November 2004CONAE Workshop, Cordoba, Argentina51 23-27 November 2004CONAE Workshop, Cordoba, Argentina52 23-27 November 2004CONAE Workshop, Cordoba, Argentina53 23-27 November 2004CONAE Workshop, Cordoba, Argentina54 23-27 November 2004CONAE Workshop, Cordoba, Argentina55 23-27 November 2004CONAE Workshop, Cordoba, Argentina56 23-27 November 2004CONAE Workshop, Cordoba, Argentina57 23-27 November 2004CONAE Workshop, Cordoba, Argentina58