Retrieval of ammonia abundances and cloud opacities on Jupiter from voyager IRIS spectra |
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| Institution: | 1. Université de Lyon, Université Lyon 1, Ens de Lyon, CNRS, UMR 5276, Laboratoire de Géologie de Lyon, F-69622, Villeurbanne, France;2. Bayerisches GeoInstitut (BGI), University of Bayreuth, 95444 Bayreuth, Germany;3. European Synchrotron Radiation Facility, BP 220, F-3804 Grenoble Cedex, France;1. Ministero dell’Istruzione, dell’Università e della Ricerca (M.I.U.R.)-Istruzione, Viale Unità di Italia 68, 70125, Bari (BA), Italy;2. Dipartimento di Fisica, Università di Torino, Via Pietro Giuria 1, 10125 Torino, Italy;3. DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy;4. INFN, Sezione di Torino, Via Pietro Giuria 1, 10125 Torino, Italy;5. Dipartimento di Fisica E. Caianiello, Università di Salerno, Via Giovanni Paolo II 132, Fisciano (Sa), Italy;6. INFN, Sezione di Napoli, Gruppo Collegato di Salerno, Napoli, Italy;7. CASPER, Physics Department, Baylor University, Waco, TX 76798-7310, USA;8. Instituto de Física, Pontificia Universidad de Católica de Valparaíso, Casilla 4950, Valparaíso, Chile |
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| Abstract: | A method is formulated to retrieve gaseous ammonia abundance and cloud opacities at 45 and 5 μm from Voyager IRIS data using a simplified atmospheric model and a two-stream radiative transfer approximation. Our goal is to obtain sufficient computational efficiency to permit global mapping of the relative horizontal variations of these parameters. A single cloud layer is invoked with a base pressure of 680 mbar and a scale height equal to 0.14 times the gas scale height. The NH3 vertical distribution is modeled with a scale height equal to that of the cloud above 680 mbar and with a mole fraction independent of height at deeper levels. Measurements of brightness temperature as a function of emission angle from selected locations on the planet are used to verify the validity of the model and to constrain certain model parameters. It is found that the cloud particles can be treated as pure absorbers at 45 μm, but scattering must be included at 5 μm where a single scattering albedo of ～0.75 is inferred. These results are used to develop a simple algorithm for the retrieval of ammonia abundance and cloud optical depths at 45 and 5 μm from measurements at 216, 225, and 2050 cm?1. |
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