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Analysis of Saturn's Thermal Emission at 2.2-cm Wavelength: Spatial Distribution of Ammonia VaporThis work focuses on determining the latitudinal structure of ammonia vapor in Saturn's cloud layer near 1.5 bars using the brightness temperature maps derived from the Cassini RADAR (Elachi et al., 2004) instrument, which works in a passive mode to measure thermal emission from Saturn at 2.2-cm wavelength. We perform an analysis of five brightness temperature maps that span epochs from 2005 to 2011, which are presented in a companion paper by Janssen et al. (2013a, this issue). The brightness temperature maps are representative of the spatial distribution of ammonia vapor, since ammonia gas is the only effective opacity source in Saturn's atmosphere at 2.2-cm wavelength. Relatively high brightness temperatures indicate relatively low ammonia relative humidity (RH), and vice versa. We compare the observed brightness temperatures to brightness temperatures computed using the Juno atmospheric microwave radiative transfer (JAMRT) program which includes both the means to calculate a tropospheric atmosphere model for Saturn and the means to carry out radiative transfer calculations at microwave frequencies. The reference atmosphere to which we compare has a 3x solar deep mixing ratio of ammonia (we use 1.352x10(exp -4) for the solar mixing ratio of ammonia vapor relative to H2; see Atreya, 2010) and is fully saturated above its cloud base. The maps are comprised of residual brightness temperatures-observed brightness temperature minus the model brightness temperature of the saturated atmosphere.
Document ID
20140016852
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1016/j.icarus.2013.06.017
Authors
Laraia, A. L. (California Inst. of Tech. Pasadena, CA, United States)
Ingersoll, A. P. (California Inst. of Tech. Pasadena, CA, United States)
Janssen, Michael A. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Gulkis, Samuel (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Oyafuso, Fabiano A. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Allison, Michael D. (NASA Goddard Inst. for Space Studies New York, NY, United States)
Date Acquired
December 2, 2014
Publication Date
June 27, 2013
Publication Information
Publication: Icarus
Volume: 226
Issue: 1
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN15237
Funding Number(s)
CONTRACT_GRANT: 10-CDAP10-0051
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Atmospheres
structure
atmosphere
composition
Atmospheres
Saturn

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