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The temporal power spectrum of atmospheric fluctuations due to water vapor

Lay, O. P. (1997) The temporal power spectrum of atmospheric fluctuations due to water vapor. Astronomy and Astrophysics Supplement Series, 122 (3). pp. 535-545. ISSN 0365-0138. doi:10.1051/aas:1997154.

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Irregular variations in the refractivity of the atmosphere cause fluctuations in the phase measured by interferometers, limiting the spatial resolution that can be obtained. For frequencies up to the far infrared, water vapor is the dominant cause of the variations. The temporal power spectrum of the phase fluctuations is needed to assess correction schemes such as phase referencing using a nearby calibrator and water vapor radiometry. A model is developed for the temporal power spectrum of phase fluctuations measured by an interferometer through a layer of Kolmogorov turbulence of arbitrary thickness. It is found that both the orientation of the baseline with respect to the wind direction and the elevation of the observations can have a large effect on the temporal power spectrum. Plots of the spectral density distribution, where the area under the curve is proportional to phase power, show that substantial contributions from length scales as long as 100 times the interferometer baseline are possible. The model is generally consistent with data from the 12-GHz phase monitor at the Owens Valley Radio Observatory, and allows the data to be extrapolated to an arbitrary baseline, observing frequency and elevation. There is some evidence that there can be more than one component of turbulence present at a given time for the Owens Valley. The validity of the frozen turbulence assumption and the geometrical optics approximation is discussed and found to be reasonable under most conditions. The models and data presented here form the basis of an analysis of phase calibration and water vapor radiometry (Lay 1997).

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Additional Information:© European Southern Observatory (ESO), 1997. Received May 17; accepted August 2, 1996. The author would like to thank Rachel Akeson, John Carlstrom, Peter Papadopoulos and David Woody for many useful comments, and acknowledges a Robert A. Millikan Fellowship from Caltech.
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Robert A. Millikan FellowshipUNSPECIFIED
Subject Keywords:atmospheric effects / instrumentation: interferometers / site testing / techniques: interferometric
Issue or Number:3
Record Number:CaltechAUTHORS:20180413-125836325
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Official Citation:The temporal power spectrum of atmospheric fluctuations due to water vapor O. P. Lay Astron. Astrophys. Suppl. Ser., 122 3 (1997) 535-545 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85834
Deposited By: George Porter
Deposited On:13 Apr 2018 20:31
Last Modified:15 Nov 2021 20:32

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