TY - JOUR
T1 - Measurement of correlation functions and power spectra in clouds using the NRL WARLOC radar
AU - Fliflet, Arne W.
AU - Manheimer, Wallace M.
N1 - Funding Information:
Manuscript received May 24, 2005; revised May 5, 2006. This work was supported by the Office of Naval Research. A. W. Fliflet is with the Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 USA (e-mail: [email protected]). W. M. Manheimer is with the Plasma Physics Division, Naval Research Laboratory Washington, DC 20375 USA, and also with Icarus Research, Inc., Bethesda, MD 20824 USA. Digital Object Identifier 10.1109/TGRS.2006.879114
Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2006/11
Y1 - 2006/11
N2 - The Naval Research Laboratory W-band Advanced Radar for Low Observable Control (WARLOC) is a high-power 94-GHz radar, with 3-10-kW average and 80-kW peak power, now set up on the western shore of the Chesapeake Bay. It has three orders of magnitude more power and sensitivity than other W-band radar systems. This enables cloud reflectivity to be measured with high signal-to-noise ratios and a resolution of about 15 m over a two (or three)-dimensional region, which can be as large as tens of kilometers on a side. This allows imaging of the internal structure of clouds over great distances in very great detail. At the shortest scale lengths, the structure has a speckle pattern indicating that it is governed at least in part by stochastic processes. The WARLOC data allow the reflectivity correlation function and its Fourier transform, which is the power spectrum, to be computed for scale lengths ranging from 30 m to 10 km. For measurements taken of cirrus clouds on several occasions as well as one case of a precipitating cloud, it was found that for small correlation distance r, the correlation function usually decreases as r 2/3, or, equivalently, the wavenumber spectrum scales as k -5/3, where k is the wavenumber. This suggests that fluid turbulence in the inertial range is playing a role; however, unlike classical fluid turbulence, the results suggest that the turbulence here is generally quite anisotropic. Furthermore, for longer scale lengths (the outer range according to the Kolmogorov theory), the reflectivity fluctuations usually show a wavelike behavior in the vertical direction but only occasionally in the horizontal direction.
AB - The Naval Research Laboratory W-band Advanced Radar for Low Observable Control (WARLOC) is a high-power 94-GHz radar, with 3-10-kW average and 80-kW peak power, now set up on the western shore of the Chesapeake Bay. It has three orders of magnitude more power and sensitivity than other W-band radar systems. This enables cloud reflectivity to be measured with high signal-to-noise ratios and a resolution of about 15 m over a two (or three)-dimensional region, which can be as large as tens of kilometers on a side. This allows imaging of the internal structure of clouds over great distances in very great detail. At the shortest scale lengths, the structure has a speckle pattern indicating that it is governed at least in part by stochastic processes. The WARLOC data allow the reflectivity correlation function and its Fourier transform, which is the power spectrum, to be computed for scale lengths ranging from 30 m to 10 km. For measurements taken of cirrus clouds on several occasions as well as one case of a precipitating cloud, it was found that for small correlation distance r, the correlation function usually decreases as r 2/3, or, equivalently, the wavenumber spectrum scales as k -5/3, where k is the wavenumber. This suggests that fluid turbulence in the inertial range is playing a role; however, unlike classical fluid turbulence, the results suggest that the turbulence here is generally quite anisotropic. Furthermore, for longer scale lengths (the outer range according to the Kolmogorov theory), the reflectivity fluctuations usually show a wavelike behavior in the vertical direction but only occasionally in the horizontal direction.
KW - Clouds
KW - Gyrotrons
KW - Millimeter-wave radar
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U2 - 10.1109/TGRS.2006.879114
DO - 10.1109/TGRS.2006.879114
M3 - Article
AN - SCOPUS:33750800748
SN - 0196-2892
VL - 44
SP - 3247
EP - 3261
JO - IEEE Transactions on Geoscience and Remote Sensing
JF - IEEE Transactions on Geoscience and Remote Sensing
IS - 11
M1 - 1717719
ER -