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Simon P. Alexander, Toshitaka Tsuda, and Junichi Furumoto

convection or cold fronts. The virtual Brunt–Väisälä frequency squared N   2 is given by where the gravitational acceleration g = 9.81 m s −2 and Γ = 9.76 K km −1 is the dry adiabatic lapse rate. From the polarization relation and for wave periods of less than several hours, temperature perturbations T  ′ are proportional to changes in Brunt–Väisälä frequency N ( Fritts et al. 1988 ): where u ′ is the horizontal wind perturbation. Thus, we expect that an increase in atmospheric

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Mark A. Donelan, Neils Madsen, Kimmo K. Kahma, Ioannis K. Tsanis, and William M. Drennan

1. Introduction Measurements of flow properties in the atmospheric surface layer over natural wind-generated waves have been made with varying degrees of accuracy over the last few decades. Generally speaking such measurements have been motivated by one of three goals: (i) estimation of interfacial fluxes of momentum, heat, and mass; (ii) exploration of the rate of wave generation by wind; and (iii) investigation of the transmission of electromagnetic radiation in the turbulent near

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Alexander V. Ryzhkov and Dusan S. Zrnić

and maximal if Ψ = ± π /2. In the former case, polarization of the incident wave is linear (45° slanted), whereas in the latter case it is circular. In both the simultaneous and alternate transmission/reception modes, Z DR measurements are almost identical if Ψ = 0. Acknowledgments Funding for this study was provided by the NOAA/Office of Oceanic and Atmospheric Research under NOAA–University of Oklahoma Cooperative Agreement NA17RJ1227, U.S. Department of Commerce, and from the U

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P. Racette, R. F. Adler, J. R. Wang, A. J. Gasiewski, D. M. Jakson, and D. S. Zacharias

610 JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY VOLUME 13An Airborne Millimeter-Wave Imaging Radiometer for Cloud,Precipitation, and Atmospheric Water Vapor Studies P. RACETTE, R. F. AOLER, J. R. WAnGNASA/Goddard Space Flight Center, Greenbelt, Maryland A. J. GAS~EWSK~ ~D D. M. JAXSONDepartment of Electrical Engineering, Georgia Institute of Technology, Atlanta, Georgia D. S. ZAC

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Benjamin D. Reineman, Luc Lenain, and W. Kendall Melville

1. Introduction Measurements of sea state and air–sea fluxes have historically been made from ships, buoys, and other platforms, but these essentially fixed-point measurements, over the time scales of surface wave and atmospheric processes, provide no observations of the spatial evolution and distribution of surface fluxes and the wave field. Aircraft-based measurements are an effective means to sample atmospheric and oceanic phenomena over a wide range of conditions and locations, and are also

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Qi Hu, Zhaoning Liang, and Michael W. Hoffman

this goal of deducing source regions of intraseasonal waves in the tropical atmosphere from observational data. Beamforming has been used since the 1960s–70s. Adaptive beamformers using a spaced array of sensors have been developed and applied extensively in detection of sources of seismic signals (e.g., Lacoss 1968 ). Application of beamformers to atmospheric waves and variations has however only been made in a retrieval of high-accuracy wind profile from atmospheric Doppler radars with arrays of

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Yuling Wu and Bo-Wen Shen

1. Introduction Recent intense tropical storms have caused substantial financial damage to human societies and have threatened human life (e.g., Shen et al. 2006 , 2013a , b ). Therefore, improving our understanding of tropical cyclone (TC) genesis and prediction is an active topic in atmospheric research. The association of TCs with tropical waves has now been studied for several decades (e.g., Landsea 1993 ; Frank and Roundy 2006 ). Landsea (1993) indicated that over 85% of intense

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Thomas R. Parish and Larry D. Oolman

emphasized the roles of wind speed, atmospheric stability, and terrain height in establishing flow streamlines and mountain wave features. Corby (1954) offers a review of early studies of mountain waves. As air is forced over terrain, the restoring force resulting from the difference between an air parcel’s density and that of the ambient environment at the same level will accelerate the air parcel back toward an equilibrium level. The oscillation of disturbed flow in a stable environment has been

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Stephen M. Sekelsky

1. Introduction Meteorological radars normally measure atmospheric targets that lie in the far-field or Fraunhofer region where r ≥ r f . The far-field distance, r f , is defined as r f = 2 D 2 / λ. (1) Here D is antenna diameter and λ is the radar wavelength. The r f is sometimes referred to as the Rayleigh distance ( Clarke and Brown 1980 ) and it approximately represents the transition between the Fresnel region and the far field. Millimeter-wave (MMW) cloud

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Timothy A. Coleman, Kevin R. Knupp, and Daryl E. Herzmann

1. Introduction During the morning hours of 6 May 2007, an intense atmospheric bore, with a pressure perturbation of 4 hPa, was generated over eastern Iowa. The bore was undular, with a train of distinctive gravity waves following its passage. A “Webcam” in Tama, Iowa, captured over 40 min of video showing the effects of the gravity waves on cloud features. Photographs of the cloud features associated with bores have been published previously (e.g., Clarke et al. 1981 ; Wakimoto and Kingsmill

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