Proceedings with Extended Abstracts (single PDF file) - Radio ...

the beamwidth, α is the zenith angle, u z =dU/dz, v z =dV/dz, and R is the range of the sample2 2volume. The difference, σU-σ V, is given by Eq. (3).Because U >V and |u z |~|v z | for conditions typically found at MU in the uppertroposphere and lower stratosphere, Eq. (3) predicts σ > σ (the final term on the right side2is usually negligible). Nastrom and Tsuda (2001) found that σV> σ 2 Uat MU and at WhiteSands, New Mexico, and that the magnitude of the anisotropy was proportional to themagnitude of U for fixed V. Predictions such as this could be inferred from the recent resultsof Chu (2002), although they did not use observations. Figure 1 shows the results at MU andconfirm the anisotropy is related to zenith angle, as predicted by eq. 3.2 2 2242[ U cos α + V − 2Ucosαsin αuR + sin α( u R)] 2σ22 2 θσU= σturb+zz+wave(1)322 2 θ 2 2 2242σ [ cos 2 cos sin sin ( ) ] 2V= σturb+ V α + U − V α αvzR+ α vzR+ σwave(2)32 22 2 θ sin α 2 22 2 2σ [ 2 cos ( ) sin ( )]2V− σU= U −V+ R α Uuz−Vvz− αRuz− vz(3)34. ReferencesChu, Y.-H., 2002: Beam broadening effect on oblique MST radar Doppler spectrum. J.Atmos. Oceanic Technol., 19, 1955-1967.Nastrom, G.D., and T. Tsuda, 2001: Anisotropy of Doppler spectral parameters in the VHFradar observations at MU and White Sands, Ann. Geophys., 19, 883-888.VanZandt , T.E., G.D. Nastrom, J. Furumoto, T. Tsuda, and W.L.Clark, 2002: A Dual-Beamwidth Method for observing atmospheric turbulence intensity with radar, Geophys.Res. Lettr., 29(12), 10.1029/2001GL0142832V2 UFigure 1. Left: Median TKE for observations using the entire antenna: upper (lower) at 20º(10º) zenith angle. Right: Median wind speeds.209