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

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The upper panels of Fig. 2 show σ t2estimated using (3), called σ t 2 -2BW. Thelower panels show σ t2estimated using traditional beam-, shear-, and wave-corrections,(Atlas, 1964; Hocking, 1985; Nastrom, 1997) called σ t 2 -Trad. Below about 7 km (8 km)during April (May) results from both methods are relatively large, ranging between about0.1 and 0.3 m 2 s -2 , corresponding to the altitudes of active convection. Values for the westbeam are consistently smaller than those from the other beams in April below 6 km; from 6to 7.5 km values for both beams in the zonal plane are smaller than those in the meridionalplane. During May there is no apparent anisotropy at the lower altitudes. Above 7 or 8 kmall values become less than 0.02 m 2 s -2 at all altitudes except in the regions of strong winds(discussed below); the σ t 2 -Trad values are slightly smaller than those for σ t 2 -2BW. Notethat negative values, where the corrections are larger than σ obs 2 , appear in Fig. 2. The Mayresults near 17 km illustrate the differing effects of the correction terms; i.e., for σ t 2 -Tradthe beam-broadening corrections due to the large zonal wind speeds cause values for allfour beams to be negative while for σ t 2 -2BW only the meridional beams’ values arenegative. A similar, but smaller, effect is seen near 18 km during April. σ t 2 -2BW may beexpected to be more reliable as it is not influenced by thin-layer effects or other beamfillingproblems. The curves in Fig. 2 are very similar where the winds are less than about10 m/s.4. ReferencesAtlas, D., Advances in radar meteorology, Adv. Geophys., 10, eds. H. Landsberg and J. vanMieghem, Academic, 317-478, 1964.Hocking, W.K., Measurement of turbulent energy dissipation rates in the middleatmosphere by radar techniques: a review, <strong>Radio</strong> Sci., 20, 1403-1422, 1985.Nastrom, G.D., Doppler radar spectral width broadening due to beamwidth and wind shear.Annales Geophysicae, 15, 786-796, 1997.VanZandt , T.E., G.D. Nastrom, J. Furumoto, T. Tsuda, and W.L.Clark, A Dual-BeamwidthMethod for observing atmospheric turbulence intensity <strong>with</strong> radar, Geophys. Res. Lettr.,29(12), 10.1029/2001GL014283, 2002.212

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