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As explained in the "Why polarization diversity?" sidebar, WIVERN overcomes this dilemma by estimating the Doppler velocity using the polarization-diversity pulse-pair (PDPP) technique (Pazmany et al.
WIVERN would trace out a quasi-circular ground track of diameter 800 km on the ground, advancing 50 km along track for each rotation with the footprint traveling at 335 km [s.sup.-1] or 1 km in 3 ms.
To gauge the number of sufficiently accurate wind observations expected from the proposed WIVERN satellite and their susceptibility to ghosts, an analysis of reflectivity profiles averaged over a 20-km along-track integration for four years of CloudSat data is displayed in Fig.
If the winds from WIVERN are to be assimilated, it will be necessary to identify regions where LOS winds are affected by convection and are not a representative component of the large-scale horizontal wind.
The shape of the clutter signal is determined by the combined effect of the WIVERN antenna pattern, its pulse shape, and the illumination geometry while its intensity is driven by the surface backscattering properties (Meneghini and Kozu 1990).
The clutter expected for a WIVERN configuration when observing a flat surface with [[sigma].sub.0] = 0 dB is illustrated in Fig.
At the WIVERN incidence angles, atmospheric targets like melting hydrometeors and columnar crystals can produce LDRs up to -12 dB (Wolde and Vali 2001) while surface clutter tends to depolarize more over land (LDR values of-9 [+ or -] 3 dB) than over sea (characteristic value of-15 dB; Battaglia et al.
Figure 6 shows simulated WIVERN observations of reflectivity and LDR of a stratiform precipitating system over the Pacific observed on 10 January 2008 and reconstructed by tilting and wrapping the vertical CloudSat curtain so as to be along the WIVERN scanning direction.
A month of CloudSat data (January 2008) have been used to simulate WIVERN profiles and the ghosts generated by [T.sub.hv] values of 5, 20, and 40 [micro]s, taking into account the SNR, the SGR, and the SCR for each 5-km along-track integration length in order to assess the fraction of profiles for which WIVERN is expected to produce winds with accuracy better than 2 m [s.sup.-1] (Fig.
The degree to which ghost echoes and/or vertical gradients in reflectivity combined with vertical wind shear can lead to increased random errors or biases in the wind estimates made from space by WIVERN can be assessed using recent observations made with the 94-GHz radar at Chilbolton in southern England pointing 45[degrees] off zenith with a time resolution of 6 s and gate length of 60 m.
5b, with the shading of the WIVERN sampling volume indicating the strength of the backscattered signal.
The main impact of the WIVERN wind observations should be realized through their assimilation into global NWP models.
4 and 7 indicates that about 1.3 million winds with a resolution of 20 km along track would be obtained each day for WIVERN. If these were thinned to 50 km, similar to the ECMWF value planned for aircraft winds in 2018, then the number assimilated could be about 500,000 per day.
It is stimulating and may be important, but I do not see that King Wivern shows it all that clearly.
It may be this disappearance that accounts for some of the frustration that accompanies the rich intellectual experience in reading Holbek, a frustration that da Silva has competently grappled with in his re-reading of the King Wivern fairy tale.
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