The winds from WIVERN are only line of sight but Horanyi et al.
Our analysis suggests that winds from WIVERN should only be biased when they are affected by ground clutter and that such regions should be easy to identify.
4 and 7) suggests that one advantage of the WIVERN winds should be the absence of the current midlevel gap in coverage.
When predicting the performance of WIVERN, we assume a thinning to 80 km, close to the current ECMWF value for aircraft winds, and use the CloudSat data to calculate for every 80-km along-track segment how often there is a cloud echo of at least 5-km length where the reflectivity exceeds -18 dBZ, for which (from Fig.
The main thrust of the WIVERN mission is to provide winds, but the satellite would also measure profiles of reflectivity over the 800-km-wide ground track.
We expect that the proposed polarization diversity Doppler radar for WIVERN would be able to provide the horizontal component line-of-sight winds with an accuracy of 2 m [s.sup.-1], 50-km resolution in the horizontal, and <1-km resolution in the vertical over an 800-km-wide ground track, for clouds having a 20-km along-track extent and a reflectivity exceeding -20 dBZ.
If the pulses are close together, they would both be in the cloud at the same time: to distinguish them, WIVERN transmits pairs of pulses with alternating polarization--H (red) and V (blue)--spaced by a short time separation, [T.sub.hv], and receives the return signals in both polarizations (Fig.
Daily coverage for a possible WIVERN 500-km orbit with 800-km-wide ground track and 651-km slant path.
Theoretical random error in the LOS-retrieved Doppler velocity for WIVERN as a function of target reflectivity for a 20-[micro]s H-V pulse separation and a 3.5 m [s.sup.-1] Doppler width due to satellite motion.
WIVERN surface clutter and viewing geometry, (a) WIVERN surface clutter for a flat surface with [[sigma].sub.0] = 0 dB.
Reconstructed WIVERN reflectivity from a stratiform precipitation event observed by CloudSat over the western Pacific between 19[degrees] and 7[degrees]S using a 5-km integration length, (left) The black dashed line corresponds to the contour where the standard deviation of the Doppler velocity is 2 m [s.sup.-1] while the magenta line corresponds to the region where the SCR = 20 dB.
The fraction of WIVERN profiles, integrated along track for 5 km, where winds at a given height can be derived with an accuracy of 2 m [s.sup.-1] for various [T.sub.hv] values, derived from CloudSat profiles with an assumed LDR value and recent observations of surface clutter returns over the ocean (blue) and over land (red), excluding mountains and cities.