A generalized simulation capability for rotating- beam scatterometers

Rotating-beam wind scatterometers exist in two
types: rotating fan-beam and rotating pencil-beam. In our
study, a generic simulation frame is established and verified
to assess the wind retrieval skill of the three different scat-
terometers: SCAT on CFOSAT (China France Oceanogra-
phy SATellite), WindRad (Chinese Wind Radar) on FY-3E,
and SeaWinds on QuikSCAT. Besides the comparison of the
so-called first rank solution retrieval skill of the input wind
field, other figures of merit (FoMs) are applied to statisti-
cally characterize the associated wind retrieval performance
from three aspects: wind vector root mean square error, am-
biguity susceptibility, and wind biases. The evaluation shows
that, overall, the wind retrieval quality of the three instru-
ments can be ranked from high to low as WindRad, SCAT,
and SeaWinds, where the wind retrieval quality strongly de-
pends on the wind vector cell (WVC) location across the
swath. Usually, the higher the number of views, the better
the wind retrieval, but the effect of increasing the number of
views reaches saturation, considering the fact that the wind
retrieval quality at the nadir and sweet swath parts stays rela-
tively similar for SCAT and WindRad. On the other hand, the
wind retrieval performance in the outer swath of WindRad is
improved substantially as compared to SCAT due to the in-
creased number of views. The results may be generally ex-
plained by the different incidence angle ranges of SCAT and
WindRad, mainly affecting azimuth diversity around nadir
and number of views in the outer swath. This simulation
frame can be used for optimizing the Bayesian wind retrieval
algorithm, in particular to avoid biases around nadir but also
to investigate resolution and accuracy through incorporating
and analyzing the spatial response functions of the simulated
Level-1B data for each WVC.