Speed ambiguity in SAR hurricane wind retrievals

1
Speed ambiguity in SAR hurricane wind retrievals
Will Perrie1, Hui Shen2 and Yijun He2 1Bedford
Institute of Oceanography 2Institute of
Oceanology, Chinese Academy of Sciences, Qingdao,
China
Recent progress on the remote sensing of ocean
surface winds suggests that Synthetic Aperture
Radar (SAR) is capable of giving valuable
measurements of ocean surface winds with high
spatial resolution and high accuracy. We focus on
wind retrieval from SAR images for low- to-
moderate wind conditions, as well as under high
wind conditions, such as hurricanes. Examples are
hurricanes Isabel (2003) and Rita (2005).
Rita
Isabel
SAR-derived winds
High wind SAR ambiguity
Radar backscatter
Polar grid
For each of three neighboring blocks
Three equations and 6 variables
High wind NRCS ? 2 possible wind speed solutions
for each NRCS.
M.Powell (2006)
Least-square-method
Jarosz et al. 2007
QuikSCAT wind
SAR wind
bigger solutions
SAR wind vs. QuikSCAT
smaller solutions
Conclusions (1) A hurricanes cyclonic
structure, and quasi-constant wind speed
equi-changing wind direction along any concentric
circle allow a new wind retrieval method (2)
highly accurate GMF model is needed for precise
high wind retrieval from SAR (3) wind speed
ambiuity is more severe at nearside of radar
range, when wind blows to the radar, (based on
typical hurricane structure CMOD5 and HWGMF a
speed removal method is established He,Y., W.
Perrie (2005 IEEE Trans. GRS, 43, 1453-1458),
Perrie, W. (2007, in press WAF), Shen, H.,
Perrie (2006 In press GRL) He, Y., Shen, H.,
Perrie, W., (2006 In press J. Tech.) He, Y.,
Perrie, W. (2004 IEEE Trans. GRS 42, 2623-2631).
final solution - NHC winds