Improving the intercalibration of ?0 values for the Jason-1 and Jason-2 altimeters
Improving the intercalibration of ?0 values for the Jason-1 and Jason-2 altimeters
The normalized backscatter from a radar altimeter, ?0, is a measure of the surface roughness at scales of a few
radar wavelengths; over the ocean this is used to infer wind speed. Long-term studies of wind speed rely on consistent
measurements within an altimetric mission and good intercalibration between missions. For the Jason-1 and Jason-2
altimeters the derivation of ?0 from the full waveform data is known to be sensitive to the recovered value for ?2, a
term encompassing both mispointing and inhomogeneities within the altimetric footprint. The six months of data from
the Jason-1/2 tandem mission reveal that different ?0 corrections are needed for these two causes of non-zero ?2
values. With these corrections implemented, the r.m.s. difference of Ku-band ?0 values for Jason-1 and Jason-2 drops
from 0.15 dB to 0.05 dB, with the bias between the two showing a clear trend with wind speed; Jason-1 being 0.04 dB
greater in high winds but 0.19 dB greater in low winds. No clear change in offset is noted during the 6 months of
overlapping data. Implementation of this correction will improve consistency of Jason-1 ?0 values and may impact on
orbit-fitting procedures.
altimeter, sigma0, Jason-1, Jason-2, cal/val, tandem mission
538-542
Quartly, Graham D.
3d1e4e87-f001-4d18-b95f-9bca4db6ff9d
July 2009
Quartly, Graham D.
3d1e4e87-f001-4d18-b95f-9bca4db6ff9d
Quartly, Graham D.
(2009)
Improving the intercalibration of ?0 values for the Jason-1 and Jason-2 altimeters.
IEEE Geoscience and Remote Sensing Letters, 6 (6), .
(doi:10.1109/LGRS.2009.2020921).
Abstract
The normalized backscatter from a radar altimeter, ?0, is a measure of the surface roughness at scales of a few
radar wavelengths; over the ocean this is used to infer wind speed. Long-term studies of wind speed rely on consistent
measurements within an altimetric mission and good intercalibration between missions. For the Jason-1 and Jason-2
altimeters the derivation of ?0 from the full waveform data is known to be sensitive to the recovered value for ?2, a
term encompassing both mispointing and inhomogeneities within the altimetric footprint. The six months of data from
the Jason-1/2 tandem mission reveal that different ?0 corrections are needed for these two causes of non-zero ?2
values. With these corrections implemented, the r.m.s. difference of Ku-band ?0 values for Jason-1 and Jason-2 drops
from 0.15 dB to 0.05 dB, with the bias between the two showing a clear trend with wind speed; Jason-1 being 0.04 dB
greater in high winds but 0.19 dB greater in low winds. No clear change in offset is noted during the 6 months of
overlapping data. Implementation of this correction will improve consistency of Jason-1 ?0 values and may impact on
orbit-fitting procedures.
Text
Quartly_GRSL_Psi2_6pp.pdf
- Accepted Manuscript
More information
Submitted date: March 2009
Published date: July 2009
Keywords:
altimeter, sigma0, Jason-1, Jason-2, cal/val, tandem mission
Identifiers
Local EPrints ID: 66226
URI: http://eprints.soton.ac.uk/id/eprint/66226
ISSN: 1545-598X
PURE UUID: 15baf823-5f47-4e38-8791-5b9d0f2a75c9
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Date deposited: 18 May 2009
Last modified: 13 Mar 2024 18:11
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Author:
Graham D. Quartly
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