Jason-1 Along-Track Near Real-Time Sea Surface Height Anomaly Data

Jason-1 Operational Sensor Data Record Sea Surface Height Anomaly (OSDR-SSHA)
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Date: December 7, 2009

The Jason-1 OSDR-SSHA product is aimed towards providing near-real-time
(NRT) sea surface height anomaly (SSHA) measurements from the Jason-1
mission. The product is very similar to the NRT OSTM/Jason-2 GPS-OGDR-SSHA
product. Both are provided as NetCDF files.

The primary difference between the two products is that the most accurate
NRT SSHA measurements are provided in the field:
ssha_dyn - on the Jason-1 OSDR-SSHA product
gps_ssha - on the OSTM/Jason-2 GPS-OGDR-SSHA product.

WARNING: The field "ssha_dyn" on the Jason-1 product has been globally
leveled to "gps_ssha" on the OSTM/Jason-2 product. So, for example,
"ssha_dyn" and "gps_ssha" both have a bias of approximately 174 mm
with respect to absolute calibration sites, such as the Harvest
platform. This facilitates easier simultaneous application of the
Jason-1 and Jason-2 NRT SSHA products for operational oceanography.

The OSDR-SSHA product is available with a typical latency of 7 hours from
the last available measurement on each data file, and the orbit altitude
used to generate ssha_dyn has accuracies of <= 2 cm (RMS).

Note that the OSDR-SSHA product also provides an alternative SSHA
measurement in a field named "ssha". This field is identical to "ssha_dyn"
except that it is derived using the DORIS-DIODE orbit altitudes from the
Jason-1 OSDR, which have accuracies of 10-20 cm.

The Jason-1 OSDR-SSHA product is available via ftp at the Physical
Oceanography Distributed Active Archive Center (PO.DAAC):
ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/j1_nrtssha/

Note that the Jason-1 OSDR-SSHA product is a research-grade product that is
generated on a best efforts basis by the Orbiter and Radio Metric Systems
group at JPL.

Please refer questions or comments to:
Shailen Desai ([e-mail])

Sources of data on the Jason-1 OSDR-SSHA product
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The Jason-1 OSDR-SSHA product is generated from:
1) Altimeter and radiometer data provided on the Jason-1 Operational Sensor
Data Record (OSDR).
2) Forecast pressure fields from the National Center for Environmental
Prediction (NCEP). There are used for the dry troposphere and inverse
barometer corrections.
3) Pole location predictions from the International Earth Rotation Service
(IERS) Bulletin A product, for the pole tide correction.
4) Ancillary geophysical models (solid Earth and ocean tides, mean sea
surface, sea state bias) that are consistent with the Jason-1 GDR-C
standards. The one exception is that the S1 and M4 ocean tides are not
included in the ocean tide model field, ocean_tide_sol1.
5) Orbit altitudes derived from SSHA crossover differences with
measurements on the NRT OSTM/Jason-2 GPS-OGDR-SSHA product.
This implicitly levels ssha_dyn, from the Jason-1 OSDR-SSHA product, and
gps_ssha, from the OSTM/Jason-2 GPS-OGDR-SSHA product.