Envisat: Near Real Time Processing
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Envisat: Near Real Time Processing and Oceanography. Envisat CCVT Meeting. Kirk Whitmer Gregg Jacobs JE Sverdrup/NRL Stennis Space Center, MS, USA. ALPS and ODDITIES. ALPS : Near real time data processing system Data is quality checked at each step and suspect data is flagged

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Envisat near real time processing and oceanography

Envisat: Near Real Time Processing

and Oceanography

Envisat CCVT Meeting

Kirk Whitmer

Gregg Jacobs

JE Sverdrup/NRL

Stennis Space Center, MS, USA


Envisat near real time processing and oceanography

ALPS and ODDITIES

  • ALPS: Near real time data processing system

  • Data is quality checked at each step

  • and suspect data is flagged

  • Must err on the side of caution because of

  • subsequent subsystems

  • Run daily at NRL and NAVO

  • ODDITIES: Graphical data analysis system

  • Results displayed on

    The Real Time Ocean Environment website

  • www.ocean.nrlssc.navy.mil/altimetry

  • Run daily at NRL

Envisat imar data fed into the systems…


Envisat near real time processing and oceanography

read: data is read from gdrs

into ALPS format

  • Smooth electromagnetic bias and

  • wet troposphere along track

  • Apply correction terms to height:

  • Wet troposphere, Dry troposphere

  • Inverse barometer, Solid tide

  • Ionosphere, Electromagnetic bias

  • Check for minimum number of high rate values (>15)

  • Check flag for water (sea ice?)


Envisat near real time processing and oceanography

Ionosphere drop plot

Ku band correction only

Doris Ku band correction only

All ionosphere corrections applied:

Ku band correction

Doris Ku band correction

Model Ku band correction


Envisat near real time processing and oceanography

interp: data is interpolated to

reference ground tracks

  • Minimum number of points needed to interpolate

  • Interpolation incorporates the geoid gradient

  • Along track smoothing


Envisat near real time processing and oceanography

  • Data too sparse to interpolate to ground tracks

  • Single largest contributor to “dropped” data points


Envisat near real time processing and oceanography

aptide:tides are removed

  • got00.2 tide model applied

  • No points are dropped


Envisat near real time processing and oceanography

orbgem:orbit correction calculated

and applied

  • Long term mean and climactic mean removed

  • Iterative sinusoidal fit calculation

  • Return means

  • Apply correction based on fit


Envisat near real time processing and oceanography

Orbit correction magnitude

Mean: 60.7 cm

RMS: 74.0 cm


Envisat near real time processing and oceanography

  • Even after orbit correction, still considerable noise.


Envisat near real time processing and oceanography

apply: mean removed

  • Along track “box car” filter

  • Sanity checks


Envisat near real time processing and oceanography

Sea ice issue?

High latitude makes

ice more important

Detection algorithm

or flag desireable

SSH anomaly plot suggests many

sea ice points remaining


Envisat near real time processing and oceanography

ERS-2

GFO


Envisat near real time processing and oceanography

  • Jason-1

  • Multiple causes for ice point drops

  • Lower latitude reduces importance


Envisat near real time processing and oceanography

Percent data utilized

Jason (osdr)84.73/85.20 %

Jason (igdr)90.17/90.17 %

Ers-284.22/90.26 %

GFO (doppler)87.49/87.49 %

GFO (laser)90.30/90.30 %


Envisat near real time processing and oceanography

Sea Surface Height Anomaly

14 October 2002


Envisat near real time processing and oceanography

Altimeter cross track intercomparisons

  • High latitude values sea ice influenced


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