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Wind speed over water (QuikSCAT)

Access

RESTRICTED only accessable in CEN/MPI network or via CliSAP login What does that mean?

View data via LAS

Access data via OPeNDAP

Data access via file system: /data/icdc/atmosphere/quikscat

 

Description

Introduction:

  • Launched: June 19, 1999 on a Titan II launch vehicle at Vandenberg Air Force Base, California, aboard the SeaWinds satellite
  • On board: two rotating pencil-beam microwave radar sensors. These measure at a frequency of 13.4 Gigahertz and obtain the surface roughness at two different incidence angles (46° and 54°). Using the obtained ocean-surface roughness wind speed and direction can be derived.
  • Last measurement was on Nov. 23, 2009 (satellite still in orbit, still measuring, but antennas are not rotating anymore because of a malfunction of the mechanics)

Objectives and applications:

  • Acquire high resolution wind data over global oceans
  • Better understand mechanisms of global climate change and weather patterns Improve Weather Forecasts
  • Improve storm warning and monitoring
  • Obtain sea-ice extent and ice edge
  • Obtain sea-ice type (seasonal / multiyear ice)

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Parameters

Name Units
Wind speed m/s
Wind direction degrees (0 ... 360°)
u-component m/s
v-component m/s
   

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Coverage, spatial and temporal resolution

Period and temporal resolution:

  • 19th July 1999 to 19th November 2009
  • Daily, as 3-Day composite

Coverage and spatial resolution:

  • Global, over open water
  • Spatial resolution: 0.25° x 0.25°, cartesian grid
  • Geographic longitude: 0°E to 360°E
  • Geographic latitude: -90°N to 90°N
  • Dimension: 1440 columns x 720 rows
  • Altitude: 0.0 m

Format:

  • netCDF

Note: We are offering 3-day composites, mainly because the resulting fields cover the complete ocean (rain flag excluded).

Upon request we also offer data of the single satellite overpasses. These have data gaps however. The advantage of this data is that the overpass time is available for each overpass, allowing to compare this data with, e.g., buoy data.

Note: Wind direction 0° (180°) is a wind blowing TOWARDS north (TOWARDS south) - according to the oceanographic convention; u- and v-component however are as usual POSITIVE pointing towards east and north, respectively.

 

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Data quality

The data set offered here does not include any explicit uncertainty estimations.

The following things have be taken into account when using this data set.

1) Radar backscatter intensities of the water surface as measured by QuikSCAT are as accurate as 0.2 dB.

2) Wind speed retrieval is carried out using a model function which translates between wind-induced water surface roughness and the measured radar backscatter intensity. This translation is straight forward and retrieved wind speeds compare to buoy observations with about 0 m/s difference and an RMS below 1 m/s. The retrieval of the wind direction is more difficult because of signal ambiguities. These are mitigated by including NCEP/NCAR model derived wind directions into the retrieval.

3) The offered 3-day composites comprise wind vector estimates of a maximum of 6 (minimum of 2) QuikSCAT overpasses (both ascending and descending). In areas of highly varying wind speeds and directions the obtained mean values might not reflect the real strength and direction of the wind.

4) Precipitation influences the measured radar backscatter intensity either directly by scattering of the microwave radiation by the precipitation particles or indirectly by adding to the water surface roughness due to precipitation particles impinging on the water surface. These areas are flagged invalid in these data. The data flag either relies directly on the QuikSCAT data and the model function or it may rely in addition on precipitation rates retrieved from near-coincident satellite passive microwave observations.

 

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Contact

Remote Sensing Systems
Santa Rosa, CA, U.S.A.
email: support (at) remss.com

Stefan Kern
ICDC / CEN / University of Hamburg
email: stefan.kern (at) uni-hamburg.de

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Data citation

When using these 3-day composites please include the following note:

SeaWinds data are produced by Remote Sensing Systems and sponsored by the NASA Ocean Vector Winds Science Team. Data are available at www.remss.com, distributed in netCDF format by the Integrated Climate Data Center (ICDC, icdc.cen.uni-hamburg.de) University of Hamburg, Hamburg, Germany.

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