AVHRR - ANNUAL MEAN OF SKIN SST IMAGE BASED ON AVHRR GAC DATA

Y. Yu (University of Colorado, USA)

Announced availability: 1 June 1995

Data Access

An annual mean of skin SST image based on AVHRR/GAC data is available upon request from NOAA's National Oceanographic Data Center (NODC) in Silver Spring, MD (http://www.nodc.noaa.gov).

Beginning June 1996, data will also be archived at NOAA's National Climatic Data Center (NCDC) in Asheville, NC (http://www.ncdc.noaa.gov) and at the National Center for Atmospheric Research (NCAR) in Boulder, CO (http://dss.ucar.edu/pub/toga_coare/).

Background

The Advanced Very High Resolution Radiometer is a five-channel scanning radiometer that was installed on the NOAA-11 and NOAA-12 Polar Orbiting Satellites. The radiometer provides day and night imaging in the visible (VIS) and infrared (IR), sea surface temperature (SST) determination, estimation of heat budget components and identification of snow and sea ice. The near-IR channel (channel 3: 3.55-3.99 um) and the two IR channels (channel 4: 10.2-11.5 um; channel 5: 11.5-12.5 um) are used to compute SST.

Full resolution data are processed onboard the satellite into low resolution, 4 km Global Area Coverage (GAC) data, which is recorded only for readout by CDA stations. GAC data contain only one out of three original AVHRR lines and the data volume and resolution are further reduced by averaging every four adjacent samples and skipping the fifth sample along the scan line. Low-resolution images are being broadcasted using a weather fax format, permitting reception with inexpensive receivers and omnidirectional antennas.

The image that was made available by the University of Colorado, shows the annual mean of Skin Sea Surface Temperature (SST) for the period 1 September 1992 through 27 August 1993. The spatial coverage ranges from 15S - 25N and 120E - 160W (200E in the image). The original resolution of the image was 5 km (AVHRR GAC data), but was reduced to be about 20 km in this gif format image. The original resolution image can be posted if requested.

Data File Information

Directory name: AVHRR_GAC
Number of image files: 2 (avhrr_gac.gif, avhrr_gac.tiff)
Dataset format: Compuserve Image format
Dataset volume: 72 KB

Data Processing

The GAC data were provided by NCAR (for 92's and early 93's) and by NASA/GSFC (rest of 93's). Ten-day composites of the Skin SST, MCSST, and NLSST were first done with a combined cloud filter of dynamic threshold and band (latitude) threshold method. The 4-sigma method was used for further cloud filtering after the 10-day composite. Interpolation was then applied on the composite SST data. Mean SSTs were computed from these 36 10-day composite results.

Results from the Skin SST, MCSST and NLSST show almost the same pattern of SST in both the individual 10-day composite data and the annual mean SST, with some differences in absolute value.

For more information regarding this image, please contact:

Yu Yunyue
Colorado Center for Astrodynamics Research
Department of Aerospace Engineering
University of Colorado
Campus Box 431
Boulder, CO 80309
USA

email: yuy@frodo.colorado.edu
Phone: (303)492-8868
FAX: (303)492-2825

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