GOES-8 Evaluation Activities

GOES-8 was launched on April 13, 1994 and became the first of a new series of operational geostationary satellites. GOES I-M will provide improved observing capabilities over the current GOES/VAS system, especially for moisture sensing. These new satellites will be the only U.S. geostationary platforms for moisture mapping for the next 15-20 years. Our research develops and evaluates the utility of GOES-8 products for hydrologic studies. Thus, it pursues a goal of a major NASA research initiative called GVaP, specifically, a better understanding of atmospheric water vapor at all spatial and temporal scales. Additionally, measurements from GOES I-M will play a vital role in a major new experiment (GCIP) to better understand the hydrologic cycle over the continental United States.

The NASA/Marshall GOES-8 research objectives are:

1. to quantifying the accuracy and information content of GOES-8 imagery and derived products, including various measures of water vapor content and water vapor tracked winds,
2. to develop new procedures for examining atmospheric water vapor that take advantage of the enhanced capabilities of the GOES-8 over those now available with VAS, and
3. as a result of the above, further the goal of improving our understanding of the importance of atmospheric water vapor in the hydrologic cycle.

Marshall's research has focused on retrieval algorithm refinements and retrieval performance with simulated GOES 8 imager and sounder data for integrated water content (IWC). Most significant is the improvement in quality of IWC retrievals seen in the simulated results stemming from high radiometric quality and increased resolution of the GOES-8 data over that of VAS. Specifically, the findings for simulated GOES-8 imager and sounder data indicate that:

• retrieved values of IWC for the GOES 8 imager and sounder are significantly more accurate than those from VAS. The affect of random noise on the retrievals is suppressed by 1-2mm,
• an increase in the spatial density of IWC with GOES-8 results from the increased resolution of the GOES-8 data. A trade-off between resolution and accuracy will allow single pixel (4 or 8 km) retrievals with the accuracy of VAS 32 km retrievals,
• during the day, GOES-8 imager split window channels perform as well as those of the sounder, and both perform as well or better than VAS, and
• at night, the accuracy of IWC retrievals with the sounder are significantly better than those from the imager (but both are poor in quality). This poor performance of the retrieval schemes has been attributed to a physical limitation of the retrieval of IWC at night.

Last updated on: November 2, 1999