Effects of Atmospheric Water Vapor on the Detection of Mesoscale Oceanographic Features from GEOSAT
Abstract
The GEOSAT Ocean Applications Programs (GOAP) is using near-real-time altimeter data to map mesoscale fronts and eddies in the Gulf Stream region. This effort is hampered in part by the fact that atmospheric water vapor can attenuate the altimeter pulse and produce erroneous undulations in the resultant sea surface topography. This report identifies the magnitude and spatial scales associated with water vapor attenuation so that the GOAP analyst can better anticipate the problem at hand. The task is approached by using SEASAT scanning multichannel microwave radiometer data to define water vapor gradients over the Gulf Stream. The 1978 data clearly reveals that attenuation due to water vapor alone can be 20-40% as large as the 50-100 cm signal characteristic of ocean fronts and eddies. These water vapor gradients also occur on the same scale (100-250 km) as the mesoscale ocean features, illustrating the point that the GOAP analyst must interpret individual track information with caution to avoid errors in analysis. A study was also done do simulate what effect these water vapor errors would have on objectively contoured topographic fields while attenuation due to water vapor has some impact, it is outweighed by the problems associated with low data density and consequent distortion introduced by the interpolation scheme. The track spacing is thus the dominant problem and will remain so until the GEOSAT Extended Repeat Mission brings about a more appropriate distribution of data. When combined with water vapor data from the special sensor microwave objective mapping will likely become more feasible.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1986
- Accession Number
- ADA176365
Entities
People
- Jeffrey D. Hawkins
- Peter M. Smith
Organizations
- United States Naval Research Laboratory