Uncertainties in Oceanic Microwave Remote Sensing: The Radar Footprint, the Wind-Backscatter Relationship, and the Measurement Probability Density Function

• Main Author: Johnson, Paul E.
• Format: Others
• Published: BYU ScholarsArchive 2003
• Subjects: microwave remote sensing; scatterometry; Cramer-Rao; periodogram; power spectrum estimation; NSCAT; NASA Scatterometer; wind modeling error; air-sea interaction; radar backscatter; Electrical and Computer Engineering
• Online Access: https://scholarsarchive.byu.edu/etd/71; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=1070&context=etd

Oceanic microwave remote sensing provides the data necessary for the estimation of significant geophysical parameters such as the near-surface vector wind. To obtain accurate estimates, a precise understanding of the measurements is critical. This work clarifies and quantifies specific uncertainties in the scattered power measured by an active radar instrument. While there are many sources of uncertainty in remote sensing measurements, this work concentrates on three significant, yet largely unstudied effects. With a theoretical derivation of the backscatter from an ocean-like surface, results from this dissertation demonstrate that the backscatter decays with surface roughness with two distinct modes of behavior, affected by the size of the footprint. A technique is developed and scatterometer data analyzed to quantify the variability of spaceborne backscatter measurements for given wind conditions; the impact on wind retrieval is described in terms of bias and the Cramer-Rao lower bound. The probability density function of modified periodogram averages (a spectral estimation technique) is derived in generality and for the specific case of power estimates made by the NASA scatterometer. The impact on wind retrieval is quantified.