455 
Figure 2. - Values of z and L-band a^v f° r vegetated patches at Stauning (♦) and desert 
test sites (CD) in Southern California. 
height, and these data were used to calculate z Q . At the grass sites no direct measurement of z Q was available. 
Instead, values were estimated as suggested by Brutsaert, 1982, assuming z Q = 0.55 H, where H is grass height. 
CONCLUSION 
The resultant relationship of 0° to z Q is plotted in Figure 2 together with our previous desert results. Note that CJ° is 
plotted in decibels (dB) against log z Q , so the plot is essentially a log-log plot of height against returned power. For 
seven of the vegetated areas (the agricultural fields) the radar backscatter values are of the same order of magnitude 
(in dB), and the Spruce site is much brighter. Although all of the vegetated sites are both brighter in backscatter and 
rougher than the previous study, there is an overall good correlation between the two data sets. Coefficient of fit 
(R^) is 0.79 for the entire plot. 
We are now prepared to continue this study towards our ultimate goal of having a predictive model. First we will 
investigate the relationship in the more complicated case of a heterogeneous roughness, with scattered vegetation. 
Second, we plan to establish a theoretical basis for the 0° - z Q association so that we may more comfortably extend 
the empirical relationship into a predictive model. 
ACKNOWLEDGEMENT 
We would like to thank M. Kobrick and M. Vogt for arranging the DC-8 overflight, H. Kampskole for assistance in 
deploying comer reflectors, and the Riso National Laboratory for meteorological data. Parts of the research 
described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under 
contract with the National Aeronautics and Space Administration. 
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