75° W 



37" N 



73° W 



37* N 



36° N 



76° W 



74° W 



35° N 



73° W 



Figure 22. Comparison of simultaneous NIMBUS II HRIR (orbit 238} and aircraft 

 radiometric night-time measurements (0300 to 0630 GMT) of sea surface temperature 

 near northern Gulf Stream boundary, June 2, 1966. Heavy dots represent Gulf Stream 

 boundary detected in aircraft. Numbers along tracks of aircraft horizontal temperature 

 profiles are average sea surface temperatures between tick marks. (NASA photo) 



quencies, involves the Fourier transform of a sea 

 surface photograph. 



The cloud cover constraint on optical tech- 

 niques has led to the study of passive microwave 

 radiation and radar reflectance for sea-state de- 

 termination. Both of these measurements can be 

 made with no appreciable attenuation in the 

 presence of storms and clouds. Microwave 

 radiometry data has yielded unique signatures as a 

 function of viewing angle for different surface 

 roughness. 



Airborne radar scatterometer data indicate that 

 the return signal yields signatures characteristic of 

 the sea surface energy spectrum, which in turn can 

 be related to the sea-surface winds. If this 

 approach becomes practical, a spacecraft in a near 

 polar orbit would be capable of providing regu- 

 larly spaced wind speed reports as well as the 



intermediate sea-surface roughness data over the 

 oceans.' 



Plans are now being made for a major field 

 experiment during early 1969, involving several 

 aircraft using sensors operating in different fre- 

 quency bands. In addition to analysis of radar 

 scatterometer data, the Doppler-shift spread due 

 to reflection by the "rough" sea surface will be 

 analyzed. The Ocean Station Ships in the North 

 Atlantic will provide "ground truth." 



Television and infrared sea ice data have been 

 regularly obtained from the polar-orbiting 

 meteorological sateUites (TIROS, ESSA, NIM- 



Pierson, W. J., 1968: A proposed method for the 

 analysis of surface wind field for the Southern Hemi- 

 sphere using land stations, ship reports, and spacecraft 

 cloud and radar scatterometer data. Paper delivered 

 before • 49th Annual Meeting, American Geophysical 

 Union, April 8-11, 1968, Washington, D.C. 



11-44 



