reported temporal measurements of laser backscattered signals in connec- 

 tion with airborne hydrographic experiments (O'Neil, 1981; Hoge and Swift, 

 1980) have shown a reasonable capability of making these measurements with 

 present state-of-the-art instrumentation and technology. 



The microwave radiometers, classified as "passive" remote sensors, measure 

 the natural microwave emission of the water surface. The emissivity of the 

 water is a function of water temperature and conductivity, and hence, 

 salinity. This technique has been developed to provide a remote measure- 

 ment of water surface temperature and salinity with relative precisions on 

 the order of 0.5°C and 0.5 part per thousand (ppt), respectively (Blume 

 et al., 1981; Kendall and Blanton, 1981). 



2.4 FLUOROMETER IN SITU SENSING 



Over short time periods, spatial resolution of surface phytoplankton popu- 

 lations in local areas can now be reasonably well resolved by laser mapping 

 of chlorophyll fluorescence in the path of an aircraft (Campbell and 

 Thomas, 1981). The temporal resolution of this technique is poor, however. 

 It lacks the ability to make routine biological measurements with depth, at 

 time scales similar to physical variables currently measured with moored 

 arrays of current, temperature, and conductivity sensors. As the first 

 step towards a biological analog to a current meter (Carder, 1981), in situ 

 fluorescence has been measured for a 2- to 3-week periods with Turner 

 Designs model 10-005RU f luorometers, equipped with a high-pressure cuvette 

 and housed in water-tight aluminum cases (Whitledge and Wirick, 1982). 



These fluorometers were suspended within electromagnetic current meter 

 arrays (Figure 2-5) on the shallow (30 m) shelf off Long Island, New 

 York, during August 1977, September-October 1977, and April-May 1979. 

 Water samples were continuously pumped through each fluorometer at 

 approximately 0.6 min" , the fluorescence data were averaged for 20- 

 minute periods, and telemetered in real-time ashore. Power to operate 

 the fluorometers and reduce the output data was derived from the same 

 large battery package and jn_ situ data processor-telemetry system 

 developed for the current meter arrays (Scott and Csanady 1976; Walsh et 

 al., 1978; Beardsley et al., 1981). 



2-14 



