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152 OCEANOGRAPHY IN THE NEXT DECADE 



concentrations and rainfall, sea surface temperature, ocean color, 

 sea ice distributions, ocean surface topography, and gravity. The 

 potential of satellite oceanography is almost unlimited, although 

 its usefulness for most purposes depends on in situ calibration of 

 the remote measurements. 



Atmospheric water vapor must be measured because it is used 

 in computing ocean surface evaporation and thermal forcing and 

 is needed to correct altimetry data. Sea surface temperature ob- 

 served by infrared sensors is the surface signature of ocean tem- 

 perature changes. It is a vital parameter in estimating surface 

 heat fluxes and evaporation, and can be used to infer some circu- 

 lation features. 



Remote sensing of ocean color is a key element for under- 

 standing the global ocean carbon budget. To obtain long-term 

 continuous global ocean color measurements, the Sea-viev^^ing Wide 

 Field Sensor (SeaWiFS) sensor will be launched on a satellite in 

 1993. Future ocean color instruments should include improve- 

 ments in spectral coverage and calibration. An ocean color sensor 

 and scatterometer should be combined on a future satellite be- 

 cause of the close connection between wind stress and productiv- 

 ity. With future sensors, data from more wavelengths may be 

 collected. This should allow estimation of various colored dis- 

 solved organic materials and, perhaps, separation of phytoplank- 

 ton pigment groups. Sun-stimulated fluorescence at 683 nanom- 

 eters (Chamberlin et al., 1990) may be a good indicator of the 

 photosynthetic state of the phytoplankton and thus be useful in 

 improving primary productivity models. 



Passive microwave sensors measure concentrations of open 

 water versus sea ice and may, in the future, be able to estimate 

 the emitting temperature of the upper layer of the ice, which is 

 related to the surface heat balance. The large-scale shape of the 

 ocean surface (the geoid) is primarily related to Earth's gravity 

 field because the ocean surface tends to form a level surface per- 

 pendicular to the force of gravity at any given location. Devia- 

 tions from this level surface are caused primarily by ocean cur- 

 rents. Ocean currents can be studied by a combination of altimeter 

 measurements of the ocean surface height and gravity measure- 

 ments of the geoid. 



Precise satellite geodetic measurements, providing informa- 

 tion on crustal deformation, continental drift, and plate tectonics, 

 Earth and ocean tides, and changes in Earth's geopotential, have 

 been carried out since 1976 in a joint project between the United 

 States and Italy with the Laser Geodynamics Satellite. 



