THE INFRARED SURVEY TECHNIQUE AS A MEANS OF DETERMINING MISSISSIPPI RIVER 

 DISCHARGE PATTERNS AND SURFACE FLOW ALONG THE NORTHERN GULF COAST 



by K, L. Drennan, Gulf Coast Research Laboratory, 

 Ocean Springs, Mississippi 



INTRODUCTION 



The Gulf Coast Research Laboratory under sponsorship of the Geophysics Branch of 

 the Office of Naval Research is conducting a study of the circulation along the northern coast 

 of the Gulf of Mexico. The program, conducted on a rather limited scale during the past 

 three years , was confined to a study of the distribution of temperature and salinity in the 

 upper layers of the area immediately east of the Mississippi Delta. Drift bottles were re- 

 leased in conjunction with the study to obtain approximations of surface current speed and 

 direction. 



These data along with some direct current measurements have enabled us to de- 

 termine, to some extent, the seasonal variations in Mississippi River discharge patterns 

 and surface currents in the area. 



Previous investigations have shown that water masses of the area could in some in- 

 stances be delineated on the basis of temperature alone. This is particularly true during 

 fall, winter, and spring when the inshore and Mississippi River waters were in some instances 

 30 - 35 °F colder than the open Gulf waters. 



A monthly aerial temperature survey was initiated along the northern Gulf Coast which 

 would provide near synoptic surface temperature data from the area, and from these data, 

 the space-time variations in surface flow could possibly be determined. The initial flight was 

 made in November 1963. 



INSTRUMENTS 



Sea surface temperature measurem.ents are made using the Barnes model IT-2S in- 

 frared radiation thermometer (IRT). The thermometer and complementary equipment are 

 mounted in a Grumman Albatross, the Coast Guard and Navy's standard search and rescue 

 aircraft, and measurements are made from an altitude of 300 feet and speed of approximately 

 140 knots. The sensing head is directed from near vertical position toward sea surface 

 through lower half of rear emergency exit. Complementary equipment includes an Accurate 

 Instrument Company model APS-9AB-1 28VDC to 115 volt 60 cycle inverter. The inverter 

 has a frequency tolerance of ±.05% with input variations of 24 - 32 VDC. A Nesco model 212 

 dual pen strip chart recorder is used to record temperature and variations in line voltage. 



-69- 



