INTRODUCTION 



The U.S. Naval Oceanograpiiic Office (IWVOCEANO) is investigating 

 thermal changes in the ocean as part of its various operational comrait- 

 ments connected with oceanographic prediction. Specifically, the air- 

 sea interface portion of the thermal structure -was studied some years 

 ago in relation to wave forecasting, because thermal stability of the 

 layer of air near the ocean surface was believed to affect prediction 

 of wave heights. For this purpose, daily synoptic charts of air-sea 

 temperature difference and thermal gradients in the ocean were con- 

 structed from 1952 to 1953. The impetus for this investigation 

 resulted from a theoretical study of the effects of weather on the 

 thermal structure of the ocean (reference 1). 



These preliminary studies resulted in a multi-ship experiment 

 during June and July 1953 "by the USS SAN PABLO (AGS- 30) and the USS 

 REHOBOTH (AGS- 50) which were anchored for periods of time on a seamount 

 northeast of Bermuda. A report concerning internal temperature fluctu- 

 ations observed during that cruise (Operation STANDSTILL) was published 

 by NAVOCEANO (reference 2). More recently, reflectivity of the ocean 

 was Investigated by Olson (reference 3) using solar radiation measure- 

 ments from this operation. 



The specific observational technique initiated on Operation STAND- 

 STILL (BT measurement every 30 minutes) was followed during research 

 experiments conducted in support of Antisubmarine Warfare Environmental 

 Prediction Services (ASWEPS). Abundant BT data existed for the various 

 United States weather ships; however, these data were collected at vary- 

 ing time intervals and contained many gaps. In order to compare the 

 existing data with observations made at fixed 30-minute intervals, a 

 series of experiments was conducted at Ocean Weather Station ECHO (35°N, 

 i+8°VJ) with the cooperation of the U.S. Coast Guard. These experiments 

 were conducted from 8 to 29 November 195^^ 28 February to I6 March 1959, 

 20 May to 8 June 1959, and 2 to 21 September 1959. 



The ECHO cruises were designed to sample the thermal structure 

 during all seasons: November represented a season of rapid cooling 

 of the upper oceanic thermal structure; May- June, a period of warming; 

 February-March, a winter situation; and September, a late summer situ- 

 ation. Tn.e thermal structure in winter is characterized by convection 

 to depths of 600 feet or more, so that studies of heat budget charac- 

 teristics are affected by vertical motion of the water. In summer, 

 surface heating exerts the major control over the vertical changes, 

 and, thus, daily effects are more prominent. For this reason, the 

 author examined the physical processes readily evident in the diurnal 

 heating cycle at this mid-ocean location (reference h) . A study of 

 some 900 BT's reduced to punchcard readings at 20-foot intervals con- 

 cluded that convection during nighttime hours reached a depth of 60 

 feet and that some of the anomalous hourly temperature changes could 

 be explained by stationary internal waves on a very weak thermocline 

 at 60 feet. Salinity data supported this theory. 



