to 0.23°C. The system error for the XBT system used by the FLIP during the CAPER 

 experiments was not determined, since adequate concurrent hydrocast or CTD/SV 

 measurements were not made. 



SURFACE TEMPERATURE ACCURACY OF 460-m SYSTEMS 



One or more independent surface temperatures were measured simultaneously with 

 XBT measurements during the Gulf of Alaska, SUDS I, CAPER, and RAPLOC/DEEPTOW 

 experiments. During the Gulf of Alaska experiments, surface temperatures were measured 

 with the hydrocast, STD/SV, and SVTP systems. In addition, surface temperatures were 

 measured continuously during environmental surveys 1 and 2 and during propagation loss 

 experiments Al , A2, and A3, by means of a towed thermistor system. During SUDS I, 

 surface temperatures were measured with the hydrocast, STD/SV, and thermistor chain 

 systems. During CAPER and RAPLOC/DEEPTOW, measurements were obtained with the 

 CTD/SV system and a bucket thermometer. Also during CAPER, three measurements were 

 obtained by the hydrocast system. In this section, these measurements will be compared 

 with the XBT surface temperature measurements. 



COMPARISON WITH HYDROCAST 



During the SUDS I experiments, six hydrocast surface temperature measurements 

 were made concurrently with XBT measurements. Three each were made by the LEE and 

 the DE STEIGUER. The average of these six comparisons was -0.03°C, with the differences 

 varying from -0.14°C to 0.07°C.* 



During the CAPER experiments, three hydrocast surface temperature measurements 

 were made by the MOANA WAVE concurrently with XBT measurements. These 

 differences were -1 .41 , -0.57, and -0.39°C. These three large differences suggest a major 

 problem with the MOANA WAVE's XBT system. More information on this problem will 

 be developed when the CTD/SV and bucket temperature comparisons are discussed. 



COMPARISON WITH STD/SV 



STD/SV surface temperature measurements concurrent with XBT measurements 

 were made during the Gulf of Alaska, SUDS I, CAPER, and RAPLOC/DEEPTOW exper- 

 iments. The results of these comparisons are summarized in table 18. Shown are the 

 number of comparisons, the average difference, and the standard deviation of the average 

 difference. The large average difference and the very large standard deviation of the 

 22 CAPER comparisons provide additional confirmation that the MOANA WAVE XBT 

 system was experiencing a major problem and therefore was not measuring the surface 

 temperature accurately. Inspection of the individual CAPER differences showed them to 

 range from -2.36°C to 2.19°C. Of the 12 negative differences, nine were greater than 

 1.00°C, and of the 10 positive differences, four were greater than 1.00°C. An inspection of 

 the individual Gulf of Alaska differences showed that all of the last 1 2 differences were 

 negative, varying from -0.06°C to -0.46°C. The average of these 12 differences was 

 -0.24°C, and the average of the first 32 differences was 0.02°C. These data suggest that 

 the XBT system was not operating properly during the latter part of the measurement 

 program. This feature will be substantiated presently by comparison of the XBT surface 

 temperatures with the towed thermistor temperatures. 



*A minus difference indicates that the XBT measurement was lower than the comparison measurement, and 

 a positive difference indicates that the XBT measurement was higher. 



36 



