APPENDIX B 



B-l A METHOD FOR DETERMINING 

 PRESSURE COEFFICIENTS OF UNPRO- 

 TECTED REVERSING THERMOMETERS 



AT SEA. — The pressure coefficients (Q) of 

 unprotected thermometers must be known in 

 order to calculate thermometric depths. Ordi- 

 narily these Q-factors are determined by care- 

 fully controlled tests conducted at tlie Bureau 

 of Standards or at one of the oceanographic 

 laboratories. Occasionally new thermometers 

 must be put to use before Q-factors have been 

 determined. In such cases the Q-f actors can 

 be determined at sea provided there are one or 

 more unprotected thermometers with known Q- 

 factors available to use with those that are 

 unknown. 



For purposes of illustration assume that there 

 are three unprotected thermometers with known 

 Q-factors available and that it is desired to 

 determine the Q-factors for four other ther- 

 mometers at 1,000, 2,000, and 3,000 meters. 

 This is carried out as follows: 



1. Using five Nansen bottles, place the 3 un- 

 protected thermometers of known Q-factors 

 in the top, center and bottom bottles of the 

 cast. Pair with these the best available pro- 

 tected thermometers. On the bottles between 

 these, place the 2 pairs of unknown unpro- 

 tected thermometers. 



2. Space the Nansen bottles on the wire 10 

 meters apart and lower the top of the cast to 

 1,000 meters. It is desirable to do this at a 

 time when wire angles are slight. Allow 10 

 minutes for the thermometers to come to 

 temperature before reversal. Allow ample time 

 for all bottles to reverse then recover the cast. 



3. Take an oxygen sample from each bottle. 

 The oxygen determination serves as a quick 

 check on the validity of the reversing of each 

 bottle. Discard the remaining water. The 

 oxygen values should be checked against the 

 normal figure for the depth, if known. 



4. When the thermometers have come to 



equilibrium at air temperature, it is best to 

 have two or more persons with experience in 

 reading thermometers make separate readings. 



5. Repeat items 2, 3, and 4. 



6. Repeat items 2, 3, and 4, but send the 

 bottles to 2,000 meters for 2 casts. 



7. Repeat items 2, 3, and 4, but send the 

 bottles to 3,000 meters for 2 casts, if the range 

 of the thermometers permit. 



8. Correct the readings for the paired pro- 

 tected and unprotected thermometers in the 

 top, center, and bottom bottles and compute 

 their thermometric depth. Prepare an L-Z 

 graph and determine the accepted depths for 

 each cast. By interpolation, determine the 

 accepted depths for the remaining bottles. 



9. Plot the values of Tu, against depth and 

 construct a curve through the points. From 

 this graph the temperatures, for the bottles 

 without protected thermometers, are read off 

 and used to correct the readings of the un- 

 known unprotected thermometers, thus T^ is 

 determined for them. 



10. From 8. and 9. above, the values for 

 Tu—Ta and Z (using the accepted depth) are 

 established. Pm for each depth may be deter- 

 mined from figure 3-3 or from table 17. The 

 pressure coefficient, Q, at each depth is calcu- 

 lated for the unknown, unprotected thermom- 

 eters by applying the above values in the fol- 

 lowing formula, where all values are defined in 

 section 3-10: 



11. Although the Q for a given thermometer 

 may be different for the 1,000-, 2,000-, and 

 3,000-meter depths, the Q for each cast at the 

 same depth must agree to 1X10"^ (to 1 unit 

 at the fifth decimal place) to be considered 

 valid. If such agreement is not made, then 

 additional casts should be made to obtain 

 further comparisons. 



H. O. 607 



171 



