INSTRUCTIONS TO MARINE METEOROLOGICAL OBSERVERS 49 



The air temperature rfiould be read and entered on the form to 

 the nearest tenth of a degree, Fahrenheit (or Centigrade), if possi- 

 ble. When the ship is scheduled to send a meteorological observation 

 by radio to the Weather Bureau, the air temperature should be re- 

 ported in whole degrees^ Fahrenheit, according to the scale 00 to 99. 

 Temperatures below 0° F. or above 100° F. may be encountered 

 on very rare occasions, but only when the ship is extremely close 

 to the land, in which case it is not necessary to send a radio report. 

 Consequently, no provision is made herein for the reporting of tem- 

 peratures outside these limits. 



If temperatures on the Centigrade scale are converted to readings 

 in degrees Fahrenheit for entry on Form 1210A, care should be taken 

 in the use of the conversion table. Observers sometimes take tem- 

 j)eratures from the wrong line, thus obtaining Fahrenheit readings 

 that are in error by the equivalent of 1°, 5°, or even 10° Centigrade; 

 for example, the reading 15.6 is by mistake converted to degrees 

 Fahrenheit when the actual reading is 5.6 C. 



Temperature of the ocean surface. — The temperature of the ocean 

 surface has a more or less marked effect upon the weather and the 

 climate of adjacent land areas, depending upon the relative posi- 

 tion of water and land with respect to the prevailing winds. It 

 exerts, also, a considerable influence upon the character of the 

 weather experienced at sea. The general and accurate observance 

 of the temperature of the surface water of the oceans, particularly 

 of the principal currents, is, therefore, a matter of greatest im- 

 portance. In order to obtain the true temperature of the sea surface 

 it is necessary, just as in measuring the temperature of the air, that 

 a reliable thermometer be employed and that it be properly exposed 

 and accurately read. 



The sea-surface temperature may be obtained either by measuring 

 the temperature of a sample of water hauled up from the sea in a 

 bucket or by measuring the temperature of the water that flows 

 through the injection pipe to the cooling system in the engine 

 room. When the bucket method is used, the observer should follow 

 the instructions given below in order to attain the greatest possible 

 accuracy. 



1. Use a dry bucket, or at least empty all residual water before a 

 throw. 



2. From as far forward as possible, heave the bucket overboard; 

 if the bucket is warm from exposure to sunshine or contact with 

 steam pipes, give it time to cool off before hauling it up. 



3. Haul up the bucket as quickly as is consistent with getting 

 most of its contents safely on deck without spilling. 



4. Carry the bucket immediately to a sheltered place where wind 

 or sunshine cannot affect the original temperature of the sample. 



5. Plunge the thermometer into the bucket and stir the water with 

 it until the thermometer has taken on the temperature of the water. 

 This will be indicated when the instrument shows a constant tem- 

 perature. A thermometer with a cylindrical bulb responds more 

 readily to temperature clianges than one with a spherical bulb. 



6. Read the thermometer, but in so doing do not remove it from 

 the bucket. Tilt it within the bucket so that the scale can be viewed 

 squarely, but make sure that the bulb of the thermometer remains 



