68 



UNITED STATES COAST GUARD 



19. OCEAN WINDS, WEATHER AND CURRENTS. 



What is the meaning of the term 

 "dew point"? 



What is a hygrometer? 

 What is an "isotherm"? 

 Referring to the sketch : 



(a) What is the name of the in- 

 strument, used to I'ecord temperature? 



(b) State how the bimetallic ele- 

 ment causes changes in temperature to 

 be recorded. 



What is "saturation"? Explain in 

 full. 



Convert ( — ) 15° Celsius (Centi- 

 grade) into the temperature Fahren- 

 heit. 



Desci-ibe the type of precipitation as- 

 sociated with the approach of a warm 

 front and cold front. 



How is the barometric pressure at 

 sea level indicated on a weather map 

 at sea and on a ship's report (the sym- 

 bol PPP designates the pressure on the 

 standai'd form for reports) ? 



How is atmospheric pressure ex- 

 pressed in meteorology; i.e., in what 

 units is it measured? 



Explain how the hair hygrograph 

 records the humidity. 



Explain how the temperature, pres- 

 sure, and volume of gas are related. 

 State in words or in mathematical nota- 

 tion the gas laws. 



How is the pressure affected by the 

 passage of a front? 



Define: 



(a) A bar. 



(b) A millibar. 

 What is a "gradient"? 

 What is "advection fog"? 

 What is an "air mass"? 



How does a body of air acquire char- 

 acteristic properties? 



What are the phenomena, charac- 

 teristic of the passage of a cold front, 

 which are associated with wind shifts? 



What is the "Wave period"? 



How is the "Wave period" deter- 

 mined? 



What is the name of the cloud type 

 which gives rise to halos of the sun and 

 moon? 



How is altrostratus distinguished 

 from cirrostratus and nimbostratus? 



Name six atmospheric processes which 

 cause air to be cooled below its dew 

 point, thus causing condensation and 

 clouds. 



What sequence of cloud types is char- 

 acteristic of the approach of a warm 

 front? 



What are the signs that may indicate 

 the proximity of ice? 



What is a "lead" in ice? 



What are the causes of packing of 

 compact slush, or packing of hum- 

 mocked-ice? 



How should an ice field be entered? 



Why is it standard procedure to rig 

 for towing before reaching ice, when 

 vessels are to proceed in an ice convoy? 



How are ships moored to ice? 



What precautions should be taken by 

 a vessel which is drifting with engines 

 stopped during the night or during a 

 period of poor visibility in an area 

 where icebergs are prevalent? 



What influence has the earth's rota- 

 tion on air currents moving from a 

 position of high pressure to a position 

 of relatively low pressure? 



When a vessel transmits a radio mes- 

 sage advising of a tropical storm, is the 

 vessel liable for the cost of the mes- 

 sage? 



How are messages concerning storms 

 preceded when transmitted by radio- 

 telegraphy? 



What infoimation should be included 

 in a message from a vessel warning of 

 a tropical storm? 



