5-49. "The time interval between consecutive 

 troughs of a wave," defines wave 



1. height 



2. speed 



3. period 



4. length 



5-50. Which term is used to describe the average 

 height of the highest one-third of the 

 waves? 



1. Mean wave height 



2. Significant wave height 



3. Median wave height 



4. Average wave height 



In items 5-55 through 5-58, select from column B 

 the definition of each type of winds aloft obser- 

 vation listed in column A. 



A. Types 



5-55. 



PIBAL 



5-56. 



RABAL 



5-57. 



RAW IN 



5-58. 



Rawinsonde 



B. Definitions 



1. A measurement by elec- 

 tronic means of wind 

 direction and speed 

 from calculations which 

 combine the angular 

 elevation and azimuth 

 of a radiosonde signal 

 with the computed 

 height of the radio- 

 sonde 



Learning Objective: Recognize 

 standard procedures for observing 

 and recording sea conditions. 



5-51. The best position on a ship from which 

 wave period observations may be made is 



1. the windward side of the stern 



2. amidships near the centerline 



3. the deck above the bridge 



4. the windward side of the bow 



5-52. Which of the following statements is cor- 

 rect with respect to wave height observa- 

 tions? 



1. Low waves tend to be underestimated; 

 high waves tend to be overestimated 



2. Both low waves and high waves tend 

 to be underestimated 



3. Both low waves and high waves tend 

 to be overestimated 



4. Low waves tend to be overestimated; 

 high waves tend to be underestimated 



5-53. Which of the following wave height 



categories is to be recorded when wave 

 height observations are made? 



1. Average of the highest waves 



2. One-half the average of the highest 

 waves 



3. Average of all wave heights 



4. Significant wave height 



2. A simultaneous measure- 

 ment by electronic 

 means of pressure, 

 temperature, wind 

 direction, and speed 



of the air above the 

 earth's surface 



3. A measurement of wind 

 direction and speed by 

 visually observing with 

 a theodolite the suc- 

 cessive positions of a 

 free balloon which is 

 assumed to have a 

 fixed ascensional rate 



4. A measurement of wind 

 direction and speed by 

 visually observing a 

 radiosonde's ascent 

 with a theodolite 



Learning Objective: Recognize the 

 schedule, code, basic content, and 

 forms used for upper air/wind 

 observations. 



5-54. Waves which are uniformly shaped, low, and 

 have rounded tops and regular heights are 

 classified as 



1. storm action waves 



2. swell waves 



3. following waves 



4. sea waves 



Learning Objective: Identify various 

 types of winds aloft observations. 



5-59. At what times are upper wind observations 

 desired from fleet units? 



1. 0000 and 1200 GMT 



2. 0600 and 1800 GMT 



3. 0600 and 1800 LST 



4. 0000 and 1200 LST 



5-60. Which form is used to plot computed wind 

 direction and speed to corresponding 

 altitudes for coding purposes? 



1. MF5-20N 



2. 0PNAV 3140-27 



3. MF1-12 



4. OPNAV 3140-14 



31 



