INSTRUCTIONS FOR MAKING PILOT BALLOON OBSERVATIONS 21 



49. Patching balloons. — Occasionally balloons, when received from 

 the manufacturers, will be found to have small "pinholes." In 

 some cases such holes may develop during inflation due to small 

 "air bubbles" or other defects. These defective balloons should 

 not be discarded, but can and should be patched for use on days 

 when clouds are low or a short observation is anticipated for any 

 reason. Pieces of burst balloons, with ordinary rubber cement, may 

 be used for this purpose. Better results are obtained when the 

 patch is placed on the inside of the balloon. 



50. Coloring balloons. — Occasions may arise when the supply of 

 colored balloons will become exhausted. One of the uncolored type 

 may be satisfactorily colored in the following manner: Take a small 

 quantity of printer's ink, red, blue, or black as desired, and add a 

 sufficient quantity of linseed oil to make a thick sirup or paste. 

 Place a small quantity of the mixture within the balloon and knead 

 until the color is evenly distributed over the inside. 



51. Deterioration of pilot balloons. — Pilot balloons deteriorate rap- 

 idly with age, especially during the summer months. If possible, 

 they should be kept in a cool place of more or less even temperature. 

 As far as possible, the balloons should be used while fresh, and when 

 a new supply of balloons is received at a station the old supply should 

 be exhausted before the fresh ones are used. 



52. Ascensional rate oj pilot balloons. — The ascensional rate of 

 the 30-gram pilot balloons is determined by the following formula: 



which may also be written 



/ 73 \ 0.208 



wherein 



T^= ascensional rate in meters per minute. 

 /=the free lift, or the actual lifting force in 

 grams of the inflated balloon. 

 i= the total lift, or the free lift, I, plus the 

 Aveight of the balloon. 



53. It has been found that the altitudes of balloons, as determined 

 by the above formula, agrees best with the actual altitudes (i.e., for 

 30-gram balloons with a free lift of 125 grams) if the rate of ascent 

 for the first minute be increased by 20 percent, the second and third 

 minutes by 10 percent, and the fourth and fifth minutes by 5 percent. 

 These additive corrections are used by the Weather Bureau. 



54. To provide more wind information for higher levels without 

 increasing the observation time, the use of larger (100-gram) pilot 

 balloons was recently inaugurated by the Weather Bureau. They 

 have been used, thus far, for only the 5:00 p. m. (E. S. T.) observa- 

 tions at a selected list of stations, but the extension of their use to all 

 stations and all observations is contemplated. The following tentative 

 ascensional rate formula for these balloons has been developed: 



F=22.7(£iY 



.L^J 



