DAILY ATMOSPHERIC-ELECTRIC RESULTS 



EXPLANATORY NOTES AND COMMENTS 



In accordance with procedures and instructions out- 

 lined in section II of this volume, observations were 

 made each day, if weather permitted, of several atmos- 

 pheric-electric elements. Generally, the observations 

 were made between ten hours and fifteen hours local 

 mean time and they required between one and two hours 

 for completion. During the observing period note was 

 made of the prevailing meteorological conditions. The 

 elements observed were: Potential-gradient, positive 

 and negative conductivity, small-ion concentration, nu- 

 clei concentration, and rate of ion production by pene- 

 trating radiations. 



Potential-Gradient . - -Only eye-reading measure- 

 ments of potential-gradient were available for use in the 

 present table up to July 10, 1928; thereafter, until Au- 

 gust 14, 1928, recorder values were used for some days 

 and eye-reading values for others. From August 14, 

 1928, for the balance of the table, recorder values have 

 been given exclusively. Recorder values have the ad- 

 vantage of being obtainable from the photographic record 

 for the exact period of time occupied in making the three 

 sets (occasionally two) of measurements of conductivity 

 and small-ion concentration which were obtained each 

 day, and each recorder value of potential-gradient given 

 in this table is a mean value for that period. 



On some days the values of potential-gradient are 

 omitted and the letter e inserted instead; this notation 

 indicates that the ship's main engine was operating dur- 

 ing the observing period, and that exhaust gases coming 

 from the exhaust pipe near the water line under the 

 stern rail had affected the potential-gradient and given a 

 spurious value that could not be used. Inspection of the 

 photographic records indicated when this effect was 

 present; on many occasions no effect from the exhaust 

 gases could he noted. Apparently the wind, on these lat- 

 ter occasions, would blow sufficiently strongly across 

 the stern of the ship to carry the exhaust gases away so 

 rapidly that no effect would be produced. 



Conductivity and Small-Ion Concentration. - -The 

 daily observations of conductivity consisted generally of 

 two measurements of conductivity of one sign separated 

 by one measurement of the conductivity of opposite sign. 

 On occasions when diurnal-variation observations were 

 made over a twenty-four-hour period, however, the 

 program consisted of one measurement of a given sign 

 of conductivity, followed by twenty-four measurements 

 of opposite sign, and one final measurement of the orig- 

 inal sign. On these occasions therefore, there were two 

 instead of three measurements available for inclusion in 

 the present table, the beginning and ending pairs of 

 measurements being used to represent two successive 

 days. Observations of small-ion Concentration were 

 made simultaneously with the conductivity measure- 

 ments on all possible occasions, but rain, mist, and 

 spray interrupted the small-ion measurements much 

 more frequently than they did the conductivity measure- 

 ments and the small-ion data are less complete. Care 

 was taken to insure that the concentration of ions 

 measured was of the same sign as the conductivity being 

 measured at any given time. From these simultaneous 

 measurements the ionic mobility was computed. 



Computed Small-Ion Mobilitv. --The computed mo- 



bility values in this table are found to be reasonably 

 consistent up to October 16, 1929. From this date until 

 Noveml)er 6, 1929, numerous high values are encoun- 

 tered. Careful examination of the observational data 

 has failed to disclose a reason for the high values of 

 this period. High values of mobility similarly are found 

 in the last two sets of diurnal-variation data in the table 

 in section VI. These two sets were obtained October 21- 

 22, 1929, and November 4-5, 1929, both of which occa- 

 sions are within the period just mentioned. 



Computed Air-Earth Current Density. --From the 

 conductivity measurements and simultaneous values of 

 potential gradient, values of air-earth current density 

 have been computed and included in this table. The 

 values range, in general, between 5.0 and 15.0 x 10" ' 

 esu but there is a considerable group of very low values 

 for the period August 11 to August 24, 1928. After Sep- 

 tember 3, 1929, when only one sign of conductivity was 

 measured each day, the other sign was computed from 

 the relation X+A . = 1-10, and this computed value used 

 in the computation of air-earth current density. 



Penetrating Radiation Data. --Values of ion-pairs 

 produced per cubic centimeter per second in penetrating 

 radiation apparatus 1 during each daily observing period 

 of approximately one hour, are tabulated as measured, 

 no correction being made for residual ionization. In- 

 spection of the tabulated values indicates that the resid- 

 ual ionization probably is nearer one ion-pair per cubic 

 centimeter per second than two. 



Meteorological Data. --For brevity, various conven- 

 tional symbols are used in presenting the meteorological 

 data, as follows. 



Cloud Types 



cirrus ci 



cirrocumulus cicu 



cirrostratus cist 



altocumulus acu 



altostratus ast 



cumulus cu 



fractocumulus frcu 



stratocumulus stcu 



stratus st 



cumulonimbus cunb 



nimbus nb 



nimbostratus nbst 



Wind Force (Beaufort) 



calm 



1 light air 



2 light breeze 



3 gentle breeze 



4 moderate breeze 



5 fresh breeze 



6 strong breeze 



7 moderate gale 



8 fresh gale 



9 strong gale 



10 whole gale 



11 storm 



12 hurricane 



Weather Notes 



d drizzling q 



f fog r 



h hail s 



1 lightning t 



m mist z 



p passing showers 



squalls or squally 



rain 



spray 



thunder 



haze 



Cloud amount on scale of for cloudless to 10 for 

 overcast. 



Visibility on scale of 1 for poor visibility, with no- 

 ticeably hazy or smoky air, to 3 for good visibility with 

 air very clear. Visibility 2 represents conditions not 

 poor enough for the former nor good enough for the latter. 



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