NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 2/9 



EFFECT OF THE SHORT-PERIOD VARIATIONS OF SOLAR RADIATION ON 



THE PRESSURE GRADIENT AND TEMPERATURE AT 



BERGEN, NORWAY 



Dr. Abbot has kindly given us the measurements of the " solar 

 constant," made at Mount Wilson during the months of June to 

 September, 191 5, and June to October, 1916. The series of obser- 

 vations made during the year 1915 are especially good and complete. 

 Most of the observations were made under very favorable cir- 

 cumstances, and may therefore be considered to be especially trust- 

 worthy. 



We have compared the changes in the " solar constant " ob- 

 tained during this year with the simultaneous meterological changes 

 at Bergen on the west coast of Norway (60° 23' N.). Having 

 before found that the changes in temperature depend, to a very 

 great extent, on the changes in the pressure gradient, we have 

 first computed the changes in the latter by taking the difference 

 between the air pressure at Christiania and the air pressure at Ber- 

 gen at 8 o'clock every morning. We have then computed the con- 

 secutive seven-day means of the " solar constant " as well as of 

 the pressure difference between Christiania and Bergen. When 

 there were less than three measurements of the " solar constant " 

 during seven days the values of the seven-day means were con- 

 sidered as doubtful. The correlation factor r for these two sets of 

 seven-day means of the " solar constant " and the pressure dif- 

 ference was now computed by the following formula, worked out 

 by Karl Pearson, and used JDy Dr. Clayton : 



We then found the following values of the correlation factor : 



CORRELATION OF SOLAR RADIATION WITH PRESSURE DIFFERENCE BE- 

 TWEEN CHRISTIANIA AND BERGEN FROM CONSECUTIVE SEVEN-DAV 

 MEANS, FOR THE PERIOD JUNE 8 TO SEPTEMBER 6, 1915. 



Days following solar 



observations o i 2 3 4 S 6 7 8 9 10 11 12 13 14 15 16 



Correlation Factor.. .22 .33 .45 .55 .61 .63 .60 .57 -Si -38 .22 .07 —.08 —.21 —.30 —.35 —.38 



These values of the correlation factor are comparatively high 

 and amount to as much as 0.63 on the fifth day. This proves that 

 there is a very well-developed positive correlation between the solar 

 radiation and the pressure gradient between Christiania and Ber- 

 gen. The maximum effect of the changes in the solar radiation 

 follows five days later in the pressure difference. This correlation 



