NO. 15 WEATHER AND SOLAR ACTIVITY CLAYTON 23 



are south of the Equator, the greatest minus correlations are found 

 south of the Equator in the Indian Ocean near Madagascar and in 

 central South America. 



In Dr. G. C. Simpson's excellent paper on " Further Studies in 

 Terrestrial Radiation," "" he considers what should be the effect of 

 I percent change in solar radiation. He finds that such an increase 

 might be balanced ( i ) by an increase of 2° C. in surface temperatures, 

 or, (2) by an increase of i°.5 in the temperature of the stratosphere, 

 or, (3) by an increase of .01 percent in cloudiness. However, what 

 should not be overlooked in this connection is that an increase in 

 cloudiness involves a coincident increase in temperature and a result- 

 ing decrease in pressure in order to produce the increase in cloudiness. 

 This is particularly true in the equatorial belt. The calculations given 

 in table 3, coefificient b, show that in the centers of action in that region 

 the change of pressure for i percent change of solar radiation does 

 not exceed — 1.2 mm. To produce this fall would require a rise in the 

 mean temperature of the air column of about o°.4 C.^ If there were 

 no errors in the solar measurements, the correlation coefficients r and h 

 would probably be larger, but in no case would the resulting tempera- 

 tures exceed the amounts calculated by Simpson. 



In high latitudes the coefficient h becomes larger and in the centers 

 of action rises to 5 mm for i percent change in solar radiation ; but 

 in this region the air is approaching the axis of rotation of the earth, 

 and the deflecting effect of the rotation plays a part in lowering the 

 pressure within normal centers of low pressure which are intensified 

 by the increased solar radiation. The height above the surface at 

 which the greatest absorption of solar radiation by water vapor takes 

 place is yet to be determined, but certainly in some cases it is within 

 or above the cloud level. 



In order to study the variation of position of the centers of action 

 with varying intensity of solar radiation, the monthly departure from 

 lo-year normals of solar radiation were arranged according to in- 

 tensity in the following six classes: (i) over -l-.oio calories, (2) 

 + .006 to +.010, (3) +.001 to +.005, (4) -.000 to -.005, (5) 

 — .006 to —.010, (6) under —.010. The normal was taken as 1.940 

 calories per square centimeter per minute, and the absolute values may 

 be obtained by adding this value to the departures given. The mean 

 pressures for the 10 years 1921-1930 were then determined for each 

 station in a world-wide net of stations for each class of solar radiation 



Mem. Roy. Meteorol. Soc, vol. 3, no. 21, pp. 19-22, 1928. 

 .See World Weather, p.' 275, Macmillan and Co., 1923. 



