388 
correlation was found. This negative result constitutes 
statistical (but by no means conclusive) evidence 
against an important role of variable solar activity in 
the anomalous fluctuations of the general circulation. 
Our qualitative and quantitative knowledge of the 
physical characteristics of the variable solar emissions, 
of their direct effects in the higher atmosphere, and of 
their possible indirect effects in the lower atmosphere, 
is utterly madequate either for the certain designation 
of suitable indices of solar activity, or for any estimate 
of the probable manifestation of their complex and in- 
direct effects on the circulation of the earth’s tropo- 
sphere. One rather surprising bit of evidence for a direct 
solar influence on the zonal distribution of pressure on 
both hemispheres is furnished by highly consistent, but 
not significantly high, negative correlation between 
monthly mean zonal pressure anomalies in the lower 
latitudes, and the contemporary monthly mean solar 
pyrheliometric values as determined by all recording 
stations in Europe and North America [28]. In the polar 
latitudes of the Northern Hemisphere there is a seasonal 
reversal of the sign of this correlation from summer to 
winter, a reversal which cannot be checked on the 
Southern Hemisphere for lack of pressure data. 
3. Without comparison the highest correlations which 
have been found between basic parameters of the gen- 
eral circulation pattern are those based on Starr’s 
concept [23] of the thermodynamics of the general cir- 
culation. By this concept the index character of the 
circulation pattern limits the effective poleward trans- 
port of heat. The fact that these correlations pertain 
to the anomalous fluctuations of the general circula- 
tion, with specific implications for the tropical-polar 
heat balance, is cited as further possible evidence for 
the direct role of variable solar energy in the anomalous 
fluctuations. 
4. One final item in evidence of direct solar influence 
on the general circulation pattern must be mentioned 
as of particular interest in that it indicates a clear day- 
to-day progression of the disturbing effect. Duell and 
Duell [6] show that during the winter months (Novem- 
ber—February) of years of low sunspot activity (relative 
sunspot number less than 40), following geomagnetically 
disturbed days (presumably days of strong particle 
emission by the sun), pressure falls on the average by 
about 2 mb at European stations within two to three 
days, while at stations in the Greenland-Iceland area the 
pressure rises by an equal or larger amount. Hence by 
the second day following the disturbance, the pressure 
gradient from Greenland to northwestern Europe is 
imereased by 5 mb on the average, representing defi- 
nitely a trend towards a low-index or glacial weather 
pattern. On the other hand, Duell and Duell found that 
during the same period of time the pressure variation in 
northwest Europe after quiet geomagnetic days is in the 
opposite direction, that is, toward higher pressure a few 
days after the quiet conditions. Craig has carried out 
similar investigations for many other geographical 
points i the Northern Hemisphere. He has found that 
the pressure variations after disturbed geomagnetic 
days are, to a highly significant degree, negatively cor- 
COSMICAL METEOROLOGY 
related with the variations at the same location and 
during the same period of time after quiet days. How- 
ever, the patterns of change after disturbed days are 
not always the same and seem to depend markedly on 
initial conditions in the atmosphere.1 
A less extensive investigation of the pressure changes 
followimg days of strong solar flares (presumably repre- 
senting strong outbursts of solar ultraviolet radiation) 
gives indications of a reverse trend of the pressure 
pattern, towards a higher index condition. This trend is 
noted irrespective of season and sunspot number. 
Duell and Duell’s results need extension and further 
verification. Taken at their face value, their results 
appear to be highly significant, mm the first place as a 
clear indication of direct solar influence on the day-to- 
day weather changes of the basic index type, and in the 
second place as a possible physical clue to the opposite 
effects of major and of minor sunspot-maxima on the 
world weather patterns as first determined by Hanzlik. 
SUGGESTIONS FOR FUTURE RESEARCH 
As long as there remains a reasonable possibility 
that irregular weather changes may be linked with 
solar variations, the subject deserves expanded and 
careful study. The possibility of long-range weather 
forecasting as a result of such studies holds the promise 
of great returns for the efforts involved. The suggestions 
for future research that follow are based on the convic- 
tion that such a reasonable possibility exists. 
First of all, an attempt should be made to investi- 
gate, independently of the Smithsonian Institution, 
the variations of the solar constant. It seems rather 
incongruous to discuss the effects of solar variability, 
when variations in solar energy over the entire spectral 
range above 3000 A are not definitely established. 
Despite the fine efforts of the Smithsonian imvestiga- 
tors, probably the present controversy can best be re- 
solved by an independent study. In particular, there 
should be additional direct determinations of solar 
variability in the ultraviolet, from the earth’s surface 
in the case of the 3000-3500 A spectral region and from 
rockets or balloons at shorter wave lengths. 
Secondly, the theoretical and physical meteorologist 
must give attention to the question of how impulses 
received in the upper atmosphere can affect the tropo- 
sphere. Duell and Duell’s results have no explanation 
at present. If they stand up under future investigation, 
they become an important clue to the whole problem 
of solar-weather relationships. 
Thirdly, if the effects of ultraviolet solar variability 
on the weather become established, there is room for 
much synoptic and statistical study of interrelationships 
between the troposphere and the stratosphere. The 
question is of great interest, in any case, as a strictly 
meteorological problem. 
Finally, and most obviously, the statistical study of 
day-to-day, week-to-week, and secular weather varia- 
1, (Added in press.) Consult R. A. Craig, “Atmospheric 
Pressure Changes and Solar Activity.” Trans. N.Y. Acad. Scv., 
Ser. 2, Vol. 13, No. 7 (1951). 
