SOLAR ENERGY VARIATIONS AND ANOMALOUS WEATHER CHANGES 
the secular weather cycles. The connection between 
sunspots and weather is so complex and indirect that 
it remains completely unexplained physically, but un- 
fortunately sunspots are the only index of irregular 
solar activity for which the record of reliable observa- 
tion is sufficiently long to be useful for extended correla- 
tion. Among the many studies of this kind which have 
been made, the following might be mentioned briefly 
as among the more significant: 
1. K6ppen [13], Walker [25], and others have demon- 
strated beyond question the reality of an eleven-year 
sunspot cycle of temperature in many regions, pri- 
marily in the tropics, such that lower temperature 
occurs with the sunspot maximum. 
2. Helland-Hansen [11], and others, have indicated 
that at least across the North Atlantic Ocean prevailing 
storm tracks tend to be displaced equatorward during 
periods of high sunspots. Some of Tannehill’s graphs 
[24] indicate a similar latitudinal displacement of storm 
tracks on the west coast of the United States. 
3. Hanzlik [8, 9] finds quite impressive changes of 
the world-wide distribution of pressure, particularly 
during the winter season, from the three years centered 
at sunspot minimum to the three years at the following 
sunspot maximum. The most striking feature of 
Hanzlik’s pattern studies is that, in high latitudes, 
the pressure changes in effect give a decreasing zonal 
index as a major sunspot maximum commences, and 
an increasing zonal index as a minor sunspot maxi- 
mum commences. This double sunspot cycle of pressure 
rise in the higher latitudes is confirmed by Clayton 
[5], and by Wexler (unpublished manuscript) from the 
Weather Bureau Northern Hemisphere historical maps. 
Both of these investigations indicate, on alternating 
successive minor and major sunspot maxima, anomalous 
zonal pressure rises which reach their peaks at about 
50°N and north of 60°N, respectively. Willett [28] has 
confirmed Hanzlik’s alternating high- and low-index 
patterns of pressure anomaly on successive sunspot 
maxima, and has found further that the anomaly pat- 
terns of temperature and precipitation manifest cor- 
responding characteristics. In fact the contrasting 
anomaly trends of pressure, temperature, and rainfall 
going into successive sunspot maxima correspond in a 
small degree over both North America and northern 
Europe to the contrast between the Pleistocene glacial 
and the interglacial pattern of climate. The occurrence 
of the high- versus low-index pattern contrast in con- 
nection with the double sunspot cycle is particularly 
suggestive of a primary solar role in this basic change 
of the general circulation pattern. 
4. Baur [3] has produced some impressive statistical 
evidence, from temperature records of 160 years in the 
northeastern United States and of 180 years in north- 
central Europe, that the occurrence of severe winters in 
both localities shows a marked preference for certain 
phases of the sunspot cycle, notably just preceding and 
shortly following the sunspot maximum. According to 
Baur the years of sunspot minimum and maximum are 
times of the least probable occurrence of a severe winter 
in these localities. Other miscellaneous relationships of 
387 
this type have been found by a number of investiga- 
tors for specific localities, but they contribute little to 
any improved understanding of the physical control 
of the secular weather fluctuations. However, it cer- 
tainly can be stated that the solar factor is the one 
which is usually implicated in most of the secular 
fluctuations of climate. 
Anomalous (Weekly, Monthly, or Seasonal) Fluctua- 
tions of the World Weather Pattern. The week-to- 
week and month-to-month anomalous fluctuations of 
the general circulation pattern manifest quite clearly 
essentially the same type of high- versus low-index — 
contrast that is evidenced by the secular, postglacial, 
and glacial-interglacial fluctuations. In fact, it is pri- 
marily from these relatively short-period fluctuations 
that the index types were recognized, and their essential 
characteristics identified. The recognition of essentially 
identical characteristics in the longer-period anomalous 
fluctuations of the general circulation followed. Con- 
sequently the question naturally arises as to the extent 
to which variable solar activity, for which there is so 
much evidence as the controlling factor in the longer 
period fluctuations, also exerts primary control on the 
anomalous fluctuations. This question is particularly 
pertinent because the major single or double sunspot 
cycle is very long in comparison to the weekly, monthly, 
and seasonal anomalous fluctuations. There are a num- 
ber of observational and deduced facts which have a 
direct bearing on the probability of such solar control, 
notably as follows: 
1. Besides the longer periods of variable solar activity 
as evidenced by the so-called eleven-year sunspot cycle 
and multiples thereof, the sun is almost continuously 
undergoing a great variety of short-period sudden dis- 
turbances and almost eruptive outbursts, as evidenced 
by faculae, flocculi, flares, prominences, etc., and by a 
two or three fold or larger variation of sunspot numbers 
from week to week and month to month (see pp. 379- 
381). Hence there occur outbursts of solar activity of 
variable frequency and intensity corresponding to the 
large-scale variable weather activity. Maris [14], Haur- 
witz [10], and others have indicated that the sudden 
emission of short-wave radiation which apparently ac- 
companies this eruptive activity of the sun is capable 
of producing considerable heating of the higher atmos- 
phere in only a few hours, and thus leads indirectly 
to substantial poleward displacement of atmosphere in 
the higher levels, that is, to a rise of sea-level pressure 
poleward from the latitudinal zone of maximum heat- 
ing. This reasoning suggests one possibility of a mech- 
anism by which sudden solar outbursts can change the 
index character (zonal pressure distribution) of the 
general circulation. 
2. As mentioned earlier, Willett’s results [26, 27, 28] 
may be interpreted as an indication of the existence of 
some primary external control of the anomalous fluctua- 
tions of the general circulation, for example, variable 
solar activity. To test this hypothesis statistically, 
Willett [28] correlated daily and five-day mean values 
of a number of indices of solar activity with correspond- 
ing indices of the general circulation, but no significant 
