SUMMARYIn order to form more definite ideas regarding t h e oscillations named the North Atlantic, t h e North Pacific and t h e Southern, series of figures have been derived to express the variations of each, a n d from these have been obtained their relations with pressure, temperature, and rainfall over wide regions as well as the relations of t h e three oscillations with each other a n d with sunspots.T h e southern oscillation in t h e southern winter i s found to be extremely persistent, and its departure h a s a C.C. of '84 with t h a t of the following summer, thus providing a basis for foreshadowing seasonal conditions. T h e effects of Antarctic conditions and of Ocean temperatures a r e considered, but a satisfactory physical basis for t h e oscillations h a s still to be found. DISCUSSION Dr. G. C. SIMPSON remarked that Sir Gilbert Walker had ascribed the low temperature to the ice in Baffin Bay. H e would like himself to suggest that the ice had little effect on the temperature of the air, but that in the years of much ice there were many Nly. winds, it being the Nly. winds which brought down the ice. These Nly. winds would be cold quite irrespective of the ice and they owed their temperature to their origin and not to the ice in Baffin Bay. In the same way, he did not think that the high temperatures in Scandinavia were due to the warm sea water brought by SW. winds. The relatively high temperature in Scandinavia was due to a n increased frequency of SW. winds and had little to do with the temperature of the sea water.Sir Gilbert Walker had given the impression that the origin of the southern oscillation was variation in solar radiation. If this were true, why should not the Same case apply to the North Atlantic oscillation and the South Pacific oscillation? If all these oscillations are due to variations of solar radiation there should be a close correlation between them, but he understood that Sir Gilbert had not been able to find any clear correlation between the three oscillations. His own opinion was that a real and permanent increase of solar radiation would not necessarily result in intensifying the differences of temperature or differences of pressure between sea and land, but would rather result in a n increase of temperature throughout the whole of each zone of latitude.Dr. C. E. P. BROOKS said we owe Sir Gilbert Walker our thanks for this comprehensive discussion of the relations between the weather of distant regions. World meteorology is a complex problem, into which Sir Gilbert introduces the simplifying idea that it is dominated by three great meteorological circulations, in the North Atlantic, the North Pacific, and a third, termed the Southern Oscillation, which really covers the greater part of the world. The two northern ones are cam-
SUMMARY.Correlation coefficients a r e given with pressure, temperature, rain, ice a n d wind, a n d it i s shown (a) t h a t t h e Nile flood takes p a r t in t h e southern oscillation as a member of the first group, (b) t h a t equatorial temperatures are in inverse relation to the Nile flood, a n d (c) t h a t the winter North Atlantic circulation varies inversely with the preceding Nile flood. St. Helena pressure h a s no contemporary relationship with the Nile flood. A formula is derived for prediction on June I with a joint coefficient of 0.72. DISCUSSION.The PRESIDENT (Sir Gilbert Walker) remarlced that the similarity of the variations of the Nile Roods to those of the Indian monsoon rainfall had long been known; but Mr. Bliss had shown that the Nile is an even better representation of the southern oscillation in world weather -the oscillation between the Pacific and the Indian Oceans. Abyssinia aIso resembles India and Japan in that the effect of its rainfall as a world factor is greater than that of the pressure a t sea level in the region of rainfall. Cairo, in summer, tends to vary with the Azores, and oppositely to Iceland, in the following winter; and a high Nile is thus followed by a feeble Atlantic circulation. The contribution of Mr. Bliss was important in linking up the winters of N.W. Europe with the oscillations of the southern hemisphere.[I should have stated that the association of abundant India monsoon rainfall with weak contemporary Atlantic trade winds and low temperature in Germany in the succeeding winter was pointed out by W. Georgii in the Annalen d . Hydrographie u. Alaritimen hleteorologie, January, 1923.1'Mr. D. BRUNT suggested that as Mr. Bliss had investigated a very large number of records, and had finally selected the three which proved most favourable for his purpose, it would have been of interest to see whether the coefficients of correlation which he put forward could be regarded as stable. T h e investigation would have gained in interest if Mr. Bliss had evaluated the coefficients of correlation for the years 1882-1g15, and had then used his formula to forecast the Nile flood for the next ten years, giving a comparison with the actual observations. Mr. Brunt also pointed out that he had compared Mr. Bliss's figures for Nile flood 1869 to 1905 with the annual mean temperatures a t Stockholm during those years, and found high Nile floods and high temperatures a t Stockholm in the years 1878, 1887, 1890, 1894 and rgo3, and low values for both these factors in the years 1881, 1888, 1893 and 1902. I t therefore appears that there should be a positive correlation between 1 Note added 1st December, 1926.
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