METEOROLOGY 



SYMPOSIUM ON GENERAL METEOROLOGY OF THE 

 TROPICAL PACIFIC 



SOLAR ACTIVITY AND AIR-PRESSURE FLUCTUATIONS OVER 

 THE SOUTH PACIFIC OCEAN 



By H. P. Berlage, Meteorological and Geophysical Service, Indonesia 



The existence of an approximate three-year oscillation in the weather 

 elements of the South Pacific and Indian Oceans is perhaps most clearly 

 demonstrated by a graphical representation of the deviations from 

 normal of the six-monthly overlapping means of air-pressure in the 

 tropical low extending from South India to North Australia. Let us 

 take as such the Batavia air-pressure curve (Fig. 1). 



In previous publications I have tried to establish a theory of the 

 successive strengthening and weakening of the air and water circulation 

 in the South Pacific Ocean, which would explain the long-period os- 

 cillations considered here. I was led to this theory by three empirical 

 facts — 



(1) Temperature in our region fluctuates with air-pressure in parallel 



waves, however, showing a phase lag of seven months. 



(2) Air-pressure in the permanent high-pressure region of the South 



Pacific Ocean centred at Easter Island and air-pressure in the 

 region considered here oscillate in balance. If air-pressure is 

 above normal in one region it is below normal in the other 

 (Sir G. Walker). 



(3) Low sea-surface temperatures in our region cause air-pressure to 



rise, high sea-surface temperatures cause air-pressure to fall. 



The normal cycle which occurs is probably as follows : if air-pressure 

 is abnormally high in the region Bombay-Darwin, it is abnormally low 

 in the sub-tropic high of Easter Island. Consequently, the atmospheric 

 circulation round this high is weakened. This causes the water circu- 

 lation to be weakened also. The Humboldt current is weakened. Less 

 cold water is driven northward along the west coast of South America. 

 The south equatorial current is weaker and warmer than usual. 

 Temperature in the seas of our region rises. Consequently air-pressure 

 is lowered. Hence when air-pressure is abnormally low in the region 

 Bomba3'-Darwin it is abnormally high in the sub-tropic high of Easter 

 Island. So the balance has swung from one side to the other, and after 

 another turn the cycle is closed. 



Theory proves that if the phase-lag between temperature deviations 

 and air-pressure deviations is seven months the period of the oscillation 

 becomes four times seven, or twenty-eight months — that is, 2-3 years. 



Now, this oscillation would experience the damping of every natural 

 oscillation if it were not sustained by the continuous in-flow of energy 

 from the sun. We may therefore expect that such oscillations as the 

 air-pressure fluctuations at Batavia, here exhibited, will show the influence 



