NO. 3 SOLAR RADIATION AND THE WEATHER CLAYTON 5 1 



I submit herewith a plot of the solar observations and of the daily means 

 of temperature in Buenos Aires during the interval covered by the forecasts 



(fig- 17). 



It will be seen that the solar observations are very much interrupted by 

 adverse atmospheric conditions, but notwithstanding this, it is evident that 

 every high value of solar radiation during the past summer has been followed 

 some three to four days later by high temperatures in Buenos Aires. Compare 

 the high solar values of December 4 to 7 with the high temperatures in Buenos 

 Aires from December 7 to lo, the high solar value of December 21 with the 

 temperature of December 25 to 26, the high value of January 3 with the tem- 

 perature of January 5 to 7, and the high values of January 18 with the temper- 

 atures of January 21 to 22. 



In February and March there was a series of more rapid and smaller oscil- 

 lations which were all reflected in changes of temperature in Buenos Aires, 

 as will be seen by comparing the two lower curves in the diagram. The solar 

 maxima marked c, d, e, f, g, and h, all show corresponding maxima of temper- 

 ature. On the 20th the rise was interfered with by local conditions. The 

 probable general course on that and two succeeding days is indicated by a 

 dotted line. As the temperature at Buenos Aires oscillates synchronously with 

 the temperature changes over all of Central Argentina, a plot of the mean 

 temperature of that region would not differ greatly from that of Buenos 

 Aires. 



The solar values are received on the day following the observations, so there 

 still remain two and one-half days of anticipation of the changes of weather 

 in Central Argentina. 



Perhaps more important than that of temperature is the aid given by solar 

 observations in anticipating rainfall. A dimunition of the temperature of the 

 air gives rise to rain by condensing the moisture of the air, while a rise of 

 temperature is generally attended by fine weather. Hence, since a decrease of 

 solar radiation is followed by a fall of temperature in Central Argentina 

 three to four days later, it is also followed by rain at about the same interval. 

 The decrease of solar radiation on December 5 to 6 was followed by rain in 

 eastern Argentina on the 9th to loth, and the marked decrease on December 7 

 to 8 was followed by general and heavy rain on December 11 to 12. After this 

 date the solar record was broken until January. There Was a marked decrease 

 of solar radiation between January 3 and 6, and this was followed by general 

 and heavy rains between January 7 and 10. The next marked solar decrease on 

 January 11 to 12 was followed by rains on the 15th to i6th and the marked 

 decrease between January 18 and 24 was followed by heavy rains between 

 January 23 and 26. In the same way the marked decreases on February 9 to 

 10, 14 to 15, 17 to 18, 25 to 26, were followed in each case by heavy rains 

 three to five days later. As the solar record is complete day by day from 

 February 6 to 19, this interval was selected for illustrating with maps the 

 areas of rain following decreases of solar radiation. Rainfall maps for each 

 day from February 17 to 21 are shown at the end of this paper. The maps in 

 each case are made for 8 A. M. of the date given on the chart and show the 

 rainfall for the preceding 24 hours. In the average, the rainfall follows the 

 solar decrease after about three days in southern Buenos Aires and the Pampa, 

 after about four days in northern Buenos Aires, Entre Rios, Santa Fe, Cordoba 

 and San Luis, and after about five days from Corrientes to Tucuman. 



