METEOROLOGY m 



ological Committee," which latter is the representative of the numerous meteorological 

 congresses and conferences that have been held since 1872. This Codex is a very convenient 

 and useful codification of the numerous conclusions expressed by European meteorologists 

 at these meetings. At Paris in 1896 an independent organisation was recognised, for purposes 

 of collaboration, namely the "International Commission for Scientific Balloon Ascensions." 

 This Commission held meetings in 1898, 1903, 1904, 1906, 1909 and 1912, its first report 

 to the International Committee being made in 1906. The work of the International Com- 

 mission for Scientific Ballooning has been much promoted by the discussions at Milan 

 (1906), Monaco (1909), and Vienna (1912). 



The study of upper strata in England has been greatly helped by the freedom with which 

 W. H. Dines of Pyrton Hill, Wallington, and E. J. P. Cave, of Ditcham Park, Petersfield, 

 have published their laborious observations with kites and balloons. Mr. Cave's work with 

 pilot balloons can easily be repeated in any portion of the globe. 



The observations with kites and balloons at the Royal Aeronautical Observatory at 

 Lindenberg, under Assmann, have been continued steadily, and among the results sum- 

 marised by Fischli we may mention that he finds the directions of the wind at various altitudes 

 indicate changes in the weather very much as do the passage of areas of maximum and 

 minimum pressure, or the so-called highs and lows, at the earth's surface. The atmospheric 

 layers in which inversions take place vary with the season of the year and with the direction 

 of the wind, and especially with the condensation of aqueous vapour. The changes of wind 

 direction at different levels are one cause of variations from the regular diurnal periods of 

 temperature. The upper layer of inversion, or the so-called isothermal stratum, was attained 

 at an average height of a little over 12,000 metres in anticyclonic areas, while in cyclonic 

 areas it was a little over 10,000 during 1910; the mean temperatures were minus 91.2 C. at 

 the former altitude and minus 51.5 C. at the latter. 



In European regions the limits of upper inversion at which the temperature begins to 

 increase are higher in summer than in winter. The American observations by Rotch and 

 Blair also seem to show that the isothermal stratum is higher in summer than in winter, 

 which may be due to the greater dry ness of the American climate. In the United States 

 the limit is higher than in Central Europe, so far as the limited number of observations can 

 justify an average. The warm layer exists above the ocean as well as above the land. The 

 altitude of the layer over the North Sea is about the same as over Europe, whereas Hergesell 

 found it much higher, viz. 13,000 meters over the South Atlantic. The general law seems to 

 be that the upper inversion layer is lower near the poles and higher under the equator; a 

 similar law seems to hold good for each of the cloud formations. Assmann is probably cor- 

 rect in considering the isothermal layer as a feature of the general atmospheric circulation, 

 being the upper branch of the interchange of air going on between the equator and the poles, 

 but this is only a partial explanation of its o'rigin and temperature. In 1909 E. Gold of Lon- 

 don and W. J. Humphreys of Washington published quite independently their proofs that 

 the upper inversion must be due to the absorption, by the aqueous atmosphere, of heat 

 radiated from the earth and the ocean. The total quantity of aqueous vapour contained in 

 the atmosphere is sufficient to render the radiation from the atmosphere equivalent to that of 

 a surface of water, or an absolute perfect radiator, at the altitude of 4,000 metres; therefore 

 the effective surface of terrestrial radiation is at this altitude where the mean annual tempera- 

 ture is about 263 degrees absolute scale; so that the planet or combined earth and atmosphere 

 radiates like a black body at this altitude. ' The absorption of heat above 4,000 metres and 

 its penetration beyond, explain the existence and the temperature of the stratosphere, while 

 the changes in the quantity of aqueous vapour in the atmosphere explain the variations in 

 the altitude of this layer, which must be higher in the summer and higher in dry climates 

 but must surround the globe over continents and oceans and polar snows alike. 



Teisserenc de Bort in his memoir of 1909 states as the result of his investigation at Trappes 

 that the temperature of the thermal layer from 8 to 17 kilometres upward departs rarely 

 less than 2 degrees, or more than 10 degrees, and on the average only 6 degrees C., from the 

 temperature appropriate to adiabatic diminution. His balloon ascensions, some of which 

 attained 27 km., show that in most cases after penetrating through the thermal zone the 

 temperature returns to that which it had lower down when it entered the thermal zone. 

 The same results are given by observations in Lapland and in the Atlantic Ocean, except 

 only that the altitude of the stratosphere diminishes a few thousand metres as we pass from 

 the equator to the Arctic zone. There are apparently precise relations existing between 

 these altitudes and the lower meteorological conditions. The altitudes are in general higher 

 within areas of high pressure than in those of low pressure. The greatest altitude is on 

 that side of a high pressure area that is in advance of the low pressure. On the other hand 

 the altitude of the stratosphere is lowest in the rear of a low pressure area and especially low 

 in a trough of low pressure. jj..i. . -i.;> 



The important aeronautic expedition to Central East Africa led by Prof. Berson in 1908 

 attained the isothermal layer or upper inversion stratum at about 17,000 metres. At these 

 high altitudes Berson found a strong west wind, evidently a return current, that may possibly 

 prevail over large areas in equatorial regions, while an easterly wind prevails below. 



