8 4 



DYNAMIC METEOROLOGY AND HYDROGRAPHY. 



Simultaneous ascents from a system of stations for aeronautical meteorology 

 may therefore be organized, and the problem will present itself, how to use the 

 results of these ascents for the daily forecasts of the weather. The meteorologist 



at each station must therefore be 

 able, as soon as possible, to send 

 oft* a telegram giving the main re- 

 sult of his ascent. We shall here 

 take under consideration the pre- 

 paratory work for sending this tele- 

 gram as far as the hydrostatic state 

 of the atmosphere above the sta- 

 tion is concerned. The further 

 work at the central bureau after 

 the reception of the telegrams will 

 be discussed in the next chapter. 



The hydrostatic state of the at- 

 mosphere above a station is given 

 if we know the height above sea- 

 level of the standard isobaric sur- 

 faces. To enable the central 

 bureau to find these heights it will 

 be sufficient if the telegram con- 

 tain (i) the height of the lowest 

 standard isobaric surface; (2) the 

 average virtual temperature of the 

 standard isobaric sheets. 



We have thus to show what 

 the meteorologist at the station has to do from the moment he receives the mete- 

 orogram representing the results of the ascent on his table, in order to find the re- 

 sults (1) and (2) to be telegraphed. 



Discussions of instrumental technics will not be taken up in this treatise. But 

 it is important to remind the reader of the existence of two kinds of registering 

 meteorographs. The first, which is most commonly used, contains a clock, and all 

 the meteorological elements are registered as functions of the time. The second 

 contains no clock. The barometer produces the motion of the paper on which the 

 curves for the other meteorological elements are thus registered as functions of the 

 atmospheric pressure. We shall show how to interpret a meteorogram obtained by 

 each of these two kinds of instruments. 



(A) Meteorological elements registered as a function of time. Fig. 10 

 represents a meteorogram obtained by a kite flight from Tegel at Berlin, August 

 28, 1901.* The circle-arcs are coordinate curves of equal time. The curve in the 



Time 

 Fig. 10." Meteorogram, Berlin, August 28, 1901 



* R. Assmann und A. Berson : Ergebnisse der Arbeiten am Aeronautischen Observatorium 1900-1901, p. 

 259. The figure is changed, in as much as the coordinate curves on the barogram are drawn form-bars instead of 

 for millimeters of mercury. 



