THE HYDROSTATIC PROBLEM FOR THE ATMOSPHERE. 



85 



fi~essure 

 rn-tars 



600 



Average 



virtual 



temperature 



ofstrm/Uzrd 



sheets . 



wo 



300 



IOOO 



-10 -10 



Terrmemtwe C 

 Fig. 11. Virtual-temperature diagram, Ber- 

 lin, Augu6t 28, 1901. 



first section of the diagram represents the variation of temperature, that in the 

 second the variation of pressure, and that in the third the variation of humidity, 

 all as functions of time. If there are instrumental errors, the corrections are sup- 

 posed to be introduced graphically upon the 

 diagram, the curves of fig. 10 being such cor- 

 rected curves. 



In order to derive from this meteorogram the 

 curve of virtual temperature, we have to deter- 

 mine sets of corresponding values of pressure, 

 temperature, and humidity. To do this most 

 conveniently, we start with the points where the 

 barometer-curve cuts the lines for 1000, 950? 

 900, . . . m-bars. Using a pair of compasses, 800 

 we mark the corresponding points on the ther- 

 mometer and hygrometer curves. Reading the 

 temperature corresponding to the marked points 

 on the temperature curve, we draw the curve of 

 true temperature in the diagram (fig. 11). Then, 

 using the virtual-temperature divisions, we draw 

 the curve of virtual temperature for saturated 

 air. Finally, using the humidities correspond- 

 ing to the marked points on the hygrometer 

 curve of fig. 10 we draw in the diagram fig. 11 the curve of virtual temperature 

 between the two other curves. The vertical segments of the line giving the aver- 

 age virtual temperatures of the standard sheets are drawn, as well as the segment 

 (invisible on account of its shortness), giving the average virtual temperature 

 (+ 16) of the air between the lowest standard surface and the earth. By means of 

 this temperature and the pressure 1001.2 at the station, we find the height 10 

 dynamic meters of the 1000 m-bars surface above the earth, using tables iim and 

 12 m as described previously. Adding the height (39) of the station, we get the 

 height (49) of this standard surface above sea-level. The figures to be telegraphed 

 are then 

 (a) 49, 12, 4, '1, -5 



the first, 49, being the height of the 1000 m-bars surface, and the tour other num- 

 bers the virtual temperature of the standard sheets. 



The interval of time from the moment the meteorologist has obtained the 

 meteorogram (fig. 10) on his desk until he has found the figures () to be tele- 

 graphed ought not to exceed ten to fifteen minutes. 



(B) Meteorological elements registered as function of pressure. The curve 

 to the left in fig. 12 is recorded by Professor Assmann's baro-thermograph* at an 

 ascent with a registering balloon on July 4, 1901.^ 



* R. Assmann und A. Berson, I. c, p. 42. 



fR. Assmann und A. Berson, /. e,, p. 209. The original figure is changed by introduction of coordinate curves 

 representing the pressure in m-bars, and by change of positive direction on the axis of temperatures. 



