72 



DYNAMIC METEOROLOGY AND HYDROGRAPHY. 



Example 2. Observed height (meters), temperature (C), and humidity (per cent). 

 (Table K) . The observed geometric height (column 2) is changed into dynamic height (column 5 ) . 

 From these heights and the observed temperatures the curve of true temperature is drawn (curve to 

 the left in fig. 6). By means of table S m the curve of virtual temperature for saturated air is drawn 

 (curve to the right). Using the percentages of humidity (column 4) the curve of virtual tempera- 

 ture is drawn between the two others. 



Eaght 

 dyruTn&ers 



10000 



9000 



8000 



70OO 



eooo 



5000 



woo 



3000 



WOO 



100O 



Pressure 

 rrt-bars 



300 



wo 



$00 



GOO 



700 



800 



900 



1000 



SW 



10 20 



30 



30 20 10 



Temperature C. 

 Fig. 6. Virtual-temperature diagram, with dynamic height as ordinate 



The heavy horizontal lines represent the standard isobaric surfaces, successively drawn according 

 to the estimated thickness of the standard sheets (section 52). The vertical segments of line give the 

 average virtual temperatures of the sheets (column 7) by which the more accurate thickness of the 

 sheets (column 8) and the heights of the surfaces (column 9) are determined. 



The solution of the inverse problem, the determination of the pressure at a given height (columns 

 12 to 19) is found mainly by the same method as in the preceding example, except that one operation 

 less is necessary to find the required virtual temperatures (column 15). Not to complicate the figure, 

 the vertical segments giving these temperatures are not drawn. 



