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ANNUAL REPORT SMITHSONIAN INSTITUTION, 1939 



Figure 1. — Typical synoptic weather map, showing extratropical cyclone and anticyclone. 

 The attendant wind circulations are shown by the arrows, which fly with the wind ; 

 isobars (solid lines) connect stations that have equal barometric pressures ; isotherms 

 (dotted lines) connect stations that have equal temperatures ; shaded circles indicate 

 clouded skies, R, rain, 8, snow, and cross-hatched areas are regions over which precipi- 

 tation has fallen during the preceding 24 hours. CW indicates cold wave warning ; 

 and the heav^y dotted line encloses a region of marked temperature fall during the pre- 

 ceding 24 hours. (Compare with examples of analyzed maps, figure 3 and plate 3, 

 figures 1 and 2.) 



of meteorology explicitly on principles of physics ; even an empirical 

 understanding of the storms and irregular weather changes of temp- 

 erate regions was slow to develop. The standard method of repre- 

 senting the weather conditions over a given region at any particular 

 time is by means of the familiar synoptic map which is prepared 

 from observations taken simultaneously at a network of stations dis- 

 tributed over the region, and which shows the geographic distribu- 

 tion of the meteorological elements (fig. 1). The synoptic map was 

 introduced into meteorology early in the nineteenth century by 

 Brandes and Eedfield; and after the invention of the electric tele- 

 graph it came into daily use, for delineating and forecasting weather 

 conditions, among the national meteorological services that were 

 established in the principal countries of the world soon after daily 

 telegraphic charts were first regularly issued in France in 1863. The 

 daily synoptic map has been a powerful aid to meteorological in- 

 vestigation, while weather forecasting from these maps has rendered 

 invaluable service ever since its inception ; but even long after the de- 

 velopment of theoretical meteorology on an exact physical basis had 



