228 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 9 



Solberg, 1922) and others; in an idealized schematic form, it is repre- 

 sented in figures 5 and 6, although of course actual cyclones usually 

 depart more or less from the ideal. Much yet remains to be learned, 

 however, about the detailed structure and the dynamical mechanism 

 of the cyclone, concerning which several different theories exist. 



Thus, it is not the cyclones and anticyclones as such that are im- 

 portant in determining the weather, but rather the interactions be- 

 tween the various moving air masses that are involved in the systems 



Januari/_^2, /936 - S /FM 



2 /?M. pos/f/'or? ofco/c/ fronf 



Figure 3. — Synoptic map of easteru United States at 8 p. m., 75 meridian time, January 

 22, 1936. The heavy solid line shows the boundary or "front" of advancing cold air, 

 just before it reached Washinston and produced the eflEects shown in figure 2. Arrows 

 fly with the wind, and the number of barbs indicates the wind strength ; the number 

 to the right of each station is the Fahrenheit temperature ; the number to the left or 

 below is the net change in the barometer (in hundredths of an inch) during the pre- 

 ceding 3 hours, and the accompanying symbol shows the character of the barograph 

 trace during that interval. Note the comparative uniformity in temperature over large 

 areas ahead of the front, and the abrupt decrease at and behind the front ; note also 

 the abrupt change in the barometric tendencies at the front. See also figure 4. 



