122 



N CLIMATOLOGY 



4.3.4. Continental Cross Sections 



The vertical profile data obtained for the stations of figure 4.15 provide 

 a means to construct A'^o cross sections traversing varied climatic zones 

 and geographic regions. 



The first cross section of this series, figure 4.26, is taken along the 

 Pacific coast of central North America from Canada to Mexico. Intru- 

 sion of polar air at the northern end of the wintertime cross section is 

 responsible for the relatively flat N gradient over Tatoosh. The 320 

 A^'o-isopleth covering most of the coast southward from Tatoosh shows the 

 uniform modifying influence of the ocean which, at this time of year, is 

 considerably warmer than the continent. Over southern California the 

 low at 500 m results from the drying-out effects of the Pacific high inver- 

 sion. On the summer cross section moderate A'"o-values typify the coast. 

 The minimum at Oakland stems perhaps from the upwelling of relatively 

 cool ocean waters off the California coast. Striking evidence of the 

 Pacific inversion is apparent from the low at 1 km between Oakland and 

 San Diego that results from significant decreases in the vapor pressure 

 term contribution to N within the dry subsiding air aloft. 



SAN TTI 

 2 



DISTANCE (KmxIO') 



Figure 4.26. North-south No cross section along the western coast of the United States. 



