AVERAGE No STRUCTURE 



117 



Figure 4.21. Diurnal, seasonal, and vertical variation 0/ No for Washington, D.C. 



(DCA). 



The strong warm-season influx of tropical maritime air from the Gulf 

 of Mexico up the Mississippi Valley is spectacularly in evidence at 

 Columbia, Mo. (CBI), figure 4.25. The most significant feature of these 

 charts is the weak year-round diurnal range of 10 A^ units or less accom- 

 panied by a strong seasonal range of nearly 50 N units. 



In summary, it is seen that the west-coast stations display a rather 

 uniform low average value of A^o accompanied by small seasonal and 

 diurnal ranges. This is due to the continual onshore advection of cool 



