98 



N CLIMATOLOGY 



rapidly with respect to horizontal distance. As a further practical con- 

 sequence, one notes the remarkable similarity between the A^'o contours 

 of figures 4.4 and 4.7, even though the latter contours were derived from 

 only two-thirds of the original data. This indicates that any desired level 

 of accuracy may be maintained with fewer stations (and less expense) by 

 the use of No. 



Table 4.2. Deviations of estimated 8-year means of Ns {calculated from contour charts) 

 from actual 8-year means selected at random from 20 Weather Bureau stations 



Test station 



Sacramento, Calif.. 



Portland, Oreg 



San Diego, Calif... 



Mobile, Ala 



Fresno, Calif 



Boston, Mass 



Grand Rapids, Mich. 



Columbia, Mo 



Minneapolis, Minn... 

 Cincinnati, Ohio 



Des Moines, Iowa 



Pendleton, Oreg 



Billings, Mont 



Burns, Oreg 



Salt Lake City, Utah. 



Reno, Nev 



Pocatello, Idaho 



Denver, Colo 



Colorado Springs, Colo. 

 Flagstaff, Ariz 



Root mean square deviation. 



Height 



meters 

 7 

 8 

 11 

 66 

 86 



210 

 239 

 255 

 271 



294 



455 



1,088 



1,262 



1,288 



1.340 

 1,355 

 1,625 

 1.882 

 2,131 



February 1400 



Actual 



8-yr 

 mean 

 value 



of JV, 



N units 

 315.6 

 316.2 

 314.2 

 326.6 

 310.6 



308.6 

 304.4 

 300.8 

 301.1 

 302.5 



300.9 

 295.9 

 269.3 

 268.1 

 266.3 



259.6 

 264.7 

 244.9 

 237.1 

 237.8 



Deviation* 



map 



N tinits 

 7.6 

 4.2 

 -5.8 

 6.6 

 9.6 



-6.4 



0.4 



-.2 



.1 



-.5 



3.9 



1.9 



-2.3 



-23.9 



1.3 



-20.4 

 -2.3 

 -8.1 

 -15.9 

 -26.2 



10.7 



No 

 map 



A'^ units 

 0.8 

 -.5 

 -2.4 

 4.8 

 3.4 



-0.5 



-5.9 



2.4 



0.6 



.7 



2.3 



0.4 



.1 



-3.2 



-0.8 



-6.8 



0.4 



.7 



-.6 



2.3 



2.7 



August 0200 



Actual 

 8-yr 

 mean 

 value 

 of iV, 



A'' units 

 329.6 

 337.7 

 348.1 

 376.0 

 326.2 



347.5 

 340.5 

 348.7 

 338.5 

 344.1 



343.1 

 300.9 

 285.6 

 271.3 

 279.5 



277.6 

 269.7 

 276.6 

 272.4 

 261.4 



Deviation 



Ns 

 map 



A'' units 

 1.0 

 19.7 

 16.1 

 6.0 

 5.2 



-7.5 

 -1.5 

 -2.3 

 -0.5 

 -2.9 



-1.9 



2.9 



5.6 



-15.7 



8.5 



-29.4 

 -3.3 

 -1.4 

 -6.6 



-36.6 



13.0 



ATo 

 map 



A^ units 

 1.8 

 6.0 

 3.5 

 0.6 

 4.2 



-0.4 



.1 



-2.5 



2.7 



-2.8 



-0.1 

 -3.1 



1.2 

 -4.4 



4.4 



1.6 



0.0 



.3 



1.1 



-2.2 



2.7 



♦Deviation equals the actual long-term mean minus the value obtained from map contours. 



4.2.3. Worldwide Values of N„ 



Mean values of No were calculated at each of the 306 selected stations 

 and charts were prepared for each month of the year. The charts for 

 February and August are given on figures 4.8 and 4.9. It is seen that 

 the values of No for sea-level stations vary from 390 in the maritime 

 tropical areas to 290 in the deserts and high plateaus. The interiors of 

 continents and mountain chains in middle latitudes are reflected by low 

 values as compared to those of coastal areas. Further, such pronounced 

 climatic details as the Indian monsoon and the effects of coastal mountain 

 ranges blocking prevailing winds and producing rain shadows are indi- 

 cated by these No contours. Regional climatological data of No for the 

 United States are given in chapter 9. 



