20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. Ill 



Interstation correlations. — Table 9 shows the trend coefficients 

 and ratios of opposed trends between Chacon, the nearest station to 

 Hohnan Pass, and six other stations for eight selected time intervals. 

 These intervals were chosen on the basis of their possible influence on 

 tree growth. On the whole, the correlations show a remarkable con- 

 sistency. Those comparisons which do not include part or all of 

 the summer rainfall are commonly higher than those which do. 

 Furthermore, the longer the interval under comparison is, the poorer 

 the correlation in general. Black Lake, the nearest to Chacon in 

 distance as well as elevation, does not have the best correlation with 

 Chacon. Las Vegas has the greatest similarity, a station farther 

 away, 2,100 feet lower, and out beyond the foot of the main range 

 of mountains. Santa Fe rainfall correlates with that of Chacon to 

 a degree equal to the correlation between Black Lake and Chacon. 

 Even Albuquerque is httle less in degree of similarity. The best 

 correlations are for the March-April intervals with Black Lake and 

 Albuquerque which show ratios of opposite trends with respect to 

 Chacon of 0.12 and 0.09. 



It is scarcely necessary here to do more than refer briefly to the 

 many observations of difi:'erences in rainfall at gauges spaced rather 

 closely together. For instance. Stout ® records a study of July 1948 

 rainfall on a plot centering at El Paso, 111. Two stations, 10 miles 

 apart, had 10.44 and 5.93 inches of rainfall. Two other stations, 3 

 miles apart, showed a difference of yy percent. Localization of single 

 storms is on occasion even more pronounced. On June 30, 1947, near 

 Lubbock, Tex., 4 to 5 inches of rain fell in a belt about 2 miles wide, 

 whereas none fell 2 miles to the west and 0.26 inches 8 miles to the 

 east. Of course, this may be unusual, but at least it is more or less 

 typical of extreme forest-border conditions. 



Furthermore, it must be remembered in comparing tree growth with 

 the rainfall of a station that, as pointed out by Landsberg,^ a rain 

 gauge samples but does not measure rainfall and therefore "the areal 

 significance of precipitation amounts caught at a station is very re- 

 stricted. . . ." These characteristics of rainfall must be duly weighed 

 when the growth of selected trees is compared with the record of a 

 station some miles distant. The trees may respond to the rainfall 

 they themselves receive but differ somewhat from that received by 

 the weather station. 



8 Weatherwise, vol. i, pp. 11 2- 113, 1948. 



" Landsberg, H., Critique of certain climatological procedures, Bull. Amer. 

 Meteor. Soc, vol. 28, pp. 187-191, 1947. 



