Air temperature differences between southwest and northeast exposures were small 

 and somewhat inconsistent. Maximum temperatures averaged 0.4° F. (o = 1.1)-^ and 1.4° F. 

 (0 = 1.0) higher on the southwest than on the northeast exposures at the 7,100- and 

 8,200-foot elevations, respectively. Minimum temperatures averaged 0.8° F. (o = 1,3) 

 lower on the southwest than on the northeast exposure at an elevation of 7,100 feet, 

 but were 0.4° F. {o = 1.4) lower on the northeast than on the southwest exposure at an 

 elevation of 8,200 feet. The reason for this inconsistency is unknown. 



Differences in air temperature extremes were much greater between elevations than 

 between exposures. As expected, both maximum and minimum temperatures at 7,100 feet 

 were higher than those at 8,200 feet. The difference in maximum temperatures was 5.5° F. 

 (o = 1.6) on southwest exposures, and 6.4° F. (o = 1.6) on northeast exposures. Mini- 

 mum temperatures on both exposures were approximately 2.5° F. (o = 1.8) higher at the 

 lower stations than at the upper stations. 



Although the duration of maximum temperatures did not differ between exposures , 

 that of minimum temperatures did. Minimum temperatures lasted 0.3 hour (o = l.l) 

 longer on northeast than on the southwest exposures at the lower stations and 1.0 hour 

 = 1.2) longer at the upper stations. 



Both maximum and minimum temperatures lasted longer at the upper stations than at 

 the lower stations. This difference was about 0.3 hour (o = 1.0) for maximum tempera- 

 tures on both exposures and for minimum temperatures, 1.5 hours - 1.3) on southwest 

 exposures and 2.5 hours (o = 1.7) on northeast exposures. 



Thus, not only did the stations at 8,200 feet have lower minimum temperatures than 

 the stations at 7,100 feet but these minimums lasted much longer as well. Although con- 

 spicuously higher maximum temperatures were reached at the 7,100-foot stations, they 

 did not last quite as long as those at the upper stations. 



Soil Temperature 



Maximum temperatures of the shaded soil surface closely parallel maximum air tem- 

 peratures, but are a few degrees higher (fig. 5). The monthly means of these maximum 

 temperatures are 3° to 8° F. above those taken in the standard Weather Bureau shelter 

 (tables 4 and 6). 



However, maximum surface temperatures of the soil taken in full sunlight are much 

 greater than maximum air temperatures. Monthly means were 23° to 53° F. higher (tables 

 4 and 7). The greatest difference occurred in late July when the weekly average of 

 maximum soil surface temperatures in the sun reached 135° F. (fig. 5). 



Over the 5-year period, the absolute maximum temperature of the unshaded soil sur- 

 face was 152° F. This was 66° F. higher than the highest air temperature recorded. 

 Temperatures above 135° F. were recorded at one time or another throughout July and 

 August (fig. 5). 



Minimum temperatures on the soil surface did not differ nearly as much from air 

 temperatures as the maximums. Monthly means of minimum temperatures of the soil surface 

 taken in the shade were about the same as those of air temperature and those taken on 

 the unshaded soil surface were only 4° to 10° F. lower than minimum air temperatures 

 (tables 4, 6, and 7). Therefore, minimum temperatures of the unshaded surface were 



■^The standard deviation (a) characterizes the dispersion about the mean of dif- 

 ferences in readings between stations. 



10 



