CORRELATION OF DISTRIBUTIONAL FEATURES. 521 



encountered in the Transition Zone. The moisture-temperature index 

 possesses almost as narrow an ampUtude as that characteristic of the 

 western section of the Northern Forest region. 



Alleghanian Zone (fig. 38). — The temperature conditions of this 

 zone, excepting the length of the frostless season, are very similar to 

 those of the Transition Zone, while the precipitation and other moisture 

 conditions are quite unlike. The frostless season ranges from a length 

 of 106 days to one of 211 days, extremes which lie well within those of 

 the Transition Zone. The amplitude and extremes in the number of 

 hot days and the number of cold days are very similar, while the 

 normal daily mean of the coldest 14 days of the year is somewhat 

 higher in its extremes, although very similar in its amplitude. 



In all of the precipitation and other moisture data the Alleghanian 

 Zone exhibits much narrower amplitudes than those of the Transition 

 Zone, because of the high values characteristic of the portions of the 

 latter zone which lie in the extreme Northwest. In nearly all cases 

 extremes for the Alleghanian Zone lie within those of the Transition 

 Zone, the exceptions being the number of days in the longest normal 

 rainy and dry periods in the frostless season. Owing to the winter 

 occurrence of rainfall in the Northwest, these features indicate more 

 moist conditions for the Alleghanian than for the Transition Zone. 

 The amplitude of sunshine duration for the Alleghanian Zone is much 

 less than that for the Transition, ranging from low values upward 

 through about one-third of the entire amplitude for the country. The 

 moisture-temperature index has a much wider amplitude in the former 

 than in the latter zone, slightly exceeding the amplitude for the eastern 

 section of the Northern Mesophytic Evergreen Forest. 



TCMPCRATURC 



Davs in Normal Frostless Season (F. S.> C 

 Hot Days. F. S. ■ 



Cold Oavs. F. S. I 



Phvsiolocical Summation. F. S. QI 



Normal Daily fMcAN. coldest 14 days op Year ■ 



Normal Daily Mean. Year C 



PR EC I station 



Normal Daily Mean. F. S. 

 Days in longest Normal Rainy Period. F. S. 

 Days in longest Normal Dry Period. F. S. 

 Mean Total, Year 



EVAf»ORATION 



Daily Mean, 1687-8. F. S. 



Moisture Ratios 

 Normal P/E. F. S. 

 Normal rr/C. F. S. 

 Normal P/E, Year 



Humidity 

 Normal Mean. F. S. I 



Sunshine 

 Normal Daily Duration. F. S. i J 



MOISTURE-TCMPCRATURC INDICES 



Normal P/E. x T. F. S., Physiological Method C 



Fig. 38. Climatic extremes for the Alleghanian Zone. 



