ARCTIC ZONE 



Climatic conditions of the Arctic Zone are 

 unique and contrast sharply with conditions in 

 other zones. 



The effectiveness of the Brooks Range in 

 influencing the climate of the land area to the 

 north has not been definitely established, al- 

 though the Range is a topographic barrier. 



Variations in temperature here are confined 

 to narrower limits than in the Interior Basin. 

 Extremely low temperatures in this zone range 

 between — 45° and — 60° F. Seldom do maxi- 

 mum temperatures reach 80°F. Even during the 

 prolonged period of continual daylight, the sun's 

 rays reach the earth's surface at such low angles 

 that they cause little surface warming. 



Mean hourly windspeeds in summer aver- 

 age from 11 to 15 miles per hour. Maximum 

 summertime windspeed has reached 52 miles 

 per hour at Point Barrow. 



Average annual precipitation for this zone 

 is from 5 to 10 inches, although 16 inches occurs 

 near Cape Lisburne. Annual snowfall totals 

 average about 50 inches east of Cape Lisburne 

 and from the Arctic Coast to the Brooks Range. 

 Kotzebue experiences the warmest average tem- 

 peratures and consequently receives a smaller 

 ratio of snowfall to total precipitation than 

 the remaining portion of the zone. The low 

 moisture-carrying capacity of the colder air that 

 prevails over the area accounts for this zone's 

 having such light precipitation. 



The average freeze-free period contrasts 

 with that in other zones,- it ranges from 65 days 

 in the Shungnak area to just short of 90 days at 

 Kotzebue. The coastal area north of the Brooks 

 Range has minimum readings averaging near or 

 below freezing for all months of the year; vege- 

 tal growth is limited to those species that can 

 endure the vicissitudes of this rigorous climate. 



WEATHER FACTORS THAT AFFECT FIRE 

 BEHAVIOR AND CONTROL 



Weather conditions are highly important to 

 ignition and spread of wildfire. The amount and 

 frequency of precipitation, air temperature, air 

 moisture, and air movement combine to produce 



the dryness and consequently the flammability 

 of fuels. Other atmospheric conditions also 

 strongly influence behavior of a going fire. For 

 example, a thunderstorm not only starts light- 

 ning fires, but its presence may often cause er- 

 ratic winds that blow the fire out of control. 



To interpret the normal weather patterns at 

 various places and at different times of day, 

 month, and year, weather records from 18 sta- 

 tions have been analyzed for the period 1950- 

 58. 4 Observations taken from these 18 stations 

 sample the climates experienced in their respec- 

 tive climatic zones (fig. 20). The individual sta- 

 tions are widely separated and only represent 

 the heterogeneity of climes experienced in the 

 State. The recorded data show the normal con- 

 ditions that can be expected; however, local or 

 temporary weather situations are often abnor- 

 mally worse. 



PRECIPITATION 



Precipitation varies widely throughout the 

 State, but generally decreases from south to 

 north (figs. 26 and 27). Successive east-west 

 mountain ranges prevent moist maritime air 

 from reaching interior regions. 



Great variation in summer rainfall is indi- 

 cated by the records at representative weather 

 stations in the Interior Basin, West Central, and 

 Cook Inlet climatic divisions. (See table 1 and 

 figs. 21 through 25). 



The combination of time of year with 

 amount of precipitation that falls then is an im- 

 portant factor influencing fire behavior. The 

 length of time between summer rains has an 

 important bearing on the amount of growth and 

 the degree of curing in the herbaceous species; 

 duration of these periods likewise affects the 

 moisture content of dead material. Long periods 

 of dry weather hasten the curing date of herba- 

 ceous vegetation, and thus extend the period of 

 high flammability. 



Table 2 indicates distribution of rainfall 

 among the 4 summer months and the ratio of 

 this season's precipitation to the annual total. 



4 Summary of the analyses appears in the appendix and is 

 highlighted in this chapter. 



25 



