Climate, Snow Cover, Microclimate, and Hydrology 35 



leys so that hilltops a few hundred meters in elevation may be warmer 

 than the valleys below. Less frequently, the front retreats poleward and 

 thus allows the entire area to be warmed by land winds. An analysis of 

 the Arctic Front by Streten (1974), using very high resolution radiometer 

 (VHRR) imagery from the NOAA-2 satellite, showed considerable varia- 

 bility in cloudiness associated with the frontal zone. It also confirmed the 

 front's northward advance from early to midsummer, as determined by 

 Barry (1967), and its southward retreat by August. By October, the circu- 

 lation regime has reverted back to its winter mode as the arctic inversion 

 redevelops over the snow-covered land. 



Annual precipitation on the Arctic Slope is light, although data are 

 inadequate to describe regional trends in any detail. Clebsch and Shanks 

 (1968) found that amounts in July and August 1956 were 50% greater at 

 stations located 2, 15 and 55 km inland than at the first-order weather 

 station at Barrow. Theoretically, easterly airflow along the arctic coast 

 should tend to produce divergence and suppression of precipitation over 

 the coastal strip (Bryson and Kuhn 1961), although this effect is less in 

 higher latitudes than in low latitudes. At the present time, data on sur- 

 face and upper winds and on precipitation amounts are inadequate to 

 test this hypothesis. Total precipitation is undoubtedly higher to the 

 south and in the Brooks Range, with an estimated 500 mm falling on the 

 upper McCall Glacier at 2275 m (Wendler et al. 1974). Kilday (1974) indi- 

 cated that annual totals exceed 500 mm over most of the Brooks Range 

 and are 1000 mm in the wettest eastern section. In the coastal tundra at 

 Barrow, rainfall intensity is low, with frequent drizzle and light snow 

 falling during May and June from the coastal stratus clouds. Freezing 

 rain also occurs during this season as well as during the autumn transi- 

 tion. The maximum 6-hour total rainfall recorded is 15 mm (Miller 

 1963); a 24-hour snowfall of 38 cm has been recorded in October. 



Interannual Variability and the 

 Representativeness of the Biome Years 



The interannual variability, expressed by the standard deviation of 

 mean monthly temperature, is approximately 3 °C during the winter 

 months, October through February, but declines to just over 1 °C in July 

 and August. The winter variability is associated with shifts in the Arctic 

 Frontal zone. The extreme variations from the 1924-73 mean occurred in 

 January 1930, with a deviation of + 11.4°C, and January 1925, with a 

 deviation of -8.1°C. During the summer months there is less departure 

 from the long-term average; the extremes are -i-4.9°C in August 1954 

 and -3.6°C in August 1956. 



Another approach to calculating interannual variability using cumu- 



