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Climate of the taiga ecosystemIntroductionThe distribution of climatic zones in Alaska is largely controlled by topography (Bowling 1979). Interior Alaska, bounded by the Brooks Range to the north and the Alaska Range to the south, experiences a strongly continental climate characterized by low annual precipitation, low humidity, low cloudiness, and large diurnal and annual temperature ranges (Haugen et al. 1982). The physical barrier created by the mountains creates a rain shadow, preventing the intrusion of maritime air masses except from the west, and also results in rapid warming in winter as "chinook" type winds flow down the north slope of the mountains. 
Midnight sun at summer solstice (June 21) at the arctic circle. Photo by Fred Hirschmann in the 1997 Alaska Weather Calendar. Air TemperatureAir temperature extremes range from -50o to +35o C. The mean annual temperature of -3.3o C at Fairbanks results in the formation of permanently frozen soils (permafrost) on north-facing slopes and poorly drained lowlands. July is the warmest month with a mean daily temperature of 16.4o C and January is the coldest with an average temperature of -24.9o C. The mean annual number of days with freezing temperatures is 233, and freezing temperatures have been reported in every month except July. Temperature differences at various elevations are often extreme; much of the Alaskan taiga is subject to steep and persistent winter temperature inversions, with inversions as steep as 21oC/100m occuring during periods of extreme cold (Slaughter and Viereck 1986).Solar RadiationSolar radiation is the driving force for climate (Slaughter and Viereck 1986). Because of its location at high latitude, BNZ experiences extremes of day length and sun angle which result in large differences in available solar radiation. At winter solstice in Fairbanks (65oN latitude), day length is 3 hours, 42 minutes with a maximum sun angle of 1o 42', while at summer solstice there are 21 hours, 50 minutes of sunlight and the maximum sun angle is 48o 42'. This results in average daily solar radiation of 231 KJ.m-2.day-1 in December and 22,375 KJ.m-2.day-1 in June.
The range of solar elevation angles in interior Alaska (64oN). From Seifert (1981). A consequence of the low sun angles at high latitudes is the accentuation of the effects of topography (slope, aspect, shading) on solar radiation received at the ground surface.The relatively shallow sun angle also results in markedly longer periods of twilight than exist at lower latitudes PrecipitationThe average annual precipitation at Fairbanks is 269 mm. Most precipitation falls as rain in the summer months, a result of short-duration thunder storms and moist air masses that move in from the Bering Sea. Approximately 35 percent of the annual precipitation falls as snow from mid-October through April and remains as a permanent cover for 6 to 7 months each year (Slaughter and Viereck 86). Maximum snow depths, averaging 75 cm, are commonly reached in February and March. The water equivalent at this time averages 11 cm. August is the wettest month with an average precipitation of 48 mm.References CitedBowling, S.A. 1979. Alaska's weather and climate. pp. 1-25 in G. Weller, ed. Alaska's weather and climate. Geophysical Institute, University of Alaska, Fairbanks, AK. UAGR-269. 153 pp. Haugen, R.K., Slaughter, C.W., Howe, K.E., and Dingman, S.L. 1982. Hydrology and Climatology of the Caribou-Poker Creeks Research Watershed, Alaska. (CRREL Report 82-26): U.S. Army Cold Regions Research and Engineering Laboratory. Hanover, N.H. Seifert, Richard D. 1981. A solar design manual for Alaska. Bulletin of the Institute of Water Resources. Volume I. University of Alaska, Fairbanks, AK. Slaughter, C.W., and Viereck, L.A. 1986. Climatic characteristics of the taiga in interior Alaska. In Forest Ecosystems in the Alaskan Taiga: a Synthesis of Structure and Function. Edited by K. Van Cleve, F.S. Chapin III., P.W. Flanagan, L.A. Viereck and C.T. Dyrness. Springer-Verlag. New York. pp. 9-21. |
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The Bonanza Creek LTER, including this website, is supported by the National Science Foundation through awards DEB-0620579, DEB-0423442, DEB-0080609, DEB-9810217, DEB-9211769, DEB-8702629 and by the USDA Forest Service, Pacific Northwest Research Station through agreement number RJVA-PNW-01-JV-11261952-231. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the supporting agencies or the program as a whole.
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