32 J. E. Hobbie 

 Climate 



The Barrow area has short, cool summers and long, cold winters 

 (Table 2-1). At this latitude the sun is below the horizon from 18 

 November to 24 January but never sets between 10 May and 2 August. 

 Usually, snow is on the ground for 9 months of the year. 



The solar radiation is high during April and May but the albedo 

 (reflection) of the snow cover is also high (80 to 90%) so little of the energy 

 is available for warming or melting of the snow (Figure 2-4). After late 

 May, the albedo gradually drops to 70% and then, during a 4- or 5-day 

 period in mid-June, drops to 10% during the thaw (Kelley 1973). Albedos 

 average 18% during summer but by mid-October they return to the winter 

 levels. Solar radiation in the summer (Table 2- 1 ) is strongly affected by the 

 very cloudy weather and frequent fogs so that most of the annual solar 

 radiation at Barrow occurs before the tundra ponds have melted. 



Temperatures at Barrow average — 12.4°C but there are only 109 

 days when the average temperature is higher than 0°C. Daily minimum 

 temperatures are above 0°C for only 41 days each year so that low water 

 temperatures and even snow can occur at any time during the summer. In 

 winter, the low temperatures and the thin snowpack (Table 2-2) cause the 

 ponds to freeze completely. February is generally the coldest month and 

 July the warmest. Because of the nearness of the Arctic Ocean to Barrow 

 and to the IBP site, the summer climate is strongly affected by the highly 

 variable ice conditions in the ocean as well as by coastal fogs. As a result, 

 temperatures are warmer in summers with little ice. While temperatures at 

 the research site may be a little higher than those at the Barrow Weather 

 Station, the main effect of the distance between the two stations seems to 

 be lower insolation at Barrow than at the research site. Often the sun 

 shone at the IBP site while fog covered Barrow only 2 km away. 



The mean annual precipitation is 10.8 cm (as water). About 50% of 

 this falls as snow; October and November have the highest amounts. 

 During the summer, most of the precipitation falls as rain. Despite the low 

 total precipitation, the relatively low evaporation and the impervious soils 

 mean that the tundra has a great deal of water available, particularly in the 

 early summer when the soils are saturated. The average snowpack is 40 cm 

 in depth but there is tremendous variability due to drifting caused by the 

 constant easterly winds. Drifts fill all depressions while ridge tops may be 

 blown free of snow. 



Winds at Barrow are almost continual and almost always from the 

 east. The monthly averages of wind speed are remarkably uniform (Table 

 2-1) but some strong storms do occur in September and October. These 

 data, however, are taken at 9 m and may not reflect the wind effect on the 

 small ponds. Frequently we have observed a microinversion over a pond 

 such that the pond surface was completely calm when there was wind at 

 a 1.5 m height. Additional information on the decrease of wind close to 

 the ground surface comes from 1971 micrometeorological data from the 



