Climate, Snow Cover, Microclimate, and Hydrology 45 



Net 

 Radiation 



A 



1.5 

 Winter 



1 



Pre- Melt 



5.8 



Melt 



15.9 



Post- Melt 



0.0 



Summer 



T. I 



Freeze -Up 



Heoting Heating 



Soil Snow Air 



MJ m"^ day'' 



0.2 



1.0 



1.2 



1.4 



0.2 







1.2 



1 



0.3 



i 



I.I 



2.9 



/^ 



3.2 



0.9 



Melting/ 

 Evaporation 



0.1 



i ^t 



0.3 



3.5 



11.6 



6.6 



i H 



3.2 



Typical 

 Dotes 



I Oct - 31 May 



I Jun - 10 Jun 



II Jun -20 Jun 



21 Jun -30 Jun 



I Jul- 31 Aug 



I Sep- 30 Sep 



FIGURE 2-8. Heat balances of the coastal tundra at Barrow for six 

 different seasons. The width and direction of the arrows indicate 

 magnitude and direction of energy flux. The numbers at the base of 

 each arrow give typical rates in MJ m'^ day' (1 J = 0.239 cal). 

 Evaporation rates are for open water. (After Weller and Holmgren 

 1974a.) 



R„ = Q(l-a) + (0i-0t) 



where R„ = net radiation (shortwave plus longwave) 



Q - incoming shortwave radiation or insolation (0.3 to 3 ^m 



wavelength) 

 a - surface reflectivity (albedo) 



0t = longwave outgoing radiation (2 to 100 ^m wavelength) 

 Bi = longwave incoming radiation (2 to 100 ym wavelength). 



