When spring finally arrives in the mountains, the snow pack may be two meters deep, composed of 50% ice and 50% air. Direct sunlight provides about. 1000 watts/m2 to earth’s surface, but the snow might reflect 90% of this energy. Estimate how many weeks the snow pack should last, if direct solar radiation is the only source of energy.
For we will calculate the volume of snow-air mixture which has a depth of 2 meters.
The volume is, .
Energy received at a rate of .
The energy absorbed by volume is .
The snow reflects 90% of the energy so, the absorbed energy is .
For 1 area , it is 100 J/s.
The heat of fusion of water is, .
The mass of volume of this mixture is 2 kg from which 1 kg is snow.
The heat required to change the phase is,