Gloomisman
Your post got me thinking, so I dug out an old Earth Science textbook (Earth Science, Tarbuck and Lutgens). I have too much time on my hands right now, so here you go:
The fraction of the total radiation that is reflected by a surface is called its Albedo. This is about 30% for Earth as a whole. It varies greatly depending on cloud cover and particulate matter in the air, the angle of the Sun's rays, and the nature of the surface.
The amount reflected is as follows:
Clouds-average of all types and thickness 50-55%
Concrete 17-27
Crops, green 5-25
Forrest, green 5-10
Meadows, green 5-25
Ploughed fields, moist 14-17
Road, blacktop 5-10
Sand, white 30-60
Snow, fresh-fallen 80-90
Soil, dark 5-15
Soil, light (or desert) 25-30
Water 8*
*Typical Albedo for a body of water. The Albedo of a water surface varies greatly depending on the Sun angle. If the Sun angle is greater than 30 degrees, the Albedo is less than 5%. When the Sun is near the horizon (Sun angle less than 3%), the Albedo is more than 60%.
Among the reasons for differential heating of land and water are the following:
1. The specific heat (amount of energy needed to raise 1 gram of a substance 1degree C) is far greater for water than for land. Thus, water requires a great deal more heat to raise its temperature the same amount as an equal quantity of land.
2. Land surfaces are opaque, so heat is absorbed only at the surface. Water, being more transparent, allows some solar radiation to penetrate to a depth of many meters.
3. The water that is heated often mixes with water below, thus distributing the heat through an even larger mass.
4. Evaporation (a cooling process) from water bodies is greater than from land surfaces.