Evaporation and Precipitation Balance

The hydrologic cycle is very familiar to us and describes the balance between evaporation and precipitation thus the path of water through our environment. The oceans cover about 70 percent of the earth s surface. 

The presence of water on our planet regulates the climate and is essential for life. Oceans store heat and release it slowly. Wind currents distribute heat in the latent energy of water vapor. In the tropics warm, humid air rises and is transported to cooler latitudes. 

There are estimates that the water in the deep lithosphere is of the amount of 27 X 10 tons or 94.7% of the global total. 

As it has been stressed already, oceans strongly influence the climate by storing heat. Moreover, there are also currents that transport warm water from the equator to higher latitudes and cold water from the poles to the equator. The Gulf Stream flows from the coast of North America toward northern Europe, at a flow rate of 10-12 km/hour. This current carries 100 times more water than all rivers on earth put together. In tropical seas the water is warmed by the sun, diluted by rainwater and aerated by waves. In higher latitudes surface waters are cold and more dense. Those dense waters sink to the bottom to the ocean floors flowing toward the equator, warm water however is less dense and floats on top of this cold water. Also different salinity plays an important role in these processes. 

Glaciers, ice caps and snowflelds tie up 90 percent of the fresh water (which makes 2.4 percent of liquid water). During the last ice age, 18 000 years ago, about one-third of the continental landmass was covered by ice sheets and since then most 

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