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Hydrologic Cycle: Definition & Influence of The Atmoshere, Sun, & Earth's surface

Author:          Paul Hay

e-mail:            paul.hay@phcjam.com

profile:           www.linkedin.com/in/phcjam

Figure 1:  Hydrologic Cycle (units = cubic kilometers) & water quality 

[Source: Mechanical & Electrical Equipment for Buildings]

1.0   DEFINITION OF THE HYDROLOGIC CYCLE

1.1_      Water is an important for human existence to fulfill the functions of: (a) nourishment, (b) cleansing and hygiene, (c) ceremonial uses, (d) cooling, and (d) embellishment.

1.2       Water is important in building construction for (a) manufacture of building components, (b) production of energy, (c) cooling, (d) fire protection, and (e) sewage disposal.

1.3       The Hydrologic Cycle is the process by which water in any of its forms moves from the ocean to the atmosphere, to land, and returns to the ocean.

2.0   WATER VAPOUR IS STORED IN THE ATMOSPHERE

2.1       The earth's atmosphere is classified by temperature distribution into five layers.

2.2       These layers can be grouped into two distinct layers:

2.2.1   The upper atmosphere, or stratosphere, comprises two cold layers having 90% of the ozone layer;

2.2.2   The lower atmosphere, or troposphere, comprises three warm layers which comprises 86% of the atmosphere by mass.

2.3       The troposphere is often humid, comprising practically all cloud formation and precipitation.

2.4       0.001% of the Earth's water is stored in the atmosphere:

2.4.1   Water vapour is most prevalent;

2.4.2   Aerosol particles constitute atmospheric haze;

2.4.3   Water droplets form clouds and fog; and

2.4.4   Larger particles constitute precipitation.

3.0  EVAPORATION INCREASES AS SOLAR RADIATION INCREASES

3.1       Clouds are mainly responsible for reflecting 28% of solar radiation.

3.2       The atmosphere absorbs 25% of the solar radiation.

3.3       The Earth's surface absorbs 47% of the solar radiation:

3.3.1   Solar energy re-circulates water by evaporation and condensation;

3.3.2   Higher latitudes receive less solar radiation and are therefore cooler;

3.3.3   Hadley cells develop between latitudes 30 deg. N and 30 deg. S;

3.3.4   Annual evaporation is highest between latitudes 15 - 20 deg. N and 10 - 20 deg. S.

4.0   MAJORITY OF THE EARTH IS COVERED BY WATER

Figure 2: Average Annual Precipitation

[Source: Essentials of Physical Geography Today]

      

4.1       70% of the Earth's surface is covered with water:

4.1.1   Oceans store 98% of the Earth's water;

4.1.2   Polar Ice Caps store 75% of the Earth's non-saline water; and

4.1.3   Fresh water lakes and rivers store 0.009%.

4.2       Terrestrial radiation passes between clouds and ground, some escaping the atmosphere to cool the earth:

4.2.1   Dry land readily heats and cools giving rise to land and sea breezes;

4.2.2   Winds transfer 10% of evaporation from oceans, saline lakes, and seas daily to land as precipitation.

4.3       Precipitation and run-off in the form of springs and rivers are the most accessible sources of water.

4.4       Soil moisture comprises 0.005% of the Earth's water:

4.4.1   Soil moisture neither evaporates nor contributes to evaporation; but

4.4.2   Soil moisture is transpired (evaporated) by plants to the atmosphere.

4.5       Ground water comprises 0.61% of the Earth's water:

4.5.1   Ground water represents a zone of earth which is saturated;

4.5.2   The top of the ground water is called the water table.

4.5.3   Aquifers are deposits from which ground water can be obtained naturally (e.g. springs) or artificially (e.g. wells).

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FURTHER READING

Mechanical and Electrical Equipment for Buildings, Benjamin Stein & John S. Reynolds, John Wiley & Sons Inc., U.S.A.