Water

Rain

The mechanism by which clouds evolve and the rainfall have been mentioned in many verses of the holy quran.In each of these verses some scientific points concerning these natural phenomenon have been dealth with in extreme beauty and delicacy.

The Formation of Rainfall :

Besides moderating the temperature,winds also displace the humidity resulted from the seas and damp areas.In order for these particles of steam to return to the Earth,they should turn into liquid and in the form of heavy drops,so that they can get out of the clouds and then fall to the ground.This requires a drop in the temperature and also hypersaturation of dampness in the air.The drop in the temperature is usually brought about as a result of the climb of the currents of air,or because of the neighbouring and mixing with cold currents of air.The accumulation and piling up of damp currents also cause the state of hypersaturation of dampness in a region. Of course,althogh the drop in temperature and high humidity are essential for the rainfall to happen they are not enough because in such a case no clouds could ever evolve since liquid drops would immediately separate from the air and fall to the ground,and being light enough,the fine drops would also remain suspended in the air may be for days and vaporize after being heated again.Another important factor is the existence of nuclei of distilation.Wind and waves cause the sea water to spray into the air in fine droplets. After the evaporation of these droplets fine particles of salt remain suspended in the air.These salt particles can absorb humidity, and are infact centers for the accumulation of humidity and the formation of rain drops. To some extent dust and soot particles also play the same role.The contact and the mixing of these particles also accelerate the process of the development of raindrops. Bergeron the transfer of water vapor to the solid surface of ice particles is also another factor which causes the formation and the acceleration in the development of raindrops.

Rains are classified on the basis of such criteria as the type of cloud they originate from the kind of effective winds and the diameter of drops.

For example,on the basis of the winds affecting the rainfall,three types of rain are recognized,

1- when the climb of the wind is resulted from it contact with ground ridges,that is highmountains, the rain evolved is called mountainous rain,which may be of two kinds: simple or beach mountainous.

2- whenthe rain forms following the contact between the two cold and warm fronts of wind , the possible rainfall is called frontal rain.

3- when the warm area and the humid warm air cause a disturbance leading to rainstorms, the rain is called storm rain.

There has also been a classification made on the basis of the type of cloud originating rain and the diameter of raindrops.For example,drizzle evolves from nimbus clouds which are near the ground and in a quiet sky.Rainstorm is produced from cumulonimbus clouds which are in high altitudes in this kind of rain the diameter of the drops gets bigger in the course of rainfall.Very heavy rains known as showers fall briefly and intermitenty,but an abundant amount of water gets to the ground.

Other forms of precipitation such as snow and hail might evolve depending on the condition under which the rain falls.If the temperature of the land on which,it rains drops a certian amount because of a current of cold air or elevation ,on their way the rain drops freeze and turn into small solid crystalized particles which one generally hexagonal and are know as snow.Hail forms when falling raindrops pass through a very cold air stratum and hence freeze.

Cloud

When as a result of the exchange of heat and/or upward movement and exapansion,the temperature of the air decreases so much that the relative humidity reaches %001, a portion of the steam molecules in the air becomes dense ;this densitiy emerges following cloud formation in this state water has no longer a gaseous form , but changes to liquid droplets or tiny suspended solid crystals.Cloud can be considered as a collection of liquid droplets or tiny crystals of ice immediately after being formed.The diameter of these droplets varies from 2 to 100 microns usually 10 to 25 microns ,and their number in one cubic centimeter amounts to 1000 to 2500.Almost all clouds are formed in the troposphere layer upto 12 km.from the ground level.

For the recognition and classification of clouds it must first be determined how clouds are formed in a specific time and also how they are transformed and scattered.In general all clouds are formed as a result of the occurance of density in the lower layers of the atmosphere.This happens because the humid air climbs to the upper and middle layers of troposphere . Different kinds of vertical movements which take place in the atmosphere are as follows :

1- mechanical disturbances,
2- convection ,
3- mountainous climb ,

4- soft graduall climb when the ascending current of air is quick,the clouds produced have a high vertical development and density . On the contrary , if the ascending current of air proceeds moderately and slowly , the clouds thus produced will form layers which depending on the amount of density , with thick or thin strata.

Meteorologists divide clouds into four groups usually on the basis of height :

1- upper clouds,
2- middle clouds,
3- lower clouds,

4- clouds which have vast vertical developments the height of these clouds in areas with average latitude is 5 to 13 km. from the ground level for upper clouds, 2 to 7 km. for middle clouds and atmost 2 km for lower clouds.

Among all major groups of clouds,two main ones are of immense importance,the group known as Stratus clouds,is evolved in the form of strate in middle troposphere,when the existing steam cools and becomes dense, the other group known as Cumulus forms following the quick ascending local current of humid air.In these clouds there is great distance between the upper and the lower strata.

The international cloud Atlas issued by World Meteorological Organization WMO contains detailed information regarding the classification of clouds.According to the ratification by WMO,clouds have been divided into 4 families and 10 independent typesthere has recently been some important changes in the first international cloud atlases such as the deletion of nimbuses and the addition of nimbostratus.

Generally,the main types of clouds are as follows :

1 - Cirrus , ci ,
2 - Cirrostratus , cs
3 - Cirrocumulus,cc ,
4- Altostratus ,as
5 - Altocumulus , ac ,
6 - Stratus , st
7- Stratocumulus ,sc,
8- Nimbostratus,ns
9 - Cumulus , cu ,
10 - Cumulonimbus,cb. At present cloud divisions have become very vast and complicated.The division of clouds is based on such criteria as factor affecting their formation , the shape and type of precipitation resulting from them.

Salt water and fresh water seas

The contiguity and clash of two seas , two water currents , or two kinds of water have long occupied the minds of interpretors of Quran ; on the basis of the scientific knowledge of the time , they have given different interpretations in connection whit the these verses , such as metaphormic and figurative interpretations,the two Roman and Persian seas , and underground deposits and oceans.What is far sure is that wonderful sea currents such as the Gulf stream,which flows like a gigantic river that is 150 km.Wide and a few hundred meters deep , sparkles for ever in the midst of the Atlantic ocean , and what is more it does not mix whit its adjacent waters. This huge water current is one of the mysteries of creation and also a mgnificent scene of the incarnation of the Lord's greatness which follows its course apart from any interpretation.

Anyhow,many research studies concerning sea and water currents have so far been carried on.The results obtained from such studies are briefly taken up in two section: factors involved in the emergence of water currents,and kinds of water currents. Factors involved in the emergence of sea currents.

1- Tides : It has been proved that the Moon , like the Earth has a gravitational field , and exerts a force of attraction on the Earth. Considering the greatness of the size of the Earth in relation to that of the Moon, the hemisphere of the Earth which is closer to the Moon is more under the Moon's gravitational force than the other one. On the other hand,it is quite obvious that ocean water is closer to the Moon that the land at is bottom and is , therefore, more under the Moon's gravitational force. Consequently ocean water is convexly attracted towards the Moon.Because of the movement of the Earth and the Moon , this condition changes every few hours and cause currents known as flow and ebb currents.

2- The Earth's rotation : The Earth rotates around its axis once every 24 hours , and hence we , on the Earth , are turning towards the east at the speed of 82 kilometers per second.The tow elements of air and water however , are not attached to the Earth , therefore , they don't turn with the Earth at the same speed so they roll away in wave form causing sea currents and winds. These currents lean towards the right in the north hemisphere,and to the left in the south hemisphere this fact was first recognized and stated by Coriolis , a french engineer, and is therefore known as Coriolis force.

3- convection : The sea water around the pole becomes cold and as a result hevier , so it moves down; to take its place ,the warmer water on the surface of the sea moves towards the pole. The reverse of this process occurs in the equator and causes water currents . This exchange of warm equatorial water whit cold polar water is one of the most important water movements in oceans.

4 - Winds : Convectional currents of the air cause wind, and because of the cold air in the pole and the warm air in the equator , winds , on the surface of the seas are always blowing from the pole towards the equator,these winds are known as prevailing winds,they,inturn,cause water currents.

5 - Water pressure : When water passes a narrow passage,it moves faster Bernoullis' principle ; this fact is also true for sea water ,and cause water current.This phenomenon is more seen at the mouth of gulfs and straits.

6 - Water density : The relative density of sea water is the ratio of the weight of the unit volume of sea water is to the weight of distillted water of equal volume at 4 degree c. Density is effective in the formation of currents because it regulates the equilibrium condition between water masses in such away that the more dense water always flows at a lower level.For example in the Mediterranean sea which the surface sea water evaporates a lot , the density of water rises and as a result it moves downward to the bottom of the sea.This water is replaced by the lighter water entering the Mediterranean sea from Gibraltar strait;and the hevier water at the bottom of the Mediterranean sea passes the mouth of Gibraltar strait and enters the lower level of the Atlantic ocean waters; the same phenomenon occurs in the Baltic Sea too.

7 - Waves : Sea waves themselves cause water currents. As waves approach seashores , they deviate move until they become parallel to the shore. These waves are convergent at the two ends of the shore and divergent in the middle. Therefore ,it is expected that the waves be more intense and higher at the convergent site,and at the divergent site they be less intense and shorter . The difference in the intensity of these waves becomes a current towards the divergent site . Such currents are called wave made currents.

Types of water currents :

1 - Warm currents : These currents come about as a result of the movement of warm waters to higher latitudes, like Gulf stream current in the North Atlantic ocean and the Kuroshio current in the North Pacific ocean.

2 - Cold currents :

A : These currents come about following the movement of cold waters to colder latitudes like the Falkland current in the South Atlantic ocean.

B : Currents which are formed following the upward movement of deep waters to the surface of the sea , such as the Peruvian current in the current of California in the West Coast of the North America.

C : Deep currents are among slow currents about which there exists little information.

Seas

More than %70 of the Earth is covered with water.The seas and oceans account for %97 of this water the oceans cover 361 million square kilometers.

The extent of the seas and oceans used to be different.Before the first geological era, all the lands on the Earth were connected together . The Urasia was on the northern hemesphere , and on the southern hemesphere there was the Gondwana.During some geological changes in the history of the planet Earth, the first breaking of the land took place in the first geological era and as a result the Thetis sea was formed;then gradually due to different geological events and also the important process of horizontal movement of the crust of the Earth the continents got separated from each other the separation theory of continents and hence , various oceans were formed.

The present oceans are :

1 - The Pacific ocean with the surface area of 177 million square kilometers and maximum depth of 11000 m.

2- The Atlantic ocean with the surface area of 106 million square kilometers and maximum depth of 8380 m.

3 - The Indian ocean with the surface area of 77 million square kilometers and maximum depth of 7450 m.

4 - The Arctic ocean with the surface area of 14 million square kilometers and maximum depth of 5450 m.

5 - The Antarctic ocean which lies on the southern hemesphere.

The main difference between the oceans and seas lies in their relative hugeness.Oceans are vast expanses of water which separate continents from each other,and their surface area can reach up to tens or hundreds of millions of square kilometers,while seas, which are generally located on the edges of oceans never exceed more than few million square kilometers.There are some cuts in a varieties of forms at the edges of oceans near where they meet the land which are, in some places,more or less deep;in fact, these cuts form seas and gulfs.

Seas are divided into two distinct groups according to their morphology :

1- the seas which are somehow connected with the oceans and are generally separated from them by a group of islands or peninsulas . The free connection between oceans and these seas is the main reason for the very close relationship which exists between the morine life and the water temperature and saltiness in these two environments. Examples of these are the Bering and the Barents and the Japan seas.2- the seas which have fully and deeply penetrated the land and formed semi-closed basins of water.These basins are separated from the oceans by under sea ridges. Connection between these seas and oceans is very difficult.The only way of connection is through the semi-deep and narrow straits, like the Black Sea and the Mediterranean Sea. Each sea is divided into four zones according to its depth :

1- The coastal or tidal zone littoral zone. This is a zone located between the flow and ebb of the sea.

2- The shallow zone neritic zone starts from the lower limit of the littoral zone and extends upto the depth of 200 m.This zone is also called the continental shelf.

3- The average depth zone of the sea bathgal zone which begins from the depth of 200 m ,and extends downward for 2000 to 3000 m.

4- The deep zone abyssal zone consists of some parts with the depth of more than 3000 m the lowest part of the Earth or the deepest part of the oceans of the world is near Japan and is called Marien graben with the depth of more than 11 km.

The bottom surface of the seas and oceans are not even or flat , but are similar to lands with heights and depressions such as valleys, rifts , ocean ridges , mountains subduction areas . Old volcanic cones or guyots and corals.

The surface of the seas are also constantly on the move and changing. Most of the waves seen on the surface of the seas are caused by winds. Of course single, dangerous waves are sometimes resulted from earthquakes and explosions happening under the seas. Studies show that the top surfaces of the oceans are also changing in the same way as level of the underground water . On a world scale these changes are called static changes . These phenomena are affected by such factors as newly formed oceanic water basin which are the result of the separation of continents and the melting of icebergs.

The degree of saltiness of ocean waters varies in different parts it varies according to time and location. Generally the degree of saltiness increases from the equator to the Cancer Orbit and the Capricorn Orbit , and decreases as it reaches the poles.It is worth mentioning that the degree of saltiness largely depends on the evaporation process. There are different gases dissolved in the waters of the oceans the most important one is oxygen.The main role of this gas is for the respiration of marine life.

Hail

Hail is the crystalized particles or drops of water pieces of ice which sometimes has a regular shape and is often seen in the shape of oval.Pyramid,sphere,and semisphere. The outer surface of the hail is sometimes smooth and sometimes rough and bumpy. Hailstones usually get their final shape in several stages.When the first step in the production of hail,like that of the rain is formed,as a result of a vertical movement of a current of air upwards,the tiny particles of water in the current quickly reach the freezing point and immediately freez.As these frozen particles move downwards,other water and ice drops attach to them and hence they grow.But when they reach the lower levels of clouds,because of the rising of a current of the air inside the clouds which take place as a result of certain processes,the frozen particles move upwards again.This cycle repeats until the current of the air upwards can support the weight of the particles,at this time the hails leave the clouds and the precipitation happens.

Hail generally takes place in clouds of cumulonimbus type,because these clouds have a very high vertical extension and inside them swift horizontal movements,whose speed sometimes gets to twelve to thirty m/s,are seen.These are suitable environments for the formation and the development of hailstones. Hailstones are divided into three groups according to size and shape :

1.smooth hail frost is made of white icy particles which are relatively round and opaque ; their structure is like that of snow and they are often in the shape of a cone , their diameter is varies from 2 to 5 millimeters.The smooth hail cracks and smashes as soon as it gets to the ground.In most cases this kind of hail appears in the form of shower in zero degrees temperatures along with snow or before the snow.

2.tiny hail icicle is made of spherical semi-transparent particles which on rarely conic and their diameter varies from 2 to 5 millimeters.This kind of hail forms when air temperature is several degrees below zero on the centigrade scale.

3.hail is formed from icy particles whose diameter varies from 5 to 50 millimeter and sometimes even more because of the frequent cycles and steps in which hail develops,it consists of transparent,semi-transparent, opaque and milky layers.It often hails in the form of showers in spring. Each hailstone usually consists of three sections :

A - a white core which is usually like a snowball,B - a great number of white fiber-like layers which are seen around the core,C - a thin froze shell which surrounds the hailstone this shell is sometimes missing.

Hail temperature is usually below zero degrees centigrade,but it might occasionally reach that , it which case it carries some water.It usually hails in spring or other transitional seasons of the year,because during these seasons severe atmospheric disturbances make the condition suitable for the formation of hail.