You can find a detailed and comprehensive chapter on Ocean Currents on following website;

www.irbs.com/bowditch/pdf/chapt32.pdf

OTHER FORMS OF PRECIPITATION

DRIZZLE OR MIST


Sometimes precipitation occurs as very small uniform water droplets so small that they semms to float or dance in the air.It commonly falls from low stratus clouds,in such type of precipitation the droplets donot goes through the ususal ice crystal process.On the other hand they form in low clouds.they have a little chance to grow by collision.


SNOW

Snow is a form of prec. in which water droplets directly change into snow neddles. this process of conversion is known as sublimation.the process occured at temperature below then freezing point.



ICE NEDDLES

These are small ice crystals,they seems floating in the air.they are formed at very low temperature,the source region of ice neddles are cold areas and high elevated areas.



DEW


In the day time by the process of evaporation water vapours continously enters into the atmosphere. in the night time when earth release its heat, things get cool down,but surrounding air still warm and moist. when this warm and moist air strike with these cooled subjects its temperature drops .the process of condensation start and some amount of water droplets gather on the surface of grass, leaves and stones as dew.



FOG

Its a kind of cloud which are very near to the surface of earth.when warm moist air strike a cool surface or snoe covered surface,its temperautre drops and water droplets take the form of fog.



FROST


When air started movment or move fast temperautre of the moving air drops more than before when it was still.the suspended mist particles take the shape of ice crystals which freezes on different objects as frost.


regards sabahat.

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GEO to aise k sab tumhara ha,MARO to aisa jaise tmhara kuch bhi nhi.

Maza deti han zindagi ki thokerin unko,jinhen NAAM-E-KHUDA le kar sanbhal janey ki adat ho.

respected members
i am planning to opt geography in place of british history.i have no back ground in geography except a very mild understanding of almost all topics related to physical geography, because i ve gone through them in a css academy. i am opting it purely due to its consistent good scoring potential. is it possible to score good by preparing geo for 2012. i am also doing a govt job in grade 17 and doesnt have a fixed routine of study. being from punjab and having optional of pol sci,c.law and punjabi i thought to op geography, in hope of ending up with a good group.
plz guide

yes geography has consistently been scoring subject, and its very easy to understand and prepare. it may prove good scoring in upcoming exams but we can only speculate..... scores depend upon one's own capability and preparation. if u will be able to prepare any subject well (not cramming the books only, but developing understanding of topics and be prepared to answer any sort of question) u will definitely end up with good scores. ur combination is quite scoring so opting geography will hopefully boost ur scores. GOOD LUCK

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Don't judge my path... for you haven't walked my journey...

@dicey. Yeah u can study the subject while doing a job. The main thing is to give proper time to course. No matter u have studied geo before or not, u may cover it.

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Try not to become a man of success but a man of value.

@sabahat. WHy cirus clouds dont move while cumuculous move?

regards

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Try not to become a man of success but a man of value.

Maps and its types pe bhi Roshni daalain.

Pls keep up your good work!

Regards.

if you are talking about cirrocumulous and cirus then

first of all both are high level clouds In most cases, the direction of movement of the higher level clouds do not necessarily represent the wind direction at the ground level. In fact, the wind at upper and ground levels often differ.



Cirrus tend to move in the direction of the wind at that level which differ to that at the surface. The most common direction of motion of these clouds are from a westerly direction. This varies with factors such as the latitude, weather conditions and time of the year. Their apparent velocities are relatively slow as compared to lower clouds.


cirrocumulous
cirrocumulus clouds do not produce precipitation and are normally associated with fine weather. so they mostly dont look like moving.

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GEO to aise k sab tumhara ha,MARO to aisa jaise tmhara kuch bhi nhi.

Maza deti han zindagi ki thokerin unko,jinhen NAAM-E-KHUDA le kar sanbhal janey ki adat ho.

another answer is that cirrus clouds are found in the middle of troposphere somwhat close to the surface of earth, the movement of wind is high in troposhere near the surface. so they look fastly moving.

cirrocumulous clouds are found near tropopause which is the boundry of troposhere and its a transitional belt without any movement of air so they look calm.



waise apka question ulta ha. agar sedha karun to sochna pare ga. so wait for seedha answer.


aariz i have just given my interview so i am totally lost may be i have not given answer in that way which i supposed i should.i will review it again and will answer you in an appropriate way.

so

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GEO to aise k sab tumhara ha,MARO to aisa jaise tmhara kuch bhi nhi.

Maza deti han zindagi ki thokerin unko,jinhen NAAM-E-KHUDA le kar sanbhal janey ki adat ho.

CAHPTER NO:- 4

TOPIC NO:- 1

OCEAN CURRENTS

DEFINITION


The general movement of a mass of water in fairly defined direction under various forces internal as well as external is known as the ocean currents.
The ocean currents do not follow any straight route. They have been found to follow some zigzag courses, which do not have equal width everywhere. They are branched into smaller streams and at places many smaller branches unit to form broader streams. Due to these characteristics, the ocean currents are sometimes called ocean rivers.




Causes of the Origin of Ocean Currents


1:-Temperature Differences.

Temperature is low at the poles and high at Equator. The polar water cools and becomes heavy while that at the Equator warms and becomes lighter. The heavy water sinks and the warm water floats. This makes a difference in the level of the sea. To maintain the balance, the water from the equator moves towards the poles in the form of currents. To counter this, polar currents flow towards the equator under the surface.

2:-Salinity Differences. Saline water is heavy and therefore subsides. To take its place, the less saline water surrounding it rushes towards the area of high salinity. To maintain the balance, a current of high saline water moves towards the area of lower salinity under the surface of sea.


3;-Axial Relation of the Earth. The Earth rotates one rotation around its axis in 24 hours. This rotation is responsible for the origin of currents




1) Centrifugal Force.

Every revolving body develops a centrifugal force at its centre and makes it move away from it. This force increases as the distance of the body increases from the centre of the Earth due to the centrifugal force. The centrifugal force at the Equator is greater than that at the poles because the Great circle at the time of revolution coincides with the equator. The variation of this force causes the equatorial water to move towards the poles.

(ii) Ferrel's Law.

Ferrel studied the rotational influence of the earth on the courses of ocean currents and stated that the ocean currents tend to deflect towards the right hand in the northern hemisphere and towards the left in the southern hemisphere. This influence diverts the flow of ocean currents and creates branches from the main currents.


4:-Atmospheric Pressure. The atmospheric pressure affects the ocean currents in two ways.

(i) It is not the same at all places on the Earth. The water is pressed down when the atmospheric pressure is high and it rises up when the atmospheric pressure is low. Due to the difference in the levels of sea water caused by the differences in atmospheric pressure, water from higher level flows towards that of lower level. This originates ocean currents.

(ii) The prevailing winds also create ocean currents. The prevailing winds are those permanent winds, which blow, in the same direction throughout the year. Differences in atmospheric pressure originate them. These winds try to carry the ocean water along with them by friction. It is due to trade winds that the equatorial ocean currents flow from east to west. Due to the westerlies the Gulf Stream and the Keurosiwo ocean currents move towards east from the west.

5:-Evaporation and Rain. More evaporation takes place in equatorial areas than in other latitudes. Evaporation reduces the amount of water in the ocean and increases salinity and density. The combined effect of all these things reduces the sea level and is the main cause of the movement of currents. This, is why the equatorial ocean currents travel towards Tropic of Cancer and that of Capricorn, Similarly ocean currents flow from polar areas towards middle latitudes. In order to maintain equilibrium ocean currents flow in opposite directions under the sea level.

6:-The Changes of Seasons. Due to change of season the prevailing winds undergo changes in direction and in areas. It has an effect on ocean currents. When the sun is vertical in northern hemisphere, the flow areas of ocean currents shift a little towards the north. When the sun is vertical in the southern hemisphere, the areas of ocean currents shift a little towards the south.
The greatest effect of seasonal changes is experienced by the Monsoon winds. A change from summer to winter reverses the direction of the winds. Similar effect is seen on the directions of oceans currents.


7:-The Shape of Coasts.

The shape of coasts also creates ocean currents. The best example is offered by Cape San Roque. South equatorial current strikes at it and is divided into two branches (i) one branch travels north along the Brazilian coast and joins with the North Equatorial Current. (ii) The second branch flows south along the Brazil coast and is known as Brazil current.

The Gulf of Mexico has such a shape that it turns the northern branch of the South Equatorial Current into northeast and when the currents comes out of the Gulf, it is known as the Gulf Stream


Types of Ocean Currents.

Ocean currents are classified on the bases of temperature and speed.




(1) On the Bases of Speed.

The ocean water current, which flows fast, is called a stream and that which flows slowly is called a drift. A good example of stream is the Gulf Stream in the Atlantic and that of drift is the West Wind Drift along Southern Australia.

(2) On the Bases of Temperature.

Ocean currents, which have high temperature, are known as Warm Stream and those, which have low temperature, are called Cold Stream. Example of warm currents is the Gulf Stream Kuro Shio etc., and those of cold stream are Banguella, Labrador, etc.

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GEO to aise k sab tumhara ha,MARO to aisa jaise tmhara kuch bhi nhi.

Maza deti han zindagi ki thokerin unko,jinhen NAAM-E-KHUDA le kar sanbhal janey ki adat ho.