Wind and Ocean. current

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What are the topics covered in the lecture?

The lecture covers Wind, Cyclones, and Ocean Currents (पवन चक्रवात और महासागरीय जलधाराएं).

Why does wind blow?

Wind blows due to pressure difference (दाब में अंतर). This pressure difference is caused by differential heating.

Why does differential heating occur?

Differential heating occurs because the Earth's surface is not flat and is inclined on its axis at 23.5° (and 66.5° on its orbital plane), resulting in uneven reception of insolation.

How does heating relate to pressure?

Where there is more heating, low pressure forms because the warm air rises. Where there is less heating, the air is colder and sinks, forming high pressure.

In what direction does wind always blow?

Wind always blows from high pressure to low pressure (उच्च दाब से निम्न दाब की तरफ).

Where does the most heating occur on Earth and what kind of pressure forms there?

The Equator (भूमध्य रेखा) experiences the most heating, leading to the formation of low pressure.

What kind of pressure exists at the poles?

The poles have high pressure because they are very cold.

What are the various pressure zones and atmospheric cells mentioned?

Air rises at the Equator, forming a low pressure zone. As it subsides, it creates a subtropical high pressure zone. Further poleward, rising air creates a subpolar low. The atmospheric circulation creates cells: Hadley Cell (near the Equator), Ferrel Cell (a mechanical cell in the middle latitudes), and Polar Cell (near the poles).

What is the Coriolis Force and what causes it?

The Coriolis Force deflects (मोड़ देता है) things, including wind and ocean water. Its main cause of origination is the Earth's rotation (पृथ्वी का घूर्णन).

How does the Coriolis Force deflect things in the Northern and Southern Hemispheres?

In the Northern Hemisphere, it deflects things to the right. In the Southern Hemisphere, it deflects things to the left.

Where is the Coriolis Force zero and where is it maximum?

The Coriolis Force is zero at the Equator. It increases as you move towards the poles and is maximum at the poles. It also depends on wind speed; higher wind speed results in a greater Coriolis Force.

What are the names of the major global winds?

The major global winds are:
* North East Easterlies and South East Easterlies: Collectively known as Trade Winds (व्यापारिक पवनें).
* Westerlies (वेस्टर्लीज़).
* Polar Easterlies (पोलर ईस्टलीज़).

What is the Intertropical Convergence Zone (ITCZ)?

The Intertropical Convergence Zone (ITCZ) (अंतः उष्णकटिबंधीय अभिसरण क्षेत्र) is the zone where the North East Easterlies and South East Easterlies meet. This zone is also known as Doldrums. The ITCZ is not fixed; it shifts its position with the apparent movement of the sun.

Why do Westerlies blow very fast in the Southern Hemisphere, and what are they called there?

Westerlies blow very fast in the Southern Hemisphere because there is less landmass (भूभाग कम है), resulting in less friction. They are called "Roaring Forties," "Furious Fifties," and "Shrieking Sixties" based on the latitudes (40°, 50°, 60°) where they blow.

What are Horse Latitudes?

Horse Latitudes (अश्व अक्षांश) are zones where winds subside. They are roughly located at 30-35° North and South latitudes and are associated with subtropical highs.

What are Isobars and Isotherms?

Isobars (समदाब रेखाएं) are lines that connect points with the same pressure. Isotherms are lines that connect points with the same temperature. Both are somewhat parallel to latitudes.

What are Geostrophic Winds?

Geostrophic Winds (भूगर्भिक पवनें) are winds that blow parallel to isobars. This occurs at higher altitudes (like near the tropopause) where there are fewer obstructions, allowing winds to achieve very high speeds. The increased Coriolis Force at these speeds causes them to deflect significantly until they become parallel to the isobars.

What are some examples of Local Winds?

Local winds mentioned include:
* Warm Winds: Sahara, Chinook (also known as "snow eater"), Harmattan (also known as "Doctor Wind"), Sirocco (causes "blood rain" due to picking up sand from Sahara Desert), Khamsin, Foehn, Loo (in India), and Brickfielder (in Australia).
* Cold Winds: Blizzard, Pampero, Bora, and Mistral.

Explain Land Breeze and Sea Breeze.

Land Breeze and Sea Breeze occur in coastal areas due to the differential heating of land and water. Land heats up and cools down faster than water.
* Sea Breeze (दिन के समय - Day Time): Land heats faster, creating low pressure over land. The sea heats slower, creating relatively high pressure over the sea. Wind blows from the sea to the land.
* Land Breeze (रात के समय - Night Time): Land cools faster, creating high pressure over land. The sea cools slower, retaining relatively low pressure over the sea. Wind blows from the land to the sea.

What are the two main types of Cyclones?

There are two types of cyclones: Tropical Cyclones and Temperate Cyclones.

What are the differences between Tropical and Temperate Cyclones?

• Tropical Cyclones: Form only in the sea. Caused by heating of the ocean. Move from East to West (due to Easterlies). Are very frequent and very disastrous.
  • Temperate Cyclones: Form in both land and sea. Caused by frontal formation (frontogenesis). Move from West to East (due to Westerlies). Are less frequent and less disastrous.

What are the favorable conditions for Tropical Cyclone formation?

• Large sea surface temperature (at least 27°C).
  • Coriolis Force (for rotation).
  • Small variation in vertical wind speed.
  • Pre-existing weak low-pressure area.

What is the "eye" of a cyclone?

The central part of a cyclone is called the eye of the cyclone. It is characterized by calm conditions and no cloud formation.

What is the "eye wall" of a cyclone?

The eye wall is the area around the eye where winds rise, forming Cumulonimbus clouds. These clouds bring heavy rain and thunderstorms and have an anvil-top shape.

How do cyclones and anticyclones rotate in the Northern and Southern Hemispheres?

• Cyclones: Rotate anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. They form around low pressure.
  • Anticyclones: Rotate clockwise in the Northern Hemisphere and anticlockwise in the Southern Hemisphere. They form around high pressure.

What is the weather like during anticyclones?

Anticyclones bring calm conditions and clear weather.

What is Frontogenesis and what are Fronts?

Frontogenesis is the formation of a Front. A Front is formed when a warm air mass meets a cold air mass.
* Warm Air Front: When warm air moves towards cold air.
* Cold Air Front: When cold air moves towards warm air.
* In both cases, warm air must rise to form clouds (often stratiform or layered clouds in temperate cyclones, cumulonimbus in warm front but generally less intense than tropical cyclones).
* Occluded Front: Occurs when cold air completely lifts the warm air mass, leaving no warm air below.

Where do cyclones not form?

Cyclones form in every sea except the South Atlantic and South-Eastern Pacific Oceans.

What are the different regional names for Cyclones?

• Indian Ocean: Cyclone.
  • Australia: Willy-Willy.
  • Western Pacific (South China Sea, Japan, Philippines): Typhoon.
  • Atlantic Ocean: Hurricane.

What are Ocean Currents?

Ocean currents are the flow of ocean water. Ocean water is divided into surface water (10%) and deep sea water (90%).

What are Thermocline and Halocline?

Thermocline is a line in the ocean where temperature suddenly drops. Halocline is a line where salinity suddenly increases. The thermocline is typically found around 1000 meters deep.

How is ocean salinity defined, and what are examples of highly saline bodies of water?

Water is considered saline when its salinity is 24.7 parts per thousand (as per NCERT data) or 27 parts per thousand.
* Lake Vonn, Turkey: 330 parts per thousand.
* Dead Sea (Israel, Jordan): 238 parts per thousand.

What are the reasons for the movement of Ocean Currents?

• Differential heating of the Sun.
  • Winds (especially for surface water).
  • Coriolis Force (for deflection/gyres).
  • Density differences (cold water is denser and often more saline).

What is the trick to remember cold ocean currents?

The trick is: "BP company ne golf ka World Cup khela California mein".
* B - Benguela.
* P - Peru (also known as Humboldt).
* G - Greenland (Correction: GULF stream was mentioned as a mistake here, Greenland is the correct cold current).
* O - OyaShio.
* L - Labrador.
* F - Falkland.
* W - West Australian Current.
* C - Canary Current.
* California - California Current.
* Note: Cold currents always flow from poles to the Equator, while warm currents flow from the Equator to the poles. All other currents not in this list are generally warm. Examples of warm currents mentioned are Gulf Stream, Alaska, Brazil, Agulhas, East Australia, Kuroshio, Norwegian.

Why are deserts generally found on the western side of continents?

There are multiple reasons:
* Cold ocean currents: Cold currents cool the air, preventing rainfall.
* Easterlies: Easterly winds bring rain to the eastern coasts but become dry by the time they reach the western coasts. If Westerlies approach the western coast, cold currents cool them, preventing rain.
* Offshore winds: For western coasts, the prevailing winds (Easterlies) are often offshore, meaning they carry moisture away from the land.
* Continentality effect: Inland areas experience extreme temperature ranges (hot summers, cold winters) and reduced rainfall due to being far from the moderating influence of the sea. This effect is distinct from cold currents. An example of a desert formed by continentality is the Gobi Desert.

Where are the best fishing zones found and why?

The best fishing zones are created where warm and cold ocean currents meet. These areas also experience foggy conditions. This mixing brings up nutrients, leading to abundant fish. Examples include the meeting points of OyaShio and Kuroshio currents near Japan's East Coast, and near **Newfoundland, Cana