Physical Geography 2

Question 1

Atmosphere

Answer 1

is a mixture of different gases and it envelopes the earth all round.

Question 2

Composition of the atmosphere

Answer 2

composed of gases, water vapour and dust particles.

Question 3

Gases in the atmosphere

Answer 3

78% nitrogen 21% oxygen 1% other gases. CO2 is a greenhouse gas, transparent to incoming radiation, reflecting a part, absorbing another, opaque to outgoing radiation. Increased concentration causing global warming. Ozone absorbs ultraviolet rays, found 10-50 km abve surface.

Question 4

Water Vapour in atmosphere

Answer 4

Water vapour is also a variable gas in the atmosphere, which decreases with altitude. In the warm and wet tropics, it may account for four per cent of the air by volume, while in the dry and cold areas of desert and polar regions, it may be less than one per cent of the air. It also absorbs parts of the insolation from the sun and preserves the earths’ radiated heat. Water vapour also contributes to the stability and instability in the air.

Question 5

Dust Particles

Answer 5

Dust particles generally concentrated in the lower layers but convectional air currents may transport them to great heights. Higher concentration of dust particles is found in subtropical and temperate regions due to dry winds in comparison to equatorial and polar regions. Dust and salt particles act as hygroscopic nuclei around which water vapour condenses to produce clouds.

Question 6

Structure of the atmosphere

Answer 6

Density is highest near the surface of the earth, and near the equator. reduces upward and towards poles. Five different layers depending upon the temperature condition. They are: troposphere, stratosphere, mesosphere, thermosphere and exosphere.

Question 7

Troposphere

Answer 7

Its average height is 13 km. This layer contains dust particles and water vapour. All changes in climate and weather take place in this layer.

Question 8

Tropopause

Answer 8

The zone separating the tropsophere from stratosphere. Temperature is about minus 80 degrees over the equator and about minus 45 degrees over the poles. The temperature here is nearly constant, hence name

Question 9

Stratosphere

Answer 9

Extends up to a height of 50 km. Contains the ozone layer which absorbs ultra-violet radiation and shields life on the earth from intense, harmful form of energy.

Question 10

Mesosphere

Answer 10

extends up to a height of 50-80 km. The upper limit of mesosphere is known as the mesopause.

Question 11

The ionosphere

Answer 11

is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence, it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by this layer

Question 12

Thermosphere

Answer 12

2nd last

Question 13

Exosphere

Answer 13

Last, rarefied

Question 14

Discuss elements of Weather and Climate

Answer 14

temperature, pressure, winds, humidity, clouds and precipitation.

Question 15

The energy received by the earth from sun is known as

Answer 15

incoming solar radiation which in short is termed as insolation.

Question 16

Aphelion

Answer 16

During its revolution around the sun, the earth is farthest from the sun (152 million km) on 4th July. This position of the earth is called aphelion.

Question 17

Perihelion

Answer 17

On 3rd January, the earth is the nearest to the sun (147 million km). This position is called perihelion.

Question 18

Does variation of insolation have great weather/climate effects? in terms of distance between earth and sun

Answer 18

This variation in the solar output does not have a great effect on daily weather changes on the surface of the earth because the effect of this variation in the solar output is masked by other factors like the distribution of land and sea and the atmospheric circulation.

Question 19

factors determining Variability of Insolation at the Surface of the Earth

Answer 19

(i) the rotation of earth on its axis; (ii) the angle of inclination of the sun’s rays; (iii) the length of the day; (iv) the transparency of the atmosphere; (v) the configuration of land in terms of its aspect. The last two however, have less influence.

Question 20

Form in which earth receives its energy

Answer 20

Short wavelengths

Question 21

What is The Passage of Solar Radiation through the Atmosphere?

Answer 21

The atmosphere is largely transparent to shortwave solar radiation. The incoming solar radiation passes through the atmosphere before striking the earth’s surface. Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation.

Question 22

Spatial Distribution of Insolation at the Earth’s Surface- latitude, season, land/ocean

Answer 22

​​The insolation received at the surface varies from about 320 Watt/m2 in the tropics to about 70 Watt/m2 in the poles. Maximum insolation is received over the subtropical deserts, where the cloudiness is the least. Equator receives comparatively less insolation than the tropics. Generally, at the same latitude the insolation is more over the continent than over the oceans. In winter, the middle and higher latitudes receive less radiation than in summer.

Question 23

Discuss the heating and cooling of the atmosphere (processes)

Answer 23

The air in contact with the land gets heated slowly and the upper layers in contact with the lower layers also get heated. This process is called conduction. Conduction takes place when two bodies of unequal temperature are in contact with one another, there is a flow of energy from the warmer to cooler body. The transfer of heat continues until both the bodies attain the same temperature or the contact is broken. Conduction is important in heating the lower layers of the atmosphere.
The air in contact with the earth rises vertically on heating in the form of currents and further transmits the heat of the atmosphere. This process of vertical heating of the atmosphere is known as convection.
The transfer of heat through horizontal movement of air is called advection. Horizontal movement of the air is relatively more important than the vertical movement. In middle latitudes, most of dirunal (day and night) variation in daily weather are caused by advection alone. In tropical regions particularly in northern India during summer season local winds called ‘loo’ is the outcome of advection process.

Question 24

The earth after being heated by insolation transmits the heat to the atmospheric layers near to the earth in which form?

Answer 24

long wave form

Question 25

Discuss Terrestrial Radiation

Answer 25

1.The insolation received by the earth is in short waves forms and heats up its surface. The earth after being heated itself becomes a radiating body and it 2. radiates energy to the atmosphere in long wave form. This energy heats up the atmosphere from below. This process is known as terrestrial radiation. 3. The long wave radiation is absorbed by the atmospheric gases particularly by carbon dioxide and the other green house gases. Thus, the atmosphere is indirectly heated by the earth’s radiation. The atmosphere in turn radiates and transmits heat to the space. Finally the amount of heat received from the sun is returned to space, thereby maintaining constant temperature at the earth’s’ surface and in the atmosphere.

Question 26

Heat Budget of the Planet Earth

Answer 26

The earth as a whole does not accumulate or loose heat. It maintains its temperature. This can happen only if the amount of heat received in the form of insolation equals the amount lost by the earth through terrestrial radiation.

Question 27

What is the albedo of the earth?

Answer 27

The amount of radiation that the earth reflects back

Question 28

Variation in the Net Heat Budget at the Earth’s Surface

Answer 28

There are variations in the amount of radiation received at the earth’s surface. Some part of the earth has surplus radiation balance while the other part has a deficit. There is a surplus of net radiation balance between 40 degrees north and south and the regions near the poles have a deficit. The surplus heat energy from the tropics is redistributed pole wards and as a result the tropics do not get progressively heated up due to the accumulation of excess heat or the high latitudes get permanently frozen due to excess deficit.

Question 29

Temperature

Answer 29

The interaction of insolation with the atmosphere and the earth’s surface creates heat which is measured in terms of temperature. While heat represents the molecular movement of particles comprising a substance, the temperature is the measurement in degrees of how hot (or cold) a thing (or a place) is.

Question 30

Factors Controlling Temperature Distribution

Answer 30

The temperature of air at any place is influenced by (i) the latitude of the place; (ii) the altitude of the place; (iii) distance from the sea, the air-mass circulation; (iv) the presence of warm and cold ocean currents; (v) local aspects.

Question 31

How does latitude impact temperature?

Answer 31

The temperature of a place depends on the insolation received. It has been explained earlier that the insolation varies according to the latitude hence the temperature also varies accordingly.

Question 32

How does altitude impact temperature?

Answer 32

The atmosphere is indirectly heated by terrestrial radiation from below. Therefore, the places near the sea-level record higher temperature than the places situated at higher elevations. In other words, the temperature generally decreases with increasing height.

Question 33

How does Distance from the sea impact temperature?

Answer 33

Compared to land, the sea gets heated slowly and loses heat slowly. Land heats up and cools down quickly. Therefore, the variation in temperature over the sea is less compared to land. The places situated near the sea come under the moderating influence of the sea and land breezes which moderate the temperature.

Question 34

How do Air-mass and Ocean currents impact temperature?

Answer 34

Like the land and sea breezes, the passage of air masses also affects the temperature. The places, which come under the influence of warm air- masses experience higher temperature and the places that come under the influence of cold air-masses experience low temperature. Similarly,the places located on the coast where the warm ocean currents flow record higher temperature than the places located on the coast where the cold currents flow.

Question 35

Isotherms

Answer 35

The Isotherms are lines joining places having equal temperature.

Question 36

Plank’s law

Answer 36

States that hotter a body, the more energy it will radiate and shorter the wavelength of that radiation.

Question 37

In the southern hemisphere, isotherms are mostly parallel to the latitudes and the variation in temperature is more gradual than in the northern hemisphere, why?

Answer 37

Because the effect of ocean waters is more. The sea heats and cools more gradually than land, and exerts a moderating influence. Meanwhile, the northern hemisphere is more affected due to continentality, there is more temperature variation due to relatively more rapid heating and cooling.

Question 38

Normal lapse rate

Answer 38

Normally, temperature decreases with increase in elevation.

Question 39

Temperature inversion

Answer 39

When normal lapse rate is reversed temporarlily, i.e. temperature increases with increase in altitude. Especially common during winters on a clear night land gets colder. Causes fogs in morning, especially in hills and mountains. Cold air almost acts like water and moves down the slope to pile up deeply in pockets and valley bottoms with warm air above. This is called air drainage. Temperature inversion is normal at the poles.

Question 40

Atmospheric pressure

Answer 40

The weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere is called the atmospheric pressure. The atmospheric pressure is expressed in units of milibar.

Question 41

Measurement of atmospheric air pressure device

Answer 41

Mercury barometer or the aneroid barometer

Question 42

Variations in air pressure vertical and horizontal

Answer 42

Vertically, The pressure decreases with height. Horizontally, At any elevation it varies from place to place and its variation is the primary cause of air motion, i.e. wind which moves from high pressure areas to low pressure areas.

Question 43

Why do we not experience strong upward winds due to vertical pressure of air?

Answer 43

Because it is balanced by a nearly equal but opposite gravitational force.

Question 44

Isobars

Answer 44

Isobars are lines connecting places having equal pressure.

Question 45

Discuss the World Distribution of Sea Level Pressure

Answer 45

Equatorial low
Near the equator the sea level pressure is low and the area is known as equatorial low.
Subtropical highs
Along 30° N and 30o S are found the high-pressure areas known as the subtropical highs.
Subpolar lows
Further pole wards along 60o N and 60o S, the low-pressure belts are termed as the sub polar lows
Polar highs
Near the poles the pressure is high and it is known as the polar high.
These pressure belts are not permanent, move with sun. In the northern hemisphere in winter they move southwards and in the summer northwards.

Question 46

Wind

Answer 46

Air in motion

Question 47

Forces Affecting the Velocity and Direction of Wind

Answer 47

Pressure Gradient Force, Frictional Force, Coriolis Force

Question 48

Pressure Gradient Force

Answer 48

wind blows from high pressure to low pressure. The rate of change of pressure with respect to distance is the pressure gradient. The pressure gradient is strong where the isobars are close to each other and is weak where the isobars are apart.

Question 49

Frictional Force wrt atmosphere

Answer 49

It affects the speed of the wind. It is greatest at the surface and its influence generally extends upto an elevation of 1 - 3 km. Over the sea surface the friction is minimal.

Question 50

Coriolis Force

Answer 50

The rotation of the earth about its axis affects the direction of the wind. It deflects the wind to the right direction in the northern hemisphere and to the left in the southern hemisphere. It is maximum at the poles and is absent at the equator, because higher the pressure, higher the deflection.

Question 51

geostrophic wind

Answer 51

When isobars are straight and when there is no friction (2-3 km above surface), the pressure gradient force is balanced by the Coriolis force and the resultant wind blows parallel to the isobar.

Question 52

cyclonic circulation and anticyclonic circulation

Answer 52

The wind circulation around a low is called cyclonic circulation. Around a high it is called anticyclonic circulation.

Question 53

Wind behaviour in low and high pressure areas

Answer 53

Generally, over low pressure area the air will converge and rise. Over high pressure area the air will subside from above and diverge at the surface.

Question 54

General circulation of the atmosphere depends upon, and importance

Answer 54

The pattern of planetary winds largely depends on : (i) latitudinal variation of atmospheric heating; (ii) emergence of pressure belts; (iii) the migration of belts following apparent path of the sun; (iv) the distribution of continents and oceans; (v) the rotation of earth.
The circulation of atmosphere influences ocean temperature and movement, thus shaping climate.

Question 55

Atmospheric circulation/General circulation of the atmosphere

Answer 55

The pattern of the movement of the planetary winds is called the general circulation of the atmosphere.
1.The air at the Inter Tropical Convergence Zone (ITCZ) rises because of convection caused by high insolation, creating a low pressure zone.
2. This air rises upto 13 km where it encounters cold stratospheric air, then begins moving polewards, but at the subtropical area, encounters incoming cold air from the poles, thus subsiding downwards and branching off in two directions, creating a high pressure zone at the tropics. Air from the subtropical zone moves towards the equator. This air circulation here is called the Hadley Cell.
3. Meanwhile the air branching on to the other side towards poles collides with the colder air coming from the poles from the opposite direction at the subpolar zone, thus causing a convergence of air upwards, creating subpolar lows. This movement is called the ferrel cell.
4. Depending upon the season, this pattern changes. In the northern hemisphere in winter they move southwards and in the summer northwards, and vice versa for the southern hemisphere.
5.polar easterlies, sub tropical westerlies, tropical easterlies/trade winds created due to pressure belts and move right in N and left in S due to the coriolis effect.

Question 56

ENSO

Answer 56

1.pacific ocean and its temperature important
2.ENSO- El Nino and Southern Oscillation.
3. La Nina- tropical trade winds- easterlies push warm currents towards West, causing air to warm, rise high and rain due to convection in Asia, Australia. This warm air when reaches stratosphere becomes cold, loses moisture and becoming dry and moves towards East completing the Walker circulation while colder ocean current off coast of South America near Peru, making the temperature of this area cold.
4.El Nino- trade winds easterlies weak, warm ocean current water moves towards western pacific and causes air to warm up above, causing rains in South America. As the air raches the end of the troposphere, it cools down, loses moisture, and moves westward towards Asia Australia where there are already cold ocean currents
(thermocline), causing this region to become cold and dry.
5.This change in pressure condition over Pacific is known as the southern oscillation. In the years when the ENSO is strong, large-scale variations in weather occur over the world.

Question 57

Types of winds

Answer 57

Seasonal Wind, Local Winds, Land and Sea Breezes, Mountain and Valley Winds

Question 58

Seasonal Wind

Answer 58

modified in different seasons due to the shifting of regions of maximum heating, pressure and wind belts. The most pronounced effect of such a shift is noticed in the monsoons, especially over southeast Asia.

Question 59

Local Winds

Answer 59

Differences in the heating and cooling of earth surfaces and the cycles those develop daily or annually can create several common, local or regional winds.

Question 60

Land and Sea Breezes

Answer 60

the land and sea absorb and transfer heat differently. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results

Question 61

Mountain and Valley Winds

Answer 61

In mountainous regions, during the day the slopes get heated up and air moves upslope and to fill the resulting gap the air from the valley blows called valley breeze. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind.

Question 62

Katabatic wind and adiabatic wind

Answer 62

Anabatic Winds – These Winds are upslope winds driven by warmer surface temperatures on a mountain slope than the surrounding air column. Katabatic Winds – Katabatic winds are downslope winds created when the mountain surface is colder than the surrounding air and creates a downslope wind.

Question 63

Air Masses

Answer 63

When the air remains over a homogenous area for a sufficiently longer time, it acquires the characteristics of the area. The homogenous regions can be the vast ocean surface or vast plains. The air with distinctive characteristics in terms of temperature and humidity is called an airmass. It is defined as a large body of air having little horizontal variation in temperature and moisture.

Question 64

Fronts, process of formation, types

Answer 64

When two different air masses meet, the boundary zone between them is called a front. The process of formation of the fronts is known as frontogenesis. There are four types of fronts: (a) Cold; (b) Warm; (c) Stationary; (d) Occluded. When the front remains stationary, it is called a stationary front. When the cold air moves towards the warm air mass, its contact zone is called the cold front, whereas if the warm air mass moves towards the cold air mass, the contact zone is a warm front. If an air mass is fully lifted above the land surface, it is called the occluded front.

Question 65

Wind systems

Answer 65

1.polar easterlies- 90-60 degree N and S
2.subpolar westerlies- 30-60 degree N and S
3.trade winds to east- 30 degree N and S

Question 66

Tropical cyclones

Answer 66

1.Originate over oceans in tropical areas 30 degree N-S, move towards coast bringing destructive storms but end as land appears as moisture supply cut off
2.They are known as Cyclones in the Indian Ocean, Hurricanes in the Atlantic, Typhoons in the Western Pacific and South China Sea, and Willy-willies in the Western Australia.
3.combination of pressure belts formed due to solar radiation, coriolis effect
4. Air of ocean warms, rises up, creating a low pressure area. Colder air rushes in which in turn gets warm and rises up, generating a spiral that turns clockwise due to the coriolis force deflecting winds to the right in N hemisphere and anti clockwise in S hemisphere.
5.the eye of the storm is the centre, area of low pressure and calm and subsiding air.. Around the eye, the eye wall exists with strong spiralling up air reaching the tropopause. Wind velocity reaches 250 km. from the eye wall, rainbands may radiate outwards and trains of cumulus and cumulonimbus clouds may drift into the outer region. The diameter of the storm over the Bay of Bengal, Arabian sea and Indian ocean is between 600 - 1200 km. The system moves slowly about 300 - 500 km per day.

Question 67

Extra tropical/middle latitude cyclone

Answer 67

1.develop over mid and high latitudes, mostly 30-60 degree N and S, over both land and sea
2. Form along the polar front. Initially front stationary. In the northern hemisphere, warm air blows from the south and cold air from the north of the front (westerlies, deflated eastward due to coriolis effect) then when low pressure area develops, warm air rises up and cold air towards it, setting in motion an anti clockwise cyclone in N and clockwise in S.
3.pockets and fronts of warm and cold air, forming cumulus clouds and precipitation. The cold front moves faster than the warm front ultimately overtaking the warm front (occluded front), and the storm dissipates.

Question 68

Differences between Extra Tropical Cyclones and Tropical Cyclones

Answer 68

1.The extra tropical cyclones move from west to east but tropical cyclones, move from east to west.
2.place ET- mid-high latitudes 30-60 degree N and S T-Tropics 30 degree N and S
3.ET- land and ocean (much larger area) T-ocean only
4.wind velocity and devastation higher in T over ET
5.ET- cumulus T- cumulus and cumulonimbus clouds

Question 69

Thunderstorms

Answer 69

A thunderstorm is a well-grown cumulonimbus cloud producing thunder and lightening. Local, short duration, violent storms
Intense convection on moist hot days.
If not enough moisture, dust storms. If reaches sub zero cold temperature, hailstorm.
These violent storms are the manifestation of the atmosphere’s adjustments to varying energy distribution. The potential and heat energies are converted into kinetic energy in these storms and the restless atmosphere again returns to its stable state.

Question 70

Tornadoes

Answer 70

From severe thunderstorms sometimes spiralling wind descends like a trunk of an elephant with great force, with very low pressure at the centre, causing massive destruction on its way. Such a phenomenon is called a tornado. Tornadoes generally occur in middle latitudes. The tornado over the sea is called water spouts.