Climate of the World

2020-04-28 23:13:27

Climate of the World

Solar Radiation, Heat Balance and Temperature

Solar Radiation

Earth’s surface receives most of its energy in short wavelengths aka incoming solar radiation or insolation
Earth is farthest from the sun (152 million km) on 4th July this position is called the aphelion.
On 3rd January, the earth is the nearest to the sun this is called the perihelion.

Factors that Cause Variability in Insolation Are

rotation of earth on its axis
Angle of inclination of sun’s rays
length of the day
transparency of atmosphere
Landforms eg Mountain, plains etc.
Maximum insolation is received by subtropical deserts due to ==absence of cloudiness==. Equator receive comparitively less insolation, least on the poles.

Heating and Cooling of Atmosphere

Earth reflects in long wave form which heats up the atmosphere this process is called terrestrial radiation : it is 51% of the total radiation that reaches it.
Convection is vertical heating, ==confined only to troposphere==.
The transfer of heat through horizontal movement of air is called as advection ex Loo.
Insolation more over continent than over oceans at similar latitudes.
Earth as a whole does not accumulate or loose heat, maintains its temp.
- The reflected amount of radiation is about 64% it is called the albedo of the earth. #important
Rate of dec of temp is 6.5 C per 1000mts.
Effect of land is pronounced in Northern Hemisphere, vice versa is true for oceans in Southern H.

Inversion of Temperature

temp inc w/ inc in elevation but is only for a short duration.
requires long winter nights, clear skies; common in ==polar areas==.
Heat is radiated during night by morning earth is cooler than air above.
Surface inversion takes place due to accumulation of dust.
in hills cold air moves down slope -> cooling of valleys aka air drainage.

Atmospheric Circulation and Weather System

The pressure decreases by about 1 mb for each 10m inc in elevation
Vertical pressure is greater than Horizontal but is balanced by gravitational force
Near Equator seal level pressure is low called equatorial low
Subtropical highs found along 30N and 30S; 60N and 60S subpolar lows are seen
Pressure is high near poles called polar highs

Forces Affecting Velocity and Direction of Wind

The horizontal winds near the earth’s surface respond to the combined effect of :
- Pressure gradient force
  - pressure gradient is strong where isobars are close, weak when apart
- Frictional force - greatest at surface min at sea; affects speed of the wind
- Coriolis force
  - deflects wind towards Right in northern hemisphere and Left in southern hemisphere
  - acts perpendicular to pressure gradient force
  - Max at the poles and absent at equator and is directly proportional to the angle of latitude
When isobars are straight and there is no friction, the pressure gradient force is balance by Coriolis force and wind blows parallel to the Isobars called Geostrophic winds.
Why cyclones are not formed near equators?

![[kegy210.pdf#page=4]]

General Circulation of the Atmosphere

The pattern of planetary winds aka general circulation of the atmosphere depends upon :
- latitudnal variation of temp pressure belts
- Emergence of pressure Belts
- their migration
- distribution of continents and oceans
- rotation of the earth
ITCZ is convergence of air/easterlies from tropics at 30°N and S
Large scale atmospheric cell in which air rises at the equator and sinks at 30° latitudes(middle lats) are called Hadley cell
Sinking cold air from poles and rising hot air from sub-tropical high forms a cell at surface called Ferrel cell
The sinking cold air from poles blows towards middle latitudes forming a polar cell
These 3 cells set the pattern of general circulation of atmosphere
Seasonal winds like Monsoon, Local winds, Land and Sea Breeze are also influenced by the GPoCoA
Valley Breeze : heated air from valley blows up the slope during day time; Mountain Wind : dense cool air blows down the slope during night
Cool air of high plateaus and ice fields draining into the valley is called Katabatic wind

![[Climate-of-the-World—image1-00090827.jpg|300x300]]

Air Masses :

distinct characteristics in terms of temp and humidity ex Warm tropical, Maritime Polar, Maritime Tropical etc
When different air masses meet the boundary zone between them is called a Front
- Ex Cold, Warm, Occluded and Stationary
- Occur in middle latitudes, cause abrupt changes in temp and rain

Extra Tropical Cyclones :

dev in middle or extra tropical latitudes
caused due to passage of fronts

Cyclones

Conditions for the formation of tropical cyclones? #important ![[kegy210.pdf#page=7]]
- Large sea surface temp > 27°C
- Coriolis Force
- Small variation in vertical wind speed
- prexisting weak low pressure area/ low level cyclonic circulation
- Upper divergence above sea level system
Tropical Cyclones aka Cyclones in the Indian Ocean, Hurricanes in Atlantic, Typhoons in the Western Pacific and South China Sea, Willy-willies in Western Australia.
Energy comes from Cummulonimbus clouds, moisture from sea strengthens it further
Wind velocity highest in the eye, torrential rains occur here ^30e6d0

Extratropical Cyclones	Tropical Cyclones
Have a clear frontal system	absent
Cover a large area	cover a much smaller area
Originates over both land and sea	originate only over seas on reaching land they dissipate
Less wind velocity, less destructive	high wind velocity, very destructive
Move from West to East	Move East to west

Thunderstorms

are caused by intense convection on moist hot days
- is a well grown cummulonimbus cloud
- Hails are formed when cloud reaches sub zero temp
- Spiralling winds descend from severe thunderstorms towards low pressure area forming Tornadoes
  - generally occur in the middle latitudes.
  - Over the sea they are called Water Spouts.

Water in the Atmosphere

Absolute humidity : actual amount of water vapour present in atmosphere or weight of water per unit vol of air.
Relative humidity : percentage of moisture present in atmosphere as compared to its full capacity at a given temperature.
Dew point : temp at which saturation occurs in a given sample of air.

Evaporation and Condensation

Latent heat of vaporisation : Temp at which water starts evaporating

Condensation

water vapour -> liquid water
direct conversion to solid water is called sublimation
Causes :
- cooling around hygroscopic nuclei
- moist air comes in contact w/ colder object
- temp reduces closer to dew point
Influenced by volume of air, temp, pressure and humidity

Forms of Condensation :

Dew :

ideal conditions are clear sky, calm air, high relative humidity, cold and long nights and dew point needs to be above the freezing point

Frost :

Forms on cold surfaces
Conditions of formation are similar to dew except air temperature must be at or below the freezing point

Fog and Mist :

temp of air mass fall suddenly, hygroscopic nuclei are responsible
Fogs are clouds formed very close to the ground
Mist contains more moisture than fog, frequent over mountains

Clouds

Cirrus

formed at high altitudes viz 8,000 - 12,000m
thin and detatched having feathery appearance
always white in colour
absorb more infrared than they reflect this process exacerbates global warming. Cirrus cloud thinning technique is used to counter this which cools the Earth #PrelimsPYQ ![[Climate-of-the-World—image2-00090827.jpg]]

Cumulus clouds

look like acotton wool and have a *flat base
generally formed at height of 4,000 - 7,000m
exist in patches and are scattered ![[Climate-of-the-World—image3-00090827.jpg]]

Stratus

layered clouds covering large portions of the sky.
formed either due to loss of heat or mixing of air masses of different temp ![[Climate-of-the-World—image4-00090827.jpg]]

Nimbus clouds

black or dark gray in colour
Form at middle levels or very near to the surface
shapeless masses of thick vapour. ![[Climate-of-the-World—image5-00090827.jpg]]

Combination Clouds

High clouds = Cirrus, Cirroculums, Cirrostratus
Middle clouds = Altostratus, Altocumulus, Nimbostratus
Low clouds = Stratus, Stratocumulus, Fair weather cumulus
Clouds w/ extensive vertical development = Comulonimbus and towering Cumulus

Precipitation

Besides rain and snow, other forms of precipitation are sleet and hail.

Sleet

frozen raindrops and refrozen melted snow-water.
forms when a layer of air with temperature above freezing point overlies a subfreezing layer near the ground. ![[Climate-of-the-World—image6-00090827.jpg |300x200]]

Types of Rain

Convectional rainfall

common in the summer or in the hotter part of the day
esp in equator and interior parts of continents
particularly in northern hemisphere

Orographic

also known as the relief rain
area situated on the leeward side, which gets less rainfall is known as the rain-shadow area

Cyclonic Rains

![[#^30e6d0]]

Distribution of Rainfall

Coastal areas receives more, More in oceans than in continents
b/w 35-40°N and S heavier on eastern coast dec towards west
b/w 45-65°N and S first received in western margins due to westerlies

Various Local Winds

Alizé	Maritime wet, fresh northerly wind across west central Africa.
Bora	northeasterly from eastern Europe to northeastern Italy
Cape Doctor	dry south-easterly wind that blows on the South African coast in summer
Chinook	warm dry westerly off the Rocky Mountains
Diablo	hot, dry, offshore wind from the northeast in the San Francisco bay
Etesian	northerly across Greece and Turkey
Elephanta	strong southerly or southeasterly wind on the Malabar coast of India
Föhn	warm dry southerly off the northern side of the Alps and the North Italy
Fremantle Doctor	afternoon sea breeze from the Indian Ocean which cools Perth, Western Australia during summer
Harmattan	dry northerly wind across central Africa
Kali Andhi	the violent dust squalls that occur before monsoon in the northwestern parts of the Indo-Gangetic Plain region of the Indian Subcontinent.
Karaburan	a Spring and winter Katabatic wind of central Asia
Khamsin	southeasterly wind from North Africa to the eastern Mediterranean
Loo	hot wind which blows over plains of India and Pakistan.
Maestro	cold northerly in the Adriatic sea
Mistral	cold northerly from central France and the Alps to Mediterranean
Monsoon	mainly south-westerly winds combined with heavy rain in various areas close to the equator
Nor’easter	strong storm with winds from the northeast on the north eastern coast of the United States (particularly New England states) and the east coast of Canada (Atlantic Canada)
Nor’wester	wind that brings rain to the West Coast, and warm dry winds to the East Coast of New Zealand’s South Island, caused by the moist prevailing winds being uplifted over the Southern Alps, often accompanied by a distinctive arched cloud pattern
Pampero (Argentina)	very strong wind which blows in the Pampa
Passat	medium strong, constant blowing wind at sea in tropical areas
Rashabar(“black wind”)	a strong wind in the Kurdistan Region of Iraq, particularly in Sulaimaniya.
Santa Ana winds	southern California
Shamal	a summer northwesterly wind blowing over Iraq and the Persian Gulf states
Simoom	strong, dry, desert wind that blows in the Sahara, Israel, Jordan, Syria, and the desert of Arabia
Sirocco	southerly from north Africa to southern Europe
Southerly Buster	rapidly arriving low pressure cell that dramatically cools Sydney, Australia during summer
Sou’wester	strong wind which blows from the southwest, and also a type of waterproof hat designed to protect from and repel wind and rain
Squamish	strong, violent wind occurring in many of the fjords of British Columbia
Vendavel	westerly through the Strait of Gibraltar
Zonda	on the eastern slope of the Andes in Argentina.

Types of Deltas :

Name	Rivers	Properties
Wave Dominated Deltas	Nile River	action of wave determines size and shape of delta. Has fewer distributaries.
Tide Dominated	Ganga and Brahmaputra	have more distributaries, sandbars and ridges are prominent
Gilbert Deltas	Lake Bonneville and Okanagan Lake	formed by the deposition of coarse sediments at the mouth of a river, only occurs where there is R. empties into freshwater lakes
Estuarine	Yellow river and Tagus of Portugal	does not directly empty into sea
Archuate	Nile	have typical deltaic shape, arc like or fan shaped.
Cuspate	Tiber R. near Rome in Tyrrhenian sea	formed in regions of stronger waves, shape is more pointed towards sea.
Birds Foot Delta	Mississippi	not exactly triangular, distributaries widely spaced
Inverted Delta	Sacramento-San Joaquin R. in California	distrbutaries network faces inland while single stream leads to sea
Inland Delta	Okavango R. in Bostswana	delta empties into a plain not into a water body.
Abandoned Delta	Mississippi R.	dry delta bed left after river discards its former channel due to silt build up.

Continents and Highest Mountains :

Continent	Name	Country
Asia	Everest	Nepal
	K2	POK
	Kachendzonga	India
Europe	Elbrus	Geogrgia and Russia
	Dykh Tau	Russia and Georgia
	Shkhara	Georgia
Africa	Kilimanjaro	Tanzania
	Batian	Kenya
	Stanley	Democratic Rep of Congo and Uganda
Oceania	Carstensz/ Puncak Jaya	Indonesia(Sudirman Range)
	Sumantri	Indonesia
	Mandala	Indonesia
Antarctica	Mt. Vinson Massif	Sentinel Range Antarctica
	Mt. Tyree	B/w Patton Glacier and Cervellati Glacier
	Mt. Shinn	b/w Ramorino Glacier and Crosswell glacier
South America	Aconcagua	Argentina
	Ojos Del Salado	Argentina - Chile Border
	Pissis	Argentina - Chile Border
North Amercia	Denali/ Mt Mckinley	US
	Mt. Logan	Canada
	Orizaba	US

La Nina, El Nino, Walker Circulation

EL Nino Explanation

El Nino and La Nina are part of the El Nino Southern Oscillation ENSO cycle.

Image unavailable in web version: Image

Hot Wet Equatorial Climate

Climate

5° to 10° S and N of Equator viz Amazon, Congo, Malaysia,
Temp uniform throughout and No winter
Cloudiness, Heavy precipitation, land and sea breeze moderates daily temp; annual and diurnal range is small
Heavy rainfall ==150-250cm== peaks during equinoxes, no month w/o rain, distinct dry season missing
morning bright, sunny → convectional, torrential rains
Mountains show orographic“/relief rains

Vegetation

is equatorial
Tropical rain forest called ==Selvas== in Amazon
Evergreen trees, palm trees, Climbers like Lianas, Rattans, Ferns viz orchids and Lalang
Thick canopy, layer like arrangement height wise of trees
Trees not found in pure stands of 1 single species → commercial timber exploitation becomes difficult
Lumbering, Shifting cultivation have cleared rain forests, in Coastal areas Mangrove thrive

Life

Sparsely populated, shifting cultivation, food is abundant
Tribes such as Indian tribes in Amazon, Pygmies in Congo Basin gather nuts, Orang Asli in Malaysia collect canes etc thrive
Crops viz Tapioca, yams, maize, banans, groundnuts. Plantation are common ex. Rubber, ==Cocoa== esp in West Africa, Oil palm.
High heat, humidity → physical and mental enervation, decreases work efficiency
Diseases like Malaria etc, insects, pests common
Lalangs are undesirable long grasses that choke crops
Soils deteriorates rapidly, humus present makes it fertile but otherwise soil is not productive
No grasslands handicaps livestock farming

Tropical Monsoon Type Climate

Found in India, Burma, Thailand, Laos, Cambodia, North Australia, South China

Climate

Differential heating of Land and sea causes Central Asian land mass to be an intense low pressure area
Whereas Australia winter making it a high pressure area.
Winds from AUS blow as SE become SW after crossing equator
During winter this condition is reversed and NE Monsoon winds blow

Seasons

Cool dry winters, Winter rains in Punjab is vital for Rabi crops
NE winds bring rainfall to areas of Tamil Nadu
Summers are hot and dry, SW Monsoons torrential downpour cools it → is characteristic feature

Tropical Marine Climate

Along Eastern coast of tropical lands ex Brazil
recieves rainfall from Trade winds it is both orographic and convectional
most of it occurs during Jan, Feb; no month w/o rainfall

Tropical Monsoon Forests

Deciduous trees, Forests have hardwood trees ex teak, sal, acacia, eucalyptus
these forests often thin out to scrubland and savanna during summer

Agriculture

farming is intense, dominant occupation and mainstay of economy
Rice most staple has 2 main varieties Wet and Dry paddy; rainfall required is 150cm
Lowland tropical cash crops viz Sugarcane, Jute, Manila Hemp, Indigo, Cotton, Bananas, Coconut and Spices
Higland plantation crops viz Tea, Coffee
Lumbering is still carried out esp of Teak on the banks of Chindwin, Irrawaddy
Shifting Cultivation is common done entirely for subsistence
- Called Ladang in Malaysia, Taungya in Burma, Tamrai in Thailand, Caingin in Phillipines, Humah in Java, Chena in Sri Lanka, Milpa in Africa and Central America. #important
Soils are mainly latosolic, leaching is rapid, easily exhausted.

Savannah or Sudan Type Climate

[[kegy208 3.pdf]] - Composition and Structure of Atmosphere. [[kegy209.pdf]] - Solar Radiation, Heat Balance and Temperature. [[kegy210 1.pdf]] - Atmospheric Circulation adn Weather Systems. [[kegy211 1.pdf]] - Water in the Atmosphere [[kegy212.pdf]] - World Climate and Climate Change