# The Earth and Its Atmosphere: 1. Vertical structure 2. Weather and climate

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The earth’s atmosphere is a mixture of many gases. In a volume of dry air near the surface, nitrogen (N2) occupies about 78 percent and

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Water vapor, which normally occupies less than 4 percent in a volume of air near the surface, can condense into liquid cloud droplets or

transform into delicate ice crystals. Water is the only substance in our atmosphere that is found naturally as a gas (water vapor), as a liquid (water) and as a solid (ice).

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Both water vapor and carbon dioxide (CO2) are important greenhouse gases.

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Ozone (O3) in the stratosphere protects life from harmful ultraviolet (UV) radiation. At the surface, ozone is the main ingredient of

photochemical smog.

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The majority of water on our planet is believed to have come from its hot interior through outgassing.

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Atmospheric pressure at any level represents the total mass of air above that level, and atmospheric pressure always decreases with increasing height above the surface.

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Mass M:

property of matter,

SI unit: kg. Other units: 1kg=1000 g, 1 lb=450 g

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Weight :

a force, has a magnitude and direction (vector).

weight = mass x gravity g(Earth)= 9.78 m/s2

SI unit: kg m/s2 -> N g(Mars)= 3.7 m/s2

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Density ρ:

mass per unit volume: density = mass / volumeSI unit: kg/m3, Other: g/cm3

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Pressure p:

p= force/area

SI units: Pa=N/m2, Other: 1bar=100 Pa

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99.9%

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Troposphere:

The temperature T decreases with height at a rate of 6.5 K/km.Well mixed as a result of turbulence and convection

Weather phenomena

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Tropopause:

Isothermal (T constant)

Located 8-15 km above the ground.

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Stratosphere:

The temperature T increases with height ♦ O3 layer at 25 km altitude

The atmosphere is very stable

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Stratopause: T=const

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Mesosphere:

T is decreasing with height: effective cooling through IR emission.

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Mesopause: the coldest region on Earth.

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Mixing: ♦ Homosphere:

well mixed,

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the chemical composition is constant. ♦ Heterosphere:

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no turbulence and mixing,

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diffusive separation of gases

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Ionization:

Ionosphere: part of the

atmospheric gas is ionized through photo ionization

or impact ionization.

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### The Terrestrial Planets

Me r c ur y Ve nus Ea r t hMa r s Pl ut o Di s t a nc e AU. Ra di us RE. De ns i t y . Gr a v i t y . Ro t a t i o na l pe r i o d Or bi t a l pe r i o d. Obl i qui t y 1 1 1 2 3 . 4 9 . 7 8 5 . 5 2 4 1 0 . 3 9 0 . 0 5 5 0 . 3 8 0 3 . 6 2 5 . 4 3 1 4 0 7 0 . 2 4 0 . 7 2 0 . 8 1 5 0 . 9 5 2 . 7 8 . 5 7 5 . 2 4 5 8 3 2 0 . 6 1 . 5 0 . 1 0 . 5 3 2 5 3 . 7 3 . 9 4 2 4 . 6 1 . 8 8 3 9 . 4 0 . 0 0 2 5 0 . 1 7 6 6 2 0 . 3 2 1 5 3 2 4 7 Ma s s ME. 260 480 T=15 C -60 -110 -190 -215 -225 -235 Ma i n c o mpo ne nt s - CO2 N2, O2 CO2 CH4

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### The Giant Planets

J upi t e r Ne pt une Ea r t h Sa t ur nUr a nus Di s t a nc e AU Ra di us RE De ns i t y Gr a v i t y Ro t a t i o na l pe r i o d Or bi t a l pe r i o d Obl i qui t y 1 1 1 2 3 . 4 9 . 7 8 5 . 5 2 4 1 5 . 2 3 1 8 1 1 3 2 2 . 9 1 . 3 1 1 0 1 1 . 9 9 . 5 9 4 . 5 9 . 5 2 7 9 0 . 6 9 1 0 2 9 . 5 1 9 . 2 1 4 . 5 4 9 8 8 . 7 1 . 2 9 1 8 8 4 3 0 1 7 3 . 9 3 0 1 1 1 . 6 4 1 9 1 6 5 Ma s s ME Ma i n c o mpo ne nt s H2, He N2, O2 H2, He H2,He,CH4 H2, He

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isotherm

isobar

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Meteorology is the study of the atmosphere and its phenomena

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In “Meteorologica” (340 B.C.) Aristotle discussed

meteors (things which fall from the sky)

weather and climate, astronomy, geography…

clouds, rain, snow, wind, hail, thunder, hurricanes…

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Invention of weather instruments in the Middle Ages

Pressure: barometer (1643, E. Torricelli)

Humidity: hygrometer (1783, H. de Saussure)

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Rapid exchange of weather information (telegraph, 1843)

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Crude weather maps (1869)

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Norwegian model of storm development (1920’s)

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Air balloon and high-flying aircraft observations (1940)

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High-speed computers and numerical predictions (1950-)

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Weather satellites (1960-) de Saussure Aristotle

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### Weather phenomena: a preview

Clouds and thunderstorms

Ice storm