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EG4508: Issues in environmental science. Meteorology and Climate Dr Mark Cresswell The Atmosphere 1. Suggested References #1. Text Books:. Ahrens, C. Donald. (2000) Meteorology today : an introduction to weather, climate, and the environment.

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Eg4508 issues in environmental science

EG4508: Issues in environmental science

Meteorology and Climate

Dr Mark Cresswell

The Atmosphere 1


Suggested references 1
Suggested References #1

Text Books:

  • Ahrens, C. Donald. (2000) Meteorology today : an introduction to weather, climate, and the environment.

  • Harvey, Danny. (2000) Climate and global environmental change

  • Burroughs, William James. (2001) Climate change : a multidisciplinary approach.

  • Climate change 2001 : The scientific basis / edited by J.T. Houghton

  • McGuffie K and Henderson-Sellers A. (1997). A climate modelling primer. Published by John Wiley, England.


Suggested references 2
Suggested References #2

Scientific Journals:

  • Quarterly Journal of the Royal Meteorological Society

  • Monthly Weather Review

  • Meteorological Applications

  • Journal of Climatology

SEE UKSCIENCE METEOROLOGY PAGES FOR MORE INFO


Suggested references 3
Suggested References #3

Internet:

  • KNMI climate explorer:

    • http://climexp.knmi.nl

  • Royal Meteorological Society:

    • http://www.royal-met-soc.org.uk/

  • The Met. Office:

    • http://www.meto.gov.uk/

  • NOAA-ENSO:

    • http://nsipp.gsfc.nasa.gov/enso/


WWW.UKSCIENCE.ORG  EGS UNITS  EG4508 LINK


General points
General Points

  • The atmosphere behaves like a fluid

  • The atmosphere is a mixture of different gases, aerosols and particles

  • The atmosphere remains around the earth as an envelope because of gravity

  • Much of the observed motion in the atmosphere results from solar radiation


Basic astronomy
Basic Astronomy

  • For most of the Earth, energy varies on daily (diurnal) and seasonal (annual) time-scales.

  • Changes from daytime to night and progression through the four seasons depends on the configuration of the Earth-Sun orbit




Basic astronomy1
Basic Astronomy activity

  • The Earth completes a single rotation about its axis in approx 24 hours (23.9345 hours!) - this period is known as a day


Basic astronomy2
Basic Astronomy activity

  • The Earth completes a single revolution around the Sun in approx 365 days (365.256 days) - period is known as a year


Basic astronomy3
Basic Astronomy activity

  • Energy received at different points on the earth’s surface is not constant

  • As we move from the equator to the poles the quantity of energy decreases

  • This is due to Earth curvature

  • The same amount of energy is spread over a greater area and has to pass through a thicker layer of the atmosphere


Basic astronomy4
Basic Astronomy activity

  • Axis about which the earth rotates tilts

Spring

Summer

Winter

Autumn


Basic astronomy5
Basic Astronomy activity

SUMMER (N. Hemisphere) WINTER (N. Hemisphere)


Basic astronomy6
Basic Astronomy activity

  • The Earth does not spin perfectly about its axis - but tilts to trace a cone in space - caused by the combined Sun and Moon’s gravitational pull and is called precession

  • This tilt angle varies - between about 22º and 25º - it is currently 23.5º


Basic astronomy7
Basic Astronomy activity

  • In addition to tilt - the elliptical orbit the Earth takes around the Sun varies also

  • Mean distance between the Earth and the Sun is 1AU (1.496 x 108 km). Minimum distance is 0.983AU and the maximum distance is 1.017AU


Basic astronomy8
Basic Astronomy activity

  • In addition, the Earth’s path along its ellipse will vary slightly due to differential gravitation pull. This is known as the eccentricity of the orbit.


Basic astronomy9
Basic Astronomy activity

  • The combination of factors such as orbital eccentricity, precession, tilt angle, distance from the Sun etc greatly affect our climate by varying the quantity of solar energy received

  • Collective term is Orbital Forcing

  • May have influenced the magnitude and period of past ice ages


Basic astronomy10
Basic Astronomy activity

  • The gravitational pull of the moon affects our tides and also moderates energy levels in the oceans

  • Ocean dynamics greatly influences our Earth’s climate system



Vertical structure of the atmosphere
Vertical structure of the atmosphere activity

  • Weight is the mass of an object multiplied by the acceleration of gravity

    Weight = mass x gravity

  • An object’s mass is the quantity of matter in the object


Vertical structure of the atmosphere1
Vertical structure of the atmosphere activity

  • The density of air is determined by the mass of molecules and the amount of space between them

    Density = mass/volume

  • Density tells us how much matter is in a given space (or volume)


Vertical structure of the atmosphere2
Vertical structure of the atmosphere activity

  • Each time an air molecule bounces against an object it gives a tiny push

  • This small pushing force divided by the area on which it pushes is called pressure

    Pressure = force/area


Vertical structure of the atmosphere3
Vertical structure of the atmosphere activity

  • In meteorology we discuss air pressure in units of hectopascals (hPa) (previously called millibars mb)

  • The average atmospheric pressure at the Earth surface is 1013.25 hPa

  • We can sense sudden changes in pressure when our ears ‘pop’ such as that experienced in old aircraft


Relationship between pressure and height
Relationship between pressure and height activity

  • As we climb in elevation (up a mountain or in a hot air balloon) fewer air molecules are above us:

    atmospheric pressure always decreases with increasing height


Energy basic laws and theory
Energy: basic laws and theory activity

  • Energy is the ability or capacity to do work on some form of matter

  • Energy is transformed when it interacts with matter - e.g. potential energy is transformed into kinetic energy when a brick falls to the ground

  • Matter can neither be created nor destroyed - only change form


Energy basic laws and theory1
Energy: basic laws and theory activity

  • The energy stored in an object determines how much work it can do (e.g. water in a dam). This is potential energy

PE = mgh

PE = potential energy

m = mass of the object g = acceleration of gravity

h = object’s height above the ground


Energy basic laws and theory2
Energy: basic laws and theory activity

  • A volume of air aloft has more potential energy than the same volume of air above the surface

  • The air aloft has the potential to sink and warm through a greater depth of the atmosphere

  • Any moving object possesses energy of motion or kinetic energy


Energy basic laws and theory3
Energy: basic laws and theory activity

  • The kinetic energy of an object is equal to half its mass multiplied by its velocity squared:

KE = ½ mv2

  • The faster something moves, the greater its kinetic energy. A strong wind has more kinetic energy than a light breeze


Energy basic laws and theory4
Energy: basic laws and theory activity

  • Temperature is a measure of the average speed of the atoms and molecules, where higher temperatures correspond to faster average speeds

  • If a volume of air within a balloon were heated the molecules would move faster and slightly further apart - making the air less dense

  • Cooling air slows molecules down and so they crowd together becoming more dense


Energy basic laws and theory5
Energy: basic laws and theory activity

  • Heat is energy in the process of being transferred from one object to another because of the temperature difference between them


Temperature scales
Temperature scales activity

  • Hypothetically, the lowest temperature attainable is absolute zero

  • Absolute zero is -273.15 ºC

  • Absolute zero has a value of 0 on a temperature scale called the Kelvin scale - after Lord Kelvin (1824-1907)

  • The Kelvin scale has no negative numbers


Temperature scales1
Temperature scales activity

  • The Celsius scale was introduced in the 18th century. The value of 0 is assigned to the freezing point of water and the value 100 when water boils at sea-level

  • An increasing temperature of 1 ºC equals an increase of 1.8 ºF


Specific heat and latent heat
Specific heat and latent heat activity

  • Liquids such as water require a relatively large amount of heat energy to bring about just a small temperature change

  • The heat capacity of a substance is the ratio of the amount of heat energy absorbed by that substance to its corresponding temperature rise


Specific heat and latent heat1
Specific heat and latent heat activity

  • The heat capacity of a substance per unit mass is called specific heat

  • Specific heat is the amount of heat needed to raise the temperature of one gram (g) of a substance by one degree Celsius

  • 1g of liquid water on a stove would need 1 calorie (cal) to raise its temperature by 1 ºC


Specific heat and latent heat2
Specific heat and latent heat activity

  • When water changes its state (solid to liquid, liquid to gas etc) heat energy will be exchanged

  • The heat energy required to change a substance from one state to another is called latent heat

  • Evaporation is a cooling process

  • Condensation is a warming process


Energy transfer in the atmosphere
Energy transfer in the atmosphere activity

  • Conduction: transfer of heat from molecule to molecule (hot spoon)

  • Convection: transfer of heat by the mass movement of a fluid (such as water and air)

  • Radiation: Movement of energy as waves - the electromagnetic spectrum


Electromagnetic spectrum with enhanced detail for visible region of the spectrum

Note the large range of wavelengths encompassed in the spectrum - it is over twenty orders of magnitude!


Emr and the sun atmosphere system
EMR and the Sun-atmosphere system region of the spectrum

  • About 50% of incoming solar radiation is lost by the atmosphere: scattered (30%) and absorbed (20%)

  • Scattering involves the absorption and re-emission of energy by particles

  • Absorption (unlike scattering) involves energy exchange


Emr and the sun atmosphere system1
EMR and the Sun-atmosphere system region of the spectrum

  • Wavelengths less than and greater than 0.8µm (800nm) are often referred to as shortwave and longwave radiation respectively

  • The shortwave solar radiation consists of ultraviolet and visible

  • The terrestrial longwave component is known as infrared


Emr and the sun atmosphere system2
EMR and the Sun-atmosphere system region of the spectrum

  • Just under 50% of the radiation reaching the Earth’s surface is in the visible range

  • Components of visible light are referred to as colours

  • Each colour behaves differently and white light can be separated out by use of a prism


Emr and the sun atmosphere system3
EMR and the Sun-atmosphere system region of the spectrum

  • The human eye cannot see infrared radiation

  • Infrared radiation is absorbed by water vapour and carbon dioxide in the troposphere

  • The atmosphere’s relative transparency to incoming solar (SW) radiation, and ability to absorb/re-emit outgoing infrared (LW) radiation is the natural greenhouse effect


The earth s energy balance
The Earth’s energy balance region of the spectrum

  • Incoming solar (shortwave) energy should be balanced by outgoing terrestrial (longwave) energy

  • Without a balance the Earth would heat up or cool down uncontrollably

  • Energy may take a tortuous path from Sun to ground and back to space.


Greenhouse effect
Greenhouse effect region of the spectrum

  • The natural greenhouse effect maintains a stable climate for life on earth

  • Outgoing radiation (longwave) is absorbed by molecules such as water vapour and carbon dioxide

  • Energy is then re-emitted in all directions - forming a blanket


Greenhouse region of the spectrum

Effect


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