Met 2204 meteorology
This presentation is the property of its rightful owner.
Sponsored Links
1 / 69

MET 2204 METEOROLOGY PowerPoint PPT Presentation


  • 118 Views
  • Uploaded on
  • Presentation posted in: General

MET 2204 METEOROLOGY. Presentation 3: Atmosphere. Recapitulate. Lets recap what we have done last week: Definition of Meteorology Different between Weather and Climate Importance of Meteorological in Aviation. Presentation Outline. Introduction Layers of Atmosphere

Download Presentation

MET 2204 METEOROLOGY

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Met 2204 meteorology

MET 2204METEOROLOGY

Presentation 3: Atmosphere

Presented by Mohd Amirul for AMC


Recapitulate

Recapitulate

  • Lets recap what we have done last week:

    • Definition of Meteorology

    • Different between Weather and Climate

    • Importance of Meteorological in Aviation


Presentation outline

Presentation Outline

  • Introduction

  • Layers of Atmosphere

  • Variation in Atmosphere

  • Air Stability

  • Conclusion

Part 1

Part 2


Learning outcomes

Learning Outcomes

  • At the end of this session, student should be able to:

    • Outline the composition and structure of earth atmosphere

    • Identify the temperature, humidity, pressure, and density variation vertically and horizontally in atmosphere.

    • Understand the concept of air stability.

Presented by Mohd Amirul for AMC


Introduction

Introduction

  • Earth view:

    • Altitude

      • Vertical height

        from earth

        surface.

    • Longitude

    • Latitude


Met 2204 meteorology

Cont.

  • Air is one of the primary things that makes life on Earth possible. Air is a synonym for atmosphere. The Earth’s atmosphere or air is made up of a variety of gases and other particles.


Met 2204 meteorology

Cont.

  • What is the Atmosphere??

    • layer of gases surrounding the planet Earth that is retained by Earth's gravity.

  • Gases in atmosphere:

    • 78% - Nitrogen

    • 21% - Oxygen

    • 1% - Other gases (Argon,

      Carbon Dioxide, Neon,

      Helium)


Met 2204 meteorology

Cont.

*In fact the air never completely dry!! (it contains some water vapor 0-5% by volume)

*This proportion remains constant until at least 60 km – 70 km altitude.


Layers structure of atmosphere

Layers (Structure) of Atmosphere


Met 2204 meteorology

Cont.

  • Troposphere

    • Temperature will decrease with altitude.

    • 75% of weight of atmosphere.

    • Contains almost all weather

    • Altitude (height) vary with:

      • Latitude: lower at poles and higher at equatorial

      • Seasons: higher in summer than winter

    • Almost all clouds in this layer.

    • Most commercial aircraft flying in this altitude


Met 2204 meteorology

Cont.

  • Tropopause

    • Boundary between troposphere and stratosphere.

    • Temperature stop to decrease.

    • Not a continuous line

      (Usually a gap at 40° of latitude between polar and tropical)


Met 2204 meteorology

Cont.

  • Height vary with:

    • Latitude:

      • Thickest in tropic (20 km or 65000 ft from sea level)

      • Thinnest near poles (7km or 23000ft from sea level)

  • Height of tropopause is important because it marks:

    • Max. Height of Cloud.

    • Presence of Jetstream.

    • Presence of Clear Air Turbulence (CAT).


Met 2204 meteorology

Cont.

  • Stratosphere

    • Very small increase in temperature (almost constant) except at the top where temperature is zero at 50 kms.


Variation in atmosphere

Variation in Atmosphere

  • The earth’s atmosphere varies vertically and horizontally in

    • Temperature

    • Pressure

    • Density

    • Humidity


Met 2204 meteorology

Temperature


Definition

Definition

  • What are the differences between heat and temperature?


Temperature scale of measurement

Temperature Scale of Measurement

  • Fahrenheit scale: from -32 to 212 deg

  • Celcius(centigrade) scale: from 0 to 100 deg

  • Kelvin (absolute) scale: from -273 to 373 deg


Met 2204 meteorology

Cont.


Radiation

Radiation

  • Energy transmit in the form of rays, waves, or particles.

  • Solar = relating to the sun

  • Terrestrial = relating to the earth (e.g. land)


Solar radiation sr

Cont.

Solar Radiation (SR)

  • The sun is a main source of heat for earth

  • Emitted from the sun to the earth.

  • Much of SR reflected back, absorbed by atmosphere upper layers

  • Only average 45% SR reach the earth surface


Terrestrial radiation tr

Cont.

Terrestrial Radiation (TR)

  • Energy emitted from earth to atmosphere


Solar and terrestrial radiation

Cont.

Solar and Terrestrial radiation

SOLAR RADIATION

TERRESTRIAL RADIATION


Difference between solar terrestrial radiation on the earth surface

Cont.

Difference between Solar & Terrestrial Radiation on the Earth Surface

INCOMING=OUTGOING

MAX TEMP

1300H-1500H

RADIATION

INCOMING (SR)

OUTGOING (TR)

SUNRISE

NOON

SUNSET

INCOMING =OUTGOING

MIN TEMP

SUNRISE +1HR


Temperature variations in atmosphere

Temperature Variations in Atmosphere

  • Temperature will vary with:

    • Diurnal Variation (Time of Day)

    • Latitude

    • Season

    • Nature of Surface

    • Altitude.


Temperature variation with diurnal

Temperature Variation with Diurnal

  • Change of temperature from day to night (brought by daily rotation of earth):

    • Day:

      • The earth receives heat during the day by solar radiation and losses heat by terrestrial radiation.

      • Warming and cooling depend on imbalance of solar and terrestrial radiation.

      • During day, solar radiation will be more than terrestrial radiation. Therefore surface becomes warmer.


Met 2204 meteorology

Cont.

  • Night:

    • Solar radiation stop. But terrestrial radiation continues and cool the surface. Thus temperature will drop.

    • Cooling continues after sunrise until solar radiation exceeds terrestrial radiation.


Met 2204 meteorology

Cont.

Diurnal variation of surface temperature

The warmest time about 1500h & coldest at 0500h

At both of these times the incoming SR & outgoing TR are roughly balance


Temperature variation with season

Temperature Variation with Season

  • The earth revolves in a complete orbit around the sun

  • Northern Hemisphere is warmer in June, July and August because it receives more solar energy

  • Southern Hemisphere is colder in December, January and February because it receives less solar energy.


Temperature variation with latitude

Temperature Variation with Latitude

  • The sun is nearly overheaded in equatorial regions at latitude.

  • Therefore, equatorial regions will receive more radiant energy and are warmest.

  • Poles will receive less radiant energy.


Temperature variation with topography

Temperature Variation with Topography

  • Different earth surfaces have different capabilities in absorption and radiation of energy.

  • Major difference applies between land & water

  • Land -heats & cools quickly

  • Sea/water surfaces- heats & cools longer

  • Thus, water absorb and radiates energy with less temperature change than land.


Met 2204 meteorology

Cont.

  • Land surface – bare rock, sand and concrete attain higher temperature.

  • Wet soil and grassland – attain lower temperature.

  • Snow-

    • reflect solar radiation (colder)

    • However snow doesn’t prevent the earth from radiating its heat and therefore the air over snow will become colder day by day.


Temperature variation with altitude

Temperature Variation with Altitude

  • When the altitude increase the temperature will decrease (mostly in troposphere).

  • We define this as lapse rate.

  • Average lapse rate = 2°C per 1000 ft.


Met 2204 meteorology

Cont.

  • But in fact, temperature increase with height sometimes.

  • We call this as inversion (lapse rate are inverted)

    • E.g. The ground radiates and cools much faster than air in the cool night. Air contact with ground becomes cold while temperature a few hundred feet above change a little. So this time, temperature increase with altitude.

      *Notes: Inversion are common in stratosphere


Atmospheric pressure

Atmospheric Pressure


Definition1

Definition

  • Atmospheric Pressure:

    • The weight of air in the column above unit area of earth surface.

    • Pressure is the force per unit area:

F

P =

A


Met 2204 meteorology

Cont.

  • Pressure is the cumulative effect of air molecules colliding with a surface.

  • Air Pressure Depends On:

  • The mass of the molecules

  • (density)

  • Temperature


Pressure scale of measurement

Pressure Scale of Measurement

  • Pressure can be in the unit of millimeter mercury (mmHg), atmosphere (atm), Pascal (Pa) , milibar (mb), Inch of mercury etc.

  • In meteorology we us the units millibars(mb) / hectopascal (hp)

  • “Typical” sea-level pressure (reference standard) is approximately 1013 mb or 29.92 inch. Of mercury.


Met 2204 meteorology

Cont.


Pressure measurement instrument

Pressure Measurement Instrument

  • Device to measure

    - Mercurical Barometer

    - Aneroid Barograph


Met 2204 meteorology

Cont.

  • Mercurical Barometer

    • Pressure is determine by balancing air pressure against weight of a column of mercury in evacuated glass tube.

    • Greater air pressure will increase the rise of mercury within tube.

    • Always be vertical

      • Mount in the aircraft using gimbals. So it keep vertical despite rolling/pitching.


Met 2204 meteorology

Cont.

  • Aneroid Barometer

    • Consist of thin walled metal box. It contracts and expands depend on the pressure.

    • Connect to the dial by lever (rigid bar pinned) system.


Met 2204 meteorology

Cont.

  • Barograph (weather instrument)

    • Used for recording atmospheric pressure.

    • Barometer

      • Allow us to measure pressure tendency.

      • Important forecasting tool.

Barograph

Barometer


Pressure variation in atmosphere

Pressure Variation in Atmosphere:

  • Pressure will vary with:

    • Altitude

    • Temperature

    • Diurnal Variation


Pressure variation with altitude

Pressure Variation with Altitude

  • Weight are less when increase in altitude.

  • At troposphere (pressure decrease 1 inch for each 1000 ft increase in altitude)

  • Higher altitude, slower rate of decrease.


Pressure variation with temperature

Pressure Variation with Temperature

  • Rate of decrease of pressure with height in warm air is LESS than standard.

  • Rate of decrease of pressure with height in cold air is GREATER than standard.


Met 2204 meteorology

Cont.

  • Horizontal Difference in Temperature:

    • Creates horizontal difference in pressure.

Consider two columns of air

Warm

Cool

Ps

Ps

Ps

Ps

Pressure is the weight of the

air above you.

Warm one side and cool

the other side. Maintain

a constant surface pressure.


Met 2204 meteorology

Cont.

Consider an airplane flying at a

constant height. What are the

pressures?

Warm

Cool

Ps

Ps


Met 2204 meteorology

Cont.

So we see a high pressure, at the altitude of the plane, in the

warm column and a low pressure in the cool air.

Low

High

Warm

Cool

Ps

Ps

The horizontal difference in temperature creates

a horizontal difference in pressure.


Pressure variation with diurnal

Pressure Variation with Diurnal

  • Change of pressure during DAY

    • 1mb-3mb (max. 3mb usually in tropics)

      So what about change in pressure during NIGHT??

      -Ans: It’ll be lower than change of pressure during day.


Pressure analysis

Pressure Analysis

  • There is two types of pressure considered in aviation:

    • QFE: barometric pressure at the level of airfield

    • QFF: barometric pressure at stated place based on Mean Sea Level (MSL). (QFE converted to MSL).

      *Mean sea level (MSL) is a measure of the average height of the ocean's surface


Met 2204 meteorology

Cont.

  • Isobars

    • A line joining places of the same atmospheric pressure.


Met 2204 meteorology

Cont.

  • Use of Isobar:

    • reveal surface pressure pattern

    • Deduce wind condition (e.g. Isobar closer, wind will blow harder)


Density

Density


Definition2

Definition

  • Density : mass per unit volume (m/v)

  • Density directly proportional to pressure

  • Density inversely proportional to temperature.

    • When air heated (temperature increase), the volume of air will expand. Therefore the mass of air decreases and lead to density decreases.


Density variation in atmosphere

Density Variation in Atmosphere:

  • Density will vary with:

    • Altitude

    • Latitude


Density variation with altitude

Density Variation with Altitude

  • Air near surfacemore dense than air at higher surface.


Density variation with latitude

Density Variation with Latitude

  • At surface: density increase with increase in latitude

  • At 26000 ft (7.9 km): density constant with increase in latitude

  • Above 26000 ft (7.9 km): : density decrease with increase in latitude


Change of density affect the a c operation

Change of Density affect the a/c operation

  • A/C and engine performance

    • Low density will reduce lift, increase take off run, and reduce maximum takeoff weight.

    • Most likely to occur at hot airfields (e.g. Africa, South East Asia)


Humidity

Humidity


Definition3

Definition

  • Humidity is the amount of water vapor in the air.

  • Water vapor: water in its gaseous state


Measurement of humidity

Measurement of Humidity

  • Humidity can be measured in the following ways:

    • Absolute humidity

      • The weight of water vapor in unit volume of air usually expressed in grammes per cubic metre.

    • Relative Humidity

      • The amount of water vapor in a volume of air divided by the maximum amount of which that volume can hold at that temperature and expressed as a percentage. 100% relative humidity equals saturation.

        (If rel. humidity is less than 100%: air dry

        if rel. humidity is 100%: air wet)


Met 2204 meteorology

Cont.

  • Humidity Mixing Ratio

    • The weight of water vapor in unit mass of dry air, usually expressed in grammes per kg.


Diurnal variation with humidity

Diurnal Variation with Humidity

  • During day, relative humidity decrease as temperature decrease.

  • When temperature falls after 3.00 pm, the relative humidity will increase.

  • At night, relative humidity higher than day (formation of mist and fog especially in autumn and winter)


Air stability

Air Stability

  • Idea:

    • Stable: When put a disturbance it can go back to original position.

    • Unstable: Continues to move away from a normal position.

  • Stable air : resist any upward or downward displacement

  • Unstable air: Allows upward or downward disturbance to grow into vertical or circulation flow.


Met 2204 meteorology

Cont.

  • When cool air mass moves over warm region/surface, it will create an air mass less stable as temperature change quite rapidly.

  • If warm air mass moves over a cold region/surface, air becomes more stable (as convective (transfer of heat through a fluid) process slow)

    *air mass: large volume of air where the humidity and temperature are more/less constant.


Conclusion

Conclusion

  • The Earth’s atmosphere or air is made up of a variety of gases, other particles and in form of several layers.

  • The physical condition of atmosphere different for each layer.

  • The earth’s atmosphere varies vertically and horizontally in temperature, pressure, density and humidity.

Presented by MohdAmirul for AMC


Key points

Key Points

  • What is the Atmosphere?

  • Composition of Atmosphere

  • Layers of Atmosphere

  • Variation in Atmosphere

  • Air stability

Presented by Mohd Amirul for AMC


End of presentation 2

End of Presentation #2

5 Minutes for Q/A session

Presented by Mohd Amirul for AMC


Quote of the day

Quote of the Day

  • Experience is that marvelous thing that enables you to recognize a mistake when you make it again.

    Franklin P. Jones

Presented by Mohd Amirul for AMC


  • Login