Weather
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Weather Presentation Transcript

  • 1. Weather Part 1 Temperature
  • 2. Introduction to weather
      • Weather
        • Is the short term condition of the atmosphere at any location
        • It is made up of the connection and relationship of
          • Temperature
          • Humidity
          • Air pressure
          • Wind
  • 3. Temperature Introduction
      • at any given place temperature is connected to the heat energy present in the atmosphere at that location
      • Solar radiation is the amount and how long the sun is on a particular location and how strong it is.
      • Therefore anything that changes solar radiation will also change the air temperature
  • 4. What are factors that can effects solar radiation ?
      • The following are factors that can change the amount of solar radiation a place has
        • The angle that solar radiation hits the Earth
          • this changes throughout the day because of the Earth rotation
            • Solar radiation is only present during the day
          • similar changes also happen when the Earth moves around the sun
            • we call these slower changes seasons
        • number of hours of solar radiation during the day
        • the reflection
        • refraction
        • absorption of solar radiation
          • for example clouds block and absorb the amount and intensity of the sun
        • and the type of surface (ex: water and land)
  • 5. How do we measure air temperature?
      • Temperature is measured with thermometers
        • Works on a simple principle
          • Matter expands when heated and contracts as it cools.
      • There are many scales of measuring temperature that are named after the people who made them up
        • Celsius
        • Fahrenheit
        • Kelvin
      • We use in the USA Fahrenheit the rest of the world uses Celsius
      • Meteorologist ( people who study weather ) use a thermograph as a thermometer
  • 6. Weather Part 2 Air Pressure
  • 7. Introduction
      • Air is a mixture of different gases
      • Gas consists (made up of) many different tiny molecules that move around rapidly and are far apart from each other.
        • They are kept contained either by a container or in the case of the atmospheres by the Earth’s Gravity
      • Gases put pressure on the surfaces that they are in contact with.
      • In the case of air pressure this pressure is due to the gas particles bumping into the surface
        • Since they move rapidly in all direction they balance out this pressure in all directions
  • 8. How does air pressure help us forecast weather
      • You cant sense air pressure like you can with temperature
      • Nor can you forecast the weather based on the air pressure in a location
      • BUT since we have isoclines of the air pressure, we can study the changes of the air pressure and the different masses and temperatures that come with it.
        • Rising pressure usually means fair weather
        • Low Pressure usually means an approach of a storm
  • 9. How is air pressure measured?
    • We use a barometer to measure air pressure.
          • there are two common barometers used
    • 1. Mercury Barometer
    • 2. Aneroid barometer
    • air pressure is measured based on units of force per a unit area
            • atmosphere (atm) is the average air pressure at sea level
  • 10. Mercury Barometer
    • air pressure forces liquid mercury up a tube
    • the more pressure the higher the mercury level will be
    • we usually name the number with inches or millimeters attached to the number
  • 11. Aneroid Barometer
    • aneroid means no liquid
    • it is a can with a spring scale on it
    • the amount of pressure on the sides of the can will either push down or loosen the spring scale
  • 12. Weather Part 3 Wind
  • 13. Air Movements
      • The reason why air circulates is because of density differences
        • How thick the air is.
  • 14. Air Currents
        • Air currents are the rising and sinking vertical movements of the air
        • When these air currents sink and they reach the earth’s surface it does spread out horizontally. When the rising air expands it also spreads out horizontally.
  • 15.
        • When these air currents expand horizontally it forms wind.
          • Wind is described by
            • Speed
            • Direction
  • 16.
    • is measured by an instrument called an Anemometer.
        • An Anemometer is 3-4 cups mounted on an axis that is attached to a compass.
        • The wind moves the cups causing the axis to spin.
        • The speed of the axis’s movements depends on the speed of the wind.
        • Wind Speed is measured by knots
          • 1 knot= 1.15 miles an hour
  • 17.
    • Measured by a wind vane
        • A wind vane is a pointer on an axis that is also attached to a compass
        • The tail of the pointer is larger than the tip
        • This makes sure more pressure is put on the tail
    • Therefore it will point to the direction that the wind is coming
  • 18. Weather Part 4 Humidity
  • 19. Introduction to humidity
        • Is the amount of Moisture in the air
        • IT IS NOT a liquid water in the air but rather it is water vapor (gas)
          • water vapor is a colorless, odorless gas that enters the atmosphere when liquid water evaporates or ice sublimes ( changes straight from solid to gas)
  • 20. Humidity is Important
        • Humidity is a very important weather factor because the water vapor in the air is what condenses to form
          • cloud
          • fogs
          • precipitation
  • 21. Changes of water
        • Water molecules are always changing from the three forms of matter
          • solid
          • liquid
          • gas
        • So therefore it looks like this
    • Ice Water
    • Water Vapor
  • 22. How does water enter the atmosphere?
      • Most water enters the atmosphere from the form of liquid to gas
        • called evaporation
      • or ice to gas
        • called sublimation
  • 23. How does water leave the atmosphere?
    • Condensation
          • Water forming and leaving the atmosphere
    • (We will talk later why water falls)
      • Deposition
        • Is when the vapor form into solid crystal without turning into water first
  • 24. Point of Information
    • This constant flow of water molecules throughout these phrases results in the change of humidity
  • 25. Most of the change is between atmosphere and hydrosphere
        • The molecule of water from the hydrosphere gain energy from sunlight and surroundings may become energetic enough to escape the liquid phrase and turn into water vapor
        • When water vapor molecule come in contact with the hydrosphere they sometimes get attached and stay there
        • it is a two way street.
  • 26. Evaporation
        • Is when the molecules get enough energy and form into water vapor in the atmosphere
          • at higher temperatures molecules have more energy so more molecules will have the energy to escape and form into vapor
    • HIGHER TEMP MORE EVAPORATE
  • 27. Condensation
    • Is when the water vapor molecules form a liquid and attach themselves onto the surface
    • This depends on how densely populated the molecules are. The more populated in a small area the more will attach themselves onto the surface
        • like being squeezed out of an elevator
  • 28. Net evaporation and net condensation
        • Net evaporation
          • is when there is more molecules leaving the surface than there are attaching to the surface
        • Net condensation
          • is when there is more molecules leaving the atmosphere and attaching to the surface than those leaving the surface
  • 29. They go in a circle
          • if there is a net evaporation the more water vapor there is in the air which means the denser it will get and more vapor gets pushed out and stuck to the surface
          • eventually a point is reached where their is an equilibrium
          • If the temperature drops suddenly then the water vapor will be more then the equilibrium
  • 30. Relative Humidity /Absolute humidity
        • The amount of water vapor in the air is usually referred to absolute or relative humidity
  • 31. Absolute Humidity
      • is the amount of vapor found 1 cubic meter of the air.
          • since it is very hard to isolate the water vapor in the air in order to measure it absolute humidity is very rarely measured
  • 32. Relative humidity
    • is the ratio of water vapor present in the atmosphere to the water vapor present when evaporation and condensation are equal at that temperature X 100
    Water vapor in atmosphere Relative humidity = ------------------------------------------------------ X100 Water vapor in atmosphere at equilibrium
  • 33. Relative humidity
    • relative humidity is a way to of comparing the flows of water molecules leaving and arriving at a surface
    • it is useful in predicting how the air will feel to a person AND whether evaporation or condensation would more likely occur
  • 34. Point of Information
    • Relative humidity 20% means that the air only has 20% of the water vapor it would have during equilibrium
    • relative humidity of 100% means that the air contains 100% of the water vapor it has during equilibrium
  • 35. Relative humidity con’t
      • The higher the relative humidity the (stickier) the air will feel.
      • If the relative humidity is 100% it does not mean that the air is 100% water vapor it still has oxygen and nitrogen etc……..
  • 36. High relative humidity
      • Means that the WV in the air is close to it’s equilibrium amount
      • A decrease in temperature (will also decrease the temperature amount needed for condensation) will decrease equilibrium amount needed for condensation which makes fog, clouds, or precipitation
  • 37. Dew point
      • This leads us to dew point
    • Dew point is the temperature at which water vapor in the air will begin to condense into liquid water
    • THIS IS THE TEMPRATURE AT WHICH THE AMOUNT OF WATE VAPOR IN THE AIR EQUALS THE AMOUNT OF EQUALIBRUIM FOR THAT TEMP
  • 38. How is humidity measured?
    • There are two different tools used to measure humidity
      • Hygrometer
      • Psychrometer
  • 39. Hygrometer
    • Consists of strands of human hair attached to a pointer
    • Human hair grows slightly as humidity increases
    • and shrinks when it decreases
      • The pointer changes position based on the length of the hair
  • 40. Psychrometer
      • Is made of two thermometers
      • Dry bulb
      • - The bulb is kept dry
      • Wet bulb – the bulb is kept wet by a covered cloth wick soaked in water
          • Evaporation from the wet wick causes cooling because the fastest molecules in liquid water are the ones that have enough energy to escape
          • The slower molecules have a lower average energy.
          • Therefore the liquid temperature decreases due to the loss of energy.
  • 41.
      • This cooling effect is KEY to measuring relative humidity
      • The lower the relative humidity the more water can evaporate from the wet bulb and the more the thermometer is cooled.
      • The Dry Bulb Temp. remains unchanged.
        • Therefore the difference between the dry bulb and wet bulb temperature is directly related to the relative humidity of the air.
  • 42. How do we figure out Relative humidity?
      • You subtract the dry bulb e from the wet bulb temp
    • Find in the table where the dry bulb temp (right side) and the difference temp # meet
      • That number is your relative humidity percent
  • 43. How do we figure out the Dew Point?
    • The difference between the wet and dry bulb is also directly related to dew point.
    • The higher the relative humidity the closer the air is being filled to capacity.
    • Cooling air decreases the capacity to hold water
    • So we will use a different table
    • you will figure out the difference between Wet and dry
    • You will then see where it meets with the dry bulb temperature
    • That number at the intersection is the dew point in degrees of C.
  • 44. Weather How do these variables relate to each other?
  • 45. What are the relationships amongst the variables – Introduction
      • The atmospheric variables that we learned previously are interrelated (there is a direct correlation)
      • A change in one would probably affect another
      • This is best understood even though we have the kinetic theory of gases
  • 46. Kinetic gas theory
    • Gas is made out of tiny, individual that do not interact with each other except when they collide
    • The molecules are far apart and constantly moving
    • Temperature of gas is proportional to the speed in which it is traveling.
  • 47. The relationship between air temperature and air pressure
  • 48. What we already know
      • Air pressure is the result of the forces of gas colliding with each other and surfaces
      • Air temperature depends on the speed of gas molecules
  • 49. If there was a change in temperature
    • Air pressure and temperature are related because both involve the motion of the molecules
    • You would therefore think………….
      • The higher the temperature the more force they collide with higher the air pressure
      • Therefore it would make sense the higher the temperature the higher the air pressure. HOWEVER………..
  • 50. THIS IS FALSE…….
    • This is not true because the atmosphere does not have walls rather its has open space
    • When the atmosphere’s temperature increases the molecules move faster and collide more vigorously
    • As a result the molecules will bounce father away from each other at the atmosphere expands
    • Even though the molecules are moving faster there are fewer collisions because they are farther apart.
  • 51. So what is the relationship is the temorature changes
    • THEREFORE WE SEE A DECREASE IN AIR PRESSURE WHEN THE AIR TEMPRATURE INCREASES.
  • 52. Let us say there is a change in the air pressure what would happen to the air temperature?
    • The main cause of change in the air pressure is the rising or falling of the air in convection currents.
      • convection currents are fluid movements set in motion by fluid density changes
    • So if a group of air sinks there would be less (more density) if the group of air rises there will be more room to expand.
    • Any gas that is allowed to expand because the surrounding expanded will become cooler
    • Any gas that shrinks in space will become warmer
  • 53. TIME OUT Adiabatic changes
    • Are the rise and fall of temperature that has NOTHING to do with heat being added from outside forces?
  • 54. So therefore……………
    • SO if the gas is rising and is allowed to expand then their will be more room form the molecules to live in and less collision would occur.
    • But if the space for the air is reduced than their will be more collisions and higher temperatures
  • 55. The results are
    • IF AIR PRESSURE GOES UP- TEMP GOES UP
    • IF PRESSURE GOES DOWN TEMP WILL GO DOWN
  • 56. The relationship between air pressure and humidity
  • 57.
      • The greater the mass of molecules the more collisions will occur
      • The mass of elements in the air depends on the mass composition of the air
      • The air as we know is mostly nitrogen and oxygen they are both denser then water vapor molecules
        • The more water vapor in the air takes the place of the nitrogen and oxygen the lighter the force of air pressure it will be
  • 58.
      • SO THE HIGHER THE HUMIDITY THE LOWER THE AIR PRESSURE
      • THE LOWER THE HUMIDITY THE HIGHER THE AIR PRESSURE
        • When it is very humid outside and then it rains you can feel the release of air pressure in the air.
  • 59. Air temperature and humidity
  • 60.
      • We know the higher the air temperature the more water vapor is going to be in the air before equilibrium
        • Therefore warmer air contains more vapor than cooler air
        • At any given temp a fixed amount of vapor will be present in the air when we reach equilibrium
        • At a higher temperature more of the molecules will be able to break free and become vapor
          • As the vapor becomes more crowded with molecules it is more likely that it will condense
        • Therefore the water vapor warm air will increase until a new equilibrium status is reached 9depends on the Temp.)
        • The amount of vapor in the air is greater in temp than lower temps
  • 61.
      • Since the amount of water vapor in the air at equilibrium changes with temperature = the relative humidity is also affected by the temperature
      • So if the temperature increases that will cause the equilibrium mark to increase which will make the relative humidity decrease.
        • Because the higher the temperature and equilibrium mark. The more vapor is needed to raise the humidity.
  • 62.
      • The reverse is true as well. If the temperature decreases the equilibrium mark will decrease and the amount of vapor in the air remains the same, relative humidity will increase.
      • As we know, as the temp decreases it eventually reaches the dew point.
        • At that point the relative humidity is 100 percent
      • If the temp decreases more, than condensation will form at a faster rate. Than evaporation until equilibrium is reestablished.
      • Therefore, as temperature reaches dew point precipitation becomes more likely.
  • 63. Air Pressure and Wind
  • 64. General rule…….
      • Winds blow from regions (places) of high air pressure to regions of low pressure.
        • IN OTHER WORDS AIR BEING PUSHED BY HIGH AIR PRESSURE WILL ADVANCE AGAINST THE PERSON SIR BEING PUSHED WITH LOW AIR PRESSURE.
      • The net movement of air is from HIGH pressure to LOW Pressure
  • 65. Land and sea breezes
        • Land and sea show the air movement from high to low pressure very clearly
          • difference of air pressure between adjacent (next to ) places occur when ever land and water meet
  • 66. During the day
    • SO DURING THE DAY when sunlight is out. The land gets hotter than the sea
    • Therefore land during the day will have a higher air temperature than the water during the day.
    • Since warm air has less pressure than cool air the pressure over the land will be cooler
    • THEREFORE wind during the day will go from the water inwards to the land.
    • This wind is called SEA BREEZE
  • 67. At Night……..
    • Land cools faster than water and therefore will have more pressure than the water.
    • The wind will therefore will blow from the land out to sea.
    • This is called a land breeze
  • 68.
        • Differences in pressure between regions also effect on a global scale
        • Unequal heating of the atmosphere at different latitudes cause three large atmospheric convention cells to form in the northern and southern hemisphere
        • Rising air in these convection cells produces LOW pressure belts that circle the earth at the equator, artic circle(60) and the Antarctic circle (90)
  • 69.
        • Sinking air makes high pressure belts at the poles , tropic of cancer (30) and Capricorn (30 S)
        • THEREFORE A SERIES OF ALTERNATING HIGH AND LOW PRESSURE BELTS CIRCLE EARTH, GIVING RISE TO A SERIES OF GLOBAL WIND BELTS AS AIR MOVES FROM REGIONS OF HIGH PRESSURE TO REGIONS OF LOW PRESSURE
          • (look at the wind belt diagram) the global wind that blow from high pressure belts at 30 N and south towards low pressured equator
            • This is called trade winds.
  • 70. Coliotis Effect
      • is the deflection of motion due to the rotation of the earth
        • This causes these large scale winds to curve to the right in the Northern hemisphere
        • They blow North east
        • This also causes the wind to curve to the left in the Southern Hemisphere
        • They blow South east
  • 71.
      • Winds blow from regions (places) of high air pressure to regions of low pressure.
        • IN OTHER WORDS AIR BEING PUSHED BY HIGH AIR PRESSURE WILL ADVANCE AGAINST THE PERSON SIR BEING PUSHED WITH LOW AIR PRESSURE.
    • The net movement of air is from HIGH pressure to LOW Pressure
  • 72.
        • Global winds also blow from the high pressure belts at 30 S and N towards the low pressure belts at the 60 N and S
          • They are called Prevailing winds
          • The colitis effect causes these winds to blow southwest in the north and South east in the South
  • 73.
      • The global winds that blow from regions over the poles towards the low pressure regions of 60 N and S are known as polar easterlies.
    • The coriolis effect causes these winds to blow from the northeast in the north and southeast in the south