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Weather Factors page 51
Weather Factors
Recall that Weather is defined as the state of atmosphere at a specific time and place and that most weather occurs in the troposphere.
Wind, clouds, and precipitation are all the result of the atmosphere responding to uneven heating of the Earth by the Sun.
The uneven heating causes temperature differences, which in turn causes wind, which then moves the heat to a new place.
The atmosphere thus becomes a giant "heat engine", continuously driven by the sun.
m
What causes weather?• Caused by the transfer of energy between
these 3 things:- The Sun, Earth’s surface, and the Atmosphere.
• Caused by the transfer of energy between these 3 things:- The Sun, Earth’s surface, and the Atmosphere.
Hot air rises and cools
The sun warms earth’s surface - increasing its temperature.
Water vapor condenses to form clouds & precipitation
The sun’s energy is used to evaporate water and put moisture into the air.
Unequal heating and differences in air pressure cause wind.
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Is - the branch of science dealing with weather forecasting.
Atmospheric conditions that are typically measured to provide information for weather forecasts and to study the weather and climate include: temperaturebarometric pressurehumiditywind speed & directionprecipitation
Condition: Partly Cloudy
Humidex: 30 o CPressure: 101.4 kPa
Mr. Fetch’s Earth Science Classroom
Temperature – a measurement of heat Temperature is a factor of particle motion.
Faster moving particles create more heat
Temperature is measured with a thermometer
Factors affecting the temperature of an area include such things as
locationamount of sunshineseason weather and pressure systems
Mr. Fetch’s Earth Science Classroom
Examples of Factors that affect temperature
Cities are WarmerCities are Warmer Mountains are ColderMountains are Colder
Cloudy daysCloudy daysare Coolerare Cooler
Cloudy nightsCloudy nightsare Warmerare Warmer
Mr. Fetch’s Earth Science Classroom
Wind
Wind is moving air
It is caused by differences in air pressure within the atmosphere.
Air under high pressure moves toward areas of low pressure
Wind Direction is measured with a weather vane or wind sock
Blunt end of arrow is where the wind is coming fromPointy end of arrow is where the wind is blowing to
Sketch a picture of these two devices
What is the wind direction shown?
Answer: Wind is blowing FROM the SW
Wind direction is reported by the direction from which it originates
Wind Speed is measured with an Anemometer
An anemometer is an instrument with three or four small metal cups that catch the wind. An electrical device records the revolutions of the cups and calculates the wind speed (km/hr)
Mr. Fetch’s Earth Science Classroom
Barometric Pressure
Atmospheric/air pressure is measured with a barometer in units of inches of mercury or millibars
Barometric pressure is the force exerted on objects by the weight of the atmosphere above them.
Mr. Fetch’s Earth Science Classroom
Precipitation: Change of State
MELTINGUses Heat
FREEZINGGives off Heat
Sublimation
Uses Heat
Deposition
Gives off Heat
Gives off Heat
Uses Heat
EVAPORATION
CONDENSATION
Freezing/Melting point of water/ice is 00C
+ Add energy
- Subtract energy
Amounts of precipitation are measured with a rain or snow gauge.
Relative HumidityRelative humidity is a
measure of the amount of water vapor in the air compared to the maximum amount of water vapor the air can hold at that temperature.
A psychrometer is one instrument that measures relative humidity.
Mr. Fetch’s Earth Science Classroom
Hot air holds more moisture than cold air.
Dew Point and HumidexThe dew point is the temperature which water
vapor in air will condense into liquid water. Condensed water is called dew when it forms on a solid surface (like grass) or a cloud when it forms in the sky.
The humidex (short for "humidity index") is a number used to describe how hot the weather feels to the average person. The humidex is a unit-less number based on the dew point, and is equivalent to the dry temperature in degrees Celsius.
Answer Questions on page 55
Answer key for page 551. 56 2. 41 3. 74.4 4. 94
5. a. N b. S6. a. SW b. NE7. a. N b. S
8.a. Melting + b. Condensation -c. Sublimation + d. Deposition -e. Freezing - f. Evaporation +
9. A. Time and Place B. Boiling (liquid to gas) C. Zero celcius D. Increasing by 1 degree E. Downtown/city that has cement to absorb more heat and pollution to trap it and keep it there F. Wind sock or weather vane G. Anemometer H. Barometer I. Sun, earth’s surface, atmosphere J. Higher K. Wind turns cups, cups spin, speed of wind calculated from speed of revolving cups