1. L.O: THE WEATHER

2. WEATHER is a short-term
condition of the atmosphere
Weather is the result of
temperature, humidity, air pressure
and winds

3. Air Temperature: measured with
a thermometer.
Complete the questions on page 142.

4. Humidity:
• Humidity measures the amount of moisture in the
air.
• Dew point: the temperature at which the air is
saturated with moisture.
• As the dewpoint temperature reaches the air
temperature, the chance of precipitation increases.
• When the dew point is reached, it precipitates.
• Relative humidity how much moisture in air.

5. As the dewpoint temperature reaches
the air temperature, the chance of
precipitation increases

6. A psychrometer is used to determine
dewpoint and relative humidity.

7. How to determine dewpoint and
relative humidity
• Find the dry bulb temperature (the air
temperature).
• Find the wet bulb temperature.
• Subtract to find the different.
• Use the ESRT charts on page 12

8. As relative humidity increases
the chances of rain increases.

9. WHICH STATION MODEL SHOWS THE
HIGHEST HUMIDITY? HOW DO YOU KNOW

10. THIS STATION MODEL BECAUSE THE AIR
TEMP (DRY BULB) & THE DEWPOINT ARE
CLOSE IN NUMBER.

11. Complete the questions on page
131- 144

12. Air pressure
• The air presses down on us, this is called “air
pressure”.
• Air pressure is measured with a barometer.
• The units are millibars (mb) and inches of
mercury (Hg).
• Isobars are lines that connect equal air pressure
readings.
• High pressure brings good, clear weather
• Low pressure brings bad weather.

13. Air pressure decreases as
altitude increases.

14. Air pressure decreases as
humidity increases.

15. Air pressure decreases as
temperature increases.

16. Complete the questions on page
146.

17. Winds (and breezes)
• Winds are movements of air caused by
pressure differences.
• Wind speed measured with anemoemter
• Winds ALWAYS blow from high pressure to low
pressure.
• Winds are named for where they come from.
• In the USA the prevailing westerly tends to
move weather from west to east.

18. In the USA winds bring weather
usually from west to east.

19. Clouds: are made of tiny water
droplets or ice crystals that float in the
air.
• Clouds need condensation nuclei to form.
• Condensation nuclei are dust particles, dirt particles
that float in the atmosphere on which water
droplets can form.

20. Clouds and precipitation form on the
windward side of mountains.
On the windward side:
warm, moist air:
• Rises
• Expands
• Cools to the dewpoint
• And thus a cloud is
formed.

21. The water cycle: The continual
movement of water thru the Earth’s
systems
• Precipitation: water falling from sky.
• Evaporation: liquid water into gas (water
vapor)
• Transpiration: water from the leaves of plants.
• Together called “evapotranspiration”
• Infiltration: water soaks into ground.
• Run off: water flowing over land.

22. Water Infiltration happens when
ground is NOT saturated and the slope
is gentle.

23. WATER INFILTRATES (SOAKS IN) GENTLE
SLOPE & SOIL IS NOT SATURATED.

24. Water run off happens when ground
is saturated and the slope is steep.

25. SOIL POROSITY & INFILTRATION:

26. EVEN THOUGH THEY ARE DIFFERENT SIZE
PARTILCE, THIS TWO SOIL SAMPLES HAVE
THE SAME POROSITY

27. IF MADE OF THE SAME
MATERIAL, DIFFERENT SIZE
PARTICLES, HAVE THE SAME POROSITY

28. IF MADE OF THE SAME
MATERIAL, DIFFERENT SIZE
PARTICLES, HAVE THE SAME POROSITY
BUT…

29. BUT…WATER INFILTRATES FASTER THRU
LARGE SIZE PARTICLES.

30. Energy
transfer:

31. Energy transfer: energy can be
transferred through:
• Conduction: energy thru a
solid
• Convection: energy through
liquid or air
• Radiation: energy through
vacuum (empty space).

32. Convection cells: when energy flows
through air or through a liquid due
to density differences.