1. The diagram shows
weather instruments
A and B.
Which table correctly indicates the name of the weather instrument and the weather variable that it measures?

2. Weather?

3. L LOW pressure air Less dense Weighs less Tends to rise Warm Wet
1012
1008
1004
Less dense
Weighs less
Tends to rise
Warm
Wet
Lousy weather (rainy, snowy, etc…) L

4. H HIGH pressure air More dense Weighs more Tends to sink Cool Dry
1004
1008
1012
More dense
Weighs more
Tends to sink
Cool
Dry
Nice weather (sunny, blue sky, etc…) H

5. In late October cool weather is relatively H pressure
In late October cool weather is relatively H pressure. Watch the L pressure storm develop:
LOW PRESSURE
means...
Warmer
More Humid

6. Is HIGH or LOW pressure normal?
At the Equator? On a sunny day? On a winter day? On a rainy day? At the North Pole?
Low
High

7. Unequal heating of Earth’s surface.
Two reasons why air becomes HIGH or LOW pressure :
Unequal heating of Earth’s surface.
Change in humidity.
--we will discuss water vapor later--

8. Texture Color Specific Heat…
Why would the sun make the ground hot in one place
and not as hot in another place?
Color
Texture
Specific Heat…

9. At pressure centers…
Different surfaces absorb different amounts of energy (color, texture, specific heat, etc…)

10. At pressure centers…
Different surfaces absorb different amounts of energy (color, texture, specific heat, etc…)
Low density air is created above warm surface.

11. Then things get interesting!
At pressure centers…
Different surfaces absorb different amounts of energy (color, texture, specific heat, etc…)
Low density air is created above warmer surface.
Density change causes air to move…
Then things get interesting!

12. Which transfer of energy occurs mainly through
the process of convection?
(1) electromagnetic energy transferred from the
Sun to the Moon
(2) solar energy transferred through space to
Earth’s surface
(3) heated air in the lower atmosphere transferred
upward by density differences
(4) heat from radioactive decay transferred by
molecular collisions to surrounding mantle
rock

13. Air pressure decreases as air heats above a warm Earth surface.
Warm, LOW
Density Air
Cold, HIGH
Density Air
Low density air wants to float!

14. As HIGH pressure air sinks, it hits surface and diverges (spreads out).
As LOW pressure air rises, more air converges (comes together) to fill empty space.

15. It’s a CONVECTION CURRENT

18. Air moving horizontally from higher to lower pressure is WIND.

19. Air moving horizontally from higher to lower pressure is WIND.

20. Air moves like water...
Big gradient = Fast
Small gradient = Slow
The larger the AIR PRESSURE GRADIENT, the faster the wind moves from HIGH to LOW pressure!

22. The larger the pressure gradient, the faster the wind!

23. Which location most likely recorded the highest wind speed?
(1)A (3)C
(2)B (4)D

24. Gradient = 0.056 mb/ Km Gradient = Change in field value/ distance
The map at left shows pressure measured in mb. The distance between the points is 500 Km. CALCULATE the pressure gradient.
Gradient = Change in field value/ distance
Gradient = 1004 mb – 976 mb/ 500 Km = 28 mb/ 500 Km
Gradient = mb/ Km