Observing Climate

1
Observing Climate - Surface
Science Concepts Definition Forces Pressure
Versus Height
Pressure Barometer Mercury Aneroid
The Earth System (Kump, Kastin Crane) Chap.
3 (pp. 44-45)
2
Observing Climate - Pressure
What is pressure? How do we feel
pressure? Definition Pressure is a force per
unit area Atmospheric pressure is felt as the
force that the air molecules exert of a
surface. The magnitude of this force per area
equals the weight of the air above that surface
area Surface pressures magnitude equals the
weight of the air above the Earth's
surface Mean sea-level (MSL) pressures
magnitude equals the weight of air above the
Earth's mean sea-level
What is pressure? How do we feel pressure?
Perks of being over 50 Your joints are more
accurate meteorologists than the national weather
service
3
Observing Climate - Pressure
Pressure Versus Altitude Pressure decreases
as one goes up through the atmosphere
Why doesnt it decrease linearly?
50
Above 99.9
30
1 mb
40
5 mb
20
Above 99
10 mb
30
Altitude (miles)
Altitude (km)
25 mb
50 mb
20
10
Above 90
100 mb
10
Above 50
500 mb

5.5 km
Mt. Everest
0
0
300
500
700
900
100
Pressure (mb)
4
Observing Climate - Pressure
http//galileo.imss.firenze.it/ museo/b/etorric.ht
ml
Science quotes of 5th and 6th graders - Vacuums
are nothings. We only mention them to let them
know we know they're there.
Barometer Invented by Evangelista
Torricelli (Galileo's assistant) in 1643
used water in column Mercury Barometer
Vacuum
Mercury
Atmospheric Pressure
Atmospheric Pressure
Atmospheric Pressure


Known Weight

Vacuum
http//www.windandweather.com/ cgi-bin/wind/dyna/d
ynaZ37088
5
Observing Climate - Pressure
Barometer (Cont) Aneroid (without liquid)
barometer - Barograph gt
Traditional barograph - Changes in
atmospheric pressure cause the
bellows assembly to either contract or
expand, thereby moving the pen-holding
lever
http//marinestore.co.uk/thestore/instbg.html
6
Observing Climate - Pressure
Barometer (Cont) Aneroid barometer
(Cont) - Nassau M60 Aneroid Barometer
http//www.weathershop.com/nassau_m60barometer.htm
7
Observing Climate - Pressure
Units Standard atmosphere mean sea-level (MSL)
values - 14.7 lb / in2 - Height of mercury
29.92 inches 76.0 cm 760
mm - 1013.25 millibars Range of surface
pressure - Highest recorded msl pressure, 1085.7
mb (32.06 inches of Hg), occurred at
Tonsontsengel, Mongolia, 19 Dec. 2001 - Lowest
recorded non-tornadic msl pressure, 869.96 mb
(25.69 inches of Hg), occurred in the Western
Pacific during Typhoon Tip on 12 Oct.
1979 (2005 Hurricane Katrinas lowest pressure
was 902 mb 2005 Hurricane Wilma set record
Atlantic hurricane low pressure
882) Conversion 1 inch of mercury 33.8639 mb
Burt, Christopher C., (2004) Extreme Weather, A
Guide Record Book. W. W. Norton Company