Transcript Document

Textbook:
Meteorology
Understanding the Atmosphere
2nd Edition
Ackerman & Knox
Prof. Steve Ackerman
University of Wisconsin
2009 Teaching Excellence Award
American Meteorological Society
your topics of interest in ATSC 2000
topic
score
Chapter 11) thunderstorms and tornadoes
53
Chapter 15) human influences on climate
29
Chapter 6) atmospheric forces and wind
19
Chapter 7) global-scale winds
17
Chapter 8) hurricanes & El Nino
16
Chapter 2) the energy cycle
13
Chapter 9) air masses and fronts
13
Chapter 3) temperature
8
Chapter 4) water in the atmosphere
8
Chapter 10) extra-tropical cyclones and anticyclones
8
Chapter 5) observing the atmosphere
7
Chapter 13) past & current climate
5
topics I propose we cover in this course
topic
score
Chapter 11) thunderstorms and tornadoes
53
Chapter 15) human influences on climate
29
Chapter 6) atmospheric forces and wind
19
Chapter 7) global-scale winds
17
Chapter 8) hurricanes & El Nino
16
Chapter 2) the energy cycle
13
Chapter 9) air masses and fronts
13
Chapter 3) temperature
8
Chapter 4) water in the atmosphere
8
Chapter 10) extra-tropical cyclones and anticyclones
8
Chapter 5) observing the atmosphere
7
Chapter 13) past & current climate
5
and of course Chapter 1) Introduction
chapter 1: Introduction
1.1 Weather vs climate
1.2 Atmospheric composition
– Focus on greenhouse gases
1.3 Atmospheric structure
– Focus on the ozone hole
History of meteorology
• Babylonians, Chinese: astrometeorology
• Aristotle: “meteorologia”
• 16th-17th century: instruments and scientific
method (Descartes)
•
•
•
•
•
– barometer (Torricelli, 1643, mercury)
– thermometer (Galileo, 1592, Fahrenheit, 1714)
1843: real-time data via telegraph
1920’s: polar front theory (Bergen school)
1940’s: upper-air observations (radiosondes)
1950’s: radar
1960’s: first satellites and NWP models
Chapter 1.1: weather vs. climate
weather …
our own weather server
more weather links
Hurricane Katrina
8/28/05 17 UTC
precipitation
topography
January mean temperature
North America
Europe
London
Boston
Off Labrador in March
Scotland in March
Define weather and climate…
Your turn!
• Weather:
– A depiction of the state of the atmosphere at one point
in time.
• Climate:
– A depiction of the ‘typical’ weather, based on
observations taken over a period of time.
Which one is a statement about
weather, which one about climate?
• Yesterday’s high in
Laramie was 69°F
• That’s 4 degrees
below the average
high for this time of
the year.
Click here for the current Laramie weather forecast
weather or climate ?
from 3-monthly to
daily precip
weather or climate ?
image source
What is an ‘anomaly’?
• A departure from ‘normal’.
– Especially climate data are often shown as anomalies, e.g. a
drought.
For how many days can we predict the weather?
10 days
Why?
The atmosphere, like any other fluid, behaves chaotically
Edward Lorenz, 1963: Deterministic nonperiodic flow. Journal of Atmospheric Sciences. Vol.20 : 130—141.
Edward Lorenz in Wikipedia
“climate” is not constant!
last 150,000 years
last 1,000 years
instrument record: last 125 years
regional variations in long-term change: global
regional variations in long-term change: USA
US temperature trend 1941-2005
long-term change in Wyoming
Can we predict climate fluctuations?
• We know that weather becomes unpredictable after ~10 days
• So how can the CPC produce a seasonal outlook for the drought?
• Climate anomalies tend to persist for some time, months to seasons.
• Why ?
El Niño: a
change in SST,
winds, and
rainfall in the
equatorial
Pacific
El Niño has global impacts...
El Niño has some effect on precipitation in the US.
winter precipitation anomaly
Why?
1998 El Niño: SST & jet stream
anomalous
sea surface temperature
jet stream
Coupled atmosphere-ocean models predict the SST out to
about a year.
An El Niño is predicted for next winter …
source
Conclusion: there is some limited guidance for
the season ahead, but wrong predictions should
not be a surprise.
• That does not mean that long-term climate change is even less
certain.
• We cannot predict that July 2035 will be an ‘unusually’ warm
month compared to what is typical then, but we are confident
that that the 2030s will be warmer than the current decade.
• This is based on climate model predictions that take into account
changes in greenhouse gases, earth surface conditions, and
clouds.
Predicted global mean
temperature change between
2000 and 2100
for 5 different CO2 emission
scenarios.
source
Both study the
atmosphere
Key atmospheric observations
Chapter 1.2: atmospheric composition
360 ppm
Recent trend in atmospheric CO2
Recent trend in atmospheric CO2
The long-term rise in CO2 levels parallels fossil fuel use.
the global carbon cycle
A visit from Mars …
Pop quiz
• The Earth’s atmosphere consists mostly of:
–
–
–
–
a: carbon dioxide;
b: oxygen;
c: water vapor;
d: nitrogen.
Discussion: our atmosphere is key to the habitability of the
Earth. Are we alone in that regard, or do other planets have
an atmosphere as well ?
feature
mean distance from the Sun
(millions of km)
mean surface temperature C
main gas in atmosphere
surface pressure hPa
gravitational acceleration m/s
Mars
2
Mars
228
Earth
150
Venus
108
-50
95% CO2
6
3.8
12
78% N2
1,013
9.8
460
97% CO2
90,000
8.8
Earth
Venus
Pop quiz
• Compared to the Earth, both Mars and Venus:
–
–
–
–
a: are warmer;
b: have a higher surface pressure;
c: are closer to the Sun;
d: have relatively more CO2 in their atmosphere.
Chapter 1.3: Vertical structure of the
atmosphere
radiosonde balloon
satellites
real-time soundings plotted
ICAO standard atmosphere
altitude:
km
0
1
2
2.22
3
4
5
9
15
altitude: temperature: temperature: pressure:
1000 ft
°C
°F
hPa
0
15
59
1013
3
9
48
900
6.5
2
36
795
7.3
1
34
778
10
-5
23
700
13
-11
12
616
16
-18
0
530
29
-44
-47
307
49
-83
-117
120
Pop quiz
• The lowest two layers of the atmosphere are:
–
–
–
–
a: thermosphere, stratosphere;
b: troposphere, ionosphere;
c: mesosphere, stratosphere;
d: troposphere, stratosphere.
magnetosphere
Aurora Australis, May ’91
Space Shuttle Discovery
O3
“Good” vs. “Bad” Ozone
• “Good”: Stratospheric
ozone, which screens
out much of the
incident UV radiation
from the sun.
• “Bad”: Tropospheric
ozone, an anthropogenic air pollutant ,
damages health and
the environment.
Chapman cycle
textbook, p. 446-449
Formation:
• O2 +hn  2O
(l<0.25 mm - UV-c)
• O + O 2 + M  O3 + M
Destruction:
• O3 +hn  O + O2
• O + O3  2 O2
(l<0.31 mm - UV-b)
CFC gases destroy the “good” ozone
Montreal protocol (1987): complete phase-out of CFC production
UV radiation penetrating to the Earth surface
UV-c
UV-b
(skin cancer, eye cataracts ...)
UV-a
M
O3
Surface observations
Surface observations
temperature (°F)
sea level pressure (mb)
weather
5
wind direction
and speed
visibility (miles)
dewpoint (°F)
cloudiness
learning applet
Weather
symbols
Cloud
cover
Sea level pressure
If reported value greater than 500:
Initial 9 is missing. Place it on left, then divide by 10.
For example: 827 becomes 982.7 mb.
If reported value less than 500:
Initial 10 is missing. Place it on left, then divide by 10.
For example: 027 becomes 1002.7 mb.
wind
1 Knot = 1.15 MPH
direction
speed
current surface
observations
summary
• Chapter 1, intro to the atmosphere
– weather vs climate
– vertical structure of the atmosphere
– atmospheric gas composition
• Chapter 15, human influence on climate
– climate change
- to be revisited
(p. 441-443 and p. 453-464)