Textbook: Meteorology Understanding the Atmosphere 2nd Edition Ackerman & Knox Prof. Steve Ackerman University of Wisconsin 2009 Teaching Excellence Award American Meteorological Society
topics I propose we cover in this course 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
January mean temperature North America Europe London Boston Scotland in March Off Labrador 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.
Yesterday’s high in Laramie was 69°F That’s 4 degrees below the average high for this time of the year. Which one is a statement about weather, which one about climate? 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
regional variations in long-term change: USA US temperature trend 1941-2005
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 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
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 ?
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.
radiosonde balloon satellites real-time soundings plotted
Pop quiz • The lowest two layers of the atmosphere are: • a: thermosphere, stratosphere; • b: troposphere, ionosphere; • c: mesosphere, stratosphere; • d: troposphere, stratosphere.