Structure of Earth’s Atmosphere Meteorology 10 - Weather and Climate Fall 2008 CHAPTER 1 FOCUS: atmospheric composition

The atmosphere didn’t always look like this...

The primitive atmosphere was probably comprised of hydrogen and helium Earth’s First Atmosphere billion years ago These gases were lost to space early in Earth's history, because: Weak gravity allowed lighter gases to escape

Second atmosphere - 4 billion years ago Comet impacts (H 2 O) Second Atmosphere’s Composition Mostly water vapor (80%) CO times more than present (10%) Small amounts of nitrogen, sulfur, methane Trace amounts of O 2 Result: Very Tall and Dense Atmosphere! Almost no Oxygen! ‘Outgassing’ from volcanoes (H 2 O, CO 2, N 2, SO 2 )

And then two major events came into play…

1) As Earth cooled, precipitation started… Rain resulted in fundamental changes to atmosphere: B) Most carbon dioxide (CO 2 ) was removed -Dissolved into rainwater and -ocean surface -Carbonic acid leached into rocks and deposited carbon Result: Atmosphere became MUCH thinner... ~ most of the atmosphere was locked up on the earth’s surface A) Most water vapor (H 2 O) moved from atmosphere to global oceans

LIFE 2) Then… LIFE emerged - toward the modern atmosphere Result : Oxygen became abundant in the Earth’s atmosphere Oxygen in the atmosphere is a telltale sign of life!!! 2.8 BY ago: cyanobacteria first appeared Photosynthesis CO 2 + H 2 O + Light » CH 2 O + O 2 Cyanobacteria Origin of O 3

Chapter 1: The Earth’s Atmosphere Overview of the Earth’s atmosphere Vertical structure of the atmosphere Weather and climate

Overview of the Earth’s Atmosphere The atmosphere, when the earth is scaled to the size of an apple, is no thicker than the skin on that apple.

Composition of the Atmosphere permanent gases variable gases roles of nitrogen and oxygenroles of nitrogen and oxygen role of water vaporrole of water vapor

Table 1-1, p. 3

Composition of the Atmosphere Carbon dioxide and the greenhouse gases ozone aerosols pollutants Ozone at high altitudes (stratosphere) is “good”; ozone at low altitudes (troposphere) is “bad.”Ozone at high altitudes (stratosphere) is “good”; ozone at low altitudes (troposphere) is “bad.”

The modern atmosphere - composition Nitrogen - (N 2 ) - 78% - inert Oxygen (O 2 ) - 21% Argon - 0.9% Carbon Dioxide - (CO 2 ) % Water Vapor - (H 2 O) - 0% to 4% Trace Gases (neon, helium, methane, hydrogen, ozone) The atmosphere’s composition is in balance!

The composition of Earth’s Atmosphere is maintained in balance by interactions with life and the Earth’s surface

JanuaryMarch May July SeptemberNovember Global Vegetation - Seasonal Change NDVI Vegetation Index (NASA) In what month is there the least amount of carbon dioxide in the atmosphere??

Upward trend Related to fossil fuel burning and global warming Annual Cycle Related to the growing season of vegetation in the Northern Hemisphere Ahrens

FIGURE 1.3 The main components of the atmospheric carbon dioxide cycle. The gray lines show processes that put carbon dioxide into the atmosphere, whereas the red lines show processes that remove carbon dioxide from the atmosphere. Stepped Art Fig. 1-3, p. 4

A Brief Recap of Air Pressure and Air Density air density air pressure sea-level pressure Baseballs travel farther in higher-altitude air (Denver) than they do in lower-altitude air.Baseballs travel farther in higher-altitude air (Denver) than they do in lower-altitude air.

Layers of the Atmosphere vertical temperature profile troposphere stratosphere mesosphere thermosphere Temperatures, winds, humidity and pressures high above the ground are measured twice-daily by radiosonde.Temperatures, winds, humidity and pressures high above the ground are measured twice-daily by radiosonde.

Segway: The Ionosphere electrified regions of the atmosphere D, E and F regions radio waves When the radio was invented by G. Marconi in the early 20th century, it was not known how radio waves traveled long distances through the atmosphere.When the radio was invented by G. Marconi in the early 20th century, it was not known how radio waves traveled long distances through the atmosphere.

Fig. 1-11, p. 13

Vertical temperature structure: “layers of the atmosphere” Homosphere: The region of the atmosphere below about 85 km where the composition of the air remains fairly constant Heterosphere: The region of the atmosphere above 85 km where the composition of the air varies with height.

Two Criteria Two criteria are used to organize the layers of Earth’s atmosphere –Temperature or how temperature changes in the layer – lapse rate –And the depth or extent of that layer Use these two criteria to characterize each layer

Troposphere (0 - 12km) Lapse rate: Air cools with height, 6.5 o C per kilometer (lapse rate) Atmosphere heated from below, causing air to rise “Tropopause” All weather is in this layer

All weather that affects us occurs in the troposphere….. Rondônia, Brazil

Stratosphere ( km) Ozone production heats the stratosphere Stratopause Temperature increases with height (means something is adding heat there) No weather

Mesosphere ( km) Meteors burn up here Temperature decreases with height Thin ‘noctilucent’ clouds Mesopause

Even though weather occurs only in the troposphere, in these upper atmospheric layers, there are some “clouds”…

Noctilucent Clouds in the Mesosphere (~70km altitude)

Ionized Meteor Trail in the Mesosphere (~60 km)

Thermosphere ( km) Realm of the aurora “Ionosphere” High temperatures from few, high energy, gas molecules Low-orbit satellites fly here

Ionosphere: aurora (ionized gas) seen from surface

Aurora in the ionosphere as seen from the space shuttle

Exosphere (above 500 km) Just a few stray molecules….

Weather and Climate What is the difference?

Elements of Weather air temperature air pressure humidity clouds precipitation visibility wind Certain weather elements, like clouds, visibility and wind, are of particular interest to pilots.Certain weather elements, like clouds, visibility and wind, are of particular interest to pilots.

Climate average weather, over time, for a given region extremes – comparatively short duration, but the frequency of these events also help to distinguish and determine the climate of one region compared to another similar region

A Satellite’s View of the Weather geostationary satellites Atmospheric observation from satellites was an important technological development in meteorology. Other important developments include computer modeling, internet, and Doppler radar.Atmospheric observation from satellites was an important technological development in meteorology. Other important developments include computer modeling, internet, and Doppler radar.

Storms of all Sizes midlatitude cyclonic storms hurricanes and tropical storms thunderstorms tornadoes Storms are very exciting, but they also play an important role in moving heat and moisture around throughout the atmosphere. Lets take another look.Storms are very exciting, but they also play an important role in moving heat and moisture around throughout the atmosphere. Lets take another look.

A Look at a Weather Map wind speed and direction cyclones and anticyclones fronts Wind direction is defined in the opposite way as ocean currents: a southerly current means water is moving towards the south.Wind direction is defined in the opposite way as ocean currents: a southerly current means water is moving towards the south.

Fig. 1-13, p. 17

Weather and Climate in our Lives wind chill, frostbite and hypothermia heat exhaustion and heat stroke cold spells, dry spells and heat waves severe thunderstorms and flash floods The mathematical formula for determining the wind chill temperature has recently been revised due to new experiments.The mathematical formula for determining the wind chill temperature has recently been revised due to new experiments.

Fig. 1-16, p. 19 Figure 1.16: Ice storm near Oswego, New York, caused utility poles and power lines to be weighed down, forcing road closure.

Fig. 1-18, p. 20 Figure 1.18: Flooding during April, 1997, inundates Grand Forks, North Dakota, as flood waters of the Red River extend over much of the city.