ATMOSPHERE, WEATHER AND CLIMATE

The Atmosphere:In this segment we discuss the composition and structure of the atmosphere, and its influence on earth’s physical systems

Earth’s atmosphere has evolved over the last 4 .6 billion years – Now, its composition and structure is relatively stable

Characteristics of the AtmosphereOur atmosphere is a dynamic mixture of various gases that envelops earth and protects it from excessive and harmful solar radiation, and other onslaught, from outer space

It is a thin film of air, extending for about 300 miles above Earth

It serves as an insulator, maintaining viable temperatures on Earth

It also serves as a shield, blocking out much of sun’s ultraviolet radiation, and protecting us from meteor showers

Permanent or “Constant” Gases

• Nitrogen (78%)

• Oxygen (21%)

• Argon (0.93%)

These gases are called "permanent gases" because their concentration remainedvirtually the same for much of recent earth history.

These are important for maintaining life and driving a number of processes near Earth’s surface

Composition of the Atmosphere

Variable or “Greenhouse” Gases

Even though they represent a tiny portion of the atmosphere as a whole (‹ 0.07%), they exert a great control over our environment

• Carbon Dioxide Carbon dioxide

• Methane Methane

• Ozone Ozone • Water Vapor Water vapor + Particulates Particulates

• Carbon Dioxide (CO2) makes up only .036% of the atmosphere by

volume. Carbon dioxide is essential to the photosynthesis processes of plants, in which oxygen is a byproduct • Methane (CH4) makes up far less of the atmosphere (.0002%) than

carbon dioxide, but it is 20+ times more potent than CO2 as a

greenhouse gas. Methane has been on the rise over the last several decades • Ozone (O3) is both beneficial and harmful to life on Earth. Much of the

ozone in the atmosphere is found in the stratosphere [stratosphere] There, ozone absorbs UV light from the Sun, preventing it from reaching the surface

Without this blanket, humans would be exposed to serious sunburn and potential risk of skin cancer.

• Ozone is also found in the lowest layer of the atmosphere, the troposphere [troposphere]

Antarctica Here ozone can act as an eye and respiratory irritant. Ozone also causes cellular damage inside the leaves of plants, impairing carbon dioxide uptake and disrupting the photosynthetic apparatus. Human-produced compounds such as chlorofluorocarbons (CFCs) and halides containing chlorine and bromine destroy ozone, and have disrupted the fragile stratospheric ozone layer over and the Arctic -- the “Ozone Hole”

Water Vapor

It is an extremely important gas found in the atmosphere. It can vary from 4% in the steamy tropics to nearly nonexistent in the cold dry regions of the Antarctic. Water vapor is a good absorber of earth's outgoing radiation and thus is considered a greenhouse gas.

Ozone Hole over Antarctica

Sep 2009 – 9.2 Million Square Miles

Particulates

• Particulates play several important roles in atmospheric processes. • Particulate matter includes dust, dirt, soot, smoke, and tiny particles of pollutants. Major natural sources of particulates are volcanoes, fires, wind-blown soil and sand, sea salt, and pollen.

Human sources such as factories, power plants, trash incinerators, motor vehicles, andconstruction activity also contribute particulates to the atmosphere.

The most spectacular sunrises and sunsets are a result of light being refracted from particulates in the atmosphere.

Also, see p. 94:

“Colors of the Atmosphere”Due to atmospheric scattering of the wavelengths of the visible light spectrum

Structure of the Atmosphere:Vertical Layersby TemperatureCharacteristics

Troposphere(the Lower Atmosphere)

Stratosphere(the Upper AtmosphereStarts here)

The properties of the first two layers – Troposphere and Stratosphere – affect most of what we study in physical geography, especially weather & climate

Together, these 2 layers extend to about 35 miles above Earth’s surface

Layers above the stratopause have relatively little impact on our environment

99.9 percent of the gases (by volume) that comprise earth’s atmosphere is to be found in these two layers

Most of the water vapor and particulates in the atmosphereare concentrated in one layer – the troposphere

Most of the ozone concentration – the ozone layer – is confined within the stratosphere

Mesosphere and Beyond

• In the mesosphere air temperatures begin to decrease with increasing altitude

• The air of the mesosphere is thus extremely thin and air pressure very small

• The Mesopause separates the mesosphere from the thermosphere above • In the Thermosphere temperature increases

with increasing altitude – temperatures are generally high, but the heat content is very low due the low density of air at this level

Layers by Functional Characteristics

Another system, using protective function identified two atmospheric layers: the Ozonosphere and the Ionosphere

The ozonosphere is the concentrated layer of ozone found in the stratosphere, 10 – 30 miles above the surface. seasonal fluctuations of ozone, especially

over the Arctic and Antarctic, are common.

The ionosphere, 40 – 250 miles above the surface, is not really a layer of the atmosphere, but an electrified field of ions and free electrons –

The spectacular display of aurora lights are generally

found in this region.

Layers by Function

Layers by ChemicalComposition

Heating the Atmosphere:

Sun’s energy passes through Earth’s Atmosphere, Insolation, or Incoming Solar Radiation, depends on many factors:

• Latitude• Time of Day• Time of Year• Atmospheric Thickness

All the above are related to the angle of sun’s rays

• The Transparency of the Atmosphere (which includes the amount of cloud cover, moisture/water vapor, carbon dioxide, and particles in t he air)

Together, all these factors determine what is called:Earth’s Radiation Budget (See diagram 4.11, p. 93)

Processes of Heat Energy Transfer:

Sun’s energy passes through Earth’s Atmosphere, Insolation, or Incoming Solar Radiation,

Radiation: The process by which electromagnetic energy is transferred from Sun to Earth.

• Shortwave radiation from sun reaches earth and heats its surface

•Conduction: Heat transferred between two touching objects•Heat flows from Warmer to Cooler part.

•Convection : The vertical transfer of heat through • the atmosphere, like boiling water.

•Advection: horizontal heat transfer, e.g., from Equator to Polar regions, through wind and ocean currents

Earth’s Radiation Budget

To summarize the Radiation Budget: 34% of the insolation is returned to space; 19% is retained in the atmosphere, and 47% eventually reaches the surface.

The 47% received at the surface is ultimately returned to the atmosphere by various Heat Energy Transfer processes, and the Earth’s Radiation Budget is said to be in Equilibrium.

However, the radiation budget is a dynamic one

concern that human activity, will cause theatmosphere to absorb more Earth-emittedenergy,

raising global temperatures.[Greenhouse Gases]

The Greenhouse Effect• Greenhouses keep the temperature inside warmer than outside. •Sunlight (shortwave radiation) passes through the panes of glass. Materials within the greenhouse (plants, floors, walls, benches, etc.) absorb this energy.

• Absorbed radiation is reradiated as heat (long-wave radiation). •The glass panes block the long wave radiation, thus trapping the heat,• keeping the air warm inside the greenhouse.

Earth as a Greenhouse

The Greenhouse Effect in the Earth context is defined as a system in which sun’s shortwave radiation enters freely and is absorbed, then reradiated as long-wave infrared radiation.

The long-wave radiation is largely retained within the system, hereby continuing the Greenhouse Effect.

Without Greenhouse Effect, the heat would escape to outer space Average temperature of the Earth would drop

from an average of +15 degrees to -18 degrees Celsius (59˚F to – 65˚F)

Life as we know it could not survive!

Negative ConsequencesHow can the Greenhouse Effect be harmful to us?

Rising levels of greenhouse gases cause a rise in global temperatures:

Global mean surface temperatures have increased by .5 - 1˚ F since the later part of the 19th century

Rising temperatures have caused a decrease in snow cover and sea ice in the Northern Hemisphere

Global sea level has risen by 4-8 inches over the past hundred years – sea level rise and inundation of coastal regions is feared as

Antarctic ice sheets and shelves, and smaller alpine glaciers melt

The frequency of extreme precipitation events has increased throughout the U.S. and the world (e.g., 2010 Pakistan Floods)

  Watch "Global Warming 101" Courtesy of National Geographic

Weather and ClimateWeather: refers to the condition of atmospheric elements at a given time, and for a specific area.

Climate: average of weather conditions for 30+ years (including atmospheric anomalies).

Weather and Climate are of prime interest to the Physical Geographer because they affect and are interrelated with all of Earth’s environments.

Obvious Next Questions: How do insolation and heat energy transfer processes relate to Weather and Climatephenomena on Earth?

5+ Basic Elements of the Atmosphere– the main ingredients of weather and climate

-- Also called Elements of Weather and Climate

• Solar Energy-- Insolation and Heat Energy Transfer

• Temperature• Pressure• Wind• Precipitation+ Air Masses (and Fronts)

to be discussed later in conjunction withWeather Systems

As we will see in the next set of topics, Earth’s Weather and Climate are the results of the intricateinterrelationships between Earth and the Sun, and between the component spheres of our Atmosphere and our Geosphere: