Weather and ClimateWeather and Climate

Geography 101Geography 101

Dr. R. B. Schultz

Elmhurst College

Chapter 1: Introduction to the Atmosphere

Weather and ClimateWeather refers to the state of the atmosphere at

a given time and place. It is constantly changing, sometimes from hour to hour and other times from day to day.

Climate is an aggregate of weather conditions, the sum of all statistical weather information that helps describe a place or region.

The nature of both weather and climate is expressed in terms of the same basic “elements”, those quantities or properties measured regularly.

Elements of Weather

The most important elements are:

(1) air temperature,

(2) humidity,

(3) type and amount of cloudiness,

(4) type and amount of precipitation,

(5) air pressure, and

(6) the speed and direction of the wind.

A Typical “Weather” Map

Catastrophic Events and Associated DeathsCatastrophic Events and Associated Deaths

The Relevance of Weather Events

Earth’s SpheresEarth's four spheres include:

the atmosphere (gaseous envelope), the lithosphere (solid Earth), the hydrosphere (water portion), and the biosphere (life).

Each sphere is composed of many interrelated parts and is intertwined with all other spheres. The energy exchanges that continually occur between the atmosphere and Earth's surface, and between the atmosphere and space, produce the effects we call weather.

Earth’s HydrosphereEarth’s Hydrosphere

SystemsA system is a group of interacting or

interdependent parts that form a complex whole.

The Earth System involves the intricate and continuous interaction between the lithosphere, hydrosphere, atmosphere, and biosphere.

The two primary sources of the energy that power this system are:

(1) solar energy that drives the external processes that occur at, or above, Earth's surface, and

(2) Earth's interior, heat remaining from when the planet formed and heat that is continuously generated by radioactive decay.

The Carbon CycleThe carbon cycle illustrates the movement of material and

energy from one sphere to another in the Earth system.

Carbon is a basic building block of life. Through the process of photosynthesis, plants absorb carbon dioxide from the atmosphere to produce the essential organic compounds needed for their growth. Plants and animals also return carbon dioxide to the atmosphere.

Further, over long periods of geologic time, considerable biomass is buried and under the right conditions converted to fossil fuels—coal, petroleum, or natural gas.

Besides the movement from the atmosphere to the biosphere and back again, carbon also moves from the lithosphere and hydrosphere to the atmosphere and back via volcanic activity and as very weak carbonic acid in rain water.

The Carbon CycleThe Carbon Cycle

Our AirAir is a mixture of many discrete gases and its composition

varies from time to time and place to place.

After water vapor, dust, and other variable components are removed, two gases, nitrogen and oxygen, make up 99 percent of the volume of the remaining clean, dry air.

Carbon dioxide, although present in only minute amounts (0.036 percent), is thought to be an efficient absorber of energy emitted by Earth and thus, influences the heating of the atmosphere.

Because of the rising level of carbon dioxide in the atmosphere during the past century (since the Industrial Revolution) attributed to the burning of ever increasing quantities of fossil fuels, many scientists believe that a warming of the lower atmosphere will trigger global climate change.

However, we will explore new, However, we will explore new, more scientificmore scientific conceptions of conceptions of the “Global Warming” theory in this course.the “Global Warming” theory in this course.

Variable Air ComponentsThe variable components of air include:

•water vapor,

•dust particles, and

•ozone.

Like carbon dioxide, water vapor absorbs heat given off by Earth as well as some solar energy. When water vapor changes from one state to another, it absorbs or releases heat.

Latent Heat and AerosolsIn the atmosphere, water vapor

transports this latent ("hidden") heat from one region to another, and it is the energy source that helps drive many storms.

Aerosols (tiny solid and liquid particles) are meteorologically important because these often invisible particles act as surfaces on which water can condense and are also absorbers and reflectors of incoming solar radiation.

OzoneOzone, a form of oxygen that combines three

oxygen atoms into each molecule (O3), is an important gas concentrated in the 10 to 50 kilometer height in the atmosphere that absorbs the potentially harmful ultraviolet (UV) radiation from the Sun.

Over the past half century, people have placed Earth's ozone layer in jeopardy by polluting the atmosphere with chlorofluorocarbons (CFCs) which remove some of the gas.

Ozone concentrations take an especially sharp drop over Antarctica during the Southern Hemisphere spring (September and October).

Ozone (cont.)Furthermore, scientists have also discovered

a similar but smaller ozone thinning near the North Pole during spring and early summer.

Because ultraviolet radiation is known to produce skin cancer, ozone depletion seriously affects human health, especially among fair-skinned people and those who spend considerable time in the Sun.

In late 1987, the Montreal Protocol, which represents a positive international response to the ozone problem, was concluded under the auspices of the United Nations.

Investigating the AtmosphereInvestigating the Atmosphere

BalloonsBalloons play a significant role in the play a significant role in the systematic investigation of the atmosphere systematic investigation of the atmosphere by carrying by carrying radiosondesradiosondes (lightweight (lightweight packages of instruments that send back packages of instruments that send back data on temperature, pressure, and relative data on temperature, pressure, and relative humidity) into the lower atmosphere. humidity) into the lower atmosphere.

Rockets, airplanes, satellites, and weather Rockets, airplanes, satellites, and weather radar are also among the methods used to radar are also among the methods used to study the atmosphere. study the atmosphere.

Atmospheric Boundary?No sharp boundary to the upper atmosphere

exists. The atmosphere simply thins as you travel away from Earth until there are too few gas molecules to detect.

The change that occurs in atmospheric pressure (the weight of the air above) helps understand the vertical extent of the atmosphere:• One-half of the atmosphere lies below an

altitude of 5.6 kilometers (3.5 miles), and

• 90 percent lies below 16 kilometers (10 miles).

• However, traces of the atmosphere extent for thousands of kilometers beyond Earth's surface.

“Layers” of Our Atmosphere

Atmospheric temperature drops with increasing height above Earth's surface. Using temperature as the basis, the atmosphere is divided into four layers:

The temperature decrease in the troposphere, the bottom layer in which we live, is called the environmental lapse rate. Its average value is 6.5°C per kilometer, a figure

known as the normal lapse rate. The environmental lapse rate is not a constant and must be regularly measured using radiosondes.

Temperature InversionA temperature inversion, where

temperatures increase with height, is sometimes observed in shallow layers in the troposphere.

The thickness of the troposphere is generally greater in the tropics than in polar regions.

Essentially all important weather phenomena occur in the troposphere.

The StratosphereBeyond the troposphere lies the

stratosphere; The boundary between the troposphere

and stratosphere is known as the tropopause.

In the stratosphere, the temperature at first remains constant to a height of about 20 kilometers (12 miles) before it begins a sharp increase due to the absorption of ultraviolet radiation from the Sun by ozone.

Mesosphere and Thermosphere

The temperatures continue to increase until the stratopause is encountered at a height of about 50 kilometers (30 miles).

In the mesosphere, the third layer, temperatures again decrease with height until the mesopause, some 80 kilometers (50 miles) above the surface.

The fourth layer, the thermosphere, with no well-defined upper limit, consists of extremely rarefied air that extends outward from the mesopause.

Atmospheric CompositionBesides layers defined by vertical variations

in temperature, the atmosphere is often divided into two layers based on composition.

The homosphere (zone of homogeneous composition), from Earth's surface to an altitude of about 80 kilometers (50 miles), consists of air that is uniform in terms of the proportions of its component gases.

Above 80 kilometers, the heterosphere (zone of heterogeneous composition) consists of gases arranged into four roughly spherical shells, each with a distinctive composition.

Heterospheric GasesHeterospheric GasesWith increasing altitudes, the four layers With increasing altitudes, the four layers

consist of:consist of:

1.1. molecular nitrogen (Nmolecular nitrogen (N22), ),

2.2. atomic oxygen (O), atomic oxygen (O),

3.3. helium (He) atoms, and helium (He) atoms, and

4.4. hydrogen (H) atoms, respectively. hydrogen (H) atoms, respectively.

The stratified nature of the gases in the The stratified nature of the gases in the heterosphere varies according to their heterosphere varies according to their weights, with the outermost gas, weights, with the outermost gas, hydrogen, being the lightest. hydrogen, being the lightest.

The IonosphereThe Ionosphere

Occurring in the altitude range between 80 Occurring in the altitude range between 80 and 400 kilometers (50-250 miles) is an and 400 kilometers (50-250 miles) is an electrically charged layer known as the electrically charged layer known as the ionosphereionosphere. .

Here molecules of nitrogen and atoms of Here molecules of nitrogen and atoms of oxygen are readily ionized as they absorb oxygen are readily ionized as they absorb high-energy, short-wave solar energy. high-energy, short-wave solar energy.

Three layers of varying ion density (from top Three layers of varying ion density (from top to bottom, the to bottom, the D, E, and FD, E, and F layers layers respectively) make up the ionosphere. respectively) make up the ionosphere.

Auroras

Auroras (the aurora borealis, northern lights, and its Southern Hemisphere counterpart the aurora australis, southern lights) occur within the ionosphere.

Auroras form as clouds of protons and electrons ejected from the Sun during solar-flare activity enter the atmosphere near Earth's magnetic poles and energize the atoms of oxygen and molecules of nitrogen, causing them to emit light—the glow of the auroras.

Key TerminologyKey TerminologyClimateClimate Temperature inversionTemperature inversion

AtmosphereAtmosphere TroposphereTroposphere

HydrosphereHydrosphere StratosphereStratosphere

BiosphereBiosphere Radiosondes Radiosondes MesosphereMesosphere

AirAir ThermosphereThermosphere

Montreal ProtocolMontreal Protocol HomosphereHomosphere

OzoneOzone StratopauseStratopause

Aerosols Aerosols MesopauseMesopause

Carbon CycleCarbon Cycle TropopauseTropopause

SystemSystem HeterosphereHeterosphere

WeatherWeather Heterospheric gasesHeterospheric gases

LithosphereLithosphere IonosphereIonosphere

Environmental lapse rateEnvironmental lapse rate Aurora borealisAurora borealis

Aurora australisAurora australis

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CLASS INSTRUCTIONAL WEB SITES...CLOUDS AND PRECIPITATIONTORNADOES: A SATELLITE AND RADAR PERSPECTIVE