Atmosphere

Greenhouse Effect

is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions.

a layer of gases surrounding the planet Earth that is retained by Earth's gravity.

Greenhouse Gas(GHG)

is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range.The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

Atmosphere

The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

Global and Environmental Issues

*ppmv:

• parts per million by volume

780, 840 ppmv (78.084%)

209, 460 ppmv (20.946%)

9, 340 ppmv (0.9340%)

387 ppmv (0.0397%)

18.18 ppmv (0.001818%)

5.24 ppmv (0.000524%)

1.79 ppmv (0.000179%)

1.14 ppmv (0.000114%)

0.55 ppmv (0.000055%)

0.325 ppmv (0.0000325%)

0.1 ppmv (0.00001%)

0.09 ppmv (0.000009%)

0.0 to 0.07 ppmv (0 to 7x10^-6%)

0.02 ppmv (0.000002%)

0.01 ppmv (0.000001%)

trace

VOLUME

Composition of the Atmosphere

Composition of dry atmosphere by volume

Not included in above dry atmosphere:

Water Vapor(H2O) -------- ~0.25% by mass over full atmosphere, locally 0.001%-5%

Nitrogen (N2)

Oxygen (O2)

Argon (Ar)

Carbon Dioxide (CO2)

Neon (Ne)

Helium (He)

Methane (CH4)

Krypton (Kr)

Hydrogen (H2)

Nitrous Oxide (N20)

Carbon Monoxide (CO)

Xenon (Xe)

Ozone (O3)

Nitrogen Dioxide(NO2)

Iodine (I2)

Ammonia (NH3)

GAS

Importance of some of the atmospheric gases:

• Nitrogen - The addition of this nitrogen to the Earth's surface soils and various water bodies supplies much needed nutrition for plant growth.
• Oxygen and Carbon Dioxide - important for the process of PHOTOSYNTHESIS and living respiration.
• Ozone - helps the enhancement of greenhouse effect.

• Global Warming
• Climate Change
• Greenhouse Effect
• Ozone Depletion

• The eleven most abundant gases of the Earth
• Importance of some of the Atmospheric Gases

Greenhouse effect

• A process by which thermal radiation from a planetary surface is absorb by atmospheric greenhouse gases, and is re-radiated in all directions.
• The primary gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

The table indicates that nitrogen and oxygen are the main components of the atmosphere by volume. Together these two gases make up approximately 99% of the dry atmosphere.

Climate Change

A significant and lasting change in the statistical distribution of weather over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions

Global Warming

• The rise in the average temperature of Earth's atmosphere and oceans since the late 19th century and its projected continuation. Since the early 20th century, Earth's mean surface temperature has increased by about 0.8 degrees Celsius (1.4 degrees Fahrenheit), with about two-thirds of the increase occurring since 1980
• Primarily cause by increasing concentrations of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation

Ozone Depletion

Describes two distinct but related phenomena observed since the late 1970s: a steady decline of 4% per decade in the total volume of ozone in Earth's stratosphere(the ozone layer), and a much larger springtime decrease in stratosphere ozone over Earth's polar regions.

• Stages
• Cumulus
• Air is lifted and cools adiabatically to the dew point and a cumulus cloud develops.
• Heat of vaporization is released and accelerates the uplift.
• Mature
• When the moisture that is produced reaches the surface of the Earth
• This series of updrafts, downdrafts, and precipitation release electrical charges which become the lightening associated with the storm
• Final
• All of the updrafts are cut off and only downdrafts exist.
• Lightning
• Thunder
• Hail

Waves and Cyclones

• Occluded Front
• One that has been lifted completely off the ground
• Has s low pressure center and cyclonic activity
• Cyclone
• a low pressure area with winds moving into the low pressure area and being forced upward.
• Friction and the Coriolis effect cause the air to move to the right of the direction of movement.
• Anticyclone
• A high pressure center

Tornados

• Most violent, focused storm on Earth
• Speeds in excess of 300 km/hr (200 mi/hr)

Hurricanes

• A hurricane is a violent storm that is produced over the warm tropical ocean near the equator.
• Tropical Cyclone
• Typhoon

Warm Front

• When a warm air mass moves into an area, displacing the cold air mass
• A gently sloping front as the Warm air moves over top of the cooler air.

Stationary Front

• When the edge of a front ceases to advance

Air Mass Weather

• When the weather in an area is under the influence of an air mass

Weather Fronts

Front

• A boundary between two different air masses

Cold Front

• When a cold air mass moves into a warmer area, displacing the warm air mass
• Provides lift to adiabatically cool the warm air, resulting in towering cumulus and thunderclouds.

Major types of air masses

• Continental Polar
• Cold
• Dry
• Maritime Polar
• Cold
• Moist
• Continental Tropical
• Warm
• Dry
• Maritime tropical
• Warm
• Moist

Air Masses

• Polar Air Mass
• An air mass that moves from a cold region
• Tropical Air Mass
• An air mass that moves from a warm region
• Continental Air Mass
• Moves in from a land mass
• Maritime Air Mass
• Moves in from over an ocean

Water Producers

There is a shift in weather during the changes of the seasons that is related to:

• Movement of air masses
• Leading fronts of air masses
• High and low pressure areas

Hydrological Cycle - 4 main parts

• Evaporation of water from the oceans
• Transport of water vapor in the atmosphere
• Return of water to ocean by rivers and streams
• Condensation and precipitation

Precipitation is water in the liquid or solid form that returns to the surface of the eartH

• Very little energy transfers, however, due to the lack of molecules (very few molecules to collide with objects.)

Supercooled

• If water remains in the liquid state after the temperature is below the freezing point.

Ice-forming nuclei

• Solid particles on which the ice forms

Clouds and Precipitation

Main events of the hydrologic cycle:

(1) The evaporation of water from the ocean;

(2) The transport of water vapor through the atmosphere;

(3) Condensation and precipitation of water on the land; and

(4) Return of water to the ocean by rivers and streams.

• Temperature is extremely high here due to the average kinetic energy of the molecules.

Upward Air Movement

• Convection resulting from differences in temperature
• Barriers such as mountain ranges which provide lift to air masses
• Meeting of moving air masses with different densities.

Origin of Precipitation

• Processes of precipitation formation
• Coalescence

When water droplets merge with millions of other water droplets.

• Growth of ice crystals

Ice crystals can capture other water molecules and grow to enormous sizes.

The structure of the atmosphere based on temperature differences. Note that the "pauses" are actually not lines, but are broad regions that merge.

Cloud-forming Processes

Thermosphere

• Temperature again begins to rise due to the presence of molecular fragments which absorb radiation from space.

Wet Adiabatic Lapse Rate

• The lapse rate for a parcel of air at a slow rate and releasing the temperature equal to its latent heat of vaporization

Supersaturated

• When the air contains more water vapor than is the normal amount of water vapor

Adiabatic Cooling

• Decrease in temperature of an expanding gas

Adiabatic Heating

• Heating of a gas as it undergoes compression

Dry Adiabatic Lapse Rate

• Rate of cooling in the absence of condensation
• About 10 OC for each increase or decrease of 1 km (5.5OF/1,000 ft)

Atmospheric Stability

• Stability
• When the atmosphere lapse rate is less than the dry adiabatic lapse rate

• Instability
• When the atmospheric lapse rate is greater than the dry adiabatic lapse rate.

Weather and Climate

Mesosphere

• Temperature again begins to decrease due to a decrease in gas molecules to absorb radiation
• This is also the layer in which a lot of meteors burn up while entering the Earth's atmosphere.

Ionosphere

• Alternative name for the thermosphere and upper mesosphere.
• Due to the occurrence of free electrons and ions.
• It is the electrons and ions in this layer that cause radio waves to be able to be reflected around the world.

Exosphere

• Outermost layer of the atmosphere where molecules merge with the vacuum of space.
• The high kinetic energy of the molecules at this height are significant enough to cause them to be able to escape into space.

Weather

• The state of the atmosphere at a given time and place, with respect to variables such as temperature, moisture, wind velocity, and barometric pressure.
• These changes usually affect daily life one way or another, but some of them seem more inconvenient than others.

Layers of the Atmosphere

On the average, the temperature decreases about 6.5OC/1,000 km, which is known as the observed lapse rate. An inversion is a layer of air in which the temperature increases with height.

• Clouds and Precipitation
• Weather Producers
• Climate

Structure of the Atmosphere

Observation Lapse Rate

• The temperature decreases approximately 6.5 degrees Celsius for each kilometer of altitude (3.5 degrees Fahrenheit / 1,000 ft)

Inversion

• When a layer of the Atmosphere increases with altitude.

Troposphere

• The lowest layer of the Earth's atmosphere
• The layer of the atmosphere from the surface of the Earth up to where it stops decreasing in temperature.
• Up to a height of about 11 km (6.7 mi)
• Air is constantly mixed due to denser air being above less dense air.
• Weather occurs in the Earth's troposphere

Climate

• is a generalized pattern for weather over a period of time

Local Climates

• Cities
• Materials used to build cities have a higher heat holding capacity that natural materials.
• Also change wind direction and speeds
• Microclimates
• A local pattern of climate influenced greatly by the local conditions.

Major Climate Groups

• Factors Determining Weather
• Temperature
• Moisture
• Movement of Air

Regional Climate Influence

Altitude

• Higher altitudes radiate more energy back into space.
• Temperature decreases with altitude

Mountains

• Decreasing temperature with altitude
• Uplifting effect on air masses

Tropopause

• The upper boundary of the Troposphere
• The temperature remains constant with increasing altitude

Describing Climates

Major Climate Zones

Maritime Climate

• Influenced by air masses from the ocean

Continental Climate

• Influenced by air masses from land

Arid

• dry
• Less than 25 cm (10 in) of rain per year

Large Bodies of Water

• High specific heat and loses energy by evaporation.
• This has the effect of keeping the temperatures more constant from night to day on a land mass near a large body of water

Ocean Currents

• Currents move large amounts of water from different parts of the world.
• Can warm or cool land depending upon the origin of the current

Tropical Climate Zone

• Near the equator and receives the greatest amount of sunlight throughout the year.

Polar Climate Zone

• The Sun never sets during the summer and never rises during the winter.

Temperate Climate Zone

• Average temperatures that are between the two extremes

Stratopause

• Where the temperature reaches a maximum of 10 degrees Celsius (50 degrees Fahrenheit)

Ozone Shield

• A layer of ozone that absorbs much of the ultraviolet radiation that enter the atmosphere
• Provides a significant shield to the Earth below from damaging UV radiation

Stratosphere

• The temperature begins increase with height.
• Very stable as denser air is below less dense air
• Up to about 48 km (30 mi)
• Temperature increases as a result of interactions between high energy UV radiation and ozone (O3)

Low Latitudes

• Have vertical solar radiation at noon some times of the year

High Latitudes

• Have no vertical solar radiation at noon some times of the year.

Middle Latitudes

• Between high and low latitudes.

Humid

• Moist
• More than 50 cm (20 in) of rain per year

Semiarid

• Between arid and humid
• 25 - 50 cm (10 - 20 in) of rain per year

photo credit Nasa / Goddard Space Flight Center / Reto Stöckli