TABLE OF CONTENTS Part 1 ATMOSPHERE I. Composition of the atmosphere II. Layers of the atmosphere III. Energy transfer throughout the atmosphere IV. Auroras V. Ozone VI. Properties of the atmosphere, how they interact, and how they change with altitude.
TABLE OF CONTENTS continued… Part 2 CLOUDS I. How clouds are formed II. Basic cloud types and groups III. The Water Cycle IV. Orthographic Lifting
Composition of the Atmosphere The atmosphere is the envelope of gases surrounding earth which are held in place by gravity.
Atmosphere Composition • The atmosphere is composed of: • 78% Nitrogen, • 21% Oxygen, • 1% Argon, • 0.03% Carbon Dioxide, and • 0.01% other gases (including water).
Layers of the Atmosphere There are four main layers of the earth’s atmosphere. Troposphere (lowest) Stratosphere (contains ozone layer) Mesosphere Ionosphere
Troposphere • The lowest layer is the troposphere which extends from the ground to about 18 km. This layer contains half of the earth’s atmosphere. Weather also takes place in this layer
Stratosphere • Next is the stratosphere which extends from 18km to 50km. The ozone layer (10km to 50km) is mostly in this layer of the atmosphere.
Mesosphere • The mesosphere (literally middle sphere) is the third highest layer in our atmosphere, occupying the region 50 km to 80 km above the surface of the Earth, above the troposphere and stratosphere, and below the thermosphere.
Ionosphere Then there is the Ionosphere. This layer is between 65 and 100 km above the earth. Ions and electrons reflect radio waves off of this layer, hence the name.
Tropopause: The boundary zone or transition layer between the stratosphere and the troposphere. Characterized by a decrease in temperature with increasing altitude.
Energy transfer Radiation: the transfer of heat as electromagnetic radiation (i.e. sunlight). Conduction: The transfer of heat due to contact (heat always flows from hotter objects to cooler objects).
Advection: the transfer of warm or cold air by horizontal winds. Convection: it is the transfer of heat due to movement of a fluid (air or water). Warmer air expands, becomes less dense, and thus rises forming a convection current. So, essentially, it is simply air mass rising.
Auroras • The beautiful, dancing patterns of light in the sky known as auroras • created by the radiant energy emission from the sun and its interaction with the earth's upper atmosphere over the middle and high latitudes.
Location of Auroras They are seen near the magnetic poles of each hemisphere. In the Northern Hemisphere, they are known as the aurora borealis or Northern Lights, especially in Alaska, obviously… In the Southern Hemisphere, these phenomena are called the aurora australis. Typical auroras are 100 to 250 km above the ground.
Once in a lifetime (literally), very rare auroras occur that are a deep blood red (usually with a little bit of yellow in the “centers”
Ozone Ozone is a gaseous molecule that contains three oxygen atoms (O3). Ozone exists high in the atmosphere, where it shields the Earth against harmful ultraviolet rays from the sun.
Ozone Depletion • Depletion of stratospheric ozone by manmade chlorofluorocarbons (CFCs) is a serious global concern due to the potential increase in ultraviolet radiation that may reach the surface of the Earth as a result of stratospheric ozone layer thinning.
Temperature Inversion Temperature inversion: when the air at the surface is colder than the air above it.
Temperature Temperature: the amount of molecular kinetic energy in a substance.
Heat Heat: transfer of energy that occurs because of a difference in temperature between substances.
Humidity • Humidity: The amount of water vapor in the air.
Relative Humidity Relative Humidity: The how much water vapor the air is capable of holding.
Terms continued… Density: measure of how much mass is contained in a given unit volume
Wind Wind: air moving (sometimes with considerable force) from an area of high pressure to an area of low pressure.
Air Pressure Air Pressure: the force exerted on a surface by the weight of the air above it
These properties interact several different ways. Take dew point for example.
Dew Point Dew point: the temp. to which air must be cooled at constant pressure to reach saturation. So obviously, the temp. plays a huge factor in the dew point, which is explained in its (the dew points) definition.
Relative Humidity Also, the relative humidity varies with temperature. As the temp. increases, the air would most likely hold more moist air.
Temperature and Pressure: If an air mass usually maintains a certain density, it proportionally increases or decreases with the temp.
Temperature and Density Temperature and Density: If an air mass maintains a certain pressure, as temp. increases, density decreases and vice versa. So, in other words, air becomes less dense
AS TEMP. PRESSURE AS TEMP. PRESSURE AS TEMP. DENSITY AS TEMP. DENSITY
CLOUDS The formation of clouds can be linked back to convection and more in the previous section.
How clouds form. Clouds are formed when air containing water vapor is cooled below a critical temperature called the dew point and the resulting moisture condenses into droplets on microscopic dust particles (condensation nuclei) in the atmosphere.
Convection that Creates Clouds • The air is normally cooled by expansion during its upward movement. • Upward flow of air in the atmosphere may be caused by convection resulting from intense solar heating of the ground; • by a cold wedge of air (cold front) near the ground causing a mass of warm air to be forced aloft; • or by a mountain range at an angle to the wind.
Mixing Currents Cause Clouds Clouds are occasionally produced by a reduction of pressure aloft or by the mixing of warmer and cooler air currents.
Cloud groups There are essentially four cloud types: High clouds: 6-13km Middle Clouds: 2-6 km Low Clouds: Ground level to 2km Clouds with vertical development: as the name suggests, these clouds usually start low in the atmosphere and extend far up into the upper layers.
High Clouds Cirrus: these are white clouds that are described as “feather” and/or “wispy”. Many people know these clouds as “mares tails”. Usually, these clouds are a sign of bad weather to come… Cirrocumulus: white louds that look like ripples or waves. One of the more popular descriptions for these clouds is “globular” or “globular masses”. These clouds indicate fair weather, but might indicate the coming of a storm. Cirrostratus: these “halo” clouds are veillike and layer. They usually cause rings to appear around the moon or sun. The same weather predictions can be gotten from these as cirrocumulus.
Middle Clouds Altocumulus: these light gray clouds look like broken-up cirrocumulus clouds. They are small patches in the sky. Usually, these are associated with fair weather, but can cause thunderstorms. Altostratus: these clouds are blanket layers, and can be either gray or bluish. On occasion, the produce light rain.