Transcript ATMOSPHERE AND CLOUDS

ATMOSPHERE AND CLOUDS
By Anton Weissenberg
TABLE OF CONTENTS
Part 1
I.
II.
III.
IV.
V.
VI.
ATMOSPHERE
Composition of the atmosphere
Layers of the atmosphere
Energy transfer throughout the
atmosphere
Auroras
Ozone
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. 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 three main layers of the earth’s atmosphere.
The lowest layer is the troposphere which extends from
the ground to about 18,000 km. This layer contains half
of the earth’s atmosphere. Weather also takes place in
this layer… 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. Next is the stratosphere which extends
from 18,000km to 50,000km. The ozone layer (10,000km
to 50,000km) is mostly in this layer of the atmosphere.
Then there is the Ionosphere. This layer is between 65
and 100,000 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 mesosphere. 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).
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.
Advection: the transfer of warm or cold air by
horizontal winds.
Auroras
The beautiful, dancing patterns of light in the sky
known as auroras are created by the radiant
energy emission from the sun and its interaction
with the earth's upper atmosphere over the
middle and high latitudes. 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. 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.
Terms
Temperature inversion: when the air at the
surface is colder than the air above it.
Temperature: the amount of molecular kinetic
energy in a substance.
Heat: transfer of energy that occurs because of
a difference in temperature between substances.
Humidity: The amount of water vapor in the air.
Terms continued…
Relative Humidity: The how much water vapor the air
is capable of holding.
Density: measure of how much mass is contained in
a given unit volume
Wind: air moving (sometimes with considerable force)
from an area of high pressure to an area of low
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: 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.
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:
If an air mass maintains a certain
pressure, as temp. increases, density
decreases and vice versa. So, in other
words, air becomes less dense
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. 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. 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.
Cirrus
Cirrocumulus
Cirrostratus
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.
Altocumulus
Altostratus
Low Clouds
Stratocumulus: these are soft, gray patches that
may for a continuous layer.
Stratus: these are dense, lower layers of gray
clouds. They sometimes cover the entire sky.
Sometimes associated with light rain. When
these clouds are low to the ground, they are
called fog.
Nimbostratus: a large, thick layer of dark clouds
that, on occasion, block out the sun. These are
usually associated with steady, drawn out
precipitation.
Stratocumulus
Stratus
Nimbostratus
The Water Cycle
The Sun's heat provides energy to evaporate water
from the Earth's surface (oceans, lakes, etc.). Plants
also lose water to the air (this is called transpiration).
The water vapor eventually condenses, forming tiny
droplets in clouds. When the clouds meet cool air over
land, precipitation (rain, sleet, or snow) is triggered,
and water returns to the land (or sea). Some of the
precipitation soaks into the ground. Some of the
underground water is trapped between rock or clay
layers; this is called groundwater. But most of the
water flows downhill as runoff (above ground or
underground), eventually returning to the seas as
slightly salty water.
Orographic Lifting
Orographic Lifting: where the flow of air is
forced up and over barriers such as
highlands or mountains. Moist air being
forced aloft begins to cool, thus
condensation forms, and rain or snow
begins to fall. By the time the air reaches
the leeward side of the barrier, it sinks and
warms, resulting in decreasing relative
humidity, ending of precipitation, and the
dissipation of clouds.