Transcript ATMOSPHERE AND CLOUDS

ATMOSPHERE AND CLOUDS
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.
Atmosphere Composition
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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).
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
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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
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.
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.