Download Unit 1 Notes - Auburn CUSD 10

Meteorology
Unit 1
Basic Parts and Characteristics of
the Atmosphere
Meteorology, Weather, Climate
 Meteorology - The study of the atmosphere
and the phenomena that we call weather.
 Weather – The state of the atmosphere at a
given time and place.
 Climate – a generalization of long term
weather patterns for a given area.
 Today the high temperature is 93 degrees
with a heat index of 100 degrees.
 Weather or Climate
 In Illinois, we have 4 distinct seasons with a
moderately cold winter and a hot humid
summer.
 Weather or Climate
Observing the Atmosphere
 1593 – Galileo invented an early version of
the thermometer.
 1643 – Torricelli built the first barometer to
measure air pressure.
 1661 – Robert Boyle discovered the basic
relationship between pressure and volume
in gas.
Earth’s Four Spheres
 Geosphere – solid part of the Earth.
 Atmosphere – gaseous envelope
surrounding the Earth.
 Hydrosphere – All of the water on Earth
including the water in the atmosphere.
 Biosphere – All of the life on Earth.
 The atmosphere is often described as the
thickness of the lacquer on a globe.
 The Earth is a closed system for the most
part except for the energy from the sun.
 Human activity has the biggest effect on the
Earth’s system.
Composition of the Atmosphere
 The composition of the
Earth’s atmosphere
varies from time to
time and place to
place.
 Nitrogen and Oxygen
make up 99% of the
Earth’s atmosphere.
Nitrogen
Oxygen
All Others
Carbon Dioxide
 Represents .038 percent of the atmosphere
but has the ability to absorbs the Sun’s
energy that is radiated out from the Earth.
 CO2 is the most important greenhouse gas.
Water Vapor
 The amount of water vapor in the air varies
considerably from practically none to 4%.
 Water Vapor is responsible for all clouds.
 Water vapor carries latent heat or hidden
heat.
 When it changes form, heat is released or
absorbed.
Thermal Structure of the
Atmosphere
 Troposphere – the layer in which we live.
– The temperature decreases as altitude increases.
– 6.50C per kilometer (3.60F per 1000 ft.)
 Stratosphere – Temperature remains constant
then increases as altitude increases.
 Mesosphere – Temperatures decrease as altitude
increases. The Mesopause is the coldest part of
the atmosphere.
 Thermosphere – The air is extremely thin and hot,
but the heat can not be detected because of a lack
of air particles.
Ionosphere
 Located between 80 and 400 kilometers
above the Earth’s surface.
 Atoms of Nitrogen and Oxygen absorb solar
energy and become ions when they lose
electrons they create electric fields.
 The Auroras – a magnetic occurrence
between the charged ionosphere and the
charged particles emitted from the sun.
– The energized particles of Oxygen and Nitrogen
emit light.
– The auroras are most prevalent when there are
solar flares.
– Northern lights = Aurora Borealis
– Southern lights = Aurora Australis
Heating Earth’s Surface and
Atmosphere
 The Earth’s Surface is heated by the Sun.
 The Earth intercepts only 1 / 2,000,000,000
of the energy given off by the Sun.
 This miniscule percentage is still several
hundred thousand times greater that the
entire electrical generating capacity of the
United States.
 Solar radiation represents more than 99.9%
of the energy that heats our planet.
 Solar energy is not distributed equally.
 This unequal heating causes winds which
drive ocean currents and help to distribute
the heat.
 Variations in solar heating are caused by the
motions of the Earth relative to the Sun and
by the various land/sea structures of the
Earth.
Earth’s Motions
 Rotation and Revolution
 Rotation – the spinning of the Earth about
it’s axis.
– Produces the daily cycle of daylight and
darkness.
 Revolution – the orbit of the earth around
the Sun.
Seasons
 Caused by the combination of changes in
the length of day and the angle of the noon
Sun.
 Why does this happen?
– The Earth’s axis is tilted 23.5º from
perpendicular.
Solstices and Equinoxes
 Summer Solstice – June 21st or 22nd.
– Vertical Rays are 23.5º North of the Equator.
– First official day of summer. (northern
hemisphere)
 Autumnal Equinox – Sept. 22nd or 23rd.
– Vertical rays strike along the equator.
 Winter Solstice – Dec. 21st or 22nd.
 Spring (Vernal) Equinox – March 21st or
22nd.
– Vertical rays strike along the equator.
Discuss diagrams on pages 36-39.
 Watch cd-rom for further explanation (183)
Heat Transfer

How does heat flow?
– From warmer substances to cooler
substances.

This can happen three different ways.
1. Conduction – heat is transmitted through
electron and molecular collisions. Ex: cast iron
skillet.
2. Convection – heat transfer that involves the
actual movement of a substance. Ex: ocean
currents.
3. Radiation – Does not need a medium
(substance) to travel through. Radiation can
travel through the vacuum of space. Ex: Sun
Solar Radiation
 Solar radiation – energy from the sun that
includes all parts of the electromagnetic
spectrum.
Visible Light
 The range of wavelengths that we can see.
– Often referred to as white light although it is
made of a broad spectrum of colors
(ROYGBIV).
Infrared Radiation
 The portion of solar radiation that we feel as
heat.
 Wavelengths are slightly longer than visible
light.
Ultraviolet radiation
 Responsible for sunburns.
 Wavelengths are slightly shorter than visible
light.
Laws of Radiation
1. All objects continually emit radiant energy
over a range of wavelengths.
2. Hotter objects radiate more total energy
per unit area than do cold objects.
3. The hotter the radiating body, the shorter
the wavelength of maximum radiation.
4. Objects that are good absorbers of
radiation are also good emitters.
What happens to incoming
radiation?






See figure 2-13 on page 49.
50% absorbed by land and sea.
5% reflected by land and sea.
20% absorbed by atmosphere.
20% reflected by atmosphere.
5% backscattered to space by atmosphere.
 Albedo – the rate at which an object reflects
radiation.
Earth’s Radiation
 The Earth radiates energy as well.
 Clouds play an important role in our
weather.
– They absorb radiation from the sun and
reradiate back to space to help keep us cooler.
– They also absorb Earth’s radiation and reradiate
it back to Earth.
 Clear nights equal cool nights. Cloudy nights equal
warm nights.
Temperature
 One of the basic elements of weather.
 Measurement of the heat present.
 Daily mean temperature – average of the 24
hourly temperature readings.
 Daily temperature range – the difference
between the highest daily reading and the
lowest daily reading.
 Isotherm – a line that connects points on a
map that have the same temperature.
– Isotherms clearly mark the temperature
distribution and the temperature gradient (how
quickly the temperature changes).
Why Temperatures Vary
1.
2.
3.
4.
5.
Differential heating of land and water
Ocean currents
Altitude
Geographic position
Cloud cover and albedo
Why do land and water heat and
cool differently?
1. Water experiences convection currents
while land does not.
2. Heat is absorbed only at the surface of
land due to its opaque nature.
3. Water requires more energy to raise its
temperature than land does.
4. Energy in water is used for evaporation
which takes away from the energy used for
heating.
Ocean Currents
 Surface currents – movement of ocean
water set into motion by the wind.
– See page 73
– Gulf stream vs. California current
– Coastal areas of southern California have
milder summers than the coastal areas of the
eastern coast.
– Surface currents help to equalize latitudinal
differences in heat/energy.
– Ocean currents account for ¼ of this heat
transport and wind accounts for the other ¾
Leeward vs. Windward
 Leeward coast – prevailing winds blow from
the land to the ocean.
– Decreases the coastal effect.
– Ex: US East Coast
 Windward coast – prevailing winds blow
from ocean to land.
– Increases the coastal effect.
– Ex: US West Coast
Temperature Scales
 Celsius vs. Fahrenheit
 F = (1.8 x C) + 32
 C = (F – 32)/1.8
 Example – 100 C = ? F
F = (1.8 X 100) + 32
F = 180 + 32
F = 212
Moisture and Atmospheric Stability
 Water Vapor – colorless, odorless gas that
changes states at temperatures that we
experience on Earth.
– This allows for the hydrologic (water) cycle.
– Evaporation – changing from a liquid to a gas.
– Condensation – changing from a gas to a liquid.
– Melting – changing from a solid to a liquid.
– Freezing – changing from a liquid to a solid.
– Sublimation – changing from a solid to a gas.
– Deposition – changing from a gas to a solid.
Humidity

Humidity – How much water is in the air.
1. Absolute humidity – the mass of water vapor in a
given volume of air.
2. Mixing ratio – mass of water vapor compared to the
remaining mass of dry air.
3. Vapor pressure – pressure changes with the amount
of water vapor in the air.
4. Relative humidity – how near the air is to saturation.
5. Dew point – the temperature at which the air needs to
be cooled to reach saturation. (becoming a more
popular measure of humidity than relative humidity)
Dew Point Thresholds
 Less than 10 deg. F – Significant Snowfall is
inhibited.
 Greater than 55 deg. F – Minimum for severe
thunderstorms.
 Greater than 65 deg. F – considered humid by
most people.
 Greater than 70 deg. F – typical of rainy tropics.
 Greater than 75 deg F – considered oppressive by
most.
Humidity
 Humidity is a main factor in weather and comfort.
 Hygrometer – instrument used to measure
humidity.
 Sling psychrometer – two identical thermometers
mounted side by side. One is dry, the other is wet.
As water evaporates from the wet bulb the temp
will drop. The amount the temp drops tells you
how much moisture is in the air.
 See page 497 &498 for demo.
Sling
Psychrometer
Adiabatic Temperature Changes
 Adiabatic Temperature Changes are the
basis for cloud formation.
 Q: What is Adiabatic Temperature Change?
 A: It is the difference between a bicycle
pump and a can of air. HUH??
 Explanation – as air expands, it cools; as air
is compressed, it warms
Adiabatic Cooling and Condensation
 Any time a parcel of air moves upward, it
passes through regions of lower pressure.
 The result is adiabatic cooling as the air
expands.
 Unsaturated air cools at a constant rate of
10 deg. C per 1000 meters.
 This is known as the dry adiabatic cooling
rate.
 If a parcel of air rises high enough, it will
eventually cool to its dew point.
 Condensation begins and this point which is called
the condensation level.
 This process of condensation releases the latent
heat that the water vapor has and the adiabatic
rate slows down.
 This is called the wet adiabatic rate and can be
anywhere from 5 deg. C per 1000m to 9 deg. C
per 1000 meters.
Dry and Wet Adiabatic Rates
Processes that Lift Air
1. Orographic Lifting – air is forced to rise
over a mountainous barrier.
2. Frontal Wedging – warmer, less dense air,
is forced over cooler, denser air.
3. Convergence – a pile-up of horizontal air
flow results in upward movement.
Lifting Processes
Orographic
Death Valley
Rain Shadow Desert:
Dry area caused from adiabatic
warming on the leeward side of
mountains.
Wetter
Windward
Locations
and
Leeward
Rain
Shadows
Frontal Wedging
Convergence
Convergence
over
Southern Florida
Localized Convective Lifting
 Rising air caused by the uneven heating of
the Earth’s surface.
 Can cause short lived showers. Generally
happens on warm, fair weather, summer
days.
Convection
Atmospheric Stability
 Air that wants to sink or stay stationary is
called stable air.
 Air that wants to rise is called unstable air.
 Atmospheric Stability is the critical
weathermaker. What does that statement
mean?
Absolute Stability
The environmental lapse rate is less
than the wet adiabatic rate.
Absolute Instability
The environmental lapse rate is greater than the dry adiabatic
rate. This often leads to localized convective lifting on clear
warm days.
Conditional Stability
Moist air with an environmental lapse rate between the dry
and wet adiabatic rates.
Atmospheric Stability