Download Meteorology

Meteorology
What is Meteorology?
• Meteorology is the study of atmospheric
phenomena
• Anything that’s high in the sky: raindrops,
rainbows, dust, snowflakes, fog and
lightning
• All of these are examples of meteors?
What is Meteorology?
• Atmospheric phenomena are classified as
types of meteors
• Cloud droplets (rain, sleet, snow) are
types of hydrometeors.
• Smoke, haze, dust – any particles
suspended in the atmosphere are
lithometeors.
What is Meteorology?
• Short term variations in atmosphere
phenomena that affect the environment
and life on Earth is weather.
– These variations can be minutes, hours, days,
weeks up to years long.
• Climate is the long term average in
weather for a particular area
Heating Earth’s Surface
• Sunlight is always heating some part of
Earth
• Over time the amount of thermal energy
Earth gets is the same amount that Earth
radiates back to space.
• How is this solar radiation distributed
around Earth?
Imbalanced Heating
• In January, which is warmer? Miami or
New York City?
• One reason is that Earth is tilted. Miami
gets more solar radiation in January.
• Another is that Earth is a sphere and
different places are at different angles to
the sun.
Thermal Energy Redistribution
• Places on Earth maintain about the same
average temperatures over time due to
the movement of air and water between
land, water and atmosphere.
Air Masses
• An air mass is a large volume of air with
the same humidity and temperature as its
source region.
• A source region is the area where an air
mass forms.
• Most form over tropical waters or polar
regions.
Types of Air Masses
• Tropical air masses form in tropical bodies
of water and are responsible for our hot,
humid summers
• Polar air masses form over the cold waters
of the North Atlantic and North Pacific.
These bring our really cold air in winter.
• The flip side?
Learning Targets
• Compare and contrast weather vs climate
• Analyze how imbalances in the heating of
Earth’s surface create weather
• Identify five types of air masses and
explain how air masses form
Global Wind Systems
• If the Earth didn’t rotate, two large
convection currents would cover the
Earth.
• Colder air would sink to the tropics where
it would force warm air to rise.
• This air would cool as it got higher and on
and on
Global Wind Systems
• Earth rotating from west to east prevents
this from happening.
• The directions of our winds are influenced
by the Earth’s rotation.
• Its called the Coriolis effect.
Coriolis Effect
• Causes fluids and objects to move in a
curved path.
• Moving air curves to the right in the
northern hemisphere
• Moving air curves to the left in the
southern hemisphere
• http://www.youtube.com/watch?v=mcPs_
OdQOYU
Global Wind Systems
• The Coriolis effect and the heat imbalance
on Earth create distinct global wind
systems.
• There are three main zones or wind
systems: polar easterlies, prevailing
westerlies and trade winds.
Global Wind Systems
• Polar easterlies
– Between 60o N latitude and the north pole
and 60o S latitude and the south pole
– Begin as dense polar air that sinks
– As the Earth spins, this cold air is deflected in
an easterly direction: usually weak and
sporadic
Global Wind Systems
• Prevailing westerlies
– Found between 30oN and 60oN and 30oS and
60oS
– Surface winds move toward the poles in a
westerly direction (again due to the Earth’s
rotation)
– These move much of the weather across the
US
Global Wind Systems
• Between the polar easterlies and the
prevailing westerlies lie an area called the
polar front.
• This can bring stormy weather to us.
Global Wind Systems
• Trade winds are between 30oN and 30oS
• These circulation belts move toward the
equator in an eastern path
Jet Streams
• Atmospheric conditions and events that
happen at the boundaries between wind
zones strongly influence our weather.
• On either side of the boundaries, surface
air and upper level air differ in
temperature and pressure.
Jet Streams
• The difference in air pressure at the
boundaries causes wind.
• Wind is the movement of air from an area
of high pressure to an area of low
pressure.
Jet Streams
• A large temperature gradient in upper
level air combined with the Coriolis effect
gives us strong westerly winds called jet
streams.
• Jet streams are narrow bands of fast
moving winds.
• Its speed varies with the temperature
differences..
Jet Streams
• The position of the jet stream varies with
the season.
• Its usually found in the region of strongest
temperature differences on a line from the
equator to a pole.
• It is the strongest core of winds.
• http://www.youtube.com/watch?v=CgMW
wx7Cll4
Types of Jet Streams
• Polar jet streams separate the polar
easterlies from prevailing westerlies; the
major jet stream
• Weaker jet streams are subtropical jet
streams; found where trade winds meet
prevailing westerlies
• Most storms form along jet streams and
bring large scale weather systems
Fronts
• A collision of two air masses is a front; a
narrow region between two air masses of
different densities
• Fronts can cover thousands of square
miles
Cold Fronts
• Cold front: cold, dense air displaces warm
air
• Less dense warm air rises, cools and
condenses: intense precipitation occurs
• A blue line with evenly spaced blue
triangles is a cold front on a weather map
Warm Front
• Advancing warm air displaces cold air
• Can cause widespread light precipitation
• A red line with evenly spaced red
semicircles
Stationary Front
• Two air masses meet but neither
advances; the boundary between them
stalls
• A line of evenly spaced, alternating cold
and warm symbols pointing in opposite
directions
Pressure Systems
• Low Pressure
– Air from outside replaces rising air, this air
spirals inward to the center and then up in a
counter clockwise direction
– Rising air cools and condenses into clouds and
precipitation
Pressure Systems
• High pressure systems
– Sinking air moves away from the system’s
center
– Coriolis effect causes sinking air to move to
the right, making air circulate in a clockwise
direction in our hemisphere
– Fair weather
Learning Targets
• Compare and contrast the three major
wind systems
• Identify four types of fronts and
differentiate between each
Gathering Weather Data
• Meteorologists measure atmospheric
conditions such as
– Temperature
– Air pressure
– Wind speed
– Relative humidity
• Two important factors in weather
forecasting are the accuracy of the data
and the amount of data available
Tools for measuring
atmospheric conditions
• A thermometer measures temperature in F
or C.
• A barometer measures air pressure.
• An anemometer measures wind speed.
• A hygrometer measures humidity.
Thermometers
• Usually some type of glass tube containing
a liquid.
• When heated the liquid expands when
causing the column of liquid to rise.
• When the liquid cools, the column drops.
Barometer
• Some have a column of mercury in a glass
tube.
• Changes in air pressure change the height
of the mercury.
Anemometer
• The simplest has four
cupped arms positioned
at right angles from
each other.
• The arms rotate when
the wind blows.
• The wind’s speed is
calculated by the
number of revolutions
of the cups over a
specific period of time
Hygrometer
• Some have a wet bulb and a
dry bulb thermometer and
requires a conversion table to
calculate.
• The National Weather Service
uses an automated surface
observing system to gather
data 24 hours a day
Data From the Upper
Atmosphere
• Weather is largely the result of conditions
in the upper atmosphere.
• An instrument that measures those
conditions is a radiosonde.
– Contains a package of sensors suspended in a
balloon that enters the upper atmosphere that
collect data
Weather Radar
• Radar stands for radio detection and
ranging
• It generates radio waves and transmits
them through an antenna at the speed of
light.
• The waves reflect when they hit particles
(rain)
Doppler Radar
• Doppler effect is the
change in pitch or
frequency that occurs due
to the relative motion of a
waves.
• Doppler radars measure
the speed of precipitation
as it moves toward and
away from the radar.
Weather Satellites
• Some satellites move high above the earth
using infrared imagery to make
observations at night.
• The imagery can detect differences in
frequencies to map cloud cover or surface
temperatures.
Weather Satellites
• Other satellites use visible light to
photograph Earth.
• These photos are sent back to weather
stations to analyze cloud cover.
Learning Targets
• Discuss the importance of accurate
weather data
• Summarize the instruments used to collect
weather data from Earth’s surface
• Analyze the strengths and weaknesses of
weather radar and weather satellites
Surface Weather Analysis
• Weather reports are generated from the
data received from radars and satellites.
• Station models
– A record of weather data for a specific spot at
a particular time
– Symbols are used to represent the weather
data
– The symbols allow for the reporting to be
uniform
Surface Weather Analysis
• Plotting station model data
– To plot data nationally meteorologists use
lines to connect points of equal or constant
values
– Lines of equal pressure are called isobars
– Lines of equal temperature are called
isotherms
Interpreting Station Model Data
• Using isobars, isotherms, and station
model data, meteorologists can analyze
current weather conditions.
Types of Forecasts
• Digital forecasts
• Created by applying physical properties and math to
atmospheric variables and then making a prediction
• Analog forecasts
– Based on comparing current weather patterns
with weather patterns of the past
Short Term Forecasts
• The most accurate of all forecasts because
weather conditions are fluid and change
over time
Long Term Forecasts
• Forecasts for months or seasons are based
on weather cycles or patterns.
• Forecasts of 5 to 7 days are made using
upper level atmospheric measurements
and patterns.
Learning Targets
• Analyze a basic surface weather chart
• Distinguish between digital and analog
forecasting
• Describe problems with long term
forecasts