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Weather and Climate Chemistry 2014
Weatherand
ClimateChemistry 2014
Weather- “the state of the atmosphere with respect to heat or cold, wetness or dryness, calm or storm, clearness or cloudiness”.
Climate – “the average course or condition of the weather at a place usually over a period of years (at least 30 yrs) as exhibited by temperature, wind velocity, and precipitation”
Weather & Climate Definitions
Temperature Dewpoint Barometric Pressure Wind Speed and
Direction Cloud Cover & Type Present Weather
Ships Buoys Commercial Aircraft
(ACARS) Satellite
All of this data goes into forecast models
Types of Weather Observations:
Measuring Weather Conditions
• A thermometer measures temperature, or how hot or cold the air is.
• An anemometer measures how fast the wind is blowing.
• A rain gauge measures how much rain or snow has fallen.
• A wind vane shows which direction the wind is blowing. It points to the direction the wind is coming from.
• Barometers are used to measure air pressure
Beaufort Wind Speed Scale is has a range from 0 for calmto 12 for a hurricanewith waves greater than 37 feet
Amount and height Cloud type is done by sight
onlyClouds
Why is there wind? Why does it blow from one direction one day and another the next?
Why is it rainy one day and dry the next?
How come it’s cold in the winter?
How can we have hail in the summer?
What causes snow and freezing rain?
WHY DO WE HAVE WEATHER ?
Earth’s AtmosphereEarth’s Atmosphere
exosphere—contains few particles that move into and from space.
thermosphere—temperature increases with height. low air pressure
The International Space Station orbits Earth in this layer.
mesopause—boundary between mesosphere and thermosphere; coldest place on Earth.
mesosphere—the layer in which most meteors burn up
stratosphere—contains the ozone layer; the layer where volcanic gases can affect the climate
Notice layers of atmwhere temp increaseswith altitude and where temp decreases with altitude
troposphere—layer closest to Earth’s surface -Most atmospheric mass
-Where weather occurs-Where air pollution collects-Temperature decreases with height
• Daily concerns – what to wear, flight delays, etc
• Travel • Agriculture and Food concerns• Safety• Insurance and property damage• Future
Why do we care about weather and climate?
You might pick heat or sun….but another good choice would be
Convection
If we were to pick one term to help explain why we have weather?
Convection is the transfer of heat,usually in gases or liquids.
After the atmosphere is warmed by radiation and conduction, the heat is transferred throughout the atmosphere by convection.
Since warmed air has more space between the molecules (expands), it’s less dense and rises
Cooled air is more dense (condenses) and tends to sink
◦ In general, air near the equator tends to rise and air near the poles tends to sink Jet streams are usually found
somewhere between 10-15 km (6-9 mi) above the earth's surface
As solar energy reaches the Earth, equatorial regions heat up more than the poles.
Warm air and water at the equator travel pole-
ward while cold air and water at the poles travel equator-ward in an attempt to equalize this temperature contrast.
It is the atmosphere's continual struggle for temperature balance that brings us our changing weather.
Air Temperature
The Weather Highways
Additionally, the rotation of the earth creates the Coriolis effect.
The Coriolis effect causes the air and water to be deflected to the right, north of the equator.
This creates global weather highways
The Westerlies Because of our latitude,
most of our weather comes from the west
Looking at the top weather map, what type of weather might we expect?
What type of weather might we expect in a few days? What is the
prediction for this weathermap?
Let’s break for a short review1. Weather occurs in the _____ layer of the
atmosphere.
2. Transfer of heat in liquids or gases is_____
3. _____ air is dense and tends to sink.
4. Cold air holds _____ moisture than warm air
5. The Coriolis effect causes the air and water to be deflected to the _____ of the equator
How did you do?1. TROPOSPHERE
2. CONVECTION
3. COLD
4. LESS
5. RIGHT
Now What? Ok, so we know that the weather moves
around on these highways and that warm air rises and cold air sinks.
But why is it sunny one day, and rainy the next?
air pressure is caused by the weight of the air pressing down on the Earth, the ocean and on the air below
the pressure depends on the amount of air above the measuring point and falls as you go higher
air pressure changes with weather
Air Pressure
The lowest atmospheric pressure is found at the center of a low pressure system, labeled with a capital L on a weather map.
L
air in a high pressure area compresses and warms as it descends (drops)
the warming inhibits the formation of clouds, meaning the sky is normally sunny in high-pressure areas
haze and fog might form the opposite occurs in an area of low
pressure
… and Weather
Let’s take another look at the weather map Notice that there
are H’s and L’s on the map
There are also blue lines with spikes and red lines with half circles
Let’s take a closer look!
High Pressure Areas When cooler air
sinks and is warmed, the air can hold more moisture
This usually means sunny skies
Winds tend to move clockwise around a high
H over your home areameans likely fair weather
Low Pressure Areas When warm air rises
and is cooled, the air can not hold as much moisture
Often, these areas are associated with precipitation and stormy weather
Winds tend to move counter clockwise around the low
L over your home areameans probably
stormy weather
Fronts and Air Masses An air mass is a large body of air whose temperature and moisture are fairly similar
at a given altitude
Fronts are boundaries separating different air masses
The Air Masses (continental polar) : cold, dry stable (continental tropical) : hot, dry, stable air
aloft, unstable at the surface (maritime polar) : cool, moist, unstable (maritime tropical) : warm, moist, unstable
Ok, now we see the difference in the air masses
Let’s look at the different fronts and their impact on weather
Can you see the four different types of fronts on the map?
Warm Fronts A warm front is
warm air displacing cool air diagram
Shallow leading edge warm air must “overrun” cold air
These are usually slow moving
Cold Fronts Cold air advances into
region of warm air
Intensity of precipitation greater, but short lived
Clearing conditions after front passes
Usually approaches from W or NW
Stationary Fronts
Surface positions of the front do not move
Often a region of clouds
Occluded Fronts Cold front overtakes
warm front
Often found close to the low pressure center
Ready for a little quiz?You’ll need a sheet of paper
Write your answers as we go
Here we go!
1. Winds in a low pressure system move _____ around the low.
2. What type of front can be found close to point D ?
3. Which of these fronts would you expect to havegreater precipitation, but be short lived as the front passes?
LL
4. Give the name of the air mass that would have the following characteristics: cool, moist, unstable
5. That important weather word that refers to the
transfer of heat.
6. This causes air and water to be deflected to the right, north of the equator.
7. Which of the weather highways usuallycontrols our weather?
8. Warm air holds ( more or less ) moisture than cold air?
9. If there is a big H on the weather map where you live, would you expect fair or stormy weather?
10. Generally, what happens to air near the
equator and air near the poles?
Bonus: What is wind?
HH
Answers 1. Counterclockwise 2. Cold 3. Cold 4. Maritime polar 5. Convection 6. Coriolis Effect
7. Westerlies8. More9. Fair10. In general, air near
the equator tends to rise and air near the poles tends to sink
Bonus: horizontal movement of air from are of high pressure to an area of lower pressure
CLOUDS
Cloud Types
Picture taken from: http://commons.wikimedia.org/wiki/File:Cloud_types.jpg
**** Cloud making demo?
Cloud Formation•Rising Air•Lifted Condensation
Level / Dew Point
•Condensation Nuclei-Small droplets in the atmosphere around which cloud droplets can form
•Clouds form from millions of
droplets
Cloud Types
Cloud Types• Low Clouds (Cumulus, Stratus)
– 0 to 2000 meters• Middle Clouds (Altostratus, Altocumulus)
– 2000 to 6000 meters• High Clouds
(Cirrus, Cirrocumulus, Cirrostratus)– 6000 meters and above
• Rain Clouds (Cumulonimbus, Nimbostratus)
Precipitation• Coalescence
– Cloud droplets collide to form larger droplets• Precipitation
– Rain, Snow, Sleet, Hail
Hail Formation
• 97% salt water, 3% fresh water
Severe Weather
Thunderstorms• Can produce some of the most violent weather
conditions on Earth • May have hail, strong winds, lightening,
thunder, rain and tornadoes• Supercells – self-sustaining, extremely powerful
storms with intense, rotating updrafts• Can last for several hours with updrafts up to
240km/hr• 10% of storms are considered severe
• moist air rises due to frontal zone lifting causing loss of heat leading to cumulus clouds with updrafts
• severe thunderstorms occur when cold front approaches warm front (which supplies moisture and energy)– winds over 60 mph– hail > 3/4 inch
Lightning• Electricity caused by a rapid rush of air
in a cumulonimbus cloud• Friction between updrafts and
downdrafts separate electrons• Positive atoms at the top of the cloud• Negative atoms at the bottom of the
cloud• Transfer of energy in form of heat,
sound, and light• Lightening strikes has about million
volts• 5x hotter than heat from sun
Tornadoes• A violent, whirling column of air in contact
with the ground• speeds of 300 mph+
• center of tornado is extreme low pressure which causes buildings to implode
• tornado alley is from Texas to Indiana (usually trailer homes)
Tornado Formation• A change in wind direction and speed creates a
horizontal rotation• Strong updrafts tilt the rotating air from
horizontal to vertical• A tornado forms within the rotating winds
Tornadoes_.asf
cause most property damage and loss of life
winds speeds greater that 74 mph at the center
begin over warm oceans of the tropics
solar insolation (water >80oF) provides energy for huge evaporation, cloud formation, and atmospheric lifting
Severe Weather - Hurricanes
Severe Weather - Hurricanes• stages
– separate thunderstorms over tropical ocean– cyclonic circulation which causes them to pick up
more moisture and heat energy from ocean– winds speeds of 23 to 40 mph lead to Tropical
Depression– Tropical Storms have lower pressure and higher wind
speeds (40-75 mph)• center is the eye • rainfall may exceed 24 inches in 24 hours
Other Weather Phenomenon
top 30 amazing weather phenomenon (video)
http://www.youtube.com/watch?v=rDNFeILZsSg
20 amazing phenomenon (pics/explanations)http://listverse.com/2008/04/19/20-amazing-and-unusual-weather-phenomena/
10 more amazing weather phenomenon (pics/explanations)
http://listverse.com/2010/12/19/10-more-amazing-weather-phenomena/
