Barometer - measures air pressure (mercury and aneroid)

Anemometer measures wind speeds ten meters above the ground.

Psychrometer measures humidity.

Thermometer measures temperature

Wind vane – determine the direction of winds

Tools of Meteorology

Composition of the Atmosphere

Then…. (early Earth )

• Gases released from volcanoes filled the atmosphere with:

– Carbon dioxide

– Sulfur dioxide

– Water vapor

– Nitrogen

and Now…

• 78% Nitrogen

• 20% Oxygen

How Heat Energy Moves Through the Atmosphere

• Radiation – transfer of energy through space in the form of visible light, UV rays, and other types of electromagnetic waves. (from the sun)

• Conduction – transfer of heat energy through collisions of the atoms or molecules of a substance. (walking barefooted on the hot pavement – contact)

• Convection – transfer of heat energy in a liquid or gas through the motion of the liquid or gas caused by different densities. (hot air rises, cool air sinks)

Energy Budget

• Incoming solar radiation is called Insolation.

• On land insolation only heats the top few centimeters of soil, but can reach and heat meters in water (and convection helps it).

• Lines separating temperature zones on a map are called isotherms.

Energy Budget

• Much of the heat energy is reflected back to space. (Remember: Albedo - % energy reflected back to space)

• Carbon dioxide and water vapor in the atmosphere prevent some from radiating back into space (Carbon dioxide is a greenhouse gas – it traps heat energy in the atmosphere so Earth can warm)– This helped Earth thrive as the planet it is today.

– However, now we may have too much carbon dioxide in our atmosphere which some say are causing global warming.

Humans Impacting the Atmosphere

• Air pollutants – any airborne particle that could harm humans or the environment.– CO2 from car exhaust. CO2, NO2, SO2 from burning

fossil fuels, etc.

• Produces acid rain and smog (ozone on ground level – causes lung problems)

• Ozone depletion – which allows more UV rays to enter Earth and cause skin cancers, etc.

• Global warming – causing increase because deforestation and increase of burning fossil fuels.

Layers of the Atmosphere• Thermosphere – above 90km , 4th layer, thin atmosphere,

temps increase with altitude from -80ºC to above 1000ºC – Ionosphere is part of thermosphere

(about 90-500km above Earth), where auroras take place.

• Mesosphere – 3rd layer, 50-90km above Earth’s surface, temps drop with increasing altitude from -20ºC to -90ºC– Meteors are burnt up in top

• Stratosphere – 2nd layer, clear, dry layer, lower portion is cold about -60ºC to upper portion about-20ºC. – Temperature increase caused by ozone layer (ozone

absorbs ultraviolet rays from sun and then releases some of it energy in form of heat.

• Troposphere – lowest layer of Earth’s atmosphere, temperatures decrease with altitude from 18ºC to -60ºC, – contains most of water vapor in atmosphere so

most of weather occurs here, planes fly here.

Layers of the Atmosphere

Layers of the Atmosphere

Ch. 18 – Humidity and Clouds

Humidity – the water vapor in the airWater vapor in the air (you can feel it), the more water vapor

the more humid it is. • Specific Humidity – the actual amount of water vapor in

the air.• Saturated – lots of water vapor in the air, this is when the

rate of condensation = the rate of evaporation. – Like water droplets on the side of a bottle. The warmer the air

the more water vapor it can hold.

• Relative humidity – compares the actual water vapor in the air with the amount it can hold.– Relative humidity = X 100%

• Dew Point – temperature where saturation occurs and condensation begins

• Pyschrometer is the tool that measures the amount of humidity in the air.

Specific humiditymaximum capacity

Saturated

Water vapor in the air can Condense and form Clouds

Cloud Types are classified by altitude:

• High – above 7,000m• Cirrus, cirrostratus,

cirrocumulus

• Middle - ~2,000-7,000m• Altostratus, altocumulus

• Low – Below 2,000m• Stratus, nimbostratus,

stratocumulus

• Vertical • Cumulus, cumulonimbus

• Cirrus & cirro = high, feathery, icy

• Alto = between 2,000-7,000m

• Nimbus & nimbo = dark, rain

• Stratus & strato = low, form in layers

• Cumulus & cumulo = fluffy with a flat base, grow upward

Cloud name meanings:

The shape of the clouds shows how air moves through them.

Label cloud types

When the clouds get full they Precipitate

• Most precipitation occurs:

– with warm, moist air that rises high in large quantities

– near the equator (almost daily Thunderstorms

– on the windward side of mountains

– with low pressuresystems

Ch. 19 – Air Pressure/Winds

• Air Pressure – weight of the atmosphere pushing down on Earth (we don’t feel it because air is pushing on all sides, not just down from the top.)

• Barometer – tool that measures air pressure.– Use millibars to

show pressure onmaps = they makeisobars when connected.

Connect the same numbers to draw in the isobars.

So why does air pressure change?

• Elevation

• Temperature (warm air is low pressure, and may get rain)

• Humidity (rising air pressure is cooler, drier air/fair weather)

Reading Pressure on a Map

• Isobars = lines showing air having thesame pressure.

• High pressure area (or a High)– Rotates clockwise

• Low pressure area (or a Low)– Rotates counterclockwise

• Pressure gradient = pressure change

– Lines close together show that pressure is quickly changing (and we will have strong winds)Lines further apart shows weak pressuregradient (and we will have week winds).

Distance coverage

Winds Blow Because…• Air flows from an area of High pressure to an

area of Low Pressure

• Coriolis Effect - the apparent curve of a moving object due to the Earth’s rotation– Causes curve to the right in the Northern Hemi

– Causes curve to the left in the Southern Hemi.

• Jet Stream – fast moving winds near the top of the troposphere (winds 120-240 kph)– In the US the jet streams supplies energy to

storms and directs their paths.

• Anemometer – tool that measures wind speed

HL

to

Global Wind Patterns• Doldrums or Intertropical Convergence Zone

(ITCZ) – Low pressure in tropics– Hot, humid, little to no wind, rain is common.

• Subtropical highs or Horse Latitudes – between 20-35 degrees– Deserts – because sinking cooler air with no

precipitation is near.

• Tradewinds – between 35-60 degrees latitude– Warm, steady, winds

• Polar highs – High pressure above 60 degrees latitude (in the poles)– Where cold air sinks at the poles, usually easterly

surface winds.

Global Wind Patterns

Effects of seasons on winds…

• With a change in air pressure the direction of winds changes

• So winds change direction with the seasons

–Monsoons

• Occur southern Asia

• Heavy rains

Ch. 20 Fronts & Severe Weather

Ch. 20 Fronts & Severe Weather

• Air mass – large body of air in the lower troposphere with similar characteristics.

– Has characteristics of climate where it is and when it travels brings those temps, so can change depending on where it is travelling to and from.

• Fronts – a boundary that separates opposing air masses.

– Fronts usually bring precipitation.

Types of Fronts (and the Precipitation along Fronts)

• Cold Front – cold air moving in displacing warm air. (Cold air is more dense than warm air, so the cold air slides underneath the warm air and forces the warm air upward.)

– Steep slopes, quick T-storms over a small area because cold fronts tend to move relatively quickly.

• Warm Front – warm air moves in displacing cold air

– Gradual slope, high cirrus clouds, then cirrostratus, then nimbostratus clouds, steady rain over a large area for long periods of time (maybe a day or more).

Types of Fronts

• Occluded Front – when a fast cold front moves in and catches up to a warm front

– You get warm air caught between two colder air masses and it forces warm air up. Cold Cold

• Stationary Front – front that is not moving

– May have clouds, precipitation, and flooding if still in one area for too long.

Warm

Cold Front

• Steep slopes between air masses as the cold air slides in underneath and pushes the warm air up and out, quick T-storms over a small area

Warm Front• Gradual slope between air masses as the warm air

moves in and rises up along the cold air to push it out, high cirrus clouds, then cirrostratus, steady rain over a large area for long periods of time.

Occluded and Stationary Fronts

FrontsFronts are usually connected

to a mid-latitude low-pressure system. (Remember: low pressure brings precipitation)

It generally takes 12-24 hours for a low-pressure system to pass through 1st 2 stages, when it reaches occluded front the low can last for 3 days or more.

Fronts

• To find a front on a weather map you will need temperature, wind direction, and dew point.

• Here are the rules to follow:

– Wind direction changes behind fronts

– Temperature changes sharply across fronts

– Dew point changes sharply across fronts.

Low and High Pressure Systems and the Upper-Air Flow

Upper-air flow (jet streams) controls the high and low pressure systems path and intensity on the surface.

• High pressure systems are associated with fair weather because the air in a high pressure system is sinking so the skies clear up.

– Clear skies

– Days may be hot and nights may be cold

– Air is still

Weather Associated with Pressure Systems

Weather Associated with Pressure Systems

• If a low pressure system passes north of us we will likely have a warm front move over us followed by a cold front. (so here is the weather we may receive from a low)– 1st when the warm front is approaching we will get high

clouds (cirrus) and then steady snow or rain, then drizzle

– 2nd after warm front passes, we will have warm temps, winds will shift, and skies slowly clearing

– 3rd as the cold front starts to approach we will get scattered showers and possible thunderstorms

– 4th after cold front passes, the temps will drop, winds will shift and skies will clear.

Severe Weather

• Thunderstorms – have lightning, thunder, rain, winds, and sometimes hail. Cumulonimbus clouds.

– Form in warm, moist, unstable air (air colliding with an opposing wind).

– Consist of 1 or more convection cells that usually last an hour or less.

– Often form along fronts (cold fronts)

Severe Weather• Tornado – violently rotating column of air that

usually touches the ground. – Forms from a severe thunderstorm that has rotating

updraft called a mesocyclone (when winds at different altitudes are moving in different directions).

– Air pressure at its center is very low and air is sucked into the funnel, expands and cools

– Usually occurs at the back edge of a thunderstrom and travels with the thunderstorm.

– Most occur in “Tornado Alley” (from Texas north to South Dakota)

– Use the Fujia Tornado Intensity Scale to categorize tornadoes.

Severe WeatherTornado - Fujita Tornado Scale

Severe Weather

• Hurricane – large rotating storm of tropical origin that has sustained winds of at least 119 kph that

form between 5 – 20 degrees latitude.

– Air pressure at the center is very low.

– Gets its energy from the heat of surface ocean water.

– At the outer edge rain and winds are mild and both increase as you move inward and are strongest at the eye wall. (inside the eye is mild)

– Can produce storm surge – rising sea level meters

– Use the Saffir-Simpson to categorize hurricanes.

Severe WeatherHurricane – Saffir-Simpson Scale

Severe Weather• Winter Storms – heavy snow or ice.

– Nor’easter – occurs on east coast of US.

• Heavy snow (however usually not cold enough to be classified as a blizzard)

– Blizzard – high winds, low temperatures, and falling or blowing snow.

• Winds must exceed 56 kph or 34 mph

• Temperatures must be below -7 C or 44 F

• Falling and/or blowing snow must reduce visibility.

Severe Weather Watches and Warnings

• Severe Weather Watch – a chance for severe weather to form

• Severe Weather Warning – severe weather has formed, been spotted, and is approaching your area.

– Need to take appropriate measures to keep yourself safe

Reading Weather on a Map

Station Model –symbols used to fit lots of information about the weather onto a compact map. (like temp, dew point, weather conditions, winds, pressure, cloud coverage)

Reading Weather on a Map – so let’s try it…

34260

55

9335

30

Reading Weather on a Map – so let’s try it…

• How many kinds of fronts are on map?

• What is the symbol for a cold front?

• Which color represents areas of low pressure, how do you know?