Meteorology: The Atmosphere, Weather, & Climate
What is the atmosphere?
Thin envelope of mixed gases surrounding earth
Composition: ESRT
Composition doesn’t vary
Only water vapor and carbon dioxide
Layers and boundaries between the layers of the atmosphere
ESRT page 14
Layers: troposphere, stratosphere, mesosphere, thermosphere
Basis for division is based on temperature shifts/changed (cooling/heating)
Boundaries: Tropopause, stratopause, mesopause
Named for layer below boundary
The Troposphere
Temp cools as altitude increases
b/c moving away from surface which reradiates heat (infrared) and warms air
Highest moisture content
Causes weather
Highest pressure
Bc weight of more air molecules above
The Stratosphere
Temp increases as altitude increases
Bc ozone (O3) absorbs UV and reradiates some of the energy as heat (infrared)
The Mesosphere
Temp decreases as altitude increases
Bc of lack of ozone
Far from ground (& the heat it reradiates)
The Thermosphere
Temp increases as altitude increases
Bc N2 and O2 atmos absorb solar energy
Thins into space
Energy
A major source of energy for most of Earh’s processes is the Sun
How is energy measured?
Temp = measurement of avg. kinetic energy (KE) of particles
Faster moving →more KE → higher temp
Measured with a thermometer
Heat = total KE of particles
Measured in Joules (J)
Always flows with high temp (source) to low temp (sink)
What is electromagnetic (EM) energy?
A type of energy that is radiated, or given off in the form of waves from all matter
Only given off above absolute zero (0 Kelvin or -273C, the lowest theoretical temp)
Types are classified by their different wavelengths
Wavelength: Distance from one crest to the next crest
What are the characteristics and types of EM energy?
Visible light Is the only EM energy that can be seen by human eyes
Infrared = heat (energy can be felt from warm obects)
Instruments must be used to observe other forms of EM energy, such as UV rays
How does EM energy interact with the environment?
Reradiated
Absorbed and released as heat
Refraction
Bent when passes through materials w/diff densities
Reflected
Bounced of materials
Scattered
Deflected into many diff directions
Transmitted
Passed through material without being changed
Absorbed
Taken into material
Material heats up
Releases heat in form of infrared
Reradiation
What are three ways energy is transferred?
Conduction
Molecules colliding w/each other
Solids
Convection
Due to density differences
Warm rises
Liquids and gases
Radiation
By EM waves
Anything transparent
How is the Earth’s atmosphere heated?
Insolation
Incoming solar radiation
Most directly heated by Earth’s surface
Radiation: Insolation is absorbed by Earth’s surface
Conduction: Earth’s surface heats air molecules that come in contact with it
Convection: Heat travels through atmosphere in currents due to density differences
What is the Greenhouse Effect?
Contributes to heat of the atmosphere
Short waves absorbed by Earth’s surface
Long wave infrared radiation/heat is reradiated
Most IR escapes, some IR is trapped by greenhouse gases in the atmosphere
(CO2, H2O, methane, etc.)
Causing heating
The more greenhouse gases in the atmosphere, the more heat absorbed
Causes and effects of the enhance greenhouse effect
Burning fossil fuels
Deforestation
Cattle ranching
Enhanced greenhouse effect
Temp rise and climate change
More severe hurricanes
Desertification
Impact on health (ex. insect-borne disease)
Habitat alteration (and migration patterns)
Sea level rise
How to minimize the amount of carbon dioxide released into the atmosphere and decrease reliance on fossil fuels:
Use alternative energy, minimize use of cars
What type of insolation reaches Earth’s surface?
Visible light = dominant form of energy from Sun that reaches surface
Most energy does not reach surface bc absorbed by atmosphere
Ex. ozone in stratosphere absorbs harmful UV radiation
Humans are depleting the ozone layer by using chemicals like chlorofluorocarbons (CFCs). This allows more UV rays to reach Earth, which can cause skin cancer and eye damage.
The Heat Balance of Earth and the Atmosphere
Overall flow of energy into/out of the atmosphere balances
Important bc:
Keeps temp at a level that makes life possible
Balance can be upset…
Energy in > out = heating
Energy out > in = cooling
If energy flow into and out of the atmosphere is in balance, what causes Earth’s temperature to vary from place to place and time to time?
Main reason = uneven heating of the surface due to:
Differences in intensity of insolation
Aount of insolation reaching the surface
Amount of insolation absorbed by the surface
What factors affect the intention of insolation?
Which angle would have the:
Most intense insolation?
90 degrees bc most direct (most concentrated)
Least intense insolation?
0 degrees bc least direct (most spread out/least concentrated)
Which latitudes would have the:
Most intense insolation?
0 degrees (Equator) bc highest angle of insolation
Least intense insolation?
90 N/S (poles) bc lowest angle of insolation
Which time(s) of day would have the:
Most intense insolation?
Noon bc highest angle of insolation
Least intense insolat?
Sunrise/sunset bc lowest angle of insolation
In NY (N. Hemi.) which season(s) would have the:
Most intense insolation?
Summer bc tilted towards the Sun
Least intense insolation?
Winter bc tiled away from the Sun
How much insolation reaches Earth’s surface?
Atmospheric transparency (how much insolation reaches Eath’s surface) depends on reflection, refraction, scattering, and absorption of insolation by clouds, dust, etc.
Which would be warmer:
Clear day or cloudy day?
Clear day bc more insolation reaches surface
Clear night or cloudy night?
Cloudy night bc clouds act like a blanket trapping heat re0radiated by surface
Dust from volcanic ash, pollution, meteor impacts, forest fires blocks sunlight from reaching Earth, and can result in cooling
What factors affect how much insolation is absorbed by Earth’s surface?
Albedo (ability to reflect light)
what types of surfaces would have:
Low ‘albedo’
Dark, dull, rough (absorbs more insulation)
High ‘albedo’
Light, shiny, smooth (relects more insolation)
Specific heat (amt. of heat needed to raise 1g of a substance by 1C/resistance to heating/cooling)
Which material heats & cools faster/slower?
Faster = land, low specific heat
Slower = water, high specific heat
ESRT pg 1
Good absorbers of energy are also good radiators (& vice versa)
What else causes Earth’s temperature to vary from place to place and time to time?
Geographic location
Which location has a greater temp range (continental/maritime)?
Greater temp range = Continental (inland & leeward coast)
Smaller temp range = Maritime (windward coast) wind blowing from water towards the coast) water helps to moderate temp bc of high specific heat
How do currents affect a location’s temp?
Warm currents help to moderate climate
Altitude
Which altitude is warmer?
Near sea-level = warmer
Higher altitude (above sea-level) = cooler
Adiabatic temp changes
Rate of change ~1C/160m (= normal lapse rate)
Adiabatic temp changes caused by expansion/compression of air as altitude changes
Rising → expansion = cooling
Sinking → compression = heating
Why Did the Isotherms Shift with the Seasons?
Land (w/ low specific heat) heats and cools more readily than water (w/ high specific heat)
Shift is more dramatic over land than water
Weather
What is weather?
Short-term state of atmosphere at given time and place
Use senses and different tools to observe
Weather factors are interrelated; when one changes, one or more of the others change
To try to predict the weather you need to:
Observe weather factors over a period of time
And look for patterns in how these factors change relative to each other
What factors affect weather? - Temperature
Recall.. Temp = measurement of avg. kineti energy of particles
Faster moving particles → greater avg. kinetic energy → higher temp.
Measured with thermometer
Celcius, Fahrenheit, Kelvin scales
ESRT pg 13
Isotherms connect equal temperatures on maps
Temp goes up, density goes down
Warm air rises/cold air sinks
Altitude in troposphere goes up, temp goes down
Farther from surface reradiating hear
ESRT pg 14
What factors affect weather? - Humidity
amount of water vapor in air
Most important gas when it comes to understanding atmospheric process
Mositure capacity = amount of H2O vapor air can hold
Warm air can hold more moisture (more space between particles)
Relative humidity (RH)
Amount of H2O vapor in air compared to moisture capacity (expressed as %)
100% RH means air is saturated (full of water) and at its dew point (DP) temperature (condensation occurs)
Clouds can form and precipitation is likely
Measure RH and DP w/sling psychrometer
Determining RH
Sling psychrometer
Dry bulb thermometer: measures normal air temperature
Wet bulb thermometer: has a wet cloth on the bulb which causes the thermometer’s temp to lower due to the cooling effect of evaporation
→ How to use
Wet wick on wet bulb
Spin psychrometer for a specified amount of time
Read temps on both wet and dry bulbs
Wet bulb temp should always be equal or cooler than dry bulb temp. due to expiration of water
Record data
Use RH chart
Calculate difference
Locate difference on the RH chart
Locate dry bulb temp
Find where they intersect
IT’S THE SAME PROCESS FOR DEW POINT, JUST THE OTHER CHART
What is the relationship between air temp, DP, and RH?
Closer air temp and DP, the higher the RH
Precipitation more likely
Farther apart air temp and DP, lower the RH
Precipitation less likely
How do Clouds form?
Parcel of warm air rises, expands, and cools to DP temp where RH = 100% (at condensatino level), confesses onto condensation nuclei (ex. dust, salt, etc.)
Cloud shape depends on air movement
Types of precipitation
Drizzle
Very fine water droplets that fall slowly and close together
Rain
Larger droplets that fall faster than drizzle
Snow
Ice crystals collide and clump
Sleet
Supercooled raindops that freeze in the air
Freezing rain
Supercooled raindrops freeze instantly when hit surface
Causes sheet ice or glaze
Hail
Layers of ice, snow, and water formed by many movements in thunderstorm clouds
Characteristics of Water
Recall..
Solid water = ice
Liquid water = water
Gases water = water vapor
Phase changes require energy transfer in the form of heat
Latent heat = energy absorbed or released during phase change
Phase changes
Melting
Solid → liquid
Requires addition of 334J/g of energy
Freezing
Liquid → solid
Requires release of 334J/g of energy
Vaporization
Liquid →gas
Requires addition of 2260J/g of energy
Condensation
Gas → liquid
Requires release of 2260J/g of energy
Why is Evaporation of Cooling Process?
Molecules enter atmosphere as vapor → taking energy with them → slower molecules left behind and have less average energy → causing cooling
What factors affect exaporation rates?
Temperature
Warm = higher rate
Humidity
Low = higher rate
Winds
High/fast = higher rate
Surface area
Larger = higher rate
Covering
Uncovered = higher rate
What factors affect weather? - Air Pressure
Aka atmospheric or barometric pressure
Weight of gases pushing on Earth’s surface
High pressure → more gases pushing down
Low pressure → less gases pushing down
Measured with a barometer
Aneroid (units = millidars_
Mercury (units = inches)
ESRT pg 13
Isobars
Connect points of equal pressure
Air pressure is affected by:
Humidity
Dry air, more dense, sink → high pressure
Humid air, less dense, rises → low pressure
Altitude
Low altitude, more air above → high pressure
High altitude, less air above → low pressure
Temp
Cold air, more dense, sinks →high pressure
Warm air, less dense, rises → low pressure
All are inverse relationships
Barometric trends can tell us what weather to expect…
When air pressure is:
Increasing over time → clear/fair weather is coming
Decreasing over time → stormy weather is coming
Pressure center: highest or lowest pressures on a weather map
Isboars form circles, or “bulls-eye,” around the pressure centers
What is a High-Pressure Center/System?
As move towards center of closed isobars, pressure increases
Aka “high” or “anticyclone”
“Heavy”/dense, cool, dry air
Circulates clockwise
“Right-hand rule”
Thumb goes down
Sinks/hits and diverges
Fair, “happy” weather
What is a Low-Pressure Center/System?
As move toward center of closed isobars, pressure decreases
Aka “low” or “cyclone”
“Light”/less dense, warm, wet air
Circulates counterclockwise
“Right-hand rule”
Thumb goes up
Converges and lights
Stormy, “lowsy”
What factors affect weather? - Wind
Horizontal movement of air
Caused by density differences due to uneven heating
Always blow from hight pressure (cool) to low pressure (warm)
Named for direction from which they blow (ex. noth wind blows FROM north)
Direction indicated by wind vane
Arrowhead points into wind (where blowing from)
Speed
Depends on pressure gradients (change in pressure over change in distance)
Greater (steep) gradient → faster wind
Isobars close together
Lower (gentle) gradient → slower wind
Isobars father apart
Measured with anemometer
How does specific heat of land vs. water affect wings?
Sea (ocean) breeze: during the day, the surface wind blows from the water (cooler w/high pressure) towards the land (warmer w/low pressure)
Land breeze: at night, the surface wind blows from the land (cooler w/ high pressure) towards the water (warmer w/ low pressure)
Mon soons: Seasonal reversing of winds and precipitation patterns caused by large temp diff of land and ocean water in certain seasons
Summer: heavy rain occur when moist wind flows from ocean onto land
Winter: dry conditions occur when dry wind flows from the land to ocean
How can all of these weather factors be shown on a map at the same time?
Station model: simple diagram that summarizes 10 pieces of weather information
A station model shows no units!
A/N : A SEPARATE NOTE WILL BE MADE REGARDING STATION MODELS
What is an air mass? How do air masses originate?
Air mass = immense body of air with uniform properties (temperature and moisture content)
Originate when: Air maintains some position for days/weeks over a large, uniform surface where winds are light
Source region/where forms affects main properties
Temp depends on if air is from tropics or poles
Humidity depends on if air is from land or see
Maritime Tropical (mT)
Warm and humid
Source region = over water near equator
Maritime Polar (mP)
Cool/cold and humid
Source region = over water near high lat./poles
Continental Tropical (cT)
Warm and dry
Source region = over land near equator
Continental Polar (cP)
Cold and dry
Source region = over land near mid to high lat./poles
Continental Arctic (cA)
Very cold and dry
Source region = over land near high lat./poles
**Don’t really need to know much about it
How do air masses affect weather?
May take days to pass
Weather of the place air mass move to becomes like the weather of the source region
Fast-moving air masses bring more extreme weather than slow-moving ones
Which air masses are most important to us in NY?
The weather in NY is most influenced by two air masses:
cP from Central Canada
mT from Gulf of Mexico
Global Winds, Air Masses, and Weather Systems
Large global winds (the westerlies) generally move air masses and weather systems from west to east in the US
Fronts
Beginning edge of an air mas
Where two air masses with different temperature & humidity (& density) meet
Brings weather changes
Precipitation usually occurs along (or in front of) the front
Generally named by the air mass behind it
Extend outward from low-pressure center
Causes changes in:
Precipitation
Temperature
Humidity
Air pressure
Wind direction
Stationary Front
Warm, air & cold air push against each other, neither get displaced/move
Very little mixing of air
Weather ‘sits’ in an area for a long time
Often light rain over several days
Symbols point in direction of movement, one on each side of the line
Cold Front
Cold (dense) air advances and pushes warmer (less dense) air upward
Air behind front brings colder/drier air
Pressure increases
Severe storms can occur along/on front
Symbols point in direction of movement
Warm Front
Warm air tries to push cold air (& warm, less dense air slides on top of cold air)
Air behind front brings warmer/more humid air
Pressure decreases
Long, steady rain can occur ahead of front
Symbols point in direction of movement
Occluded Front
Warm air mass is squeezed between two cold air masses (as advancing cold air catches up to it) and warm air mass is pushed upwards
Thunderstorms form along front
After front passes sky is usually clear and dry
Mid-latitude cyclones (lows) can form
Symbols point in direction of movement
How are maps used to determine current weather conditions and to presdict future weather conditions?
Weather maps may show:
Station models
Temperature (isotherms)
Air pressure (isobars)
High ad low-pressure centers
Fronts
Wind speed (spacing of isobars)
Air masses
Precipitation locations (around the low[pressure center, at the cold fronts, and ahead of the warm front)
Satellite maps can show areas of precipitation and clouds
How are maps usedd to predict future weather conditions?
Weather forecasting: forecast over next few hours..days based upon direction pressure centers and fronts are moving
Storm track: in US, storms move from w→e dues to prevailing global winds (westerilies)
Typically look at weather conditions in the midwest to predict our future weather conditions in NY
How does radar help scientists determine changes in weather?
Doppler radar: a radio tracking system that uses Doppler effect to determine the location and velocity of a storm, clouds, and precipitation
Storms and Severe Weather
What are the Characteristics of Thunderstorms?
Cumulonismbus (thunderhead) clouds
Lightning and thunder
Strong up-and-down air motion
Winds do not flow in inward spiral
Gusty winds, heavy rain, hail
How do Thunderstorms form?
Formed by strong upward movement of warm, unstable air
What causes unstable air associated with thunderstorms?
Localized heating of land
Causes: Convective lift
Fronts
Usually cold
Can also occur along a warm front bc warm air rising and cooling to dew point
When do thunderstorms usually occur?
Spring and summer
Greater humidity
Warmer temps
Causes air rising, cooling to DP, forming clouds and precipitation
What are the Characteristics of Tornadoes?
Rapidly rotating column of extermely low pressure air extneding down from thunderstorm
Usually accompanied by rain, lightning, and hail
Most violent of all storms
Often vortex/funnel - shaped (w/ flying debris)
Usually narrow (~100 ft diameter)
Most only last a few minutes
How do tornados form?
Two large air masses with marying “opposing” temp and humidit collide over land with warm air in lower layer and cold air in uppoer layer
Causes rotating updraft (mesocyclone) w/ extremely low pressure at center forms
Air gets sucked in, expands, and cools
Causes air to reach DP, water vapor condenses, and wall cloud mat become visible at base of storm
When do tornados form?
Usually late afternoon in spring/summer
Atmosphere is warmest and unstable
Where do tornados form?
MOSTLY in “Tornado Alley” (Texas, N to S.Dakota)
cP and mT air masses collide
What is a tornado that forms over water?
Called a waterspout
Can tornados be predicted?
Its difficult; improvements have been made
Tools:
Conventional radar → map precipitation
Doppler radar → identify which way winds are moving within sotmr
Can identify rotating mesocyclone and give people ~20 min advance-warning
What is the difference between a tornado watch and warning?
Watch → tornado MAY form
Warning → tornado spotted
How are tornados classified?
Fujita scale based on intensity
F0 (weakest) to F5 (most violent)
What are some of the effects of tornadoes?
Uprooted trees
Damage to homes
Broken windows
Roof damage
Desruction of walls
Torn off foundation
Damage to vehicles
Downed power lines
Flying debris
Loss of life
What are the characteristics of hurricanes?
Large, cyclonic (counterclockwise) low-pressure storm
Sustained winds of 119+ km/hr (74+ mph)
Heavy rains
What is the difference between a hurricane, typhoon, and cyclone?
Location
Atlantic? Hurricane
Pacific? Typhoon
Indian? Cyclone
How do hurricanes form?
Mild atmospheric disturbance over warm tropical water causes humid air to rise
Causes more water to condense and release heat
Must begin to rotate counterclockwise (in N. Hemi) bc of Coriolis effect
Evaporation of warm water powers the hurricane
Loses power when moves over colder waters or land
What are the 3 main parts of a hurricane?
Rain bands
Clouds that spin out and make storm bigger
Eye wall
Outer edge of eye
Strongest wing and rain bc strongest convergence of air
Eye
Lowest pressure
Calmest part of storm bc converging winds never fully reach center
When is hurricane season in the US?
June 1 - November 30
August - October is peak
In which direction do most atlantic hurricanes move?
Generally, omve west or NW
Then, often north and may eventually head east due to global wind patterns
Predicting the path of a hurricane
Actual paths can vary considerably: shown by “cone of uncertainty”
What is the difference between a hurricane watch and warning?
Watch → expected to arrive w/in 24-36 hours
Warning → expected to arrive w/in <24 hours
How do scientists classify tropical storms/hurricanes?
Wind speed
Tropical depression → up to 61 km/hr
Tropical storm → 61-119 km/hr
Hurricane →119+ km/hr
Saffir - Simpson scale to rate strength
What are some of the effects of hurricanes?
Wind damage
Inland flooding
Storm surge
Large wave of water from strong winds of eye wall
Blow water into a dome
Waves
Coastal erosion
Loss of life
What are the characteristics of winter storms?
Strong mid-latitude cyclone (lows) that form and grow along polar front
2 conditions must be met:
Enough mositure
Temps cold enough for snow
What is a blizzard?
Snowstorm w/high winds and low temps
What causes lake-effect snow?
Cold, dry air picks up poisture and heat by passing over a relatively warmer lake
When is lake effect snow likely to occur
Late fall into early winter bc lake temperatures are at warmest, relative to colder air moving over the,
Once lakes freeze over moisture/heat source lost, lake-effect snow hard time forming
How should we prepare for storms?
General storm prep
Have a family and city emergency storm plan
Listen to weather reports for the latest information and instructions in your area
Have storm supply kit for your home and car
First aid kit and meds
Non-perishable food
Water
Battery operated flashlight and radio
Protective clothing and blankets
Backup generator
Cash
Climate
What is climate?
Conditions of the atmosphere over a large region over a long period of time (30+ years)
Affected by:
Temp and precipitation
Affects:
Vegetation in an area
Animals in an area
Landscape features
What factors affect temperature and precipitation, and therefore climate?
Latitude
Elecation
Planetary Winds
Nearness to Large Bodies of Water
Ocean Currents
Mountain Ranges
How do planetary (prevailing) winds affect climate?
Planetary windsL general movement of winds in the troposphere that bend due to earth’s rotation (and Coriolis effect)
Winds are named for where they are coming from
ESRT page 14: NY (40-45N) is in the SW wind belt
How do planetary winds affect climate?
Winds from:
High latitudes (polar) cause a colder climate
Lower latitude (equatorial) cause a warmer climate
Off of ocean cause a wetter climate
Off the land cause a drier climate
Global Wind and Pressure Belts
“Lower Pressure Belts = moist latitudes: 0, 60N, 60S
Air rises, cools, and causes water vapor to condense (causes rain)
"High Pressure Belts” = Dry latitudes: 30N, 30S, 90N, 90S
Air sinks causing it to warm. When air warms, no condensation is possible
What is El Niño?
A natural event that changes worldwide weather patterns
Caused when surface ocean temp along the weast coast of S. America increases, caysing ocean currents to reverse (or slow) and winds to weaken causing a disruption of normal weather patterns
Effects:
Winters are warmer and drier in NY
Increase temp and precipitation on west coast of S. America
Decrease in fishing industry in S. America
Droughts in Australia and SE Asia
Heavy rains in southern US
How do mountain ranges affect climate?
Orographic effect: Changes in climate caused by mountain barriers
Windaward: faces toward direction wind is coming from (wind hits windward side)
On windward side, air is pushed upward to higher altitude. As air rises, it:
Expands bc air is thinner
Cools
Condenses into a liquid, causing clouds and precipitation to occur
Leeward: side of mountain range that faces away from wind (wind is leaving)
As air sinks down the leeward side, it:
Is compressed
Wamrs
No condensation can occur in warming air, so its very dry and forms “rain shadow desert”