Danea Sanders

What is space?

Geography 1112: 

Intro to Weather and Climate

Final Exam Study Guide: 

Key Terms:

 Weather- short-term occurrence; the condition of the atmosphere at a  

given time and place.

 Climate- long-term patterns of the condition of the atmosphere;  

depends on where you live.

 Space- the region beyond the Earth’s atmosphere between celestial  Don't forget about the age old question of What is judicial activism?

bodies of the universe

 Density- mass divided by volume (Mass/Volume)

 Concentration- number of molecules of a gas divided by the number of  all gases in the atmosphere (# Molecules of gas/# of All Molecules in  Atmosphere); It can be expressed as percent (%), per million (ppm), or  

What is permanent gas?

per billion (ppb)

 Equilibrium- input is equal to output (input = output)

 Residence time- how long a molecule remains in the atmosphere; to  calculate this use the formula: Concentration (# of molecules)/ Rate of  input or output (# of molecules per second); in other words,  We also discuss several other topics like A method of sampling acquiring a list of all possible subjects in the population.

concentration divided by the rate of input or output

 Permanent gas- a gas that stays in the atmosphere for a long time  Variable gas- a gas that changes in space and time; these gases are  

not permanent; they are also greenhouse gases

 Aerosol particles- any solid and/or liquid particles other than water,  that exist in the atmosphere; aerosols can cause acid rain, and effect,  visibility, human health, hurricanes, clouds, and climate; (Ex: Saharan  Dust Storm- aerosol particles traveled a far distance from the Saharan  dessert to North and South America affected air quality); aerosols are  both natural and anthropogenic (caused by humans. Natural causes

What is aerosol particles?

If you want to learn more check out Movement of water across a membrane.

include: sea sprays, dust, plants, combustion, air pollution, and smoke.  

Anthropogenic causes include: car/modes of transportation emissions.  Pressure- force exerted per unit of area measured in hPa (hectopascal) o Force of pressure- change in pressure divided by change in  

distance (change in pressure/ change in distance); the force of  

pressure can act in all directions, not just up and down

Formula: Fpg= P2-P1/ Z2-Z1 (“Fpg” means force of pressure  gradient, “P2” means pressure 2, “P1” means pressure 1, “Z2”  

means distance 2, and ‘Z1” means distance 1)

 Air pressure- weight of air at a specific location; it decreases with  greater altitudes/heights because there is less mass away from the  surface; so, pressure changes more rapidly near the surface; it also the force that pushes gravity back from low heights to higher heights  (don’t get confused it also means from high pressure, which occurs at  If you want to learn more check out Circular muscles surrounding, and able to close a body opening.

low heights, to low pressure, which occurs at higher heights)  Hydrostatic balance- the balance between gravitational force and  

pressure force (it is what holds air up); the pressure force has to be  strong near the surface, in order to balance gravity; occurs when  

gravitational force = pressure force

Formula: Fpg=Fe (“Fpg” means force of pressure gradient and “Fe”  

means force of gravity)

 Force of gravity- mass times acceleration (mass x acceleration);  Formula: Fg= -mg (“Fg” means force of gravity…this may be confusing  

but keep in mind that the force of gravity is represented as Fe in the  hydrostatic balance equation, “m” means gravitational force, which is  

negative because gravity is down, and “g” means gravity)  Horizontal pressure gradient- differences in pressure in the horizontal  

direction; causes wind (movements of air); in extreme cases horizontal  pressure gradients can cause hurricanes and tornados, but are not as  strong as vertical pressure gradients…there is more pressure holding  Don't forget about the age old question of What are congressional primaries?

the winds back from being as strong)

 Vertical pressure gradient- differences in pressure in the vertical  direction; greater than horizontal pressure gradients because as

pressure decreases with altitude, the winds become stronger…there is  

little pressure holding the winds back from being strong)   Radiosonde- a small expandable instrument package below a balloon  Don't forget about the age old question of What are the three monosaccharides?

with sensors that measure pressure, temperature, and relative  humidity; they are launched daily at 0 to 12 GMT (8 am – 8 pm EST); a  typical flight of the balloon lasts 60-90 minutes; it reaches up to 30 m  and travels about 30 km; worldwide there are about 1,300 radiosonde  

sites  

 Ideal Gas Law- describes the relationships between pressure, density,  

and temperature

Formula: p = pRT (p means pressure, in units Nm-3, p means density,  in units kgm-3, R means a gas constant, in units kgm-3, and T means  temperature, in K…Kelvin) (*the negative numbers next to the units  

are exponents*)

 Latitude (0 to 90 degrees)- North (N) to South (S) (Includes: Tropic of  Cancer 23.5 degrees N, Tropic of Capricorn 23.5 degrees S, Equator 0  

degrees, Arctic Circle 66.5 degrees N, Antarctic Circle 66.5 degrees S)  Longitude (0 to 180 degrees)- East (E) to West (W) (Includes: Prime  

Meridian 0 degrees, International Date Line 180 degrees  Solar Intensity- the energy per area; it is affected by latitude and angle

of Sun to the surface

 Beam depletion- sunlight that is reflected as it enters the atmosphere,  

decreasing the sunlight’s intensity

 Circle of illumination- the difference between night and day on the  

earth

 Energy- the capacity to do work; measured in Joules (J)  Power- how quickly you move energy; measured in Watts (W)  Specific Heat- how much energy is takes to change the temperature  Potential energy- energy stored

 Kinetic energy- energy in motion

 Conduction- energy transferred when objects touch

 Convection- fluid (liquid or gas) moves from one place to another  Radiation- energy that travels through space and waves  Sensible heat- energy transferred by temperature

 Latent heat- energy carried in the atmosphere

 Solar radiation- energy given off by the Sun

 Terrestrial radiation- energy given off by the Earth

 Stefan-Boltzmann Law- focuses on the amount of energy; states that  hot objects emit much more energy than cold objects at all  

wavelengths

Formula: F = T^4 W/m^2 (This formula calculates the amount of  energy emitted) = 5.67 x 10^ -8 W/m^2/K^4 (This is a constant,  

meaning this value remains unchanged)  

 Wien’s Law- focuses on wavelength; states that hot objects have a  peak (or maximum intensity) at shorter wavelengths than cold objects

Formula: max = b/ T b is approximately 2,900 umK  

( um means mirocmeters)

(this formula calculates peak wavelength)

 Transmission- waves of radiation that pass straight through the  

atmosphere to the surface

 Albedo (a)- refers to how much reflection; high albedo means a lot of  

reflection, a low albedo indicates less reflection and more absorption Formula: R/T (“R” means reflection, “T” means temperature

 Precipitable water- total amount of water if all vapor is condensed out of  the

entire column in the atmosphere. (squishing all water vapor together to measure the amount of actual water in the form of precipitation)

 Trade winds- wind and water vapor travels from east to west.  Westerlies- wind and water vapor travels west to east

 Heat Index- aka apparent temperature; a measure of how hot it really feels when relative humidity is combined with actual air temperature; hot areas with humidity make it harder for humans to cool off (Ex: California’s hot weather vs Georgia’s hot weather)

 Humidity- amount of water vapor in the air; humidity is gas not liquid or  solid

states of water (clods, fog, rain)

 Relative humidity (RH)- how much water vapor is in the air compared to the

amount of water vapor the air can hold, until water vapor is condensed  (water

vapor turns into clouds); Formula: RH = SH / SSH x 100

 Specific humidity (SH)- measure of water vapor in the air in a given  location;

thought of as a parcel of air or a small volume of air; mass of water vapor relative to the total mass of all molecules in the air; measured in units g/kg; specific humidity does NOT change as a parcel of air expands as long as the total mass inside is the same

 Saturation specific humidity (SSH)- the specific humidity of air when it is saturated; measured in units g/kg

 Saturation- maximum amount of water vapor the atmosphere in a given location can hold; it occurs when condensation is equal to the evaporation rate; REMEMBER: saturation is the max of how much the air COULD hold, not how much it actually holds.

 Dew-point temperature- temperature at which saturation occurs in the air;  it is

dependent on the amount of water vapor present (higher dew-point temperatures = higher amounts of moisture); dew-points can only be LESS or EQUAL to the actual temperature

 Phase diagram- indicates the temperature and pressure when water  changes

phases; (just to know: water boils at lower temperatures when you’re at higher altitudes, so, water takes longer to boil at higher altitudes

Hydrological (Water) Cycle: 

 Evaporation- water heated turns into water vapor

 Transpiration- water evaporated from the leaves of plants  Condensation- water vapor condenses to form clouds

 Precipitation- water in liquid form

 Sublimation- ice turns directly into water vapor (Ex: Dry ice)  Deposition- water vapor turns directly into ice

Water Vapor Distribution Globally: 

 Highest amounts at the Equator (Tropics)

 Lowest amounts at the poles (North and South)

 The water vapor distribution coincides with humidity, which is higher at

the equator and lower at the poles)

 Water vapor amounts are also highest near the surface and lowest  higher in the atmosphere

Measures of Water in the Atmosphere: 

 Specific Humidity- mass of water vapor/ total mass of all gases (Units:  g/ kg) Sidenote: Specific humidity does not change as the parcel of air  

expands, as long as the total mass inside is the same

 Saturation specific humidity- the specific humidity of air  when it is saturated (max amount of water vapor the air  

can hold)

 Saturation and Temperature- at low temperature changes, saturation  vapor pressure increases slowly, but saturation vapor pressure  

increases rapidly at higher temperature changes

 Relative humidity- amount of water vapor/ max water vapor the  

atmosphere can hold times 100 (Units: percentage %)

 Dew point temperature- temperature of saturation; a higher dew point  means there is more water vapor in the air; a lower dew point  temperature means there is less water vapor in the air; REMEMBER:  dew points can only be less than or equal to the actual temperature, it  can NEVER be higher than the actual temperature

Processes that Cause Saturation: 

1.)Adding water vapor

2.) Mixing cold and warm air

3.)Cooling air to its dew point temperature

-Ways to cool air to its dew point temperature:

 Diabatic Processes (add/remove heat; aids fog  

development)

 Adiabatic Processes (no heat added/removed, but  

temperature changes because of the Ideal Gas Law; aids in

formation of clouds)

o Adiabatic Processes Lapse Rates: DALR (-10 degrees  

Celsius per km), SALR (-6 degrees Celsius per km),  

ELR (given by the problem/situation)

o Atmospheric Stability: Absolutely Stable (parcel  

colder than the environment), Absolutely Unstable 

(parcel warmer than the environment), Conditionally  

Unstable (ELR is between the SALR and DALR)

Mechanisms that Lift Air Up: 

1.) Orographic Lifting (air parcel rising up a mountain)

2.) Frontal Lifting (one air mass meets another causing the warm air to  

rise)

3.)Convection (surface heating by the sun, causing warm air parcels to  

rise)

4.)Convergence (2 colliding air masses cause air to rise)

Factors that Influence ELR (ELR can change because of): 

1.) Heating/cooling of lower atmosphere (the ground warms faster than  the atmosphere, but this is opposite at night, because the Earth gives  

off heat to the atmosphere, making the atmosphere warmer)  The point at which the environment increases in temperature  

with height is the inversion layer 

2.)Advection of cold or warm air at different levels

3.)Advection of movement of an air mass with a different ELR Condensation at and Above the Surface: 

 Dew- liquid condensation (water) on the surface; surface temperatures  are above freezing

 Frost- forms when surface temperatures are below freezing (deposition  occur, instead of condensation, which means water vapor changes  

directly to ice, instead of clouds)

 Frozen Dew- normal dew forms then temperatures drop below freezing  Fog- a surface cloud that forms when air cools to the dew point, has  

moisture added, or cool air mixes with warm moist air

 Radiation- when land cools overnight, lowering the temperature;  

usually occurs in the Winter

 Advection- warm moist air blows over a cool surface such as  

snow cover or cold water

 Upslope- forms when wind blows air up a slope and cools as it  

rises (Ex: orographic lifting)

 Evaporation- forms when rain evaporates before reaching the  ground and causes air near the surface to become saturated

Clouds: 

 Appearance:  

 Cirrus- curls

 Stratus- layers (blocks the sun)

 Cumulus- heap (cotton balls)

 Nimbus- rainy

 Height:

 High Clouds- above 6,000 m

 Middle Clouds- have the “alto” prefix; 2,000 – 6,000 m

 Low Clouds- below 2,000 m

Condensation of Cloud Droplets: 

 Water condenses to tiny droplets  

 Aerosol particles rise with air parcels, which are housed within  

clouds

 These aerosol particles are called cloud condensation nuclei  

because they are important for all cloud formation

 Aerosol particles are either hydrophilic (attracted to water) or  

hydrophobic (not attracted to water)

 Ice nuclei are aerosol particles with the same structure as ice  crystals, which helps to form snow/ice

 Typical raindrops have a radius of 100 times bigger than cloud  

droplets

 Terminal velocity for rain is 650 times more than for cloud droplets Growth of Cloud Droplets: 

 Cloud droplets form in warm clouds (temperature above 0 degrees  Celsius) can be found at the tropics and midlatitudes during the  

Summer)

 Collision-Coalescence: larger droplets (collecter droplets) fall faster  than smaller ones; larger droplets collide (collision) with smaller ones  to make a larger droplet (coalescence)

Growth of Ice Crystals: 

 Ice crystals form in cold clouds (temperatures less than 0 degrees  

Celsius)

 Ice crystals can grow by colliding with other liquid drops/ice  Accretion and Aggregation: riming occurs as liquid water freezes  

onto ice crystals which causes rapid growth. This is accretion. Pretty snowflakes occur when multiple ice crystals join together. This is  

aggregation.

 Bergeron Process: water molecules leave liquid droplets and  deposits onto ice; no touching of water/ice needed; this occurs  because saturation values for ice are less than water because ice  molecules have a stronger bond

Distribution of Precipitation: 

 Rain- reaches the ground as liquid (It rains most in the Southeast  

and Northwest, also near the Rockies)

 Freezing Rain- almost reaches the ground as liquid and immediately freezes very near the surface (Freezing rain is mostly in the  

Northeast and Canada)

 Snow- frozen from the cloud to the ground (Snow is mostly at high  latitudes like the Rockies, Canada, and at the Great Lakes)

 Sleet- ice at first, then it melts in the atmosphere, then freezes at  

the surface  

 Groupel- ice crystals that undergo riming and lose their 6-sided  shape; groupel either falls to the ground or becomes the nucleus of

hail

 Hail- groupel that is updrafted by wind into clouds and collects  more liquid droplets that freezen (Hail is mostly in the Central  

Plains region)

*Precipitation moves North and South with seasons*

 Lake Effect Snow:  

-As the warm lake waters evaporate, wind blows the moist air over  

a cold land surface where it cools, a cloud forms, and then it snows. -You can tell which way the wind blew from by which side of the  

lake has snow (Ex: If the East side of the lake has snow, then the  wind blew from the West side)

Cloud Coverage: 

 Clear- no clouds in the sky

 Scattered- a few clouds in the sky

 Broken- more clouds in the sky than empty space (there are areas  

where the clouds are not covering the entire sky)

 Overcast- clouds cover the sky

Measurements of Precipitation: 

1. Rain Gauge- measures rainfall at a specific location; the depth of water

in the gauge equals the total amount of precipitation

2. Radar- provides information on areal (a large region) precipitation, not  just at a single location; precipitating droplets and ice scatter the  radiation back to the radar unit and the backscatter intensity gives a  

measure of rainfall

3. Satellite Measurements- provide global scale precipitation coverage;  satellites are used because point measurements measure the amount  of precipitation that has fallen at a single location, but don’t measure

the precipitation over bodies of water; satellites also provide 3D cloud  and rain data

What to Also Know: 

 The number of molecules in a fixed volume of air decreases with  height. (This means that as height increases, volume decreases  

within the air).

 Within the Stratosphere, 99.9% of mass is below 50 km.   Within the Troposphere 90% of mass is below 20 km. (This indicates  

that at lower heights, the mass is greater).

 Earth’s radius is about 637 km.

 The deepest part of the ocean is about 10 km.

 Atmosphere pressure, density, and temperature all change  

significantly from the ground up.

 Most of the atmosphere is jammed near the surface. (Over 50% of  

the atmosphere is located below 5,500 m or 18,000 ft.

 Most of the air is made up of oxygen and nitrogen near the surface.  1 hPa (hectopascal) = 1 mb (millibar) (*Reminder: hPa is the unit  

used to measure pressure*)

 1 W = 1 J/s (one Watt is equal to 1 Joule per second)

 Lowest point on Earth: Dead Sea- it is 430 m below sea level and  

has a pressure of 106.5 hPa

 Highest point on Earth: Mount Everest- it is 8,848 m above sea level

and has a pressure of 330.7 hPa

 The mesosphere and thermosphere only account for 0.1% of the  

total mass of the atmosphere.

 Objects with more energy have higher temperatures

 The speed of light = 3 x 10^8 m/s (3 times 10 raised to the 8  

meters per second)

 Wavelengths are measured in micrometers/ one-millionth of a meter  The Sun gives off visible radiation

 The earth gives off infrared radiation

 Temperature and wavelength have an inverse relationship. (As  temperature increases, wavelength decreases, as temperature  

decreases, wavelength increases)

 The Sun is about 5,800 K

 The Earth is about 290 K

 The sun is 20 times hotter than the earth

 Earth’s average albedo is 31%

Where is Water: 

v 7% of Earth is water (the other 93% is land).

v Of the 7%, 96.5% of water is in the ocean.

v Water exists in the air, rivers, lakes, icecaps, glaciers, and in the ground soil.

Water Vapor within the Air: 

v Higher temperatures indicate higher amounts of water vapor. v This means the air can hold more water vapor when it is warmer, instead of when the air is colder.

v The equator has the most water vapor

v There is 0­1% of water vapor above the arctic circle region v There is 0­1% of water vapor below the arctic circle region. v There is 1­3% of water vapor within the mid­latitude region. v There is 2­4%of water vapor within the tropics region.

v More water vapor is near the surface, and less is in the atmosphere. (This is because it is warmer near the surface, and cooler higher up in the atmosphere.

v The main source of water vapor is evaporation, especially near the surface. v Water vapor is important for drinking water, cloud formation (which controls energy for storms and the greenhouse effect), and the human heat index. Forms of Humidity: 

1. Precipitable water

2. Specific Humidity

3. Relative Humidity­ energy given off of ALL objects

4. Dew Point Temperature

*When dew­point temp = actual temp, this also equals saturation and the relative humidity will be 100%*

SO, dew­point temp = actual temp = saturation = relative humidity of 100% Saturation and Temperature Relationship: 

v Saturation and temperature have a nonlinear relationship

v For lower temperatures, the saturation specific humidity increases slowly v For higher temperature, the saturation specific humidity increases rapidly Forces that Impact Horizontal Wind: 

1. Pressure Gradient Force (PGF)-  

o Change in pressure divided by the change in distance

o Wind speed is proportional to PGF

o Air moves from high pressure to low pressure

o Steep PGFs are indicated by isobars that are close together o Warmer areas have higher pressure than colder areas

o Air moves from warmer areas to colder areas

2. Coriolis Force/Effect 

o Wind goes to the right in the Northern Hemisphere, and to the  left in the Southern Hemisphere

o Its strength depends on how close you are to the equator o The force gets stronger near the poles  

o This is why hurricanes never cross the equator

o In the Northern Hemisphere wind spins counterclockwise o In the Southern Hemisphere, the wind spins clockwise

o The Coriolis force only acts on motion for long distances and  times

o Stronger winds= big Coriolis force

o No wind= no Coriolis force

Motion in North-South Direction 

a. The speed of rotation at the equator gets lower as you move  toward the poles, the wind has eastward momentum, making the wind/object veer off to the right

b. If it accelerates North, it will move to the East  

c. If it accelerates South, it will move to the West  

Motion in East-West Direction

a) If wind accelerates to the East, it will move to the South b) If wind accelerates to the West, it will move to the North

3. Friction 

o Impacts wind speed and direction; acts in the opposite direction  of wind; initiated at the surface, but extends and decreases up  o Friction is important for wind in about 1.5 km of the surface, the  planetary boundary layer

o Winds at the surface slow due to friction and cross isobars  (pressure lines)

o Coriolis deflection still occurs but is reduced

o Different surfaces have more friction than others

Wind in the Upper Atmosphere: 

1. Geostrophic flow- balance between PGF and Coriolis

2. Gradient flow- winds that follow the lines and move in a curved path,  which can be either sub geostrophic (low pressure) (centrifugal forces  due to curved path is opposite of the PGF so winds are slower than  geostrophic) super geostrophic (high pressure) (centrifugal forces due  to curve path adds to the PGF so winds are faster than geostrophic)  3. Wind moving counterclockwise= faster  

4. Wind moving clockwise= slower

 Cyclones: 

 Air converges toward low pressure centers called cyclones  Ascending air cools to form clouds and rain

 With increasing height, there is less horizontal convergence  The flow is counterclockwise in the northern hemisphere and clockwise  in the southern hemisphere

 Anticyclones: 

 Air diverges away from high pressure centers

 Descending air warms, creating clear sky conditions

 Less horizontal divergence with increasing height

 The flow is clockwise in the Northern Hemisphere and counter clockwise in the Southern Hemisphere

 Synoptic Scale:

 Circulation in the atmosphere can occur over a range of scales  Cyclones and anticyclones occur at the synoptic scale

 The synoptic scale is a few hundred to thousands of kilometers

Important to Know: 

 Above the surface PGF and Coriolis cause geostrophic force  Steep pressure gradients are indicated by close isobars (vice versa for  weak PGFs)

 Strong PGF near low pressure center (PGF points away from low  pressure center)

 Weak PGF near high pressure center (PGF points toward high pressure  center)

 Geopotential height- height of constant pressure level  

 Contour maps show height differences plotted on constant pressure  levels

 PGF initiates atmospheric motion because pressure can vary from  place to place

 Coriolis deflects air in motion, but does not initiate motion  Objects in the atmosphere are influenced by Earth’s rotation  The eye of the storm is a low pressure center

 In the Northern Hemisphere, air circulates clockwise around high  pressure and counterclockwise around low pressure systems  In the Southern Hemisphere, air circulates counterclockwise around  high pressure and clockwise around low pressure systems   Convergence- coming together; arrows cross the lines/isobars  Divergence- moving away; arrows are parallel to lines/isobars  At a low pressure center, convergence occurs at the surface and  divergence occurs in the atmosphere; air is sent up

 At a high pressure center, divergence occurs at the surface, and  convergence occurs in the atmosphere; air is pulled down  High pressure = clear weather

 Low pressure = cloudy weather

Atmospheric Circulation and Global Winds 

Global Scale Winds: 

 Wind pattern is driven by:

1. There is more energy into the tropics than the poles

2. The earth is rotating around its axis

 More solar energy is absorbed in the tropics and less is absorbed near the poles.

 More longwave energy is emitted in the subtropical region.

 The difference between energy in and out indicates surplus or deficit, circulation direction  Differences in energy in and out must be balanced by horizontal transport of energy by  atmosphere and oceans (Ex: Circulation)

 The movement of the air and oceans allows energy to be transported from the equator to the  poles.

 Warm air = higher pressure    Colder air= lower pressure

Three Cell Model:  

1. Hadley Cell­ circulates in tropics to subtropics

2. Ferrel Cell­ circulates air in middle latitudes

3. Polar Cell­ circulates air near each of the poles

 Each cell has rising air over low surface pressures, a cone of sinking air over surface high  pressures, and surface wind from high to low turned by Coriolis.

 Problems­ 

1. It explains surface level winds, but not upper level wind

2. The topography of the land isn’t reflected

3. Differences in pressure distributions isn’t well reflected

 Solving the problem

1. Use semi­permanent pressure cells: associated with sinking motions in the subtropic  highs, which promotes deserts in certain latitudes

    ITCZ: 

 It rains the most in the ITCZ (Inter­tropical zone)

 Monsoons­ seasonal rainfall; indicate a reversal in large­scale winds; monsoons occur  because of thermal difference between land and water and shifting Intertropical  Convergence Zone (ITCZ)

 The ITCZ shifts seasonally, causing heavy to no rainfall

 The land heats up faster in the summer, and cools off faster in the winter  The East Asian monsoon is characterized by dry, offshore flow conditions during cool  months, and wet, onshore flow during warm months

 Orographic lifting brings larger amounts of rain in the Himalayas, which has some of the  highest precipitation amount on Earth

Sea and land breezes: 

 Wind due to temp differences between land and sea, which are from different heat  capacities of water and land.

 During the day, land surface is warmer than the water.

 During the night the water s warmer than the land.

 A low pressure develops over the warm region, air converges into the low, ascends, and  produces clouds and possibly rain.

Upper level winds: 

 At most latitudes except the equator these winds are westerly

 The winds are caused by a temperature difference between the poles and the equator  Pressure decreases more quickly in cold columns than warm columns  At the same altitude higher pressure exists at the equator than the poles  Upper­air PGF is directed toward the poles, but it is redirected to an eastward trajectory  because of Coriolis deflection

Fronts and Jet Streams: 

 Fronts­ strong boundaries that occur between warm and cold air

 In the midlatitudes the polar front marks this thermal discontinuity at about 6o degrees  north between cold air over the pole and warm air in the south

 The polar jet stream s a fast stream of air in the upper troposphere

 At about 30 degrees north, the subtropical jet stream occurs at edge of the Hadley Cell  Jet streams occur at the tropopause, which is just below the stratosphere  In the winter, the polar jet stream position shifts toward the equator

 The jet stream is faster in the winter when the poles are the coldest

 Important Jet Streams:

1. Polar Front Jet 35 degrees in the winter and 65 degrees in the summer 2. Subtropical Jet 20 degrees in the winter and 35 degrees in the summer  Jet streams are important for day to day weather

 They transport war air north and cold air south

 They contribute to the development of synoptic scale storm systems, especially in the  winter

Conditions for Hurricane Development:

 Need Coriolis for rotation (forms 5 to 20 degrees latitude)

 Cold atmosphere (unstable above), so the surface is warm 

 Warm ocean surface (>27 degrees Celsius)

 Low pressure level and low­level convergence

 High humidity above the surface from evaporation

 Weak wind shear (lighter winds in the atmosphere)

Hurricane Structure:

 A central eye­ downward motions, surrounded by large cumulonimbus thunderstorms  within the eye wall)

 Strongest wind speeds and greatest PGF along the eye wall

 Few clouds and low precipitation between cloud bands, because of downward motion  Large pressure gradients into the center of the storm 

 Within the spiral rain bands, there is upward motion

 A tropical storm becomes a hurricane at 74 mph. This will be a category 1 hurricane. 

The Saffir­Simpson Scale (Hurricane Intensity Scale):

 This scale doesn’t tell you about precipitation and other factors, this scale indicates wind  speeds 

 Greater wind speed = greater storm surge (the rising of the sea, due to the storm)

Tropical Storm Names:

 Tropical storm naming began in 1953, with only female names

 In 1978, they began to use female and male names alternatively

 The tropical storm names occur in alphabetically order 

 A huge/drastic storm has its name retired (Ex: Hurricane Katrina) 

Hurricane Destruction:

Wind Speeds:

 Hurricane winds exceed 120 km/hr (74 mph)

 Hurricane force winds can cause severe damage to buildings and homes  Ex: Hurricane Irma sustained 185 mph winds for 37 hrs (the longest record of  intense winds)

Heavy Rain:

 Hurricanes can produce intense 10 in/day (25 cm/day)

 Rainfall can cause extreme flooding and mudslides in mountainous regions  Heavy rain causes property damage and death

 Ex: Hurricane Harvey produced 19 trillion gallons of rain (over 60 inches in one  location)

Storm Surges:

 Storm surge is a rise in water level caused by a hurricane

 Water piles due to heavy winds and low atmospheric pressure

 High surf can occur atop a storm surge, increasing damage

 Winds and storm surge are typically most intense in the right front quadrant of the storm where winds combine with the storm’s movement

Climate Change and Hurricanes:

 Number of hurricanes is believed to decrease

 The strength of hurricanes is believed to increase, depending on the sea surface  temperatures, which go up with climate change

 Rainfall from hurricanes is likely to increase, depending on the amount of moisture in the air, which goes up with climate change

 Strom surge from hurricanes are likely to increase, depending on the sea level, which  goes up with climate change

Thunderstorms  

 A thunderstorm or cumulonimbus cloud, is a localized storm that typically develops  during warm months

Types of Thunderstorms:

Single Cell (AKA Air Mass): 

 can be non­severe or severe thunderstorm

 Relatively small, local, and short­lived (less than 30 mins) without strong winds or  hail

 Consist of many updrafts following this sequence:

o Cumulus Stage­ uplift begins and clouds form (just updraft)

o Mature Stage­ precipitation begins to fall (updraft and downdraft)

o Dissipating Stage­ precipitation diminishes (just downdraft) Multi Cell: 

 can be non­severe or severe thunderstorm

 Multiple storms that form together

 Clusters can develop from the same origin or exist because some cells lead to the  development of others

 Mesoscale Convective Systems (MCS) = organized groups of thunderstorms that  form and develop together

o Types of MCS:

1. Circular Cell Structure

2. Squall Lines (linear band cells)

o Clusters can develop from the same origin or exist because some cells lead to  the formation of others

Super Cell: 

 A severe thunderstorm

 One powerful cell

 Severe rotating storms can have wind speeds more than 93 km/hr (58 mph), large  hail, and can last for hours

 Strong wind shear is needed, high water vapor, uplift, and instability are all needed  for severe thunderstorms (super cell thunderstorms)

 Smaller than squall lines or mesoscale convective complexes, but can produce  tornados

 Where downward motion and upward motion crosses each other, spiral rotation  occurs

 All of these thunderstorms need: 

1. Moisture 

2. An unstable atmosphere 

3. Some way to get the atmosphere moving (an unstable environment) 

 All of these thunderstorms are associated with strong wind, severe flooding, lighting,  tornados, and thunder 

 There are about 14.5 million thunderstorms the occur around the world  The southeast U.S has the highest number of storms annually 

 There are few thunderstorms in the West 

Tornados (General Characteristics):

 Tornados are zones of extremely rapid, rotating winds beneath the base of cumulonimbus clouds 

 Weak tornados have speeds of 65 mph (105 km/hr)

 Fast tornados have speeds about 280 mph (450 km/hr)

 Within the U.S, most tornados occur in early Summer when contrast between warm and  cold air in the atmosphere is the greatest 

 Later in Spring and early in Summer tornados occur further to the north 

Tornado Development:

 Spinning vortex tubes created by wind shear

 Strong updraft carries vortex tube into thunderstorm

 Tornados can produce 2 rotating columns oriented vertically

  Non­supercell tornado development is not really predictable

 The U.S has the most tornados world­wide

 The Central U.S has the most tornados

Needed for Tornado Development in the U.S

1. Weather systems with fronts 

2. Unstable air 

3. Vertical wind shear

Other Types of Severe Wind/Hazards Associated with Thunderstorms:

 Downbursts­ gusts of wind that can reach speeds of 165 mph (270 km/hr) and are  potentially deadly

o Strong downdrafts associated with thunderstorms can produce large scale  horizontal winds called derechos (which means straight ahead; they can last for  hours)

o Downbursts with diameters less than 4 km are called microbursts (they can  produce dangerous situations at airports)

 Hail­ causes about $1 billion in damage to crops and property each year  Lightning­ 

o A separation of negative and positive charges into different regions of the cloud o Positive charges go to the top of the cloud and negative charges go to the bottom  of the cloud

o The negative charge will continue to move down toward the surface following a  path called “stepped leader”, which creates the lighting structure (jagged,  branched)

o As the stepped leader moves down, tall objects become positively charged,  creating a positive upward streamer

o Once the step leader makes contact with a streamer, the negative charge flows  rapidly to ground as a return stroke that we see as a flash or lightning

o Within the cloud, updraft carries small ice crystals upward while graupel falls,  and collisions transfer electrons from crystals to graupel 

o 20% of lightning is from the cloud to the ground

o 80% of lightning is from one cloud to the other cloud

 Thunder­ air expands explosively due to a massive increase in temperature with lightning stroke and causes thunder

o Lightning can heat the air to 30,000 degrees Celsius (54,000 degrees Fahrenheit) o The air expands explosively, initiating a shock wave

o You see lightning faster than you hear thunder because sound travels slower than  light (3 sec/km)

o Lightning without thunder is called heat lightning

o About 70 people are killed yearly by lightning in the U.S.

Different Scales of What We’ve Learned So Far:

 Thunderstorms are measured by mesoscale 

 Tropical Cyclones are measured by synoptic scale

Human Influences on Climate 

 The Southeast U.S. is the highest region at risk due to climate change  Climate change refers to the global average temperature change 

 The global average temperature change has increased 1.2 degrees Fahrenheit  The Northern regions globally tend to heat up faster because these regions would  normally be covered with snow, but they change from reflecting sunlight (because of  snow) to absorbing it (because of the lack of snow)

 Around the world, glaciers are melting and thinning

 Glaciers supply fresh water throughout the summer

 Changes in sea level (rising), sea ice decline, and changes in rainfall are all factors that  reveal climate change 

 The Industrial Revolution (1850s) was the beginning of humans emitting excessive  carbon into the air 

 China emits more emissions as a whole, because the population is larger.  So, the U.S emits more emissions by person, than any other country in the world