Earth moves around the Sun in an elliptical orbit

-Aphelion = Earth is at its furthest point from the sun

-Perihelion = Earth is at its closet point to the sun

-Varies between 91 and 96 million miles.

Circle of illumination = The line on the earth's surface dividing light from darkness

Question? Does the sun rise? Explain.

Planet earth- 71% water 29% land

Does that cause much of a role in the weather on earth?

Does it make a difference if the water is cold or warm?

Tropic of Cancer 23.5 degrees N

Tropic of Capricorn 23.5 degrees S

Question? What does the Tropic's location have to do with the Arctic and Antarctic


December 21== Southern Hemispheres summer

Specific heat = amount of heat energy held at a specific temp. by a substance

Highest specific heat of all liquids except ammonia = H20

-Shallow H20 heats up faster than deep H20

Question? Is that statement about shallow water always true? Explain.

Greenhouse effect = Short wave radiation can go through atmosphere/glass but

reflecting Long waves cannot pass through. Why does that phenomenon occur and what

are the implications to our weather.

Question? What does it have to do with Woburn, Mass being the former carnation

growing center of America?

LCL = That is the altitude at which clouds form.

Question? What is the difference between condensation and precipitation?

90% of all Earth's weather happens in the Troposphere

Hot air rises => lighter => holds more moisture

Cold air sinks => dense => holds less moisture

100% RH (relative humidity) = precipitation

This occurs at dew point temperature and altitude.

Question? What has occurred that causes snow?

Solar Radiation = Heated atmosphere

Vaporizes H20 = formation of clouds

100% moisture = precipitation

Depending on temperature precipitation is either liquid or solid

Moved by upper air movement => Jet stream moves surface air

Vector = Direction of wind

Low pressure gives higher temp.

Question? What is the relationship between low temperature and high pressure?

Thermometry = measurement of infrared heat

-Calorie = amount of heat necessary to raise 1 gram by 1 degree Celsius

-Calibrated by Fahrenheit, Celsius, or Kelvin Scales.

Question? How are those scales interchangeable? Do they measure the same things?


-Mercury = silver

-Alcohol = red or blue

-Bio-metallic = aluminum & copper

Question? Why are mercury thermometers becoming obsolete?

Calories measure energy and the ability to do work

Suns energy comes to earth as potential energy

Question? Is that the only kind of energy? Can we create energy?

Barometers = measure air pressure

-Aneroid =>14.7 psi (BP @ sea level)

-Torricelli =>mercury ex. 29.92 inches

-Barograph => graph based on millibars ex. 1013.2

-Hair Hygrometer

Barometric pressure often goes up or down

Question? What can cause the barometric tendency to vary?

-Warmer, moisture, stormy = Low pressure

-Cooler, drier, clearer = High pressure

-29.92 = neutral point

Question? Why is it not only important to observe the difference between mean

barometric pressure, but also its prior reading or value?

Storm =They may be episodic or long term (gale vs. tornado). It is a condition of the

atmosphere that brings an extreme weather condition to a specific area for a different

period of time.





1.) Convectional storm

-Dew point has reached the saturation point. Rising air from the surface reaches

the condensation point (LCL). While the warm air is rising, cold dense air is sinking or a

rain event that results from unequal heating of the land surface such that a rising column

of air cools beyond the dew point and becomes unstable producing a cumulonimbus

cloud, typically exhibiting violent local wind, high intensity rainfall over a small area and

for a short duration, hail, thunder and lightening.

2.) Monsoon

- Any major seasonal wind system reverses its direction causing wet and dry

seasons. Most of the large monsoons are in Africa and southern Asia, the

smaller ones can be found all over the world, such as in the Gulf Coast of the

US and Central Europe. Could be 7 months of wet weather. It is very regular

around 5-15 degrees north or south of the equator. It is primarily caused by a

reversal of oceanic and land Pressures. Stations on the ground usually

experience 10 times normal monthly amount of rain along with a short dry

period. This is also used to describe a climate that has monsoon rains.

3.) Orographic Storm

-Deals with weather near and around mountainous regions .It is cased by

mountain barriers and mechanically forced rising of winds. They are relater to continental

location and cold ocean currents.

-Air cools at about 5.5 degrees Fahrenheit for every 1000 feet in altitude. In

precipitation it is 3 degrees for every 1000 feet.

-When mountain is near ocean (windward side), the cool moist ocean winds rise

up the mountain and cool according to the rise in altitude, once wind reach peak of

mountain they fall down dry side (leeward side) and warm according to altitude.

-As the moist wind rises up windward side the condensation point and dew point

are reached and the air can no longer hold moisture, thus precipitation will fall. Once

wind reaches peak précis stops. The wind has now reached the LCL. As the wind goes

down the leeward side (Chinook wind) it now warms and expands causing deserts.

Hadley Cell = Low latitude air movement toward the equator that with heating, rises

vertically, with pole ward movement in the upper atmosphere. This forms a convection.

cell that dominates tropical and sub-tropical climates.

Question? Does this have anything to do with the jet streams and our weather?

Synoptic Weather = Structure and behavior of atmospheric circulation systems, practical

weather analysis and forecasting techniques. This directly involves acquisition,

manipulation and display of real-time data sets. This is primarily a descriptive process

based on factual observations.

For ever)? 1000 feet air rises in altitude, the temperature drops an average of 5.5 degrees

in unsaturated air. The rate differs m saturated air. It is 3.0 degrees/ lOOQfeet.

Question? Why are there differences between saturated and un saturated air?

Saturation point =>condensate => precipitate

-Solid = snow, hail, sleet

-Liquid = rain, drizzle, mist, fog

-Precipitation less than 150mm is drizzle

Relative Humidity = the ratio of the amount of water vapor actually present in the air to

the greatest amount possible at the same temperature

Humidity = read by a hydrometer, it is the specific amount of vapor in the air

Dew point= the temperature at which a vapor begins to condense is the location at which

a cloud becomes saturated, altitude/temperature/ amount of moisture

Howard’s Clouds Classification

-Lower Altitudes => Sea level to 6500 feet

-Stratus (ST) Stratiform = layers of clouds, low clouds

-Alto Stratus = higher end

- Middle Altitudes @6500 feet =>Cumuliform = middle clouds, fluffy

-Anvil cloud/ thunderhead = Cumulonimbus

-Point of anvil = direction of cloud movement

-Alto cumuli = up higher

-High Altitude@ 20,000 to 75,000 feet. Cirroform are wispy clouds.

Question? Why do we have less of the sky covered with high clouds and more of the sky

covered with low clouds? How does that differ for CN clouds?

Blanket effect = Clouds keep in the heat and insulate the earth, especially at night.

Question? Why does an early and continuous snow protect ground cover?

Wind = horizontal movement of air from a region of high pressure to a region of low


The change in pressure measured across a given distance is called a pressure gradient.

The steeper the gradient is, the greater velocity of the wind.

Question? Why do hurricanes have winds greater than 75 miles per hour?

The pressure gradient force is responsible for triggering the initial movement of air

-The higher the pressure gradient the greater the wind.

Question? How does the Beaufort Scale relate to wind velocity/ Why is it possible that a

gale may do more damage to Boston Harbor than a hurricane?

Air also moves vertically, light warm air rises while cold dense air sinks

Planetary winds

-Between 60 degrees and 90(H) degrees north = Polar easterly

-Between 30 degrees and 60(L) degrees north = South West Trades

-Between the equator and 30(H) degrees north = North East Trades

-Equator = ITCZ (L)

-Between equator and 30(H) degrees south = South East Trades

-Between 30 degrees and 60(L) degrees south = North West trades

-Between 60 degrees and 90(H) degrees south = Polar easterly

At this point you should really consult the text for diagrams on planetary winds.

Understanding this concept is key to critical understanding of the course.

Question? What are calms, doldrums and horse latitudes?

Local Winds

Winter winds

-Land (H) ==>H2O (L) = land breeze

Summer winds

-H20(H) ==>land(L) = sea breeze

Those are specific for the northern hemisphere.

Questions? Will the same be true in the southern hemisphere?

Define Foehn, Chinook. Mistral, Bora, Scirocco and Santa Ana winds.

Nautical mile is equal to 6069 feet (just distance)

Knots are computed by nautical distance/time

The earth completes a full rotation (360 degrees) at a speed of 1000 mph

Beaufort Scale is used to determine the force of wind

-Hurricane = wind in excess of 75 mph

-Full gale is 60 mph

-There is also gale, light breeze, full breeze, calm...

4.) Frontal Storms or Air Mass Storms

-The transition zone or interface between two air masses of different density usually

means different temperatures. For example, the area of convergence between warm,

moist air and cool, dry air will produce a frontal storm.

The clash between a cold frontal air mass and a warm frontal air mass will produce

differing forms of precipitation depending upon temperature.

-Cold air travels 2x faster than warm air.

-Degree of frontal slope = wind velocity.

-As fronts approach wind velocity increases, precipitation will occur in collision

area, warm front over rides cold front, wind shifts, high pressure takes over and the storm

passes and weather clears. In this area it means that the wind now is coming from the


Warm front:

- The interface between an advancing mass of air that is warmer than the one it

is replacing, usually at the point of contact with the ground surface. This is

associated with a low barometric pressure.

Cold Front:

-The interface between an advancing mass of air that is colder than the one it is

replacing, usually at the point of contact with the ground surface. This is usually

associated with a high barometric pressure.

Stationary front

-Locks everything in place for a while creating temperature inversion. Episodic.

This is referred to as an occluded front.

Question? What is the relationship to public health and summer stationary fronts?

-At night reverse blanket effect.

-Traps Nitrous Oxide in atmosphere (bad air day)

-Happens in summer: Haze => smaze: photochemical smog

Side note on pollutants:

-Iron and steel are brutal on environment, manufacturing of these leads to

poor air quality

-Air quality hazardous occupations: Traffic cop, diesel mechanics

Due to temperature inversion, another type of episodic storm is a Hurricane

-Low-pressure storms originate over warm ocean water and have winds in excess

of 75 miles per hour.

-Torrential precipitation


-Ocean Currents

New England Blizzard of 78' was actually a hurricane.

-Struck from SE 158 miles offshore

-Extreme Low pressure

-Highest tide of the year

Hurricane season is usually July through October

-Wettest Months in the tropics are August and September

-Northern Hemisphere Cyclone spins counter clockwise.

-Point of intersection is maximum wind and pressure drop

-These storms produce Surplus of electronic energy: lightning and thunder

Thunderstorms are episodic 1 to two hours or even 30 minutes

Twister or Tornado also episodic, usually five minute in one area of path

-Winds in excess of 200 mph

-Over ocean twister is called a water spout

Question? Why can tornados be among the most destructive storms?

Is it possible to find them in New England?