VocabularyWeatherGradientDensityFieldIso-linePollutionIsoline map

SizeTime FrequencyPressureCyclic ChangeAtmospheric carbon dioxideInterfaceAir masses

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UNIT 5: WEATHER & CLIMATE

PACKET 6: STATION MODELS, FORECASTING, FRONTS, SEVERE WEATHER, AIR MASSES

EARTH SCIENCEMS. GILL

NOTE PACKET #6

NAME:_____________________ CLASS:____ DATE:______ ________

Whoa! Its raining buckets out there!

P.S. I’m Harley

Cold frontWarm frontstationary frontSolar energyInsolationAtmosphereabsorbedOzoneWater vaporReflectradiationConductionEvaporationConvectionWeatherSeasonal changesAtmosphereHydrosphereDensity differencesWeather patternsWeather variablesAir temperatureAir pressureMoistureRelative humidityDew pointPrecipitationRainSnow HailSleetWind speedWind directioncloud coverInstrumentsThermometers

barometerPsychrometerPrecipitation gaugesAnemometersWind vanesProbability of precipitationAir pressure gradientVertical atmospheric movementRadarSatellite imagesWeather mapsStation modelsIsobarsFrontsAtmospheric cross-sectionComputer modelsJet streamWindAir massesFrontal boundariesCyclonic systemTornadoesThunderstormsHurricanesGlobal temperature zonesPlanetary windOcean current patternsMonsoonsFloodingSevere weatherCalorimetersAluminum barsHeat transferPredictWeather eventNatural disaster

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Use your ESRT to answer the following questions:

1. What happens to the temperature of the atmosphere as altitude increases through the troposphere?

____________________________________________________________2. In what layer of the atmosphere is the most water vapor found? ____________________

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Weather is the __________________________________________________________________

It is the result of the interrelationship of the following 4 atmospheric variables:

I. Temperature: measures how much ____________________ the air molecules have

II. Air Pressure: caused by the __________________ of atmosphere pushing down

III. Wind: Horizontal Movement of air caused by ___________________in pressure

IV. Humidity: Moisture content of the atmosphere

In what layer of our atmosphere does our weather occur? ______________________________

What is our atmosphere made of? __________________, _________________, ___________

3. What is the exact altitude, in miles, of the Stratopause? _______________________4. What is the pressure at an altitude of 15km? _________________________5. What is the temperature at an altitude of 50 miles? __________________6. What is the temperature at an altitude of 0 miles? __________________7. What is the temperature at an altitude of 30km? ____________________8. What happens to the temperature of the atmosphere as altitude increases through the strato-

sphere?____________________________________________________________

9. How does pressure change with altitude? ______________________________10. What is the exact altitude, in kilometers, of the Tropopause? ___________________

I. Temperature:

Temperature is a measure of how much kinetic energy the air molecules have in a parcel of air, or simply a mass of air. The average kinetic energy of the particles is dependent on energy transfer. Re-member, Earth is always trying to achieve equilibrium, and distributes energy from areas of high tem-perature to areas of low temperature. In other words energy will always flow from the warmer energy source to the cooler energy sink.

The major source of energy for Earth is our Sun. Insolation from our sun heats the ground and bodies of water covering earth’s surface. In turn, these surfaces reradiate the sun’s energy as infrared radiation that heats the air. However, there are many factors that contribute to how much of the insola-tion is actually absorbed and reradiated by Earth’s surface. This unequal absorption causes unequal heating of our atmosphere. Once again, since energy always flows from high to low, convection currents form in our atmosphere to try to distribute the heat energy evenly.

There several properties of earth’s atmosphere and surface that affects the amount of insolation that is absorbed. The more solar energy that reaches and is absorbed by earth’s surface, the hotter the air above it will become. Lets look at some of the variables that cause unequal heating of earth’s atmos-phere.Properties of the Atmosphere and Lithosphere that effect Intensity of InsolationA) Particulate Matter prevents Insolation from reaching earth’s Surface:Aerosols like water droplets, volcanic dust, ice crystals and pollutants can LOWER the air temperature because they cause SCATTERING that result in LESS insolation reaching Earth’s surface. B) Clouds:During the day clouds scatter insolation and prevent insolation from reaching earth’s surface. Thus it is colder on a cloudy day. However, at night the water vapor acts as a greenhouse gas and traps the rera-diated infrared heat energy. Thus it is warm and humid on a cloudy night. C) Surface over which air ExistsAir is warmed by reradiated infrared radiation from the surface over which the air exists. Convection currents then distribute the warm, less dense air in the atmosphere. Therefore, a dark rough surface will have warmer air mass above it than a light colored smooth surface. D) Latitude and Season Due to earth’s revolution and the tilt of our axis, different latitudes on earth experience variations in in-solation though out the year. In general the tropical latitudes receive the most intense angle of insola-tion where as the poles receive less intense insolation.

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Convection currents form in our atmosphere due to this unequal heating. Warmer air is less dense and therefore will rise, whereas cold air is more dense and will sink. This is due to the fact that fluids (gas and liquids) tend to layer based on density, with densest fluids beneath less dense fluids. However when cool dense air sinks, it eventually hits the earth’s surface. It has nowhere to go except to flow horizontally across earth’s surface. You experience this phenomenon when you stand in the wind. The cool dense air rushes down and across earth surface to a region where air is rising and needs to be replaced. You might recall this concept from our energy unit, this type of energy transfer is called a convection current.

B.. The Affects of Air Temperature:1. Which container has more kinetic energy?__2. Which container has higher air pressure?___3. Which container has greater density?___4. Which container can hold more water?___

Summary:*Hot air has more kinetic NRG*Hot air has less pressure *hot air can hold more water*hot air is less dense*hot air rises

II. Air Pressure: Air pressure is the result the weight of atmosphere pushing down on Earth’s Surface. We live on the bottom of an ocean of air; therefore the pressure is highest at low elevations because there is a tall column of air molecules above you. As you increase your elevation, less air molecules are above you, so air pressure decreases and your ear’s pop. Humans have evolved

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I. Air temperature: Total Kinetic energy of air particles

A. Three scales used to measure Temperature:

1. _____________________ 2. _____________________ 3. ______________________

IceBoiling waterFahrenheitCelsiusKelvin

Absolute Zero: (Zero degrees Kelvin) ____________________ NO KINETIC ENERGY! MOLECULES ARE NOT MOVING!

You need to know the following weather instruments:

over the last 20 million years to be strong and accustomed to this pressure. Therefore your body does not notice small changes in air pressure, nor do you “feel” the weight of the air nor-mally.

Moisture in the Air affects Air pressure too!Dry air is made up mostly of Nitrogen and Oxygen… theses are

heavy gases because they have many protons. Furthermore, cooler air is dry since the particles are closer together (more dense) and there isn’t a lot of room for water to fit. These heavy densely pack molecules in dry air exert a lot of pressure on earth’s surface.

Moist air on the other hand is usually characteristic of less dense warm air. Also water vapor is made up of hydrogen and oxygen. Hydrogen is a much lighter gas compared to nitrogen and so moist air in general is lighter than dry air. The light, less dense molecule of moist air does not ex-ert as much pressure on earth’s surface as dry air does.

II. Air Pressure: Caused by the weight of the atmosphere pushing down. A) As Altitude increases, Pressure decreases!

Graph the following relationships:

Pressure Pressure

Altitude Air Temperature6

Air will either Rise or Sink based on its temperature, this results in LOW and HIGH Pressure systems to an observer on earth’s surface.

Whenever you watch the weather channel you will often see giant red “L’s” and blue “H’s” over different parts of the U.S. on a synoptic weather map. This indicates the vertical movement of air and the weather that results from it.

In a low pressure system, air is rising because it is warm and less dense. (We can model this using our hand above our head. If you move your hand upward away from the top of your head, you will not exert pressure on you head.) This rising moist air leads to cloud development and bad weather!

However in a High pressure system, air is sinking because it is cool and more dense. (This can also be modeled using your hand. If you lower your hand toward your head, allowing your hand to “sink” you will exert a high amount of pressure on your head) Sinking air is associated with good weather and no rain, so give your friend next to you a “HIGH FIVE” for nice weather! (PUN INTENDED)

This vertical movement of air is best visualized using an atmospheric cross section like the one below:

B) Affects of Water Vapor on Atmospheric Pressure:Atmospheric Pressure is affected by

_______________________________________________

Water vapor is very _______________________ compared to dry air.

So, when water vapor is added to dry air, the air pressure ____________________

In Summary:

Pressure

Humidity

To summarize: In the diagrams below place curved arrows to indicate the direction the wind is blowing. Note that the circles are isobars and that this diagram represents an aerial view. In low pressure winds blow In high pressure winds blow ( in or out ) ( in or out ) ( clockwise or counter clockwise ) ( clockwise or counterclockwise )

Cold HotHeavier LighterMore Dense Less DenseMore Pressure Less Pressure

Holds More Water

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A barometer measures: pressure in ___________________________ or millibars.

Standard pressure is _________________or ____________________ (See reference tables page 13)

1040.0 millibars = _____________________ inches of mercury

LAerial View

Lows and HighsA. Portions of the troposphere with low pressure centers are called LOWS or ________________________. Wind direction in a low pressure air mass (in the Northern Hemisphere) is _______________________________ toward it’s center. Usually associated with ____________________, ____________________ and _________________ weather.

B. Portions of the troposphere with high pressure centers are called HIGHS or ________________________. Wind direction in a high pressure air mass (in the Northern Hemisphere) is _______________________________ away from it’s center. Usually associated with ____________________, ____________________ and _________________ weather.

H

The diagram below shows a cross-sectional view of how theses air masses move over land

III. Humidity: The amount of water in the air can be measured in different ways. The specific humidity

of air is a measure of how much water is in the air. Warmer air can hold more water than colder air. When the air reaches its capacity, it is saturated. This capacity doubles for about every 11°C rise in temperature. The term more often used is relative humidity. This is the measure of how much water is in the air divided by how much it can hold. The relative humid-ity reading is given as a percent. The relative humidity for saturated air is 100 percent. Lets look at the diagrams below to see if you can figure out why warm air has the ability to hold more water vapor than cold air:

Since the particles in warm air are more spread out, there is more room for water vapor to oc-cupy. Cold air is more dense on the other hand and is not able to hold as much water vapor.

Temperature effect on the Amount of Water Vapor in the Air:Temperature is a measure of the kinetic energy of the particles. As the temperature in-

creases, the motion of the particles in the material increases. As the temperature of a liquid

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Side View

increases, the speed of the liquid particles increases. As particle speed increases, the particles move farther and farther apart until finally they separate and are in a gas state. So an in-crease in temperature increases the evaporation rate of a liquid. The more evaporation that takes place, the more moisture there will be in the air.

Moisture in the Air affects Air pressure too!Dry air is made up mostly of Nitrogen and Oxygen… theses are heavy gases because

they have many protons. Furthermore, cooler air is dry since the particles are closer together (more dense) and there isn’t a lot of room for water to fit. These densely pack molecules in dry air exert a lot of pressure on earth’s surface because they are heavier. Moist air on the other hand is usually characteristic of less dense warm air. Also water vapor is made up of hydrogen and oxygen. Hydrogen is a much lighter gas compared to nitrogen and so moist air in general is lighter than dry air. The light, less dense molecule of moist air does not exert as much pressure on earth’s surface as dry air does.

1. The diagram below shows the temperature readings on a weather instrument.

Based on these readings, the relative humidity of the air is closest to1) 32% 2) 8% 3) 11% 4) 60%

2. What is the dewpoint if the relative humidity is 100% and the air temperature is 20ºC?1) 16°C 2) 18°C 3) 20°C 4) 21°C

3. What is the dewpoint when the dry-bulb temperature is 24°C and the wet-bulb temperature is 21°C?9

Dew Point and Relative Humidity!Dew Point Temperature: The temperature at which the air is holding the ____________ amount of water. The air is _____________Relative Humidity: The ratio of the amount of water vapor in the air, to the maximum amount it can hold. It is usually expressed as a __________. As the temperature increases, the maximum absolute humidity _____________ but the relative humidity will decreaseThe dew point and relative humidity are determined by using an instrument called a ___________________The psychrometer has two thermometers, a dry bulb and a wet bulb. The psychometer is whirled in the air so that evaporation will occur. The lower the moisture content of the air, the ________ evaporation will occur from the wet bulb and the wet bulb temperature will be _________

1) 20°C 2) 6°C 3) 24°C 4) 14°C4. On a cold winter day, the air temperature is 2°C and the wet-bulb temperature is –1°C. What is the relative humidity at this location? 1) 37% 2) 6% 3) 83% 4) 51%5. Which statement best explains why an increase in the relative humidity of a parcel of air generally increases the chance of precipitation?

1) The amount of moisture in the air is greater, making the air heavier.2) The specific heat of the moist air is greater than the drier air, releasing energy.3) The air temperature is closer to the dewpoint, making cloud formation more likely.4) The dewpoint is farther from the condensation point, causing rain.

Rising Air Results in clouds!!!!! What are some situations that will cause air to rise...

1. When to diffent air masses meet (frontal boundaries)2. Windward side of a mountain3. Above hot surfacese that cause the air to get less dense and rise!

D. Effects of a Mountain Range: __________________________________

Label the diagram.

1. The side of the mountain with the moist prevailing winds is called the _______________________ Summary:

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C. Basic Cloud Types:

1. Cirrus: high and feathery (____________ weather)

2. Cumulus: White and puffy (_____________ weather)

3. Stratus: covers the sky like a blanket (_____________________________)

4. Nimbus: Low Clouds Alto: Middle Clouds Cirrus: High Clouds

III: The Formation of CloudsA. Cloud: a large group of water droplets suspended in _________.

B. Steps involved in cloud formation: ________________________________________________________________________________________________________

____________________(gas to liquid phase change in which water vapor changes to droplets)

1. Describe the mass of air that would lead to cloud formation in terms of temperature, humidity, density._______________________, ________________________, ____________________________

2. The air will __________________ because of ____________________ density.

3. Describe what the air does as it rises:_______________________, ________________________, ________________________

4. Clouds will form if this rising moist air:a. cools to the ___________________ temperature and there by change phase can occur.

b. has ___________________________available, such as dust, pollutants, etc.

Steps involved in cloud formation:-WARM MOIST AIR RISES due to LOW DENSITY-This parcel of air COOLS DUE TO EXPANSION (adiabatic cooling process) -Water vapor CONDENSES when the DEW POINT Temperature is REACHED -Water droplets coalesce AND EVENTUALLY PRECIPITATE

HOT MOIST AIR RISES, EXPANDS, _______ AND THEN CONDENSES! if air is forced to expand, the air will cool down because molecules will not hit into each other as often and energy will dissipate (decrease due to spreading out in all directions) and therefore the energy will disperse into the atmosphere. Once the hot moist air begins to cool, it the water vapor condenses because cold air can not ________ as much water as hot air, thus producing rain.

2. The air descends to the other side of the mountain which is called the _______________________ Summary:DRY AIR SINKS COMPRESSES AND THEN _______. Since all the moisture has been “wrung” out on the windward side the air on the leeward side is dry. Due to gravity and weight this dry air sinks, the force of this sinking air causes air pressure to increase. Since the close air molecules hit into each other more often, more friction between molecules takes place, therefore the air temperature begins to increase again or ____________.

E. Precipitation:

1. Describe what causes precipitation. Precipitation forms around ___________ particles (pollutants) droplets combine (____________________) and therefore become heavier and eventually ___________.

2. Explain why precipitation cleans the atmosphere.As precipitation forms around dust or pollutants…. They are removed from the atmosphere as precipitation falls.

3. When the dew point temperature and air temperature approach each other what happens to the chance of precipitation and why?The chance of precipitation _____________ because the air is more __________________.

IV. Wind: Wind is the horizontal movement of air caused by differences in pressure between two

adjacent air masses. Wind refers to any flow of air relative to the earth's surface in a horizon-tal direction. In meteorology winds are named for the direction that they blow from. This is be-cause although we might have an idea which way the wind will blow, we never know for sure because it has not happen yet and could change direction at any time.

There are two types of winds: local and planetary. Breezes that blow back and forth from a body of water to land areas— land and sea breezes—are examples of local wind. Plane-tary Winds are driven by much larger pressure systems that exist above the tropics and the poles. These great wind belts comprise the earth's atmospheric circulation as a whole.

The ultimate cause of Earth's winds is solar energy. When sunlight strikes Earth's sur-face, it heats that surfaces differently depending on their specific heat, texture and color. Newly turned soil, for example, absorbs more heat than does snow. This uneven heating of Earth's surface, in turn, causes differences in air pressure at various locations. On a weather map, these pressure differences can be found by locating isobars, lines that connect points of equal pressure. The pressure at two points on two different isobars will be different. A pres-sure gradient is said to exist between these two points. It is this pressure gradient that pro-vides the force that drives air from one point to the other, causing winds to always blow from high pressure to low pressure. The magnitude of the winds blowing between any two points is determined by the pressure gradient between those two points. The closer the isobars the steeper the gradient and the faster the wind.

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In many locations, wind patterns exist that are due to local topography and or water masses. In most cases, unusual topographic or geographic features are responsible for influ-encing local wind direction. Land and sea breezes are typical of such winds. Because water heats up and cools down more slowly than does dry land, the air along a shoreline is alter-nately warmer over the water and cooler over the land. These differences account for the fact that winds tend to blow offshore during the evening and on-shore during the day.

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III. Wind: the horizontal movement of air due to differences in air pressure.

A) Winds are described by the direction they ____________________________.

B) Winds distribute energy. They blow from ______________ pressure to ___________ pressure.

C) Fastest winds occur where the isobars are _______________________________________.

Wind!There are two types of winds, regional and local. Regional winds extend over a large area such as several states of the United States. These are called planetary wind belts and are huge global systems. Local winds are those that extend only for a few miles before they die out.

-Wind blows from HIGH PRESSURE TO LOW PRESSURE AREAS.- a difference in air pressure between to places is called a pressure gradient. - A STEEP pressure gradient means that pressure changes quickly, isobars are close together, and wind speeds are high. -A gentle pressure gradient means that pressure changes slowly, isobars are widely spaced, and wind speeds are low.

Convection Currents form in our Atmosphere due to this Unequal heating. Warmer air is less dense and therefore will rise, whereas cold air is more dense and will sink. This is due to the fact that fluids (gas and liquids) tend to layer based on density, with densest fluids beneath less dense fluids. However when cool dense air sinks, it eventually hits the earth’s surface. It has nowhere to go except to flow horizontally across earth’s surface. You experience this phenomenon when you stand in the wind. The cool dense air rushes down and across earth surface to a region where air is rising and needs to be replaced. You might recall this concept from our energy unit, this type of energy transfer is called a convection current.

The Coriolis Effect:1) Winds move from high to low pressure but they do NOT move in straight lines2) The coriolis effect caused by Earth’s rotation, causes winds to be deflected and curve to right in

the northern hemisphere and the left in the southern hemisphere.

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C) The Earth is always trying to achieve ____________________________.

Energy is constantly being re-distributed flowing from ________________ to ______________

How can we decrease pressure without changing our elevation?Increase _______________ and Increase __________________

Low pressure = Warmer and Wet!!!

High Pressure = Cooler and Dry!!!

Poles EquatorTemperature

Pressure

Density

Humidity

V. Convection Cells and Prevailing Winds1) The sun heats the Earth UNEVENLY because the angle of INSOLATION is great near the equator

than at the poles. This creates a TEMPERATURE GRADIENT.

2) Warm air rises because it is less dense, while colder, more dense air sinks. This causes CYCLIC currents in the troposphere called convection cells.

3) Around the Earth, there are several alternatingbands of dry, high pressure air, and humid lower pressure air. Between these bands are the prevailing wind belts. PREVAILING WIND BELTS refer to the common wind direction and speed at a given location and time of year. In New York State, winds blow from the west and southwest more than from any other direction. These winds are called the prevailing westerlies,or southwest winds. Look at the surface winds shownin diagram to the right. Winds are named for the directionfrom which they blow.

4) Look at the two diagrams below. Remember, if the Earth did not rotate, patterns or convection would be simple. Air would descend in high pressure regions and blow directly toward low pressure centers. All winds would be north and south winds. However, the rotation of the Earth causes the wind pattern to be more complex. On a small scale, the winds blow straight but as they cover larger distances, the planet moves underneath them, causing them appear to be deflected. This causes east and west winds. Rotation also causes the formation of six smaller convection cells in the upper atmosphere. Regional weather systems (highs and lows) complicate the matter even more! Winds can come from any direction depending on changes in the pressure gradient.

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Global Wind Patterns:Global air circulation is influenced by:

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Intended

Actual due to Coriolis (rotation)

Planetary Wind Belts:

Planetary Wind Pattern would be simple if the Earth Didn’t Rotate!Cold air would _______________ at the poles and flow along the surface of the Earth toward the ___________________. Air would then warm at the equator and ________________(due to ________________ density)) and flow back to the _________________This would create two great _______________________cells over the Earth

Use your Reference Table page 14 to describe the wind direction for the following latitudes:1) 42 N __________________ 2) 23 ½ N __________________3) 23 ½ S ____________________ 4) 70 N __________________

5) Which planetary wind belt is New York State located? _______________________

6) The Coriolis effect causes winds to curve to the ____________ in the N. Hemisphere.

_________________ Effect causes the winds to be deflected to the _____________ in the Northern Hemisphere and to the _____________ in the Southern Hemisphere. This causes the two convection cells to break into __________ convection cells. See Reference Tables page 14. Label converging and diverging zones

*** If the Earth didn’t rotate, cold air would form over the poles and flow along the surface toward the Equator. Air would then warm at the equator and flow back to the poles. This would create two giant convections cells over the earth.

*** However due to the Earth’s rotation the two convection cells break into six! See page 14 in ESRT

-Rising hot air and sinking cold air-Earth’s rotation, through the Coriolis effect.-The result of these influences is the…

Three Cell Circulation Model:-Each hemisphere has 3 zones, or cells, of circulation-The boundaries are latitudes of 0º, 30º, 60º and 90º -Patterns are due to alternating bands of H and L pressure.-Wind patterns are different in each cell and are called…

Prevailing Winds: (Highlight the words naming these winds in YELLOW)-The term prevailing winds belts refers to the general direction of wind in each cell. -Winds are named for the direction from which they come.-Prevailing winds flow from high pressure bands to low pressure bands, and are deflected by the Coriolis effect.

Zones of Convergence (Highlight these in BLUE)Low pressure bands are called zones of convergence because air flows toward them.Air is hot and humid and there is little or no wind.Historically called the doldrums, because sailing ships could be stranded for days.

Zones of Divergence (Highlight these in PINK) High pressure bands are called zones f divergence, because air flows away from them.Cooler, dry air & many deserts found in these zones.Historically called the horse latitudes.

Trade Winds are the same as Strong Prevailing Winds! (Highlight these in GREEN)The Trade Winds are a zone of steady, strong wind, between the doldrums and the horse latitudes.They are named trade winds because sailing ships would use them as trade routes.

Jet Streams: (Highlight these in ORANGE) Jet streams are narrow bands of fast moving, high-altitude wind which separates the cold polar air from the warmer air to the south. Jet stream blow from the West to the East and circle the planet at about 200 mph. Airlines have to think about these winds when planning their flight paths. You can cut about one half hour off your travel time if you fly from west to east with the jet stream. You can plan to lose time if you hit one going the other way from east to west. Jet streams wander and can give rise to weather systems and steer their movement.

Local Wind: Caused by the unequal heating of land and water. This creates density difference!

Coastal Breezes:When large areas of land an water are adjacent, temperature differences can create winds that easily observed. By the coast, wind direction can reverse on a daily cycle due to the difference in specific heats between the land and the water

SEA BREEZE:

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On a sunny day, land heats up quicker than water because land has a lower specific heat. Radiation and conduction from the lands surface heat the air over the land. This heated air expands and becomes less dense causing it to rise. The result is a breeze that comes from the water to replace the rising air over the land. Sea breezes are light winds that blow from the water to the land. The breeze will continue until the land cools in the evening.

LAND BREEZE: During the night, land cools off quicker than water because land has a lower specific heat. When the land cools, the air above the land also cools. The air over the water is now warmer than the air over the land, so the air above the water begins to rise. This causes the wind to change direction, blowing from the land to the water.

MonsoonsMonsoons are seasonal changes in the direction of the prevailing winds. They are similar to land and sea breezes but last for months and move over greater distances. Rainfall in India depends on these seasonal changes. During the winter, high pressure air over Asia brings dry wind to India, making rain scarce. In the summer, warm, low pressure air over Asia draws in moist wind from the Indian Ocean bringing rain to India.

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Wind Influence on Ocean Currents:

VI. How air masses and fronts influence the weather:An Air Mass: is a large body of air (in the troposphere) with similar reading (amounts) of

_____________________, ______________________and ________________________

Where Air Masses Come From:A. Regions where air masses come from are called ____________________ ____________________B. List the characteristics that an air mass picks up from its place of origin:

1. ______________________ 2. __________________________

C. If the air mass forms at a high latitude (nearer the poles), it will have a____________ temperature.

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Ocean Currents: Most interactions between the oceans and the atmosphere are not understood. It is known, however, that ocean currents are caused by the wind. Winds blow over the ocean, causing surface water to drift along with them. Moving water piles up, creating pressure gradients within the water. These pressure gradients produce currents that transfer heat from the equator to the poles. As surface water drifts away with the wind, cold nutrient rich water from below rises in a process called upwelling. This also is an example of heat transfer. The oceans have a huge capacity for storing heat energy. As they slowly warm, they also slow the rate at which the atmosphere warms.

D. If the air mass forms at a low latitude ( nearer the equator), it will have a ___________ temperature

E. If the air mass originates over water it will be ___________________

F. If the air mass originates over land it will be ____________________

Using page 13 in your E.S. reference tables complete the chart below

Symbol Origin ( where it formed) Describe the air mass

continental

maritime

tropical

polar

arctic

Air Mass Track: the _______________ an air mass takes as it travels. In general, air masses and weather systems move toward the ___________ over the U.S. because the U.S. is located in the __________________ wind belt.

Air Masses: The map below shows the source regions for air masses that affect North America. The gray area is the North American continent. The white areas are oceans and other bodies of water. Use the Air Mass symbols key on page 13 of your ESRT to properly name each of the numbered air masses. Your answers must be CASE SENSITIVE (use the proper upper and lower case letters)!

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Describe the temperature and moisture characteristics for each of the air masses numbered in the diagram (#1 is done for you):

1. cold and moist

2.

3.

4.

VII. Fronts: the boundaries between two air-masses-Usually ___________________-Often produce _____________________________________________________________

Front Symbols (draw front symbols on lines provided)The Half circles and the triangles point in the direction of the air masses and front are moving.

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___________ 4. A Stationary Front: occurs when a warm air-mass and a cold-mass are side by side with neither air mass moving. Weather is similar to that of a warm front. Note gentle interface slope

*Note: Generally, at fronts between air masses that have different temperatures, Warm air will ________. This creates unstable weather conditions, and produces much of the ____________

that falls on the continental United States.

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___________ 1. A Cold Front: is the interface between an advancing (moving forward) cold air mass and stationary slow moving warmer air. The cold air pushes the warmer air up producing cumulous clouds and short but violent thunderstorms. During this abrupt weather change winds shift from southerly to northerly. Note the steep slope of the interface.

___________ 2. A Warm Front: the interface between an advancing warm air mass and a retreating mass of ________________________ air. When this warm air meets and rises over the cold air on the ground, it causes extended periods of precipitation. Note the long gentle slope of the interface.

___________ 3. An Occluded Front: occurs when a faster moving cold front overtakes a slower moving warm front and completely lifts the warmer air off the ground.

A to C 12 –24 hours

D can last for 3 – 4 days

Mid-latitude Cyclones- Begins when cold air pushes down from the north, changing a stationary front into a pair of

warm & cold fronts moving around a low pressure center.- As the low moves eastward, the cold front overtakes the slower-moving warm front, producing

an occluded front.- In general these low pressure systems move toward the NORTHEAST in the United States

VIII. Station Models & Synoptic Weather MapsAtmospheric variables are collected from thousands of weather stations around the world four times each day.1. Station ModelProvides a summary of the current atmospheric conditions in an area.

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Change from abbreviated form:(Decode to read off station model)999 ____________370 ____________

Change the following to abbreviated form:(ENCODE to place on station model)

1028 ____________

998.1 ____________

The Barometric Pressure on a Station Map is in code… The number 9 or 10 has been omitted from the front. Rule for converting the code into millibars:1. 887 = _____ if the first digit is 5 or greater add ________ and place a decimal point before

the last digit.

2. 165 = _____ if the first digit is less than 5 add ________ and place a decimal point before the last digit.

Construct the following Station Model:75% cloudswinds from the N.W.wind speed 35 knotsair temperature 28F, dew point temp. 20Fvisibility 5 milesbarometric pressure 1032.5barometric trend -1.1 and still fallingpresent weather is snow

Construct the following Station Model:Cloud cover: 50 %Air temp = 20°CAir pressure = 996 mbDew point temperature = 18 °C Wind speed 25 knotsWind direction SWAdd Rain and A steady 1.9mb rise in the past 3 hours, still rising.

Read the station model below:

Wind Speed:____ Direction: ___Temperature:___ C ___ F __ KDew Point: ___ C ____ FCloud Cover:____ Pressure: ___ mb ___ inchesCurrent Weather: _________

1 2 3

City 2-Temperature- warm, steady-Pressure- steady-Precipitation- none, but humid

City 1 -Temperature- decrease

-Pressure- increase -Precipitation- brief, heavy, thunderstorms.

- Cyclones are “driven” by heat energy released by condensation, causing the low pressure to be-come even lower, thereby strengthening the winds.

- In summer, cyclones move about 800km a day, while in winter they move about 1,100 km a day. A mid-latitude cyclone may cover as much as one-half of the entire continental United States at one time.

Sequence of events if you were to experience the passing or a mid-latutide cyclone:1. Warm front would approach and bring a long period of light precipitation.2. Then you would have a period of clearing and warm humid weather3. The cold front would arrive with brief heavy showers, followed by clearing and cooling

Sequence of events if you were to experience the passing or a mid-latutide cyclone:

City 3-Temperature- increase-Pressure- decrease-Precipitation- light, steady, long lasting rain

IX. Synoptic Weather Maps:

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A Synoptic Weather Map is an extremely useful tool used by meteorologists to predict the weather. These maps analyze large-scale weather systems, particularly high- and low-pressure systems and hurricanes. The word “Synoptic” comes from the Greek meaning “at the same time.” Therefore a synoptic weather map summarizes several weather variables that are occurring simultaneously (at one particular time).

Weather variables that can be gathered using a synoptic weather map include:- Likelihood of precipitation due to the presence of high and low pressure systems.- Wind direction and velocity using isobars and pressure gradient- Local weather and cloud cover indicated by station models- Air mass tracks and the movement of frontal boundaries associated with mid-latitude

cyclones.

The primary reason that our society invests so much money and time into Meteorology is so that people can prepare for rain or severe weather! Don’t you want to know if you should plan a nice beach trip or if you should stay in and read a book? So let’s first look at the process the causes precipitation to occur.

Moral of the story: in order for precipitation to occur there must be upward vertical movement of moist air! Lows Pressure Systems and Fronts on a Synoptic Weather Map indicate this vertical

movement of air.

Did you know that "Synoptic" comes from the Greek meaning

"at the same time". So a Synoptic weather map allows us to view many weather variables

that are occurring simultaneously

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Large Scale Weather Systems: Low and High Pressure Systems

Whenever you watch the weather channel you will often see giant red “L’s” and blue “H’s” over different parts of the U.S. on a synoptic weather map. This indicates the vertical movement of air and the weather that results from it.

In a low pressure system, air is rising. We can model this using our hand above our head. If you move your hand upward away from the top of your head, you will not exert pressure. Remember rising moist air leads to cloud development and bad weather!

However in a High pressure system, air is sinking. This can also be modeled using your hand. If you lower your hand toward your head, allowing your hand to “sink” you will exert a high amount of pressure. Sinking air is associatedwith good weather (no precipitation) so give your friend next to you a “HIGH FIVE” for nice weather! (PUN INTENDED)

This vertical movement of air is best visualized using a atmospheric cross section like the one below:Highs and Lows on a Synoptic Weather

Map:

When examining a synoptic weather map… we are viewing earth from an aerial view, as if in a plane looking down on Earth. The surface winds will always flow from High Pressure to Low Pressure. This makes sense since sinking air in a high pressure system will hit the ground and have no choice but to move horizontally along the surface toward a low pressure system, where it can replace rising air. This cycle of air movement is known as a convection current and is due to density differences.

Surface winds move toward lows and away from highs. The greater pressure gradient the faster the winds will blow. Therefore, closely spaced isobars indicate fast winds.

A. Portions of the troposphere with low pressure centers are called LOWS or CYCLONES. Wind direction in a low pressure air mass (in the Northern Hemisphere) is COUNTERCLOCKWISE AND toward it’s center. Lows are usually associated with RAINY weather (Low and Lousy). Draw three arrows to indicate the surface wind direction.

B. Portions of the troposphere with high pressure centers are called HIGHS Or ANTICYCLONES. Wind direction in a high pressure air mass (in the Northern Hemisphere) is CLOCKWISE away from it’s center. Usually associated with FAIR weather (High and Dry! High Five). Draw three arrows to indicate the surface wind direction.

Application Questions:

In summary the presence of Low pressure systems and High pressure systems on a Synoptic Weather map enable a meteorologist to predict the probable chance of precipitation on a large scale map.

Directions: Draw the following onto the Synoptic Weather Map on the next page and answer the questions. Label the cold front, the warm front and the occluded front (USE Your ESRT). Remember the

combination of these fronts surrounding a Low is called a Mid-Latitude Cyclone.

Find and label the mT air mass associated with this Mid- Latitude Cyclone. Is there a high probability that it is raining here? _____ Describe the temperature and humidity of this mT air mass. ________________ & ______________

Place a red “x” over the area experiencing the greatest wind speeds. Site the evidence shown on the map that enabled you to determine this location:________________________________________________

Draw a green arrow to indicate the wind direction between the High and Low on the Map. Name this wind: ____________________

With a blue pencil, shade the area on the map that is most likely experience precipitation.

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Bonus Question:In what compass direction will the center of this Mid- Latitude Cyclone most likely move if it follows a normal storm track. (Hint use the planetary wind diagram on page 14 in your Reference table)

X. Storms and Severe WeatherA storm is violent episode of heavy precipitation, strong wind, lightning and the danger of flash floods. Most storms are associated with low-pressure systems, rising warm air, clouds and precipitation.

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Types of storms include: Mid-latitude or cyclonic Storms: Movement of air masses along the polar front can result in the formation of Mid-latitude cyclones with LOW pressure. The counter-clockwise rotation of the air is the result of the earth’s rotation,Which is known as the ___________________________ effect.

Hurricanes: In late summer and early fall LOW pressure centers form over warm tropical ocean water. Winds can exceed 74 miles per hour. Hurricanes have high winds, high waves, flooding from rain and storm surges of ocean water along coastlines. If you are in the path of a hurricane you should have food, water and all necessary supplies and stay indoors. If you live in a flood prone area you should go to an emergency shelter. Board up windows. Bring in outdoor objects that could blow away. Make sure you know which county or parish you live in. Know where all the evacuation routes are.

Thunderstorms: Usually form along a cold front producing heavy rainstorms accompanied by thunder and lightning. Thunderstorms may have strong wind, hail, deadly lightning and produce flash flooding. People in the path of a thunderstorm should seed shelter indoors, close all windows stay off the phone, turn off appliances and stay away from flood areas. Stay away from trees if there is no shelter around you.

Tornadoes: rapidly rotating, extremely LOW pressure funnel that hangs down from thunderstorm clouds. They form when very cold air meets very warm air. Tornadoes are most common in the Midwest where cold, dry air from Canada meets warm, moist air from the Gulf of Mexico. The tornadoes may stay on the ground for a few minutes or a few hours. The path of the Tornado is unpredictable. The greatest danger to humans from a tornado is flying debris picked up by extremely strong winds. People in the path of a tornado should seek low shelter immediately or go into or under a sturdy structure. Go to a basement. If you do not have a basement, go to an interior room without windows on the lowest floor such as a bathroom or closet. If you can, get under a sturdy piece of furniture, like a table. Have a disaster plan. Make sure everyone knows where to go in case a tornado threatens. Prepare a disaster supplies kit.

Blizzards: associated with heavy snow and winds. Drifting snow can stop transportation. An ice storm can disrupt electric and phone services. Ice storms can occur suddenly as rainfall begins to freeze. There is a danger of frostbite and hypothermia. People should stay indoors, not drive, stay warm and have food, water and medical supplies available.

Emergency Preparedness for Storms:Describe 4 ways you can prepare for a storm.____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

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Climate:XI. CLIMATE: Average long term condition

of the atmosphereI. Latitude & TemperatureLocations at low latitudes have HIGH average temperatures Locations at high latitudes have LOW average

temperatures

II. Latitude & Moisture

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HurricanesA hurricane is a huge storm! It can be up to

600 miles across and have strong winds spiraling inward and upward at speeds of 75 to 200 mph. Each hurricane usually lasts for over a week, moving 10-20 miles per hour over the open ocean. Hurricanes gather heat and energy through contact with warm ocean waters. Evaporation from the seawater increases their power. Hurricanes rotate in a counter-clockwise direction around an "eye." The center of the storm or "eye" is the calmest part. It has only light winds and fair weather. When they come onto land, the heavy rain, strong winds and large waves can damage buildings, trees and cars.

Hurricanes only form over really warm ocean water of 80°F or warmer. The atmosphere (the air) must cool off very quickly the higher you go. Also, the wind must be blowing in the same direction and at the same speed to force air upward from the ocean surface. Winds flow outward above the storm allowing the air below to rise. Hurricanes typically form between 5 to 15 degrees latitude north and south of the equator. The north easterly prevailing winds bring these hurricanes westward from the ocean onto the land. The Coriolis Force is needed to create the spin in the hurricane and it becomes too weak near the equator, so hurricanes can never form there.

TornadoesAlthough tornadoes occur in many parts of the world, these destructive forces of nature are found most frequently in the United States. They most often occur to east of the Rocky Mountains during the spring and summer months. In an average year, 800 tornadoes are reported nationwide, resulting in 80 deaths and over 1,500 injuries. A tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long. Once a tornado in Broken Bow, Oklahoma, carried a motel sign 30 miles and dropped it in Arkansas!

They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider sense, to name any closed low pressure circulation.Thunderstorms develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes. Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather pattern. Several states may be affected by numerous severe thunderstorms and tornadoes.

Where there is low pressure, near the EQAUTROR and at mid-latitudes (60°N & 60S °)…Air rises, expands, cools and CONDENSES… which leads to PRECIPITATION.

This results in a HUMID climate. At high pressure belts, (near 30°N & 30S °), the air SINKS and temperatures RISE…This results in an ARID (dry) climate.

III. Latitudinal Climate Patterns:The combined effect of temperature and moisture results in a distribution of 4 major climate

types around the world.These Climate Types are:

a) HUMID >1.2 b) SUBHUMID .8-1.2c) SEMIARID 0.4-0.8

d) ARID <0.4

Climate zones are based on the ratio between :PRECIPITATION (P ) and POTENTIAL EVAPOTRANSPIRATION (EP)

Potential evapotranspiration depends on temperature (INSOLATION)

IV. Effect of Large Bodies of Water on Climate:Large bodies of water modify (change) the climate of an area because of the SLOW heating up

and cooling off of the water.

Summary: (for the same latitude)-MARINE CLIMATES: have COOLER summers and WARMER winters and a SMALLER range of

annual temperatures. -CONTINENTAL CLIMATES: have HOTTER summers and COLDER winters and a LARGER range of annual temperatures.

V. Effect of Large Land Masses on Climate: Because land heats up and cools off faster than water, temperatures over a CONTINENT (in mid-latitudes) are WARMER than the oceans in the summer and COLDER in winter.

VI. Storm Tracks & Climate:In the mid-latitudes (including the continental U.S.) temperatures & moisture are affected by a

succession of low pressure (storm) systems. Generally, these storm centers follow a WEST to EAST path across the Continental U.S.

VII. Ocean Currents & Climate: SEE Reference Table!!!Coastal climates are modified by ocean currents, for example, a cold ocean current will cause

a coastal area to have COLDER temperatures, and LESS precipitation. Currents flowing away from the equator carry WARMER water to higher latitudes. Currents

flowing toward the equator carry COLDER water to lower latitudes.

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VIII. Elevation & Climate:The higher the altitude ( at any given latitude), the COLDER it is.

Questions:1. Why do areas at higher altitudes have less precipitation than lower altitudes?

_________________________________

2. What is the climate type of an area with an annual precipitation of 1089 mm. of water and a potential evapotranspiration rate of 865 mm. of water?

3. What factors affect the potential evapotranspiration rate of an area? _________________________________________________________________________________________________________

___________________________________________________________________________________________________________________________

4. Which side of a mountain has a more humid climate? _________________________________________________________________________________________________________

___________________________________________________________________________________________________________________________

5. List the factors which effect the climate :____________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Use your Reference Table page 14 to describe the wind direction for the following latitudes:6. 42 N __________________ 7. 23 ½ N __________________8. 23 ½ S ____________________ 9. 70 N __________________

10. Which planetary wind belt is New York State located? _______________________

11. The Coriolis effect causes winds to curve to the ____________ in the N. Hemisphere.

12. The Coriolis effect causes winds to curve to the ____________ in the S. Hemisphere.

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El Nino & La Nina:

Lake Effect Snow:Lake-effect snow is produced during cooler atmospheric conditions when cold winds move across long expanses of warmer lake water, providing energy and picking up water vapor which freezes and is deposited on the leeward shores.

The most likely setting for this localized type of snowfall is when very cold Arctic air rushes over warmer water on the heels of a passing cold front, as often happens in the Great Lakes region during winter.

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La Nina refers to the normal Oceanic Circulation of the Pacific Ocean:Cold water comes up from the depths of Antarctica and travels up beside Peru. It brings nutrients up to the surface and the fishing is good. The sinking high pressure zone above the water pushes down onto the cooler currents emerging from below. This forces the water and the air to the west, since the surface of the ocean is joined to the bottom of the air. The water is an easterly current going to the west pushed along by the easterly winds. Easterly winds bring moisture from the sea and by the time they arrive on the Australian coast they are rain-laden.

El Nino:

El Nino is a regularly occurring climatic feature of our planet. Every two to five years, El Nino reappears and lasts for several months or even a few years. El Nino takes place when warmer than usual sea water exists off the coast of South America. This causes the easterly winds to reverse or weaken and become westerly winds. El Nino causes climate effects around the world.Peruvian fishermen noticed that the arrival of El Nino often coincided with the Christmas season so named the phenomenon after the "the baby boy" Jesus. The warmer water of El Nino reduced the number of fish available to catch. The warm water that causes El Nino is usually located near Indonesia during non-El Nino years. However, during periods of El Nino the water moves eastward to lie off the coast of South America.

El Nino increases average ocean surface water temperature in the region. This mass of warm water is what causes climatic change around the world. Closer to the Pacific Ocean, El Nino causes torrential rains across the west coast of North America and South America.

Winds accompanying Arctic air masses generally blow from a west or northwest direction, causing lake effect snow to fall on the east or southeast sides of the lakes.

Whether an area gets a large amount of snow from lake effect is dependent on the direction of the winds, the duration they blow from a particular direction, and the magnitude of the temperature difference between the water and air.

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