Weather...

You can’t see me, but you feel me, you can’t touch me, but I can touch you. I have been called the “Breathe of the Gods”, or the killer and giver of life, gentle and fierce, friendly and enemy, angry and happy. The Native Americans called me Moriah, and Snow Eater (Chinook). The Japanese call me Kaze and in Russia I am called Veter. I can shatter homes, or wake a child from a peaceful sleep or bring relief in times of need. I can spread the most dreaded diseases or bring a welcome freshness. What am I?

Weather is....

The current state of the atmosphere...what is happening right now

BUT… Climate is differentClimate – longer time scale (the average

conditions , temperature, humidity, rainfall, winds, and other meteorological elements over a long period of time

Main points to remember as we learn about weather:

The sun warms the earth’s surface and therefore all the air above the surface

The earth is warmed most at the equator and least at the poles---why?

The air above land is warmed more quickly than air above water.

Warm air expands and rises, creating an area of low pressure; cold air is dense and sinks, creating an area of high pressure

What are weather What are weather variables?variables?

TemperatureTemperature Barometric (air) pressureBarometric (air) pressure Wind speed/ Wind DirectionWind speed/ Wind Direction Humidity (Relative humidity)Humidity (Relative humidity) PrecipitationPrecipitation

The Station ModelThe Station Model

Weather Factors

Weather: The state of the atmosphere at a specific time and place

TEMPERATURE= the average motion of molecules↑ TEMP= ↑movement of molecules= feels hot

↓ TEMP= ↓movement of molecules= feels cold

Instruments to measure Instruments to measure weather variablesweather variables

TemperatureTemperature

Measured with a Measured with a thermometerthermometer

2 common scales are 2 common scales are Farenheit*** and CelciusFarenheit*** and Celcius

Air Pressure- the force exerted by a column of air at a given point

Warm air= expanding or rising air= leaves behind L pressure

Cold Air=sinking air= leaves an area of H pressure

The higher the altitude… the lower the pressure

Air PressureAir Pressure Air pressure (H or Air pressure (H or

L) is measured L) is measured with a device with a device called a called a barometerbarometer

Units of pressure: millibars and inches of mercury

Air pressure rulesAir pressure rules

When air pressure is noted on station When air pressure is noted on station model as greater than 500, we place model as greater than 500, we place a 9 in front of the number and a a 9 in front of the number and a decimal point at the tenths place. Ex decimal point at the tenths place. Ex 506 = 950.6 mB of air pressure506 = 950.6 mB of air pressure

When the air pressure is noted as less When the air pressure is noted as less than 500, we place a 10 in front of the than 500, we place a 10 in front of the number and a decimal at the tenths number and a decimal at the tenths place Ex 467 = 1046.7 mB of air place Ex 467 = 1046.7 mB of air pressurepressure

Trends in Atmospheric Trends in Atmospheric PressurePressure

If the pressure is falling… stormy If the pressure is falling… stormy weather lies ahead weather lies ahead

If the pressure is rising… clear If the pressure is rising… clear skies are comingskies are coming

Wind -moving air Direction and speed are needed to describe the

wind Wind direction is the direction that wind is

blowing from Wind moves from High Pressure to Low Pressure Large pressure gradient= strong winds The The knotknot is a unit of speed equal to one is a unit of speed equal to one

nautical mile per hour, which is equal to exactly nautical mile per hour, which is equal to exactly 1.852 km/h and approximately 1.151 mph1.852 km/h and approximately 1.151 mph

What causes winds? A wind is a A wind is a

horizontal horizontal movement of air movement of air from a area of from a area of high pressure to high pressure to an area of low an area of low pressurepressure

It is this It is this difference in difference in pressure that pressure that makes the air makes the air move=windmove=wind

Winds are measured by direction and speed

The anemometer is the tool we use to measure this

Wind chill=↑ cooling the wind causes

Wind speedWind speed

Wind speed is Wind speed is measured using an measured using an anemometeranemometer. Speed is . Speed is measured in mph or measured in mph or knots (1.15 mph = 1 knots (1.15 mph = 1 knot)knot)

Feathers are used to Feathers are used to show wind speed on a show wind speed on a station modelstation model

Wind directionWind direction

Wind direction is Wind direction is found by using a found by using a wind vane.wind vane.

Wind direction is Wind direction is always always described as the described as the direction FROM direction FROM which the wind which the wind movedmoved

Local WindsLocal Winds The land cools and heats faster than the

ocean. Water holds heat longer than land, and takes longer to heat or cool.

SEA BREEZE During the day, the land gets hotter faster than the water. The heated air rises, leaving behind an area of low pressure. Wind from the cooler sea blows in to take the place of that warmer air. These happen during the day!

Land BreezesLand Breezes At night the lands cools off faster

than the sea. Cool air sinks creating an area of high pressure. Wind blows from the land to the sea.

Wind Speed and IsobarsWind Speed and IsobarsIsobars- Isolines of equal pressure

The larger the pressure gradient the faster the

The closer the isobars the faster the wind

Coriolis deflects winds to the Coriolis deflects winds to the right in the northern right in the northern hemispherehemisphere

Wind speed (con’t)Wind speed (con’t)

Draw the tail feather Draw the tail feather on a station modelon a station model

A. A 5 knot wind blows from the NA. A 5 knot wind blows from the N B. A 10 knot wind blows from the NB. A 10 knot wind blows from the N C. A 15 wind blows from the NC. A 15 wind blows from the N D. A 20 knot wind blows from the ND. A 20 knot wind blows from the N E. A 30 knot wind blows from the NE. A 30 knot wind blows from the N F. A 35 Knot wind blows from the NF. A 35 Knot wind blows from the N G. Repeat A-F for a Southerly Wind, a North Easterly Wind and a G. Repeat A-F for a Southerly Wind, a North Easterly Wind and a

South Westerly WindSouth Westerly Wind

Humidity

-the amount of water vapor in the air (mass of water vapor/total mass of air)

The hotter the air… the more water vapor it can hold

Relative Humidity -the amount of water vapor in the air

compared to what the air can hold (before the air is saturated)

Relative humidityRelative humidity is defined as the ratio of is defined as the ratio of the water vapor compared to the amount the water vapor compared to the amount of water vapor that the water could hold. of water vapor that the water could hold. Relative humidity is expressed as a Relative humidity is expressed as a percentagepercentage

High relative humidity= muggy feel or rain

Relative HumidityRelative Humidity

Relative humidity Relative humidity is described as is described as the amount of the amount of water vapor in the water vapor in the air compared to air compared to the total it can the total it can hold. (ex. sponge)hold. (ex. sponge)

Measured with a Measured with a sling sling psychrometerpsychrometer

Relative Humidity

-the amount of water vapor in the air compared to what it could hold Dry air= 0% Saturated = 100%

The hotter the air… the more water vapor it can hold

Dew Point

-the temperature at which water vapor condenses out of the air

- the temperature at which air is saturated

Dew in the moring

The hotter the air… the more water vapor it can hold

Dry air is more dense than Dry air is more dense than moist airmoist air

Humid air is less dense than dry air Humid air is less dense than dry air because a molecule of water (mass because a molecule of water (mass =1+1+16 ≈ 18 ) is less massive =1+1+16 ≈ 18 ) is less massive than a molecule of nitrogen than a molecule of nitrogen (mass= 14 +14 ≈ 28) and a (mass= 14 +14 ≈ 28) and a molecule of oxygen (16+16 ≈ 32). molecule of oxygen (16+16 ≈ 32).

Pressure and Moisture also have an inverse relationship

ReviewReview

As altitude, As altitude, temperature and temperature and moisture increasesmoisture increases, ,

density and density and pressure decreasepressure decrease

Cloud Formation Clouds form when water

vapor condenses on aerosols (dust, salt particles in the air) Factors needed for cloud

formation… The temperature in which

condensation begins is called the dew point

TYPES OF CLOUDS

Cirrus Clouds: wispy, feathery clouds Form only at high

levels, therefore are made of ice crystals

Types of Clouds

Cumulus Clouds: are puffy white cotton ball looking clouds

Cumulonimbus Clouds

These are thunderstorm clouds

Types of Clouds

Stratus Clouds: clouds that form in flat layers- cover all or most of the sky and are low level clouds

PrecipitationPrecipitation FALLING FALLING

LIQUID OR LIQUID OR SOLID WATER SOLID WATER FROM CLOUDS FROM CLOUDS (RAIN, (RAIN, DRIZZLE, DRIZZLE, SNOW, SLEET SNOW, SLEET FREEZING FREEZING RAIN, HAIL)RAIN, HAIL)

PrecipitationPrecipitation

A A rain gauge rain gauge is is used to measure used to measure the amount of the amount of precipitation over precipitation over a period of timea period of time

Types of precipitationTypes of precipitation Rain- Falls from clouds above Freezing and air Rain- Falls from clouds above Freezing and air

above freezingabove freezing Drizzle- Small precipitation <0.5 mmDrizzle- Small precipitation <0.5 mm Snow- Falls from clouds below freezing and air Snow- Falls from clouds below freezing and air

below freezingbelow freezing Sleet- Falls from clouds above freezing but air Sleet- Falls from clouds above freezing but air

below freezingbelow freezing Hail-up and down movement of rain in clouds Hail-up and down movement of rain in clouds

multiple freezing as altitude goes up and downmultiple freezing as altitude goes up and down Freezing Rain-Hail-Falls from clouds and air above Freezing Rain-Hail-Falls from clouds and air above

freezing but ground below freezingfreezing but ground below freezing

Haze, Fog and Smog are Haze, Fog and Smog are NOT forms of NOT forms of PRECIPICATIONPRECIPICATION

Problem Set 3Problem Set 3

Identify the forms of precipiationIdentify the forms of precipiation

Reading a weather map

ISOBAR= connects areas of equal pressure BAR comes from BARometric pressure

Reading a weather map...

Isotherm: Connects areas of equal temperature; therm means temperature

Aim Masses &Aim Masses & Source Source RegionsRegions

Air Mass is an extremely large body of air whose properties of temperature and moisture content (humidity), at any given altitude, are fairly similar in any horizontal direction.

Source Regions are simply geographic areas where an air mass originates. Should be: uniform surface composition - flat light surface winds

Air Mass ClassificationAir Mass Classification4 general air mass classifications categorized according to the source region. polar latitudes P - located poleward of 60 degrees north and south

tropical latitudes T - located within about 25 degrees of the equator

continental c - located over large land masses--dry

marine m - located over the oceans----moist

Types of Air MassesTypes of Air Masses

cP continental polar cold, dry, stable cT continental tropical hot, dry, stable air aloft--unstable surface air mP maritime polar cool, moist, and unstable mT maritime tropical warm, moist, usually unstable

Air masses are masses of air that have the same characteristics of the surface over which it develops

Pressure Systems descending (going down)=H

pressure ascending (going up)=L pressure

Air Masses

Fronts: Fronts: the boundary between 2 air masses

Warm Front: warm air slides over departing cold air- large bands of precipitation form

This is the symbol on a map for a warm front

Cold Fronts

Cold air pushes under a warm air mass. Warm air rises quickly=narrow bands of violent storms form

This is the symbol for a cold front

Occluded Front

2 air masses merge and force warm air between them to rise quickly. Strong winds and heavy precipitation will occur

This is the weather map symbol for an occluded front

Stationary Front

Warm or cold front stops moving. Light wind and precipitation may occur across the front boundary

This is the weather map symbol for a stationary front

Problem Set Problem Set

What type of weather is associated with each type of front

Draw the symbol for each front

Wind blows from high Wind blows from high pressure areas to low pressure areas to low pressure areaspressure areas

The pressure gradient and coriolis The pressure gradient and coriolis force cause low’s to spin counter force cause low’s to spin counter clock-wise and highs to spin clockwiseclock-wise and highs to spin clockwise