Atmospheric Moisture and PrecipitationAtmospheric Moisture and Precipitation

More WeatherMore Weather•_______________________-_______________________- The The

condition of the atmosphere at a condition of the atmosphere at a certain place and time.certain place and time.

• When talking about weather, you are When talking about weather, you are actually describing what is happening actually describing what is happening in the_________________________________.in the_________________________________.

• Weather is constantly changing.Weather is constantly changing.• Without the_______________________, Without the_______________________,

there would be no weather!there would be no weather!

Factors Of WeatherFactors Of Weather

• These are the most important factors These are the most important factors that influence weatherthat influence weather– ________________________________________________________________________– ________________________________________________________________________– ________________________________________________________________________– ________________________________________________________________________

________________________________________________

• Remember the water cycle, the sun Remember the water cycle, the sun causes_________________________________, causes_________________________________, which bring moisture to the air. which bring moisture to the air.

• The amount of water vapor in the air The amount of water vapor in the air is___________________________________.is___________________________________.

• This varies from day to day.This varies from day to day.

• The amount of water vapor the air can The amount of water vapor the air can hold depends on the temperature of the hold depends on the temperature of the air. air.

Humidity

_________________________________: compares the amount of water vapor present in the air to the maximum amount that the air can hold at that temperature

Expressed as a _____________________:

At 100% relative humidity, air is saturated.

Humidity

Relative Humidity changes when:

1. Atmosphere gains or loses water vapor

•Evaporation

2. Temperature changes

•__________________________________ relative humidity rises

•__________________________________ relative humidity decreases

•Thus, warmer air can hold more water vapor than cooler air.

__________________________________________________

• Example: If you hear a meteorologist say Example: If you hear a meteorologist say that the relative humidity is that the relative humidity is ________________,that means that the air on ________________,that means that the air on that day is only holding 50% of the water that day is only holding 50% of the water vapor is capable of holding.vapor is capable of holding.

• When air is holding all of the moisture it When air is holding all of the moisture it possibly can- that means it is said to be possibly can- that means it is said to be saturated saturated . Thus, saturated air has 100% . Thus, saturated air has 100% humidity. humidity.

• We are very sensitive to humidity. _____________________________________keeps our body cool and maintain its current temperature.

• If the air is at 90% relative humidity, ____________________________will not evaporate into the air. As a result, we feel much hotter than the actual temperature when the relative humidity is high.

• If the relative humidity is_______________, we can feel much cooler than the actual temperature because our sweat evaporates easily, cooling the body.

Relative Humidity

How relative humidity (RH) is measured?Wet- and Dry Bulb__________________________

• It consists of two identical _______________________thermometers,

one of which has a wet cotton or linen wick around its bulb.

• Evaporating water from the wick absorbs heat

from the thermometer bulb, causing the thermometer reading to drop.

• The difference between dry-bulb and wet-bulb temperatures is compared on psychrometric charts.

Relative Humidity

How relative humidity (RH) is measured?Wet- and Dry Bulb ________________

Wet - and Dry Bulb Psychrometer

Relative Humidity

How relative humidity (RH) is measured?

Wet- and Dry Bulb Psychrometer Psychrometric Chart.

If the difference between wet and dry bulb is 6º F and the temperature is 72º F (dry bulb), then the RH is 54%.

Relative Humidity

The “Dry Bulb”The “Dry Bulb”

• Don’t let it fool Don’t let it fool you. It is just a you. It is just a thermometer.thermometer.

• It measures the It measures the _________________t_________________temperature.emperature.

• Duh!Duh!

20°C

The “Wet Bulb”The “Wet Bulb”

• Has a little wet Has a little wet booty tied to booty tied to the bottom.the bottom.

• Gets cool when Gets cool when water water evaporates.evaporates.

12°C

Wet Booty

Dry-bulb temperature is your air temperature.

The formula for calculating Relative Humidity is as followed:

________ Temperature

_

________Temperature

=

Difference Between Wet and Dry Bulb Value.

Then compare results on the chart First, look for the Dry Bulb Temperature on the left.

Example= 20 °C

14 °C

4 °C

Subtract (the difference) between the dry bulb and wet bulb

14°C20°C

20-14=6

16°C18°C

18-16=2

8°C20°C

20-8=12

Put it all together

Relative Humidity = 11%

10°C14°C

14-10=4

Relative Humidity = 60%

•______________________: temperature at which air with a given humidity will reach saturation when cooled without changing its pressure.

•The dew point temperature is the ________________________for really measuring the amount of moisture in the air. It tells you the temperature in which “dew” will start to form. Meaning its saturation point.

Humidity

10°C14°C

14-10=4

Dew Point = 6°C

The Dew Point Chart works the same way

____________________________________________

• Think about the water cycle again, Think about the water cycle again, clouds form has humid air is cooled clouds form has humid air is cooled to its dew point and condense. to its dew point and condense.

• The condensing water vapor forms The condensing water vapor forms tiny drops of water around dust tiny drops of water around dust particles in the atmosphere. When particles in the atmosphere. When millions of these drops form millions of these drops form together, a cloud forms. together, a cloud forms.

________________________

• Yes, there is a classification system Yes, there is a classification system to identify clouds. to identify clouds.

• This system though, helps tell you This system though, helps tell you what kind of weather is going to what kind of weather is going to occur. occur.

• In addition this system classifies In addition this system classifies clouds based on shape and altitude. clouds based on shape and altitude.

Cloud TypesCloud Types

• Guess What? There are actually Guess What? There are actually different cloud types.different cloud types.

• These clouds can help you determine These clouds can help you determine what kind of __________________you what kind of __________________you are going to have. are going to have.

CloudsClouds

• Clouds are divided into categories, in Clouds are divided into categories, in fact 4 of themfact 4 of them– ______________________500-18,000 ______________________500-18,000

metersmeters– _____________________above 6,000 _____________________above 6,000

metersmeters– __________________2,000 to 6,000 meters__________________2,000 to 6,000 meters– ____________________below 2000 meters____________________below 2000 meters

Vertical CloudsVertical Clouds

• 500-18,000 meters500-18,000 meters

• Two TypesTwo Types– ________________________________________________________________________– ________________________________________________________________________

__________________________ • These are towering clouds, they These are towering clouds, they

spread out to top to form an anvil spread out to top to form an anvil shape.shape.

• Associated with thunderstorms, Associated with thunderstorms, heavy rain, and hail.heavy rain, and hail.

• A.K.A “____________________________” A.K.A “____________________________”

______________________________________________

• Dense, _______________________cloudsDense, _______________________clouds

• Associated with fair weather, but Associated with fair weather, but may produce precipitation.may produce precipitation.

High CloudsHigh Clouds

• Above 6,000 metersAbove 6,000 meters– ______________________________________________________________________– ______________________________________________________________________– ______________________________________________________________________

_______________________

*These are the ______________________clouds.*They are made of____________________, not water.•They are associated with fair weather. •They are thin wispy clouds. Feather – like.

Middle CloudsMiddle Clouds

• 2,000 to 7,000 meters2,000 to 7,000 meters– __________________________________________________________________________– __________________________________________________________________________

                                                                 

         

Mid-Level Clouds “______________" Clouds

Clouds with the prefix "alto" are middle level clouds that have bases between 2000 and 7000 m (6500 to 23,000 ft.). Because of their lower altitudes, they are composed primarily of water droplets, however, they can also be composed of ice crystals when temperatures are cold enough.

Low CloudsLow Clouds

• Below 2,000 meters or below.Below 2,000 meters or below.– ________________________________________________________________________– __________________________________________________________________________– __________________________________________________________________________

__________________________________________________

• Thick layer or dark clouds that block Thick layer or dark clouds that block the sun.the sun.

• Associated with steady precipitation.Associated with steady precipitation.

__________________

*Thick, clouds that cover the sky. *Associated with __________________ systems.*They bring precipitation. •They act as a blanket- it keeps in_________. •They are usually low level clouds.

____________________________________________________

• Fog is simply Fog is simply __________________clouds right next to __________________clouds right next to the ground.the ground.

• This caused by air that is cooled to This caused by air that is cooled to its dew point near the ground and its dew point near the ground and condenses. condenses.

Clouds

•______________________formed when temperature of the air at ground level falls below dew point

•______________________forms when warm moist air moves over a cold surface

•Common over oceans (“sea fog”)

Fog is a cloud layer at or close to Earth’s surface

____________________________________________________• Precipitation is a step in the water cycle.

It occurs when the clouds cannot hold anymore moisture.

• all precipitation occurs because of condensation

• Precipitation occurs in different forms based on the temperature of the air.– _________________________– _________________________– __________________________– ___________________________– __________________________

___________________________________

•The rain shadow effect is when on the___________________ side of a mountain/mountain chain receives a lot of precipitation due to the fact that the air ( usually rich in moisture) is forced to be lifted up the side of the mountain. As the air is cooled, it condenses, clouds form and then it rains/snows.

•After the air is lifted over the peak of the mountain, the air has to go down. As the air goes down, it is warmed, and the clouds break and usually ___________precipitation.

•Thus, on the _____________________side of the mountain, it is very dry due to little precipitation.

Orografic effects in orogens

____________________________

• Hail forms when__________________of Hail forms when__________________of water in layers around a small water in layers around a small nucleus of ice. nucleus of ice.

• Hail forms in_______________________. Hail forms in_______________________. They grow larger as they are tossed They grow larger as they are tossed up and down by rising and falling air up and down by rising and falling air currents in a storm.currents in a storm.

_________________________!!_________________________!!

• Coffeyville,___________________, in Coffeyville,___________________, in 1970. The largest hailstone ever 1970. The largest hailstone ever documented, it weighs 0.75 documented, it weighs 0.75 kilograms (1.67 pounds), and spans kilograms (1.67 pounds), and spans 14.4 centimeters (5.67 inches). 14.4 centimeters (5.67 inches).

_____________________

Sleet forms when ________________passes through a layer of warm air, melts and then ________________________near the ground. It requires a deep layer of cold air near the ground.

How Does Sleet Form? How Does Sleet Form?

Freezing RainFreezing Rain

_________________________*It causes a glaze on objects.*Cause for most____________________.*As snow falls from the clouds, it melts ____________________________and there is a shallow layer of cold air at the surface and causes it to______________________________.

______________*_____________________is a function of subfreezing temperatures through out the atmosphere and the surface. * It does not _____________________at all as it falls from the upper atmosphere.

LAKE-EFFECT SNOWLAKE-EFFECT SNOW

Overview of the Lake-Effect Overview of the Lake-Effect ProcessProcess• Occurs to the____________________ Occurs to the____________________

of the Great Lakes during the cool of the Great Lakes during the cool seasonseason

• Polar/arctic air travels across a Polar/arctic air travels across a lake, picks up heat and moisture, lake, picks up heat and moisture, and is destabilized.and is destabilized.

Lake-Effect-type Lake-Effect-type Phenomena in Other Phenomena in Other RegionsRegions

• Lake-effect (_____________________)Lake-effect (_____________________)

• Lake-effect (Finger Lakes, NY)Lake-effect (Finger Lakes, NY)

• Bay-effect (Chesapeake, Delaware, Bay-effect (Chesapeake, Delaware, Massachusetts Bays)Massachusetts Bays)

• Ocean-effect (Gulf Stream, Sea of Ocean-effect (Gulf Stream, Sea of Japan)Japan)

LAKE-EFFECTLAKE-EFFECT

from Eichenlaub (1979)from Eichenlaub (1979)

Occurs during the unstable season when mean lake Occurs during the unstable season when mean lake temperatures exceed mean land temperatures…temperatures exceed mean land temperatures…aka, the __________________is warmer than the land. aka, the __________________is warmer than the land.

Mean annual snowfall exceeds 100 inches in the Mean annual snowfall exceeds 100 inches in the snowbelts to the lee of the lakes, and exceeds 200 snowbelts to the lee of the lakes, and exceeds 200 inches in the Tug Hill Plateau in New York, to the inches in the Tug Hill Plateau in New York, to the lee of Lake Ontario and on the Keweenaw Peninsula lee of Lake Ontario and on the Keweenaw Peninsula of northern Michigan, to the lee of Lake Superior. of northern Michigan, to the lee of Lake Superior. Occurs heavily in____________________________, on Occurs heavily in____________________________, on lee of_________________________.lee of_________________________.

Basic Concepts of Basic Concepts of FormationFormation

The warm water provides thermalenergy and moisture to theoverlying cold air – rememberthat thermal energy transportis from warm to cold.

Basic Concepts of Basic Concepts of FormationFormation

The rising air condenses to formprecipitation, and snow fallsdownwind of the shore line. Thegreater the air-water temperaturecontrast, the heavier the snowfall

Review On How Lake Effect Review On How Lake Effect Happens.Happens.

Cold Outbreak: Frigid air flows over warm water and is warmed from below. Moisture evaporates into the air.

Heavy Snow: Warmer more moist air rises downwind of the lakes and often forms heavy snow squalls.

Effect of OrographyEffect of Orography

Snow ___________________……Snow ___________________……Sometimes lake-effect snow clouds develop enough up and down motion to create "thundersnow" - a snow storm with ________________________________________________.

____________________________________________________• _____________________ _____________________ measure air measure air

temperature. Thermometers work temperature. Thermometers work because matter expands when because matter expands when heated. Most thermometers are heated. Most thermometers are closed glass tubes containing closed glass tubes containing liquids such as alcohol. When air liquids such as alcohol. When air around the tube heats the liquid, around the tube heats the liquid, the liquid expands and moves up the liquid expands and moves up the tube. A scale that shows the the tube. A scale that shows the temperature is on, or attached to, temperature is on, or attached to, the tube.the tube.

____________________________________________________

• A A ___________________mea___________________measures air pressure. An sures air pressure. An Italian scientist named Italian scientist named Torricelli built the first Torricelli built the first barometer in 1643. barometer in 1643. People still use mercury People still use mercury barometers based on barometers based on Torricelli's design to Torricelli's design to measure air pressure.measure air pressure.

Glass tube from which the air has been removed is inserted into a dish of mercury. The air pressing down on the mercury in the dish forces some of the mercury up into the glass tube. At the Earth's surface, air pressure pushes the mercury about 30 inches up into the tube - give or take close to a couple of inches.

__________________________________________________

• An instrument An instrument used for used for measuring the measuring the water vapor water vapor content of the content of the atmosphere.atmosphere.

• A A psychrometerpsychrometer measures measures relative relative humidityhumidity

Sling PsychrometerSling Psychrometer

• It consists of two glass thermometers containing It consists of two glass thermometers containing a liquid, usually mercury. One thermometer a liquid, usually mercury. One thermometer measures the air temperature while the other one measures the air temperature while the other one measures the wet-bulb temperatures.measures the wet-bulb temperatures.

• After the wick is dipped in distilled water, a After the wick is dipped in distilled water, a weather observer whirls the sling psychrometer weather observer whirls the sling psychrometer around, using the handle. As the instrument is around, using the handle. As the instrument is whirled, water evaporates from the wick on the whirled, water evaporates from the wick on the wet-bulb thermometer and cools the wet-bulb thermometer and cools the thermometer.thermometer.

_________________________._________________________.

• The lowest temperature that can be obtained by The lowest temperature that can be obtained by evaporating water into the air at constant evaporating water into the air at constant pressure. The name comes from the technique of pressure. The name comes from the technique of putting a wet cloth over the bulb of a mercury putting a wet cloth over the bulb of a mercury thermometer and then blowing air over the cloth thermometer and then blowing air over the cloth until the water evaporates. Since evaporation until the water evaporates. Since evaporation takes up heat, the thermometer will cool to a lower takes up heat, the thermometer will cool to a lower temperature than a thermometer with a dry bulb at temperature than a thermometer with a dry bulb at the same time and place. Wet bulb temperatures the same time and place. Wet bulb temperatures can be used along with the dry bulb temperature can be used along with the dry bulb temperature to calculate dew point or relative humidityto calculate dew point or relative humidity

Sling PsychrometerSling Psychrometer

____________________________________________________• Is an instrument that measures wind Is an instrument that measures wind

speed.speed.

____________________________________________________

• Measures Wind Measures Wind Direction!!!Direction!!!

Combined-Wind Vane and Combined-Wind Vane and AnemometerAnemometer

• Most weather Most weather stations combine stations combine these two these two instruments. instruments.

______________________________________________

• The most common rain gauge used today by The most common rain gauge used today by official forecasters and airports was invented official forecasters and airports was invented over _________________________ years ago.over _________________________ years ago.

• it consists of a large cylinder with a funnel and it consists of a large cylinder with a funnel and a smaller measuring tube inside of it. The a smaller measuring tube inside of it. The official rain gauge has a 50 centimeter high official rain gauge has a 50 centimeter high cylinder with a 20 centimeter in diameter cylinder with a 20 centimeter in diameter funnel that collects water into a measuring funnel that collects water into a measuring tube that has exactly one-tenth the cross tube that has exactly one-tenth the cross sectional area of the top of the funnel.sectional area of the top of the funnel.

_________________________me_________________________measure the upper air!!!asure the upper air!!!

• Weather balloons carry instrument packages Weather balloons carry instrument packages called _______________________________high into the called _______________________________high into the atmosphere that gather essential upper-air data atmosphere that gather essential upper-air data needed to forecast the weather. These needed to forecast the weather. These instruments are launched twice a day at instruments are launched twice a day at ____________________ sites around the world. ____________________ sites around the world. Temperature, ______________________and air Temperature, ______________________and air pressure are measured at various altitudes and pressure are measured at various altitudes and transmitted via radio waves to a receiving station. transmitted via radio waves to a receiving station. Radio navigation supplies wind speed and Radio navigation supplies wind speed and direction at each altitude.direction at each altitude.

Up and Away:Balloon lifts a milk carton-sized box of instruments 20 miles into the atmosphere.

Radiosonde: Instruments in the box measure three things: _________________, _________________ and _________________

The Descent: The balloon pops and the radiosonde floats back to earth by a parachute.