moisture, clouds, & precipitation chapter 18 200

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  • Moisture, Clouds, & PrecipitationChapter 18200

  • Water in the Atmosphere ch. 18.1When it comes to understanding atmospheric processes, water vapor is the most important gas in the atmosphere.

  • Waters Changes of State

  • HumidityWhat is humidity?general term for amount of water vapor in the airThere are two types of humidity:absolute (specific) humidityrelative humidity

  • What is water vapor capacity?amount of water air can hold at a given temperatureHow does temperature affect the amount of water vapor needed to saturate the air?Warm air can hold more water than cold air.Humidity

  • HumidityWhat is specific (absolute) humidity?the actual amount of water vapor in the air (for a given time & place)How do we express it?specific humidity = mass of H2O vapor (g) 1 kg of air

  • HumidityWhat is relative humidity (RH)?ratio of how close the air is to maximum capacity (How full of water vapor the air is.)How do we express it?relative humidity = specific humidity X 100 maximum capacityRH = ?100%

  • What is the relative humidity of each container?50%How can they be the same????b/c both are full to capacity

    Humidity50%50%

  • Relative humidity can be changed in two ways.adding or removing water vaporchanging the air temperatureHumidity

  • Relative Humidity & TemperatureHow does temp. affect relative humidity?As air temp goes down, RH goes up.Why?b/c cold air can hold less water than warmAs temp goes up, RH goes down.Why?b/c warm air can hold more water than cold

  • HumidityWhen air has 100% relative humidity it is also calledsaturated& air is full of water vapor (has reached capacity)

  • HumidityWhat is the special name for the temp. at which saturation (100% RH) occurs?dew point (temperature)What happens at the dew point temp?condensation (& precipitation)gas liquid

  • Saturation & TemperatureHow does temp. affect saturation? It takes more water to saturate warm air & less to saturate cold air.Why?b/c warm air can hold more water & cold air can hold less.

  • What information can we gather from these figures?

  • Using a sling psychrometer:1. Wet the wick on the wet bulb.2. Spin the psychrometer for the specified amount of time.3. Read temperatures on both the wet & dry bulbs.The wet bulb temp. should always be equal or cooler than the dry bulb temp. due to the evaporation of the water.4. Record your data.Measuring Relative Humidity

  • Using the RH chart1. Calculate difference between wet & dry bulb temperatures2. Locate difference on the (top of) RH chart3. Locate dry bulb temp. on the (left of) RH chart4. Where they intersect gives the RH (in %)

    Measuring Relative HumidityInteractive Relative Humidity Chart

  • Example: What is the RH?If the wet bulb temp. = 16C & dry bulb temp. = 26C, what is the Relative Humidity?34%

    Interactive Relative Humidity Chart

  • Same method as determining relative humidity, except use dew point chartDetermining Dew Point TemperatureInteractive Dew Point Chart

  • If the wet bulb temp. = 16C & dry bulb temp. = 26C, what is the dew point?9 Celsius

    Example: What is the Dew Point?Interactive Dew Point Chart

  • Practice Determining Dew Point & Relative Humidity Using Psychrometer ReadingsDry Bulb Temp.Wet Bulb Temp.Diff. BetweenDew point Temp. in C% Relative Humidity 24 C 17 C

    20 C 16 C712 C49%EX.

    EX.

    414 C66%

  • Cloud Formation ch. 18 sec. 2Where, in the atmosphere, can clouds form?anywhere in troposphereWhy?b/c only layer w/ water vaporWhat are clouds made of?water (liquid or ice)condensation nuclei

  • Cloud FormationHow do clouds form?warm ground heats air above itair rises & cools until reaches dew point & condenses (gas liquid) or undergoes deposition (gas solid)cloud forms (LIQUID or solid water NOT gas)What is the name for the atmospheric level where condensation occurs?condensation level

  • Internet Investigation ES1806 Which Way Does the Wind Blow?What is the orographic effect?rainfall that results from the lifting of air over mountainsdifferent effects on windward & leeward sides of mountainwindward moist air forced over mountain & rises the air expands and cools precipitationleeward air is now dry & cool at top air sinks & warms less rain/cloud cover = rain shadow desert

    Processes that Lift Air

  • Orographic Lifting & the Orographic Effect

  • The Wind Blew Over the Mountain Tune: For He's a Jolly Good Fellow Written By: Unknown/Copyright Unknown The wind blew over the mountain, The wind blew over the mountain, The wind blew over the mountain, And it was wet on the windward side wet on the windward side wet on the windward side The leeward side of the mountain, The leeward side of the mountain, The leeward side of the mountain, Was as dry as it could be Was as dry as it could be, Was as dry as it could be, The leeward side of the mountain, Was as dry as it could be!

  • frontal wedgingmasses of warm & cold air collide producing a frontwarmer, less dense air rises over cooler, more dense airProcesses that Lift Air

  • convergenceair flows horizontally, collides, & gets pushed upwardProcesses that Lift Air

  • localized convective liftingair is warmed more than surrounding air, becomes less dense, risesProcesses that Lift Air

  • CondensationWhat causes condensation?as air is cooled, water vapor capacity decreases (& RH )When air reaches dew point temperature, air becomes saturated (100% RH)condensation occurs (gas liquid)forms dew, clouds, fog, precipitation

  • CondensationBesides cooling air to the dew point, what else is needed for condensation to occur?material for water vapor to condense ontocondensation nucleidust, sand, salt, aerosol particles

  • Cloud Types & Precipitation ch. 18 sec. 3Where, in the atmosphere, can clouds form?anywhere in troposphereWhy?b/c only layer w/ water vaporWhat are clouds made of?water (liquid or ice)condensation nuclei

  • Cloud TypesNames formed from one or more of 5 words/word parts

    Classified according to:shapestratus or strato-layers cumulus or cumulo-upward puffs/heapsaltitude (height in atm)low stratus, nimbostratus, cumulus, stratocumulusalto (middle)altostratus, altocumuluscirrus or cirro- (high)cirrus, cirrostratus, cirrocumulus

    dark, rain cloudsnimbus or nimbo-nimbostratus, cumulonimbusvertical developmentch. 18 sec. 3

  • Low Clouds

  • Middle Clouds

  • High Clouds

  • Dark, Rain Clouds

  • PrecipitationWhat is precipitation?any form of water that falls to Earth from a cloudH2O droplets/ice crystals have to be heavy enough to fallexamples:drizzlerainglaze/freezing rainsnowsleethailFormation of Hail Animation

  • Measuring PrecipitationNational Weather Service (NWS) measures in hundredths of an inch

    What instruments are used to measure precipitation?rain?rain gaugesnow?measuring stick

    http://wc.pima.edu/Bfiero/tucsonecology/climate/concepts.htm

    **Molecules are ALWAYS in motion!Only substance that commonly exists in all 3 states (solid, liquid, gas)Solid (ice) 0 C & belowLiquid between 0 C & 100 CGas (water vapor = invisible gas) above 100 C Cant see, but sometimes can feel (humidity)Water often changes state in the atmosphereBy absorbing energy (heating) Ex. evaporation Liquid gas (vapor) Ex. melting Solid liquid Dew, fog, cloudsBy giving off energy (cooling)Ex. condensation Gas (vapor) liquid Dew, fog, cloudsEx. freezing Liquid solid snow, hail, frost

    *1 L of water = 1 kg or 1 mL of water = 1 g

    *amount of water vapor needed to saturate the air = water vapor capacity Think about it like the size of the containerWarmer air = bigger container; colder air = smaller containerHow does temperature affect the amount of water air can hold?Warmer air can hold more water (has a higher maximum capacity); colder air holds less water (has a lower maximum capacity)

    *What is specific (absolute) humidity? the actual amount of water vapor in the air (for a given time & place)How do we express it?Specific Humidity = Mass of water vapor (grams) 1 kg of air Water Example = 15 g H20 / 1 kg of air1 L of water = 1 kg1 mL of water = 1 g

    *Relative humidity (RH): how close the air is to maximum capacity (being full of water vapor) (for a given time & place)Compares actual amount of water vapor in air with maximum amount (capacity) it can hold (at that temp. & pressure)Expressed as a %:To calculate: Relative Humidity = Specific Humidity X 100 Maximum capacitySaturated (full) air RH = 100% What is the special name for the temperature @ which this occurs? Dew point tempAir that contains NO water vapor RH = 0%Relative humidity can be changed in two ways. First, it can be changed by adding or removing water vapor. In nature, moisture is added to air mainly by evaporation from the oceans and smaller bodies of water.*50% for both b/c both are full to capacity**How does temperature affect the relative humidity? As temp goes down, RH goes up (b/c cold air can hold less water lower maximum capacity & therefore air is more full of water for that new temp) As temp goes up, RH goes down (b/c warm air can hold more water higher maximum capacity & therefore air is less full of water for that new temp)Think about it as if: When water-vapor content stays the same & air gets warmer, beaker gets bigger so w/ same amount of water, its now less full so, lower RHair gets cooler, beaker gets sma