Have out your notes on Air Masses and Fronts Please! And Thank-you!

Weather: a study in Variables Water

Variable Review G Atmosphere G Structure G composition G Heat G Global Heat uneven G Convection, conduction, radiation G Pressure G Gravity, depth G Water, temperature G Causes wind G Atmosphere G Structure G composition G Heat G Global Heat uneven G Convection, conduction, radiation G Pressure G Gravity, depth G Water, temperature G Causes wind

From Lab: Earth is heated unevenly G Land and water heat differently. G Water won’t heat or cool as fast as land. G Water won’t reach the temperature extremes that land will. G Land close to large bodies of water will have a more moderate climate. (Hint: Where does the majority of a population live? Where are the big cities?) G Higher elevations are cooler. G Global location/latitude makes a difference. G Land and water heat differently. G Water won’t heat or cool as fast as land. G Water won’t reach the temperature extremes that land will. G Land close to large bodies of water will have a more moderate climate. (Hint: Where does the majority of a population live? Where are the big cities?) G Higher elevations are cooler. G Global location/latitude makes a difference.

Review: Changes of State G Require the transfer of heat G Energy has to be moved into or out of molecules to make them change state. G Energy(heat) in = more movement/disorganized G Energy(heat) out = less movement/organized G Temperature doesn’t change during a change of state. G Require the transfer of heat G Energy has to be moved into or out of molecules to make them change state. G Energy(heat) in = more movement/disorganized G Energy(heat) out = less movement/organized G Temperature doesn’t change during a change of state.

Changes of State Blue arrows = latent energy released to atmosphere = atmosphere heated! (From water to Atmosphere) Red arrows = latent energy “stored” in water = atmosphere cooled! (From atmosphere to water) Solid Gas Liquid

Latent Heat G Water has a high specific heat = energy stored/released to change temperature 1 o C G physical property of matter G Acts like a sponge, can absorb lots of heat without changing temperature G Latent heat = “hidden” heat energy G energy that is absorbed or released by water G Can do so without changing temperature during changes of state G Water acts like a heat energy “piggy bank” G Water has a high specific heat = energy stored/released to change temperature 1 o C G physical property of matter G Acts like a sponge, can absorb lots of heat without changing temperature G Latent heat = “hidden” heat energy G energy that is absorbed or released by water G Can do so without changing temperature during changes of state G Water acts like a heat energy “piggy bank”

Latent Heat in Atmosphere Energy stored & atmosphere cools Energy released & atmosphere warms

Water G Already know it can cause pressure differences. G Need to know: G Relative humidity G Capacity G Already know it can cause pressure differences. G Need to know: G Relative humidity G Capacity

Capacity G Maximum amount of H 2 O air can hold G Like a cup! 8 oz, 12 oz, 20 oz G Warmer air has higher capacity than cooler air. G There is more space between air molecules for water to fit into. G Maximum amount of H 2 O air can hold G Like a cup! 8 oz, 12 oz, 20 oz G Warmer air has higher capacity than cooler air. G There is more space between air molecules for water to fit into.

Relative Humidity G Ratio of actual water vapor in the air compared with CAPACITY G Like a grade! 80/100= 80%=B G Can change relative humidity in two ways: G Adding/removing H 2 0 (99/100 or 70/100) G Changing temperature of air (changes capacity, 80/80) G Ratio of actual water vapor in the air compared with CAPACITY G Like a grade! 80/100= 80%=B G Can change relative humidity in two ways: G Adding/removing H 2 0 (99/100 or 70/100) G Changing temperature of air (changes capacity, 80/80)

What can change relative humidity? You NEED to KNOW this! What can change relative humidity? You NEED to KNOW this! G Adding/removing H 2 0 (dumping/adding H 2 O) G Large bodies of water (add) G Large lakes, oceans (add) G Mountains (remove) G Changing temperature/capacity (size of cup) G Most likely source of a change in R.H. G Adding/removing H 2 0 (dumping/adding H 2 O) G Large bodies of water (add) G Large lakes, oceans (add) G Mountains (remove) G Changing temperature/capacity (size of cup) G Most likely source of a change in R.H.

Cool Air = Smaller capacity for water in air Hot Air = Large capacity for water in air Temperature Changes Capacity

100% Relative Humidity G Maximum amount of H 2 O air can hold. G Saturation = 100% of capacity G Water evaporating equals water condensing G Adding more water or cooling temperatures further will “overflow” the cup! G Tend to reach 100% RH by cooling air. G Maximum amount of H 2 O air can hold. G Saturation = 100% of capacity G Water evaporating equals water condensing G Adding more water or cooling temperatures further will “overflow” the cup! G Tend to reach 100% RH by cooling air.

Dew Point Temperature G AKA Dew Point G Represents the temperature at which a parcel of air will reach saturation. G Temperature where the cup is FULL. G For example, 20 o C (70 o F) & 50% relative humidity. G To reach Dew Point would have to cool air to 10 o C (50 o F), relative humidity = 100%. G Higher dew points = moist air G Lower dew points = dry air G AKA Dew Point G Represents the temperature at which a parcel of air will reach saturation. G Temperature where the cup is FULL. G For example, 20 o C (70 o F) & 50% relative humidity. G To reach Dew Point would have to cool air to 10 o C (50 o F), relative humidity = 100%. G Higher dew points = moist air G Lower dew points = dry air

Condensation G Air cooled past the dew point will condense. G Overflowing cup! G Water condenses out of the air. G Results in: G Clouds G Fog G Dew G Frost G Air cooled past the dew point will condense. G Overflowing cup! G Water condenses out of the air. G Results in: G Clouds G Fog G Dew G Frost

Application G Recall Temperature and Pressure relationship G Me: Hot Stuff, You: G Me: Cold Stuff, You: G What happens to the temperature as warm air rises? G Decreases G What does that do to the capacity? G Decreases G What does that do to the relative humidity? G Increases G So What?!? = Clouds and rain! G Recall Temperature and Pressure relationship G Me: Hot Stuff, You: G Me: Cold Stuff, You: G What happens to the temperature as warm air rises? G Decreases G What does that do to the capacity? G Decreases G What does that do to the relative humidity? G Increases G So What?!? = Clouds and rain!

Air masses & Fronts Last Page: Application Where are clouds? Why do they form there? Last Page: Application Where are clouds? Why do they form there?

Where? Why? G Where: Just behind the cold front edge G Why: Cold front pushes into the area where warm air was. This lifts the warm air and cools it. As it cools, it will reach dew point and form a cloud. Enough H 2 O present, and it will rain. G Where: Just behind the cold front edge G Why: Cold front pushes into the area where warm air was. This lifts the warm air and cools it. As it cools, it will reach dew point and form a cloud. Enough H 2 O present, and it will rain. Marker line COLDWARM

Adiabatic Temperature Changes G Changes of Temperature without energy being added/removed G When air expands, it cools G Expansion due to air rising in the atmosphere G Lower pressure = expansion G When air is compressed, it warms G Compression due to air sinking in the atmosphere G Higher pressure = compression G Changes of Temperature without energy being added/removed G When air expands, it cools G Expansion due to air rising in the atmosphere G Lower pressure = expansion G When air is compressed, it warms G Compression due to air sinking in the atmosphere G Higher pressure = compression

Dry Adiabatic Rate G 10 o C for every 1000 meters G Air at 20 o C rises 1000 meters will COOL to 10 o C. G Air at 20 o C sinks 1000 meters will WARM to 30 o C. G What if it rises, and therefore cools to its dew point? Water CONDENSES G 10 o C for every 1000 meters G Air at 20 o C rises 1000 meters will COOL to 10 o C. G Air at 20 o C sinks 1000 meters will WARM to 30 o C. G What if it rises, and therefore cools to its dew point? Water CONDENSES

Wet Adiabatic Rate G After air cools to its dew point, latent heat becomes a factor. G DUE TO CONDENSATION G Gas > Liquid G Energy goes from the water into the atmosphere G Warms the atmosphere! G Dew Point = clouds, fog, dew, frost, rain G Flat bottom clouds G Air rising, flat bottom = point where air has cooled to condensation point. G After air cools to its dew point, latent heat becomes a factor. G DUE TO CONDENSATION G Gas > Liquid G Energy goes from the water into the atmosphere G Warms the atmosphere! G Dew Point = clouds, fog, dew, frost, rain G Flat bottom clouds G Air rising, flat bottom = point where air has cooled to condensation point.

Wet Adiabatic Rate G When water condenses, latent heat is released. G Air will still cool, but at a slower rate because latent heat is opposing the cooling. G Wet adiabatic rate = 6 o C for every 1000 meters (average, varies 5 o C-9 o C) G Air at 20 o C rises 1000m after reaching dew point will cool to 14 o C G When water condenses, latent heat is released. G Air will still cool, but at a slower rate because latent heat is opposing the cooling. G Wet adiabatic rate = 6 o C for every 1000 meters (average, varies 5 o C-9 o C) G Air at 20 o C rises 1000m after reaching dew point will cool to 14 o C

Review Changes of State Processes G Gas to liquid = G condensation G Liquid to gas = G evaporation G Liquid to solid = G freezing G Solid to liquid = G melting G Gas to solid = G deposition G Solid to gas = G sublimation G Gas to liquid = G condensation G Liquid to gas = G evaporation G Liquid to solid = G freezing G Solid to liquid = G melting G Gas to solid = G deposition G Solid to gas = G sublimation