Warmup Wednesday 9/30 1) As you go up into the atmosphere, is it hotter or colder (in general) 2) Does the air around us have a weight? EXTRA: What is a “barometer?”… anybody know?

Key Concepts today 1. Convection 2. Low & High pressure in the atmosphere 3. Hurricane formation 4. Classification and power of hurricanes

Basic “convection” Heat goes up, cold goes down… Heat goes up, cold goes down… Increasing heat makes things expand, makes density less and thus it rises if it can Increasing heat makes things expand, makes density less and thus it rises if it can Taking away heat makes things contract, thus MORE dense and sink Taking away heat makes things contract, thus MORE dense and sink

Hurricanes – the largest & strongest storms on this planet!

How do they form? First – you need to understand how convection works, and Then a little more about high pressure and low pressure in the atmosphere. And then we can tackle how a hurricane forms

The air on us has “pressure”… why don’t we feel it?

Barometers measure air pressure Original barometers used Mercury – how much mercury would the air hold up in a vacuum tube Original barometers used Mercury – how much mercury would the air hold up in a vacuum tube Modern barometers use an enclosed cell that expands or contracts and moves a lever Modern barometers use an enclosed cell that expands or contracts and moves a lever

Low and High pressure Air tries to move from ________ to __________

How does a “low pressure” form? CONVECTION!!!!!!!!!! As the air is heated, rises…. Leaving a “hole” Air will be pulled in to replace it Equator HOT warm

As warm humid air rises, it cools and the water vapor eventually will condense back into water to form a cloud and eventually rain RELEASING LOTS OF ENERGY AS IT DOES

Low pressure sucks, highs blow If hot air rising creates “low” pressure, If hot air rising creates “low” pressure, What might cause a “high” pressure?

So, the center of a hurricane is a “super low”, sucking in all the hot humid air around it… but Why do hurricanes to spin counterclockwise

Warmup: 10/1 Thursday 1) Over long distances, moving things in the atmosphere will turn to the ________ in the northern hemisphere 2) The force that causes them to turn is the __________ effect 3) ________________ causes an area of low pressure.

Anything in the north hemisphere moving will turn to the right! (Coriolis effect)

South:Left North:right

Pause, then back to hurricanes: Lets detail “Coriolis” Coreolis is simple… yet very very confusing 1) Because we are on a spinning ball, even something going straight appears to curve over a long distance 2) This effect gets magnified by everything else turning! (no, this has nothing to do with toilet water spinning and no toilets don’t spin the other way in the southern hemisphere)

The Coriolis Effect An object moving across a rotating surface keeps the same direction and speed, but looks seems it curves if you are on the rotating surface. In the fixed frame of reference, the black ball moves in a straight line. However, the observer (red dot) standing in the rotating frame of reference sees the object as following a curved path.

This turning to the right, causes hurricanes to spiral counter clockwise in the north In the southern hemisphere they spin clockwise In the southern hemisphere they spin clockwise

Hurricanes really “suck” Base of the eye is a hot area of low pressure Surrounding warm humid air moves toward the low, spiraling, getting warmer and rising up, losing moisture

Anatomy of a hurricane Winds are breezy at the edge of the storm and increase to a maximum in the eyewall. Winds are relatively light in the ‘eye’ itself.

Or another view

OK, so far 1) Still hot humid air rises (Convection) causing low pressure “hole” 2) Air moving in to fill the low will turn to the right & it is FULL OF WATER VAPOR!!!!!!! 3) Air spirals and rises, ALL THE WATER CONDENSES – FORMING HUGE THICK CLOUDS & RELEASING LOTS OF ENERGY

If the “low” is just temporary and small.. = thunderstorm 1) Still hot humid air rises (Convection) causing low pressure “hole” 2) Air moving in to fill the low will turn to the right & it is FULL OF WATER VAPOR!!!!!!! 3) Air spirals and rises, ALL THE WATER CONDENSES – FORMING HUGE THICK CLOUDS & RELEASING LOTS OF ENERGY

If the “low” is long lasting, very hot and a large area…. = Cyclone! 1) Still hot humid air rises (Convection) causing low pressure “hole” 2) Air moving in to fill the low will turn to the right & it is FULL OF WATER VAPOR!!!!!!! 3) Air spirals and rises, ALL THE WATER CONDENSES – FORMING HUGE THICK CLOUDS & RELEASING LOTS OF ENERGY

Tropical Cyclones go by different names… (why do they all go west?

Ingredients for a hurricane: Ocean is very warm and the warm is deep (80 degrees down to 150ft) Ocean is very warm and the warm is deep (80 degrees down to 150ft) Everything is calm (low winds), so air heats up Everything is calm (low winds), so air heats up Air rises quickly and creates a “super low” pressure area Air rises quickly and creates a “super low” pressure area HOT, humid, water carrying air zooms into the “super low” pressure carrying crazy amounts of water and heat energy into the storm HOT, humid, water carrying air zooms into the “super low” pressure carrying crazy amounts of water and heat energy into the storm As it spirals up the eye it loses all it moisture and we get massive condensation (rain clouds)! As it spirals up the eye it loses all it moisture and we get massive condensation (rain clouds)!

Storm Surge – the most deadly part of the hurricane!!!!! The “LOW” pressure sucks in more than just air. It actually pulls the ocean surface up! Add this to the huge waves caused by wind…

CategoriesPressure (normal ly above 1000) Winds mph Storm surge ft Damage …. Tropical storm >993<741-3Flood large areas H1 > Take out trees H Rip roof off H Knock small buildings down H Destroy even large buildings H5 < Extreme damage

Before and after pictures