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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… • 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 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 • 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 HOT Equator warm 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, 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. http://en.wikipedia.org/wiki/Image:Corioliskraftanimation.gif This turning to the right, causes hurricanes to spiral counter clockwise in the north • 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 2) 3) low pressure “hole” Air moving in to fill the low will turn to the right & it is FULL OF WATER VAPOR!!!!!!! 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 2) 3) low pressure “hole” Air moving in to fill the low will turn to the right & it is FULL OF WATER VAPOR!!!!!!! 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 2) 3) low pressure “hole” Air moving in to fill the low will turn to the right & it is FULL OF WATER VAPOR!!!!!!! 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) Everything is calm (low winds), so air heats up 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 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… Categories Pressure (normal ly above 1000) Tropical >993 storm H1 >993 Winds mph Storm surge ft Damage …. <74 1-3 Flood large areas 74-95 4-5 Take out trees H2 979-965 96-110 6-8 Rip roof off H3 964-945 111-130 9-12 Knock small buildings down H4 944-920 131-155 13-18 Destroy even large buildings H5 <920 155+ Extreme damage 19+ Before and after pictures