Lecture 38 Outline of Last Lecture I. RemindersII. Weather of the dayIII. Mountain SnowstormsIV. Orographic Clouds in the RockiesV. Water Rights in the WestVI. Major IssuesVII. Rocky Mountain Eastern Slope Upslope StormsVIII. Cold Air Damming Outline of Current Lecture II. Final Exam Review Current LectureFinal Review Session RemindersHomework 7 due todayCloud Project due SundayFinal Exam next WednesdayThere is a review session today and Sunday with Stephen.Study GuideFinal is Wednesday 12/17 at 12:25 in Agr Hall 125 Part 1 10 questions from test 1Part 2 10 questions from test 2 Atm Ocn 100 1nd EditionPart 3 40 questions on subjects covered since last test: Tropical Cyclones, Extratropical Cyclones, Fronts, Lake effect storms, Mountain snowstormsThis study guide is about the last section of the class that we covered: Differences between cyclones and anticyclones:It really is about the roles in energy transferCyclones unlike anticyclones spin in the same sense as the earth. The earth is spinning counterclockwise like cyclones in the northern hemisphere. In the southern hemisphere the earth would appear to be spinning clockwise and so do the cyclones there. Cyclones spin in the same sense as the earth. Why is that? The reason for this is that air turns it because of coriolis effect. But there is something more basic and simple about it. Cyclones spin in the same sense as the earth because in every case cyclones represent air rushing toward a point. If air is rushing toward a point in all directions it concentrates and gets faster and spins. Things moving toward the cyclone are like a skater pulling in his arms and he goes faster. On that earth in one particular place the air is rushing toward a place and spinning up. Why would it spin the opposite sense for an anticyclone then? Because in an anticyclone air is rushing away from a point, it is air splatting away. If you throw cold air that hits the bottom of the earth, it then splats out. It is like the skater putting out his arms. You will then reduce the spin relative to the earth. Because the air splats out it spins less fast. An anticyclone splatting out slows down the spin, so relative to the earth looking at a weather map relative to the earth it appears to be turning the opposite sense of the earth which is clockwise in the northern hemisphere and counter clockwise in the southern hemisphere. The way these are turning is a big hint to the process that created it. Things coming together are a cyclone; things going apart are anticyclones.Differences between extratropical cyclone and tropical cyclone:Different roles in energy transfer, but for both extratropical and tropical things are rushing toward the middle toward the point of action. For tropical cyclone: excess heat at the bottom and cold air above and it wants to overturn. Air rises from a campfire, the flames go up this is because warm air rises. Air is always going toward the fire. Airis coming from all directions into the fire at the bottom and then it goes up and spreads out. Circulation into the fire is like that. If that fire was on a turntable or rotating vortex of air, the air would spin and the fire would look like a tornado. A hurricane is like this too, in a hurricane air is rising air is coming in from all sides and rising up. Because the earth is spinning, air rising up in a hurricane spins in the same sense as the earth. Extratropical cyclone: air again rushing toward the middle. But why? Is it because warm air is rising up? No. The reason the air rushes toward the middle is because air is being drawn to the middle because there is a process of overturning where cold air is next to warm air. What happens is that cold air is dense and is heavier per unit volume then the warm air. So if there is a barrier keep warm and cold air apart. But if you remove barrier, cold air drops and sinks underneath. And when this happens the cold air would leave a void and a low pressure. The low pressure would suck from high pressure where the air is coming together…As it sucks the air what happens is as it comes down it will transfer air to the surface and draw warm air into the cold air and pull it over the top. The cold air sinks and warm air rises up and come together at low pressure. It could form a vortex or a front. But even a shear can produce a circulation to begin, the pressure will be low at a point and draw air in from all directions and spin up a vortex which is an extratropical cyclone. They are not vertical like campfire or tropical cyclone it is slanted. It is tilted with height. We have terms for this: The role of energy transfer that is to bring warm air from below upward. In an extratropical cyclone side-by-side, cold air underneath and so on but starts as side by side.Baroclinicity: Isotherms at angle to isobars on horizontal map. It means that you have horizontal difference of warm air and cold air relative to the pressure. A system that is this and has a gradient of temperature is cold airside by side with warm air. The stronger this is, the stronger contrast between warm air and cold air. If cold air next to warm air it would be a baroclinic stage because big difference of energy. Defines potential energy in a system. On the earth you get a lot of this because poles are cold and lower latitudes are warm. The baroclinicity is energy available to overturn. The problem is that it doesn’t do it easily because there has to be barriers overcome to allow it to overturn. That involves the rotation of the earth. It supports barrier that separates the cold air from the warm air. It doesn’t easily release the energy, but the cyclone does do this.Another step to the south every time this happens, and then the sun continually heating the earth unevenly builds it back up again…Warm air is derived from a warm ocean…When earth is 2/3rds water the sun warms the water as opposed to heating the ground. The water doesn’t get that much warmer in temperature just a little bit. 90% of energy goes into heating water. Sun shines, heats water and then water evaporates into the air and then energy becomes vapor which rises condenses and turns into latent heat which is now in the air and can do something with regards to the rest of the atmospheric circulation which drives baroclinic circulations and soon when it gets higher. This transfer mechanism allows from sun to heat atmosphere by evaporating and rising above. The tropical cyclone is a small occurrence from