ATMS 120 1st Edition Exam 2 Study Guide Lectures 11 17 Lecture 11 March 4 Atmospheric Optics The visible spectrum for humans the range that allows us to see objects is between 0 38 micrometers to 0 78 micrometers Rods allow us to see light They respond to all wavelengths of visible light They allow us to see light and dark black and white If we only had rods we would be color blind Cones respond to different wavelengths of light Some cones are stimulated by red while others are stimulated by blue or green etc Our eyes are also able to create colors by combining other colors Colors such as magenta or brown are not in the visible color spectrum but our eyes are able to perceive them as colors White all colors are perceived by the eye at the same intensity Black the absence of color either because it is blocked or because it is absorbed Technically we have never seen the color black Color visible light of a different frequency that strikes the eye Colors are either refracted or emitted Reflection vs emission Yellow traffic light emission the light is hot energy is being released in the form of heat Yellow color in fire emission same as the traffic light Yellow shoe reflection the shoe is not giving off energy Sun emission Fun facts The wavelength of maximum emission on the sun is actually blue not yellow Oceans appear to be blue because the sky is blue the ocean is actually clear Long wavelength Short wavelength Red Orange Yellow Green Blue Indigo Violet Visible light is scattered by air molecules The efficiency of the scattering is dependent on wavelength Blue light is 10 times more efficiently scattered than red light Blue indigo and violet have shorter wavelengths of light When these shorter wavelengths hit the top of the atmosphere they scatter more than the longer wavelengths of light do the reds oranges and yellows When the sun is directly overhead its path is shorter On the horizon the amount of light that gets scattered increases and longer wavelengths get scattered When the sun sets the path of the sun s rays through the atmosphere is at its longest The shorter wavelength light is completely scattered away while the longer wavelengths red orange yellow survive the trip Really red sunsets tell you that the air is dirty other wavelengths get blocked by the particles in the air Refraction the bending of light as it passes from one medium to another Light goes through a series of refraction reflection refraction in a rain drop to produce a rainbow The density of the rain drop is less than the density of the air which causes the light to get refracted and ultimately bends light Within the process of refraction reflection refraction the different light wavelengths get bent at different angles within the rain drop The difference in angle between red and violet is 2 degrees which is the angle that a rainbow is bowed at In order to see a rainbow you need to face the rain with the sun to your back Rainbows technically make a complete circle we just can t see it from our position on the ground but small planes can fly through these circles The view geometry of a rainbow changes with you so when you move the rainbow moves and therefore you are technically the only person who can see that particular rainbow If a double rainbow is present the second rainbow has its colors switched violet is the top color of the rainbow and red is the bottom color Lecture 12 March 6 Hurricanes Part 1 Tropical cyclones are called different names based on their location around the world In North America they re called hurricanes Around Eastern Asia they re referred to as typhoons By India and the southern hemisphere around Australia they re called cyclones Only 10 of tropical storms occur in the Atlantic Ocean 66 of all tropical cyclones occur in the Northern Hemisphere The impact of tropical cyclones on humans is greatest in Asia The impact on the economy is greatest in the U S No tropical cyclones occur on the equator because of the Coriolis effect No tropical cyclones form too far north or south because the waters are too cold It is impossible for a tropical cyclone to cross the equator There has only been one tropical cyclone tracked in the southern Atlantic Ocean off the east coast of South America Tropical cyclones don t usually form there because the waters are too cold and the change of wind speed and direction is too high In the northern hemisphere tropical cyclones spin counter clockwise In the southern hemisphere tropical cyclones spin clockwise The rest of the lecture will focus on hurricanes tropical cyclones in the Atlantic Ocean that affect the U S A typical track of a hurricane moves from the east to the west and then curves to the north These hurricanes are steered westward by the trade winds They get turned north by the Coriolis Force and then circulate around the subtropical high pressure system Hurricane season is June 1 through December 1 when the sea surface temperatures are warm enough September 10 is the peak of hurricane season Cape Hatteras has the most frequent hurricane strikes followed by Florida Hurricane Katrina hit the US twice it hit Florida before it hit New Orleans She was a Cat 3 in strength when she made landfall in New Orleans then increased to a Cat 5 She started as a tropical depression then strengthened into a tropical storm and hit Florida then strengthened into a Cat 1 upon landfall on Florida which is unusual because storms usually decrease in strength once they make landfall Hurricane Sandy was interesting because she made a hard left turn in her track which rarely ever happens If a hurricane in the northern hemisphere were heading north the fastest winds and greatest storm surge would be on the eastern side If a hurricane in the southern hemisphere were heading south the fastest winds and greatest storm surge would still be on the eastern side Lecture 13 March 11 Hurricanes Part 2 The average clean up costs in the U S per year is 10 billion The average number of deaths per year in the U S is 47 Stages of tropical cyclone development Tropical disturbance Cluster of tropical thunderstorms Watched or investigated for further development Tropical depression Organized cluster of tropical thunderstorms with sustained winds between 22 28 mph Surface low pressure area develops in the center of the storm Tropical depressions are assigned a number Tropical storm Cluster of intense thunderstorms circulating around a deep low pressure center with sustained winds of 39 73