The Atmosphere. All weather occurs here 99% of water vapor found here ~75 % of total mass of the atmosphere

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1 The Atmosphere Structure/Layers Contains 4 major layers See E.S.R.T pg 14 o Troposphere All weather occurs here 99% of water vapor found here ~75 % of total mass of the atmosphere o Stratosphere Contains ozone (03) which absorbs uv-radiation o Mesosphere Meteorites burn up in this layer (shooting stars) o Thermosphere Satellites orbit the earth in this layer Layers are defined by changes in temperature see E.S.R.T. pg 14 E.S.R.T. Composition of the Troposphere 78 % nitrogen 21 %oxygen 1% other o small % of these other gases are greenhouse gases Greenhouse gases GHG absorb long-wave radiation (heat) given off by the earth which heat up the atmosphere o water vapor o carbon dioxide given off my volcanoes produced when fossil fuels are burned o methane naturally produced when plants decay in water & by livestock

2 Heating of the Atmosphere 1. Radiation o Short-wave radiation (light) heats the surface of the earth 2. Conduction The few centimeters of air in contact with the surface 3. Convection The air heated by the surface rises because it now less dense than the surrounding air Cold air sinks down and fills in the space created Greenhouse Effect Short-wave radiation from the sun is absorbed by the surface causing it to heat up That energy is then re-radiated back into the atmosphere as long-wave radiation (heat) The gases in the atmosphere don t absorb light, but GHG do absorb heat. o This heats up the atmosphere w/o GHG the average temperature on earth would be 0 0 C (32 o ) Origin and Evolution of the Atmosphere Original atmosphere came from outgassing associated with volcanoes o CO2, H2O(v), methane, deadly gases o No oxygen was present Evolution of cyanobacteria (stromoatolites) used photosynthesis and converted CO2 to oxygen Some of this oxygen reacted with sunlight in the upper atmosphere creating ozone (O3)

3 Notes - Water in the Atmosphere States of Matter Water Energy Transfer During Phase Changes (latent heat) The temperature of water doesn t change when ice is melting or water is evaporating b/c the energy that is added to the water is used to break the hydrogen bonds that are linking the water molecules together This energy is taken from the environment and is Hydrogen bonds linking molecules known as latent heat o This is why you cool down when you sweat Water uses the energy from the environment (your body) and uses it to evaporate When water condenses or freezes it releases the energy it took back into the environment o See Properties of Water on the cover of E.S.R.T.

4 Humidity Humidity - is the amount of water vapor in the air o Warm air holds more moisture than cold air Relative humidity is the % of water vapor in the air (relative to how much it can hold) o as the air cools the humidity may stay the same (total amount of water), but the relative humidity will increase b/c cold air can t hold as much when the relative humidity is 100% the air is saturated (full) and condensation occurs o the temperature at which this occurs is called the dewpoint sling psychrometer instrument used to determine dewpoint o refer to page 12 in E.S.R.T. for dewpoint and relative humidity charts

5 Notes Cloud Formation Air Pressure Air pressure is caused by the weight of the overlying air Air pressure decreases with elevation o Due to less air above Barometric pressure is another way of saying atmospheric pressure Barometer is an instrument used to measure air pressure o Some barometers measure pressure in millibars others measure in mm Hg (millimeters of mercury) Relationship B/W Pressure and Temperature Direct relationship b/w these two variables As pressure drops the air expands which results in the temperature to drop Cloud Formation When air rises it experiences less barometric pressure This causes the air to expand and therefore cool When the air cools to the dewpoint the vapor in the air condenses on dust (condensation nuclei) o Dust can be soil, pollen, salt ect. that is picked up by the wind o Condensation nuclei is needed for cloud formation b/c the water needs something to condensation on

6 Process that Lift Air Mountains Fronts a front is a boundary between different air masses o refer to pg 13 in E.S.R.T. for symbols for fronts and air masses o air masses air will take on the characteristics of the land below it (source region) ex: source region is tropical water = air mass maritime tropical (mt) continental = dry & maritime = moist

7 Converging Air o When air converges is has nowhere to go but up o This can occur at areas of low pressure and/or as a result of convection cells Due to the lower specific heat land heats up and cools down faster than water. Differences in temp = differences in air density = differences in air pressure = convection cells forming

8 Wind Wind wind is the result of the unequal heating of the earth o some places are warmer than other places latitude - equator is warmer than polar regions specific heat land heats up & cools down faster than water color dark surfaces absorb more energy than light surfaces o b/c air rises over warm areas and sinks over cooler airs the air pressure changes rising air creates lower pressure sinking air creates higher pressure Air (wind) moves from areas of higher pressure to areas of lower pressure wind is named after the direction it comes from o westerly wind = the wind is coming from the west & therefore is blowing towards the east Instruments wind vane wind direction anemometer wind speed Types of Local Winds due to the specific heat of materials, water requires more energy to heat it up than land so it takes a longer time to heat up or cool down water This will generate differences in temperature = differences in density = differences in pressure = wind Sea Breeze Land Breeze

9 Coriolis Effect Due to earth s rotation air doesn t move in a straight line H L Instead the rotation of the earth causes fluids (water and air) to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere In the northern hemisphere, this results in air around a low pressure system rotating counterclockwise and clockwise around a high pressure system Global Wind Patterns Large convection cells are generated globally due to the equator being warmer than the poles This combined with the rotation of the earth causes smaller convection cells (about every 30 o latitude) & global wind patterns found on pg. 14 of the E.S.R.T. the jet stream which are strong upper winds determine the direction weather patterns will travel o most of the weather in NYS comes from the west

10 Notes - Weather Maps Isotherm Map Isotherm a line that connects points of equal temperature Isobar Map Isobar a line that connects points of equal barometric pressure b/c wind is caused by differences in barometric pressure the greater the pressure gradient the faster the wind o closer isobars = stronger wind Reading a Station Model refer to Key to Weather Map Symbols on pg 13 in the E.S.R.T. Below are resources for how to read this part of the reference table o pg in the Earth Science Reference Tables Workbook o

11 Notes - Climate Climate is the typical weather conditions in an area over a long period of time, usually 30 years. o It s not just the average b/c it includes extremes such as droughts, cold winters, ect. There are 6 major factors that affect climate and some other minor ones o Major Factors Latitude Elevation Mountain Ranges Large Bodies of Water Ocean Currents Global Wind Patterns Major Factors Latitude o Minor Factors Urban Heat Island Effect Cities tend to be warmer that the surrounding country sides b/c the building give off heat and there is a lot of darker materials (i.e. roads/parking lots) in cities Vegetation Plants give off water (transpiration) so areas downwind from forests will be moist Deforestation can result in an area being dry (desertification) The Insolation, which is incoming solar radiation from the sun, hits the earth at different angles depending on latitude o This is due to the fact that the rays are parallel and the earth is round The angle of insolation decreases as the latitude increases This means that the insolation at the equator is striking at a higher angle and therefore is more concentrated = warmer temperatures The insolation that strikes the polar regions is at a lower angle and therefore spreads out more, making it less concentrated = lower temperatures

12 Elevation As elevation increases temperature decreases This is due to the fact that as elevation increases pressure decreases o As pressure decreases the air expands causing it to cool Mountain Ranges As wind blows towards a mountain range, it is forced to rise causing the air to cool and the water vapor to condense creating clouds o As a result the climate on the windward side of the mountain is cooler and wet The air that goes over the mountain is now deprived of moisture o Also as the air descends it warms up fast because there is little water in the air o This results in the leeward side of the mountain to be dry and warm (deserts) Large Bodies of Water Because water has a high specific heat it cools and warms very slowly As a result cities near oceans/large lakes have a more moderate climate (lower annual temperature range) o i.e. cooler summers & mild winters o this is especially true for cities that have prevailing winds that come off of the ocean

13 Global Wind Patterns Due to the fact that the equator receives more concentrated insolation it is warmer. This creates an area of low pressure and therefore results in a wet climate This rising air sinks around 30 o N and S latitude creating an area of high pressure. As a result these locations tend to be dry. Although they are not global, wind patterns can also create something called Lake Effect Snow o When cold dry air blows over the relatively warm Great Lakes, moisture is picked up from the lakes. o When that moist air moves over land it is cooled creating clouds and snow o This effect is amplified along the Tug Hill Plateau by the rise in elevation Monsoons are also a result in changes in wind patterns a monsoon is typically thought of as a wet (rainy) season, however it is really a change in wind patterns. o Monsoons are really just large scale land and sea breezes Although monsoons occur on every continent, the most famous monsoons are located in SE Asia/India o in the summer the continent of Asia is warmer than the Indian ocean so as a result there is a low pressure system that develops over Asia or Siberia this generates a strong sea breeze that brings moisture off of the Indian Ocean and results in a rainy season the Himalayas amplify this effect o In the winter the ocean is warmer than the land so the wind direction changes. Now the winds are coming from the land so the air is dry resulting in a dry season.

14 Ocean Currents Prevailing surface winds create ocean currents These ocean currents move heated water from the equator towards the polar regions If an area is near a warm ocean current, this warm water brings with it warm air causing the area to have a climate that is warmer than it normally would be o The most well-known example of this is the Gulf Stream current. o This warm current delivers warm air to Western Europe

15 Notes Hurricanes Formation Hurricanes form in late summer and early fall over warm oceans They tend to start out as large thunderstorms called Tropical Depressions (TD) As they grow they turn into Tropical Storms (TS) When the wind speed exceeds a certain amount they are considered Hurricanes Hurricanes can be categorized 1-5 o 1 is the weakest When they move over land or colder water they lose their energy and start to die Path For the United States o Hurricanes tend to form in the Atlantic or Gulf of Mexico o They initially move west and around 30 o N latitude they change direction as a result of changing global wind patterns Effects Damage from hurricanes are caused by the strong winds, excessive rain, and storm surges Storm surges are large waves that cause flooding along coastal cities o they are created by the strong winds generated during a hurricane which push the water in the ocean onto land