ATMS 100 Exam 3 Study Guide
ATMS 100 Exam 3 Study Guide ATMS 100
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This 19 page Study Guide was uploaded by Stef Antonopoulos on Thursday April 28, 2016. The Study Guide belongs to ATMS 100 at University of Illinois at Urbana-Champaign taught by Jeffrey Frame in Spring 2016. Since its upload, it has received 191 views. For similar materials see Introduction to Meteorology in General Science at University of Illinois at Urbana-Champaign.
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Date Created: 04/28/16
ATMS 100 Exam 3 Study Guide What is the difference between satellites and radars? Satellite view of the clouds from space Radar views precipitation from the ground How is wind direction defined? it is defined by the direction that the wind is coming from. How do winds blow about high and low pressure systems in the Northern Hemisphere? High winds blow clockwise and outward Low winds blow counterclockwise and inward What is pressure and how does it change with height? Pressure is force/area. Atmospheric pressure ALWAYS decreases with height. 1 mb with every 10 m What is an inversion? Layer in which the temperature increases with height What is latent heat? energy absorbed or released during a phase change. "hidden" energy What is advection? transfer of heat (or moisture) through horizontal movements of air. What is saturation? What mathematical relationships are true at saturation? evaporation rate= condensation rate vapor pressure= saturated vapor pressure relative humidity= 100% What is relative humidity? How can it be changed? Ratio of water vapor in the air to that required for saturation (=vp/svp) x 100%. A higher relative humidity means closer to saturation. To increase relative humidity add moisture to the air (increase vp) cool the air (decrease SVP) To decrease relative humidity remove moisture from the air (decrease VP) warm the air (increase SVP) What is dewpoint? Why is it useful? The dewpoint temperature is the temperature at which saturation occurs. The higher the dew point means always there is more moisture in the air. How do clouds form? First, we need rising air either from surface heating/ convection, uplifting by mountains, surface convergence or fronts. Second, the amount of water vapor in the air does not change as the air rises. The relative humidity increases, air eventually rises high enough (cools enough to become saturated (RH=100%) and a cloud forms. How do you read a station model? See example on labs. What is a constant pressure surface? assume uniform surface pressure and temperature. Constant pressure surfaces are parallel to constant height surfaces. How are low and high heights related to temperature and weather? High Heights warm air below pressure surface analogous to high pressure on constant height surfaces a high is high Low Heights cold air below pressure surface analogous to low pressure on constant height surface a low is a low How do you identify ridges and troughs? Ridge: an area of higher heights or pressures Trough: an area of lower heights or pressures can not only look at the shapes of contours, but the values. What is the pressure gradient force? In what direction does it act? PGF is the change in pressure/ distance. Tightly packed isobars mean strong pressure. PGF is directed from areas of high pressure to low pressure or higher heights to lower heights on constant pressure surface. Acts perpendicular to isobars (height contours). How does the pressure gradient force influence the wind speed? Causes the wind to blow. The stronger the PGF, the faster the wind blows. What is a cyclone? An area of low pressure, center of a cyclone is the center of a low. What is an anticyclone? a large atmospheric circulation system around a high with winds flowing clockwise in northern hemisphere. Forms from air masses cooling more then their surroundings How do you determine the surface wind direction from isobars? wind direction crosses isobars at an angle, they do NOT flow parallel because of friction. Surface wind direction is a right angle with CF. Coriolis force is to the right of wind direction. What is convergence? Divergence? Convergence= when air flows together wind converges into low pressure systems at the surface counterclockwise in NH air rises, cools, water vapor condenses forms clouds and precipitation air diverges aloft Divergence= when air flows apart clockwise air sinks, dries out, inhibiting cloud formation, air converges aloft How are convergence and divergence related to the development of surface highs and lows? Divergence decreases surface pressure subtract molecues from air column Convergence increases surface pressure adds weight to column Why is vertical motion important? faster rising air caues clouds and can cause more interesting weather What is a jet stream? Where are jet streams found? What causes jet streams? The jet stream is a river of fast moving air in the upper atmosphere. It exists near the tropopause level (about 10 km) and its flow is parallel to height contours. Flow is not the same speed everywhere What is an air mass? How are they classified? A large body of air with similar temperature and moisture concentrations. Horizontal only. Air masses form over flat, homogeneous regions of the earth's surface. Boundaires are around low pressure called fronts, centers are high pressure systems. They are classified based on moisture and temperature (two letters) Moisture Continental (c) Dry Maritime (m) moist Temperature Tropical (T) warm/ hot Polar (P) cool/cold Arctic (A) frigid What is a front? It is the boundary between air masses of different densities. warm air is less dense than cold air moist air is less dense then dry air FRONTS are NOT airmasses fronts strongest at the surface How are fronts represented on weather maps? Lines with symbols pointing in direction front is moving cold front= blue with triangles warm front red with half circles stationary front= combination cold/warm occluded front= purple What is a dryline? seperates the mT air (to the east) from the cT air (to the west). Typically found in KS/OK/TX during spring. What is a midlatitude cyclone? also called an extratropical cyclone. It is an are of low pressure where the center of cyclone is center of low. It usually lasts several days to a week+ and can be as large as 1000+ miles across. Weather includes thunderstorms and tornadoes, blizzards and ice storms, widespread snow and rain. Where is warm air and cold air found with respect to a surface low? Warm air is usually east and cold is usually south How do MidLatitude cyclones influence the weather? brings cold air southward and warm air northward, provides precipitation to many regions in world and can produce severe weather What is the Gulf Stream? a strong, fast moving, warm ocean current that originates in the gulf of mexico and moves to the atlantic ocean. What is the thermocline? the rapid temperature decrease with depth a few hundred meters below the surface How does oceanic temperature vary with depth? the temperature decreases with depth What is upwelling? How does it affect oceanic temperature? upwelling is the vertical transport of deep ocean waters upward, resulting in cooler surface water temperatures. What is ENSO? El nino Southern Oscillation (atmospheric oscillation over south pacific ocean encompasses both el nino and la nina) What is El Nino? warmer than average water in the pacific ocean off South America What is La Nina? cooler then average water in the pacific off South America How do the phases of ENSO affect the weather in the eastern Pacific? The western? Under normal conditions, ENSO will send water from the east to the west because of trade winds, as it moves it is warmed by sunlight causing a deeper layer of warm water to the west. This causes surface low near indonesia with clouds and rain and high pressure near South America. Walker Circulation reverses and so then everything switches. What is the difference between a hurricane and a typhoon? They are structurally the same, but form in different regions of the world What is a typical hurricane track in the Atlantic Ocean? starts in atlantic, moves toward florida and then hooks back up parallel to the east coast. What are the names and relative intensities of tropical cyclones in the Atlantic Ocean? 1. Tropical Disturbance/ Tropical Wave cluster of showers and thunderstorms 2. Tropical Depression winds less then 39 mph or 34 knots 3. Tropical Storm tropical cyclone with winds between 4073 mph (3464 knots) 4. Hurricane Strong tropical cyclone with winds greater than 74 mph (65 knots( and eyewall development When are hurricanes most likely? Why? Hurricanes are most likely during the month of September. What ingredients are required for hurricane formation? Why are these ingredients necessary? 1. Seasurface temperature (SST) greater then 26.5 degrees celcius. (aids thunderstorm development) 2. Deep layer of warm water in upper ocean (because hurricanes stir up water) 3. Cluster of thunderstorms (usually in form of tropical disturbance or tropical wave) 4. Moist air in the midtroposphere 5. Weak vertical wind shear (<15 knots) 6. Latitude poleward of 5 degrees (Coriolis force is zero at equator, allows system to rotate) What is ITCZ? Where the Northeast trade winds in the northern hemisphre converge with the southeast tradewinds in the southern hemisphere. Belt of thunderstorms found near the equator. What is a tropical wave? A cluster of showers and thunderstorms What is vertical wind shear? How does it affect hurricanes? The change in wind direction or speed with height. Strong vertical wind shear is usually associated with strong winds aloft. Strong vertical wind shear is bad for hurricanes because it rips them apart. They are favorable for thunderstorms, tornadoes, midlatitude cyclones. How do hurricanes intensify? The warmer the water and the greater the wind speed, the greater the transfer of sensible and latent heat into the air above. Warmer ocean surface, the lower the minimum pressure of the storm, and higher its winds. What is the eye of a hurricane? Weather conditions? The center of the hurricane, where the lowest pressure is. The weather is clear and calm and warm. What is the eye wall? Weather conditions? The eye wall is the walls of the eye. It has the strongest pressure gradient forces so therefore the strongest winds, heaviest rain and worst weather. How are the left and right side of a hurricane defined? If you are moving with the hurricane, the right of the hurricane is your right and your left is the hurricanes left. Right and East are NEVER interchangeable as well as up and north. What are the main hazards associated with hurricanes? 1. Strong winds 2. Storm Surge 3. Inland Flooding 4. Tornadoes How does storm motion affect the winds around a hurricane? The winds of a hurricane are strongest on the right side of circulation because the speed of storm and wind speeds are additive. Storm motion and winds are in the same direction. They are opposite directions on the left side of the storm, subtract (weaker winds) What is the SaffirSimpson scale? Do not memorize the table. A scale the measures the strength of of a hurricane. It is determined by the maximum sustained winds speed. It is Classified by Category (#15, 5 being strongest) What is storm surge? Where is it the most intense? How is it created? a rise in the sea level due to a tropical cyclone. winds pile up water against the coast, low pressure allows the sea level to rise and it is most intense in the right front quadrant of a hurricane. because of the low pressure at the surface of the hurricane's eye, the ocean is allowed to bulge upward beneath there. How did Hurricane Katrina flood New Orleans? Because of storm surge, water came into new orleans from the north and new orleans sits below sea level. much of the water funneled into lake Pontchartrain. Where are tornadoes most prevalent with respect to the eye of a hurricane? To the right of the eye in the spiral bands. What is the difference between forced and buoyant ascent? Force ascent is when some mechanism forces air aloft, buoyant ascent is when the air becomes buoyant by contact with the warm ground. Buoyant ascent is ascent caused by a parcel being less dense than its environment. Forced ascent is caused by an obstacle like a mountain or a very dense airmass. Consider walking up to a barrier you can't go around. How do you cross it? You rise over the barrier. How does temperature affect air density? The hotter the air, the less dense. The cooler the air, the more dense. How does the temperature of air change as it rises and sinks? Why? As air rises, it cools and expands. As air sinks, it warms and contracts. How do you read a sounding? right line is always the temperature. left line is always the dewpoint What are the dry and moist adiabatic lapse rates? Why are they different? Be able to do basic calculations with them. Dry Adiabatic Lapse Rate= the rate at which a rising unsaturated air parcel cools. It is constant (equal to 10 degrees C/km). Sinking unsaturated air also warms at this rate. Remember that unsaturated air means that temperature and dewpoint are not the same. Moist Adiabatic lapse rate= rising saturated air also cools, but at a different rate. this is varaible, but will take to be 6 degrees C/ km. Sinking saturated air also warms at this rate. Satuarted: temp=dewpoint. What is the environmental lapse rate? How is it measured? The rate of decrease of environmental temperature with height. It says nothing about how temperature of rising or sinking air parcel changes. It is related to the slope of the temperature line. lapse rate= rate of temperature change with height. Define LCL and identify on sounding? Lifting Condensation Level level at which a rising surface air parcel becomes saturated. Changes from dry to moist adiabatic lapse rate. look for inflection in parcel temperature. Look for Temp=Dewpt Temp Define LFC and find on sounding? Level of Free Convection level at which a rising surface air parcel becomes positively buoyant (warmer than its environment) Parcel temperature crosses to the right of environmental temp. Define EL and find on sounding? Level at which a rising surface air parcel is no longer positively buoyant (typically found near tropopause). Parcel temperature crosses back to left of environment temp. Define CAPE and find on sounding? Convective Available Potential Energy. Area between parcel temperature and the environmental temperature when the parcel is warmer than the environment. (Between LFC and EL). The bigger the CAPE, the bigger the storm. Rising air parcel warmer then the environment. Define CIN and find on sounding? Convective INhibition. Area between parcel temp and environmental temp when the parcel is cooler than the environment. (below the LFC) want small or zero for storms to form. Rising air parcel cooler then the environment. How is the lifted index calculated? Why is it useful (lab 13)? 1. To calculate, lift pare from surface to 500mb. Find the temperature of the parcel at 500mb. 2. Subtract parcel temperature at 500 from environmental temp at 500. LI= T(env)T(parcel) Negative LI means that rising air parcel warmer than environment and thunderstorms possible. Positive LI means thunderstorms not likely. How can the atmosphere be stabilized? Destabilized? Make air more stable warm air aloft cool the surface (nocturnal cooling, cold air advection) atmosphere typically most stable at sunrise. Unstable cold the air aloft warm the surface (solar heating, warm air advection) atmosphere typically most unstable in late afternoon. What is a thunderstorm? A tall, vertically developed cloud that produces lightning and thunder. Can't have thunder without lightning. Usually produces heavy precipitation. Thunderstorm clouds are call cumulonimbus clouds. What is required for all thunderstorms to form? All thunderstorms require instablility (warm/moisten low levels, cool aloft, steep lapse rate (rapid temp decrease with height)) What mechanisms can trigger thunderstorms? How? 1. Fronts or drylines 2. Sea breezes (or lake breezes) 3. Outflow boundaries (gust fronts) 4. Mountains What is a severe thunderstorm? 1. Wind gusts at the surface greater than 50 mph (57.5 knots) 2. Hail with a diameter greater than 1 inch, roughly quarter sized. new definition from january 2010 3. Tornado ANY of these classify as a sever thunderstorm. What are the stages of thunderstorm development? 1. Cumulus Stage warm air rises, and cools. Water vapor condenses and forms cloud. Rising air is called the updraft. Air rises due to buoyancy. Thunderstorm can't happen without updraft. As cloud gets deeper, precipitation particles begin to form. 2. Mature Stage updraft may eventually reach tropopause, a very stable area. It acts as a lid on the storm. Air diverges outward when reaches tropopause and forms anvil cloud. Top of updraft may penetrate into stratosphere called overshooting top. Precipitation particles grow, become heavy and getting to fall into updraft, some rain evaporates cooling air even more. when air is cooler than surround it sinks, this is the downdraft. Precipitation is required to for a downdraft. When cold down draft reaches ground spreads out. Boundary between cold outflow and warm inflow is called gust front our outflow boundary. This why temperature drops and winds increase before thunderstorm. 3. Dissipation Stage rain falls into updraft, cools updraft, drags rising air downward. updraft weakens, replaced by downdraft, surging outflow cuts off supply of warm, moist, unstable air needed to feed updraft. Updraft dissipates, thunderstorm dominated by downdrafts and precipitation, thunderstorm quickly dissipates. What is an updraft? rising air What is a downdraft? falling air What is a cold pool? when cold downdraft reaches the ground and spreads out of a thunderstorm. What is an anvil? when the air diverges when it reaches the tropopause. What is a cumulonimbus cloud? a towering vertical cloud that is very tall and dense and produces thunderstorms. What is a gust front? boundary between cold outflow and warm inflow below a thunderstorm. How does the cold pool form? the cold downdraft reaches the ground and spreads out. What best discriminates between ordinary and severe thunderstorm environments? weak vertical wind shear= ordinar, strong vertical wind shear= severe Why do ordinary thunderstorms only last for about an hour? Ordinary thunderstorms typically last for about an hour because in the mature stage, the precipitation falls into the updraft. As the rain falls into the updraft, it drags air downward with it and also cools the air. The updraft is weakened and is replaced by a downdraft. The updraft dissipates, so then the thunderstorm dissipates. How do ordinary thunderstorms dissipate? rain falls into updraft, cools updraft, drags rising air downward. updraft weakens, replaced by downdraft, surging outflow cuts off supply of warm, moist, unstable air needed to feed updraft. Updraft dissipates, thunderstorm dominated by downdrafts and precipitation, thunderstorm quickly dissipates. What is a downburst? Cause? A strong downdraft that comes in contact with the ground. The sinking air must be colder than the air around it. rain drags the air downward with it. rain falls into unsaturated air and evaporates, this cools the air. the cold air sinks, can be as fast as 4050mph. straightline winds often result after downburst hits the ground. What is a microburst? Cause? A smaller and often more intense downburst. rain drags the air downward with it. rain falls into unsaturated air and evaporates, this cools the air. the cold air sinks, can be as fast as 4050mph. straightline winds often result after downburst hits the ground. What are straightline winds? How do they form? intense winds blowing in the same direction. Wind in a tornado rotates. Straightline winds often result from downbursts or microbursts and can reach 100 mph. All of the debris falls in the same direction. How can one determine if damage was caused by straight line winds or a tornado? If all debris falls in the same direction, then straight line winds. If not then tornado. What is an MCS? Where are the primary severe weather threats from one? Mesoscale Convective System a large complex of thunderstorms, can be over an entire state producing a lot of rainfall. It is important for agriculture in midwest. Hazards include flooding, straightline winds, and occasional weak tornadoes. What are the two components of MCS structure as seen by radar? bow echo and a trailing stratiform region, squall line Why is vertical wind shear important to MCS maintenance? it is important to the development of thunderstorm complexes and prevents gust front from moving too far in front of updrafts. It also generates more lift at the gust front. What is the rear flank inflow jet? How does it form? When strong downdrafts that form to the rear of the squall line form, the heavy cooler air then descends and drags some of the surrounding air with it. If coo air descends rapidly, it may concentrate into a rather narrow band of fast moving air called the rear flank inflow jet. It will sometimes bring with it strong upper=level winds from aloft. They can cause damaging straightline winds. What is a shelf cloud? Where can it be found? How does it form? when warm air is lifted at the gust front and rises it causes a shelf cloud. It can be found at the front of the storm. What is a bow echo? known for producing prolific wind damage. When the thunderstorm forms the shape of a bow, think of bow and arrow. What is a squall line? a line of sever thunderstorms that form along or ahead of a cold front. What is a derecho? A line of intense, widespread, and fastmoving windstorms and sometimes thunderstorms that moves across a great distance and is characterized by damaging winds What is the charge separation in a typical thunderstorm? the bottom of the cloud has a negative charge, the top of the cloud has a positive charge. The area below the cloud has a positive charge. Why is there a charge separation in thunderstorms? Ice particles of different sizes collide in could and transfer electrical charges. The large ice particles become negatively charged and fall downward. The smaller ice particles become positively charged and stay higher in cloud. What are the three types of lightning? 1. Cloud to Ground (only 20% of strokes) 2. Cloud to Cloud 3. IntraCloud What is sheet lightning? "Heat Lightning"? when lightning is scattered by clouds and rain making it appear as though the entire sky is lit up. You may not hear thunder because it is too far away. Heat lightning is not correct it is a misconception. How does a lightning strike occur? 1. WHen the negative charge near the bottom of the cloud becomes large enough to overcome the air's resistance, a flow of electrons, the stepped leader, rushes toward the earth. 2. AS electrons approach the ground, a region of positive charge moves up into the air through any conducting object. 3. When the downward flow of electrons meets the upward surge of positive charge, a strong electric currentreturn stroke carries positive charge upward into cloud. What is the relationship between lightning and thunder? Lightning heats the air around it, causing the air to expand violently, forming a sound wave. We then hear this sound as thunder. Light travels much faster than sound this is why we see lightning first then hear the thunder. If you hear thunder you are in danger of being struck by lightning. Where is the safest places to be during a lightning storm? What places should be avoided? Safest place to be is in doors or in a car. Avoid being in an open field, under trees, near metal objects or by water. If you need to be outsize, minimize contact with the ground. Crouch on the balls of your feet. What is hail? How is it formed? Frozen precipitation that falls from thunderstorms. It requires strong updrafts and hence supercell thunderstorms. 1. Supercooled water droplets and ice crystals form at high altitudes in updraft. 2. ice particles fall through supercooled water and grow into graupel (soft ice) particles. 3. Few graupel particles swept back into the updraft from the side. 4. Hail embryo is suspended in updraft and grows via accretion of supercooled water. 5. Hailstone moves out of updraft region and rapidly falls to earth. How do hailstones acquire layers? graupels of particles are swept back into the updraft from the side, the hail embryo is suspended in updraft and then grows because of supercooled water. What are the three main types of floods and the dangers from each? 1. Flash Floods can cause fatalities 2. Widespread Floods fewer casualties but more damage 3. Coastal Floods Why is it dangerous to drive through flood waters? Because only two feet of water can sweep your car away. What weather conditions are favorable for the formation of supercell thunderstorms? 1. Vertical Wind Shear 2. Lowlevel jet (provides lowlevel shear) 3. Jet Stream aloft westerly flow 4. Instability warm moist air at surace cold air aloft 5. Trigger front, dryline, or outflow boundary trough in jet stream to west What is a supercell? longlived, rotating thunderstorm cells can only last for hours often isolated always rotate they are the strongest and most rare type of thunderstorm, always sever and produce hail and violent tornadoes Why are supercells able to persist for hours while ordinary thunderstorms do not? Supercells are able to persist for hours while ordinary thunderstorms do not because supercells have strong winds aloft. The strong winds blow the precipitation downwind of the updraft. Therefore, the air in the updraft is not dragged downward, so the updraft is not weakened. What is a mesocyclone? a persistent rotating updraft. supercell rotation begins horizontal due to vertical wind shear and then updraft tilts this rotation to vertical What is a wall cloud? a lowered cloud beneath the updraft base. if the wall cloud is rotating it indicates that a tornado may form. What are mammatus clouds? cellular pattern of pouches hanging from the base of a cloud. looks like bumps What is the RFD? How is it visually manifested? Why? a region of dry air wrapping around the back of a mesocyclone in a supercell thunderstorm. This air is thought to be crucial in the formation of tornadoes. Clear slot near the updraft base. What is an HP supercell? highprecipitation: Significant precipitation near the updraft What is an LP supercell Low precipitation Little precipitation everywhere In which type of supercell are tornadoes most likely? In the Classic supercell What is a tornado? A violently rotating column of air in contact with the ground. Typically visible as a funnel cloud. They most likely form in supercells, look for hook echo. What defines when a tornado has "touched down"? When rotation makes contact with the ground, usually see dust or debris swirl How do tornadoes acquire their rotation? A horizontal spinning vortex tube is created by wind shear that rotates like a pencil. This is called the vortext tube. What is meant by tilting and stretching? The strong updraft in the developing thunderstorm causes the horizontal vortex tube into the thunderstorm, producing a rotating air column that is oriented in the vertical plane. What is a hook echo? How does it form? The shape on an echo on a doppler radar screen that indicates the possible presence of a tornado. Where in a supercell are tornadoes most likely? ... What is a multiple vortex tornado? Strong tornadoes can form multiple vortex tornadoes, less intense tornadoes have rising air in center, but central downdraft can form in strong tornadoes. This downdraft in the center breaks circulation into smaller vortices. Smaller vortices rotate around center of tornado. What are landsprouts and watersprouts? How do they differ from supercell tornadoes? Landsprout: a nonsupercell tornado that forms over land near converging air boundaries Watersprout: a rotating column of air that is connected to a cumuliform cloud over a large body of water. They are less intense and smaller then supercell tornadoes and tend to move more slowly.They also do not occur in association with a preexisting wall cloud or mid level mesocyclone. What is the Enhanced Fujita Scale? On what is it based? Do not just memorize table Based on Damage and quality of construction Which type of tornadoes are the most deadly? Why? EF5 Tornado. This is because they are capable of wiping foundation clean. How can radar be used to detect tornadoes? doppler radar is able to detect rotation within a tornado What is the safest place to be during a tornado? interior room on lowest floor of a sturdy structure. Basements prefered, if one is not available use a closet or bathroom. stay away from windows protect yourself from flying debris if possible
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