Presentation on theme: "Air Pressure, Clouds and Weather"— Presentation transcript:
1Air Pressure, Clouds and Weather Laura Schofield, Ipswich Public SchoolsTina Ciarametaro, Ipswich Public SchoolsUniversity of MA, Amherst STEMSJan. 26, 2013
2Today’s Driving Questions: 1) What are basis characteristics of the atmosphere?2) What is the horizontal and vertical movement of air in a “High” and “Low?”3) How do clouds form and what can they tell us?4) How are temperature, pressure and clouds related?5) Applying concepts to real-time data
3Today’s Schedule Highs and Lows (PowerPoint & Application) Short Break 2) Clouds (PowerPoint & Application)3) WeatherCycler (Application)4) Real Time Data (Application and Resources
4Earth’s Atmosphere Ocean of air **3-dimensional We live on the bottom of this “ocean”Air moves horizontally and vertically
5Air Mass Body of air that covers thousands of kilometers2 Horizontally homogenous in temperature and humidityCharacteristics determined by type of surface over which the air mass resides or travels
6Air Mass Tropical: “warm” Polar: “cold” and Continental: “dry” Maritime: “humid”Continental tropical (cT)Maritime tropical (mT)Maritime polar (mP)Continental polar (cP)Arctic (A)
7Weather vs. Climate “Weather tells you what to wear on any given day; State of atmosphere at a specific time and place, variables include:TemperatureHumidityCloudinessPrecipitationWind (speed & direction)Weather, of a given location, averaged over a period of timeIncludes extremes in weather behavior observed during the same time periodHow the weather behaves over relatively long periods of time“Weather tells you what to wear on any given day;climate tells you what wardrobe to have.”
8H = “highs” or high pressure system L = “lows” or low pressure system
9Highs vs. LowsHigh or “H,” symbol on a weather map, the center of a high pressure system - where air pressure is relatively high compared to the *air pressure in surrounding areaLow or “L” signifies the center of low pressure system - where *air pressure is relatively low compared to surrounding air*air pressure is calibrated to sea level measurements
10Air PressureWeight of a column of air above a per unit area
11Highs are associated with fair weather Lows are associated with stormy weather
12Horizontal Movement at surface in Highs (anticyclone) Air near the center of Highs flows outward toward lower pressure.Earth’s rotation makes this air spiral outwardIn the northern hemisphere and as seen from above this air moves outward and clockwise
21Vertical Movement in a High Air sinks from above with Highs and replaces outward spiraling airSinking air in Highs warms due to compressionClouds, if present, vaporize and skies tend to clear
22Horizontal movement of air at surface in Lows (cyclone) Air flows toward the center of a lowEarth’s rotation makes this air spiral inwardIn the northern hemisphere and as seen from above this air moves inward and counter clockwise
31Vertical Movement in a Low Air spiraling into low produces an upward motionRising air expands and coolsClouds form and precipitation can develop
32Activity: Highs and Lows Modeling vertical and horizontal air movements using your hands.
33of motion & conditions of the air in which they exist Clouds are Evidenceof motion & conditions of the air in which they existCloud Appreciation Society
34Clouds are:Is a visible suspension of minute water droplets and/or ice crystals in the atmosphere above Earth’s surfaceFog is a cloud in contact with Earth’s surfaceClouds form as a result of condensation or deposition of water vapor in ascending air
35Global Water CycleThe end circulation of a fixed amount of water among Earth’s ocean, atmosphere and terrestrial reservoirs.
36Movement of between Earth’s surface and the atmosphere Evaporation – Process of liquid water molecules absorbing heat energy and changing to water vaporCondensation – Process of water vapor releasing heat energy to the atmosphere and changing to liquid waterTranspiration – Process by which water is taken up by roots of plants and released as water vapor through tiny leaf poresSublimation – Process of ice absorbing heat energy and changing directly to water vaporDeposition - Process of water vapor releasing heat energy to atmosphere and changing directly to icePrecipitation – when water, in liquid or solid form falls from clouds
37Water Vapor in the atmosphere All air contains water vapor, although the amount can vary greatlyAmount of water vapor air can hold has a limit which is dictated by air temperatureWarmer air can “hold” more water vapor than cold airSaturation – air can’t “hold” any more water vaporUnsaturated air can become saturated bya) More water vapor evaporating orb) Cooling the air temperature****
38Most clouds are made by the cooling of air, as air moves upward Boundary between two air masses of different densities Also called an air frontFronts are mapped where the boundary touches Earth’s surface
42Most clouds are made when air cools as it moves upward Air FrontMoving up the slopes of a mountain or hillAir near ground heats up causing less dense air to riseWhere surface winds converge (L) or Low
43Clouds Sky watcher Chart Strong vertical motions, updraftsLong, flat clouds indicate more horizontal air motionShapes, numbers, sizes and motion of clouds gives us clues to what the invisible air is doing.
44Activity: Clouds, Air Pressure and Temperature How to make a cloud appear and disappear?
46Current Weather Studies 1A General info about isobars: An isobar is a line passing through locations having the same air pressure By U.S. conventions, isobars are drawn at 4-mb intervals (e.g., 996 mb, 1000 mb, 1004 mb) In Europe the convention is to use 5-mb intervals
47CWS 1A - Drawing IsobarsDraw an isobar so that air pressure readings greater than the isobar’s value are always on one side of the isobar and lower values are on the other sideAssume a uniform pressure change between neighboring stations. E.g. a 1012-mb isobar would be drawn between 1010 and 1013 about 2/3s the way to 1010.Adjacent isobars tend to have similar shapes. Isobars will generally align with the curves of its neighboring isobars because the horizontal changes in air pressure from place to place are usually gradualDraw isobar until it reaches boundary of map or “closes” to form a loopIsobars never stop or end within a data field, they never fork, or cross one anotherIsobars CANNOT be skipped if their values fall within the range of air pressures reported on the map
48CWS 1B – Air Pressure & Wind Direction Wind direction is identified by the direction from which it is coming…”I want to know where my air is coming from…down from the arctic or from the south.”Air moves from higher pressure area to lower pressure area
49Real Time Data Resources AMS Datastreme AtmosphereUnanalyzed (“Pressures”) with the analyzed (“Isobars & Pressures”) surface pressure mapsWeather maps and maps showing water vaporBlue Hill Observatory in Milton, MANational Weather ServiceSupplies and other resourcesThermometers, American Meteorological SocietyThe WeatherCycler, The Weather SchoolTextbook, Weather Studies by Joseph M. Moran
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