Chapter 5 . Air Pollution Meteorology

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Chapter 5 . Air Pollution Meteorology. Selami DEMR Asst. Prof. Outline. Introduction Solar Radiation Atmospheric Pressure Lapse rate & Potential Temperature Atmospheric Stability Coriolis Force & Gravitational Force Pressure Gradient Force Overall Atmospheric Motion - PowerPoint PPT Presentation

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<ul><li><p>Chapter 5. Air Pollution MeteorologySelami DEMRAsst. Prof.</p><p>S. Demir</p></li><li><p>*S. Demir*OutlineIntroductionSolar RadiationAtmospheric PressureLapse rate &amp; Potential TemperatureAtmospheric StabilityCoriolis Force &amp; Gravitational ForcePressure Gradient ForceOverall Atmospheric MotionEquations of MotionWind Speed Profile</p><p>S. Demir</p></li><li><p>*S. Demir*Introduction (1/2)Air pollutant cycleEmissionTransport, diffusion, and transformationDeposition Re-insertion In large urban areas, there are several concentrated pollutant sourcesAll sources contribute to pollution at any specific siteDetermined by mainly meteorological conditionsDispersion patterns must be establishedNeed for mathematical models and meteorological input data for models</p><p>S. Demir</p></li><li><p>*S. Demir*Introduction (2/2)Three dominant dispersion mechanismsGeneral mean air motion that transport pollutants downwindTurbulent velocity fluctuations that disperse pollutants in all directionsDiffusion due to concentration gradients</p><p>This chapter is devoted to meteorological fundamentals for air pollution modelling</p><p>S. Demir</p></li><li><p>*S. Demir*Solar Radiation (1/6)Solar constant 8.16 J/cm2.min0.4-0.8 visible range, maximum intensityRef: http://www.globalwarmingart.com/images/4/4c/Solar_Spectrum.png </p><p>S. Demir</p></li><li><p>*S. Demir*Solar Radiation (2/6)Distribution of solar energy on earthRef: OpenLearn Web Site, http://openlearn.open.ac.uk/file.php/1697/t206b1c01f26.jpg </p><p>S. Demir</p></li><li><p>*S. Demir*Solar Radiation (3/6)At right angle on June, 21 Tropic of cancerAt right angle on December, 21 Tropic of capricornAt right angle on March, 21 and september, 21 Equatorhttp://upload.wikimedia.org/wikipedia/commons/8/84/Earth-lighting-equinox_EN.png </p><p>S. Demir</p></li><li><p>*S. Demir*Solar Radiation (4/6)Example: What is the Suns angle over Istanbul on June, 21? Note that Istanbul is located on 40 N latitude.Solution: Sunlight reaches Tropic of Cancer (23 27) at right angle on June, 21.</p><p>Where = Suns angle at the given latitudeL2 = Latitude of given regionL1 = Latitude of region where sunlight reaches surface at right angle</p><p>S. Demir</p></li><li><p>*S. Demir*Solar Radiation (5/6)Example: What is the Suns angle over a city located on 39 N latitude when the sunlight reaches surface at right angle on 21 S latitude? Solution:</p><p>S. Demir</p></li><li><p>*S. Demir*Solar Radiation (6/6)Homework (due 18.04.2008)Make a brief research on Stefan-Boltzman Law and write a one page report for your research.Comment on what would happen if earths inclination were 24 instead of 2327.What determines the seasons? Why some regions of earth get warmer than other regions.Calculate the sunlight angle over Istanbul on March, 21on June, 21on September, 21on December, 21</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Pressure (1/4)Force on earth surface due to the weight of the atmosphereDefined as force exerted per unit surface areaUnits of measurement Pascal (Pa), atmospheric pressure unit (apu, atm), newtons per meter-squared (N/m2), water column (m H2O), etc.1 atm = 101325 Pa1 atm = 10.33 m H2O1 atm = 760 mm Hg1 Pa = 1 N/m2Atmospheric pressure at sea level is 1 atm</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Pressure (2/4)Consider a stationary air parcel as shownForce balance (assuming no horizontal pressure gradient)</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Pressure (3/4)Integrating from h = z0 to h = z produces</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Pressure (4/4)Homework (due 18.04.2008)Make a research about pressure measurement devices and prepare a one-page report for your research. Give brief explanations for each type.Calculate the atmospheric pressure on top of Everest if it is 1013 mb at sea level.</p><p>S. Demir</p></li><li><p>*S. Demir*Lapse Rate &amp; Potential Temperature (1/5)Adiabatic no heat exchange with surroundingsConsider an air parcel moving upward so rapidly that it experiences no heat exchange with surrounding atmosphereEnthalpy change:whereH1 = initial enthalpy of air parcelH2 = final enthalpy of air parcelU1 = initial internal energyU2 = final internal energyV1 = initial volumeV2 = final volume</p><p>S. Demir</p></li><li><p>*S. Demir*Enthalpy change is a function of only temperature when pressure is constant</p><p>Substituting differential pressure as follows:</p><p>Since the process is adiabatic, no heat exchange occurs</p><p>Lapse Rate &amp; Potential Temperature (2/5)By enthalpys definition </p><p>In infinitesimal expression</p><p>Internal energy substitution</p><p>By internal energy definition</p><p>S. Demir</p></li><li><p>*S. Demir*Lapse Rate &amp; Potential Temperature (3/5)This approximation assumed there is no phase change in the air parcelcalled Dry Adiabatic Lapse Rate (DALR)If any phase change takes place during the motion, the temperature change will be far more different from DALRCalled Saturated (Wet) Adiabatic Lapse Rate (SALR, WALR)Variable, must be calculated for each caseAlso significant in some cases; this course does not focus on itFor standardization purposes, Standard Lapse Rate (SLR), also known as Normal Lapse Rate (NLR), has been definedOn average, in middle latitude, temperature changes from 1C to -56.7CSLR = -0.66C/100 m </p><p>S. Demir</p></li><li><p>*S. Demir*Lapse Rate &amp; Potential Temperature (4/5)Lapse rate measurements are taken by a device called RadiosondeResults of measurements are plotted to obtain Environmental Lapse Rate (ELR)ELR is real atmospheric lapse rateAnother significant concept is Potential TemperatureDefined as possible ground level temperature of an air parcel at a given altitude</p><p>where = Tp = potential temperature of air parcelT = Temperature of air parcelH = Height of air parcel from groundDALR = Dry adiabatic lapse rate</p><p>S. Demir</p></li><li><p>*S. Demir*Lapse Rate &amp; Potential Temperature (5/5)Homework (due 18.04.2008)Calculate potential temperature for given data</p><p>Calculate the atmospheric temperature at 800 m from the ground if the atmosphere shows adiabatic characteristic and the ground level temperature is 12C.</p><p>Height, mTemperature, C35087502120014</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Stability (1/8)If ELR &lt; DALR ThenSuperadiabatic meaning unstableElseIf ELR = DALR ThenNeutralElseIf DALR &lt; ELR &lt; 0 ThenSubadiabatic meaning stable (weakly stable)ElseIf DALR &lt; 0 &lt; ELR ThenInversion meaning strongly stableEndIf</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Stability (2/8)Superadiabatic</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Stability (3/8)Neutral</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Stability (4/8)Subadiabatic</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Stability (5/8)Inversion</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Stability (6/8)If d/dz &lt; 0 ThenSuperadiabaticElseIf d/dz = 0 ThenNeutralElseIf d/dz &gt; 0 ThenSubadiabaticEndIf</p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Stability (7/8)Example: Calculate vertical temperature gradient and comment on atmospheric stability condition if the atmospheric temperature at 835 m is 12 C when the ground temperature is 25 C.Solution:</p><p>The atmosphere is said to be unstable since ELR &lt; DALR </p><p>S. Demir</p></li><li><p>*S. Demir*Atmospheric Stability (8/8)Homework (due 25.04.2008)Following measurements are taken over Istanbul at different times. Determine atmospheric stability condition for each case.</p><p>Briefly explain stable air, unstable air, neutral air and inversion.Make a brief research about the role of atmospheric stability in dispersion of pollutants in the atmosphere and prepare a-one-page report for your research.What is conditional stability? Explain.</p><p>Height, mTemperature, CCase 1Case 2Case 3Case 40142217410008876</p><p>S. Demir</p></li><li><p>*S. Demir*Coriolis ForceThe Coriolis effect is an apparent deflection of moving objects from a straight path when they are viewed from a rotating frame of reference. Coriolis effect is caused by the Coriolis force, which appears in the equation of motion of an object in a rotating frame of reference. (Wikipedia Web Site, http://en.wikipedia.org/wiki/Coriolis_Force)</p><p>S. Demir</p></li><li><p>*S. Demir*Gravitational Force (1/3)The force exerted by the earth on an object in earths attraction rangeCaused by attraction forces between two masses</p><p>m1 being the mass of earth (M) and m2 is that of an object near earth surfaceFA = attraction force = 6.668*10-11 Nm2/kg2m1,m2 = objects massesr = distance bw masses</p><p>S. Demir</p></li><li><p>*S. Demir*Gravitational Force (2/3)Example: Determine the acceleration of an object near the Eraths surface due to gravitational attraction forceSolution:</p><p>S. Demir</p></li><li><p>*S. Demir*Gravitational Force (3/3)Homework (due 25.04.2008)Determine the acceleration of an object near the Martian surface due to gravitational attraction forceDetermine the acceleration of an object near the Moons surface due to gravitational attraction force</p><p>S. Demir</p></li><li><p>*S. Demir*Pressure Gradient ForceConsider an air parcel accelerating in a horizontal direction</p><p>In three dimensional representation,</p><p>S. Demir</p></li><li><p>*S. Demir*Overall Atmospheric Motion (1/7)Consider an air parsel accelerating around the EarthOverall acceleration</p><p>S. Demir</p></li><li><p>*S. Demir*Overall Atmospheric Motion (2/7)Neglecting vertical terms and re-arranging, we getu = velocity of atmospheric motion in east-west directionv = velocity of atmospheric motion in north-south direction = rotational speed of earth = 7.29*10-5 r/s = latitude on which the motion occurs</p><p>S. Demir</p></li><li><p>*S. Demir*Overall Atmospheric Motion (3/7)Example: Briefly explain the mechanisms that forced radioactive pollutants towards Turkeys coasts after Chernobyl. Tell about the meteorological conditions then. Show the pressure centers and wind patterns on the day of accident and two day after the accident on a brief map. Consider the aspects of geostrophic winds. </p><p>S. Demir</p></li><li><p>*S. Demir*Overall Atmospheric Motion (4/7)Solution</p><p>S. Demir</p></li><li><p>*S. Demir*Overall Atmospheric Motion (5/7)Example: Isobars are shown in the figure below, for 40 latitude in the Northern Hemisphere, at an altitude of 5600 meters. Determine the geostrophic wind speed in km/hour </p><p>Temperature at 5600 m : -28CCoriolis force: 2 V sin = 7.3 x 10-5 radians/s; = Latitude degrees ; V= geostrophic wind speed1 mb = 100 N/m3</p><p>S. Demir</p></li><li><p>*S. Demir*Overall Atmospheric Motion (6/7)Example:Suppose a nuclear accident occurs at a place of 3,000 km west of Istanbul. Radioactive pollutants are pumped above the planetary boundary layer (PBL) with the power of explosion. On the day of nuclear accident, the radiosonde data taken at different places of Europe shows that atmospheric pressure is decreasing towards north at a rate of 0.0015 N/m3 and this pattern is valid for the whole Europe. Will the radioactivity affect Istanbul? If yes, when? Note that Istanbul is located on 40 northern latitude and worlds angular speed of rotation is 7.3 * 10-5 radians/sec. You may assume the density of air at the level where geostrophic wind equations apply as 0.70 kg/m3. </p><p>S. Demir</p></li><li><p>*S. Demir*Overall Atmospheric Motion (7/7)Solution</p><p>S. Demir</p></li><li><p>*S. Demir*Equations of Motion (1/3)Eularian ApproachThe observer stays stationary and observes the change in the value of a function f (concentration, atmospheric parameters, etc.)The coordinate system (reference frame) is stationaryThe objective is movingLagregian ApproachThe observer moves with the moving objective and observes the change in the value of a function fThe coordinate system is moving with the objective at the same speed and direction</p><p>S. Demir</p></li><li><p>*S. Demir*Equations of Motion (2/3)Lagregian Approach (contd)</p><p>S. Demir</p></li><li><p>*S. Demir*Equations of Motion (3/3)Examples will be given later</p><p>S. Demir</p></li><li><p>*S. Demir*Wind Speed Profile (1/2)Due to friction near surface, wind speed increases with height exponentiallyWind speed is measured by a device called anemometer10 m should be chosen for anemometer height</p><p>Stability ClassPA0.15B0.15C0.20D0.25E0.40F0.60</p><p>S. Demir</p></li><li><p>*S. Demir*Wind Speed Profile (2/2)Homework (due 25.08.2008)Calculate wind speeds for Class B stability at 20, 30, 50, 100, 200, and 500 m if it is 1.2 m/sec. Plot the results.Comment on how the wind speed would change with altitude if the stability class were Class E.</p><p>S. Demir</p><p>**********</p></li></ul>

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