Chapter 5. Air Pollution Meteorology Selami DEMİR Asst. Prof

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<ul><li> Slide 1 </li> <li> Chapter 5. Air Pollution Meteorology Selami DEMR Asst. Prof. </li> <li> Slide 2 </li> <li> 12.09.2015 S. Demir2 Outline Introduction Solar Radiation Atmospheric Pressure Lapse rate &amp; Potential Temperature Atmospheric Stability Coriolis Force &amp; Gravitational Force Pressure Gradient Force Overall Atmospheric Motion Equations of Motion Wind Speed Profile </li> <li> Slide 3 </li> <li> 12.09.2015 S. Demir3 Introduction (1/2) Air pollutant cycle Emission Transport, diffusion, and transformation Deposition Re-insertion In large urban areas, there are several concentrated pollutant sources All sources contribute to pollution at any specific site Determined by mainly meteorological conditions Dispersion patterns must be established Need for mathematical models and meteorological input data for models </li> <li> Slide 4 </li> <li> 12.09.2015 S. Demir4 Introduction (2/2) Three dominant dispersion mechanisms General mean air motion that transport pollutants downwind Turbulent velocity fluctuations that disperse pollutants in all directions Diffusion due to concentration gradients This chapter is devoted to meteorological fundamentals for air pollution modelling </li> <li> Slide 5 </li> <li> 12.09.2015 S. Demir5 Solar Radiation (1/6) Solar constant 8.16 J/cm 2.min 0.4-0.8 visible range, maximum intensity Ref: s/4/4c/Solar_Spectrum.png s/4/4c/Solar_Spectrum.png </li> <li> Slide 6 </li> <li> 12.09.2015 S. Demir6 Solar Radiation (2/6) Distribution of solar energy on earth Ref: OpenLearn Web Site, </li> <li> Slide 7 </li> <li> 12.09.2015 S. Demir7 Solar Radiation (3/6) At right angle on June, 21 Tropic of cancer At right angle on December, 21 Tropic of capricorn At right angle on March, 21 and september, 21 Equator </li> <li> Slide 8 </li> <li> 12.09.2015 S. Demir8 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. Where = Suns angle at the given latitude L 2 = Latitude of given region L 1 = Latitude of region where sunlight reaches surface at right angle </li> <li> Slide 9 </li> <li> 12.09.2015 S. Demir9 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: </li> <li> Slide 10 </li> <li> 12.09.2015 S. Demir10 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, 21 on June, 21 on September, 21 on December, 21 </li> <li> Slide 11 </li> <li> 12.09.2015 S. Demir11 Atmospheric Pressure (1/4) Force on earth surface due to the weight of the atmosphere Defined as force exerted per unit surface area Units of measurement Pascal (Pa), atmospheric pressure unit (apu, atm), newtons per meter-squared (N/m 2 ), water column (m H 2 O), etc. 1 atm = 101325 Pa 1 atm = 10.33 m H 2 O 1 atm = 760 mm Hg 1 Pa = 1 N/m 2 Atmospheric pressure at sea level is 1 atm </li> <li> Slide 12 </li> <li> 12.09.2015 S. Demir12 Atmospheric Pressure (2/4) Consider a stationary air parcel as shown Force balance (assuming no horizontal pressure gradient) </li> <li> Slide 13 </li> <li> 12.09.2015 S. Demir13 Atmospheric Pressure (3/4) Integrating from h = z 0 to h = z produces </li> <li> Slide 14 </li> <li> 12.09.2015 S. Demir14 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. </li> <li> Slide 15 </li> <li> 12.09.2015 S. Demir15 Lapse Rate &amp; Potential Temperature (1/5) Adiabatic no heat exchange with surroundings Consider an air parcel moving upward so rapidly that it experiences no heat exchange with surrounding atmosphere Enthalpy change: where H 1 = initial enthalpy of air parcel H 2 = final enthalpy of air parcel U 1 = initial internal energy U 2 = final internal energy V 1 = initial volume V 2 = final volume </li> <li> Slide 16 </li> <li> 12.09.2015 S. Demir16 Enthalpy change is a function of only temperature when pressure is constant Substituting differential pressure as follows: Since the process is adiabatic, no heat exchange occurs Lapse Rate &amp; Potential Temperature (2/5) By enthalpys definition In infinitesimal expression Internal energy substitution By internal energy definition </li> <li> Slide 17 </li> <li> 12.09.2015 S. Demir17 Lapse Rate &amp; Potential Temperature (3/5) This approximation assumed there is no phase change in the air parcel called Dry Adiabatic Lapse Rate (DALR) If any phase change takes place during the motion, the temperature change will be far more different from DALR Called Saturated (Wet) Adiabatic Lapse Rate (SALR, WALR) Variable, must be calculated for each case Also significant in some cases; this course does not focus on it For standardization purposes, Standard Lapse Rate (SLR), also known as Normal Lapse Rate (NLR), has been defined On average, in middle latitude, temperature changes from 1C to -56.7C SLR = -0.66C/100 m </li> <li> Slide 18 </li> <li> 12.09.2015 S. Demir18 Lapse Rate &amp; Potential Temperature (4/5) Lapse rate measurements are taken by a device called Radiosonde Results of measurements are plotted to obtain Environmental Lapse Rate (ELR) ELR is real atmospheric lapse rate Another significant concept is Potential Temperature Defined as possible ground level temperature of an air parcel at a given altitude where = T p = potential temperature of air parcel T = Temperature of air parcel H = Height of air parcel from ground DALR = Dry adiabatic lapse rate </li> <li> Slide 19 </li> <li> 12.09.2015 S. Demir19 Lapse Rate &amp; Potential Temperature (5/5) Homework (due 18.04.2008) Calculate potential temperature for given data Calculate the atmospheric temperature at 800 m from the ground if the atmosphere shows adiabatic characteristic and the ground level temperature is 12C. Height, mTemperature, C 3508 7502 120014 </li> <li> Slide 20 </li> <li> 12.09.2015 S. Demir20 Atmospheric Stability (1/8) If ELR &lt; DALR Then Superadiabatic meaning unstable ElseIf ELR = DALR Then Neutral ElseIf DALR &lt; ELR &lt; 0 Then Subadiabatic meaning stable (weakly stable) ElseIf DALR &lt; 0 &lt; ELR Then Inversion meaning strongly stable EndIf </li> <li> Slide 21 </li> <li> 12.09.2015 S. Demir21 Atmospheric Stability (2/8) Superadiabatic </li> <li> Slide 22 </li> <li> 12.09.2015 S. Demir22 Atmospheric Stability (3/8) Neutral </li> <li> Slide 23 </li> <li> 12.09.2015 S. Demir23 Atmospheric Stability (4/8) Subadiabatic </li> <li> Slide 24 </li> <li> 12.09.2015 S. Demir24 Atmospheric Stability (5/8) Inversion </li> <li> Slide 25 </li> <li> 12.09.2015 S. Demir25 Atmospheric Stability (6/8) If d/dz &lt; 0 Then Superadiabatic ElseIf d/dz = 0 Then Neutral ElseIf d/dz &gt; 0 Then Subadiabatic EndIf </li> <li> Slide 26 </li> <li> 12.09.2015 S. Demir26 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: The atmosphere is said to be unstable since ELR &lt; DALR </li> <li> Slide 27 </li> <li> 12.09.2015 S. Demir27 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. 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. Height, m Temperature, C Case 1Case 2Case 3Case 4 01422174 10008876 </li> <li> Slide 28 </li> <li> 12.09.2015 S. Demir28 Coriolis Force The 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, </li> <li> Slide 29 </li> <li> 12.09.2015 S. Demir29 Gravitational Force (1/3) The force exerted by the earth on an object in earths attraction range Caused by attraction forces between two masses m 1 being the mass of earth (M) and m 2 is that of an object near earth surface F A = attraction force = 6.668*10 -11 Nm 2 /kg 2 m 1,m 2 = objects masses r = distance bw masses </li> <li> Slide 30 </li> <li> 12.09.2015 S. Demir30 Gravitational Force (2/3) Example: Determine the acceleration of an object near the Eraths surface due to gravitational attraction force Solution: </li> <li> Slide 31 </li> <li> 12.09.2015 S. Demir31 Gravitational Force (3/3) Homework (due 25.04.2008) Determine the acceleration of an object near the Martian surface due to gravitational attraction force Determine the acceleration of an object near the Moons surface due to gravitational attraction force </li> <li> Slide 32 </li> <li> 12.09.2015 S. Demir32 Pressure Gradient Force Consider an air parcel accelerating in a horizontal direction In three dimensional representation, </li> <li> Slide 33 </li> <li> 12.09.2015 S. Demir33 Overall Atmospheric Motion (1/7) Consider an air parsel accelerating around the Earth Overall acceleration </li> <li> Slide 34 </li> <li> 12.09.2015 S. Demir34 Overall Atmospheric Motion (2/7) Neglecting vertical terms and re-arranging, we get u = velocity of atmospheric motion in east- west direction v = velocity of atmospheric motion in north- south direction = rotational speed of earth = 7.29*10 -5 r/s = latitude on which the motion occurs </li> <li> Slide 35 </li> <li> 12.09.2015 S. Demir35 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. </li> <li> Slide 36 </li> <li> 12.09.2015 S. Demir36 Overall Atmospheric Motion (4/7) Solution </li> <li> Slide 37 </li> <li> 12.09.2015 S. Demir37 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 Temperature at 5600 m : -28C Coriolis force: 2 V sin = 7.3 x 10 -5 radians/s; = Latitude degrees ; V= geostrophic wind speed 1 mb = 100 N/m 3 180 km 500 mb 504 mb N </li> <li> Slide 38 </li> <li> 12.09.2015 S. Demir38 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. </li> <li> Slide 39 </li> <li> 12.09.2015 S. Demir39 Overall Atmospheric Motion (7/7) Solution </li> <li> Slide 40 </li> <li> 12.09.2015 S. Demir40 Equations of Motion (1/3) Eularian Approach The observer stays stationary and observes the change in the value of a function f (concentration, atmospheric parameters, etc.) The coordinate system (reference frame) is stationary The objective is moving Lagregian Approach The observer moves with the moving objective and observes the change in the value of a function f The coordinate system is moving with the objective at the same speed and direction </li> <li> Slide 41 </li> <li> 12.09.2015 S. Demir41 Equations of Motion (2/3) Lagregian Approach (contd) </li> <li> Slide 42 </li> <li> 12.09.2015 S. Demir42 Equations of Motion (3/3) Examples will be given later </li> <li> Slide 43 </li> <li> 12.09.2015 S. Demir43 Wind Speed Profile (1/2) Due to friction near surface, wind speed increases with height exponentially Wind speed is measured by a device called anemometer 10 m should be chosen for anemometer height Stability ClassP A0.15 B C0.20 D0.25 E0.40 F0.60 </li> <li> Slide 44 </li> <li> 12.09.2015 S. Demir44 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. </li> </ul>