# 3. Urban Heat Island StudyPresentation on Reno average night time temperature over time. Data sheet for infrared thermometer measurements of various surface temperatures (pdf) and (msword) formats.EPA website on the Urban Heat Island Effect. Energy savings methods for reducing the Urban Heat Island Effect.

 Average Monthly Energy Use by State: Click on image for larger version.

# 5. Solar and infrared radiation in the atmosphere discussion and demonstration notes.

Questions:
Use an visible wavelength range spectrometer covering from 350 nm to 1000 nm (more or less).
Be sure the software makes the wavelength axis visible with large fonts.
Discuss a little bit about how diffraction gratings work, and dispersion of light, maybe using a CD or DVD, or simple diffraction grating to make the point.
It may be useful to demonstrate the spectrometer made from plumbing parts, with a slit on the end, diffraction grating or CD, and eye as detector.
Look at the spectra of 405 nm, 650 nm, and 532 nm laser pointers. 532 nm laser pointers also often have 808 nm and 1064 nm lines from the way they are made.
Talk briefly about the lasers in general (explain what lasing is all about), laser diodes, and the optics of the 532 nm laser pointer.
Measure fluorescence of paper, or a construction piece of clothing, etc, using the 405 nm laser diode as the source.
Look at the spectrum of light from a cell phone light source. Show how it is enhanced in the blue, and that the broad part of the spectrum extends to about 700 nm.
Discuss how the light is made from the cell phone light source; LED to drive a fluorescing material, and a decent use of electrical power since the light is covering the visible
spectrum, but not the near IR or UV.
Then show the spectrum of a flashlight that uses an incandescent light bulb. Notice how a large amount of the radiation is in the near IR, not useful for lighting for the human eye
as a detector. Notice that the light warms bare skin because the near IR is absorbed. Talk about the blackbody nature of this radiation source, and the relatively lower efficiency for visible light production compared with the LED source. Then proceed with the questions below, using the spreadsheet mentioned above.
1. What wavelength range comprises solar radiation at the Earth's surface?
2. How is solar radiation affected by the Earth's atmosphere and surface?
3. What is the equivalent black body temperature of the Sun with regard to the solar spectrum we see at the top of the Earth's atmosphere?
4. How much solar radiation (irradiance) is present at the top of the Earth's atmosphere in watts per square meter units?
5. How many one square meter, 20% efficient solar panels would be needed at the top of the Earth's to run a 2000 watt hair dryer?
6. What are the primary atomic and molecular properties are involved with absorption of solar radiation at wavelengths from the UV to the near IR?
7. What is the peak wavelength of solar radiation?
Infrared Radiation (review the link in the title to obtain the demonstrations made using the IR camera).
8. We did a 'high five' in class by pointing our hands towards each other and letting the infrared photons fly. Assuming human skin is a perfect blackbody emitter and absorber, and that the hand is at normal body temperature (expressed in Kelvin units), use the Stefan Boltzmann law to calculate how much radiation in watts per square meter is emitted by your hand. What fraction is this compared with the solar radiation at the top of the atmosphere?
9. Use Wien's displacement law to calculate the peak wavelength of infrared emission by your hand, using the same temperature from question 8, and the sun's equivalent blackbody temperature from question 3.
10. Suppose that one hand was dipped in water and then you waved dry air over your hand to cause it to evaporate. What does the infrared camera show for your hand show for your wet hand temperature compared with your dry hand temperature, and why?
11. When looking at a person with an infrared camera, why is the face warm while the hair, nose, glasses, and clothes look cool by comparison?
12. In the experiment with a small square of aluminum foil put on a student's forehead, it was observed that the aluminum foil looked dramatically cool, even though the aluminum foil is at the same temperature as the forehead. From this observation we can learn about how aluminum interacts with infrared radiation: describe this.
13. We were able to write a message on the wall just by vigorously rubbing it in the pattern of letters, and observing it with the infrared camera. How does this work? Could we make a cool message by putting a thin film of water on the wall and evaporating it? (try this).
14. We did a demonstration with the dinner plate that was transparent at visible wavelengths, and argued that it must be a strong absorber because we can't see the infrared radiation emitted by a hand if the plate is between the hand and the camera. Describe how the plate is like the Earth's atmosphere in its effect on visible and infrared radiation, and the 'greenhouse' effect. Which gases in the atmosphere are infrared active as 'greenhouse' gases?
15. We did a demonstration of visualizing atmospheric convection by having the camera visualize the hot air, from use of a propane torch below the camera field of view, rise into the field of view of the camera. We also did a demonstrate of thermal conduction by heating the glass rod with the propane torch. Which process is more effective at transferring heat in the atmosphere above the Earth's surface? By the way, why does the hot air rise? And why is the hot air visible -- what are the gases produced by combustion of the propane, and are they infrared active gases that can absorb and emit infrared radiation?
16. As time permits, we will also fill a transparent container with water and use the infrared camera to view the water. Is water a strong absorber and emitter of infrared radiation? How can you figure this out? Can you observe thermally induced convection in the water using the camera? Would you expect ice to behave the same as water in its interaction with infrared radiation?
This laboratory (pdf version; MSword version) further explores the role of infrared radiation in climate, and the impacts of infrared active species such as water vapor, carbon dioxide, and clouds. The summary graph is here, based on the model approach described in this lab exercise. Click on the image for a larger version.

Here is a classic paper that looks at this issue is a more comprehensive manner.
Here is a counter point to the classic paper.
Here is an update of the classic paper.

# 6. Skew T log P Lab and Stability Demonstration

Why Skew T?
Shows the thermodynamic state of the atmosphere, and potentially hazardous conditions (ultra stable, unstable).

Notes:
Hot air rises cold air sinks. (example of July in Oklahoma, image showing updraft, and storm vertical wind speed)
5 curves on the graph: Pressure, temperature, water vapor mixing ratio, dry adiabats, moist adiabats.
Examples of pressure: Reno, Donner summit, Mt. Whitney, Mt Everest (make a table of elevations, read pressure from skewT.)

 Location Elevation (feet) Elevation (kilometers) Pressure (mb) Reno 4506 1.373 Donner Summit 7056 2.151 Mt Whitney 14,505 4.421 Mt Everest 29,029 8.848

Measure room temperature, wet bulb temperature, pressure; get the lifting condensation level (cloud base), dew point temperature, and relative humidity (using skewT) and Normand's rule:
Stability (graph of options)
Lab: go to your favorite place and interpret the skew T for a specific time. (may use both the text and gif image).
Useful for the lab: Normand's rule and stability.

First demonstrate Archimedes principle.
Get a transparent tank filled with water. Discuss how the pressure varies with height from the top of the water surface. P=(density*g*height into fluid).
Show that metal pipes sink, but hollow metal spheres float. Ask for reasons why.
Test various vegetables, fruits, and objects to see if they float or sink. Note how close to the top they are as they float. Discuss.
For things that sink, discuss object density and absolute stability, that a dense air parcel (compared with surroundings), will sink.
For things that float, demonstrate instability by pushing the object to the bottom of the tank and releasing it. Being less dense than the surrounding fluid, it rises up.
Release a metal sphere, or better, ping pong ball, from the bottom of the tank and let it rise quickly to overshoot it's equilibrium position. Discuss how this is like a strong thunderstorm with a high updraft.
Write down the ideal gas law in terms of the density, pressure, temperature, and gas constant. Discuss how density depends on these variables.
Advanced courses: Write down the total force as an integral of pressure over the surface; use the gradient theorem to convert to a volume integral and solve for a cube. (Here's one discussion).

Next, use a water proof temperature sensor to measure first the air temperature; then put a cotton sleeve over the thermometer and tie it in place with thread; have a student report the air temperature. Show at first there is not much of a temperature change. Then twirl it around on its chord to evaporate water and cool the sensor. Measure the resulting wet bulb temperature. Talk about how it's necessary to use clean water for this, and the relation with Raolt's law (lowering the vapor pressure). Use a skew T graph; ask the student's for their impression of the absolute atmospheric pressure, having measured it in advance (not sea level equivalent pressure); show the air temperature and wet bulb temperature on it for the surface pressure. Go up from the air temperature along the dry adiabat through that point, and up a moist adiabat through the wet bulb temperature until they intersect -- that's the lifting condensation level (LCL). Talk about the significance of that. Then go down from the LCL following the line of constant mixing ratio to arrive at the same pressure level and read off the dew point temperature. Summarize about everything that can be learned from those two temperature measurements.

Next: Use this website to look at soundings for Barrow Alaska in March for a very stable sounding, and Oklahoma in summer for unstable conditions with a lot of convective available potential energy (CAPE). For the Oklahoma sounding, calculate the maximum updraft speed W in meters per second at the equilibrium level using W=SQRT(2 * CAPE) and discuss how this is potential energy converted into kinetic energy. Convert to miles per hour using 1 meter per second = 2.24 miles per hour.

Next, do the Skew T log P lab:
Here's the lab in MSword format.
Here's the lab in PDF format.
Practice skew T presentation.
Skew T as a gif file.

# 7. WAVES IN THE ATMOSPHERE AND INTERESTING THINGS.

Demonstration longitudinal, transverse, linear, circular and elliptical polarization of waves using a slinky.

Atmospheric basics, circulation, and waves:
Rossby Waves
1. Basics of pressure. Pressure dropping off with height in the atmosphere.
2. Scale height of the atmosphere H=RT/g, and sketch versus latitude.
3. Pressure gradients aloft driving air north from the equator sketch.
4. Wind as a result of air moving north from the equator where rotational velocity is greater than at poles. (angular momentum conservation).
5. Cold air spilling out of the Arctic: Sharp temperature gradient giving rise to strong winds; jet stream.
6. Meander of jet stream giving rise to upward motion, low pressure at the surface, storms.
7. Current jet stream from weather models. (go to upper dynamics, 250 mb level). (Example from November 2019).
8. Idea of the tropopause.
9. Large scale atmospheric circulation. Another view with vertical structure.
10. Model calculations of the dynamical tropopause showing the clash of cold and warm air and Rossby waves.
Gravity Waves
11. Atmospheric gravity waves forced by flow over mountains. Formation of gravity waves in the atmosphere and associated clouds (slides 6-28).
12. Use NASA Worldview to look for gravity waves on different days.
Sound Waves
13. Sound waves in the atmosphere and the observability of thunder. (slides 2-5)
Kelvin Helmholtz Instability (Wind Shear) Waves
14. View Guadalupe Island using Google Earth online and MODIS imagery from NASA Worldview for cloud examples of Von Kármán vortex street circulation downwind of the island.
15. KH waves observed in Colorado Clouds.

Diffraction by cloud droplets, and direct and diffuse radiation:
Electromagnetic Waves
16. Diffraction in general. Diffraction in the atmosphere. My solar corona photo. My diffuse corona photo from dust during Mexico project. Cloud iridescence from diffraction by uniform cloud droplets.
17. Demonstrate diffraction with a laser pointer hitting a 'hair' suspended on a business card.
18. Demonstrate diffraction from a diffraction grating. Bring two lasers if possible (blue and red).
19. Demonstrate refraction and focusing with the laser pointer and dimpled bathroom glass. Fold and cusp caustics due to the 4 fold symmetry. Fold is analogous to a rainbow.
20. Demonstrate diffuse radiation from a cotton stratus and cumulus clouds. Diffuse radiation through a hand and through the cheek.
21. Multiple scattering within a graupel particle (cloud droplets frozen to a falling snow crystal).

Falling Hailstones:
Just Plain Awesome

22. Record setting hailstone falls in Vivian South Dakota.
23. Speed of falling objects once they reach their terminal velocity.
24. Speed of falling cloud and drizzle droplets and rain drops.