The total maximum points were 100.
Using the tables of Apparent Temperature and Heat Stress Hazards in your text book (pages 129-130), determine the apparent temperatures for the following set of air temperatures and relative humidities. Indicate what human hazards are possible. (8 pts)
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(3 pts)
Does this situation appear reasonable? Why? Explain with personal examples.
Yes, this situation is very reasonable since greater evaporation of perspiration (sweat) occurs when the relative humidity is low, making a person feel cooler due to the latent heat of evaporation. Any one who has traveled to the Desert Southwest or other places in the West where the moisture content of the air is low (low dewpoints or low relative humidities) typically would remark that they do not feel as hot as in the more humid Southeast. Even in Madison, days where a hot conditions associated with a west wind with lower humidities do not feel as uncomfortable as those days when a south wind would carry humid tropical air masses from the Gulf of Mexico.
(2 pts)
How is heat lost most effectively from the human body on a hot summer day?
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(11 pts,. 4 pts each for a and b, 3 pts for c)
a. Name two (2) requirements for the collision-coalescence theory:
1. Warm clouds with temperatures greater than 0° C.
2. Non uniform sized droplets
b. Name two (2) requirements for the ice crystal (Bergeron) theory:
1. Cold clouds with temperatures less than 0° C
2. A mixture of ice crystals and supercooled water droplets.
c. Why is the simple diffusion-condensation process not considered a plausible precipitation formation process?
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(6 pts)
d. By how many times does the volume of a typical cloud droplet (with a diameter of 20 micrometers) have to increase to form a typical rain drop (diameter of 2 millimeter)? (Please show your work for partial credit!)
Recall that the volume of a sphere is proportional to the cube of the sphere's radius. So, you can form a proportion between the radii (or one half the diameter) after you have converted the radii to common units:
Radius of the cloud droplet is 20 micrometers/2 = 0.01 millimeter
Radius of the droplet is 200 millimeters/2 = 1 millimeter
Thus, the ratio between the radii is 1/100, but the ratio of the volumes is the ratio of the cubes of the radii or 1/1,000,000.
In other words, the volume of the raindrop in this example is million (1,000,000) times the volume of the droplet.
(6 pts)
Distinguish between freezing rain and ice pellets:
Freezing rain: Freezing rain contains raindrops that freeze upon contact with a cold surface (temperatures at or below the nominal freezing point of 0°C or 32°F). These droplets do not bounce, but form a glaze. Large accumulations of ice or glaze in a freezing rain storm is also known as an ice storm. Freezing rain occurs when only a relatively shallow layer of cold air remains near the surface, while a deep layer of warm air (temperatures above freezing) occur aloft.
Ice pellets:
Ice pellets (also known as sleet) are frozen raindrops that have frozen in a relatively deep (as compared with the above freezing rain situation) layer of cold air that lies above the surface, but below a deep warm air layer. Ice pellets bounce when they hit the ground.
(9 pts - 3 pts. each)
Last winter, Madison received four major snowstorms with total snowfall amounts for each storm totaling 4 inches or more. On 27 Nov 1995, 7.6 inches of snow fell, with a liquid water equivalent of 1.33 inch. On 26 to 27 Jan 1996, 13.4 inches of snow fell, with a liquid water equivalent of 1.00 inch. Calculate the snow to liquid ratio (the number of inches of snow to every inch of liquid water equivalent) for each storm.
27 Nov 1995 . The snow to liquid ratio is 7.6 inches of snow to 1.33 inches, or forming a proportion so as to state the ratio with one inch in the denominator requires dividing 7.6 to 1.33 or 5.71 to 1.
26 to 27 Jan 1996. The snow to liquid ratio is 13.4 to 1
Which storm had the "fluffy stuff" (as compared with the heavy, wet snow with a high liquid content)?
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How do these ratios for the two storms compare with the typical 10 to 1 ratio often used?
The 10 to 1 ratio is only a rough rule of thumb - since in the first case, the snow was heavier and gave a ratio that was about half the typical ratio (meaning that the standard ratio would underestimate the liquid content from the snow depth), while in the second case the snow was more fluffy and would pile to a 30% greater depth than would be estimated from the liquid equivalent (or stated differently, the liquid equivalent would be overestimated from the snow depth).
(9 pts)
Where is the greatest annual total precipitation in the United States?
How much precipitation typically is observed at this locale? Note: This question should have read:
.What was the greatest amount of rain that has been recorded in one day in the United States?
Where was this daily record rainfall recorded?
Approximately how long is the world record dry spell?
What was the record amount of snow that has fallen in one day in the United States?
Where was this daily record snowfall recorded?
Where is the greatest annual total snow fall in the United States?
How much snow fell at this station?
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(36 pts for a, 8 pts for b and 4 pts for c)
a. For the following atmospheric optical phenomena, identify:
PHYSICAL CAUSE(S): Refraction of light by density differences in the atmosphere
THE AGENT(S): Lower atmosphere with a strong vertical temperature -- and ultimately vertical density gradient.
WHERE (WHEN) FOUND: Large vertical temperature and density gradients, such as the hot pavement and cool air immediately above, or the cold lake and warm overlying air mass.
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PHYSICAL CAUSE(S): Refraction and dispersion of light entering the raindrop, the internal reflection of this light from the back surface of the drop and the refraction of the reflected light.
THE AGENT(S): Falling liquid raindrops.
WHERE (WHEN) FOUND: Look away from the low sun (due to geometry considerations, the sun should be no higher than 42 above the horizon) and toward a rain shaft of falling raindrops.
b. What is the physical difference between Rayleigh and Mie scattering? Identify the characteristics of the particles responsible for each type of scatter.
Rayleigh scatter occurs when the incoming radiation (typically polychromatic sunlight) is scattered by gas molecules or other particles in the atmosphere that have a diameter typically less than one tenth the size of the wavelength of the incident radiation - or on the order of 0.05 micrometers. This type of scattering is wavelength dependent, with the short or blue and violet wavelengths preferentially scattered more than the longer wavelength red light.
Mie scatter occurs when the incoming radiation is scattered by large aerosols or cloud droplets that have wavelengths at least as large as the wavelength of the incoming radiation. This type of radiation is independent of wavelength, meaning that the polychromatic white light is scattered and still appears as a milky white light.
Cite an example of each of these two scattering processes.
Blue skies - an example of Rayleigh scatter
White clouds (at least when viewed from the side or above) - an example of Mie scatter.
Note red sunsets in relatively clean air would represent Rayleigh scatter, but if sufficient aerosol loading of the atmosphere were present, vivid red sunsets would indicate Mie scatter.
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