The relative humidity is 77 on a january day when the

Question

Assignment - Answer 20 questions.

Question 1 - To determine the maximum altitude of the sun in the sky at a particular location on a particular day of the year, you must know the difference between the latitude of the location and the latitude at which the sun is directly overhead on that particular day. If we call the difference D, then the maximum altitude of the sun (in degrees) at the latitude of interest is 90-D.

For example, if you are in Washington, DC (latitude approximately 39^oN), and the sun is overhead that day at latitude 10^oN, then D = 29^o. The maximum altitude of the sun in Washington, DC that day would be 90^o - 29^o = 61^o.

Determine the maximum altitude of the sun at your latitude on the equinoxes and on the solstices.

Question 2 - The table below gives the elevation above sea level (in ft) and the annual average temperature (in ^oF) for several locations at approximately the same latitude along a line from central Tennessee eastward across the Appalachian Mountains to central North Carolina.

	Elevation (ft)	Average Annual Temperature (oF)
Crossville, TN	1880	55.5
Knoxville, TN	981	58.4
Marshall, NC	2000	52.9
Hickory, NC	1188	58.7
Salisbury, NC	700	59.8
Raleigh, NC	440	59.6

a. On a sheet of graph paper, plot the average annual temperature (on the vertical axis) versus elevation (on the horizontal axis) for these stations.

b. Your points will not lie precisely on a straight line. However, because air temperature generally decreases with elevation in the troposphere, the points should tend to orient themselves in a linear fashion. Draw a straight line of best fit to your plotted data, and compute the slope of your line, thereby providing a numerical estimate of the effect of elevation on average temperature. How close is your estimate to the average environmental lapse rate? (Hint: to draw a straight line of best fit through a set of points, think of the points as sculptures scattered in a large room of an art museum. You want to get as close as possible to all the sculptures, but you are required to walk through the room in a straight line. The most efficient path for you to navigate will give you a sense for a straight line of best fit through the points.)

Question 3 - The January and July average monthly temperatures (in ^oF) for four cities are given in the table below. The cities are Seattle, WA; Minneapolis, MN; Dallas, TX; and Miami, FL. Match each city to its data. Present brief arguments to justify your decisions.

	Average January Temperature (oF)	Average July Temperature (oF)
City A	44.1	85.0
City B	13.1	73.2
City C	40.9	65.3
City D	68.1	83.7

Question 4 - Figure 3.36 shows the average January minimum temperature (in ^oF) for many locations in New York State.

a. Draw all isotherms that are multiples-of-five.

b. Describe the general location of the highest average minimum temperatures. Why do the highest average minimums occur in these areas?

c. In general, temperatures are lower in northern New York State (not unexpected owing to the higher latitude). However, what feature of the temperature pattern would lead you to believe that an interior area of upstate New York is also higher in elevation?

Question 5 - Figure 3.38 shows isopleths of the annual range in surface temperature (in ^oC) for the globe. The annual range is, essentially, the difference between the average temperatures of the warmest and coldest months of the year-also known as seasonality. Latitude and longitude lines and continental boundaries are not shown, but there are patterns to the data that should provide some geographical bearing.

a. Label North America, South America, Asia, Europe, Africa and Australia. Also label the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, and the Sahara Desert.

b. What general principles guided your decisions in part (a)?

c. Where are the largest seasonalities in the world? Why is this area an ideal location for large temperature swings from winter to summer?

Question 6 - You and a friend have precisely calibrated thermometers that can be read to the nearest tenth of a degree Fahrenheit. In New York City, you remain at street level while your friend walks 102 stories (whew!) to the observation deck of the Empire State Building (elevation 1250 ft, or 381 m). Your thermometer at ground level registers 80.4^oF (26.9^oC). Assuming the average environmental lapse rate, what will your friend's thermometer register (to the nearest tenth of a degree Fahrenheit)? Show your work.

Question 7 - Figure 3.42 shows a week's worth of temperature observations for a mid-latitude location in the spring. Based solely on this temperature information, which day was most likely the least cloudy? Which day was most likely the cloudiest? What characteristic of the temperature trace helped you decide?

Question 8 - Remember that the relative humidity depends on temperature; thus, the relative humidity can change even if the water vapor content of the air remains constant. With this in mind:

a. Assume that from 7 P.M. one evening until 7 A.M. the next morning, temperature decreases (in a typical nighttime way). Further assume that during this period, the dew point remains constant. Describe the variation of relative humidity during this period.

b. The difference between the temperature and the dew point is called the dew-point depression. For the same time period in part (a), describe the variation of the dew-point depression. What is the relationship between dew-point depression and relative humidity?

Question 9 - Figure 4.49 is a photograph of the sky over Nauru, a tiny is-land in the tropical western Pacific Ocean. Note the lack of haze, despite the rather high relative humidity in the lower troposphere over this warm ocean. This lack of haze and the high visibility are typical of tropical air masses. In a brief paragraph, explain why the sky over the tropical oceans is typically not very hazy.

Question 10 - Determine the values of the missing entries (represented by letters) in the following table of relative humidity, vapor pressure, and equilibrium vapor pressure. Be sure to include units in your answers.

	Relative Humidity (percent)	Vapor Pressure (mb)	Equilibrium Vapor Pressure (mb)
City 1	75	9	A
City 2	30	B	12
City 3	C	2.5	10
City 4	5	D	20
City 5	90	4.5	E
City 6	F	11	11

Question 11 - Parts (b)-(d) of this question require you to assess whether a cloud will develop from the mixing of two parcels of air of various temperature and moisture characteristics.

a. Which figure serves as the "Operator's Manual" to help you answer parts (b)-(d)?

b. A volume of air with a temperature of 68^oF and a vapor pressure of 10 mb mixes with a volume of air of temperature 86^oF and vapor pressure 30 mb. Does a cloud form? Explain your answer.

c. You exhale on a day when the air temperature is 40^oF and the vapor pressure is about 9 mb. Do you see your breath? Explain your answer. What about on a day when the air temperature is 40^oF and the vapor pressure is 4 mb? Again, explain your answer.

d. Assume that the water-air interface over a hot tub has a temperature of 104^oF and a vapor pressure of 70 mb. The environmental air (the air above the water-air interface) at this time has a temperature of 60^oF and a vapor pressure of 10 mb. Does steam fog form above the hot tub? Explain your answer.

Question 12 - Figure 4.54 is a satellite view of the eastern Atlantic Ocean off the coast of France (the southwestern corner of England is seen at the upper right of the image). The long, narrow stripes of cloud are that formed from the exhaust of large shipping vessels crisscrossing the Atlantic. Essentially, ship trails are the maritime version of contrails.

a. Categorize these ship trails according to the mechanism by which they formed. In other words, did they form as a result of cooling by lifting, cooling by contact with the earth's surface, or mixing?

b. Given that these ship trails were fairly long-lived, qualitatively describe the relative humidity off the coast of France around this time (in other words, was it high or low?). Explain how the high or low relative humidity contributed to the long life spans of the ship trails by focusing on and comparing rates of evaporation and condensation.

c. Were there likely more condensation nuclei in a given volume of cloudy air within the ship trails or within the naturally formed low clouds over the open sea where there weren't any ships at this time? Briefly explain.

Question 13 - Figure 4.58 is a portion of a meteogram from Billings, MT from 00Z to 12Z on a recent December day. The time traces of temperature and dew point, along with the symbols for obstructions to visibility, are shown.

Explain, in a brief paragraph, the drop in temperature and corresponding rise in dew point from 04Z to 06Z. Include specific references to the physical processes that caused these changes.

Question 14 - In this question, you learned that certain geographical features (such as rivers and lakes) can be easy to identify on infrared satellite imagery at certain times of the year.

a. In Figure 5.39a, you are given the minimum temperatures (in ^oF) recorded across the Upper Middle West early on the morning of September 28, 2004. These lows were several degrees below average for late September. What were the optimal nighttime sky conditions and surface wind speeds that likely paved the way for these temperatures? Briefly explain your answer. You may assume that there was dramatic net radiational cooling during the nighttime hours.

b.Figure 5.39b is the 1115Z infrared satellite image over the Northern Plains and Upper Middle West on September 28, 2004. What was the local time in central South Dakota at 1115Z (in Mountain Daylight Saving Time)? Was this time before or after sunrise in central South Dakota? Hint: Sunrise over central South Dakota occurred a few minutes after 6:30 A.M. MDT on this date.

c. In light of your answer in part (a) (regarding sky conditions during the nighttime), what is the thin, dark feature that meanders across central South Dakota on the infrared satellite image? You may need to consult an atlas.

d. Is this feature cooler or warmer than the surrounding land? Briefly explain, invoking principles for interpreting infrared satellite imagery and the concept of seasonal temperature lag. Keep in mind that it's September.

Question 15 - Figure 5.40a is an infrared satellite image at 1145Z on November 16, 2006, showing portions of the western Gulf States.

a. What was the local time in Central Standard Time?

b. Was the sky cloudy or clear over most of Mississippi? Explain your answer using principles you learned about infrared satellite imagery.

c. Was the sky cloudy or clear over most of Louisiana and eastern Texas? Again, explain your answer using principles about infrared satellite imagery.

Question 16 - Visible satellite imagery is almost completely useless at night. We say "almost" because some low-flying defense satellites equipped with very sensitive low-light sensors can "see in the dark" On clear nights, such satellites can detect light from cities. Figure 5.43 is an example of such an image of the eastern United States. Cities, with their huge output of artificial light, show up as bright splotches. Using this image:

a. Find the following cities: Atlanta; Cleveland; Boston; Montreal; Chicago; the Washington/Baltimore area; Orlando; Memphis; Detroit; Miami.

b. Note the streaks of light over the Atlantic Ocean. What do you think these are? (Hint: They are not lights on islands or lights from ships, but rather a natural meteorological phenomenon.)

Question 17 - In southern California, a warm dry east or northeast wind that descends (downslopes) from the elevated desert plateaus is called a Santa Ana. Such winds dramatically dry out vegetation and heighten the risk for a particular phenomenon.

Figure 5.45 is a special satellite image showing southern California and adjacent Pacific waters on October 26, 2003. The image was created using a combination of visible and infrared wavelengths. In the context of Santa Ana winds (which were blowing at the time), what do the red splotches likely represent? What is the bluish-gray pall over the Pacific Ocean?

Question 18 - Figures 5.46 is a visible satellite image taken a few hours after sunrise on a mid-February day. This image shows a nearly linear dark band oriented in a general northeast-to-south-west direction across central Pennsylvania. Considering the time of day and the time of year when the image was made, offer an explanation for how this dark band was produced. It will help to know that the clouds to the east of the dark band were higher than the clouds located directly to the west.

Question 19 - The temperature outside i.s 88 degrees with a dewpoint of 66. Calculate the water-vapor pressure, the relative humidity and the mixing ratio in proper units. Do not use tables.

Question 20 - The relative humidity is 77% on a January day when the temperature is 25 degrees Fahrenheit. Calculate the dewpoint and mixing ratio without consulting tables.