ERTH 360 Test #2 Key Fall pts

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1 DEPARTMENT OF EARTH & CLIMATE SCIENCES SAN FRANCISCO STATE UNIVERSITY Nov 29, 2016 ERTH 360 Test #2 Key Fall pts Each question is worth 4 points. Indicate your BEST CHOICE for each question on the Scantron Form. Turn in and and put your name on your Scantron Form. Part 1. Weather Forecast Products The portal website that we just have been using to access forecast weather maps is shown below. The selection chart from one of the models, known as the GPS, is reproduced below as Table 1. Assume that the choices indicate forecast weather maps for 24 hours in the future. Questions 1 through 5 refer to choices that appear in rows in Figure 1. Figure 1: Selection Choices for the GFS State which choice you would choose to find: 1. The wind conditions at approximately ft a. 300 mb b. 500 mb c. SLP/Thickness/Pcpn d. 700 mb/rh e. (a) and (b) both. 1

2 2. The Sea level weather (isobars) map a. 300 mb b. 500 mb c. SLP/Thickness/Pcpn d. 700 mb/rh e. (a) and (b) both. 3. The wind conditions at approximately ft a. 300 mb b. 500 mb c. SLP/Thickness/Pcpn d. 700 mb/rh e. (a) and (b) both. 4. The position of mid and upper tropospheric troughs and ridges. a. 300 mb b. 500 mb c. SLP/Thickness/Pcpn d. 700 mb/rh e. (a) and (b) both. 5. The model heading is GFS. This is an abbreviation of a. Guidance for Frontal Systems b. Graded Flight Selections c. Grouped Forecast Selections d. Gridded Forecast Solutions e. Global Forecast System Part 2. Special Assignment. Figure 2 is taken from the Documentary you watched on the El Reno OK May 31, 2013 tornado. Questions 6, 7, 8, and 9 ask you questions about the videos you watched. Figure 2: Screen capture from video on the El Reno OK tornado of 31 May On Figure 2, the yellow line 2

3 a. shows the route of an airplane intercept of the El Reno tornado. b. shows the boundary of a Tornado Warning for the storm. c. shows the path taken by a mobile mesonet in intercepting the storm. d. shows the track of a secondary subvortex circling the parent tornado that struck the vehicle in which Tim Samaras, Paul Samaras, and Karl Young were driving. e. is Interstate 40 in Oklahoma. 7. The closest position of the Reed Timmer team with respect to the Wray CO tornado was dangerous because a. the obvious tornado is often surrounded by tornado strength winds outside of visible funnel. b. the obvious tornado motion is often erratic and can double back, reverse, speed up on its own path. c. The team put itself at risk from being struck by any secondary tornado associated with the visible tornado. d. The team put themselves at risk because the diameter of the tornado can expand rapidly. e. all of the above. 8. The TWISTEX team made which of the following mistakes in their attempt to deploy instruments in the path of the El Reno tornado. a. The team was driving too fast and missed an important turn. b. The team made a navigational error that took them into the center of the parent tornado. c. The team put itself at risk from being struck by any secondary tornado associated with the visible tornado. d. The team put themselves at risk by sheltering from heavy rain in the wrong location. e. The team stopped to eat lunch and lost track of the tornado. 9. The closest position of the Brunin-Magowan team with respect to the Katie OK tornado was dangerous because a. the obvious tornado is often surrounded by tornado strength winds outside of visible funnel. b. the obvious tornado motion is often erratic and can double back, reverse, speed up on its own path. c. The team put itself at risk from being struck by any secondary tornado associated with the visible tornado. d. The team put themselves at risk because the diameter of the tornado can expand rapidly. e. all of the above. Part 3. Use and Interpretation of Weather Maps Figure 3 is the 300 mb chart for 06 UTC 31 October Note Lines A, B, C, D, and E and also note the Arrows Labeled 1, 2, 3, 4, and 5 3

4 Figure mb Chart for 0600 UTC 31 October On Fig. 3, a ridge is at Line(s) a. B and A (both) b. A and E (both) c. C d. D e. A 11. On Fig. 3, a (surface dynamic high would be located at a. A and E (both) b. D and E (both) c. C d. D e. B 12. On Fig. 3, divergence is probably occurring at Location a. A b. B c. C d. D e. E 4

5 13. On the basis of your interpretation of Fig. 3, the arrow which best shows the position of the polar jet stream is a. 1 b. 2 c. 3 d. 4 e. 5 Figure 4 is the surface chart for 12 UTC 9 November Note the pressure systems at A and B and the frontal lines at locations a, b and c. 14. On Fig. 4, the pressure system at A is a. a warm core low b. a dynamic low c. a dynamic high d. a wave cyclone e. b. and d. Figure 4. Surface Chart, 1200 UTC 9 November On Fig. 4, Line a is a(n) a. Occluded Front b. Stationary Front c. Cold Front d. Warm Front e. Dry Line 5

6 16. On Fig. 4, Line c is probably a a. Occluded Front b. Stationary Front c. Cold Front d. Warm Front e. Dry Line Figure 5 is the Meteogram for Saint Louis, 2000 UTC 8 to 2000 UTC 9 November Questions 17 through 19 refer to this figure Figure 5. Meteogram for Saint Louis, 2000 UTC 8 to 2000 UTC 9 November The direct evidence (seen on the meteogram given in Fig. 5) of a frontal passage at Saint Louis is a. the wind shift between 8 UTC and 9 UTC. b. the lowest pressure that occurred around 8 to 9 UTC. c. the rainfall that occurred between 9 UTC and 14 UTC d. a., b., and c. above. e. sharp temperature drop between 9 UTC and 14 UTC 18. The indirect evidence (seen on the meteogram given in Fig. 5) of a frontal passage at Saint Louis is a. the wind shift between 8 UTC and 9 UTC. b. the lowest pressure that occurred around 8 to 9 UTC. c. the rainfall that occurred between 9 UTC and 14 UTC d. a., b., and c. above. e. sharp temperature drop between 9 UTC and 14 UTC 6

7 19. The evidence (seen on the meteogram given in Fig. 5) suggests that the front passing Saint Louis was a. a cold front. b. a warm front. c. a stationary front. d. an occluded front. e. no front passed Saint Louis. Part 3. Statistical Measures Important in Characterizing the Climate of an Area 20. The term normal (in the context of normal rainfall or normal temperature) is a. the usual rainfall or temperature expected in an area. b. defined as the average rainfall or temperature for the whole period of record. c. defined as the mean for the 30 yr period ending in the last year of the last decade (currently ) d. a measure of correlation. e. the standard deviation expressed as a percentage. 21. Correlation measures the degree to which a. the given relationship between the events is not due to chance alone and there is a systematic reason for the relationship. b. the average rainfall or temperature for the whole period of record does not change. c. the mean for the 30 yr period ending in the last year of the last decade (currently ) reflects the long term mean. d. the occurrence of one event is linked, by statistical test to the occurrence of another event. e. the standard deviation is expressed as a percentage. 22. Which of the following measures the range (either as a number or a ratio) of precipitation values relative to the average that can be expected 67% of the time (meaning, 67% of the years in the long term record will have rainfall values within the range) a. standard deviation b. correlation coefficient. c. coefficient of variation d. extreme values. e. (a) and (c) above. 23. In the context of correlation, the given relationship between the events is not due to chance alone and there is a systematic reason for the relationship is the definition for a. average or mean value. b. correlation coefficient. c. coefficient of variation d. statistical significance e. standard deviation Part 4. California Rainfall Variability Refer to Figure 6, a diagram that shows the seasonal rainfall for the period for the period of record for Downtown San Francisco. Questions 24 through 26 refer to this chart. 7

8 Figure 6. Seasonal Rainfall, San Francisco, Downtown, Period of Record 24. The term seasonal rainfall implies a. that the rainfall shown is only for the winter season. b. that the rainfall shown is only for the summer season. c. that the rainfall shown comes seasonally. d. that the rainfall shown is calculated for the period July 1 of one year to June 30 of the next. e. that the rainfall shown is calculated only for the winter season. 25. The dashed red lines on shown on Fig. 6 encompass approximately a. 67% of the seasonal rainfall totals. b. the extreme values. c. the wettest year. d. the driest year. e. the correlation coefficient. 26. The coefficient of variation shown on Fig. 6 was obtained by a. subtracting the standard deviation from 100. b. dividing the temperature by the dew point temperature. c. comparing San Francisco s rainfall with that of New York d. multiplying the correlation coefficient with the rainfall. e. dividing the standard deviation by the mean seasonal rainfall. 27. Two stations report the same average annual rainfall. One station reports a coefficient of variation of 50% and the other a coefficient of variation of 20%. The station with the higher coefficient of variation a. has more than 67% of its yearly rainfall totals either greater or lesser than one standard deviation and, therefore has higher rainfall variability. b. has annual rainfall totals that depart more greatly from the average value and, therefore 8

9 has higher rainfall variability. c. has lower rainfall variability. d. has higher areal variabilty of rainfall. e. has a lower standard deviation of rainfall. Fig. 7 shows the 30 year running mean of seasonal rainfall for downtown San Francisco. Questions 28 tthrough 30 refer to this chart. Fig. 7, a chart that shows the 30 year running mean of seasonal rainfall for downtown San Francisco. Questions 27 to 30 refer to this chart. 28. The 30 year running mean smooths out the season-to-season rainfall variations so that longer term shifts in climate can be deduced. a. T b. F 29. The information shown on Fig. 7 suggests that a. rainfall variability was great in the mid 20 th century. b. the standard deviation of rainfall was great in the 20 th century. c. the late 19 th century was relatively dry. d. the 20 th century was relatively dry. e. the climate is getting drier currently. 30. One way of interpreting the graph given in Fig. 7 is that it shows the variation in the normal rainfall over the period shown. a. T 9

10 b. F Fig. 8 is a chart that shows the coefficient of variation for the 30 year running means given in the previous figure. Questions 31 and 32 refer to this chart. Fig. 8, a chart that shows the coefficient of variation for the 30 year running means given in the previous figure. Questions 31 to 37 refer to this chart 31. The first value plotted on Fig. 8 for the 30 years ending in is This means that a. 67% of the seasonal values during that 30 year period varied plus or minus 38% from the long term average. b. 33% of the seasonal values during that 30 year period varied plus or minus 38% from the long term average. c. the standard deviation was 0.38 d. the long term average was accurate only 38% of the time. e. the seasonal rainfall was highly reliable 38% of the time. 32. An examination of Figs. 7 and 8 together suggests that in recent years (compared to the mi 20 th century) a. the seasonal rainfall has increased and that the average value of rainfall has become a more reliable indicator of the rainfall that might occur in any given year. b. precipitation has decreased and so too has the rainfall variability. c. the rainfall variability has increased but that the mean seasonal rainfall has decreased. 10

11 d. the seasonal rainfall has increased, but that the average value of rainfall has become a less reliable indicator of the rainfall that might occur in any given year. e. the tendency for extreme values to occur has decreased. Part 5: Summer and Fall Weather Patterns 33. The Mediterranean Climate stations in California experience a very dry summer because a. thunderstorms, a key feature of the summer climate of areas further east, do not occur usually. b. the polar jet stream is not present during the summer. c. the cold fronts that pass are usually not associated with clouds. d. California is a desert. e. (a) and (b) above. 34. The average monthly rainfall for January, the wettest month on average, at San Francisco Downtown is about 4.5 inches. The average monthly rainfall for the wettest month (July) at Cherrapunji, India (a station that experiences the rainfall associated with the Asian monsoon) is roughly a. 1 inch b. 10 inches c. 100 inches d inches e inches Figure 9 shows the mean July surface (1000 mb) temperature for the period Questions 35 to 37 refer to this chart. 11

12 Figure 9. Average surface (1000 mb) July temperatures (Kelvin) for the period If there were no other factors that would influence pressure patterns, Fig. 9 suggests that, at the SURFACE a. there would be a low pressure area at A and B. b. there would be a low pressure area at A. c. there would be a high pressure area at B. d. there would be a low pressure area at B. e. there would be a high pressure area at A and B. 36. The area of maximum surface heating seen in Figure 9 is not in the geometric center of the North American continent because a. of the influence of the mountains isolating the Great Basin/Southwest US from the moderating influences of the oceans. b. of upwelling. c. of the Gulf Stream. d. of the California Current. e. b. and d. above are correct. 37. The colder temperatures (relative to those on the continent at a given latitude) seen in Figure 9 are more extreme along the West Coast because a. of the influence of the mountains isolating the Great Basin/Southwest US from the moderating influences of the oceans. b. of upwelling. c. of the Gulf Stream. d. of the California Current. e. b. and d. above are correct. Figure 10a and 10b give the 500 mb and surface weather charts, respectively, for 12UTC 22 October Questions 38 to 42 relate to these figures. 12

13 38. Fig. 10a and 10b could be used to illustrate a. the weather pattern associated with advection fog. b. the weather pattern associated with summer thunderstorms. c. the weather pattern associated with tule fog. d. the weather pattern associated with snow. e. the weather pattern associated with Diablo winds. Figure 10a (left) and Figure 10b (right). 500 mb and surface weather charts for 12Z 22 October Diablo Winds are examples of a general class of winds called a. foehn winds. b. chinook winds. c. Santa Ana winds. d. gust front winds. a. upslope winds. 40. Diablo winds are hot because they sink from high elevation to low elevation, warming compressionally, and because a. they are hot to begin with, originating over the Great Basin in the warm season. b. they come from the warm tropics. c. they are associated with a warm front. 13

14 d. they are associated with low dew point temperatures. e. they come from the Gulf of Mexico. 41. Diablo winds are associated with low relative humidity because they are associated with high temperatures and low dew point temperatures to begin with and because, as they sink to sealevel, the difference between the temperature and dew point gets even larger. a. T b. F 42. The Diablo Wind weather pattern can occur any time during the year. Yet, these winds are often associated with fires only during the late summer and fall. Which of the following represents your best estimate of the factor that might be important in the late summer and fall absent in other times of the year. a. the impact of irrigation. b. the peak frequency of Diablo Winds comes after the normal six months dry season and the vegetation tends to be dried out. c. the migration of various species of animals. d. that there is a relation of fires to highways. e. that there is a the relation of fires to transmission towers. Part 6. Winter Patterns Figures 11 and 12 show the surface weather map and a meteogram for Modesto, CA on November 26, 2012, charts that we discussed in class. Questions 43 to 50 relate to these figures. Figure 11. Plot of surface weather observations in the Bay Area at 17 UTC November 26,

15 Figure 12. Surface weather map for 12 UTC November 26, The high pressure area on Fig. 12 over the Pacific Northwest and northern Great Basin is probably a a. thermal high. b. dynamic low. c. wave cyclone. d. dynamic high. e. North American Thermal Low. 44. The map (and the data on it) given in Figure 12 suggests that Diablo Winds were occurring in the Bay Area. a. T b. F 45. The weather observations for the stations around the Bay Area (shown in Fig. 12) are mostly reporting a. very high dew points. b. thunderstorms. c. strong winds. d. light rain. e. moderate or heavy fog. 46. On Fig. 11, at 09 UTC 26 November, Modesto reported light rain. a. T b. F 15

16 47. On Fig. 11, at 12 UTC 26 November, Modesto reported a. dust storm. b. heavy drizzle. c. moderate snow. d. moderate rain. e. moderate fog. 48. On Fig. 11, which of the following Modesto observations is not a recognized circumstance in the development of radiation fog in the hours leading up to 12 UTC a. low to no visibility. b. pressure of around 1015 mb. c. small to no difference between temperature and dew point temperature. d. light to calm winds. e. clear skies. 49. Note the sharp temperature drop seen in Fig. 11 around 0000 UTC 26 November. This was because a. a thunderstorm was nearby. b. winds were northwesterly. c. a cold front went through. d. the sun went down. e. the pressure was around 1014 mb. 50. The local name given to the fog reported in Modesto on 26 November is a. advection fog. b. tule fog. c. steam fog. d. upslope fog. e. frontal fog. 16