Course Answers

COURSE ANSWERS

1. Answer: d. Both methane and carbon dioxide helped keep the earth warm in its early days, even as the sun was not as bright.

2. Answer: a. Plants were responsible for the large deposition of waste carbon onto the earth. This carbon later became things like petroleum and other carbon products used today.

3. Answer: c. The Eocene epoch was a time of increased global temperatures in recent millennia so that trees and animals inconsistent with the northern latitudes today thrived in that environment.

4. Answer: b. The percent volume of nitrogen in the air is nearly 78 percent.

5. Answer: a. The percent volume of oxygen in dry air is relatively stable throughout the earth at around 21 percent.

6. Answer: b. The exosphere is by far the widest layer of our atmosphere, extending from 700 to 10,000 kilometers.

7. Answer: b. Stratosphere. This is where you will exclusively see the ozone layer.

8. Answer: d. The stratosphere has polar nacreous clouds in it; these are essentially the only clouds you'll see routinely in this layer.

9. Answer: b. The heat in the thermosphere is barely felt because the hot gas molecules are so far apart; the air is not very dense at all in this layer.

10. Answer: b. The ionosphere is made by the ionization of particles from solar radiation. This phenomenon creates the aurorae.

11. Answer: d. 1° longitude or latitude is about 69 miles anywhere on the earth.

12. Answer: c. The prime Meridian was arbitrarily selected to be in Greenwich England.

13. Answer: b. Of these choices, latitude by itself has no impact on the air pressure, while the others do affect it.

14. Answer: a. Each of these is a factor in measuring air density except for volume, which is used to calculate density but does not affect it.

15. Answer: c. Plant grow lights will emit heat that is radiating from the lights to heat the plants. This is the only example of radiation among these choices.

16. Answer: a. Thermal energy transfer with convection means that heated liquid or gaseous media expand, become less dense, and rising from the bottom the top of the system.

17. Answer: c. A higher albedo means more light is reflected as it arrives from the sun. The poles are known to have the highest albedo on earth.

18. Answer: b. There is a balance of heat on earth because the heat taken in by the equator moves to balance the deficits in the poles. About 20 percent of the equatorial heat gets transferred to the poles.

19. Answer: d. September 20th is the day of the autumnal Equinox; the rate of day change is the fastest with the days getting shorter. This is because the sunrise and sunset are on a sine curve.

20. Answer: a. December 20th is marked by the sun crossing high above the Tropic of Capricorn; this represents the shortest day of the year in the Northern Hemisphere.

21. Answer: a. UVA and UVB rays are both responsible for the development of sunburn by damaging the skin surface. The rays are long enough, however, that they do not get far into the body to do any internal damage.

22. Answer: d. Water vapor contribute to more than half of the greenhouse effect. This has been true since the earth had gaseous water around it as part of the atmosphere.

23. Answer: d. Carbon dioxide comes from these two major sources. Combustion of plants as is seen in deforestation also affects the CO2 levels on earth.

24. Answer: b. Carbon dioxide levels have increased greatly from industrialization that has led to burning of fossil fuels and deforestation practices.

25. Answer: d. The standard international unit for temperature. It is used in many scientific circles but not used much in meteorology because it is wieldy and the common person does not know this scale.

26. Answer: c. The Stevenson screen will protect the thermometer inside from the effects of each of these things, except for humidity, which does not actually affect thermometers at all.

27. Answer: d. The temperature is always rising in the thermosphere but just above the mesopause, the rate of temperature change is the greatest.

28. Answer: b. The highest recorded temperature on earth to date is 54 degrees. If you reached a temperature of 55 degrees, this would just exceed the world record.

29. Answer: a. Each of these is a downside to using liquid in glass thermometers in large-scale meteorology except for inaccuracy. These are very accurate and stable instruments for recording temperature.

30. Answer: b. The radiometric thermometer is a lot like an infrared heat sensor that can say gradations and can be calibrated to some accuracy but will not be completely accurate in giving local air temperatures.

31. Answer: a. Only the radiometric temperature sensor could efficiently be used with satellites to get a water surface temperature reading.

32. Answer: c. The radiosonde has sensors that measure air pressure, air temperature, and humidity but not wind speed.

33. Answer: d. You would expect a maximum temperature at about three to five PM, because the earth stores heat before radiating it back to the atmosphere. This accounts for the lag time between high noon and the maximum temperature you experience in the neighborhood.

34. Answer: c. In reality, higher elevations mean that the earth cools more rapidly and that there will be a higher diurnal variation in temperature in those locations.

35. Answer: b. The major factors determining climate are temperature, amount of precipitation, and timing of precipitation.

36. Answer: d. In reality, Russia is in a relatively high latitude situation and is away from large bodies of water, so it is mostly in the continental climate region.

37. Answer: a. While coconut trees will grow in some other areas, they certainly grow best in tropical regions where there is year-round moisture and heat

38. Answer: c. The precipitation in the region will cause a 6 degree decline in the temperature after 1000 meters.

39. Answer: b. Each of these involves a direct phase change in water, except for percolation, in which water flows from one area underground to another in the same phase as a liquid.

40. Answer: c. The 2 major processes that transfer water between the air and the ground are evaporation and precipitation. Other factors play a minor role.

41. Answer: d. The vast majority of water on earth exists in our many oceans.

42. Answer: d. The phase change of condensation results in a decrease in kinetic energy of the water molecule of 600 calories per gram. The only phase change decrease greater than this would be deposition.

43. Answer: b. Evaporation is the entire basis of sweating. When you sweat, energy is taken from your body to help the evaporation take place on your skin. This heat is lost from your body, so you are cooler.

44. Answer: c. Only in windy conditions will you have evaporation favored but condensation somewhat more inhibited. The other factors will either favor condensation or will favor both phase changes.

45. Answer: a. Had there been a dry day the previous day, there would be little water vapor in the air and the chances of dew would be reduced.

46. Answer: c. Hoarfrost conditions are seen in all of these situations except for sunny days, which will not promote this type of sublimation.

47. Answer: d. You need each of these conditions have proper fog formation. In general, fog occurs on cooler days where the temperature is close to the dewpoint.

48. Answer: c. Condensation nuclei can be made of many different things; however, they are not generally made out of pre-existing water droplets. It is hard for water droplets stick to themselves and condense without some other aerosol contributing to the nucleus.

49. Answer: d. Cirrus clouds are considered high-level clouds. The rest of these are all low-level clouds.

50. Answer: b. These clouds are often early harbingers of an incoming warm front.

51. Answer: c. Cumulonimbus clouds are also called tower clouds; they extend many kilometers into the air and lead to short deluges of rain.

52. Answer: d. Cumulus clouds are small puffy clouds that come in unique shapes and signal good or fair weather.

53. Answer: c. In an air parcel the temperature and pressure are always the same throughout the air parcel. It can be any size or volume.

54. Answer: b. The actual dry adiabatic lapse rate of air mass is 9.8 degrees Celsius per kilometer. This is approximately 10 degrees Celsius per kilometer.

55. Answer: a. Temperature of an air parcel is the factor that most determines where it sits in relation to other air masses in any given environment and at any altitude.

56. Answer: c. Sounding involves a weather balloon with a radiosonde that will measure temperature, pressure, and other parameters as the weather balloon ascends in order to get a complete picture of the temperature differential at a specific location.

57. Answer: a. The diagram is able to plot the line between saturated and unsaturated air using temperature as the x axis and % saturation as the y axis.

58. Answer: b. Contrails are also called condensation trails. They are caused by vapor being released by aircraft as they are flying through the sky. Many of these in one spot often look like clouds.

59. Answer: c. You exhale moisture laden warm air from your body, which sends moisture to air that cannot tolerate so much of it at that temperature. The end result is cloud formation.

60. Answer: d. Each of these would contribute to aerosols in the atmosphere; these would cause cloud condensation nuclei, which would contribute to rain. Recent rain would wash these aerosols out of the atmosphere so it would not contribute aerosols to the atmosphere.

61. Answer: c. Sodium chloride is salt, which is very hygroscopic and attracts water vapor at relatively low levels of humidity.

62. Answer: b. Any type of deep cumulus cloud as the cumulonimbus cloud will have updrafts, which allow raindrop to spend a longer time within the cloud. This leads to larger raindrops.

63. Answer: a. Water can be supercooled to as low as -40 degrees Celsius before it must be solid, regardless of the conditions.

64. Answer: d. Homogeneous freezing involves supercooled liquid droplets that become solid in absence of any nucleus. The temperature needs to be below 40 degrees Celsius in order to have this.

65. Answer: b. If a raindrop is less than 0.02 inches in diameter, you would call it drizzle unless the raindrops themselves were scattered far apart as they fell.

66. Answer: c. Any clump of ice greater than one fourth inch diameter is referred to as hail, although hail can be much larger than this.

67. Answer: d. Snowflakes are the only type of frozen precipitation that is actually in the shape of a real ice crystal would see microscopically. You know this as the 6 pointed star shape.

68. Answer: d. The tipping bucket rain gauge tips whenever it is full. This means you will get data anytime the bucket is tipping, which is when you get a recording. In harder rain, the bucket will tip faster.

69. Answer: a. A tipping bucket rain gauge is the only rain gauge that actually measures the depth of the rainfall. The others measure other aspects of rain besides the depth.

70. Answer: c. A Doppler rain sensor specifically detects the rate or speed of rainfall, but does not detect the actual depth of rain or size of raindrops.

71. Answer: c. Subtropical high-pressure air passes are seen above or below the equatorial regions. The air is very warm and dry, with much of the water vapor being sucked into the equatorial regions.

72. Answer: a. One of the main reasons why air pressure is higher at the poles and lower at the equator is because the earth is not completely spherical and effects of gravity or greater at the poles as result.

73. Answer: d. Each of these will affect the air pressure with the exception of air composition, which plays no role in actual air pressure changes on earth.

74. Answer: b. The phenomenon of advection means there is horizontal flow of air on the ground from high-pressure to low-pressure. You experienced this as wind.

75. Answer: b. You need high plateaus to have a high enough land mass to cool down in winter; this allows air to flow at high velocities down to the lower elevations.

76. Answer: c. You need each of these things to cause a Chinook winds, except for a desert, which is not necessary for these winds but is created by them instead.

77. Answer: d. Santa Ana winds cause dry and hot air to blow westward over areas that are already dry. This can precipitate the rapid spread of forest fires, leading to devastation of homes and communities nearby.

78. Answer: a. The terms haboob, dust devil, and whirlwinds are related to hot and dry winds kicking up desert dusts. You will get monsoon rains but not blizzards.

79. Answer: d. There are three major convection cells per hemisphere, which leads to a total of 6 cells around the earth.

80. Answer: a. The boundary between the polar and Ferrell cells is what creates the polar jet stream. It is fast moving air because of the temperature difference between these cells.

81. Answer: c. Earth's rotation causes air flow to be shifted to the right or eastward in the Northern Hemisphere and to the left or westward in the southern hemisphere.

82. Answer: a. A trough is a section of low-pressure on a weather map, while a ridge is similar but represents an elongated section of high-pressure.

83. Answer: a. The line shows a coming cold front and indicates that rain or snow would be likely in your area soon.

84. Answer: b. Anemometers can be purchased for individual use. These can predict the wind speed and direction in your area.

85. Answer: c. At 60 degrees north or south latitude, you will see the greatest deficit of heat on the earth's surface. This is explained by the incoming angle of the sun's rays and the amount of heat loss exhibited at this latitude.

86. Answer: b. If there were just one cell between the equator and the poles, it would be called the Hadley cell. On the surface, there would move from North to South.

87. Answer: a. In the doldrums, which is near the equator, you will see each of these things except for clear and sunny skies. There is too much humidity in the air and too much cloud formation to have sunny skies.

88. Answer: a. The area over Hawaii is called the Pacific high or the Hawaiian high. This is a semipermanent area of high pressure.

89. Answer: c. Remember that a trough is a long line where a low-pressure system would be. Along the equator is the equatorial trough.

90. Answer: a. Both land breezes and katabatic breezes tend to occur during the nighttime hours.

91. Answer: a. Each of these is a major factor in the development of turbulence and wind shear. This is not seen if there is just one mountain. It takes a mountain range to do this.

92. Answer: c. Flying at constant altitude will not generally cause clear air turbulence, but the others can do this. Need to understand, however, that nothing will totally prevent this phenomenon.

93. Answer: d. Eddies are formed when strong winds approach rough terrain. After going through the terrain on the leeward side, swirling eddies can be seen.

94. Answer: c. Hurricanes always develop near the equator at the equatorial lowpressure regions. As you know is a low-pressure belt around the earth at the equator. It is from this belt that hurricanes begin.

95. Answer: b. Each of these contributes to the cooling of the Eastern Pacific compared to the Western Pacific Ocean. The natural tilt of the earth wouldn't contribute to this cooling.

96. Answer: c. Under normal conditions, the Walker circulation allows cooler and drier air to flow along the surface above the ocean area where it warms and becomes more moist. This leads to more precipitation in the area.

97. Answer: a. As a result of global warming, the frequency of El Niño years has increased and has been an increase in the intensities of both extremes in the southern oscillation.

98. Answer: c. A La Niña year will be a time when you see each of these features except that there will be 4 fishing along the coastline of Peru and Ecuador due to lack of nutrients in the water and a lowering of the thermocline.

99. Answer: b. You would choose the letters CA because the air mass would come from a continental area and it would come from the Arctic. This leads to the specific designation of CA.

100. Answer: d. You would not describe an air mass as being windy or calm. Instead, you would use terms to suggest its warmth or humidity. By definition, an air mass itself will not be windy.

101. Answer: d. The warm and moist air on the east side of the dryline in the US comes from the moister air in the Gulf of Mexico.

102. Answer: c. The source region must hang onto its airmass for about a week before the air can attain the characteristics from the source region.

103. Answer: c. In areas of Canada to the North you will get air masses with stable and uniform characteristics that are both dry and cold.

104. Answer: d. This would be a maritime equatorial air mass so you would label it with the mE designation.

105. Answer: a. An occluded front is one that is in front of a low pressure system. The weather is extremely severe behind these systems. They represent areas where a cold front overtakes a warm front.

106. Answer: c. The latitude cyclones can be far larger than hurricanes. They are also located much more to the North and do not originate in the tropical areas as is true of hurricanes.

107. Answer: d. The mid-latitude cyclones will always rotate counterclockwise and in all cases they will have a low-pressure system in the center.

108. Answer: b. Nor'easters are very intense low pressure cyclones that will carry strong winds and heavy storms along the eastern seaboard.

109. Answer: c. Alberta clippers you not carry much precipitation but are very fastmoving storms. They tend to be dry because there is no moisture in the areas they develop.

110. Answer: a. Geostationary satellites take pictures of the same part of the earth every thirty seconds or so.

111. Answer: b. Polar satellites travel in a north south direction from pole to pole so that they are able to capture an entire image of the rotating earth twice per day.

112. Answer: c. Each of these represents a phenomenon on earth that is easily caught using a polar satellite. They are much harder to capture on a geostationary satellite, except for hurricanes which are easily shown in their entirety on this type of satellite.

113. Answer: a. Each of these is something that is gathered through these automated weather systems. The exception is the sunrise and sunset time, which is predicted through other means.

114. Answer: c. The global data assimilation system can take information from different forecasts and different systems around the world to get a current forecast that is as accurate as it can be, with sixteen days advance warning as to the weather.

115. Answer: c. The climate forecast system can predict the seasons in a reasonable period of time up to about nine months in advance.

116. Answer: a. Each of these is part of how we forecast the weather in some way. The rapid refresh system gives us an hour by hour forecast of the weather eighteen hours in advance.

117. Answer: c. The weather depiction chart is a map of an area for meteorologists and aviators. It shows weather conditions but does not show temperature.

118. Answer: c. The weather prognostic chart will help you get the weather for flying up to 48 hours in advance of a trip. These charts only go up to this point in predicting the weather.

119. Answer: d. Downbursts involve heavy, strong downward winds that strike the ground at the leading edge of a storm. These can be very damaging even though they are not tornadic.

120. Answer: a. Hook echoes on radar will show the presence of a probable tornado in the area of large thunderstorms.

121. Answer: b. Each of these is a visible feature of a thunderstorm. You will not be able to see hook echoes with the naked eye unless you have a Doppler radar.

122. Answer: c. Scud clouds are clouds with ragged edges that hang low enough to sometimes touch the ground on the backside of a thunderstorm. While confused often with tornadoes, these are not dangerous.

123. Answer: d. Each of these can cause coastal flooding; however, you will not see this with sea breezes that tend to be fairly innocuous.

124. Answer: d. While the common definition of heavy snow is six inches in twelve hours, this is somewhat inaccurate as snows in the southern part of the United States can be called heavy snow with half that much snowfall rate.

125. Answer: c. The designation heavy snow warning is no longer in use. The term Winter storm warning applies to all sorts of inclement winter weather.

126. Answer: b. The criteria for a Winter weather warning is broad and includes weather that is either imminent, ongoing, or expected within forty-eight hours.

127. Answer: a. The tornado emergency is most severe and indicates the greatest potential for loss of life because it indicates the tornado is large and is approaching a major metropolitan area.

128. Answer: b. While severe thunderstorm watches can last up to eight hours, warnings last only up to one hour in total duration.

129. Answer: c. The cutoff for a severe thunderstorm warning is fifty-eight miles per hour. Above this, you would indicate this type of warning. Below this, you would indicate a severe weather advisory.

130. Answer: d. A flash flood warning generally means is been a sudden event leading to actual flooding or imminent flooding. It would least likely be issued in the case of gradual snowmelt.

131. Answer: c. When you issue an areal warning, you mean to indicate a small area, such as a river, stream, storm drain area, or street. There are separate flood warnings for coastlines.

132. Answer: d. While most of these can indicate flooding near the coastlines for any reason, a storm surge warning is issued almost exclusively for hurricanes or tropical cyclones.

133. Answer: b. You would release a beach hazard statement if there was some kind of biological hazard along the shoreline to include red algae growing nearby.

134. Answer: a. So far, extreme cold mornings only issued in Alaska and are only issued when the air temperature is less than forty degrees Fahrenheit.

135. Answer: c. If you expect the temperatures to fall to twenty-eight degrees Fahrenheit or lower, you would likely issue a hard freeze warning to the area if crops were involved.

136. Answer: d. You need to issue each of these warnings and watches during the growing season in a given area where crops are being grown. The exception is the wind chill advisory, which is not associated with crops or crop losses.

137. Answer: b. The thunderstorm dissipates when the downdrafts exceed the updrafts.

138. Answer: d. Downdrafts are caused by colder air in the tall thunderclouds. This air is laden with heavy rain so the combination of factors causes air to drop downward.

139. Answer: c. A cell is defined according to the number of updrafts associated with the thunderstorm. A single-cell storm has just one updraft in it.

140. Answer: a. The bow echoes inside a thunderstorm will be most associated with straight line winds but will have a variety of storm-related phenomena as well.

141. Answer: c. Each of these is a weather system seen with mesoscale convective systems. The exception is blizzards, which are not seen with these systems.

142. Answer: a. These are all reasons that contribute to having a flash flood. The exception is snowmelt, which tends to be gradual and much more predictable.

143. Answer: d. Each of these is a reason you might see coastal flooding. The exception is snowmelt, which is not a common reason for coastal flood.

144. Answer: b. Each of these can cause flooding but tsunamis can definitely contribute to a catastrophic flood.

145. Answer: a. Perhaps the most important thing you need in order to have the ability to predict floods in a given area is historical records showing past flooding. These are combined with present-day information in order to predict whether or not a flood will occur.

146. Answer: c. The most severe rating on the enhanced Fujita scale is an EF5 tornado. The EF scale goes from zero to five.

147. Answer: b. Each of these is a factor used to describe a tornado that is also used to rate a tornado on a common rating scale. The exception is eyewitness accounts, which are not needed to create these ratings.

148. Answer: d. A tornado is defined as a wind vortex extending from cloud to ground. It can have varying intensities and differing levels of damage to ground structures.

149. Answer: b. You need surface winds of at least 40 miles per hour in order to call something a tornado. If you do not see this, you will call it a funnel cloud.

150. Answer: d. You would designate a waterspout as a tornado only if land was somehow affected because of the waterspout's activity.

151. Answer: a. Tornadoes begin their life cycle as mesocyclones. They then pull down from the clouds and draw in moist downdraft air as they continue to develop.

152. Answer: b. The definition of hurricane is made by having sustained winds of greater than 74 miles per hour.

153. Answer: a. Hurricane season in the Northern Hemisphere ends on November 30th .

154. Answer: c. In this part of the world, hurricane season begins on June first.

155. Answer: d. The maximum known lifespan of a hurricane is 31 days in which the hurricane met the criteria for being one. This was Hurricane John in 1994.

156. Answer: a. These early hurricanes or tropical depressions begin as disorganized and stormy areas along the west coast of Africa, traveling in our direction along with the trade winds.

157. Answer: d. You will define a storm as being tropical depending on where it gains its energy. It will get its energy from the ocean if it is tropical but will get its energy from the atmosphere if it is not tropical.

158. Answer: c. Of the 100 tropical cyclones we get each year, only about half or 50 of these become mature hurricanes or typhoons.

159. Answer: d. When a tropical storm reaches its 39 mile per hour mark or more, it is named and keeps its name as it progresses to become a hurricane, if it will do this at all.

160. Answer: d. All categories of hurricanes will be dangerous, even category 1 storms.

161. Answer: d. Each level is four times as great as the next. If you go up two levels, you would increase the damage by a factor of 16.

162. Answer: a. The eyewall or wall cloud is the ring of cumulonimbus clouds surrounding the eye of the hurricane.

163. Answer: b. The intensity is determined by measuring the winds at 10 meters above the ground.

164. Answer: a. The 1900 Galveston Hurricane cost the area as many as 12,000 lives. This was followed fifteen years later in the same area by another than killed 8000 more people. They built a seawall after this.

165. Answer: b. Lightning is not particularly common or dangerous in hurricanes or other tropical cyclones. The other phenomena, however, are very dangerous.

166. Answer: c. Squall lines in a hurricane represent a sudden increase in wind speeds, which can be extremely damaging to lives and property.

167. Answer: a. Most tornadoes are concentrated in the right frontal area of the hurricane or other tropical cyclone.

168. Answer: c. Each of these is an aspect of hurricane rotation and the development of the low pressure in a hurricane except for evaporation, which does not play a role in this process.

169. Answer: b. The main issues that dissipate the storm include increased friction over land, passage of the storm over cooler air, and lack of moisture to feed the hurricane. They cool down rather than warm up as they dissipate.

170. Answer: a. Each of these is a major factor that plays into the Milankovitch cycles; however, the distance of the earth from the sun is not necessarily part of this directly.

171. Answer: b. On or about July 4, the earth is furthest from the sun so we get fewer of the sun's rays during that time. We are closest to the sun in early January.

172. Answer: c. The cycle that depends on how elliptical the Earth's orbit is around the sun spans approximately one hundred thousand years. It affects the difference between the amount of the sun's rays we get in the summertime versus the wintertime.

173. Answer: c. The earth is tilted on its axis in a range of between 22.1 to 24.5 degrees. It varies on a forty-one thousand year cycle.

174. Answer: d. Droughts are defined not by length of time but by their severity so they need to be severe enough to affect water supply and crops only. There is no minimum time frame.

175. Answer: c. Each of these is a type of drought, except for geopolitical drought. Added to this list is hydrological drought to round out the four types of drought.

176. Answer: d. Each of these is an issue you can get from drought in the US, except that it doesn't necessarily increase the risk of diseases.

177. Answer: a. Lack of wet winters reduces the snowmelt in spring. This has the greatest effect on the amount of drinking water to many different areas of the world.

178. Answer: a. Each of these is a situation where there is information gotten about the early climate. Carbon-14 dating is not particularly helpful in this process.

179. Answer: d. While you will see each of these factors as a direct adverse effect of a heatwave, you will not see an increased risk of infectious diseases. Instead, you will see a risk of hyperthermia in humans.

180. Answer: b. A cold wave is mostly determined by the rate at which the temperature falls, usually defined as a rapid temperature reduction within twenty-four hours.

181. Answer: c. Each of these will cool the earth and has a disruptive effect on our climate. The exception is carbon dioxide, which is a warming greenhouse gas.

182. Answer: d. The Arctic oscillation is minor and doesn't affect the globe as a whole. It will alter the North Pole temperatures and those of parts of Europe and North America in minor ways.

183. Answer: c. The carbon footprint relates to the overuse of petroleum products, which are basically made of carbon and hydrogen. This is why we talk about the carbon footprint.

184. Answer: b. The description of the Holocene extinction involves all human activities that have led to the decline and extinction of resources.

185. Answer: a. Each of these is related to raising livestock and is causing an environmental hazard. The exception is use of water resources, which is not really as big a problem as the rest of those listed.

186. Answer: b. You will see each of these events, but the exception is reduced precipitation overall. Some areas will be wetter, while others may be drier instead.

187. Answer: b. Particulate matter is most likely to stick in the lungs or leach toxins into the bloodstream, leading to a higher risk of cancer not seen when you inhale other types of air pollution.

188. Answer: a. Sulfur dioxide is noticeable by its smell. It smells like rotten eggs at very low concentrations in the air.

189. Answer: c. Methane is part of natural gas, which is a fossil fuel found deeper in the earth. It has the ability to burn more cleanly than other petroleum products, wood, and coal.

190. Answer: c. Garbage burning is a major problem in places like India, where they tend to burn garbage as a way to get rid of it rather than putting it in landfills, etcetera.

191. Answer: a. Ozone exists as a layer around the earth's atmosphere. It absorbs UV rays entering the atmosphere from the sun.

192. Answer: d. CFCs stay in the atmosphere from between 55 to 140 years, with an average of approximately one hundred years. This means that our reduction in CFC production will not eliminate the problem for quite some time.

193. Answer: a. Each of these has the potential to worsen a thermal inversion, except for wind. Windy conditions will mix the atmosphere and actually lessen an inversion.

194. Answer: b. The strength of a thermal inversion is largely determined by the temperature differential between the different layers of the atmosphere involved in the inversion.

195. Answer: d. When you talk about thermal inversions, you are talking about the warm air that is trapping the cooler air beneath it as being the inversion layer itself.

196. Answer: d. You cannot get Los Angeles smog without sunlight, which is not a gaseous substance. Nevertheless, sunlight facilitates the process of developing smog from ground emissions.

197. Answer: c. The high density of traffic seen in urban areas is the most common cause and the largest contributor to Urban air pollution.

198. Answer: b. In areas of the Middle East and northern Africa, particulate matter mostly comes from the desert in the form of dust as well as from Dusty roadways.

199. Answer: c. Dry acid is more dangerous to humans than any other type of acid deposition, because these particles can enter human lungs and endanger our health directly.