Atmospheric Sciences 3 Fall 1999 Exam #3

Choose the best answer for each question.

1 High heights of a particular pressure level are associated with relatively ____ air temperature because the density of such air is relatively ____. high; low low; high high; high low; low 2 A(n) ____ barometer can be made portable, so that one can carry it around on a hike and forecast weather based on pressure changes. hair aneroid mercury adiabatic bimetallic 3 The pressure gradient force is strongest where the height contours are farthest apart where the height contours are closest together in the center of high pressure systems in the center of low pressure systems 4 If a wind blows toward the Equator in the Southern Hemisphere, it will be deflected by the Coriolis force and become a more ____ wind. northerly westerly southerly easterly 5 A wind vane points ____ the direction of the wind. to the left of to the right of in against 6 Friction works on winds that are within ___ km of the ground, and causes the winds to become ____. 1; geostrophic 1; subgeostrophic 2; faster than before 5; slower than before 7 Which diagram depicts the surface wind blowing around a Northern Hemisphere surface high? 8 Which diagram depicts the surface wind blowing around a Southern Hemisphere low? 9 Which of the following statements is not correct concerning the pressure gradient force? The PGF points from low to high pressure in the Southern Hemisphere. The PGF points from high to low pressure in the Northern Hemisphere. It is non-existent when the difference in pressure between two locations is zero. It causes the air to move as wind. Its magnitude does not depend on the rotation speed of the Earth. 10 Figure 1 For this and next six questions, see Figure 1. Assume we are in the Northern Hemisphere, and the isobars/height contours are oriented the same way at the surface and at altitudes greater than 1 km above the ground. Choose the appropriate force or direction vector for the pressure gradient force aloft. . . . . . 11 Choose the appropriate force or direction vector for Coriolis force aloft. . . . . . 12 Choose the appropriate force or direction vector for the surface wind. . . . . . 13 Choose the appropriate force or direction vector for the Pressure Gradient Force at the surface . . . . . 14 Choose the appropriate force or direction vector for the Coriolis Force at the surface . . . . . 15 Choose the appropriate force or direction vector for friction at the surface . . . . . 16 Choose the appropriate force or direction vector for the surface wind if the Earth was not rotating . . . . . 17 The Chinook wind is so dry (low relative humidity) because clouds always form on the windward side of the mountains and precipitate the moisture out of the air. the air decreases in temperature, raising the saturation vapor pressure, and lowering the RH. the sun heats up the air as it travels, which evaporates the water vapor away. the dew point of the air decreases while it descends to the lower altitudes. 18 Wind shear resulting from a difference in the wind speed with respect to altitude can produce wave clouds mammatus clouds monsoon winds turbulence 19 Sea and land breezes are _____ phenomena. global scale microscale synoptic scale mesoscale 20 The summer monsoon in eastern and southern Asia is characterized by ____ weather and winds blowing from ____ . dry; land to sea dry; sea to land wet; land to sea wet; sea to land 21 In a thermally induced circulation, the surface wind blows from low to high pressure from ocean to land from cold to warm regions from humid to dry regions 22 The single (Hadley) cell model of global circulation cannot exist on our Earth because random air motions destroy the single cell symmetry. the Earth is heated unevenly by the sun. ocean circulation decreases the Equator-pole temperature difference. the Earth rotates and produces a Coriolis effect on the wind. 23 Prevailing Westerlies are the globally averaged surface winds between latitudes 0° and 30°. between latitudes 30° and 60°. between latitudes 60° and 90°. in the Hadley Cells. at the poles. 24 Instead of uniform circumpolar bands of high and low pressure, there will be semi-permanent cells of high and low pressure around the Earth. The usually-fair weather experienced in Southern California is mainly a result of the semi-permanent feature called the Eastern Pacific High Bermuda-Azores High Icelandic Low Aleutian Low 25 The subpolar jet is located above the zone where the trade winds meet the prevailing westerlies. the interface between the Hadley cells of the Northern and Southern Hemispheres. the zone where cold and warm air masses converge at 60oN latitude. the North Pole. Subpolar International Airport 26 The winds aloft over the Southern Hemisphere are generally from the North South West East 27 The La Nina is downwelling of sea water along the coast of Peru. unusually high precipitation amounts in the United States. unusually warm sea surface temperatures in the tropics. unusually cold sea surface temperatures in the tropics. 28 The air mass that most likely has the highest actual water vapor content is mT cT mP cP 29 In the middle of the United States, the air masses that meet there and produce frontal storms are mP and cP mT and cP mT and cT cP and cT mP and cT 30 The air mass that enters the Southern California region from the southwest is mT cT mP cP 31 Figure 2: This question and the next refer to Figure 2. This picture is the side view of a(n) ____ front. cold warm stationary occluded 32 The coldest air mass is located at point ___. . . . . 33 Before the passage of a cold front, the dew point is relatively ____, and after the passage of a cold front, the dew point is relatively ____. high; low low; high high; high low; low 34 Before a cold front passes, the winds are ____; after it passes, the winds are ____. northwesterly; northwesterly southwesterly; northwesterly southwesterly; southwesterly northwesterly; southwesterly 35 Before a warm front passes, the air temperature is relatively warm. stratiform clouds are observed to gradually lower over time. showers of rain or snow fall. the wind blows strongly out of the west. 36 The atmospheric surface pressure is lowest when a cold front is just passing. an occluded front is approaching. a cold front has passed about an hour ago. a warm front is approaching. 37 The major shortcoming of the Norwegian Polar Front Model is that a UCLA professor-to-be came up with the idea. that it was developed from observations of Norwegian storms, which are not like the U.S. storms. the lack of upper air observations to support the development of the surface low. the lack of electronic instrumentation to record the changes in temperature and pressure as fronts passed. that it was not tested in the Southern Hemisphere before the results were published. 38 Figure 3: This and the following five questions refer to Figure 3. Assume we are in the middle latitudes the U.S. Midwest, and the features shown are measured or depicted at the Earth's surface. Choose the appropriate location for the lowest surface pressure. . . . . . 39 Choose the appropriate location for the coldest air. . . . . . 40 Choose the appropriate location for rain or snow showers. . . . . . 41 Choose the appropriate location for stratiform clouds. . . . . . 42 Choose the appropriate location for temperatures that will drop significantly in the next few hours. . . . . . 43 Choose the appropriate location for the warmest air. . . . . . 44 During the "developing phase" of the Norwegian Polar Front Model, the pressure in the center of the surface low decreases. a warm front is in the process of catching up to a cold front. the boundary between the warm and cold air masses is stationary. the low aloft is directly over the surface low and is filling in. the two fronts travelling around the low pressure center have merged. 45 According to the model of the life cycle of a middle latitude cyclone, the storm system reaches maximum intensity when the trough tilts westward with increasing altitude. when the fronts first occlude. when the cold front and warm front form a 90o angle. as a stationary front. 46 For the surface cyclone to intensify, the winds aloft should be increasing in speed converging diverging blowing straight west to east. 47 The phase of an air mass thunderstorm's development where there are updrafts everywhere inside the storm is the _____ phase. mature precipitating dissipating cumulus stratus 48 An air mass thunderstorm reaches maximum intensity when precipitation is just beginning to fall. the updraft tilts. there are updrafts everywhere. there are downdrafts everywhere. the gust front begins to force more air to flow into the storm. 49 The feature found in a supercell thunderstorm that allows it to survive for a much longer time than an air mass thunderstorm is a tilted updraft. a cold precipitation downdraft. rising warm, moist air. surface convergence. an anvil top. 50 In thunderstorms, charge separation mechanisms usually involve _____ and produce net _____ charge near the cloud base. ice particles; negative ice particles; positive large raindrops; negative large raindrops, positive 51 A lightning return stroke is brightest and travels in steps from the cloud to the ground. in steps from the ground to the cloud. directly from the cloud to the ground. directly from the ground to the cloud. 52 This results in multiple return strokes in a single spot for the same discharge event. stepped leader return stroke dart leader tall tree or chimney