Geology Multiple Choice Q&A
A Surface Air Pressure Patterns and Winds
“1. On Figure 1A-1, the lowest plotted pressure is 1006 mb and the highest plotted value is ___1035___ mb.”
“2. By U.S. convention, isobars on surface weather maps are drawn with the same interval as that described for the Figure 1A-1 map. This isobar interval is ______ mb. The isobar interval is selected to provide the most useful resolution of the field of data; too small an interval (for example, 1 mb) would clutter the map and too great an interval (for example, 10 mb) would not adequately define the pattern.
Also by U.S. convention, isobars drawn on surface weather maps are a series of values divisible by 4, (e.g., 1000 ÷ 4 = 250). The progression of isobaric values can be found by adding 4 sequentially to 1000 and/or subtracting 4 sequentially from 1000 until the full range of pressures reported on the map can be evaluated.
3. Which of the following numbers would not fit such a sequence of isobar values?
The change of pressure over distance is the pressure gradient. On surface weather maps, the directions of the horizontal pressure gradients (greatest pressure change over distance) are always oriented perpendicular to the isobars. The closer together the isobars appear on a map, the stronger the pressure gradients.
4.From the isobar pattern you drew on Figure 1A-1, the horizontal pressure gradient is stronger across __ Iowa to Michigan ___.
“5.Based on Figure 1A-2, which of the following best describes the surface wind circulation around the center of a low-pressure system?
c.Counterclockwise and inward spiral
6.Based on Figure 1A-4, which of the following best describes the surface wind circulation around the center of a high-pressure system?
b.Clockwise and outward spiral
7. On your surface maps, repeat the hand twists for the low- and high-pressure system models. Note the vertical motions of the palm of your hand. For the Low, the palm of your hand _ rises _____ during the rotating motion. In the case of the High, the palm of your hand __ falls ____ during the rotating motion.
8. Imagine the motions of your palms during these rotations represent the directions of vertical air motions in Highs and Lows. Vertical air motion in a Low is therefore __ upward ____ and in a High vertical air, motion is __ downward ____.
9. Considering the complete air motions of the low-pressure system, air flows __ downward and outward in a clockwise spiral ____.
10.In a high-pressure system, air flows __ upward and inward in a counterclockwise spiral
1B Surface Air Pressure Patterns and Winds Applications
“1. The highest plotted air pressure observed on the map of 1022 mb is located in ___ Texas
2. The lowest reported pressure was __1007____ mb, in the Canadian province of Quebec (north of New England).
3. The isobars in the conventional series to complete the pressure analysis between the lowest and highest values on this map are ______ mb.
c.1008, 1012, 1016, 1020
“4. In Pennsylvania, the 1012-isobar bisects the state near Williamsport with a line running north-south. Given the 4-mb interval convention, this line will separate values where the lower values on the map remain on one side while higher values are on the other side. The pressure values of locations west of Williamsport are ____ greater than __ 1012 mb.
“5. The overall isobar patterns on the two maps over the conterminous U.S., particularly for the Great Lakes Low and the central High, are generally __ similar ____. Also included are shadings for precipitation around the country based on radar reports.
“6.Therefore, the wind direction at Grand Junction, in western Colorado was generally from the ___ east ___. (Because of the map projection used, the north may not be precisely at the top of the map. In the Colorado area, a north-south line would be nearly parallel to the Colorado-Utah straight-line border.)
7.Knowing the direction from which the wind at Grand Junction was blowing, it would be reported as a(n) __ east ____ wind.
Optional: One knot (1 kt = 1 nautical mile per hour = 1 NM/hr) is about 1.2 land (statute) miles per hour. Wind speed is reported by a combination of long (10 kts) and short (5 kts) “feathers” attached to the direction shaft. Grand Junction had a 5-kt wind (one short feather). A double circle without a direction shaft, such as seen in Brownsville, TX, Denver, CO, and Reno, NV, signifies calm conditions. A shaft plotted without feathers would denote 1–2 kts.
One tool for wind speed conversions between miles per hour and knots (as well as other quantities) and their formulas can be found at Link 1B-4.
8. Three bold blue Hs are marked on the map for the centers of high pressure. Compare the hand-twist model (Link 1B-5) of a High to the wind directions at stations in the several-state area flanking the high-pressure centers. (The central H is a slightly better example due to a lesser topographic influence.) The wind direction at these stations suggests that, as seen from above in Figure 1B-3, the air was circulating ____ clockwise __ around the Northern Hemisphere high-pressure center.
9. The winds at stations in the states around the high-pressure center indicated the air also spiraled __ outward from____ the high-pressure center.
10. This wind flow pattern, concerning the high center, is therefore __ consistent with ____ the hand-twist model of a High. (Refer to Investigation 1A in the Manual for the hand-twist models of Lows and Highs.)
2A Surface Weather Maps and the Atmosphere in the Vertical
“1. Examine the surface weather map presented in Figure 2A-1. The weather map symbols are those typically seen online, on television, and in newspapers. The Hs and Ls identify centers of high or low air pressure compared to their surroundings. Moving outward horizontally in any direction from the blue H positioned in Texas, air pressure ___ decreases ___.
“2. Moving outward horizontally in any direction from the red L in Lower Michigan, air pressure ___ increases ___.
“3.The front plotted in the Southeastern U.S. is a __ cold ____ front.
4.According to the map, people living in South Carolina can expect ___ colder ___ weather after the front
5.Precipitation is often depicted on weather maps by a variety of symbols, as shown in Figure 2A-1, including stars or asterisks (*) that represent __ snow ____. For a list of the frequently occurring weather symbols see the User’s Guide linked from the Weather Studies Maps & Links, or go to Link 2A-1. For a more exhaustive set of 100 possible weather symbols used in station models, go to the NWS JetStream Max site at Link 2A-2.
6. Two or three, whole or broken horizontal lines symbolize _ fog _____.
9.Wind direction is shown by the arrow shaft drawn into the station circle. North is to the top on the map and east is to the right. Wind is always named for the direction it blows from. In the above depiction, the wind direction was generally from the _ northwest
d. 10.Wind speed is rounded off to the nearest 5 kts (1 kt = 1.2 mph) and is symbolized by the combination of feathers drawn on the clockwise side of the wind-direction shaft. A wind-direction shaft without feathers depicts a 1–2 kt wind and a circle drawn around the station circle signifies calm conditions (0 kts wind speed). In this case, the reported wind speed was __20____ kts.
11.Air pressure (adjusted to sea level) is reported in the station model as a coded number to the nearest tenth of a millibar (mb). The air pressure reported at Brownsville, TX was __1021.7____ mb.
12.Sky cover is reported inside the station circle and expressed as a percentage or descriptors (scattered, broken, overcast, obscured). An empty circle indicates no clouds, and a half-shaded circle means 50% of the sky is cloud covered. The reported cloud cover at Brownsville was _ overcast (100%)_____.
13.Current weather is plotted to the left of the station circle, at the “9 o’clock” position, with a variety of symbols representing the current weather conditions. The two dots are the symbol of ____ rain
14. Other stations on the map segment show additional wind, sky cover, and current weather conditions. Marfa, TX in the western “Big Bend” of the Rio Grande River, has a temperature of 28°F and the current weather conditions (stars or asterisks) is __ snow ____.
15. Lafayette, the station in south-central Louisiana, showed a weather symbol for the intensity of that type of precipitation. The triplet symbol indicated that the precipitation intensity at that station was ___moderate___.
16. Several buoys in the Gulf of Mexico northeast of Brownsville showed the current weather condition of an infinity symbol. These symbolized __ Haze ____.
2B Surface Weather Maps and the Atmosphere in the Vertical Applications
“Weather Map Evolution”
“1. It is notable from Figure 2B-1 that the total number of concentric, circular isobars surrounding Marco (to the southeast of the Louisiana coastline) is __.greater ____ than the number surrounding Laura (just south of Cuba). This helps explain why, at this time, Laura was a stronger tropical system than Marco with faster winds overall.
“2.Recall the 4 hr time difference between universal time (Z) and Eastern Daylight Time. In Miami, FL at 15Z 25 August 2020, it is ______ EDT and along the rest of the Gulf Shore it is ______ CDT.
b.11 a.m. … 10 a.m.
3.Multiple stations on this map, most notably in Arkansas and central Texas, do not have a wind barb or feather present, instead have only the circle. This indicates that these stations were experiencing ___ calm ___ winds.
4.Along the Gulf of Mexico coastline in Figure 2B-2 in the Florida panhandle and southern Alabama, two stations displayed a symbol of two green circles  at the “9 o’clock” position alongside the station circle. This symbol showed that a continuous fall of rain occurred at a __ moderate ____ intensity.
5. Parts of extreme southern Florida experienced similar weather. Yet one of these rain symbols  in Miami, FL looked different than Key West, FL. This indicates that the rain in Miami was _ about the same intensity _____ compared to Key West.
6. The precipitation in #4 and #5 was influenced by the tropical systems. The rain in Alabama and the Florida panhandle was related to the approach of _ Tropical Storm Laura _____ and the rain in Miami-Key West was related to __ Hurricane Marco ____.
7. In addition to weather symbols that indicate precipitation type and intensity, other symbols report reduced visibility. In Figure 2B-2 for central Georgia, there are multiple stations with the symbol of two green horizontal lines [=] at the “9 o’clock” position alongside the station circle. This symbol showed that __ mist/thin fog ____ was occurring.
“8.Wind directions at the stations in the region about the center of the relatively warm and humid air mass in the Carolinas are generally ______ as seen from above. The stations surrounding the High along the North and South Carolina border display this circulation pattern. The hand-twist model also further confirms this.
b.counterclockwise and inward
9.One of the cooler regions of the U.S. was in the Pacific Northwest, where Eureka, CA (in northern California) reported one of the coldest temperatures at ____74__°F.
10.Eureka also reported a dewpoint temperature of ____66__°F, making conditions there very near or at saturation.
11.The sky cover (reported within the station circle) at Eureka indicated __ overcast ____ conditions, likely due to the mist/fog in the region.
12.Winds at stations are symbolized by the direction from which they blow. The wind at Eureka, while very light, was generally _ from the north _____.
Locations further south of Eureka and also further inland (e.g., Las Vegas, NV) observed temperatures much higher at map time in Figure 2B-3. In fact, Las Vegas reported a temperature of 85℉. The dewpoint had not increased much from Eureka, however, so the hotter air in Las Vegas was much drier. Winds (or lack thereof) at Las Vegas were also similar to Eureka. Meanwhile, further south and near the coast (e.g., Los Angeles), was still warm but under a marine layer of clouds. Winds in Los Angeles were coming on shore from the Pacific Ocean.
13.The wind speed in Los Angeles, rounded off to the nearest 5 kts, is shown by a combination of feathers along the direction shaft, where a long feather denotes 10 kts and a short feather is 5 kts. A single short feather near the tail end of the arrow shaft signifies Los Angeles’ wind speed was about ___10___ kts.
14. The pressure value at Los Angeles was plotted as 111, meaning the actual atmospheric pressure corrected to sea level was ___1011.1___ mb.
15. A blue line with triangles was found across southeastern Ontario, extending southwest into the western shore of Lake Superior and northeast Minnesota. These symbols indicate the position of a ___ stationary ___ front.
16. The front curving outward to the northwest from the front identified in #15, near the low pressure in Ontario, Canada, has purple semicircles on the northern flank, which identifies it as a(an) ____ cold __ front.
17. Irregular light green, yellow, orange, and red shadings scattered across the map (such as off the coastlines of Texas, Florida, and Alabama) indicated where the national network of weather radars detected precipitation. The radar shadings showing the most intense precipitation at map time were generally located __ near the center of the major high pressure ____. (Much of the light green in the High Plains on Figure 2B-3 are the likely result of a morning temperature inversion, creating false returns. More details on this phenomenon can be found at Link 2B-1.)
“18.On 28 January at 12Z, from the surface (976 mb) up to about the 300-mb pressure level, the atmosphere over Detroit was _ colder than _____ Standard Atmosphere conditions.
The tropopause is a defined boundary that separates the atmospheric layers of the troposphere (below) from the stratosphere (above). In the troposphere, temperatures generally decrease significantly as the altitude increases. In the lower stratosphere, temperatures typically become nearly constant (isothermal) or begin to increase with altitude (temperature inversion). This pattern change, defined by the rate of temperature change with altitude, is the tropopause.
19.Based on the temperature pattern in the Detroit data you plotted, the tropopause above Detroit at 12Z on 28 January 2020 was located at a pressure level of ___300___ mb.
20.The tropopause over Detroit occurred at an altitude near __16____ km above sea level according to the altitude scale on the Stüve diagram. This can be confirmed from the observed altitude reported in Table 1.
21.This Detroit tropopause was at ___ a higher ___ altitude compared to the altitude of the tropopause in the Standard Atmosphere. (Recall from earlier, the Standard Atmosphere tropopause occurs at 11 km or 11,000 m.)
22.From the Detroit radiosonde data in Table 1, at 12Z 28 January 2020, the pressure of 500 mb occurred at an altitude of ___5440___ m. 500 mb is about one-half of the atmospheric pressure at sea level. Since air pressure is determined by the weight of the overlying air, this means about one-half of the mass of air over Detroit’s atmosphere was above this altitude and one half below.
23.In the Standard Atmosphere, a pressure of 500 mb occurs at an altitude of 5574 m (18,289 ft.). The altitude of the 500-mb level over Detroit at the time of this sounding was __ higher than ____ the 500-mb level of the Standard Atmosphere. This relatively cold atmospheric column reflected the conditions that generally exist throughout the troposphere during mid-winter in the middle latitudes.
24.The Stüve diagram is scaled to allow plotting of atmospheric data up to a pressure of 100 mb (about 16,000 m). At a level where the atmospheric pressure is 100 mb, about ___10___% of the atmosphere’s mass remains above.
3A Solar and Terrestrial Radiation
“1.Figure 3A-1 shows average daily solar radiation at the top of the atmosphere varies the least over a year at ___ equatorial ___ regions. At that location, the period of daylight is 12 hrs in length throughout the year.
2.Figure 3A-1 shows a six-month period during which no sunlight is received at the __ polar ____. At this location there is only one period of daylight per year, but it is six months long!
3.Comparing the three annual radiation curves indicates the annual range (the difference between the curves’ maximum and minimum) of solar radiation received daily __ increases ____ as latitude increases.
4.Based on how solar radiation received varies with latitude, it can be inferred that seasonal temperature contrasts would ____ increase __ as latitude increases.
5.Of the three latitudes, the location that annually experiences two maxima and two minima periods of incoming solar radiation at the top of the atmosphere is the __ equatorial ____ location.
6.The pattern of sunlight received at the equator over the course of a year indicates that tropical locations ___ do not ___ experience warm and cold seasons, as is characteristic of the higher latitudes.
“7.Figure 3A-2’s depiction of the local sky at the equator shows that the variation in average daily solar radiation over the year, as reported in Figure 3A-1, must be due to changes in the daily ___ path of the Sun across the sky ___.
8.In Figure 3A-1, it can be seen there is a period during the year more than 2 months long when both the mid-latitude and polar locations receive more solar radiation on a daily basis than the equator ever does on a daily basis. It can be inferred from Figure 3A-2 that the major factor that makes this happen at the North Pole is the __ daily length of daylight ____ at that latitude.
9.From the same NASA data set used in Figure 3A-1, the average daily insolation averaged over a year is 10.02 kWh/m2/day at the equator, 7.34 kWh/m2/day at 45°N, and 4.13 kWh/m2/day at the North Pole. The mid-latitude location receives about 73% as much solar energy as the equator and the North Pole receives __41%____ as much solar energy as the equator. This nonuniform receipt of energy sets the stage for Earth’s weather and climate.
10.Infer the seasonal weather contrasts at the middle and higher latitudes by comparing insolation values during the months centering on the summer and winter solstices. As seen from the mid-latitude curve in Figure 3A-1, the June-July average top of the atmosphere insolation is about 11.4 kWh/m2/day while the December-January average is about 3.1 kWh/m2/day. This indicates that during the June-July period the mid-latitude location receives about __3.7 times ____ the amount of top-of-the atmosphere solar energy received during December-January.
“11. Look at Figure 3A-4, the 23 September image. The Earth’s axis is perpendicular to the Sun’s rays, so the sunset line and Earth’s axis line up together in this perspective. Each latitude line, including the equator, is half in sunlight and half in darkness. Because the Earth rotates once in 24 hrs, the period of daylight is ___12___ hrs everywhere except right at the poles.
“12. Now look at Figure 3A-5, the 21 December satellite image. On the Northern Hemisphere’s winter solstice, Earth’s the North Pole reaches its maximum tilt away from the Sun for the year. Consequently, poleward from the Arctic circle, the daily period of daylight is _0__ hrs.
“13.Examine the Northern Hemisphere latitude lines in the 21 December satellite image and compare how much of each line is in sunlight with the amount that is in darkness. At all latitudes in the Northern Hemisphere, the daily period of daylight is __ less than ____ the daily period of darkness.
14. Poleward from the Antarctic Circle on 21 December, the daily period of daylight is _24_____ hrs. This is the time of the South Pole’s maximum tilt toward the Sun for the year.
15. Now look at Figure 3A-6, the 21 June satellite image. On the Northern Hemisphere’s summer solstice, Earth’s the North Pole attains its maximum tilt toward the Sun. Consequently, on 21 June, poleward from the Arctic Circle, the period of daylight is __24____ hrs and poleward from the Antarctic Circle, the period of daylight is __ 0____hrs.
3B Solar and Terrestrial Radiation Applications
“1.A red symbol () marks the sub-satellite point, the spot on Earth’s surface directly under the satellite, in the center of each image at the intersection of 75°W and the equator. The sub-satellite point is located in __ South ____America.
The left image in Figure 3B-1 was produced by reflected sunlight (visible radiation) and the right image by emitted infrared (heat) radiation. The infrared image is less affected by atmospheric water vapor. It is useful for detecting clouds at all times of day and night because all of Earth radiates infrared radiation continually. The colors in the infrared image also identify the temperature of clouds and, therefore, their height.
2.On the visible satellite image, the Sun’s rays would be reaching Earth from the __Southeast_
3.Because Earth rotates eastward, local time at the sub-satellite point is soon after ____ sunrise __.
4.Using reflected visible light, the satellite sensor “sees” clouds and surface features as we do. In the visible image, the appearance of the clouds in the illuminated portion of the image is __ white ____.
5.Albedo is the percentage of the sunlight striking a body that is reflected. The expanse of clouds across much of the ocean areas to the east and west of South America illustrates this point. Compared to the cloud-free land and ocean areas, clouds must have a __ higher ____ albedo.
6.An important advantage of infrared imagery is that it can be used to observe the planet both day and night. The image produced by infrared radiation emitted by the Earth-atmosphere system demonstrates there are clouds in __ both the daylight and night portions
____ at the time of Figure 3B-1.
c. 7.In the infrared image, relatively warm land and ocean surfaces appear dark, cooler low cloud tops are gray, and cold high cloud tops are bright white. Warmer cloud top temperatures, indicating lower cloud top heights, are represented by blue to green while colder cloud top temperatures, indicating higher cloud tops, are represented by orange, yellow, and red. Observe the contrast in the appearance of clouds in the subtropical Atlantic Ocean, north of South America (and northeast of the Caribbean islands) with the clouds extending over the central bodymass of South America. The tops of the clouds north of the South American coast (in the Atlantic) were at relatively _ low _ levels.
“8.At the time of the visible satellite image in Figure 3B-2, sunlight reached the U.S. from the __ east ____.
9.Cloud conditions are not seen across the western quarter of the U.S. and Canada in the image because ___ the Sun had not yet risen there, leaving darkness ___.
Note the dashed-yellow line on the left side of Figure 3B-2. This line represents a terminator, a line separating day and night, at 1231Z on 3 September 2020. This particular terminator can also be called the sunrise line, as it was progressing westward across Earth’s surface as the planet rotated eastward.
10.The Texas-New Mexico border approximates a north-south line of longitude. The terminator line seen on Figure 3B-2 is (roughly) _ parallel_____ to this north-south border. This line of longitude is also roughly approximate to the El Paso, TX sunrise time for this day, since El Paso is along the terminator. The terminator’s orientation relative to north-south longitude lines does, however, change throughout the year.
“11.Compared to the visible image (Figure 3B-2), the infrared image (Figure 3B-3) __ does ____ shows extensive cloudiness in the Ohio Valley region.
12.As seen in Figure 3B-3, in infrared images very cold surfaces, such as high cloud tops which emit little infrared radiation, appear _ bright white _____, while surfaces with intermediate temperatures appear in varying grays. In contrast, land during much of the year, water, and low clouds are warm surfaces that appear relatively _ darker _____ on infrared images.
13.At 1231Z on 3 September 2020, the lumpy, amorphous batch of clouds centered in the eastern Texas region displayed a brightness in the infrared image that showed those cloud tops to be relatively ____ cold __. This was also true for the semi-circle of clouds surrounding an area of low pressure along and north of Lake Superior.
14.In Figure 3B-3, the shading of those blobs of rain showers in eastern Texas, as well as those in the Lake Superior region, suggest those cloud tops extended relatively __ high ____ into the troposphere.
15.Comparatively, the small regions of clouds located in Alabama and along the Missouri-Kansas border in the visible Figure 3B-2 image, appeared in the Figure 3B-3 infrared image as a relatively uniform gray. Based on this color difference, the cloud tops in Figure 3B-3 for Alabama and Missouri-Kansas were relatively ____ warmer __ than the brighter white cloud tops over eastern Texas.
The Alabama and Missouri-Kansas clouds were hard to distinguish from the gray background in the Figure 3B-3 because their tops were at lower altitudes with temperatures similar to the ground.
16.If you wished to create a complete 24-hour time-lapse of the cloud patterns across the U.S. from satellite images from each hour, you should choose ___ infrared ___ images, because ___ visible ___ images would appear completely black during nighttime hours.
“17.The orientation of the Figure 3B-4 sunrise terminator line across North America ______ closely coincides with the sunrise-terminator line on Figure 3B-2 where sunrise was at 7:31 a.m. CDT.
18.The sub-solar point in Figure 3B-4 shows that at this time of year, the noontime sun was directly overhead ___ in the Northern Hemisphere ___.
Compare the width of the daylight portions of the map along the 45°N and 45°S latitudes (dashed-blue lines) in each hemisphere, especially at the poles. The widths of the lighter portions north and south of the equator are proportional to the length of daylight in those hemispheres. Across the U.S., the east is in the light and while the darkness is receding in the west.
19.The width of mid-latitude daylight in Figure 3B-4 implies that during September the daylight period is ______ for daylight segments at the same latitude. As the Northern Hemisphere’s summer season transitions to winter, future images of this map will show narrower daylight-illumination bands and lesser sun exposure over the northern latitudes.