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167 Cards in this Set
- Front
- Back
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How does Dalton's law apply to the atmosphere? |
Dalton's law states that the total pressure exerted by amixture of gases equals the sum of the pressures produced by each constitutegas. The pressure balance is a condition in the atmosphere because at any pointin a gas, or a mixture of gases, pressure is exerted equally in all directions. |
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Provide a definition of air pressure that applies to Earth's surface and any altitude within the atmosphere. |
The air pressure at agiven location on Earth’s surface can be thought of as the weight per unit areaof the column of air above that location. The pressure at any point within theatmosphere is equal to the weight per unit area of the atmosphere above thatpoint. |
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Compare the advantages and disadvantages of mercury barometer versus an aneroid barometer. |
An aneroid barometer is more portable but less accurate than a mercury barometer. |
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Explain how pressure tendency can be a useful indicator of future weather. |
As a general rule,the weather becomes (or remains) fair as air pressure at Earth’s surface risesand the weather turns stormy as the air pressure falls. Pressure tendency is anindication of an approaching low pressure (stormy weather) system or anapproaching high pressure (fair weather) system. |
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Air is a compressible mixture of gases. How does this property of air affect the rate of which air pressure decreases with increasing altitude? |
Gravity causes themaximum air density to be at Earth’s surface. As altitude increases, the airbegins to thin rapidly, which is accompanied by a decline in air pressure. |
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How does a change in temperature affect air density? How does a change in humidity affect air density? |
When air is heated, air density usually decreases. When theconcentration of water vapor (humidity) increases, air density usuallydecreases as well. |
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Why does a cold, dry air mass exert a greater surface air pressure than an equally cold but more humid air mass? |
A cold dry air masshas a greater density than a more humid air mass. This would mean that thehumid air mass has lower air pressure. Thisis because the molecular weight of water is less than the molecular weight ofdry air. |
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Why are air pressure readings adjusted to what they would be if the weather station were actually located at sea level? |
Pressure readings are adjusted to sea level in order toobserve changes in air pressure on a horizontal plane. It helps scientistsidentify air masses and weather changes and helps aid in weather forecasting. |
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Distinguish between Charles' law and Boyle's law. |
Charles’ law definesthe relationship between density and temperature in an ideal gas with constantpressure. Boyle’s law defines the relationship between pressure and densitywhen temperature is held constant. Together these two laws make the ideal gaslaw. |
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Why is the dry adiabatic lapse rate greater than the moist adiabatic lapse rate? |
Because of the release of latent heat accompanying phasechanges of water vapor, a saturated air parcel cools more slowly than anunsaturated air parcel. This causes the moist adiabatic lapse rate to be lower. |
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The atmosphere consist of... |
Molecules that are moving rapidly in all directions and have mass. |
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Air exerts a force on the surface of all objects that it contacts. a. True b. False |
a. True |
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Define force |
A push or pul on an object and is computed as mass times acceleration. |
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Explain Dalton's law. |
The total pressure exerted by a mixture of gases equals the sum of the pressures produced by each constituent gas. |
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Define barometer. |
The instrument used to measure air pressure and monitor its changes. |
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Define air pressure tendency. |
The change in air pressure over a specific time interval, such as several hours. |
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Define air density. |
The atmosphere's gas molecules are most closely spaced at Earth's surface, and the spacing between molecules increases with increasing altitude. |
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Define Avogadro's Law. |
Equal volumes of all gases measured under the same conditions of temperature and pressure contain the same number of molecules. When water molecules enter the atmosphere as a vapor with the temperature and pressure of the air remains constant, they dispalce other gas molecules, principally nitrogen and oxygen. |
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What usually accompanies the replacement of one air mass by another of different temperatures, that is, by cold air advection or warm air advection. |
Change in surface air pressure. |
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Convergence or divergence is produced by... |
A circulation pattern in which horizontal winds blow toward or away from some location or wind speed changes in a downstream direction. |
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Define diverging winds. |
Suppose that the Earth's surface, horizontal winds blow away from a column of air in all directions. This is diverging winds. |
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Define converging winds. |
Horizontal winds aloft blow toward the air column. |
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Define an isobar. |
A line passing through locations having the same air pressure. |
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What is a large-scale high known as? |
An anticyclone. |
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What is a large-scale low known as? |
A cyclone. |
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What weather usually accompanies a High? |
Fair weather. |
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What weather usually accompanies a Low? |
Stormy weather. |
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Surface winds blow ______ and ______ from the center of a High. a. Clockwise and outward b. Counterclockwise and inward |
a. Clockwise and outward. |
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Surface winds blow ______ and _____ from the center of a Low. a. Clockwise and outward b. Counterclockwise and inward |
b. Counterclockwise and inward. |
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Define air parcels. |
An arbitrary amount of air useful for visualizing atmospheric processes, containing a fixed number of molecules. It's volume can change, but its mass remains the same, meaning that the density changes. At a fixed temp, pressure is directly proportional to density. |
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As air temperature rises.... |
Air expands, air density decreases, and air pressure at the Earth's surface falls. |
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One of the important consequences of the decline of air pressure with altitude is.... |
The expansion or compression of air parcels as they move up or down. As an air parcel ascends and expands, its temperature drops; as an air parcel descends and is compressed, its temperature rises. |
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Define expansional cooling. |
Wherever a gas expands, the temp of gas drops. |
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Define compressional warming. |
As the pressure on an air parcel increases, the air parcel is compressed and its temp rises. |
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What is the law of energy conservation? |
Applies to expansional cooling and compressional warming of air parcels moving vertically in the atmosphere. According to the law, we can account for all the original energy in any physical or biological system regardless of the energy transformations that take place. |
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Define internal energy. |
Encompasses all the energy in a substance, that is, the kinetic energy of atoms and molecules plus the potential energy arising from forces between atoms and molecules. |
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Define adiabatic process. |
No heat is exchanged between air parcel and it surroundings. |
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Pressure values fall as a _____ approaches or a _____ departs, and pressures rise with approaching _____ or departing _____. a. High, Low, Low, High b. Low, High, High, Low |
b. Low, High, High, Low. |
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Identify and describe the various phase change processes involving water. |
Evaporation: water changesphase from liquid to vapor. Condensation: water changes phase from vapor toliquid. Deposition: water changes phase from vapor to solid without firstbecoming liquid. Sublimation: water changes phase from solid to vapor withoutfirst becoming liquid. Freezing: water changes phase from a liquid to a solid.Melting: water changes phase from a solid to a liquid. |
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Explain how the Sun drives the global water cycle. |
Solar radiation from theSun strikes Earth’s surface and is absorbed (converted to heat). Some of thisheat evaporates water or sublimates snow and ice. The water vapor in the aircondenses or deposits to cause cloud particles to form, which can lead toprecipitation. Solar radiation, therefore, powers the water cycle. |
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How does distillation convert seawater to fresh water? |
As water evaporates fromthe ocean surface, materials dissolved in seawater, such as salt, are leftbehind. The atmospheric water vapor subsequently condenses and eventually fallsas fresh water. |
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Define vapor pressure. How does Dalton's law of partial pressures apply to vapor pressure? |
Vapor pressure is thepressure exerted by the water vapor component of air. Dalton’s law of partialpressures states that the total pressure of a gas mixture (e.g., air) is equalto the sum of the pressures of each constituent gas. Therefore, each gasconstituent, including water vapor, exerts a pressure as though it were theonly gas present. |
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If the mixing ratio equals the saturation mixing ration, what is the relative humidity? |
When the actualconcentration of water vapor (mixing ratio) in the air equals the water vaporconcentration at saturation (saturation mixing ratio), the relative humidity is100%. |
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On a clear calm day, why does the relative humidity usually decrease from a maximum shortly after sunrise to a minimum in the early or mid afternoon? |
At constant vapor pressure,relative humidity varies inversely with the air temperature because thesaturation vapor pressure increases with rising air temperature. As the airtemperature rises from its daily minimum on a clear calm day near sunrise to amaximum in the early to mid-afternoon, the saturation vapor pressure alsoincreases. Because the air is calm and there is no gain or loss of water vapor,the actual vapor pressure remains essentially constant. Consequently, therelative humidity is highest when the air temperature and saturation vaporpressure are lowest (near sunrise) and it is lowest when the air temperatureand saturation vapor pressure are highest (mid-afternoon). |
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Why does the amount of precipitable water vary with the mean temperature of the troposphere? |
The saturation vapor pressureincreases as temperature increases. The greater the temperature of the troposphereis, the greater the “capacity” of the air to hold water vapor. Assuming theavailability of water at Earth’s surface, the mean air temperature of thetroposphere decreases as you move poleward, causing evaporation to decreasewith an increase in latitude. This results in less precipitable water in polarregions. In general, warmer air has more precipitable water than colder air dueto evaporation rates. |
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Describe the principal mechanism whereby clouds form in the atmosphere. |
Water evaporates, and the aircontaining the water vapor ascends in the troposphere. As the air rises,pressure decreases, and the air expands and cools causing the relative humidityto increase. Once the relative humidity of the air reaches saturation,condensation occurs on cloud nuclei and a cloud forms. |
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Why are clouds and precipitation more likely on the windward slopes of a mountain range than the leeward slopes? |
As air is forced to ascend thewindward slopes of mountain ranges, it expands and cools, resulting in anincrease in relative humidity. The air continues to cool as it rises,eventually reaching saturation and producing clouds. When air descends the leewardslopes of a mountain range, it is compressed and warms. This causes cloudparticles to evaporate. When the clouds have evaporated away, the relativehumidity decreases as the subsiding air continues warming by compression. |
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What is the significance of a rain shadow for agriculture? |
Rain shadows are regions ofdry conditions on the leeward sides of mountain ranges. In these dry regions,an irrigation system may be needed in order to grow crops. Only certain typesof crops can be grown in these regions. |
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Why is gravity an important player? |
This attractive force keeps water molecules from escaping to space, as well as causing water to fall from the sky as precipitation and to flow from the continents to the ocean. |
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Within the ranges of air temperature and air pressure on Earth, all 3 phases of water can coexist naturally. a. False b. True |
b. True |
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If more water molecules return to the water surface as liquid than enter the atmosphere as vapor, what happens? |
A net gain of liquid water mass results in a process called condensation. |
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What is transpiration? |
The process whereby water that is taken up from the soil by plant roots eventually escapes as vapor through tiny pores on the undersides of leaves. |
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Sublimation is the process whereby.... |
Ice or snow becomes vapor without first becoming a liquid. |
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What is deposition? |
The process whereby water vapor becomes ice without first becoming a liquid. |
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What happens to about 1/3 of the precipitation that falls on land? |
It runs off to the ocean. |
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What is humidity a general term for? |
Referring to any one of many different ways of describing the amount of water vapor in the air. |
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Define the mixing ratio. |
The mass of water vapor per mass of the remaining dry air, usually expressed as so many grams of water vapor per kilogram of dry air. |
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Define specific humidity. |
The ratio of the mass in grams of water vapor to the mass of the air including the water vapor. |
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Liquid water becomes vapor at.... |
The same rate that water vapor becomes liquid. |
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What is precipitable water? |
The depth of water that would be produced if all the water vapor in a vertical column of air were condensed into liquid water. |
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What is a hygrometer? |
An instrument that measures the water vapor concentration of air. |
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What is a hair hygrometer? |
It uses human hair as the sensing element? |
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What is a hygrogrpah? |
It provides a continuous trace of fluctuations in relative humidity with time. |
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What is an electronic hygrometer? |
Based on changes in the electrical resistance of certain chemicals as they absorb water vapor from the air. |
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How is atmospheric stability determined? |
By comparing the temperature change of an ascending or descending air parcel with the temperature profile, or sounding, of the ambient air which the parcel ascends or descends. |
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Within a stable air layer, an ascending air parcel becomes cooler (denser) than the ambient air, and a.... |
Descending air parcel becomes warmer (less dense) than the ambient air. |
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Generally, an air layer becomes... |
more stable when it descends but less stable when it ascends. |
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What is sensible heating (conduction and convection)? |
A means of heat transfer between Earth's surface and atmosphere. |
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Cumulus clouds may form where? |
Where convection currents ascend and the sky is generally cloud-free where convection currents descend. |
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The higher the altitude reached by ascending convection currents... |
The greater the amount of expansional cooling, and the more likely it is the clouds will form. |
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Convection currents that soar to great altitudes within the troposphere typically spawn _____. |
Thunderstorms. |
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What are most clouds the consequence of? |
Saturation brought about by uplift and expansional cooling of air. |
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What is fog? |
A cloud that forms near or in contact with Earth's surface. |
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Why is cloud formation and essential part of the global water cycle? |
Because without clouds there would be no rain or snow. |
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A cloud is the visible product of what? |
Condensation or deposition of water vapor within the atmosphere. |
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What does the curvature of a water surface affect? |
The ability of water molecules to escape (vaporize) from the water surface. |
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The surface of a small droplet has... |
A greater curvature than the surface of a large droplet. |
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Where do clouds form more readily? |
Where hygroscopic nuclei are abundant. |
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Cloud condensation nuclei promote condensation of water vapor at temperatures.... |
both above and below the freezing point of water. |
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Ice forming nuclei are much less common than.... |
CCN and most promote formation of ice crystals only at temps well below freezing. |
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What are the most efficient ice-forming nuclei? |
Substances having a crystal structure similar to that of ice and most are almost insoluble in water. |
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What type of soil particles are excellent ice-forming nuclei? |
Clayey |
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What are freezing nuclei? |
Particles on which water vapor condenses and subsequently freezes. Most are active at temperatures below -9 C. |
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What are deposition nuclei? |
Particles on which water vapor deposits directly as ice without first becoming liquid and are not fully active until the temperature drops below about - 20 C. |
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What do cloud condensation nuclei promote? |
Condensation of water vapor at temperatures both above and below 0 C. |
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Why is cloud classification useful? |
Because different types of clouds tell us something about atmospheric processes responsible for the formation and may provide clues as to future weather. |
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What are the 4 cloud classifications? |
1. General appearance 2. Altitude of cloud base 3. Temperature 4. Composition |
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What does a cirriform cloud look like? |
Wispy or fibrous. |
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What does a stratiform cloud look like? |
Layered. |
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What does a cumuliform cloud look like? |
Heaped or puffy. |
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The temperature in a warm cloud is greater than.... |
0 C |
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The temperature in a cold cloud is at or less than.... |
0 C |
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High clouds are _____ than low clouds. a. Warmer b. Colder |
b. Colder |
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What are cold clouds made up of? |
Ice crystals and/or supercooled water droplets. |
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What do cirrus clouds look like? |
Nearly transparent and occur as delicate silky strands. |
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What are the strands of cirrus clouds made of? |
Falling ice crystals being blown laterally by strong winds. |
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What do cirrostratus clouds look like? |
The are nearly transparent. They form a thin, white veil or sheet that partially or totally covers the sky. |
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What do cirrocumulus clouds look like? |
Small, white, rounded patches arranged in a wavelike or mackerel pattern. Rarely do these clouds cover the entire sky. |
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What is the rule about high clouds? |
No high cloud is thick enough to prevent objects on the ground from casting shadows during daylight hours. |
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What do altostratus clouds look like? |
Uniformly gray or bluish white layers that totally or partially cover the sky. Usually they are sufficiently thick that the sun is only dimly visible, as if viewed through a frosted glass. |
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What do altocumulus clouds look like? |
Roll-like patches or puffs that often form waves and parallel bands. |
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What do stratocumulus clouds consist of? |
Large, irregular puffs or rolls separated by areas of clear sky. |
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What do stratus clouds look like? |
Uniform gray layer stretching from horizon to horizon. |
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Viewed from the ground, what do nimbostratus clouds resemble? |
Stratus except that they are darker gray and have a less uniform, more ragged base. |
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The altitude at which condensation begins to occur through convection is known as.... |
The convective condensation level and coincides with the altitude of cumuliform cloud base. |
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What do cumulus clouds look like? |
Small puffy clouds that resemble balls of cotton floating in the sky on a fair weather day. |
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What is the upper portion of a cumulonimbus cloud made of? Middle portion? Lower portion? |
The upper portion is made of mostly ice crystals. The middle is supercooled water droplets or a mixture of supercooled water droplets and ice crystals. The lower portion of the cloud consist of water droplets. |
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Define wind shear. |
Any change in wind direction or wind speed with distance. |
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Where do most clouds occur? |
The tropopause. |
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What is the most important source of water vapor in the mesosphere? |
The flux of water vapor from the lower atmosphere to the mesosphere associated with the meridional summer circulation. |
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What are nacreaous clouds? Where do they occur? |
They occur in the stratosphere. They have a soft, pearly luster. They are rarely seen and often known as mother-of-pearl clouds. They probably play a major role in the formation of the Antarctic ozone hole. |
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When may fog develop? |
When air becomes saturated through radiational cooling, adevective cooling, addition of water vapor, or expansional cooling. |
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Fog formed by advective cooling is known as... |
Advection fog. |
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What is steam fog? |
Develops late in fall or winter when extremely cold and dry air flows over a large unfrozen body of water. |
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What types of clouds produce the bulk of precipitation? |
Nimbostratus and cumulonimbus. |
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What is the terminal velocity? |
The constant speed attained by a particle falling through a motionless fluid such as water or air. |
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What must clouds do to precipitate? |
Cloud particles must grow large enough that their terminal velocities overwhelm the updrafts. |
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How many cloud droplets does it take to form a single raindrop? |
1 million. |
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What does collision efficiency refer to? |
The fraction of all droplets in the path of a falling larger droplet that comes in contact with the larger droplet. |
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Holes in clouds.... |
are not unusual. Also called hoe punch clouds or canal clouds. |
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What generated from inadvertent seeding of clouds when aircraft fly through the cloud layer. |
Ice particles |
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All snowflake crystals exhibit what? |
Hexagonal symmetry deriving from the hexagonal lattice formed by the ordered arrangement of water molecules in an ice crystal. |
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What does snowlfake size depend on? |
On the availability of water vapor during crystal growth. |
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What are snow pellets and how are they formed? |
Soft conical or spherical particles of ice. They form when supercooled cloud droplets collide and freeze on ice crystals. |
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What are snow grains and how are they formed? |
They are flat or elongated opaque white particles of ice. They originate much in the same way as a drizzle except the freeze prior to reaching the ground. |
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Why are cloud particles and precipitation slightly acidic? |
Because they naturally dissolve some atmospheric carbon dioxide, producing a weak carbonic acid. |
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What does acid deposition refer to? |
It refers to the delivery of acidic particles to Earth's surface. |
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What is designated acid rain? |
The normal pH of rainwater saturated with CO2 is 5.6 and any rain having a pH below this value. |
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What is radar? |
A valuable remote sensing tool for determining the location, movement, and intensity of areas of precipitation. Radar emits microwave signals and receives reflected signals from targets as its beam continually scans a large volume of the lower atmosphere. |
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What does the doppler effect refer to? |
A shift in the frequency of sound waves or electromagnetic waves eminating from a moving source. |
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Define force. |
A push or pull that can cause an object at rest to move or that alters the movement of an object already in motion. |
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What is Newton's second law of motion? |
Force=mass x acceleration |
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When does an air pressure gradient exist? |
Whenever air pressure varies from one place to another. |
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What is a pressure gradient force? |
The force that causes air parcels to move as the consequence of an air pressure gradient. |
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What does curved motion imply? |
That an unbalanced force is operating, whereas steady, straight-line motion implies a balance of forces. |
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What is the Coriolis Effect? |
The deflection experienced with the Earthbound rotating coordinate system. |
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Define friction.
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The resistance that an object or medium encounters as it moves in contact with another object or medium. |
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What is viscosity? |
The friction of fluid flow. |
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What is molecular viscosity? |
A source of fluid friction that is the random motion of molecules composing a liquid or gas. |
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What is eddy viscosity? |
Friction that arises from much larger irregular motions, called eddies, which develop within fluids. |
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Define the atmospheric boundary layer. |
The atmospheric zone to which frictional resistance (eddy viscosity) is essentially confined. |
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What is turbulence? |
Fluid flow characterized by eddy motion. |
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What is the geostrophic wind? |
An un-accelerated, horizontal movement of air that follows a straight path at altitudes above the boundary layer. |
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What's the difference between a geostrophic wind and a gradient wind? |
Geostrophic wind blows in a straight path whereas the path of the gradient wind is curved. |
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An anticyclone is a dome of _____ pressure air. a. Low b. High |
b. High |
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A cyclone is a center of _____ pressure air. a. Low b. High |
a. Low |
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What is the Beaufort scale? |
A graduated sequence of wind strength ranging from 0 for calm air to 12 for hurricane strength winds. |
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How is it possible for cloud droplets tobecome supercooled? |
Cloud droplets aredescribed as “supercooled” if their temperature is below the freezing point ofwater (0 °C) and yet remain liquid. Cloud droplets normally supercool andremain liquid at sub-zero temperatures until foreign particles in the water actas ice-forming nuclei, initiating freezing. |
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Explain why rain isnormally slightly acidic in a non-polluted atmosphere. Define acid rain. |
Rain is normally slightlyacidic (pH of 5.6) because it dissolves some atmospheric carbon dioxide,producing weak carbonic acid. Acid rain is rain that is more acidic thannormal, with a pH lower than 5.6. |
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. How does weather radaroperating in the reflectivity mode locate and plot the motion of areas ofprecipitation? |
In reflectivity mode, weatherradars emit short pulses of microwave energy. These radar signals are reflectedby precipitation-size particles (such as rain, snow, or hail) back to areceiving unit where the information is electronically processed and displayedon a computer as a radar echo. |
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What is the value ofweather radar operating in the Doppler mode in forecasting severethunderstorms, including those that may spawn tornadoes? |
Doppler mode allows theforecaster to determine horizontal air motions within a weather system bymonitoring motion of precipitation particles moving directly toward or awayfrom the radar antenna. This makes it possible for a forecaster to locaterotation within a storm, providing potential areas for severe thunderstorm ortornado development. |
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. What is the significanceof the Schaefer point? |
a. The Schaefer point is theminimum temperature to which a cloud droplet could cool without freezing (-39°C). Any additional cooling would lead to homogeneous nucleation. |
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Identify the variousatmospheric conditions that influence the height of the base of a cumuliformcloud. What controls the altitude to which a cumulonimbus cloud builds in theatmosphere? |
The convective condensationlevel (CCL) is the altitude in the atmosphere at which a rising air parcelbecomes saturated and condensation begins to occur through convection. Thislevel coincides with the altitude of a cumuliform cloud’s base. The height thata cumulonimbus cloud reaches depends on the stability of the troposphere. Ifthe air aloft is stable, vertical growth is inhibited. Unstable air promotesvertical motion, and clouds will grow upward. |
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Explain why cumuliformclouds are relatively rare over cold-water surfaces and snow-covered surfaces. |
Cumuliform clouds rarelyoccur over cold-water and snow-covered surfaces because cold surfacetemperatures inhibit convection. |
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In hilly terrain, radiation fog is most commonin low areas such as marshes and river valleys. Please explain why. |
Radiational cooling causesair near the surface to cool. Cooling causes air density to increase. In hillyterrain, the cooler, denser air flows downslope into low lying areas. Thisphenomenon is known as cold air drainage. Fog will form in these low lyingareas if cooling lowers the air temperature to and below the temperature atwhich saturation is achieved, while the hilltops will often remain clear. |
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At the same subfreezingtemperature, the saturation vapor pressure surrounding a supercooled waterdroplet is greater than the saturation vapor pressure surrounding an icecrystal. Why the difference and why is this important? |
Water molecules are more active(greater kinetic energy) and more readily escape from a liquid water surfacethan from an ice surface. Hence, the saturation vapor pressure is higher in theair surrounding a supercooled water droplet than an ice crystal at the sametemperature. This is important because the differences in vapor pressures causethe water molecules to diffuse toward the ice and ice crystals begin to grow. |
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What are the advantages ofthe new dual-polarization weather radar over conventional Doppler weatherradar? |
Conventional weather radarsends out an electromagnetic wave in one direction, providing a nearlyhorizontal measurement of an object. By contrast, dual-polarization radar useselectromagnetic waves transmitted in two dimensions, both horizontal andvertical. This provides a 2-D picture of the size and shape of an object, aswell as the distribution of many objects. Thus, dual-polarization radar allowsforecasters to identify rain, hail, snow, or ice pellets within a radardisplay, and filter out non-meteorological targets. It can also detect tornadodebris, providing confirmation that a radar-indicated tornado is actually onthe ground. In addition, dual-polarization radar greatly improves theestimation of rainfall amounts. |
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Provide a definition ofwind. |
Wind is the local motion ofair measured relative to Earth’s surface. |
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What causes horizontal airpressure gradients? How do air parcels respond to a horizontal air pressuregradient? |
Horizontal air pressure gradients are caused by air pressurechanges along a surface of constant altitude, such as at sea level. Consequently,horizontal air pressure gradient forces act directly toward lowest pressure andperpendicular to isobars, causing air parcels to move toward lowest pressure. |
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What is the relationshipbetween the horizontal wind speed and the spacing of isobars on a surfaceweather map? |
Horizontal wind speed isstrong where the air pressure gradient is steep, indicated by closely spacedisobars. Horizontal wind speed is light or calm where the horizontal airpressure gradient is weak, indicated by widely spaced isobars. |
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Why does the CoriolisEffect reverse direction between the Northern and Southern Hemispheres? |
The reversal in direction of Coriolis Effect between theNorthern and Southern Hemispheres stems from the contrast in our perspective ofEarth’s rotational direction in the two hemispheres. To an observer high abovethe North Pole, Earth appears to rotate in a counterclockwise direction whereasto an observer high above the South Pole, Earth appears to rotate in aclockwise direction. |
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Describe how the Coriolis Effect varies with wind speed andlatitude. |
The Coriolis Effect causesthe horizontal wind to be deflected to the right of its initial direction inthe Northern Hemisphere, and to the left of its initial direction in the SouthernHemisphere. The magnitude of the Coriolis Effect varies with wind speed; thefaster the wind the greater the Coriolis Effect. The amount of deflection alsovaries with latitude, with the maximum deflection at the poles and nodeflection at the equator. |
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How does the roughness of Earth’s surface affect horizontalwind speed and direction within the atmospheric boundary layer? |
Earth’s surface roughness (frictional resistance) slows thewind and causes the wind to blow more directly across isobars and toward lowpressure. |
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Provide an example of how gravity influences air motion. |
Gravity causes air parcelsto be pulled toward Earth. It influences air that is ascending or descending,such as updrafts or downdrafts in a thunderstorm or the downhill drainage ofcold air in the mountains. |
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What forces are balanced inthe geostrophic wind? |
The geostrophic wind results from a balance between thehorizontal air pressure gradient force and the Coriolis Effect. |
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Why does the circulationwithin an anticyclone favor generally fair weather? |
Viewed from above, surfacewinds in a Northern Hemisphere anticyclone blow clockwise and outward. Assurface winds diverge from the center of the anticyclone, air descends fromaloft. Descending air undergoes compressional warming and the relative humiditydecreases so that fair weather is usually associated with an anticyclone. |
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Why does the circulationwithin a cyclone usually bring cloudy, stormy weather? |
Viewedfrom above, surface winds in a Northern Hemisphere cyclone blowcounterclockwise and inward. As surface winds converge toward the center of thecyclone and air ascends. Ascending air undergoes expansional cooling and therelative humidity increases. If saturation is achieved, clouds will form andprecipitation may result. Consequently, cloudy, stormy weather is usuallyassociated with a cyclone. |
