ATSC 110 Test 1
Convection is the transfer of heat by the upward and downward motion of a fluid or gas. Therefore air in the troposphere is rising and descending. How does the temperature of a parcel of air change when it is rising and falling?
A rising parcel of air will expand as it moves into an environment of lower atmospheric pressure values and therefore cool. A sinking or subsiding air parcel will compress while moving into an environment of higher atmospheric pressure values and therefore warm.
What is a 'sensible temperature'?
A wind-chill temperature and heat index temperature are both considered sensible temperatures. These are temperatures that the body feels like in contrast to the actual temperature of the environment as measured with a thermometer. In extreme cases, very low wind-chill and high heat index temperatures can be life threatening.
Why do air pressure and density always decrease with increasing height above the surface?
As we climb in elevation, fewer air molecules are above us; hence, air pressure and density decrease with increasing height.
Name the phase change processes for water and the amount of energy need to do each process. You will need to look this answer up in the book or lecture notes since the question is fairly detailed and important to understand. The answer to this question is one that you will want to memorize.
Condensation +600cal/gr Evaporation - 600cal/gr Freezing +80cal/gr Melting - 80cal/gr Deposition (vapor → ice) +680cal/gr Sublimation (ice → vapor) - 680cal/gr + heat energy added to the environment - heat energy taken from the environment
Name and define the three 'Heat Transfer' mechanisms.
Conduction → The transfer of heat form molecule to molecule within a substance, hot to cold. Convection → The transfer of heat by the mass movement of a fluid (water & air) - convection is vertical movement - advection is horizontal movement Radiation → Energy received from the sun and all things whose temperature is above absolute zero.
What process contributes to the earth's albedo being 30%?
Contributing factors to the earth's albedo being 30% are: 4% is reflected back to space by the earth's surface, 6% by gases within the atmosphere, and 20% by clouds.
What weather conditions are best suited for the formation of a cold night and a strong radiation inversion in Grand Forks?
Grand Forks will experience its coldest nights and strongest radiational inversions during the winter months when, skies are clear, winds are calm, air is dry, and snow is on the ground.
Explain how the atmosphere "protects" inhabitants on the earth's surface.
Ozone shields plants, animals, and humans from the sun's harmful ultraviolet radiation.
In the Northern Hemisphere, why are summers warmer than winters, even though the earth is actually closer to the sun in January?
The earth is 3.1 million miles closer to the sun in January than in July but due to the 23.5˚ tilt in the earth's axis the sun angle is at its lowest point in the Northern Hemisphere during the end of December and first part of January. The sunlight beam that strikes at an angle is spread across a greater surface area, and is therefore a less intense heat source than a beam striking the earth surface directly. Another important factor is that the daylight hours are shorter in the Northern Hemisphere during the winter months.
Explain how the atmosphere near the earth's surface is warmed from below.
The earth's atmosphere is warmed in part by conduction between the warm surface and a thin layer of air near the surface which will then rise causing thermals, and in part by infrared radiation being emitted from the surface and absorbed by mainly water vapor and carbon dioxide in the lower atmosphere.
The earth's radiative equilibrium temperature is 0˚F but the earth's average surface temperature is 59˚F, why the difference?
The earth's radiative equilibrium temperature (0˚F) only takes into account the earth's surface which acts like a blackbody. The earth's average surface temperature (59˚F) is higher because it includes the absorption and emitting properties of infrared (longwave) radiation by the earth's atmosphere which does not behave like a blackbody.
Identify the major dates that correspond to the change of astronomical seasons in the Northern Hemisphere.
Sept 22nd Autumn Equinox 0˚ Equator Dec 21st Winter Solstice 23½˚S Tropic of Capricorn Mar 20th Vernal Equinox 0˚ Equator June 21st Summer Solstice 23½˚N Tropic of Cancer
How will the heating rate of objects with a high specific heat value compare with objects with a lower specific heat value?
Since 'specific heat' is defined as the amount of energy needed to raise the temperature of 1 gram of substance 1 degree Celsius, the substances with the higher specific heat values will warm and cool slower than substances with smaller specific heat values. In other words water at a specific value of 1 cal/gram ˚C will warm and cool slower than land at a specific heat value of 0.3 cal/gram ˚C
If it is winter and January in New York City, what is the season in Sydney, Australia?
Since Sydney, Australia (33½˚ S Lat) is in the Southern Hemisphere, it would be summer but the month of the year is still January.
How would the heating of a surface area be affect after receiving it's first major snowfall of the season?
Since snow has a high albedo do to the whiteness of the snow, daytime surface temperatures would have a hard time recovering since 75 - 90% of the incoming solar radiation would be reflected off the snow pack and not used for heating of the lower atmosphere.
If the earth's surface continually radiates infrared or longwave radiation, why doesn't it become colder and colder?
The earth's surface does not become colder and colder because objects not only radiate energy but they absorb it as well. If an object radiates more energy than it absorbs, it gets colder; if it absorbs more energy than it emits, it gets warmer.
What is the difference between the 'heat capacity' and 'specific heat' of an object? What are the "specific heat values" for water, ice and the earth surface?
The heat capacity of a substance is the ratio of the amount of heat energy absorbed by that substance to its corresponding temperature rise. The heat capacity of a substance per unit mass is called specific heat. In other words, specific heat is the amount of heat (calories) needed to raise the temperature of one gram of substance one degree Celsius. Specific Heat Values: Water → 1.0 cal/gram ˚C Ice → 0.5 cal/gram ˚C Earth surface (land) → 0.3 cal/gram ˚C
Explain why the warmest time of the day is usually in the afternoon, even though the sun's rays are most direct at solar noon.
Solar noon depicts the time when incoming solar radiation is the greatest. But there continues to be a surplus of incoming solar radiation versus outgoing infrared radiation until late afternoon. Therefore, maximum temperatures usually coincide with this time reach is typically 2-4 hours later than the time of peak incoming solar radiation.
Identify and provide the average elevations of the standard atmospheric pressure levels? Level (mb) Height (ft) Height (mi) 1000 ________ ________ 850 ________ ________ 700 ________ ________ 500 ________ ________ 300 ________ ________ 200 ________ ________
Level (mb) Height (ft) Height (mi) 1000 Near sea level 850 5,000 1.0 700 10,000 2.0 500 18,000 3.5 300 30,000 5.5 200 40,000 7.5
In what atmospheric layer do we find the lowest average air temperature? 2. The highest average temperature? 3. The highest concentration of ozone?
Mesosphere, average value of -130˚F 2. Thermosphere "hot layer", but due to the air density being so low, air temperatures are not measured directly. 3. Stratosphere, 97% of atmospheric ozone is found in the stratosphere
Why does Grand Forks, ND have much colder temperatures than Seattle, WA in January even though they are both located at roughly the same latitude (48˚ N)?
Mid-ocean surface temperatures change relatively little from summer to winter compared to the much larger annual temperature changes over the middle of continents. This is due to the difference in specific heat values between water (1.0 Cal/gr˚C) and land (0.3 Cal/gr˚C). Water will heat and cool slower than land due to its larger heat capacity and therefore moderate the air temperatures in Seattle since it is located near the coast, versus Grand Forks, located in the middle of the North American continent.
What is the primary source of energy for the earth's atmosphere?
The sun
What is the average decrease in temperature with height , or standard lapse rate, in the troposphere?
The temperature on average will decrease by 6.5˚C per 1000 meters (or) 3.6˚F per 1000 feet rise in elevation within the troposphere.
Based on the temperature profile, list the layers of the atmosphere from the lowest to the highest in elevation
Troposphere (sfc to 11km) temperatures decrease with height Stratosphere (11 to 50km) temperatures increase with height Mesosphere (50 to 85km) temperatures decrease with height Thermosphere (85 to 500km) temperatures increase with height
Which variable gas show the most variation at earth's surface?
Water vapor
List the most abundant greenhouse gasses in our atmosphere
Water vapor and Carbon Dioxide.
Explain the concept of air pressure in terms of mass of air above a level. In other words, how do air pressure values change with height?
with an increase in height, pressure values will decrease.
What is kinetic energy?
Any body in motion has kinetic energy, therefore kinetic energy is the energy within a body that is a result of its motion.
List the two most abundant permanent gases in today's atmosphere
Nitrogen (78.09%) and Oxygen (20.95%)
Identify and name the major lines of latitude starting north and working south.
90˚ N North Pole 66½˚ N Arctic Circle 23½˚ N Tropic of Cancer 0˚ Equator 23½˚ S Tropic of Capricorn 66½˚ S Antarctic Circle 90˚ S South Pole
Define terms used to describe the Daily, Monthly, and Yearly temperature values. 1. Daily or Diurnal Range of Temperature 2. Mean or Average Daily Temperature 3. Mean or Average Monthly Temperature 4. Annual Range of Temperature 5. Mean or Average Annual Temperature
. Daily or Diurnal Range of Temperature The difference between the daily maximum and minimum temperature 2. Mean or Average Daily Temperature The average of the highest and lowest temperature for a 24-hour period 3. Mean or Average Monthly Temperature The average of the mean daily temperatures for that month (GFK: Jan 6.4°F, July 68.6°F 4. Annual Range of Temperature The difference between the average monthly temperature of the warmest and coldest months GFK: 68.6 - 6.4 = 62.2°F 5. Mean or Average Annual Temperature The average temperature for the entire year which represents the average of the twelve average monthly temperatures GFK = 40.0°F
1. During the winter, 12 UTC would be _________ in Grand Forks. 2. During the summer, 12 UTC would be ________ in Grand Forks.
1. 6:00 AM 2. 7:00 AM
What are some important roles that water plays in our atmosphere?
1. Only substance that can exist as a solid, liquid, or gas at normal temps near the earth's surface 2. Releases large amounts of heat called latent heat when water vapor changes to liquid or ice. This is an important source for storm development 3. Potent greenhouse gas.
How would you construct an instrument shelter that holds thermometers to measure atmospheric temperature?
1. Paint it white 2. Face it to the north 3. Put slots in the side for free air flow 4. Place it 5.0 to 5.5 feet above the ground 5. Make sure it is located above a grassy surface and away from buildings and surface concrete and/or pavement
How many total calories are required to raise the temperature of a 40 gram block of ice from -20°C to 0°C, melt the 40 gram block of ice, and then raise the temperature of the melt water from 0°C to 10°C?
1. Raise temp of ice 20°C. 40gr X 20°C X 0.5cal/gr°C = 400 cal 2. Melt the 40 gram block of ice. 40gr X 80cal/gr = 3,200 cal 3. Raise temp of water 10°C. 40 gr X 10°C X 1.0cal/gr°C = 400 cal 4. Total calories used in process. 400 + 3,200 + 400 = 4,000 calories
How does the temperature of an object influence the radiation that it emits?
According to the Stefan-Boltzmann law (E = σT4); as the temperature of an object increases, more total radiation is emitted each second. Consequently, a small increase in temperature results in a large increase in the amount of radiation emitted because doubling the temperature of an object increases the maximum energy output by a factor of 16 (24).
What are aerosols, and list some of the aerosols in our atmosphere?
Aerosols are impurities found in the atmosphere Dust and soil particles, microscopic salt particles, smoke, volcanic ash
At the same pressure, why is cold air more dense than warm air?
Air temperature is a measure of the average speed of the molecules. In the cold volume of air, the molecules move more slowly and crowd closer together. In the warm volume, they move faster and farther apart. Since the molecules are closer together in the cold volume, the density is greater.
Define 'albedo'. What are the albedo values for these surfaces? You will need to look up these values in the book or on-line. Snow Clouds The earth and atmosphere Dry dark land Water Forest
Albedo → The percent of radiation returning from a given surface compared to the amount of radiation initially striking that surface. Snow (Fresh) 75 - 90% Clouds (Thick) 60 - 90% The earth and atmosphere 30% Dry dark land 5 - 20% Water 10% Forest 3-10%
The overnight skies are clear and the wind is calm in Grand Forks. The overnight skies are cloudy and the wind is calm in Fargo. Which city should experience the coldest morning low temperature?
Both cities have calm winds but Grand Forks is clear and Fargo is cloudy. The cloud cover over Fargo is able to capture some of the emitted infrared radiation from the surface while most of the emitted infrared radiation in Grand Forks will escape into space since the skies are clear. Therefore Fargo has an enhanced 'Greenhouse Effect' with the cloud cover and will stay warmer during the overnight hours versus Grand Forks.
What nighttime weather conditions would create the greatest temperature gradient from the surface to areas just a few feet above the surface?
Clear, calm conditions. As night progresses, the ground and the air in contact with it continue to cool more rapidly than the air a few meters higher. This is due to the ground and air above the ground radiating infrared energy, a process called radiational cooling. Radiational cooling is most efficient under clear skies and calm winds. An increase in cloud cover and/or windy conditions will decrease the effects of radiational cooling.
Why has CO2 been on the increase over the past 100 years?
Decay of vegetation, volcanic eruptions, fossil fuels, deforestation. Mainly fossil fuels and deforestation
Explain why the daily range of temperature is normally greater (a) in dry regions than in humid regions and (b) on clear days than on cloudy days.
Dry regions have clearer skies and less water vapor in the atmosphere versus a humid region, therefore, incoming solar radiation is greater during the day in dry regions because the sun's energy is not reflected by clouds (higher temps) and radiational cooling is greater during the overnight hours in a dry regions because less water vapor is available to re-radiate outgoing infrared radiation back to the surface (lower temps). Clear days maximize daytime incoming solar radiation and nighttime radiational cooling (maximum daily temp range) while cloud cover will decrease daytime incoming solar radiation and hamper radiational cooling (minimal daily temp range).
During the Northern Hemisphere's summer, the daylight hours in the far northern latitudes are longer than those in the mid-latitudes, but the temperatures are not warmer farther north. Why?
Even though the far northern latitudes are receiving more hours of sunlight in the summer, the sun angle is still considerably low. It is true that the northern latitudes are receiving more solar radiation at the top of the atmosphere, but the sunlight penetrating through the northern atmosphere will be partially scattered by fine dust and air molecules, reflected by clouds, and absorbed by atmospheric gases. These factors combined, reduce the amount of solar radiation reaching the ground. The solar radiation that does reach the ground, is partially reflected by ice and snow, is used to melt ice, snow and frozen ground and heat the lower atmosphere.
What is the standard atmospheric pressure at sea level in: Inches of Mercury ("Hg) Millibars (mb)
Inches of mercury 29.92" Hg Millibars 1013.25 mb
Which wavelength carries the most energy - infrared, visible, or ultraviolet?
Infrared - greater than .70 μm Visible - between .40 and .70 μm Ultraviolet - less than .40 μm
The earth is closet to the sun in January when the Southern Hemisphere is experiencing their summer season. So why are the Southern Hemisphere summers are not warmer than Northern Hemisphere summers?
It is true that the sun is closet to the earth during the period when the Southern Hemisphere is experience summer (January 4th) but the larger amount of water in the Southern Hemisphere (81%) versus the Northern Hemisphere (61%) causes summer temperatures to be cooler in the Southern Hemisphere. But the water's larger heat capacity will also cause the Southern Hemisphere winters to be warmer than the Northern Hemisphere winters, with the exception of the Antarctic due to its large snow and ice pack.
Name and describe the three different temperature scales.
Kelvin scale → starting point is absolute zero (0K), freezing point (273K) and boiling point (373K) at sea level. The Kelvin scale contains no negative numbers and is therefore quite convenient for scientific calculations. Celsius scale → The number 0 (zero) is assigned to the temperature at which pure water freezes and 100 to the temperature at which pure water boils at sea level. (100 divisions between the two) Fahrenheit scale → The number 32 is assigned to the temperature at which pure water freezes and 212 to the temperature at which pure water boils at sea level. (180 divisions between the two)
Define 'Latent Heat'. Define 'Sensible Heat'.
Latent heat is the heat energy required to change a substance, such as water, from one state, or phase, to another. Sensible heat is the heat we can feel, 'sense', and measure with a thermometer.
What is the difference between latitude and longitude?
Latitude (Parallels) are lines that run east-west and measure distance north-south. Lines of latitude are parallel to one another with 1˚ of latitude equaling 60 nautical miles. Longitude (Meridians) are lines that run north-south and measure distance east-west. Lines of longitude are not parallel and converge towards the poles therefore there is no equal distance between degrees of longitude.
What is a Wind Chill Temperature?
Once the wind starts to blow, the insulating layer of warm air is swept away, and heat is rapidly removed from the skin by the constant bombardment of cold air. When all other factors are the same, the faster the wind blows, the greater the heat loss, and the colder we feel. How cold the wind makes us feel is usually expressed as a Wind-Chill Index (WCI)
What is potential energy?
Potential energy (PE) is the energy a body possesses by virtue of its position with respect to other bodies in the field of gravity.
What daytime weather conditions in the summer would create the greatest temperature gradient from the surface to an area just a few feet above the surface?
Sunny, calm conditions. The sun heats the ground which in turn heats the air in contact with it by conduction. Because air is such a poor conductor of heat, there exists a thermal boundary separating the hot surface air from the slightly cooler air above. On windy days, however, turbulent eddies are able to mix hot surface air with the cooler air above reducing the temperature gradient from the surface upward.
Distinguish between temperature and heat.
Temperature is a measure of molecular motion; Heat is energy in the process of being transferred from one object to another because of the temperature difference between them.
How does the average speed of air molecules relate to the air temperature?
Temperature is a measure of the average speed of the atoms and molecules, where higher temperatures correspond to faster average speeds of atoms and molecules.
Explain how the earth's atmospheric 'Greenhouse Effect' works?
The 'Greenhouse Effect' works because atmospheric gases such as water vapor and carbon dioxide are good absorbers of infrared (longwave) radiation but poor absorbers of visible (shortwave) radiation. This allows visible (shortwave) radiation to reach the earth's surface. The earth's surface will then re-radiate this energy as infrared (longwave) radiation. The re-radiated infrared (longwave) radiation can now be absorbed by the various greenhouse gases (water vapor and carbon dioxide) which results in an increase in the earth's temperature.
What are the main factors that determine seasonal temperature variations?
The 23.5˚ tilt in the earth's axis combined with the earth's elliptical orbit around the sun are the main factors that determine seasonal temperature variations. The angle at which a sun beam strikes the earth and the length of daylight hours are directly related to the tilt of the earth's axis and the location that the earth is at in its orbit around the sun.
Why do air pressure and density decrease more rapidly near the earth's surface than aloft?
The air pressure and density decrease rapidly at first because air is compressed near the surface due to the gravitational force.
Explain how radiational cooling at night produces a radiation temperature inversion.
The ground and air near the ground will cool quicker than the air above by radiating infrared radiation (radiation cooling). The warmer temperatures aloft do transfer some heat downward but the process is slow due to the air's poor thermal conductivity. Therefore, by late night or early morning, the coldest air is found next to the ground, with slightly warmer air above (radiational inversion).
What gases appear to be responsible for the enhancement of the earth's Greenhouse Effect?
The main cause of global warming appears to be an increase in carbon dioxide concentrations over the past 100 years primarily due to the burning of fossil fuels and to deforestation. Today, carbon dioxide concentrations continue to increase but other gases such as methane, nitrous oxide, and chlorofluorocarbons have collectively been shown to have an effect almost equal to that of carbon dioxide.
What atmospheric layer contains a vast majority of our weather?
The troposphere.
What is the difference between Universal, Greenwich and Zulu Time?
There is no difference.
Can a thermometer measure a Wind Chill Temperature?
Thermometers can only measure the 'ambient' air temperature. A wind-chill temperature is a 'sensible' temperature or a temperature that we perceive. In the case of wind-chill, the 'sensible' temperature is a temperature in which 'we feel' colder than it actual is outside.
Describe each of the controls of temperature. Time of Year Latitude Land vs Water Distribution Ocean Currents Elevation
Time of Year - determines the location of the earth in its orbit around the sun which determines what season you are in Latitude - determines the amount of incoming solar radiation, slant angle of sun and duration of daylight hours, at a given latitude Land vs Water distribution - areas with more water (Southern Hemisphere) will have smaller seasonal temperature variations. Areas located in the middle of continents (Grand Forks) will have a much greater seasonal temperature variation than areas along the coast Ocean Currents - warm vs cold currents will affect coastal temperatures Elevation - higher elevations are colder due to decreasing temperatures with height but they also experience smaller temperature variations.
Why is the atmosphere not considered a blackbody?
Unlike the earth, the atmosphere absorbs some wavelengths of radiation and is transparent to others. Objects that selectively absorb and emit radiation, such as carbon dioxide and water vapor in our atmosphere, are known as selective absorbers. Remember: A blackbody is any object that is a perfect absorber and a perfect emitter of radiation, at its given temperature.
How does the amount of radiation emitted by the sun differ from that emitted by the earth when comparing the same time frame and area?
Using the Stefan - Boltzmann law, with the sun's surface temperature at 6000 K and the earth's average surface temperature at 288 K, one can calculate that the sun emits nearly 160,000 times more energy during a given time period over the same size area.
How does weather differ from climate?
Weather is conditions of the atmosphere at any particular time and place. It is comprised of the elements of: air temperature, air pressure, humidity, clouds, precipitation, visibility, and wind. Climate is a specified interval of time that will give us the "average weather" for a region. It also includes the extremes of weather, therefore weather records are part of the climatology for a specific site or region.
How do the wavelengths of maximum radiation emitted by the sun differ from the wavelengths of maximum radiation emitted by the surface of the earth?
When using a temperature of 6000 K for the sun's surface, the maximum wavelength at which maximum radiation is emitted from the sun occurs at .48 μm. The earth's maximum wavelength is 10.06 μm when using the earth's average surface temperature of 288 K
Explain how "latent heat" plays an important role as a source of atmospheric energy?
When water vapor changes to a liquid or ice cloud particle, a tremendous amount of heat energy is released into the environment due to the release of latent heat during the phase change. This heat provides energy for storms, such as hurricanes, mid-latitude cyclones, and thunderstorms.
Calculate the cooling degree-day for Grand Forks on a day with a minimum temperature of 71˚F and maximum temperature of 95˚F.
You must first calculate the mean (average) daily temperature. In this example, with a high of 95˚F and low 71˚F the average temperature is 83˚F. Then subtract the base temperature (65˚F) from the mean daily temperature (83˚F) and you get a cooling degree-day of: 83˚F - 65˚F = 18.
Calculate the heating degree-day for Grand Forks on a day with a minimum temperature of -26˚F and maximum temperature of -10˚F.
You must first calculate the mean (average) daily temperature. With a high of -10˚F and low of -26˚F, the average temperature for the day would be -18˚F. Then subtract the mean daily temperature (-18˚F) from the base temperature of (65˚F) and you get a heating degree-day of: 65˚F - (-18˚F) = 83.
