Term
| In the Northern Hemisphere, why are summers warmer than winters, even though the earth is actually closer to the sun in January? |
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Definition
| 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. |
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Term
What are the main factors that determine
seasonal temperature variations? |
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Definition
| 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. |
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Term
| Identify and name the major lines of latitude starting north and working south. |
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Definition
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 |
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Term
| 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? |
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Definition
| 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 factorscombined, 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. |
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Term
| If it is winter and January in New York City, what is the season in Sydney, Australia? |
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Definition
| Since Sydney, Australia (33½˚ S Lat) is in the Southern Hemisphere, it would be summer but the month of the year is still January. |
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Term
| 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? |
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Definition
| 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. |
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Term
| 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? |
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Definition
| 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. |
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Term
| What nighttime weather conditions would create the greatest temperature gradient from the surface to areas just a few feet above the surface? |
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Definition
| 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. |
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Term
| 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. |
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Definition
| 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 the time when incoming solar radiation and outgoing infrared radiation become equal or just before outgoing infrared radiation is greater than incoming solar radiation. |
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Term
| Explain how radiational cooling at night produces a radiation temperature inversion. |
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Definition
| 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). |
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Term
| What weather conditions are best suited for the formation of a cold night and a strong radiation inversion in Grand Forks? |
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Definition
| 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. |
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Term
| Name three methods that farmers can use to protect their crops against the cold. Explain the physical principle behind each method. |
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Definition
1. Orchard Heaters – They circulate the air by setting up convection currents
2. Wind Machines – They mix cooler surface air with warmer air above
3. Coat with Ice – Sprinklers emit a fine spray of water which freezes to the vegetation. The release of latent heat when the water changes to ice keeps the ice at ≈ 32˚F, protecting the vegetation beneath the ice. |
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Term
Describe each of the controls of temperature.
1. Time of Year
2. Latitude
3. Land vs Water Distribution
4. Ocean Currents
5. Elevation |
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Definition
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. |
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Term
| 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)? |
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Definition
| 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. |
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Term
| How to calculate the heating degree-day. |
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Definition
| Find the day's average temperature by adding the day's high and low temperatures and dividing by two. If the number is above 65, there are no heating degree days that day. If the number is less than 65, subtract it from 65 to find the number of heating degree days. |
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Term
| Calculate the cooling degree-day for Grand Forks on a day with a minimum temperature of 71˚F and maximum temperature of 95˚F. |
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Definition
| You must first calculate the mean (average) daily temperature. In this example it 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 18. |
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Term
| What is a ‘sensible temperature’? |
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Definition
| 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. |
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Term
| How would you construct an instrument shelter that holds thermometers to measure atmospheric temperature? |
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Definition
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 |
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Term
| What weather conditions are best suited for the formation of a cold night and a strong radiation inversion in Grand Forks? |
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Definition
| 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. |
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Term
| 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)? |
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Definition
| 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. |
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Term
| Calculate the cooling degree-day for Grand Forks on a day with a minimum temperature of 71˚F and maximum temperature of 95˚F. |
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Definition
| You must first calculate the mean (average) daily temperature. In this example it 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 18. |
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Term
| What is a ‘sensible temperature’? |
|
Definition
| 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. |
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Term
| How would you construct an instrument shelter that holds thermometers to measure atmospheric temperature? |
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Definition
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 |
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Term
| What is potential energy? |
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Definition
| Potential energy is energy which results from position or configuration. |
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Term
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Definition
Any body in motion has kinetic energy, therefore kinetic energy is the energy within a body that is a result of its motion. (KE = ½ mv2) where: m is the object’s mass and v is the object’s
velocity.
Examples:
Heat Energy → molecular motion
Radiant energy → that received from the sun |
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Term
| How does the average speed of air molecules relate to the air temperature? |
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Definition
| 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. |
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Term
| Distinguish between temperature and heat. |
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Definition
| 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. |
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Term
| At the same pressure, why is cold air more dense than warm air? |
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Definition
| 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. |
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Term
| Name and describe the three different temperature scales. |
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Definition
Fahrenheit, Celsius and Kelvin.
Fahrenheit temperature scale is a scale based on 32 for the freezing point of water and 212 for the boiling point of water, the interval between the two being divided into 180 parts.
Celsius temperature scale also called centigrade temperature scale, is the scale based on 0 for the freezing point of water and 100 for the boiling point of water.
Kelvin temperature scale is the base unit of thermodynamic temperature measurement in the International System (SI) of measurement. It is defined as 1/ 273.16 of the triple point (equilibrium among the solid, liquid, and gaseous phases) of pure water. The kelvin (symbol K without the degree sign []) is also the fundamental unit of the Kelvin scale, an absolute temperature scale named for the British physicist William Thomson, Baron Kelvin. Such a scale has as its zero point absolute zero, the theoretical temperature at which the molecules of a substance have the lowest energy. |
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Term
| What is the difference between the ‘heat capacity’ and ‘specific heat’ of an object? |
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Definition
| 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. |
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Term
| What are the “specific heat values” for water, ice and the earth surface? |
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Definition
Specific Heat Values:
Water → 1.0 cal/gram ˚C
Ice → 0.5 cal/gram ˚C
Earth surface (land) → 0.3 cal/gram ˚C |
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Term
| How will the heating rate of objects with a high specific heat value compare with objects with a lower specific heat value? |
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Definition
| 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 |
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Term
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Definition
| Latent heat is the heat energy required to change a substance, such as water, from one state, or phase, to another |
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Term
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Definition
| Sensible heat is the heat we can feel, ‘sense’, and measure with a thermometer. |
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Term
| 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. |
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Definition
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
[image] |
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Term
| Explain how “latent heat” plays an important role as a source of atmospheric energy? |
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Definition
| 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. |
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Term
| Name and define the three ‘Heat Transfer’ mechanisms. |
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Definition
Conduction → The transfer of heat from 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. |
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Term
| 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? |
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Definition
| 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. |
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Term
| How does the temperature of an object influence the radiation that it emits? |
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Definition
| 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). |
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Term
| 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? |
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Definition
| 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. |
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Term
| 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? |
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Definition
According to Wien’s law,(λmax = constant / T )
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 288K. |
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Term
| Which wavelength carries the most energy – infrared, visible, or ultraviolet? |
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Definition
| Longer waves carry less energy than shorter waves, therefore, we must determine which one has the shortest wavelength. Infrared – greater than .70 μm (Longwaves) Visible – between .40 and .70 μm (Visible light) Ultraviolet – less than .40 μm (Shortwaves) Therefore, ultraviolet wavelengths carry the most energy out of the three types of radiation mentioned here. |
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Term
| If the earth’s surface continually radiates energy, why doesn’t it become colder and colder? |
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Definition
| 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. |
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Term
| Why is the atmosphere not considered a blackbody? |
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Definition
| 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. |
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Term
| Explain how the earth’s atmospheric ‘greenhouse effect’ works? |
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Definition
| The ‘greenhouse effect’ works because atmospheric gases such as water vapor, carbon dioxide, nitrous oxide, and methane are good absorbers of infrared radiation but poor absorbers of visible radiation. This allows the visible radiation to reach the earth’s surface which is then re-radiated as infrared radiation. The re-radiated infrared radiation can now be absorbed by the various greenhouse gases which results in an increase in air temperature. |
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Term
| What gases appear to be responsible for the enhancement of the earth’s greenhouse effect? |
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Definition
| 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. |
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Term
| 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? |
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Definition
| 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. |
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Term
| What process contributes to the earth’s albedo being 30%? |
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Definition
| 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. |
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Term
| How would the heating of a surface area be affect after receiving it’s first major snowfall of the season? |
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Definition
| 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. |
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Term
| Explain how the atmosphere near the earth’s surface is warmed from below. |
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Definition
| 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. |
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Term
| List the two most abundant permanent gases in today’s atmosphere. |
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Definition
1. Nitrogen (N2) 78.08%
2. Oxygen (O2) 20.95% |
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Term
| When looking at the variable gases in our atmosphere, which one shows the greatest variation at the earth’s surface? |
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Definition
| Water Vapor varies greatly from place to place and from time to time. Close to the surface in warm, steamy, tropical locations, water vapor may account for up to 4% of the atmospheric gases, whereas in cold arctic areas, its concentration may dwindle to a mere fraction of a percent. |
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Term
| What are some of the important roles that water plays in our atmosphere? |
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Definition
| By phase transformations between gaseous, liquid and solid it is involved in energy transformation and transport and weather formation. Because of its ability to absorb infrared radiation it plays an important role for the warming of the atmosphere. |
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Term
| Why has “Carbon Dioxide (CO2)” been on the increase over the past 100 years? |
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Definition
| CO2 (0.038% of air by volume) enters the atmosphere mainly form the decay of vegetation, but it also comes from volcanic eruptions, the exhalations of animal life, the burning of fossil fuels, and from deforestation. CO2 is removed from the atmosphere by plants consuming CO2 to produce green matter (photosynthesis). The increase in CO2 appears to be due mainly to the burning of fossil fuels (80%) and deforestation of the rain forest (20%) over the past 100 years. |
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Term
| List the two most abundant greenhouse gases in our atmosphere. What makes them greenhouse gases? |
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Definition
| Water vapor and Carbon Dioxide. They both trap a portion of the earth’s outgoing energy. Consequently, with everything else being equal, as the atmospheric concentration of CO2 increases, so should the average global surface air temperature. |
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Term
| Explain how the atmosphere “protects” inhabitants on the earth’s surface. |
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Definition
| The atmosphere contains a gas called “ozone”. This key element, small in concentration (0.002% by volume), is more concentrated in the upper atmosphere (Stratosphere). Ozone shields plants, animals, and humans from the sun’s harmful ultraviolet radiation. |
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Term
| What are aerosols, and list some of the aerosols in our atmosphere? |
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Definition
Aerosols are impurities found in the atmosphere that are from both natural and human sources. Some of these aerosols are:
1. Dust and soil particles
2. Microscopic salt particles
3. Smoke
4. Volcanic ash |
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Term
| 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? |
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Definition
| The weight of the air molecules acts as a force upon the earth. The amount of force exerted over an area of surface is called “air pressure”. The pressure at any level in the atmosphere may be measured in terms of the total mass of air above any point. So with an increase in height, pressure values will decrease. |
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Term
| Why does air pressure always decrease with increasing height above the surface? |
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Definition
| As we climb in elevation, fewer air molecules are above us; hence, air pressure always decreases with increasing height, rapidly at first, then more slowly at higher levels. |
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Term
What is the standard atmospheric pressure at sea level in:
Inches of Mercury (“Hg)
Millibars (mb) |
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Definition
Inches of mercury
29.92” Hg
Millibars
1013.25 mb |
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Term
Identify and provide the average elevations of the standard atmospheric pressure levels?
Level (mb) Height (ft) Height (mi)
1000 ________ ________
850 ________ ________
700 ________ ________
500 ________ ________
300 ________ ________
200 ________ ________ |
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Definition
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 |
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Term
| What is the average or standard lapse rate in the troposphere? |
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Definition
| The temperature on average will decrease by 6.5˚C per 1000 meters (or) 3.6˚F per 1000 feet rise in elevation. |
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Term
| Based on the temperature profile, list the layers of the atmosphere from the lowest to the highest in elevation. |
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Definition
1) Troposphere (sfc to 11km) temperatures decrease with height
2) Stratosphere (11 to 50km) temperatures increase with height
3) Mesosphere (50 to 85km) temperatures decrease with height
4) Thermosphere (85 to 500km) temperatures increase with height |
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Term
| What atmospheric layer contains a vast majority of our weather? |
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Definition
| The troposphere. A severe thunderstorm with overshooting tops can extend into the lower levels of the stratosphere. |
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Term
1. In what atmospheric layer do we find the lowest average air temperature?
2. The highest average temperature?
3. The highest concentration of ozone? |
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Definition
1. 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 |
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Term
| What is the difference between latitude and longitude? |
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Definition
Both are used to measure earth coordinates.
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. |
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Term
| What is the difference between Universal, Greenwich and Zulu Time? |
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Definition
| There is no difference. All three refer to the same Time Coordinate System. In Meteorology we use one time zone for the whole world that is based on the time along the prime meridian (0˚ longitude) which runs through Greenwich, England. The names given to this time coordinate system vary as stated above. In Grand Forks there is a -6 hour difference during standard time and a -5 hour difference during daylight saving time between Universal time and Local time. |
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