Chapter 5

Question 1

The layered structure of the atmosphere

Answer 1

• atmosphere extends from a very shallow depth within the earth to a height of about 480km
• most of the atmosphere’s mass lies below an altitude of 30km
• contains 4 distinct layers: troposphere, stratosphere, mesosphere, thermosphere
• layers are distinguished by temperature and also by the elements they contain

Question 2

Layers and temperature patterns in the atmosphere

Answer 2

troposphere

• average thickness = 12km, 16km at the equator & 8km at the poles
• where most weather occurs

stratosphere

• extends to 50km
• airliners travel in the stratosphere

mesosphere

• extends to 80km
• meteors burn up from friction in the mesosphere

thermosphere

• extends to 480km
• auroras

Question 3

Troposphere

Answer 3

• the lowermost thermal (heat) layer of the atmosphere, which lies between Earth’s surface and an altitude of approximately 12km
• most active zone, with the vigorous moving of currents of air
• substances constantly re-entering the troposphere and settling back out of it, so vertical mixing is common
• contains the vast majority of nonmarine living organisms and is the zone where the most weather occurs (rain, wind, snow), because the troposphere contains the most atmospheric water vapour and particulates
• warmed by longwave radiation emitted from the earth, temperature decreases with increasing altitude from the surface at the environmental lapse rate
• as altitude increased, the average temperature drops 6.5 degrees C per 1000m
• upper limit of the troposphere = tropopause, where the temperature stops decreasing and begins to increase into the next layer
• tropopause found at -57 degrees C (varies depending on latitude)
• thickness of the troposphere is dependant on the temperature at the earth’s surface, so it varies with season & latitude (low latitudes have a net surplus of radiation), so near the equator there is more radiation transferred back to the atmosphere as longwave radiation, which heats the lower atmosphere, the higher temperature makes the atmospheric gases expand and making the tropopause extend higher at the equator
• during the summer, thermal expansion of the lower atmosphere and the presence of warm updrafts push the upper boundary of the tropopause to higher altitudes
• conditions sometimes develop when warm air overlies cold air, which is temperature inversion and can develop at any altitude within the troposphere
• temperature inversions associated with local weather patterns, like when the ground cools quickly on a clear night, or along coastlines when cold ocean water cools the air close to the ground
• inversions can develop when a warmer, less dense air mass moves over a cooler, denser air mass, the cool air becomes trapped near the surface unable to rise, causing pollutants to be trapped, can result in fog, or cause smog
• inversions can last for hours or days

Question 4

The environmental lapse rate in the troposphere

Answer 4

• the average temperature decreases with increasing altitude until it reaches -57 degrees C

Question 5

Environmental lapse rate

Answer 5

• the decrease in temperature that generally occurs with respect to the altitude in the troposphere
• this rate is generally 6.5 degrees C per km

Question 6

Tropopause

Answer 6

• the top part of the troposphere, which is identified by where the air temperature reaches -57 degrees C

Question 7

Temperature inversion

Answer 7

• a layer of the troposphere where the air temperature increases, rather than cools, with altitude

Question 8

Stratosphere

Answer 8

• the layer of the atmosphere, between the troposphere and mesosphere, that ranges between about 12km and 50km in altitude
• contains the ozone layer (occurs between 20-50km), the concentration of ozone in this portion is 10 parts per million by volume (ppmv) whereas it is only 0.04 ppmv in the troposphere
• ozone layer filters UV radiation from the sun and re-radiates it as infrared energy, stratospheric temperature trends reflect this filtering and the overall thickness of the ozone layer
• from the top of the tropopause to the base of the ozone layer, the temperature is consistent around -57 degrees C, but above that altitude temperature increases with altitude because of the ozone absorbing Uv energy from the sun, lower altitudes have less absorption efficiency than higher altitudes
• top of the stratosphere = stratopause, marked by the altitude where temperature stops increasing (average temperature around -5 degrees C)
• portion of the atmosphere where commercial jets fly, as it contains very little water vapour and few clouds, the air is relatively calm because air flows parallel to the surface of the earth

Question 9

Stratopause

Answer 9

• the upper boundary of the stratosphere where the temperature reaches its highest point

Question 10

Mesosphere

Answer 10

• a layer of decreasing temperature in the atmosphere that occurs about 50-80km in altitude
• the coldest of the atmospheric layers
• vertical temperature trends have a positive lapse rate because temperature decreases with increasing distance from the ozone layer
• the altitude at which temperature stops decreasing is the mesopause and the upper boundary of the mesosphere, where the temperature is about -100 degrees C
• solar radiation reduces gas molecules to individual electrically charged particles called ions, can disrupt communications between astronauts and ground control and interfere with various satellite communications such as the transmission of television signals
• the layer where most meteors burn up, destroyed because they collide with billions of ions and gas particles, the collisions creating sufficient heat to burn the tiny fragments way before they can reach the ground (occasionally the largest fragments reach the earth’s surface, called meteorites)

Question 11

Mesopause

Answer 11

• the upper boundary of the mesosphere where the temperature reaches its lowest point

Question 12

Temperature inversions

Answer 12

• a temperature inversion develops when warm air overlies cold air at some altitude within the troposphere,

Question 13

Thermosphere

Answer 13

• upper layer of the atmosphere, which occurs between about 80km and 480km in altitude
• atmospheric gases sorted into sublayers based on their molecular mass
• this portion of the atmosphere also known as the heterosphere, because gases are sorted in a heterogenous manner by gravity based on their molecular weights (heavier elements, nitrogen and oxygen, found at the base of the layer, and lighter elements, helium and hydrogen, found at the top of the layer)
• oxygen molecules few and many km’s apart from each other so the boundary with space is very diffuse and difficult to precisely determine
• temperature increases drastically above the mesopause, reaching 1200 degrees C and continues to climb even higher, these high temperatures occur because intense solar radiation interacts with the upper part of the atmosphere, causing the few oxygen molecules to vibrate at very high speeds creating kinetic energy (specifically contained within the molecules by virtue of their spatial relationship to other oxygen molecules)
• thermosphere is important for human communications, enables radio waves from one location at the surface to bounce off and be received at locations beyond the horizon
• thermosphere does not feel hot, because the individual oxygen molecule are so far apart and hardly come in contact with one another, so very little heat is transferred

Question 14

Heterosphere

Answer 14

• upper portion of the earth’s atmosphere, where gases are sorted according to their molecular weights

Question 15

Homosphere

Answer 15

• the lower portion of the earth’s atmosphere, where gases are evenly dispersed

Question 16

Kinetic Energy

Answer 16

• the energy an object possesses due to its motion

Question 17

Surface and air temperatures

Answer 17

• global surface and air temperatures measure the amount of sensible heat at the surface or in the atmosphere
• atmospheric temperature: a measure of kinetic energy contained within a unit of geographical space within the air
• surface temperature: a measure of kinetic energy contained in a region very close to the earth’s surface, so changes in surface temperature measure the ebb and flow of energy at ground level
• variation in energy on earth depends on net radiation, a net surplus of radiation = temperature increase due to the surface absorbing more radiant energy than it is emitting in longwave form, a net deficit of radiation = temperature decreases because the surface emits more energy than it absorbs
• air temperature: the degree of warmth of a portion of the atmosphere, usually measured about 1.2m above the ground’s surface, air temperature differs from ground temperature but the amount of heat energy in the ground influences the temperature of the air above it
• air temperature measured by thermometers or thermistors
• 3 temperature scales: Celsius, Fahrenheit, and the kelvin scale

Question 18

Human Interactions: Humidex and Windchill

Answer 18

• wind chill index (winter): based on the loss of heat from the face
• humidex (summer): combines temperature and relative humidity measurements into one number to reflect the perceived temperature

Question 19

Large-scale geographic factors that influence air temperature

Answer 19

Latitude

• differences in the angle of incidence cause the same amount of energy to be directed at smaller or larger areas on the Earths surface
• larger area covered = lower incidence angle, occurring at high latitudes, less energy per unit area

Seasons and Length of Day

• Earths axial tilt causes seasonal migration of the subsolar point because the Northern and Southern Hemisphere’s are tilted toward or away from the sun depending on the time of year
• migration of the subsolar point occurs in the tropics ( between 23.5N and 23.5S) but results in dramatic changes in the angle of incidence at all latitudes and influences net radiation
• axial tilt and seasons cause the length of the day to fluctuate depending on latitude, longer days equalling more radiation received, influencing temperature

Time of Day

• sun arcs westward across the sky during the day
• solar noon = the sun at its highest point, the day’s most intense solar radiation
• temperature usually increases as the sun rises and decreases as the sun sets
• temporal lag occurs between the highest sun angle and the warmest temperature of the day, so the warmest part of the day occurs after the peak of insolation and net radiation
• with respect to insolation: the amount of insolation is greater on June solstice than December solstice
• with respect to net radiation: seasonal variation results in a greater surplus of net radiation during summer months than winter months
• with respect to air temperature: temperature is related to insolation and net radiation in that the maxima and minima of each factor occur at about the same time

Question 20

Temporal lag

Answer 20

• the difference in time between two events, such as when peak insolation and peak temperature occur

Question 21

Land skin temperature

Answer 21

• land skin temperature reflects the pure heating of the ground by solar radiation, the atmosphere, and other heat flows
• different kinds of surfaces vary in temperature based on factors such as albedo, dryness of the soil, character of sediment, degree of shade
• highest land skin temperature found in deserts (clear sky, dry soil, light wind, low albedo)

Question 22

Local factors that influence air temperature

Answer 22

Maritime vs continental locations

• large bodies of water store tremendous amounts of thermal energy, because water has a high specific heat
• solar radiation can penetrate to great depths in the ocean, heating water below the surface
• ocean currents mix this warm water with the cooler water not exposed to sunlight, resulting in large water bodies maintaining a more/less constant temperature for most of the year (the effect can be enhanced if the ocean current near the coast is a cold or warm current)
• in maritime regions, as water evaporates from the ocean, energy is transferred to the atmosphere in the form of latent heat and moderates the air temperature of coastal places (magnified on the west coast of North America as winds are westerly, blowing relatively mild, moist air off the ocean onto the coast)
• continental locations do not store as much thermal energy, because of low specific heat (heats and cools quickly), and radiation does not reach great depths in landmasses, as a result, continental localities exhibit dramatic annual temperature variations compared to maritime places

Other local factors that influence temperature

• altitude (temperature tends to decrease with increased elevation)
• the position of topographic barriers (ex. in areas where wind descends a mountain range, temperature can warm considerably due to increased molecular friction as the air is compacted)
• wind flow patterns

Question 23

Maritime vs continental effect

Answer 23

• the difference in annual and daily temperature that exists between coastal locations, and those surrounded by large bodies of land

Question 24

Maritime

Answer 24

• a place that is close to a large body of water that moderates temperature

Question 25

Continental

Answer 25

• a place that is surrounded by a large body of land and that experiences a large annual range of temperature

Question 26

Specific heat

Answer 26

• the amount of energy it takes to raise one gram of a substance by one degree of C
• waters specific heat is 5x greater than that of land surfaces

Question 27

Maritime vs continental contrasts

Answer 27

insolation on water:

• high specific heat (heats slowly)
• radiation penetrates to lower depths
• heated water mixes with cooler water
• high evaporation rate

insolation on land:

• lower specific heat (heats quickly)
• radiation does not penetrate the surface
• no mixing of heated with cooler land
• low evaporation rate

Question 28

Global sea-surface temperatures during January and June

Answer 28

• sea surface temperature in the pacific ocean shows a small change between the months
• ocean areas do not experience extreme changes in temperature variability throughout the year

Question 29

The annual range of surface temperature (A Holistic Assessment)

Answer 29

• hypothetical continent, bordered on the east and west by oceans
• straddles the equator
• contains, as a point of reference, the hypothetical position of the 15 degree C isotherm in January and July
• due to seasonality: isotherm shifts into the SH during that hemispheres summer (January) and back into the NH during July, this migration occurs due to a net surplus of radiation occurring in each hemisphere during the respective summer months due to high angles of incidence and increased insolation
• maritime vs continental effect: evident in the range of latitude that the isotherm shifts in each hemisphere, in the oceans the isotherm does not move as much as on the landmass
• considering the broad-scale range cycle of temperature on Earth
• January: landmasses in the Northern Hemisphere are quite cold but much warmer at higher latitudes along the west coast of North America
• January: for the southern hemisphere summer, high-latitude temperatures are relatively warm, the only deviation occurring in western South America where cool temperatures penetrate into very low latitudes (due to the Andres mountains following much of the coastline)
• July: Northern hemisphere landmasses are much warmer, experiencing an annual temperature range of 60 degrees C at high latitudes
• July: Southern hemisphere doesn’t experience a high range of temperature

Why these geographical patterns exist:

• seasonality
• insolation
• net radiation
• latitude
• maritime vs continental effect
• environmental lapse rate of the troposphere

Some patterns explained:

• the consistency of warm temperatures in the tropics is due to the high angle of incidence and associated intense radiation
• extreme range of temperature in high latitudes of the Northern Hemisphere is explained by the variable amount of radiation received over the year due to changes in orbital position and the angle of incidence
• southern hemisphere continents are much smaller than northern hemisphere continents, so the SH is covered by more water, thus more maritime effect occurs in the SH and more continental effect occurs in the NH

Question 30

Human Interactions: Urban Heat Islands

Answer 30

• human influence is another factor that influences air temperature
• human-induced change in land cover can cause a measurable temperature increase in and around cities in a variety of ways, resulting in urban heat islands where temperatures may be 3-4 degrees C warmer than the surrounding countryside

Urban environments are warmer than rural areas for several reasons:

• urban surfaces consist of metal, glass, asphalt, concrete, compared to rural areas that are covered in soil, forest, grass
• urban surfaces darker, lower albedo, greater net radiation (up to 70% of net radiation converted to sensible heat)
• urban surfaces conduct more energy and are thus warmer
• urban environments have solar radiation strike more directly and are absorbed to later be released as longwave radiation, but this re-radiation tends to be trapped for longer periods of time in cities further warming them
• decreased airflow reduces loss of heat
• urban surfaces sealed by pavement/buildings so water does not absorb into the ground, precipitation runs into storm drains
• impact of human activities: in the summer months, the production of electricity to cool homes/businesses releases energy, as much as 25-50% of insolation, during the winter months, sensible heat is generated through artificial heating

Question 31

Urban heat island

Answer 31

• the relatively warm temperatures associated with cities that occur because paved surfaces and urban structures absorb and release radiation differently from the surrounding countryside