Chapter 16

Does air pressure increase or decrease with an increase in altitude? Is the rate of change constant or variable? Explain.

Air pressure changes with altitude: The rate of pressure decrease with increase in altitude is not constant. Pressure decreases rapidly near Earth's surface and more gradually at greater heights. Put another way, the graph shows that the vast bulk of the gases making up the atmosphere are very near Earth's surface and that the gases gradually merge with the emptiness of space. The rate of change is variable.

Which area on Earth experiences the highest annual temperature range?

Asian Continental Interior

What factors cause albedo to vary from time to time and from place to place on Earth?

Cloud cover, particulate matter in the air, angle of the Sun's rays, nature of the surface.

How does cloud cover influence the maximum temperature on an overcast day? How is the nighttime minimum influenced by clouds?

Cloud tops have a high albedo and reflect much incoming sunlight away from Earth's surface, making temperatures at the surface cooler on an overcast day. Clouds absorb outgoing nighttime radiation from the Earth, acting as a blanket and keeping minimum temperatures warmer than they otherwise would be.

Describe the three basic mechanisms of heat transfer. Which mechanism is least important as a means of heat transfer in the atmosphere?

Convection - this is mass movement or circulation of heat in a substance. Radiation - this is radiant energy that reaches Earth from the Sun. Conduction - this is heat transfer from molecule to molecule within a substance. It is the least important in the atmosphere.

How are the following temperature data calculated: daily mean, daily range, monthly mean, annual mean, and annual range?

Daily mean - adding the maximum and minimum daily temperatures and dividing by two. Daily range - finding the difference between the maximum and minimum temperature for a day. Monthly mean - adding the daily means for each day of the month and dividing by the number of days in that month. Annual mean - averaging the 12 monthly means. Annual range - finding the difference between the highest and lowest monthly means.

Explain why the atmosphere is heated chiefly by radiation emitted from Earth's surface rather than by direct solar radiation.

Earth's atmospheric gases are more efficient at trapping longer wavelengths of radiation such as those emitted by the Earth; these gases tend to allow solar radiation to pass through the atmosphere.

Write two brief statements about your current location: one that relates to weather and one that relates to climate.

East Texas has a humid and subtropical climate. The weather in Bullard Texas is very cold right now.

Describe the relationship between the temperature of a radiating body and the wavelengths it emits.

Hotter objects emit radiation at shorter wavelengths.

What are isotherms, and what is their purpose?

Isotherms are lines of equal temperature on a weather map. They connect places that have the same temperature gradients and distribution patterns.

What are the three paths taken by incoming solar radiation?

It can be scattered, reflected, or absorbed.

Do the annual variations in Earth-Sun distance adequately account for seasonal temperature changes? Explain.

No, because Earth is tilted on its axis. Distance from the Sun is negligible in seasonal temperature changes.

What is ozone? Why is ozone important to life on Earth? What are CFCs, and what is their connection to the ozone problem?

Ozone is three oxygen molecules bonded together. It is important because it blocks much of the harmful UV radiation from the Sun. CFCs are chlorofluorocarbons and chemically interact with ozone molecules to break them apart; when this happens enough an ozone hole may be generated.

Quito, Ecuador, is located on the equator and is not a coastal city. It has an average annual temperature of only 13°C (55°F). What is the likely cause for this low average temperature?

Quito is at a high elevation

After examining Table 16.1, write a general statement that relates the season, latitude, and length of daylight.

Regions closer to the equator experience little variation in day length among the seasons, while areas closer to the poles experience extremely long hours of daylight in summer and little to none in winter.

Is air a specific gas? Explain.

Sometimes the term air is used as if it were a specific gas, but it is not. Rather, air is a mixture of many discrete gases, each with its own physical properties, in which varying quantities of tiny solid and liquid particles are suspended.

Distinguish between heat and temperature.

Temperature is the average speed of air molecules, while heat is a measure of energy transfer between objects or regions of different temperatures.

In what part of the electromagnetic spectrum does the Sun radiate maximum energy? How does this compare to Earth?

The Sun emits its maximum energy in the visible portion of the spectrum. Earth is much cooler and emits most of its radiation as long wave radiation.

Why are temperatures in the thermosphere not strictly comparable to those experienced near Earth's surface?

The atmosphere and gas concentration in the thermosphere is very sparse and thin.

Is the outer edge of the atmosphere clearly defined? Explain.

The fourth layer extends outward from the mesopause and has no well-defined upper limit. It is the thermosphere, a layer that contains only a tiny fraction of the atmosphere's mass. In the extremely rarefied air of this outermost layer, temperatures again increase, due to the absorption of very short-wave, high-energy solar radiation by atoms of oxygen and nitrogen. It is difficult to determine where it ends.

Why do isotherms generally trend east-west?

The heating of Earth's surface by solar radiation is a function of latitude and similar latitudes have similar temperatures.

In what ways can geographic position be considered a control of temperature?

The main factor the geographical position determines is the relationship between the location and the ocean. If the position is near the coast and gets winds off the ocean then that location will tend to have cool summers and mild winters compared to a location blocked from the ocean by a mountain range. Places close to an ocean will experience the moderating effects of an ocean. A windward coast will experience more prevailing winds than a leeward coast also.

List the basic elements of weather and climate.

The most important elements are (1) air temperature, (2) humidity, (3) type and amount of cloudiness, (4) type and amount of precipitation, (5) air pressure, and (6) the speed and direction of the wind. These elements are the major variables from which weather patterns and climate types are deciphered.

Briefly explain the primary cause of the seasons.

The tilt of Earth on its axis allows some locations on Earth to receive more direct solar radiation at some times of the year because those locations are tilted towards the Sun; this would be summer.When a hemisphere is tilted away from the Sun it receives less direct radiation and experiences winter.

Why do isotherms shift north and south from season to season?

There is differential heating of different latitudes with the seasons depending upon the angle at which the Sun is striking them.

Why are the Tropic of Cancer and the Tropic of Capricorn significant?

These represent the most northern and most southern locations on Earth at which the noon sun will ever be directly overhead.

Where do isotherms shift most: over land or water? Explain.

They shift most over land because water has a high specific heat and takes longer to heat up and cool off.

What is the environmental lapse rate, and how is it determined?

This is the temperature decrease with altitude in the troposphere. It is determined by sending a radiosonde balloon up to make temperature measurements.

The atmosphere is divided vertically into four layers, on the basis of temperature. List and describe these layers in order, starting with the one closest to Earth. In which layer does practically all our weather occur?

Troposphere - temperature decreases with increasing height. Has the highest pressure of all four layers. Stratosphere - temperature increases with increasing height. This layer contains most of Earth's protective ozone layer. Mesosphere - temperature decreases with increasing height and contains the coldest temperatures in the atmosphere. It is the least explored of the four layers. Thermosphere - temperature increases with increasing height up to the edge of space. Temperatures can be very high. Almost all of Earth's weather occurs in the troposphere.

What are the two major components of clean, dry air? What proportion does each represent?

Two gases—nitrogen and oxygen—make up 99 percent of the volume of clean, dry air. Although these gases are the most plentiful components of air and are of great significance to life on Earth, they are of minor importance in affecting weather phenomena. The remaining 1 percent of dry air is mostly the inert gas argon (0.93 percent) plus tiny quantities of a number of other gases.

Why are water vapor and aerosols important constituents of Earth's atmosphere?

Water vapor is an important greenhouse gas that makes the planet habitable. It also contains huge amounts of latent heat that provide the power for weather systems globally. Aerosols are small solid particles suspended in the air. They can serve as nuclei on which water can condense and they can absorb, scatter, and reflect incoming solar radiation.

List the factors that cause land and water to heat and cool differently.

Water's relatively high specific heat, transparency of water, vertical mixing of water, evaporation from water is greater than that from land.

What is an element?

Weather and climate are expressed in terms of the same basic elements—quantities or properties that are measured regularly.

Distinguish between weather and climate.

Weather is constantly changing, sometimes from day to day and sometimes from hour to hour. It is a term that refers to the state of the atmosphere at a given time and place. Whereas changes in the weather are continuous and sometimes seemingly erratic, it is nevertheless possible to arrive at a generalization of these variations. Such a description of aggregate weather conditions is termed climate.