The temperature of the troposphere is highest near the surface of the Earth and decreases with altitude. On average, the temperature gradient of the troposphere is 6.5o C per 1,000 m (3.6o F per 1,000 ft) of altitude. Earths surface is the source of heat for the troposphere. Rock, soil, and water on Earth absorb the Suns light and radiate it back into the atmosphere as heat, so there is more heat near the surface. The temperature is also higher near the surface because gravity pulls in more gases. The greater density of gases causes the temperature to rise. Notice that in the troposphere warmer air is beneath cooler air. This condition is unstable since warm air is less dense than cool air. The warm air near the surface rises and cool air higher in the troposphere sinks, so air in the troposphere does a lot of mixing. This mixing causes the temperature gradient to vary with time and place. The rising and sinking of air in the troposphere means that all of the planets weather takes place in the troposphere.
Sometimes there is a temperature inversion, in which air temperature in the troposphere increases with altitude and warm air sits over cold air. Inversions are very stable and may last for several days or even weeks. Inversions form: Over land at night or in winter when the ground is cold. The cold ground cools the air that sits above it, making this low layer of air denser than the air above it. Near the coast, where cold seawater cools the air above it. When that denser air moves inland, it slides beneath the warmer air over the land. Since temperature inversions are stable, they often trap pollutants and produce unhealthy air conditions in cities (Figure 1.1). Smoke makes a temperature inversion visible. The smoke is trapped in cold dense air that lies beneath a cap of warmer air. At the top of the troposphere is a thin layer in which the temperature does not change with height. This means that the cooler, denser air of the troposphere is trapped beneath the warmer, less dense air of the stratosphere. Air from the troposphere and stratosphere rarely mix. Click image to the left or use the URL below. URL:
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clouds are in this layer of the atmosphere.
a) mesosphere --> b) troposphere c) stratosphere d) thermosphere
if a mountaintop is 10,000 feet higher than the valley below, we can expect the temperature to be about
--> a) lower by about 36of. b) higher by about 36of. c) the same. d) different, but it is not possible to estimate the difference.
in an inversion
a) stratospheric air sits over tropospheric air. b) tropospheric air sits over stratospheric air. --> c) warm air sits over cold air. d) cold air sits over warm air.
inversions are very stable and may last for several days or even weeks.
--> a) true b) false
air from the troposphere and stratosphere commonly mix.
a) true --> b) false
in large western cities in winter, like phoenix or salt lake city, inversions are visible because
a) they trap carbon monoxide. --> b) they trap smoke from wood fires. c) they trap ozone. d) all of the above
what is the heat source for the troposphere?
--> a) earths surface b) earths core c) the sun d) both a and c
the temperature decreases with altitude in the troposphere because
a) heat radiates from earths surface. b) the density of atmospheric gases is higher. c) sunlight radiates toward the surface. --> d) a & b
air in the troposphere does a lot of mixing because
a) solar energy is stronger at the top of the troposphere than at the bottom. b) cooler air is beneath warmer air, which is unstable. --> c) warmer air is beneath cooler air, which is unstable. d) a & b
an inversion at night in a valley when
a) warm ground warms the air above it so that it rises and gets above the cold air above it. b) cold ground cools the air above it --> c) cold ground cools the air above it so that it is dense and does not mix with the warmer d) all of the above
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