Background Information: Troposphere
Characteristics:
- Altitude: This is the layer of air which we live in and a region which extends upward -10 km from the earth surface.
- Composition: (i) This region contains approximately 75 percent of the atmospheric gases. Due to the weight of air, it is most dense at or below sea level. (ii) It contains almost all the water vapor of the atmosphere. Thus, clouds and storms are present in this region but not in the higher regions.
- Temperature Air Movement: (i) Most radiation from the sun is absorbed by the earth's surface and so the troposphere is heated from below. It is the reflected radiation which is responsible for heating the troposphere. Temperature varies in this region, usually decreasing with increasing altitude. (ii) On average, the rate of decrease in temperature with altitude is - 6.5 degrees Celsius per kilometer in the lower half and - 7.5 degrees Celsius per kilometer in the upper half of this region. (iii) Due to the variation in temperature, barometric pressure and the interaction of atmospheric gases, notably the amount of water vapor present, there is a lot of air movement, air rises and sinks.
