Troposphere
The troposphere is the lowest layer of the
The term troposphere derives from the Greek words tropos (rotating) and sphaira (sphere) indicating that rotational turbulence mixes the layers of air and so determines the structure and the phenomena of the troposphere.[2] The rotational friction of the troposphere against the planetary surface affects the flow of the air, and so forms the planetary boundary layer (PBL) that varies in height from hundreds of meters up to 2 km (1.2 mi; 6,600 ft). The measures of the PBL vary according to the latitude, the landform, and the time of day when the meteorological measurement is realized. Atop the troposphere is the tropopause, which is the functional atmospheric border that demarcates the troposphere from the stratosphere. As such, because the tropopause is an inversion layer in which air-temperature increases with altitude, the temperature of the tropopause remains constant.[2] The layer has the largest concentration of nitrogen.
Structure of the troposphere
Composition
The Earth's planetary atmosphere contains, besides other gases, water vapour and carbon dioxide, which produce carbonic acid in
Pressure
The maximum air pressure (weight of the atmosphere) is at
where:
- gn is the standard gravity
- ρ is the density
- z is the altitude
- P is the pressure
- R is the gas constant
- T is the thermodynamic (absolute) temperature
- m is the molar mass[3]
Temperature
The planetary surface of the Earth heats the troposphere by means of
Altitude
The temperature of the troposphere decreases with increased altitude, and the rate of decrease in air temperature is measured with the Environmental Lapse Rate () which is the numeric difference between the temperature of the planetary surface and the temperature of the tropopause divided by the altitude. Functionally, the ELR equation assumes that the planetary atmosphere is static, that there is no mixing of the layers of air, either by vertical atmospheric convection or winds that could create turbulence.
The difference in temperature derives from the planetary surface absorbing most of the energy from the sun, which then radiates outwards and heats the troposphere (the first layer of the atmosphere of Earth) while the radiation of surface heat to the upper atmosphere results in the cooling of that layer of the atmosphere. The ELR equation also assumes that the atmosphere is static, but heated air becomes buoyant, expands, and rises. The dry
Altitude Region | Lapse rate | Lapse Rate |
---|---|---|
(m) | (°C / km) | (°F / 1000 ft) |
0.0 – 11,000 | 6.50 | 3.57 |
11,000 – 20,000 | 0.0 | 0.0 |
20,000 – 32,000 | −1.0 | −0.55 |
32,000 – 47,000 | −2.8 | −1.54 |
47,000 – 51,000 | 0.0 | 0.0 |
51,000 – 71,000 | 2.80 | 1.54 |
71,000 – 85,000 | 2.00 | 1.09 |
Compression and expansion
A
The compression and the expansion of an air parcel are reversible phenomena in which energy is not transferred into or out of the air parcel; atmospheric compression and expansion are measured as an
Humidity
If the air contains
Environment
The environmental lapse rate (), at which temperature decreases with altitude, usually is unequal to the adiabatic lapse rate (). If the upper air is warmer than predicted by the adiabatic lapse rate (), then a rising and expanding parcel of air will arrive at the new altitude at a lower temperature than the surrounding air. In which case, the air parcel is denser than the surrounding air, and so falls back to its original altitude as an air mass that is stable against being lifted. If the upper air is cooler than predicted by the adiabatic lapse rate, then, when the air parcel rises to a new altitude, the air mass will have a higher temperature and a lower density than the surrounding air and will continue to accelerate and rise.[2][3]
Tropopause
The tropopause is the atmospheric boundary layer between the troposphere and the stratosphere, and is located by measuring the changes in temperature relative to increased altitude in the troposphere and in the stratosphere. In the troposphere, the temperature of the air decreases at high altitude, however, in the stratosphere the air temperature initially is constant, and then increases with altitude. The increase of air temperature at stratospheric altitudes results from the ozone layer's absorption and retention of the ultraviolet (UV) radiation that Earth receives from the Sun.[7] The coldest layer of the atmosphere, where the temperature lapse rate changes from a positive rate (in the troposphere) to a negative rate (in the stratosphere) locates and identifies the tropopause as an inversion layer in which limited mixing of air layers occurs between the troposphere and the stratosphere.[2]
Atmospheric flow
The general flow of the atmosphere is from west to east, which, however, can be interrupted by polar flows, either north-to-south flow or a south-to-north flow, which
Three-cell model
The three-cell model of the atmosphere of the Earth describes the actual flow of the atmosphere with the tropical-latitude
Zonal flow
A
Meridional flow
When the zonal flow buckles, the atmosphere can flow in a more longitudinal (or meridional) direction, and thus the term "
See also
References
- ^ "Troposphere". Concise Encyclopedia of Science & Technology. McGraw-Hill. 1984.
It [the troposphere] contains about four-fifths of the mass of the whole atmosphere.
- ^ a b c d e f Danielson W, Levin J, Abrams E (2003). Meteorology. McGraw Hill.
- ^ a b Landau and Lifshitz, Fluid Mechanics, Pergamon, 1979
- ^ Lydolph, Paul E. (1985). The Climate of the Earth. Rowman and Littlefield Publishers Inc. p. 12.
- ^ Kittel C, Kroemer H (1980). Thermal Physics. Freeman. chapter 6, problem 11.
- ^ Landau LD, Lifshitz EM (1980). Statistical Physics. Part 1. Pergamon.
- ^ "The Stratosphere — Overview". University Corporation for Atmospheric Research. Archived from the original on 29 May 2018. Retrieved 25 July 2018.
- ^ "Meteorology – MSN Encarta, "Energy Flow and Global Circulation"". Encarta.Msn.com. Archived from the original on 2009-10-28. Retrieved 2006-10-13.
- ^ "American Meteorological Society Glossary – Zonal Flow". Allen Press Inc. June 2000. Archived from the original on 2007-03-13. Retrieved 2006-10-03.
- ^ "American Meteorological Society Glossary – Meridional Flow". Allen Press Inc. June 2000. Archived from the original on 2006-10-26. Retrieved 2006-10-03.
External links
- "Layers of the Atmosphere". U.S. National Weather Service. Archived from the original on 2017-05-13.
- Chemical Reactions in the Atmosphere