Troposphere - Troposphere

Japanese: 対流圏 - たいりゅうけん（英語表記）troposphere

The part of the atmosphere surrounding the Earth that begins at the Earth's surface and reaches an altitude of 10 to 17 kilometers. The top of the troposphere is called the tropopause, or simply the tropopause, and its altitude ranges from around 10 kilometers in high latitudes to as high as 17 kilometers in tropical regions. In the standard atmosphere, which models the atmosphere at mid-latitudes, the altitude is 11 kilometers.

In the troposphere, temperature decreases with height, at a rate of 6.5°C per kilometer in standard atmosphere. This condition is unstable with respect to the vertical movement of air, which accompanies the condensation of water vapor, and therefore active convection occurs. After the discovery of the stratosphere, where the temperature is almost constant, it was named the troposphere. Cumulus clouds, which can be seen on sunny days, and cumulonimbus clouds, which are common in summer, are manifestations of convection. Groups of cumulonimbus clouds are always scattered throughout the tropics, and the most notable of these become tropical cyclones.

The troposphere also experiences extratropical cyclones, which are large-scale atmospheric disturbances caused by temperature differences between the north and south. These disturbances cause clouds to form and precipitation such as rain and snow to occur, resulting in changes in the weather. Such weather phenomena do not occur in the atmosphere above the stratosphere. These movements (disturbances) cause the air in the troposphere to be thoroughly stirred up and down and north and south, and substances that exist in one place will spread throughout the entire troposphere in about 30 days.

[Taro Matsuno]

Ocean

This refers to the part that includes the surface water, central water, and the upper part of the equatorial water, and is part of the warm water sphere. In the troposphere, there is active exchange of energy such as heat with the atmosphere through the ocean surface, and there are also convection currents and strong ocean currents, so there are large differences in water temperature and salinity depending on location. In mid-latitude ocean areas, there are also significant seasonal changes in temperature and salinity.

[Masao Hanzawa]

[Reference] | Atmosphere

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

地球を取り巻く大気のうち、地表面から始まり高度10～17キロメートルの範囲をいう。対流圏の上端を対流圏界面、または単に圏界面とよぶが、その上端の高度は高緯度地域で低く10キロメートル前後、熱帯地域では高く17キロメートルに達する。中緯度の大気をモデル化した標準大気では11キロメートルである。

　対流圏では、気温は高さとともに減少し、その割合は、標準大気では1キロメートル当り6.5℃とされている。このような状態は、水蒸気の凝結を伴う空気の鉛直運動に対して不安定であり、したがって盛んに対流がおこる。ほとんど温度一定の成層圏が発見されたのちに、それに対して対流圏と名づけられた。晴れた日に見られる積雲や、夏に多く見られる積乱雲（入道雲）は対流の現れである。熱帯域にはつねに積乱雲の集団が散在し、そのなかで著しいものは熱帯低気圧となる。

　対流圏では、南北の温度差に起因する大規模な大気擾乱(じょうらん)である温帯低気圧も発生する。これらの擾乱に伴って雲が生じ、雨や雪のような降水現象もおこる。すなわち天気の変化がみられる。成層圏以上の大気中には、このような天気現象はない。これらの運動（擾乱）によって、対流圏内の空気は上下・南北によく攪拌(かくはん)されており、ある場所に存在した物質は約30日で対流圏全体に行き渡る。

［松野太郎］