Why are the coldest temperatures at the 50 km height from the surface of the Earth, occur generally at tropical tropopause?
The coldest temperatures at the 50 km height from the Earth's surface generally occur at the tropical tropopause due to a combination of several factors.
Firstly, the tropopause is the boundary between the troposphere (lowest layer of the Earth's atmosphere) and the stratosphere (layer above the troposphere). The troposphere is where weather phenomena occur, and it is also where temperature typically decreases with increasing altitude. In contrast, the stratosphere contains the ozone layer, which absorbs a significant amount of the Sun's ultraviolet radiation and leads to a temperature increase with altitude.
At the tropical tropopause, these two layers, the troposphere and the stratosphere, meet. The coldest temperatures at this height are primarily a result of a well-known atmospheric feature called the "cold trap."
The cold trap effect occurs due to the presence of water vapor in the atmosphere. Water vapor is an important greenhouse gas that absorbs and emits thermal radiation, leading to a warming effect. However, as air rises in the tropical troposphere, it cools due to expansion. This cooling causes the water vapor to condense into ice particles, which releases latent heat, further warming the air and preventing the temperature from decreasing as rapidly as it does in the troposphere.
When the air reaches the tropopause, the temperature becomes extremely cold due to the absence of water vapor and the limited warming effect of the stratosphere. In addition, the winds at the tropical tropopause known as the "tropical easterly jet" play a role in maximizing the cooling effect. These winds transport cold air from higher latitudes towards the equator, reinforcing the already cold temperatures.
To obtain more specific information and data on temperature profiles at different altitudes, scientists use various instruments such as weather balloons, satellites, and aircraft equipped with atmospheric probes. These instruments collect atmospheric data, including temperature, which allows for a detailed understanding of the temperature patterns at different heights and locations in the atmosphere.