The space above the surface of our planet is divided into multiple layers of the atmosphere. Humans live in the lowest layer called the troposphere. It is also the layer where all weather conditions occur. The layers above it are called the stratosphere, the mesosphere, and the thermosphere. In this article, we will take a closer look at the first layer of the atmosphere.
The troposphere contains 75% of the entire mass of the atmosphere. It also contains 25% of the entire mass of water vapor and aerosols. On average, the troposphere reaches the height of around 43,000 feet. The height is a bit higher in the tropics, and it drops significantly in the polar regions.
The lowest part of the troposphere is largely under the influence of the surface of the Earth. More correctly, the surface influences the airflow. This layer is called the planetary boundary layer. The height of this layer normally extends up to 6,600 feet above the surface, but that can change depending on the time of the day.
The Composition Of The Troposphere
The highest point of the troposphere is called the tropopause. It marks the border between it and the layer that is placed above it, the stratosphere. The stratosphere is the layer of the atmosphere in which airplanes fly. The tropopause is often categorized as an inversion layer. This means that in it, the temperature of the air stops decreasing with height, and it remains the same constantly.
The composition of the dry air in the troposphere is not that complex. It contains 75% nitrogen, 20% oxygen, and the rest is split between argon, carbon dioxide, and extremely small amounts of other gases. There is also a significant amount of water vapor contained there. The water vapor arrives in the troposphere through the evaporation of the waters on the surface of the Earth. The higher up we go, the temperature of the troposphere becomes lower and lower. As the temperature decreases, saturation vapor pressure starts to decrease drastically as well.
Temperatures In The Troposphere
The pressure of our atmosphere is the strongest at the sea level. It starts to decrease with altitude. The temperature of the troposphere decreases with high intensity as we increase in altitude. The temperature decreases at a specific rate which is called the environmental lapse rate (ELR). The easiest way to calculate the ELR is by determining the difference in temperature between the tropopause and the surface, and then divide that number by the height. When calculating this, we always assume that the air is completely still, meaning that there are no winds or the mixing of layers of air.
This difference in temperature exists because the ground absorbs the energy of the sun. This heats the lower levels of our atmosphere, which is the troposphere. The easiest way to explain this would be that it happens because the troposphere is in direct contact with the surface. The upper parts of the atmosphere are cooler because of the radiation there.