The mesosphere is the third layer of the Earth’s atmosphere. It lies directly above the stratosphere and is directly below the thermosphere. With altitude, the temperature of the mesosphere decreases. This layer is the coldest of all of the planet’s atmospheres. Because of its coldness, it protects Earth from the sun’s rays.
Polar mesosphere
During summer, the polar mesosphere is colder than at other times of the year. This is due to the presence of waves that can cause drag, which can accelerate winds. The waves also deposit energy. These waves can be generated by several processes, such as convective instability or shear-driven instability.
Polar mesosphere summer echoes (PMSEs) are strong radar echoes that occur in the mesosphere near the polar mesopause in summer. PMSEs have been observed for more than three decades and are a natural tracer of complicated atmospheric dynamics. They are particularly strong and intense at latitudes poleward of 65deg.
Observations have been made using both radar and lidar. Lidar is a laser light-based technique, whereas radar uses radio waves. Using lidar, the most significant ice particles can be detected as they fall into the mesosphere, while the smaller ones can be detected as they are sublimated.
Several radars have been used to measure PMSEs, including the Poker Flat MST radar, the EISCAT (European Incoherent SCATter) radar, and the Machu Picchu station. Combined with lidar, the data obtained has helped elucidate several models and theories related to PMSEs.
In addition, these observations have revealed a connection between the PMSE probability and the low seasonal mesopause temperatures. In fact, the PMSE probability curve resembles the mean seasonal curve of low mesopause temperatures. Thus, observing PMSEs can provide diagnostics for the impact of industrial activities on the lower atmosphere.
Another important feature of the polar mesosphere is the presence of noctilucent clouds, which can be seen from space. These clouds are visible to ground-based observers at latitudes 25deg to 40deg away from the summer pole. Currently, the AIM (Advanced Imaging Modal) satellite is being funded by NASA for further studies of the polar mesosphere. Ultimately, understanding the seasonal changes in the thermal structure of the mesosphere requires a detailed general circulation model.
Moreover, the solar wind variability and the space traffic exhaust may change the water vapor budget of the polar mesosphere. These variations can also affect the spectrum of non-thermal particles in the atmosphere. By investigating the seasonal changes in the mesosphere, researchers can find new insights into the mesospheric wind and turbulence.
Coldest part of Earth’s atmosphere
The coldest part of Earth’s atmosphere is located in the mesosphere. It is a thin layer of air that stretches upward from 50 to 80 kilometers above the surface. At this height, temperature decreases rapidly with altitude. For instance, the top of the mesosphere can be -130 degrees Fahrenheit. In this layer, a meteor will burn up.
The upper part of the mesosphere is usually warmer than the lower mesosphere. However, it is still much colder than the surface. This is because the gases in the upper mesosphere have very low density. These gases are very thin and do not have enough kinetic energy to move up in the stratosphere.
Air at the top of the mesosphere is extremely thin and feels very cold. At this altitude, water vapor from the upper mesosphere can form noctilucent clouds. During certain times of the day, these clouds can be visible.
The mesosphere is a very important part of Earth’s atmosphere because it protects our planet from solar radiation. It also is where most meteors burn up. Some meteors may even reach the ground.
Most of the mass of the atmosphere is in the troposphere. Temperatures in the troposphere are dependent on the amount of energy the Sun provides. Above the troposphere, temperatures increase to become thermally stable. As temperatures rise, the sun is less active and the Sun’s energy is absorbed by molecules in the thermosphere.
The mesosphere is surrounded by the thermosphere and the ionosphere. These three layers are separated by a boundary called the mesopause. When the mesopause is reached, the temperature of the upper mesosphere drops to about -90 degrees Celsius.
The stratosphere is the next layer of Earth’s atmosphere. Temperatures in the stratosphere are very dependent on latitude. Usually, the coldest parts of the atmosphere are near the poles during the summer and winter. There is also a cold spot in the East Antarctic Plateau during the polar winter.
The thermosphere is a very thick layer of air that reaches up to 600 kilometers above the Earth’s surface. It is composed of a few gases and has a low density. With increasing temperature, the gases become denser.
Protects Earth from sun’s damaging rays
The sun’s UV rays can cause serious damage to life on Earth, but our atmosphere acts as a protective layer. This is especially true in the stratosphere, where the ozone layer is found. Ozone is a naturally occurring gas that is formed by oxygen reacting with a short-wave ultraviolet light. Most ozone is formed in the stratosphere. A large ozone hole was discovered in Antarctica in the mid-1980s. Today, the ozone layer is being depleted at a rate of about 60 percent each spring.
There are two main layers of our atmospheric soup: the troposphere, which extends from six to thirty miles above the surface, and the stratosphere, which reaches an altitude of about five to fifty miles. In the troposphere, most human activities take place. As the stratosphere ascends, the air becomes thinner and cooler, and weather patterns are driven by convect.
For our purposes, the most interesting of the various layers is the stratosphere, where ozone plays a critical role in preventing harmful ultraviolet light from reaching the planet’s surface. While ozone is not the only shield atop the stratosphere, it does play a major role in preserving life on our planet.
The most important thing to know is that the stratosphere is not the only place where the sun’s UV rays can cause harm. Although ozone is a key component of the stratosphere, the ozone layer’s protective role is lessened by the emission of ozone-depleting gases such as chlorofluorocarbons (CFCs), which are used in refrigerants and flame-retardants.
While there is not a perfect way to determine the amount of UV rays that reach our planet, the best estimate is that 70% of the sunlight reaching Earth is absorbed by our atmosphere. The other 30% is reflected back into space. Since the atmosphere is a complex system of interconnected layers, the aforementioned 30% is a small percentage of the total. Thus, the ozone layer is crucial to protecting the planet’s ecosystems and human health.
However, ozone is a complex and volatile compound that is difficult to maintain. As such, the phase out of controlled ozone-depleting substances has made a significant contribution to global efforts to address climate change.
Sources of nuclei
Cloud condensation nuclei (CCNs) are a subset of aerosols that can affect cloud formation and the overall atmosphere. This group of particles are known as cloud seeds and can influence the cloud’s radiative properties. Research into the effects of CCNs has shown that their presence can impact atmospheric properties, such as ozone levels and the rate at which methane is decomposed. As well, naturally produced CCNs can affect human health and natural environmental phenomena.
CCNs are typically 0.2 um in size and are made of water molecules. When water vapor enters the cloud, it begins to condense onto the condensation nuclei. In turn, the condensation process causes water to form droplets, or microclouds, with a diameter of about 20 micrometers.
