View from the Üetliberg towards Lake Zug, Lake Lucerne and the Alps. A very dirty atmosphere can be detected near the ground (www.roundshot.com )
Dust, soot from the combustion of fossil fuels and aerosols, which were created by chemical reactions with solar radiation, were able to accumulate in the lowest layers of the atmosphere during the past few days of high pressure. In addition, some Saharan dust is also playing a role today. Read more about how this accumulation occurs during winter high pressure conditions
here
.
But how do the aerosols get out of the atmosphere? The most efficient way would be a change in air mass. For example, a cold front with a lot of wind, followed by a polar air outbreak that brings in fresh, clean air and displaces the aged air mass. But what we really want to know is how the aerosols get out of the atmosphere, not how we can get fresher air.
The key word is deposition A distinction is made between dry and wet deposition
The horizontal axis shows the aerosol diameter, the vertical axis shows the residence time of a particle in the atmosphere.
The horizontal axis represents the aerosol diameter, the vertical axis represents the residence time of a particle in the atmosphere. (Translated by Jaenicke (1982).)
Three forms of deposition can be seen in the graphic above. Sedimentation is the process by which aerosols fall out of the atmosphere on their own. This is a decisive factor, especially for larger particles such as Sahara dust. The further away the Sahara dust is transported from its source area, the more the comparatively large aerosols sink. For philippines phone number library example, a particle with a radius of 10 µm sinks a full 3.17 cm/s. In one hour, this would be 114 meters (in completely still air).
However, as particle size decreases, sedimentation as a deposition very quickly becomes inefficient. For particles with a diameter of less than 1 µm, the natural sinking speed is almost negligible. This includes the majority of fine dust (PM2.5). Soot from combustion, for example, has a size of 0.005 – 0.03 µm and has almost no natural sinking. This is where wet deposition comes into play. With wet deposition, a distinction is made between so-called “rain-out” and “wash-out”. In the former, water from the atmosphere is deposited around the aerosols. Small droplets then form, which grow and fall out of the atmosphere as rain. The so-called “wash-out” is the part of the aerosols that is carried away by the falling rain below the cloud.
These are the processes by which we free our atmosphere
of aerosols. Cleaning would be at least partly the you’re not wasting resources on addresses wrong term, because the transport of Saharan dust into the oceans or nearby regions represents an important nutrient awb directory input. On the other hand, most human-caused aerosols are undesirable in the atmosphere.
To make the above graphic complete, we will briefly discuss coagulation. This is the joining together of very small particles to form a larger clumped aerosol construct, which is then removed from the atmosphere via the processes mentioned above.
Simulated precipitation from the ECMWF ensemble model. Only a few mm of precipitation will fall by Thursday morning. However, just a few mm are enough to effectively clean the atmosphere of aerosols.
Simulated precipitation from the ECMWF ensemble model. Only a few mm of precipitation will fall by Thursday morning. However, just a few mm are enough to effectively clean the atmosphere of aerosols. (MeteoSwiss.
