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  • Dr. Sebastian Otto

What's meteorology again?

Now, I ask, what is weather? Science says: weather is the local and temporal state of the atmosphere. "Local" and "temporal" means that this state depends on the place and time. Yes, you might say, the sun is shining here and it might be raining in the neighboring town. And I say, it's precisely these "circumstances" that matter, which is why weather is not so "simple". Because we're dealing with a highly complex physical system, as science adds.

So what makes this system, for example, a piece of the atmosphere being considered, so complex? We have gases that absorb and scatter the sun's light. For example, carbon dioxide absorbs light energy and converts it into heat, a process that is initially easy to observe and describe with simple formulas. But even here, quantum mechanical details show that the "exact" calculation of the absorption processes of all gases present in the atmosphere is anything but simple. The same applies to scattering by gas molecules and the equally significant question of why the sky is blue. What else do we have in the atmosphere? - Science tells us about so-called aerosol particles and cloud hydrometeors. The former consist of various materials, depending on the way they are formed. The most important aerosols are mineral dust particles, small mineral grains that get into the air over the deserts of the earth. They can be transported for thousands of kilometers under "circumstances".

Then there is volcanic aerosol, which is carried up to great heights and can linger there for a long time. Then we have marine aerosol (salt grains) like aerosol produced by large-scale forest fires (ash particles). And cities also produce characteristic aerosols. This excerpt shows how diverse the atmosphere is composed of.

But we also have cloud hydrometeors. As the name suggests, they consist mainly of water in two forms, that is, water or ice. However, they do not form independently of the aerosols. Usually, when droplets form, water is attached to the aerosol particles, and the droplets grow and fall to the ground as rain. Under "circumstances", however, no droplets form but ice crystals in the most bizarre shapes. Snow falls. Is everything simple? By no means. Because the aerosol particles and cloud hydrometeors also undergo diverse (atmospheric) chemical transformations during their "life," and they also absorb and scatter sunlight individually. This also affects the atmosphere.

These are the material things we find in the atmosphere and which we can summarize as "air". But they are not simply there, they feel the force of gravity and the rotation of the earth and much more. But above all, the air forms a moving medium, as science tells us, which heats up differently depending on location and time, resulting in characteristic movements and individual thermal effects with the aforementioned feedback on the medium and thus on itself. Everything changes spatially and temporally, guided by the physics of the atmosphere. That's meteorology. But no, that's not all. So far, we have only mentally grasped the atmosphere and perhaps modeled it somewhat in the language of mathematics. To do this, of course, you first have to observe and measure a lot.

And what to do about it? Well, we can also try to calculate or even predict the weather by designing computer models and simply letting them calculate. But even that is not so "simple" because these models can never accurately represent the diversity of our atmosphere. They also require certain information to deliver good and meaningful results, which then reach you, for example, via the weather report. This information comes from constant measurements that are carried out on the atmosphere every day, whether from the ground or from satellites or through balloon flights and much more, and are incorporated into the models. There are various models that describe very local weather over a small time horizon of hours as well as those that calculate the globally and temporally averaged weather, which science refers to as climate.

So, it is about describing and calculating weather and climate. The associated physical processes in the atmosphere, that is, in the air we breathe, form the most complex physical system on earth. This is meteorology.

Read here on this website how the project continues and what results we have achieved. We hope to have given you a good insight into the motivation behind CityCLIM.

Your Meteologix AG/Kachelmann GmbH team!

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