Atmospheric pressure decreases with altitude; The higher the altitude the more difficult breathing becomes. Moslems say that this is what Allah says. The Quran says that as we ascend to the sky it becomes more difficult for us to breathe:
During cloud formation water can become supercooled, that is, it can get below freezing point but remain not frozen! This stage is so unstable that we can add some catalyst molecules to trigger rain. Historically humans used silver iodide, frozen carbon dioxide and some salts to trigger rain. This is known as cloud seeding.
However nature uses different material to seed the clouds. Nature uses both sea salt and land dust to trigger rain: Wind at the surface of the seas causes waves to roll. Those waves release aerosols into the air carrying the sea salt. The wind carries both the sea salt and the land dust to the clouds. The sea salt and land dust cause the supercooled water to coalesce and trigger precipitation.
The difference in temperature, salinity and CO2 concentrations in seas cause water to separate into layers. This was only known recently.