Water helps steer our weather

I recently scheduled to have my sprinklers blown out. I suppose most folks with sprinkler systems have to take care of that one way or another, or risk having burst pipes sometime during the winter. That task got me thinking about the amazing properties of water. Water in all its forms is not only a tangible part of what we call “weather,” but also an integral part in steering the type of weather we experience.

Water in its gaseous form, also called water vapor, is a good absorber of long wave radiation. It is one of the so-called “greenhouse” gases, which can trap heat that would otherwise be radiated and lost back to space. In its solid form, water can take on the graceful structure of a delicate snowflake floating to the ground, or become a destructive hailstone damaging crops and even automobiles. In its liquid form, fresh, clean water is the lifeblood of our existence – but too much of it at once results in the perils of flooding.

Pure water itself is made of two elements, two parts hydrogen to one part oxygen – hence the name H2O. Most of us learned sometime in school that when substances are heated they expand, and when they cool, they contract. This is evident in people’s wooden floors which will develop gaps during the cold winter as the boards shrink.

One of the unique properties of water is that it actually expands when it is frozen. This is due to the way the molecules bind themselves together when the water becomes a solid. Water actually becomes less dense in its frozen form than in its liquid form. This explains why ice cubes will float, rather than sink, in liquid water. While most substances reach their maximum density in their solid form, water is most dense at 40 degrees Fahrenheit. This helps explain why a body of water will always freeze from the top down. As the water temperatures cools toward freezing, the warmer water (i.e. at 40 degrees) will actually sink toward the bottom while the cooler water remains at the top.

The different phases of water are one of things we notice in precipitation when we go up or down in elevation. While mountains are getting coated with snow, rain may be falling in the valleys below. What goes on during such a phase change plays a big part in how our atmosphere and weather is influenced. When it is hot outside (and especially if the air is dry), water evaporating from our skin will cool us off. This is because heat is used to change the liquid water into vapor. Likewise, what starts off as rain, may turn into snow when rain falls into a dry layer of air and evaporates. This cooling effect may help other falling snowflakes remain in their frozen form until they make it to the ground. At the other end of this process, as water vapor rises into the atmosphere and condenses back into its liquid form (forming a cloud), heat is released. This heat release is a large part of the fuel that keeps thunderstorms, and even hurricanes, raging along.

In the near term, even with the recent chillier temperatures, it does look like we’ll just be dealing with any water in its liquid form when it comes to precipitation, though the mountains will have the opportunity for snow.