Explainer: what is ‘precipitable water’, and why does it matter?

Get ready for heavier rain.

As the planet warms, rainfall and weather patterns will change. As temperatures rise, the amount of water in the atmosphere will increase. Some areas will become wetter, while others, like southern Australia, will likely be drier.

One measure of atmospheric moisture is called “precipitable water”. You may not have heard the term before, but will likely hear about it more often in the future. Both climate scientists and meteorologists are increasingly looking at it when studying weather charts.

There is a lot of uncertainty about future rainfall patterns, but there is one aspect that models have consistently emphasised — a larger proportion of rainfall will be heavy, even in some areas that are becoming drier. Atmospheric moisture is a part of this, and precipitable water is one measure of it.

So why do climate models project that we will get more heavy rainfall as the planet warms? At the heart of it is basic physics, which tells us that a warmer atmosphere can hold more water vapour than a cooler one — about 7% more for every 1℃ rise in temperature.

Read the story on The Conversation - “Explainer: what is ‘precipitable water’, and why does it matter?”