Behind the Forecast: Water cycle changes can lead to big weather problems

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Published: Aug. 27, 2021 at 8:49 AM EDT
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LOUISVILLE, Ky. (WAVE) - Our water cycle is vital to the weather around the globe. However, changes to the water cycle are leading to significant and sometimes deadly weather events.

The hydrological cycle, or water cycle, is responsible for water’s movement in various states (gas, liquid, solid) from the atmosphere to the Earth’s surface and even underground. The sun helps to guide this cycle. The sun evaporates water from bodies of water like rivers and lakes, turning it into water vapor. Plants also transpire water which then evaporates; this is evapotranspiration. Sublimation is another way that water vapor can enter the atmosphere. It occurs when ice transforms from its solid state directly into water vapor.

All of this water vapor rises and condenses into clouds. Air circulating the planet helps to move these clouds as they grow. Eventually, it all falls as precipitation. That precipitation will return from where it fell back into the atmosphere as water vapor.

Most of the planet’s water (97.4%) is salt water. Only 2.6 percent is fresh water; ice caps and glaciers contain most of Earth’s fresh water (68.7%). Since another 30% is underground, only around 1 percent of the planet’s fresh water is on the surface.

Hotter temperatures allow the atmosphere to hold more water. In fact, the atmosphere can hold seven percent more water per 1.8° of warming. Since the atmosphere can contain more moisture on warmer days, storms, on those days, can create more intense precipitation. More precipitation can lead to significant weather events like deadly flooding.

Hotter temperatures also increase evaporation, which can lead to significant droughts in some parts of the world. Droughts can limit a population’s water supply dramatically and also allow wildfires to occur more easily. It is difficult for the drought-ridden ground to absorb heavy rain; this can lead to flash flooding in some circumstances.

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