Virga

I know that virga is rain that evaporates before it hits the ground because our atmosphere is so dry. Why are we so concerned about watering the lawns between 6:00p.m. and 10:00a.m.. It seems that if we watered when some of the water could evaporate, we would be doing ourselves a favor so the virga could turn to rain. Am I way off in my thinking?

Ann S.

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Ann, it certainly is great you are questioning our weather, however, while I can see where you are coming from, your plan won't work unfortunately.

If that were true, then all of our water evaporating all the time like in our lakes and oceans would fuel rainshowers constantly!

Here's the deal, Virga is rain that doesn't reach the ground like you have said, it evaporates before it gets here. This is a nuisance a lot of the time since we almost always need rain and while it looks like it's raining, it doesn't get here and we end up frustrated.

We water late in the day because we don't want to waste water. By watering late at night, the water can settle into the soil and doesn't evaporate away like it would in the day time. Watering during the peak afternoon hours isn't a wise idea, feel free to encourage your friends to not do this.

For example, if we were to water our lawns during the day (which we shouldn't), the water will evaporate into the air. Where does that water go? Does it go into the clouds? Does it go into your house, or onto a tree? When water evaporates, it does go back into the air, does it form rain right way to solve the virga issue? Sorry, it doesn't. But it does go into the air, we breathe it in, or it can help to form more clouds eventually.

The point of watering during the night is so our SOIL gets the water not the air. The air has water vapor in it all the time, by adding more into it, you're just forcing the water cycle instead of letting it occur naturally.

90% of the water in our air comes from seas, rivers, lakes and oceans, the other 10% comes from evapotranspiration from plants and trees. The water cycle though is naturally occuring and in balance by itself. On a scale around the world, the water going into the air is about the same amount as the water going out (as rain or snow). Also, once a water molecule goes into the air, it spends about 10 days there.

If we take more water from our resources like lakes and reservoirs, it will go back into the sky for sure to complete the balance of the hydrologic cycle. Will it help our Virga here in Utah, not really, sorry on that one! We'd just be wasting water by watering during the day and evaporating that water back into the sky instead of putting into the soil, where we also need it and remember, the grass and the trees will evaporate water back into the air as well. We just don't want all the water going up during the daytime, the plants need time to absorb the water in order to grow.

Answered by KSL Meteorologist Dina Freedman.