With all the technology that surrounds us these days, it has become common to back things up in the cloud.  We do that here on the farm to protect our important data. But some nights we prefer to rely on good old fashioned Mother Nature to back us up as we try protect our tender fruit blooms from frost.  And clouds, real clouds, not those virtual clouds, can make a huge difference.

Clouds and blooms

The best way to describe why clouds make a difference at night is the same as when we all go to bed in the winter.  We can lie on top of the covers and we get chilled, if not downright cold.  Why?  Because we are radiating our body heat away from us and there is nothing to stop the loss.  If the air around us is cold, we get cold.  But crawl under a soft down comforter and we warm up right away.  That comforter reflects and traps our body heat and helps to keep us warm.

On a cold, clear night those tender fruit blossoms are in the same predicament.  They are lying out there on top of the covers and they are radiating heat to outer space.  There is nothing between them and the black, frigid depths of the universe and their temperature drops.  If the air around them is warm, then they can stay warm by getting heat from that air, but if that air mass is cold, then they can freeze.  Brrrrrr.  It gives me chills to even think about it.

With our wind machines we try to mix warm air that has risen above the trees with the cold, dense air that has settled around the blooms.  We are attempting to keep those blooms warm with that warmer air.  But a wind machine isn’t a down comforter.  And it can only do so much.

This is where  clouds make a difference.  As they move over the trees, they act like that comforter.  They trap the heat that the blooms and the ground are giving off and reflect that heat back down.  They help to keep the trees all snuggly and warm.

This may seem pretty esoteric.  How can a cloud really do that?  It doesn’t envelop the trees like a comforter.  But on a cold clear night I have watched temperatures jump by six degrees within minutes as the edge of a cloud moves overhead.  And that is real.  And crucial on a cold night.

I was up babysitting trees this past Wednesday night.  At dusk the sky cleared, the wind settled, and the temperatures plummeted as cold air settled in around the trees.  During the day we were at 60 degrees, but by 10 p.m. the temperatures had dropped to 26-28 degrees around the trees – temperatures that will freeze those tender buds.  I was scrambling to turn on wind machines to mix the warm air above into that cold air.  The machines were helping, but it looked like it would be a long night.   It would be nine hours before the light of sun warmed things up again and stopped that heat loss to outer space.

And then a cloud bank appeared to the west and started to move overhead.  In a matter of ten minutes the temperatures rebounded to 36-38 degrees.  Well above that feared freezing mark and well above what our wind machines were gaining.  I paused in my scramble to turn on machines and as the clouds thickened, I reversed direction and started to turn off machines that were no longer needed.  Those clouds stayed over us all night and kept temperatures above freezing until right at dawn.  As they left, I turned wind machines back on as temperatures dropped back into the high 20’s.  But we only needed them for less than an hour and the buds seemed to have made it through another nail biting night.

Thank you to those down comforter clouds for backing us up in such a real way.  We will keep our important data in the cloud, but our most important things, our blooms, we will hope to keep warm under the cloud.

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