Dark, UV-rich Mornings: The effect of clouds on a plant's light requirements

Emanon

Mame
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San Diego, CA
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10a
When they (the Internet including gov. Web sites/nurseries) tell you that a particular tree should receive around 4 hours of direct sunlight, does it matter if it is cloudy for those 4 hours?

I recently moved outland (or the opposite of inland...I'm not sure of the right word) 5 minutes to literally right on the beach. A short distance but it seems to have its different weather patterns here: many, many more mornings (almost all) are now overcast. Prior to the move I had kept some of my trees so that they received full sun in the morning and afternoon shade, and they thrived under these conditions. I'm wondering if I should now reverse this (afternoon direct sunlight, morning shade) so that they get "better" (i.e. brighter) sunlight. Obviously afternoon sun is different than morning sun though, if for no other reason than the increased heat.

With my children, I always make sure that they wear sunscreen on cloudy days. I only learned of this necessity as an adult after observing a neighbor using a parasol on cloudy days. I then looked it up on the Internet and read things like " According to the American Academy of Dermatologists, 80 percent of the sun’s rays still make it to the ground on a cloudy day." UVA rays "reach your skin through clouds, smog or glass." Or, finally, the presence of clouds can sometimes increase UV radiation: "ometimes UV rays can reflect off the cloud's edge, intensifying the level of UV rays. Therefore, partly cloudy days can be misleading; you believe you are protected from the sun's rays when behind the cloud but you may, in fact, be getting stronger UV rays on a cloudy day."

So, am I fine if my trees are getting their direct sunlight on cloudy/overcast mornings or should I switch it up so that they get their direct sunlight in the hotter afternoon sun that is always bright? Is it light or UV radiation that makes a difference? (Please excuse my ignorance -- I have zero familiarity with the hard sciences...) Thank you!
 
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