While we will see variable amounts of cloudiness over the weekend, it’s unlikely they will produce any rain, at least down here in the valley. A weak cold front will drop Saturday high temperatures a few degrees, but we should still see daytime highs in the 60s through the weekend. The next chance for showers (and it is only a slight one at this point) comes midway through next week.

Sun

An Erupting Prominence. Prominences are huge clouds of relatively cool, dense plasma suspended in the Sun’s hot, thin corona. Like this large, twirling prominence, they can sometimes erupt and escape the Sun’s atmosphere. SOHO, January 18, 2000

So while the sun can heat the air a little by conduction, it is a lot more efficient at transferring energy to your skin by radiation. Radiation from the sun travels through air relatively unscathed (the air only absorbs a minor amount of the sun’s radiation), and when it hits you, it excites the molecules of your skin, generating heat. That’s why you feel so much hotter if you are in direct sunlight as opposed to being in the shade. Even though it may not seem like it, if you measure the air temperature in and out of the sun, there’s almost no difference. Air is mostly diathermic, which means it allows energy to pass through it without being affected by it.

Sun radiation

Many will disagree with that, and they might seek to prove their point by taking a thermometer and laying it in the sun. See?! Look at how the reading immediately rises when it is in the sun. The air must be warmer.

Thermometer in the sun

But here’s the problem: While the reading on the thermometer will be much higher in the direct sunlight, that doesn’t mean the air temperature is higher, only that the temperature of the thermometer is higher. Just as the sun’s radiation heats your skin and makes it hotter than the surrounding air, so also it heats the thermometer casing. That’s why it is so important to place your thermometer in a well ventilated, shaded location in order to assure an accurate air temperature reading.

 

 

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