Why it is very sunny in severe frost
The sun is blinding, the day is wonderful. Has winter really given us a break? We throw off an extra layer of clothing, put on a thinner hat, and joyfully run outside. And out there a frost of -25 is already waiting to grab us by our unprotected spots. And we run back and, cursing, pull on our thermal underwear. Why is it that in wild frosts the sun is so deceptively "warming"?
Yes, the sun shines at full strength, but its rays, alas, give no warmth. On the contrary, a bright frosty day becomes drier and harsher. The frosty dryness of the air under a clear sun is determined by the arrival of anticyclones. They form mainly in the Arctic. Then, having gathered strength, the flows of cold air rush toward us through Siberia.
In winter the Sun is very stingy with warmth. That is because the cause of such «behavior» is radiative cooling – when the amount of energy emitted by the surface is greater than what it receives from the source. For example, on average over a day, in clear winter weather a patch of ground loses more heat at night. And by day the Sun, for all its efforts, cannot make up for it in the necessary amount.
«It is true: the coldest winter days — are sunny ones. The snow cover, always present on the coldest days, effectively reflects the small amount of daytime heat contained in the weak winter sunlight», – explained meteorologist Tom Skilling.
Why it rains when there are no clouds in the sky
You glance at the sky – it is clear and bright, which means the bulky umbrella can be left at home. And an hour or two later you are running through the rain, trying to take shelter under an awning so as not to get soaked. It's frustrating, because there were no clouds.
In fact, there were – they are simply elusive to the human eye. They are so thin that spotting them in the sky is nearly impossible. So in this case you should not trust your eyes, and if the weather forecast promised rain – it is better to play it safe.
In addition, a phenomenon such as a «blind» or «mushroom» rain occurs even under a clear sky and bright sun. Such rain is very light and brief; it is usually caused by the wind carrying a small stream of droplets through the air from an area where precipitation has fallen.
However, nature can play the opposite trick as well – we see a huge dark cloud in the sky and expect the heaviest downpour. Armed with protective gear in the form of an umbrella and rubber boots, we hurry to meet it. But the storm cloud turns out to be only a menacing yet harmless phenomenon. And what about the downpour?
Usually such clouds form on especially hot days. The cloud absorbs moisture from the air and slowly rises upward. The higher it rises, the more massive and darker it becomes, and all the moisture it has gathered forms into crystals. The cloud turns into a gray storm cloud. And it turns out that the intensity of the color has no bearing whatsoever on the presence of precipitation. Even the blackest and most frightening cloud may not break into rain. It will simply float by over our heads.
Strong wind in summer heat and deceptive spring warmth
Surprisingly, in summer the risk of catching a cold increases, and the chance of catching cold in spring is also very high. In spring we are fooled by the long-awaited warmth – we waited for it through the long winter months and are ready to shed the tiresome jackets and hats that hung on us like a heavy weight. And here a fresh spring breeze and the drafts that come with it are already lying in wait for people grown languid from the deceptive spring warmth. The thing is that in the first two months of spring the air, like the ground, is still only warming up. The temperature fluctuates – a sudden but brief cold snap may set in, which is then replaced by warmth.
Strong wind in the heat is most often the cause of colds. In addition, it can cause inflammation of the mucous membrane of the eyes, since in the absence of precipitation it kicks up dust into the air. That is why it is important to wear glasses in summer not only as protection from the sun's rays, but also from dust.
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