why does the overnight temperatue decrease a little as the sun comes up durinf winter?as?

Question

many of us are aware, durin the cold winter months the low temp. will drop a couple more degrees just as the eastern skyline begins to lighten. it seems to be more noticeable during very cold nights.

Answer 1

The issue relates to time and the relatively weak power of the sun just above the horizon on a winter's morning. Back up a few hours to the middle of the night. The temperature is dropping due to heat radiating from the ground into space (at least on a clear night, which is what your question implies). As time goes on the temperature continues to drop. The weak winter sun can't reverse this until it gets a few degrees above the horizon. Finally, the sun climbs high enough in the winter sky to begin to heat the ground and the temperature drop reverses and begins to climb.

It is not unlike a car traveling down a highway. It does not stop the moment you put on the brakes due to its momentum to keep going. The cooling night acts in an analogous fashion. It keeps cooling until the sun finally turns things around by heating the ground.

Answer 2

Good question. Good observation. Do you also notice that the temperature goes up a little just before it starts to snow? That's because the 'heat content' of the water in the clouds has to be given up in order for the moisture to freeze. So the heat is transferred to the surrounding air. The opposite happens during the circumstances you describe. Not only are the nights very cold, but they are also very clear- meaning no clouds, little moisture in the air - low heat content. As the sun comes up, the ground air will rise making the temperature at ground level drop a few degrees. Do you ever hear the expression, "It's too cold to snow."? That's what is meant. The air is too cold to hold much moisture in some locations.,

Answer 3

Yes remember temperature measurements are made in Stevenson screens aboout 5 feet above the ground. The air near the ground is often colder on a calm, clear night (grass-minimum temperature). When the sun hits the ground ths layer of air warms slightly (but it's still cold) and rises to the screen's level.

Also, until enough solar radiation comes in to overcome what is being radiated out, the temperature will continue to drop. This can take a few minutes to an hour.

Answer 4

Assuming no frontal passages or other things going on, the temperature will decrease as long as the outgoing infrared radiation emitted by the earth is greater than the incoming solar radiation. This will often happen even as the sun rises, until the radiation is intense enough to start increasing the temperature. In winter, the presence of reflective snow and ice and the low sun angle contribute greatly to the problem.

Answer 5

.that occurs all year round, and not just winter. The cold air sinks and it compacts just after the sun rises, and the lowest temps. are often read just a few minutes before to after the sun rises over the horizon.