I’ve been getting up pretty early, and i’ve been noticing that on these early-winter mornings, the air temperature will drop just after sunrise…why is this? My theory: as the sun starts to heat the earth, it generates updrafts, that cause colder air from higher altitudes. to rush in and dispace the air near the ground. This would explain what I’m seeing…is this correct?
The most basic cause is that the area of the earth that is experiencing sunrise is still losing more heat than it is gaining from the sun. That will start to reverse as the sun rises further. It’s the same priniciple as to why the mid-afternoon is warmer than at noon time.
My memory is faulty then, I thought the reversal of falling temperatures happens about a half hour *before * sunrise. 
I’m assuming you live in a geographic area where the wind blows from east to west.
As the sun shines on the ground, the air around initially heats up, and rises.
This air rises on a thermal, creating a low pressure area. Air blowing in from a geographic area west of the terminator (the dividing line between daylight and nighttime) has not yet been warmed by the sun, and thus is cooler.
Ah, but wait…why would the air in your geographical area be warmer to start with, since it was also behind the terminator before dawn?
Ah…um…gotta think about this more.
There are also very few places in the U.S. where the wind normally blows from east to west. Just the opposite.
CRAP!
Meant to say west to east.
You don’t have to rely upon your faulty memory. Check your daily newspaper for the time of sunrise and then check it for the hourly temps. You will find that the temperature continues to drop, in most instances, for at least another hour. There will be occasional days when this does not occur for various and sundry reasons, such as a colder air mass moving in. This morning, in Charleston, SC, the temp was actually at its lowest before sunrise, but this is most unusual. I believe the reason for today’s quick rise was due to the fact that the temp was already as cold as the air mass over the area would allow. You will find that sometimes when a colder air mass envelops any region early in the evening, the temps will quickly drop but then level off, and may even rise, because the temps were already as cold as the air mass moving in.
I don’t know the reason for the usual delay in rising temps, but I’ve always assumed that it is due to the air over the land delaying the warmth to reach the ground, where the temps are taken (actually a few feet above the ground). Altho the light from the sun has reached your eyes, its heating effect has not.
WAG - on snow or frost, sunshine causes melt and evaporation, raising the humidity and causing the air to feel colder.
I’m pretty sure this has to do with latent heat. When water changes from a liquid to a gas it requires a lot of heat energy and some of this energy comes from the surrounding surface. In the morning the sun is evaporating surface water and subsequently cooling the surface. End result, surface temperatures continue to fall after sun rise until the sun provides enough heat to the surface to counteract the heat loss.
Similar effect to what happens when you sweat. Sweat evaporates and takes heat away from your body, cooling it. If your sweat didn’t evaporate (if the air was very humid for example) then you wouldn’t get the cooling effect.