Colder after Sunrise

NewForester

Well-Known Member
I try to be in my highseat an hour before official sunrise. I often find that I become colder after sunrise.

I guess that it could just be my body cooling down. But I think that the sun may causing more of a breeze which causes the cooling.

Anyone else noticed this cooling after sunrise?
 

flying felix

Well-Known Member
Not taking the wind into account the coldest time is the hour before sunrise.

But you are correct, all weather is caused by the sun heating up the surface which then causes low air pressures. Air from high pressure areas then move towards the low pressure ones. Depending on whether the moving air is warmer or colder than the ground it moves over will cause it either warm up or cool down. This is what's called the "wind chill factor" when the air is colder than the surrounding ground temp.
 

L1A1

Well-Known Member
After many years in the Air Force with many pre dawn duties I often found that it felt colder after the sun had just risen.
I don't know any science about it but I d agree.
 

flying felix

Well-Known Member
Another effect is the heating of the sun removes the cloud cover, which in turn removes the insulation that's kept the ground warm overnight.
 

Old melv

Well-Known Member
Yes I agree it often feels colder just after sunrise. Many years ago I used to work nights and one of my jobs was to start a big press up ready for the day shift I would turn on the air compressor and then sit by the river churnet that ran through the factory for 30 minutes or so until the air tank had reached its pressure.
Often it got colder just after the sun had risen. As a bonus you could sometimes see a kingfisher.
 

Heym SR20

Well-Known Member
The sun will start warming the ground causing air to rise, which means cold air will fall into the vacuum. That’s why you also get frost pockets.

You really experience this If you sit on a sunny hillside you will feel the breeze stop, then it gets warmer as a bubble of warm air starts to develop and rise, a few minutes later you get a cold wind filling in the space. This sets up into a rhythmic cycle that you almost set your watch by.
 

Merlyn

Well-Known Member
When you walk to the high seat your body temperature rises and you sweat. Then you sit still and the moisture around your body - the sweat - cools quicker than your insides do. You feel cold and then you get cold.
Walk to the high seat in your shirtsleeves. Put your top layers on when you settle in the seat. You will feel warm.
This is how wildfowlers do it in mid winter on the marshes. Been doing it for 50+ years.
 

Merlyn

Well-Known Member
And I notice a marked drop in the breeze around sunset too.
Diurnal variation of the surface wind. Cooling effect so there is less mixing of the air in the lower levels. The air at two thousand feet is going slightly faster and in a different, again slightly, direction to the surface wind.
 

Heym SR20

Well-Known Member
When you walk to the high seat your body temperature rises and you sweat. Then you sit still and the moisture around your body - the sweat - cools quicker than your insides do. You feel cold and then you get cold.
Walk to the high seat in your shirtsleeves. Put your top layers on when you settle in the seat. You will feel warm.
This is how wildfowlers do it in mid winter on the marshes. Been doing it for 50+ years.
Or take an Ansitzsacke - they are toasty warm and make a huge difference if sitting out.


Even a lightweight fleece blanket to wrap around your legs and lower body can make a huge difference. I have a very warm down sleeping bag that I have used on more than one occasion on an overnight session in a high seat. Take your boots and coat off, get into the bag, draw it up to your armpits and then coat on over the top.
 

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