Why does it get colder at sunrise?

[Rat]

DWG, what location did you pull that report from?

[Rat]

Air temp will NEVER drop below the dew point temp. Their are a few instances when super-saturation has occured but it is rare and very brief.

Supersaturation occures every day, that is what forms clouds, fog and contrails on airplane wings. Wether or not the air temp is lower than dew-point is hotly debated, but I don't see how it can't be lower, the moisture content is greater than 100%, dew point must be higher.

[Ouch]

Huh?

What was the question?

I'm cold.

[Target-panic]

But whose on first???????????????????

[Brute Killer]

DWG, that top graph does not show dewpoint temp below air temp, accoring to my eyes. The red line is always above the green.

[Mike Murphey]

What...???!!!
How about the colder air in the upper atmosphere comes down due to the sun heating it up....the warmer air goes up making the cooler air to come down...(or something like that)...it could also be the equation of the train going 50 mph going West, is like a train goes SW at 40 mph on the third Thursday of an even numbered month or something like that in (I slept that day in college)....

[DWG]

DWG, that top graph does not show dewpoint temp below air temp, accoring to my eyes. The red line is always above the green.

My bad I looked at it wrong. ( Rat) That graph came off wunderground.com

[Tmag]

I'm going with Smart on this one. He's a brainiac!

[Brute Killer]

http://ww2010.atmos.uiuc.edu/(Gh)/guides/maps/upa/dewp.rxml
Dew Point Temperature is defined as the temperature at which air would have to cool (at constant pressure and constant water vapor content) in order to reach saturation. Dew points provide insight into the amount of moisture in the air. The higher the dew point temperature, the higher the moisture content for air at a given temperature.

When the dew point temperature and air temperature are equal, the air is said to be saturated. Dew point temperature is NEVER GREATER than the air temperature. Therefore, if the air cools, moisture must be removed from the air and this is accomplished through condensation. This process results in the formation of tiny water droplets that can lead to the development of fog, frost, clouds, or even precipitation.

[Brute Killer]

[refugioco]

I have noticed this phenoma for a while. I go out at 5 and get the paper cars are unfrosted, go to leave at 7 frozen. I studied it this past week in Uvalde the temperature would drop 4- 6 degrees as the sun came up. I dont know the answer but it does happen.

[Brute Killer]

http://www.newton.dep.anl.gov/askasci/wea00/wea00042.htm

This guy says temp drop is related to barometric pressure.

[WCB]

I can't beleive some thinks 25 is a bunch colder than 28...

[Chad_E]

What's on Second?

[DavisHollow]

So get two thermometers, one at your feet and one at your head (presumably you are not short), and see if there is an inverse correlation between the temp at your feet when the temp at your head drops just after sunrise.

I buy the argument that the sun, as it rises, burns off (dissipates) a magical radition barrier in the upper atmosphere (much like a thin cloud layer keeps the temps warmer at night) which allows for a brief moment of additional radiation cooling until the sun materially begins to heat the surface.

Sounds good anyway.

And guys, the temp does not fall below the dew point, by definition. The dew point is, by definition, the point at which air is saturated with water. Any further cooling would cause enough moisture to condense or sublimate out of the air, so the dew point tracks the temp, as colder air can hold less moisture. An interesting factoid is that as moisture sublimates or condenses out of the air, heat is released, this is what keeps the temp from droping further. The opposite of what happens when water evaporates, the temp drops (we sweat, it evaporates, we stay cool but stink).