Wavy temperature profile. Why?

[Crocodile23]

 Observing the temperature of a level in the atmosphere, e.g at 850 hPa of Madrid(Spain), we can identify a wavy pattern of it, with a specific periodic behaviour of it with a maximum after the noon and then a minimum early in the morning.

You have to ignore of course the general tendency of the temperature via many days where it is being affected by genera; circulation heat or cold surges, so we actually speak about local minimum and maximum over each day.

 Then looking at another place's temperature which is much southern than Madrid, so let's take Granada which is about 3° southern of Madrid, we see that this wavy pattern again, but its amplitude(its vertical spread -or if you like the difference of maximum from minimum) is smaller.

This can be seen much better with another 2 cities, this time of Greece, Athens and Thessaloniki, where in Thessaloniki the wavy pattern of temperature in 850 hPa is much more obvious than in Athens. I.e the difference of maximum temperature from minimum in every day is a lot bigger in Thessaloniki than in Athens and in Athens the wavy pattern is actually very weak.

 

We should also note that this wavy behavior is not happening in 500 hPa.

 

So let's see all that via GFS's diagrams for the current period:

 

Madrid (40.4°N , 3.7°W) :

 

Granada (37.4°N , 3.7°W) :

 

Athens (38°N , 24°E) :

 

Thessaloniki (40.7°N , 22.9°E) :

 

 

◙◙◙ Now my question is:

a)WHY this is happening? Why there is this wavy pattern in the temperature profiles in 850 hPa? And why there is NOT in 500 hPa.

b)Also why as we go southern(we are talking about the north hemisphere always) this wavy pattern is weakening? And so why in Athens it becomes so small?

 

 An obvious try to explain a), is that the height where 850 hPa is, is inside PBL so it is heated by the earth's surface, which is heated by the sun, so it reaches its maximum temperature a little after the sun's maximum height in the sky every day, and that is a little after the noon. Similarly at night where the sun is below horizon its temperature will normally fall and we would get a minimum around the time, or a bit after it, where the sun will appear again above the horizon.

But is this really the correct and full explanation for the wavy pattern?

 

And anyway, the above doesn't explain .

 

Furthermore if we look at the temperature profile of various heights(for Madrid-it's the same for other places also):

 

We can see that this wavy pattern(with local maximum/minimum for each day) is valid for all atmospheric levels up to 800 hPa approximately.

c)So does that mean that my previous explanation of the PBL is correct and that 850 hPa, 830 hPa, 800 hPa, etc, are being heated by the earth's surface so that's why we have this wavy pattern? Or something else is true?

d)So in what height is the PBL aproximately in these diagrams? I thought it is lower than 850 hPa but i guess i'm wrong, right?

The important question remains though.

 

 

BTW this obvious wavy pattern starts to appear in these countries in late April most of the time, so that strengthens my aforementioned explanation for a), as then the sun is getting to affect in a greater degree the lower atmosphere in the north hemisphere.

[Ellinwood]

Wavy temperature profiles are created by diurnal heating, which affects the surface temps the most. Its influence decreases as you increase in height as the wind mixes the surface-warmed air with the air aloft.

All other variables equal, the amplitude of the diurnal temperature profile is largely a function of how dry the air is. Drier air will warm and cool faster than moist air, so you will see higher amplitudes in places like deserts and lower amplitudes in more marine/tropical areas.

[ohleary]

If it's a constantly occurring larger-amplitude temp profile, it could be that the station is at a higher altitude, so that the 850 mb level is closer to the surface and more affected by diurnal heating/cooling.  Alternatively, a station at sea level would have a smaller amplitude temp profile at 850 mb.  It seems at least.

[famartin]

Also, a drier climate is more likely to see a greater change at 850 mb because of greater vertical mixing.  Sometimes we can dry adiabatically mix to above 500 mb in Elko.  Mind you, we are starting at 850 mb, not sea level, but that's still more than10,000 feet of mixing!

 

http://weather.uwyo.edu/cgi-bin/sounding?region=naconf&TYPE=GIF%3ASKEWT&YEAR=2012&MONTH=07&FROM=1300&TO=1300&STNM=72582