Quote:
Originally Posted by forgotten username
oh yeah, Bolzano. Fohn effect ? Great climate there.
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Foehn effect can be an hypothesis, but in this period of the year another frequent phenomenon in the Po valley is the temperature inversion. I don't know how the situation is in Bolzano, but in here the situation is pretty similar and the answer is definitively the second. In fact Foehn effect is really easy to spot because it is characterized by windy condition, a significant drop of humidity and a rise of temperatures. And this is not what is happening right now.
In the Po valley, during this period of the year and when you see fog and smog in the plain, the main suspected is the temperature inversion instead. And it usually last for several days, until a new perturbation arrives.
https://en.wikipedia.org/wiki/Inversion_(meteorology)
And this is really bad for smog and pollution
Milan's Quick Fix for Bad Smog: Cheap Public Transportation - CityLab
For example, here there are some temperature maps of my area (it is a zoom around the Turin and my valley).
All data are from our regional regional agency (ARPA piemonte) in here-->
Dati meteorologici in tempo reale
This morning at 8:45 am (temperatures in °C)
The whole region:
The general pattern is that the plain has some of the coldest temperatures, the warmest are the station just above the plains (500-800 m = 1640- 2624 ft of altitude, indicatively) and above the temps progressively decrease again for altitude.
This afternoon at 5:30 pm (temperatures in °C)
The temperature pattern this afternoon is quite similar to this morning.
Then, I looked for the records for the weather stations indicated with the arrows:
Red arrow points toward Turin (altitude 239 m = 784 ft)
The two graphs show the temperature and the relative humidity since the 9th of December. I'm particularly interested in the last two days, in which you can notice that the city had a RH close to 100% for the most of the time (which means that the city remained covered by fog for the most of the time. Yesterday in particular there was a really thick fog even in the middle of the day).
Yesterday temperatures: 0.1 - 5.9°C = 32 - 43 °F
Today temperatures (up to now): 0.0 - 6.6°C = 32 - 44°F
The green arrow is for the closest station to my place, in Susa (altitude 520 m = 1706 ft)
In here it was sunny and warmer than usual for the most of the period (just Sunday was slightly cloudy). Anyway, we didn't have fog not low clouds for ages. With the graphs I just wanted to show you that in here it was generally warmer than in Turin, and a much more dynamic situation (temperature and RH changed more during the day)
yesterday temps: 1.9 12.8°C = 35 - 55°F
today temps (up to now): 0.3 9.3°C = 32,5 - 49 °F
The blue arrow is probably the most interesting, because it is an example of a place at a quite high altitude. It is Bardonecchia, at 1353 m = 4438 ft of altitude (it is the westernmost municipality of Italy too)
Even if it is at a much higher altitude than Turin the temperatures are not so different, the highs are even higher than in Turin. Also the weather conditions are completely different, you can see that over there the RH is not high at all and they are having a sunny and warm period too.
Yesterday temps: 0.0 - 11.4°C = 32 - 52,5 °F
Today temps (up to now): -0.9 - 6.1°C = 30 - 43 °F
In practice, in these days when I go to Turin I really have the impression that I'm entering a cold, foggy and polluted air trap. The difference with my place is striking.
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