My elevation is 750ft. I have noticed that my cloud base never goes below 750. Is this correct. It seems that when we are fogged in the base should be at or near zero. Can someone set me straight. TIA
There’s a whole long thread about the calculation somewhere, but the bottom line is that the value is ASL.
ASL – Above sea level? So does that mean if I’m fogged in that the lowest I will ever see is 750 ft (my height above sea level)?
Yes, Above Sea Level, it’s a very simple estimate of the altitude at which the air temp is equal to the dew point. Here’s what Brian wrote a while ago.
The cloud base is based on the dew point, which is based on the humidity and temperature from the station.and it is based on a assumed adiabatic environmental elapse rate…(dry air assumption), and so the height at which the temperature reaches the dew point due to cooling as you increase in altitude, is the estimated cloud height.
by setting a altitude, under units, this then creates an offset for the cloud height formula.
if you live at altitude, your temperature will be lower …and there fore the dew point depression will be lower…and this then creates a lower cloud height estimate
i.e
the formula is simply the dew point depression*412 (estimated cloud height in feet)but this is from assumed sea level…
so you do need to have your altitude set…which is need for QFE barometer option as well…
Cheers
Brian