Menu
▾
▴
#1982 Cumulus clouds are too high when air pollution value is high
When air pollution value is high or with combination of high air pollution and max visiblity set to lower value (80km) cumulus clouds are at 8000 AGL, which is too high. Altocumulus clouds usually form at that height (or even lower height), but this is too high for cumulus clouds. This happens when I use offline weather engine
OS: Windows 10 Creators update
GPU: Nvidia GTX 1050
Driver version:384.84
Here is a picture. This aso happens with cirrus clouds and when they are higher they have this weird look. This mainly happens when using fair weather scenario.
Last edit: Mihajlo 2018-08-23
The base of Cu clouds is determined by the condensation level which in turn depends on the dew point.
If the air is sufficiently dry, Cu clouds will form higher - there's no physics reason known to me why they should not form at 8000 ft AGL.
(This has nothing to do with air pollution which the weather system doesn't even know about or visibility - although visibility and dew point are somewhat correlated in reality of course).
Well if clouds form at 8000ft due to convection it's usually Altocumulus and if the atmosphere is unstable Altocumulus castellanus will form. It may be possible for Cumulus cloud to form at 8000ft but it's probably extremely rare (at least I've never seen it in my region and I follow METAR of other regions as well) .I know that air pollution shouldn't infulence weather system,but I'm convinced that I've seen correlation between air pollution and cloud height. When I increase air pollution and decrease max visiblity clouds tend to form higher (not just Cu clouds).Maybe even not the first time after the change is made but after a few times of using AW i see that. When air pollution is low clouds tend to form at lower height. I've mostly noticed this in fair weather,but in other scenarios as well.
Altocumulus is usually not created by convection from the ground but by instability higher, so Ac won't ever replace Cu development - it's a different mechanism.
I'm sorry, but I won't discuss whether a parameter that does not even appear in the convective cloud code influences the cloudbase. The cloudbase in the code is determined by the spread between temperature and dew point, there's a good reason for that determined by the dry and moist lapse rates, the cloud base can be to a degree pushed up locally by mountains and that's it.
Well,I guess the only thing I can say is that I'm sorry you don't believe me.
I've run a grep over AW to see where pollution is used and looked again over the Cu code altitude determination, neither of which shows a mechanism how what you say can happen. If someone tells you that the result of x+y is dependent in addition on a parameter z and you can see the equation x+y in the code - what more would you do?
As they say - extraordinary claims require extraordinary evidence, and in a random system it's easy to get some fake correlation unless you systematically gather lots of data.
I get your point. I myself don't understand why I'm seeing this,and it's possible that it's something else or like you said fake correlation (I did think that maybe I'm imagining things),and I don't have hard evidence (I only measured cloudbase height with aircraft altimetar and changed air pollution and visibility settings) and it could be just my (subjective) impression (which is not evidence).