Anthropogenic cloud
The intermediate layers of the troposphere are the regions with less influence of human activity. This region is far enough from the surface for not being affected by the surface emissions. Additionally, commercial and military flights only cross this region during ascending or descending maneuvers. Moreover, in this region there exist two types of clouds with a large horizontal extension: "Nimbostratus" and "Altostratus", which cannot originate from human activity. Consequently, it is assumed that there are no anthropic clouds of these two "genera". However, what can occur is enhancing existing "Nimbostratus" or "Altostratus" due to the additional water vapor or condensation nuclei emitted by a thermal power plant, for instance.
Castellanus
Castellanus that are unfavourable to soaring can be easily identified and are nicknamed ""rocket clouds"."
The visual difference between a cumulus and a castellanus is that the former has a flat base while the latter generally has no clearly defined base. However, a visual observation of the cloud may not be sufficient, since in some cases the hybrid castellanus (pseudo cumulus) may have a flat base. The only sure way to distinguish between these two types of clouds is through an atmospheric sounding preceding the flight. If the base of these false cumulus is higher than the convective condensation level, the pilot is probably close to unwanted cumulonimbus. Moreover, when a cumulus breaks down, there may still exist an updraft column under the cloud base that did not originate from the ground. In particular, at the end of the day, the airmass can be stable up to 2000 feet and unstable above this stable layer. The cumulus turn into stratocumulus or altocumulus depending on their height. Before the 1956 version of the International Cloud Atlas, these clouds were called stratocumulus or altocumulus "vesperalis". Directly under these clouds, updrafts are still present. The meteorologist Corfidi explains that these seemingly innocuous clouds that break down rapidly can be a harbinger of nocturnal thunderstorms.