Plumes above storm tops |
As already shown in the previous section, an area of the increased 3.7 µm cloud top reflectivity sometimes resembles a "plume like” shape (hereafter referenced as "plume"), distinctly different from all the other forms of the 3.7 µm features found at (or above) tops of deep convective storms. It should be emphasized here that this form of the increased 3.7 µm cloud top reflectivity (plume) is observed much less frequently than all the other possible forms.
Before proceeding to a detailed description of plumes, as an example here is a "classic” case, one of the first ones recorded and probably the most spectacular one:
(however, this case is not quite typical - this storm exhibits a "split” plume while majority of plumes has a single form).
European observations, summarized in (Levizzani and Setvák, 1996), though based on "snapshots" of the AVHRR instrument only, have shown several important characteristics of the plumes:
(Please note that the "plumes" we are speaking about on these pages are a different phenomenon than those which you can find occasionally elsewhere and which are called "anvil plume" or "storm plume". Those terms refer to storm anvils which are significantly elongated by upper level winds and which are built up by storm updrafts. "Our" plumes typically originate in the lee of the updraft region and are vertically separated from the anvil top.)
Now seems to be the right time for more (European) cases. When looking at these, please notice how they match the above summarized characteristics - these will not be repeated in the notes accompanying the individual cases.