'Open Cell' Cloud Structure

The clouds methought would open and show riches
Ready to drop upon me; that, when I wak'd ...
William Shakespeare, "The Tempest", Act III, Scene II
Structure Description
Global Occurrence
Observation Diagrams
Examples: OCS / ECS

Home > Contents > 'Open Cell' Structure & 'Enhanced Cumulus' Structure - Description

"Convective Cells"
'Open Cell' Structure (OCS) & 'Enhanced Cumulus' Structure (ECS)

An open cell consists of convective clouds, which top reaches only the lower layers of the troposphere.
Within the cell vertical circulation takes place: the streams of the air go up in the zone close to its vertical borders (the cell sides) and then go down in an "empty place" (in the middle of the cell where there are almost no clouds).
Seen from above, an open cell ideally looks like a hexagon with the sides formed by rising clouds.
However, a separate cell can be found quite seldom; they usually make up fields that ideally look (from above) like honeycomb and in reality resemble chain amour.
The size of a cell is up to 70 km (not rarely up to 100 km).
The cloud top height of an open cell is 1.5-2.5 km, (sometimes up to 3 km).
The cloud top height of Enhanced Cumulus Clouds is up to 4-6 km, (rather often up to 7 km).
Accordingly albedo increases from ~0.5 to ~0.8 (and even to 0.85).
Space pictures often enable to see open and close cells sharing one and the same cloud field.
Open cells are present in convection cells cloud streets that in most cases emerge as the result of strong cold wind blowing over polar seas.

The Enhanced Cumulus Clouds represent a particular kind of the open sells.
They form above polar seas and seas in the middle latitudes as the season may be.
The cold air moving over the sea surface heats from below as its temperature is lower than that one of the water. As the result of this heating there appears instability in the surrounding atmosphere and the warm masses of the air go up, cooling.
The condensation goes with the release of latent heat that holds the vertical streams. Owing to the cooling of the air that is being raised this support is accompanied with the enhancement of condensation.
From the upper layers of the atmosphere the cold dry air is going down towards the rising stream. That is why the movement upward is limited in the convective cells and in some time there appears the balance between the rising and descending streams of the air. As the result large fields of cold cells emerge often causing a great amount of precipitation.
In the upper level of outlet channel inside cold air masses following the cold front under strong wind caused by the instability in the atmosphere the sides of the cell perpendicular to the direction of the wind become higher and (when seen from above) thicker. Not seldom such an effect occurs in the cold areas on the backside of large cyclone swirls.

Global Occurrence Diagram
Global occurrence of 'Enhanced Cumulus' Structure


Integrated Publishing - Aerographer/Meteorology

Clouds From Space

Japan Meteorological Agency 2002
Analysis and Use of Meteorological Satellite Images, Chapter 3, Cloud patterns
Winter Meteorological Processes in the Atmosphere

Visible Earth. A catalog of NASA images and animations of our home planet