Actiniae Cloud Patterns
Ernie Agee
27 April 2005
Some Terminology
Anemone (Greek) – plants/animals with
radial extensions (tentacles, arms, etc.)
Sea Anemone – Predatory sea animals that
look like flowers. They have tentacles that
sting.
Anemometer – (definition not needed)
Actinia (singular); Actiniae (plural) …consisting of arms, tentacles, etc.
Actinia Clouds – clouds with radial arms
Early and Recent Satellite Images of
Actiniae Clouds
Open and closed cells over the Peru
current (10S, 95W) at 1813 GMT
15 September 1964. (Agee, 1984)
Observed in the eastern North Pacific on 17 June
1997 1500 GMT.
(http://cimss.ssec.wisc.edu/wxwise/swirl/actinae2.htm)
(a) First satellite image of an actinoform cloud from TIROS V (2322 UTC 16 Aug 1963, 17.5N, 155W). Cloud is over 300
km in diameter (Picture of the Month in Mon. Wea. Rev. 1965, Vol. 93, p. 212). (b) First Picture of the Month image (Mon.
Wea. Rev. 1963, Vol. 91, p. 2). Series of actinoform clouds observed by TIROS V (1500 UTC 7 Oct 1962, 7S, 87-97W).
(c) Picture of the Month April 1965 (Mon. Wea. Rev. 1965, Vol. 93, p. 212). Actinoform clouds from TIROS VIII (1713 UTC
18 Jul 1964, 15S, 100W). (d) Composite of four photographs by astronaut from space (STS51G-31-10 to -13). Cloud
feature extends hundreds of kilometers (1600 UTC 17 Jun 1985, 27N, 122 – 118W). (e) Detail of astronaut photograph
STS043-96-54 showing actinoform cloud northeast of Canary Islands (0800 UTC 7 Aug 1991, 26N, 16.5W)
Mesoscale Cellular Convection in Polar
Air Stream over the North Atlantic
Global Climatology of Mesoscale
Cellular Convection (Agee,1984)
"It becomes increasingly clear that
instabilities and nonlinear behavior,
leading to structure formation far from
equilibrium, are ubiquitous in large classes
of physical systems such as isotropic
fluids …Whether one likes it or not,
thermal convection cells …do exist and
refuse to be exorcised."
G. Nicolis (1986), Am. J. Phys.
To paraphrase  "Convection Cells are
Forever"
The Author's Principle of Natural Efficiency
"The geometry of any R-B convective system in the
laboratory (or atmosphere) represents the most efficient
mode for the vertical transport of heat, and reflects a
natural response to all the physical properties and
constraints of the fluid system.“
The closest existing parallel principle is
Le Chatelier's Principle
"Any inhomogeneity that somehow develops in a system
should induce a process that tends to eradicate the
inhomogeneity.“
For R-B convection, the imposed inhomogeneity is a
vertical thermal stress, and the fluid responds with bulk
motions in an attempt to reduce the thermal stress by
convecting heat.
Satellite photograph (NOAA Nimbus 7) showing atmospheric flow with
organized parallel “streets” of cumulus clouds sitting atop the planetary
boundary layer.
Classical and Recent Laboratory and Theoretical
Studies of Thermal Convection
Geometry
2-d
3-d
chains/beads
bi-modal
cross-modal
actinia
pan-am
spiral defect
non-defect spiral
bi-harmonic
spoke-pattern
oscillatory
herring-bone
6-arm hexagons
12-arm hexagons
skewed varicose
knot
zig-zag
spiral rotors
vortices at vertices
turbulent
slime mold
(etc.)
Conditions/Properties
at rest
motion
lateral boundaries
infinite boundaries
constant physical properties
variable physical properties
motion (no shear)
motion (with shear)
rotation
no rotation
Hadley mode
no Hadley mode
sub-critical Re
super-critical Re
weak super Rac
moderate super Rac
large super Rac
(etc.)
The familiar patterns of a self-propagating reaction
appear when individual cells of slime mold aggregate, at
one stage of their life cycle, to form larger communities of
cooperating cells. (From Newell and Ross 1982.)
Rayleigh Number (Ra) versus Prandtl Number (Pr)
in Laboratory Experiments
Vertical Velocity Asymmetry in -plane
(Krishnamurti, 1975)
Atmospheric Analog of Ra-Pr
Stability Diagram
Laboratory hexagonal cells showing six lines (left) at RRc
and twelve lines (right) of symmetry at R10Rc.
Convective Structures in CH4O
(Busse, UCLA – personal communication)
A top view of seven rotating hexagonal cells.
Univ. of Wisconsin SSEC Movie
http://cimss.ssec.wisc.edu/wxwise/swirl/actinae2.htm