Actiniae Cloud PatternsActiniae Cloud Patterns

Ernest M. AgeeErnest M. Agee

Presented at thePresented at the1414thth Conference on Interaction of the Conference on Interaction of the

Sea and AtmosphereSea and Atmosphere31 January 200631 January 2006

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.Actiniae Clouds – clouds with radial arms

Early and Recent Satellite Images of Actiniae Clouds

Open and closed cells over the Peru current (10S, 95W) 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, 155W). 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, 87-97W). (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, 15S, 100W). (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, 27N, 122 – 118W). (e) Detail of astronaut photograph STS043-96-54 showing actinoform cloud northeast of Canary Islands (0800 UTC 7 Aug 1991, 26 N, 16.5W).(taken from Garay et al. 2004)

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 isLe 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 TheoreticalStudies of Thermal Convection

Geometry

2-d3-dchains/beadsbi-modalcross-modalactiniapan-amspiral defectnon-defect spiralbi-harmonicspoke-patternoscillatoryherring-bone6-arm hexagons12-arm hexagonsskewed varicoseknotzig-zagspiral rotorsvortices at verticesturbulentslime mold(etc.)

Conditions/Properties

at restmotionlateral boundariesinfinite boundariesconstant physical propertiesvariable physical propertiesmotion (no shear)motion (with shear)rotationno rotationHadley modeno Hadley modesub-critical Resuper-critical Reweak super Racmoderate super Raclarge 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)

Laboratory hexagonal cells showing six lines (left) at RRc and twelve lines (right) of symmetry at R10Rc.

Convective Structures in CH4O (Busse, UCLA – personal communication)

An actinia transition cell embedded in RB convection, formed in vegetable oil at Pr = 800 and Ra = 300 x Rac; depth = 2.0 cm and T =

(44.5C - 40C)

Atmospheric Analog of Ra-Pr Stability Diagram

A top view of seven rotating hexagonal cells.

Univ. of Wisconsin SSEC Moviehttp://cimss.ssec.wisc.edu/wxwise/swirl/actinae2.htm

(- 15-image Java animation -)

Conclusions

• Classical convection structures and geometry continue to show their presence in convective marine PBLs.

• Actiniae cloud structures are viewed as a puzzle piece in the geometry pattern of R-B convection.

• Actiniae may be found in Type II CTBLs, but not in Type I CTBLs.

• Convective events in marine PBLs are viewed to operate according to the “principle of efficiency,” viewed as a meteorological extension of the Le Chatelier Principle.