Multi-Scale Physics Faculty of Applied Sciences The formation of mesoscale fluctuations by boundary layer convection Harm Jonker

Multi-Scale Physics Faculty of Applied Sciences Cold Air Outbreak Peter Duynkerke, IMAU Utrecht University Agee, Atkinson and Zhang ……

Stratocumulus Aircraft Observations log E(k) log k

Atmospheric Observations: Sc Nucciarone & Young 1991 w u q 

Multi-Scale Physics Faculty of Applied Sciences Sun and Lenschow, 2006

Multi-Scale Physics Faculty of Applied Sciences Sun and Lenschow, 2006

Multi-Scale Physics Faculty of Applied Sciences Sun and Lenschow, 2006

Multi-Scale Physics Faculty of Applied Sciences L = 25.6km Dx = Dy = 100m t = hr, liquid water path LES of Stratocumulus

L = 6.4km (8hr) Dx = Dy = 100m L = 12.8km (12hr) L = 25.6km (16hr) LES of Sc (ASTEX) Liquid water path “Large Eddy Simulations: How large is large enough?”, de Roode, Duynkerke, Jonker, JAS 2004 “How long is long enough when measuring fluxes and other turbulence statistics?”, Lenschow, et al. J. Atmos. Oceanic Technol., 1994

Multi-Scale Physics Faculty of Applied Sciences

w qtu lwp

Intermediate Conclusions 1) the formation of dominating mesoscale fluctuations is an integral part of PBL dynamics! - no mesoscale forcings - what is the origin (mechanism) ? - latent heat release - radiative cooling - entrainment - inverse cascade Atkinson and Zhang Fiedler, van Delden, Muller and Chlond, Randall and Shao, Dornbrack, ……

Multi-Scale Physics Faculty of Applied Sciences Convective Atmospheric Boundary Layer penetrative convection zizi heat flux entrainment tracer flux 

w  passive scalar c variance spectra LES FFT (2D) w c w  passive scalar c Jonker,Duynkerke,Cuypers, JAS, 1999

Saline convection tank Laser Induced Fluorescence (LIF) fresh water salt water (2%) fresh water + fluorescent dye buoyancy flux & tracer flux Laser  (z) digital camera pp Han van Dop, IMAU Mark Hibberd, CSIRO Jos Verdoold, Thijs Heus, Esther Hagen

Laser Induced Fluorescence

Laser Induced Fluorescence (LIF) “bottom-up” tracer boundary layer depth structure (Verdoold, Delft, 2001) (see also van Dop, et al. BLM 2005)

Intermediate Conclusions 1) the formation of dominating mesoscale fluctuations is an integral part of PBL dynamics! 2) latent heat and radiation are not essential - latent heat release - radiative cooling - entrainment - inverse cascade -

Multi-Scale Physics Faculty of Applied Sciences Inverse Cascade? P D k E(k) PD k P 2-D or not 2-D: that’s the question

Spectral variance budget scale by scale variance budget production dissipation spectral interaction

sink source 16 sections Scale Interaction Matrix C   passive scalar

sink source 16 sections Scale Interaction Matrix C   dynamics

k E(k) or pdf of spectral flow 

upscale transfer downscale transfer

Intermediate Conclusions 1) the formation of dominating mesoscale fluctuations is an integral part of PBL dynamics! 2) latent heat and radiation are not essential - latent heat release - radiative cooling - entrainment - inverse cascade 3) budgets show: no inverse cascade (significant backscatter on all scales)

Multi-Scale Physics Faculty of Applied Sciences Mechanism… PD k E(k) P P D k

Multi-Scale Physics Faculty of Applied Sciences PD k E(k) P weak production, weak transfer

mechanism (CBL) spectral large scales transport (Jonker, Vila, Duynkerke, JAS, 2004) weak production, weak transfer. w crucial! (Leith, 1967) (Corrsin, ‘68)

w qtu lwp

Multi-Scale Physics Faculty of Applied Sciences Spectral budget w buoyancy production subgrid dissipation pressure correlation spectral transfer

budget spectrum

Multi-Scale Physics Faculty of Applied Sciences Spectral budget u shear production subgrid dissipation pressure correlation spectral transfer

budget spectrum

budget spectrum

Multi-Scale Physics Faculty of Applied Sciences Spectral budget scalar spectral budget gradient production subgrid dissipation spectral transfer variance budget

spectrum

production buoyancy production pressure break the chain …

wlwpu reference w filtered test 1:

Multi-Scale Physics Faculty of Applied Sciences 41 reference

Multi-Scale Physics Faculty of Applied Sciences 42 test 1:

production buoyancy production pressure break the chain …

wlwpu reference q,  filtered test 2:

Multi-Scale Physics Faculty of Applied Sciences 45 reference

Multi-Scale Physics Faculty of Applied Sciences test 2:

Multi-Scale Physics Faculty of Applied Sciences Concluding: The spectral gap … (Stull)

Multi-Scale Physics Faculty of Applied Sciences Cold Air Outbreak time

Multi-Scale Physics Faculty of Applied Sciences Conclusions 1) the formation of dominating mesoscale fluctuations is an integral part of PBL convective dynamics! 2) latent heat and radiation are not essential (but speed up the process considerably) 3) budgets: no inverse cascade on average. significant backscatter (on all scales) 4) production: ineffective (slow), but spectral transfer is just as ineffective 5) the spectral behaviour of w at large scales is crucial

Multi-Scale Physics Faculty of Applied Sciences

Jonker,Duynkerke,Cuypers, JAS, 1999

Length scales of conserved quantities in the CBL at t=8h

Multi-Scale Physics Faculty of Applied Sciences dissipationproductionchemistryspectral transfer Spectral Model Leith (1967)

(Jonker, Vila, Duynkerke, JAS 2004)

Multi-Scale Physics Faculty of Applied Sciences dissipationproductionchemistryspectral transfer Spectral Model: scale analysis …at large scales