The formation of mesoscale fluctuations by boundary layer convection
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Transcript of The formation of mesoscale fluctuations by boundary layer convection
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Multi-Scale Physics Faculty of Applied Sciences
The formation of mesoscale fluctuations by boundary layer
convection
Harm Jonker
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Multi-Scale Physics Faculty of Applied Sciences
Cold Air Outbreak
Peter Duynkerke, IMAUUtrecht University
Agee,Atkinson and Zhang……
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Stratocumulus Aircraft Observationslo
g E
(k)
log k
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Multi-Scale Physics Faculty of Applied Sciences
Sun and Lenschow, 2006
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Multi-Scale Physics Faculty of Applied Sciences
Sun and Lenschow, 2006
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Multi-Scale Physics Faculty of Applied Sciences
Sun and Lenschow, 2006
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Multi-Scale Physics Faculty of Applied Sciences
L = 25.6km Dx = Dy = 100m
t = 1...16hr, liquid water path
LES of Stratocumulus
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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
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Multi-Scale Physics Faculty of Applied Sciences
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w
qt u
lwp
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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 ZhangFiedler, van Delden, Muller and Chlond, Randall and Shao,Dornbrack, ……
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Multi-Scale Physics Faculty of Applied Sciences
Convective Atmospheric Boundary Layer
penetrative convection
zi
heat flux
entrainment
entrainment
tracer flux
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wpassive scalar c
variance spectra
dkkExdcxc c
0
22 )()(
LES
FFT (2D)
w
c
w
passive scalar c
Jonker,Duynkerke,Cuypers, JAS, 1999
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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
Han van Dop, IMAUMark Hibberd, CSIROJos Verdoold, Thijs Heus, Esther Hagen
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Laser Induced Fluorescence
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Laser Induced Fluorescence (LIF)“bottom-up” tracer
boundary layer depth structure
(Verdoold, Delft, 2001)(see also van Dop, et al. BLM 2005)
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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-
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Multi-Scale Physics Faculty of Applied Sciences
Inverse Cascade?
P D
k
E(k)
P D
k
E(k)
P
2-D or not 2-D: that’s the question
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nccccc .....21
Spectral variance budget
scale by scale variance budget
CDPcdt
d 2
Pproduction D dissipation
C
spectralinteraction
)klog(
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sink
source
16 sections
Scale Interaction Matrix C
passive scalar
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sink
source
16 sections
Scale Interaction Matrix C
dynamics
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k
E(k)
)(P
or
pdf of spectral flow
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upscale transfer
downscale transfer
)(P
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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)
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Multi-Scale Physics Faculty of Applied Sciences
Mechanism…
P D
k
E(k)
PP D
k
E(k)
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Multi-Scale Physics Faculty of Applied Sciences
P D
k
E(k)
P
weak production, weak transfer
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mechanism (CBL)
...
jj x
cu
z
Cwc
t
spectral
l
cu
z
Cw lll ~
22 ~ l
u
wc
l
ll
large scales
3~)( kkEc
)(
1~)(
3 kWkkt
..... transfer )(ˆ)(ˆ
z
Ckwkc
t
transport
(Jonker, Vila, Duynkerke, JAS, 2004)weak production, weak transfer.w crucial!
....
l
cu
z
Cwc
tll
ll
(Leith, 1967)
(Corrsin, ‘68)
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w
qt u
lwp
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Multi-Scale Physics Faculty of Applied Sciences
Spectral budget w
wz
pww
gw
t
0
2
buoyancyproduction
subgriddissipation
pressurecorrelation
)()()()()( kTkDkPkBkEt wwww
0)( dkkTw
spectraltransfer
2)( wdkkEw
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)(kEw
budget
)(kEt w
spectrum
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Multi-Scale Physics Faculty of Applied Sciences
Spectral budget u
ux
pu
z
uuwu
t
2
)()()()()( kTkDkPkSkEt uuuuu
shearproduction
subgriddissipation
0)( dkkTu
pressurecorrelation
spectraltransfer
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)(kEu
budget
)(kEt u
spectrum
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)(kEv
budget
)(kEt v
spectrum
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Multi-Scale Physics Faculty of Applied Sciences
Spectral budget scalar
qt
tt z
qwqq
t
2
spectral budget )()()()( kTkDkPkE
t qqqq
gradient production
subgriddissipation
spectraltransfer
variancebudget
0)( dkkTq
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)(kEq
budget
)(kEt q
spectrum
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LSw
LStqproduction
LSl
LSv
buoyancy production
pressure
LSu 0)1 LSwbreak the chain …
0,)2 LSl
LStqor
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w lwp u
reference
w filtered
0LSwtest 1:
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Multi-Scale Physics Faculty of Applied Sciences
40
reference
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Multi-Scale Physics Faculty of Applied Sciences
41
0LSwtest 1:
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LSw
LStqproduction
LSl
LSv
buoyancy production
pressure
LSu 0)1 LSwbreak the chain …
0,)2 LSl
LStqor
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w lwp u
reference
q, filtered
0,0 LSl
LStq test 2:
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Multi-Scale Physics Faculty of Applied Sciences
44
reference
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Multi-Scale Physics Faculty of Applied Sciences
0,0 LSl
LStq test 2:
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Multi-Scale Physics Faculty of Applied Sciences
Concluding: The spectral gap …
(Stull)
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Multi-Scale Physics Faculty of Applied Sciences
Cold Air Outbreak
time
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Multi-Scale Physics Faculty of Applied Sciences
Conclusions1) 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
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Multi-Scale Physics Faculty of Applied Sciences
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Jonker,Duynkerke,Cuypers, JAS, 1999
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Length scales of conserved quantities in the CBL at t=8h
r w' ' T
w' ' 0
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Multi-Scale Physics Faculty of Applied Sciences
)()()()()( 2 kSkEjkEkDz
ckEkE
dt
dcccwcc
dissipationproduction chemistry spectraltransfer
)()()( 32/13 kEkWk
dk
dk
dk
dkS c
Spectral Model
Leith (1967)
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(Jonker, Vila, Duynkerke, JAS 2004)
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Multi-Scale Physics Faculty of Applied Sciences
)()()()()( 2 kSkEjkEkDz
ckEkE
dt
dcccwcc
dissipationproduction chemistry spectraltransfer
)(~)()( kSkkWkkEc
Spectral Model: scale analysis …at large scales
ic z
ckEkWkP *)()(~)(
3~)( kkEc
2/13 )(~)(
kWkkt
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)(P
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