An integral approach to modeling PBL transports …...PBL transports and clouds 11-2006 Martin...
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PBL transports and clouds 11-2006 Martin Köhler 1 An integral approach to modeling PBL transports and clouds Martin Köhler and Roel Neggers • EDMF @ ECMWF now and future – dry PBL – stratocumulus – shallow cumulus • stratocumulus: evaluation against observations – EPIC marine stratus field experiment – GLAS cloud and cloud top height • ongoing work – down-drafts (short-hand for draughts) – shallow cumulus (Roel)
Transcript of An integral approach to modeling PBL transports …...PBL transports and clouds 11-2006 Martin...
PBL transports and clouds 11-2006 Martin Köhler 1
An integral approach to modeling PBL transports and cloudsMartin Köhler and Roel Neggers
• EDMF @ ECMWF now and future– dry PBL– stratocumulus– shallow cumulus
• stratocumulus: evaluation against observations– EPIC marine stratus field experiment– GLAS cloud and cloud top height
• ongoing work– down-drafts (short-hand for draughts)– shallow cumulus (Roel)
PBL transports and clouds 11-2006 Martin Köhler 2
GCSS Pacific Cross-Section Intercomparison Project
pres
sure
[hPa
]
100200300400500600700800900
1000
pres
sure
[hPa
]
100200300400500600700800900
1000
GFLD AM2 NCAR CAM3 NCEP
HadGAM ARPEGE ECMWF ERA-40
liquid water [g/kg]
0.30.150.080.040.030.020.010
JJA1998Joao Teixeira
EquatorDateline
California EquatorDateline
California EquatorDateline
California EquatorDateline
California
PBL transports and clouds 11-2006 Martin Köhler 3
Integral appraoch to PBL transports: EDMF
M1M
K
M2
Shallow cumulus Deep cumulusStratocumulusdry BL
zcb
zi
zi
KbotM
Ktop
KbotKbot
operational
PBL transports and clouds 11-2006 Martin Köhler 4
EDMF: two box M/K decomposition(Siebesma and Cuijpers, 1995)
u
uuu φφφ +′=e
eee φφφ +′=
e
e
u
u aa φφφ )1( −+=
a
)()1( φφφφφ −+′′−+′′=′′ uu
e
e
u
u wawawaw
M
M-fluxenv. fluxsub-core flux
zK∂∂
−φ
PBL transports and clouds 11-2006 Martin Köhler 5
A statistical mass flux framework for organized eddies
Top % of updrafts that are explicitly modelled
K diffusion
{w, θl , qt}
( )' ' φφ φ φ∂= − + −
∂ uw K Mz
dry PBL
Dry updraft
PBL transports and clouds 11-2006 Martin Köhler 6
A statistical mass flux framework for organized eddies
Top % of updrafts that are explicitly modelled
K diffusion
{w, θl , qt}
( )' ' φφ φ φ∂= − + −
∂ uw K Mz
Stratocumulus UP
Cloudy updraft
PBL transports and clouds 11-2006 Martin Köhler 7
A statistical mass flux framework for organized eddies
Cloudy updraft
Top % of updrafts that are explicitly modelled
K diffusionCloudy downdraft
{w, θl ,+/-qt}
( ),' ' φφ φ φ∂= − + −
∂ ∑ i u ii
w K Mz
Stratocumulus UP / DOWN
Bottom % of downdrafts that are explicitly modelled
PBL transports and clouds 11-2006 Martin Köhler 8
A statistical mass flux framework for organized eddies
Dry updraft
Cloudy updraft
Top % of updrafts that are explicitly modelled
K diffusion
{w, θl , qt}
( ),' ' φφ φ φ∂= − + −
∂ ∑ i u ii
w K Mz
Shallow Convection
Roel Neggers
PBL transports and clouds 11-2006 Martin Köhler 9
Stratocumulus UP: EPIC column from 3D forecasts
PBL transports and clouds 11-2006 Martin Köhler 10
ECMWF vs GLAS cloud fraction
ECMWF
GLASres: 76m
Maike AhlgrimmITCZ off ChileARM
SGP
PBL transports and clouds 11-2006 Martin Köhler 11
ECMWF vs GLAS cloud top height
SC top too low!
GLAS observations Sc topGLAS # of samples CC>80%
ECMWF Sc top (and base)ECMWF # of samples CC>80%
cloud top < 2km Maike Ahlgrimm
PBL transports and clouds 11-2006 Martin Köhler 12
stratocumulus organized eddies: DYCOMS-II LES simulation
up-draft
vertical velocity & cloudBjorn Stevens (dx=35m, dz=5m)
down-draft
PBL transports and clouds 11-2006 Martin Köhler 13
stratocumulus down-drafts: scaling arguments
3x zx
up
L L 10 su w
τ ∼ ∼ ∼
IRx
p entr
RT 1Kc z
τρ Δ
∼ ∼IR cooling:
parcel time scale:
mixing & IR cooling
zLupw downw
xτ
xL
1/3top*top
v iv
gw w ' ' z 1m / sθθ⎛ ⎞
= ⎜ ⎟⎝ ⎠
∼
PBL transports and clouds 11-2006 Martin Köhler 14
ΔT~0.5K
LES DYCOMS-II: mixing line scatterplot of qt and θl
Steve Krueger, LES, dz=6m
PBL transports and clouds 11-2006 Martin Köhler 15
CLW [g/kg]
LES DYCOMS-II: entrainment properties
w [m
/s]
Steve Krueger, LES, dz=6m
PBL air free troposphere air
PBL transports and clouds 11-2006 Martin Köhler 16
SCM DYCOMS-II: up- and down-drafts
0.6
0.4
0.2
CLW
[g/k
g]
Time [days]
Hei
ght [
m]
Cloud Boundaries
Cloud top
Cloud base DOWN
Cloud base UP
0.5
0.4
0.1
Time [days]
Hei
ght [
m]
Cloud Liquid Water
PBL transports and clouds 11-2006 Martin Köhler 17
EDMF @ ECMWF
• dry PBL• stratocumulus
– updraft– downdraft
• momentum• plume solution• shallow convection
– dual M– dual cloud
Roel
Martin
( )' ' φφ φ φ∂= − + −
∂ ∑ i uii
w K Mz
