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Treatment of S mall S cale Land S urface Heterogeneity for A tmospheric M odelling (SSSAM). Günther Heinemann (1) and Michael Kerschgens (2). 1 Meteorologisches Institut der Universität Bonn, Auf dem Hügel 20, 53121 Bonn - PowerPoint PPT Presentation
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Treatment of Small Scale Land Surface Heterogeneity for Atmospheric Modelling
(SSSAM)
Günther Heinemann (1) and Michael Kerschgens (2)
1 Meteorologisches Institut der Universität Bonn, Auf dem Hügel 20, 53121 Bonn2 Institut für Geophysik und Meteorologie der Universität zu Köln, Kerperner Str. 13, 50923 Köln
Regional Evaporation at Grid / Pixel Scale over Heterogeneous Land Surfaces
Effects of land surface heterogeneity on atmospheric transports
Landsat TM 50m (Statistisches Bundesamt, 1997)
False colours0.63-0.690.76-0.901.55-1.75μm
20 km
Measurement areaLindenberg experimentsLITFASS 1998-2003
°C
Scha
rmüt
zels
ee
FOOT 250m (20km, 80x80)
Isamp=2
F=FalkenbergL=LindenbergW=WulfersdorfH=HerzbergK=Forst Kehrigk
idealizedFOOT simulationLITFASS 199817 June, 11 UTC
Mesoscale and convective organized transports (dynamical transports) Feedback processes between dynamical transports and subgrid turbulence
Dynamical effect
Effects of land surface heterogeneity on atmospheric transports
Investigation of the dynamical effect and its role in the vertical energy- and momentum transport
Goals SSSAM
Development of averaging strategies for vertical transports on the scale of weather forecast and regional climate models (Grid / Pixel Scale)
Non-hydrostatic numerical model FOOT3DKparameterizations:Vegetation and soil moisture: ISBA, Noilhan and Planton (1989)turbulent fluxes: SL: Louis (1979)PBL: prognostic TKE closuresubsurface heat flux: 2 layer modelradiation (two-stream)moist convection (Tiedke, 1989, modified Sogalla and Kerschgens, 2001)
grid:Arakawa-C40x40, 80x800.25-48 km21-31 -levelsnon-hydrostatic
input data:initial fields: LM (7km)synthetic data
Idealized simulations for idealized inhomogeneities and for the Lindenberg area: T/q profiles for 17 June 1998, idealized geostrophic forcing
Realistic simulations for the Lindenberg area
LM 7km FOOT 1km FOOT 0.25km
u, v, w, T, q, p, ug, vg
CLW, RRSoil: type, T, W
u, v, w, T, q, p, ug, vg
CLW, RRSoil: type, T, W
Treatment of heterogeneity effects for surface energy fluxes
w a k T V q za a
zL Sa eff' ' , , ,
( )
,,
00
0
Mahrt (1996) w a C V w V a a za e ff fc sg' ' ( ) ( ),
0
2 2 2
1 / 2
0
u v V sg
* *2 2 2 subgrid velocity scalewfc=w*= convection velocity scale
Ca,eff = effective exchange coefficient (e.g. from effective z0)
Mosaic method w aN
k T T V q q za a
zm o s aF x
' ' , , ,,0 0 0 0
01
w a k T V w q za a
zL S wa eff' ' , , ,
( )
, , ** ,
0
22
1 / 2
0
0
Standard mosaic method: T0, q0, a0 from 1D-SVAT model
‘Optimal‘ mosaic method: T0, q0, a0 from sub-grid model
Aggregation method
Aggregation methodmodified with w*
250m, LC = 4 km, Vg = 2 m/s, Fx = 12km
3 6 9 12 15 18 21
U TC
0
100
200
300
H0
,E0
in W
/m²
H0
H0,LS
H0,LS,w*
H0,LS m os
E0
E0,LS
E0,LS,w*
E0,LS m os
Idealized simulations meadow/bare soil
3 6 9 12 15 18 21
U TC
0
100
200
300
H0
,E0
in W
/m²
H0
H0,LS
H0,LS,w*
H0,LS m os
E0
E0,LS
E0,LS,w*
E0,LS m os
250m, LC = 4 km, Vg = 8 m/s, Fx = 12km
3 6 9 12 15 18 21
U TC
0
100
200
300
H0
,E0
in W
/m²
H0
H0,LS
H0,LS,w*
H0,LS m os
E0
E0,LS
E0,LS,w*
E0,LS m os
1 km, LC = 16 km, Vg = 2 m/s, Fx = 48km
3 6 9 12 15 18 21
U TC
0.8
1
1.2
1.4
Ra
tio
1km vg2 ratio sim /mosaic
LC1LC2LC4LC8LC16
3 6 9 12 15 18 21
U TC
0
100
200
300
H0
,E0
in W
/m²
H0
H0,LS
H0,LS,w*
H0,LS m os
E0
E0,LS
E0,LS,w*
E0,LS m os
250 m, LITFASS, Vg = 2 m/s, Fx = 12km, W = 60%
Idealized simulations LITFASS area
Realistic simulations LITFASS area 17 June 1998, nesting LM7
250 m, LITFASS, vg(LM)≈14 m/s , Fx = 12km, W = W(LM)
3 6 9 12 15 18 21
U TC
0
100
200
300
H0
,E0
in W
/m²
H0
H0,LS
H0,LS,w*
H0,LS m os
E0
E0,LS
E0,LS,w*
E0,LS m os
3 6 9 12 15 18 21
U TC
0
1
2
3
TK
E in
m²/
s²
250m_vg2_nes1km_12.km*12.km(48*48)
SKE
TKE
Idealized simulations LITFASS area
a a a a * ' T K E u i 1
22' S K E u i
1
2
2*
Subgrid and mesoscale TKE
3 6 9 12 15 18 21
U TC
0
1
2
3T
KE
in m
²/s
²
250m_n1km_litfass98_12.km*12.km(48*48)
SKE
TKE
Realistic simulations LITFASS area 17 June 1998, nesting LM7
TKE/SKE at 30m
vg(LM)≈14 m/s , Fx = 12 kmVg = 2 m/s, Fx = 12km
Non-linear effects for area-averaged surface fluxes
Q H E Bo 0 0 0
Energy balance
Q0H0
Q: net radiationE: latent heat fluxH: sensible heat fluxB: soil heat flux
E0
B0
Q H E Bo 0 0 0
w a ka
za' '0
B k WT
zSS
0 ( )
Q T q z N z0 0 , ( ( )), ( ), ...
1D Area average
Dependence on averaging scale
0 4 8 12
A veraging scale km
100
150
200
250
300
H0
,E0
in W
/m²
H0
H0,LS
H0,LS,w*
H0,mos
E0
E0,LS
E0,LS,w*
E0,mos
250m_n1km_litfass98
Realistic simulations LITFASS area 17 June 1998, nesting LM7
Average 9-17 UTC
250 m, LITFASS, vg(LM)≈14 m/s, W = W(LM)
0 4 8 12
A veraging scale km
100
150
200
250
300
H0
,E0
in W
/m²
H0
H0,LS
H0,LS,w*
H0,mos
E0
E0,LS
E0,LS,w*
E0,mos
250m_vg2_nes1km
Idealized simulations LITFASS area
Average 9-17 UTC
250 m, LITFASS, Vg = 2 m/s, W = 60%
H in W/m² H in W/m²
Idealized simulations LITFASS area
250 m, Fx = 2 km, vg=2 m/s250 m, Fx = 250 m, vg=2 m/s
250 m, Fx = 2 km, vg=2 m/s250 m, Fx = 2 km, vg=2 m/s
H0-H0,mosa in W/m²E0-E0,mosa in W/m²
Variance ff(30m) in m²/s²Variance T(0m) in K²
Summary
Method: FOOT3DK simulations (resolution down to 250m)idealized and realistic surfaces and synoptic forcings (LITFASS98)
Assessment of the dynamic effect for averaging methods (mosaic and aggregation) for scales of 10-20 km- dependence on the scale/structure of the heterogeneity- mosaic method yields good results for wind speeds exceeding 4 m/s
Scale dependence of area-averaged surface fluxes caused by non-linear effects- sub-grid TKE (SKE)- radiation and clouds- surface temperature and soil moisture
Outlook
LindenbergexperimentLITFASS 2003
EC
Profiles
Precip.
Precip./G
Scintillometer