grid scale parameterization of topographic effects on radiation
DESCRIPTION
Grid scale parameterization of topographic effects on radiation. Matteo Buzzi, Mathias W. Rotach and Marco Arpagaus MeteoS wiss. Overview. Introduction The topographic problem General aspects Topographic parameters Parameterization scheme Corrections factors - PowerPoint PPT PresentationTRANSCRIPT
aLMo
Grid scale parameterization of topographic effects on radiation
Matteo Buzzi, Mathias W. Rotach and Marco Arpagaus
MeteoSwiss
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
aLMoOverview
Introduction The topographic problemGeneral aspects
Topographic parametersParameterization scheme
Corrections factorsCorrected surface radiation components
Case studiesSummary, conclusions and outlook
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
aLMoThe problem: shortwave radiation
.
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
aLMoThe problem: thermal downward radiation
T 4eff
T 4slopeT 4
slope
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
55
aLMoIntroduction
NWP mesoscale models resolution tends to the order of magnitude of 1 km: topographic effects become important
Topographic shadowing (horizon, sun elevation)Slope angleSlope aspectSky view (horizon)
aLMo radiation scheme (Ritter and Geleyn,1992): surface radiation is computed on horizontal surfaces, topographic effects are not consideredIdea: try a simple approach with correction factors for surface radiation components Müller and Scherrer (2005)
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
56
aLMoOverview
The topographic problem IntroductionTopographic parametersParameterization scheme
Corrections factorsCorrected surface radiation components
Case studiesSummary, conclusions and outlook
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
57
aLMoTopographic parameters: slope aspect (7 km)
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
58
aLMoTopographic parameters: slope aspect (2 km)
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
59
aLMoTopographic parameters: slope angle (7 km)
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
0
aLMoTopographic parameters: slope angle (2 km)
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
1
aLMoOverview
The topographic problemIntroductionTopographic parametersParameterization scheme
Correction factorsCorrected surface radiation components
Case studiesSummary, conclusions and outlook
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
2
aLMoSky view factor: 7 km
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
3
aLMoSky view factor: 2 km
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
4
aLMoCorrection factor for direct radiation
2004-12-11 08 UTC (7 km)
radiation on horizontal surface radiation on inclined and oriented surface
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
5
aLMoCorrection factor for direct radiation
2004-12-11 08 UTC (2 km)
Shadowing NW slope
SE slope increased radiation
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
6
aLMoCorrection factor for direct radiation
2004-12-11 12 UTC (7 km)
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
7
aLMoCorrection factor for direct radiation
2004-12-11 12 UTC (2 km)
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
8
aLMoCorrection factor for direct radiation
2004-12-11 15 UTC (7 km)
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
51
9
aLMoCorrection factor for direct radiation
2004-12-11 15 UTC (2 km)
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
0
aLMoDirect solar radiation
angleazimuthsun
aspectslope
angleelevationsun
angleslope
maskfcor
S
N
S
N
NSS
Nshadow
:
:
:
:
)cos(tantan
1
φφθθ
φφθθ
⎟⎠
⎞⎜⎝
⎛−⋅+=
Müller and Scherrer (2005)
dirdir SWfcorSW ↓↓ ⋅=*
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
1
aLMoDiffuse downwelling solar radiation
factorviewskyf
fSWfSWSW
sky
skydiffskydiffdiff
:
)1(* −⋅+⋅= ↑↓↓
Müller and Scherrer (2005)
factorviewskyf
anglehorizon
f
sky
h
jjhsky
:
:
)sin(1241 23
015,
θ
θ ⎟⎟⎠
⎞⎜⎜⎝
⎛−= ∑
=°⋅
Assumptions: Diffuse downwelling radiation considered isotropic Adjacent areas have the same upwelling diffuse radiation
Reduced sky view
Reflections by adjacent areas
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
2
aLMoThermal downwelling radiation
factorviewskyf
facfLWfLWLW
sky
skysky
:
)1(* ⋅−⋅+⋅= ↑↓↓
Modified from Müller and Scherrer (2005)
factorviewskyf
anglehorizon
f
sky
h
jjhsky
:
:
)sin(1241 23
015,
θ
θ ⎟⎟⎠
⎞⎜⎜⎝
⎛−= ∑
=°⋅
Assumptions: fac = ratio of the upwelling thermal radiation of a grid-point
and its adjacent points (at higher elevation): considers a horizontal length scale (7 or 4 km), a mean slope angle (sky view) and a mean vertical temperature lapse rate (6.5°C/1000m)
Reduced sky view
Radiation from adjacent areas
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
3
aLMoOverview
IntroductionTopographic parametersParameterization scheme
Correction factorsCorrected surface radiation components
Case studies2004-12-11: aLMo 3.15, 7 km and 2 km2003-06-22: aLMo 3.15, 7 km and 2 km
Summary, conclusions and outlook
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
4
aLMoResults: 7 km, 2004-12-11 00 UTC +09
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
5
aLMoResults: 7 km, 2004-12-11 00 UTC +12
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
6
aLMoResults: 7 km, 2004-12-11, grid-point
controlcorrected
Correction factor NET solar radiation
Surface temperature Sensible heat flux at the surface
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
7
aLMoResults: 7 km, 2004-12-11, grid-point
controlcorrected
Correction factor NET solar radiation
Surface temperature Snow amount
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
8
aLMoResults: 2 km, 2004-12-11 00 UTC +09
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
52
9
aLMoResults: 2 km, 2004-12-11 00 UTC +12
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
0
aLMoResults: 2 km, 2004-12-11 00 UTC +14
Total cloud cover difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
1
aLMoResults: 2 km, 2004-12-11 00 UTC +12
10 m wind vectors difference
controlcorrected
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
2
aLMoResults: 7 km, 2003-06-22 00 UTC +08
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
3
aLMoResults: 7 km, 2003-06-22 00 UTC +12
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
4
aLMoResults: 2 km, 2003-06-22 00 UTC +08
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
5
aLMoResults: 2 km, 2003-06-22 00 UTC +12
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
6
aLMoResults: 2 km, 2003-06-22 00 UTC +12
Total cloud cover difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
7
aLMoResults: 2 km, 2003-06-22 00 UTC +14
Total cloud cover difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
8
aLMoOverview
IntroductionTopographic parametersParameterization scheme
Correction factorsCorrected surface radiation components
Case studiesSummary, conclusions and outlook
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
53
9
aLMoSummary and conclusions
The Müller and Scherrer (2005) scheme for topographic effects on radiation has been implemented into the aLMoSome sensitivity case studies have been carried outThe impact of the topographic effects (shadowing, slope angle, slope aspect and sky view) is substantial at high resolution Some significant indirect impacts (feedbacks) even at 7km: related to snow melt, stability (turbulence) and low cloudsHigher impact during the winter time due to sun elevation and snow conditionsSignificant secondary effects on clouds cover at 2kmSurface thermal changes at high resolution have also secondary effects on thermal circulation
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
0
aLMoOutlook
Next step: systematic validation with observationsExtension of the domain to the entire aLMo operational domain (7 km and 2 km) and start test suiteCompare implementation results with the sub-grid-scale version of the Müller and Scherrer (2005) scheme (differences in preprocessor)Indirect effects (feedbacks) on clouds and stability (turbulence) have to be further investigatedHow to solve the problem of clouds at high resolution?
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
2
aLMoImplementation into the LM
Preprocessor: prior to model integrationComputes corrections factors (time dipendent) + sky view factor (time indipendent) and save results in binary file
LM reads the correction factors (parallelized)Corrections take place in the fesft.incf radiation subroutine
In spectral loop for solar radiation (direct and diffuse)After the spectral loop for thermal radiation: the two components (up and down) have to be recomputed from the thermal radiation balance, corrected and added to a new radiation balance
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
3
aLMoTopography: 7 km
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
4
aLMoTopography: 2 km
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
5
aLMoThe problem: clouds at high resolution
Reality: cloud cover
Model: no cloud cover
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
6
aLMoResults: 2 km, 2003-06-22 00 UTC +12
10 m wind vectors difference
controlcorrected
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
7
aLMoResults: 2 km, 2004-12-11 00 UTC +12
Total cloud cover difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
8
aLMoResults: 7 km, 2003-06-22 00 UTC +14
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
54
9
aLMoResults: 7 km, 2004-12-11 00 UTC +15
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
55
0
aLMoResults: 7 km, 2003-08-07 00 UTC +15
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
55
1
aLMoResults: 2 km, 2004-12-11 00 UTC +14
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
55
2
aLMoResults: 7 km, 2003-08-07 00 UTC +08
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
55
3
aLMoResults: 7 km, 2003-08-07 00 UTC +12
Surface temperature difference
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
55
4
aLMoResults: 7 km, 2003-08-07 00 UTC +12
Total cloud cover
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
55
5
aLMoResults: 2 km, 2004-12-11 00 UTC +12 Wind speed difference ctrlcorr
Matt
eo.b
uzz
i@M
ete
oS
wis
s.c
hC
OS
MO
Meeti
ng
, W
G 3
, 2
0.0
9.2
00
55
6
aLMoThe problem: shortwave radiation (1)
.