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Application of an adaptive radiative transfer parameterisation
in a mesoscale numerical weather prediction model
DWD Extramural research
Annika Schomburg1) , Victor Venema1), Felix Ament2), Clemens Simmer1)
1) Department of Meteorology, University of Bonn, Germany
2) University of Hamburg
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #2
Outline
• The adaptive radiative transfer scheme– General idea– Implementation
• Results– 3in1 runs– Single runs– Preliminary new result
• Outlook
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #3
Adaptive parameterizations
• Accurate parameterization– Process-based– Computationally expensive
• Fast parameterization– Less processes (statistical)– Typically: biased
• Adaptive scheme– Combine: accurate and fast parametrization– Accurate one corrects biases of fast one
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #4
Adaptive RT: Spatial scheme
• Uses spatial correlations• Update every 2.5 minutes
one out of 5x5 columns• For other 24 columns: search
for similar column in the vicinity (search region 5x5 pixels)
• Similarity index to be minimised:
dwtwwIWVwLWPwCCTwCCLw 7654321
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #5
Implemented in COSMO 4.0
• Adaptive scheme– Called every 2.5 minutes
• Reference high-resolution – δ-two-stream approximation (Ritter & Geleyn)– Full field computed every 2.5 min
• Comparison– Coarse-scheme COSMO-DE (2x2 columns)– Called every 15 minutes
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #6
Diurnal cycle error net fluxB
ias
SW LW
RM
SD
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #7
Diurnal cycle error heating ratesB
ias
SW LW
RM
SD
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #8
Error height profile heating ratesB
ias
SW LW
RM
SD
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #9
Scale dependent errors
Surface net flux Atmospheric heating rate
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #10
Errors net flux for COSMO-EU
SW LW
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #11
Physical consistency: LWP
SW LW
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #12
Consistency: diurnal cycle
SW LW
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #13
Spread single runs
Total precipitation 2m-TemperatureSurface pressure
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #14
Selection column accurate computation
• Optimized pattern: as before in this talk• Global difference: largest difference in full field• Local difference: largest difference in 5x5 regions• Spiral pattern: regular pattern, close togetherPreliminary new results
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #15
Conclusions
• Adaptive radiative transfer makes computations more accurate (or efficient)
• Employs spatial and temporal correlations in atmosphere
in error fields of simplified computations
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #16
Outlook
• Develop a temporal spatial adaptive scheme– Improve our results for heating rates
• Question: what is a good error measure?– Bias & RMSD– Scales (temporal, spatial)– Locations (layers, regions)– Heating rates, fluxes & PAR
• Other parameterizations– Surface module (looking for 2 PhD students)– Aerosols, etc.
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #17
References
Schomburg, A., V. Venema, F. Ament, and C. Simmer. Application of an adaptive radiative transfer scheme in a mesoscale numerical weather prediction model. Quarterly Journal of the Royal Meteorological Society, accepted 2011.
Venema, V.K.C., A. Schomburg, F. Ament, and C. Simmer. Two adaptive radiative transfer schemes for numerical weather prediction models. Atmospheric Chemistry and Physics, 7, 5659-5674, doi: 10.5194/acp-7-5659-2007, 2007.
Download:
http://www2.meteo.uni-bonn.de/venema/articles/
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #18
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #19
(a) (b) (c)
(d) (e) (f)
(g)Bias: 5 W m-2RMS: 77 W m-2
(h)Bias: 6 W m-2RMS: 43 W m-2
(i)Bias: 2 W m-2RMS: 31 W m-2
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Errors in the solar heating rates (W m-2) in the LM at the surface for 12.30 h UTC. (a) The two-stream calculation of the solar surface flux is the reference field(b) Cloud cover of low clouds (c) Total cloud cover (d) the 1-h persistence assumption, (e) the adaptive perturbation scheme, (f) the adaptive search scheme. The corresponding errors are shown in the same order in the third row.
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #20
The Idea: Adaptive parameterisation
calculate error-estimator based on
a simple radiation scheme for
each grid point
Grid points where…
…Δ ‘large‘
…Δ ‘small‘
Apply „perturbation method“
for surface fluxes
Recalculate radiation
fluxes with exactscheme
Perturbation method:
)()(
)()(
tFttFF
FtFttFsimplesimplesimple
simple
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #21
RMSE perturbation methods
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #22
Approach
• Simple radiation scheme:
→ Multivariate linear regression
• Predictands:
– longwave:
– shortwave: transmissivity:
• Distinction of 4 categories,
with different sets of predictors:
surL
ec
solarcloud free
infraredcloud free
solarcloudy
infraredcloudy
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #23
Simple radiation scheme
Cloudfree Cloudy
Cosine of solar zenith angle LWP
IWV CLCL
Surface pressure CLCT
Continental aerosols Cosine of solar zenith angle
Cloud thickness
IWV
Temperature at cloud base
Predictors: SOLAR
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #24
Simple radiation scheme:
Cloudfree Cloudy
IWV IWV
Surface temperature Temperature at cloud base
Cosine of zenith angle Surface temperature
CLCT
Cloud thickness
CLCL
Cosine of zenith angle
LWP
Predictors INFRARED
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #25
Approach
Implementation of adaptive scheme into LM – First tests and configuration on PC
(small model domain) – After successfull implementation:
exemplary cases on LMK-domain on parallel machine at DWD
• Horizontal resolution: 2.8 km• Frequency of call to adaptive
scheme: 2.5 min
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #26
Approach
• Problem: Radiation of 3 separate model runs not comparable due to different evolution of cloud field → Development of a model version „3 in 1“:– Calculation of the radiation fluxes
• hourly• adaptive• frequently (every 2.5 min)
... in the same model run– Dynamics only influenced by frequent radiation
• Test for 3 summer days characterised with much
convection
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #27
Correlation lengths for error fields (15:30 UTC)
The covariance functions of the errors in the solar (a) and infrared (b) fluxes at the surface.
Hourly
Adaptive
Hourly
Adaptive
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #28
Instantaneous RMSE
with adaptive scheme smoother error curves
21June 2004
Victor Venema, [email protected], COSMO General meeting, Rome, 5th September 2011, #29
Smoother developing of model variables with time
Adaptive approach prevents „wavy“ structure of developing of variables with time
Surface temperature
21 June 2004