could data assimilation be useful for cloud verification · 2009-08-28 · dtc verification...
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DTC Verification Workshop - Aug. 26~28, 2009, Boulder 1
Could Data Assimilation Be Usefulfor Cloud Verification?
Zhiquan Liu ([email protected])NCAR/MMM
With slides contributed from MMM and DATC colleagues
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 2
• Data assimilation process• DA linkage to verification• Potential extension for cloud verification• Synergy with MET
Outline
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 3
• Data assimilation process• DA linkage to verification• Potential extension for cloud verification• Synergy with MET
Outline
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 4
Data Assimilation:correct “background” with observations
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 5
Variational Data Assimilation:Incremental Formulation
J(!x) =1
2
T!x
"1B !x +
1
2[
TH!x " d] "1
R [H!x " d]
Find an optimal atmospheric state Xa by minimizing a cost function
!x = x - xb
(increment)
d = y ! H (xb)
(departure of obs minus background) in obs space (time, location, quantity)
Background in model space, often a short-term model forecast
Observation operator
Also called “innovation”, an important by-product from DA
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 6
H - Observation operatorH maps variables from “model space” to “observation space” x y
– Interpolations from model grids to observation locations– Extrapolations using PBL schemes– Time integration using full NWP models– Transformations of model variables (u, v, T, q, ps, etc.) to “indirect” observations (e.g.
satellite radiance, radar radial winds, etc.)• Simple relations like PW, radial wind, refractivity, …• Radar reflectivity
• Radiance: Radiative transfer models (CRTM, RTTOV)
• Precipitation using simple or complex models• …
Z = Z(T , IWC, LWC, RWC,SWC)
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 7
WRFDA Observations In-Situ:
- Surface (SYNOP, METAR, SHIP, BUOY).- Upper air (TEMP, PIBAL, AIREP, ACARS, TAMDAR).
• Remotely sensed retrievals:- Atmospheric Motion Vectors (geo/polar).- SATEM thickness.- Ground-based GPS Total Precipitable Water/Zenith Total Delay.- SSM/I oceanic surface wind speed and TPW.- Scatterometer oceanic surface winds.- Wind Profiler.- Radar radial velocities and reflectivities.- Satellite temperature/humidity/thickness profiles.- GPS refractivity (e.g. COSMIC).
Radiances (or Brightness Temperature):– HIRS from NOAA-16, NOAA-17, NOAA-18, METOP-2– AMSU-A from NOAA-15, NOAA-16, NOAA-18, EOS-Aqua, METOP-2– AMSU-B from NOAA-15, NOAA-16, NOAA-17– MHS from NOAA-18, METOP-2– AIRS from EOS-Aqua– SSMIS from DMSP-16– ……… many other instruments can be included.
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 8
• Data assimilation process• DA linkage to verification• Potential extension for cloud verification• Synergy with MET
Outline
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 9
MET Verification(point-stat)
Obs in prepbufr
pb2nc
Obs in netcdf
stat_analysispoint_stat
Get matched obs/fcstpairs and 71 continu-ous statistics value
Providing sum-mary statisticalinformation
Fcst in netcdf
WPP
Fcst in grib
pikc2ncl.f90
Pick up obs/fcstmatched pairsand BIAS, RMSE
NCLsctips
Figures for U,V, TMP, SPFH
Analysis/Forecast
X in NETCDF
Observations y
in prepbufr/ascii
WRF-VarInnovations
d = y - H(x)
Statistics &Visualization
WRFDA-based verification(vs. observations)
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 10
Advantages of DA-based Verification• Can make use of build-in QC procedure in DA system
– Obs QC is necessary before verification: reject outliers
• Can make use of built-in observation operators– particularly those for non-conventional data: radar, satellite radiances
• Calculation of OMF is parallelized for most DA system.
• Provide also offline statistics and visualization package– WRF-Var: BIAS, ABIAS, RMSE; profile and time series
Disadvantage of DA-based Verification• Only basic statistics provided
– It is not specially designed for verification, it is more like a by-product of DA.
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 11
Verification against NCEP prepbufr Obs.WRF-Var generated score MET generated score
U V
T Q
outlier
Obs outliers entered into the statistics
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 12
• Data assimilation process• DA linkage to verification• Potential extension for cloud verification
• Satellite Radiances: cloud & precip.• Limited vertical information
• CloudSat: vertical cloud information• Synergy with MET
Outline
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 13
Model cloud/rain and Synthetic SSMIS radiances affected by cloud/rain(use CRTM within WRF-Var)
Column-Integrated cloud water Column-Integrated rain water Radar Reflectivity
Simulated Ch2 Tbs Simulated Ch17 Tbs Scatter plots of observed v. calculated Tb
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 14------ OMB before bias correction------ OMB after bias correction
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 15
Tropical Storm Ernesto (2006/08/29)CloudSat path: 18:46:25 - 18:48:24
WRF 19h forecast (4km) from GFDL IC, valid at 2006-08-29-19Z.
Black line is CloudSat path
TPW
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 16
Doppler Radar Reflectivity (diagnosed from RIP)
WRF 4km Forecast at 19h
CloudSat Radar Reflectivity
Could have a better way to compare model cloud with CloudSat radar reflectivity
Use Radar Simulator “QuickBeam” (Haynes et al., 2007)as part of obs operator in DA system
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 17
• Data assimilation process• DA linkage to verification• Potential extension for cloud verification• Synergy with MET
• Make use of WRFDA’s capacity of calculating OMF,specially for Radar and Satellite radiances
• Combine with MET’s advanced statistics features(e.g., MODE)
• Use radiances from geostationary satellites• High time/spatial resolution
Outline
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 18
ECMWF: validate model from geostationaryimages: Forecasted Tbs: WV channel
• 42-hour forecast vs. observed
RTTOV computed Radiances
DTC Verification Workshop - Aug. 26~28, 2009, Boulder 19
Answer is YES!