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Introduction to KENDA as COSMO Priority Project. Christoph Schraff Deutscher Wetterdienst, D-63067 Offenbach, Germany. KENDA : Km-scale ENsemble-based Data Assimilation. Motivation, implementation, status Current & future work. - PowerPoint PPT Presentation
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[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014 1
Introduction to KENDA as COSMO Priority Project
Christoph Schraff
Deutscher Wetterdienst, D-63067 Offenbach, Germany
• Motivation, implementation, status
• Current & future work
KENDA: Km-scale ENsemble-based Data Assimilation
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014
ensemble-based data assimilation component missing & required
convection-permitting NWP: after ‘few’ hours, a forecast of convection is a long-term forecast deliver probabilistic (pdf) rather than deterministic forecast need ensemble forecast and data assimilation system
(strategic aims in COSMO)
forecast component: COSMO-DE EPS developed & operational at DWD
perturbations: LBC + IC + physics
GME, IFS, GFS, GSM
perturb.
Motivation : Why develop Ensemble-Based Data Assimilation ?
replace current nudging-based DA by state-of-the-art DA with flow-dependent B
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014 3
GermanyGreece
ItalyPoland
RomaniaRussia
Switzerland
similar
configurationsx = 1 – 3 km ~ 2016 : x 2 km , LETKF
Local Ensemble Transform Kalman Filter (LETKF, Hunt et al., 2007) ,(because of its relatively low computational costs)
Motivation : Why develop Ensemble-Based Data Assimilation ?
data assimilation: priority project within COSMO consortium
Km-scale ENsemble-based Data Assimilation (KENDA):
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014
• analysis step (LETKF) outside COSMO code ensemble of COSMO runs, collecting obs – f.g. 4D -LETKF separate analysis step code, LETKF included in 3DVAR package of DWD
LETKF (km-scale COSMO) :implementation
ensemble
K
deterministic
• analysis for a deterministic forecast run : use Kalman Gain K of analysis mean
deterministic run must use same set of observations as the ensemble system ! deterministic run may have higher resolution (not optimal if deterministic f.g. deviates strongly from ensemble mean f.g.)
xA = xB + K [yo – H(xB)]
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014
• CNMCA (Lucio Torrisi Lucio Torrisi et al.) : LETKF for 10-km COSMO operational
• perturbed lateral BC : IFS EPS (MCH, ARPA-SIM)
Lateral BC /other LETKF implementations
lower resolution analysis
ensemble (40 members)
high resolution deterministic
analysis
(or at DWD) hybrid EnVar for ICON (GME)variational formulation
(Buehner et al 2005)
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014
main development of LETKF at DWD (Hendrik Reich Hendrik Reich , Andreas Rhodin),main implemented features:
•adaptive multiplicative covariance inflation (based on Desroziers statistics)
•adaptive estimation of obs errors in obs space
•adaptive estimation of obs errors in ensemble space (to account for limited Nens)
•adaptive localisation to keep effective Nobs constant (to account for limited Nens)
•multi-step analysis
implementation of LETKF featuresin KENDA
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014
• DWD:
stand-alone scripts for 2-day period: many LETKF tests, e.g. adaptive methods
LETKF in operational experimentation system NUMEX slow (archive)
‘BACY’ (basic cycling scripting environment for KENDA, Hendrik ReichHendrik Reich):
• fast (speed: DA with BACY ~ 1 – 2, i.e. ~ 5 – 10 times faster than with NUMEX)
• largely portable (if obs / GME fields provided)
• automatic plotting suite
• model equivalent calculation (MEC) from forecasts for input to verification potential: tool to ease collaboration with academia
• scripting environments for LETKF DA cycle also at
MeteoSwiss: 1-hourly LETKF DA cycle for 1 month using conventional obs
ARPA-SIM: first tests, setting up OSSE (Chiara MarsigliChiara Marsigli)
implementation & LETKF tests(so far using TEMP, aircraft, surface, wind profiler)
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014
Main aim: reach operationability in (mid/end) 2015
•system complete (e.g. ana + perturb surface / soil) + robust + efficient
•quality KENDA ≥ quality nudging-based opr. DA (incl. LHN) (deterministic)(using similar obs set)
•additional: provide IC perturbations for EPS
evaluation of EPS:
•EPS: how to use KENDA IC perturbations for EPS (COSMO-DE-EPS) (PP COTEKINO / Richard KeaneRichard Keane, DWD) replace or rather combine with current IC perturbations
HErZ LMU: structure & impact of KENDA IC perturbations (Florian HarnischFlorian Harnisch)
•Diagnostics: FSO (forecast sensitivity of observations) (Matthias SommerMatthias Sommer, LMU)
KENDA : main short-term goal
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014 9
KENDA : short-term tasks
• general testing, tuning, optimization of LETKF setup
specification of observation errors
use of adaptive methods (localisation, cov. inflation, R in ensemble space),
multi-step and multi-scale analysis with different obs / localisation scales
ensemble size (40 ?),
update frequency at ? RUC 1 hr at 15 min ! (high-res. obs)
non-linearity vs. noise / lack of spread / 4D property ?• inclusion of additive covariance inflation,
probably using self-evolving perturbations (Lucio TorrisiLucio Torrisi, CNMCA)
• testing SPPT in DA cycle, possibly also perturbed physics parameters
• inclusion of LHN (latent heat nudging) (as long as reflectivity not ready for use)
• robustness: create new ensemble members, if few crash
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014 10
Extended Use of Observations (1)
Aim: (implementation,) forecast improvements from using these observations
•3D radar radial velocityComplete obs operator and efficient approximations suitable for DA developed,thinning and superobbing strategies implemented, preliminary DA cycles
Yuefei Zeng, Uli Blahak Yuefei Zeng, Uli Blahak (DWD)(Status of Y. Zeng after June 2014 or other resources at DWD unclear)
•3D radar reflectivity (direct use)Complete obs operator and efficient approximations suitable for DA developed,thinning and superobbing strategies implemented, preliminary DA cycles
Virginia Poli, Tiziana Paccagnella Virginia Poli, Tiziana Paccagnella (ARPA-SIM); Klaus Stephan Klaus Stephan (DWD), Theresa Bick Theresa Bick (U. Bonn)
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014 11
Extended Use of Observations (2)
• GPS Slant Path DelayObs operators (incl. ray tracer) implemented in DWD global 3DVar;Aim: implement complete and efficient obs operator in COSMO by end of 2014
Michael Bender ; Erdem Altunac Michael Bender ; Erdem Altunac (tomography) (DWD)No resources available yet after 2014 for use in LETKF(challenge to use horizontally + vertically non-local obs in LETKF)
• Cloud Top Height (CTH) derived from Meteosat SEVIRI Fully implemented, single-obs experiments, cycled DA with dense obs for low-stratus cases
Annika Schomburg Annika Schomburg (DWD, talk on Monday)
• Direct use of SEVIRI IR window channels in view of assimilating cloud infoObs operator (RTTOV) + data flow implemented, next monitoring + DA tests
Africa Perianez Africa Perianez , DWD, until Feb. 2015, no resources yet thereafter
• Exploratory: SEVIRI VIS/NIR window channels (Leonhard ScheckLeonhard Scheck. LMU)
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014 12
Extended Use of Observations (3) :Future
• Mode-S (high-resolution) wind and temperature data (from aircraft)and application to high-res airport model COSMO-MUC (with radar data)Heiner Lange, Tijana Janjic-Pfander Heiner Lange, Tijana Janjic-Pfander (HErZ LMU)
• Screen-level observations (T-2m, q-2m, uv-10m) (C. Schraff, DWD) (+ Master Thesis at MeteoSwiss on station selection)
• Direct use of SEVIRI WV channels (for T, qv; for cloud info; linked to IR window)Great interest by HErZ-LMU for a project, starting 2015
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014 13
thank you for your attention
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• implementation following Hunt et al., 2007
• basic idea: perform analysis in the space of the ensemble perturbations
– computationally efficient, but also restricts corrections to subspace spanned by the
ensemble
– explicit localization (doing separate analysis at every grid point,
select only obs in vicinity and scale R-1)
– analysis ensemble members are locally linear combinationsof first guess ensemble members
LETKF for km-scale COSMO :method
analysis membersforecastmembers
[email protected] to KENDAKENDA Mini-Workshop., Munich, 28 Feb. 2014 15
KENDA : Analysis & Perturbation of Lower Boundary Fields
• Snow cover and depth, idea:apply snow analysis independently to ensemble members (with perturbed obs ?)
• Sea surface temperature (SST), idea: add perturbations to deterministic analysis
• Soil moisture (soil temperature) perturbations only: as in EPS (COTEKINO)
Longer-term additional tasks
•Soil moisture (soil temperature) analysis, by using screen-level obs ; 2 ideas: add 1 analysis level in LETKF for the soil, and
apply strong localization for calculating the transform matrix for this level use the ensemble in current stand-alone variational SMA (perturbations ?)
•Soil moisture analysis (+ perturbations) using satellite soil moisture data in LETKFEumetsat fellowship at CNMCA