UM 4D-Var Regional Reanalysis
Progress
Richard Renshaw, Stephen Oxley, Adam Maycock, Peter Jermey,
Dale Barker, DingMin Li
© Crown copyright Met Office
Contents
Progress with technical work
First attempt at reanalysis
Developments for 2012/13
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WP2.1 Building capacity for advanced
regional data assimilation
Set up and demonstrate an advanced regional
reanalysis system
Based on operational North Atlantic/Europe LAM
Planning to analyse 2010 & 2011
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MetO Regional Reanalysis:
Horizontal Domain
12km grid
480 x 384
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Technical work
Build a reanalysis system
• to run at ECMWF
• taking observations,
start file,
boundary conditions
from ECMWF archives
• storing analyses in ECMWF archives
• and producing data to validate the reanalysis.
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ECMWF
“interface”
Met Office
Running at
ECMWF
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Technical Highlights
• Set up Met Office systems on ECMWF IBM
• Use observations from mars (ECMWF BUFR format)
• Preprocess satellite radiances
• reconstruct level 1b files from BUFR data
• convert level 1b counts to level 1c radiances (AAPP)
• map between instrument grids (e.g. AMSU+MHS to IASI)
• Convert and map ERA-Interim GRIB files to UM file
format, for start files and boundary conditions
• Use ‘CYLC’ to develop and run a reanalysis suite
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CYLC: Scheduling System
CYLC, written by Hilary Oliver (NIWA)
http://hjoliver.github.com/cylc/
+
ROSE – adds interfaces and
configuration management
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Why CYLC ?
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Will replace ageing Met Office system
Can build, run, monitor suites of any complexity
Portable – Open source
Flexible
Intelligent job scheduling
- define dependencies for each task
- tasks will run early if possible
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sample CYLC suite
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Dale’s challenge
Regional
reanalysis
- why bother ??!
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Evidence from operational NWP
25km Global
vs
12km NAE
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...the benefits of resolution
global 25km
NAE 12km
screen
temperature
rms error (K)
forecast range
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...and the disadvantage of boundaries!
NAE
global
mean sea
level pressure
rms error (Pa)
forecast range
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ERA-Interim vs 12km EURO4M
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T255 (80km), 60 levels
T159 (125km) 4D-Var
12-hour analysis window
assimilate:
• conventional obs
• satellite radiances
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12km, 70 levels
36km 4D-Var
6-hour analysis window
assimilate:
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conventional obs incl vis
satellite radiances
Ground-based GPS
Cloud
Precipitation
• Initial state and boundary
conditions from ERAInterim analyses
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model
orography
ERA-Interim
Model T255 (80km)
Var T159 (125km)
Met Office
Model 12km
Var 36km
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First attempt at reanalysis...
• Floods in Poland,
eastern Europe
May 2010
June 2010
• Severe storms
France/Spain
July 2010
• Russian heatwave
spreading West,
forest fires
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Poland floods, 16th May 2010
e-obs
gridded
24hr
rainfall
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http://eca.knmi.nl/
Poland floods, 16th May 2010
radar
24hr
rainfall
Czech Hydrometeorological Institute
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Poland floods, 16th May 2010
e-obs
12km reanalysis
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Poland floods, 16th May 2010
e-obs
ERA-Interim
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Russian heatwave, July 2010
e-obs
Tmax, 10-07-2010
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ERA-Interim
obs
12km EURO4M
Tmax
10-07-10
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Verification vs Radiosonde
Temperature rms error
T+0
T+6
ERA-Interim
EURO4M 12km
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Verification vs Radiosonde
Vector wind rms error
T+0
T+6
ERA-Interim
EURO4M 12km
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Developments for 2012/13
• Variational bias correction
• ODB – obs monitoring
• Extend observations dataset
• Cloud and Precipitation assimilation
• Validation – extreme statistics
• Collaborate on cross-validation
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Variational Bias Correction
Airmass-dependent bias correction of satellite radiances
(based on Harris and Kelly, 2001)
bias  c
n
scan
  ci air f ( xb )
i 1
Currently coeffs c are calculated off-line monthly
VarBC will give smooth and automatic updating
Work is underway – finish in 2012
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(DingMin Li, Dale Barker, Andrew Lorenc)
ODB – obs monitoring database
• Established ECMWF database + utilities
• Array of tools available “for free”
• Metview macros (quick look)
• Obstat (detailed stats / graphics)
• Replaces several diverse monitoring tools at MO
• Joint development
• Currently ~1.5 years into 3 year joint funded post at
ECMWF (Peter Kuchta)
• Setting up Obstat at MO
• Other NMSs already using ODB (CAWCR, KMA)
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Extend observations dataset
• Work with UEA (WP2.5) to extend surface
and sonde datasets
• Seeking sub-daily raingauge data...
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Cloud + Precip assimilation
• Operational UK models assimilate cloud products
(satellite) and rainfall (radar, latent heat nudging)
• For EURO4M, plan to assimilate cloud reports and
raingauge accumulations from surface stations
• Needs development work (2012/13):
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source sub-daily raingauge accumulations
decode and interpret surface reports (Peter Francis)
quality control
assimilate rainfall accumulations in 4D-Var
reduce effect that analysis increments trigger rain in model
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Validation - Extremes
• High impact weather
• Should show a benefit for regional reanalysis
• Focus on:
• precipitation
• temperature
• winds
• Need to look at probability distributions (pdf’s), e.g.
• number of values outside 10th/90th percentile
• count consecutive days with high/low values
• accumulated precipitation over several days
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Collaboration – Cross-Validation
Compare our reanalysis against:
• SMHI
• ERA
• Obs climatologies
• Others ?
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Summary
• Reanalysis system ready to run
• Already better than ERA-Interim in some features,
but not all (yet!)
• Science development and testing this year
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Questions ?
With thanks to:
Tom Green, Nigel Atkinson, Sreerekha Tr, others...
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Extra slides...
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First attempt at reanalysis...
May 2010
June 2010
July 2010
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• 3 x 1 month runs, with overlap
How long to spin up ?
rms
surface
pressure
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How long to spin up ?
rms screen
temperature
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Impact of Var resolution
12km 4D-Var
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100km 4D-Var
Verification vs Radiosonde
Relative Humidity rms error
T+0
T+6
ERA-Interim
EURO4M 12km
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Global ODB trial output
NH Surface T mean (o-b)
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