UM 4D-Var Regional Reanalysis Progress

© Crown copyright Met Office

UM 4D-Var Regional Reanalysis ProgressRichard Renshaw, Stephen Oxley, Adam Maycock, Peter Jermey,

Dale Barker, DingMin Li


Contents

Progress with technical work

First attempt at reanalysis

Developments for 2012/13


Set up and demonstrate an advanced regional reanalysis system

Based on operational North Atlantic/Europe LAM

Planning to analyse 2010 & 2011

WP2.1 Building capacity for advanced regional data assimilation


12km grid

480 x 384

MetO Regional Reanalysis: Horizontal Domain


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.


Running atECMWF

ECMWF

“interface”

Met Office


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


CYLC: Scheduling System

CYLC, written by Hilary Oliver (NIWA)http://hjoliver.github.com/cylc/

+ROSE – adds interfaces and configuration management

http://hjoliver.github.com/cylc/


Why CYLC ?

• 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


sample CYLC suite


Dale’s challenge

Regional reanalysis - why bother ??!


Evidence from operational NWP

25km Global

vs

12km NAE


...the benefits of resolution

forecast range

screen temperature rms error (K)

global 25km

NAE 12km


...and the disadvantage of boundaries!

forecast range

mean sea level pressure rms error (Pa)

global

NAE


ERA-Interim vs 12km EURO4M

• 12km, 70 levels• 36km 4D-Var• 6-hour analysis window• assimilate:

• conventional obs incl vis• satellite radiances• Ground-based GPS• Cloud• Precipitation

• Initial state and boundary conditions from ERA-Interim analyses

• T255 (80km), 60 levels• T159 (125km) 4D-Var• 12-hour analysis window• assimilate:

• conventional obs• satellite radiances


model orography

ERA-Interim

Model T255 (80km)

Var T159 (125km)

Met Office

Model 12km

Var 36km


First attempt at reanalysis...

May 2010

June 2010

July 2010

• Floods in Poland, eastern Europe

• Severe storms France/Spain

• Russian heatwave spreading West, forest fires


Poland floods, 16th May 2010

http://eca.knmi.nl/

e-obsgridded

24hr rainfall



Czech Hydrometeorological Institute

radar24hr rainfall


12km reanalysise-obs



ERA-Interime-obs



Russian heatwave, July 2010

Tmax, 10-07-2010

e-obs


Tmax10-07-10

ERA-Interim

12km EURO4M

obs


Verification vs Radiosonde

T+0 T+6Temperature rms error

ERA-Interim

EURO4M 12km



T+0 T+6Vector wind rms error

ERA-Interim

EURO4M 12km


Developments for 2012/13

• Variational bias correction

• ODB – obs monitoring

• Extend observations dataset

• Cloud and Precipitation assimilation

• Validation – extreme statistics

• Collaborate on cross-validation


n

ib

airi

scan xfccbias1

)(

Variational Bias Correction

Airmass-dependent bias correction of satellite radiances (based on Harris and Kelly, 2001)

Currently coeffs c are calculated off-line monthly

VarBC will give smooth and automatic updating

Work is underway – finish in 2012

(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)


Extend observations dataset

• Work with UEA (WP2.5) to extend surface

and sonde datasets

• Seeking sub-daily raingauge data...


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):• 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


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


Collaboration – Cross-Validation

Compare our reanalysis against:• SMHI• ERA• Obs climatologies• Others ?


Summary

• Reanalysis system ready to run

• Already better than ERA-Interim in some features, but not all (yet!)

• Science development and testing this year


Questions ?

With thanks to:

Tom Green, Nigel Atkinson, Sreerekha Tr, others...


Extra slides...


First attempt at reanalysis...

May 2010

June 2010

July 2010

• 3 x 1 month runs, with overlap


How long to spin up ?

rms surface pressure


How long to spin up ?

rms screen temperature


100km 4D-Var12km 4D-Var

Impact of Var resolution



T+0 T+6Relative Humidity rms error

ERA-Interim

EURO4M 12km


Global ODB trial output

NH Surface T mean (o-b)

UM 4D-Var Regional Reanalysis Progress

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