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Recent & planned developments to the Met Office Global and Regional Ensemble Prediction System (MOGREPS)Richard Swinbank,

Warren Tennant, Sarah Beare, Christine Johnson, Neill Bowler, Ken Mylne, Nigel Roberts and Adam Clayton

GIFS-TIGGE Working Group meeting #9, Sept 2011

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• 24-member ensemble designed for short-range forecasting

• Regional ensemble over Atlantic and Europe (NAE)to T+54 at 06Z and 18Z(18km grid, 70 levels)

• Global ensemble to T+72 at 00Z and 12Z(~60 km grid, 70 levels)

• Medium-range version of MOGREPS-G: MOGREPS-15, used for TIGGE.

• ETKF for initial condition perturbations

• Stochastic physics

• Aim to assess uncertainty in short-range, eg.:• Rapid cyclogenesis

• Local details (wind etc)

• Precipitation

• Fog and cloud

MOGREPS –The Met Office ensemble

MOGREPS has been runningsince August 2005, and was made Operational in September 2008.

NAE

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Recent (2010-11) upgrades

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Increased MOGREPS resolution (2010)

• Global N144 (~90km) to N216 (~60km)

• Regional (NAE) 24km to 18km

• Both systems 38L to 70L:

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Summary of 2010 MOGREPS upgrades- not just resolution changes

Global Regional

PS23(Spring)

N144L38 to N216L70L70 physics changes SKEB2 implementation ETKF vertical localisationMOGREPS-15 as Global

NAE 24km L38 to 18km L38minimal physics changes

PS24(Summer)

IAU - Increments added at T+0 ETKF & OPS changes RP2 – additional BL parametersSKEB2 – add KE term

NAE 18km L38 to 18km L70Physics changes for L70

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Met Office hybrid implementation (Adam Clayton, Dale Barker, Andrew Lorenc, ...)

• Basic details:• “Alpha control variable” hybrid, with localisation in control variable space (streamfunction,

velocity potential, unbalanced pressure, humidity).

• 23 error modes from MOGREPS-G.

• Static localisation in horizontal and vertical.

• 80% climatological / 50% ensemble covariance. (Total variance inflated to maintain analysis fit to obs.)

• Performance: ~1% improvement against obs and ECMWF analyses.

• Operational implementation: July 2011.

Dec uncoupled (29 days) Jun coupled (28 days)

RMSE changes vs. obs:

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Future upgrades

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Plans for MOGREPS changes following HPC mid-life upgrade

• Allows further improvements in resolution of operational forecast models

• For MOGREPS we will use a two-step nesting strategy:• Global ensemble MOGREPS-G grid ~40 km

• Regional ensemble MOGREPS-EU ~12 km

• UK convective-scale ensemble MOGREPS-UK 2.2 km

• The short-range ensemble forecasts will run four times a day, with 12 members (1 control + 11 perturbed)

• Products calculated from pairs of lagged forecasts

• The ETKF will use 22 (later, more) perturbed members with a 6-hour cycle

• MOGREPS-15 will continue to run twice a day

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Proposed (schematic) schedule• Each configuration to run 3 hours after driving ensemble

to obtain freshest boundary conditions.

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Proposed new MOGREPS-EU domain

• Adopt new set of 70 levels to improve resolution in lower troposphere

• Also used for EURO4M reanalysis project, covering EEA countries & Mediterranean.

• Covers Storm Surge and ocean Atlantic Margin model domains

• Will investigate sensitivity to western boundary.

Aim to use 12km grid for MOGREPS-EU, so that MOGREPS-EU control run can directly replace 12km NAE – to be retired

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UKV Model Domainfor MOGREPS-UK

• Variable resolution, 2.2km in inner domain

• Based on 1.5km UKV model used for convective-scale deterministic forecasting

• Same 70-level set as MOGREPS-EU

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Implementation schedule

• Originally planned as “big bang” implementation at PS29 (Spring 2012), but due to delay in IBM P7 delivery, implementation will be phased:

• PS28 (Autumn 2011)• 4 cycles per day with current models, but using new

schedule.

• PS30 (late Spring 2012)• Introduce MOGREPS-UK in time for Olympics

• PS31 (Autumn 2012) • MOGREPS-EU

• Other resolution & physics changes at PS31 or PS32

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Medium-range and Seamless Forecasting

• Currently the medium-range ensemble, MOGREPS-15 is essentially the same as MOGREPS-G but run to 15 days using UK member-state computer time at ECMWF.

• Met Office strategy is to make forecasts consistent across different timescales, from short-range NWP to climate prediction.

• We are planning to bring together ensemble prediction systems on the medium-range and monthly to seasonal timescales, including.

• Initial condition perturbations from ETKF and, in longer term, Ensemble Data Assimilation System;

• Coupled model to better represent ocean-atmosphere interactions.

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Suite 120 members15 days

Suite 22 members2 months

Suite 32 members 7 months

Suite 4X members Hindcast

Medium-range products

Monthlyproducts

Seasonalproducts

Schematic of possible coupled medium-range/ monthly/ seasonal EPS

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Any Questions?