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Data Assimilation Developments at the Met Office

Recent operational changes, and plansAndrew Lorenc, DAOS, Montreal, August 2014

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ENDGame Model Upgrade

• Improved Accuracy, Stability, Scalability

• Implemented July 2014 in global, Feb 2015 in LAMs

• Global resolution increase 25km → 17km & will facilitate further increases on future computers

• Better “activity”, jets, “weather”, TC forecasts& most, but not all, scores

• 4DVar increment resolution increase 60km → 40km but PF & adjoint model formulation not upgraded

• Large package of satellite DA improvements

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ENDGame in a nutshellCloser to a centred semi-implicit approach

Impact in UKV Lee Wave test: New DynamicsENDGame

Simon Vosper

108hr

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Extra-tropical circulationExample forecast: frontal rain: 6-7th July 2012

• General synoptic evolution similar

• Deeper low pressure in 17km GA6.1

• More realistic rainfall structure in 17km GA6.1

N512 GA3.1 N768 GA6.1

• When evolutions differ, no clear signal

• When similar, N768 GA6.1 generally better

30hr

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Tropical circulation Major improvements in Tropical Cyclone forecasts

Impact of science upgrade

N512 GA6.1 vs N512 GA3.1

Impact of science + resol’n

N768 GA6.1 vs N512 GA3.1

Mean abs. PMSL error reduction 3.0 hPa 3.6 hPa

Central pressure reduction 7.1 hPa 11.1 hPa

Mean abs. |v| error reductions 6.7 kt 9.0 kt

Mean max. |v| increase 8.9 kt 13.4 kt

850hPa vorticity increase 79% 155%

Track error reduction 7.3% 8.6%*

Track skill score increase 3.8% 4.5%

* Biggest reduction in TC track error in a single UM upgrade for 20 years

Average impacts from PS32-based trials:

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Example of scalability

• ENDGame required for 17km in PS34

• N768 GA6.1 on 96 nodes currently runs in ≈ 40 mins

• Allows further resolution upgrades over next 10 years

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• Reduced thinning of:• IASI (×2 increase in data)• ATOVS (30% )• Scatterometer data (50% )

• Improved assimilation of GPS Radio Occultation data (allowing for tangent point drift)

• Introduction of Meteosat-7 MVIRI clear sky radiances over the Indian Ocean

• Changes to snow analysis (use of JULES snow depth and amount)

Satellite packageSA package of additional changes for PS34

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Development Strategy

• ENDGame gives us time to develop new model design (GungHo) and software infrastructure (LFRic)

• We will not decide on (nor start) 4DVar development at least until these are more mature and stable

• 4DEnVar is being developed at least to bridge the gap and probably as a long-term replacement.

• First hybrid-4DEnVar was 3% worse than hybrid-4DVar (Lorenc et al. 2014).

Improving this needs bigger & better ensemble and better localisation / covariance filtering.

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Convective Scale

• Dropped NAE regional system.

• UKV 1.5km, stretching to nest in global.

• Current UKV uses 3-hr cycle of 3km 3DVar of obs including doppler radar winds, high-resolution AMVs, SEVERI radiances, IR & surface clouds, visibility, …+ LHN of radar ppn.

• Plan to introduce 1-hr 4DVar RUC for nowcasting on new computer in 2016.

• UK ensemble: 12 members at 2.2km are currently nested in & initialised from global 33km ensemble. Investigating cycling, recentring, etc. for next upgrade in 2015.

• Longer term research in EnKF starting.

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Demonstrating added valueNWP Index (UK-Global)

( cf ~2% annual increase in UK Index)

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Questions and answers