© Crown copyright Met Office Data Assimilation Developments at the Met Office Recent operational changes, and plans Andrew Lorenc, DAOS, Montreal, August 2014

© Crown copyright Met Office Andrew Lorenc 2 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

© Crown copyright Met Office Andrew Lorenc 3 ENDGame in a nutshell Closer to a centred semi-implicit approach Impact in UKV Lee Wave test: New Dynamics ENDGame Simon Vosper

108hr © Crown copyright Met Office Andrew Lorenc 4 Extra-tropical circulation Example forecast: frontal rain: 6-7 th July 2012 General synoptic evolution similar Deeper low pressure in 17km GA6.1 More realistic rainfall structure in 17km GA6.1 N512 GA3.1N768 GA6.1 When evolutions differ, no clear signal When similar, N768 GA6.1 generally better 30hr

© Crown copyright Met Office Andrew Lorenc 5 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 reduction3.0 hPa3.6 hPa Central pressure reduction7.1 hPa11.1 hPa Mean abs. |v| error reductions6.7 kt9.0 kt Mean max. |v| increase8.9 kt13.4 kt 850hPa vorticity increase79%155% Track error reduction7.3% 8.6%* Track skill score increase3.8%4.5% * Biggest reduction in TC track error in a single UM upgrade for 20 years Average impacts from PS32-based trials:

© Crown copyright Met Office Andrew Lorenc 6 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

© Crown copyright Met Office Andrew Lorenc 7 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 package SA package of additional changes for PS34

© Crown copyright Met Office Andrew Lorenc 8 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.

© Crown copyright Met Office Andrew Lorenc 9 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 UK ensemble: 12 members at 2.2km are currently nested in & initialised from global 33km ensemble. Investigating cycling, recentring, etc. for next upgrade in Longer term research in EnKF starting.

© Crown copyright Met Office Andrew Lorenc 10 Demonstrating added value NWP Index (UK-Global) ( cf ~2% annual increase in UK Index)

© Crown copyright Met Office Questions and answers