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© Crown copyright Met Office
Data Assimilation Developments at the Met Office
Recent operational changes, and plansAndrew 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 nutshellCloser to a centred semi-implicit approach
Impact in UKV Lee Wave test: New DynamicsENDGame
Simon Vosper
108hr
© Crown copyright Met Office Andrew Lorenc 4
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
© 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 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:
© 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 packageSA 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 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.
© Crown copyright Met Office Andrew Lorenc 10
Demonstrating added valueNWP Index (UK-Global)
( cf ~2% annual increase in UK Index)
© Crown copyright Met Office
Questions and answers