DIAbatic influences on MEsoscale structures in extratropical sTorms DIAMET DIAbatic influences on MEsoscale structures in extratropical sTorms Geraint Vaughan A proposal to increase understanding of, and capability to predict, mesoscale structures in extra-tropical cyclones.

Overarching scientific questions for DIAMET What is the role of diabatic processes in generating mesoscale potential vorticity (PV) and moisture anomalies in cyclonic storms?, and What are the consequences of those anomalies for the weather we experience? In this proposal, we focus on two key diabatic processes: latent heating/cooling and air-sea fluxes of heat and moisture.

Questions from AO (a) How are potential vorticity and moisture anomalies generated in cyclonic storms, what is their morphology, and what consequences do they have for the weather? (b) How can these physical processes be parameterized for NWP, both at very high horizontal resolution (~1 km) and at resolutions that are more appropriate for longer-range prediction (10-20 km)? (c) What is the real-world structure of cyclonic storms at the meso-convective scale? (d) How can we improve numerical weather prediction models and data-assimilation methods for better “nowcasts” and forecasts of cyclonic storms at meso to convective scale?

Structure of proposal: work packages Questions a and c WP A. Detailed modelling and measurements WP B. Parameterisations WP C. Predictability Question b Questions a and d

Work Package A Real-world mesoscale structures High-resolution modelling of past cases Field campaigns: autumn 2011, summer 2012 High-resolution modelling of observed cases Statistical analysis of precipitation structures observed by radar (student project) Modelling microphysical sensitivity of storm dynamics (student project) Dynamical consequences of PV and heating anomalies Exploits novel tracer method for partitioning PV changes by physical process (in a numerical model)

T-NAWDEX pre-frontal wave Flight of 24th November 2009 Knippertz et al 2010

PV SOURCE/SINK ANALYSIS: T-NAWDEX Pilot, 24th Nov 2009 PV sources/sink accumulated from 00 UTC on 22 November 2009, UM 12 km run The strip of high PV along the cold front is diabatically generated. Main contributions are from boundary-layer heating, cloud microphysics, and convection schemes. The high PV strip is involved in the generation of a large- amplitude gravity wave packet. Upper-level trough Strip of high PV above surface front Source: Jeffrey Chagnon 5

Latitude-height cross section along 50 N Total PV The total potential vorticity [panel (a)] indicates a tropopause fold to the north of front as well as several slantwise-oriented anomalies along the front. The diabatic contributions owing to b) the convection scheme, c) the cloud microphysics scheme, and d) the boundary-layer scheme are integrated and advected over a 36 hour period Convection Microphysics BL scheme

DIAMET flying programme Autumn 2011 3 months SOP, based at Cranfield Includes 2 week detachment to Exeter or Prestwick 8 IOPs planned, 4 double and 4 single flights July-August 2012 Cranfield-based Focus on high-impact rainfall 2 double, 3 single flights

Field campaign: example flight T-NAWDEX pilot flight 3/11/09 overlain on 11UTC radar image. Strong cold front propagating to SE Heavy precipitation beginning to break out over England under tropopause fold behind surface front Heavy precip was not forecast. Case of mid-level destabilisation of convection? White dots: dropsondes; Pink dot: aircraft location, 11.00

Work Package B Physical Processes and Parameterisations Tracer method applied to moisture in the UM Approaches to parameterising mid-level and embedded convection within cyclones Air-sea fluxes and impact on storm development Distribution of latent heating from microphysical processes (ice and liquid water) Improvements to microphysical schemes in idealised model, motivated by new aircraft observations

Work Package C Predictability Use ensemble forecasts at varying resolution to determine: Predictability of mesoscale features within cyclones Association of forecast skill for high-impact weather variables (precipitation and high surface winds) with mesoscale features Sources of model error on the mesoscale/ convective scale, and error covariance structures Alternatives to geostrophic and hydrostatic balance in data assimilation, valid at finer scales (<50km) Investigate the benefits of an ensemble 4-D var assimilation system (student project)

Partnership with Met Office Observation-based Research (Jon Taylor) - Participation in field campaigns (staff time, dropsondes, extra instruments) JCMM (Sue Ballard) – data assimilation at high resolution and new data streams JCMM (Humphrey Lean) – surface fluxes, microphysical parameterisation and access to high resolution forecasts Radar group (Malcolm Kitchen) – high resolution radar data Microphysical parameterisation – Paul Field Ensemble Forecasting Group (Richard Swinbank and Ken Mylne) – feature tracking and forecast skill Data Assimilation Group (Dale Barker) - co-supervision of studentship and DA experiments on JRP computer.

Management Responsibilities Project Management Board* + secretary, 20% PI (20%) Dr Ian Renfrew. Management of impact plan Dr Keith Bower. Management of field campaign WP leaders, responsible for project deliverables Met Office partners on individual WPs * Details pending decision on management of Storms programme

Impact continues downstream through NCAS and NCEO core programmes Pathways to Impact Specific project deliverables Exchange of expertise Forecast model advances Met Office Weather services EUMETCAL Forecaster training Educational resources (web based) Field campaign blog Video conference Leaflets Heather Reid and R Met. Soc Schools and public outreach Impact continues downstream through NCAS and NCEO core programmes

Links to Deliverables 2 and 3 How realistic are the mesoscale structures in high-resolution climate model runs? (1  2) How important is upscaling of mesoscale structures in NWP/climate predictions? (21) Can Predictability WP of DIAMET inform Deliverable 3 about improved error estimates in NWP forecasts?

Management Plan Six-monthly project meetings More frequent meetings of individual WPs, e.g. to plan field campaign or papers. Use of teleconferencing and (possibly) video conferencing Project web site (hosted by NCAS): key documents, progress against plan, draft papers Exploit existing NCAS and NCEO management structures. Large group of scientists with experience of working together (NCAS, T-NAWDEX)

International Weather Research THORPEX (Improving high impact forecasts, 2-15 days lead) T-NAWDEX North Atlantic Waveguide World Meteorological Organisation World Weather Research Programme DIAMET Mesoscale events, < 2 days Diabatic processes research focus