1. 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.

2. 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.

3. 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?

4. 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

5. 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)

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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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)

13. 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.

14. 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

15. 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

16. 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?

18. 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)

19. 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