1. Diabatic modification of PV and weather systems
John Methven,
Department of Meteorology, University of Reading
Thanks to the DIAMET team.
Figures from Jeffrey Chagnon, Oscar Martinez-Alvarado, Geraint Vaughan, Laura Baker & Hylke de Vries

2. DIAbatic influences on Mesoscale structures in Extratropical sTorms
DIAMET
DIAbatic influences on Mesoscale structures in Extratropical sTorms
Geraint Vaughan, Manchester PI
John Methven, Reading PI
Ian Renfrew, East Anglia PI
Doug Parker, Leeds PI

3. Looking Ahead Ideas pulling together work within DIAMET
National activities
Relation to current NERC projects in SRM and CWC
Future national activities
International activities
PANDOWAE-2
T-NAWDEX Falcon experiment
THORPEX/WGNE conference on model errors
Future of THORPEX and related WMO programmes
T-NAWDEX international experiment plans

4. DIAMET Aims
To describe the structure, origin and dynamical consequences of heating (condensation/evaporation on the mesoscale – e.g., fronts).
To make a link between the simulation of mesoscale structure and forecasts of surface weather (high winds and precipitation).
To investigate the implications for predictability and the skill of numerical weather prediction
Especially convection-resolving forecasts (1-2 days)

5. Ideas for integrative work
Contrast between winter and summer cyclone cases
Relating structure of vertical motion to cyclone speed
Water vapour transport and cloud processes
Relation to hemispheric wave patterns on jetstream
TEMPEST – representation in climate models
Processing of air along WCBs
Net modification associated with different processes
Link with climate work on “atmospheric rivers”
Origin and relevance of segmentation along cold fronts
Shear instability and role of diabatic processes
Link to severe weather (e.g. tornados)
Predictive skill of convection-resolving ensembles
Origin of predictability for “weather variables”
Design of ensembles

6. Link to NERC programmes
Storm Risk Mitigation
TEMPEST
Have submitted their papers for IPCC AR5 on representation of stormtracks in CMIP5 models
Open to ideas linking in with DIAMET
SRM integration project
DEMON
Flood action on 1st May 2012 case
Changing Water Cycle
HYDEF
Statistics of atmospheric rivers from analyses and climate models
PAGODA
Stormtrack/blocking behaviour and link to heat waves/ water scarcity

7. Storm risk mitigation integration
Project linking DIAMET, TEMPEST and DEMON
(PIs: Len Shaffrey, John Methven and Kevin Hodges)
Held metric workshop – characteristics of cyclones important to flooding
Case study from summer 2007 using climate model down to 1.5km (Met Office Unified Model)
Using 5-day accumulated precip (over UK) to sample long HIGEM climate run and pull out related cyclones
Characteristics of these cyclones?
Statistics of precipitation accumulations cf England-Wales Precip
OK on daily, although low bias across precip histogram
cf, ERA-Interim ~ 76% of EWP observed
Extremes greatly underestimated for longer accumulations (relevant for flooding)

8. Future national programmes
LWEC Drought Programme
Call in November
UK-centric
Outline had two components
Persistent behaviour in precipitation
Links to large scale dynamics and blocking
Angling for “predictability” rather than “climatology”
Will probably have some hydrology component linking precip to river and ground water levels
Impacts on environment, society and economy
Trying to cover multi-disciplinary remit
“messy” in town meeting in Birmingham (October 15th)

9. International Activities PANDOWAE-2
Linking with DIAMET (Oscar and Jeffrey) on WCBs
Focus on T-NAWDEX pilot flight 24/11/09
Comparing humidity tracers influenced by different model processes in MetUM with similar partition using German COSMO model
DIAMET using tracer fields and all processes
PANDOWAE (Joos, Böttcher, Wernli) using trajectories and focus on microphysics (with finer partition between processes)
Grand goal is a “virtual field experiment” considering systems on the North Atlantic waveguide and influence of diabatic processes on downstream development.

10. Periods of interest in autumn
DIAMET field campaigns
16-30 Sep 2011
Frontal waves across UK
25 Nov – 15 Dec 2011
Severe cyclone sequence across Scotland (into Jan 2012)
PANDOWAE case study focus
11 Sep 2011
Extratropical transition and downstream development
7-10 Oct 2011
Downstream development and extreme precip (N. Alps)
7-8 Nov 2011
“Medicane” and extreme precip (S. Alps)

11. International Activities T-NAWDEX Falcon experiment
Aiming to perform quasi-Lagrangian experiment focussing on diabatic processes within warm conveyor belts
Aircraft time: 5-18th October 2012
Achieved two IOPs:
11/12th Oct – WCB inflow over S. France eve of 11th (link with HYMEX)
- downstream flight in WCB ascent over N. Italy
14/15th Oct – WCB inflow on eve of 14th
- two flights sampling WCB: 9-13LT and 16-20LT

12. International Activities: THORPEX Meetings
THORPEX conference on ensembles and predictability (Talagrand)
Toulouse next week
THORPEX/WGNE conference on model error (Andy Brown)
Exeter, April 2013
Abstract deadline has just passed (officially)
Remit to link model error with physical processes responsible
research activity proposed by PDP/WGNE, two themes:
extratropical cyclones
monsoons
Important because WGNE has strong influence on research priorities of operational centres
DIAMET work very relevant to it

13. Total diabatic PV in section across tropopause fold
Positive diabatic PV above (on strat side) of tropopause
Negative diabatic PV beneath (on trop side) of tropopause
Tropopause elevation not significantly altered by direct diabatic PV modification
Chagnon, Gray and Methven, QJRMetS (2012)

14. Partitioning of diabatic PV among physical processes
Boundary-lyr heating
LW radiation
Large-scale cloud
Convection

15. Net diabatic PV near the tropopause
Chagnon, Gray and Methven, QJRMetS (2012)

16. Ramifications for synoptic scale evolution
PV conservation equation
Using observation of little direct diabatic PV modification at tropopause:
However, diabatic effects are felt mainly through induced wind, ui
Indirect PV modification by diabatic processes via changes to winds.
Links directly with moist baroclinic wave theory (De Vries et al, 2010).
Cooperative coupling between diabatic PV in troposphere and Rossby waves along tropopause or lower boundary.

17. Shading = total diabatic PV anomaly (8.8 km level)
Dashed contour = 2PVU for advection-only PV
Solid contour = 2PVU for total PV
Positive diabatic PV above (on strat side) of tropopause
Negative diabatic PV beneath (on trop side) of tropopause
Tropopause elevation not significantly altered by direct diabatic PV modification
Chagnon, Gray and Methven, QJRMetS (2012)

18. Diabatic PV near the tropopause
Implications for
Stratosphere-troposphere exchange
LW cooling max at tropopause
 “diabatic PV dipole” but no direct PV change at tropopause
+ continuous diabatic mass transport downwards across tpp.
Theory of moist baroclinic waves – growth and propagation

19. International Activities: THORPEX and beyond
Currently has 3 WGs: Predictability and Dynamical Processes, TIGGE/GIFS and Data Assimilation and Observing Systems.
DAOS  its own WWRP programme with wider remit
TIGGE  group will merge with new activity on subseasonal-seasonal prediction (new database of longer-range forecasts like TIGGE)
PDP  disbanding
Some WG activity continuing in “polar prediction project”
Not a WG relating to mid-latitude predictability and dynamics
Group may merge into WGNE

20. T-NAWDEX International Experiment
Re-igniting international experiment that was thwarted by HALO delays.
Science remit related to DIAMET but with focus on systems crossing North Atlantic and influences on the waveguide.
Still linking to high impact weather forecasts (but longer lead time)
German/Swiss (Heini Wernli)
PANDOWAE-2 will end 2014 – no continuation
Jones and Craig planning a different “weather consortium”
HALO and Falcon possible
USA (Pat Harr)
Strong interest – Chris Davis, Lance Bosart + NCAR mesoscale
Want to use G-V (similar to HALO)
Need cost estimate by 15th Nov 2012
Need science objectives and experimental design docs by Jan 2013
Earliest field phase would be autumn 2015
France (Gwendal Riviere)
Has project similar to PANDOWAE – invited to re-submit in Jan 2013

21. How would this group like to proceed?
DIAMET has been successful in bringing together weather, dynamics and predictability research across UK
Bringing together obs, process understanding and prediction in a concrete fashion
Better integration between NCAS and NCEO on weather
Building activity with Met Office across more groups
DIAMET has been a high profile project for them
It has been fun!
A small community (cf climate)
There is more to “climate” than simulation

22. Trajectory analysis 1800 UTC
Wind speed (shading)
650-hPa Relative humidity (RH>80% stippled)
850-hPa Equivalent potential temperature
Trajectory position (black dots)

23. Trajectory analysis 1200 UTC
Pressure (hPa)
Height (m)
Wind speed (m s-1)
Relative humidity (%)

24. Preliminary results IOP8
DIAMET IOP8 cyclone did contain a sting jet
Air descending from tip of cold conveyor belt into hook
Observed twice, before and after Scotland?
First aircraft observations through a sting jet cyclone
Cloud banding around cyclone was not slanting
Origin of banding?
Q.Is evaporation of ice falling into dry air essential for bringing sting jet winds towards ground?

25. Feature tracking in ensembles Cyclone Friedhelm 8th Dec 2011 (T+36hr)
Here cyclonic features coloured by max wind speed at 1km within a 300km radius
Cyclonic features identified using methodology of Hewson and Titley (2010), Met. Apps.
Identified from the 23 forecasts of the Met Office MOGREPS ensemble

26. Evolution of one ensemble forecast