This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Figures from Geraint Vaughan, Jeffrey Chagnon, Tom Frame, Nigel Roberts, Alan Blyth & Chris Dearden
Building on 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
Science Objectives- to examine:
I. Role of surface fluxes in cyclone development and WCB outflow– Behaviour of turbulent fluxes at high wind speed– Horizontal moisture flux convergence within BL– Influence on properties of WCB inflow– Sporadic nature of meridional heat fluxes and link to the
climate research (taking obs relevant to them)– Influence of turbulent fluxes on sea state and forcing of ocean
II. Two-way interaction between clouds and mesoscale dynamics – Importance of clouds for distribution of diabatic heating– Effects of heating on dynamics, vertical motion and cloud– Relation to turbulence and mixing within WCBs
III. Transformation of air masses via diabatic processes and mixing– net change in θ and influence on WCB outflow structure
Science Objectives- to examine:
IV. Structure and effects of diabatic PV anomalies– On induced circulation → indirect diabatic modification– PV lenses in WCB outflow and their effects on cloud, radiative
transfer and remote diabatic PV anomalies (e.g., above tpp)– Influence of diabatic PV on downstream propagation
V. Downstream impacts on predictability of mesoscale phenomena– How much is ensemble spread downstream influenced by
diabatic processes upstream (e.g., Rodwell et al, BAMS, 2013)?
– Relation to mesoscale structure and high impact weather?– Phenomena: frontal cyclones, multiple rainbands, sting jets, …
DIAMET Observations- and relation to science objectives
I. Role of surface fluxes in cyclone development and WCB outflow
Momentum exchange coefficient obtained from turbulence probe measurements from 26 flights.
Stronger wind dependence than in current parameterisations.
Requires straight legs at z=30-50m ASL.
Wind direction important.Higher CD for cross-wind legs.Evidence for anisotropy in turbulence.
Cook and Renfrew, QJ, 2013
DIAMET Observations- and relation to science objectives
II. Interaction between clouds and mesoscale dynamics
Example
Distinctive precipitation banding observed on south side of intense cyclone (DIAMET IOP8)
Vaughan et al, BAMS, submitted
DIAMET Observations- and relation to science objectives
II. Interaction between clouds and mesoscale dynamics
Example
Distinctive precipitation banding observed on south side of intense cyclone (DIAMET IOP8)
Aircraft crossed banding at several levels in strong wind region
Vaughan et al, BAMS, submitted
DIAMET Observations- and relation to science objectives
II. Interaction between clouds and mesoscale dynamics
Cloud bands contain mixed phase
Heating by deposition onto ice within bands, but evaporational cooling inbetween
Wind speed lower within bands
Both a signature of mesoscale circulations?
Recent research- and relation to science objectives
III. Transformation of air masses by diabatic processes
Example from T-NAWDEX pilot, flight 3
Collaboration between DIAMET and PANDOWAE
WCB branches have similar origins, but
WCB1 experiences stronger net heating, reaches higher θ and turns anticyclonically.Heating occurs in narrow line at cold front.
WCB2 experiences slower ascent at later stage crossing warm front.
Martinez-Alvarado, Joos et al, QJ, 2013
Recent research- and relation to science objectives
IV. Structure and effects of diabatic PV anomalies
Chagnon , et al QJ, 2013
PV tracers accumulate tendencies from different processes (in model)
Total PV = sum of diabatic PV tracers + I.C. tracer
e.g., flight 3 of T-NAWDEX pilot
Total diabatic PV in section across tropopause foldTotal diabatic PV in section across tropopause fold
Positive diabatic PV above (on strat side) of tropopauseNegative diabatic PV beneath (on trop side) of tropopauseTropopause elevation not significantly altered by direct diabatic PV modification
Chagnon, Gray and Methven (2013), Q J R Met S
Recent research- and relation to science objectives
V. Downstream impacts on predictability of mesoscale phenomena
Precipitation rate from 4 ensemble members of a high resolution forecast for the IOP8 cyclone.
Trial of Met Office MOGREPS-UK ensemble (2.2km grid)
Some members match radar out to T+36 for scales of 25km and greater – therefore some skill in forecasts of mesoscale banding
Vaughan et al, BAMS, submitted
Recent research- and relation to science objectives
V. Downstream impacts on predictability of mesoscale phenomena
Wind speed (850 hPa) from the same 4 ensemble members.
Strongest winds occur between the precip bands.
Also, seen in surface obs.
Implications for predictability of wind damage in intense cyclones.
Vaughan et al, BAMS, submitted
I. Role of surface fluxes in cyclone development and WCB outflow– Low level aircraft legs with turbulence probe and high res SST– Near WCB inflow region (SE USA)– Frontal box patterns (along and across cold front)
II. Two-way interaction between clouds and mesoscale dynamics – In situ aircraft legs with cloud physics instruments– Best aircraft position, East coast USA (in WCBs)– Research radar in the UK (Chilbolton)
III. Transformation of air masses via diabatic processes and mixing– Quasi-Lagrangian expt with FAAM aircraft upstream at low
levels, downstream aircraft in upper tropospheric ridge
IV. Structure and effects of –ve PV lenses in WCB outflow– In collaboration with downstream aircraft
V. Downstream impacts on predictability of mesoscale phenomena– Enhancing ground-based network across UK
Observing strategy- and relation to science objectives
FAAM aircraft from NCAR C130 during RICO. Courtesy of Bjorn Stevens
Observational capabilities
FAAM aircraft and UK ground networks
One of the two pylons with cloud physics and and aerosol instruments.