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Convective organization and its importance to large scale flows Brian Mapes, U of Miami with Baohua Chen (UM) Richard Neale (NCAR) Emily Riley (UM)

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Presentation on theme: "Convective organization and its importance to large scale flows Brian Mapes, U of Miami with Baohua Chen (UM) Richard Neale (NCAR) Emily Riley (UM)"— Presentation transcript:

1 Convective organization and its importance to large scale flows Brian Mapes, U of Miami with Baohua Chen (UM) Richard Neale (NCAR) Emily Riley (UM)

2 Organ-ization From Greek organon – about instrumentality or working order

3 "Organized" convection 1.(weak) Something is making it patterned – perhaps it is forced or orchestrated 2.(too strong) It acts as an organ in an organism – it is performing some function 3.(agnostic) It is far from random in structure – has coherent (contiguous) entities

4 Organized used many ways multicellular (every cb is) – visual or radar mesoscale patch or blob – or satellite 'cloud cluster' line/arc structure as opposed to blobby patchy on synoptic scale

5 A process view of organization In PDF language: – Extreme (tail) events in space of {w,T,q,scale,depth} – Vanishingly unlikely in naive multi-normal PDF – Taps an energy source, so natural selection acts – We can treat org as a positive effect negative rare events (rogue gravity waves) are not reinforced in that way, and also not important – BUT: it doesn't mean optimal always happens no wild eyed entropy extremal theorems here

6 effect of org. on convection Thermo: protects penetrative updrafts from getting diluted by modal (mean or env.) air Dyn: Assists in transfers/loans of energy to exploit metastability (triggered instability) (Exotic momentum transport effects)

7 Coherent structures may deserve separate treatment like we add a 'plume' idealization for very asymmetric moist turbulence multiplume / cooperating-plume structure an obvious generalization for org. convection

8 LS impacts of organization? Foreshadowing: one idea "The Maritime Continent...presents a major challenge to models, which tend to systematically underestimate the precipitation in this region. "It is argued that the diurnal cycle... [and]... circulation patterns generated by land–sea contrasts are crucial for... the mean climate."

9 LS impacts of organization? An observational view: use wide cloud systems as a working definition of organized Emily Riley poster (2 nd floor south end)

10 LS impacts of organization? Observational backdrop: use wide cloud systems as a working definition of organized Emily Riley poster (2 nd floor south end)

11 LS impacts of organization? Observational backdrop: use wide cloud systems as a working definition of organized Emily Riley poster (2 nd floor south end)

12 LS impacts of organization May be esp. important in convective margins like – upwind of deep tropics in the trades e.g. in SE Pacific (Mar-Apr double ITCZ) – W African monsoon MCS dominated – western margin of Indian monsoon Regions of GCM difficulties/biases?

13 organized convection can survive dryness where cu are suppressed 850

14 Example

15 Representative JJA cloudsat radar echo objects <200km in horizontal width

16 now with >200km sample in red

17 GCMs and organized convection If org is what protects upflow from dilution, then GCMs deep convective plumes tuned to give a realistic stability have org everywhere GCMs don't lack org, they lack its absence in deep convective onset situations – in the morning over land – in gradually moistening inflows to tropical rain – etc.

18 Our experimental CAM5 version ZM deep convection turned off Instead, 2 Park-Bretherton plumes – w/ different environmental mixing rates Less-dilute plume's activity is an increasing function of organization W Org. obeys: d  /dt = -  + Sources Mapes and Neale 2011, JAMES

19 2 Sources of Organization W in our CAM5-UW-org-ens version 1.Source1 is proportional to precip evaporation 2.Source2 >0 in coastal grid cells (optional) JJA 0.25 degree TRMM climo

20 Results I: Effect of W feedback (when it rains it organizes) precip. variability  unstable mean state stable deep convection less dilute more dilute Long-known tradeoff "entrainment dilemma" (Mapes and Neale 2011) obs W gets us closer W gets us closer

21 Results II: Effect of coastal W source Sense of result obvious (more coastal rain) Sense of result obvious (more coastal rain) What the heck??

22 Mystery is local to MC Coastal  source everywhere but in MC

23 Coastal  source only in MC Mystery is local to MC

24 Why less MC rain with coastal  source? more mass flux in plume #2...

25 ...because Mean Sounding is drier and capped Average in mysterious (less rain w/ coastal org) MC region: 5S-10N, 90E-100E Average in mysterious (less rain w/ coastal org) MC region: 5S-10N, 90E-100E

26 With Coast 10-days Hourly Data With Coast 10-days Hourly Data Without Coast 10-days Hourly Data Without Coast 10-days Hourly Data... CIN > TKE (closure)?

27 ...but Mean Sounding is drier so there is re-evap? Average in mysterious (less rain w/ coastal org) MC region: 5S-10N, 90E-100E Average in mysterious (less rain w/ coastal org) MC region: 5S-10N, 90E-100E

28 Perhaps this happens in nature? Too much  JJA 0.25 degree TRMM climo

29 Summary Organized convection is coherent structures Would be vanishingly rare in naive PDF view Natural selection makes it common Protects core updrafts in nature's deep convection Standard GCM deep convection schemes imply org. is ubiquitous (not "missing") Prognostic  created by rain evap (a positive feedback) helps w/ "entrainment dilemma" (unwanted tradeoff btw. unstable bias  vs.  variability) Coastal  source makes most coasts wetter, but core of Maritime continent drier (nonintuitive!)


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