Convective organization and its
importance to large scale flows
Brian Mapes, U of Miami
with
Baohua Chen (UM)
Richard Neale (NCAR)
Emily Riley (UM)
Organ-ization
• From Greek organon
– about instrumentality or working order
"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
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
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
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)
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
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."
LS impacts of organization?
• An observational view: use wide cloud
systems as a working definition of organized
Emily Riley poster (2nd floor south end)
LS impacts of organization?
• Observational backdrop: use wide cloud
systems as a working definition of organized
Emily Riley poster (2nd floor south end)
LS impacts of organization?
• Observational backdrop: use wide cloud
systems as a working definition of organized
beyond the
margins of where
(narrow)
deep conv. can
Emily Riley poster (2nd floor south end)
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?
organized convection can survive dryness
where cu are suppressed
850
Example
Representative JJA 2006-9 cloudsat
radar echo objects
<200km in horizontal width
now with >200km sample in red
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.
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: dW/dt = -W/t + Sources
Mapes and Neale 2011, JAMES
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
deep convection
less dilute
obs
unstable
mean state
stable
Results I: Effect of W feedback
(when it rains it organizes)
more dilute
precip. variability 
Results II: Effect of coastal W source
Sense of result obvious
(more coastal rain)
What the heck??
Mystery is local to MC
Coastal W source everywhere but in MC
Mystery is local to MC
Coastal W source only in MC
Why less MC rain with coastal W source?
• more mass flux in plume #2...
...because Mean Sounding is drier and capped
Average in mysterious (less rain w/ coastal org)
MC region: 5S-10N, 90E-100E
... CIN > TKE
(closure)?
With Coast
10-days Hourly Data
Without Coast
10-days Hourly Data
...but Mean Sounding is drier so there is re-evap?
Average in mysterious (less rain w/ coastal org)
MC region: 5S-10N, 90E-100E
Perhaps this happens
in nature?
Too much W?
JJA 0.25 degree
TRMM climo
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 W created by rain evap (a positive
feedback) helps w/ "entrainment dilemma"
• (unwanted tradeoff btw. unstable bias  vs.  variability)
• Coastal W source makes most coasts wetter, but
core of Maritime continent drier (nonintuitive!)