Tropical Convection: A Half Century Quest for Understanding
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Transcript of Tropical Convection: A Half Century Quest for Understanding
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Tropical Convection: A Half Century Quest for Understanding
Bjerknes Memorial Lecture, AGU, San Francisco, 4 December 2012
Robert HouzeUniversity of Washington
UW Atmospheric Sciences Colloquium, Seattle, 18 January 2013
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A personal story of three great field campaigns and the evolution of
meteorological satellites
Tropical Convection: A Half Century Quest for Understanding
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Before Satellites
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Small cumulus
Cumulus congestus
Cumulonimbus
Visual Observation
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Radiosonde data in the tropics
Riehl & Malkus 1958
“Hot tower hypothesis”
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TIROS I1960
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…the atmospheric sciences require worldwide observations and, hence, international cooperation…
John F. Kennedy, New York, 1961
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“If we are genuinely interested in forecasting a few weeks in advance, we should give serious consideration to enlarging our network of observing stations, particularly over the oceans.”
Edward Lorenz, NYAS, 1963
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Detente
The promise of global prediction
Satellites
Global Atmospheric Research Program
“ GATE ”
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The era of field campaigns
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GATE 1974
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Convective parameterization
Glo
bal m
odel
grid
Problem: How to deal with tropical convection in a global model
Small area assumption
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Satellite Observations produced an
“inconvenient truth”
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Convective cloudsare actually large
…“mesoscale”
“No particular significance is attached to the interaction between the [mesoscale]
and the other scales.”
…NAS Plan for U.S. Participation in GATE
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Satellite view of the tropical cloud population
• Explained satellite pictures • Retained the hot tower notion • Included smaller clouds
Prevailing view of tropical convection in the early 1970’s
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The grandest field campaign:GATE 1974
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197440 ships!
12 aircraft!
4 shipborne scanning digital
C-band radars
16 sounding sites
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The GATE radarsled to a
second “inconvenient truth”
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Houze et al. (1980)
Post-GATE view of the tropical cloud population
Global model grid
Hot Tower
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Houze 1982
Heating and cooling processes in a mesoscale system
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Simplified Mesoscale System Heating Profiles
Schumacher et al. 2004
Hei
ght (
km)
Deg K/day
Convective
Stratiform
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Mesoscale System Heating Profiles
Hei
ght (
km)
Deg K/day
0% stratiform
40% stratiform
70% stratiform
Schumacher et al. 2004
Does this matter?
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0% stratiform
250 mb stream function, 400 mb heatingK/day
Schumacher et al. 2004
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250 mb stream function, 400 mb heatingK/day
Schumacher et al. 2004
40% stratiform
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More Field Projects
BoB 1979
JASMINE1999
EPIC 2001TEPPS
1997
(Dashed: No sounding network)
Soundings and radars on aircraft, ships, and islands
AtlanticGATE1974
W. PacificTOGA COARE
1992-3Indian Ocean
DYNAMO2011-12
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The West Pacific, 1992-93TOGA COARE Array
Shipborne and airborne Doppler radars
+ Rawinsondes
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Cu congestusSmall Cb
“Trimodal distribution”
Richard Johnson’s
analysis of the TOGA COARE
rawinsonde data
Johnson et al. 1999
TOGA
COARE
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ARM’s Manus Island cloud
radar confirmed the “trimodal distribution”
Hollars, Fu, Comstock, & Ackerman 1999
XMANUS
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Madden and Julian 1971, 1972
The “MJO”
TOGA COARE
West Pacific 1
2
3
7
8
5
6
4
“Active Phase” ~1-2 weeks
Wheeler & Hendon 2004
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Doppler radar sampling relative to the MJO in TOGA COARE
RossbyGyres
Kelvin WaveConvergence
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Moncrieff’s Mesoscale Layer Model of Tropical Convection
Moncrieff 92
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Synthesis of TOGA COARE Doppler radar observationsconfirms Moncrieff’s model
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TOGA COARE Airborne Doppler Observations of MCSs
25 convective region flightsShow deep layer of inflow to updrafts
Kingsmill & Houze 1999
<
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Kingsmill & Houze 1999
TOGA COARE Airborne Doppler Observations of MCSs
25 stratiform region flights
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Houze 1982
Empirical Model of an MCS
Layer inflow
Midlevel
inflow
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BoB 1979
JASMINE1999
EPIC 2001TEPPS
1997
(Dashed: No sounding network)
AtlanticGATE1974
W. PacificTOGA COARE
1992-3Indian Ocean
DYNAMO2011-12
DYNAMO: The third of the 3 great field campaigns
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DYNAMO-AMIE-CINDY
Two radarsRawinsondeOceanography
Two radarsRawinsondeOceanography
Four radarsRawinsonde Falcon aircraft
Rawinsonde P3 aircraft
IndianOcean
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Focus of DYNAMO/AMIE:
Convective cloudpopulation
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Multi-radar ApproachTo document more aspects of the convective population
HUMIDITY
DYNAMO/AMIE:DUAL WAVELENGTH
Water vapor
GATE:CM-WAVELENGTH
Precipitation
DYNAMO/AMIE:MM-WAVELENGTHNon-precipitating
Cumulus
CUMULUS
DYNAMO/AMIE:MM-WAVELENGTH
Anvil cloud
ANVIL
TOGA COARE: DOPPLER
Air motions
DYNAMO/AMIE:POLARIMETRYMicrophysics
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Stretched Building Block HypothesisMapes et al. 2006
Large-scale wave structure at the same times
Cloud population at three different times
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“We speculate that there is a natural selection in the atmosphere for wave packets whose phase structure produces a local, Eulerian sequence of cloud zone-supporting anomalies that aligns with the convective cloud system life cycle.”
Mapes et al. 2006
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Indian Ocean
1
2
3
4
5
6
7
8
The MJOover the Indian Ocean
4
5
6
“Active Phase” ~1-2 weeks
DYNAMO Wheeler & Hendon 2004
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October Active Period
November Active Period
December Active Period
Rain seen by the S-PolKa radar
Zuluaga and Houze 2013
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Zuluaga and Houze 2013
Composite large-scale divergence and vertical motion during 2-day rainfall episodes
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Variation of the DYNAMO radar echo population
Composite of all 2-day rainfall episodes
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Vertical structure of the MJO
Moncrieff 2004
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TRMM Radar Observations of the MJO over the Indian Ocean
Phase 7
Active Phase Suppressed Phase
Deep Convective
Cores
Broad Stratiform
Rain Areas
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Summary & ConclusionsThe three great oceanic field campaigns
• GATE 1974 • Mesoscale systems• Heating profiles
• TOGA COARE 1992-3 • Trimodality• Mesoscale circulations
• DYNAMO/AMIE 2011-2• Convective population• Relation to large-scale waves
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Summary & ConclusionsSatellites (& reanalysis)
• TIROS 1960• Global awareness
• TRMM 1997 • Precipitation radar in space
• A-Train 2000’s• Cloud radar and lidar in space
• Next generation & beyond• GPM, Earth Care, MeghaTropique, …
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End
This research was supported by NASA grants NNX10AH70G, NNX10AM28G,
NSF grants, AGS-1059611DOE grant DE-SC0008452