Tropical Convection: A Half Century Quest for Understanding Bjerknes Memorial Lecture, AGU, San Francisco, 4 December 2012 Robert Houze University of Washington

A personal story of three great field campaigns and the evolution of meteorological satellites Tropical Convection: A Half Century Quest for Understanding

Before Satellites

Small cumulus Cumulus congestus Cumulonimbus Visual Observation

Radiosonde data in the tropics Riehl & Malkus 1958 “Hot tower hypothesis”

TIROS I 1960

…the atmospheric sciences require worldwide observations and, hence, international cooperation… John F. Kennedy, New York, 1961

“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

Detente The promise of global prediction Satellites Global Atmospheric Research Program “ GATE ”

The era of field campaigns

GATE 1974

Convective parameterization Global model grid Problem: How to deal with tropical convection in a global model  Small area assumption

Satellite Observations produced an “inconvenient truth”

Convective clouds are 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

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

The grandest field campaign: GATE 1974

ships! 12 aircraft! ships! 12 aircraft! 4 shipborne scanning digital C-band radars 16 sounding sites

The GATE radars led to a second “inconvenient truth”

Houze et al. (1980) Post-GATE view of the tropical cloud population Global model grid Hot Tower

Houze 1982 Heating and cooling processes in a mesoscale system

Simplified Mesoscale System Heating Profiles Schumacher et al Height (km) Deg K/day Convective Stratiform

Mesoscale System Heating Profiles Height (km) Deg K/day 0% stratiform 40% stratiform 70% stratiform Schumacher et al Does this matter?

0% stratiform 250 mb stream function, 400 mb heating K/day Schumacher et al. 2004

250 mb stream function, 400 mb heating K/day Schumacher et al % stratiform

More Field Projects BoB 1979 JASMINE 1999 EPIC 2001 TEPPS 1997 (Dashed: No sounding network) Soundings and radars on aircraft, ships, and islands Atlantic GATE 1974 W. Pacific TOGA COARE Indian Ocean DYNAMO

The West Pacific, TOGA COARE Array Shipborne and airborne Doppler radars + Rawinsondes

Cu congestus Small Cb “Trimodal distribution” Richard Johnson’s analysis of the TOGA COARE rawinsonde data Johnson et al TOGACOARETOGACOARE

ARM’s Manus Island cloud radar confirmed the “trimodal distribution” Hollars, Fu, Comstock, & Ackerman 1999 X MANUSMANUS

Madden and Julian 1971, 1972 The “MJO” “Active Phase” ~1-2 weeks Wheeler & Hendon 2004

Doppler radar sampling relative to the MJO in TOGA COARE Rossby Gyres Kelvin Wave Convergence

Moncrieff’s Mesoscale Layer Model of Tropical Convection Moncrieff 92

Synthesis of TOGA COARE Doppler radar observations confirms Moncrieff’s model

TOGA COARE Airborne Doppler Observations of MCSs 25 convective region flights Show deep layer of inflow to updrafts Kingsmill & Houze 1999 <

TOGA COARE Airborne Doppler Observations of MCSs 25 stratiform region flights

Houze 1982 Empirical Model of an MCS Layer inflow Midlevel inflow

BoB 1979 JASMINE 1999 EPIC 2001 TEPPS 1997 (Dashed: No sounding network) Atlantic GATE 1974 W. Pacific TOGA COARE Indian Ocean DYNAMO DYNAMO: The third of the 3 great field campaigns

DYNAMO-AMIE-CINDY Two radars Rawinsonde Oceanography Two radars Rawinsonde Oceanography Four radars Rawinsonde Falcon aircraft Rawinsonde P3 aircraft Indian Ocean

Focus of DYNAMO/AMIE: Convective cloud population

* Multi-radar Approach To document more aspects of the convective population HUMIDITY DYNAMO/AMIE: DUAL WAVELENGTH Water vapor GATE: CM-WAVELENGTH Precipitation DYNAMO/AMIE: MM-WAVELENGTH Non-precipitating Cumulus CUMULUS DYNAMO/AMIE: MM-WAVELENGTH Anvil cloud ANVIL TOGA COARE: DOPPLER Air motions DYNAMO/AMIE: POLARIMETRY Microphysics

Stretched Building Block Hypothesis Mapes et al Large-scale wave structure at the same times Cloud population at three different times

“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

The MJO over the Indian Ocean “Active Phase” ~1-2 weeks Wheeler & Hendon 2004

October Active Period November Active Period December Active Period Rain seen by the S-PolKa radar Zuluaga and Houze 2013

Composite large-scale divergence and vertical motion during 2-day rainfall episodes

Variation of the DYNAMO radar echo population Composite of all 2-day rainfall episodes

Vertical structure of the MJO Moncrieff 2004

TRMM Radar Observations of the MJO over the Indian Ocean Phase 7 Active PhaseSuppressed Phase Deep Convective Cores Broad Stratiform Rain Areas

Summary & Conclusions The three great oceanic field campaigns GATE 1974 GATE 1974 Mesoscale systemsMesoscale systems Heating profilesHeating profiles TOGA COARE TOGA COARE TrimodalityTrimodality Mesoscale circulationsMesoscale circulations DYNAMO/AMIE DYNAMO/AMIE Convective populationConvective population Relation to large-scale wavesRelation to large-scale waves

Summary & Conclusions Satellites (& reanalysis) TIROS 1960 TIROS 1960 Global awarenessGlobal awareness TRMM 1997 TRMM 1997 Precipitation radar in spacePrecipitation radar in space A-Train 2000’s A-Train 2000’s Cloud radar and lidar in spaceCloud radar and lidar in space Next generation & beyond Next generation & beyond GPM, Earth Care, MeghaTropique, …GPM, Earth Care, MeghaTropique, …

End This research was supported by NASA grants NNX10AH70G, NNX10AM28G, NSF grants, AGS DOE grant DE-SC