Mesoscale Convective Systems in AMMA

What has been learned from previous campaigns?•GATE—off the coast of west Africa •COPT81—over the west African continent

What has been learned since these campaigns?•TOGA COARE •TRMM

What can we learn from AMMA?

How can we learn it?

How can this new MCS knowledge help the overall goals of AMMA?

Pre-GATE view of tropical cloud population

Houze et al. (1980)

Post-GATE view of tropical cloud population

GATE & COPT 81: MCS water, mass, and heat budgets

GATE(Gamache & Houze 1983)

.60R .40R

1.17R .41R

.29R

.37R

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.13R

.16RCOPT81

(Chong & Hauser 1989)

Water Budget of a West African Mesoscale Convective Systemover ocean (GATE) and land (COPT81)

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Assumed heating profilesMCS heating profiles seen in GATE & elsewhere

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Stratiform

Assumed heating profilesMCS heating profiles seen in GATE & elsewhere

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Assumed heating profiles

0% stratiform

Assumed heating profiles

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40% stratiform

Assumed heating profiles

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70% stratiform

Assumed heating profiles

TRMM: Global mapping of MCSs

Nesbitt, Zipser & Cecil (2000)

Contribution of convective system type to rainfall

AFRICA S. AMER. E. PAC. W. PAC.

Schumacherand Houze (2003)

TRMM precipitation radar rain amount subdivided intoconvective and stratiform components

Total rain

Convective rain

Stratiform rain

Stratiform rain fraction

TRMM PR Jan-Apr 1998El Niño precipitation, observed % stratiform, El Niño basic state

250 mb stream function, 400 mb heatingK/day

Schumacher, Houze, and Kracunas (2003)

TOGA COARE: Implications of tropical MCSs for momentum transport in large-scale waves

1000 km

1000

kmTOGA COARE

MCS momentum transport in strong westerlies

Moncrieff &Klinker 1997

plan view

cross section

A B

A B

strong westerly region westerlyonset region

TOGA COARE: Ship and aircraft radar data relative to Kelvin-Rossby wave structure

Houze et al. 2000

SW NE

Houze et al. 2000

TOGA COARE: Strong Westerly case of 11 February 1993

stratiformecho

Downward momentumtransport

Where do we stand now with west African MCSs?• GATE & COPT81 showed us the existence and prominent importance of the MCSs in the west African phenomenology

• TOGA COARE & TRMM have shown us the global importance of mesoscale organization (esp. sf regions) in water budgets, vertical distribution of heating and momentum transports.

What’s missing?• We haven’t determined the mechanisms of interaction on the meso-to-synoptic scales.

Why AMMA?• AMMA is best place to use latest technology to see better how the meso-to-synoptic scale interaction occurs, esp in the context of AEJ and AEW.

• AMMA not only will allow this fundamental interaction to be studied but will allow the downstream effects on hurricane formation to be determined.

Technology in GATE & COPT81• Upper-air sondes in GATE—poor quality winds

• Ship radar in GATE--precip only, no Doppler, no polarimetry, no S-band

• Land radar in COPT81 --dual-Doppler, no polarimetry, limited coverage, no S-band, no large-scale context

• Aircraft in GATE—mostly in situ flight track met obs, some dropsondes, photos out the window

Technology available for AMMA• Better rawinsondes, ISS (integrated sounding systems), profilers

• Mobile S-band for land deployment, with polarimetry

• Doppler radar on ship

• Airborne Doppler radar

• Long range dropsondes, driftsondes

• Doppler lidars

• More diverse set of satellites

NSF/NCAR S-pol radar

• Polarimetric• Doppler• S-band, 10.7 cm• Zh, Vr, Zdr, Kdp, Ldr

•Portable—Deployed successfully in TRMM/LBA (Brazil), MAP (Italian Alps) and other difficult sites

Integrated Sounding Systems

•UHF Doppler wind profiler (~ 0.1 – 7 km agl)•Radio-Acoustic Tv profiler (~0.2 – 2 km agl)•GPS rawinsonde sounding system •Automated surface met obs•Seatainer packaged•Soundings , > 2/day + event-based

Proposed Use of the R/V Ronald H. Brown During AMMA

Instruments

• Radar (Scanning C-band Doppler; Vertically pointing Ka-band Doppler)

• Rawinsonde

• 915 MHz wind profiler

• DIAL/Mini-MOPA LIDAR

• Multi-spectral radiometers

• Air-sea flux system

• Meteorological observation (T,RH, P), rain gauges and ceilometer

• Oceanographic measurements including SST, CTD and ADCP

Summary: MCSs in AMMA

GATE & COPT81 showed that mesoscale organization was an important part of the tropical cloud population, both on land and offshore

Since GATE & COPT81, the mesoscale organization of tropical cloud populations has been seen to have global significance, esp. via TRMM & TOGA COARE

•Water budgets & precipitation•Heating profiles•Momentum transports

AMMA is the best place to use new technology to understand the meso-synoptic scale connection, since the interaction ofwest African MCSs & larger-scale dynamics is so robust:

•AEJ & AEWs•Saharan air layer•Tropical cyclone formation

These meso-synoptic scale linkages are essential to the overall picture of the west African monsoon sought by AMMA

Convection, microphysics, & lightning in AMMA

S. A. Rutledge

AMMA domain is a natural laboratory to study aerosol/cloud interactions and associated feedbacks to cloud dynamics.

Lightning: Recent work from TRMM-LBA (Brazil) suggeststhat aerosols may exert a fundamental control on flash rate and cloud dynamics. This issue can be further evaluated in AMMA.

Precipitation microphysics: Need to understand the microphysical aspects of the formation of the stratiform anvil precipitation.

Overarching issue: Microphysical aspects of African convective systems virtually unexplored.

Global frequency and distribution of lightning as observed from space

Christian, Hugh J. , Richard J. Blakeslee, Dennis J. Boccippio, William L. Boeck, Dennis E. Buechler, Kevin T. Driscoll, Steven J. Goodman, John M. Hall, William J. Koshak, Douglas M. Mach, and Michael F. Stewart, Global frequency and distribution of lightning as observed from space by the Optical Transient Detector, J. Geophys. Res., accepted, 2002.

01/99 - 03/99 Lightning Activity - Daily Detections(5 day moving average)

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12/99 - 03/00 Lightning Activity - Daily Detections(5 day moving average)

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= East regime

Brazilian Lightning Detection Network (BLDN):

• Oscillations apparent

• East (west) anomalies =more (less) lightning.

CCN higher in east regime;argued to lead to more lightning; a competinghypothesis is that CAPE is higher in East regime compared to West regime

Hydrometeor Identification-Example from STEPS 2000

Retrieve mixing ratio estimates

from polarimetric data

Performance of the S-POL radar rainfall estimate relative to rain gauges for

February 1999 TRMM-LBAMethod BIAS STANDARD

ERROR

S-POL Optimal

-4.8% 14.4%

S-POL Median -10.7% 17.9%

S-POL Closest -11.1% 20.6%

Using polarimetric techniques,accurate rain rates can becalculated and used for budget calculations and hydrological applications

Summary: Convection, microphysics, & lightning in AMMA

S. A. Rutledge

West Africa is the best place to study aerosol effects on tropical convection

Ice phase microphysics are critical in both the MCS stratiform anvil precipitation and in lightning—aerosol may affect both

S-band polarimetric radar provides the basic tool for pursuing this work