Transcript 030306_AMMARoadshowV13_Houze.ppt

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
Post-GATE view of tropical cloud population
Houze et al. (1980)
GATE & COPT 81:
MCS water, mass, and heat budgets
Water Budget of a West African Mesoscale Convective System
over ocean (GATE) and land (COPT81)
0
.13R
.37R
1.17R
.41R
GATE
(Gamache & Houze 1983)
COPT81
.16R
(Chong & Hauser 1989)
.29R
.60R
.40R
Height (km)
MCS heating
profiles seen
in GATE
& elsewhere
Assumed
heating
profiles
Convective
Deg K/day
MCS heating
profiles seen
in GATE
& elsewhere
Assumed
heating
profiles
Height (km)
Stratiform
Convective
Deg K/day
Height (km)
Assumed heating profiles
Assumed heating profiles
0% stratiform
Deg K/day
Assumed heating profiles
Assumed heating profiles
Height (km)
40% stratiform
0% stratiform
Deg K/day
Assumed heating profiles
Assumed heating profiles
70% stratiform
Height (km)
40% stratiform
0% stratiform
Deg K/day
TRMM: Global mapping of MCSs
Contribution of convective system type to rainfall
Nesbitt,
Zipser
& Cecil
(2000)
AFRICA
S. AMER.
E. PAC.
W. PAC.
TRMM precipitation radar rain amount subdivided into
convective and stratiform components
Total rain
Schumacher
and Houze
(2003)
Convective rain
Stratiform rain
Stratiform rain fraction
TRMM PR Jan-Apr 1998
El Niño precipitation, observed % stratiform, El Niño basic state
Schumacher,
Houze, and
Kracunas (2003)
K/day
250 mb stream function, 400 mb heating
TOGA COARE: Implications of tropical MCSs for
momentum transport in large-scale waves
A
MCS momentum
transport in
strong
westerlies
plan view
1000 km
TOGA COARE
B
Moncrieff &
Klinker 1997
1000 km
cross section
A
B
TOGA COARE: Ship and aircraft radar data relative to
Kelvin-Rossby wave structure
Houze et al. 2000
strong westerly region
westerly
onset region
TOGA COARE: Strong Westerly case of 11 February 1993
stratiform
echo
SW
NE
Downward
momentum
transport
Houze et al. 2000
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 Sband
• 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
•Portable—Deployed
successfully in
TRMM/LBA (Brazil), MAP
(Italian Alps) and other
difficult sites
• Polarimetric
• Doppler
• S-band, 10.7 cm
• Zh, Vr, Zdr, Kdp, Ldr
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) suggests
that 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.
Brazilian Lightning Detection
Network (BLDN):
• Oscillations apparent
• East (west) anomalies =more
(less) lightning.
= East regime
CCN higher in east regime;
argued to lead to more
lightning; a competing
hypothesis 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-LBA
Method
BIAS
S-POL
Optimal
S-POL Median
-4.8%
STANDARD
ERROR
14.4%
-10.7%
17.9%
S-POL Closest
-11.1%
20.6%
Using polarimetric techniques,
accurate rain rates can be
calculated 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