US-Contributions to the AMMA Field Campaign
1. Background
The AMMA-US science plan was created in November 2003 and is available at the AMMA-US
website at http://www.joss.ucar.edu/amma. After discussions with various U.S. agencies
including NSF, NOAA and NASA, it was decided that the large programme promoted in that
document could not proceed as a coordinated multidisciplinary effort. Despite this, the AMMAUS SSG continues to promote the multidisciplinary science and focused field efforts described in
that document. A brief summary of the various funded and proposed US contributions to the
AMMA field program is provided here.
2. US Contributions to AMMA Field Programme in 2006
2.1 Tropical Atlantic Observations for Climate
PIs: J. Carton (Univ. Maryland), S. Garzoli (NOAA/AOML), P. Lamb (Univ. Oklahoma), B.
Molinari (NOAA/AOML), C. Zhang (Univ. Miami), Chris Fairall (NOAA-ETL), R. Houze (U.
Washington), S. Rutledge (CSU)
Science Objectives:



Improve understanding of processes that influence the WAM seasonal cycle
Improve understanding of processes that determine the seasonal evolution of the cold
tongue-ITCZ-WAM system.
Improve understanding of processes that determine interannual variability of tropical
Atlantic SSTs and West African land surface conditions.
U.S. observations for the climate component of AMMA include portions of existing global
observing networks that are in place and will continue through the three phases of AMMA, LOP,
EOP and SOP (i.e., they are supported as components of the U.S. contribution to the sustained
global observing networks of GOOS and GCOS). In addition, support for enhancements to these
networks will be sought. The global networks include:
(a) Argo profiling floats: The U.S. and France will coordinate deployments in the tropical
Atlantic to obtain the desired 3 degrees of latitude by 3 degrees of longitude Argo grid. U.S.
deployments will primarily be from Voluntary Observing Ships (VOS). The design life of Argo
floats is 4 years.
(b) The Global Drifter program: The U.S. will deploy drifters in the eastern tropical Atlantic as a
component of the global drifter program. These drifters provide SST observations on a 5 degrees
of latitude by 5 degrees of longitude grid. The U.S. will support 175 drifters in the tropical and
south Atlantic.
(c) VOS temperature profiles: The U.S. will continue to support two expendable
bathythermograph (XBT) lines, one that crosses the equator in the central Atlantic and the other
in the western Atlantic. We also provide XBT's to French scientists for deployment in the
tropical Atlantic.
(d) PIRATA array: U.S. scientists from NOAA's Pacific Marine Environmental Laboratory
provide the buoys used in the French and Brazilian components of the PIRATA program.
Funds are being sought to enhance the following sustained observing networks to increase
resolution and/or improve measurement techniques:
(a) Meteorological sensors and thermistor chains on drifters: Sea level pressure and surface
wind sensors will be placed on a portion of the tropical Atlantic array in the Gulf of Guinea and
eastern tropical Atlantic. Similarly, thermistor chains will be placed on a subset of drifters to
enhance the PIRATA and 3-degree Argo resolution of subsurface temperature observations.
(b) Improved meteorological packages on VOS: The IMET system provides better quality
surface meteorological data than the typical VOS array. These systems will be placed on the VOS
ships that traverse the eastern tropical Atlantic.
(c) Enhanced PIRATA array: Four additional moorings will be deployed, 3 along 23W at
approximately, 5N, 10N and 20N and one along 38W at 20N. If these moorings are supported,
yearly cruises to the eastern Atlantic will service the moorings and collect additional atmospheric
and oceanic data.
SOP U.S. Cruise 2006 (with implications for EOP and LOP cruises)
This cruise is scheduled for May-June 2006. During this cruise, in addition to classical current
and hydrological measurements in the upper ocean layers, 2 ATLAS buoys will be deployed at
positions along 23°W to be determined but in the vicinity of the blue stars in the figure below. In
addition, surface drifters (all equipped with SST sensors and some with wind and atmospheric
pressure sensors) and ARGO profilers will be deployed in the green shaded area to the right.
Support will also be requested for two other ATLAS moorings to be deployed in 2007 (i.e.,
implying yearly cruises to the region to maintain the ATLAS buoys). These ATLAS buoys along
with the ones located along 10°E will collect data in both the ocean and atmosphere boundary
layers and the variability on both sides of the ITCZ during all the phases of the WAM.
Funding Status for SOP-2006 Cruise
A letter of intent has been submitted to NOAA’s Office of Global Programs. The request is
presently included in OGP’s FY06 budget plan.
2.2 Observations of key weather systems and processes
US PIs propose to make strong contributions to the field campaign over the continent and
downstream tropical Atlantic during summer 2006. The opportunity exists to observe the key
weather systems that characterise the West African Monsoon (key for addressing scale interaction
issues and the diurnal cycle; important for both weather and climate) as well as how these
systems evolve and interact with the environment downstream (important for addressing tropical
cyclogenesis and tropical cyclone intensity change issues). Figure 1 shows the location of funded
and proposed major US-platforms during the SOP-2006 (supported by tropical Atlantic
observations already described above).
NOAA: Targeted Missions
Dropsondes with G-IV
NASA (ASHE)
Targeted Missions with
Aerosondes
DRIFTSONDE
(THORPEX):
SYNOPTIC AND
TARGETTED
ENHANCEMENTS
US-Surface-based research
radars
Climate Transect
French-funded dual-dopplar
radars
NASA: N-Pol, Groundbased obs and Citation
NSF: S-Pol, C-Band,
S-band profiler and ISSs
DOE: ARM Mobile
Facility
NOAA: Rawinsondes and
Pilots
(i) AMMA-Weather (NSF)
PIs: C. Thorncroft (SUNY/Albany), C. Davis (NCAR), R. Houze (U. Washington),
R. Johnson (CSU), S. Rutledge (CSU), B. Smull (U. Washington)
Science Objectives
 Improve understanding of the processes that influence the relationship between African
Easterly Waves, MCSs and Convection.
 Quantify the impact of MCSs on the synoptic scale.
 Determine the relative roles played by dynamics, microphysics and aerosols on the nature
of MCSs and their electrical properties.
 Improve our understanding of the processes that determine the diurnal cycle of
precipitation and regional circulations in the West African monsoon
Major Facilities (July/August 2006)
Facility
Funding Source
2 ISSs and NSF
sondes
(750
sondes)
Additional
EU/UK/GCOS/US
Sondes (900)
S-Pol and C- NSF
Band radar
S-band vertical NSF
profiler
Location
PIs
Gao/Tahoua (see figure Thorncroft/Johnson
below for locations)
Niamey/ Parakou
Ouagadougou
Niamey
EU/UK PIs
Thorncroft/Johnson
Houze/Rutledge/Smull
Niamey
Houze/Rutledge/Smull
Funding Status
The Science Overview Document for AMMA-Weather was submitted to NSF in summer 04 and
can be found at the AMMA-US website. The budget is proposed to cover 2 ISSs, Sondes and
radars. Proposals for soundings and radars are in preparation and are due in June 2005. A decision
is not expected until late fall 2005 at the earliest.
Proposed enhancements to the sounding network during July/August 2006. The Red quadrilateral of rawinsonde
stations is centered on AMMA-Weather radars at Niamey and will be supported by AMMA-Weather, GCOS and
European colleagues. The blue quadrilateral is centered on French radars and will be supported by Europeans.
(ii) Radiative Atmospheric Divergence using ARM Mobile Facility, Gerb Data, and AMMA
Stations (RADAGAST), (DOE)
PIs: A. Slingo, (University of Reading, UK), A. Diehdiou (IRD-Niger, Niger), J. Harries
(Imperial College, UK), J. Haywood (Met Office, UK), P. Lamb, (University of Oklahoma,
USA), T. Lebel (LTHE, France), D. Parker (University of Leeds, UK), Jean-Luc Redelsperger
(CNRM, France), Didier Tanre (Universite des Sciences et Techniques de Lille, France), C.
Thorncroft, (SUNY/Albany, USA)
Scientific Objectives


Make the first direct measurements of the divergence of solar and thermal radiation in the
unique West African atmospheric environment.
Make simultaneous measurements of the corresponding atmospheric vertical structure,
with the temporal sampling necessary to address fundamental questions about the
radiative forcing of climate.
Major Facilities
 New ARM Mobile Facility (AMF) would be deployed at Niamey, Niger (13.5°N, 2°E)
during the AMMA Special Observing Periods in 2006 to provide information on the
atmospheric structure (including aerosol loading) that is necessary to interpret radiative
flux measurements.
Funding Status: Funded by DOE.
(iii) NASA-Radar and other measurements near Dakar
PIs: Everette Joseph (Howard University), Gregory Jenkins (Howard University), John Gerlach
(NASA), Paul Kucera (U of N. Dakota), Jose Fuentes (UVA), Amadou Gaye (LPASF, Senegal)
Scientific Objectives:
 To characterize precipitation (intensity, type, PSD) and its relationship to the
thermodynamic/dynamic state of the atmosphere.
 To examine the transition of convective systems as they transition from continental to
oceanic regions.
 To compare satellite derived rain estimates to ground based measurements.
 To link convective systems passing Dakar, to the downstream tropical systems.
 To examine the linkages between Saharan dust/convective intensity/cloud microphysics.
Major Facilities
Facility
NPOL (July 15
– Sep 15)
North Dakota
Citation (Aug
1– Sep 15)
MPL
Funding Source
NASA
Location
Senegal
PI
Joseph
NASA (proposal Senegal
submitted)
Poellot
NASA
Welton/Gaye/Tanre
Mbour
Funding Status: Primary funding will come from NASA.
*Deployment for Rain gauges will begin during the summer of 2005.
**All other instruments will be deployed during the late spring/early summer of 2006.
(iv) Enhanced Rawinsondes and Pilot Balloons (NOAA)
GCOS Rawinsondes
Howard Diamond at NOAA/NESDIS/National Climatic Data Center has been interacting with
AMMA on the GCOS stations. This may include provision of extra soundings at GCOS stations
during the SOP. For example it is possible that order 6 sondes per day could be provided at one
GCOS station (e.g. Niamey) for two months during the SOP.
Pilot balloons
Michael Douglas (NOAA – NSSL) is preparing a proposal to deploy pilot balloons during the
SOP. This proposal will request funds to establish and operate a pilot balloon network in west
Africa. The objectives of these observations, to last 6 months, are (i) to supplement the AMMA
rawinsonde network, (ii) to provide measurements over a longer time frame than possible from
many other AMMA special observation platforms and (iii) to provide an impetus for a sustainable
wind sounding system in west Africa that is quantitatively and qualitatively improved over the
current observing network.
Funding Status
The GCOS soundings can be included in the GCOS FY06 budget and the pilot balloon proposal
will be submitted to NOAA OGP.
(v) AMMA-Seedling Hurricanes Experiment (ASHE)
PIs: G. Holland (Aerosonde), F. Marks (NOAA-HRD), J. Dunion (NOAA-HRD), D. Parsons
(NCAR, THORPEX), J. Simpson (NASA), P. Webster (Georgia Tech), Naomi Surgi (NCEP)
Science Objectives
 Scale interactions are critical to the genesis of tropical cyclones. This is a highly dynamic
and transient process involving wave dynamics, mesoscale convective systems1, their
associated vortices, and the convective processes leading to establishment and
maintenance of an upper-level warm core. The main hypothesis to be tested is that:
The formation of tropical cyclones in the eastern Atlantic arises initially from
an accumulation of Rossby-mode wave energy and its associated down-scale
transfer cyclonic vorticity.
Should a suitable platform become available, we would also investigate the
smaller-scale interactions between mesoscale convective vortices and tropical
cyclone development.

1
Vertical windshear is well known as an inhibitor of tropical cyclone development.
However, we suggest that not all windshear regimes are bad. In particular we hypothesise
that:
A small amount of easterly windshear is beneficial for tropical cyclone
development, as it inhibits leakage of wave energy in the vertical.
By mesoscale, we infer spatial scales of up to several hundred km.

Thermodynamic processes, including the effects of dry and dust laden mid-tropospheric
air and boundary layer energetics may prevent or enhance the potential for the scaleinteractions to develop a hurricane. Whilst we do not have an hypothesis to be tested
here, we plan to take observations of both the dust layer and the boundary layer which
will help lead to a better understanding of these processes.
Major Facilities
Facility
Aerosondes
Funding Source
NASA
Rawinsondes
G-IV
Driftsonde
(THORPEX)
NOAA
US/France
Location
Key US PIs
Dakar or Conakry or Holland/Simpson/Webster
SAL
Conakry
Holland
Based in Barbados
Dunion/Marks
Launched from Chad
Parsons
Status of Funding
Partial support for Driftsonde and Aerosonde, additional funds to be applied for. G-IV
commitment in principle, subject to first priority being for hurricanes affecting US east Coast.
3. Atlantic Marine ITCZ (AMI): 2007
This is a US-CLIVAR endorsed project to study climate processes of the Atlantic marine ITCZ in
the eastern Atlantic. It is being led by Y. Kushnir (Lamont) and C. Zhang (Univ. Miami). It
focuses on field campaigns that complemented by modeling and diagnostic activities. AMI field
studies joins together with the AMMA climate component over the ocean in two campaigns: 2006
with measurements of the upper ocean, air-sea fluxes, atmospheric boundary layer, clouds and
upper-air temperature, humidity and winds from R/V Ron Brown and 2007 with multiple
platforms (ship and aircraft) in the tropical eastern Pacific, augmented by AMMA sounding
network over West Africa. There are also plans for this to include an aerosol component along the
lines originally discussed in the AMMA-US Science plan.