TT1: Sounding of the Atmosphere
Fink, Serge Janicot and Doug Parker
Sounding of the Atmosphere (latest update: 23.02.2006, pdf, 0.5 MB)
Scientific justification and objectives
It is the general
goal of the AMMA Radiosonde Group (ARG or TT1 group) to assist in the development
and maintenance of a coordinated network of radiosonde, PILOT balloon, VHF/UHF
and GPS Total Columnar Water Vapour (TCWV) stations during the AMMA EOP period
and beyond to address specific AMMA scientific objectives for atmospheric research
AMMA is planned around
three nested timescales that will be referred to in the following text:
- LOP studies are
based on long-term observations, including archived data and rescued datasets;
- EOP (Extended
Observing Period) studies are to be based around the years 2005 to 2007, during
which a coordinated set of observations of the atmosphere, land and ocean
systems will be obtained. Multi-season observations are to be made in order
to evaluate variability in the system, as well as mechanisms of 'memory' between
- SOP (Special
Observing Period) studies will take place in the summer of 2006. The SOP is
aimed at intensive observations of particular processes and is subdivided
into four periods according to particular scientific goals:
Dry season processes: January/February 2006
Monsoon onset: 1 June - 30 June 2006
Monsoon maximum: 1 July - 15 September 2006
Late Monsoon: 15 September - 30 September 2006
The upper air networks of radiosoundings, pilot balloons, UHF/VHF profilers
and GPS stations are crucial for the success of AMMA. Good upper air observations
are essential for the generation of reliable model analyses, which are in turn
necessary for environmental monitoring over the continent and the downstream
Atlantic. Upper air data is also needed for quantifying the basic physical processes
of the atmosphere. The current operational network consists of some stations
that have a good recent record of soundings, and a number which are experiencing
problems. AMMA aims at upgrading the existing stations and will also add a few
additional stations for the EOP. AMMA strives for the new stations at Tamale,
Abuja and Cotonou to be incorporated in the long term operational network.
The most extensive
set of upper air measurements over the continent was conducted during the GATE
experiment in 1974. These soundings remain a valuable resource for monsoon studies
(and are soon to be archived at the British Atmospheric Data Centre (BADC)).
ERA-40 reanalyses assimilating the radiosondes from the GATE year are also now
available. However, during GATE much of the emphasis, including the majority
of the observational subprograms, was focused on weather systems over the Atlantic
Ocean; during AMMA we aim to integrate the atmospheric sounding network with
observations of both the continental and ocean systems.
The WAMEX project of 1979 also involved increased soundings over the continent.
These data are stored as part of the FGGE archive.
Six stations in the region (Dakar, Niamey, Abidjan1, Tamanrasset, Addis Ababa
and Douala), are currently members of the GCOS Upper Air Network (GUAN), and
are therefore subject to scrutiny by the GUAN group.
One of the objectives
of the AMMA radiosonde group will be to arrange similar support and attention
to other key stations within the African Monsoon domain.