TT1: Sounding of the Atmosphere

TT-leaders: Andreas Fink, Serge Janicot and Doug Parker

Detailed information: TT1-Document: 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 and monitoring.

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 seasons.
• 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:
  1. SOP0 Dry season processes: January/February 2006
  2. SOP1 Monsoon onset: 1 June - 30 June 2006
  3. SOP2 Monsoon maximum: 1 July - 15 September 2006
  4. SOP3 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.