West African Monsoon and Rainfall Enhancement Studies - Mali

Objective

Map: West Africa. Mali Region. RAL Rainfall enhancement program area.
Target Region: Mali within the bounded region.
(click map to enlarge)

Water stresses often occur in West Africa. Increasing demands for water require that the potential for enhancing the sources, storage, and recycling of freshwater be examined carefully. Also, destruction and loss of life due to extreme weather events (e.g. flash flooding, extreme winds, etc.), which has the potential to be amplified with population growth and changing demographics, can have a large impact on human lives of the region.  There is a need to examine ways to reduce these impacts. Recently, Mali has been conducting cloud seeding operations in hopes of augmenting precipitation to off-set the growing demands for water resources.

To increase our understanding of the the potential for cloud seeding to enhance rainfall, Mali has implemented   an operational cloud seeding program to conduct these studies and assessment. NCAR is helping to support the operations by focusing on the evaluation and assessment studies on the potential for rainfall enhancement through cloud seeding experiments, airborne sampling, radar analysis, and randomized seeding trials.

Furthermore, understanding of the West African Monsoon and associated precipitation physics is critical in assessing the potential for cloud seeding to enhance rainfall in this region of the world. In addition, there is evidence that human activities such as the emission of industrial air pollution can alter atmospheric processes on scales ranging from local precipitation patterns to global climate (NRC, 2003). Documentation of anthropogenic effects on the weather strengthens the physical basis for the viability of deliberate attempts to alter the weather.  However, to understand these inadvertent impacts on weather and climate require a concerted research effort.

Main Goal: To assist Mali and field personnel in conducting a feasibility study to assess the potential for rainfall enhancement using cloud seeding techniques. The feasibility study is conducted  during the Monsoon season, which generally occurs between June and October.  The program includes the latest technologies that have been developed in this field to conduct an airborne measurement program. The collaborative work will entail all necessary aspects of the project, including cloud physics and will build on the experience obtained in programs in other parts of the world.  The first three years (2006, 2007, 2008) focused on sampling of clouds and aerosols with aircraft and radar observations along with a preliminary randomized seeding program.  The 2009 program (June-September) will continue to sample clouds and aerosol along with the continuation of an exploratory randomized seeding program.

RADAR

Mali Radar map
Radar locations in Mali

The use of radar in rainfall and storm structure studies has become an important tool over the past twenty years. Because meteorological radars provide a wealth of information about precipitating cloud systems, it has also become essential to employ state-of-the-art software systems to display and analyze the data. While networks of weather radars are common in many western countries, large parts of Africa and other developing countries are currently not covered by weather radars. Recently, several African countries have also started to acquire weather radars but in many cases lacked the infrastructure to maintain, calibrate the radars, and interpret and analyze the data collected from these radars. Additional measurement capabilities in Mali and adjacent (e.g., Burkina and Senegal) regions will fill an important gap in the observational area of the Sahel, This region spans the transition zone between the Sahara desert regions and the more wet tropical southern areas of West Africa. The additional observational capabilities in this region could help in understanding the interaction between the Saharan dust layer and thetropical airmasses that propagate into the Sahel region from the south and the evolution of MCS's and CS's in this transition region and associated changes in rainfall patterns in the region.

This website provides real-time displays from radars (Bamako, Manantalli, and Mopti) located in Mali. View radar information and data.

Aircraft Observations

Of additional interest is the influence of aerosols and cloud microphysics (size and concentration of water droplets and ice particles inside clouds) on buoyancy, convergence, intensification of convection, and potential for enhancement of the natural precipitation. Aircraft operations are being conducted to assess the feasibility of any future precipitation enhancement potential in Mali. No previous airborne aerosol and microphysical measurements have been conducted in Mali. The aerosol and microphysical measurements will determine the optimal seeding method that may have potential for enhancing precipitation in Mali. The potential for such manmade increases is strongly dependent on the natural microphysics and dynamics of the clouds that are being seeded. These factors can differ significantly from one geographical region to another, and even between seasons in the same region. In some instances, clouds may not be suitable for seeding, or the frequency of occurrence of suitable clouds may be too low to warrant the investment in a cloud seeding program. Both factors need to be evaluated in a climatological sense. It is therefore important to conduct preliminary studies on the microphysics and dynamics of the naturally forming clouds prior to commencing a larger experiment. It is also important to conduct hydrological studies relating rainfall with river flows and reservoir levels, and to determine hydrological regions where reservoir catchments are most efficient.

Real-time Forecasting

Guidance for the aircraft observations is provided by the radar network in Mali as well as a real-time forecast model run at NCAR/RAL.