Can commercial cellphone providers help to gather high quality rainfall information?

The knowledge of spatio-temporal distribution of precipitation is of crucial importance for the scientific understanding of the regional hydrological cycle and for sustainable water management. High quality rainfall information is the prerequisite for e.g. decision making in agriculture, the operation of hydroelectric power production and also urban flash flood warning. Installation- and maintenance costs in combination with limited financial abilities make it more and more difficult for national meteorological and hydrological services to provide precipitation information in requested high spatial and temporal resolution on a country wide scale, particularly in West Africa.

It is the microwave links operated by commercial cellphone providers that may allow now for highly valuable complementary precipitation information: the attenuation occurring between emitted and received power at the link antennas highly correlates with precipitation intensity along the link-paths. Advantage is that the technical infrastructure, i.e. the MW-link network, is already in operation and maintained by the companies. While data retrieval techniques and respective algorithm development has proceeded in Europe and the Near East in the last years, great potential is particularly seen in the general data scarce region of West Africa. WASCAL has now co-sponsored and organized a 4-day workshop in Ouagadougou on this technique, jointly with experts from the University of Ouagadougou, Germany (Karlsruhe Institute of Technology and University of Augsburg), France (IRD and GET), The Netherlands (University of Wageningen and KNMI), Israel (Tel Aviv University), and Switzerland (EAWAG), forming jointly the Raincell Africa initiative.

87 students, scientists and met service representatives from Burkina Faso, Ghana, Benin, Senegal, Niger, Mali, Togo, Nigeria, Senegal, Ivory Coast, Kenya, Tanzania, Cameroon and the US followed the scientific presentations of the international experts and a 2 day training course offered by the experts from KIT, University of Wageningen and KNMI. Topics included the physics of microwave attenuation, the detection of wet and dry periods under a noisy received signal level, and the explicit rain rate estimation. Further focus was set on the effect of wet antennas and the spatial interpolation of individual link information. Algorithms were based on two public domain and open source programming languages, namely Python and R. It is particularly the use of these free open source software environments that can foster a wide distribution and application of the tools at West African universities, research institutes, met services or climate service centers like WASCAL. First MW-link attenuation data were already made available from TELECEL to the University of Ouagadougou. Representatives of the participating cellphone company TELMOB/ONATEL started now to elaborate further steps jointly with WASCAL and the University of Ouagadougou to realize an automatic and even countrywide data access, -analysis and -use.

Prof. Dr. Harald Kunstmann and Dr. Boubacar Barry, WASCAL, organizing committee of the Raincell Africa Workshop.