Wondering why you get bad reception on your phone during heavy rainfall? Well, scientists in Karlsruhe Institute of Technology have an explanation for you. Radio waves transmitted between antennas borne on cell phones masts (the carriers of telecom signals) are typically in the frequency range of 15 to 40 gigahertz. Atmospheric scientist, Angela Fritz explains; at these frequencies, the radio signals are significantly disturbed by rainfall in two ways; first, raindrops absorb a portion of the radio signals. Secondly, the raindrops strew a portion of the signals away from their normal path. The result of these two phenomena is a reduction in the signal level at the receiving end of the antenna—which is basically the antenna that picks up your cell phone signals.
Telecommunication Signals Are Disturbed By Rainfall; Great To Turn Problem Into an Ingenious Idea
This might be a problem for telecommunication service providers because they are unable to provide good reception for their subscribers, but it might be a solution for rainfall collection (Leijnse et al., 2007). For scientists, the reduction in signal level is enough to discern rainfall intensities (how hard it rains) for smaller areas. In a study published in journal of science, 2006, researchers at Tel-Aviv University in Israel first used fluctuations in signal level to calculate rainfall intensities. Since then, several researchers including Leijnse et al. (2007) in The Netherlands, Chwala et al. (2012) in Germany etc. have improved upon the technology. Quite recently, researchers at University of Ouagadougou in Burkina Faso tested the idea in West Africa. Comparing their results to ground based rainfall measurements, the scientist concluded that rainfall calculated from fluctuations in telecom signal level can detect rainfall occurrence with 95% reliability and with comparable rainfall estimates to ground measurements from rain gauges or weather radars.
What Does This Mean For Rainfall Observation In Africa?
Collecting rainfall intensity data is difficult in many parts of Africa due to expensive or unreliable equipment. Usually, rainfall trends in Africa are monitored using rain gauges, which are mostly limited in number and sparse in distribution. Thus making it less effective to monitor rainfall trends in the region. Weather radars are mostly absent due to cost of acquisition, implementation and operation. Satellite products also give information on rainfall but are generally unreliable. According to the Global System Mobile Association, GSMA, there are over 200, 000 telecom towers across Africa. This presents an enormous opportunity to use this already existing infrastructure for rainfall monitoring at low cost.
But, Why Is Rainfall Collection Imperative?
Already, many countries in Africa experience adverse effects of weather and climate in the agricultural sector and other aspects of livelihood. Through accurate rainfall collection using preexisting infrastructure to create an out of box innovative approach, Africa can benefit from documenting these rainfall trends to better prepare for droughts, floods, and other matters that make growing food an added risk.
Current Research On Rainfall With Telecom In East Africa
Researchers at the University of Twente, Faculty of Geo-Information Science and Earth Observation in Netherlands are focusing on combining signal information from mobile telephone service providers in Kenya (East Africa) with satellite data to study rainfall trends for large areas in Kenya. Their aim is to develop a low cost, realistic and sustainable alternative to weather radars which at the moment remains prohibitive to adapt in most parts of Africa due to its cost. Once developed for Kenya, the system is expected to be easy to implement in other countries in Africa, at a minimal cost.
References:
Angela, F. (2014). Another milestone toward making cell phones the future of weather observations. Retrieved July 18, 2016, from https://www.washingtonpost.com/news/capital-weather-gang/wp/2014/09/04/another-milestone-toward-making-cell-phones-the-future-of-weather-observations/
Chwala, C., Kunstmann, H., Hipp, S., Siart, U., & Eibert, T. (2012). Precipitation observation using commercial microwave communication links. In International Geoscience and Remote Sensing Symposium (IGARSS) (pp. 2922–2925). doi:10.1109/IGARSS.2012.6350714
Leijnse, H., Uijlenhoet, R., & Stricker, J. N. M. (2007). Hydrometeorological Application Of A Microwave Link: 2. Precipitation. Water Resources Research, 43(4), 1–9. doi:10.1029/2006WR004989
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