Since the end of the 1960s West Africa has continuously been suffering hard drought. The rainfall deficit for the 1970s and 1980s, calculated to compare with the 1950s and 1960s, thus reached as high as 50% over the northern part of the Sahel. The hydrological cycle as a whole is affected by this drought, which results in serious consequences for agriculture and food security.
IRD researchers, aiming to understand the mechanisms behind this situation, examined rainfall data from 1950 to 1990. Two sub-periods emerge : a wet one (1951-1969), followed by a dry one (1970-1990). This finding led them to modify drastically the classic model which presents the monsoon as a process that unfurls in a continuous sweep from South to North. Two rainfall dynamics regimes are in evidence, distinct in time and in space, separated by a sharp transition. The mean date for this, a jump heralding the monsoon onset, is around 22 June, which proved to be highly constant for both the wet and the dry sub-periods.
The proposed model predicts that the first monsoon phase starts off from the Atlantic coast in February and propagates steadily northwards. By May it has reached the central Sahel (13°N longitude, Niamey). After a period of stabilization, rainfall abruptly becomes much heavier. It touches the whole Sahel zone simultaneously. A short dry season then appears on the coast before a second rainy season arises there from September, linked to the retreat of the monsoon towards the South.
Marie-Lise Sabrie | alfa
Five-point plan to integrate recreational fishers into fisheries and nature conservation policy
20.03.2019 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
Rain is important for how carbon dioxide affects grasslands
06.03.2019 | University of Gothenburg
DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.
The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...
Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.
The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...
Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.
Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.
A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...
Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.
"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...
11.03.2019 | Event News
01.03.2019 | Event News
28.02.2019 | Event News
22.03.2019 | Life Sciences
22.03.2019 | Life Sciences
22.03.2019 | Information Technology