A cloud of dust impressed residents of the interior of São Paulo and Minas Gerais on Sunday (26), reaching cities such as Franca, Ribeirão Preto, Araçatuba, Barretos and Presidente Prudente.
According to information published by the Climatempo portal, the wind gusts reached the mark of 92 km/h and the registered relative humidity was 19%.
According to Professor Pedro Luiz Côrtes, from the Post-Graduate Program in Environmental Science at the Institute of Energy and Environment of the University of São Paulo (IEE/USP), the phenomenon is due to a confluence of factors.
The arrival of strong winds that precede the rains, the soil prepared for cultivation and the arid condition of the climate all add up and help to create the dust cloud scenario.
“The topsoil breaks down into very fine particles that are easily carried by these strong winds, especially in flatter regions. It happened basically because we have an extreme drought in the interior of the state of São Paulo. If you have a soil with certain moisture, these finer particles are aggregated, so the wind has no way of transporting it.”
The professor explains that this event is rare in Brazil, but occurs globally in regions and continental scales.
“We have winds carrying dust from North Africa to Italy or from North Africa to Central America, for example. This type of phenomenon in global terms is something common”.
In Brazil, the researcher points out that the dust cloud does not form often because areas marked by chronic water scarcity, such as the semi-arid region of the Northeast, present very aggregated soil, which makes it dry and hard.
“When there is manipulation of the soil for cultivation, then yes, there is the disaggregation of these more superficial parts for you to place seed, and this favors the occurrence of this type of phenomenon”, complements Côrtes.
“But it is not common because when the preparation for cultivation is done, normally you have soils with a certain humidity. What really triggered it, the last factor necessary for this to happen was the situation of extreme aridity that we have today in São Paulo”, points out the professor.
The phenomenon may also repeat itself again in the region where the dust cloud was recorded, but, according to the researcher from USP, this should not happen exactly in the next few days because the wind registered in the region was followed by rain. The arrival of precipitation helps to moisten the soil.
“But, if this condition of extreme drought persists, this could happen again, also because the forecasts of intense heat remain throughout the spring and with a low amount of rain”, points out Côrtes.
Edition: Anelize Moreira