Is it true that he snowed in San Paolo in 1918?

The atypical cold event generated confusion in the company of San Paolo of the last century.

In the famous notebook Visit waiter Keep by the writer Oswald de Andrade on Rua Líbero Badaró, nicknamed “Líbero Street Plus”, there is a reference that snowed on June 25, 1918.

The event, in an atypical cold, really generated confusion in the San Paolo company.

But at least since there are weather measurements in the city, the snow has never fallen to San Paolo. What happened on June 25, 1918 – and also on other occasions, such as 24 and 28 July 1925 – was a strong frost.

“There was no snow. The confusion made is because the snow crystal is the same as the Frost crystal”, the meteorologist Mario Festa, of the Institute of Astronomy, Geophysics and atmospheric sciences of the University of São Paolo (IAG/USP) explains to the BBC News Brazil.

“Only Frost does not fall. We speak popularly that ‘the dew has fallen, the peaceful has fallen, the frost has fallen’, but this is a wrong term.”

As detailed, since Frost cannot have clouds in the snow of the sky, you must have them.

“To get the snow, he must have a cloud,” says Party.

“Because, for the frost, the sky must be completely clean, so that the stored heat is dissipated. This very fast cooling causes humidity near the surface, under certain conditions, freezes. Or, in the case of dew, they simply form liquid drops.”

So, check the registers maintained by IAG/USP itself on what happened in San Paolo on June 25, 1918: The Five Markings, all day, indicated nebulosity 0, none.

It made very cold very cold: 1.2 negative degree. This scenario must have caused a rare frost, leaving the population embarrassed.

“Snow is a form of precipitation and rain”, the meteorologist and scientific promoter Samantha Martins, author of the Meteoropole blog, explains to the BBC News Brazil.

He explains that the geographical conditions make the snow very unlikely in the city of San Paolo.

“Although we are on a plateau, it is not high enough: it is located about 800 meters above sea level. The latitude is not high enough, we are in the tropical area, not close to the South Pole, so there are conditions to have an intense polar mass that will act in the formation of the snow,” he says.

And the hail?

On the other hand, the rain of hail takes place in San Paolo with relative frequency.

In a nutshell, the difference between snow and hail is particles size: while the snow is very small, the hail goes from millimeters to 10 centimeters in diameter, explains the party.

He explains that hail forms in the clouds of cumulonimbus storms.

At high altitudes, clouds usually have frozen particles. Most of the time, however, they melt in rainfall as they approach the ground due to the maximum temperature – instead of the snow, the rain turn; This is the reason why it takes temperatures on the ground close to zero so that the snow occurs.

In the case of Cumulonimbus, the nature of the cloud allows larger particles formations.

In the strong storms, these ice oscillations fall and reach the ground before melt. It is hail.

“Unlike microscopic wheat, snow crystals, in the case of hail are an ice sphere, which can have absurd diameters,” comments the party.

History of Paulistana’s meteorology

It was not only on June 25, 1918, in the episode of False Snow, which San Paolo recorded 1.2 negative degree. This temperature, until today, was repeated in the city, was repeated in three other dates: on 6 and 12 July 1942 and 2 August 1955.

The IAG is the oldest institute in the country to perform systematically and continuously meteorological measurements. The measurements began in 1910. The body is the result of the geographical and geological commission, created by the provincial government in 1886, bringing together a group of intellectuals and researchers from various areas.

In meteorological terms, however, there is a problem in this 110 -year historical series.

The measurements have not always been carried out at the same address, today in Água Fund, south of San Paolo. The first meteorological station was in the middle of Paulista Avenue, next to the civil engineer José Nunes Belfort de Mattos, appointed director of the site.

With the growth of tram traffic in Paulista, atmospheric observation devices have started to present inaccuracies caused by the trepidations. In 1933, therefore, the current station was inaugurated in Água Fund. The measurements continued to be held to Paulist until 1935.

Before the IAG, there are documents from other weather observations in San Paolo, according to the points of the meteorologist Paulo Marques Dos Santos in his book USP Astronomical and Geophysical Institute: Memory about its training and evolution.

The precursors were the Portuguese astronomers Bentos Sanches Dorta and Francisco de Oliveira Barbosa, between 1788 and 1789.

The English naturalist William John Burchell also made a record of San Paolo in 1827.

Santos also highlights the long historical series, from 1848 to 1856, recorded by the Brigade José Joaquim Machado de Oliveira and, sporadically during the 19th century, the observations of the English civil engineer Henry Batson Joyner and the Capuchin Germano of Annecy.

The meteorologist cites, in his book, that there were two private observers in San Paolo, at the end of the 19th century. One was by Professor José Feliciano de Oliveira. The other, of General Couto de Magalhães.

*This report was originally published on August 21, 2020

Source: Terra

Rose

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