Autumn 2023 begins at 6:25 pm (Brasília time) this Monday (20). The season is marked by milder temperatures and, in this period, rainfall is scarce in the interior of Brazil, especially in the northeastern semi-arid region. “It is considered a transition season between the hot and humid summer and the cold and dry winter, mainly in Central Brazil”, explained the National Institute of Meteorology (Inmet), in a statement. He added that, in the northern part of the Northeast and North regions, autumn is still a time of heavy rain, especially if there is persistence of the Intertropical Convergence Zone further south of its climatological position for the period. This zone is the area where the trade winds converge, which blow from the tropics to the region of the Equator and which, because they are very humid, cause rain in these surroundings. At the other extreme, autumn is also characterized by inflows of cold air masses from the south of the continent, which cause a drop in air temperatures, mainly in the South Region and in part of the Southeast Region. “It is also worth mentioning that, during the season, it is possible to observe the first formations of adverse phenomena, such as fog in the South, Southeast and Midwest regions; frosts in the South and Southeast regions and in Mato Grosso do Sul; snow in the mountainous areas and on the plateaus of the South Region, and cold weather in the south of the North Region and in the states of Mato Grosso do Sul, Mato Grosso and even in the south of Goiás”, explained Inmet. The beginning and end of the seasons are associated with astronomical phenomena called solstices (summer and winter) and equinoxes (spring and autumn), which are defined by the Earth’s position in its orbit around the Sun, as well as the inclination of the axis of rotation. relative to the orbit. On March 20th, the autumnal equinox occurs in the southern hemisphere, a time when the length of the day is approximately equal to the length of the night, the same as happens on the spring equinox. As time goes by, the days get shorter and the nights longer until the winter solstice, which will be on June 21, at 11:58 am (Brasília time), when autumn ends and winter begins. Already on the summer solstice, the day has its longest peak in the entire year. La Niña According to Inmet, the La Niña phenomenon has been losing intensity and forecasts indicate a transition to normality and subsequent formation of El Niño between the end of autumn and the beginning of winter. La Ninã has contributed to the occurrence of more frequent rains in the North and Northeast regions, as well as the scarcity of rains in the South Region of Brazil, especially in Rio Grande do Sul, during this summer that is ending. It is a climatic phenomenon caused by the cooling of the surface waters of the Pacific Ocean, which bathe the west of South America, in Chile, Peru, Ecuador and Colombia. This cooling alters the tropical atmospheric circulation and impacts temperatures and rainfall around the world. El Niño is the warm phase of the phenomenon. Forecast by region The forecast for autumn in the North Region indicates that rainfall should remain above the climatological average, with volumes that may exceed 800 millimeters, mainly in areas of northeast Pará and northwest of Amazonas due to the persistence of rainy days. In the south of Pará, the probabilities indicate rains slightly below the average. The Inmet forecast also indicates the predominance of temperatures close to and slightly above average in much of the North Region, with values that may exceed 26ºC. In the Northeast, the forecast for the next quarter indicates above-average rainfall in much of the region, and between the months of April and May, rains should persist in areas further north due to the permanence of the Intertropical Convergence Zone. In addition, the warmer waters near the northeastern coast increase the chances of rain until the end of autumn. In the east of the region, rainfall normally exceeds 400 millimeters in the quarter with the onset of the rainy season. Temperatures will remain close to the average, from the coast of Maranhão to Alagoas, however, in the interior of the northeast, the forecast is for higher temperatures. In the Midwest Region, rainfall should be close to or above the climatological average in Mato Grosso and the extreme north of Mato Grosso do Sul. In other areas, they should vary between close to or below average. Inmet points out that, from the month of May, the dry period begins in the central part of the country and temperatures should be above average throughout the region, mainly in the north of Goiás, where temperatures can be above 24ºC. In the Southeast, the forecast indicates below-average rainfall this fall. As in the Midwest Region, there is usually a reduction in rainfall over this region as winter approaches, starting the dry period. The average air temperature should prevail close to and slightly above the climatology of the period, however, the possibility of the entry of cold air masses that could decrease temperatures in a few days in higher altitude locations, starting in the month of May, cannot be ruled out. . Cold fronts In the south of the country, the prognosis indicates below-average rainfall in much of Paraná and Santa Catarina, except in the east of these states, where rainfall may be close to average, due to the passage of cold fronts. Meteorologists highlight the forecast of the return of more frequent rains over Rio Grande do Sul, due to the weakening of the La Niña phenomenon, “which devastated the state for three consecutive years, causing a shortage of rain”. The air temperature in the South Region should prevail above the climatology of the period, however, the possibility of frost is not ruled out, mainly in mountainous areas, as winter approaches. On the coast of the region, the rains may soften the temperatures.
Agência Brasil
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