STUDY OF HISTORICAL PRECIPITATION SERIES FROM 1988 TO 2019 IN THE CITY OF FRANCISCO BELTRÃO-PR ESTUDO DAS SÉRIES HISTÓRICAS DE PRECIPITAÇÃO DOS ANOS DE 1988 A 2019 NA CIDADE DE FRANCISCO BELTRÃO – PR

It is through rainwater that water sources are recharged and subsequently distributed to the population, which uses this water in different ways. Knowledge of rainfall variations is of great importance for the planning and management of water resources, such as the study of intense and dry rainfall. This study aimed to analyze the historical series of rainfall from 1988 to 2019 in the city of Francisco Beltrão PR, northwest region of the state of Paraná. As a methodology, annual precipitation data were taken, which is measured by monthly rainfall averages, on the website Águas Paraná Paraná), and with this information, it was possible to carry out analyzes of rainfall in the interval of thirty years, which is the minimum time. Necessary to observe significant changes in the climate. From the results found and the analysis of the historical series, it was observed that the years 1988 and 1990 had the lowest (108 rainy days) amount of precipitation and the highest (173 rainy days), respectively. The big difference between them is that in 1988 Brazil was under the influence of the La Niña phenomenon, which reduces the rainfall regime. In addition, it was noted that there was a considerable increase in precipitation, which raises the hypothesis of the expansion of pollution, which consequently increases the rate of evapotranspiration and thus leads to an increase in rainy days. In the studied timeframe, Francisco Beltrão expanded his industrial area, which, consequently, may have generated greater atmospheric emissions. Thus, it was possible to conclude that from 1988 to 2019 the rainfall regime increased, assuming the greatest amount of pollution. There were also years when El Niño and La Ninã acted more intensely, causing disturbances that directly affected agriculture and vegetation.


INTRODUCTION
The precipitation is a central element for the terrestrial life maintenance, since through it, starts the hydrological cycle, as well as the recharge and water sources, which are subsequently, distributed to the population, that uses this water in different ways, as public supply, industrial process, household cleaning, leisure, among other possibilities (ZHANG; ZHANG; CHEN, 2017).
The rains correspond to a type of precipitation, that, according to Ayoade (2003), it is subdivided into snow and hail, in which they differ mainly due to the state of the water. Thus, precipitations may have different origins and characteristics, and, according to their intensity and periodicity on the surface, they will be associated with benefits and harms relevant to human activities.
In agriculture, the precipitation of the rainfall has an economic and social importance, as farmers depend on water from planting to harvest. The periods of long droughts mainly affect subsistence agriculture, leading to rural exodus.
In contrast, high levels of precipitation are related to the intensification of erosive processes, loss of productivity of more sensitive foods and difficulty in harvesting and draining the crop (SILVA et al., 2009).
It is known the understanding of seasonal variations in the precipitation regime of a region contributes to better regional planning. Thus, among the factors that influence the distribution of precipitation are: latitude, altitude, distance from the sea or springs, orientation of the slopes and vegetation. In addition to these, it is possible to mention the phenomena "El Niño" and "La Niña" as factors that influence prolonged droughts or excessive rains for consecutive periods. (SILVA et al., 2009). Bao et al., (2017) adds that air pollution exerts an influence in increasing the precipitation regime of an environment, since the long term usage of aerosols affect the height and thickness of clouds, which in polluted places are twice higher, resulting in an increase in the amount of rainfall.
The southwestern region of Paraná, in which the city of Francisco Beltrão is located, presented a rapid urban expansion in the last 30 years, a process influenced by the installation of new industries, in which it contributed to the population increase as well as the city verticalization (MACHADO, 2013).
Thus, in this present work, analyzes of historical rainfall series from 1998 to 2019 from the city of Francisco Beltrão were used, in order to compare them and associate them with climatic phenomena.

CHARACTERIZATION OF THE STUDY AREA
Francisco Beltrão city is located in the southwest of the state of Paraná  The rains are well distributed throughout the year with a higher incidence in spring and autumn and lesser during winter (in volume). Considering the rainy days, there is an average of 11 to 14 rainy days per month between the months of September to March and 8 to 10 days between April to August.
Annual rainfall is over 2,000 millimeters, but it tends to vary widely, mainly due to events like El Niño and La Niña (NITSCHE, et al., 2019).
As for the geomorphological aspects, Francisco Beltrão is located in the third plateau of Paraná, presenting medium dissection, with an altitude varying between 340 to 860 meters with elongated tops, V-valleys and convex slopes, in which they originate from the Serra Geral formation (MINEROPAR, 2006).
The soils of the region are predominantly purple oxisol, in which stands out in flat regions. Elsewhere, it occurs litolic and gleisol soils (MINEROPAR, 2002).

METHODS AND TECHNIQUES
Initially, the city of Francisco Beltrão in Paraná was chosen as the objective of the study. Right after on the website Águas Paraná (2019), in the hydrological information systems tab, the anual rainfall data of the city was downloaded, which are collected by the Mereorological Stations of the Institute. With this information it was possible to make graphs of comparative analyzes through the Excel program, which will be analyzed and discussed in this work.

RESULTS AND DISCUSSIONS
From the combination of precipitation data plus graph generation, it was possible to arrive at the following results presented below.
Thus, from the analysis of the 30 years, it is possible to observe differences between them, especially in specific periods, such as the years 1988 and 1990 (figure 2), where they present the lowest amount of precipitation and the highest recorded in the studied historical series, respectively. Source: Adapted from Águas Paraná (2020) Analyzing the graph, it is possible to observe that in the year 1990, which was the one with the highest rainfall index, there was a significant amount of rainy days in all months, with January standing out with twenty-four (24) days, which is already qualified as a rainy period. However, there is a greater amount of rainy days in periods that are characterized as dry, such as the months of April, June and July.
On the other hand, the year 1988 presented a characteristic environment behavior of environments classified as CFA (humid tropical mesothermal climate), which is part of the Koppen climatic classifications systems (SCC), characterized by the subtropical climate having summer temperatures above 22 degrees Celsius, therefore occurring more raining days in the summer season compared to the winter season (NITSHE et. al., 2019).
Thus, the biggest difference between the two years compared is possibly explained by the La Niña phenomenon, which operated in Brazil in 1988, which explains the decrease in the rainfall regime, directly affecting agriculture and other human activities. As for the data found, while in 1990 there were 173 rainy 3=days during the year, in 1988 the total value was 108 days, with the highlight being the month of January, with a 24-day index in 1990, twice as many days in the same month in 1988.
As mentioned, El Niño and La Niña are climatic anomalies where the intensification of rainfall occurs in the south of the country while in La Niña there is a decrease in the rainfall regime. The table 1 below shows all the years that were influenced by such anomalies.  1987/1988 1988/1989 1991/1992 1998/1999 1992/1993 1999/2000 1997/1998 2007/2008 2002  Source: Adapted from Águas Paraná (2020) In addition, when analyzing the context of 30 years of the historical series, it was possible to observe an increase in the days of precipitation, in which, the possible hypothesis could be an increase in pollution, since it is associated with the intensification of the greenhouse effect, which consequently leads to an increase in temperature and evapotranspiration, thus influencing the amount of precipitation days (SANTOS, 2007).
When Silviano, Groppo and Pelegrini (2015) studied the trends of precipitation and temperature data in Brazil, they found a direct relationship between the increase in temperature and evapotranspiration throughout the national territory, with possible explanations for the increase in the greenhouse effect gas emissions.
This fact is corroborated by a study by Bao et al. (2017), which reveals that the long term usage of affect the height and thickness of clouds, which in polluted places are twice as large, resulting in an increase in the amount of rainfall. In the studied timeframe, according to Machado (2013), Francisco Beltrão expanded his industrial area, which, consequently, may have generated greater atmospheric emissions.
Another fact found is the occurrence of extreme weather events, mainly associated with high levels of precipitation in a shorter time span, in which it is associated with changes in land use and air pollution. In a study by Farias and Mendonça (2019), it showed an evolution in the amount of floods recorded in Francisco Beltrão since the 1970s.
Therewith, the data demonstrate the direct relationship between precipitation and its interference in human activities, with emphasis on agriculture and the occurrence of floods. As soon the importance of understanding the specificities is emphasized, in order to improve the environmental planning of municipalities and adjacent regions.

CLOSING REMARKS
With the analysis of the historical series of precipitation of Francisco Beltrão, it was possible to conclude that from 1988 to 2019 the rainfall regime increased, which does not mean well-supplied river systems, not least because a possible hypothesis of this increase is due to the urban expansion process itself of the city.
Furthermore, there were years when El Niño and La Ninã acted with greater intensity, especially those of 1988 and 1990 respectively, in which they caused disturbances that directly affected agriculture and other human activities.
Still, it is possible to conclude that the precipitation regime affects the quality of life, human activities and mainly the agriculture, being essential the knowledge of its dynamics in order to carry out a planning consistent with the specificities of the region.