Abstract
ABSTRACT The objective of this study was to characterize the rainfall climatology in Veranópolis, Rio Grande do Sul, Brazil, through analyses of means, variabilities related to El Niño Southern Oscillation (ENSO), and temporal trends, using a 60-year data series (1956-2015). Descriptive statistics of annual, monthly and seasonal rainfall were used to characterize the rainfall climatology. The differences between seasons, and influence of ENSO were evaluated using analysis of variance and the Duncan’s test. Rainfall trends were evaluated by the Mann Kendall test. The local average annual rainfall is 1,683 mm and the average monthly rainfall is 140 mm, varying from 109 (May) to 182 mm (September). The annual rainfall has high interannual (standard deviation of 327 mm), monthly (60-100 mm) and seasonal (124-183 mm) variabilities, which should be considered in non-irrigated agricultural systems using rainfall as the main source of water supply to plants. Although autumn presents lower average rainfall (346 mm) than the other seasons, its average percentages were similar to the total annual rainfall (21-28%), and the rainfalls are well-distributed in the seasons. Differences between ENSO events occurred in the spring; La Niña years showed lower rainfall (385 mm) than El Niño (549 mm) and neutral (481 mm) years. The annual rainfall tended to increase by 6.3 mm per year (p < 0.01), with increases of 2.5 mm in spring and 1.9 mm in winter (p < 0.10) in the period analyzed.
Highlights
Agriculture is the most dependent economic activity on weather and climate conditions, climate characterization is essential to reduce risks in agricultural production
The objective of this study was to characterize the rainfall climatology in Veranópolis, Rio Grande do Sul, Brazil, through analyses of means, variabilities related to El Niño Southern Oscillation (ENSO), and temporal trends, using a 60-year data series (1956-2015)
The annual rainfall in the northern Rio Grande do Sul, which includes the Encosta Superior da Serra do Nordeste, is higher than 1,500 mm, and it is less than 1,500 mm in the south of the state
Summary
Agriculture is the most dependent economic activity on weather and climate conditions, climate characterization is essential to reduce risks in agricultural production. Long-term historical data series, with more than 30 years of meteorological observations, can define the local climate by expressing averages of climatic variables, allowing the evaluation of interannual variability, trends, and climate changes. Most climate change studies have a global scale, and the regionalization of their projections can be misleading. Regional studies are essential to characterize shortterm climatic variability and analyze local trends and possible changes (Baethgen, 2010). Studies have shown tendencies of increase in annual rainfall for the state of Rio Grande do Sul, Brazil. Cordeiro (2010) found increases in total annual rainfall using averages of 14 meteorological stations in different ecoclimatic regions of the state of a 60-year data series (1950-2009). Cera & Ferraz (2015) found increases in rainfall in large part of the state using a 25year data series (1982-2006). Cordeiro (2010) found increases in total annual rainfall using averages of 14 meteorological stations in different ecoclimatic regions of the state of a 60-year data series (1950-2009). Sansigolo & Kayano (2010) found a trend of increase in annual rainfall, especially for summers, using a 94-year data series (1913-2006) of six municipalities of the state
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