Classic and innovative trend analysis of long term annual precipitation in Argentina

Studying rainfall trends is essential for anticipating the effects of climate change, as rainfall behaviour has a direct impact on many sectors and aspects of human and environmental life. This study presents the results of an investigation into precipitation variability in Argentina, using data from 49 stations across the country. Long-term rainfall trends were analysed using the Mann–Kendall (MK) test and the innovative trend analysis (ITA) method for annual rainfall series from 1959 to 2020. The ITA method demonstrated superior visual capabilities for identifying trends through graphical representations. The findings indicate an overall increase in precipitation during this period, with a mean of 2 mm year–1 and a maximum of 6 mm year–1. Specifically, the ITA method revealed more stations with significant trends otherwise obscured when using one of the traditional methods. The ITA method allows the analysis of changes in precipitation by separating them according to percentiles. The highest precipitation values (fourth quartile) show a significant, mainly positive trend at half of the stations studied, with changes of 12% on average. However, the most extreme cases of increase or decrease are found at the lowest levels (first quartile), with changes of up to 50%. In conclusion, the graphical method provides a complementary perspective for easily identifying trends alongside traditional methods.