Analysis of extreme events: Large coverage drought and daily precipitation events in Jalisco, Mexico

The objectives of the present study are to analyze: (1) drought events with large coverage and their possible response to El Niño Southern Oscillation (ENSO) and (2) extreme daily precipitation (EDP) events, both during the 1980-2019 period considering daily precipitation data from climatological stations during the summer months (July-September) in the state of Jalisco, Mexico. For the first objective, a drought analysis was performed using the Standardized Precipitation Index (SPI) at time scales of three (SPI-3) and 12 months (SPI-12), calculating seasonal (July-September) and annual (January-December) series. For the second objective, an EDP event was defined by filtering records greater than 30 mm from the selected stations, then adjusting them to a probability distribution to obtain the 99th percentile (P99) of each series. Values above P99 were identified as EDP events. The results indicate that drought events with large coverage (SPI-12) occurred under La Niña conditions in the 1989-1990 and 2011-2012 periods, affecting 71.4 and 64.3% of the state, respectively, where the coastal region was the least affected. A total of 57 EDP events were identified, but no particular ENSO pattern was determined. The most frequent peak activity occurred in 1987, 1999, 2010, and 2013, representing 31.6%, concentrated in 11 out of 28 climatological stations. While ENSO influences are weaker in these regions, other drivers, such as tropical cyclones, need adaptive disaster preparedness measures. Strengthening early warning systems, improving urban drainage infrastructure, and updating zoning regulations can mitigate flood impacts, reduce economic losses, and protect lives.