Projected Changes in Precipitation Extremes Across the Mississippi River Basin Using the NASA Global Daily Downscaled Datasets NEX‐GDDP‐CMIP6

ABSTRACT This study comprehensively analyzes historical and projected changes in various precipitation parameters within the Mississippi River basin. These parameters include annual total values, simple daily intensity index, consecutive dry and wet spells, as well as heavy precipitation event related indices, such as maximum one‐day, three‐day, five‐day, and seven‐day consecutive precipitation. We examine the quantity exceeding specific percentile‐based thresholds (95th and 99th) as well as the frequency of days surpassing absolute thresholds (1, 10, 20, 50 mm). Additionally, we assess the percentage contribution of various extreme precipitation events to the annual total. The study employs a total of 32 Climate Models with a spatial resolution of 0.25° (approximately 25 km) for the historical period spanning from 1985 to 2014, and the projected period from 2015 to 2094. A comparison is made between climate models and ground‐based observations during the historical period. Using climate models, projected deviations in future periods are then computed, specifically the near future (2025 to 2054) and far future (2065 to 2094), with respect to the historical period. These climate models are part of the Coupled Model Inter‐comparison Project phase 6 (CMIP6), and have undergone downscaling and bias‐correction by the NASA Earth Exchange Global Daily Downscaled Projections project, referred to as NEX‐GDDP‐CMIP6. The findings across the Mississippi River basin reveal an increasing trend in precipitation extremes, particularly in frequency and intensity rather than annual totals. In terms of annual totals, which averaged around 1045 ± 260 mm during the historical period, the precipitation total is projected to reach 1095 ± 285 mm under SSP245 or 1110 ± 293 mm under SSP585 in the far future. Occurrences surpassing the 95th and 99th percentiles, as well as the maximum consecutive precipitation, are projected to substantially increase under both shared socioeconomic pathways (SSP245 and SSP585) in the future, with a more pronounced increase in the severe scenario (SSP585). This study highlights the potential impact of human‐induced activities on precipitation extremes. It is crucial that these findings inform the development of climate change adaptation and mitigation strategies for the future.