The world has been getting drenched as a result of climate change. Heavy downpours in the United States have become more frequent over the last 3 to 5 decades, and global warming is thought to have increased rainfall in some of the world’s driest regions. Because of the high impact these extreme precipitation events could have on society—by potentially triggering, for example, devastating flooding events—it is important to understand the atmospheric conditions that set the stage for these incidents.
In a new study, Loriaux et al. cataloged atmospheric conditions that accompany extreme precipitation events at midlatitudes.The researchers analyzed surface data from more than 30 automated weather stations across the Netherlands, collected from 1995 to mid-2014. Then, they used a regional climate model to provide additional atmospheric conditions and tendencies over the same period.
From these data, the scientists identified more than 44,000 separate precipitation events in the Netherlands, and for each event, the team determined the peak precipitation intensity. Then, they investigated if certain atmospheric conditions—moisture content, atmospheric stability, and large-scale upward winds—correlated with the stronger precipitation events.
Overall, the results suggested that no single factor correlated perfectly with heavy rainfall. Warmer temperatures and increased moisture in the atmosphere seemed to correlate more with heavier precipitation events than with weaker ones. Although the strongest precipitation events also took place when the atmosphere was less stable than it typically is during weaker events, an unstable atmosphere itself does not always foreshadow heavy rainfall. (Journal of Geophysical Research: Atmospheres, doi:10.1002/2015JD024274, 2016)
—Wudan Yan, Freelance Writer