Study key findings & significance

• Though recent years have seen tremendous advances in our understanding of this extreme climate phenomenon, substantial work remains to fill scientific gaps and to address the drought early warning and mitigation needs of practitioners and policy-makers.

Abstract

Flash droughts, characterized by their unusually rapid intensification, have garnered increasing attention within the weather, climate, agriculture, and ecological communities in recent years due to their large environmental and socioeconomic impacts.

Study key findings & significance

• The paper highlights recent research on the phenomenon of flash drought and reviews the literature to present the case for a preferred definition.
• Some researchers focus on duration, but Otkin is advocating for a different definition, one that incorporates the concept of a rapidly intensifying drought, focusing on rate of development as opposed to its duration.

Study key findings & significance

• The Western U.S.

Study key findings & significance

• Using a new detection scheme, a 69 yearlong catalog of atmospheric rivers land-falling upon western North America is created and validated 
• AR landfalls show a marked seasonal progression from the Gulf of Alaska in the early fall to northern California in early winter 
• The seasonal intensity of AR landfalls varies from year to year and from decade to decade in relation to Pacific SST variability

Abstract

A new method for automatic detection of atmospheric rivers (ARs) is developed and applie

Study key findings & significance

• Although previous work has identified an anthropogenic influence on extreme precipitation at hemispheric scales, this study finds robust results for a continental scale. 
• The study establishes that anthropogenic climate change has contributed to the intensification of continental and regional extreme precipitation. 
• Furthermore, the study shows that the anthropogenic influence on North American regional precipitation will lead to more frequent and intense precipitation extremes in the future.

Autho

Study key findings & significance

• This study expands on previous work analyzing historical climate data, which demonstrated how greenhouse gas emissions have increased the probability of recording-breaking hot, wet and dry events in the present climate.
• Now, the group analyzed similar models to estimate the probability of extreme weather events in the future under two scenarios of the Paris Agreement: increases of 1.5 to 2 degrees

Study key findings & significance

• The study finds concurrent increasing trends in extreme precipitation and precipitable water aggregated in large regions of the US.

Abstract

Trends of extreme precipitation (EP) using various combinations of average return intervals (ARIs) of 1, 2, 5, 10, and 20 years

Study key findings & significance

• The long-term station data have strong decreases everywhere in the lowest minimum temperature. 
• Considering the area experiencing cold waves over the last decades, the most notable feature is a sharp decline of this area since the 1980s.
• An analysis of the entire northern midlatitudes confirms the steady decrease in severity and frequency of cold waves over the last decades in the observations.

Study key findings & significance

• The study assesses recent changes in the occurrence of simultaneous large heatwaves.
• The average number of days between May and September with at least one large heat wave in the Northern Hemisphere doubled between the 1980s and the 2010s, to around 152 from 73. But the number of days with two or more heat waves was seven times higher, growing to roughly 143 from 20.

Study key findings & significance

• For the country as a whole and when evaluated regionally, heat waves are more frequent and show greater persistence when defined using daily maximum versus daily minimum temperatures. This was true for all four of the temperature variables examined, including temperature itself and three variables incorporating atmospheric moisture.
• There are notable regional variations in heat wave occurrence.
• Statistically significant upward trends in the frequency of heat wave occurrence are identified for most U.S.