Assessing the Causes of the Post-1996 Shift in Extreme Precipitation Over the Northeastern United States
Abstract
In the Northeastern United States (hereafter Northeast), extreme precipitation (EP, precipitation falling in the 99th percentile of wet days) increased by ~50% after 1996 relative to 1901—1995. Landfalling late-season tropical cyclones are the primary cause of this shift. A warmer Atlantic, partially driven by a change in the phase of the Atlantic Multidecadal Oscillation (AMO), appears to be important to the post-1996 increase in EP. However, the contribution of anthropogenic forcing to the 1996 EP shift remains unresolved due to open questions about forced changes in the AMO, the confounding effects of aerosols, and increasing sea surface temperatures due to climate change. Using both the GHCN-Daily observations and two large initial condition ensembles of 20th century climate (the CESM1 LENS and its associated single forcing runs that partition anthropogenic emissions), we analyze the relationships between aerosols, AMO, anthropogenic greenhouse gas concentrations, and Northeast EP to address the following questions: How have anthropogenic greenhouse gases and aerosols influenced Atlantic sea surface temperatures and thus Northeast extreme precipitation? Can such forcings be disentangled from climate variability? Preliminary results show that the large ensemble simulations reasonably capture observed AMO and Northeast EP, laying the foundation for further attribution of the EP shift.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC43F1344H
- Keywords:
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- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 1637 Regional climate change;
- GLOBAL CHANGE;
- 4313 Extreme events;
- NATURAL HAZARDS