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Increasing extreme rainfall in the Northeast US
The Northeast US has experienced the most rapid increasing frequency of extreme precipitation within the US in the past few decades (reference). Here we use a high-resolution climate model, SPEAR (Seamless system for Prediction and EArth system Research), developed at NOAA GFDL, to detect and project the increasing frequency of extreme precipitation over the Northeast US. We also examine the causes of the increase in extreme precipitation over the Northeast US in both current and future climates.
We employed a variety of horizontal resolutions in the atmosphere/land components of the model, ranging from 100km to 25km, to demonstrate that a finer resolution model facilitates a more realistic simulation of extreme precipitation frequency than a coarser resolution model. (Fig. 1)
We used the same model for future projections. By the mid-21st century, the model projects unprecedented rainfall events over the region, driven by increasing anthropogenic radiative forcing and distinguishable from natural variability. Very extreme events (>150mm/day) may be six times more likely by 2100 than in the early 21st century. (Fig. 1)
The increase in extreme precipitation since the 1990s is primarily linked to events associated with tropical cyclones. In the future, tropical cyclones-related extreme precipitation is expected to continue to increase, based on the projection from the 25-km SPEAR, despite fewer projected tropical cyclones. (Fig. 2)
The increase in extreme precipitation over the Northeast US, however, will be dominated by increasing atmospheric rivers. (Fig. 2)
For more details about our work, please see our publications!
Jong, B.-T., T. L. Delworth, W. F. Cooke, K.-C. Tseng, and H. Murakami (2023): Increases in extreme precipitation over the Northeast United States using high-resolution climate model simulations. npj Clim. Atmos. Sci., 6, 18. http://doi.org/10.1038/s41612-023-00347-w
Jong, B.-T., H. Murakami, T. L. Delworth, and W. F. Cooke (2024): Contributions of tropical cyclones and atmospheric rivers to extreme precipitation trends over the Northeast US. Earth's Future, 12, e2023EF004370. http://doi.org/10.1029/2023EF004370
Fig.1 Time series showing the changes in frequency of extreme precipitation in each year from 1951-2100. (a) Extreme events are defined as exceeding the 99th percentile threshold based upon 1951-2020. (b)-(d) As in (a), but extreme events are defined as exceeding thresholds of 50mm/day, 100mm/day, and 150mm/day. The observation is shown in black lines. The ensemble mean of SPEAR_LO, SPEAR_MED, and SPEAR_HI historical and SSP5-8.5 simulations are shown in green dotted, dashed, and solid lines, respectively. Only the spreads of SPEAR_HI ensemble members are shown.The time series are smoothed with a 7-year running mean to remove the interannual variability, emphasizing the long-term trend and variability.
Fig 2. Bar graph from 1959 to 2100 using SPEAR_HI to show the projected frequency of extreme precipitation days for pure AR, TC-related, and other events. There is a long-term increasing trend projected over this entire bar graph.
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