Future Changes in Active and Inactive Atlantic Hurricane Seasons

Previous studies have largely focused on mean changes in TC activity, however, changes in the distribution of seasonal TC activity have received less attention. It is important to understand how the extremes in seasonal TC activity may change in the future, as it is the extremely active seasons that tend to cause societal impacts. Here, we analyzed how active and inactive Atlantic hurricane seasons may change in the future using the high resolution Energy Exascale Earth System Model (E3SM). In the historical climate, La Niña and the positive phase of the Atlantic Meridional Mode (AMM) tend to drive active Atlantic hurricane seasons, and El Niño and the negative AMM often drive inactive seasons.  Therefore, we performed atmosphere-only simulations forced by sea-surface temperature patterns characteristic of La Niña and the positive AMM jointly, and El Niño and the negative AMM jointly, in historical and future climates. Notably, we found that the patterns of ocean variability that currently drive the most active Atlantic hurricane seasons in the historical record, when paired with climate change, have the potential to produce hurricane seasons that are even more active. In addition, the simulations indicate that the ocean variability patterns that typically help to reduce Atlantic TC impacts by suppressing TCs in the historical climate become less effective at doing so in the future. Altogether, the simulated shift in the future extremes in seasonal Atlantic TC activity represents a potential worsening of Atlantic TC impacts in the future.

• Sena, A. C. T., Patricola, C. M., & Loring, B. (2022). Future Changes in Active and Inactive Atlantic Hurricane Seasons in the Energy Exascale Earth System Model. Geophysical Research Letters, 49, e2022GL100267.

This research was supported by the U.S. Department of Energy Office of Science (BER RGCM program) under Early Career Research Program Award Number DE-SC0021109 and under Award Number DE-AC02-05CH11231.  E3SM simulations were performed using BER Earth System Modeling program's Compy computing cluster located at Pacific Northwest National Laboratory.  High-performance computing resources also provided by the National Energy Research Scientific Computing Center (NERSC).

Future Changes in Historically Impactful Tropical Cyclone Events

There is no consensus on whether climate change has yet affected the statistics of tropical cyclones, owing to their large natural variability and the limited period of consistent observations. In addition, projections of future tropical cyclone activity are uncertain, because they often rely on coarse-resolution climate models that parameterize convection and hence have difficulty in directly representing tropical cyclones. Here we used convection-permitting regional climate model simulations to investigate whether and how recent destructive tropical cyclones would change if these events had occurred in pre-industrial and in future climates. We found that, relative to pre-industrial conditions, climate change so far has enhanced the average and extreme rainfall of hurricanes Katrina, Irma and Maria, but did not change tropical cyclone wind-speed intensity. In addition, future anthropogenic warming would robustly increase the wind speed and rainfall of 11 of 13 intense tropical cyclones (of 15 events sampled globally). Additional regional climate model simulations suggest that convective parameterization introduces minimal uncertainty into the sign of projected changes in tropical cyclone intensity and rainfall, which allows us to have confidence in projections from global models with parameterized convection and resolution fine enough to include tropical cyclones.

• Patricola CM, Wehner MF (2018) Anthropogenic Influences on Major Tropical Cyclone Events. Nature, 563, 339-346.

This research was supported by the U.S. Department of Energy Office of Science (BER RGCM program).  High-performance computing resources provided by the National Energy Research Scientific Computing Center (NERSC).

Tropical Cyclone - Ocean Coupling

This study aims to quantify the impacts of atmosphere–ocean coupling on simulated and projected tropical cyclone (TC) precipitation globally. We used global climate model (GCM) simulations over 1950–2050 from the High Resolution Model Intercomparison Project (HighResMIP) and compared its fully coupled atmosphere–ocean GCMs (AOGCMs) with atmosphere-only GCMs (AGCMs). We find that ocean coupling generally leads to decreased TC precipitation over ocean and land. Large-scale sea surface temperature (SST) biases are critical drivers of the precipitation difference, with secondary contributions from local TC–ocean feedbacks via SST cold wakes. The AOGCMs and AGCMs consistently project TC precipitation increases in 2015–2050 relative to 1950–2014 over ocean for all basins, and for landfalling TCs in the North Atlantic and western North Pacific.

• Huang H, Patricola CM, Collins WD (2021) The Influence of Ocean Coupling on Simulated and Projected Tropical Cyclone Precipitation in the HighResMIP-PRIMAVERA Simulations, Geophysical Research Letters, 48, e2021GL094801.

This research was supported by the U.S. Department of Energy Office of Science (BER RGCM program) under Early Career Research Program Award Number DESC0021109 and under DE-AC02-05CH11231.  High-performance computing resources provided by the National Energy Research Scientific Computing Center (NERSC).

_{updated 12/9/2022}