Improving Understanding of the Interacting Factors that Influence the Evolution and Severity of U.S. Droughts in Present and Future Climates
Our ability to accurately forecast individual droughts is limited by internal atmospheric variability. This variability is inherently unpredictable at the monthly and yearly scales, which are most relevant to predict seasonal and decadal drought.
One area of potential progress is our understanding of the role of feedback loops in altering drought severity and impacts. Atmospheric feedbacks are complex. Understanding all the relevant feedback processes that play a role in drought evolution, representing them accurately in our models, and understanding how feedback processes are projected to change will enhance our capacity to predict drought impacts.
Using the Community Earth System Model (CESM), this project sought to understand the role of feedback processes from the land surface and the atmosphere that govern drought severity. The research team evaluated how the inclusion of a variety of land-atmosphere processes impacts the modeled evolution and severity of drought events. They also studied how these impacts may change in a warmer climate. These processes include plant hydraulics, dust emissions, irrigation, wildfires, and dynamic vegetation.
This project is part of the NIDIS/MAPP Drought Task Force IV.
For more information, please contact Joel Lisonbee (joel.lisonbee@noaa.gov).
Research Snapshot
Isla Simpson, National Center for Atmospheric Research
Results of This Research
Key Takeaways:
- Overall, this project advanced our fundamental understanding of the representation of the complex interactions in the hydrological cycle that influence drought severity and long-term hydrological trends in earth system models. The research generated global earth system model simulation output, and the data will be archived for public access in the NCAR Climate Data Gateway.
- This project investigated the processes involved in the 2020 drought in the U.S. Southwest and their representation in the Community Earth System Model (CESM).
- This work identified a major discrepancy between earth system models and observations in the representation of historical trends in near-surface humidity.
- While models depict a rise in near-surface humidity since 1980, this rise has not occurred in reality. This points towards a potential major misrepresentation of hydrological cycle processes in the models, with relevance to drought and its future projections.
- This work improved our understanding of how unconstrained parameters in the land surface component of earth system models can impact solutions. This research has demonstrated that this parameter uncertainty can exceed scenario uncertainty in certain aspects.
- This project demonstrated internal variability leads to large uncertainty in the relationship between terrestrial water storage and land-carbon uptake. This project also questioned the findings from previous work, which considered whether earth system models adequately capture the relationship between terrestrial water storage and land-carbon uptake, and suggested that this relationship has changed in a way that is different from model simulations.
Research Publications:
- Mankin, J. S., I. Simpson, A. Hoell, R. Fu, J. Lisonbee, A. Sheffield, and D. Barrie. (2021.) NOAA Drought Task Force Report on the 2020-2021 Southwestern U.S. Drought. NOAA Drought Task Force, MAPP, and NIDIS.
- Hoell, A., X.-W. Quan, M. Hoerling, H. F. Diaz, R. Fu, C. He, J. Lisonbee, J. S. Mankin, J. S., R. Seager, A. Sheffield, I. R. Simpson, and E. R. Wahl. (2022.) Water Year 2021 Compound Precipitation and Temperature Extremes in California and Nevada. Bulletin of the American Meteorological Society, 103, E2905-E2911.
- Hoell, A., X.-W. Quan, M. Hoerling, R. Fu, J. Mankin, I. Simpson, R. Seager, C. He, F. Lehner, J. Lisonbee, B. Liveneh, and A. Sheffield. (2022.) Record Low North American Monsoon Rainfall in 2020 Reignites Drought over the American Southwest. Bulletin of the American Meteorological Society, 103, S26-S32.
- Seager, R., M. Ting, P. Alexander, J. Nakamura, H. Liu, C. Li, and I. R. Simpson. (2022.) Mechanisms of a Meteorological Drought Onset: Summer 2020 to Spring 2021 in Southwestern North America. Journal of Climate, 35, 7367–7385.
- Simpson, I. R., K. A. McKinnon, D. Kennedy, D. M. Lawrence, F. Lehner, and R. Seager. (2024.) Observed Humidity Trends in Dry Regions Contradict Climate Models. Proceedings of the National Academy of Sciences, 121 (1) e2302480120.
- Jacobson, T. W. P., R. Seager, A. P. Williams, I. R. Simpson, K. A. McKinnon, and H. Liu. (2024.) An Unexpected Decline in Spring Atmospheric Humidity in the Interior Southwestern United States and Implications for Forest Fires. Journal of Hydrometeorology, 25, 373-390.
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