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Abstract Anthropogenic climate change has already affected drought severity and risk across many regions, and climate models project additional increases in drought risk with future warming. Historically, droughts are typically caused by periods of below‐normal precipitation and terminated by average or above‐normal precipitation. In many regions, however, soil moisture is projected to decrease primarily through warming‐driven increases in evaporative demand, potentially affecting the ability of negative precipitation anomalies to cause drought and positive precipitation anomalies to terminate drought. Here, we use climate model simulations from Phase Six of the Coupled Model Intercomparison Project (CMIP6) to investigate how different levels of warming (1, 2, and 3°C) affect the influence of precipitation on soil moisture drought in the Mediterranean and Western North America regions. We demonstrate that the same monthly precipitation deficits (25th percentile relative to a preindustrial baseline) at a global warming level of 2°C increase the probability of both surface and rootzone soil moisture drought by 29% in the Mediterranean and 32% and 6% in Western North America compared to the preindustrial baseline. Furthermore, the probability of a dry (25th percentile relative to a preindustrial baseline) surface soil moisture month given a high (75th percentile relative to a preindustrial baseline) precipitation month is 6 (Mediterranean) and 3 (Western North America) times more likely in a 2°C world compared to the preindustrial baseline. For these regions, warming will likely increase the risk of soil moisture drought during low precipitation periods while simultaneously reducing the efficacy of high precipitation periods to terminate droughts.
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This content will become publicly available on July 1, 2026
Comparative Frequency Analysis of NASPA and Seasonal CMIP6 Precipitation in North America
This study compares the frequency spectra of seasonal precipitation during the last millenium from climate model simulations, tree-ring-based reconstructions, and gauge-based gridded observations of the twentieth century. Climate model simulations are from phase 6 of the Coupled Model Intercomparison Project (CMIP6) past1000 experiment, while tree-ring reconstructions are derived from the North American Seasonal Precipitation Atlas (NASPA). NASPA and CMIP6 model output are analyzed to understand their unique frequency biases in high-, mid-, and low-frequency ranges for both paleo-climatic millennium and recent centennial time series across North America. This was accomplished by first extracting signals from periodic ranges of 2–6, 4–15, 10–30, 20–50, and 30–110 years and then analyzing the result in Fourier space. This study reveals that the NASPA shows better alignment with observations in the frequency domain than global climate models (GCMs) even for low-frequency components. Moreover, the spatial distributions of the spectral biases indicate that there are significant disagreements between NASPA and GCMs in the east during cool seasons and in the west of North America during warm seasons for both historical centennial and preindustrial millennial periods. This is likely caused by NASPA tree-ring sensitivity, as its distribution roughly mirrors NASPA skill metrics. Notably, the spatial patterns of spectral biases differ between the modern and preindustrial eras, suggesting a changing bias through time. This study provides a new frequency-based metric to evaluate climate models and reconstructions and provides a first comparison of the two for North America.
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- Award ID(s):
- 2002539
- PAR ID:
- 10642760
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of Hydrometeorology
- Volume:
- 26
- Issue:
- 7
- ISSN:
- 1525-755X
- Page Range / eLocation ID:
- 917 to 931
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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