Future changes in extreme precipitation over the San Francisco Bay Area: Dependence on atmospheric river and extratropical cyclone events

Patricola, Christina M.; Wehner, Michael; Bercos‐Hickey, Emily; Maciel, Flor Vanessa; May, Christine L.; Mak, Michael; Yip, Olivia; Roche, Anna; Leal, Susan

doi:10.1016/j.wace.2022.100440

Cited by 28 publications

(23 citation statements)

References 76 publications

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“…1, A and B ) [e.g., ( 28 )] and climate change [e.g., ( 34 )], although the 30-day mean low-level (850-hPa) flow pattern exhibits a slightly more zonal pattern (with less of a meridional component over the northeastern Pacific) in ARkFuture relative to ARkHist. Visual inspection of movies S1 and S2 further confirm that both 30-day scenario storm sequences are characterized by the occurrence of multiple deep extratropical cyclones just west of or over California, which is consistent with recent results in ( 35 ), which found that AR-associated precipitation in the San Francisco Bay Area increased more for ARs directly associated with extratropical cyclones than those without.…”

Section: Resultssupporting

confidence: 87%

Climate change is increasing the risk of a California megaflood

Huang

Swain

2022

Sci. Adv.

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Despite the recent prevalence of severe drought, California faces a broadly underappreciated risk of severe floods. Here, we investigate the physical characteristics of “plausible worst case scenario” extreme storm sequences capable of giving rise to “megaflood” conditions using a combination of climate model data and high-resolution weather modeling. Using the data from the Community Earth System Model Large Ensemble, we find that climate change has already doubled the likelihood of an event capable of producing catastrophic flooding, but larger future increases are likely due to continued warming. We further find that runoff in the future extreme storm scenario is 200 to 400% greater than historical values in the Sierra Nevada because of increased precipitation rates and decreased snow fraction. These findings have direct implications for flood and emergency management, as well as broader implications for hazard mitigation and climate adaptation activities.

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Section: Resultssupporting

confidence: 87%

Climate change is increasing the risk of a California megaflood

Huang

Swain

2022

Sci. Adv.

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“…Traditionally, Pearl causal inference attribution statements are made with long simulations of global climate models, usually in pairs forced with both anthropogenic and natural forcing factors (Stott et al., 2016). However, another more conditional form of Pearl causal inference attribution statements can be formulated with an imposed‐global warming hindcast attribution method (Bercos‐Hickey & Patricola, 2021; Bercos‐Hickey et al., 2021; Patricola & Wehner, 2018; Patricola et al., 2022; Schär et al., 1996; Wehner et al., 2019). In this approach, ensembles of regional climate model (ReGCM) simulations are performed with historical initial and boundary conditions, referred to as historical or hindcast simulations.…”

Section: Dynamical Models and Experimental Designmentioning

confidence: 99%

Anthropogenic Contributions to the 2021 Pacific Northwest Heatwave

Bercos‐Hickey

O’Brien

Wehner

et al. 2022

Geophysical Research Letters

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Daily maximum temperatures during the 2021 heatwave in the Pacific Northwest United States and Canada shattered century old records. Multiple causal factors, including anthropogenic climate change, contributed to these high temperatures, challenging traditional methods of attributing human influence. We demonstrate that the observed 2021 daily maximum temperatures are far above the bounds of Generalized Extreme Value distributions fitted from historical data. Hence, confidence in Granger causal inference statements about the human influence on this heatwave is low. Alternatively, we present a more conditional hindcast attribution study using two regional models. We performed ensembles of simulations of the heatwave to investigate how the event would have changed if it had occurred without anthropogenic climate change and with future warming. We found that global warming caused a ∼0.8°C–1°C increase in heatwave temperatures. Future warming would lead to a ∼5°C increase in heatwave temperature by the end of the 21st century.

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“…In California, for example, ARs contribute 20%–50% of the state's precipitation and streamflow (Dettinger et al., 2011) and have gained traction in the scientific and water management communities as being important drivers of annual precipitation (Ralph, Dettinger, et al., 2017). The role which ARs play in contributing to annual precipitation totals may also be intensified under a warming climate, where several studies point to the Clausius‐Clapeyron relationship which suggests enhanced intensity of AR‐related precipitation under climate change (Gao et al., 2015; Gershunov et al., 2019; Michaelis et al., 2022; O’Brien et al., 2022; Patricola et al., 2022; Payne et al., 2020; Radić et al., 2015; Rhoades et al., 2021; Rhoades, Jones, Srivastava, et al., 2020; Shields & Kiehl, 2016). Despite the significance of ARs in augmenting current and future water resources, little is known about how AR dynamics impact the above‐ and below‐ground hydrologic cycle, including groundwater resources.…”

Section: Introductionmentioning

confidence: 99%

The Role of Atmospheric Rivers on Groundwater: Lessons Learned From an Extreme Wet Year

Siirila‐Woodburn

Dennedy‐Frank

Rhoades

et al. 2023

Water Resources Research

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In the coastal regions of the western United States, atmospheric rivers (ARs) are associated with the largest precipitation generating storms and contribute up to half of annual precipitation, but the impact of ARs on the integrated hydrologic cycle, specifically on groundwater storage and hydrodynamics, is largely unknown. To better explore the hydrologic behavior of AR versus non‐AR event precipitation, we present a novel combination of two water tracking methods (one in the atmosphere and one in the subsurface) to explicitly track the full lifecycle of water parcels generated by ARs. Simulations of northern California's Cosumnes River watershed during the record wet 2017 water year are performed via the coupling of a high‐resolution regional climate model and a land surface‐groundwater model accounting for lateral groundwater flow. Despite ARs contributing more precipitation than non‐AR storms, we find less AR water is preferentially stored in aquifers by year end. Fractionally, ARs result in 300% less snow derived groundwater‐recharged compared to non‐AR precipitation. Rain‐on‐snow (RoS) plays an important role in AR‐driven discharge, where over 50% of total discharge from ARs snow is from RoS events. Finally, despite record‐breaking annual precipitation, simulated groundwater depletion occurs by year end due to estimates of groundwater pumping activities. The results from these simulations serve as a partial analogue of future hydrologic conditions where ARs are expected to intensify and provide a greater fraction of annual precipitation due to climate change.

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Future changes in extreme precipitation over the San Francisco Bay Area: Dependence on atmospheric river and extratropical cyclone events

Cited by 28 publications

References 76 publications

Climate change is increasing the risk of a California megaflood

Climate change is increasing the risk of a California megaflood

Anthropogenic Contributions to the 2021 Pacific Northwest Heatwave

The Role of Atmospheric Rivers on Groundwater: Lessons Learned From an Extreme Wet Year

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