Publications – Alex Hall's Research Group

Rahimi, Stefan; Huang, L; Norris, J; Hall, A; Goldenson, N; Krantz, W; Bass, B; Thackeray, C; Lin, H; Chen, D; Dennis, E; Collins, E; Lebo, ZJ; Slinskey, E; Graves, S; Biyani, S; Wang, B; Cropper, S

An overview of the Western United States Dynamically Downscaled Dataset (WUS-D3) Journal Article

In: Geoscientific Model Development, vol. 17, no. 6, pp. 2265-2286, 2024.

Abstract | Links | BibTeX

@article{2532,

title = {An overview of the Western United States Dynamically Downscaled Dataset (WUS-D3)},

author = {Stefan Rahimi and L Huang and J Norris and A Hall and N Goldenson and W Krantz and B Bass and C Thackeray and H Lin and D Chen and E Dennis and E Collins and ZJ Lebo and E Slinskey and S Graves and S Biyani and B Wang and S Cropper},

url = {https://doi.org/10.5194/gmd-17-2265-2024},

year  = {2024},

date = {2024-01-01},

journal = {Geoscientific Model Development},

volume = {17},

number = {6},

pages = {2265-2286},

abstract = {Predicting future climate change over a region of complex terrain, such as the western United States (US), remains challenging due to the low resolution of global climate models (GCMs). Yet the climate extremes of recent years in this region, such as floods, wildfires, and drought, are likely to intensify further as climate warms, underscoring the need for high-quality and high-resolution predictions. Here, we present an ensemble of dynamically downscaled simulations over the western US from 1980–2100 at 9 km grid spacing, driven by 16 latest-generation GCMs. This dataset is titled the Western US Dynamically Downscaled Dataset (WUS-D3). 

	We describe the challenges of producing WUS-D3, including GCM selection and technical issues, and we evaluate the simulations’ realism by comparing historical results to temperature and precipitation observations. The future downscaled climate change signals are shaped in physically credible ways by the regional model’s more realistic coastlines and topography. (1) The mean warming signals are heavily influenced by more realistic snowpack. (2) Mean precipitation changes are often consistent with wetting on the windward side of mountain complexes, as warmer, moister air masses are uplifted orographically during precipitation events. (3) There are large fractional precipitation increases on the lee side of mountain complexes, leading to potentially significant changes in water resources and ecology in these arid landscapes. (4) Increases in precipitation extremes are generally larger than in the GCMs, driven by locally intensified atmospheric updrafts tied to sharper, more realistic gradients in topography. (5) Changes in temperature extremes are different from what is expected by a shift in mean temperature and are shaped by local atmospheric dynamics and land surface feedbacks. Because of its high resolution, comprehensiveness, and representation of relevant physical processes, this dataset presents a unique opportunity to evaluate societally relevant future changes in western US climate.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Predicting future climate change over a region of complex terrain, such as the western United States (US), remains challenging due to the low resolution of global climate models (GCMs). Yet the climate extremes of recent years in this region, such as floods, wildfires, and drought, are likely to intensify further as climate warms, underscoring the need for high-quality and high-resolution predictions. Here, we present an ensemble of dynamically downscaled simulations over the western US from 1980–2100 at 9 km grid spacing, driven by 16 latest-generation GCMs. This dataset is titled the Western US Dynamically Downscaled Dataset (WUS-D3).
We describe the challenges of producing WUS-D3, including GCM selection and technical issues, and we evaluate the simulations’ realism by comparing historical results to temperature and precipitation observations. The future downscaled climate change signals are shaped in physically credible ways by the regional model’s more realistic coastlines and topography. (1) The mean warming signals are heavily influenced by more realistic snowpack. (2) Mean precipitation changes are often consistent with wetting on the windward side of mountain complexes, as warmer, moister air masses are uplifted orographically during precipitation events. (3) There are large fractional precipitation increases on the lee side of mountain complexes, leading to potentially significant changes in water resources and ecology in these arid landscapes. (4) Increases in precipitation extremes are generally larger than in the GCMs, driven by locally intensified atmospheric updrafts tied to sharper, more realistic gradients in topography. (5) Changes in temperature extremes are different from what is expected by a shift in mean temperature and are shaped by local atmospheric dynamics and land surface feedbacks. Because of its high resolution, comprehensiveness, and representation of relevant physical processes, this dataset presents a unique opportunity to evaluate societally relevant future changes in western US climate.

Close

Marshall, Adrienne M; Abatzoglou, JT; Rahimi, S; Lettenmaier, D; Hall, A

California’s 2023 snow deluge: Contextualizing an extreme snow year against future climate change Journal Article

In: Proceedings of the National Academy of Sciences, vol. 121, no. 20, pp. e2320600121, 2024.

Abstract | Links | BibTeX

@article{2531,

title = {California’s 2023 snow deluge: Contextualizing an extreme snow year against future climate change},

author = {Adrienne M Marshall and JT Abatzoglou and S Rahimi and D Lettenmaier and A Hall},

url = {https://doi.org/10.1073/pnas.2320600121},

year  = {2024},

date = {2024-01-01},

journal = {Proceedings of the National Academy of Sciences},

volume = {121},

number = {20},

pages = {e2320600121},

abstract = {The increasing prevalence of low snow conditions in a warming climate has attracted substantial attention in recent years, but a focus exclusively on low snow leaves high snow years relatively underexplored. However, these large snow years are hydrologically and economically important in regions where snow is critical for water resources. Here, we introduce the term “snow deluge” and use anomalously high snowpack in California’s Sierra Nevada during the 2023 water year as a case study. Snow monitoring sites across the state had a median 41 y return interval for April 1 snow water equivalent (SWE). Similarly, a process-based snow model showed a 54 y return interval for statewide April 1 SWE (90% CI: 38 to 109 y). While snow droughts can result from either warm or dry conditions, snow deluges require both cool and wet conditions. Relative to the last century, cool-season temperature and precipitation during California’s 2023 snow deluge were both moderately anomalous, while temperature was highly anomalous relative to recent climatology. Downscaled climate models in the Shared Socioeconomic Pathway-370 scenario indicate that California snow deluges—which we define as the 20 y April 1 SWE event—are projected to decline with climate change (58% decline by late century), although less so than median snow years (73% decline by late century). This pattern occurs across the western United States. Changes to snow deluge, and discrepancies between snow deluge and median snow year changes, could impact water resources and ecosystems. Understanding these changes is therefore critical to appropriate climate adaptation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Slinskey, Emily; Hall, A; Goldenson, N; Loikith, PC; Norris, J

Subseasonal Clustering of Atmospheric Rivers Over the Western United States Journal Article

In: Journal of Geophysical Research: Atmospheres, vol. 128, no. 22, pp. e2023JD038833, 2023.

Abstract | Links | BibTeX

@article{2513,

title = {Subseasonal Clustering of Atmospheric Rivers Over the Western United States},

author = {Emily Slinskey and A Hall and N Goldenson and PC Loikith and J Norris},

url = {https://doi.org/10.1029/2023JD038833},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Geophysical Research: Atmospheres},

volume = {128},

number = {22},

pages = {e2023JD038833},

abstract = {The serial occurrence of atmospheric rivers (ARs) along the US West Coast can lead to prolonged and exacerbated hydrologic impacts, threatening flood-control and water-supply infrastructure due to soil saturation and diminished recovery time between storms. Here a statistical approach for quantifying subseasonal temporal clustering among extreme events is applied to a 41-year (1979–2019) wintertime AR catalog across the western United States (US). Observed AR occurrence, compared against a randomly distributed AR timeseries with the same average event density, reveals temporal clustering at a greater-than-random rate across the western US with a distinct geographical pattern. Compared to the Pacific Northwest, significant AR clusters over the northern Coastal Range of California and Sierra Nevada are more frequent and occur over longer time periods. Clusters along the California Coastal Range typically persist for 2 weeks, are composed of 4–5 ARs per cluster, and account for over 85% of total AR occurrence. Across the northwest Coast-Cascade Ranges, clusters account for ~50% of total AR occurrence, typically last 8–10 days, and contain 3–4 individual AR events. Based on precipitation data from a high-resolution dynamical downscaling of reanalysis, the fractions of total and extreme hourly precipitation attributable to AR clusters are largest along the northern California coast and in the Sierra Nevada. Interannual variability among clusters highlights their importance for determining whether a particular water year is anomalously wet or dry. The mechanisms behind this unusual clustering are unclear and require further research.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Cropper, S; Thackeray, CW; Emile-Geay, J

Revisiting a Constraint on Equilibrium Climate Sensitivity From a Last Millennium Perspective Journal Article

In: Geophysical Research Letters, vol. 50, no. 20, pp. e2023GL104126, 2023.

Abstract | Links | BibTeX

Bass, B; Goldenson, N; Rahimi, S; Hall, A

Aridification of Colorado River Basin&$#$39;s Snowpack Regions Has Driven Water Losses Despite Ameliorating Effects of Vegetation Journal Article

In: Water Resources Research, vol. 59, no. 7, pp. e2022WR033454, 2023.

Abstract | Links | BibTeX

@article{2416,

title = {Aridification of Colorado River Basin&$#$39;s Snowpack Regions Has Driven Water Losses Despite Ameliorating Effects of Vegetation},

author = {B Bass and N Goldenson and S Rahimi and A Hall},

url = {https://doi.org/10.1029/2022WR033454},

year  = {2023},

date = {2023-01-01},

journal = {Water Resources Research},

volume = {59},

number = {7},

pages = {e2022WR033454},

abstract = {The Colorado River Basin is an important natural resource for the semi-arid southwestern United States (US), where it provides water to more than 40 million people. While nearly 1.5°C of anthropogenic warming has occurred across this region from the 1880s to 2021, climate models show little agreement in the precipitation change during the same historical period, with no trend in the mean of the latest (sixth) generation of Global Climate Models. As such, here we focus on how the CO2 increase and associated anthropogenic warming over the historical period has impacted runoff across the Colorado Basin. We find that the Colorado Basin’s runoff over the historical period has decreased by 8.1% per degree Celsius of warming (°C-1). However, the magnitude of this sensitivity is reduced to 6.8% °C-1 when considering vegetation response to historical CO2. For present-day conditions, this translates to runoff reductions of 10.3% due to anthropogenic increases in both temperature and CO2 since 1880. We demonstrate that Colorado Basin’s natural flow has been decreased by roughly the storage of Lake Mead during the 2000–2021 megadrought due to this long term anthropogenic influence, suggesting the basin’s first shortage in 2021 would likely not have occurred without anthropogenic warming. We further show warming has led to disproportionate aridification in snowpack regions, causing runoff to decline at double the rate relative to non-snowpack regions. Thus, despite only making up ~30% of the basin’s drainage area, 86% of runoff decreases in the Colorado Basin is driven by water loss in snowpack regions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Abatzoglou, JT; Kolden, CA; Williams, AP; Sadegh, M; Balch, JK; Hall, A

Downslope Wind-Driven Fires in the Western United States Journal Article

In: Earth’s Future, vol. 11, no. 5, pp. e2022EF003471, 2023.

Abstract | Links | BibTeX

@article{2402,

title = {Downslope Wind-Driven Fires in the Western United States},

author = {JT Abatzoglou and CA Kolden and AP Williams and M Sadegh and JK Balch and A Hall},

url = {https://doi.org/10.1029/2022EF003471},

year  = {2023},

date = {2023-01-01},

journal = {Earth’s Future},

volume = {11},

number = {5},

pages = {e2022EF003471},

abstract = {Downslope wind-driven fires have resulted in many of the wildfire disasters in the western United States and represent a unique hazard to infrastructure and human life. We analyze the co-occurrence of wildfires and downslope winds across the western United States (US) during 1992–2020. Downslope wind-driven fires accounted for 13.4% of the wildfires and 11.9% of the burned area in the western US yet accounted for the majority of local burned area in portions of southern California, central Washington, and the front range of the Rockies. These fires were predominantly ignited by humans, occurred closer to population centers, and resulted in outsized impacts on human lives and infrastructure. Since 1999, downslope wind-driven fires have accounted for 60.1% of structures and 52.4% of human lives lost in wildfires in the western US. Downslope wind-driven fires occurred under anomalously dry fuels and exhibited a seasonality distinct from other fires—occurring primarily in the spring and fall. Over 1992–2020, we document a 25% increase in the annual number of downslope wind-driven fires and a 140% increase in their respective annual burned area, which partially reflects trends toward drier fuels. These results advance our understanding of the importance of downslope winds in driving disastrous wildfires that threaten populated regions adjacent to mountain ranges in the western US. The unique characteristics of downslope wind-driven fires require increased fire prevention and adaptation strategies to minimize losses and incorporation of changing human-ignitions, fuel availability and dryness, and downslope wind occurrence to elucidate future fire risk.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Bass, Benjamin; Rahimi, S; Goldenson, N; Hall, A; Norris, J; Lebow, Z J

Achieving Realistic Runoff in the Western United States with a Land Surface Model Forced by Dynamically Downscaled Meteorology. Journal Article

In: Journal of Hydrometeorology, vol. 24, no. 2, pp. 269-283, 2023.

Abstract | Links | BibTeX

@article{2388,

title = {Achieving Realistic Runoff in the Western United States with a Land Surface Model Forced by Dynamically Downscaled Meteorology.},

author = {Benjamin Bass and S Rahimi and N Goldenson and A Hall and J Norris and Z J Lebow},

url = {https://doi.org/10.1175/JHM-D-22-0047.1},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Hydrometeorology},

volume = {24},

number = {2},

pages = {269-283},

abstract = {In this study, we calibrate a regional climate model’s (RCM) underlying land surface model (LSM). In addition to providing a realistic representation of runoff across the hydroclimatically diverse western United States, this is done to take advantage of the RCM’s ability to physically resolve meteorological forcing data in ungauged regions, and to prepare the calibrated hydrologic model for tight coupling, or the ability to represent land surface–atmosphere interactions, with the RCM. Specifically, we use a 9-km resolution meteorological forcing dataset across the western United States, from the fifth generation ECMWF Reanalysis (ERA5) downscaled by the Weather Research Forecasting (WRF) regional climate model, as an offline forcing for Noah-Multiparameterization (Noah-MP). We detail the steps involved in producing an LSM capable of accurately representing runoff, including physical parameterization selection, parameter calibration, and regionalization to ungauged basins. Based on our model evaluation from 1954 to 2021 for 586 basins with daily natural streamflow, the streamflow bias is reduced from 24.2% to 4.4%, and the median daily Nash–Sutcliffe efficiency (NSE) is improved from 0.12 to 0.36. When validating against basins with monthly natural streamflow data, we obtain a similar reduction in bias and a median monthly NSE improvement from 0.18 to 0.56. In this study, we also discover the optimal setup when using a donor-basin method to regionalize parameters to ungauged basins, which can vary by 0.06 NSE for unique designs of this regionalization method.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Norris, Jesse; Hall, A; Thackeray, C; Chen, Di; Madakumbura, G

Evaluating Hydrologic Sensitivity in CMIP6 Models: Anthropogenic Forcing versus ENSO Journal Article

In: Journal of Climate, vol. 35, no. 21, pp. 6955-6968, 2022.

Abstract | Links | BibTeX

Chen, Di; Norris, J; Thackeray, C; Hall, A

Increasing precipitation whiplash in climate change hotspots. Journal Article

In: Environmental Research Letters, vol. 17, no. 12, pp. 124011, 2022.

Abstract | Links | BibTeX

Norris, Jesse; Chen, D; Hall, A; Thackeray, C

Moisture-Budget Drivers of Global Projections of Meteorological Drought From Multiple GCM Large Ensembles Journal Article

In: Journal of Geophysical Research: Atmospheres, vol. 127, no. 24, pp. e2022JD037745, 2022.

Abstract | Links | BibTeX

@article{2381,

title = {Moisture-Budget Drivers of Global Projections of Meteorological Drought From Multiple GCM Large Ensembles},

author = {Jesse Norris and D Chen and A Hall and C Thackeray},

url = {https://doi.org/10.1029/2022JD037745},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Geophysical Research: Atmospheres},

volume = {127},

number = {24},

pages = {e2022JD037745},

abstract = {Future projections of global meteorological drought are evaluated in the Multi-Model Large Ensemble Archive, including an evaluation of the atmospheric moisture budget, conditioned on drought years. Drought is defined as 5-year running-mean annual precipitation below some threshold, for example, 10th percentile. Drought increases in frequency over the subtropics, in addition to certain tropical regions, consistent with previous studies. The moisture-budget decomposition allows drought to be defined as mean-flow, eddy, or feedback droughts, depending on which term in the equation contributes the largest negative interannual anomaly. In the historical climate, mean-flow droughts constitute most droughts at low latitudes; eddy droughts are equally common at higher latitudes; feedback droughts (i.e., droughts exacerbated by land–atmosphere feedbacks) constitute almost all droughts in water-limited subtropical/Mediterranean regions. The future drought increases are predominantly due to increases in feedback droughts in regions where these droughts are common historically but also over the Amazon. However, over most Mediterranean-type regions mean-flow droughts are also large contributors, resulting from dynamics. Eddy droughts also contribute to future increases along the equatorward flanks of historical eddy-driven jets, likely reflecting poleward shifts therein. Model uncertainty is particularly large over the Amazon and Australia, a reflection of model diversity in processes associated with land-atmosphere interaction. Based on these results, an availability of 3-D atmospheric data from a wider swath of global climate model large ensembles could help constrain global drought projections based on the representation of drought mechanisms in the historical climate.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Bass, Benjamin; Norris, J; Thackeray, C; Hall, A

Natural Variability Has Concealed Increases in Western US Flood Hazard Since the 1970s Journal Article

In: Geophysical Research Letters, vol. 49, no. 7, pp. e2021GL097706, 2022.

Abstract | Links | BibTeX

Thackeray, Chad; Hall, A; Norris, J; Chen, D

Reducing uncertainty in simulated increases in heavy rainfall occurrence. Journal Article

In: Nature Climate Change, vol. 12, no. 5, pp. 424-425, 2022.

Abstract | Links | BibTeX

Dong, Chunyu; Williams, A; Abatzoglou, J; Lin, K; Okin, G; Gillespie, T; Long, D; Lin, Y; Hall, A; MacDonald, G

The season for large fires in Southern California is projected to lengthen in a changing climate. Journal Article

In: Communications Earth & Environment, vol. 3, no. 22, 2022.

Abstract | Links | BibTeX

Rahimi, Stefan; Krantz, W; Lin, Y; Bass, B; Goldenson, N; Hall, A; Lebo, Z; Norris, J

Evaluation of a Reanalysis-Driven Configuration of WRF4 Over the Western United States From 1980-2020. Journal Article

In: Journal of Geophysical Research: Atmospheres, vol. 127, no. 4, pp. e2021JD035699, 2022.

Abstract | Links | BibTeX

@article{2330,

title = {Evaluation of a Reanalysis-Driven Configuration of WRF4 Over the Western United States From 1980-2020.},

author = {Stefan Rahimi and W Krantz and Y Lin and B Bass and N Goldenson and A Hall and Z Lebo and J Norris},

url = {https://doi.org/10.1029/2021JD035699},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Geophysical Research: Atmospheres},

volume = {127},

number = {4},

pages = {e2021JD035699},

abstract = {Dynamical downscaling remains a powerful tool for studying regional climate processes, and the genesis of high-resolution historical and future climate data. This technique is particularly important over areas of complex terrain, such as the western United States (WUS), where global models are especially limited in representing regional climate. After identifying a suite of WRF options that best simulate snow and precipitation for an average water year (2010) over the WUS, we evaluate the performance of the dynamically downscaled European Centre for Medium-range Weather Forecasting’s fifth Reanalysis (ERA5) from 1980 to 2020 on 45-km, 9-km, and two 3-km grids. We find that by decreasing the horizontal grid spacing within WRF, improvements to Sierra Nevada and Northern Rocky Mountain snow, Santa Ana and Diablo winds, and coastal meteorology occur. For landfalling atmospheric rivers (ARs), the downscaled reanalysis simulates greater upstream integrated vapor transport (IVT) than ERA5. However, WRF skillfully simulates the positioning of the IVT and the timing and magnitude of AR precipitation. This potential IVT bias, in conjunction with increasing resolution, leads to a wet precipitation bias across the Sierra Nevada in the 3-km experiment. This conclusion is supported by streamflow analysis, although we note that the bias in the 3-km experiment can also be explained by in situ undercatch issues. Meanwhile, the 9-km experiment is more biased than the 3-km experiment across the Northern Rocky Mountains compared to in situ measured SWE and precipitation, indicating a geographic sensitivity to biases.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Robbins, Zachary; Xu, C; Aukema, B; Buotte, P; Chitra-Tarak, R; Fettig, C.; Goulden, M; Goodsman, D; Hall, A; Koven, C; Kueppers, L; Madakumbura, G; Mortenson, L; Powell, J; Scheller, R

Warming increased bark beetle-induced tree mortality by 30% during an extreme drought in California. Journal Article

In: Global Change Biology, vol. 27, no. 23, 2021.

Abstract | Links | BibTeX

@article{2318,

title = {Warming increased bark beetle-induced tree mortality by 30% during an extreme drought in California.},

author = {Zachary Robbins and C Xu and B Aukema and P Buotte and R Chitra-Tarak and C. Fettig and M Goulden and D Goodsman and A Hall and C Koven and L Kueppers and G Madakumbura and L Mortenson and J Powell and R Scheller},

url = {https://doi.org/10.1111/gcb.15927},

year  = {2021},

date = {2021-01-01},

journal = {Global Change Biology},

volume = {27},

number = {23},

abstract = {Quantifying the responses of forest disturbances to climate warming is critical to our understanding of carbon cycles and energy balances of the Earth system. The impact of warming on bark beetle outbreaks is complex as multiple drivers of these events may respond differently to warming. Using a novel model of bark beetle biology and host tree interactions, we assessed how contemporary warming affected western pine beetle (Dendroctonus brevicomis) populations and mortality of its host, ponderosa pine (Pinus ponderosa), during an extreme drought in the Sierra Nevada, California, United States. When compared with the field data, our model captured the western pine beetle flight timing and rates of ponderosa pine mortality observed during the drought. In assessing the influence of temperature on western pine beetles, we found that contemporary warming increased the development rate of the western pine beetle and decreased the overwinter mortality rate of western pine beetle larvae leading to increased population growth during periods of lowered tree defense. We attribute a 29.9% (95% CI: 29.4%–30.2%) increase in ponderosa pine mortality during drought directly to increases in western pine beetle voltinism (i.e., associated with increased development rates of western pine beetle) and, to a much lesser extent, reductions in overwintering mortality. These findings, along with other studies, suggest each degree (°C) increase in temperature may have increased the number of ponderosa pine killed by upwards of 35%–40% °C-1 if the effects of compromised tree defenses (15%–20%) and increased western pine beetle populations (20%) are additive. Due to the warming ability to considerably increase mortality through the mechanism of bark beetle populations, models need to consider climate’s influence on both host tree stress and the bark beetle population dynamics when determining future levels of tree mortality.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Zhuang, Yizhou; Fu, R; Santer, B; Dickinson, R; Hall, A

Quantifying contributions of natural variability and anthropogenic forcings on increased fire weather risk over western United States. Journal Article

In: Proceedings of the National Academy of Sciences, vol. 118, no. 45, pp. e2111875118, 2021.

Abstract | Links | BibTeX

Chen, Di; Dai, A; Hall, A

The Convective-To-Total Precipitation Ratio and the “Drizzling” Bias in Climate Models Journal Article

In: Journal of Geophysical Research: Atmospheres, vol. 126, no. 16, pp. e2020JD034198, 2021.

Abstract | Links | BibTeX

Madakumbura, Gavin D.; Thackeray, C; Norris, J; Goldenson, N; Hall, A

Anthropogenic influence on extreme precipitation over global land areas seen in multiple observational datasets Journal Article

In: Nature Communications, vol. 12, pp. 3944, 2021.

Abstract | Links | BibTeX

Chen, Di; Norris, J; Goldenson, N; Thackeray, C; Hall, A

A Distinct Atmospheric Mode for California Precipitation Journal Article

In: Journal of Geophysical Research: Atmospheres, vol. 126, no. 12, pp. e2020JD034403, 2021.

Abstract | Links | BibTeX

@article{2261,

title = {A Distinct Atmospheric Mode for California Precipitation},

author = {Di Chen and J Norris and N Goldenson and C Thackeray and A Hall},

url = {https://doi.org/10.1029/2020JD034403},

year  = {2021},

date = {2021-01-01},

journal = {Journal of Geophysical Research: Atmospheres},

volume = {126},

number = {12},

pages = {e2020JD034403},

abstract = {The hydrologic cycle in California is strongly influenced by wet-season (November–April) precipitation. Here, we demonstrate the existence of an influential mode of North Pacific atmospheric pressure variability that regulates wet-season precipitation variability over both northern and southern California. This mode, named as the “California precipitation mode” (CPM), is statistically distinct from other well-known modes of pressure variability such as the Pacific-North American pattern. In addition to controlling wet-season mean precipitation, positive days of the CPM coincide with up to 90% of the extreme (>99th percentile) precipitation days and 76% of detected atmospheric rivers (ARs) days, while the negative days correspond with 60% of the dry days. CMIP6 models capture the CPM remarkably well, including its statistical separation from the other well-known modes of pressure variability. The models also reproduce the CPM’s strong association with California wet-season precipitation, giving confidence in the models’ dynamics relating to regional hydrologic extremes. However, the models also exhibit biases in regional hydrologic extremes. The CPM is a useful way to understand the origins of those biases and select the more credible models for further analysis: Models with unrealistically strong gradients in the CPM pressure pattern generally oversimulate larger wet extremes and produce excessively long dry intervals in the historical period. Thus the hydrologic biases can be traced to the particular aspects of North Pacific atmospheric dynamics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Norris, Jesse; Hall, A; Neelin, JD; Thackeray, C; Chen, D

Evaluation of the Tail of the Probability Distribution of Daily and Subdaily Precipitation in CMIP6 Models Journal Article

In: Journal of Climate, vol. 34, no. 7, pp. 2701–2721, 2021.

Abstract | Links | BibTeX

@article{2248,

title = {Evaluation of the Tail of the Probability Distribution of Daily and Subdaily Precipitation in CMIP6 Models},

author = {Jesse Norris and A Hall and JD Neelin and C Thackeray and D Chen},

url = {https://doi.org/10.1175/JCLI-D-20-0182.1},

year  = {2021},

date = {2021-01-01},

journal = {Journal of Climate},

volume = {34},

number = {7},

pages = {2701–2721},

abstract = {Daily and subdaily precipitation extremes in historical phase 6 of the Coupled Model Intercomparison Project (CMIP6) simulations are evaluated against satellite-based observational estimates. Extremes are defined as the precipitation amount exceeded every x years, ranging from 0.01 to 10, encompassing the rarest events that are detectable in the observational record without noisy results. With increasing temporal resolution there is an increased discrepancy between models and observations: for daily extremes, the multimodel median underestimates the highest percentiles by about a third, and for 3-hourly extremes by about 75% in the tropics. The novelty of the current study is that, to understand the model spread, we evaluate the 3D structure of the atmosphere when extremes occur. In midlatitudes, where extremes are simulated predominantly explicitly, the intuitive relationship exists whereby higher-resolution models produce larger extremes (r = -0.49), via greater vertical velocity. In the tropics, the convective fraction (the fraction of precipitation simulated directly from the convective scheme) is more relevant. For models below 60% convective fraction, precipitation amount decreases with convective fraction (r = -0.63), but above 75% convective fraction, this relationship breaks down. In the lower-convective-fraction models, there is more moisture in the lower troposphere, closer to saturation. In the higher-convective-fraction models, there is deeper convection and higher cloud tops, which appears to be more physical. Thus, the low-convective models are mostly closer to the observations of extreme precipitation in the tropics, but likely for the wrong reasons. These intermodel differences in the environment in which extremes are simulated hold clues into how parameterizations could be modified in general circulation models to produce more credible twenty-first-century projections.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Williamson, Mark S.; Thackeray, C; Cox, P; Hall, A; Huntingford, C; Nijsse, F

Emergent constraints on climate sensitivities Journal Article

In: Review of Modern Physics, vol. 93, no. 2, pp. 025004, 2021.

Abstract | Links | BibTeX

@article{2247,

title = {Emergent constraints on climate sensitivities},

author = {Mark S. Williamson and C Thackeray and P Cox and A Hall and C Huntingford and F Nijsse},

url = {https://doi.org/10.1103/RevModPhys.93.025004},

year  = {2021},

date = {2021-01-01},

journal = {Review of Modern Physics},

volume = {93},

number = {2},

pages = {025004},

abstract = {Despite major advances in climate science over the last 30 years, persistent uncertainties in projections of future climate change remain. Climate projections are produced with increasingly complex models that attempt to represent key processes in the Earth system, including atmospheric and oceanic circulations, convection, clouds, snow, sea ice, vegetation, and interactions with the carbon cycle. Uncertainties in the representation of these processes feed through into a range of projections from the many state-of-the-art climate models now being developed and used worldwide. For example, despite major improvements in climate models, the range of equilibrium global warming due to doubling carbon dioxide still spans a range of more than 3. Here a promising way to make use of the ensemble of climate models to reduce the uncertainties in the sensitivities of the real climate system is reviewed. The emergent constraint approach uses the model ensemble to identify a relationship between an uncertain aspect of the future climate and an observable variation or trend in the contemporary climate. This review summarizes previous published work on emergent constraints and discusses the promise and potential dangers of the approach. Most importantly, it argues that emergent constraints should be based on well-founded physical principles such as the fluctuation-dissipation theorem. This review will stimulate physicists to contribute to the rapidly developing field of emergent constraints on climate projections, bringing to it much needed rigor and physical insights.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Thackeray, Chad W.; Hall, A; Zelinka, MD; Fletcher, C

Assessing Prior Emergent Constraints on Surface Albedo Feedback in CMIP6 Journal Article

In: Journal of Climate, vol. 34, no. 10, pp. 3889–3905, 2021.

Abstract | Links | BibTeX

Goldenson, Naomi; Thackery, C; Hall, A; Swain, DL; Berg, N

Using Large Ensembles to Identify Regions of Systematic Biases in Moderate-to-Heavy Daily Precipitation Journal Article

In: Geophysical Research Letters, vol. 48, no. 9, pp. e2020GL092026, 2021.

Abstract | Links | BibTeX

Norris, Jesse; Hall, A; Chen, D; Thackery, C; Madakumbura, G

Assessing the Representation of Synoptic Variability Associated With California Extreme Precipitation in CMIP6 Models Journal Article

In: Journal of Geophysical Research: Atmospheres, vol. 126, no. 6, pp. e2020JD033938, 2021.

Abstract | Links | BibTeX

Madakumbura, G; Goulden, M; Hall, A; Fu, R; Moritz, M; Koven, C; Kueppers, L; Norlen, C; Randerson, J

Recent California tree mortality portends future increase in drought-driven forest die-off Journal Article

In: Environmental Research Letters, vol. 15, no. 12, pp. 124040, 2020.

Abstract | Links | BibTeX

Walton, D; Berg, N; Pierce, D; Maurer, E; Hall, A; Lin, Y; Rahimi, S; Cayan, D

Understanding differences in California climate projections produced by dynamical and statistical downscaling. Journal Article

In: Journal of Geophysical Research: Atmospheres, vol. 125, no. 19, pp. e2020JD032812, 2020.

Abstract | Links | BibTeX

Huang, X; Stevenson, S; Hall, A

Future warming and intensification of precipitation extremes: A &$#$39;double whammy&$#$39; leading to increasing flood risk in California. Journal Article

In: Geophysical Research Letters, vol. 47, no. 16, pp. e2020GL088679, 2020.

Abstract | Links | BibTeX

Huang, X; Swain, DL; Hall, A

Large ensemble downscaling of atmospheric rivers. Journal Article

In: Science Advances, vol. 6, no. 29, pp. e2020GL088679, 2020.

Abstract | Links | BibTeX

Payne, AE; Demory, ME; Leung, LR; Ramos, AM; Shields, CA; Rutz, JJ; Siler, N; Villarini, G; Hall, A; Ralph, FM

Responses and impacts of atmospheric rivers to climate change Journal Article

In: Nature Reviews Earth & Environment, vol. 1, pp. 143–157, 2020.

Abstract | Links | BibTeX

Huang, X; Swain, DL; Walton, DB; Stevenson, S; Hall, A

Simulating and Evaluating Atmospheric River-Induced Precipitation Extremes Along the U.S. Pacific Coast: Case Studies From 1980–2017 Journal Article

In: Journal of Geophysical Research: Atmospheres, vol. 125, no. 4, 2020.

Abstract | Links | BibTeX

@article{2043,

title = {Simulating and Evaluating Atmospheric River-Induced Precipitation Extremes Along the U.S. Pacific Coast: Case Studies From 1980-2017},

author = {X Huang and DL Swain and DB Walton and S Stevenson and A Hall},

url = {https://dx.doi.org/10.1029/2019JD031554},

year  = {2020},

date = {2020-01-01},

journal = {Journal of Geophysical Research: Atmospheres},

volume = {125},

number = {4},

abstract = {Atmospheric rivers (ARs) are responsible for a majority of extreme precipitation and flood events along the U.S. West Coast. To better understand the present-day characteristics of AR-related precipitation extremes, a selection of nine most intense historical AR events during 1980–2017 is simulated using a dynamical downscaling modeling framework based on the Weather Research and Forecasting Model. We find that the chosen framework and Weather Research and Forecasting Model configuration reproduces both large-scale atmospheric features—including parent synoptic-scale cyclones—as well as the filamentary corridors of integrated vapor transport associated with the ARs themselves. The accuracy of simulated extreme precipitation maxima, relative to in situ and interpolated gridded observations, improves notably with increasing model resolution, with improvements as large as 40–60% for fine scale (3 km) relative to coarse-scale (27 km) simulations. A separate set of simulations using smoothed topography suggests that much of these gains stem from the improved representation of complex terrain. Additionally, using the 12 December 1995 storm in Northern California as an example, we demonstrate that only the highest-resolution simulations resolve important fine-scale features—such as localized orographically forced vertical motion and powerful near hurricane-force boundary layer winds. Given the demonstrated ability of a targeted dynamical downscaling framework to capture both local extreme precipitation and key fine-scale characteristics of the most intense ARs in the historical record, we argue that such a configuration may be highly conducive to understanding AR-related extremes and associated changes in a warming climate.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Thackeray, CW; Hall, A

An emergent constraint on future Arctic sea-ice albedo feedback Journal Article

In: Nature Climate Change, vol. 9, pp. 972–978, 2019.

Abstract | Links | BibTeX

Thackeray, CW; Derksen, C; Fletcher, CG; Hall, A

Snow and climate: Feedbacks, drivers, and indices of change Journal Article

In: Current Climate Change Reports, vol. 5, no. 4, pp. 322–333, 2019.

Abstract | Links | BibTeX

Heinze, C; Eyring, V; Friedlingstein, P; Jones, C; Balkanski, Y; Collins, W; Fichefet, T; Gao, S; Hall, A; Ivanova, D; Knorr, W; Knutti, R; Löwc, A; Ponater, M; Schultz, MG; Schulz, M; Siebesma, P; Teixeira, J; Tselioudis, G; Vancoppenolle, M

Climate feedbacks in the Earth system and prospects for their evaluation Journal Article

In: Earth System Dynamics, vol. 10, pp. 379–452, 2019.

Abstract | Links | BibTeX

@article{1965,

title = {Climate feedbacks in the Earth system and prospects for their evaluation},

author = {C Heinze and V Eyring and P Friedlingstein and C Jones and Y Balkanski and W Collins and T Fichefet and S Gao and A Hall and D Ivanova and W Knorr and R Knutti and A Löwc and M Ponater and MG Schultz and M Schulz and P Siebesma and J Teixeira and G Tselioudis and M Vancoppenolle},

url = {https://dx.doi.org/10.5194/esd-10-379-2019},

year  = {2019},

date = {2019-01-01},

journal = {Earth System Dynamics},

volume = {10},

pages = {379–452},

abstract = {Earth system models (ESMs) are key tools for providing climate projections under different scenarios of human-induced forcing. ESMs include a large number of additional processes and feedbacks such as biogeochemical cycles that traditional physical climate models do not consider. Yet, some processes such as cloud dynamics and ecosystem functional response still have fairly high uncertainties. In this article, we present an overview of climate feedbacks for Earth system components currently included in state-of-the-art ESMs and discuss the challenges to evaluate and quantify them. Uncertainties in feedback quantification arise from the interdependencies of biogeochemical matter fluxes and physical properties, the spatial and temporal heterogeneity of processes, and the lack of long-term continuous observational data to constrain them. We present an outlook for promising approaches that can help to quantify and to constrain the large number of feedbacks in ESMs in the future. The target group for this article includes generalists with a background in natural sciences and an interest in climate change as well as experts working in interdisciplinary climate research (researchers, lecturers, and students). This study updates and significantly expands upon the last comprehensive overview of climate feedbacks in ESMs, which was produced 15 years ago (NRC, 2003).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Close

Sun, F; Berg, N; Hall, A; Schwartz, M; Walton, DB

Understanding end-of-century snowpack changes over California&$#$39;s Sierra Nevada Journal Article

In: Geophysical Research Letters, vol. 46, no. 2, pp. 933–943, 2019.

Abstract | Links | BibTeX

Eyring, V; Cox, P; Flato, G; Gleckler, P; Abramowitz, G; Caldwell, P; Collins, W; Gier, B; Hall, A; Hoffman, F; Hurtt, G; Jahn, A; Jones, C; Klein, SA; Krasting, J; Kwiatkowski, L; Lorenz, R; Maloney, E; Meehl, G; Pendergrass, A; Pincus, R; Ruane, A; Russell, J; Sanderson, B; Santer, B; Sherwood, S; Simpson, I; Stouffer, R; Williamson, M

Taking climate model evaluation to the next level Journal Article

In: Nature Climate Change, vol. 9, no. 2, pp. 102–110, 2019.

Links | BibTeX