Spatial and Temporal Variability of Drought Patterns over the Continental United States from Observations and Regional Climate Models

AbstractUnderstanding future precipitation changes is critical for water supply and flood risk applications in the western United States. The North American COordinated Regional Downscaling EXperiment (NA-CORDEX) matrix of global and regional climate models at multiple resolutions (~ 50-km and 25-km grid spacings) is used to evaluate mean monthly precipitation, extreme daily precipitation, and snow water equivalent (SWE) over the western United States, with a sub-regional focus on California. Results indicate significant model spread in mean monthly precipitation in several key water-sensitive areas in both historical and future projections, but suggest model agreement on increasing daily extreme precipitation magnitudes, decreasing seasonal snowpack, and a shortening of the wet season in California in particular. While the beginning and end of the California cool season are projected to dry according to most models, the core of the cool season (December, January, February) shows an overall wetter projected change pattern. Daily cool-season precipitation extremes generally increase for most models, particularly in California in the mid-winter months. Finally, a marked projected decrease in future seasonal SWE is found across all models, accompanied by earlier dates of maximum seasonal SWE, and thus a shortening of the period of snow cover as well. Results are discussed in the context of how the diverse model membership and variable resolutions offered by the NA-CORDEX ensemble can be best leveraged by stakeholders faced with future water planning challenges.

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Performance evaluation of bias adjustment methods for wave climate projections in the Mediterranean Sea

10.5194/egusphere-egu21-13557 ◽

2021 ◽

Author(s):

Andrea Lira Loarca ◽

Giovanni Besio

Keyword(s):

Bias Correction ◽

Temporal Variability ◽

Climate Models ◽

Regional Climate ◽

Regional Climate Models ◽

Wave Climate ◽

Mapping Method ◽

Climate Projections ◽

Bias Adjustment ◽

Distribution Mapping

Global and regional climate models are the primary tools to investigate the climate system response to different scenarios and therefore allow to make future projections of different atmospheric variables which are used as input for wave generation models to assess future wave climate. Adequate projections of future wave climate are needed in order to analyze climate change impacts and hazards in coastal areas such as flooding and erosion with waves being the predominant factor with varied temporal variability.&#160;Bias adjustment methods are commonly used for climate impact variables dealing with systematic errors (biases) found in global and regional climate models.&#160; While bias correction techniques are extended in the climate and hydrological impact modeling scientific communities, there is still a lack of consensus regarding their use in sea climate variables (Parker & Hill, 2017; Lemos et al, 2020; Lira-Loarca et at, 2021)In these work we assess the performance of different bias-adjustment methods such as the Empirical Gumbel Quantile Mapping (EGQM) method as a standard method which takes into the account the extreme values of the distribution takes, the Distribution Mapping method using Stationary Mixture Distributions (DM-stMix) allowing for a better representation of each variable in the mean regime and tails and the Distribution Mapping method using Non-Stationary Mixture Distributions (DM-nonstMix) as an improved methods which allows to take into account the temporal variability of wave climate according to different baseline periods such as monthly, seasonal, yearly and decadal. The performance of the different bias adjustment methods will be analyzed with particular interest on the futural temporal behavior of wave climate. The advantages and drawbacks of each bias adjustment method as well as their complexity will be discussed.&#160;References:<ul><li>Lemos, G., Menendez, M., Semedo, A., Camus, P., Hemer, M., Dobrynin, M., Miranda, P.M.A. (2020). On the need of bias correction methods for wave climate projections, Global and Planetary Change, 186, 103109.</li> <li>Lira-Loarca, A., Cobos, M., Besio, G., Baquerizo, A. (2021) Projected wave climate temporal variability due to climate change. Stoch Environ Res Risk Assess.</li> <li>Parker, K. & Hill, D.F. (2017) Evaluation of bias correction methods for wave modeling output, Ocean Modelling 110, 52-65</li> </ul>

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Will Future Climate Favor More Erratic Wildfires in the Western United States?

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-12-0317.1 ◽

2013 ◽

Vol 52 (11) ◽

pp. 2410-2417 ◽

Cited By ~ 22

Author(s):

Lifeng Luo ◽

Ying Tang ◽

Shiyuan Zhong ◽

Xindi Bian ◽

Warren E. Heilman

Keyword(s):

United States ◽

Climate Models ◽

Regional Climate ◽

Fire Behavior ◽

Regional Climate Models ◽

Future Climate ◽

Lower Atmosphere ◽

Western United States ◽

Mountainous Regions ◽

Increased Risk

AbstractWildfires that occurred over the western United States during August 2012 were fewer in number but larger in size when compared with all other Augusts in the twenty-first century. This unique characteristic, along with the tremendous property damage and potential loss of life that occur with large wildfires with erratic behavior, raised the question of whether future climate will favor rapid wildfire growth so that similar wildfire activity may become more frequent as climate changes. This study addresses this question by examining differences in the climatological distribution of the Haines index (HI) between the current and projected future climate over the western United States. The HI, ranging from 2 to 6, was designed to characterize dry, unstable air in the lower atmosphere that may contribute to erratic or extreme fire behavior. A shift in HI distribution from low values (2 and 3) to higher values (5 and 6) would indicate an increased risk for rapid wildfire growth and spread. Distributions of Haines index are calculated from simulations of current (1971–2000) and future (2041–70) climate using multiple regional climate models in the North American Regional Climate Change Assessment Program. Despite some differences among the projections, the simulations indicate that there may be not only more days but also more consecutive days with HI ≥ 5 during August in the future. This result suggests that future atmospheric environments will be more conducive to erratic wildfires in the mountainous regions of the western United States.

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A Maieutic Exploration of Nudging Strategies for Regional Climate Applications Using the WRF Model

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-17-0360.1 ◽

2018 ◽

Vol 57 (8) ◽

pp. 1883-1906 ◽

Cited By ~ 6

Author(s):

Tanya L. Spero ◽

Christopher G. Nolte ◽

Megan S. Mallard ◽

Jared H. Bowden

Keyword(s):

United States ◽

Climate Models ◽

Weather Prediction ◽

Regional Climate ◽

Wrf Model ◽

Regional Climate Models ◽

The United States ◽

Spectral Nudging ◽

Temperature And Precipitation ◽

Quality Health

AbstractThe use of nudging in the Weather Research and Forecasting (WRF) Model to constrain regional climate downscaling simulations is gaining in popularity because it can reduce error and improve consistency with the driving data. While some attention has been paid to whether nudging is beneficial for downscaling, very little research has been performed to determine best practices. In fact, many published papers use the default nudging configuration (which was designed for numerical weather prediction), follow practices used by colleagues, or adapt methods developed for other regional climate models. Here, a suite of 45 three-year simulations is conducted with WRF over the continental United States to systematically and comprehensively examine a variety of nudging strategies. The simulations here use a longer test period than did previously published works to better evaluate the robustness of each strategy through all four seasons, through multiple years, and across nine regions of the United States. The analysis focuses on the evaluation of 2-m temperature and precipitation, which are two of the most commonly required downscaled output fields for air quality, health, and ecosystems applications. Several specific recommendations are provided to effectively use nudging in WRF for regional climate applications. In particular, spectral nudging is preferred over analysis nudging. Spectral nudging performs best in WRF when it is used toward wind above the planetary boundary layer (through the stratosphere) and temperature and moisture only within the free troposphere. Furthermore, the nudging toward moisture is very sensitive to the nudging coefficient, and the default nudging coefficient in WRF is too high to be used effectively for moisture.

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Characterizing Predictability of Precipitation Means and Extremes over the Conterminous United States, 1949–2010*

Journal of Climate ◽

10.1175/jcli-d-15-0560.1 ◽

2016 ◽

Vol 29 (7) ◽

pp. 2621-2633 ◽

Cited By ~ 4

Author(s):

Mingkai Jiang ◽

Benjamin S. Felzer ◽

Dork Sahagian

Keyword(s):

United States ◽

Pacific Northwest ◽

West Coast ◽

Climate Models ◽

Regional Climate ◽

Regional Climate Models ◽

The United States ◽

Monthly Precipitation ◽

The West ◽

Precipitation Seasonality

Abstract The proper understanding of precipitation variability, seasonality, and predictability are important for effective environmental management. Precipitation and its associated extremes vary in magnitude and duration both spatially and temporally, making it one of the most challenging climate parameters to predict on the basis of global and regional climate models. Using information theory, an improved understanding of precipitation predictability in the conterminous United States over the period of 1949–2010 is sought based on a gridded monthly precipitation dataset. Predictability is defined as the recurrent likelihood of patterns described by the metrics of magnitude variability and seasonality. It is shown that monthly mean precipitation and duration-based dry and wet extremes are generally highly variable in the east compared to those in the west, while the reversed spatial pattern is observed for intensity-based wetness indices except along the Pacific Northwest coast. It is thus inferred that, over much of the U.S. landscape, variations of monthly mean precipitation are driven by the variations in precipitation occurrences rather than the intensity of infrequent heavy rainfall. It is further demonstrated that precipitation seasonality for means and extremes is homogeneously invariant within the United States, with the exceptions of the West Coast, Florida, and parts of the Midwest, where stronger seasonality is identified. A proportionally higher role of variability in regulating precipitation predictability is demonstrated. Seasonality surpasses variability only in parts of the West Coast. The quantified patterns of predictability for precipitation means and extremes have direct applications to those phenomena influenced by climate periodicity, such as biodiversity and ecosystem management.

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Changes in winter precipitation extremes for the western United States under a warmer climate as simulated by regional climate models

Geophysical Research Letters ◽

10.1029/2011gl050762 ◽

2012 ◽

Vol 39 (5) ◽

pp. n/a-n/a ◽

Cited By ~ 94

Author(s):

F. Dominguez ◽

E. Rivera ◽

D. P. Lettenmaier ◽

C. L. Castro

Keyword(s):

United States ◽

Climate Models ◽

Regional Climate ◽

Regional Climate Models ◽

Winter Precipitation ◽

Precipitation Extremes ◽

Western United States

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Evaluation of the southerly low-level jet climatology for the central United States as simulated by NARCCAP regional climate models

International Journal of Climatology ◽

10.1002/joc.4636 ◽

2016 ◽

Vol 36 (13) ◽

pp. 4338-4357 ◽

Cited By ~ 5

Author(s):

Ying Tang ◽

Shiyuan Zhong ◽

Julie A. Winker ◽

Claudia K. Walters

Keyword(s):

United States ◽

Climate Models ◽

Regional Climate ◽

Regional Climate Models ◽

Low Level ◽

Central United States ◽

Low Level Jet

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Simulations of Present and Future Climates in the Western United States with Four Nested Regional Climate Models

Journal of Climate ◽

10.1175/jcli3669.1 ◽

2006 ◽

Vol 19 (6) ◽

pp. 873-895 ◽

Cited By ~ 81

Author(s):

P. B. Duffy ◽

R. W. Arritt ◽

J. Coquard ◽

W. Gutowski ◽

J. Han ◽

...

Keyword(s):

United States ◽

Boundary Conditions ◽

Water Content ◽

Climate Models ◽

Regional Climate ◽

Regional Climate Models ◽

Western United States ◽

Lateral Boundary ◽

Present Climate ◽

Lateral Boundary Conditions

Abstract In this paper, the authors analyze simulations of present and future climates in the western United States performed with four regional climate models (RCMs) nested within two global ocean–atmosphere climate models. The primary goal here is to assess the range of regional climate responses to increased greenhouse gases in available RCM simulations. The four RCMs used different geographical domains, different increased greenhouse gas scenarios for future-climate simulations, and (in some cases) different lateral boundary conditions. For simulations of the present climate, RCM results are compared to observations and to results of the GCM that provided lateral boundary conditions to the RCM. For future-climate (increased greenhouse gas) simulations, RCM results are compared to each other and to results of the driving GCMs. When results are spatially averaged over the western United States, it is found that the results of each RCM closely follow those of the driving GCM in the same region in both present and future climates. This is true even though the study area is in some cases a small fraction of the RCM domain. Precipitation responses predicted by the RCMs in many regions are not statistically significant compared to interannual variability. Where the predicted precipitation responses are statistically significant, they are positive. The models agree that near-surface temperatures will increase, but do not agree on the spatial pattern of this increase. The four RCMs produce very different estimates of water content of snow in the present climate, and of the change in this water content in response to increased greenhouse gases.

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