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Future changes in the number of dry days per year can either reinforce or counteract projected increases in daily precipitation intensity as the climate warms. We analyze climate model projected changes in the number of dry days using 28 coupled global climate models from the Coupled Model Intercomparison Project, version 5 (CMIP5). We find that the Mediterranean Sea region, parts of Central and South America, and western Indonesia could experience up to 30 more dry days per year by the end of this century. We illustrate how changes in the number of dry days and the precipitation intensity on precipitating days combine to produce changes in annual precipitation, and show that over much of the subtropics the change...
This presentation aired as part of the Great Basin LCC webinar series on October 11, 2017. Speakers included Erica Fleishman, U.C. Davis, and Jimi Gragg, Utah Division of Wildlife Resources.Description: As the distribution and abundance of non-native cheatgrass (Bromus tectorum) in the Great Basin has increased, the extent and frequency of fire in the region has increased by as much as 200%. These changes in fire regimes are associated with loss of the sagebrush (Artemisia tridentata) and native grasses and forbs in which many native animals, including Greater Sage-grouse (Centrocercus urophasianus), breed and feed. Managers have suggested changes in fire regimes, fuels treatments and post-fire restoration with...
This study examines the health impacts of recent heat waves statewide and for six subregions of California: the north and south coasts, the Central Valley, the Mojave Desert, southern deserts, and northern forests. By using canonical correlation analysis applied to daily maximum temperatures and morbidity data in the form of unscheduled hospitalizations from 1999 to 2009, 19 heat waves spanning 3–15 days in duration that had a significant impact on health were identified. On average, hospital admissions were found to increase by 7% on the peak heat-wave day, with a significant impact seen for several disease categories, including cardiovascular disease, respiratory disease, dehydration, acute renal failure, heat...
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To understand potential climate change impacts on ecosystems, water resources, and numerous other natural and managed resources, climate change data and projections must be downscaled from coarse global climate models to much finer resolutions and more applicable formats. This project conducted comparative analyses to better understand the accuracy and properties of these downscaled climate simulations and climate-change projections. Interpretation, guidance and evaluation, including measures of uncertainties, strengths and weaknesses of the different methodologies for each simulation, can enable potential users with the necessary information to select and apply the models.
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FY2015This effort complements a project, supported by the Joint Fire Science Program, to explore relations among cheatgrass-driven fire, climate, and sensitive-status birds across the Great Basin. With support from the NW and SW Climate Science Centers and the GB CESU, we aim to engage managers at local, state, and regional levels, and to involve both field-level and director-level personnel, during all stages of the proposed project. Our methods of engagement are intended to save managers time and decrease some of the uncertainty in planning and decision-making rather than to create additional pressures on managers time. We will conduct field visits, workshops, and interactive briefings to build trust and increase...
Abstract (from http://link.springer.com/article/10.1007%2Fs00382-015-2517-1): Daily precipitation variability as observed from weather stations is heavy tailed at most locations around the world. It is thought that diversity in precipitation-causing weather events is fundamental in producing heavy-tailed distributions, and it arises from theory that at least one of the precipitation types contributing to a heavy-tailed climatological record must also be heavy-tailed. Precipitation is a multi-scale phenomenon with a rich spatial structure and short decorrelation length and timescales; the spatiotemporal scale at which precipitation is observed is thus an important factor when considering its statistics and extremes....
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The complex mountain and valley chains of the Southwest exert a strong influence on precipitation and wind patterns. Atmospheric rivers deliver some of the most extreme precipitation events to west-southwest-facing slopes of the mountains where strong gusty downslope winds can also spread wildfires. Climate change is making the southwest warmer and dryer resulting in more fire-prone vegetation and more frequent and extreme atmospheric rivers. Understanding this changing system is critical for managing water resources and wildfire in the region. This project will study how climate change is impacting precipitation and winds to create fire weather and drive fire spread on heavily vegetated slopes of coastal mountains....
This paper is a product from the SW CSC FY 11 project, "Climate change impacts in the Southwest: An assessment of next generation climate models for making projections and derivations". Abstract: Natural climate variability will continue to be an important aspect of future regional climate even in the midst of long-term secular changes. Consequently, the ability of climate models to simulate major natural modes of variability and their teleconnections provides important context for the interpretation and use of climate change projections. Comparisons reported here indicate that the CMIP5 generation of global climate models shows significant improvements in simulations of key Pacific climate mode and their teleconnections...
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Natural climate variability can obscure or enhance long-term trends in experienced weather due to climate change. This can happen temporarily on timescales of a season to several years to a decade or two. Natural variability is poorly described and attributed to specific causes, contributing to uncertainty and misunderstandings about the nature of climate change that stakeholders and resource managers attempt to anticipate. There exists, therefore, a need to clarify the magnitude and causality of natural climate variability. This connection needs to be explained for locally-experienced weather and particularly for daily extreme events, whose seasonal behavior impacts both resources and imagination. Conversely, it...
A statistical model based on canonical correlation analysis (CCA) was used to explore climatic associations and predictability of June-August (JJA) maximum and minimum surface air temperatures (Tmax and Tmin) as well as the frequency of Tmax daily extremes (Tmax90) in the central and western United States (west of 90 degrees W). Explanatory variables are monthly and seasonal Pacific Ocean SST (PSST) and the Climate Division Palmer Drought Severity Index (PDSI) during 1950-2001. Although there is a positive correlation between Tmax and Tmin, the two variables exhibit somewhat different patterns and dynamics. Both exhibit their lowest levels of variability in summer, but that of Tmax is greater than Tmin. The predictability...
Atmospheric rivers (ARs) and Santa Ana winds (SAWs) are impactful weather events for California communities. Emergency planning efforts and resource management would benefit from extending lead times of skillful prediction for these and other types of extreme weather patterns. Here we describe a methodology for subseasonal prediction of impactful winter weather in California, including ARs, SAWs and heat extremes. The hybrid approach combines dynamical model and historical information to forecast probabilities of impactful weather outcomes at weeks 1–4 lead. This methodology uses dynamical model information considered most reliable, that is, planetary/synoptic-scale atmospheric circulation, filters for dynamical...
Categories: Publication; Types: Citation
Abstract (from http://iopscience.iop.org/article/10.1088/1748-9326/10/12/124023/meta): Temperature variability in the Southwest US is investigated using skew-normal probability distribution functions (SN PDFs) fitted to observed wintertime daily maximum temperature records. These PDFs vary significantly between years, with important geographical differences in the relationship between the central tendency and tails, revealing differing linkages between weather and climate. The warmest and coldest extremes do not necessarily follow the distribution center. In some regions one tail of the distribution shows more variability than does the other. For example, in California the cold tail is more variable while the warm...
    map background search result map search result map Analysis of Downscaled Climate Simulations and Projections and Their Use in Decision Making for the Southwest Understanding and Communicating the Role of Natural Climate Variability in a Changing World Engagement of Managers and Researchers on Relations among Cheatgrass-driven Fire, Climate, and Sensitive-status Birds across the Great Basin How do Atmospheric Rivers and Downslope Winds Affect Wildfire Risk and Water Resources in the Arid Southwest? Engagement of Managers and Researchers on Relations among Cheatgrass-driven Fire, Climate, and Sensitive-status Birds across the Great Basin Analysis of Downscaled Climate Simulations and Projections and Their Use in Decision Making for the Southwest How do Atmospheric Rivers and Downslope Winds Affect Wildfire Risk and Water Resources in the Arid Southwest? Understanding and Communicating the Role of Natural Climate Variability in a Changing World