scholarly journals Capacity of Two Sierra Nevada Rivers for Reintroduction of Anadromous Salmonids: Insights from a High‐Resolution View

2021 ◽  
Author(s):  
David A. Boughton ◽  
Lee R. Harrison ◽  
Sara N. John ◽  
Rosealea M. Bond ◽  
Colin L. Nicol ◽  
...  
Keyword(s):  
High Resolution ◽  
Sierra Nevada

scholarly journals High-Resolution Simulations of Lee Waves and Downslope Winds over the Sierra Nevada during T-REX IOP 6

2012 ◽  
Vol 51 (7) ◽  
pp. 1333-1352 ◽  
Author(s):  
Peter Sheridan ◽  
Simon Vosper
Keyword(s):  
High Resolution ◽  
Sierra Nevada ◽  
Cross Sections ◽  
Weather Prediction ◽  
Vertical Motion ◽  
Owens Valley ◽  
Downslope Winds ◽  
Lee Waves ◽  
Rotor Experiment ◽  
Intensive Observation

AbstractThe downslope windstorm during intensive observation period (IOP) 6 was the most severe that was detected during the Terrain-Induced Rotor Experiment (T-REX) in Owens Valley in the Sierra Nevada of California. Cross sections of vertical motion in the form of a composite constructed from aircraft data spanning the depth of the troposphere are used to link the winds experienced at the surface to the changing structure of the mountain-wave field aloft. Detailed analysis of other observations allows the role played by a passing occluded front, associated with the rapid intensification (and subsequent cessation) of the windstorm, to be studied. High-resolution, nested modeling using the Met Office Unified Model (MetUM) is used to study qualitative aspects of the flow and the influence of the front, and this modeling suggests that accurate forecasting of the timing and position of both the front and strong mountaintop winds is crucial to capture the wave dynamics and accompanying windstorm. Meanwhile, far ahead of the front, simulated downslope winds are shallow and foehnlike, driven by the thermal contrast between the upstream and valley air mass. The study also highlights the difficulties of capturing the detailed interaction of weather systems with large and complex orography in numerical weather prediction.

A PRELIMINARY HIGH-RESOLUTION LATE HOLOCENE DIATOM STRATIGRAPHY AND HYDROCLIMATIC RECONSTRUCTION FROM JUNE LAKE (EASTERN SIERRA NEVADA)

2018 ◽  
Author(s):  
Laura C. Streib ◽  
◽  
Jeffery R. Stone ◽  
Eva Lyon ◽  
Susan H. Zimmerman ◽  
...  
Keyword(s):  
High Resolution ◽  
Sierra Nevada ◽  
Late Holocene ◽  
Diatom Stratigraphy ◽  
Eastern Sierra Nevada

scholarly journals The Value of Accurate High-Resolution and Spatially Continuous Snow Information to Streamflow Forecasts

2019 ◽  
Vol 20 (4) ◽  
pp. 731-749 ◽  
Author(s):  
Dongyue Li ◽  
Dennis P. Lettenmaier ◽  
Steven A. Margulis ◽  
Konstantinos Andreadis
Keyword(s):  
High Resolution ◽  
Sierra Nevada ◽  
Snow Accumulation ◽  
Forecast Errors ◽  
Streamflow Forecasting ◽  
Streamflow Forecast ◽  
Physically Based ◽  
Streamflow Forecasts ◽  
Seasonal Streamflow ◽  
The Impact

Abstract Previous studies have shown limited success in improving streamflow forecasting for snow-dominated watersheds using physically based models, primarily due to the lack of reliable snow water equivalent (SWE) information. Here we use a hindcasting approach to evaluate the potential benefit that a high-resolution, spatiotemporally continuous, and accurate SWE reanalysis product would have on the seasonal streamflow forecast in the snow-dominated Sierra Nevada mountains of California if such an SWE product were available in real time. We tested the efficacy of a physically based ensemble streamflow prediction (ESP) framework when initialized with the reanalysis SWE. We reinitialized the SWE over the Sierra Nevada at the time when the Sierra Nevada had domain-wide annual maximum SWE for each year in 1985–2015, and on 1 February of the driest years within the same period. The early season forecasts on 1 February provide valuable lead time for mitigating the impact of drought. In both experiments, initializing the ESP with the reanalysis SWE reduced the seasonal streamflow forecast errors; compared with existing operational statistical forecasts, the peak-annual SWE insertion and the 1 February SWE insertion reduced the overall root-mean-square error of the seasonal streamflow forecasts by 13% and 23%, respectively, over the 13 major rivers draining the Sierra Nevada. The benefits of the reanalysis SWE insertion are more pronounced in areas with greater snow accumulation, while the complex snow and runoff-generation processes in low-elevation areas impede the forecasting skill improvement through SWE reinitialization alone.

Holocene vegetation and climate change recorded in alpine bog sediments from the Borreguiles de la Virgen, Sierra Nevada, southern Spain

2012 ◽  
Vol 77 (1) ◽  
pp. 44-53 ◽  
Author(s):  
Gonzalo Jiménez-Moreno ◽  
R. Scott Anderson
Keyword(s):  
Climate Change ◽  
Magnetic Susceptibility ◽  
High Resolution ◽  
Sierra Nevada ◽  
High Elevation ◽  
High Impact ◽  
Southern Spain ◽  
Pollen Record ◽  
Arboreal Pollen ◽  
Vegetation And Climate

High-resolution pollen and magnetic susceptibility (MS) analyses have been carried out on a sediment core taken from a high-elevation alpine bog area located in Sierra Nevada, southern Spain. The earliest part of the record, from 8200 to about 7000 cal yr BP, is characterized by the highest abundance of arboreal pollen andPediastrum, indicating the warmest and wettest conditions in the area at that time. The pollen record shows a progressive aridification since 7000 cal yr BP that occurred in two steps, first shown by a decrease inPinus, replaced by Poaceae from 7000 to 4600 cal yr BP and then by Cyperaceae,Artemisiaand Amaranthaceae from 4600 to 1200 cal yr BP.Pediastrumalso decreased progressively and totally disappeared at ca. 3000 yr ago. The progressive aridification is punctuated by periodically enhanced drought at ca. 6500, 5200 and 4000 cal yr BP that coincide in timing and duration with well-known dry events in the Mediterranean and other areas. Since 1200 cal yr BP, several changes are observed in the vegetation that probably indicate the high-impact of humans in the Sierra Nevada, with pasturing leading to nutrient enrichment and eutrophication of the bog,Pinusreforestation andOleacultivation at lower elevations.

scholarly journals Fuel dynamics and reburn severity following high-severity fire in a Sierra Nevada, USA, mixed-conifer forest

Fire Ecology ◽  
2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Jamie M. Lydersen ◽  
Brandon M. Collins ◽  
Michelle Coppoletta ◽  
Melissa R. Jaffe ◽  
Hudson Northrop ◽  
...  
Keyword(s):  
High Resolution ◽  
Sierra Nevada ◽  
Dead Wood ◽  
Fire Severity ◽  
Additive Models ◽  
Fuel Load ◽  
Shrub Cover ◽  
High Severity ◽  
Space And Time ◽  
Fuel Dynamics

Abstract Background High-severity fire in forested landscapes often produces a post-fire condition of high shrub cover and large loads of dead wood. Given the increasing patch size of high-severity fire and the tendency for these areas to reburn at high severity in subsequent wildfires, post-fire management often targets restoration of these areas. However, these areas are challenging to manage, in part due to limited knowledge of post-fire fuel dynamics over space and time and uncertainties in how specific fuel components such as snags and logs influence future fire severity. In this study, we used high-resolution aerial imagery collected nine years after a wildfire to measure snags, logs, and shrub cover within high-severity patches, and to assess how fuel development influenced reburn severity in a subsequent wildfire. Results The abundance of snags, logs, and shrubs following high-severity fire varied with elevation and slope steepness; however, generalized additive models explained only 6 to 21% of their variation over the post-fire landscape. High densities of both snags and logs were associated with high reburn severity in a subsequent fire, while shrub cover had a marginally insignificant (P = 0.0515) effect on subsequent fire severity. Conclusions Our results demonstrate that high levels of large dead wood, which is often not considered in fire behavior modeling, corresponded with repeated high-severity fire effects. Future research should leverage the increasing availability of high-resolution imagery to improve our understanding of fuel load patterns in space and time and how they may impact landscape resilience to facilitate management planning for post-fire forest landscapes.

scholarly journals Two decades of distributed global radiation time series across a mountainous semiarid area (Sierra Nevada, Spain)

2020 ◽  
Author(s):  
Cristina Aguilar ◽  
Rafael Pimentel ◽  
María J. Polo
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Sierra Nevada ◽  
Global Radiation ◽  
Mountainous Area ◽  
Mountain Range ◽  
Wet Season ◽  
Extreme Statistics ◽  
Variation Characteristics ◽  
Weather Stations

Abstract. The main drawback of the reconstruction of high resolution distributed global radiation (Rg) time series in mountainous semiarid environments is the common lack of station-based solar radiation registers. This work presents nineteen years (2000–2018) of high spatial resolution (30 m × 30 m) monthly and annual global radiation maps derived using the model proposed by Aguilar et al. (2010), driven by in situ daily global radiation measurements, from sixteen weather stations with historical records in the area, and a high resolution digital elevation model in a mountainous area in southern Europe: Sierra Nevada (SN) Mountain Range (Spain). The applicability of the modeling scheme was validated against daily global radiation registers at the weather stations with mean RMSE values of 2.63 MJ m−2 day−1 and best estimations on clear-sky days. Filled daily Rg at weather stations revealed quite stable minimum daily Rg values and greater variations in the maximum daily Rg, but no clear trends with altitude in any of the statistics unlike the analysis at the monthly and annual scale when there is an increase in the high extreme statistics with the altitude of the weather station, especially above 1500 m a.s.l. Monthly distributed Rg time series showed significant spatial differences of up to 200 MJ m−2 month−1 that clearly followed the terrain configuration. July and December were clearly the months with the highest and lowest values of Rg received and the highest dispersion in the monthly Rg values was found in the spring and fall months. The great heterogeneity found in the monthly distribution of Rg along the study period (2000–2018), especially at the wet season, finally determined the inter annual differences of up to 800 MJ m−2 year−1 in the incoming global radiation in SN. The time series of the surface global radiation datasets here provided can be used to analyze trends, inter-annual and seasonal variation characteristics of the global radiation received in SN with high spatial detail (30 m). Datasets are available at https://doi.pangaea.de/10.1594/PANGAEA.921012 (Aguilar et al., 2020).

scholarly journals An Improved Method for Extracting, Sorting, and AMS Dating of Pollen Concentrates From Lake Sediment

2021 ◽  
Vol 9 ◽  
Author(s):  
Irene Tunno ◽  
Susan R. H. Zimmerman ◽  
Thomas A. Brown ◽  
Christiane A. Hassel
Keyword(s):  
High Resolution ◽  
Sierra Nevada ◽  
Lake Sediment ◽  
Sediment Cores ◽  
Pollen Grains ◽  
Complete Separation ◽  
Improved Method ◽  
Surface Samples ◽  
Common Technique ◽  
Ams Dating

High-resolution chronologies are crucial for paleoenvironmental reconstructions, and are particularly challenging for lacustrine records of terrestrial paleoclimate. Accelerator Mass Spectrometry (AMS) radiocarbon measurement of terrestrial macrofossils is the most common technique for building age models for lake sediment cores, but relies on the presence of terrestrial macrofossils in sediments. In the absence of sufficient macrofossils, pollen concentrates represent a valuable source of dates for building high-resolution chronologies. However, pollen isolation and dating may present several challenges, as has been reported by different authors in previous work over the last few decades. Here we present an improved method for extracting, purifying and radiocarbon-dating pollen concentrates using flow cytometry to improve the extraction efficiency and the purity of the pollen concentrates. Overall, the nature of the sediments and the abundance of the pollen represent major considerations in obtaining enough pollen grains and, consequently, enough carbon to be dated. Further, the complete separation of pollen from other forms of organic matter is required to ensure the accuracy of the dates. We apply the method to surface samples and sediment cores recovered from two contrasting lake basins on the eastern side of the Sierra Nevada (California), and describe the variations that may be used to optimize pollen preparation from a variety of sediments.

scholarly journals Characterization of submicron particles influenced by mixed biogenic and anthropogenic emissions using high-resolution aerosol mass spectrometry: results from CARES

2012 ◽  
Vol 12 (17) ◽  
pp. 8131-8156 ◽  
Author(s):  
A. Setyan ◽  
Q. Zhang ◽  
M. Merkel ◽  
W. B. Knighton ◽  
Y. Sun ◽  
...  
Keyword(s):  
High Resolution ◽  
Sierra Nevada ◽  
Oxidation Products ◽  
Biogenic Emissions ◽  
Anthropogenic Emissions ◽  
Mass Loading ◽  
Large Variability ◽  
Air Masses ◽  
Aerosol Mass ◽  
Urban Plumes

Abstract. An Aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed during the Carbonaceous Aerosols and Radiative Effects Study (CARES) that took place in northern California in June 2010. We present results obtained at Cool (denoted as the T1 site of the project) in the foothills of the Sierra Nevada Mountains, where intense biogenic emissions are periodically mixed with urban outflow transported by daytime southwesterly winds from the Sacramento metropolitan area. During this study, the average mass loading of submicrometer particles (PM1) was 3.0 μg m−3, dominated by organics (80%) and sulfate (9.9%). The organic aerosol (OA) had a nominal formula of C1H1.38N0.004OM0.44, thus an average organic mass-to-carbon (OM/OC) ratio of 1.70. Two distinct oxygenated OA factors were identified via Positive matrix factorization (PMF) of the high-resolution mass spectra of organics. The more oxidized MO-OOA (O/C = 0.54) was interpreted as a surrogate for secondary OA (SOA) influenced by biogenic emissions whereas the less oxidized LO-OOA (O/C = 0.42) was found to represent SOA formed in photochemically processed urban emissions. LO-OOA correlated strongly with ozone and MO-OOA correlated well with two 1st generation isoprene oxidation products (methacrolein and methyl vinyl ketone), indicating that both SOAs were relatively fresh. A hydrocarbon like OA (HOA) factor was also identified, representing primary emissions mainly due to local traffic. On average, SOA (= MO-OOA + LO-OOA) accounted for 91% of the total OA mass and 72% of the PM1 mass observed at Cool. Twenty three periods of urban plumes from T0 (Sacramento) to T1 (Cool) were identified using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). The average PM1 mass loading was considerably higher in urban plumes than in air masses dominated by biogenic SOA. The change in OA mass relative to CO (ΔOA/ΔCO) varied in the range of 5-196 μg m−3 ppm−1, reflecting large variability in SOA production. The highest ΔOA/ΔCO was reached when air masses were dominated by anthropogenic emissions in the presence of a high concentration of biogenic volatile organic compounds (BVOCs). This ratio, which was 97 μg m−3 ppm−1 on average, was much higher than when urban plumes arrived in a low BVOC environment (~36 μg m−3 ppm−1) or during other periods dominated by biogenic SOA (35 μg m−3 ppm−1). These results demonstrate that SOA formation is enhanced when anthropogenic emissions interact with biogenic precursors.

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