The Impacts of California’s San Francisco Bay Area Gap on Precipitation Observed in the Sierra Nevada during HMT and CalWater

2015 ◽  
Vol 16 (3) ◽  
pp. 1048-1069 ◽  
Author(s):  
Allen B. White ◽  
Paul J. Neiman ◽  
Jessie M. Creamean ◽  
Timothy Coleman ◽  
F. Martin Ralph ◽  
...  
Keyword(s):  
San Francisco ◽  
Sierra Nevada ◽  
Winter Season ◽  
Water Vapor Transport ◽  
Atmospheric Rivers ◽  
Northern Site ◽  
Bay Area ◽  
Orographic Rainfall ◽  
Sierra Nevada Foothills ◽  
Southern Site

Abstract Atmospheric rivers (ARs) are narrow regions of enhanced water vapor transport, usually found on the warm-sector side of the polar cold front in many midlatitude storms formed primarily over the oceans. Nonbrightband (NBB) rain is a shallow orographic rainfall process driven by collision and coalescence that has been observed in some of these storms. NBB rain accounts for about one-third, on average, of the total winter season rainfall occurring at a coastal mountain site in Northern California. During the California Energy Commission’s CalWater project, nearly the same fraction of NBB rain was observed at a northern Sierra Nevada foothills site as compared to the coastal mountains, whereas less than half of the fractional amount of NBB rain was observed at a southern Sierra Nevada foothills site. Both Sierra Nevada sites often experience terrain-induced blocked flow, that is, Sierra barrier jet (SBJ) during landfalling winter storms. However, the northern Sierra Nevada site often is oriented geographically downwind of a gap in the coastal terrain near San Francisco during AR landfall. This gap allows maritime air in the AR to arrive at the northern site and enhance the collision–coalescence process in orographic feeder clouds as compared with the southern site. As a result, a greater amount and intensity of NBB rain and overall precipitation was produced at the northern site. This study uses a variety of observations collected in the coastal and Sierra Nevada ranges from the Hydrometeorology Testbed and CalWater field campaigns to document this behavior. A detailed case study provides additional context on the interaction between AR flow, the SBJ, and precipitation processes.

scholarly journals A 142-Year Climatology of Northern California Landslides and Atmospheric Rivers

2019 ◽  
Vol 100 (8) ◽  
pp. 1499-1509 ◽  
Author(s):  
Jason M. Cordeira ◽  
Jonathan Stock ◽  
Michael D. Dettinger ◽  
Allison M. Young ◽  
Julie F. Kalansky ◽  
...  
Keyword(s):  
Water Vapor ◽  
San Francisco ◽  
San Francisco Bay ◽  
San Francisco Bay Area ◽  
Water Vapor Transport ◽  
Atmospheric Conditions ◽  
Sea Level Pressure ◽  
Winter Storms ◽  
Atmospheric Rivers ◽  
Bay Area

AbstractWe compare a novel dataset of San Francisco Bay Area landslides from 1871 to 2012 to corresponding atmospheric conditions commonly associated with Pacific winter storms and landfalling atmospheric rivers (ARs). Landslides in the San Francisco Bay Area occur primarily during winter months, coinciding with enhanced integrated water vapor transport (IVT) magnitudes ≥250 kg m–1 s–1 at the coast 76% of the time and with landfalling ARs over the near-offshore northeast Pacific 82% of the time. Results illustrate that days, or the first in a series of days, with a landslide (i.e., landslide onset days) typically occur in association with NOAA Twentieth Century Reanalysis–derived IVT magnitudes ≥250 kg m–1 s–1 that persist for ∼20 h and temporal maxima in precipitation rates. Composite analyses of sea level pressure, integrated water vapor, and IVT during 3-month periods during September–May on landslide onset days further illustrate that these events coincide with regions of low pressure to the northwest of California and high pressure to the south, synoptic-scale flow conditions associated with strong onshore flow, and water vapor transports in the form of landfalling ARs.

scholarly journals Hourly Analyses of the Large Storms and Atmospheric Rivers that Provide Most of California’s Precipitation in Only 10 to 100 Hours per Year

2018 ◽  
Vol 16 (4) ◽  
Author(s):  
Maryam Lamjiri ◽  
Michael Dettinger ◽  
F. Martin Ralph ◽  
Nina Oakley ◽  
Jonathan Rutz
Keyword(s):  
San Francisco ◽  
Sierra Nevada ◽  
Southern California ◽  
Extreme Rainfall ◽  
Annual Rainfall ◽  
North Coast ◽  
Northern California ◽  
Rainfall Events ◽  
Atmospheric Rivers ◽  
The North

California is regularly impacted by floods and droughts, primarily as a result of too many or too few atmospheric rivers (ARs). This study analyzes a two-decade-long hourly precipitation dataset from 176 California weather stations and a 3-hourly AR chronology to report variations in rainfall events across California and their association with ARs. On average, 10-40 and 60-120 hours of rainfall in southern and northern California, respectively, are responsible for more than half of annual rainfall accumulations. Approximately 10-30% of annual precipitation at locations across the state is from only one large storm. On average, northern California receives 25-45 rainfall events annually (40-50% of which are AR-related). These events typically have longer durations and higher event-precipitation totals than those in southern California. Northern California also receives more AR landfalls with longer durations and stronger Integrated Vapor Transport (IVT). On average, ARs contribute 79%, 76%, and 68% of extreme-rainfall accumulations (i.e., top 5% events annually) in the north coast, northern Sierra, and Transverse Ranges of southern California, respectively. The San Francisco Bay Area terrain gap in the California Coast Range allows more AR water vapor to reach inland over the Delta and Sacramento Valley, and thus, influences precipitation in the Delta’s catchment. This is particularly important for extreme precipitation in the northern Sierra Nevada, including river basins above Oroville Dam and Shasta Dam. This study highlights differences between rainfall and AR characteristics in coastal versus inland northern California, differences that largely determine the regional geography of flood risks and water-reliability. These analyses support water resource, flood, levee, wetland, and ecosystem management within the catchment of the San Francisco estuary system by describing regional characteristics of ARs and their influence on rainfall on an hourly timescale.

Philip Tyson's 1849 study of California gold prospects

2017 ◽  
Vol 36 (1) ◽  
pp. 30-40
Author(s):  
K. R. Aalto
Keyword(s):  
San Francisco ◽  
Sierra Nevada ◽  
Cross Sections ◽  
Coast Range ◽  
Central California ◽  
Franciscan Complex ◽  
General Geology ◽  
Basement Rocks ◽  
Sierra Nevada Foothills ◽  
Fluvial Sedimentation

Philip Thomas Tyson (1799–1877) toured privately through central California, from San Francisco through the Sierra Nevada foothills gold prospects in 1849, to assess their potential and the general geology of the region. He produced the first regional map with geologic notations and several rough topographic/geologic cross-sections. He described Coast Range basement rocks, now described as Franciscan Complex mélange and broken formation, the stratigraphic configuration of the Great Valley, and general geology of the Sierra Nevada foothills. He recognized that the older Coast Range and Sierran basement were deformed prior to recent volcanism and extensive terrestrial fluvial sedimentation, likely Neogene in age.

Sierra Barrier Jets, Atmospheric Rivers, and Precipitation Characteristics in Northern California: A Composite Perspective Based on a Network of Wind Profilers

2013 ◽  
Vol 141 (12) ◽  
pp. 4211-4233 ◽  
Author(s):  
Paul J. Neiman ◽  
Mimi Hughes ◽  
Benjamin J. Moore ◽  
F. Martin Ralph ◽  
Ellen M. Sukovich
Keyword(s):  
San Francisco ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Atmospheric Rivers ◽  
The North ◽  
Windward Slope ◽  
Barrier Jets ◽  
Sierra Foothills ◽  
North End ◽  
Wind Profilers

Abstract Five 915-MHz wind profilers and GPS receivers across California's northern Central Valley (CV) and adjacent Sierra foothills and coastal zone, in tandem with a 6-km-resolution gridded reanalysis dataset generated from the Weather Research and Forecasting Model, document key spatiotemporal characteristics of Sierra barrier jets (SBJs), landfalling atmospheric rivers (ARs), and their interactions. Composite kinematic and thermodynamic analyses are based on the 13 strongest SBJ cases observed by the Sloughhouse profiler between 2009 and 2011. The analyses show shallow, cool, south-southeasterly (i.e., Sierra parallel) flow and associated water vapor transport strengthening with time early in the 24-h compositing period, culminating in an SBJ core at <1 km above ground over the eastern CV. The SBJ core increases in altitude up the Sierra's windward slope and poleward toward the north end of the CV, but it does not reach the westernmost CV. Above the developing SBJ, strengthening southwesterly flow descends temporally in response to the landfalling AR. The moistening SBJ reaches maximum intensity during the strongest AR flow aloft, at which time the core of the AR-parallel vapor transport slopes over the SBJ. The inland penetration of the AR through the San Francisco Bay gap in the coastal mountains contributes to SBJ moistening and deepening. The SBJ subsequently weakens with the initial cold-frontal period aloft, during which the shallow flow shifts to southwesterly and the heaviest precipitation falls in the Sierra foothills. An orographic precipitation analysis quantitatively links the Sierra-perpendicular (nearly AR parallel) vapor fluxes to enhanced precipitation along the Sierra's windward slope and the SBJ-parallel fluxes to heavy precipitation at the north end of the CV.

scholarly journals Regional-scale correlations of accreted units in the Franciscan Complex, California, USA: A record of long-lived, episodic subduction accretion

2021 ◽  
Author(s):  
Francisco E. Apen ◽  
John Wakabayashi ◽  
Howard W. Day ◽  
Sarah M. Roeske ◽  
A. Kate Souders ◽  
...  
Keyword(s):  
San Francisco ◽  
Sierra Nevada ◽  
Detrital Zircon ◽  
Regional Scale ◽  
Northern Coast ◽  
Accretionary Complex ◽  
Central California ◽  
Franciscan Complex ◽  
Bay Area ◽  
History Of

ABSTRACT The Franciscan Complex of California, the type example of an exhumed accretionary complex, records a protracted history of voluminous subduction accretion along the western margin of North America. Recent geochronological work has improved our knowledge of the timing of accretion, but the details of the accretionary history are disputed, in part, due to uncertainties in regional-scale correlations of different units. We present new detrital zircon U-Pb ages from two sites on opposite sides of San Francisco Bay in central California that confirm previously proposed correlations. Both sites are characterized by a structurally higher blueschist-facies unit (Angel Island unit) underlain by a prehnite-pumpellyite-facies unit (Alcatraz unit). The Angel Island unit yields maximum depositional ages (MDAs) ranging from 112 ± 1 Ma to 114 ± 1 Ma (±2σ), and the Alcatraz unit yields MDAs between 94 ± 2 Ma and 99 ± 1 Ma. Restoration of post-subduction dextral displacement suggests these sites were originally 44–78 km apart and much closer to other Franciscan units that are now exposed farther south in the Diablo Range. Comparison with detrital zircon dates from the Diablo Range supports correlations of the Bay Area units with certain units in the Diablo Range. In contrast, correlations with Franciscan units in the northern Coast Ranges of California are not robust: some units are clearly older than those in the Bay Area whereas others exhibit distinct differences in provenance. Integration of age data from throughout the Franciscan Complex indicates long-lived and episodic accretion from the Early Cretaceous to Paleogene. Although minor, sporadic accretion began earlier, significant accretion occurred during the interval 123–80 Ma and was followed by minor accretion at ca. 53–49 Ma. Periods of accretion and nonaccretion were associated with arc magmatism in the Sierra Nevada–Klamath region, cessation of arc activity, and reorganization of paleodrainage systems, which implicates plate dynamics and sediment availability as major controls on the development of the Franciscan Complex.

scholarly journals A Surface Observation Based Climatology of Diablo-LikeWinds in California’s Wine Country and Western Sierra Nevada

Fire ◽  
2018 ◽  
Vol 1 (2) ◽  
pp. 25 ◽  
Author(s):  
Craig Smith ◽  
Benjamin Hatchett ◽  
Michael Kaplan
Keyword(s):  
San Francisco ◽  
Sierra Nevada ◽  
San Francisco Bay ◽  
San Francisco Bay Area ◽  
Early Morning ◽  
Northern California ◽  
Gust Factor ◽  
Wind Speeds ◽  
Bay Area ◽  
Area North

Diablo winds are dry and gusty north-northeasterly downslope windstorms that affect the San Francisco Bay Area in Northern California. On the evening of 8 October 2017, Diablo winds contributed to the ignitions and rapid spread of the “Northern California firestorm”, including the Tubbs Fire, which burned 2800 homes in Santa Rosa, resulting in 22 fatalities and $1.2 B USD in damages. We analyzed 18 years of data from a network of surface meteorological stations and showed that Diablo winds tend to occur overnight through early morning in fall, winter and spring. In addition to the area north of the San Francisco Bay Area, conditions similar to Diablo winds commonly occur in the western Sierra Nevada. Both of these areas are characterized by high wind speeds and low relative humidity, but they neither tend to be warmer than climatology nor have a higher gust factor, or ratio of wind gusts to mean wind speeds, than climatology.

scholarly journals Characteristics of Diablo-like Wind conditions in Northern California Based on a Climatology from Surface Observations

2018 ◽  
Author(s):  
Craig Smith ◽  
Benjamin Hatchett ◽  
Michael Kaplan
Keyword(s):  
San Francisco ◽  
Sierra Nevada ◽  
Early Morning ◽  
Northern California ◽  
Gust Factor ◽  
Wind Speeds ◽  
Bay Area ◽  
Sierra Nevada Mountains ◽  
Rapid Spread ◽  
Area North

Diablo winds are dry and gusty north-northeasterly downslope windstorms that affect the Northern California. On the evening of October 8, 2017, Diablo winds contributed to the ignitions and rapid spread of the “Northern California Firestorm”, including the Tubbs Fire, which burned 2,800 homes in Santa Rosa, resulted in 22 fatalities and $1.2B USD in damages. We analyzed 18 years of data from a network of surface meteorological stations and show that Diablo winds tend to occur overnight through early morning in Fall, Winter and Spring. Conditions similar to Diablo winds occur commonly in the Sierra Nevada Mountains in addition to the area North of the San Francisco Bay Area including the Northern Coastal Ranges. Diablo winds are characterized by high wind speeds and low relative humidity, but they tend to neither be warmer than climatology nor do they have a higher gust factor, or ratio of wind gusts to mean wind speeds, than climatology.

scholarly journals Remains of the 19th Century: Deep storage of contaminated hydraulic mining sediment along the Lower Yuba River, California

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Tyler K. Nakamura ◽  
Michael Bliss Singer ◽  
Emmanuel J. Gabet
Keyword(s):  
19Th Century ◽  
San Francisco ◽  
Sierra Nevada ◽  
Gold Mining ◽  
Environmental Damage ◽  
Ecological Problem ◽  
Hydraulic Mining ◽  
Sierra Nevada Foothills ◽  
The 19Th Century ◽  
And Storage

Since the onset of hydraulic gold mining in California’s Sierra Nevada foothills in 1852, the environmental damage caused by displacement and storage of hydraulic mining sediment (HMS) has been a significant ecological problem downstream. Large volumes of mercury-laden HMS from the Yuba River watershed were deposited within the river corridor, creating the anthropogenic Yuba Fan. However, there are outstanding uncertainties about how much HMS is still contained within this fan. To quantify the deep storage of HMS in the Yuba Fan, we analyzed mercury concentrations of sediment samples collected from borings and outcrops at multiple depths. The mercury concentrations served as chemostratigraphic markers to identify the contacts between the HMS and underlying pre-mining deposits. The HMS had mercury concentrations at least ten-fold higher than pre-mining deposits. Analysis of the lower Yuba Fan’s volume suggests that approximately 8.1 × 107 m3 of HMS was deposited within the study area between 1852 and 1999, representing ~32% of the original Yuba Fan delivered by 19th Century hydraulic gold mining. Our estimate of the mercury mass contained within this region is 6.7 × 103 kg, which is several orders of magnitude smaller than what was estimated to have been lost to the mining process. We suggest that this discrepancy is likely due to a combination of missing (yet to be found) mercury masses stored upstream, overestimated losses during mining, and high delivery of mercury to the lowland Sacramento Valley and to the San Francisco Bay-Delta system, where it poses a great risk to sensitive ecosystems.

A Qualitative Study of Ecstasy Sellers in the San Francisco Bay Area

2004 ◽  
Author(s):  
Sheigla Murphy ◽  
Paloma Sales ◽  
Micheline Duterte ◽  
Camille Jacinto
Keyword(s):  
Qualitative Study ◽  
San Francisco ◽  
San Francisco Bay ◽  
San Francisco Bay Area ◽  
Bay Area

Transportation and the Environment

2017 ◽  
Vol 94 (3) ◽  
pp. 37-61
Author(s):  
Douglas R. Littlefield
Keyword(s):  
Nineteenth Century ◽  
San Francisco ◽  
Sierra Nevada ◽  
Mississippi River ◽  
San Joaquin Valley ◽  
Eastern United States ◽  
Major Health ◽  
San Joaquin River ◽  
Natural Wetlands ◽  
Prevailing View

Some histories of California describe nineteenth-century efforts to reclaim the extensive swamplands and shallow lakes in the southern part of California's San Joaquin Valley – then the largest natural wetlands habitat west of the Mississippi River – as a herculean venture to tame a boggy wilderness and turn the region into an agricultural paradise. Yet an 1850s proposition for draining those marshes and lakes primarily was a scheme to improve the state's transportation. Swampland reclamation was a secondary goal. Transport around the time of statehood in 1850 was severely lacking in California. Only a handful of steamboats plied a few of the state's larger rivers, and compared to the eastern United States, roads and railroads were nearly non-existent. Few of these modes of transportation reached into the isolated San Joaquin Valley. As a result, in 1857 the California legislature granted an exclusive franchise to the Tulare Canal and Land Company (sometimes known as the Montgomery franchise, after two of the firm's founders). The company's purpose was to connect navigable canals from the southern San Joaquin Valley to the San Joaquin River, which entered from the Sierra Nevada about half way up the valley. That stream, in turn, joined with San Francisco Bay, and thus the canals would open the entire San Joaquin Valley to world-wide commerce. In exchange for building the canals, the Montgomery franchise could collect tolls for twenty years and sell half the drained swamplands (the other half was to be sold by the state). Land sales were contingent upon the Montgomery franchise reclaiming the marshes. Wetlands in the mid-nineteenth century were not viewed as they are today as fragile wildlife habitats but instead as impediments to advancing American ideals and homesteads across the continent. Moreover, marshy areas were seen as major health menaces, with the prevailing view being that swampy regions’ air carried infectious diseases.

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