Winter Storm Conditions Leading to Excessive Runoff above California’s Oroville Dam during January and February 2017

2019 ◽  
Vol 100 (1) ◽  
pp. 55-70 ◽  
Author(s):  
Allen B. White ◽  
Benjamin J. Moore ◽  
Daniel J. Gottas ◽  
Paul J. Neiman
Keyword(s):  
Sierra Nevada ◽  
Debris Flows ◽  
Heavy Rain ◽  
Heavy Precipitation ◽  
Western Slope ◽  
Winter Storm ◽  
Atmospheric Rivers ◽  
Orographic Forcing ◽  
First Time ◽  
Precipitation Events

AbstractDuring winter 2016/17, California experienced numerous heavy precipitation events linked to land-falling atmospheric rivers (ARs) that filled reservoirs and ended a severe, multiyear drought. These events also caused floods, mudslides, and debris flows, resulting in major socioeconomic disruptions. During 2–11 February 2017, persistent heavy precipitation in the northern Sierra Nevada culminated in a rapid increase in the water level on Lake Oroville, necessitating the activation of an emergency spillway for the first time since the Oroville Dam was installed and forcing the evacuation of 188,000 people. The precipitation, which mostly fell as rain due to elevated freezing levels, was focused on the western slope of the Sierra Nevada in connection with orographic forcing linked to two successive ARs. Heavy rain fell on saturated soils and a snowpack produced by antecedent storms and thereby resulted in excessive runoff into Lake Oroville that led to a damaged spillway and complicated reservoir operations.

scholarly journals The effect of atmospheric rivers on cold-season heavy precipitation events in Iran

2020 ◽  
Author(s):  
Neda Esfandiari ◽  
Hassan Lashkari
Keyword(s):  
Extreme Events ◽  
Heavy Precipitation ◽  
Cold Season ◽  
Western Slope ◽  
Arid Areas ◽  
Gulf Of Aden ◽  
Zagros Mountains ◽  
Atmospheric Rivers ◽  
Semi Arid ◽  
Precipitation Events

Abstract Atmospheric rivers (ARs) as massive and concentrated water vapour paths can have a critical impact on extreme events in arid and semi-arid areas. This study investigated the effect of ARs on heavy precipitation events during the cold, rainy months (November–April) in Iran for 11 years. The results showed that 107 ARs had an influence on heavy precipitation, which providing partial moisture for Iran's precipitation. On average, 11 heavy precipitation days were linked to the presence of ARs in the six cold months of each year. During the study period, ARs accounted for almost 20–50% of the country's total heavy precipitation monthly. Although most ARs entered the country from the south through coastal areas, the western part of Iran, especially elevated stations along the western slope of the Zagros Mountains, received the highest heavy precipitation. Accordingly, about 66% of ARs directly originated from the Red Sea and the Gulf of Aden. Moreover, December experienced the highest frequency of ARs linked to heavy precipitation during the statistical period.

scholarly journals Earthquake-induced debris flows at Popocatépetl Volcano, Mexico

2020 ◽  
Author(s):  
Velio Coviello ◽  
Lucia Capra ◽  
Gianluca Norini ◽  
Norma Dávila ◽  
Dolores Ferrés ◽  
...  
Keyword(s):  
Debris Flows ◽  
Horizontal Stress ◽  
Structural Features ◽  
Volcanic Edifice ◽  
Western Slope ◽  
Slope Failures ◽  
Ground Shaking ◽  
Seismic Records ◽  
Maximum Horizontal Stress ◽  
First Time

Abstract. The M7.1 Puebla-Morelos earthquake that occurred on 19 September 2017, with epicenter located ∼ 70 km SW from Popocatépetl volcano, severely hit central Mexico. Seismic shaking of the volcanic edifice induced by the earthquake triggered hundreds of shallow landslides on the volcanic flanks, remobilizing loose pyroclastic deposits and saturated soils. The largest landslides occurred on the slopes of aligned ENE-WSW-trending ravines on opposite sides of the volcanic cone, roughly parallel to the regional maximum horizontal stress and local volcanotectonic structural features. This configuration may suggest transient reactivation of local faults and extensional fractures as one of the mechanisms that has weakened the volcanic edifice and promoted the largest slope failures. The seismic records from a broadband station located at few kilometers from the main landslides are used to infer the intensity of ground shaking that triggered the slope failures. The material involved in the larger landslides, mainly ash and pumice fall deposits from late Holocene eruptions with a total volume of about 106 cubic meters, transformed into two large debris flows on the western slope of the volcano and one on its eastern side. The debris flows were highly viscous and contained abundant large woods (about 105 cubic meter). Their peculiar rheology is reconstructed by field evidences and analyzing the grain size distribution of samples from both landslide scars and deposits. This is the first time that such flows were observed at this volcano. Our work provides new insights to constrain a multi-hazard risk assessment for Popocatépetl and other continental active volcanoes.

scholarly journals Snow Level Characteristics and Impacts of a Spring Typhoon-originating Atmospheric River in the Sierra Nevada, USA

2018 ◽  
Author(s):  
Benjamin Hatchett
Keyword(s):  
Sierra Nevada ◽  
Debris Flows ◽  
Heavy Precipitation ◽  
Extratropical Cyclone ◽  
Snow Avalanches ◽  
Northeast Pacific ◽  
Atmospheric River ◽  
Super Typhoon ◽  
Wet Snow

On 5-7 April 2018 a landfalling atmospheric river resulted in widespread heavy precipitation in the Sierra Nevada of California and Nevada. Observed snow levels during this event were among the highest snow levels recorded since observations began in 2002 and exceeded 2.75 km for 31 hours in the northern Sierra Nevada and 3.75 km for 12 hours in the southern Sierra Nevada. The anomalously high snow levels and over 80 mm of precipitation caused flooding, debris flows, and wet snow avalanches in the upper elevations of the Sierra Nevada. The origin of this atmospheric river was super typhoon Jelawat, whose moisture remnants were entrained and maintained by an extratropical cyclone in the northeast Pacific. This event was notable due to its April occurrence, as six other typhoon remnants that caused heavy precipitation with high snow levels (mean = 2.92 km) in the northern Sierra Nevada all occurred during October.

scholarly journals Improving WSR-88D Radar QPE for Orographic Precipitation Using Profiler Observations

2014 ◽  
Vol 15 (3) ◽  
pp. 1135-1151 ◽  
Author(s):  
Youcun Qi ◽  
Jian Zhang ◽  
Brian Kaney ◽  
Carrie Langston ◽  
Kenneth Howard
Keyword(s):  
Sierra Nevada ◽  
West Coast ◽  
Heavy Rain ◽  
Moisture Flux ◽  
Heavy Precipitation ◽  
The United States ◽  
The West ◽  
Radar Beam ◽  
Orographic Enhancement ◽  
Coast Region

Abstract Quantitative precipitation estimation (QPE) in the West Coast region of the United States has been a big challenge for Weather Surveillance Radar-1988 Doppler (WSR-88D) because of severe blockages caused by the complex terrain. The majority of the heavy precipitation in the West Coast region is associated with strong moisture flux from the Pacific that interacts with the coastal mountains. Such orographic enhancement of precipitation occurs at low levels and cannot be observed well by WSR-88D because of severe blockages. Specifically, the radar beam either samples too high above the ground or misses the orographic enhancement at lower levels, or the beam broadens with range and cannot adequately resolve vertical variations of the reflectivity structure. The current study developed an algorithm that uses S-band Precipitation Profiler (S-PROF) radar observations in northern California to improve WSR-88D QPEs in the area. The profiler data are used to calculate two sets of reference vertical profiles of reflectivity (RVPRs), one for the coastal mountains and another for the Sierra Nevada. The RVPRs are then used to correct the WSR-88D QPEs in the corresponding areas. The S-PROF–based VPR correction methodology (S-PROF-VPR) has taken into account orographic processes and radar beam broadenings with range. It is tested using three heavy rain events and is found to provide significant improvements over the operational radar QPE.

scholarly journals Moisture Pathways into the U.S. Intermountain West Associated with Heavy Winter Precipitation Events*

2015 ◽  
Vol 16 (3) ◽  
pp. 1184-1206 ◽  
Author(s):  
Michael A. Alexander ◽  
James D. Scott ◽  
Dustin Swales ◽  
Mimi Hughes ◽  
Kelly Mahoney ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Heavy Precipitation ◽  
Empirical Orthogonal Functions ◽  
Water Vapor Transport ◽  
Intermountain West ◽  
Orthogonal Functions ◽  
Back Trajectories ◽  
Synoptic Conditions ◽  
The U.S ◽  
Precipitation Events

Abstract Two methods were used to identify the paths of moisture transport that reach the U.S. Intermountain West (IMW) during heavy precipitation events in winter. In the first, the top 150 precipitation events at stations located within six regions in the IMW were identified, and then back trajectories were initiated at 6-h intervals on those days at the four Climate Forecast System Reanalysis grid points nearest the stations. The second method identified the leading patterns of integrated water vapor transport (IVT) using the three leading empirical orthogonal functions of IVT over land that were first normalized by the local standard deviation. The top 1% of the associated 6-hourly time series was used to construct composites of IVT, atmospheric circulation, and precipitation. The results from both methods indicate that moisture originating from the Pacific that leads to extreme precipitation in the IMW during winter takes distinct pathways and is influenced by gaps in the Cascades (Oregon–Washington), the Sierra Nevada (California), and Peninsular Ranges (from Southern California through Baja California). The moisture transported along these routes appears to be the primary source for heavy precipitation for the mountain ranges in the IMW. The synoptic conditions associated with the dominant IVT patterns include a trough–ridge couplet at 500 hPa, with the trough located northwest of the ridge where the associated circulation funnels moisture from the west-southwest through the mountain gaps and into the IMW.

scholarly journals Winter Orographic Precipitation Ratios in the Sierra Nevada—Large-Scale Atmospheric Circulations and Hydrologic Consequences

2004 ◽  
Vol 5 (6) ◽  
pp. 1102-1116 ◽  
Author(s):  
Michael Dettinger ◽  
Kelly Redmond ◽  
Daniel Cayan
Keyword(s):  
Sierra Nevada ◽  
Large Scale ◽  
Precipitation Amount ◽  
Heavy Precipitation ◽  
Winter Precipitation ◽  
Orographic Precipitation ◽  
Simple Experiment ◽  
Westerly Direction ◽  
Winter Flood ◽  
Precipitation Events

Abstract The extent to which winter precipitation is orographically enhanced within the Sierra Nevada of California varies from storm to storm, and season to season, from occasions when precipitation rates at low and high altitudes are almost the same to instances when precipitation rates at middle elevations (considered here) can be as much as 30 times more than at the base of the range. Analyses of large-scale conditions associated with orographic precipitation variations during storms and seasons from 1954 to 1999 show that strongly orographic storms most commonly have winds that transport water vapor across the range from a more nearly westerly direction than during less orographic storms and than during the largest overall storms, and generally the strongly orographic storms are less convectively stable. Strongly orographic conditions often follow heavy precipitation events because both of these wind conditions are present in midlatitude cyclones that form the cores of many Sierra Nevada storms. Storms during La Niña winters tend to yield larger orographic ratios (ORs) than do those during El Niños. A simple experiment with a model of streamflows from a river basin draining the central Sierra Nevada indicates that, for a fixed overall basin-precipitation amount, a decrease in OR contributes to larger winter flood peaks and smaller springtime flows, and thus to an overall hastening of the runoff season.

scholarly journals RADAR CHARACTERISTICS OF CLOUD SYSTEMS DURING HEAVY RAIN EVENTS

2020 ◽  
pp. 113-124
Author(s):  
Sergey V. Kostarev ◽  
◽  
Andrey L. Vetrov ◽  
Bogdan A. Sivkov ◽  
Anna A. Pomortseva ◽  
...  
Keyword(s):  
Heavy Rain ◽  
Heavy Precipitation ◽  
Maximum Height ◽  
Doppler Weather Radar ◽  
Statistical Features ◽  
Cloud Systems ◽  
Geometrical Features ◽  
Radar Echo ◽  
Rain Events ◽  
Precipitation Events

The paper analyzes radar characteristics of mesoscale precipitation systems associated with heavy precipitation in Western Urals. The characteristics under study, obtained from the Doppler weather radar, include the maximum height of the radar echo of clouds and precipitation, meteorological phenomena, speed and direction of the radar echo movement. An attempt was made to classify mesoscale precipitation systems with respect to their horizontal scales and geometrical features as well as precipitation patterns. Statistical features of radar characteristics of cloud systems causing heavy rain were calculated taking into account their classification by horizontal scales. Radar meteorological characteristics were obtained from instruments in the Izhevsk city and Ufa city for the warm period of 2016–2017. The results can be used during nowcasting of heavy precipitation events.

scholarly journals The Role of Moisture Pathways on Snowfall Amount and Distribution in the Payette Mountains of Idaho

2020 ◽  
Vol 148 (5) ◽  
pp. 2033-2048
Author(s):  
Matthew D. Cann ◽  
K. Friedrich
Keyword(s):  
Sierra Nevada ◽  
Central Valley ◽  
Heavy Precipitation ◽  
The United States ◽  
The Other ◽  
Atmospheric Conditions ◽  
Intermountain West ◽  
The Pacific ◽  
Precipitation Events

Abstract The pathways air travels from the Pacific Ocean to the Intermountain West of the United States are important for understanding how air characteristics change and how this translates to the amount and distribution of snowfall. Recent studies have identified the most common moisture pathways in the Intermountain West, especially for heavy precipitation events. However, the role of moisture pathways on snowfall amount and distribution in specific regions remains unclear. Here, we investigate 24 precipitation events in the Payette Mountains of Idaho during January–March 2017 to understand how local atmospheric conditions are tied to three moisture pathways and how it impacts snowfall amount and distribution. During one pathway, southwesterly, moist, tropical air is directed into the Central Valley of California where the air is blocked by the Sierra Nevada, redirected northward and over lower terrain north of Lake Tahoe into the Snake River Plain of Idaho. Other pathways consist of unblocked flows that approach the coast of California from the southwest and then override the northern Sierra Nevada and southern Cascades, and zonal flows approaching the coast of Oregon overriding the Oregon Cascades. Air masses in the Payette Mountains of Idaho associated with Sierra-blocked flow were observed to be warmer, moister, and windier compared to the other moisture pathways. During Sierra-blocked flow, higher snowfall rates, in terms of mean reflectivity, were observed more uniformly distributed throughout the region compared to the other flows, which observed lower snowfall rates that were predominantly collocated with areas of higher terrain. Of the total estimated snowfall captured in this study, 67% was observed during Sierra-blocked flow.

Dynamic Forcing and Mesoscale Variability of Heavy Precipitation Events over the Sierra Nevada Mountains

2008 ◽  
Vol 136 (1) ◽  
pp. 62-77 ◽  
Author(s):  
Heather Dawn Reeves ◽  
Yuh-Lang Lin ◽  
Richard Rotunno
Keyword(s):  
Sierra Nevada ◽  
Heavy Precipitation ◽  
Horizontal Gradient ◽  
First Case ◽  
Northern Half ◽  
Sierra Nevada Mountains ◽  
Dynamic Forcing ◽  
Rain Rates ◽  
Upstream Flow ◽  
Precipitation Events

Abstract The aim of this research is to investigate the causes for an isolated maximum in precipitation that is typically found along the northern half of the Sierra Nevada mountains of California, in the vicinity of Plumas National Forest (PNF), during moderate to heavy precipitation events. Particular attention was paid to the role various mesoscale (i.e., <200 km) terrain features may have played in localizing the precipitation at PNF. Numerical simulations and sensitivity experiments for two cases of heavy precipitation at PNF reveal that the extent to which terrain acts to focus precipitation is case sensitive. In the first case, the upstream flow was characterized by a strong horizontal gradient in wind speed and moisture. This gradient led to differential deflection of airstreams incident to the range and, consequently, localized convergence and enhanced rain rates at PNF. This localized enhancement occurred regardless of whether any terrain variations were present in the simulations or not. The second case was characterized by more a horizontally uniform upstream flow and showed a much stronger sensitivity to terrain variations, in particular, short- and long-wavelength undulations along the leading (west) edge of the Sierra Nevada range. When these undulations were removed, no localized maxima in precipitation occurred.

scholarly journals Detecting Water Vapor Variability during Heavy Precipitation Events in Hong Kong Using the GPS Tomographic Technique

2017 ◽  
Vol 34 (5) ◽  
pp. 1001-1019 ◽  
Author(s):  
Biyan Chen ◽  
Zhizhao Liu ◽  
Wai-Kin Wong ◽  
Wang-Chun Woo
Keyword(s):  
Hong Kong ◽  
Water Vapor ◽  
Heavy Rain ◽  
Heavy Precipitation ◽  
Radiosonde Data ◽  
Weather Forecasts ◽  
Moisture Variation ◽  
Tomographic Technique ◽  
Rain Events ◽  
Precipitation Events

AbstractWater vapor has a strong influence on the evolution of heavy precipitation events due to the huge latent heat associated with the phase change process of water. Accurate monitoring of atmospheric water vapor distribution is thus essential in predicting the severity and life cycle of heavy rain. This paper presents a systematic study on the application of tomographic solutions to investigate water vapor variations during heavy precipitation events. Using global positioning system (GPS) observations, the wet refractivity field was constructed at a temporal resolution of 30 min for three heavy precipitation events occurring in Hong Kong, China, in 2010–14. The zenith wet delay (ZWD) is shown to be a good indicator in observing the water vapor evolution in heavy rain events. The variabilities of water vapor at five altitude layers (<1000, 1000–2000, 2000–3000, 3000–5000, and >5000 m) were examined. It revealed that water vapor above 3000 m has larger fluctuation than that under 3000 m, though it accounts for only 10%–25% of the total amount of water vapor. The relative humidity fields derived from tomographic results revealed moisture variation, accumulation, saturation, and condensation during the heavy rain events. The water vapor variabilities observed by tomography have been validated using European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis and radiosonde data. The results positively demonstrated the potential of using water vapor tomographic technique for detecting and monitoring the evolution of heavy rain events.

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