scholarly journals Internal Bore Evolution Across the Shelf Near Pt. Sal CA interpreted as a Gravity Current

2021 ◽  
Author(s):  
M. S. Spydell ◽  
S. H. Suanda ◽  
D. J. Grimes ◽  
J. Becherer ◽  
J. M. McSweeney ◽  
...  
Keyword(s):  
Internal Wave ◽  
Water Depth ◽  
Arrival Time ◽  
Gravity Current ◽  
Wave Speeds ◽  
Central California ◽  
Linear Internal Wave ◽  
Energy Saturation ◽  
Internal Bore

AbstractOff the central California coast near Pt. Sal, a large amplitude internal bore was observed for 20 h over 10 km cross-shore, or 100 m to 10 m water depth (D), and 30 km alongcoast by remote sensing, 39 in situ moorings, ship surveys, and drifters. The bore is associated with steep isotherm displacements representing a significant fraction of D. Observations were used to estimate bore arrival time tB, thickness h, and bore and non-bore (ambient) temperature difference ΔT, leading to reduced gravity g′. Bore speeds c, estimated from mapped tB, varied from 0.25 m s−1 to 0.1 m s−1 from D = 50 m to D = 10 m. The h varied from 5 to 35 m, generally decreased with D, and varied regionally alongisobath. The bore ΔT varied from 0.75 to 2.15 °C. Bore evolution was interpreted from the perspective of a two-layer gravity current. Gravity current speeds U, estimated from the local bore h and g− compared well to observed bore speeds throughout its cross-shore propagation. Linear internal wave speeds based on various stratification estimates result in larger errors. On average bore thickness h = D/2, with regional variation, suggesting energy saturation. From 50–10 m depths, observed bore speeds compared well to saturated gravity current speeds and energetics that depend only on water depth and shelf-wide mean g′. This suggests that this internal bore is the internal wave analogue to a saturated surfzone surface gravity bore. Alongcoast variations in pre-bore stratification explain variations in bore properties. Near Pt. Sal, bore Doppler shifting by barotropic currents is observed.

scholarly journals Testing the effect of water in crevasses on a physically based calving model

2012 ◽  
Vol 53 (60) ◽  
pp. 90-96 ◽  
Author(s):  
S. Cook ◽  
T. Zwinger ◽  
I.C. Rutt ◽  
S. O'Neel ◽  
T. Murray
Keyword(s):  
Finite Element ◽  
Water Depth ◽  
Surface Mass Balance ◽  
Two Dimensional ◽  
Finite Element Code ◽  
Surface Mass ◽  
Starting Point ◽  
Physically Based ◽  
Calving Rate

AbstractA new implementation of a calving model, using the finite-element code Elmer, is presented and used to investigate the effects of surface water within crevasses on calving rate. For this work, we use a two-dimensional flowline model of Columbia Glacier, Alaska. Using the glacier’s 1993 geometry as a starting point, we apply a crevasse-depth calving criterion, which predicts calving at the location where surface crevasses cross the waterline. Crevasse depth is calculated using the Nye formulation. We find that calving rate in such a regime is highly dependent on the depth of water in surface crevasses, with a change of just a few metres in water depth causing the glacier to change from advancing at a rate of 3.5 kma–1 to retreating at a rate of 1.9 km a–1. These results highlight the potential for atmospheric warming and surface meltwater to trigger glacier retreat, but also the difficulty of modelling calving rates, as crevasse water depth is difficult to determine either by measurement in situ or surface mass-balance modelling.

Modelling of an Internal Wave Gravity Current Using Eulers Equations

2002 ◽  
Author(s):  
Deborah J. Wood
Keyword(s):  
Internal Wave ◽  
Wave Speed ◽  
Gravity Current ◽  
Laboratory Scale ◽  
Navier Stokes ◽  
Linear Wave ◽  
Field Observations ◽  
Medium Density ◽  
Sloping Bottom

In nature where thermoclines exist an internal wave may form, and if a sloping bottom is also present then a gravity current may occur. In this study we use a Navier-Stokes solver to solve Eulers equations to simulate the generation and evolution of such a wave. The thermoclines used in this study are similar to those seen in nature except scaled down to the laboratory scale used by some ongoing experiments. We find that the Navier-Stokes solver generates and evolves a wave similar to experimental observations. The head of the gravity current is dominated by medium density fluid with the thermocline thickness growing and becoming thickest at the centre of the head. Maximum velocities of approximately 0.5 of the linear wave speed are found which are similar to experimental and field observations.

scholarly journals Dimensionless Assessment Method of Landslide Dam Formation Caused by Tributary Debris Flow Events

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Kun-Ting Chen ◽  
Xiao-Qing Chen ◽  
Gui-Sheng Hu ◽  
Yu-Shu Kuo ◽  
Yan-Rong Huang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Water Depth ◽  
Debris Flows ◽  
Landslide Dam ◽  
Assessment Method ◽  
Main Stream ◽  
Deposition Thickness ◽  
The Relationship ◽  
Prepared Response

In this study, we develop a dimensionless assessment method to evaluate landslide dam formation by considering the relationship between the run-out distance of a tributary debris flow and the width of the main stream, deposition thickness of the tributary debris flow, and the water depth of the main stream. Based on the theory of debris flow run-out distance and fan formation, landslide dam formation may result from a tributary debris flow as a result of two concurrent formation processes: (1) the run-out distance of the tributary debris flow must be greater than the width of the main stream, and (2) the minimum deposition thickness of the tributary debris flow must be higher than the in situ water depth of the main stream. At the confluence, one of four types of depositional scenarios may result: (1) the tributary debris flow enters into the main stream and forms a landslide dam; (2) the tributary debris flow enters into the main stream but overflow occurs, thus preventing complete blockage of the main stream; (3) the tributary debris flow enters into the main stream, does not reach the far bank, and sediment remains partially above the water elevation of the main stream; or (4) the tributary debris flow enters into the main stream, does not reach the far bank, and sediment is fully submerged in the main stream. This method was applied to the analysis of 11 tributary debris flow events during Typhoon Morakot, and the results indicate that the dimensionless assessment method can be used to estimate potential areas of landslide dam formation caused by tributary debris flows. Based on this method, government authorities can determine potential areas of landslide dam formation caused by debris flows and mitigate possible disasters accordingly through a properly prepared response plan, especially for early identification.

In-situ stress measurements near the San Andreas Fault in central California

1979 ◽  
Vol 84 (B4) ◽  
pp. 1583 ◽  
Author(s):  
W. S. Keys ◽  
R. G. Wolff ◽  
J. D. Bredehoeft ◽  
Eugene Shuter ◽  
J. H. Healy
Keyword(s):  
San Andreas Fault ◽  
In Situ Stress ◽  
Central California ◽  
Stress Measurements ◽  
San Andreas ◽  
In Situ Stress Measurements

Comparison of Water-Lifting Aerator Type for Algae Inhibition in Deep Reservoirs

2013 ◽  
Vol 295-298 ◽  
pp. 1053-1056
Author(s):  
Xin Sun ◽  
Meng Dan Zhang ◽  
Wei Li Zhao ◽  
Ting Lin Huang
Keyword(s):  
Water Depth ◽  
Stable State ◽  
Inhibition Zone ◽  
Circulation Flow ◽  
The Core ◽  
Fluent Software ◽  
Flow Domain ◽  
Algae Control ◽  
Control Technologies

Water-lifting aeration technology is one of the effective in-situ algae control technologies in deep reservoirs. Effects of water-lifting aerator type on the in-situ algae inhibition using water-lifting aeration technology was numerically analyzed with the help of FLUENT software. Under stable state, one large clockwise circulation flow was generated outside non-submerged and submerged water-lifting aerators, but the core algae inhibition zone was farther away from the non-submerged aerator under each water depth. When the water depth was increased from 77.25 m to 97.25 m, the percentage of the core algae inhibition zone to the whole flow domain was decreased from 56.01% to 47.34% for the submerged water-lifting aerator case, while that was decreased from 55.48% to 40.15% for the non-submerged water-lifting aerator case.

scholarly journals Morphological and physiological response strategies of Vallisneria natans at different water depths and light conditions

2020 ◽  
Author(s):  
Qingchuan Chou ◽  
Jianfeng Chen ◽  
Wei Zhang ◽  
Wenjing Ren ◽  
Changbo Yuan ◽  
...  
Keyword(s):  
Resource Allocation ◽  
Water Depth ◽  
Control Experiment ◽  
Light Availability ◽  
Field Investigation ◽  
Leaf Length ◽  
Light Conditions ◽  
Water Depths ◽  
Light Acquisition

AbstractPhenotypic plasticity is an important adaptation to spatial and temporal environmental variations. For submerged macrophytes, adaptation to water depth and light variation is particularly important. To determine the morphological and physiological adaptive strategies of Vallisneria natans at different water depths and light conditions, we combined field investigation, light control experiment and in situ physiological response experiment. In the field investigation and the light control experiment, both water depth and light intensity had prominent effects on the morphological of V. natans, especially in fresh weight and leaf length. The leaf length elongated more rapidly at intermediate water depth sites with lower light intensity. In the in situ experiment, the survival boundary of V. natans is 5.5 m in Lake Erhai. Below this depth, the chlorophyll-a content increased gradually with increasing water depth. Our results demonstrated that V. natans can adapt to water depth and light availability by changing morphological, physiological and resource allocation. At low light condition, V. natans invested more resource for light acquisition, simultaneously, changing the photosynthetic pigment content to compensate for light attenuation; conversely, more resource was directed towards reproduction. These results will provide new insight for species selection when conducting aquatic plants restoration in freshwater ecosystem.HIGHLIGHTSWater depth and light availability affect the morphology, physiology, and resource allocation of V. natans.An alternative resource allocation pattern of V. natans could shift between light acquisition and reproduction.

scholarly journals A new method for indirectly estimating infiltration of paddy fields in situ

2018 ◽  
Vol 379 ◽  
pp. 205-210
Author(s):  
Yunqiang Xu ◽  
Baolin Su ◽  
Hongqi Wang ◽  
Jingyi He
Keyword(s):  
Water Depth ◽  
Paddy Field ◽  
Crop Coefficient ◽  
Paddy Fields ◽  
New Method ◽  
Lake Basin ◽  
The Mean ◽  
Monteith Equation ◽  
Coefficient Method

Abstract. Infiltration is one of the major procedures in water balance research and pollution load estimation in paddy fields. In this study, a new method for indirectly estimating infiltration of paddy fields in situ was proposed and implemented in Taihu Lake basin. Since when there were no rainfall, irrigation and artificial drainage, the water depth variation process of a paddy field is only influenced by evapotranspiration and infiltration (E+F). Firstly, (E+F) was estimated by deciding the steady decreasing rate of water depth; then the evapotranspiration (ET) of the paddy field was calculated by using the crop coefficient method with the recommended FAO-56 Penman-Monteith equation; finally, the infiltration of the paddy field was obtained by subtracting ET from (E+F). Results show that the mean infiltration of the studied paddy field during rice jointing-booting period was 7.41 mm day−1, and the mean vertical infiltration and lateral seepage of the paddy field were 5.46 and 1.95 mm day−1 respectively.

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