LONG WAVELENGTH STATIC ESTIMATION

Geophysics ◽  
1976 ◽  
Vol 41 (5) ◽  
pp. 939-959 ◽  
Author(s):  
Aaron H. Booker ◽  
A. Frank Linville ◽  
Cameron B. Wason
Keyword(s):  
Surface Effects ◽  
Mackenzie Delta ◽  
Model Data ◽  
Static Structure ◽  
Near Surface ◽  
Long Wavelength ◽  
Time Profiles ◽  
Common Depth Point ◽  
Theoretical Performance ◽  
Structural Anomalies

Estimation and removal of near‐surface effects in common‐depth‐point (CDP) data have been frequently discussed in the literature. A common problem with many automated statics techniques is their inability to extract statics whose spatial wavelengths are longer than a spread length. This, of course, can result in false structural anomalies. This paper describes an approach which extends the useful static estimation bandwidth to wavelengths of the order of 4 to 8 spread lengths. Traveltimes from one or more reflecting horizons are picked at each depth point and CDP offset. The time profiles are then decomposed into source static, receiver static, structure, and residual normal moveout (RNMO) estimates, and the process is iterated if required. A suite of analytical displays provides the user with direct QC measures of the traveltime picking performance. The technique will be demonstrated on model data to illustrate the theoretical performance over slowly changing near‐surface weathering anomalies. In addition, field examples will be shown from the Mackenzie Delta where permafrost variability in the near‐surface can create large traveltime anomalies.

Investigation of surface and near-surface effects on hydrogen desorption kinetics of MgH2

2014 ◽  
Vol 39 (2) ◽  
pp. 862-867 ◽  
Author(s):  
Sandra Kurko ◽  
Igor Milanović ◽  
Jasmina Grbović Novaković ◽  
Nenad Ivanović ◽  
Nikola Novaković
Keyword(s):  
Surface Effects ◽  
Hydrogen Desorption ◽  
Desorption Kinetics ◽  
Near Surface ◽  
Kinetics Of

A New Assessment of Offshore Wind Profile Relationships

2018 ◽  
Author(s):  
Gus Jeans ◽  
Dave Quantrell ◽  
Andrew Watson ◽  
Laure Grignon ◽  
Gil Lizcano
Keyword(s):  
Wind Energy ◽  
Engineering Design ◽  
Wind Profile ◽  
Numerical Models ◽  
Data Sources ◽  
Offshore Wind ◽  
Wind Gust ◽  
Model Data ◽  
Near Surface ◽  
Wide Range

Engineering design codes specify a variety of different relationships to quantify vertical variations in wind speed, gust factor and turbulence intensity. These are required to support applications including assessment of wind resource, operability and engineering design. Differences between the available relationships lead to undesirable uncertainty in all stages of an offshore wind project. Reducing these uncertainties will become increasingly important as wind energy is harnessed in deeper waters and at lower costs. Installation of a traditional met mast is not an option in deep water. Reliable measurement of the local wind, gust and turbulence profiles from floating LiDAR can be challenging. Fortunately, alternative data sources can provide improved characterisation of winds at offshore locations. Numerical modelling of wind in the lower few hundred metres of the atmosphere is generally much simpler at remote deepwater locations than over complex onshore terrain. The sophistication, resolution and reliability of such models is advancing rapidly. Mesoscale models can now allow nesting of large scale conditions to horizontal scales less than one kilometre. Models can also provide many decades of wind data, a major advantage over the site specific measurements gathered to support a wind energy development. Model data are also immediately available at the start of a project at relatively low cost. At offshore locations these models can be validated and calibrated, just above the sea surface, using well established satellite wind products. Reliable long term statistics of near surface wind can be used to quantify winds at the higher elevations applicable to wind turbines using the wide range of existing standard profile relationships. Reduced uncertainty in these profile relationships will be of considerable benefit to the wider use of satellite and model data sources in the wind energy industry. This paper describes a new assessment of various industry standard wind profile relationships, using a range of available met mast datasets and numerical models.

Cessation of ice-wedge development during the 20th century in spruce forests of eastern Mackenzie Delta, Northwest Territories, Canada

2007 ◽  
Vol 44 (11) ◽  
pp. 1503-1515 ◽  
Author(s):  
S V Kokelj ◽  
M FJ Pisaric ◽  
C R Burn
Keyword(s):  
20Th Century ◽  
Ice Age ◽  
Spruce Forest ◽  
Mackenzie Delta ◽  
Study Region ◽  
Near Surface ◽  
Spruce Forests ◽  
Surface Temperatures ◽  
Forest Sites ◽  
Ice Wedge

Ice wedges are presently inactive in white spruce (Picea glauca) forests of eastern Mackenzie Delta as shown by the absence of vein ice above ice wedges, the maintenance of intact breaking cables, and the abundance of rootlets propagating across ridge–trough sequences. At spruce forest sites, near-surface ground cooling rates and minimum near-surface temperatures from the years 2003–2005 were above ice-wedge cracking thresholds. Ground thermal conditions associated with cracking were recorded at a tundra peatland with active ice wedges. Annual mean permafrost temperatures at the spruce forest sites ranged from –1.8 to –2.9 °C, whereas at the tundra peatland, the permafrost was colder than –6 °C. Although winter air temperatures are similar throughout the study region, deeper snow cover, thicker active layers, and warmer permafrost account for the more gradual seasonal cooling and warmer near-surface temperatures recorded at the subarctic forest sites. The subtle ridge to trough relief, 12–35 cm of permafrost above wedge ice, roots up to 80 years old grown across ice wedges, and negligible tritium levels in wedge ice indicate that thermal contraction cracking in the spruce forests has been infrequent throughout much of the last century. The proximity of wedge ice to the base of the aggrading permafrost table and the absence of old spruce roots spanning ice-wedge troughs suggest that ice-wedge cracking did occur in the forest environments during the cold and dry conditions associated with the Little Ice Age and early part of the 20th century. When these ice wedges cracked, minimum temperatures at the top of permafrost were probably at least 3–8 °C colder than presently observed and similar to present conditions at the tundra peatland.

Passivation and surface effects in long-wavelength infrared HgCdTe photoconductors

1995 ◽  
Author(s):  
Charles A. Musca ◽  
John F. Siliquini ◽  
Brett D. Nener ◽  
Lorenzo Faraone
Keyword(s):  
Surface Effects ◽  
Long Wavelength ◽  
Long Wavelength Infrared

scholarly journals Near-Surface Effects of Free Atmosphere Stratification in Free Convection

2015 ◽  
Vol 159 (1) ◽  
pp. 69-95 ◽  
Author(s):  
Juan Pedro Mellado ◽  
Chiel C. van Heerwaarden ◽  
Jade Rachele Garcia
Keyword(s):  
Free Convection ◽  
Surface Effects ◽  
Free Atmosphere ◽  
Near Surface

Near‐surface faulting effects on seismic reflection times

Geophysics ◽  
1983 ◽  
Vol 48 (8) ◽  
pp. 1140-1142 ◽  
Author(s):  
W. Honeyman
Keyword(s):  
Seismic Reflection ◽  
Small Time ◽  
Time Curve ◽  
Near Surface ◽  
Common Depth Point ◽  
Offset Distance ◽  
Large Spread ◽  
Offset Time ◽  
Seismic Sections ◽  
Zero Offset

The depth conversion of seismic reflection records has been the subject of many papers, particularly where faults or other geologic features are present. The common‐depth‐point (CDP) stacked seismic sections with large spread lengths of the order of 2 km have resulted in different interpretation problems. Al‐Chalabi (1979) considered the effect on stacking velocities of subsurface inhomogeneities where different rays in the CDP gather do not penetrate the same type of earth column. He showed that small time delays of 10 msec produce steps in the hyperbolic offset distance‐time curve of the CDP gather and produce stacking velocity variations of the order of ten percent. Levin (1973) considered a time delay in only one ray of the CDP gather and its effect on both stacking velocity and the zero‐offset time [Formula: see text]. This paper models the effect of near‐surface faults on the zero‐offset time [Formula: see text] of deeper layers as determined by the CDP method. This is particularly important since the zero‐offset time is plotted on the processed final record.

Sign in / Sign up

Export Citation Format

Share Document