scholarly journals Continuous borehole optical televiewing reveals variable englacial debris concentrations at Khumbu Glacier, Nepal

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Katie E. Miles ◽  
Bryn Hubbard ◽  
Evan S. Miles ◽  
Duncan J. Quincey ◽  
Ann V. Rowan ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Water Supply ◽  
Depth Profile ◽  
Variable Thickness ◽  
Surface Melting ◽  
High Mountain ◽  
Ablation Area ◽  
The Mean ◽  
Surface Melt ◽  
The Vertical Distribution

AbstractSurface melting of High Mountain Asian debris-covered glaciers shapes the seasonal water supply to millions of people. This melt is strongly influenced by the spatially variable thickness of the supraglacial debris layer, which is itself partially controlled by englacial debris concentration and melt-out. Here, we present measurements of deep englacial debris concentrations from debris-covered Khumbu Glacier, Nepal, based on four borehole optical televiewer logs, each up to 150 m long. The mean borehole englacial debris content is ≤ 0.7% by volume in the glacier’s mid-to-upper ablation area, and increases to 6.4% by volume near the terminus. These concentrations are higher than those reported for other valley glaciers, although those measurements relate to discrete samples while our approach yields a continuous depth profile. The vertical distribution of englacial debris increases with depth, but is also highly variable, which will complicate predictions of future rates of surface melt and debris exhumation at such glaciers.

scholarly journals On the spatial variability of the regional aerosol distribution as determined from ceilometers

2020 ◽  
Author(s):  
Matthias Wiegner ◽  
Alexander Geiß ◽  
Ina Mattis ◽  
Fred Meier ◽  
Thomas Ruhtz
Keyword(s):  
Vertical Distribution ◽  
Mixing Layer ◽  
Data Set ◽  
Integrated Backscatter ◽  
Aerosol Distribution ◽  
Mixing Layer Height ◽  
Aerosol Sources ◽  
The Mean ◽  
Two Parameters ◽  
The Vertical Distribution

Abstract. Measurements of the vertical distribution of aerosol particles are typically only available at selected sites leaving the question of their representativeness for urban and regional scales unanswered. As a contribution to solve this problem we have investigated ceilometer signals from two testbeds in Munich and Berlin, Germany. For each testbed measurements of 24 months from 6 ceilometers were available. This constitutes a unique data set, in particular as the same type of instruments are deployed and the same data evaluation schemes applied. Two parameters are discussed: the mixing layer height (MLH) as an indicator for the vertical distribution and the integrated backscatter as a proxy for the amount of aerosols in the mixing layer. The MLH was determined by the COBOLT algorithm, the integrated backscatter from the Klett (backward and forward) inversion scheme. It was found that the mean difference of the MLH at two sites within a testbed typically only varies by less than 50 m, slightly increasing with the distance of the corresponding sites. Almost 60 % of all intercomparisons agree within ±100 m. MLHs are typically correlated with R > 0.9 in particular for the Berlin-testbed. With respect to the integrated backscatter the correlation is in the range of 0.7 < R < 0.9. This is expected from the diversity of local aerosol sources within a given testbed. We conclude from our data that the MLH determined from a single ceilometer is applicable for a whole metropolitan area. However, the integrated backscatter of particles within the mixing layer exhibits a variability of 15–25 % suggesting that one ceilometer is not representative, especially if atmospheric processes shall be investigated.

Travelling disturbances in the ionosphere

1950 ◽  
Vol 202 (1069) ◽  
pp. 208-223 ◽  
Keyword(s):  
Seasonal Variation ◽  
Vertical Distribution ◽  
Sudden Change ◽  
Frequent Occurrence ◽  
Vertical Movements ◽  
Short Period ◽  
The Mean ◽  
The Vertical Distribution

Methods have been developed for the examination of the horizontal and vertical movements of short-period disturbances in the ionosphere. It has been found that quasi-periodic travelling disturbances with periods of from 10 to 60 min. are of frequent occurrence in the F region by day. They appear as temporary variations in the vertical distribution of ionization which show a horizontal progression and a vertical progression downwards. The horizontal directions of travel have a well-defined mean direction on most days. The mean direction shows a marked seasonal variation with a sudden change at each equinox. The horizontal rate of travel is usually between 5 and 10 km./min., and the rate of vertical progression downwards is approximately half the horizontal rate. The disturbances are considered to be variations of a compressional type in the atmosphere resulting in changes in the distribution of ionization.

Some factors affecting the respiration of intertidal Asterina gibbosa (Echinodermata: Asteroidea)

1987 ◽  
Vol 67 (4) ◽  
pp. 717-727 ◽  
Author(s):  
Christine T. Murphy ◽  
M. B. Jones
Keyword(s):  
Vertical Distribution ◽  
Neap Tide ◽  
High Water ◽  
Rocky Shores ◽  
Rock Pools ◽  
Factors Affecting ◽  
Upper Limits ◽  
The Mean ◽  
The Vertical Distribution ◽  
Inadequate Food Supply

In Britain, the cushion star Asterina gibbosa Pennant 1897 (Echinodermata, Asteroidea) is confined to the west coast, where it occurs on rocky shores, often sympatrically with the closely related Asterina phylactica Emson & Crump 1979 (Crump & Emson, 1983; Emson & Crump, 1984). The vertical distribution of A. gibbosa extends from about 100 m depth, into the intertidal; however, littoral cushion stars occupy rock pools and relatively damp habitats such as gulley walls, crevices, overhangs and the underside of boulders, generally on the lower shore (Emson, 1979). On shores with rock pools, cushion stars may extend their upper limits of vertical distribution but not beyond the mean high-water neap-tide level (Crump & Emson, 1978). Absence of A. gibbosa from higher shore levels has been related to intolerance to desiccation and high temperature, inadequate food supply, and complex behavioural responses to gravity and light (Crozier, 1935; Emson, 1979; Crump & Emson, 1983). Prior to the present study, it has not been possible to discuss the influence of respiratory requirements on the vertical distribution of this species.

Submersible observations on the daytime vertical distribution of Aequorea ?forskalea off the west coast of southern Africa

2005 ◽  
Vol 85 (3) ◽  
pp. 519-522 ◽  
Author(s):  
Conrad Sparks ◽  
Andrew S. Brierley ◽  
Emmanuelle Buecher ◽  
Dave Boyer ◽  
Bjøern Axelsen ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Southern Africa ◽  
West Coast ◽  
Sea Surface ◽  
The West ◽  
Spatial Overlap ◽  
The Mean ◽  
The Vertical Distribution

The vertical distribution of the hydromedusa Aequorea ?forskalea was investigated using observations from the research submersible ‘Jago’ collected during 36 dives off the west coast of southern Africa during November 1997 and April 1999. The mean population depth of Aequorea ?forskalea deepened with increasing sea surface temperature. We suggest that this behaviour enables individuals to avoid offshore advection, to minimize spatial overlap with other large medusae and to maintain their position over the middle of the shelf.

scholarly journals Bursting-Layer Modeling Based on the Assumption of the Averaged Sea Surface for Strong Wind-Driven Currents

2008 ◽  
Vol 38 (4) ◽  
pp. 896-908 ◽  
Author(s):  
Tomokazu Murakami ◽  
Takashi Yasuda
Keyword(s):  
Vertical Distribution ◽  
Wind Wave ◽  
Trough Level ◽  
Sea Surface ◽  
Strong Wind ◽  
Wave Trough ◽  
Mean Water Level ◽  
The Mean ◽  
Wind Driven Currents ◽  
The Vertical Distribution

Abstract In the sea, which is affected by strong winds that cover the water surface with wind-wave breakers, the sea surface layer, called the bursting layer by authors, is generated immediately below the mean water level. For treatment of strong wind-driven currents, it is necessary to model the bursting layer correctly based on observed data. However, an essential difficulty occurs in that, because of large water surface displacement caused by developed wind waves, water particle velocities above the wave trough level cannot be measured continuously in the Eulerian coordinates when measuring the velocity of strong wind-driven currents. Consequently, it is impossible to apply the Reynolds average rule to the velocity field above the wave trough level. In this study, an experiment that uses a wind-wave tank with a double bottom is performed to measure the horizontal velocity of currents driven only by the wind stress. The vertical distribution up to the mean water level is determined to make its vertically integrated value agree with the total mass flux of the wind-driven currents. Furthermore, the vertical distribution of the Reynolds stress is derived by solving a Reynolds equation; its solution agrees with the given velocity distribution. Numerical simulation was performed to reproduce the strong wind-driven currents. Results showed that the bursting-layer model can correctly calculate the steep vertical distribution of the current velocity in the bursting layer.

PATTERNS OF FEEDING INJURY TO POTATO BY THE POTATO FLEA BEETLE (COLEOPTERA: CHRYSOMELIDAE) IN MANITOBA

1996 ◽  
Vol 128 (5) ◽  
pp. 791-804
Author(s):  
S.F. Pernal ◽  
D.G. Senanayake ◽  
N.J. Holliday
Keyword(s):  
Vertical Distribution ◽  
Repeated Measures ◽  
Seasonal Pattern ◽  
Flea Beetle ◽  
Control Measures ◽  
Potato Plants ◽  
Flea Beetles ◽  
The Mean ◽  
The Vertical Distribution ◽  
Potato Flea Beetle

AbstractThe amount and distribution of foliar feeding injury by adult potato flea beetles, Epitrix cucumeris (Harris), were examined on individually caged potato plants grown in field plots in Manitoba. Plants were either maintained as uninfested controls, or were exposed throughout the growing season to different insect densities that mimicked the natural seasonal pattern of infestation. In 1984, a trial was conducted using cv. ‘Norland’ exposed to four different densities of potato flea beetles. In 1989 and 1990, cv. ‘Russet Burbank’ was exposed to potato flea beetles, and in some treatments, plants were exposed to early summer infestations of Colorado potato beetles, Leptinotarsa decemlineata (Say). In each trial, during the late summer period of high potato flea beetle density, the amount and distribution of flea beetle feeding injury were assessed at weekly intervals. Counts of feeding punctures in single leaflets were made from leaves in the upper, middle, and lower third of each caged plant, and these data were subjected to repeated measures analysis of variance. In each of the 3 years, increasing the number of flea beetles increased the mean number of feeding punctures per leaflet in an approximately linear fashion; however, the number of punctures per beetle varied between cultivars and years. In 1984 and 1990, the number of feeding punctures per leaflet was least in the upper third of the plants, and greater in the lower, or middle and lower, third of plants. However, in 1989, the vertical distribution of feeding punctures was relatively even. Previous feeding by Colorado potato beetles increased the mean number of flea beetle feeding punctures per leaflet and changed the vertical distribution of feeding punctures. Rainfall and temperature were correlated with patterns of flea beetle injury; injury was concentrated on lower leaflets during weeks of greater rainfall, and upper leaflets were injured most during weeks with higher average temperatures. It is concluded that flea beetles exhibit preferences for feeding in specific portions of potato plants, and that these preferences change in response to previous defoliation and are influenced by meteorological conditions. Consequently, counting feeding punctures would not be a reliable method of assessing whether control measures for potato flea beetles are justified.

The Motion of Simulated Convective Storms as a Function of Basic Environmental Parameters

2007 ◽  
Vol 135 (9) ◽  
pp. 3033-3051 ◽  
Author(s):  
J. Cody Kirkpatrick ◽  
Eugene W. McCaul ◽  
Charles Cohen
Keyword(s):  
Vertical Distribution ◽  
Temporal Variability ◽  
Convective Available Potential Energy ◽  
Environmental Parameters ◽  
Vertical Shear ◽  
Cloud Base ◽  
Base Temperature ◽  
Storm Evolution ◽  
The Mean ◽  
The Vertical Distribution

Abstract Based on results from a three-dimensional cloud-resolving model, it is shown that simulated convective storm motions are affected by thermodynamic as well as kinematic properties of the environment. In addition to the mean wind and its vertical shear, the effect on isolated storm motion of parameters such as bulk convective available potential energy (CAPE), the vertical distribution of buoyancy in the profile, the heights of the lifting condensation level (LCL) and level of free convection (LFC), and cloud-base temperature is considered. Storm motions show at least some sensitivity to all input parameters. Consistent with previous studies, hodograph radius has the most pronounced effect, but the vertical distribution of shear (which also influences the mean wind) affects storm evolution and propagation, even when the effective hodograph radius is unchanged. Among the thermodynamic parameters, the most significant variations occur when the LCL–LFC configuration is modified or when cloud-base temperature is changed. The effects of increases in bulk CAPE act mainly to increase the temporal variability of storm motions. This temporal variability is found to consist both of oscillations about a mean state and trends (accelerations) and is related to increases in the complexity of storm evolution with increasing CAPE. The results point to the importance of environmental factors that enhance storm intensity and rotation, which play a key role in determining storm deviate motion.

scholarly journals Satellite Observations of Snowfall Regimes over the Greenland Ice Sheet

2019 ◽  
Author(s):  
Elin A. McIlhattan ◽  
Claire Pettersen ◽  
Norman B. Wood ◽  
Tristan S. L'Ecuyer
Keyword(s):  
Large Scale ◽  
Dominant Role ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Orthogonal Polarization ◽  
Ice Dynamics ◽  
Cloud Characteristics ◽  
The Mean ◽  
Surface Melt ◽  
The Vertical Distribution

Abstract. The mass of the Greenland Ice Sheet (GIS) is decreasing due to surface melt and ice dynamics. Snowfall both adds mass to the GIS and has the capacity to reduce surface melt by increasing surface brightness, reflecting additional solar radiation back to space. This study leverages the synergy between two satellite instruments, CloudSat's Cloud Profiling Radar (CPR) and CALIPSO's Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), to identify snowfall cases over the GIS and partition them into two regimes: those associated with exclusively ice-phase cloud processes (IC) and those involving mixed-phase processes indicated by the presence of super-cooled liquid water (CLW). Overall, most CPR observations of snowfall over the GIS come from IC events (70 %), however, during the summer months, close to half of the snow observed is produced in CLW events (45 %). IC snowfall plays a dominant role in building the GIS, producing ~80 % of the total estimated 399 Gt yr−1 accumulation. Beyond the cloud phase that defines the snowfall regimes, the macrophysical cloud characteristics are distinct as well; the mean IC geometric cloud depth (~4 km) is consistently deeper than the CLW geometric cloud depth (~2 km), consistent with previous studies based on surface observations. Two-dimensional histograms of the vertical distribution of CPR reflectivities show that IC events demonstrate consistent growth toward the surface while CLW events do not. Analysis of ERA5 reanalyses shows that IC events are associated with cyclone activity and CLW events occur under large scale anomalous high pressure. Ground-based data is used to estimate the sensitivity of CloudSat's CPR to the two snowfall regimes, finding that the space-based radar is sensitive enough to detect ~95 % of IC snowfall cases and ~75 % of CLW snowfall cases seen at the surface.

scholarly journals Dynamics of the daily course of water temperature in Polish lakes

2016 ◽  
Vol 31 (1) ◽  
pp. 149-156 ◽  
Author(s):  
Rajmund Skowron ◽  
Adam Piasecki
Keyword(s):  
Surface Water ◽  
Vertical Distribution ◽  
Water Temperature ◽  
Experimental Measurements ◽  
Surface Water Temperature ◽  
Short Term ◽  
Yearly Cycle ◽  
The Mean ◽  
The Vertical Distribution ◽  
Daily Changes

AbstractThe study focuses on short-term changes in surface water temperature in Polish lakes, and is based upon the experimental measurements of water temperature conducted every 60 minutes during the years 1971–2015. 19 lakes were selected on the grounds of their morphometric properties. The examinations were carried out in the system of expeditionary measurements (up to 8 days) and stationary measurements (over 2 months), and included temperature of surface water and its vertical distribution. The analysis of the results showed that temperature differences of water (daily amplitudes) were observed in both time and spatial distribution. The biggest differences in water temperature occurred during spring warming, and often reached 4–5°C, while rarely exceed 2°C in the remaining periods of the yearly cycle. The mean day value occurs twice; in the morning between 8:00 (7:00 GMT) and 11:00 (10:00 GMT), and in the evening at 20:00 (19:00 GMT) and 22:00 (21:00 GMT). Daily changes in the vertical distribution of water temperature are clearly visible down to the depth of 2.5–3.5 m, whereas are just perceptible to the depth of 5.5–7.0 m.

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