A System Response Convolution Routine for Improved Near Surface Sensitivity in SkyTEM Data

2015 ◽  
Author(s):  
K. K. Andersen ◽  
N.S. Nyboe ◽  
C. Kirkegaard ◽  
E. Auken ◽  
A.V. Christiansen
Keyword(s):  
System Response ◽  
Near Surface ◽  
Surface Sensitivity

scholarly journals Winter seal-based observations reveal glacial meltwater surfacing in the southeastern Amundsen Sea

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Yixi Zheng ◽  
Karen J. Heywood ◽  
Benjamin G. M. Webber ◽  
David P. Stevens ◽  
Louise C. Biddle ◽  
...  
Keyword(s):  
Heat Fluxes ◽  
System Response ◽  
Small Scale ◽  
Earth System ◽  
Amundsen Sea ◽  
Near Surface ◽  
Glacial Meltwater ◽  
Ice Shelves ◽  
Using Data ◽  
Earth System Models

AbstractDetermining the injection of glacial meltwater into polar oceans is crucial for quantifying the climate system response to ice sheet mass loss. However, meltwater is poorly observed and its pathways poorly known, especially in winter. Here we present winter meltwater distribution near Pine Island Glacier using data collected by tagged seals, revealing a highly variable meltwater distribution with two meltwater-rich layers in the upper 250 m and at around 450 m, connected by scattered meltwater-rich columns. We show that the hydrographic signature of meltwater is clearest in winter, when its presence can be unambiguously mapped. We argue that the buoyant meltwater provides near-surface heat that helps to maintain polynyas close to ice shelves. The meltwater feedback onto polynyas and air-sea heat fluxes demonstrates that although the processes determining the distribution of meltwater are small-scale, they are important to represent in Earth system models.

Transient electromagnetic smoke rings in a halfspace during active transmitter excitation

Geophysics ◽  
2021 ◽  
pp. 1-38
Author(s):  
Adam Smiarowski ◽  
Greg Hodges
Keyword(s):  
Current Distribution ◽  
Current System ◽  
Primary Field ◽  
Depth Of Penetration ◽  
Near Surface ◽  
Surface Sensitivity ◽  
Field Coupling ◽  
Transient Electromagnetic ◽  
Smoke Ring ◽  
Off Time

The smoke ring concept is a useful device for understanding how the electromagnetic fields induced in a 1-D earth propagate and diffuse through a medium. Aside from facilitating a physical understanding of field propagation, the smoke ring concept has been used to interpret behavior of vertical and radial magnetic fields at the surface and used to estimate depth of penetration for conductivity-depth transforms. Past studies have focused on the current distribution during the off-time. We calculate and illustrate the current in a halfspace from a half-sine excitation (which provides a continuous induction). In comparison, the current pattern from a continuously excited waveform is more densely distributed near-surface than the off-time current system, suggesting that measurements during a continuously excited on-time are more sensitive to shallow targets. For airborne applications, where the primary field coupling changes and is an important noise source, a primary field-stripping algorithm impacts the current distribution but does not deleteriously affect near-surface sensitivity.

scholarly journals Assessing the near surface sensitivity of SCIAMACHY atmospheric CO<sub>2</sub> retrieved using (FSI) WFM-DOAS

2007 ◽  
Vol 7 (13) ◽  
pp. 3597-3619 ◽  
Author(s):  
M. P. Barkley ◽  
P. S. Monks ◽  
A. J. Hewitt ◽  
T. Machida ◽  
A. Desai ◽  
...  
Keyword(s):  
Near Infrared ◽  
Vegetation Indices ◽  
Correlation Coefficients ◽  
The United States ◽  
Atmospheric Co2 ◽  
Carbon Surface ◽  
Near Surface ◽  
Surface Sensitivity ◽  
Vegetation Activity

Abstract. Satellite observations of atmospheric CO2 offer the potential to identify regional carbon surface sources and sinks and to investigate carbon cycle processes. The extent to which satellite measurements are useful however, depends on the near surface sensitivity of the chosen sensor. In this paper, the capability of the SCIAMACHY instrument on board ENVISAT, to observe lower tropospheric and surface CO2 variability is examined. To achieve this, atmospheric CO2 retrieved from SCIAMACHY near infrared (NIR) spectral measurements, using the Full Spectral Initiation (FSI) WFM-DOAS algorithm, is compared to in-situ aircraft observations over Siberia and additionally to tower and surface CO2 data over Mongolia, Europe and North America. Preliminary validation of daily averaged SCIAMACHY/FSI CO2 against ground based Fourier Transform Spectrometer (FTS) column measurements made at Park Falls, reveal a negative bias of about −2.0% for collocated measurements within ±1.0° of the site. However, at this spatial threshold SCIAMACHY can only capture the variability of the FTS observations at monthly timescales. To observe day to day variability of the FTS observations, the collocation limits must be increased. Furthermore, comparisons to in-situ CO2 observations demonstrate that SCIAMACHY is capable of observing a seasonal signal that is representative of lower tropospheric variability on (at least) monthly timescales. Out of seventeen time series comparisons, eleven have correlation coefficients of 0.7 or more, and have similar seasonal cycle amplitudes. Additional evidence of the near surface sensitivity of SCIAMACHY, is provided through the significant correlation of FSI derived CO2 with MODIS vegetation indices at over twenty selected locations in the United States. The SCIAMACHY/MODIS comparison reveals that at many of the sites, the amount of CO2 variability is coincident with the amount of vegetation activity. The presented analysis suggests that SCIAMACHY has the potential to detect CO2 variability within the lowermost troposphere arising from the activity of the terrestrial biosphere.

scholarly journals Assessing the near surface sensitivity of SCIAMACHY atmospheric CO<sub>2</sub> retrieved using (FSI) WFM-DOAS

2007 ◽  
Vol 7 (1) ◽  
pp. 2477-2530 ◽  
Author(s):  
M. P. Barkley ◽  
P. S. Monks ◽  
A. J. Hewitt ◽  
T. Machida ◽  
A. Desai ◽  
...  
Keyword(s):  
Near Infrared ◽  
Vegetation Indices ◽  
Correlation Coefficients ◽  
The United States ◽  
Atmospheric Co2 ◽  
Carbon Surface ◽  
Near Surface ◽  
Surface Sensitivity ◽  
Vegetation Activity

Abstract. Satellite observations of atmospheric CO2 offer the potential to identify regional carbon surface sources and sinks and to investigate carbon cycle processes. The extent to which satellite measurements are useful however, depends on the near surface sensitivity of the chosen sensor. In this paper, the capability of the SCIAMACHY instrument on board ENVISAT, to observe lower tropospheric and surface CO2 variability is examined. To achieve this, atmospheric CO2 retrieved from SCIAMACHY near infrared (NIR) spectral measurements, using the Full Spectral Initiation (FSI) WFM-DOAS algorithm, is compared to in situ aircraft observations over Siberia and additionally to tower and surface CO2 data over Mongolia, Europe and North America. Preliminary validation of daily averaged SCIAMACHY/FSI CO2 against ground based Fourier Transform Spectrometer (FTS) column measurements made at Park Falls, reveal a negative bias of about −2.0% for collocated measurements within ±1.0\\degree of the site. However, at this spatial threshold SCIAMACHY can only capture the variability of the FTS observations at monthly timescales. To observe day to day variability of the FTS observations, the collocation limits must be increased. Furthermore, comparisons to in-situ CO2 observations demonstrate that SCIAMACHY is capable of observing lower tropospheric variability on (at least) monthly timescales. Out of seventeen time series comparisons, eleven have correlation coefficients of 0.7 or more, and have similar seasonal cycle amplitudes. Additional evidence of the near surface sensitivity of SCIAMACHY, is provided through the significant correlation of FSI derived CO2 with MODIS vegetation indices at over twenty selected locations in the United States. The SCIAMACHY/MODIS comparison reveals that at many of the sites, the amount of CO2 variability is coincident with the amount of vegetation activity. It is evident, from this analysis, that SCIAMACHY therefore has the potential to detect CO2 variability within the lowermost troposphere arising from the activity of the terrestrial biosphere.

scholarly journals A measurement system for vertical seawater profiles close to the air/sea interface

2017 ◽  
Author(s):  
Richard P. Sims ◽  
Ute Schuster ◽  
Andrew J. Watson ◽  
Ming Xi Yang ◽  
Frances E. Hopkins ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
System Response ◽  
Vertical Profiles ◽  
Near Surface ◽  
Wind Speeds ◽  
Small Frame ◽  
System Response Time ◽  
Wave Heights ◽  
Gas Measurements ◽  
Vertical Gradients

Abstract. This paper describes a Near Surface Ocean Profiler, which has been designed to precisely measure vertical gradients in the top 10 m of the ocean. Variations in the depth of seawater collection are minimised when using the profiler compared to conventional CTD/rosette deployments. The profiler consists of a remotely operated winch mounted on a tethered yet free floating buoy, which is used to raise and lower a small frame housing sensors and inlet tubing. Seawater at the inlet depth is pumped back to the ship for analysis. The profiler can be used to make continuous vertical profiles or to target a series of discrete depths. The profiler has been successfully deployed during wind speeds up to 10 m s−1 and significant wave heights up to 2 m. We demonstrate the potential of the profiler by presenting measured vertical profiles of the trace gases carbon dioxide and dimethylsulfide. Trace gas measurements use an efficient microporous membrane equilibrator to minimise the system response time. The example profiles show vertical gradients in the upper 5 m for temperature, carbon dioxide and dimethylsulfide of 0.15 °C, 4 μatm and 0.4 nM respectively.

scholarly journals A measurement system for vertical seawater profiles close to the air–sea interface

Ocean Science ◽  
2017 ◽  
Vol 13 (5) ◽  
pp. 649-660 ◽  
Author(s):  
Richard P. Sims ◽  
Ute Schuster ◽  
Andrew J. Watson ◽  
Ming Xi Yang ◽  
Frances E. Hopkins ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
System Response ◽  
Vertical Profiles ◽  
Near Surface ◽  
Wind Speeds ◽  
Small Frame ◽  
System Response Time ◽  
Wave Heights ◽  
Gas Measurements ◽  
Vertical Gradients

Abstract. This paper describes a near-surface ocean profiler, which has been designed to precisely measure vertical gradients in the top 10 m of the ocean. Variations in the depth of seawater collection are minimized when using the profiler compared to conventional CTD/rosette deployments. The profiler consists of a remotely operated winch mounted on a tethered yet free-floating buoy, which is used to raise and lower a small frame housing sensors and inlet tubing. Seawater at the inlet depth is pumped back to the ship for analysis. The profiler can be used to make continuous vertical profiles or to target a series of discrete depths. The profiler has been successfully deployed during wind speeds up to 10 m s−1 and significant wave heights up to 2 m. We demonstrate the potential of the profiler by presenting measured vertical profiles of the trace gases carbon dioxide and dimethylsulfide. Trace gas measurements use an efficient microporous membrane equilibrator to minimize the system response time. The example profiles show vertical gradients in the upper 5 m for temperature, carbon dioxide and dimethylsulfide of 0.15 °C, 4 µatm and 0.4 nM respectively.

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