The fog/low stratus clouds in the Arctic: detection with multispectral satellite imagery

2020 ◽  
Author(s):  
Daria Tatsii ◽  
Natalia Fedoseeva
Keyword(s):  
Satellite Imagery ◽  
Complex Structure ◽  
Far Infrared ◽  
The Arctic ◽  
Underlying Surface ◽  
Polar Regions ◽  
Stratus Clouds ◽  
Spectral Bands ◽  
Multispectral Satellite Imagery ◽  
Important Challenge

<p>            The safe operation of aviation and shipping, particularly in areas of insufficient coverage of automatic meteorological stations in the Arctic requires accurate interpretation of satellite images. Operational detection of fog and low stratus clouds and recognizing of them on the background of snow and ice cover and cloudiness of the upper layer is very important challenge. </p><p>           The verified images obtained by Aqua and Terra satellites with a scanning radiometer MODIS, which operates in 36 spectral bands, with wavelengths from 0.4 µm to 14.4 µm, were collected.  With the Beam VISAT 5.0 software, which was designed to work with satellite data in raster format, thematic digital techniques of satellite multispectral information, based on difference in the values of the integral brightness of the images, both in optical and far-infrared ranges of the spectrum, have been developed.  These techniques, models of additive color synthesis, improve the quality of interpretation of fogs and low stratus clouds in terms of the complex structure of cloudiness and underlying surface in polar regions. Developed RGB combinations, which are based on the selected MODIS bands are:</p><ol><li>RGB (1.6 µm; 0.8 µm; 0.6 µm)</li> <li>RGB (0.8 µm; 3.9-8.7 µm; 10.8 µm)</li> <li>RGB (0.8 µm; 1.6 µm; 3.9-8.7 µm)</li> <li>RGB ((0-12)-(0-11) µm, (0-11)-(0-3.8) µm, (0-11) µm)</li> </ol><p>          Analysis of the obtained images has shown that the developed models of color synthesis help to distinguish the fog/low stratus clouds under different conditions of cloudiness and underlying surface accurately.</p><p>Key words: remote sensing, satellite imagery, additive color synthesis, fog, low stratus clouds, polar regions</p>

scholarly journals Optimized Performance Parameters for Nighttime Multispectral Satellite Imagery to Analyze Lightings in Urban Areas

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3313 ◽  
Author(s):  
Jasper de Meester ◽  
Tobias Storch
Keyword(s):  
Spatial Resolution ◽  
Satellite Imagery ◽  
Urban Areas ◽  
Near Infrared ◽  
Atmospheric Effects ◽  
Spectral Bands ◽  
Multispectral Satellite Imagery ◽  
Radiation Sources ◽  
Yellow Orange ◽  
Band Combinations

Contrary to its daytime counterpart, nighttime visible and near infrared (VIS/NIR) satellite imagery is limited in both spectral and spatial resolution. Nevertheless, the relevance of such systems is unquestioned with applications to, e.g., examine urban areas, derive light pollution, and estimate energy consumption. To determine optimal spectral bands together with required radiometric and spatial resolution, at-sensor radiances are simulated based on combinations of lamp spectra with typical luminances according to lighting standards, surface reflectances, and radiative transfers for the consideration of atmospheric effects. Various band combinations are evaluated for their ability to differentiate between lighting types and to estimate the important lighting parameters: efficacy to produce visible light, percentage of emissions attributable to the blue part of the spectrum, and assessment of the perceived color of radiation sources. The selected bands are located in the green, blue, yellow-orange, near infrared, and red parts of the spectrum and include one panchromatic band. However, these nighttime bands tailored to artificial light emissions differ significantly from the typical daytime bands focusing on surface reflectances. Compared to existing or proposed nighttime or daytime satellites, the recommended characteristics improve, e.g., classification of lighting types by >10%. The simulations illustrate the feasible improvements in nocturnal VIS/NIR remote sensing which will lead to advanced applications.

scholarly journals The Polar Radiant Energy in the Far InfraRed Experiment: A New Perspective on Polar Longwave Energy Exchanges

2021 ◽  
pp. 1-46
Author(s):  
Tristan S. L’Ecuyer ◽  
Brian J. Drouin ◽  
James Anheuser ◽  
Meredith Grames ◽  
David Henderson ◽  
...  
Keyword(s):  
Thermal Emission ◽  
Radiant Energy ◽  
Far Infrared ◽  
Temporal Variations ◽  
Infrared Emission ◽  
The Arctic ◽  
Energy Budgets ◽  
Polar Regions ◽  
Spectral Variation ◽  
Energy Exchanges

AbstractThe Earth’s climate is strongly influenced by energy deficits at the poles that emit more thermal energy than they receive from the sun. Energy exchanges between the surface and atmosphere influence the local environment while heat transport from lower latitudes drives midlatitude atmospheric and oceanic circulations. In the Arctic, in particular, local energy imbalances induce strong seasonality in surface-atmosphere heat exchanges and an acute sensitivity to forced climate variations. Despite these important local and global influences, the largest contributions to the polar atmospheric and surface energy budgets have not been fully characterized. The spectral variation of far-infrared radiation that makes up 60% of polar thermal emission has never been systematically measured impeding progress toward consensus in predicted rates of Arctic warming, sea ice decline, and ice sheet melt.Enabled by recent advances in sensor miniaturization and CubeSat technology, the Polar Radiant Energy in the Far InfraRed Experiment (PREFIRE) mission will document, for the first time, the spectral, spatial, and temporal variations of polar far-infrared emission. Selected under NASA’s Earth Ventures Instrument (EVI) program, PREFIRE will utilize new light weight, low-power, ambient temperature detectors capable of measuring at wavelengths up to 50 micrometers to quantify Earth’s far-infrared spectrum. Estimates of spectral surface emissivity, water vapor, cloud properties, and the atmospheric greenhouse effect derived from these measurements offer the potential to advance our understanding of the factors that modulate thermal fluxes in the cold, dry conditions characteristic of the polar regions.

scholarly journals Enhanced Viral Activity in the Surface Microlayer of the Arctic and Antarctic Oceans

2021 ◽  
Vol 9 (2) ◽  
pp. 317
Author(s):  
Dolors Vaqué ◽  
Julia A. Boras ◽  
Jesús Maria Arrieta ◽  
Susana Agustí ◽  
Carlos M. Duarte ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Food Web ◽  
Physicochemical Characteristics ◽  
The Arctic ◽  
Microbial Food Web ◽  
Surface Microlayer ◽  
Polar Regions ◽  
Nutrient Inputs ◽  
Viral Activity ◽  
The Impact

The ocean surface microlayer (SML), with physicochemical characteristics different from those of subsurface waters (SSW), results in dense and active viral and microbial communities that may favor virus–host interactions. Conversely, wind speed and/or UV radiation could adversely affect virus infection. Furthermore, in polar regions, organic and inorganic nutrient inputs from melting ice may increase microbial activity in the SML. Since the role of viruses in the microbial food web of the SML is poorly understood in polar oceans, we aimed to study the impact of viruses on prokaryotic communities in the SML and in the SSW in Arctic and Antarctic waters. We hypothesized that a higher viral activity in the SML than in the SSW in both polar systems would be observed. We measured viral and prokaryote abundances, virus-mediated mortality on prokaryotes, heterotrophic and phototrophic nanoflagellate abundance, and environmental factors. In both polar zones, we found small differences in environmental factors between the SML and the SSW. In contrast, despite the adverse effect of wind, viral and prokaryote abundances and virus-mediated mortality on prokaryotes were higher in the SML than in the SSW. As a consequence, the higher carbon flux released by lysed cells in the SML than in the SSW would increase the pool of dissolved organic carbon (DOC) and be rapidly used by other prokaryotes to grow (the viral shunt). Thus, our results suggest that viral activity greatly contributes to the functioning of the microbial food web in the SML, which could influence the biogeochemical cycles of the water column.

Early Holocene ocean conditions off the Zachariæ Isstrøm, Northeast Greenland

2021 ◽  
Author(s):  
Joanna Davies ◽  
Anders Møller Mathiasen ◽  
Kristiane Kristensen ◽  
Christof Pearce ◽  
Marit-Solveig Seidenkrantz
Keyword(s):  
Climate Change ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Atlantic Water ◽  
The Arctic ◽  
Future Climate Change ◽  
Polar Regions ◽  
Ice Shelf ◽  
Outlet Glacier ◽  
The Impact

<p>The polar regions exhibit some of the most visible signs of climate change globally; annual mass loss from the Greenland Ice Sheet (GrIS) has quadrupled in recent decades, from 51 ± 65 Gt yr<sup>−1</sup> (1992-2001) to 211 ± 37 Gt yr<sup>−1</sup> (2002-2011). This can partly be attributed to the widespread retreat and speed-up of marine-terminating glaciers. The Zachariae Isstrøm (ZI) is an outlet glacier of the Northeast Greenland Ice Steam (NEGIS), one of the largest ice streams of the GrIS (700km), draining approximately 12% of the ice sheet interior. Observations show that the ZI began accelerating in 2000, resulting in the collapse of the floating ice shelf between 2002 and 2003. By 2014, the ice shelf extended over an area of 52km<sup>2</sup>, a 95% decrease in area since 2002, where it extended over 1040km<sup>2</sup>. Paleo-reconstructions provide an opportunity to extend observational records in order to understand the oceanic and climatic processes governing the position of the grounding zone of marine terminating glaciers and the extent of floating ice shelves. Such datasets are thus necessary if we are to constrain the impact of future climate change projections on the Arctic cryosphere.</p><p>A multi-proxy approach, involving grain size, geochemical, foraminiferal and sedimentary analysis was applied to marine sediment core DA17-NG-ST8-92G, collected offshore of the ZI, on  the Northeast Greenland Shelf. The aim was to reconstruct changes in the extent of the ZI and the palaeoceanographic conditions throughout the Early to Mid Holocene (c.a. 12,500-5,000 cal. yrs. BP). Evidence from the analysis of these datasets indicates that whilst there has been no grounded ice at the site over the last 12,500 years, the ice shelf of the ZI extended as a floating ice shelf over the site between 12,500 and 9,200 cal. yrs. BP, with the grounding line further inland from our study site. This was followed by a retreat in the ice shelf extent during the Holocene Thermal Maximum; this was likely to have been governed, in part, by basal melting driven by Atlantic Water (AW) recirculated from Svalbard or from the Arctic Ocean. Evidence from benthic foraminifera suggest that there was a shift from the dominance of AW to Polar Water at around 7,500 cal. yrs. BP, although the ice shelf did not expand again despite of this cooling of subsurface waters.</p>

Sr Isotope Chemostratigraphy and Pb–Pb Age of the Riphean Carbonate Deposits of the Kharaulakh Uplift (Northeastern Margin of the Siberian Platform)

2021 ◽  
Vol 62 (03) ◽  
pp. 377-387
Author(s):  
B.B. Kochnev ◽  
A.B. Kuznetsov ◽  
D.R. Sitkina ◽  
A.Yu. Kramchaninov
Keyword(s):  
Siberian Platform ◽  
Sedimentary Cover ◽  
Complex Structure ◽  
The Arctic ◽  
86Sr Ratio ◽  
Sr Isotope ◽  
Upper Riphean ◽  
Carbonate Deposits

Abstract —The least altered limestones of the Ukta and Eselekh formations in the Precambrian section of the Kharaulakh uplift have a minimum 87Sr/86Sr ratio of 0.70673–0.70715. The lowest 87Sr/86Sr ratio of the overlying Neleger and Sietachan formations is 0.70791–0.70817. Based on these data, along with the earlier obtained positive δ13С values (up to 8‰) for the Kharaulakh section, we have estimated the age of the Ukta and Eselekh formations at 800–670 Ma and the age of the Neleger and Sietachan formations at ~640–580 Ma. The Pb–Pb isochron age of the least altered limestones of the Eselekh Formation calculated from eight samples is 720 ± 30 Ma. This age permits us to define the lower part of the Kharaulakh section of the Ukta and Eselekh formations to be the late Tonian of the International Chronostratigraphic Chart or to the Upper Riphean of the General Stratigraphic Scale of Russia. The presence of reliably dated Upper Riphean sediments in the Kharaulakh uplift indicates a more complex structure of the Precambrian sedimentary cover on the Arctic margin of the Siberian Platform than assumed earlier.

scholarly journals Wave measurements on sea ice: developments in instrumentation

2006 ◽  
Vol 44 ◽  
pp. 108-112 ◽  
Author(s):  
M.J. Doble ◽  
D.J.L. Mercer ◽  
D.T. Meldrum ◽  
O.C. Peppe
Keyword(s):  
Satellite Communications ◽  
Weddell Sea ◽  
Data Recovery ◽  
The Arctic ◽  
Polar Regions ◽  
Constant Attention ◽  
Wave Measurements ◽  
Wire Strain ◽  
Propagation Of Waves ◽  
Communications System

AbstractTraditional methods of measuring the propagation of waves originating from ocean swell and other sources have relied on wire strain gauges, accelerometers or tiltmeters. All methods required constant attention to keep in range, while data recovery has demanded that the instrument site be revisited. In this paper, we describe the use of ultra-sensitive tiltmeters and novel re-zeroing techniques to autonomously gather wave data from both polar regions. A key feature of our deployments has been the use of the Iridium satellite communications system as a way of ensuring continuous data recovery and remote control of the instrumentation. Currently four instruments have been successfully reporting from the Arctic Ocean for over 18 months, with two further units deployed in 2005, one in the Weddell Sea, Antarctica, and one additional unit in the Arctic.

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