Byongjun (Phil) Hwang

Byongjun (Phil) Hwang
University of Huddersfield

PhD

About

59
Publications
8,132
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729
Citations

Publications

Publications (59)
Preprint
The sea ice floe size distribution (FSD) is an important component for sea ice thermodynamic and dynamic processes, particularly in the marginal ice zone. Recently FSD-related processes have been incorporated in sea ice models, but the sparsity of existing observations limits the evaluation of FSD models, so hindering model improvements. In this st...
Article
Sea ice is composed of discrete units called floes. Observations show that these floes can adopt a range of sizes spanning orders of magnitude, from metres to tens of kilometres. Floe size impacts the nature and magnitude of interactions between the sea ice, ocean, and atmosphere including lateral melt rate and momentum and heat exchange. However,...
Preprint
Full-text available
Sea ice is composed of discrete units called floes. The size of these floes can determine the nature and magnitude of interactions between the sea ice, ocean, and atmosphere including lateral melt rate, momentum and heat exchange, and surface moisture flux. Large-scale geophysical sea ice models employ a continuum approach and traditionally either...
Article
Full-text available
Preserving wild coffee in the natural forest, especially in southwest Ethiopia, is important for maintaining the genetic diversity of Arabica coffee and sustaining coffee production. To monitor the changes in wild coffee in the natural forest, we conducted an in situ baseline survey in 2015, and 30 of those survey sites were re-visited in 2019. Tho...
Article
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The high forests in southwest Ethiopia, some of the last remaining Afromontane forests in the country, are home to significant forest coffee production. While considered as beneficial in maintaining forests, there have been growing concerns about the degradation caused by intensive management for coffee production in these forests. However, no suit...
Article
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The thermal evolution of melt ponds on Arctic sea-ice was investigated through a combination of autonomous observations, and two-dimensional high-resolution fluid dynamics simulations. We observed one relatively fresh pond and one saline pond on the same ice floe, with similar depth. The comparison of observations and simulations indicates that the...
Article
Full-text available
The size distribution of ice floes in the polar seas affects the dynamics and thermodynamics of the ice cover, and ice-ocean models are beginning to include the floe size distribution (FSD) in their simulations. The FSD has previously been reported to follow a power law of the form χ-α, where χ is the floe size and -α characterizes how steeply the...
Article
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The interplay between sea ice concentration, sea ice roughness, ocean strati cation, and momentum transfer to the ice and ocean is subject to seasonal and decadal variations that are crucial to understanding the present and future air-ice-ocean system in the Arctic. In this study, continuous observations in the Canada Basin from March through Decem...
Article
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An array of novel directional wavebuoys was designed and deployed into the Beaufort Sea ice cover in March 2014, as part of the Office of Naval Research 'Marginal Ice Zone' experiment. The buoys were designed to drift with the ice throughout the year and monitor the expected breakup and retreat of the ice cover, forced by waves travelling into the...
Article
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Breakup of the near-continuous winter sea ice into discrete summer ice floes is an important transition that dictates the evolution and fate of the marginal ice zone (MIZ) of the Arctic Ocean. During the winter of 2014, more than 50 autonomous drifting buoys were deployed in four separate clusters on the sea ice in the Beaufort Sea, as part of the...
Article
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In this study, we present an algorithm for summer sea ice conditions that semi-automatically produces the floe size distribution of Arctic sea ice from high-resolution satellite Synthetic Aperture Radar data. Currently, floe size distribution data from satellite images are very rare in the literature, mainly due to the lack of a reliable algorithm...
Article
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To better simulate the seasonal evolution of sea ice in the Arctic, with particular attention to the marginal ice zone, a sea ice model of the distribution of ice thickness, floe size, and enthalpy was implemented into the Pan-arctic Ice–Ocean Modeling and Assimilation System (PIOMAS). Theories on floe size distribution (FSD) and ice thickness dist...
Article
A comprehensive set of autonomous, ice-ocean measurements were collected across the Canada Basin to study the summer evolution of the ice-ocean boundary layer (IOBL) and ocean mixed layer (OML). Evaluation of local heat and freshwater balances and associated turbulent forcing reveals that melt ponds (MP’s) strongly influence the summer IOBL-OML evo...
Article
Full-text available
Melt ponds are believed to play an important role in sea ice dynamics because they accelerate the melting of sea ice in the warmer spring and summer months. Additionally, they are known to absorb solar radiation rather than reflect it as the surrounding sea ice does. However, the size and distribution of melt ponds are highly variable, and thus, th...
Article
Full-text available
Using a mooring package comprising an acoustic Doppler current profiler (ADCP) and holographic imaging system, a 1-day ice camp study was performed under the Arctic sea ice in the northern Chukchi Plateau to estimate vertical and temporal variations in total suspended particulate matter (SPM). In early August, the SPM in the upper mixed layer (~15...
Conference Paper
The Sea Ice that grows in the open seas like the Arctic sea, forms varying shapes and size due to the fracturing as well as thickening caused by the strong gale force winds and sea waves. Over the winter season, due to the cooler temperature, these sea-ice regions combine with each other to make a stronger and larger sea ice block. In the summer ho...
Article
Small-scale (~100 to 200 m) deformations of an Arctic sea ice floe were detected from multiple GPS-equipped buoys that were deployed on the same ice floe. Over a nine-month period three deformation events were recorded. At each case the event was of limited duration, each lasting less than a day. The events were highly compressive in nature with th...
Conference Paper
A new approach for Synthetic Aperture Radar (SAR) based sea ice image segmentation for the retrieval of floe size distribution (FSD) is proposed. This method consists of three stages. The first stage involves the pre-processing of the SAR image to reduce the speckle noise in the image by median filtering. The second stage involves an initial segmen...
Article
Mooring observation of hydrography, hydrodynamics and suspended particles distribution under a drifting sea ice revealed the mixing and entrainment pattern in the upper mixed layer (ML) of the marginal ice zone. The ice floe where the mooring system was installed drifted as near-inertial motion with approximately 12-hour cycle. The mixing pattern i...
Conference Paper
Full-text available
A series of high-resolution Synthetic Aperture Radar images (TerraSAR-X) has been acquired from 2011 winter until 2012 summer, tracking a cluster of autonomous observing platforms including Arctic Ocean Flux Buoy (AOFB-25) and sea ice mass balance buoy (IMB-2011J). These buoys were deployed on a multiyear ice floe in Beaufort Sea on August 6, 2011....
Article
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In this study, three low-resolution and three medium-resolution ice motion products were compared to ice-tethered profiler ITP global positioning system GPS data over a 2 year period. The ice motion products were the Advanced Microwave Scanning Radiometer Earth Observing System AMSR-E, merged Advanced Scatterometer + Special Sensor Microwave/Imager...
Article
Remote sensing of SAR images is suitable for sea ice observations to obtain the sea ice data if clouds or weather conditions change. There are various types of sea ice, classification results can be seen more easily to detect the change by types of sea ice. In this study, we classified the image by supervised classification method, which is minimum...
Article
Full-text available
Melt pond statistics (size and shape) have previously been retrieved from aerial photography and high-resolution visible satellite data. These submeter- or meter-resolution visible data can provide reasonably accurate information on melt ponds, but are greatly constrained by the limited solar illumination and frequent cloud cover in the Arctic regi...
Article
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To classify the landfast ice in the north of the Greenland, observation data, multifrequency Synthetic Aperture Radar (SAR) images and texture images were used. The total four types of sea ice are first year ice, highly deformed ice, ridge and moderately deformed ice. The texture images that were processed by K-means algorithm showed higher accurac...
Article
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In this paper, we have investigated the relationship between the depolarization effects and the wintertime sea ice thickness in the landfast ice region where smooth thick first-year ice (FYI) and deformed old ice coexisted by using C- and X-band spaceborne polarimetric synthetic aperture radar (SAR) data (RADARSAT-2 and TerraSAR-X). We have found a...
Article
We here simulated the distribution and variation of sea-ice in the Arctic Sea using an ice-coupled Ocean General Circulation Model (OGCM). The OGCM used in this study is the Regional Ocean Model System (ROMS) version 3.4, which is a three dimensional, s-coordinate, primitive equation ocean model with a free surface. The model area covers the region...
Conference Paper
Sea ice is an important component of the climate system affecting ocean-atmospheric interactions and global energy balance. The assessment of sea ice thickness using satellite and airborne laser altimetry is largely dependent upon isostatic buoyancy relationships between snow, ice, slush and ocean water. The use of these relationships in estimating...
Conference Paper
In this study we investigated the relationship between the depolarization effects and winter-time sea ice thickness in the landfast ice region where smooth first-year ice and deformed old ice co-existed, by using C- and X-band polarimetric satellite SAR data. Acquisitions of high-resolution SAR data with multiple satellite platforms (TerraSAR-X and...
Conference Paper
Full-text available
Due to its great extent in winter and retreat in summer, sea ice in the Southern Ocean has a great influence on regional and global energy balances. Satellite radar data provide high-resolution, all-time (day/night) and all-weather images of the mostly cloud-covered Southern Ocean. In this study, TerraSAR-X (TSX) dual-pol observations are analyzed...
Article
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In this study, detection of icebergs that have broken off from Wilkinson glacier in West Antarctica is carried out by extracting various polarimetric parameters from high resolution C-band fully polarimetric RADARSAT-2 SAR data. In the unsupervised H/A/alpha classification result, some of the icebergs (unclassified) in the SAR image with similar in...
Article
Full-text available
Variation of sea ice is one of the most evident indicators of climate change on our planet. Thinning of sea ice has been regarded as the major contributing factor that leads to the massive sea ice loss in Arctic sea. Direct measurement of sea ice can be made available by drilling a hole through the ice and/or by using Electromagnetic Induction syst...
Article
Full-text available
A study of the polarimetric backscattering response of newly formed sea ice types under a large assortment of surface coverage was conducted using a ship-based C-band polarimetric radar system. Polarimetric backscattering results and physical data for 40 stations during the fall freeze-up of 2003, 2006, and 2007 are presented. Analysis of the copol...
Conference Paper
In this study, we derived the relationship between target depolarization factor and physical parameters of sea ice in order to estimate the thickness using dual-polarization C-and X-band space-borne Synthetic Aperture Radar (SAR) data. The target depolarization factor, the cross-polarized ratio of C-band SAR data, which can explain the target depol...
Data
A study of the polarimetric backscattering response of newly formed sea ice types under a large assortment of surface coverage was conducted using a ship-based C-band polarimetric radar system. Polarimetric backscattering results and physical data for 40 stations during the fall freeze-up of 2003, 2006, and 2007 are presented. Analysis of the copol...
Article
The Arctic is in a state of change as the decrease in perennial multiyear sea ice pack gives way to the successive areal expansion of new annual sea ice. Young ice is much more saline and structurally different, meaning that significant differences in the behaviour across the ocean - sea ice - atmosphere (OSA) interface can be expected. In addition...
Article
Full-text available
This letter examines the performance of two Advanced Microwave Scanning Radiometer-EOS (AMSR-E) ice temperature algorithms over first-year sea ice during the spring transition period where ice concentrations are close to 100%. The results showed, before snow melt, that the old AMSR-E algorithm overestimated the ice temperature by up to 18 K, which...
Article
Full-text available
Changing extent, location, and motion of the Arctic perennial pack affect the annual evolution of seasonal ice zones. Canadian Ice Service digital ice charts covering the southern Beaufort Sea and Amundsen Gulf are used to illustrate summer and winter conditions and trends between 1980 and 2004 for several sea ice stages of development. Results ill...
Article
Full-text available
This study examines the impact of ice temperature on microwave emissivity over thin, newly formed sea ice at 6, 19, and 37 GHz during October 2003 in the southern Beaufort Sea, where the physical properties of newly formed sea ice were coincidently measured with microwave emissions. Six ice stations with distinct properties were selected and divide...
Thesis
Full-text available
The Arctic is regarded as a herald to global climate mainly because of strong interactions between the Arctic sea ice and the climate system. Understanding the roles of sea ice in the climate system is therefore critical in improving our knowledge of past and future climate changes on our planet. The primary objective of my dissertation is to inves...
Article
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In this study we examine the critical linkages between thermophysical properties and microwave emissions of landfast snow-covered first-year sea ice during spring melt. For this we analyzed the temporal evolution of radiation fluxes, electro-thermophysical properties and microwave emissions, and perform model simulations to evaluate the observation...
Conference Paper
Full-text available
Surface-scale passive microwave signatures of newly formed sea ice were collected using ship-based radiometers in the Southern Beaufort Sea and Amundsen Gulf between mid October and mid November 2003. Sea ice in the region was highly spatially and temporally variable. Over a heterogeneous area of open water and thin ice, polarization ratios showed...
Article
Full-text available
[1] This study examines the role of newly formed sea ice geophysical state on microwave emission. Coincident with sea ice geophysical sampling, ship-based passive microwave emission data (dual-polarized at 19, 37 and 85 GHz) were collected in the Cape Bathurst Polynya during 18 October and 13 November 2003. Using polarization ratios (PRs), we found...
Article
The physical, structural, and optical properties of newly formed ice types were studied in the Cape Bathurst polynya (71°N, 127°W) during fall freezeup in October to early November 2003. Variable meteorological conditions with occasional snowfall resulted in the formation of numerous ice types and surface conditions. Ice samples were collected from...
Article
Full-text available
A snow water equivalent (SWE) algorithm has been developed for thin and thick snow using both in situ microwave measurements and snow thermophysical properties, collected over landfast snow covered first-year sea ice during the Canadian Arctic Shelf Exchange Study (CASES) overwintering mission from December 2003 to May 2004. Results showed that the...
Article
This study examines the relationship between albedo and microwave emissions over thin newly formed Arctic sea ice using in-situ measurements collected 19 Oct - 13 Nov 2003 in the Cape Bathurst Polynya, southern Beaufort Sea. Regression analysis show that statistically significant relationships exist between the microwave polarization ratio (PR(19))...
Article
Observed reduction in recent sea ice areal extent and thickness has focused attention on the fact that the Arctic marine system appears to be responding to global-scale climate variability and change. Passive microwave remote-sensing data are the primary source underpinning these reports, yet problems remain in geophysical inversion of information...
Article
Among the regression-based algorithms for deriving SST from satellite measurements, regionally optimized algorithms normally perform better than the corresponding global algorithm. In this paper, three algorithms are considered for SST retrieval over the East Asia region (15°–55°N, 105°–170°E), including the multi-channel algorithm (MCSST), the qua...
Article
Full-text available
A new algorithm for the detection of fog/stratus over the ocean from the GMS-5 infrared (IR) channel data is presented. The new algorithm uses a clear-sky radiance composite map (CSCM) to compare the hourly observations of the IR radiance. The feasibility of the simple comparison is justified by the theoretical simulations of the fog effect on the...
Article
Full-text available
Since the satellites provide frequent and global observations of atmospheric and terrestrial environment, attempts have been made to use satellite data for long-term monitoring of land reflectances, vegetation indices and clouds properties. Although the construction and characteristics of spaceborne instruments may be quite similar, they are not id...
Article
Full-text available
The purpose of this study is to investigate the baroclinic response of the upper-layer of two-layered fluid when the lower-layer motion is driven by pumping an external fluid into the lower-layer or by pumping out the lower-layer fluid. Recent observations of the barotropic nature of deep water movements in the East Sea (fakematsu et al., 1994; KOR...

Projects

Project (1)
Project
The research investigates the relationships between the different ice types and snow or ice-surface properties and the radar backscatter response regarding their potential to improve satellite applications to sea ice characterization, particularly as backscatter evolves in correspondence with temperatures and changing surface conditions.