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Analysis of GOES data for the SOL2012-06-29T04:09 flare, class C4.6, shows a thermal character of the energy release for several minutes before the impulsive stage. Plasma heating to temperatures above 10 MK leads to the appearance of plasma jets along open field lines and in large loops. This work examines the relationship between the heated plasma and the flare structure and its dynamics, using observations in the X-ray, extreme ultraviolet (EUV), and radio-wave ranges. Particular attention is drawn to the detection of narrow-band fine temporal structures of radio emission before and after the impulsive stage of the flare in dynamic spectra. In the initial stage, broadband pulses in the decimeter range are observed which can be associated with the formation of thermal fronts in the jets. A series of super-bright drifting bursts in the centimeter range occurs after the end of the impulsive energy release in the flare kernel. Using data from the Siberian Solar Radio Telescope (5.7 GHz), we managed to localize the position of the source of the fine structure of drifting bursts at the remote footpoint of the large-scale flare loop.

Based on satellite-observed and reanalysis data, this study investigates a thermal front east of the Gulf of Thailand (TFEGT) during the winter from 1982 to 2021. TFEGT exhibits distinct seasonal and interannual variation, emerging in December, peaking in February, gradually diminishing in March, and completely dissipating in April. Notably, the occurrence probability, area, and intensity of the thermal front are significantly higher in January and February compared with December and March. Through the application of a mixed temperature equation, we identify that geostrophic advection, driven by windinduced western boundary current in the South China Sea (SCS), plays a crucial role in the formation of the TFEGT. In winter, the prevailing northeast monsoon propels the western boundary current through wind stress curl, causing the southward transport of cold water from north to south. This cold water encountered warm water within the Gulf of Thailand (GoT), leading to the formation of TFEGT. Furthermore, the interannual variation of TFEGT is closely associated with the El Niño-Southern Oscillation (ENSO). In El Niño (La Niña) years, the northeast monsoon weakens (enhances), resulting in a weaker (stronger) western boundary current, ultimately influencing the weakening (enhancement) of TFEGT. [ABSTRACT FROM AUTHOR]

Wintertime thermal front west of Luzon Island (WTFWLI) plays a vital role in local marine biogeochemical environment, geostrophic thermal advection of Luzon cold eddy (LCE) was once recognized as the causation of WTFWLI. However, current investigation based on multi‐source data revealed poor spatial correspondence between WTFWL and LCE over an interannual scale during 1993–2022, highlighting the necessity of revisiting the mechanism of WTFWLI. Our analysis shows that formation of WTFWLI was mainly caused by a northward warm tongue caused by geostrophic thermal advection of a northward current west of Luzon Island. The northward warm tongue encounters cold water west of Luzon Island and forms the WTFWLI at the boundary of cold and warm water. Our study provides a new explanation for the formation mechanism of WTFWLI, which will help deepen people's understanding of thermal front dynamics. Plain Language Summary: Wintertime thermal front west of Luzon Island (WTFWLI) plays an important role in sea‐air interaction and marine ecosystem, previous studies pointed out that the formation of WTFWLI was related with the Luzon cold eddy (LCE). Warm (cold) water was located in the southeast (northwest) part of the LCE due to geostrophic thermal advection, then leading to the formation of WTFWL at the boundary of cold and warm water. However, current investigation shows that there was poor spatial correspondence between WTFWLI and LCE in winter from 1993 to 2022, which is inconsistent with previous conclusions. Further analysis shows that formation of WTFWLI was mainly caused by a northward warm tongue caused by geostrophic thermal advection of a northward current west of Luzon Island. The northward warm tongue encounters cold water west of Luzon Island and forms the WTFWLI at their boundary. This study provides a new insight into the formation mechanism of WTFWLI, which will raise people's awareness of thermal front dynamics. Key Points: A new insight was provided into the formation mechanism of thermal front west of Luzon Island in winterThe thermal front west of Luzon Island was mainly caused by the encounter of a northward warm tongue and cold waterThe northward warm tongue was caused by a northward current west of Luzon Island [ABSTRACT FROM AUTHOR]

The thermal front in the oceanic system is believed to have a significant effect on biological activity. During an era of climate change, changes in heat regulation between the atmosphere and oceanic interior can alter the characteristics of this important feature. Using the simulation results of the 3D Regional Ocean Modelling System (ROMS), we identified the location of thermal fronts and determined their dynamic variability in the area between the southern Andaman Sea and northern Malacca Strait. The Single Image Edge Detection (SIED) algorithm was used to detect the thermal front from model-derived temperature. Results show that a thermal front occurred every year from 2002 to 2012 with the temperature gradient at the location of the front was 0.3 °C/km. Compared to the years affected by El Niño and negative Indian Ocean Dipole (IOD), the normal years (e.g., May 2003) show the presence of the thermal front at every selected depth (10, 25, 50, and 75 m), whereas El Niño and negative IOD during 2010 show the presence of the thermal front only at depth of 75 m due to greater warming, leading to the thermocline deepening and enhanced stratification. During May 2003, the thermal front was separated by cooler SST in the southern Andaman Sea and warmer SST in the northern Malacca Strait. The higher SST in the northern Malacca Strait was believed due to the besieged Malacca Strait, which trapped the heat and make it difficult to release while higher chlorophyll a in Malacca Strait is due to the freshwater conduit from nearby rivers (Klang, Langat, Perak, and Selangor). Furthermore, compared to the southern Andaman Sea, the chlorophyll a in the northern Malacca Strait is easier to reach the surface area due to the shallower thermocline, which allows nutrients in the area to reach the surface faster. [ABSTRACT FROM AUTHOR]

The accurate temperature and thermal front prediction in aquifer thermal energy storage systems during reinjection are crucial for optimal management and sustainable utilization. In this paper, a novel two-way fully coupled thermo–hydro model was developed to investigate the dynamic thermal performance and fronts for multiple aquifer thermal energy storage systems. The model was validated using a typical model, and the evolution characteristics of wellbore temperature before and after the breakthrough of the hydraulic front and thermal front were deeply studied. Sensitivity analysis was conducted to delineate the influence of various reservoir and reinjection factors on the thermal extraction temperature (TET). The results revealed that thermal conductivity significantly impacts the thermal extraction rate among the various reservoir factors. In contrast, volumetric heat capacity has the weakest influence and negatively correlates with the TET. Concerning the reinjection factors, the effect of the reinjection volume rate on the TET was significantly more significant than the reinjection temperature. Furthermore, the correlation between the TET and different properties was observed to be seriously affected by the exploitation period. The coupled model presented in this study offers insight into designing the exploitation scheme in deep reservoirs and geothermal resources. [ABSTRACT FROM AUTHOR]

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Using observational data from multiple satellites, we studied seasonal variations of the shape and location of the Luzon cold eddy (LCE) northwest of Luzon Island. The shape and location of the LCE have obvious seasonal variations. The LCE occurs, develops, and disappears from December to April of the next year. During this period, the shape of the LCE changed from a flat ellipse to a circular ellipse, and the change in shape can be reflected by the increase of the ellipticity of the LCE from 0.16 to 0.82. The latitude of center location of the LCE changes from 17.4°N to 19°N, and the change in latitude can reach 1.6°. Further study showed that seasonal variation of the northeast monsoon intensity leads to the change in the shape and location of the LCE. The seasonal variation of the LCE shape can significantly alter the spatial distribution of the thermal front and chlorophyll a northwest of the Luzon Island by geostrophic advection. [ABSTRACT FROM AUTHOR]

The Gerlache Strait is a narrow channel that separates the western coast of the Antarctic Peninsula (WAP) from the Palmer Archipelago. This area is characterized by the presence of interconnected fjords, bays, islands, and channels that serve as a refuge for megafauna during summer. Through the framework of FjordPhyto – a citizen science collaboration with the International Association of Antarctica Tour Operators (IAATO) vessels – we assessed phytoplankton biomass and composition in surface waters of six under-explored nearshore areas connected to the Gerlache Strait (between 64° and 65° S) during three consecutive seasons, from November to March (2016–2019). During the first two seasons, we found significant differences in the phytoplankton community distribution and successional patterns to the north and south of the sampling area; the greatest differences were evidenced mainly in the months of high biomass, December and January. During December, cryptophytes bloomed in the north, while microplanktonic diatoms dominated in the south, and during January, small centric diatoms dominated in the north, while prasinophytes bloomed in the south. This spatial distinction in phytoplankton communities were mainly associated with the occurrence of a surface thermal front in the Gerlache Strait around 64.5° S. The presence of the front separating warm waters to the north and colder waters to the south, during the months of December to February, was confirmed by the analysis of 10 years of remote sensing data. By contrast, during the third season, low biomass prevailed, and no differences in the phytoplankton composition between the north and south areas were observed. The third season was the coldest of the series, with smaller differences in water temperature north and south of the usual front location. This study shows for the first time a complete overview of the phytoplankton composition throughout the entire growth season (November through March) in the nearshore areas of the WAP between 64° and 65° S. The results of this work contribute to the understanding of the phytoplankton community in relation to small scale physical features during the Antarctic austral summer.

Coastal fronts play vital roles in local biogeochemical environment. An abrupt change of Zhejiang-Fujian coastal front (ZFCF) during early spring was well captured by multi-source satellite-retrieved sea surface temperature images. Here in this study, we investigated the mechanism of the abrupt decay with a combination of satellite observation and numerical simulation. Correlation analysis of long-term reanalysis data indicates that the variability of wind, heat flux and the Zhejiang-Fujian coastal current (ZFCC) have significant relationships with the variation of ZFCF in winter. Following heat budget analysis points out that net heat flux and horizontal advection are important in determining the net temperature tendency difference between two water masses of ZFCF during this process. To further explore the intrinsic physical roles of different dynamic factors, a comprehensive numerical investigation was conducted. Compared with the observations, the model reproduced the abrupt change process of the ZFCF satisfyingly. Sensitive experiments reveal that the weakening of the ZFCC, caused by the relaxation of the monsoon, contributes to the abrupt decay of ZFCF in the first half period, and heating effect of the Kuroshio Intrusion (KI) water gives rise to the following half period of the decay under the recovered monsoon. Further, with the impact of the KI water after the change, the ZFCF can be maintained even if the ZFCC is weak, whereas in January, the contribution of the KI water to the formation of the ZFCF seems to be limited under the prevailing monsoon. Besides, the riverine discharge and the tidal forcing can also modulate the spatiotemporal variation of ZFCF, the decrease of the river input also intensifies that decay, while tides fix the front at a specific depth.

In the spring of 2021, a large number of Salpa fusiformis suddenly appeared along the east coast of the Korean Peninsula and invaded a nuclear power plant (NPP) in large numbers. To understand the mechanisms and causes of the mass appearance and intrusion of S. fusiformis, field surveys were undertaken and collected observational data such as temperature, salinity, and ocean currents, and wind data were tabulated and analyzed. Field surveys in the offshore area of the NPP revealed that warm, saline, and less-oxygenated water flowed northward at approximately 25 km from the coastline, and that this water mass was that of the East Korean Warm Current (EKWC), with aggregated individuals (blastozooids) dominating the population of S. fusiformis. In the EKWC region, S. fusiformis were more abundant in the coastal area than in the center of the EKWC. Sea surface temperature and surface currents from satellite data showed that a thermal front was formed between the EKWC and the cold coastal waters off the NPP. The main path of the EKWC was close to the coast, and on days when S. fusiformis invaded the NPP in large numbers, the wind direction near the NPP was west-northwest. We suggest that large-scale invasions of the NPP by S. fusiformis can be predicted by incorporating appropriate field survey data into a particle tracking model that considers the direction and speed of the EKWC, the abundance of S. fusiformis in the EKWC, the location of thermal fronts, and wind direction and speed. [ABSTRACT FROM AUTHOR]

Thermal front has been widely used as a parameter for determining fishing zones. Tis study aimed to determine the thermal front distribution and to analyze its association with the Bali Sardinella fishing zones in the Bali Strait. Termal front generated using sea surface temperature (SST) from Aqua MODIS imagery. Meanwhile, the fishing point data of Bali Sardinella were collected to validate our analysis results. Te data were analyzed into Spatio-temporal information. Te main facts that stand out are that the thermal front was predominantly found in the peak of first (April) and second (September) transitional season, which was the peak season for the thermal front to occur in a year. Te least of the thermal front occurred in the South-west monsoon. Te linear relationship was found when the peak of thermal front occurrence compared to the number of catch yields. Based on matching distance analysis, the maximum distance used (twenty kilometres buffer) show 36 matching points from 101 data compared or at range 35.6%. In conclusion, there is a linear relationship between the thermal front parameter and catch yield. It is still used to predict the fishing zone, even though the correlation is not significantly found.

Ketersediaan informasi tentang informasi Potensi Penangkapan Ikan (PPI) sangat diperlukan untuk meningkatkan produktivitas perikanan. Secara tradisional, nelayan memanfaatkan indera dan kebiasaan turun-temurun mereka untuk menentukan PPI. Secara tradisional, nelayan memanfaatkan panca indra dan kebiasaan yang bersifat turun-temurun untuk menentukan PPI. Cara ini, selain kurang efisien, juga bisa menyebabkan ekploitasi berlebihan jika kegiatan penangkapan ikan dilakukan pada tempat yang sama secara terus-menerus. Keberadaan teknologi penginderaan jauh dapat dimanfaatkan untuk penentuan PPI secara lebih cepat dengan tetap memperhatikan aspek akurasi dan sebaran spasial. Salah satu metode penentuan PPI berbasis data penginderaan jauh, memetakan daerah thermal front terlebih dahulu sebelum menentukan PPI melalui interpretasi manual berdasarkan keberadaan piksel diantara suhu perairan yang hangat dan dingin. Interpretasi manual memiliki keterbatasan, diantaranya: tergantung pada manusia dan memerlukan waktu yang lama. Untuk mengatasi keterbatasan tersebut, dalam penelitian ini, metode Single Image Edge Detection (SIED) yang dikembangkan oleh Cayulla dan Cornillon diaplikasikan dalam bentuk toolbox agar bisa digunakan secara otomatis. Data Suhu Permukaan Laut (SPL) yang diperoleh dari MODIS Level 2 (6 April 2018) selanjutnya diproses dengan menggunakan toolbox ini dan berhasil mendeteksi 22 titik PPI di perairan selatan Pulau Jawa. Sementara itu, deteksi PPI dengan metode Temperature Gradient Analysis (TGA) yang dilakukan secara manual menghasilkan 28 titik. Terdapat 20 lokasi titik yang sama menggunakan dua metode ini. Penggunaan metode SIED berbasis toolbox dapat mempercepat pemrosesan data, mengurangi kesalahan manusia dengan tingkat akurasi 64%.

Makassar Strait has been identified as an area of interesting studies for marine science and operational fisheries. It provides the unique ocean structures such as topographic feature, the main path of the Indonesia Throughflow (ITF) and dynamics of thermal fronts. The aims of this study were to map the dynamic spatial and temporal of the thermal fronts, and to describe their implications to the pelagic fisheries. We used satellite data of sea surface temperature (SST) for the period of January-December 2018 with spatial and temporal resolutions of 4 km and monthly, respectively. For fishery data, we used sampling data of skipjack tuna fishing ground distributions in October and December 2018. Thermal fronts throughout the year were estimated using a Single Image Edge Detection (SIED) algorithm and the available fishing ground data were overlain on the SST front map. The results showed that the spatial distributions of thermal fronts along Makassar Strait tended to be different every month. However, the thermal fronts were consistently detected near the upwelling area from June to September. Skipjack tuna fishing grounds associated with fish aggregating devices (FADs) developed in the northern area of upwelling in October. Two month later, the FADs and free swimming skipjack fishing grounds again well formed around the same location. It implies that the formation of the thermal fronts after upwelling contributes the positive effect on development of pelagic fishery especially skipjack in Makassar Strait.

A new conceptual framework, based on ocean bio-physical observations from different satellites, has been proposed to track fishing ground parameters to identify Potential Fishing Zones (PFZ) in the Bay of Bengal (BoB). The proposed technique also attempts to provide a short-term forecast based on feature propagation, even under cloudy conditions. The current study has been carried out to understand the link between possible fish catch availability and satellite-derived parameters such as chlorophyll concentration, sea surface temperature, sea-level anomaly, ocean surface currents and wind vectors. Net Ekman transport obtained from the upfront and downfront components of the wind relative to the frontal direction provides valuable information on the forecast of PFZ regions and its possible shift. Comparison of the identified PFZs with limited in situ fish catch data proves that the suggested approach holds the promise in improved monitoring of possible fish catch locations. The study provides a novel approach for the monitoring and short-term forecasting of PFZ even for cloud-contaminated regions by using all possible ocean information from space-based platforms. [ABSTRACT FROM AUTHOR]

Thermal front has been widely used as a parameter for determining fishing zones. This study aimed to determine the thermal front distribution and to analyze its association with the Bali Sardinella fishing zones in the Bali Strait. Thermal front generated using sea surface temperature (SST) from Aqua MO DIS imagery. Meanwhile, the fishing point data of Bali Sardinella were collected to validate our analysis results. The data were analyzed into Spatio-temporal information. The main facts that stand out are that the thermal front was predominantly found in the peal( of first (April) and second (September) transitional season, which was the peak season for the thermal front to occur in a year. The least of the thermal front occurred in the South-west monsoon. The linear relationship was found when the peak of thermal front occurrence compared to the number of catch yields. Based on matching distance analysis, the maximum distance used (twenty kilometres buffer) show 36 matching points from 101 data compared or at range 35.6%. In conclusion, there is a linear relationship between the thermal front parameter and catch yield. It is still used to predict the fishing zone, even though the correlation is not significantly found. [ABSTRACT FROM AUTHOR]

The diurnal fluctuation of acoustic propagation in a cold dome region was studied by using the output of the high-resolution Finite Volume Coastal Ocean Model. The 3-D acoustic propagation in this region was studied first, and the results suggest that the diurnal fluctuation of the ocean environment results in the fluctuation of acoustic propagation. However, the variation pattern cannot be determined with only few outputs, and comprehensive analysis was needed. Then, a feature model for the thermal front on the edge of the cold dome was proposed. By analyzing the output of the ocean model, fluctuations were found to mainly occur in the two aspects of the feature model: first, horizontal excursion of the thermal front and second, vertical motion of the isothermal lines in the cold dome. The variation pattern of acoustic propagation over the two kinds of fluctuations was quantified. Results suggest that both kinds of fluctuations of model parameters result in great transmission loss (TL) variation in some cases. Typically, acoustic propagation with high frequency and deep source experience great influence from the fluctuations. The TL versus range usually experience influence from the fluctuations of the first kind from an approximately 40-km range and from the start for the second kind. The reason is that the vertical motion of the isothermal lines of the cold dome induces variation over the temperature profile from the start until the end, whereas the horizontal excursion of the thermal front brings influence mainly over the temperature profiles near the thermal front. [ABSTRACT FROM AUTHOR]

Heat fluxes in a district heating pipeline systems need to be controlled on the scale from minutes to an hour to adjust to evolving demand. There are two principal ways to control the heat flux - keep temperature fixed but adjust velocity of the carrier (typically water) or keep the velocity flow steady but then adjust temperature at the heat producing source (heat plant). We study the latter scenario, commonly used for operations in Russia and Nordic countries, and analyze dynamics of the heat front as it propagates through the system. Steady velocity flows in the district heating pipelines are typically turbulent and incompressible. Changes in the heat, on either consumption or production sides, lead to slow transients which last from tens of minutes to hours. We classify relevant physical phenomena in a single pipe, e.g. turbulent spread of the turbulent front. We then explain how to describe dynamics of temperature and heat flux evolution over a network efficiently and illustrate the network solution on a simple example involving one producer and one consumer of heat connected by "hot" and "cold" pipes. We conclude the manuscript motivating future research directions. • Advection-Diffusion-Loss of heat in district heating networks is analyzed. • Parameters of the basic model follow from turbulence phenomenology. • Superposition of running and spreading fronts forms a typical transient. • We suggest an efficient computational scheme to describe the transients. [ABSTRACT FROM AUTHOR]

Three seabed-mounted TD/CTD chains and two upward-looking acoustic Doppler current profilers (ADCPs) in the southwest of Zhangzi Island are used and a simultaneous cruise observation in the northern North Yellow Sea (NYS) is conducted to study temperature variation in the bottom thermal front zone of the NYS Cold Water Mass (NYSCWM) during the summer of 2009. In the flood-ebb tidal cycles, the bottom temperature decreases (increases) during flood (ebb) tides, which are dominated by the tidal-current induced horizontal advection. The ebb tide-induced temperature increase is larger than the flood tide-induced temperature decrease due to seasonal warming. In the spring-neap tidal cycles, the temperature and the vertical temperature structure show notable fortnightly variation from 16 July to 25 August. The bottom temperature increases from neap to spring tides and decreases from spring to neap. The Richardson number demonstrates strengthened vertical mixing during spring tides but enhanced stratification during neap tides. The spring-neap variation in vertical shear caused by tidal current is the dominant factor that induces the fortnightly variation in vertical mixing and thus bottom temperature. [ABSTRACT FROM AUTHOR]

• Segmented packed bed thermal energy storage is studied experimentally. • Axial pipe injections divide the bed domain into one, two, or three layers. • Thermal exergy efficiency increases with flow rate and number of layers. • At 0.0061 m3/s, the exergy efficiency goes from 55% to 80% from one to three layers. • Modeling results show thermal dispersion losses decrease with the number of layers. This paper presents the experimental results of thermal behavior in an air-alumina packed bed storage system using a new technique for charging/discharging processes. A normal packed bed system, 100 cm in length, is divided into layers via pipes inserted internally along the axial length of the bed. Alumina beads were used as solid storage material and air was used as the heat transfer fluid (HTF) with an inlet temperature of 150 °C. This study analyzes the thermal behavior for full charge/discharge processes by dividing the bed domain into layers, focusing on the thermal exergetic efficiency for different charging/discharging schemes. One, two, and three layer configurations are considered along with various schemes including duration and magnitude of mass flow to each layer. In the most efficient configuration, the thermal exergetic efficiency increases with the number of layers from 53.2% to 69.6% for 0.0048 m3/s and 55.4% to 73.4% for 0.0061 m3/s, from one layer to two layers. At these same flow rates, thermal exergetic efficiencies increase to 76.8% and 80.3% for three layers. To determine the contributions of axial thermal dispersion and heat losses, a numerical model was run for a full charge/discharge cycle in adiabatic and non-adiabatic cases. The model results show that the dispersive effect is reduced by 23.2% in the best two-layer case and 25.6% in the best three-layer case for 0.0048 m3/s and by 22.8% in the best two-layer case and 26.5% in the best three-layer case for 0.0061 m3/s, resulting in these gains in exergetic efficiency. [ABSTRACT FROM AUTHOR]

A calibrated, coupled model of the Bohai and Yellow Seas is developed to investigate sediment transport and deposition processes around a distinct clinoform east of the Shandong Peninsula. On the clinoform, deposition patterns vary seasonally with the regional hydrography and the East Asian Monsoon. A local maximum in sediment deposition is located offshore from spring to autumn, whereas sediment deposition is greater near the coast and decreases seaward in winter. From spring to autumn, a thermal front develops around the Yellow Sea Cold Water Mass and limits sediment transport seaward, enhancing sediment deposition and leading to high deposition rate in a focused region offshore. Sediment is transported to the region by the southward basin-scale cyclonic circulation, and the cross-shelf gradient in stratification, sediment resuspension, and vertical mixing at the front lead to a convergence in sediment transport and deposition. Sediment deposition over the clinoform is the greatest during the transition from summer to autumn when the thermal front persists but sediment supply increases. This results from weakened stratification and greater resuspension near the coast due to stronger winds, waves, and sea-surface cooling. A seasonal seaward shift of the frontal position toward deeper water is consistent with the decreasing heat flux, and the corresponding shift in location of maximum sediment deposition shifts seaward. In winter, the thermocline disappears and vertical mixing increases throughout the region. SSC over the clinoform increases due to active resuspension and net deposition decreases, and instead sediment is transported seaward and deposits in the South Yellow Sea. Current velocity, SSC and sediment deposition rates decrease seaward, in contrast to the focused trapping at the thermal front from spring to autumn. The deposition rates around the thermal front from spring to autumn are greater than in the winter, so the high net sediment accumulation over an annual cycle occurs in the same region as the longer-term accumulation preserved in the omega-shaped clinoform. • Sediment deposition rates are increased at a thermal front from spring to autumn at east of the Shandong Peninsula. • Seasonal shifts of the position of thermal front and sediment depo-center broaden the sediment accumulation region. • The monsoonal climate plays a dominant role in the seasonally varying circulation and sediment transport in the Yellow Sea. [ABSTRACT FROM AUTHOR]

Coastal and offshore waters are generally separated by a barrier or “ocean front” on the continental shelf. A basic question arises as to what the representative spatial scale across the front may be. To answer this question, we simply corrected skin sea surface temperatures (SSTs) estimated from Landsat 8 imagery with a resolution of 100 m using skin SSTs estimated from geostationary meteorological satellite Himawari 8 with a resolution of 2 km. We analyzed snapshot images of skin SSTs on 13 October 2016, when we performed a simultaneous ship survey. We focused in particular on submesoscale thermal fronts on the Pacific shelf off the southeastern coast of Hokkaido, Japan. The overall spatial distribution of skin SSTs was consistent between Landsat 8 and Himawari 8; however, the spatial distribution of horizontal gradients of skin SSTs differed greatly between the two datasets. Some parts of strong fronts on the order of 1 °C km−1 were underestimated with Himawari 8, mainly because of low resolution, whereas weak fronts on the order of 0.1 °C km−1 were obscured in the Landsat 8 imagery because the signal-to-noise ratios were low. The widths of the strong fronts were estimated to be 114–461 m via Landsat 8 imagery and 539–1050 m via in situ ship survey. The difference was probably attributable to the difference in measurement depth of the SST, i.e., about 10-μm skin layer by satellite and a few dozen centimeters below the sea surface by the in situ survey. Our results indicated that an ocean model with a grid size of no more than ≤100–200 m is essential for realistic simulation of the frontal structure on the shelf.

Abstract Fronts are ubiquitous phenomena in oceans, and they play a significant role in marine hydrodynamics and ecology. During the stratified season of a shelf sea, the coastal front is usually considered as a single front, i.e., the tidal mixing front. However, using high resolution (~1 km) Multi-scale Ultra-high Resolution (MUR) analysis sea surface temperature (SST) data, this study observes persistent double fronts along the Yellow Sea coast in summertime. The double fronts comprise the well-known offshore tidal mixing front and a nearshore front, and the nearshore front has not been previously reported. The climatological (2002–2017) monthly mean result shows that the double fronts with two SST gradient peaks exceeding ~2 °C/100 km and opposite SST gradient directions basically remain unchanged from June to August, whereas the frontal spacing decreases in September. Analyses based on a two-layer concept model suggest that a topographic slope along with tidal mixing could induce the pattern of double fronts. The frontogenesis of nearshore thermal front could be associated with the different responses of the water column of different water depths to insolation. The offshore movement of the nearshore front in September could be related to the fast cooling of nearshore water and intensified offshore wind, and the topographic slope is important for determining the pattern of double fronts (loose or tight). This study shows a new pattern of coastal fronts in the stratified season, and indicates the significance of high resolution satellite data. The discovery of the double front pattern implies the influence of coastal fronts during the stratified season on marine ecology and environment in a shelf sea might be underestimated. Highlights • SST double fronts in the Yellow Sea in the summertime were observed using high resolution (~1 km) satellite analysis data. • The double fronts consist of a nearshore front and an offshore tidal mixing front with opposite SST gradient directions. • A two-layer concept model suggests that a topographic slope along with tidal mixing could induce the double fronts. [ABSTRACT FROM AUTHOR]

The ear-shaped thermal front (ESTF), formed by the convergence of the Yellow Sea Warm Current (YSWC) and the Shandong Coastal Current (SCC), is a very important oceanic phenomenon in the Yellow Sea (YS) in winter. In situ measurements and reanalysis datasets all demonstrate that the ESTF has been weakening during 1950s-1990s, and a similar weakening trend is also found in winter monsoon over the YS. Numerical experiments show that the weakening of winter monsoon can induce an anomalous circulation in the YS on multi-decadal timescale with northward anomalous currents along China's coast and southward anomalous currents in the central YS-generally opposite to seasonal mean circulation. The anomalous circulation causes slowdown of the YSWC and the SCC, and thus weakens the ESTF. Since the ESTF plays important roles in regional ocean dynamics and air-sea interactions, its weakening has important implications for regional climate in the YS in winter. [ABSTRACT FROM AUTHOR]

An exact integral solution for transient temperature distribution, due to injection-production, in a heterogeneous porous confined geothermal reservoir, is presented in this paper. The heat transport processes taken into account are advection, longitudinal conduction and conduction to the confining rock layers due to the vertical temperature gradient. A quasi 2D heat transport equation in a semi-infinite porous media is solved using the Laplace transform. The internal heterogeneity of the geothermal reservoir is expressed by spatial variation of the flow velocity and the effective thermal conductivity of the medium. The model results predict the transient temperature distribution and thermal-front movement in a geothermal reservoir and the confining rocks. Another transient solution is also derived, assuming that longitudinal conduction in the geothermal aquifer is negligible. Steady-state solutions are presented, which determine the maximum penetration of the cold water thermal front into the geothermal aquifer.

Oceanic fronts play an important role in ocean dynamics and ecology systems. The ear-shape front (ESF), first detected in the1980s, is a winter thermal front to the east of the Shandong Peninsula in the Yellow Sea. Using high-resolution satellite observation and ocean reanalysis data, we investigated the interannual variation in ESF and underlying dynamics during 2006–2020. The results indicate that ESF shows a strengthening trend of approximately 0.1–0.5 °C/100 km/year, accompanying the temperature on its eastern side. This was caused by the westward shift and enhancement of the Yellow Sea Warm Current (YSWC) through transporting more warm water to the eastern side of the ESF. Further analyses indicate that changes in the YSWC resulted from the decrease in wind stress divergence. Decreasing wind stress divergence induced increasing sea surface height (SSH) anomalies in the central Yellow Sea. The resultant positive SSH anomalies generated an anti-cyclonic gyre anomaly via geostrophic effects, which led to the westward shift and enhancement of the YSWC on the eastern side of the ESF. • Winter ear-shape front east of the Shandong Peninsula increased during 2006–2020. • Increase in front was caused by the westward shift and enhancement of the YSWC. • Decreasing wind stress divergence induced an anti-cyclonic gyre anomaly in central YS. [ABSTRACT FROM AUTHOR]

Infrared and microwave satellite images used for sea-surface temperature (SST) retrieval often have distortions such as noise and blurring of thermal front lines that decrease the quality of SST charts. In order to solve this problem, it is proposed to use an approach based on the Mumford-Shah model that approximates an image with a piecewise smooth function. In order to combine the advantages of the proposed approach and conventional methods for noise filtering and image restoration it is proposed to divide images into flat and frontal zones and process them separately. The SST quality is enhanced by the use of edge-preserving noise filtering and restoration algorithms. The latter use the features of radiometers and different stages of the SST construction procedure to improve their accuracy. The images obtained using the MTSAT/VISSR, METEOR-M/MSU-MR, and AQUA/AMSR-E radiometers are used for testing the developed approach. [ABSTRACT FROM AUTHOR]

Surveys carried out in the 1980s showed that 8,000-10,000 Balearic shearwaters regularly gathered in inshore waters of central and northern Biscay, particularly off the coast of Vendée and in the Mor-Braz area, western France. This distribution, apparently linked to particular oceanographical conditions (thermal front), was strikingly overlapping with that of clupeid fish, particularly anchovies. Recent surveys (1999-2000) have shown that the species has become far less numerous in these "traditional" haunts. Conversely, its abundance has increased in the western Channel, some hundreds of kilometres to the North, during the 1990s. Reasons for this northward shift (e.g. changes in prey distribution due to fishing activities or water warming in Biscay) remain hypothetical and further study is needed.

Hot brine injection is one of the most effective dissociation methods of natural gas hydrate, and the movement of thermal front is a key parameter to evaluate the production performance by hot brine injection. Based on the principle of energy conservation, a mathematical model for thermal front movement of gas hydrate dissociation by hot brine injection is developed, which is derived through Laplace transform. In addition, an experimental study on the movement of thermal front is conducted with a self-designed 1D natural gas hydrate dissociation apparatus. The thermal front movement of the experiment is compared with that calculated from the mathematical model established in this paper as well as other two models proposed by Selim and Sloan (1990) and Tang et al. (2006), respectively. It turns out that what fits better with the experimental data is the energy conservation model, which includes the effect of heat used to warm the dissociated reservoir, heat absorption by hydrate dissociation and heat loss to the cap and base sediments. Therefore, this energy conservation model is an effective method to analyze the thermal front of gas hydrate dissociation by hot brine injection. [ABSTRACT FROM PUBLISHER]

Interannual variability of thermal front west of Luzon Island during the winter of 1993-2013 is examined with the method of singular value decomposition (SVD) and a suite of satellite measurements in this paper. It is found that both the area and intensity of the thermal front west of Luzon Island show apparent interannual variability. Further study based on SVD shows that the interannual variability of the thermal front is highly associated with El Niño and Southern Oscillation (ENSO), and the correlation coefficient between Niño3.4 index and the first Principal Component (PC1) of thermal front can reach-0.65. The mechanism can be described as follows. In El Niño (La Niña) years, the East Asian winter monsoon (EAWM) is weakened (enhanced), inducing weaker (stronger) local wind stress curl (WSC) west of Luzon Island, and resulting in weakened (enhanced) Luzon cold eddy, which finally leads to the weakening (enhancement) of the thermal front. [ABSTRACT FROM AUTHOR]

A numerical study on the effect of complex fracture aperture geometry on propagation of thermal front in a coupled single fracture-matrix system has been carried out. Sinusoidal and logarithmic functions have been used to capture the variation in fracture aperture. Modifications have been made to existing coupled partial differential governing equations to consider the variation of fracture aperture. Effect of temperature on the thermal and physical properties of rock have been incorporated. A fully implicit finite difference scheme has been used to discretize the coupled governing equations. Thermal convection, dispersion and conduction are the major transport processes within fracture, while conduction is the major transport process within rock matrix. The results suggest that variation of fracture aperture increases the heat transfer rate at the fracture-matrix interface. Sensitivity analysis on rock thermal conductivity and fracture aperture have been carried out. The results suggest that the heat transfer from rock matrix to fracture for the case of the parallel plate model is greatly dependent on the rock thermal conductivity ( λ) as compared to variable aperture model. Further, the thermal front propagation for both parallel plate model and variable aperture model is sensitive to changes in fracture aperture. The heat transfer rate at the interface is greater at smaller fracture apertures and decreases with increase in aperture. [ABSTRACT FROM AUTHOR]