Heat Advection Research Articles

Eastward propagation of mid-latitude near-surface thermohaline anomaly and link to marine heat waves in the eastern North Pacific

Eastward propagations of near-surface and isopycnal thermohaline disturbances at 25.5–26.3σθ with a zonal speed of in-situ geostrophic current were observed in the mid-latitude (40–50° N) North Pacific and were linked to the marine heat wave (MHW) ‘The Blob’ in the Gulf of Alaska (GOA: 150–130° W and 40–50° N). Isopycnal depth anomalies were formed corresponding to wind-stress curl anomalies and propagated eastward. A warm and low-salinity disturbance was formed in the central Pacific in 2011–2012 under the negative maximum of Pacific Decadal Oscillation (PDO). This warm, low-salinity and low-density disturbance propagated eastward and was warmed by heating anomaly of surface heat flux, reduced entrainment and northward heat advection in 2013 due to the weakened westerly wind. The disturbance propagated further eastward and reached the GOA in early 2014. During the 2014–2015 MHW, heating by reduced entrainment and horizontal heat advection maintained the MHW, even though surface heat flux worked as cooling anomaly. The reduced entrainment was caused by the enhanced density stratification of the warm and low-density surface water, together with the entrainment of warm-saline subsurface water which was formed in 2013 in the area west of the GOA and subducted and propagated eastward as subsurface isopycnal warm-saline anomaly. Pycnocline heaving due to wind-induced upwelling corresponding to the strengthened Aleutian Low Pressure under the 2014–2015 El-Niño contributed to the stratification enhancement. The heating of the horizontal heat advection was due to weakened westerly wind on the northern side of strengthened and southward-shifted Aleutian Low Pressure under the El-Niño and positive PDO.

Linking Radiative‐Advective Equilibrium Regime Transition to Arctic Amplification

AbstractEmission of anthropogenic greenhouse gases has resulted in greater Arctic warming compared to global warming, known as Arctic amplification (AA). From an energy‐balance perspective, the current Arctic climate is in radiative‐advective equilibrium (RAE) regime, in which radiative cooling is balanced by advective heat flux convergence. Exploiting a suite of climate model simulations with varying carbon dioxide () concentrations, we link the northern high‐latitude regime variation and transition to AA. The dominance of RAE regime in northern high‐latitudes under reduction relates to stronger AA, whereas the RAE regime transition to non‐RAE regime under increase corresponds to a weaker AA. Examinations on the spatial and seasonal structures reveal that lapse‐rate and sea‐ice processes are crucial mechanisms. Our findings suggest that if concentration continues to rise, the Arctic could transition into a non‐RAE regime accompanied with a weaker AA.

High‐Resolution Analysis of Severe Heat Wave Dynamics and Thermal Discomfort Across India

ABSTRACTThe study explores variability and dynamical characteristics of heatwaves during March–June for 1990–2020 over India. Normalised Tmax anomaly is used to identify different heatwave spells in vulnerable regions of North‐central India (NCI) and Southeast coast of India (SECI) using India Meteorological Department (IMD, 1° × 1° resolution) observations, Indian Monsoon Data Assimilation and Analysis (IMDAA, 0.12° × 0.12°), and ECMWF Reanalysis v5 (ERA5, 0.25° × 0.25°). Results highlight that IMDAA exhibited a total 202 days (181 days) heatwaves duration in NCI (SECI) regions while ERA5 exhibited a total 132 days (89 days), respectively, compared with those of IMD (195 and 163 days). The primary heatwave periods for NCI (10 April to 20 June) and SECI region (1 May to 10 June) are well captured by IMDAA, unlike ERA5. The average length of the heatwave is 7.8, 7.5, and 7.76 days (8.15, 7.72, and 6.1 days) over NCI (SECI) in IMD, IMDAA, and ERA5, respectively. The high heat stress is more frequent in SECI than in the NCI region and is common during May–June (May only), as seen in IMDAA (ERA5). The middle to upper‐level anticyclone over NCI is stronger than SECI during heatwaves. Heat advection with stronger 850‐hPa north‐westerlies (~10 ms−1) abates sea breeze in the coastal region, aiding longer heatwaves in the SECI region. Ascending motion induced by surface heating is confined to the lower levels due to the subsidence by the upper‐level anomalous anticyclone, stagnating higher temperatures in the lower atmosphere, depicting a heat dome. The surface temperatures are slightly higher in NCI (31°C–39°C) than in SECI (30°C–37°C). However, the double moist heat dome in SECI has witnessed higher heat stress conditions than NCI. Higher relative humidity in the SECI region is contributed by maritime winds from the Bay of Bengal and Arabian Sea, soil moisture, and so forth. The study highlights the value of atmospheric moisture in differentiating the study regions for heat stress conditions.

Interactions between megathrust behavior and forearc deformation in the Andreanof segment of the Aleutian Subduction Zone, offshore Alaska, USA

To explore controls on megathrust behavior and its connection with forearc deformation, we studied the Andreanof segment of the Aleutian Subduction Zone (offshore Alaska, USA), which has a simple geological history as a relatively young intra-oceanic subduction zone. Here, the forearc shows greater uplift and compression in the strongly coupled Adak region compared to the weakly coupled Atka region. Using multichannel seismic reflection data, we found that the incoming plate in both regions exhibits similar characteristics along the segment, suggesting that its properties do not account for the varying megathrust behavior and forearc deformation. Instead, differences between the Atka and Adak regions in the thickness of the methane hydrate stability zone, as marked by a bottom-simulating reflector, suggest more heat advection, and thus dewatering, in the Adak region, where the more developed fault network may enable fluid drainage, thereby lowering pore pressure at the megathrust and promoting coupling. Higher coupling allows for seismic and stress cycling that would sustain forearc permeability by faulting. Our results suggest a feedback between deformation and coupling that may be active or latent in other more complex subduction zones but in concert with or masked by other factors.

A New Capillary and Adsorption‒Force Model Predicting Hydraulic Conductivity of Soil During Freeze‒thaw Processes

AbstractUnderstanding the change in soil hydraulic conductivity with temperature is key to predicting groundwater flow and solute transport in cold regions. The most commonly used models for hydraulic conductivity during freeze‒thaw cycles only consider the flow of capillary water in the soil and neglect water flowing along thin films around the particle surface. This paper proposed a new hydraulic conductivity model of frozen soil via the Clausius–Clapeyron equation based on an unsaturated soil hydraulic conductivity model over the entire moisture range using an analogy between freeze‒thaw and dry‒wet processes in soils. The new model used a single equation to describe the conductivity behaviors resulting from both capillary and adsorption forces, thus accounting for the effect of both capillary water and thin liquid film around soil. By comparison with other existing models, the results demonstrated that the new model is applicable to various types of soils and that the predicted hydraulic conductivity is in the highest agreement with the observed data, while reducing the root mean square error by 38.9% compared to the van Genuchten–Mualem model. Finally, our new model was validated with thermal–hydrological benchmark problem and laboratory experiment result. The benchmark results indicated that the advective heat transfer was more significant, and the phase change was completed earlier when considering both capillary and adsorption forces than when only considering capillary forces. Furthermore, the coupled flow–heat model with the new hydraulic conductivity expression replicated well the results from a laboratory column experiment.

Physics-based numerical evaluation of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) in the Upper Jurassic reservoir of the German Molasse Basin

Abstract. Concepts of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) (> 50 °C) are investigated in this study for system application in the Upper Jurassic reservoir (Malm aquifer) of the German Molasse Basin (North Alpine Foreland Basin). The karstified and fractured carbonate rocks exhibit favourable conditions for conventional geothermal exploitation of the hydrothermal resource. Here, we perform a physics-based numerical analysis to further assess the sustainability of HT-ATES development in the Upper Jurassic reservoir. With an estimated heating capacity of approx. 19.5 MW over half a year, our approach aims at determining numerically the efficiency of heat storage under the in situ Upper Jurassic reservoir conditions and projected operation parameters. In addition, the hydraulic performance of the HT-ATES system is further evaluated in terms of productivity and injectivity index. The numerical models build upon datasets from three operating geothermal sites at depths of approx. 2000–3000 m TVD, located in a subset of the reservoir dominated by karst-controlled fluid fluxes. Commonly considered as a single homogeneous unit, the 500 m thick reservoir is subdivided into three discrete layers based on field tests and borehole logs from the three considered sites. The introduced vertical heterogeneity with associated layer-specific enhanced permeabilities allows to examine potentially arising favourable heat transfer, and in combination with the facilitated high operation flow rates (100 kg s−1) to evaluate thermal recoveries in the multilayered reservoir. All simulations account for fluid density and viscosity variation based on thermodynamically consistent equations of state (EOS). Computation results reveal that the reservoir layering induces preferential fluid and heat migration primarily into the high-permeability zone, while thermal front propagation into the lower permeable rock matrix is inhibited. The simulations further display a gradual temperature increase in the warm wellbore and its surrounding host rock, and a consequent progressive improvement in the heat recovery efficiency. Despite the elevated permeability that may trigger advective heat losses, heat recovery factor values range from approx. 0.7 over the first year of operation to over 0.85 after 10 years of operation. An additional scenario is examined with fluid injection solely in the high permeable zone, in order to quantify potential enhancement in the recovery efficiency by omitting fluid injection in the lower-permeability layers where heat propagation is diminished. This is due to the geometrical shape of the thermally perturbed rock volume as heat losses occur during thermal equilibration between injected fluid and reservoir rock, as well as at the contact-surface area between propagating thermal front and adjacent rock matrix. Results suggest that under the stratified reservoir configuration, additionally constrained by the selected spatial distribution of rock properties, heat storage performed only into the upper high-permeability zone corresponds to an improved thermal performance. Simulation results further indicate that density-induced buoyant fluxes, which would considerably decrease thermal efficiencies are inhibited in the system, and the prevailing heat transport mechanism is forced convection.

Vertical Structures of Marine Heatwaves in the South China Sea: Characteristics, Drivers and Impacts on Chlorophyll Concentration

AbstractMarine heatwaves (MHWs) are characterized as extreme ocean warming events, which have multifaceted impacts on marine ecosystems. The warming of the ocean associated with MHWs can extend into the deep ocean. In the study, five main types of MHWs in the South China Sea (SCS) are identified with various vertical structures, including shallow, surface‐extension‐reversed, surface‐extension‐intensified, deep, and surface‐extension‐intensified‐reversed. Different types of MHWs have different spread patterns and depths. Shallow and surface‐extension‐reversed MHWs are common in coastal areas, and surface‐extension‐intensified MHW events often occur in deep areas. The vertical structures of MHWs are affected by ocean dynamical processes, particularly vertical processes and horizontal heat advection. These MHWs can alter ocean chlorophyll concentration to varying degrees and locations, contingent on their vertical thermal profiles. Furthermore, an analysis of the impacts of a long‐lived MHW event in the SCS in 2020 revealed that the MHWs could alter chlorophyll concentration. These results help to better understand the physical drivers of localized MHWs and their potential impacts in the context of climate change.

Two distinct interannual modes of the north pacific oscillation: role of ocean-atmosphere coupling and transient eddies

The interannual variability of the North Pacific Oscillation (NPO) in boreal winter displayed a significant interdecadal shift, characterized by a local north-south seesaw pattern before the mid-1980s but a global-scale wave-train pattern afterwards, and the dynamic nature associated with these two distinct interannual modes remains unexplored. An analysis with the geopotential tendency equation shows the distinct roles of ocean-atmospheric coupling and transient eddies in modulating the two modes. The local north-south seesaw mode before the mid-1980s was dominated by high-frequency eddies, vorticity advection, and diabatic heating. The high-frequency eddies were conducive to moisture convergence in the low-level cyclonic mean flow and further led to intensification of precipitation process. The anomalous surface heat flux forced by the cyclonic mean flow strengthened the meridional temperature gradient and thus atmospheric baroclinicity in the subtropics, which in turn induced more active high-frequency eddies and maintained the NPO structure. After the mid-1980s, the local diabatic heating response and high-frequency eddy activities associated with the global-scale wave-train mode became weaker whereas the upstream anomalies were significant. Low-frequency eddies provided most of momentum flux through zonal-eddy coupling and primarily contributed to the zonal distribution of the NPO-related circulation anomalies across Eurasia and the Arctic.

Clouds in Partial Atmospheres of Lava Planets and Where to Find Them

With dayside temperatures hot enough to sustain a magma ocean and a silicate atmosphere, lava planets are the best targets for studying the atmosphere of a rocky world. In the absence of nightside heating, the entire atmosphere collapses near the day–night terminator, so condensation seems inevitable, but the impact of clouds on radiative transfer, dynamics, and observables has not yet been studied in the nonglobal atmospheric regime. Therefore, we simulate cloud formation and determine which lava planets should be most affected by clouds. We find that despite the scattering of visible light by clouds, heat advection compensates for the cooling effect of clouds in the atmosphere. On the other hand, surface temperatures are significantly affected and can drop by 100–200 K under a cloudy sky. We find that among our targets, HD213885b and HD20329b are most affected by cloud formation: there is a discernible difference between having clouds and not having them, but the precision required to make such an inference is at the limit of current instruments.

Dynamics of a severe summer Shamal wind and its induced dust storm in the Middle East: A diagnostic study based on numerical simulation

This study investigates the formation and dynamics of the Summer Shamal Wind (SSW) and its associated dust storms over the Middle East. A regional climate model, RegCM4, coupled with a dust module, is employed to simulate a severe dust storm event on June 12, 2006. To gain deeper insights, a novel dynamical mechanism is proposed. This mechanism highlights the crucial role of both mechanical and thermal forcing in shaping the regional atmospheric circulation. The vertical heat advection from the Zagros Mountains (ZAG), combined with the mechanical forcing from a shallow incident flow originating from the Turkmenistan anticyclone, triggers upward motion over the ZAG. This synergistic effect leads to the development of a mid-tropospheric anticyclone over the ZAG, which, in turn, induces a westward-propagating Rossby wave. The downward motion and descending air associated with this wave over Mesopotamia establish a terrain-induced local circulation. Consequently, the SSW emerges within a shallow layer at the null-vorticity zone of a coupling-pressure pattern formed by the Arabian anticyclone and the Zagros trough, which is itself a product of the terrain-induced circulation. The study concludes that the intensification and southward movement of the Turkmenistan anticyclone play a pivotal role in the formation of severe SSWs and subsequent dust storms over the Middle East.

Evolution and Drivers of Extreme Subsurface Marine Heatwaves in the Western Tropical Pacific Ocean during 2008 and 2010–11

Abstract Marine heatwaves (MHWs) have adverse impacts on marine ecosystems and fisheries, yet extreme MHWs in the western tropical Pacific Ocean remain largely unexplored. Here, we investigate the evolution and drivers of the two strongest subsurface MHWs in the western tropical Pacific Ocean on record, in 2008 (MHW-08) and 2010–11 (MHW-11). The two events have similar evolutions, as they were both initiated and developed locally in tropical regions during their onset phase and gradually dissipated with multiple cores during the decay phase. We examined the physical processes during the evolution of MHW-08 and MHW-11 and performed a heat budget analysis for the subsurface layer in each case. We find that the onset of both events were mainly controlled by convergence and vertical heat advection due to anomalous Ekman downwelling, while the decay of both events was mainly controlled by horizontal heat advection due to anomalous horizontal currents and withdrawal of anomalous convergence. The relationship between the subsurface MHWs and El Niño–Southern Oscillation is discussed. We suggest that the anomalous heat advections plus the La Niña–related background warming lead to the extreme subsurface MHW events. Our findings may have important implications for environmental change and marine life in the western tropical Pacific Ocean.

PICL: Physics informed contrastive learning for partial differential equations

Neural operators have recently grown in popularity as Partial Differential Equation (PDE) surrogate models. Learning solution functionals, rather than functions, has proven to be a powerful approach to calculate fast, accurate solutions to complex PDEs. While much work has been performed evaluating neural operator performance on a wide variety of surrogate modeling tasks, these works normally evaluate performance on a single equation at a time. In this work, we develop a novel contrastive pretraining framework utilizing generalized contrastive loss that improves neural operator generalization across multiple governing equations simultaneously. Governing equation coefficients are used to measure ground-truth similarity between systems. A combination of physics-informed system evolution and latent-space model output is anchored to input data and used in our distance function. We find that physics-informed contrastive pretraining improves accuracy for the Fourier neural operator in fixed-future and autoregressive rollout tasks for the 1D and 2D heat, Burgers’, and linear advection equations.

Impact of fluvial meander-belt sedimentary heterogeneity on the efficiency of low-enthalpy geothermal doublets: heat-transport simulations of forward stratigraphic models

In the present study, different geocellular models of meander-belt stratigraphic architectures were produced that are representative of the sedimentary products of sand-bed meandering rivers and their petrophysical heterogeneity. The static models were created combining a rule-based stratigraphic modelling approach with geostatistical modelling, and were applied in groundwater-flow and heat-transport simulations using MODFLOW-2005 and MT3D-USGS. Overall, histories of injected cold-water plume propagation were examined considering (i) three architectural frameworks as representative of different river morphodynamics, (ii) four scenarios of facies architecture, and (iii) alternative well layouts. The presence, size and spatial distribution of sedimentary heterogeneities related to river hydrodynamics, channel-form abandonment, or to modes of meander-transformation are seen to control the shape of the thermal plume, thereby affecting well-doublet performance. The considered scenarios of facies make-up for point-bar deposits have a modest influence on temperature decline near the abstraction well. The presence of sandstone beds in the lower heterolithic parts of abandoned-channel fill does not facilitate significant thermal-plume expansion beyond mud-plug. The effect of basal lags made of open-framework conglomerates on heat advection depends on their geometry, but is effectively negligible when it makes up less than 1% of deposits. Relatively thin mud drapes lying on point-bar accretion surfaces are seen to act as baffles to flow, but their impact is minimal in view of their small number. The study provides useful and novel insight on the potential impact of sedimentary heterogeneity in fluvial reservoirs, which can be applied to the design of well doublets, and highlights areas deserving further investigations.

Compound Tropical Cyclone Heat (TC‐Heat) Hazard in Hong Kong: Amplifying Urban Heat Extremes With Storm Position‐Driven Peripheral Warming and Urban Footprint

AbstractCompound hazards involving tropical cyclones and extreme heat (“TC‐heat”) have rarely been examined in prior research. Peripheral subsidence associated with cyclones can warm an area to varying degrees, depending on the cyclone's strength and position. Meanwhile, the peripheral airflow also overwhelmed the land‐sea breeze circulation system in coastal cities and favored downwind urbanized heat advection on the Southern China coastline. Here, we systematically applied ERA5 global reanalysis data, local surface‐level observations, MODIS‐based land‐cover data and HYSPLIT backward trajectories to evaluate how the position of distant TCs may divert the monsoon system and foster the surface heat advection from upwind urban agglomerate amplifying air temperature in downwind coastline. The analysis suggests when a distant TC is situated in a favorable area (the vicinity of Taiwan and Luzon Strait) at roughly 500–1,250 km to the east of Hong Kong, it forms a unique meteorological condition which allows the surface heat transport from the Greater Bay Area to Hong Kong, reflecting that regional build‐up of heat could be an important mechanism for producing local heat extremes.

Out of the Darkness: High-resolution Detection of CO Absorption on the Nightside of WASP-33b

We observed the ultrahot Jupiter WASP-33b with the SpectroPolarimètre InfraRouge on the Canada–France–Hawaii Telescope. Previous observations of the dayside of WASP-33b show evidence of CO and Fe emission indicative of a thermal inversion. We observed its nightside over five Earth nights to search for spectral signatures of CO in the planet’s thermal emission. Our three pretransit observations and two posttransit observations are sensitive to regions near the morning or evening terminators, respectively. From spectral retrievals, we detect CO molecular absorption in the planet’s emission spectrum after transit at ∼6.6σ. This is the strongest ground-based detection of nightside thermal emission from an exoplanet and only the third ever. CO appearing in absorption suggests that the nightside near the evening terminator does not have a temperature inversion; this makes sense if the dayside inversion is driven by absorption of stellar radiation. On the contrary, we do not detect CO from the morning terminator. This may be consistent with heat advection by an eastward jet. Phase-resolved high-resolution spectroscopy offers an economical alternative to space-based full-orbit spectroscopic phase curves for studying the vertical and horizontal atmospheric temperature profiles of short-period exoplanets.

Hydrography of the Inner Basins in Hornsund (Svalbard): Heat Advection Near Tidewater Glaciers

AbstractAtlantic‐type hydrography is becoming more dominant in the Svalbard fjords. Advected warm waters affect sea‐ice formation and melting rates of tidewater glaciers. Therefore, it is important to study hydrographic variability in fjords. Here, we use hydrographic data from Hornsund fjord to investigate the presence of warm water masses close to tidewater glaciers. Data span from May to October of 2015–2023 and cover several inner basins: Brepollen, Samarinvågen, Burgerbukta West, and Burgerbukta East, in addition to the main fjord. Average temperatures above 2C are observed during August–October in the surface–50 m layer of all the inner basins, and during September–October in the 50 m–bottom layer of all the inner basins except Burgerbukta East. The surface–50 m layer of both Burgerbukta basins is colder and fresher compared to Brepollen, despite Burgerbukta basins being closer to the fjord mouth. These spatial differences likely arise from counter‐clockwise currents that advect warm and saline shelf waters to Brepollen along the southern side of the fjord, and relatively cold and fresh mixed shelf‐fjord waters to Burgerbukta as they exit along the northern side of the fjord. Burgerbukta East is the coldest and freshest inner basin. The differences between the two Burgerbukta basins suggest a strong influence of underwater sills and site‐specific environmental processes such as glacier ablation and local circulation on the water properties. Observed differences in the water temperatures of these closely‐spaced inner basins match the spatial variability in the glacier retreat rates, and indicate the importance of ocean forcing for the ice mass loss.

The Relative Importance of Ocean Advection and Surface Heat Fluxes During the Madden–Julian Oscillation in a Coupled Ocean–Atmosphere Model

AbstractIntraseasonal variability of ocean surface mixed layer temperature (MLT) in the tropics can be linked to the Madden–Julian Oscillation (MJO), the main source of intraseasonal atmospheric variability in the tropics. Here, we conduct a boreal winter mixed layer heat budget using 10‐day forecast composites of a coupled ocean–atmosphere Numerical Weather Prediction model of the UK Met Office to reveal that ocean advection plays a major role in modulating intraseasonal anomalies of MLT over the tropical Indian Ocean and the Maritime Continent. Large scale ( 10) intraseasonal anomalies of MLT ( 0.1 C) are driven by net surface heat flux. Ocean advection dominates at smaller horizontal scales ( 1), contributing up to 0.5 C to the intraseasonal MLT anomaly. Prior to the development of the enhanced MJO convection in the western Indian Ocean (phases 8 and 1), ocean advection reinforces the net heat flux warming in this region. However, ocean advection opposes the net heat flux warming in the Maritime Continent prior to the development of suppressed MJO convection in this region. When the MJO convection develops over the central Indian Ocean (phase 3), ocean advection (net surface heat flux) drives the intraseasonal MLT anomalies in the western Indian Ocean (central Indian Ocean and the Maritime Continent). Our results demonstrate the importance of ocean dynamics during the initiation and growth of the MJO, and raise implications for models that do not resolve these processes.

Varying free-gas zone (FGZ) and bottom-simulating reflection (BSR) response across a deep graben off Trujillo, central Peru

The complexity of marine gas hydrate systems at the Peruvian convergent margin has been linked to the post-Miocene history of vertical tectonics and subduction erosion that affected the forearc. Here, multichannel seismic data and published findings reveal that such a complexity has been further extended by the occurrence of the pre-Miocene deep Morsa Norte Graben (MNG) off Trujillo (8°–9° S) in the Central Peru margin. At water depths of 650–750 m in the upper slope, directly above the MNG depocentre (which has a 4–6 km overburden thickness), continuous bottom-simulating reflections (BSRs) and concentrated sub-BSR high-amplitude reflections are confined beneath a layered basin with a low–moderate near-seafloor heat flow (7–33 mW m −2 ). A deeper BSR modelled with a thermogenic gas composition is associated with the enhanced reflections. At a water depth of 900 m, sub-BSR reflections become less frequent in an area with a layered sediment cover defined by a moderate near-seafloor heat flow (15–33 mW m −2 ). At a water depth of 1200 m, where the MNG is relatively thick (3–4 km overburden thickness), faults connect patchy BSRs with a moderate–high near-seafloor heat flow (52–110 mW m −2 ). There, sub-BSR enhanced reflections are scarce. Immediately above the top of the gas hydrate stability zone (GHSZ), the near-seafloor heat flow reaches 81 mW m −2 . Modelling suggests a water depth-dependent transport of heat towards the seafloor with respect to the top of the GHSZ, implying that the closer the seafloor is to the top of the GHSZ, the lower the advection of heat, and vice versa. Recent seafloor-related depositional and structural features amplify such relations in agreement with near-seafloor heat-flow variability. However, towards the area outside the extent of the MNG (<3 km overburden thickness), continuous BSRs are not linked either to a deeper BSR or to sub-BSR enhanced reflections. The continuity of one of these BSRs is deflected upwards beneath a slump, suggesting an incomplete thermal re-equilibration of the GHSZ. Therefore, we conclude that the BSR responds to: (1) the confinement and thickening of the free-gas zone (FGZ) above the MNG depocentre due to the sealing effect of recent sedimentation close to the top of the GHSZ; (2) the seepage of gas-rich fluids from a thinned FGZ above the relatively thick MNG, due to the enabling effect of faults cutting the GHSZ far from the top of the GHSZ; (3) the undisturbed state of the FGZ outside the extent of the MNG; and (4) the disequilibrium state of the base of the GHSZ due to the unloading of sediments in an unstable slope environment prone to failure.

Downwind Warming of Cities? Inequal Heat Distribution Attributed to Winds

Heat exposure within urban areas is strikingly uneven, posing disproportionate risks to certain communities. While nature-based solutions have gained attention, the role of wind in distributing heat remains less understood in an urban planning scale. This study assessed the interaction between wind direction, speed, and heat advection in Taipei Basin during summers from 2011 to 2020, using data from densely installed meteorological stations. A novel method was developed to capture multiple wind directions while accounting for local terrain and urban effects. Results revealed that wind-induced heat advection is complicated by local terrain and nearby cities in the conurbation, varying heat distribution. Windy conditions were mostly warmer than calm conditions, with north-westerly and westerly winds causing the strongest heat advection. Heat advection increased with wind speeds up to 5.4 m/s and decreased thereafter. Substantial intra-urban differences in heat advection were observed, reaching 4.33°C daytime and 3.34°C nighttime. Upwind areas were not necessarily cooler, while some downwind areas at mountain foot experienced greater warming. Up to 2.6SD of advected heat magnitude was found downwind at night. These findings underscore inequitable heat transfer to areas that do not generate heat and the critical need for wind-sensitive planning for both city-region and inter-urban areas.

Modeling of the Black Sea circulation using equations of heat and salt advection–diffusion having discrete nonlinear invariants

In this work the accuracy of reconstructing the Black Sea circulation by using new approximations of nonlinear terms in the transport equations, ensuring the conservation of temperature and salinity to a power greater than two, is analyzed based on the results of forecast calculations. Three numerical experiments with differences in the schemes for calculating temperature and salinity are carried out. In the first experiment – traditional schemes are used to conserve of temperature and salinity in the first and second degrees; in the second one – the temperature is conserved in the first and fifth degrees, salinity in the first and third; in the third one – the temperature in the first and third, salinity in the first and fifth degrees. Calculations are performed on the basis of the MHI model with a resolution of 1.6 km and taking into account realistic atmospheric forcing for 2016. Validation of the results is carried out based on comparison of model fields with in-situ and satellite measurements of temperature and salinity in 2016. Analysis of mean and root mean square errors showed that new schemes for the advection-diffusion equations of heat and salt, ensuring the conservation of predictive parameters to a power greater than two, improve the accuracy of reconstructing the salinity in the Black Sea upper 100m layer throughout the year compared with traditional approximation. The root mean square errors in the salinity field are reduced by 15–20%, the thickness of the upper mixed layer in winter and the depth of the upper boundary of the thermocline layer in summer in the central part of the sea are modeled approximately 10% more accurately. Based on the results of three experiments, the smallest deviations from observational data are obtained when using approximations that ensure the conservation of temperature to the third power and salinity to the fifth power.