Intense Surface Heating Research Articles

Exploring the atmospheric conditions increasing fire danger in the Iberian Peninsula

AbstractThe fire danger is particularly sensitive to meteorological conditions. The present study discusses the atmospheric conditions during three periods to evaluate how they can increase fire danger. A set of three convection‐permitting simulations was configured at 2.5 km resolution using the Meso‐NH model. In the first period, the intense surface heating induced by a heatwave favoured the development of the Iberian thermal low in July 2019, leading to the formation of precipitating systems and resulting in convective outflows that affected the central Iberian Peninsula. The outflows were shown to be an important feature in evaluating fire danger during the period; however, the simulation also highlighted the orographic effect as another phenomenon playing an important role in fire development and consequently enhancing the fire danger in some regions such as in the extreme southwest of Portugal. The orographic effect in this specific region was identified and analyzed in detail for two megafire events that occurred in Monchique in August 2003 and 2018. The Monchique Mountain's shape and orientation interacting with the airflow induced upslope and downslope winds that favoured the rapid propagation of the fire fronts in August 2018. The third experiment showed that the circulation of a sea breeze from the southern coast of Portugal may act as an enhancer for fire danger in the region when interacting with the regional mountain, such as verified in the 2003 megafire. The study shows that the fire danger over specific regions can be increased by different atmospheric phenomena and explored from atmospheric modelling. The convective outflows were an important factor enhancing fire danger; however, the orographic effect was confirmed as the main factor producing two megafires events in the extreme southwest of Portugal.

Convective heat transfer from a spherical concave surface due to swirling impinging jets issuing from a circular pipe

Impinging jet heat transfer from curved surfaces is available in many industrial applications, such as cooling of gas turbine leading edge and deicing of airplane wing leading edge (heating). Most of the published studies on this topic involve non-swirling jet impingement from flat surfaces. Swirling jets are also used in some applications with the anticipation of heat transfer augmentation. Swirling impinging jet flow characteristics are significantly different from that of the non-swirling jet. However, fundamental studies of swirling jet impingement onto curved surfaces are very limited. As such, flow dynamics and convective heat transfer from a heated concave surface due to swirling impinging jets from a circular nozzle are numerically investigated using the RANS approach and the realizable k-ε turbulence model. Various flow and geometric parameters, such as the jet Reynolds number (Re) in the range of 11,600–35,000; the swirl number (Sw) in the range of 0–2.4; and the jet-to-surface separation distance (H) of 0.5–8 times the nozzle diameter, at a fixed impingement surface curvature (diameter) are studied. The results show that two counter-rotating recirculation zones appear near the target surface for near-field impingement (H ≤ 1) and higher swirl numbers (Sw ≥ 1.2), whereas for far-field impingements (H > 2), they are formed inside and outside of the main jet stream. An intense surface heat transfer zone develops only for near-field impingement in the range 1 ≤ S ≤ 3 at higher swirl numbers, where S is the distance along the impingement surface from the domain axis. More uniform thermal distribution along the curved surface is found for far-field impingement at Sw ≥ 0.8. Whilst the transitional Sw and H for Re = 11,600 are 0.8 and 2 respectively, the transitional Sw and H for Re = 35,000 are 0.8–1.2 and 4, respectively. Maximum heat transfer zones are found to be correlated with strong turbulence. Correlations are developed for the average Nusselt number as a function of the jet Reynolds number, jet exit to impingement surface separation distance, and swirling strength.

Experimental and theoretical determination of the role of ions in atomic layer annealing

The use of a heavier noble gas such as Kr in atomic layer annealing results in higher crystallinity due to higher momentum transfer leading to a more localized and intense surface heating effect occurring over picosecond timescales.

Verification and validation of mHIT code over TMAP for hydrogen isotopes transport studies in fusion-relevant environments

The accurate prediction of tritium inventory and permeation fluxes in the breeding blanket of a D-T fusion reactor is a key aspect for future thermonuclear power plants licensing. Tritium permeation into structural materials could give rise to potential issues concerning the fuel self-sufficiency and can be lost into the environment with resulting radiological risks for the population. In the frame of hydrogen isotopes transport modelling, the Tritium Migration Analysis Program (TMAP) code is considered a referred code for the safety design of nuclear fusion power plants. It is mainly applied to Plasma Facing Components (PFCs), which are subjected to intense particles implantation and surface heat fluxes.Due to some code limitations and to the need of having a more easy-to-use computer code in a multiphysics framework, in the last years the commercial software COMSOL Multiphysics has been used to assess tritium transport studies as an application to ITER, DEMO and CFETR fusion reactors, but it was never validated against TMAP. Within this paper, a COMSOL-based code named mHIT (multi-trapping Hydrogen Isotopes Transport code) is presented. A set of verification and validation (V&V) problems were addressed, with the aim of substantiating the capabilities of the code in common fusion-relevant experimental set-ups and to include different physics according to the level of detail needed for a given application.

The atmospheric blocking influence over the South Brazil Bight during the 2013–2014 summer

The 2013–2014 summer in the Southeast Brazil region set records for negative precipitation anomalies and the highest sea surface temperatures. Such event was attributed to the anomalous presence of atmospheric blocking, which prevented the propagation of a cold front towards the Equator and the establishment of the South Atlantic Convergence Zone, two phenomena that regulate the precipitation regime in this area. These blocking episodes are relatively important to the climate in mid-latitudes, but the feedback of the coastal ocean is still poorly understood under these anomalous conditions. This paper investigates, from a numerical perspective, the impacts on the thermohaline properties and circulation in the South Brazil Bight (SBB). We found that enhanced shortwave radiation leads to intense surface heating and that the presence of northeasterly winds strengthens the coastal upwelling nearby Cabo Frio. The South Atlantic Coastal Waters, transported into the SBB, regulate the extreme heating in the northern half of the domain, while, in the southern half, the absence of cold waters leads to the development of a warm-water pool. The final thermohaline structure induced an enlargement and intensification of the northwestward currents south of São Sebastião Island. Between Ubatuba and Cabo Frio, in the northern half, the northeasterly winds developed an intense surface advection towards offshore, and in the northern region, compensated by an opposite advection, towards the coast. We conclude that the coastal ocean feedback could present extreme anomalous conditions during atmospheric blocking events, leading to impacts upon the thermodynamical properties. Further studies are needed to understand the impacts of these events on biogeochemical properties.

Temporal dynamics and drivers of lake ecosystem metabolism using high resolution observations in a shallow, tropical, eutrophic lake (Laguna Lake, Philippines)

The physical, chemical, and biological dynamics under changing atmospheric conditions of Laguna Lake, Philippines were analyzed from intensive observations. Diel measurements were conducted for 48 continuous hours for both dry and wet tropical seasons in addition to fine resolution long-term monitoring. Results revealed significant vertical and diel variations of lake variables in spite of a shallow water depth (2.5 m) caused by the intense surface heating from solar irradiance (~800 W m−2) and accentuated by the lake's high turbidity (16–32 ftu). Late afternoon land-lake breeze (~5–7 m s−1) regularly breaks daytime thermal stratification, and convective cooling at night maintains isothermal condition until dawn of the next day. The stratified condition demonstrated a wind-driven, density-induced 2-layer current pattern with a windward moving epilimnion (~4 folds faster) and a compensating hypolimnetic flow in the general lake circulation direction. Laguna Lake was observed to have a dominating diel cycle but also undergoes significant seasonal limnological variations brought primarily by climate, hydrology, and its interaction with the adjacent sea. Significantly correlated variations of pH, chlorophyll-a and DO in the dry season were indicative of the higher biological activity associated with the intrusion of polluted waters from Metro Manila. The non-occurrence of thermal over-turn was observed to be regularly followed by bottom hypoxic conditions (2–4 mg L−1), indicative of the eutrophic condition of the lake and the importance of diel wind-induced mixing in the bottom supply of DO. Laguna Lake was found to be predominantly net heterotrophic (GPP:R < 1, NEP < 0).

Pulsed laser surface heating: A tool for studying pyrolysis product chemistry in molecular beams

Laser pulses directed at surfaces can produce rapid and intense surface heating. Heating from laser pulses out of the absorbance range of compounds on the surface will cause compound desorption; pyrolytic products increase at higher pulse energies. Depending on the timing of the photoionization or ion extraction, species in different portions of the gas pulse can be mass analyzed. Using “thermometer” ions to characterize the results, we show that it is possible to study either lower or higher temperature regime pyrolysis products. It is possible to query initial pyrolytic products that have undergone either more or less subsequent associative chemistry.

Dynamics of Downwelling in an Eddying Marginal Sea: Contrasting the Eulerian and the Isopycnal Perspective

AbstractIn this study, we explore the downward branch of the Atlantic meridional overturning circulation (AMOC) from a perspective in depth space (Eulerian downwelling) as well as from a perspective in density space (diapycnal downwelling). Using an idealized model, we focus on the role of eddying marginal seas, where dense water is formed by deep convection due to an intense surface heat loss. We assess where diapycnal mass fluxes take place, investigate the pathways of dense water masses, and elucidate the role of eddies. We find that there are fundamental differences between the Eulerian and diapycnal downwelling: the strong Eulerian near-boundary downwelling is not associated with substantial diapycnal downwelling; the latter takes place in the interior and elsewhere in the boundary current. We show that the diapycnal downwelling appears to be more appropriate to describe the pathways of water masses. In our model, dense water masses are exported along two routes: those formed in the upper part of the boundary current are exported directly; those formed in the interior move toward the boundary along isopycnals due to eddy stirring and are then exported. This study thus reveals a complex three-dimensional view of the overturning in a marginal sea, with possible implications for our understanding of the AMOC.

Nonstationary Heat Conduction in a Curvilinear Plate with Account of Spatial Nonlocality

At the present time, an important stage in the creation and use of new structurally sensitive materials is the construction of mathematical models allowing one to describe the behavior of these materials in a wide range of variation of external effects. In this work, a model of heat conduction in structurally sensitive materials is suggested that accounts for the nonlocality of the medium over the space and the curvature of the plate. With the use of the integrointerpolation method, a difference scheme is constructed and a numerical solution of the problem of highly intense surface heating is found. The influence of the nonlocality and plate curvature parameters on temperature distribution has been investigated.

The energy mechanism controlling the continuous development of a super-thick atmospheric convective boundary layer during continuous summer sunny periods in an arid area

In the arid regions of the world, due to the specific climatic and environmental background, a super-thick convective boundary layer (SCBL) often develops on sunny days in summer, whereas such phenomena rarely occur in other areas. This special boundary layer structure has an important synoptic and climatic significance, but there have been few studies of its development mechanism in arid areas, which greatly restricts the parametric improvement of the SCBL and our understanding of the interaction between weather and climate processes. This study was conducted in Dunhuang, which is located in the hinterland of northwest China. Based on data obtained from land-air interaction experiments and long-term operational sounding observations in this region, the energy mechanism controlling the development of the CBL and the developmental process of the SCBL were systematically analyzed. In arid northwest China, it is possible that the thickness of the CBL can extend to over 3 km for most of the year, except winter. Even in the early summer, when there is little rain and strong solar radiation, the thickness of the CBL may reach an extreme state of 5.4 km. The thickness of the CBL at this time is higher than that observed in midsummer, when there is slightly more precipitation in this area. This is basically consistent with the extreme thickness of the CBL recently discovered in the Sahara Desert in Africa. In the general mechanism that controls the development of the CBL, there is a close relationship between the development of the CBL and the sensible heat flux of the surface. However, the correlation between the thickness of the CBL and the surface sensible heat flux at the same time is not strong, whereas the correlation between the thickness of the CBL and the cumulative surface sensible heat flux is very strong. This indicates that the development of the CBL is the result of the continuous accumulation of the sensible heat flux on the surface, which is consistent with the energy mechanism controlling the CBL. Although the development of the CBL is closely related to the cumulative heating effect of the daytime surface sensible heat flux, the CBL would still continue to increase even if the integral value of the daytime surface sensible heat flux remained unchanged or even weakened during the continuous clear sky period. The energy provided through sensible heat does not fully explain the energy required to develop the CBL. This is mainly because the deep near-neutral residual layer (RL) background plays an important role in the development of the SCBL. The entrainment energy from the deep RL to the CBL is the key energy supply for the continuous development of the CBL. The sum of the entrainment energy and surface sensible heat energy coincides with the energy absorbed by the development of the SCBL. The reason for the occurrence of an SCBL in arid areas is not only the strong sensible heating in summer but also the persistent clear skies in such areas. In each continuous clear sky period, the positive feedback mechanism between the CBL and the RL will become operational. Under this mechanism, the daily maximum thickness of the CBL and the thickness of the RL will increase continuously. The thickness of the SCBL is generally over 3 km, although depths of over 5 km can develop through a cyclic growth mechanism during periods of strong surface heating. Otherwise, the thickness of the CBL can only reach 2–3 km in summer, and it is unlikely that an SCBL will develop. Strong sensible heating is the key trigger of the positive feedback cycle growth mechanism between the CBL and the RL, which explains why the SCBL phenomenon can only occur in dry areas, with intense surface heating in summer.

An Automated Detection Methodology for Dry Well-Mixed Layers

AbstractThe intense surface heating over arid land surfaces produces dry well-mixed layers (WML) via dry convection. These layers are characterized by nearly constant potential temperature and low, nearly constant water vapor mixing ratio. To further the study of dry WMLs, we created a detection methodology and supporting software to automate the identification and characterization of dry WMLs from multiple data sources including rawinsondes, remote sensing platforms, and model products. The software is a modular code written in Python, an open-source language. Radiosondes from a network of synoptic stations in North Africa were used to develop and test the WML detection process. The detection involves an iterative decision tree that ingests a vertical profile from an input data file, performs a quality check for sufficient data density, and then searches upward through the column for successive points where the simultaneous changes in water vapor mixing ratio and potential temperature are less than the specified maxima. If points in the vertical profile meet the dry WML identification criteria, statistics are generated detailing the characteristics of each layer in the profile. At the end of the vertical profile analysis, there is an option to plot analyzed profiles in a variety of file formats. Initial results show that the detection methodology can be successfully applied across a wide variety of input data and North African environments and for all seasons. It is sensitive enough to identify dry WMLs from other types of isentropic phenomena such as subsidence layers and distinguish the current day’s dry WML from previous days.

A multi‐scale study of Australian fairy circles using soil excavations and drone‐based image analysis

AbstractFairy circles (FCs) are extremely ordered round patches of bare soil within arid grasslands of southwestern Africa and northwestern Australia. Their origin is disputed because biotic factors such as insects or abiotic factors such as edaphic and eco‐hydrological feedback mechanisms have been suggested to be causal. In this research, we used a multi‐scale approach to shed light on the origin of Australian FCs. At a local scale, we investigated the potential cause of FCs using analyses of soil compaction and texture within FCs, the surrounding matrix vegetation, and in nearby large bare‐soil areas. We found that soil hardness and clay content were similarly higher inside the FCs and in the large bare‐soil areas. When compared to the matrix soils with protective grass cover, the 2.6–2.8 times higher clay content in FCs and large bare‐soil areas is likely sourced via multiple abiotic weathering processes. Intense rainfall events, particle dispersion, surface heat, evaporation, and mechanical crust building inhibit plant growth in both areas. At the landscape scale, a systematic survey of 154 soil excavations within FCs was undertaken to evaluate the presence of pavement termitaria that could inhibit plant growth. We show that in up to 100% and most of the excavations per plot, no hard pavement termitaria were present in the FCs. This fact is substantiated by the observation that small, newly forming FCs are initiated on soft sand without evidence of termite activity. At the regional scale, we investigated the spatial properties of FCs and common termite‐created gaps in Western Australia, using spatially explicit statistics. We mapped three 25‐ha FC plots with a drone and compared them with three aerial images of typical vegetation gaps created by harvester and spinifex termites. We demonstrate that the small diameters, the lower ordering, and the heterogeneous patterns of these common termite gaps strongly differ from the unique spatial signature of FCs. Our multi‐scale approach emphasizes that FCs are not trivial termite gaps and that partial correlation with termites at some sites does not imply causation. Instead, we highlight the need to study the edaphic and eco‐hydrological drivers of vegetation‐pattern formation in water‐limited environments.

Four-year Measurements of Wet Mercury Deposition at a Tropical Mountain Site in Central Taiwan

ABSTRACT Rainwater samples were collected between 2010 and 2013 at Lulin Atmospheric Background Station (LABS) to study the distribution and characteristics of wet mercury (Hg) deposition, and possible driving mechanisms. Sample Hg concentrations ranged from 0.8 to 35.1 ng L–1 with an overall volume-weighted mean (VWM) concentration of 9.2 ng L–1. Annual wet Hg deposition fluxes ranged between 24.4 and 48.9 µg m–2 with a mean value of 32.3 µg m–2. This mean annual wet flux was about 1.5–6.0 times the values measured at 15 sites in the U.S. and 4–16 times the values reported from mountain and high-elevation sites in China. Both rainwater Hg concentration and rainfall amount contributed to this geographical difference, but rainfall amount played a more important role. This indicated that tropical mountains in East and Southeast Asia, especially the windward maritime slopes with abundant rainfall, could be hot spots of wet Hg deposition. Wet Hg deposition flux was high in summer because of elevated rainwater Hg concentrations and high rainfall. The seasonal pattern of rainwater Hg concentrations was different from that of the East Asian air pollutant export, indicating other factors, e.g., rainfall type, were also influencing rainwater Hg concentrations. A clear difference in seasonal frequency distribution of rainfall types was observed, with rain events associated with the Pacific high pressure type (PH) occurring more frequently in summer months. PH rainfall type had the highest VWM Hg concentration (13.5 ng L–1), 2.3–6.2 ng L–1 greater than those of the other rainfall types. Because of intense surface heating under summer PH conditions, precipitation systems usually form locally due to strong convection, resulting in afternoon shower. Therefore, the elevated rainwater Hg levels in summer at LABS were likely due to the scavenging of free tropospheric gaseous oxidized Hg (GOM) by deep convection.

Dry Intrusions: Lagrangian Climatology and Dynamical Impact on the Planetary Boundary Layer

Dry-air intrusions (DIs) are dry, deeply descending airstreams from the upper troposphere toward the planetary boundary layer (PBL). The significance of DIs spans a variety of aspects, including the interaction with convection, extratropical cyclones and fronts, the PBL, and extreme surface weather. Here, a Lagrangian definition for DI trajectories is used and applied to ECMWF interim reanalysis (ERA-Interim) data. Based on the criterion of a minimum descent of 400 hPa during 48 h, a first global Lagrangian climatology of DI trajectories is compiled for the years 1979–2014, allowing quantitative understanding of the occurrence and variability of DIs, as well as the dynamical and thermodynamical interactions that determine their impact. DIs occur mainly in winter. While traveling equatorward from 40°–50° latitude, DIs typically reach the lower troposphere (with maximum frequencies of ~10% in winter) in the storm-track regions, as well as over the Mediterranean Sea, Arabian Sea, and eastern North Pacific, off the western coast of South America, South Africa, and Australia, and across the Antarctic coast. The DI descent is nearly adiabatic, with a mean potential temperature decrease of 3 K in two days. Relative humidity drops strongly during the first descent day and increases in the second day, because of mixing into the moist PBL. Significant destabilization of the lower levels occurs beneath DIs, accompanied by increased 10-m wind gusts, intense surface heat and moisture fluxes, and elevated PBL heights. Interestingly, only 1.2% of all DIs are found to originate from the stratosphere.

Feedback between surface air temperature and atmospheric circulation in high‐temperature weather in East China: a diurnal perspective

AbstractThis study proposes the generality of surface air temperature (SAT)–atmospheric circulation feedback during high‐temperature weather in late July 2003 over East China by using the Advanced Research Weather Research and Forecasting model (WRF; Version 3) simulations with a succession of 24‐h integrations, i.e. on a daily scale, the SAT increase leads to a weakened ridge of the western Pacific subtropical high in the lower troposphere (i.e. negative feedback), whereas it leads to a strengthened ridge in the upper troposphere (i.e. positive feedback) and vice versa. Additionally, using the balance equation of temperature, the feedbacks are clarified from the diurnal‐variation perspective. This shows many complex details, e.g. the changes in geopotential heights are more complex than those in air temperatures, and the overall daily feedback appears to be dominated by the feedback during the phase with intense daytime surface heating. All of the WRF‐modified land surface conditions can lead to large changes in the maximum, minimum, and average SATs over the mean diurnal scale, with generally larger differences induced by land surface schemes than those induced by initial soil moisture, suggesting that the SAT–circulation feedback can be greatly reduced (or amplified) by different land conditions over the diurnal weather scale and that diurnal variations could substantially contribute to longer timescale climate.

Sea dynamics impacts on the macroaggregates: A case study of the 1997 mucilage event in the northern Adriatic

We analysed the 1997 summer mucilage event in the northern Adriatic and showed that macroaggregates were formed in the upper layers of the water column in central parts of large gyres and were dispersed by currents which seem to be of geostrophic origin. Beside Cylindrotheca closterium, an already established regular opportunistic species of the mucilage phenomenon, originating from the sediment, we detected another benthic species, Thalassionema nitzschioides, of sporadic character. Both were present in scarce amounts in the water column at the time of sampling first macroaggregates, but reached high abundances after/close to the mucilage event ending. The first, and the most intense surface heat loss episode, on 18 July (heat loss of around 240Wm−2, during episode of NW wind), in time of first macroaggregates formation, introduced C. closterium from sediment into the water column and enabled dispersion of T. nitzschioides, present in central region both in water and in first macroaggregate samples, eastwards and westwards. The later, less intense surface heat loss episodes, between end of July and mid of August (30–160Wm−2, induced mostly by NE winds) were efficient (1) in tearing already formed macroaggregates, enabling in that way release of opportunistic species from a macroaggregate into the surrounding water column, and (2) in transporting lower salinity waters of specific species populations with macroaggregates form west to east, extending the event to large area. We hypothesise, first, that summer surface heat loss episodes play a role in sustaining mucilage events by introduction of C. closterium from the sediment and/or decaying macroaggregates in the water column. Second, that geostrophic currents are important in spreading of various types of aggregates, including marine snow, over the wider marine areas.

3T MRI induced post-traumatic stress disorder: a case report

IntroductionMRI is considered a safe and well tolerated imaging technique with risks largely limited to heating and/or displacement of implanted ferromagnetic metal in the patient’s body, worsening anxiety, triggering claustrophobia, and gadolinium induced nephrogenic systemic fibrosis.Case presentationWe present a case of a 26 year old Asian American man with no significant past medical or psychiatric history and two months of left T4 radicular pain. During 3T-MRI of the whole spine, the patient experienced acute agitation, fear, anxiety, tachypnea, tachycardia with palpitations, and dizziness. He felt intense surface heat over segments of his body and very loud noises. He perceived impending serious bodily harm by the scanner. The scan was aborted at the lumbar spine, and cervical and thoracic spine was unremarkable. The patient’s pain resolved in the weeks following with over the counter analgesics, however, he developed increased arousal, re-experiencing the event, persistent avoidance, and significant psychosocial impairment consistent with DSM-IV-TR criteria for post-traumatic stress disorder (PTSD).ConclusionThis is the first reported case of MRI induced PTSD. Theoretically, the high-magnetic field of the 3T scanner may have contributed to the development of symptoms.

Plate tectonics on super-Earths: Equally or more likely than on Earth

The discovery of extra-solar super-Earths has prompted interest in their possible mantle dynamics and evolution, and in whether their lithospheres are most likely to be undergoing active plate tectonics like on Earth, or be stagnant lids like on Mars and Venus. The origin of plate tectonics is poorly understood for Earth, likely involving a complex interplay of rheological, compositional, melting and thermal effects, which makes it challenging to make reliable predictions for other planets. Nevertheless, as a starting point it is common to parameterize the complex processes involved as a simple yield stress that is either constant or has a Byerlee's law dependence on pressure. Because the simplifying assumptions made in developing analytical scalings may not be valid over all parameter ranges, numerical simulations are needed; one numerical study on super-Earths finds that plate tectonics is less likely on a larger planet (O'Neill and Lenardic (2007)), in apparent contradiction of an analytical scaling study (Valencia et al. (2007)). To try and understand this we here present new calculations of yielding-induced plate tectonics as a function of planet size, focusing on the idealized end members of internal heating or basal heating as well as different strength profiles, and compared to analytical scalings. In the present study we model super-Earths as simple scaled up versions of Earth, i.e., assuming constant physical properties, keeping the ratio of core/mantle radii constant and applying the same temperature difference between top/bottom boundaries and the same internal heating rate. Effects that originate outside of the planet, such as tidal forces, meteor impacts and intense surface heating from a nearby star are not considered. We find that for internally-heated convection plate tectonics is equally likely for terrestrial planets of any size, whereas for basally-heated convection plate tectonics becomes more likely with increasing planet size. This is indicated both by analytical scalings and the presented numerical results, which agree with each other. When scalings are adjusted to account for increasing mean density with increasing planet size, plate tectonics becomes more likely with increasing planet size for all scenarios. The influence of the pressure variation of viscosity, thermal expansivity and conductivity may, however, act in the opposite sense and needs to be determined in future studies. At least in the simplest case, factors other than planet size, such as the presence of surface water, are likely most important for determining the presence or absence of plate tectonics.

Sensitivity of the Humboldt Current system to global warming: a downscaling experiment of the IPSL-CM4 model

The impact of climate warming on the seasonal variability of the Humboldt Current system ocean dynam- ics is investigated. The IPSL-CM4 large scale ocean cir- culation resulting from two contrasted climate scenarios, the so-called Preindustrial and quadrupling CO2, are downscaled using an eddy-resolving regional ocean circu- lation model. The intense surface heating by the atmo- sphere in the quadrupling CO2 scenario leads to a strong increase of the surface density stratification, a thinner coastal jet, an enhanced Peru-Chile undercurrent, and an intensification of nearshore turbulence. Upwelling rates respond quasi-linearly to the change in wind stress asso- ciated with anthropogenic forcing, and show a moderate decrease in summer off Peru and a strong increase off Chile. Results from sensitivity experiments show that a 50% wind stress increase does not compensate for the surface warming resulting from heat flux forcing and that the associated mesoscale turbulence increase is a robust feature.

The reflectivity of alumina ceramics under intense surface heating and subsequent free cooling

The results are given of measurements of the normally hemispherical reflectivity of alumina ceramics in the semitransparency region for the wavelengths of 0.488, 0.6328, 1.15, and 3.39 μm. The measurements are performed both in the process of fast heating of ceramics in the air by concentrated radiation of a CO2 laser with fluxes of different densities from room temperature to ∼2900 K with the formation of a thin layer of melt and in the process of subsequent cooling after the heating radiation is discontinued. The heating time is approximately 2.25 s, with the density of heating radiation flux of approximately 1200 W/cm2 and 1600 W/cm2. It is demonstrated that the reflectivity in the process of heating depends significantly on the flux density. By the end of the heating period and under the effect of a flux of higher density, the layer of melt formed on the ceramic surface is optically infinite for reflection at all wavelengths, while no optical infinity is attained at a lower flux density. The effect of abrupt variation of the absorption coefficient during melting and solidification on the thermal-radiation characteristics is analyzed.