Vertical Temperature Research Articles

Transient simulation and experimental analysis for the response of dual-cycle air-carrying energy radiant diffuse terminal

A novel air-carrying energy radiant diffuse terminal is proposed, and the response of the terminal is investigated by field experiment and numerical simulation. This paper explores the dynamic operation characteristics of the new system to guide the optimal operation of the system. A transient simulation method of three factors (conduction, convection, and radiation) with dual-circulation (air-carrying energy zone and occupied zone) is put forward for the radiant diffuse terminal with a fresh air system. This transient simulation sets up the porous baffle model coupling radiation model concurrently, revealing the dynamic thermal performance for the system's response accurately, quickly, and comprehensively. This method avoids the limits for the complexity of mini porous (Pore size of 1 mm–3mm) geometric models and the transient uncertainty in multiple combination models. The results show that the average error between the convective-conductive model and the convective-conductive-radiative model is about 8% at five different heights. This system has high response performance, which can quickly heat the room while maintaining the comfort requirements of vertical temperature. The radiated heat transfer between the radiant diffuse terminal and the occupied zone is greater than the convective heat transfer (Radiation accounts for 74%). This system has a short response time, high energy efficiency, uniform airflow, and eliminates draught rating. Moreover, the indoor non-uniform transient thermal and humid environments, the thermal comfort, and air quality for the response of the terminal with fresh air system under four different diffuser placements are compared using computational fluid dynamic simulation. The results indicate that introducing heating strategies featuring higher-positioned fresh air inlet and lower-positioned recirculation return air outlet for this system leads to a temperature efficiency increase by 5%, velocity uniformity by 8%, and age of air reduction by 16–50% in human-breathed zone and the response time by 25%, which shows substantial potential for energy savings. The transient simulation and experiments in the paper are beneficial to optimize design parameters and carry out energy-saving applications of operation energy consumption for the response of this terminal with a fresh air system in the future.

The Relationship between Vertical Kinematic Eddy Heat Flux, Air Temperature and Turbulent Kinetic Energy in Atmospheric Boundary Layer: Baghdad City

Studying the heat flux in the boundary layer and understanding its relationship to the various atmospheric variables reflects positively on understanding the nature of turbulence in this layer and thus understanding the nature of the spread and movement of pollutants and the transmission and distribution of energy in this layer, also, the vertical heat flux is considered a significant influence on the movement of buoyancy and stability in the boundary layer and its effect on the horizontal wind movement, and therefore it is considered one of the important studies indirectly involved in the estimates of wind energy production, pollutant diffusion, and turbulence. This study involved the calculation of the Eddy Heat Flux and turbulent kinetic energy across Baghdad city. Our investigation revealed a correlation between the Eddy Heat Flux, temperature, and Turbulent Kinetic Energy (TKE). The observations have been made for wind speed with three components (u, v, w) and temperature by using a fast-response anemometer. As for the atmospheric pressure data, it was obtained from the automatic weather station located in the department of Atmospheric Sciences at Mustansiriyah University. The range of observations extended through the duration of thirty days for 24 hours from 1st July 2016 to 30th July 2016 every second. The maximum Eddy Heat Flux value was 0.092 J/(m2.s) at 10:00 on 23th July 2016, while the minimum Eddy Heat Flux value was -0.013 J/(m2.s) at 21:00 hour on 25th July 2016, the negative sign refer to a change in the direction of heat transfer,. It was also found that there is a positive relationship between the eddy heat flux and temperatures with a correlation coefficient of 0.93, as well as between the eddy heat flux and the turbulent kinetic energy with a correlation coefficient of 0.8.

PIV experimental study on natural convective flows at high Rayleigh numbers in industrial buildings

High heat loads in industrial buildings potentially form strong natural convective flows. These flows exhibit significant unsteadiness and anisotropy, which can profoundly impact indoor air distribution. To study the flow characteristics of thermal convective flows in large indoor spaces, we built a large-scale test bench with controllable thermal boundaries. Under three different heat source intensities represented by Rayleigh numbers (Ra = 3 × 1010, 6 × 1010, and 1 × 1011) that are typical in industrial buildings, we used 2-dimensional particle image velocimetry to capture the large-scale convective airflow by splicing nine subregions, each with 800 instantaneous flow fields sampled at a frequency of 3 Hz. The results show that the convective airflow exhibited large-scale circulation patterns. The velocity near the wall gradually increased with the increased Ra number, while the velocity at the center remained low. The turbulence intensity near the wall was less than 1, while that at the center was larger than 5 and fluctuated greatly. The dominant fluctuation frequency of the airflow under the high Ra was 0.1 Hz. Through proper orthogonal decomposition, it is found that even for horizontal flows, the main transient fluctuations still exhibit an up-and-down fluctuating flow structure. Additionally, the calculation of the velocity structure function revealed that the airflow near the wall is anisotropic, while the airflow at the center is isotropic. The Reynolds number of the flow generated by vertical temperature differences exhibits a power function relationship with the Rayleigh number. This study provides a basis for the optimization of air distribution design in industrial buildings.

Characteristics of planar buoyant jets and plumes in a turbulent channel crossflow from direct numerical simulations

AbstractThis paper is motivated by an interest in understanding the characteristics of buoyant fluids discharged from the bottom wall of channels, such as encountered during tunnel fires or in river effluent discharge. Direct numerical simulation is used to model the upward release of a planar buoyant jet or plume from the bottom wall of a channel into an incoming turbulent crossflow. The well-studied jet-in-crossflow with only a momentum source is simulated first, and subsequently, fixing the incoming Reynolds number, buoyancy source as heat flux is added alongside varying momentum source, with two cases where only a buoyancy source is present. Appropriate five non-dimensional parameters relevant for this flow are defined, of which three are fixed and two—source to channel momentum ratio and Richardson number—are varied. The changes in turbulence characteristics as the buoyant jet or plume evolves downstream are presented. In all cases with buoyancy, except for the pure jet case, the plume is initially confined to the lower half of the channel before it suddenly lifts to the top half, an effect that occurs at an increasingly smaller downstream distance with increasing buoyancy, and dividing the flow into a near and far field. The distributions of mean and Reynolds stresses in the near and far field of the source are reported, and it is found that the channel flow becomes more turbulent downstream of the source, and further, the turbulent vertical temperature flux switches sign from near to far field owing the a change in the mean temperature gradient sign. From the input parameters and using the integrated temperature equation a reasonable estimate of the far field mean channel temperature can be obtained by a reference temperature based on the heat conservation that includes the convective and diffusive source heat flux. A monotonic behaviour of the back-layering distance is also observed a function of this reference temperature, which was difficult to obtain with the two specified non-dimensional parameters.

Detecting the role of Stokes drift under typhoon condition by a fully coupled wave-current model

The impacts of Stokes drift and sea-state-dependent Langmuir turbulence (LT) on the three-dimensional ocean response to a tropical cyclone in the Bohai Sea are studied through two-way coupled wave-current simulations. The Stokes drift is calculated from the simulated wave spectrum of the wave model, Simulating Waves Nearshore (SWAN), and then input to the Princeton Ocean Model with the generalized coordinate system (POMgcs) to represent the Langmuir effect. The Langmuir circulation is included in the vertical mixing of the ocean model by adding the Stokes drift to the shear of the vertical mean current and by including LT enhancements to the Mellor-Yamada 2.5 turbulent closure submodel. Simulations are assessed through the case study of Typhoon Masta in 2005 with a set of diagnostic experiments that incorporated different terms of Stokes production (SP) respectively. It is shown that with the consideration of SP, a deeper mixed layer, an enhanced vertical mixing coefficient KMS, and a more accurate representation of the vertical temperature distribution could be derived. Moreover, the effect of LT in elevating the turbulence mixing is stronger than that of Coriolis Stokes force (CSF) and Craik-Leibovich vortex force (CLVF). LT has a greater influence on the vertical mixing during typhoon than that in normal weather.

A study of evaporation duct characteristics in the South China Sea during the Winter of 2017

The evaporation duct (ED) near the sea surface is the most frequent type of duct that traps and redirects electromagnetic waves over longer or shorter distances. This study uses radiosonde data from the South China Sea Two-Island Monsoon Experiment (SCSTIMX) in 2017 and the Weather Research and Forecasting (WRF) model to study the ED and ED height (EDH). We enhanced the vertical resolution to 26 layers in the lowest 134 m. The simulations indicate that EDs were prevalent throughout the South China Sea (SCS) area in winter 2017, where the prevailing surface winds are strong northeasterly. The EDH exhibits diurnal variations and significant variability across the SCS. The WRF simulations of ED and EDH generally agree with observations of the trajectory of Taiwan-O.R.1. Our results indicate that the WRF model can simulate the pattern of ED and EDH over SCS. Results reveal that Yonsei University (YSU) boundary layer (BL) parameterization more accurately simulates the vertical temperature and humidity variations in the lower atmosphere, with stronger winds and higher EDH in most areas. The YSU and the Medium Range Forecast Model (MRF) BL schemes show similar ED patterns to the Taiwan-O.R.1 SCS radiosonde observations but consistently underestimate the EDH. While strong surface winds in the winter SCS may contribute to a higher EDH, the strong surface wind-induced vertical mixing also modifies sea surface air temperature, relative humidity, and vapor pressure, affecting the vertical refractivity. Our results indicate that sea surface air temperature is a more reliable factor affecting EDH in the simulations.

The Inversion of Three-Dimensional Ocean Temperature and Salinity Fields for the Assimilation of Satellite Observations

The lack of dimensionality of ocean observations makes it difficult to utilize multi-scale data assimilation to correct model errors with limited observations. Since satellite observations can provide high-resolution and time-continuous sea surface information, this study utilizes sea surface temperature (SST), sea surface salinity (SSS), and sea surface height (SSH) anomalies to invert the vertical temperature and salinity fields and thus realize multi-scale data assimilation in the three-dimensional space. We propose a temperature and salinity inversion network (TSI-Net) for reconstructing the mapping of the sea surface’s spatial distribution features to vertical structural features to obtain pseudo-observed fields. In this study, measured satellite remote-sensing data and temperature and salinity profiles are used to correct the model errors in the waters around the China Sea. The sensitivity analysis shows that the multi-component inversion can better fit the temperature field relationship, with a correlation coefficient of about 0.87. The results of the assimilation experiments show that the analytical field obtained by assimilating the pseudo-observed field is more consistent with the target field in terms of the spatial distribution characteristics.

On the deformation of CRTS-Ⅲ ballastless track during the casting process of self-compacting concrete: Numerical simulations and random forest-based prediction models

CRTS (China railway track system)-Ⅲ slab track is a main structural type of ballastless track in Chinse high-speed railway (HSR), which requires precise positioning of prefabricated concrete track slabs. However, the cast-in-place process of the self-compacting concrete (SCC) filling layer induces a large deformation as the flowing SCC generates an up-lift force on the bottom of the track slab. Currently, the deformation mechanism and influencing factors of the track slab during the SCC casting process have not been thoroughly studied. In this work, a fluid-solid interaction finite element model (FEM) is created to calculate the upward deformation of the CRTS-Ⅲ track slab caused by the flowing SCC. The main influencing factors, including the SCC’s casting height and speed, SCC’s viscosity, constraint stiffness of the limiting beams, and vertical temperature gradient, have been systematically analyzed and discussed. The relationship between the influencing factors and the track slab’s deformation is obtained. Furthermore, machine learning prediction models using random forest algorithms are developed to evaluate the deformation and up-lift force. A dataset comprising 603 calculation cases obtained from FEM simulations is used to train the prediction models. The random forest-based models developed in this study give an accurate estimation of the deformation and up-lift force based on the SCC properties and construction parameters. In addition, the feature importance of each influencing factor is obtained and studied. The findings of this study can provide guidance for the control of the deformation in CRTS-Ⅲ track slab during the SCC construction process.

Nucleation of ice particles below the snow line

An increase in the total surface area of icy dust aggregates was numerically investigated. The temperature of icy dust aggregates in a protoplanetary disk changes through their vertical motion induced by turbulence. The ice becomes vapor if the maximum temperature exceeds the condensation temperature. The vapor molecules recondense when cooling proceeds. Depending on the cooling rate and the amount of the remaining aggregate, the vapor molecules form pure ice particles through homogeneous nucleation or recondense onto the remaining icy aggregates through heterogeneous nucleation. If homogeneous nucleation dominates, the total surface area substantially increases from the original value. The increase in the total surface area was determined for various ice species and vertical temperature distributions. H2O, NH3, and H2S ice particles can be formed through homogeneous nucleation. The total surface area is increased by a factor of up to 400. The increase in the total surface area can affect protoplanetary disk’s surface density and temperature distributions.

Experimental Study on Effects of Moisture Content and Tree Height on Crown Fire Behaviors of Live Cypress Trees

ABSTRACT Once a fire occurs in urban green belts, the live foliage of some tree and shrub species with larger moisture content than dead fuel can support fire spread, which poses a great threat to the wildland-urban interface (WUI). Cypress tree is widely used as an ornamental vegetation worldwide. This work aims to study the fire and spread behaviors through cypress trees. Experiments were conducted using three tree heights between 0.8 m and 1.6 m and five values of fuel moisture content (FMC) between 30% and 160%. The fuel mass loss, flame shape, vertical temperature distribution and outward vertical heat fluxes were measured. The results showed that for a given tree height, a small enough FMC promoted the burning process and decreased both the maximum heat release rate (HRR) and the time to reach peak HRR compared to a larger FMC. The tree height correlated strongly with the flame height, while the influence of FMC was much smaller. Then, a correlation between the normalized maximum flame height and the normalized maximum HRR was established by taking the crown height as the characteristic length. Reducing the FMC did not necessarily promote the fire spread and trees with large FMCs can support relatively large flame front spread rates. The effect of the tree height on the radiant heat flux was greater than the effect of FMC.

Experimental investigation on flame morphology and wall-attached flame temperature of jet flame under the coupled effect of nozzle angle and nozzle-wall spacing

Jet flames caused by fuel leaks in engineering often occur in complex environments. A total of 140 experiments were conducted to investigate the coupling effect of nozzle angle and nozzle-wall distance on the jet flame characteristics. The results indicate that for upward-tilted jet flame (0° ≤ θ ≤ 90°), the flame trace length has an overall decreasing trend with increasing nozzle angle; when the nozzle is further rotated to a downward slope (θ = 120°), the effect of the nozzle angle on the flame trace length is not consistent as the heat release rate (HRR) increases. In addition, the growth rate of the flame trace length and the flame vertical length are relatively low compared to the growth rate of HRR. Moreover, it was found that the wall-attached flame temperature had a similar trend of decay along the wall upward for different HRRs; and the maximum wall-attached flame temperature showed an overall decreasing trend as the nozzle-wall spacing increased. Furthermore, new physical models were developed to describe the flame trace length, flame vertical length and temperature rise of wall-attached flame. This work may contribute positive significance to the study of the mechanism of impingement jet flames and the search for preventive solutions.

Experimental and numerical study of the three-dimensional temperature field in the arch ribs of the reinforced concrete ribbed arch bridge during construction

The unique structural design of an arch ring featuring varying inclination angles for individual segments causes variations in the longitudinal distribution of the temperature field d along the arch axis. This study aims to enhance the understanding of temperature fields in reinforced concrete (RC) arch bridges with diverse arch ring structural configurations during their construction phases. A comprehensive investigation into the three-dimensional distribution pattern of solar-induced temperature fields within arch ribs during the construction of RC ribbed arch bridges was conducted. A field test specifically measuring the temperature distribution across arch rib cross-sections was conducted on-site, involving an RC arch bridge constructed using the cable-stayed cantilever cast in situ method. Analyzing the monitored on-site temperature data revealed the distribution characteristics of temperature fields at the arch foot cross-section under solar radiation. By comparing these findings with international standards, a vertical temperature gradient fitting model for arch rib cross-sections under solar radiation was formulated. Drawing upon meteorological records and solar radiation principles, an adaptive numerical simulation finite element model was developed to depict the temperature field within an arch rib section. This model was rigorously verified. Subsequently, a comprehensive analysis of the three-dimensional temperature field of the arch rib under solar radiation was performed. Additionally, a three-dimensional temperature gradient fitting model was proposed, accounting for the longitudinal inclination of the bridge.

Change in sound signal propagation at the place of formation of the diffusive convection (DC) structure; in the west of the Strait of Hormuz

Double diffusion (DD) structures, in two types of diffusive convection (DC) and salt-fingering (SF), occur due to vertical temperature and salinity gradients with different diffusion coefficients. Areas such as the Strait of Hormuz, which has a thermohaline exchange between the Persian Gulf and the Sea of Oman, are suitable places for the formation of DD structures. Based on the results, the formation of DC structure is significant compared to other processes in the west of the Strait of Hormuz in December. Fluctuations in temperature and the growth of DC structure cause mixing and changing the depth of the boundary layer of temperature and salinity in the water. So that in the presence of the DC structure, the decrease in the value of the sound speed (1552 m/s) extends to a depth of 40 m, but the sound speed increases to 1555 m/s at the place where the warm water rises. The results show that the sound transmission loss increases by 5-15 dB in the place of strong DC structure. When the sound frequency increases, the transmission loss caused by the DC structure decreases. But for rays with a small propagation angle, a significant expansion is created in the propagation steps and wavelength of the rays, which increases up to 2 times with the increase in the depth of the sound source.

Jumbo Flying Squid Distribution within Anticyclonic Eddies under Anomalous Climatic Conditions

Anticyclonic eddies are widely distributed off Peru, producing obvious effects on climate-environment-sensitive jumbo flying squid Dosidicus gigas . However, how the habitat of D. gigas changes within anticyclonic eddies during El Niño events is still unknown. Therefore, this study constructed a habitat model with different weights and screened the optimal performance model using fishery data from September to December during 2015 to 2019, as well as vertical water temperature data (sea surface temperature and 50 m water depth temperature) and surface chlorophyll concentration data (Chl-a). Then, combined with the eddy tracking dataset, the differences in the variation of resource abundance and habitat of D. gigas within the anticyclonic eddy between the 2015 El Niño year and the 2019 normal year were further comparatively analyzed based on the optimal habitat model. Compared with the normal year of 2019, the 2015 El Niño event occurred with a lower intensity of eddy activity, and both temperature in the fishing ground and near-surface sea water temperature within the anticyclonic eddy became warmer, with a small decrease in Chl-a; the percentage of suitable near-surface water temperature within the anticyclonic eddies decreased significantly, and suitable Chl-a decreased slightly; the suitable habitat for D. gigas was reduced dramatically, which was unfavorable to D. gigas survival. Our finding suggested that that anomalous climatic events can have an impact on eddy strength, as well as on the suitable environment and habitat within the anticyclonic eddies, resulting in variations in the abundance of D. gigas .

An experimental case study of natural ventilation effects on the residential thermal environment and predicted thermal comfort in Kunming

The use of natural ventilation for cooling in summer in mild climate areas can positively improve the indoor thermal environment and thermal comfort. In this paper, Kunming, China was chosen as a case to study experimentally the natural ventilation effects on the residential thermal environment and thermal comfort in mild climate rural areas. The effects of natural ventilation on the indoor thermal environment and thermal comfort under the typical hottest sunny days in summer in Kunming were investigated with seven different combinations of ventilation methods with the opening/closing of doors/windows. The results show that natural ventilation can considerably improve the indoor thermal environment. Furthermore, the uniformity of indoor thermal environments at different heights was assessed. Additionally, the vertical temperature difference between the head and foot areas around the human body remained below 3 °C. Moreover, the adaptive predicted mean vote (APMV) model was used to evaluate the thermal comfort under natural ventilation, and values of APMV ranged from −0.84 to 0.84 under six scenarios, considering an acceptable temperature range based on occupant satisfaction rates of over 80%. This study's outcomes offer valuable insights for the design of self-built housing in the extensive rural areas within mild climate zones in China.

Temperature Inversion and Particulate Matter Concentration in the Low Troposphere of Cergy-Pontoise (Parisian Region)

This study aims to elucidate the influence of meteorological conditions on particle levels in Cergy-Pontoise. It explores the temporal variability of PM10 pollution days by associating them with the vertical temperature profile derived from conventional radiosondes from 2013 to 2022 (regional station). The results indicate that nearly 80% of exceedance days were associated with thermal inversions, primarily observed in winter and typically lasting 1 to 3 days. Analysis of winter thermal inversion characteristics suggests that those linked to pollution primarily occur near the ground, with higher intensity in December (12.1 °C) and lower in February (10.3 °C). Persistent inversions (extended nocturnal by diurnal inversion) account for 91.4% of the total inversions associated with high concentrations. Captive balloon soundings and temperature measurements at different altitudes were conducted during the winter of 2022/2023 to clarify thermal inversion in the Oise Valley at the center of Cergy-Pontoise. The results highlight three nocturnal wind circulation mechanisms in the valley, including downslope flow, circulation influenced by an urban heat island, and mechanical air evacuation under an inversion layer towards the less steep East side of the valley. Analysis of PM with the temperature gradient in the Oise Valley shows a significant correlation, suggesting an increase in concentrations during locally detected inversions and a decrease during atmospheric disturbance.

Dimensionless correlations of indoor thermal stratification in a non-enclosed large-space building under heating and cooling conditions

Indoor thermal stratification is a prevailing phenomenon in large-space buildings, which poses great pressure on their energy consumption and indoor built environment. This paper revealed the mechanism of indoor thermal stratification in a non-enclosed large-space building under heating and cooling conditions. It can be abstracted as a joint effect of the cold and hot air inflow (i.e., HVAC system and outdoor air infiltration), which are respectively depicted by two newly-defined Archimedes numbers (i.e., Arc and Arh). Then, we developed dimensionless correlations between the indoor thermal stratification (quantified by the dimensionless factor of the vertical temperature profile, CT) and the two streams of air inflow (quantified by Arc and Arh). For application, the dimensionless correlations can be coupled with our previously proposed theoretical model to accurately predict the air infiltration rate in a large-space building. Moreover, the dimensionless analysis reveals a principle of indoor vertical temperature profile control to minimize the buoyancy driving force of air infiltration in large-space buildings: Achieving a vertically uniform indoor thermal environment under heating condition and an effectively stratified indoor thermal environment under cooling condition. These findings help to provide practical guidelines to minimize buoyancy-driven air infiltration in large-space buildings.

Use of distributed temperature sensing (DTS) coupled to ground source heat exchangers for geological thermo-stratigraphic correlation

The thermal characterisation of a geosonde field, consisting of four boreholes at the ENEA-Casaccia Research Centre (Rome, Italy), was carried out by processing the temperature values measured by DTS (Distributed Temperature Sensing) fibre optics positioned vertically in each well. By correlating the vertical temperature profiles, it was possible to estimate the thermal conductivity of each stratigraphic level and the contribution of the groundwater on the heat exchange between ground and geothermal probes. The theoretical model has been confirmed by the experimental data obtained through direct measurement of thermal conductivity on soil/rock samples collected at different depths.In the first 10 m of depth, temperature variations are influenced by seasonal climatic fluctuations, the amplitude of which decreases with depth, to regularise and assume a linear trend, compatible with the movement of groundwater.The work carried out has shown that the area investigated is affected by the upwelling of hydrothermal fluids from the deep aquifer, which infiltrate the fractured lavas reaching the most superficial layers of the subsurface. The results of this research could be useful for estimating the geothermal potential of the areas within the ‘Cesano geothermal field’, whose lithotypes belong to the Sabatini volcanic province.

Understanding the vertical temperature structure of recent record-shattering heatwaves

Abstract. Extreme heatwaves are one of the most impactful natural hazards, posing risks to human health, infrastructure, and ecosystems. Recent theoretical and observational studies have suggested that the vertical temperature structure during heatwaves limits the magnitude of near-surface heat through convective instability. In this study, we thus examine in detail the vertical temperature structure during three recent record-shattering heatwaves, the Pacific Northwest (PNW) heatwave in 2021, the western Russian (RU) heatwave in 2010, and the western European and UK (UK) heatwave in 2022, by decomposing temperature anomalies (T′) in the entire tropospheric column above the surface into contributions from advection, adiabatic warming and cooling, and diabatic processes. All three heatwaves exhibited bottom-heavy yet vertically deep positive T′ extending throughout the troposphere. Importantly, though, the T′ magnitude and the underlying physical processes varied greatly in the vertical within each heatwave, as well as across distinct heatwaves, reflecting the diverse synoptic storylines of these events. The PNW heatwave was strongly influenced by an upstream cyclone and an associated warm conveyor belt, which amplified an extreme quasi-stationary ridge and generated substantial mid- to upper-tropospheric positive T′ through advection and diabatic heating. In some contrast, positive upper-tropospheric T′ during the RU heatwave was caused by advection, while during the UK heatwave, it exhibited modest positive diabatic contributions from upstream latent heating only during the early phase of the respective ridge. Adiabatic warming notably contributed positively to lower-tropospheric T′ in all three heatwaves, but only in the lowermost 200–300 hPa. Near the surface, all three processes contributed positively to T′ in the PNW and RU heatwaves, while near-surface diabatic T′ was negligible during the UK heatwave. Moreover, there is clear evidence of an amplification and downward propagation of adiabatic T′ during the PNW and UK heatwaves, whereby the maximum near-surface T′ coincided with the arrival of maximum adiabatic T′ in the boundary layer. Additionally, the widespread ageing of near-surface T′ over the course of these events is fully consistent with the notion of heat domes, within which air recirculates and accumulates heat. Our results for the first time document the four-dimensional functioning of anticyclone–heatwave couplets in terms of advection, adiabatic cooling or warming, and diabatic processes and suggest that a complex interplay between large-scale dynamics, moist convection, and boundary layer processes ultimately determines near-surface temperatures during heatwaves.

The radiative and dynamical impact of clouds in the atmosphere of the hot Jupiter WASP-43 b

Context. Hot Jupiters are tidally locked gaseous exoplanets that exhibit large day-night temperature contrasts. Their cooler nightsides are thought to host clouds, as has been suggested by numerous observations. However, the exact nature of these clouds, their spatial distribution, and their impact on atmospheric dynamics, thermal structure, and spectra is still unclear. Aims. We investigate the atmosphere of WASP-43 b, a short period hot Jupiter recently observed with James Webb Space Telescope (JWST), to understand the radiative and dynamical impact of clouds on the atmospheric circulation and thermal structure. We aim to understand the impact of different kinds of condensates potentially forming in WASP-43 b, with various sizes and atmospheric metallicities. Methods. We used a 3D global climate model (GCM) with a new temperature-dependent cloud model that includes radiative feedbacks coupled with hydrodynamical integrations to study the atmospheric properties of WASP-43 b. We produced observables from our GCM simulations and compared them to spectral phase curves from various observations to derive constraints on the atmospheric properties. Results. We show that clouds have a net warming effect, meaning that the greenhouse effect caused by clouds is stronger than the albedo cooling effect. We show that the radiative effect of clouds has various impacts on the dynamical and thermal structure of WASP-43 b. Depending on the type of condensates and their sizes, the radiative-dynamical feedback will modify the horizontal and vertical temperature gradient and reduce the wind speed. For super-solar metallicity atmospheres, fewer clouds form in the atmosphere, leading to a weaker feedback. Comparisons with spectral phase curves observed with HST, Spitzer, and JWST indicate that WASP-43 b's nightside is cloudy and rule out sub-micron Mg2SiO4 cloud particles as the main opacity source. Distinguishing between cloudy solarand cloudy super-solar-metallicity atmospheres is not straightforward, and further observations of both reflected light and thermal emission are needed.