Solar Warming Research Articles

Bioinspired Superhydrophobic All-In-One Coating for Adaptive Thermoregulation.

The development of scalable and passive coatings that can adapt to seasonal temperature changes while maintaining superhydrophobic self-cleaning functions is crucial for their practical applications. However, the incorporation of passive cooling and heating functions with conflicting optical properties in a superhydrophobic coating is still challenging. Herein, an all-in-one coating inspired by the hierarchical structure of a lotus leaf that combines surface wettability, optical structure, and temperature self-adaptation is obtained through a simple one-step phase separation process. This coating exhibits an asymmetrical gradient structure with surface-embedded hydrophobic SiO2 particles and subsurface thermochromic microcapsules within vertically distributed hierarchical porous structures. Moreover, the coating imparts superhydrophobicity, high infrared emission, and thermo-switchable sunlight reflectivity, enabling autonomous transitions between radiative cooling and solar warming. The all-in-one coating prevents contamination and over-cooling caused by traditional radiative cooling materials, opening up new prospects for the large-scale manufacturing of intelligent thermoregulatory coatings.

A Janus Textile Capable of Radiative Subambient Cooling and Warming for Multi-Scenario Personal Thermal Management.

Textiles with radiative cooling/warming capabilities provide a green and effective solution to personal thermal comfort in different climate scenarios. However, developing multiple-mode textiles for wearing in changing climates with large temperature variation remains a challenge. Here a Janus textile is reported, comprising a polyethersulfone (PES)-Al2 O3 cooling layer optically coupled with a Ti3 C2 Tx warming layer, which can realize sub-ambient radiative cooling, solar warming, and active Joule heating. Owing to the intrinsically high refractive index of PES and the rational design of the fiber topology, the nanocomposite PES textile features a record high solar reflectance of 0.97. Accompanied by an infrared (IR) emittance of 0.91 in the atmospheric window, sub-ambient cooling of 0.5-2.5°C is achieved near noontime in humid summer under ≈1000W m-2 solar irradiation in Hong Kong. The simulated skin covered with the textile is ≈10°C cooler than that with white cotton. The Ti3 C2 Tx layer provides a high solar-thermal efficiency of ≈80% and a Joule heating flux of 66W m-2 at 2V and 15°C due to its excellent spectral selectivity and electrical conductivity. The switchable multiple working modes enable effective and adaptive personal thermal management in changing environments.

Causes and Characteristics of Electrical Resistivity Variability in Shallow (<4 m) Soils in Taylor Valley, East Antarctica

AbstractAirborne electromagnetic surveys collected in December 2011 and November 2018 and three soil sampling transects were used to analyze the spatial heterogeneity of shallow (<4 m) soil properties in lower Taylor Valley (TV), East Antarctica. Soil resistivities from 2011 to 2018 ranged from ∼33 Ωm to ∼3,500 Ωm with 200 Ωm assigned as an upper boundary for brine‐saturated sediments. Elevations below ∼50 m above sea level (masl) typically exhibit the lowest resistivities with resistivity increasing at high elevations on steeper slopes. Soil water content was empirically estimated from electrical resistivities using Archie's Law and range from ∼<1% to ∼68% by volume. An increase in silt‐ and clay‐sized particles at low elevations increases soil porosity but decreases hydraulic conductivity, promoting greater residence times of soil water at low elevations near Lake Fryxell. Soil resistivity variability between 2011 and 2018 shows soils at different stages of soil freeze‐thaw cycles, which are caused predominantly by solar warming of soils as opposed to air temperature. This study furthers the understanding of the hydrogeologic structure of the shallow subsurface in TV and identifies locations of soils that are potentially prone to greater rates of thaw and resulting ecosystem homogenization of soil properties from projected increases in hydrological connectivity across the region over the coming decades.

Ice and mixed-phase cloud statistics on the Antarctic Plateau

Abstract. Statistics on the occurrence of clear skies, ice clouds, and mixed-phase clouds over Concordia Station, in the Antarctic Plateau, are provided for multiple timescales and analyzed in relation to simultaneous meteorological parameters measured at the surface. Results are obtained by applying a machine learning cloud identification and classification (CIC) code to 4 years of measurements between 2012–2015 of downwelling high-spectral-resolution radiances, measured by the Radiation Explorer in the Far Infrared – Prototype for Applications and Development (REFIR-PAD) spectroradiometer. The CIC algorithm is optimized for Antarctic sky conditions and results in a total hit rate of almost 0.98, where 1.0 is a perfect score, for the identification of the clear-sky, ice cloud, and mixed-phase cloud classes. Scene truth is provided by lidar measurements that are concurrent with REFIR-PAD. The CIC approach demonstrates the key role of far-infrared spectral measurements for clear–cloud discrimination and for cloud phase classification. Mean annual occurrences are 72.3 %, 24.9 %, and 2.7 % for clear sky, ice clouds, and mixed-phase clouds, respectively, with an inter-annual variability of a few percent. The seasonal occurrence of clear sky shows a minimum in winter (66.8 %) and maxima (75 %–76 %) during intermediate seasons. In winter the mean surface temperature is about 9 ∘C colder in clear conditions than when ice clouds are present. Mixed-phase clouds are observed only in the warm season; in summer they amount to more than one-third of total observed clouds. Their occurrence is correlated with warmer surface temperatures. In the austral summer, the mean surface air temperature is about 5 ∘C warmer when clouds are present than in clear-sky conditions. This difference is larger during the night than in daylight hours, likely due to increased solar warming. Monthly mean results are compared to cloud occurrence and fraction derived from gridded (Level 3) satellite products from both passive and active sensors. The differences observed among the considered products and the CIC results are analyzed in terms of footprint sizes and sensors' sensitivities to cloud optical and geometrical features. The comparison highlights the ability of the CIC–REFIR-PAD synergy to identify multiple cloud conditions and study their variability at different timescales.

Prospective impacts of oil spills on floodplain vegetation: Both crude oil and diluted bitumen increase foliar temperatures, senescence and abscission in three cottonwood (Populus) species.

Oil pipelines are vulnerable at river crossings since floods can expose and rupture pipes, releasing oil that floats and coats floodplain vegetation. This study investigated the consequences of oil coatings on leaves of cottonwoods (riparian poplars), the predominant trees in floodplain woodlands around the Northern Hemisphere. The study compared conventional crude oil (CO) versus diluted bitumen (dilbit, DB), heavy oil originating from the Alberta oil sands; with petroleum jelly (PJ) as a reference. The treatments increased leaf surface temperatures (Tleaf) in narrowleaf and plains cottonwoods (Populus angustifolia, P. deltoides) and balsam poplars (P. balsamifera) (Control = 21.8°C, PJ = 23.7°C; CO = 26.2°C; DB = 28.1°C; Tair = 25°C). The leaf warming followed stomatal occlusion from the foliar coating, which would reduce transpiration and evaporative cooling, combined with increased solar warming with the darker oils. Tleaf varied across the three cottonwood species, with cooler, narrow, narrowleaf cottonwood leaves; intermediate plains cottonwood leaves; and warmer, darker, balsam poplar leaves (average Tleaf: narrowleaf = 23.8°C, plains = 24.3°C, and balsam = 26.7°C), with similar warming in each species following the different treatments. Across species and treatments, Tleaf was tightly correlated with foliar condition, which assessed turgor versus wilting of leaf blades and petioles, along with leaf necrosis and senescence (r2 = 0.980, narrowleaf; 0.998, plains; 0.852, balsam). This tight association indicates validity of both Tleaf and foliar condition as diagnostic measures. Crude oil and dilbit had similar foliar impacts, and for both, leaf abscission occurred within 2 to 3 weeks. Consequently, following an oil spill, remediation should commence quickly but extending vegetation removal beyond a few weeks would have limited benefit since the contaminated leaves would have abscised.

The avian "hibernation" enigma: thermoregulatory patterns and roost choice of the common poorwill.

Compared to mammals, there are relatively few studies examining heterothermy in birds. In 13 bird families known to contain heterothermic species, the common poorwill (Phalaenoptilus nuttallii) is the only species that ostensibly hibernates. We used temperature-sensitive radio-transmitters to collect roost and skin temperature (Tskin) data, and winter roost preferences for free-ranging poorwills in southern Arizona. Further, to determine the effect of passive rewarming on torpor bout duration and active rewarming (i.e., the use of metabolic heat to increase Tskin), we experimentally shaded seven birds during winter to prevent them from passively rewarming via solar radiation. Poorwills selected winter roosts that were open to the south or southwest, facilitating passive solar warming in the late afternoon. Shaded birds actively rewarmed following at least 3days of continuous torpor. Average torpor bout duration by shaded birds was 122h and ranged from 91 to 164h. Active rewarming by shaded birds occurred on significantly warmer days than those when poorwills remained torpid. One shaded bird remained inactive for 45days, during which it spontaneously rewarmed actively on eight occasions. Our findings show that during winter poorwills exhibit physiological patterns and active rewarming similar to hibernating mammals.

Calculation of the external surface temperature of a multi-layer wall considering solar radiation effects

ABSTRACT Infrared thermography has become a valuable tool for providing reliable information on the constructive components of the envelope of existing buildings and for checking if the thermal behaviour of a construction is consistent with the design parameters. However, infrared thermography has a limited capacity to offer quantitative accurate experimental results when the solar radiation incident on the facades is significant. The current study presents a methodology for theoretically calculating the external surface temperature of a multi-layer wall exposed to diurnal variations of the external environment temperature, which are caused by solar warming, hence validating a set of in situ measurements conducted using a thermographic camera over a time interval of interest. The measured external surface temperature is related to the theoretical equivalent sol-air temperature and the external and internal air temperatures by the numerical solution of the heat equation that is used to estimate the heat flux through a non-homogeneous medium. In addition, the numerical results are successfully compared with those obtained using the analytical standard admittance method. Thus, the instantaneous measurements of the external surface temperature can be generalised to calculate the heat flux into the building while considering the solar radiation effects during extended periods of time.

A century and a half of research on the evolution of insect flight

The gill and paranotal lobe theories of insect wing evolution were both proposed in the 1870s. For most of the 20th century, the paranotal lobe theory was more widely accepted, probably due to the fundamentally terrestrial tracheal respiratory system; in the 1970s, some researchers advocated for an elaborated gill (“pleural appendage”) theory. Lacking transition fossils, neither theory could be definitively rejected.Winged insects are abundant in the fossil record from the mid-Carboniferous, but insect fossils are vanishingly rare earlier, and all earlier fossils are from primitively wingless insects. The enigmatic, isolated mandibles of Rhyniognatha (early Devonian) hint that pterygotes may have been present much earlier, but the question remains open.In the late 20th century, researchers used models to study the interaction of body and protowing size on solar warming and gliding abilities, and stability and glide effectiveness of many tiny adjustable winglets versus a single, large pair of immobile winglets. Living stoneflies inspired the surface-skimming theory, which provides a mechanism to bridge between aquatic gills and flapping wings. The serendipitously discovered phenomenon of directed aerial descent suggests a likely route to the early origin of insect flight. It provides a biomechanically feasible sequence from guided falls to fully-powered flight.

Global Estimates of Lateral Springtime Restratification

AbstractSubmesoscale frontal dynamics are thought to be of leading-order importance for stratifying the upper ocean by slumping horizontal density gradients to produce vertical stratification. Presented here is an investigation of submesoscale instabilities in the mixed layer—mixed layer eddies (MLEs)—as a potential mechanism of frontal slumping that stratifies the upper ocean during the transition from winter to spring, when wintertime forcings weaken but prior to the onset of net solar warming. Observations from the global Argo float program are compared to predictions from a one-dimensional mixed layer model to assess where in the world’s oceans lateral processes influence mixed layer evolution. The model underestimates spring stratification for ~75% ± 25% of the world’s oceans. Relationships between vertical and horizontal temperature and salinity gradients are used to suggest that in 30% ± 20% of the oceans this excess stratification can be attributed to the slumping of horizontal density fronts. Finally, 60% ± 10% of the frontal enhanced stratification is consistent with MLE theory, suggesting that MLEs may be responsible for enhanced stratification in 25% ± 15% of the world’s oceans. Enhanced stratification from frontal tilting occurs in regions of strong horizontal density gradients (e.g., midlatitude subtropical gyres), with a small fraction occurring in regions of deep mixed layers (e.g., high latitudes). Stratification driven by MLEs appears to constrain the coexistence of sharp lateral gradients and deep wintertime mixed layers, limiting mixed layer depths in regions of large lateral density gradients, with an estimated wintertime restratification flux of order 100 W m−2.

Naturally triggered persistent deep slab avalanches in western Canada Part I: avalanche characteristics and weather trends from weather stations

ABSTRACTA database of difficult-to-forecast natural persistent deep slab avalanches was analyzed to determine thresholds for parameters that contribute to their release in western Canada. The database included avalanche observations and weather station data. The avalanches were grouped based on their primary cause-of-release, either precipitation loading, wind loading, solar warming or air temperature warming using a multivariate classification tree, which first split using a solar warming parameter. The precipitation group had a median 24 h snowfall of 15 cm and 3 d snowfall of 38 cm at weather stations, mostly at or below treeline. These amounts were likely closer between 20–30 and 50–80 cm at alpine start zones. The wind loading group experienced the most wind-transported snow potential. The solar warming group had predicted solar warming of 5.2°C, 10 cm into the snowpack, on the days of release. The air temperature warming group experienced the highest median maximum air temperature (5°C) on the days of release. These thresholds may be useful to forecast the likelihood of similar avalanches with experienced-based forecasting or with decision aids, although many false alarms are possible. A companion paper, Part II, relates weather model data to avalanche occurrences.

Naturally triggered persistent deep slab avalanches in western Canada Part II: weather trends from model forecasts

ABSTRACTFor 175 difficult-to-forecast persistent deep slab avalanches, weather data were obtained from Global Environmental Multiscale (GEM) models produced by Environment Canada. The focus was to determine critical parameters and thresholds for avalanche forecasting from GEM and compare them with weather station data analyzed in Part I (Conlan and Jamieson, this issue). The high-resolution GEM-limited-area model (2.5 km resolution) forecasted higher median precipitation amounts than both the lower-resolution GEM15 (15 km resolution) and weather stations within a small dataset. Air temperatures were lower for both weather models compared with the weather station data, likely because of elevation differences. A multivariate classification tree created with GEM15 data correctly classified 29 of 36 avalanches by their primary cause-of-release, using a primary split of modelled solar warming of 5.9°C, 10 cm into the snowpack. For all 175 avalanches, GEM15 forecasted significantly less precipitation than observed at the weather stations, particularly with multi-day cumulative amounts. The majority of GEM15 surface wind speeds were between 0 and 10 km h−1, producing negligible wind loading amounts. The parameter values may be helpful for predicting future persistent deep slab avalanches. However, GEM output is not always representative of field conditions and should be used in conjunction with other sources.

A potential hidden layer of meteorites below the ice surface of Antarctica

Antarctica contains some of the most productive regions on Earth for collecting meteorites. These small areas of glacial ice are known as meteorite stranding zones, where upward-flowing ice combines with high ablation rates to concentrate large numbers of englacially transported meteorites onto their surface. However, meteorite collection data shows that iron and stony-iron meteorites are significantly under-represented from these regions as compared with all other sites on Earth. Here we explain how this discrepancy may be due to englacial solar warming, whereby meteorites a few tens of centimetres below the ice surface can be warmed up enough to cause melting of their surrounding ice and sink downwards. We show that meteorites with a high-enough thermal conductivity (for example, iron meteorites) can sink at a rate sufficient to offset the total annual upward ice transport, which may therefore permanently trap them below the ice surface and explain their absence from collection data.

Reexamining the Relationship between Climate Sensitivity and the Southern Hemisphere Radiation Budget in CMIP Models

Abstract Recent efforts to narrow the spread in equilibrium climate sensitivity (ECS) across global climate models have focused on identifying observationally based constraints, which are rooted in empirical correlations between ECS and biases in the models’ present-day climate. This study reexamines one such constraint identified from CMIP3 models: the linkage between ECS and net top-of-the-atmosphere radiation biases in the Southern Hemisphere (SH). As previously documented, the intermodel spread in the ECS of CMIP3 models is linked to present-day cloud and net radiation biases over the midlatitude Southern Ocean, where higher cloud fraction in the present-day climate is associated with larger values of ECS. However, in this study, no physical explanation is found to support this relationship. Furthermore, it is shown here that this relationship disappears in CMIP5 models and is unique to a subset of CMIP models characterized by unrealistically bright present-day clouds in the SH subtropics. In view of this evidence, Southern Ocean cloud and net radiation biases appear inappropriate for providing observationally based constraints on ECS. Instead of the Southern Ocean, this study points to the stratocumulus-to-cumulus transition regions of the SH subtropical oceans as key to explaining the intermodel spread in the ECS of both CMIP3 and CMIP5 models. In these regions, ECS is linked to present-day cloud and net radiation biases with a plausible physical mechanism: models with brighter subtropical clouds in the present-day climate show greater ECS because 1) subtropical clouds dissipate with increasing CO2 concentrations in many models and 2) the dissipation of brighter clouds contributes to greater solar warming of the surface.

Atmospheric stability varying wind shear coefficients to improve wind resource extrapolation: A temporal analysis

Based on a 3-year (2011–2013) dataset of 10-min records collected at 10, 20, 40, and 80 m from the met mast of Cabauw, a time-varying investigation of the wind shear coefficient (WSC) relationship with atmospheric stability was addressed. WSC interdaily and interannual variability was analysed according to a 2-D combined representation, which confirmed a clear oval-shaped “solar shadow” caused by solar warming observed during diurnal unstable hours, and large WSCs occurring under strong stable conditions during the summer nights.Three different power law based approaches were compared to extrapolate wind resource to the turbine hub height according to the following WSC settings: (i) site's previously measured overall yearly average; (ii) site's previously measured stability-varying yearly averages; (iii) 10-min theoretically predicted values by applying the Panofsky and Dutton (PD) model. The latter proved to be the finest approach, providing extrapolated wind resource biased by 1–5% and energy yield by 5.51–10.57%, and showing the highest accuracy occurring under the most frequent (and most energetic) neutral conditions, when Weibull distribution's tail including the highest wind speed bins is particularly finely reproduced.This work confirmed how instrumental availability of detailed information on site's atmospheric stability classification is for wind energy studies.

Modeling temperature and humidity profiles within forest canopies

Physically-based models are a powerful tool to help understand interactions of vegetation, atmospheric dynamics, and hydrology, and to test hypotheses regarding the effects of land cover, management, hydrometeorology, and climate variability on ecosystem processes. The purpose of this paper is to evaluate recent modifications and further refinements to a multi-layer plant canopy model for simulating temperature and water vapor within three diverse forest canopies: a 4.5-m tall aspen thicket, a 15-m tall aspen canopy, and a 60-m tall Douglas fir canopy. Performance of the model was strongly related to source strength and profile stability within the canopy. Root mean square deviation (RMSD) between simulated and observed values tended to be higher for the summer periods when there was much more heat and vapor added to the canopy space due to solar warming and transpiration. Conversely, RMSD for vapor pressure was lowest for the winter periods when vapor additions within the canopy space were minimal. RMSD for temperature ranged from 0.1°C for the top of the 15-m aspen canopy during the winter to 1.6°C for the bottom of the 4.5-m aspen thicket during the summer period. RMSD for vapor pressure ranged from 0.002kPa for the top of the 15-m aspen canopy during winter to 0.141kPa for the bottom of the 4.5-m aspen thicket during the summer. Unstable profile conditions were simulated better by the model than stable conditions for all sites. RMSD for temperature at the bottom of the 4.5-m aspen, 15-m aspen and 60-m Douglas fir were 0.89, 0.77, and 0.85°C, respectively, for unstable conditions compared to 1.44, 0.89 and 1.16°C for stable conditions. Stable profiles are more challenging to accurately simulate because dispersion within a stable profile is lower thereby creating larger gradients. Temperature differences between the bottom and above canopy sensors were within 3°C for unstable conditions for all sites, but were as much as −10°C under stable conditions. The model exhibited the greatest discrepancies relative to measurements in the 4.5-m aspen thicket under stable conditions, likely due to horizontal ejections from this relatively small patch of vegetation that could not be addressed by the one-dimensional model. At each site, the model performed best near the top of canopy where the air was well mixed and gradients between it the meteorological conditions above the canopy used to force the model were minimal.

Solar warming of the south-central Pacific

Surface solar radiation is found to have contributed significantly and positively to the record warming event in the south-central Pacific (SCP) that peaked in December of 2009. The SCP region is within a positive teleconnection pattern between sea surface temperature anomalies in the equatorial Pacific and basin-wide surface solar radiation, as revealed by a 24-year time series; the pattern extends southeast from the western equatorial Pacific toward the SCP region. The results are consistent with the ‘atmospheric bridge postulation’ on El Niño teleconnection with extratropical sea surface temperature anomalies, but with the extension to cloud cover and surface solar radiation over the mid-latitude southern oceans.

On the absence of solar evolution‐driven warming through the Phanerozoic

AbstractReconstructed temperatures through the Phanerozoic indicate a gradual cooling or, at best, no significant temperature trend, despite a 4.4% increase in solar heating. It is possible that an underlying warming trend has simply been swamped by ‘noise’ due to significant data‐errors and/or natural fluctuations. Alternatively, the lack of warming may indicate cooling by biological and/or geological processes, which happen to have the right amplitude to cancel the effects of solar warming. This paper demonstrates that the absence of Phanerozoic warming cannot be explained as a warming trend hidden by noise. It also shows that, given widely accepted estimates of climate sensitivity, it cannot be explained as cancellation by negative feedback in the climate system. The Gaia hypothesis, anthropic selection or some other unconventional mechanism may therefore have to be invoked to explain the absence of long‐term warming through the Phanerozoic.

Characteristics of ground thermal properties in Harbin, China

Eleven representative sites were selected in this study to present the characteristics of ground thermal properties in Harbin, China. The initial ground temperature field was measured, and the temperature ranges of the solar warming, constant temperature, and increasing temperature layers were determined. The 22 thermal response tests (TRTs) for 11 boreholes were examined with two heating powers (4.2kW and 6.5kW). Analysis of thermal properties was performed in the laboratory. A total of 337 representative samples of rock and soil were analyzed, and their thermal properties were measured in laboratory tests, and the results of these tests are not consistent with those of TRTs. The overall characteristics of ground thermal conductivity are determined according to overall distribution.

Measurements and weather observations at persistent deep slab avalanches

Persistent deep slab avalanches are generally hard to forecast and can release under diverse conditions ranging from storms to clear days to locally induced stress on the snowpack. For the formation of many natural avalanches, a point is reached where the mass loading of overlying snow exceeds the mechanical properties of the weak layer. This can occur from additional loading above the weak layer, such as from precipitation or wind loading. Furthermore, natural failure can occur from solar warming and temperature variations. External stresses applied to the snowpack from skiers, snowmobilers, and other forces can also trigger deep slab avalanches. We accessed and made field measurements at 41 persistent deep slab avalanches that released after the avalanche cycle of the respective persistent weak layer. These measurements included the properties of the failure layers, slab load, and preceding weather to determine trends and correlations between such variables. The failure planes were analyzed using the Deep Tap test (DT), Propagation Saw Test (PST), shear frame tests, and hand hardness. The overlying loads were calculated using density measurements. Spatial variability across the crowns was also assessed by the use of multiple profiles and tests. Precipitation, temperature, and wind data were obtained from the nearest automatic weather station to the respective avalanche start zone. DTs often yielded sudden (Q1) fractures and the cut length in PSTs was usually less than 60% of the column length when the fracture propagated to the end. Tests were repeated at multiple sites for a few deep slab avalanches and they indicated that DT taps and shear strength of the failure layer tended to increase with crown height. Crown height typically varied substantially at each deep slab avalanche. Preceding weather prior to the accessed deep slab avalanches showed an increase in precipitation and change in temperature for some releases and little change in wind speed and direction for many releases.

Solar warming of near-bottom water over a fringing reef

Solar warming of near-bottom water over a fringing reef