Absorption Of Solar Radiation Research Articles

Clothing color effect as a target of the smallest scale climate change adaptation.

The purpose of this study is to understand a physical mechanism to determine the surface temperature of clothes in calm and fine conditions of outdoors. We observed surface temperatures of polo shirts of the same material and design but different colors. The shirts were placed in unshaded and well-ventilated outdoor, open spaces on sunny summer days. The maximum difference between dark green or black and white was more than 15°C during calm, fine weather and was greatest when the solar radiation was strong. If the transmission of solar radiation energy through a shirt is ignored to calculate the absorption by the shirt, the difference in solar radiation absorption due to different colors is as much as 24% in the maximum, and if considered, we concluded that an absorption difference of 34% led to a temperature difference of 15℃. When we compared the brightness of the colors, we found that the albedo of both the visible and NIR bands explained why the red and green colors were so different with respect to the surface temperatures we observed. The reflection in the NIR bands was also an important determinant of the surface temperature. An additional experiment using masks showed that the temperature difference between white and black was almost eliminated at a wind speed of ~ 3m/s. The color of clothing is therefore a target for small-scale adaptation to climate change.

High reflectivity and latent heat synergetic TiO2/Cs0.33WO3-PU double-layer materials with zero transmittance

Passive Cooling Technology, as a method of achieving long-term refrigeration without the need for external energy input, has emerged as an alternative to traditional energy-intensive cooling, garnering increasing attention from academia and industry. However, current passive cooling technology faces challenges such as incomplete solar energy reflection, overcooling, and inevitable absorption of solar radiation and surrounding environmental heat. This paper presents a passive cooling bilayer film with latent heat storage capability, composed of a solid–solid phase change polyurethane (PU) matrix with added TiO2 and Cs0.33WO3.TiO2/Cs0.33WO3-PU exhibits minimal solar transmittance, with reflectance and emissivity rates of 84.46 % and 93.08 %, respectively. The solid–solid phase change matrix effectively mitigates overcooling and heat input issues, reducing temperature fluctuations and peaks, and thereby enhancing passive cooling performance. At the phase transition temperature (306 K), TiO2/Cs0.33WO3-PU achieves cooling powers of 113.77 W/m2(day time) and 173.19 W/m2(night time), the temperature can be reduced by 14.3 °C under 100 mW/cm2sunlight. Additionally, TiO2/Cs0.33WO3-PU demonstrates outstanding thermal stability and reliabitity, hydrophobicity, as well as resistance to UV aging. Moreover, it offers the flexibility to adjust the phase transition temperature and latent heat of the solid–solid phase change matrix according to specific environmental conditions. TiO2/Cs0.33WO3-PU combines passive cooling materials with phase change materials, and complements each other’s advantages. TiO2/Cs0.33WO3-PU not only improves the cooling power, but also provides a new solution to the problem of heat input and supercooling of passive cooling materials. TiO2/Cs0.33WO3-PU also provides new possibilities for the application of passive cooling materials in the fields of long-term outdoor building cooling, human heat management, food preservation and electrical equipment cooling.

Luminescent boron carbon oxynitride phosphors: a cost-efficient strategy to boost solar cell spectral responsiveness

The incorporation of a Luminescent down-shifting (LDS) layer has emerged as a compelling approach for augmenting the light absorption sensitivity and power conversion efficiency of solar cells, particularly in the short-wavelength light spectrum. In this investigation, we propose the utilization of low-cost, environmentally benign Boron carbon oxynitride (BCNO) phosphors as a viable material for the enhancement of solar radiation absorption in the ultraviolet-blue range. We synthesized BCNO phosphors through a combustion method and conducted a comprehensive analysis of the structural and spectral attributes concerning the impact of temperature. The synthesized boron carbon oxynitride phosphors exhibit a hexagonal boron nitride structure, with an irregular shape and an average particle size of 2447.9 nm. The analysis of photoluminescence spectra reveals that BCNO phosphors effectively capture photons within the 300–500 nm wavelength range and subsequently re-emit them at longer wavelengths. This phenomenon aligns with the overarching goal of optimizing solar cell performance, as it is in the longer wavelength range that solar cells exhibit enhanced efficiency. These findings support the promising potential of BCNO phosphors as a compelling choice for deployment as an LDS layer material on the periphery of solar cells. By facilitating increased photon absorption in the short-wavelength region, BCNO phosphors have the capacity to significantly enhance device performance.

Floral thermal biology in relation to pollen thermal performance in an early spring flowering plant.

The floral microenvironment impacts gametophyte viability and plant-pollinator interactions. Plants employ mechanisms to modify floral temperature, including thermogenesis, absorption of solar radiation, and evaporative cooling. Whether floral thermoregulation impacts reproductive fitness, and how floral morphological variation mediates thermoregulatory capacity are poorly understood. We measured temperature of the floral microenvironment in the field and tested for thermogenesis in the lab in early spring flowering Hexastylis arifolia (Aristolochiaceae). We evaluated whether thermoregulatory capacity was associated with floral morphological variation. Finally, we experimentally determined the thermal optimum and tolerance of pollen to assess whether thermoregulation may ameliorate thermal stress to pollen. Pollen germination was optimal near 21 °C, with a 50% tolerance breadth of ~18 °C. In laboratory conditions, flowers exhibited thermogenesis of 1.5-4.8 °C for short intervals within a conserved timeframe (08:00-09:00 h). In the field, temperature inside the floral tube often deviated from ambient - floral interiors were up to 4 °C above ambient when it was cold, but some fell nearly 10 °C below ambient during peak heat. Flowers with smaller openings were cooler and more thermally stable than those with larger openings during peak heat. Thermoregulation maintained a floral microenvironment within the thermal tolerance breadth of pollen. Results suggest that H. arifolia flowers have a stronger capacity to cool than to warm, and that narrower floral openings create a distinct floral microenvironment, enhancing floral cooling effects. While deviation of floral temperature from ambient conditions maintains a suitable environment for pollen and suggests an adaptive role of thermoregulation, we discuss adaptive and nonadaptive mechanisms underlying floral warming and cooling.

Synergetic integration of machining metal scrap for enhanced evaporation in solar stills: A sustainable novel solution for potable water production

The global water crisis necessitates innovative solutions for sustainable potable water production. Solar stills represent a promising technology for harnessing solar energy to meet this demand. However, solar stills often face limitations regarding yield and cost-effectiveness. This research addresses the pressing need to augment the performance of solar stills by introducing amendments such as utilizing black-coated metal scrap as a photothermal absorber in the absorber basin. These modifications aim to boost the absorption of solar radiation, thereby increasing potable water yield and improving the system’s economic viability. The study explores the utilization of black-coated metal scrap as a photothermal absorber to modify the absorber basin. Experimental results demonstrate a significant improvement in potable water yield, with a 129.85 % increase on day 1 and 127.21 % on day 2, reaching 3080 mL/m2 and 3090 mL/m2, respectively. Compared to conventional solar stills, the newly developed double slope solar still with an absorber basin featuring metal scrap exhibits a remarkable economic advantage, with a payback period (PBP) of 5.4 months, as opposed to 9.45 months for the traditional system. Additionally, the cost per liter (CPL) of potable water generated by the innovative system is 75.53 % lower than that of the conventional solar still system.

Pollution characteristics, source apportionment and absorption spectra of size-resolved PAHs in atmospheric particles in a cold megacity of China

Polycyclic aromatic hydrocarbons (PAHs) have the capability for solar radiation absorption related to climate forcing. Herein, pollution characteristics and absorption spectra of size-resolved PAHs in atmospheric particles in a cold megacity were comprehensively investigated. The mean concentrations of Σ18PAHs in all the 11 particle size ranges were 3.95 ± 4.77 × 104 pg/m3 and 2.17 ± 1.54 × 103 pg/m3 in heating period (HP) and non-heating period (NHP), respectively. Except for most PAHs with 2 and 3 benzene rings in NHP, most other PAHs showed a unimodal distribution pattern with the peak at 0.56–1.0 µm in both periods, which was caused by PAH emission sources. The PAH-related climate forcing was mainly caused by the solar radiation absorptions at ∼325 (∼330) nm and ∼365 nm. In general, the absorption intensities were higher in HP than NHP. The absorption intensity in the particle size range of 0.56–1.0 µm was the highest, and benzo[e]pyrene was the dominant contributor. In colder periods in HP, higher PAH concentrations caused more intensive PAH-related climate forcing. This study provided new insights for pollution characteristics and absorption spectra of size-resolved PAHs in atmospheric particles, which will be useful for better understanding PAH-related climate forcing.

Water and methanol soluble aerosol brown carbon over Bhopal, central India – Changes in optical properties and radiative effects during the COVID-19 lockdowns

Water-soluble organic carbon (WSOC) and methanol-soluble organic carbon (MeS-OC) in ambient PM2.5 over Bhopal, central India, were optically characterized during the COVID-19 lockdowns year (2020) to assess the influence of source reductions on these species and the induced changes in their radiative effects. During the lockdowns (23 March – May 31, 2020), the light absorption coefficients (babs-405) of WSOC and MeS-OC had higher values (75 %–105 %) compared to the corresponding period in 2019. MeS-OC light absorption at 365 nm and 550 nm were about thrice and twice, respectively, compared to WSOC absorption at these wavelengths. Increased fire counts and higher MAC405 (Mass Absorption Cross-section) of MeS-OC and WSOC (8 %–58 %) during the lockdowns compared to the corresponding period in 2019, indicated frequent biomass burning events because vehicular and industrial sources were completely shutdown during this period. Fractional solar radiation absorption (f300–400 nm) by MeS-OC and WSOC normalized by EC absorption was higher (15 % ± 9 % and 9 % ± 4 %, respectively) during the lockdowns compared to the corresponding period in 2019. The SFE300–400nm (Simple Forcing Efficiency) values for MeS-OCthisstudy→literature and WSOCthis study→literature were 8 % ± 5 % and 13 % ± 5 % higher, respectively, during lockdowns compared to the same period in 2019. Overall, the results suggested that biomass burning emissions during COVID-19 lockdowns offset (and overtook) any source emissions reduction induced aerosol radiative heating gains.

Seasonality of spectral radiative fluxes and optical properties of Arctic sea ice during the spring–summer transition

The reflection, absorption, and transmittance of shortwave solar radiation by sea ice play crucial roles in physical and biological processes in the ice-covered Arctic Ocean and atmosphere. These sea-ice optical properties, particularly during the melt season, significantly impact energy fluxes within and the total energy budget of the coupled atmosphere-ice-ocean system. We analyzed data from autonomous drifting stations to investigate the seasonal evolution of the spectral albedo, transmittance, and absorptivity for different sea-ice, snow, and surface conditions measured during the MOSAiC expedition in 2019–2020. The spatial variability of these properties was small during spring and increased strongly after melt onset on May 26, 2020, when liquid water content on the surface increased, largely accounting for the enhanced variability. The temporal evolution of surface albedo and sea-ice transmittance was mostly event-driven, thus containing episodic elements. Melt ponds reduced the local surface albedo by 31%–45%. Over the melting season, single ponding events increased the energy deposition of the sea ice by 35% compared to adjacent bare ice. Thus, single melt ponds may impact the summer energy budget as much as seasonal evolution over 1 month. Absorptivity and transmittance showed strong temporal and spatial variabilities independently of surface conditions, possibly due to the different internal sea-ice properties and under-ice biological processes. The differences in seasonal evolution shown for different sea-ice conditions strongly impacted the partitioning of shortwave solar radiation. This study shows that the formation and development of melt ponds, in reducing albedo by a third of bare ice sites, can notably increase the total summer heat deposition. The vastly different seasonal evolutions, different sea-ice conditions, and timing and duration of ponding events need to be considered when comparing local in-situ observations with large-scale satellite remote sensing datasets, which we suggest can help to improve numerical models.

Effects of reduced snowpack due to climate warming on abiotic and biotic soil properties in alpine and boreal forest systems

Reduction in snow cover, depth, onset, and duration of seasonal snow in mid-latitude regions due to climate warming has multiple global and local scale ecosystem impacts. These effects include modulations of the hydrological cycles and increases in land surface solar radiation absorption due to decreased albedo. Changes in snow cover characteristics also affect underlying soils. Snow has an insulating effect on soils by decoupling air and soil temperatures, thus seasonal snow cover reduction leads to overall lower soil temperatures and an increase in freeze-thaw cycles. This is especially prominent during the fall and spring thaw seasons when the snow cover is not as extensive. This in turn has downstream impacts on soil physical, chemical, and biological properties. Among these impacts are soil moisture reduction, temperature, frost regimes, soil pH shifts, and alteration in nutrient flux dynamics during winter, snowmelt period and the following summer growing season. These changes in soil physicochemical properties due to snowpack reduction can then impact the biological soil properties via increased plant root mortality, reduced abundance and diversity of soil arthropods, and shifts in composition, abundance and activity of soil microbial communities. All these soil biotic factors can in turn alter the dynamics of soil nutrient fluxes and future greenhouse gas emissions. Here, we integrate data on the effects of snow cover reduction on abiotic and biotic soil properties, with focus on temperate alpine and forest ecosystems and with an outlook on future impacts.

Exploration Of Key Approaches to Enhance Evacuated Tube Solar Collector Efficiency

Exploration Of Key Approaches to Enhance Evacuated Tube Solar Collector Efficiency

Thermally-stable solar energy absorber structure with machine learning optimization

Major problems that the world is currently confronting include global warming and the energy crisis, and the optimal absorption of solar spectrum radiation is a pivotal stage for a green future for the effective usage of solar thermal energy. The available solar absorbers are temperature sensitive and do not provide perfect absorption for a wide operation range. The major objectives of the proposed paper are to overcome these limitations and present an ultrawideband thermally stable solar absorber. The developed absorber utilizes a high melting point material comprising a Ti reflector element, a Si3N4 dielectric layer, and a pi-shaped top TiN metal layer. Within the spectral range spanning from 200 to 2500 nm, a notable average absorption rate of 97.69 % is attained. This structure has also demonstrated exceptionally under the AM1.5 conditions with a spectral absorption efficiency of 96 %. This work presents a novel optimization approach for solar absorbers, employing K-nearest neighbor (KNN) regression models to enhance design optimization by simulation time reduction with an R2 score of 0.999. The novelty resides in the absorber surface shape, utilization of cost efficient, sustainable, and thermally stable materials, as well as the KNN regression model for optimization of proposed solar absorber structure. Due to the angle and polarization insensitive characteristics, this structure can be potentially utilized for solar energy harvesting and shielding.

Dust storms from the Taklamakan Desert significantly darken snow surface on surrounding mountains

Abstract. The Taklamakan Desert (TD) is a major source of mineral dust emissions into the atmosphere. These dust particles have the ability to darken the surface of snow on the surrounding high mountains after deposition, significantly impacting the regional radiation balance. However, previous field measurements have been unable to capture the effects of severe dust storms accurately, and their representation on regional scales has been inadequate. In this study, we propose a modified remote-sensing approach that combines data from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite and simulations from the Snow, Ice, and Aerosol Radiative (SNICAR) model. This approach allows us to detect and analyze the substantial snow darkening resulting from dust storm deposition. We focus on three typical dust events originating from the Taklamakan Desert and observe significant snow darkening over an area of ∼ 2160, ∼ 610, and ∼ 640 km2 in the Tien Shan, Kunlun, and Qilian mountains, respectively. Our findings reveal that the impact of dust storms extends beyond the local high mountains, reaching mountains located approximately 1000 km away from the source. Furthermore, we observe that dust storms not only darken the snowpack during the spring but also in the summer and autumn seasons, leading to increased absorption of solar radiation. Specifically, the snow albedo reduction (radiative forcing) triggered by severe dust deposition is up to 0.028–0.079 (11–31.5 W m−2), 0.088–0.136 (31–49 W m−2), and 0.092–0.153 (22–38 W m−2) across the Tien Shan, Kunlun, and Qilian mountains, respectively. This further contributes to the aging of the snow, as evidenced by the growth of snow grain size. Comparatively, the impact of persistent but relatively slow dust deposition over several months during non-event periods is significantly lower than that of individual dust events. This highlights the necessity of giving more attention to the influence of extreme events on the regional radiation balance. This study provides a deeper understanding of how a single dust event can affect the extensive snowpack and demonstrates the potential of employing satellite remote sensing to monitor large-scale snow darkening.

Rational sonochemical engineering of Ag2CrO4/g-C3N4 heterojunction for eradicating RhB dye under full broad spectrum

In this novel research, S-scheme Ag2CrO4/g-C3N4 heterojunctions were generated by sonochemical hybridization of different compositions of Ag2CrO4 nanoparticles [EVB = +2.21 eV] and g-C3N4 sheets [ECB = −1.3 eV] for destructing RhB dye under artificial solar radiation. The as-synthesized nanocomposites were subjected to X-ray diffraction [XRD], diffuse reflectance spectrum [DRS], X-ray photoelectron spectroscopy [XPS], N2-adsorption-desorption isotherm, photoluminescence [PL] and high resolution transmission electron microscope [HRTEM] analysis to explore the interfacial interactions between g-C3N4 sheets and Ag2CrO4 nanoparticles. Spherical Ag2CrO4 nanoparticles deposited homogeneously on the wrinkles points of g-C3N4 sheets at nearly equidistant from each other facilitating the uniform absorption of solar radiations. The absorbability of solar radiations was enhanced by introducing 20 wt % Ag2CrO4 on g-C3N4 sheets. The surface area of g-C3N4 sheets was reduced from 37.5 to 16.4 m2/g and PL signal intensity diminished by 80 % implying the successful interfacial interaction between Ag2CrO4 nanoparticles and g-C3N4 sheets. The photocatalytic performance of heterojunctions containing 20 % Ag2CrO4 and 80 % g-C3N4 destructed 96 % of RhB dye compared with 60 and 33 % removal on the surface of pristine g-C3N4 sheets and Ag2CrO4, respectively. Benzoquinone and ammonium oxalate are strongly scavenged the dye decomposition revealing the strong influence of valence band holes of Ag2CrO4 and superoxide radicals in destructing RhB dye under solar radiations. S-scheme charge transportation mechanism was suggested rather than type II heterojunction on the light of scavenger trapping experiments results and PL spectrum of terephthalic acid. Overall, this research work illustrated the manipulation of novel S-scheme heterojunction with efficient redox power for destructing various organic pollutants persisted in water resources.

Performance evaluation and economic analysis of inclined solar dryer for Capsicum annuum L. (Red chilli) drying

This study presents an assessment of the performance and economic viability of solar dryers for drying perishable agricultural products. The dryer was constructed using locally sourced materials such as galvanized iron sheet, M.S. angle, glass, and S.S. wire mesh. The ability to tilt the dryer allows for optimal solar radiation absorption throughout the year in Jodhpur, India. It is well-established that a tilted surface captures more solar radiation compared to a horizontal plane, hence the utilization of a solar dryer in this research. A drying experiment was carried out in January 2023 using the dryer to dehydrate red chilli (Capsicum annuum L.). The maximum stagnation temperature inside the drying chamber was recorded at 65°C, which decreased to 55°C when loaded with 10 kg of chilli, while the outside ambient temperature was 26°C on a clear sky day (from 08:00 h to 18:00 h) in January 2023. Over the course of seven days, the moisture content of the chilli decreased from 80% (wet basis) to approximately 9%. The open sun drying method took 14 days for reducing the moisture content of red chillies to the same level. The dryer's thermal efficiency was calculated to be 16.25%. The economic analysis of the solar dryer indicated a high internal rate of return (IRR) of 82.5% and a short payback period of 1.50 years, highlighting its cost-effectiveness. The cost-benefit ratio was found to be 1.98, demonstrating the potential of solar dryers as a substitute for traditional drying methods. Economic parameters such as net present value (₹40220) and system annuity (₹5430) confirmed the economic feasibility of the system. Inclined solar dryers in remote or rural areas have the potential to significantly reduce postharvest losses and carbon emissions. The adoption of solar dryers would greatly benefit farmers in the arid region of Rajasthan.

Intelligent Space Thermal Control Radiator Based on Phase Change Material with Partial Visible Transparency

Coating structures with dynamically adjustable infrared emissivity are crucial in spacecraft components to cope with the transient thermal environments of space. For a long time, thermochromic phase change materials have been widely used in applications requiring emissivity adjustment, and optimizing the range of adjustable infrared emissivity has always been at the forefront of research. However, reducing the absorption of solar radiation has significant implications for the practical application and thermal stability of spacecraft components in space environments. In this paper, we propose a multilayer film structure based on the phase change material VO2 combined with the materials ZnSe and ITO to achieve low solar radiation absorption and adjustable infrared emissivity for intelligent thermal radiators in space. Through finite element simulation analysis of the structure, we achieve a solar radiation absorption rate of 0.3 and an adjustable infrared emissivity of 0.49. According to Stefan–Boltzmann’s law, the structure exhibits strong radiative heat dissipation at high temperatures and weak energy dissipation at low temperatures to maintain the thermal stability of the device and ensure efficient operation. The intelligent thermal radiator operates based on the principles of Fabry–Perot resonance. Therefore, the multilayer structure based on the phase change material VO2 demonstrates excellent performance in both solar radiation absorption and adjustable infrared emissivity, showcasing its tremendous potential in the field of intelligent thermal control in aerospace.

Artificial neural network analysis of the flow of nanofluids in a variable porous gap between two inclined cylinders for solar applications

Copper (Cu) nanoparticles (NPs) and polyvinyl alcohol (PVA) are utilized to enhance heat transfer (HT) which is used in the efficiency of solar energy systems. Copper nanoparticles have excellent thermal conductivity (TC) properties that enable them to conduct heat efficiently. In this arrangement, the gap between the two cylindrical channels is settled for the hybrid nanofluids (HNFs) flow in an inclined position that is favourable to sunlight. The nanomaterials consist of a mixture of PVA and Cu nanoparticles (NPs), to execute HNFs. Solar radiation is present on the hot side of the system. The porous gap between the two channels is considered variable which plays a crucial role in enhancing heat transfer and energy conversion. The varying permeability of the gap is adjusted to control the flow resistance and improve the stability of the system. It is observed that higher porosity allows for better convective heat transfer and reduced pressure drop. The transformed equations are solved through an artificial neural network (ANN) while the control volume finite element method (CVFEM) is also used to handle the governing equations. The Cu and PVA (HNF) improves solar radiation absorption and protects components, ultimately increasing the performance and efficiency of the systems.

How heating tracers drive self-lofting long-lived stratospheric anticyclones: simple dynamical models

Abstract. Long-lived “bubbles” of wildfire smoke or volcanic aerosol have recently been observed in the stratosphere, co-located with ozone, carbon monoxide, and water vapour anomalies. These bubbles often survive for several weeks, during which time they ascend through vertical distances of 15 km or more. Meteorological analysis data suggest that this aerosol is contained within strong, persistent anticyclonic vortices. Absorption of solar radiation by the aerosol is hypothesised to drive the ascent of the bubbles, but the dynamics of how this heating gives rise to a single-sign anticyclonic vorticity anomaly have thus far been unclear. We present a description of heating-driven stratospheric vortices, based on an axisymmetric balanced model. The simplest version of this model includes a specified localised heating moving upwards at fixed velocity and produces a steadily translating solution with a single-signed anticyclonic vortex co-located with the heating, with corresponding temperature anomalies forming a vertical dipole, matching observations. A more complex version includes the two-way interaction between a heating tracer, representing the aerosol, and the dynamics. An evolving tracer provides heating which drives a secondary circulation, and this in turn transports the tracer. Through this two-way interaction an initial distribution of tracer drives a circulation and forms a self-lofting tracer-filled anticyclonic vortex. Scaling arguments show that upward velocity is proportional to heating magnitude, but the magnitude of peak quasigeostrophic vorticity is O(f) (f is the Coriolis parameter) and independent of the heating magnitude. Estimates of vorticity from observations match our theoretical predictions. We discuss 3-D effects such as vortex stripping and dispersion of tracer outside the vortex by the large-scale flow, which cannot be captured explicitly by the axisymmetric model and are likely to be important in the real atmosphere. The large O(f) vorticity of the fully developed anticyclones explains their observed persistence and their effective confinement of tracers. To further investigate the early stages of formation of tracer-filled vortices, we consider an idealised configuration of a homogeneous tracer layer. A linearised calculation reveals that the upper part of the layer is destabilised due to the decrease in tracer concentrations with height there, which sets up a self-reinforcing effect where upward lofting of tracer results in stronger heating and hence stronger lofting. Small amplitude disturbances form isolated tracer plumes that ascend out of the initial layer, indicative of a self-organisation of the flow. The relevance of these idealised models to formation and persistence of tracer-filled vortices in the real atmosphere is discussed, and it is suggested that a key factor in their formation is the time taken to reach the fully developed stage, which is shorter for strong heating rates.

Absorption of Solar Radiation by Noctilucent Clouds in a Changing Climate

AbstractThe expected increase in climate change related methane emissions will result in an increase in middle atmospheric water vapor abundance. This will in turn amplify the brightness of noctilucent clouds (NLC). To examine how NLC will impact the absorption of solar radiation, we utilized both an atmospheric background model and a microphysical model spanning the period from 1950 to 2100. At a latitude of 69 ± 3°N, UV absorption at λ = 126 nm is projected to rise from ∼3% to ∼7%. In specific regions, the absorption may spike to approximately 30% by the year 2100. In the visible spectrum, we observe an absorption increase from 0.0030% in 1950 to 0.020% by 2100. Local absorption reach up to 0.35% by the year 2100. These trends are similar at 79 ± 3°N, but are smaller at 58 ± 3°N. Future average absorptions are comparable to solar cycle fluctuations, but local increases are significantly more pronounced. The ice mass contained in NLC is projected to surge from 677 to 1871 tons between 1950 and 2100.

Comparing the simulated influence of biomass burning plumes on low-level clouds over the southeastern Atlantic under varying smoke conditions

Abstract. Biomass burning plumes are frequently transported over the southeast Atlantic (SEA) stratocumulus deck during the southern African fire season (June–October). The plumes bring large amounts of absorbing aerosols and enhanced moisture, which can trigger a rich set of aerosol–cloud–radiation interactions with climatic consequences that are still poorly understood. We use large-eddy simulation (LES) to explore and disentangle the individual impacts of aerosols and moisture on the underlying stratocumulus clouds, the marine boundary layer (MBL) evolution, and the stratocumulus-to-cumulus transition (SCT) for three different meteorological situations over the southeast Atlantic during August 2017. For all three cases, our LES shows that the SCT is driven by increased sea surface temperatures and cloud-top entrainment as the air is advected towards the Equator. In the LES model, aerosol indirect effects, including impacts on drizzle production, have a small influence on the modeled cloud evolution and SCT, even when aerosol concentrations are lowered to background concentrations. In contrast, local semi-direct effects, i.e., aerosol absorption of solar radiation in the MBL, cause a reduction in cloud cover that can lead to a speed-up of the SCT, in particular during the daytime and during broken cloud conditions, especially in highly polluted situations. The largest impact on the radiative budget comes from aerosol impacts on cloud albedo: the plume with absorbing aerosols produces a total average 3 d of simulations. We find that the moisture accompanying the aerosol plume produces an additional cooling effect that is about as large as the total aerosol radiative effect. Overall, there is still a large uncertainty associated with the radiative and cloud evolution effects of biomass burning aerosols. A comparison between different models in a common framework, combined with constraints from in situ observations, could help to reduce the uncertainty.

Observed Energetic Adjustment of the Arctic and Antarctic in a Warming World

Abstract Satellite observations reveal that decreasing surface albedo in both polar regions is increasing the absorption of solar radiation, but the disposition of this absorbed energy is fundamentally different. Fluxes of absorbed solar radiation, emitted thermal radiation, and net energy imbalances are assessed for both polar regions for the last 21 years in the Clouds and Earth’s Radiant Energy System record. Arctic absorbed solar radiation is increasing at 0.98 ± 0.69 W m−2 decade−1, consistent with the anticipated response to sea ice loss. However, Arctic thermal emission is responding at a similar rate of 0.94 ± 0.55 W m−2 decade−1. This is surprising since the radiative impact of ice loss would be expected to favor increasing solar absorption. We find however, that clouds substantially mask trends in Arctic solar absorption relative to clear sky while having only a modest impact on thermal emission trends. As a result, the Arctic net radiation imbalance has not changed over the period. Furthermore, variability of absorbed solar radiation explains two-thirds of the variability in annual thermal emission suggesting that Arctic thermal fluxes rapidly adjust to offset changes in solar absorption and re-establish equilibrium. Conversely, Antarctic thermal emission is not responding to the increasing (although not yet statistically significant) solar absorption of 0.59 ± 0.64 W m−2 decade−1 with less than a third of the annual thermal variability explained by accumulated solar absorption. The Arctic is undergoing rapid adjustment to increasing solar absorption resulting in no change to the net energy deficit, while increasing Antarctic solar absorption represents additional energy input into the Earth system. Significance Statement The polar regions of Earth are undergoing ice loss through ongoing global warming, reducing the ice cover and decreasing solar reflectivity, which would be expected to warm these regions. We use satellite observations to measure the trends in solar absorption and emitted thermal radiation over the Arctic and Antarctic for the last two decades. Arctic thermal emission is increasing at a compensating rate to solar absorption with a close relationship between these processes. Conversely, Antarctic thermal emission is not responding to solar absorption demonstrating that Antarctic surface temperatures are not significantly influenced by the region’s reflectivity. The Arctic is undergoing rapid adjustment to increasing solar absorption through warming, while increasing Antarctic solar absorption represents additional energy input into the Earth system.