Reduction In Solar Irradiance Research Articles

A mathematical modelling for solar irradiance reduction of sunshades and some near-future albedo modification approaches for mitigation of global warming

To address the global warming problem, one of the space-based geoengineering solutions suggests the construction of an occluding disc that can work as a solar curtain to mitigate solar irradiation penetration to the earth atmosphere. A widely discussed concept needs the construction of a large-scale sunshade system near the Sun–Earth L1 equilibrium point in order to control the average global temperature. However, to improve the accuracy of theoretical estimations, more consistent modeling of the Sun-Curtain-Earth system and solar irradiance reduction rate are required. This study revisits the mathematical modeling of the solar irradiance reduction system and considers the fundamentals of shading physics. Simplified mathematical modeling of solar irradiance reduction rate is derived based on the solar flux density. For the climate control, controllability of the reduction rate by using some physical parameters (e.g., flux reflection rate and angle of the curtain) is discussed. Based on the results of this model, the technical challenges and feasibility of constructing a sunshade system at L1 Lagrange point are evaluated. Some technologically feasible, near-future options for the warming problem are discussed briefly.

Development of Advanced Solid-State Thermochromic Materials for Responsive Smart Window Applications.

This study introduces the synthesis and detailed characterization of a novel thermochromic material capable of reversible alterations in its thermotropic transmittance. Through an emulsion polymerization process, this newly developed material is composed of 75-85% octadecyl acrylate and 0-7% allyl methacrylate, demonstrating a pronounced discoloration effect across a narrow yet critical temperature range of 24.5-39 °C. The synthesized powder underwent a battery of tests, including differential scanning calorimetry and thermogravimetric analysis, as well as scanning electron microscopy. These comprehensive evaluations confirmed the material's exceptional thermal stability, uniform particle size distribution, and strong anchoring properties. Building upon these findings, we advanced the development of thermochromic polyvinyl butyral films and laminated glass products. By utilizing a coextrusion technique, we integrated these films into laminated glass, setting a new benchmark against existing glass technologies. Remarkably, the incorporation of thermochromic PVB films into laminated glass led to a significant reduction in solar irradiance of 20-30%, outperforming traditional double silver low-emissivity glass. This achievement demonstrates the exceptional shading and thermal insulation properties of the material. The research presented herein not only pioneers a valuable methodology for the engineering of smart materials with tunable thermotropic transmittance but also holds the key to unlocking enhanced energy efficiency across a spectrum of applications. The potential impact of this innovation on the realm of sustainable building materials is profound, promising significant strides toward energy conservation and environmental stewardship.

Assessment of solar geoengineering impact on precipitation and temperature extremes in the Muda River Basin, Malaysia using CMIP6 SSP and GeoMIP6 G6 simulations

The concept of solar geoengineering remains a topic of debate, yet it may be an effective way for cooling the Earth's temperature. Nevertheless, the impact of solar geoengineering on regional or local climate patterns is an active area of research. This study aims to evaluate the impact of solar geoengineering on precipitation and temperature extremes of the Muda River Basin (MRB), a very important agricultural basin situated in the northern Peninsular Malaysia. The analysis utilized the multi-model ensemble mean generated by four models that contributed to the Geoengineering Model Intercomparison Project (GeoMIP6). These models were configured to simulate the solar irradiance reduction (G6solar) and stratospheric sulfate aerosols (G6sulfur) strategies as well as the moderate (SSP245) and high emission (SSP585) experiments. Prior to the computation of extreme indices, a linear scaling approach was employed to bias correct the daily precipitation, maximum and minimum temperatures. The findings show that the G6solar and G6sulfur experiments, particularly the latter, could be effective in holding the increases in both annual and monthly mean precipitation totals and temperature extremes close to the increases projected under SSP245. For example, both G6solar and G6sulfur experiments project increases of temperature over the basin of 2 °C at the end of the 21st century as compared to 3.5 °C under SSP585. The G6solar and G6sulfur experiments also demonstrate some reliability in modulating the increases in precipitation extreme indices associated with flooding to match those under SSP245. However, the G6sulfur experiment may exacerbate dry conditions in the basin, as monthly precipitation is projected to decrease during the dry months from January to May and consecutives dry days are expected to increase, particularly during the 2045–2064 and 2065–2084 periods. Increases dry spells could indirectly affect agricultural and freshwater supplies, and pose considerable challenges to farmers.

Impacts of topographic shadows cast by surrounding terrain on the solar irradiance on glaciers' surface in High Mountain Asia (HMA)

High Mountain Asia (HMA) hosts a large number of mountain glaciers, where the terrains are complex and mountain shadows prevail. Solar radiation is an important factor influencing the surface energy balance of glacier and hence glaciers mass balance, as mountain shadows will inevitably decrease the direct solar irradiance on glaciers' surface. Although shadows caused by slope self-shading (SS) have been widely considered in previous research, the influence of topographic shadows (TS) cast by surrounding terrains on solar irradiance on glaciers' surface in HMA still remains unknown. In this study, a topographic solar radiation model was developed, and mountain shadows (including SS and TS) were simulated and validated against manually interpreted and automatically extracted shadows on the basis of Landsat images. Then the influence of TS on solar irradiance on glaciers' surface were evaluated. Results show that, the calculated mountain shadows have a good precision, with a mean mapping accuracy of 0.76, a mean user accuracy of 0.9, and a mean Tanimoto coefficient of 0.74. In HMA, the mean shadow duration over all glaciers is about 1385.5 h per year, accounting for about 30.5% of the daylight time, and exceeding 1900 h for many glaciers, even reaching 3000 h for some glaciers. The average TS shading time over all glaciers is about 719.6 h per year. In Karakoram and Western Tien Shan, the TS shading time is higher than 1000 h per year for many glaciers. For most glaciers, the TS shading time accounts for about one half of the total shading time. The reduction in annual solar irradiance caused by TS exceeds 5.0 W/m2 (3.5% of the annual mean) over 40%, and 7.9 W/m2 (5.7% of the annual mean) over 20% of the glaciers in HMA. On average, the mean ratio of shaded incoming direct solar irradiance caused by TS to the total caused by both TS and SS is about 49.4% over all glaciers. Overall, the solar irradiance reduction is minimal in the interior of the Qinghai-Tibet Plateau, followed by the Himalayas and the Transverse Range, and with the Western Tien Shan and Karakoram being the strongest. In a word, the solar irradiance reduction caused by TS is remarkable, ignoring it could pose a significant impact on the calculation of glacier mass balance in HMA.

Impact of centennial-scale solar activity reduction on the weakened Asian monsoon event at 9.2 ka BP

The weakened Asian monsoon event at 9.2 ka has been documented in many proxy-based reconstructions, but its underlying causes are uncertain. In this study, we investigated this event from a regional monsoon perspective by analysing simulations of Holocene transient solar activity forcing using the Community Earth System Model and high-resolution proxies. Our results revealed two separate periods of decreasing precipitation in the western North Pacific (WNP) and South Asian (SA) monsoons from 9.5 to 9.2 ka, each lagging behind two remarkable weakening events (0.38 and 0.21 W m−2) in solar forcing. However, there was no significant change in East Asian summer monsoon precipitation at 9.2 ka based on our experiment. Moisture budget analysis indicated that the dynamic effects term (i.e., anomalous descending motion) figured prominently in decreasing WNP and SA monsoon precipitation. Such a change was affected by an anomalous WNP anticyclone, which was maintained by the ‘wind-evaporation-sea surface temperature’ feedback during the decay phase of the centennial-scale El Niño-like event. The development of centennial El Niño-like conditions was caused by a reduction in solar irradiance. Reduced solar irradiance induced cooling over northern Australia, generating anomalous zonal sea level pressure gradients and westerlies over the tropical Pacific, ultimately resulting in the development of an El Niño-like pattern.

Impact of solar geoengineering on wildfires in the 21st century in CESM2/WACCM6

Abstract. We quantify future changes in wildfire burned area and carbon emissions in the 21st century under four Shared Socioeconomic Pathways (SSPs) scenarios and two SSP5-8.5-based solar geoengineering scenarios with a target surface temperature defined by SSP2-4.5 – solar irradiance reduction (G6solar) and stratospheric sulfate aerosol injections (G6sulfur) – and explore the mechanisms that drive solar geoengineering impacts on fires. This study is based on fully coupled climate–chemistry simulations with simulated occurrence of fires (burned area and carbon emissions) using the Whole Atmosphere Community Climate Model version 6 (WACCM6) as the atmospheric component of the Community Earth System Model version 2 (CESM2). Globally, total wildfire burned area is projected to increase over the 21st century under scenarios without geoengineering and decrease under the two geoengineering scenarios. By the end of the century, the two geoengineering scenarios have lower burned area and fire carbon emissions than not only their base-climate scenario SSP5-8.5 but also the targeted-climate scenario SSP2-4.5. Geoengineering reduces wildfire occurrence by decreasing surface temperature and wind speed and increasing relative humidity and soil water, with the exception of boreal regions where geoengineering increases the occurrence of wildfires due to a decrease in relative humidity and soil water compared with the present day. This leads to a global reduction in burned area and fire carbon emissions by the end of the century relative to their base-climate scenario SSP5-8.5. However, geoengineering also yields reductions in precipitation compared with a warming climate, which offsets some of the fire reduction. Overall, the impacts of the different driving factors are larger on burned area than fire carbon emissions. In general, the stratospheric sulfate aerosol approach has a stronger fire-reducing effect than the solar irradiance reduction approach.

Comparison of the carbon cycle and climate response to artificial ocean alkalinization and solar radiation modification

Carbon dioxide removal and solar radiation modification (SRM) are two classes of proposed climate intervention methods. A thorough understanding of climate system response to these methods calls for a good understanding of the carbon cycle response. In this study, we used an Earth system model to examine the response of global climate and carbon cycle to artificial ocean alkalinization (AOA), a method of CO2 removal, and reduction in solar irradiance that represents the overall effect of solar radiation modification. In our simulations, AOA is applied uniformly over the global ice-free ocean under the RCP8.5 scenario to bring down atmospheric CO2 to the level of RCP4.5, and SRM is applied uniformly over the globe under the RCP8.5 scenario to bring down global mean surface temperature to the level of RCP4.5. Our simulations show that with the same goal of temperature stabilization, AOA and SRM cause fundamentally different perturbations of the ocean and land carbon cycle. By the end of the 21st century, relative to the simulation of RCP8.5, AOA-induced changes in ocean carbonate chemistry enhances global oceanic CO2 uptake by 983 PgC and increases global mean surface ocean pH by 0.42. Meanwhile, AOA reduces land CO2 uptake by 79 PgC and reduces atmospheric CO2 concentration by 426 × 10−6. By contrast, relative to the simulation of RCP8.5, SRM has a minor effect on the oceanic CO2 uptake and ocean acidification. SRM-induced cooling enhances land CO2 uptake by 140 PgC and reduces atmospheric CO2 concentration by 63 × 10−6. A sudden termination of SRM causes a rate of temperature change that is much larger than that of RCP8.5. A sudden termination of AOA causes a rate of temperature change that is comparable to that of RCP8.5 and a rate of ocean acidification that is much larger than that of RCP8.5.

Computational fluid dynamics modelling of microclimate for a vertical agrivoltaic system

The increasing worldwide population is leading to a continuous increase in energy and food demand. These increasing demands have led to fierce land-use conflicts as we need agricultural land for food production while striving towards renewable energy systems such as large-scale solar photovoltaic (PV) systems, which also require in most of the cases agricultural flat land for implementation. It is therefore essential to identify the interrelationships between the food, and energy sectors and develop sustainable solutions to achieve global goals such as food and energy security. A technology that has shown promising potential in supporting food and energy security, as well as supporting water security, is agrivoltaic (AV) systems. This technology combines conventional farm activities with PV systems on the same land. Understanding the microclimatic conditions in an AV system is essential for an accurate assessment of crop yield potential as well as for the energy performance of the PV systems. Nevertheless, the complex mechanisms governing the microclimatic conditions under agrivoltaic systems represent an underdeveloped research area. In this study, a computational fluid dynamics (CFD) model for a vertical AV system is developed and validated. The CFD model showed PV module temperature estimation errors in the order of 0–2 °C and ground temperature errors in the order of 0–1 °C. The shading caused by the vertical PV system resulted in a reduction of solar irradiance by 38%. CFD modelling can be seen as a robust approach to analysing microclimatic parameters and assessing AV system performance.

Optimal generation scheduling and operating reserve management for PV generation using RNN-based forecasting models for stand-alone microgrids

Photovoltaic (PV) generation can drop sharply under reductions in solar irradiance due to cloud cover, resulting in adverse impacts on the performance of stand-alone microgrids. In addition, due to the stochastic nature of solar irradiance, it has remained challenging to forecast PV generation accurately. Therefore, a sufficient amount of operating reserve must be allocated for the variability and uncertainty of PV generation. However, excess operating reserve can decrease the economic efficiency of microgrids. This paper proposes an optimal generation scheduling and operating reserve management scheme for stand-alone PV-integrated microgrids, which comprises three core models. First, a two-stage recurrent neural network-based model is proposed for solar irradiance and cloud cover forecasting. Second, the operating reserve required for PV is managed more effectively based on weather conditions. Finally, an optimal generation scheduling model is applied based on the forecasting and operating reserve management models. The proposed scheme is applied to representative case studies to validate its advantages. The forecasting accuracy of the proposed model outperforms a conventional model. Under clear-sky conditions, the operating reserve for PV can be reduced down to 30% of PV output. Subsequently, the optimal operation scheduled by the proposed scheme can produce substantial savings of more than 5.5%.

The 2020 Patagonian solar eclipse from the point of view of the atmospheric electric field

In this study, the response of atmospheric electrical and meteorological variables at three different sites of Argentina are studied during the total solar eclipse of December 14, 2020: Valcheta (100% darkening), Buenos Aires (73%) and El Leoncito (71%). The reduction insolar irradiance caused by the solar eclipse was expected to directly affect the near-surface electric field, known as the potential gradient (PG), through a reduction in turbulence and an increase in air conductivity. From the analysis of the observed meteorologicalparameters (temperature, relative humidity, and wind), no effects on the PG were observed that can be unequivocally attributed to this event based solely on boundary layer dynamics. The prevailing synoptic situation altered the response that the boundary layer could have given, namely, a clear drop in radiation, particularly at Valcheta, which was very close to a frontal zone and had occasional cloud coverage and reports of atmospheric suspended dust. PG measurements at Valcheta during the eclipse showed PG values several ordersof magnitude higher and of opposite sign to the global daily mean fair weather (FW) PG curve and the local FW-PG curves calculated at CITEDEF (940 km away) and CASLEO (1200 km away). The PG values at Valcheta were shown to be more closely related to disturbed weather conditions than FW. On the contrary, at the other two locations studied, CITEDEF and CASLEO, further north and more distant from the frontal zone, the observed PG values on the day of the eclipse showed a higher consistency with the local daily mean FW-PG curves. A comparison between the FW-PG local curves at these two sites and the evolution of PG during the day of the eclipse, however, reveals a drop in PG values during the eclipse.

Modeling the Shading Effect of Vancouver’s Urban Tree Canopy in Relation to Neighborhood Variations

Background: Cities consume a disproportionate amount of energy for internal temperature regulation. Being able to reduce cities’ cooling load on hot summer days can decrease energy consumption while improving occupants’ thermal comfort. The urban canopy is an effective shading agent, adding cooling benefits to existing buildings and streets while providing other ecological and physiological values. Yet the building and street shading dynamic is a highly complex system that involves micro-level building components and macro-level variables. Introducing urban canopy to such a complex system creates another challenge, as urban canopy variables can also interact with buildings at both micro- and macro-levels. In order to accurately represent the urban canopy shading effect, it is necessary to account for the interactions among buildings, streets, and urban canopies. Methods: This study simulates the shading effect of urban canopy measured by aerial laser scanning (ALS) in the City of Vancouver, Canada, through the integration of a Radiance daylight simulation engine and geographic information system (GIS) data. All trees detected by ALS were included in the analysis. Results: The results indicate that street surfaces receive more solar irradiance reduction than building roofs and façades (i.e., exterior walls). Neighborhoods with less density and lower buildings were shaded noticeably better than areas with higher density and taller buildings. Among Vancouver’s 22 neighborhoods, 2 neighborhoods, Kitsilano and the West End, demonstrated a promising sign where both building density/height and urban canopies are maintained. There was evidence of high canopy shading and high-density urban morphologies. Conclusion: Overall, this work provided an authentic canopy assessment from single building to city scale, creating opportunities to investigate intracity urban canopy variations, equality, and the balance between urban greening and urban densification.

Overview of solar eclipse of 21st June 2020 and its impact on solar irradiance, surface ozone and different meteorological parameters over eight cities of India

• First time study of annular solar eclipse effect simultaneously at eight stations of India. • Stations are located nearly perpendicular to the eclipse axis with magnitude 98.6% to 77.2%. • Substantial reduction in solar radiation, surface ozone & temperature is evident. • Atmospheric cooling from eclipse induced dynamical changes to the meteorological parameters. The present study is aimed to investigate the variation in solar radiance, surface ozone, temperature, relative humidity and wind velocity during the most recent and one of the most significant annular solar eclipses of 21st June 2020. Effects of solar eclipse have been analyzed first time at eight different cities of India located nearly perpendicular to the eclipse axis having an eclipse magnitude from 98.6 % to 77.2 %. Significant reductions in solar irradiance at different stations were found during the maximum phase of the solar eclipse due to the occultation of the Sun by the Moon. With the progression of the solar eclipse, surface ozone concentrations were also found to be decreasing and reached to its minimum value during the maximum phase of eclipse and then after the end of the eclipse started regaining their original behavior. Overall, the change in ozone was found to be proportional to eclipse magnitude. A decrease of ozone levels ranged from 30 % to 65 % over all the stations. In addition to the above, atmospheric cooling from the solar eclipse of 21st June 2020 induced dynamical changes to the meteorological parameters (temperature, relative humidity and wind speed) with the change being most prominent during the maximum phase of the solar eclipse.

Forecasting dust impact on solar energy using remote sensing and modeling techniques

The present study focuses on assessment of dust impact on forecasting solar irradiance and energy, during an extreme dust event. We utilize surface-based Aeronet measurements, satellite observations (MODIS and CALIPSO), and ModIs Dust AeroSol (MIDAS) dust database in conjunction with Weather Research and Forecasting (WRF) model simulations, based on inputs from Indian Solar Irradiance Operational System (INSIOS) and Copernicus Atmosphere Monitoring Service (CAMS) forecast. This work presents a novel approach of CAMS aerosol optical depth (AOD) ingestion into WRF model for analyzing dust impact on solar irradiance. The study region is the northwestern part of Indian subcontinent, an area with some of the largest solar power projects in India. A set of three consecutive and deadly dust storms occurred in May 2018 with one having high intensity and values of AOD and dust optical depth reaching up to 2. Dust events of this extent leads to a significant reduction in solar irradiance and affect the capacity of energy exploitation through Photovoltaic installations and Concentrating Solar Power plants due to the solar aerosol-related extinction. The dust plume resulted in an average decrease of 76 W/m2 and 275 W/m2 for global horizontal irradiance (GHI) and direct normal irradiance (DNI), respectively, and a maximum reduction of 100 W/m2 (10%) and 400 W/m2 (40%) in GHI and DNI, respectively. The proposed methodology can support solar energy producers, for optimum energy production forecasting, management, and maintenance (e.g. soiling) as well as transmission and distribution system operators, taking into account the effect of dust aerosols into their day-to-day market operations.

Solar Irradiance Reduction Using Optimized Green Infrastructure in Arid Hot Regions: A Case Study in El-Nozha District, Cairo, Egypt

In the Middle East and North Africa (MENA) region, studies focused on the relationship between urban planning practice and climatology are still lacking, despite the fact that the latter has nearly three decades of literature in the region and the former has much more. However, such an unfounded relationship that would consider urban sustainability measures is a serious challenge, especially considering the effects of climate change. The Greater Cairo Region (GCR) has recently witnessed numerous serious urban vehicular network re-development, leaving the city less green and in need of strategically re-thinking the plan regarding, and the role of, green infrastructure. Therefore, this study focuses on approaches to the optimization of the urban green infrastructure, in order to reduce solar irradiance in the city and, thus, its effects on the urban climatology. This is carried out by studying one of the East Cairo neighborhoods, named El-Nozha district, as a representative case of the most impacted neighborhoods. In an attempt to quantify these effects, using parametric simulation, the Air Temperature (Ta), Mean Radiant Temperature (Tmrt), Relative Humidity (RH), and Physiological Equivalent Temperature (PET) parameters were calculated before and after introducing urban trees, acting as green infrastructure types that mitigate climate change and the Urban Heat Island (UHI) effect. Our results indicate that an optimized percentage, spacing, location, and arrangement of urban tree canopies can reduce the irradiance flux at the ground surface, having positive implications in terms of mitigating the urban heat island effect.

Trace pollutant fluctuations observed in Calicut city, India, during the annular solar eclipse on 26 December 2019

Atmospheric boundary layer perturbations were monitored during an annular solar eclipse event on December 26, 2019 to understand its impact on the meteorological parameters (temperature, relative humidity, wind speed, and wind direction) and trace gas concentrations (O3, NO, NO2, NH3, CO, and HONO) at Calicut (11.24° N, 75.78° E), a tropical city along the coastal belt of Arabian Sea in the southwest coast of Indian Subcontinent. The solar eclipse started at 8:05 IST (5.5 h ahead of UTC), reached to a maximum coverage of 93.28% at 09:27 IST and ends at 11:07 IST. Eclipse day data were compared with the nearby days' records from this site. The rapid fall in the irradiance caused cooling of the surface air by ~0.7 °C and weakened the wind speed, whereas the relative humidity, as expected, was increased by 5.1%. A gradual decrease in the surface O3 along with the reduction in solar irradiance was observed during the eclipse, due to the decreased efficiency in the photochemical formation of ozone. There was a decrease in mixing ratios of NO2 during the eclipse period, which was a result of the fall in ozone concentrations. No significant variation was observed in HONO levels, whereas variations in concentrations of NO and NH3 have followed the night time chemistry. The NO3 radical mixing ratios were below the detection limit during the eclipse event.

Dramatic weakening of the East Asian summer monsoon in northern China during the transition from the Medieval Warm Period to the Little Ice Age

Abstract Changes in the intensity of the East Asian summer monsoon (EASM) are critical for regulating the regional hydrology, ecology, and human civilization, especially in the vicinity of the summer monsoon limit (SML). However, the detailed spatial variations of the SML in mainland China over the past 2000 years are uncertain due to the lack of high-resolution paleoclimate archives. As a result, the accurate location of the SML during the transition from the Medieval Warm Period (MWP) to the Little Ice Age (LIA), as well as its impacts on ecology and society, are poorly understood. Here, we report a potential location of the SML during the late Holocene by combining data from a lake sedimentary record and a compilation of paleoclimate records from arid northern China. We find that EASM intensity was strong during the MWP and that the SML in arid northern China was roughly located along the Yinshan Mountains, Yabulai Mountains, and north of Lake Qinghai. EASM intensity dramatically weakened during the MWP-LIA transition, and the SML retreated southeastward significantly, which may have primarily but nonlinearly been a response to the reduction in solar irradiance and its associated changes in atmospheric circulation (e.g., El Niño–Southern Oscillation and Siberian High) and could have had profound impacts on hydrology, ecology, and human civilization across northern monsoonal Asia.

β-Diversity of morphological groups as indicator of coralligenous community quality status

Abstract Sciaphilous organisms compose the Mediterranean coralligenous assemblages which have solar irradiance reduction in the water column as a main structuring environmental factor. These communities and associated habitats are taken into consideration for protection at European level, and monitoring activities of their status are mandatory (Marine Strategy Framework Directive, 2008/56/EC) representing hot spots of biodiversity. However, sampling activities of these habitats are often very expensive, thus, in recent years, remote surveys performed by underwater robots (ROVs) are more and more applied. In the present investigation Morphological Groups (MGs), which are parataxonomic proxies allowing to describe coralligenous assemblages using ROV images, are used to assess community structure and diversity of six randomly chosen sites in the Gulf of Naples, as representative of three substrate types (boulders/debris, rocky cliff and sand/mud) at two depths (De Results show that the most abundant MGs in all substrates and depths are represented by crustose coralline algae and encrusting sponges, which account for significant quantitative differences only among sites (p Such findings suggest that, i) similar coralligenous assemblages structures are strictly related to edaphic factors; ii) the apparent contradiction between high CBQI values and low heterogeneities might be explained by the long successional process of bioconstruction formation, converging in similar assemblages coherently with substrate and depth-related factors. Thus, to this respect, a low small-scale heterogeneity of assemblages (as a proxy of β-diversity measure) may be considered as a reliable indicator of high quality status.

Ensuring the completion of solar cooking process under unexpected reduction in solar irradiance

One of the big challenges in the solar cooking process is ensuring the completion of cooking process under unexpected reduction in the sunshine due to cloudiness. The popularity of solar cookers is hindered because of the uncertainty in the accomplishment of cooking process, resulting in spoilage of food and wastage of time, leading to inconvenience and loss. The completion of cooking activity certainly requires a definite amount of stored heat at above the cooking temperature and a parameter to provide the related information for design incorporation. Because of the complex nature of the cooking process, the present work considers rice as the food item. In the process, it proposes an alternative to heating based test procedure to determine more realistic value of thermal performance parameter (TPP) for the solar cookers. The relevant parameter is determined utilizing novel cooling test. Two different designs of cookers have been tested to establish the proposal.

Impacts of stratospheric sulfate geoengineering on tropospheric ozone

Abstract. A range of solar radiation management (SRM) techniques has been proposed to counter anthropogenic climate change. Here, we examine the potential effects of stratospheric sulfate aerosols and solar insolation reduction on tropospheric ozone and ozone at Earth's surface. Ozone is a key air pollutant, which can produce respiratory diseases and crop damage. Using a version of the Community Earth System Model from the National Center for Atmospheric Research that includes comprehensive tropospheric and stratospheric chemistry, we model both stratospheric sulfur injection and solar irradiance reduction schemes, with the aim of achieving equal levels of surface cooling relative to the Representative Concentration Pathway 6.0 scenario. This allows us to compare the impacts of sulfate aerosols and solar dimming on atmospheric ozone concentrations. Despite nearly identical global mean surface temperatures for the two SRM approaches, solar insolation reduction increases global average surface ozone concentrations, while sulfate injection decreases it. A fundamental difference between the two geoengineering schemes is the importance of heterogeneous reactions in the photochemical ozone balance with larger stratospheric sulfate abundance, resulting in increased ozone depletion in mid- and high latitudes. This reduces the net transport of stratospheric ozone into the troposphere and thus is a key driver of the overall decrease in surface ozone. At the same time, the change in stratospheric ozone alters the tropospheric photochemical environment due to enhanced ultraviolet radiation. A shared factor among both SRM scenarios is decreased chemical ozone loss due to reduced tropospheric humidity. Under insolation reduction, this is the dominant factor giving rise to the global surface ozone increase. Regionally, both surface ozone increases and decreases are found for both scenarios; that is, SRM would affect regions of the world differently in terms of air pollution. In conclusion, surface ozone and tropospheric chemistry would likely be affected by SRM, but the overall effect is strongly dependent on the SRM scheme. Due to the health and economic impacts of surface ozone, all these impacts should be taken into account in evaluations of possible consequences of SRM.

Direct and semi-direct effects of aerosol climatologies on long-term climate simulations over Europe

This study compares the direct and semi-direct aerosol effects of different annual cycles of tropospheric aerosol loads for Europe from 1950 to 2009 using the regional climate model COSMO-CLM, which is laterally forced by reanalysis data and run using prescribed, climatological aerosol optical properties. These properties differ with respect to the analysis strategy and the time window, and are then used for the same multi-decadal period. Five simulations with different aerosol loads and one control simulation without any tropospheric aerosols are integrated and compared. Two common limitations of our simulation strategy, to fully assess direct and semi-direct aerosol effects, are the applied observed sea surface temperatures and sea ice conditions, and the lack of short-term variations in the aerosol load. Nevertheless, the impact of different aerosol climatologies on common regional climate model simulations can be assessed. The results of all aerosol-including simulations show a distinct reduction in solar irradiance at the surface compared with that in the control simulation. This reduction is strongest in the summer season and is balanced primarily by a weakening of turbulent heat fluxes and to a lesser extent by a decrease in longwave emissions. Consequently, the seasonal mean surface cooling is modest. The temperature profile responses are characterized by a shallow near-surface cooling and a dominant warming up to the mid-troposphere caused by aerosol absorption. The resulting stabilization of stratification leads to reduced cloud cover and less precipitation. A decrease in cloud water and ice content over Central Europe in summer possibly reinforce aerosol absorption and thus strengthen the vertical warming. The resulting radiative forcings are positive. The robustness of the results was demonstrated by performing a simulation with very strong aerosol forcing, which lead to qualitatively similar results. A distinct added value over the default aerosol setup of Tanre et al. (1984) was found in the simulations with more recent aerosol data sets for solar irradiance. The improvements are largest under low cloud conditions, while overestimated cloud cover in all setups causes a common underestimation of low and medium values of solar irradiance. In addition, the prevalent cold bias in the COSMO-CLM is reduced in winter and spring when using updated aerosol data. Our results emphasize the importance of semi-direct aerosol effects, especially over Central Europe in terms of changes in turbulent fluxes and changes in cloud properties. We also suggest to replace the default Tanre et al. (1984) aerosol climatology with more recent and realistic data sets. Thereby, a better model performance in comparison to observations can be achieved, or the masking of model shortcomings due to a too strong direct aerosol forcing thus far is prevented.