Changes In Radiative Fluxes Research Articles

Assessing the Impacts of Falling Ice Radiative Effects on the Seasonal Variation of Land Surface Properties

AbstractThe impacts of falling ice radiative effects (FIREs) on land‐atmosphere feedback processes were examined, with a focus on the fidelity of land surface properties and their variability as inferred by global climate models (GCMs). We conducted a pair of sensitivity experiments using the National Center for Atmospheric Research (NCAR) Community Earth System Model Version 1 (CESM1) in fully coupled modes with FIREs turned on and off. This allowed us to investigate the seasonal response of land surface properties to changes in radiation fluxes and land surface temperature (LST) associated with FIREs across global land areas. Our findings indicate that during boreal winter, excluding FIREs results in less surface downward longwave and net flux (∼5–15 Wm−2), leading to a colder land surface (∼2–4 K) and air temperatures (∼1–4 K) at mid‐ and high latitudes. Consequently, the surface frozen soil layer and snow cover persist through spring, delaying snowmelt and thawing until summer. This delay reduces liquid soil moisture, thereby suppressing vegetation productivity in subsequent seasons. Conversely, tropical regions, exhibit contrasting responses, with a warmer land surface (∼0.5 K) and warmer air temperatures (∼0.1–0.5 K) due to increased surface downward shortwave and net flux (∼2–10 Wm−2). This enhancement in radiation fosters increased vegetation productivity throughout the seasonal cycle. These findings illustrate a local response of land surface properties to changes in the surface energy balance and LST, highlighting the significant role that FIREs play in land surface modeling within GCMs.

Evolution of the Climate Forcing During the Two Years After the Hunga Tonga‐Hunga Ha'apai Eruption

AbstractWe calculate the climate forcing for the 2 ys after the 15 January 2022, Hunga Tonga‐Hunga Ha'apai (Hunga) eruption. We use satellite observations of stratospheric aerosols, trace gases and temperatures to compute the tropopause radiative flux changes relative to climatology. Overall, the net downward radiative flux decreased compared to climatology. The Hunga stratospheric water vapor anomaly initially increases the downward infrared radiative flux, but this forcing diminishes as the anomaly disperses. The Hunga aerosols cause a solar flux reduction that dominates the net flux change over most of the 2 yrs period. Hunga induced temperature changes produce a decrease in downward long‐wave flux. Hunga induced ozone reduction increases the short‐wave downward flux creating small sub‐tropical increase in total flux from mid‐2022 to 2023. By the end of 2023, most of the Hunga induced radiative forcing changes have disappeared. There is some disagreement in the satellite measured stratospheric aerosol optical depth (SAOD) observations which we view as a measure of the uncertainty; however, the SAOD uncertainty does not alter our conclusion that, overall, aerosols dominate the radiative flux changes.

Strengthened impact of late autumn Arctic sea ice on Asian winter cold extremes after 1999/2000

Winter cold extremes (WCEs) frequently plague densely populated areas of Asia, leading to substantial economic losses and even fatalities. It has been found that the late autumn sea ice concentration (SIC) anomalies in the northern (SICN) and southern Arctic (SICS) are significantly positively and negatively correlated with the occurrence frequency of WCE in Asia, respectively (Wang and Su 2024). Our study demonstrates that the impacts of SICN and SICS have strengthened after 1999/2000. Specifically, before 1999/2000, the influences of SICN and SICS on the Asian WCE (AWCE) were relatively weak, possibly related to the weak intensity of SICS and the limited correlation between SICN and SICS. After 1999/2000, the interannual variability of SICS became larger and anti-correlated with that of SICN, resulting in a stronger teleconnection between the Arctic SIC and AWCE. It is revealed that after 1999/2000, the greater loss of SICS modified atmospheric stability through changes in surface heat fluxes and surface upward longwave radiation fluxes. This alteration weakened the magnitudes of westerly winds and increased the frequency of blocking events over the northern Eurasian continent, leading directly to a higher occurrence of cold extremes in Asia. These interdecadal differences in the influence of Arctic SIC on AWCE may be associated with long-term climate change.

Aerosol impacts on the East Asian winter monsoon: Insights from TaiESM1 and CMIP6 simulations

AbstractThe East Asian winter monsoon (EAWM) is an important climate pattern in Southeast Asia. This study delved into the aerosol effects on the EAWM by analysing simulations conducted with the Taiwan Earth System Model version 1 (TaiESM1) model, part of the Coupled Model Intercomparison Project Phase 6 (CMIP6). Our assessment, validated against observational and reanalysis data, revealed that TaiESM1 effectively replicates the robust circulation of the EAWM and aerosol concentrations, placing its performance above average level among CMIP6 models. Notably, the simulated global mean aerosol optical thickness exhibited an approximately 20% increase from 1850 to 2014. The increased aerosols corresponded to a weakened Aleutian Low and an intensified Siberian High, leading to a weakened EAWM in the lower atmosphere over extratropical areas. In addition, the cooling across the Northern Hemisphere might affect enhanced northerly winds at approximately 10°N, which are situated in the southern part of the EAWM. An analysis of the near‐surface temperature budget indicated that the aerosol‐induced cooling in East China and India was primarily driven by changes in shortwave and longwave radiation fluxes, albeit slightly offset by sensible heat and latent heat fluxes. Furthermore, our study also reveals that while the mechanisms through which anthropogenic aerosols affect the northern portion of the EAWM vary across most CMIP6 models, their impacts on the tropical region remain consistent.

Observed Cloud Type‐Sorted Cloud Property and Radiative Flux Changes With the Degree of Convective Aggregation From CERES Data

AbstractCloud‐radiation interactions are a critical mechanism for convective self‐aggregation, especially the longwave radiative cooling of low clouds and environments. In this study, two data products from CERES observations combined with MERRA‐2 reanalysis are used to understand the changes of cloud properties and radiative fluxes by cloud type with the degree of convective aggregation at the 1000‐km scale, which is represented by the number of cloud objects (N), simple convective aggregation index (SCAI), modified SCAI (MCAI) or convective organization potential (COP). The changes with SCAI are similar to those with N as an index, agreeing with previous studies using grid‐averaged properties. For changes from weak to strong degrees of aggregation using N and SCAI, area fractions of middle‐ and high‐level cloud types decrease by up to 4% but those of low‐level cloud types increase by up to 2%, and more infrared radiation is emitted to space (2–8 W m−2) from optically thin cloud types but more solar radiation is reflected (2–4 W m−2) from optically‐thick cloud types. However, using COP (MCAI to lesser extent), area fractions of optically‐thick cloud types increase, which emit less infrared radiation and reflect more solar radiation, whereas the area fractions of low‐level clouds decrease. These results can be explained by greater expansion of cloud object sizes for COP than MCAI/SCAI as the degree of convective aggregation increases, which also explains the difference between SCAI and MCAI pertaining to the opposite changes of optically‐thick high‐level clouds. These results can have implications for understanding convective self‐aggregation.

The Global Patterns of Instantaneous CO2 Forcing at the Top of the Atmosphere and the Surface

Abstract The radiative forcing of carbon dioxide (CO2) at the top of the atmosphere (TOA) has a rich spatial structure and has implications for large-scale climate changes, such as poleward energy transport and tropical circulation change. Beyond the TOA, additional CO2 increases downwelling longwave at the surface, and this change in flux is the surface CO2 forcing. Here we thoroughly evaluate the spatiotemporal variation of the instantaneous, longwave CO2 radiative forcing at both the TOA and surface. The instantaneous forcing is calculated with a radiative transfer model using ERA5 reanalysis fields. Multivariate regression models show that the broadband forcing at the TOA and surface are well predicted by local temperatures, humidity, and cloud radiative effects. The difference between the TOA and surface forcing, the atmospheric forcing, can be either positive or negative and is mostly controlled by the column water vapor, with little explicit dependence on the surface temperature. The role of local variables on the TOA forcing is also assessed by partitioning the change in radiative flux to the component emitted by the surface versus that emitted by the atmosphere. In cold, dry regions, the surface and atmospheric contribution partially cancel out, leading to locally weak or even negative TOA forcing. In contrast, in the warm, moist regions, the surface and atmospheric components strengthen each other, resulting in overall larger TOA forcing. The relative contributions of surface and atmosphere to the TOA forcing depend on the optical thickness in the current climate, which in turn is controlled by the column water vapor.

Historical Changes in Wind‐Driven Ocean Circulation Can Accelerate Global Warming

AbstractMitigation and adaptation strategies for climate change depend on accurate climate projections for the coming decades. While changes in radiative heat fluxes are known to contribute to surface warming, changes to ocean circulation can also impact the rate of surface warming. Previous studies suggest that projected changes to ocean circulation reduce the rate of global warming. However, these studies consider large greenhouse gas forcing scenarios, which induce a significant buoyancy‐driven decline of the Atlantic Meridional Overturning Circulation. Here, we use a climate model to quantify the previously unknown impact of changes to wind‐driven ocean circulation on global surface warming. Wind‐driven ocean circulation changes amplify the externally forced warming rate by 17% from 1979 to 2014. Accurately simulating changes to the atmospheric circulation is key to improving near‐term climate projections.

Dying in the Sun: Direct evidence for elevated UV-B radiation at the end-Permian mass extinction

Land plants can adjust the concentration of protective ultraviolet B (UV-B)-absorbing compounds (UACs) in the outer wall of their reproductive propagules in response to ambient UV-B flux. To infer changes in UV-B radiation flux at Earth's surface during the end-Permian mass extinction, we analyze UAC abundances in ca. 800 pollen grains from an independently dated Permian-Triassic boundary section in Tibet. Our data reveal an excursion in UACs that coincide with a spike in mercury concentration and a negative carbon-isotope excursion in the latest Permian deposits, suggesting a close temporal link between large-scale volcanic eruptions, global carbon and mercury cycle perturbations, and ozone layer disruption. Because enhanced UV-B radiation can exacerbate the environmental deterioration induced by massive magmatism, ozone depletion is considered a compelling ecological driver for the terrestrial mass extinction.

The Shortwave Radiative Flux Response to an Injection of Sea Salt Aerosols in the Gulf of Mexico

AbstractMarine cloud brightening (MCB) has been proposed as a potential means of geoengineering the climate, temporarily providing cooling to offset some of the effects of climate change. Marine sky brightening (MSB), involving the direct scattering of sunlight from sea salt injection into the marine boundary layer, has been proposed as an additional geoengineering method that could work in areas that are not regularly cloudy. Here, we use a regional atmospheric model to simulate MCB and MSB over the Gulf of Mexico and nearby land, a highly populated and economically important region that is not characterized by persistent marine stratocumulus cloud cover. Injection of sea salt in the Aitken mode from a region in the central Gulf of Mexico equivalent to 10.8 Tg yr−1 produces an upwards 8.4 W m−2 radiative flux change across the region at the top of the atmosphere, largely due to cloud property changes. Comparatively, a similar mass injection in the accumulation mode produces a 3.1 W m−2 radiative flux change driven primarily by direct scattering. Injection of even larger particles produces a much smaller radiative flux change. Shortwave flux changes due to clouds are largely driven by an increase in cloud droplet number concentration and an increase in cloud liquid water path (each contributing about 45% to the flux change), with a much lower contribution from cloud fraction changes (10%).

Composite Analysis of Aerosol Direct Radiative Effects on Meteorology During Wintertime Severe Haze Events in the North China Plain

AbstractPrevious studies on the impacts of severe haze episode on meteorology were generally focused on single episodes. This study aimed to obtain the common features of the influence of aerosol direct radiative effects on meteorology during severe particulate pollution events by composite analyses on model results from the Weather Research and Forecasting Model with online chemistry. Five heavily polluted events (15–17 January 2014, 13–15 January 2015, 8–10 December 2015, 21–23 December 2015, and 29–31 December 2016) in the North China Plain (NCP, 35.4–41.2°N, 113.3–119.3°E) were selected, which were representative of the most frequently observed weather patterns for severe haze. Model results showed that aerosols in the five heavily polluted events led to strong negative changes in radiative flux of 52.1–86.7 W m−2, reductions in the 2‐m temperature by 0.28–0.97°C, and the reductions in planetary boundary layer heights by 23.1–58.5 m, when averaged over the areas with PM2.5 concentrations >150 μg m−3. The magnitudes of aerosol induced changes in the 2‐m temperature were found to be influenced not only by aerosol concentration but also by wind speed, wind direction, and the convergence or divergence of winds. High wind speed diluted the aerosol‐induced cooling, the convergence of wind limited the temperature change to local area, and the intrusion of cold air mass near the surface enhanced the aerosol‐induced cooling. In all the cases, aerosols induced an anti‐cyclone at 500 hPa around NCP and anomalous northerlies or northeasterlies at the surface in the eastern NCP.

Orographic resolution driving the improvements associated with horizontal resolution increase in the Northern Hemisphere winter mid-latitudes

Abstract. In recent years much attention has been devoted to the investigation of the impact of increasing the horizontal resolution of global climate models. In the present work, a set of atmosphere-only idealized sensitivity simulations with EC-Earth3 has been designed to disentangle the relative roles of increasing the resolution of the resolved orography and of the atmospheric grid. Focusing on the Northern Hemisphere winter, it is shown that if the grid is refined while keeping the resolved orography unchanged, model biases are reduced only on some specific occasions. Conversely, increasing the resolved (or mean) orography is found to clearly reduce several important systematic model errors, including synoptic transient eddies, the North Atlantic jet stream variability, and atmospheric blocking frequency and duration. From an analysis of the radiation budget it is concluded that the large changes in radiative fluxes caused by the resolution increase – something commonly observed in climate models – have a relevant impact on the atmospheric circulation, partially offsetting the benefits obtained from the increase in orographic resolution. These findings point to the necessity of always tuning climate models to fully exploit the benefits of high horizontal resolution.

Anthropogenic Aerosols Modulated 20th-Century Sahel Rainfall Variability Via Their Impacts on North Atlantic Sea Surface Temperature.

The Sahel rainfall has a close teleconnection with North Atlantic sea surface temperature (NASST) variability, which has separately been shown to be affected by aerosols. Therefore, changes in regional aerosols emission could potentially drive multidecadal Sahel rainfall variability. Here we combine ensembles of state‐of‐the‐art global climate models (the CESM and CanESM large ensemble simulations and CMIP6 models) with observational data sets to demonstrate that anthropogenic aerosols have significantly impacted 20th‐century detrended Sahel rainfall multidecadal variability through modifying NASST. We show that aerosol‐induced multidecadal variations of downward solar radiative fluxes over the North Atlantic cause NASST variability during the 20th century, altering the ITCZ position and dynamically linking aerosol effects to Sahel rainfall variability. This process chain is caused by aerosol‐induced changes in radiative surface fluxes rather than changes in ocean circulations. CMIP6 models further suggest that aerosol‐cloud interactions modulate the inter‐model uncertainty of simulated NASST and potentially the Sahel rainfall variability.

Оценка распространения тепловой радиации в особых условиях

Increase of the requirements for the safety of hazardous production facilities stimulates the development and improvement of the methodological approaches to accidents consequences assessment on the main gas and other pipelines. Existing models for determining heat fluxes from radiating flame surfaces are focused on assessing damage under standard conditions when the epicenter of the accident is at the same altitude level with potential recipients and there are no barriers between them. In practice, special conditions are often implemented, in particular: fires on the pipelines located in the mountainous areas, safe passage of aircraft near the burning site, protection of objects from thermal radiation by installing impenetrable screens. Approaches are proposed related to assessing heat fluxes at the receiving sites located at different altitude levels with the fire source, as well as during accidents with ignition on the gas pipelines in the presence of screens protecting against thermal radiation. A parameter is introduced that describes the effect of the multilevel location of the source and the recipient on radiation — the coefficient of change in the thermal radiation flux from the side surface of a column-type fire in the absence of a wind, depending on the location height and distance in relation to the ground source of combustion of the site receiving the radiation. An expression is given for determining safe height of the flight of aircraft over a column-type fire in the range of flame heights from 50 to 850 m. Isolines of the fields of heat fluxes from the flame of a high-speed flat jet are calculated when the radiation is screened by a wall located at a normalized distance. The results obtained make it possible to predict the consequences of accidents on the main gas pipelines with gas ignition considering the relief, to assess the boundaries of safe corridors for flights of the aircraft near gas pipelines, and to efficiently develop means of protecting objects surrounding the main pipelines from thermal radiation from a flat torch.

Atmospheric Circulation Sensitivity to Changes in the Vertical Structure of Polar Warming

AbstractThis study examines the effects of the vertical structure of polar warming on the remote atmospheric circulation. We apply thermal forcing at different vertical levels in the Northern Hemisphere polar region in two atmospheric global climate models of different complexity, both coupled to an aquaplanet slab ocean. The efficacy of polar heating in perturbing the remote climate increases with the altitude at which it is applied. This robust sensitivity arises from the dominance of surface temperature contribution to the outgoing longwave radiation owing to the large emissivity of the polar troposphere. An upper‐level polar heating has a smaller fraction of forcing balanced by radiative flux changes and a larger contribution from atmospheric energy transport changes, which provokes larger shifts in the extratropical jet and Hadley circulation. Our results suggest increasingly far‐reaching impacts of Arctic warming as a less surface‐trapped profile is projected for seasonally ice‐free conditions in the near future.

Extreme Aerosol Events Over Eastern North America: Part 2. Responses to Changing Emissions

AbstractThe Weather Research and Forecasting model with coupled Chemistry is used to study the impact of anthropogenic emission changes between 2005 and 2015 on historical extreme aerosol optical depth (AOD) events that occurred during 2003–2007 over the eastern USA. An ensemble of simulations is generated where individual and all combined emissions of SO2, NOx, and NH3 are perturbed relative to the 2005 levels for three subregions (Midwest, Northeast, and Southeast). These simulations are used to quantify fractional changes in the spatial and temporal characteristics of mean and peak AOD and near‐surface particulate matter (PM2.5), as well as changes in radiative forcing. Simulated AOD exhibits a spatially averaged decrease of 39%–63% during the six extreme events in response to the combined perturbed emissions. The impact on near‐surface PM2.5 concentrations is larger, with average decreases of ∼41%–69%. Peak AOD is reduced to below 1 in the perturbed simulations from initial values of 1.73–3.02 in the control runs driven by 2005 emissions. Radiative fluxes at the ground and top‐of‐the‐atmosphere exhibit considerably smaller and less consistent fractional changes across events, although changes in radiative fluxes during these extreme events are found to be larger than previously reported changes in seasonal mean values over the period 2005 to 2015.

Hot Air, Hot Lakes, or Both? Exploring Mid‐Holocene African Temperatures Using Proxy System Modeling

AbstractClimate models predict Africa will warm by up to 5°C in the coming century, stressing African societies. To provide independent constraints on model predictions, this study compares two notable reconstructions of East African temperatures to those predicted by Paleoclimate Model Intercomparison Project (PMIP3) and transient TraCE (Transient Climate Evolution) simulations, focusing on the Mid‐Holocene (MH, 5–8 kyr B.P.). Reconstructions of tropical African temperature derived from lake sedimentary archives indicate 1–2.5°C of warming during the MH relative to the 20th century, but most climate models do not replicate the warming observed in these paleoclimate data. We investigate this discrepancy using a new lake proxy system model, with attention to the (potentially non‐stationary) relationship between lake temperature and air temperature. We find amplified lake surface temperature changes compared to air temperature during the MH due to heightened seasonality and precessional forcing. Lacustrine processes account for some of the warming, and highlight how the lake heat budget leads to a rectification of the seasonal cycle; however, the simulated lake heating bias is insufficient to reconcile the full discrepancy between the models and the proxy‐derived MH warming. We find further evidence of changes in mixing depth over time, potentially driven by changes in cloud cover and shortwave radiative fluxes penetrating the lake surface. This may confound interpretation for glycerol dialkyl glycerol tetraethers (GDGT) compounds which exist in the mixed layer, and suggests a need for independent constraints on mixed layer depth. This work provides a new interpretive framework for invaluable paleoclimate records of temperature changes over the African continent.

Assessing the Effects of Spatial Scales on Regional Evapotranspiration Estimation by the SEBAL Model and Multiple Satellite Datasets: A Case Study in the Agro-Pastoral Ecotone, Northwestern China

Evapotranspiration (ET) estimation is important for understanding energy exchanges and water cycles. Remote sensing (RS) is the main method used to obtain ET data over large scales. However, owing to surface heterogeneities and different model algorithms, ET estimated from RS products with different spatial resolutions can cause significant uncertainties, whose causes need to be thoroughly analyzed. In this study, the Surface Energy Balance Algorithm for Land (SEBAL) model was selected to explore spatial resolution influences on ET simulations. Three satellite datasets (Landsat Thematic Mapper (TM), Moderate Resolution Imaging Spectroradiometer (MODIS), and Advanced Very High-Resolution Radiometer (AVHRR)) were selected to independently estimate ET in SEBAL model to identify the influence of the spatial scale on ET estimation, and analyze the effects and causes of scale aggregation. Results indicated that: (1) the spatial distributions of ET estimated from the three satellite datasets were similar, with the MODIS-based ET having the largest uncertainty; and (2) aggregating input parameters had limited changes in the net radiation and soil heat fluxes. However, errors in the sensible heat and latent heat fluxes were relatively larger, which were caused by changes in the selection of hot and cold pixels and the NDVI and surface albedo parameters during scale aggregation. The scale errors caused by the model mechanisms were larger than those caused by the land use/cover pattern in the SEBAL model. Overall, this study highlights the impact of spatial scale on ET and provides a better understanding of the scale aggregation effect on ET estimation by RS.

ENSO evolution asymmetry: EP versus CP El Niño

Through an oceanic mixed-layer heat budget analysis, the dominant processes contributing to the largest decay rate (− 0.37 °C/mon) in EP El Nino, the moderate delay rate (− 0.22 °C/mon) in CP El Nino and the smallest decay rate (0.13 °C/mon) in La Nina, are identified. The result shows that both dynamic (wind induced equatorial ocean waves and thermocline changes) and thermodynamic (net surface solar radiation and latent heat flux changes) processes contribute to a fast decay and thus phase transition in EP El Nino composite, whereas the thermodynamic process has less effect on the decay rate for both CP El Nino and La Nina due to the westward shift of sea surface temperature anomaly (SSTA) centers. Thus, the difference in surface wind stress forcing is critical in contributing to evolution asymmetry between CP El Nino and La Nina, while the difference in both the wind stress and heat flux anomalies contribute to evolution asymmetry between EP El Nino and La Nina. It is interesting to note that El Nino induced anomalous anticyclone over the western North Pacific is stronger and shifts more toward the east during EP El Nino than during CP El Nino, while compared to CP El Nino, the center of an anomalous cyclone during La Nina shifts further to the west. As a consequence, both EP and CP El Nino decay fast and transform into a La Nina episode in the subsequent year, whereas La Nina has a much slower decay rate and re-develops in the second year.

ЕКСПЕРИМЕНТАЛЬНЕ ВИЗНАЧЕННЯ ПОТОКУ СОНЯЧНОГО ВИПРОМІНЮВАННЯ ІЗ ЗАСТОСУВАННЯМ ПАСПОРТНИХ ПАРАМЕТРІВ МОДУЛЯ ФОТОЕЛЕКТРИЧНИХ ПЕРЕТВОРЮВАЧІВ

To organize natural studies of the energy characteristics of photovoltaic systems, data on the current level of solar radiation incoming to the receiver surface are required. When using standard methods for measuring of the solar radiation flux, specialized meteorological instruments or reference solar cells are applied. Such devices are quite expensive. At the same time, an ordinary serial solar cell or module can also play the role of a reference cell under the stipulation that its passport characteristics are known for some radiation intensity. In this paper, a method for determining of the solar radiation flux based on the passport parameters of photovoltaic modules under standard test conditions and the values of short-circuit current and module temperature directly measured in natural conditions is proposed. Based on the equation of the solar cell current-voltage characteristic and the linear dependence of the short-circuit current and the temperature on the light flux a mathematical expression for solar radiation flux is obtained. This expression relates solar flux to the short-circuit current under standard test conditions, the temperature coefficient of the current and the measured values of the short-circuit current and the module temperature. It is shown that proposed method for determining of the solar radiation flux is correct and can be used in practice. A convenient for practical application analytical expression has been obtained for a silicon photovoltaic module 120P/12. The expression makes it possible to determine the incited on the module surface solar flux from the measured values of the short-circuit current and the module temperature. Experimental testing of the developed method was carried out for the module 120P/12 as an example. It is shown that fluctuations in the short-circuit current from 0.73 A to 0.76 A observed during the measurements correspond to changes in the solar radiation flux in the range from 105 W/m 2 to 110 W/m 2 . Keywords: solar radiation flux, solar cell, short-circuit current, temperature, temperature coefficient of the current, standard test conditions

Assessment of the intensity and flow of straight solar radiation falling onto the horizontal surface of a room

The paper presents the results of experimental studies of straight solar radiation in the Central Chernozem region of Russia. The intensity and flow of straight solar radiation falling onto a horizontal surface of a room were evaluated. Measurements were made of the flow of straight solar radiation on a horizontal surface through a translucent structure. Experimental data were obtained using a high-class measuring device in the period from July 1 to August 1. The measurement results showed an intense wave-like change in the solar radiation flux over 8 hours. The paper describes a method for estimating the intensity and flow of straight solar radiation falling onto a horizontal surface of a room. This method of evaluating daytime radiation allows one to determine the density of the total and straight radiation flux. Using this estimate to calculate solar installations used in the Central Chernozem region, their efficiency will increase by 10%.