CL2.1

What is the Earth’s incoming energy, that is, the value of the total solar irradiance (TSI) powering the entire Earth’s climate system on an absolute scale? How accurate are the instruments providing these data? How stable are they on climate-relevant timescales? How well can the 43-year spaceborne TSI measurement record from over a dozen instruments be put into a single time-series composite for the climate- and solar-research communities? How can that composite be extrapolated to historical times using other solar-activity proxies via reconstructions? How do these historical-reconstruction models differ from each other, and how well do they agree with the current measurements? And what is the future of those measurements?

How to cite: Kopp, G.: The TSI Instruments – What’s Old, What’s New, and What’s Next, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10660, https://doi.org/10.5194/egusphere-egu22-10660, 2022.

With a few exceptions, spaceborne measurements of Earth’s top-of-atmosphere (TOA) outgoing reflected shortwave and emitted longwave radiation have been made over broad spectral bands covering the entirety of the solar spectral region, terrestrial infrared spectral region or the combination of both. Evidence suggests that separating the solar band into just two sub-bands, roughly equal in incoming solar irradiance levels but coincidently, where the atmosphere is nearly transparent to solar radiation in the visible (λ<700nm) and partially absorbing in the near-infrared sub-band (λ >700nm) primarily due to water vapor and clouds, provides great insight into the deposition of radiative energy in the atmosphere. Moreover, the two sub-bands also demarcate reflectance differences at the ground from different surface types such as vegetation, desert, ice and snow. Therefore, TOA reflected shortwave radiation in the two sub-bands are differently affected by changes in surface and atmospheric properties and support the characterization of processes relevant for shortwave absorption by the climate system, climate feedbacks, and Earth’s albedo variability with added insight into hemispheric albedo symmetry given the hemispheric differences in ocean, continent and cloud distributions. A new NASA Earth Radiation Budget mission, Libera, will directly measure the two sub-bands. We use UKESM1 simulations, Fu-Liou RTM calculations, SCIAMACHY reflectance and CLARREO OSSE output as proxies for Libera’s future data record to demonstrate applications of the shortwave sub-band knowledge in climate science.

How to cite: Hakuba, M., Pilewskie, P., Stephens, G., and Science Team, T. L.: Libera's Split-shortwave Measurements and Their Application in Climate Research, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13306, https://doi.org/10.5194/egusphere-egu22-13306, 2022.

The imagery from geostationary meteorological satellites (GEO) is broadly used to produce various datasets describing the Earth's surface and atmosphere, or else energy fluxes. Some GEOs are not on a strictly geostationary orbit, with an inclination relatively to the equatorial plane that can reach several degrees. A striking example is Meteosat-8: due to operation constraints, its orbit is currently oscillating on a daily basis between latitudes circa 7° N and 7° S. A consequence is that the actual viewing geometry differs from the simple calculation based on the stationary nominal subsatellite position. In the case of Meteosat-8, the viewing zenith angles can differ up to ±7°.

We study how these differences of viewing angles can influence top-of-atmosphere (TOA) reflectance of Earth scenes. To achieve this, we simulate both clear-sky (i.e. cloudless) and overcast TOA reflectances corresponding to nominal and non-stationary viewing geometries of Meteosat-8 for the 0.6 µm channel during the period 2017-2018. Simulations are performed using the 1-D radiative transfer model DISORT within the libRadtran software package. They consider notably the anisotropy of surface reflectance which is modeled by the RossTick-LiSparse model of bidirectional reflectance distribution function and associated parameters of the product MCD43C1v6 derived from the imagery of the Moderate Resolution Imaging Spectroradiometer (MODIS). Overcast TOA reflectances are modeled with a plane-parallel thick liquid cloud.

In this presentation, we will describe how errors on TOA reflectances due to erroneous viewing geometry are distributed on the Meteosat-8 field of view and for different solar geometries. Both for clear-sky and overcast conditions, typical absolute errors range between 0.01 and 0.05, but can reach much higher values for specific geometries, notably close to the forward scattering direction.

How to cite: Tournadre, B., Chen, X., Gschwind, B., and Blanc, P.: Geostationary or not: can we consider Meteosat-8 viewing geometries as stationary?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8860, https://doi.org/10.5194/egusphere-egu22-8860, 2022.

The Earth’s Energy Imbalance (EEI) represents the balance of heat fluxes between
the Earth and outer space in response to radiative forcings and associated climate feedbacks,
and as such is a key metric to understand and define global climate change. Recent
publications have shown that the EEI has doubled in the last two decades, which would have
major impacts on the different components of the Earth’s system. However, these results also
show inconsistencies in the quantification of this increase depending on the observing system
considered. In this study, we investigate two independent ways to estimate EEI from ocean
observations and from energy budget at the top of the atmosphere inferred from satellite. We
show that these two observing systems lead to consistent estimates of EEI variability and
amplitude over the period 2005-2019. Global Ocean Heat Content (GOHC) is derived from a
suite of ocean in situ temperature products, and is also compared to satellite estimate and to
ocean reanalysis estimate. We provide recommendations on how to achieve a consistent and
optimized observation-based comparison between estimates for the EEI budget constraint
approach from independent global climate observing system components and at different
time-scale ranging from interannual to decadal.

How to cite: Minière, A., von Schuckmann, K., Monier, M., Le Traon, P.-Y., and Sallée, J.-B.: Observation-based reconciliation of the Earth's Energy Imbalance budget constraint, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13305, https://doi.org/10.5194/egusphere-egu22-13305, 2022.

Global energy budget studies often state that “radiative energy exchanges between Sun, Earth and space are accurately quantified from satellite missions; much less is known about the magnitude of the energy flows within the climate system and at the Earth surface, which cannot be directly measured by satellites.” However, there are long-known theoretical tools to constrain surface energy flows to the top-of-atmosphere (TOA) fluxes by using Schwarzschild’s equation of radiation transfer. We control the validity of this equation in the annual global mean on two decades of CERES observations by creating four versions of it (clear-sky and all-sky, for the net and total radiation), and find them satisfied within less than ±3 Wm-2 for the individual equations, and with a difference of 0.005 Wm-2 only for the four equations together. The two net equations constrain the convective fluxes at the lower boundary and the hydrological cycle unequivocally to energy flows at the upper boundary (implementing a fundamental stability criterion); the other two represent specific conditions with a given optical depth, connecting total energy absorption at the surface to energy flows at TOA. Applying known definitions, these four equations can be solved, and the solution appears as a set of small integers related to a unit flux (example: surface downward longwave radiation = 13 units = 346.84 Wm-2, see Figures). As a remarkable feature, the solution can be extended to further flux components not being involved in the original equations, including solar reflections at TOA both for all-sky and clear-sky, and a separation of the convective flux into its sensible and latent heat components in all-sky. This way, the complete annual global mean energy flow system can be presented as the function of TOA fluxes, without any reference to the atmospheric gaseous composition or lapse rate. — This theoretical description differs essentially from the picture given by the IPCC where Schwarzschild’s equations do not occur. Without these standard university textbook relationships (e.g., Houghton 1977, Eq. 2.13), the physical science basis is incomplete and misleading. This is a self-regulating system where feedbacks contradicting the stability criteria are not possible. If we change an atmospheric constituent (CO2, for example), energetic requirements will maintain the theoretical state by modifying other components (H2O, temperature distribution, clouds, etc.). We propose an explanation based on a concept of Graeme Stephens: principles define the radiation processes that prescribe the properties of the atmosphere, rather than the opposite way. But as one and the same global mean state can be maintained through several seasonal, regional and local distributions and their changes are always possible at unknown magnitudes and time scales, emissions control is still necessary. — Comments on Trenberth (2022) global energy budget will also be presented.

Further readings:

Zagoni, M.: Sir John Houghton and radiation transfer, EGU General Assembly 2021, April 2021
https://meetingorganizer.copernicus.org/EGU21/EGU21-1.html

CERES 35^th Science Team Meeting presentation (May 2021)
https://ceres.larc.nasa.gov/documents/STM/2021-05/34_Zagoni_CERES_STM35.pdf

CERES 36^th Science Team Meeting presentation (October 2021)
https://ceres.larc.nasa.gov/documents/STM/2021-09/MP4files/26_MZagoni_presentation2.mp4

AMS2022 102nd Annual Meeteing, Kevin Trenberth Symposium presentation (January 2022)
https://ams.confex.com/ams/102ANNUAL/meetingapp.cgi/Paper/387827

How to cite: Zagoni, M.: Earth energy flow system as the solution of four radiative transfer constraint equations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-49, https://doi.org/10.5194/egusphere-egu22-49, 2022.

Recent work has shown that the hemispheric asymmetry in cloud albedo is maximized over extratropical oceans: the Southern Ocean exhibits greater climatological cloud albedo than its northern counterpart. We investigate the dynamical causes of such asymmetry by evaluating how albedo responds to a series of cloud controlling factors, namely: sea surface temperature (SST), pressure velocity at 500mb (ω₅₀₀), Estimated Inversion Strength (EIS), Marine Cold Air Outbreak (MCAO) index, SST-T_2m (ΔT_sfc), and surface wind (V_sfc). A cloud albedo parameterization applied to MODIS optical thickness and fractional cloud cover is used in conjunction with ERA-Interim reanalysis products over oceanic points in the 50°–65° bands and for a 15-year period. Cloud properties are bin-averaged according to the range of variability of each predictor, using a 1-day timescale. We find that although ω₅₀₀ strongly controls cloud albedo, it cannot explain the observed hemispheric asymmetry. Instead, we find that surface wind most skillfully explains the hemispheric albedo difference, due to the much greater winds in the Southern Ocean. We further show that V_sfc is not only a predictor of cloud albedo but it also controls physical processes in the boundary layer such that stronger winds ultimately lead to thicker and more horizontally extended cloud decks. The interhemispheric albedo asymmetry is significantly reduced in winter, responding to a strengthening of winds in the North Atlantic and Pacific Oceans during this season. Our findings have significant implications regarding GCM cloud biases over the Southern Ocean for the current climate, as well as for cloud feedback in a warming planet.

How to cite: Blanco, J., Caballero, R., Bony, S., Datseris, G., Stevens, B., Kaspi, Y., and Hadas, O.: Cloud albedo's hemispheric asymmetry: why is the Southern Ocean cloudier?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7962, https://doi.org/10.5194/egusphere-egu22-7962, 2022.

Over the last decade, the total global anthropogenic emissions of aerosol precursors have declined according to the most recent Community Emissions Data System (CEDS) emission inventory. The CEDS emission inventory used in CMIP6 (CEDSv17) has recently been updated and extended from 2014 until 2019 (version v_2021_02_05, CEDSv21). The role of the updated emissions and the trend beyond 2014 on the modeled atmospheric composition and radiative forcing (RF) using an atmospheric chemistry transport model (OsloCTM3), radiative transfer and kernel calculations will be presented. The results post 2014 are also compared to results with SSP2-4.5 scenario emissions as input. In addition, we present consistent modeling results for 2020, with CEDSv21 emissions for 2019 combined with the 2020 CovidMIP-emission perturbation, as aerosol precursor emissions declined further due to containment policies to combat the COVID-19 pandemic.

For sulphate, the radiative forcing in 2014 relative to 2010 is stronger positive (+0.03 W m^-2) using CEDSv21 compared to a neglectable RF using CEDSv17. In 2017 the RF using the SSP scenario and the updated CEDS are equal (+0.07 W m^-2) as the SO₂ emission reduction in China was included at the starting point of the scenarios (year 2015), but not in the historical emissions (CEDSv17) ending in 2014. Including the effect of COVID-19, the sulphate RF in 2020 was +0.11 W m^-2 with 2010 as baseline, with the strongest positive forcing in Eastern China followed by the eastern part of the US. No regions show a negative sulphate RF in 2020 with respect to 2010.

For the total aerosol-radiation RF (including Black Carbon, primary organic aerosol, SOA, nitrate, and biomass burning aerosols) the RF was +0.05 W m^-2 in 2019 relative to 2010 based on OsloCTM3 simulations and the most recent CEDS emission inventory. Extending the results to 2020 using estimates for COVID-19 emissions, the forcing is further strengthened to +0.07 W m^-2.

How to cite: Skeie, R. B., Myhre, G., and Lund, M. T.: Changes in aerosol atmospheric composition and radiative forcing in OsloCTM3 over the past two decades – the effect of the updated CEDS emission inventory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6320, https://doi.org/10.5194/egusphere-egu22-6320, 2022.

In this communication, we have found that the broadband longwave radiative effect of the cloud-aerosol transition zone conditions is of the order of 8.0 ±3.7 W m⁻² by combining satellite measurements with radiative transfer modeling. It is often required to differentiate clouds and aerosols from each other in atmospheric studies, but the decision on where the boundaries of the clouds should be put is a point of debate. As a result, what detected as cloud by one method/instrument may be labeled differently by another. This is because 1) clouds and aerosols often co-exist and interact with each other, and 2) change in the state of sky from cloudy to cloudless (or vice versa) comprises an additional condition called “transition zone” (or “twilight zone”) at which the characteristics of the particle suspension lay between those corresponding to pure clouds and atmospheric aerosols [Koren et al. (2007) GRL, 34(8): L08805. 10.1029/2007GL029253]. Nevertheless, a vast area that potentially may represent the transition zone is usually neglected in the observations or assumed as an area that contains either aerosols or optically thin clouds. In this communication, we provide quantitative information about the broadband longwave radiative effects of the transition zone conditions at the top of the atmosphere based on the radiative observations made by the CERES and MODIS instruments onboard Aqua spacecraft and radiative transfer simulations. Specifically, we used the MODIS measurements to look for CERES footprints with homogeneous transition zone and clear-sky conditions over the Southeast Atlantic Ocean for August 2010. Then, CERES observations under homogeneous transition and clear-sky conditions were compared with the corresponding clear-sky radiances, which were simulated using the SBDART radiative transfer model, fed with ERA5 reanalysis atmospheric profiles. For the studied period and domain, transition zone broadband longwave radiative effect was on average equal to 8.0 ±3.7 W m⁻² (heating effect; median: 5.4 W m⁻²), although cases with radiative effects as large as 50 W m⁻² were observed. Furthermore, low-level transition zone conditions defined as those with suspension top height below 2 km (determined based on the difference between the layer top and surface temperature) on average produced a radiative effect of about 4.6 W m⁻². The lowest layers (temperature difference less than 4 K) produced on average a radiative effect of 0.8 W m⁻².

How to cite: Jahani, B., Andersen, H., Calbó, J., González, J.-A., and Cermak, J.: How Significant are the Longwave Radiative Effects of the Cloud-Aerosol Transition Zone?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2298, https://doi.org/10.5194/egusphere-egu22-2298, 2022.

The climate sensitivity is the central metric for evaluating the amplitude of climate change. It is inversionally proportional to the climate feedback parameter which can be estimated with observations of surface temperature (T), radiative forcing (F) and Earth energy imbalance (EEI). Since EEI is proportional to the time derivative of the ocean heat content, EEI can be derived from in situ temperature/salinity measurements or, equivalently, from the thermosteric component of sea level rise. Here we use a regression method applied to T, F and in situ temperature as well as thermosteric sea level to estimate the climate feedback parameter over the 20^th century. Several recent climate studies have shown that the feedback parameter changes with time, because of the spatial pattern of warming. We evaluate the time variations of the climate feedback parameter over 1900- 2020 by applying the regression method to different periods within the 20^th century. For the first time, we confirm with observations that the climate feedback parameter does change with time, and responds to external forcings such as major volcanic eruptions, as well as to climate internal variability. We also demonstrate that we need a consistent and reliable observing systems across time to derive a credible climate feedback parameter time series.

How to cite: Chenal, J., Meyssignac, B., and Guillaume-Castel, R.: Observational study of time-varying climate feedback parameter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3359, https://doi.org/10.5194/egusphere-egu22-3359, 2022.

How to cite: Guillaume-Castel, R., Meyssignac, B., Roca, R., and Chenal, J.: Dynamics of the global energy budget with a time dependent climate feedback parameter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7956, https://doi.org/10.5194/egusphere-egu22-7956, 2022.

Climate sensitivity – the response of the Earth’s surface temperature to radiative forcing – and climate feedbacks are important and widely used metrics to gauge global climate change. In recent years it has become clear that climate sensitivity and feedback change over time in numerical climate model experiments but the reasons for this change are not yet well understood. We investigate the abrupt4xCO2 experiment as simulated by multiple members of the Coupled Model Intercomparison Project (CMIP) phases 5 and 6 and apply a radiative kernel method to decompose climate feedback into contributions from physical processes. We extract two groups of models, one with small (G1) and one with large (G2) global mean lapse-rate feedback change over time. It is found that the model groups differ with respect to warming and feedback patterns and that the Arctic stands out as the region with the biggest between-group differences. We retrace these Arctic changes to the different evolution of Arctic sea ice in both model groups. A further finding is that G1 members exhibit much more warming over the simulation period than G2s members. This appears to result from a more positive early cloud feedback in G1 than in G2. Further investigation is needed to uncover possible cause-effect relationships between Arctic changes and global feedbacks.

How to cite: Eiselt, K.-U. and Graversen, R.: On differences in climate feedback evolution in abrupt4xCO2 climate model experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5457, https://doi.org/10.5194/egusphere-egu22-5457, 2022.

There is much current debate about the way in which the earth's climate and temperature are responding to anthropogenic and natural forcing. Current forecasts are dependent on the accuracy of how Equilibrium Climate Sensitivity (ECS) is evaluated. In the recent wide-ranging ECS sensitivity review and assessments of Sherwood et al (2020, Rev. Geophys. 58, e2019RG000678), they report a baseline ECS 5%–95% with a range of 2.3 °C to 4.7 °C. While this is an important and much needed quantification – this wide ECS uncertainty range, based largely on uncertainty around total radiative forcing (TRF), is also problematic for our geophysical based community. The ECS value as viewed by policy and global strategy negotiators is currently only understood to a 70% (= 2.4 / 3.5) physically resolved level of resolution. An open question (to discuss in this talk) is it possible to resolve this physical measurement more accurately and what are the current main issues that need to be accommodated? As part of this discussion we present the work of Young, Allen and Bruun (2021): a re-evaluation of the Earth's surface temperature response to radiative forcing (2021, ERL, 16, 054068). In that paper we have re-assessed the current evidence at the globally averaged level by adopting a generic 'data-based mechanistic' modelling strategy that incorporates statistically efficient parameter estimation. This identifies a low order, differential equation model that explains how the global average surface temperature variation responds to the influences of total radiative forcing. The model response includes a novel, stochastic oscillatory component with a period of about 55 years (range 51.6–60 years) that appears to be associated with heat energy interchange between the atmosphere and the ocean. These 'quasi-cycle' oscillations, which account for the observed pauses in global temperature increase around 1880, 1940 and 2001, appear to be related to ocean dynamic responses, particularly the Atlantic multidecadal oscillation. The model explains 90% of the variance in the global average surface temperature anomaly and yields estimates of the equilibrium climate sensitivity (ECS) (2.29 °C with 5%–95% range 2.11 °C to 2.49 °C) and the transient climate response (TCR) (1.56 °C with 5%–95% range 1.43 °C to 1.68 °C), both of which are smaller than most previous estimates. When a high level of uncertainty in the TRF is taken into account, the ECS and TCR estimates are unchanged but the ranges are increased to 1.43 °C to 3.14 °C and 0.99 °C to 2.16 °C, respectively. This then gives the 70% physical resolution limit in ECS mentioned above. Current work is in progress to test this ECS re-evaluation approach using the CMIP6 models. We will discuss some on-going findings of these model signal assessments which include a specific focus on resolution of Atlantic and Pacific Ocean pentedecadal modes.  

Peter C Young, P Geoffrey Allen and John T Bruun (2021). A re-evaluation of the Earth's surface temperature response to radiative forcing, Environ. Res. Lett. 16 054068, https://iopscience.iop.org/article/10.1088/1748-9326/abfa50.

How to cite: Bruun, J., Young, P., Allen, P. G., and Collins, M.: A discussion of Earth's climate sensitivity and its long term dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6540, https://doi.org/10.5194/egusphere-egu22-6540, 2022.

How to cite: Yuan, M., Leirvik, T., and Wild, M.: Global Trends in Downward Surface Solar Radiation from Spatial Interpolated Ground Observations during 1961-2019, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4120, https://doi.org/10.5194/egusphere-egu22-4120, 2022.

For the explanation of the observed decadal variations in surface solar radiation (known as dimming and brightening) the relative importance of clouds and the cloud-free atmosphere (particularly aerosols) is currently disputed. Here we investigate this issue using daily data from the prominent long-term observational radiation record at Potsdam, Germany, over the 71-years period 1947-2017. We identify cloud-free days based on synop cloud observations as well as on days with maximum atmospheric transmission. Irrespective of the cloud-screening method, strong dimming and brightening tendencies in the atmospheric transmission are evident not only under all-sky, but also of similar magnitude under clear-sky conditions, causing multidecadal variations in surface solar radiation on the order of 10 Wm^-2. This points to the cloud-free atmosphere as a main responsible for dimming and brightening in Central Europe and suggests that these variations are anthropogenically forced rather than of natural origin, with aerosol pollutants as likely major drivers.

This study has been published in Geophysical Research Letters (Wild et al. 2021)

Reference:

Wild, M., Wacker, S., Yang, S., and Sanchez-Lorenzo, A. (2021). Evidence for clear-sky dimming and brightening in central Europe. Geophysical Research Letters, 48, e2020GL092216. https://doi. org/10.1029/2020GL092216

How to cite: Wild, M., Wacker, S., Yang, S., and Sanchez-Lorenzo, A.: Evidence for clear-sky dimming and brightening in the long-term Potsdam radiation record, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1194, https://doi.org/10.5194/egusphere-egu22-1194, 2022.

Decadal trends in Surface solar radiation (SSR) have gained attention in the last few decades after several studies identified the non stable behaviour of such measurements. Also referred to as Global Dimming and Global Brightening, these decadal trends are known to be spatially heterogeneous, meaning that different regions might experience different trends, associated with different causes. While measurements have allowed the identification of trends around the world, the understanding of the causes of those trends is limited to a few regional studies mostly focusing on developed countries. The lack of data in developing countries leads to an underrepresentation of those regions in what regards to global dimming and brightening research. In this work, we use around 39 years  (1967-2005) of daily SSR measurements of two stations in Zimbabwe, and apply a new method for clear-sky derivation, using satellite cloud fraction to identify optimal daily transmittance thresholds for clear-sky identification. The all-sky and clear-sky time series of SSR are then compared to cloud fraction and water vapor data from ERA5 reanalysis and to aerosol emissions from the EDGAR database. The SSR time series show a persistent dimming of similar magnitude both in all-sky and clear-sky. The cloud fraction does not show any significant trends, reinforcing the hypothesis that the dimming was caused by cloud-free radiative processes in the atmosphere. The water vapour time series also does not show any significant trend which could justify the negative trends in SSR. However, the monthly interannual variability show that the dimming is stronger between July and September, months with higher emission of biomass burning aerosols in that region. This might also indicate an anthropogenic related cause of the dimming observed in southern Africa. This study intends to contribute to the understanding of the global dimming and brightening phenomena in southern Africa, but also to highlight the importance of studies focusing in underrepresented regions of the world.

How to cite: Ferreira Correa, L., Wild, M., Folini, D., and Chtirkova, B.: Evidence for biomass burning-forced dimming in southern Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2888, https://doi.org/10.5194/egusphere-egu22-2888, 2022.

The NASA/GEWEX Surface Radiation Budget (SRB) project produces 3-hrly shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. The new Release 4 Integrated Product (IP) uses the newly recalibrated and processed ISCCP HXS product as its primary input for cloud and radiance data, replacing ISCCP DX with a ninefold increase in pixel count (10 km instead of 30 km).  This first version retains a 1°x1° resolution enabling intercomparison against previous versions and other data sets such as CERES, but spans 34 years from July 1983 through June 2017 and was announced by Kummerow et al. 2019 (GEWEX News). This new IP product also uses an atmospheric temperature and moisture dataset known as nnHIRS and other parameters such as near surface and skin temperatures from SeaFlux and LandFlux data sets.  In addition to the input data improvements, several important algorithm improvements have been made since Release 3. These include recalculated SW atmospheric transmissivities and reflectivities, updated ocean and snow/ice albedos, and variable total solar irradiance consistent with SORCE measurements. The LW code has been updated to improve the optical property treatment for clouds and aerosols are included in this version.  Radiative treatment of ice clouds is also improved in the LW. The variable aerosol optical properties for the SW and LW are specified using a detailed aerosol history from the Max Planck Institute Aerosol Climatology (MAC).

Here we present an assessment of the LW radiative fluxes and the uncertainty of those fluxes relative to the various inputs to surface SW/LW flux measurements from BSRN and PMEL buoys measurements.  We review the validation of the SW and LW fluxes and then in terms of time series and then assess the products in terms of their long-term variability of the surface SW and LW net fluxes compared to multiple other data products including atmospheric reanalysis products.  The comparisons of radiative estimates to observations are performed at various temporal scales and aimed at investigation of agreement at longer time averages but accessing potential change in diurnal magnitude and daily variability.  Utilizing this uncertainty information, to access long-term variability of surface radiation components at selected region and global scales, considering satellite sampling/calibration “artifacts” as necessary.  At the longer time scales, the net SW and net LW the TOA and surface have implications toward closure of the energy budgets at the surface, we assess these compared to other studies on energy budget closure for the same selected global and regional scales.

How to cite: Stackhouse, P., Cox, S., Mikovitz, J. C., and Zhang, T.: Assessing Uncertainties and Variability 34 Years of Surface Radiative Fluxes and Radiative Closure Using GEWEX SRB Release4-IP, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13489, https://doi.org/10.5194/egusphere-egu22-13489, 2022.

The incoming surface solar radiation has been defined as an essential climate variable by GCOS. Long term monitoring of this part of the earth’s energy budget is required to gain insights on the state and variability of the climate system. In addition, climate data sets of surface solar radiation have received increased attention over the recent years as an important source of information for solar energy assessments, for crop modeling, and for the validation of climate and weather models.

The EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF) is deriving climate data records (CDRs) from geostationary and polar-orbiting satellite instruments. Within the CM SAF these CDRs are accompanied by operational data at a short time latency to be used for climate monitoring. All data from the CM SAF are freely available via www.cmsaf.eu.

Here we present the new edition of the SARAH climate data record of surface solar radiation from the CM SAF. The regional SARAH-3 climate data record (Surface Solar Radiation Dataset – Heliosat) is based on observations from the series of Meteosat satellites. SARAH-3 provides high-resolution data (temporal and spatial) of the surface solar radiation (global and direct) and the sunshine duration from 1983 to 2020 for the full view of the Meteosat satellite (i.e, Europe, Africa, parts of South America, and the Atlantic ocean). For the first time, this edition of the SARAH data record also provides user-oriented data of spectral radiation, namely the photosynthetic active radiation (PAR) and the daylight (DAL); UV radiation parameters are also available upon request.

In this contribution we introduce the results from the comparison of the satellite-derived surface radiation with available surface measurements; the evaluation addresses the accuracy and the temporal stability of the satellite data using data from regional and global networks, e.g., BSRN, GEBA, ECA&D, CLIMAT, as well as, in the case of PAR and DAL, from individual stations. We present the improvements of the edition 3 of the SARAH data record compared to previous editions, in particular over snow-covered surfaces. The high accuracy and stability of these data records allow the assessment of the spatial and temporal variability and trends.

How to cite: Trentmann, J., Pfeifroth, U., Drücke, J., and Cremer, R.: Quality Assessment of SARAH-3: The new regional satellite-based Surface Solar Radiation data set from the CM SAF, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5605, https://doi.org/10.5194/egusphere-egu22-5605, 2022.

Ground-based measurements of downwelling surface solar irradiance (DSSI) play an important role in many topics, such as the design and operation of solar energy systems, the study of the Earth radiation budget, and the validation of gridded DSSI products such as those derived from satellite imagery and reanalyses. For our purpose of validating satellite-based estimates of DSSI over China, we use ground-based hourly measurements at 99 stations operated by China Meteorological Administration (CMA). The measurements might not be perfect, including outliers, biases, sudden shifts or slow instrumental drifts that an extended quality check (QC) can detect. Physical threshold methods like the one proposed by Long and Dutton (2002) are frequently used to detect some of the physically impossible data records on an hourly or sub-hourly basis. However, in our case, we observed many inconsistent measurements that can pass such threshold-based QC. This is especially because diffuse and/or direct components of DSSI are not measured for most CMA stations and only global irradiance-based check for DSSI can be realized.

To detect drifts or jumps that might last for weeks or months in the time series of measured DSSI, we carried out the QC by comparing the clearness indices (i.e., the ratio between DSSI and horizontal irradiance at the top of atmosphere) from measurements with those from the ERA-5 reanalysis, in a similar approach to Urraca et al. (2017). Consistency of ERA-5's clearness indices was checked at first by comparison with high quality measurements from Baseline Surface Radiation Network. The same quality check was then applied to the hourly datasets at CMA stations. Over the years 2017-2018, our QC method led us to keep 52 stations fully and 19 stations partly.

Reference:

Long C.N. and Dutton E.G. BSRN Global Network recommended QC tests, V2.0, BSRN Technical Report, pp 3, 2002.

Urraca R., Gracia-Amillo A., Huld T., et al. Quality control of global solar radiation data with satellite-based products, Solar Energy 158, pp 49-62, 2017. https://doi.org/10.1016/j.solener.2017.09.032.

How to cite: Chen, X., Tournadre, B., Saint-Drenan, Y.-M., Gschwind, B., Qin, K., and Blanc, P.: Quality check of ground-based hourly measurements of downwelling surface solar irradiance in China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8847, https://doi.org/10.5194/egusphere-egu22-8847, 2022.