ST4.7 | Advances in Determining the Earth Energy Imbalance, Solar Irradiance, and ToA Outgoing Radiation
Advances in Determining the Earth Energy Imbalance, Solar Irradiance, and ToA Outgoing Radiation
Co-organized by AS3/OS4
Convener: Margit Haberreiter | Co-conveners: Martin Snow, Steven Dewitte, Nolwenn PortierECSECS
| Wed, 17 Apr, 08:30–10:10 (CEST)
Room 0.51
Posters on site
| Attendance Tue, 16 Apr, 16:15–18:00 (CEST) | Display Tue, 16 Apr, 14:00–18:00
Hall X3
Posters virtual
| Attendance Tue, 16 Apr, 14:00–15:45 (CEST) | Display Tue, 16 Apr, 08:30–18:00
vHall X3
Orals |
Wed, 08:30
Tue, 16:15
Tue, 14:00
Disk-integrated solar irradiance is the primary input of energy to the Earth climate system. Precise estimates of the absolute irradiance and how it varies are essential for understanding the dynamics of the Earth’s atmosphere. The Sun’s spectrum changes on all timescales, from seconds for space weather events to climate-relevant periods of centuries or longer.
Moreover, for understanding the state of the Earth's climate, the Earth Energy Imbalance (EEI) is the key parameter. It is the global annual mean difference between the incoming solar and reflected solar and emitted terrestrial radiation. A positive EEI corresponds to the heat continuously accumulated in the Earth's climate system – mainly the oceans, and which will - with a time delay - cause the global warming of the surface and the atmosphere. The exact knowledge of the EEI and its trend is key for a predictive understanding of global warming and assessing the efficiency of global carbon reduction policies. To determine the EEI with higher accuracy and stability, independent measurement approaches are required.
We invite contributions describing recent successes in solar irradiance observations, composite datasets, calibration reanalysis, and modelling the solar atmosphere. Measurement concepts with an emphasis on space observations, but also ground-based and in-situ measurements, as well as modeling efforts that help to better determine the energy storage in the Earth's system and the terrestrial outgoing radiation are also warmly welcome.

Orals: Wed, 17 Apr | Room 0.51

Chairpersons: Margit Haberreiter, Martin Snow
Earth Energy Imbalance
On-site presentation
Benoit Meyssignac

The Earth energy imbalance (EEI) is a fundamental climate variable that characterizes the energy state of the climate system. When integrated over multiple years, EEI estimates provide the net energy gain (or loss) by the climate system. In addition, measuring accurately the EEI along with surface temperature and atmospheric composition is essential to separate the role of different radiative forcing from the role of feedbacks on the global energy budget enabling further to constraint effective and equilibrium climate sensitivities. In this presentation I review the current EEI observing system performance and uncertainty. I intercompare the different EEI datasets, originating from in-situ and space-based observing systems to evaluate their differences and to assess their uncertainty.

Since 2000 the Clouds and the Earth’s Radiant Energy System (CERES) project provides satellite-based observations of the Earth radiation budget and the EEI with the highest precision (±0.3W.m-2 -1s- on a monthly basis). Nevertheless, because of limitation in the absolute calibration of CERES radiometers the CERES final product needs a bias correction (of about ±2.5W.m-2 -1s-) on the EEI mean. The current best approach to estimating the mean EEI is to estimate the ocean heat uptake (OHU)  which represent 89% of the energy storage  due to the EEI.  Today, the OHU can be derived with the highest accuracy (±0.18W.m-2 -1s- on the mean OHU), from in situ ocean temperature measured by Argo or from the thermal expansion estimated by the difference between satellite altimetry sea level and ocean mass from GRACE. On 2-yr and longer time scales, OHU and CERES EEI estimates show good agreement in EEI variability. But OHU approaches cannot resolve the EEI variability below 1 yr because the energy gain (or loss) induced by EEI over such small time-scales is of the same order of magnitude as the global exchanges of energy between the atmosphere and the ocean.

The different EEI measurements have enabled since 2005 a robust estimate of the mean EEI of +0.75±0.18W.m-2 that is essentially due to anthropogenic emissions of greenhouse gases (GHG). They have also allowed to detect a significantly positive trend in EEI of 0.4±0.3W.m-2 per decade, leading to a doubling of the EEI during the past 20 years in response to continued increases in GHG emissions combined with decreases in aerosol emissions. In addition, on interannual time scales, they showed that the variability in EEI is mostly sensitive to low cloud variability, with ENSO controlling the ±0.5W.m-2 variability on the 4-7yr time scale.  Today, new scientific challenges related to EEI are emerging like the closure of the energy budget from top of the atmosphere to the bottom of the ocean at monthly to decadal time scales, the estimate of the current effective climate sensitivity, the monitoring of the physical climate system response to GHG mitigation policies and others. These new challenges lead to new requirements on the EEI observing system ranging from sustained continuity to higher precision and accuracy. I discuss briefly the need to refine these requirements and some opportunities to meet them in the future.

How to cite: Meyssignac, B.: Mean, Trend, variability and uncertainty in Earth's Energy Imbalance over the last two decades, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16610,, 2024.

On-site presentation
Robin Fraudeau, Florence Marti, Benoit Meyssignac, Alejandro Blazquez, Sebastien Fourest, Michael Ablain, Victor Rousseau, Gilles Larnicol, Marco Restano, Jérôme Benveniste, Roberto Sabia, and Gérald Dibarboure

The Earth energy imbalance (EEI) at the top of the atmosphere (TOA) is the cause of the energy accumulation in the climate system. Measuring the EEI is challenging because it is a globally integrated variable whose variations are small (0.5-1 W.m−2) compared to the amount of energy entering and leaving the climate system (~ 340 W.m-2). 91% of the excess of energy stored by the planet in response to the EEI is accumulated in the ocean in the form of heat making the ocean heat content (OHC) change an accurate proxy of EEI.

In this work, we adopt the space geodetic approach which relies on the sea level budget equation to estimate the OHC changes. The thermosteric sea level change is derived at regional scale from a combination of space altimetry and space gravimetry observations, and divided by the integrated expansion efficiency of heat  to estimate the OHC changes. The global OHC (GOHC) change is then estimated by a spatial integration of the regional OHC changes. The uncertainty in GOHC is estimated by propagation of the uncertainty of input data using the input data error variance-covariance matrix to account for the instrumental and post-processing errors and for the time correlation in errors.

Regional estimates of the OHC changes are validated over the Atlantic Ocean directly against data from in-situ Argo profiles and indirectly by an energy budget approach. In the energy budget approach, surface heat flux derived from ERA5 and CERES TOA radiation budget are combined with regional OHC changes to estimate the north Atlantic meridional heat transport which is then validated against in-situ RAPID and OSNAP estimates. Both validations show good agreement in terms of signal amplitudes and variability with time correlations above 0.6. 


Over the period 1993-2022, the GOHC shows a significant positive trend of 0.75 W m-2 [0.61, 1.04] at the 90% confidence level, indicating a positive mean ocean heat uptake or EEI. Comparisons with GOHC estimates based on in-situ ocean temperature measurements over the full ocean depth show good agreement over 2005-2019 (Marti et al. 2023, in review). Over 2000-2020, the ocean heat uptake presents a positive trend of 0.33 W/m²/decade, significant at the 90% confidence level and in agreement with CERES estimate. This EEI trend  reflects an acceleration in ocean warming.


The two space geodetic products based on space altimetry and space gravimetry are freely available on the AVISO website. One estimating the GOHC and EEI (, the other estimating regional OHC over the Atlantic Ocean (

How to cite: Fraudeau, R., Marti, F., Meyssignac, B., Blazquez, A., Fourest, S., Ablain, M., Rousseau, V., Larnicol, G., Restano, M., Benveniste, J., Sabia, R., and Dibarboure, G.: Estimate of the global and regional Ocean Heat Content changes from space gravimetry and altimetry observations to assess the Earth Energy Imbalance variations and trend, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16132,, 2024.

On-site presentation
Nigel Fox, Thorsten Fehr, Andrea Marini, Thomas August, and John Remedios

TRUTHS (Traceable Radiometry Underpinning Terrestrial- and Helio-Studies) is an operational climate mission, aiming to enhance, up to an order-of-magnitude, our ability to estimate the Earth radiation budget, spectrally resolved to support attribution. Through direct measurements of incoming total and spectrally resolved solar irradiances and Earth reflected radiances, spatially resolved, it establishes ‘benchmarks’ against which change/trends can be detected in as short a time as possible. These fiducial reference data sets can be combined with data from other sensors and also serve as ‘gold standard’ references to anchor and upgrade the performance of other space sensors through in-orbit calibration.

TRUTHS will become a founding member of a new class of satellites called SITSats, SI-Traceable Satellites, with payloads explicitly designed to achieve and evidence an uncertainty, in-orbit, at a level commensurate with the exacting goals of long-time-base climate studies. SITSats also facilitate interoperability and enhanced trust in the data from the Earth observation system as a whole, helping to provide observational evidence-based confidence in actions addressing the climate emergency. 

The unprecedented uncertainty of TRUTHS’ globally sampled hyperspectral data underpins many additional applications:

  • Establishing an interoperable, harmonised Earth Observing system incorporating agency and commercial satellites: large and small
  • Top and Bottom of atmosphere reflectances impacting carbon cycle (e.g. land cover, ocean colour, vegetation, methane etc together with similar applications of other hyper/multi-spectral missions). Low uncertainty also facilitates improvements in retrieval algorithms.
  • Transferring radiometric reference values to existing Cal/Val infrastructure (e.g. RadCalNet, Pseudo-Invariant Calibration sites, In-situ ocean colour reference observations; selected surface reflectance test-sites (fluxnet, …), both nadir and multi-angular) and Moon observations.

The mission comprises an “agile” satellite capable to point and image the Earth, Moon and Sun from a 90°polar orbit by the Hyperspectral Imaging Spectrometer (HIS). The HIS provides spectrally continuous observations from 320 to 2400 nm, with a spectral sampling between 2 and 6 nm and a spatial sampling of 50 m. The payload utilises a novel SI-traceable on-board calibration system (OBCS), comprising of the Cryogenic Solar Absolute Radiometer (CSAR), able to realise SI-traceability in space and also measure incoming solar radiation. Together with other optical elements the OBCS links the HIS observations to the CSAR with a target expanded uncertainty 0.3% (k=2).

TRUTHS is implemented by the European Space Agency (ESA) as a UK-led Earth Watch mission in collaboration with Switzerland, Czech Republic, Greece, Romania and Spain. The mission was conceived by the UK national metrology institute, NPL, in response to challenges highlighted by the worlds space agencies, through bodies such as CEOS addressing observational needs of GCOS. The mission is under development by an industrial consortium led by Airbus Defence and Space UK, with a target launch date of 2030 and minimal operations life-time of 5 years with a goal of 8 yrs.

Together with FORUM (ESA) and IASI-NG (CNES/EUMETSAT) it will provide spectrally resolved Earth radiance information from the UV to the Far-Infrared in the coming decade, and in partnership with CLARREO-Pathfinder (NASA) and CSRB (CMA) inaugurate a future constellation of SITSats.

How to cite: Fox, N., Fehr, T., Marini, A., August, T., and Remedios, J.: Traceable Radiometry Underpinning Terrestrial- and Helio- Studies (TRUTHS) – A ‘gold standard’ imaging spectrometer in space for radiation imbalance and in support of the climate emergency , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18864,, 2024.

On-site presentation
Thomas Hocking, Thorsten Mauritsen, and Linda Megner

The Earth’s energy imbalance (EEI), i.e. the difference between incoming solar radiation and outgoing reflected and emitted radiation, is the one quantity that ultimately controls the evolution of our climate system. Despite its importance, the exact magnitude of the energy imbalance is not well known, and because it is a small net difference of about 1 Wm−2 between two large fluxes (approximately 340 Wm−2), it is difficult to measure directly. There has recently been a renewed interest in applying wide-field-of-view radiometers onboard satellites to measure the outgoing radiation, and hence deduce the global annual mean energy imbalance.

Here we investigate how to sample with a limited number of satellite orbits, in order to correctly determine the global annual mean imbalance. Using observational and model data, we have investigated the importance of the local and global diurnal cycles, as they are observed by a satellite, in the determination of the EEI. We simulate satellites in polar (90° inclination), sun-synchronous (98°) and precessing orbits (73°, 82°), as well as constellations of these types of satellite orbits. We present the results of ongoing work concerning different orbits, and how they affect the estimated global annual mean EEI.

How to cite: Hocking, T., Mauritsen, T., and Megner, L.: Sampling the diurnal and annual cycles of Earth’s energy imbalance with constellations of satellite-borne radiometers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15999,, 2024.

On-site presentation
Tomasz Zapadka, Mirosława Ostrowska, Damian Stoltmann, and Marcin Paszkuta

Global climate change, which causes, among other things, an accumulation of energy in the oceans, may cause irreversible changes to their ecosystems. This can be particularly quickly apparent in bodies of water that are shallow and small in relation to the Oceans, such as the Baltic Sea. In the SatBałtyk System (, which aims to observe the state of the Baltic Sea environment based on satellite data, maps of the distributions of values of a number of physical biological and chemical parameters of the sea are collected and made available. Within the framework of this System, the SBRB (SatBałtyk Radiation Budget) model was launched, determining data on radiation budget (NET) at the sea surface. Daily maps of the spatial distribution of the radiation budget  and its components at the Baltic Sea surface are created based on data from SEVIRI, AVHRR, MODIS, SBUV/2, TOVS radiometers, and forecast auxiliary models. The component algorithms of this model were developed and validated against empirical data measured directly in the Baltic Sea (Zapadka et al. 2020). The uncertainties in the estimation of the radiation budget for the monthly averages are: RMSD 4 Wm-2 and BIAS -0.5 Wm-2. The individual downward and upward shortwave radiation fluxes are determined with an accuracy of RMSD 3 Wm-2, 1 Wm-2, BIAS 3 Wm-2, 0.1 Wm-2 respectively, and downward and upward longwave radiation fluxes are RMSD 4.5 Wm-2, 3.7 Wm-2, BIAS -0.8 Wm-2, 2.6 Wm-2 respectively. The uniform methodology used since 2010 has enabled an analysis of the variability of the radiation budget and its components at the surface of the Baltic Sea covering 14 years. Despite the natural variation in NET values and its components year-on-year, the analyses showed an annual growth trend of c. 0.7 Wm-2. Interestingly, the increasing trend applies to all NET components. An analysis of the possible causes of the trend observed in recent years may confirm the role of the anthropological factor in these changes.

How to cite: Zapadka, T., Ostrowska, M., Stoltmann, D., and Paszkuta, M.: Radiation budget at the Baltic Sea surface in 2010 – 2023 from SatBałtyk System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11721,, 2024.

On-site presentation
Katcha Winther, Peter Thejll, and René Fléron

The average global temperature of Earth is governed by the energy balance equation, comparing energy entering and leaving the Earth system. A key parameter in this balance is the Earth’s albedo, determining the ratio of the Sun’s energy being reflected from or absorbed by Earth. The global albedo varies on several different timescales – daily due to changes in cloud cover, seasonally due to changes in foliage and snowfall, and on greater timescales a change in albedo is a reflection of our changing climate. To measure these changes, multi-decadal data is needed.

Data of top-of-the-atmosphere shortwave radiation used in albedo estimation, are primarily gathered by LEO satellites using absolute measurement techniques. These are however affected by the harsh space environment, especially radiation, which causes drift errors in the data, requiring in-flight calibration. The purpose of NASA’s and ESA’s upcoming missions CLARREO and TRUHTS respectively, is to provide state of the art calibration data to account for these errors. However, they do not remove the issue all together.

As an alternative to these absolute measurements, the space based earthshine telescope juLIET (ju Lunar Imaging Earthshine Telescope) aims to estimate the albedo through relative measurements. The Earthshine albedo technique is based on comparing the intensity of Moonlight coming from the visible dayside of the Moon and the Earthshine reflected off the visible nightside of the Moon. As a relative measurement, it is more resilient to calibration drift.

Albedo measurements using the Earthshine technique have been successfully carried out from Earth, but due to Moonlight being several magnitudes brighter than Earthshine, atmospheric scattering of Moonlight reduces the possible precision on the Earthshine intensity. While the issue of atmospheric scattering is removed by going into orbit, measuring the dim Earthshine with a sufficiently high precision to be used for albedo estimation, using the same sensor that measures the Moonlight, still poses a significant challenge, due to scattering and diffraction of Moonlight within the telescope.

To determine the feasibility of the juLIET instrument, an analysis of the optical noise of the telescope is conducted. This analysis is carried out using Zemax OpticStudio and MATLAB, where main contributors to the uncertainty of the measurement are isolated and quantified.

The results of this noise analysis will be extended to determine which lunar phases juLIET can provide measurements of the Earth albedo, during its mission time as primary payload on the small-sat ROMEO developed by IRS, University of Stuttgart. 

How to cite: Winther, K., Thejll, P., and Fléron, R.: Lunar Imaging Earthshine Telescope, juLIET, for Earth Albedo Measurements , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10172,, 2024.

Solar Irradiance Variability
On-site presentation
Erik Richard, Odele Coddinton, Dave Harber, Peter Pilewskie, and Tom Woods

The NASA’s Total and Spectral Solar Irradiance Sensor (TSIS-1) launched on December 15th, 2017 and was integrated on the International Space Station (ISS) to measure long-term total solar irradiance (TSI) and solar spectral irradiance (SSI). The direct measurement of the SSI is made by the LASP Spectral Irradiance Monitor (SIM) and provides data essential to interpreting how the Earth system responds to solar spectral variability. Extensive advances in TSIS-1 SIM instrument design and new SI-traceable spectral irradiance calibration techniques have resulted in improved absolute accuracy with uncertainties of less than 0.5% over the continuous 200 to 2400 nm spectral range. Furthermore, improvements in the long-term spectral stability corrections provide lower trend uncertainties in SSI variability from those of the previous SORCE SSI instruments. We present the early mission results of the TSIS-1 SIM SSI observations for the first 5 years of operations – a time-period that includes the descending phase of solar cycle 24, the last solar minimum, and the ascending phase of solar cycle 25. Comparisons are made to previous spectral measurements both in the absolute scale of the solar spectrum and the time dependence of the SSI variability. The TSIS-1 SIM SSI spectrum shows lower IR irradiance (by as much as 6% near 2400 nm) and small visible irradiance increases (~0.5%) from the previous ATLAS3 and WHI reference solar spectra, but more consistent agreement with recent SCIAMACHY and SOLAR2 reanalysis results. We also show initial comparisons to current NRLSSI2 and SATIRE-S SSI model results both for short-term (solar rotation) spectral variability and, for the first time, the longer-term (near half solar cycle) spectral variability across the solar spectrum from the UV to the IR.

How to cite: Richard, E., Coddinton, O., Harber, D., Pilewskie, P., and Woods, T.: Long-term Solar Spectral Irradiance Observations by the TSIS-1 Spectral Irradiance Monitor, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2928,, 2024.

On-site presentation
Kalevi Mursula, Alexei Pevtsov, Timo Asikainen, Ismo Tähtinen, and Anthony Yeates

The Sun experienced a period of unprecedented activity during solar cycle 19 in 1950s and 1960s, now called the Modern Maximum (MM). The decay of the MM has changed the Sun, the heliosphere and the planetary environments in many ways. However, this decay may not have proceeded synchronously in all solar parameters. One of the related key issues is if the relation between the two long parameters of solar activity, sunspot number and the solar 10.7cm radio flux, has remained the same during this decay. While a number of studies agree that this relation has indeed changed, no consensus on its validity exists. A recent study argues that there is an inhomogeneity in the 10.7cm radio flux in 1980, which led to a step-like jump ("1980 jump") in this relation. If true, this would imply that the 10.7cm radio flux is ineligible for long-term studies, which would seriously impede versatile studies of the Sun during the MM.

Here we use the 10.7cm radio flux and four other, independent radio flux measurements, the sunspot number, the MgII index and the number of solar active regions in order to study their mutual relations during the decay of MM. We find that all the five radio fluxes depict an increasing trend with respect to the sunspot number from 1970s to 2010s. This excludes the interpretation of the "1980 jump" as an inhomogeneity in the 10.7cm flux, and re-establishes the 10.7cm flux as a reliable and homogeneous long-term measure of solar activity.

We find that the fluxes of longer radio waves increased with respect to the shorter waves, which implies a long-term change in the solar spectrum at radio frequencies. We also find that both the MgII index and the number of active regions increased with respect to the sunspot number, indicating a difference in the long-term evolution in chromospheric and photospheric parameters.

Our results give evidence for important structural changes in solar magnetic fields and solar atmosphere during the decay of the MM when solar activity weakened considerably. These changes have not been reliably documented so far. We also emphasise that the changing relation between the different (e.g. photospheric and chromospheric) parameters should be taken into account when using sunspot number or any single parameter in long-term studies of solar activity.

How to cite: Mursula, K., Pevtsov, A., Asikainen, T., Tähtinen, I., and Yeates, A.: A change in solar radio spectrum during the decay of the Modern Maximum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11445,, 2024.

On-site presentation
Benoit Tremblay, Robert Jarolim, Anna Jungbluth, Andrés Munoz-Jaramillo, Kyriaki-Margarita Bintsi, Miraflor Santos, James P. Mason, Angelos Vourlidas, and Sairam Sundaresan

Multiple satellites capture images of the Sun in Extreme Ultraviolet (EUV) light. However, only the Solar Dynamics Observatory (SDO) was equipped with instruments that measure the Sun's EUV spectral irradiance (i.e., MEGS-A and MEGS-B onboard the Extreme Ultraviolet Variability Experiment (EVE) suite). The MEGS-A instrument malfunctioned in 2014, making it impossible to measure the full irradiance spectrum ever since. 


Using AI, we explore the translation of a set of EUV images of the Sun into spectral irradiance, effectively replacing the malfunctioning MEGS-A instrument onboard SDO. In other words, we generate a virtual irradiance instrument, MEGS-AI, for SDO. Using an Image-to-Image translation tool (ITI), this virtual instrument can also be trained and added on other EUV-observing satellites like STEREO, GOES, SolO, and the upcoming VIGIL satellite, enabling unprecedented irradiance estimates from additional satellite missions. In the case of the STEREO twin-satellites and VIGIL, this enables estimates of spectral irradiance prior to the Sun rotating into Earth’s view, which directly enables the forecast of enhanced irradiance. Additionally, we explore different combinations of images in different EUV channels and evaluate their contributions in estimating different irradiance channels. Finally, when combined with a neural radiance field model of the Sun (SuNeRFs), MEGS-AI can estimate spectral irradiance from any viewpoint in the solar system, enabling for the first time a complete 4pi spectral irradiance map of the Sun. This can be directly used to estimate the Sun’s impact on other planets in the solar system and to determine the total solar irradiance output in multiple EUV spectral bands.

How to cite: Tremblay, B., Jarolim, R., Jungbluth, A., Munoz-Jaramillo, A., Bintsi, K.-M., Santos, M., Mason, J. P., Vourlidas, A., and Sundaresan, S.: AI to Enhance the Capabilities of EUV-observing Satellites and Estimate Spectral Irradiance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13691,, 2024.

Posters on site: Tue, 16 Apr, 16:15–18:00 | Hall X3

Display time: Tue, 16 Apr 14:00–Tue, 16 Apr 18:00
Chairperson: Margit Haberreiter
Maya Nocet-Binois

The accurate determination of sea surface height begins with the precise characterization of the orbit of altimetric satellites with respect to the Earth’s center of mass. To produce precise estimates of the orbital height of such altimetric satellites, Precision Orbit Determination (POD) combines satellite-tracking information with force models, including gravity, atmospheric drag, radiation, and others, which govern the motion of these satellites.
However, it’s important to note that uncertainties arising from the modeling of non-gravitational forces, stemming from the interaction between photons, molecules, atoms, and satellite surfaces, constitute a significant source of error.

With the goal of achieving radial orbit errors below 0.1 mm/year at regional and decadal time scales, an update in the modeling of non-gravitational forces, specifically addressing Earth radiation pressure, was performed. Indeed, the traditional model used in CNES' ZOOM orbit determination software was based on an average approach (Knocke et al., 1988) accounting for latitude and time dependent reflected/emitted radiations which did not consider the spatial and temporal complexity of reflection phenomena, such as cloud dynamics.

To address this issue, an approach involving the use of observations from Earth radiation fluxes, such as CERES (NASA) and ERA5 (ECMWF), was adopted and tested during the lifetime of the Sentinel-6A and CryoSat-2 satellites. These efforts led to substantial improvements in the dynamic modeling of satellite orbits. Comparisons were made between the resulting satellite orbits and those based on the legacy model, with the aim of assessing their impact on sea level measurements. Although a slight discrepancy was observed between the two derived orbits, this difference was attributed to the introduction of empirical forces, typically employed to correct dynamic modeling errors. Consequently, an analysis of these empirical forces confirmed their relevance and underscored the value of the new force model

How to cite: Nocet-Binois, M.: Enhancing satellite orbit accuracy for sea level monitoring through Earth radiation pressure modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6134,, 2024.

Steven Penton, Martin Snow, Stéphane Béland, Don Woodraska, and Odele Coddington

The GOES-R series of geostationary satellites include a redesigned instrument for solar spectral irradiance: 
the Extreme ultra-violet and X-ray Irradiance Sensor (EXIS). Our team will be using the Sun Position Sensor (a set of high-cadence broadband visible light diodes) on GOES-16 and GOES-18 EXIS instruments to construct a high-cadence proxy for Total Solar Irradiance (TSI). This has two advantages over the existing TSI measurements: 
1) the measurements are taken at 4 Hz, so the cadence of our TSI proxy is much faster than existing measurements, such as the 6 to 24-hour measurements produced by SORCE or TSIS-1, and 
2) from a geostationary position, the time series of measurements is virtually uninterrupted.

Our calibration of the GOES-R EXIS diode measurements includes thermal and sun-satellite distance corrections, 
while the irradiance calibration relies on TSIS-1 TIM TSI composites. Another measurement from GOES-EXIS that will be used is the Magnesium II core-to-wing ratio. The MgII index is a proxy for chromospheric activity and is measured by EXIS every 3 seconds. The combination of the two proxies is used to generate a model of the full solar spectrum similar to the NRLSSI2 empirical model.

We are in the final year of a four-year grant to develop the TSI proxy and the SSI model.

How to cite: Penton, S., Snow, M., Béland, S., Woodraska, D., and Coddington, O.: GHOTI: Using the GOES-R EXIS/SPS detectors to create a low-latency, high-cadence, TSI proxy and spectral models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20938,, 2024.

Jean-Philippe Montillet, Wolfgang Finsterle, Margit Haberreiter, Daniel Pfiffner, Ping Zhu, Duo Wu, Silvio Koller, Xin Ye, Dongjun Yang, Wei Fang, Jin Qi, and Peng Zhang

Since the late 1970s, successive satellite missions have been monitoring solar activity and recording Total Solar Irradiance (TSI) data. The Digital Absolute
Radiometer (DARA) on board the Chinese FY3E spacecraft was launched on July 4, 2021, and  has since been recording TSI observations. Here, we analyze these observations and assess the performance of DARA, including sensor degradation of 5 ppm after 2 years in orbit, resulting from exposure to ultraviolet and extreme ultraviolet radiation. Comparing the new dataset’s mean values with observations from active  instruments on other spacecraft (i.e., PMO6 on board the VIRGO/SOHO and the TIM/TSIS), along with the Solar Irradiance Absolute Radiometer (SIAR) also on board  FY3E/JTSIM, we find that DARA observations closely align with TIM/TSIS, with a difference of approximately 0.07 W/m2. Based on these findings, we generate a new TSI dataset (JTSIM-DARA product) at a 6-hour sampling interval. Finally, we have incorporated this new dataset into the TSI composite time series released by the PMOD/WRC. The results indicate that the inclusion of DARA-recorded observations does not alter the consistency, reliability, and stability of the time series.

How to cite: Montillet, J.-P., Finsterle, W., Haberreiter, M., Pfiffner, D., Zhu, P., Wu, D., Koller, S., Ye, X., Yang, D., Fang, W., Qi, J., and Zhang, P.: The JSTIM-DARA  product derived from the TSI Observations Recorded by the FY3E/JTSIM/DARA Radiometer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5966,, 2024.

Margit Haberreiter, Julien Amand, Edward Baudrez, Wolfgang Finsterle, Nigel Fox, Dave Harber, Norman Loeb, Mustapha Meftah, Jean-Philippe Montillet, Stijn Nevens, Peter Pilewskie, Bill Swartz, Martin Wild, Duo Wu, Xin Ye, and Ping Zhu

A positive Earth Energy Imbalance (EEI) is the energy, which is continuously stored by the Earth and will ultimately released to the atmosphere, causing global warming. The "imperative to monitor Earth’s energy imbalance” (von Schuckmann et al., 2016) has been continuously reported by the Earth’s climate community. The EEI has been identified to be around 0.5 to 1.0 Wm−2. To determine its exact value both the Total Solar Irradiance (TSI) and the Top of the Atmosphere (ToA) Outgoing Radiation (TOR) need to be measured with unprecedented accuracy and precision.However, so far, the EEI could not be determined as the measurements were not sufficiently accurate. This calls for improved instrument technologies as well as a traceable calibration chain of the space instrumentation. To pave the way in that direction, the ISSI International Team "Towards Determining the Earth Energy Imbalance from Space" has been established. We collect the current knowledge of ERB measurements and identify missing elements for measuring EEI from space. Specifically, we collect past and ongoing measurements of the ERB components obtained with instruments such as CLARA, RAVAN, SIMBA, GERB, and CERES. The goal is to evaluate the performance and uncertainty of each of the instruments to identify observational challenges that need to be overcome to be able to measure both TSI and the Earth’s outgoing radiation with the required accuracy to ultimately be able to determine the absolute level of EEI from space.

How to cite: Haberreiter, M., Amand, J., Baudrez, E., Finsterle, W., Fox, N., Harber, D., Loeb, N., Meftah, M., Montillet, J.-P., Nevens, S., Pilewskie, P., Swartz, B., Wild, M., Wu, D., Ye, X., and Zhu, P.: Towards Determining the Earth Energy Imbalance from Space - Outcome of a recent ISSI International Team, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12284,, 2024.

Martin Snow and William McClintock

One of the instruments on the Geostationary Operational Environmental Satellites is the Extreme and Ultraviolet Sensor (EUVS).  Channel C of EUVS measures the Magnesium II core-to-wing ratio with high signal-to-noise ratio at a cadence of three seconds.  This presentation will describe the design of the instrument and give an overview of the data collected so far.  Available data products range from the full-cadence operational data measured every three seconds to science-quality daily averages. 


The instrument measures the spectrum of the Sun from 275 to 285 nm with a spectral resolution of 0.1 nm.  It uses a diode array with a sampling width of 0.02 nm, providing five samples per slit width. 


The first of these instruments became operational in January 2017 and continues through the present.

How to cite: Snow, M. and McClintock, W.: High Precision, High Time Cadence Measurements of the Mg II Index of Solar Activity by the Extreme Ultraviolet Sensor aboard the NOAA GOES-R Series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15007,, 2024.

Air-Sea fluxes during the EUREC4A2020 Experiment
Denis Bourras, Sébastien Stragapède, Hubert Branger, Christopher Luneau, Saïd Benjeddou, Nicolas Geyskens, Gilles Reverdin, and Sabrina Speich
The Earth Climate Observatory (ECO) space mission concept for the monitoring of the Earth Energy Imbalance (EEI)
(withdrawn after no-show)
Nicolas Clerbaux and Steven Dewitte

Posters virtual: Tue, 16 Apr, 14:00–15:45 | vHall X3

Display time: Tue, 16 Apr 08:30–Tue, 16 Apr 18:00
Chairperson: Margit Haberreiter
Daniel Brandt and Aaron Ridley

The ubiquitous usage of solar proxies in the nowcasting and forecasting of ionospheric and thermospheric conditions has seen the application of a multitude of techniques to ensure high fidelity representation of the effects of solar EUV forcing on the atmospheric state. The inherent limitations of reliance on a single solar proxy have encouraged the development of numerous EUV irradiance models in which the EUV irradiance in multiple bands is reconstructed from F10.7 solar flux. These models have progressed from lower to higher resolution, as well as higher-fidelity parameterization of time-varying components of the EUV irradiance. We contribute to this development in presenting NEUVAC, a simple, but novel empirical solar EUV model trained on FISM2 data. NEUVAC models the solar EUV irradiance from F10.7 and 81-day averaged F10.7 in 59 wavelength bands between 1 and 1750 Angstroms using a nonlinear parameterization, and performs uncertainty quantification in each band with the assistance of exclusively data-driven methods that exploit the dynamical properties of EUV, and intercorrelations between irradiance in each band. The irradiances provided by NEUVAC highlight the success of the FISM2 program, are suitable for direct ingestion into global ionosphere-thermosphere models, and are structured so that ensembles of irradiance estimates can be generated for principled forecasting and statistical assessment of downstream parameters generated by ionosphere-thermosphere models.

How to cite: Brandt, D. and Ridley, A.: A Novel Empirical EUV Model with Uncertainty Quantification, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10791,, 2024.