G5.1

Ionosphere comparison study of VGOS and global maps of Total Electron Content.

Nataliya Zubko, Minghui Xu, Niko Kareinen, Tuomas Savolainen, Markku Poutanen.

Total Electron Content (TEC) of the ionosphere is an important characteristic whose accurate estimation is needed in various application which are based on measurements in radio wave band. There is a number of Global TEC models designed to describe conditions of ionosphere in different parts of the world. We have conducted a comparative study of the two selected TEC global maps with the results from the observations of the VLBI Global Observing System (VGOS). VGOS network has been established recently and it is continuously growing. The estimated differential TEC (dTEC) from VGOS data has high precision with the formal error of dTEC is of about 0.01-0.2 TECU. It can be used in evaluation of the TEC global maps, as well as an additional data source for the further improvement of the TEC map models.

VLBI measures radio waves emitted by Active Galactic Nuclei (AGN) using a network of radio telescopes distributed around the globe. The measured signal propagates through different parts of ionosphere having different local properties, since distances between radio telescopes spans the range from 400 km to more than 10,000 km. To account for the ionosphere delay effect, geodetic VLBI estimates dTEC for each observing baseline that is formed by a pair of radio telescopes.

Precision of the estimated dTEC with VGOS has been improved considerably compared to the traditional geodetic S/X VLBI observations. One needs to note that VGOS dTEC still have both instrumental (slowly varying) and source structure systematic contributions that will need to be decoupled from the ionosphere measurement. We have compared VGOS ionosphere product with the dTEC calculated using global ionosphere TEC maps. For analysis, we selected two TEC global models, CODE GIM and Neustrelitz TEC Model Global (NTCM-GL). The comparison was performed for the VGOS observations made in 2019, when the solar activity was at about its minimum. The comparison shows a good agreement between VGOS dTEC and dTEC obtained using global TEC maps. However, it also reveals shortages of the global TEC models in some locations. The VGOS data can be considered as an additional information source and, hence, they can be used for the further improvement of the global TEC models.

How to cite: Zubko, N., Xu, M., Kareinen, N., Savolainen, T., and Poutanen, M.: Ionosphere comparison study of VGOS and global maps of Total Electron Content, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9798, https://doi.org/10.5194/egusphere-egu21-9798, 2021.

The ionospheric signal delay is one of the largest error sources in GNSS applications and may cause in case of a single-frequency receiver a positioning error of up to several meters. To avoid such an inaccuracy some of the Ionosphere Associated Analysis Centers (IAAC) of the International GNSS Service (IGS) provide the user the Vertical Total Electron Content (VTEC) as Real-Time Global Ionosphere Maps (RT-GIM) via streaming formats. Currently, the only data format used for the dissemination of these ionospheric corrections is based on the State Space Representation (SSR) message and the RTCM standards.

Mathematically most of the RT-GIMs are based on modeling VTEC as series expansions in spherical harmonics (SH) up to a highest degree of n = 15 which corresponds to a spatial resolution of 12° in latitude and longitude and is therefore, too low for modern GNSS applications such as autonomous driving. However, the SSR VTEC message allows the dissemination of SH coefficients only up to a maximum degree of n = 16.

To avoid the drawbacks of expanding VTEC in SHs other approaches such as a voxel representation or a B-spline series expansion have been proven to be appropriate candidates for global and regional modelling with an enhanced resolution. In order to provide in these cases the significant model parameters to the user, the application of the SSR VTEC message requires a transformation of the model parameters into SH coefficients. In this contribution a methodology will be presented which describes a fast transformation of the B-spline approach into a SH representation with high accuracy by minimizing the information loss.

To test the method, a high-resolution VTEC GIM modeled as a series expansion in B-splines is transformed into SH representations of different highest degree values; the results are validated via dSTEC analysis as well as via an example of single frequency positioning and show a significantly improved accuracy compared to the IGS GIMs.

How to cite: Goss, A., Hernández-Pajares, M., Schmidt, M., and Erdogan, E.: Dissemination of High-Resolution Ionosphere Information from VTEC B-spline Expansions for Single-Frequency Positioning, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14179, https://doi.org/10.5194/egusphere-egu21-14179, 2021.

In this work, we present a new method for assessing global ionospheric maps (GIM) by means of ionosonde data. The method proposed is based on the critical frequency at the F₂ layer directly measured by pairs of ionosondes to assess VTEC (vertical total electron content) values from GIMs. Four strategies were investigated and, the best one was the linear interpolation of squared f_oF₂ based on the VTEC ratio. The analysis was based on the root mean square (RMS) of the differences between the measured and estimated f_oF₂ values at the first ionosonde from each pair. The f_oF₂ were estimated using the values measured at the second ionosonde and interpolated to the position of the first ionosonde with the VTEC values from the GIMs. Besides the RMS values, additional ionospheric indicators (slab thickness and shape function peak) were used to complement the daily analysis. This method was tested over one of the most challenging scenarios, the Brazilian region and near the last solar cycle peak. The assessment considered four ionosondes (combined in six pairs) and thirteen GIM products available at CDDIS (Crustal Dynamics Data Information System), CORG, CODG, EHRG, ESRG, ESAG, IGRG, IGSG, JPLG, UPRG, UPCG, UQRG, WHRG and WHUG. Analysis was conducted using daily, weekly, one year, and four years of data. The analysis with daily data showed that slab thickness and shape function peak could be helpful to identify periods and regions where this method could be applied. The weekly analysis was performed to select the best strategy to interpolate the f_oF₂ values. The analysis of one-year data (2015) was performed considering all GIMs previously mentioned. CODG, IGSG, JPLG, UQRG, WHRG, and WHUG provided the best results, with mean rates of improvement up to 42% in comparison to not using any GIM. The four-year time series (2014-2017) were analyzed considering the two products with better performance for the one-year analysis (CODG and UQRG). With data from 2014-2017, CODG and UQRG provided improvement rates of up to 49%. In general, regional and temporal ionospheric influences could be noticed in the results, with expected larger errors closer to the solar cycle peak in 2014 and at locations with pairs of ionosondes with the larger distance apart. Therefore, we have confirmed the viability of the developed approach as an assessment method to analyze GIMs quality based on ionosonde data.

How to cite: Jerez, G., Hernández-Pajares, M., Prol, F., Alves, D., and Monico, J.: Assessment of global ionospheric maps performance in the Brazilian region using ionosonde data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5440, https://doi.org/10.5194/egusphere-egu21-5440, 2021.

Global ionospheric total electron content (TEC) map has been employed in many high-precision areas. However, its spatial and temporal resolution is not ideal since the ground-based Global Navigation Satellite Systems (GNSS) stations distributed unevenly. Fortunately, many low earth orbit (LEO) satellite constellations will provide a large number of observations that can be used for ionospheric monitoring in the future. In this contribution, we presented two methods, which are the single-layer normalization (SLN) method and the dual-layer superposition (DLS) method, for ionospheric modeling based on the simulative and real data of GNSS+LEO satellites.

For simulative data, a constellation with 192 LEO satellites is simulated. And then,  the global ionospheric maps (GIMs) are estimated by all Multi-GNSS and simulative LEO satellite observations. The results showed that the root mean square (RMS) is reduced by approximately 25% and 21% for SLN method and DLS method, respectively. For real data,  20 available scientific LEO satellites, such as Jason-2/3, COSMIC-1/-2, Swarm missions, etc.,  are employed in the ground-based GNSS ionospheric modeling. The results showed that the differences between the ionospheric model estimated by GNSS+LEO and that by GNSS data are mainly over the oceanic region, which may exceed ±20 TECU. The improvement of RMS over the oceanic region is about 15% for the ionospheric model estimated by GNSS+LEO. The RMS of the ionospheric model improved approximately 4.0% compared with that by GNSS data using the dSTEC assessment method.

How to cite: Ren, X., Chen, J., and Zhang, X.: High-resolution and high-accuracy  global ionosphere maps estimated by GNSS and LEO constellations: simulative and real data experimental results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10527, https://doi.org/10.5194/egusphere-egu21-10527, 2021.

Owing to the advantages of high vertical resolution, global coverage, high precision, and all-weather operation, GNSS occultation has been widely used for ionospheric weather monitoring and meteorological forecast. Aiming to obtain the meteorological, climatic, and ionospheric information, FORMOSAT-7/COSMIC-2, the successor constellation of COSMIC-1, is jointly launched by the United States and Taiwan on June 25, 2019. As a new generation occultation constellation, COSMIC-2 consists of six low-latitude satellites with an orbital inclination of 24 degrees and an altitude of 520km. In contrast, COSMIC1 consists of the high-latitude satellites with an orbital inclination of 72 degrees and an orbital altitude of 720km. These differences in constellation structure, orbital altitude, and inclination inevitably lead to the difference in observation quality.

Firstly, in this contribution, the qualities of satellite-based GNSS observations from COSMIC-2 and COSMIC-1 are both analyzed and compared. The result shows that the satellite-based observation data of COSMIC-2 are improved significantly compared with COSMIC-1. The multipath effect reduced by more than 40%, and the probability of cycle slip decreased by three times. Then the occultation observations of the two constellations are also analyzed. Next, using the observations of COSMIC-2 satellites in 2020, an ionospheric total electron content (TEC) model was established. Finally, the TEC model was adopted for investigating the ionospheric disturbances under extreme space weather in 2020.

Keywords: COSMIC-2; Ionospheric TEC Model; Extreme Space Weather

How to cite: Li, A.: Evaluation the quality of FORMOSAT-7/COSMIC-2 Observation Data and its application for ionospheric monitoring during the extreme space weather, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12067, https://doi.org/10.5194/egusphere-egu21-12067, 2021.

Among the many error sources affecting GNSS (Global Navigation Satellite System) positioning accuracy, the ionosphere is the cause of those of the greatest value. The ionized gas layer, where also free electrons are present, extends from the upper atmosphere to 1,000 km above the Earth's surface (conventionally). As the GNSS satellite orbits altitude is more than 20,000 km, the wave transmitted from the satellite to the receiver on the Earth’s ground passes through this layer, but not unscathed. The ionosphere is a dispersive medium for the electromagnetic waves in the microwave band, including UHF (Ultra High Frequency) waves transmitted by GNSS satellites. As a result, the group velocity of the wave decreases, while its phase velocity – increases.

Ionospheric delay compensation methods include among others multi-frequency measurements;  however, when considering measurements on one frequency, the usage of ionospheric models is an option. The key element is the number of free electrons, its inclusion in the course of calculations is possible thanks to the TEC (Total Electron Content) maps. Taking into account the variability of the coefficient in the daily and annual course, as well as depending on the activity of the Sun and its 11-year cycle, it is important to use the current value for a given place and time.

For the European Galileo satellite system a dedicated ionospheric model NeQuick-G was developed. As a simple modification of the formula allows it to be applied to other satellite systems, it can be considered in a broader context, regardless of the system and receiver location. In our study the TEC maps published by IGS are used as the comparative data. As a reference, the station located in Warsaw, Poland, is adopted.

The subject of this research is the reliability and validity of the model in equatorial region. The analysis is performed for the stations belonging to the IGS (International GNSS Service) network, located in the discussed area. For each hour of the day, independently for each month of 2019, statistic parameters are determined for both models as well as for the difference between them. The results are analysed taking into account the local time of individual stations. The decisive element is the comparison of the station position time series during disturbed and quiet ionospheric conditions (selected based on the K-index), using each of the models (single-frequency observations). The station coordinates are determined from GPS (Global Positioning System) data using the PPP (Precise Point Positioning) method; the position determined for the iono-free combination (dual-frequency observations) is used as a reference.

The ionospheric delay is directly proportional to the value of the TEC parameter. The difference between the models, exceeding on average even 20 TECU (Total Electron Content Unit) during some periods, translates into a station coordinate differences. The presented analysis may indicate the need for local improvement of global ionospheric models in the discussed region, which will consequently affect the GNSS positioning quality.

How to cite: Woźniak, P., Świątek, A., and Jaworski, L.: Comparative analysis of global ionospheric models used in GNSS data processing based on selected stations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12632, https://doi.org/10.5194/egusphere-egu21-12632, 2021.

The development of space-geodetic observation techniques has brought out a wide range of applications such as positioning and navigation, where the Global Navigation Satellite System (GNSS) is the main tools to provide surveying measurements in these applications. Though GNSS signals enable the calculation of receiver's position, some errors restrict their accuracy. Among these errors, the ionospheric delay is considered as an important error source in the Standard Point Positioning (SPP) applications. Empirical ionospheric models such as Klobuchar, International Reference Ionosphere (IRI), and NeQuick are often applied for computing the Total Electron Content (TEC) within ionosphere and its equivalent delays. However the simulation and forecasting skills of these models are limited due to the simplified model structures and model sensitivity to the calibration period. In this study, we present a novel sequential Calibration approach based on the Ensemble Kalman Filter (C-EnKF) to improve the performance of TEC estimations for SPP applications. To demonstrate the results, the IRI model is used as our basis and the TEC estimates from 56 IGS stations in Europe are applied as observation. The C-EnKF is applied to calibrate some selected model parameter so that IRI can be tuned over Europe. The numerical assessments are performed against the TEC estimates from dual frequency GNSS measurements and against the final IONEX products (that are available with 11 days delays). Based on the forecasting results (during September 2017), we show that the accuracy of TEC estimates from the C-EnKF is improved in the range of 3.7-64.87% compared to IRI. Keywords: Ionosphere, Sequential Calibration, Ensemble Kalman Filter (EnKF), IRI, Total Electron Content (TEC), Standard Point Positioning (SPP), GNSS

How to cite: Forootan, E., Kosary, M., Farzaneh, S., and Schumacher, M.: A sequential calibration technique to improve IRI using TEC estimates of the GNSS network in Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4190, https://doi.org/10.5194/egusphere-egu21-4190, 2021.

Natural hazards such as shallow earthquakes and volcanic explosions are known to generate acoustic and gravity waves at infrasonic velocity to propagate in the atmosphere layers. These waves could induce the layers of the ionosphere by change the electron density based on the neutral particles and free electrons coupling. Recently, some studies have dealt with some manmade hazards such as buried explosions and underground nuclear explosions which could cause a trigger to the ionosphere. The Global Navigation Satellite Systems (GNSS) provide a good way to measure ionospheric total electron content (TEC) through the line of sight (LOS) from satellite to receiver. The carrier-to-code leveling (CCL) technique is carried out for each continuous arc where CCL eliminates potential ambiguity influence and it degrades the pseudo-range noise. Meanwhile, the CCL retains high precision in the carrier-phase. In this study, we focus on the Beirut Explosion on August 4, 2020, to check slant TEC (STEC) variations that may be associated with the blast of Beirut Port. The TECs were analyzed through the Morlet wavelet to check the possible ionospheric response to the blast. An acoustic‐gravity wave could be generated by the event which could disturb the ionosphere through coupling between solid earth-atmosphere-ionosphere during the explosion. To verify TEC disturbances are not associated with space weather, disturbance storm-time (Dst), and Kp indices were investigated before, during, and after the explosion. The steady-state of space weather before and during the event indicated that the observed variations of TEC sequences were caused by the ammonium nitrate explosion. There was a large initial explosion, followed by a series of smaller blasts, about ~30 seconds, a colossal explosion has happened, a supersonic blast wave radiating through Beirut City. As a result of the chemistry behind ammonium nitrate’s explosive, a mushroom cloud was sent into the air. We suggest that these different explosions in strength and time could be the reason for different time arrival of the detected ionospheric disturbances over GNSS ground-based stations.

How to cite: Freeshah, M., Zhang, X., Şentürk, E., Ren, X., Adil, M. A., and Xu, G.: Could the Beirut Explosion perturb the Ionosphere? Pre-results Using TEC-GNSS observations., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8990, https://doi.org/10.5194/egusphere-egu21-8990, 2021.

The objective of the Cold Atom Space Payload Atmospheric Drag Mission (CASPA-ADM) study, which is supported by ESA, is to develop a mission concept for observing thermospheric mass density with an accelerometer based on Cold Atom Interferometry (CAI) as a technology demonstrator. CAI technology has undergone rapid development in the recent years and experimental systems have been flown on the International Space Station and in sounding rockets for CAI research purposes.  Despite this, CAI has not yet been used as the fundamental sensor technology in a science mission, so CASPA-ADM would be a significant advancement.  CAI relies on cooling a vapour of atoms in a vacuum chamber close to absolute zero temperature using lasers and using the properties of the atoms to form a matter-wave interferometer that is extremely sensitive to accelerations. A key advantage over classical accelerometers is that the CAI measurements are not affected by any biases or scale factors. Transforming acceleration measurements to thermospheric density observations requires also measurements of the atmospheric composition, temperature, and wind. For that purpose, a neutral mass spectrometer and a wind sensor will be part of the scientific payload. For validation, the payload will include a multi-frequency GNSS receiver that allows to infer non-gravitational acceleration observations, albeit at much lower resolution along the orbit. All of these instruments will be built into a 16U CubeSat, which will be launched into an inclined orbit at an altitude of initially 400 km to achieve a fast sampling of local times and address the present observational gaps in thermosphere density observations. In this presentation, we will provide an overview of the mission objectives, explain the mission concept, and report the results from the ESA study.

How to cite: Siemes, C., Maddox, S., Carraz, O., Cross, T., George, S., van den IJssel, J., Kiss-Toth, M., Pastena, M., Riou, I., Salter, M., Sweeney, H., Trigatzis, M., Valenzuela, T., and Visser, P.: CASPA-ADM – a mission concept for observing thermospheric mass density, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6009, https://doi.org/10.5194/egusphere-egu21-6009, 2021.

Within the project SWEETS (funded by the FFG Austria) it is intended to develop a forecasting model, to predict the expected impact of solar events, like coronal mass ejections (CMEs), on satellites at different altitudes between 300-800 km. For the realization, scientific data, such as kinematic orbit information and accelerometer measurements, from a wide variety of satellites are incorporated. Based on the evaluation of the impact of several hundred solar events on the thermosphere the forecasting will be realized through a joint analysis and evaluation of solar wind plasma and magnetic field data observed at the Lagrange point L1.
In this contribution we show first preliminary results of thermospheric densities estimates based on kinematic orbit information for different satellite missions (e.g., TerraSAR-X, TanDEM-X, Swarm A-C, GRACE, GRACE-FO, CHAMP). To validate the outcome, we compare the results with state-of-the-art thermospheric models as well as with densities estimated from accelerometer measurements if available. Finally, for some specific CME events we will perform a comparison between the post-processed density estimates and results from our preliminary forecasting tool.

How to cite: Krauss, S., Suesser-Rechberger, B., Behzadpour, S., Mayer-Guerr, T., Temmer, M., Kroisz, S., and Drescher, L.: Current status of project SWEETS: Estimating thermospheric neutral mass densities from satellite data at various altitudes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4174, https://doi.org/10.5194/egusphere-egu21-4174, 2021.

We present a comprehensive comparison of the impact of solar activity on forecasting the ionosphere and thermosphere. Here we investigate the response of physics-based TIE-GCM (thermosphere-ionosphere-electrodynamics general circulation model) in a data assimilation scheme through assimilating radio occultation (RO)-derived electron density (Ne) using an ensemble Kalman filter (KF). Constellation observations of Ne profiles offer opportunities to assess the accuracy of the model forecasted state on a global scale. In this study, we emphasise the importance of understanding how the assimilation results vary with solar activity, which is one of the primary drivers of thermosphere-ionosphere dynamics.

We validate the assimilation results with independent RO-derived GRACE (Gravity Recovery and Climate Experiment mission) Ne data. The main result is that the forecast Ne agree best with data during the solar minimum compared to solar maximum. The results also show that the assimilation scheme significantly adjusts both the nowcast and forecast states during the two solar activity periods. The results show that TIE-GCM significantly underestimate Ne in low altitudes below 250 km and the assimilation of Ne is not as effective in these lower altitudes compared to higher altitudes. The results demonstrate that assimilation of Ne significantly impacts the neutral mass density estimates via the KF state vector. This impact is larger during solar maximum than solar minimum relative to a control run. The results also demonstrate that the impact of assimilation of Ne on neutral mass density state persists through to forecast state better during solar minimum compared to solar maximum. The results are useful to explain the inherent model bias, to understand the limitations of the data, and to demonstrate the capability of the assimilation technique.

How to cite: Kodikara, T., Zhang, K., Pedatella, N. M., and Borries, C.: The Impact of Solar Activity on Forecasting the Upper Atmosphere via Assimilation of Electron Density Data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10756, https://doi.org/10.5194/egusphere-egu21-10756, 2021.

The response of the Ionosphere - Thermosphere (IT) system to severe storm conditions is of great importance to fully understand its coupling mechanisms. The challenge to represent the governing processes of the upper atmosphere depends, to a large extent, on an accurate representation of the true state of the IT system, that we obtain by assimilating relevant measurements into physics-based models. Thermospheric Mass Density (TMD) is the summation of total neutral mass within the atmosphere that is derived from accelerometer measurements of satellite missions such as CHAMP, GOCE, GRACE(-FO) and Swarm. TMD estimates can be assimilated into physics-based models to modify the state of the processes within the IT system. Previous studies have shown that this modification can potentially improve the simulations and predictions of the ionospheric electron density. These differences could also be interpreted as an indicator of the ionosphere-thermosphere interaction. The research presented here, aims to quantify the impact of data satellite based TMD assimilation on numerical model results.

Subject of this study is the Coupled Thermosphere-Ionosphere-Plasmasphere electrodynamics (CTIPe) physics-based model in combination with the recently developed Thermosphere-Ionosphere Data Assimilation (TIDA) scheme. TMD estimates from the ESA’s Swarm mission are assimilated in CTIPe-TIDA during the 16 to the 20 of March 2015. This period was characterized by a strong geomagnetic storm that triggered significant changes in the IT system, the so-called St. Patrick day storm 2015. To assess the changes in the IT system during storm conditions due to data assimilation, the model results from assimilating SWARM mass density normalized to the altitude of 400 km are compared to independent thermospheric estimates like GRACE-TMDS. In order to evaluate the impact of the data assimilation on the ionosphere, the corresponding output of electron density is compared to high-quality electron density estimates derived from data-driven model of the DGFI-TUM.

How to cite: Fernandez-Gomez, I., Goss, A., Schmidt, M., Kosary, M., Kodikara, T., Forootan, E., and Borries, C.: The impact of severe storms on forecasting the Ionosphere-Thermosphere system through the assimilation of SWARM-derived neutral mass density into physics-based models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10552, https://doi.org/10.5194/egusphere-egu21-10552, 2021.

The JWG3 aims at investigating different approaches to monitor space weather events using the data from different space geodetic techniques and, in particular, combinations thereof. Simulations will also be considered since these could be beneficial to identify the contribution of different techniques and prepare for the analysis of real data. Different strategies for the combination of data are also to be investigated, in particular the weighting of estimates from different techniques in order to increase the performance and reliability of the combined estimates.

Furthermore, existing algorithms for the detection and prediction of space weather events shall be explored and improved to the extent possible. Additionally, the geodetic measurement of the ionospheric electron density will be complemented by direct observations from the Sun gathered from existing spacecraft, such as SOHO, ACE, SDO, Parker Solar Probe, among others. The combination and joint evaluation of multiple datasets from different space geodetic observation techniques (e.g., geodetic VLBI) is still a great challenge. In addition, other indications for solar activity - such as the F10.7 index on solar radio flux, SOLERA as EUV proxy or rate of Global Electron Content (dGEC), provide additional opportunities for comparisons and validation.

As per JWG3 objectives, these include the identification of the key parameters useful to improve real time/prediction of ionospheric/plasmaspheric VTEC, Ne estimates, as well as ionospheric perturbations, in case of extreme solar weather conditions. In general, we are on the way to gain a better understanding of space weather events and their effect on Earth’s atmosphere and near-Earth environment.

How to cite: Garcia-Rigo, A. and Soja, B. and the "GGOS's JWG3 - Improved understanding of space weather events and their monitoring" team: Status of GGOS JWG3 on Improved understanding of space weather events and their monitoring, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14292, https://doi.org/10.5194/egusphere-egu21-14292, 2021.