# Workshop - Mutual benefits between atmospheric research and radio based science over polar regions

UTC
Meridian Room (Royal Observatory of Belgium)

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
Description

Mutual benefits between atmospheric research and radio based science over polar regions

The neutral and ionised atmosphere can significantly affect radio waves propagation and this can lead to misinterpretations of data and models.  Earth science studies using e.g. INSAR, LOFAR and GNSS data should therefore definitely take up-to-date atmospheric parameters into account. This is the case for studies on surface deformation, cryosphere dynamics etc. in the polar regions.

To pose a solid bridge between the atmospheric and impacted scientific communities, this workshop solicits contributions to facilitate exchange of information on their respective states of the art as well as on their future needs in Polar Regions (Antarctica and Arctic).

Contributions are welcome on both aspects:

•       The workshop foresees the participation of scientists studying the neutral and/or the ionized part of the atmosphere, from the lower to further upper regions such as the magnetosphere. Presentations dealing with climatology studies on their characteristics and abnormal behaviours during extreme events are welcome.
•       Contributions from researchers of Arctic and Antarctic operations that need to remove or mitigate the atmospheric contribution from their measurements (such as geophysicists, geologists, geodesists, radio astronomers and remote sensing researchers) are also encouraged.

This workshop is organised with the support of the Solar-Terrestrial Centre of Excellence and the Scientific Commitee on Antarctic Research.

• 10:00 10:35
Welcome coffee and drinks Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
• 10:35 11:15
Introduction Session: STCE-SCAR and Project Initiative Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
Convener: Mr Jean-Marie Chevalier (Royal Observatory of Belgium)
• 10:35
The Solar-Terrestrial Center of Excellence 10m
This is an overview of the The Solar-Terrestrial Center of Excellence (STCE) activities. The Solar-Terrestrial Centre of Excellence is a scientific project which aims at the creation of an international expert centre and the valorization of Solar-Terrestrial research and services. The STCE clusters the know-how of 3 Belgian Federal institutes: Royal Observatory of Belgium ROB, Royal Meteorological Institute RMI, Belgian Institute for Space Aeronomy BIRA-IASB. The goal is to: - Integrate the existing Belgian research groups in one overarching structure - Stabilize and consolidate the existing knowhow scattered over different existing institutes - Support visiting fellows & communication The solid base of the STCE is our experience in fundamental solar and earth atmospheric physics research, our involvement in earth-based and space missions and a fully operational eligible space weather application centre. Our scientists act at different levels within the frame of internal, national and international collaborations of scientific and commercial oriented partners.
Speaker: Dr Ronald Van der Linden (Royal Observatory of Belgium)
• 10:45
THE SCAR EXPERT GROUP "GRAPE": STATE OF THE ART AND FUTURE PERSPECTIVE 15m
Presentation to be given during the one day workshop organized at ROB, reporting on the state of the art of the GRAPE Expert Group.
Speaker: Dr Giorgiana De Franceschi (INGV)
• 11:00
RESOURCE: An international initiative for atmospheric research at the poles 15m
Speaker: Dr Lucilla Alfonsi (Istituto Nazionale di Geofisica e Vulcanologia)
• 11:15 12:00
Ionised atmosphere data and models I Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
Convener: Dr Lucilla Alfonsi (Istituto Nazionale di Geofisica e Vulcanologia)
• 11:15
Some GNSS ionospheric monitoring techniques implemented in real-time and rapid latencies at global and polar scales 15m
We present the Global Navigation Satellite Systems (GNSS) ionospheric monitoring techniques developed by the authors and implemented in terms of associated products, which are being computed globally, in real-time and rapid latencies. We will focus on the potential contributions to the improvement of GNSS performance and Ionospheric Science in polar regions, in terms of Space Weather monitoring, Scintillation activity and Vertical Total Electron Content (VTEC) distribution. Indeed UPC-IonSAT has developed a set of different ionospheric products on daily, fifteen-minutes and 30-seconds basis, at different associated latencies of 1 day, 15 minutes and 30 seconds. since 1998 in the context of the International GNSS Service (IGS), and since 2011 in the context of MONITOR ESA funded project, a set of different ionospheric products on daily, fifteen-minutes and 30-seconds basis, at different associated latencies of 1 day, 15 minutes and 30 seconds. Our discussion is focused on: 1) Global ionospheric tomography and associated VTEC Global Ionospheric Maps (latencies of 1-day and 15 minutes). 2) Rate of TEC Index, typically over +200 worldwide GNSS receivers in real-time (latencies of 30 seconds and 15 minutes). 3) Sidereal-day VTEC variation, also in real-time for +200 worldwide GNSS receivers. 4) Solar EUV flux rate (SOLERA), SOLERA rate (formerly known as GSFLAI) and the specific solar flare indicator SISTED. 5) Single Receiver Medium Scale Travelling Ionospheric Disturbances (SRMTID) index.
Speaker: Prof. Manuel Hernández-Pajares (UPC-IonSAT)
• 11:30
Climatological behaviour of the Ionospheric-Plasmaspheric Total Electron Content over Antarctica 15m
The understanding of the impact of solar activity on polar regions upper atmosphere is not as strong as compare to low and mid-latitudes due to lack of experimental observations, especially over Antarctica. To characterize the differences in the ionosphere-plasmasphere total electron content (TEC) climatological patterns over Antarctica, we reprocessed the GNSS (GPS + GLONASS) data available since 1999 up to now for stations situated at latitudes below S50°. For that, we used the data from POLENET/IGS networks and stations installed around the Princess Elisabeth polar Base (Utsteinen, North-East Antarctica). The estimated TEC data set is then employed to constrain an empirical model to predict the TEC from F10.7P solar index in entrance using a least-square adjustment. To minimize the differences between the modelled and observed vTEC we considered: (1) an eight-order polynomial function with monthly coefficients between the TEC and F10.7P; (2) a discretization with respect to different zones over Antarctica region to highlight different climatological patterns; (3) different time definitions such as Solar Local Time, Magnetic Local Time, and UTC. From the output of this model we discuss the different climatological behaviors identified in the ionosphere- plasmasphere TEC at these high latitudes. Finally, we show some examples of typical TEC disturbances observed during extreme solar events.
• 11:45
Ionospheric scintillation climatology at Ny-Ålesund across solar cycle 23 and 24 15m
INGV operates a network of GNSS receivers acquiring data at 50 Hz incorporating a firmware especially modified to provide several parameters useful to monitor the perturbations of the high latitudes upper atmosphere. In particular, the first GPS receiver was installed in 2003 at Ny-Ålesund (Svalbard Island, 78°55’N 11°55’E). Currently, three receivers are operating at Ny-Ålesund, recording GPS, GLONASS, Galileo signals. The analysis exploits the scintillation parameters (S4 and sigmaphi), TEC and its rate of change (ROT) measured by INGV receivers to study the behaviour of the high latitudes ionosphere during the different phase of a solar cycle. The analysis is supported by the climatological reconstruction of the probability of the scintillation occurrence sorted also according different conditions of the geospace and of the geomagnetic field. This would enable to infer the relationship between the physical processes ruling the morphology of the high latitudes ionosphere and the amplitude and phase scintillations on GNSS signals. The knowledge of such relationship is necessary in view of a long term forecasting of the disruptive effects of the ionosphere on the L-band signals affecting the applications based on GNSS such as precise positioning and navigation.
Speaker: Dr Luca Spogli (Istituto Nazionale di Geofisica e Vulcanologia)
• 12:00 12:20
Coffee break 20m Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
• 12:20 13:05
Ionised atmosphere data and models II Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
Convener: Dr Lucilla Alfonsi (Istituto Nazionale di Geofisica e Vulcanologia)
• 12:35
The effect of the ionosphere on astronomical observations below 100 MHz 15m
The Low-Frequency Array (LOFAR) is a hierarchical collection of thousands of dipole antennas which make it the most sensitive radio interferometer operating at low-frequencies ($10-240$ MHz). His main goal is low-frequency radio astronomy. LOFAR antennas are grouped into stations (aperture arrays capable of multi-beam forming) each about the size of a football field. LOFAR has 38 stations in the Netherlands and 13 international stations spread across seven European countries. LOFAR uses two antenna types: the High Band Antenna (HBA, sensitive between $110-240$ MHz) and the Low Band Antenna (LBA, sensitive between $10-90$ MHz). Here I will show how we used the LOFAR LBA system to obtain information on the ionosphere differential total electron content (TEC) with milliTEC precision, in hundreds of directions, on timescales of few seconds, and spatial scales of arc-minutes. I will also show the effect of phase and amplitude scintillations on our data and how we can reconstruct them. Finally, I will explore the higher order ionospheric effects that LOFAR can measure with high precision such as Faraday rotation.
Speaker: Dr Francesco de Gasperin (Leiden University)
• 12:50
Plasmaspheric study with VLF antennas installed in Antarctica and in Belgium and with an empirical plasmaspheric model 15m
In January-February 2016, we have installed a compact magnetic antenna augmented with data processing equipment at the Belgian Princess Elisabeth station (71°57’S - 23°20’E; 1380 m altitude; L$\sim$5.5R$_{E}$). This VLF antenna is composed of two search coils in a waterproof plastic box, inside a wooden thermal insulated box, fixed on the top of a wooden table. This antenna records VLF (Very Low Frequency, 3-30 kHz) whistler waves, from which we can infer information about the state of the plasmasphere, an inner region of the Earth’s magnetosphere. The Princess Elisabeth station is a very interesting place for such an instrument because of the low electromagnetic activity at and around the station, which usually perturb the measurements. Also, this location at very high magnetic latitude provides information on variations in the plasmaspheric boundary position. Such an antenna complements another antenna that we have installed seven years ago in Humain, Belgium (50°12’N - 5°15’E; 240 m altitude; L$\sim$2.3R$_{E}$). This VLF antenna is made of two perpendicular magnetic loops, oriented North-South and East-West, and with an area of approximately 50 m$^{2}$ each. Those two antennas are part of the international global network AWDA (Automatic Whistler Detector and Analyzer). The ultimate goal of this network is to provide data to feed a data-assimilative model of the plasmasphere. Data from both stations can be compared with an empirical plasmaspheric model, developed here at BIRA-IASB. This 3D dynamical model is based on the interchange instability mechanism using the convection electric field model E5D. It is a function of the level of geomagnetic activity level index Kp observed during the date given as input and 24 hours before. This model provides the plasmapause location in terms of radial distance and magnetic local time, as well as the electron density and temperature of the plasmasphere.
Speaker: Dr Fabien Darrouzet (Royal Belgian Institute for Space Aeronomy (IASB-BIRA))
• 13:05 14:00
Lunch break (Sandwiches and refreshments offered to the participants) 55m RMI Canteen ()

### RMI Canteen

• 14:00 14:45
Neutral atmosphere data and models Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
Convener: Dr Claudio Cesaroni (INGV)
• 14:00
Atmospheric Water Vapour Observations at ROB and RMI for Weather and Climate Monitoring 15m
Both institutes, the Royal Observatory of Belgium (ROB) and the Royal Meteorological Institute (RMI) of Belgium, are monitoring and studying the atmospheric water vapour using several ground-based (GNSS), satellite-based (GOME,SCHIAMACHY, GOME-2, AIRS), and in-situ (radiosonde) measuring techniques but also atmospheric models (ERA-interim, ALARO). These activities mainly aim at improving weather forecasts, and understanding the climate system by monitoring its recent history. Concerning the weather forecasts, ROB participates for more than a decade in the EUMETNET E-GVAP program by maintaining a GNSS analysis centre for continuous remote sensing of the troposphere. Thanks to this analysis centre, ROB monitors the tropospheric water vapour based on GNSS observations, and provides operationally (e.g. every hour, 24x7x365) the meteorologists with tailored products for weather forecasting (data assimilation in their Numerical Weather Prediction (NWP) models and nowcasting applications). If the use of GNSS-based products for improving weather forecasts is today a well-established technique and operationally used, its use in climate science remains a quite pioneering field of research. Recently (2013-2017), a European COST Action ES1206 “GNSS4SWEC” (Advanced Global Navigation Satellite Systems tropospheric products for monitoring severe weather events and climate, http://www.cost.eu/COST_Actions/essem/ES1206) was partly dedicated to the use of GNSS in the climate observing system. Within GNSS4SWEC, ROB and RMI joined their efforts in order to exploit GNSS-based tropospheric products for monitoring and studying the recent climate. To achieve this, the 20+ year long water vapour time series obtained from GNSS remote sensing observations needs to be homogenised. RMI and ROB co-leaded such an activity in the context of GNSS4SWEC, an activity that is continued within the IAG JWG 4.3.8: "GNSS Tropospheric Products for Climate" (http://iag-gnssclimate.oma.be/). Another potential usage of GNSS for climate is the model validation. Both institutes also participates in the nationally funded project CORDEX.be (COordinated Regional Climate Downscaling EXperiment and beyond, http://cordex.meteo.be/), regrouping the 9 major Belgian actors in climate modelling and impact studies, and used the GNSS-based products for high-resolution climate model run assessment over Belgium. In this presentation, we will review the major ongoing activities at ROB and RMI in the field of meteorology and climate, identify synergies, and try to bridge them with ongoing and potential activities in Antarctica/polar regions.
Speaker: Dr Eric Pottiaux (Royal Observatory of Belgium (ROB))
• 14:15
Ground-based remote sensing of the neutral Polar atmosphere by microwave spectrometers 15m
Ground-based microwave remote sensing is extremely useful for monitoring the atmospheric composition and physical properties. It is effective during both daytime and nighttime, in clear sky or mild overcast weather, and is therefore particularly suited for observing the Polar regions where darkness (or direct sunlight) lasts throughout an entire winter (summer) season. Most techniques in this frequency range observe the spectral lines emitted by the chemical species present in the atmosphere and estimate their vertical distribution by studying the shape of the emitted lines, dominated by pressure broadening. Critical parameters of the specific microwave instrument employed are therefore the overall spectral passband and its frequency resolution (or number of independent channels). At INGV we recently developed a water vapor spectrometer, VESPA-22, capable of observing the 22 GHz water vapor emission line with a 500 MHz passband and a frequency resolution of 31 kHz. The collected spectra are inverted using an optimal estimation algorithm in order to retrieve water vapor vertical profiles from about 25 to 75 km with an overall uncertainty between 5 and 12%. Every 30 minutes the spectrometer also performs tipping curve measurements by observing the sky emission at various zenith angles. This procedure allows both the calibration of the spectrometer and the measurement of the sky opacity, which then provides an estimate of the water vapor total column with an uncertainty of 5%. In July 2016, VESPA was installed at the Thule High Arctic Atmospheric Observatory located at Thule Air Base (76.5° N, 68.8° W), Greenland (http://www.thuleatmos-it.it/). VESPA-22 has been operating in an autonomous mode since its installation, with very few short periods of data gaps.
Speaker: Dr Giovanni Muscari (INGV)
• 14:30
Precipitable Water retrieval over Antarctica from Satellite Microwave Humidity sounders 15m
Atmospheric water vapor is an important constituent of the global hydrological cycle; it transports humidity and heat and it is the most important greenhouse gas. While over open ocean total precipitable water vapor (PW) is routinely surveyed with satellite microwave imagers like SSMI(S) and AMSR-E/2, large-scale observations in polar regions with low water vapor burden are much more difficult because of the low water vapor signal and, over sea ice and land ice, the high and highly varying surface emissivity. However, a procedure has been suggested exploiting the data of the satellite humidity sounders SSM/T2, AMSU-B and MHS aboard the DMSP, Aqua and Metop satellites or satellite series, respectively. The basic idea is to use three channels of neighbouring frequencies. The surface contribution in the observed brightness temperatures is excluded by considering the ratio of brightness temperature differences. The resulting quotient is closely related to the atmospheric opacity from which in turn the PW can be inferred. The original version [1] used the three dual-band channels centred around the water vapor absorption line near 183 GHz (183 ± 3, ± 5, and ± 7 GHz) plus the 150 GHz channels in two different 3-channel combinations for the ranges 0 to 1.5 kg/m2 and 1 to 7 kg/m2, resp.. Later, the procedure has been adapted to the microwave humidity sounders AMSU-B and MHS with channels at 183 ± 1, ± 3, and ± 7 GHz [2]. Moreover, the method has been extended to also use the 89 GHz channel by introducing knowledge about the emissivity of Arctic sea ice. This allows for a retrieval up to 14 kg/m2. Results for Antarctica based on the original algorithm will be presented, including two years (2006-2007) of new data. In coastal Antarctic areas, Global Positioning System (GPS) and radiosounding (RS) stations are available and their long time series of observations can be used to retrieve PW. To ensure the utmost accuracy of the results homogeneous, consistent and up-to-date processing strategies for these data-sets were adopted and the content and variations of the PW were obtained at five Antarctic sites (Negusini et al 2016). The resulting time series will be compared to satellite based retrievals at the places of the stations. After correcting the satellite based retrievals based on the comparisons with the GPS and radiosonde based PW observations at the places of the stations, the satellite data will be used to extend the PW retrieval over whole Antarctica. References 1. Miao, J., K. Kunzi, G. Heygster, T. A. Lachlan-Cope, J. Turner, 2001: Atmospheric water vapor over Antarctica derived from SSM/T2 data. J. Geophys. Res., 106, D10 (May 27), 10187--10203. 2. C. Melsheimer, G. Heygster 2008: Improved retrieval of total water vapor over polar regions from AMSU-B microwave radiometer data. IEEE Trans. Geosci. Remote Sens. 46(8), p.2307-2322, doi:10.1109/TGRS.2008.918013. 3. Negusini M, Petkov BH, Sarti P, and Tomasi C. 2016. Ground based water vapor retrieval in Antarctica: an assessment. IEEE Trans. Geosci. Remote Sens. (TGRS) 54 (5), p. 2935-2948, doi:10.1109/TGRS.2015.2509059.
Speaker: Dr Georg Heygster (University of Bremen, Germany)
• 14:45 15:30
Radio wave-based applications I Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
Convener: Dr Nicolas Bergeot (Royal Observatory of Belgium)
• 14:45
Learning ionosphere inversion priors via Gaussian processes 15m
The spatially and temporally varying electron density of the ionosphere causes complex distortions to passing radio wavefronts, becoming dominant at frequencies $\leq 1$ GHz. Using a probabilistic description of the system we apply Bayesian inference to study and derive the phase distortions of radio astronomical data in multiple directions. The relative improvement to image quality is studied using this solution. The inferred correlation structures will, in a subsequent study, provide priors for a general tomographic inverse problem, in which we model the components responsible for the phase distortions from first principles. The Bayesian inferred phase screens are completely dependent on the calibration process of the measured phase distortions, and no systematic biases can hope to be overcome. The phase screens inferred from the general inverse problem, being from first principles, are more free from bias. In this talk we will give a brief overview of Bayesian inference, and then focus on the data and results.
Speaker: Mr Joshua Albert (Leiden Observatory)
• 15:00
On the relevance of radio observations of meteors from polar regions. 15m
I will review the importance of carrying out radio or radar observations of meteors from South polar regions. From an astronomical point of view, totally different radiants can be observed than with radars at intermediate latitudes. From a space weather perspective, this provides complementary observations to build a more complete dust risk impact model. For atmospheric applications, measurements of the Doppler of meteor trails allow to estimate wind speeds in the Mesosphere-Lower Thermosphere, a region that cannot be accessed either via balloons or spacecraft. I will briefly discuss the possibilities and challenges of running a radar or a forward scatter system similar to BRAMS at or near the PES.
Speaker: Dr Hervé Lamy (Royal Belgian Institute for Space Aeronomy)
• 15:15
RF diagnostics of troposphere-ionosphere coupling at the Ukrainian Antarctic station Akademik Vernadsky 15m
Speaker: Dr Andriy Zalizovski (Institute of Radio Astronomy, National Academy of Sciences of Ukraine)
• 15:30 15:50
Coffee break 20m Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
• 15:50 16:35
Radio wave-based applications II Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
• 15:50
Antarctic cosmic rays observatory and the Space Weather program of the LAGO collaboration 15m
The LAGO (LAGO: Latin American Giant Observatory) project is a collaborative network formed by eleven countries (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guatemala, Mexico, Peru, Spain, and Venezuela). The network of WCDs has nodes at sites with different rigidity cut-offs and different altitudes. One of the aims of LAGO is to study the flux of the secondary particles at ground level, and to link them with the associated primary fluxes to better understand the modulation of CRs in the helisphere. Another main aim is to monitor this flux to provide operative Space Weather information. We present an update of the state of the art of the LAGO Antarctic node, to be deployed in the Argentine Marambio base, in the Antarctic peninsula. In particular we present studies of the atmosphere in Marambio and the effects of the geomagnetic field on the arrival of cosmic rays to this antarctic site. This node will have the minimum rigidity cut-off (Rc ~ 2 GV) of the collaboration, and will be the only LAGO node that will be able to observe GLEs. We present the LAGO antarctic campaign of 2017-2018 in Marambio, where a meteorological station will be installed, a thermal control system will be tested, and several tests of telemetry from Antarctic to Buenos Aires will be done.
Speaker: Dr Sergio Dasso (Instituto de Astronomía y Física del Espacio (IAFE), Argentina)
• 16:05
Heating of the Atmosphere by Auroral Processes 15m
Speakers: Dr Daniel Whiter (University of Southampton), Dr Joshua Chadney (University of Southampton)
• 16:20
Atmospheric and ionospheric artifacts in SAR interferometry 15m
Basis concepts of SAR interferometry (InSAR) will be presented, stressing problems related to atmosphere and/or ionosphere-induced artefacts. InSAR applications related to the cryosphere study will be presented.
Speaker: Dr Dominique De Rauw (Centre Spatial de Liège)
• 16:35 17:00
Open Discussion Meridian Room

### Meridian Room

#### Royal Observatory of Belgium

Ringlaan 3, 1180 Brussels, Belgium
Convener: Dr Giorgiana De Franceschi (INGV)