Over the past two decades, satellite-based GNSS radio occultation (RO) technology has become a standard method for global atmospheric remote sensing. GNSS RO data are used worldwide, primarily in weather forecasting and climate research. With GNSS RO precise and globally distributed vertical profiles of atmospheric parameters such as temperature, water vapor or the electron density in the ionosphere can be derived. Special advantages of the method are weather independence, long-term stability, global availability and high accuracy combined with a high vertical resolution.
GFZ scientists have played a key role in developing GNSS RO technology and made groundbreaking contributions. The German CHAMP satellite mission, which was coordinated by GFZ, is particularly outstanding. CHAMP data (2001-2008) were made available continuously and operationally for the first time worldwide and were first used in 2006 to improve global weather forecast models. From 2006-2017, GFZ provided RO data from the GRACE mission. The RO data from GRACE-FO (since 2020), TerraSAR-X (since 2008) and Tandem-X (since 2011) are currently being operationally processed at GFZ and made available to the world's leading weather service centers. Thus, GFZ is continuously contributing to the global RO data set. An overview of other RO missions and data can be found at UCAR.
In addition, the RO analysis results are also used at GFZ as a basis for scientific investigations, including observation of temperature changes in the upper troposphere and lower stratosphere and tropopause dynamics (climate monitoring), the analysis of atmospheric gravity waves or the occurrence of ionospheric disturbances (sporadic E layers, equatorial "plasma bubbles").
The latest IPCC report uses RO data for the first time to characterize climate change in the upper troposphere and lower stratosphere. The integration of sporadic E layers into the International Reference Ionosphere is in preparation.
Scientists from the GNSS radio occultation working group are currently working on a DFG research project on the observation and modelling of space weather and in other national and international programs and committees (APARC ATC, IROWG, IAGA), and as Associate Editor for “Advances in Space Research”.
The working group is also responsible for the operation of the water vapor radiometer at GFZ and the evaluation of the data.
The work of the GNSS radio occultation working group at GFZ is carried out within the framework of Topic 1 “The Atmosphere in Global Change” of the Helmholtz research program “Changing Earth - Sustaining our Future” (POF4).
Current research and projects
- Monitoring and Modeling of Space Weather Phenomena Using Novel Satellite Observations (in cooperation with National Central University, Taiwan)
- International Radio Occultation Working Group, Climate
- Atmospheric Temperature Changes and their Drivers
Completed Projects
- 2015-2022, DFG priority project „DynamicEarth“: Global observation of ionospheric sporadic E-layers and their relation to atmospheric and ionospheric phenomena, more information here
- 2015-2020, StRATEGy (DFG): "Characterization of atmospheric processes related to hydro-meteorological extreme events over the south-central Andes" as part of the „International Research Training Group“ at University of Potsdam
- 2014-2019, AGWOM (BMBF): „Atmospheric Gravity Waves: Observation and Modeling“ in cooperation with the University of Leipzig and Austral University Buenos Aires
- MuSE (Multi-satellite ionosphere-plasmasphere electron density reconstruction)
Literature
Alexander, P., de la Torre, A., and Schmidt, T. (2024): Global stratospheric properties of gravity waves from 1 year of radio occultations. Journal of Geophysical Research: Atmospheres, 129, e2023JD040609. doi.org/10.1029/2023JD040609.
Alexander P., Schmidt T., and de la Torre, A. (2018): A method to determine gravity wave net momentum flux, propagation direction, and “real” wavelengths: A GPS radio occultations soundings case study. Earth and Space Science, 5, 222–230, doi.org/10.1002/2017EA000342.
Anthes, R.A. (2011): Exploring Earth's atmosphere with radio occultation: contributions to weather, climate and space weather. Atmos. Meas. Tech., 4, 1077-1103, doi:10.5194/amt-4-1077-2011.
Arras, C., Resende Chagas, L. C., Senevirathna, G., Kepkar, A., Wickert, J. (2022): Sporadic E layer characteristics at equatorial latitudes as observed by GNSS Radio Occultation measurements. - Earth Planets and Space, 74, 163. https://doi.org/10.1186/s40623-022-01718-y
Arras, C., and Wickert, J. (2017): Estimation of ionospheric sporadic E intensities from GPS radio occultation measurements, Journal of Atmospheric and Solar-Terrestrial Physics, doi: 10.1016/j.jastp.2017.08.006.
Hierro, R., Burgos Fonseca, Y., Ramezani Ziarani, M., Llamedo, P., Schmidt, T., de la Torre, A., Alexander, P. (2020): On the behavior of rainfall maxima at the eastern Andes, Atmospheric Research, 234, 104792, https://doi.org/10.1016/j.atmosres.2019.104792.
Jacobi, C., Kandieva, K., Arras, C. (2023): Migrating and nonmigrating tidal signatures in sporadic E layer occurrence rates. - Advances in Radio Science, 20, 85-92, https://doi.org/10.5194/ars-20-85-2023
Jacobi, C., Arras, C. (2019): Tidal wind shear observed by meteor radar and comparison with sporadic E occurrence rates based on GPS radio occultation observations. - Advances in Radio Science, 17, 213-224, https://doi.org/10.5194/ars-17-213-2019
Jacobi, C., Arras, C., Geißler, C., Lilienthal, F. (2019): Quarterdiurnal signature in sporadic E occurrence rates and comparison with neutral wind shear. - Annales Geophysicae, 37, 273-288, https://doi.org/10.5194/angeo-37-273-2019
Kepkar, A., Arras, C., Wickert, J., Schuh, H., Alizadeh, M., Tsai, L.-C. (2020): Occurrence climatology of equatorial plasma bubbles derived using FormoSat-3 ∕ COSMIC GPS radio occultation data. - Annales Geophysicae, 38, 611-623, https://doi.org/10.5194/angeo-38-611-2020
Lilienthal, F., Jacobi, C., Schmidt, T., de la Torre, A., and Alexander, P. (2017): On the influence of zonal gravity wave distributions on the Southern Hemisphere winter circulation, Ann. Geophys., 35, 785–798, https://doi.org/10.5194/angeo-35-785-2017.
Ramezani Ziarani, M., Bookhagen, B., Schmidt, T., Wickert, J., de la Torre, A., Deng, Z., Calori, A. (2021): A Model for the Relationship between Rainfall, GNSS-Derived Integrated Water Vapour, and CAPE in the Eastern Central Andes, Remote Sens. 2021, 13(18), 3788; https://doi.org/10.3390/rs13183788.
Ramezani Ziarani, M., Bookhagen, B., Schmidt, T., Wickert, J., de la Torre, A., Hierro, R. (2019): Using Convective Available Potential Energy (CAPE) and Dew-Point Temperature to Characterize Rainfall-Extreme Events in the South-Central Andes, Atmosphere 2019, 10(7), 379, https://doi.org/10.3390/atmos10070379.
Resende, L. C. A., Zhu, Y., Denardini, C. M., Moro, J., Da Silva, L. A., Arras, C., Chagas, R. A. J., Chen, S. S., Marchezi, J. P., Carmo, C. S., Picanço, G. A. S., Silva, R. P., Wang, C., Li, H., Liu, Z. (2022): Worldwide study of the Sporadic E (Es) layer development during a space weather event. - Journal of Atmospheric and Solar-Terrestrial Physics, 241, 105966, https://doi.org/10.1016/j.jastp.2022.105966
Resende Chagas, L. C., Shi, J. K., Denardini, C. M., Batista, I. S., Nogueira, P. A. B., Arras, C., Andrioli, V. F., Moro, J., Da Silva, L. A., Carrasco, A. J., Barbosa, P. F., Wang, C., Liu, Z. (2020): The Influence of Disturbance Dynamo Electric Field in the Formation of Strong SporadicELayers Over Boa Vista, a Low‐Latitude Station in the American Sector. - Journal of Geophysical Research: Space Physics, 125, 7, e2019JA027519, https://doi.org/10.1029/2019JA027519
Schmidt, T., Schreiner, P., and Wickert, J. (2024): GNSS radio occultation data for weather forecast and climate research, DKT-13-45, https://doi.org/10.5194/dkt-13-45.
Schmidt, T., Schreiner, P., and Wickert, J., Iijima, B.A., Ao, C.O., Tien, J.Y., and Meehan, T.K. (2022): GRACE-FO Radio Occultation Data Processing, GSTM2022-101, https://doi.org/10.5194/gstm2022-101.
Schmidt, T., P. Alexander, A. de la Torre (2016): Stratospheric gravity wave momentum flux from radio occultations. J. Geophys. Res. Atmos., 121, doi:10.1002/2015JD024135.
Schmidt, T., Schoon, L., Dobslaw, H., Matthes, K., Thomas, M., Wickert, J. (2016): UTLS temperature validation of MPI-ESM decadal hindcast experiments with GPS radio occultations, Meteorologische Zeitschrift, Vol. 25, No. 6, 673-683, doi:10.1127/metz/2015/0601.
Schmidt, T., J. Wickert, A. Haser (2010): Variability of the upper troposphere and lower stratosphere observed with GPS radio occultation bending angles and temperatures. Adv. Space Res., 46(2), 150-161, doi:10.1016/j.asr.2010.01.021.
Sobhkhiz-Miandehi, S., Yamazaki, Y., Arras, C., Themens, D. (2023): A comparison of FORMOSAT-3/COSMIC radio occultation and ionosonde measurements in sporadic E detection over mid- and low-latitude regions. - Frontiers in Astronomy and Space Sciences, 10, 1198071, https://doi.org/10.3389/fspas.2023.1198071
Sobhkhiz-Miandehi, S., Yamazaki, Y., Arras, C., Miyoshi, Y., Shinagawa, H. (2023): Correction: Comparison of the tidal signatures in sporadic E and vertical ion convergence rate, using FORMOSAT-3/COSMIC radio occultation observations and GAIA model. - Earth Planets and Space, 75, 160, https://doi.org/10.1186/s40623-023-01906-4
Steiner, A.K., Ladstädter, F., Randel, W.J., Maycock, A.C., Fu, Q., Claud, C., Gleisner, H., Haimberger, L., Ho, S.-P., Keckhut, P., Leblanc, T., Mears, C., Polvani, L.M., Santer, B.D., Schmidt, T., Sofieva, V., Wing, R., and Zou, C.-Z. (2020): Observed Temperature Changes in the Troposphere and Stratosphere from 1979 to 2018, Journal of Climate, https://doi.org/10.1175/JCLI-D-19-0998.1.
Steiner, A. K., Ladstädter, F., Ao, C. O., Gleisner, H., Ho, S.-P., Hunt, D., Schmidt, T., Foelsche, U., Kirchengast, G., Kuo, Y.-H., Lauritsen, K. B., Mannucci, A. J., Nielsen, J. K., Schreiner, W., Schwärz, M., Sokolovskiy, S., Syndergaard, S., and Wickert, J. (2020): Consistency and structural uncertainty of multi-mission GPS radio occultation records, Atmos. Meas. Tech., 13, 2547–2575, https://doi.org/10.5194/amt-13-2547-2020.
de la Torre, A., Alexander, P., Schmidt, T., Llamedo, P., and Hierro, R. (2018): On the distortions in calculated GW parameters during slanted atmospheric soundings, Atmos. Meas. Tech., 11, 1363–1375, doi.org/10.5194/amt-11-1363-2018.
Wang, W., Shangguan, M., Tian, W., Schmidt, T., and Ding, A. (2019): Large uncertainties in estimation of tropical tropopause temperature variabilities due to model vertical resolution, Geophysical Research Letters, 46, 10,043–10,052. doi.org/10.1029/2019GL084112.
Wilhelmsen, H., Ladstädter, F., Schmidt, T., and Steiner, A. K. (2020): Double tropopauses and the tropical belt connected to ENSO. Geophysical Research Letters, 47, e2020GL089027, https://doi.org/10.1029/2020GL089027
Wickert, J., Michalak, G., Schmidt, T., Beyerle, G., Cheng, C. Z., Healy, S. B., Heise, S., Huang, C. Y., Jakowski, N., Köhler, W., Mayer, C., Offiler, D., Ozawa, E., Pavelyev, A. G., Rothacher, M., Tapley, B., Arras, C. (2009): GPS radio occultation: results from CHAMP, GRACE and FORMOSAT-3/COSMIC. - Terrestrial Atmospheric and Oceanic Sciences, 20, 1, 35-50, doi:10.3319/TAO.2007.12.26.01(F3C).
Wickert, J. (2002): Das CHAMP-Radiookkultationsexperiment: Algorithmen, Prozessierungssystem und Ergebnisse, Scientific Technical Report STR02/07, GFZ, Potsdam.
Yamazaki, Y., Arras, C., Andoh, S., Miyoshi, Y., Shinagawa, H., Harding, B. J., Englert, C. R., Immel, T. J., Sobhkhiz-Miandehi, S., Stolle, C. (2022): Examining the Wind Shear Theory of Sporadic E With ICON/MIGHTI Winds and COSMIC‐2 Radio 2 Occultation Data. - Geophysical Research Letters, 49, 1, e2021GL096202, https://doi.org/10.1029/2021GL096202
