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Abstract:
Climate change as a potential enhancement of hazards globally, plays a significant role for world’s society.The Earth’s axis of rotation varies on different time scales i.e., ranging from hours to decades, plus a long-term trend. These variations are mainly excited by many relevant internal geophysical processes such as changes in the fluid core, by atmospheric tides, hydrosphere, and ocean tides, and external processes such as libration effects. The internal and external processes affect Earth's rotational axis relative to its crust and have an impact on its rotational speed. As opposed to most external effects, the influence of the internal processes on the Earth rotation is not accurately known. The internal effects must be separated from the weather-induced variations. Making use of precise Earth Rotation Parameters, previously estimated from space geodetic VLBI observations from 1979 till now, this work focuses on how long-wavelength weather processes in space and time drive Earth rotation. We assess how long time series of polar motion and UT1-TAI, as well as the time derivatives thereof, correlate with climatic phenomena such as El-Nino, Madden-Julian Oscillation, North Atlantic Oscillation changes in the effective angular momentum such as Atmospheric Angular Momentum and Oceanic Angular Momentum. To study the relationship between Earth rotation and climatic phenomena, we applied the statistical tool method of ‘wavelet-based semblance analysis’. This investigation is a contribution to climate research by comparing on Earth rotation variations recovered by VLBI with climate indices obtained from numerical weather models.PWV Distribution During of Severe Weather Events in Black Sea Region of Turkey Derived From GPS Measurements, ERA-Interim/ERA-5 and Radiosonde E. Tanır Kayıkçı (1), M. Yalçınkaya (1), V. Tornatore (2), S. Zengin (1), S. C. Tuncer (3), M. Demircan (4)(1) Karadeniz Techn. Univ., (2) Politecnico di Milano, (3) Hitit University, (4) Turkish State Meteorol. ServiceIn this study, we present the retrieval of PWV (precipitable water vapour) by GNSS observations to monitor severe weather events. In order to determine PWV distribution by GNSS meteorology, four new GNSS stations (SAME, SOMU, TRAB, MACK), established in cities of Samsun and Trabzon of Black Sea Region of Turkey within the TUBITAK research project 116Y186 have been used. Additionally, some GNSS stations from existing 15 CORS-TR network belonging to Turkish continuously operating network and IGS/EPN network have been added. All calculations to get ZTD (Zenith Total Delay) were carried out with Bernese GNSS Software version 5.2. The four GNSS stations in Samsun and Trabzon are not equipped with meteorological sensors. To overcome this limitation, we interpolated surface pressure and temperature from all available meteorological stations located in the area of the study. Alternatively, The GPT3 empirical and ECMWF numerical weather model were used to provide meteorological parameters at those stations. For the conversion from GNSS ZTD to PWV, we used surface pressure and temperature derived by those three methods. PWV estimations from GNSS meteorology, radiosonde and ERA-Interim heve been evaluated during severe events, in May and June 2019, happened in the region.
