The conversion between the line-of-sight slant total electron content (STEC) and the vertical total electron content (VTEC) depends on the mapping function (MF) under the widely used thin layer ionospheric model. The thin layer ionospheric height (TLIH) is an essential parameter of the MF, which affects the accuracy of the conversion between the STEC and VTEC. Due to the influence of temporal and spatial variations of the ionosphere, the optimal TLIH is not constant over the globe, particularly in the polar regions. In this paper, a new method for determining the optimal TLIH is proposed, which compares the mapping function values (MFVs) from the MF at different given TLIHs with the “truth” mapping values from the UQRG global ionospheric maps (GIMs) and the differential TEC (dSTEC) method, namely the dSTEC- and GIM-based thin layer ionospheric height (dG-TLIH) techniques. The optimal TLIH is determined using the dG-TLIH method based on GNSS data over the Antarctic and Arctic. Furthermore, we analyze the relationship between the optimal TLIH derived from the dG-TLIH method and the height of maximum density of the F2 layer (hmF2) based on COSMIC data in the polar regions. According to the dG-TLIH method, the optimal TLIH is mainly distributed between 370 and 500 km over the Arctic and between 400 and 500 km over the Antarctic in a solar cycle. In the Arctic, the correlation coefficient between the hmF2 and optimal TLIH is 0.7, and the deviation between them is 162 km. Meanwhile, in the Antarctic, the correlation coefficient is 0.60, with a phase lag of ~3 months, with the hmF2 leading the optimal TLIH, and the deviation between them is 177 km.

Xi, H.; Zhang, Z., and Lu, Y., 2020. A quasi-decadal oscillation of sea-level variation in the South China Sea. Journal of Coastal Research, 36(2), 228–237. Coconut Creek (Florida), ISSN 0749-0208.To investigate the sea-level variation (SLV) in the South China Sea (SCS), independent multisource datasets, including observations from satellite altimetry and satellite gravity missions, sea-level reconstruction data, tide gauge data, and ocean model and oceanographic temperature and salinity observation, are used. Fast Fourier transform analysis indicates that the SLV and its steric component appear to exhibit significant quasi-decadal oscillation. Cross wavelet and wavelet coherence analysis show that high common power and significant antiphase coherence appear between the Pacific decadal oscillation (PDO) and steric SLV at the decadal scale. High common power also exists between the sunspot cycles and the steric SLV, but with in-phase coherence. Further analysis shows that the impacts of both PDO and sunspot activity on the sea surface temperature are more significant than those on the sea surface salinity. As a result, the quasi-decadal oscillation in the SLV of the SCS is associated with PDO and with the solar activity represented by the sunspot. It is useful to understand the mechanism of the rising sea level.