Status of CAS global ionospheric maps after the maximum of solar cycle 24

Abstract As a new Ionosphere Associate Analysis Center (IAAC) of the International GNSS Service (IGS), Chinese Academy Sciences (CAS) started routine computation real-time, rapid, and final Global Ionospheric Maps (GIMs) in 2015. The method for generation CAS rapid GIMs recent updates are presented paper. quality post-processed is assessed during 2015–2018 after maximum solar cycle 24. To perform an independent fair assessment, Jason-2/3 Vertical Total Electron Contents (VTEC) first used as references over ocean. GPS differential Slant TECs (dSTEC) generated from 55 Multi-GNSS Experimental (MGEX) stations IGS also employed, which provides complementing way to evaluate ability electron content models reproduce spatial temporal gradients ionosphere. During test period, Jet Propulsion Laboratory (JPL) present significantly positive deviations compared Jason VTEC dSTEC. Technical University Catalonia (UPC) GIM UQRG exhibits best performance both dSTEC analysis. show comparable with results four IAACs IGS. expected, poor all equatorial regions high latitudes southern hemisphere. consideration generating multi-layer or three-dimensional ionospheric maps emphasized mitigate inadequacy single-layer assumption presence pronounced latitudinal gradients. use observations constellations other space- ground-based observation techniques suggested future GIMs, given sparse GPS/GLONASS