Evaluation and validation of various rapid GNSS global ionospheric maps over one solar cycle

Abstract

Compared with the final global ionospheric maps (GIMs) product on a weekly basis, rapid GIMs products on a daily basis have significant improvement in the availability, and are an important ionospheric information source for timely studies of global, regional, or local space weather events and corresponding other applications. Therefore, it is essential to analyze and validate the performance of different rapid products. In this contribution, we evaluate the accuracy and consistency of nine rapid GIMs released by different international GNSS service (IGS) ionosphere associate analysis centers (IAACs) from various aspects in detail, including IGS final GIMs, JASON-2/-3 ionospheric data, the difference of slant total electron content (dSTEC) data over one solar cycle from January 2009 to December 2020. In comparison with the IGS final GIMs, the variation trend of the standard deviation (STD) is consistent with the solar activities, and accompanied by seasonal and annual periodic variations. The mean bias (MEAN) between IGS and individual IAAC is approximately −2 to 2 TECU, and the STD is approximately 0.7 to 4.0 TECU. Over oceanic regions, the MEAN values of the different rapid GIMs with regard to JASON-2 are about 2 to 3 TECU and that of JASON-3 are about 4 to 5 TECU, except for JPRG. The STD performance of the various GIMs relative to the JASON-2 and JASON-3 vertical total electron content (VTEC) is both within 3 TECU. Over continental regions, the validation with the dSTEC data shows that the STD values of the external and internal verification range from 0 to 4.5 TECU and from 0 to 3 TECU, respectively, and the STD performance of the UQRG is the best.