Abstract
Abstract. The Global Navigation Satellite System (GNSS) atmospheric radio occultation (RO) has been an effective method for exploring Earth's atmosphere. RO signals propagate through the ionosphere before reaching the neutral atmosphere. The GNSS signal is affected by the ionospheric irregularity including the sporadic E (Es) and F region irregularity mainly due to the multipath effect. The effect of ionospheric irregularity on atmospheric RO data has been demonstrated by several studies in terms of analyzing singe cases. However, its statistical effect has not been investigated comprehensively. In this study, based on the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO data during 2011–2013, the failed inverted RO events occurrence rate and the bending angle oscillation, which is defined as the standard deviation of the bias between the observed bending angle and the National Center for Atmospheric Research (NCAR) climatology model bending angle between 60 and 80 km, were used for statistical analysis. It is found that at middle and low latitudes during the daytime, the failed inverted RO occurrence and the bending angle oscillation show obvious latitude, longitude, and local time variations, which correspond well with the Es occurrence features. The F region irregularity (FI) contributes to the obvious increase of the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime over the geomagnetic equatorial regions. For high latitude regions, the Es can increase the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime. There also exists the seasonal dependency of the failed inverted RO event and the bending angle oscillation. Overall, the ionospheric irregularity effects on GNSS atmospheric RO measurement statistically exist in terms of failed RO event inversion and bending angle oscillation. Awareness of these effects could benefit both the data retrieval and applications of RO in the lower atmosphere.
Highlights
Radio occultation (RO) is a technique originally developed in the late 1960s and early 1970s for planetary atmosphere exploration
To study the ionospheric irregularity effects on RO, we focus on analyzing two parameters: the failed inverted RO event occurrence rate and the bending angle oscillation defined as the mean standard deviation of the bias between the observed bending angle and the National Center for Atmospheric Research (NCAR) climatology model bending angle during the 60–80 km altitude interval
We focus on the ionospheric irregularity effects on Global Navigation Satellite System (GNSS) atmospheric RO
Summary
Radio occultation (RO) is a technique originally developed in the late 1960s and early 1970s for planetary atmosphere exploration. Healy and Culverwell (2015) found a good correlation between the RIE and the difference between GPS L1 and L2 bending angles at the same impact parameter They proposed a correction method using the “kappa” parameter under the ionospheric spherical symmetry assumption. Liu et al (2018) have analyzed the ionospheric structure influences on RIE in bending angles based on ray tracing simulations and further developed a “bilocal correction approach” to calculate the RIE through an equation. The small-scale irregularities in the ionosphere have an impact on the GNSS signal and affect the atmospheric RO products. There is no comprehensive study giving statistical analysis of ionospheric irregularity and atmospheric RO products, which is quite important to quantify this effect and benefit atmospheric RO data retrieval and application.
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