A Comparison of Sporadic-E Occurrence Rates Using Ionosondes and GPS Radio Occultation Measurements

Sporadic-E (Es) occurrence rates from Global Position Satellite radio occultation (GPS-RO) measurements have shown to vary by nearly an order of magnitude between studies, motivating a comparison with ground-based measurements. In an attempt to find an accurate GPS-RO technique for detecting Es formation, occurrence rates derived using five previously developed GPS-RO techniques are compared to ionosonde measurements over an eight-year period from 2010-2017. GPS-RO measurements within 170 km of a ionosonde site are used to calculate Es occurrence rates and compared to the ground-truth ionosonde measurements. Each technique is compared individually for each ionosonde site and then combined to determine the most accurate GPS-RO technique for binary (present or absent) Es measurements. Overall, the Yu et al. (2020) S4 method showed the closest agreement with ionosonde measurements between 2010-2017and is the recommended technique for future GPS-RO based Es climatologies