Global ionosonde and GPS radio occultation sporadic-E intensity and height comparison

Abstract

A multi-year global comparison between mid-latitude and equatorial sporadic-E (Es) height and intensity derived from COSMIC GPS radio occultation (GPS-RO) data and blanketing E frequency (fbEs) from ground-based Digisonde measurements is performed. The Es layer intensity from GPS-RO measurements was estimated using the S2 scintillation index and total electron content (TEC) assuming constant and variable Es cloud thicknesses individually. GPS-RO crossings were limited to within 150 km and 30 min of fbEs occurrences at each Digisonde. Intensities derived from the TEC with constant thickness method agreed more closely with the Digisonde fbEs measurements in terms of relative error and spread. Es path lengths estimated from the variable thickness method were also significantly larger than the average Es cloud length indicating that tube geometry assumptions between thickness and length do not apply to sporadic-E. Furthermore, intensities calculated from the S2 technique generally placed the frequency of fbEs between 2.7 and 5.3 MHz. Mean fbEs predictions from the S2 and constant thickness TEC methods are found to be statistically similar to the mean Digisonde fbEs. Both TEC and S2 methods underestimated the altitude of the fbEs events, but the S2 technique performed better overall. The mean heights calculated from both of the GPS-RO methods show a statistically significant difference with the mean Digisonde calculated heights, suggesting a bias in the height estimates.