Small-scale fluctuations and scintillations in high-resolution GPS/CHAMP SNR and phase data

Amplitude (SNR) and phase fluctuations are frequently observed in 50-Hz GPS/CHAMP radio occultations. These fluctuations reflect perturbations of electron density in the ionosphere (e.g., Sporadic-E) and small-scale temperature/density in the lower stratosphere and upper troposphere. Analyses with the raw SNR and phase data offer new and useful information on variations and distributions of small-scale atmospheric/ionospheric variabilities, which is normally discarded in the retrieved temperature profiles. The derived SNR and phase variances show strong annual variations in the ionosphere due to sporadic-E activity. The intensity of polar Es activity reduces gradually since 2001, as solar activity weakens from the 2000 maximum. Near the tropical tropopause, the small-scale SNR and phase variances maximized, which is dominated by a seasonal variation of the tropopause height. In the lower stratosphere, tropical variances exhibit a quasi-biannual oscillation (QBO) with amplitudes maximized at altitudes of 15-30 km and progressing downward in time. The amplitude maxima occur just below the heights of the zero wind line where QBO changes from the easterly to westerly phase.