CUPRI observations of pre‐sunrise vertical type‐I echoes from the equatorial electrojet above Alcântara, Brazil

Abstract

The Cornell University Portable Radar Interferometer (CUPRI) made high resolution vertical radar measurements of the equatorial electrojet above Alcântara, Brazil from mid‐August to mid‐October, 1994, as part of the Guará Dip Equator Campaign. Spectra obtained during the period of a few hours before sunrise show the usual nighttime persistence asymmetry wherein there is a preponderance of downward type‐I phase velocities as a function of time. These are the first high resolution measurements in South America of this effect at a location other than Jicamarca, Peru. Furthermore the CUPRI interferometer phase data clearly indicate that when changes in the sign of the dominate type‐I peaks occur, they are tied to the normal phase progressions of the large scale waves. No reversal of the asymmetry (as does occur in the daytime) was seen in this nighttime period.