| The dynamics and small-scale vertical structure of Polar Mesosphere Summer Echoes (PMSE) are studied using the multiple-frequency Range IMaging (RIM) and the spaced antenna (SA) techniques. These techniques were implemented on the European Incoherent SCATter (EISCAT) VHF radar during two experimental campaigns conducted during the summers of 2002 and 2003. In the 2002 campaign, the first RIM measurements of PMSE were obtained revealing ubiquitous vertical layering in the PMSE. The PMSE structures were observed to be dynamically connected through the vertical velocities characteristics. In the 2003 campaign, RIM and SA were implemented simultaneously in order to study the connection of the layering structure with a component of the horizontal wind. Dynamical activity found in these experiments include gravity waves, wind corners, and possible Kelvin-Helmholtz instabilities. Due to the inherent EISCAT VHF radar receiver system design, unavoidable phase errors were introduced producing degraded RIM images. In order to mitigate these phase errors, a novel phase calibration technique based on genetic concepts was devised. Using an enhanced numerical radar simulator, in which data from multiple sampling volumes are simultaneously generated, the proposed phase calibration method was validated. Subsequently, calibrated RIM images of power, radial velocity, and spectral width from actual data revealed enhanced images facilitating interpretation. |
