Aspect sensitivity of double-layer polar mesosphere summer echoes at VHF based on an experimental case

Abstract

Using the EISCAT VHF (224 MHz) radar data, an experimental case of aspect sensitivity and the characteristics of volume reflectivity of Polar Mesosphere Summer Echoes (PMSE) are presented. The data from the PMSE region during 24–28 June and 1 July 2013, when the beam pointed the off-vertical elevation angles (the largest is 28°), are used. It is found that the distribution curve of the volume reflectivity occurrence rate (OR) at different elevation angles obeys a Gaussian distribution as a whole, but there are some differences at different elevation angles. We investigated the aspect sensitivity parameters (θs) at different elevation angles, and found that θs shows a decrease at the altitude range of 82–84 km. In addition, the aspect sensitivity parameters (θs) of the upper and lower layers were calculated respectively when there is double-layer PMSE. The experimental results showed that in the case of double-layer PMSE, the aspect sensitivity of the lower PMSE layer is stronger than that of the upper PMSE layer. This indicates that the lower PMSE layers are associated with more anisotropic turbulence scattering. It provides new evidence on the dependence of PMSE aspect sensitivity on altitude. And possible explanations of the presented results are discussed.