Seasonal occurrence of polar mesosphere summer echo variations with different layers

Polar Mesosphere Summer Echoes (PMSE) are strong radar echoes that have been observed typically by the VHF radar in summer polar mesosphere and have closely relation with charged dust particles. Theoretical analysis and extensive experimental data show that polar mesosphere summer echoes (PMSE) present some kind of regular periodic changes, such as semidiurnal variations, diurnal variations, day-to-day variations, seasonal variations, year-to-year variations, obvious layered phenomena and so on. To obtain the trends of PMSE occurrence rate with different layers, data detected by the European Incoherent Scatter Scientific Association (EISCAT) VHF radar in 12 years is used to analyze corresponding PMSE occurrence. The year-to-year variations of PMSE occurrence rate with one-, two- and triple-layered are given, and the effect of geomagnetic activities are discussed in the paper. The results indicate new recommendation for studying PMSE in the future.