Studies of mesospheric radar echoes at polar and middle latitudes

During summer months, at mid and polar latitudes very strong non-turbulent related VHF-radar echoes are observed at mesospheric altitudes (80-90 km), that are called Mesosperic Summer Echoes (MSE). At polar latitudes (PMSE) they occur more often and are stronger then their midlatitude counterparts. On the other hand, winter echoes (PMWE and MWE) are more seldom observed below 80 km during equinoctial and winter months, and are believed to be related to turbulence.