Polar mesosphere summer echo studies at 51.5 MHz at Resolute Bay, Canada: Comparison with Poker Flat results

摘要

We present a study of seasonal and diurnal variations of polar mesosphere summer echoes (PMSE), along with temperature and wind data collected during summer 1998 using the 51.5 MHz VHF radar located in Resolute Bay, Canada (75°N, 95°W). The latitudinal dependence of PMSE occurrence and strength are examined by comparing Resolute Bay observations with earlier Poker Flat (65°N, 147°W) observations. Temperatures measurements at Resolute Bay using the radar in the meteor mode are compared with satellite measurements at similar latitudes of Resolute Bay and Poker Flat. The temperature measurements are in good agreement, and, as expected, PMSE is strongly controlled by the seasonal temperature variations. Differences found in the daily composite and monthly average winds, and in the monthly evolution of the amplitudes and phases of the diurnal and semidiurnal tides at Resolute Bay and Poker Flat, are discussed in order to establish the role that they play in the occurrence of PMSE. In general, we find that the diurnal occurrence of PMSE at Resolute Bay also follows the diurnal variation of temperature. The echoes tend to occur more frequently and with greatest intensity when the temperatures are the coldest, in a period centered around local noon. We show that the diurnal wind components at Resolute Bay appear to correlate with the occurrence of PMSE, as also seen at Poker Flat. PMSE at Resolute Bay are not as strong or as frequent as reported at Poker Flat, differing with what we had expected since strongest and more frequent echoes have been observed in the European sector approaching the pole. New observations are needed to establish a possible longitudinal dependence of PMSE occurrence given that the present American sector data are compared with data taken over 10 years ago.