Extended observations of polar mesosphere winter echoes over Andoya (69 degrees N) using MAARSY

摘要

abstract_textpContinuous observations of Polar Mesosphere Winter Echoes (PMWE) have been conducted at the Norwegian island Andoya (69.30 degrees N, 16.04 degrees E) since autumn 2004 using the ALWIN VHF radar (until 2008) and the Middle Atmosphere Alomar Radar System (MAARSY) (since 2011). Using the more sensitive MAARSY compared to the ALWIN radar results in more detections characterized by smaller volume reflectivity values down to 4 . 10(-18)m(-1) and a greater altitudinal coverage, 50-88 km compared to previous observations between 65 and 75 km. The results obtained by MAARSY show that the PMWE season starts clearly at the beginning of September with a mean seasonal occurrence rate of about 16, but a strong seasonal variability with maxima up to 70 in the seasonal variation of the individual years. The end of the winter season is hard to determine since mesospheric echoes have also been observed below altitudes of 80km during nonwinter months, particularly around the end of May, i.e., the beginning of the polar mesospheric summer echo season, indicating that the physical mechanism for creating the lower mesospheric echoes is present during the early summer months as well./p/abstract_text