The Middle Atmosphere Alomar Radar System (MAARSY) on the North‐Norwegian island Andøya is a 53.5 MHz monostatic radar with an active phased array antenna consisting of 433 Yagi antennas. The 3‐element Yagi antennas are arranged in an equilateral triangle grid forming a circular aperture of approximately 6300 m2. Each individual antenna is connected to its own transceiver with independent phase control and a scalable power output up to 2 kW. This arrangement provides a very high flexibility of beam forming and beam steering with a symmetric radar beam of a minimum beam width of 3.6° allowing classical beam swinging operation as well as experiments with simultaneous multiple beams and the use of interferometric applications for improved studies of the Arctic atmosphere from the troposphere up to the lower thermosphere with high spatio‐temporal resolution. The installation of the antenna array was completed in August 2009. The radar control and data acquisition hardware as well as an initial expansion stage of 196 transceiver modules was installed in spring 2010 and upgraded to 343 transceiver modules in November 2010. The final extension to 433 transceiver modules has recently been completed in May 2011. Beside standard observations of tropospheric winds and Polar Mesosphere Summer Echoes, the first multi‐beam experiments using up to 97 quasi‐simultaneous beams in the mesosphere have been carried out in 2010 and 2011. These results provide a first insight into the horizontal variability of polar mesosphere summer and winter echoes with time resolutions between 3 and 9 minutes. In addition, first meteor head echo observations were conducted during the Geminid meteor shower in December 2010.
[1] Between 2003 and 2005, 12.9 h (8 events) of noctilucent clouds (NLC) and 250 h of mesospheric summer echoes (MSE) were observed above Kühlungsborn (54°N, 12°E) by lidar and radar, respectively. The ice-layer seasons typically last for 50 (NLC) and 70 days (MSE). The observations are compared with simultaneous lidar temperature soundings. Altogether, 79 soundings were performed in the periods 10 May to 8 August of each year. These profiles revealed a minimum mesopause temperature of 145 K at 87 km shortly after summer solstice. The mean temperatures are below the frost point temperature for a period of $15 days after summer solstice and in the altitude range $85-89 km. Simultaneous observations of temperature, MSE/NLC, and winds by radar and lidar show that ice particles occur primarily during southward winds and during the cold phases of gravity waves and tides, providing temperatures up to $20 K lower than the mean. Water vapor saturation profiles are calculated from the temperatures and modeled water vapor concentrations, showing that the ice layers occur at the bottom of the supersaturated region. Only about one fifth of all supersaturation events below 85 km in fact yield NLC above our site. Even saturation ratios of 10-100 lasting for at least 4 h do not necessarily lead to the formation of NLC. We conclude that NLC at midlatitudes are strongly coupled to the advection of preexisting ice particles from northern latitudes. If the ice particles have sublimated prior to the observation, they do not form again even in the cold phases of waves.
[1] During the three summer seasons of the years 1998, 2000 and 2001 mid-latitude mesosphere summer echoes (MSE) were observed with the OSWIN VHF radar. The radar is located at Kühlungsborn (54.1°N, 11.8°E). Based on nearly continuous operation of the radar a large data set with altogether more than 200 hours of MSE observations with signal-to-noise ratios greater than 0 dB has been obtained. We present and discuss the results of the three years observation. Mid-latitude mesosphere summer echoes occur much more seldom than their corresponding polar mesosphere summer echoes (PMSE) in polar regions. Both phenomena are characterized by very strong radar returns with a high aspect sensitivity and a restriction to the summer mesosphere. But beside these analogies their main differences will be discussed also. MSE occur in a shorter time interval in the summer months and normally only during daytime. They are still observable although the low temperatures and the sufficient degree of saturation necessary for the existence of ice particles cannot be reached at all times. Furthermore we show MSE distribution, scattering characteristics, aspect sensitivity, and turbulence characteristics as functions of height.
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