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Author: Vierinen, J.P. × Publisher: Göttingen : Copernicus GmbH ×

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    Multi-static spatial and angular studies of polar mesospheric summer echoes combining MAARSY and KAIRA
    (Göttingen : Copernicus GmbH, 2018) Chau, J.L.; McKay, D.; Vierinen, J.P.; La Hoz, C.; Ulich, T.; Lehtinen, M.; Latteck, R.
    Polar mesospheric summer echoes (PMSEs) have been long associated with noctilucent clouds (NLCs). For large ice particles sizes and relatively high ice densities, PMSEs at 3m Bragg wavelengths are known to be good tracers of the atmospheric wind dynamics and to be highly correlated with NLC occurrence. Combining the Middle Atmosphere ALOMAR Radar System (MAARSY) and the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA), i.e., monostatic and bistatic observations, we show for the first time direct evidence of limited-volume PMSE structures drifting more than 90 km almost unchanged. These structures are shown to have horizontal widths of 5-15 km and are separated by 20-60 km, consistent with structures due to atmospheric waves previously observed in NLCs from the ground and from space. Given the lower sensitivity of KAIRA, the observed features are attributed to echoes from regions with high Schmidt numbers that provide a large radar cross section. The bistatic geometry allows us to determine an upper value for the angular sensitivity of PMSEs at meter scales. We find no evidence for strong aspect sensitivity for PMSEs, which is consistent with recent observations using radar imaging approaches. Our results indicate that multi-static allsky interferometric radar observations of PMSEs could be a powerful tool for studying mesospheric wind fields within large geographic areas. © Author(s) 2018.
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    Novel specular meteor radar systems using coherent MIMO techniques to study the mesosphere and lower thermosphere
    (Göttingen : Copernicus GmbH, 2019) Chau, J.L.; Urco, J.M.; Vierinen, J.P.; Volz, R.A.; Clahsen, M.; Pfeffer, N.; Trautner, J.
    Typical specular meteor radars (SMRs) use one transmitting antenna and at least a five-antenna interferometric configuration on reception to study the mesosphere and lower thermosphere (MLT) region. The interferometric configuration allows the measurement of the angle-of-arrival (AOA) of the detected meteor echoes, which in turn is needed to derive atmospheric parameters (e.g., mean winds, momentum fluxes, temperatures, and neutral densities). Recently, we have shown that coherent MIMO configurations in atmospheric radars, i.e., multiple input (transmitters) and multiple output (receivers), with proper diversity in transmission can be used to enhance interferometric atmospheric and ionospheric observations. In this study we present novel SMR systems using multiple transmitters in interferometric configuration, each of them employing orthogonal pseudorandom coded transmitted sequences. After proper decoding, the angle of departure (AOD) of the detected meteor echoes with respect to the transmitter site are obtained at each receiving antenna. We present successful bistatic implementations of (1) five transmitters and one receiver using coded continuous wave (CW) (MISO-CW), and (2) five transmitters and five receivers using coded CW (MIMO-CW). The latter system allows simultaneous independent observations of the specular meteor trails with respect to the transmitter (AOD) and with respect to the receiver (AOA). The quality of the obtained results is evaluated in terms of the resulting mean winds, the number of detections and the daily diffusion trail vs. altitude behavior. We show that the proposed configurations are good alternatives to explore the MLT region. When combined with multi-static approaches, they can increase the number of meteor detections, thereby improving the quality of atmospheric estimates and allowing the measurement of new atmospheric parameters (e.g., horizontal divergence, vorticity), The use of multiple collocated transmitters for interferometric AOD determination makes building a multi-static radar network easier logistically, as only one receiver per receiving site antenna is sufficient. © 2019. This work is distributed under the Creative Commons Attribution 4.0 License.