Abstract
Abstract. A 31 MHz meteor radar located in Svalbard was used to observe polar mesospheric echoes (PMSEs) during summer 2020. Data from 19 July were selected for detailed analysis, with a focus on extracting additional information to characterize the atmosphere in the PMSE region. The use of an all-sky meteor radar adds an additional use to data collected for meteor observations and enables the detection of PMSE layers across a wide field of view. Comparison with data from a 53.5 MHz narrow-beam mesosphere–stratosphere–troposphere (MST) radar shows good agreement in the morphology of the layer as detected between the two systems. Doppler spectra of PMSE layers reveal fine structure, including regions of enhanced return that move across the radar's field of view. Examination of the relationship between range and Doppler shift of off-zenith portions of the layer enables the estimation of wind speeds with high temporal resolution during PMSE conditions. Trials demonstrate good agreement between wind speeds obtained from PMSE Doppler spectra and those calculated from specular meteor trail radial velocities. Combined with the antenna polar diagram of the radar, this same relationship was used to infer the aspect sensitivity of observed PMSE backscatter, yielding a mean backscatter angular width of 6.8±3.3∘. A comparison of underdense meteor radar echo decay times during and outside of PMSE conditions did not demonstrate a strong correlation between the presence of PMSEs and shortened underdense meteor radar echo durations.
Highlights
Temperatures in the summer polar mesosphere can fall below the local sublimation point of water vapor, allowing ice crystals to form, when other types of aerosols contribute as condensation nuclei
Polar mesospheric clouds (PMCs) in general are of particular interest to atmospheric studies, as they can be a proxy for changes in climate and the impact of solar activity on the middle atmosphere (Thomas, 1996; DeLand et al, 2006)
The Svalbard SOUSY Radar (SSR) is a narrow-beam MST radar located at 78.170◦ N, 15.990◦ that transmits at 53.5 MHz with a peak power of 8 kW
Summary
Temperatures in the summer polar mesosphere can fall below the local sublimation point of water vapor, allowing ice crystals to form, when other types of aerosols contribute as condensation nuclei. Larger ice crystals have long been observed as noctilucent clouds (NLCs) at high latitudes (Leslie, 1885). Radar can detect these layers as what Hoppe et al (1988) coined polar mesospheric summer echoes (PMSEs) (see, e.g., Cho and Röttger, 1997; Rapp and Lübken, 2004). There has been interest in observing PMSEs using meteor radars These systems are usually comprised of six antennas in total, with a much smaller array footprint than the more sensitive narrow-beam MST radars. Most recently, Hall et al (2020) provided an initial report of simultaneous detections of PMSEs by the same narrow-beam MST radar and all-sky meteor radar used in this study
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