Radar efficiency and the calculation of decade-long PMSE backscatter cross-section for the Resolute Bay VHF radar

摘要

The Resolute Bay VHF radar, located in Nunavut, Canada (75.0° N,95.0° W) and operating at 51.5 MHz, has been used to investigatePolar Mesosphere Summer Echoes (PMSE) since 1997. PMSE are a uniqueform of strong coherent radar echoes, and their understanding hasbeen a challenge to the scientific community since their discovery morethan three decades ago. While other high latitude radars have recorded stronglevels of PMSE activities, the Resolute Bay radar has observedrelatively lower levels of PMSE strengths. In order to deriveabsolute measurements of PMSE strength at this site, a technique isdeveloped to determine the radar efficiency using cosmic (sky) noisevariations along with the help of a calibrated noise source. VHFradars are only rarely calibrated, but determination of efficiencyis even less common. Here we emphasize the importance of efficiencyfor determination of cross-section measurements. The significantadvantage of this method is that it can be directly applied to anyMST radar system anywhere in the world as long as the sky noisevariations are known. The radar efficiencies for two on-site radarsat Resolute Bay are determined. PMSE backscatter cross-section isestimated, and decade-long PMSE strength variations at this locationare investigated. It was noticed that the median of the backscattercross-section distribution remains relatively unchanged, but overthe years a great level of variability occurs in the high power tailof the distribution.