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• Ratios of E-CHAIM model-to-RISR radar measured electron density are close to one at heights near F2 peak. • On average, E-CHAIM underestimates electron density at ionospheric topside and bottomside by ∼ 20 % • E-CHAIM underestimations are strongest in summer and equinoctial nighttime at bottomside and in autumn nighttime at topside. In this study, predictions of the E-CHAIM ionospheric model are compared with measurements by the incoherent scatter radars RISR at Resolute Bay, Canada, in the northern polar cap. Reasonable coverage was available for all seasons except winter for which no conclusions were drawn. It is shown that ratios of the model-to measured electron densities are close to unity in the central part of the F layer, around its peak. This is particularly evident for summer daytime. Distributions of the ratios are wider for other seasons indicating larger number of cases when the model underestimates or overestimates. E-CHAIM underestimates the electron density at ionospheric topside and bottomside by ∼ 10–20 %. At the bottomside, the underestimations are strongest in summer and equinoctial nighttime. At the topside, the underestimations are strongest in autumn nighttime. Model overestimations are noticeable in the middle part of the F layer during dawn hours in autumn. Overall, the model tends to not predict highest-observed peak electron densities and the largest-observed heights of the peak. [ABSTRACT FROM AUTHOR]

The performance of constant false alarm rate (CFAR) detectors is often severely degraded in clutter edge and under multiple target interference. CFAR detection in the above environments often uses generalised likelihood ratio method or mean ratio method to find out the clutter edge demarcation line and suppress the sharp increase of false alarm rate, or remove the interference and modify the threshold factor to suppress the interference and improve the detection performance, but this sacrifices the detection gain from the number of clutter samples. In this paper, the feature information is fused to construct feature vectors, and the edge location is judged by the modulus of the cross product of the feature vector pair (MCPFVP), this edge demarcation line detection method fusing with features can be implemented without the need of clutter statistical distribution information. In addition, this paper reconstructs the sea clutter masked by multiple target interference by fusing the sea clutter amplitude correlation information, and these reconstructed sea clutter samples are used for power estimation together with the unmasked sea clutter without changing the threshold factor. This method can not only suppress the target masking effect of multiple target interference as the censoring type CFAR detector, but also maintain the detection gain from the number of clutter samples, which is not possible with the traditional censoring type CFAR detector. In addition, the relative weighted ratio summation (RWRS) is proposed to detect the multiple target interference, which takes into account the asymmetry of the shape of the statistical distribution. Both simulated and real sea clutter data are used to validate the above methods. The measured data are obtained from radar data collected at Yantai Yangma Island, China, Darmouth, Canada and Grimsby, Canada. (The latter two datasets are collected by the IPIX radar - Ice Multiparameter Imaging X-Band Radar). [ABSTRACT FROM AUTHOR]