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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]

Abstract: Height measurements from small-footprint discrete-return LiDAR and backscatter coefficients from C- and L-band radar were used independently and in combination to estimate above-ground component and total biomass for a coniferous temperate forest, located on Vancouver Island, British Columbia, Canada. Reference biomass data were obtained from plot-level data and used for comparison against the LiDAR and radar-based biomass models. For the LiDAR-only model, height metrics such as mean first return height and percentiles (e.g., 10th and 90th) of first returns correlated best to total above-ground and stem biomass. While percent of first returns above 2m and percentiles (75th and 90th) of first returns height metrics correlated best to crown biomass. A comparison between above-ground components and total biomass indicate that stem biomass displayed the highest relationship with the LiDAR measurements while crown biomass showed the lowest relationship with relative root mean squared error ranging from 16% to 22%, respectively. Alternatively, the radar-only models indicated that for C-band radar, a combination of HH and VV backscatter demonstrated the most significant correlation with forest biomass compared to coherence based models with a relative root mean squared error of 53%. For L-band radar, a combination of HH and HV backscatter showed the most significant correlation compared to coherence based models with a relative root mean squared error of 44%. Exploring a mixture of C- and L-band backscatter and coherence based models revealed that a combination of C-HV and L-HV coherence magnitudes provided the best radar relationship with forest biomass with a relative root mean squared error of 35%. Also for all radar-based models, L- and C-band backscatter and coherence magnitudes were poorly correlated with individual biomass components when compared to total above-ground biomass. The addition of C- and L-band backscatter and coherence variables to the LiDAR-only biomass model was also investigated. The results showed that the integration of C-band HH backscatter to the LiDAR-only model significantly improved the relationship with forest biomass by explaining an additional 8.9% and 6.5% of the variability in total aboveground and stem biomass respectively, while C-band polarimetric entropy explained an additional 17.9% of the variability in crown biomass. Improvements in the relative root mean squared errors were also observed ranging from 7.1% to 11.7%. The study suggests that for a temperate forest dominated by coniferous stands, the addition of C-band radar variables to a best LiDAR-only linear model provides improved estimates of above-ground component and total biomass. [Copyright &y& Elsevier]

Abstract: This paper presents some new concepts in the petroleum systems of the northern Labrador and southern Baffin Island offshore region of eastern Canada. The focus of this work is the region of the Hekja O-71 gas discovery of 1979 by Aquitaine, one of only five wells drilled between 1976 and 1980 within an area covering some 166,000 square kilometers within the Saglek Basin. This study emerged from a broad scale re-examination of the petroleum potential of this area “from the crust up” using regional reflection, refraction and potential field data. An opportunity to use SAR (synthetic aperture radar) data from the RADARSAT-1 Earth observation satellite was taken to incorporate alternative data sources to support this exploratory review and resource assessment. Examination of the final map of interpreted slick-like features on the sea surface, revealed a close correlation of some of these occurrences to several bathymetric features which have underlying seismic signatures similar to previously identified gas hydrate “pipes” or chimney anomalies as seen in data from offshore Nova Scotia and in the Irish Sea. Globally, many active marine hydrocarbon seeps appear on the seafloor as “pockmarks”; in this case no seafloor depressions were seen on conventional multi channel 2-D seismic data associated with active seepage. Instead, very distinct mound-like structures are seen associated with seeps at two locations east of Hudson Strait. The presence of significant cold water coral in close proximity to the active seepage sites may show a link between seafloor petroleum seepage and coral reef development similar to that observed offshore Norway. Close examination of the near surface seismic character led to the interpretation of what was originally seen as seismic noise in vintage data, as likely being fluid escape chimneys or gas pipes, along the eastern edge of the Hekja structural complex, where favourable hydrocarbon trapping conditions are present. No active seeps were seen there; this may be due to other factors, such as the nature of the fluids that are escaping or the possibility of self sealing activity by biological agents such as bacterial matting with associated carbonate hard-ground formation. One seep anomaly was noted relatively close to the major basaltic eruptive complex near the Gjoa G-37 well. This may be due to the presence of volcaniclastic- hosted hydrocarbons similar in style to those recently discovered at the Rosebank field in Paleocene volcanics in the Faroe-Shetland Basin. The occurrence of an active seep in a volcanically-dominated terrain raises the potential for a radical shift in accepted types of petroleum leads and where they may occur. The presence of apparent oil seepage versus the past history of finding only gas-prone accumulations is a strong indicator that a second, oil-prone petroleum system exists in the Saglek Basin. The signs of active petroleum systems as shown by oil seep anomalies with confirming seismic evidence of discrete sea floor structures in close proximity makes a compelling argument for re-examining these areas with an eye towards stratigraphic instead of structural plays. [Copyright &y& Elsevier]

The seasonal transition of the boreal forest between frozen and non-frozen conditions affects a number of ecosystem processes that cycle between winter dormant and summer active states. The relatively short Ku-band wavelength (2.14 cm) of the space-borne NASA scatterometer (NSCAT) is sensitive to changes in dielectric properties, associated with large-scale changes in the relative abundance and phase (frozen or thawed) of canopy and surface water. We used a temporal change detection analysis of NSCAT daily radar backscatter measurements to characterize the 1997 seasonal spring thaw transition period across the 106 km2 BOREAS study region of central Canada. In the spring, air temperature transitions from frozen to non-frozen conditions and surface observations of seasonal snow cover depletion were generally coincident with decreases in radar backscatter of more than 2.9 dB, regardless of regional landcover characteristics. We used a temporal classification of NSCAT daily differences from 5-day smoothed backscatter values to derive three simple indices describing the initiation, primary event and completion of the spring thaw transition period. Several factors had a negative impact on the relative accuracy of NSCAT-based results, including periodic gaps in NSCAT daily time-series information and a large (i.e., >2 cm day−1) spring rainfall event. However, these results were generally successful in capturing the seasonal transition of the region from frozen to non-frozen conditions, based on comparisons with regional weather station network information. These results illustrate the potential for improved assessment of springtime phenology and associated ecosystem dynamics across high latitude regions, where field based and optical remote-sensing methods are substantially degraded by frequent cloud cover, low solar illumination and sparse surface weather station networks. [Copyright &y& Elsevier]

Single-hole radar reflection and cross-hole radar tomography surveys have been used to assist in characterizing a 105-m3 block of granite rock at AECL''s Underground Research Laboratory (URL) in southeast Manitoba, Canada. The surveys were conducted in a series of seven boreholes drilled in moderately fractured granite rock from the URL 240 meter level. The RAMAC borehole radar system with rated dipole antenna frequencies of 22 and 60 MHz was used for these surveys. Results of single-hole radar reflection surveys revealed several linear reflectors and hyperbolic diffractions events. Some of the linear reflectors were interpreted to be reflections from fracture planes; others were from boreholes near or within the survey area. The hyperbolic diffractions are from point reflectors related to discrete vertical fractures or inhomogeneities in the rock. The 60-MHz surveys provided high-resolution reflection records and detected reflectors up to 50 m away from the boreholes. Compared to 60-MHz surveys, the 22-MHz reflection data showed marked decrease in resolution but considerable increase in probing-range (∼100 m). Both the 22- and 60-MHz surveys were able to detect water-saturated discrete fractures and fracture zones a few centimeters thick. Reflections from the HQ size (96-mm diameter) boreholes were also detected in both the 22- and 60-MHz reflection surveys. The radar velocities in the Moderately Fractured Rock (MFR) study block varied from 105 to 125 m/μs, which translates to a total velocity variation of 8–10% in the URL granite (with average velocity 120 m/μs). Results from borehole radar surveys were compared with core log data and hydraulic test results from the boreholes. The single-hole reflection data correlate well with fractures and fracture zones observed in the core logs. Combined interpretation identified low dipping fracture zones (with 10–30° dip) and two sets of subvertical fractures trending northeast and southwest. In addition, the radar velocity images from tomographic surveys show good correlation with the geologic model reconstructed from core log data. Above-average radar velocities correlate with more competent rock and lower velocities with more fractured rock. The tomography interpretations are also consistent with transmissivity values from hydraulic tests in the boreholes. The regions of low radar velocity anomalies correspond to transmissivity values of 1×10−6–1×10−8 m2/s in the boreholes, and high radar velocities to transmissivity values of 10−12–10−13 m2/s. In addition, the lower radar velocities correlate with increase in permeability as observed from groundwater flow measurements (e.g. 22 l/min in borehole MF12) and higher radar velocities corresponding to lower groundwater flow rates (e.g. 0.5–0.8 l/min in borehole MF6). [Copyright &y& Elsevier]