Borehole gravity has been used in mineral exploration recently with the advent of slim-hole gravimeters. It is logical to perform inversion to utilize the information in the newly acquired data. The inversions were ca...Borehole gravity has been used in mineral exploration recently with the advent of slim-hole gravimeters. It is logical to perform inversion to utilize the information in the newly acquired data. The inversions were carried out by using cokriging,which is a geostatistical method of estimation that minimizes the error variance by applying cross-correlation between several variables. In this study the estimated densities are derived by using boreholes gravity and known densities along the borehole. This method does not need iterative process and computes efficiently. The selection of examples demonstrates that this method has the ability to include physical property from borehole measurements in the inversion. The synthetic examples demonstrate the density variation along a borehole can be well determined without depth constraints in the inversion. The resolution of the recovered model can be further improved by including the densities along the borehole for inversion. However,this capability decreases dramatically with the increasing of distance between the anomalous body and the borehole.展开更多
Satellite-derived surface radiative fluxes have been recently improved and extended.However,the accuracy of recent satellite-derived surface radiative fluxes in the Arctic is not well characterized.Here,the authors as...Satellite-derived surface radiative fluxes have been recently improved and extended.However,the accuracy of recent satellite-derived surface radiative fluxes in the Arctic is not well characterized.Here,the authors assess the accuracy of the net surface radiative flux （NETSRF） in the Arctic,focusing on the ice-covered ocean,for three satellite products against four in situ measurements collected from different areas in the Arctic.The three satellite products are the Surface Radiation Budget project （SRB）,the International Satellite Cloud Climatology Project （ISCCP）,and the Extended AVHRR Polar Pathfinder version-2 （APP-x）.Our comparisons suggest that：（1） in terms of the overall bias,root-mean-square error,and correlation,the NETSRF of ISCCP is closer to in situ observations than that of SRB and APP-x;（2） in terms of the diurnal variation of the biases,it is not very clear which satellite product is superior to the others;and （3） in terms of the interannual variability of the bias,the NETSRF of ISCCP is more accurate than that of SRB and APP-x.This comparison may provide useful guidance to the community as to which data-set may provide the smallest bias in NETSRF展开更多
In this paper, we propose the novel method of complex least squares adjustment （CLSA） to invert vegetation height accurately using single-baseline polarimetric synthetic aperture radar interferometry （PollnSAR） da...In this paper, we propose the novel method of complex least squares adjustment （CLSA） to invert vegetation height accurately using single-baseline polarimetric synthetic aperture radar interferometry （PollnSAR） data. CLSA basically estimates both volume-only coherence and ground phase directly without assuming that the ground-to-volume amplitude radio of a particular polarization channel （e.g., HV） is less than -10 dB, as in the three-stage method. In addition, CLSA can effectively limit errors in interferometric complex coherence, which may translate directly into erroneous ground-phase and volume-only coherence estimations. The proposed CLSA method is validated with BioSAR2008 P-band E-SAR and L-band SIR-C PollnSAR data. Its results are then compared with those of the traditional three-stage method and with external data. It implies that the CLSA method is much more robust than the three-stage method.展开更多
基金Supported by the National High Technology Research and Development Program(863 Program)(No.2014AA06A613)by Project of Graduate Innovation Fund of Jilin University(No.2014066)
文摘Borehole gravity has been used in mineral exploration recently with the advent of slim-hole gravimeters. It is logical to perform inversion to utilize the information in the newly acquired data. The inversions were carried out by using cokriging,which is a geostatistical method of estimation that minimizes the error variance by applying cross-correlation between several variables. In this study the estimated densities are derived by using boreholes gravity and known densities along the borehole. This method does not need iterative process and computes efficiently. The selection of examples demonstrates that this method has the ability to include physical property from borehole measurements in the inversion. The synthetic examples demonstrate the density variation along a borehole can be well determined without depth constraints in the inversion. The resolution of the recovered model can be further improved by including the densities along the borehole for inversion. However,this capability decreases dramatically with the increasing of distance between the anomalous body and the borehole.
基金supported by the National Major Research High Performance Computing Program of China[grant number 2016YFB0200800]the National Natural Science Foundation of China[grant number 41676185]the NOAA Climate Program Office[grant number NA14OAR4310216]
文摘Satellite-derived surface radiative fluxes have been recently improved and extended.However,the accuracy of recent satellite-derived surface radiative fluxes in the Arctic is not well characterized.Here,the authors assess the accuracy of the net surface radiative flux （NETSRF） in the Arctic,focusing on the ice-covered ocean,for three satellite products against four in situ measurements collected from different areas in the Arctic.The three satellite products are the Surface Radiation Budget project （SRB）,the International Satellite Cloud Climatology Project （ISCCP）,and the Extended AVHRR Polar Pathfinder version-2 （APP-x）.Our comparisons suggest that：（1） in terms of the overall bias,root-mean-square error,and correlation,the NETSRF of ISCCP is closer to in situ observations than that of SRB and APP-x;（2） in terms of the diurnal variation of the biases,it is not very clear which satellite product is superior to the others;and （3） in terms of the interannual variability of the bias,the NETSRF of ISCCP is more accurate than that of SRB and APP-x.This comparison may provide useful guidance to the community as to which data-set may provide the smallest bias in NETSRF
基金supported by the National Basic Research Program of China(Grant No.2013CB733303)National Natural Science Foundation of China(Grant Nos.41274010,41371335)supported by PA-SB ESA EO Project Campaign of"Development of methods for Forest Biophysical Parameters Inversion Using POLIn SAR Data"(Grant No.ID.14655)
文摘In this paper, we propose the novel method of complex least squares adjustment （CLSA） to invert vegetation height accurately using single-baseline polarimetric synthetic aperture radar interferometry （PollnSAR） data. CLSA basically estimates both volume-only coherence and ground phase directly without assuming that the ground-to-volume amplitude radio of a particular polarization channel （e.g., HV） is less than -10 dB, as in the three-stage method. In addition, CLSA can effectively limit errors in interferometric complex coherence, which may translate directly into erroneous ground-phase and volume-only coherence estimations. The proposed CLSA method is validated with BioSAR2008 P-band E-SAR and L-band SIR-C PollnSAR data. Its results are then compared with those of the traditional three-stage method and with external data. It implies that the CLSA method is much more robust than the three-stage method.
