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
The amplitudes of the Earth＇s free oscillations have a close relationship to earthquake focal mechanisms. Focal mechanisms of large earthquakes can be well analyzed and constrained with observations of long period fr...The amplitudes of the Earth＇s free oscillations have a close relationship to earthquake focal mechanisms. Focal mechanisms of large earthquakes can be well analyzed and constrained with observations of long period free oscillations. Although the 2013 Lushan earthquake was only moderately sized, observable spherical normal modes were excited and clearly observed by a su- perconductive gravimeter and a broadband seismometer. We compare observed free oscillations with synthetic normal modes corresponding to four different focal mechanisms for the Lushan earthquake. The results show that source parameters can be analyzed and constrained by spherical normal modes in a 2.3-5 mHz frequency band. The scalar seismic moment M~ has a major influence on the amplitudes of free oscillations; additionally, the strike, dip, rake and depth of the hypocenter have mi- nor influences. We found that the synthetic modes corresponding to the focal mechanism determined by the Global Centroid Moment Tensor show agreement to the observed modes, suggesting that earthquake magnitudes predicted in this way can readily reflect the total energy released by the earthquake. The scalar seismic moment obtained by far-field body wave inver- sion is significantly underestimated. Focal mechanism solutions can be improved by joint inversion of far- and near-field data.展开更多
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. 2014CB845902)National Natural Science Foundation of China (Grant Nos. 41174022, 4127408 and 41021003)
文摘The amplitudes of the Earth＇s free oscillations have a close relationship to earthquake focal mechanisms. Focal mechanisms of large earthquakes can be well analyzed and constrained with observations of long period free oscillations. Although the 2013 Lushan earthquake was only moderately sized, observable spherical normal modes were excited and clearly observed by a su- perconductive gravimeter and a broadband seismometer. We compare observed free oscillations with synthetic normal modes corresponding to four different focal mechanisms for the Lushan earthquake. The results show that source parameters can be analyzed and constrained by spherical normal modes in a 2.3-5 mHz frequency band. The scalar seismic moment M~ has a major influence on the amplitudes of free oscillations; additionally, the strike, dip, rake and depth of the hypocenter have mi- nor influences. We found that the synthetic modes corresponding to the focal mechanism determined by the Global Centroid Moment Tensor show agreement to the observed modes, suggesting that earthquake magnitudes predicted in this way can readily reflect the total energy released by the earthquake. The scalar seismic moment obtained by far-field body wave inver- sion is significantly underestimated. Focal mechanism solutions can be improved by joint inversion of far- and near-field data.
