The leaf area index(LAI)is an important parameter to quantitatively describe the structure of vegetation and crops.Uncertainty in the relationship between the LAI and polarimetric parameters is the key problem for LAI...The leaf area index(LAI)is an important parameter to quantitatively describe the structure of vegetation and crops.Uncertainty in the relationship between the LAI and polarimetric parameters is the key problem for LAI estimation from polarimetric synthetic aperture radar(POLSAR)data.However,the existing POLSAR data have difficulties meeting the demand of the aforementioned research.This paper analyses the correlations between the LAI and the polarimetric parameters derived from Cloude and Freeman decompositions using simulated POLSAR data based on a coherent scattering model for maize and wheat.The results show:(1)The POLSAR data at C-band with a large incidence angle(40 degrees)are very suitable for finding the LAI for maize and wheat.(2)For maize there is a strong correlation between the scattering type angle and the LAI at C-band with a large incidence angle,and the coherency entropy,anisotropy,and the power of the double-bounce scattering power component also have significant correlations with the LAI.(3)For wheat at Cband with a high incidence angle,although the correlation coefficient is low,there is still a correlation between the entropy,anisotropy and LAI.Besides,the volume scattering is suitable for extracting the LAI for wheat at X-band.展开更多
The hail size discrimination algorithm(HSDA)and its capacity to identify hail in Shandong Province are analyzed to satisfy the localized requirement by China’s S-band dual-polarization radars.A modified HSDA is obtai...The hail size discrimination algorithm(HSDA)and its capacity to identify hail in Shandong Province are analyzed to satisfy the localized requirement by China’s S-band dual-polarization radars.A modified HSDA is obtained by using optimized membership function thresholds based on the statistics of Shandong hail data.The results are verified by a supercell storm process.1)The modified HSDA improves the identification of large hail and giant hail.The results are consistent with the analysis of the scattering and polarization parameter characteristics of different-size hails,the dynamic and microphysical characteristics for supercell,and the real situation.2)The horizontal and vertical hail-size distribution characteristics are consistent with the analysis about the growth process of larger hails and the precipitation particles filtering mechanisms in supercells.Small hail first forms at the suspension echo,then is injected into the larger hail growth area above the bounded weak echo area driven by updrafts,colliding with the abundant supercooled water in the KDP column.Finally,large hail and giant hail fall near the direction of the updrafts to form a strong echo wall,and giant hail falls 6–12 km from the central updraft.3)The maxima of the ZDR and KDP columns can be used to predict the hail-growth trend,which exceeds the−20°C isotherm for the heavy-hail growth stage at high-altitude in the supercell storm.When hail falls to the ground,the ZDR column shortens and the KDP column disappears,which provides the observation basis from polarimetric radars for the consumption of supercooled water by hail growth.展开更多
The shift of polarization orientation angle y at the maximum of co-polarized or cross-polarized back-scattering signature can be used to estimate the surface slopes. It has been utilized to generate the digital elevat...The shift of polarization orientation angle y at the maximum of co-polarized or cross-polarized back-scattering signature can be used to estimate the surface slopes. It has been utilized to generate the digital elevation mapping (DEM) and terrain topography using two-pass fully polarimetric SAR or interferometric SAR (INSAR) image data. This paper presents an approach to DEM inversion by using a single pass of polarimetric SAR data. The y shift is derived, by using the Mueller matrix solution, as a function of three Stokes parameters, Ivs, Ihs, Us, which are measured by the SAR polarimetry. Using the Euler angles transformation, the orientation angle y is related to both the range and azimuth angles of the tilted surface and radar viewing geometry, as has been discussed by many authors. When only a single-pass SAR data is available, the adaptive thresholding method and image morphological thinning algorithm for linear textures are proposed to first determine the azimuth angle. Then, making use of full multi-grid algorithm, both the range and azimuth angles are utilized to solve the Poisson equation of DEM to produce the terrain topography.展开更多
Historically,Lop Nur was a large and famous salt lake that acted as an important geographic position along the ancient‘Silk Road’,and was associated with the surrounding old civilizations,such as Loulan and Haitou.H...Historically,Lop Nur was a large and famous salt lake that acted as an important geographic position along the ancient‘Silk Road’,and was associated with the surrounding old civilizations,such as Loulan and Haitou.However,it dried up before 1972.It shows a clear‘Ear’feature on synthetic aperture radar(SAR)images.The objective of this paper is to interpret Lop Nur’s environmental evolution during its drying-up process based on an analysis of its sodium sedimentary feature.The genetic algorithm-partial least squares approach is introduced as a modeling method to retrieve the subsurface sodium content from polarimetric parameters obtained by Cloude decomposition.As a result,the R2 and root-mean-square error can reach 0.7 and 9.1 g/kg.It is suggested that the subsurface salt content was the primary reason for the bright-grey strips textures on SAR images.Furthermore,our results show that the sodium content along the same strip changed,with its distribution exhibiting consistency with the lake body’s movement driven by the strong wind.In future,high-precision topographical data will be considered,and should be helpful in the analysis of lake body movement.The method of this paper can also be applied in other similar dried salt lakes.展开更多
基金Natural Science Foundation of China(NO.40730525)973 Basic Research Program of China(NO.2009CB723906)Natural Science Foundation of China(NO.41001268).
文摘The leaf area index(LAI)is an important parameter to quantitatively describe the structure of vegetation and crops.Uncertainty in the relationship between the LAI and polarimetric parameters is the key problem for LAI estimation from polarimetric synthetic aperture radar(POLSAR)data.However,the existing POLSAR data have difficulties meeting the demand of the aforementioned research.This paper analyses the correlations between the LAI and the polarimetric parameters derived from Cloude and Freeman decompositions using simulated POLSAR data based on a coherent scattering model for maize and wheat.The results show:(1)The POLSAR data at C-band with a large incidence angle(40 degrees)are very suitable for finding the LAI for maize and wheat.(2)For maize there is a strong correlation between the scattering type angle and the LAI at C-band with a large incidence angle,and the coherency entropy,anisotropy,and the power of the double-bounce scattering power component also have significant correlations with the LAI.(3)For wheat at Cband with a high incidence angle,although the correlation coefficient is low,there is still a correlation between the entropy,anisotropy and LAI.Besides,the volume scattering is suitable for extracting the LAI for wheat at X-band.
基金supported by the Shandong Provincial Natural Science Foundation of China(Nos.ZR2020MD052 and ZR2022MD072)the National Natural Science Foundation of China(Grant No.41675029)+2 种基金East China Regional Collaborative Innovation Fund for Meteorological Science and Technology(No.QYHZ202101)Project of Xiamen Bureau of Science and Technology(No.3502Z20214ZD4005)Key Project of Shandong Meteorological Bureau(Nos.2021SDQXZ09 and SDLD2022-02)。
文摘The hail size discrimination algorithm(HSDA)and its capacity to identify hail in Shandong Province are analyzed to satisfy the localized requirement by China’s S-band dual-polarization radars.A modified HSDA is obtained by using optimized membership function thresholds based on the statistics of Shandong hail data.The results are verified by a supercell storm process.1)The modified HSDA improves the identification of large hail and giant hail.The results are consistent with the analysis of the scattering and polarization parameter characteristics of different-size hails,the dynamic and microphysical characteristics for supercell,and the real situation.2)The horizontal and vertical hail-size distribution characteristics are consistent with the analysis about the growth process of larger hails and the precipitation particles filtering mechanisms in supercells.Small hail first forms at the suspension echo,then is injected into the larger hail growth area above the bounded weak echo area driven by updrafts,colliding with the abundant supercooled water in the KDP column.Finally,large hail and giant hail fall near the direction of the updrafts to form a strong echo wall,and giant hail falls 6–12 km from the central updraft.3)The maxima of the ZDR and KDP columns can be used to predict the hail-growth trend,which exceeds the−20°C isotherm for the heavy-hail growth stage at high-altitude in the supercell storm.When hail falls to the ground,the ZDR column shortens and the KDP column disappears,which provides the observation basis from polarimetric radars for the consumption of supercooled water by hail growth.
文摘The shift of polarization orientation angle y at the maximum of co-polarized or cross-polarized back-scattering signature can be used to estimate the surface slopes. It has been utilized to generate the digital elevation mapping (DEM) and terrain topography using two-pass fully polarimetric SAR or interferometric SAR (INSAR) image data. This paper presents an approach to DEM inversion by using a single pass of polarimetric SAR data. The y shift is derived, by using the Mueller matrix solution, as a function of three Stokes parameters, Ivs, Ihs, Us, which are measured by the SAR polarimetry. Using the Euler angles transformation, the orientation angle y is related to both the range and azimuth angles of the tilted surface and radar viewing geometry, as has been discussed by many authors. When only a single-pass SAR data is available, the adaptive thresholding method and image morphological thinning algorithm for linear textures are proposed to first determine the azimuth angle. Then, making use of full multi-grid algorithm, both the range and azimuth angles are utilized to solve the Poisson equation of DEM to produce the terrain topography.
基金This work was funded by the National Natural Science Foundation of China[grant number 41571363][grant number 41431174]+4 种基金[grant number U1303285][grant number 41201346][grant number 61471358]the fund of the State Key Laboratory of Remote Sensing Science[grant number Y1Y00201KZ]and major special industry application projects[grant number 05-Y30B02–9001–13/15–03].
文摘Historically,Lop Nur was a large and famous salt lake that acted as an important geographic position along the ancient‘Silk Road’,and was associated with the surrounding old civilizations,such as Loulan and Haitou.However,it dried up before 1972.It shows a clear‘Ear’feature on synthetic aperture radar(SAR)images.The objective of this paper is to interpret Lop Nur’s environmental evolution during its drying-up process based on an analysis of its sodium sedimentary feature.The genetic algorithm-partial least squares approach is introduced as a modeling method to retrieve the subsurface sodium content from polarimetric parameters obtained by Cloude decomposition.As a result,the R2 and root-mean-square error can reach 0.7 and 9.1 g/kg.It is suggested that the subsurface salt content was the primary reason for the bright-grey strips textures on SAR images.Furthermore,our results show that the sodium content along the same strip changed,with its distribution exhibiting consistency with the lake body’s movement driven by the strong wind.In future,high-precision topographical data will be considered,and should be helpful in the analysis of lake body movement.The method of this paper can also be applied in other similar dried salt lakes.
