The melting process of ice crystal particles has a significant effect on weather forecasting and global climate.Millimeter waveband is an excellent frequency range for exploring the optical characteristics of ice crys...The melting process of ice crystal particles has a significant effect on weather forecasting and global climate.Millimeter waveband is an excellent frequency range for exploring the optical characteristics of ice crystal particles.In this study,a new nonspherical and inhomogeneous ice crystal particle model is built based on the melting process of ice crystal particles.The single-scattering characteristics of ice crystal particles with different frequencies,sizes,shapes and ice crystal content(ICC)are investigated using the discrete dipole approximation(DDA)method.The results show that the single-scattering characteristics of ice crystal particles are closely related to the equivalent radius,frequency,morphology and mixing state.The single-scattering properties of the particles change regularly with the melting process of the ice crystal particles.Specifically,in the early stage of the ice crystal particle melting process,the single-scattering characteristics of ice crystal particles change significantly.With further melting,the change in the single-scattering characteristics of ice crystal particles gradually slows down when the ICC is less than 0.5.The results also show that in the early stage of the melting process,the shape of the ice crystal particles has a huge influence on the single-scattering characteristics of the particles,and in the late stage of the melting process,the single-scattering characteristics of the ice crystal particles are basically independent of the morphology of the ice crystal nuclei.This means that the influence of the morphology of the ice crystal nuclei needs to be considered in phases when simulating the scattering characteristics of the melting ice crystal particles.In summary,the results of this study should improve our understanding of the effect of size parameter,morphology and mixing state on the millimeter-wave scattering characteristics of ice clouds during the melting process and provide a reference for the remote sensing inversion of ice cloud microphysical characteristics.展开更多
In this study,waveform data obtained from Western Sichuan Seismic Array(WSSA)in China was utilized to reveal the temporal variations in coda attenuation around the eastern Tibet Plateau and Western Sichuan.Based on th...In this study,waveform data obtained from Western Sichuan Seismic Array(WSSA)in China was utilized to reveal the temporal variations in coda attenuation around the eastern Tibet Plateau and Western Sichuan.Based on the single-scattering model,coda attenuation factor QC^(-1) is calculated in narrower overlapping frequency bands at 1.0-24 Hz by measuring the coda decay rates for local earthquakes before and after the Wenchuan mainshock.The temporal variations in coda attenuation are investigated within three periods.The periodⅠlasted from January 2007 to the end of 2007.The periodⅡlasted from January 2008 till Wenchuan earthquake.The periodⅢlasted from the mainshock to the end of 2008.The resulted temporal variations demonstrate an increase in average QC^(-1) by approximately 35%-45%in the vicinity of Longmenshan and 30%-35%in Sichuan Basin after the Wenchuan earthquake in lower frequency bands within 1.25-8 Hz.On the contrary,the average QC^(-1) is shown to decrease by approximately10%-18%in southern segment of Longmenshan,15%-38%in the Chuan-Dian block,and 10-12%in the South China block.These results are confirmed by a statistical t-test at 99.9%confidence level No statistically significant change in QC^(-1)(<10%)is found in the Songpan-Ganzi block after the mainshock.Temporal variations of coda attenuation differ significantly in individual blocks after the mainshock.The coda attenuation is proposed to be a beacon to tectonic static stress changes associated with the Wenchuan earthquake.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2019YFA0706004)the Key Projects of Science and Technology Research of Henan Province(Grant No.222102320087)the Key Scientific Research Project of Colleges and Universities in Henan Province(Grant No.25B170004).
文摘The melting process of ice crystal particles has a significant effect on weather forecasting and global climate.Millimeter waveband is an excellent frequency range for exploring the optical characteristics of ice crystal particles.In this study,a new nonspherical and inhomogeneous ice crystal particle model is built based on the melting process of ice crystal particles.The single-scattering characteristics of ice crystal particles with different frequencies,sizes,shapes and ice crystal content(ICC)are investigated using the discrete dipole approximation(DDA)method.The results show that the single-scattering characteristics of ice crystal particles are closely related to the equivalent radius,frequency,morphology and mixing state.The single-scattering properties of the particles change regularly with the melting process of the ice crystal particles.Specifically,in the early stage of the ice crystal particle melting process,the single-scattering characteristics of ice crystal particles change significantly.With further melting,the change in the single-scattering characteristics of ice crystal particles gradually slows down when the ICC is less than 0.5.The results also show that in the early stage of the melting process,the shape of the ice crystal particles has a huge influence on the single-scattering characteristics of the particles,and in the late stage of the melting process,the single-scattering characteristics of the ice crystal particles are basically independent of the morphology of the ice crystal nuclei.This means that the influence of the morphology of the ice crystal nuclei needs to be considered in phases when simulating the scattering characteristics of the melting ice crystal particles.In summary,the results of this study should improve our understanding of the effect of size parameter,morphology and mixing state on the millimeter-wave scattering characteristics of ice clouds during the melting process and provide a reference for the remote sensing inversion of ice cloud microphysical characteristics.
基金supported by the National Natural Science Foundation of China(No.41874161 and No.41720104006)the Youth Innovation Promotion Association Foundation of the Chinese Academy of Sciences(No.2019069)Guangdong Provincial Key R&D Program(No.2019B111105002)。
文摘In this study,waveform data obtained from Western Sichuan Seismic Array(WSSA)in China was utilized to reveal the temporal variations in coda attenuation around the eastern Tibet Plateau and Western Sichuan.Based on the single-scattering model,coda attenuation factor QC^(-1) is calculated in narrower overlapping frequency bands at 1.0-24 Hz by measuring the coda decay rates for local earthquakes before and after the Wenchuan mainshock.The temporal variations in coda attenuation are investigated within three periods.The periodⅠlasted from January 2007 to the end of 2007.The periodⅡlasted from January 2008 till Wenchuan earthquake.The periodⅢlasted from the mainshock to the end of 2008.The resulted temporal variations demonstrate an increase in average QC^(-1) by approximately 35%-45%in the vicinity of Longmenshan and 30%-35%in Sichuan Basin after the Wenchuan earthquake in lower frequency bands within 1.25-8 Hz.On the contrary,the average QC^(-1) is shown to decrease by approximately10%-18%in southern segment of Longmenshan,15%-38%in the Chuan-Dian block,and 10-12%in the South China block.These results are confirmed by a statistical t-test at 99.9%confidence level No statistically significant change in QC^(-1)(<10%)is found in the Songpan-Ganzi block after the mainshock.Temporal variations of coda attenuation differ significantly in individual blocks after the mainshock.The coda attenuation is proposed to be a beacon to tectonic static stress changes associated with the Wenchuan earthquake.
