A series of heavy rainfall events occurred over the Yangtze River Valley(YRV)in summer 2014,which were modulated by the 10-20-day quasi-biweekly oscillation(QBWO).Thus,the strongest QBWO cycle for the period 10-24 Jul...A series of heavy rainfall events occurred over the Yangtze River Valley(YRV)in summer 2014,which were modulated by the 10-20-day quasi-biweekly oscillation(QBWO).Thus,the strongest QBWO cycle for the period 10-24 July was used as a representative case to reveal the dynamical mechanism for the QBWO of the YRV rainfall from the potential vorticity(PV)perspective and based on MERRA-2 reanalysis data.The quasi-biweekly YRV rainfall was found to depend closely on the QBWO of the upper-tropospheric South Asian high(SAH),with the SAH configuration modified by the southward-intruding midlatitude high PV stream along with southwestward-advected high PV,altering the divergent condition over the YRV.Quantitative diagnoses for the anomalous vertical motion demonstrated that,in the wet phase of the QBWO cycle,the upper-tropospheric southward-intruding high PV stream acted as a positive PV advection,while negative PV advection was generated due to the lower-tropospheric southerlies,thereby forming a positive vertical gradient of horizontal PV advection to induce evident isentropic-displacement ascending motion.On the other hand,the southward-intruding high PV stream extended downward to the middle troposphere,causing the isentropic surfaces to become more sloping,thus producing a strong isentropic-gliding ascending component.Subsequently,the stronger diabatic heating-related ascending motion was induced to generate positive rainfall anomalies over the YRV.The opposite situation arose in the dry phase,with weak descending motion in magnitude.展开更多
New energy development is essential to achieving carbon peaks and neutrality and promoting green technological innovation.Identifying the causal relationship between new energy demonstration city construction and gree...New energy development is essential to achieving carbon peaks and neutrality and promoting green technological innovation.Identifying the causal relationship between new energy demonstration city construction and green technological innovation is crucial for the expansion and promotion of new energy demonstration cities.In this study,we take the construction of new energy demonstration cities as a quasi-natural experiment,study their impact on green technological innovation using difference-indifference(DID),and conduct a robustness test using DID after propensity score matching(PSM-DID).The research results indicate the following:First,energy structure optimization can significantly improve the level of urban green technological innovation(this result was shown to be valid using PSM-DID and other tests involving the effects of placebo and instrumental variables).Second,new energy demonstration city construction mainly improves the level of urban green technological innovation through technology research and development,the improvement of the industrial innovation environment,and the promotion of environmental performance.Third,the impact of energy structure optimization on green technological innovation has regional,financial,and economic development heterogeneity.Finally,new energy demonstration city policy affects the flow of capital,labor,technology,and other production factors to pilot areas according to new energy demonstration city policy,forming a“siphon effect”.The carbon reduction effect of new energy demonstration city construction is greater than its pollution reduction effect.Given the results of the study,policy recommendations to promote the expansion of new energy demonstration cities are proposed.展开更多
基金jointly supported by the Strategic Priority Re-search Program of the Chinese Academy of Sciences[grant number XDB40000000]the National Key Research and Development Program of China[grant number 2018YFC1506004]the National Natural Science Foundation of China[grant numbers 41730963 and 41876020].
文摘A series of heavy rainfall events occurred over the Yangtze River Valley(YRV)in summer 2014,which were modulated by the 10-20-day quasi-biweekly oscillation(QBWO).Thus,the strongest QBWO cycle for the period 10-24 July was used as a representative case to reveal the dynamical mechanism for the QBWO of the YRV rainfall from the potential vorticity(PV)perspective and based on MERRA-2 reanalysis data.The quasi-biweekly YRV rainfall was found to depend closely on the QBWO of the upper-tropospheric South Asian high(SAH),with the SAH configuration modified by the southward-intruding midlatitude high PV stream along with southwestward-advected high PV,altering the divergent condition over the YRV.Quantitative diagnoses for the anomalous vertical motion demonstrated that,in the wet phase of the QBWO cycle,the upper-tropospheric southward-intruding high PV stream acted as a positive PV advection,while negative PV advection was generated due to the lower-tropospheric southerlies,thereby forming a positive vertical gradient of horizontal PV advection to induce evident isentropic-displacement ascending motion.On the other hand,the southward-intruding high PV stream extended downward to the middle troposphere,causing the isentropic surfaces to become more sloping,thus producing a strong isentropic-gliding ascending component.Subsequently,the stronger diabatic heating-related ascending motion was induced to generate positive rainfall anomalies over the YRV.The opposite situation arose in the dry phase,with weak descending motion in magnitude.
基金supported by the National Natural Science Foundation of China (No. 91320201 and No. 61471262)the International (Regional) Collaborative Key Research Projects (No. 61520106002)
基金the National Social Science Fund of China(22CJL004).
文摘New energy development is essential to achieving carbon peaks and neutrality and promoting green technological innovation.Identifying the causal relationship between new energy demonstration city construction and green technological innovation is crucial for the expansion and promotion of new energy demonstration cities.In this study,we take the construction of new energy demonstration cities as a quasi-natural experiment,study their impact on green technological innovation using difference-indifference(DID),and conduct a robustness test using DID after propensity score matching(PSM-DID).The research results indicate the following:First,energy structure optimization can significantly improve the level of urban green technological innovation(this result was shown to be valid using PSM-DID and other tests involving the effects of placebo and instrumental variables).Second,new energy demonstration city construction mainly improves the level of urban green technological innovation through technology research and development,the improvement of the industrial innovation environment,and the promotion of environmental performance.Third,the impact of energy structure optimization on green technological innovation has regional,financial,and economic development heterogeneity.Finally,new energy demonstration city policy affects the flow of capital,labor,technology,and other production factors to pilot areas according to new energy demonstration city policy,forming a“siphon effect”.The carbon reduction effect of new energy demonstration city construction is greater than its pollution reduction effect.Given the results of the study,policy recommendations to promote the expansion of new energy demonstration cities are proposed.
