汉江流域是中国重要的调水水源区,研究其降水特征对防涝抗旱具有重要意义。基于汉江流域62个国家气象站降水资料及美国国家环境预报中心/国家大气研究中心(National Center for Envi⁃ronmental Prediction/National Center for Atmosphe...汉江流域是中国重要的调水水源区,研究其降水特征对防涝抗旱具有重要意义。基于汉江流域62个国家气象站降水资料及美国国家环境预报中心/国家大气研究中心(National Center for Envi⁃ronmental Prediction/National Center for Atmospheric Research,NCEP/NCAR)再分析资料,通过百分位数、相关分析和T-N波作用通量,探讨了2021年伏秋(8—10月)连汛期间汉江降水的季内差异特征及其与大气环流和海温的关系。结果表明:2021年伏秋期间,汉江上游流域出现破纪录降水,极端性强、总量大。降水在伏夏和秋季两个时段均偏多,但秋季的多雨区位置更偏北。伏夏期间,北大西洋经西伯利亚向东频散的Rossby波使得欧亚上空维持“两槽两脊”,冷空气较强,同时西太平洋副热带高压(简称“副高”)强势西伸,通过西南和偏东两支通道向北输送暖湿水汽;冷暖空气在高空急流南侧对峙并辐合上升,导致降水异常偏多。秋季,北太平洋频散的Rossby波使得欧亚上空维持“两槽一脊”,冷空气较弱;副高断裂导致水汽通道偏南,高空急流北抬使冷暖空气辐合上升位置偏北,造成雨区偏北。2021年汉江流域伏夏降水异常受热带东大西洋海温正异常影响,秋季受赤道中太平洋冷海温影响。展开更多
In late July and early August 2018,Northeast China suffered from extremely high temperatures,with the maxium temperature anomaly exceeding 6°C.In this study,the large-scale circulation features associated with th...In late July and early August 2018,Northeast China suffered from extremely high temperatures,with the maxium temperature anomaly exceeding 6°C.In this study,the large-scale circulation features associated with this heat wave over Northeast China are analyzed using station temperature data and NCEP–NCAR reanalysis data.The results indicate that strong anomalous positive geopotential height centers existed from the lower to upper levels over Northeast China,and the related downward motions were directly responsible for the extreme high-temperature anomalies.The northwestward shift of the western Pacific subtropical high(WPSH)and the northeastward shift of the South Asian high concurrently reinforced the geopotential height anomalies and descending flow over Northeast China.In addition,an anomalous Pacific–Japan pattern in the lower troposphere led to the northwestward shift of the WPSH,jointly favoring the anomalous geopotential height over Northeast China.Two wave trains emanating from the Atlantic region propagated eastwards along high latitudes and midlatitudes,respectively,and converged over Northeast China,leading to the enhancement of the geopotential height anomalies.展开更多
Motivated by ageostrophic interactions of wave and basic flow,the generalized relationships between 3-dimensional Eliassen-Palm flux and basic flows,which are suitable for small-amplitude and finite-amplitude disturba...Motivated by ageostrophic interactions of wave and basic flow,the generalized relationships between 3-dimensional Eliassen-Palm flux and basic flows,which are suitable for small-amplitude and finite-amplitude disturbances,are derived.The local area-averaged and density-weighted mean flows are chosen as the basic flows.Under the assumption that the steady basic flows vary slowly in time and space,a quasi-conservative law of small amplitude wave activity is derived from Ertel's potential vorticity equation in isentropic coordinates. The expressions of the new 3-D Eliassen-Palm flux and wave activity are presented in terms of Eulerian quantities so that they can be readily calculated by using observation data or model output data.展开更多
文摘汉江流域是中国重要的调水水源区,研究其降水特征对防涝抗旱具有重要意义。基于汉江流域62个国家气象站降水资料及美国国家环境预报中心/国家大气研究中心(National Center for Envi⁃ronmental Prediction/National Center for Atmospheric Research,NCEP/NCAR)再分析资料,通过百分位数、相关分析和T-N波作用通量,探讨了2021年伏秋(8—10月)连汛期间汉江降水的季内差异特征及其与大气环流和海温的关系。结果表明:2021年伏秋期间,汉江上游流域出现破纪录降水,极端性强、总量大。降水在伏夏和秋季两个时段均偏多,但秋季的多雨区位置更偏北。伏夏期间,北大西洋经西伯利亚向东频散的Rossby波使得欧亚上空维持“两槽两脊”,冷空气较强,同时西太平洋副热带高压(简称“副高”)强势西伸,通过西南和偏东两支通道向北输送暖湿水汽;冷暖空气在高空急流南侧对峙并辐合上升,导致降水异常偏多。秋季,北太平洋频散的Rossby波使得欧亚上空维持“两槽一脊”,冷空气较弱;副高断裂导致水汽通道偏南,高空急流北抬使冷暖空气辐合上升位置偏北,造成雨区偏北。2021年汉江流域伏夏降水异常受热带东大西洋海温正异常影响,秋季受赤道中太平洋冷海温影响。
基金supported by the National Natural Science Foundation of China under Grant 41775073
文摘In late July and early August 2018,Northeast China suffered from extremely high temperatures,with the maxium temperature anomaly exceeding 6°C.In this study,the large-scale circulation features associated with this heat wave over Northeast China are analyzed using station temperature data and NCEP–NCAR reanalysis data.The results indicate that strong anomalous positive geopotential height centers existed from the lower to upper levels over Northeast China,and the related downward motions were directly responsible for the extreme high-temperature anomalies.The northwestward shift of the western Pacific subtropical high(WPSH)and the northeastward shift of the South Asian high concurrently reinforced the geopotential height anomalies and descending flow over Northeast China.In addition,an anomalous Pacific–Japan pattern in the lower troposphere led to the northwestward shift of the WPSH,jointly favoring the anomalous geopotential height over Northeast China.Two wave trains emanating from the Atlantic region propagated eastwards along high latitudes and midlatitudes,respectively,and converged over Northeast China,leading to the enhancement of the geopotential height anomalies.
基金the National Natural Science Foundation of China under Grant No.40175017the Innovation Project of Chinese Academy of Sciences under Grant No.KZCX3-SW-217
文摘Motivated by ageostrophic interactions of wave and basic flow,the generalized relationships between 3-dimensional Eliassen-Palm flux and basic flows,which are suitable for small-amplitude and finite-amplitude disturbances,are derived.The local area-averaged and density-weighted mean flows are chosen as the basic flows.Under the assumption that the steady basic flows vary slowly in time and space,a quasi-conservative law of small amplitude wave activity is derived from Ertel's potential vorticity equation in isentropic coordinates. The expressions of the new 3-D Eliassen-Palm flux and wave activity are presented in terms of Eulerian quantities so that they can be readily calculated by using observation data or model output data.
