Ionospheric TEC （total electron content） time series are derived from GPS measurements at 13 stations around the epicenter of the 2008 Wenchuan earthquake. Defining anomaly bounds for a sliding window by quartile an...Ionospheric TEC （total electron content） time series are derived from GPS measurements at 13 stations around the epicenter of the 2008 Wenchuan earthquake. Defining anomaly bounds for a sliding window by quartile and 2-standard deviation of TEC values, this paper analyzed the characteristics of ionospheric changes before and after the destructive event. The Neyman-Pearson signal detection method is employed to compute the probabilities of TEC abnormalities. Result shows that one week before the Wenchuan earthquake, ionospheric TEC over the epicenter and its vicinities displays obvious abnormal disturbances, most of which are positive anomalies. The largest TEC abnormal changes appeared on May 9, three days prior to the seismic event. Signal detection shows that the largest possibility ofTEC abnormity on May 9 is 50.74%, indicating that ionospheric abnormities three days before the main shock are likely related to the preparation process of the Ms8.0 Wenchuan earthquake.展开更多
To detect seismic disturbances in the lower ionosphere, we have used the signals of very-lowfrequency radio transmitters and natural radio signals—electromagnetic emission of lightning discharges—atmospherics. On ea...To detect seismic disturbances in the lower ionosphere, we have used the signals of very-lowfrequency radio transmitters and natural radio signals—electromagnetic emission of lightning discharges—atmospherics. On earlier results of observation of atmospherics, it was obtained that the earthquake effects are displayed as weight-hourly amplitude increases on the day of event or within 3 days after them. Possible earthquake precursors are also manifested as one-day (within one to several hours) increases in the amplitude of atmospherics on average 5 - 12 days before the event. Analysis shows that seismic effects in the amplitude of atmospherics have been observed in the case of sufficiently strong (magnitude M > 4.5) and not very deep (usually no deeper than 50 km) earthquakes. The effects of the events of the earthquake with magnitude of 8.2 occurring in the Sea of Okhotsk on 24.05.13 not far from the Kamchatka Peninsula at a depth of 609 km considered in this work have shown that even deep earthquakes may have precursors in the form of disturbances in the lower ionosphere.展开更多
Thirty strong Madden–Julian Oscillation（MJO） events in boreal winter 1982–2001 are selected to investigate the triggering processes of MJO convection over the western equatorial Indian Ocean（IO）.These MJO events...Thirty strong Madden–Julian Oscillation（MJO） events in boreal winter 1982–2001 are selected to investigate the triggering processes of MJO convection over the western equatorial Indian Ocean（IO）.These MJO events are classified into three types,according to their dynamic and thermodynamic precursor signals in situ.In Type I,a remarkable increase in low-level moisture occurs,on average,7 days prior to the convection initiation.This low-level moistening is mainly due to the advection of the background mean moisture by easterly wind anomalies over the equatorial IO.In Type II,lower-tropospheric ascending motion anomalies develop,on average,4 days prior to the initiation.The cause of this ascending motion anomaly is attributed to the anomalous warm advection,set up by a suppressed MJO phase in the equatorial IO.In Type III,there are no clear dynamic and thermodynamic precursor signals in situ.The convection might be triggered by energy accumulation in the upper layer associated with Rossby wave activity fluxes originated from the midlatitudes.展开更多
东亚夏季风强度的变化与中国雨带和旱涝分布密切相关。为了做好东亚夏季风强度的短期气候预测,采用小波分析、Lanczos滤波器、交叉检验等方法,研究了东亚夏季风强度的多尺度变化特征,在年际与年代际尺度上分别寻找了它在前冬海温场、200...东亚夏季风强度的变化与中国雨带和旱涝分布密切相关。为了做好东亚夏季风强度的短期气候预测,采用小波分析、Lanczos滤波器、交叉检验等方法,研究了东亚夏季风强度的多尺度变化特征,在年际与年代际尺度上分别寻找了它在前冬海温场、200 h Pa纬向风场上的前兆信号,并利用最优子集回归建立了东亚夏季风强度的多尺度统计物理预测模型。结果表明:东亚夏季风强度存在准4年、准13年和准43年的周期振荡。年际尺度上,前冬赤道东太平洋(10°N^10°S,160°W^80°W)海温与东亚夏季风强度有最强的显著负相关,且它与东亚夏季风强度在200 h Pa纬向风场上的前兆信号有较强的负相关;年代际尺度上,南半球60°S与35°S附近200 h Pa纬向风之差与东亚夏季风强度有最强的显著正相关,且它与东亚夏季风强度在热带印度洋、低纬度东南太平洋、低纬度南大西洋的海温及亚洲副热带200 h Pa纬向风等前兆信号有强的正相关。通过探讨这两个前兆因子对东亚夏季风强度的预测意义,揭示了他们影响东亚夏季风强度年际和年代际变化的可能物理过程。所建立的东亚夏季风强度多尺度最优子集回归预测模型,不仅对东亚夏季风强度的年际变化具有较好的预测能力,而且对异常极值年份也具有一定的预测能力。展开更多
基于主成分回归法,利用1981—2010年黑龙江省15个地面气象站夏季降水观测资料、1980—2015年NCEP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research)再分析资料和NOAA(National Oceanic a...基于主成分回归法,利用1981—2010年黑龙江省15个地面气象站夏季降水观测资料、1980—2015年NCEP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research)再分析资料和NOAA(National Oceanic and Atmospheric Administration)月平均海表温度资料,建立了黑龙江省夏季降水统计预测模型,并分析了影响黑龙江省夏季降水主模态的前兆信号。结果表明:影响黑龙江省夏季降水主模态异常型前兆信号为前一年11月新地岛和喀拉海以南地区的高度场、前冬北太平洋中部海温和加利福尼亚附近区域海温的反相变化、南印度洋的异常海温。1981—2010年逐年交叉回报检验和4 a独立样本预测检验均表明,建立的降水预测模型对黑龙江省夏季降水具有较好的预报能力,并在2015年实现业务化,对2015年黑龙江省夏季降水的预测效果较好,具有一定的参考价值。展开更多
基金supported by the Key Technology Research and Development Program of China (2008BAC35B02)
文摘Ionospheric TEC （total electron content） time series are derived from GPS measurements at 13 stations around the epicenter of the 2008 Wenchuan earthquake. Defining anomaly bounds for a sliding window by quartile and 2-standard deviation of TEC values, this paper analyzed the characteristics of ionospheric changes before and after the destructive event. The Neyman-Pearson signal detection method is employed to compute the probabilities of TEC abnormalities. Result shows that one week before the Wenchuan earthquake, ionospheric TEC over the epicenter and its vicinities displays obvious abnormal disturbances, most of which are positive anomalies. The largest TEC abnormal changes appeared on May 9, three days prior to the seismic event. Signal detection shows that the largest possibility ofTEC abnormity on May 9 is 50.74%, indicating that ionospheric abnormities three days before the main shock are likely related to the preparation process of the Ms8.0 Wenchuan earthquake.
文摘To detect seismic disturbances in the lower ionosphere, we have used the signals of very-lowfrequency radio transmitters and natural radio signals—electromagnetic emission of lightning discharges—atmospherics. On earlier results of observation of atmospherics, it was obtained that the earthquake effects are displayed as weight-hourly amplitude increases on the day of event or within 3 days after them. Possible earthquake precursors are also manifested as one-day (within one to several hours) increases in the amplitude of atmospherics on average 5 - 12 days before the event. Analysis shows that seismic effects in the amplitude of atmospherics have been observed in the case of sufficiently strong (magnitude M > 4.5) and not very deep (usually no deeper than 50 km) earthquakes. The effects of the events of the earthquake with magnitude of 8.2 occurring in the Sea of Okhotsk on 24.05.13 not far from the Kamchatka Peninsula at a depth of 609 km considered in this work have shown that even deep earthquakes may have precursors in the form of disturbances in the lower ionosphere.
基金supported by the China National 973 Project Grant No.2015CB453200)the National Natural Science Foundation of China Grant Nos.41475084 and 41230527+1 种基金the Office of Naval Research Grant No.N000141210450the International Pacific Research Center(IPRC) sponsored by the Japan Agency for Marine-Earth Science and Technology
文摘Thirty strong Madden–Julian Oscillation（MJO） events in boreal winter 1982–2001 are selected to investigate the triggering processes of MJO convection over the western equatorial Indian Ocean（IO）.These MJO events are classified into three types,according to their dynamic and thermodynamic precursor signals in situ.In Type I,a remarkable increase in low-level moisture occurs,on average,7 days prior to the convection initiation.This low-level moistening is mainly due to the advection of the background mean moisture by easterly wind anomalies over the equatorial IO.In Type II,lower-tropospheric ascending motion anomalies develop,on average,4 days prior to the initiation.The cause of this ascending motion anomaly is attributed to the anomalous warm advection,set up by a suppressed MJO phase in the equatorial IO.In Type III,there are no clear dynamic and thermodynamic precursor signals in situ.The convection might be triggered by energy accumulation in the upper layer associated with Rossby wave activity fluxes originated from the midlatitudes.
文摘东亚夏季风强度的变化与中国雨带和旱涝分布密切相关。为了做好东亚夏季风强度的短期气候预测,采用小波分析、Lanczos滤波器、交叉检验等方法,研究了东亚夏季风强度的多尺度变化特征,在年际与年代际尺度上分别寻找了它在前冬海温场、200 h Pa纬向风场上的前兆信号,并利用最优子集回归建立了东亚夏季风强度的多尺度统计物理预测模型。结果表明:东亚夏季风强度存在准4年、准13年和准43年的周期振荡。年际尺度上,前冬赤道东太平洋(10°N^10°S,160°W^80°W)海温与东亚夏季风强度有最强的显著负相关,且它与东亚夏季风强度在200 h Pa纬向风场上的前兆信号有较强的负相关;年代际尺度上,南半球60°S与35°S附近200 h Pa纬向风之差与东亚夏季风强度有最强的显著正相关,且它与东亚夏季风强度在热带印度洋、低纬度东南太平洋、低纬度南大西洋的海温及亚洲副热带200 h Pa纬向风等前兆信号有强的正相关。通过探讨这两个前兆因子对东亚夏季风强度的预测意义,揭示了他们影响东亚夏季风强度年际和年代际变化的可能物理过程。所建立的东亚夏季风强度多尺度最优子集回归预测模型,不仅对东亚夏季风强度的年际变化具有较好的预测能力,而且对异常极值年份也具有一定的预测能力。
文摘基于主成分回归法,利用1981—2010年黑龙江省15个地面气象站夏季降水观测资料、1980—2015年NCEP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research)再分析资料和NOAA(National Oceanic and Atmospheric Administration)月平均海表温度资料,建立了黑龙江省夏季降水统计预测模型,并分析了影响黑龙江省夏季降水主模态的前兆信号。结果表明:影响黑龙江省夏季降水主模态异常型前兆信号为前一年11月新地岛和喀拉海以南地区的高度场、前冬北太平洋中部海温和加利福尼亚附近区域海温的反相变化、南印度洋的异常海温。1981—2010年逐年交叉回报检验和4 a独立样本预测检验均表明,建立的降水预测模型对黑龙江省夏季降水具有较好的预报能力,并在2015年实现业务化,对2015年黑龙江省夏季降水的预测效果较好,具有一定的参考价值。
