Analysis Of Ionospheric TEC Anomaly Along Typhoon Track

The ionosphere is an important component of the earth's environment,which has both positive and negative effects on people's life.In order to give full play to the advantages of the ionosphere and avoid the adverse effects of its disturbance,the research on the ionosphere has always been a hot topic.Total electron content is often used to describe the shape of the ionosphere and characterize the changes of the ionosphere.To analyze the variation of TEC is an important angle to analyze the temporal and spatial distribution characteristics of the ionosphere.The state of the ionosphere is affected by many factors.Typhoon is one of the factors that cause ionospheric disturbance.Taking the typhoon event as the link,TEC is selected as an important parameter to show the change of ionospheric.Focusing on the abnormal characteristics of the ionosphere over the path of typhoon,and exploring the temporal and spatial variation law of TEC,so as to provide a reference for further describing the coupling relationship between typhoon and ionosphere.The main research work and results of this paper is as follows:(1)The selection,acquisition and preprocessing methods of Ionospheric TEC data are introduced.Based on the global total electron content grid data with spatial resolution of 5 °(Longitude)× 2.5 °(Latitude)and temporal resolution of 2 h released by IGS,the Ionospheric TEC at the reference point of typhoon path is calculated by bilinear interpolation method.(2)The anomalous characteristics of Ionospheric TEC time series during typhoon are studied.In this paper,the theoretical basis of the sliding quartile method is introduced.And the principle of anomaly extraction of the Ionospheric TEC by using the sliding quartile method is also introduced.The results show that: the Ionospheric TEC anomalies first appear seven days before the typhoon onset,and last until one day after the typhoon disappeared.The anomalies appear at 0:00-8:00 UTC and 18:00-22:00 UTC with the highest frequency.The influence of typhoon on the ionosphere before typhoon formation is greater than after.The greater the maximum wind speed of typhoon,the stronger the influence on the ionosphere.The abnormal attribute of TEC anomaly is uncertain,most of them coexist with positive and negative anomalies.When both positive and negative anomalies exist,the anomaly of the maximum belongs to negative anomaly.(3)The anomalous characteristics of the spatial distribution of Ionospheric TEC during typhoon track are studied.Based on the analysis of Ionospheric TEC time series anomaly,further study the spatial distribution of Ionospheric TEC anomaly during typhoon track.The results show that: the anomaly area will move from West to East with the passage of time.The anomaly area will be highly consistent with the typhoon path,which directly proves that the occurrence of typhoon weather must have an impact on the ionosphere.From the extraction results of spatial distribution,the specific period of abnormal occurrence is highly similar to the anomaly detection results of time series.The abnormal probability of 18:00-22:00 UTC is higher.The abnormal rate of change increases with the expansion of the abnormal area.The peak of abnormal rate of change with the highest frequency appears at the time when the abnormal area is the largest.The abnormal probability of 18:00 UTC is higher.The peak value of the relative rate of change appears on the typhoon path or in the southwest direction of the typhoon path,with the highest frequency.The difference in specific location may be related to the typhoon's own wind speed,moving path and other factors.(4)The TEC anomaly characteristics of the path of typhoon with the same wind force are studied.The influence of typhoon with the same level on the ionosphere is compared.The results show that: The longer the life cycle of typhoon with the same wind intensity is,the lower the impact on ionosphere and the lower the peak value of the rate of change is.The influence of typhoon with the same wind intensity on the ionosphere under the condition of 5-8 days typhoon life cycle is very similar from the perspective of TEC relative change rate.