Group drought and flood sudden change event identification method and system

Abstract

The invention discloses a group drought and flood sudden change event identification method and system, and relates to the technical field of natural disaster risk assessment, and the method comprises the following steps: S1, collecting day-by-day rainfall data of a certain time period; s2, calculating an early-stage rainfall index (IAP) based on the day-by-day rainfall data, and standardizing the early-stage rainfall index (IAP) to obtain a standardized early-stage rainfall index (IsAP); s3, based on a run-length theory, respectively screening out a drought event and a flood event; s4, identifying a single-station drought and flood sudden change event, and calculating drought and flood sudden change intensity and sudden change point parameters; and S5, on the basis of the single-station drought and flood sudden change event, identifying a group-occurring drought and flood sudden change event, defining the comprehensive strength of the group-occurring drought and flood sudden change event, and performing grade judgment. The method is clear in physical significance, high in operability and capable of accurately recognizing the group drought and flood sudden turning events.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural disaster risk assessment, and particularly relates to a group drought-flood abrupt change event identification method and system. BACKGROUND

[0002] Drought and flood disasters, as main meteorological disasters, are the most economically damaging natural disasters in the world. With climate warming, the intensity and frequency of drought and flood events have increased. If drought and flood occur alternately in a short time, drought-flood abrupt change events are formed, including "drought to flood" and "flood to drought". Drought-flood abrupt change is a manifestation of seasonal precipitation anomaly, caused by the dramatic change and extreme imbalance of precipitation in a short time.

[0003] OBJECT

[0004] At present, the identification of drought-flood abrupt change events is mainly concentrated on the single station level, and cannot identify drought-flood abrupt change events in a regional range. The collected flood and drought data of each station in the region cannot be effectively planned and processed, and accurate, rigorous and unified data support cannot be provided for the study of drought-flood abrupt change phenomena and their occurrence rules. The monitoring and prediction ability of drought-flood abrupt change events is insufficient. SUMMARY

[0005] The present application aims to provide a group drought-flood abrupt change event identification method and system to solve the problems in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a group drought-flood abrupt change event identification method and system, comprising the following steps: S1, collecting daily precipitation data in a certain period; S2, calculating a previous precipitation index based on the daily precipitation data I AP , and calculating a standardized previous precipitation index I SAP ; S3, screening out drought events and flood events based on the run theory; S4, single-station drought-flood abrupt change event identification, calculating drought-flood abrupt change intensity and abrupt change point parameters; S5, group drought-flood abrupt change event identification, defining the comprehensive intensity and making grade determination; S6, a group drought-flood abrupt change event identification system.

[0007] Preferably, in S2, the previous precipitation index (PPI) is calculated according to the following formula: I AP ; In the formula,​I AP (i) is the daily precipitation in the past P (i-d) ) is accumulated with weight, the weight of daily precipitation is 1, and the weight of precipitation decreases exponentially with the increase of time distance K d . d k (0 < a < 1) is the attenuation coefficient, k k The value of a indicates the influence of the previous precipitation on I AP , the greater the value of a, the greater the influence of the previous precipitation. k

[0008] Standardized previous precipitation index: the calculation method is referred to the calculation method of standardized precipitation index in Appendix D of Meteorological Drought Grading (GB / T 20481-2017), and the standardized previous precipitation index S4 is obtained I SAP . I SAP The value less than -0.5 indicates that the drought index is reached, I SAP and the value greater than or equal to 0.5 indicates that the flood index is reached.

[0009] Preferably, the identification of the S3 drought event and the flood event is as follows: Drought event identification: when I SAP the drought index is reached for n1 consecutive days, it is determined that a drought event occurs, the starting day of the drought event is the date when the drought index is reached on the first day, and during the drought occurrence period, when I SAP the drought index is not reached for n2 consecutive days, the drought event ends, the ending date is the date when the drought index is reached on the last day, and the time period from the start to the end of the drought event is the drought duration; Flood event identification: when I SAP the flood index is reached for n3 consecutive days, it is determined that a flood event occurs, the starting day of the flood event is the date when the flood index is reached on the first day, and during the flood occurrence period, when I SAP the flood index is not reached for n4 consecutive days, the flood event ends, the ending date is the date when the flood index is reached on the last day, and the time period from the start to the end of the flood event is the flood duration; The above n1, n2, n3, and n4 can be determined according to the actual situation; Preferably, the identification of the S4 single-station drought-flood rapid transition event and the calculation method of the drought-flood rapid transition intensity and the rapid transition point parameter are as follows: ​​​If a drought event and a flood event occur successively in a period, and the time interval between the end of the drought event and the beginning of the flood event is less than n days, it is judged as a "drought-to-flood" event, otherwise, it is judged as a "flood-to-drought" event. n can be determined according to the actual situation.

[0010] The turning point is the date when the drought or flood event after the turning point starts.

[0011] The turning intensity is the intensity of the drought and flood events before and after the turning point I SAP The absolute value of the difference between the average values is calculated as follows: ; In the above formula, n5 and n6 are the number of days of the drought or flood period before and after the turning point, respectively.

[0012] Preferably, the method for identifying the group occurrence of drought-flood turning events in S5 is as follows: more than 10% of the stations in the region occur drought-flood turning events within 5 days, and the distance between adjacent stations is not more than 200 km, which is defined as a group occurrence of drought-flood turning events.

[0013] The method for defining the comprehensive intensity of the group occurrence of drought-flood turning events is as follows: the average intensity and the average influence range of a group occurrence of drought-flood turning events are considered comprehensively to determine the comprehensive intensity; the calculation method is as follows: Z = I 0.6 × N 0.4 The above I is the average intensity of the group occurrence of drought-flood turning events, which is specifically the average value of the drought-flood turning intensities of the stations constituting the group occurrence of drought-flood turning events; N is the influence range of the group occurrence of drought-flood turning events, which is represented by the percentage of the number of stations where the group occurrence of drought-flood turning events occurs to the total number of stations.

[0014] The comprehensive intensity of the group occurrence of drought-flood turning events is evaluated and divided into grades: the percentile method is adopted, based on the last three complete decades (1991-2020), the comprehensive intensity of the group occurrence of drought-flood turning events is divided into four grades according to the following table standards: general, relatively strong, strong and extremely strong, as shown in Table 1, the threshold values of each grade of events are given, and according to the threshold values, the group occurrence of drought-flood turning events can be graded.

[0015] Table 1: Division of grades and standards for comprehensive intensity of group occurrence of drought-flood turning events

[0016] Preferably, the S6 group of one group of drought and flood sudden change event identification system, including data acquisition module, drought and flood index calculation module, single station drought and flood sudden change event identification module and group of drought and flood sudden change event identification module. The data acquisition module is communicatively coupled with the drought and flood index calculation module; the single station drought and flood sudden change event identification module is communicatively coupled with the drought and flood index calculation module; the group of drought and flood sudden change event identification module is communicatively coupled with the single station drought and flood sudden change event identification module.

[0017] Preferably, the data acquisition module is used for data acquisition and data preprocessing of daily precipitation data; The drought and flood index calculation module calculates the antecedent precipitation index based on the data provided by the data acquisition module and standardizes it; The single station drought and flood sudden change event identification module identifies the drought and flood sudden change event based on the standardized antecedent precipitation index data delivered by the drought and flood index calculation module, calculates the drought and flood sudden change intensity and the sudden change point parameter; The group of drought and flood sudden change event identification module realizes the group of drought and flood sudden change event identification work based on the data delivered by the single station drought and flood sudden change event identification module, and calculates the comprehensive intensity of the group of drought and flood sudden change event.

[0018] Compared with the prior art, the beneficial effects of the present application are: When the present application is used, a practical and effective group of drought and flood sudden change event identification method is provided according to actual data, the physical meaning is clear, the operability is strong, and technical support can be provided for further research on drought and flood sudden change phenomenon and its occurrence rule, which has important significance for improving the understanding and monitoring ability of drought and flood sudden change event, and can provide scientific reference for impact assessment and adaptive strategy planning of drought and flood sudden change event. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The present application is a schematic diagram of the meteorological station and its altitude data in the Haihe River Basin; Figure 2 It is the identification result of part of the drought event in the Haihe River Basin; Figure 3 It is the identification result of part of the flood event in the Haihe River Basin; Figure 4 It is a schematic diagram of the single station drought and flood sudden change (drought to flood) identification method of the present application; Figure 5 It is a schematic diagram of the station distribution and intensity of the strong group of drought and flood sudden change event in the Haihe River Basin on August 9-12, 1984; Figure 6 It is a schematic diagram of the group of drought and flood sudden change event identification system. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] Example: Figures 1-6 As shown, the present invention provides a technical solution for a method and system for identifying sudden drought-flood transition events. Taking the Haihe River Basin as an example, the complete calculation steps are explained: S1. Collect daily precipitation data for a certain period of time. In the embodiment, daily precipitation data of 159 national meteorological stations in the Haihe River Basin from 1961 to 2023 are used; the research area, station distribution and station altitude data are shown in Figure 1 The diagram shows the meteorological stations in the Haihe River Basin and their altitude data. The altitude unit is m.

[0022] S2. Calculate the previous precipitation index based on daily precipitation data ( I AP ), and normalize it to obtain the standardized antecedent precipitation index ( Is AP ).

[0023] Previous precipitation index ( I AP ), calculated as follows:

[0024] Where: I AP (i) is the daily precipitation in the past ( P (i-d) )by K d The weight is accumulated, the weight of precipitation on the day is 1, and the weight of precipitation on the day is 1. d The weight of increasing precipitation decreases exponentially. k (0< k ≤1) is the attenuation coefficient, k The value indicates the effect of the previous precipitation on I AP The impact of k The larger the value, the greater the impact of the previous precipitation. k Take 0.9.

[0025] Standardized Antecedent Precipitation Index ( Is AP ): The calculation method refers to the calculation method of the standardized precipitation index in Appendix D of the Meteorological Drought Grade (GB / T 20481-2017) to obtain the standardized pre-precipitation index.I SAP . I SAP value less than -0.5 indicates reaching the drought index, I SAP value greater than or equal to 0.5 indicates reaching the flood index.

[0026] S3, based on the run theory, respectively, screening out the Haihe River basin drought event and flood event.

[0027] Drought event identification: when I SAP reaching the drought index for consecutive n1 days, it is determined that a drought event occurs, the starting day of the drought event is the date of reaching the drought index on the first day, and during the drought period, when I SAP the drought event ends when the drought index is not reached for consecutive n2 days, the ending date is the date of reaching the drought index on the last day, and the duration of the drought event from the beginning to the end is the drought duration; Flood event identification: when I SAP reaching the flood index for consecutive n3 days, it is determined that a flood event occurs, the starting day of the flood event is the date of reaching the flood index on the first day, and during the flood period, when I SAP the flood event ends when the flood index is not reached for consecutive n4 days, the ending date is the date of reaching the flood index on the last day, and the duration of the flood event from the beginning to the end is the flood duration; The above n1, n2, n3, n4 can be determined according to the actual situation; in the embodiment, n1=n2=10, n3=n4=5; To verify the discrimination ability of the standardized antecedent precipitation index on drought and flood events, the embodiment takes Jizhou District of Tianjin as an example for comparative analysis. Figure 2 and Figure 3 are the identification results of larger drought and flood events of Jizhou National Meteorological Station, respectively, and it can be seen that the present application can accurately identify drought and flood events.

[0028] S4, single-station drought and flood rapid transition event identification: if a drought event and a flood event occur in a period, and the time interval between the end of the drought event and the beginning of the flood event is less than n days, then it is judged as a "drought to flood" event, otherwise, it is judged as a "flood to drought" event, n can be determined according to the actual situation, in the embodiment, n=5. This embodiment only gives the result of "drought to flood". Figure 4 Schematic diagram of single-station drought and flood rapid transition (drought to flood) identification method.

[0029] The calculation method of drought and flood rapid transition intensity and rapid transition point parameters is as follows: The turning point is the date when the drought or flood event starts after the turning point.

[0030] The turning intensity is the intensity of the drought and flood events before and after the turning point I SAP The absolute value of the difference between the average values is calculated as follows:

[0031] In the above formula, n5 and n6 are the number of days of drought or flood period before and after the turning point (in the example, the drought period is taken as 44 days if it exceeds 44 days, and the actual number of days if it is less than 44 days, and the flood period is taken as 5 days).

[0032] S5, group drought and flood turning event recognition, and define its comprehensive intensity, grade determination. The method of group drought and flood turning event recognition is as follows: within 5 days, more than 10% (in the example, 15 stations are taken) of the stations in the basin occur drought and flood turning events, and the distance between adjacent stations does not exceed 200 km, which is defined as a group drought and flood turning event.

[0033] The comprehensive intensity of group drought and flood turning event: the average intensity and the average influence range of a group drought and flood turning event are considered to determine the comprehensive intensity, and the calculation method is as follows: Z = I 0.6 × N 0.4 The above I is the average intensity of group drought and flood turning event, specifically the average value of the drought and flood turning intensity of each station constituting the group drought and flood turning event; N is the influence range of group drought and flood turning event, which is represented by the percentage of the number of stations of a group drought and flood turning event to the total number of stations.

[0034] The comprehensive intensity of group drought and flood turning event is evaluated and divided into grades: the percentile method is adopted, based on the last three whole decades (1991-2020), the comprehensive intensity of group drought and flood turning event is divided into four levels according to the following table standard: general, stronger, strong and very strong, as shown in Table 1, the threshold value of each grade event is given, and the threshold value is used to classify the group drought and flood turning events.

[0035] Table 1 Classification and standard of comprehensive intensity of group drought and flood turning event

[0036] According to the identification method provided by S1-S5, through statistical calculation, from 1961 to 2023, there were 115 group drought and flood rapid transition events in the Haihe River Basin. According to the classification of group drought and flood rapid transition event comprehensive intensity evaluation, there were 5 times of super strong drought and flood rapid transition events, 18 times of strong group drought and flood rapid transition events, 27 times of relatively strong group drought and flood rapid transition events and 65 times of general group drought and flood rapid transition events. Among them, 5 times of super strong drought and flood rapid transition events occurred on August 9-12, 1984, May 2-6, 1988, September 9-13, 1997, June 12-16, 2001 and September 16-20, 2005. Among the 5 strong group drought and flood rapid transition events, 3 occurred in the southern part of the Haihe River Basin, including the Daqing River system, Ziya River system, Zhangwei River system, Heilonggang Yundong and Tuhai Majia River system, and 2 occurred in the eastern part of the Haihe River Basin, including the Luanhe River system, Beisanhe River system, Haihe River main stream, lower reaches of Daqing River system and Ziya River system, Heilonggang Yundong and Tuhai Majia River system. The strongest group drought and flood rapid transition event occurred on August 9-11, 1984 Figure 5 According to the records of Beijing, Tianjin and Hebei volumes of China Meteorological Disaster Encyclopedia, on August 9-11, 1984, heavy rain occurred in Beijing, Tianjin, Tangshan, Qinhuangdao, Hengshui, Cangzhou, Langfang, Shijiazhuang and Heilonggang River Basin, floods occurred in many places, which reversed the previous drought situation and caused a large-scale drought and flood rapid transition event. The evaluation results of group drought and flood rapid transition are basically consistent with the actual situation.

[0037] Since drought and flood rapid transition is a compound extreme event, its suddenness and loss and impact are usually greater than that of drought or flood disaster alone, and group drought and flood rapid transition event is an extreme phenomenon that occurs in a certain area within a short time, its influence is wider and the influence is greater. The present application provides a practical and effective identification method for group drought and flood rapid transition event, which has clear physical meaning and strong operability, can provide support for further research on drought and flood rapid transition phenomenon and its occurrence regularity, and has important significance for improving the understanding and monitoring ability of drought and flood rapid transition event, and can provide scientific reference for impact assessment and adaptation strategy planning of drought and flood rapid transition event.

[0038] Specifically, as shown in Figure 6 A group drought and flood rapid transition event identification system is composed of a data acquisition module, a drought and flood index calculation module, a single station drought and flood rapid transition event identification module and a group drought and flood rapid transition event identification module, wherein the data acquisition module and the drought and flood index calculation module are communicatively coupled; the single station drought and flood rapid transition event identification module and the drought and flood index calculation module are communicatively coupled; the group drought and flood rapid transition event identification module and the single station drought and flood rapid transition event identification module are communicatively coupled, so as to realize stable and effective delivery of data.

[0039] The data acquisition module is used for data acquisition and data preprocessing of daily scale precipitation data; the drought-flood index calculation module calculates drought-flood index based on the data provided by the data acquisition module and standardizes the drought-flood index; the single-station drought-flood abrupt change event identification module identifies drought-flood abrupt change events based on the standardized drought-flood abrupt change index data delivered by the drought-flood index calculation module, calculates the parameters of drought-flood abrupt change intensity and abrupt change point; the group drought-flood abrupt change event identification module realizes group drought-flood abrupt change event identification based on the data delivered by the single-station drought-flood abrupt change event identification module, and calculates the comprehensive intensity of the group drought-flood abrupt change event. Based on the single-station drought-flood abrupt change event, the group drought-flood abrupt change event is defined, and the identification method is given. Through the group drought-flood abrupt change event identification system, the single-station drought-flood abrupt change events in a time period collected in a systematic manner are taken as parameters for calculation, the comprehensive intensity of the group drought-flood abrupt change event is judged, the physical meaning is clear, the operability is strong, the group drought-flood abrupt change event can be accurately identified, the support for in-depth research on the drought-flood abrupt change phenomenon and its occurrence rule is provided, and it is of great significance for improving the understanding and monitoring ability of the drought-flood abrupt change event.

[0040] It will be obvious to a person skilled in the art that the application is not limited to the details of the above-described exemplary embodiments, but that the application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. The embodiments should therefore be considered in all respects as illustrative and not restrictive, the scope of the application being defined by the appended claims rather than by the above description, and it is therefore intended that all changes and modifications that fall within the meaning and range of equivalents of the claims be embraced therein. Any reference signs in the claims should not be construed as limiting the claims to the figures in which the reference signs are used.

Claims

1. A method for identifying clustered drought-flood transition events, characterized by: The following steps are involved: S1. Collect daily precipitation data for a certain period of time; S2. Calculate the previous precipitation index based on daily precipitation data I AP , and then calculate the standardized antecedent precipitation index I SAP ; S3. Based on the travel theory, drought events and flood events are screened out respectively; S4, identification of drought-flood transition events at a single station, calculation of drought-flood transition intensity and transition point parameters; S5. Identify clustered drought-flood transition events, define their comprehensive intensity, and make level determinations; S6. A system for identifying clustered drought-flood transition events.

2. The method and system for identifying mass drought-flood transition events according to claim 1, characterized in that: In step S2, the calculation method of the early precipitation index is as follows: (1) Where: I AP (i) is the daily precipitation in the past ( P (i-d) )by K d The weight is accumulated, the weight of precipitation on the day is 1, and the weight of precipitation on the day is 1. d The weight of increasing precipitation decreases exponentially. k (0< k ≤1) is the attenuation coefficient, k The value indicates the effect of the previous precipitation on I AP The impact of k The larger the value, the greater the impact of previous precipitation. Standardized Antecedent Precipitation Index ( I SAP ): The calculation method refers to the calculation method of the standardized precipitation index in Appendix D of the Meteorological Drought Grade (GB / T 20481-2017) to obtain the standardized pre-precipitation index. I SAP . I SAP A value less than -0.5 indicates that the drought index has been reached. I SAP A value greater than or equal to 0.5 indicates that the flood index has been reached.

3. The method for identifying a sudden drought-flood transition event according to claim 1, wherein: The S3 is based on the run theory and uses the standardized antecedent precipitation index to identify drought and flood events; Drought event identification: I SAP If the drought index is reached for n1 consecutive days, it is determined that a drought event has occurred. The starting day of the drought event is the day when the drought index is reached on the first day. I SAP The drought event ends when the drought index is not met for n2 consecutive days. The end date is the date when the drought index is met on the last day. The time from the beginning to the end of the drought event is the drought duration. Flood event identification: I SAP If the flood index is reached for n3 consecutive days, it is determined that a flood event has occurred. The starting date of the flood event is the date when the flood index is reached on the first day. During the flood period, I SAP The flood event ends when the flood index is not met for n4 consecutive days. The end date is the date on which the flood index is met on the last day. The time from the beginning to the end of the flood event is the flood duration. The above n1, n2, n3, and n4 can be determined according to local actual conditions.

4. The method for identifying a sudden drought-flood transition event according to claim 1, wherein: The method for identifying drought-flood transition events at a single station in S4 and calculating drought-flood transition intensity and transition point parameters is as follows: If a drought event and a flood event occur successively in a certain period, and the time interval between the end of the drought event and the beginning of the flood event is less than n days, then it is judged as a "drought-to-flood" event. Otherwise, it is judged as a "flood-to-drought" event. n can be determined according to the actual local situation. The turning point is the date when the drought or flood event begins after the turning point. The intensity of the sudden change is the drought and flood events before and after the sudden change I SAP The absolute value of the difference between the means is calculated as follows: ； In the above formula, n5 and n6 are the number of days of drought or flood before and after the sudden change, respectively.

5. The method for identifying a sudden drought-flood transition event according to claim 1, characterized in that: The method for identifying clustered drought-flood transition events in S5 is as follows: within 5 days, if more than 10% of the stations in the region experience drought-flood transition events, and the distance between adjacent stations does not exceed 200 km, it is defined as a clustered drought-flood transition event. The comprehensive intensity of a cluster of drought-flood transition events is defined as follows: the average intensity and average impact range of a cluster of drought-flood transition events are considered to determine the comprehensive intensity; the calculation method is as follows: Z = I 0.6 × N 0.4 above I is the average intensity of cluster drought-flood transition events, specifically the average of the drought-flood transition intensities of each station that constitutes the cluster drought-flood transition event; N is the impact range of the cluster drought-flood sudden change event, which is expressed as the percentage of the number of stations where the cluster drought-flood sudden change event occurs to the total number of stations. Comprehensive intensity evaluation and classification of clustered drought-flood transition events: Based on the percentile method and the last three full years (1991-2020), the comprehensive intensity of clustered drought-flood transition events is divided into four levels according to the standards in the following table: general, strong, strong and extremely strong. The details are shown in Table 1. The thresholds of each level of events are given. According to the thresholds, all clustered drought-flood transition events can be classified. Table 1 Classification and standards of comprehensive intensity of clustered drought-flood transition events 6. A system for identifying sudden drought-flood transition events, applicable to the method for identifying sudden drought-flood transition events according to any one of claims 1 to 5, characterized in that: It includes data collection module, drought and flood index calculation module, single-station drought and flood sudden transition event identification module and group drought and flood sudden transition event identification module.

7. The system for identifying sudden drought-flood transition events according to claim 6, characterized in that: The data acquisition module is communicatively coupled to the drought-flood index calculation module; the single-station drought-flood rapid transition event identification module is communicatively coupled to the drought-flood index calculation module; and the mass drought-flood rapid transition event identification module is communicatively coupled to the single-station drought-flood rapid transition event identification module.

8. The system for identifying sudden drought-flood transition events according to claim 6, characterized in that: The data acquisition module is used for data acquisition and data preprocessing of daily precipitation data; The drought and flood index calculation module calculates the previous precipitation index based on the data provided by the data acquisition module and standardizes it; The single-station drought-flood transition event identification module identifies drought-flood transition events based on the standardized previous precipitation index data transmitted by the drought-flood index calculation module, and calculates the drought-flood transition intensity and the transition point parameters. The cluster drought-flood transition event recognition module realizes cluster drought-flood transition event recognition based on the data transmitted by the single-station drought-flood transition event recognition module, and calculates the comprehensive intensity of the cluster drought-flood transition event.

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