Method and system for identifying heat wave-drought composite event, and electronic equipment

Abstract

The invention discloses a heat wave-drought composite event identification method and system and electronic equipment, and the method comprises the following steps: S0, determining a research region and a time period, collecting meteorological data, and carrying out the preprocessing; the method comprises the following steps: S1, constructing a peak value heat wave index PHI based on a peak value index and a high temperature index to define and identify a heat wave event; s2, calculating a standardized rainfall evapotranspiration index SPEI based on the rainfall and the potential evapotranspiration amount so as to define and identify a drought event; s3, based on a time overlapping principle, defining and identifying that a heat wave event occurring in a drought period is a heat wave-drought composite event; and S4, establishing a composite heat wave-drought grading standard, and classifying the severity of the identified composite event. According to the method, the influence of the air temperature peak value on the heat wave-drought composite event is fully considered, the occurrence process and severity level of the heat wave-drought composite event can be effectively and accurately identified, and technical support is provided for effectively taking sunstroke prevention and drought resistance measures.

Description

Technical Field

[0001] The present invention relates to the field of extreme weather and climate technology, and in particular to a method, system and electronic equipment for identifying a heat wave-drought compound event. Background Art

[0002] In recent years, the continuous increase in heatwave-drought combined events has attracted widespread attention. Both heatwaves and droughts are extremely destructive natural disasters. When heatwaves and droughts occur at the same time, the severity of the damage to water supply, agriculture, ecosystems, socio-economic activities and human health is much greater than that of a single disaster. Therefore, accurately identifying heatwave-drought combined events and their levels is crucial for disaster prevention.

[0003] At present, there is no clear definition of heat wave-drought combined events. Research on the identification of heat wave events is only based on the average temperature, while ignoring the impact of the peak temperature in the heat wave event and the relationship between the peak and the mean. This makes the previous definition of heat wave events have obvious limitations. In addition, the classification standard of composite events does not take into account the severity of heat waves and droughts at the same time. Therefore, it is difficult for existing technologies to effectively identify heat wave-drought combined events. Summary of the invention

[0004] The purpose of the present invention is to provide a method, system and electronic device for identifying a heat wave-drought compound event in view of the deficiencies in the prior art, so as to accurately identify the development process and severity level of a heat wave-drought compound event, and provide a certain scientific reference for the monitoring and prediction of a heat wave-drought compound event.

[0005] Technical solution: A method for identifying heat wave-drought composite events, comprising the following steps:

[0006] S0, determine the research area and time period, collect meteorological data and perform preprocessing;

[0007] S1, construct the peak heat wave index PHI to define and identify heat wave events;

[0008] S11, based on the relationship between the peak temperature in the past 3 days, the past 30 days and the long term, the peak index PT is constructed; the peak index PT consists of two parts, the first part PT 1 It indicates the ratio of the temperature in the past three days to the long-term peak temperature. The second part is PT 2 It represents the ratio of the peak temperature in the past 3 days to the peak temperature in the past 30 days. The formula involved is as follows:

[0009]

[0010] In the formula, i is the date sequence, T i is the daily maximum temperature (℃); E(T i ,T i-1 ,Ti-2 ) is the average of the daily maximum temperature in the past three days, indicating the peak temperature in the past three days; E(T i ,…,T i-n ) is the average daily maximum temperature over a period of 20 years or more, indicating the long-term temperature peak; E(T i ,…,T i-29 ) is the average of the daily maximum temperature in the past 30 days, indicating the peak temperature in the past 30 days;

[0011] S12, based on the relationship between the average temperature of the past 3 days, the past 30 days and the long term, the high temperature index MT is constructed; the high temperature index MT is divided into two parts, the first part MT 1 Indicates the difference between the average temperature of the past three days and the long-term temperature threshold. The second part MT 2 It represents the difference between the average temperature of the past three days and the average temperature of the past 30 days. The formula involved is as follows:

[0012]

[0013] Where, t i is the daily average temperature (℃), Indicates the average temperature of the past three days; t 95％ The 95th percentile of the daily average temperature for a period of 20 years or more, arranged in ascending order, is used as the long-term temperature threshold; It indicates the average temperature in the past 30 days;

[0014] S13, combining the peak index PT and the high temperature index MT to construct the peak heat wave index PHI; the peak heat wave index PHI is divided into two parts, the first part PHI 1 Indicates the relationship between the daily temperature in the past three days and the long-term temperature threshold and peak value. The second part PHI 2 It represents the relationship between the daily temperature in the past three days and the temperature in the past 30 days. The formula involved is as follows:

[0015]

[0016] Among them, PHI represents the peak heat wave index, and max() represents the maximum value;

[0017] S14, using the peak heat wave index PHI to define and identify heat wave events; defining that when the peak heat wave index PHI>0 for one day, a high temperature event is identified; when the peak high temperature index PHI>0 for three consecutive days, a heat wave event is identified; if the peak heat wave index PHI>0 for multiple three consecutive days, it is also identified as a single heat wave event.

[0018] S2, calculate the standardized precipitation evapotranspiration index (SPEI) to define and identify drought events;

[0019] S21, calculate monthly potential evapotranspiration based on the Thornthwaite method; the calculation formula for potential evapotranspiration PET is as follows:

[0020]

[0021] Where t e is the average monthly temperature (℃), and I is the annual temperature efficiency index: (m is the number of months), ζ is the function of the heat index: ζ = 67.5 × 10 -8 I 3 -77.1×10 -6 I 2 +0.0179I+0.492, C is the correction factor for converting the calculation period from month to day: Where d is the average monthly sunshine hours (h), and N is the number of days per month;

[0022] S22, the difference between monthly precipitation and potential evapotranspiration forms a precipitation and potential evapotranspiration difference series;

[0023] S23, normalize the difference sequence and calculate the cumulative function F(x) based on the 3-parameter log-logistic probability distribution;

[0024] S24, standardize the cumulative probability density to obtain the standardized precipitation evapotranspiration index SPEI. The SPEI index formula is as follows:

[0025]

[0026] In the formula, c0, c1, c2, d1, d2, d3 are all constants, ω is the probability weighted moment, When the cumulative probability P≤0.5, P=F(x); when the cumulative probability P>0.5, P=1-F(x);

[0027]

[0028] Where f(x) is the probability density function, F(x) is the probability distribution function, α is the scale parameter, β is the shape parameter, and γ is the origin parameter;

[0029] S25, the Standardized Precipitation Evapotranspiration Index (SPEI) is used to define and identify drought events; the Standardized Precipitation Evapotranspiration Index (SPEI) on a monthly scale is expanded to a daily scale, that is, the SPEI value of a certain day is the same as that of the month, and drought occurs on that day when the daily SPEI is ≤ -1.0.

[0030] S3, define and identify heatwave events occurring during drought periods as heatwave-drought composite events;

[0031] When one heat wave event occurs in a drought period, it is a heat wave-drought composite event; when multiple heat wave events occur in a drought period, multiple heat wave-drought composite events occur.

[0032] S4, establish a grading standard for combined heatwave-drought events to classify the severity of identified combined events;

[0033] S41. Establish a heat wave event classification standard to determine the severity level of heat wave events. The severity level of heat wave events is classified as follows: The PHI corresponding to the cumulative probability of 60% of the peak heat wave index (PHI) values ​​of all heat wave events during the study period is 60％ is the classification threshold, and the corresponding PHI when the PHI cumulative probability is 100% 100％ is the maximum value, if PHI≤PHI 60％ A mild heat wave will occur. If PHI 60％ <PHI≤PHI 100％ A severe heat wave occurred.

[0034] S42, establish a drought event classification standard and determine the severity level of drought events; the severity level of drought events is classified as follows: the standardized evapotranspiration index SPEI = -2.0 is used as the classification threshold, if -2.0<SPEI≤-1.0, a mild drought occurs, and if SPEI≤-2.0, a severe drought occurs.

[0035] S43, comprehensively identify the levels of heat waves and droughts in the composite event, establish the grade classification standard for heat wave-drought composite events, and determine the severity level of the composite event; the classification principle of heat wave-drought composite events is: if the heat wave and drought in the composite event are of the same level, the composite event is of that level; if the heat wave and drought in the composite event differ by one level, the composite event is of the corresponding intermediate level.

[0036] On the other hand, a heat wave-drought composite event recognition system is also provided, comprising:

[0037] The calculation module is used to calculate the peak heat wave index PHI and the standardized precipitation evapotranspiration index SPEI. Based on the daily average temperature and maximum temperature, the peak heat wave index PHI is calculated using the constructed peak heat wave index formula; based on the monthly precipitation, average temperature and sunshine hours, the potential evapotranspiration is calculated using the Thornthwaite method, and the standardized precipitation evapotranspiration index SPEI is calculated.

[0038] The first determination module is used to determine whether a heat wave-drought composite event occurs in a certain period of time. The peak heat wave index PHI and the standardized precipitation evapotranspiration index SPEI of a certain period of time are analyzed, and whether a heat wave or drought event occurs in a certain period of time is determined according to the critical value of the index; based on the overlapping relationship between the drought and heat wave events in a certain period of time, whether a heat wave-drought composite event occurs in a certain period of time is further determined.

[0039] The second determination module is used to determine the level of the heat wave-drought composite event. According to the level thresholds of the heat wave and drought, the levels of the heat wave and drought events in the composite event are determined. The level of the heat wave-drought composite event is determined according to the level classification standard of the composite event based on the levels of the heat wave and drought in the composite event.

[0040] On the other hand, an electronic device is also provided, comprising a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, they are used to execute the above-mentioned heat wave-drought combined event identification method.

[0041] On the other hand, a storage medium is also provided, on which program instructions are stored, and the program instructions are used to execute the above-mentioned heat wave-drought combined event identification method when running.

[0042] On the other hand, a computer program product is also provided, comprising computer program instructions, which are used to execute the above-mentioned heat wave-drought combined event identification method when running.

[0043] Compared with the prior art, the present invention has the following significant effects:

[0044] The present invention constructs a peak heat wave index PHI that includes a temperature peak function to accurately identify heat wave events, further defines heat wave events in drought periods as heat wave-drought composite events, and establishes a grade classification standard for heat wave-drought composite events, in order to more effectively, comprehensively and accurately identify the occurrence process and severity level of heat wave-drought composite events, provide theoretical support for the monitoring, forecasting and early warning of heat wave-drought composite events, reduce the negative impact of heat wave-drought composite events on agricultural production, ecosystems and human society, and provide guidance for real-time scheduling of water resources and disaster prevention and mitigation work in different regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the process of the heat wave-drought composite event identification method of the present invention;

[0046] Figure 2 is a schematic diagram of the results of the heat wave-drought compound event identification process of the site according to the embodiment of the present invention;

[0047] Figure 3It is a schematic diagram of the proportion of heat wave-drought composite events of different levels in the regions and stations described in the embodiments of the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0049] The purpose of the present invention is to provide a method, system, electronic device and storage medium for identifying a heat wave-drought composite event, aiming to accurately identify a heat wave-drought composite event. In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0050] Taking a certain area as an example, the flow chart is as follows Figure 1 As shown, the specific implementation steps are as follows:

[0051] Step C0, collects daily-scale meteorological station data such as average temperature, maximum temperature, precipitation and sunshine hours in a certain area during a statistical period, and pre-processes the original meteorological data; the specific processing steps are as follows:

[0052] Step C01, interpolate the missing values ​​in the original meteorological data; in the original series of average temperature, maximum temperature, precipitation and sunshine hours, if the number of missing days is less than or equal to 5 days, use the data of the previous and next days for linear interpolation; if the number of missing days is greater than 5 days and less than 30 days, use the multi-year average value of the same day to fill in the missing values. The missing values ​​in the original precipitation series are filled in with the multi-year average value of the same day.

[0053] Step C02, retain the daily average temperature and maximum temperature after interpolating the missing values ​​to calculate the heat wave peak index PHI, and convert the daily average temperature, precipitation and sunshine hours after interpolating the missing values ​​to the monthly scale to calculate the standardized precipitation evapotranspiration index SPEI; the average temperature of each month is the average value of the daily average temperature in each month, and the precipitation and sunshine hours of each month are the cumulative values ​​of the daily precipitation and sunshine hours in each month.

[0054] Step C1, construct the peak heat wave index PHI to define and identify heat wave events at each station;

[0055] The following steps C11 to C14 take a certain station in a certain area as an example, calculate the peak index and the high temperature index to obtain the peak heat wave index PHI of the station and identify the heat wave events during the statistical period of the station. The remaining stations in the area use the same steps C11 to C14 to identify the heat wave events that occurred during the statistical period.

[0056] Step C11, taking a station in a certain area as an example, construct a peak index PT based on the peak temperature relationship between the station in the past 3 days, the past 30 days and the long term; the peak index PT includes two parts, the first part PT 1 It indicates the ratio of the temperature in the past three days to the long-term peak temperature. The second part is PT 2 It represents the ratio of the peak temperature in the past 3 days to the peak temperature in the past 30 days. The formula involved is as follows:

[0057]

[0058] In the formula, i is the date sequence, T i is the daily maximum temperature (℃); E(T i ,T i-1 ,T i-2 ) is the average of the daily maximum temperature in the past three days, indicating the peak temperature in the past three days; E(T i ,…,T i-n ) is the average daily maximum temperature over a period of 20 years or more, indicating the long-term temperature peak; E(T i ,…,T i-29 ) is the average daily maximum temperature in the past 30 days, indicating the peak temperature in the past 30 days.

[0059] Step C12, construct a high temperature index MT based on the relationship between the average temperature of the station in the past 3 days, the past 30 days and the long term; the high temperature index MT is divided into two parts, the first part MT 1 Indicates the difference between the average temperature of the past three days and the long-term temperature threshold. The second part MT 2 It represents the difference between the average temperature of the past three days and the average temperature of the past 30 days. The formula involved is as follows:

[0060]

[0061] Where, t i is the daily average temperature (℃), Indicates the average temperature of the past three days; t 95％ The 95th percentile of the daily average temperature for a period of 20 years or more, arranged in ascending order, is used as the long-term temperature threshold; It indicates the average temperature in the past 30 days.

[0062] Step C13, combining the site peak index PT and the high temperature index MT to construct a peak heat wave index PHI; the peak heat wave index PHI is divided into two parts, the first part PHI 1 Indicates the relationship between the daily temperature in the past three days and the long-term temperature threshold and peak value. The second part PHI 2 It represents the relationship between the daily temperature in the past three days and the temperature in the past 30 days. The formula involved is as follows:

[0063]

[0064] Among them, PHI represents the peak heat wave index, and max() represents the maximum value.

[0065] Step C14, using the peak heat wave index PHI to define and identify the heat wave event of the site; defining that when the peak heat wave index PHI>0 for one day, it is identified as a high temperature event, when the peak high temperature index PHI>0 for three consecutive days, it is identified as a heat wave event, and if the peak heat wave index PHI>0 for multiple three consecutive days, it is also identified as a single heat wave event.

[0066] Step C2, calculate the standardized precipitation evapotranspiration index SPEI to define and identify drought events at each station;

[0067] Steps C21 to C25 are to take a certain station in a certain area as an example, calculate the standardized potential evapotranspiration index SPEI and identify drought events during the statistical period of the station, and the remaining stations in the area use the same steps C21 to C25 to identify drought events that occurred during the statistical period.

[0068] Step C21, taking a station in a certain area as an example, based on the monthly average temperature and sunshine hours of the station, the Thornthwaite equation is used to calculate the monthly potential evapotranspiration PET j , the specific calculation formula is:

[0069]

[0070] Where, t e is the average monthly temperature; I is the annual temperature efficiency index: (m is the number of months); ζ is the function of the heat index: ζ = 67.5 × 10 -8 I 3 -77.1×10 -6 I 2 +0.0179I+0.492; C is the correction factor for converting the calculation period from month to day: Where d is the average monthly sunshine hours (h), and N is the number of days per month.

[0071] Step C22: calculate the monthly precipitation P of the station. j Potential evaporation emission PETj The difference between the precipitation and potential evapotranspiration constitutes the sequence D j ;

[0072] D j =P j -PET j (5)

[0073] Where D j is the monthly difference between precipitation and potential evapotranspiration, P j is the monthly precipitation, PET j is the monthly potential evapotranspiration.

[0074] Step C23, normalize the precipitation and potential evapotranspiration difference sequence D of the station j , use the 3-parameter log-logistic probability distribution and find the cumulative function F(x) of the log-logistic probability distribution:

[0075]

[0076] Where f(x) is the probability density function, F(x) is the probability distribution function, α is the scale parameter, β is the shape parameter, and γ is the origin parameter.

[0077] Step C24, standardize the cumulative probability density and calculate the standardized precipitation evapotranspiration index SPEI at a certain time of the station:

[0078]

[0079]

[0080] Where ω is the probability weighted moment, P is the cumulative probability (when P≤0.5, P=F(x); when P>0.5, P=1-F(x)), c 0 、c 1 、c 2 and 1 ,d 2 ,d 3 They are all constants, usually taken as c 0 =2.515527, c 1 =0.802853, c 2 =0.010328, d 1 =1.432788, d 2 =0.189269, d 3 =0.0013.

[0081] Step C25, expand the monthly scale standardized precipitation evapotranspiration index SPEI to the daily scale, that is, the SPEI value of a certain day is the same as that of the current month, and define that when the daily SPEI is ≤ -1.0, drought occurs at the station on that day.

[0082] Step C3, defining and identifying heat wave events occurring during drought periods as heat wave-drought composite events;

[0083] Heatwave-drought composite events are identified at each station in a region according to the following definition: heatwave events occurring during drought events are heatwave-drought composite events; if heatwave events occur during the drought period, composite drought-heatwave events occur during the overlapping period of drought and heatwave events; if heatwave events do not occur during the drought period, composite events do not occur during the drought period. When one or more heatwave events (PHI>0 for 3 consecutive days or more) occur during the drought period (SPEI≤-1.0), it is one or more heatwave-drought composite events.

[0084] A typical station in a certain area was selected, and the identification process of heat wave-drought compound events from May to September 2000 was as follows: Figure 2 shown.

[0085] Step C4, establishing a grading standard for composite heat waves and droughts, and classifying the severity of composite events at each identified station;

[0086] Taking a station in a certain area as an example, a classification standard for heat wave-drought composite events suitable for the station is established to determine the severity level of the heat wave-drought composite event at the station. The classification standard is as follows:

[0087]

[0088] Note: PHI 60％ is the PHI critical value corresponding to the cumulative probability of PHI values ​​of all heat wave events at the station during the statistical period of 60%; PHI 100％ is the PHI critical value corresponding to the corresponding cumulative probability of 100%.

[0089] The criteria and methods for determining the severity of heat wave-drought events at other stations in the region are the same as above. Determine the severity level of heat wave-drought events at all stations in a region, and count the proportions of heat wave-drought events at different severity levels at all stations in the region, to provide reference and support for the response strategy for heat wave-drought events in the region.

[0090] The proportion of heat wave-drought composite event levels in a certain region and a typical station from May to September from 1980 to 2017 is as follows Figure 3 shown.

[0091] This embodiment also provides a heat wave-drought compound event recognition system, the recognition system comprising:

[0092] The calculation module is used to calculate the peak heat wave index PHI and the standardized precipitation evapotranspiration index SPEI of each station in a certain area. Based on the meteorological data sets such as the average temperature, maximum temperature, precipitation and sunshine hours of a certain area during the statistical period, the peak heat wave index PHI and the standardized precipitation evapotranspiration index SPEI of a certain area during the statistical period are calculated.

[0093] The first determination module is used to determine whether a heat wave-drought composite event occurs in a certain period of time. The peak heat wave index PHI and the standardized precipitation evapotranspiration index SPEI of each station in the target area are analyzed, and whether a heat wave or drought event occurs in a certain period of time is determined based on the index critical value. Based on the overlapping relationship between drought and heat wave events in a certain period of time, it is further determined whether a heat wave-drought composite event occurs in a certain period of time.

[0094] The second determination module is used to determine the level of heat wave-drought composite events at each station in a certain area. According to the level thresholds of heat wave and drought, the levels of heat wave and drought events in the composite events at each station are determined. The level of heat wave-drought composite events at each station is divided according to the following principles: if the heat wave and drought in the composite event are of the same level, the composite event is of that level; if the heat wave and drought in the composite event differ by one level, the composite event is of the corresponding intermediate level.

[0095] This embodiment further provides an electronic device, which includes a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, they are used to execute the above-mentioned heat wave-drought combined event identification method.

[0096] In addition, the present embodiment further provides a storage medium. Program instructions are stored on the storage medium. When the program instructions are executed by a computer or a processor, the computer or the processor executes the corresponding steps of the method for identifying the level of the heat wave-drought compound event in the embodiment of the present application, and is used to implement the corresponding modules in the heat wave-drought compound event level identification system or the corresponding modules in the electronic device according to the present embodiment. The storage medium may include, for example, a memory card of a smart phone, a storage component of a tablet computer, a hard disk of a personal computer, a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a portable read-only memory (CD-ROM), a USB memory, or any combination of the above storage media. The computer-readable storage medium may be any combination of one or more computer-readable storage media.

[0097] This embodiment also provides a computer program product, including computer program instructions, which are used to execute the above-mentioned heat wave-drought combined event identification method when running.

[0098] A person of ordinary skill in the art can understand the specific implementation and beneficial effects of the above-mentioned heat wave-drought combined event identification system, electronic device, storage medium and computer program product by reading the above-mentioned detailed description of the heat wave-drought combined event identification method, and will not be described in detail here for the sake of brevity.

[0099] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0100] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for identifying heat wave-drought composite events, characterized in that: The steps include: S0, determine the research area and time period, collect meteorological data and perform preprocessing; S1, construct the peak heat wave index PHI based on the peak index and high temperature index to define and identify heat wave events; S2, calculate the Standardized Precipitation Evapotranspiration Index (SPEI) based on precipitation and potential evapotranspiration to define and identify drought events; S3, based on the principle of temporal overlap, heatwave events occurring during drought periods are defined and identified as heatwave-drought composite events; S4. Establish a grading standard for combined heatwave-drought events to classify the severity of identified combined events.

2. The method for identifying a heat wave-drought composite event according to claim 1, characterized in that: The step S1 comprises: S11, construct the peak index PT based on the relationship between the temperature peaks in the past 3 days, the past 30 days and the long term; S12, constructs the high temperature index MT based on the relationship between the average temperature of the past 3 days, the past 30 days and the long term; S13, combining the peak index PT and the high temperature index MT to construct the peak heat wave index PHI; S14, the peak heat wave index (PHI) is used to define and identify heat wave events.

3. The method for identifying heat wave-drought combined events according to claim 2, characterized in that: The peak index PT in step S11 includes two parts. The first part PT1 represents the ratio of the temperature peak in the past three days to the long-term temperature peak, and the second part PT2 represents the ratio of the temperature peak in the past three days to the temperature peak in the past 30 days. The formula is as follows: Where i is a date sequence; T i is the daily maximum temperature, in °C; E(T i ,T i-1 ,T i-2 ) is the average of the daily maximum temperature in the past three days, indicating the peak temperature in the past three days; E(T i ,…,T i-n ) is the average daily maximum temperature over a period of 20 years or more, indicating the long-term temperature peak; E(T i ,…,T i-29 ) is the average of the daily maximum temperature in the past 30 days, indicating the peak temperature in the past 30 days; In step S12, the high temperature index MT is divided into two parts. The first part MT1 represents the difference between the average temperature of the past three days and the long-term temperature threshold, and the second part MT2 represents the difference between the average temperature of the past three days and the average temperature of the past 30 days. The formula is as follows: Where, t i is the daily average temperature in °C; Indicates the average temperature of the past three days; t 95％ The 95th percentile of the daily average temperature for a period of 20 years or more, arranged in ascending order, is used as the long-term temperature threshold; It indicates the average temperature in the past 30 days; In step S13, the peak heat wave index PHI is divided into two parts. The first part PHI1 represents the relationship between the temperature in the past three days and the long-term temperature threshold and peak value. The second part PHI2 represents the relationship between the temperature in the past three days and the temperature in the past 30 days. The formula is as follows: Among them, PHI represents the peak heat wave index, and max() represents the maximum value; In step S14, it is defined that when the peak heat wave index PHI>0 for one day, a high temperature event occurs; when the peak high temperature index PHI>0 for three consecutive days, a heat wave event occurs; if the peak heat wave index PHI>0 for multiple three consecutive days, a single heat wave event also occurs.

4. The method for identifying a heat wave-drought composite event according to claim 1, characterized in that: Step S2 includes: S21, calculation of monthly potential evapotranspiration based on the Thornthwaite method; S22, the difference between monthly precipitation and potential evapotranspiration constitutes a precipitation and potential evapotranspiration difference sequence; S23, normalize the difference sequence and calculate the cumulative function F(x) based on the log-logistic probability distribution; S24, standardized cumulative probability density to obtain the standardized precipitation evapotranspiration index SPEI; S25, the Standardized Precipitation Evapotranspiration Index (SPEI) is used to define and identify drought events.

5. The method for identifying a heat wave-drought composite event according to claim 4, characterized in that: The calculation formula for potential evaporation PET in step S21 is as follows: Where, t e is the average monthly temperature in °C; I is the annual temperature efficiency index: m is the number of months; ζ is the function of the heat index: ζ = 67.5 × 10 -8 I 3 -77.1×10 -6 I 2 +0.0179I+0.492; C is the correction factor for converting the calculation period from month to day: Where d is the average monthly sunshine hours in h, and N is the number of days per month; The formula involved in step S24 is as follows: Where c0, c1, c2, d1, d2, d3 are all constants; ω is the probability weighted moment, When the cumulative probability P≤0.5, P=F(x); when the cumulative probability P>0.5, P=1-F(x); Where f(x) is the probability density function, F(x) is the probability distribution function, α is the scale parameter, β is the shape parameter, and γ is the origin parameter; In step S25, the monthly scale standardized precipitation evapotranspiration index SPEI is expanded to the daily scale, that is, the SPEI value of a certain day is the same as that of the current month, and drought occurs on that day when the daily SPEI is ≤ -1.

0.

6. The method for identifying a heat wave-drought composite event according to claim 1, characterized in that: In step S3, a heat wave-drought composite event is defined as a heat wave event occurring during a drought period; When one heat wave event occurs in a drought period, it is a heat wave-drought composite event; when multiple heat wave events occur in a drought period, multiple heat wave-drought composite events occur.

7. The method for identifying a heat wave-drought compound event according to claim 1, characterized in that: The step S4 comprises: S41, establish a standard for classifying heat wave events and determine the severity of heat wave events; S42, establish a drought event classification standard to determine the severity of drought events; S43, comprehensively identify the levels of heat waves and droughts in composite events, establish the classification standards for heat wave-drought composite events, and determine the severity level of composite events.

8. The method for identifying heat wave-drought combined events according to claim 7, characterized in that: In step S41, the severity of heat wave events is divided into the following levels: the PHI corresponding to the cumulative probability of 60% of the heat wave peak index PHI values ​​of all heat wave events in the study period 60％ is the classification threshold, and the corresponding PHI when the PHI cumulative probability is 100% 100％ is the maximum value; if PHI≤PHI 60％ A mild heat wave will occur. If PHI 60％ <PHI≤PHI 100％ A severe heat wave occurs; In step S42, the severity of the drought event is classified as follows: taking the standardized evapotranspiration index SPEI = -2.0 as the classification threshold, if -2.0 < SPEI ≤ -1.0, a mild drought occurs; if SPEI ≤ -2.0, a severe drought occurs; In step S43, the principle of dividing the level of heat wave-drought composite events is: if the heat wave and drought in the composite event are of the same level, the composite event is of this level; if the heat wave and drought in the composite event differ by one level, the composite event is of the corresponding intermediate level.

9. A heat wave-drought composite event recognition system, characterized in that: include: Calculation module, used to calculate the peak heat wave index PHI and the standardized precipitation evapotranspiration index SPEI; Based on the daily average temperature and maximum temperature, the peak heat wave index (PHI) was calculated using the constructed peak heat wave index formula; based on the monthly precipitation, average temperature and sunshine hours, the potential evapotranspiration was calculated using the Thornthwaite method, and the standardized precipitation evapotranspiration index (SPEI) was calculated; The first determination module is used to determine whether a heat wave-drought composite event occurs in a certain period of time; The peak heat wave index PHI and the standardized precipitation evapotranspiration index SPEI of a certain period of time are analyzed, and whether a heat wave or drought event occurs in a certain period of time is judged according to the critical value of the index; based on the overlapping relationship between drought and heat wave events in a certain period of time, whether a heat wave-drought composite event occurs in a certain period of time is further judged; The second determination module is used to determine the level of the heat wave-drought composite event; determine the respective levels of the heat wave and drought events in the composite event according to the respective level thresholds of the heat wave and drought; comprehensively consider the levels of the heat wave and drought in the composite event, and determine the level of the heat wave-drought composite event according to the level classification standard of the composite event.

10. An electronic device comprising a processor and a memory, characterized in that: The memory stores computer program instructions, which are used by the processor to execute the heat wave-drought combined event identification method according to any one of claims 1 to 8 when the processor is running.

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