Three-dimensional meteorological-hydrological drought propagation identification and matching method, storage medium and program product

Abstract

The application discloses a three-dimensional meteorological-hydrological drought propagation identification and matching method, a storage medium and a program product, and comprises the following steps: based on a meteorological drought index matrix and a hydrological drought index matrix, a minimum drought area proportion parameter and a minimum overlapping area proportion parameter are calibrated by using an elbow method, and all meteorological drought events and hydrological drought events are identified in combination with a moderate drought standard threshold; the identified meteorological drought events and hydrological drought events are paired to generate meteorological-hydrological drought event pairs; the meteorological-hydrological drought event pairs are grouped according to whether the drought events repeatedly appear in all meteorological-hydrological drought event pairs to generate drought event groups; and the features of the meteorological drought event to the hydrological drought event transmission process are extracted in the drought event group unit. The application can quantitatively identify the feature change in the meteorological-hydrological drought propagation process, directly reveal the propagation characteristics of meteorological drought to hydrological drought, and clarify the propagation mechanism between meteorological drought and hydrological drought.

Description

Technical Field

[0001] This invention belongs to the field of drought propagation identification technology, specifically relating to a three-dimensional meteorological-hydrological drought propagation identification and matching method, storage medium, and program product. Background Technology

[0002] Currently, most domestic and international research on drought is based on drought events at grid points, using run theory to identify these events. While run theory identifies drought events from a temporal perspective, it loses significant spatial information due to its singular focus on time, failing to comprehensively reflect the spatiotemporal variations of drought events. Drought, as a meteorological phenomenon developing simultaneously in both time and space, is a complex process requiring analysis from a three-dimensional perspective.

[0003] Lettenmaier et al. first proposed the severity-area-duration (SAD) method to track the spatiotemporal variations of drought. This method has been widely applied in drought studies at the watershed, continental, and even global scales. Subsequently, V. Diaz et al. adopted a drought migration tracking method based on the distance from the drought centroid and applied it at both watershed and continental scales. Wu Chuanhao et al. improved the traditional SAD method and compared its effectiveness, comparing the performance of two-dimensional and three-dimensional methods.

[0004] Despite significant advancements in three-dimensional drought identification methods, considerable uncertainty remains. Temporally, the continuity of a drought event is conceptual or parameterized, failing to accurately reflect the drought transmission process and thus limiting its ability to identify transmission characteristics. For example, V. Diaz and Liu et al. calculated the overlap area between consecutive time slices of each drought patch, leading to temporal discontinuities for rapidly evolving droughts. Utilizing the propagation links between meteorological and hydrological droughts, matching drought events and grouping them into one-to-one, one-to-many, and many-to-many pairs for group-based research can reduce the impact of errors in three-dimensional drought identification. Therefore, comprehensively matching drought events based on their temporal and spatial characteristics, calibrating the identification methods, and quantitatively identifying drought transmission characteristics are key issues that need to be addressed to clarify the transmission mechanisms between droughts. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a three-dimensional meteorological-hydrological drought propagation identification and matching method, storage medium, and program product. This method can comprehensively match the characteristics of drought events in the temporal and spatial dimensions, quantitatively identify the characteristic changes in the meteorological-hydrological drought propagation process, intuitively reveal the propagation characteristics of meteorological drought to hydrological drought, and elucidate the propagation mechanism between meteorological drought and hydrological drought.

[0006] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a three-dimensional meteorological-hydrological drought propagation identification and matching method, comprising:

[0008] Based on raster precipitation, runoff, and evapotranspiration data with longitude-latitude-time dimensions, a meteorological drought index matrix and a hydrological drought index matrix with longitude-latitude-time dimensions are calculated.

[0009] Based on the meteorological drought index matrix and the hydrological drought index matrix, the elbow method was used to determine the minimum drought area as a percentage of the whole basin and the minimum overlap area as a percentage of the basin. Combined with the moderate drought standard threshold, all meteorological drought events and hydrological drought events during the study period were identified.

[0010] The identified meteorological drought events and hydrological drought events are paired to generate meteorological-hydrological drought event pairs;

[0011] The meteorological-hydrological drought event pairs are grouped according to whether the drought event recurs in all meteorological-hydrological drought event pairs to generate drought event groups.

[0012] Using drought event groups as units, we extract the characteristics of the transmission process from meteorological drought events to hydrological drought events and analyze the spatiotemporal propagation process of meteorological-hydrological drought.

[0013] In conjunction with the first aspect, optionally, the calibration methods for the minimum drought area as a percentage of the entire watershed and the minimum overlap area as a percentage include:

[0014] Define the minimum overlap area ratio parameter as b, and the minimum drought area ratio parameter as p;

[0015] Let b = 0.01, and p be the variable. Starting from 0.01, with a step size of 0.01 and an upper bound of 1, drought events are identified successively based on the meteorological drought index matrix and the hydrological drought index matrix.

[0016] A curve is generated by using the number of drought events as the vertical axis and p as the horizontal axis, and the horizontal axis value of the maximum inflection point of the curve is taken as the calibrated p.

[0017] Let p remain at the calibrated value, and b be used as a variable, starting from 0.01 with a step size of 0.01 and an upper bound of 1. Based on the meteorological drought index matrix and the hydrological drought index matrix, drought events are identified and recorded one by one.

[0018] A curve is generated by using the number of drought events as the vertical axis and b as the horizontal axis, and the horizontal axis value of the maximum inflection point of the curve is taken as the calibrated b.

[0019] In conjunction with the first aspect, optionally, the method for identifying meteorological drought events and hydrological drought events includes:

[0020] For the meteorological drought index matrix and the hydrological drought index matrix, grid points with drought indices less than the moderate drought standard threshold on a monthly scale are selected, and drought patches are formed based on the selected grid points using the Euclidean distance clustering algorithm.

[0021] The number of grid points in a drought patch is calculated, and the area of ​​the drought patch is calculated using the resolution of a single grid point. If the area of ​​the drought patch is greater than the minimum patch area, the drought patch is considered valid; otherwise, the drought patch is discarded.

[0022] Perform time-history connection of drought patches, calculate the overlap area ratio between drought patches in adjacent months. If the calculated overlap area ratio is less than the minimum overlap area ratio parameter, then mark the two drought patches as two independent drought events; otherwise, mark the two drought patches as the same drought event.

[0023] All meteorological drought events and hydrological drought events during the study period were numbered to identify them.

[0024] In conjunction with the first aspect, optionally, the overlapping area ratio is calculated using the following formula:

[0025]

[0026] In the formula, P overlap As the ratio of overlapping areas, A * A represents the area of ​​overlapping drought patches. t Let A be the number of grid points in the drought patch at time t. t+1 This represents the number of grid points in the drought patch at time t+1.

[0027] In conjunction with the first aspect, optionally, the minimum patch area is calculated using the following formula:

[0028] S min =p×S;

[0029] In the formula, S mindenoted as the minimum patch area, p is the minimum drought area as a percentage of the total watershed area, and S is the watershed area.

[0030] In conjunction with the first aspect, optionally, the moderate drought standard threshold is -1, the minimum drought area as a percentage of the entire watershed is 0.06, and the minimum overlapping area as a percentage is 0.2.

[0031] In conjunction with the first aspect, optionally, the method for generating the meteorological-hydrological drought event pair includes:

[0032] Identify whether meteorological three-dimensional drought events and hydrological three-dimensional drought events intersect in space and time. If they intersect, record the numbers of the intersecting meteorological drought event and hydrological drought event respectively.

[0033] Determine the chronological order of all intersecting meteorological and hydrological drought events. If a meteorological drought event occurs earlier than a hydrological drought event, the intersecting meteorological and hydrological drought events are considered a successfully matched drought event pair. If a meteorological drought event occurs later than a hydrological drought event, calculate the proportion of the intersection volume in the case where the meteorological drought event occurs later than the hydrological drought event to the average volume of the meteorological and hydrological drought events. If the proportion is greater than a set threshold, the intersecting meteorological and hydrological drought events are considered a successfully matched drought event pair. Other event cases are considered drought matching failures.

[0034] In conjunction with the first aspect, optionally, the drought event group consists of drought event pairs, including the following three cases:

[0035] Scenario 1: Meteorological drought events and hydrological drought events have a one-to-one relationship.

[0036] In this case, a pair of drought events forms a drought event group;

[0037] Scenario 2: Meteorological drought events and hydrological drought events have a one-to-many relationship:

[0038] In this case, all the drought event pairs involved are grouped into a drought event group;

[0039] Scenario 3: Meteorological drought events and hydrological drought events have a many-to-many relationship.

[0040] In this case, all the drought event pairs involved are grouped into a drought event group, in which the number of meteorological drought events and hydrological drought events is greater than 1.

[0041] In a second aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the three-dimensional meteorological-hydrological drought propagation identification and matching method described in any one aspect.

[0042] Thirdly, the present invention provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the three-dimensional meteorological-hydrological drought propagation identification and matching method described in any one of the first aspects.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] This invention optimizes drought event identification by calibrating drought identification parameters and finding the optimal whole-basin proportion parameter and the lowest overlap area percentage parameter within the selectable parameter range. This reduces the interference of small-scale drought events on drought characteristics and reasonably distinguishes consecutive drought events. Furthermore, by recombining drought event pairs, related drought event pairs are regrouped, causing misidentified multiple drought events to be merged into a single group, thus achieving reasonable drought event identification, reducing the interference of misidentification, and enabling accurate extraction of drought event features. This invention, through drought identification parameter calibration and drought event pair recombination, achieves drought event identification and feature extraction, improving the drought feature extraction effect to a certain extent. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0046] Figure 1 This is one of the flowcharts illustrating the three-dimensional meteorological-hydrological drought propagation identification and matching method in one embodiment of the present invention;

[0047] Figure 2 This is a second schematic flowchart of a method for identifying meteorological drought events and hydrological drought events in one embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the intersection volume of drought events in drought event matching in one embodiment of the present invention;

[0049] Figure 4 This is a diagram illustrating the transmission process of a typical meteorological-hydrological drought event pair in a "one-to-one" manner, according to one embodiment of the present invention.

[0050] Figure 5 This is a diagram illustrating the transmission process of a typical meteorological-hydrological drought event pair in a "one-to-many" manner, as described in one embodiment of the present invention.

[0051] Figure 6This is a diagram illustrating the transmission process of a typical meteorological-hydrological drought event pair in a "many-to-many" manner, as described in one embodiment of the present invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0053] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0054] Example 1

[0055] This invention provides a three-dimensional meteorological-hydrological drought propagation identification and matching method, such as... Figure 1 As shown, it includes the following steps:

[0056] (1) Based on the grid precipitation, runoff and evapotranspiration data with longitude-latitude-time dimensions, the meteorological drought index matrix and the hydrological drought index matrix with longitude-latitude-time dimensions are calculated.

[0057] (2) Based on the meteorological drought index matrix and the hydrological drought index matrix, the elbow method is used to determine the minimum drought area ratio of the whole basin and the minimum overlap area ratio. Combined with the moderate drought standard threshold, all meteorological drought events and hydrological drought events during the study period are identified, along with their duration, cumulative intensity, and maximum impact range.

[0058] (3) Pair the identified meteorological drought events and hydrological drought events to generate meteorological-hydrological drought event pairs;

[0059] (4) The meteorological-hydrological drought event pairs are grouped according to whether the drought event is repeated in all meteorological-hydrological drought event pairs to generate drought event groups;

[0060] (5) Taking drought event groups as units, extract the characteristics of the transmission process from meteorological drought events to hydrological drought events, and analyze the spatiotemporal meteorological-hydrological drought propagation process. In specific implementation, the analysis of the spatiotemporal meteorological-hydrological drought propagation process specifically refers to: analyzing the duration, cumulative intensity, maximum impact range, development and dissipation process of meteorological and hydrological drought, as well as the spatial transfer process of the drought centroid, and using this to characterize the spatiotemporal meteorological-hydrological drought propagation process.

[0061] In one specific embodiment of the present invention, the method for calculating the meteorological drought index matrix and the hydrological drought index matrix includes:

[0062] Based on actual needs, drought indicators and drought time scales are selected; in the specific implementation process, the drought indicators include the standardized precipitation evapotranspiration index (i.e., meteorological drought index) and the standardized runoff generation index (i.e., hydrological drought index); the drought time scale is generally selected as one month; the calculation process of the standardized precipitation evapotranspiration index and the standardized runoff generation index is existing technology, therefore, it will not be described in detail in this invention.

[0063] Based on the potential evapotranspiration and runoff data in the raster precipitation, runoff and evapotranspiration data with longitude-latitude-time dimensions, a three-dimensional meteorological drought index matrix and a hydrological drought index matrix are calculated according to the drought index calculation method. The parameter in the meteorological drought index matrix is ​​the standardized precipitation evapotranspiration index; the parameter in the hydrological drought index matrix is ​​the standardized runoff index.

[0064] A suitable minimum drought area as a percentage of the entire watershed, parameter *p*, allows for the filtering out of droughts with excessively small impact areas and high frequency during drought event identification, while retaining large-scale droughts, reducing interference from smaller droughts, and reasonably reflecting the drought characteristics of the region. A suitable minimum overlap area percentage parameter *b* can reasonably distinguish between two drought events that overlap in time and space, without misclassifying a single drought event as two separate events. Therefore, in a specific embodiment of this invention, the calibration method for the minimum drought area as a percentage of the entire watershed parameter and the minimum overlap area percentage parameter includes:

[0065] Define the minimum overlap area ratio parameter as b, and the minimum drought area ratio parameter as p;

[0066] Let b = 0.01, and p be the variable. Starting from 0.01, with a step size of 0.01 and an upper bound of 1, drought events are identified successively based on the meteorological drought index matrix and the hydrological drought index matrix. The identification of drought events refers to the identification of meteorological drought events and hydrological drought events.

[0067] A curve is generated by using the number of drought events as the vertical axis and p as the horizontal axis, and the horizontal axis value of the maximum inflection point of the curve is taken as the calibrated p.

[0068] Let p remain at the calibrated value, and b be used as a variable, starting from 0.01 with a step size of 0.01 and an upper bound of 1. Based on the meteorological drought index matrix and the hydrological drought index matrix, drought events are identified and recorded one by one.

[0069] A curve is generated by using the number of drought events as the vertical axis and b as the horizontal axis, and the horizontal axis value of the maximum inflection point of the curve is taken as the calibrated b.

[0070] In one specific embodiment of the present invention, such as Figure 2 As shown, the methods for identifying meteorological drought events and hydrological drought events include:

[0071] For the meteorological drought index matrix and the hydrological drought index matrix, grid points with drought indices less than the moderate drought standard threshold on a monthly scale are selected, and drought patches are formed based on the selected grid points using the Euclidean distance clustering algorithm.

[0072] The number of grid points in a drought patch is calculated, and the area of ​​the drought patch is calculated using the resolution of a single grid point. If the area of ​​the drought patch is greater than the minimum patch area, the drought patch is considered valid; otherwise, the drought patch is discarded.

[0073] Perform time-history connection of drought patches, calculate the overlap area ratio between drought patches in adjacent months. If the calculated overlap area ratio is less than the minimum overlap area ratio parameter, then mark the two drought patches as two independent drought events; otherwise, mark the two drought patches as the same drought event.

[0074] All meteorological drought events and hydrological drought events during the study period were numbered to identify them.

[0075] In one specific embodiment of the present invention, the overlapping area ratio is calculated using the following formula:

[0076]

[0077] In the formula, P overlap As the ratio of overlapping areas, A * A represents the area of ​​overlapping drought patches. t Let A be the number of grid points in the drought patch at time t. t+1 This represents the number of grid points in the drought patch at time t+1.

[0078] In one specific embodiment of the present invention, the minimum patch area is calculated using the following formula:

[0079] S min =p×S;

[0080] In the formula, S min denoted as the minimum patch area, p is the minimum drought area station's proportion parameter across the entire watershed, and S is the watershed area.

[0081] In one specific embodiment of the present invention, the moderate drought standard threshold is -1, the minimum drought area as a percentage of the entire watershed is 0.06, and the minimum overlapping area as a percentage is 0.2.

[0082] In one specific embodiment of the present invention, such as Figure 3 As shown, the method for generating the meteorological-hydrological drought event pair includes:

[0083] Identify whether meteorological three-dimensional drought events and hydrological three-dimensional drought events intersect in space and time. If they intersect, record the numbers of the intersecting meteorological drought event and hydrological drought event respectively.

[0084] Determine the chronological order of all intersecting meteorological and hydrological drought events. If a meteorological drought event occurs earlier than a hydrological drought event, the intersecting meteorological and hydrological drought events are considered a successfully matched drought event pair. If a meteorological drought event occurs later than a hydrological drought event, calculate the proportion of the intersection volume in the case where the meteorological drought event occurs later than the hydrological drought event to the average volume of the meteorological and hydrological drought events. If the proportion is greater than a set threshold, the intersecting meteorological and hydrological drought events are considered a successfully matched drought event pair. Other event cases are considered drought matching failures.

[0085] In the process of identifying drought events, errors in drought event identification are inevitable, resulting in a single drought event being divided into multiple drought events. However, by recombining drought event pairs, related meteorological and hydrological droughts can be merged back into the same group, eliminating the interference of incorrect drought event identification on drought characteristics. Therefore, in a specific embodiment of this invention, the drought event group consists of drought event pairs, including the following three cases:

[0086] Scenario 1: Meteorological drought events and hydrological drought events have a one-to-one relationship.

[0087] In this case, a pair of drought events forms a drought event group;

[0088] Scenario 2: Meteorological drought events and hydrological drought events have a one-to-many relationship:

[0089] In this case, all the drought event pairs involved are grouped into a drought event group;

[0090] Scenario 3: Meteorological drought events and hydrological drought events have a many-to-many relationship.

[0091] In this scenario, all involved drought event pairs are grouped into a single drought event group, where the number of meteorological drought events and hydrological drought events in the group is both greater than one. The drought event group generated under scenario one is defined as a simple drought event group, where both meteorological and hydrological drought events represent the same drought event. The drought event groups generated under scenarios two and three are defined as complex drought event groups.

[0092] In one specific embodiment of the present invention, the characteristics of the transmission process from meteorological drought event to hydrological drought event include: the maximum impact range of the drought event, the duration of the drought event, the cumulative drought intensity of the drought event, the spatiotemporal centroid of the drought event, the duration of the drought event group, the cumulative drought intensity of the drought event group, and the spatial centroid movement of the drought event group. The extraction process of these characteristics from meteorological drought event to hydrological drought event is implemented using existing technology; therefore, it will not be elaborated upon further in this embodiment of the present invention.

[0093] In this embodiment, taking the meteorological and hydrological drought in the Yellow River Basin from 1961 to 2022 as an example, the execution process of the three-dimensional meteorological-hydrological drought propagation identification and matching method based on the recombination of drought event pairs is specifically explained.

[0094] The Yellow River basin spans arid, semi-arid, and semi-humid regions. Due to its vast area and significant east-west elevation differences, the basin experiences complex and variable hydrological and meteorological conditions, resulting in varying degrees of drought across different areas. Precipitation in the Yellow River basin is mostly between 200-650 mm, concentrated from June to September. The average annual evaporation is 1100 mm, and the average annual natural river runoff is 53.48 billion m³. The per capita water availability within the basin is less than 600 m³. 3 It accounts for only a quarter of the national average, and the drought situation is more prominent. Between 1966 and 2010, there were 16 years of severe drought or worse, which caused reduced grain production and huge economic losses.

[0095] In this embodiment, the CN05.1 dataset with a resolution of 0.25°×0.25° gridded from the Climate Change Research Center is used, and the VIC model is used to simulate daily hydrological processes, providing 0.25°×0.25° gridded runoff.

[0096] In this embodiment, a three-dimensional meteorological-hydrological drought propagation identification and matching method based on the recombination of drought event pairs is adopted to match meteorological-hydrological drought event pairs in the Yellow River Basin and quantitatively identify the propagation characteristics of meteorological-hydrological drought event pairs.

[0097] 1. Results of meteorological drought event and hydrological drought event identification

[0098] Using drought identification methods, 262 meteorological drought events and 181 hydrological drought events were identified in the Yellow River Basin from 1961 to 2022. Based on the grouping of drought events, drought characteristics were extracted by event group. The average duration of meteorological drought was 1.62 months, the average affected area of ​​meteorological drought was 43.4% of the entire basin, and the average intensity of meteorological drought was 10.72 * 10⁵ months * km². 2 The average duration of hydrological drought was 1.38 months, the average affected area of ​​hydrological drought was 21.5% of the entire basin, and the average intensity of hydrological drought was 4.49 × 10⁵ months × km². 2 .

[0099] 2. Transmission characteristics of meteorological-hydrological drought events

[0100] After matching and recombinating drought events, 81 drought event groups were formed. Among them, there were 62 "one-to-one" groups, 18 "one-to-many" groups, and 1 "many-to-many" group.

[0101] Figure 4 This is a case study of a "one-to-one" drought event group. The meteorological drought occurred one month prior to the hydrological drought. As the meteorological drought developed, it advanced from the southeast to the northwest, with the drought centroid shifting 15.9 degrees (approximately 1700 kilometers) northwestward, reaching its maximum extent in September. Subsequently, the meteorological drought began to subside, the drought centroid shifted back southeastward, and fragmentation and dissipation of the drought began to occur.

[0102] Figure 5 This is a case of a "one-to-many" drought event group. This situation mainly occurs when meteorological droughts last for a long period. In the autumn of 1998, a large-scale drought occurred in North China, which rapidly subsided after November. However, due to surface conditions, hydrological drought was not identified in October. However, as the meteorological drought moved northeastward, some areas began to experience hydrological drought in January and February 1999.

[0103] Figure 6This is a complex group of drought events. This meteorological drought event developed very rapidly and was characterized by short-duration, persistent drought. Under the identified parameters, the event was divided into two distinct meteorological droughts. Similarly, due to the influence of bottom surface factors, the hydrological drought was also split into two events. In traditional drought matching methods, meteorological drought events (e.g., event number 147) may not be able to be linked to subsequent monthly drought events due to low overlap, leading to incomplete and inaccurate understanding of drought event characteristics. However, by employing this method, two January drought events can be reorganized into a single drought event group. This method reduces the impact of sporadic events on the overall drought characteristic analysis by recombining the characteristics of drought events.

[0104] In the embodiments of the present invention Figures 4-6 Meteorological drought and hydrological drought refer to meteorological drought and hydrological drought, respectively; LAT and LON refer to longitude and latitude, respectively.

[0105] Example 2

[0106] Based on the same inventive concept as in Embodiment 1, this embodiment of the invention provides a computer-readable storage medium storing a computer program thereon, characterized in that, when the program is executed by a processor, it implements the three-dimensional meteorological-hydrological drought propagation identification and matching method described in Embodiment 1.

[0107] Example 3

[0108] Based on the same inventive concept as Embodiment 1, this embodiment of the invention provides a computer program product, including a computer program / instruction, characterized in that, when the computer program / instruction is executed by a processor, it implements the three-dimensional meteorological-hydrological drought propagation identification and matching method described in Embodiment 1.

[0109] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0110] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0111] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0112] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0113] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

[0114] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A three-dimensional meteorological-hydrological drought propagation identification and matching method, characterized in that, include: Based on raster precipitation, runoff, and evapotranspiration data with longitude-latitude-time dimensions, a meteorological drought index matrix and a hydrological drought index matrix with longitude-latitude-time dimensions are calculated. Based on the meteorological drought index matrix and the hydrological drought index matrix, the elbow method was used to determine the minimum drought area as a percentage of the whole basin and the low overlap area as a percentage of the basin. Combined with the moderate drought standard threshold, all meteorological drought events and hydrological drought events during the study period were identified. The identified meteorological drought events and hydrological drought events are paired to generate meteorological-hydrological drought event pairs; The meteorological-hydrological drought event pairs are grouped according to whether the drought event recurs in all meteorological-hydrological drought event pairs to generate drought event groups. Using drought event groups as units, we extract the characteristics of the transmission process from meteorological drought events to hydrological drought events and analyze the spatiotemporal propagation process of meteorological-hydrological drought. The calibration methods for the parameters of the minimum drought area as a percentage of the entire watershed and the minimum overlap area as a percentage include: Define the minimum overlap area ratio parameter as follows The parameter for the minimum drought area as a percentage of the entire watershed is: ; make As variables, starting from 0.01, with a step size of 0.01 and an upper bound of 1, drought events are identified and recorded successively based on the meteorological drought index matrix and the hydrological drought index matrix. The number of drought events is used as the vertical axis. Using the horizontal axis as the x-axis, a curve is generated, and the horizontal axis value of the curve's maximum inflection point is used as the calibrated value. ; make Keep it as the calibrated value. As variables, starting from 0.01, with a step size of 0.01 and an upper bound of 1, drought events are identified and recorded successively based on the meteorological drought index matrix and the hydrological drought index matrix. The number of drought events is used as the vertical axis. Using the horizontal axis as the x-axis, a curve is generated, and the horizontal axis value of the curve's maximum inflection point is used as the calibrated value. ; The methods for generating the meteorological-hydrological drought event pairs include: Identify whether meteorological three-dimensional drought events and hydrological three-dimensional drought events intersect in time and space. If they intersect, record the numbers of the intersecting meteorological drought event and hydrological drought event respectively. Determine the chronological order of all intersecting meteorological and hydrological drought events. If a meteorological drought event occurs earlier than a hydrological drought event, the intersecting meteorological and hydrological drought events are considered a successfully matched drought event pair. If a meteorological drought event occurs later than a hydrological drought event, calculate the proportion of the intersection volume in the case where the meteorological drought event occurs later than the hydrological drought event to the average volume of the meteorological and hydrological drought events. If the proportion is greater than a set threshold, the intersecting meteorological and hydrological drought events are considered a successfully matched drought event pair. Other event cases are considered drought matching failures.

2. The three-dimensional meteorological-hydrological drought propagation identification and matching method according to claim 1, characterized in that: The methods for identifying meteorological drought events and hydrological drought events include: For the meteorological drought index matrix and the hydrological drought index matrix, grid points with drought indices less than the moderate drought standard threshold on a monthly scale are selected, and drought patches are formed based on the selected grid points using the Euclidean distance clustering algorithm. The number of grid points in a drought patch is calculated, and the area of ​​the drought patch is calculated using the resolution of a single grid point. If the area of ​​the drought patch is greater than the minimum patch area, the drought patch is considered valid; otherwise, the drought patch is discarded. Perform time-history connection of drought patches, calculate the overlap area ratio between drought patches in adjacent months. If the calculated overlap area ratio is less than the minimum overlap area ratio parameter, then mark the two drought patches as two independent drought events; otherwise, mark the two drought patches as the same drought event. All meteorological drought events and hydrological drought events during the study period were numbered to identify them.

3. The three-dimensional meteorological-hydrological drought propagation identification and matching method according to claim 2, characterized in that: The overlap area ratio is calculated using the following formula: ； In the formula, The percentage of overlapping area. This represents the area of ​​overlapping drought patches. For the first The number of grid points in a drought patch at a given time. For the first The number of grid points in a drought patch at each time point.

4. The three-dimensional meteorological-hydrological drought propagation identification and matching method according to claim 2, characterized in that: The minimum patch area is calculated using the following formula: ； In the formula, For the minimum patch area, This is the parameter representing the minimum proportion of drought-stricken area to the entire watershed. The area is the catchment area.

5. The three-dimensional meteorological-hydrological drought propagation identification and matching method according to claim 1, characterized in that: The threshold for moderate drought is -1, the minimum drought area as a percentage of the entire watershed is 0.06, and the minimum overlapping area as a percentage of the entire watershed is 0.

2.

6. The three-dimensional meteorological-hydrological drought propagation identification and matching method according to claim 1, characterized in that: The drought event group consists of drought event pairs, including the following three cases: Scenario 1: Meteorological drought events and hydrological drought events have a one-to-one relationship. In this case, a pair of drought events forms a drought event group; Scenario 2: Meteorological drought events and hydrological drought events have a one-to-many relationship: In this case, all the drought event pairs involved are grouped into a drought event group; Scenario 3: Meteorological drought events and hydrological drought events have a many-to-many relationship. In this case, all the drought event pairs involved are grouped into a drought event group, in which the number of meteorological drought events and hydrological drought events is greater than 1.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the three-dimensional meteorological-hydrological drought propagation identification and matching method as described in any one of claims 1 to 6.

8. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the three-dimensional meteorological-hydrological drought propagation identification and matching method as described in any one of claims 1 to 6.

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