Method and system for quantifying the drought transfer inhibitory effect of soil moisture under drought stress.

Abstract

To provide a method and system for quantifying the drought transfer inhibitory effect of soil moisture under drought stress. [Solution] This method includes the steps of: acquiring meteorological data, soil moisture data, and vegetation remote sensing observation data of a monitored area; standardizing the acquired data to obtain a standardized precipitation evapotranspiration index, a standardized soil moisture index, and a standardized vegetation index; constructing a three-dimensional simultaneous distribution function based on the standardized precipitation evapotranspiration index, a standardized soil moisture index, and a standardized vegetation index; calculating the drought transmission time and drought transmission probability based on the three-dimensional simultaneous distribution function; calculating the drought transmission index based on the drought transmission time and drought transmission probability; and calculating the drought transmission inhibition rate based on the drought transmission index to complete the quantification of the drought transmission inhibition effect.

Description

[Technical Field]

[0001] This invention belongs to the field of early warning technology for drought in hydrological water resources, and more specifically, relates to a method and system for quantifying the drought transmission inhibiting effect of soil moisture under drought stress. [Background technology]

[0002] Meteorological droughts caused by insufficient precipitation are a source of drought in vegetation ecosystems. Drought signals are generated in the meteorological system and then transmitted stepwise through the soil and groundwater systems to terrestrial vegetation ecosystems. In this cascading transmission process, drought signals are often accompanied by temporal delays and attenuation of intensity. Soil water plays a crucial inhibitory role in the drought transmission process as a vital point of contact mediating water and energy exchange between vegetation and the atmosphere. On the one hand, because soil moisture has long temporal memory, previous soil moisture can supply water to vegetation for a period even after the onset of a meteorological drought, directly mitigating and delaying the adverse effects of meteorological drought on vegetation. On the other hand, soil water can indirectly reduce the risk of causing vegetation ecological droughts by cooling the area near the surface through evaporation, thereby suppressing the occurrence of dry-high-temperature complex events and wildfires. The delay and attenuation of soil water's effect on meteorological drought signals in the cascading transmission process of drought is generally defined as the inhibitory effect of soil water.

[0003] Conventional research on early drought warnings has primarily focused on soil moisture deficiency as a key drought stressor, examining its impact on terrestrial ecosystem functions through land-air coupling processes. However, the resistance and inhibitory effects of early soil moisture itself on meteorological droughts have often been overlooked. Against the backdrop of accelerating climate change and global warming, the hydrological cycle is accelerating, and both the frequency and intensity of droughts are increasing significantly. Scientifically quantifying the inhibitory effect of soil moisture on drought is of great importance for a deeper understanding of drought formation and disaster mechanisms, and is particularly valuable for achieving precise drought prediction and targeted control. However, currently, there is still a lack of an indicator system that can comprehensively reflect drought transmission risk information, making it difficult to effectively quantify the inhibitory effect of early soil moisture on drought transmission. Therefore, constructing a model to quantify the inhibitory effect of soil moisture on drought transmission is one of the urgent issues that must be resolved in the process of establishing an ecological drought early warning platform. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention aims to solve the shortcomings of the prior art by providing the following technical scheme. [Means for solving the problem]

[0005] A method for quantifying the drought transfer inhibitory effect of soil moisture under drought stress, The process involves acquiring weather data, soil moisture data, and vegetation remote sensing observation data for the monitored area, and then standardizing the acquired data to obtain a standardized precipitation evapotranspiration index, a standardized soil moisture index, and a standardized vegetation index. The steps include constructing a three-dimensional simultaneous distribution function based on the standardized precipitation evapotranspiration index, the standardized soil moisture index, and the standardized vegetation index, Calculating the drought transmission time and the drought transmission probability based on the three-dimensional simultaneous distribution function, and calculating a drought transmission index based on the drought transmission time and the drought transmission probability; Calculating a drought transmission inhibition rate based on the drought transmission index and completing the quantification of the drought transmission inhibition effect, including.

[0006] Preferably, the method for constructing the three-dimensional simultaneous distribution function includes the following formula:

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[0007] [[ID=,30]] Preferably, the method for calculating the drought transmission index is Calculating a drought transmission matrix considering the influence of soil moisture in the early summer,

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[0008] Preferably, the method for calculating the drought transmission inhibition rate includes the step of calculating the drought transmission inhibition rate based on the first drought transmission index and the second drought transmission index: [Number] Here, DR represents the drought transmission inhibition rate.

[0009] The present invention also provides a system for quantifying the drought transfer inhibitory effect of soil moisture under drought stress, the system applying the above method and including a data acquisition module, a function construction module, an index calculation module and an inhibition rate calculation module. The data acquisition module is used to acquire weather data, soil moisture data, and vegetation remote sensing observation data of the monitored area, and to perform standardization processing on the acquired data to obtain a standardized precipitation evapotranspiration index, a standardized soil moisture index, and a standardized vegetation index. The function construction module constructs a three-dimensional simultaneous distribution function based on the standardized precipitation evapotranspiration index, the standardized soil moisture index, and the standardized vegetation index. The index calculation module calculates the drought transmission time and drought transmission probability based on the three-dimensional joint distribution function, and calculates the drought transmission index based on the drought transmission time and drought transmission probability. The inhibition rate calculation module calculates the drought transmission inhibition rate based on the drought transmission index and completes the quantification of the drought transmission inhibition effect.

[0010] Preferably, the workflow of the function building module includes the following equation:

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[0011] Preferably, the workflow of the exponential calculation module is: Calculate the drought transmission matrix considering the influence of soil moisture in the early summer, [Number] Here, PP i_csm represents the drought transmission matrix considering the influence of soil moisture in the early summer, P represents the transmission probability, i represents the SPEI cumulative scale, SNDVI represents the normalized vegetation index, SSMI represents the normalized soil moisture index, SPEI represents the standardized precipitation evapotranspiration index, F SNDVI represents the marginal normal distribution function of summer vegetation, F SSMI represents the marginal normal distribution function of the previous SSMI, F SPEI represents the marginal normal distribution function of the previous SPEI, C 21 represents the step of the two-dimensional joint distribution function between SSMI and SPEI, and Calculate the drought transmission matrix without considering the influence of soil moisture in the early summer: [Number] Here, PP i_ncsm represents the drought transmission matrix without considering the influence of soil moisture in the early summer, C 22 represents the step of the two-dimensional joint distribution function between SNDVI and SPEI, and Extract the first drought transmission time and the first drought transmission probability from the drought transmission matrix considering the influence of soil moisture in the early summer, and extract the second drought transmission time and the second drought transmission probability from the drought transmission matrix without considering the influence of soil moisture in the early summer, Calculate the first drought transmission index considering the influence of soil moisture in the early summer based on the first drought transmission time and the first drought transmission probability, and calculate the second drought transmission index without considering the influence of soil moisture in the early summer based on the second drought transmission time and the second drought transmission probability, [Number] [Number] Here, the steps include: DPI_csm represents the first drought transmission index, PP_csm represents the first drought transmission probability, PT_csm represents the first drought transmission time, DPI_ncsm represents the second drought transmission index, PP_ncsm represents the second drought transmission probability, and PT_ncsm represents the second drought transmission time.

[0012] Preferably, the workflow of the inhibition rate calculation module is: The step of calculating the drought transmission inhibition rate based on the first drought transmission index and the second drought transmission index is included:

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[0013] Compared to the conventional technology, the beneficial effects of the present invention are as follows:

[0014] This invention solves the long-standing problem of difficulty in quantifying the drought transmission inhibitory effect of early-stage soil moisture, provides a drought transmission index that comprehensively reflects drought transmission risk, and enables the precise quantification of the soil's inhibitory capacity by obtaining a transmission inhibition rate. This provides scientific guidance for achieving precise drought prediction and targeted control, as well as for constructing an ecological drought early warning platform. [Brief explanation of the drawing]

[0015] To more clearly explain the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. As is clear, the drawings described below represent only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these without any creative work. [Figure 1] This is a schematic diagram of the method flow of an embodiment of the present invention. [Figure 2] This is a block diagram of the method flow of an embodiment of the present invention. [Modes for carrying out the invention]

[0016] The following describes, with reference to the drawings relating to embodiments of the present invention, a technical solution relating to embodiments of the present invention will be clearly and completely explained. However, the embodiments described are only a selection of embodiments of the present invention, not all embodiments. All other embodiments that can be obtained by those skilled in the art without creative work based on embodiments of the present invention are within the scope of the protection of the present invention.

[0017] To make the above-mentioned objectives, features, and advantages of the present invention easier to understand, the present invention will be described in more detail below with reference to the drawings and specific embodiments.

[0018] Example 1

[0019] In this example, as shown in Figures 1 and 2, the method for quantifying the drought transfer inhibitory effect of soil moisture under drought stress includes the following steps.

[0020] S1 acquires weather data, soil moisture data, and vegetation remote sensing observation data for the monitored area. The acquired data is then standardized to obtain a standardized precipitation evapotranspiration index, a standardized soil moisture index, and a standardized vegetation index.

[0021] In this example, first, meteorological data (precipitation, temperature, solar radiation, wind speed, surface pressure, dew point temperature), soil moisture data, and summer vegetation remote sensing observation data (normalized vegetation index, NDVI) are collected for a certain region. Next, the standardized precipitation evapotranspiration index (SPEI) is calculated using the meteorological data to represent meteorological drought. The standardized soil moisture index (SSMI) is calculated using the soil moisture data to represent the soil moisture state in the early period. The standardized vegetation index (SNDVI) is calculated using the NDVI data to represent ecological drought in summer. Considering that the sensitivity period of summer vegetation to pre-summer soil moisture may differ in different regions, before specifically quantifying the inhibitory effect of soil moisture, the correlation coefficient between NDVI and SSMI on a 1-12 month pre-summer scale is calculated, and the corresponding scale with the largest positive correlation coefficient is selected as the pre-summer soil moisture period that has the greatest impact on summer vegetation growth. Subsequent quantitative calculations are performed using SSMI within this period range.

[0022] Specifically, the SPEI is calculated first. Using the collected meteorological data (precipitation, temperature, solar radiation, wind speed, surface pressure, dew point temperature), the Penman-Monteith method is used to calculate the potential evapotranspiration PET for a given period. Subtracting PET from precipitation gives the water deficit D for a given area. Next, the cumulative probability of D is calculated, and after standardization, the SPEI is obtained. A three-parameter log-logistic probability distribution function is used to fit the changes in water deficit. The specific calculation formula is as follows:

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[0023] The calculation process for SSMI is similar to that of SPEI. Since the SSMI index is fitted using a normal distribution based on soil moisture data, the formula can be simplified as follows:

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[0024] The calculation steps for SNDVI are the same as those for the two indices described above. The present invention fits the summer NDVI using five candidate distribution functions optimized by the AIC criterion (including the normal distribution, gamma distribution, Weibull distribution, log-normal distribution, and generalized extreme value distribution), and similarly obtains the SNDVI index after standardizing the cumulative probability value of the NDVI.

[0025] A three-dimensional simultaneous distribution function is constructed based on S2, the standardized precipitation evapotranspiration index, the standardized soil moisture index, and the standardized vegetation index.

[0026] The method for constructing the three-dimensional joint distribution function includes the following equation:

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[0027] S3 calculates the drought transmission time and drought transmission probability based on the three-dimensional joint distribution function, and calculates the drought transmission index based on the drought transmission time and drought transmission probability.

[0028] The method for calculating the drought transmission index includes the following: In this embodiment, a comprehensive drought transmission risk assessment system is constructed based on drought transmission probability and transmission time. Drought transmission time (PT) effectively reflects the speed of drought signal transmission, and drought transmission probability (PP) can reflect the likelihood of transmission occurring. This invention combines PT and PP, and by dividing PP by PT, obtains a drought transmission index (DPI) to comprehensively reflect drought transmission information.

[0029] Specifically, first, drought transmission probability matrices are calculated for cases where the influence of early soil moisture is considered and cases where the influence of early soil moisture is not considered. When calculating the drought transmission probability matrix considering the influence of early soil moisture, it is necessary to select the vegetation's sensitivity period to early soil moisture in advance. Taking the case of summer drought as an example, the correlation coefficients between summer vegetation (NDVI) and SSMI on a 1-12 month scale prior to summer are calculated, and the corresponding scale with the largest positive correlation is selected. This scale is then used as the sensitivity period for early soil moisture, which has the greatest influence on the growth of summer vegetation, and subsequent calculations are performed. After identifying the early soil moisture sensitivity period, the magnitude of the transmission probability that meteorological drought causes vegetation ecological drought when early soil moisture is in a normal state is calculated using a conditional probability formula based on the three-dimensional joint distribution function between SPEI, SSMI, and SNDVI constructed in step 2. Taking an extreme level of weather-related drought as an example, we calculated a drought transmission matrix that takes into account the effects of early summer soil moisture:

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[0030] Calculate the drought transmission matrix without considering the influence of the previous summer soil moisture:

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[0031] The first drought transmission time and the probability of the first drought transmission are extracted from the drought transmission matrix that considers the effect of early summer soil moisture, and the second drought transmission time and the probability of the second drought transmission are extracted from the drought transmission matrix that does not consider the effect of early summer soil moisture. After obtaining the drought transmission probability matrix, PT is extracted by setting certain extraction criteria. An example of the specific procedure when extracting PT_csm considering the effect of early soil moisture is given: Set the extraction probability threshold interval to [0.5, 0.7]. First, using the upper limit of the interval 0.7 as the threshold, the probability matrix (PP 1~48_csm Starting from the bottom of ), the cumulative pre-summer weather drought scale i was progressively examined from week 1 to week 48, PP i_csm The system progressively verifies whether the value reaches 0.7 or higher. When the extraction threshold condition is met for the first time, the corresponding cumulative scale i is determined to be the transmission time (PT) from meteorological drought to summer ecological drought, and simultaneously, PP i_csm This represents the drought transmission probability (PP) corresponding to the PT. After verification, if the transmission probability at all cumulative scales does not reach 0.7 or higher, the probability threshold requirement is reduced in -0.1 increments, and the above operation is repeated to extract PTs. However, if the transmission probability matrix still does not satisfy the extraction requirement even after the extraction threshold has decreased to 0.5, it is considered that it is not possible to directly induce a vegetation response and cause a vegetation ecological drought under the current drought scenario.

[0032] After obtaining the drought transmission time and transmission probability, a drought transmission index (DPI_csm) considering the inhibitory effect of early-season soil moisture and a drought transmission index (DPI_ncsm) ignoring the effect of early-season soil moisture can be further calculated. The DPI index, by combining transmission time and transmission probability, can effectively reflect the risk of transmission from meteorological drought to ecological drought, and its value ranges from 0 to 1. A larger DPI index value indicates a higher probability of inducing drought transmission, a shorter transmission time, and a greater overall risk of drought transmission. Specifically, the first drought transmission index, considering the effect of early-season summer soil moisture, is calculated based on the first drought transmission time and first drought transmission probability, and the second drought transmission index, ignoring the effect of early-season summer soil moisture, is calculated based on the second drought transmission time and second drought transmission probability:

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[0033] S4. Calculate the drought transmission inhibition rate based on the drought transmission index and complete the quantification of the drought transmission inhibition effect.

[0034] A method for calculating the drought transmission inhibition rate includes the step of calculating the drought transmission inhibition rate based on the first drought transmission index and the second drought transmission index:

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[0035] Example 2

[0036] In this embodiment, the system for quantifying the drought transfer inhibition effect of soil moisture under drought stress includes a data acquisition module, a function construction module, an index calculation module, and an inhibition rate calculation module.

[0037] The data acquisition module acquires weather data, soil moisture data, and vegetation remote sensing observation data for the monitored area. The acquired data is then standardized to obtain a standardized precipitation evapotranspiration index, a standardized soil moisture index, and a standardized vegetation index.

[0038] The function construction module constructs a three-dimensional simultaneous distribution function based on the standardized precipitation evapotranspiration index, standardized soil moisture index, and standardized vegetation index.

[0039] The workflow for the function building module includes the following:

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[0040] The index calculation module calculates the drought transmission time and drought transmission probability based on a three-dimensional joint distribution function, and then calculates the drought transmission index based on the drought transmission time and drought transmission probability.

[0041] The workflow for the index calculation module calculates the drought transmission matrix considering the effects of early summer soil moisture:

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[0042] The inhibition rate calculation module calculates the drought transmission inhibition rate based on the drought transmission index and completes the quantification of the drought transmission inhibition effect.

[0043] The workflow for the inhibition rate calculation module includes the step of calculating the drought transmission inhibition rate based on the first drought transmission index and the second drought transmission index:

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[0044] The embodiments described above merely illustrate preferred embodiments of the present invention and do not limit the scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the present invention, without deviating from the spirit of the invention, should all fall within the scope of protection defined by the claims of the present invention.

Claims

1. The process involves acquiring weather data, soil moisture data, and vegetation remote sensing observation data for the monitored area, and then standardizing the acquired data to obtain a standardized precipitation evapotranspiration index, a standardized soil moisture index, and a standardized vegetation index. The steps include constructing a three-dimensional simultaneous distribution function based on the standardized precipitation evapotranspiration index, the standardized soil moisture index, and the standardized vegetation index, The steps include: calculating the drought transmission time and drought transmission probability based on the three-dimensional joint distribution function, and calculating the drought transmission index based on the drought transmission time and drought transmission probability; A method for quantifying the drought transmission inhibiting effect of soil moisture under drought stress, comprising the steps of: calculating a drought transmission inhibition rate based on the aforementioned drought transmission index and completing the quantification of the drought transmission inhibition effect.

2. The method for constructing the aforementioned three-dimensional joint distribution function includes the following equation: [Math 1] Here, C ３ represents the three-dimensional joint distribution function, u １ represents the marginal normal distribution of the standardized precipitation evapotranspiration index, u ２ represents the marginal normal distribution of the standardized soil moisture index, u ３ This represents the marginal normal distribution of the standardized vegetation index. [Math 2] represents the correlation matrix between the standardized precipitation evapotranspiration index, the standardized soil moisture index, and the standardized vegetation index, and w represents the integral variable matrix. [Math 3] A method for quantifying the drought transmission inhibitory effect of soil moisture under drought stress according to claim 1, characterized in that represents the inverse function of the normal distribution function.

3. The method for calculating the aforementioned drought transmission index is: We calculated a drought transmission matrix that takes into account the effects of early summer soil moisture. [Math 4] Here, PP ｉ＿ｃｓｍ represents the drought transmission matrix considering the influence of soil moisture in the early summer, P represents the transmission probability, i represents the SPEI cumulative scale, SNDVI represents the normalized difference vegetation index, SSMI represents the normalized soil moisture index, SPEI represents the standardized precipitation evapotranspiration index, F ＳＮＤＶＩ represents the peripheral normal distribution function of summer vegetation, F ＳＳＭＩ represents the peripheral normal distribution function of the previous SSMI, F ＳＰＥＩ represents the peripheral normal distribution function of the previous SPEI, C ２１ represents the step of the two-dimensional joint distribution function between SSMI and SPEI, and Calculate the drought transmission matrix without considering the effects of early summer soil moisture: [Math 5] Here, PP ｉ＿ｎｃｓｍ This represents the drought transmission matrix, which does not take into account the effects of soil moisture in the early summer, and C ２２ This represents the two-dimensional joint distribution function between SNDVI and SPEI, and The steps include: extracting the first drought transmission time and the first drought transmission probability from the drought transmission matrix that takes into account the influence of early summer soil moisture; and extracting the second drought transmission time and the second drought transmission probability from the drought transmission matrix that does not take into account the influence of early summer soil moisture; Based on the first drought transmission time and the first drought transmission probability, the first drought transmission index is calculated considering the effect of early summer soil moisture, and based on the second drought transmission time and the second drought transmission probability, the second drought transmission index is calculated without considering the effect of early summer soil moisture. [Math 6] [Number 7] A method for quantifying the drought transmission inhibitory effect of soil moisture under drought stress according to claim 2, characterized by comprising the step of, where DPI_csm represents the first drought transmission index, PP_csm represents the first drought transmission probability, PT_csm represents the first drought transmission time, DPI_ncsm represents the second drought transmission index, PP_ncsm represents the second drought transmission probability, and PT_ncsm represents the second drought transmission time.

4. The method for calculating the drought transmission inhibition rate is as follows: The step of calculating the drought transmission inhibition rate based on the first drought transmission index and the second drought transmission index is: [Number 8] A method for quantifying the drought transmission inhibition effect of soil moisture under drought stress, as described in claim 3, characterized in that, here, DR represents the drought transmission inhibition rate.

5. A system for quantifying the drought transfer inhibitory effect of soil moisture under drought stress, wherein the system applies the method described in any one of claims 1 to 4 and includes a data acquisition module, a function construction module, an index calculation module, and an inhibition rate calculation module. The data acquisition module is used to acquire weather data, soil moisture data, and vegetation remote sensing observation data of the monitored area, and to perform standardization processing on the acquired data to obtain a standardized precipitation evapotranspiration index, a standardized soil moisture index, and a standardized vegetation index. The function construction module constructs a three-dimensional simultaneous distribution function based on the standardized precipitation evapotranspiration index, the standardized soil moisture index, and the standardized vegetation index. The index calculation module calculates the drought transmission time and drought transmission probability based on the three-dimensional joint distribution function, and calculates the drought transmission index based on the drought transmission time and drought transmission probability. The inhibition rate calculation module is a system for quantifying the drought transmission inhibition effect of soil moisture under drought stress, characterized by calculating the drought transmission inhibition rate based on the drought transmission index and completing the quantification of the drought transmission inhibition effect.

6. The workflow of the aforementioned function building module includes the following equation: [Number 9] Here, C ３ represents the three-dimensional joint distribution function, u １ represents the marginal normal distribution of the standardized precipitation evapotranspiration index, u ２ represents the marginal normal distribution of the standardized soil moisture index, u ３ This represents the marginal normal distribution of the standardized vegetation index. [Number 10] represents the correlation matrix between the standardized precipitation evapotranspiration index, the standardized soil moisture index, and the standardized vegetation index, and w represents the integral variable matrix. [Math 11] The system for quantifying the drought transmission inhibitory effect of soil moisture under drought stress according to claim 5, characterized in that represents the inverse function of the normal distribution function.

7. The workflow for the aforementioned exponential calculation module is as follows: We calculated a drought transmission matrix that takes into account the effects of early summer soil moisture. [Math 12] Here, PP ｉ＿ｃｓｍ represents the drought transmission matrix considering the effects of early summer soil moisture, P represents the transmission probability, i represents the SPEI cumulative scale, SNDVI represents the standardized vegetation index, SSMI represents the standardized soil moisture index, SPEI represents the standardized precipitation evapotranspiration index, and F ＳＮＤＶＩ This represents the marginal normal distribution function of summer vegetation, F ＳＳＭＩ This represents the marginal normal distribution function of the earlier SSMI, and F ＳＰＥＩ This represents the marginal normal distribution function of the earlier SPEI, and C ２１ This represents the two-dimensional joint distribution function between SSMI and SPEI, and Calculate the drought transmission matrix without considering the effects of early summer soil moisture: [Number 13] Here, PP ｉ＿ｎｃｓｍ This represents the drought transmission matrix, which does not take into account the effects of soil moisture in the early summer, and C ２２ This represents the two-dimensional joint distribution function between SNDVI and SPEI, and The steps include: extracting the first drought transmission time and the first drought transmission probability from the drought transmission matrix that takes into account the influence of early summer soil moisture; and extracting the second drought transmission time and the second drought transmission probability from the drought transmission matrix that does not take into account the influence of early summer soil moisture; Based on the first drought transmission time and the first drought transmission probability, the first drought transmission index is calculated considering the effect of early summer soil moisture, and based on the second drought transmission time and the second drought transmission probability, the second drought transmission index is calculated without considering the effect of early summer soil moisture. [Number 14] [Number 15] A system for quantifying the drought transmission inhibitory effect of soil moisture under drought stress according to claim 6, characterized by comprising the step of, where DPI_csm represents the first drought transmission index, PP_csm represents the first drought transmission probability, PT_csm represents the first drought transmission time, DPI_ncsm represents the second drought transmission index, PP_ncsm represents the second drought transmission probability, and PT_ncsm represents the second drought transmission time.

8. The workflow for the aforementioned inhibition rate calculation module is as follows: The step of calculating the drought transmission inhibition rate based on the first drought transmission index and the second drought transmission index is: [Number 16] The system for quantifying the drought transmission inhibition effect of soil moisture under drought stress, as described in claim 7, wherein DR represents the drought transmission inhibition rate.

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