Assessment method for high-temperature drought composite disasters of crops based on dynamic cumulative stress degree

Abstract

The invention discloses a dynamic cumulative stress degree-based crop high-temperature and drought composite disaster assessment method, which comprises the following steps of: acquiring meteorological data of a research area, determining a composite day according to a high-temperature and drought composite day judgment condition, and identifying a high-temperature and drought composite event according to definition; constructing a day-by-day temperature suitability function by combining the three-base-point temperatures of the crops in different growth periods, and quantifying the instant recovery capability of the crops to the high temperature; calculating the composite stress intensity day by day, and accumulating the duration of the high-temperature drought composite event to obtain an accumulated stress degree; and according to the cumulative stress degree, dividing the high-temperature drought composite disasters into four levels of light, medium, heavy and extremely heavy, and realizing risk assessment. According to the crop high-temperature and drought composite disaster assessment method based on the dynamic cumulative stress degree, the crop high-temperature and drought composite disaster can be dynamically assessed, the stress accumulation and recovery capability can be quantified, disaster grades can be divided, and scientific support is provided for accurate disaster prevention and grain safety guarantee.

Description

Technical Field

[0001] This invention relates to the field of agricultural meteorological disaster monitoring technology, specifically to a method for assessing combined crop high temperature and drought disasters based on dynamic cumulative stress. Background Technology

[0002] Against the backdrop of global warming, the frequency of simultaneous high temperatures and droughts is showing a significant upward trend, creating superimposed stress on the growth and development of major food crops such as corn, wheat, and rice. This leads to physiological metabolic disorders and decreased photosynthetic efficiency, ultimately causing significant fluctuations in yield and seriously threatening regional food security.

[0003] Traditional agricultural meteorological disaster research often treats high temperature and drought as independent disaster types, using indicators such as the number of extreme high temperature days and the duration of heat waves to characterize high temperature disasters, and using indicators such as the standardized precipitation index (SPI) and precipitation anomaly to monitor drought disasters. Such methods are difficult to capture the nonlinear synergistic stress effect of "high temperature and drought superposition" and cannot accurately reflect the actual impact of compound disasters on crops.

[0004] In recent years, although some technologies have attempted to assess combined high-temperature and drought disasters, they still rely on fixed thresholds and static statistics, which have many limitations, specifically manifested in three aspects: Insufficient depiction of dynamic processes: Most methods characterize disaster intensity using "snapshot" data or time-period statistics of disaster events, ignoring the dynamic competition mechanism between "continuous high temperature and drought leading to continuous stress accumulation" and "low night temperature and intermittent precipitation bringing physiological recovery", and thus failing to present the daily evolution of disaster intensity.

[0005] Lack of parameterization of resilience: Although the field of ecology has proposed a stress-recovery-resilience assessment framework, most of the relevant indicators are post-disaster statistical values. Crop recovery efficiency is not introduced into the assessment model as an endogenous variable that changes dynamically with ambient temperature, making it difficult to quantify the differences in recovery capacity between regions and the chain effect of "recovery failure amplifying subsequent stress shocks".

[0006] Weak intensity-loss link: Existing assessment indices mostly rely on empirical regression or descriptions of disaster rarity, lacking critical thresholds that combine crop growth period sensitivity, and cannot clearly answer "what cumulative stress burden will cross the crop physiological instability threshold and cause irreversible yield reduction", resulting in a frequent disconnect between disaster intensity assessment results and actual yield loss in the field.

[0007] Therefore, there is an urgent need for a crop high-temperature and drought combined disaster assessment method based on dynamic cumulative stress, which takes into account the assessment framework of "multi-factor coupling-dynamic accumulation-quantitative loss", and realizes daily tracking and risk warning of high-temperature and drought combined disasters under the condition of operational data requirements. Summary of the Invention

[0008] The purpose of this invention is to provide a method for assessing the combined disasters of high temperature and drought on crops based on dynamic cumulative stress, so as to achieve the integration of "daily monitoring - graded early warning - loss prediction" and provide quantitative basis for irrigation scheduling, insurance claims and related decision-making.

[0009] To achieve the above objectives, this invention provides a method for assessing combined crop heat and drought disasters based on dynamic cumulative stress, comprising the following steps: S1. Obtain meteorological data for the study area, including daily maximum temperature, daily minimum temperature, and daily precipitation; S2. Based on the meteorological data, according to the criteria for determining a combined high-temperature and drought day, a combined high-temperature and drought day is obtained, and according to the definition of a combined high-temperature and drought event, a combined high-temperature and drought event is identified. S3. Combining the three cardinal temperatures of crops at different growth stages, a daily temperature suitability function is constructed to quantify the immediate recovery capacity of crops to combined high temperature and drought stress. S4. Calculate the intensity of the combined stress on a daily basis, and accumulate the cumulative stress degree during the duration of the combined high temperature and drought event; S5. Based on the magnitude of the cumulative stress, the combined high temperature and drought disaster is divided into four levels: light, medium, severe, and extremely severe, to achieve risk assessment.

[0010] Preferably, the conditions for determining the combined high temperature and drought day include temperature conditions and humidity conditions; The temperature condition is: the daily maximum temperature is higher than the 80th percentile threshold for the same period in history; The humidity condition is: the daily standardized precipitation evapotranspiration index (SPEI) is below -0.5.

[0011] Preferably, the high temperature and drought complex event is defined as a continuous process that lasts for at least 3 consecutive days and meets the criteria for determining a high temperature and drought complex day each day. If a normal day with no more than 2 days that is not a combined high-temperature and drought day occurs during the continuous process, it is considered an internal interruption of the combined high-temperature and drought event. Subsequent combined high-temperature and drought days will continue to be counted as the same event. If three consecutive normal days occur during the aforementioned period, the current high-temperature and drought complex event is considered to have ended on the previous high-temperature and drought complex day.

[0012] Preferably, the three cardinal temperatures are the lower limit temperatures of the crop's current growth stage. Optimal temperature and upper limit temperature .

[0013] Preferably, the expression for the temperature suitability function is: ; in, B represents the average temperature of a certain day, and B is the slope ratio of the temperature range. The temperature suitability of the i-th day is determined by the actual daily average temperature and the three cardinal point temperatures. The expression for the slope ratio of the temperature range is: .

[0014] Preferably, the formula for calculating the combined stress intensity is: ; ; in, Let the intensity of the combined stress on day i be , The highest temperature on day i; This is the 80th percentile of the historical daily maximum temperature for the area. is the absolute value of the SPEI value on day i.

[0015] Preferably, the formula for calculating the cumulative stress degree is: ; in, Let t be the cumulative stress degree on day t, and n be the total number of days in a high-temperature and drought complex event, with a minimum value of 3.

[0016] Preferably, the specific content of the disaster level classification includes: S501. Collect production data corresponding to different cumulative stress levels under historical disasters, and establish a database of cumulative stress levels and relative production losses; S502. Based on the database, perform linear regression on the cumulative stress degree versus relative production loss, and extract the cumulative stress degree corresponding to production reductions of 10%, 20%, and 30% as critical thresholds. , , ; S503. Establish a level mapping table. It is a minor disaster. The disaster was classified as moderate. It is classified as a severe disaster. It is classified as an extremely severe disaster.

[0017] Preferably, the changes in disaster level can be predicted based on the magnitude of cumulative stress, providing advance guidance for zoned irrigation and disaster prevention and mitigation.

[0018] The present invention employs the above-mentioned method for assessing combined crop heat and drought disasters based on dynamic cumulative stress, and its beneficial effects are as follows: (1) Shift from single factor to compound event-driven: taking the simultaneous occurrence and compound effect of high temperature and drought on a daily scale as the basic unit for event definition, and considering the influence of daily average temperature on the intensity of compound events, more accurately reflects the synergistic stress nature of "high temperature and drought superposition" rather than simply superimposing two independent events; (2) From static threshold to dynamic accumulation process: A dynamic, daily accumulation stress degree model is proposed, which also considers the cumulative effect of short-term high temperature and drought combined events. It can not only determine whether the event occurs, but also quantify its intensity dynamics and cumulative effect over time, so as to achieve a fine characterization of the event process. (3) The shift from phenomenon description to mechanism quantification: By introducing the recovery factor and the physically meaningful amplification effect factor (|SPEI|), we attempt to quantify the system's resilience and the nonlinear amplification effect of drought on high temperature stress, and reveal the intrinsic physical process driving the intensity of events. (4) Integration of meteorological indicators with crop growth meteorological indicators: When calculating the recovery effect, crop three-point temperature is considered to reflect more biological information, so that the assessment results are more in line with the actual response of the affected object.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a core flowchart of the crop high temperature and drought combined disaster assessment method based on dynamic cumulative stress degree of the present invention; Figure 2 This is an example of the crop high temperature and drought combined disaster assessment method based on dynamic cumulative stress degree of the present invention, which is a flowchart for the classification of high temperature and drought combined disaster levels and disaster prevention and mitigation guidance. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0023] like Figure 1 As shown, the method for assessing combined crop heat and drought disasters based on dynamic cumulative stress includes the following steps: S1. Obtain meteorological data for the study area, including daily maximum temperature, daily minimum temperature, and daily precipitation; S2. Based on the meteorological data, according to the criteria for determining a combined high-temperature and drought day, a combined high-temperature and drought day is obtained, and according to the definition of a combined high-temperature and drought event, a combined high-temperature and drought event is identified. S3. Combining the three cardinal temperatures of crops at different growth stages, a daily temperature suitability function is constructed to quantify the immediate recovery capacity of crops to combined high temperature and drought stress. S4. Calculate the intensity of the combined stress on a daily basis, and accumulate the cumulative stress degree during the duration of the combined high temperature and drought event; S5. Based on the magnitude of the cumulative stress, the combined high temperature and drought disaster is divided into four levels: light, medium, severe, and extremely severe, to achieve risk assessment.

[0024] Example 1 This embodiment establishes a correlation threshold between cumulative stress and yield loss during the flowering-grain-filling stage of maize, achieving accurate classification of disaster levels and verifying the effectiveness of the method in assessing the combined high temperature and drought disasters of maize.

[0025] Meteorological data from June to September 2000 to 2024 were collected to establish a daily maximum temperature sequence and calculate the 80th percentile threshold.

[0026] The criteria for determining a combined high-temperature and drought day are: the daily maximum temperature is higher than the 80th percentile threshold for the same period in history; and the daily standardized precipitation evapotranspiration index (SPEI) is lower than -0.5.

[0027] A high-temperature drought complex event is defined as a continuous process that lasts for at least 3 consecutive days and meets the criteria for a high-temperature drought complex day each day. If there are no more than 2 normal days that are not high-temperature drought complex days during the continuous process, the high-temperature drought complex event is considered to be interrupted internally, and subsequent high-temperature drought complex days will continue to be counted as the same event. Only if there are three consecutive normal days during the continuous process is the current high-temperature drought complex event determined to have ended on the previous high-temperature drought complex day.

[0028] Meteorological data is acquired from June to September of the current year, daily SPEI is calculated, high-temperature and drought composite days are counted according to the criteria for determining high-temperature and drought composite days, and high-temperature and drought composite events are counted according to the definition of high-temperature and drought composite events.

[0029] Table 1. T1, T2, and T0 values ​​of maize at different developmental stages.

[0030] From June to September, maize is in the flowering-filling stage, as shown in Table 1. The three cardinal temperatures are taken as T1 = 14℃, T0 = 25.5℃, and T2 = 32℃. Calculate the slope ratio of the temperature ranges: =0.57; The expression for the temperature suitability function is: ; in, B represents the average temperature of a certain day, and B is the slope ratio of the temperature range. The suitability of the i-th day's temperature, determined by the actual daily average temperature and the three base point temperatures, represents the resilience.

[0031] Then calculate the daily combined stress intensity using the following formula: ; ; in, Let the intensity of the combined stress on day i be , The highest temperature on day i; This is the 80th percentile of the historical daily maximum temperature for the area. is the absolute value of the SPEI value on day i.

[0032] The formula for calculating cumulative stress is: ; in, Let t be the cumulative stress degree on day t, and n be the total number of days in a high-temperature and drought complex event, with a minimum value of 3.

[0033] like Figure 2 As shown, data on different cumulative stress levels and corresponding yields in the local area over the years were collected to establish a database of cumulative stress levels and relative yield loss ΔY; Based on the aforementioned database, a linear regression was performed on the cumulative stress level versus relative production loss ΔY. The cumulative stress levels corresponding to production reductions of 10%, 20%, and 30% were extracted as critical thresholds D1, D2, and D3, respectively, yielding D1 (ΔY = 10%). t =3.1, D2 (ΔY=20%) corresponds to D t =5.8, D3 (ΔY=30%) corresponds to D t =8.5.

[0034] Then, a level mapping table is created. It is a minor disaster. The disaster was classified as moderate. It is classified as a severe disaster. It is classified as an extremely severe disaster.

[0035] Because the process is dynamic, we can predict in advance when the level jumps to "severe disaster," and the county agricultural technology center can promptly issue sprinkler irrigation dispatch instructions to reduce yield losses.

[0036] This embodiment demonstrates that the crop high-temperature and drought combined disaster assessment method based on dynamic cumulative stress can achieve a refined and dynamic assessment of high-temperature and drought combined disasters during the crop growth period. By combining the three cardinal temperatures of maize during the flowering-grain-filling stage to quantify the crop's temperature recovery capacity, and then coupling the degree of high temperature exceedance with the degree of drought to calculate the daily stress intensity and cumulative stress, it can accurately correlate the degree of disaster accumulation with crop yield loss. Moreover, the disaster level classification based on the yield loss threshold can effectively match the actual disaster situation in the field. At the same time, this method can identify the trend of disaster level escalation in advance, providing clear quantitative basis for agricultural technology departments to initiate disaster prevention and mitigation measures (such as zoned sprinkler irrigation), verifying the scientific nature, practicality, and operability of the method, and possessing the potential for operational promotion.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for assessing combined crop heat and drought disasters based on dynamic cumulative stress, characterized in that, Includes the following steps: S1. Obtain meteorological data for the study area, including daily maximum temperature, daily minimum temperature, and daily precipitation; S2. Based on the meteorological data, according to the criteria for determining a combined high-temperature and drought day, a combined high-temperature and drought day is obtained, and according to the definition of a combined high-temperature and drought event, a combined high-temperature and drought event is identified. S3. Combining the three cardinal temperatures of crops at different growth stages, a daily temperature suitability function is constructed to quantify the immediate recovery capacity of crops to combined high temperature and drought stress. S4. Calculate the intensity of the combined stress on a daily basis, and accumulate the cumulative stress degree during the duration of the combined high temperature and drought event; S5. Based on the magnitude of the cumulative stress, the combined high temperature and drought disaster is divided into four levels: light, medium, severe, and extremely severe, to achieve risk assessment.

2. The method for assessing combined crop heat and drought disasters based on dynamic cumulative stress degree according to claim 1, characterized in that, The criteria for determining a combined high-temperature and drought day include temperature and humidity conditions. The temperature condition is: the daily maximum temperature is higher than the 80th percentile threshold for the same period in history; The humidity condition is: the daily standardized precipitation evapotranspiration index (SPEI) is below -0.

5.

3. The method for assessing combined crop heat and drought disasters based on dynamic cumulative stress degree according to claim 1, characterized in that, The high temperature and drought complex event is defined as a continuous process that lasts for at least 3 consecutive days and meets the criteria for determining a high temperature and drought complex day each day. If a normal day with no more than 2 days that is not a combined high-temperature and drought day occurs during the continuous process, it is considered an internal interruption of the combined high-temperature and drought event. Subsequent combined high-temperature and drought days will continue to be counted as the same event. If three consecutive normal days occur during the aforementioned period, the current high-temperature and drought complex event is considered to have ended on the previous high-temperature and drought complex day.

4. The method for assessing combined crop heat and drought disasters based on dynamic cumulative stress degree according to claim 1, characterized in that, The three cardinal temperatures are the lower limit temperatures for the current growth stage of the crop. Optimal temperature and upper limit temperature .

5. The method for assessing combined crop high-temperature and drought disasters based on dynamic cumulative stress degree according to claim 1, characterized in that, The expression for the temperature suitability function is: ； in, B represents the average temperature of a certain day, and B is the slope ratio of the temperature range. The temperature suitability of the i-th day is determined by the actual daily average temperature and the three cardinal point temperatures. The expression for the slope ratio of the temperature range is: 。 6. The method for assessing combined crop high-temperature and drought disasters based on dynamic cumulative stress degree according to claim 1, characterized in that, The formula for calculating the combined stress intensity is as follows: ； ； in, Let the intensity of the combined stress on day i be , The highest temperature on day i; This is the 80th percentile of the historical daily maximum temperature in the area. is the absolute value of the SPEI value on day i.

7. The method for assessing combined crop high-temperature and drought disasters based on dynamic cumulative stress degree according to claim 1, characterized in that, The formula for calculating the cumulative stress degree is as follows: ； in, Let n be the cumulative stress degree on day t, and n be the total number of days in a combined high-temperature and drought event, with a minimum value of 3.

8. The method for assessing combined crop high-temperature and drought disasters based on dynamic cumulative stress degree according to claim 1, characterized in that, The specific content of disaster level classification includes: S501. Collect production data corresponding to different cumulative stress levels under historical disasters, and establish a database of cumulative stress levels and relative production losses; S502. Based on the database, perform linear regression on the cumulative stress degree versus relative production loss, and extract the cumulative stress degree corresponding to production reductions of 10%, 20%, and 30% as critical thresholds. , , ; S503. Establish a level mapping table. It is a minor disaster. The disaster was classified as moderate. It is a severe disaster. It is an extremely severe disaster.

9. The method for assessing combined crop high-temperature and drought disasters based on dynamic cumulative stress degree according to claim 1, characterized in that, Based on the magnitude of cumulative stress, changes in disaster levels can be predicted, providing advance guidance for zoned irrigation and disaster prevention and mitigation.

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