Specific disaster weather and climate crop output reduction risk assessment method and system

Abstract

The invention relates to the technical field of agricultural meteorology, and provides a specific disaster weather climate crop output reduction risk assessment method comprising the following steps: S1, calculating a relative meteorological output; s2, calculating the average yield reduction rate; s3, calculating a yield reduction variation coefficient; s4, the output reduction probability is calculated; s5, calculating a yield reduction probability index; and S6, calculating a yield reduction risk index. The invention also correspondingly provides a crop output reduction risk assessment system. The invention further provides a crop output reduction risk assessment system for specific disaster weather and climate. The invention provides a quasi-normalized crop yield reduction risk index, and the risk index has the advantages of high indication, intuition and understandability, and facilitates the development of application services.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural meteorology, and more specifically, to a method and system for assessing the risk of crop yield reduction under specific weather and climate conditions. Background Art

[0002] Crops (including grain, oil, cotton crops, and other specialty crops) require light, temperature, and water for growth, and are significantly affected and restricted by meteorological and climate conditions. Therefore, crop planting has obvious regional and climate difference characteristics. Different crops in different regions are also affected differently by certain specific meteorological disasters and climate events, and will suffer varying degrees of yield reduction. This yield reduction risk can be quantified and evaluated by constructing indicators.

[0003] The risk of crop yield reduction is determined by the losses caused by agricultural meteorological disasters and their occurrence probabilities. The losses of agricultural disasters can be directly reflected by the yield reduction rate. A large yield reduction rate indicates a great impact of agricultural meteorological disasters. Moreover, the degree of impact of crops in a region by meteorological disasters is also greatly related to the frequency of disasters and the volatility of disaster intensity. Therefore, when constructing indicators for the risk of crop yield reduction under specific disaster weather and climate conditions, the above three aspects need to be considered, that is, the risk of crop yield reduction can be comprehensively evaluated by the yield reduction rate, the coefficient of variation of the yield reduction rate, and the probability of yield reduction.

[0004] The quantitative assessment of the risk of crop yield reduction can be used for agricultural climate zoning and refined agricultural production, guiding agricultural disaster prevention and mitigation, and agricultural insurance pricing, etc. Summary of the Invention

[0005] In view of the problems in the background art, the present invention proposes a method for assessing the risk of crop yield reduction under specific disaster weather and climate conditions, including: S1, calculating the percentage of the crop meteorological yield relative to the trend yield, which is called the relative meteorological yield, and forming a relative meteorological yield sequence with the relative meteorological yields of consecutive years; S2, calculating the average yield reduction rate for the relative meteorological yield sequence; S3, calculating the coefficient of variation of yield reduction based on the relative meteorological yield and the average yield reduction rate; S4, calculating the probability of yield reduction according to the relative meteorological sequence; S5, calculating the yield reduction probability index based on the probabilities in different yield reduction intervals; S6, calculating the yield reduction risk index based on the average yield reduction rate, the coefficient of variation of the yield reduction rate, and the yield reduction probability index.

[0006] The present invention also proposes a system for assessing the risk of crop yield reduction under specific disaster weather and climate conditions, which includes a computer-executable program. When the program is executed, the method described above is implemented.

[0007] The beneficial effects of the present invention are as follows: on the one hand, in the case of missing meteorological disaster intensity data or difficult to quantitatively evaluate, the corresponding indicators that can indirectly reflect the disaster intensity can be calculated by using crop yield data to evaluate the size of the crop yield reduction risk; on the other hand, by constructing a quasi-normalized crop yield reduction risk index, the size of the crop yield reduction risk can be basically characterized by a numerical value from 0 to 1, with strong indicativeness, intuitiveness and understandability, which is convenient to carry out application services with it. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a better understanding of the present invention, the present invention will be described in more detail by referring to the specific embodiments shown in the accompanying drawings. These drawings only depict the typical embodiments of the present invention and should not be considered as limiting the protection scope of the present invention.

[0009] Figure 1 It is a flowchart of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0010] The embodiments of the present invention will be described below with reference to the accompanying drawings, so that those skilled in the art can better understand the present invention and be able to implement it, but the listed embodiments are not the limitations of the present invention. Without conflict, the following embodiments and the technical features in the embodiments can be combined with each other, and the same components are represented by the same reference numerals. The present invention provides a method and system for evaluating the crop yield reduction risk of specific disaster weather and climate, especially for the method and system for evaluating the crop yield reduction risk of a specific agricultural meteorological disaster (such as high temperature, drought, frost, etc.) or a specific climate event (such as El Niño or La Nina, etc.). As Figure 1 shown, the method of the present invention includes.

[0011] S1. Calculate the percentage of the crop meteorological yield relative to the trend yield, which is called the relative meteorological yield, and form a relative meteorological yield sequence with the relative meteorological yields of consecutive years.

[0012] First, perform yield separation, that is, separate the crop meteorological yield from the actual crop yield (yield per unit area) as shown in the following formula (1): (1), wherein, is the trend yield, which can be obtained by modeling through linear regression or polynomial operation based on the actual crop yield sequence and is the fitted value.

[0013] Then, calculate the relative meteorological yield , as shown in the following formula (2): (2), Form a relative meteorological yield sequence {}, which is the relative meteorological yield .

[0014] S2. Calculate the average reduction rate based on the relative meteorological yield sequence obtained from S1.

[0015] For a relative meteorological yield sequence { }, if < 0, the corresponding year is defined as a reduction year, and the calculation of the average reduction rate is shown in formula (3) as follows: (3), wherein, is the relative meteorological yield, and n is the total number of samples of the relative meteorological yield sequence { } where < 0.

[0016] The average reduction rate can reflect the average reduction level of crop yields over the years. A large average reduction rate indicates a greater impact of meteorological disasters on yields in a region. Correspondingly, the risk of meteorological disasters is greater.

[0017] S3. Calculate the reduction coefficient of variation based on the relative meteorological yield obtained from S1 and the average reduction rate obtained from S2.

[0018] The volatility presented by the reduction rates of all reduction years is called the reduction rate coefficient of variation , and the calculation method is shown in formula (4): (4), wherein, represents the reduction rate coefficient of variation, is the relative meteorological yield and < 0. n is all reduction years corresponding to , is the average value of is the average reduction rate.

[0019] The reduction rate coefficient of variation can describe the interannual fluctuation of the reduction rate. The larger the absolute value, the greater the volatility of the reduction rate, the worse the stability of the impact of meteorological disasters on crop yields, and correspondingly, the greater the risk of meteorological disasters faced.

[0020] S4. Calculate the reduction probability based on the relative meteorological sequence obtained from S1.

[0021] Due to the uncertainty of crop yields caused by different meteorological conditions, agricultural production measures, etc. every year, the relative meteorological yield sequence over a relatively long period of time has the characteristics of a sequence of random continuous variables. Relevant research also shows that meteorological yields generally follow a normal distribution. By conducting a normality test on all samples of the research object, it is proved that the relative meteorological yield sequence of crops has the characteristics of a normal distribution. Therefore, based on the sample mean and the sample standard deviation of the relative meteorological yield sequence { }, a probability density function (Formula 5) is established: (5), Then, according to the distribution function curve, calculate the probabilities of crop yields occurring in different yield increase and decrease rate intervals (see Formula (6)): (6), In the formula, is the relative meteorological yield, is the specific yield increase or decrease rate.

[0022] Then, the probability of a certain yield increase or decrease interval [x 1 , x 2 ) is obtained through Formula (7): (7), The probability of small yield reduction is large and the probability of large yield reduction is large, and the meteorological disaster risks faced are significantly different. Therefore, the probability sizes at different yield reduction levels can reflect the risk size of crop yield reduction in a region.

[0023] S5. Calculate the yield reduction probability index based on the probabilities of different yield reduction intervals obtained in S4.

[0024] The yield reduction probability index comprehensively considers the probability sizes of different yield reduction intervals and integrates them into a normalized index to characterize the comprehensive influence status of the probability sizes at different yield reduction levels.

[0025] Divide the yield reduction rate interval [-1, 0) into different sub-intervals [-1~x n-1 ), [x n-1 , x n-2 ), …, [x 2 ~x 1 ), [x 1 ~0), where -1 < x n-1 < x n-2 < … < x 2 < x 1 < 0, corresponding to different yield reduction levels respectively. Denote the yield reduction probabilities corresponding to the above intervals as p n , p n-1 , …, p2 , p 1 , a reduction probability index can be constructed, as shown in Equation (8): (8), where a n is the weight value corresponding to the reduction interval [x n ~ x n-1 ).

[0026] According to the overall situation of agricultural meteorological disasters, generally, the reduction rate interval [-1, 0) can be set as 6 sub-intervals, namely [-100% ~ -15%), [-15% ~ -10%), [-10% ~ -7%), [-7% ~ -5%), [-5% ~ -3%), [-3% ~ 0), and the weight values decrease in turn, which are set as 6, 5, 4, 3, 2, 1 respectively; C is a constant, C = 6. If the reduction rate interval [-1, 0) is set as N sub-intervals, then C = N.

[0027] It can be seen from Equation (8) that the reduction probability index is a comprehensive evaluation of the occurrence probability and its impact of different reduction levels in a region, the larger it is, the greater the reduction probability and the higher the high-reduction risk level.

[0028] S6. Calculate the reduction risk assessment index based on the average reduction rate obtained from S2, the coefficient of variation of the reduction rate obtained from S3, and the reduction probability index obtained from S5.

[0029] Three crop reduction risk indicators constructed according to Equation (3), Equation (4), and Equation (8): average reduction rate d , coefficient of variation of the reduction rate v , reduction probability index , to construct the reduction risk assessment index of different crops in different regions under specific disasters (or climate events) , which is called the reduction risk index, as shown in Equation (9).

[0030] (9), where = 3, and are adjustment coefficients respectively. Generally, = 5 and = 2.

[0031] The reduction risk index is a quasi-normalized index, and its value is basically between 0 and 1, the larger the value, the higher the reduction risk.

[0032] The construction principle is explained as follows: Average reduction rated , Coefficient of variation of yield reduction v , Yield reduction probability index Theoretically, all three factors are indicators ranging from 0 to 1. Therefore, by taking the arithmetic mean of the three factors, normalization can be carried out, so n = 3. Usually, the average yield reduction rate of crops d is generally within 20% (i.e., d < 0.2). Although cases exceeding 20% exist, they are extremely rare. Therefore d the threshold of v is usually (0, 0.2); actual calculations show that 0 < v < 1, and the distribution is relatively uniform, that is v the threshold of is generally (0, 1); through theoretical estimation and calculation of under comprehensive meteorological disasters and specific climate events of different crops in different regions of the world, it is shown that is generally less than 0.5, that is the threshold of

[0033] is generally (0, 0.5).

[0033] If the above three factors are directly added and simply averaged arithmetically, not only does it objectively and artificially reduce the weight of the average yield reduction rate and the yield reduction probability index in risk assessment, but also the resulting yield reduction risk index is much less than 1. Therefore, set the adjustment coefficient = 5 and the adjustment coefficient = 2, and set the two factors of the average yield reduction rate and the yield reduction probability index to a numerical range (0, 1) close to the coefficient of variation of yield reduction v . Then, take the arithmetic mean of the three adjusted factors, which not only balances the influence weights of the average yield reduction rate d and the yield reduction probability index , but also can set the risk indices of different crops in different regions within the range of 0 to 1.

[0034] If the average yield reduction rate in a region is greater than 20% (i.e., d > 0.2), and at the same time the yield reduction probability index is greater than 0.5 (i.e., p c > 0.5), then there may be greater than 1, and both of these situations indicate extremely extreme weather and climate conditions.

[0035] Therefore, through formula (9) and the adjustment coefficients and , a quasi-normalized crop yield reduction risk index can be obtained, such that the index is generally between 0 and 1. If it exceeds 1, it indicates an extremely rare ultra-high risk level for a certain crop in a certain region under specific disaster weather or climate events, which is consistent with the indicative meaning of the risk index.

[0036] The present invention has been experimented, simulated and applied in different sub-regions and different crops in six continents with agricultural areas around the world, and can objectively and intuitively reflect the yield reduction risks of different crops in different regions of the world under specific meteorological disasters or climate events (see Table 1).

[0037] Table 1 Yield reduction risk indices of different crops in major grain-producing countries of the world under El Niño or La Nina

[0038] Note: (The higher the index value, the higher the risk.) The present invention also correspondingly proposes a specific disaster weather and climate crop yield reduction risk assessment system, which includes a computer-executable program that, when executed, implements the method as described above.

[0039] The above-described embodiments are only relatively preferred specific implementation manners of the present invention. The present specification uses phrases such as "in one embodiment", "in another embodiment", "in yet another embodiment" or "in other embodiments", which may all refer to one or more of the same or different embodiments according to the present disclosure. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for assessing the risk of crop yield reduction due to specific disaster weather and climate, characterized in that: include: S1, calculate the percentage of crop meteorological yield relative to trend yield, called relative meteorological yield, and combine the relative meteorological yields of consecutive years into a relative meteorological yield sequence; S2, calculating the average reduction rate for the relative meteorological yield sequence; S3, calculating a coefficient of variation of reduction in production based on the relative meteorological production and the average reduction rate in production; S4, calculating the probability of production reduction according to the relative meteorological production sequence; S5, calculating a production reduction probability index based on the probabilities of different production reduction intervals; S6, calculating a production reduction risk index based on the average production reduction rate, the production reduction coefficient of variation and the production reduction probability index.

2. The crop yield reduction risk assessment method according to claim 1, characterized in that: In step S1, the relative meteorological yield The calculation methods include: 1) Crop meteorological yield From the actual crop yield Separate it out, the formula is as follows: , where is the trend output; 2) Calculate relative meteorological output , the formula is as follows: .

3. The crop yield reduction risk assessment method according to claim 1, characterized in that: In step S2, the average reduction rate The calculation formula is as follows: ， In the formula, is the relative meteorological output, n is <0 relative meteorological production series { }Total number of samples.

4. The crop yield reduction risk assessment method according to claim 1, characterized in that: In step S3, the coefficient of variation of the reduction rate , the calculation formula is as follows: ， In the formula, represents the coefficient of variation of the yield reduction rate, is the relative meteorological yield and <0, n is the corresponding All the years of production reduction, for The average value of is the average reduction rate.

5. The crop yield reduction risk assessment method according to claim 1, characterized in that: In step S4, the method for calculating the probability of production reduction includes: 1), according to the relative meteorological yield series {x i The sample mean of and the sample standard deviation To establish the probability density function, the formula is as follows: ， 2) According to the distribution function curve, the probability of crop yield occurring in different yield increase and yield decrease ranges is calculated. The formula is as follows: ， Where p is the specific increase or decrease rate, 3) Calculate the probability of a certain production reduction interval [x1, x2) using the following formula: 。 6. The crop yield reduction risk assessment method according to claim 1, characterized in that: In step S5, the calculation method of the production reduction probability index is as follows: The reduction rate interval [-1,0) is divided into different sub-intervals [-1~x n-1 ),[ x n-1 , x n-2 ),…,[x2~ x1)、[x1~0)、where -1<x n-1 <x n-2 <…<x2<x1<0, corresponding to different production reduction levels, the production reduction probability corresponding to the above intervals is recorded as p n ,p n-1 ,…, p2,p1, the calculation formula of the production reduction probability index is as follows: ， In the formula, a n is the corresponding production reduction interval [x n ~ x n-1 )’s weight value.

7. The crop yield reduction risk assessment method according to claim 4, characterized in that: In step S6, the quasi-normalized production reduction risk index is calculated by the following formula: : ， in, =3, and are the adjustment coefficients, =5 and =2.

8. Specific disaster weather and climate crop yield reduction risk assessment system, including: A computer executable program, when the program is executed, implements the method according to any one of claims 1 to 7.

Images