CN117093813A - Composite drought index calculation method - Google Patents

Composite drought index calculation method Download PDF

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CN117093813A
CN117093813A CN202311141390.XA CN202311141390A CN117093813A CN 117093813 A CN117093813 A CN 117093813A CN 202311141390 A CN202311141390 A CN 202311141390A CN 117093813 A CN117093813 A CN 117093813A
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drought
rainfall
vegetation
ndvi
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田莉
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Institute of Geographic Sciences and Natural Resources of CAS
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Abstract

The application relates to the technical field of climate research, in particular to a composite drought index calculation method, which calculates a Precipitation Condition Index (PCI), a soil humidity index (SMCI), a Temperature Condition Index (TCI) and a vegetation state index (VCI) by using precipitation, soil humidity, surface temperature, vegetation state and crop information data. Based on the method, 3 composite drought indexes including a Temperature Vegetation Drought Index (TVDI), an Optimized Vegetation Drought Index (OVDI) and a process-based cumulative drought index (PADI) are further calculated, and the applicability of the 3 indexes in drought prone areas of three major agricultural main areas of China is analyzed through linear correlation analysis and comparison of agricultural drought conditions with SPI-3 so as to provide reference for drought monitoring and evaluation work of typical agricultural areas of China.

Description

Composite drought index calculation method
Technical Field
The application relates to the technical field of climate research, in particular to a composite drought index calculation method.
Background
Drought formation and development are determined by both moisture supply and moisture demand, and occur simultaneously under both global scale climate activity anomalies and local scale environmental conditions. To cope with increasingly severe drought conditions, monitoring and evaluation of drought is urgently needed to achieve dynamics, systemization, multisource and integration.
In order to efficiently cope with new normalcy of increasing sensor resources, a set of theory and method of satellite-ground multi-sensor cooperation is urgently needed to be established, the monitoring advantage of the multi-sensor cooperation is fully exerted, a novel drought index is further developed, and efficient drought monitoring and accurate disaster assessment are finally achieved.
The natural variables closely related to drought are: precipitation, snow, relative humidity, atmospheric temperature, surface temperature, soil moisture, surface runoff, vegetation status, and the like. At present, most of drought monitoring is in an index form, and natural variables are monitored, synthesized and evaluated, so that the characteristics of an index model are considered to be single-factor index, simple multi-factor comprehensive index and complex comprehensive index.
Single factor indices include simple single factor indices and complex single factor indices, where complex single factor indices also employ only a single drought variable, but the calculation process is generally more complex and scientific.
The simple multi-factor comprehensive index is generally used for simultaneously examining various drought variables, and the comprehensive expression of the drought state is obtained through simple calculation, so that the index is easy to understand, the calculation process is not difficult, and the business monitoring product can be formed rapidly. However, the drought index model and the threshold value thereof generally have specific regional applicability, and weight variables may be introduced in the calculation process, so that the universality of each region cannot be completely ensured.
The complex multi-factor comprehensive index is similar to the simple multi-factor comprehensive index, and meanwhile, various drought variables are considered, but the difference is that a calculation model of the index generally adopts a hydrothermal balance process, a data mining process or a connection function and the like, and because the states of various early-dry variables are fused, the complex multi-factor comprehensive index can provide more accurate drought information than the single-factor index and the simple multi-factor comprehensive index, but because the calculation process needs to be fused with various parameters and the calculated amount is larger, the calculation process needs to be checked and corrected for a longer time. In order to pursue more accurate drought monitoring results, current research on drought monitoring continues to introduce new and more drought indicating variables on one hand, and continues to discuss new models for multiple drought variable synthesis on the other hand.
The occurrence, development and impact of drought are extremely complex. At present, complex comprehensive indexes achieve good performance in early-dry monitoring, and mostly realize the coordination of various observation data through methods such as linear models, data mining, complex water balance equations or connection functions. And the current multi-sensor cooperation research is still in the research stage of single drought element, and can not answer how the multi-sensor cooperation is closely coupled with the multi-variable monitoring in the drought monitoring process, so that the deep integration problem is finally realized.
Therefore, a composite drought index calculation method needs to be designed, the observation capability of a sensor is systematically and completely analyzed, the defects of the existing research are overcome, a multi-sensor cooperation method is enriched, a satellite-ground cooperation soil moisture reconstruction method and a satellite-ground cooperation monitoring method facing the drought process realize capability cooperation of remote sensing and ground sensors theoretically, continuous monitoring and accurate evaluation of the drought occurrence and development process are realized based on multi-sensor cooperation, the drought cumulative influence degree is realized, the efficiency improvement level compared with the existing monitoring means is obtained, and technical support is provided for a decision maker in drought disaster emergency response.
Disclosure of Invention
The application aims to overcome the defects of the prior art, provides a composite drought index calculation method, systematically and completely analyzes the observation capability of a sensor, overcomes the defects of the prior study, enriches a multi-sensor cooperation method, a satellite-ground cooperation soil moisture reconstruction method and a satellite-ground cooperation monitoring method facing the drought process, theoretically realizes the capability cooperation of remote sensing and ground sensors, realizes continuous monitoring and accurate evaluation of the drought occurrence and development process based on the multi-sensor cooperation, realizes the drought cumulative influence degree, obtains the efficiency improvement level compared with the prior monitoring means, and provides technical support for a decision maker in the drought disaster emergency response.
In order to achieve the above purpose, the application provides a composite drought index calculation method, which calculates a precipitation condition index PCI, a soil humidity index SMCI, a vegetation index NDVI, a temperature condition index TCI and a vegetation state index VCI by using precipitation, soil humidity, surface temperature, vegetation state and crop information data, further calculates a temperature vegetation drought index TVDI on the basis, optimizes three composite drought indexes of a vegetation drought index OVDI and a cumulative drought index PADI based on a process, and compares the three composite drought indexes with the SPI-3 linear correlation analysis, the water conservancy department and the periodical statistics of agricultural drought to monitor and evaluate a drought easy-to-develop area.
The formula of the precipitation condition index PCI is:
P、P max and P min Respectively representing the current month rainfall of a certain pixel, and the historical maximum rainfall and the historical minimum rainfall; the historical maximum rainfall and the historical minimum rainfall are obtained from rainfall data of the same pixel position in the previous 30 years, the value range of PCI is 0-1, and the level of the rainfall is from very few to very many; before PCI calculation, outliers are removed from a time sequence consisting of monthly rainfall, and when the threshold value of PCI is 0.5, whether the rainfall is abnormal or not is effectively distinguished.
The formula of soil moisture index SMCI is:
SM,SM max and SM min The soil moisture value of a pixel in a month, the maximum value and the minimum value of the pixel in history, and the threshold value of SMCI is 0.5; if the total soil moisture content is less than 0.5, the soil moisture content is abnormal, and if the SMCI value is abnormal after the PCI value is abnormal, the soil moisture content is abnormal, and the weather drought is developed into the agricultural drought.
The formula of vegetation index NDVI is:
NIR is near infrared band reflectivity, R is red light band reflectivity, and NDVI ranges from-1 to 1; when NDVI is negative, it indicates that the ground has a covering that is highly reflective to visible light, when NDVI is 0, it indicates that the ground has bare earth rock, NIR is approximately equal to R, when NDVI is positive, it indicates that the ground has vegetation coverage, and the value increases with coverage.
The formula of the vegetation state index VCI is:
NDVI,NDVI max and NDVI min An NDVI value representing a pixel, and the maximum and minimum NDVI values for the pixel over a historical period; VCI is a weekly value, and the threshold of VCI is 0.6; when the VCI is lower than 0.6, the vegetation is influenced by drought, and the agricultural drought enters the development stage.
The calculation formula of the temperature condition index TCI is:
LST is the surface temperature, LST max And LST min Is the highest and lowest surface temperature.
The formula for optimizing the vegetation drought index OVDI is:
objective function:
wherein the method comprises the steps of
Wherein the constraint conditions:
the optimal weight combination of the OVDI on 4 variables of precipitation, soil humidity, vegetation state and surface temperature is different according to the weight combination obtained by different space differences;
x is a standardized rainfall index SPI-3 or a standardized rainfall evaporation index SPEI-3, Y is OVDI, and alpha, beta and gamma are optimization parameters;
f (x, y) represents the condition of maximum correlation between x and yCondition, sigma x Sum sigma y Standard deviation of x and y, mu x Sum mu y Is the mean of x and y, E is the mathematical expectation; and when the OVDI is calculated, unifying the spatial resolution of the single drought index calculation result.
The beneficial technical effects of the application are as follows:
theoretically, the observation capability of the sensor is systematically and completely analyzed, and the defects of the existing research are overcome.
A network foundation for multi-sensor cooperation is established, and several typical cooperation methods among satellite remote sensing sensors, among ground sensors and among ground and satellite remote sensing sensors are provided at the same time, so that a multi-sensor cooperation method system is enriched.
Especially, the method for reconstructing the satellite-ground cooperative soil moisture and the method for monitoring the satellite-ground cooperative facing the drought process realize the capability cooperation of remote sensing and a ground sensor in theory.
In application, aiming at the outstanding problems in the current drought monitoring and evaluating field, continuous monitoring and accurate evaluation of the drought occurrence and development process can be realized based on multi-sensor cooperation, the drought accumulation influence degree is realized, the efficiency improvement level compared with the existing monitoring means is obtained, and technical support is provided for a decision maker in drought disaster emergency response.
Meanwhile, the thought and the method of multi-sensor cooperation reflected by the research are not only suitable for drought monitoring, but also generate new elicitations for monitoring and evaluating flood and disaster chains.
Reference numerals illustrate:
FIG. 1 is a schematic diagram illustrating the algorithm index of the main model of the present application.
Detailed Description
Referring to fig. 1, the application provides a composite drought index calculation method, which calculates a rainfall condition index PCI, a soil humidity index SMCI, a vegetation index NDVI, a temperature condition index TCI and a vegetation state index VCI by using rainfall, soil humidity, surface temperature, vegetation state and crop information data, further calculates a temperature vegetation drought index TVDI on the basis, optimizes three composite drought indexes of a vegetation drought index OVDI and a process-based accumulated drought index PADI, and monitors and evaluates drought-prone areas by comparing with SPI-3 linear correlation analysis, water conservancy and periodical statistics of agricultural drought.
The formula of the precipitation condition index PCI is:
P、P max and P min Respectively representing the current month rainfall of a certain pixel, and the historical maximum rainfall and the historical minimum rainfall; the historical maximum rainfall and the historical minimum rainfall are obtained from rainfall data of the same pixel position in the previous 30 years, the value range of PCI is 0-1, and the level of the rainfall is from very few to very many; before PCI calculation, outliers are removed from a time sequence consisting of monthly rainfall, and when the threshold value of PCI is 0.5, whether the rainfall is abnormal or not is effectively distinguished.
The formula of soil moisture index SMCI is:
SM,SM max and SM min The soil moisture value of a pixel in a month, the maximum value and the minimum value of the pixel in history, and the threshold value of SMCI is 0.5; if the total soil moisture content is less than 0.5, the soil moisture content is abnormal, and if the SMCI value is abnormal after the PCI value is abnormal, the soil moisture content is abnormal, and the weather drought is developed into the agricultural drought.
The formula of vegetation index NDVI is:
NIR is near infrared band reflectivity, R is red light band reflectivity, and NDVI ranges from-1 to 1; when NDVI is negative, it indicates that the ground has a covering that is highly reflective to visible light, when NDVI is 0, it indicates that the ground has bare earth rock, NIR is approximately equal to R, when NDVI is positive, it indicates that the ground has vegetation coverage, and the value increases with coverage.
The formula of the vegetation state index VCI is:
NDVI,NDVI max and NDVI min An NDVI value representing a pixel, and the maximum and minimum NDVI values for the pixel over a historical period; VCI is a weekly value, and the threshold of VCI is 0.6; when the VCI is lower than 0.6, the vegetation is influenced by drought, and the agricultural drought enters the development stage.
The calculation formula of the temperature condition index TCI is:
LST is the surface temperature, LST max And LST min Is the highest and lowest surface temperature.
The formula for optimizing the vegetation drought index OVDI is:
objective function:
wherein the method comprises the steps of
Wherein the constraint conditions:
the optimal weight combination of the OVDI on 4 variables of precipitation, soil humidity, vegetation state and surface temperature is different according to the weight combination obtained by different space differences;
x is a standardized rainfall index SPI-3 or a standardized rainfall evaporation index SPEI-3, Y is OVDI, and alpha, beta and gamma are optimization parameters;
f (x, y) represents the case where the correlation between x and y is the largest, σ x Sum sigma y Standard deviation of x and y, mu x Sum mu y Is the mean of x and y, E is the mathematical expectation; and when the OVDI is calculated, unifying the spatial resolution of the single drought index calculation result.
The above is only a preferred embodiment of the present application, only for helping to understand the method and the core idea of the present application, and the scope of the present application is not limited to the above examples, and all technical solutions belonging to the concept of the present application belong to the scope of the present application. It should be noted that modifications and adaptations to the present application may occur to one skilled in the art without departing from the principles of the present application and are intended to be within the scope of the present application.
The application fundamentally solves the problems of drought monitoring and evaluation in the prior art, aims at the defects and defects of various index models and the defects of other influencing factors under the condition of increasing remote sensing sensor resources, simultaneously provides a plurality of typical collaborative methods among satellite remote sensing sensors, among ground sensors and among ground and satellite remote sensing sensors by establishing a multi-sensor collaborative network foundation, enriches the multi-sensor collaborative methods, realizes continuous monitoring and accurate evaluation, realizes drought accumulated influence degree, obtains efficiency improvement level compared with the existing monitoring means, and provides technical support for decision makers in drought disaster emergency response. Meanwhile, the thought and the method of multi-sensor cooperation are not only suitable for drought monitoring, but also can generate new elicitations for monitoring and evaluating flood and disaster chains.

Claims (7)

1. A composite drought index calculation method is characterized in that rainfall condition index PCI, soil humidity index SMCI, vegetation index NDVI, temperature condition index TCI and vegetation state index VCI are calculated by utilizing rainfall, soil humidity, surface temperature, vegetation state and crop information data, temperature vegetation drought index TVDI is further calculated on the basis, three composite drought indexes including vegetation drought index OVDI and accumulated drought index PADI based on the process are optimized, and the monitoring and evaluation of drought-prone areas are made by comparing with SPI-3 linear correlation analysis and agricultural drought of water conservancy and periodical statistics.
2. The method of claim 1, wherein the precipitation condition index PCI is formulated as:
said P, P max And P min Respectively representing the current month rainfall of a certain pixel, and the historical maximum rainfall and the historical minimum rainfall; the historical maximum rainfall and the historical minimum rainfall are obtained from rainfall data of the same pixel position in the previous 30 years, the value range of the PCI is 0-1, and the level of the representing rainfall is extremely high from extremely low; and before PCI calculation, outliers are removed from a time sequence consisting of monthly rainfall, and when the threshold value of the PCI is 0.5, whether the rainfall is abnormal or not is effectively distinguished.
3. The method of claim 1, wherein the soil moisture index SMCI is formulated as:
the SM, SM max And SM min The soil moisture value of a pixel in a month and the maximum value and the minimum value of the pixel in history are respectively, and the threshold value of the SMCI is 0.5; if the total quantity of the soil water is less than 0.5, the soil water is deficient and abnormal, and if the SMCI value is abnormal after the PCI value is abnormal, the soil water is deficient and abnormal, and the soil water is deficient and abnormal, the SMCI value is abnormal after the PCI value is abnormal, and the soil water is deficient and abnormal, and the SMCI value is abnormal, and represents weather drought to develop into agricultural drought.
4. The method of claim 1, wherein the vegetation index NDVI is formulated as:
the NIR is the reflectivity of a near infrared band, the R is the reflectivity of a red light band, and the range of the NDVI is-1 to 1; when the NDVI is negative, it indicates that the ground has a covering highly reflective of visible light, when the NDVI is 0, it indicates that the ground has bare earth rock, the NIR is approximately equal to the R, when the NDVI is positive, it indicates that the ground has vegetation coverage, and the value increases with coverage.
5. The method of claim 1, wherein the vegetation state index VCI is formulated as:
the NDVI, NDVI max And NDVI min An NDVI value representing a pixel, and the maximum and minimum NDVI values for the pixel over a historical period; the VCI is a weekly value, and the threshold of the VCI is 0.6; when the VCI is lower than 0.6, the vegetation is influenced by drought, and the agricultural drought enters a development stage.
6. The method of claim 1, wherein the temperature condition index TCI is calculated by the formula:
the LST is the surface temperature, the LST max And LST min At the highest and lowest surface temperaturesDegree.
7. The method of claim 1, wherein the formula for optimizing the vegetation drought index OVDI is:
objective function:
wherein the method comprises the steps of
Wherein the constraint conditions:
the optimal weight combination of the OVDI on 4 variables of precipitation, soil humidity, vegetation state and surface temperature is different according to the weight combination obtained by different space differences;
the X is a standardized rainfall index SPI-3 or a standardized rainfall evaporation index SPEI-3, the Y is OVDI, and the alpha, beta and gamma are optimization parameters;
the f (x, y) represents the case where the correlation between x and y is the largest, the sigma x And the sigma y Standard deviation of x and y, said μ x Sum mu y Is the mean of x and y, and E is the mathematical expectation; and unifying the spatial resolution of the single drought index calculation result when calculating the OVDI.
CN202311141390.XA 2023-09-06 2023-09-06 Composite drought index calculation method Pending CN117093813A (en)

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