1. A method for determining an agricultural drought monitoring index is characterized by comprising the following steps:

acquiring potential evaporation capacity data, precipitation data and soil water content data;

calculating a monthly potential evaporation rate, a monthly average precipitation rate and a monthly soil water content per month from the potential evaporation rate data, the precipitation data and the soil water content data;

calculating the water deficit from the monthly potential evaporation capacity, the monthly average precipitation capacity, the monthly soil water content and the soil consumption factor for each month;

calculating the deviation between the water deficit and the average water deficit for years in the corresponding month, and determining the deviation as a vegetation soil water deficit index.

2. The method of claim 1, wherein the calculating the monthly potential evaporation, the monthly average precipitation and the monthly soil water content per month from the potential evaporation data, the precipitation data and the soil water content data comprises:

extracting a monthly potential evaporation amount of each month from the potential evaporation amount data;

calculating the average precipitation per month from the precipitation data;

extracting soil moisture data from the soil moisture data and the water density; the calculation formula of the soil moisture data is as follows: S-Raw data/rho_waterWherein S represents soil moisture data, Raw data represents soil moisture data, and rho_waterRepresenting the water density;

calculating the soil water content of each month according to the soil water content data; the formula for calculating the water content of the monthly soil is as follows:

wherein S is_iA monthly soil moisture content of month i; s_MayA monthly soil moisture content of 5 months; s_0-10Is 0-10cm layer of soil in soil moisture dataSoil moisture; s_Jun-AugA monthly soil moisture content of 6 months to 8 months; s_10-40The soil moisture of 10 cm-40 cm layers in the soil moisture data is obtained; s_0-40The average soil moisture is the soil moisture of 0-10cm layers and the soil moisture of 10-40cm layers; s_SepMonthly soil moisture content of 9 months.

3. The method for determining the agricultural drought monitoring index according to claim 1, wherein the water deficit is calculated by the following formula:

VSWD_i＝P_i+ρ*S_i-PET_i；

wherein the VSWD_iIndicates water shortage of month i, P_iAverage monthly precipitation for month i, S_iWater content of soil in month i, PET_iThe monthly potential evaporation for month i, ρ is the soil consumption factor.

4. The method for determining the agricultural drought monitoring index according to claim 1, wherein the calculation formula of the vegetation soil water deficit index is as follows:

VSWD represents the vegetation soil water deficit index, VSWD_iIndicating the water deficit in month i, N the total years,representing the average water deficit in N years in month i, VSWD_jIndicating the water deficit in month i in year j.

5. The method for determining the agricultural drought monitoring index according to claim 1, wherein the obtaining of the potential evaporation data, the precipitation data and the soil water content data specifically comprises:

collecting potential evaporation data in a set time period by adopting a medium-resolution imaging spectrometer;

acquiring precipitation data in the set time period by adopting a tropical rainfall measurement task satellite;

acquiring soil water content data in the set time period by adopting a global land surface data assimilation system; the soil water content data comprises water content data of different soil depths.

6. An agricultural drought monitoring index determination system, comprising:

the data acquisition module is used for acquiring potential evaporation capacity data, precipitation data and soil water content data;

a monthly data calculation module for calculating monthly potential evaporation capacity, monthly average precipitation and monthly soil water content per month from the potential evaporation capacity data, the precipitation data and the soil water content data;

a water deficit and deficit module for calculating a water deficit and deficit per month from the monthly potential evaporation capacity, the monthly average precipitation capacity, the monthly soil water content, and the soil consumption factor;

and the drought index determining module is used for calculating the deviation between the water deficit and the average water deficit of each month and the average water deficit of the corresponding months for years and determining the deviation as the vegetation soil water deficit index.

7. The agricultural drought monitoring index determining system according to claim 6, wherein the monthly data calculating module specifically comprises:

a month potential evaporation amount calculation unit for extracting a month potential evaporation amount per month in the potential evaporation amount data;

the monthly average precipitation calculating unit is used for calculating monthly average precipitation of each month according to the precipitation data;

a soil moisture data extraction unit for extracting soil moisture data from the soil moisture data and the water density; the calculation formula of the soil moisture data is as follows: S-Raw data/rho_waterWherein S represents soil moisture data, Raw data represents soil moisture data, and rho_waterRepresenting the water density;

the monthly soil water content calculating unit is used for calculating the monthly soil water content of each month according to the soil water content data; the formula for calculating the water content of the monthly soil is as follows:

wherein S is_iA monthly soil moisture content of month i; s_MayA monthly soil moisture content of 5 months; s_0-10The soil moisture of 0-10cm layers in the soil moisture data; s_Jun-AugA monthly soil moisture content of 6 months to 8 months; s_10-40The soil moisture of 10 cm-40 cm layers in the soil moisture data is obtained; s_0-40The average soil moisture is the soil moisture of 0-10cm layers and the soil moisture of 10-40cm layers; s_SepMonthly soil moisture content of 9 months.

8. The agricultural drought monitoring index determination system according to claim 6, wherein the water deficit in the water deficit module is calculated by the formula:

VSWD_i＝P_i+ρ*S_i-PET_i；

wherein the VSWD_iIndicates water shortage of month i, P_iAverage monthly precipitation for month i, S_iWater content of soil in month i, PET_iThe monthly potential evaporation for month i, ρ is the soil consumption factor.

9. The agricultural drought monitoring index determination system of claim 6, wherein the calculation formula for the vegetation soil water deficit index in the drought index determination module is:

VSWD represents the vegetation soil water deficit index, VSWD_iIndicating the water deficit in month i, N the total years,representing the average water deficit in N years in month i, VSWD_jIndicating the water deficit in month i in year j.

10. The agricultural drought monitoring index determining system according to claim 6, wherein the data acquisition module specifically comprises:

the first data acquisition unit is used for acquiring potential evaporation data in a set time period by adopting a medium-resolution imaging spectrometer;

the second data acquisition unit is used for acquiring precipitation data in the set time period by adopting a tropical rainfall measurement task satellite;

a third data acquisition unit, configured to acquire soil water content data within the set time period by using a global land data assimilation system; the soil water content data comprises water content data of different soil depths.

Background

Drought is considered to be a devastating disaster worldwide with severe impact on agriculture, ecology and socioeconomic performance. Fundamentally, drought can be defined as temporarily varying degrees of water supply deficit relative to a long-term average condition. Although the damage of drought is well documented, there is no uniform definition of drought. From different perspectives, drought is divided into four categories, meteorological drought, agricultural drought, hydrographic drought, and socioeconomic drought. At present, the existing drought monitoring index usually only considers water supply and does not consider water demand of crops, and neglects the importance of balance of supply and demand, so that the time, range and degree of agricultural drought occurrence cannot be accurately determined, and agricultural management and irrigation implementation cannot be accurately realized.

Disclosure of Invention

Based on the method and the system, the vegetation soil water deficit index is established based on the principle of water supply and demand relationship balance, so that the time, the range and the degree of agricultural drought are accurately determined, and decision help is provided for agricultural management and irrigation implementation.

In order to achieve the purpose, the invention provides the following scheme:

a method for determining an agricultural drought monitoring index, comprising:

acquiring potential evaporation capacity data, precipitation data and soil water content data;

calculating a monthly potential evaporation rate, a monthly average precipitation rate and a monthly soil water content per month from the potential evaporation rate data, the precipitation data and the soil water content data;

calculating the water deficit from the monthly potential evaporation capacity, the monthly average precipitation capacity, the monthly soil water content and the soil consumption factor for each month;

calculating the deviation between the water deficit and the average water deficit for years in the corresponding month, and determining the deviation as a vegetation soil water deficit index.

Optionally, calculating the monthly potential evaporation rate, the monthly average precipitation rate and the monthly soil water content of each month from the potential evaporation rate data, the precipitation data and the soil water content data specifically includes:

extracting a monthly potential evaporation amount of each month from the potential evaporation amount data;

calculating the average precipitation per month from the precipitation data;

extracting soil moisture data from the soil moisture data and the water density; the soil moisture dataThe calculation formula of (2) is as follows: S-Raw data/rho_waterWherein S represents soil moisture data, Raw data represents soil moisture data, and rho_waterRepresenting the water density;

calculating the soil water content of each month according to the soil water content data; the formula for calculating the water content of the monthly soil is as follows:

wherein S is_iA monthly soil moisture content of month i; s_MayA monthly soil moisture content of 5 months; s_0-10The soil moisture of 0-10cm layers in the soil moisture data; s_Jun-AugA monthly soil moisture content of 6 months to 8 months; s_10-40The soil moisture of 10 cm-40 cm layers in the soil moisture data is obtained; s_0-40The average soil moisture is the soil moisture of 0-10cm layers and the soil moisture of 10-40cm layers; s_SepMonthly soil moisture content of 9 months.

Optionally, the water shortage amount calculation formula is as follows:

VSWD_i＝P_i+ρ*S_i-PET_i；

wherein the VSWD_iIndicates water shortage of month i, P_iAverage monthly precipitation for month i, S_iWater content of soil in month i, PET_iThe monthly potential evaporation for month i, ρ is the soil consumption factor.

Optionally, the calculation formula of the vegetation soil water deficit index is as follows:

VSWD represents the vegetation soil water deficit index, VSWD_iIndicating the water deficit in month i, N the total years,indicates month i isN years average water deficit, VSWD_jIndicating the water deficit in month i in year j.

Optionally, acquiring the potential evaporation capacity data, the precipitation data and the soil water content data specifically includes:

collecting potential evaporation data in a set time period by adopting a medium-resolution imaging spectrometer;

acquiring precipitation data in the set time period by adopting a tropical rainfall measurement task satellite;

acquiring soil water content data in the set time period by adopting a global land surface data assimilation system; the soil water content data comprises water content data of different soil depths.

The invention also provides an agricultural drought monitoring index determining system, which comprises:

the data acquisition module is used for acquiring potential evaporation capacity data, precipitation data and soil water content data;

a monthly data calculation module for calculating monthly potential evaporation capacity, monthly average precipitation and monthly soil water content per month from the potential evaporation capacity data, the precipitation data and the soil water content data;

a water deficit and deficit module for calculating a water deficit and deficit per month from the monthly potential evaporation capacity, the monthly average precipitation capacity, the monthly soil water content, and the soil consumption factor;

and the drought index determining module is used for calculating the deviation between the water deficit and the average water deficit of each month and the average water deficit of the corresponding months for years and determining the deviation as the vegetation soil water deficit index.

Optionally, the month data calculation module specifically includes:

a month potential evaporation amount calculation unit for extracting a month potential evaporation amount per month in the potential evaporation amount data;

the monthly average precipitation calculating unit is used for calculating monthly average precipitation of each month according to the precipitation data;

a soil moisture data extraction unit for extracting a moisture content of the soilExtracting soil moisture data from the data and the water density; the calculation formula of the soil moisture data is as follows: S-Raw data/rho_waterWherein S represents soil moisture data, Raw data represents soil moisture data, and rho_waterRepresenting the water density;

the monthly soil water content calculating unit is used for calculating the monthly soil water content of each month according to the soil water content data; the formula for calculating the water content of the monthly soil is as follows:

wherein S is_iA monthly soil moisture content of month i; s_MayA monthly soil moisture content of 5 months; s_0-10The soil moisture of 0-10cm layers in the soil moisture data; s_Jun-AugA monthly soil moisture content of 6 months to 8 months; s_10-40The soil moisture of 10 cm-40 cm layers in the soil moisture data is obtained; s_0-40The average soil moisture is the soil moisture of 0-10cm layers and the soil moisture of 10-40cm layers; s_SepMonthly soil moisture content of 9 months.

Optionally, the water shortage in the water shortage module is calculated according to the following formula:

VSWD_i＝P_i+ρ*S_i-PET_i；

wherein the VSWD_iIndicates water shortage of month i, P_iAverage monthly precipitation for month i, S_iWater content of soil in month i, PET_iThe monthly potential evaporation for month i, ρ is the soil consumption factor.

Optionally, the calculation formula of the vegetation soil water deficit index in the drought index determination module is as follows:

VSWD represents the vegetation soil water deficit index, VSWD_iWater deficit in the month iThe shortage, N, represents the total number of years,representing the average water deficit in N years in month i, VSWD_jIndicating the water deficit in month i in year j.

Optionally, the data obtaining module specifically includes:

the first data acquisition unit is used for acquiring potential evaporation data in a set time period by adopting a medium-resolution imaging spectrometer;

the second data acquisition unit is used for acquiring precipitation data in the set time period by adopting a tropical rainfall measurement task satellite;

a third data acquisition unit, configured to acquire soil water content data within the set time period by using a global land data assimilation system; the soil water content data comprises water content data of different soil depths.

Compared with the prior art, the invention has the beneficial effects that:

the embodiment of the invention provides a method and a system for determining an agricultural drought monitoring index, which comprises the following steps: acquiring potential evaporation capacity data, precipitation data and soil water content data; and calculating the water deficit amount of each month according to the potential evaporation amount data, the precipitation data and the soil water content data, and determining the deviation between the water deficit amount of each month and the average water deficit amount of the corresponding month for years as a vegetation soil water deficit index. The invention considers the factors and action process related to crop water demand as much as possible, adopts the potential evaporation data, the precipitation data and the soil water content data, and establishes the vegetation soil water deficit index based on the principle of water supply and demand relationship balance, and the index not only considers the water supply but also considers the crop water demand, thereby accurately determining the time, range and degree of agricultural drought, and providing decision help for agricultural management and irrigation implementation.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a flow chart of a method for determining an agricultural drought monitoring index provided by an embodiment of the present invention;

fig. 2 is a structural diagram of a method for determining an agricultural drought monitoring index according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

Drought is caused by multiple factors such as precipitation, soil humidity and potential evapotranspiration, and under the condition of the existing data set, factors and action processes related to crop water demand should be considered as much as possible. The existing drought index has the following defects: 1) the existing drought index usually only considers water supply and does not consider crop water demand, and the importance of supply and demand balance is ignored; 2) at present, the agricultural drought index lacks mechanicalness; 3) the influence of root depth on crop drought is not considered.

Based on this, the embodiment provides a method for determining an agricultural drought monitoring index based on the principle of soil moisture balance, where the soil moisture balance refers to a balance relationship between water obtained in a certain soil volume and water consumed and lost by crops in a certain period. Generally refers to the difference between the water content obtained and the water content lost in a soil layer with a certain depth in a certain period of time in a certain range of the crop roots.

The embodiment establishes the vegetation water deficit index based on the principle of water supply and demand relationship balance by utilizing long-time sequence multi-source remote sensing data, aims to more accurately evaluate the time, range and degree of agricultural drought occurrence, and provides decision help for agricultural management and irrigation implementation.

The method of the embodiment is different from other drought index methods in that 1) precipitation, soil moisture content, potential evapotranspiration and other factors influencing vegetation drought are considered; 2) establishing a drought index based on a water supply and demand relationship, so that the physical mechanism of the drought index is more reasonable; 3) the depth of the root system of the crops in different growth periods is considered to be different.

(1) The calculation of the vegetation soil water deficit index takes various factors influencing drought into consideration: precipitation, soil water and evapotranspiration data.

When a desired data set is available, drought due to various factors such as precipitation, soil moisture and potential evapotranspiration should be assessed by considering as many relevant factors/processes as possible, and existing agricultural drought should be assessed by considering precipitation or soil moisture, or combining precipitation or soil moisture with potential evapotranspiration.

(2) The vegetation soil water deficit index is established based on a vegetation water supply and demand balance principle.

The method is different from the prior agricultural drought index, the index is established based on the principle of vegetation water supply and demand balance, and due to the fact that the water storage capacity of crops in different growth periods is different, potential evapotranspiration data capable of representing the water demand of the crops are selected by utilizing the advantage of remote sensing in data diversity, and the condition of crop water shortage is calculated through the difference between rainfall and soil water for providing water for the vegetation.

(3) And (4) selecting the water contents of soil layers with different depths according to the difference of root system depths by considering the vegetation soil water deficit index.

Due to the growth characteristics of crops, the root system depths of the crops in different growth periods are different, the depths of soil layers mainly absorbing water are different, the main water source with the shallower root system at the initial stage depends on the shallower soil layers, and the main water source goes from shallow to deep along with the growth of the crops and the growth period.

The method for determining the agricultural drought monitoring index of this example is described in detail below.

Referring to fig. 1, the method includes:

step 101: and acquiring potential evaporation data, precipitation data and soil water content data.

The step 101: the method specifically comprises the following steps:

11) potential evaporation data over a set period of time was collected using a mode-resolution Imaging spectrometer (MODIS).

MODIS is a large space remote sensing instrument developed by the United states space administration and used for understanding the change situation of global climate and the influence of human activities on the climate. Potential Evapotranspiration (PET): which is both an important component of the water cycle and an important component of the energy balance, which means the maximum evapotranspiration that a fixed underlying surface may reach when the water supply is not limited under certain meteorological conditions, also known as reference crop evapotranspiration. The potential evapotranspiration data of this example was taken from MODIS, first, covering the entire area of study requiring two images (h26v05, h27v05), an eight day product with a resolution of 1km (MYD16A2), acquired using the Wget tool, and mosaiced and projected using the MODIS re-projection tool. This example uses the PET data from 2008 + 2017 from 5 to 9 months.

12) And acquiring precipitation data in a set time period by adopting a Tropical Rainfall measurement Mission satellite (TRMM).

The TRMM is a meteorological satellite specially used for quantitatively measuring tropical and subtropical rainfall, belongs to the Earth Observation System (EOS), and is jointly developed by the American national aeronautics and astronautics administration (NASA) and the Japanese space development institute (NASDA). NASA is responsible for the satellite body, 4 instruments and operating systems, and NASDA is responsible for the rain radar and satellite transmission.

TRMM is a joint task established for weather and climate research. And rainfall data is from TRMM 3B43 product. Precipitation data from 2008 to 2017 during the growing season (months 5 to 9) were obtained by the Wget tool of GES DISC (https:// DISC2.gesdisc. eosdis. nasa. gov/data/TRMM _ L3/TRMM _3B 43.7). The precipitation data are given in terms of monthly precipitation rates (mm/h) with spatial resolution of 0.25 ° and 0.1 °. In this example, a spatial resolution of 0.25 ° is selected to match the spatial resolution of the soil moisture product.

13) Acquiring soil water content Data in a set time period by adopting a Global Land Data Acquisition System (GLDAS); the soil water content data comprises water content data of different soil depths.

GLDAS is a product of ingesting satellite and ground based observation data using ground surface modeling and data assimilation techniques to generate optimal ground surface states and flux fields. The soil water content data is taken from soil moisture products provided by GLDAS in four layers, and the soil moisture products provided by GLDAS in four layers comprise 0-10cm, 10-40cm, 40-100 cm and 100-200 cm of soil moisture. This example obtained 0-10cm and 10-40cm soil moisture data sets from a GLDAS 2.1NOAH model at 0.25 ° x 0.25 ° for the growing season of 2008-. The soil moisture content data of this example were selected for soil moisture of 0-10cm and 10-40 cm.

Step 102: calculating a monthly potential evaporation rate, a monthly average precipitation rate and a monthly soil water content per month from the potential evaporation rate data, the precipitation data and the soil water content data. Specifically, a remote sensing image processing platform ENVI-IDL is adopted to calculate different data to obtain the monthly potential evaporation capacity, the monthly average precipitation and the monthly soil water content.

The step 102 specifically includes:

data conversion is required because the space-time dimensions of the three types of data sets, latent evaporation data, precipitation data and soil water content data, are inconsistent and cannot be used directly.

21) The precipitation data from TRMM was converted to monthly average precipitation in (mm/month).

22) The potential evaporation amount data extracted from the MODIS 8-day composite product summarizes the weight values of the 8-day composite product in the data processing month into month data, thereby realizing extraction of the month potential evaporation amount in each month from the potential evaporation amount data.

23) The unit of soil water content data from GLDAS was kg/m²The calculation formula of the soil moisture data needs to be converted into the soil moisture data.

24) Finally, the spatial resolution of the data from GLDAS, TRMM and MODIS was resampled to 1km and the data was UTM 51 spatially projected using IDW interpolation.

Wherein, in the step 23), the method specifically comprises the following steps:

firstly, soil moisture data is calculated, and the calculation formula is as follows:

wherein S represents soil moisture data, Raw data represents soil moisture data, and rho_waterRepresenting the density of water.

The soil moisture data collected from the GLDAS soil moisture product was then stratified for different crop growth stages. During the crop growing season, the root depth of the crop increases, thus changing the main root area from which the crop can extract water. However, it is difficult to determine the root depth for different months. Evidence suggests that eighty percent of roots are distributed at depths of 0-40cm, although the maximum root depth of the crop (maize is the main crop in Jilin province) can reach 1-2m throughout the growth period. Therefore, 0-40cm of soil is considered the primary water source for crop growth. Since the GLDAS product provides four layers of soil moisture, i.e., 0-10cm, 10-40cm, 40-100 cm and 100 + 200cm, the first two layers are used in this example to represent the available water in the soil, i.e., the first 40cm of soil. In addition, to reflect changes in root depth with the season of crop growth, soil layers between 0-10cm and 10-40cm soil layers were conceptualized to create a drought index representing root depths between 10cm and 40 cm. And comparing the soil water content of 0-10cm and 10-40cm, and the average weighting result of 0-10cm and 10-40cm with the drought index. Table 1 shows the correlation between the moisture content of different soil layers and the drought index for different months. Depending on the results, appropriate soil moisture was selected for different soil depths in different months. Thus, the monthly soil moisture content per month may be calculated from the soil moisture data using the following equation:

wherein S is_iA monthly soil moisture content of month i; s_MayA monthly soil moisture content of 5 months; s_0-10The soil moisture of 0-10cm layers in the soil moisture data; s_Jun-AugA monthly soil moisture content of 6 months to 8 months; s_10-40The soil moisture of 10 cm-40 cm layers in the soil moisture data is obtained; s_0-40The average soil moisture is the soil moisture of 0-10cm layers and the soil moisture of 10-40cm layers; s_SepMonthly soil moisture content of 9 months.

TABLE 1 correlation of soil horizon water content with different in situ indices for different months

The normalized precipitation and evapotranspiration index (SPEI) in table 1 represents the degree of departure of a dry-wet condition from a year by normalizing the difference between potential evapotranspiration and precipitation, is a new ideal index for analyzing the drought evolution trend, and has been widely applied to the fields of drought evaluation, water resource management and the like at present.

Step 103: calculating the water deficit from the monthly potential evaporation capacity, the monthly average precipitation capacity, the monthly soil water content and the soil consumption factor for each month.

The water shortage amount calculation formula is as follows:

VSWD_i＝P_i+ρ*S_i-PET_i；

wherein i represents a month number, is different from 5 months to 9 months, and is the change year of 2008-2017; VSWD_iIndicating water deficit for month i; p_iA monthly average precipitation for month i; s_iA monthly soil moisture content of month i; PET_iA monthly latent evaporation capacity for month i; ρ is a soil consumption factor. The soil consumption factor is a function of the atmospheric evaporation capacity, which represents the amount of water that a crop can extract from the soil before it is subjected to pressure. The current soil water content is taken as the total available water volume, ρ ═ ρ_FAO+0.04(5-ET_c)，ρ_FAOThe consumption factor value shown in the FAO56 method of the grain and agriculture organization; ET_cDenotes the actual evapotranspiration (mm/day), ET_cCan be extracted from the actual evapotranspiration product ET of MODIS.

Step 104: calculating the deviation between the water deficit and the average water deficit for years in the corresponding month, and determining the deviation as a vegetation soil water deficit index.

It is difficult to directly compare VSWD values of different regions because the VSWD values of different regions are greatly different due to climate differences between regions. Thus, a long-term average VSWD value is introduced to calculate the deviation of the monthly VSWD value for the area from the average for the years of the month.

The calculation formula of the vegetation soil water deficit index is as follows:

VSWD represents the vegetation soil water deficit index; VSWD_iIndicating water deficit for month i; n represents the total number of years; the total years in this example are 10 years;represents the average water deficit in N years in month i; VSWD_jIndicating the water deficit in month i in year j. Therefore, the vegetation soil water deficit index is an index which is established by taking the principle of soil water balance into consideration and is used for detecting vegetation drought by utilizing data such as precipitation, soil water and potential evapotranspiration.

The method for determining the agricultural drought monitoring index of the embodiment establishes the vegetation soil water deficit index based on the water balance principle (crop water supply and demand relation) by using the multi-source remote sensing data as a data source, wherein the large-area agricultural drought monitoring can be realized by using the multi-source remote sensing data as the data source, and the vegetation soil water deficit index based on the water balance principle enables the agricultural drought monitoring to be more accurate, so that the occurrence, the range and the degree of the agricultural drought can be more accurately monitored compared with the traditional drought monitoring index; by utilizing the multilayer soil water content data and the correlation analysis of the corn root depths in different growth periods and the crop water depths, the drought influence of the different growth periods is considered to be added into the drought monitoring model, and the agricultural drought monitoring accuracy is further improved.

The invention also provides an agricultural drought monitoring index determination system, which comprises the following components in percentage by weight with reference to fig. 2:

and the data acquisition module 201 is used for acquiring potential evaporation capacity data, precipitation data and soil water content data.

A monthly data calculating module 202 for calculating monthly potential evaporation, monthly average precipitation and monthly soil water content per month from the potential evaporation data, the precipitation data and the soil water content data.

A water deficit and deficit module 203 for calculating a water deficit and deficit per month from the monthly potential evaporations, the monthly average precipitation, the monthly soil water content, and the soil consumption factors.

And the drought index determining module 204 is used for calculating the deviation between the water deficit amount of each month and the average water deficit amount of the corresponding months for years and determining the deviation as the vegetation soil water deficit index.

As an optional implementation manner, the month data calculation module 202 specifically includes:

a month potential evaporation amount calculation unit for extracting a month potential evaporation amount per month in the potential evaporation amount data.

And the monthly average precipitation calculating unit is used for calculating the monthly average precipitation of each month according to the precipitation data.

A soil moisture data extraction unit for extracting soil moisture data from the soil moisture data and the water density; the calculation formula of the soil moisture data is as follows: S-Raw data/rho_waterWherein S represents soil moisture data, Raw data represents soil moisture data, and rho_waterRepresenting the density of water.

The monthly soil water content calculating unit is used for calculating the monthly soil water content of each month according to the soil water content data; the formula for calculating the water content of the monthly soil is as follows:

wherein S is_iA monthly soil moisture content of month i; s_MayA monthly soil moisture content of 5 months; s_0-10The soil moisture of 0-10cm layers in the soil moisture data; s_Jun-AugA monthly soil moisture content of 6 months to 8 months; s_10-40The soil moisture of 10 cm-40 cm layers in the soil moisture data is obtained; s_0-40The average soil moisture is the soil moisture of 0-10cm layers and the soil moisture of 10-40cm layers; s_SepMonthly soil moisture content of 9 months.

As an alternative embodiment, the water deficit in the water deficit module 203 is calculated by the following formula:

VSWD_i＝P_i+ρ*S_i-PET_i；

wherein the VSWD_iIndicates water shortage of month i, P_iAverage monthly precipitation for month i, S_iWater content of soil in month i, PET_iThe monthly potential evaporation for month i, ρ is the soil consumption factor.

As an alternative embodiment, the calculation formula of the vegetation soil water deficit index in the drought index determination module 204 is as follows:

VSWD represents the vegetation soil water deficit index, VSWD_iIndicating the water deficit in month i, N the total years,representing the average water deficit in N years in month i, VSWD_jIndicating the water deficit in month i in year j.

As an optional implementation manner, the data obtaining module 201 specifically includes:

and the first data acquisition unit is used for acquiring potential evaporation data in a set time period by adopting a medium-resolution imaging spectrometer.

And the second data acquisition unit is used for acquiring precipitation data in the set time period by adopting a tropical rainfall measurement task satellite.

A third data acquisition unit, configured to acquire soil water content data within the set time period by using a global land data assimilation system; the soil water content data comprises water content data of different soil depths.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.