Regional field moisture capacity estimation method based on microwave remote sensing

Abstract

The invention relates to the technical field of calculation, reckoning or counting, in particular to a regional field moisture capacity estimation method based on microwave remote sensing, and the method comprises the steps: obtaining and processing target data; based on the target data information, determining the precipitation level of the saturated soil and the water recession duration of the saturated soil; based on the rainfall data, determining a microwave soil moisture data selection date serving as the remote sensing field moisture capacity; and calculating the field moisture capacity of the remote sensing area based on the microwave soil moisture data and the selected date. By means of the method, large-range field moisture capacity data of the root system layer with high precision can be rapidly obtained, scientific, effective and practical help is at least provided for drought monitoring, drought resistance management and farmland irrigation, through the method, unnecessary financial resource and material resource expenditure is reduced, the obtaining cost is greatly reduced, and the actual drought resistance management work efficiency can be remarkably improved.

Description

Technical Field

[0001] The present application relates to the field of calculation, estimation or counting technology, and in particular to a method for estimating regional field water holding capacity based on microwave remote sensing. Background Art

[0002] The rapid development of remote sensing technology has made it possible to monitor droughts in a high-precision manner in a region. Given its ability to obtain global surface temporal and spatial information and its economic and efficient advantages, remote sensing is far ahead in the application of regional drought monitoring. Among them, microwave remote sensing has unique advantages in soil moisture monitoring. It is not affected by weather conditions and has a certain penetration ability. It can capture soil moisture information on the vertical profile of the soil. At present, the acquisition of field water holding capacity mainly relies on ground measurement and model estimation. Although ground measurement is more accurate, it cannot obtain regional data. Although model calculation can obtain large-scale data, it is affected by the estimation model and the data accuracy is difficult to meet the needs of actual regional drought monitoring.

[0003] Based on this, the ground measurement method can only obtain the field water holding capacity of the site, and the site data is poorly representative at the regional scale and cannot meet the needs of regional drought monitoring. At the same time, the field water holding capacity data calculated based on the soil transfer function model has poor applicability at the regional scale and low data accuracy, which does not meet the needs of accurate regional drought monitoring. Summary of the invention

[0004] Drought is one of the major natural disasters in my country. For the natural environment, drought will cause grassland degradation, natural oases will gradually shrink due to lack of water resources, and in severe cases, vegetation coverage will drop significantly. The situation of land desertification is serious, which will further erode the soil structure and threaten biological diversity. For human activities, drought will lead to reduced crop yields, and in severe cases, it will affect domestic water use, industrial production and other social and economic activities. Therefore, carrying out effective drought monitoring and forecasting is an important means to mitigate the adverse effects of drought, which is of great significance to disaster prevention and mitigation and promoting social and economic development.

[0005] The purpose of this application is to provide a method for estimating regional field water holding capacity based on microwave remote sensing, and to solve the technical problem that the existing technology cannot provide a method for estimating the field water holding capacity of crop root zone soil with high precision and over a large range through remote sensing technology.

[0006] According to one aspect of the present application, a method for estimating regional field water holding capacity based on microwave remote sensing is provided, including: acquiring and processing target data; determining the precipitation level of saturated soil and the dewatering time of saturated soil based on the target data information; determining the selection date of microwave soil moisture data as the remote sensing field water holding capacity based on the precipitation data; and calculating the field water holding capacity of the remote sensing area based on the microwave soil moisture data and the selection date.

[0007] In some embodiments, the acquired target data information includes at least microwave soil moisture data, precipitation data, and administrative division data of the estimated area; and the data processing includes at least statistical analysis of precipitation data and clipping of microwave soil moisture data.

[0008] In some embodiments, the determining of the precipitation level of saturated soil and the time for saturated soil to drain water at least includes: determining the precipitation level required for saturated soil and determining the time for saturated soil to drain water.

[0009] In some embodiments, the determination of the date for selecting microwave soil moisture data includes at least: determining the date on which the soil in each district and county reaches saturation based on precipitation data and the precipitation level required for saturated soil; and determining the date on which the remote sensing field water holding capacity occurs based on the duration of water withdrawal, in units of districts and counties.

[0010] In some embodiments, the calculation of the field water holding capacity of the remote sensing area is specifically as follows: averaging the microwave soil moisture on the day when the field water holding capacity of each district and county occurs to obtain the field water holding capacity of each district and county; and obtaining the regional remote sensing field water holding capacity data by data splicing.

[0011] Compared with the prior art, the present application has the following advantages and beneficial effects: the method of the present application can quickly obtain field water holding capacity data of a large range and root layer with high precision, and at least provide scientific, effective and practical assistance for drought monitoring, drought resistance management, and farmland irrigation. Through this method, unnecessary financial and material expenditures can be reduced, the acquisition cost can be greatly reduced, and the efficiency of actual drought resistance management work can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 It is a schematic diagram of the field water holding capacity estimation of the root zone of the estimation method of the present application;

[0014] Figure 2This is a comparison chart of soil moisture data based on SMAP and precipitation and measured soil moisture data in this application;

[0015] Figure 3 This is a data graph of the precipitation level required for the soil of different soil textures with a thickness of 40 cm to reach saturation in this application;

[0016] Figure 4 It is the soil moisture content variation characteristic diagram of this application;

[0017] Figure 5 It is the surface field water capacity distribution map estimated by remote sensing in this application;

[0018] Figure 6 It is the distribution map of field water holding capacity of the root layer estimated by remote sensing in this application. DETAILED DESCRIPTION

[0019] The following will be combined with the attached examples of the present application Figure 1-6 The technical solutions in the embodiments of the present application are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0020] In order to better understand this application, some terms are now explained:

[0021] 1. Microwave soil moisture data: refers to the soil moisture data obtained through microwave remote sensing technology;

[0022] 2.SMAP: refers to the Soil Moisture Satellite;

[0023] 3. Root layer: refers to the crop root distribution layer such as the 0-20 cm soil surface layer and the 0-40 cm soil root layer.

[0024] Application Overview

[0025] At present, there are many microwave soil moisture products, which have the advantages of wide coverage, relatively stable data series, and low economic input costs. Soils of different textures have different water holding capacities. In the actual drought monitoring application process, microwave soil moisture content cannot be used as a direct basis for judging the severity of the drought. The soil moisture content is converted into soil relative humidity through field water holding capacity, and drought monitoring can be achieved according to the drought grade classification rules. At present, the relevant methods for remote sensing estimation of field water holding capacity in undisclosed areas are not disclosed in the existing public technology. Based on this, the present application takes the traditional field water holding capacity measurement method as the basis, and realizes the improvement and optimization of the traditional method from point to surface; at the same time, in addition to the drought management business field, the method of the present application can also be used in water resources, farmland irrigation, flood forecasting and other fields.

[0026] Exemplary Methods

[0027] The present application provides a method for estimating regional field water holding capacity based on microwave remote sensing. Specifically, the method includes: acquiring and processing target data; determining the precipitation level of saturated soil and the time for saturated soil to drain based on target data information; determining the date for selecting microwave soil moisture data as remote sensing field water holding capacity based on precipitation data; and calculating the field water holding capacity of the remote sensing region based on microwave soil moisture data and the selected date. The method of the present application has good applicability for estimating the field water holding capacity of root layer soil, and can be applied to estimating the field water holding capacity of root layer soil in most areas, providing an efficient and practical new method for estimating the field water holding capacity of a large range of soils. The method is based on remote sensing soil moisture data and ground station precipitation data, and determines the date when the soil reaches saturation according to the precipitation level required for saturated soil and the time for saturated soil to drain, and determines the date when field water holding capacity appears according to the time for saturated soil to drain, thereby estimating field water holding capacity data using microwave remote sensing soil moisture data.

[0028] Below, each step is described in detail:

[0029] In some embodiments, the target data information includes at least microwave soil moisture data, precipitation data, and estimated regional administrative division data. Data processing includes classifying meteorological stations according to their districts and counties, counting the daily cumulative precipitation data of each station, cutting the soil surface and root layer SMAP soil moisture data by district and county, and referring to the attached Figure 2 .

[0030] In some embodiments, determining the precipitation level of saturated soil and the time for saturated soil to drain away includes at least: determining the precipitation level required for the soil to reach saturation, determining the date when the soil reaches saturation, and determining the time for saturated soil to drain away.

[0031] Different soil textures have different infiltration properties in determining the precipitation level required for saturated soil. The higher the sand content in the soil, the more favorable it is for water infiltration, which is manifested in faster infiltration speed and deeper penetration depth. Clay particles are the opposite. Therefore, different soil textures have different precipitation conditions to reach saturation. Please refer to the attached Figure 3 The precipitation level required for soil of different soil textures to reach saturation with a thickness of 40 cm.

[0032] In determining the time for saturated soil to dewater, based on relevant research on field water holding capacity and combined with the data characteristics of the method of this application, it is determined that the surface remotely sensed soil moisture reaches the field water holding capacity one day after the precipitation stops, and the root layer remotely sensed soil moisture reaches the field water holding capacity two days after the precipitation stops, that is, the surface remotely sensed soil moisture reaches the field water holding capacity one day after the soil saturation date, and the root layer remotely sensed soil moisture reaches the field water holding capacity two days after the soil saturation date.

[0033] In some embodiments, determining the date for selecting microwave soil moisture data includes at least: based on precipitation data and the precipitation level required for saturated soil, determining the date that meets the precipitation level requirements and no precipitation events occur the next day as the date when the soil in each district and county reaches saturation; based on the time it takes for saturated soil to dewater, determining the date on which remote sensing field water holding capacity occurs in units of districts and counties.

[0034] In some embodiments, the field water holding capacity of the remote sensing region is calculated, specifically: the microwave soil moisture of each district and county on the day when the field water holding capacity occurs is averaged to obtain the field water holding capacity of each district and county; and the regional remote sensing field water holding capacity data is obtained by data splicing.

[0035] It should be noted that the estimation method proposed in this application is used in the Jilin Province Drought Monitoring and Early Warning Integrated Platform and Soil Moisture Remote Sensing Monitoring System developed by our unit, and is used to estimate the field water holding capacity of the surface and root layers of cultivated land in the province.

[0036] Among them, the efficiency of the application method is mainly reflected in reducing measurement costs, improving data accuracy, and meeting the business requirements of large-scale field water holding capacity estimation and drought monitoring and evaluation. Practical application shows that the soil relative humidity product calculated based on remote sensing field water holding capacity products is better than the current SMAP soil relative humidity product and the soil relative humidity product calculated based on the field water holding capacity of the World Soil Database.

[0037] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or basic features of the present application. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present application is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present application. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0038] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for estimating regional field water holding capacity based on microwave remote sensing, characterized in that: include: Target data acquisition and processing; Based on the target data information, determine the precipitation level of saturated soil and the time for saturated soil to drain; Based on precipitation data, determine the date for selecting microwave soil moisture data as remote sensing field water holding capacity; Based on microwave soil moisture data and selected dates, the field water holding capacity of the remote sensing area was calculated.

2. The method according to claim 1, characterized in that The acquired target data information at least includes: microwave soil moisture data, precipitation data and administrative division data of the estimated area; the data processing at least includes statistical analysis of precipitation data and clipping of microwave soil moisture data.

3. The method according to claim 1, characterized in that The determining of the precipitation level of saturated soil and the time for saturated soil to drain water at least includes: determining the precipitation level required for saturated soil and determining the time for saturated soil to drain water.

4. The method according to claim 1, characterized in that The method of determining the microwave soil moisture data selection date at least includes: Based on precipitation data and the precipitation level required to saturate the soil, determine the date when the soil in each district and county will reach saturation; Based on the duration of water withdrawal, the date of occurrence of remote sensing field water holding capacity is determined in districts and counties.

5. The method according to claim 1, characterized in that The calculation of the field water holding capacity of the remote sensing area is specifically as follows: The microwave soil moisture on the day when the field water holding capacity of each district and county appeared was averaged to obtain the field water holding capacity of each district and county; Regional remote sensing field water holding capacity data was obtained through data splicing.

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