A method for estimating regional field water holding capacity based on microwave remote sensing

Abstract

The present application relates to the field of calculation, extrapolation, or counting technology, and in particular to a method for estimating regional field water holding capacity based on microwave remote sensing. The method comprises acquiring and processing target data; determining the precipitation level of saturated soil and the duration of saturated soil dewatering based on the target data information; determining the date for selecting 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 region based on the microwave soil moisture data and the selection date. The method of the present application can quickly obtain large-scale, root-layer field water holding capacity data with high accuracy, providing scientific, effective, and practical assistance for at least drought monitoring, drought relief management, and farmland irrigation. Through this method, unnecessary financial and material expenditures can be reduced, acquisition costs can be greatly reduced, and the efficiency of actual drought relief management can be significantly 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 high-precision regional drought monitoring possible. Given its ability to obtain global spatiotemporal surface information, coupled with its economical and efficient nature, remote sensing holds a significant advantage in regional drought monitoring. Microwave remote sensing offers unique advantages in soil moisture monitoring. Unaffected by weather conditions, it possesses a certain degree of penetration, enabling it to capture soil moisture information across vertical soil profiles. Currently, field water holding capacity is primarily determined through ground measurements and model estimation. While ground measurements are relatively accurate, they cannot capture regional data. Model estimation can capture data over a large area, but due to the limitations of the estimation model, the data accuracy is insufficient to meet the requirements of actual regional drought monitoring.

[0003] Therefore, ground-based measurements can only capture field water holding capacity at a specific site. These data are poorly representative at the regional scale and cannot meet the needs of regional drought monitoring. Furthermore, field water holding capacity data derived from soil transfer function models is poorly applicable at the regional scale and lacks high accuracy, making them unsuitable for precise regional drought monitoring. Summary of the Invention

[0004] Drought is one of my country's major natural disasters. Naturally, it can cause grassland degradation and the gradual shrinkage of natural oases due to water scarcity. In severe cases, it can significantly reduce vegetation cover, leading to severe desertification, further eroding soil structure and threatening biodiversity. Humanly, drought can lead to reduced crop yields and, in severe cases, impact domestic water use, industrial production, and other socioeconomic activities. Therefore, effective drought monitoring and forecasting is a crucial means of mitigating the adverse effects of drought and is crucial for disaster prevention and mitigation, as well as promoting socioeconomic 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 field water holding capacity of crop root zone soil with high precision and 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 time for saturated soil to dewater based on the target data information; determining the date for selecting 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, determining the precipitation level of saturated soil and the time it takes for saturated soil to drain water at least includes: determining the precipitation level required for saturated soil and determining the time it takes 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 when 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 remote sensing field water holding capacity appears 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 existing technology, 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 are reduced, the acquisition cost is 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0013] Figure 1 This is a schematic diagram of the principle of estimating the field water holding capacity of the root zone of the estimation method of this application;

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

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

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

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

[0018] Figure 6 This 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 is a combination of the appended 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, not all of the embodiments.

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

[0021] 1. Microwave soil moisture data: refers to 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, including the 0-20 cm soil surface layer and the 0-40 cm soil root layer.

[0024] Application Overview

[0025] There are already 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 application of drought monitoring, microwave soil moisture content cannot be used as a direct basis for judging the severity of the drought. 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 existing public technology does not disclose the relevant methods for remote sensing estimation of field water holding capacity in the region. 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: target data acquisition and processing; based on target data information, determining the precipitation level of saturated soil and the time for saturated soil to dewater; based on precipitation data, determining the date for selecting microwave soil moisture data as remote sensing field water holding capacity; and calculating the field water holding capacity of the remote sensing region based on microwave soil moisture data and the selection 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 large-scale soil. The method is based on remote sensing soil moisture data and ground station precipitation data. According to the precipitation level required for saturated soil and the time for saturated soil to dewater, the method determines the date when the soil reaches saturation, and determines the date when field water holding capacity appears based on the time for saturated soil to dewater, thereby estimating field water holding data using microwave remote sensing soil moisture data.

[0028] The following is a detailed description of each step:

[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, calculating the daily cumulative precipitation data of each station, and clipping the soil surface and root layer SMAP soil moisture data by district and county. Figure 2 .

[0030] In some embodiments, determining the precipitation level of saturated soil and the time it takes for the saturated soil to dehydrate includes at least determining the precipitation level required for the soil to reach saturation, determining the date the soil reaches saturation, and determining the time it takes for the saturated soil to dehydrate.

[0031] The infiltration performance of different soil textures is different 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. The opposite is true for clay. Therefore, the precipitation conditions for different soil textures to reach saturation are different. Figure 3 The precipitation levels required to saturate a 40 cm thick soil for different soil textures.

[0032] In determining the time it takes 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 on which 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 appears in units of districts and counties.

[0034] In some embodiments, the field water holding capacity of a remotely sensed region is calculated by averaging the microwave soil moisture of each district and county on the day when the field water holding capacity occurs to obtain the field water holding capacity of each district and county; and obtaining the regional remotely sensed field water holding capacity data 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 this 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 assessment. Practical application shows that the soil relative moisture product calculated based on remote sensing field water holding capacity product is better than the current SMAP soil relative moisture product and the soil relative moisture 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. It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and that 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 appended claims rather than the above description, and it is intended that all changes that fall within the meaning and range of equivalents of the claims are included in the present application. Any figure mark in the claims should not be construed as limiting the claim to which it relates.

[0038] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method 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 can also be appropriately combined to form other implementation methods 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 it takes for saturated soil to drain; Based on precipitation data, the date for selecting microwave soil moisture data as remote sensing field water holding capacity was determined; Calculate the field water holding capacity of the remote sensing area based on microwave soil moisture data and selected dates; The acquired target data information includes at least microwave soil moisture data, precipitation data, and administrative division data of the estimated area; the data processing includes classifying meteorological stations according to their districts and counties, calculating daily cumulative precipitation data for each station, and clipping the soil surface and root layer SMAP soil moisture data by district and county; Determining the precipitation level for saturated soil involves determining the precipitation level required to saturate a 40 cm thick soil of different soil textures; Determining the time for saturated soil to dewater includes determining that the surface remote sensing soil moisture reaches the field capacity one day after the precipitation stops, and the root layer remote sensing soil moisture reaches the field capacity two days after the precipitation stops; Determining the date for selecting microwave soil moisture data includes at least the following: 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 appears, based on the district and county. 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.

Images