A method for inverting snow water equivalent and soil moisture content based on neutron flux

Abstract

The present invention discloses a method for inverting snow water equivalent and soil water content based on neutron flux, which relates to the field of meteorological science and technology, and includes: conducting a calibration experiment at an experimental site, measuring the thermal neutron count rate, epithermal neutron count rate, soil water content and snow water equivalent, substituting the experimental results into a database, and calibrating parameter N e0 and N t0 ; setting an epithermal neutron detector at the experimental site, and then selecting any one of the thermal neutron detector, soil water content sensor, and snow water equivalent sensor to conduct detection at the experimental site; taking the detection result as the original data, and finding the sample point data closest to the original data in the database, which is the inversion result of the snow water equivalent and soil water content. The method of the present invention corrects the influence of snow water equivalent in the actual measurement of soil water content by the cosmic ray neutron method, or corrects the influence of soil water content in the measurement of snow water equivalent, and can also determine the snow water equivalent and soil water content simultaneously by measuring the ground epithermal neutron and thermal neutron count rates.

Description

Technical Field

[0001] The invention relates to the field of meteorological science and technology, and in particular to a method for inverting snow water equivalent and soil moisture content based on neutron flux. Background Art

[0002] Soil moisture content and snow water equivalent of surface snow are important parameters that affect the earth's water cycle. Accurately measuring these two indicators on a large scale is of great significance to fields such as agriculture, meteorology and ecology. Cosmic-Ray Neutron Sensing (CRNS) is a non-contact measurement method that is used for large-scale continuous measurement of soil moisture content or snow water equivalent. Through continuous monitoring of the CRNS cosmic ray neutron detector system, time series information of neutron count rate can be obtained, which reflects the neutron flux near CRNS. The soil moisture content or snow water equivalent measurement results at that point in time can be obtained by correction and inversion of neutron counts.

[0003] However, the traditional CRNS method faces a major technical bottleneck in practical applications: since both soil moisture content and snow water equivalent can modulate the neutron flux, existing technologies cannot effectively distinguish the independent contributions of the two. This results in significant errors when measuring soil moisture content due to the presence of snow cover; conversely, when monitoring snow water equivalent, fluctuations in soil moisture content can also seriously affect measurement accuracy. Existing studies have attempted to solve this problem in the following ways: (1) pre-measuring soil moisture content before snowfall and predicting winter soil moisture changes based on this; (2) using the empirical relationship between the ratio of thermal neutron to fast neutron count rates and snow water content for correction. However, even after correction according to these methods, the accuracy is still not high and there is a lack of theoretical basis. Summary of the invention

[0004] To solve the above technical problems, the present invention discloses a method for inverting snow water equivalent and soil moisture content based on neutron flux. The method is based on the neutron counting rate of the CRNS detector, and simultaneously inverts soil moisture content and snow water equivalent, or effectively corrects the interference of one parameter when measuring another parameter.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for inverting snow water equivalent and soil moisture content based on neutron flux comprises the following steps:

[0007] (1) Conduct a calibration experiment at the experimental site to measure the thermal neutron count rate, epithermal neutron count rate, soil moisture content, and snow water equivalent. Substitute the experimental results into the database and calibrate the epithermal neutron normalization coefficient N. e0 and thermal neutron normalization factor N t0 ;

[0008] (2) Setting up an epithermal neutron detector at the experimental site, and then selecting any one of the thermal neutron detectors, soil moisture sensors, and snow water equivalent sensors to set up at the experimental site for detection;

[0009] (3) The detection result obtained in step (2) is used as the original data, and the sample point data closest to the original data is found in the database. The data is the inversion result of snow water equivalent and soil moisture content.

[0010] Optionally, step (1) specifically includes: using a cosmic ray neutron detector in the experimental site to monitor the epithermal neutron count rate N epi and thermal neutron count rate N the , and at the same time measure the soil moisture content and snow water equivalent at the location of the detector, and compare the snow water equivalent and soil moisture content with all the sample point data in the database. Each sample point data in the database contains four information: soil moisture content, snow water equivalent, normalized epithermal neutron count and normalized thermal neutron count. Match the sample point data closest to the measured snow water equivalent and soil moisture content in the database, and read the normalized epithermal neutron count N corresponding to the sample point data en , normalized thermal neutron count N tn , the normalized epithermal neutron count N en , normalized thermal neutron count N tn , epithermal neutron count rate N epi and thermal neutron count rate N the Substituting into the following formula, we can get the epithermal neutron normalization coefficient N e0 and thermal neutron normalization factor N t0 The values ​​of are used to complete the calibration of these two parameters;

[0011] ;

[0012] .

[0013] Optionally, step (2) specifically includes: combining the epithermal neutron detector with the thermal neutron detector, recording the epithermal neutron detector count and the thermal neutron detector count; combining the epithermal neutron detector with the snow water equivalent sensor, recording the epithermal neutron detector count and the snow water equivalent sensor result; combining the epithermal neutron detector with the soil moisture sensor, recording the epithermal neutron detector count and the soil moisture sensor result. Generally speaking, the experimental site is close to the experimental site in step (1).

[0014] Optionally, step (3) specifically includes: using the detection result obtained by cooperating the epithermal neutron detector with the thermal neutron detector as the original data, comparing and matching it with the sample point data in the database, obtaining the sample point data information in the database that is closest to the original data, and inverting the soil moisture content and snow water equivalent; using the detection result obtained by cooperating the epithermal neutron detector with the snow water equivalent sensor as the original data, comparing and matching it with the sample point data in the database, obtaining the sample point data information in the database that is closest to the original data, inverting the soil moisture content, and correcting the influence of snow water equivalent; using the epithermal neutron detector with the soil moisture content sensor as the original data, comparing and matching it with the sample point data in the database, obtaining the sample point data information in the database that is closest to the original data, inverting the snow water equivalent, and correcting the influence of soil moisture content.

[0015] The beneficial effect of the present invention is that the method of the present invention can effectively reduce the influence of snow water equivalent when measuring soil moisture content using the cosmic ray neutron method; at the same time, the interference of soil moisture content can be significantly reduced when measuring snow water equivalent. In addition, by measuring the ground epithermal neutron and thermal neutron count rates, the snow water equivalent and soil moisture content can be accurately determined at the same time. Compared with traditional methods, the present invention has achieved breakthroughs in theoretical models and algorithm design. By comprehensively considering the joint effects of soil and snow on neutron flux, a coupled inversion database is established, thereby significantly improving the accuracy of measurements. This innovative method not only overcomes the limitations of the traditional cosmic ray neutron method, but also provides a new technical path for large-scale, high-precision monitoring of soil moisture and snow water equivalent. It has important scientific value and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of a method for inverting snow water equivalent and soil moisture content based on neutron flux according to the present invention;

[0017] Figure 2A It is the response database of superthermal neutrons to soil moisture content and snow water equivalent in the present invention;

[0018] Figure 2B It is the response database of thermal neutrons to soil moisture content and snow water equivalent in the present invention;

[0019] Figure 3 It is the experimental result of snow water equivalent observation at Binggou Pass Station in the application example of the present invention. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] A method for inverting snow water equivalent and soil moisture content based on neutron flux, such as Figure 1 As shown, the following steps are included:

[0022] (1) Conduct a calibration experiment at the experimental site to measure the thermal neutron count rate, epithermal neutron count rate, soil moisture content, and snow water equivalent. Substitute the experimental results into the database and calibrate the epithermal neutron normalization coefficient N. e0 and thermal neutron normalization factor N t0 ; Specifically include:

[0023] Monitoring of epithermal neutron count rate N using cosmic ray neutron detectors in the experimental site epi and thermal neutron count rate N the , and at the same time measure the soil moisture content and snow water equivalent at the location of the detector, and compare the snow water equivalent and soil moisture content with all the sample point data in the database. Each sample point data in the database contains four information: soil moisture content, snow water equivalent, normalized epithermal neutron count and normalized thermal neutron count. Match the sample point data closest to the measured snow water equivalent and soil moisture content in the database, and read the normalized epithermal neutron count N corresponding to the sample point data en , normalized thermal neutron count N tn , the normalized epithermal neutron count N en , normalized thermal neutron count N tn , epithermal neutron count rate N epi and thermal neutron count rate N the Substituting into the following formula, we can get the epithermal neutron normalization coefficient N e0 and thermal neutron normalization factor N t0 The values ​​of are used to complete the calibration of these two parameters;

[0024] ;

[0025] .

[0026] (2) An epithermal neutron detector is set up at the experimental site, and then any one detector is selected from the thermal neutron detector, soil moisture content sensor, and snow water equivalent sensor to be set up at the experimental site for detection; specifically, the epithermal neutron detector is combined with the thermal neutron detector to record the epithermal neutron detector count and the thermal neutron detector count; the epithermal neutron detector is combined with the snow water equivalent sensor to record the epithermal neutron detector count and the snow water equivalent sensor result; the epithermal neutron detector is combined with the soil moisture content sensor to record the epithermal neutron detector count and the soil moisture content sensor result.

[0027] (3) Using the detection result obtained in step (2) as the original data, find the sample point data closest to the original data in the database, and the sample point data is the inversion result of snow water equivalent and soil moisture content. Specifically, it includes: using the detection result obtained by combining the epithermal neutron detector with the thermal neutron detector as the original data, comparing and matching with the sample point data in the database, obtaining the sample point data information closest to the original data in the database, and inverting the soil moisture content and snow water equivalent; using the detection result obtained by combining the epithermal neutron detector with the snow water equivalent sensor as the original data, comparing and matching with the sample point data in the database, obtaining the sample point data information closest to the original data in the database, inverting the soil moisture content, and correcting the influence of snow water equivalent; using the epithermal neutron detector with the soil moisture content sensor as the original data, comparing and matching with the sample point data in the database, obtaining the sample point data information closest to the original data in the database, inverting the snow water equivalent, and correcting the influence of soil moisture content. The above-mentioned database is a database obtained based on the Monte Carlo numerical simulation method.

[0028] Application Examples

[0029] The cosmic ray neutron detector combined with the soil moisture sensor measurement results were used to invert the nearby snow water equivalent information and compare it with the monitoring results of the SSG-2 snow water equivalent observation system on the experimental site. The experimental site was selected as the Binggou Pass Snow Observation Site in Qilian County, Qinghai Province. The vegetation type is mainly alpine meadow, the terrain feature is plateau meadow, the terrain is relatively open, and the meteorological conditions are relatively extreme, including strong sunshine and large temperature difference between day and night. The measurement time is from August 2024 to October 2024.

[0030] (1) A fixed cosmic ray neutron soil moisture observation system equipped with an epithermal neutron detector was used in combination with the SSG-2 snow water equivalent observation system and a soil moisture sensor at a depth of 4 cm underground for parameter calibration.

[0031] The time when snow was present was selected to record epithermal neutron counts. At the same time, the SSG-2 snow water equivalent observation system and the soil moisture sensor at a depth of 4 cm underground were used to measure the snow water equivalent and soil moisture content near the cosmic ray neutron detector. Figure 2A and Figure 2B Compare all the sample point data in the database shown in the figure, match the sample point data closest to the measured snow water equivalent and soil moisture content, and read the normalized epithermal neutron count N corresponding to the sample point data. en , normalized thermal neutron count N tn , the normalized epithermal neutron count N en , normalized thermal neutron count N tn , epithermal neutron count rate N epi and thermal neutron count rate N the Substituting into the following formula, we can get the epithermal neutron normalization coefficient N e0 and thermal neutron normalization factor N t0 The value of .

[0032] ;

[0033] .

[0034] (2) Start the cosmic ray neutron detector to continuously record the epithermal neutron count information of the epithermal neutron detector, and at the same time turn on the soil moisture sensor at a depth of 4 cm underground to continuously collect soil moisture information.

[0035] (3) After obtaining the measurement results of the epithermal neutron detector and the soil moisture sensor, the measured raw data are matched and compared with all the sample point data in the database to find the sample point data information in the database that is closest to the original data. The snow water equivalent value corresponding to the sample point data is used as the snow water equivalent inversion result and compared with the observation results of the SSG-2 snow water equivalent observation system, such as Figure 3 shown.

[0036] Comparison between this method and the measured data of the SSG-2 snow water equivalent observation system shows that the measurement results of the two are highly consistent (R²=0.92). This statistical verification shows that the inversion algorithm of the present invention has achieved centimeter-level accuracy in snow water equivalent estimation and has a reliable basis for engineering applications.

[0037] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for inverting snow water equivalent and soil moisture content based on neutron flux, characterized in that: The steps include: (1) Conduct calibration experiments to measure thermal neutron count rate, epithermal neutron count rate, soil moisture content, and snow water equivalent, substitute the experimental results into the database, and calibrate the epithermal neutron normalization coefficient N e0 and thermal neutron normalization factor N t0 ; (2) setting up an epithermal neutron detector at the experimental site, and then selecting any one of the thermal neutron detectors, soil moisture sensors, and snow water equivalent sensors to set up at the experimental site for detection; (3) Using the detection result obtained in step (2) as the original data, finding the sample point data closest to the original data in the database, wherein the sample point data is the inversion result of snow water equivalent and soil moisture content; Step (1) specifically includes: Monitoring of epithermal neutron count rate N using cosmic ray neutron detectors in the experimental site epi and thermal neutron count rate N the , and at the same time measure the soil moisture content and snow water equivalent at the location of the detector, and compare the snow water equivalent and soil moisture content with all the sample point data in the database. Each sample point data in the database contains four information: soil moisture content, snow water equivalent, normalized epithermal neutron count and normalized thermal neutron count. Match the sample point data closest to the measured snow water equivalent and soil moisture content in the database, and read the normalized epithermal neutron count N corresponding to the sample point data en , normalized thermal neutron count N tn , the normalized epithermal neutron count N en , normalized thermal neutron count N tn , epithermal neutron count rate N epi and thermal neutron count rate N the Substituting into the following formula, we can get the epithermal neutron normalization coefficient N e0 and thermal neutron normalization factor N t0 The values ​​of are used to complete the calibration of these two parameters; Step (2) specifically includes: Combine the epithermal neutron detector with the thermal neutron detector to record the epithermal neutron detector count and the thermal neutron detector count; combine the epithermal neutron detector with the snow water equivalent sensor to record the epithermal neutron detector count and the snow water equivalent sensor result; combine the epithermal neutron detector with the soil moisture sensor to record the epithermal neutron detector count and the soil moisture sensor result.

2. The method for inverting snow water equivalent and soil moisture content based on neutron flux according to claim 1, characterized in that: Step (3) specifically includes: The detection results obtained by cooperating with the epithermal neutron detector and the thermal neutron detector are taken as the original data, which are compared and matched with the sample point data in the database to obtain the sample point data information in the database that is closest to the original data, and the soil moisture content and snow water equivalent are inverted; the detection results obtained by cooperating with the epithermal neutron detector and the snow water equivalent sensor are taken as the original data, which are compared and matched with the sample point data in the database to obtain the sample point data information in the database that is closest to the original data, and the soil moisture content is inverted, and the influence of snow water equivalent is corrected; the detection results obtained by cooperating with the epithermal neutron detector and the soil moisture content sensor are taken as the original data, which are compared and matched with the sample point data in the database to obtain the sample point data information in the database that is closest to the original data, and the snow water equivalent is inverted, and the influence of soil moisture content is corrected.

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