Carbon dioxide advection observation method based on multi-path concentration difference

Abstract

The application discloses a kind of carbon dioxide advection observation methods based on multi-path concentration difference, including in the observation region within the layout arbitrary angle rotation ground CO2 differential absorption lidar and three-dimensional wind radar;Rotary laser radar, in turn, the observation angle position of radar corresponds the x-axis in three-dimensional wind speed coordinate system, the middle of x-axis and z-axis, the middle of y-axis and z-axis, y-axis, to obtain the CO2 concentration profile average value and wind speed profile average value on corresponding observation angle;Based on CO2 concentration profile average value and wind speed profile average value, through corresponding calculation, the total amount of CO2 three-dimensional advection flux in observation region is obtained.The advantage is: first realize the CO2 advection observation on regional scale, solve the problems such as poor space representation, equipment synchronization difficulty, high cost and the like of traditional method.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ecological meteorological observation and remote sensing technology, and in particular to a carbon dioxide advection observation method based on multi-path concentration difference. BACKGROUND

[0002] At present, CO2, as a major greenhouse gas, its spatial distribution and transport process has important influence on the carbon cycle of ecological system and global carbon budget. The existing carbon flux observation technology mainly adopts the eddy covariance method to measure the vertical direction turbulent flux. However, in the complex terrain conditions, the horizontal advection flux caused by the surface relief and local wind field change often accounts for a significant part of the total CO2 flux, and even can become an important factor in the analysis of carbon budget. Therefore, accurate measurement of horizontal advection flux has key significance for quantitative analysis of regional ecological system carbon cycle and carbon source and sink identification.

[0003] According to the continuous gas equation (formula as follows), the complete CO2 material exchange between the atmosphere and the ground is mainly composed of storage term, advection term and turbulent term.

[0004]

[0005] Among them, represents the storage flux, which can be determined by the CO2 gradient profile; represents the turbulent flux, which can be determined by the eddy covariance system; represents the advection flux.

[0006] The accurate observation of advection flux needs to obtain the CO2 concentration gradient information at different horizontal positions to realize the accurate characterization of the concentration field and the flux calculation. However, the current advection observation method is difficult, and some studies try to observe through CO2 gradient profile, including: fixed point gradient observation method and mobile observation method. In fixed observation, a CO2 gradient profile is not representative enough; therefore, some studies observe through arranging multiple CO2 gradient profiles, but face the problem of system synchronization. In addition, there are studies using horizontal moving method of CO2 gradient profile, but there are problems of difficult arrangement and high cost. These methods have obvious limitations in spatial representativeness, synchronous observation, cost control and real-time performance. The existing technology has the following deficiencies in observing advection flux:

[0007] 1. The spatial representativeness of single CO2 profile gradient observation method is insufficient, which can only provide local vertical CO2 concentration distribution information, and cannot capture the horizontal concentration gradient and spatial heterogeneity characteristics on the regional scale, thereby leading to large uncertainty in the estimation of advection flux.

[0008] 2. Deploying multiple CO2 gradient observation profiles can improve spatial coverage to some extent, for example, by using four CO2 gradient profiles for observation. However, the deployment of multiple gradients and the construction of tower bases are very costly. At the same time, the poor time synchronization between multiple observation devices and the differences in instrument response between different devices make it difficult for the observation data to accurately reflect the spatial gradient of the true concentration field, which seriously affects the accuracy of flux calculation.

[0009] 3. While constructing concentration profiles using horizontally moving CO2 gradient observation equipment can theoretically improve spatial representativeness, practical operation involves significant costs for equipment transportation, deployment, and maintenance. Furthermore, challenges in field observations, such as complex mobile device positioning, intricate observation path planning, and difficulties in real-time data acquisition, limit the application of this method. Summary of the Invention

[0010] The purpose of this invention is to provide a carbon dioxide advection observation method based on multipath concentration difference, thereby solving the aforementioned problems existing in the prior art.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] A method for observing carbon dioxide advection based on multipath concentration differences includes the following steps:

[0013] S1. Instrument deployment: Deploy ground-based CO2 differential absorption lidar and three-dimensional wind measurement radar that can be rotated at any angle within the observation area of ​​the eddy covariance observation system.

[0014] S2. Observation method: Rotate the ground-based CO2 differential absorption lidar and the three-dimensional wind measurement radar. The observation angle positions of the ground-based CO2 differential absorption lidar and the three-dimensional wind measurement radar are sequentially aligned with the x-axis, the middle of the x-axis and z-axis, the z-axis, the middle of the y-axis and z-axis, and the y-axis in the three-dimensional wind speed coordinate system, so as to obtain the average CO2 concentration profile and the average wind speed profile at the corresponding observation angle within the preset time period.

[0015] S3. Calculation of Flow Quantity: Based on the average CO2 concentration profile at each observation angle, obtain the CO2 concentration gradient along the x, y, and z axes at different heights; the CO2 concentration gradient along the z axis and the x and y axes at the lowest height are calculated separately from the CO2 concentration gradient along the x and y axes at other heights; based on the CO2 concentration gradient along the x, y, and z axes at different heights and the average wind speed profile at each height, obtain the CO2 flow quantity density per unit area in the corresponding direction; based on the CO2 flow quantity density per unit area in the corresponding direction, obtain the total three-dimensional flow quantity of CO2 within the observation area according to the continuous gas conservation equation.

[0016] Preferably, step S1 is specifically that the ground-based CO2 differential absorption lidar and the three-dimensional wind lidar are arranged in the observation area of the eddy covariance observation system, and the ground-based CO2 differential absorption lidar and the three-dimensional wind lidar are fixed on a motor rotating platform, and the motor rotating platform can rotate at any angle, so as to control the ground-based CO2 differential absorption lidar and the three-dimensional wind lidar to observe the CO2 concentration profile and the wind speed profile in any direction respectively.

[0017] Preferably, step S2 specifically includes the following contents,

[0018] S21, start single observation, the motor rotating platform adjusts the observation angle, so that the ground-based CO2 differential absorption lidar and the three-dimensional wind lidar are parallel to the ground to observe the CO2 concentration profile and the wind speed profile respectively, the observation angle position corresponds to the x-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C x is recorded.

[0019] S22, the motor rotating platform adjusts the observation angle, so that the ground-based CO2 differential absorption lidar is inclined to observe the CO2 concentration profile at an angle of 45° away from the ground, the observation angle position corresponds to the middle of the x-axis and the z-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C xz is recorded.

[0020] S23, the motor rotating platform adjusts the observation angle, so that the ground-based CO2 differential absorption lidar and the three-dimensional wind lidar are perpendicular to the ground to observe the CO2 concentration profile and the wind speed profile respectively, the observation angle position corresponds to the z-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C z is recorded.

[0021] S24, the motor rotating platform adjusts the observation angle, so that the ground-based CO2 differential absorption lidar is inclined to observe the CO2 concentration profile at an angle of 45° away from the ground, the observation angle position corresponds to the middle of the y-axis and the z-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C yz is recorded.

[0022] S25, the motor rotating platform adjusts the observation angle, so that the ground-based CO2 differential absorption lidar and the three-dimensional wind lidar are parallel to the ground to observe the CO2 concentration profile and the wind speed profile respectively, the observation angle position corresponds to the y-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C y is recorded; and the single observation is ended.

[0023] S26, steps S21-S25 are repeated in a preset time period to obtain the average values of the CO2 concentration profile and the wind speed profile under the corresponding observation angle in the preset time period.

[0024] Preferably, step S3 specifically includes the following contents,

[0025] S31, adopt the concentration profile C x , C y and C z Estimate the CO2 concentration gradient in the x-axis, y-axis and z-axis directions; since the horizontal advection is different at different heights, the lowest height and other heights are calculated separately;

[0026] Wherein, the CO2 concentration gradient in the x-axis and y-axis directions of the z-axis and the lowest height is respectively adopted by the concentration profile C x , C y , C z The concentration values of the two adjacent concentration points and the distance between the two adjacent concentration measurement points on the corresponding concentration profile are calculated and obtained;

[0027] The advection flux in the x-axis and y-axis directions of other layer heights is respectively adopted by the inclined concentration profile C xz and C yz The difference between the vertical concentration profile C z and the corresponding CO2 concentration point in the x-axis and y-axis directions of the inclined concentration profile and the vertical concentration profile at a certain height is calculated and obtained;

[0028] S32, using the average value of the wind speed profile in the x, y and z-axis directions and the CO2 concentration gradient in the x, y and z-axis directions, respectively, to obtain the CO2 advection flux density per unit area in the x, y and z-axis directions;

[0029] S33, since the horizontal advection at high altitude is relatively small, the horizontal advection flux density estimated by the inclined profile is taken as the advection flux in the horizontal boundary length of the whole region; according to the continuous gas conservation equation, the total amount of CO2 three-dimensional advection flux in the boundary volume of the observation region is calculated by using the CO2 advection flux density per unit area in the x, y and z-axis directions.

[0030] The beneficial effects of the present application are: the method provided by the present application realizes the CO2 advection observation on the regional scale for the first time, solves the problems of poor spatial representativeness, difficult equipment synchronization and high cost of traditional methods. Through remote sensing means, without densely arranging ground equipment, the observation cost and maintenance difficulty are greatly reduced, the advection flux estimation accuracy and regional carbon cycle monitoring ability are significantly improved, and strong technical support is provided for regional carbon management and ecological environment protection. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is the flow chart of the observation method in the embodiment of the present application;

[0032] Figure 2 is a schematic diagram of the layout mode of the laser radar in the embodiment of the present application;

[0033] Figure 3is a schematic diagram of horizontal advection estimation in the embodiment of the application (taking the y-axis direction as an example). DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0035] In the embodiment, in order to solve the problems in the prior art, a carbon dioxide advection observation method based on multi-path concentration difference is provided, which aims to realize regional scale continuous, real-time and refined CO2 horizontal concentration field observation and accurately estimate horizontal advection flux, and is suitable for advection flux observation in complex terrain regions such as forests. The method specifically includes the following three parts,

[0036] I. Instrument layout

[0037] The advection flux measurement needs to be combined with the eddy covariance observation system, so the ground-based CO2 differential absorption lidar and three-dimensional wind radar are arranged in the observation area of the eddy covariance observation system. The radar is fixed on a motor rotating platform, and the motor rotating platform can rotate at any angle to control the radar to observe the CO2 concentration gradient and three-dimensional wind speed profile in any direction.

[0038] II. Observation method

[0039] (1) Start single observation, adjust the observation angle of the ground-based CO2 differential absorption lidar and three-dimensional wind radar on the motor rotating platform, so that the ground-based CO2 differential absorption lidar and three-dimensional wind radar observe the CO2 concentration profile and wind speed profile parallel to the ground, respectively. The observation angle position corresponds to the x-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C x .

[0040] (2) Adjust the observation angle of the motor rotating platform, so that the ground-based CO2 differential absorption lidar observes the CO2 concentration profile at an angle of 45° away from the ground. The observation angle position corresponds to the middle of the x-axis and the z-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C xz .

[0041] (3) Adjust the observation angle of the motor rotating platform, so that the ground-based CO2 differential absorption lidar and three-dimensional wind radar observe the CO2 concentration profile and wind speed profile perpendicular to the ground, respectively. The observation angle position corresponds to the z-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C z .

[0042] (4) The motor rotating platform adjusts the observation angle to make the ground-based CO2 differential absorption lidar tilt 45° from the ground to observe the CO2 concentration profile, and the observation angle position corresponds to the middle of the y-axis and z-axis in the three-dimensional wind speed coordinate system. Record the CO2 concentration profile C yz .

[0043] (5) The motor rotating platform adjusts the observation angle to make the ground-based CO2 differential absorption lidar and the three-dimensional wind speed radar parallel to the ground to respectively observe the CO2 concentration profile and the wind speed profile. The observation angle position corresponds to the y-axis in the three-dimensional wind speed coordinate system. Record the CO2 concentration profile C y ; single observation ends.

[0044] (6) After the completion of a single observation, continue to repeat steps (1-5). Record the average values of the repeated observations of the CO2 concentration profile and the wind speed profile within a predetermined time period (such as 30 minutes).

[0045] III. Calculation of advection flux

[0046] (1) The advection flux is calculated by the average value of the CO2 concentration profile within 30 minutes. It is necessary to calculate the CO2 concentration gradient in the x, y, and z-axis coordinate directions in turn. Due to the large difference in horizontal advection at different heights, the lowest height is calculated separately from other heights.

[0047] wherein the CO2 concentration gradients in the x-axis, y-axis, and z-axis directions of the lowest height and the z-axis are calculated by the concentration profile C x , C y , and C z respectively. The concentration values of the two adjacent concentration points and the distances between the two adjacent concentration measurement points on the corresponding concentration profile are calculated and obtained. The calculation formula is as follows:

[0048]

[0049] In the formula: are the CO2 concentration gradients in the x-axis and y-axis directions respectively; Δx and Δy represent the distances between the two adjacent concentration measurement points on the concentration profile C x and C y ; C(C x+Δx ) and C(C x ) represent the concentration values of the two adjacent concentration points on the concentration profile C x ; C(C y+Δy ) and C(C y ) represent the concentration values of the two adjacent concentration points on the concentration profile C y .

[0050] (2) Calculate the CO2 concentration gradient in the z-axis direction The calculation formula is the same as that in step (1). The x zThe CO2 concentration profile is obtained, and the CO2 concentration gradient along the z-axis is calculated.

[0051] (3) The CO2 concentration gradients in the x-axis and y-axis directions of other layer heights were respectively represented by inclined concentration profiles C xz and C yz Compared with vertical concentration profile C z The difference between the two concentrations is calculated by taking the distances along the x and y axes between the CO2 concentration points corresponding to the inclined and vertical concentration profiles at a certain height (using a segment of concentration difference to represent the entire boundary layer length during the calculation). The calculation formula is as follows:

[0052]

[0053] Where Δ(xz-z) represents C at a certain height. xz and C z The distance of the corresponding CO2 concentration point in the x-direction; C(C xz ) and C(C z ) are C at the corresponding heights xz and C z The concentration value of CO2 at a certain height; Δ(yz-z) is the concentration of CO2 at a certain height. yz and C z The distance in the y-direction corresponding to the CO2 concentration point; C(C yz ) and C(C z ) are respectively the corresponding heights below and above C yz and C z The concentration value of CO2 at the specified concentration point.

[0054] (4) The translational flux density of CO2 in different directions is determined by the coupling of the following two factors: the product of the average wind speed profile and the CO2 concentration gradient in any direction is the CO2 translational flux density per unit area in that direction (for example, the product of the average wind speed profile and the CO2 concentration gradient in the x-axis direction is the CO2 translational flux density per unit area in that direction. The calculation for the y and z directions is similar). The calculation formula is as follows:

[0055]

[0056] in, These represent the components of the CO2 translational flux density in the observation area along the x, y, and z axes, respectively. These are the average wind speed profiles along the x, y, and z axes at the current location, respectively.

[0057] (5) Calculate the total amount of the advection flux in the boundary volume of the region. In the entire horizontal boundary of the region, the near-surface canopy region is the main contribution of horizontal advection, and the present application observes the CO2 concentration profile of the complete boundary length near the surface; while the horizontal advection at high altitude is relatively small, so the horizontal advection flux density estimated by the inclined profile and the vertical profile is taken as the advection flux in the entire horizontal boundary length of the region. According to the continuous gas conservation equation, the CO2 three-dimensional advection flux total amount in the boundary volume of the observation region is calculated by using the CO2 advection flux density per unit area in the x, y and z axis directions. The calculation formula is as follows:

[0058]

[0059] Wherein, F adv is the CO2 three-dimensional advection flux total amount in the observation region; L is the length of the horizontal boundary of the observation region; H m is the upper limit of the atmospheric height of the vertical boundary of the observation region.

[0060] By using the above technical scheme disclosed by the present application, the following beneficial effects are obtained:

[0061] The present application provides a carbon dioxide advection observation method based on multi-path concentration difference, which realizes CO2 advection observation at the regional scale for the first time, solves the problems of poor spatial representativeness, difficult equipment synchronization and high cost of traditional methods. Through remote sensing means, without densely arranging ground equipment, the observation cost and maintenance difficulty are greatly reduced, the advection flux estimation accuracy and regional carbon cycle monitoring ability are significantly improved, and strong technical support is provided for regional carbon management and ecological environment protection.

[0062] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for observing carbon dioxide advection based on multi-path concentration difference, characterized in that: Comprising the following steps, S1, instrument layout: layout the ground-based CO2 differential absorption lidar and three-dimensional wind radar rotating at any angle in the observation area of the eddy covariance observation system; S2, observation mode: rotate the ground-based CO2 differential absorption lidar and three-dimensional wind radar, and sequentially correspond the observation angle position of the ground-based CO2 differential absorption lidar and three-dimensional wind radar to the middle of x-axis, x-axis and z-axis, the middle of y-axis and z-axis, and y-axis in the three-dimensional wind speed coordinate system, so as to respectively obtain the CO2 concentration profile average value and the wind speed profile average value at the corresponding observation angle in a preset time period; S3, calculation of the advection flux: based on the CO2 concentration profile average value at each observation angle, the CO2 concentration gradient in the x, y and z axis coordinate directions at different heights is obtained; wherein the CO2 concentration gradient in the x-axis and y-axis directions at the lowest height and the z-axis is calculated separately from the CO2 concentration gradient in the x-axis and y-axis directions at other heights; based on the CO2 concentration gradient in the x, y and z axis coordinate directions at different heights and the wind speed profile average value in the corresponding direction at each height, the CO2 advection flux density per unit area in the corresponding direction is obtained; based on the CO2 advection flux density per unit area in the corresponding direction, the total amount of CO2 three-dimensional advection flux in the observation area is obtained according to the continuous gas conservation equation.

2. The method of claim 1, wherein: Step S1 is specifically that the ground-based CO2 differential absorption lidar and three-dimensional wind radar are laid out in the observation area of the eddy covariance observation system, and the ground-based CO2 differential absorption lidar and three-dimensional wind radar are fixed on the motor rotating platform, which can rotate at any angle, so as to control the ground-based CO2 differential absorption lidar and three-dimensional wind radar to observe the CO2 concentration profile and wind speed profile in any direction respectively.

3. The method of claim 2, wherein: Step S2 specifically includes the following contents, S21, start of single observation, the motor rotating platform adjusts the observation angle, so that the ground-based CO2 differential absorption lidar and three-dimensional wind radar observe the CO2 concentration profile and wind speed profile respectively parallel to the ground, the observation angle position corresponds to the x-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile Cx is recorded; S22, the motor rotating platform adjusts the observation angle, so that the ground-based CO2 differential absorption lidar observes the CO2 concentration profile at an angle of 45° away from the ground, and the observation angle position corresponds to the middle of x-axis and z-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile Cxz is recorded; S23, the motor rotating platform adjusts the observation angle, so that the ground-based CO2 differential absorption lidar and the three-dimensional wind measuring radar respectively observe the CO2 concentration profile and the wind speed profile, the observation angle position corresponds to the z-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C z ; S24, the motor rotating platform adjusts the observation angle, makes the foundation CO2 differential absorption laser radar tilt away from the ground 45° to observe the CO2 concentration profile, the observation angle position corresponds to the middle of the y axis and the z axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C is recorded yz ; S25, the motor rotating platform adjusts the observation angle, so that the ground CO2 differential absorption lidar and the three-dimensional wind measuring radar are parallel to the ground to respectively observe the CO2 concentration profile and the wind speed profile. The observation angle position corresponds to the y-axis in the three-dimensional wind speed coordinate system, and the CO2 concentration profile C y ; single observation ends; S26, repeat steps S21-S25 in a preset time period to obtain the CO2 concentration profile average value and the wind speed profile average value at the corresponding observation angle in the preset time period.

4. The method according to claim 3, wherein: Step S3 specifically includes the following contents, S31, adopt concentration profile C x , C y and C z Estimate the CO2 concentration gradient in the x-axis, y-axis and z-axis directions; because the difference of horizontal advection at different heights is large, the lowest height and other heights are calculated separately; Wherein, the CO2 concentration gradient in the direction of x-axis, y-axis and z-axis of the lowest layer height is respectively calculated by the concentration profile C x , C y , C z The concentration value of the two adjacent concentration points and the distance of the two adjacent concentration measurement points on the corresponding concentration profile are calculated and obtained. The other layer height x-axis and y-axis direction's horizontal flux respectively uses the inclined concentration profile C xz and C yz The difference between the vertical concentration profile C z The distance of the corresponding CO2 concentration points in the x-axis and y-axis directions of the certain height under the corresponding inclined concentration profile and the vertical concentration profile is calculated and obtained. S32, using the wind speed profile average value in the x, y and z axis directions and the CO2 concentration gradient in the x, y and z axis directions, the CO2 advection flux density per unit area in the x, y and z axis directions is obtained respectively; S33, because the horizontal advection of high place is relatively small, so the horizontal advection flux density of the tilt profile estimation is taken as the advection flux of the whole region horizontal boundary length; according to the continuous gas conservation equation, the total amount of CO2 three-dimensional advection flux in the boundary volume of the observation region is calculated by using the unit area CO2 advection flux density in x, y and z axis directions.

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