A dynamic height threshold-based boundary layer height retrieval method

Abstract

The application provides a boundary layer height inversion method based on a dynamic height threshold, and relates to the technical field of boundary layer height inversion. The method comprises the following steps: acquiring a laser radar signal and preprocessing; identifying a cloud layer height according to a zero-crossing point of the signal based on a slope method; determining a height range searched when there is a cloud, adjusting an upper limit height according to the size of the signal in the range, and generating a limited range searched when there is a cloud; under the condition of a cloud, judging whether the cloud layer is in the boundary layer according to the slope size of the signal in the corresponding limited range, and in the two cases that the cloud layer is in the boundary layer and the cloud layer is out of the boundary layer, then recording the first target height or the second target height in the corresponding limited range as the boundary layer height according to the slope size. Through the method of dynamically adjusting the height threshold, the upper limit height threshold is adjusted in real time according to different situations, and the influence of complex stratification such as the cloud layer, the suspended aerosol layer and the residual layer is effectively eliminated.

Description

Technical Field

[0001] This application relates to the technical field of boundary layer height inversion, and in particular to a boundary layer height inversion method based on a dynamic height threshold. Background Technology

[0002] Generally, as altitude increases, a complex layer structure typically emerges near the boundary layer, such as suspended aerosol layers, lifted aerosol layers, residual layers, and clouds. When ground-based lidar encounters these complex layer structures during actual detection, the corresponding echo signals become extremely complex, exhibiting multiple peaks in localized areas along the profile. Therefore, directly using traditional methods cannot accurately identify the actual boundary layer height, leading to misjudgments.

[0003] Currently, some researchers have adopted a height restriction method to reduce the impact of strong signal gradients from clouds above the boundary layer on the boundary layer height inversion results. This method sets a height threshold and uses only radar signals below the threshold to determine the boundary layer height. For example, since the boundary layer height is usually below 2.5 km, 2.5 km is directly set as the upper limit. Below 2.5 km, the gradient method is used for boundary layer height inversion, filtering out interference from complex upper layer structures.

[0004] However, the applicability of this subjectively set threshold varies across different regions. For example, studies have shown that the boundary layer height can reach 4 km in arid areas of Northwest China. Therefore, to address these issues, it is necessary to improve traditional inversion methods to filter out interference from complex stratifications such as suspended aerosol layers and low-level clouds in actual boundary layer height inversion. Summary of the Invention

[0005] Therefore, it is necessary to provide a boundary layer height inversion method based on dynamic height threshold to address the above-mentioned technical problems. By dynamically adjusting the height threshold, the upper limit height threshold can be adjusted in real time for different situations, effectively eliminating the influence of complex stratifications such as cloud layers, suspended aerosol layers, and residual layers.

[0006] This application provides a boundary layer height inversion method based on a dynamic height threshold, including:

[0007] Acquire and preprocess the lidar signal to generate a lidar distance correction signal;

[0008] Cloud height is identified based on the zero-crossing point of the distance correction signal using the slope method; where cloud height includes the height of the cloud base, cloud peak, and cloud top.

[0009] Determine the altitude range for searching when there are clouds, and adjust the upper limit of the altitude range according to the magnitude of the distance correction signal within the altitude range to generate the limited range for searching when there are clouds; wherein, the upper limit altitude is initially the lowest cloud base altitude;

[0010] In the presence of clouds, the slope of the distance correction signal within the corresponding defined range is used to determine whether the cloud layer is within the boundary layer. If the cloud layer is within the boundary layer, the height of the first or second target within the corresponding defined range is recorded as the boundary layer height based on the slope. If the cloud layer is not within the boundary layer, the presence of an aerosol layer is determined based on the slope. If it is not present, the height of the second target within the corresponding defined range is recorded as the boundary layer height. If it is present, the upper limit of the defined range is adjusted to the height of the bottom of the aerosol layer, and the height of the first target within the adjusted defined range is recorded as the boundary layer height. The first target height is the height of the point closest to the minimum slope among the minimum points with a slope less than 0 within the corresponding defined range, which is used as the boundary layer height. The second target height is the height of the point with the minimum slope within the corresponding defined range.

[0011] In one embodiment, identifying cloud height based on the zero-crossing point of the distance correction signal using a slope method includes:

[0012] Calculate the slope of the sampling points adjacent to the zero point. If the slope changes from negative to positive, the zero point position is identified and recorded as a suspected cloud base or suspected cloud top; if the slope changes from positive to negative, the zero point position is identified and recorded as a suspected cloud peak.

[0013] Starting from the set cloud search starting point, when a suspicious cloud base and a suspicious cloud peak meet the set first condition, the suspicious cloud base or cloud peak is identified as a cloud base, and the corresponding suspicious cloud peak is identified as the cloud peak corresponding to the cloud base; when the location of a suspicious cloud peak meets the set second condition, the location of the suspicious cloud peak is identified as a cloud peak; the process of identifying cloud bases, cloud peaks and cloud bases is repeated until all cloud layers are found;

[0014] The first set condition includes that the current suspicious cloud peak signal has no upward trend and the current suspicious cloud peak signal value is greater than the first threshold, and the current suspicious cloud bottom signal value is less than the second threshold; the second set condition includes that the current suspicious cloud top signal has no downward trend and the current suspicious cloud top signal value is less than the second threshold.

[0015] In one embodiment, if the first suspicious cloud peak is lower than the first suspicious cloud base, the first suspicious cloud peak is removed.

[0016] In one embodiment, if the highest cloud peak is not a zero-crossing point, the inflection point above the cloud peak of the highest cloud layer is searched, and the nearest inflection point whose signal value satisfies the second set condition is taken as the highest cloud peak.

[0017] In one embodiment, adjusting the upper limit height of the height range based on the magnitude of the distance correction signal within the height range includes:

[0018] Determine if there is a distance correction signal less than 0 within the height range; if so, adjust the upper limit height to the height at which the distance correction signal changes from positive to negative within the height range; if not, keep the upper limit height unchanged.

[0019] In one embodiment, determining whether a cloud layer is within a boundary layer based on the slope of a distance correction signal within a corresponding defined range includes: if the slope of a distance correction signal within the corresponding defined range is less than a first slope threshold, then the cloud layer is outside the boundary layer; if the slope of a distance correction signal within the corresponding defined range is less than the first slope threshold, then the cloud layer is within the boundary layer.

[0020] In one embodiment, the height of the first target or the height of the second target within the corresponding defined range is recorded as the boundary layer height based on the slope magnitude, including:

[0021] If the slope of a distance correction signal within the defined range is less than the second slope threshold, the height of the first target within the defined range is recorded as the boundary layer height; if the slope of a distance correction signal within the defined range is less than the second slope threshold, the height of the second target within the defined range is recorded as the boundary layer height.

[0022] In one embodiment, determining the presence of an aerosol layer based on the slope magnitude includes: if the slope magnitude of a distance correction signal within a defined range is less than a third slope threshold, then an aerosol layer is present; if the slope magnitude of a distance correction signal within a defined range is less than the third slope threshold, then an aerosol layer is absent.

[0023] In one embodiment, the method further includes:

[0024] Determine the search altitude range when there are no clouds, and adjust the upper limit of the altitude range based on the magnitude of the distance correction signal within the altitude range;

[0025] In the absence of clouds, the height of the first or second target within the corresponding defined range is recorded as the boundary layer height based on the height corresponding to the minimum slope of the distance correction signal within the defined range.

[0026] In one embodiment, the height of the first target or the second target within the corresponding defined range is recorded as the boundary layer height based on the height corresponding to the minimum slope of the distance correction signal within the corresponding defined range, including:

[0027] If the height corresponding to the minimum slope of the distance correction signal within the defined range is less than the first height threshold, then the height of the first target within the defined range is recorded as the boundary layer height; if the height corresponding to the minimum slope of the distance correction signal within the defined range is not less than the first height threshold, then the height of the second target within the defined range is recorded as the boundary layer height.

[0028] This application employs the aforementioned boundary layer height inversion method based on a dynamic height threshold, which has the following beneficial effects:

[0029] 1. By dynamically adjusting the height threshold, the upper limit height threshold is adjusted in real time for different situations, effectively eliminating the influence of complex stratifications such as cloud layers, suspended aerosol layers, and residual layers;

[0030] 2. By using signal zero-crossing detection to determine the position of change from negative to positive or from positive to negative, suspicious cloud bases (cloud tops) and suspicious cloud peaks are identified respectively. Compared with the traditional gradient method, this avoids the noise amplification problem caused by direct differentiation and achieves smoother and more robust boundary identification.

[0031] 3. Based on zero-crossing detection, a dual threshold constraint mechanism is introduced: by setting a lower threshold for cloud peak signal value and an upper threshold for cloud base (cloud top) signal value, combined with the trend change relationship of the signal, false peaks and non-cloud disturbances can be effectively eliminated, and accurate screening of cloud areas can be achieved;

[0032] 4. By dynamically screening suspicious points through trend judgment rules, the algorithm can automatically identify multi-layer cloud structures, solve the problem of mismatch between cloud base and cloud top under the condition of multi-layer cloud superposition, and improve the applicability of the algorithm under complex atmospheric conditions. Attached Figure Description

[0033] Figure 1 This is a flowchart of a boundary layer height inversion method based on a dynamic height threshold in one embodiment;

[0034] Figure 2 This is a flowchart of cloud identification based on zero crossing points using a threshold method in one embodiment;

[0035] Figure 3 This is a schematic diagram illustrating the profile treatment within the boundary layer for situations involving suspended aerosols in one embodiment; wherein, Figure 3 (a) in the figure is a schematic diagram of the distance-corrected square signal when suspended aerosols occur; Figure 3 (b) in the diagram is a schematic diagram of the slope at the corresponding position of the signal;

[0036] Figure 4 This is a schematic diagram illustrating the profile processing within the boundary layer in one embodiment for situations without interference from other complex layered structures; wherein, Figure 4(a) in the diagram is a schematic diagram of the distance-corrected squared signal in the absence of other complex layered interference; Figure 4 (b) in the diagram is a schematic diagram of the slope at the corresponding position of the signal;

[0037] Figure 5 This is a schematic diagram illustrating the profile processing of clouds within the boundary layer in one embodiment; wherein, Figure 5 (a) in the figure is a schematic diagram of the distance-corrected squared signal of the cloud within the boundary layer; Figure 5 (b) in the diagram is a schematic diagram of the slope at the corresponding position of the signal;

[0038] Figure 6 This is a schematic diagram of profile processing under clear sky conditions in one embodiment; wherein, Figure 6 (a) in the diagram is a schematic diagram of the distance-corrected square signal under clear sky conditions; Figure 6 (b) in the diagram is a schematic diagram of the slope at the corresponding position of the signal;

[0039] Figure 7 This is a schematic diagram comparing the results of using a traditional boundary layer height inversion method and the boundary layer height inversion method of this application in one embodiment; wherein, Figure 7 (a) in the figure is a schematic diagram of the results using the traditional boundary layer height inversion method; Figure 7 (b) in the figure is a schematic diagram of the results obtained using the boundary layer height inversion method of this application. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0041] This application provides a boundary layer height inversion method based on a dynamic height threshold, including:

[0042] S100 acquires and preprocesses the lidar signal to generate a lidar distance correction signal.

[0043] S200 identifies cloud height based on the zero-crossing point of the distance correction signal using the slope method; where cloud height includes the height of the cloud base, cloud peak, and cloud top.

[0044] In one embodiment, based on the slope method, the cloud height is identified according to the zero-crossing point of the distance correction signal, including: calculating the slope of the sampling points adjacent to the zero-crossing point. If the slope changes from negative to positive, the zero-crossing point position is identified and recorded as a suspected cloud base or a suspected cloud top; if the slope changes from positive to negative, the zero-crossing point position is identified and recorded as a suspected cloud peak. Starting from the set cloud search starting point, when the suspected cloud base and the suspected cloud peak meet the set first condition, the suspected cloud base or the cloud top is identified as the cloud base, and the corresponding suspected cloud peak is identified as the cloud peak corresponding to the cloud base; when the suspected cloud top position meets the set second condition, the suspected cloud top position is identified as the cloud top; the process of identifying the cloud base, the cloud peak, and the cloud base is repeated until all clouds are found. The first set condition includes that the current suspected cloud peak signal has no upward trend, and the current suspected cloud peak signal value is greater than the first threshold, and the current suspected cloud base signal value is less than the second threshold; the second set condition includes that the current suspected cloud top signal has no downward trend and the current suspected cloud top signal value is less than the second threshold.

[0045] In one embodiment, when the first suspected cloud peak is lower than the first suspected cloud base, the first suspected cloud peak is removed.

[0046] In one embodiment, when the topmost cloud top is not a zero-crossing point, search for the inflection point above the cloud peak of the topmost cloud layer, and use the nearest inflection point whose signal value meets the second set condition as the topmost cloud top.

[0047] In actual cloud identification, first, use the lidar distance correction data after removing the background to solve its zero-crossing point, that is, the slope. Among all the points of the signal zero-crossing points, those with a slope changing from negative to positive are recorded as suspected cloud bases or suspected cloud tops, and those with a slope changing from positive to negative are recorded as suspected cloud peaks. Here, it is possible that the first suspected cloud peak is lower than the first suspected cloud base. In this case, the first suspected cloud peak is removed. Set two thresholds: the lower limit of the cloud peak signal value Th1 (cloud peak signal value > Th1), and the upper limit of the cloud base or cloud top signal value Th2 (cloud base or cloud top signal value < Th2). The above thresholds need to be determined by statistical analysis of the lidar data of the observation site.

[0048] Starting from the set cloud search starting point, if the following conditions are met, the current suspected cloud base is considered as the cloud base and the current suspected cloud peak is considered as the cloud peak: 1. The current suspected cloud peak signal has no upward trend (the subsequent suspected cloud peak signal value is less than the current suspected cloud peak signal value); 2. The current suspected cloud peak signal value > Th1; 3. The current suspected cloud base signal value < Th2.

[0049] After finding the cloud base and the corresponding cloud peak, continue to search the array of suspected cloud bases (cloud tops). When the following conditions are met, the current suspected cloud top is considered as the cloud top: 1. There is no downward trend under the current suspected cloud top (the subsequent suspected cloud top signal value is greater than the current cloud top); 2. The suspected cloud top signal < Th2. And so on to find all cloud layers.

[0050] For the highest cloud peak, there may be cases where it is not a zero-crossing point. In this case, we determine the inflection point above the cloud peak of the highest cloud layer and search for the nearest inflection point whose signal value meets the cloud peak condition as the last cloud peak.

[0051] S300, determine the altitude range for searching when there are clouds, adjust the upper limit of the altitude range according to the magnitude of the distance correction signal within the altitude range, and generate the limited range for searching when there are clouds; wherein, the upper limit altitude is initially the lowest cloud base altitude.

[0052] In one embodiment, adjusting the upper limit height of the height range based on the magnitude of the distance correction signal within the height range includes: determining whether there is a case where the distance correction signal within the height range is less than 0; if so, adjusting the upper limit height to the height at which the distance correction signal within the height range changes from positive to negative; if not, keeping the upper limit height unchanged.

[0053] S400, in the presence of clouds, determine whether the cloud layer is within the boundary layer based on the slope of the distance correction signal within the corresponding limited range; if the cloud layer is within the boundary layer, record the first or second target height within the corresponding limited range as the boundary layer height based on the slope; if the cloud layer is not within the boundary layer, determine whether an aerosol layer exists based on the slope; if it does not exist, record the second target height within the corresponding limited range as the boundary layer height; if it exists, adjust the upper limit of the limited range to the height of the bottom of the aerosol layer, and record the first target height within the adjusted limited range as the boundary layer height; wherein, the first target height is the height of the point closest to the minimum slope among the minimum points with a slope less than 0 within the corresponding limited range as the boundary layer height; the second target height is the height of the point with the minimum slope within the corresponding limited range.

[0054] In this application, the minimum point is the point where the function first decreases and then increases. Here, it is the point where the slope (equivalent to the dependent variable y) first decreases and then increases with the increase of height (equivalent to the independent variable x).

[0055] In one embodiment, determining whether a cloud layer is within a boundary layer based on the slope of a distance correction signal within a corresponding defined range includes: if the slope of a distance correction signal within the corresponding defined range is less than a first slope threshold, then the cloud layer is outside the boundary layer; if the slope of a distance correction signal within the corresponding defined range is less than the first slope threshold, then the cloud layer is within the boundary layer.

[0056] In one embodiment, the height of the first target or the second target within the corresponding defined range is recorded as the boundary layer height based on the slope magnitude, including: if the slope magnitude of the distance correction signal within the defined range is less than a second slope threshold, then the height of the first target within the corresponding defined range is recorded as the boundary layer height; if the slope magnitude of the distance correction signal within the defined range is less than the second slope threshold, then the height of the second target within the corresponding defined range is recorded as the boundary layer height.

[0057] In one embodiment, determining the presence of an aerosol layer based on the slope magnitude includes: if the slope magnitude of a distance correction signal within a defined range is less than a third slope threshold, then an aerosol layer is present; if the slope magnitude of a distance correction signal within a defined range is less than the third slope threshold, then an aerosol layer is absent.

[0058] S400, determine the search altitude range when there are no clouds, and adjust the upper limit of the altitude range according to the magnitude of the distance correction signal within the altitude range;

[0059] In the absence of clouds, the height of the first or second target within the corresponding defined range is recorded as the boundary layer height based on the height corresponding to the minimum slope of the distance correction signal within the defined range.

[0060] In one embodiment, the height of the first target or the second target within the corresponding defined range is recorded as the boundary layer height based on the height corresponding to the minimum slope of the distance correction signal within the corresponding defined range. This includes: if there is a height within the defined range corresponding to the minimum slope of the distance correction signal that is less than a first height threshold, then the height of the first target within the corresponding defined range is recorded as the boundary layer height; if there is no height within the defined range corresponding to the minimum slope of the distance correction signal that is less than the first height threshold, then the height of the second target within the corresponding defined range is recorded as the boundary layer height.

[0061] After identifying clouds using zero-crossing points and thresholds, two cases are handled: one is complex stratification with clouds, and the other is clear weather with no clouds. In this application, we take a first slope threshold of -4, a second slope threshold of -2, and a third slope threshold of -6 as examples; and a first altitude threshold of 0.5km as an example for illustration.

[0062] Specifically, for clouds, it's necessary to determine the coupling between the cloud and the boundary layer, i.e., whether the cloud is inside or outside the boundary layer. First, the search altitude range is set from 0.2km to the lowest cloud base. Next, check if the distance correction signal within this range is less than 0. If so, set the upper limit altitude to the altitude at which the distance correction signal changes from positive to negative; otherwise, maintain the original upper limit altitude to avoid interference from invalid signals.

[0063] After the initial adjustment to the upper limit altitude, if a slope < -4 exists within the defined range, it indicates that the cloud is outside the boundary layer. In the above case, if a slope < -6 still exists (…), then… Figure 3 The red asterisks indicate the boundary layer height identified by the algorithm. The upper limit height is then adjusted back to the height of the minimum slope, i.e., the height of the bottom of the suspended aerosol layer, eliminating interference from the suspended aerosol layer. Finally, within the new limit, the height of the point closest to the minimum slope among the minimum points with a slope less than 0 is taken as the boundary layer height. If there is no slope < -6 (…), then… Figure 4 The red asterisks shown indicate the boundary layer height identified by the algorithm, indicating that there is no complex layer structure inside the boundary layer, and the height where the minimum slope is located is taken as the boundary layer height.

[0064] like Figure 5 As shown, if there is no slope < -4 within the defined range, it indicates that the cloud is within the boundary layer. Next, the system searches for slopes within the defined range. If a slope < -2 exists, the height of the point closest to the minimum slope among the minimum points with slopes less than 0 is taken as the boundary layer height. If no slope < -2 exists, the height of the point with the minimum slope is taken as the boundary layer height.

[0065] For cloudless conditions, first check if the distance correction signal within the specified range is less than 0. If so, change the upper limit height to the distance correction signal from positive to negative. If not, maintain the original upper limit height (this is to avoid interference from invalid signals).

[0066] Next, within the defined range, find the altitude of the minimum slope. If the altitude of the minimum slope is less than 0.5 km, take the altitude of the minimum slope as the boundary layer altitude; otherwise, if the altitude of the minimum slope is less than 0.5 km (e.g., ...), the boundary layer altitude is determined. Figure 6 As shown in the figure, the height of the point closest to the minimum slope among the minimum points with a slope less than 0 is taken as the boundary layer height.

[0067] After processing several profiles for a day, the boundary layer heights of the cloudy areas are grouped together, and interpolation is performed on the jump points with large differences to correct outliers; the same process is applied to the cloudless areas to finally obtain the true boundary layer height.

[0068] like Figure 7 As shown, actual received lidar data was processed, and a distance-corrected spatiotemporal distribution pseudo-color map clearly shows that the weather on that day was quite complex, with complex stratification including clouds, residual layers, and suspended aerosol layers; in the figure, the red dashed line represents the upper limit altitude, and the black dashed line represents the boundary layer altitude. Figure 7In the image above, without the dynamic height threshold algorithm, it's clear that the traditional algorithm incorrectly identified some cloud layers and the top of the residual layer as boundary layer height. In the image below, after using the dynamic height threshold algorithm, the upper limit height threshold is adjusted in real time for different situations, effectively eliminating the influence of complex stratifications such as clouds, suspended aerosol layers, and residual layers. Furthermore, after applying the dynamic height threshold algorithm to lidar data, the growth process of the convective boundary layer is clearly shown.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A boundary layer height inversion method based on a dynamic height threshold, characterized in that, include: Acquire and preprocess the lidar signal to generate a lidar distance correction signal; Cloud height is identified based on the zero-crossing point of the distance correction signal using the slope method; where cloud height includes the height of the cloud base, cloud peak, and cloud top. Determine the altitude range for searching when there are clouds, and adjust the upper limit of the altitude range according to the magnitude of the distance correction signal within the altitude range to generate the limited range for searching when there are clouds; wherein, the upper limit altitude is initially the lowest cloud base altitude; In the presence of clouds, the slope of the distance correction signal within the corresponding defined range is used to determine whether the cloud layer is within the boundary layer. If the cloud layer is within the boundary layer, the height of the first or second target within the corresponding defined range is recorded as the boundary layer height based on the slope. If the cloud layer is not within the boundary layer, the presence of an aerosol layer is determined based on the slope. If it is not present, the height of the second target within the corresponding defined range is recorded as the boundary layer height. If it is present, the upper limit of the defined range is adjusted to the height of the bottom of the aerosol layer, and the height of the first target within the adjusted defined range is recorded as the boundary layer height. The first target height is the height of the point closest to the minimum slope among the minimum points with a slope less than 0 within the corresponding defined range; the second target height is the height of the point with the minimum slope within the corresponding defined range.

2. The method according to claim 1, characterized in that, Cloud height identification based on the zero-crossing point of the distance correction signal using the slope method includes: Calculate the slope of the sampling points adjacent to the zero point. If the slope changes from negative to positive, the zero point position is identified and recorded as a suspected cloud base or suspected cloud top; if the slope changes from positive to negative, the zero point position is identified and recorded as a suspected cloud peak. Starting from the set cloud search starting point, when a suspicious cloud base and a suspicious cloud peak meet the set first condition, the suspicious cloud base or cloud peak is identified as a cloud base, and the corresponding suspicious cloud peak is identified as the cloud peak corresponding to the cloud base; when the location of a suspicious cloud peak meets the set second condition, the location of the suspicious cloud peak is identified as a cloud peak; the process of identifying cloud bases, cloud peaks and cloud bases is repeated until all cloud layers are found; The first set condition includes that the current suspicious cloud peak signal has no upward trend and the current suspicious cloud peak signal value is greater than the first threshold, and the current suspicious cloud bottom signal value is less than the second threshold; the second set condition includes that the current suspicious cloud top signal has no downward trend and the current suspicious cloud top signal value is less than the second threshold.

3. The method according to claim 2, characterized in that, If the first suspicious cloud peak is lower than the first suspicious cloud base, the first suspicious cloud peak is removed.

4. The method according to claim 2, characterized in that, If the highest cloud peak is not a zero-crossing point, search for the inflection point above the cloud peak of the highest cloud layer, and take the nearest inflection point whose signal value meets the second set condition as the highest cloud peak.

5. The method according to claim 1, characterized in that, Adjust the upper limit of the height range based on the magnitude of the distance correction signal within the height range, including: Determine if there is a distance correction signal less than 0 within the height range; if so, adjust the upper limit height to the height at which the distance correction signal changes from positive to negative within the height range; if not, keep the upper limit height unchanged.

6. The method according to claim 1, characterized in that, Determining whether a cloud layer is within the boundary layer based on the slope of the distance correction signal within the corresponding defined range includes: if the slope of the distance correction signal within the corresponding defined range is less than a first slope threshold, then the cloud layer is outside the boundary layer; if the slope of the distance correction signal within the corresponding defined range is less than the first slope threshold, then the cloud layer is inside the boundary layer.

7. The method according to claim 1, characterized in that, Based on the slope, the height of the first or second target within the defined range is recorded as the boundary layer height, including: If the slope of a distance correction signal within the defined range is less than the second slope threshold, the height of the first target within the defined range is recorded as the boundary layer height; if the slope of a distance correction signal within the defined range is less than the second slope threshold, the height of the second target within the defined range is recorded as the boundary layer height.

8. The method according to claim 1, characterized in that, The presence of an aerosol layer is determined based on the slope magnitude, including: if the slope magnitude of the distance correction signal within the defined range is less than the third slope threshold, then an aerosol layer is present; if the slope magnitude of the distance correction signal within the defined range is less than the third slope threshold, then an aerosol layer is absent.

9. The method according to claim 1, characterized in that, The method also includes: Determine the search altitude range when there are no clouds, and adjust the upper limit of the altitude range based on the magnitude of the distance correction signal within the altitude range; In the absence of clouds, the height of the first or second target within the corresponding defined range is recorded as the boundary layer height based on the height corresponding to the minimum slope of the distance correction signal within the defined range.

10. The method according to claim 9, characterized in that, The height of the first or second target within the corresponding defined range is recorded as the boundary layer height based on the height corresponding to the minimum slope of the distance correction signal within the defined range, including: If the height corresponding to the minimum slope of the distance correction signal within the defined range is less than the first height threshold, then the height of the first target within the defined range is recorded as the boundary layer height; if the height corresponding to the minimum slope of the distance correction signal within the defined range is not less than the first height threshold, then the height of the second target within the defined range is recorded as the boundary layer height.

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