Improved atmospheric waveguide correction refractive index profile fusion processing method

Abstract

The application discloses an improved atmospheric waveguide modified refractive index profile fusion processing method and belongs to the technical field of atmospheric waveguide monitoring. The method comprises the following steps: obtaining a sea-surface waveguide model; obtaining a second modified refractive index profile based on the sea-surface waveguide model; obtaining a first modified refractive index profile based on meteorological data of a FY-4 satellite; and fusing the first modified refractive index profile and the second modified refractive index profile through a filter based on a cosine function to obtain a fused profile. The second modified refractive index profile based on the sea-surface waveguide model and the first modified refractive index profile based on the meteorological data are fused to improve the accuracy of the fused profile and improve the atmospheric waveguide monitoring capability based on the meteorological data.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of atmospheric waveguide monitoring, and particularly relates to an improved atmospheric waveguide corrected refractive index profile fusion processing method. BACKGROUND

[0002] Effective monitoring of atmospheric waveguide requires accurate understanding of the structural characteristics of sea-attached waveguide and non-sea-attached waveguide, and the use of Fengyun-4 satellite can effectively monitor non-sea-attached waveguide data to a certain extent, but there are certain difficulties in monitoring sea-attached waveguide. Although the data calculated by the sea-attached waveguide model can make up for the deficiency of the Fengyun-4 satellite in monitoring sea-attached waveguide, the atmospheric corrected refractive index results given by the two are discontinuous, which is inconsistent with the continuous and gradual change characteristics of the actual atmospheric corrected refractive index. In order to fuse the atmospheric corrected refractive index profile calculated by the Fengyun-4 satellite data and the atmospheric corrected refractive index profile calculated by the sea-attached waveguide model, the present application proposes a new fusion algorithm, and verifies different filters of the fusion method. The test results show that the atmospheric corrected refractive index after fusion by the new fusion algorithm is consistent with the actual atmospheric corrected refractive index, which shows that the proposed fusion algorithm can effectively improve the ability of monitoring multiple types of atmospheric waveguide by using the Fengyun-4 satellite. SUMMARY

[0003] In view of the above technical problems existing in the prior art, the present application provides an improved atmospheric waveguide corrected refractive index profile fusion processing method, which fuses the atmospheric corrected refractive index profile calculated by the Fengyun-4 satellite data and the atmospheric corrected refractive index profile calculated by the sea-attached waveguide model, realizes atmospheric waveguide monitoring in a large sea area, and improves the ability of monitoring multiple types of atmospheric waveguide by using the Fengyun-4 satellite.

[0004] The present application discloses an improved atmospheric waveguide corrected refractive index profile fusion processing method, which comprises the following steps: obtaining a sea-attached waveguide model; obtaining a second corrected refractive index profile based on the sea-attached waveguide model; obtaining a first corrected refractive index profile based on meteorological data of the Fengyun-4 satellite; and fusing the first corrected refractive index profile and the second corrected refractive index profile by a filter based on a cosine function to obtain a fused profile.

[0005] Preferably, the fused profile is represented as:

[0006] M Blend (z)=α(z)M Low (z)+(1-α(z))M Upp (z)(z BL ≤z≤z2) (3)

[0007] wherein M Blend(z) is a second modified refractive index profile, M l o w (z) is a second modified refractive index profile, M Upp (z) is a first modified refractive index profile, z is represented as height, a(z) is represented as a filter based on cosine function, z2 is represented as the highest height of the fusion interval, Z BL is the lowest height of the fusion interval.

[0008] Preferably, the filter comprises a formula selected from the following:

[0009] a(z) = cos(aπz) (31)

[0010] a(z) = (cos(aπz) + 1) / 2 (32)

[0011]

[0012] wherein a is represented as a coefficient.

[0013] Preferably, a is selected from the following values: 1 / 50, 1 / 150, 1 / 250, 1 / 350, 1 / 450, 1 / 550 and 1 / 650.

[0014] Preferably, based on the sea surface waveguide model, a second modified refractive index of the sea surface waveguide is obtained; and according to the second modified refractive index, a second modified refractive index profile is obtained.

[0015] The calculation formula of the second modified refractive index is:

[0016]

[0017] wherein z0 is a sea surface roughness length, R ib is a total body Richardson number, z d is represented as a sea surface waveguide height, L is represented as a Monin-Obukhov length, Ms is represented as an atmospheric modified refractive index at the waveguide height, M(z) is represented as a second modified refractive index at z height;

[0018] function Solved by Newton iteration method through the following equation:

[0019]

[0020] Preferably, when 0≤R ib ≤1

[0021]

[0022] when R ib < 0

[0023]

[0024] In the formula, ΔN p is the difference between the atmospheric refractive index of the sea surface and the atmospheric refractive index at the edge of the sea and the atmosphere, A = -0.125B / ΔN p ; B = ln(z / z0)-Ψ, and the calculation formula of Ψ is:

[0025]

[0026] Preferably, the method for obtaining the first corrected refractive index profile comprises:

[0027] Obtaining meteorological data of the Fengyun-4 satellite, wherein the meteorological data comprises water vapor pressure, air pressure and temperature;

[0028] Preprocessing the meteorological data to obtain a data set;

[0029] According to the data set, a first corrected refractive index is obtained;

[0030] According to the first corrected refractive index, a first corrected refractive index profile is obtained.

[0031] Preferably, the calculation method of the atmospheric refractive index comprises:

[0032] M UPP (z) = N + 0.157z

[0033]

[0034]

[0035] wherein N represents the atmospheric refractive index, T is the atmospheric temperature, P represents the atmospheric pressure, e is the water vapor pressure, q represents the specific humidity, and D and E are constants.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] The second corrected refractive index profile based on the sea surface waveguide model and the first corrected refractive index profile based on the meteorological data are fused to improve the accuracy / effectiveness of the fused profile and improve the atmospheric waveguide monitoring capability based on meteorological data. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a flowchart of the atmospheric waveguide corrected refractive index profile fusion processing method of the present application;

[0039] Figure 2 is a simulation diagram of the corrected refractive index based on formula 41;

[0040] Figure 3is a modified refractive index simulation graph based on formula 42;

[0041] Figure 4 is a modified refractive index simulation graph based on formula 43;

[0042] Figure 5 is a profile contrast graph of the northern sea area;

[0043] Figure 6 is a profile contrast graph of the eastern sea area;

[0044] Figure 7 is a profile contrast graph of the southern sea area;

[0045] Figure 8 is a system logic block diagram of embodiment 2. DETAILED DESCRIPTION

[0046] To make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0047] The present application will be described in further detail below with reference to the drawings:

[0048] An improved atmospheric waveguide modified refractive index profile fusion processing method, as shown in Figure 1 The method comprises the following steps:

[0049] Step S1: Obtain a sea-surface waveguide model. For example, a PJ model, a MGB model, an A model, etc., but not limited thereto. The height of the sea-surface waveguide is generally below 40 meters.

[0050] Step S2: Obtain a second modified refractive index profile based on the sea-surface waveguide model.

[0051] Step S3: Obtain a first modified refractive index profile based on meteorological data of the FY-4 satellite.

[0052] Step S4: Fuse the first modified refractive index profile and the second modified refractive index profile through a filter based on a cosine function to obtain a fused profile.

[0053] The meteorological data of the FY-4 satellite has weak sea-surface waveguide monitoring capability. The second modified refractive index profile based on the sea-surface waveguide model and the first modified refractive index profile based on the meteorological data are fused to improve the accuracy of the fused profile and improve the atmospheric waveguide monitoring capability based on the meteorological data.

[0054] In step S3, the method for obtaining the first corrected refractive index profile includes:

[0055] Step 101: Obtain meteorological data from the Fengyun-4 satellite, including water vapor pressure, air pressure, and temperature.

[0056] Step 102: Preprocess the meteorological data to obtain a dataset. For example, remove outlier data.

[0057] Step 103: Obtain the first corrected atmospheric refractive index based on the dataset.

[0058] The atmospheric refractive index can be calculated using the following method:

[0059]

[0060]

[0061] Where N represents the atmospheric refractive index, T represents the atmospheric temperature, P represents the atmospheric pressure, e represents the water vapor pressure, q represents the specific humidity, ε represents the relative permittivity of the atmosphere, and D and E are constants that can be determined experimentally. In one specific embodiment, D = 77.6 K·hPa -1 E = 4810 K, ε = 0.622; given the air pressure P, temperature T, and specific humidity q, the atmospheric refractive index N can be calculated. Since the air pressure P, temperature T, and specific humidity q of N are related to the altitude z, the atmospheric refractive index can be written as N(z).

[0062] Formula 1 can also be written as: The atmospheric refractive index affected by the Earth's curvature is defined as the corrected atmospheric refractive index M (dimensionless, M units). The expression for the corrected atmospheric refractive index is:

[0063] M(z)=N+0.157z (12)

[0064] Where M(z) represents the corrected atmospheric refractive index.

[0065] Formula 12 can also be written as: M UPP (z) = N + 0.157z, where M Upp (z) represents the first corrected refractive index.

[0066] Step 104: Based on the first corrected refractive index, obtain the first corrected refractive index profile and the data / parameters of the atmospheric waveguide.

[0067] The atmospheric refractive index and the first modified refractive index profile are obtained through the meteorological data of the Fengyun-4 satellite; the atmospheric waveguide is generated due to the atmospheric refraction effect, and therefore the parameters of the atmospheric waveguide can be obtained according to the atmospheric refractive index and the first modified refractive index profile, so as to realize effective monitoring of the atmospheric waveguide in a large sea area.

[0068] Embodiment 1

[0069] Step 301: Obtain meteorological data of the Fengyun-4 satellite through the Fengyun remote sensing satellite data service network. Specifically, obtain regional atmospheric profile products from the GIIRS channel matching data set, and select atmospheric temperature and humidity profile products, which include pressure, temperature and humidity information of 101 layers from 0 hPa to 1100 hPa.

[0070] Obtain sounding data, including temperature, dew point temperature, potential height, wind speed and wind direction and other meteorological elements in the near-space layer to the high layer, for evaluating the reliability of atmospheric waveguide monitoring based on meteorological data.

[0071] Step 302: Select a satellite sampling point near the sounding point of the sounding data, and obtain meteorological data of the satellite sampling point; match the sounding data and the meteorological data in space and time, so as to facilitate the verification of atmospheric waveguide monitoring data based on meteorological data through the sounding data. The selected satellite sampling point and the sounding point are matched in longitude and latitude in the horizontal direction; in the vertical direction, they are matched through similar pressure layers. If there is no corresponding satellite data for the sounding data, the data of the pressure layer is discarded.

[0072] Step 303: Preprocessing, removing abnormal data, obtaining a data set.

[0073] After removing the abnormal data, the mean value of the temperature deviation of each pressure layer is reduced, the root mean square error is significantly reduced, and the mean value of the humidity deviation of each pressure layer is significantly reduced.

[0074] In the specific data analysis, the first data set is grouped and analyzed according to 700 hPa-800 hPa, 800 hPa-900 hPa, 900 hPa-1000 hPa and 1000 hPa-1100 hPa four pressure layers; and the satellite data is divided into northern sea area, eastern sea area and southern sea area. For example, the atmospheric refractive index is calculated according to formula 1. The pressure range is used to describe the height range.

[0075] Step 304: Obtain the second modified refractive index profile based on the sea-surface waveguide model. The bottom layer sea-surface waveguide model can adopt the PJ model, but is not limited thereto. The sea-surface waveguide is close to the sea surface and can occur almost all the time, with a height generally within 40 meters.

[0076] The second modified refractive index can be calculated by the following formula:

[0077]

[0078] wherein z0 is the sea surface roughness length, generally taking the value of 0.00015m, R ib is the total Richardson number, when 0≤R ib ≤1, it is stable state; when R i b<0, it is unstable state; zd represents the height of the waveguide close to the sea surface, L represents the Monin-Obukhov length, Ms represents the atmospheric modified refractive index at the waveguide height, and M(z) represents the second modified refractive index at the height of z.

[0079] wherein the function can be solved by Newton iteration method by the following equation:

[0080]

[0081] when 0≤R ib ≤1

[0082]

[0083] when R ib <0

[0084]

[0085] in the formula, ΔN p is the difference between the atmospheric refractive index of the sea surface and the atmospheric refractive index at the edge of the sea and the atmosphere, A=-0.125B / ΔN p ; B=ln(z / z0)-Ψ, and the calculation formula of Ψ is as follows:

[0086]

[0087] If the height of the waveguide close to the sea surface is greater than 0 or greater than the Monin-Obukhov length, the height of the waveguide close to the sea surface needs to be corrected, and the correction formula is:

[0088]

[0089] wherein the total Richardson number is represented as:

[0090]

[0091] T a is the air temperature around the sea surface (unit: K), T b is the sea surface temperature (unit: K), and U is the wind speed of the sea surface (unit: m / s).

[0092] Step 305: obtaining a first modified refractivity profile based on meteorological data of Fengyun-4 satellite.

[0093] Step 306: fusing the first modified refractivity profile and a second modified refractivity profile to obtain a fused profile by a filter based on a cosine function.

[0094] The fused profile is expressed as:

[0095] M Blend (z) = a(z)M Low (z) + (1 - a(z))M Upp (z) (z BL ≤ z ≤ z2) (3)

[0096] wherein M Blend (z) is expressed as the fused profile, M l o w (z) is expressed as the second modified refractivity profile, M Upp (z) is the first modified refractivity profile, z is expressed as height, a(z) is expressed as the filter based on the cosine function, z2 is expressed as the highest height of the fusion interval, and z BL is expressed as the lowest height of the fusion interval.

[0097] wherein the filter is selected from the following formulas:

[0098] a(z) = cos(aπz) (31)

[0099] a(z) = (cos(aπz) + 1) / 2 (32)

[0100]

[0101] wherein a is expressed as a coefficient. In one simulation test, it is selected from the following values: 1 / 50, 1 / 150, 1 / 250, 1 / 350, 1 / 450, 1 / 550 and 1 / 650.

[0102] Figures 2-4 is a simulation diagram of the fused modified refractivity, wherein z1 and z2 are the lowest height and the highest height of the modified refractivity profile obtained by meteorological data, z ed is expressed as the waveguide height close to the sea surface, and the dashed line shows the fused profile with different a values, and z p is expressed as the upper limit of the modified refractivity profile. Figure 3 wherein z ed < z1, z p < z2, the waveguide height Z ed obtained by the modified refractivity profile calculated by the PJ model is greater than z1, so as to avoid changing the waveguide height after fusion, in this case, the fusion interval should be from Zed Start at z1 and end at z2. Figure 4 Z ed Start at z1 and end at z2. p Z ed Start at z1 and end at z2. BL Z ed Z BL Z ed Z Figures 2-4 The dashed line in Z

[0103] The three filters have different characteristics. The filter cos(απz) is close to the sea-surface waveguide model from the start of fusion, and the calculated modified refractive index profile is obviously not in compliance with the required value of α. There are two values of α, and the fusion curve is obviously close to the curve of z2. The value of α is 1 / 450. The filter (cos(απz)+1) / 2 is close to the modified refractive index profile from the start of fusion. There are three values of α that are obviously not in compliance with the required value, and the fusion curve is obviously close to the curve of z2. The values of α are 1 / 550 and 1 / 650. The filter The three filters can all meet the fusion requirements well, but the speed of α reaching the optimal value during fusion will be different.

[0104] Step 307: Compare the sounding profile of the sounding data with the fusion profile and the first modified refractive index profile.

[0105] Figures 5-7 The profile comparison graphs of the northern sea area, the eastern sea area, and the southern sea area are shown respectively. It can be seen from the graphs that, compared with the first modified refractive index profile before processing, the fusion profile is closer to the sounding profile. The sounding profile is established according to the sounding data.

[0106] 0m-3000m is divided into three regions: the first region is 0m-50m, which is the sea-surface waveguide high-frequency appearance region; the second region is 50m-300m, which is the surface waveguide high-frequency appearance region; and the third region is 300m-3000m, which is the suspended waveguide high-frequency appearance region. Statistical analysis is performed on the data after fusion processing and the data before processing, and the results are shown in Table 2.

[0107] Table 2

[0108]

[0109] The average error and root mean square error of the processed FY-4 satellite data in the three intervals are significantly reduced, and the correlation coefficient is significantly increased, which shows that the processed satellite data is closer to the actual sounding station data. From the data, the monitoring accuracy of the FY-4 satellite for the suspended waveguide at 300m-3000m is better than that of the other two intervals, and the monitoring accuracy of the FY-4 satellite for the sea-surface waveguide at 0m-50m is weaker than that of the other two intervals. Considering that the root mean square errors of the three intervals are not large (less than 6.5N), it is considered that the meteorological data of the FY-4 satellite can effectively monitor the atmospheric waveguide. The root mean square error of the first modified refractive index profile before processing is 7.82N, which is slightly larger than the accuracy of the sounding instrument.

[0110] Embodiment 2

[0111] The embodiment provides a system for implementing the above-mentioned atmospheric waveguide monitoring method, as shown in the figure, comprising a sea-surface waveguide module 6, an atmospheric waveguide analysis module 3 and a fusion module 7, Figure 8 The sea-surface waveguide module 6 is used to obtain a sea-surface waveguide model; and based on the sea-surface waveguide model, a second modified refractive index profile is obtained.

[0112] The atmospheric waveguide analysis module 3 is used for the meteorological data of the FY-4 satellite to obtain a first modified refractive index profile.

[0113] The atmospheric waveguide analysis module 3 is used for the meteorological data of the FY-4 satellite to obtain a first modified refractive index profile.

[0114] The fusion module 7 is used to fuse the first modified refractive index profile and the second modified refractive index profile by a filter based on a cosine function to obtain a fusion profile.

[0115] The system further comprises a collection module 1 and a preprocessing module 2,

[0116] The collection module 1 is used to collect meteorological data based on the FY-4 satellite.

[0117] The preprocessing module 2 is used to preprocess the meteorological data.

[0118] The atmospheric waveguide analysis module 3 is used to obtain a first modified refractive index profile based on the preprocessed meteorological data.

[0119] The above is only a preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An improved atmospheric waveguide correction refractive index profile blending method, characterized by, The method comprises: obtaining a sea surface waveguide model; obtaining a second modified refractive index profile based on the sea surface waveguide model; obtaining a first modified refractive index profile based on meteorological data of the Fengyun-4 satellite; fusing the first modified refractive index profile and the second modified refractive index profile through a filter based on a cosine function to obtain a fused profile; The fused profile is represented as: （3） where M Blend (z) is a first modified refractive index profile, z is represented as height, a(z) is represented as a filter based on a cosine function, z2 is represented as a highest height of a fusion interval, and z low is represented as a second modified refractive index profile, M Upp (z) is a first modified refractive index profile, z is represented as height, a(z) is represented as a filter based on a cosine function, z2 is represented as a highest height of a fusion interval, and z BL is represented as a second modified refractive index profile, M The calculation formula of the second modified refractive index is: where z0is the sea surface roughness length, R ib is the total Richardson number, is the height of the waveguide to the sea surface, L is the Monin-Obukhov length, Msis the refractive index of the atmosphere at the height of the waveguide, and M(z) is the second refractive index at the height of z. Function Solve by Newton iteration method using the following equation: ； When time When Time where ΔN p is the difference between the atmospheric refractive index at the sea surface and the atmospheric refractive index at the sea and air interface, ; , is calculated as: ； The calculation method of the first modified refractive index comprises: wherein, where N is expressed as the atmospheric refractive index, T is the atmospheric temperature, P is expressed as the atmospheric pressure, e is the water vapor pressure, q is expressed as the specific humidity, and D and E are constants.

2. The atmospheric waveguide refractive index profile fusion processing method of claim 1, wherein The filter is selected from the following formula: （31） （32） （33） Wherein, α represents a coefficient.

3. The atmospheric waveguide refractive index profile fusion processing method of claim 2, wherein, α is selected from the following values: 1 / 50, 1 / 150, 1 / 250, 1 / 350, 1 / 450, 1 / 550 and 1 / 650.

4. The atmospheric waveguide refractive index profile tailoring process method of claim 1, wherein, The method for obtaining the first modified refractive index profile comprises: Obtaining meteorological data of the Fengyun-4 satellite, the meteorological data including water vapor pressure, air pressure and temperature; Pretreating the meteorological data to obtain a data set; According to the data set, a first modified refractive index and a first modified refractive index profile are obtained.

Images