CN108663727B - A method for estimating the height of the evaporative duct in the world sea area using the evaporation rate - Google Patents

Abstract

The invention relates to a method for estimating the height of an evaporation waveguide in the world sea area by utilizing the evaporation rate, compared with the prior method for directly measuring or indirectly estimating the atmospheric refractive index profile to obtain the height of the evaporation waveguide, the method does not need to measure or estimate the whole atmospheric refractive index profile and then obtain the height of the evaporation waveguide, but directly obtains the estimated value of the height of the evaporation waveguide by measuring a single evaporation rate parameter. By utilizing the method provided by the invention, a quantitative relation database of the evaporation waveguide height and the evaporation rate in the world sea area can be pre-established, and the quantitative relation database is embedded into the existing evaporation waveguide environment historical database, is used for the implementation evaluation of the current evaporation waveguide environment by marine ship formation in different sea areas, and is used for the assistant decision of systems such as communication, radar, guidance, electronic countermeasure and the like.

Description

A method for estimating the height of the evaporative duct in the world sea area using the evaporation rate

technical field

The invention belongs to the technical fields of marine environment monitoring and the like, relates to a method for estimating the height of an evaporation waveguide, and in particular relates to a method for estimating the height of an evaporation waveguide in the world sea area by using an evaporation rate.

Background technique

Evaporative duct is a natural channel formed by the exponential decay of atmospheric humidity with height due to seawater evaporation. Evaporation on the sea surface exists all the time, so evaporative duct is an inherent phenomenon in the offshore atmospheric environment. According to statistics, the sea area around my country is a high incidence area of evaporative ducts, with an occurrence probability of about 85%. The evaporative waveguide has a unique atmospheric refractive index structure, which causes the propagation trajectory of the microwave signal in the waveguide to produce obvious anomalies relative to the standard atmospheric environment. The height of the evaporative waveguide refers to the height difference between the point corresponding to the minimum value of the modified refractive index and the sea surface on the waveguide section. The height of the evaporative waveguide is an important parameter used to describe the ability of the evaporative waveguide to trap microwave signals. The communication system works within the height of the evaporative duct or above the height of the evaporative duct, and the performance is quite different. Therefore, it is necessary to obtain the height of the evaporative duct around the ship in time, which is an important condition to ensure the performance of the ship's radar, communication, navigation, electronic countermeasures and other radio systems.

At present, the main method to obtain the height of the evaporation waveguide is to first obtain the atmospheric refractive index profile of the evaporation waveguide, and then use the position of the minimum value of the corrected refractive index to determine the waveguide height. According to the different acquisition methods of the atmospheric refractive index profile, it can be divided into direct measurement and indirect estimation , indirect estimation can be divided into three categories: model prediction, numerical prediction and inversion prediction. Direct measurement is to directly measure the atmospheric refractive index profile with a microwave refractometer. The height corresponding to the minimum value of the refractive index profile is the height of the evaporation waveguide. However, the microwave refractometer is expensive and can only obtain single-point data information at the measurement point. Moreover, it is greatly affected by the wind direction, the measurement error is large, and it is difficult to install on the ship. Model prediction is to use meteorological sensors to measure meteorological parameters such as air temperature, relative humidity, atmospheric pressure, wind speed, seawater surface temperature, etc., and to calculate the atmospheric refractive index profile data in combination with the prediction model of the evaporative duct, so as to obtain the height of the evaporative duct. The disadvantage is that five meteorological parameters need to be measured, and the measurement is greatly affected by the hull, the estimation error is large, and only single-point data information of the measurement point can be obtained. The numerical prediction method is to use the meteorological forecast numerical model to first forecast the meteorological parameters such as air temperature, relative humidity, atmospheric pressure, wind speed, seawater surface temperature in a certain area, and then combine the evaporative duct prediction model to calculate the atmospheric refractive index data and evaporative duct height. . The advantage of the numerical prediction method is that it can give the predicted value of the refractive index distribution for a large area of sea area and several hours or dozens of hours in the future, which is suitable for qualitative analysis. The disadvantage is that the accuracy of the forecast depends on the accuracy of the weather forecast, and there is still a relatively large forecast error. The inversion prediction is to use the collected electromagnetic wave signals to invert the atmospheric refractive index profile in the evaporation waveguide and determine the height of the evaporation waveguide.

From the above four methods, it can be seen that the actual measurement operation is difficult in the current method of obtaining the height of the evaporation waveguide, and the indirect method generally involves a large amount of calculation, which cannot meet the real-time rapid estimation.

Therefore, it has become an urgent and important problem to seek other methods to quickly obtain the height of the evaporative waveguide in real time to provide auxiliary decision-making for the correct operation of the ship's radar communication system.

SUMMARY OF THE INVENTION

technical problem to be solved

In order to avoid the shortcomings of the prior art, the present invention proposes a method for estimating the height of the evaporation waveguide in the world sea area by using the evaporation rate, so as to solve the problem of further estimating the height of the evaporation waveguide on the offshore surface based on directly or indirectly obtaining the refractive index profile. with deficiencies.

Technical solutions

A method for estimating the height of an evaporation waveguide in the world sea area by using the evaporation rate, characterized in that the steps are as follows:

Step 1: Establish a three-parameter statistical regression model of evaporation rate and evaporation waveguide height EDH=αEVP ^β e ^ε , where EVP and EDH represent the evaporation rate and evaporation waveguide height data, respectively, e ^ε is a random factor, ε means 0 and variance is σ ² . α, β and σ are the unknown coefficients to be fitted;

Step 2: Obtain the atmospheric temperature at a height of 2 meters above the sea surface, wind speed at a height of 10 meters above the sea surface, atmospheric pressure at the sea surface, Relative humidity, sea surface temperature, atmospheric and marine environment data; use the evaporative duct model based on the air-sea flux 3.0 algorithm to calculate the height of the evaporative duct, and obtain the historical data set of the evaporative duct height within the corresponding time span and plane coverage;

Obtain the latent heat flux and sea surface temperature atmospheric ocean environment data of a certain time span and plane coverage from the "NCEP _CFSR Reanalysis Database", and use the formula EVP=LHF/ρ _w Le to calculate the evaporation rate, where EVP represents the evaporation rate , LHF represents the latent heat flux, ρ _w is the density of seawater, which is _1027kg m ^-3 , Le represents the latent heat of evaporation, which can be calculated by using the formula Le = [[ _2.501- (0.00237×SST)]]×10 ⁶ , SST represents the sea surface temperature, and obtains the historical data set of evaporation rate within the corresponding time span and plane coverage;

Step 3: Take the natural logarithm on both sides of the three-parameter statistical regression model established in step 1 to linearize it, and obtain the linearized model ln(EDH)=ln(α)+βln(EVP)+ε, which is obtained in step 2. The evaporation waveguide height and evaporation rate data are substituted into the linearization model, and the coefficients α and β are obtained by fitting the least squares method, and then the obtained α and β are substituted into the linearization model to calculate the residual ε, and σ is the standard of the residual ε. After each parameter is solved, the range of the height of the evaporation waveguide is obtained according to the real-time evaporation rate data.

Change the latitude and longitude, repeat steps 2 to 3, establish the parameter database of α, β and σ under different latitude and longitude, and obtain the latitude and longitude-three-parameter model database, that is, the quantitative relationship database between the height of the evaporation duct and the evaporation rate in different sea areas.

In the step 3, the data collection time range for solving the statistical regression model of the evaporation rate and the height of the evaporation waveguide is not less than 1 year.

beneficial effect

A method for estimating the height of the evaporation waveguide in the world sea area by using the evaporation rate proposed by the present invention. Since the evaporation waveguide itself is generated by the evaporation of seawater, the height of the evaporation waveguide is greatly affected by evaporation, so the evaporation rate and the height of the evaporation waveguide are greatly affected. There is a great correlation in the nature of physics. Compared with the existing methods of directly measuring or indirectly estimating the atmospheric refractive index profile to obtain the height of the evaporation waveguide, the present invention does not need to measure or estimate the entire atmospheric refractive index profile first and then obtain the height of the evaporation waveguide, but by measuring a single evaporation rate parameter, Directly obtain an estimate of the height of the evaporative waveguide. Using the method proposed in the present invention, a quantitative relationship database between the height of the evaporation waveguide and the evaporation rate in the world sea area can be established in advance, embedded in the existing historical database of the evaporation waveguide environment, and used for the current evaporation waveguide environment in different sea areas of the marine fleet. Carry out evaluation and use it to assist decision-making in communication, radar, guidance, electronic countermeasures and other systems.

Description of drawings

Figure 1: Flow chart for calculating the height of the evaporative waveguide using the evaporative waveguide model.

Figure 2: Flow chart for calculating evaporation rate.

Figure 3: Flow chart for building a three-parameter regression statistical model.

Figure 4: Comparison of the results of estimating the height of the evaporative waveguide with the true value using the three-parameter model.

Detailed ways

The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

The technical scheme proposed by the present invention comprises the following steps:

Step 1: Establish a three-parameter statistical regression model of evaporation rate and evaporation waveguide height EDH=αEVP ^β e ^ε , where EVP and EDH represent the evaporation rate and evaporation waveguide height data respectively, e ^ε is a random factor, ε means 0 and variance is σ ² . α, β and σ are the unknown coefficients to be fitted.

Step 2: From the "NCEP CFSR (National Centers for Environmental Prediction Climate Forecast System Reanalysis) reanalysis database", obtain the atmospheric temperature at a height of 2 meters above the sea surface, wind speed at a height of 10 meters above the sea surface, Atmospheric pressure, relative humidity at a height of 2 meters above the sea surface, and sea surface temperature atmospheric and marine environment data, the evaporative duct height is calculated using the evaporative duct model based on the air-sea flux 3.0 algorithm, and the evaporative duct height within the corresponding time span and plane coverage is obtained. historical dataset.

Step 3 (parallel to Step 2): Obtain the latent heat flux and sea surface temperature atmospheric and marine environmental data of a certain time span and plane coverage from the "NCEP CFSR Reanalysis Database", and use the formula EVP=LHF/ _{ρwL e} to calculate Evaporation rate, where EVP is the evaporation rate, LHF is the latent heat flux, ρ _w is the seawater density, the value is 1027kg m ^-3 , L _e is the latent heat of evaporation, the formula L _e =[[2.501-(0.00237×SST) ]]×10 ⁶ is calculated, SST represents the sea surface temperature, and the historical data set of evaporation rate in the corresponding time span and plane coverage is obtained.

Step 4: Take the natural logarithm on both sides of the three-parameter statistical regression model established in step 1 to linearize it to obtain a linearized model ln(EDH)=ln(α)+βln(EVP)+ε, and step 2 and 3 The evaporation waveguide height and evaporation rate data obtained in , are substituted into the linearization model, and the coefficients α and β are obtained by fitting the least squares method, and then the obtained α and β are substituted into the linearization model to calculate the residual ε, where σ is the residual ε The standard deviation of , after each parameter is solved, the range of the height of the evaporation waveguide can be obtained according to the real-time evaporation rate data;

The data collection time range for solving the statistical regression model of evaporation rate and evaporation waveguide height is not less than 1 year, and the latitude, longitude and time point of the data are matched at the same time. The data can include historical evaporation rate data, evaporation waveguide height data, and evaporation rate data. It can be directly obtained from various reanalysis databases or calculated by using meteorological parameter data. The height data of evaporation duct can be calculated from measured data or meteorological parameter data combined with the prediction model of evaporation duct.

Step 5: Repeat the method proposed in Step 4 to establish the parameter database of α, β and σ under different longitude and latitude, and obtain the longitude and latitude-three-parameter model database, that is, the quantitative relationship database between the height of the evaporation duct and the evaporation rate in different sea areas .

Step 6: In the actual use process, the measured evaporation rate data can be substituted into the corresponding three-parameter model according to the actual latitude and longitude coordinate position, and the estimated value of the evaporation waveguide height at the current position can be obtained.

Specific examples:

Fig. 1 is a flow chart of calculating the height of the evaporation waveguide using the evaporation waveguide model, and the specific implementation of the method is as follows:

Step 1: Obtain the atmospheric and marine environment data on the offshore surface from the NCEP CFSR reanalysis database, including atmospheric temperature, wind speed, atmospheric pressure, sea surface temperature, relative humidity, etc., and substitute the data into the TOGA COARE 3.0 air-sea flux algorithm to calculate the Monin -Obukhov scale parameters θ _* and q _* .

和

得到温度、湿度和气压随高度变化的剖面，其中T表示温度，q为湿度，z_0θ和z_0q分别为温度和湿度粗糙度高度，k为卡曼常数，Γ_d为干绝热递减率，z为距离海面高度，L为Obukhov长度，R为干空气气体常数，g为重力加速度，T_v为高度z₁和z₂处的虚温的平均值。Step 2: Utilize the formula

and

The profiles of temperature, humidity and air pressure with height are obtained, where T is temperature, q is humidity, z _0θ and z _0q are temperature and humidity roughness height, respectively, k is Karman constant, Γ _d is dry adiabatic lapse rate, z is the height from the sea surface, L is the Obukhov length, R is the dry air gas constant, g is the acceleration of gravity, and T _v is the average value of the virtual temperature at heights z ₁ and z ₂ .

其中T为大气温度,P为气压，e为水汽压，z为距离海面高度，得到修正折射率剖面M(z)，剖面上修正折射率M最小值所对的高度即为蒸发波导高度，得到相应时间跨度和空间范围内的蒸发波导高度历史数据集。Step 3: Substitute the temperature, humidity and air pressure profiles obtained in Step 2 into the modified refractive index calculation formula

where T is the atmospheric temperature, P is the air pressure, e is the water vapor pressure, and z is the height from the sea surface, and the modified refractive index profile M(z) is obtained. Evaporated waveguide height history dataset over the corresponding time span and spatial extent.

Fig. 2 is a schematic diagram of calculating evaporation rate and establishing a historical data set of evaporation rate. The specific implementation of the method is as follows: From the NCEP CFSR reanalysis database, obtain atmospheric latent heat flux and sea surface temperature in a certain time span and spatial range For marine environmental data, the evaporation rate is calculated using the formula EVP=LHF/ρ _w Le, where EVP is the evaporation rate, LHF is the latent heat flux, ρ _w is the seawater density, which is _1027kg m ^-3 , and L _e is the latent heat of evaporation, It can be calculated by using the formula L _e =[2.501-(0.00237×SST)]×10 ⁶ , SST represents the sea surface temperature, and the historical data set of evaporation rate in the corresponding time span and space range can be obtained.

Fig. 3 is a flow chart of establishing a three-parameter regression statistical model, and the specific implementation of the method is as follows: the selected South China Sea area sea area (17°N-19°N, 114°E-116°E) 1979-2000 will be exemplified The evaporation waveguide height data and evaporation rate data in the 22-year time range are substituted into the statistical regression model EDH=αEVP ^β e ^ε and linearized, and α=23.2057 and β=0.4074 are obtained by the least square fitting algorithm, and then return them to Substitute into the linearization model ln(EDH)=ln(α)+βln(EVP)+ε, the standard deviation of residual ε is obtained by statistics σ=0.0884, and finally the three-parameter statistical model corresponding to the selected example sea area can be obtained from α=23.2057 , β=0.4074, σ=0.0884 is uniquely determined.

Figure 4 is the result of verifying the three-parameter statistical model determined by the above method using the evaporation waveguide height data and evaporation rate data in an example sea area from 2001 to 2010. (1) is a scatter plot of evaporation rate and actual evaporation waveguide height data, and (2) is a scatter plot of evaporation rate and predicted evaporation waveguide height data. The solid red line in the figure is obtained by fitting the scatter data in the scatter plot using the linear regression method.

Claims (3)

1. a method for estimating evaporation waveguide height in the world sea area using evaporation rate, is characterized in that the steps are as follows: Step 1: Establish a three-parameter statistical regression model of evaporation rate and evaporation waveguide height EDH=αEVP ^β e ^e , where EVP and EDH represent the evaporation rate and evaporation waveguide height data, respectively, e ^e is a random factor, the mean value of e is 0 and the variance is σ ² , α, β and σ are the unknown coefficients to be fitted; Step 2: Obtain the atmospheric temperature at a height of 2 meters above the sea surface, the wind speed at a height of 10 meters above the sea surface, the atmospheric pressure at the sea surface, and the relative air temperature at a height of 2 meters above the sea surface for a certain time span and plane coverage from the "NCEPCFSR Reanalysis Database". Humidity, sea surface temperature, atmospheric and marine environment data; use the evaporative duct model based on the air-sea flux 3.0 algorithm to calculate the height of the evaporative duct, and obtain the historical data set of the evaporative duct height within the corresponding time span and plane coverage; Obtain the latent heat flux and sea surface temperature atmospheric and marine environment data of a certain time span and plane coverage from the " _NCEPCFSR Reanalysis Database", and use the formula EVP=LHF/ρ _w Le to calculate the evaporation rate, where EVP represents the evaporation rate, LHF is the latent heat flux, _ρw is the density of seawater, the value is 1027kgm ^-3 , L _e is the latent heat of evaporation, which can be calculated by the formula L _e =[2.501-(0.00237×SST)]×10 ⁶ , SST is the sea surface temperature to obtain a historical dataset of evaporation rates within the corresponding time span and plane coverage; Step 3: Take the natural logarithm on both sides of the three-parameter statistical regression model established in step 1 to linearize it, and obtain the linearized model ln(EDH)=ln(α)+βln(EVP)+e, which is obtained in step 2. The evaporation waveguide height and evaporation rate data are substituted into the linearization model, and the coefficients α and β are obtained by least squares fitting, and then the obtained α and β are substituted into the linearization model to calculate the residual error e, and σ is the standard of the residual error e After each parameter is solved, the range of the height of the evaporation waveguide is obtained according to the real-time evaporation rate data. 2. The method according to claim 1 for estimating the height of the evaporation waveguide in the world sea area by utilizing the evaporation rate, characterized in that: changing the latitude and longitude, repeating steps 2 to 3 to establish a parameter database of α, β and σ under different latitude and longitude , and obtain the latitude and longitude-three-parameter model database, that is, the quantitative relationship database between the height of the evaporation duct and the evaporation rate in different sea areas. 3. The method for estimating the height of the evaporation waveguide in the world sea area by using the evaporation rate according to claim 1, wherein the data collection time range for solving the statistical regression model of the evaporation rate and the height of the evaporation waveguide in the step 3 is different. less than 1 year.

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