A joint detection method for inverting marine atmospheric temperature and humidity profiles

Abstract

The invention discloses a method for inverting the temperature and humidity profile of the marine atmosphere through joint detection, which specifically relates to the field of marine detection technology. Firstly, the temperature and liquid water content of clouds on the sea surface are obtained by millimeter-wave cloud radar, and the cloud liquid water absorption coefficient is calculated; the pitch angle and roll angle are obtained by using the attitude sensor on board a ship, the zenith angle of microwave radiometer observation is calculated, and the zenith correction is added; then, the pressure profile is calculated according to the pressure-height formula by using the pressure sensor configured by the microwave radiometer; finally, the differential evolution algorithm is used to further accurately invert the temperature and humidity profile of the marine atmosphere; the invention takes into account the influence of cloud absorption on microwave radiation transmission, uses the rich cloud information obtained by the millimeter-wave cloud radar carried by the ship platform, and adds the cloud liquid water absorption coefficient to the atmospheric microwave radiation transmission equation. Therefore, the inverted temperature and humidity profile of the marine atmosphere is more accurate, which can provide data support for marine meteorological research.

Description

Technical Field

[0001] The present invention relates to the field of marine detection technology, and more specifically, to a method for joint detection and inversion of marine atmospheric temperature and humidity profiles. Background Art

[0002] The atmospheric temperature and humidity profile is a key parameter for space radio wave environment assessment. Real-time, long-term, and automated detection of the atmospheric temperature and humidity profile at sea has important scientific significance and practical application value in many fields, such as marine radio system performance evaluation, radio wave refraction correction, and weather forecasting.

[0003] In clear sky conditions, the atmospheric temperature and humidity profile of the land-based fixed platform microwave radiometer has a high inversion accuracy. However, in cloudy and cloudy conditions, due to the large uncertainty in the distribution of cloud absorption coefficients, clouds have a great impact on the temperature observed by the microwave radiometer. The impact of clouds is usually related to cloud height, cloud temperature, cloud thickness and the path of liquid water in the clouds. The thermal infrared channel configured by the microwave radiometer itself has very limited cloud measurement capabilities and cannot obtain information related to microwave radiation intensity such as cloud thickness and cloud liquid water distribution, resulting in insufficient information required for inversion and serious rank deficiency in the inversion matrix. As a result, the inversion of atmospheric temperature and humidity profiles on cloudy days has large deviations, especially the humidity profile, which may even seriously disagree with the environmental values, greatly reducing the inversion confidence of the microwave radiometer on cloudy days.

[0004] Millimeter-wave cloud radar uses the scattering characteristics of electromagnetic waves of cloud particles to analyze and understand the various microphysical characteristics of clouds through the cloud echoes, and can obtain accurate macro and micro parameters inside the cloud. The present invention uses the cloud microphysical information detected by the ship-borne millimeter-wave cloud radar to provide detailed cloud liquid water auxiliary information for the microwave radiometer. On cloudy days, the ship-borne microwave radiometer is combined with the millimeter-wave cloud radar to detect and invert the marine atmospheric temperature and humidity profile more accurately.

[0005] Due to the severe weather conditions at sea and the complex and changeable environment, floating unstable platforms such as ships are easily affected by wind, waves, surges, currents, etc., and their motion posture changes all the time. The microwave radiometer actually observes the atmospheric radiation on the oblique path. In subsequent applications, if the oblique path atmospheric radiation is directly regarded as the zenith atmospheric radiation, it will inevitably lead to certain errors in the inverted atmospheric temperature and humidity profiles. This error is caused by the use environment and has nothing to do with the measurement accuracy of the microwave radiometer. Therefore, the influence of the platform attitude must be considered. Summary of the invention

[0006] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a method for jointly detecting and inverting the marine atmospheric temperature and humidity profile. The present invention takes into account the influence of cloud absorption on microwave radiation transmission, utilizes the rich cloud information obtained by the millimeter-wave cloud radar carried by the ship platform, and adds the cloud liquid water absorption coefficient to the atmospheric microwave radiation transmission equation. Therefore, the inverted marine atmospheric temperature and humidity profile is more accurate, which can provide data support for marine meteorological research to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for jointly detecting and inverting the temperature and humidity profile of the marine atmosphere, the specific steps of which are as follows:

[0008] S1. First, the temperature and liquid water content of the cloud layer on the sea surface are obtained by millimeter wave cloud radar, and the cloud liquid water absorption coefficient is calculated;

[0009] S2. Use the ship-borne attitude sensor to obtain the pitch angle and roll angle, calculate the zenith angle value of the microwave radiometer observation, and add the zenith correction; then use the pressure sensor configured by the microwave radiometer to calculate the pressure profile according to the pressure-altitude formula.

[0010] S3, invert the atmospheric temperature and humidity profile through microwave radiometer, and construct the atmospheric temperature and humidity profile calculation function;

[0011] S4. Finally, the differential evolution algorithm is used to further accurately invert the ocean atmospheric temperature and humidity profile, which can provide data basis for radio system performance evaluation, radio wave refraction correction and weather forecast.

[0012] In a preferred embodiment, the millimeter wave cloud radar uses the scattering characteristics of electromagnetic waves by cloud particles to invert liquid water. For cloud liquid water, under the premise of given ion average radius and total particle number density, the particle spectrum distribution of cloud liquid water follows a modified log-normal distribution, and its function is as follows:

[0013] Among them, N T is the total particle number density; r is the particle radius; r g is the mean geometric radius; σ log is the geometric standard deviation.

[0014] In a preferred embodiment, in the microwave frequency band f of the microwave radiometer, the total absorption coefficient α(h) is the sum of the oxygen absorption coefficient, the water vapor absorption coefficient, the cloud liquid water absorption coefficient and the atmospheric trace gas absorption coefficient, that is, Among them, the atmospheric trace gas absorption coefficient α Δ ≈0, T c is the cloud temperature, ω cis the cloud liquid water content. After adding the liquid water measured by the millimeter-wave cloud radar, the total absorption coefficient α(h) is mainly the oxygen absorption coefficient and water vapor absorption coefficient The function of Should be

[0015] In a preferred embodiment, the atmospheric microwave radiation transmission equation is calculated as follows: Where T(θ,f) is the simulated brightness temperature, θ is the zenith angle, f is the observation channel frequency, and T ∞ is the cosmic background brightness temperature, which is 2.75K, T(h) is the atmospheric temperature at height h, α(h) is the atmospheric absorption coefficient, which is the sum of the absorption coefficients of the various components in the atmosphere, that is, + is the radiation from the cosmic background radiation that reaches the ground after being attenuated by the atmosphere. It is the radiation of each layer of the atmosphere itself, and then through Simulated brightness temperature It is only a function of the temperature and humidity profile. The brightness temperature measured by the microwave radiometer is T B , the calculation function for constructing the atmospheric temperature and humidity profile is: T(h), H(h) that satisfies min f is the desired atmospheric temperature and humidity profile.

[0016] In a preferred embodiment, the differential evolution algorithm steps are specifically as follows:

[0017] A1. Determine the fitness function T B is the measured value of microwave radiometer, represents the calculation of brightness temperature using the atmospheric microwave radiation transmission model, where It is a binary function of the atmospheric temperature profile T(h) and the relative humidity profile H(h);

[0018] A2. Determine the number and dimension of variables; set the population size (S=60), genetic generation and termination accuracy; set the crossover probability and mutation probability; set the temperature and humidity decreasing or increasing constraints

[0019] A3. Perform mutation, crossover, and selection operations according to the set conditions, continuously iterate and calculate, update the fitness of the new individual, and output the fitness individual obtained in the evolution process as the optimal solution to be selected;

[0020] A4. Eliminate solutions that do not conform to conventional phenomena (such as H(h)<0, H(h)>100, T(h)<0 and T(h)>373) from the set of solutions to be selected. If there is still more than one set, take the weighted average. The solution at this time is the inverted atmospheric temperature and humidity profile.

[0021] In a preferred embodiment, the number of variables refers to two variables, temperature and humidity, the dimension refers to N layers of atmospheric stratification, the genetic generation number M=6 and the termination accuracy le=0.1; the given crossover probability ξ=0.7 and the mutation probability η=0.1.

[0022] Technical effects and advantages of the present invention:

[0023] The present invention specifically studies the influence of cloud absorption on microwave radiation transmission, utilizes the rich cloud information obtained by the millimeter-wave cloud radar carried by the ship platform, and adds the cloud liquid water absorption coefficient to the atmospheric microwave radiation transmission equation. Therefore, the inverted marine atmospheric temperature and humidity profile is more accurate, which can provide data support for marine meteorological research. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example

[0026] This embodiment provides a method for joint detection and inversion of marine atmospheric temperature and humidity profiles, and the specific steps are as follows:

[0027] S1. First, the temperature and liquid water content of the cloud layer on the sea surface are obtained by millimeter wave cloud radar, and the cloud liquid water absorption coefficient is calculated;

[0028] In this embodiment, it should be specifically explained that the millimeter wave cloud radar uses the scattering characteristics of cloud particles on electromagnetic waves to invert liquid water. For liquid water in the cloud layer, under the premise of given average ion radius and total particle number density, the particle spectrum distribution of liquid water in the cloud layer follows a modified log-normal distribution, and its function is as follows:

[0029]

[0030] Among them, N T is the total particle number density; r is the particle radius; r g is the mean geometric radius; σ log is the geometric standard deviation; parameter r g , σ log The calculation method is as follows:

[0031]

[0032] σ log =lnσ g ;

[0033] Under the assumption of modified log-normal distribution, cloud liquid water is LWC, which is calculated by the following formula:

[0034]

[0035] Under Rayleigh scattering conditions, the cloud droplet reflectivity factor measured by millimeter-wave cloud radar is related to the backscattering cross section of the cloud droplets, that is, it is proportional to the sum of the sixth power of the cloud droplet particle diameter. The calculation formula of the radar reflectivity factor is:

[0036]

[0037] Combining the above two equations A and B, we get the formula: Among them, LWC and Z are functions of height h, satisfying the empirical quadratic function Relationship, regression coefficient ρ w =10 6 g / m 3 The regression coefficient a is generally given by the calibration coefficient of the millimeter-wave cloud radar. You can also fly a drone on the ship and substitute the particle spectrum parameters obtained from the detection data into the above formula to get the corresponding a value, thereby obtaining the precise relationship between LWC and Z. The millimeter-wave cloud radar is used as a beneficial supplement to the cloud measurement capability of the microwave radiometer, providing rich cloud liquid water information.

[0038] It should be specifically noted that in the microwave frequency band of the microwave radiometer, the total absorption coefficient α(h) is the sum of the oxygen absorption coefficient, the water vapor absorption coefficient, the cloud liquid water absorption coefficient and the atmospheric trace gas absorption coefficient, that is, Among them, the atmospheric trace gas absorption coefficient α Δ ≈0, T c is the cloud temperature, ω c is the cloud liquid water content. After adding the liquid water measured by the millimeter-wave cloud radar, the total absorption coefficient α(h) is mainly the oxygen absorption coefficient and water vapor absorption coefficient The function of

[0039] It should be noted that the oxygen absorption coefficient and water vapor absorption coefficient It can be calculated by the following formula:

[0040] Where, f is the observation channel frequency, unit GHz, f0 = 60GHz, spectral line width parameter;

[0041] Among them, the line width parameter is

[0042] ρ v is the water vapor density, R d =287.05J / (kg·K),

[0043] e(h) is the water vapor pressure,

[0044] Where H(h) is the relative humidity of the atmosphere, t(h) is the Celsius temperature, t(h) = T(h)-273.16, a, b, c are calculation coefficients,

[0045] S2. Use the ship-borne attitude sensor to obtain the pitch angle and roll angle, calculate the zenith angle value of the microwave radiometer observation, add the zenith correction, and then use the pressure sensor configured by the microwave radiometer to calculate the pressure profile according to the pressure-height formula;

[0046] In this embodiment, it is necessary to specifically explain that the pitch angle α and roll angle β output by the ship-borne attitude sensor are used to calculate the sky-ground angle observed by the microwave radiometer. The calculation formula is θ=arccos(cosαcosβ). P(h) can be given by the pressure-height formula, that is, the air pressure sensor configured by the microwave radiometer is used, and its measured value is used as the sea surface air pressure P0. The air pressure profile is calculated according to the following formula: Among them, H is in m, P a The unit is hPa. The pressure profile is calculated using the pressure-height formula and is not explained in detail here.

[0047] S3, invert the atmospheric temperature and humidity profile through the microwave radiometer, and construct the atmospheric temperature and humidity profile calculation function; what needs to be specifically explained in this embodiment is the calculation of the atmospheric microwave radiation transmission equation, and the algorithm is as follows: Where T(θ,f) is the simulated brightness temperature, θ is the zenith angle, f is the observation channel frequency, and T ∞ is the cosmic background brightness temperature, which is 2.75K, T(h) is the atmospheric temperature at height h, α(h) is the atmospheric absorption coefficient, which is the sum of the absorption coefficients of the various components in the atmosphere, that is, + is the radiation from the cosmic background radiation that reaches the ground after being attenuated by the atmosphere. It is the radiation of each layer of the atmosphere itself.

[0048] It should be noted that in cloudy mode, α cloud(h)≠0. Due to the large uncertainty in the distribution of cloud absorption coefficients, clouds have an important impact on the brightness temperature observed by microwave radiometers. Although the infrared channel of microwave radiometers has a certain cloud measurement capability, its information volume is very limited. It cannot penetrate the surface of thick clouds to detect their vertical and horizontal scales and internal structures, and cannot accurately reflect the ever-changing cloud parameter information. Due to the lack of accurate cloud liquid water information, that is, α cloud (h) is unknown, which leads to large errors in the atmospheric temperature and humidity profiles inverted by the microwave radiometer in cloudy mode. Therefore, the next step of calculation is carried out by constructing a function.

[0049] It is necessary to explain in detail that Simulated brightness temperature It is only a function of the temperature and humidity profile. The brightness temperature measured by the microwave radiometer is T B , the calculation function of atmospheric temperature and humidity profile is constructed as T(h), H(h) that satisfies min f is the desired atmospheric temperature and humidity profile.

[0050] S4. The atmospheric temperature and humidity profile is obtained from the atmospheric microwave radiation transmission equation, and the differential evolution algorithm is used to further invert the atmospheric temperature and humidity profile over the sea, which can provide data basis for radio system performance evaluation, radio wave refraction correction and weather forecasting.

[0051] What needs to be specifically explained in this embodiment is that the steps of the differential evolution algorithm are specifically as follows:

[0052] A1. Determine the fitness function T B is the measured value of microwave radiometer, represents the calculation of brightness temperature using the atmospheric microwave radiation transmission model in, It is a binary function of the atmospheric temperature profile T(h) and the relative humidity profile H(h);

[0053] A2. Determine the number and dimension of variables; set the population size (S=60), genetic generation and termination accuracy; set the crossover probability and mutation probability; set the temperature and humidity decreasing or increasing constraints

[0054] It should be specifically noted that the number of variables refers to the two variables of temperature and humidity, the dimension refers to the N-layer atmospheric stratification, the genetic generation number M=6 and the termination accuracy le=0.1; given the crossover probability ξ=0.7 and the mutation probability η=0.1, the specific parameters of this embodiment can be flexibly modified according to actual conditions and are not specifically limited here.

[0055] A3. Perform mutation, crossover, and selection operations according to the set conditions, continuously iterate and calculate, update the fitness of the new individual, and output the fitness individual obtained in the evolution process as the optimal solution to be selected;

[0056] A4. Eliminate solutions that do not conform to conventional phenomena (such as H(h)<0, H(h)>100, T(h)<0 and T(h)>373) from the set of solutions to be selected. If there is still more than one set, take the weighted average. The solution at this time is the inverted atmospheric temperature and humidity profile.

[0057] The solutions that do not conform to the conventional phenomena may be relative humidity profile H(h)<0, relative humidity profile H(h)>100, atmospheric temperature profile T(h)<0 and atmospheric temperature profile T(h)>373.

[0058] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for joint detection and inversion of marine atmospheric temperature and humidity profiles, characterized in that: The specific steps are as follows: S1. First, the temperature and liquid water content of the cloud layer on the sea surface are obtained by millimeter wave cloud radar, and the cloud liquid water absorption coefficient is calculated; among which, the cloud liquid water absorption coefficient T c is the cloud temperature, ω c is the cloud liquid water content; oxygen absorption coefficient and water vapor absorption coefficient Calculated by the following formula: Where, f is the observation channel frequency, unit GHz, f0 = 60GHz, spectral line width parameter; Among them, the line width parameter is ρ v is the water vapor density, R d =287.05J / (kg·K), e(h) is the water vapor pressure, Where H(h) is the relative humidity of the atmosphere, t(h) is the Celsius temperature, t(h) = T(h)-273.16, a, b, c are calculation coefficients, The atmospheric microwave radiation transmission equation is calculated using the following algorithm: Where T(θ,f) is the simulated brightness temperature, θ is the zenith angle, f is the observation channel frequency, and T ∞ is the cosmic background brightness temperature, which is 2.75K, T(h) is the atmospheric temperature at height h, α(h) is the atmospheric absorption coefficient, which is the sum of the absorption coefficients of the various components in the atmosphere, that is, It is the radiation that reaches the ground after the cosmic background radiation is attenuated by the atmosphere. It is the radiation of each layer of the atmosphere itself, and then through Simulated brightness temperature is only a function of the temperature and humidity profile, The brightness temperature measured by the microwave radiometer is T B , the calculation function of atmospheric temperature and humidity profile is constructed as T(h), H(h) that satisfy minf is the desired atmospheric temperature and humidity profile; S2. Use the ship attitude sensor to obtain the pitch angle and roll angle, calculate the value of the microwave radiometer observation zenith angle, add the zenith correction; then use the pressure sensor configured by the microwave radiometer to calculate the pressure profile according to the pressure-height formula; S3, invert the atmospheric temperature and humidity profile through microwave radiometer, and construct the atmospheric temperature and humidity profile calculation function; S4. Finally, the differential evolution algorithm is used to further accurately invert the ocean atmospheric temperature and humidity profile, which can provide data basis for radio system performance evaluation, radio wave refraction correction and weather forecast.

2. The method for inverting the marine atmospheric temperature and humidity profile by joint detection according to claim 1 is characterized in that: The millimeter wave cloud radar uses the scattering characteristics of cloud particles on electromagnetic waves to invert liquid water. For cloud liquid water, under the premise of given ion average radius and total particle number density, the particle spectrum distribution of cloud liquid water follows a modified log-normal distribution, and its function is as follows: Among them, N T is the total particle number density; r is the particle radius; r g is the mean geometric radius; σ log is the geometric standard deviation.

3. The method for inverting the marine atmospheric temperature and humidity profile by joint detection according to claim 2 is characterized in that: In the microwave frequency band of the microwave radiometer, the total absorption coefficient α(h) is the sum of the oxygen absorption coefficient, the water vapor absorption coefficient, the cloud liquid water absorption coefficient and the atmospheric trace gas absorption coefficient, that is, Among them, the atmospheric trace gas absorption coefficient α Δ ≈0, T c is the cloud temperature, ω c is the cloud liquid water content. After adding the liquid water measured by the millimeter-wave cloud radar, the total absorption coefficient α(h) is mainly the oxygen absorption coefficient and water vapor absorption coefficient The function of 4. The method for inverting the marine atmospheric temperature and humidity profile by joint detection according to claim 1 is characterized in that: The steps of the differential evolution algorithm are specifically as follows: A1. Determine the fitness function T B is the measured value of microwave radiometer, represents the calculation of brightness temperature using the atmospheric microwave radiation transmission model, where It is a binary function of the atmospheric temperature profile T(h) and the relative humidity profile H(h); A2. Determine the number and dimension of variables; set the population size (S=60), genetic generation and termination accuracy; set the crossover probability and mutation probability; set the temperature and humidity decreasing or increasing constraints A3. Perform mutation, crossover, and selection operations according to the set conditions, continuously iterate and calculate, update the fitness of the new individual, and output the fitness individual obtained in the evolution process as the optimal solution to be selected; A4. Eliminate solutions that do not conform to conventional phenomena from the set of solutions to be selected. If there is still more than one set, take the weighted average. The solution at this time is the inverted atmospheric temperature and humidity profile.

5. The method for inverting the marine atmospheric temperature and humidity profile by joint detection according to claim 4 is characterized in that: The number of variables refers to the two variables of temperature and humidity, the dimension refers to the N layers of atmospheric stratification, the genetic number of generations, i.e., M=6, and the termination accuracy, i.e., le=0.1; the given crossover probability, i.e., ξ=0.7, and the mutation probability, i.e., η=0.1, are modified according to user customization.

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