A method for selecting temperature measurement channels of ground-based microwave radiometer

Abstract

The present invention discloses a method for selecting a temperature measurement channel of a ground-based microwave radiometer, belonging to the technical field of ground-based microwave radiometers, and comprising the following steps: S1, establishing a relationship model between the radiation brightness temperature of the microwave radiometer temperature measurement channel and liquid water; S2, classifying the temperature measurement channels; and S3, eliminating temperature measurement channels that are significantly affected by liquid water, correcting temperature measurement channels that are less affected by liquid water, and directly adopting temperature measurement channels that are substantially unaffected by liquid water. By the above-mentioned method, the present invention can effectively solve the problem of inaccurate measurement results of microwave radiometers in rainy weather, by selecting a suitable temperature measurement channel of the microwave radiometer to measure the channel brightness temperature and correcting the temperature measurement channel that is less affected by liquid water.

Description

Technical Field

[0001] The present invention relates to the technical field of ground-based microwave radiometers, and in particular to a method for selecting a temperature measurement channel of a ground-based microwave radiometer. Background Art

[0002] A ground-based microwave radiometer is a device that measures the atmospheric radiation brightness temperature (abbreviated as brightness temperature) in the oxygen and water vapor frequency bands through passive remote sensing, and inverts atmospheric parameters such as the atmospheric temperature profile, relative humidity profile, and water vapor density profile through methods such as neural networks.

[0003] Currently, known ground-based microwave radiometers typically use a temperature measurement channel corresponding to the oxygen absorption frequency band for brightness temperature detection, thereby enabling atmospheric temperature detection. The detection frequency range is 51 GHz to 59 GHz. The specific temperature measurement channel varies between manufacturers, and there is currently no clear method for determining whether a temperature measurement channel is appropriate.

[0004] At the same time, analysis found that when using microwave radiometers to measure temperature, liquid water significantly affects the brightness temperature measurements of some temperature measurement channels, thereby affecting the measurement accuracy of the atmospheric temperature profile. In particular, during rainfall, the microwave radiometer data is often invalid.

[0005] Based on this, the present invention designs a method for selecting temperature measurement channels of a ground-based microwave radiometer to solve the above problems. Summary of the Invention

[0006] In response to the problem in the prior art that it is impossible to measure the channel brightness temperature and correct the brightness temperature by selecting an appropriate temperature measurement channel of a microwave radiometer, resulting in inaccurate measurement results of the microwave radiometer in weather such as rain, the present invention provides a method for selecting the temperature measurement channel of a ground-based microwave radiometer.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A method for selecting a temperature measurement channel of a ground-based microwave radiometer comprises the following steps:

[0009] S1. Establish a model for the relationship between the radiation brightness temperature of the microwave radiometer temperature measurement channel and liquid water:

[0010] (3)

[0011] Where T(s') is the physical temperature of the atmosphere at altitude s'; is the liquid water absorption coefficient; is the total atmospheric attenuation along the path from s' to s;

[0012] S2. Classification of temperature measurement channels: temperature measurement channels that are greatly affected by liquid water, temperature measurement channels that are less affected by liquid water, and temperature measurement channels that are basically not affected by liquid water;

[0013] S3. Eliminate the temperature measurement channels that are significantly affected by liquid water, use formula 13 to correct the temperature measurement channels that are less affected by liquid water, and directly use formula 13 for the temperature measurement channels that are basically not affected by liquid water;

[0014] The correction formula for the radiation brightness temperature of a certain channel in the temperature measurement channel of a microwave radiometer is:

[0015] (13)

[0016] in, represents the brightness temperature measured by the radiometer after eliminating the influence of liquid water; TB represents the brightness temperature originally measured by the microwave radiometer; TL represents the radiation brightness temperature of the microwave radiometer on the liquid water sensitive channel; a, b, and c are statistically obtained constant terms.

[0017] Furthermore, the specific steps of step S1 are:

[0018] S11. Using the atmospheric transport equation and historical sounding data sets, we can derive an expression for the effect of liquid water on the brightness temperature of different temperature measurement channels.

[0019] S12. Based on the expression for the influence of liquid water on the radiation brightness temperature of different temperature measurement channels and the formula for the atmospheric absorption coefficient, an expression for the influence of liquid water on the radiation brightness temperature of the temperature measurement channel is obtained.

[0020] Furthermore, in step 1, the atmospheric transmission equation is the atmospheric radiation brightness temperature equation:

[0021] (1)

[0022] Where T(s') is the physical temperature of the atmosphere at altitude s'; is the atmospheric absorption coefficient, in Np / m; is the total atmospheric attenuation along the path from s' to s; is the total atmospheric radiation brightness temperature, in K; is the brightness temperature of the cosmic background radiation, in K.

[0023] Furthermore, in step 1, the atmospheric absorption coefficient formula is:

[0024] (2)

[0025] in, is the total absorption coefficient, is the dry air absorption coefficient, is the water vapor absorption coefficient, is the liquid water absorption coefficient.

[0026] Furthermore, step 1 also includes: using the single Debye model to calculate the dielectric constant of water at 51 GHz to 59 GHz, the microwave radiometer operates, thereby obtaining the absorption coefficient of liquid water. for:

[0027] (4)

[0028] Among them, for water, The value is 1g / cm 3 , for ice, The value is 0.916g / cm 3 ; is the complex permittivity of water or ice, Represents the density of water or ice.

[0029] Furthermore, in step 2, the temperature measurement channel that is substantially unaffected by liquid water is expressed as:

[0030] (10)

[0031] In formula (10), It represents the brightness temperature error of the i-th temperature measurement channel affected by liquid water. Such temperature measurement channels meet the measurement accuracy requirements without any correction.

[0032] Furthermore, in step 2, the temperature measurement channel that is less affected by liquid water is expressed as:

[0033] (11)

[0034] In formula (11), represents the influencing factor of the i-th temperature measurement channel; represents the brightness temperature error of the i-th temperature measurement channel affected by liquid water; represents the true value of the simulated brightness temperature of the i-th temperature measurement channel; is the minimum acceptable impact factor value.

[0035] Furthermore, in step 2, The value used was 0.01.

[0036] Furthermore, in step 2, the temperature measurement channel that is more affected by liquid water is expressed as:

[0037] (12)

[0038] This type of temperature measurement channel is greatly affected by liquid water, and even after temperature measurement channel correction, it still cannot meet the accuracy requirements.

[0039] Beneficial effects

[0040] The present invention provides a method for selecting a temperature measurement channel by establishing a relationship model between the radiation brightness temperature of the temperature measurement channel of a microwave radiometer and liquid water. By constructing the relationship between the radiation brightness temperature of the frequency band where the temperature measurement channel is located and liquid water, the influence of liquid water on different detection frequencies can be effectively identified and evaluated, thereby providing a basis for frequency point selection when measuring temperature with a ground-based microwave radiometer.

[0041] The present invention measures the channel brightness temperature by selecting a suitable temperature measurement channel of a microwave radiometer, eliminating the temperature measurement channels that are greatly affected by liquid water, correcting the temperature measurement channels that are less affected by liquid water, and directly adopting the temperature measurement channels that are basically not affected by liquid water. This can effectively solve the problem of inaccurate measurement results of microwave radiometers in weather such as rain. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0043] Figure 1 This is a flow chart of a method for selecting a temperature measurement channel of a ground-based microwave radiometer according to the present invention;

[0044] Figure 2 This is the impact factor diagram of each frequency point affected by liquid water. DETAILED DESCRIPTION

[0045] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0046] The present invention will be further described below with reference to the embodiments.

[0047] Example 1

[0048] Please refer to the instruction manual Figure 1-2, a method for selecting a temperature measurement channel of a ground-based microwave radiometer, comprising the following steps:

[0049] 1. Establish a model for the relationship between the brightness temperature of the microwave radiometer temperature measurement channel and liquid water;

[0050] Specifically, the following steps are included:

[0051] A. Using the atmospheric transport equation (Formula 1) and historical sounding data sets (which contain fixed parameter information such as atmospheric temperature and dew point temperature), we derive an expression for the effect of liquid water on the brightness temperature of different temperature measurement channels, providing a basis for subsequent channel selection.

[0052] Among them, the atmospheric transmission equation is the atmospheric radiation brightness temperature equation:

[0053] (1)

[0054] Where T(s') is the physical temperature of the atmosphere at altitude s'; is the atmospheric absorption coefficient, in Np / m; is the total atmospheric attenuation along the path from s' to s; is the total atmospheric radiation brightness temperature, in K; is the brightness temperature of the cosmic background radiation, in K;

[0055] The atmospheric absorption coefficient formula is:

[0056] (2)

[0057] in, is the total absorption coefficient, is the dry air absorption coefficient, is the water vapor absorption coefficient, is the liquid water absorption coefficient;

[0058] B. Based on formulas (1) and (2), the expression for the effect of liquid water on the radiation brightness temperature of the temperature measurement channel is obtained:

[0059] (3)

[0060] Among them, in the 51GHz-59GHz working frequency of the microwave radiometer, the single Debye model can be used to calculate the dielectric constant of water, thereby obtaining the absorption coefficient of liquid water for:

[0061] (4)

[0062] in, The value is 1 g / cm 3(for water), the value is 0.916 g / cm 3 (for ice), is the complex permittivity of water or ice, Represents the density of water or ice.

[0063] 2. Classification of temperature measurement channels: temperature measurement channels that are greatly affected by liquid water, temperature measurement channels that are less affected by liquid water, and temperature measurement channels that are basically not affected by liquid water;

[0064] Currently, temperature measurement channels are typically measured at different frequencies between 51 and 59 GHz, typically with intervals of 1 GHz. Liquid water affects different temperature measurement channels differently: some are significantly affected, some are less affected, and some are largely unaffected. To invert temperature profiles, the brightness temperature accuracy of microwave radiometer temperature measurement channels is generally required to be ≤1 K (compared to sounding data).

[0065] Therefore, temperature measurement channels can be divided into the following three categories:

[0066] (1) A temperature measurement channel that is basically unaffected by liquid water, namely:

[0067] (10)

[0068] In formula (10), It represents the brightness temperature error of the i-th temperature measurement channel affected by liquid water. Such temperature measurement channels meet the measurement accuracy requirements without any correction and can be used directly.

[0069] (2) Temperature measurement channel that is less affected by liquid water, namely:

[0070] (11)

[0071] In formula (11), represents the influencing factor of the i-th temperature measurement channel; represents the brightness temperature error of the i-th temperature measurement channel affected by liquid water; represents the true value of the simulated brightness temperature of the i-th temperature measurement channel; The minimum acceptable impact factor value can be obtained through simulation analysis. The recommended value here is 0.01. This type of temperature measurement channel is less affected by liquid water, so some corrections are required after selecting the temperature measurement channel to ensure measurement accuracy.

[0072] (3) Temperature measurement channels that are greatly affected by liquid water, namely:

[0073] (12)

[0074] This type of temperature measurement channel is greatly affected by liquid water. Even after temperature measurement channel correction, it still cannot meet the accuracy requirements. This type of temperature measurement channel needs to be eliminated.

[0075] 3. Eliminate the temperature measurement channels that are greatly affected by liquid water, correct the temperature measurement channels that are less affected by liquid water, and directly adopt the temperature measurement channels that are basically not affected by liquid water.

[0076] Example 2

[0077] In Example 1, Formula 13 is used to correct the temperature measurement channel that is less affected by liquid water;

[0078] Generally, ground-based microwave radiometers also have a separate channel for measuring liquid water. Therefore, the effect of liquid water on the temperature measurement channel can be statistically analyzed, and the brightness temperature of the temperature measurement channel can be corrected by the brightness temperature of the radiation on the liquid water-sensitive channel. The brightness temperature of a microwave radiometer on a temperature measurement channel can be corrected as follows:

[0079] (13)

[0080] in, represents the brightness temperature measured by the radiometer after eliminating the influence of liquid water; TB represents the brightness temperature originally measured by the microwave radiometer; TL represents the radiation brightness temperature of the microwave radiometer on the liquid water sensitive channel; a, b, and c are statistically obtained constant terms.

[0081] The present invention provides a method for selecting a temperature measurement channel by establishing a relationship model between the radiation brightness temperature of the temperature measurement channel of a microwave radiometer and liquid water. By constructing the relationship between the radiation brightness temperature of the frequency band where the temperature measurement channel is located and liquid water, the influence of liquid water on different detection frequencies can be effectively identified and evaluated, thereby providing a basis for frequency point selection when measuring temperature with a ground-based microwave radiometer.

[0082] The present invention measures the channel brightness temperature by selecting a suitable temperature measurement channel of a microwave radiometer, eliminating the temperature measurement channels that are greatly affected by liquid water, correcting the temperature measurement channels that are less affected by liquid water, and directly adopting the temperature measurement channels that are basically not affected by liquid water. This can effectively solve the problem of inaccurate measurement results of microwave radiometers in weather such as rain.

[0083] Example 3

[0084] Taking the temperature measurement channel used by a microwave radiometer as an example, the alternative frequencies of its temperature measurement channel are: 51.26, 52.28, 53.86, 54.94, 55.50, 56.66, 57.30, and 58.00 GHz.

[0085] Through calculation, we can get the influence factors of liquid water on each frequency point as shown in the attached figure. Figure 2 shown.

[0086] Therefore, the frequency selection recommendations for each temperature measurement channel of the microwave radiometer are given as follows:

[0087]

[0088] Among them, “√” represents the frequency point that can be used directly, “○” represents the frequency point that needs to be corrected, and “×” represents the frequency point that needs to be eliminated.

[0089] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for selecting a temperature measurement channel of a ground-based microwave radiometer, characterized in that: The following steps are involved: S1. Establish a model for the relationship between the radiation brightness temperature of the microwave radiometer temperature measurement channel and liquid water: （3） Where T(s') is the physical temperature of the atmosphere at altitude s'; is the liquid water absorption coefficient; is the total atmospheric attenuation along the path from s' to s; S2. Classification of temperature measurement channels: temperature measurement channels that are greatly affected by liquid water, temperature measurement channels that are less affected by liquid water, and temperature measurement channels that are basically not affected by liquid water; S3. Eliminate the temperature measurement channels that are significantly affected by liquid water, use formula 13 to correct the temperature measurement channels that are less affected by liquid water, and directly use formula 13 for the temperature measurement channels that are basically not affected by liquid water; The correction formula for the radiation brightness temperature of a certain channel in the temperature measurement channel of a microwave radiometer is: （13） in, represents the brightness temperature measured by the radiometer after eliminating the influence of liquid water; TB represents the brightness temperature originally measured by the microwave radiometer; TL represents the brightness temperature of the microwave radiometer on the liquid water sensitive channel; a, b, and c are constant terms obtained by statistics; In step 2, the temperature measurement channel that is basically unaffected by liquid water is expressed as: （10） In formula (10), represents the brightness temperature error of the i-th temperature measurement channel affected by liquid water. Such temperature measurement channels meet the measurement accuracy requirements without any correction; In step 2, the temperature measurement channel that is less affected by liquid water is expressed as: （11） In formula (11), represents the influencing factor of the i-th temperature measurement channel; represents the brightness temperature error of the i-th temperature measurement channel affected by liquid water; represents the true value of the simulated brightness temperature of the i-th temperature measurement channel; is the minimum acceptable impact factor value; In step 2, the temperature measurement channel that is more affected by liquid water is expressed as: （12） This type of temperature measurement channel is greatly affected by liquid water, and even after temperature measurement channel correction, it still cannot meet the accuracy requirements.

2. The method for selecting a temperature measurement channel of a ground-based microwave radiometer according to claim 1, characterized in that: The specific steps of step S1 are: S11. Using the atmospheric transport equation and historical sounding data sets, we can derive an expression for the effect of liquid water on the brightness temperature of different temperature measurement channels. S12. Based on the expression for the influence of liquid water on the radiation brightness temperature of different temperature measurement channels and the formula for the atmospheric absorption coefficient, an expression for the influence of liquid water on the radiation brightness temperature of the temperature measurement channel is obtained.

3. The method for selecting a temperature measurement channel of a ground-based microwave radiometer according to claim 2, characterized in that: In step 1, the atmospheric transmission equation is the atmospheric radiation brightness temperature equation: （1） Where T(s') is the physical temperature of the atmosphere at altitude s'; is the atmospheric absorption coefficient, in Np / m; is the total atmospheric attenuation along the path from s' to s; is the total atmospheric radiation brightness temperature, in K; is the brightness temperature of the cosmic background radiation, in K.

4. The method for selecting a temperature measurement channel of a ground-based microwave radiometer according to claim 3, characterized in that: In step 1, the atmospheric absorption coefficient formula is: （2） in, is the total absorption coefficient, is the dry air absorption coefficient, is the water vapor absorption coefficient, is the liquid water absorption coefficient.

5. The method for selecting a temperature measurement channel of a ground-based microwave radiometer according to claim 4, characterized in that: Step 1 also includes: using the single Debye model to calculate the dielectric constant of water at 51GHz-59GHz, the microwave radiometer operates at, to obtain the absorption coefficient of liquid water for: （4） Among them, for water, The value is 1g / cm 3 , for ice, The value is 0.916g / cm 3 ; is the complex permittivity of water or ice, Represents the density of water or ice.

6. The method for selecting a temperature measurement channel of a ground-based microwave radiometer according to claim 1, characterized in that: In step 2, The value used was 0.01.

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