CN115060368A - Method for observing absolute solar radiation brightness temperature by using microwave radiometer - Google Patents
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Abstract
The invention discloses a method for observing the absolute solar radiation brightness temperature by using a microwave radiometer, which can realize the observation and analysis of the absolute solar radiation brightness temperature by only using a foundation microwave radiometer to remotely sense and observe the solar radiation intensity without other test instruments and meters and special test environments. The method does not need professional and complex instrument observation and other instrument and equipment assistance, can directly calculate and obtain the absolute radiation brightness temperature of the sun only by automatically tracking and observing the sun through the microwave radiometer, has low requirement on an observation environment, is easy to realize, can realize automatic tracking and observation, and has simple operation and simpler calculation party.
Description
[ technical field ] A method for producing a semiconductor device
The invention belongs to the field of passive microwave remote sensing detection, and particularly relates to a method for observing the absolute solar radiation brightness temperature by using a microwave radiometer.
[ background ] A method for producing a semiconductor device
A multi-channel microwave radiometer based on foundation is a passive atmospheric remote sensing detection device and can obtain parameters such as atmospheric temperature and humidity profiles with high space-time resolution. At present, the method is widely applied to atmospheric remote sensing detection.
The radiant brightness temperature is also called the characterization temperature, and mainly refers to the radiant energy of an object, and the radiant energy is an 'external' expression of the energy state of the object. While the sun acts as a strong radiation source and radiates over the full frequency range. In a microwave band, the solar radiation brightness temperature is about 6000-20000K, and the radiation comes from different solar atmospheres, so that the detection method is complex, a precise instrument is required for observation and calculation, and the operation and calculation methods are complex, so that an observation method microwave radiometer which is convenient to operate and simple in calculation method is urgently needed, has the characteristic of high sensitivity, and can be used for observing solar radiation.
[ summary of the invention ]
Aiming at the problems, the invention provides a method for observing the absolute solar radiation brightness temperature by using a microwave radiometer, which does not need the assistance of other instruments and equipment, has low requirement on the observation environment, is easy to realize, can realize automatic tracking observation, and has simple operation and simpler calculation party.
The invention is realized by the following technical scheme, and provides a method for observing the absolute solar radiation brightness temperature by using a microwave radiometer, which comprises the following steps:
s1, calculating the azimuth angle and the altitude angle of the sun in real time;
s2, controlling a radiometer rotary table to enable the antenna to point to the sun, wherein the radiometer rotary table is an azimuth rotary table and a pitching rotary table;
s3, fixing the elevation angle of the antenna, controlling the azimuth and the pitching rotary table of the microwave radiometer in a stepping mode to enable the antenna to point to the center position of the sun, controlling the azimuth rotary table to rotate the antenna to carry out azimuth scanning on the sun, and observing the brightness temperature in each direction;
s4, moving the azimuth of the antenna to enable the sun to be far away from the center of the antenna beam, fixing the azimuth, controlling the antenna to tilt to scan the sky in elevation, and calculating the atmospheric attenuation of each elevation by using the tilt sky scanning data;
s5, calibrating atmospheric attenuation, and calculating the radiation brightness temperature of the antenna reached by the solar radiation scanned and observed when no atmospheric attenuation exists;
s6, calculating the ratio of the solid angle of the sun in the antenna beam according to the S4 scanning observation result, namely the filling coefficient of the sun in the antenna beam;
s7 calculating the absolute solar radiation light temperature according to S5 and S6 by using the light temperature and the filling factor observed by the antenna aiming at the solar central radiometer.
Specifically, the S1 calculates the solar azimuth angle A according to the space-day relationship Z And a height angle E l Specifically, the calculation is performed according to the following formula:
T 0 ＝(t s -12)·15° (1)，
E l ＝arcsin(sinθ lat sinδ+cosδcosT 0 ) (2)，
in the formula (1), t s In the formula (2) and the formula (3), δ is solar declination, and θ is solar angle lat The latitude of the microwave antenna.
Particularly, the azimuth turntable in the S3 rotates at-10 degrees to 10 degrees on both sides of the azimuth of the sun, and scans the sun to fit the maximum brightness temperature value, namely the radiation brightness temperature aligned with the sun center, so as to eliminate the pointing error.
Specifically, the temperature alarm in S3 includes: the solar radiation bright temperature reaches the bright temperature of the antenna and the atmospheric self radiation bright temperature after beam space averaging and atmospheric attenuation, and when the sun is in the antenna beam, the bright temperature observed by the antenna is calculated according to the following formula:
when the sun is not in the antenna beam, the lighting temperature when the sky is observed is calculated according to the following formula:
the brightness temperature of the solar radiation reaching the antenna through beam space averaging and atmospheric attenuation is obtained by subtracting the formula (4) and the formula (5), and the following formula is obtained after the subtraction:
in the formulas (4) to (6), the
Is the azimuth angle of the antenna, theta is the pitch angle, T m Mean radiant brightness temperature of atmosphere, T bg 2.75K is cosmic background radiation, Ω s For solid angle of solar beam, omega A Is the antenna beam solid angle, Δ T' sun Bright temperature, T ', received for radiometer observation of the sun' sky Atmospheric radiation brightness temperature, delta T ', received when atmospheric is observed for a radiometer' sun 2.75K is the bright temperature, T, of the solar radiation received by the radiometer after atmospheric attenuation in the antenna beam sun 2.75K is the mean radiant bright temperature of the sun, τ (θ) is the thickness of the atmosphere in the direction in which the antenna is pointed, and is related to the atmospheric conditions, only the elevation angle in a clear day or when the distribution of the atmosphere is uniform, and is not related to the azimuth.
Specifically, the atmospheric attenuation in S4 is calculated according to the following formula:
specifically, the S5 performs the calibration to be attenuated as follows:
substituting the formula (7) into the formula (6) to carry out atmospheric attenuation calibration, and obtaining the following formula after finishing:
in the formula (8), Δ T sun For the bright temperature of the solar radiation received by the radiometer without atmospheric attenuation, the equation (8) is a bright temperature observation model of the solar radiation reaching the microwave radiometer antenna.
Specifically, the S6 is specifically implemented as follows:
when the antenna of the S61 microwave radiometer scans the sun, the observed sunlight radiation brightness temperature calibrated by the atmosphere is expressed by the following formula:
ΔT sun (x，y)＝A d G(x，y) (9)，
in the formulas (9) and (10), x and y are the position difference between the center of the sun and the center of the antenna, A d The observed light temperature for the antenna aligned with the center of the sun, G is the antenna gain model, which can be expressed using a Gaussian model, θ A When the radiometer scans the sun, fitting the scanning data by using a Gaussian function model to obtain the antenna beam width;
s62 the filling factor of the sun in the antenna beam is expressed by the antenna gain model, because the antenna gain model can be expressed by a Gaussian function, when the antenna is opposite to the center of the sun, the filling factor R of the sun in the antenna beam can be obtained by integration, and the filling factor R is calculated according to the following formula:
in formulae (11) and (12), θ s Is the angular radius of the sun, r is the sun's radius, and d is the distance from the sun to the earth.
Specifically, in S62, the distance d between the sun and the ground is calculated as follows:
in equation (13), e is the eccentricity of the spherical orbit, e is 0.01672, a is the semi-major axis of the orbit, ω is the polar angle, where ω and d are periodic functions with respect to time, and the relationship between polar angle ω and time is expressed by the following equation according to keplerian's law and the elliptic orbit equation:
in the formula (14), T is the number of days calculated from 1 month and 1 day, T is the number of days of a year, the polar angle of each day can be obtained by means of iterative calculation, and accurate sun-ground distance, solar angle radius and ratio of the solar solid angle to the antenna solid angle, namely the filling coefficient R can be obtained by substituting the formula (13), the formula (12) and the formula (11).
Specifically, the solar absolute radiant brightness temperature in S7 is calculated according to the following formula:
in the formula (15), Δ T max The maximum value of the solar radiation brightness temperature obtained by observation of the radiometer after atmospheric attenuation calibration.
The invention provides a method for observing the absolute solar radiation brightness temperature by using a microwave radiometer, which has the following beneficial effects:
1) the invention has low requirement on the environment, can realize the observation of the absolute solar radiation brightness temperature without other precise test instruments, can also realize the measurement of the beam width of the antenna, and reduces the complexity of the observation;
2) the invention realizes the observation of the solar radiation brightness temperature by using the microwave radiometer, and the calculation process is simple and the result is accurate;
3) the invention can be used for monitoring solar radiation change and expands the application field of the microwave radiometer.
[ description of the drawings ]
FIG. 1 is a graph of solar radiation brightness and temperature at 6 Mey of month as measured by a microwave radiometer at 22.235, 26.235, 30 GHz;
FIG. 2 is a graph showing the change of the solar radiation brightness and temperature from 12 months to 2 months in the following year, which is observed at 22.235, 26.235, 30GHz by a microwave radiometer;
FIG. 3 is a graph comparing the observation results provided by the present invention with the observation results of a conventional precision instrument, wherein the square is the observation result obtained by conventional observation, the circle is the observation result obtained by the method of the present invention, and the short line represents the variance.
[ detailed description ] embodiments
In the invention, the azimuth scanning refers to that the elevation angle of the antenna of the microwave radiometer is fixed, only the antenna azimuth turntable is rotated for observation, and the pitching scanning refers to that the antenna azimuth turntable is fixed and the antenna pitching turntable is rotated for elevation angle scanning observation. In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.
The invention provides a method for observing the absolute solar radiation brightness temperature by using a microwave radiometer, which comprises the following steps of:
s1 real-time calculating sun azimuth A according to the track relation of sun and ground Z Angle of elevationE l Specifically, the calculation is performed according to the following formula:
T 0 ＝(t s -12)·15° (1)，
E l ＝arcsin(sinθ lat sinδ+cosδcosT 0 ) (2)，
in the formula (1), t s In the formula (2) and the formula (3), δ is solar declination, and θ is solar angle lat The latitude of the microwave antenna.
S2 controls the radiometer turret to point the antenna at the sun, the turret being an azimuth and elevation turret.
S3, fixing the elevation angle of the antenna, controlling the azimuth and the pitching rotary table of the microwave radiometer in a stepping mode to enable the antenna to point to the center position of the sun, fixing the elevation angle, controlling the azimuth rotary table to rotate the antenna to carry out azimuth scanning on the sun, and observing the brightness temperature in each direction, wherein the observed brightness temperature comprises the brightness temperature when the radiation of the sun reaches the antenna through atmospheric attenuation and the atmospheric radiation brightness temperature;
when the sun is within the antenna beam, the observed light temperature of the antenna is calculated as follows:
when the sun is not in the beam, the observed sky glow is calculated as follows:
the brightness temperature of the solar radiation reaching the antenna through atmospheric attenuation is obtained by subtracting the formula (4) from the formula (5), and the formula is obtained after the subtraction:
in the formulas (4) to (6), the
Is the azimuth angle of the antenna, theta is the pitch angle, T m Mean radiant brightness of atmosphere, T bg 2.75K is cosmic background radiation, Ω s For the solid angle of the sun beam, Ω A Being the solid angle of the antenna beam, T' sun Bright temperature, T ', received for radiometer observation of the sun' sky Atmospheric radiation brightness temperature, delta T ', received when atmospheric is observed for a radiometer' sun 2.75K is the bright temperature, T, of the solar radiation received by the radiometer after atmospheric attenuation in the antenna beam sun 2.75K is the mean radiant bright temperature of the sun, τ (θ) is the thickness of the atmosphere in the direction in which the antenna is pointed, and is related to the atmospheric conditions, only the elevation angle in a clear day or when the distribution of the atmosphere is uniform, and is not related to the azimuth.
S4, moving the azimuth of the antenna (not less than 10 degrees), so that the sun is not in the beam of the antenna, controlling the pitching of the antenna to scan the sky, neglecting the atmospheric change in the scanning process due to short scanning time, and calculating the atmospheric attenuation of each elevation angle by using the pitching sky scanning data, wherein the atmospheric attenuation is specifically calculated according to the following formula:
in equation (7), the average atmospheric radiation temperature T m The ground atmospheric temperature can be used for approximate substitution, or the radiation transmission mode can be used for carrying out statistical regression by combining with the sounding data, and the relation between the ground temperature and humidity pressure parameter and the atmospheric average radiation temperature is established for estimation. When the sun is not in the antenna beam, calculating to obtain the atmospheric attenuation in the elevation angle direction after measuring the atmospheric radiation brightness temperature at different elevation angles; under the condition of even atmosphere, the atmospheric attenuation can be considered to be only related to elevation and independent of azimuth, so the method can be directly used for the atmospheric attenuation calibration at the same elevation when the sun is scanned.
S5 calibrating atmospheric attenuation, calculating the radiant brightness temperature of the antenna reached by the solar radiation observed when there is no atmospheric attenuation, specifically calculating as follows:
substituting the formula (7) into the formula (6) to carry out atmospheric attenuation calibration, and obtaining the following formula after finishing:
in the formula (8), Δ T sun The formula is a bright temperature observation model of solar radiation reaching the antenna of the microwave radiometer.
S6, calculating a ratio of a solar solid angle in the antenna beam, i.e. a fill factor of the sun in the antenna beam, specifically as follows:
because the sun is far away and can be regarded as a point source, the scanning process of the radiometer antenna to the sun is a process for measuring an antenna directional diagram, the antenna directional diagram can be assumed to be a gaussian antenna model, and the scanned brightness and temperature can be expressed as the following formula by using a gaussian function:
ΔT sun (x，y)＝A d G(x，y) (9)，
in the formula (9) and the formula (10), x and y are the position difference between the center of the sun and the center of the antenna, respectively, and A d The brightness temperature observed by aligning the antenna with the center of the sun is G, which is an antenna gain model, and a Gaussian antenna gain model can be used A Is the antenna beam width. When the radiometer scans the sun, the scanning data is fitted by using the Gaussian function model, and the beam width of the antenna can be obtained.
The filling coefficient of the sun in the antenna beam can be expressed by an antenna gain model, and the antenna gain model can be expressed by a Gaussian function, so that when the antenna is over against the center of the sun, the calculation formula of the filling coefficient R of the sun in the antenna beam can be obtained by integration
In formula (11), θ s The angular radius of the sun is related to the radius of the sun and the distance between the sun and the ground, and according to the relationship between the sun and the ground, the angular radius of the sun can be calculated by the following formula:
in the formula (12), r is the sun radius, and d is the distance between the sun and the ground.
The orbit of the earth is an ellipse, and the distance between the sun and the ground changes periodically along with time, so that the solar angular radius also changes periodically along with time, the change of the solar angular radius directly causes the periodic change of the filling coefficient of the sun in an antenna beam, and the distance between the sun and the ground needs to be accurately calculated in order to accurately calculate the absolute radiation brightness temperature of the sun. The earth orbit is an ellipse, and in a polar coordinate system, the earth orbit equation can be expressed by the following formula:
in the formula (13), e is the eccentricity of the earth orbit, e is 0.01672, a is the orbit major semi-axis, ω is the polar angle, ω and d are periodic functions with respect to time, the relationship between the polar angle ω and time can be expressed approximately by the following equation according to keplerian's law and the elliptic orbit equation,
in the formula (14), T is the number of days counted from 1 month and 1 day, and T is the number of days of the year, so that the polar angle of each day can be obtained by iterative calculation, and the polar angle is substituted into the formula (13), and the accurate sun-ground distance, solar angle radius and ratio of the solar solid angle to the antenna solid angle, namely, the filling factor R can be obtained in the formula (12) and the formula (11).
S7, calculating the absolute solar radiation brightness temperature by using the brightness temperature and the filling coefficient observed by the antenna aiming at the solar central radiometer, specifically calculating according to the following method:
in the formula (15), Δ T max The model of the solar absolute radiation bright temperature can be obtained through the observation of the microwave radiometer through calculation for the solar radiation bright temperature which is observed by the radiometer when the antenna is aligned with the solar center and is subjected to atmospheric attenuation calibration.
In the invention, a microwave radiometer is adopted to observe the solar absolute radiation brightness temperature for a long time, and the calculation is carried out according to the observed data by the method as above, and finally the model of the solar absolute radiation brightness temperature is obtained. The sun observation experiment was carried out using a MWP967KV model ground-based multichannel microwave radiometer located at Qinling atmospheric science test base, Xian.
The method utilizes a microwave radiometer to continuously track and observe the sun, the microwave radiometer can observe solar radiation information, and absolute solar radiation brightness and temperature on three frequency points observed by 22.235, 26.235 and 30.0GHz (not limited to the frequencies) are respectively displayed, and the results are shown in fig. 1 and fig. 2. Fig. 1 is an observation result graph of 6 and 18 days in 2020, fig. 2 is a daily average value long-term variation graph of absolute solar radiation brightness temperature observed from 12 and 2019 to 2 months 2021, and fig. 3 is a comparison graph of the method provided by the present invention and the existing observation method, so that although there is no result which can be directly compared at the same frequency point, it can be seen from the distribution comparison of spectrum brightness temperature that the observation result of the method is closer to the previous observation, which shows that the method provided by the present invention can obtain more accurate observation results on the premise of convenient operation and simple calculation.
Claims (9)
1. A method for observing the absolute solar radiation brightness temperature by using a microwave radiometer is characterized by comprising the following steps of:
s1, calculating the azimuth angle and the altitude angle of the sun in real time;
s2, controlling a radiometer rotary table to enable the antenna to point to the sun, wherein the radiometer rotary table is an azimuth rotary table and a pitching rotary table;
s3, fixing the elevation angle of the antenna, controlling the azimuth and the pitching rotary table of the microwave radiometer in a stepping mode to enable the antenna to point to the center position of the sun, controlling the azimuth rotary table to rotate the antenna to carry out azimuth scanning on the sun, and observing the brightness temperature in each direction;
s4, moving the azimuth of the antenna to enable the sun to be far away from the center of the antenna beam, fixing the azimuth, controlling the antenna to tilt to scan the sky in elevation, and calculating the atmospheric attenuation of each elevation by using the tilt sky scanning data;
s5, calibrating atmospheric attenuation, and calculating the radiation brightness temperature of the antenna reached by the solar radiation scanned and observed when no atmospheric attenuation exists;
s6, calculating the ratio of the solid angle of the sun in the antenna beam according to the scanning observation result of S4, namely the filling factor of the sun in the antenna beam;
s7 calculating the absolute solar radiation light temperature according to S5 and S6 by using the light temperature and the filling factor observed by the antenna aiming at the solar central radiometer.
2. The method for observing the absolute solar radiation brightness and temperature by using a microwave radiometer as claimed in claim 1, wherein said S1 is used for calculating the solar azimuth angle a according to the spatial relationship between the day and the earth Z And elevation angle E l Specifically, the calculation is performed according to the following formula:
T 0 ＝(t s -12)·15°
(1)，
E l ＝arcsin(sinθ lat sinδ+cosδcosT 0 )
(2)，
in the formula (1) In, t s In the formula (2) and the formula (3), δ is solar declination, and θ is solar angle lat The latitude of the microwave antenna.
3. The method as claimed in claim 2, wherein the azimuth turntable is rotated at-10 ° to 10 ° on both sides of the azimuth of the sun in S3, and the sun is scanned to fit the maximum value of the solar temperature, i.e. the radiant solar temperature of the sun center, to eliminate pointing error.
4. The method of claim 3, wherein the step of providing the bright temperature report in S3 comprises: the solar radiation brightness temperature reaches the brightness temperature of the antenna and the self-radiation brightness temperature of the atmosphere after beam space averaging and atmospheric attenuation, and when the sun is in the antenna beam, the brightness temperature observed by the antenna is calculated according to the following formula:
when the sun is not within the antenna beam, the observed sky glow temperature is calculated as follows:
the brightness temperature of the solar radiation reaching the antenna through beam space averaging and atmospheric attenuation is obtained by subtracting the formula (4) and the formula (5), and the following formula is obtained after the subtraction:
in the formulas (4) to (6), the
Is the azimuth angle of the antenna, theta is the pitch angle, T m Mean radiant brightness temperature of atmosphere, T bg 2.75K is cosmic background radiation, Ω s For solid angle of solar beam, omega A Being the solid angle of the antenna beam, T' sun Bright temperature, T 'received when the sun was observed for radiometer' sky Atmospheric radiation brightness temperature, delta T ', received when atmospheric is observed for a radiometer' sun 2.75K is the bright temperature, T, of the solar radiation received by the radiometer after atmospheric attenuation in the antenna beam sun 2.75K is the mean radiant bright temperature of the sun, τ (θ) is the thickness of the atmosphere in the direction in which the antenna is pointed, and is related to the atmospheric conditions, only the elevation angle in a clear day or when the distribution of the atmosphere is uniform, and is not related to the azimuth.
5. The method for observing the absolute solar radiation brightness temperature by using a microwave radiometer as defined in claim 4, wherein the atmospheric attenuation at S4 is calculated according to the following formula:
6. the method for observing the absolute solar radiation brightness temperature by using a microwave radiometer according to claim 5, wherein the step S5 is performed to be attenuated and calibrated specifically as follows:
substituting the formula (7) into the formula (6) to carry out atmospheric attenuation calibration, and obtaining the following formula after finishing:
in the formula (8), Δ T sun The formula (8) is a bright temperature observation model of solar radiation reaching the antenna of the microwave radiometer.
7. The method for observing the absolute solar radiation brightness temperature by using a microwave radiometer according to claim 6, wherein the step S6 is specifically implemented as follows:
when the antenna of the S61 microwave radiometer scans the sun, the observed sunlight radiation brightness temperature calibrated by the atmosphere is expressed by the following formula:
ΔT sun (x，y)＝A d G(x，y) (9)，
in the formulas (9) and (10), x and y are the position difference between the center of the sun and the center of the antenna, A d The observed light temperature for the antenna aligned with the center of the sun, G is the antenna gain model, which can be expressed using a Gaussian model, θ A When the radiometer scans the sun, fitting the scanning data by using a Gaussian function model to obtain the beam width of the antenna;
s62 the filling factor of the sun in the antenna beam is expressed by using an antenna gain model, since the antenna gain model can be expressed by a gaussian function, when the antenna is directly opposite to the center of the sun, the filling factor R of the sun in the antenna beam can be obtained by integration, and the filling factor R is calculated according to the following formula:
in formulae (11) and (12), θ s Is the angular radius of the sun, r is the sun's radius, and d is the distance from the sun to the earth.
8. The method for observing the absolute solar radiation brightness temperature by using a microwave radiometer as defined in claim 7, wherein the distance d between the sun and the ground in S62 is calculated according to the following formula:
in equation (13), e is the eccentricity of the spherical orbit, e is 0.01672, a is the semi-major axis of the orbit, ω is the polar angle, where ω and d are periodic functions with respect to time, and the relationship between polar angle ω and time is expressed by the following equation according to keplerian's law and the elliptic orbit equation:
in the formula (14), T is the number of days counted from 1 month and 1 day, T is the number of days of a year, the polar angle of each day can be obtained by iterative calculation, and the precise sun-ground distance, the solar angle radius and the ratio of the solar solid angle to the antenna solid angle, namely the filling coefficient R can be obtained by substituting the formula (13), the formula (12) and the formula (11).
9. The method of claim 8, wherein the absolute solar radiation bright temperature at S7 is calculated according to the following formula:
in the formula (15), Δ T max The maximum value of the solar radiation brightness temperature obtained by observation of the radiometer after atmospheric attenuation calibration.
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