CN113985489A - Method and device for obtaining earth surface microwave dielectric constant field - Google Patents
Method and device for obtaining earth surface microwave dielectric constant field Download PDFInfo
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Abstract
The invention provides a method and a device for acquiring a microwave dielectric constant field on the earth surface, wherein the method comprises the following steps: s1, acquiring vertical polarization and horizontal polarization microwave radiation brightness temperature data of a specified waveband in an observation range of the satellite-borne passive microwave sensor, and performing data preprocessing on the acquired dual-polarization microwave radiation brightness temperature data; s2, acquiring the surface physical temperature in the observation range of the satellite-borne passive microwave sensor; s3, acquiring the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of a specified waveband in the observation range of the satellite-borne passive microwave sensor; and S4, acquiring a microwave dielectric constant field of a specified wave band in the observation range of the satellite-borne passive microwave sensor. The invention utilizes the radiation data of the passive microwave satellite to carry out real-time, dynamic and large-area observation on the microwave dielectric constant field on the earth surface, can improve the observation efficiency and is used for the research on the real-time change of the global ground stress field and the geological disaster.
Description
Technical Field
The invention relates to the field of microwave remote sensing earth observation, in particular to a method and a device for acquiring a microwave dielectric constant field on the earth surface.
Background
The microwave radiation information of the earth surface (including land and sea) received by the passive microwave satellite sensor mainly depends on the physical temperature and microwave emissivity of the earth surface, the real part of the microwave dielectric constant (complex number) is a main factor influencing the microwave emissivity and the microwave radiation, and the imaginary part reflects the dielectric loss characteristic of the material. Compared with the surface microwave radiation change caused by the physical temperature change, the microwave radiation change caused by the surface microwave dielectric property change is more obvious. The existing research shows that the microwave dielectric constant of land ground objects (rock, concrete, soil and the like) can be influenced by factors such as stress change, humidity change and the like, and the microwave dielectric constant of the ocean water body can be influenced by factors such as bubble effect (caused by seabed stress change), waves, salt content and the like. The large earthquake is necessarily accompanied by the drastic change of the ground stress field before and after occurrence, and the stress change can cause the remarkable change of the dielectric property and the microwave radiation intensity of the land and the water body. The method estimates the microwave dielectric constant field on the earth surface in real time by using the radiation data of the passive microwave satellite, is favorable for researching the real-time change of the global crustal stress field, lays a foundation for the inversion of the crustal stress field by the passive microwave radiation satellite, and provides a possible path for the prediction of global sea and land strong earthquake.
The existing methods for testing the microwave dielectric constant of solid and liquid materials comprise a resonant cavity method, a transmission line method, a coaxial probe method, a space wave method and the like, require severe experimental conditions and strict experimental procedures, and cannot be popularized to global large-scale application. The satellite microwave remote sensing has the characteristics of large scale, all weather and the like, passive microwave radiation is closely related to the dielectric property of the ground object, and a clear and scientific theoretical calculation formula exists. The existing method for estimating the dielectric constant of the surface microwave by using microwave radiation data is limited to ground small-range observation. Therefore, there is a need in the art for a new method and apparatus for acquiring a large range of microwave permittivity fields from the earth's surface in real time.
Disclosure of Invention
The invention aims to provide a method and a device for acquiring a microwave dielectric constant field on the earth surface, which utilize dual-polarized satellite microwave radiation brightness temperature data and earth surface (land and ocean) physical temperature data of specified wave bands to automatically generate a real-time and dynamic global earth surface microwave dielectric constant field for real-time observation of global earth surface dielectric constant and research of geological disasters.
Therefore, the present invention firstly provides a method for obtaining a microwave permittivity field of the earth surface, comprising the following steps:
s1, acquiring vertical polarization and horizontal polarization microwave radiation brightness temperature data of a specified waveband in an observation range of the satellite-borne passive microwave sensor, and performing data preprocessing on the acquired dual-polarization microwave radiation brightness temperature data;
s2, acquiring the surface physical temperature in the observation range of the satellite-borne passive microwave sensor, wherein in the step S2, the position information and the time information of pixel-by-pixel centers in the vertical polarization microwave radiation brightness temperature data and the horizontal polarization microwave radiation brightness temperature data of the specified wave band acquired in the step S1 need to be utilized;
s3, calculating and obtaining the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of the appointed wave band in the observation range of the satellite-borne passive microwave sensor according to the vertical polarization microwave radiation brightness temperature data and the horizontal polarization microwave radiation brightness temperature data obtained in the step S1 and the surface physical temperature data obtained in the step S2;
and S4, acquiring a microwave dielectric constant field of the specified wave band in the observation range of the satellite-borne passive microwave sensor according to the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of the specified wave band in the observation range of the satellite-borne passive microwave sensor acquired in the step S3.
In a specific embodiment, the data preprocessing in step S1 includes the following steps:
s1.1, removing edge points of an observation range,
s1.2, removing abnormal points in the observation range,
s1.3, removing sea-land mixed points in the observation range,
the steps S1.1, S1.2 and S1.3 are in any sequence.
In a specific embodiment, the removing of the edge points of the observation range in step S1.1 includes setting a microwave radiation brightness temperature value corresponding to an X-circle pixel point at the outermost periphery of the obtained microwave radiation brightness temperature data to be a null value, where X is a natural number in 1-10.
In a specific embodiment, the removing of the abnormal points in the observation range in step S1.2 includes the following steps:
s1.2.1, dividing the acquired microwave radiation brightness temperature data into a plurality of sub-strips with the width of 1 pixel along the direction of the latitude line of the earth;
s1.2.2, clustering according to the earth surface coverage type of the corresponding position of each pixel in each sub-strip to obtain a plurality of pixel sub-classes with the same earth surface coverage type, and calculating the mean value mu and the variance sigma of all microwave radiation brightness and temperature values corresponding to each pixel sub-class;
s1.2.3, setting abnormal threshold values of K1= mu + Y sigma and K2= mu-Y sigma, and identifying the pixel points with the microwave radiation brightness temperature value larger than K1 or smaller than K2 in each pixel subclass as abnormal points, and setting the microwave radiation value of the corresponding position as null values; y is a natural number of 1-3;
s1.2.4, repeating S1.2.3 operations, and setting the microwave radiation brightness temperature values corresponding to the abnormal points of all the sub-strips as null values.
In a specific embodiment, the elimination of sea-land mixed points inside the observation scope in step S1.3 comprises the following steps:
s1.3.1, extracting coordinates (x, y) of center points of all pixels of the acquired microwave radiation brightness temperature data and pixel size;
s1.3.2, judging whether the range covered by each pixel has intersection with the global sea-land boundary line pixel by pixel according to the extracted pixel center point coordinates and the pixel size, and if so, setting the point as null value.
In one specific embodiment, step S2 includes the following steps:
s2.1, acquiring the verticality of the specified waveband in the observation range of the satellite-borne passive microwave sensorGeographic coordinates (x 1, y 1), observation time t and observation angle corresponding to single pixel in directly polarized and horizontally polarized microwave radiation brightness and temperature dataθThe vertical polarization and horizontal polarization microwave radiation brightness and temperature values are respectively recorded as
s2.2, searching a ground appearance station comprising a land observation station and a sea observation station in a range with (x 1, y 1) as a center and R as a radius, recording the geographical coordinates of the ground appearance station in the acquired range as { (xi, yi), i =2,3, … … n }, and recording the observed value of the surface physical temperature of the surface observation station at the time t as
S2.3, obtaining the surface physical temperature value of the pixel point with the geographic coordinate (x 1, y 1) through space weighting according to the surface physical temperature value of the surface appearance station obtained in the S2.2, and recording the surface physical temperature value as the surface physical temperature value
(ii) a Preferably, the calculation formula for obtaining the surface physical temperature value of the pixel point with the geographic coordinate (x 1, y 1) through spatial weighting according to the surface physical temperature value of the surface appearance station is as follows:
in the formulae (1) and (2),
is the physical temperature value of the pixel point with coordinates (xi, yi) at the time t
D is the euclidean distance between the pixel point with coordinates (x 1, y 1) in the obtained range and the coordinate (xi, yi) of the earth appearance station with the farthest distance;
and S2.4, repeating the operation of S2.1-S2.3 to obtain the surface physical temperature of all pixel points in the observation range of the satellite-borne passive microwave sensor.
In one specific embodiment, step S3 includes the following steps:
s3.1, according to the vertical polarization and horizontal polarization microwave radiation brightness temperature values of a single pixel point (x 1, y 1) in a specified wave band
And
surface physical temperature value
According to Rayleigh's Law, the vertical polarization microwave emissivity of the coordinate point (x 1, y 1) at the specified wave band f at the observation time t is calculated
And horizontally polarized microwave emissivity
：
And S3.2, repeating the operation of the S3.1 to obtain the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of the appointed wave band f of all the pixel points in the observation range of the satellite-borne passive microwave sensor at the observation time t.
In one specific embodiment, step S4 includes the following steps:
s4.1, according to the designation of the pixel point (x 1, y 1) acquired in the step S3The vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of the wave band f are establishedeFrequency offAngle of observationθAnd dielectric constant of microwave
The relationship between:
in the formulas (5) and (6), the dielectric constant of microwave
Is actually a complex number whose expression is
Wherein
Is the real part of the dielectric constant of the microwave,
is the imaginary part of the microwave dielectric constant;
s4.2, combining the formulas (3), (4), (5) and (6) in the S3.1 and the S4.1 to form an equation set as follows:
solving two unknowns, namely the real part and the imaginary part of the dielectric constant, by using the two equations (7) and (8), can be theoretically solved, but the analytic solution is too complex; therefore, the optimal numerical solution of the equation set is solved by adopting an iterative calculation mode, and the surface microwave dielectric constant with the coordinates (x 1, y 1) at the designated wave band f time t can be obtained
And S4.3, repeating the operations of S4.1 and S4.2 to obtain the surface microwave dielectric constant of the specified wave band f of all the pixel points in the observation range of the satellite-borne passive microwave sensor at the moment t, and further obtaining the microwave dielectric constant field in the observation range of the satellite-borne passive microwave sensor.
The invention also provides a device for acquiring the microwave dielectric constant field on the earth surface, which comprises:
the data acquisition module is used for acquiring real-time microwave radiation observation data of the earth surface and earth surface physical temperature data provided by earth surface observation stations;
the preprocessing module is used for preprocessing the satellite microwave radiation observation data acquired in real time;
and the estimation module is used for estimating the microwave dielectric constant of the earth surface in the observation range according to the obtained real-time microwave radiation observation data and the obtained earth surface physical temperature data.
In a specific embodiment, the data acquisition module includes: the earth surface microwave radiation data acquisition submodule is used for acquiring real-time on-orbit earth surface microwave radiation observation data of the satellite microwave radiation sensor and recording the geographic coordinate, observation time and observation angle of each pixel point in an observation range; the land surface physical temperature acquisition submodule is used for acquiring surface physical temperature observation data which are provided by a land observation station and are synchronous with surface microwave radiation data, and recording the geographic coordinate of each observation station and the observation time of each observation data; the ocean water surface temperature acquisition submodule is used for acquiring ocean surface physical temperature data which is provided by ocean observation stations and is synchronous with surface microwave radiation data, and recording the geographic coordinates of each observation station and the observation time of each observation data;
the preprocessing module comprises: the edge point removing submodule is used for removing edge pixel points in the observation range of the satellite passive microwave sensor; the internal abnormal point removing submodule is used for removing microwave radiation value abnormal points which possibly appear along the track direction; the sea-land mixed point removing submodule is used for removing a mixed pixel which has an intersection with a sea-land boundary line;
the estimation module comprises: the emissivity estimation submodule is used for calculating the microwave emissivity of the earth surface according to the obtained earth surface microwave radiation observation data and the earth surface synchronous physical temperature data and the Rayleigh Ginss law; and the dielectric constant solving module is used for solving the optimal numerical solution of the surface microwave dielectric constant through iterative calculation.
In step S1.2, the abnormal points in the track direction are removed from the acquired microwave radiation brightness temperature data. In step S2.3, the surface physical temperature of the target point is obtained by using the temperature data of the land observation station and the temperature data of the ocean observation station through space weighting. In steps S3 and S4, the earth surface microwave emissivity is calculated by using the earth surface microwave radiation observation data and the earth surface physical temperature data, and the earth surface microwave dielectric constant is estimated in an iterative mode.
In general, the invention utilizes the radiation data of the passive microwave satellite to carry out real-time, dynamic and large-area observation on the microwave dielectric constant field on the earth surface, can improve the observation efficiency and is used for the research on the real-time change of the global ground stress field and the geological disaster.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the embodiments will be briefly described below, and it should be understood that the drawings are provided to provide further understanding of the embodiments of the present invention and constitute a part of the specification, and together with the detailed description below, serve to explain the embodiments of the present invention, but do not constitute a limitation of the embodiments of the present invention. The attached drawings comprise:
FIG. 1 is a flow chart of one embodiment of the present invention.
FIG. 2 is a schematic diagram of sub-modules for acquiring surface microwave radiation observation data and surface physical temperature data according to one embodiment of the present invention. In fig. 2: 1. the method comprises the earth surface of land and ocean, 11 ground observation stations, 12 ocean observation stations, 2 observation ranges, 3 satellite-borne passive microwave sensors and 4 satellite orbit directions.
FIG. 3 is a schematic structural diagram of an apparatus for acquiring a microwave permittivity field of the earth's surface according to an embodiment of the present invention.
Detailed Description
In an embodiment of the present invention, as shown in fig. 1, in a first aspect, the present invention is a flowchart of a method for estimating a surface microwave dielectric constant field in real time by using surface microwave radiation observation data and surface physical temperature data, and the specific steps include:
s1, acquiring vertical polarization and horizontal polarization microwave radiation brightness and temperature data of a specified waveband in an observation range through a satellite-borne passive microwave sensor, and performing data preprocessing on the acquired dual polarization microwave radiation brightness and temperature data;
specifically, the satellite-borne passive microwave sensor is a passive remote sensing device for measuring heat radiation electromagnetic waves of earth surface microwave bands based on a satellite platform, preferably a satellite-borne microwave imager, and only receives radiation information of land, sea and atmosphere, and does not actively transmit microwave radiation information to the earth surface. The satellite-borne passive microwave sensor has the characteristics of multiband and dual polarization, and can observe microwave radiation information of the earth surface in different wavebands and different polarizations.
In the present embodiment, the vertically polarized and horizontally polarized microwave radiation data of 10.65GHz (the center frequency of the band) provided by the AMSR-2 sensor mounted on the AQUA satellite platform is selected, but this does not constitute a limitation to the selected band.
Further, the data preprocessing in step S1 includes the following steps:
s1.1, eliminating edge points of an observation range.
S1.2, removing abnormal points in the observation range.
S1.3, removing sea-land mixed points in the observation range.
Further, the elimination of the observation range edge points in the step S1.1 includes: and setting the microwave radiation brightness temperature value corresponding to the X circle pixel point at the outermost periphery of the acquired microwave radiation brightness temperature data as a null value. In this embodiment, X is an empirical value of 3. When the satellite microwave radiation sensor collects microwave radiation data and generates microwave brightness temperature data, error values may often occur at edge points of an observation range, and therefore the edge points need to be removed in advance before calculation.
Further, the elimination of the abnormal points in the observation range in step S1.2 includes the following steps:
s1.2.1, dividing the acquired microwave radiation brightness temperature data into a plurality of sub-strips with the width of 1 pixel along the direction of the latitude line of the earth. When the satellite microwave radiation sensor acquires earth surface data, a strip formed by periodic abnormal pixels occasionally appears along the track direction, so that the microwave radiation data along the satellite track direction needs to be divided along the direction of the latitude line of the earth, and further, earth surface temperature difference caused by different latitudes in sub-strips is avoided, so that abnormal values can be judged and eliminated conveniently. The size of the observation range in step S1 is, for example, several tens of kilometers by several tens of kilometers, or several hundreds of kilometers by several hundreds of kilometers. Specifically, the microwave radiation data with the same or substantially the same latitude is divided into the same sub-bands.
S1.2.2, clustering according to the earth surface coverage type of the corresponding position of each pixel in each sub-strip to obtain a plurality of pixel sub-classes with the same earth surface coverage type, and calculating the mean value mu and the variance sigma of all microwave radiation brightness and temperature values corresponding to each pixel sub-class.
S1.2.3, setting abnormal threshold values of K1= mu + Y sigma and K2= mu-Y sigma, and identifying the pixel points with microwave radiation brightness temperature values larger than K1 or smaller than K2 in each pixel subclass as abnormal points, and setting the microwave radiation values of the corresponding positions as null values; in this embodiment, the value of Y is 3, which is an empirical value, and the abnormal value in each band is removed by using the 3 σ principle. Within the limited observation range of the satellite microwave radiation sensor at a certain moment, the dielectric properties of the same ground objects in each sub-strip are similar, the microwave radiation values of the satellite microwave radiation sensor are concentrated near a certain characteristic value, and the microwave radiation values which deviate from the characteristic value and exceed the set threshold value are regarded as abnormal values.
S1.2.4 repeating S1.2.3 the operation, setting the microwave radiation brightness temperature value corresponding to the abnormal point of all sub-strips as null value.
Further, the elimination of sea-land mixed points inside the observation range in step S1.3 includes the following steps:
s1.3.1, extracting the coordinates (x, y) and the pixel size of the center point of all the pixels of the acquired microwave radiation brightness temperature data, wherein the specified wave band is 10.65GHz in the embodiment, and the pixel size of the AMSR-2 sensor data in the wave band is 50 km. Generally, the smaller the pixel size, the better, the higher the description accuracy; when the specified waveband is 10.65GHz, the size of the conventional pixel is 50km at least.
S1.3.2, judging whether the range covered by each pixel has intersection with the global sea-land boundary line pixel by pixel according to the extracted pixel central point coordinate and the pixel size, and if so, setting the point as null value. The sea-land boundary line data selected in this embodiment is a Landcover (0= sea, 1= land) data set provided by the NCEP FNL Operational Model Global Tropspheresis analysts.
S2, acquiring the surface physical temperature (Kelvin K) in the observation range of the satellite-borne passive microwave sensor;
further, the step S2 of acquiring the surface physical temperature in the observation range of the satellite-borne passive microwave sensor includes the following steps:
s2.1, obtaining geographic coordinates (x 1, y 1), observation time t and observation angle corresponding to a single pixel in vertical polarization microwave radiation brightness temperature data and horizontal polarization microwave radiation brightness temperature data of a specified waveband in an observation range of the satellite-borne passive microwave sensorθThe vertical polarization and horizontal polarization microwave radiation brightness and temperature values are respectively recorded as
S2.2 searching earth surface appearance stations (including land observation stations and ocean observation stations) in a range with (x 1, y 1) as a center and R as a radius, recording the geographic coordinates of the earth surface physical temperature stations in the acquired range as { (xi, yi), i =2,3, … … n }, and recording the earth surface physical temperature value at the time t as { (xi, yi), i =2,3, … … n }, wherein
. In this embodiment, if (x 1, y 1) is located in a land area, the R value is set to 200km, and if (x 1, y 1) is located in a sea area, the R value is set to 500km, the distribution density of land observation sites is generally greater than that of sea observation sites, and thus different search radii need to be set for different areas.
S2.3, obtaining the surface physical temperature value of the pixel point with the geographic coordinate (x 1, y 1) through space weighting according to the surface physical temperature value of the surface appearance station obtained in the S2.2, and recording the surface physical temperature value as the surface physical temperature value
In this embodiment, the selected calculation formula is:
in the formulae (1) and (2),
is the physical temperature value of the pixel point with coordinates (xi, yi) at the time t
D is the euclidean distance between the pixel point with coordinates (x 1, y 1) in the obtained range and the coordinate (xi, yi) of the earth appearance station with the farthest distance;
and S2.4, repeating the operations of S2.1-S2.3 to obtain the surface physical temperatures of all pixel points in the observation range of the satellite-borne passive microwave sensor.
S3, acquiring the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of 10.65GHz in the observation range of the satellite-borne passive microwave sensor;
further, the step S3 of acquiring the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of 10.65GHz within the observation range of the satellite-borne passive microwave sensor includes the following steps:
s3.1 according to the vertical polarization and horizontal polarization microwave radiation brightness temperature values of the pixel point (x 1, y 1)
And
surface physical temperature value
Calculating the vertical polarization microwave emissivity of the coordinate point (x 1, y 1) at the observation time t of the specified waveband 10.65GHz by utilizing Rayleigh's Law
And horizontally polarized microwave emissivity
：
And S3.2, repeating the operation of S3.1 to obtain the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of all pixel points in the observation range of the satellite-borne passive microwave sensor at the observation time t of the wave band of 10.65 GHz.
S4, acquiring the microwave dielectric constant field of the specified wave band in the observation range of the satellite-borne passive microwave sensor.
Further, the step S4 of acquiring the dielectric constant of the microwave in the specified wavelength band within the observation range of the satellite-borne passive microwave sensor includes the following steps:
s4.1, according to the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of 10.65GHz obtained in the step S3, establishing a microwave emissivityeFrequency offAngle of observationθAnd dielectric constant of microwave
The relationship between:
in the formulas (5) and (6), the dielectric constant of microwave
Is actually a complex number, expressed as
Wherein
The real part of the dielectric constant of microwaves having a frequency of 10.65GHz,
is the imaginary part of the dielectric constant of microwaves at a frequency of 10.65 GHz.
S4.2: the equations (3), (4) and (5), (6) in S3.1 and S4.1 are combined to form the following equation set:
the two unknowns are solved by the two equations (7) and (8), which can be solved theoretically, but the analytic solution is too complex. Therefore, the optimal numerical solution of the equation set is solved by iterative computation by using the optimest function in the embodiment, and the surface microwave dielectric constant with the coordinates (x 1, y 1) at the time t of 10.65GHz can be obtained
And S4.3, repeating the operations of S4.1 and S4.2 to obtain the surface microwave dielectric constant of all pixel points in the observation range of the satellite-borne passive microwave sensor at the time t of 10.65GHz, and further obtaining the microwave dielectric constant field in the observation range of the satellite-borne passive microwave sensor. The satellite passive microwave sensor continuously acquires earth surface data at the height of a fixed orbit, the real-time observation range of the satellite passive microwave sensor continuously changes along with t, the observation range of the satellite passive microwave sensor covers all positions of the earth surface along with time migration, and dynamic estimation results of the global earth surface microwave dielectric constant field can be acquired by continuously calculating microwave radiation data acquired in real time.
In a second aspect, the present invention provides an apparatus for acquiring a microwave permittivity field of the earth's surface, said apparatus comprising:
the data acquisition module 100 is configured to acquire real-time microwave radiation observation data of the earth surface and earth surface physical temperature observation data provided by an earth surface observation station;
the preprocessing module 200 is used for preprocessing satellite microwave radiation data of specified wave bands acquired in real time;
and the estimation module 300 is used for estimating the earth surface microwave dielectric constant in the observation range according to the acquired earth surface microwave radiation data and the earth surface physical temperature data.
Specifically, the data acquisition module 100 includes:
the earth surface microwave radiation data acquisition submodule 101 is used for acquiring earth surface microwave radiation observation data of an on-orbit specified wave band of the satellite microwave radiation sensor in real time, and recording the geographic coordinate, observation time and observation angle of each pixel point in an observation range;
the land surface physical temperature acquisition submodule 102 is configured to acquire surface physical temperature observation data provided by a land observation station and synchronized with surface microwave radiation data, and record a geographic coordinate of each observation station and observation time of each observation data;
and the marine water surface temperature acquisition submodule 103 is used for acquiring marine surface physical temperature data which is provided by the marine observation station and is synchronous with the surface microwave radiation data, and recording the geographic coordinates of each observation station and the observation time of each observation data.
Specifically, the preprocessing module 200 includes:
the edge point removing submodule is used for removing edge pixel points in the observation range of the satellite passive microwave sensor;
and the internal abnormal point removing submodule is used for removing the microwave radiation value abnormal points which possibly appear along the track direction.
And the sea-land mixed point removing submodule is used for removing the mixed pixels which have intersection with the sea-land boundary line.
Specifically, the estimation module 300 includes:
the emissivity estimation submodule is used for calculating the microwave emissivity of the earth surface according to the obtained earth surface microwave radiation observation data and the earth surface synchronous physical temperature data and the Rayleigh Ginss law;
and the dielectric constant solving module is used for solving the optimal numerical solution of the surface microwave dielectric constant through iterative calculation.
The above modules may be one or more integrated circuits (ASICs), or one or more microprocessors (DSPs), etc., configured to implement the operations described above.
In step S2.3 of the present invention, the formula (1) in the spatial weighting calculation method is only a preferred calculation method, and other methods that depend on the spatial distance between two points for weight matching should be regarded as being capable of achieving the object of the present invention. For example, the weighting is directly performed according to the inverse distance ratio between two points as shown in equation (9):
in addition, in step S2 of the present invention, the obtained surface physical temperature within the observation range of the satellite-borne passive microwave sensor may also be obtained by inverting the multi-channel infrared radiation brightness temperature synchronously obtained by other satellite-borne infrared radiation sensors at the same time.
Accordingly, the data acquisition module should include the following two parts:
the earth surface microwave radiation data acquisition submodule 103 is used for acquiring real-time on-orbit earth surface microwave radiation observation data of the satellite microwave radiation sensor and recording the geographic coordinate, observation time and observation angle of each pixel point in an observation range;
and the earth surface temperature acquisition submodule is used for acquiring earth surface temperature data obtained by inverting the multi-channel infrared radiation data of the satellite infrared radiation sensor, and recording the geographic coordinates of the pixel points corresponding to each earth surface temperature data and the observation time of each earth surface temperature data.
While the embodiments of the present invention have been described in detail with reference to the drawings, the embodiments of the present invention are not limited to the details of the embodiments, and various simple modifications can be made to the technical solutions of the embodiments of the present invention within the technical concept of the embodiments of the present invention.
Claims (10)
1. A method of obtaining a microwave permittivity field of the earth's surface, said method comprising the steps of:
s1, acquiring vertical polarization and horizontal polarization microwave radiation brightness temperature data of a specified waveband in an observation range of the satellite-borne passive microwave sensor, and performing data preprocessing on the acquired dual-polarization microwave radiation brightness temperature data;
s2, acquiring the surface physical temperature in the observation range of the satellite-borne passive microwave sensor, wherein in the step S2, the position information and the time information of pixel-by-pixel centers in the vertical polarization microwave radiation brightness temperature data and the horizontal polarization microwave radiation brightness temperature data of the specified wave band acquired in the step S1 need to be utilized;
s3, calculating and obtaining the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of the appointed wave band in the observation range of the satellite-borne passive microwave sensor according to the vertical polarization microwave radiation brightness temperature data and the horizontal polarization microwave radiation brightness temperature data obtained in the step S1 and the surface physical temperature data obtained in the step S2;
and S4, acquiring a microwave dielectric constant field of the specified wave band in the observation range of the satellite-borne passive microwave sensor according to the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of the specified wave band in the observation range of the satellite-borne passive microwave sensor acquired in the step S3.
2. The method according to claim 1, wherein the data preprocessing in step S1 comprises the following steps:
s1.1, removing edge points of an observation range,
s1.2, removing abnormal points in the observation range,
s1.3, removing sea-land mixed points in the observation range,
the steps S1.1, S1.2 and S1.3 are in any sequence.
3. The method according to claim 2, wherein the elimination of the observation range edge points in step S1.1 includes setting a microwave radiation brightness temperature value corresponding to an X-circle pixel point at the outermost periphery of the acquired microwave radiation brightness temperature data to be a null value, and X is a natural number in the range from 1 to 10.
4. Method according to claim 2, characterized in that the elimination of outliers inside the observation scope in step S1.2 comprises the following steps:
s1.2.1, dividing the acquired microwave radiation brightness temperature data into a plurality of sub-strips with the width of 1 pixel along the direction of the latitude line of the earth;
s1.2.2, clustering according to the earth surface coverage type of the corresponding position of each pixel in each sub-strip to obtain a plurality of pixel sub-classes with the same earth surface coverage type, and calculating the mean value mu and the variance sigma of all microwave radiation brightness and temperature values corresponding to each pixel sub-class;
s1.2.3, setting abnormal threshold values of K1= mu + Y sigma and K2= mu-Y sigma, and identifying the pixel points with the microwave radiation brightness temperature value larger than K1 or smaller than K2 in each pixel subclass as abnormal points, and setting the microwave radiation value of the corresponding position as null values; y is a natural number of 1-3;
s1.2.4, repeating S1.2.3 operations, and setting the microwave radiation brightness temperature values corresponding to the abnormal points of all the sub-strips as null values.
5. Method according to claim 2, characterized in that the elimination of sea-land mixing points inside the observation scope in step S1.3 comprises the following steps:
s1.3.1, extracting coordinates (x, y) of center points of all pixels of the acquired microwave radiation brightness temperature data and pixel size;
s1.3.2, judging whether the range covered by each pixel has intersection with the global sea-land boundary line pixel by pixel according to the extracted pixel center point coordinates and the pixel size, and if so, setting the point as null value.
6. The method of claim 1, wherein step S2 comprises the steps of:
s2.1, obtaining geographic coordinates (x 1, y 1), observation time t and observation angle corresponding to the center of a single pixel in vertical polarization microwave radiation brightness temperature data and horizontal polarization microwave radiation brightness temperature data of a specified waveband in the observation range of the satellite-borne passive microwave sensorθThe vertical polarization and horizontal polarization microwave radiation brightness and temperature values are respectively recorded as
s2.2, searching a ground appearance station comprising a land observation station and a sea observation station in a range with (x 1, y 1) as a center and R as a radius, recording the geographical coordinates of the ground appearance station in the acquired range as { (xi, yi), i =2,3, … … n }, and recording the observed value of the surface physical temperature of the surface observation station at the time t as
S2.3, according to the surface physical temperature value of the surface appearance station acquired in the S2.2, obtaining the surface physical temperature value of the pixel point with the geographic coordinate (x 1, y 1) through space weighting, and recording the surface physical temperature value as the surface physical temperature value
(ii) a Preferably, the surface physical temperature of the station is measured according to the surface appearanceThe calculation formula of the earth surface physical temperature value of the pixel point with the geographic coordinate (x 1, y 1) obtained by spatial weighting is as follows:
in the formulae (1) and (2),
is the physical temperature value of the pixel point with coordinates (xi, yi) at the time t
D is the euclidean distance between the pixel point with coordinates (x 1, y 1) in the obtained range and the coordinate (xi, yi) of the earth appearance station with the farthest distance;
and S2.4, repeating the operation of S2.1-S2.3 to obtain the surface physical temperature of all pixel points in the observation range of the satellite-borne passive microwave sensor.
7. The method of claim 1, wherein step S3 comprises the steps of:
s3.1, according to the vertical polarization and horizontal polarization microwave radiation brightness temperature values of a single pixel point (x 1, y 1) in a specified wave band
And
surface physical temperature value
According to Rayleigh's Law, the vertical polarization microwave emissivity of the coordinate point (x 1, y 1) at the specified wave band f at the observation time t is calculated
And horizontally polarized microwave emissivity
：
And S3.2, repeating the operation of the S3.1 to obtain the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of the appointed wave band f of all the pixel points in the observation range of the satellite-borne passive microwave sensor at the observation time t.
8. The method of claim 1, wherein step S4 comprises the steps of:
s4.1, establishing a microwave emissivity according to the vertical polarization microwave emissivity and the horizontal polarization microwave emissivity of the appointed wave band f of the pixel point (x 1, y 1) obtained in the step S3eFrequency offAngle of observationθAnd dielectric constant of microwave
The relationship between:
in the formulas (5) and (6), the dielectric constant of microwave
Is actually a complex number whose expression is
Wherein
Is the real part of the dielectric constant of the microwave,
is the imaginary part of the microwave dielectric constant;
s4.2, combining the formulas (3), (4), (5) and (6) in the S3.1 and the S4.1 to form an equation set as follows:
solving two unknowns, namely the real part and the imaginary part of the dielectric constant, by using the two equations (7) and (8), can be theoretically solved, but the analytic solution is too complex; therefore, the optimal numerical solution of the equation set is solved by adopting an iterative calculation mode, and the surface microwave dielectric constant with the coordinates (x 1, y 1) at the designated wave band f time t can be obtained
And S4.3, repeating the operations of S4.1 and S4.2 to obtain the surface microwave dielectric constant of the specified wave band f of all the pixel points in the observation range of the satellite-borne passive microwave sensor at the moment t, and further obtaining the microwave dielectric constant field in the observation range of the satellite-borne passive microwave sensor.
9. An apparatus for acquiring a microwave permittivity field of the earth's surface, said apparatus comprising:
the data acquisition module (100) is used for acquiring real-time microwave radiation observation data of the earth surface and earth surface physical temperature data provided by earth surface observation stations;
the preprocessing module (200) is used for preprocessing the satellite microwave radiation observation data acquired in real time;
and the estimation module (300) is used for estimating the microwave dielectric constant of the earth surface in the observation range according to the obtained real-time microwave radiation observation data and the obtained earth surface physical temperature data of the earth surface.
10. The apparatus of claim 9,
the data acquisition module (100) comprises:
the earth surface microwave radiation data acquisition sub-module (101) is used for acquiring real-time on-orbit earth surface microwave radiation observation data of the satellite microwave radiation sensor and recording the geographic coordinate, observation time and observation angle of each pixel point in an observation range;
the land surface physical temperature acquisition sub-module (102) is used for acquiring surface physical temperature observation data which are provided by a land observation station and are synchronous with surface microwave radiation data, and recording the geographic coordinate of each observation station and the observation time of each observation data;
the marine water body surface temperature acquisition submodule (103) is used for acquiring marine surface physical temperature data which is provided by a marine observation station and is synchronous with surface microwave radiation data, and recording the geographical coordinates of each observation station and the observation time of each observation data;
the pre-processing module (200) comprises:
the edge point removing submodule is used for removing edge pixel points in the observation range of the satellite passive microwave sensor;
the internal abnormal point removing submodule is used for removing microwave radiation value abnormal points which possibly appear along the track direction;
the sea-land mixed point removing submodule is used for removing a mixed pixel which has an intersection with a sea-land boundary line;
the estimation module (300) comprises:
the emissivity estimation submodule is used for calculating the microwave emissivity of the earth surface according to the obtained earth surface microwave radiation observation data and the earth surface synchronous physical temperature data and the Rayleigh Ginss law;
and the dielectric constant solving module is used for solving the optimal numerical solution of the surface microwave dielectric constant through iterative calculation.
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