Microwave radiometer, also known asMicrowave radiometer, which is used to receive various objects within the antenna field of viewradiation、scatteringorreflexAnd equivalent transform it into blackbodytemperatureA kind of passive microwaveremote sensingElectronic instrument。It can penetrate clouds, work day and night, and receive fog, rain, snow, etcmeteorologicalAdvantages of less impact.In addition, it also has the ability to observe the characteristics under the surface of the object, and can obtain infrared andvisible lightAdditional information not available.[1]
Chinese name
Microwave radiometer
English name
microwave radiometer
definition
The utility model relates to an atmospheric remote sensing instrument that passively receives the electromagnetic radiation energy in the microwave band.
Applied discipline
Atmospheric Science (Level I Discipline), Atmospheric Detection (Level II Discipline)
Microwave radiometer, also known asMicrowave radiometer, which is used to receive various objects within the antenna field of viewradiation、scatteringorreflexAnd equivalent transform it into blackbodytemperatureA kind of passive microwaveremote sensingElectronic instruments.It can penetrate clouds, work day and night, and receive fog, rain, snow, etcmeteorologicalAdvantages of less impact.In addition, it also has the ability to observe the characteristics under the surface of the object, and can obtain infrared andvisible lightAdditional information not available.[1]
working principle
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Microwave radiometer is usedmicrowaveThe microwave receiver that carries out remote sensing to detect the ground objects is used to detect the atmosphere, ocean, vegetation andsoilAnd so on, whiledata processingAs an important part of the microwave radiometer, the and control unit undertakes all the driving and control functions, and has strict requirements on timing and accuracy.Because the system requires high reliability, the single chip microcomputer is used as the core of the numerical control unit of the 220GHz microwave radiometer. Through precise timing control, data acquisition, antenna control, state extraction, serial communication and other functions are realized.At the same time, the NC unit has the characteristics of low power consumption, high sampling accuracy, simple interface, etc.Microwave radiometer is a passive ground-based microwave remote sensing device that uses passive reception and microwave signals of temperature radiation from various heights to judge temperature and temperature curves. Microwave remote sensing starts later than visible light and infrared remote sensing.But compared with visible light and infrared remote sensing, microwave radiometer can work around the clock.Visible remote sensingIt can only work in the daytime. Although infrared remote sensing can work at night, it cannot penetrate clouds.Microwave radiometer is a highly sensitive receiver for measuring microwave thermal radiation of objects.Retrieve the brightness temperature of the observed target by measuring the radiation power received by the antenna;The measured physical quantity is brightness temperature (K).The radiation energy received by the radiometer antenna comes from the transmitted radiation and reflected radiation of the ground object. According to the Rayleigh Kings formula, the power transmitted by the object is proportional to the temperature.The emission characteristics of objects are characterized by radiometric brightness temperature.The main parameters characterizing the performance of microwave radiometer areTemperature resolution(Sensitivity) andspatial resolution (angular resolution).[2]
Principle of measuring sea surface temperature with microwave radiometer: the wavelength of microwave is 0.1~100 cm, and microwave can be subdivided intoMillimeter wave, centimeter wave, decimeter wave, etc.Microwave is characterized by its ability to penetrate clouds and fog and its all-weather operation.Microwave remote sensing is divided intoActive microwave remote sensingAnd passive microwave remote sensing.Without considering the contribution of various particles in the atmosphere, the sea surface brightness temperature Tb (f) detected by the microwave radiometer has a simple relationship with the sea surface temperature TS.takeRayleigh-Jeans Law Substitute into the formula to obtain T (f, θ, φ, TSST)=e (f, θ, φ) TSST (1) where T (f, θ, φ, TSST) represents the sea surface brightness temperature detected by the microwave radiometer;TSST is the temperature of a thin layer of seawater on the sea surface, which represents the thermodynamic temperature of the sea surface. Of course, it is slightly different from the sea surface temperature measured by the conventional bucket water extraction method at a certain depth.If the sensor is located on a platform at a sufficient height above the sea surface, such as an aircraft or satellite, atmospheric correction should also be considered, that is, the spontaneous emission term of atmospheric air and atmospheric transmissivity factor should be supplemented in Formula (1).According to Kirchhoff's law, the relationship between the emissivity e of calm sea surface and the Fresnel reflectivity ρ is e HV (f, θ, φ)=1 - ρ HV (f, θ, φ) (2), where the subscripts H and V represent the horizontal and vertical polarization states of electromagnetic waves respectively;F is the microwave frequency;θ is observedZenith angle, which represents the included angle between the observation direction of the satellite and the sea surface normal, referred to as the observation angle or incidence angle for short;φ is the azimuth angle, which represents the included angle between the observation direction of the radiometer and the wind direction[2]
Basic composition
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Microwave radiometer is actually a highly sensitive receiver receiving irregular noise signals.The signal it receives is weak incoherent and uncontrollable noise, which has no essential difference from the noise signal generated by the elements and devices inside the receiver.In order to measure the received external noise, it is necessary to eliminate the output voltage generated by the internal noise at the terminal. The most effective way to eliminate the voltage is to continuously compare the antenna output and the output of the standard noise source.
The typical microwave radiometer is provided with spatial resolution byMicrowave antennaIt is composed of a receiver that provides frequency selection and amplification, a square law wave pickup that ensures that the output voltage is proportional to the radiation power of the receiving voltage, a signal processor that eliminates the internal noise and outputs the voltage at the terminal and obtains the radiation temperature output, and equipment that processes, records, and displays data.[1]
classification
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The radiometer can be classified according to its use and characteristics.According to the working environment, it can be divided into laboratory, ground field, airborne and spaceborne radiometers;It can be divided into radio astronomyAtmospheric sounding, mapping and tracking radiometer;According to the circuit characteristics, it can be divided into full power radiometer, modulation radiometer, correlation radiometer and phase switch radiometer;In addition, it can also be divided into two categories: the lock switch and the non lock switch.[1]
Application occasions and tasks
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Microwave radiometer is mainly used for medium and small scaleWeather phenomenon, such as storm, lightningHeavy rainfall, fog, ice and boundary layer turbulence.For small and medium-sized weather disasters generated or dissipated in a short time, although they are only regional, some events are more harmful.In the process of monitoring mesoscale weather phenomena,Sounding balloonandweather radarIt is a commonly used means.Sounding balloons will be limited by time and space;The weather radar data is basically limited to the lack of rainfall without rainfall;There are large errors in satellite remote sensing data within 5km from the ground.The emergence of passive ground-based microwave radiometer fills the gap in the monitoring of the above research methods and is an effective complementary means.Microwave radiation can work independently in almost all kinds of environmental conditions, and is very suitable for automatic weather stations.It is used to retrieve the complete atmospheric profile, and the retrieved data and original data are all saved.Provide complete customized or global standard algorithms.The main applications are as follows: temperature, humidity and liquid water in tropospheric profile, weather and climate model research, satellite tracking (GPS, Galileo) wet/dry delay and humidity profile,Proximity forecastAtmospheric stability (disastrous weather detection),temperatureInversion detection, fog, air pollution, absolute calibration cloud radar, wet/dry delay correction VLBI technology.
In 2021, China will establish a microwave radiometer observation network in the troposphere of the Qinghai Tibet Plateau, which can conduct real-time continuous unattended observation in almost all weather conditions.
In June 2024, Qinghai Tibet Plateau Research Institute, Chinese Academy of SciencesThe scientific research team obtained the connection of tropospheric atmospheric profiles on the Qinghai Tibet Plateau for the first timeObserved data for the next three yearsIt can provide data support for the research on the weather process and environmental change of the Qinghai Tibet Plateau, and the forecast of severe weather approaching.[4]
Surface telemetry of upper troposphere temperature
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The atmospheric temperature stratification can be remotely measured by measuring the brightness temperature at different elevation angles with the microwave radiometer at the frequency of 52-56 GHz on the ground.The temperature in the upper troposphere (above 500mb) is measured remotely at a frequency of 53.1 GHz.[3]
