Retrieval Method And Application Of Multichannel Ground-based Microwave Radiometer

China is one of the countries which are most likely and frequently affected by the meteorological disaster. In order to reduce the huge threat of disastrous weather to the agriculture and national economy, the more modernized meteorological observation techniques should be developed to improve the ability of the weather modification. The ground-based multi-channel microwave radiometer (MMR) works using passive receiving way and without the need for external electromagnetic waves emitted. In addition, the MMR has the unique advantages of small volume, low power consumption, and long continuous working time, unattended and facilitate networking. In some developed countries, the MMR has replaced the radiosonde balloons and played crucial roles on the research fields, such as, the numerical weather prediction, the weather modification and climate change. In this paper, we developed a set of retrieval of atmospheric temperature and humidity and liquid water profile algorithm for the comparative observation in the satellite-based radar calibration flight test and estimating the path integration of radar attenuation by using the observational datasets of the TP/WVP-3000(12channels). In addition, we successfully developed the principle prototype of the ground-based microwave radiometer MWP967KV (35channels), designed a set of the methods of calibration and an inversion algorithm for the atmospheric temperature and humidity profile. Furthermore, we developed a software control system for radiometer and realized the real time visualization by using Visual VC++, and compared with the field observations.First, the historical radiosonde data is grouped into two types:cloud and cloud free after the data conversion and interpolation processing for the recent two decades. Then, the microwave brightness temperature set of cloud free conditions is calculated by using MWMOD Microwave Radiative transfer model. According to the relative humidity profile, we simulated the liquid water profile and the corresponding brightness temperature by using the adiabatic liquid water content model analysis method. Using the revised calculation model of BP neural network, we get the regionally representative coefficient by training neural network, for the inversion calculation of atmospheric temperature, water vapor density, relative humidity and liquid water profile. Compared with the GPS sounding data, the derived profile of atmospheric temperature below the7Km height has the error is within3K, the derived water vapor density profile below the6Km height has error within3g/m2, and the derived results are very good at the lower level, which is accordant with the observational data based on the GPS. At the same time, the derived cloud water profile can make up the shortages of the GPS sounding via estimating the path integration attenuation, therefore the MMR can be used for testing radar precipitation inversion.From2009to2013, Lanzhou University and Xi’an Electronic Engineering Research Institute, jointly developed the microwave radiometer principle prototype for the ground-based MWP967KV (35channels) successfully, which can detect the water vapor with the band in22-30GHz, the oxygen with the band in51～59GHz, and the brightness temperature measurement range from0to400K with the precision of0.5K. In addition, we developed successfully the system of radiometer, including antenna turntable, composition, receiver, data processing unit, realized the overall design, the integration of multi sensor integration, compact dual band antenna assembly, small step multi-channel radiation sweep frequency detection, and realize the combination of the cold and heat source of artificial calibration and automatic calibration measures. We mastered the small high performance millimeter wave antenna assembly technology, broadband low sidelobe millimeter feed technology, broadband low loss millimeter wave beam distribution technology, high performance millimeter wave broadband antenna technology, broadband parametric intensive channel receiver technology, weak signal detection technique, precision high frequency multi sensor integrated design technology, and so on.Based on the hardware of the microwave radiometer MWP967KV, we designed the calibration method and procedure of a radiometer; developed a ground-based35channel radiometer inversion algorithm based on MWMOD microwave transmission mode and the neural network technology, and achieved the retrieval of atmospheric temperature and humidity, liquid water profile and accumulated water vapor and cloud water content. The vertical resolution:50m@0～500m,100m@500m～2km,250m@2～10km. At the same time, we developed the software system, the radiometer storage technology of complex data and the real-time visual image display technology by using Visual VC++development environment. Then, we developed a ground-based microwave radiometer MWP967KV (35channels) for the comparative analysis and the test validation. Based on the MWP967KV, eight observational tests are carried out in Shaanxi, Hebei, Beijing, Gansu, Jilin, Shanxi and other six provinces or cities to verify the accuracy of MWP967KV. The accumulated working time is more than six thousand hours. Comparison results show that, the difference between the brightness temperature values on K band and the sounding simulation is less than1K, with the correlation coefficient greater than0.98. As for V band, the correlation coefficient is above0.99. Compared with the radio sounding, the average deviation of the derived temperature profile is less than2K; the maximum error of the derived water vapor profiles is less than1.5with the correlation coefficient of more than0.98; the correlation coefficient between the derived integral moisture value and the observational data of MP-3000can reach0.989. MWP967KV is independently developed China, which is an automated, multifunctional atmospheric microwave remote sensing detection equipment with high precision and international advanced level. It not only provides a powerful instrument equipment support for China’s meteorological sounding and weather modification, but also has an important value for the weather changes in the real-time, continuous monitoring and theoretical research.