DEVELOPMENT AND CALIBRATION OF A K-BAND GROUND-BASED HYPERSPECTRAL MICROWAVE RADIOMETER FOR WATER VAPOR MEASUREMENTS

In this paper, a K-band ground-based hyperspectral microwave radiometer for atmospheric sounding is proposed, which improves the profile error and vertical resolution of moisture profiling under the high water vapor condition. The hyperspectral microwave radiometer (80 K-band spectral channels) can observe the rapidly changing weather with high sensitivity and accuracy of brightness temperature by using a stable high-speed receiver and an improved tipping calibration method. By combining several advantages of traditional microwave receiver, the MMIC receiver has good ultra-wideband performance, high linearity, and short measuring time. Moreover, through correcting the calibration parameters of traditional tipping calibration, the proposed calibration method can increase calibration accuracy based on the radiative transfer equation in the atmosphere. Measurement results demonstrate that the radiometer achieves a sensitivity of 0.1 K for 2 s of integration time and an accuracy of better than 0.77 K. For the water vapor profile, the variational retrievals method is used to extract the redundant information under the microwave hyperspectral condition. Preliminary comparisons of measured water vapor profiles with traditional results show good improvement of the profile error and vertical resolution.