Spaceborne radar-based precipitation retrieval: Sensitivity analysis

The accuracy of the FY-3G PMR prototype algorithm is evaluated using the data of GPM KuPR. Based on the result, the sensitivity of precipitation rate retrieval to initial relation of $R$- $D_{\mathrm{m}}$, phase, and the correction factor paramNUBF for NUBF is analyzed. Firstly, the $R$- $D_{\mathrm{m}}$ relation of stratiform and convection are adjusted and the DSD profiles, radar reflectivity factor profiles, and precipitation rate profiles are compared. Secondly, sensitivity experiments are conducted to analyze the impact of phase misjudgment on the accuracy of precipitation rate retrieval. Finally, the sensitivity of paramNUBF to precipitation rate retrieval is evaluated by setting different paramNUBF. The results indicate that the FY-3G PMR prototype algorithm is well consistent with GPM KuPR in the retrieval of precipitation structure and intensity distribution, and the relative error is less than 10% while the correlation coefficient is greater than 0.95. The retrievals of radar reflectivity factor profiles and precipitation rate profiles are not sensitive to $R$- $D_{\mathrm{m}}$, but the retrieved DSD profiles are relatively more sensitive to $R$- $D_{\mathrm{m}}$. Misjudgment of phase in the bright band layer, especially between mixed phase state and solid or between mixed phase state and liquid state, affects precipitation rate retrieval near the 0 degree layer but has little impact on ground precipitation rate retrieval. ParamNUBF is a highly sensitive factor, and the greater the difference from the true value, the greater the error of the precipitation rate profile. The sensitivity analysis on spaceborne radar precipitation rate retrieval algorithms can not only deepen our understanding of precipitation rate retrieval theories and methods and improve the accuracy of precipitation rate retrieval, but also provide design ideas for the upcoming field experiments of FY-3G PMR.