Filling observational gaps in spaceborne precipitation radars

Abstract This study analyzed long-term data from the Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR) and the Dual-frequency Precipitation Radar (DPR) aboard the Global Precipitation Measurement (GPM) Core Observatory to determine inconsistencies in observation characteristics and irregular statistics related to precipitation intensity. Reference statistics were employed to quantify the effects of three observational gaps: the low-level precipitation profile (LPP) and shallow precipitation deficiency (SPD), both arising from the incidence angle dependence, and the weak precipitation deficiency (WPD), attributable to limited sensor sensitivity. The findings revealed that the LPP, the SPD, and the WPD contributed to considerable underestimation of precipitation, particularly at large incidence angles, in high-latitude areas, low-precipitation zones, and mountainous regions. Adjusting for these gaps increased overall TRMM PR precipitation estimates by approximately 12% and GPM DPR Ku-band Precipitation Radar (KuPR) precipitation estimates at higher latitudes by approximately 19%. These increases result from improved vertical representation of precipitation intensity at low altitudes and more consistent statistics for shallow and weak precipitation. Compared to the TRMM PR, the GPM DPR KuPR demonstrated stronger adjustment effects for LPP and SPD, whereas the influence of WPD was less substantial. By accounting for these effects, along with sensitivity degradation and increased clutter altitude following the orbit boosts of both satellites, the reliability of long-term, large-scale variability data is improved. Overall, this study underscores the importance of sustaining and enhancing high-precision observations of precipitation structure to resolve statistical patterns that are otherwise challenging to capture.