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MicroWave Radiation Imagers (MWRIs) onboard the afternoon FengYun-3B (FY-3B) and midmorning FengYun-3C (FY-3C) satellites provide global observations almost 4 times a day at any location. This study examines the diurnal cycle of the liquid water path (LWP) over the southeast Pacific Ocean using MWRI data. A double-difference calibration method is first used to evaluate the MWRI calibration bias based on Tropical Rainfall Measuring Mission Microwave Imager (TMI) measurements. LWP diurnal cycle characteristics are derived from FY-3B/C MWRI data measured in 2014. The diurnal variation of LWP from combined FY-3B/C MWRI measurements are consistent with that derived from Tropical Rainfall Measuring Mission Microwave Imager data. Maximum and minimum LWPs occurred in the early morning and afternoon, respectively. The largest diurnal amplitude (similar to 40% of the mean LWP) was located near 85 degrees W/20 degrees S. The diurnal amplitude varied from season to season. MWRI data can provide important constraints for models simulating the cloud diurnal cycle.

Plain Language Summary MicroWave Radiation Imager (MWRI) dual-polarization measurements at 10.65, 18.7, 23.8, 36.5, and 89GHz can be combined to retrieve the liquid water path (LWP) in the atmosphere over ocean surfaces. The Chinese FengYun-3B and FengYun-3C satellites provide MWRI observations during their midmorning and afternoon orbits, respectively, allowing the diurnal variations of LWP to be observed globally by such polar-orbiting satellites. The diurnal variations of LWP are important for understanding hydrometeorological processes in the atmosphere and for validating LWP numerical weather prediction models. It is shown that in 2014, FengYun-3B and FengYun-3C MWRI-derived LWP retrievals compared well with those derived from the Tropical Rainfall Measuring Mission Microwave Imager over the southeast Pacific Ocean. The intensity of the diurnal cycle varied from season to season and the largest diurnal amplitude (similar to 40% of the mean LWP) was located near 85 degrees W/20 degrees S.