The Constellation Observing System for Meteorology,Ionosphere,and Climate(COSMIC-2) has more powerful GPS receiver antennas,a twice higher sampling rate of 100 Hz,and a three times smaller inclination of 24° than those of COSMIC-1.COSMIC-2 will,therefore,provide an unprecedented ample number of radio occultation(RO) data in the tropics.Assimilation of RO data in the tropics is challenging due to unique features such as large horizontal gradients of refractivity,spherical asymmetry,and impact multipath in the moist tropical lower troposphere.Bending angle data assimilation in the tropical lower troposphere is done in this study using a two-dimensional(2D) limited-ray-path raytracing operator and a one-dimensional(1D) Abel transform operator.An impact multipath quality control(QC) developed in our previous study is incorporated to eliminate occurrences of impact multipath in bending angle simulations.The fractional differences in bending angle simulations between the limited-path-length raytracing operators and the original 2D raytracing operator have zero bias,and their standard deviations are more than three times smaller than those between the 1D Abel transform operator and the 2D raytracing operator.The highest accuracy and precision are achieved for the 2D limited-ray-path raytracing operator if the ray path is confined within±400 km.Use of the physically based impact multipath QC is shown to improve COSMIC data assimilation and forecast results using either the 1D Abel transform or the 2D limited-ray-path observation operators of bending angle in the tropical lower troposphere.