Title: GPS RO Bending Angle Data Assimilation Using a Limited-ray-path 2D Raytracing Operator and an Impact Multipath Detection Algorithm
Lecturer: Prof. Xiaolei Zou （1 Earth System Science Interdisciplinary Center (ESSIC), University of Maryland；2 Joint Center of Data Assimilation for Research and Application, Nanjing University of Information Science & Technology）
Date: Friday, May 17, 2019 at 14:00 PM
Venue： Lecture Hall D103, School of Atmospheric Sciences
Abstract： The Constellation Observing System for Meteorology, Ionosphere and Climate, COSMIC-2, have more powerful GPS receiver antennas, a twice higher sampling rate of 100 Hz, and a three times smaller inclination of 24o than those of COSMIC-1. Therefore, COSMIC-2 will provide unprecedented ample number of radio occultation (RO) data in the tropics. Assimilation of RO data in the tropics is challenging due to unique features of large horizontal gradients of refractivity, spherical asymmetry and impact multipath in the moist tropical lower troposphere. In this study, a two-dimensional (2D) limited-ray-path raytracing operator and a one-dimensional (1D) Abel transform operator are used for bending angle data assimilation in the tropical lower troposphere. An impact multipath detection algorithm is developed in our previous study is incorporated to eliminate occurrences of impact multipath in bending angle simulations. The fractional differences of 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 if the ray path is confined within 400 km for the 2D limited-ray-path raytracing operator. It is finally shown that use of the physically based impact multipath quality control improves 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.