Monitoring of the ducting by a ground-based GPS receiver
Sheng Zheng (盛峥)a b, Fang Han-Xian (方涵先)a
a College of Meteorology and Oceangraphy, PLA University of Science and Technology, Nanjing 211101, China; b Sate Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, China
Abstract In this paper, we describe the estimation of low-altitude refractivity structure from simulation and real ground-based GPS delays. The vertical structure of the refractive environment is modeled using three parameters, i.e., duct height, duct thickness, and duct slope. The refractivity model is implemented with a priori constraints on the duct height, thickness, and strength, which might be derived from soundings or numerical weather-prediction models. A ray propagation model maps the refractivity structure into a replica field. Replica fields are compared with the simulation observed data using a squared-error objective function. A global search for the three environmental parameters is performed using genetic algorithm. The inversion is assessed by comparing the refractivity profiles from the radiosondes to those estimated. This technique could provide near-real-time estimation of ducting effect. The results suggest that ground-based GPS provides significant atmospheric refractivity information, despite certain fundamental limitations of ground-based measurements. Radiosondes typically are launched just a few times daily. Consequently, estimates of temporally and spatially varying refractivity that assimilate GPS delays could substantially improve over-estimates using radiosonde data alone.
Fund: Project supported by the National Natural Science Foundation of China (Grant No. 41105013); the National Natural Science Foundation of Jiangsu Province, China (Grant No. BK2011122); the Specialized Research Fund for State Key Laboratories, China (Grant No. 201120FSIC-03); and the City Meteorological Scientific Research Fund, China (Grant No. IUMKY&UMRF201111).
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