Inversion for atmosphere duct parameters using real radar sea clutter
Sheng Zheng(盛峥)a)b) and Fang Han-Xian(方涵先)a)†
a. Institute of Meteorology, PLA University of Science and Technology, Nanjing 211101, China;
b. Sate Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, China
Abstract This paper addresses the problem of estimating the lower atmospheric refractivity (M profile) under nonstandard propagation conditions frequently encountered in low altitude maritime radar applications. The vertical structure of the refractive environment is modeled using five parameters and the horizontal structure is modeled using five parameters. The refractivity model is implemented with and without a priori constraint on the duct strength as might be derived from soundings or numerical weather-prediction models. An electromagnetic propagation model maps the refractivity structure into a replica field. Replica fields are compared with the observed clutter using a squared-error objective function. A global search for the 10 environmental parameters is performed using genetic algorithms. The inversion algorithm is implemented on the basis of S-band radar sea-clutter data from Wallops Island, Virginia (SPANDAR). Reference data are from range-dependent refractivity profiles obtained with a helicopter. The inversion is assessed (ⅰ) by comparing the propagation predicted from the radar-inferred refractivity profiles with that from the helicopter profiles, (ⅱ) by comparing the refractivity parameters from the helicopter soundings with those estimated. This technique could provide near-real-time estimation of ducting effects.
Fund: Project supported by the National Natural Science Foundation of China (Grant No. 41105013), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2011122), and the Specialized Research Fund for State Key Laboratories, China (Grant No. 201120FSIC-03).
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