Statistical characteristics of the surface ducts over the South China Sea from GPS radiosonde data
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摘要: 基于全球定位系统无线电探空近海面数据,南海近海表面波导进行了统计分析.结果表明,南海近海面波导年发生概率为64%,波导高度和强度主要分布在18-42 m和-0.3—0.2 M units/m,该部分占约80%;南海表面波导日变化缓慢,都超过60%,白天发生次数比黑夜多,但大部分都低于32m.另外,除了波导厚度几乎保持不变约33 m外,南海表面波导各项统计特征季节变化明显,其中发生概率最高为秋季为71%,其次为夏季、春季和冬季.在春季,表面波导顶高大都超过48 m.南海表面波导强度从春季到冬季逐渐变强,其强度梯度变化范围为-0.26—-0.16 M units/m.在考虑数据分辨率情况下,该结果与其他研究成果一致.该南海表面波导统计估计是可靠的,可为海上雷达探测及通信应用系统提供环境支持,也可为沿海气象雷达提供精确有用信息.Abstract: Based on the global position system (GPS) radiosonde data near the sea surface, the surface duct characteristics over the South China Sea (SCS) were statistically analyzed. The annual surface duct occurrence over the SCS was about 64%. Of the observed surface ducts, duct heights mainly distributed between 18 and 42 m, with M slopes in the range of -0.3 to -0.2 M units/m. Those ducts accounted for about 80% of the ducting cases. For the total profiles, the duct occurrences in a day changed slowly and were more than 60% in all times. The surface ducts formed more easily in the daytime than in the nighttime and most of the duct height were at bellow about 32 m. Additionally, The seasonal variation of the SCS ducts appeared to be evident, except that the mean duct thickness was almost constant, about 33 m for all seasons. The highest occurrence was about 71% in the autumn, followed by in the summer, spring and winter. In spring, their top-height existed more often at a height of more than 48 m. Their mean duct strength became stronger trend from spring to winter, with the M-slope in the range between -0.26 and -0.18 M units/m. Those results agreed well with other studies, provided considering the data resolution. The statistical analysis was reliable and gave the duct estimation for the SCS. Such duct climatology not only has important implications for communication systems and the reliability of the radar observation, but also can provide useful information to improve the accuracy of the meteorological radar measurements.
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Key words:
- GPS radiosonde /
- surface ducts /
- distribution /
- daily variation /
- seasonal variation
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