Statistical analysis of signatures and contributing factors of atmospheric ducts based on the sounding data

As one special type of atmospheric refraction, duct can make VHF-band radio waves and above form transhorizon propagation, playing an important role in communication and radar detection. So it is necessary to study the characteristics and contributing factors of duct. Based on the sounding data in Qingdao during 2005-2013, the signatures of duct, temperature inversion and intense humidity gradient are analyzed. The results of statistic show that temperature inversion and intense humidity gradient have a bearing on the occurrence of ducts while the effect of intense humidity gradient is more remarkable and direct compared to temperature inversion.