Statistical analysis of the occurrence probability and the characteristics of the lower atmospheric ducts in the Yellow Sea

Based on the radiosonde data of the Global Telecommunication System (GTS) from 2010 to 2018, the occurrence probability and the characteristic quantities of the lower atmospheric ducts at eight stations around the Yellow Sea are statistically analyzed. The results show that the annual occurrence probability of the lower atmospheric ducts around the Yellow Sea is 20%−50%, and the occurrence probability in the eastern stations is higher than the western. The top height and intensity of surface duct are about 100 m and 10 M unit respectively, the cut-off frequency does not exceed 1500 MHz, and the critical angle is greater than 0.2°. The top height, layer bottom height and bottom height of elevated duct are generally between 1000 and 2000 m, the intensity is about 10 M unit, the cut-off frequency does not exceed 300 MHz, and the critical angle is greater than 0.2°. The monthly occurrence probability of the lower atmospheric ducts at each station is the lowest in winter, and the distributions of Gwangju and Gyeonggi in the eastern Yellow Sea are similar, while the distributions of Dandong, Dalian and Chengshantou in the northwest Yellow Sea are consistent. The monthly occurrence probability of the entire Yellow Sea is lowest in winter, not exceeding 20%, and gradually increases in spring, reaches more than 40% in summer, begins to decrease in October, and the downward trend continues into winter, while is closely related to the meteorological changes in the Yellow Sea. The statistical results can serve as a reference for the design and operation of radio systems such as radar and communication in the Yellow Sea.