Characteristics of the atmospheric ducts over the South China Sea pre- and post-monsoon onset in 1998

摘要

The atmospheric duct has great scientific significance and great value for propagations of radio waves and functions of surveillance equipments. Based on the Global Positioning System (GPS) sounding data during the South China Sea (SCS) Monsoon Experiment (SCSMEX) in 1998, the characteristics of the atmospheric duct were analyzed pre- and post-summer monsoon onset. The occurred probability of the atmospheric ducts became lower after the summer monsoon onset. The heights of the duct layers over the north SCS were elevated and those of the south SCS were reduced by summer monsoon prevailing. But duct-height amplitudes of variation in altitude were all within 300 m. In addition, except that the duct strength of the north SCS changed a little during the active summer monsoon period, the other duct parameters of the SCS decreased especial duct characteristics of the south SCS such as about 40 m in thickness and 1 M unit in strength. Those changes of the duct characteristics indicated the summer monsoon had important influence on the duct environment over the SCS.