Statistical estimations of atmospheric duct over the South China Sea and the tropical eastern Indian Ocean

In 2010–2012 spring, atmospheric duct observation experiments were performed throughout three open cruises over the South China Sea and the Tropical Eastern Indian Ocean. The data used for ducting analysis were measured by high resolution balloon-borne GPS radiosondes. Through data quality control and diagnostic analysis, the probability of ducting occurrence and characteristic quantities of the three typical ducts were given. The total percentage occurrence of evaporation duct, surface-based duct and elevated duct were 75.3%, 5% and 43.7%, respectively. The mean evaporation duct height was 15.3 m. The mean values of duct height, thickness and magnitude were 84.1 m, 14.9 m and 10 M-units for surfaced-based duct, and 1003.6 m, 62.2 m and 7.9 M-units for elevated duct. These preliminary statistical results can serve as a basis for future comprehensive and comparative studies of atmospheric duct for the research region.