Characteristics of CloudPrecipitation and the Impact of Weather Modification Activities on the Opening Day of the Beijing 2008 Olympics

Strong convective clouds existed in Beijing and its surrounding areas during the opening ceremony of the 2008 Olympic Games. Clouds developed vigorously especially in the directions of southwest and northeast. They moved towards Beijing city zone and an encirclement trend was formed. Such impending clouds and precipitation posed a significant threat to the ongoing ceremony activities at the National Stadium. According to the actual weather condition, weather modification organizations implemented cloud seeding operations by firing lots of special rockets to mitigate or suppress precipitation. Using the rainfall data of automatic weather stations, radar detection of clouds and precipitation, and two cloud parameters retrieved from satellite data, the authors analyzed the main characteristics of cloudprecipitation together with some physical evidence from weather modification activities during the period of the opening ceremony. The results displayed that strong convection developed in the southwest and northeast outskirts of Beijing in the evening and night on 8 Aug 2008. From 1900 LST to 2300 LST, precipitation was concentrated in Fangshan district and Huairou, Miyun county of Beijing. Strong convective clouds and the followed rainfall distribution in the north and northeast mainly moved slowly towards northeast. There also occurred a bit extending to the west and south. In the southwest, convective clouds stepped slowly after they entered into Fangshan district. The rainfall distribution moved toward northeast and posed a serious threat to the city zone and the National Stadium. Then the main body of it moved slowly toward southeast and finally away from Beijing. Combining with the sites distribution of groundbased rocket launchers and the operation time of cloud seeding, some changes of the macromicro characteristics of cloud and precipitation derived from automatic weather stations rainfall, radar detection, and satellite data retrieval showed that the intense large scale firing rockets and seeding clouds with AgI had played a certain role in inhibiting the formation and development of cloud and precipitation in the target area.