A weather-monitoring balloon from Nanjing University has been missing since Dec. 5, literally gone with the wind after its string was accidentally cut. A wanted notice for the missing balloon went viral among Nanjing citizens after the university called for help on its official graduate student WeChat platform.

According to the platform, the balloon belongs to a research team led by Professor Wang Tijian, also vice dean of the School of Atmospheric Sciences. It was used for data monitoring on several indices such as wind, temperature and ozone, as well as PM2.5 and PM10 pollutant density.

The balloon was monitored 24 hours a day, with 12 students divided into three groups to supervise the equipment and collect data every three hours.

"It got blown away because the wind suddenly picked up. At that height, the wind speed was about 10 meters per second. It flew up and down with the wind and the string was severed when it approached a construction site, probably by the reinforcing bars. Then we also lost its GPS signal, perhaps because it approached the downtown area where conflicting signals were strong," explained a team member.

Wang said the loss of the balloon meant not only economic damage, but more importantly disruption of the team's research due to missing data.

"If it was blown away, the data it collected during that strong wind must be of great value," the professor pointed out.

Team members said this was not the first weather balloon that has gone missing due to strong winds; such equipment often becomes stuck on rooftops or in trees.