Clouds may look tranquil from the ground, but inside them, tiny droplets and invisible electric fields are constantly shifting. Now, scientists have used a tethered balloon to make detailed measurements inside clouds over the Tibetan Plateau, revealing how aerosols shape cloud droplets and offering rare observations of weak electrical activity in clouds without lightning.
The field campaign, led by Dr. Husi Letu at the Aerospace Information Research Institute, Chinese Academy of Sciences, with collaborators from several Chinese institutions, reports a comprehensive tethered-balloon campaign specifically designed to simultaneously investigate cloud microphysics, aerosols, and electric fields over this vast high-altitude region. The initial findings are published in Advances in Atmospheric Sciences .
Clouds are central to Earth's climate and water cycle, yet their internal processes remain hard to observe. Aircraft sample clouds only briefly as they pass through. A tethered balloon, by contrast, can slowly ascend, descend, or hover inside a cloud, capturing how properties change over small vertical distances.
During a field campaign in Lulang, southeastern Tibet, researchers combined balloon measurements with ground observations and satellite data. The balloon carried instruments to measure cloud droplets, aerosols, meteorological conditions, and electric fields.
"With the tethered balloon, we can stay in the cloud and observe how its microphysical and electrical properties change with height," said Dr. Huazhe Shang, who helped design and coordinate the campaign.
The observations revealed a strong link between aerosols near cloud base and the droplets above. Clouds with more aerosols contained more droplets, but with smaller average sizes. Cloud water also increased with aerosol abundance. This relationship was especially clear under the relatively clean conditions of the plateau, where aerosol particles capable of forming droplets may strongly control cloud development.
Droplets generally grew larger and cloud water increased with height, consistent with vapor condensing as air rises. In some profiles, droplet numbers decreased—likely due to surrounding air mixing into the cloud.
"These observations raise the possibility that aerosols may play a more pronounced role in shaping cloud microphysics under clean conditions," said Dr. Hengqi Wang, who took part in the campaign from planning through execution.
Previous cloud-electrification studies focused mainly on thunderstorms. This campaign instead examined warm clouds without lightning. Observed electric fields were weak, with no clear linear relationship to droplet number or size, and field strength differed little inside versus outside the clouds. The findings suggest that in weakly electrified warm clouds, the local electric field may be shaped by the background atmospheric electrical environment, not just the cloud itself.
Yet "no lightning" does not mean "no electricity." Some field variability remained. Though much weaker than in thunderstorms, these perturbations could affect the electromagnetic environment experienced by aircraft and other flying platforms.
The campaign, in collaboration with several research institutions and universities across China, including the Institute of Tibetan Plateau Research, the Institute of Atmospheric Physics, Xi’an University of Technology, the National University of Defense Technology, the National Satellite Meteorological Center, Peking University, and Tsinghua University, demonstrates a powerful way to study clouds over complex terrain.
"This campaign is only a beginning," said Dr. Husi Letu, the corresponding author of the paper. "In the next step, we will coordinate multi-platform observations from aircraft, tethered balloons, satellites, and ground-based radars to further investigate and compare the microphysical and electrical characteristics of warm, mixed-phase, and ice clouds under different environmental conditions."
From a small tethered balloon floating into the clouds, scientists are opening a new window into the hidden world inside clouds.
Advances in Atmospheric Sciences
Exploring Cloud Microphysics and Electric Fields in Non-Lightning Clouds over the Third Pole: First Results from a Tethered-Balloon Campaign
22-Sep-2026