Scientists to decode the mystery of night-time thunderstorms

Armed with more than 100 scientific instruments, researchers from across North America are set to spend six weeks this summer probing night-time thunderstorms that mysteriously form without a prod from the sun's heat.

From June 1 to July 15, the researchers will study the nocturnal thunderstorms on the Great Plains, where storms are more common at night than during the day.

Also, called Great American Desert, the Great Plains form a major physiographic province of North America.

The research effort will use lab-equipped aircraft, ground-based instruments, and weather balloons to better understand the atmospheric conditions that lead to storm formation and evolution after sunset.

Their results may ultimately help improve forecasts of these devastating storms.

"Night-time thunderstorms are an essential source of summer rain for crops but are also a potential hazard through excessive rainfall, flash flooding, and dangerous cloud-to-ground lightning," said Ed Bensman from the US National Science Foundation.

"Weather forecast models often struggle to accurately account for this critical element of summer rainfall on the Great Plains," Bensman noted.

The NASA-supported Plains Elevated Convection at Night (PECAN) field campaign will involve scientists, students, and support staff from eight research laboratories and 14 universities.

Thunderstorms that form during the day are less puzzling than night-time storms. The sun heats the Earth's surface, which in turn, warms the air directly above the ground. When that warm air is forced to rise, it causes convection -- a circulation of warm updrafts and cool downdrafts -- and sometimes creates a storm.

The formation of thunderstorms at night, however, when the sun is not baking the land, is less well understood.

"At night, the entire storm circulation is elevated higher off the ground," PECAN principal investigator Tammy Weckwerth from US National Center for Atmospheric Research (NCAR) pointed out.

"This makes observations of the conditions leading to night-time thunderstorms much more challenging because that part of the atmosphere is not well covered by the network of instruments we normally rely on," Weckwerth noted.

The vast array of instruments available to PECAN researchers will allow them to collect data higher in the atmosphere, NCAR said in a statement.