In the Clouds

This is the second installment of In the Clouds, a new educational campaign from the North Dakota Department of Water Resources.

How does cloud seeding affect the development of precipitation in a cloud?

Silver iodide or dry ice is released in the updraft or placed directly in the cloud. Both are excellent at attracting and freezing supercooled water droplets at warmer temperatures than other particles in the atmosphere.

The ice crystals that grow large enough to fall toward the ground melt into raindrops along the way. Seeding enhances the ability of the cloud to produce raindrops large enough to reach the earth.

To reduce a potential hailstorm, seeding provides more ice particles for droplets to attach to, making more, smaller particles and spreading the energy of the storm over a larger area.

Not all clouds are good candidates for seeding

For warm weather cloud seeding, only clouds that possess a sustained updraft of moist air, lack natural ice, and grow to heights cold enough to contain supercooled liquid water droplets are suitable for cloud seeding.

Why does hail sometimes fall from seeded storms?

Storm structure (seeding works better on some storm types than others).
The ability to seed targeted storms safely and effectively (sometimes safety criteria preclude effective treatment of targeted storms).
Working with limited resources (sometimes there are more storms occurring at one time than there are resources available to adequately seed them at the time).

Who seeds clouds and what kind of training is required?

The Atmospheric Resource Board (ARB) manages contracts for aircraft, seeding equipment, and pilots for cloud seeding operations. Pilots must meet specific certification and flight-time requirements, while meteorologists need a bachelor’s degree in meteorology or Atmospheric Science. The ARB also runs an intern program with the University of North Dakota’s John D. Odegard School of Aerospace Sciences, offering hands-on training for weather modification intern pilots. Additionally, meteorology students can gain summer experience as intern meteorologists at the Bowman and Stanley radar sites. Before each project, the ARB conducts a ground school to cover all key aspects of the program.

In our third and final installment of In the Clouds, we will focus on the economics behind cloud seeding programs, and what the dollar-impact is in North Dakota.

CONTACT: Cam Wright

camwright@nd.gov

701.328.2782