DOE’s Atmospheric Science Research Program Profiles Prof. Adele Igel

During a three-year ASR project, a California researcher is doing foundational work that will improve models of cloud cover in polar regions

Atmospheric scientist Adele Igel is an assistant professor at the University of California, Davis. She and her Cloud Physics Group investigate phenomena quite distant from the Mediterranean-like climate of California’s Central Valley: mixed-phase arctic clouds. (Those are the kind that contain both ice crystals and liquid cloud droplets.)

Much of the data for the ongoing arctic project, in fact, comes from northern Alaska, where temperatures are barely above freezing only 120 days a year and where the Arctic Ocean nudges the coastline.

Igel uses lidar and other measurements from that region for a 2018 to 2021 project funded by Atmospheric System Research at the U.S. Department of Energy (DOE). It looks at how surface aerosol concentrations are linked to the way mixed-phase arctic clouds dissipate.

Aerosols—ultrafine liquid and solid particles suspended in the air—influence cloud formation, precipitation, and surface energy budgets. The concentrations of aerosols in the region are extremely low.

If such cloud-aerosol links are absent or weak, how do such clouds―known to be persistent and common―sustain themselves?

An Arctic Aerosols-Clouds Puzzle

One explanation Igel and her team are exploring is what aerosol populations look like both above and below mixed-phase arctic clouds, which are low-lying and have tops averaging 2 kilometers (1.2 miles) high. So far, little is known about how the properties of aerosols vary with height in polar regions.Adele Igel, at right, poses with former student Shuang (Lea) Tong at the American Meteorological Society’s Polar Meteorology and Oceanography meeting in 2019. Tong’s poster, pictured, presented the first results from Igel’s ASR project. Photo is courtesy of Igel.

The fate and physics of these clouds are important. They persist for days or weeks at a time and influence the surface energy budget―how much solar energy comes and goes. Because of their longevity, mixed-phase arctic clouds have profound implications for seasonal ice melt and other phenomena impacting climate change. (Over land in midlatitude regions, in California, for instance, typical cumulus clouds have lifespans measured in hours.)

“From a climate standpoint, we care a lot about whether these low-level clouds are present or not,” says Igel, “particularly from the perspective of the surface-energy budget. They influence whether ice is growing or melting.”

Meanwhile, global models to date only poorly simulate such clouds. To address such deficiencies, Igel and her team are busy designing and testing high-resolution models for insight into the aerosol-cloud puzzle.

They want to unpack the relationship between cloud-dissipation events and aerosols, arriving at a sense of the microphysics involved. They also want to model vertical profiles of aerosol properties and draw a picture of those properties above and below the boundary layer.

The boundary layer is the part of the atmosphere nearest the ground. It is affected by transfers of heat, moisture, and momentum from the Earth’s surface.

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