At the Edge of the Clouds
Learning from the Boundaries of Polar Mesospheric Clouds
Space weather can affect the weather we see on Earth’s surface, disrupt communications, and provide valuable insight into issues like climate change. There are many variables and much to learn, according to Brentha Thurairajah, an ECE research scientist who is studying the atmospheric dynamics surrounding polar mesospheric clouds—clouds that form about 84 km (52 miles) above Earth’s surface, usually at high latitudes.
Specifically, Thurairajah is looking at the sharp boundaries that sometimes separate these clouds from cloud free regions. Understanding these cloud structures will help answer the question of how energy is transported from the troposphere (the part of the atmosphere from Earth’s surface to about 14 km off the ground) to the mesosphere (about 50–85 km off the ground).
Looking at the data, the cloud areas are colder than the surrounding areas. “We think this phenomenon is similar to what we see on Earth, where fronts cause a boundary between warm and cold air, and influence the weather,” Thurairajah says.
One possible explanation is the presence of an inversion layer: an area where temperature increases with altitude instead of decreasing like it usually does in this part of the atmosphere. “We think this is caused by atmospheric gravity waves,” she says. We’re exploring whether these waves can propagate upward from the troposphere and influence the mesosphere.
The mesosphere is a gateway region between the atmosphere on the ground and geospace, she notes, “but our models have a missing piece about atmospheric gravity waves. They’re so small you can’t simulate them.” Thurairajah’s goal? To analyze data from different satellites to fit this missing piece into the puzzle.
Thurairajah is using data from two different satellites that have taken measurements of the same clouds and their environment: one from NASA’s Aeronomy of Ice in the Mesosphere (AIM) mission and one from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission.
Although Thurairajah notes that it’s challenging to get the right data from two separate satellites, she needs the different kinds of measurements each satellite can provide. She will characterize these front-like structures using images, coincident meteorological data, and gravity wave ray-tracing simulations.
Thurairajah hopes to show that the data and models agree, adding to our understanding of this part of the atmosphere, and of the atmosphere as a system.
Thurairajah has previously investigated other aspects of polar mesospheric clouds, including looking into how one hemisphere can influence the clouds in the opposite hemisphere. Her research continues adding pieces to the puzzle, helping us understand the world around us—and how it is impacted by the world above us.