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Fall 2003

Project Studies Night Clouds, Radar Echoes

Unusual and beautiful, noctilucent clouds glow in the northern twilight sky and may be an indication of global climate change. ECE’s Wayne Scales is studying these clouds and their relationship to strong radar echoes that often accompany them. (Photo by Pekka Parviainen, Polar Image)
ECE's Wayne Scales is developing a model that he hopes will help researchers understand high altitude clouds that glow electric blue in the evening sky and are generally considered indicators of global climate change.

Twilight Clouds of Electric Blue
Noctilucent clouds are the highest clouds in the earth's atmosphere: uncommon phenomena that typically glow electric blue, white, gold or red in the summer twilight of northern latitudes. Noctilucent clouds are often observed simultaneously with strong radar echoes—called polar summer mesospheric echoes (PSMEs)—in the 50 MHz to 1.3 GHz frequency range.

Noctilucent clouds have been increasing steadily since their discovery in 1885 and are believed to provide evidence of global climate changes on earth and indicators of the evolution and dynamics of the near earth space environment.

Relationship Between Clouds and Radar Echoes
With a $270,000 grant from the National Science Foundation (NSF), Scales and co-investigator Joseph Wang (AOE) are attempting to develop a model to explain the generation of PSMEs and their relationship to noctilucent clouds. "We believe that PMSEs may be a crucial remote sensing diagnostic for interpreting the creation, evolution, and dynamics of noctilucent clouds," Scales said.

Scales and Wang plan to develop a new model for PMSE generation based on the electrodynamic structure of noctilucent clouds. They are using data from simultaneous observations by rocket, radar, and lidar. Measurements of electron density, charged dust/aerosol density, and DC and AC electric field were taken in situ simultaneously with ground-based radar observations of PMSEs.

"Our model considers the boundary layer of the clouds as a primary source region for PMSE generation," Scales said. "Our investigation will provide a new methodology and approach to gaining fundamental insight into the importance of noctilucent cloud boundary layers."

Computationally Intense Simulations
The models and simulations are computationally intense and will be run on supercomputing facilities at Virginia Tech and the Jet Propulsion Laboratory (JPL).

Scales and Wang have extensive modeling and analytical experience with ice clouds in the upper atmosphere. Scales was a member of the team that first simulated the dust clouds of ice that form from rocket exhaust and can interfere with communication and navigation systems. Such electrically charged dusty clouds, including noctilucent clouds, are typically studied in the realm of dusty plasma physics.

 
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Last updated: Tue, Nov 4, 2003