Noctilucent clouds are rare ‘space clouds’ that are believed to be sensitive indicators of global climate trends. Too high to reach by aircraft yet too low to reach by satellite, IIAS explores these clouds using balloons and human-tended payloads on suborbital spacecraft through its research affiliate, Project PoSSUM.
What Are Noctilucent Clouds?
Noctilucent clouds are the highest clouds in the Earth’s atmosphere, 83 km (50 miles) and are observed slightly below the mesopause in the polar summertime. These clouds are of special interest, as they are sensitive to both global climate change and to solar/terrestrial influences. The first recorded sightings of noctilucent clouds were reported in 1885 and both satellite and ground-based observations over the past four decades have indicated that the presence of these clouds has been increasing in both frequency and brightness. Scientists now realize that these clouds are very sensitive indicators for what is going on in the atmosphere at higher altitudes as small changes in the atmospheric environment can lead to large changes in the properties of these clouds. Further, since these clouds form on condensation nuclei through cold temperatures and the presence of water vapor – and these properties of the mesosphere are tied to carbon dioxide and methane, the anthropogenic causes of climatic change may be directly related to the presence of noctilucent clouds.
Balloon Noctilucent Cloud Imagery
PoSSUM members, working together with Integrated Spaceflight Services, develop high-altitude balloon camera systems as part of the NASA-Funded PMC Turbo Experiment. PMC Turbo flew over Greenland and Nunavut in July 2018, obtaining imagery of unprecedented resolution and data from the first balloon-borne lidar.
PMC-Turbo: A NASA-Funded Noctilucent Cloud Mission
Chief Scientist Dr. Dave Fritts and Executive Director Dr. Jason Reimuller were selected as part of a $1.4M NASA-funded experiment to fly PoSSUM camera systems on a high-altitude, unmanned balloon in support of the imagery experiment around the Arctic polar vortex for six days in July 2018. Project PoSSUM works in partnership with GATS, Columbia University, and Integrated Spaceflight Services. PoSSUM Graduates are engaged in the instrument development, operations, and educational outreach efforts in this novel experiment that will study atmospheric dynamics that can only be viewed in exquisite detail through very high resolution imagery techniques.
Science Objectives
The images obtained during the campaign will be used to analyze how waves generated at lower altitudes dissipate via instability and turbulence processes. These processes account for the deposition of significant energy and momentum transported by the waves from lower altitudes. They also play key roles in weather and climate throughout the atmosphere, but are poorly understood at present. Imaging of noctilucent clouds provides a unique window on these processes that is not available at any other altitude. Thus, this largely inaccessible region has the potential to educate us about important processes occurring throughout the atmosphere.
Airborne Noctilucent Cloud Tomography
Fundamentally, high-resolution time-lapse imagery may be used to test theories of noctilucent cloud formation, sublimation, advection and gravity wave perturbations. Together with the Royal Canadian Air Force (RCAF), Columbia University and the University of Alberta, PoSSUM graduates observe and analyze the time evolution of the noctilucent cloud field over many hours from high-resolution cameras designed for high-altitude balloon flight that will be coordinated with ground and satellite observations. PoSSUM has worked with the RCAF to make these measurements from a CT-155 ‘Hawk’ high performace aircraft and also led citizen science research campaigns from High Level, Alberta as part of AER 103, where airborne observations using a Turbo Mooney aircraft are coupled with two ground stations, one near High Level, AB. and the other near Garden Creek, AB. The research aircraft will fly a carefully-crafted flight plan at altitudes of up to 21,000’ employing scientific camera systems qualified for high-altitude balloon and suborbital noctilucent cloud imagery.
IIAS Royal Canadian Air Force Noctilucent Cloud Research
IIAS studied noctilucent clouds using a CT-155 ‘Hawk’, training aircraft, thanks to CAE, located at the Royal Canadian Air Force’s 15 Wing at Moose Jaw, Saskatchewan. Operating from the Edmonton International Airport, a series of night flights were conducted along the 56th parallel at altitudes of up to 45,000 ft. From these altitudes, the IIAS team was able to image fine structures of noctilucent clouds that the team hopes will reveal more about the highly complex patterns of turbulence and instability in our upper atmosphere. The research was coordinated with NASA’s Science Mission Directorate’s PMC Turbo balloon, led by PoSSUM Chief Scientist Dr. Dave Fritts, which was the first dedicated mission to explore the small-scale dynamics of our mesosphere.
PoSSUM Airborne Noctilucent Cloud Research
PoSSUM airborne noctilucent cloud campaigns have several objectives: 1) validate camera systems on noctilucent clouds structures, 2) characterize jitter and focal capability in varying flight environments, 3) obtain imagery data to assist preliminary design of image algorithms, 4) perform tomographic imagery synchronous with ground station(s), and 5) facilitate EPO efforts.
Coordinated Ground Noctilucent Cloud Observation
As noctilucent clouds are widely believed to appear more frequently, strongly and at more equatorial latitudes in the past decade, their study using ground-based observation surveys becomes paramount to attempt to understand why and how they do so. Thanks to the combined development of IT and social media, the more affordable imaging technology and a general increase of NLC awareness in the general population, more reports are correlatively being made.
PoSSUM Citizen-Science Noctilucent Cloud Research
In 2018, IIAS EPO, science communication coordinator Adrien Mauduit created a Facebook group called ‘Noctilucent clouds around the World’, aiming firstly at alerting NLC-chasing amateurs of possible cloud appearance as well as sharing their reports among them. As the platform quickly grew, the opportunity arose of a citizen-science based project to survey seasonal occurrence of NLC by gathering each willing participant’s yearly reports in one place. As it has been done in recent years for aurora research, we want to demonstrate that social media platform can contribute to NLC science thanks to bulk worldwide reports that would not have been possible using a network of a few cameras.
Each citizen participant of the group has been urged to provide a report sheet at the end of this 2019 northern hemisphere NLC season. It will contain their number of total sightings, and for each of them, a detailed description with the location (coordinates), date, time, direction, brightness and duration. Finally each report will be documented by a picture taken by the citizen scientist. By forming a consistent and extensive database through the social media group, we want to study the inter-seasonal and geographical variation in NLC occurrence.