Dislike Turbulent Flights?
This FAA Group Works to Make Your Ride Smoother
By Eric Spears and Tammy Flowe, FAA Office of NextGen
Pilots and passengers hate turbulence. The frequencies are full of pilots requesting “ride reports” and altitude changes from air traffic control to avoid bumpy air. It’s not about just comfort; turbulence can cause injury to passengers and crew, damage to the aircraft, or even lead to an accident. Help is on the way! To reduce turbulence-related accidents and injuries in the National Airspace System (NAS), the National Transportation Safety Board (NTSB) conducted a study to address forecasting, reporting, and additional risk-mitigation measures. The study generated a report that included over 20 recommendations to the FAA, the National Weather Service (NWS), and air carrier associations.
Although NTSB’s report indicated that there is still work to do in forecasting and mitigating the impacts of turbulence on aviation, the FAA has made great strides in its nearly 30 years of turbulence-related research and development (R&D).
Currently, the FAA’s NextGen Aviation Weather Division (AWD) is the office responsible for much of the FAA’s weather-related R&D work. AWD is made up of meteorologists, engineers, human factors scientists, and other professionals who research the effects of weather on the NAS and explore ways to mitigate its impact on aviation.
AWD’s work involves developing and transitioning new weather detection and forecasting capabilities and information to the NWS, as well as translating and integrating current and emerging weather information into the decision-support processes and tools for Air Traffic Managers, pilots, dispatchers, and airport operators.
“The NTSB report showed that while we’ve made significant progress in identifying areas of turbulence and intensity, as well as improvements in forecasting turbulence, there is still work to do,” said Randy Bass, AWD manager. “NTSB also highlighted one of our initiatives, the Graphical Turbulence Guidance (GTG) Nowcast (GTGN), and recommended it for transition into operations as soon as possible.”
AWD’s work in mitigating the potential effects of turbulence has traditionally been focused on observation and reporting of real-time turbulence information from aircraft (known as in situ), forecasting of turbulence for airspace operations, and nowcasting turbulence, which are extremely short-term forecasts for use in tactical decision-making.
Observation and Reporting Real-Time In Situ Turbulence Information
In the early 1990s, the FAA’s Aviation Weather Research Program (AWRP) began developing an automated turbulence reporting capability at the National Center for Atmospheric Research (NCAR). This capability would help address shortfalls in manual (i.e., not autogenerated) Pilot Reports (PIREPs), which today remain an important source of real-time information about turbulence that pilots encounter.
While there are several different methods for obtaining turbulence information from aircraft, the FAA chose to invest in NCAR’s Eddy Dissipation Rate (EDR) algorithm, which is installed on an aircraft’s avionics system and uses data from existing sensors (e.g., winds, pressure) as well as derived information from other existing sensors (e.g., angle of attack, roll angle) to calculate a measure of the atmospheric turbulence that an aircraft is transiting.
Because EDR is a measure of the state of the atmosphere, it is aircraft independent and applicable across airframe types. In 2008, the International Civil Aviation Organization (ICAO) named EDR the official metric for reporting in situ turbulence.
As of Sept. 10, 2021, there were more than 1,250 equipped U.S. aircraft, reporting an average of greater than 68,000 measurements per day. The FAA and the NWS actively use these data in the production and dissemination of weather advisories throughout the NAS.
In addition, the FAA’s Weather Technology in the Cockpit (WTIC) program is currently funding promising research to derive turbulence information from Automatic Dependent Surveillance-Broadcast (ADS-B) data. Thanks to the large number of ADS-B-equipped aircraft, ADS-B Turbulence has the potential to provide vast amounts of additional automated turbulence information to supplement in situ EDR data without the need for additional equipment and sensors installed on the aircraft. ADS-B Turbulence is still in development, but research conducted so far has shown an accuracy in reporting turbulence encounters in space and time and in identifying encounters with turbulence. The primary focus of the current research is to improve the output scaling so that ADS-B Turbulence outputs are consistently closer in value to in-situ EDR measures. The goal for these outputs is to have the same result in operational decisions as an in situ EDR output when encountering the same level of turbulence.
In the late 1990s, the FAA and NWS recognized the need for a forecast product specifically geared toward turbulence information. Initially under NWS funding and then transitioned to the FAA’s AWRP, NCAR developed the GTG product.
Implemented operationally in 2003, the first GTG product has undergone regular upgrades, with the current operational generation of GTG, GTG3, providing turbulence forecast at 13-kilometer (km) horizontal grid spacing for both clear-air turbulence and mountain-wave turbulence.
Furthermore, GTG3 presents data in 1,000-ft increments for all atmospheric levels from the surface to 45,000 feet, valid in 1-hour increments (out to 18 hours) and updated hourly. GTG3 products are available through the NWS’ aviationweather.gov website.
Currently in development by the FAA and planned for NWS operational implementation in 2023, GTG4 will add convectively induced turbulence as well as machine learning techniques and a finer horizontal grid spacing of 3 km. This finer grid space should greatly improve the detection of small-scale turbulence features that may not be revealed at the current 13 km spacing.
Another capability under development is a probabilistic forecast versus the deterministic forecast currently in use because this has become a global requirement in civil aviation. Additionally, the FAA is working in collaboration with the World Area Forecast System to update the current global GTG product with a probabilistic capability by 2026.
Nowcasting Turbulence Information for Tactical Decision-Making
While the previously mentioned operational GTG product is useful for strategic flight planning, it has long been recognized that, for useful cockpit applications, a short-term forecast — known as a nowcast — is necessary.
In 2007, the FAA began funding the development of GTGN at NCAR. GTGN uses the 1-hour GTG forecast (updated every 15 minutes with the current in situ EDR data) as well as PIREPs and weather radar-inferred in-cloud turbulence information to provide an extremely short-term forecast of turbulence.
Evaluations with airline users during development were highly positive, with some crewmembers calling it a “game-changer.” Since completing development in 2016, GTGN has undergone a formal Quality Assessment, a Technical Review Panel (TRP), and a Safety Risk Management Panel (SRMP) evaluation. Both the TRP and SRMP unanimously approved GTGN for transition to operations.
The FAA and NWS are actively collaborating on a transition plan with a proposed transition to operations in 2024. In the meantime, the FAA funds the production of GTGN at NCAR in a pseudo-operational mode. While this is not intended to be a permanent solution, users view the product as so promising that the FAA believes it is beneficial to the Agency to do so until it is operationalized by the NWS. Users are actively providing feedback on the pseudo-operational GTGN to NCAR, which is helping to improve the product.
Cockpit Turbulence Applications
The WTIC program sponsored the Remote Oceanic Meteorological Information Operational (ROMIO) project, which provides near-real-time contours of thunderstorm areas over oceanic regions using Cloud Top Height and Convective Diagnosis Oceanic (CDO) products. CDO depicts locations and intensities of convective weather areas. These products are updated frequently and can be transmitted to the cockpit during transoceanic flights every 15 minutes. Pilots can then use the contours to maintain distance from a storm at flight altitude to avoid the convective turbulence areas. While designed for use in the cockpit, it can also be used in Oceanic Air Route Traffic Control Centers as well as in Airline Operations Center flight dispatch operations.
In addition, WTIC recently completed a Technical Transfer Package for the Global Weather Note algorithm, which provides cockpit notification of impending turbulence or other adverse weather conditions within the next 3–20 minutes.
Global Weather Note runs on the ground, projecting each aircraft’s position forward in time (based on the aircraft’s flight plan, speed, and heading), and calculating a qualitative categorical turbulence severity (light, moderate, severe) based on a given weather grid and parameterized thresholds along the aircraft’s path.
Global Weather Note was recently merged into ROMIO to provide even more situational awareness information for aircrews and operators.
“Our focus is keeping the flying public safe. That’s what we’ve been doing for the last 30 years,” said Tammy Flowe, research meteorologist and turbulence project lead in the FAA’s NextGen Aviation Weather Division.
Eric Spears is a senior technical writer in the FAA’s NextGen Portfolio Management and Technology Development Directorate.Tammy Flowe is a research meteorologist and turbulence project lead in the FAA’s NextGen Aviation Weather Division.