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Next Generation Air Transportation

Turbulence

Background

The Next Generation Air Transportation System (NextGen) is now beginning to take shape on the design board of several federal agencies under the auspices of the Joint Program Development Office (JPDO). The JPDO has parsed the complex next generation system into several components and has endorsed the concept of Interagency Working Groups to coordinate the R&D associated with each. One such Working Group is dedicated to developing the weather information needs of NextGen and providing common weather–related decision information to all stakeholders within the system. The NextGen System is a national priority to meet the air transportation needs of the U.S. in the 21st century – in particular, a significant growth in demand for air traffic services, possibly on the order of three times today's demand levels. Since weather conditions can seriously restrict aircraft operations and levels of service available to system users, the manner by which weather is observed, forecast, disseminated, and used in decision–making is of critical importance.

In situ measurements

InSituFig. 1

Verification of the in situ eddy dissipation rate (EDR, m 23/s) measurements against pilot reports (PIREPs) continued, and International Civil Aviation Organization (ICAO) documentation on the algorithm was completed. Fleet–wide implementation of the winds–based EDR algorithm on the Delta Airlines 737–800 fleet (70 aircraft) was completed. Initial implementation of the algorithm on the Southwest Airlines 737–700 fleet (280 aircraft) was begun and will be completed in FY10. These implementations were based on heartbeat (tied to routine Meteorological Data Collection and Reporting System (MDCRS) reporting) and threshold reports (immediate transmission when one–minute peak or mean above a certain threshold is exceeded), thus substantially reducing communication costs from previous implementations.

An example of EDR reports received from the DAL fleet over a 24–hr time period is shown in the figure above. The colors are peak EDR values. We are currently in discussions with United Airlines to implement the algorithm on their Airbus A320 (97 aircraft) and B–777 (52 aircraft) fleets which will provide expanded national coverage as well as some international coverage.

A feasibility study using ACARS–AMDAR wind and temperature measurements to estimate EDR was completed. Initially this was used to construct a global climatology of turbulence, but with expanded data coverage may also allow real–time estimates of turbulence levels. A description of this method was written up and has been accepted for publication in the Journal of Applied Meteorology and Climate (JAMC).

Remote sensing measurements

Remote_SensingFig. 2 Feasibility studies of using GPS scintillation measurements continued.

Development and implementation of the second version of the NEXRAD Turbulence Detection Algorithm (NTDA–2) which provides observations of in–cloud turbulence levels (EDR) continued in response to recent changes to NEXRAD operational modes (super–resolution, phase coding, and new volume coverage patterns), which will provide improved accuracy and coverage. A mosaic of the NTDA–2 product based on 133 NEXRADs over the CONUS has been prototyped and is running operationally at NCAR. An example of the mosaic NTDA display is shown below. Discussions are in progress with United Airlines to provide them cockpit uplinks of flight specific NTDA–derived turbulence, similar to what was done in FY08.

An example of EDR reports received from the DAL fleet over a 24–hr time period is shown in the figure above. The colors are peak EDR values. We are currently in discussions with United Airlines to implement the algorithm on their Airbus A320 (97 aircraft) and B–777 (52 aircraft) fleets which will provide expanded national coverage as well as some international coverage.

A feasibility study using ACARS–AMDAR wind and temperature measurements to estimate EDR was completed. Initially this was used to construct a global climatology of turbulence, but with expanded data coverage may also allow real–time estimates of turbulence levels. A description of this method was written up and has been accepted for publication in the Journal of Applied Meteorology and Climate (JAMC).

Nowcasting/forecasting

NowcastFig. 3 A WRF–based GTG system was retuned for operational use over the Taiwan airspace.

The Graphical Turbulence Guidance version 2 (GTG2) which provides RUC–based forecasts of turbulence should become "operational" and available on NOAA's Operational ADDS web site (http://adds.aviationweather.gov/turbulence/) in early CY10. It is currently available to users through the Experimental ADDS web site (http://weather.aero/turbulence/). This product produces forecasts of clear–air turbulence sources out to 12 hours, and is updated hourly at 1000 ft increments from 10,000 to 45,000 ft MSL. Work will continue to more efficiently use the high density of in situ EDR measurements within the next version of GTG (GTG3) which will also include all flight levels from the surface to 45,000 ft.

FY2009 Accomplishments:

Work continued on the GTG nowcast (GTG–N) product, which combines all observations of turbulence (including NTDA–2, in situ EDR, pilot reports, and satellite–based diagnostics) with GTG3 analyses to produce a NAS–wide representation of turbulence updated at 15 minute intervals. The GTG–N product also provides estimates of near cloud convectively–induced turbulence (CIT), and substantial effort has been invested in developing both a better physical understanding of the mechanisms responsible for CIT (two papers have been published on this in FY09 and another is in preparation) and development of an ingredients–based CIT diagnostic algorithm (DCIT).

FY2010 Plans:

An initial version of a global turbulence forecast (Global GTG) product has been developed in FY09 and will continue to be improved in FY10. The global product also provides rapid updates of satellite–derived convection locations and intensities (cloud top heights). These forecasts use Global Forecast System (GFS) model data, which can be used to provide upper–level turbulence forecasts globally out to 36 hours. The figure below is an example of the combined cloud–top (magenta), turbulence forecast (green–yellow–red) product as well as observations from in situ EDR data and pireps.

Juneau Terrain-Induced Turbulence

FY2009 Accomplishments:

RAL continued operation and maintenance of the prototype warning system (JAWS–P). In December 2008 the Executive Council of the FAA approved completion of the system and directed RAL to proceed with implementation of the JAWS–H version (a "hybrid" containing an FAA communications front end and the NCAR developed algorithm and display back end). The JAWS–H architecture was developed, and hardware was procured and installed at the Juneau International Airport. The FAA communications equipment was integrated into the JAWS–H rack and communications paths from mountaintop sensors and from wind profilers was tested. New software was developed for JAWS–H and a prototype version loaded in Juneau for testing.

FY2010 Plans:

In FY10, RAL will continue to operate the prototype warning system. A new JAWS–H software version will be released and loaded early in FY2010, and the JAWS–H system will be evaluated in a side–by–side comparison with JAWS–P to ensure continuity of alerts. Once the evaluation is satisfactorily completed, the JAWS–P system will be shut down and dismantled, and JAWS–H will commence operations. At that point the FAA will start taking over some maintenance activities from NCAR. Documentation of the JAWS–H system will continue and several documents will be delivered to the FAA for inclusion in their technical manuals. The end–state JAWS Operational Ready Date is still on schedule for the end of FY2011.