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5. Providing World-Class Observational Facilities and Services

NCAR Strategic Priority: Developing New Instrumentation

Highlight: Advanced Weather Radar Techniques for Aviation


RAL is working under the sponsorship of the FAA's Aviation Weather Research Program to develop radar products that will utilize current and future capabilities of weather radars to support the detection and prediction of aviation hazards.  This leads to two very different tasks: implementing and obtaining approval for operational deployment of new radar algorithms; and conducting research and development of radar products that will utilize future capabilities of weather radars.

FY2007 Accomplishments

RAL scientists have worked for more than 15 years to improve the detection of turbulence.  Over the past several years they have developed the  NEXRAD Turbulence Detection Algorithm (NTDA), a new approach to processing data from the National Weather Service’s network of Next Generation Radars (NEXRADs). While aviation users commonly use reflectivity from onboard radars or ground-based radar mosaics to gauge the intensity of a storm, the NTDA detects the wind variations that can shake an aircraft.  By directly measuring the in-cloud turbulence intensity, the NTDA will provide airline dispatchers, air traffic managers, and pilots an important new source of information for tactical turbulence avoidance.  The performance of the NTDA was evaluated via comparison with research aircraft data and automated in situ turbulence reports from commercial aircraft, and it was shown to have good skill.  RAL scientists and engineers also prototyped a 3-D Mosaic of NTDA turbulence measurements and are currently collaborating with National Severe Storms Laboratory on further development and implementation of an operational, real-time version that will cover the contiguous U.S.  Finally, a RAL investigation into the NEXRAD spectrum width measurement technique revealed a problem with its accuracy that can limit the NTDA’s ability to discriminate null from light or light-to-moderate turbulence.  Following presentations at a conference and a TAC meeting, the FAA has formally requested that the accuracy requirements for NEXRAD spectrum width be tightened and that the implementation of a RAL-developed technique that provides improved accuracy be considered.

Techniques are also under development to determine whether precipitation detected with dual-polarization radars is rain, snow, mixed-phase, or freezing drizzle. Activities this past year focused on evaluating both polarimetric and non-polarimetric radar products for detecting the freezing level (essentially establishing the lower boundary of potential icing layers in the atmosphere) and the designation of freezing drizzle conditions in the terminal area.  These products are being developed in conjunction with a polarimetric radar-based Hydrometeor Classification Algorithm (HCA) for detecting winter weather hazards for the aviation community.  Results from case studies show good skill.

FY2008 Plans:

NTDA has won final approval from the NEXRAD Technical Advisory Committee (TAC) and the NEXRAD Software Recommendation and Evaluation Committee, and the software package has been delivered to the NEXRAD Radar Operations Center. Final testing and deployment are expected to occur in Summer 2008.  A pilot program with United Airlines to test the uplink of the NTDA to the cockpit is expected to be expanded. Changes to the WSR-88D NEXRAD radars (super-resolution, range-velocity mitigation techniques, dual-pol, etc.) will necessitate a maintenance upgrade, the NTDA-2.  This product, which will also contain an improved data quality algorithm, will be implemented and will begin the approval process for inclusion in the NEXRAD system.  The NTDA 3-D mosaic will continue to undergo development and testing.

RAL scientists and engineers, in conjunction with the In Flight Icing team, will begin implementation of real-time versions of the freezing level and freezing drizzle algorithms.  This will allow for the evaluation and ultimately inclusion of these products into icing hazard detection algorithms such as RAL’s Current Icing Potential (CIP).

The national network of WSR-88Ds is targeted to be upgraded for dual-polarimetric capabilities beginning in FY08.  Specific long-term project goals are to develop remote sensing capabilities for discriminating between rain and snow, designating icing conditions in the terminal area (freezing drizzle and rain) and in-cloud, quantifying winter precipitation in support of aircraft deicing operations, and estimating precipitation-impacted visibility. 


Objective Plume Detection

HIAPER Instrumentation

The Microwave Temperature Profiler (MTP) is a passive radiometric sensor that measures brightness temperature at multiple frequencies and elevation angles. Retrieval algorithms applied to the measurements yield temperature profiles above and below the aircraft. Earlier versions of the MTP were developed and deployed by Jet Propulsion Laboratory (JPL) which is tasked to build a customized MTP for the NCAR G-V aircraft (HIAPER). JPL and NCAR staff are working together to certify and install the sensor on the G-V. The JPL Principal Investigator, Michael Mahoney, will also provide training to NCAR staff on sensor operation and maintenance, as well as data processing, quality control, and analysis.

FY2007 Accomplishments:

A critical design review (CDR) was held in October, 2006. Substantial progress has been made this year on sensor hardware development and fabrication of the aerodynamic fairing for the sensor. The prototype instrument is approximately 1 month from completion. Mahoney and the NCAR P.I., Julie Haggerty, have met several times this year for training on data acquisition and analysis software.

FY2008 Plans:

Upon completion of the prototype sensor early November, 2007, a mechanical load analysis of the sensor and fairing will be conducted by NCAR/DFS to ensure that the system will meet FAA certification requirements. Following the load analysis, the instrument and housing will be assembled by December, 2007, and associated documents will be submitted for FAA certification. This schedule will allow for delivery and certification of the MTP in time for the HIAPER Experiment Test Flights (HEFT) in February, 2008. The first scientific deployment of the MTP will occur in the Spring of 2008 in the START08 program.