Publications

The John F. Kennedy International Airport (JFK) and LaGuardia Airport (LGA) are protected from wind shear exposure by the New York Terminal Doppler Weather Radar (TDWR), which is currently located at Floyd Bennet Field, New York. Because of a September 1999 agreement between the Department of the Interior and the Department of Transportation, this location is required to be vacated no later than January 2023. Therefore, a study based on model simulations of wind shear detection probability was conducted to support future siting selection and alternative technologies. A total of 18 candidate sites were selected for analysis, including leaving the radar where it is. (The FAA will explore the feasibility of the latter alternative; it is included in this study only for technical analysis.) The 18 sites are: Six candidate sites that were identified in the initial New York TDWR site-survey studies in the 1990s (one of which is the current TDWR site), a site on Staten Island, two Manhattan skyscrapers, the current location of the WCBS Doppler weather radar in Twombly Landing, New Jersey, and eight local airports including JFK and LGA themselves. Results clearly show that for a single TDWR system, all six previously surveyed sites are suitable for future housing of the TDWR. Unfortunately, land acquisition of these sites will be at least as challenging as it was in the 1990s due to further urban development and likely negative reaction from neighboring residents. Evaluation results of the on-airport siting of the TDWR (either at JFK or at LGA) indicate that this option is feasible if data from the Newark TDWR are simultaneously used. This on-airport option would require software modification such as integration of data from the two radar systems an dimplementation of "overhead" feature detection. The radars on the Manhattan skyscrapers are not an acceptable alternative due to severe ground clutter. The Staten Island site and most other candidate airports are also not acceptable due to distance and/or beam blockage. The existing Airport Surveillance Radar (ASR-9) Weather Systems Processor (WSP) at JFK and the Bookhaven (OKX) Weather Surveillance Radar 1988-Doppler (WSR-88D, commonly known as NEXRAD) on Long Island cannot provide sufficient wind shear protection mainly due to limited wind shear detection capability and/or distance.

This report provides recommendations for aligning new Collaborative Air Traffic Management Technologies (CATM-T) with evolving aviation weather products to improve NAS efficiency during adverse (especially severe) weather conditions. Key gaps identified include 1. Improving or developing pilot convective storm avoidance models as well as models for route blockage and capacity in severe weather is necessary for automated congestion prediction and resolution. 2. Forecasts need to characterize uncertainty that can be used by CATM tools and, explicitly forecast key parameters needed for translation of weather products to capacity impacts. 3. Time based flow management will require substantial progress in both the translation modeling and in predicting appropriate storm avoidance trajectories. Near term efforts should focus on integration of the Traffic Management Advisor (TMA) with contemporary severe weather products such as the Corridor Integrated Weather System (CIWS). 4. Human factors studies on product design to improve individual decision making, improved collaborative decision making in "difficult" situations, and the use of probabilistic products are also essential. 5. Studies need to be carried out to determine how well en route and terminal capacity currently is being utilized during adverse weather events so as to identify the highest priority areas for integrated weather-CATM system development.

Severe weather avoidance programs (SWAP) due to convective weather are common in many of the busiest terminal areas in the US National Airspace System (NAS). In order to make efficient use of available airspace in rapidly evolving convective weather, it is necessary to predict the impacts of the weather on key resources (e.g., departure and arrival routes and fixes), with frequent updates as the weather changes. Currently, this prediction is a mental process that imposes a significant cognitive burden on air traffic managers. As a result, air traffic management in SWAP is often inconsistent and decisions result in less than optimal performance. The Route Availability Planning Tool (RAPT) is a prototype automated decision support tool, intended to help air traffic managers in convective weather SWAP, by predicting the impacts of convective weather on departure routes. Originally deployed in New York in August, 2002, RAPT has recently undergone two field evaluations (2007 and 2008) in order to test and refine its concept of operations, evaluate the accuracy and usefulness of its decision guidance, and estimate observed and potential delay reduction benefits that may be achieved as a result of its use. This paper presents the results of the 2008 performance evaluation, focusing on the concept of operations and the quality of decision support guidance. A second paper [1] presents analyses of delay reduction benefits and the operational decision making environment in which RAPT is deployed.

A series of fatal commercial aviation accidents in the 1970s led to the development of systems and strategies to protect against wind shear. The Terminal Doppler Weather Radar (TDWR), Low Level Wind Shear Alert System (LLWAS), Weather Systems Processor (WSP) for Airport Surveillance Radars (ASR-9), pilot training and on-board wind shear detection equipment are all key protection components. While these systems have been highly effective, there are substantial costs associated with maintaining and operating ground-based systems. In addition, while over 85% of all major air carrier operations occur at airports protected by one of these ground-based wind-shear systems, the vast majority of smaller operations remain largely unprotected. This report assesses the technical and operational benefits of current and potential alternative ground-based systems as mitigations for the low-altitude wind-shear hazard. System performance and benefits for all of the current TDWR (46), ASR-9 WSP (35), and LLWAS (40) protected airports are examined, along with 40 currently unprotected airports. We considered in detail several alternatives and/or combinations for existing ground-based systems. These included the option to use data from current WSR-88D (or NEXRAD) and two potential future sensor deployments: (1) a commercially built pulsed-Doppler Lidar and (2) an X-band commercial Doppler weather radar. Wind-shear exposure estimates and simulation models for each wind shear protection component were developed for each site in order to accurately comare all alternatives. For the period 2010-2032, the current combination of wind-shear protection systems reduces teh $3.0 billion unprotected NAS overall wind-shear safety exposure to just $160 million over the entire study period. Overall, tehre were few alternatives that resulted in higher benefits than the TDWR, TDWR-LLWAS, and WSP configurations that currently exist at 81 airports. However, the cheaper operating costs of NEXRAD make it a potential alternative especially at LLWAS and non-wind-shear protected sites.

The Tower Flight Data Manager (TFDM) is a new terminal automation platform that will provide an integrated tower-user display suite including an extended electronic flight strip or "flight data management" (FDM) display. The integrated information exchange and processing environment established by TFDM will support a suite of automation-assisted user support tools collectively designated as the Arrival/Departure Management Tool or A/DMT. A/DMT will develop and manage an integrated plan for arrival, scheduled (and to the extent possible) non-scheduled departure operations at the airport, based on 4D-trajectory assignments. A primary concern of A/DMT is the efficient use of the runway complex to meet service demand from both arrivals and departures. In addition, A/DMT seeks to reduce fuel usage and engine emissions on the airport surface, to permit more efficient use of gates and holding areas, and to enhance the safety of surface operations. We first put forth a strategy for developing a scalable TFDM-A/DMT Information Management Architecture (TIMA) employing standard information exchange models, services and data formats. This architecture will be consistent with evolving System Wide Information Management (SWIM) technologies and data standards, and will support efficient insertion of processing algorithms (e.g. surface trajectory management algorithms) developed by the research community and/or industry. Next, we describe TIMA . While TIMA makes use of Service-Oriented Architecture (SOA) principles, it is primarily an information-oriented architecture; we discuss why this architectural style is necessary for TFDM, and how it is also beneficial for SWIM. We conclude with a description of a general model for managing temporal aspects of information within TFDM. TIMA needs to support not only real-time operations, but post-facto analysis as well. A major difficulty in conducting analyses involving different data sources is time synchronization of data. We describe a method for associating temporal information with data sources in a data-agnostic manner, so that data can be retrieved from a variety of sources in a uniform manner.

Three-dimensional mesoscale numerical simulations were performed over Niger in order to investigate dry cyclogenesis in the West African intertropical discontinuity (ITD) during the summer, when it is located over the Sahel. The implications of dry cyclogenesis on dust emission and transport over West Africa are also addressed using the model results, together with spaceborne observations from the Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The study focuses on the case of 7-8 July 2006, during the African Monsoon Multidisciplinary Analysis (AMMA) Special Observing Period 2a1. Model results show the formation of three dry cyclones in the ITD during a 24-h period. Simulations are used to investigate the formation and the development of one of these cyclones over Niger in the lee of the Hoggar-Air Mountains. They show the development of the vortex to be associated with (1) strong horizontal shear and low-level convergence existing along the monsoon shearline and (2) enhanced northeasterly winds associated with orographic blocking of air masses from the Mediterranean Sea. The dry cyclone was apparent between 0700 and 1300 UTC in the simulation, and it was approximately 400 km wide and 1500 m deep. Potential vorticity in the center of vortex reached nearly 6 PVU at the end of the cyclogenesis period (1000 UTC). The role of the orography on cyclogenesis along the ITD was evaluated through model simulations without orography. The comparison of the characteristics of the vortex in the simulations with and without orography suggests that the orography plays a secondary but still important role in the formation of the cyclone. Orography and related flow splitting tend to create low-level jets in the lee of the Hoggar and Air mountains which, in turn, create conditions favorable for the onset of a better defined and more intense vortex in the ITD region. Moreover, orography blocking appears to favor the occurrence of a longer-lived cyclone. Furthermore, model results suggested that strong surface winds (~11 m s−1) enhanced by the intensification of the vortex led to the emission of dust mass fluxes as large as 3 ug m−2 s−1. The mobilized dust was mixed upward to a height of 4–5 km to be made available for long-range transport. This study suggests that the occurrence of dry vortices in the ITD region may contribute significantly to the total dust activity over West Africa during summer. The distribution of dust over the Sahara-Sahel may be affected over areas and at time scales much larger than those associated with the cyclone itself.

This paper will discuss the progress the Multi-function Phased Array Radar (MPAR) research program has made over the last 18 months as well as insight into the program strategy for moving forward. Current research activities include evaluating the impact of MPAR's faster scanning rates to aviation weather algorithms (e.g., how it will help in predicting storm growth and decay) and exploring dual polarization for phased array radars. Additionally, the Department of Homeland Security (DHS) has expanded the MPAR multi-agency partnership and is sponsoring research into the mitigation of wind-farm interference on weather sensing. Significant research in semi-conductor technology and advances in transmit/receive module design and phased array architectures are beginning to create a pathway towards system affordability. The MPAR program plan calls for a technology demonstration phase followed by the initiation of a prototype development effort within the next five years. This paper will provide the updates on these and other program activities.

Dozens of Ground Delay Programs (GDPs) are implemented each summer for San Francisco International Airport (SFO) in order to cope with reduced capacity caused by the presence of warm-season stratus in the approach zone. The stratus prevents the use of dual approaches to SFO's closely-spaced parallel runways, which essentially reduces the arrival capacity by half. In 2004, a prototype system for providing probabilistic stratus forecast guidance was transitioned from the research community to NWS Monterey. This system was intended to be used as a tool for improving the daily forecast of stratus clearing time from the approach zone, and correspondingly improve the efficiency of GDP implementation strategy. Since its transition to the NWS in 2004, the automated forecast guidance system has continued to produce reliable forecasts of daily stratus clearing time. However, this success has not adequately translated to a marked improvement in GDP efficiency. Analysis by the NWS indicates that the existing mechanisms for introducing the forecast guidance information into the GDP decision process, as well as the GDP implementation strategy itself, are not suited for taking full advantage of the forecast skill demonstrated by the system. A historical examination of SFO GDP implementation based on the probabilistic forecasts provided by the automated forecast guidance system is currently in process, with the objective being a recommendation for a more effective GDP strategy. An important consideration is understanding the risk/reward associated with the decision process. In this instance, the reward is increased efficiency seen as reduced aircraft delays, at the risk of creating increased delay, aircraft diversions, and controller workload in the event that an incorrect optimistic forecast results in the premature release of ground-held aircraft. This investigation is being performed in concert with the weather-integration objectives of the current FAA modernization program, particularly the integration of weather information that is delivered in a probabilistic format. Shortcomings within the current GDP strategy are described to provide context for potential improvements that exploit the probabilistic forecasts currently emerging from the research community.

Air traffic congestion caused by convective weather in the US has become a serious national problem. Several studies have shown that there is a critical need for timely, reliable and high quality forecasts of precipitation and echo tops with forecast time horizons of up to 12 hours in order to predict airspace capacity (Robinson et al. 2008, Evans et al. 2006 and FAA REDAC Report 2007). Yet, there are currently several forecast systems available to strategic planners across the National Airspace System (NAS) that are not fully meeting Air Traffic Management (ATM) needs. Furthermore, the use of many forecasting systems increases the potential for conflicting information in the planning process, which can cause situational awareness problems between operational facilities. One of the goals of the Next Generation Air Transportation System (NextGen) is to consolidate these redundant and sometimes conflicting forecast systems into a Single Authoritative Source (SAS) for aviation uses. The FAA initiated an effort to begin consolidating these systems in 2006, which led to the establishment of a collaboration between MIT Lincoln Laboratory (MIT LL), the National Center for Atmospheric Research (NCAR) Research Applications Laboratory (RAL), the NOAA Earth Systems Research Laboratory (ESRL) Global Systems Division (GSD) and NASA, called the Consolidated Storm Prediction for Aviation (CoSPA; Wolfson et al. 2008). The on-going collaboration is structured to leverage the expertise and technologies of each laboratory to build a CoSPA forecast capability that not only exceeds all current operational forecast capabilities and skill, but that provides enough resolution and skill to meet the demands of the envisioned NextGen decision support technology. The current CoSPA prototype for 0-6 hour forecasts is planned for operation as part of the NextGen Initial Operational Capability (IOC) in 2013. CoSPA is funded under the FAA's Aviation Weather Research Program (AWRP). The first CoSPA research prototype demonstration was conducted during the summer of 2008. Technologies from the Corridor Integrated Weather System (CIWS; Evans and Ducot 2006), National Convective Weather Forecast (NCWF; Megenhardt et al. 2004), and NOAA’s Rapid Update Cycle (RUC; Benjamin et al. 2004) and High Resolution Rapid Refresh (HRRR; Benjamin et al. 2009) models were consolidated along with new technologies into a single high-resolution forecast and display system. Historically, forecasts based on heuristics and extrapolation have performed well in the 0-2 hour window, whereas forecasts based on Numerical Weather Prediction (NWP) models have shown better performance than heuristics past 3-4 hours (Figure 1). One of the goals of CoSPA is to optimally blend heuristics and NWP models into a unified set of aviation-specific storm forecast products with the best overall performance possible. The CoSPA prototype demonstration began in July 2008 with 2-6 hr forecasts of Vertically-Integrated Liquid water (VIL) that seamlessly matched with the 0-2 hr VIL forecasts available in CIWS. These real-time forecasts have been made available to the research team and FAA management only through a web-based interface. This paper discusses the system infrastructure, the forecast display, the forecast technology and performance of the 2-6 hr VIL forecast. Our early assessment based on the 2008 demonstration is that CoSPA is showing tremendous promise for greatly improving strategic storm forecasts for the NAS. Early user feedback during CoSPA briefings suggested that the 6 hr forecast time horizon be extended to 8 hours to better meet their planning functions, and that forecasts of Echo Tops must also be included.

Airspace capacity constraints caused by adverse weather are a major driver for enhanced Traffic Flow Management (TFM) capabilities. One of the most prominent TFM initiatives introduced in recent years is the Airspace Flow Program (AFP). AFPs are used to plan and manage flights through airspace constrained by severe weather. An AFP is deployed using "strategic" (i.e., 4-6 hour) weather forecasts to determine AFP traffic throughput rates. These rates are set for hourly periods. However, as convective weather continuously evolves, the achievable en route airspace throughput can fluctuate significantly over periods as short as 15-30 minutes. Thus, without tactical AFP adjustments, inefficiencies in available airspace usage can arise, often resulting in increased air traffic delay. An analysis of AFP usage in 2007 was conducted in order to (1) better understand the relationship between AFP parameters and convective weather characteristics, and (2) assess the potential use of an objective model for forecasting tactical AFP throughput. An en route airway blockage-based algorithm, using tactical forecast information from the Corridor Integrated Weather System (CIWS), has been developed in order to objectively forecast achievable flow rates through AFP boundaries during convective weather. A description of the model and preliminary model results are presented.