Publications

In this paper, the revised RAPT algorithm and display are described and evaluated. The fidelity of the RAPT operational model is assessed by comparing RAPT departure status with observed departure flows (i.e., trajectories, weather avoidance maneuvers and storm penetrations) on several days when convective weather SWAPs were in effect in New York. Real-time in-situ observations at RAPT facilities (described in a companion paper at this conference; Robinson, 2008), user feedback from RAPT playbacks and the REPEAT web site are used to support this post-event evaluation. For example, real time observations provide the time and operational rationale for a specific departure route closure identified in the traffic flow analysis. This information is necessary to identify closures or flow restrictions that are the result of factors outside of the current RAPT algorithm domain (e.g., traffic restrictions due to volume, downstream congestion, etc.). Real time observations are also used to identify specific times when critical, weather-related operational decisions were made. The RAPT guidance at these critical decision points is analyzed to determine if RAPT provided information that enabled (or could have enabled, had it been used) more timely or effective decisions. The effect of forecast uncertainty on RAPT performance is also examined, particularly in convective weather situations where the location, severity and operational impact were difficult to predict. Strategies that mitigated risks associated with forecast uncertainty are presented. These include the use of additional information provided in the RAPT display, such as echo top heights encountered along the departure route, to confirm or modify RAPT guidance and the consideration of the departure status of two or more adjacent routes to 'average out' variations in the departure status timelines.

There is currently great interest in improving the ability to quantitatively assess how well U.S. Air Traffic Control (ATC) services are being provided as new weather-air traffic management (ATM) decision support capabilities are added. One of the three proposed metrics currently under study by the Federal Aviation Administration (FAA) and airlines is resource utilization, which has been defined as "the safe and efficient use of available airport or airspace capacity." Measurement of capacity utilization is particularly difficult during convective weather since storms cause capacity reductions in both en route and terminal airspace. In particular, en route capacity loss results in network congestion that cannot be readily characterized by scalar metrics. This paper proposes the use of (i) models for translating 3-D weather radar data into time-varying estimates of the capacity reductions in affected en route sectors, terminal airspace, and airports, together with (ii) automatically-generated, broad-area ATM strategies that utilize the time-varying estimates of airspace capacity and demand to determine optimal reroute strategies or, when necessary, minimally disruptive ground or airborne delay programs to assess how the available capacity could best been utilized. By comparing actual vs. optimal capacity utilization, one can assess how effective the actual weather-ATM system was at utilizing the available capacity. Examples of applying this methodology to severe convective weather events from 2005 and 2006 will be presented.

There is an urgent need to enhance the efficiency of United States (U.S.) air traffic management (ATM) decision-making when convective weather occurs. Thunderstorm ATM decisions must be made under considerable time pressure with inadequate information (e.g., missing or ambiguous), high stakes, and poorly defined procedures. Often, multiple decisions are considered simultaneously; each requiring coordination amongst a heterogeneous set of decision-makers. Recent operational experience in the use of improved convective weather decision support systems in the Northeast quadrant of the U.S. is reviewed in the context of literature on individual and team decision-making in complex environments. Promising areas of research are identified.

Possible alternatives to the Terminal Doppler Weather Radar (TDWR) are assessed. We consider both the low altitude wind shear detection service provided by TDWR and its role in reducing weather-related airport delays through its input to the Integrated Terminal Weather System (ITWS). Airborne predictive wind shear (PWS) radars do not provide the broad area situational awareness needed to proactively reroute aircraft away from the affected runways. We considered in detail the alternative of using the ASR-9 Weather Systems Processor (WSP) and NEXRAD in lieu of TDWR. An objective metric for wind shear detection capability was calculated for each of these radars at all TDWR equipped airports. TDWR was uniformly superior by this metric, and at a number of the airports, the ASR-9/NEXRAD alternative scored so low as to raise questions whether it would be operationally acceptable. To assess airport weather delay reduction impact, we compared the accuracy of the high-benefit ITWS "Terminal Winds" product with and without TDWR input. Removal of the TDWR data would have increased the mean estimate error by a factor of 3 near the surface.

The Air Traffic Control (ATC) productivity benefits attributed to the Corridor Integrated Weather System (CIWS) were assessed using real-time observations of CIWS product usage during three multi-day thunderstorm events in 2005 at eight U.S. Air Route Traffic Control Centers (ARTCCs). CIWS improved ATC productivity by: reducing the time required to develop, coordinate, and implement weather impact mitigation plans; increasing the number of safety and capacity-enhancing plans that were executed (e.g., more efficient, proactive rerouting and greater ability to keep routes open; [and] assisting with FAA staffing decisions. Time savings per consecutive weather day for Traffic Management Coordinators (TMCs) in an ARTCC typically were 20-95 minutes. The overall frequency of capacity-enhancing decisions increased by 177% relative to the CIWS benefits study conducted in 2003. The annual CIWS delay savings are in excess of 92,000 hours. Corresponding airline direct operations cost (DOC) savings exceeded $94M and passenger value of time (PVT) savings exceeded $201M. Annual jet fuel savings exceeded 11M gallons. The ability of the Cleveland ARTCC to develop and execute weather impact mitigation plans improved significantly (e.g., by 50-80%) when CIWS products were available to Area Supervisors as well as to the TMCs.

In an era of significant federal government budget austerity for civil aviation operations, it has become essential to improve Air Traffic Control (ATC) productivity. This report summarizes the results of an exploratory field measurement program conducted during summer 2005 to assess ATC productivity benefits of the Corridor Integrated Weather System (CIWS). Real-time observations of CIWS product usage during multi-day thunderstorm events were carried out at eight U.S. Air Route Traffic Control Centers (ARTCC). The real time observations data were used in conjunction with specific in-depth case study analyses to assess the CIWS productivity enhancements associated with convective weather impact mitigation plan development and implementation. Comparisons of ARTCC operations between facilities with and without access to CIWS were alos made to further identify CIWS contributions to improved ATC productivity.

Air traffic congestion in the United States (US) National Airspace System (NAS) has increased significantly in the past ten years. This congestion has resulted in a rise of air traffic delays, which can cause massive monetary and human costs. When convective weather impacts jet routes and airport terminals, particularly within the most congested airspace sectors, it causes a reduction in traffic capacity that can lead to significant delays. In an effort to increase airspace capacity and reduce air traffic delays, the Massachusetts Institute of Technology Lincoln Laboratory (MIT LL), in collaboration with the National Center for Atmospheric Research (NCAR) and the National Oceanic and Atmospheric Administration (NOAA) are tasked by the Federal Aviation Administration (FAA) to provide aviation weather decision support tools for the air traffic management (ATM) community. To determine which weather products and data dissemination approaches will provide the greatest benefit in terms of increasing airspace capacity, MIT LL is performing ongoing marketing research analyses. The method consists of three primary steps (Ballentine 1994; Evans and Robinson 2005; Evans et al. 2003): 1) Study the system 2) Identify benefits 3) Prioritize opportunities In practice, the execution of these three steps is an iterative process. It is critical to understand how the air traffic system operates to assess the benefits of a weather product. For this reason many studies have been conducted by MIT LL where ATM users have been interviewed, use of decision support tools has been observed, and flight track data have been analyzed to extract the behavior of the pilot (Evans et al. 2003; Evans and Robinson 2005; Robinson et al. 2004; Rhoda et al. 2002; Allan et al. 2001; Bieringer et al. 1999; Rhoda and Pawlak 1999; Forman et al. 1999). These studies have provided valuable insight into how the NAS operates during weather impacts. Weather impacts on the air traffic system can be classified into three basic types: 1) Terminal impacts (≤ 5 nm) 2) En route impacts 3) Transition impacts (between Air Route Traffic Control Centers (ARTCC) sectors and terminal operations) Terminal impacts are those that occur in and around the airport, and are generally less than 5 nm from the runways. These impacts are small in dimension and occur at low altitude, and have been shown to be relatively insignificant to the overall delay problem (Evans et al. 2005). En route impacts occur within ARTCC's jet routes and sectors. These impacts can result in a route being totally or partially blocked and lead to a reduction in capacity. The en route impacts generally occur at high altitude. Transition impacts are those that occur within the zone between the ARTCC sectors and the terminal approaches. By understanding the system one can then identify elements or areas of opportunities that can be exploited to help solve the airspace capacity problem. Weber et al. (2005) identifies four key elements for maintaining capacity during convective weather events: 1) Forecasts of convective weather 2) Capacity models where weather is an input 3) Strategy tools for ATM with weather as an input 4) Airspace capacity enhancements Forman et al. (1999) studied the terminal impact problem and found that the ATM users required precipitation forecasts that were reliable, updated rapidly (5-6 minutes), had high resolution (1 km), short lead times (1-2 hours), and were issued with fine time steps (10-15 minutes). MIT LL used this information to refine its terminal convective weather forecast (TCWF) and received very positive feedback from ATM personnel (Hallowell et al. 1999). Subsequently, the precipitation forecast was extended out to 2-hourtime horizons and was provided to the traffic managers working in busy Midwest and Northeast ARTCCs as part of the Corridor Integrated Weather System (CIWS) (See Klingle-Wilson and Evans (2005) for a description of the CIWS product). However, it was quickly determined that the precipitation product alone was not sufficient for identifying usable en route airspace, since occasionally significant precipitation (≥ level 3)1 had relatively low storm tops (≤ 30 kft). Due to feedback from ATM users, MIT LL produced a high resolution (1 km) enhanced Echo Tops Mosaic weather product (Evans et al. 2003) that is used as a proxy for the cloud top height. Since the operational inception of the CIWS enhanced Echo Tops Mosaic product in August 2002, FAA and airline traffic managers have become acutely aware of the benefits of high-resolution storm top information for efficient en route air traffic control (ATC) operations. CIWS field use assessment campaigns in 2003 revealed significant benefits attributed to use of the Echo Tops Mosaic product (Robinson et al. 2004). During interviews, traffic managers explained that in the past, if an aircraft deviated around a storm in high-traffic airspace, jet routes were closed by default, since pilot behavior was the only easily assessable information available about three-dimensional storm structure. After the CIWS Echo Tops Mosaic was introduced, traffic managers were able to differentiate between isolated storm top concerns, which are easily handled by keeping routes open and absorbing occasional, local deviations, and significant high-topped storm events, which legitimately require route closures and reroutes. Post-event interviews in 2003 revealed that though FAA and airline users were very pleased with the availability and quality of the CIWS Echo Tops Mosaic product, they also needed to know both the past trend and predicted behavior of storm top heights. The CIWS Echo Tops Forecast (ETF) was introduced in May 2005 to meet some of the traffic management requests. This paper discusses the ETF product currently operational in CIWS. We will discuss the generation of the forecast algorithm and provide an initial assessment of the use of the ETF in the field.

Major Federal Aviation Administration (FAA) planning documents (e.g., the FAA Flight Plan 2005-2008, the FAA Air Traffic Organization Fiscal Year 2005 Business Plan, and the Operational Evolution Plan) stress the importance of: Improving National Airspace System operations efficiency by increasing safety and capacity (e.g., reducing delays) and Providing FAA services more efficiently, such that operations costs can be reduced while improving safety and capacity. Continued improvements in air traffic delay mitigation in the NAS are imperative, given expectations for significant increases in near-term air traffic demand. The latest FAA aerospace growth forecast projects a 30% increase in Air Route Traffic Control Center (ARTCC) operations by 2015 (FAA Office of Aviation Policy and Plans, 2005). Improving Air Traffic Control (ATC) productivity during convective weather impact events is particularly important. Air traffic demand is escalating in an airspace network near capacity even in clear-weather. This will limit the ability to exploit advancements made in mitigating en route convective weather delays, unless fielded decision support systems are able to improve traffic management efficiency. Moreover, it is also essential that ATC productivity (e.g., as measured by the number of employees and overtime) be improved, given the reduction in Aviation Trust funding from the passenger ticket tax and overall federal funding constraints. We have previously described how a contemporary convective weather decision support system - the Corridor Integrated Weather System (CIWS) - can facilitate significantly improved capacity enhancing decisions, such as keeping routes open longer and proactive rerouting (e.g., Evans et al. 2005; Robinson et al. 2004). These CIWS-enabled capacity enhancements were shown to result in significant reductions in air traffic delays, airline operating costs, and delay-incurred passenger costs (Robinson et al. 2004). A study of the CIWS contributions to ATC productivity enhancements began in 2005. As part of this effort, real-time observations of CIWS product usage and the time to accomplish weather impact mitigation planning decisions during multiday thunderstorm events were carried out at 8 U.S. ARTCCs. A description of the design (and methodological challenges) of this experiment are presented in Section 2 of this paper. Improved ATC productivity was found to have two components: (1) Reduced workload and increased operational efficiency, as characterized by the amount of time required to develop and implement convective weather mitigation plans and the ability to enhance staffing decisions (2) Increased frequency of capacity enhancing decisions. Results demonstrating how CIWS helped traffic managers reduce workload and increase operational efficiency through time-savings and improved decision-making are presented in Section 3. Important factors such as the variation in performance from ARTCC to ARTCC are discussed in some detail. We show that a very important factor in this performance is whether the Area Supervisors at an ARTCC have direct access to CIWS products. The paper concludes by discussing future plans for CIWS ATC productivity enhancement investigations.

This paper investigates methods for quantifying aviation convective weather delay reduction benefits for nowcasts and short term forecasts.

This paper investigates methods for quantifying convective weather delay reduction benefits for weather/ATM systems and recommends approaches for future assessments. This topic is particularly important at this time because: 1. Convective weather delays continue to be a dominant factor in the overall National Airspace System (NAS) delays, and 2. Benefits quantification and NAS performance assessment have become very important in an era of significant government and airline budget constraints for civil aviation investments. Quantifying convective weather delay benefits for ATM systems has proven to be quite difficult since the delays arise from complicated, highly variable, poorly understood interactions between convective weather and a very complex aviation system. In this paper, we consider key aspects of convective weather disruptions of the aviation system, how the weather severity can be characterized, and discuss practical experience with benefits quantification by a variety of approaches. The paper concludes with recommendations for a methodology to be used in future convective weather delay reduction quantification studies.