Aviation Weather Applications of Earth Science Enterprise Data
By John J. Murray

Prior to the terrorist attacks on the United States on September 11, 2001, our national airspace system (NAS) was rapidly reaching its capacity. At some future point, transportation requirements for people, goods and services will once again begin to strain that capacity. Many influences converge to affect the efficiency and hence the capacity of the NAS. Weather is one factor that can significantly augment or impede both the efficiency and the safety of air transportation. In NASA’s recently released Blueprint for Aeronautics, the agency identified weather as presenting two of the major challenges that must be addressed if the nation is to successfully implement its national airspace system of the future. The two challenges include reducing disruptions of enroute traffic due to bad weather and eliminating delays in terminal-area airspace. To address those challenges, the NASA Earth Science Enterprise is developing satellite remote sensing systems that will provide the frequent, densely distributed observations necessary to enable an NAS unfettered by concerns of capacity or safety.

Sparse observations and imprecise short-range forecasts limit the accuracy of aviation weather information, decreasing the efficiency of the air transportation system by imposing very conservative air traffic safety margins. With the advent of improved observing systems, aviation weather information and the air traffic management system will both experience a "generational" change.

Over the short term, the impact of weather on aviation can be lessened substantially if satellite weather information is employed more effectively. Aviation weather products can be infused with data provided by polar orbiting and geostationary environmental satellites developed by the NASA Earth Science Enterprise. Beyond this, one of the great challenges to NASA and the National Oceanic and Atmospheric Administration (NOAA) over the next 10 to 20 years will be to integrate new high-spatial- and temporal-resolution satellite weather observations into the basic fabric of the NAS. This precise data and its derived products will be incorporated into the nation’s transportation information infrastructure as early in this century as possible to enable unrestricted travel and commerce for all sectors of society.

Understanding Aviation Weather Requirements

Precise knowledge of the current and predicted state of the atmosphere is required so as to operate the nation’s airports and to utilize its airspace effectively. Our current understanding of the state of the atmosphere is constrained by time and space limitations of weather observations and weather forecasts relative to the typical duration of air travel. A domestic flight commonly lasts one to two hours. At most, cross-country travel might take four to six hours, including interim stops. Therein lies the rub–the current state of the art in weather forecasting often results in decision-making that uses predictions based on six- to 12-hour-old measurements. Numerical forecast models are initialized by hourly observations taken at many ground stations, but precise observations of the atmosphere above the ground are few and infrequent. These atmospheric soundings are critical to the accurate performance of weather forecasting systems and are especially important for the production of accurate aviation weather products.

Balloon soundings taken twice daily from over 180 stations in the United States form the backbone of the nation’s upper-air observing system. These observations have been recently augmented by temperature profiles and enroute measurements made by large passenger carriers from major airports around the country. Aviation meteorologists are hungry for more high-accuracy, upper-air data, but current satellite soundings do not contain sufficient vertical resolution to support most aviation weather requirements. However, this situation is about to change. The nominal vertical accuracy of current Geostationary Operational Environmental Satellite (GOES) temperature and moisture soundings is about 18,000 feet. Practically speaking, this level of accuracy means that one can identify a cloud by using GOES data, but errors in excess of three miles will exist when estimating the cloud’s height. Once the NASA Earth Observing 3 mission is carried out, the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) will improve the vertical resolution of GOES by a factor of six, or from 18,000 feet to 3000 feet. More importantly, GIFTS will increase the number of soundings by several orders of magnitude. Using its large focal plane array of 16,384 pixels, the GIFTS imaging interferometer is expected to retrieve more than 100,000 high-vertical-resolution soundings per minute. At ground level, these soundings will be spaced only 2.5 miles apart, allowing a precise three-dimensional analysis of the entire continental U.S. at least once every hour. Developing weather systems will be identified several hours before clouds appear, and well before the forecast models’ scheduled runtimes. These systems will then be targeted for frequent observations by the satellite. When GIFTS technology becomes operational on future GOES satellites, the NAS will enjoy the benefit of ubiquitous temperature, moisture and wind information. Numerical forecast models and aviation weather applications will also have access to this data for all flight levels: everywhere and at any time.

To fully appreciate the impact of the new NASA Earth Science Enterprise satellite observations on air transportation, it is important to understand the weather-related challenges facing the aviation sector. In addressing serious disruptions to enroute traffic, the Federal Aviation Administration (FAA) and the NASA Aviation Safety Program have identified weather as a factor in 30 percent of aviation accidents in the United States. These accidents have an estimated annual cost of $3 billion for damage, injuries, delays, and unanticipated operating costs. Weather-related accidents are most common in privately owned aircraft. These aircraft are involved in 80 percent of all turbulence accidents, and 90 percent of all turbulence-related fatalities. Ceiling and visibility accidents are especially problematic among privately owned aircraft, and most of these accidents result in fatalities. These fatalities usually occur when visual-flight-rule pilots inadvertently fly into instrument-flight-rule conditions, as was the case in the high-profile incident that took the life of John F. Kennedy, Jr. and his passengers several years ago. The potential annual benefit in this area alone, as identified by the FAA, exceeds $100 million.

Satellite Data for the FAA Aviation Weather Research Program

Satellite data are used only marginally to support the NAS. Only 14 percent of all current satellite data are being used operationally by meteorological forecasting operations nationwide, primarily because of the low vertical resolution of satellite soundings. The National Weather Service’s Aviation Weather Center in Kansas City, which provides aviation products to the NAS, uses satellite imagery primarily in traditional, qualitative ways. The FAA’s dedicated Aviation Weather Research Program develops parameter-specific products for the Aviation Weather Center but has yet to fully develop its capacity to utilize satellite soundings and other quantitative, satellite-derived data. Scientists with the NASA Aviation Safety Program at the Langley Research Center (Hampton, Va.) have formed a partnership with the FAA to infuse current and future satellite sounding data, imagery and derived products into various FAA-developed expert systems; for example, weather products that blend various types of data using fuzzy logic principles. This effort is focused on such high-cost aviation weather hazards as in-flight icing, turbulence, convective weather, visibility, and winter weather.

The FAA’s Terminal Convective Weather Forecast product, which saves $79.5 million annually at the three New York metropolitan area airports by reducing departure and arrival delays, could be significantly improved by identifying areas of convective instability through current satellite imagery. This improvement should occur once high-resolution satellite soundings become available to identify areas of convective initiation. Another candidate for satellite data infusion, the Integrated Turbulence Forecast Aid, was developed by the FAA to attempt to lower the $135 million annual nationwide cost of turbulence accidents. Research on vertical wind shear data from next-generation satellite sounders could shed significant light on this problem. The in-flight icing problem also stands to benefit significantly once vertically resolved temperature, moisture and water vapor phase data become available from high-resolution, geostationary, space-based interferometers pioneered by GIFTS.

Another NASA study is underway at the NOAA Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin, and at the National Center for Atmospheric Research. This study is assessing the impact of infusing GOES satellite data into FAA products. Preliminary findings show that the potential for improving convection, turbulence, icing, and ceiling and visibility products is strongly indicated. The study is also developing a strategy for infusing the new, high-resolution data into FAA products, first from the next generation of low-Earth-orbit satellites such as the recently launched Atmospheric Infrared Sounder, and then from the Cross-track Infrared Sounder that will be launched in 2005. This will be followed by data from geostationary-Earth-orbit sounders such as the GIFTS, and eventually by data from the GOES-R that will fly the GIFTS interferometer as the new Hyperspectral Environmental Sounder. Basic research to develop hyperspectral aviation weather products will begin in 2003 because the first hyperspectral, low-Earth-orbit satellite-the Atmospheric Infrared Sounder-is just beginning to provide data. GIFTS will fly in 2006, and GOES-R will be launched in 2012.

High vertical-, horizontal- and temporal-resolution satellite measurements will produce very precise numerical weather forecasts and aviation weather products. One of the greatest impacts of the new sounders will be the creation of very-high-resolution wind fields everywhere the sounders will operate. These winds will be derived not by cloud tracking, which provides limited wind estimates, but by water vapor flux tools tied to the assimilation of hyperspectral sounding data by next-generation numerical weather prediction systems. This wind data will greatly improve many FAA products and is generally expected to increase the efficiency and fuel economy of all aircraft. The NASA Earth Science Enterprise and the NASA Aviation Safety Program have undertaken an Advanced Satellite Aviation-weather Products initiative with the FAA to help realize the maximum aviation weather impact of the new Earth Science Enterprise systems as soon as possible. The implementation of this initiative will follow an eight- to 10-year roadmap, beginning with the enhancement of aviation weather products using data from current-generation satellites, especially GOES. This partnership will then begin to bridge the aviation weather product development gap, first by using airborne hyperspectral soundings, and then followed by the next generation of Earth Science Enterprise satellites, including GIFTS. The ultimate goal of both NASA and the FAA is to ensure that when NOAA’s GOES-R becomes operational in 2012, the NAS will be fully prepared to employ the data it acquires.

Transitioning Research to Operations

Issued by the Office of the Federal Coordinator for Meteorology in 1997, the National Aviation Weather Program Strategic Plan noted NASA’s unique role in developing space-based remote sensing capabilities to support aviation weather services. Experience with the current generation of GOES has taught NASA the importance of having an end-to-end plan for the development of remote sensing capabilities and for the utilization of the data. When GOES sounder data first became available, it took nearly three years before methods were fully developed to use the data operationally. As noted earlier, the aviation sector has yet to realize many of the benefits of these data in the production of aviation weather products. To ensure that future satellite data are fully utilized as soon as possible, the NASA Earth Science Enterprise is an active member of the Committee on NASA-NOAA Transition from Research to Operations. This committee was organized by the National Academy of Science’s National Research Council and is chaired by the Council’s Space Studies Board. Committee members span the government, non-profit and for-profit sectors; their task is to identify and recommend a more responsive, systematic approach for transitioning NASA and NOAA research results to operational status. The committee is scheduled to deliver its findings and recommendations in the first quarter of 2003.

Mr. Sean O’Keefe, the NASA administrator, recently highlighted the importance of developing applications of Earth science enterprise data to support aviation safety. In his testimony before the House Committee on Science on February 27, 2002, he stated, "The goal of the applications, education and outreach activities is to expand and accelerate the realization of economic and societal benefits from Earth science, information and technology. NASA has developed a new applications strategy to guide plans over the next 10 years to partner with local governments, academia and the commercial remote sensing industry to demonstrate new applications of remote sensing data. Central to this applications strategy are partnerships with service provider organizations such as NOAA, FEMA and USDA who define the needs, work with NASA to demonstrate new applications, and implement them with various commercial and local partners. For example, the administration believes that a powerful opportunity exists to develop and apply Earth sciences capabilities to solve important aviation challenges. Air travel in the United States and worldwide is seriously limited by poor short-term (0-6 hour) weather forecasts, vaguely defined icing and turbulence boundaries, and other weather issues. High-resolution sensing and precision forecasting using advanced spaceborne systems offer breakthrough opportunities for improving the operational efficiency and safety of air travel."

Worldwide Airspace Systems Of The Future

After September 11, 2001, the White House established a blue ribbon commission on the future of the aviation industry. Expanding on ideas from the NASA Aeronautics Blueprint, the commission established broad strategic objectives, including the development of an integrated "digital Earth" and "digital atmosphere." Inherent in these concepts are requirements for precise, widespread environmental knowledge. The airspace system of the future will distribute timely, ubiquitous weather information; more importantly, it will synthesize and integrate this information into an omnibus, automated air-traffic management system. The NASA Earth Science Enterprise, through the development of remote sensing technologies and their applications, will play a major role in the future of the national airspace system. Today’s efforts will eventually yield a globally integrated network of space-based, precision atmospheric sensors that will feed high-fidelity weather prediction systems and aviation weather applications. In turn, these precise prediction systems and applications will generate accurate aviation weather information that ultimately will be integrated into an automated, worldwide air transportation information network.

Acknowledgments

This work is funded by the NASA Earth Science Enterprise Applications Division and the NASA Aviation Safety Program. The Aviation Safety Program is a joint endeavor between NASA and the FAA to develop and demonstrate technologies that contribute to a reduction in the aviation fatal accident rate by a factor of five by the year 2007, and by a factor of 10 by the year 2022. Aviation safety is a key element of the NASA Earth Science Enterprise National Applications Strategy.

About the Author:

John Murray is a senior atmospheric scientist at the NASA Langley Research Center. He currently manages Advanced Satellite Aviation-weather Products, a joint undertaking by the Earth Science Enterprise and the NASA Aviation Safety Program. Mr. Murray is also the deputy measurement concept provider for the Earth Observing 3 Geosynchronous Imaging Fourier Transform Spectrometer mission, currently scheduled for launch in November 2005. He may be reached via e-mail at [email protected].

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