Specific Priorities
RAL’s priorities in aviation weather research encompass both basic and applied aspects. To keep improving diagnoses and forecasts of aviation weather hazards, an improved understanding of the atmosphere must be translated into better algorithms, interpretations of observations, and numerical weather models. On the product development side, a high priority in the near future is the preparation for “free flight,” for availability of weather information in the cockpit and for automated decision-making algorithms. Specific priorities are listed under the themes that follow.
Examples of TCWF (top) on operational ITWS display and NCWF-2 (bottom) on Experimental ADDS (click on images to enlarge).
Convection
The current convective weather products developed by RAL emphasize the 0-2 h timeframe and are primarily based upon feature extraction and extrapolation techniques, although numerical weather model output ingest is beginning. These include the Collaborative Convective Forecast Product (CCFP), the National and Terminal Convective Weather Forecasts (NCWF and TCWF,) and the Thunderstorm Auto Nowcaster, which has been implemented at a variety of aviation and NWS sites. Aviation users have identified a need for a 0-6 h forecast, which brings new challenges in incorporating model output and in blending that output with an extrapolated forecast. For example, the ability to predict whether thunderstorms will be isolated or occur in solid lines, and whether portions of preexisting lines will either strengthen or weaken would be of considerable practical benefit. To do this, research must focus on model development including improved model initialization and better convective parameterization. Information for both extrapolation techniques and model initialization may be available from new sources, including advanced radar and satellite products. Consolidation of the numerous available convective weather products (CCFP, NCWF, SIGMETS, ITWS, etc.) is needed to streamline the research and development process so that duplicate or conflicting information is not issued. A better definition and evaluation of forecaster’s role in automated convective forecast preparation is also needed to progress. For oceanic convective forecasts in data-sparse areas, advances in combining satellite information with global-scale models must be made. Along with weather research, RAL will explore methods to combine air traffic management decision making and weather nowcasts by quantifying the effects of convective weather on airspace capacity, defining and evaluating uncertainty, coupling intelligent forecast algorithms with automated traffic flow models, and evaluating air traffic management-required forecast specificity at various forecast periods out to 36 h. Planning and participation in community-wide convective storm evolution field programs and continuing leadership in studies and implementation of refractivity measurements on operational radars to obtain high-resolution, near-surface water vapor field are needed to further this research. This aviation application of convective storm forecasting is just one part of a bigger problem, and further planned research on this topic is highlighted later in a section on hydrometeorological needs.
Current icing potential product (top) shown on Operational ADDS and NASA LaRC cloud phase satellite product for same valid time (bottom)
Icing
Current and Forecast Icing Potential products (CIP and FIP) are now available in operational and experimental formats. An upgrade to CIP is under development and will be implemented in late 2006; this combines an improved icing severity algorithm with icing probability to meet stated user requirements. RAL will continue to improve automated icing diagnosis and forecast algorithms to determine location and severity of icing hazards by upgrading those algorithms as operational models are upgraded (e.g., WRF), as well as investigating and incorporating new data sets – such as NASA Langley’s advanced satellite products and Airdata’s Tropospheric Airborne Meteorological Data Report (TAMDAR) – and learning to use existing data sets more intelligently (such as more comprehensive radar data). Collaborations with airframers and aerospace engineers will result in improved descriptions and depictions of icing severity. Better parameterization of cloud processes in numerical weather models for 0-6 h in-flight icing forecasts will be focused on weakly-forced cloud systems, the impact of cloud-active aerosols and parameterizations of size distributions for water drops and ice crystals. RAL will also improve short-term forecasting of winter precipitation (amount and type) using high-resolution models through enhanced assimilation of radar data (reflectivity and Doppler radial velocity), temperature, and water vapor, four-dimensional data assimilation for smaller domain sizes and increased horizontal resolution allowing for the depiction of individual snow bands. Global applications using combinations of global weather models and satellite information will be developed to support oceanic flight routes and ETOPS (Extended Twin Engine Operations) decisions, as well as to provide guidance for re-entry of space vehicles. RAL will also seek opportunities to work with NASA and industry on improved terminal-area in-flight icing detection systems (such as the NASA Icing Remote Sensing System) incorporating previous research results into operational facilities.
WSDM display of radar reflectivity and extrapolated motion vectors along with additional information for de-icing decision-makers (top) and the hot-plate precipitation sensor used in the WSDM systemWinter Weather
RAL has successfully transferred the Weather Support for Deicing Decision-making (WSDM) system to the private sector (Vaisala, Inc.), which is implementing the system in airports across the U.S. WSDM combines a radar feature extraction and extrapolation algorithm with high-resolution surface precipitation liquid-equivalent measurements to estimate how much water substance will fall on aircraft between de-icing and takeoff. Further research and development for winter weather support for aviation does not stop with the implementation of this system, however. Research activities will be focused on basic research to answer these questions: how are snowbands organized and how can their movement and behavior be accurately predicted; and how can we identify precipitation types in real time? Research is also involved with the development of improved deicing fluid test systems, snowgauge evaluations, and supporting operational WSDM systems. RAL will also investigate means to either expand the product suite available on WSDM to include summer and other winter weather hazards, or to combine WSDM detection and prediction capability with that of another system (e.g., the Integrated Terminal Weather System) to provide this information to end-users.
Development continues on a 0-6 h snowband modeling system for use in WSDDM, based on RAL’s Real-Time Four Dimensional Data Assimilation (RTFDDA) system. The goal of the research is to use real-time radar reflectivity and Doppler velocity efficiently in a nudging mode to improve the forecast of snow at an airport. RAL priorities are to develop methods to appropriately incorporate latent heating into the model to prevent the pre-mature fall out of precipitation, investigate the use of 3DVar and Ensemble Kalman filter techniques to assimilate the radar data, investigate the use of satellite data assimilation to improve forecast and microphysical improvements. To improve microphysics parameterizations in numerical weather models, measurements of hydrometeor shapes, size distributions, and terminal velocities in winter storms will be obtained and analyzed. These activities will be coordinated with those involving convective weather and in-flight icing.
Experimental ADDS display showing in situ turbulence reports overlaid on contours of the Graphical Turbulence Guidance (GTG) product, and web-based Java display of in-cloud turbulence detected by the NEXRAD algorithm with overlaid aircraft tracks depicting measured turbulence.Turbulence
Prediction of turbulence using numerical models will continue to challenge RAL scientists. The Graphical Turbulence Guidance (GTG) has operational and experimental versions that predict clear-air turbulence related to upper-level features out to 12 h using RUC model output. An en-route, NEXRAD-based turbulence product is being tested for dispatcher and cockpit use. Additionally, RAL has developed and deployed two terminal-area terrain-induced turbulence warning systems based on anemometers and wind profilers at Hong Kong and Juneau, AK. Future research will focus on expanding these systems. GTG will include terrain-induced turbulence and turbulence associated with convection, thus expanding the altitude range covered as well as the utility of the product. Research will also be conducted on better turbulence parameterizations in research models (and subsequent transfer to operational models), better use of increased resolution in operational models (e.g., WRF), increased understanding of all forcing mechanisms (e.g., CAT, convection, and terrain), and incorporation of new data sets (NASA Langley advanced products). This will be done through model simulations and by pursuing opportunities for collecting in situ data from research aircraft.
RAL will seek opportunities to apply local-scale, high-resolution models to the terrain-induced turbulence problem (terminal area) as it pursues development and deployment of automated turbulence warning systems at affected airports (e.g., Anchorage, Reno). In related research, the 2006 Terrain-Induced Rotor Experiment (T-REX) will provide a basis to better understand the dynamics of mountain-wave turbulence, low-level terrain-induced turbulence, and rotors.
A turbulence detection network based on NEXRAD radars will be expanded and will be incorporated into the GTG automated forecasting system. The GTG’s altitude range will continue to be expanded, and will include convective and orographically-forced turbulence. Operational measurements will be augmented, with in situ turbulence measurements (from commercial airlines and TAMDAR sensors) displays to supplement PIREPs and airborne radar forward-looking turbulence detection algorithm (in cloud). Finally, diagnostic and prognostic techniques for turbulence and wind shear above the tropopause will be developed to support space launch operations.
Real-time national ceiling analysis (top) and experimental Northeast C&V display (bottom)
Ceiling and Visibility
RAL was a participant in the development of a ceiling and visibility (C&V) prediction system based on the onset and burn-off of fog in the San Francisco International Airport vicinity. Following this successful deployment, attention is turning to a similar system or systems for the northeastern United States (the “Northeast Corridor,” the busiest air traffic area in the U.S.), using similar technology that combines 1-D model output with satellite and sodar data to predict airport ceiling and visibility conditions. A national ceiling and visibility product that depicts VFR/IFR conditions across the CONUS is being tested prior to experimental and operational acceptance. This product combines model output with observations to produce a diagnosis of flight conditions across the U.S.; forecasts are done using model data alone. The research activities in this area are relatively young and model improvements and better use of existing and new products are needed. Tracking and trending techniques (<3 h) and numerical weather prediction models (3-12 h) will be incorporated into the Northeast Corridor product. As with other aviation weather products, forecasts will move toward probabilistic depictions. The ceiling and visibility investigators will work with others to advance numerical model development including improved resolution, assimilation capability and model physics related to cloud/fog and precipitation formation and dissipation. Translation algorithms will be improved for weather prediction models to convert, for example, precipitation rate into visibility. The physics package for the 1-D model used in terminal-area forecasts will also be improved. Climatological information will be incorporated into fog forecasts, along with improved satellite-based techniques for real-time fog detection. Multi-spectral satellite data will be incorporated with real-time surface observations and databases of background surface characteristics to improve the interpretation of satellite signatures associated with fog and low cloud. For northern latitudes (including Alaska), Polar Orbiter satellite data will be incorporated. The use of ceiling and visibility information in decision support systems for improved short-term forecasts of flight category and precision landing conditions will be explored. Finally, current C&V diagnostic and prognostic techniques will include space vehicle recovery zones.
Volcanic Ash
Volcanic ash research and development activities are in their early stages at RAL. The main thrust has been coordinating and disseminating already-available information on current and future location of the ash cloud. In the future, more attention will be put into collaboration with groups within and outside RAL to improve dispersion models on scales appropriate for volcanic ash tracking, and for satellite detection of ash cloud. Effective dissemination methods and media will be explored to build an effective international detection and warning system.
Advanced Dissemination Techniques
Dissemination of information to appropriate users is a critical component of RAL’s aviation weather research. While RAL is not a 24/7 weather information provider, it is important for the organization to be involved in this activity for two reasons: designing displays for user feedback during the development process, and learning to use existing or evolving dissemination systems to optimize product content, format and use. The Aviation Digital Data Service (ADDS) hosted at NCEP’s Aviation Weather Center was developed as a means to disseminate to end-users products developed by RAL and its collaborators in the universities and other labs. It has also served as a basis for gathering valuable feedback from the end users to aid the ongoing development process. Several examples of ADDS-delivered graphics are shown in the figures above. ADDS is now the “gold standard” for a single web location for a broad spectrum of aviation weather user needs. Still, there are additional opportunities to pursue. Pilots need weather information directly into the cockpit, and RAL is and will continue to collaborate with FAA, NASA and private sector weather vendors to test means and formats for cockpit-appropriate products. Those organizations can provide guidance on building displays compliant with existing guidelines on color, information content, and symbols, and can facilitate work with users to determine optimal scales and lead times for information. Early cockpit weather products have been incorporated by United Airlines into a laptop computer termed an “Electronic Flight Bag.” This is a useful first approach for getting advanced weather information to pilots; it doesn’t invoke aircraft certification issues and could be followed up by other airlines. RAL engineers will work to enable ADDS to become an FAA "Qualified Internet Content Provider (QICP)" so that its products and services can be utilized by airlines as an official weather source. They will also develop enhanced features such as user-selected and saved display characteristics. Looking farther into the future, there will be a need for weather in space vehicles, to provide direct readouts of winds aloft and shear indices to pilot and provide graphical presentation of weather parameters at the vehicle recovery site.
System Integration
RAL deployed an integrated aviation weather data ingest and display system in Taiwan and is working with Peak Weather, Inc. on a feasibility study of a similar one for Colombia. This is a further means of applying RAL’s expertise in solving aviation weather problems to new situations. RAL will pursue new opportunities in this area as countries seek to modernize their aviation weather systems. Aspects of these activities include the integration of model output with instrumentation, selection of weather hazards appropriate for the region (convection, icing, turbulence, C&V, volcanic ash), and upgrades of existing systems to state-of-the-art instrumentation and data collection, dissemination and display facilities.
Verification
Verification of products to insure their quality and compare them to existing products will continue to be an integral part of RAL’s aviation weather research. In addition to current activities, RAL will seek the use of improved in situ (i.e., TAMDAR) and remotely-sensed (i.e., NASA Langley cloud products) observations available for verification of turbulence and icing forecasts. Specific research topics and approaches are discussed later in the section “Forecast Verification and Quality Assessment.”
Additional forecast attributes will also be included in verification activities, such as cloud tops and convective organization. RAL will also expand the verification work into new and useful areas: understanding how weather affects air traffic, and use of this information to develop operationally-relevant verification measures and developing methods for evaluation of forecasts in terms of economic and other benefits.