Translating weather into traffic flow management impacts for NextGen

The uncertainties of weather, and its uncertain impact on traffic flow management (TFM), significantly affect the overall performance of the national airspace system (NAS). For NextGen, there are several steps involved with identifying and eventually mitigating the impacts caused by weather hazards on safe and efficient TFM. The NextGen vision looks toward resolving weather impacts through more precise weather forecast information integrated into Decision Support Tools (DSTs) and weather information assimilated into NextGen decision loops for air traffic management (ATM).

The first step toward mitigating weather impact is to define the impact itself—that is, by type of hazard and the preferred pilot, airline, and aircraft response to that hazard. This has been pursued to date with greatest emphasis for convective weather hazards. However, we present weather impact models for turbulence and in-flight icing to gain further insight into a more general weather hazard model for NextGen. Our model includes convective, turbulence, icing, and other hazard types in a Weather Impact Interaction Grid (WIIG). In particular, we describe:

• Incorporation of a Convective Weather Avoidance Model (CWAM) as described in the literature for en route and in the terminal area

• Incorporation of a Clear Air Turbulence (CAT) Weather Avoidance Model (CATWAM) for en route, based on actual observed pilot and aircraft responses to Graphical Turbulence Guidance (GTG) forecast data

• Incorporation of in-flight Icing Weather Avoidance Model (IWAM) for expected pilot and aircraft responses in the terminal and transition airspace icing hazards

• An important classification of weather hazards as either hard or soft constraints:

o Hard constraints are formed by weather hazards through which no aircraft can safely fly (e.g., severe convection, turbulence or icing).

o Soft constraints are formed by weather hazards through which some pilots or airlines decide to fly, while others do not (e.g., moderate turbulence or icing)

• Mathematical modeling of deterministic and probabilistic weather forecasts, as well as the modeling of deterministic and probabilistic weather impacts.

Second, through modeling the weather hazard and simulation of future, NextGen traffic flows within NASA's Future ATM Concepts Evaluation Tool (FACET), we draw conclusions about the systemic affects of the individual preferred responses. Through these simulations, we begin to define TFM strategies that will help mitigate both individual and NAS-wide TFM impacts in the NextGen environment. Results from the simulations demonstrate the NAS impacts of imprecise weather forecasts and uncertain aircraft responses. We conclude the paper by suggesting how such a simulation capability can be used in the development of requirements for more precise weather forecasts for NextGen.