Weather Impacts on Air Route Capacity

Lincoln Laboratory is actively conducting research to translate 3D convective weather information into en route capacity impacts. The capacity impact model combines weather avoidance fields (WAFs) from the Lincoln Laboratory developed convective weather avoidance model (CWAM) with en route airway geometry to estimate the capacity reduction due to convective weather along the route. Sector capacity reduction is calculated as the demand-weighted average of the route capacity reduction of all routes in the sector. The model is illustrated in Figure 1. Figure 2 illustrates an example of sector capacity reductions for low, high and super-high altitude sectors in the Cleveland Air Route Traffic Control Center (ZOB ARTCC) at 1900Z on July 27, 2007. Note that the capacity reductions are higher for lower altitude sectors, since pilots at higher altitudes are more likely to be able to fly over convection (and therefore not have to deviate).

NY weather impact movie stillExample of the far-reaching impact of weather on air traffic. Local weather impacting the major New York airports causes many incoming flights along numerous jet routes to go into circular holding patterns until the terminal area weather impacts cease. View movie (7.36MB)

Sector Capacity Model Validation

The sector capacity model has been validated for all sectors in the complete CIWS domain on three different case days. The time varying demand for each airway was estimated as the average of observed traffic on three different fair weather days. Observed traffic counts were calculated for each sector every minute and compared to the capacity calculated using the weather impact model. The results for all three days are summarized in Figure 3. The agreement between observed and estimated traffic is quite good: the observed traffic counts were within +/- 1 aircraft of the traffic count estimated by the model in more than half of sectors with non-zero weather impact,. The model accuracy is equally good for sectors with capacity reductions > 50%, although in sectors with higher impact the model tends slightly to overestimate impacts. Potential sources of error are illustrated in Figure 4, and are due mainly to the simplicity of the weather impact model. Continued work to develop realistic models for airspace usage that can capture this sort of operational flexibility is ongoing.

Uses of Weather Impact Model

The weather impact model is being incorporated into several research efforts and prototypes. The 2008 revision of the RAPT algorithm uses the route impact model to estimate route blockages. Sector capacity impacts are also input to the post-event analysis tool being used to estimated unavoidable delay due to convective weather.



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