Aviation Weather Testbed Blog: Capacity Reduction Fields

One of the tools that has been used to diagnose the potential impacts to air traffic is the probability of airspace capacity reduction fields produced by the NCAR Research Applications Lab. This tool uses members of the Air Force Weather Agency ensemble to diagnose the potential reduction of airspace due to weather. This product can be thought of as a geometry problem, with each member analyzed to determine the extent to which flow into and out of a 100-km grid box will be obstructed using a mincut technique. The capacity reduction for each of the members are then combined to produce a field that depicts the probability of a certain amount of airspace reduction, at a certain level, and in a certain direction of flow.

Note that because this problem simply uses the geometry of the grid to determine capacity reduction, it does not take into account planned or actual traffic.
Thus, using a simple example, if the number of planes that can fly through a particular portion of airspace over an hour is 80, and the demand for this hour is only 25 aircraft, a 50% reduction of airspace capacity (in the geometric sense, as is diagnosed in these products) will not impact aviation operations through this region.

Shown here are fields of 50% reduction in airspace capacity at FL300 (30,000 ft). This shows the proportion of AFWA members that show a blockage of at least 50% for that particular 100-km grid box. These are computed for two directions of flow: east-to-west/west-to-east, and north-to-south/south-to-north. To get an idea of how these fields are derived, plots of the individual members are shown below the capacity reduction fields.

The first set of images is valid at 1700, when the AFWA members are capturing the system off the Atlantic coast. The first frame depicts the reduction in the north-south direction, with the second frame depicting the east-west capacity reduction. Because the line is oriented southwest-to-northeast fashion, the difference between the two directions is not as pronounced. Another contribution to this similarity is the scale at which these fields are produced.

Probability of 50% reduction of FL300 air capacity in North-South direction at 1700 UTC.

Probability of 50% reduction of FL300 air capacity in East-West direction at 1700 UTC.

AFWA ensemble members showing simulated composite reflectivity >= 40 dBZ at 1700 UTC.

The next three images are valid at 2000 UTC, after several members of the AFWA are developing convection along the coastal sea breeze. The difference between the two orientations is a bit more pronounced in this case, especially along the South Carolina coast. The capacity reduction product indicates that the flow will face a greater (geometric) constraint in the north-south direction than in the east-west direction, which can be seen by looking at the individual solutions in the third image. Along the Florida and Georgia Atlantic coast there is more reduction in the east-west direction due to the orientation of the convection in this region.