Real-time Module

The real-time module combines passes over marine surface platforms with one or more figure four patterns in the core of the hurricane. The aircraft flies at or below 1500 m (ideally at 750 m), so that flight level winds can be adjusted to 10 m to combine with measurements from marine surface platforms. Flight-level data collected near the platforms will be used to validate the adjustment method. Doppler data collected in the figure four will be analyzed with EVTD in real-time on the HRD workstation. The lowest level of the EVTD analysis may be sent to NHC where the Doppler winds can also be adjusted to the surface and made available to HRD's real-time surface wind analysis system. Note that if the storm is outside of WSR-88D Doppler range then the figure four pattern could be repeated before returning home.

For example, if a hurricane moves within range of Melbourne, Florida, then we could fly a pattern to take advantage of buoys 41009 and 41010. The aircraft descends at the initial point and begins a low-level figure 4 pattern, modifying the legs to fly ov er the buoys (Fig. 3).

Whenever the drift angle permits the radar will be in FAST mode, except in the eye penetrations. If time permits the aircraft would make one more pass through the eye and then fly the dual-Doppler module. In this example the pattern would be completed in about 2.5 h.

Dual-Doppler Option 1:

If the tropical cyclone moves within Doppler range of a coastal WSR-88D ( 230 km), then we will fly a second module, to collect a time-series of dual-Doppler data from the storm's inner core. Note that the optimal volume scans for this pattern will be ob tained when the storm is 60-150 km from the radar, because beyond 150 km the lowest WSR-88D scan will be above 1500 m which is too high to resolve the low-level wind field. Within 60 km the volume scan will be incomplete, because the WSR-88D does not scan above 19.5 deg.

The pattern will depend on the location of the storm relative to the coastal radar. Continuing our example for the Melbourne WSR-88D, after completing the real-time module the aircraft flies to an initial point on the track intersecting the storm center and the coastal radar (Fig. 4).

Depending on safety and operational considerations, the aircraft could fly this portion of the experiment at a higher altitude, although 1500m would still be preferred. The aircraft then makes several passes through the eyewall (A-B in Fig. 3), with the t ail radar scanning perpendicularly to the track.

Depending on the size of the eyewall each pass should last 10 to 20 minutes. It is essential that these passes be flown as straight as possible, because turns to fix the eye will degrade the Doppler radar coverage. After each pass the aircraft turns quick ly and heads back along the same track, adjusted to keep the storm center and the coastal radar on the same line. In 2 hours 6-12 volume scans will be collected. The last pass should be followed by a pass through the eye perpendicular to the other legs, t o provide data for EVTD and pseudo-dual Doppler analyses. If time permits, the real-time module could be repeated before returning home.

Dual-Doppler Option 2:

If dual-Doppler data are desired over a larger area, then another module will be flown where the aircraft flies along three WSR-88D radials to survey both the inner core and surrounding rainbands (Fig. 4).

In the example shown, this pattern could be flown in about 2 h. Note that the legs outside the inner core should be flown with the tail radar in FAST mode because the drift angle would be smaller. This would give triple Doppler coverage in the rainbands. In the example the module concludes with a pass south along the coast.


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