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<---Aircraft as KMZ |
Puff Simulation as KMZ---> |
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Puff simulation of Ash-Aircraft encounter from December 1989 Mt. Redoubt Volcano Eruption |
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Redoubt volcano (60.42oN, 152.74oW, 3108 m ASL) is situated 166 km (103 miles) south west from Anchorage, see Figure 1 (adapted from Miller and Chouet, 1994). During December 1989, Mount Redoubt volcano produced numerous volcanic eruptions and on December 15th, an international aircraft flying from Amsterdam to Anchorage encountered a resulting volcanic ash cloud that shut all 4 engines down. This eruption resulted in a nearly catastrophic encounter between airborne ash and the Boeing 747 jet aircraft (most of southern Alaska was completely covered by meteorological clouds on that day). The eruption started at 10:15 am AKST (19:15 UTC) and produced an ash cloud to 40,000 ft altitude. The Boeing 747 aircraft entered the ash cloud at approximately 25,000 ft, 150 miles north-northeast from Mount Redoubt. Table 1 below show the details of the aircraft encounter, from Figure 2 (adapted from Casadevall, 1994). |
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Figure 1 Redoubt volcano Location map )
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Figure 2 747 route on December 15th )
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Table 1: Aircraft encounter timings
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2. The volcanic eruption parameters and Puff model predictions
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The Puff model (Searcy et al, 1998) will be used to simulate the volcanic eruption from Mount Redoubt that the Boeing 747 aircraft encountered. Table 2 shows a list of the eruption parameters. The model requires information on eruption length, plume height, start time, Mass distribution be height and ash particle size. Numerical weather prediction wind fields are used for simulating the ash cloud movement. The ash particles are tracered, in time, as they diffuse, disperse and settle within the atmosphere. The event that the aircraft encountered, occured at 19:15 UTC on December 14 1989. From USGS (1992) and Miller and Chouet (1994), the eruption lasted for 40 minutes and produced an ash plume to greater than 12km, with its azmiuth to NNE. Table 2 shows a list of the eruption parameters used for the Puff simulations. |
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Table 2: December 15th 1989 eruption parameters
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Figure 3 Schematic of Poisson Vertical Distribution. )
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From these eruption parameters, the Puff model was used to track the ash cloud movement. Figures 4 and 5 illustrate this. Here the ash cloud moves in a NNE direction over the Anchorage area. These images show the ash cloud height via color coded by altitude. However, these images do not allow us to illustrate the true three dimensional nature of the ash cloud or show the aircraft-ash cloud encounter. This is were Google EarthTM comes into its own..... |
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Figure 4a Puff image of ash cloud at the start of eruption )
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Figure 4b Puff images of ash cloud further into the eruption )
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Figure 4c Puff animation of volcano ash cloud movement
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For the analysis of the aircraft-ash encounter with Google Earth, we first determine its movement from Figure 1 (from Casedevall, 1994). This provided us with the timings and locations of the aircraft at the most important points. For a smooth movement of the aircraft, we interpolated its location between these points as a linear movement in time. Using the timestamping option within KML and the time-slider, we were able to aminate the aircrafts movement. Figure 5 show the aircraft used and its movement in Google Earth. A model was used of the aircraft from the Google Earth 3D warehouse (see link). |
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Figure 5a and b Snapshot and Animation of the KLM flight with Google Earth |
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For the Puff mode simulation, we have the location of the ash particles every time output for the length of the simualtion. We are tracking 10,000 particles, so to display them in Google Earth we use 'Placemarkers'. Each ash particle, per time output, becomes a placemarker using a semi-transparent png image for the ash particle. Then all the ash particles per time output are 'timestamped'. This allows us to use the time-slider within Google Earth to animate the movement of the ash particles. Figures 6 and 7 shows a time snapshot of the Puff simulation and then how the time slider allows animating the ash particles. |
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Figure 6 Time Snapshot of the Puff simulated ash particles |
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Figure 7 Animation of Puff prediction |
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Once we had the aircraft and ash clouds movement as KMZ files, we were able to display them together within Google Earth and examine in 3D and in great detail the aircraft-ash encounter. Figures 8 and 9 show the encounter in 3D within Google Earth. We found analyzing both together, that the aircraft only encountered the distal edge of the ash cloud. This sort of analysis would have been much harder without the use of Google Earth to show both datsets in 3D. Google Earth allowed us to show the position of the aircraft to the ash cloud in 3D as well as allowing us to move around the encounter, examing it from mutliple directions and elvations.... |
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Figure 8 Time Snapshot of the Aircraft-ash cloud encounter |
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Figure 9 Animation of the Aircraft-ash cloud encounter |
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4. References
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Casadevall, T. J. (1994). The 1989/1990 eruption of Redoubt Volcano Alaska: impacts on aircraft operations. Journal of Volcanology and Geothermal Research. 62 (30). 301- 316 Keith, T. E. C., (ed.), 1995. The 1992 eruptions of Crater Peak Vent, Mount Spurr volcano, Alaska. U.S. Geological Survey Bulletin. 2139, 220 p. Miller, T. P., and Chouet, B. A., 1994, The 1989-1990 eruptions of Redoubt volcano: an introduction: in Miller, T. P. and Chouet, B. A., (eds.), The 1989-1990 eruptions of Redoubt Volcano, Alaska, Journal of Volcanology and Geothermal Research, 62, (1), 1-10. Searcy, C., Dean, K. and Stringer, W. (1998). PUFF: A high-resolution volcanic ash tracking model. Journal of Volcanology and Geothermal Research. 80. 1 - 16. |