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Here we illustrate the opportunity that WRF gives as a wind field model for Puff. WRF or the Weather Research and Forecasting model is generated on a 7.5 km horizontal resolution grid for the Alaska region at ARSC, University of Alaska Fairbanks. The animations below show the effect of having the WRF model to be used for predictions of the movement of volcanic ash. Figure 1 is a time series animation of a hypothetical eruption from Mount Spurr on 18th October 2006 at 00:00 UTC. This is for a 3 hour eruption, outputs of location of the ash cloud every 10 minutes. This shows the 2D top view of the volcanic ash movement. This is for the North American Mesoscale model or NAM grid 216. This has a horizontal resolution of 40 km and this runs hows the ash movement towards the North and Northeast of Mount Spurr.
Figure 2 shows the same eruption but using the 7.5 km resolution WRF data. You can see the interaction with the topography once the ash cloud reaches the Alaska Range. Here the eastern edge of the ash cloud is forced upwards as a result of the topographically forced wind fields in the WRF data. In addition, you can see the western edge of the ash cloud staying at lower levels and moving around the topography and carrying on further North. This feature is not seen in the model run from the NAM wind fields. Here we can see that the WRF wind fields better represent the airflow over and around the Alaska Range.
Figure 3 shows a top view of the same ash cloud in Google Earth showing how the data from Puff can be showed in an easy to view geographical context.
Figure 4 is a side view looking at the same ash cloud. You can see the ash cloud being forced to move vertically as a result of the interaction with the Alaskan range. The WRF data not only provides improved wind fields over topographic features but also at the volcano location. Given the 7.5 km resolution to the 40km NAM216 grid then the wind fields at the volcanoes location are better represented with the WRF model as there will be a grid point location closer to the volcanoes location.
Figure 5 shows the ash cloud at 07:30 UTC on 18th October, dropping down from a top view to a side view. This clearly shows the interaction that the ash cloud has had with the Alaskan Range. As the animation drops down, the section of the ash cloud that has been forced upwards becomes clear to the eastern side of the animation.
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