Very-high-resolution single-sounding tornado simulations
Simulation and Prediction of May 3, 1999 Oklahoma City F5 Tornado (work of Daniel Dawson)
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Simulation and Prediction of May 3, 1999 Oklahoma City F5 Tornado (work of Daniel Dawson)A new multi-moment ice microphysics package from Milbrandt and Yau (MY05) was recently implemented inside the ARPS. The package contains single, double, triple (or 1, 2 and 3) moment options and a 2.5-moment option (referred to as MY1, MY2, MY3 and MY2.5 hereafter). Ph.D. student Daniel Dawson applied the MY scheme to the May 3rd, 1999 OKC F5 tornado case, initializing it using the ADAS and cloud analysis package but with special though still preliminary treatments for additional moments within the assimilation cycles. The results show that the two- and three- moment options produce cold pools and storm structures that agree much better with observations than those using any of several single-moment ice microphysics schemes available in the ARPS. Using a 100 m x, the ARPS model is able to produce a tornado in both runs using MY1 and MY2 (Fig. 5), although the tornadogenesis processes appear to be dramatically different in the two runs. In the MY1 run, the downdraft and cold pool are much stronger, and the simulated storm exhibits the structure of a high-precipitation supercell with a strong FFD and associated precipitation core (Fig. 4a). The cold pool in the MY2 case is much weaker and rear flank gust front is only poorly defined (Fig. 4b) and the storm appears more like the classic supercell with weak precipitation core and FFD. The first tornado in the MY1 run formed shortly before one hour (Fig. 4a) at the classic occlusion point of gust fronts while in the MY2 run, the first tornado formed half an hour later and is weaker (Fig. 4b). 
Fig. 4. Surface perturbation potential temperature (gray shading), reflectivity (blue contours), vertical vorticity (color shading), and horizontal wind vectors at the time of largest vertical vorticity using 100 m resolution and with MY1 (a) and MY2 (b) schemes The 3D cloud and vorticity structure of these two simulations are also very different at the time of their first tornadogenesis (Fig. 5). Preliminary examination of the 3D fields indicate that RFD does exist in the MY2 case, but is closely wrapped around the tornado vortex, and it contains a smaller number of large raindrops that limits rain evaporation. Such low precipitation pattern was actually observed for this case.  
Fig. 5. Vis5D visualization of the cloud field (gray surface), and 0.3 s-1 vertical vorticity iso-surface (yellow) from the 100 m simulations using MY1 (left) and MY2 (right) schemes, for times shown in Fig. 4. Above work was done on Ranger. Directory: pub pub -> Project Scoring Template Pre-Construction Phase New Core/Branch Campus Projects pub -> Acm word Template for sig site pub -> The german unification, 1815-1870 pub -> Baltic Olympiads in Informatics: Challenges for Training Together pub -> Preparation of Papers for ieee transactions on medical imaging pub -> Forthcoming meetings and conferences pub -> Asilomar Conference on Circuits, Systems & Computers, Pacific Grove, ca, November 1978, pp. 55 58 pub -> Forthcoming meetings and conferences pub -> Harmonised compatibility and sharing conditions for video pmse in the 7 9 ghz frequency band, taking into account radar use Download 0.63 Mb. Share with your friends:
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