Proceedings with Extended Abstracts (single PDF file) - Radio ...

Figure 8 shows the profile of virtual temperature(Tv) at 2030 JST on 29 Dec. and at 0030JST on 30 Dec. derived from the surface measurement,a radio sonde, the tower and RASS.The Tv measured with the radio sonde has agood agreement with RASS at 2030 JST; theTv from the sonde is almost within the error barof RASS measurement. The bias of the RASSmay be attributable to the increase of Tv withtime in the observation. Indeed, the Tv at thesurface increased 4 K over four hours. The Tvfrom RASS at 0030 JST has a good agreementwith the tower measurement at altitude of 150m and 200 m. These results show that the Tvprofile measured with RASS is trustable.Figure 9 indicates the profile of the square ofthe Scorer parameter derived from the profilerand RASS. The propagation speeds of the solitarywave are assumed to be the same and twotimes as fast as that of the gravity current in thecalculation. This figure shows a region of negativeK 2 is just above the solitary wave.Figure 10 shows the profile of the square ofthe Brunt Väisälä frequency. This figure alsoshows a negative region of N 2 just above thesolitary wave. These facts show that there aresome layers that determine the top of the solitarywave.4. ConclusionThe MVD method has better accuracy than theVTB method. The MVD is less sensitive to theclutter and to the second trip echo. The maximumw seen at the top of solitary wave is notdue to an error of the MVD method but is dueto wave duct for a BDO type of solitary wave.The MVD method is shown to be trustable forvertical airflow analysis.Height [m AGL]Height [m AGL]800600400200Radiosonde (2030 JST)RASS (2030 JST)Tower (0030 JST)RASS (0030 JST)Surface (0030 JST)0274 276 278 280 282Tv [K ]Fig. 8. Profile of virtual temperature Τv at 2030JST on 29 Dec. and 0030 JST on 30 Dec. Theerror bars represent 2σ in RASS observation.800600400200Cs = 2CgCs = Cg0-10 -5 0 5 10 15 20K 2 [10 -5 S -2 ]Fig. 9. Profile of the square of the Scorer parameterΚ 2 at 0030 JST on 30 Dec. derived from theprofiler with RASS. The solid line is for the solitarywave propagating at the same speed as the gravitycurrent, while the dashed line is for two timesfaster than that of the gravity current.ReferenceEcklund, W. L., D. A. Carter and B. B. Balsley,A UHF wind profiler for the boundary layer:Brief description and initial results, J. Atmos.Oceanic Technol., 5, 432-441,1988.Gossard, E. E., D. E. Wolfe, K. P. Moran, R.A. Paulus, K. D. Anderson and L. T. Rogers,Measurement of clear-air gradients and turbulenceproperties with radar wind profilers, J.Atmos. Oceanic Technol., 15, 321-342,1998.Haase, S. P. and R. K. Smith, The numericalsimulation of atmospheric gravity currents. PartII. Environments with stable layers, Geophys.Astrophys. Fluid Dynamics, 46, 35-51, 1989.Jin, Y., S. E. Koch, Y.-L. Lin, F. M. Ralph andC. Chen, Numerical simulations of an observedgravity current and gravity waves in an environmentcharacterized by complex stratificationand shear, J. Atmos. Sci., 53, 3570-3588,1996.Rottman, J. W. and F. Einaudi, Solitary wavesin the atmosphere, J. Atmos. Sci., 50, 2116-2136,1993.Height [m AGL]8006004002000-1.0 -0.5 0 0.5 1.0 1.5 2.0N 2 [10 -4 S -2 ]Fig. 10. Profile of the square of the Brunt Väisäläfrequency N 2 at 0030 JST on 30 Dec. derived fromthe profiler with RASS.Strauch, R. G., B. L. Weber, A. S. Frisch, C.G. Little, D. A. Merritt, K. P. Moran and D. C.Welsh, The precision and relative accuracy ofprofiler wind measurements, J. Atmos. OceanicTechnol., 4, 563-571, 1987.301