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<br />The profiles for 16 November 1998, in figure 7c, show a period of virga at KBIS and KABR that covers <br />only a minor portion of the radar view. The KMPX pattern indicates almost total virga; only trace <br />amounts reach the surface. KMVX and KDLH start as virga and change to a precipitation gradient <br />(increasing downward) before becoming weak echoes covering only minor portions of the radar view. <br /> <br />Figures 7d-e show that the storm of 18-19 November 1998, starts as virga at all five radars. Towards the <br />end of the 18th, there is precipitation to the ground at the three more northern radars, KBIS, KMVX, and <br />KDLH. On the 19th precipitation reaches the ground at all radars. KBIS changes to virga, as does KABR <br />at the very end. At KDLH and KMPX the precipitation weakens to very light and scattered <br />accumulations. <br /> <br />Our opinions about VPR were verified at the 11 June 1999 QPE workshop in Reno, Nevada. A <br />presentation was made, based on a paper proposed by Dong-Jun Seo, J. Breidenbach, R. Fulton, D. <br />Miller, and T. O'Bannon, that showed the utility of a VPR correction. The cases presented showed <br />strong bright band effects, which were removed by the algorithm. Their algorithm appeared to be <br />superior to what we had been considering for testing. Their algorithm would not only correct for bright <br />band (warnings and corrections) but also correct for virga and underestimation with range. It appears <br />that work should continue on efforts to incorporate the use of the VPR into the SAA. <br /> <br />The vertical profile graphs presented here (figures 1 and 7 a-e) could be the basis for a simpler VPR <br />analysis, and therefore, the coding for generating them is presented in appendix A. It may be possible to <br />analyze these hourly graphs within the SAA and generate decisions about virga presence, bright band <br />presence, and the vertical profile of reflectivity. The latter might feed into a range correction scheme. <br />These goals are beyond the scope of this project but could be investigated in the future. <br /> <br />7.4 Virga Removal <br /> <br />In addition to the vertical profile graphs, virga can <br />be seen as echoes at far range, typically in a partial <br />to full ring around the radar, with nothing at close <br />range. Figure 8 gives an example of virga <br />contamination on a 24-hr SAA product for <br />18 November, 1998, for KMPX. Virga produced <br />rings of accumulation around the edges of the view <br />while there was nothing accumulated at close <br />ranges. The range correction (a factor of <br />3 increase at 230 km) accentuated the edge values. <br />For major storms, the range correction appeared to <br />be correct (see discussion for figures 6 a-e) out to <br />far ranges, beyond ranges for which it was <br />calibrated. Eliminating range correction was unac- <br />ceptable for major storms. Without range <br />correction, accumulations decreased markedly with <br />range, producing a bull' s eye pattern around the <br />radar . <br /> <br />~~;-I~~".c.'~~~ <br /> <br />.',Ii. <br /> <br />", <br />" <br />.\ <br />\ <br /> <br /> <br />KMPX <br />ending <br />18 Nov. 1998 12Z <br /> <br />Figure a.-Virga creates a donut pattern around the radar <br />in the SAA products. <br /> <br />16 <br />