Wednesday, 14 January 2004: 1:45 PM
Improved Super-Ob Radar Radial Wind Precision for the NCEP Data Assimilation and Forecast System
The spatial and temporal densities of WSR-88D raw radar radial wind represent a rich source of high resolution observations for initializing numerical weather prediction models (NWP). A characteristic of these observations, in terms of NWP, is the presence of a significant degree of redundant information. The variance of radar returns of radial wind due, for example, to beam widening and other phenomena is one factor in decreasing the information content. A sufficiently high resolution numerical weather prediction model, with suitable schemes to assimilate and analyze the radar radial winds with other conventional and non-conventional observations, is necessary to utilize high resolution observations. In addition, the large amount of level II radar data poses a bandwidth problem to deliver the observations to a central site and given both above mentioned variance of radar returns and model utilization, it is desirable to effect whatever data compression the fresh observations allow while minimizing any degradation of the information content. It is thought that the precision and information content of the radial wind can be improved if data at each radar site is directly utilized at the resolution and precision of the WSR-88D radar. In addition, with data compression, the total volume of data is reduced allowing quality control information to be included. The radar radial wind super-ob product (Alpert et al., 2003), takes the result of radar scans and averages data points within a prescribed 3-dimensional volume before transmission and central collection of base data. A test of the impact of radar radial wind super-ob will be done using the NCEP Eta Data Assimilation System. These will be compared with currently used NEXRAD Information Dissemination Service (NIDS) radial winds.
A SUPER-OB FOR THE WSR-88D RADAR RADIAL WINDS FOR USE IN THE NCEP OPERATIONAL ASSIMILATION SYSTEM. 2003: Jordan C. Alpert, NOAA/NWS/NCEP, Camp Springs, MD; and P. Pickard, Y. Song, M. Taylor, W. B. Facey, M. Istok, and D. F. Parrish, 19 Conf IIPS, Long Beach, P1.51.