CLIMATOLOGICAL CHARACTERIZATION OF 3-DIMENSIONAL STORM STRUCTURE FROMOPERATIONAL RADAR AND RAIN-GAUGE DATA

Three algorithms extract information on precipitation type, structure, and amount from operational radar and rain gauge data. Tests on one m onth of data from one site show that the algorithms perform accurately and provide products that characterize the essential features of the precipitation climatology. Input to the algorithms are the operational ly executed volume scans of a radar and the data from a surrounding ra in gauge network. The algorithms separate the radar echoes into convec tive and stratiform regions, statistically summarize the vertical stru cture of the radar echoes, and determine precipitation rates and amoun ts on high spatial resolution. The convective and stratiform regions a re separated on the basis of the intensity and sharpness of the peaks of echo intensity. The peaks indicate the centers of the convective re gions. Precipitation not identified as convective is stratiform. This method avoids the problem of underestimating the stratiform precipitat ion. The separation criteria are applied in exactly the same way throu ghout the observational domain and the product generated by the algori thm can be compared directly to model output. An independent test of t he algorithm on data for which high-resolution dual-Doppler observatio ns are available shows that the convective-stratiform separation algor ithm is consistent with the physical definitions of convective and str atiform precipitation. The vertical structure algorithm presents the f requency distribution of radar reflectivity as a function of height an d thus summarizes in a single plot the vertical structure of all the r adar echoes observed during a month (or any other time period). Separa te plots reveal the essential differences in structure between the con vective and stratiform echoes. Tests yield similar results (within les s than 10%) for monthly rain statistics regardless of the technique us ed for estimating the precipitation, as long as the radar reflectivity values are adjusted to agree with monthly rain gauge data. It makes l ittle difference whether the adjustment is by monthly mean rates or pe rcentiles. Further tests show that l-h sampling is sufficient to obtai n an accurate estimate of monthly rain statistics.