An Application of Reflectivity Climatology in Constructing Radar Hybrid Scans over Complex Terrain

Abstract

Three years' worth of radar reflectivity data from four radars in an area of complex terrain (Taiwan) from 2005 to 2007 were analyzed and a reflectivity climatology was developed. The climatology was applied in the construction of new hybrid scans to minimize the impacts of ground clutter and beam blockages. The reflectivity climatology showed significant seasonal variations and captured distributions of ground/sea clutters, beam blockages, and anomalous propagations in addition to precipitation systems in the radar domains.By comparing the reflectivity climatology with gauge observations, it was found that 15 (20) dBZ was a good approximation for rain/no-rain segregation during cool (warm) seasons. Comparisons between the standard (i.e., based on terrain and scan strategies only with the assumption of standard propagations) and nonstandard (i.e., standard plus the clutter and blockage mitigation using the reflectivity climatology) hybrid scans showed that the former did not accurately reflect the clutter and blockage distributions in the real atmosphere. The application of the reflectivity climatology was shown to significantly reduce the impacts of clutter and blockages and provided improved radar quantitative precipitation estimates (QPEs) in the complex terrain.

Warm Season Afternoon Thunderstorm Characteristics under Weak Synoptic-Scale Forcing over Taiwan Island

“…The mosaic grid has a spatial resolution of 0.01258 on the latitude-longitude coordinate system and a 10-min update cycle. Before the mosaic was developed, reflectivity observations were quality controlled (Chang et al 2009) to remove nonprecipitation echoes. The complex terrain around the radars results in beam blockage in some directions and ground clutter in other directions and creates difficulties in using radar to characterize thunderstorms over the CMR and eastern Taiwan.…”

“…The complex terrain around the radars results in beam blockage in some directions and ground clutter in other directions and creates difficulties in using radar to characterize thunderstorms over the CMR and eastern Taiwan. Chang et al (2009), following the procedures of others (Krajewski and Vignal 2001;Overeem et al 2009), conducted a comprehensive study using the Taiwan radars and rain gauges to identify radar beams that are blocked or partially blocked by terrain. Chang's study used radar reflectivity data from the four CWB radars and rainfall data from at least 370 rain gauges for the 3-yr period from 2005 to 2007.…”

“…Hybrid scans are a set of radar bins, from the lowest elevation angle, that do not have significant blockage or clutter (O'Bannon 1997; Maddox et al 2002). In the current study, reflectivity observations are quality controlled by the hybrid scans constructed by Chang et al (2009). These data were then used to identify and characterize afternoon thunderstorms.…”

“…Figure 2 shows the total accumulated rainfall for the 277 undisturbed days. Figure 2 was created by using an inverse distance-weighting function with a 30-km radius of influence (Chang et al 2009). The areas in which the total rainfall accumulation exceeds 1000 mm are principally located on the western side of the Snow Mountain Range (SMR) and the CMR (Fig.…”

On the Implementation of a Regional X-Band Weather Radar Network

“…Undoubtedly, weather radars are among the most relevant tools for accurately monitoring precipitation events, therefore they are a key instrument for the development of nowcasting and early warning systems. In addition, radar systems have been and still are an indispensable tool for observing weather and increasing the knowledge on precipitation dynamics and hydrometeor statistics [1][2][3][4], subjects of primary interest both in meteorology and in climatology.…”