Precipitation and Attenuation Estimates from a High Resolution Weather Radar Network (PATTERN) - Design of the Experiment

Precipitation plays an important role in driving the energy and hydrological cycle of the atmospheric boundary layer. High resolution in situ and ground based remote sensing observations are needed to gain detailed insight in these processes for flood forecasting, urban hydrology, hydro-meteorological applications and management of risk and uncertainty. Rainfall products of conventional radar systems used in nationwide or larger networks are generally based on reflectivity measurements at S- or C-band wavelength. These radar systems cannot meet all present and future demands of resolution. For the different practical applications the requested spatial resolution is 0.1 km with a temporal resolution of 1 minute or below (Einfalt, 2003). Therefore, radar systems which are capable of producing reliable and accurate quantitative estimates of rainfall at high temporal and spatial resolution are required. Besides the higher resolution, radars operating at high frequencies benefit from lower costs because of smaller antenna size compared to long wave radars (Bringi et al., 1990). In recent years novel, low-cost high resolution weather radar (HRWR) systems have been developed. These systems are able to scan precipitation with spatial resolution of 60 meters in range and temporal resolution of 30 seconds. HRWRs operate in the X-band frequency range. As many authors stated since the early weather radar meteorology, microwaves are affected by attenuation due to rain (e.g. Atlas and Banks, 1951; Gunn and East, 1954, Wexler and Atlas, 1963; Dutton, 1967; Atlas and Ulbrich, 1977). The project Precipitation and Attenuation Estimates from a High Resolution Weather Radar Network (PATTERN) intends to demonstrate that a HRWR network can overcome this apparent drawback. In regions covered by more than one radar, it is possible to derive both intrinsic reflectivity and specific attenuation. The relation between specific attenuation and precipitation rate varies less than the commonly used relation between reflectivity and precipitation rate. Specific attenuation as additionally observed quantity will likely improve the accuracy of rain rate estimates.