Sutherland-Stacey, L.; Shucksmith, P.; Austin, G.; A mobile rain radar for high resolution hydrological observations in New Zealand,
Rain processes operate at a wide range of spatial and temporal scales, and significant variability in precipitation occurs over physical extents and timeframes that are poorly sampled by operational observing systems, even by the comparatively fine sampling capabilities of national radar networks. At present, measurements with the highest spatial and temporal resolution are made with research radars. This paper describes an X-band mobile weather radar system that has been constructed at the University of Auckland, New Zealand, to make observations with high spatial (≈100 m) and temporal (≈15 sec) resolution. A description of some recent field work is presented, with particular attention to sampling scale problems. The radar was deployed overlooking a small (≈150 km2), steep, catchment in the central North Island of New Zealand during the winters of 2008 and 2009. Data from the field work is used to qualitatively demonstrate the need for high resolution measurements for rigorous observation of small-scale structures such as discrete convective cells and larger systems with embedded convection. The sampling representivity errors associated with such meteorological systems are discussed for X- and C-band radars. X-band radar rainfall rate retrievals are also compared to a gauge network. Statistical analysis of the comparison for short ranges (<15km) gave RMS error statistics of c. 1mm/hr, but agreement was poorer at longer ranges (>15km) due to site limitations and to low radar power and attenuation limitations. The implications of the scale limitations of conventional measurement techniques for sampling rainfall accumulation over small catchments are also discussed, with an illustrative example from the field work.