The New Zealand Reanalysis (NZRA) : development and preliminary evaluation

The New Zealand Reanalysis (NZRA) is the first high-resolution convection-permitting atmospheric regional reanalysis model over Aotearoa New Zealand (NZ). NZRA has a spatial horizontal grid spacing of 1.5km and is forced using data from the Bureau of Meteorology Atmospheric high-resolution Regional Reanalysis for Australia (BARRA-R) with approximately 12km horizontal grid spacing. This paper outlines the development of NZRA, including the numerical weather forecast model and driving model. In addition, the performance of NZRA is compared against BARRA-R and global reanalysis products (ERA - Interim and ERA5) and validated against observational data collected during June-July 2014 as part of the Deep Propagating Gravity Wave Experiment (DEEPWAVE) field campaign. The results demonstrate that dynamically downscaling BARRA-R to NZRA considerably enhances the wind and temperature predictions, particularly capturing well the diurnal temperature cycle, wind speeds above 95th percentile, and gust wind speeds over the high elevation regions of NZ. In addition, NZRA provides better estimates of total precipitation over the North Island, Canterbury region, West Coast and the southern part of the South Island compared to the Virtual Climate Station Network (VCSN) gridded observation-based product, other reanalyses and NIWA's operational convective-scale forecast model, NZCSM, as was run in 2014.