Extreme rainfall affects communities’ safety, agriculture, and infrastructure.  Climate change is changing precipitation patterns around world, in part due to changing synoptic and mesoscale processes.

This work focuses on identifying the synoptic and mesoscale processes behind extreme rainfall in southeastern Australia.  High resolution precipitation reanalysis data is used from The Bureau of Meteorology Atmospheric high-resolution Regional Reanalysis for Australia (BARRA-R) from 2010 to 2015.  The regional reanalysis has hourly 12 km resolution data.

Verification of BARRA-R for rainfall and rainfall extremes was undertaken by comparing rainfall indices to both daily AWAP data and hourly automatic weather station data.  Spatial patterns of daily indices in BARRA-R was compared to re-gridded AWAP for the same time period over southeastern Australia, and hourly rainfall characteristics including precipitation timing and intensity in BARRA-R were compared to automatic weather station data in Victoria.  This verification gives confidence that BARRA-R can represent the spatial precipitation patterns over hourly to daily timescales, including local effects such as topography.  Automatic weather typing is used to correlate regional scale features, such as mean sea level pressure, to local rainfall patterns.

Weather typing leads directly to using CMIP projections to analyse how the frequency of these driving patterns is expected to change in the future, and therefore how extreme rainfall incidence is expected to change.  This work will be useful for planning infrastructure to be suitable for future climate. Weather typing and downscaling will also be useful for forecasting events on shorter timescales.