Precipitation over the Australian Alps (AA) constitute an important source of water to south-eastern Australia, supplying fresh water for agriculture, industry, and domestic use particularly on the Murray and Murrumbidgee Rivers. In addition, Snowy Hydro LTD actively redistributes water towards the Murray basin that would otherwise flow into the Tasmanian Sea through the Snowy River. This water management greatly benefits from accurate prediction of precipitation both spatially and temporally wise.

The current precipitation estimates available for this region have been shown to have worrisome biases, with underestimation of precipitation more pronounced along the windward slopes. We carried an intensive observation campaign during the 2018 winter, which for the first time provides a comprehensive dataset with ground morphology and radar measurements in various locations. We had 3 sites at different heights in the windward slope of the mountain range, supported by a wide network of rain gauges. This allowed us to elucidate the specific dynamical and microphysical processes that produce precipitation over these mountains.

Although the campaign took place during a relatively dry year, 43% less precipitation compared to the local climatology, we observed 12 precipitation events during the measurement period. For the high altitude sites, above 60% of the total precipitation was in the form of snow while 10% was observed as supercooled liquid water (SLW). Convective to stratiform transition was associated during the events with highest total precipitation as well as orographic increase in snowfall frequency. We found that about 70% of the precipitation on the high altitude sites was associated with post-frontal conditions while this bias was not as strong in the low altitude sites. Models with microphysics schemes that can replicate the observations of SLW should be able to better represent the region’s precipitation.