An object-based climatology of precipitation systems in Sydney, Australia

Abstract

The climate is warming and this is changing some aspects of storms, but we have relatively little knowledge of storm characteristics beyond intensity, which limits our understanding of storms overall. In this study, we apply a cell-tracking algorithm to 20 years of radar data at a mid-latitude coastal-site (Sydney, Australia), to establish a regional precipitation system climatology. The results show that extreme storms in terms of translation-speed, size and rainfall intensity usually occur in the warm season, and are slower and more intense over land between ~ 10 am and ~ 8 pm (AEST), peaking in the afternoon. Precipitation systems are more frequent in the cold season and often initiate over the ocean and move northward, leading to precipitation mostly over the ocean. Using clustering algorithms, we have found five precipitation system types with distinct properties, occurring throughout the year but peaking in different seasons. While overall rainfall statistics don't show any link to climate modes, links do appear for some system types using a multivariate approach. This climatology for a variety of precipitation system characteristics will allow future study of any changes in these characteristics due to climate change.

Identification of Rainfall Events and Heavy Rainfall Events From Radar Measurements in Southeastern Australia

“…Ayat et al. (2022b) used an object‐oriented tracking algorithm to analyze the characteristics of precipitation systems in the Sydney region, and found that precipitation systems are most frequent during autumn and winter, but systems classed as extreme in terms of size, translation speed and rainfall intensity are most common during the spring and summer.…”

“…The Australian Unified Radar Archive (AURA) collates more than a decade of radar rainfall estimates across the operational weather radars deployed by the Bureau of Meteorology using a coherent and well‐calibrated methodology (Soderholm et al., 2022). While this data set has been used in previous studies to provide innovative insights into precipitation in specific regions (Ayat et al., 2022a, 2022b; Hitchcock et al., 2021), it also provides an opportunity to exploit radar observations to characterize and compare rainfall events in different regions across the Australian continent for the first time.…”

“…They were able to obtain valuable information pertaining to the attributes of linear systems in the study region, and found that linear systems occurring on heavy rainfall days tend to be larger and longer-lasting than linear systems on other days. Ayat et al (2022b) used an object-oriented tracking algorithm to analyze the characteristics of precipitation systems in the Sydney region, and found that precipitation systems are most frequent during autumn and winter, but systems classed as extreme in terms of size, translation speed and rainfall intensity are most common during the spring and summer.…”