Interactions of convective cloud ensembles with the large-scale atmosphere as revealed by nearly 20 years of radar data in Darwin, Australia.

Description

The Tropics are a key player for the Earth atmospheric system. In particular, tropical atmospheric convection has been identified as both a key process and a key uncertainty in understanding and simulating both past and future climates. Scanning radar systems are one tool to study convection, yet ground radar data available for research are quite rare and generally short term in the tropics. The C-band POLarimetric (CPOL) radar stationed at Gunn Point (~20 km from the Darwin ARM site), Australia, since 1998 is a great tool for atmospherics studies in tropical area. CPOL is a research focused dual-polarization Doppler radar that has produced more than 350,000 plan position indicator scans over 17 wet seasons. One of the key questions that remains largely unresolved is how the structure of a convective cloud ensemble relates to the large-scale state of the atmosphere. Using the 17 seasons of CPOL data we examine the influence of the large-scale atmosphere on tropical convective cloud properties. We characterize the cloud ensemble through the cloud area fraction and its vertical structure and further break this down into number, size, and depth distributions. We investigate how those vary with the large scale state, which we characterize through both daily meteorological regimes as well as large-scale parameters derived from a variational analysis approach applied to the same 17 years of data that are available from the radar.