Abstract:

Understanding the complex interactions between aerosol, clouds, and precipitation is an important and necessary step towards understanding the climate system and the development of accurate global and regional climate models. To develop a comprehensive view of aerosol-cloud indirect effects (AIEs) and further improve these models, observations and analyses of the 1st, 2nd and semi-direct AIEs during extreme events are needed. Here, we study the relationships between aerosols, clouds, and precipitation during “Black Summer,” Australia’s extreme 2019-2020 biomass burning event. This study will focus on aerosol-cloud indirect effects over the Pacific Ocean (from Australia’s coast to South America) during this unprecedented event. To evaluate the impact of the plume on clouds and precipitation we use gridded aerosol properties (optical depth (AOD), aerosol index (AI)), fire counts, and cloud properties (cloud fraction (CF), effective radius (Re), cloud top pressure (CTP)) from Aqua-MODIS and TRMM/GPM Precipitation (R) and NCEP NCAR Reanalysis data for meteorological background. Using data from December and January 2002-2018 we establish a baseline for aerosol-cloud-precipitation interactions and identify years with the lowest and highest aerosol conditions. We evaluate the 2019-2020 data to quantify how extreme changes in cloud properties and precipitation are with respect to these past observations.