Atmospheric Processes Illustration (IMAGE) DOE/Brookhaven National Laboratory Caption Scanning the pristine skies above the Amazon rainforest revealed that small aerosol particles that form naturally in the upper atmosphere are carried to the lower atmosphere by rapid downdrafts associated with rainfall. There, volatile organic compounds (VOCs) emitted by trees react with oxidants, and the oxidation products condense on the small particles and make them grow into the "nuclei" around which clouds form. Studying this process in a clean environment will help scientists improve their understanding of the effects of industrial era emissions on climate. Credit Luiz. A. T. Machado, National Institute for Space Research, São José dos Campos, São Paulo, Brazil Usage Restrictions OK for use with stories about this research. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.