High Rate Determinations of Dimethyl Sulfide and Sulfur Dioxide during Rain In Cumulus over the Ocean (RICO)

Drexel University, Philadelphia PA

Investigators

Abstract

Dimethyl sulfide (DMS) is produced in and released from the ocean but decays slowly in the atmosphere (primarily by oxidation to sulfur dioxide). It is also nearly insoluble in cloud water, so it provides a good tracer for boundary-layer air in oceanic clouds. In contrast, sulfur dioxide dissolves readily in cloud water so the decay of sulfur dioxide in clouds can provide a measure of cloud lifetime. In this study, the investigators will measure DMS and sulfur dioxide as part of the broader "Rain in Cumulus over the Ocean" (RICO) experiment, a multi-investigator study of warm-rain formation and the characteristics of trade-wind Cumuli. They will use DMS to track boundary-layer air as it moves into clouds and mixes with DMS-free air from above, and they will use sulfur dioxide concentration as an indicator of cloud lifetime. A primary objective of RICO is to understand the rate of warm-rain formation, so the measurement of cloud age will be a valuable contribution to that broader study. The DMS measurements will also indicate how much dilution of cloud parcels occurs by mixing with drier air from above. In addition, the investigators will examine the oxidation processes in and near clouds and the roles of such processes in the formation of new particles or the growth of existing particles. If successful, these measurement techniques can have broad applications in future studies of clouds. Other contributions to future capabilities include the training of a new investigator in this area of research and a contribution to the planned RICO graduate-student seminar that will expose graduate students to many of the leaders in this field of research.