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Rivers in the Atmosphere: from Water Vapor to Aerosol Particles

Friday, September 17, 2021 - 09:00 to 10:00
Online via zoom
Dr. Sudip Chakraborty
Postdoctoral Researcher, NASA Jet Propulsion Laboratory, USA

Ever since Zhu and Newell in 1994 identified that the filamentary river-like structures in the atmosphere transport a high amount of water vapor as high as the Amazon or the Mississippi River, there has been a growing interest in the scientific community to understand the role of the atmospheric rivers (AR) on rainfall, especially over the midlatitudes. ARs, covering only 5% of the earth area, transport over 90% of the moisture in the midlatitudes, are responsible for 90% of the flooding events, and contribute to a significant amount (40%) of freshwater supply in the U.S. Owing to ARs’ tremendous importance on the global climate, moisture transport, and precipitation, there have been many attempts to develop a detection algorithm to identify the ARs, both temporally and spatially- out of which, the algorithm, recently developed by Guan and Waliser (2015) has been the most successful one and widely-acclaimed in the scientific community. Leveraging the concept and importance of ARs on climate, it has also become necessary to investigate if such filamentary transports can be detected to other important constituents of the atmosphere like particulate matters or aerosols and gaseous pollutants that can have profound impacts on climate and air quality. Aerosols can influence climate through their interactions with clouds and precipitation, solar and infrared radiation, and also have adverse impacts on visibility and human health. Such influences are not confined to their source regions as aerosols and trace gases can be transported long distances, often across and between continents. Despite the strong impacts that aerosols and trace gases have on climate and air quality, significant gaps remain in our knowledge concerning their long-range transport, especially extreme transport events. With the above motivations in mind, this study introduces the extension and application of an already established AR detection algorithm (Guan et al., 2018; Guan and Waliser, 2015, 2019) to aerosols as a new and an alternative approach for understanding and quantifying aerosol transport extremes, hereafter referred to as “Atmospheric Aerosol Rivers” (AARs) using the Modern-Era Retrospective analysis for Research and Applications, Version 2 reanalysis (Chakraborty et al., 2021a). This presentation characterizes and quantifies various details of AARs that have never been studied before, such as AARs’ climatology, vertically integrated aerosol transport, seasonality, event characteristics, vertical profiles of aerosol mass mixing ratio as well as wind speed, and the fraction of total annual aerosol transport conducted by AARs. An analysis is also performed to quantify the sensitivity of AAR detection to the criteria and thresholds used by the algorithm.

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