Evaluating the Meteorological Conditions Associated With Dusty Atmospheric Rivers

摘要

Trans-Pacific dust has been shown to influence the micro-physical characteristics of atmospheric rivers that make landfall along the U.S. west coast. Atmospheric Rivers (AR) reaching North America provide valuable water resources, but also can produce damaging floods. While substantial research has been devoted to understanding the structure and meteorological drivers of atmospheric rivers, far less is known about the conditions that lead to the presence of dust within and around these storms. Here, we utilize an 18-year record of the dust content of AR surroundings combined with satellite, reanalysis, and observational meteorological data to understand the drivers of ARs embedded within dusty environments, or "dusty ARs," as compared to ARs in more pristine environments. We find that dusty ARs are associated with transport of dust from the east Asian coast to North America. Dusty ARs are characterized by conditions that are especially conducive to transport of dust across the Pacific; namely, enhanced mid- to upper-tropospheric westerly winds over Asian dust source regions and over the Pacific. In contrast, ARs in more pristine environments are associated with a persistent ridge over the central Pacific, which blocks zonal westerly flow, as well as continental dust. We also show that while trans-Pacific dust is largely confined to the 600-200 hPa levels, this dust flows downward along post-cold frontal isentropic surfaces into the AR environment in the lower troposphere.