Abstract
The study investigates the effect of aerosol long-range transport on precipitation over Northern California during atmospheric river (AR) events in the 2017 cold season (January–April). ARs in 2017 were one of the strongest to date, and the intense precipitation associated with the ARs resulted in flooding, destruction of property, and contamination of water supplies. The Aerosol Optical Depth (AOD) from Moderate Resolution Imaging Spectroradiometer (MODIS) data shows Asian dust traveling across the Northern Pacific Ocean along with AR events. Aerosol measurements in California, provided by the Interagency Monitoring of Protected Visual Environments (IMPROVE), show that more Asian dust tends to be observed over the coast, while non-Asian/localized dust is observed inland. A mixture of Asian and localized dust is observed over the mountains, although higher amounts of both are observed in the spring (March–April). Back trajectory analysis confirms that Asian aerosols are transported along the air parcels, and each AR event has its own transport pattern in terms of horizontal advection and vertical lifting. Correlation between precipitation and aerosols is low. This suggests that aerosols contribute little to the decrease of local precipitation during the 2017 AR events.
Highlights
In April 2017, California lifted its State of Emergency that had been declared in January 2014 in response to a five-year drought [1]
Aerosol measurements in California, provided by the Interagency Monitoring of Protected Visual Environments (IMPROVE), show that more Asian dust tends to be observed over the coast, while non-Asian/localized dust is observed inland
It is hypothesized that there is a positive correlation between aerosols and precipitation, in that aerosols will have contributed to the precipitation enhancement of the 2017 atmospheric river (AR) events
Summary
In April 2017, California lifted its State of Emergency that had been declared in January 2014 in response to a five-year drought [1]. While Creamean et al (2013) [10] and Ault et al (2011) [16] showed IN formation due to dust, which contributes to an increase in precipitation, Patil et al (2017) [17], on the other hand, found in their study that an increase in Asian dust aerosols inhibited deep convective clouds and ice water paths, leading to an increase in cloud top pressure, almost opposite of what was recorded by the other two studies. The question of how the long-range transport of Asian aerosols affect precipitation amounts, system location, and AR frequency, for the 2017 events, remains. The study will compare the properties of six 2017 AR events to a ten year (2006–2016) climatology, in order to (1) understand the effect of Asian long-range aerosol transport on different locations over Northern California during. It is hypothesized that there is a positive correlation between aerosols and precipitation, in that aerosols will have contributed to the precipitation enhancement of the 2017 AR events
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