Authors

Nathan New

Document Type

Internship Report

Publication Date

Spring 2013

Abstract

This study focuses on six separate dust events from the month of July 2012 that reached Miami, FL. Using backward trajectories, the time and location of the dust lifting from near the surface were found as well as the meteorological conditions for the surface, 850mb, and 600mb levels. This process allowed for determination of (?) the relationship between time the dust spent aloft and origin location and the strength of the dust as measured by Aerosol Optical Depth. The meteorological conditions of the entire month of July 2012 were examined against climatological averages in an effort to find a signal for the numerous dust events. Finally the daily averaged conditions were analyzed to find the transport mechanism for the dust to reach South Florida, as well as a comparison of the subtropical ridge during periods of activity during the month and a prolonged period of inactivity. Saharan dust has well- documented effects on people’s health and the ecosystem (Tobias et al. 2008; Walsh and Steidinger 2001). However, the effects of dust on precipitation and local weather (e.g. thunderstorms, cloud cover, etc) are not completely clear (Susan et al. 2009; Zhao eta!. 2011; Albrecht 1989) and are active areas of research. Neither the time the dust was aloft nor the origin of the dust was necessarily indicative of the strength when the dust reached Miami. Dust lifting occurred in two major locations: One on the Libya/ Algeria border, and another in Niger, with Event 2 outlying in western Mauritania. Nigerien events are all similar in strength (0.325 to 0.375 AOD), but the far North African origins ranged from the strongest to weakest events. It was also found that the 850mb chart best represented dust travel, and each event followed a ridge extending into the periphery of the subtropical high. The orientation of the subtropical ridge was found to be crucial for transporting dust to South Florida, with southerly and westerly maxima and an East-West elongation of the ridge most conducive for transport. The fastest movements of dust across the Atlantic came from westward expansion of the high causing a moving reference frame for the ridge carrying the dust. Forecasters at the Miami forecast office can use the results presented in this paper to increase the situational awareness during the summer months concerning Saharan dust events. This is expected to increase the accuracy of dust forecasting in South Florida.

Comments

Department : MPO

MPS Track: WFC

Location: National Weather Service - Miami Weather Forecast Office

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