Identifying Soufrière Hills volcanic ash particles and Saharan dust using Aerosol Robotic Network (AERONET) sun photometer, satellite imagery and trajectory models

The island of Puerto Rico (PR) is in the path of seasonal influence of Saharan dust (SD) aerosols and Soufrière Hills volcanic eruptions. There are numerous reports on the identification and characterization of SD in the eastern Caribbean. However, identification of volcanic ash clouds from Soufrière Hills Volcano (SHV) using ground-based measurements is not well understood. In this ongoing project we used surface data (e.g. Aerosol Optical Thickness, Fine/Coarse Fraction, and Angstrom Exponent) from the NASA Aerosol Robotic Network (AERONET) station in La Parguera, southwester PR. These data were supplemented by satellite retrievals (i.e. MODIS Rapid Response) and Model outputs (i.e. Hysplit Back Trajectory). Our analysis focuses on the month of October 2009 due to numerous ash advisories issued by the Washington Volcanic Ash Advisory and the National Weather Service Forecast Office in San Juan, PR. AERONET-derived optical properties from ash events reaching PR were compared to a SD event that reached the island during this period to better understand differences in their microphysical properties. Our goal is to ascertain which optical properties can provide the best discrimination of Saharan dust from ash clouds reaching our study area.