Field assessment of optical transparency in the low-level marine boundary layer: preliminary data from coastal New England sites

ABSTRACT Estimating the v ariation in the spectral transmission and scattering of optical and near -IR radiation near the sea surface under a range of conditions should be feasible using historical data collected off the coast of New Hampshire USA and along the coastline in the Gulf of Maine. Presented here are long-term offshore aerosol optical depth measurements collected using an A ERONET sun photometer from 2007 -2011 and near -surface wind and (3 m) horizontal visibility measurements collected using surface meteorological buoys from 2001 -present. Future analysis of these data can address their correlation with ne ar-surface meteorological and sea state conditions and to exploit an intensive but limited subset of historical aerosol particle measurements collected here both during a large research ship surveys (ICARTT) as well as with a dedicated aerosol measur ement station in summer 2005. Refractive index variation and r elevant altitude -dependent differences in meteorological scalars are also investigated using unique offshore long-term measurements at 3 and 32 m above sea level . Overall project results should provi de new information for assessment against several existing models for aerosol extinction in marine environments. Keywords: index of refraction, marine aerosols, aerosol optical thickness, particle size distribution, marine atmospheric layer, structure fu nctions for turbulent flow