MODIS derived fine mode fraction characteristics of marine , dust , and 3 anthropogenic aerosols over the ocean , constrained by GOCART , 4 MOPITT , and TOMS

7 [1] One year (December 2003 to November 2004) of Terra Moderate Resolution Imaging 8 Spectroradiometer (MODIS), Total Ozone Mapping Spectrometer (TOMS), and 9 Measurement of Pollution in the Troposphere (MOPITT) data over the open ocean are 10 used in conjunction with Goddard Chemistry Transport Model (GOCART) to 11 characterize differing aerosol types as a function of satellite observable parameters. 12 GOCART model output is used to select regions that are dominated (at least 80% of the 13 total aerosol optical thickness from a single aerosol species) by anthropogenic (black 14 carbon + organic carbon + sulfate), dust (DU) and sea salt regions (SS). Aerosol optical 15 thickness (AOT) and fine mode fraction (FMF) retrieved from MODIS are averaged 16 for each aerosol species region at 1 month intervals to examine the observational 17 differences among each aerosol species. Anthropogenic (AN) aerosols are further 18 separated into those produced primarily from biomass burning (BB) versus those from 19 combustion and industrial pollution (PO). TOMS ultraviolet absorbing aerosol index (AI) 20 in conjunction with MOPITT carbon monoxide (CO) data sets on Terra are used to 21 contrast the differences between BB and PO aerosol properties. Annually averaged 22 estimates for SS, DU, and AN MODIS FMF are 0.25 ± 0.07, 0.45 ± 0.05, and 0.84 ± 0.04, 23 respectively, in agreement with or slightly lower than previous estimates. However, FMF 24 values were observed to change substantially as a function of space and time as 25 regions dominated by single aerosol types shrink, expand, and move around from month 26 to month. The greatest variability in FMF was observed for SS and DU aerosols. SS are 27 associated with regions of high near-surface wind speeds in the Southern Hemisphere, 28 which have large temporal and spatial variations. Dust transport off of the Saharan 29 Desert is maximized in the Northern Hemisphere summer, increasing the area of 30 predominately dust aerosols. MODIS aerosol effective radius for each aerosol type also 31 showed a similar trend with SS, DU, and AN values of 1.03, 0.68, and 0.32 mm. 32 TOMS-AI values for DU exceeded SS and AN values up to 100% between April and 33 October 2004 in association with the greatest dust concentrations in the North Atlantic. 34 For BB and PO components of AN aerosols, no significant difference in MODIS FMF 35 were observed; however, substantial differences in TOMS-AI and MOPITT values 36 were observed between BB and PO aerosols, especially between June and November. For 37 both TOMS-AI and MOPITT CO, BB aerosols are generally associated with higher 38 values than are PO aerosols. The use of GOCART to constrain regions where a dominant 39 aerosol species exists has allowed a comprehensive analysis of the satellite observed 40 properties of various aerosol species.