Quantitative interpretation of satellite and surface measurements of aerosols over North America.

摘要

This thesis assesses the relationship of ground-level fine particulate matter (PM2.5) concentrations versus remote-sensed PM2.5 determined from satellite-measured column aerosol optical depths (AOD). A global chemical transport model is used to simulate the theoretical factors affecting the relation between AOD and PM2.5. Significant spatial variation of annual mean ground-based measurements of PM2.5 with PM2.5 determined from satellite is found (r=0.54--0.68, slope=0.66--0.91). The vertical profile of aerosol extinction is the most important factor affecting the spatial relationship between satellite and surface measurements of PM 2.5; neglecting this parameter would reduce the spatial correlation to 0.29. In contrast, temporal variation in AOD is the most influential parameter affecting the temporal relationship between satellite and surface measurements of PM2.5; neglecting daily variation in this parameter would decrease the correlation in eastern North America from 0.7 to 0. Other aerosol properties, such as effective radius and extinction efficiency have a minor role.; This thesis also investigates how recently suggested pathways for production of secondary organic aerosol (SOA) affect the consistency of modeled simulated organic aerosol (OA) mass versus surface measurements. More accurate representation of rate constants and speciation of SOA precursors reduces simulated SOA mass concentrations by a maximum of 0.3 ug/m3 over southeast United States during summer. A sensitivity study in which isoprene oxidation products contribute to SOA formation increases simulated OA mass concentrations by 0.4--0.6 ug/m3 and reduces a regional model bias. A second sensitivity study in which inorganic aerosols act as condensation sites for SOA formation increases simulated OA mass concentrations by 1.5--2.0 ug/m 3 during summer and by 0.5--1.0 ug/m3 during spring and summer, with mixed effects on the consistency versus ground measurements.