Wd. Collins et al., Simulating aerosols using a chemical transport model with assimilation of satellite aerosol retrievals: Methodology for INDOEX, J GEO RES-A, 106(D7), 2001, pp. 7313-7336
A system for simulating aerosols has been developed using a chemical transp
ort model together with an assimilation of satellite aerosol retrievals. Th
e methodology and model components are described in this paper, and the mod
eled distribution of aerosols for the Indian Ocean Experiment (INDOEX) is p
resented by Rasch et al. [this issue]. The system generated aerosol forecas
ts to guide deployment of ships and aircraft during INDOEX. The system cons
ists of the Model of Atmospheric Transport and Chemistry (MATCH) combined w
ith an assimilation package developed for applications in atmospheric chemi
stry. MATCH predicts the evolution of sulfate, carbonaceous, and mineral du
st aerosols, and it diagnoses the distribution of sea salt aerosols. The mo
del includes a detailed treatment of the sources, chemical transformation,
transport, and deposition of the aerosol, species. The aerosol forecasts in
volve a two-stage process. During the assimilation phase the total column a
erosol optical depth (AOD) is estimated from the model aerosol fields. The
model state is then adjusted to improve the agreement between the simulated
AOD and satellite retrievals of AOD. During the subsequent integration pha
se the aerosol fields are evolved using meteorological fields from an exter
nal model. Comparison of the modeled AOD against estimates of the AOD from
INDOEX Sun photometer data show that the differences in daily means are -0.
03 +/- 0.06. Although the initial application is limited to the Indian Ocea
n, the methodology could be extended to derive global aerosol analyses comb
ining in situ and remotely sensed aerosol observations.