where n is the number density and D is the particle diameter.

M0 is the total number (N) of particles, M2 is proportional to

the total particulate surface area, and M3 is proportional to

the total particulate volume. The size distribution of fine

particles changes in response to coagulation between

particles, growth by condensation from gas/vapor phase

species, new particle production from vapor phase

precursors, transport of particles, and emission of new

particles. The algorithms describing these processes are

extensions of those developed for the Regional Particulate

Model (RPM) [92]. As in the RPM, PM2.5 in the CCTM is

represented by the two lognormal sub-distributions called

the Aitken and accumulation modes. The total particle size

distribution is represented by the superposition of Aitken

and accumulation modes with variable standard deviations

and a coarse mode distribution with a fixed standard

deviation of 2.2. The ISORROPIA model is used to

calculate the thermodynamic equilibrium between inorganic

aerosol species (nitrate, ammonium, and water) and gasphase

concentrations [93, 94].

To demonstrate the evolutionary characteristics of the

distributions of moments, we reproduced Figure 4 from

Figures 1, 2, and 3 in Binkowski and Roselle [91]. The

initial values for the clear, urban and hazy cases are

provided following Seigneur et al. [95]. For the clean

background, the number density distribution has a typical

peak in the size range 0.01 to 0.1 μm or in the Aitken mode

(Whitby [96]). The volume (mass) distribution peaks in the

size range larger than 1 μm, showing that the main

contribution to the total mass of the total size distribution is

in the coarse mode. The second peak for volume (mass) is

in the size range 0.1 to 1.0 μm or in the accumulation mode.

The size distribution of surface area has contributions from

both the Aitken and accumulation modes. For a typical

polluted urban case, the number distribution peaks in the

Aitken mode. The mass, however, peaks in the

accumulation mode with a second peak in the coarse mode.

Surface area has a small contribution from the Aitken mode,

but is dominated by particles in the accumulation mode.

The initial number concentrations for the hazy case show a

peak in the 0.03 μm size range. The curves shown as the

final values in Figure 4 are from the single-cell calculation

with the CMAQ aerosol module after 12-hours of evolution.

Only the coagulation process was present for the clear and

urban cases while the hazy case was with the added sulfate

condensation process. This ideal simulation was designed to



n1051 - n1052 - n1053 - n1054 - n1055 - n1056 - n1057 - n1058 - n1059 - n1060 - n1061 - n1062 - n1063 - n1064 - n1065 - n1066 - n1067 - n1068 - n1069 - n1070 - n1071 - n1072 - n1073 - n1074 - n1075 - n1076 - n1077 - n1078 - n1079 - n1080 - n1081 - n1082 - n1083 - n1084 - n1085 - n1086 - n1087 - n1088 - n1089 - n1090 - n1091 - n1092 - n1093 - n1094 - n1095 - n1096 - n1097 - n1098 - n1099 - n1100


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