cld, subcld, and rescld represent cloud,

sub-grid scale cloud, and resolved cloud, respectively. The

sub-grid cloud effects are accounted for once an hour on the

half hour while the resolved cloud effects are determined at

each call. In CMAQ, the subgrid clouds are considered only

for horizontal grid resolutions on the order of 8 km or more,

and therefore for grid resolutions below 8 km, only resolved

clouds are represented.

45

The effects of subgrid clouds on grid-averaged

concentrations are modeled by the mixing, scavenging,

aqueous chemistry, and wet deposition of a “representative

cloud” within the grid cell. Subgrid clouds can be either

precipitating or non-precipitating, and the non-precipitating

sub-grid clouds are further categorized as pure fair weather

clouds and non-precipitating clouds coexisting with

precipitating clouds. RADM used the total precipitation

(sum of convective and nonconvective precipitation amounts

 

provided by MM5) to drive the sub-grid cloud model. The

CMAQ implementation differs from RADM in that only the

convective precipitation amounts from a meteorology model

(in this case MM5) are used to drive the sub-grid

precipitating cloud, and the nonconvective precipitation is

used in the resolved cloud model. The mixing in the subgrid

convective cloud takes into account air transported

vertically – from below the cloud, entrained from above the

cloud (for precipitating clouds), and entrained from the sides

of the cloud.

In the resolved cloud module, the pollutants, cloud, and rain

are assumed to be uniformly distributed in a grid cell. No

additional cloud dynamics are considered for the resolved

cloud in CMAQ because any convection and/or mixing

would have been treated by the vertical transport. The

CMAQ resolved cloud model processes scavenging,

aqueous chemistry, and wet deposition with the total

condensed cloud and rain water using the same procedures

as in the sub-grid clouds.

 

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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castellano: DIS CUS DES  RAD   english: DIS CUS DES RAD  

 

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français:  DIS CUS DES RAD