"DOE Atmospheric Radiation Measurement Program. Gary Hodges and Joe Michalsky participated in the DOE Atmospheric Radiation Measurement (ARM) annual meeting in Albuquerque, NM. Global dimming of shortwave radiation has been suggested in a number of recent papers. Gary analyzed total horizontal, diffuse horizontal, and direct normal irradiance data from northern Oklahoma for the past ten years of the ARM program that suggest no statistically significant trend in these data, and if anything a slight upward trend in the summer months, although this is not statistically significant at the 95% confidence level. Joe gave a presentation on the second diffuse horizontal irradiance intensive observation period. The purpose is to establish a working standard in ARM and the BSRN for this measurement, which has persistently been found lower than model predictions for even the simple clear-sky case. Joe also gave a presentation on the aerosol climatology at the southern Great Plains site suggesting that tropospheric aerosols may be indicating a long-term change in their character, perhaps associated with changes in the chemical composition of the atmosphere in northern Oklahoma."

"In collaboration with EPA’s Office of Air Quality Planning and Standards, the Division performed an annual simulation of the Models-3 Community Multiscale Air Quality (CMAQ) for the year 2001. The continental-scale simulation, which used the CB-IV chemical mechanism, and the 2001 National Emissions Inventory, was performed using a 36-km horizontal grid cell size. The model results were compared with the observational data from four different networks: CASTNet, AIRS, IMPROVE, and STN. Preliminary results indicate that the model simulates sulfate well with correlations ®) ranging from 0.78 to 0.92; Normalized Mean Biases (NMB) ranging from -6.0 to 4.0% and Normalized Mean Error (NME) ranging from 24 and 43%; depending on the network. Simulations of ammonium and PM2.5 were also fairly good (ammonium r: 0.58- 0.82; NMB: 7- 25%; NME: 34-66%; PM 2.5: r: 0.52-0.68; NMB: 7.0-9.0%; NME: 47.0-50.0%). The quality of the nitrate, elemental and organic carbon simulations, while considerably better than those in the past, is still lagging the performance of the other species (nitrate r: 0.42-0.73; NMB: -5.0-27.0% ; NME: 76.0-102.%; EC r: 0.46, NMB: -2.4% ; NME:61.6%; OC r:0.34; NMB: 34.5%; NME: 82.6%). The evaluations were also examined over seasons and over different parts of the modeling domain space."