Effect of temporal averaging of vertical eddy diffusivity on the forecast accuracy of surface O3 Pius Lee, Youhua Tang, Jeff McQueen, Ho-Chun Huang, Marina Tsildulko, Geoff DiMego, Sarah Lu and Geoff DiMego NOAA/NCEP Environmental Modeling Center Ivanka Stajner, Ken Carey, and Paula Davidson Office and Science and Technology, NWS Jon Pleim, Rohit Mathur, Hsin-Mu Lin, Daiwen Kang, George Pouliot, Jeff Young, Shaocai Yu, Daniel Tong, Tianfang Chai U.S. EPA

Elevated O3 episode Aug 3rd, 2006

Sensitivity cases Case name Description Base Real-time NCEP production CMAQ-4.5 RADM PBL scheme NAM Kh Directly read in NAM instantaneous Kh to plug in CMAQ’s vertical diffusion NAM hrly Kh As above but uses hourly averaged Kh ( scheme used is analogous to precip buckets emptied at full hours )

Kz (m2 s-1) over Table Mountain, CA on August 2nd-3rd, 2006 @2285m 18UTC Ozonesonde launched at 20:52UTC 20UTC 21UTC 00UTC TKE-PBL Inferred PBLH From ozonesonde Temporal smoothing used in this study postponed vigorous turbulent mixing.

Kz (m2 s-1) over Boulder, CO on August 2nd-3rd 2006 @1745m 19UTC TKE-PBL Inferred PBLH From ozonesonde 20UTC 23UTC 02UTC Ozonesonde launched at 19:28UTC

Kz (m2 s-1) over Huntsville, AL on August 2nd, 2006 @196m TKE-PBL Inferred PBLH From ozonesonde 15UTC 17UTC 21UTC 18UTC Ozonesonde launched at 17:36UTC

Kh (m2 s-1) over Beltsville, MD on August 2nd, 2006 @24m TKE-PBL Inferred PBLH From ozonesonde 19UTC 15UTC 23UTC 20UTC Ozonesonde launched at 19:18UTC

Time-height on NO2 at Table Mountain on Aug 2nd-3rd, 2006 NAM Kh Base NAM hrly Kh There is considerable amount of NO2 at night. (Table Mount is roughly 80 km to the North east of L.A. at elevation of 2285 m.)

18UTC, 2nd 21UTC, 2nd 02UTC, 3rd 00UTC, 3rd Surface O3 diff cases: Kh - hrly_Kh on Aug 2nd-3rd, 2006 18UTC, 2nd 21UTC, 2nd 02UTC, 3rd 00UTC, 3rd Very minor difference; if any is due to delayed mixing

Time-height on O3 at Table Mountain on Aug 2nd-3rd, 2006 NAM Kh Base At 2285 m foggy near ground NAM hrly Kh Inferred PBLH From ozonesonde

Time-height on O3 at Boulder on Aug 2nd-3rd, 2006 NAM Kh Base Inferred PBLH From ozonesonde NAM hrly Kh

Time-height on O3 at Huntsville on Aug 2nd-3rd, 2006 NAM Kh Base Inferred PBLH From ozonesonde NAM hrly Kh

Time-height on O3 at Beltsville on Aug 2nd-3rd, 2006 NAM Kh Base Rather large overshot of PBLH NAM hrly Kh Inferred PBLH From ozonesonde

Summary Direct use of NAM Kh has been attempted by: Use of instantaneous Kh at hourly data exchange from NAM Use hourly averaged Kh from NAM These two approaches both showed better agreement in reflecting atmospheric column where turbulent mixing actually takes place when looking at selected sites during the studies period of August 2nd, 2006. There is not much impact on daily maximum surface O3 concentration, as Kh temporal averaging tends to delay the peak occurrence by some 10’s minutes but does not alter the hourly or 8 h daily max.

Backups

Correlation of daily 8h max O3 with AIRNOW obs (7/30-8/4, 2008) PC UM Base NAM Kh NAM hrly Kh SE RM NE LM

RSME of daily 8h max O3 with AIRNOW obs (7/30-8/4, 2008) PC UM RM SE Base NAM Kh NAM hrly Kh LM NE

PBL-Height verification across CONUS between July20-27, 2006 12 hr PBL verification from launcher runs; Valid 00z