Utah Wintertime PM2.5 Modeling and Utah Wintertime PM2.5 Modeling and PCAPS OverviewPCAPS Overview

Lance AveyUtah Division of Air Quality

Salt Lake Basin

Types of Cold Air Pools

Dust

PM2.5 Speciation

Other 5%Elemental Carbon

5%

2%

5%

Organic Carbon 20% Ammonium Nitrate

58%

Ammonium Sulfate

58%

Ammonium Sulfate 9%

• Investigate the processes leading to the formation, maintenance and destruction of persistent winter t t i i th ttemperature inversions that form in the Salt Lake basin

• 1 Dec. 2010 – 7 Feb. 2011 • Modeling component being

carried out by Michigan St. (Sharon Zhong)

http://pcaps.utah.edu/

UDAQ experience with cold pool modeling:

Higher Vertical and Higher Resolution in WRFEnsemble WRF and MM5 modeling with NCARgAdjust eddy diffusivity and vertical diffusion of stable conditionsInfluence of the Great Salt LakeTested sensitivity to horizontal diffusion, roughness length, friction velocityAlbedo to adjust for wintertime snow coverAlbedo to adjust for wintertime snow cover

Strategies that improved model performance the best:Strategies that improved model performance the best:

Nudging in WRF to a modified surface analysis (FDDA) grid file to slow surface windsTurning off CMAQ vertical advectionAdding NH3 to emission fileAdding NH3 to emission file

Salt Lake City – Surface Wind Speedsph

mp

Blue – obsRed – WRF

Hours

Yellow – WRF with modified surface FDDA

CMAQ Nitrate (ug/m3)

Vertical Advection Off Vertical Advection On*Gilliam modified surface grid file *Gilliam modified surface grid file

70V t Ad ti OFF

30

40

50

60M

2.5

(ug/

m3)

Vert. Advection OFFVert. Advection ONObs.

0

10

20

30

24-h

r PM

9-Jan 11-Jan 13-Jan 15-Jan 17-Jan 19-Jan 21-Jan 23-JanSalt Lake City -- 2007

30

40

ug/m

3)

Vert. Advection OFFVert. Adection ONObs.

10

20

24-h

r Nitr

ate

(u

09-Jan 11-Jan 13-Jan 15-Jan 17-Jan 19-Jan 21-Jan 23-Jan

Salt Lake City -- 2007

Conclusions

Utah DAQ is moving forward with the 24-hr PM2.5 SIP

Challenges remain:Meteorological modeling of cold poolsWintertime (snow) ChemistryEmissions inventory