Overview of Predicting the PBL. Robert Elleman EPA Region 10

Transcription

1 Overview of Predicting the PBL Robert Elleman EPA Region 10

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3 Predicting the PBL Why might we be interested Review of PBL air quality studies Regional-scale, Eulerian PBL Performance in the PNW Interested in performance in all environments, but Focus is on stable boundary layer for 35 µg/m hour PM 2.5 standard Goals for this Session

4 Why We Care Seems too obvious Pollution emitted into boundary layer We live in the boundary layer Large number of important boundary layer effects to model Volume to mix into Degree of mixing Deposition/emission Residual boundary layer Transport (wind speed and direction) Temperature, humidity, clouds Cliff Mass: Meteorological model community says PBL is the biggest deficiency

5 PBL on Policy Choices Choice of PBL changes effect of ozone control strategies by 5-10% domain-wide, more in places Ku et al., Environ. Fluid Mech., 2001

6 AQ Sensitivity to PBL Inputs Pollutants Location PBL Type Communication Alapaty, 1998 Ozone and precursors Kansas Convective paper Boylan, 2003 PM species Southeast US Convective and stable presentation Byun, 2001 Ozone and precursors Eastern US Convective paper Fast, 2005 Ozone Mexico City Convective presentation Han, 2007 SO2,NOx,Ozone East Asia Convective presentation Kim, 2006 Ozone and precursors Eastern US Covective and stable presentation Ku, 2001 Ozone Eastern US Convective paper Mallet, 2006 Ozone Western Europe Convective paper Misensis, 2007 Ozone, PM2.5, NOx, CO Houston Convective presentation Pérez, 2006 Ozone, NOx, CO Barcelona Convective paper Mao, 2006 SO2,NOx,Ozone Eastern US Convective and stable presentation Pleim, 2005 Ozone and precursors Eastern US Stable (Summer nighttime) presentation Pleim, 2001 Ozone and precursors Northeast US Convective paper

7 Example Results PM 2.5 in Southeast Boylan, Presentation to National RPO Meeting, 2003

8 Example Results Ozone in Eastern US PBL scheme changes vertical distribution, transport, diurnal cycle, maximum value, and minimum value Ku et al., Environ. Fluid Mech., 2001

9 Example Results Ozone in Western Europe Of all processes, turbulent and chemical mechanisms introduce the highest uncertainty in ozone concentrations Mallet et al., J. Geophys. Res., 2006

10 Example Results Ozone in Barcelona Ozone not very sensitive to PBL scheme this study Pérez et al., Atmos. Environ., 2006

11 General Summary Ozone results differ by a few ppb to up to 30 ppb Results depend on Location Process of interest Species Probably modeling strategy as well Most results are for summertime and little topographical influence Less for PM 2.5, little attention paid to stable wintertime inversions, and no focus on Pacific Northwest

12 Stable Boundary Layer Boundary layer physics become more important for AQ in wintertime stable inversions Stable boundary layer modeling complicated by: Sensitivity to intermittent turbulence» local katabatic winds, low-level jets, inertial oscillations, gravity waves Resolution» Requires detailed knowledge of topography and roughness elements» Requires fine model vertical (and horizontal?) resolution Difficulties in sampling weak turbulence at small vertical scales

13 Wintertime Stable PBLs in PNW YSU not stable enough, GB (UW) too stable Both have trouble with low-level jets Too high, too diffuse, too late

14 Questions for the Group How important is PBL modeling, among all of our AQ modeling challenges? Is there anything we can do? Mesoscale modeling will never get it right? Problem is bigger than our regional capabilities? What would we do to make a difference? Specific ideas for proposal outline Not a real proposal, just a framework

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16 Example Results O 3 and PM 2.5 in Houston Moderate sensitivity to PBL choice Normalized Mean Biases (NMBs), % O 3 NO NO 2 CO PM 2.5 Noah/YSU N_Y Noah/MYJ N_M Slab/YSU S_Y RUC/YSU R_Y Misenis, Presentation to CMAS Conference, 2007

17 Example Results Ozone in Eastern US 2-6 ppb ozone change from PBL choice Kim et al., Presentation to AMS Annual Meeting, 2006