An exploration of model concentration differences between cmaq and camx
Download
1 / 32

An Exploration of Model Concentration Differences Between CMAQ and CAMx - PowerPoint PPT Presentation


  • 136 Views
  • Uploaded on

An Exploration of Model Concentration Differences Between CMAQ and CAMx. Brian Timin, Karen Wesson, Pat Dolwick, Norm Possiel, Sharon Phillips EPA/OAQPS [email protected] October 3, 2007. Introduction. OAQPS conducted 2001 base case modeling with CMAQ and CAMx

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'An Exploration of Model Concentration Differences Between CMAQ and CAMx' - zada


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
An exploration of model concentration differences between cmaq and camx

An Exploration of Model Concentration Differences Between CMAQ and CAMx

Brian Timin, Karen Wesson, Pat Dolwick,

Norm Possiel, Sharon Phillips

EPA/OAQPS

[email protected]

October 3, 2007


Introduction
Introduction CMAQ and CAMx

  • OAQPS conducted 2001 base case modeling with CMAQ and CAMx

    • Both models used the same “raw” emissions and meteorological data

  • Large differences were seen in predicted ozone concentrations as well as other precursors and species

  • We conducted several analyses to help examine differences in the models

    • Sensitivity model runs with CAMx and CMAQ

    • Analysis of existing information


2001 model platforms
2001 Model Platforms CMAQ and CAMx

  • Both models were run with a very similar setup


Cmaq vs camx ozone concentration
CMAQ vs. CAMx- Ozone Concentration CMAQ and CAMx

July 17, 2001 at 21Z

CAMx (w/O’Brien)

CMAQ


Cmaq vs camx co concentration
CMAQ vs. CAMx- CO Concentration CMAQ and CAMx

July 17, 2001 at 21Z

CAMx (w/O’Brien)

CMAQ


Cmaq vs camx form
CMAQ vs. CAMx- FORM CMAQ and CAMx

July 17, 2001 24-hour average

CAMx (w/O’Brien)

CMAQ


Cmaq vs camx sulfate concentration
CMAQ vs. CAMx- Sulfate Concentration CMAQ and CAMx

July 19, 2001 24-hour average

CAMx (w/O’Brien)

CMAQ


Analyses
Analyses CMAQ and CAMx

  • Chemical mechanism

  • Photolysis rates

  • Cloud attenuation of radiation

  • Vertical mixing

  • Dry deposition


Analysis of chemistry and clouds
Analysis of Chemistry and Clouds CMAQ and CAMx

  • CAMx (mechanism 4) uses a hybrid version of CB-IV which contains additional reactions (CB-IV+) compared to CMAQ CB-IV

  • Photolysis rates are generally higher in CAMx and with CB05 compared to CMAQ CB-IV

  • Cloud attenuation of radiation differs between the models

  • These differences between the models were judged not likely to cause significant regional ozone differences between the models


Vertical mixing
Vertical Mixing CMAQ and CAMx

  • Vertical mixing is governed by vertical diffusion coefficients (Kv)

    • CMAQ v4.5 used “ACM” mixing

    • CAMx used “O’Brien” Kv’s

  • There is an option in MM5CAMX to generate “CMAQ like” Kv’s

    • Comparison of actual CMAQ Kv’s and “CMAQ like” Kv’s confirmed similar magnitudes and spatial patterns

  • We conducted a CAMx sensitivity run which used “CMAQ like” Kv’s and compared the results to O’Brien

    • CMAQ like Kv’s (and actual CMAQ Kv’s) are generally much higher than O’Brien Kv’s

      • Expect higher ozone with CMAQ like Kv’s in NOx limited areas


Camx ozone change cmaq like vs o brien kv s
CAMx Ozone Change- CMAQ and CAMx“CMAQ-like” Vs. O’Brien KV’s

Change in CAMx hourly ozone at 15Z on July 17, 2001

Change in CAMx hourly ozone at 20Z on July 17, 2001

Blue= lower ozone with “CMAQ-like” Kv’s


Camx kv s and ozone atlanta example
CAMx KV’s and Ozone- Atlanta Example CMAQ and CAMx

CMAQ-like Kv’s are (almost) always higher than O’Brien and tend to drop off at a higher layer

Ozone concentrations in CAMx and CMAQ are similar at 15z, but CAMx becomes much higher at 20z


Maximum daytime pbl comparison
Maximum Daytime PBL Comparison CMAQ and CAMx

  • We compared maximum PBL heights in Atlanta from observations, predictions from MM5 (MCIP), and from CMAQ and CAMx

  • CMAQ tends to mix to a higher layer compared to the PBL heights from MCIP

    • This example for Atlanta is not representative of all days and areas

Note: CAMx and CMAQ mix up to the top of discrete model layers (as defined in the table above)


Dry deposition
Dry deposition CMAQ and CAMx

  • CAMx uses a Wesely based dry deposition scheme

  • CMAQ uses the M3Dry scheme

    • Closely tied to the Pleim-Xiu land surface model

      • Accounts for enhanced deposition to wetted surfaces (soluble species)

    • Contains more recent science

    • RADM dry deposition scheme (similar to Wesely) is optional in CMAQ (MCIP 3.2 and prior)

  • Examination of dry deposition velocities (Vd) revealed large differences between models


Dry deposition velocities camx vs cmaq ozone
Dry Deposition Velocities CMAQ and CAMxCAMx vs. CMAQ- Ozone

CMAQ (M3Dry) ozone Vd at 16Z

on July 17, 2001

CAMx ozone Vd at 16Z

on July 17, 2001


Dry deposition velocities camx vs cmaq co
Dry Deposition Velocities CMAQ and CAMxCAMx vs. CMAQ- CO

CMAQ (M3Dry) CO Vd at 16Z

on July 17, 2001

CAMx CO Vd at 16Z

on July 17, 2001


Dry deposition velocities camx vs cmaq no
Dry Deposition Velocities CMAQ and CAMxCAMx vs. CMAQ- NO

CAMx NO Vd at 16Z

on July 17, 2001

CMAQ (M3Dry) NO Vd at 16Z

on July 17, 2001


Dry deposition velocities camx vs cmaq no 2
Dry Deposition Velocities CMAQ and CAMxCAMx vs. CMAQ- NO2

CAMx NO2 Vd at 16Z

on July 17, 2001

CMAQ (M3Dry) NO2 Vd at 16Z

on July 17, 2001


Dry deposition velocities camx vs cmaq form
Dry Deposition Velocities CMAQ and CAMxCAMx vs. CMAQ- FORM

CAMx FORM Vd at 16Z

on July 17, 2001

CMAQ (M3Dry) FORM Vd at 16Z

on July 17, 2001


Dry deposition sensitivities
Dry Deposition Sensitivities CMAQ and CAMx

  • Two CMAQ sensitivity runs were conducted to examine dry deposition issues

    • Alternative mesophyll resistance values with M3Dry

    • Alternative dry deposition scheme (RADM)

  • The platform for these CMAQ runs was CMAQ v4.6 with CB05 chemistry

    • Ran CMAQ for 2 weeks in August 2002 (plus 7 day ramp-up)


Cmaq dry deposition sensitivity no 1 mesophyll resistance
CMAQ Dry Deposition Sensitivity No. 1 CMAQ and CAMxMesophyll Resistance

  • M3Dry Vd values for CO, NO, and NO2 were found to be too high

    • Added a mesophyll resistance value in MCIP* for:

      • NO = 9400 S/M

      • NO2= 500 S/M

      • CO = 100,000 S/M

    • Ran MCIP and CMAQ with the new values

      • August 2002 period

*The mesophyll resistance values for NO, NO2, and CO were later incorporated into MCIP 3.3


Cmaq co vd m3dry vs m3dry w modified mesophyll resistance
CMAQ CO Vd- M3Dry vs. M3Dry w/modified Mesophyll Resistance

M3Dry CO Vd at 16Z on August 10, 2002 (w/mesophyll resistance)

M3Dry CO Vd at 16Z on August 10, 2002


Cmaq co concentration and change in concentration due to mesophyll resistance
CMAQ CO Concentration and Change in Concentration Due to Mesophyll Resistance

Change in CMAQ CO concentration on August 5, 2002 (w/mesophyll resistance) (24 hour avg.)

CMAQ CO concentration on August 5, 2002 (24 hour avg.)


Cmaq ozone concentration and change in concentration due to mesophyll resistance
CMAQ Ozone Concentration and Change in Concentration Due to Mesophyll Resistance

Change in CMAQ ozone concentration on August 5, 2002 (w/mesophyll resistance) (8 hour max.)

CMAQ ozone concentration on August 5, 2002 (8 hour max.)


Cmaq dry deposition sensitivity no 2 radm dry
CMAQ Dry Deposition Sensitivity No. 2 Mesophyll ResistanceRADM Dry

  • The RADM dry deposition routine is an option in MCIP*

    • Formulation is based on Wesely, 1989

      • Very similar to CAMx

  • Ran MCIP and CMAQ with RADM dry

    • August 2002 period

*RADM Dry was removed from MCIP v3.3


Cmaq ozone vd m3dry vs radm
CMAQ Ozone Vd- M3Dry vs. RADM Mesophyll Resistance

M3Dry ozone Vd at 16Z on August 10, 2002

RADM Dry ozone Vd at 16Z on August 10, 2002


Cmaq form vd m3dry vs radm
CMAQ FORM Vd- M3Dry vs. RADM Mesophyll Resistance

M3Dry FORM Vd at 16Z on August 10, 2002

RADM Dry FORM Vd at 16Z on August 10, 2002


Cmaq ozone concentration and change in concentration due to radm dry deposition
CMAQ Ozone Concentration and Change in Concentration Due to RADM Dry Deposition

CMAQ ozone concentration on August 5, 2002 w/M3Dry (8 hour max.)

Change in CMAQ ozone concentration on August 5, 2002 (w/RADM Dry) (8 hour max.)


Cmaq sulfate concentration and change in concentration due to radm dry deposition
CMAQ Sulfate Concentration and Change in Concentration Due to RADM Dry Deposition

Change in CMAQ sulfate concentration on August 5, 2002 (w/RADM Dry) (24 hour avg.)

CMAQ sulfate concentration on August 5, 2002 w/M3Dry (24 hour avg.)


Conclusions
Conclusions to RADM Dry Deposition

  • We examined numerous differences between CMAQ and CAMx

    • The majority of the ozone differences can be attributed to different implementations of vertical diffusion and dry deposition

      • Numerous other smaller differences were also identified

    • CO concentrations were too low in CMAQ due to high CO Vd (corrected by adding a mesophyll resistance value)

    • Other species (including secondary aerosols) are also affected by mixing and dry deposition


Recommendations
Recommendations to RADM Dry Deposition

  • Further testing of vertical mixing is needed in both models

    • Need more comparisons between observed PBL and CMAQ/CAMx mixing

      • Does CMAQ “overmix” compared to MM5 predicted PBL?

      • Does O’Brien have too little mixing?

    • More vertical layers may be needed in the AQM boundary layer

  • Further examination of dry deposition velocities is needed

    • Evaluate diurnal pattern of Vd

      • Are afternoon Vd values too high in CMAQ?

    • Does the Wesely scheme need to be replaced?


Recommendations1
Recommendations to RADM Dry Deposition

  • Various combinations of chemical mechanisms (CB-IV, CB05, SAPRC), vertical diffusion (O’Brien, ACM, ACM2) and dry deposition (M3Dry, Wesely, AERMOD) can give very different results

    • Each process needs to be individually evaluated

    • Operational ozone evaluation should not be used to determine the “best” model formulation


ad