Transcript What is this AMET thing anyway?

Evaluation of CMAQ v4.7 Sulfate
Predictions for 2002 – 2006
K. Wyat Appel and Shawn J. Roselle
8th Annual CMAS Conference, Chapel Hill, NC
October 21, 2009
Office of Research and Development
National Exposure Research Laboratory, Atmospheric Modeling and Analysis Division
October 21, 2009
Acknowledgements
• EPA (CDC PHASE Project)
– Alice Gilliland
– Fred Dimmick
– Eric Hall
– Tom Pierce
– Norm Possiel
– Tyler Fox
• EPA AMAD
– Rohit Mathur
– Prakash Bhave
• Computer Sciences Corporation
– Lucille Bender
– Nancy Hwang
– Lara Reynolds
Office of Research and Development
Atmospheric Modeling Division, National Exposure Research Laboratory
CMAQ Simulations
•
•
•
•
Consistent annual simulations from 2002-2006
36-km CONUS and 12-km Eastern U.S. annual simulations
MM5 Meteorology with 34 vertical layers
GEOS-CHEM boundary conditions
– Based on 2002 GEOS-CHEM simulation
– Vary monthly/spatially, but same set of monthly values used for each
year
• Emissions based on 2002 National Emissions Inventory
– Year-specific updates to fires, mobile and EGU point (CEMS data)
emissions
• CMAQ v4.7
– 24 vertical layers
– CB05 Chemical Mechanism
– Base model only (i.e. criteria pollutants only)
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CASTNET SO42- – 2002 through 2006
August 2006
NMB = -13.0%
Incremental Test
Periods for CMAQ
v4.7
January 2006
NMdnB = -14.0%
2002
2003
2004
2005
2006
At the CASTNET sites, Sulfate is underpredicted in the summer of all years, with
the largest overpredictions in 2002 and 2005.
IMPROVE SO42- – 2002 through 2006
2002
2003
2004
2005
2006
At the rural IMPROVE sites, Sulfate is underpredicted in the summer, with the
largest overpredictions in 2002 and 2005.
CSN SO42- – 2002 through 2006
2002
2003
2004
2005
2006
At the urban CSN sites, Sulfate is underpredicted in the summers of 2002 and
2005, but nearly unbiased in the summers of 2003, 2004 and 2006
SO42- Monthly Average Normalized Mean Bias
30
IMPROVE
CSN
CASTNET
20
NMB (%)
10
0
-10
-20
-30
2003
2002
2005
2004
2006
-40
1
3
5
7
9
11
1
3
5
7
9
11
1
3
5
7
9
11
1
3
5
7
9
11
1
3
5
7
9
11
Month
2Since
Of 180
SOmonth/network
observations,
during the
only
summer
34 show
months,
a positive
our focus
bias; Of
has
4 is most important
those
been
34,
on26
the
occur
summertime
between underprediction
September and of
December.
SO42-.
NADP SO42- Wet Deposition – 2002 through 2006
2002
2003
2004
2005
2006
SO42- wet deposition is only slightly overpredicted in the summer,
particularly in July of 2002, 2004 and 2005.
Large positive biases in precipitation
correlate to the large positive biases in
SO42- wet deposition in July of 2002,
2004 and 2005.
NADP Precipitation – 2002 through 2006
However, biases in
SO42- wet deposition do
not account for all the
underprediction in
ambient SO42- during
the summers of 2002
through 2006.
2002
Office of Research and Development
Atmospheric Modeling Division, National Exposure Research Laboratory
2003
2004
2005
2006
Current/Future Work To Address Sulfate Underprediction
• Gas-phase sulfate production
– Issues with cloud predictions
– Clear-sky photolysis sensitivity
Office of Research and Development
Atmospheric Modeling Division, National Exposure Research Laboratory
CMAQ Sulfate Predictions with Clear Sky Photolysis
July 2005
Absolute Difference
Ratio
Average increase at observation sites of ~3.5 - 4.5%.
Current/Future Work To Address Sulfate Underprediction
• Gas-phase sulfate production
– Issues with cloud predictions
– Clear-sky sensitivity
– Results indicate that too little gas-phase SO42- production not the
culprit
• Sulfate particle size distribution
– Comparisons to MOUDI data from 2003 and 2004
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MOUDI
CMAQ
Sulfate particle
size distribution
too broad and
shifted toward
larger particle
sizes.
See poster by Bhave et al. for more details regarding comparisons of
CMAQ with MOUDI data.
Office of Research and Development
Atmospheric Modeling Division, National Exposure Research Laboratory
Current/Future Work To Address Sulfate Underprediction
• Gas-phase sulfate production
– Issues with cloud predictions
– Clear-sky sensitivity
– Results indicate that too little gas-phase SO42- production not the
culprit
• Sulfate particle size distribution
– Comparisons to MOUDI data from 2003 and 2004
– Results show particle size distribution too large and broad in some
regions
• Sensitivity to vertical structure
Office of Research and Development
Atmospheric Modeling Division, National Exposure Research Laboratory
Ratio of 34 layer / 14 layer CMAQ predicted sulfate
SO42- concentrations higher with more vertical layers. Average
increase in SO42- at observation sites is ~5-6%.
Current/Future Work To Address Sulfate Underprediction
• Gas-phase sulfate production
– Issues with cloud predictions
– Clear-sky sensitivity
– Results indicate that too little gas-phase SO42- production not the
culprit
• Sulfate particle size distribution
– Comparisons to MOUDI data from 2003 and 2004
– Results show particle size distribution too large and broad in some
regions
• Sensitivity to vertical structure
– More vertical layers results in slightly higher SO42- concentrations
• Vertical distribution of SO42-
Office of Research and Development
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Regionally-Averaged Vertical Profiles
ICART Time Period (Summer 2004)
CMAQv4.7
Eta-CMAQ (~v4.5)1
SO42- (ug/m3)
SO2 / Total S
from Mathur et al., 2008
SO42- (ug/m3)
SO2 / Total S
from CDC PHASE simulations
Overprediction in SO42- is lower with CMAQv4.7, but still largely overpredicted aloft.
Office of Research and Development
Atmospheric Modeling Division, National Exposure Research Laboratory
Current/Future Work To Address Sulfate Underprediction
• Gas-phase sulfate production
•
•
•
•
– Issues with cloud predictions
– Clear-sky sensitivity
– Results indicate that too little gas-phase SO42- production not the
culprit
Sulfate particle size distribution
– Comparisons to MOUDI data from 2003 and 2004
– Results show particle size distribution too large and broad in some
regions
Sensitivity to vertical structure
– More vertical layers results in slightly higher SO42- concentrations
Vertical distribution of SO42– Analyses show too much SO42- aloft
New cloud scheme based on Grell cloud model
– Still in development
Office of Research and Development
Atmospheric Modeling Division, National Exposure Research Laboratory
Summary
• Ambient SO42- underpredicted during the summer, particularly in the summers of 2002 and
•
•
•
•
2005
– Underprediction appears to be at least in part related to dry/hot summers
– Summer/Fall of 2005 was an active tropical year, which may have contributed as well
Ambient SO42- overpredicted in the fall of 2003, 2004 and 2006
– This issue remains to be investigated, but is a lower priority than summer underprediction
SO42- wet deposition fairly well predicted in the summer
– Some overpredictions could contribute to underpredictions in ambient SO42– However, errors in wet deposition are not the main factor contributing to underprediction in
ambient SO42Near-term investigations into summertime SO42- underprediction
– Clear-sky photolysis sensitivity resulted in small increase in SO42– Errors in SO42- particle size distribution are still being investigated
– Vertical resolution plays a small role, with more vertical layers resulting in more SO42– Limited analysis showed too much SO42- aloft; however, aloft prediction is improved from
previous version of CMAQ.
Future Work
– Additional sensitivities and analysis related to meteorological predictions
– Implementing a new cloud scheme (Grell) in CMAQ will force additional analysis into this
issue.
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“I was gratified to be able to answer promptly.
I said I don't know.” - Mark Twain
Questions?
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Supplementary Slides
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IMPROVE
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CSN
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