Transcript Document

Photo
SEARCH: Overview of
Data for Model
Performance
Evaluation
Eric Edgerton, ARA, Inc.
PM Model Performance Workshop
Chapel Hill, NC
February 10, 2004
SEARCH: Southeastern Aerosol
Research and Characterization Study
rural
urban
suburban
Yorkville (YRK)
North Birmingham (BHM)
Jefferson Street (JST)
Centreville (CTR)
Oak Grove (OAK)
Outlying Landing Field #8 (OLF)
Gulfport (GFP)
Pensacola (PNS)
SEARCH Objectives
 Develop a Particulate Matter Climatology for 8 Sites
 Understand Composition and its Variability
– Year to Year, Season to Season (1999-2005)
– Rural vs. Urban
– Coastal vs. Inland
 Test, Improve, and Deploy Measurement Methods for
Pollutant Gases and Continuous PM Components
 Estimate Source Contributions Understand Formation
Processes
 Provide Comprehensive Data Set for Use in SIP Development
 Collaborate with States and Others
SEARCH Measurements - Continuous
Category
Observables
Trace Gases
O3, NO, NO2, HNO3, NHx,
NOy, CO, SO2, CO2
Fine Particles
Mass, BC, Bscat SO42-,NO3,
NH4+
TC
Surface
Met.
T, RH, BP, WS, WD
SR, precip.
Temporal
Resolution
1 min.
1 min. or
60 min. (TC)
1 min.
SEARCH Measurements - Discrete
Frequency
Category
Analytes
(2000-2005)
PM2.5
Mass
Daily
PM2.5
SO42-,NO3-, NH4+
OC, EC, Trace Elem.
1/3
PMcoarse
Mass
1/3
PMcoarse
SO42-,NO3-, NH4+
Trace Elem.
1/6
PMcoarse
OC, EC
Trace Gas
NH3 (started 10/1/03)
1/6 (2 sites)
1/3
Need to Benchmark Continuous Data
with Filter Data
Example of SEARCH Continuous PM Data Validation
Process – Raw Scatter
CONTINUOUS SO4
SO4 vs PCM1 Teflon
10
9
8
7
6
5
4
3
2
1
0
y = 0.59x + 0.31
2
R = 0.78
0
1
2
3
4
5
6
7
PCM1 TEFLON SO4
8
9
10
Example of SEARCH Continuous PM Data Validation
Process – Raw Ratio Cont./Flt.
Ratio of C-SO4/PCM1 SO4
1/
1/
2
2/ 002
1/
3/ 200
1/ 2
2
4/ 002
1/
2
5/ 00
1/ 2
2
6/ 002
1/
2
7/ 00
1/ 2
2
8/ 002
1/
2
9/ 002
1
10 /20
/1 02
11 /200
/1 2
12 /20
/1 02
/2
00
2
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Example of SEARCH Continuous PM Data Validation
Process – Adjusted Scatter
CONTINUOUS SO4
SO4 vs PCM1 Teflon
10
9
8
7
6
5
4
3
2
1
0
y = 1.05x - 0.25
2
R = 0.87
0
1
2
3
4
5
6
7
PCM1 TEFLON SO4
8
9
10
Example of SEARCH Continuous PM Data Validation
Process – Adjusted Time Series
20
15
10
5
PCM1 Tef SO4
C-SO4
Dec-02
Nov-02
Oct-02
Sep-02
Aug-02
Jul-02
Jun-02
May-02
Apr-02
Mar-02
Feb-02
0
Jan-02
Mass, ug/m3
C-SO4 and PCM1 Tef SO4 Time-Series
Time Series of Hourly SO42JST – August 2002
25
ARA SO4
SO4 (ug/m3)
20
15
10
5
0
PILS SO4
Time Series of Hourly NO3JST – August 2002
3.5
ARA NO3
3.0
NO3 (ug/m3)
2.5
2.0
1.5
1.0
0.5
0.0
PILS NO3
Continuous vs. Filter Data
24-Hr Averages (JST)
SO4 (30)
Filter
Mean
5.59
Mean
5.26
NH4 (19)
1.89
1.70
-10.2
0.29
12.6
NO3 (23)
0.45
0.33
-26.8
0.15
27.7
SO4 (36)
Filter
Mean
5.82
Mean
6.10
NH4 (32)
2.15
2.10
-2.1
0.20
9.6
NO3 (35)
0.45
0.54
22.0
0.13
34.5
PILS
%E
MAE
MAPE
-5.8
0.51
9.9
ARA
%E
MAE
MAPE
4.8
0.43
8.5
MAE = median abs. error; MAPE = median abs. % error
/ 20
03
3/1
/20
03
0/2
00
3
3/1
3/2
00
3
3/1
6/2
00
3
3/1
9/2
00
3
3/2
2/2
00
3
3/2
5/2
00
3
3/2
8/2
00
3
3/3
1/2
00
3
4/3
/20
03
4/6
/20
03
4/9
/20
03
4/1
2/2
00
3
4/1
5/2
00
3
4/1
8/2
00
3
4/2
1/2
00
3
4/2
4/2
00
3
4/2
7/2
00
3
3/7
/20
03
3/4
3/1
12
9
TEOM PMc
PMc
Filter-based and Continuous PMcoarse
JST: March-April 2003
21
21
Filter PMc
TEOM PMc
TEOM = 0.909*filter + 0.35
R2 = 0.952
18
18
15
15
6
6
3
3
0
0
0
3
6
(units are µg/m3)
1:1 line
12
9
9
filter PMc
12
15
18
21
Filter-based and Continuous PMcoarse JST:
October 2003
18
18
TEOM PMc
1:1 line
TEOM = 0.954*filter + 0.23
R2 = 0.959
15
15
12
12
TEOM PMc
PMc
Filter PMc
9
9
6
6
3
3
0
0
0
10/1/2003
10/4/2003
2
10/7/2003 10/10/2003 10/13/2003 10/16/2003 10/19/2003 10/22/2003 10/25/2003 10/28/2003
(units are µg/m3)
4
6
8
10
filter PMc
12
14
16
18
00
00
00
10
:0
0
11
:0
0
12
:0
0
13
:0
0
14
:0
0
15
:0
0
16
:0
0
17
:0
0
18
:0
0
19
:0
0
20
:0
0
21
:0
0
22
:0
0
23
:0
0
9:
1000
O3
800
80
600
60
400
40
200
20
0
0
NOy, O3 (ppb) .
CO
8:
00
00
7:
0
00
NOy
6:
0
00
20
5:
200
00
40
4:
400
00
60
3:
600
00
80
2:
800
00
100
1:
O3
CO (ppb) .
CO
NOy, O3 (ppb) .
1000
0:
00
10
:0
0
11
:0
0
12
:0
0
13
:0
0
14
:0
0
15
:0
0
16
:0
0
17
:0
0
18
:0
0
19
:0
0
20
:0
0
21
:0
0
22
:0
0
23
:0
0
9:
8:
00
00
7:
6:
00
00
5:
4:
00
00
3:
2:
00
00
1:
0:
CO (ppb) .
Diurnal CO, NOy, O3 Profiles at Jefferson Street
January 2002 (left), August 2002 (right)
NOy
100
3
3
0
0
9:
00
10
:0
0
11
:0
0
12
:0
0
13
:0
0
14
:0
0
15
:0
0
16
:0
0
17
:0
0
18
:0
0
19
:0
0
20
:0
0
21
:0
0
22
:0
0
23
:0
0
6
8:
00
6
7:
00
12
6:
00
12
5:
00
15
4:
00
15
3:
00
18
2:
00
Conc. (ug/m3) .
18
1:
00
9
OM
BC
SO4
NH4
NO3
0:
00
9:
00
10
:0
0
11
:0
0
12
:0
0
13
:0
0
14
:0
0
15
:0
0
16
:0
0
17
:0
0
18
:0
0
19
:0
0
20
:0
0
21
:0
0
22
:0
0
23
:0
0
8:
00
7:
00
6:
00
5:
00
4:
00
3:
00
2:
00
1:
00
0:
00
Conc. (ug/m3) .
Diurnal PM2.5 Profiles at Jefferson Street
January 2002 (left), August 2002 (right)
9
OM
BC
SO4
NH4
NO3
SO2 Oxidation Rates
CFPPs in Vicinity of Yorkville
(distances in km)
44
25
86
55
57/53
151
150
SO2 and NOy 8/20/02 Event
70
NOy
SO2
60
50
40
30
20
10
0
8/20/2002 0:00
8/20/2002 4:00
8/20/2002 8:00
8/20/2002 12:00
8/20/2002 16:00
8/20/2002 20:00
SO2 vs. NOy 8/20/02 Event
70
SO2 =
4.69*NOy - 19.7
2
R = 0.991
60
SO2 (ppb)
50
40
30
20
10
0
0
5
10
15
NOy (ppb)
20
25
8/1
9/
0
8/1 1 0:
00
9/
0
8/1 1 3:
00
9/
0
8/1 1 6:
00
9/
8/1 01 9
:0
9/
0
0
8/1 1 12
:0
9/
0
0
8/1 1 15
:
9/
01 00
8/1
18
:
9/
01 00
8/2 21:
00
0/
0
8/2 1 0:
00
0/
0
8/2 1 3:
00
0/
0
8/2 1 6:
00
0/
8/2 01 9
:0
0/
0
0
8/2 1 12
:0
0/
0
0
8/2 1 15
:
0/
01 00
8/2
18
:
0/
01 00
8/2 21:
00
1/
0
8/2 1 0:
00
1/
0
8/2 1 3:
00
1/
0
8/2 1 6:
00
1/
8/2 01 9
:0
1/
0
0
8/2 1 12
:0
1/
0
0
8/2 1 15
:
1/
01 00
8/2
18
:
1/
01 00
21
:0
0
Bowen
SO2/NOx Ratio (Molar)
Plant Bowen CEM Data
6.0
5.5
3-hour average = 4.86
5.0
4.5
4.0
3.5
3.0
Trajectory and CEM data point to Plant Bowen
SO2 and SO4 8/20/02 Event
70
5
SO2
SO4 ZERO
60
4
50
SO4 (ppb)
SO2 (ppb)
3
40
30
2
20
1
10
0
8/20/2002 0:00
0
8/20/2002 4:00
8/20/2002 8:00
8/20/2002 12:00
8/20/2002 16:00
8/20/2002 20:00
SO4 vs. SO2, 8/20/02 Event
5
SO4 = 0.074*SO2 + 1.09
2
R = 0.982
4
SO4 (ppb)
3
2
1
0
0
10
20
30
40
50
60
SO2 (ppb)
Estimated transit time of 2.8 hours yields conversion rate of 2.5%/hour
Mean SO2 conversion rate by season
and time of day
3
Fall-Winter
Spring-Summer
Conversion Rate (%)
2.5
2
1.5
1
0.5
0
5:00
7:00
9:00
11:00
13:00
Time Midpoint
15:00
17:00
19:00
Urban vs. Biomass (ER)CO
NOy
PM2.5
TC
(ppb/ppm)
(ug/m3/ppm)
(ug/m3/ppm)
Urban
137 (12)
38 (9)
11(2)
Biomass
23 (13)
220 (60)
69 (19)
6.0
0.17
0.16
U/B
Urban data from Jefferson Street, Atlanta, GA SEARCH Site
Comparison of ERs with Literature Values
FUEL
NOy (as NO)
ER (g/kg CO)
SO2
PM2.5
TC*
BC*
Savannah/Grassland
60
5.4
83
57
3.1
Trop. Forest
15
5.5
88
64
6.4
non-Trop. Forest
28
9
121
78
5.2
Biofuels
27
3.5
92
51
7.6
Ag. Residues
27
4.3
42
36
7.5
This Study (Fires)
This Study (Urban)#
28+/-14
147 +/-10
5.0 +/-2/7 195 +/- 54 63 +/- 14
n.d.
33 +/- 8
Andreae and Merlet. Global Geochem Cyclec 15(4):955-966. 2001. (A&M)
* A&M TC and BC based on TSP
# Based on Jefferson Street, Atlanta, GA SEARCH data
9.6 +/- 2.1
15 +/- 6.1
n.d.
Ammonia First Look (4th Quarter 2003)
SEARCH NH3 Measurements
rural
urban
N.Birmingham
24-hour denuder
(1/3 day) all sites
Starting 10/1/03
Yorkville
Centreville
Oak Grove
OLF
Gulfport
suburban
Pensacola
Jefferson St.
Continuous at
Yorkville (9/15/03)
and Oak Grove
(7/1/04)
SEARCH NH3 and %NHy 4th Quarter 2003
3.0
2.5
80
ruralagricultural
urbanindustrial
NH3
% TRN
64
urban-res./ind.
urbanresidential
1.5
ruralforested
1.0
urbanresidential
ruralforested
48
% TRN
NH3 (ppb)
2.0
suburban
32
16
0.5
0.0
0
BHM
CTR
JST
YRK
GFP
OAK
PNS
OLF
Hourly NH3 and particulate-NH4+
Yorkville, GA – November 2003
25
NH3
NH4
Conc. (ppb)
20
15
10
5
0
01-Nov-03
04-Nov-03
07-Nov-03
10-Nov-03
13-Nov-03
16-Nov-03
19-Nov-03
22-Nov-03
25-Nov-03
28-Nov-03
Continuous NH3 vs. Wind Direction
Yorkville, GA – November 2003
12
300
n
10
250
8
200
6
150
4
100
2
50
0
0
0
18
36
54
72
90
108
126
144
162
180
WD
198
216
234
252
270
288
306
324
342
Count
Mean NH3 (ppb)
NH3
The Smoking Chicken
2 km
1 km
Poultry operations within
several km of Yorkville
(crosshair) line up with
NH3 spikes.
Continuous NH4+ and NO3- vs. Wind Direction
Yorkville, GA - November 2003
1.8
NO3
NH4
1.5
Conc. (ug/m3) .
1.2
0.9
0.6
0.3
0.0
0
18
36
54
72
90
108 126 144 162 180 198 216 234 252 270 288 306 324 342
Continuous NH4+ and NO3Oak Grove 11/11/03
2.0
NO3
NH4
Conc. (ug/m3) .
1.5
1.0
0.5
0.0
-0.5
11/11/03 0:00
11/11/03 6:00
11/11/03 12:00
11/11/03 18:00
Comparison of ERs with Literature Values
FUEL
NOy (as NO)
ER (g/kg CO)
SO2
PM2.5
TC*
BC*
Savannah/Grassland
60
5.4
83
57
3.1
Trop. Forest
15
5.5
88
64
6.4
non-Trop. Forest
28
9
121
78
5.2
Biofuels
27
3.5
92
51
7.6
Ag. Residues
27
4.3
42
36
7.5
This Study (Fires)
This Study (Urban)#
28+/-14
147 +/-10
5.0 +/-2/7 195 +/- 54 63 +/- 14
n.d.
33 +/- 8
Andreae and Merlet. Global Geochem Cyclec 15(4):955-966. 2001. (A&M)
* A&M TC and BC based on TSP
# Based on Jefferson Street, Atlanta, GA SEARCH data
9.6 +/- 2.1
15 +/- 6.1
n.d.
Emissions from Biomass Burning
HMS Fire and Smoke Summary for 2345 10/21/03
Oak Grove
http://www.firedetect.ssd.nesdis.noaa.gov/index.htm
360
WD and Bsp for Oak Grove –
10/21/03
Bsp
270
7.5E-05
180
5.0E-05
90
2.5E-05
-1)
Bsp (m
Bsp (m**-1)
WDR (deg.)
WDR
1.0E-04
0
10/21/03 0:00
0.0E+00
10/21/03 4:00
10/21/03 8:00
10/21/03 12:00
10/21/03 16:00
10/21/03 20:00
Comparison of ERs with Literature Values
FUEL
NOy (as NO)
ER (g/kg CO)
SO2
PM2.5
TC*
BC*
Savannah/Grassland
60
5.4
83
57
3.1
Trop. Forest
15
5.5
88
64
6.4
non-Trop. Forest
28
9
121
78
5.2
Biofuels
27
3.5
92
51
7.6
Ag. Residues
27
4.3
42
36
7.5
This Study (Fires)
This Study (Urban)#
28+/-14
147 +/-10
5.0 +/-2/7 195 +/- 54 63 +/- 14
n.d.
33 +/- 8
Andreae and Merlet. Global Geochem Cyclec 15(4):955-966. 2001. (A&M)
* A&M TC and BC based on TSP
# Based on Jefferson Street, Atlanta, GA SEARCH data
9.6 +/- 2.1
15 +/- 6.1
n.d.
Ammonium Sulfate
Continuous PM at Jefferson Street
August 16, 2001
50
15
SO4
NO3
NH4
PM2.5
SO4, NO3, NH4 (ug/m3)
9
30
6
20
3
10
0
0
8/16/01
0:00
8/16/01
2:00
8/16/01
4:00
8/16/01
6:00
8/16/01
8:00
8/16/01
10:00
8/16/01
12:00
8/16/01
14:00
8/16/01
16:00
8/16/01
18:00
8/16/01
20:00
8/16/01
22:00
PM2.5 (ug/m3)
40
12
SO4, xsNH4 and Molar Ratio
15
2.5
SO4
NH4
Ratio
Ammonium sulfate
2.0
9
1.5
6
Ammonium bisulfate
3
0.5
Sulfuric acid
0
8/16/01
0:00
1.0
0.0
8/16/01
2:00
8/16/01
4:00
8/16/01
6:00
8/16/01
8:00
8/16/01
10:00
8/16/01
12:00
8/16/01
14:00
8/16/01
16:00
8/16/01
18:00
8/16/01
20:00
8/16/01
22:00
Molar Ratio
SO4, NH4 (ug/m3)
12
Background adjusted Molar Ratio
14
2.5
SO4
adjRatio
12
2.0
1.5
8
adjRatio
SO4 (ug/m3)
10
6
1.0
4
0.5
2
0
8/16/01 0:00
0.0
8/16/01 4:00
8/16/01 8:00
8/16/01 12:00
8/16/01 16:00
8/16/01 20:00
Sources of Carbon
Emission Ratios for CO2 and NOy
JST 11/16-17/01
600
CO2
NOy
CO2 = 46.4*CO + 365
R2 = 0.79
CO (ppm), NOy (ppb)
500
400
300
NOy = 0.142*CO - 7.05
R2 = 0.91
200
100
0
0
500
1000
1500
2000
CO (ppb)
2500
3000
3500
Emission Ratios for PM2.5, TC and BC
JST 11/16-17/01
120
PM2.5
BC
PM2.5 = 0.0156*CO + 49.363
R2 = 0.79
TC
100
Conc. ug/m3
80
60
TC = 0.0093*CO + 12.5
R2 = 0.66
40
20
BC = 0.0025*CO + 0.89
R2 = 0.75
0
0
500
1000
1500
2000
CO (ppb)
2500
3000
3500
Summary of Observed (ER)CO
JST, Atlanta
NOy
ppb/ppm
n
PM2.5
TC
BC
ug/m3-ppm ug/m3-ppm ug/m3-ppm
18
18
18
18
Mean
0.138
0.152
0.088
0.026
s.d.
0.009
0.022
0.015
0.005
6.5
14.5
17.0
CV (%)
19.2
Simplified Carbon Source Matrix
and Applicable Tools
Sources of Primary OC in PM2.5
(F)
(M)
(F)
(F)
(M)
(M)
(F/M ?)
(Secondary F/M?)
Primary Carbon Speciation Sites
SEARCH & EPA-STN
STN-Urban
STN-Rural
STN-Suburban
SEARCH-Urban
SEARCH Rural
SEARCH-Suburban
Carbon-14 and OC Data
Atlanta, GA (JST)
1
20
OC
F Modern
0.8
0.62
0.59
12
0.6
8
0.4
4
0.2
0
0
F Modern
OC (ug/m3)
16
OC Source Matrix
Atlanta, GA – January
Primary*
Secondary
Total #
Modern
64
<5
61 +/-5
Fossil
36
<5
39 +/-5
* 2000 Data: Zheng et al., ES&T, 2002.
# from 14Cdata
OC Source Matrix
Atlanta, GA – July 2001
Primary*
Secondary
Total
#
Modern
<5
>50
59 +/-5
Fossil
40*
<5
41 +/-5
* Zheng et al. Source Apportionment of Fine Particles at Atlanta, GA, AAAR 2002
# from 14C data
Five-year Trends
JST
-5
YRK
BHM
CTR
PNS
OLF
GFP
1999
2000
2001
2002
2003
1999
2000
2001
2002
2003
1999
2000
2001
2002
2003
1999
2000
2001
2002
2003
1999
2000
2001
2002
2003
1999
2000
2001
2002
2003
1999
2000
2001
2002
2003
1999
2000
2001
2002
2003
ug/m3
Annual Average Speciated PM2.5
25
Other
Major Metal Oxides
20
Organic Matter
Elemental Carbon
Ammonium
Nitrate
15
Sulfate
PM2.5
10
5
0
OAK
PMcoarse at Jefferson Street, GA
(Inorganic Species Account for < 50% of Mass)
12
PMcoarse (ug/m3) .
10
8
Other
cNH4
cSO4
cNO3
cMMO
6
4
2
0
1999
2000
2001
2002
2003
5-Year mean
Plant (Carbon) Material in PMcoarse Sample
Centreville, AL
3700x
PMcoarse Speciation with OC and EC
OM= OC*1.4, or OC*1.7, or OC*2.0
Other
12%
Other
19%
cMMO
37%
cMMO
38%
OM1.7
39%
OM1.4
33%
cNO3
4%
cNO3
4%
cEC
3%
cNH4
1%
cSO4
3%
cEC
3%
Other
5%
cMMO
38%
OM2.0
46%
cNO3
4%
cEC
3%
cNH4
1%
cSO4
3%
cNH4
1%
cSO4
3%
Continuous NOy, PM2.5, TEOM PMcoarse
JST: January 21, 2004
240
60
NOy
PM2.5
TEOM PMc
50
160
40
120
30
80
20
40
10
0
0:00
0
4:00
8:00
12:00
16:00
20:00
PM2.5, TEOM PMc, ug/m3
NOy, ppb
.
.
200
FRM versus Best Estimate:
Composition Recipes
• FRM Equivalent
– Include Field Blank (0.3 µg/m3)
– Use components from Teflon filter (PCM1)
and front Quartz filter (PCM3)
• Best Estimate
– Blank correct all components
– Add volatile NO3
– Add volatile NH4 (equiv. to NO3)
– Add estimated volatile OC (backup Quartz)
SEARCH FRM Equivalent and Best Estimate
PM2.5 Composition (percent) Jefferson Street,
Atlanta, GA 1999-2002
Average FRM Equivalent mass = 17.7 ug/m3
Average Best Estimate mass = 19.0 ug/m3
1.7%
13.4%
14.7%
25.3%
27.3%
2.7%
2.5%
5.6%
1.1%
34.3%
33.7%
9.6%
9.1%
10.5%
8.5%
Use Of SEARCH “Best Estimate”
Fractions For DV Calculations
• Future-year PM2.5 design values are calculated using a
combination of observed data and PM modeling results
• For this analysis, RRFs were calculated based on 1996 and
2010 IAQR modeling results from REMSAD
• To examine the uncertainties associated with the use of
speciation measurements we calculated the 2010 DVs using
– FRM base values and fractions
– FRM base values and “best estimate” fractions
Use of SEARCH “Best Estimate”
Fractions For DV Calculations
• FDVs calculated for all 8 SEARCH sites, with and without
assumption that 50% of “other” is PBW associated with nitrates
and sulfates
• Over the four combinations, 2010 FDVs differ by as much as 0.5
gm-3
• For example:
OBS
FRM
BE
FRMPBW
BEPBW
Birmingham
18.5
16.6
16.3
16.4
16.1
Atlanta
17.1
14.7
14.6
14.5
14.4
Yorkville
13.8
12.5
12.2
12.3
12.0
Pensacola
13.6
12.1
12.0
11.9
11.8
Use of SEARCH “Best Estimate”
Fractions For DV Calculations
• Considering the best estimate fraction for each species
separately, the largest differences come from nitrate
• For the Birmingham site:
FRM
BE
Sulfate only
16.6
16.2
Nitrate only
16.6
17.4
Organics only
16.6
16.6
Black carbon only
16.6
16.5
Other inorganics only
16.6
16.5
Unattributed mass only
16.6
16.0
Summary
• SEARCH network will provide comprehensive PM/trace gas
data through 2005
• Filter data needed to characterize continuous PM
technologies
– Data adjustments
– Data uncertainty
• Carbon speciation work underway (primary vs.secondary,
Modern vs. Fossil)
• NH3 measurements begun in the SE
– Primary species: high and variable near sources, expect
lower and less variable near sinks
• Combination of continuous PM and Gas measurements
shows promise
– SO4 neutralization variability
– Contributions from biomass burning
– gas/particle conversion
• Differences between FRM Equivalent and Best Estimate are
Significant and Need to be Understood
– Model Evaluation
– FDVs