Effect of NO 2 on Geostationary Satellite Chlorophyll Retrieval In Coastal Water:
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Effect of NO 2 on Geostationary Satellite Chlorophyll Retrieval In Coastal Water: False Diurnal Variation Jay Herman & Maria Tzortziou Annual Average NO2 Climatology from OMI
description
Effect of NO 2 on Geostationary Satellite Chlorophyll Retrieval In Coastal Water: False Diurnal Variation Jay Herman & Maria Tzortziou. Annual Average NO2 Climatology from OMI. Examples of NO 2 Diurnal Variation. OMI. - PowerPoint PPT Presentation
Transcript of Effect of NO 2 on Geostationary Satellite Chlorophyll Retrieval In Coastal Water:
Effect of NO2 on Geostationary Satellite Chlorophyll Retrieval In
Coastal Water:False Diurnal VariationJay Herman & Maria Tzortziou
Annual Average NO2 Climatology from OMI
OMI
Examples of NO2 Diurnal Variation
OMI observed pixel NO2 variability for Sept. 30, 2005 over eastern and central US with clouds. Areas covered with clouds have no current NO2 information.
Ad =17.1O
40ONSZA
~4.5O~35.5O
0.5*12756
~36000 + 0.5*12756
Angular Diameter = Ad = 2 arctan (0.5*12756/(36000 + 0.5*12756)) = 17.1 deg
Geostationary Ray Path Geometry
350 400 450 500 550 600 6500.044
0.046
0.048
0.050
0.052
0.054
0.056
0.058
0.060
Ref
lect
ivity
Wavelength (nm)
Measured Reflectivity for Chesapeake Bay
Tzortziou et al. [2007]
Input to Radiative Transfer Equation
Measured Reflectivity of Chesapeake Bay[Tzortziou et al., 2007]Including Chlorophyll and CDOM
300 350 400 450 500 5500
5
10
15
300 350 400 450 500 550-505
1015202530354045
300 350 400 450 500 550-5
0
5
10
15
20
25
30
0 - 20
3040
50
60
70
SZA = 80 O3 = 330 DUR = 0.05NO2 from 0 to 2 km
Percent Error in nLw per DU of NO2
Perc
ent E
rror
Percent Error in nLw per DU of NO2
0 - 20
3040
50
60
70
SZA = 80 O3 = 330 DUR = 0.05NO2 from 0 to 4 km
Wavelength (nm)
Percent Error in nLw per DU of NO2
0 - 20
3040
50
60
70
SZA = 80
O3 = 330 DUR = 0.05NO2 from 0 to 3 km
Perc
ent E
rror
Wavelength (nm)
The Effect of NO2 Altitude Distribution
Use 0 - 3 km CaseIn following slides
0–2 km 0–4 km
0–3 km
300 350 400 450 500 550-505
101520253035404550
0
50
60
70
Wavelength Dependent Reflectivity
Perc
ent E
rror
Wavelength (nm)
0 10 20 30 40 50 60 70 80
SZAeff
80
Output from Radiative Transfer Equation
Reflectivity Change per DU of NO2
dR/R = -0.01*(3.84243 + 0.08821*exp(SzaEff/14.91337)) Wvl=490 nm
dR/R = -0.01*(7.42119 + 0.40409*dexp(SzaEff/18.29943)) Wvl=443 nm
0 20 40 60 8068
10121416182022242628303234363840
y0= 7.42119A1=0.40409t1=18.29943
y = A1*exp(SZA/t1) + y0
Perc
ent E
rror
SZA
443 nm Error vs szs R=Maria variable vs wvl NO2=1DU 0-3km
0 20 40 60 802468
1012141618202224
490 nm Error vs szs R=Maria variable vs wvl NO2=1DU 0-3km
y0= 3.84243A1=0.08821t1=14.91337
y = A1*exp(SZA/t1) + y0
Perc
ent E
rror
SZA
490 nm
443 nm
-10 0 10 20 30 40 50 60 70 80 90
-60
-40
-20
0
20
40
60
80
100
120
140 R = 0.03
dR/R
*100
dP/
P*10
0
SZA
Coastal
R = 0.05
Percent Change in Pigment per DU of NO2
dP/P = -3.03552 dR/R Coastal (Hydrolight)
dP/P = -2.35105 dR/R Open Ocean (Mobley)
0 5 10
0
2
4
6
8
Pigm
ent =
CA
(R)
R = R443/R550
Ca = 2.5104 R-3.03552
R = ratio of Blue to Green
Chlorophyll Blue/Green Ratio From MODIS Website data a0,a1,a2,a3,a4/ 0.3660,-3.0670, 1.9300, 0.6490,-1.5320/ x = log10( ratio(i)) x2 = x*x; x3 = x2*x; x4 = x3*x Ca(i) = 10**( a0 + a1*x + a2*x2 + a3*x3 + a4*x4 )
Retrieval Error per DU of NO2
P = Ca = A R –N
dP/P = -N dR/R * [NO2]
The Power Coefficient N is the key to the magnitude of the NO2 false diurnal variation effect on retrieved chlorophyll values
Case 1
Case 3
Case 2
Measured NO2 Amounts vs Time of Day
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
0
5
10
15
20
25
30dP
/P (P
erce
nt)
Time (hours)
Percent Error in Chlorophyll RetrievalLat = 40 Look angle = 4.5 Ray_angle = 35.5
for R443/R550 and R490/R550
Case 1
NO2ref = 0.3 DU
0.0
0.1
0.2
0.3
0.4
0.5
0.6
dNO
2 (D
U)
dNO2
dP/P
Case 1: An Example of False Diurnal Variation in Chlorophyll
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
10
20
30
40
50
60
dNO2
dP/P
dP/P
(Per
cent
)
Time (hours)
-0.5
0.0
0.5
1.0
1.5
NO2ref = 0.3 DU
Percent Error in Chlorophyll RetrievalLat = 40 Look angle = 4.5 Ray_angle = 35.5
for R443/R550 and R490/R550
dNO
2 (D
U)
Case 2
Case 2: An Example of False Diurnal Variation in Chlorophyll
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
-20
-10
0
10
20
30
40
50
60
OMI NO2ref = 0.75 DU
Percent Error in Chlorophyll RetrievalLat = 40 Look angle = 4.5 Ray_angle = 35.5
for R443/R550 and R490/R550
dP/P
dNO2
dP/P
(Per
cent
)
Time (hours)Case 3
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
dNO
2 (D
U)
Case 3: An Example of False Diurnal Variation in Chlorophyll
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19-5-4-3-2-10123456789
10111213
Case 3
OMI NO2ref = 0.75 DU
Percent Error in Acdom RetrievalLat = 40 Look angle = 4.5 Ray_angle = 35.5
for R490/R550
d(A
cdom
) A
cdom
Time
dNO2
d(Acdom) Acdom
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
dNO
2 (D
U)
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 192
4
6
8
10
12
14
16
Case 2
d(A
cdom
) A
cdom
Time
-0.5
0.0
0.5
1.0
1.5
NO2ref = 0.3 DU
Percent Error in Acdom RetrievalLat = 40 Look angle = 4.5 Ray_angle = 35.5
for R490/R550
dNO2
d(Acdom) Acdom
dNO
2 (D
U)
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
0
1
2
3
4
5
6
7 Percent Error in Acdom Retrieval
Lat = 40 Look angle = 4.5 Ray_angle = 35.5for R490/R550
dNO2
d(Acdom) Acdom
d(A
cdom
) A
cdom
Time
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Case 1
NO2ref = 0.3 DU
dNO
2 (D
U)
Case 1,2,3: An Example of False Diurnal Variation in Acdom
Since Acdom, depends R490,the percent error per DU of NO2is reduced compared to retrievals based on R443
Summary
• NO2 can be highly variable throughout the day.
• Using an incorrect assumed value of NO2 affects the retrieved water leaving radiance nLw and can be interpreted incorrectly as chlorophyll absorption.
• Chlorophyll retrievals errors can be over 50% based on using an assumed NO2 amount from another instrument or climatology.
• NO2 should be measured at the same time that coastal ocean water leaving radiances are measured.
