some practical considerations for the geo-cape mission
DESCRIPTION
Some Practical Considerations for the GEO-CAPE Mission Sensitivity, Saturation, Sun glint, Cloud cover, etc Chuanmin Hu, Zhongping Lee, Keping Du, Antonio Mannino. NASA GEO-CAPE Science Working Group Meeting 11-13 May 2011, Boulder, Colorado. Some practical considerations - PowerPoint PPT PresentationTRANSCRIPT
Some Practical Considerations
for the GEO-CAPE MissionSensitivity, Saturation, Sun glint, Cloud cover, etc
Chuanmin Hu, Zhongping Lee, Keping Du, Antonio Mannino
NASA GEO-CAPE Science Working Group Meeting11-13 May 2011, Boulder, Colorado
Some practical considerations
for the GEO-CAPE missionSensitivity, Saturation, Sun glint, Cloud cover, etc
Objectives
Help define sensor constraints
Help implement measurement plans
NASA GEO-CAPE Science Working Group Meeting11-13 May 2011, Boulder, Colorado
SeaWiFS Florida Strait
MODIS/Aqua Florida Strait
Sensitivity versus Saturation
MODIS RGB (land bands) MODIS FLH (ocean bands)
Sensitivity versus Saturation
551 (555) 667 (670) 748 (765) 869 (865)
MODIS Saturation
6.96 3.50 2.23 1.30
SeaWiFS Knee
6.00 3.35 2.46 2.03
MODIS versus SeaWiFS
Units: mWcm-2m-1sr-1
How Precise are MODIS Chl?
Month in 2003
1 2 3 4 5 6 7 8 9 10 11 12 13
Chl
(m
g m
-3)
0.00
0.02
0.04
0.06
0.08
28oS, 105
oW
5-10% RMS speckle noise. Resolves to <0.005 mg m-3 at low concentrations
MODIS Fluorescence Sensitivity
MODIS/Aqua Chl, Sargasso Sea MODIS FLH
Not sufficient to resolve Chl < 0.1 mg m-3
Then, how do we choose the trade between sensitivity and dynamic range (saturation)?
MODIS versus SeaWiFS
Radiance (L) units: mWcm-2m-1sr-1. Numbers in () are for SeaWiFS
1 DN of MODIS 678 band is corresponding to 0.1 – 0.2 mg m-3 Chl
Band
(nm) Res. L (1 DN) NEL
1 620-670 250 m 0.0217 0.0170
2 841-876 250 m 0.0083 0.0123
3 459-479 500 m 0.0167 0.0145
4 545-565 500 m 0.0145 0.0127
438-448 1 km 0.0039 (0.0136) 0.0050 (0.0130)
546-556 1 km 0.0018 (0.0076) 0.0028 (0.0080)
673-683 1 km 0.0007 (0.0042) 0.0008 (0.0056)
MODIS/Aqua Lt (typical)
0 = 75o
0 = 70o
0 = 65o
0 = 45o
0 = 30o
MODIS/Aqua data
500 1000 1500 2000
(nm)
10-2
10-1
100
101
MO
DIS
Lt
(mW
cm
-2m
sr-1
)
(nm)
500 1000 1500 2000
MO
DIS
Lt_
max
fro
m c
loud
s
0
10
20
30
40
50
0 = 70o
0 = 25o
Lt maximum, mW cm-2 m-1 sr-1
MODIS/Aqua Lt (max)
Lt Dynamic Range
70deg SZA 0.33* Lmax(Barnes) 0.7* Lmax(Barnes)ACE GEO GEO ~45SZA 70 deg SZA ACE reduced 70 deg SZA ACE
Band
Center1 Minimum
SNR Ltyp(Hu)2,3
Lmax
(Barnes)1,3
ACE
Ltyp(Ahmad)1,
3 Lmax(70) LmaxDYNAMI C
RANGEDYNAMI C
RANGE350 500 39.26 356.0 74.60 117.48 249.2 2.99 3.34360 500 38.00 376.0 72.20 124.08 263.2 3.27 3.65385 1000 32.16 381.0 61.10 125.73 266.7 3.91 4.36412 1000 41.77 602.0 78.60 198.66 421.4 4.76 5.36425 1000 40.63 585.0 69.50 193.05 409.5 4.75 5.89443 1000 37.51 664.0 70.20 219.12 464.8 5.84 6.62460 1000 33.14 724.0 68.30 238.92 506.8 7.21 7.42475 1000 30.25 722.0 61.90 238.26 505.4 7.88 8.16490 1000 29.25 686.0 53.10 226.38 480.2 7.74 9.04510 1000 24.23 663.0 45.80 218.79 464.1 9.03 10.13532 1000 20.09 651.0 39.20 214.83 455.7 10.69 11.63555 1000 16.11 643.0 33.90 212.19 450.1 13.17 13.28583 1000 14.56 624.0 28.10 205.92 436.8 14.14 15.54617 1000 11.25 582.0 21.90 192.06 407.4 17.07 18.60640 1000 9.39 564.0 19.00 186.12 394.8 19.82 20.78655 1000 8.33 535.0 16.70 176.55 374.5 21.20 22.43665 1000 7.83 536.0 16.00 176.88 375.2 22.59 23.45678 1000 7.37 519.0 14.50 171.27 363.3 23.24 25.06710 1000 5.36 489.0 11.90 161.37 342.3 30.10 28.76748 600 4.89 447.0 9.30 147.51 312.9 30.17 33.65765 600 3.62 430.0 8.30 141.90 301 39.18 36.27820 600 2.82 393.0 5.90 129.69 275.1 46.04 46.63865 600 2.54 333.0 4.50 109.89 233.1 43.26 51.801245 300 0.560 158.0 0.88 52.14 110.6 93.11 125.681640 250 0.280 82.0 0.29 27.06 57.4 96.64 197.932135 100 0.060 22.0 0.08 7.26 15.4 121.00 192.50
Question
With these MODIS-based settings, can GEO-CAPE differentiate fluorescence quantum
efficience changes at large solar zenith angles?
Chlorophyll fluorescence quantum yield
Morrison (2003, L&O)
Decrease
d
Photochemica
l
Quenching
Increased Non-
Photochem
ical
Quenching
Qu
antu
m Y
ield
PAR ( molem-2s-1)1 10 100 1000
0= 60o
0= 70o
0= 80o
Surface PAR
Dec. 22
June 22
GMT: 18:30Longitude: 95oW
-80
-60
-40
-20
0
20
40
Lat
itu
de
(deg
ress
)60
80
0 500 1000 1500 2000 2500
Surface PAR ( mole m-2 s-1)
Hours from Sunrise and Sunset
June 22
Solar zenith = 60o
Solar zenith = 70o
Solar zenith = 80o
-60 -40 -20 0 20 40 60
Latitude (degrees)
0.0
1.0
2.0
3.0
4.0
5.0H
ours
fro
m s
unri
se a
nd s
unse
t
PAR
~ 9
70
PAR ~ 60
0
PAR ~ 250
Sensitivity of Lw685 to solar/viewing geometry
[0 - 70o], [0 - 180o]
Lw
685
(mW
cm
-2
m-1
sr-1
)
0.00
0.01
0.02
0.03
0.04
0.05
0 = 40o
Chl = 0.5 mg m-3, fluorescence efficiency = 2%
0 = 60o
0 = 70o
0 = 80o
Sensitivity of fluorescence (Lw685 and FLH) to solar/viewing geometry
MODIS NEL (678 nm) ~ 0.001 mWcm-2m-1sr-1
0 [0 - 80o]
20 40 60 80
Lw
685
and
FLH
(m
W c
m-2
m
-1 s
r-1)
0.0001
0.001
0.01
0.1
Empty: Lw685; Solid: FLHFLH wavelengths: 665, 685, 750 nm
Chl = 0.1 0.5 1.0 5.0
Fluorescence efficiency = 2%
(PAR ~ 250)(970)(600)
Chlorophyll fluorescence quantum yield
Morrison (2003, L&O)
Decrease
d
Photochemica
l
Quenching
Increased Non-
Photochem
ical
Quenching
Qu
antu
m Y
ield
PAR ( molem-2s-1)1 10 100 1000
0= 60o
0= 70o
0= 80o
Sensitivity of fluorescence (Lw685 and FLH) to solar/viewing geometry
MODIS NEL (678 nm) ~ 0.001 mWcm-2m-1sr-1
Assuming MODIS sensitivity on GEO-CAPE and a constant fluorescence efficiency (quantum yield) of 2%, for Chl = 0.5, FLH decreased by 0.002 mWcm-2m-1sr-1 (nearly halved) from 0=60o to 70o.
Quantum efficiency nearly doubled from 0=60o to 70o, resulting in similar FLH changes if everything else remains the same.
Conclusion: With MODIS sensitivity on GEO-CAPE, it is possible to derive fluorescence quantum efficiency changes in the non-photochemical regime for Chl ~> 0.5 mg m-3
June 22. # of hourly observations with non-photochemical quenching (100 < PAR < 1000)
Dec. 22. # of hourly observations with non-photochemical quenching (100 < PAR < 1000)
Summary on Sensitivity
MODIS sensitivity can serve as a good template
Sufficient to resolve fluorescence quantum efficiency changes between 0=60o to 80o for Chl ~ 0.5 or higher
Saturation radiance determined from MODIS measurements (together with ACE missions). May need adjustment when global dataset is considered.
Twice/day versus once/dayTwice/day versus once/day
Cloud-free percentage from daily MODIS and SeaWiFS data from 1 June to 15 October 2003. Zero value means no data collection.Area: 22 to 31
oN, 91 to 79
oW
MODIS Daily Average: 48.88%SeaWiFS Daily Average: 25.72%
0 20 40 60 80 100
MODIS percentage of cloud-free pixels (daily)
0
20
40
60
80
100
SeaW
iFS
perc
enta
ge o
f cl
oud-
free
pix
els
(dai
ly)
Cloud Avoidance - TBD
June 22. # of hourly observations with o< 80o
June 22. # of hourly observations with sun glint (wind = 6 m/s)
Sun Glint Considerations
Dec. 22. # of hourly observations with o< 80o
Dec. 22. # of hourly observations with sun glint (wind = 6 m/s)
Sun Glint Considerations
Sun Glint Is Not Always A Bad Thing
% of days showing surface oil presence, April 22 – July 31, 2010
Makes it easier to detect oil spills
FLH Shows Greener NEGOM
Cyanobacteria (Trichodesmium erythraeum) blooms observed by GOES and MODIS
What Time Is Desirable to Capture Diurnal Changes?
WFS
5/22/2004
Conclusions- MODIS sensitivity can be followed
- Saturation radiance may need adjustment
- Need to implement a data acquisition matrix to optimize performance for science needs
- Timing and frequency of measurements
- Synoptic or targeted mode, where/when
- Clouds and glint considerations
NASA GEO-CAPE Science Working Group Meeting11-13 May 2011, Boulder, Colorado