1. DCC method implementation in FY3/MERSI and FY2
Lin Chen, Xiuqing Hu, Na Xu, Peng Zhang
CMA GPRC,
National Satellite Meteorology Center
7th Conference of GSICS Research Working Group (GRWG)
Beijing, China, 5-8 March,2012

2. OUTLINE
Background
DCC for Instrument Performance Monitoring of FY-3/MERSI
DCC for Instrument Performance Monitoring of FY2D &FY2E/VISSR
Summary

3. Background WHY DCC Advantage Disadvantage No need navigation;
Many targets;
No sharp BRDF;
Suitable for both GEO and LEO ……
Disadvantage
Effect of stratosphere aerosols ;
Rely on Thermal IR
Too many data ……

4. Radiative Transfer Model Simulation
SBDART model
Surface: Sea water
Background Tropospheric Aerosols : Oceanic 0.1; Background Stratospheric Aerosols: 0.02
Cloud Parameters: Ice cloud, Size 106um, Height 2-12km
Ratio=
The change of Reflectance with COD
when COD>100, the ratio tend to 0

5. Aerosols Effect Tropospheric Aerosols: Oceanic with AOD 0.1,0,2,0.5
Stratospheric Aerosols:
Background 0.1 and 0.2
Fresh Volcano Ash 0.1 and 0.2

6. effect the DCC Reflectance Angle Distribution Models
Angles Effect
Different Angles will
effect the DCC Reflectance
Angle Distribution Models
Should be Considered
R， Anisotropic Factor
Anisotropic Factor at SZA 15°（a）、25°（b）、35°（c）and 45°（d） over Ocean for Clear Sky of ice cloud with optical depth 50
ADMs based on CERES TRMM
observations

7. DCC as IPM for FY3/MERSI Methodology
DCC identification: Thermal IR TBB <205K;
Latitude: 15°S to15°N； Longitude：0-360°；
Surface： Ocean;
Uniformity test: TBB in 3*3 grid box all less than 205K;
STD of TBB in 3*3 grid box <1k
STD of Ref in 3*3 grid box <1.5%
Angles: Sun Zenith Angle<30°；View Zenith Angle<40°
Statistics Bin: 10d or 30d
Using the Pre-Launch Calibration table to calculate the nominal reflectance

8. Spectral specification of MERSI bands
Center wl
(mm)
Width (mm)
IFOV (m)
NEDρ(%)/
NEDT (300K)
Signal Dynamic Range 1
0.470
0.05
250
0.45
100% 2
0.550
0.4 3
0.650 4
0.865 5
11.25
2.5
0.54 K
330k 6
1.640
1000
0.08
90% 7
2.130
0.07 8
0.412
0.02
0.1
80% 9
0.443 10
0.490 11
0.520 12
0.565 13 14
0.685 15
0.765 16 17
0.905
0.10 18
0.940 19
0.980 20
1.030
4 channels IFOV 250m
2 shortwave IR channels (1640;2130)
4 channels central wavelength below 500nm(470nm 250m;412nm; 443nm;490nm)
3 water vapor channels

9. Comparison 10d and 30d bin
10d disperse

10. normalization 2σ
2σ :Double STD of DCC means to the fit curve

11. Degradation has a little
Blue Channels
10.4
13.0
470(250m) 17
443
Degradation
(%)
Wavelength
(nm)
490
30.9
412
Shorter the channels
wavelength is,
Degradation is faster
Degradation has a little
bit nonlinear effect
with time
Significant Degradation

12. Red Channels(1) Need specific BRDF correction 2.9 565 5.4 550(250m)
Degradation
(%)
Wavelength
(nm)
520

13. Red Channels(2) Seem to be a lit bit rise -0.7 685 -1.1 650
Degradation
(%)
Wavelength
(nm)
-1.7
650(250m)
Seem to be a lit
bit rise

14. Near Infrared Channels
The most stable
channel
-0.7
865
-1.1
865(250m)
Degradation
(%)
Wavelength
(nm)
1030
-1.7
765
12.8

15. Water Vapor Channels 6.7 980 7.4 940 Degradation (%) Wavelength (nm)
5.1
905

16. Shortwave Infrared Channels
Jump
Jump

17. DCC as IPM for FY2 Methodology
DCC identification: Thermal IR TBB <205K;
For the time of later August 2011, <203K
Latitude: 20°S to20°N； Longitude：85°E to 125°E(FY2E)；
55°E to 95°E(FY2D)；
Surface： Ocean;
Uniformity test: TBB in 3*3 grid box all less than 205K/ <203K;
STD of TBB in 3*3 grid box <1.5k
STD of Ref in 3*3 grid box <1.5%
Angles: 15°<Sun Zenith Angle<40°；View Zenith Angle<30°
Statistics Bin: 30d
For FY2E images time is between 5:00 and 8:00；
For FY2D images time is between 3:00 and 6:00；

18. About 5% Degradation of FY2E in the past 2 years
Compare to FY2E, FY2D is quite stable
Big difference of DCC reflectance between FY2D and FY2E
Degradation of FY2D?
SRF differ from those two?

19. DCC results on Website

20. Summary
DCC have been improved a good method to monitoring instruments performance both GEO and LEO by using FY2 and FY3/MERSI data;
Degradation of Channel 1,2,8,9,10,17,18, 19,20 of FY3/MERSI are more than 5% since FY3 launched by DCC monitoring;
FY2E has about 5% Degradation in the past 2 years;
The DCC IPM results have been displayed on website, however they processed off-line;

21. Comments or Suggestions
Thanks!
Comments or Suggestions