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

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

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 ……

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

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

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

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

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

Comparison 10d and 30d bin 10d disperse

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

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

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

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

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

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

Shortwave Infrared Channels Jump Jump

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； 2010.01-2012.02

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?

DCC results on Website

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;

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