Workshop on the Data Utilization of GOSAT “IBUKI”,
Toranomon, Tokyo, November 5, 2008

Data Processing (1)
データ処理手法(1)
Short Wavelength Infrared Bands ofthe TANSO-FTS
短波長赤外バンド
Tatsuya Yokota

横田 達也

NIES GOSAT Project Leader
Center for Global Environmental Research (CGER)
National Institute for Environmental Studies (NIES), Japan

Contents 報告内容
Radiative Transfer Forward Model for the SWIR bands
短波長赤外バンドで利用する放射伝達モデル


DISORT-based and HSTAR (Terry Nakajima) codes
Solar Fraunhofer lines --- Robert Kurucz’s new data
太陽フラウンホファー線情報： Kurucz博士の新データPolarization
偏光Pstar2 code

Data filtering データの事前フィルタリング
 Data Retrieval Method
データ処理手法


MAP法

Error sources and strategy 解析の誤差要因と取り扱い


5-Nov-08

Maximum A Posteriori (MAP) method

Against disturbances of cirrus clouds and aerosolsÎ Two step method
巻雲とエアロゾルの扱い Î 2ステップ法
1

Observational Mode（TANSO-FTS）

Sun Glint Pointing Mode
Pointing along the truckcrossthe truck
IFOV=10km（海上 → 鏡面反射点）
サングリント点（陸上 → 直下／斜方視）5-Nov-082

TANSO-FTSSWIR (L1B)

TANSO-CAI (L1A)

CAI L1B Processing

事前処理Pre-processing
気象データ準備処理
Meteorological DataPreparation

CAI L1B

Meta-files

CAI L2 Cloud JudgeCAI L2Cloud flag

大気輸送モデル
計算結果準備処理
AtmosphericTransport Model
Preparation
フィルタリング処理
Data Filtering

L2 processing of
1
TANSO-FTS-SWIR (1)5-Nov-08

DEM(GTOPO30)

気象データ Meteorol.
Data (GPV)

大気輸送モデル
計算結果
ATM Output
大気輸送モデル計算処理
Atmospheric T.M. Process.

エアロゾル輸送モデル
計算結果
Aerosol TM Output
エアロゾル輸送モデル計算
Aerosol T. M. Process.
(SPRINTARS)

3

1
CAI L1B
中間ファイルInterim Data

フィルタリング処理
Data Filtering

CAI L2 エアロゾル物理量算出
Aerosol Parameter calc.

先験値設定処理
CAI L2
エアロゾルパラメータ
Aerosol Parameter

Prior Setting

MODIS 地表面反射率
MODIS GroundSurface Albedo Data

カラム量算出処理
Column retrieval
プロダクト作成処理
Products compilation

TANSO-FTSSWIR (L2)

L2 processing of
TANSO-FTS-SWIR (2)5-Nov-08

4

TANSO-FTS SWIR L2 Data Processingxˆ = x（先験情報; prior）
0
気温・気圧
T, P

地表面特性
Albedo装置の特性
ILS

Algorithm

放射伝達計算アルゴリズム（多重散乱，偏光）
Radiative Transfer
6400cm-1

5800cm-1

Iteration MAP method

比較

観測輝度スペクトル
Observed Spectra
6400cm-1

Comp.

2.5
2.0
1.5
1.0
0.5

5800cm-1

3.0

3.0

Radiance (W/m2/micron/str)

アルゴリズムスペクトル残差の重み付き二乗和が最小になるように未知パラメータ（カラム濃度）を調整 〔繰り返し演算〕

大気の状態Atmosphere

理論輝度
スペクトル
SynthesizedSpectra

2.5
2.0
1.5
1.0
0.5
0.0

0.0

1.60

1.60

5-Nov-08+ Δ（観測に基づく修正量x; posterior）

Radiance (W/m2/micron/str)

初期値
Initial

1.65
Wavelength (micron)

1.70

1.65
Wavelength (micron)

1.70

5

Channel selection andSolar Fraunhofer lines
During the analyses of the field campaign, we found the disagreement
between the Fraunhofer lines of the solar spectrum database and thoseof observed spectrum. The solar spectrum database are updated, butchannels overlapped with the Fraunhofer lines are excluded in the
retrieval analysis for safety.

5-Nov-08(Analyzed by Y. Yoshida (NIES))

6TANSO-FTS Configuration
Configuration
GroundPointing
Scanning
Mechanismand Fore
Field of view
opticsFourier
Transform
Spectrometer

Speed

Cross Track (+/- 35 deg）
Along Track (+/- 20 deg)
IFOV <10.5 km
790 km (scan width) (latitude of 30 deg)
0.25, 0.5, 1 (Interferogram)/sec
1P,
1S

2P,
2S

3P,
3S

4

Coverage

0.75 µm
0.78 µm1.56 µm
1.72 µm

1.92 µm
2.08 µm

5.5 µm14.3 µm

resolution(cm-1)

0.50.20.2

0.2

Detector

SiInGaAs

InGaAs

PC-MCT

Spectral band

Calibration
5-Nov-08

2-axes scanner (fully redundant) for pointing

Solar Irradiance, DeepSpace, Moon, Diode Laser

Blackbody,Deep space
7

Incident light is devided by two polarized component by PBS.

⎛I⎞
⎜ ⎟ To simulate the⎜ Q ⎟ observed spectra,⎜ ⎟ we have to know I,⎜U ⎟ Q, and U of the⎜ ⎟ incident light.
⎜V ⎟⎝ ⎠MEASURED SPECTRA

Incident light is devided by two polarized component by PBS.

Version 1I⎞⎛(ScalarRT code)⎜ ⎟ To simulate thetotal intensity I⎟⎜Reconstructspectra,Q observed⎟ measured spectra.
⎜from
we have to know I,⎜U ⎟ Q, and U of the⎜ ⎟ incident light.

⎜V ⎟⎝ ⎠MEASURED SPECTRA

Incident light is devided by two polarized component by PBS.

Version 2(Vector RT code)
To simulate
the spectra
Simulatemeasuredobserved spectra,directly.
we have to know I,
Q, and U of theincident light.

MEASURED SPECTRA

Radiative transfer model: Hstar and Pstar2.
 High spectral resolution version of the System for Transfer ofAtmospheric Radiation (Hstar); [Nakajima et al.]
¾ Scalar radiative transfer (radiance calculation only).
¾ Hybrid model: Discrete-ordinate / matrix-operator (adding)method (Nakajima and Tanaka, 1986).
¾ Multilayer multiple scattering media.
¾ The delta-M truncation method.
¾ Exact single scattering correction; TMS- and IMS-method(Nakajima and Tanaka, 1988).
¾ Rough ocean surface model (Nakajima and Tanaka, 1983) /Lambert surface.
¾ Direct multi-solar beam (for LUT calculation).
¾ Arbitrary viewing geometry (Source function integration).
 Vector radiative transfer model (Pstar2).
¾ Same as the above radiative transfer scheme.
¾ Coupled atmosphere-ocean system including polarization effect.
2008/11/05

11

Measurement Data Filtering
CAI L1B

Parallel Filtering Items(並行判定基準）
・Solar Zenith Angle <70 deg.

Signal Saturation
Low intensity, …
観測信号の飽和，低輝度

太陽天頂角判定
CAI L2Cloud Flag

・Surface elevation variability
地表面凹凸判定 Diff. <25 m・Cloud Mask Flag by CAICAI雲判定 < 1 pixcel

Aerosol Transport
Model(SPRINTARS)

FinalJudgment
総合判定・Cloud Estim. from FTS-TIRTIR雲判定
・Aerosol at higher altitudes
高高度エアロゾル判定

Filtering Results
フィルタリング結果

・Scattering Particles (cirrus)
2μm帯散乱物質判定
5-Nov-08

12

Operational Data Retrieval MethodNon-linear Least square fit of the spectra for both SWIRand TIR data Constrained Gauss-Newton Method (Maximum A
Posteriori method; MAP)(−1xi +1 = xi + K Sε K i + STi) [K S ( y − F (x )) − S (x − x )]−1 −1aTi−1εi−1aia

F(x): Radiance Spectrum
K = ∂F(x)/∂x: Jacobian matrix

J (x ) = [ y − F (x )] Sε−1 [ y − F (x )] + (x − xa ) S a−1 ( x − xa ) → min .
TTSWIR bands Î Column abundances of CO2 & CH4
 TIR band Î Volume mixing ratio profiles of CO2


5-Nov-08

13

Operational Data Retrieval MethodNon-linear Least square fit of the spectra for both SWIRand TIR data Constrained Gauss-Newton Method (Maximum A
Posteriori method; MAP)(−1xi +1 = xi + K Sε K i + STi) [K S ( y − F (x )) − S (x − x )]−1 −1aTi−1εi−1aiaF(x): Radiance Spectrum
K = ∂F(x)/∂x: Jacobian matrix

J (x ) = [ y − F (x )] Sε−1 [ y − F (x )] + (x − xa ) S a−1 ( x − xa ) → min .
Tmeasurement

Ta priori

SWIR bands Î Column abundances of CO2 & CH4
 TIR band Î Volume mixing ratio profiles of CO2


5-Nov-08

14

SWIR Data Retrieval Method
Simultaneous retrieval of column-GHGs, surface
albedo spectra (@Band 2), cirrus parameters(height, optical thickness), and other linear factor
possibly caused by instrument calibration error CO2 and CH4 are retrieved separately
 Non-linear Least square fit of the spectra Constrained Gauss-Newton Method
 (Maximum A Posteriori method; MAP)
Interim VMR profile retrieval Î Columnabundances Î XCO2, XCH4
 (Always assuming cirrus-existing condition)
5-Nov-08

15

SWIR Data Retrieval Method
Simultaneous retrieval of column-GHGs, surface
albedo spectra (@Band 2), cirrus parameters(height, optical thickness), and other linear factor
possibly caused by instrument calibration error CO2 and CH4 are retrieved separately
6400cm5800cm Non-linear Least3.0square fit of the spectra
HO2.5
 Constrained Gauss-Newton
Method2.0
 (Maximum A Posteriori method; MAP)
Radiance (W/m2/micron/str)

-1-1

2

1.5

Interim VMR profile
retrieval Î Column
1.0 COCH absorption,
Xabundances Î0.5 Xabsorption
CO2CH4bands
band0.0
 (Always assuming cirrus-existing
condition)
1.60
1.65
1.70


2

4

Wavelength (micron)
5-Nov-0816

Data retrieval simulation
under cirrus-existing condition（巻雲への対処手法）Retrieval of column-CO2, groundsurface albedo, cirrus height, cirrus
optical thickness, …

Reflection from cirrus/aerosol

cirrusaerosols

Cirrus effects will be cancelled witha two-step estimation method byusing the H2O saturated spectral
region of the 2.0 µm band
5-Nov-08

Some types of the aerosols(e.g. including large particles) willaffect serious error on the retrieval.
We are now investigating a way to
overcome the aerosol effects.
18

Info. about cirrus height and OPD• Step #1: The cirrus optical depth (τ), the cirrus cloudcenter height (h), and ground surface albedo (α0.76 , at
50 cm-1 intervals) at the 0.76 µm (O2-A) band are
estimated from the 0.76 µm band and the H2O saturated
spectral region of the 2.0 µm band
• Step #2: Simultaneous retrieval of column density of CO2,
ground surface albedo (α1.6 at 50 cm-1 intervals), andre-estimation of τ from the 1.6 µm band

Cirrus height

OD=0.5

cirrus(Ground surface)x 105-Nov-08

19

Concluding Remarks
ま と めKey issues of the TANSO-FTS-SWIR processing:Data Filtering & Retrieval「フィルタリング」と「導出処理」が要点

GOSAT radiative transfer (DISORT and HSTARbase) codes and data retrieval algorithms (MAPmethod) will be improved year by year.
Polarized data utilization「MAP法」(非線形最小二乗法)により導出する。
手法の改良も予定。偏光の取り扱いが重要。

5-Nov-0820