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GCOM-C

What is GCOM-C / SGLI?

GCOM-C is a JAXA satellite. SGLI is a sensor on the GCOM-C satellite. SGLI data are free. It is low spatial resolution (250 m ~ 1 km) but high temporal resolution (every 2~3 day).

JAXA website for GCOM-C data manual, tools, etc.

https://gportal.jaxa.jp/gpr/information/tool?lang=ja

How to get GCOM-C/SGLI data

  1. Go to G-Portal website of JAXA.
  2. Register yourself in G-Portal
  3. Access G-Portal, search, and get the data!

FTP is easy and useful. Here is an example:

$ sftp -oPort=2051 AP12345@ftp.gportal.jaxa.jp
password: ******
sftp> ls standard/GCOM-C/GCOM-C.SGLI/L2.LAND.LAI_/1/2018/11/10/
sftp> get standard/GCOM-C/GCOM-C.SGLI/L2.LAND.LAI_/1/2018/11/10/GC1SG1_20181110D01D_T1413_L2SG_LAI_Q_1000.h5

How to look inside a GCOM-C/SGLI data file

(in case of Ubuntu Linux)
$ h5dump -n GC1SG1_20181215D01D_D0000_3MSG_LST_F_1000.h5
$ h5dump -d /Image_data/LST GC1SG1_20181215D01D_D0000_3MSG_LST_F_1000.h5
$ qgis GC1SG1_20181215D01D_D0000_3MSG_LST_F_1000.h5

Filename rule

(P12~15 of https://gportal.jaxa.jp/gpr/assets/mng_upload/GCOM-C/SGLI_Higher_Level_Product_Format_Description_jp.pdf)

example of level3 product: GC1SG1_20181215D01D_D0000_3MSG_LST_F_1000.h5

GC1: (satellite) GCOMC-1
SG1: (sensor) SGLI1
20181215: (observation timing) 2018 December 15
D: (orbit; descending or ascending) descending
01D: (temporal coverage) 1-day
D0000: (spatial coverage) global? (perhaps)
3M: (level and "map or binned") level3 map
S: "standard"
G: "global" ... L: "near real time local", N: "near real time global"
LST_: (parameter) land surface temperature
F: (spatial resolution) 1/24 deg spatial resolution ... "K": 1 km, "H": 0.5 km, "Q": 0.25 km
1: algorithm version
000: parameter version
h5: (file format) HDF5 format

example of level2 product: GC1SG1_20181110D01D_T1413_L2SG_LAI_Q_1000.h5

GC1: GCOMC-1
SG1: SGLI1
20181110: 2018 November 10
D: Descending
T: Mapping
1413: Tile number 
L2: level2 
S: "Standard"
G: "Global"
LAI: LAI product
Q: Resolution 250m
1: Algorithm version
000: parameter version
h5: HDF5 format 

orbit

D (descending)
A (ascending)

Temporal Coverage (Statistics Period)

01D: 1-Day
08D: 8-Day
01M: 1-Month

Spatial coverage

scene
half-path
tile ... sinusoidal projection tile. one tile is about 1100 x 1100 km
   0529: central Japan
   0528: west and north Japan
   0428: north Japan and Hokkaido
global ... latlon projection (equal rectangular projection; plate caree)

Mapping

You can see the definition and characteristics of mapping method here (Chapter4 of https://gportal.jaxa.jp/gpr/assets/mng_upload/GCOM-C/GCOM-C_SHIKISAI_Data_Users_Handbook_en.pdf) .

ID names of products (parameters)

SGC-180024 気候変動観測衛星「しきさい」(GCOM-C)データ利用ハンドブックより

  • AAEL aerosol angstrom index over land (UV)
  • AAEO aerosol angstrom index over ocean
  • AAEP aerosol angstrom index over land (polarization)
  • AGB_ above ground biomass and roughness index
  • AOTL aerosol optical thickness on land (UV)
  • AOTO aerosol optical thickness on ocean
  • AOTP aerosol optical thickness on land (polarization)
  • ARNP aerosol non-polarimetric
  • ARPL aerosol polarimetric
  • ASSA aerosol single scattering albedo on land
  • CDOM colored dissolved organic matter (Level 3, ocean)
  • CERW cloud (water) particle size
  • CFR1~9 cloud amount (Level3, atmosphere)
  • CFRA~M cloud amount (Level3, atmosphere)
  • CHLA chlorophyll A concentration (Level 3, ocean)
  • CLFG cloud flag
  • CLPR cloud parameters
  • CLTH cloud top height
  • CLTT cloud top temperature
  • COTI cloud (ice) optical thickness
  • COTW cloud (water) optical thickness
  • EVI_
  • FPAR
  • GEOx geolocation of x (V: VNR-NP, I: IRSm P: VNR-PL)
  • IWPR (water quality product)
  • L380 normalized water leaving radiance (Level 3)
  • L412 normalized water leaving radiance (Level 3)
  • L443 normalized water leaving radiance (Level 3)
  • L490 normalized water leaving radiance (Level 3)
  • L530 normalized water leaving radiance (Level 3)
  • L565 normalized water leaving radiance (Level 3)
  • L670 normalized water leaving radiance (Level 3)
  • LAI_ leaf area index (& FPAR for Level 2)
  • LCLR radiance at top of atmosphere after cloud removal
  • LST_ land surface temperature
  • LTOA radiance at top of atmosphere
  • NDVI
  • NWLR normalized water leaving radiance
  • OKID Okhotsk sea ice distribution
  • PAR_ photosynthetically active radiation (Level 3, ocean)
  • RVxx VNR-NP band xx reflectance
  • RSxx IRS-SWIR band xx reflectance
  • RTxx IRS-TIR band xx Brightness temperature (unit: K)
  • RPxx VNR-PL band xx reflectance
  • RNxx VNR-NP band xx reflectance matched to VNR-PL
  • RLAx relative azimuth angle (?) of x (V: VNR-NP, I: IRSm P: VNR-PL)
  • RSRF land surface reflectance
  • SDI_ shadow index
  • SGSL snow grain size
  • SICE snow & sea ice distribution
  • SIPR snow surface parameters
  • SIST snow surface temperature
  • SLZx solar zenith angle (?) of x (V: VNR-NP, I: IRSm P: VNR-PL)
  • SNZx sensor zenith angle (?) of x (V: VNR-NP, I: IRSm P: VNR-PL)
  • SST_ sea surface temperature
  • T670 atmospheric correction parameter (Level 3, ocean)
  • T865 atmospheric correction parameter (Level 3, ocean)
  • TSM_ suspended material (Level 3, ocean)
  • VGI_ vegetation index
  • VRI_ vegetation roughness index

How to get the physical quantities from DN numbers

if we want to use physical quantities like reflectance, we need to convert DN value stored in the file by using "slope" and "offset". The following equation converts DN value to physical quantities (L). If you are interested in more details of product descriptions, it's recommended to read this document ( https://gportal.jaxa.jp/gpr/assets/mng_upload/GCOM-C/SGLI_Higher_Level_Product_Format_Description_en.pdf ).

L=(DN)*(Slope)+(Offset)

Slopes and offsets for level-2 products are shown below.

  • Slope (Reflectance of RVxx and RSxx): 0.0001
  • Offset (Reflectance of RVxx and RSxx): 0.0
  • Slope (Brightness temperature of RTxx): 0.01
  • Offset (Brightness temperature of RTxx): 0.0

DN value "65535" is used for the indication of error value.

Spatial resolution

K: 1km
H: 500m
Q: 250m
F: 1/24deg.
C: 1/12deg.
Last modified:2020/01/21 15:58:43
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