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Release of ACOS CO2 Data, Version 3.5

CO2 data Version 3.5, from the Atmospheric CO2 Observations from Space (ACOS), are now available

Release of ACOS CO2 Data, Version 3.5

Global amounts of column CO2 in 2013, from the ACOS v3.5 algorithm (warn levels below 10) using spectral radiances from the Fourier Transform Spectrometer on "Ibuki" (GOSAT).

Release of ACOS CO2 Data, Version 3.5

The Orbiting Carbon Observatory-2 (OCO-2) Team and the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) are pleased to announce the availability of Atmospheric CO2 Observation from  Space (ACOS) Version 3.5, Level 2 data.

The ACOS project is utilizing calibrated L1B radiances from the Thermal And Near-infrared Sensor for carbon Observation - Fourier Transform Spectrometer (TANSO-FTS) sensor on board the Greenhouse gases Observing SATellite (GOSAT).


The most important changes to the ACOS L2 standard product (ACOS_L2S)  encompass:

+ Residual EOF fitting properly trained on v161160 L1B data.

+ Use Modern Era Retrospective-analysis for Research and Applications (MERRA) aerosol climatology to determine two prior aerosol types for each sounding, rather than always using the same aerosol types. 

+ The prior & first guess Atmospheric Optical Depth (AOD) for each of these two types is also take from the climatology. 

+ Implemented “warn levels” in addition to empirical screening of data quality. 

+ The XCO2 bias correction has its overall scale factor determined from the latest version of the Total Carbon Column Observing Network (TCCON) version GGG2014, as opposed to GGG2012 (used in earlier releases). 


More information on the new Version 3.5 data is available in the User's Guide:


GES DISC Product Page:


Questions or comments? Email the NASA GES DISC Help Desk:

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Last updated: May 06, 2016 03:44 PM ET