Climate Change Research Program Japanese

Core Project2. Greenhouse gas observation from space and use of the observations to estimate global carbon flux distribution

Research Plan > Core Research Projects > 2007 Research Results

[2007 Research Results]

This project is lead by three research groups and their findings are reflected in the task of the NIES GOSAT Project Office. Major achievements in 2007 are summarized below.

Developing and improving algorithms for processing data obtained from GOSAT

We evaluated how variation in amounts of cirrus clouds and atmospheric aerosols affects the accuracy and precision of the column abundances of carbon dioxide (CO2) and methane (CH4) derived via our two-step method. We confirmed that we can meet our target accuracy in most of the atmospheric conditions, except some cases with large aerosols present.

The retrieval error in the CO2 column abundance with an assumption of "no aerosol presence".

(click to enlarge)


Study of retrieving column amount of carbon dioxide from satellite-based near-infrared observation of solar scattered light in clear sky condition   - Error estimation and optimization of vertical pressure grid -
Y. Ota, Y. Yoshida, and T. Yokota
J. Remote Sens. Soc. Japan, 28, 152-160, 2008.

Validation of GOSAT products

We classified target parameters (e.g., CO2 and CH4 column abundances, height and optical thickness of aerosols) according to their importance for the validation of the data retrieval algorithms. This way we made sure to perform experiments and/or observations to obtain parameters with higher priorities.
We investigated different experimental methods for validating data products after the launch of GOSAT.

The retrieved column abundances of CO2 and CH4 will be validated via various methods. Instruments involved in the validation measure the parameters such as height and optical thickness of aerosols that affect the retrieval results.

(click to enlarge)

We plan to use a ground-based high-resolution Fourier Transform Spectrometer (FTS; Bruker 120HR, located at NIES) for the validation of the GOSAT data product. We processed the data from this instrument with the daily pressure variation data. We were able to derive the column abundances with the precisions shown on the figure. We confirmed that our retrieval method is not affected by initial guess values (Ohyama et al.).
To evaluate the uncertainty associated with the data obtained with a ground-based high-resolution FTS, we are preparing the direct-measurement experiment using an aircraft and other instruments.

Developing and using a model to estimate global CO2 flux

We performed a simulation to estimate by how much we can reduce errors of the yearly regional carbon fluxes estimated by an inverse model when using the CO2 column abundances from GOSAT in addition to the data from an existing network of ground-based stations. In our study, we assumed that we can only use data over cloud-free region over which GOSAT will be able to measure CO2 column abundances and that the CO2 column abundances obtained from GOSAT will be precise within about 5 ppm. We found that GOSAT will reduce the error by about 10% over the regions such as North America and Europe where many ground-based stations measuring CO2 concentrations already exist, while large reduction of errors (as large as by 30 to 50%) will be achieved over Africa and South America which currently have only few CO2 observing stations (Maksyutov et al., 2008).

Reduction of uncertainty in estimated regional carbon fluxes due to GOSAT (relative to no GOSAT data case).

Maksyutov S., N. Kadygrov, Y. Nakatsuka, P. K. Patra, T. Nakazawa, T. Yokota, G. Inoue, Projected impact of the GOSAT observations in regional CO2 flux estimations as a function of total retrieval error, J. Remote Sens. Soc. Japan, 28(2), 190-197, 2008.

NIES GOSAT Project Office

Development of GOSAT Data Handling Facility

NIES GOSAT Project is developing GOSAT Data Handling Facility (GOSAT DHF), where GOSAT data sent from JAXA will be processed. In addition to GOSAT data, many other reference data are needed for further data analysis and processing. As a result, a huge processing capacity is necessary and GOSAT DHF will operate with the help of external data processing centers. As output products, column abundances of the greenhouse gases such as CO2 and CH4 will be generated as well as their absorption and emission. These products will be stored on hard disks and tapes, and the total amount of the products is expected to exceed 300 TB after its 5 years of operation. After the validation stage, products will be available to the public, and general users can search and request stored products. Now, GOSAT DHF is under preparation for the launch scheduled in early 2009.

(click to enlarge)

System configuration of GOSAT DHF
Page Top