Global Greenhouse Gas Observation by Satellite

Model application: GOSAT Level 4 Product (CO₂ and CH₄)
Level 4 Product consists of Level 4A (L4A) Product and Level 4B (L4B) Product. L4A Product isa dataset of net monthly fluxes estimated by dividing the entire globe into 64 regions for CO₂ and43 regions for CH₄ on a subcontinental scale (several thousand kilometers square); whereas,
L4B Product represents a global three-dimensional distribution simulated based on L4A Product withan atmospheric tracer transport model. These products have been made available to the general public.

LatestData

Level 4A monthly global flux and Level 4B 3-dimensional concentrations (CO₂ and CH₄)

Uncertainty Jul. 2015

Flux Jun. 2009

CH4 (Ver.1.04)

Uncertainty Jun. 2009

Flux Dec. 2014

Uncertainty Dec. 2014

Flux Jun. 2015

Uncertainty Jun. 2015

Level 4B (L4B) Product is the result of
atmospheric tracer transport model
simulation based on L 4 A monthly
global flux. L4B Product stores global
3-dimensional concentrations in every
2.5 degree mesh in intervals of six hours
at 17 vertical levels ranging from near
the surface to the top of the atmosphere.
The 3-dimensional distributions for each
latitude level and period (L4B maps) are
shown at https://data2.gosat.nies.go.jp/index_en.html (“Gallery” – “L4B”).

Figure 8. Maps of regional CO₂ and CH₄ flux estimates and their uncertainties (L4A).

http://www.gosat.nies.go.jp/en/* The column-averaged dry-air mole fraction is the ratio of the total amount of a gas specie to the total amount of dry air contained in a vertical column from the ground surface
to the top of the atmosphere.
** The column-averaged dry-air mole fractions for CO₂ and CH₄ are denoted as XCO₂ and XCH₄.
Monthly mean CO2
CO2 trend

国立研究開発法人

国立研究開発法人

宇宙航空研究開発機構

Monthly mean CH4CH4 trend

Figure 1. Whole-atmosphere monthly mean CO₂ and CH₄ concentrations
and their trend. Shown are concentrations averaged over the entire
atmosphere (from the surface to the top) using GOSAT data. This
indicates that the monthly mean CO₂ concentration ( ●, ● ) increases
gradually with seasonal fluctuations and the trend lines ( ● ) rises
monotonously.
For more details and latest data:
http://www.gosat.nies.go.jp/en/recent-global-co2.html
http://www.gosat.nies.go.jp/en/recent-global-ch4.html

Anthropogenic CO2 concentrations in megacities
Globe

Anthropologic CO2 concentration derived fromemission inventories (ppm)North America

Anthropologic CO2 concentration derived fromemission inventories (ppm)South to East Asia

Japan

Anthropologic CO2 concentration derived fromemission inventories (ppm)

環境省

Whole atmosphere mean
CH4 concentration (ppb)

Flux Jul. 2015

The Greenhouse gases Observing SATellite, GOSAT (nicknamed IBUKI), was successfully launched on January 23, 2009,and has been collecting data globally under cloud-free conditions for estimating column-averaged dry-air mole fractions*of major greenhouse gases such as carbon dioxide (CO₂) and methane (CH₄). For data quality improvement, we haveupdated our algorithm used to estimate XCO₂** and XCH4**, and validated the retrieved values by comparing them tohigh-precision ground-based measurements. These validated values have been distributed to researchers and the generalpublic as GOSAT Level 2 Product. The latest data have been processed with the algorithm (Version 2.80). Using Level 2Product, higher-level products such as monthly estimates of CO₂ and CH₄ regional fluxes, are generated. Also based onthese flux estimates, concentrations of CO₂ and CH₄ in 3-dimensional space are simulated. These data have been madeavailable to the general public as GOSAT L4A (regional flux) and L4B (3-dimensional concentration distributions) products.
* The column-averaged dry-air mole fraction is the ratio of the total amount of a gas specie to the total amount of dry air
contained in a vertical column from the ground surface to the top of the atmosphere.

Anthropologic CO2 condensation acquired by Ibuki [ppm]Uncertainty Jan. 2015

Level 4A (L4A) Product stores net global
flux data in a regional scale estimatedfrom GOSAT Level 2 Product and groundbased data. The L4A estimation process istwofold. First, ground- and GOSAT-based
CO₂ and CH₄ concentrations are predictedby an atmospheric tracer transport model
simulation using a priori flux data as input
values, which include anthropogenic
emission data, wildfire emission data, andmodel estimates of CO₂ and CH₄ exchange
between the terrestrial biosphere andthe atmosphere, and between the ocean
and the atmosphere. Secondly, thepredicted concentrations are matchedto the observed values by adjusting thea priori flux data used in the simulation.
In CO₂ flux estimation, the adjustment
is performed only for the terrestrial andoceanic exchanges; whereas, in CH₄ flux
estimation, all input data are adjusted. As
for CO₂ flux, many regions in the Northern
Hemisphere are net sinks (absorbers)in summer but net sources (emitters) inwinter (Figure 8).

Anthropologic CO2 condensation acquired by Ibuki [ppm]Flux Jan. 2015

(June, 2019)

Whole atmosphere mean
CO2 concentration (ppm)

Uncertainty Jul. 2009

Anthropologic CO2 condensation acquired by Ibuki [ppm]

CO2 (Ver.2.05)

Anthropologic CO2 condensation acquired by Ibuki [ppm]Flux Jul. 2009

Anthropologic CO2 concentration derived fromemission inventories (ppm)

Figure 2. Relationships between anthropogenic CO2 concentrations
estimated from emissions inventories and those from GOSAT data.

We estimated anthropogenic CO₂ concentrations in the Tokyo
metropolitan area in addition to other megacities in the world, basedon GOSAT data collected over the megacities and their surroundings
for the five and half years from June 2009 through December
2014. The anthropogenic CO₂ concentrations in Japan estimatedfrom GOSAT measurements were found to be generally consistentcomparing with those from CO₂ emission data derived fromstatistics (inventories). This result suggests that GOSAT-like spacebased observations potentially enable us to monitor and verify CO₂emissions that all nations are required to report under the Paris
Agreement. We will further accumulate satellite data and improve
the analysis methods, and continue to compare observational datafrom GOSAT and GOSAT-2 with emissions inventories.

Figure 3. Regions with high anthropogenic CO₂ concentration based on GOSAT data,averaged over the period from Jun. 2009 to Dec. 2014. (1°grid is equivalent to 100 km at theequator; only grids with 25 or more observational data points are plotted.) The color shows
the level of the anthropogenic CO₂ concentration.

Seasonal variations and annual trends of greenhouse gas concentrations(June, 2019)1.87412Jul. 2010

*The season shown in brown italics is referred to that of theNorthern Hemisphere.

408

Summer*Global Greenhouse Gas Observing by Satellite

XCH4 (ppm)

XCO2 (ppm)

398
396

394
392
390

1.81
1.80
1.79
1.78
1.77

388

1.76

386

1.75

384

1.74

382

1.73

380
2010/04

2011/04

2012/04

2013/04

2014/04

2015/04

2016/04

2017/04

2018/04

2019/04

1.72
2009/04

2010/04

2011/04

2012/04

2013/04

2014/04

2015/04

2016/04

2017/04

2018/04

2019/04

Year/month

Year/month

Figure 6. Time series of monthly averages of XCO₂ and XCH₄ in North America (blue) and Australia (magenta).
(Monthly averages (without bias-correction) for each region are connected with a straight line).
GOSAT (V02.80) (NorthAmerica)

GOSAT (V02.80) (NorthAmerica)

GOSAT (V02.80) (Australia)

GOSAT (V02.80) (Australia)

Figure 6 plots monthly averaged values of XCO₂ and XCH₄ over the southern half of North America and entire
Australia, as shown in the figures inset. The data plotted are calculated from Level 2 data accumulated since 2009,
showing that the values of XCO₂ and XCH₄ are increasing year by year. The seasonal variation of XCO₂ in North
America (the Northern Hemisphere) is larger than that in Australia (the Southern Hemisphere), and the seasonalincrease and decrease patterns in both areas appear almost reverse. Differently, the XCH₄ seasonal variation appears
more complex than that of XCO₂, possibly owing to the more complicated XCH₄ source distribution and regional
differences in seasonal emission patterns.

Winter*Jan. 2019
Figure 4. Maps of monthly averaged values of XCO 2 (Version2.80) for four selected months in 2018 -2019 period.

Before using GOSAT Level 2 (L2) concentration product in scientific researches, their uncertainties (bias and precision)need to be clarified. GOSAT L2 data are validated with data collected from ground-based high-resolution Fourier
Transform Spectrometers (FTSs) stationed in the Total Carbon Column Observing Network (TCCON: https://tcconwikicaltech.edu/), and from airborne measurements. Figure 7 shows validation results of L2 product (XCO₂, XCH₄ andXH₂O) compared against the TCCON data. The bias and precision for both XCO₂ and XCH₄ are found to be less than 1 %indicating the high consistency of XCO₂ and XCH₄ with the TCCON data. As for XH₂O, the bias and precision are foundto be about 1 % and 20 %, respectively. These results are acceptable as its spatial and temporal variations are large.
(L2 Ver. 2.80 (1σ): -0.3 and ±2.2 ppm for XCO₂; -2 and ±13 ppb*** for XCH₄; -0.78 and ±33 % for XH₂O)*** 1 ppb=1/1000 ppm
GOSAT FTS Level 2 (Version 2.80) XCH4 [ppm]Oct. 20182016 年
7月

Figure 5. shows maps of monthly average of XCO₂ for July in theyears 2009 to 2018 (excl. 2011; 2013; 2015; 2017) portraying bothregional differences and an increasing trend in XCO₂ in these years.

1.82

400

GOSAT FTS Level 2 (Version 2.80) XCO2 [ppm]Apr. 2018

Autumn*Jul. 2018

1.83

402

Validation of GOSAT data against ground-based reference

Spring*Jul. 20161.84404

Jul. 2012

Jul. 2014

1.85

406

378
2009/04

XCH4 (ppm)

1.86

Ground-based high-resolution FTS (TCCON) XCO2 [ppm]

Ground-based high-resolution FTS (TCCON) XCH4 [ppm]MethaneGOSAT FTS Level 2 (Version 2.80) XH2O [ppm]Jul. 2009

data, collected and archived since2009, can be used to map seasonal variations and annual
trends of XCO₂ and XCH₄ on regional and global scales.
Maps of monthly averaged XCO₂ (Version 2.80) for four
selected months in 2018-19 period are shown in Figure 4(The inset color scale shows that XCO₂ value changes fromblue-low to red-high). The maps for July (Figure 5) showthat the average value of XCO₂ for higher latitudes in the
Northern Hemisphere during summer is low because of
the active photosynthesis of vegetation during that time. In
January and April, the average value of XCO₂ in the NorthernHemisphere is higher than in the Southern Hemisphere.

XCO2 (ppm)

410

Ground-based high-resolution FTS (TCCON) XH2O [ppm]Figure 7. Validation of GOSAT Level 2 Product (Ver. 2.80) with TCCON data.
The validation period is from Apr. 2009 to Nov. 2018. The average of TCCON data observed ±30 minutes from the GOSAT overpass time at eachsite and GOSAT data measured within the ±2 degree longitude/latitude box centering each corresponding TCCON site are plotted. The dashedline represents y = x (one to one), and the straight line is a regression line for y = x + b, where b is the bias.