Estimation of anthropogenic GHG emission rate for different sources in Japanese megacity by using airborne imaging-spectrometer suites

In almost Japanese megacities, various CO₂ and CH₄ emission source like industrial activity (power plant, landfills, gas factory, water processing plants), and agricultural activity (rice cultivation, pig farm) are concentrated within a few tens kilometers region.

In order to estimate CO₂ and CH₄ emission rate for above various different sources, we newly developed airborne Imaging-spectrometer suites which consist of NIR spectrometer for O₂-A band measurement and SWIR spectrometer for CO₂/CH₄ measurement.

We also developed quick algorithm based on nonlinear fitting of synthetic spectrum to observation spectrum by optimization of column density of CO₂ / CH₄ and instrumental characteristic parameter simultaneously. The algorithm takes less than 20 second per 1 retrieval by using laptop computer, and we will challenge further acceleration by more than tens of times in order to realize real-time observation.

For the first flight, we selected the eastern part of the Nagoya urban area, in which there are large CO₂ emission sources, including a coal power plant and the transportation sector, and possible CH₄ sources from agriculture, energy manufacturing, and waste that are geographically mixed. The results of observing the Hekinan power plant (coal-fired power generation) over Aichi Prefecture on Feb. 16, 2018 are shown in Figure 1. At the Hekinan Power Station, enhancement of CO₂ column-averaged mole fractions are observed, and it can be seen that the high concentration area extends toward the downwind side. The accuracy of column density calculated by the quick algorithm will be validated by comparison with full physics algorithm such as PSTAR and with ground observation data. We will also establish advection model based on wind field calculated by WRF and then finally estimate emission rate of CO₂ of Hekinan Power plant.