Meso-scale mapping of terrestrial carbon dioxide source/sink intensity using inverse analysis of atmospheric concentration change by GA

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 15380180
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Agricultural information engineering
• Research Institution: Osaka University
• Principal Investigator: MACHIMURA Takashi Osaka University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (30190383)
• Project Period (FY): 2003 – 2005
• Keywords: terrestrial CO_2 source / sink / inverse model / meso-scale / genetic algorithm

Research Abstract

This study aimed to develop a new technique mapping terrestrial carbon dioxide source/sink intensity using an inverse model. The technique consists of the continuous atmospheric carbon dioxide concentration at one observatory, the wind field and gas diffusion simulation using a meso-scale meteorological model and the inverse analysis of source/sink intensity distribution using the genetic algorithm (GA). An atmosphere sampling system including an IRGA and an automated calibration system was developed and carbon dioxide concentration was measured continuously between December 2004 and January 2006 at Suita, Osaka. Before applying the new technique to real problems, a numerical simulation of the virtual source/sink distribution was examined in order to validate performance of the inverse analysis using GA. 4 or 16 fixed source/sinks were placed randomly in a target area of 126 km x 126 km and atmospheric concentration at a observatory was calculated using the meso-scale meteorological mo del (MM5) and the meso-scale objective analysis data. The inverse model using GA was capable to estimate the given source/sink distribution from calculated time series of the atmospheric concentration excepting a few parts of which source/sink had little influence on atmospheric concentration at the observatory. This suggested that the source/sink intensity of land use categories but its spatial distribution is more adequate as the problem to be solved. Therefore, the source sink intensity of each land use was estimated in the real problems. Carbon dioxide source intensity was the strongest in urban area among all land use and the vegetated land showed relatively small source both in winter and summer, however the absolute intensities were not accurate. The possible reasons were error in the atmospheric concentration measurement and the inadequate background concentration value. Relative source/sink intensity of the land uses and its seasonal change could be estimated reasonably by the new technique.