Improvement of Atmospheric CO2 Inversion Analysis at JMA

Abstract:

The Japan Meteorological Agency (JMA) has developed a new inversion system of atmospheric CO₂ mole fraction and flux for better understanding of global carbon budget and contribution to global carbon cycle studies. The new system introduces a newly developed on-line atmospheric tracer transport model (GSAM-TM). Its tracer transport process is directly coupled with a low resolution version (TL95) of JMA's operational global numerical weather prediction (NWP) model (JMA_GSM), using mass conservative semi-Lagrangian scheme and Arakawa-Shubert mass flux scheme for vertical convective transportation. It represents mass transportation, mass conservation, and structures of tracer distribution more precisely than JMA's previous transport model (CDTM), which is off-line tracer transport model using semi-Lagrangian scheme and Kuo-based convection scheme with multiplying globally uniform coefficient for mass conservation. The new system also introduces new a priori fluxes for fossil fuel consumption and oceanic CO₂ exchange.

In this study, we compare CO₂ mole fraction field and flux estimates of the new system against that of current annual JMA analysis with CDTM. The new system represents better atmospheric CO₂ distribution structure than the current system does especially vertical gradient around tropopause. Due to improvement of fossil fuel CO₂ diffusion estimates, analyzed regional budget over Eurasian Continent changed clearly. Budgets for less observation area (South America and Africa) are also changed. Globally averaged atmospheric CO₂ budget is not changed significantly.

This new system is planned to be operationally implemented in 2016, and we will further improve the CO₂ inversion analysis for understanding of carbon cycle.