Evaluation of NOAA Carbon Tracker Global Carbon Dioxide Products

Abstract. Inter-comparison between National Oceanic and Atmospheric Administration Carbon Tracker (NOAACT) CO₂ with satellite observations were carried out in this study. The satellite observations used here are mid troposphere CO₂ based on Atmosphere Infrared Sounder (AIRS) on board NASA’s Aqua and lower troposphere CO₂ based on Greenhouse-gas Observing Satellite (GOSAT) of Japanese Aerospace Exploration Agency (JAXA). There exists good agreement between the seasonal cycles as estimated by NOAACT and Satellite observations. The mid troposphere CO₂ exhibits distinct annual cycle in the northern hemisphere with positive detrended value during January–June and negative values during July–December. In the southern hemisphere, the annual cycle is less prominent and opposite phase with respect to the northern hemisphere. The lower tropospheric CO₂ in both the hemispheres exhibits mixed signature of annual and semi-annual cycle. The amplitudes of the variability are significantly larger in the northern hemisphere than the southern hemisphere. The inter-annual variability of annual growth rates from the NOAACT is comparable with satellite observations however NOAACT could not resolved the spatial patterns of long-term growth rate as observed in the satellite observations.