Variations in atmospheric CO2 at the Meteorological Research Institute, Tsukuba, Japan

Abstract

Since April 1986, measurements of the CO2 concentration in the surface air have been conducted at the Meteorological Research Institure (MRI, 36°04′ N, 140°07′ E, 25 m above sea level) in Tsukuba, located 50 km northeast of Tokyo, Japan. The CO2 data measured over times between 11:00 Japan Standard Time (JST) and 16:00 JST (C N ) were considered to be representative of the air (within a few ppmv) in the planetary boundary layer. To evaluate the representative CO2 level on a spatial scale larger than that of the C N record, the CO2 data with hour-to-hour variation less than 1 ppmv were selected (C P ). Comparison of these data with those of Ryori (39°02′ N, 141°50′ E), a continental station operated by the Japan Meteorological Agency, indicates that the C P record provides a representative CO2 level in the air on spatial scales of at least a few hundred kilometers. The C N record allows an investigation of the internanual changes in photosynthesis/respiration against changes in climatological parameters. Within a small temperature anomaly (ca.±1 °C) respiration is sensitive to the temperature change, while photosynthesis is less sensitive. When the temperature anomaly is large, however, photosynthesis and respiration tend to be competitive.