Comparison of Co-Located Air Samples at Mauna Loa Observatory and CO2 Observations at Mt. Fuji
A. Sunaga1, H. Mukai1, T. Machida1, Y. Nojiri1, T. Conway2, K. Masarie2, A. Crotwell3, E.J. Dlugokencky2, J. White4 and B. Vaughn4
1National Institute of Environmental Studies (NIES), Center for Global Environmental Research (CGER), Ibaraki, Japan; +81-29-850-2370, E-mail: sunaga.atsuko@nies.go.jp
2NOAA Earth System Research Laboratory, Boulder, CO 80305
3Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309
4Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, Boulder, CO 80309
NIES CGER and NOAA ESRL started a comparison of co-located air samples from Mauna Loa Observatory (MLO: 19.54°N, 155.58°W, 3397 m.a.s.l) in May, 2010. To complement low-frequency measurement comparisons such as the cylinder-based World Meteorologial Organization (WMO) round-robin and flask-based projects [e.g. “sausage”], it was recommended at the WMO Expert Meeting in 2009 that more laboratories participate in more high-frequency real-air measurement comparisons. ESRL and CGER cooperatively developed and installed a sampling system on an existing intake line at MLO where both laboratories’ flasks are filled from the same air stream at almost the same time. The CGER sampling part is the same as those used at other NIES sampling sites, and it was embedded in the ESRL sampling system. Samples are collected every week and analyzed data are updated every month. Although periodic re-calibration of working standard gases has not been done at CGER, due to the earthquakes in March 2011, so far most data agree relatively well for CO2, CH4 and δ18O-CO2. Continued comparison is required to determine analytical tendencies at each laboratory (e.g. when standard gases are changed) and to quantify offsets because different standard scales are used for H2 and isotopic ratios. Frequent long-term comparisons of atmospheric measurements provide useful information to improve and maintain high quality observations and analysis.
CGER also has started CO2 observation on Mt. Fuji (35.21°N, 138.43°E, 3776 m.a.s.l,) with a battery-powered automatic system. CO2 at Mt. Fuji compared to MLO flask data shows both similarities and differences. Mt. Fuji CO2 observations can capture both global and regional CO2 signals over Japan.
Figure 1. Difference between NIES and ESRL measurements of CO2 and δ18O-CO2 in co-located samples collected at MLO (sampled at 10 (HAST)). CGER data are provisional. Dotted lines show WMO targets for network compatibility.
Figure 2. Mt. Fuji CO2 (measured 1/day at 23 (JST)) compared to MLO CGER flask CO2 data.