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Atmospheric Carbon Dioxide Record from In Situ Measurements at Mt. Cimone

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Investigators

Tiziano Colombo and Riccardo Santaguida
Italian Meteorological Service,
Via delle Ville, 100-41029
Sestola (MO), Italy

Period of Record

1979-1997

Methods

Continuous atmospheric CO2 measurements have been carried out at Mt. Cimone since 1979. Since December 1988, air samples have also been collected approximately once per week in a pair of 2-L, electropolished, stainless steel cylindrical flasks. From 1979 until December 1988, a Hartmann and Braun URAS-2T NDIR gas analyzer was used for CO2 determinations. Currently, CO2 determinations are made through the use of a Siemens Ultramat-5E NDIR gas analyzer. Water vapor is eliminated by passing the air through a U-tube placed in an alcohol bath at -600°C. Calibration of the Ultramat-5E is accomplished by using two CO2-in-air working standard gases. These working standard gas concentrations are checked 10 days apart against three CO2-in-air mixtures that serve as secondary standards. The secondary standards are checked every 6 months against five other CO2-in-air primary standards. Hourly CO2 values are routinely plotted together with wind data. Anomalous concentrations and those affected by instrument failures or local sources are rejected. Atmospheric CO2 concentrations from Mt. Cimone are reported in the 1993 WMO/Scripps mole fraction scale. For further details on the measurement apparatus and sampling techniques used at Mt. Cimone, see Cundari et al. (1990).

In March 1996 the standards used at Mt. Cimone were compared to standards from the NOAA Climate Monitoring and Diagnostic Laboratory as part of a round robin-format intercomparison exercise. The average difference between the standards used at Mt. Cimone and NOAA CMDL was less than 0.06 ppmv.

The data are filtered first to remove measurements influenced by local sources during the warm season. The remaining data are then assessed according to specified within-hour variability and hour-to-hour variability criterion. Additional data are rejected based on results of an iterative method using a run-test smoothing cubic spline. Further details on the selection criteria are provided in Cundari et al. (1995).

Map showing location of Mt. Cimone, Italy

Mt. Cimone, Italy
Mountain top
44°11' N, 10°42' E
2165 m MSL

Trends

Mt. Cimone observatory, a station of the Italian Meteorological Service, has been participating in the WMO-BAPMoN program since 1978. The atmospheric CO2 record from Mt. Cimone represents the longest continuous record available for the Mediterranean area. From 1980 to 1997, the annual mean atmospheric CO2 concentration at Mt. Cimone rose from 336.79 parts per million by volume (ppmv) to 364.34 ppmv. The annual increase was ~1.5 ppmv per year. The seasonal oscillation for this same time period has a mean amplitude of 16 ppmv for raw data and 12 ppmv for selected data. This seasonal amplitude is attributable to photosynthetic depletion from vegetation below the timberline at Mt. Cimone and to the relationship between CO2 concentrations and wind direction. Ciattaglia et al. (1987) found a relationship between the behavior of selected CO2 data with prevailing winds [i.e., SW (180-290°) and NE (0-90°) winds] and episodes of Sahara dust transport: during winter, NE winds bring the high CO2 concentrations on measurement site, whereas SW winds are characterized by lower concentrations; during summer, the situation is reversed. During the cold season, Saharan transports are characterized by low CO2 and by small record variability, whereas, when these episodes occur during hot periods, CO2 concentrations show values above average. Bonasoni et al. (1996) showed the connection between Saharan dust transports and CO2 concentrations in the warm and cold seasons at Mt. Cimone.

References

  • Bonasoni, P., T. Colombo, R. Lenaz, G. Tesi, F. Evangelisti, G. Giovanelli, F. Ravegnani, and R. Santaguida. 1996. Effect of Saharan dust transport on ozone and carbon dioxide concentration. In S. Guerzoni and R. Chester (eds). The impact of desert dust across the Mediterranean. pgs. 313-322. Kluver Academic Publishers.
  • Ciattaglia, L. 1983. Interpretation of atmospheric CO2 measurements at Mt. Cimone (Italy) related to wind data. Journal of Geophysical Research 88(C2):1331-38.
  • Ciattaglia, L., V. Cundari, and T. Colombo. 1987. Further measurements of atmospheric carbon dioxide at Mt. Cimone, Italy: 1979-1985. Tellus 39(B):13-20.
  • Colombo, T., and R. Santaguida. 1995. Misure di inquinamento atmosferico di fondo a Monte Cimone. Rivista di Meteorologia Aeronautica 55:59-70.
  • Cundari, L., and G. Fiore. 1981. Atmospheric CO2 measurements at Mt. Cimone. Rivista di Meteorologia Aeronautica 41:25-31.
  • Cundari, V., and T. Colombo. 1986. Atmospheric carbon dioxide measurements at Mt. Cimone, Italy: 1979-1983. Annales Geophysics Series B, 4(1):13-20.
  • Cundari, V., T. Colombo, G. Papini, G. Benedicti, and L. Ciattaglia. 1990. Recent improvements on atmospheric CO2 measurements at Mt. Cimone Observatory, Italy. Il Nuovo Cimento Series C. Geophysics and Space Physics 13C (5): 871-82.
  • Cundari, V., T. Colombo, and L. Ciattaglia. 1995. Thirteen years of atmospheric carbon dioxide measurements at Mt. Cimone Station, Italy. Il Nuovo Cimento Series C. Geophysics and Space Physics 18C(1): 33-47.
  • World Meteorological Organization (WMO). 1981. Report of the WMO/UNEP/ICSU meeting on instruments, standardization, and measurement techniques for atmospheric CO2 (September 8-11). Geneva.

CITE AS: Colombo, T., and R. Santaguida. 1998. Atmospheric CO2 record from in situ measurements at Mt. Cimone. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.