During 1994, the meteorological data acquisition system operated 96.9% of the time and during 1995 operated 93.8% of the time. The meteorological data acquisition system gathers data from sensors that operate continuously at each of the four CMDL observatories. The performance was monitored by comparing the number of data points recorded against that expected for the year. Table 1.14 shows the performance of each system during 1994 and 1995. Due to the remoteness of the observatories, power outages are common and the main reason for data loss.

TABLE 1.14. CMDL Meteorological Operations Summary, 1994-1995

	Expected Number	Percent Data	Number of Missing
Station	of Data Points	Capture	Data Points
1994
BRW	3,006,720*	99.08%	27,678
MLO	6,832,800	94.48%	377,222
SMO	1,955,520†	99.27%	14,215
SPO	3,985,920‡	94.95%	201,128
1995
BRW	4,204,800	99.40%	25,115
MLO	6,832,800	95.85%	283,394
SMO	3,679,200	84.08%	585,716
SPO	4,204,800	95.88%	173,093

*Expected number of data points as of April 15, 1994.

†Expected number of data points as of June 21, 1994.

‡Expected number of data points as of January 20, 1994.

Hardware failure, system restarts, and system maintenance are the other reasons for data loss. At BRW, during the winter periods, rime, snow, and ice occasionally would build up on the sensors and have to be removed by station personnel. At MLO, high winds caused electrostatic buildup in the wind direction module at 38 m. High winds also caused damage to the 38 m anemometer nose cone and propeller shaft assembly. At SMO, the hygrothermometer failed. The biggest cause of data loss was due to the buildup of corrosion on the sensor connector pins and moisture getting into the RS-485 communications line. This produced noise in the communications that the data acquisition system was not able to handle. At SPO the fuse in the meteorological crate, which houses the Setra pressure transducer and the module for the non-aspirated platinum resistance probe, blew several times due to station power failures. The plastic junction box for the anemometer, which houses a circuit board, disintegrated due to the extreme cold of SPO. Periods of high winds at SPO caused static buildup along the sensors and data lines. The solution was to temporarily disconnect the AC power that would reset the modules. On at least two separate occasions, the static buildup damaged electrical components, requiring their replacement with spare parts on hand at the station.

Data is transferred to Boulder on a daily basis via the Internet. Preliminary hourly averages of wind direction and speed, barometric pressure, ambient and dewpoint temperature, and precipitation amounts are sent to the station personnel. Each month a climatic summary is prepared from edited data and distributed within CMDL and to each of the observatories.

Recently, parts for the aerosol solar radiation (ASR), CO₂, and MO3 CAMS have become very difficult to purchase. As a result, CAMS is in the process of being decommissioned. Since 1993, the CAMS system has been gradually replaced with more sophisticated data acquisition systems. These new systems are also gradually getting on the Internet so that the data can be transferred to Boulder more quickly than was possible with the CAMS system.

Acknowledgment. We wish to thank Gary Herbert and Ken Thaut (both retired) who were responsible for the installation of the new meteorological data acquisition systems at MLO in 1993, BRW, SMO, and SPO in 1994, and for their dedication to the CMDL meteorology program.

Thoning, K.W., P.P. Tans, and W.D. Komhyr, Atmospheric carbon dioxide at Mauna Loa Observatory, 2, Analysis of the NOAA GMCC data, 1974-1985, J. Geophys. Res., 95(D6), 8549-8565, 1989.

World Meteorological Organization (WMO), Guide to Meteorological Instrumentation and Observing Practices, No. 8, Tech. Paper 3, 347 pp., World Meteorological Organization, Geneva, 1969.

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