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9.0 CONCLUSION The AESOP's have shown their reliability and ability to collect quality surface weather data in the Sierra wintertime environment. In the entire test period of 3-1/2 months during the winter of 1977-78 there were no electronic fail- ures detected from either of the two AESOP's being tested in the Sierras. As is common with relative humidity sensors, the device used gave inordinately low readings during dry periods and seems to slowly degrade in an outdoor environ- ment. Future tests may employ a different type of relative humidity sensor, manufactured by Vaisala. The precipitation gage had a bridging problem in some of the very-high-intensity pre- cipitation events. This bridging could have been caused by too thick an evaporation-inhibiting oil coating on top of the ethylene glycol/methanol solution or simply because the snow rate was too high to be absorbed by the winterizing solution. Two corrective actions were taken: the oil coat- ings were reduced in thickness and the weighing buckets were wrapped with thermostatically con- trolled electric heat tapes. The problem was not encountered again. In general, the AESOP's performed much better than expected during the test period. As a result of their excellent performance, it is planned to use them operationally in some more remote areas of the SCPP during the 1978-79 win- ter season. Acknowledgments: The research reported here was supported in part by the Earth Resources Observa- tion Systems Program Office, United States Geolog- ical Survey, United States Department of the Interior. The authors are grateful to Mr. Carl Wickstrom of the National Weather Service surface weather station at Blue Canyon, California. National Oceanic and Atmospheric Administration, United States Department of Commerce, for his help in providing calibration and comparison data as well as for his cooperation during the instal- lation of the AESOP; and to Dr. James L. Smith and Mr. James A. Bergman of the Central Sierra Snow Laboratory at Soda Springs, California, Forest Service, United States Department of Agri- culture for their efforts in providing special observations to provide calibration and comparison data as well as for their assistance during the installation of the AESOP. Throughout this paper, the mention of any manu- facturer, contractor, or other commercial entity by name is not to be construed as a recommendation for, nor an endorsement of, that organization's products or services by the Bureau of Reclamation or the United States Government. References: Labarge Incorporated, 1976: Inst:zouction Manua7- for the Convertib7-e Data CoZ'Lection Platform (CDCP) and Related Equipment. Labarge Incorpo- rated, Tulsa, Oklahoma. .!'"~ ": ~ ,..~,~ Price, G. R. and V. R. Scheetz, 1977: Automatic Environmenta7- Surface Obse1'1Jation P7-atfo1'TT/ (AESOP) for the High Plains E:z:periment (HIPLEX). Final Report to Bureau of Reclamation, Electronic Tech- niques Incorporated, Fort Collins, Colorado. Reynolds, R. R. and J. Lovkay, Jr., 1972: Design Deve7-opment of the Remote Automatic Meteoro7-ogica7- Obse1'1Jation Station (RAMOS). Equipment Devel- opment Laboratory, National Weather Service, National Oceanic and Atmospheric Administration, United States Department of Commerce, Washington, D.C. United States Departments of Commerce, Defense and Transportation, 1975: Federa7- Meteol'07-ogica7- Handbook Number 7-, Surface Obse1'1Jations. United States Government Printing Office, Washington, D.C. 22