THE VALUE OF HIGH-LEVEL METEOROLOGICAL DATA IN FORECASTING CHANGES OF TEMPERATURE-A CONTRIBUTION TO THE METEOROLOGY OF MOUNT ROSE, NEVADA. This Bulletin contains the results of a study of meteorological phenomena at different heights, undertaken with the object of determining, if possible, the value of upper-air data in forecasting frost. The material employed chiefly consists of records obtained simultaneously on the summit of Mount Rose and at stations in near-by valleys. Analyses of these records have been compared with results of similar researches conducted elsewhere. The phenomena under consideration are very complex, and, in order to keep within the limits of a bulletin of this kind, this paper necessarily has been restricted to the most important features of the subject investigated. A description of the Mount Rose Observatory, including an account of its work from the beginning until 1909, was published in Bulletin No. 67 of the Nevada Agricultural Experiment Station, prepared by Dr. J. E. Church, Jr., who established the Observatory and is its Director. Since its establishment, the Observatory has continued to be the second highest mountain meteorological station in operation in this country. Personnel of the Work. Since the beginning, the very laborious ascents of Mount Rose, necessary to keep the instruments in order, have been made mostly by Dr. Church, with the assistance of friends and associates in the University and neighborhood. In 1910 the writer was employed to assist in the work and in 1911 was appointed Associate Meteorologist of the Experiment Station and Professor of Meteorology and Climatology in the University. Mr. Howard Smith was employed temporarily at various times from 1908 to 1910, and Mr. A. L. Smith has acted as Snow Observer at Lake Tahoe in 1911 and since 1913. The work of reducing the records for this Bulletin has been performed chiefly by Mr. A. L. Smith and by Messrs. Dale Pruett, A. D. Murray, and H. C. Neeld, students in the University. The cost of maintaining the work has been met by means of grants from the Hatch and Adams funds of the Experiment Station, and by an appropriation from state funds during four years. The energies of the Department have been expended chiefly upon three projects or problems: (1) Frost Forecasting from Elevated Stations; (2) The Relation of Forests to the Conservation of Snow; and (3) A Temperature Survey of the Fruit-Growing Regions of the State. The first two projects have been supported by the Adams and Hatch funds and the last chiefly by state appropriations. In work of this kind, facilities for the construction and repair of instruments are indispensable; and this department is indebted to Dr. L. W. Hartman for the free use of the shop in the Physical Laboratory, and to Dean Scrugham for the use of machine tools in the Department of Engineering. Professor E. C. Pickering, Director of Harvard College Observatory, kindly loaned the cuts for Figures 4 and 5, and to Professor Alexander McAdie, Director of Blue Hill Observatory, the author is indebted for the hourly temperatures at the Blue Hill Valley Station plotted in Figure 3. The plots of daily changes of temperature.at Pike's Peak and Fuji were copied from Blue Hill Observatory Bulletin No. 1, 1900, and those of conditions in cyclones and anticyclones at Mount Washington from the American Meteorological Journal, October, 1887. The three photographs of Mount Rose were made by Dr. Church. Buildings. The small wooden building on the summit of Mount Rose, described in Bulletin 67, is still in use as a shelter and observatory. For greater comfort and convenience a hut, supplied with bedding and provisions, was erected at the height of 2,750 meters on the northeastern side of the mountain in the autumn of 1910; also a room at the Mount Rose Ranch near the base, similarly equipped, has been leased for use as local headquarters. Instruments and Records. Records of temperature and pressure were obtained from a thermograph and barograph of the Richard pattern from 1905 until 1911, except during a part of 1910, when changes in the management of the work were under consideration. The instruments usually worked for about nine days with one winding of the clocks, and as the mountain could be ascended on an average about twice in a month, the records were not continuous, but probably cover more than one-half of this period. Extreme temperatures were obtained from maximum and minimum thermometers read at the time ascents were made. Also, there were occasional observations of wind velocity from a Weather Bureau anemometer, and records of cloudiness, precipitation, storms and optical phenomena in the form of notes. In 1907 the writer, then at Blue Hill Observatory, was commissioned to build, for use on Mount Rose, a meteorograph capable of recording temperature, pressure, humidity, and the direction and velocity of the wind during a period of six weeks with one winding of the clock. This instrument, after thorough trial at the University, was taken to the summit in the autumn of 1908. At first the record was frequently interrupted by snow, which penetrated the outer casing and clogged the mechanisms and it was not until December, 1910, that this trouble was remedied by the addition of weather-strips. Later these were replaced by a canvas jacket, which covers the instrument completely, excepting the wire cage in which are exposed the thermograph tube and hygrograph hair. In January, 1912, the clock was altered to run 90 days with one winding, although usually the record sheets are changed every six weeks or two months. Since 1911 the records of pressure, temperature, and relative humidity have been nearly complete for the entire year, and those of the direction and movement of wind complete for the summer months from May until October. Between October and May the anemometers are so frequently covered with ice and frost that the records cannot be depended upon. The performance of this instrument is considered satisfactory, making allowance for the severe conditions of temperature, moisture, etc., although experience indicates that, if the |