85 resultados para warm-season precipitation


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This is the 6th Annual Report of the Rive Exe Scale Reading Investigation for the 1971 Season by the Devon River Authority. The object of this investigation is to examine, by means of scale reading, the biology of age classes of the salmon population of the River Exe. It reviews the methods used for the collection of scales and examination of the materials. It shows the results of the survey and the number of scales studied from each of the various sea-age classes, time of running with distribution of the sea-age groups throughout the season, fish sizes and smolt ages at migration. All is summarized in tables, and figures are included showing weight distributions for each age classes and frequency distributions.

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This is the 7th Annual Report of the Rive Exe Scale Reading Investigation for the 1972 Season by the Devon River Authority. The object of this investigation is to examine, by means of scale reading, the biology of age classes of the salmon population of the River Exe. It reviews the methods used for the collection of scales and examination of the materials. It shows the results of the survey and the number of scales studied from each of the various sea-age classes, time of running with distribution of the sea-age groups throughout the season, fish sizes and smolt ages at migration. All is summarized in tables, and figures are included showing weight distributions for each age classes and frequency distributions.

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This is the Rivers Taw and Torridge scale reading investigation: the 8th annual report for the 1972 season produced by Devon River Authority in 1973. The object of the investigation is to examine by means of scale reading the biology of age classes of the salmon populations of the Rivers Taw and Torridge. The report is arranged in sections as previously and tables referred to in the report form an appendix. Scales were collected only from fish taken during the normal open season, which in 1972 was 1st April - 31st August. A weekly close time was in operation for the nets, a period of 60 hours from 6 p.m. on Friday evening to 6 a.m. on the following Monday. Thirty six licences for draft or seine nets were issued for the 1972 season and netsmen submitted samples of scales collected direct.

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The objective of this monitoring project was to determine the baseline condition for a 960-m long stream reach and its associated streamside zone, which terminates at the confluence with the Deschutes River. This stream reach had been damaged heavily in the February 1996 flood and had also received many years of overuse by livestock grazing. The monitoring project was conducted in July 1997 just after installation of riparian exclosure fencing. Future resurvey of the study area will allow determination of progress made in ecological recovery.

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After an unusually strong and persistent pattern of atmospheric circulation over the United State[s] in Fall 1985, it became quite changeable (although high amplitude anomalies still prevailed). Following a fall that was cold in the West and warm in the East with heavy precipitation, a high pressure ridge set in over the West during December, with generally light precipitation over most of the country. Throughout the winter, the central North Pacific was very active, with large negative atmospheric pressure anomalies centered at about 45°N, l60°W. This activity may have been encouraged by an enhanced meridional eastern North Pacific sea surface temperature (SST) gradient, with positive SST anomalies in the subtropics and negative anomalies in midlatitudes. However, in January, the western high pressure ridge remained strong and temperatures were remarkably warm, increasing the threat of drought in California after the two previous dry winters. However, in February, storms from a greatly expanded and southerly displaced Aleutian Low broke into the West Coast. An unusual siege from February 11 to February 20 flooded central and northern California, with very heavy precipitation and record to near-record runoff. Upwards of 50 percent of annual average precipitation fell on locations from the upper San Joaquin to the Feather River drainage basins, and the largest flow since observations began in the early 1900's was recorded on the Sacramento River at Sacramento. The atmospheric pattern that was responsible for this remarkable stormy spell developed when the western high pressure retrograded to the northwest into the Aleutians, accompanied by the strengthened and southerly extended storm tract that moved into California. Although exact details vary from case to case, this episode displayed meteorological conditions similar to those in several other historical California winter flood events. These included a long duration of very strong westerly to southwesterly winds over a long subtropical fetch into California. Much of the precipitation during this series of storms was orographically induced by the moisture laden flow rising over the Sierra ranges. Due to the warm air mass, snow levels were relatively high (about 7500 feet) during the heaviest precipitation, resulting in copious runoff.

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EXTRACT (SEE PDF FOR FULL ABSTRACT): Verified reconstructions of seasonal temperature, precipitation and sea-level pressure over North America and the North Pacific have been derived from 65 arid-site tree-ring chronologies in the North American West. Significant reconstructions were obtained for temperature for wide areas in the West and mid-continent. Precipitation reconstructions were significant only in the West, and pressure was reconstructed over wide areas of the North Pacific Ocean and the North American continent.