Friedman I, Smith G I
Science. 1972 May 19;176(4036):790-3. doi: 10.1126/science.176.4036.790.
The winter of 1968-69 produced two to three times the amount of precipitation in the Sierra Nevada area, California and Nevada, as the winter of 1969-70. The deuterium content in snow cores collected at the end of each winter at the same sites, which represents the total snowfall of each interval, shows a depletion in 1968-69 of approximately 20 per mil. The higher snowfall in 1968-69 and the depletion of deuterium can be explained by an uncommonly strong westward flow of cold air over and down the western slopes of the Sierras, which interacted with an eastward flow of moist Pacific air that overrode and mixed with the cold air; this resulted in precipitation that occurred in greater than normal amounts and at a lower than normal temperature. Pluvial periods of the Pleistocene may have had the same shift in air-mass trajectory as the wet 1968-69 year. Snow cores collected in the norrmal 1970-71 winter have deuterium concentrations that resemble those of the normal 1969-70 winter. Small and nonsystematic differences in samples from these two normal winters are due to variations in climatic character as well as to factors inherent in the sampling sites.
1968 - 1969年冬季，加利福尼亚州和内华达州的内华达山脉地区降水量是1969 - 1970年冬季的两到三倍。在相同地点每年冬季末采集的雪芯中的氘含量代表了每个时间段的总降雪量，其显示1968 - 1969年的氘含量约减少了20‰。1968 - 1969年降雪量较高以及氘含量减少的原因可以解释为，一股异常强劲的冷空气向西流经内华达山脉西坡并向下流动，与一股向东流动的潮湿太平洋空气相互作用，这股太平洋空气覆盖并与冷空气混合；这导致降水量超过正常水平且温度低于正常水平。更新世的多雨期可能与1968 - 1969年湿润年份有相同的气团轨迹变化。在正常的1970 - 1971年冬季采集的雪芯中的氘浓度与正常的1969 - 1970年冬季相似。这两个正常冬季样本中的微小且无系统性的差异是由于气候特征的变化以及采样地点固有的因素造成的。
